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

Abstract

The impact of alkali promotion on the CO2 hydrogenation activity and selectivity over 1 %Ru/Al2O3 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 γ-Al2O3 spheres (1 mm) were characterized by XRD, BET, H2 chemisorption, PSD, FT-IR, CO2-TPD, H2-TPRx and CO2 catalytic hydrogenation tests at atmospheric pressure under continuous flow conditions in the temperature range 200–430 °C. It was found that both CO2 capture capacity and methanation activity of Ru/Al2O3 catalyst were simultaneously increased only via doping with Li (nitrate), which largely reacted with alumina to form a mixed spinel phase. Therefore, Li-Ru/Al2O3 catalyst was successfully tested as a dual functional material operating the cyclic chemical looping process of CO2-capture followed by its methanation under alternating flow conditions at a fixed temperature as low as 230 °C.