α-Al2O3载体上b-轴取向MFI分子筛膜的制备

在α-Al2O3支撑的PVA表面手工组装紧密排列的b-轴取向silicalite-1分子筛晶体层,煅烧除去高聚物层后可得到很好的晶种层。采用两步法二次合成工艺,在多孔氧化铝载体表面可直接合成完备的b-轴取向MFI型分子筛膜。n（TEOS）：n（TPAOH）：n（H20）为1．0：0．2：200．0的合成液经150℃预加热处理可有效减少二次生长过程中α-轴孪晶的生成,保证制备的MFI膜为很好的b-轴取向。SEM及XRD检测表明所制备膜层的完备性及b-轴取向。另外采用多层取向晶种层经过一次晶化3h即可制备完备的b-轴取向多层MFI型分子筛膜。实现了在大孔载体上直接合成b-轴取向的MFI膜,对提高膜的应用性能有重要意义。     

多孔玻璃表面原位水热合成b轴取向MFI型分子筛膜

采用原位水热合成法,直接用川丙基氢氧化馆(TPAOH)/川乙氧基硅炕(TEOS)/H20合成液在具有较大孔径(约O.I/-lm)的多孔玻璃载体表面合成b轴取向MFI型分了饰膜。考察了载体的放置方式对成膜的影响,结果表明,将多孔玻璃完伞浸入合成液中时,载休表囱片能得到零星分市的MFI细分子筛品休;而将多孔玻璃部分浸入合成液中时,在液面以上的载体表面获得了b轴取向MFI型分子饰膜,靠近液面的载体表由形成的MFI分子筛膜比较致密。优化了合成液的配比和合成时间,发现采用合成i夜配比0.64TPAOH:lTEOS:165H20时165oc合成3h,可以在多孔玻璃表面形成大面积连续的b轴取向MFI型分了筛膜。当合成时间延长至6h时,MFI剖分子筛膜层连续数密,但呈现随机取向。     

Langmuir-Blodgett法制备高H2选择性取向ZSM-5分子筛分离膜

利用Langmuir-Blodgett（LB）技术首先在多孔氧化铝载体表面有序组装了单层b-轴取向Silicalite-1分子筛晶种层,再采用二次生长法,以溴化六丙双铵（dimer-TPABr）为结构导向剂配制二次生长合成液,在175℃反应48h制备了高度b-轴取向ZSM-5（Si/Al=120）分子筛膜。扫描电镜（SEM）表征显示ZSM-5分子筛膜致密连续且厚度约为2.6μm。X射线衍射（XRD）表征结果显示,膜的b-轴晶体优先取向值高达0.858。气体分离性能测试结果显示,制备的ZSM-5分子筛膜在高温焙烧脱除有机模板剂过程中会产生缺陷。经硅烷试剂四甲氧基硅烷（TMOS）对缺陷修复后,ZSM-5分子筛膜表现出高的H₂选择性分离性能,H₂/CO₂分离因子高达68 （T=25℃,p=0.1MPa）,对应的H₂渗透速率为1.36×10^-8mol/(m²·s·Pa)。     

MFI型沸石分子筛膜的研究进展及应用

综述了MFI型沸石分子筛膜制备方法的研究进展,突出介绍了较为成熟的水热合成法、微波合成法以及气相转移法,讨论了MFI型沸石分子筛膜在应用方面具有优势的有机物提纯、气体分离以及催化反应的研究进展,并提出了MFI型沸石分子筛膜制备和应用方面一些亟待解决的问题。     

Langmuir-Blodgett法制备高度b-轴取向TS-1分子筛膜

采用水热合成法,通过调节合成液配比,合成出粒径均一且形貌规则的TS-1分子筛晶粒;选择粒径为1.2μm×0.9μm×0.4μm的棺状TS-1分子筛晶粒作为晶种,利用Langmuir–Blodgett(LB)技术,在不锈钢载体表面组装得到厘米尺度排列紧密且呈高度b-轴取向的TS-1分子筛晶种层;分别采用合成液加入碳酸铵法和合成液预晶化法,抑制二次生长过程中孪晶的生成,获得取向的TS-1分子筛膜。结果表明:采用合成液加入碳酸铵法,不能制备高度b-轴取向的TS-1分子筛膜;采用合成液预晶化法,在170℃生长6 h即可制备连续致密且高度b-轴取向的TS-1分子筛膜,其b-轴晶体优先取向值(CPO(0k0))高达0.884,且紫外漫反射光谱结果证实所得TS-1分子筛膜具有较高的骨架钛含量。因此,利用LB法可制备骨架钛含量高、连续致密且高度b-轴取向的TS-1分子筛膜。     

四通道中空纤维MFI分子筛膜用于二甲苯异构体分离

采用二次生长法在高机械强度、高装填密度的四通道α-Al₂O₃中空纤维载体(7 cm)上制备MFI分子筛膜，探究了膜合成时间、操作温度、原料分压和吹扫气流量等条件对二甲苯异构体膜分离性能的影响。结果表明，160℃水热合成12 h制得的四通道中空纤维MFI分子筛膜对二甲苯异构体分离性能较优，在150℃、原料分压2 kPa、吹扫气流量20 ml/min时对二甲苯/邻二甲苯分离因子高达878,PX渗透性为2.1×10^-8 mol·m^-2·s^-1·Pa^-1。基于优化的制膜及分离操作条件，进一步将MFI分子筛膜制备于27 cm长的四通道中空纤维载体上，也获得了优异的对二甲苯/邻二甲苯膜分离性能，且所制得的膜材料对该体系的分离可稳定运行100 h以上。为推进中空纤维MFI分子筛膜的批量化制备和传统分离工艺的技术革新奠定了基础。     

沸石分子筛膜的合成与应用

综述了沸石分子筛膜的合成方法和应用。介绍了制备沸石分子筛膜最常州的水热合成法，包括晶种法和原位合成法，以及沸石分子筛膜在气体分离、渗透汽化和膜反应器中的应用。重点阐述了被除数广泛研究的MFI型分子筛膜的制备方法与应用。详细讨沦了多孔支撑体、晶体、水热合成条件以及合成液组成等因素对晶体生长和膜的形态以及对MFI型分子筛膜分离性能的影响，     

纳米分子筛膜的研究进展

概述了纳米分子筛膜研究及其应用的现状。介绍了纳米分子筛膜的制备方法如原位水热合成法、微波辐射合成法、预植晶种前驱体二次合成法等,以及纳米分子筛膜的一些表征方法如XRD、SEM、FT-IR、^29Si MAS NMR等,并对各种方法的优缺点进行了比较。最后为纳米分子筛膜研究提出了新的方法。     

MFI型分子筛膜中晶体间隙的在线修补及其二甲苯分离性能研究

为了提高MFI分子筛膜的二甲苯分离性能,采用水热合成法制备了管式MFI型分子筛膜,并通过1,3,5三异丙基苯(TIPB)碳化沉积方法对分子筛膜中的晶体间隙在分离操作过程中进行了在线修补。通过修补,分子筛膜在375~400℃下的对、邻二甲苯分离系数从5左右增加到30,表明膜层中的无选择性的晶体间隙被大幅度减少。     

分子筛膜的合成与应用研究进展

介绍了分子筛膜的合成方法,如水热合成法、二次生长法、连续流合成法、微波辅助合成法、杂原子掺杂法、混合基质法等,阐述了分子筛膜在分离和催化中的应用,并对分子筛膜的发展方向进行了展望,认为加强分子筛膜的成膜机理和改性研究,并深入开发分子筛膜在催化及分离中的应用,制备出具有工业应用价值的分子筛膜.     

动态水热法制备Silicalite-1分子筛膜包覆多孔缺陷Al2O3微球

采用晶种涂覆-预晶化-晶化成膜的动态水热法成功在具有多孔缺陷的氧化铝微球上合成Silicalite-1分子筛膜。以乙醇作为润湿试剂在氧化铝表面涂覆一层晶种,将涂覆过晶种的载体加入到分子筛合成液中预晶化,一层分子筛完全覆盖载体并与载体结合牢固。预晶化后的载体在动态水热条件下处理3天,得到致密分子筛膜包覆的Al₂O₃微球。运用X射线衍射（XRD）和扫描电镜（SEM）对所得材料进行表征。结果表明,包覆的分子筛膜具有典型的MFI结构,晶粒交互生长,厚度约为3μm。考察了TPAOH用量和水量对分子筛膜微观结构的影响,结果发现TPAOH用量主要影响Silicalite-1分子筛膜的形貌,当TPAOH用量为0.17时,合成的Silicalite-1分子筛膜连续致密,而水量对分子筛膜微观结构的影响较小。这种晶种涂覆-预晶化-晶化成膜的方法有助于在多孔缺陷的Al₂O₃微球上制备高质量的分子筛膜。     

含氟体系中MFI型分子筛膜的制备及其乙醇/水分离性能

以氟化铵为矿化剂、四丙基溴化铵为模板剂,在负载晶种的钇稳定氧化锆(YSZ)中空纤维支撑体表面合成了MFI型分子筛膜,并用于乙醇/水的分离;系统考察了氟硅比(n_NH4F/n_SiO2)、合成时间等条件对膜分离性能的影响,在n_NH4F/n_SiO2为0.8、合成时间为8 h下合成出高性能膜,其通量达8.2 kg·m^-2·h^-1、乙醇/水分离因子为47;同时研究了MFI型分子筛膜在乙醇/水体系中的分离稳定性,揭示出该方法所合成膜表面无Si-OH,从而避免了Si-OH与乙醇反应而带来膜分离性能的下降.     

MFI型分子筛膜的制备及表征

采用无模板剂的二次生长合成方法,在-αA l2O3基膜上合成了MFI型分子筛膜,用XRD,SEM和气体渗透实验等方法进行表征,表明合成在-αA l2O3基膜的物质为MFI型分子筛。二次生长分子筛膜的正/异丁烷理想分离系数在298 K和473 K时分别为77和70,气体分离数据表明,2种分子筛膜对气体分离是由分子筛分占主导,同时分子筛膜完整无裂缺。不同温度,通过MFI分子筛膜渗透汽化分离质量分数分别为5%、50%和95%的乙醇/水的渗透通量和分离因子,结果表明渗透通量随温度的升高而升高,而分离因子随温度的升高却降低;渗透通量随乙醇质量分数的升高而降低,分离因子却随质量分数的升高而升高。     

On the effect of morphological features on the properties of MFI zeolite membranes

MFI type zeolite membranes were prepared on alumina and stainless steel tubular supports by different synthesis procedures, giving rise to different zeolite layer structures and distributions of zeolite material with respect to the support. This was used as a base to establish a classification of zeolite membranes. SEM and EPMA analysis showed clear differences among different types of MFI zeolite membranes, concerning the morphology and location of the zeolite deposits. Three types of membranes were identified, namely: type-A membranes, in which the zeolitic material was located mainly inside the support pores; type-B membranes, with a thin layer of randomly oriented crystals on top of the support; and type-C corresponding to MFI c-oriented membranes. These morphological differences translated into diverse qualitative and quantitative behavior of the corresponding membranes, as shown by the evolution of single-gas permeances and separation selectivity with temperature, and by adsorption and temperature-programmed desorption experiments.     

Zeolite membranes: microstructure characterization and permeation mechanisms

Since their first synthesis in the 1940s, zeolites have found wide applications in catalysis, ion-exchange, and adsorption. Although the uniform, molecular-size pores of zeolites and their excellent thermal and chemical stability suggest that zeolites could be an ideal membrane material, continuous polycrystalline zeolite layers for separations were first prepared in the 1990s. Initial attempts to grow continuous zeolite layers on porous supports by in situ hydrothermal synthesis have resulted in membranes with the potential to separate molecules based on differences in molecular size and adsorption strength. Since then, further synthesis efforts have led to the preparation of many types of zeolite membranes and better quality membranes. However, the microstructure features of these membranes, such as defect size, number, and distribution as well as structure flexibility were poorly understood, and the fundamental mechanisms of permeation (adsorption and diffusion), especially for mixtures, were not clear. These gaps in understanding have hindered the design and control of separation processes using zeolite membranes. In this Account, we describe our efforts to characterize microstructures of zeolite membranes and to understand the fundamental adsorption and diffusion behavior of permeating solutes. This Account will focus on the MFI membranes which have been the most widely used but will also present results on other types of zeolite membranes. Using permeation, x-ray diffraction, and optical measurements, we found that the zeolite membrane structures are flexible. The size of defects changed due to adsorption and with variations in temperature. These changes in defect sizes can significantly affect the permeation properties of the membranes. We designed methods to measure mixture adsorption in zeolite crystals from the liquid phase, pure component adsorption in zeolite membranes, and diffusion through zeolite membranes. We hope that better understanding can lead to improved zeolite membranes and eventually facilitate the large-scale application of zeolite membranes to industrial separations.     

TMCS修饰MFI分子筛膜的制备及乙醇/水分离稳定性的研究

采用三甲基氯硅烷（TMCS）作为修饰源对MFI分子筛膜进行表面改性,系统考察了TMCS浓度以及修饰时间对于MFI分子筛膜在分离乙醇/水混合物时的性能影响。SEM、XRD、²⁹Si NMR、FT-IR、接触角实验及分离实验结果表明,TMCS可以与硅羟基反应,嫁接分子筛膜表面,在消除膜表面硅缺陷的同时提高膜的疏水性及膜分离性能的稳定性。随着TMCS浓度以及反应时间的增加,修饰后MFI分子筛膜的通量及分离因子略有下降,但稳定性增强。在TMCS的浓度为0.4%（质量）,修饰时间为2 h时,所得到的膜具有最佳渗透汽化分离性能,并可在60℃下分离5%（质量）乙醇/水混合物时保持良好的稳定性。在连续90 h渗透汽化分离过程中,其渗透通量稳定在1.61 kg·m^-2·h^-1 左右,分离因子保持在20以上。     

ZrO2 和Al2O3支撑的MFI 型沸石分子筛膜:支撑体材料对膜性能的影响

采用水热合成法，以纯SiO2为源物质，在介孔Y2O3掺杂的ZrO2(YZ)及大孔α-Al2O3支撑体上制备出高质量的MFI型沸石分子筛膜，通过H2／n-C4H10气体混合物的渗透分离和p-xylene的蒸发研究了不同支撑体上MFI型沸石分子筛膜分离性能，在较低温度范围，YZ支撑的MFI型沸石分子筛膜中n-C4H10的渗透率比Al2O3支撑的膜高很多，最大n-C4H10与H2的分离率达到500，Al2O3支撑的膜中py-xylene的蒸发流量随时间下降很快，而YZ支撑的膜中的蒸发流量则变化缓慢，用XRD对膜的晶体结构进行分析，通过多种温度下热处理不同支撑体上的膜样品研究了其热稳定性与支持体材料的关系，YZ支撑的MFI型沸石分子筛膜的MFI结构在1000摄氏度后仍能保持，而Al2O3支撑的膜950摄氏度时已完全转变为石英相，研究结果表明，YZ支撑的MFI型沸石分子筛膜比Al2O3支撑的膜表现出更好的厌不性，热稳定性以及抗阻塞性。     

Seeded synthesis of small polycrystalline NaY zeolite membrane using zeolite structure-directing agent and its pervaporation performance

Continuous and polycrystalline NaY zeolite membranes were synthesized successfully on porous α-Al₂O₃ tubes by zeolite structure-directing agent (ZSDA) method. This ZSDA method consists of two steps: preparation of NaY ZSDA and growth of NaY zeolite membranes with ZSDA by the secondary hydrothermal treatment. The synthesis parameters, such as aging time, aging temperature and the amount of ZSDA added, etc. were investigated. Scanning electron microscopy and X-ray diffraction technology were used to characterize the morphology and the crystal structure of the as-synthesized zeolite membranes, respectively. The results indicated that the growth of NaY zeolite membranes on the supports depended strongly on ZSDA, which could not only accelerate the formation of NaY zeolite membranes but also inhibit the transformation of NaY zeolite phase. It was also found that the prolonged aging time, the lower aging temperature and the increasing amount of ZSDA resulted in a crystal size diminution of the product, thus linking the aging process directly to the increasing number of formed nuclei. Compared with the larger crystal NaY zeolite membrane, the small crystal NaY zeolite membrane exhibited much higher separation selectivity. At 308 K, the highest separation selectivities achieved towards 1,3-propanediol/glycerol and 1,3-propanediol/glucose were 80 and 2,400, respectively.     

Effect of Mesoporous Silica Buffer Layer on the Orientation of MFI Zeolite Membranes

Growth of MFI zeolite membranes on porous α-alumina substrates with and without precoated mesoporous silica buffer layer has been performed by in situ crystallization. A preferentially b -oriented MFI membrane can be prepared on a mesoporous silica-coated substrate. A membrane with a randomly oriented and eventually [ h 0 h ]-oriented top layer is obtained on an uncoated α-alumina substrate. The chemical properties of the substrate are suggested to have significant effects on the membrane orientation.