Method for vapor phase pulping with alcohol and sulfur dioxide

Abstract

A method for the fractionation of lignocellulosic materials into cellulose, hemicelluloses and lignin in a batch or continuous process in a treatment with vaporous mixture of aliphatic alcohol, sulfur dioxide and water. Cooking conditions are varied to get different proportions of cellulose, hemicelluloses and lignin. Chemical recovery through pressure release is described.

1 - 23 . (canceled) 
     
     
         24 . A process for fractionating a lignocellulosic material, said process comprising:
 (a) providing a liquid solution comprising an aliphatic alcohol, water, and sulfur dioxide;   (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, and sulfur dioxide gas, and wherein a mass ratio of said liquid solution to said lignocellulosic material is from 1 to 3;   (c) delignifying said lignocellulosic material with said vapor phase in said cooking stage, to produce a mixture comprising cellulose, hemicellulose oligomers, and lignin; and   (d) removing cellulose from said mixture to generate a liquid hydrolyzate stream comprising hemicellulose oligomers and lignin.   
     
     
         25 . The process of  claim 24 , wherein said sulfur dioxide in step (a) is present in a concentration of from 9 wt % to 50 wt % of said liquid solution. 
     
     
         26 . The process of  claim 25 , wherein said sulfur dioxide in step (a) is present in a concentration of from 12 wt % to 25 wt % of said liquid solution. 
     
     
         27 . The process of  claim 24 , wherein said aliphatic alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, and any combinations thereof. 
     
     
         28 . The process of  claim 24 , wherein said vapor phase contains an alcohol-water mass ratio of said alcohol vapor to said water vapor of from 0.5 to 5. 
     
     
         29 . The process of  claim 24 , said process further comprising recovering residual aliphatic alcohol and sulfur dioxide and recycling said residual aliphatic alcohol and said sulfur dioxide to said cooking stage. 
     
     
         30 . The process of  claim 24 , wherein step (b) is conducted with a cooking temperature selected from 120° C. to 160° C. 
     
     
         31 . The process of  claim 24 , wherein step (b) is conducted with a cooking time selected from 5 minutes to 3 hours. 
     
     
         32 . The process of  claim 24 , said process further comprising 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. 
     
     
         33 . The process of  claim 32 , said process further comprising bleaching said chemical pulp product to produce paper furnish. 
     
     
         34 . A process for fractionating a lignocellulosic material, said process comprising:
 (a) contacting a lignocellulosic material with a liquid solution comprising an aliphatic alcohol, water, and sulfur dioxide in a cooking stage, wherein a mass ratio of said liquid solution to said lignocellulosic material is from 1 to 3;   (b) draining said liquid solution from said cooking stage;   (c) injecting a vapor solution comprising steam and said aliphatic alcohol into said cooking stage to reach a cooking temperature;   (d) delignifying said lignocellulosic material in a vapor phase within said cooking stage at said cooking temperature, to produce a mixture comprising cellulose, hemicellulose oligomers, and lignin; and   (e) removing cellulose from said mixture to produce a liquid hydrolyzate stream comprising hemicellulose oligomers and lignin.   
     
     
         35 . The process of  claim 34 , wherein said sulfur dioxide in step (a) is present in a concentration of from 9 wt % to 50 wt % of said liquid solution. 
     
     
         36 . The process of  claim 35 , wherein said sulfur dioxide in step (a) is present in a concentration of from 12 wt % to 25 wt % of said liquid solution. 
     
     
         37 . The process of  claim 34 , wherein said aliphatic alcohol is selected from the group consisting of methanol, ethanol, propanol, butanol, and any combinations thereof. 
     
     
         38 . The process of  claim 34 , wherein said vapor phase contains an alcohol-water mass ratio of said alcohol to said steam of from 0.5 to 5. 
     
     
         39 . The process of  claim 34 , said process further comprising recovering residual aliphatic alcohol and sulfur dioxide and recycling said residual aliphatic alcohol and said sulfur dioxide to said cooking stage. 
     
     
         40 . The process of  claim 34 , wherein said cooking temperature is selected from 120° C. to 160° C. 
     
     
         41 . The process of  claim 34 , wherein said cooking temperature is selected from 5 minutes to 3 hours. 
     
     
         42 . The process of  claim 34 , said process further comprising 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. 
     
     
         43 . The process of  claim 42 , said process further comprising bleaching said chemical pulp product to produce paper furnish.