Page 1

The Chemistry of Wood

Value Added Alternatives

Sally Krigstin Faculty of Forestry

University of Toronto

Presentation Summary • Structure of Wood • Structure of wood cell

• Chemistry of wood • • • •

Cellulose Hemicellulose Lignin Extractives

• Value-added products derived from chemical components Faculty of Forestry

University of Toronto

2 01/30/13

Wood Structure Softwoods

Faculty of Forestry


University of Toronto

3 01/30/13

Cellular Structure • Fibre diameter is 25-35 microns • Cell wall is 5-10 microns thick • Cell wall is composed of 3 layers • Layers are made up of microfibrils • Orientation of the microfibrils is specific for each layer Faculty of Forestry

University of Toronto

4 01/30/13

Structure of a Microfibril

25-30 nm

Elementary Fibrils

Faculty of Forestry

University of Toronto

5 01/30/13

Cellulose • Linear homopolymer composed of several thousand monomer units (β-D-glucose) units linked end to end.

• Absence of branches allows the chains to come in close contact and bond to one another. • 3 hydroxyl groups available on each glucose unit • Many OH groups make it very hydrophilic • Forms a very strong, rigid structure through lateral bonding of hydroxyl and oxygen. • Crystalline regions and amorphous regions 6 Faculty of Forestry University of Toronto 01/30/13

Hemicellulose (Polyoses) • Group of heteropolymers. • Softwoods (4 types) • • • •

Galactoglucomannan Glucomannan Arabinoglucuronoxylan Arabinogalactan

Hardwoods (2 types) Glucoronoxylan Glucomannan

• Molecule has shorter chain length than cellulose, branched. • 150 to 200 monosaccharides • Amorphous, strongly hydrophilic. • Industrially classified as non-cellulosic polysaccharide that are soluble in alkaline media. Faculty of Forestry

University of Toronto

7 01/30/13

Hemicellulose (Polyoses) • Chains are composed of • 6-C sugars: glucose, galactose, mannose • 5-C sugars: xylose and arabinose • Uronic and aldonic acids

Hardwood Contain: 30-35% Types: Xylans

Faculty of Forestry

Softwood 25-30% Galacto-glucomannans

University of Toronto

8 01/30/13

Lignin • Lignin is a high molecular weight, amorphous polymer • 3 dimensional structure • made from several hundred phenyl propane units Softwood 25-33% Guaiacyl

Hardwood 19-28% Guaiacyl & Syringyl

Benzyl ether Benzyl ester Phenyl glycosidic

• Acts as a binding agent to hold cells together. • Impart rigidity in cell wall- strongly bonded. • Very high energy content (26 MJ/kg versus 18 MJ/kg) Faculty of Forestry

University of Toronto

9 01/30/13

Extractives • • • • • •

2 to 15% of wood's dry weight Large variety of different compounds Non- structural component of wood Soluble in neutral solvents Contribute to color & odour of wood Some substances are toxic or deterrent to bacteria, fungi and termites

Faculty of Forestry

University of Toronto

10 01/30/13

Chemical Composition of Wood Extractives 2-15%

W. Birch

J. Pine







Cellulose 40-50%

Polyoses 20-25%

Lignin 25-30%



Elemental Composition: 50% C, 6% H, 44% O and <0.1% N Faculty of Forestry

University of Toronto

11 01/30/13

Historical Value • Use of non-wood products from forests was practiced by indigenous people. Species Picea Engelmanni Engelman spruce Pinus contorta Lodgepole pine Tsuga heterophylla Western hemlock Taxus brevifolia Pacific yew Tsuga canadensis Eastern Hemlock

Faculty of Forestry



Tonic, flu, colds

Gitksan, Wet’suet’en



Cleaner, gall bladder, swallowed sharp objects


Lung, stomach, kidney problems


Red/purple dye

University of Toronto

12 01/30/13

Historical Value • Early North American settlers fully utilized non-wood components. Species



Picea mariana


“Spruce beer”


Dyes, perfume

Leaves Oleoresin

Spring tonic Naval Stores -turpentine, pitch, tar, resin

Oak, Hemlock, Butternut,Birch Sassafras Pine

Faculty of Forestry

University of Toronto

13 01/30/13

Extractives Conversion Strategies Dry in

Animal fodder Chlorophylls Carotenoids

g/g rind ing

Solvent extraction

h. tion c Mextrac e


Leaf protein Steam distillation

Essential oils

• Extractives can be found in all parts of the tree • Foliage • Taxus …important source of “taxol” • Ginko biloba…alleviate symptoms associated with cognitive disorders such as dementia due to Alzheimer disease. Fengel & Wegener, 1984

Faculty of Forestry

University of Toronto

14 01/30/13

Extractives Conversion Strategies Dry in

Animal fodder Chlorophylls Carotenoids Resin Turpentine Natural Rubber

Birch Betulic acid Treatment of skin cancer and HIV

g/g rind ing

Solvent extraction


Stump extraction


h. tion c Mextrac e


Solvent extraction

Faculty of Forestry

Steam distillation




Tannins Phenolic Acids Waxes

Leaf protein

Taxus Ginko

Essential oils Rosin Turpentine Maple syrup Kraft pulping

Solvent extraction Tannins Terpenes Lignans Coulouring matter

University of Toronto

Turpentine Tall oil

Fengel & Wegener, 1984

15 01/30/13

Extractives 1. Terpenes & terpenoids • • •

Low molecular weight, volatile compounds Obtained by steam distillation. Hydrophobic Turpentine Rosin α-pinene, camphene abietic acid (resin acid) -clean scent Use: industrial solvent

Faculty of Forestry

-highly hydrophobic Use: varnish,soap,laquer,inks, paper sizing, wax.

University of Toronto

16 01/30/13

Extractives 2. Fats & Waxes â&#x20AC;˘

Low molecular weight, hydrophobic compounds Tall Oil â&#x20AC;˘ Fatty Acids: Oleic & linoleic acids Use: sizing paper, synthetic adhesives, surface coatings, paints, varnishes, synthesis of chemicals and pharmaceuticals

Weight loss Faculty of Forestry

University of Toronto

17 01/30/13

Extractives 3. Phenols â&#x20AC;˘ By-products of lignin synthesis â&#x20AC;˘ 4 types: simple phenols, lignans, stilbenes, flavonoids. Use: Natural tanning agent, pigments, dyes, phenol-formaldehydge resins

Catechin (Flavonoid) Anti-oxidant Faculty of Forestry

University of Toronto

18 01/30/13

Taxol • Bark of Pacific yew • 1960’s National Cancer Institute evaluated plants. Taxus brevifolia. • Extracted and tested for • • • • • •

Faculty of Forestry

cancer drug potential 1983 clinical studies 1988 active against Ovarian cancer 1992 FDA approval Forest Management strategies needed. 1993 Bristol Meyer found alternative source. $1.6 billion

University of Toronto

19 01/30/13

Cellulose Conversion Strategies Cellulose derivatives Regenerated cellulose

Cellulose Hydrolysis

Paper Biocomposites


Fengel & Wegener, 1984

Faculty of Forestry

University of Toronto

20 01/30/13

Cellulose Fibres & Derivatives • Biocomposites • Cellulose Esters • Cellulose Nitrate (celluloid) • Cellulose Acetate

• Cellulose Ethers • Carboxymethylcellulose (CMC) • Hydroxyethylcellulose(HEC)

• Regenerated Cellulose • Cellulose Xanthate (rayon, cellophane)

• Microcrystalline cellulose (MCC) Faculty of Forestry

University of Toronto

21 01/30/13

Biocomposites – Microfibrils • Matrix and reinforcing material are obtained from renewable resources. • Biodegradable

• Matrix polymer • Bioplastics • Example: • PLA (poly lactic acid) • Starch, cellulose acetate

• Reinforcing agents • Wood microfibrils • Enhance strength and stiffness Faculty of Forestry

University of Toronto

22 01/30/13

Dissolving Pulp World Pulping Capacity 2005

Mech Sulphate Sulphite Other Dissolving

• Preparation • Acidic sulfite • Prehydrolysis Kraft

8% 74%

1% 15% 2%

• St. Anne-Nackawic Pulp Co. Ltd. • $30 million investment • Export to India for processing Faculty of Forestry

• Can use both hardwood & softwoods • Yield is very low (3040%) • Composition is 9296% cellulose.

University of Toronto

23 01/30/13

Cellulose Nitrate • One of the first synthetic polymers • Reaction product of high purity cellulose and nitric acid.


Nitric Acid

• Properties


• Ignites easily • Moldable Faculty of Forestry

Cellulose nitrate

Celluloid University of Toronto

24 01/30/13

Cellulose Nitrate • Uses: • Leather finishes • Printing ink additives • Lacquers and varnishes • Molded products • Gun cotton • Dental plates

Faculty of Forestry

• Invented in 1862 • Substitute for ivory, tortoiseshell. • Very small industry today (fire hazard)

University of Toronto

25 01/30/13

Cellulose Acetate • Reaction product of high purity cellulose and acetic anhydride. Acetyl • Forms esters with acetate ions groups


Acetic anhydride

Cellulose triacetate (diacetate)

• Properties • Lowers the hydrophilic tendency • Breathable • Difficult to ignite • Tough • Transparent • Moldable Faculty •ofHigh Forestry University of Toronto impact resistance

26 01/30/13

Cellulose Acetate • Uses: • • • • • •

Airplane “dope” Used in lacquers and coatings Biotechnical applications (filters) Spun into fibre for use in textile industry Cast into films (protective film on LCD’s) Molded into products

• Industrial leaders: • Daicel Chemical Industries • Celanese Corporation

Faculty of Forestry

University of Toronto

27 01/30/13

Cellulose Ethers • Reaction of alkyl chlorides with alkali cellulose • • • • •

Methylcellulose (MC) Ethylcellulose (EC) Carboxymethylcellulose (CMC) Hydroxyethylcellulose (HEC) Cyanoethylcellullose

Faculty of Forestry

University of Toronto

28 01/30/13

Carboxymethylcellulose (CMC) • Reaction of alkali cellulose (swollen) & chloroacetic acid

• Properties: • Solubility in cold water • Depends on degree of substitution

• High viscosity • Not toxic and generally non-allergenic Faculty of Forestry

University of Toronto

29 01/30/13

CMC • Uses: • Detergents, soaps • Food products (especially dietetic foods and ice cream) • Textile manufacturing (sizing) • Coating additive for paper and paper board • Drilling muds, water based paints, • Pharmaceuticals, cosmetics (toothpaste, laxatives, lubricant) Faculty of Forestry

University of Toronto

30 01/30/13

Cellulose Xanthate (Rayon, Cellophane) • Regenerated cellulose made from dissolving pulp. • Alkali cellulose • Carbon disulphide • Cell-OCS2- Na+

• Properties: • • • •

Highly absorbent Soft and comfortable Easy to dye Drapes well Figure 1: Process of manufacture of viscose rayon fiber

Faculty of Forestry

University of Toronto

31 01/30/13

Cellulose Xanthate (Rayon) • Uses: • • • • •

Textile filament High performance tire cord 1930-40’s replaced cotton for undergarments, stockings Cellophane (sheets, tapes) 1960 Dupont produced last rayon textile yarn

• Industry Leaders: • Lenzing Modal • E. I. du Pont de Nemours and Company

Faculty of Forestry

University of Toronto

32 01/30/13

Microcrystalline Cellulose • Produced by isolating the crystalline regions of cellulose by acid hydrolysis of high purity pulp • amorphous regions are structural defects • 250 glucose molecule chain

• Properties: • Physiologically inert • highly absorptive • insoluble in water

• Uses: • Pharmaceutical tablets • Compacts easily and carries the active medicinal ingredient

Faculty of Forestry

University of Toronto

33 01/30/13

Cellulose Conversion Strategies Cellulose Hydrolysis


Hydrolysis 1. Mineral acids 2. Autohydrolysis 3. Micro-organisms (or enzyme systems)

Difficulties 1. Accessibility to cellulose (lignin & hemicellulose) 2. Crystallinity - large enzyme molecules.

Fengel & Wegener, 1984

Faculty of Forestry

University of Toronto

34 01/30/13

Pre-treatments Mechanical Ball milling Two roll milling

Hammer milling




Phosphoric acid Hydrochloric acid


White rot fungi


Sulphuric acid Pulping

Vibratory rod milling

Acetic acid

Freezing / thawing

Colloid milling




Sodium hydroxide Sulphur dioxide

Faculty of Forestry

University of Toronto

Combination Steam explosion Hightemperature milling Alkali + ball milling SO2 + steaming NO2 + irradiation Biomech.l pulping

35 01/30/13

Cellulose Conversion Strategies Cellulose Hydrolysis Hydroxymethyl furfual Levulinic acid Polyamides Polyesters Polycarbonates Expoxides MTHF

Glucose HydrogenationSorbitol

Acid treatment

Vitamin C

Fermentation Acetone


Butanol Isopropanol Gycerol 2,3-butanediol

Ethanol Ethene Butadiene

Polyethene Polystyrene Polyvinyl chloride Synthetic rubber



Proteins Vitamins (â&#x20AC;&#x2DC;Bâ&#x20AC;&#x2122;) Fat Amino acids

Acetic Lactic Citric Butyric Gluconic

Fengel & Wegener, 1984

Faculty of Forestry

University of Toronto

36 01/30/13

Polyose Conversion Strategies Polyoses Spent liquor

Paper additive



Xylose Acid treatment

atio oge n

Hyd r

Ethanol Yeast

Further processing

ena tion




Furan Tetrahydrofuran Polyurethanes

Hyd rog

n atio



Further processing

Mannose Este




Nylon 6,6

Faculty of Forestry

Furfuryl alcohol Esters

Furan carbonic acid Furan resins

Nylon 5

Furfuryl acrylic acid Acrylates

University of Toronto

Maleic acid Resins Polymers

37 1984 Fengel & Wegener, 01/30/13

Autohydrolysis of Wood Polysaccharides 1. 2. 4.

Arabinose Xylose Higher molecular weight xylooligomers 5. Acidic oligosaccharides 6. Glucose 7. Cellobiose 9. Furfural 10. Hydroxymethylfurfural 11. Levulinic acid 12. furan

Faculty of Forestry

University of Toronto

38 01/30/13

Lignin Conversion Strategies Phenols

Carbonic acids

Alka Vanillin hyd line roly Syringaldehyde sis/o Vanillic acid xida tion Combustion Energy

Adhesive Resin component


Tar n latio


Alkali fusion thy e m de i l a Alk Lignin Hydrogenolysis Phenols Tar Oil


Phenol Benzene


Dispersing agent Emulsifier Insecticides/herb. Animal food pellets Clays/pigments Concrete Phenols Synthesis gas Soap/Waxes Tanning agents Methane Ethene Rubbers Carbon monoxide Benzene Soils/road surfaces Coal Phenol formaldehyde Coal

Fengel & Wegener, 1984

Faculty of Forestry

University of Toronto

39 01/30/13

Biomass Conversion Strategies Carbon Methanol Methane Hydrocarbons monoxide &Hydrogen Synthetic Charcoal Wood Fuels gas C ar oil Chemicals bo n n o i t izat c Gasification ion efa u q i L Combustion Saccharification Glucose Wood Energy Ethanol Biomass Xylose Furfural Other Defibration Lignin products SteamPulping pressure processes Fribrous material

Pulp + Liquor Paper

Cellulose fibre

Faculty of Forestry

Energy Other products


Roughage Fiberboard

University of Toronto

Other products Fengel & Wegener, 1984

40 01/30/13

Conclusion I never knew these things came from woodâ&#x20AC;Ś Acids






Food additives

Pharmaceuticals Toys

Protein supplement

Sugars Diapers


Faculty of Forestry

Animal Fodder Glues



Liquid Fuels

Essential Oils


Filter tips


Dietary fibre


University of Toronto

Dust control

41 01/30/13