新型多级微/介孔固态胺吸附剂的制备及其CO2吸附性能研究

将HZSM-5与MCM-41按不同质量比混合得到复合分子筛载体,以四乙烯五胺(TEPA)为改性剂,采用浸渍法将其负载到复合分子筛上,制备了一系列新型的具有多级微/介孔结构的固态胺吸附剂。采用N₂吸脱附、傅里叶变换红外光谱(FT-IR)、热重分析(TGA)等手段对吸附剂进行表征。在固定床反应器中考察了HZSM-5和MCM-41的质量比、TEPA负载量、吸附温度、进气流量和CO₂分压等因素对CO₂吸附性能的影响。结果表明,当HZSM-5与MCM-41的质量比为1:1、TEPA负载量为30%、吸附温度为55℃、进气流量为30 mL/min时,平衡吸附量高达3.57 mmol/g,且经10次吸脱附循环后,吸附量仅下降8.1%。HZSM-5/MCM-41-30%TEPA对CO₂的吸附过程包括快速的穿透吸附和相对缓慢的逐渐平衡阶段,且穿透吸附量接近于平衡吸附量的80%。HZSM-5/MCM-41-30%TEPA对CO₂的吸附过程符合Avrami动力学模型,表明CO₂吸附是物理吸附和化学吸附的结果。

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.