二次水热合成制备有支撑纯ZSM-5沸石膜

用二次水热合成法得到了有支撑纯ＺＳＭ－５沸石膜。扫描电镜观察结果表明：ＺＳＭ－５结晶情况良好，尺寸比较均匀，晶粒紧密堆积成膜。沸石膜与支撑体结合紧密，膜的平均厚度为１０μｍ。     

有支撑纯NaA和NaY沸石膜的合成

本文简要介绍有支撑纯NaA和NaY沸石膜的合成方法和结构分析结果.研究结果表明,通过对支撑体进行适当碱处理,用二次水热合成由适当组成的反应混合物可以在多孔陶瓷支撑体上合成堆积紧密的纯NaA和NaY沸石膜.     

芳甲基酯在ZSM—5沸石中的光化学——尺寸及形状选择效应

本文研究了对甲基苯乙酸苄基酯及苯乙酸１－萘基酯在ＺＳＭ－５沸石中的光化学反应，研究发现，光解ＢＣＯ２Ａ在ＺＳＭ－５沸石中主要生成ＢＡ，而光解ＡＣＯ２Ｎ只生成ＡＡ及ＮＮ。两种酯的产物分布和在乙腈溶液中的光解完全不同。这些结果是由ＺＳＭ－５沸石孔腔对底物分子的尺寸及形状具有选择性而引起的。     

沸石分子筛膜的合成及其定向生长

本文综述了沸石分子筛膜的各种合成方法，介绍了有机－无机组成结构对沸石分子筛膜的定向生长和载体及其前处理对膜合成的影响。     

支撑体材料对NaA型沸石分子筛膜形成的影响

采用水热合成法制备NaA型沸石分子筛膜,实验比较了α-AI2O3、ZrO2及TiO2三种支撑体对NaA型沸石分子筛膜形成的影响。XRD测定所合成的沸石分子筛膜是NaA型。SEM和渗透实验结果表明,沸石分子筛膜的性能与支撑体有关,TiO2优于ZrO2和α-AI2O3。TiO2支撑体上合成沸石分子筛膜的H2、N2渗透系数大小基本与膜两侧平均压力无关,理想分离系数约为8,高于Kundsen扩散分离因子3．74,表现有一定的分子筛分效应。     

地质聚合物原位合成八面沸石膜及其渗透汽化性能

以煅烧高岭土和水玻璃为原料制备地质聚合物,采用水热合成法原位合成了自支撑八面沸石(简称FAU型)膜。利用X射线衍射、扫描电子显微镜、万能压力试验机表征了沸石膜材料的抗压强度和微观结构,通过渗透汽化实验及数学模型考察了乙醇/水混合物体系进料组成和温度对沸石膜的渗透通量以及分离因数的影响。结果表明:该沸石膜表面的晶粒细小,膜覆盖完全且连续致密;提高养护时间有利于提高地质聚合物的压缩强度,提高水热时间有利于改善FAU型沸石膜表面形貌和相组成。在进料温度为50℃、原料中乙醇的含量为70%的优化条件下,FAU型沸石膜具有较高的渗透通量和分离因数,其渗透通量和分离因数分别达到1.41kg/(h m2)和16.8。     

PHOTOCHEMISTRY OF ARYLMETHYL ESTERS ADSORBED ON ZSM-5 ZEOLITE──SIZE/SHAPE SELECTIVITY

本文研究了对甲基苯乙酸苄基酯（ＢＣＯ２Ａ）及苯乙酸１－萘基酯（ＡＣＯ２Ｎ）在ＺＳＭ－５沸石中的光化学反应．研究发现，光解ＢＣＯ２Ａ在ＺＳＭ－５沸石中主要生成ＢＡ，而光解ＡＣＯ２Ｎ只生成ＡＡ及ＮＮ．两种酯的产物分布和在乙腈溶液中的光解完全不同．这些结果是由ＺＳＭ－５沸石孔腔对底物分子的尺寸及形状具有选择性而引起的．     

采用二次原位法合成{111}优先取向的NaY沸石膜

采用二次原位水热合成方法在多孔α-Al2O3支撑体上生长出致密连续的{1 1 1}晶面优先取向的NaY型沸石膜.合成液的配比为10SiO2:Al2O3:14Na2O:800H2O,考察了陈化时间、陈化方式和晶化次数等因素对膜微结构的影响.通过XRD和SEM等手段对所制备的膜材料进行了表征,结果表明,一次原位水热晶化得到的膜层不连续,搅拌陈化可得到{111}晶面优先取向的NaY型沸石膜,膜层中晶粒均匀.在相同的合成条件下,搅拌陈化,二次原位水热合成可得到{111}晶面优先取向的致密连续的NaY型沸石膜,膜厚约15 μm.     

KOH热交换制备的KZSM—5分子筛碱性的研究

采用ＫＯＨ溶液在加热条件下与ＮａＺＳＭ－５分子筛交换，获得一碱性相当强的ＫＺＳＭ－５。用红外光谱，Ｘ射线衍射，Ｘ射线光电子能谱和Ｈａｍｍｅｔｔ指示剂滴定等方法表片ＫＺＳＭ－５的结构特征和碱性。以丙酮一步法合成异丙叉丙酮为探针反应研究了其催化活性并与分子筛碱性相关联。     

ATP基沸石膜的制备与表征

沸石作为一种优异的吸附材料被应用于印染废水以及重金属离子等废水处理和放射性元素的吸附,但目前存在易流失、难回收、操作困难等问题,妨碍了沸石的工业化应用。本文通过原位水热合成法在自制的凹凸棒石(ATP)基支撑体表面成功合成A型沸石膜,可以有效地解决沸石吸附剂与产物分离困难的问题。通过对支撑体表面的A型沸石进行吸附实验,结果表明:A型沸石对中性红(NR)的吸附是自发的吸热过程,反应符合准二级动力学模型。     

Modification of carbon membranes and preparation of carbon-zeolite composite membranes with zeolite growth

A novel method for the modification of carbon membranes was developed by zeolite growth on the surface of porous carbon tubes using a hydrothermal synthesis method and carbon-zeolite composite membranes were successfully obtained. Zeolite seeds for the zeolite growth were introduced to the inner surface of the tubes by using a slip-casting technique in 1 wt.% seed ethanol solution and continuous and highly intergrown zeolite layers on the seeded tubes were formed by subsequent hydrothermal synthesis. Different types of zeolite layers can be grown on porous carbon tubes by using different types of zeolite seeds. Without zeolite seeds, a zeolite layer could not be formed on the carbon surface. SEM, XRD and pure gas permeation characterization indicates that the carbon-zeolite membranes are continuous and defect-free.     

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.     

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。     

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.     

分子筛膜的制备和研究进展

本文综述了分子筛膜的各种制备方法,如原位水热合成法、晶种法、微波加热法、化学气相沉积法、脉冲激光蒸镀法等,介绍了分子筛膜在物质分离和膜催化反应等方面的应用,同时讨论了在分子筛膜制备过程中膜缺陷的形成及其消除方法,最后提出了分子筛膜的研究展望。     

Effect of cellulose buffer layer on synthesis and gas permeation properties of NaA zeolite membrane

NaA zeolite membrane coating was successfully synthesized on a porous alumina substrate by hydrothermal treatment. The effects of synthesis parameters like, seeding type (ex situ, in situ), time, temperature, sol concentration, coating stages, application of intermediate layer, etc. on membrane characteristics were investigated. A continuous membrane was formed on a seeded substrate. Surface seeding (ex situ crystallization) not only accelerates the zeolite crystallization process on the support surface, but can also enhance the formation of homogeneous NaA zeolite layer. The NaA zeolite membrane with a synthesis time of 4 h shows the best microstructure and the quality of membrane was improved by employing the multi-stage coating. But the main problem associated with membrane synthesis was crack formation, and it can be reduced by applying intermediate layer, between support surface and seed layer. A thin cellulose layer was applied to the support surface before applying seed crystals. The performance of the membranes was evaluated by gas permeation measurement. The permeance of O₂, N₂ decreased as kinetic diameter of gases increased. The permselectivity of O₂/N₂ was 1.9–2.34. This value showed the molecular sieving effect of NaA zeolite membrane.     

Sol-gel synthesis of zeolite coatings and their application in catalytic microstructured reactors

Sol-gel hydrothermal synthesis is one of the most promising methods for the obtaining of zeolitic coatings (films, membranes) on the internal surface of channels of catalytic microstructured reactors. In this review, we discuss the basic methods for the synthesis of zeolite coatings, the processes that influence the rate of crystallization and crystal growth on a substrate, and the methods for modification of the substrate surface before the hydrothermal synthesis. By the example of the synthesis of β, A, and ZSM-5 zeolite coatings, it is shown that the hydrophilic behavior of the substrate and the presence of nano- and microroughness on it have a significant effect on the rate of nucleation of zeolite crystals and the homogeneity of obtained zeolite films. Depending on zeolite type and desired Si/Al ratio in the coating, by several examples. There exists a sufficiently narrow range of conditions (temperature, mixture heating rate, and ionic strength of solution) leading to zeolite coating formation on the substrate rather than to homogeneous crystallization in the authoclave volume. The fundamental mechanisms mechanisms responsible for the formation of zeolite coatings are presented. The acceleration of the hydrothermal synthesis under the action of microwave radiation is shown. The influence of different factors that should be taken into account to scale-up the hydrothermal synthesis is presented. Potential applications fields of microreactors and microadsorbers with zeolite coatings are discussed. Most industrial companies assign microtechnologies to the “high risk-high impact” group. The high risk is attributed, first of all, to the necessity of a cardinal change in the procedure sheet and to the application of new catalysts that allow an increasing rate of processes. Meanwhile, advantages of introduction of the new technologies—the basic ones being the reduction of energy consumption and significant decrease in the formation of by-products—allow companies to reduce operation costs.     

b轴取向MFI分子筛膜的制备及应用研究进展

分子筛膜是一种新型的无机膜,具有孔道结构规整、化学和热稳定性好、机械强度高、抗污染性能好、易于改性等优点。b轴取向MFI分子筛膜因可以缩短传质路径、降低传质阻力、提高扩散效率,在膜分离和膜反应器领域有着广泛的应用前景,受到国内外学者的普遍关注。综述了b轴取向分子筛膜的制备方法及应用研究进展。详细介绍了原位水热合成法、二次生长法、微波辅助合成法、无凝胶法、固相转化法及纳米片法等。二次生长法可以控制分子筛膜的微观结构,且受载体表面性质的影响较小;微波辅助法可以缩短结晶时间,降低能耗,对工业化生产具有重要意义;无凝胶法具有制备工艺简单、环境友好等优点。在上述方法的基础上,将纳米片作为晶种可以降低膜厚。最后,展望了b轴取向MFI分子筛膜的发展前景,在制备b轴取向连续无缺陷MFI分子筛膜方面仍面临许多挑战,包括提高膜的机械强度和长期运行稳定性、实现粗糙或弯曲以及大尺寸载体表面取向膜层的制备等。     

Scale-up of NaA zeolite membranes onα-Al2O3 hollow fibers by a secondary growth method with vacuum seeding

NaA zeolite membranes were prepared by secondary growth method on the outer surface ofα-Al2O3 hollow fiber supports. Vacuum seeding method was used for planting zeolite seeds on the support surfaces. Hydrother-mal crystallization was then carried out in a synthesis solution with molar ratio of Al2O3:SiO2:Na2O:H2O=1:2:2:120 at 100 °C for 4 h. Effects of seeding conditions on preparation of hollow fiber NaA zeolite membranes were extensively investigated. Moreover, hollow fiber membrane modules with packing membrane areas of ca. 0.1 and 0.2 m2 were fabricated to separate ethanol/water mixture. It is found that the thickness of seed layer is obviously affected by seed suspension concentration, coating time and vacuum degree. Close-packing seed layer is required to obtain high-quality membranes. The optimized seeding conditions (seed suspension mass concentration of 0.5%–0.7%, coating time of 5 s and vacuum degree of 10 kPa) lead to dense NaA zeolite layer with a thickness of 6–8μm. Typically, an as-synthesized hollow fiber NaA zeolite membrane exhibits good pervaporation performance with a permeation flux of 7.02 kg·m?2·h?1 and separation factor N 10000 for sepa-ration of 90%(by mass) ethanol/water mixture at 75 °C. High reproducibility has been achieved for batch-scale production of hollow fiber NaA zeolite membranes by the hydrothermal synthesis approach.