CaO-based CO2 sorbents play a significant role in sorption enhanced methane steam reforming process for hydrogen production and CO2 emission reduction. In this work, pretreatment of CaO/Ca3Al2O6 sorbents in steam atmosphere at different temperatures was investigated for its influence on CO2 sorption capacity and cyclic stability. The sorbents were synthesized to contain a CaO to Al2O3 mass ratios of 9:1, and then subjected to cycling tests with repeated carbonation and calcination process. Results showed that the sorbents pretreated by steam at 250 °C obtained a minimum CaO grain size of 37.9 nm and a maximum surface area of 17.4 m2·g-1 . This resulted in an increase in CO2 sorption capacity, up to 8.53 mmol CO2·g-1 sorbent. After 50 cycles, the CO2 sorption capacity decreased, but still remained 10% above those for the original (no pretreatment) sample. The mechanism about the improved CO2 sorption performance of the pretreated sorbents was also postulated.
Keywords CO2 capture; CaO; steam pretreatment; sorption performance; mechanism