Nanoparticle modified Ni-based bimodal pore catalysts for enhanced CO2 methanation
Nanoparticle promoted Ni-based bimodal pore catalysts (20Ni/SiO2–Si, 20Ni/SiO2–Al, 20Ni/SiO2–Zr) were developed by the impregnation of nickel over SiO2, Al2O3 and ZrO2 nanoparticle modified SiO2 supports. The effects of nanoparticle type on the structures and performances of the catalysts for CO2 methanation were systemically studied. Catalyst characterizations indicated that bimodal pore structures were formed by the introduction of nanoparticles into the SiO2 support, which increased the surface areas of the catalysts and improved the dispersion of nickel. The activity for CO2 methanation was also enhanced significantly by the promotion of nanoparticles. The CO2 conversion increased in the order of 20Ni/SiO2 (unmodified catalyst) < 20Ni/SiO2–Si < 20Ni/SiO2–Al < 20Ni/SiO2–Zr, corresponding to the increasing order of their surface areas. It is found that the modification of ZrO2 and Al2O3 nanoparticles improved the CO2 chemisorption and dissociation, and thus resulted in extremely high CH4 selectivity (about 100%) at low reaction temperatures (<450 °C). A strong metal–support/promoter interaction was also observed in ZrO2 and Al2O3 nanoparticle promoted catalysts, which inhibited the sintering of nickel and contributed to the high stabilities of these two catalysts in CO2 methanation. Due to their excellent activity, selectivity and stability, ZrO2 nanoparticle modified Ni-based catalysts exhibited high potential for application in CO2 methanation in the future.