Dual functional materials based on Ni and different alkaline metals on alumina for the cyclic stepwise CO2 capture and methanation

Bimetallic catalysts consisting of nickel and one alkali or alkaline-earth metal (Na, K or Ba) on alumina support have been tested in the cyclic CO2 capture and subsequent methanation. The best performance was attained with a different material for cyclic tests (K-Ni/Al) than for Sabatier reaction (Ba-Ni/Al). In cyclic tests, the methane productivity shows different dependence with the temperature for each alkali and alkaline-earth metal. For temperature of 300 degrees C or above, the dual functional materials show stable cyclic performance when the capture is performed both from 5% CO2 in Ar and from simulated flue gas containing also O2 and H2O. Using the later feed, the CH4 productivity diminish reversibly compared to oxygen free conditions and nickel metal oxidises significantly. K-Ni/Al exhibited the best cyclic performance in terms of CH4 productivity and stability, which is associated to the highest reducibility of oxidised nickel species and the lowest formation of unreducible carbonates.