Balancing free and confined metallic Ni for an active and stable catalyst-A case study of CO methanation over Ni/Ni-Al2O3

We propose a new strategy to make an active and stable Ni-based catalyst which can be operated in a wide range of reaction temperatures. The ordered mesoporous alumina (OMA) with confined Ni in the pore wall (Ni-OMA) was prepared via the one-pot evaporation induced self-assembly method. By using the incipient impregnation method, different amounts of free Ni were loaded over Ni-OMA (Ni/NiOMA) at a fixed total NiO content of 15 wt%. Characterization results confirmed the formation of well structured Ni-OMA, and the ordered structure was still well preserved even after impregnating NiO at a content of as high as 12 wt%. The catalysts were evaluated for the CO methanation as a model reaction under varied conditions. Importantly, the activity and stability of Ni/Ni-OMA for the titled reaction were significantly regulated by simply changing the ratio of the confined to free Ni. Over the optimum catalyst of NiO (2 wt%)/NiO (13 wt%)-OMA, the high activity at a temperature of as low as 300 degrees C was achieved with the space-time yield of methane over 7.6 g gcat(-1) h(-1) while a long-term stability for a time-on stream of 400 h was confirmed without an observable deactivation under the conditions of 600 degrees C and an extremely high gas hourly space velocity of 120,0 0 0 mL g(-)1 h(-1). The results were well explained as the integrated merits of the free Ni for a high dispersion and the confined Ni in OMA for the anti-sintering property. (c) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.