有机胺修饰具有较大孔径介孔材料的二氧化碳吸附性能

Adsorption Capacity of Carbon Dioxide on Amine Modified Mesoporous Materials with Larger Pore Sizes

以非离子表面活性剂P123为模板剂,正硅酸甲酯为硅源,通过加入不同的扩孔剂制得具有较大孔径的SBA-15类介孔材料,并采用粉末X射线衍射(XRD)、低温氮气吸附-脱附、扫描电镜(SEM)、傅里叶变换红外(FTIR)光谱等手段对所得样品进行了表征.加入扩孔剂可以明显增大介孔材料的孔容和孔径,而异辛烷为扩孔剂的扩孔效果明显优于四氯化碳.经四乙烯五胺(TEPA)镀饰后,这些样品均表现出良好的CO2吸附性能.其中对于除去模板剂后再镀胺的样品,其CO2吸附能力与介孔材料孔道结构关系不大,而对于未除模板剂的原粉镀胺样品,CO2吸附能力则随孔道的变大而增强.此外,通过吸附等温线和CO2-程序升温脱附(TPD)手段比较了温度和压力对CO2吸附的影响,发现在较高温度下吸附时CO2的吸附能力随压力的变化存在显著差别,因而在这类TEPA修饰的介孔材料上可通过变压吸附的途径来实现对环境气流中CO2的吸附和分离.

Mesoporous silica SBA-15-like materials with large pores were synthesized using tri-block copolymer P123 as a structure-directing agent,tetramethoxysilane as the silicon source,and different organic solvents as swelling agents.The resulting materials were characterized by powder X-ray diffraction（XRD）,N2 adsorption-desorption,scanning electron microscopy（SEM）,and Fourier transform infrared（FTIR）spectroscopy.The results showed that the introduction of swelling agents effectively enlarged the pore diameter and pore volume of the SBA-15 materials,and pore swelling with isooctane was larger than that with CCl4 .When modified with tetraethylenepentamine（TEPA）,all of these composite materials exhibited excellent adsorption capacities for CO2 .The adsorption capacity of CO2 was independent of the pore structure,if the template was removed before modification with TEPA.By contrast, the adsorption capacity increased with the pore diameter when the as-synthesized mesoporous material was modified with TEPA.The effects of temperature and pressure on the CO2 adsorption capacity were investigated using adsorption isotherms and CO2 temperature-programmed desorption（TPD）.With CO2 adsorption at higher temperature,the composite materials showed different adsorption capacities with pressure variation.As a result,the adsorption and separation of CO2 on these TEPA modified mesoporous materials in ambient air flow can be realized via pressure swing adsorption.