Catalysis Today, Vol.339, 67-78, 2020
Influence of Ni/Mo ratio on the structure-performance of ordered mesoporous Ni-Mo-O catalysts for oxidative dehydrogenation of propane
A series of ordered mesoporous Ni-Mo-O catalysts with different ratios of Mo/Ni were prepared by a two-step method, which firstly prepared ordered mesoporous NiO by hard template method and then impregnation with Mo precursor. And their catalytic performance were tested for propane oxidative dehydrogenation. The catalysts were characterization by XRD, N-2-adsorption, TEM, XPS, H-2-TPR and Raman analyses. It can avoid the dissolution of surface Mo species during etching silica template by a two-step method. And the catalysts with low Mo loading amounts show highly ordered mesoporous structure. A highly proportional beta-NiMoO4 phase can exist stably in Ni-Mo-O catalysts at room temperature. And the in-situ Raman results demonstrated the transformation of alpha-NiMoO4 to beta-NiMoO4 with the increasing of temperature. The transformation temperature in this work is relatively low (250 degrees C) due to the promotion of NiO. The catalyst with Mo/Ni of 0.4 shows the highest activity with the propene yield of 15.6%. The reasons may be from the high beta-NiMoO4/alpha-NiMoO4 ratio, the mesoporous structure and the suitable redox ability.