Effects of CaO/MgO compositions on the performances of sorption enhanced water gas shift reaction: A thermodynamic analysis

The CO₂ sorption-enhanced water gas shift reaction (SE-WGSR) is a promising approach that facilitates in-situ CO₂ capture and promotes hydrogen yields by shifting the equilibrium of the WGSR towards higher CO conversion. Developing an effective sorbent/catalyst is one of the key challenges for industrial-scale applications of SE-WGSR technology. The present study investigated mixed CaO/MgO as a sorbent material for an SE-WGSR process. The performances of the SE-WGSR with various concentrations of CaO/MgO mixtures were analyzed by using the Gibbs free energy minimization method. The ultimate objective was to secure a high CO conversion and a low energy requirement for sorbent regeneration. The results showed that the increasing CaO in the CaO/MgO mixture significantly increased the CO conversion, while the increase in MgO decreased the total sorbent regeneration enthalpy. A CaO/MgO mixture of 20 mol % CaO was identified as the optimal sorbent composition, achieving a 29.3 % higher CO conversion in comparison to 100 % MgO sorbent at 40 bar pressure and 350 °C, requiring 14.1 % less regeneration enthalpy than a 100 mol % CaO sorbent. Therefore, the optimal sorbent mixture composition can result in the realization of an efficient SE-WGS process to achieve high CO conversion at the appropriate regeneration energy cost.