Co2 Separation from Ambient Air by Novel CeO2-Based Adsorbent

Abstract

CO2 direct air capture is a process for CO2 negative emission to prevent global warming. To consider an application for CO2 direct air capture using temperature swing adsorption process, CeO2-based and zeolite-based adsorbent were investigated for their CO2 adsorption and desorption characteristics under atmospheric conditions. The CeO2-based adsorbent exhibited a larger CO2 adsorption amount than zeolite-based adsorbents at atmospheric CO2 concentration under dry conditions. Remarkably, under wet conditions, the CO2 adsorption amount of the CeO2-based adsorbent remained large while the zeolite-based adsorbents exhibited almost no CO2 adsorption. A CO2 adsorption isotherm study revealed that CO2 adsorption of the CeO2-based adsorbent was stable at a low CO2 partial pressure, indicating strong CO2 chemical adsorption. The CO2 desorption of the CeO2-based adsorbent was observed at relatively low temperatures below 200 °C under both dry and wet conditions. The CO2 desorption temperature under dry conditions was lower than that under wet conditions. In situ Fourier transform infrared spectroscopy indicated that in spite of the different CO2 desorption temperatures, the CO2 adsorbed on the CeO2 formed bidentate carbonate species under both dry and wet conditions. Temperature dependence analysis of the spectra revealed that CO2 desorption was accelerated under wet conditions after liquid H2O desorption occurred, indicating that CO2 and H2O had an attractive interaction, which led to a higher CO2 desorption temperature.