Unveiling the dynamic thermal separation process of CO2 on the surface of calcium oxide: An ab-initio molecular dynamics study with experimental verification

Abstract

Heating to release CO2 captured by Calcium oxide is one of the crucial steps in CO2 capture technology. However, the molecular mechanism underlying CO2 thermal desorption and the impact of CaO hydration on CO2 desorption remain unclear. Based on ab initio molecular dynamics (AIMD), a comprehensive analysis of the desorption and regeneration mechanism of carbonized CaO surfaces was conducted. Temperature is the primary factor responsible for CO2 thermal desorption on CaO surfaces. Simulations of CO2 thermal-dynamic desorption indicate that the desorption temperature range of CO2 from a dry CaO surface was between 400 and 500 °C. The explicit solvent model was utilised to simulate the desorption of CO2 under hydration condition. In the temperature range of 25–800 °C, the desorption behaviour of CO2 is substantially inhibited in the presence of water layers and Ca(OH)2. Consistent with the AIMD results, the thermal desorption experiment following CO2 adsorption confirmed that the desorption temperature of CO2 increases considerably when the adsorbed sample hydrates. Consequently, the desorption process of CO2 on CaO surface was comprehensively elucidated by a combination of theoretical study and experimental validation, thereby guiding the development and regeneration of CaO-based adsorbents.