CO2 methanation over NiAl2O4 spinel - based catalysts

Abstract

In the present work, a series of NiO/NiAl2O4 catalysts were prepared by co-precipitation method with molar ratio of Ni/Al equal 1/2 at different precipitation temperatures (30 and 80oC) and calcination temperatures (500, 700, 900, and 1200oC). The catalyst properties were characterized by using N2 physisorption, X-ray diffraction, H2 – TPR, SEM, and TEM. The NiO/NiAl2O4 precipitated at 80oC and calcined at 900oC showed the best activity in CO2 methanation at 350oC with conversion 92% and 100% methane selectivity without CO formation. The optimal of NiO and NiAl2O4 composition at 24.7% and 75.3%wt could provide a stabilizing effect preventing the metal aggregation and to lowering the reduction temperature of NiO. Moreover, the higher calcination temperature led to larger total pore volume was good to provide sufficient exposed metallic active sites for gas reactants. Compared the unpromoted catalyst, the Ru promoted NiO/NiAl80 – 900 catalyst exhibited higher activity at low temperature (250-300oC) without CO formation due to the decrease of crystallite size of Ni metal resulting in high dispersion and enhanced reducibility of catalyst, which had a positive effect for catalytic activity.