In-situ FTIR analysis on conventional and sorption-enhanced methanation (SEM) processes over Ni, Rh, and Ru-based catalyst systems

In this work, the sorption-enhanced methanation (SEM) process, in which an H2O sorbent is combined with a catalyst to remove the produced H2O, allowing the reaction equilibrium to shift towards CH4, was implemented to enhance the conventional CO2 methanation at lower temperature. Three commercial catalysts based on Rh, Ru and Ni were catalytically tested and examined via in-situ FTIR measurements. Based on the conventional tests, Ni-based catalyst turned out to be the most efficient catalyst system (ca. 80% CO2 conversion at 250°C, GHSV = 509 Nml/h·gcat) which, was then combined with the zeolites 4A and 13X to maximise the production of CH4 in SEM conditions. The best results pointed to zeolite 4A since the zeolite 13X adsorbed a significant amount of CO2 as a feed gas, which was chemisorbed on the surface of the zeolite favouring the formation of formates and carbonates during the regeneration step. However, the same reaction mechanism was proposed for conventional methanation and SEM process.