CO2 methanation on Rh/γ-Al2O3 catalyst at low temperature: “In situ” supply of hydrogen by Ni/activated carbon catalyst

Nowadays, the control of CO2 emissions is still a challenge. A few alternatives exist but nothing concrete seems to be developed. Instead of catching and storing CO2, one possibility would be its transformation into value added molecules as methane. Rhodium catalysts are active in CO2 methanation reaction. But it seems that a competitive adsorption exist between the two reactants: CO2 and hydrogen. In order to surpass this trouble and increase hydrogen adsorption, a known active catalyst in methanation (Rh/γ-Al2O3) was put into contact with a known active catalyst in hydrogen activation (Ni/activated carbon). Catalysts were prepared by the mechanical mixing of the latter two in different proportions. Catalysts were tested in the low temperature methanation reaction using CO2 and H2. Methane is produced in all cases with a 100% of selectivity. A significant synergy appears in the catalytic activity of this mixed catalyst. Production of methane in mixtures is largely higher than the theoretical predicted values considering the individual performances. Catalysts were characterized before and after reaction by ICP-AES, N2 physisorption, XRD, CO2 chemisorption, ToF-SIMS, XPS and TPR. The synergy is due to the increase of H2 adsorption and promoting the carbon hydride formation. Furthermore the suggested hydrogen spill-over maintains Rh particles in a metallic state necessary for the reaction.

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► Rh/γ-Al2O3 catalysts were studied in CO2 methanation at low temperature.
► Enhancement of catalytic performances by mixing with nickel on activated carbon catalysts.
► Hydrogen migration from nickel catalysts to rhodium particles.