(373g) Cr-, Fe-, and Ga-Doped CaO Adsorbents for High Temperature CO2 Capture: An Adsorption and In-Situ XRD Study

Authors: 
Al-Mamoori, A., Missouri University of Science and Technology
Rownaghi, A., Missouri University of Science and Technology
Rezaei, F., Missouri University of Science and Technology
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.