Impact of sorbent-catalyst layouts on Ru/K-based DFMs for integrated CO2 capture and methanation

Dual Function Materials (DFMs) for integrated CO2 capture and methanation were investigated to assess the role of the spatial configuration between a Ru-based methanation catalyst and a K-based CO2 sorbent by combining microreactor experiments and in situ FT-IR spectroscopy. The presence of Ru and K over the same support (i.e., Ru-K/Al2O3), as in conventional DFMs, resulted in a significantly higher utilization of the adsorbed CO2 compared to a physical mixture of segregated Ru/Al2O3 and K/Al2O3. However, the physical mixture still enabled cyclic operations, achieving complete CH4 selectivity, unlike Ru-K/Al2O3. Indeed, the proximity of Ru and K introduced a trade-off between a reduced methanation rate and increased utilization of the captured CO2 during the cycle. These findings pave the way for the separate optimization of catalyst and sorbent components in integrated CO₂ capture and conversion systems, since the physical mixture outperforms conventional DFMs in some respects.