CO2 methanation over nickel-ZrO2 catalyst supported on carbon nanotubes: A comparison between two impregnation strategies

Ni-ZrO2 catalysts supported on CNT synthesized by sequential and co-impregnation were tested in the CO2 methanation reaction. The catalysts were characterized using different physico-chemical techniques including BET surface area analysis, TGA, H2-TPR analysis, CO2-TPD analysis, XRD analysis, TEM-EDS analysis and XPS. Both samples were found to be active in the CO2 methanation; however, the catalyst prepared by co-impregnation was notably less active and selective to CH4 than the catalyst synthesized by sequential impregnation method. The characterization results gave significant insight on the disposition of active phases in CNT surface. The catalyst prepared by co-impregnation showed NiO nanoparticles surrounded by ZrO2 in core-shell structures that growth over the CNT, reducing reactant access to Ni and Ni – ZrO2 interface. Additionally, TEM analysis of this catalyst prepared by sequential impregnation showed NiO nanoparticles available and deposited either on the surface or next to the ZrO2 nanoparticles, increasing the extent of the Ni – ZrO2 interface thus improving the catalytic performance.