Fabrication of the coke-resistant and easily reducible Ni/SiC catalyst for CO2 methanation

Abstract

The catalytic methanation of carbon dioxide, which is a promising process for CO2 to fuels, has been extensively investigated using Ni-based catalysts due to their high CH4 selectivity, high CO2 conversion, and affordability. However, owing to its highly exothermic nature, CO2 methanation can cause severe carbon deposition and sintering effects, resulting in catalyst deactivation. This is where high thermal conductivity SiC presents itself as a viable alternative support to enhance the performance of Ni-based catalysts. In this work, Ni catalysts supported on a cheap commercial SiC were prepared by wet impregnation method with different Ni loadings and calcination temperatures. The as-prepared and spent catalysts were characterized using N2 physisorption, X-ray diffraction, H2 temperature-programmed reduction (H2-TPR), temperature-programmed oxidation (TPO) and transmission electron microscopy. H2-TPR analysis revealed that reduction at 400 °C for 15 min is enough to convert most of NiO to active Ni0 to archive the highest activity toward CO2 methanation. The catalytic performance and long-term stability of the as-prepared Ni/SiC catalysts were evaluated for CO2 methanation at stoichiometric CO2/H2 ratio of 1/4, different gas hourly space velocities, reaction temperatures, and reduction conditions. Among the synthesized catalysts, the 10%Ni/SiC-500 exhibited highest CO2 conversion (70%) and CH4 selectivity (98%) as well as stable catalytic performance for 30 h on stream at a GHSV of 20,000 h−1 and reaction temperature of 400 °C.