Organic biomass fractionation process

Abstract

A method for fractionating fibrous biomass comprising cellulose, hemicellulose and lignin components to separate said lignin, cellulose and hemicellulose from one another comprises: (a) shredding said fibrous biomass; (b) concurrently with or subsequent to said shredding, contacting said biomass with an aqueous solution of a nitrate ion source at a concentration of about 0.1-0.3% at a temperature in the range of about 60° to about 80° C. to initiate nitration of the lignin component of said biomass; (c) submerging said partially nitrated biomass in an aqueous solution of a nitrate ion source in the presence of an aluminum compound at a temperature within the range of about 75-100° C. for a time sufficient to complete the nitration of said lignin component; (d) contacting the nitrated biomass produced in step (c) with an alkaline extraction liquor comprising NH 4 OH at an initial concentration sufficient to solubilize said nitrated lignin component and said hemicellulose component from said cellulose component of said biomass; e) recovering said cellulose from said extraction liquor containing said solubilized nitrated lignin and hemicellulose components, wherein said cellulose comprises at least about 88% alpha cellulose; (f) treating said extraction liquor with an acid to precipitate lignin contained therein, and (g) separating said lignin from soluble hemicellulose in said extraction liquor. The recovered cellulose component comprises at least 88% alpha cellulose and is useful as a starting material for the production of ethanol.

1 . A method for fractionating fibrous biomass comprising cellulose, hemicellulose and lignin components to separate said lignin, cellulose and hemicellulose from one another comprises: 
 (a) shredding said fibrous biomass;    (b) concurrently with or prior to said shredding, contacting said biomass with an aqueous solution of a nitrate ion source at a concentration of about 0.1-0.3% at a temperature in the range of about 60° to about 80° C. to initiate nitration of the lignin component of said biomass;    (c) submerging said partially nitrated biomass in an aqueous solution of a nitrate ion source in the presence of an aluminum compound at a temperature within the range of about 75-100° C. for a time sufficient to complete the nitration of said lignin component;    (d) contacting the nitrated biomass produced in step (c) with an alkaline extraction liquor comprising NH 4 OH at an initial concentration sufficient to solubilize said nitrated lignin component and said hemicellulose component from said cellulose component of said biomass;    (e) recovering said cellulose from said extraction liquor containing said solubilized nitrated lignin and hemicellulose components, wherein said cellulose comprises at least about 88% alpha cellulose;    (f) treating said extraction liquor with an acid to precipitate lignin contained therein, and    (g) separating said lignin from soluble hemicellulose in said extraction liquor.    
     
     
         2 . The method of  claim 1 , wherein said biomass comprises woody material or grassy or straw material.  
     
     
         3 . The method of  claim 1 , wherein said nitrate ion source used to initiate nitration of said lignin in step (b) comprises HNO 3.    
     
     
         4 . The method of  claim 3 , wherein said solution of said nitrate ion source in step (c) comprises about 1% to about 6% HNO 3 .  
     
     
         5 . The method of  claim 4 , wherein said biomass is contacted with said solution of said nitrate ion source in step (c) for about 30 to 180 minutes.  
     
     
         6 . The method of  claim 4 , wherein said biomass comprises straw or grass and said solution of said nitrate ion source comprises about 1.0% to about 1.5% HNO 3 .  
     
     
         7 . The method of  claim 4 , wherein said biomass comprises corn stover, hemp or kenaf and said solution of said nitrate ion source comprises about 2.0% to about 2.5% HNO 3 .  
     
     
         8 . The method of  claim 4 , wherein said biomass comprises shredded brush or hardwood and said dilute solution of said nitrate ion source comprises about 3.0% to about 4.0% HNO 3 .  
     
     
         9 . The method of  claim 4 , wherein said biomass comprises shredded coniferous wood and said solution of said nitrate ion source comprises about 5.0% to about 6.0% HNO 3 .  
     
     
         10 . The method of  claim 1 , wherein said aluminum compound comprises alum.  
     
     
         11 . The method of  claim 1 , wherein said nitrated biomass is washed prior to contacting it with said alkaline extraction liquor.  
     
     
         12 . The method of  claim 1 , wherein said alkaline extraction liquor has a pH within the range of about 11 to 12 following contact with said nitrated biomass.  
     
     
         13 . The method of  claim 12 , wherein said extraction step is carried out at a temperature within the range of about 80° and about 100° C.  
     
     
         14 . The method of  claim 1  wherein said nitrated biomass is contacted with said alkaline extraction liquor for a period of about 30-60 minutes.  
     
     
         15 . The method of  claim 1 , wherein said cellulose separated from said extraction liquor comprises at least 90% alpha cellulose.  
     
     
         16 . The method of  claim 15 , wherein said cellulose separated from said extraction liquor comprises at least about 93% alpha cellulose.  
     
     
         17 . The method of  claim 1 , wherein said extraction liquor in step (f) is treated with HNO 3  to precipitate said lignin.  
     
     
         18 . The method of  claim 17 , wherein said extraction liquor is acidified to a pH of about 5.0 to about 6.  
     
     
         19 . A method for fractionating fibrous biomass comprising cellulose, hemicellulose and lignin components to separate said lignin, cellulose and hemicellulose from one another comprises: 
 (a) shredding said fibrous biomass;    (b) concurrently with or subsequent to said shredding, contacting said biomass with an aqueous solution of HNO 3  at a concentration of about 0.1-0.3% to initiate nitration of the lignin component of said biomass;    (c) submerging said partially nitrated biomass in an aqueous solution of about 1% to about 6% HNO 3  in the presence of alum at a temperature in the range of about 75-100° C. for a time sufficient to complete the nitration of said lignin component;    (d) washing said nitrated biomass;    (e) submerging the nitrated biomass produced in step (d) in an alkaline extraction liquor comprising NH 4 OH at a concentration sufficient to extract said nitrated lignin component and said hemicellulose component from said cellulose component of said biomass;    (f) recovering said cellulose from said extraction liquor containing said nitrated lignin and hemicellulose components, wherein said cellulose comprises at least about 88% alpha cellulose;    (g) treating said extraction liquor with acid to precipitate said lignin contained therein, and    (h) separating said lignin from said hemicellulose-containing liquor.    
     
     
         20 . A method of obtaining cellulose from fibrous biomass comprising cellulose, hemicellulose and lignin components which comprises: 
 (a) shredding said fibrous biomass;    (b) concurrently with or prior to said shredding, contacting said biomass with an aqueous solution of a nitrating ion source at a concentration of about 0.1-0.3% to initiate nitration of the lignin component of said biomass;    (c) submerging said partially nitrated biomass in an aqueous solution of a nitrate ion source in the presence of an aluminum compound at a temperature of less than about 100° C. for a time sufficient to complete the nitration of said lignin component;    (d) contacting the nitrated biomass produced in step (c) with an alkaline extraction liquor comprising NH 4 OH in an amount sufficient to extract said nitrated lignin component and said hemicellulose component from said cellulose component of said biomass; and    (e) recovering said cellulose from said extraction liquor containing said nitrated lignin and hemicellulose components, wherein said cellulose comprises at least about 88% alpha cellulose.    
     
     
         21 . The method of  claim 20 , wherein said nitrate ion source used to initiate nitration of said lignin in step (b) comprises HNO 3 .  
     
     
         22 . The method of  claim 20 , wherein said solution of said nitrate ion source in step (c) comprises about 1% to about 6% HNO.  
     
     
         23 . The method of  claim 22 , wherein said biomass is contacted with said solution of said nitrate ion source in step (c) for about 30 to 180 minutes.  
     
     
         24 . The method of  claim 20 , wherein said aluminum compound comprises alum.  
     
     
         25 . The method of  claim 20 , wherein said alkaline extraction liquor has a pH within the range of about 11 to 12 following contact with said nitrated biomass.  
     
     
         26 . The method of  claim 20 , wherein said extraction step is carried out at a temperature within the range of about 80° to about 100° C.  
     
     
         27 . The method of  claim 20 , wherein said cellulose comprises at least about 90% alpha cellulose.  
     
     
         28 . A method of obtaining ethanol from fibrous biomass comprising cellulose, hemicellulose and lignin components which comprises: 
 (a) shredding said fibrous biomass;    (b) concurrently with or prior to said shredding, contacting said biomass with an aqueous solution of a nitrating ion source at a concentration of about 0.1-0.3% to initiate nitration of the lignin component of said biomass;    (c) submerging said partially nitrated biomass in an aqueous solution of said nitrate ion source in the presence of an aluminum compound at a temperature of less than about 100° C. for a time sufficient to complete the nitration of said lignin component;    (d) contacting the nitrated biomass produced in step (c) with an alkaline extraction liquor comprising NH 4 OH in an amount sufficient to extract said nitrated lignin component and said hemicellulose component from said cellulose component of said biomass;    (e) recovering said cellulose from said extraction liquor containing said nitrated lignin and hemicellulose components, wherein said cellulose comprises at least about 88% alpha cellulose;    (f) washing said recovered cellulose;    (g) converting said cellulose into glucose sugars and    (h) fermenting said glucose sugars to produce ethanol.