Methods for extracting hemicellulose from a cellulosic material

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 comprising acetic acid. The cellulosic product retains the cellulosic fiber morphology.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This is a non-provisional of U.S. Provisional Application 61 / 684,993, filed Aug. 20, 2012, the entirety of which is incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates generally to the extraction of hemicellulose from cellulose containing materials. In particular, the present invention relates to processes for extracting hemicellulose from cellulose containing materials using an extractant comprising acetic acid.BACKGROUND OF THE INVENTION[0003]Cellulose is typically obtained from wood pulp and cotton and may be further modified to create other derivatives including cellulose ethers, cellulose esters and cellulose nitrate, among others. Cellulose derivatives have a variety of commercial uses. For example, cellulose acetate is the acetate ester of cellulose and is used for a variety of products, including textiles (e.g., linings, blouses, dresses, wedding and party attire, home furnishings, draperies, ...

AI Technical Summary

Benefits of technology

[0010]In a first embodiment, the present invention is directed to a process for treating a cellulosic material, comprising: extracting hemicellulose from the cellulosic material with an extractant, wherein the extractant comprises an ionic liquid and a non-solvent comprising acetic acid; and separating the extracted hemicellulose from the cellulosic material to form a cellulosic product comprising less hemicellulose than the cellulosic material. The extractant may comprise from 10 to 40 wt. % acetic acid and from 60 to 90 wt. % ionic liquid. The cellulosic product may comprise at least 10% less hemicellulose than the cellulosic material. In some embodiments, less than 15% of the cellulose in the cellulosic material is extracted. The cellulosic product may retain a cellulosic fiber morphology. The ionic liquid may be selected from the group consisting of imidazolium salts, pyridinium salts, ammonium salts, and phosphonium salts. In some embodiments, the ionic liquid is 1-ethyl-3-methyl imidazolium acetate. The non-solvent may further comprise at least 5 wt. % water. The non-solvent may be free of dimethyl sulfoxide. The process may further comprise treating the cellulosic material with an enzyme, e.g., hemicellulose. The extracting step may be conducted at a temperature from 30° C. to 150° C. or from 90° C. to 120° C. The extracting step may occur for between 5 minutes and 180 minutes. The process may further comprise washing the cellulosic product with at least one of dimethylformamide, N-methyl pyrrolidone, methanol, ethanol, isopropanol, dimethyl carbonate, acetone and / or water. The process may further comprise repeating the extraction step to remove additional hemicellulose. The cellulosic product may have an absorbance of less than 2.0 at 277 nm, of less than 1.8 or of less than 1.5. In some embodiments, the cellulosic material comprises wood pulp, e.g., paper grade wood pulp.

[0011]In a second embodiment, the present invention is directed to a cellulosic material formed by extracting hemicellulose from a cellulosic material with an extractant, wherein the extractant comprises an ionic liquid and a non-solvent comprising acetic acid; and separating the extracted hemicellulose from the cellulosic material to form a cellulosic product comprising less hemicellulose than the cellulosic material.

[0012]In a third embodiment, the present invention is directed to a process for producing high purity α-cellulose grade pulp, comprising: extracting hemicellulose from a wood pulp by treating the wood pulp with an extractant comprising an ionic liquid and a non-solvent comprising acetic acid to form an intermediate wood pulp that retains a cellulosic fiber morphology; treating the intermediate wood pulp with an enzyme to hydrolyze hemicellulose contained therein and forming a reduced hemicellulose wood pulp; and washing the reduced hemicellulose wood pulp with a wash solution to form the high purity α-cellulose grade pulp.

[0013]In a fourth embodiment, the present invention is directed to a high purity α-cellulose grade pulp product purified by removing hemicellulose from cellulosic material using a combination of extraction with ionic liquids and acetic acid, and enzymatic hydrolysis of hemicellulose by hemicellulose-selective enzyme, wherein the high purity α-cellulose grade pulp product comprises less than 5% hemicellulose.

Problems solved by technology

Acetate-grade pulps are specialty raw materials produced in commercial pulp processes, but the cost for such pulps is high.

However, paper grade pulp also contains a high amount of impurities, such as hemicellulose, rendering it incompatible with certain industrial uses, such as making acetate flake or tow.

However, DMDO is not commercially available due to its instability.

Therefore, it is not an ideal solvent for producing large quantities of high α-cellulose pulp.

However, in order to turn cellulose containing materials into glucose, the methods disclosed in these references result in breaking down the cellulose molecules, making them unsuitable for use as starting materials to make cellulose derivatives.

This method results in the complete dissolution of the cellulose and destruction of the fiber morphology of the cellulose.

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