【作者】 王博；

【导师】 王志；

【作者基本信息】 天津大学 ， 化学工程， 2020， 博士

【摘要】 先进的CO₂分离技术是实现CO₂减排、化石能源高效利用以及CO₂资源化利用的关键。开发高性能CO₂分离膜将进一步推进CO₂分离膜技术的工业化应用。在众多CO₂分离膜中,混合基质膜同时具有聚合物和多孔材料各自的优势,具有较大的发展前景。但现有混合基质膜内的气体传递通道多为随机分布,多孔纳米材料被聚合物基质覆盖,且孔道尺寸可调控性相对有限,致使多孔材料的孔道优势无法充分发挥。因此,混合基质膜性能的提升空间有限。为解决上述问题,本文采用两种策略:构筑具有有序分布且贯通分离层气体传递通道的超薄混合基质复合膜,充分发挥多孔纳米材料的孔道作用;利用不同结构的聚合物链段占据MOF孔道体积的不同实现MOF孔道尺寸的精准调控,进而改变气体分子在孔道内的传递速率。首先,将聚乙烯基胺（PVAm）溶液与MIL-101（Cr）共混,聚醚共聚酰胺（Pebax）溶液与Ui O-66（Zr）共混,分别刮涂在涂覆硅橡胶（PDMS）中间层的聚砜（PSf）支撑体上,制备了PVAm基和Pebax基混合基质复合膜。考察了湿涂层厚度以及纳米颗粒添加量对膜性能的影响,最低分离层厚度为176 nm。探明了共混法制备混合基质复合膜性能提升有限的原因是聚合物基质与多孔材料间弱的界面相容性。其次,利用PVAm和硅烷偶联剂KH560修饰MIL-101（Cr）,制得MKP纳米颗粒。以MKP为分散相,PVAm为连续相,刮涂在聚乙烯醇（PVA）亲水改性后的PDMS/PSf支撑体上,通过重力诱导界面自组装的方法制备了超薄（～200 nm）混合基质复合膜。其中,MKP在复合膜分离层中为单层颗粒分布,且可作为贯通分离层的气体传递通道,连续相PVAm仅填充MKP颗粒间隙而不于膜表面覆盖。MKP与连续相PVAm间优良的界面相容性显著增加了MKP添加量。CO₂分子在MKP孔道中的传递方式为优先吸附-单分子层表面扩散,孔道优先吸附CO₂分子后阻碍其他气体分子的进入,实现了所制膜渗透选择性的大幅度提高。最后,在上述工作基础上,选用聚乙烯亚胺（PEI）,PVAm和Pebax聚合物分别修饰Ui O-66（Zr）,制得UKI、UKM和UKX纳米颗粒。随后,以Pebax为连续相,UKI、UKX和UKM为分散相,制备了三种具有贯通分离层气体传递通道的超薄（～130nm）混合基质复合膜。三种聚合物结构上的差异导致聚合物链段占据Ui O-66（Zr）孔道体积的不同,进而改变聚合物修饰后纳米颗粒的孔道尺寸。CO₂分子在三种纳米颗粒孔道内的传递方式均为优先吸附-单分子层表面扩散。根据孔道尺寸推测,CO₂分子在UKI、UKM和UKX孔道中分别以一个、两个和三个的形式传递。结果表明,膜内气体传递通道尺寸的变化可调控所制膜的渗透选择性。更多还原

【Abstract】 The advanced CO₂ separation technology is of primary importance for CO₂ mitigation,efficient use of fossil energy and CO₂ resource utilization.The development of high perfor-mance CO₂ separation membranes will further facilitate the industrial application of CO₂separation membrane technology.Among various CO₂ separation membranes,mixed ma-trix membranes（MMMs）show good perspective in industrial application because they combine the advantages of polymers and porous fillers.However,gas transport channels in the existing MMMs are mostly distributed at random,porous fillers are covered by polymers,and the controllability of pore size is relatively limited,so the value of the pore channels in porous materials cannot be fully utilized.Hence,the improvement of MMMs performance is limited.In order to address these concerns,this work proposed two strategies.Ultrathin mixed matrix composite membranes with ordered arrangement and unobstructed gas transport channels through separation layer were constructed,which can fully achieve the value of pore channels in porous fillers.Polymer segments with different structure can oc-cupy different volume in MOF pores,which can achieve precisely manipulation of MOF pore size,thereby changing the transport rate of gas molecules in the pores.Firstly,polyvinylamine（PVAm）solution was mixed with MIL-101（Cr）,and poly（ether-block-amide）（Pebax）solution was mixed with Ui O-66（Zr）,respectively.PVAm based and Pebax based mixed matrix composite membranes were fabricated by coating PVAm and MIL-101（Cr）dispersion,and Pebax and Ui O-66（Zr）dispersion on polysulfone（PSf）support covered with polydimethylsiloxane（PDMS）gutter layer,respectively.The influence of wet coating thickness and nanoparticle loadings on the membrane performance were investigated,the minimum thickness of separation layer was 176 nm,and the reasons for the limited improvement of the MMMs performance fabricated by common blending method were attributed to the weak interface compatibility between polymer matrix and porous materials.Secondly,MKP nanoparticles were obtained through modifying MIL-101（Cr）nano-particles with KH560 and PVAm.MKP was chosen as a dispersed phase,PVAm was cho-sen as a continuous phase.Ultrathin（～200 nm）mixed matrix composite membrane was fabricated by coating MKP and PVAm dispersion on PDMS/PSf support hydrophilically modified with polyvinyl alcohol（PVA）through the method of gravity-induced interfacial self-assembly,in which MKP nanoparticles were distributed in a single layer and used as unobstructed gas transport channels through the separation layer.Continuous phase PVAm only fill the gaps among nanoparticles and do not cover the surface.The excellent interface compatibility between MKP nanoparticles and the polymer matrix increases nanoparticle loadings siginificantly.The CO₂ molecules transport through the MKP pores in the manner of preferential adsorption-monomolecular surface diffusion,and CO₂ molecules preferen-tially adsorbed in MKP pores will hinder the entry of other gas molecules,which greatly enhances the permselectivity of the fabricated membranes.Lastly,on the basis of above work,UKI,UKM and UKX nanoparticles were obtained through modifying Ui O-66（Zr）nanoparticles with PEI,PVAm and Pebax polymers,respec-tively.After that,Pebax was chosen as a continuous phase,UKI,UKM and UKX were chosen as a dispersed phase to fabricate three ultrathin（～130 nm）mixed matrix composite membranes with unobstructed gas transport channels through separation layer.The varia-tion of polymer structure results in the difference in occupying MOF pore volume,which will change the pore sizes of the modified nanoparticles.CO₂ molecules transport through the three nanoparticles in the manner of preferential adsorption-monomolecular surface dif-fusion.Based on the pore size,it can be deduced that one,two or three CO₂ molecules can transfer through UKI,UKM and UKX pores respectively.The result showed that the perm-selectivity of the fabricated membranes can be adjusted by changing the sizes of gas transport channels in the membrane.更多还原