Low-Temperature Combustion Synthesis of Halloysite-Based Catalysts for the Deep Oxidation of Hydrocarbons and Carbon Monoxide and the Methanation of Carbon Dioxide

Supported mono- and bimetallic catalysts containing 10 wt % Ni(I), 10 wt % Co(II), and 5 wt % Co + 5 wt % Ni(III) on halloysite nanotubes have been synthesized by low-temperature combustion in porous media. The catalyst samples have been studied by XRD analysis, SEM, electron probe microanalysis, and TPR; specific surface area has been determined by the BET method according to the physical adsorption of nitrogen. The activity and selectivity of the synthesized catalysts have been studied using the example of the deep oxidation of CO and propane and the hydrogenation of CO2 at atmospheric pressure. It has been found that the highest activity in the deep oxidation of CO and propane is exhibited by the Co-containing samples, particularly the bimetallic Co-Ni catalyst. In the case of CO2 methanation in the presence of the freshly synthesized samples, the activity can be arranged in the following order: I > III > II. The reduction of the catalysts in a hydrogen stream at 400 degrees C for 1 h has led to a significant increase in their activity with a maximum at 350 degrees C, while the order of activity has remained unchanged. In the presence of reduced sample I, a CO2 conversion of 88.8% at a methane selectivity of 97.7% has been achieved.