Improving Adsorptive Performance of CaO for High-Temperature CO₂ Capture through Fe and Ga Doping

Abstract

Calcium oxide is an efficient adsorbent for high-temperature CO2 capture process, however, it suffers from rapid deactivation and capacity loss after a few cycles as a result of particle sintering. Metal oxide doping is an effective strategy to address the durability issue of CaO. In this investigation, we report development of novel metal oxide-doped CaO adsorbents with high capture capacity, fast kinetics, and long-term stability. In particular, Fe and Ga with varied concentrations were used as promoters to improve the adsorption performance of CaO adsorbent. The doped adsorbents comprising of 10% Fe@CaO and 10% Ga@CaO exhibited the highest adsorption capacities of 13.7 and 14.2 mmol/g, respectively, at 650 °C, which were at least 2-folds higher than that of the bare CaO. Moreover, the doped-CaO materials showed reversible performance by desorbing almost all of the adsorbed CO2 during desorption step at the same temperature. Through in situ X-ray diffraction measurements, it was shown that the carbonation under CO2 and desorption under N2 flow take place, resulting in efficient CO2 capture and adsorbent regeneration. The cyclic adsorption–desorption runs demonstrated the excellent stability of the materials by retaining 95% of their initial capacity after 10 cycles. Moreover, adsorption temperature was found to have a favorable impact on CO2 uptake over the doped adsorbents. The findings of this study highlight the feasibility of metal doping approach for improving the adsorptive performance of CaO adsorbents that could be used for high-temperature capture processes.