Metal Chlorides in Ionic Liquid Solvents Convert Sugars to 5-Hydroxymethylfurfural
Replacing petroleum feedstocks by biomass requires efficient methods to convert carbohydrates to a variety of chemical compounds. We report the catalytic conversion of sugars giving high yield to 5-hydroxymethylfurfural (HMF), a versatile intermediate. Metal halides in 1-alkyl-3-methylimidazolium chloride are catalysts, among which chromium (II) chloride is found to be uniquely effective, leading to the conversion of glucose to HMF with a yield near 70%. A wide range of metal halides is found to catalyze the conversion of fructose to HMF. Only a negligible amount of levulinic acid is formed in these reactions.
(A) Fructose conversion to HMF at 80°C for 3 hours. Catalytic amounts of H2SO4 or various metal halides promote the chemistry. Very little levulinic acid is formed. (B) Glucose conversion to HMF at 100°C for 3 hours. CrCl2 resulted in a 70% yield of HMF, whereas other catalysts such as H2SO4, Lewis acids, or other metal halides gave yields less than 10%.
Science 15 June 2007:
Vol. 316 no. 5831 pp. 1597-1600