Impact of varied zeolite materials on nickel catalysts in CO2 methanation

Ni catalysts supported on 4A, 5A, 13X, ZSM-5, and BEA zeolites were prepared using the vacuum -heating method for CO 2 methanation. These support materials play a pivotal role in shaping the catalysts' properties and their catalytic performance. High -resolution high -angle annular dark -field scanning transmission electron microscopy (HAADF-STEM) and energy -dispersive X-ray spectroscopy (EDS) mappings suggest a significant concentration of Ni nanoparticles situated on the external surfaces of catalysts with low Si/Al ratios zeolites (Ni-4A, Ni-5A, and Ni-13X). These Ni nanoparticles exhibit characteristics of weaker metal -support interaction, lower metal reduction temperatures, and moderate H 2 adsorption activity. Moreover, these low Si/Al ratio zeolites demonstrate robust CO 2 adsorption activity. These properties endow Ni-5A and Ni-13X catalysts with heightened CO 2 conversion (70.4-70.9%) and methane selectivity (92.4-96.4%). In contrast, high Si/Al ratio zeolite-based catalysts (Ni-ZSM-5 and Ni-BEA) exhibit smaller Ni particles, strong metal -support interaction and weaker CO 2 adsorption activity, resulting in reduced CO 2 methanation activity and decreased methane selectivity (71.2-73.4%). The normalized CO 2 conversion rate presents a correlation with the average Ni particle size.