用于C3H6/C3H8分离的ZIF-8混合基质炭膜.pdf

以ZIF-8为掺杂剂，通过对混合基质聚合物膜高温炭化制备了混合基质炭膜.通过XRD、SEM、N2 吸附等表征方法探究了ZIF-8高温热解前后微观形貌和孔结构特征对炭膜微孔结构和炭结构的影响，并考察了ZIF-8掺杂量与炭化温度对混合基质炭膜CsH/C:H：渗透分离性能的影响.结果表明，ZIF-8经550 热处理后仍能够部分保持其微观形貌和孔结构，同时ZIF-8热解衍生多孔炭的引入增加了炭膜具有筛分功能的极微孔含量，因而显著提高了混合基质炭膜对CsH/C3H：的分离选择性.在ZIF-8掺杂质量分数1%和炭化温度550下，所制备ZIF-8混合基质炭膜的C.H。渗透系数高达17 4Barrer，C H./C.H 分离选择性为14.4,与未掺杂的纯炭膜相比(C:H/C.H选择性为5.1)提高了18 2%,渗透选择性超越了聚合物膜的C.H/C.H分离上限,关键词：混合基质膜；炭膜；金属有机框架；气体分离；轻烃分离中图分类号：TQ028.8doi:10.16159/ki.issn1007-8924.2023.04.011丙烯是一种重要的有机化工原料，在其生产过程中，将丙烯与丙烷等杂质进行高效分离是重要步骤1-2 .然而，由于它们具有相似的分子动力学直径和临界温度，分离较为困难.目前，工业上常用的分离方法，如深冷分离和变压吸附法，分离能耗成本较高3.膜分离法作为新一代气体分离技术，具有操作简单和高效节能的优势，有希望实现在轻烃分离领域的工业化应用4。膜材料是膜分离技术的核心5，制备高渗透选择性的膜是膜技术大规模应用的关键.传统的聚合物膜由于受到材料本身的限制,对CH。渗透性能普遍较低,且渗透性与选择性之间相互制约,因而存文献标志码：A文章编号：10 0 7-8 9 2 4(2 0 2 3)0 4-0 0 8 4-0 7在分离上限.通过向主体基质中引人高性能的掺杂剂制备混合基质膜，有望同时提高膜的气体渗透系数与分离选择性，突破聚合物膜材料的分离上限6-8 .炭分子筛膜(简称为炭膜)是一种新型的炭基多孔膜材料.由于独特的刚性狭缝型孔道结构（极微孔径 0.7 nm)9,使其具备一定的C,H。/C,H。分离性能10-13.为了进一步提高炭膜对 C,H。/C,H。的渗透分离性能，可以向炭结构中增加可高效分离C.H/CsH：的特殊孔道结构.其中，通过向炭膜中引人具有轻烃分离能力的多孔纳米粒子来构筑炭膜对C:Hs/C.H:分离的特异性孔道体系是一种简单收稿日期：2 0 2 2-12-18；修改稿收到日期：2 0 2 3-0 5-2 2基金项目：中国博士后科学基金（2 0 2 1M690516）；国家自然科学基金项目（2 18 7 8 0 33，2 2 17 8 0 44）第一作者简介：徐笑峰（1996-），男，内蒙古通辽市人，硕士生，主要从事气体膜分离技术通讯作者，E-mail:引用本文：徐笑峰，徐瑞松，王月，等.用于C:Hs/CsH分离的ZIF-8混合基质炭膜J膜科学与技术，2 0 2 3,43（4)：8489.Citation:Xu X F,Xu R S,Wang Y,et al.ZIF-8-based mixed matrix carbon membranes for C Hs/C,Hs separationJ.Membrane Science and Technology(Chinese),2023,43(4):84-89.第4期且高效的方法14-15.ZIF-8作为一种金属-有机骨架材料(MOFs)16-18，具有较高的比表面积和永久的孔隙率，其独特的0.40 0.42 nm孔结构对C.H。/C.H。的扩散选择性可达到12 0 以上19.研究发现,ZIF-8还具有较高的热稳定性，经高温炭化衍生得到的纳米多孔炭材料仍大部分保持其丰富的孔结构和比表面积2 0 ，因此，ZIF-8可用作掺杂剂引入到炭膜中,强化高效分离CH/CsH：的孔道结构。基于此,本研究首先将ZIF-8纳米颗粒掺人炭膜前驱体聚合物中，然后经高温炭化制备了ZIF-8混合基质炭膜.考察了ZIF-8热处理前后的微观形貌和孔结构，以及其对炭膜炭结构、极微孔结构和C.H/CsH。渗透分离性能的影响.1实验材料和方法1.1材料聚芳醚酮,实验室自制；N,N-二甲基乙酰胺(DMAc)，天津科密欧试剂有限公司；硝酸锌Zn（NO 3）2 6H,O，国药集团化学试剂有限公司；2-甲基咪唑，上海阿拉丁生化科技股份有限公司.1.2分析测试仪器超声仪，上海生析超声仪器有限公司；磁力搅拌器，巩义市予华仪器有限责任公司；刮膜装置，实验室自制；NovaNanoSEM450型场发射扫描电镜，美国FEI公司;D/Max-2400型粉末X射线衍射分析仪，日本Rigaku公司；Autosorb-iQ2型全自动物理吸附仪，美国Quantachrome公司.1.3ZIF-8纳米粒子的制备在室温条件下进行ZIF-8 纳米粒子的合成2 1：首先称取一定质量的Zn(NO3）2 6HO与2-甲基咪唑并分别溶于2 0 0 mL无水甲醇中.然后将溶有2-甲基咪唑的甲醇溶液倒入溶有Zn(NO:）2 的甲醇溶液中，剧烈搅拌30 min.反应结束后，离心收集制备的ZIF-8纳米颗粒，用无水甲醇洗涤3次.最后将收集到的样品在室温条件下干燥16 h.1.4ZIF-8混合基质炭膜的制备首先将研磨过的ZIF-8纳米粒子均匀分散在DMAc溶剂中，通过超声与搅拌进一步减少团聚.然后向ZIF-8分散液中加人聚芳醚酮溶液，经充分超声搅拌后制得均匀、分散性良好的铸膜液，并在刮膜台上刮制厚度均一的混合基质聚合物膜.经真空干燥处理后在惰性气体氛围下高温炭化制备混合基徐笑峰等：用于CsHc/C.Hs分离的ZIF-8混合基质炭膜2结果与讨论2.12ZIF-8和ZIF-8热解衍生纳米粒子的微观形貌与孔结构表征对所制备的ZIF-8及其热解衍生纳米粒子进行了微观结构表征，如图1所示.合成的ZIF-8具有与标准谱图相同的晶体特征峰，表明成功制备了ZIF-8纳米粒子且具有较好的结晶度2 2 .经过550处理后,ZIF-8衍生纳米粒子仍具有ZIF-8(ne)/10图1ZIF-8与ZIF-8-550衍生纳米粒子的XRD衍射谱图Fig.1 XRD patterns of ZIF-8 and ZIF-8-550derived nanoparticles85质炭膜.将550 制备的ZIF-8纳米多孔材料与ZIF-8混合基质炭膜分别标记为“ZIF-8-550”与“ZIF-8CMSM-550.1.5月膜的气体渗透性能测试利用恒压力-变体积法对膜材料的气体渗透性能进行测试.采用实验室自制的气体渗透测试装置，用气相色谱仪检测渗透侧气体浓度.气体渗透系数的计算公式为：P=AAPFl式中:P为气体渗透系数,Barrer1Barrer=10-10cm（ST P）cm/（c m scmHg);F为测试气体渗透流量，cm（ST P)/s;A 为测试膜样品有效面积，cm；p 为测试膜样品上下游压差，cmHg;l为膜厚度,cm.气体选择性的计算方法为：PAA/B=P式中：A/B为组分A与B的分离系数;PA、PB分别为组分A与组分B的气体渗透系数.WWZIF-8-550Znol203020/()(1)(2)模拟ZIF-8405086的结构特征峰，表明部分保留了ZIF-8晶体结构.其中，位于7.3处的(0 11)衍射峰略向高角度位移,这是由于晶体中部分有机连接体发生热分解导致骨架结构发生塌2 3,并在2 0 30 范围内出现了无定炭的宽衍射峰,同时产生了ZnO的特征峰2 4,表明ZIF-8经炭化后衍生出多孔炭和ZnO金属氧化物.如图2(a)所示,ZIF-8和ZIF-8-550热解衍生纳米粒子的N吸脱附等温线均表现出标准的I1 200S eET-zIF-s=1 772 ml/g1000Vmico-ZIF-8=0.567 cm/g800Vmicn-850c=0.285 cm/g6004002000F0图2 ZIF-8与ZIF-8-550衍生纳米粒子的N2吸脱附等温线和孔径分布图Fig.2 N2 adsorption and desorption isotherms and pore size distribution of ZIF-8 and由SEM图（图3)可以看出，所制备的ZIF-8平均粒径在50 nm左右，且具有标准的菱形十二面体与六边形切面结构.较小的粒径能够保证在混合基质膜的制备过程中具有均匀的分散性，同时与主体基质保持良好的相容性，从而避免了界面缺陷的出现.经过550 热处理制备的ZIF-8衍生纳米粒子基本保持了ZIF-8的形貌结构，晶体尺寸略有减小，可能是因为晶体部分发生热分解导致骨架结构塌收缩300nm(a)ZIF-8图 3ZIF-8 与 ZIF-8-550衍生纳米粒子的SEM图Fig.3SEM images of ZIF-8 and ZIF-8-550derived nanoparticles膜科学与技术型，具有较大的比表面积与丰富的微孔结构.在相对压力0.8 1.0 区间，回滞环的出现主要是由于测试样品之间的堆积形成了介孔结构.经过550 热处理后,ZIF-8的比表面积与微孔体积虽有所降低，但仍分别高达10 54m/g和0.2 8 5cm/g.由孔径分布图图2(b)可以看出，相比于ZIF-8,ZIF-8衍生多孔炭的大孔数目减少,孔径介于0.50.7 nm范围内的极微孔数量明显增多.1.41.2(1.8.,1.03.,uu.0)/aP/AP0.80.60.4-ZIF-80.2ZIF-8-55000.20.40.60.81.0相对压力(P/P)(a)N,吸脱附等温线ZIF-8-550 d e r iv e d n a n o p a r t ic le s300nm(b)ZIF-8-550第43卷-ZIF-8550ZI F-8 热解炭0.40.650.81.01.2.2.1.41.61.82.0孔径/nm(b)孔径分布2.2ZIF-8混合基质炭膜的结构表征由质量分数10%ZIF-8混合基质炭膜的表面、断面SEM图和表面Zn元素分布图（图4)可以看出,ZIF-8热解衍生纳米粒子在炭膜内具有良好的分散性，以及与炭基质具有较好的兼容性，没有出现团聚与明显的界面缺陷.图5为质量分数10%ZIF-8混合基质炭膜和纯炭膜的孔径分布情况.与未掺杂的纯炭膜相比,ZIF-8热解衍生多孔炭的引人增加了炭膜的BET比表面积与微孔体积,分别由6 7 6 m/g和0.12 4cm/g增加到1134m/g和0.12 6 cm/g.同时ZIF-8混合基质炭膜的孔径分布向更小尺寸偏移,介于0.50.8 nm范围内的极微孔数目明显增多，表明ZIF-8衍生多孔炭的引入增加了炭膜具有筛分能力的极微孔数量.2.3气体渗透性能2.3.12ZIF-8掺杂量对炭膜C.H/CsH：渗透分离性能的影响在550 炭化温度下制备了ZIF-8混合基质炭膜,考察了ZIF-8掺杂量对炭膜C.Hc/CH：渗透分离性能的影响，如图6 所示.随着掺杂量的增第4期加,CH。的渗透系数逐渐增加,CH：的渗透系数除了掺杂量5%之外，也是一直增加.C.H/CHs的理想选择性呈现出先增加后降低的趋势，并在掺杂质量分数10%时表现出了最佳渗透分离性能，C.H。的渗透系数为17 4Barrer（渗透速率约为3.5GPU),C.Hc/C.H。的选择性为14.4.与未掺杂的纯炭膜相比，其选择性提高了18 2%，这主要归因于ZIF-8热解衍生多孔炭的引人明显增加了炭膜可高效分离CsH/CsH：的极微孔数量.当掺人少量ZIF-8时，与未掺杂的纯炭膜相比，混合基质炭膜对徐笑峰等：用于CHs/C.H：分离的ZIF-8混合基质炭膜而分离选择性明显降低.87C.H。的渗透系数有所降低,推测是由于ZIF-8热解衍生出的ZnO粒子可能阻塞了 CH。气体渗透扩散通道，而随着ZIF-8掺杂量的增加,ZIF-8衍生的多孔炭可提供更多的气体扩散通道，使得CH。渗透系数逐渐提高.但当ZIF-8掺杂质量分数高于15%时，由于掺杂量较高，在制备前驱体聚合物膜的过程中可能会产生一定团聚和分散不均的现象，从而在炭膜内产生少量没有筛分能力的界面孔2 5,导致CH。与C,H。渗透系数均大幅度提升，-50mm50um(a)膜表面SEM图图410%ZIF-8混合基质炭膜的结构表征Fig.4 Stacture characterization of 10%ZIF-8derived mixed matrix carbon membrane0.70.60.50.40.30.20.100.40.60.81.01.21.41.6孔径/nm图5纯炭膜与10%ZIF-8混合基质炭膜的孔径分布Fig.5Pore size distribution of pure carbon membraneand 10%ZIF-8 based mixed matrix carbon membrane2.3.2炭化温度对炭膜C.H6/CsH：渗透分离性能的影响在ZIF-8掺杂质量分数10%条件下制备了不同炭化温度的ZIF-8混合基质炭膜，考察了炭化温度对混合基质炭膜CsH。/C.H。渗透分离性能的影响，如图7 所示.随着炭化温度的增加，CH6与CH：的渗透系数与选择性均呈现先增加后降低的趋势，并在550 炭化温度时CsH/C.H选择性达到最高.这可能归因于炭基质主体的炭结构变化：(c)EDSZn元素分布图350o-CMSM-550300-ZIF-8CMSM-550250200150100500051.82.0ZIF-8掺杂质量分数/%图6 ZIF-8掺杂量对混合基质炭膜C.H。/CH s分离性能的影响Fig.6Effect of ZIF-8 loading amount on C:H/C,Hsseparation performance of mixed matrix carbon membrane4806 0 0 为前驱体聚合物剧烈热分解阶段2 6 ，产生了大量微孔结构，从而使得轻烃气体的渗透系数明显提升；6 0 0 7 0 0 主要为热缩聚反应阶段，炭微晶堆积逐渐致密，,因而所形成的微孔逐渐减小，导致气体渗透系数降低。2.3.3气体分离性能评价图8 为所制备的混合基质炭膜及聚合物膜的C:He/C:H：分离上限以及与文献中报道的其他炭膜的分离性能对比.可以看出,ZIF-8热解多孔炭的(d)膜断面 SEM图C,H.IC.H516HH8642010152088引人大幅度提升了炭膜对CHs/C.H分离选择性,渗透系数-选择性超越了聚合物膜的C:H。/CH：分离上限.与文献中报道的其他炭膜相比，所制备的混合基质炭膜具有优异的渗透分离性能.25014200C.H.121015081006450200480550炭化温度/图7 炭化温度对混合基质炭膜C.H。/C.H s分离性能的影响Fig.7Effect of carbonization temperature on C,H/C,H.separation performance of mixed matrix carbon membrane60分离上限PIM-6FDA-OH440C10E6FDA/BPDA-DAM 80CMatrimid550c文献2 7-2 9本工作0.11C,H,渗透系数/Barrer图8 ZIF-8混合基质炭膜与其他膜材料的C,H。/C,H。渗透分离性能对比2 7-2 9Fig.8Comparison of C:Hs/C Hs permeation andseparation performance between ZIF-8-based mixedmatrix carbon membrane and other membrane materials27-233结论通过向前驱体聚合物中掺杂ZIF-8纳米粒子，并进一步高温热处理制备了ZIF-8混合基质炭膜.高温热处理后ZIF-8仍能部分保持其丰富的微孔结构和较高的比表面积.ZIF-8衍生纳米多孔炭的引人明显增加了炭膜具有筛分能力的极微孔数目，因而提高了炭膜对C.H/C.H：的分离选择性.当ZIF-8掺杂质量分数为10%及炭化温度为550 时，与未掺杂的纯炭膜相比，所制备的ZIF-8混合基质炭膜对CsH/CsH：分离选择性提高了膜科学与技术182.4%，同时C,H。的渗透系数高达17 4Barrer，超过了聚合物膜的CsH。/Cs H：分离上限.参考文献：1 Pan Y,Tao L,Lestari G,et al.Effective separation ofIC,Hpropylene/propane binary mixtures by ZIF-8 mem-branesJ.J Membr Sci,2012,390/391:9398.2 Sholl D S,Lively R P.Seven chemical separations tochange the worldJJ.Nature,2016,532:435-437.3张敬升，李东风。炼厂干气的回收和利用技术概述J.化工进展，2 0 15，34（9)：32 0 7 32 15.4汤明，肖泽仪，史晓燕。膜技术在含烃类气体分离中600670700PIM-6FDA-OH PIM-6FDA-OH60C6FDA-APAF450C10%ZIF-8CMSM-550cCMSM-650CCMSM-550C10100第43卷的研究与前景J过滤与分离，2 0 0 5（4)：2 1一2 3.5徐南平.无机膜的发展现状与展望J化工进展，2 0 0 0(4):59.6 Park S,Abdul H M R,Jeong H.Highly propylene-se-lective mixed-matrix membranes by in situ metal-organicframework formation using a polymer-modificationstrategyJ.ACS Appl Mater Interfaces,2019,11(29):25949-25957.7J 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J.ChemCommun,2012,48:72597261.24 Wang C Y,Zhang J,Zhang Q Y,et al.Preparationand adsorption properties of ZIF-8 based porous car-bonJJ.Chem Ind Eng Prog,2017,36:299-304.25 Moore T T,Koros W J.Gas sorption in polymers,molecular sieves,and mixed matrix membranesJ.JAppl Polym Sci,2007,104(6):4053-4059.26J Xu R S,He L,Li L,et al.Ultraselective carbon mo-lecular sieve membrane for hydrogen purificationJ.JEnergyChem,2020,50:1624.27 Burns R L,Koros W J.Defining the challenges forC,H,/C,H。s e p a r a t i o n u s i n g p o l y m e r i c m e m b r a n e sJJ.JMembr Sci,2003,211(2):299-309.28 Sw a id a n R J,M a X,Pin n a u I.Sp ir o b is in d a n e-b a s e dpolyimide as efficient precursor of thermally-rear-ranged and carbon molecular sieve membranes for en-hanced propylene/propane separation JJ.J MembrSci,2016,520:983-989.29J Xu L,Rungta M,Brayden M K,et al.Olefins-selec-tive asymmetric carbon molecular sieve hollow fibermembranes for hybrid membrane-distillation processesfor olefin/paraffin separationsJJ.J Membr Sci,2012,423/424:314323.XUXiaofeng,XURuisong,WANG Yue,WANG Tonghua,LI Lin(State Key Laboratory of Fine Chemicals,Schol of Chemical Engineering,Dalian University of Technology,Dalian 116024,China)Abstract:Mixed matrix carbon membranes were prepared from the pyrolysis of mixed matrix polymericmembranes at high temperature via using ZIF-8 as dopant.The evolution of the morphology and porestructure characteristics of ZIF-8 during pyrolysis and its effect on the micropore structure and carbonstructure of carbon membranes were investigated by XRD,SEM,N2 adsorption and other characterizationmethods.The effects of ZIF-8 doping amount and carbonization temperature on the C,Ho/C,Hs separation(下转第98 页)98LI Siqil.2,ZHAO Dan,LI Hui,CHEN Zhanying,REN Jizhongl(1.National Laboratory for Clean Energy,Dalian Institute of Chemical Physics,Chinese Academy ofSciences,Dalian 116023,China;2.University of Chinese Academy of Sciences,Beijing 100049,China;3.CTBT Beijing National Data Centre Radionuclide Laboratory,Beijing 100085,China)Abstract:Cryogenic distillation is carried out by using the difference in the boiling points of gases toseparate noble gases.Compared with this traditional method,membrane technology has excellentproperties such as higher efficiency,lower consumption,and being more environmentally friendly.Theselection of membrane materials and their post-treatment are critical to the gas separation efficiency ofmembrane technology.In this paper,the polyimides PI-1(BTDA-MDA/TDA)and PI-2(PMDA/BTDA-TDA)were selected to study the effect of their distinct structures on the separation performance of noblegases.After that,the polyimide membrane with excellent performance was heat treated under differentconditions,and the influence of heat treatment temperature on gas separation performance wasinvestigated.According to the research,by changing the composition of the polyimide,the noble gasselectivity and permeability of this polyimide membrane could be adjusted.Different heat treatmentconditions could change the permeability and separation performance of the membrane by changing thechain accumulation in the membrane,forming part of the membrane structure,and removing theplasticizing effect of the residual solvent.By controlling the heat treatment conditions,the permeabilityand selectivity of the membrane can be improved at the same time.The He permeability coefficientincreased to 19.1 Barrer,and the selectivity of He/CH4 increased by 54%,while the selectivity of O2/Xeincreased by 99%.Key words:polyimide;noble gas separation;membrane separation;heat treatment膜科学与技术Noble gases separation performance of polyimide membranes第43卷(上接第8 9 页)performance of mixed matrix carbon membranes were also investigated.The results show that ZIF-8 canstill partially maintain its microstructure and pore structure after heat treatment at 550 C.Meanwhile,theintroduction of the ZIF-8 derived nanoporous carbon increases the content of ultramicropores withmolecular sieving function in carbon membrane,which significantly enhances the C,H./C,H:selectivity ofmixed matrix carbon membranes.Compared with the carbon membranes without ZIF-8 doping(the C,H./C,Hg selectivity is 5.1),the C,Hs/C,Hs selectivity of ZIF-8-based mixed carbon membrane with thedoping mass fraction of 10%and prepared at carbonization temperature of 550 C is i