Role of fiber density of amine functionalized dendritic fibrous nanosilica on CO₂ capture capacity and kinetics

Abstract

Textural properties of the solid sorbents are critical to tuning their CO₂ capture performance. In this work, we studied the effect of fiber density (in turn, pore size, distribution, and accessibility) on CO₂ capture capacity and kinetics. CO₂ solid sorbents were prepared by physisorption of tetraethylenepentamine (TEPA) molecules on dendritic fibrous nanosilica (DFNS) with varying fiber density. Among the various DFNS, the DFNS with moderate fiber density [DFNS_-3] showed the best CO₂ capture capacity under the flue gas condition. The maximum CO₂ capture capacity achieved was 24.3 wt % (5.53 mmol/g) at 75 °C for DFNS_-3 under humid gas conditions. Fiber density also played a role in the kinetics of CO₂ capture. DFNS_-1 with dense fiber density needed ∼10.4 min to reach 90 % capture capacity, while DFNS_-3 (moderate fiber density) needed only 6.4 min, which further decreased to 5.9 min for DFNS_-5 with lightly dense fibers. The DFNS-impregnated TEPA also showed good recyclability during 21 adsorption and desorption cycles under humid and dry conditions. The total CO₂ capture capacity of DFNS_-3 (14.7) in 21 cycles was 108.9 and 105.0 mmol/g under humid and dry conditions, respectively. Adsorption lifetime calculation and recyclability confirmed the fiber density-dependent CO₂ capture performance.