Porous NiO Prepared by Flame Spray Pyrolysis for 80 wt% Ni-CeO2 Catalyst and Its Activity for CO2 Methanation

NiO and CeO2 were prepared via flame spray pyrolysis. The specific surface area and total pore volume were 251 m(2) g(-1) and 2.3 cm(3) g(-1) for NiO and 338 m(2) g(-1) and 3.3 cm(3) g(-1) for CeO2, respectively. The high porosity and surface area of the NiO allowed deposition of small CeO2 particles (similar to 5 nm) by the impregnation of cerium acetate monohydrate. The particles were reduced using 5 % H-2 at 500 degrees C for 1 h which converted NiO to metallic Ni. During the reduction, the growth of Ni particles was hindered by CeO2 particles. Consequently, the Ni size was relatively small (similar to 20 nm) despite the extremely high Ni content (80 wt%), as observed by scanning transmission electron microscopy. In contrast, incorporation of Ni using nickel acetate tetrahydrate into the CeO2 support resulted in formation of inhomogeneous Ni particles (20-100 nm) after H-2 reduction. H-2 chemisorption measurement showed the surface area of Ni particles in the former catalyst was 13.7 m(2) g(-1), which was 2.4 times larger than that in the latter catalyst. The former catalyst exhibited remarkable performance for CO2 methanation (47 % CO2 conversion at 250 degrees C), 2 times higher than in the latter catalyst.

Automated summary

NiO and CeO2 catalysts prepared by flame spray pyrolysis exhibited high specific surface area and large pore volume, resulting in relatively small Ni particles during reduction. However, addition of Ni led to formation of uneven Ni particles after reduction. The former catalyst showed improved CO2 methanation performance compared to the latter catalyst, with higher CO2 conversion at 250 degrees C.