1. Wood Chemistry PSE 406
Review

2. Steam Distillation
In this procedure, volatile extractives are removed through the action of steam.
Compounds removed include:
Monoterpenes
Sesquiterpenes
Diterpenes
Triterpenes (not oids)
Tetraterpenes (not oids)
Phenols
Hydrocarbons
Some lignans

3. Ether Extraction
Ether is typically used to remove lipophillic materials.
Fats/Oils
Fatty acids
Waxes
Resin Acids
Sterols

4. Alcohol Extraction
Ethyl alcohol (typically) or methanol is used in a similar fashion to ether extraction.
Materials removed:
Tannins
Stilbenes
Flavonoids
Lignans

5. Water Extraction Hot water is used to remove the following:
Carbohydrates
Proteins
Alkaloids
Starch
Pectins
Inorganics

6. Holocellulose
Holocellulose is the term which describes the mixture of cellulose and hemicelluloses produced when lignin is removed.
Lignin can be removed through the action of chlorine followed by alcohol extraction.
Another procedure (I like this one) is delignification with acidified solutions of sodium chlorite.
There are a significantly large number of other possible procedures which have been published.
What is left from these procedures is a very white material which contains a little lignin and has lost a little bit of the carbohydrates.

7. Direct Cellulose Isolation
It is possible to directly isolate cellulose from plant matter.
Digestion of material in nitric acid and ethanol.
Refluxing material in acetyl-acetone and dioxane acidified with HCl
Treatment of material with chlorine and nitrogen dioxide in DMSO
These, and other, procedures give high purity but also highly degraded cellulose.

8. Cellulose Isolation
A Tappi Standard procedure for cellulose isolation from holocellulose is as follows:
Extract holocellulose with 5% and then 24% KOH to remove hemicelluloses. The remaining material is termed alpha-cellulose
This results in cellulose of reduced molecular weight and some yield loss. Typical recoveries are 40-60%

9. Isolation Scheme: Softwoods
HClO2
Holocellulose
KOH
Soluble
Insoluble
Hemicellulose Mixture
Residue
NaOH/Borate
Insoluble
Soluble
Cellulose
Crude Glucomannan
Ref: Timell: TAPPI 44,

10. Barium
Because of the orientation of the C2 and C3 hydroxyl groups in mannose, it will form an insoluble complex with barium ions.
Therefore the addition of Ba(OH)2 will cause glucomannans to precipitate out of solution.

11. Derivitization
Gas Chromatography - Chemicals to be analyzed must be volatile: Sugars and uronic acids are not volatile.
Blocking hydroxyl groups will make chemicals volatile.
Derivitization procedures:
Methylation
Acetylation
Silylation

12. Quantification of Lignin
Wood and non-woody materials
Acid Insoluble lignin (along with acid soluble lig)
Pulp
Kappa number
Other non woody materials (or I don’t have a large sample to work with)
Acetyl bromide

13. Tree Species Differences

14. Macroscopic Structure
Annual Rings
Outer Bark
(dead, protection, high extractives)
Phloem
(inner bark)
(transportation of water
and nutrients)
Pith
Cambium
(growth, inward wood,
outward bark)
Xylem
=wood
Heartwood
(support, dead, dark)
Earlywood
Knot
Sapwood
(younger, light color, living cells, transportation)
Latewood

15. Reaction Wood This is a very poor representation of a very bent tree
Tension Wood
(Hardwoods)
Compression Wood
(Softwoods)
Tension or
Compression
Wood

16. Microscopic Structure
Resin canals (epithelium parenchyma secretes resin epithelium parenchyma secretes resin)
Rays (transportation of water)
Tracheid (support, water transport, softwoods),
in hardwoods we have libriform fibers)
Pits (wholes, transport between fibers, different typs)
Microscopic structure of wood (Textbook of Wood Technology, Panshin, A. J., page 118

17. Microscopic Structure
W-warty layer, thin,
storage of metabolites
S (S1+S2+S3)-secondary wall, the thickest,
microfibrils - opposite direction
P-primary wall, very thin, random microfibrils,
ML-space between cells, 70-80% lignin, glue
Structure of woody cell by Cote, This figure is used by almost every wood chemistry text. It can be found in Wood Chemistry, Fundamentals and Applications by Sjostrom on page 14.

18. Fungi The wood deteriorating fungi are organized into three groups:
White rot fungi
Brown rot fungi
Soft rot fungi

19. Molds and Blue Stain Fungi
Wood is often stained by these organisms with little loss of structural integrity.
Particularly in softwoods, some strength loss in hardwoods.
Molds: Aspergillus, Penicillium etc.
Blue Stain Fungi: Philaphora, etc.
These organisms typically attack non lignified parenchyma cells and pit membranes.

20. Soil Organics
The answer to the question on the last slide is of course not, the organic material doesn’t disappear it is simple changed into the soil organics: Fulvic Acids, Humic acids, and Humins. These materials are classified by their solubility.
Fulvic Acids (Acid soluble fraction)
Humic acids (Alkali soluble fraction/ acid insoluble)
Humins (Insoluble organics)

21. Structure of Soil Organics
These soils organics are large polymers and thus like lignin structural determination is somewhat difficult.
Fulvic acid Mw~2000+, humic acids higher, humins as high as 300,000?
These materials are more difficult than lignin for structural studies because they are produced from so many different materials (unlike lignin: 3 possible precursors).

22. Proposed Humic Acid Structure
This is a proposed segment of humic acid by Stevenson*
Notice the phenolics, the sugars, and the peptides
It is obvious that this molecule does not arise directly from any component but is built from pieces of other components.

23. Wood chemicals Modifications and uses of: Cellulose Hemicelluloses
Lignin
Extractives

24. Bioenergy Pretreatment: Lecture 21 Hydrolysis: Lecture 22
What and why bioconversion?
Possible feedstocks?
Process flow diagram
Type of pretreatments (organosolv pulping, steam explosion)
Steam explosion (conditions, how does it work?)
Why using SO2 catalyst?
What is the severity factor? Why do you have to optimize the pretreatment conditions?
Hydrolysis: Lecture 22
What types of enzymes do we need for enzymatic hydrolysis and where are they coming from?
How do we do enzymatic hydrolysis (microplates, shaker flasks, reactors)? How do we measure the progress of enzymatic hydrolysis?
Fermentation: Lecture 23
What is fermentation?
Fermentation products? Why S. cerevisiae? Conversion factor 6C sugars to ethanol?
Possible inhibitors?
SHF versus SSF (pros and cons)
Biodiesel: Lecture 24
How do we produce biodiesel (transesterification)?
Why biodiesel?
Possible sources?
Compare bioethanol and biodiesel in terms of:
Fuel efficiency
Industrial maturity of the process
Sources
Complexity of the process