Patent ID: 8038842
Filing Date: 2011-10-18
Classification: D21C

Abstract:
1. A process for fractionating a lignocellulosic material, said process comprising: (a) providing a liquid solution comprising an aliphatic alcohol, water, sulfur dioxide, and ammonia, wherein said sulfur dioxide is present in a concentration of from 10 wt % to 50 wt % of said liquid solution; (b) contacting a lignocellulosic material with a vapor phase of said liquid solution in a cooking stage, wherein said vapor phase comprises water vapor, alcohol vapor, ammonia, and sulfur dioxide gas; (c) delignifying said lignocellulosic material with said vapor phase in said cooking stage at a cooking temperature selected from 115° C. to 160° C., a cooking pressure selected from 1 atm to 20 atm, and a cooking time selected from 5 minutes to 3 hours, to produce a mixture comprising cellulose, hemicellulose oligomers, and lignin; and (d) removing cellulose from said mixture and washing said cellulose with a washing solution comprising a second amount of said aliphatic alcohol and a second amount of water, to produce a chemical pulp product and a liquid hydrolyzate stream comprising sugars and lignin.