Sorption-enhanced water gas shift reaction by in situ CO2 capture on an alkali metal salt-promoted MgO-CaCO3 sorbent

CO2 capture and sequestration is one of the viable solutions to reduce the CO2 emissions from fossil fuel combustion, and sorption-enhanced water gas shift (SEWGS) is a promising technology for pre-combustion CO2 capture. In this study, a novel alkali metal salt (AMS)-promoted MgO-CaCO3 sorbent was applied to the SEWGS process, and this sorbent exhibited fast sorption rate, high capacity and good stability in 30 CO2 capture cycles. Catalyst and sorbent particles were arranged in a layer-by-layer alternating configuration in the reactor. The effects of operating conditions such as temperature, pressure and initial H2O/CO molar ratio were investigated, and the thermodynamic equilibrium analyses of the CO2 sorption on AMS-promoted MgO-CaCO3 and the SEWGS process in the layered configuration were carried out, based on which the optimization of the reactor configuration was performed. A high-purity H-2 (99.4% in dry basis) was experimentally achieved in the SEWGS process at 573 K, 12 atm and an initial H2O/CO molar ratio of 1.5 with a three catalyst/sorbent layered configuration, and the cyclic stability was demonstrated over 10 consecutive SEWGS cycles.