Catalytic activity of Ni/Ce-Zr mixed oxide catalysts modified by magnesium and manganese for methane dry reforming

Abstract

The effect of modifying Ce0.75Zr0.25O2 (CZO) mixed oxide with Mg and Mn in order to adjust its acid-base properties for use as a support of Ni-based Ce-Zr mixed oxide catalysts was investigated. The Ce0.75Zr0.25-xMg2xO2 (CZM) and Ce0.75Zr0.25-xMnxO2 (CZN) were prepared by the hydrazine digestion and urea hydrolysis, respectively, where x = 0.1 and 0.2. All of the catalysts were impregnated with 15 wt% Ni. The catalysts were characterized by several techniques e.g., BET, XRD, SEM, H2-TPR, NH3-TPD and TPO techniques. The catalysts were evaluated from 500 ℃ to 900 ℃ at atmospheric pressure, GHSV of 10,600 h-1, and CH4/C02/He molar ratio of 1:1:8. The results show that Ni/CZM-1 catalyst possessed the highest catalytic activity at a given temperature. The catalytic activity of Ni/CZN catalysts were higher than that of Ni/CZO catalysts. Of stability test for 10 h, the Mg-modified catalysts showed an insignificant variation in catalytic performance. In contrast, the Ni/CZN-2 exhibited a drastically catalytic deactivation. It was revealed that the catalyst performance is related to the acid-base properties, high surface area of support and the interaction between nickel species and the support. This indicated the improvement of both activity and stability resulting from the incorporation of Mg into ceria-zirconia lattices.