CO2 methanation over Ni–Al and Co–Al LDH-derived catalysts: the role of basicity†
Ni–Al and Co–Al mixed oxides derived from hydrotalcites were prepared by coprecipitation and evaluated in CO2 methanation. The catalysts were characterized by N2 physisorption, XRD, H2-TPR, NH3-TPD, CO2-TPD, TPO and SEM/EDS. The catalytic tests were performed at atmospheric pressure in a fixed-bed reactor, with a gas mixture of CO2/H2/N2 in a ratio of 1/4/15 and GHSV of 60 000 mL gcat−1 h−1, in the temperature range of 200−400 °C. The high density of basic sites and enhanced reducibility presented in the Ni–Al catalyst favored CO2 adsorption, which allows the achievement of around 90% CO2 conversion and 100% CH4 selectivity at 300 °C. The low number of basic sites found in Co–Al was responsible for the lower methanation activity. Both catalysts showed high stability at 400 °C for 5 h without noticeable deactivation, due to the high resistance to sintering associated with the small size of the metal crystallites.