High and efficient Li2CuO2-CO2 chemisorption using different partial pressures and enhancement produced by the oxygen addition

Abstract

CO2 chemisorption in Li2CuO2 was studied under different CO2 and O2 partial pressures, through thermogravimetric analysis. Results showed that using low PCO2 (0.05–0.2) did not impact in the final CO2 chemisorption, in comparison to the PCO2=1. When oxygen was added to the flow (PO2 between 0.03 and 0.2) the CO2 chemisorption presented different modifications: The CO2 chemisorption is produced at lower temperatures; the CO2 carbonation kinetics is improved and the material is able to perform CO2 carbonation-decarbonation cycles. CO2 chemisorption kinetic parameters were determined assuming a first order reaction between 450 and 750°C, where k and ΔH‡ values confirmed that CO2 carbonation on Li2CuO2 is importantly enhanced with oxygen addition. If oxygen is not present in the flow gas, it has to be released from the Li2CuO2 crystalline structure to complete the carbonation process, while if oxygen is supplied in the flow gas the carbonation process is strongly facilitated, as the carbonation does not depend on the oxygen crystalline diffusion. Additionally, results evidenced that Li2CuO2 recrystallization, during the cyclic process, is performed by a different reaction mechanism. During the decarbonation process, partial lithium reincorporation, to the cuprate phase, produces Li3Cu2O4. The formation of this secondary phase (Li3Cu2O4) implies a partial copper oxidation, which must be induced by the PO2. When a total decarbonation is produced, Li2CuO2 is totally recovered.