Preparation and CO₂ adsorption performance of a novel hierarchical micro/mesoporous solid amine sorbent

The mixed supports were obtained at different weight ratios of HZSM-5 to MCM-41 by physical mixing processes. Tetraethylenepentamine (TEPA) modified mixed supports sorbents were prepared by the impregnation method. The sorbents were characterized by nitrogen adsorption/desorption, Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) techniques. The effects of mixing ratios of HZSM-5 to MCM-41, TEPA loadings, adsorption temperatures, influent velocities, and CO₂ partial pressures on CO₂ adsorption capacity were investigated in a fixed bed reactor. It showed that the maximum CO₂ adsorption capacity was 3.57 mmol/g of HZSM-5/MCM-41-30%TEPA at the adsorption temperature of 55℃ and influent velocity of 30 mL/min. After ten-cycles, the CO₂ adsorption capacity decreased by 8.1%. CO₂ adsorption was determined by a two-stage process, a fast breakthrough adsorption and a gradual approaching equilibrium stage. Moreover, the breakthrough adsorption capacity accounted for approximately 80% of the equilibrium adsorption capacity. The Avrami model could fit well with the experimental data of HZSM-5/MCM-41-30%TEPA. It illustrated that the adsorption mechanism was dominated by both chemical and physical adsorption.