Influence of metallic promoters on the performance of Ni/SiO2 catalyst in the hydrodeoxygenation of anisole

Ni/SiO2 and Ni-based bimetallic Ni30M/SiO2 catalysts (with a Ni/M atomic ratio of 30; M = Fe, Co, Cu, Zn and Ga) were prepared by the impregnation method and characterized by the means of H2-TPR, XRD, H2 chemisorption, NH3-TPD and N2 sorption; the effect of M promoters on the structure and performance of Ni-based catalysts in the hydrodeoxygenation of anisole was investigated. The results indicated that the metallic promoters have a significant influence on the reducibility of nickel species, due to the interaction between M and Ni species, although the sizes of Ni-M bimetallic crystallites in Ni30M/SiO2 are similar to that of Ni crystallite in Ni/SiO2. Because of the interaction between Ni and M and the enrichment of certain M promoters on the surface of Ni-M bimetallic particles, the adsorption quantity of H2 on Ni30M/SiO2 is lower than that on Ni/SiO2. In addition, the Ni30M/SiO2 catalysts also have more acid sites (especially the weak ones) than Ni/SiO2. For the hydrodeoxygenation of anisole under 300°C, 0.1 MPa, weight hourly space velocity (WHSV) of anisole of 1.0 h−1 and H2/anisole molar ratio of 25, the Ni30M/SiO2 catalysts exhibit lower anisole conversion than Ni/SiO2, probably due to the lower H2 uptakes on the bimetallic catalysts. However, Ni30Ga/SiO2 and Ni30Zn/SiO2 give much higher selectivities to BTX (benzene, toluene and xylene) (81.7% and 76.8%, respectively) than Ni/SiO2 (71.5%). Meanwhile, Ni30Zn/SiO2 exhibits higher activity in methyl transfer and lower activity in C-C bond hydrogenolysis than other catalysts; owing to the high oxophilicity of Zn, from the aspects of increasing carbon yield and reducing H2 consumption, Ni30Zn/SiO2 is probably an appropriate catalyst in hydrodeoxygenation.