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 N-2 physisorption, XRD, H-2-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/H-2/N-2 in a ratio of 1/4/15 and GHSV of 60 000 mL g(cat)(-1) h(-1), in the temperature range of 200-400 degrees 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 degrees 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 degrees C for 5 h without noticeable deactivation, due to the high resistance to sintering associated with the small size of the metal crystallites.