Abstract
The effect of different cations (M=Zr, Sn or Ti) doping on ceria supported nickel (Ni-Ce0.8M0.2O2) catalysts and their performance in the CO2 methanation reaction has been investigated. Among the prepared catalysts, the Ni-CeO2 (CN) catalyst exhibited the best catalytic performance with a CO2 conversion of 62.9% at 400 °C. The selectivity on Ni-Ce0.8Zr0.2O2 (CZN) remained above 98.4% from 200 to 400 °C. As confirmed by in-situ DRIFTS, the dissociative adsorption of H2 mainly proceeds on Ni, by-product CO is mainly assigned to the releasing of weak-binding linearly adsorbed CO on nickel, which is from the hydrogenation of formates with adsorbed H. The CO-suppressing effect is attributed to the strong adsorption of carbon monoxide on nickel via the forming of bridging carbonyls. It was found that CO2 is adsorbed on the catalysts to form carbonate, bicarbonate and formate species. The formate species could be further hydrogenated by dissociated H and then finally release methane.
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