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
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Wood Structure Softwoods
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Hardwoods
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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
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Structure of a Microfibril
25-30 nm
Elementary Fibrils
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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 04/14/14
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
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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
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Softwood 25-30% Galacto-glucomannans
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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
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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
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Chemical Composition of Wood Extractives 2-15%
W. Birch
J. Pine
6%
9%
41%
41%
40%
30%
Cellulose 40-50%
Polyoses 20-25%
Lignin 25-30%
19%
29%
Elemental Composition: 50% C, 6% H, 44% O and <0.1% N Faculty of Forestry
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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
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Treatment/Use
Tribe
Tonic, flu, colds
Gitksan, Wet’suet’en
Tonic
Gitsan
Cleaner, gall bladder, swallowed sharp objects
Gitsan
Lung, stomach, kidney problems
Karuk
Red/purple dye
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Historical Value • Early North American settlers fully utilized non-wood components. Species
Parts
Use
Picea mariana
Twigs
“Spruce beer”
Bark
Dyes, perfume
Leaves Oleoresin
Spring tonic Naval Stores -turpentine, pitch, tar, resin
Oak, Hemlock, Butternut,Birch Sassafras Pine
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Extractives Conversion Strategies Dry in
Animal fodder Chlorophylls Carotenoids
g/g rind ing
Solvent extraction
h. tion c Mextrac e
Foliage
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
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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
Foliage
Stump extraction
Tapping
h. tion c Mextrac e
Tree
Solvent extraction
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Steam distillation
Tapping
Wood
Bark
Tannins Phenolic Acids Waxes
Leaf protein
Taxus Ginko
Essential oils Rosin Turpentine Maple syrup Kraft pulping
Solvent extraction Tannins Terpenes Lignans Coulouring matter
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Turpentine Tall oil
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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
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-highly hydrophobic Use: varnish,soap,laquer,inks, paper sizing, wax.
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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
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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
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Taxol • Bark of Pacific yew • 1960’s National Cancer Institute evaluated plants. Taxus brevifolia. • Extracted and tested for • • • • • •
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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
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Cellulose Conversion Strategies Cellulose derivatives Regenerated cellulose
Cellulose Hydrolysis
Paper Biocomposites
Glucose
Fengel & Wegener, 1984
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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
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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
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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.
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Cellulose Nitrate • One of the first synthetic polymers • Reaction product of high purity cellulose and nitric acid.
Cellulose
Nitric Acid
• Properties
Camphor
• Ignites easily • Moldable Faculty of Forestry
Cellulose nitrate
Celluloid University of Toronto
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Cellulose Nitrate • Uses: • Leather finishes • Printing ink additives • Lacquers and varnishes • Molded products • Gun cotton • Dental plates
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• Invented in 1862 • Substitute for ivory, tortoiseshell. • Very small industry today (fire hazard)
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Cellulose Acetate • Reaction product of high purity cellulose and acetic anhydride. Acetyl • Forms esters with acetate ions groups
Cellulose
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
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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
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Cellulose Ethers • Reaction of alkyl chlorides with alkali cellulose • • • • •
Methylcellulose (MC) Ethylcellulose (EC) Carboxymethylcellulose (CMC) Hydroxyethylcellulose (HEC) Cyanoethylcellullose
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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
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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
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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
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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
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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
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Cellulose Conversion Strategies Cellulose Hydrolysis
Glucose
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
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Pre-treatments Mechanical Ball milling Two roll milling
Hammer milling
Chemical
Physical
Biological
Phosphoric acid Hydrochloric acid
Steaming
White rot fungi
Wetting
Sulphuric acid Pulping
Vibratory rod milling
Acetic acid
Freezing / thawing
Colloid milling
Ammonia
Radiation
Extrusion
Sodium hydroxide Sulphur dioxide
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Combination Steam explosion Hightemperature milling Alkali + ball milling SO2 + steaming NO2 + irradiation Biomech.l pulping
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Cellulose Conversion Strategies Cellulose Hydrolysis Hydroxymethyl furfual Levulinic acid Polyamides Polyesters Polycarbonates Expoxides MTHF
Glucose HydrogenationSorbitol
Acid treatment
Vitamin C
Fermentation Acetone
Alcohols
Butanol Isopropanol Gycerol 2,3-butanediol
Ethanol Ethene Butadiene
Polyethene Polystyrene Polyvinyl chloride Synthetic rubber
Yeast
Acids
Proteins Vitamins (â&#x20AC;&#x2DC;Bâ&#x20AC;&#x2122;) Fat Amino acids
Acetic Lactic Citric Butyric Gluconic
Fengel & Wegener, 1984
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Polyose Conversion Strategies Polyoses Spent liquor
Paper additive
Hydrolysis
Fermentation
Xylose Acid treatment
atio oge n
Hyd r
Ethanol Yeast
Further processing
ena tion
Mannitol
Emulsifier
Furfural
Furan Tetrahydrofuran Polyurethanes
Hyd rog
n atio
Xylitol
rific
Further processing
Mannose Este
n
Yeast
Fermentation
Nylon 6,6
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Furfuryl alcohol Esters
Furan carbonic acid Furan resins
Nylon 5
Furfuryl acrylic acid Acrylates
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Maleic acid Resins Polymers
37 1984 Fengel & Wegener, 04/14/14
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
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Lignin Conversion Strategies Phenols
Carbonic acids
Alka Vanillin hyd line roly Syringaldehyde sis/o Vanillic acid xida tion Combustion Energy
Adhesive Resin component
DMS
Tar n latio
DMS
Alkali fusion thy e m de i l a Alk Lignin Hydrogenolysis Phenols Tar Oil
DMSO
Phenol Benzene
Pyrolysis
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
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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
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Energy Other products
Polyose
Roughage Fiberboard
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Other products Fengel & Wegener, 1984
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Conclusion I never knew these things came from woodâ&#x20AC;Ś Acids
Dyes
Gas
Fabrics
Plastics
Vitamins
Food additives
Pharmaceuticals Toys
Protein supplement
Sugars Diapers
films
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Animal Fodder Glues
Resins
Emulsifiers
Liquid Fuels
Essential Oils
Furniture
Filter tips
Explosives
Dietary fibre
membranes
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Dust control
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