Catalytic conversion of cellulose to fuels and chemicals using boronic acids
Methods and catalyst compositions for formation of furans from carbohydrates. A carbohydrate substrate is heating in the presence of a 2-substituted phenylboronic acid (or salt or hydrate thereof) and optionally a magnesium or calcium halide salt. The reaction is carried out in a polar aprotic solvent other than an ionic liquid, an ionic liquid or a mixture thereof. Additional of a selected amount of water to the reaction can enhance the yield of furans.
1. A method for producing furans from a carbohydrate substrate, the method comprising heating a reaction mixture comprising the carbohydrate substrate, a 2-substituted phenylboronic acid or a salt or hydrate thereof and optionally a magnesium or calcium halide salt, in a polar aprotic solvent other than an ionic liquid, an ionic liquid or a mixture thereof, and wherein when the carbohydrate substrate is biomass or a carbohydrate polymer, dilute acid is also added to the reaction mixture.
2. The method of claim 1 wherein the reaction mixture comprises the magnesium or calcium halide salt.
3. The method of claim 1 wherein a selected amount of water is also present in the reaction mixture.
4. The method of claim 1 wherein the 2-substituted phenylboronate is represented by formula:
where:
R is selected from the group consisting of an alkyl group, a hydrogen, an aralkyl group, and an aryl group, each of which is optionally substituted; and
R 3 -R 6 , independently, are selected from the group consisting of hydrogen, halogen, nitro, cyano, an alkyl group, an alkoxy group, an alkoxycarbonyl group, a carboxyalkyl group, an alkoxycarbonylalkyl group, an aminoalkyl group, an alkylaminoalkyl group, —COH, —COR 7 , —CO 2 R 8 , —NH 2 , —CONH 2 , —N(R 9 ) 2 , and —CON(R 9 ) 2 , where R 7 , R 8 and each R 9 are independently selected from the group consisting of an alkyl group, an aralkyl group and an aryl group and wherein one of R 3 -R 6 is optionally a linker group covalently attached to a surface or suitable for attachment of the phenylboronate to a surface or one of R 3 -R 6 is a reactive group suitable for forming a covalent attachment to a surface through a linker.
5. The method of claim 1 wherein the carbohydrate substrate is a mono- or disaccharide.
6. The method of claim 1 wherein the carbohydrate substrate is cellulose.
7. The method of claim 1 wherein the carbohydrate substrate is lignocellulosic biomass.
8. The method of claim 1 wherein the magnesium or calcium halide salt is magnesium chloride or calcium chloride.
9. The method of claim 1 wherein the polar aprotic solvent is N,N-dimethylacetamide.
10. The method of claim 1 wherein the reaction is conducted in an ionic liquid.
11. The method of claim 1 wherein the reaction is conducted in the mixture of an ionic liquid and a dipolar aprotic solvent other than an ionic liquid.
12. The method of claim 3 wherein the amount of water present in the reaction mixture is 6 or more molar equivalents with respect to the carbohydrate substrate.
13. The method of claim 1 wherein the carbohydrate substrate is lignocellulosic biomass, cellulose or hemicellulose and dilute acid is added to the reaction mixture.
14. The method of claim 1 wherein the 2-substituted phenylboronate is immobilized on a surface.
15. A method for making fructose from glucose, the method comprising heating the glucose in the presence of a 2-substituted phenylboronate, and magnesium oxide in a polar aprotic solvent, ionic liquid or a mixture thereof.
16. A catalyst for producing furans from a carbohydrate substrate, the catalyst comprising a 2-substituted phenylboronic acid or a 2-substituted phenylboronic acid immobilized on a surface; and the catalyst further comprises magnesium (II) or calcium (II).
17. The catalyst of claim 16 , wherein the catalyst comprises a magnesium or calcium halide salt.
18. The catalyst of claim 16 , wherein the 2-substituted phenylboronic is immobilized on a surface.
19. The catalyst of claim 16 wherein the 2-substituted phenylboronate is represented by formula:
where
R is selected from the group consisting of an alkyl group, a hydrogen, an aralkyl group, and an aryl group, each of which is optionally substituted; and
R 3 -R 6 , independently, are selected from the group consisting of hydrogen, halogen, nitro, cyano, an alkyl group, an alkoxy group, an alkoxycarbonyl group, a carboxyalkyl group, an alkoxycarbonylalkyl group, an aminoalkyl group, an alkylaminoalkyl group, —COH, —COR 7 , —CO 2 R 8 , —NH 2 , —CONH 2 , —N(R 9 ) 2 , and —CON(R 9 ) 2 , where R 7 , R 8 and each R 9 are independently selected from the group consisting of an alkyl group, an aralkyl group and an aryl group.
20. The catalyst of claim 19 wherein R is a hydrogen or an alkyl group having 1-3 carbon atoms.
21. The catalyst of claim 16 wherein a molar ratio of 2-substituted phenylboronate to magnesium(II), calcium (II) or a mixture thereof is 0.5 to 5.
22. The method of claim 1 wherein the 2-substituted phenylboronate is represented by formula:
where:
R is selected from the group consisting of hydrogen and an unsubstituted alkyl group; and
R 3 -R 6 , independently, are selected from the group consisting of hydrogen, halogen, nitro, cyano, an alkyl group, an alkoxy group, —COH, —COR 7 , and —CO 2 R 8 , where R 7 and R 8 are independently selected from the group consisting of an alkyl group, an aralkyl group and an aryl group.
23. The method of claim 1 wherein the 2-substituted phenylboronate is represented by formula:
where:
R is selected from the group consisting of hydrogen and an unsubstituted alkyl group; and
R 3 -R 6 , independently, are selected from the group consisting of hydrogen, an alkyl group, an alkoxy group, and —CO 2 R 8 , where R 7 and R 8 are independently selected from the group consisting of an alkyl groups.
24. The method of claim 1 wherein the 2-substituted phenylboronate is selected from the group consisting of 2-carboxy phenylboronate, 2-methoxycarbonylphenylboronate, and 2-ethoxycarbonyl phenylboronate.