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 amine oxide and a non-solvent. The cellulosic product retains the cellulosic fiber morphology.

We claim: 
     
         1 . A high purity α-cellulose grade pulp product purified by removing hemicellulose from cellulosic material using a mixture of amine oxide and water, wherein the high purity α-cellulose grade pulp product comprises less than 5% hemicellulose. 
     
     
         2 . The high purity α-cellulose pulp product of  claim 1 , wherein the mixture further comprises dimethyl sulfoxide. 
     
     
         3 . The high purity α-cellulose pulp product of  claim 1 , wherein the amine oxide is N-methylmorpholine-N-oxide. 
     
     
         4 . The high purity α-cellulose pulp product of  claim 1 , wherein the purified wood pulp product maintains a cellulosic morphology. 
     
     
         5 . The high purity α-cellulose pulp product of  claim 1 , wherein the removing comprises batch, co-current, or counter-current extraction. 
     
     
         6 . The high purity α-cellulose pulp product of  claim 1 , wherein the removing comprises use of an agitated tank, hydrapulper, screw conveyor or screw extractor. 
     
     
         7 . The high purity α-cellulose pulp product of  claim 1 , wherein solid and liquid phases are separated by a filter or centrifuge. 
     
     
         8 . A solvent system for reducing hemicellulose in a cellulosic material to form a hemicellulose reduced product, comprising 50-80 wt. % amine oxide and 20-50 wt. % water. 
     
     
         9 . The solvent system of  claim 8 , further comprising dimethyl sulfoxide, dimethylformamide, methanol, ethanol, isopropanol, acetone, acetic acid or a mixture thereof. 
     
     
         10 . A solvent system for selectively reducing hemicellulose in a cellulosic material to form a hemicellulose reduced cellulosic product, comprising from 0.8 to 95 wt. % amine oxide and from 0.1 to 99.9 wt. % non-solvent. 
     
     
         11 . The solvent system of  claim 10 , wherein the amine oxide is selected from the group consisting of oxides of trimethylamine, triethylamine, tripropylamine, monomethyldiethylamine, dimethylmonoethylamine, monomethyldipropylamine, N-dimethyl-, N-diethyl- or N-dipropylcyclohexylamine, N-dimethylmethylcyclohexylamine, pyridine, and pyridine N-oxide. 
     
     
         12 . The solvent system of  claim 10 , wherein the amine oxide is a cyclic mono (N-methylamine-N-oxide) compound. 
     
     
         13 . The solvent system of  claim 10 , wherein the amine oxide is R 1 R 2 R 3 N—O, wherein R 1 , R 2  and R 3  are alkyl chains with a chain length from 1 to 12. 
     
     
         14 . The solvent system of  claim 10 , 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. 
     
     
         15 . The solvent system of  claim 10 , wherein the non-solvent is acetonitrile. 
     
     
         16 . The solvent system of  claim 10 , wherein the non-solvent is dimethyl sulfoxide. 
     
     
         17 . The solvent system of  claim 10 , wherein the non-solvent comprises water and an organic non-solvent. 
     
     
         18 . The solvent system of  claim 17 , wherein the solvent system comprises from 0.01 to 12.5 wt. % water, from 50 to 98 wt. % organic non-solvent, and from 0.8 to 40 wt. % amine oxide. 
     
     
         19 . The solvent system of  claim 10 , wherein the solvent system comprises from 0.1 to 10 wt. % amine oxide and from 90 to 99.9 wt. % non-solvent. 
     
     
         20 . The solvent system of  claim 10 , 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.