Bi-functional Ru/Ca3Al2O6–CaO catalyst-CO2 sorbent for the production of high purity hydrogen via sorption-enhanced steam methane reforming†
Sorption-enhanced steam methane reforming (SE-SMR) combines steam methane reforming and a CO2 abstraction reaction to yield high purity hydrogen. In this work, we report on the development of a bi-functional catalyst–sorbent containing Ru as the reforming catalyst and CaO as the solid CO2 sorbent via a citrate sol–gel route. The material contains CaO, a structural stabilizer (Ca3Al2O6) and Ru nanoparticles (∼5 nm, 3 wt%) that are formed upon reduction in H2. This new material was found to outperform significantly the benchmarks Ni–CaO and Ru/limestone in terms of yield of high-purity hydrogen and coke resistance. Using highly active Ru nanoparticles for the SMR allowed to maximize the weight fraction of the CO2 sorbent CaO, hence increasing significantly the CO2 capture capacity of the material. This favorable characteristic of the material led to an appreciably extended pre-breakthrough duration. In addition, we demonstrate that the material developed was very stable over multiple SE-SMR/regeneration cycles. The excellent cyclic stability is ascribed to the presence of Ca3Al2O6 that stabilized effectively the porous structure of the material against sintering.