Extraction of lignocellulosics for production of fibers and a precipitate-free hemicellulose extract

Abstract

The present invention provides, among other things, methods including providing a biomass comprising lignin, associating the biomass with between 1-50 g/L formic acid at a temperature between 80° C. and 230° C. for at least 30 seconds to form an extraction liquor and an extraction solid, and separating at least a fraction of the extraction liquor from the extraction solid, wherein an amount of lignin equal to or less than 1.6% of the lignin present in the biomass precipitates in the extraction liquor after cooling to below 100° C.

1 . A method comprising
 providing a biomass comprising lignin;   associating the biomass with between 1-50 g/L formic acid at a temperature between 80° C. and 230° C. for at least 30 seconds to form an extraction liquor and an extraction solid; and   separating at least a fraction of the extraction liquor from the extraction solid;   
       wherein an amount of lignin equal to or less than 1.6% of the lignin present in the biomass precipitates in the extraction liquor after cooling to below 100° C. 
     
     
         2 . The method of  claim 1 , wherein the formic acid is provided as a liquid or a gas. 
     
     
         3 . The method of  claim 1 , wherein the associating step further comprises associating the biomass with water. 
     
     
         4 . The method of  claim 3 , wherein the water is provided as a liquid or a gas. 
     
     
         5 . The method of  claim 1 , further comprising washing said extraction solid by associating at least a portion of the extraction solid with water at a temperature between 80° C. and 230° C. for at least 30 seconds to form a wash liquor. 
     
     
         6 . The method of  claim 5 , wherein the water is provided as a liquid or a gas. 
     
     
         7 . The method of  claim 5 , wherein the washing step further comprises associating at least a portion of the extraction solid with between 1-50 g/L formic acid. 
     
     
         8 . The method of  claim 7 , wherein the formic acid is provided as a liquid or a gas. 
     
     
         9 . The method of  claim 5 , wherein the extraction liquor and wash liquor together comprise at least 7% of the anhydrosugars present in the biomass, based on the oven dry weight of the biomass. 
     
     
         10 . The method of  claim 5 , wherein the washing step occurs at between 100° C. and 230° C., inclusive. 
     
     
         11 . The method of  claim 5 , wherein the washing step occurs at between 150° C. to 170° C., inclusive. 
     
     
         12 . The method of  claim 5 , wherein the washing step occurs for between 30 seconds and 4 hours, inclusive. 
     
     
         13 . The method of  claim 5 , wherein an amount of lignin equal to or less than 1.0% of the lignin present in the biomass precipitates in the wash liquor after cooling to below 100° C. 
     
     
         14 . The method of  claim 5 , wherein an amount of lignin equal to or less than 0.5% of the lignin present in the biomass precipitates in the wash liquor after cooling to below 100° C. 
     
     
         15 . The method of  claim 1 , wherein the biomass is selected from: wood chips, wood sawdust, wood residuals, agricultural cellulosic biomass, municipal solid waste, and mixtures thereof. 
     
     
         16 . The method of  claim 1 , wherein the associating step occurs at a temperature between 100° C. and 230° C., inclusive. 
     
     
         17 . The method of  claim 1 , wherein the associating step occurs at a temperature between 150° C. to 170° C., inclusive. 
     
     
         18 . The method of  claim 1 , wherein the associating step occurs for between 30 seconds and 4 hours, inclusive. 
     
     
         19 . The method of  claim 1 , wherein an amount of lignin equal to or less than 1.0% of the lignin present in the biomass precipitates in the extraction liquor after cooling to below 100° C. 
     
     
         20 . The method of  claim 1 , wherein an amount of lignin equal to or less than 0.5% of the lignin present in the biomass precipitates in the extraction liquor after cooling to below 100° C. 
     
     
         21 . The method of  claim 5 , wherein at least a fraction of the extraction liquor and wash liquor are associated with each other. 
     
     
         22 . The method of  claim 1 , wherein at least one of the extraction liquor and extraction solid are cooled to below 100° C. prior to the separating step. 
     
     
         23 . The method of  claim 1 , wherein the associating step further comprises associating the biomass with sulfuric acid. 
     
     
         24 . The method of  claim 23 , wherein the biomass is associated with up to 5 g/L sulfuric acid. 
     
     
         25 . The method of  claim 23 , wherein the biomass is associated with between 1 and 2 g/L sulfuric acid, inclusive.