Methods for removing hemicellulose

Abstract

A method for treating a cellulosic material comprises extracting the cellulosic material with an extractant to selectively extract hemicellulose therein and separating the extracted hemicellulose to form a cellulosic product comprising less hemicellulose than the cellulose-containing material. The extractant comprises an ionic liquid and a non-solvent. The cellulosic product retains the cellulosic fiber morphology.

We claim: 
     
         1 . A solvent system for selectively reducing hemicellulose in a cellulosic material to form a hemicellulose reduced cellulosic product, comprising at least 0.1 wt. % ionic liquid and at least 5 wt. % non-solvent. 
     
     
         2 . The solvent system of  claim 1 , comprising from 0.1 to 95 wt. % ionic liquid and from 5 to 99.5 wt. % non-solvent. 
     
     
         3 . The solvent system of  claim 1 , wherein the ionic liquid is selected from the group consisting of 1-butyl-3-methyl imidazolium tetrachloroaluminate, 1-ethyl-3-methyl imidazolium tetrachloroaluminate, 1-ethyl-3-methyl imidalzolium hydrogensulfate, 1-butyl-3-methyl imidazolium hydrogensulfate, methylimidazolium chloride, 1-ethyl-3-methyl imidazolium acetate, 1-butyl-3-methyl imidazolium acetate, tris-2(hydroxyl ethyl)methylammonium methylsulfate, 1-ethyl-3-methyl imidazolium ethylsulfate, 1-ethyl-3-methyl imidazolium methanesulfonate, methyl-tri-n-butylammonium methylsulfate, 1-butyl-3-methyl imidazolium chloride, 1-ethyl-3-methyl imidasolium chloride, 1-ethyl-3-methyl imidazolium thiocyanate, 1-butyl-3-methyl imidazolium thiocyanate, 1-aryl-3-methyl imidazolium chloride, and mixtures and complexes thereof. 
     
     
         4 . The solvent system of  claim 1 , wherein the ionic liquid is 1-ethyl-3-methyl imidazolium acetate. 
     
     
         5 . The solvent system of  claim 1 , wherein the non-solvent is selected from the group consisting of water, alcohols, n-butanol, tert-butanol, diols, polyols, amino alcohols, aromatic solvents, halogenated solvents, aliphatic solvents, ethers, ketones esters, amides, and mixtures thereof. 
     
     
         6 . The solvent system of  claim 1 , wherein the non-solvent is selected from the group consisting of water, methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, ethanediol, propanediol, ethanolamine, diethanolamine, triethanolamine, benzene, toluene, ethylbenzene, xylene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, chlorobenzene, pentane, hexane, heptane, octane, ligroin, petroleum ether, cyclohexane, decalin, tetrahydrofuran, diethyl ether, methyl tert-butyl ether, diethylene glycol monomethyl ether, acetone, methyl ethyl ketone, ethyl acetate, dimethyl carbonate, dipropyl carbonate, propylene carbonate, formamide, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetonitrile and mixtures thereof. 
     
     
         7 . The solvent system of  claim 1 , wherein the non-solvent is acetonitrile. 
     
     
         8 . The solvent system of  claim 1 , wherein the non-solvent is dimethyl sulfoxide. 
     
     
         9 . The solvent system of  claim 1 , wherein the non-solvent comprises water and an organic non-solvent. 
     
     
         10 . The solvent system of  claim 9 , wherein the solvent system comprises from 0.1 to 50 wt. % ionic liquid and from 0.5 to 18 wt. % water. 
     
     
         11 . The solvent system of  claim 1 , wherein the non-solvent is an organic non-solvent and wherein the solvent system comprises from 92.1 to 99.9 wt. % organic non-solvent and from 0.1 to 7.9 wt. % ionic liquid. 
     
     
         12 . The solvent system of  claim 1 , wherein the solvent system comprises a first non-solvent and a second non-solvent, and further wherein the solvent system comprises from 10 to 98 wt. % second non-solvent. 
     
     
         13 . The solvent system of  claim 1 , wherein the solvent system comprises a first non-solvent and a second non-solvent, and further wherein the second non-solvent decreases the viscosity of the solvent system. 
     
     
         14 . A solvent system for selectively reducing hemicellulose in a cellulosic material to form a hemicellulose reduced cellulosic product, comprising 50-80 wt. % ionic liquid and 20-50 wt. % water. 
     
     
         15 . The solvent system of  claim 14 , further comprising dimethyl sulfoxide, dimethylformamide, methanol, ethanol, isopropanol, acetone, acetic acid or a mixture thereof. 
     
     
         16 . The solvent system of  claim 14 , wherein the ionic liquid is selected from the group consisting of 1-butyl-3-methyl imidazolium tetrachloroaluminate, 1-ethyl-3-methyl imidazolium tetrachloroaluminate, 1-ethyl-3-methyl imidalzolium hydrogensulfate, 1-butyl-3-methyl imidazolium hydrogensulfate, methylimidazolium chloride, 1-ethyl-3-methyl imidazolium acetate, 1-butyl-3-methyl imidazolium acetate, tris-2(hydroxyl ethyl)methylammonium methylsulfate, 1-ethyl-3-methyl imidazolium ethylsulfate, 1-ethyl-3-methyl imidazolium methanesulfonate, methyl-tri-n-butylammonium methylsulfate, 1-butyl-3-methyl imidazolium chloride, 1-ethyl-3-methyl imidasolium chloride, 1-ethyl-3-methyl imidazolium thiocyanate, 1-butyl-3-methyl imidazolium thiocyanate, 1-aryl-3-methyl imidazolium chloride, and mixtures and complexes thereof. 
     
     
         17 . The solvent system of  claim 14 , wherein the ionic liquid is 1-ethyl-3-methyl imidazolium acetate. 
     
     
         18 . The solvent system of  claim 14 , further comprising acetonitrile. 
     
     
         19 . A solvent system for selectively reducing hemicellulose in a cellulosic material to form a hemicellulose reduced cellulosic product, comprising at most 50 wt. % ionic liquid, at most 18 wt. % water, and at least 10 wt. % dimethyl sulfoxide. 
     
     
         20 . The solvent system of  claim 19 , wherein the ionic liquid is selected from the group consisting of 1-butyl-3-methyl imidazolium tetrachloroaluminate, 1-ethyl-3-methyl imidazolium tetrachloroaluminate, 1-ethyl-3-methyl imidalzolium hydrogensulfate, 1-butyl-3-methyl imidazolium hydrogensulfate, methylimidazolium chloride, 1-ethyl-3-methyl imidazolium acetate, 1-butyl-3-methyl imidazolium acetate, tris-2(hydroxyl ethyl)methylammonium methylsulfate, 1-ethyl-3-methyl imidazolium ethylsulfate, 1-ethyl-3-methyl imidazolium methanesulfonate, methyl-tri-n-butylammonium methylsulfate, 1-butyl-3-methyl imidazolium chloride, 1-ethyl-3-methyl imidasolium chloride, 1-ethyl-3-methyl imidazolium thiocyanate, 1-butyl-3-methyl imidazolium thiocyanate, 1-aryl-3-methyl imidazolium chloride, and mixtures and complexes thereof.