Production of hydroxymethylfurfural

Abstract

The invention provides a process for making hydroxymethylfurfural. A reaction mixture comprising a saccharide and a metal complex of an N-heterocyclic carbene is initially provided. The saccharide is then allowed to react at about 70° C. or below to form hydroxymethylfurfural. The saccharide may be a hexose or a mixture of hexoses, or a dimer, oligomer or polymer or copolymer of a hexose or a mixture thereof.

1 . A process for making hydroxymethylfurfural comprising:
 (i) providing a reaction mixture comprising a saccharide and a metal complex of an N-heterocyclic carbene wherein said saccharide is a hexose or a mixture of hexoses, or a dimer, oligomer or polymer or copolymer of a hexose or a mixture thereof; and   (ii) allowing the saccharide to react in the reaction mixture to form hydroxymethylfurfural;   
       wherein steps (i) and (ii) are conducted at about 70° C. or below. 
     
     
         2 . The process of  claim 1  wherein the saccharide comprises a monosaccharide. 
     
     
         3 . The process of  claim 2  wherein the monosaccharide comprises fructose, glucose or a mixture of these. 
     
     
         4 . The process of  claim 1  wherein the reaction mixture additionally comprises an ionic liquid. 
     
     
         5 . The process of  claim 4  wherein during step (ii) the reaction mixture is continuously or intermittently contacted with a solvent for hydroxymethylfurfural, said solvent being immiscible with the ionic liquid, so as to extract the hydroxymethylfurfural into the solvent. 
     
     
         6 . The process of  claim 4  wherein the reaction mixture is contacted with a solvent for hydroxymethylfurfural after step (ii), said solvent being immiscible with the ionic liquid, so as to extract the hydroxymethylfurfural into the solvent. 
     
     
         7 . The process of  claim 1  wherein the metal complex of the N-heterocyclic carbene is a metal complex of a monomeric N-heterocyclic carbene. 
     
     
         8 . The process of  claim 7  wherein the metal complex of the N-heterocyclic carbene is a metal complex of an imidazol-2-ylidene or of an imidazolin-2-ylidine. 
     
     
         9 . The process of  claim 1  wherein the metal complex is selected from the group consisting of a tungsten complex, a titanium complex, a zirconium complex, a ruthenium complex and a mixture of any two or more of these types of complex. 
     
     
         10 . The process of  claim 9  wherein the metal complex is a tungsten complex of an imidazol-2-ylidene or of an imidazolin-2-ylidine. 
     
     
         11 . The process of  claim 1  comprising the step of generating the metal complex of the N-heterocyclic carbene. 
     
     
         12 . The process of  claim 11  wherein the step of generating the metal complex of the N-heterocyclic carbene comprises reacting a nitrogen heterocycle salt with a base in the presence of a salt of the metal. 
     
     
         13 . The process of  claim 12  wherein the base is potassium t-butoxide. 
     
     
         14 . The process of  claim 11  comprising removing a solvent in which said step of generating is conducted, said removing being conducted after said generating. 
     
     
         15 . The process of  claim 1 , said process being a continuous reaction. 
     
     
         16 . The process of  claim 1  wherein the metal complex of the N-heterocyclic carbene is recycled following removal of the hydroxymethylfurfural from the reaction mixture. 
     
     
         17 . The process of  claim 4  wherein the ionic liquid is reused following removal of the hydroxymethylfurfural from the reaction mixture. 
     
     
         18 . A process for making a fuel comprising:
 (i) providing a reaction mixture comprising a saccharide and a metal complex of an N-heterocyclic carbene wherein said saccharide is a hexose or a mixture of hexoses, or a dimer, oligomer or polymer or copolymer of a hexose or a mixture thereof;   (ii) allowing the saccharide to react in the reaction mixture to form hydroxymethylfurfural; and   (iii) converting the hydroxymethylfurfural to the fuel;   
       wherein steps (i) and (ii) are conducted at about 70° C. or below. 
     
     
         19 . The process of  claim 18  comprising the step of separating the hydroxymethylfurfural from the reaction mixture prior to step (iii). 
     
     
         20 . The process of  claims 18  wherein the metal complex of the N-heterocyclic carbene is a tungsten complex of an imidazol-2-ylidene or of an imidazolin-2-ylidine.