Methods for conversion of carbohydrates in ionic liquids to value-added chemicals

Abstract

Methods are described for converting carbohydrates including, e.g., monosaccharides, disaccharides, and polysaccharides in ionic liquids to value-added chemicals including furans, useful as chemical intermediates and / or feedstocks. Fructose is converted to 5-hydroxylmethylfurfural (HMF) in the presence of metal halide and acid catalysts. Glucose is effectively converted to HMF in the presence of chromium chloride catalysts. Yields of up to about 70% are achieved with low levels of impurities such as levulinic acid.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims priority from and is a divisional of U.S. patent application Ser. No. 11 / 774,036 filed Jul. 6, 2007, which in turn claims priority from Provisional application 60 / 836,188 filed Aug. 7, 2006; Provisional application 60 / 851,545 filed Oct. 13, 2006; and Provisional application 60 / 938,988 filed May 18, 2007 incorporated herein their entirety.[0002]This invention was made with Government support under Contract DE-AC05-76RLO1830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.FIELD OF THE INVENTION[0003]The present invention relates to methods for conversion of carbohydrates in ionic liquids to value-added chemicals at substantial yields.BACKGROUND OF THE INVENTION[0004]Replacing petroleum feedstocks with biomass feedstocks will require efficient methods for converting carbohydrates to a diverse number of chemical compounds. A major barrier to achieving this goal is a current i...

AI Technical Summary

Benefits of technology

This approach enables high conversion and selectivity of carbohydrates to HMF and other furans, overcoming the limitations of traditional acid-catalyzed processes by providing high yields and reducing energy costs, while avoiding the use of corrosive acids and complex purification steps.

Problems solved by technology

A major barrier to achieving this goal is a current inability to effectively utilize 5-carbon (C5) and 6-carbon (C6) carbohydrate building blocks derived from nature as potential feedstocks, including such abundant sugars as, e.g., glucose and fructose.

For example, while HMF has been proposed as a key intermediate to produce liquid alkanes from renewable biomass resources [Leshkov et al., Science 312, 1933-1937 (2006)], high production costs currently limit availability and use of HMF industrially.

Further, processes that produce HMF involve use of acid catalysts and are essentially limited to fructose as a feed material [Asghari et al., Ind. Eng. Chem. Res.

Acids are corrosive, however, and have drawbacks including product contamination, and difficult recycling and waste disposal issues.

Acids further catalyze side reactions leading to byproducts that require complicated product separations for product purification that increase costs.

For example, in water under acidic conditions, HMF decomposes to levulinic acid and formic acid, making purification of HMF difficult.

Under normal processing conditions, glucose fails to convert to HMF at high yields.

Generally, glucose is poorly converted, presumably a consequence of competing reaction pathways that lead to formation of byproducts.

However, polysaccharides typically require pretreatment to depolymerize the carbohydrates and provide necessary building blocks for conversion.

However, enzyme costs are high and complexity of processing leads to high capital costs.

Consequently, while carbohydrates can be converted through various processes including hydrolysis and biological fermentation, poisoning, slow processing, high production costs, and difficult separations result in high processing costs.

Images