An adsorptive reactor for CO2 capture from flue gas and conversion to CH4–Parametric analysis

• An adsorptive/reactive process for CO 2 capture and conversion to CH 4 was studied. • The adsorptive reactor was always operated until a cyclic steady-state was achieved. • The influence of pressure, temperature, bed ratio, and its configuration was assessed. • The cyclic process allows producing CH 4 with purity >80 % and productivity up to 0.456 mol·kg −1 ·h −1 . In Power-to-Methane processes, green H 2 and CO 2 are converted into CH 4 , or synthetic natural gas, which is easily distributed or stored. This work focuses on a cyclic process that combines, in the same device, the capture of CO 2 and its catalytic conversion to CH 4 . To this end, a column was packed with a CO 2 -selective adsorbent and a methanation catalyst, both commercial materials. The column was submitted to multiple adsorption/reactive regeneration cycles at different operating conditions. During adsorption, the inlet stream comprised N 2 and CO 2 (15 %), the latter being captured by the adsorbent. During the reactive regeneration stage, the feed was H 2 , which reacted with the CO 2 , producing CH 4 and regenerating the adsorbent. The present work assessed the effect of pressure (1, 4, and 7 bar), temperature (300 and 350 °C) and for the first time also adsorbent-to-catalyst mass ratio (1, 5, and 10) and bed configuration (layered or mixed bed), providing relevant insights for the optimization of such a process. The adsorbent-to-catalyst mass ratio of 5 resulted in the best overall performance, balancing the amount of adsorbent and the quality of its regeneration by the catalyst (intimately connected with the amount of H 2 O formed in the methanation reaction). Working at a higher temperature (350 °C) was found advantageous. Operation under higher pressure was beneficial for almost all performance indicators calculated. However, when using a mass ratio of 5, the increase from 4 bar to 7 bar led to a decrease in CH 4 purity due to dilution in N 2 . The highest CH 4 productivity achieved was 0.456 mol CH4 ·kg cat+ads –1 ·h −1 , obtained at 7 bar, 350 °C and employing an adsorbent-to-catalyst mass ratio of 5. A final study aimed at CH 4 purity enhancement, being achieved CH 4 outlet contents over 80 %.