(236c) Ruddlesden-Popper Sr2MnO4 As a Phase-Transition Sorbent for Sorption-Enhanced Steam Methane Reforming

The characteristics of CO₂ sorbents play a key role in sorption-enhanced steam methane reforming (SESMR) for hydrogen production. High CO₂ sorption capacity, good cyclic stability, and small temperature swing are required for an efficient SESMR process. This study reports Ruddlesden-Popper Sr₂MnO₄ as a CO₂ sorbent for hydrogen production from SESMR. The CO₂ sorption and desorption of this sorbent are triggered by the redox cycling of Mn⁴⁺/Mn²⁺, facilitating a cyclic phase transition that significantly reduces the temperature swing between the sorption and regeneration steps. Thermogravimetry analysis showed that the carbonation degree of Sr²⁺ and CO₂ sorption capacity of Sr₂MnO₄ reached 88+% and 0.26+ g CO₂/g Sr₂MnO₄ respectively over 20 redox cycles with a temperature swing of 100 ^oC. Based on these promising characteristics, the Sr₂MnO₄ sorbent was tested in a fixed bed reactor for SESMR. The results demonstrated that the Sr₂MnO₄ sorbent effectively intensifies hydrogen production, achieving 93+ vol% H₂ purity during the pre-breakthrough period. Even when considering the entire reforming step including the low-selectivity period, the gaseous product still contained 90+ vol% H₂, with stable performance throughout the 20 reaction cycles.