Methanation of CO2 and CO on supported nickel-based composite catalysts

Abstract

Several of the iron-group metals such as Ni and Co were supported as catalyst substrate on spherical porous supports. Lanthanide oxides such as La₂O₃ and Ce₂O₃, and platinum-group metals such as Ru and Rh were combined with the substrate in atomic ratios of 0.2 and < 0.1, respectively. By regulating the impregnation depth of these catalysts, reaction limits were set to the outer zone of the catalyst sphere. Hydrogenation of carbon oxides on these catalysts was investigated by the continuous flow method with high space velocity at atmospheric pressure within a temperature range of 145 to 350°C. A bimodal macro- and meso-pore support structure was found to be beneficial to catalyst preparation and methanation rate. The combined catalyst components exerted a remarkable effect, especially in CO₂ hydrogenation, on the rate of methane formation, which was far beyond the sum of each single component catalyst. In CO₂ hydrogenation, the composite catalysts always produced > 98 % in methane-formation selectivity and gave an apparent activation energy of 19.6 kcal mol^–1, which is less than for CO hydrogenation. The synergistic effects of the composite catalysts on the methanation rate were interpreted on the basis of the increase in adsorption capabilities of the reactants and from the viewpoint of a hydrogen spillover mechanism.