Self-activation of CaO/Ca3Al2O6 sorbents by thermally pretreated in CO2 atmosphere

Abstract CaO/Ca 3 Al 2 O 6 sorbents have been proved to be a promising sorbent for CO 2 sorption. However, the sorbents still suffer from low CO 2 sorption capacity. In this work, self-activation was generated via thermally pretreating CaO/Ca 3 Al 2 O 6 sorbents in CO 2 atmosphere at various temperatures to enhance the CO 2 sorption capacity of CaO/Ca 3 Al 2 O 6 sorbents. Results showed that the thermally pretreated temperature plays an overwhelming role in the CO 2 sorption capacity and stability of the CaO/Ca 3 Al 2 O 6 sorbents. Superior CO 2 sorption capacity (8.01 mmol g −1 for C9A1-650 at 500 °C) is achieved, which is 72% higher than that of C9A1 (no pretreatment sample). After 50 carbonation-calcination cycles, the CO 2 sorption capacity of C9A1-650 still remained 20% higher than that of C9A1. The high CO 2 sorption capacity is ascribed to the smaller CaO grain size (37.1 nm) and the higher surface area (13.1 m 2  g −1 ), resulting from the self-activation process. Meanwhile, the CO 2 cyclic sorption stability is due to the small original surface free energy. Furthermore, the C9A1-650 sorbent is employed to use in sorption enhanced methane steam reforming process. It provides a H 2 concentration of 98.9% and CH 4 conversion of 98.7%, presenting greatly potential in practical application.