Experimental demonstration of a sorption-enhanced methanation (SEM) cyclic process on a lab-scale TRL-3 fixed bed reactor

In this work, the scaling-up of the sorption-enhanced methanation (SEM) process to a TRL-3 fixed bed reactor has been demonstrated. The SEM process for synthetic natural gas (SNG) production consists mainly of two stages: in the first stage, the zeolite facilitates the removal of a product from the methanation reaction, thereby enhancing CO/CO2 conversion; in the second stage, zeolite regeneration takes place. The materials chosen for the process development were zeolite 4A, combined with a Nickel-based catalyst, selected for their high H2O adsorption capacity and high catalytic activity, respectively. Various operational variables, including temperature and pressure, were optimized to enhance the performance of both components. Specifically, during the regeneration step, when the zeolite became saturated, the best results were achieved by implementing pressure variations—from 10 bar at 230 °C during the SEM reaction to atmospheric pressure—while maintaining a constant temperature throughout the entire process. These operating conditions were tested during more than 20 SEM/regeneration cycles which were performed for a feed gas containing H2/CO/CO2, achieving a stable performance throughout the cycles and a constant CH4 purity of 100 % during 25 min for the operating conditions chosen. Finally, the number of reactors needed to obtain a continuous stream of CH4 was calculated giving a process productivity of 8.00×10-4 molCH4/kgcat·s.