Organosolv delignification and saccharification process for lignocellulosic plant materials

In a process for the production of carbohydrate hydrolysates and lignins from a lignocellulosic material, by treating the material in a pressure vessel with a solvent mixture with water containing a small quantity of an acid selected from the group consisting of hydrochloric, sulphuric and phosphoric acids at an elevated temperature to solubilize the carbohydrate and lignins and until sugars are formed in solubilized form in a liquor the improvement which comprises the steps of:

• (a) supplying a solvent mixture containing the acid in an amount between 0.05 and 0.25 percent by weight of the mixture of hydrochloric acid or between 0.15 and 0.25 percent by weight of the mixture of sulfuric or phosphoric acids, water and acetone in a volume ratio of acetone to water of between 70 to 30 and 60 to 40 into the vessel under pressure to provide a limited retention time of the solvent mixture in the vessel of seven minutes or less and then removing the solvent mixture as the liquor, wherein the liquor collected initially from the vessel contains the lignin and is separated from liquor collected subsequently after the liquor with the lignin is removed which contains the sugars, and wherein the sugars from the hydrolysis are not dehydrated or degraded into non-sugars;
• (b) rapidly cooling the hydrolysis liquors as they are removed from the vessel to prevent degradation of sugars to non sugars by removing the acetone wherein the lignins in the liquor collected initially are precipitated by the removal of the acetone;
• (c) removing the precipitated lignin from the hydrolysis liquor collected initially;
• and
• (d) recovering the sugars from the hydrolysis liquors collected initially and subsequently.