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.

1 . A method for selective conversion of a glucose containing carbohydrate to produce a furan said method comprising the steps of:
 mixing said carbohydrate up to a limit of solubility with an ionic liquid; and   heating said carbohydrate in the presence of a catalyst at a reaction temperature and a reaction time sufficient for conversion of same.   
     
     
         2 . The method of  claim 1 , wherein said ionic liquid has a chemical formula 1-R 1 -3-R 2 -imidazolium chloride, where R 1  and R 2  are alkyl groups of formula (C x H 2x+1 ) where X=1 to 18. 
     
     
         3 . The method of  claim 1 , wherein said ionic liquid includes a cation of chemical formula 1-R 1 -3-R 2 -imidazolium where R 1  and R 2  are alkyl groups of formula (C x H 2x+1 ) where X=1 to 18, and an anion. 
     
     
         4 . The method of  claim 3 , wherein said anion is selected from the group consisting of halides, sulfates, sulfonates, phosphates, acetates, phosphates, triflates, hexafluorophosphates, tetrafluoroborates, hexafluoroborates, and aluminum chloride. 
     
     
         5 . The method of  claim 3 , wherein said anion is selected from the group consisting of methanesulfonate or trifluoromethanesulfonate. 
     
     
         6 . The method of  claim 1 , wherein said ionic liquid is selected from the group consisting of pyridinium salts, phosphonium salts, tetralkylammonium salts, and combinations thereof. 
     
     
         7 . The method of  claim 1 , wherein said reaction temperature is about 100° C. and said reaction time is between about 3 hours and about 8 hours. 
     
     
         8 . The method of  claim 1 , wherein said reaction temperature is about 120° C. and said reaction time is between about 1 hour and about 3 hours. 
     
     
         9 . The method of  claim 1 , wherein said catalyst is an acid. 
     
     
         10 . The method of  claim 1 , wherein said catalyst is a metal halide. 
     
     
         11 . The method of  claim 1 , wherein said metal halide is selected from the group consisting of AlCl 3 , CrCl 2 , CrCl 3 , FeCl 2 , FeCl 3 , CuCl, CuBr, CuCl 2 , CuBr 2 , VCl 3 , MoCl 3 , PdCl 2 , PtCl 2 , PtCl 4 , RuCl 3 , RhCl 3 , and combinations thereof. 
     
     
         12 . The method of  claim 1 , wherein said reaction temperature is about 80° C. and said reaction time is between about 1 hour and about 4 hours. 
     
     
         13 . The method of  claim 1 , wherein said ionic liquid is 1-ethyl-3-methylimidazolium methanesulfonate and said catalyst is methane sulfonate or its conjugate acid; and wherein said reaction temperature and said reaction time are between about 80° C. for 2 hours and about 30° C. for 12 hours. 
     
     
         14 . The method of  claim 1 , wherein yield of levulinic acid and α-angelicalactone is below about 0.1 percent by weight. 
     
     
         15 . The method of  claim 1 , wherein said catalyst is a chromium halide. 
     
     
         16 . The method of  claim 1 , wherein said furan is furfural. 
     
     
         17 . The method of  claim 1 , wherein said carbohydrate is converted in a batch reactor or a batch reactor system. 
     
     
         18 . The method of  claim 1 , wherein conversion of said carbohydrate is greater than or equal to about 80 percent and said yield of said furan is greater than or equal to about 50 percent on a mole basis. 
     
     
         19 . The method of  claim 1 , wherein said yield of said furan is at least about 35 percent by weight. 
     
     
         20 . A method for selective conversion of fructose to produce a furan said method comprising the steps of:
 mixing said carbohydrate up to a limit of solubility with an ionic liquid; and   heating said carbohydrate at a reaction temperature and a reaction time sufficient for conversion of same.   
     
     
         21 . A method for selective conversion of a carbohydrate to produce a furan said method comprising the steps of:
 mixing said carbohydrate up to a limit of solubility with an ionic liquid; and   heating said carbohydrate in the presence of a catalyst at a reaction temperature and a reaction time sufficient for conversion of same.   
     
     
         22 . The method of  claim 21  wherein said carbohydrate is selected from the group selected from cellulose, sorbitol, glucose and fructose.