Modelling and simulating CO and CO2 methanation over Ru/γ-Al2O3 catalyst: An integrated approach from carbon capture to renewable energy generation

The looping of carbon capture with power-to-gas technology is getting tremendous focus for the efficient inception of the methanation process. This will not only meet the growing energy demand but also reduce fossil fuel dependency and the climate change effects associated with it. In this work, a simulation approach was developed to model the methanation of CO and CO2 on a ppm basis over a ruthenium catalyst. The fast equilibrium reaction of CO2 to CO and slow kinetically-controlled hydrogenation of CO to CH4 was modelled within the same reactor. The catalyst particles of 0.5% Ru on gamma-Al2O3 pellet supports were simulated on the Aspen Tech program. The fixed bed reactor was split into segments, consisting of equilibrium and kinetic reactors to model the relevant reactions. The effect of the reaction temperature, feed composition, and reactor volume was investigated. These parameters affected the reactor's conversion with the reaction rate and the number of reactor segments required for convergence. An approach was developed to size a reactor for specific CO and CO2 conversions. With a reactor size of 13.85 m(3), a 99.0% and 97.55% conversion of CO and CO2, respectively was achieved with 96.50% CH4 yield. This proved to have a high level of accuracy, with a maximum difference between the graphical and simulated conversions of 1.96%. Furthermore, the reaction mechanism was also elucidated, showing associative adsorption based CO2 and CO methanation over Ru-catalyst, forming oxygenated intermediates that subsequently hydrogenated to CH4. Altogether, results suggest this combined carbon capture approach and its utilization with power-to-gas technology can effectively contribute to sustainable renewable energy.