Sorption-enhanced CO and CO2 methanation (SEM) for the production of high purity methane

Abstract

Sorption-enhanced methanation (SEM) is one of the solutions proposed for the production of high quality synthetic natural gas (SNG) under mild conditions of temperature and pressure. In this novel process, the methanation reaction is performed in the presence of an adsorbent that retains the water produced as by-product. The SEM potential of a Rh-based catalyst and a zeolite 5A adsorbent has been demonstrated for both CO and CO2 hydrogenation. Pure CH4 production was possible operating at 275 °C and atmospheric pressure under sorption-enhanced CO2 methanation conditions for space velocities of up to 514 mlCO2/gcat/h. For sorption-enhanced CO methanation, CH4 purities of 86 vol% were achieved under the same operating conditions but at lower space velocity (440 mlCO/gcat/h). Finally, SEM/regeneration cycles were performed for a feed gas containing CO and CO2, achieving stable performance throughout the cycles and a constant CH4 purity of about 60 vol% for the operating conditions chosen.