Preparation And Properties Of Amine-functionalized Micro/Mesoporous Composite Sieves For Carbon Dioxide Capture

The excessive consumption of fossil fuels has caused a significant growth of anthropogenic CO₂ emission,especially in the power plant using coal.The fossil fuels are difficult to be replaced by new and renewable energy within a short period,but reducing CO₂ emissions is becoming an increasingly urgent issue.Therefore,the development of efficient technologies for CO₂ capture and sequestration?CCS?is urgently required.Solid amine adsorbents have been studied in recent years due to their advantages,such as fast adsorption and desorption rate of CO₂,low regeneration energy consumption,and little corrosion in the equipment.However,in the process of preparation of solid amine adsorbents,the most commonly used carriers are mesoporous molecular sieves,wheresa the pore walls of the mesoporous molecular sieves are thin,the pore size is uniform,being easy to collapse under the high temperature.Therefore,to overcome the limitations of a single channel,a series of amino functionalized CO₂ adsorption materials were developed by introducing a micro/mesoporous composite sieves as a carrier.The main results are as follows:1.The micro/mesoporous composite sieves is prepared by hydrothermal crystallization of microporous zeolite silicon source,and the adsorption properties of CO₂ are investigated.The experimental results show that when the ratio of silica to alumina is 50,and the concentration of Na OH solution is about 2.5 mol/L,the adsorption performance is better.A novel tetraethylenepentamine?TEPA?modified ZSM-5/MCM-41 is prepared by a wet impregnation method,and the CO₂ adsorption performance is tested in a fixed bed reactor.When the TEPA loading of 40 wt.%,adsorption temperature of 70 °C,the CO₂ adsorption capacity reaches the maximum amounts of 4.41 mmol·g^-1.After a ten-cycle adsorption-desorption test,the adsorption capacity of ZSM-5/MCM-41-40%TEPA dropped by 7.6%,respectively.2.The L-Arg modified ZSM-5/MCM-41 is prepared by wet impregnation method,and the CO₂ adsorption performance is investigated in a fixed bed.The results show that,when the L-Arg loading of 30 wt.%,adsorption temperature of 55 °C,and intake flow of 30 mL·min^-1,the CO₂ adsorption capacity is equal to the maximum value of 3.07 mmol·g^-1.When the CO₂ concentration is 12%¹5%,the saturated adsorption capacity of ZSM-5/MCM-41-30%L-Arg is more than 2 mmol?g^-1.After a six-cycle adsorption-desorption test,the adsorption capacity of ZSM-5/MCM-41-30%L-Arg dropped by 42%,respectively.3.The adsorption equilibrium,adsorption thermodynamics and adsorption kinetics of CO₂ on amine functionalized ZSM-5/MCM-41 are analyzed.The isosteric heat of CO₂ adsorption on ZSM-5/MCM-41-40%TEPA ranges from 30 to 60 kJ·mol^-1,and the adsorption mechanism is dominated by physical and chemical adsorption.In an initial period of adsorption,there is a rapid CO₂ adsorption rate which is determined by the chemical reaction.As the adsorption increased with time,most of the active sites are gradually ocupied,the adsorption rate drops greatly due to the effect of gas diffusion.After amine modification,CO₂ adsorption rate decreases because of the increased CO₂ diffusion resistance.With increasing temperature,CO₂ adsorption rate is significantly increased.