An amine-bifunctionalization strategy with Beta/KIT-6 composite as a support for CO₂ adsorbent preparation

An amine-bifunctionalized composite strategy was used to fabricate grafted-impregnated micro-/mesoporous composites for carbon dioxide capture. The micro-/mesoporous Beta/KIT-6 (BK) composite containing a high-silica zeolite with a three-dimensional twelve-membered ring crossing channel system and cubic structural silica was used as a support, and 3-aminopropyltrimethoxysilane (APTS) and tetraethylenepentamine (TEPA) were used as the grafted and impregnated components, respectively. The amine efficiency, adsorption kinetics, thermal stability, regeneration performance, and the effects of impregnated amine loadings (30-60%) and temperatures (40-90 °C) on the CO₂ adsorption performance were investigated using a thermal gravimetric analyzer (TGA) in the mixed gases (15 vol% CO₂ and 85 vol% N₂). At 60 °C, the bifunctionalized Beta/KIT-6 (1 mL APTS g^-1 BK) displayed the highest CO₂ adsorption capacity of 5.12 mmol g^-1 at a TEPA loading of 50%. The kinetic model fitting results showed that the CO₂ adsorption process was a combination of physical and chemical adsorption, wherein the chemical adsorption is dominant. After five adsorption/desorption cycle regenerations, the saturated adsorption capacity of the composite material was 4.86 mmol g^-1, which was only 5.1% lower than the original adsorption capacity. The composites demonstrated excellent CO₂ adsorption performance, indicating the promising future of these adsorbents for CO₂ capture from actual flue gas after desulfurization.