Catalytic Hydrogenation of Levulinic Acid into Gamma-Valerolactone Over Ni/HZSM-5 Catalysts

A series of Ni/HZSM-5 catalysts with different Ni-loadings and Si/Al ratios were prepared by incipient wetness impregnation and employed for catalytic hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL). Their physicochemical properties were characterized by X-ray diffraction, nitrogen adsorption-desorption, X-ray photoelectron spectrometer, temperature-programmed desorption of ammonia,transmission electron microscopy, temperature-programmed reduction of hydrogen, and pyridine-adsorbed infrared spectroscopy. The diffraction peaks assigned to Ni phase were not observed, implying that nickel particles were small and had a high dispersion on the supports. The catalysts with a strong acidity and the appropriate ratio of Bronsted (B) acid sites to Lewis (L) acid sites (B/L = 4.9) show an excellent activity and selectivity for the hydrogenation of LA to GVL. High conversion of LA and selectivity towards GVL were achieved over 5 wt% Ni/HZSM-5-50. The maximum GVL yield of 100% over 5 wt% Ni/HZSM-5-50 was obtained under the optimized reaction conditions of 210 degrees C, 2 h, and 3 MPa initial hydrogen pressure.