Structure of Ni/HZSM-5 Catalyst and Its Catalytic Performance for Aqueous Phase Hydrogenation of Sorbitol to Alkanes

Abstract

A bifunctional Ni/HZSM-5 catalyst was prepared by the conventional impregnation method. The effects of calcination temperature on the structure properties of the catalyst and its catalytic performance for aqueous phase hydrogenation of sorbitol were studied. The results showed that C(5)similar to C(6) alkanes were effectively obtained by the hydrogenation of the C-O bond in sorbitol and the following isomerization due to the synergism of the metal center and acid support. Moreover, the catalyst calcined at 500 degrees C exhibited a maximum value of 62.0% for sorbitol conversion and 76.4% of selectivity for pentane and hexane in comparison with other catalyst samples, wherein the isohexane selectivity was about 45.4%. The catalyst samples were characterized by N(2) physical adsorption, X-ray diffraction, NH(3) temperature-programmed desorption, and H(2) temperature-programmed reduction. It was found that the surface area and pore volume of the catalyst calcined at 500 degrees C were obviously increased. Smaller grains of NiO can be formed from the decomposition of nickel nitrate on the surface of HZSM-5, which can provide with the appropriate amounts of acid and the interaction between the nickel species and acid support for easier hydrogen reduction with the Ni reducibility of 100%. All these factors are closely related to the highest catalytic performance of Ni/HZSM-5 catalyst for aqueous phase hydrogenation of sorbitol.