Lignin-coated cellulose fibers from lignocellulosic biomass

Abstract

A process is provided for producing a lignin-coated cellulose material, comprising: pre-extracting a lignocellulosic biomass feedstock in the presence of steam or hot water, depositing lignin from the liquid onto a surface of solids to generate a lignin-coated intermediate material; optionally drying the intermediate material; digesting the lignin-coated intermediate material in the presence of an acid, a solvent for lignin, and water, wherein the rate of delignification of surface lignin is lower than the rate of delignification of bulk lignin; and recovering a hydrophobic lignin-coated cellulose material. In some variations, part of the overall process is a combination of Green Power+® and AVAP® technologies. A cellulose-rich composition is provided, containing about 5 wt % to about 15 wt % total lignin, with particles having a higher average surface concentration of lignin compared to an average bulk (internal) concentration of lignin.

What is claimed is: 
     
         1 . A process for producing a lignin-coated cellulose material, said process comprising:
 (a) providing a lignocellulosic biomass feedstock;   (b) pre-extracting said feedstock in the presence of steam or hot water, thereby generating a first solids stream and a first liquid stream, wherein said first liquid stream contains hemicelluloses and lignin;   (c) depositing at least some of said lignin, from said first liquid stream, onto a surface of said first solids stream to generate a lignin-coated intermediate material comprising cellulose-rich particles with a lignin coating;   (d) optionally drying said lignin-coated intermediate material;   (e) digesting said lignin-coated intermediate material in the presence of an acid, a solvent for lignin, and water, to generate a second solids stream and a second liquid stream, wherein during said digesting, the rate of delignification of surface lignin deposited from step (c) is lower than the rate of delignification of bulk lignin, thereby retaining at least a portion of said lignin coating; and   (f) recovering said second solids stream as a lignin-coated cellulose material, wherein said lignin-coated cellulose material is at least partially hydrophobic.   
     
     
         2 . The process of  claim 1 , wherein step (b) further includes introducing an acid catalyst to enhance lignin deposition. 
     
     
         3 . The process of  claim 2 , wherein said acid catalyst includes an acid selected from the group consisting of acetic acid, formic acid, uronic acids, levulinic acid, sulfur dioxide, sulfurous acid, sulfuric acid, lignosulfonic acid, carbon dioxide, carbonic acid, and combinations thereof. 
     
     
         4 . The process of  claim 1 , wherein said drying is conducted in step (d). 
     
     
         5 . The process of  claim 1 , wherein said acid in step (e) is selected from the group consisting of sulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid, lignosulfonic acid, and combinations thereof. 
     
     
         6 . The process of  claim 5 , wherein said acid is sulfur dioxide. 
     
     
         7 . The process of  claim 1 , said process further comprising hydrolyzing said hemicelluloses to produce monomeric sugars. 
     
     
         8 . The process of  claim 1 , wherein said second liquid stream contains hemicellulose oligomers; said process further comprising hydrolyzing said hemicellulose oligomers to monomers. 
     
     
         9 . The process of  claim 8 , wherein said hemicellulose oligomers and said hemicelluloses from step (b) are combined and hydrolyzed in a single reactor. 
     
     
         10 . The process of  claim 1 , wherein said lignin-coated cellulose material includes one or more materials selected from the group consisting of pulp, dissolving pulp, fibrillated cellulose, microcrystalline cellulose, and nanocellulose. 
     
     
         11 . The process of  claim 1 , wherein said lignin-coated cellulose material is combusted as a lignin-rich cellulosic fuel. 
     
     
         12 . The process of  claim 1 , said process further comprising recovering, combusting, or further treating said lignin that does not deposit during step (c). 
     
     
         13 . The process of  claim 1 , wherein said lignin-coated cellulose material contains, on a dry basis, about 3 wt % or less hemicellulose content. 
     
     
         14 . A cellulose-rich composition comprising from about 70 wt % to about 90 wt % cellulose and about 5 wt % to about 15 wt % total lignin, wherein said cellulose-rich composition includes particles with a higher average surface concentration of lignin compared to an average bulk (internal) concentration of lignin. 
     
     
         15 . The cellulose-rich composition of  claim 14 , wherein said composition comprises from about 75 wt % to about 87 wt % cellulose. 
     
     
         16 . The cellulose-rich composition of  claim 14 , wherein said composition comprises from about 7 wt % to about 12 wt % lignin. 
     
     
         17 . The cellulose-rich composition of  claim 14 , wherein said composition comprises about 3 wt % or less hemicellulose. 
     
     
         18 . The cellulose-rich composition of  claim 17 , wherein said composition comprises about 2 wt % or less hemicellulose. 
     
     
         19 . The cellulose-rich composition of  claim 14 , wherein said composition comprises from about 1 wt % to about 2 wt % uronic acid groups. 
     
     
         20 . The cellulose-rich composition of  claim 14 , wherein said composition comprises about 2 wt % or less ash. 
     
     
         21 . The cellulose-rich composition of  claim 14 , wherein said composition is characterized by a ratio H/(C+H) of about 0.03 to about 0.04, wherein H is total hemicellulose and C is total cellulose. 
     
     
         22 . The cellulose-rich composition of  claim 14 , wherein said composition is produced by a process comprising:
 (a) providing a lignocellulosic biomass feedstock;   (b) pre-extracting said feedstock in the presence of steam or hot water, thereby generating a first solids stream and a first liquid stream, wherein said first liquid stream contains hemicelluloses and lignin;   (c) depositing at least some of said lignin, from said first liquid stream, onto a surface of said first solids stream to generate a lignin-coated intermediate material comprising cellulose-rich particles with a lignin coating;   (d) optionally drying said lignin-coated intermediate material;   (e) digesting said lignin-coated intermediate material in the presence of an acid, a solvent for lignin, and water, to generate a second solids stream and a second liquid stream, wherein during said digesting, the rate of delignification of surface lignin deposited from step (c) is lower than the rate of delignification of bulk lignin, thereby retaining at least a portion of said lignin coating; and   (f) recovering said second solids stream as a lignin-coated cellulose-rich composition, wherein said lignin-coated cellulose-rich composition is at least partially hydrophobic.   
     
     
         23 . A cellulose-containing product comprising the cellulose-rich composition of  claim 14 . 
     
     
         24 . The cellulose-containing product of  claim 23 , wherein said cellulose-containing product is selected from the group consisting of a structural object, a foam, an aerogel, a polymer composite, a carbon composite, a film, a coating, a coating precursor, a current or voltage carrier, a filter, a membrane, a catalyst, a catalyst substrate, a coating additive, a paint additive, an adhesive additive, a cement additive, a paper coating, a thickening agent, a rheological modifier, an additive for a drilling fluid, and combinations or derivatives thereof.