Wood Chemistry PSE 406 Review

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

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

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

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

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.

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.

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%

Isolation Scheme: Softwoods HClO2 Holocellulose KOH Soluble Insoluble Hemicellulose Mixture Residue NaOH/Borate Insoluble Soluble Cellulose Crude Glucomannan Ref: Timell: TAPPI 44, 88-96 1961

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.

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

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

Tree Species Differences

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

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

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

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, 1967. 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.

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

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.

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)

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).

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.

Wood chemicals Modifications and uses of: Cellulose Hemicelluloses Lignin Extractives

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