Efficient Conversion of Levulinic Acid to Ethyl Levulinate over a Silicotungstic-Acid-Modified Commercially Silica-Gel Sphere Catalyst

A silicotungstic-acid-modified commercially available silica-gel sphere was applied to the catalytic conversion of levulinic acid to give ethyl levulinate. The obtained catalysts were studied by N-2 sorption, X-ray powder diffraction, Fourier transform infrared spectroscopy, and temperature-programmed desorption of ammonia. The experimental results indicated that catalytic activity of the catalysts were influenced by the amount of acid sites, surface area, and porosity. The yield of ethyl levulinate was observed from 70 to 97% with an increase of silicotungstic acid load from 0 to 40%. The reaction parameters, including catalyst dosage, molar ratio of levulinic acid/ethanol, reaction temperature, and time, were optimized, and a 97.0% yield of ethyl levulinate was obtained at the optimal conditions. The experimental results demonstrated the potential of a silicotungstic-acid-modified commercially available silica-gel sphere catalyst for conversion of levulinic acid to ethyl levulinate under mild process conditions.