Core-shell nickel catalysts for the steam reforming of acetic acid

Abstract

To obtain a novel catalyst with high resistances to metal sintering and coke formation in the steam reforming of acetic acid, a series of nickel core-shell catalysts were prepared. The effects of the shell thickness, shell species and core particle size on the catalytic activity in the steam reforming of acetic acid were investigated. The prepared Ni@SiO2, Ni@Al2O3, Ni@CeO2 and Ni@TiO2 catalysts were characterized by BET, XRD, H2-TPR, DTG and HRTEM. The prepared core-shell catalysts showed high resistances to nickel sintering, owing to the protection of the shells, in comparison with bare nickel particles. Ni@SiO2 with a thin shell showed a higher activity than the corresponding catalyst with a thick shell due to the thin silica shell allowing the facile diffusion of reactants and products. Because of the important role of the support in steam reforming reactions, the shell species greatly affected the catalytic activity in the steam reforming of acetic acid. It was demonstrated that an alumina shell was best suited for the steam reforming of acetic acid among the studied shells owing to its excellent water dissociation ability. The Ni@Al2O3-i catalyst showed excellent activity with an almost complete conversion and a hydrogen yield up to 91.2% at 750°C due to its much smaller nickel particle size. The coke formed on the spent core-shell catalysts after the activity tests was mainly graphic carbon, and the Ni@Al2O3-i catalyst exhibited a superior coke resistance with the smallest amount of formed coke. HRTEM results of Ni@Al2O3-i indicated the alumina shell had a high hydrothermal stability and further confirmed the high sintering resistance in the steam reforming of acetic acid.