Kinetics and thermodynamics study on low energy synthesis of porous geopolymer based solid amine sorbent for efficient CO2 capture

Abstract

Geopolymers are new type of promising CO2 adsorption materials ascribing to their special zeolite-like structure, but the underdeveloped pore structure of geopolymer is still challenging when applied in CO2 capture. In this study, the pore content of geopolymer was significantly improved by nearly 71 time via a facile acid treatment strategy, and this process overcame only low energy barriers of 1.852, 4.336 kJ/mol for denatrium and dealumination. Moreover. after the amine impregnation, the resultant adsorbent exhibited high CO2 adsorption capacity up to 4.18 mmol/g at 50 °C in 15vol%CO2/85vol%N2, and the capacity remained above 95% after 5 cycles, which are significantly superior than the reported geopolymer-based CO2 adsorbents. Kinetics, thermodynamics and in-situ DRIFTs analysis confirm that the adsorption of CO2 is mainly oriented by the zwitterion reaction mechanism by forming carbamate, while the acid treatment of geopolymer greatly improved the dispersity of the amine molecules that enhanced the mass transfer of CO2 to the active adsorption site. Moreover, the silanol nest in the geopolymer matrix formed during the acid treatment process directly participated in the CO2 adsorption process, which decreased the energy barrier for the proton transfer between CO2 and amine groups, thereby exhibiting excellent CO2 capture performance.