Solvent-based processes for producing nanocellulose, and compositions and products produced therefrom

Abstract

The present invention provides a process for producing a nanocellulose material, comprising: fractionating a lignocellulosic biomass feedstock in the presence of a solvent for lignin and water, but no acid catalyst, to generate cellulose-rich solids; and then mechanically treating the cellulose-rich solids to form a nanocellulose material comprising cellulose nanofibrils and/or cellulose nanocrystals. Many organic or inorganic solvents are possible. In some embodiments, the solvent for lignin is an oxygenated organic compound, such as a C 1 -C 18 alcohol, e.g. ethanol, ethylene glycol, propanol, propanediol, glycerol, butanol, or butanediol. The solvent for lignin may be an aromatic alcohol, such as phenol, cresol, or benzyl alcohol. The solvent for lignin may be a ketone, an aldehyde, or an ether, such as methyl ethyl ketone or diethyl ether. The solvent for lignin may be a non-oxygenated alkane, olefin, or aromatic hydrocarbon. In some embodiments, the solvent for lignin is an ionic liquid.

What is claimed is: 
     
         1 . A process for producing a nanocellulose material, said process comprising:
 (a) providing a lignocellulosic biomass feedstock;   (b) fractionating said feedstock in the presence of a solvent for lignin and water, but no acid catalyst, to generate cellulose-rich solids and a liquid containing hemicellulose and lignin;   (c) mechanically treating said cellulose-rich solids to form a nanocellulose material comprising cellulose nanofibrils and/or cellulose nanocrystals, and   (d) recovering said nanocellulose material.   
     
     
         2 . The process of  claim 1 , wherein said solvent for lignin is an oxygenated organic compound. 
     
     
         3 . The process of  claim 2 , wherein said solvent for lignin is an aliphatic alcohol. 
     
     
         4 . The process of  claim 2 , wherein said solvent for lignin is an aromatic alcohol. 
     
     
         5 . The process of  claim 2 , wherein said solvent for lignin is a ketone, an aldehyde, an ether, or a combination thereof. 
     
     
         6 . The process of  claim 1 , wherein said solvent for lignin is a non-oxygenated alkane, non-oxygenated olefin, non-oxygenated aromatic hydrocarbon, or a combination thereof. 
     
     
         7 . The process of  claim 1 , wherein said solvent for lignin is an ionic liquid. 
     
     
         8 . The process of  claim 1 , wherein said solvent for lignin is water-soluble and, during step (b), forms a single phase with said water. 
     
     
         9 . The process of  claim 1 , wherein said solvent for lignin, during step (b), forms a separate phase from said water or from a water-rich phase comprising said water. 
     
     
         10 . The process of  claim 1 , wherein step (c) further comprises treatment of said cellulose-rich solids with one or more acids. 
     
     
         11 . The process of  claim 10 , wherein said one or more acids are selected from the group consisting of sulfur dioxide, sulfurous acid, lignosulfonic acid, acetic acid, formic acid, and combinations thereof. 
     
     
         12 . The process of  claim 1 , wherein step (c) further comprises treatment of said cellulose-rich solids with one or more enzymes. 
     
     
         13 . The process of  claim 1 , said process further comprising bleaching said cellulose-rich solids prior to step (c) and/or as part of step (c). 
     
     
         14 . The process of  claim 1 , said process further comprising bleaching said nanocellulose material during step (c) and/or following step (c). 
     
     
         15 . The process of  claim 1 , wherein during step (c), said cellulose-rich solids are treated with a total mechanical energy of less than about 5000 kilowatt-hours per ton of said cellulose-rich solids. 
     
     
         16 . The process of  claim 1 , wherein said crystallinity of said nanocellulose material is at least 60%. 
     
     
         17 . The process of  claim 1 , said process further comprising hydrolyzing amorphous cellulose into glucose in step (b) and/or step (c), recovering said glucose, and optionally fermenting said glucose to a fermentation product. 
     
     
         18 . The process of  claim 1 , said process further comprising recovering, fermenting, or further treating hemicellulosic sugars derived from said hemicellulose. 
     
     
         19 . The process of  claim 18 , said process further comprising fermenting said hemicellulosic sugars to produce a monomer or precursor thereof; polymerizing said monomer to produce a polymer; and combining said polymer and said nanocellulose material to form a polymer-nanocellulose composite. 
     
     
         20 . The process of  claim 1 , wherein said nanocellulose material is at least partially hydrophobic via deposition of at least some of said lignin onto a surface of said cellulose-rich solids during step (b), or via deposition of at least some of said lignin onto a surface of said nanocellulose material during step (c) or step (d).