Ni/MgO-Al2O3 Catalysts for CO2 Methanation: Deactivation Mechanism Study

Despite significant advances in catalytic activity for CO2 methanation, the catalyst stability has received less attention, limiting its application. This work prepared Ni-supported on MgO-Al2O3 with varying Mg/Al ratio (x) and studied their deactivation mechanism. The deactivation was accelerated by a stability test at 600 °C for 200 h. The activity comparison before and after the stability test reveals that the sample with x = 0.4 shows the best stability without obvious activity decline. While the sample with x = 0.3 is deactivated due to Ni sintering, samples with x = 0.5 and 0.6 are deactivated by the oxidation of Ni, which easily forms a solid solution with excess MgO but is difficult to reduce. That assertion is supported by various characterizations. Such an oxidative deactivation is first-time reported for Ni-based catalysts for CO2 methanation, which could shed light on their rational design and industrial application.