A novel (CaO/CeO2)@CeO2 composite adsorbent based on microinjection titration-calcination strategy for CO2 adsorption

Abstract

A simultaneous titration-calcination strategy was proposed to synthesize core–shell type (CaCO3/Ce(OH)CO3)@Ce(OH)CO3 precursors by titrating Ca2+ and Ce3+ into aqueous CO2 storage material (CO2SM) solution simultaneously without adding any templating agents or surfactants. After calcination at 900 °C, the novel core–shell type (CaO/CeO2)@CeO2 composite adsorbent with the strong stability of adsorption cycle was synthesized. The effects of Ca/Ce doping ratio, CO2SM dosage, drop rate and temperature conditions on the CO2 adsorption performance on the composite adsorbent during the calcium cycle were investigated. The synthetic adsorbent with a Ca/Ce doping ratio of 24: 1 had the strongest CO2 capture performance during the calcium cycle, and it mainly consisted of CaO and CeO2. The CO2 adsorption amount still maintained at about 430 mg/g after 15 cycles under the adsorption–desorption conditions at 750 °C and 900 °C. (CaO/CeO2)@CeO2 composite adsorbent is a core–shell structure with CeO2 as the shell and CaO/CeO2 as the liner, in which CeO2 is uniformly dispersed in CaO pore channels, which gives the adsorbent a stable pore structure and enhances the anti-sintering performance of Ca-based adsorbent. Due to the special property of CeO2, it can also promote the ion migration during the carbonation process, thus maintaining the adsorption activity. Density functional theory (DFT) calculations successfully explain why CeO2 can be used as an inert dopant to promote the adsorption of CO2. After that, the synthesis mechanism of core–shell adsorbent and the reaction mechanism of CO2 adsorption are proposed in conjunction with the series characterization. This work provides a new strategy for the efficient synthesis of Ca-based adsorbents with special morphology and a new idea for CO2 capture.