Methanation of carbon dioxide on Ni-incorporated MCM-41 catalysts: The influence of catalyst pretreatment and study of steady-state reaction

The methanation of carbon dioxide was carried out over Ni-incorporated MCM-41 catalysts. The Ni-MCM-41 catalysts containing 1-3 wt% Ni were prepared by incorporating the Ni ions into the framework of siliceous MCM-41 with the procedure developed in our previous work [S. Lim, G.L. Haller, J. Phys. Chem. B 106 (2002) 8437]. Pretreatment using pure H₂ at different temperatures affected the reactivity. Pretreatment at 973 K for 0.5 h was the best among the conditions tested. At this temperature, the Ni was mostly reduced but remained highly dispersed. Significant selectivity to methane (85.1%) was obtained with 1 wt% Ni-MCM-41 at a reaction temperature as low as 573 K and gas hourly space velocity (GHSV) of 5760 l kg^-1 h^-1 under atmospheric pressure. Higher selectivity (96.0%) and space-time yield (91.4 g kg^-1 h^-1) were achieved with higher Ni loading catalysts (3 wt% Ni) at the same space velocity. This selectivity was maintained at higher temperature (673 K) with increased space-time yield (633 g kg^-1 h^-1). The X-ray absorption result demonstrates that the Ni particle size does not significantly change during reaction.