Bi-functional Ru/Ca3Al2O6–CaO catalyst-CO2 sorbent for the production of high purity hydrogen via sorption-enhanced steam methane reforming

Abstract

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.