Effect of alkali promoters (Li, Na, K) on the performance of Ru/Al2O3 catalysts for CO2 capture and hydrogenation to methane

The impact of alkali promotion on the CO hydrogenation activity and selectivity over 1 %Ru/AlO catalyst was investigated varying the type of metal (Li, Na, K) and precursor salt (carbonates vs. nitrates) while keeping constant the equivalent weight load. Catalysts prepared by sequential impregnations of Ru and alkali precursors on highly resistant ?-AlO spheres (1 mm) were characterized by XRD, BET, H chemisorption, PSD, FT-IR, CO-TPD, H-TPRx and CO catalytic hydrogenation tests at atmospheric pressure under continuous flow conditions in the temperature range 200-430 °C. It was found that both CO capture capacity and methanation activity of Ru/AlO catalyst were simultaneously increased only via doping with Li (nitrate), which largely reacted with alumina to form a mixed spinel phase. Therefore, Li-Ru/AlO catalyst was successfully tested as a dual functional material operating the cyclic chemical looping process of CO-capture followed by its methanation under alternating flow conditions at a fixed temperature as low as 230 °C.