Lignin extraction

Fiber Cellulose HemiceUulo se Pectins Lignin Extractives... 

Pulping process Tree species Cellulose (%) Hemicellulose (%) Lignin (%) Extractives (%) ... 

Figure 2. Relative rates of lignin extraction as measured by the optical density at 280 m i. All reactions under nitrogen at 90°C and with 0.2N HCl in dioxane.

Ralph, J., Hatfield, R. D., Piquemal, J., Yahiaoui, N., Pean, M., Lapierre, C., Boudet, A. M., 1998, NMR characterization of altered lignins extracted from tobacco plants down-regulated for lignification enzymes cinnamyl alcohol dehydrogenase and cinnamyl-CoA reductase, Proc. Natl. Acad. Sci. USA 95 12803-12808. 

In the latter part of the 1950s, this author (Hayes, 1960) attempted to repeat the experimentation used by Waksman and Iyer (1932,1933). He exhaustively washed powdered wheat straw with boiling water, then with hot dilute hydrochloric acid, and extracted twice for 5h in an autoclave at 120 °C, each time with a 4% sodium hydroxide solution. The combined filtrates were acidified to pH 4 with hydrochloric acid and the precipitate formed was washed free of chloride and freeze-dried. A ligno-casein complex was formed by reacting three parts of the lignin extract and one part casein in a 0.1 M solution of sodium hydroxide and collecting the precipitate formed when the pH was adjusted to 4. This complex was washed free of chloride and freeze-dried. A 6 1 lignin-protein complex was formed in the same way. 

Figure 10. Fractionation of the low molecular weight lignin extract obtained after acid hydrolysis of bleached CTMP.

Apart from hemicellulose and cellulose, lignin is also a promising raw material for various applications. Huttermann et al. (2001) described various potential technologies for lignin modification for the production of new compounded materials. Pan et al. (2005) demonstrated that lignin extracted during ethanol organosolv... 

Bjorkman A, Person B (1957) Studies on finely divided wood Part 2 The properties of lignins extracted with neutral solvents from softwoods and hardwoods Sven Papperstidn 60 158-169... 

Bjorkman A, Person B (1957) Studies on finely divided wood Part 4 Some reactions of the lignin extracted by neutral solvents from Picea abies Sven Papperstidn 60 285-292 Chang H-M, Cowling EB, Brown W, Adler E, Miksche G (1975) Comparative studies on cellulolytic enzyme lignin and milled wood lignin of sweetgum and spruce Holzforschung 29 153-159... 

Lignocellulosic source Cellulose Hemicellulose Lignin Extract... 

Biomass is composed of various components such as cellulose, hemicellulose, lignin, extractives and mineral water. The composition of biomass plays a definitive role in altering the product distribution and their properties [2-3J. As is shown in earlier publications [4-S] different biomass, on pyrolysis, give different product yield with different product properties. In order to choose a biomass for a particular process (carbonisation, liquefaction, gasification or adsorbent char) knowledge on the product distribution and properties for various biomass are essential. 

Until the 1920s, wood chemistry was a significant scientific discipline. The advent of petroleum chemistry took wood chemistry out of the limelight. Over the past 20 years, the steady decline of trained people in carbohydrate, lignin extractives, and wood chemistry has reduced drastically the available work force, and these workers are scattered around the world. The easy wood chemistry questions have been answered the more difficult ones will require a well-directed, cooperative research effort. We may not be able to answer the difficult questions, but through multidisciplinary research we will, at least, be able to ask more intelligent ones. 

---