Magnesium as Promoter of CO2 Methanation on Ni-Based USY Zeolites

Abstract

CO2 methanation was studied over Ni–Mg–USY zeolite catalysts. Mg was added by incipient wetness impregnation and ion exchange. Whatever the Mg incorporation method used, Mg is able to improve the performance of the Ni-zeolite catalysts. Magnesium impregnation at lower contents (below 2.5%) over a 5%Ni/zeolite leads to an enhancement of the CO2 conversion into methane of 15% at 350–450 °C, probably due to the induced increase of the Ni particle dispersion, as well as to the possible activation of CO2 on the defects present on the MgO surface. At higher Mg contents, the stronger interaction between Ni and Mg oxides, leading to the formation of NiO–MgO solid solutions, seems to reduce the reducibility of the Ni species, decreasing the amount of nickel active sites available and thus the catalytic performance. Furthermore, important improvements of the catalytic performance (CO2 conversion and CH4 selectivity increased around 20% at 350–450 °C) were also found for the Mg-exchanged 5%Ni/zeolite. The results ar...