GB579116A - Improvements in and relating to a method for saccharifying cellulosic materials by means of diluted mineral acids - Google Patents

Abstract

A process for the manufacture of sugar from cellulosic material by successive hydrolyses with dilute solutions of mineral acids is characterized in that between successive hydrolyses the solid material is exhaustively freed from the sugar produced during the earlier hydrolysis by systematic diffusion in a battery separate from the hydrolysing chamber, preferably using the same strength aqueous acid solution as will be used for the following hydrolysis. In an example wood chips are allowed to soak in dilute acid solution, preferably 6-2 grams/litre HCl or 10-3 grams/litre H2 SO4, for 30 minutes at 90 DEG C. and after draining are cooked without further addition of acid for 45 minutes at 165 DEG C. The chips are then countercurrently extracted in a diffusion battery with acid which is more dilute than that used in the initial cooking process. The process is then repeated three times at increasing cooking temperatures up to 200 DEG C. but with decreasing acidites and in cooking vessels of decreasing size, the final extract being with water instead of acid. The resulting lignin may be utilised for the preparation of high grade charcoal. The sugar solution resulting from the first hydrolysis being rich in pentoses may be separately treated to yield furtural. In a modification the diffusion is carried out and acid is added to the extracted material before re-cooking. The sugar solutions may be processed to obtain the sugars or fermented to produce alcohol according to the method of Specification 393,082.