NIIR

Contents

Chapter 1

Coal

Ethylene  

Fischer –Tropsch Synthesis for Olefins                                    

Direct Conversion of Synthesis Gas to Ethylene                          

Ethanol from Synthesis Gas                                                  

Olefins from Methanol                                                        

Methanol Homologation                                                    

Methanol to Acetic Acid                                                      

Ethylene Glycol                                                                

Acetic Anhydride                                                              

Vinyl Acetate                                                                  

Other Chemicals                                                              

Coal Pyrolysis Processes                                                      

Acetylene                                                                      

Production of Chemicals by
Coal Liquefaction Processes                                                

Conclusion

                                                                     

Chapter 2

Analysis of Coal and Coke                                                  

Methods of Analysis                                                          

Sampling                                                                  

Determination of Constitution and Physical Properties


Functional Group Analysis                                              

Spectroscopy                                                                  

Determination of Optical Constants                                  

Electron Microscopy                                                          

Density                                                                        

X-Ray Diffraction                                                            

Specification Tests                                                        

Proximate Analysis                                                      

Ultimate Analysis                                                        

Calorific Value                                                            

Fusibility of Coal Ash                                                    

Behaviour on Healing                                                    

Equilibrium Moisture of Coal at 96-97%                              

Relative Humidity and 39oC                                            

Determination of Harcbgrobve Grindability                              

Index of Coal                                                                  

Special Constituents                                                      

Coal Classification

                                                     

Chapter 3                                                                      

Cotton                                                                        

Methods of Analysis                                                          

Modified Cottons                                                              

Finishing Agents                                                          

Separation and Identification                                          

Spectroscopic Methods                                                  

Inorganic Constituents                                                  

Chemical Methods                                                      

Spectroscopic Methods

                                                     

Chapter 4                                                                      

Lignin and Hemicellulose                                                  

Hemicellulose                                                                  

Assay systems                                                            

Classification                                                              

Thermophilic Hemicellulases                                            

Alkaline active xylanases                                                

ß - Xylosidase                                                            

Mannanases and galactanses                                          

Accessory enzymes for Hemicellulose utilization                    

Lignin                                                                          

Lignin-degrading enzymes                                              

Lignin degradation in whole cell cultures                              

Degradation by cell-free enzyme systems                            

Role of glycosides in Lignin degradation                              

Lignin-carbohydrate complexes                                            

Fractionation of Lignin and Carbohydrate in wood                                                  

Isolation of LCCs                                                        

Chemical characteristics of LC bonds                                

Ferulic and p-coimaric ester side chains                              

Frequency and stability of LC bonds                                  

Residual lignin in kraft pulp                                            

Biodegradation of LCCs                                                

Residual LC structures after exhaustiveenzymatic digestion                                                      

Solubitization of LCC by microbial activity                          

Enzymatic treatments of pulps                                        

Conclusion

                                                               

Chapter 5

Degradation of Wood                                                        

Introduction                                                                    

Gross Chemical Composition                                                

Distribution of Wall Components                                          

Component Chemistries                                                      

Microstructure and Porosity                                                  

Degradation of whole wood                                                  

Biodegradation of Lignin                                                    

Biodegradation of Cellulose                                                  

Biodegradation of Hemicellulose                                            

Applications                                                                    

Conclusion  

                                                                   

Chapter 6                                                                      

Cca-Treated Wood                                                          

Introduction                                                                    

Materials and methods                                                      

Results and Discussion                                                        

Conclusion

                                                                   

Chapter 7

Wood-Polymer Composites                                                

Introduction                                                                    

Materials and Methods                                                      

Monomers                                                                

Wood specimens                                                              

Treatment of specimens with monomers                              

Volumetric swelling and moisture content                            

Result

Swelling of wood soaked in monomers                                    

Polymer loading                                                                

Volumetric swelling of WPC specimens                              

Moisture content of WPC specimens                                  

Conclusions

                                                                   

Chapter 8

Lignocellulosic-Plastic Composites from Recycled
Materials                                                                      

Municipal Solid Waste as a Source of Lignocellulosic Fibre and Plastics

Thermoformable composites as Outlets for Waste Paper, Wood and Plastics                            

Recent Research on Wood Fiber-Thermoplastic Composites                                            

Research and Development Needs                                          

Concluding Remarks

                                                       

Chapter 9

Chemical Modification of Wood Fiber                                  

Introduction                                                                    

Experimental Procedure                                                      

Esterification Procedure                                                  

Analyses of Esterification Products                                    

Board Formation                                                        

Board Testing                                                            

Moisture sorption                                                  

Rate and extent of swelling                                        

Results and Discussion                                                        

Esterification of Wood Fiber                                            

Moisture Sorption of Esterified Fiberboards                          

Rate and Extent of Swelling of Fiberboards in Liquid Water                                                            

Plasticization of Esterified Fibers                                      

Conclusions

                                                                   

Chapter 10

Delignification of Wood with Pernitric Acid

Generation of pernitric acid                                                  

Decomposition of pernitric acid                                            

Delignification of aspen wood                                              

Conclusions                                                                    

Experimental

                                                                 

Chapter 11

Rosin and Rosin Derivatives                                                

Composition                                                                    

Reaction and derivatives                                                    

Isomerization                                                                  

Maleation                                                                      

Oxidation                                                                      

Photosensitized oxidation                                                    

Hydrogenation                                                                

Hydrogenless Hydrogenation                                                

Polymers of vinylesters of hydrogenated rosin                            

Prehydrogenation                                                              

Hydrocracking of Rosin                                                      

Dehydrogenation                                                              

Polymerisation                                                                

Analysis

Compatibility                                                                  

Solubility                                                                      

Instrumental analysis                                                        

Gas chromatography analysis                                              

Infrared Spectroscope                                                        

Nuclear magnetic resonance                                                

Ultraviolet spectroscopy                                                      

X-Ray Analysis                                                                

Mass Spectroscopy                                                            

Phenolic modification                                                        

Salt formation

With metals                                                                    

With unsaturated cyclic and acyclic hydrocarbons                      

Example-2                                                                      

Rosin-isoprene condensate (Example-3)                                  

Rosin-isobutene condensate (Example-4)                                  

Example –5                                                                    

Rosin-styrene condensalt (Example-6)                                    

Rosin-cyclopentadiene condensate (Example-7)                        

Rosin-coumarone-indene condensate (Example-8)                      

Rosin-divynylbenzene condensate (Example-9)                          

Example-10                                                                    

Esterification

With Glycerol                                                                  

With pentaerythritol and other polyhydric alcohols                      

With monoydric alcohols                                                    

Hydrogenolysis                                                                

Polyesterification                                                              

Copolyesters                                                                    

Ammonolysis                                                                  

Preparations                                                                    

Dehydroabietylamine acetate                                              

Dehydroabietylamine                                                        

Typical Uses                                                                    

Asphalt additives                                                              

Chemical Intermediates                                                      

Corrosion Inhibitors                                                          

Flotation Reagents                                                            

Preservatives

Resolving agent                                                                

Chemical and physical properties of
Amine D acetate                                                              

Stability to heat and storage                                                

Stability to heat and storage                                                

Surface Activity                                                                

Chemical Reactivity                                                          

Chemical and Physical Properties of

Amine D acetate                                                              

Solubility    

Note          

Stability to Heat and Storage                                                

Stability to Air and Sunlight                                                  

Surface Activity                                                                

Styrenation                                                                    

Decarbxylation                                                                

Hydroxymethylation and hydroxylation                                  

Methods of preparations                                                    

Nitrogenous intermediates                                                    

Methyl levopimarate (i)                                                      

Methyl neoabietate (ii)                                                      

Methyl photolevopimarate (iii)                                            

Reaction of SSI with Methyl levomarate (i)                          

Reaction of Chlorosulphonyl isocyanate with methyl neoabietate (ii)                                                  

Reaction of Chlorosulphonyl isocyanate with methyl photolevopimarate (iii)                                  

Fumaroniprile Adduct of levopimaric acid                                              

Tetracyanoethylene Adduct of levopimaric acid                                              

Acrylonitrile adducts of levopimaric acid                                              

Polyoxyalkylation

                                                           

Chapter 12

The Polymerizable Half Esters of Rosin                                

Expermental                                                                    

Preparation and properties of monomers                                  

Maleic rosin esters with reactive groups                                    

Polymerization & Copolymerization                                        

Aqueous Polymerization                                                      

Suspension Polymerization                                                  

Secondary reactions and graft copolymers                                

Reaction Involving Crosslinking                                            

Applications                                                              

Coatings                                                                        

Inks                                                                            

Textiles                                                                        

Conclusions

                                                                   

Chapter 13

Photographs of Plant & Machinery with Supplier’s



Contact Details

Sample Chapters

                                                           Coal

Coal carbonization byproducts (coal tar and coke-oven gas) were the

main sources for the production of organic chemicals till the Second

World War. However, the abundant availability of cheap petroleum and

natural gas caused a major shift from coal to these raw materials.

After the Second World War, there was a consistent increase in the

consumption of petrochemicals. In the last 10 years, with the

continuing rise in oil prices, and scarcity and uncertainty regarding

assured supplies of natural gas and petroleum oils, attention towards

achieving self-sufficiency in chemicals and production of fuels has

been focussed on exploring alternative feedstocks like coal and

biomass. In this context, there is a need for reassessing the

possibilities of obtaining organic chemicals from coal. It is

anticipated that it will be cheaper to make liquid and gaseous fuels

from coal than from oil before the end of this century.

The use of coal as a source of chemicals is at present confined mainly

to high temperature carbonization (HTC) through the recovery of by

products. A part from the traditional coking route, concerted efforts

are being made to obtain various chemicals by other coal conversion

processes, such as direct hydrogenation or solvent extraction of coal

followed by cracking, hydrotreating or hydrocracking of the products

and by synthesis of hydrocarbons via synthesis gas produced by coal

gasification.

Ethylene

Ethylene is an important basic building block of the petrochemical

industry. The production and recovery of large quantities of olefins

from petroleum refinery off-gases first started with the advent of

catalytic cracking. Rapid growth in the demand for petrochemicals

necessitated the setting up of plants to produce ethylene and other

olefin monomers by thermal cracking of a wide range of petroleum

feedstocks.

The routes considered for the production of ethylene from coal include:

(i) Fischer-Tropsch synthesis, (ii) direct conversion of synthesis gas,

(iii) conversion of coal-derived methanol, (iv) homologation of

methanol to ethanol followed by dehydration, (v) cracking of dimethyl

ether which again is derived from synthesis gas or methanol, and (vi)

cracking of synthetic liquids produced in direct liquefaction

processes.

Fischer – Tropsch Synthesis for Olefins

Fischer – Tropsch (FT) synthesis for the production of fuels from coal

has been in operation on a commercial scale since 1955 in Sasolburg,

South Africa. It is known that through proper choice of reactor,

catalyst and operating conditions, the product pattern can be changed

in FT synthesis. The dilute fluid bed or Kellogg type of reactor

(Synthol) shifts the product spectrum to lower hydrocarbons. It gives

an ethylene yield of 4.4% and also C3 and C4 olefins. Ethane produced

in the process can also be converted to ethylene. The cost of ethylene

from the recovery process is about 30 cents/lb compared to 18-19

cents/lb from the conventional gas oil cracking. In the steam cracking

of FT product, the cost of ethylene is estimated at 30 - 50cents/lb. In

the Sasol 2 plant in South Africa, the annual production of 1.5 million

tones of automotive fuels, 1,60,000 tonnes of ethylene and 50,000

tonnes of chemicals, 1,00,000 tonnes of ammonia, 90,000 tonnes of

sulphur and 2,00,000 tonnes of tar products, including tar acids, is

envisaged.

Direct Conversion of Synthesis Gas to Ethylene

Direct conversion of synthesis gas from coal to ethylene and ethanol is

now attracting attention. Efforts to get ethylene by passing synthesis

gas (CO: H2 ratio, 74:24:8) in a copper tube at 550ºC resulted in 5.6%

ethylene in the product gas, whereas when synthesis gas containing 0.6%

ethylene was passed over a CuO (3%) – Al2O3 catalyst at 250ºC and 20 –

40 atm pressure, the ethylene content increased to 7.6%. On the other

hand, Peters used a four-component catalyst system to convert synthesis

gas (46.4% CO, 42.5% H2 and 11.1% inert) to ethylene. Several iron and

cobalt-based FT catalysts have been evaluated for the conversion of

synthesis gas to C2 – C4 olefins. As the copper and the alkali contents

were increased in iron-copper-kieselguhr-K2O catalysts, the product

distribution shifted towards lower molecular weight hydrocarbons.

The activity and selectivity of Ni- or Co-based bimetallic catalysts

containing several other metals as promoters have been evaluated. The

bimetallic catalysts give a somewhat different product distribution

compared to Ni or Co catalysts. The addition of Re to Ni favours the

formation of ethane (22% at 185ºC), that of Ru favours the long chain

hydrocarbons, while addition of lr favours the formation of dimethyl

ether at 210ºC (40% at 190ºC). Co - Mn gives products containing a

higher proportion of olefins which is higher at lower temperatures and

lower H2 - CO ratios.

The favourable olefin selectivity obtained on the addition of basic

promoters to the conventional iron catalysts suggests that metal

interactions with basic or electron-donor sites in zeolites may have an

important influence on selectivity. A marked increase in the olefin

selectivity of ruthenium is observed as sodium ions in the zeolite are

replaced by potassium or caesium ions.

The work done at Pittsburgh Energy Research Center indicated that a

fused iron catalyst is particularly effective in giving high yields of

olefins. Experiments were conducted in a microreactor with temperature

range 250 - 350ºC, pressure range 20 - 68 atm, synthesis gas having

composition of 1:1, 2:1 and 3:1 of H2: CO and also mixtures containing

CO2 and hourly space velocities of 500-5000.

Ethanol from Synthesis Gas

Synthesis gas has been converted to ethanol at 250-290ºC, 50 atm and a

space velocity of 1000-4000 hr-1 in a bench scale unit using a special

rhodium cluster catalyst. The conversion of CO was 10% and the reaction

product contained 75-80% ethanol. The activity of the catalyst during

one month period of operation (8 hr-a-day) remained almost constant.

Work done at the Union Carbide Corporation showed that addition of Fe

to Rh increased the yield of ethanol at 68 atm. On the other hand,

large proportions of ethane and dimethyl ether were obtained with

alumina-supported platinum.

Olefins from Methanol

Conversion of coal-based methanol to ethylene and propylene offers an

attractive route to the use of coal as a basic raw material. The

formation of C2 - C5 olefins (1.6 mole%) was noticed by Mattox during

methanol dehydration over NaX zeolites. Similar results have been

reported by several investigators using various catalysts. The product

distribution suggests that an a-elimination process (H-CH2-OH !®H2O +

CH2) is occurring in the methanol adsorbed on the zeolite surface. The

carbene methylene species so formed can polymerize to form simple low

molecular weight olefins.

Methanol cannot dehydrate to form an olefin unless recombination of

one-carbon fragments takes place. Aromatics are produced by

dimerization and cyclization of C3, C4 and C5 olefins.

Laboratory scale experiments were conducted using tungstic acid

impregnated on zeolites, MgO or Al2O3. Zeolites exchanged with rare

earths gave higher yields ranging from 16 to 30% ethylene and 29 to 30%

propylene with methanol conversion of 80 – 90%. Dimethyl ether formed

in the process can also be converted to olefins using the same

catalyst. The reaction mechanism involves three consecutive surface

reactions. Adsorbed methanol is dehydrogenated to formaldehyde followed

by dimerization of formaldehyde and dehydration of the dimer to give

adsorbed ethylene.

The possibilities of producing ethylene and propylene from coal-based

methanol on a laboratory scale have been explored by BASF. In 1979,

BASF constructed a pilot plant with 15 tonnes per month capacity at a

cost of $ 1.5-1.6 million at Ludwigshafen, West Germany to produce

olefins from methanol. In this process, 3-4 lb of methanol is

catalytically converted (catalyst, ZSM-5 zeolite) to give 1 lb of

olefins. Methanol is first converted to dimethyl ether, which, in turn,

gives ethylene by dehydration. Propylene and C4 olefins are also

produced in varying amounts, depending on the reaction conditions.

Methanol Homologation

The best potential approach to the production of ethylene from

synthesis gas appears to be through its reaction with methanol to form

ethanol and subsequent dehydration of ethanol to ethylene. Wender

showed that methanol reacts with synthesis gas in the presence of

dicobalt octacarbonyl [CO2(CO)8] catalyst to give ethanol, but higher

alcohols, including ethanol, are relatively unreactive in this system.

The reaction was carried out in batch autoclaves at 183 – 185oC and 275

atm at 75% conversion to give about 40% of ethanol in the product.

About 4% propanol was formed together with 0.3% butanols.

The methanol homologation reaction as catalysed by Co2(CO)8 is a very

complex one, highly dependent on a variety of reaction parameters and

variables. The initial carbonylation product, acetaldehyde, is obtained

in high selectivity by proper ligand modification. A selectivity of

62.3% was obtained at 200oC and 270 atm for 3 hr process time using a

cobalt-iodine catalyst. High iodine/cobalt ratios lead to undesirable

reaction by products and catalyst deactivation. The active form of Co

in the iodine – promoted system is Co(CO)4–, as indicated by high

pressure IR spectroscopy.

Methanol to Acetic Acid

Liquid phase carbonylation of methanol has become an important

industrial process which uses iodide or carbonyl of cobalt as a

catalyst and an organic or inorganic iodide, such as methyl iodide,

hydrogen iodide or potassium iodide, as promoter.

Nickel carbonyl and some other nickel compounds are also effective at

low pressures of about 50 atm in the presence of iodide in the liquid

reaction media of some organic amines of phosphines.

In the process developed by Monsanto, a new iodide-promoted rhodium

catalyst which exhibits high activity for methanol carbonylation even

at atmospheric pressure is used. The yield of acetic acid is 99% based

on methanol and 90% based on carbon monoxide. A plant with a current

annual capacity of 143 million kilograms is now operating. About 40% of

the world’s capacity for acetic acid is based on Monsanto process.

Ethylene Glycol

The most promising route to ethylene glycol involves direct conversion

of synthesis gas using rhodium catalyst.

High yields of ethylene glycol were reported. The reaction takes place

at about 2000C and 1400 - 3000 atm over a rhodium carbonyl catalyst,

but comparatively lower pressures of the order of 400 atm may be

sufficient to achieve a reasonable degree of conversion. Such a low

pressure process using a more specific catalyst promises to be a

commercial success. In the work carried out by Union Carbide, a solvent

having a high dielectric constant to ensure ion separation and/or

complex the cations to prevent pairing with a anionic centers has been

used.

Vinyl Acetate

Halcon International has nearly completed the development of a methanol

carbonylation route to vinyl acetate. In this process, methanol is

reacted with recycled acetic acid to make methyl acetate; the methyl

acetate is reacted with synthesis gas to produce ethylidene diacetate,

which is subjected to cracking to produce vinyl acetate and acetic acid

for recycle.

Other Chemicals

Monsanto reported a method for the alkylation of toluene with methanol

over modified zeolite catalyst to produce a mixture of ethylbenzene and

styrene. At present, the product concentrations are very low (5 mol% of

styrene and ethylbenzene) and frequent catalyst regeneration is

necessary. Both BASF and Rohm and Haas have been investigating the base

catalysed addition of formaldehyde (as acetal) to methyl propionate to

form methyl methacrylate.

Coal Pyrolysis Processes

Coal tar is an inevitable byproduct in the production of metallurgical

coke. Important chemicals, such as benzene, toulene and xylenes (BTX),

can be produced from the benzole recovered from coke oven gas as well

as from the light oil obtained by the distillation of coal tar. The

other main constituents of high temperature coal tar are naphthalene

(10%), anthracene (1.8%), phenanthrene (5.0%), fluorine (2.0%),

fluoranthene (3.3%), phenol (0.4%) and pyridine (0.02%). Bulk products,

such as creosotes and pitches, are also produced from coal tar.

With the exception of limited quantities produced in USA through

dealkylation of aromatic petroleum fractions, naphthalene is almost

exclusively obtained from coal tar. Methyl naphthalene and dimethyl

naphthalenes are present in the heavier coal tar fractions (250 –

3500C). The dealkylation of these methyl naphthalenes can yield further

quantities of naphthalene. ­

The Coalite and Chemicals Products Ltd, UK, are processing the tar from

LTC into valuable chemicals (pure phenols, chlorinated phenols) and

chemical intermediates for plasticizers, pharmaceuticals and adhesives.

A phenol-free middle oil fraction was processed into diesel oil till

1965.

The pyrolysis of tars or vapours from LTC of coal is considered as a

possible route for producing olefins. Laboratory scale investigations

were conducted on cracking of vapour and tars obtained by LTC of Texas

and North Dakota lignites. When Texas lignite was carbonized at 5500C

and the tar vapours were cracked at 8000C, the yields of ethylene,

propylene and benzene were 40, 7.6 and 6 lb respectively per tonne of

lignite. However, the process was not considered economically viable.

LTC of cannel coals from West Virginia in the presence of superheated

steam followed by cracking of the vapours at 800 – 9000C gave 191-245

lb of ethylene, 20-41 lb of propylene and 21-47 lb of benzene per tonne

of coal (MAF).

Acetylene

Acetylene is an important chemical intermediate for the production of

acetaldehyde, vinyl acetate, vinyl chloride, acrylonitrile, etc. It is

generally obtained by high temperature pyrolysis of natural gas or

naphtha fractions in addition to the conventional calcium carbide

route. A process to make acetylene by pyrolysing coal in an electric

arc has been developed by Avco Everett Research Laboratory, Everett,

Mass. In this process, pulverized coal is injected into a stabilized

arc, the pyrolysis products are quenched and acetylene is separated

from the product. Pyrolysis is conducted in hydrogen atmosphere, which

increases the yield of acetylene. The process has been tested in a unit

that operates at 75-100 kW producing 0.15-0.20 lb/min of acetylene. A

pilot plant to process 10 tonnes/day of coal that would yield 3-3.35

tonnes/day of acetylene has been proposed.

Production of Chemicals by Coal Liquefaction Processes

Several investigations have been made to study the possibilities of

producing chemicals from coal liquefaction products. Dow Chemical

Company studied the feasibility of producing chemical feedstocks from

coal-derived liquids from COED, Synthoil, H-Coal and Solvent Refined

Coal (SRC) processes.

In the Exxon Donor Solvent (EDS) process, which provides a technically

feasible route to the production of liquid products from various types

of coal, the byproducts form a potential source of petrochemical

feedstock. The major source of ethylene and propylene is derived by

cracking the light gas product blend containing ethane, propane and

mixed butanes.

Analysis of Coal and Coke

Coal is a readily combustible rock containing more than 50% by weight

and more than 70% by volume of carbonaceous material, formed from

compaction or induration of variously altered plant remains similar to

those of peaty deposits. Differences in the kinds of plant materials

(type), in degree of metamorphosis (rank), and range in impurity

(grade) are characteristic of the varieties of coal. In lump form, coal

appears to be black or brownish black. The luster, fracture, and

texture vary according to type, rank, and grade. Chemically, coal

consists mainly of carbon, hydrogen, and oxygen, with minor amounts of

nitrogen, sulfur, silica, alumina, iron, and trace amounts of

fifty-three other elements. The composition varies to such an extent

that Hendricks states that no two coals are absolutely the same. Some

of the elements are inherent in the original plants; others have been

incorporated during the coalification process; and others have been

picked up as extraneous matter in mining, preparation, and

transportation.

That types, ranks, and grades of coal are dependent on the

characteristics of the original plants and the chemical, biological,

and physical processes involved in metamorphosis. Variations in the

combination of processes and the materials processed produce end

products varying in chemical and physical properties. Analytical

techniques that will consistently show numerical differences between

these products provide data with which the types, ranks, and grades can

be determined.

Each of the principal coal producing countries in the world has a

series of procedures or national standards. The Technical Committee 27

on Solid Mineral Fuels of the International Standards Organisation

(ISO) consists of representatives of Australia, Austria, Belgium,

Canada, Denmark, Spain, France, Germany, India, Italy, Netherlands,

Poland, Romania, Switzerland, Czechoslovakia, Turkey, United Arab

Republic, United Kingdom, United States, Soviet Union, and Yugoslavia

collaborating on the international standardization for coal and coke.

Even though the coke was produced and used by metallurgical plants, the

specifications were maintained by chemical and physical tests.

Uniformity is very essential in the various Processes.

Methods of Analysis

In this section, the methods for coal are discussed in detail. Testing

methods for coke are the same as for coal except the procedures for

stability, porosity, and density. More detailed information on the

testing methods can be found in the publications of the U.S. Bureau of

Mines, British Standards Institution, and the American Society for

Testing and Materials.

Sampling

Preliminary to any chemical or physical testing of coal in the

laboratory it is essential that a representative sample be provided.

The most carefully conducted analysis is meaningless unless the sample

be truly representative of the lot. This means that increments are

specified in number, weight, frequency, and method of extraction. The

properly collected gross sample must be reduced in particale size and

mass to laboratory size by a method that retains the representativeness

without gain or loss of such fleeting substances as moisture.

Determination of Constitution and Physical Properties

Knowledge of the constitution and physical properties of coal is of

great value in combustion, carbonization, gasification, and in the

utilization of coal in making nonsolid fuels and in chemical syntheses.

A number of techniques have been developed and other are in development

status to provide this vital information.

Functional Group Analysis

Essentially all of the functional groups recognized as being present in

coal are associated with oxygen. Both the nitrogen and organic sulfur

are considered to be present primarily as parts of heterocyclic systems

since there is no satisfactory evidence for any functional groups

containing either element.

Carboxyl groups, both free and as salts, are present in lignites and

brown coals and may represent as much as 14wt % of the dry lignite.

Determination of free carboxyl group generally has been carried out by

ion exchange between coal and barium or calcium acetate, followed by

titration of the liberated acetic acid. Methoxyl groups also are

present only in low-rank coals. Zeisel determination of methoxyl

contents of lignites and brown coals indicates a maximum of 2% for

lowest-rank coals. The number of carbonyl groups also decreases with

increating rank, although no satisfctory procedures have been developed

for quantitative determination of this functionalgroup in coal. Some

oxygen is also presentin heterocyclic rings.

Acetynlation. Several different acetylation procedures have been used

on coal. The one which is most widely used utilizes acetic anhydride in

pyridine

Procedure

Add a weighed sample (500-800mg) of dried coal to 10 ml of a 1:2

mixture of acetic anhydride and pyridine in a 200-ml flask. Reflux the

mixture for 24 hr, cool, and dilute with 100 ml of water. Filter the

mixture and wash the residue until free of acid Boil the acetylated

coal for 5hr in a 150-ml flask with 2 g of barium hydroxide in 40 ml of

water and keep on a steamplate overnight. Add 2 ml of 85% phosphoric

acid, and distill 24 ml into a titration flask. Titrate the acetic acid

in the distillate with sodium hydroxide. Add increments of water to the

residue and distill into the titration flask until no more acid is

observed upon titration.

Trimethylsilylation. A second method for determining the hydroxyl

content of coal involves treatment of the coal with

hexamethyldisilazane, and trimrthylchlorosilane in pyridine. This

results in the conversion of the hydroxyl groups to trimethylsilyl

ethers. Silicon analysis of the resultant coal ethers affords a

quantitative value from which the hydroxyl content can be calculated.

Alternatively, the trimethylsilyl ether content can be estimated from

the extinction coefficient of the trimethylsilyl group measured at

8.0µm.

Spectroscopy

Various spectral techniques are now applied to the study of coal. The

methods discussed here include infrared, ultraviolet and visible

absorption, mass, nuclear magnetic resonance, and electreon

paramagnetic resonance spectroscopy. A good general reference is that

of Silverstein and Bassler. Although considerable coal research work is

done by spectral methods there are as yet not many analytical

applications of spectroscopy in the coal industry.

Infrared Spectroscopy. Infrared spectroscopy is the most universally

applicable spectral method. With the exception of monatomic gases, all

substances have infrared spectra. Historically, infrared has been

applied principally to organic materials, but it is being used

increasingly on inorganic substances. Of all spectral methods infrared

has most earned the right to the title of “fingerprint method”.

Ultraviolet and Visible Absorption Spectroscopy. The principal use of

ultraviolet and visible spectroscopy is the study of aromatic compounds

particularly polynuclear condensed aromatic compounds. Because of the

prolific and characteristic spectral fine structure that results from

the electronic excitation of polynuclear condensed aromatics,

ultraviolet and visible spectroscopy is the best spectral method for

establishing identification of these compounds. Similar aromatic

compounds have radically different characteristic spectra­­­- for

example, anthracene and phenanthrene, chrysene and benz-phenanthrene,

pyrene and fluoranthene. Also the derivatives of the parent compounds

display.

Mass Spectroscopy. Since the first mass spectral studies of coal a

considerable amount of work has been done, principally at the

Pittsburgh Energy Research Center of the U.S. Bureau of Mines. Mass

spectra of pyridine extracts of bituminous coal have shown the presence

of thirteen types of aromatic compounds having molecular weights from

78 to 400.

Research investigations of various oils and pitches from coal tar have

been carried out. Many aromatic hydrocarbon types were identified along

with several nitrogen and a few oxygen compounds. Also, average

molecular weights, aromaticities, and mean size of aromatic nuclei of

these samples were calcutated from the mass spectra of oils and

pitches.

Nuclear Magnetic and Electron Paramagnetic Resonance Spectroscopy. The

application of NMR or EPR in the coal utilization industries is

limited. One development appears to be approaching the application

stage; the analysis of water in coal is being carried out on moving

conveyor belts. Belt speeds are low and throughput is small as yet but

the method has promise.

Free radicals exist in coals in relatively large amounts and are easily

detected by EPR. Unfortunately, no fine structure has been detected in

coal spectra it is therefore difficult to characterize structures.

However, considerable characterizing information is obtainable from

free radical concentrations, line widths, and spectral g-values.

Peltrographic Analysis

Coal petrography deals with descriptions of different physical parts of

coals that can be distinguished best by microscopic observation. These

small parts of coals look different because they are of different size

and shape and they modify in different ways the light that they reflect

or transmit to the eyes. Coal petrography relates these different parts

to the plants or plant parts from which they were derived and deduces

something about the changes that have occurred from plant to coal.

Another physical component of coals that may observed microscopically

is inorganic mineral matter. These mineral constituents may have been

present in the original plants, may have deposited as the peat beds

formed, or crystallized from waters percolating through the coal bed.

The principal ones are quartz, kaolinite, calcite, and pyrite. Traces

of many mineral elements are present.

Some attempts have been made to separate or concentrate different coal

components on a commercial basis to take advantage of properties

favorable to various uses. These usually depend upon differences in

resistance to breakage or differences in density.

Thin-Section Analysis. Petrographic thin– section analysis is usually

made on specimens obtained from column samples cut out of a coal bed

from top to bottom. The specimens are small blocks measuring

approximately 1× 0.8× 0.5 in. The 0.8- in. dimension is in the vertical

direction of the column or bed, so that the total of the 1×

0.8-in./faces represents a ribbon area over the entire height of the

bed, excluding the material lost in cutting between the blocks.

Microscope analysis of thin coal sections is conducted with a

biological microscope equipped with binocular eyepieces. A pair of 15×

eyepieces is used with 16 and 32 mm objectives to attain magnifications

of 60× and 150×. Anthraxylon is measured at 150× and opaque attritus,

fusain, and mineral at 60×. Translucent attritus is determined by

difference. Measurements are made by means of a Whipple micrometer disc

inserted in one of the eyepieces. This a glass disc on which is

centered a 7 mm square field divided into one hundred 0.7 mm squares

with the central one subdivided into twenty-five 0.14 mm squares. The

effective sizes of these squares under different magnification

conditions are determined by comparison with a stage micrometer.

A detailed study of the errors involved in this type of thin-section

analysis showed that the percentages of components in a column sample

of a coal bed as determined by this technique usually should not be in

error by more than 2%.

Figure l illustrates the results of thin-section analysis on a complete

vertical column of a coal bed.

polished surface analysis. Petrographic polished surface analysis is

usually made on briquets of granular coal molded with a binder. The

granular sample, usually of –20 mesh size, is representative of much

larger lots of broken coal.

A variety of grinding and polishing steps may be used. A detailed

grinding plan would include the use of 240, 400, and 600 grit papers in

succession. Similarly, a careful polishing procedure might involve

successive use of 3 mm alumina on chemotextile cloth, 1mm on

chemotextile, and 0.05 mm on two or three layers of cloth, the top

being silk or cotton. Some of these steps may be omitted, depending on

experience or the desired quality of the polish. After polshing most

coal briquets should be dried in a desiccator for a period of about 15

hr. More details or variations in specimen preparation procedures can

be found in References 54 and 55.

Reflectance Measurement. This measurement is important in petrographic

analysis and permits the determination of optical constants. Various

assemblages of equipment have been used for this purpose. A brief

description of one of these will serve to illustrate the general

principles of the measurement.

It has been found that, for accurate reflectance measurements, the

polised specimen surface must be precisely perpendicular to the optic

axis of the microscope. A commonly used hand-leveling press cannot be

relied on to attain this positioning. A reliable method involves

observation of focus preservation with an objective of at least a 60 ×

magnification as the specimen surface is traversed over about 1 in. in

two perpendicular directions. Mounting the specimen on a device capable

of controlled tilt in two directions permits adjustment of the surface

plane until the specimen remains in focus through all possible

displacements.

In this method, absolute reflectance is obtained by reference to a

standard of known refractive index and negligible absorption. The

reference to a standard of should be in the range of those of coal

components. Some investigators have used a series of glasses of

different reflectances in this range, although some surface changes by

oxidation have been encountered. Synthetic ruby and particularly

sapphire have proven satisfactory. The standard should be cut in a form

so that reflectance from the back face is not allowed to interfere with

the measurement. Measurements on several minerals of known refractive

index, in different media, provide an excellent means of checking the

accuracy of the method. If the indices calculated from the reflectance

measurements agree within an acceptable limit with the indices provided

by other means, the operation of the equipment is satisfactory.

Determination of Vol % of Macerals. Macerals commonly determined are

vitrinite, exinite, resinite, micrinite, semifusinite, and fusinite.

The equipment used is essentially that described for reflectance

measurement with the addition of devices for scanning the speciment and

for selection of areas to be identified and summed. The additional

devices are a Whipple ocular disc or a crosshair disc, a mechanical

stage, and a counter. The stage maybe operated manually or

electrically. In the latter case it maybe coupled to an electrically

actuated counter. The mechanical stage stage should be of such type

that the specimen can be advanced quickly by definite fixed increments

in two perpendicular directions. If an electrically operted stage is

used, increment steps in one direction across the specimen may be

actuated by the counter switches. The counter should be capable of

totalizing counts in at least six channels.

The specimens for automatic scanning microscopy are prepared in a way

very similar to those previously described for visual studies in

reflected light. However, because there is no element of human judgment

involved, the surfaces should be more carefully polished to attain the

least possible relief, pits, and scratches. This objective may require

modifications to the grinding and polishing steps, depending, for one

factor, on the relative importance of the results for the softer

organic components or the harder mineral, especially pyrite.

Determination of Optical Constants

Optical constants are of interest because they are the basis of the

optical descriptions of the petrographic components and because they

are related to structural atomic arrangements in coals.

One of the simplest methods of determining these optical constants

involves only the microscopic measurement of reflectance in two

different media. The measurements are made using objectives corrected

for air, oil or water immersion, preferably the first two.

The simple equation for transmission is the equation given above for

defining k. However, in practical measurements on thin sections of

coals and carbons, corrections must be made for reflections at

interfaces between the various media. The thin section usually is

supported on a transparent substrate and the radiation enters the

system on the substrate side. Reference light (Io) is usually measured

after transmission through the substrate. An equation governing

transmission through a system consisting of an absorbing medium on a

transparent substrate has been given by Born and Wolf.

Electron Microscopy

The principal procedure involved in the study of coal with an electron

microscope is the preparation of suitable specimens. At first, powdered

coal mounts were observed, but these supplied little useful

information. Replicas of polished or etched coal surfaces were later

tried with some interesting results, but these have been little used

recently. The most productive type of specimen for electron microscopy

is the ultrathin section, prepared as described previously. Preparation

of electron micrographs and electron diffraction patterns of coal

specimens involves no differences in procedure from those commonly

used.

Density

The true density of a somewhat porous material such as coal cannot be

determined in a simple way. Any satisfactory medium for displacement

should consist of molecules small enough to penetrate the pores but

should not react chemically with the coal. It has been found that

helium most satisfactorily meets these requirements. An approximation

for the density can be derived by measuring the displacement of water

by the coal, usually in granular form. However, it is questionable

whether the water molecules can penetrate into the minute pores of the

coal sufficiently to result in the determination of true density.

A blank run without a sample in a sample frame will give the scattering

due to air and background. Air scattering is appreciable only at low

angles. A few scans of the blank run are sufficient. The readings to be

subtracted must be normalized to the number of scans used in obtaining

the intensity with sample in place. An idea about the instrumental

broadening can be obtained by preparing a sample of 2.5mm diamond

powder and obtaining the scattered intensity for the diamond powder

under the same conditions. The widths of the diamond lines are largely

due to instrumental factors. If they are excessive, the observed

intensities with the coal sample can corrected by unfolding them with

those of diamond.

Consider an x-ray beam traversing a distance in the sample before

reaching a differential element of volume dV in the interior of the

sample and further consider the scattered beam traversing a distance y

in the sample before leaving it. The incident beam will undergo a

reduction in intensity by a factor exp (-mx). Where is the linear

absorption coefficient, and the scattered intensity will be reduced by

a factor exp (-my). The over all loss of intensity due to absorption

depends upon the scattering angle as well as the sample diffractometer

geometry, thus corrections must be made. Further, the scattered

intensity is polarized to a different degree at each scattering angle,

and correction must be made for polarization. Finally, the observed

intensities are in arbitrary units, they must be converted or

normalized into Thomson or atomic units.

This form of the Warren-Bodenstein equation also can be modified to

consider an assembly of stacks each containing different layers.

X-Ray Fluorescence Analysis. X-ray fluorescence analysis of elements of

relatively high atomic number is well developed. Presently the method

is practical for element down to, perhaps, fluorine, of atomic number

9. It has not yet been shown to be reliable for oxygen, nitrogen, and

carbon, although research in to these applications is progressing well.

Therefore, fluorescence analysis may now be used for virtually all the

mineral elements in coal, but cannot yet determine the composition of

the organic components.

The sample required for fluorescence analysis is about 2g. It must be

ground to an extremely fine particle size approximately 2 mm or less,

in order to minimize and to render less variable the absorption of the

fluorescence x rays by the mineral matter in the coal sample. This

extreme pulverization can be accomplished in a tungsten carbide pestle

by vibration for 5 min on a device similar to a Crescent Wig-L- Bug,

available from the Crescent Dental Manufacturing Co. Chicago. The

sample is then pressed into a frame with typical dimensions of 4cm.×

2.5 cm ×2.5 mm, under an applied pressure of about 150Kg/cm2.

For the analysis , a standard sample containing proportions of each of

the elements to be analyzed similar to those to be a expected in the

unknown samples is necessary. For coal analysis, this could be a

typical coal sample or a synthetic mixture of the various coal mineral

elements in carbon black.This sample is kept in one of the spectrometer

chambers. Reading on the standard sample are taken at regular intervals

so that those on unknown samples may normalized to minimize errors due

to variations in conditions.

Specification Tests

The American National Standards Institute, Inc. (ANSI) represents the

United States at the international standards level and corresponds in

part to the British Standards Institute (BSI) in the United Kingdom.

The ANSI is unlike the BSI in that it does not develop standards but

recognizes the work of some independent organization. For coal, the

American Society for Testing and Materials has been recognized as the

developing body. The committee for coal consists of approximately

seventy five experts equality divided in interest as producers,

consumers and general interest

The tests constituting coal analysis have been divided into three group

–Proximate, ultimate, and miscellaneous analysis. Some of the taste are

empirical and strict adherence to the specified conditions is required

in order to obtain meaningful results.

Proximate Analysis

Proximate analysis is the quantitative separation of the components of

a mixture. In the proximate analysis of coal, the amounts of moisture,

volatile matter, and are determined. The sum of the percentages of

these components is subtracted from 100 to calculate the amount of

fixed ca­r­bon present.

Moisture. The determination of the moisture content of coal is probably

the most important test. It is also one of the most difficult

components to determine accurately because of its several forms, its

fleeting nature during the collection and preparation of the gross

sample, and its strong affinity for the coal during the last stages of

drying.

Usually, three moisture values are required in the analysis of coal.

First, if the coal is too wet to crush and sieve without losing

moisture, it must be air-dried, which results in the value of air-dry

moisture. The air-dried coal is then crushed and prepared for the

laboratory where the residual moisture is determined. This laboratory

sample is used to prepare the analysis sample which is used for most of

the tests. The knowledge of the total moisture content of this sample

is necessary in order to express all items on a dry basis. The total

moisture is calculated from the air-dry and residual moisture values

and is used to convert the various dry analyses to the as-received

basis.

Residual Moisture. Two methods are given; the first is used for coals

known to be resistant to oxidation and the second is applicable to

coals subject to oxidation or to coals of unknown origin.

Procedures

oxidation-resistant coals. Transfer one of the air dried sample to a

shallow, weighed, noncorrodible metal pen to a depth of about 10 mm,

weight, and heat in a forced air circulation oven at 105-110oC to

constant weight. Calculate the % of residual moisture from the loss on

heating and weight of the air –dried sample.

other coals. Mix the air-dried sample well and place approximately 10 g

into a weighed capsule made of glass or noncorrodible metal with

close-fitting covers with a diameter of 60mm, cover, and weight to the

nearest mg. Place the cover in desiccator containing magnesium

perchlorate desiccant, and the capsule in an oven with a minimum free

space, capable of maintaining a temperature of 105-1100C and having

facilities for introducing nitrogen at a flow rate of three oven

changes per minute. Use a nitrogen containing less than 10 ppm of

oxygen. Heat the sample in the oven to constant weight; approximately 2

hr are required. Remove the capsule, cover and put on a metal plate for

10min.Transfer to desiccator until cooled to room te­m­perature, then

weigh. Calculate the % residual moisture from the loss in weight and

weight of the air-dried sample.

Total Moisture. The % total moisture is calculated from the percentage

of air-dry and residual moistures, as follows:

% total moisture = % air-dry + % residual Moisture of Analysis Sample.

This moisture value is used to calculate other analyses made to a dry

basis, using the analysis sample of 250mm size coal.

Volatile Matter. Volatile matter refers to loss of weight, corrected

for moisture, that results when coal is heated in specified equipment

and under standard conditions. It is one of the more important items in

purchase specifications of coal; it is valuable for the fuel engineer

in setting up and maintaining burning rates, and is used with other

parameters in almost all coal classification systems.

The test given below is empirical and easily performed. However, it can

lead to erroneous results if all the vital factors are not observed

strictly. If carried out properly, duplicate tests by the same operator

and equipment should agree within 0.3% for anthracite, 0.5% for

semianthracite and bituminous coals, 0.7% for subbituminous coals, and

1.0% for lignite. For the test, special high-form crucibles made of

platinum, 31 mm high, with a 25.4 mm diameter at the top and 16 mm

diameter at the bottom, are used. The crucibles are equipped with

platinum covers, 10 mm high, with a 25.5 mm diameter at the top and

25.3 mm diameter at the bottom. The total weight of the crucible and

capsule is between 14 and 15g. The heating of the sample is to be

performed in an electrically heated vertical tube or muffle furnace.

The tube furnace heating zone should be approximately 38 mm ID by 100

mm long. The crucible is suspended in the heating zone by a platinum or

nichrome wire cradle. The size of the muffle furnace should be large

enough to insert and remove the crucible conveniently. It is essential

that the heating zone of the furnace be maintained as close as possible

to 9500 C , but must not vary more than 200C.

Ash. Coal ash is the residue remaining after the combustion of coal

under specified conditions. Ash should not be confused with mineral

matter. The ash can be more than, equal to, or less then the take place

during combustion.

The quantity of ash in coal is of prime importance in purchase

specifications, utilization, and classification. Ash represents an

impurity, adds to the cost of transportation of the coal, and is costly

to dispose to after utilization. In certain methods of utilization, ash

contributes to air pollution as well as corrosion of the burning

equipment.

Fixed Carbon. The fixed carbon is calculated by subtracting the sum of

moisture, volatile matter, and ash from 100. It consists mainly of

carbon but, also contains small amounts of hydrogen, sulfur, nitrogen,

and oxygen.

Ultimate Analysis

The ultimate analysis of coal expresses the elemental composition in

terms of the determined percentages of carbon, hydrogen, nitrogen,

sulfur, and the calculated value for oxygen. The five items are

generally calculated on moisture and ash free basis. A slight more

accurate value for oxygen is obtained if the analysis computed on a

moisture and mineral-matter-free basis.

Carbon and Hydrogen. These two elements contribute virtually all the

energy derived from coal. The carbon and hydrogen contents of coal are

utilized in certain classification systems and also permit an estimate

of the calorific values of coals.

All methods employ the same basic principle of burning the sample in

oxygen in a closed system and collecting and determining quantitatively

the combustion products. The standard U.S. method carries out the

combustion at 800-850oC. A high temperature (1350oC) combustion method

has been used successfully in a number of European laboratories.

The oxygen to the combustion tube flows through the other area of the T

connection by passing the above described pressure-safety device, and

passes through a U-tube. The first arm contains soda-lime, the bottom

contains a glass-wool plug , and the second arm is filled with

magnesium perchlorate. A one-hole rubber stopper is used to seal the

open end of the combustion tube. Metal or glass tubing is used to

connect this U-tube with the tee and the combustion tube. The joints

are sealed with flexible tubing.

Repeat this procedure using an accurately weighed sample of standard

sucrose or benzoic acid. Several tests may have to be made before the

determined values for hydrogen and carbon are in satisfactory agreement

with the theoretical values. Repeat the procedure with an accurately

weighed sample of coal.

Duplicate determinations by the same operator using the same equipment

and the same analysis sample should not differ more than 0.07% for

hydrogen and 0.30% for carbon.

Nitrogen. Nitrogen occurs almost exclusively in the organic matter of

coal. The amount is rather constant and in most bituminous coals it

varies from 1.0 to 1.5 % in anthracite and low-rank coals.

The kjeldahl method is most commonly used, and consists of destructive

digestion of the coal with a mixture of concentrated sulfuric acid,

potassium sulfate, and mercury catalyst. The nitrogen is distilled from

alkaline solution as ammonia into a standard acid solution and

quantitatively determined titrimetrically.

Total Sulfur. Sulfur occurs in coal as the sulfide of iron and in

combination with the organic matter. In some weathered coals small

amounts of sulfate sulfur may also be found. Two chemical methods are

used for the determination of total sulfur. In the method given , the

coal is oxidized in an Eschka mixture. The resulting oxides of sulfur

are retained by an alkaline mixture, extracted with water, precipitated

high-temperature combustion in a closed system with oxygen, the sulfur

oxides are absorbed in aqueous hydrogen peroxide, and the sulfuric acid

formed is treated with a standard alkali. It is particularly applicable

where results are required in a very short time.

Oxygen. The oxygen content of coal can be used to estimate the degree

of oxidation of a weathered bituminous coal, and it is an indicator of

the lowest rank in the bituminous group that can be used for making a

satisfactory metallurgical coke.

Oxygen can be determated directly by a semimicro combustion method. For

most purposes it is estimated by subtracting from 100 the sum of the

percentage hydrogen, carbon, nitrogen, sulfur, moisture and ash. A more

accurate estimate can be made by converting the analysis to a

mineral-matter-free basis.

Colorific Value

The test consists of burning a weighed amount of the material in a

closed vessel under a pressure of oxygen. Heat is released and absorbed

in a fixed mass of water. The increase in temperature of the water is

directly related to the calorific value of the material. The manner of

absorbing this indicates the two principal types of calorimeters

commonly used in the isothermal calorimeter, the temperature of the

water bath surrounding the calorimeter is maintained at a contained at

a constant temperature. Since the temperature of the water surrounding

the combustion vessel or bomb varies, there is heat exchange between

the two systems, and the amount of heat gained or lost must be

determined between the two systems, and the amount of heat gained or

lost must be determined. Adiabatic calorimeters have the facilities to

adjust or raise the temperature of the outer water bath to the same

temperature of the water surrounding the combustion vessel.

Remove the bomb and release the pressure at a uniform rate in about

1min. Inspect the interior of the bomb for unburned carbon, and if it

is present discard the results and repeat the test. Wash the interior

of the bomb with water containing methyl orange indicator until all

acid is removed , collect the washings and titrate with a sodium

carbonate solution containing 20.90g/liter, 1 ml of this solution

corresponds to 10.0 Btu. If a combustible firing wire is used,

determine the weight of the unburned wire.

Fusibility of Coal Ash

This test gives an approximation of the temperatures at which the ash

remaining after the combustion of coal will sinter, melt and flow. The

correlation of the laboratory and utilization results is only

approximate, because of the homogeneity of the laboratory test piece

and the heterogeneity of the residue or ash from utilization. The

fusibility datas are of value in the procurement of coals that most

likely will perform satisfactorily.

The procedure given below consists of heating a molded trilateral

pyramid of the ash in a mildly reducing or oxidizing atmosphere and

observing the changes in shape and the temperatures at which the

changes occur. Four such temperatures are defined below.

Behavior on Healing

Some of the phenomena exhibited by coal on heating have been assigned

names that refer to essentially the same behavior; they differ only in

the rate of heating. These slight differences of operation become of

great importance when they are used in the classification of coals. The

various terms may be defined as follows:

Caking refers to the behavior of the coal when it is heated rapidly in

measuring the free-swelling index and Roga index or as the combustion

of coal. The agglomerating index refers to the behavior of coal when

heated rapidly in the volatile matter test.

Coking refers to the behavior of the coal when it is heated slowly in

the Audibert-Arnu dilatometer and Gray-King coke-type tests or as in

carbonization.

Plasticity, dilation , contraction, and agglutinating value are other

terms also used to describe the behavior of coal on heating.

Below, some of the tests used to investigate the behavior of coal

during heating are discussed more detail.

Free-Swelling Index or Crucible Swelling Number. The free-swelling

index is quite important in differentiating between groups in the

classification of coals; it also gives considerable information on the

combustion characteristics of coal. The test consists of heating the

coal under prescribed conditions and comparing the residue or button

with standard profiles as shown in Figure 5. Since the test is

empirical, the special apparatus is specified exactly.

Roga Index. The Roga index is an alternate procedure for measuring the

caking properties of coals. It requires a special drum tumbler and an

anthracite with specified properties to mix with the coal before

carbonizing. Because of the limited use of the Roga index and the

difficulty of getting the specific anthracite or suitable substitute,

the details of the test will not be given.

Agglomerating Index.The agglomerating index is required in the ASTM

classification of coals in order to differentiate between the

anthracitic and bituminous classes and between the bituminous and

subbituminous classes of coals.

The test is made by examining the residue from the platinum crucible in

the standard volatile matter determination. If the agglomerate button

shows a cell structure or swelling or supports a 500-g weight without

pulverizing, it is considered as agglomerating.

Gray-King Coke-Type Test. This test and the Audibert-Arnu dilatometer

are used alternatively for assessing the coking phenomena of coal in

the International Classification of Hard Coal by Type. The equipment

for the Gray-King coke test is more easily acquired and the technique

of operation less exacting than for the Audibert-Arnu dilatometer.

Consequently, only the procedure for the Gray-King test is given.

The test consists of heating pulverized coal out of contact with air in

a horizontal tube retort at a uniform and slow rate.

Plasticity of Coal Measured by the Gieseler Plastometer. The test is a

semiquantitative measurement of the plastic property or apparent

melting of coal on heating in the absence of air. The plasticity

phenomena have been quite closely related to carbonization and many

researchers have attempted to relate the Gleseler plasticity values

with the quality of coke produced from a particular coal or more often

a blend of coals. The detailed specifications of the testing equipment

and procedure of operation make this a very empiric test. The slightest

variation in equipmental detail or deviation in operation can results

in erroneous results.

At present, two types of equipment are in use, one utilizing a constant

torque of 40g-in. by suspended weight on the stirrer imbedded in coal,

and another which produces an equal torque by a magnetic clutch between

a constant speed motor and the stirrer. For more detailed information

on the procedures, the instruction manuals supplied with the equipment

should be consulted.

Equilibrium Moisture of Coal at 96-97% Relative Humidity and 300C

This test is used to restore wet coal and partially dried coal to the

moisture content it contained in the bed. The test results are used to

measure the degree of during and excess moisture, and in the

classification of coals by rank. It is applicable to all coals from

metaanthracite to lignite. The measurement is carried out in a moisture

oven maintained at 1050C and with provision in dry air or dry nitrogen

at a rate of two oven changes per minute. Air is used only with coals

known to be slowly oxidized.

Determination of Hardgrove Grindability Index of Coal

The Hardgrove grindability index (HI) of coal is a relative measure of

the ease of pulverizing. The test consists of grinding a specially

prepared sample in a laboratory mill of standardized design. The

Hardgrove grindability machine is available from Babcock &

Wilcox Co. Alliance, Ohio. An index is derived from a sieve analysis of

the ground product. For comparison, a standard coal sample with an

index of 100 is used.

Special Constituents

In addition to the determination of the carbon, hydrogen, nitrogen,

sulfur, and oxygen content of the coal, sometimes investigations are

carried out to determine the amount of sulfur present in various forms,

and the chlorine and mineral carbonate content of coal.

Froms of Sulfur. Sulfur occurs in coal as sulfate, pyrite, and in

combination with the organic material. Sulfate sulfur is usually less

than 0.1% except for weathered coal containing appreciable FeS2. The

pyritic sulfur content varies considerably more than the organic

sulfur, and is of more interest because it is the only form that can be

removed from coal by current preparation practices.

Chlorine. A considerable amount of the chlorine in coal is present as

sodium chloride and therefore the amount of chlorine present has been

used as an estimate of the sodium content. Sodium is suspected of

contributing to operational difficulties caused by deposits on the

heating surfaces Coals containing less than 0.15% chlorine are

considered as potentially trouble free. The chlorine content is used in

some system for the estimation of the amount of mineral matter from the

determined ash content.

In the method given, a muffle furnace, heated to 675± 250C and

ventilated at three to four air changes per minute, is used. The coal

sample is oxidized with an Eschka mixture, and the chlorine content

retained as chloride. The resulting mixture is dissolved in diluted

nitrate acid, the chloride is precipitated with silver nitrate, and the

excess of silver is titrated with potassium thiocyanate.

Mineral Carbonates. Infrequently, a coal contains mineral carbonates in

sufficient quantity to affect its carbon content, mineral matter, and

classification. The carbon dioxide of the mineral carbonates is

determined by heating the coal with dilute hydrochloric acid, absorbing

the evolved carbon dioxide in a suitable absorbent, and determining the

weight increase. Duplicate determinations by the same operator using

the same equipment and sample should not differ more than 0.05%

The second hole of the stopper in the Erlenmeyer flask is fitted with

the small end of a coil-type condenser, 300mm long. The open top end of

the condenser is connected with an approximately 300 mm long, 7 mm OD

glass tube. The top of a Stetser- Norton bulb is filled with 15 mm

glass-wool in the bottom and anhydrous calcium chloride on top. The

bottom connection of this bulb is connected with a short section of

rubber tubing to the bottom connection of a second Stetser-Norton bulb

filled two thirds full with granular pumice impregnated with anhydrous

copper sulfate; the remainder of this bulb is filled with anhydrous

calcium chloride.

Coal Classification

The wide variation in chemical and physical characteristics shown by

the several testing methods, methods, provides an opportunity to devise

numerous systems for the classification of coals. Some of the systems

have received only limited acceptance possibly because of little

practical applicability.

Three of the more widely known and used systems are briefly described

below. The British National Coal Board Coal Classification System is

based on the dry, mineral-matter-free, volatile matter and the

Gray-King coke-type test.

Cotton

Cotton is one of the plants utilized by mankind at the dawn of

civilization archeological evidence indicates that cotton was used in

the Indus Valley, in about 3000 BC, for making cloth. Cotton was

brought from India to Egypt by Alexander the Great in the fourth

century bc, and from there it spread to other countries around the;

Mediterranean Sea. Cotton was introduced from India to China during the

seventh century ad, first as a garden plant, and about 1000 ad for use

as a fiber. In America, remains of cotton bolls dating back to about

5000 bc have been found in Mexico, and discoveries indicate that it was

used for textile purposes about 2500 bc.

All wild and cultivated species of cotton plants belong to the

botanical genus gossypium. Most of the cultivated cotton belongs to

four species: Gossypium herbaceum and G. arboreum, which probably

originated in southern Arabia or northeastern Africa and were

introduced into India, G. hirsutum, which originated in southern Mexico

and Guatemala, and G. barbadense, which was found in the northern part

of South America but is also cultivated in Egypt and Sudan.

Chemical Properties. Cotton fiber, like most vegetable fibers, is

essentially cellulosic; however, the percentage of cellulose which it

contains is higher than in most other materials and may be as high as

96% of the dry weight of the unpurified fiber.

Methods of Analysis

Methods related to the identification and analysis of the nature of

cottons modified with organic reagents and organic finishings, as well

as the determination of trace inorganic elements present either as

contaminants or as additives, are discussed below.

Modified Cottons

As mentioned, superficial or partial reactions of the hydroxyl groups

of cotton cellulose produce valuable permanent finishes on cotton

products. These reactions include esterification and etherification,

further reaction with double or multiple bonds, and replacement

reactions resulting in specifically modified cottons.

Infrared Spectroscopy. The identification of the organic groups

introduced into the cellulose molecule, as well as the determination of

the degree of substitution, can be carried out by the use of infrared

spectroscopy.

The fact that infrared absorption spectra can be obtained without

modifying the crystallinity of even highly crystalline native cotton

because grinding of the sample is not required is a major advantage of

this procedure. O’Connor et al. showed that satisfactory spectra could

be obtained with very large pieces of native cotton cellulose, and

cutting 20 mesh was recommended in order to provide a reproducible

technique.

Two special methods are also of interest in the infrared investigation

of modified cotton products. The first developed by McCall, Miles, and

O’Conor utilizes the frustrated multiple internal reflectance (FMIR)

technique; the technique of Knight and co-workers permits the

measurement of cotton fibers without any cutting, grinding, sifting or

mixing with extraneous material.

The technique of direct pressing into parallel fibers was demonstrated

to give satisfactory spectra, and had the advantage that the cotton

fiber was subjected to no treatment other than mechanical pressing and

the highly oriented manner in which the fibers are aligned should be

helpful in polarization studies. This technique is the only

satisfactory manner in which the study of crystallinity by means of

deuterium and infrared measurements can be extended to include

crystallinities of short, staple cellulosic fibers of native or

modified cottons.

Finishing Agents

There are a great variety of subatances which are being used in the

chemical finishing of cotton fabric. Included in this list are

chemicals used to produce water repellency, fire resistance, resistance

to mildew, or protection from actinic radiation, lubricants,

plasticizers, softeners, antibacterial agents, deodorants, fungicides,

germicides, rot resistant agents, and resins used to obtain

durable-press or wash-and-wear characteristics. It is almost impossible

to establish a single coordinated procedure for the analysis of cotton

for any chemical finishing agent; however, two systematic methods

approach this goal.

Separation and Identification

The first systematic approach to separate and identify the chemical

agents used in cotton fabrics was developed by Skinkle in 1946. The

sample is successively extracted with five solvents, each selected to

remove by solubilizing certain classes of substances. Subsequent

evaporation of the solvent reveals the presence of the entire group.

Individual components of each group are subsequently identified either

by further separations, by application of additional solvents, or by

applying chemical tests which are valid in the presence of some or all

of the other substances within the specific group.

Spectroscopic Methods

Ultraviolet, visible, and infrared spectroscopy permit the

identification and quantitative analysis of a number of chemical

finishing agents used for cotton and cotton fabrics.

Ultraviolet and Visible Spectroscopy. The end points in the analysis of

several of the chemical finishes, after extraction and separation, as

by the scheme described above or by one of the many modifications of

this scheme, have been achieved through the production of a

characteristic color produced by reaction of the finishes in a single

group with a reagent which would produce a specific color with only one

constituent of the group. Often interfering colors, by reaction of the

selected reagent with other materials in the group or through a

reaction with the solvent, would necessitate further preseparations

before the color test could be applied.

Total Formaldehyde. An accurate quantitative method for the

determination of the total formaldehyde content of cotton fabrics

treated with a formaldehyde-containing resin is often of considerable

aid in the elucidation of the resin reactions involved. However, the

usual procedure involving distillation with dilute acid and estimation

of the formaldehyde in the distillate is not entirely satisfactory, as

it is difficult to distill formaldehyde completely from solution.

Melamine-Formaldehyde Resin. Hirt, described a method for the

determination of melamine resins used to impart wet strength to paper.

The method, which is applicable to extracted melamine resin from cotton

cellulose fabric, is based on the strong ultraviolet absorption of

melamine near 235 nm.

Cationic Surfactants. The method of Scott depends upon the chloroform

extraction of dye salt formed quaternary ammonium surfactant and excess

Orange II (p-(2-hydroxy-l-napthylazo) benzenesulfonate) in aqueous

solution. Advantage is taken of this last fact to establish a

standardization factor, related to molar absorptivity, obtained from

purified surfactants for the analysis of commercial surfactants.

Infrared Spectroscopy. Although the infrared absorption technique was

completely successful for the identification and quantitative

determination of the extent of chemical modification by reactions with

the active hydroxyl groups of cotton cellulose, its application for the

analysis of the chemical finishes encountered several difficulties.

These difficulties led to the development of complex methods. In one

such method, differential infrared spectroscopy accompanied by linear

scale expansion is utilized. The frustrated multiple internal

reflectance (FMIR) technique of McCall et al. already discussed for

chemically modified cotton fabrics also be applied for the

investigation of the cotton fabrics with chemical finishes.

Differential IR Spectroscopy. McCall, Miles, Tripp, and O’Connor

investigated cottons with chemical finish by comparing their spectra

with those obtained from untreated cotton. This method is only

practical if some estimate of the actual amount of the modifying

reagent (the so-called add-on) can be made.

The analytic scheme starts with the conventional potassium bromide disc

procedure. If this technique permits satisfactory detection,

identification, and quantitative determination of the resin finish, the

analysis is completed with minimum effort. If, however, sensitivity

problems are encountered, the same prepared sample is remeasured using

the differential and/or linear scale expansion techniques. If the resin

finish still cannot be identified or quantitatively determined, resort

is made to the acid hydrolysis procedure.

Inorganic Constituents

Because it is an agricultural product, cotton may contain a number of

metallic or nonmetallic elements or anions. These substances may also

contaminate the original native product during processing. Besides

this, a number of elements may be added in small amounts as inorganic

salts or oxides or as organometallic compounds to the cotton during

processing to produce a specific property not native to cotton.

Chemical Methods

The various elements (either metallic or nonmetallic) in cotton samples

may be identified by the chemical spot test methods developed

originally by Feigl.

These spot tests have one major disadvantage; a separate test is

required for the identification of each element. A second disadvantage

is that spot tests do not yield any real quantitative data regarding

the concentration of the specific element in the sample. For chemical

methods for the quantitative determination of the major inorganic

constituents, see Cellulose.

Spot tests have one advantage over spectroscopic techniques: they

permit distinguishing between various anion groups. Thus, tests can be

made to differentiate among sulfite, sulfate, or sulfide, between

nitrate and nitrite, chloride or chlorate, etc. The atomic

spectroscopic methods in current use permit only the identification

(and determination) of total elemental content. Thus, sulfur is

identified and measured as differentiation of the oxidation state of a

specific element as by induced electron emission are not impossible,

they have not been developed to the point where they can be said to be

tools for the use of the analytical chemist engaged in the analysis of

cotton and cellulose.

Spectroscopic Methods

Although there are about a dozen spectroscopic techniques which are of

potential application to the determination of elements, both metals and

nonmetals, only three, electronic emission, x-ray fluorescence, and

atomic absorption spectroscopy, have been used in the analysis of

cotton cellulose. It is of some importance, therefore, to consider the

respective merits and disadvantages of each of these three techniques.

The advantage of emission spectroscopy in cotton analysis is primarily

its ability to permit, with a single scan, a complete qualitative

analysis of a consi­­derable portion of the entire spectrum. If the

photographic technique is being employed, such a spectrogram permits

the operator to investigate in detail the presence or absence of almost

all specific metals. In many large spectroscopic laboratories, the use

of emission spectroscopy is confined to such qualitative surveys, and

x-ray fluorescence or atomic absorption is used (often subsequent to

the qualitative survey) when quantitative values are required.

A limitation of x-ray fluorescence analysis is that light elements may

escape detection or accurate measurement. However, techniques and

selection of accessories such as x-ray tube, analyzing crystal, and

detector have pushed these analyses down to magnesium and, with special

vacuum spectrophotometers and specially designed analyzing crystals,

such as lead stearate, analyses are being made down to boron, leaving

very few elements which cannot be detected and determined by this

technique. These latter determinations, between magnesium and boron,

can be made, however, only by a significant increase in instrumental

sophistication and expense.

Another disadvantage of x-ray fluorescence is the sophistication and

the cost of the initial equipment, which is higher than the cost of the

equipment used in the other techniques.

Emission Spectroscopy. Emission spectroscopy consists of three more or

less independent steps. First, the proper preparation of the sample;

second, the technique for obtaining the raw data, the emitted atomic

lines of the desired constituents; and third, the evaluation of these

data to properly identify and quantitatively determine the element or

elements of interest.

In the original paper of O’Connor and Heinzelman, describing the

general method for the spectrochemical analysis of plant products, two

procedures were recommended, one for samples with an ash content of

less than 1% (where there could be no matrix effect from the

composition of the ash), and another for samples with ash content of

sample over 1% (where the composition of the ash might effect the

condition for constant matrix). In later works the second procedure was

used, mainly because the cotton samples being analyzed were fabrics

chemically modified by the introduction of metal-containing substances

to produce specifically desired effects. The two procedures are given

below.

Procedures

ash-content of sample less than 1%. Accurately weigh 16.67 of the

sample into a Vycor dish with 90-mm diameter, and add 2 ml of a

solution of 250 g of magnesium nitrate hexahydrate in 1 liter of 95%

ethanol. The ratio of sample weight to the magnesium nitrate buffer is

arbitrary and can be varied for different samples depending upon the

sensitivity required, if the ratio actually used is considered in

obtaining and using the working curves. The ratio suggested here will

permit analysis with a sensitivity of about 1 part of metal in

10,000,000 parts of sample for the more sensitive metals, copper and

iron, for most types of samples.

ash content of sample over 1%. Ash exactly 5 g of sample in a tared

Vycor dish as described in the earlier procedure, but without addition

of the magnesium nitrate solution. After removal from the furnace, cool

the dish and reweigh to determine the ash content of the sample. Add a

volume of a very dilute aqueous solution of germanium dioxide so as to

introduce a quantity of the dioxide equal to 4.14% of the ash. Grind

and thoroughly mix the ash prior to analysis.

Prepare a mixture of salts representing the major constituents of a

typical ash. A suggested composition is as follows: 65.18% potassium

carbonate, 0.95% sodium chloride, 11.02% calcium carbonate, 18.70%

magnesium carbonate, and 4.14% germanium oxide. Prepare working curves

by adding graduated amounts of elements to portions of this salt

mixture.

X-ray Fluorescence Analysis. When x rays strike any material, as any

analytical sample, one usually considers their penetration, as it is

their dominant characteristic. However, if the beam of x rays is

measured before and after striking the sample, a decrease in intensity

will be found. Some of the x rays have been absorbed by the material,

the amount, of course, depending upon the nature, particularly the

density of the material, and the thickness of the sample. These

absorbed x rays can be used as a successful method of spectroscopic

analysis in a manner essentially analogous to the use of the absorption

of photons, except that absorption of x rays is an atomic process, and

absorption by a given element is independent of the chemical

combination in which the particular element occurs. Thus, x-ray

absorption is a technique for elemental analysis.

An x-ray spectrometer consists of an x-ray tube capable of emitting an

intense x-ray beam that impinges upon the sample to be analyzed.

Fluorescent rays, which appear as secondary emission, are dispersed by

utilizing crystal with a known lattice constant, frequently a bent mica

crystal, to act as a diffraction grating. The diffracted fluorescent x

rays are detected by a Geiger counter goniometer, and their intensities

may be automatically recorded as a function of the foniometer angle

which is proportional to the wavelength or frequency of the x rays.

Sections of such a tabulation are reproduced in Table 11 for the five

elements, calcium, chromium, potassium, manganese, and zirconium. All

the lines in Table 11involve the innermost orbit, as indicated by the

letter K in column 3, although in more complete tables the L and

occasionally M and N lines may occur. ABS indicates the absorption line

or edge.

For the purpose of determination by x-ray fluorescence methods, the

elements introduced into cotton through chemical and additive

modification (which are the major purposes for such analyses) fall into

two broad categories; those of atomic number 22 and higher, and the

lighter elements. The heavier elements are used to impart protection

against degradation by outdoor exposure or microorganisms (copper,

mercury, lead, cadmium, selenium, zirconium), and to impart flame

resistance (tinbromine); they are also used in certain classes of dyes

and pigments (chromium, iron, titanium) and for miscellaneous purposes,

such as catalysts.

Count rates of equivalent discs usually show a maximum difference of

2%. The relationship of percentage composition to counting rate is

found to be linear over a range of 0.01 to about 3% for most of the

elements examined. In all cases, a loss in counting rate was noted at

concentrations above 3% indicating self- absorption. This loss of

counts becomes marked at concentrations of about 10% and dilution with

pure cellulose should be employed.

Lignin and Hemicellulose

The compositions and percentages of lignin and hemicellulose very from

one plant species to another so it is difficult to arrive at

generalizations concerning structure and abundance of these polymers.

Moreover, composition varies within a single plant (roots, stems,

leaves), with age (heartwood versus sapwood), stage of growth (early

wood versus late wood in annual rings) and with the conditions under

which the plant grows. Study over many decades has elucidated the major

structural features of wood hemicelluloses and lignin’s along with the

biochemical mechanisms for their degradation. Most recently attention

has turned to the molecular characteristics of these enzymes. It is

beyond the scope of the present review to recapitulate these findings

in detail. Rather, the focus will be on specialized or recently

revealed aspects.

II. Hemicellulose

Softwoods (gymnosperms), hardwoods (angiosperms), and grasses

(graminaceous plants) have evolved separately, and they contain

different lignin and hemi cellulose constituents. Moreover their

specialized tissues have varying proportions of cellulose,

hemicellulose, lignin, pectins, proteins, and extractives. Lignin is

deposited during maturation of cell walls, and some carbohydrates

become cross linked to it. Because the lignin and hemicellulose

constituents differ, the crosslinks between these polymers differ form

plant to plant and from tissue to tissue.

A. Assay systems

Hemicellulases are most commonly assayed by measuring the rate of

reducing group formation under optimum conditions. A suitable

polysaccharide substrate is suspended in buffer and mixed with an

enzyme solution that is appropriately diluted to yield a linear

response over time Alternately, several successive two-fold dilutions

are assayed for a single fixed time (10 to 30 min), and the enzyme

titer is calculated from the average of several successive dilutions

that exhibit a consistent enzyme activity. This approach is necessary

because at very low dilutions (or long assay times) the substrate is

exhausted, and the calculated activity is not representative of the

actual value.

B. Classification

Hemicellulases are classified according to the substrates they act

upon, by the bonds they cleave and by their patterns of product

formation, Table 1, but greater variety exists among the endo-xylanases

and ß- glucosidases than is reflected in this simple classification

system. One notable distinction is made between endo-1,4-b-xylanase (EC

3.2.1.8) and xylan 1,4-b-xylosidase (EC 3.2.1.37). While the former

produces oligosaccharides from random cleavage of xylan , the latter

acts principally on xylan oligosaccharides producing xylose. Some

endo-xylanases appear to have greater specificity for straight chain

substrates, and others appear to be able to accommodate more frequent

side chains of branching.

Deacetylation makes native xylans much less soluble in water, which is

an observation that causes some consternation to trained organic

chemists. Even though acetylation makes the xylan polymer more

hydrophobic, it also blocks extensive intrachain hydrogen bonding. When

the acetyl groups are removed, hydrogen bonding leads to xylan

precipitation. Even though the substrate is less soluble, deactylation

generally increases susceptibility of the substrate to enzyme attack.

Some acetylesterses, however, show specificity for the native

acetylated substrate.

C. Thermophilic hemicellulases

Thermostable enzymes are often of interest for biotechnological

applications, and hemicellulases are no exception. Thermophilic

xylanases have been recognized for several years. Ristoph described an

extra cellular xylanase produced by the thermophilic actinomycete

Thermonospora that was stable for approximately 1 month at 55 °C and

could withstand up to 80°C in a 10 min assay. Gruninger described a

highly thermos table xylanase form a thermophilic bacillus that has a

catalytic optimum of 78° and a half life of 15 h at 75°. Both enzymes

were predominantly endo in activity and produced only trace quantities

of xylose after long periods of incubation. The thermophilic fungus

Thermoascus aurantiacus produces an extra cellular endo-xylanase that

has a temperature optimum of 80°C. At that temperature, the half life

is 54 min. These characteristics are fairly similar to thermos table

xylanases from Talaromyces emersonii, another thermophilic fungus that

grows on straws and pulps.

D. Alkaline active xylanases

An alkaline active enzyme was also purified and characterized from an

alkalophilic actinomycete. Tsujibo et al. purified three endo-xylanases

from the culture filtrate of Nocardopsis dassonvillei subsp. alba OPC-

18. The molecular weights were 23,000, 23,000 and 37,000 for

X-1,X-11,and X-111, respectively.

E. ß- Xylosidase

Endo-xylanases are much more common than ß-xylosidases, but the latter

are necessary in order to produce xylose. Most ß-xylosidases are cell

bound, and the enzymes are large relative to endo-xylanases. The

ß-xylosidase of Bacillus sterothermophilus has a molecular weight of

about 150,000 and is stable at up to 70°C Utt described a novel

bifunctional ß- xylosidase from the ruminal bacterium Butyrivibrio

fibrisolvens was cloned in E. coli and shown to consist of a 60,000Mr

protein with dual glycosidase activity.

F. Mannanases and galactanses

Mannanases and galactanses are described far less frequently than

xylanases. It is not known whether this is attributable to their lower

prevalence in nature or simply because they are sought less often.

Bacterial species known to produce mannanases include Aeromonas

hydrophila, Cellulomonas sp. and Strepromyces olivochromogenus.

Multiple endo – ß-mannanases are found in the extra cellular broth of

Polyporous versicolor.

G. Accessory enzymes for hemicellulose utilization

A number of enzymes appear to be critical in the early steps of

hemicellulose utilization. These include acetyl xylan esterases,

ferulic and p-coumaric esterases,a-l a rabinofuranosidases, and

a-4-O-methyl glucuranosidases.

Acetyl xylan esterase was first described by Biely in several species

of fungi known to degrade lignocellulose and most especially in A.

pullulans. Acetyl xylan esterase was subsequently described in a number

of different micres different microbes including (Schizophylum commune,

Aspergillus niger and Trichoderma reesei, Rhodotorula mucilaginosa and

Fibrobacter succinogenes. Acetyl xylan esterase acts in a cooperative

manner with endoxylanase to degrade xylans. This enzyme is not involved

in breaking LCbonds because the acetyl esters are terminal groups.

The ferulic acid esterase of S. commune exhibits specificity for its

substrate, and it has been separated form other enzymes. Borneman et

al. assayed feruloyl and p- coumaryl esterase activities form culture

filtrates of anaerobic fungi using dried cell walls of Bermuda grass as

a substrate. The enzyme preparations released ferulic acid more readily

than they released p-courmaric acid from plant cell walls. Assays using

methyl ferulate or methyl p-coumarate as substrates in place of dried

cell walls showed the presence of about five times as much enzyme

activity. McDermid employed ethyl esters of p-coumarate and ferulate as

substrates for these activities.

111. Lignin

Lignin is an aromatic polymer with the substituents connected by both

ether and carbon-carbon linkages. It is composed of three principal

building blocks: p-coumaryl alcohol (p-hydroxyphenyl propanol),

coniferyl alcohol (guaiacyl propanol), and sinapyl alcohol (syringyl

propanol)

A. Lignin-degradingenzymes

Recent years have witnessed an increasing interest in the enzymatic

mineralization and depolymerization of lignin. No dougbt this stemmed

in part form the description of a family of peroxidase-like enzymes

from active lignin-degrading cultures of Phanerochaete chrysosporium.

These enymes, termed lignin peroxidases (LiP) are capable of degrading

a number of lignin model compounds- including the b- aryl ether

model-and are closely associated with the mineraliation of 14C-

labelled lignin to CO2. Of particular note is the ability of enzyme

preparations from p.chrysosporium to depolymerize methylated spruce

lignin.

B. Lignin degradation in whole cell cultures

There are essentially two approaches to understanding the roles of

these various enzymes in lignin degradation. One approach is to

reconstitute a lignin- degrading system in vitro using crude, purified,

or cloned enzyme constitutents. The other is to regulate the cellular

metabolism of lignin- degrading fungi in vivo so as to produce either

LiP or MnP, and then to observe the cultures for depolymerization and

mineralization.

Studies by Perez showed that both the appearance of lignin- degrading

enzymes and mineralization of lignin are affected by the presence of

manganese. The effects, however, vary with the organisms and test

systems employed. In p.chrysosporium, elevated Mn concentrations

represses LiP while inducing MnP, and in phlebia brevispora,Mn

represses LiP while inducing both MnP and laccase. In both cases, high

rates of mineralization correlate with the appearance of LiP at low Mn

concentrations and not with the appearance of MnP or laccase D.

squalens produces only MnP and laccase, and in this organism,

mineralization correlates with the appearance of MnP.

C. Degradation by cell-free enzyme systems

Complete catalytic depolymerization of lignin has not been demonstrated

in vitro with a cell-free enzyme system. Extracellular proteins form

p.chrysosporium, Coriolis versicolor, and phlebia radiata were reported

to increase the number of hydroxyl groups, decrease the mean molecular

weight, or otherwise chemically alter various lignin preparations. Kern

investigated the action of crude and partially purified LiP form p.

chrysosporium on the molecular size distribution of 14C – labelled

lignins, and he further used pyrolysis GC mass spectrometry to

investigate changes in substrate characteristics.

The mechanism of lignin depolymerization may not be the same in all

organisms. Galliano studied lignin degradation (solubilization) by

Rigidoporous lignosu, an organism that does not produce LiP, but rather

synthesizes MnP and laccase. When the tow enzymes were puriried and

their properties studied in vitro,neither enzyme was able to solubilize

radioactive lignins. When both enzymes were added to the reaction,

mixture at the same time, lignin solubilization was extensive; the MnP

and the laccase acted synergistically. In addition, glucose oxidase

enhanced lignin solubilization by preventing repolymerization of the

radicals formed by the two oxidative enzymes.

D. Role of glycosides in lignin degradation

One of the first enzymes implicated in lignin biodegradation was

cellobiose: quinone oxidoreductase(CBQase). This enzyme catalyzes the

reduction of a quinone and the simultaneous oxidation of cellobiose

discovered this enzyme and proposed that its tole might be to prevent

repolymerization of lignin during degradation. Recent studies have not

borne this out, but the enzyme may be important monetheless. The CBQase

of P.chrysosporium binds very tightly to microcrystalline cellulose,

but such binding does not block its ability to oxidize cellobiose,

indicating that the binding and catalytic sites are in two different

domains.

An essential feature of lignin biodegradation is that degradation

products resulting form the activity of extracellular enzymes must be

taken up by the mycelium; glycosylation by b-glucosidase seems to be an

important part of this process. Whether or not sugars attached to

lignin in the native substrate by nonglycosidic linkages play a similar

role has not been addressed.

1V. Lignin-carbohydrate complexes

Lignin-carbohydrate complexes (LCCs) are heterogeneous, poorly defined

structures that are found in many plant species. Lignin is directly or

indirectly bound covalently to carbohydratate, and the resulting

complexes present a barrier to biological degradation. LLCs have proven

to be highly intractable materials that are in large part responsible

for limiting the biodegradation rate of plant materials.

A. Fractionation of lignin and carbohydrate in wood

The existence and character of LC bonds have long been studied and

debated. In 1956, Bjorkman published techniques for liberating MWL form

finely ground wood. He also obtained an LCC by exhaustive milling and

extraction. Aqueous dioxane was used to extract MWL, and

dimethylformamide, dimethylsulfoxide, and aqueous acetic acid were used

to extract LCC. The lignin contents of LCCs are similar to that of the

MWLs except that the latter contain less carbohydrate. Despite many

attempts Bjorkman could not separate carbohydratae from LCC without

resorting to chemical degradation.

B. Isolation of LCCs

The LCCs are highly heterogenous and difficult to study. Many

conventional chemical treatment, such as alkali, readily disrupt some

of the most prevalent LC bonds. The best approaches employ neutral

solvents and purified enzyme preparations. Most research has focused on

the isolation of water- soluble lLCCs, because they can be

fractionated, sized, and subjected to spectroscopic study. Larger,

insoluble LCCs exist and may even account for the bulk of LC bonds in

the substrate, but less is lnown about them. Most evidence suggests

that the chemical linkages are similar to those of the soluble LCCs.

C. Chemical characteristics of LC bonds

Existence of chemical bonds between lignin and carbohydrate has been

questioned because of the intimate physical intergration between the

lignin and carbohydrate constituents, the possibility of entrapment or

adsorption, and lability of many linkages. Several different types of

LC bonds have been proposed based on knowledge about changes in sugar

composition following digestion and about hemicellulose structures. The

proposed LCbonds include bonds to xylan, glucomannan, cellulose,

various other hemicellulosic sugars, and pectin.

D. Ferulic and p-coimaric ester side chains

Grass and bamboo lignins differ from those of hardwoods and softwoods

in that they are formed not only from guiacyl and syringyl units, but

also from p-hydroxyphenyl units. Esterified p-coumaric acid can

comprise 5% to 10% of the total weight of isolated lignin. The

participation of p-hydroxphenyl glycerol-b-aryl ether structures is of

minor importance.Based on methanolysis and spectral studies, Shimada

proposed that the majority of p-coumaric acid molecules in bamboo and

grass lignin are ester-linked to the terminal g carbon of the side

chain of the lignin molecule Fig.11. Ferulic acid is also present in

small amounts. The p-coumaric ester linkages are extremely stable as

they are not removed by methanolysis, thioglycolic acid treatment, or

catalytic hydrogenolysis.

E. Frequency and stability of LC bonds

The amount of carbohydrate remaining on the lignin can measured by

sugar analysis following acid hydrolysis. Obst found 10.8% carbohydrate

in a MWEL from loblolly pine. Afraction of this amount (11%) was

removed by dilute alkali.

F. Residual lignin in kraft pulp

Kraft pulping removes large quantities of hemicellulose and lignin and

disrupts ester linkages between lignin and carbohydrate and between

hemicellulose chains. Even so, significant amounts of carbohydratae

remain bound to the residual lignin after kraft pulping. As the

reaction progresses, however, residual lignin becomes harder to remove.

Lignin remaining in the kraft pulp cannot be removed without

unacceptable large yield losses.

to the O-6 of galactoglucomannan. Although this structure is in accord

with what is known about native LC bonds, the bonds in kraft pulp can

be very different. The nature of the covalent linkages in kraft pulp

have not been fully characterized because (1) many rearrangements occur

during pulping (2) difficulties are encountered in isolating the

residual lignin, and (3) reliable degradation and characterization

methods are lacking. At least some changes appear to result from the

formation of alkali- and acid- stable carbon- carbon bonds between

lignin and carabohydratae Several rearrangements are possible.

Particularly, primary hudroxyls of glucose and mannose can react with

the a, b or g carbons of phenylpropane units to form ether linkages.

The reducing –end groups can also react. Glucose is the most prevalent

sugar bound to residual lignins form kraft pulps, and it seems probable

that this results form the reaction of cellulose with lignin during the

pulping process. This conclusion is supported, but not proven, by the

observation that the glucose content of lignins from wood. Reactions

with the b and g hydroxyls of the phenyl propane are particularly acid

and alkali- stable and may ascape detection in methylation analysis.

Minor used methylation analysis to determine the characteristics of

polysaccharides attached to residual lignin in loblolly pine kraft

pulps. The total carbohydrate content of the residual MWEL was only

about 8%. As compared to the 12% abtained with MWEL from nataive wood,

but methylation data indicated that the carbohydratae bonding was

similar in kraft and native wood. The primary O-6 position was most

frequently found for hexans and the primary O-5 for arabinan. Xylan was

bonded to lignin at O-3, with a small amount at O-2 The predominant

methylated derivatives obtained from glactose and arabinose indicated

1®4 and 1® 5 linkages, respectively. The apparent DP ranged from 4 for

xylan to almost 13 for galactan. Because of the small differences in

methylation patterns between carbohydrates form MWELs of pine and pine

kraft pulp. Minor was not able to confirm the possible formation of LC

bonds during pulping.

G. Biodegradation of LCCs

Most carbohydrate chains or side groups appear to be attached to lignin

through the nonreducing moieties. Because exo-splitting enzymes

generally attack a substrate form the nonreducing end of a

polysaccharide, removing substituents progressively toward the reducing

end of the molecule, complete degradation is not possible. Even when

cargohydrates are attached to the lignin by the O-1 hydroxyl, a single

sugar residue could remain attached even after complete attack by

exo-splitting glycosidases.

I. Residual LC structures after exhaustive enzymatic digestion

The presence of lignin, aromatic acid, and other modifications of

hemicellulose clearly retards digestion of cellulose and hemicellulose

by ruminants. Phenolic acids associated with forage fibre are known to

decrease fibre digestion when they are in the free state. p- Coumaric,

ferulic, and sinapic acids inhibit the activity of rumen bacteria and

anaerobic fungi.

The influence of LCCs on ruminant digestion was studied by examining

the solubilization of LCCs using cell- free hemicellulase complexes

from the rumen. LCCs from grasses of increasing maturity were isolated

and treated with cell-free rumen hemicellulases. As the lignin content

increased, the extent of degradation declined, indicating that the

lignin content of the LC was the overriding factor in determining its

digestibility.

2. Solubilization of LCC by microbial activity

In recent years, studies on the solubilization of lignin from grasses

or wood labelled with 14C phenylalanine have proliferated.The bulk of

the radioactive label is incorporated into the lignin rather than into

carbohydrate or protein of the plant, but it is clear that lignin

purified from the labelled plant tissue contains significant amounts of

carbohydrate. This material is probably closer to the structure of

native lignin than is synthetic lignin prepared by in vitro

dehydrogenative polymerization of coniferyl alcohol.

In summary, research on the solubilization of LCC by microbial activity

has periodically shown that cellulases, hemicellulases, esterases, and

perhaps peroxidases all correlate with lignin solubilization. The

mineralization rates and extents reported for streptomyces are

relatively low, and the solubilized lignin is not extensively modified.

Lignin mineralization and solubilization could, therefore be

sttributable to two (or more) different enzymes. These studies require

additional rigorous clarification.

V. Enzymatic treatments of pulps

For many applications, residual lignin in kraft pulp must be removed by

bleaching. Successive chlorination and alkali extraction remove the

remaining lignin to leave a bright, strong pulp suitable for printing

papers and other consumer products. Although chlorine bleaching solves

the immediate problem of residual lignin, the chlorinated aromatic

hydrocarbons produced in the bleaching step are are recalcitranat and

toxic. These chlorinated products are hard to remove from waste

streams, and trace quantities are left in the paper, so other bleaching

processes were devised. One approach is to use hemicellulases to

facilitate bleaching.

V1. Conclusions Lignin and hemicellulose are complex polymers occuring

in plant materials. Either polymer alone presents a formidable

challenge to microbial degradation. In native substrates, however,

lignin and hemicellulose are intermeshed and chemically bonded through

covalent corss-linkages. As such they are even more resistant. Covalent

lignin – corbohydrate linkages can be divided into two types: ester

linkages through the free carboxy terminus of uronic and aromatic acids

and ether linkages through sugar hydroxyls.

Degradation of Wood

Introduction

Microbial degradation of wood should be considered on two levels. From

an organismic point of view degradation concerns the interaction of the

cell with its microenvironment. At this level, degradation is strongly

affected by diffusion of the degradative agents and the uptake of the

oligomeric products. From a biochemical perspective, degradation

concerns the molecular architecture of the biopolymers, the capacities

of the enzymatic catalysts to bind to them and the catalytic turnover

rates. Lignin reactivity is limited by the accessibility,

heterogeneity, and stability of the polymeric linkages; cellulose

reactivity is limited mostly by accessibility and crystallinity; and

hemicellulose reactivity is limited by substitution.

Distribution of Wall Components

The three principal components of wood are found throughout the wall.

Cellulose is organized into laminar crystallites which are bundled into

the microfibrils. Each micro-fibril contains regions of amorphous

cellulose interspersed and intertwined with hemi­cellulose, Fig. 1. The

latter is in turn crosslinked to lignin. Most of the cellulose is in

the secondary wall layers. Its concentration depends on the relative

portions of hemicellulose and lignin.

Component Chemistries

Lignin is a stable, highly cross-linked aromatic macromolecule arising

through dehydrogenative free radical polymerization of p-coumaryl,

coniferyl; and sinapyl alcohols. Gymnosperm lignin is made up

principally of coniferyl alcohol (guaiacyl lignin) whereas angiosperm

lignin is made up from approximately equal amounts of coniferyl and

sinapyl alcohols (syringyl/guaiacyl lignin). p-Coumaryl alcohol is

found principally as a precursor to the lignin of grasses and in

reaction wood. Cellulose microfibrils are the most conspicuous element

of the plant cell wall. The b-(1,4)-D-glucose chains which make up the

cellulose polymer can be arranged in both parallel and antiparallel

crystallites; but based on what we now know about the biosynthetic and

biodegradative mechanisms and x-ray crystallographic studies, the

parallel arrangement is almost certainly the form found in nature.

Microstructure and Porosity

Porosity and microstructure are critical in determining accessibility

of enzymes to their polyumeric substrates. The relationship between

enzyme diffusion and substrate accessibility has been shown in the

number of ways. For example, reducing particle size greatly increases

surface area and speeds up the enzymatic hydrolysis of cellulose.

Grinding or cutting wood to open all the lumina to attack will expose

considerably more surface than is available in whole wood. The total

surface area reaches about 1 m2 g-1. Once the lumina are accessible,

however, relatively little further increase in surface area occurs

following further grinding, because the cell wall thickness is very

small compared to its length. Particle size is not the only factor

important in enzymatic depolymerization. Enzymatic accessibility

depends on the structure of the wall itself.

Degradation of whole wood

Microbial degradation of whole wood occurs principally by fungi.

Although bacteria apparently possess much of the biochemical machinery

necessary for biodegradation of the wood components, they do not form

mycelia, and hence, cannot propagate through the tissue structure or

translocate nutrients into the wood or from one region to another as

decay progresses.

Biodegradation of Lignin

Biodegradation of lignin has been studied for more than 80 years with

only incremental progress over much of the time. Early assays employed

the disappearance of acid-insoluble Klason lignin. The development of

Synthetic 14C-labelled lignins enabled rapid radiorespirometric

determination of lignin degradation under controlled conditions, and a

series of experiments using this assay led to improved understanding of

the cultural and nutritional conditions under which lignin

biodegradation occurs.

Other aspects of lignin biodegradation such as the roles of oxidative

species details of biochemical mechanisms, regulation and bacterial

lignin degradation have been reviewed elsewhere.

Biodegradation of Cellulose

The biodegradation of cellulose has probably attracted more attention

world-wide than any other single biochemical event outside the filed of

medicine, yet the mechanism of cellulose hydrolysis is still

imperfectly understood. The cellulase complex from Trichoderma reesei

has been studied most thoroughly, but it is not yet clear exactly how

this complex works to depolymerize cellulose. The focus here is placed

on the biochemical mechanisms involved in hydrolysis.

When all of the cellulases are present, Valonia crystals undergo a

delamination to form bundles of microcrystallite fibrils. A similar

delamination has been observed with the purified bacterial cellulose

from Acetobacter xylinum. Although no direct evidence is available, the

delamination probably occurs between the sheets adjacent van der

Waals-bonded sheets rather than between adjacent hydrogen bonded

chains.

The distinction between CBH I and II is not confined to T. reesei. CBH

I and II are also found in the cellulase complex of Penicillium

pinophilum and in Fusarium lini. In the later instance, CBH I was found

to be active against D-xylan, whereas CBH II was not. Given the

apparent importance of the C6 carbon in forcing the half-chair

conformation during the hydrolysis of the glycosidic bond by lysozyme,

it is apparent that substrates lacking this substituent may not be

appropriate for some cellulases.

Biodegradation of Hemicellulose

Because of the diversity of hemicelluloses, it is not possible to

survey here all of the different types known. Dekker have provided an

extensive, useful compilation of this sort. Likewise have recently

reviewed the literature on microbial xylanases. Mannanases have been

studied to a lesser extent, hence, the emphasis here is placed on

xylanases.

The characterization of hemicellulase mechanisms presents numerous

difficulties not encountered with cellulase because the substrate

employed is heterogeneous and branched. Moreover, the literature is not

definitive because substrates such as larch arabino – glucuronoxylan

commonly used for hemicellulose assays – presumably because of their

easy solubility – but they are not really representative of the bulk of

hemicellulose found in wood. Selection of an appropriate substrate is

critical because the apparent specific activity of a xylanase can vary

greatly depending on the xylan preparation used for assay. Substrate

variability is not confined to the type of xylan employed, because

different batches of xylan from the same supplier can lead to apparent

changes of as much as two-fold. Native xylans tend to be highly

acetylated. Acetyl groups increase colubility but decrease the rate of

enxymatic depolymerization so the method of substrate preparation can

have a profound affect on the apparent activity.

Many xylanases are not able to remove glucuronic acid resudies from the

xylan chain probably because of the 30-fold greater stability of

glucuroniside glycolytic linkages noted earlier. By comparison, the

ester linkages connecting acetyl groups to the xylan are exceedingly

unstable and most are removed ruing isolation of the polymer. Although

synergism is observed between xylan esterases and endoxylanases during

hydrolysis of partially acetylate4d xylan, it seems unlikely that

deacetylation would be a rate-limiting step in the enzymatic hydrolysis

of xylan under most practical conditions because of the extreme

lability of the ester linkages.

Applications

Technical developments, particularly the discoveries of

xylose-fermenting yeasts and lignin-degrading enzymes have paved the

way for specific removal of hemicellulose and lignin in order to

recover cellulosic fibers and to produce useful chemicals from the

hemicellulose and lignin fractions.

An alternative approach to biological pulping which permits more direct

control over the degradation activities is to employ isolated enzymes

for lignin or hemicellulose removal. Because the lignin is cross-linked

mostly into the hemicellulose is more readily depolymerized than

lignin, it has been the initial target of treatment. Removing only a

small portion of the hemicellulose might be sufficient to open up the

polymer and ease solvent removal for the residual lignin. The principal

problem in these studies has been in obtaining selective removal of

hemicellulose without degrading the cellulose. Selective inhibition of

cellulase activity can be realized by the addition of I mM HgCl2. Xylan

was specifically removed from delignified cell walls leading to a

decrease in energy demand during beating. Removing less than 2% of the

initial dry pulp weight gave better fiber bonding due to increased

flexibility. Therefore, enzymatic treatments of pulp hold the prospect

of both decreased cost and improved fiber qualities.

CCA-Treated Wood

Wood treated with CCA is widely used in outdoor architectural projects

such as decks, walkways, gazebos and retaining walls. Although this

material was originally marketed as a maintenance-free product, most

preservatives manufacturers and end users today recognize the

advantages of protecting and beautifying CCA-treated lumber with

surface finishes. As a consequence, it frequently becomes a substrate

for a variety of coatings products. Unfortunately, little published

information is available on the performance of surface finishes over

CCA-treated wood. This has led to some confusion among preservatives

manufacturers, coatings companies, the trade, and consumers as to the

compatibility of coatings with this material. Not surprisingly, there

are a number of misconceptions about the effects of CCA treatment on

coatings performance. This project was undertaken to help clarify some

of these issues.

All of this suggests that surface finishes applied over CCA-treated

lumber would perform better than those applied over untreated wood of

the same species.

The objective of this project was to evaluate the performance of a

variety of surface finishes over untreated and CCA-treated wood and to

determine the extent of the chromium enhancement effect.

Wood-Polymer Composites

Wood is a hygroscopic material that can sorb water as a liquid or as

vapor from its surroundings. The sorbed moisture can exist in wood as

liquid or vapor in all cavities and as water bound chemically within

cell walls. Moisture in the cell walls affects all wood properties, but

moisture in voids affects all wood properties, but moisture in voids

affects only weight. The amount of moisture held in cell walls varies

according the particular piece of wood and is a function of both the

relative humidity and temperature of the surrounding air. The fiber

saturation point is the point at which cell walls are empty. Wood is

subject to dimensional changes when its moisture content fluctuates

below the fiber saturation point.

One way wood-polymer composites (WPC) are made is by saturating wood

with monomers followed by in situ polymerization of the monomers. Many

monomers used to make WPC do not penetrate the cell walls and do not

completely fill the voids after polymerization, leaving voids in the

wood because of shrinkage of the polymer. Solvents can be used to help

swell wood and aid the penetration of monomers into cell walls,

resulting in moderately high dimensional stability. Methanol has been

used to swell the wood; after methanol treatment, the wood is then

heated.

The objectives of this research were to identify monomers that swell

and penetrate the cell wall without the use of solvents, measure the

extent of swelling in individual monomers, polymerize the monomer in

the wood, and measure the volumetric swelling and moisture content of

the WPC at 90% relative humidity (RH).

Materials and Methods

Monomers

Monomers selected for this study were acrylates and metacrylates, which

can be polymerized using the thermal polymerization initiator

2,2´-azobnis-(2-ethylbutyronitrile). All monomers were used as received

without further purification or removal of inhibitors added by the

manufacturers.

Wood specimens

Maple (Acer saccharum ), northern red oak (Quercus rubra), and southern

pine (Pinus sp.) woods were used. The wood was cut into specimens 2.5

by 2.5 by 0.6 cm (radial by tangential by longitudinal). Growth rings

were oriented parallel to one side of each specimen to minimize

distortion during shrinking and swelling.

Volumetric swelling and moisture content

The WPC specimens and untreated control specimens were conditioned in a

humidity chamber at 27 C and 30% relative humidity (RH) for 7 days. The

conditioned specimens were weighed, dimensions measured, and volumes

calculated. The specimens were then placed in a humidity chamber 27 C

and 90% RH. Specimens were weighed and measured after 2,4, 6, and 24 h,

and 2, 3, 4, and 7 days. The percentage of volumetric swelling based on

the treated oven-dry volumes was calculated based on the oven-dry

untreated weight.

Volumetric swelling of WPC specimens

The rate of swelling of WPC specimens was slow for the first few hours

at 90% RH, compared to that of the control specimens Tables 6 to 8

After 6 h in 90% RH, maple red oak, and southern pine control specimens

swelled 6.6, 6.1 and 7.0%, respectively. In contrast, all maple WPC

specimens swelled less than 3%, red oak WPC specimens less than 3.6%,

and the southern pine WPC specimens less than 4.0% during the same

period moisture into the wood, which lowered the rate of swelling

compared to that of controls during the first few hours at 90% RH.

Moisture content of WPC specimens

The moisture content of WPC specimens was calculated from specimen

weight at specified time intervals in 90% RH. The rate of moisture

sorption during the first few hours was slower than it was after 24 h

in 90%RH. After 7 days at 90% RH, the moisture content calculated on

the basis of only the wood in the specimens (untreated oven-dry weight)

excluding the weight of polymer, showed that many treated specimens

sorbed more moisture than did control specimens.

Conclusions

Certain monomers can swell wood at temperatures above room

temperatures. These monomers have low molecular weights and molecular

structures that facilitate hydrogen-bonding. For wood-polymer composite

(WPC) specimens that displayed some volumetric swelling after

polymerization, cell-walk bulking had the potential to reduce the

moisture-related swelling, but this potential was counteracted by the

hygroscopicity of the polymers. This attraction of moisture to the WPC

specimens resulted in some swelling that likely would not have occurred

had the polymers not been hygroscopic.

Lignocellulosic—Plastic Composites from Recycled Materials

Use of the word “waste” projects a vision of material with no value or

useful purpose. However, technology is evolving that holds promise for

using waste or recycled wood and plastics to make an array of

high-performance products that are, in themselves, potentially

recyclable. Preliminary research at Forest Products Laboratory (FPL),

and elsewhere indicates that recycled plastics such as polyethylene,

polypropylene, or polyethylene terephthalate can be combined with wood

fiber waste to make useful reinforced thermoplastic composites.

Advantages associated with these composite products include lighter

weight and improved acoustic, impact, and heat reformability

properties—all at a cost less than that of comparable products made

from plastics alone. In addition, previous research has shown that

composite products can possibly be reclaimed and recycled for the

production of second-generation composites.

Thermoformable Composites as Outlets for Waste Paper, Wood, and

Plastics

Two general types of thermoformable composites exist, distinguished by

their very different manufacturing processes. Both processes allow and

require differences in composition and in the lignocellulosic

component. The two processes used to produce thermoformable composites

are melt blending and air laying or nonwoven mat formation.

Currently, the primary application of the thermoformed composites, both

melt blended and air laid, is for interior door panels and trunk liners

in automobiles. As noted, additional large-volume, low-to-moderate cost

applications are expected in areas such as packaging (trays, cartons),

interior building panels, and door skins.

Recent Research on Wood Fiber-Thermoplastic Composites

The following is not intended to be a comprehensive review of recent

research on wood fiber-thermoplastic composites. Instead, we simply

illustrate the effects of some important composition and processing

variables in the composite processes, including preliminary indications

of the effects of recycled ingredients.

Composites Made by Melt Blending. The 1980s brought a resurgence of

research into various aspects of melt-blended composites made from

wood-based flour or fiber in virgin thermoplastic matrices. For

example, Kokta and his colleagues have published numerous papers in

this area, emphasizing improvements in the filler-matrix bond through

coupling agents and grafting of polymers on cellulosic fiber surfaces.

Composites Made by Nonwoven Mat Technologhy. Numerous articles and

technical papers have been written and several patents have been issued

on both the manufacture and use of nonwoven fiber webs containing

combinations of textile and cellulosic fibers. This technology is

particularly well-known in the consumer products industry. For example,

Sciaraffa and others have been issued a patent for producing a nonwoven

web that has both fused spot bonds and patterned embossments for use as

a liner material for disposable diapers. Bither has found that

polyolefin pulps can serve as effective binders in nonwoven products,

many additional references could be cited in this area.

Research and Development Needs

At the FPL and the UW, we are conducting a program aimed at developing

technology to convert recycled wood fiber and plastics into durable

products that are themselves recyclable, are environmentally friendly,

and will remove the raw materials from the waste stream. This program

is being conducted in cooperation with the U.S. Environmental

Protection Agency. In support of this goal, we have defined a number of

research and development needs.

Chemical Modification of Wood Fiber

The wood composite industry has an opportunity to follow this trend and

greatly expand markets for new materials based on blends and alloys

with other materials. The research program at the Forest Products

Laboratory is focusing on wood fiber/plastic blends and alloys in an

attempt to produce materials with consistent, uniform, continuous,

predictable, and reproducible properties.

The purpose of this paper, is to present some of the initial results in

the area of wood fiber thermoplasticization. The wood fiber is a

composite made up of a crystalline, thermoset polymer (cellulose) in a

thermoplastic matrix (lignin and the hemicelluloses). The melting point

of the thermoplastic matrix is too high to allow this phase to flow at

temperatures that do not degrade the wood fiber. If the glass

transition temperature of the thermoplastic matrix of wood is reduced

through chemical modification, it is possible to plasticize the wood

fiber allowing it to become more thermo-formable through

thermopressing, extrusion, or injection.

Experimental Procedure

Esterification Procedure

Modification of the fibers using maleic (MA) and succinic (SA)

anhydrides was performed using the following procedure. Hot xylene was

saturated with each of the anhydrides in a reaction vessel. When reflux

temperature was reached, the aspen fiber was added and allowed to react

for different lengths of time to give different levels of chemical

weight gain. Excess anhydride was removed by sohxlet extraction of the

esterified fiber with xylenes for four hours. Excess xylene was removed

by evaporation and then the fiber was oven dried overnight.

Analyses of Esterification Products

FTIR spectroscopy was performed using a Nicolet 6000 Spectrophotometer.

Samples of each modification were dried, ground, and mixed with

potassium bromide in a ratio of 1 mg; 200 mg and pressed under a vacuum

to form pellets. Absorbance was measured over a range from 4000 cm-1 to

400 cm-1with air as a reference.

Scanning electron micrographs (SEM) were taken with a jeol 840 scanning

electron microscope. All samples were coated with gold. A magnification

of 750x was used.

Acetyl contents were determined by saponifying the acetyl groups and

using gas-liquid chromatography (GLC) with propionic acid as a

standard. The ester content of the MA and SA modified fibers were

calculated from the acid and saponification values using a similar

technique to that used by Matsuda.Titration of the free carboxyl groups

in the esterified wood fiber and in ester groups saponified from the

esterified wood fiber gave determinations of the ester content based on

the acid and saponification values and indicated whether the anhydride

added as a monoester or diester.

Board Formation

Five percent of a liquid phenol-formaldehyde (PF) dryprocess hardboard

resin (GP2341.50% aqueous solution), was sprayed onto the esterified

fiber followed by attrition milling to distribute the resin. The fiber

was hand formed into a mat approximately 15 by 15 cm and then pressed

in a heated Carver press at 190°C for 10 minutes to a predetermined

thickness of 6 cm and specific gravity of 0.7. for the no resin boards,

controls AA, MA, and SA modified fibers were hand formed into fiber

mats and pressed in a heated carver press at 210°C for 5 minutes at 8.5

MPa (board pressure).

Board Testing

Moisture sorption

Fiberboards were cut into 5 by 5 cm specimens and placed in separate

rooms at 27°C and 30, 65,, or 90% relative humidity. Each specimen was

weighed at the end of 21 days and the equilibrium moisture content

determined. Triplicate samples were done and the results averaged.

Esterification of Wood Fiber

Figure 1 shows the extent of modification achieved with the three types

of anhydrides based on a molar addition. The reaction with AA results

in the splitting out of byproduct acetic acid during wood

esterification while the reactions with MA and SA result in 100%

anhydride carbon skeleton added to the wood. MA showed a much lower

reactivity than SA which has the same structure except for the double

bond in MA. A possible explanation for the molecule into the cell wall

as well as the instability of the reactivity MA chemical intermediate.

Moisture Sorption of Esterified Fiberboards

Figure 2 shows that the equilbrium moisture content (EMC) of the

esterified fiberboards is independent of the type of esterification,

but is dependent on the molar gain of reacted ester in the wood fiber.

A reduction in EMC was seen for each esterification as the level of

modification was increased.

Rate and Extent of Swelling of Fiberboards in Liquid Water

Figure 4 shows the rate of fiberboard swelling in liquid water at

equivalent levels of anhydride modification. while control boards

swelled almost 25% in thickness in the first 20 minutes, all types of

esterified boards swelled less than 10%. AA reduced the swelling to

less than half of the control specimens while MA and SA modifications

reduced the swelling further. The reduction in swelling can be

attributed to the bulking of the cell wall and the reduction in

hygroscopicity of wood especially with the larger MA and SA molecules.

Delignification of Wood with Pernitric Acid

Organic peroxides such as peracetic and performic acids will

effe­­cti­vely delignify wood and other lignocellulosics. The use of

performic acid as a pulping agent is under active investigation. We

recently found that the inorganic peroxide, peroxymonosulfuric acid,

will readily delignify these materials. Hydrogen perxide is quite

ineffective, however. On the basis of these findings, it seemed highly

likely that other inorganic peroxyacids might also be effective in

delignification. Consequently, we initiated an exploratory study on

delignification of wood with other inorganic peroxyacids.

On the basis of this consideration, we decided to study the possibility

of delighifying wood with pernitric acid. We chose finely divided aspen

wood as the substrate for study because it delignifies easily. Success

with aspen delignification would suggest further pulping studies.

Generation of pernitric acid

There are several methods for preparing pernitric acid. We initially

chose the method described by Kenley, Trevor, and Lan that uses only

concentrated hydrogen peroxide and concentrated nitric acid. Several

attempts at generating pernitric acid by this method were unsuccessful.

After adding a drop of peroxide to the chilled nitric acid in an ice

bath, a puff of yellowish-brown vapor would occur arter a fraction of a

second. Apparently, when the drop of peroxide mixed with the acid, some

pernitric acid formed and then immediately decomposed to nitric acid

and oxygen.

On the basis of the large variability of the data and the ease of

obtaining explosive mixtures, it appeared that pernitric acid was quite

unstable and would readily decompose, especially at higher

concentration. If decomposition of pernitric acid in dilute aqueous was

too rapid, it might possess little ability to function as an oxidizing

agent. It would therefore lose the ability to degrade the lignin in

wood. Because of this consideration, we performed some experiments on

the decomposition of pernitric acid in dilute aqueous solutions.

Decomposition of pernitric acid

We generated pernitric acid by adding 1.35 g of chilled (from a

refrigerator) 70% hydrogen peroxide to 4.0 g 90% nitric acid in a vial

in an ice bath. After 60 min, the mixture was diluted with 24.6 g of

distilled to water. The solution was then analyzed and was 0.68 m

(5.4%) in pernitric acid. The total acidity of the solution was 1.93 m

based on the input of nitric acid. Half the solution remained at room

temperature (22°C) and the remaining half at refrigerator temperature

(6°C) with periodic analysis of each of the two samples.

Delignification of aspen wood

The generation procedure used in the decomposition work produced a 5.7%

solution of pernitric acid. Then 25 g of this solution was added to

1.00 g (o.d. basis) of finely divided aspen wood (passing a 40-mesh

screen, 6.0% moisture). The mixture was held at 22°C for 305 min. The

liquor was drained from the solid residue. The residue was washed

thoroughly with RO water, and air-dried. The residue was dried in a

vacuum oven overnight at 60% and its yield was determined. It was then

analyzes for lignin content, and its 0.5% cupriethylenediamine (CED)

viscosity was determined. Because the residue was not completely

soluble in the CED solution, it was delignified using the chlorite

procedure given in the Experimental section.

Rosin and Rosin Derivatives

Rosin is a complex mixture of mainly resin acids and small amount of

non-acidic components. Its colour, depending on the source and method

of processing, can vary from a water white through dark red to almost

black, with a tinge of red. It is generally translucent and brittle at

room temperature. The other properties which are of importance in

judging the quality of rosin are acid value, saponification value,

softening point, and unsaponification value,. However, entire rosin is

sold and purchased on the colour basis, the lightest colour bring the

highest price. Opacity in rosin some times degrades its value,

Sometimes rosin is upgraded to get better market price.

Composition

Resin acids are monocarboxylic acid having typical molecular formula

C20H30O2. The structural formulas of all the known resin acid are shown

in Fig.1, which may be divided into abietic and primaric type. The

pimaric type resin acid differs from those of abietic type, in that

they have two alkyl groups in the C-7 position in the place of

isopropyl group. When double bond occurs in one of these alkyl groups,

it can not conjugate with a cyclic double bond. Consequently the double

bo­­nds in pimaric and isopimaric acid are not conjugated and so not

very reactive.

Reaction and derivatives

The resin acid molecule possesses two chemically reactive centers, the

double bonds and the carboxyl gorup. Through these, many modifications

in structure and numerous derivatives are obtainable. Abietic acid is

customatily and conveniently used to exemplify the structural and

chemical reaction products c, constitute the bulk of commercial

products. Although the molecular weight of pure acid is 303, for rosin,

the value is usually taken as 340 due to the presence of neutal for

calculation in involving carboxyl group.

Isomerization

Pure resin acids of the abietic type are isomerized thermally or by

treatment with dilute mineral acids. The equilibrium mixture from the

mineral acid isomerization of levopimaric acid was 4% palustire, 93%

abietic and 3% meoabietic. The equilibrium mixture of a thermally

isomerized levopimaric acid was 13% palustric acid, 80% abietic acid

and 7% meobietic acid. Methyl abietate isomerised to give the same

equilibrium distribution as abietic acid. A major difference between

the two was an extensive disproportionation reaction that occurred with

the ester.

Photosensitized oxidation

An alcoholic solution of levopimaric acid containing a sensitizing dye,

e.g., methylens blue, readily absorbs one mole of oxygen, when

contacted with air, to produce quantitatively a peroxide,

8,12-peroxide-13,14 dihydroabietic acid, by 1-4 addition.

Hydrogenation

Hydrogenation is one of the more satisfactory methods for decreasing

the susceptibility of rosin to air oxidation. Because of the structural

features of the resin acids, however more vigorous conditions are

necessary than with ordinary olefins. Reduction with heavy metals and

mineral acids or which sodium amalgam and water, accomplishes only

incomplete hydrogenation, even for one double bond. On the other hand

molecular hydrogen, in the presence of noble metal catalysts, such as

palladium or platinum, will saturate one or both double bonds,

depending on the polarity of the solvent employes. By taking advantage

of solvent effect, the desired selectivity can be obtained with

palladium carbon catalyst.

Hydrogenless Hydrogenation

Resin acids can be hydrogenated by the transfer of hydrogen from sodium

formate in the presence of water and a palladium carbon catalyst. The

primary product are the dihydro derivatives Incorporation of a polar

solvent (Methyl tertiary butyl in the solvent increases the reaction

rate. Although methyl neoabierate hydrogenates faster than abictatc,

the initial rate of formation of the dihydro compounds is practically

the same, same isomerization to methyl abietate (maximumabout 25%) and

slight dehydrogenation to methyl dehydroabietate occur. The reaction

product distribution is essentially the same as for abietate: only

trace amounts of 13(15)-abietenate are produced.

Polymers of vinyl esters of hydrogenated rosin

Vinyl esters were prepared and homopolymerized in emulsion and

copolymerized with vinyl acetate, vinyl chloride, and butadiene and

thus compared to vinyl tetrahydroabietatc (VTA) and vinyl

dehydroabietate (VDA).

Prehydrogenation

One of the double bonds of rosin acid containing conjugated

unsaturation, such as abietic acid, and the exocyclic double bonds of

dextropimaric and isodextropimaric acids are easily reduced. The

endocyclic double bonds of dihydroabietic acid and pimaric acids are

more difficult to hydrogenate, but they can be reduced over a nickel

catalyst, under severe conditions. Dehydro abietic acid, which contains

a highly hindered aromatic ring, cannot be reduced at a practical rate

over conventional catalyst.

Dehydrogenation

The dehydrogenation reaction is the second means of effectively

modifying rosins to render them less susceptible to oxidation by

atmosphcric oxygen. Part of the hydrogen that is removed is readily

absorbed by the pimaric type acids, present in rosin, to produce the

stable dihydropimaric acid. Because of the absorption of a part of the

hydrogen, this reaction frequently has been described as a

disproportionation. However, the appearance of only 2-3% of

dihydroabietic type acids and the absence of tetrahydro abietic acid,

show that the disproportionation of the abietic type acid is not

involved.

Thus disproportionated rosin is chemically stable, thermoplastic resin,

by the loss of conjugation or aromatization of the molecule. This

treatment converts its total oxidation prone AA content to highly

stabilised forms of resin acids, predominantly dehydroabietic acid. As

a result this DPR has a much greater resistance to discoloration,

embrittlement, and other effects of oxidation then do pale grades of

ordinary rosin. This improved oxidation resistance, together with a

wide compatibility with polymeric thermoplastic and elastomeric

materials, makes DPR especially suitable as an ingredient of hot melt

applied adhesives and coatings for paper and paper boards substrates,

and as a tackifier and processing aid for rubber based adhesives and

molding compounds.

Polymerization

In any application only reduction in acid value of rosin does not

satisfy the performance requirements of coatings. Rosin (abietic acid)

possesses active conjugated dienoic unsaturation, which is very much

susceptible to oxidation by atmospheric oxygen. Thus, when exposed to

air, rosin and its derivatives undergo discolouration to develop

ultimately dark brown colour, On oxidation rosin becomes more brittle

and friable and changes its solubility characteristics. Enhanced

performance of rosin derivatives with their pale colour and good colour

retention properties is obtained by proper nuclear modifications of

rosin, such that the oxidation susceptible unsaturation in rosin is

reduced to a greater extent or completely eliminated by definite

chemical reactions such as polymerization.

Phenolic modification

The phenolic modified rosin is made by adding to the hot rosin either

the phenol formaldehyde condensate or the phenol and the formaldehyde

separately. The phenols commonly used are bis-phenol, phenol and

creasols. The phenolic modified rosins are usually further modified by

esterification with glycerol or pentaerythritol. The condensation

reaction is an addition reaction that takes place between the methylol

phenol and rosin or rosin esters. These esters are used in oil soluble

varnishes.

Salt formation

With unsaturated cyclic and acyclic hydrocarbons

Metal salts of the condensates of resin with unsaturated hydrocarbons,

which salts are particularly valuable for use in protective coatings

such as varnishes, having excellent bodying and drying characteristics

and forming harder films of improved water resistance.

Drier metal salts of this rosin-butadiene condensates were pepared by

heating the condensate to 235°C and then gradually adding, with

intermittent stirring, during a period of about 40 minutes, the metal

salt, while simultaneously increasing the temperature to about 320 °C.

The hot, highly viscous resins was then cooled to room temperature and

analysed.

With pentaerythritol and other polyhydric alcohols

Glycols and diethylene glycols are also used to prepare esters by

heating rosin at 20-260oC in the presence of zinc, or boric acid

catalyst. The unreacted alcohol is removed from the ester at 300oC

under reduced pressure. One of the glycol ester is prepared by the

reaction with rosin, diglycol and acetic acid. The PVC sandals made

from these esters can fully meet the international specifications.

Hydrogenolysis

Rosin has been successfully hydrogenated to produce the hydroabietyl

alcohol of commerce. The alcohol may be produced by the hydrogenation

of the methyl esters of rosin at 300oC and 5000 psi, in the presence of

copper chromite catalyst. With soluble film formers, such as casein and

zein, the alcohol is used to impart improved tack, colour and

stability. Hydro abietyl alcohol produces esters with a wide range of

physical properties, when reacted with organic and inorganic acids.

Polyesterification

Unsaturated polyester modified rosin (UPER) are prepared by reacting

first with dibasic acid glycol, maleic anhydride and then with rosin.

The mechanical and physical properties of the castings, prepared by

copolymerization with styrene are good to excellent when compared with

accepted values of commercial styrenated polyester cast resins. Foams

prepared from these polyesters shows promising use in garments as a

fabric-foam laminated. This has been due to their ability to be flame

taminated directly to the fabric without the use of an adhesive.

Copolyesters

(Copolyesterification) copolysters belongs to broad class of organic

high molecular weight compounds, which are formed by repeated

esterification reaction. They constitute one of the most important

class of plastic material. The great scope lies in the powder coatings,

solventless convertible coatings, aqueous coatings etc. The film

properties of these polysters have high dimensional stability against

change in temperature.

Ammonolysis

The action of ammonia on dehydrogenated rosin at elevated temperatures,

yields a nitrile. It is a pale yellow, waxy solid with softening points

about 65o C, containing 85-95% of nitrile from which the nitrile of

dehydroabietic acid can be crystallized with mp 87-90oC. It is used in

the production of Amine D, by catalytic hydrogenation at elevated

temperature and pressure. The amine is relatively weak base that forms

salts with both mineral and organic acids, at room temperature, in

suitable solvents or at elevated temperature.

Preparations

Dehydroabietylamine acetate

To a solution of 2.85 kg. of Amine D dissolved in 4.71 lit. of toluene

was added a solution of 654 g. (10.8 mole) of glacial acetic acid in

1.56 lit. of toluene. The solution was stored at 10oC for 2 hour. The

crystalline salt was collected, washed with cold toluene and

recrystallized from 4.23 lit. of boiling toluene. The colourless

crystals were collected, washed several times with n-pentene and air

dried to obtain 1.365 kg. (78.5%).

Methods of preparation

Sulfuric acid catalyzed condensation of abietic acid with formaldehyde:

Abietic acid, 10 g. (0.033 mole) of formaldehyde (as paraformaldehyde)

were suspended in 50 ml. of purified dioxane. On addition of 3 g. of

conc. Sulfuric acid, the solution became homogeneous, and the

temperature rose spontaneously to 60oC. The darkened solution was

maintained at 60oC for 0.5 hr. On addition of 300 ml. of water, a cream

coloured precipitate was formed which was thoroughly washed with water

and dried in vacuum at 50oC.

Experiments similar to that above were run using 2,3 and 5 moles of

formaldehyde per mole of abietic acid. These products showed neutral

equivalent values of 357,394, and 419, respectively. The product from

condensation of abietic acid with 2 moles of formaldehyde showed no

maximum in the region 220-285 mµ.

Nitrogenous intermediates

The chlorosulphonyl isocyanate, acrylonitrile, fumaronitrile,

benzoquinone, tetracyano ethylene, and many dinitrile and diamine

adducts of levopimaric acid are reported here. Diamines and isocynates

from rosin have found many industrial applications, such as

polyurethane, ingredients for adhesives and corrosion inhibitors.

The Polymerizable Half Esters of Rosin

This commucation is concerned with the partial esters of the

polymerizable rosin adducts which have at least two carboxyl group.They

are some times referred to as half esters,but in at least one case a

trivalent acid is involved .Although they are quite well known, but

there is little information published in the literature to coordinate

their behaviour and properties.

The specific interest of the partial is that while maintaining acid

functionality a wide gradition of properties from hydrophilic to

hydrophobic can be obtained and also differential solubilities in

various solvents. These properties are transmitted to various

copolymers which may be formed from them, dependent on the amount of

partial ester included and the nature of the alcohol radical.

Experimental

All the chemical used are of comical type.

Preparation and properties of monomers

The simplest method of preparing the rosin ester is by reacting a

stoichiometric quantity of the requisite alcohol with an adduct being

by far the most utilized in this respect. The general object is to

avoid simultaneous formation of the diester and free acid.

Maleic rosin esters: Maleic rosin is refluxed with absolute alcohols

until the conversion to monoester is complete. Rp increases rapidly

with temperature till 80OC and is constant to 120oC. Heating above 80oC

tends to cause diester formation. Phenol methyl isohexyl alcohol and

tert-butanol react slowly. The above experiment was carried out under

pressure. Purification of the H rosin esters may be effected by first

neutralizing the ester with sodium carbonate solution. In order to

remove diesters, the sodium salt is extracted with the solvent. At

25oC, esterificition to the half ester in acetone is extremely rapid.

Secondary alcohols fail to esterify. Preparations are as flows.

Polymerization &Copolymerization

General and non-aqueous: The dibasic do not, except under special and

rather drastic conditions, homopolymer, but they are normally

copolymerizable although with rather low reactivities. The anhydride

salt, especially maleic rosin,can be made to homopolymerize under

drastic condition, but they copolymerize very readily with a strong

tendency to alternate, e.g., with vinyl acetate or styrene.The diesters

of the dibasic adducts copolymerize readily with vinly esters,e.g.,

vinly acetate, but the reactivity ratios are somewhat unfavourable for

monomers such as styrene.