Hydrolysis of Vegetable Matter

the reaction of polysaccharides of inedible vegetable matter (wood wastes, cottonseed and sunflower-seed hulls, and so on) with water in the presence of catalysts (inorganic acids). The initial vegetable matter usually contains up to 75 percent water-insoluble polysaccharides in the form of cellulose and hemicelluloses, whose decomposition first yields intermediate compounds and then the simplest sugars, monoses. Monose formation is accompanied by their partial decomposition to furfural, organic acids, and humic acids. The rate of hydrolysis increases with increase in temperature and acid concentration.

The hydrolysis of vegetable matter is the basis of the hydrolysis industries, which manufacture important food, fodder, and industrial products. Under manufacturing conditions the products of hydrolysis are hydrolysates, which are solutions of monoses (pentoses and hexoses, particularly glucoses), volatiles (organic acids, alcohols), and a solid residue, hydrolysis lignin. The yield of monoses may be as high as 90 percent of the polysaccharides. The hydrolysates are subjected to further biochemical or chemical processing, depending on the profile of the hydrolysis industries and the kinds of commodity required.

The biochemical processing of hydrolysates to make protein-vitamin substances—nutrient yeast—is the most widespread. One of the most important products of the hydrolysis industry is ethyl alcohol, which is also made biochemically, by the fermentation of hexose hydrolysates.

Edible glucose and industrial xylose are obtained from hexose and pentose hydrolysates, respectively, by removing inorganic and organic impurities, evaporation, and crystallization. In the chemical processing of hydrolysates, the reduction of the monoses in them yields polyhydric alcohols; the hexoses yield the corresponding hexitols (sorbitol, man-nitol, dulcitol, and so on), and pentoses give pentitols (xylitol, arabitol, and others). Glycerol, propylene glycol, and ethylene glycol can be made by hydrogenolysis of polyhydric alcohols. Furfurol is obtained by dehydration of pentoses; its yield depends on the raw material composition and the conditions of hydrolysis and dehydration. Levulinic acid, which is used in a number of chemical syntheses, is formed upon dehydration of hexoses.

Lignin pyrolysis yields tars and semicoke; the latter is heat-activated to make active gas-absorbing and bleaching carbon. An active carbon, kollaktivit, is formed during the processing of hydrolysis lignin by concentrated sulfuric acid.When treated with alkalies, lignin dissolves, and subsequentacidification results in the separation of activated lignin,which is an active filler for synthetic rubber. Hydrolysislignin is also used as a fuel.