Chemical Methanation of Biogas Exhaust by External Hydrogenation with Ni-Fe/Al-Ti Catalysts in Multicomponent System

Currently biogas exhaust after CH4 /CO2 separation releases into atmosphere directly in practical applications, which causes GHG emission methanation of biogas exhaust by converting CO2 into CH4 via thermocatalytic hydrogenation could be a promising carbon sequestration technology to resolve this problem. Currently, this technology is still under development at an early stage which needs high temperature (300-400°C) and pressure (>1Mpa), which leads to high cost and energy consumption. This research developed a novel catalyst, Ni-Fe/Al-Ti, with a good performance in CO2 chemical methanation to improve the methanation efficiency at low temperature and atmospheric pressure. The experimental results showed that this new catalyst increased the catalyst activity by a factor of one-third compared with the commonly used Ni/Al2O3 and decreased the catalyst's activation temperature by 100°C. Furthermore, over 98% CO 2 conversion ratio and 100% CH 4 selectivity and high-stability in simulated biogas atmosphere were achieved. Catalyst characterization and reaction mechanism studies demonstrated that the process of the reaction was realized by the synergistic effect of the Al-Ti composite support and Fe promotion. The oxygen vacancies on the surface of composite supports and the wide dispersion of active metal caused by the addition of Fe promoters accelerated CO2 capture and oxygen reduction. Compared to the existing catalysts, the novel Ni-Fe/Al-Ti catalyst could increase the methanation efficiency significantly, which shows a great potential for practical application.