(373g) Cr-, Fe-, and Ga-Doped CaO Adsorbents for High Temperature CO2 Capture: An Adsorption and In-Situ XRD Study
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 particles sintering sintering. Metal doping is an effective strategy to address the durability issue of CaO. In this investigation, we report development of novel metal-doped CaO adsorbents with high capture capacity, fast kinetics, and long-term stability. In particular, Cr, Fe, and Ga with carried concentration were used as promoters to improve the adsorption performance of CaO adsorbent. The doped adsorbents comprising of 1% Cr@CaO, 10% Fe@CaO, and 10% Ga@CaO exhibited the highest adsorption capacities of 12.3, 13.7, and 14.2 mmol/g, respectively at 650 ºC which were at least two folds higher than that of the bare CaO. Moreover, the doped-CaO sorbents showed reversible performance by desorbing almost all of the adsorbed CO2 during desorption step at the same temperature. Through in-situ XRD 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 importance of metal-doped CaO adsorbents as promising candidates for use in calcium looping or combined capture-utilization processes.