Alcohol from Cellulosics: The Autohydrolysis-Extraction Process

摘要

A process for the preparation of glucose from cellulosics for alcoholic fermentation is described. The cellulosics discussed are hardwoods such as aspen and the eucalypts, bagasse, straws, and other agricultural crop residues. For good yields of alcohol, cellulosics require pre-treatment before hydrolysis. An effective pre-treatment is autohydrolysis, which consists in steaming the cellulosic raw material at about 200 exp 0 C for about 20 minutes. This opens up the fibre, renders the hemicellulose soluble in hot water, and depolymerizes the lignin. When conditions are properly chosen, the lignin becomes readily soluble in dilute sodium hydroxide solution, from which it can be recovered as an active chemical by acidification. Steps in the basic process described are: (1) autohydrolysis; (2) hemicellulose extraction; (3) lignin extraction; (4) hydrolysis; (5) clarification of the wood sugar solutions; (6) fermentation-distillation. Acid hydrolysis is preferred in most cases, and this paper describes a partial hydrolysis-recycle process for obtaining glucose yields of 70-80% of the theoretical from cellulose. Conditions under which enzyme hydrolysis is capable of effecting 100% glucose yields, and which may be preferable in some cases, are also described. Attention is drawn to hemicellulose and lignin by-product values. (ERA citation 06:003593)