One-pot conversion of carbohydrates into γ-valerolactone under the coordination of heteropoly acid based ionic liquid and Ru/ZrO2 in water media

BACKGROUND The chemical catalytic conversion of carbohydrates into γ-valerolactone (GVL) is a sustainable alternative to the petrochemical process starting from the depleting fossil resources. Direct conversion of carbohydrates (fructose, glucose, starch and cellulose) into GVL was achieved via the combined heteropoly acid based SO 3 H-functionalized ionic liquid (HAIL) and supported ruthenium (Ru) catalyst system in one pot and in water media. RESULTS A 63% GVL yield (based on fructose) was obtained under the catalysis of 1-methyl-3-(3-sulfopropylimidazolium)silicotungstate ([MIMPS] 4 SiW) and Ru/ZrO 2 at 180 °C, first in 0.1 MPa nitrogen (N 2 ) for 3 h (dehydration), and then in 4 MPa hydrogen (H 2 ) for 10 h (hydrogenation). Under the same reaction conditions, the GVL yields from glucose, starch and cellulose were 68%, 60% and 60%, respectively. The recyclability of the catalytic system consisting of [MIMPS] 4 SiW and Ru/ZrO 2 was investigated in four runs. The activity for [MIMPS] 4 SiW did not change after use. Partial deactivation of Ru/ZrO 2 was observed, which was ascribed to the severe carbon deposition. CONCLUSIONS In the present method, HAIL and Ru/ZrO 2 catalysts were loaded together. No separation and/or neutralization step reported in the literature was needed and only an atmosphere change (from N 2 to H 2 ) step was involved. Therefore, we provide a promising method for efficient conversion of carbohydrates into GVL. © 2019 Society of Chemical Industry