Direct conversion of carbohydrates to γ-valerolactone facilitated by a solvent effect

Abstract

The carbohydrates (cellulose, starch, inulin, maltose, sucrose, glucose and fructose) were converted efficiently into γ-valerolactone (GVL) over combined H₃PW₁₂O₄₀ and Ru/TiO₂ catalysts under mild conditions. The basicity of oxygen-containing solvents had a remarkable effect on the acid strength of H₃PW₁₂O₄₀, which resulted in great variation in the yield of GVL. H₃PW₁₂O₄₀ was more effective in 20 vol% water/γ-butyrolactone than in pure water and other water/organic solvents (methanol, ethanol and 1,4-dioxane). GVL yields for inulin and fructose reached 70.5 mol% and 67.6 mol% respectively. Meanwhile, a GVL yield of 40.5 mol% was achieved for cellulose. In addition, a practical method for catalyst recycling and GVL separation was developed by adding sugar into the reaction mixture. H₃PW₁₂O₄₀ and Ru/TiO₂ maintained their activity after three recycling runs.