K2CO3-containing composite sorbents based on a ZrO2 aerogel for reversible CO2 capture from ambient air

Abstract

Abstract In this work, K2CO3-containing composite materials were synthesized based on a mesoporous zirconia aerogel prepared by an epoxide-assisted sol-gel method using supercritical drying in ethanol. The porous ZrO2 was impregnated with an aqueous solution of potassium carbonate to obtain composite materials with K2CO3 weight content ranging from 9 to 29 wt%. All the composites were tested in the process of CO2 absorption from the air with a relative humidity of 25% followed by thermal desorption at 200 °C. The samples after the CO2 absorption step were characterized by Fourier transform infrared spectroscopy and X-ray diffraction methods. Among the materials studied, the composite sorbent containing 23 wt% K2CO3 demonstrated the highest dynamic CO2 absorption capacity (4.6 wt%) in the temperature-swing absorption (TSA) cycles. The results indicate that a certain part of K2CO3 loaded into zirconia mesopores forms surface species which do not actively participate in the CO2 absorption and desorption processes. For the composite K2CO3/ZrO2 material with the optimal K2CO3 loading, CO2 absorption capacity is higher compared to the values obtained for K2CO3/γ-Al2O3 composite sorbents studied under the same conditions. Taking into account that this material demonstrates stable CO2 absorption capacity values in the consecutive TSA cycles and needs a relatively low temperature for regeneration, it should be considered for application in Direct Air Capture units.