清液体系中高性能T型沸石分子筛膜的合成

由摩尔组成为SiO2:Al2O3:Na2O:K2O:H2O=1:0.015:0.25:0.08:25的澄清溶液,在预涂晶种的管状莫来石支撑体上水热合成T型沸石分子筛膜.在高于100℃清液体系中合成出了高性能T型沸石分子筛膜.用X射线衍射(X-ray diffraction,XRD)仪和扫描电子显微镜(scanning electron microscope,SEM)对150℃下合成35 h的分子筛膜进行了表征.XRD谱表明:T型沸石分子筛成功地生长在预涂晶种的支撑体上.支撑体的外表面覆盖着20 μm厚有取向的晶体层.从SEM照片判断,起到分离作用的是生长致密的中间层,而不是表层.在150℃下制备的膜,对水/乙醇、水/异丙醇混合物具有高渗透汽化分离性能.优异的渗透汽化性能归因于在涂有晶种的多孔支撑体上生长了一层高结晶度且缺陷较少的T型沸石分子筛晶体层.     

Synthesis and characterization of silicalite-1 membrane prepared on a novel support by the pore plugging method

The effect of the support pore size on the membrane morphology was investigated for zeolite silicalite-1 membranes synthesized by pore plugging method on supports with zirconium oxide and/or titanium oxide active layer. Parameters including surface coverage, zeolite layer thickness, crystal size and shape, zeolite penetration depth were used to quantify the membrane morphology. Five supports with different pore sizes for their active layer in the range of 0.14–1.4 μm were investigated. The X-ray diffraction (XRD) analysis showed a typical silicalite-1 zeolite structure with a high internal crystalline order grown inside the pores as well as on top of all supports. The XRD results also showed that the silicalite-1 crystals in the synthesized membranes are not randomly oriented. The crystallographic preferred orientation (CPO) analysis revealed that the degree of orientation toward either the a-axis or b-axis perpendicular to the support surface, increased by decreasing the pore size of the support. The 0.45 μm support had the most preferably oriented zeolite layer for access of molecules entering into the membrane structure with the highest number of crystals oriented with the b-axis (the one with straight channels) perpendicular to the support surface. The scanning electron micrographs (SEM) analysis of the membranes revealed a dense and continuous surface morphology with the highest crystal size of silicalite-1 around 1.5 μm on the surface of the support with the 0.45 μm pore size. SEM micrographs also showed a continuous layer grown over four supports out of five supports with different pore sizes that were investigated, with no layer observed on the 1.4 μm pore size support. The average thickness of the zeolite layer was in the range of 0.7–1.4 μm, depending on the pore size of the support. The supports with 0.2 and 0.45 μm pore sizes had the most uniform zeolite layer thickness while the support with 0.8 μm pore size active layer had the least uniform zeolite layer thickness. The electron diffraction spectrometer (EDS) analysis confirmed the formation of pure silicalite-1 layer at the surface as well as inside the pores of all supports. The highest silicalite-1 crystal penetration was for the supports with 0.45 and 1.4 μm pore sizes. Single gas permeation experiments with He and N₂ gases at 293 K illustrated that regardless of the pore size of the support, the He and N₂ permeances were constant despite the change of the pressure across the membranes. The highest permeances were observed for the membrane prepared using the 0.45 μm pore size support, while the lowest permeances were for the membrane prepared using the 1.4 μm pore size support. These results confirmed the selective properties of the prepared membranes. No matter what is the pore size of the support or the feed pressure, N₂ permeances were around three times higher than those for He.     

Synthesis of ZSM-5 Membrane on the Anodized Alumina by Adding Promoter Ions

Adding promoter ions (e.g., NO–3 and PO3–4) can shorten hydrothermal synthesis time for continuous ZSM-5 layers on the anodized alumina from several ten hours to several hours. The anodized alumina, using as a support and a source of aluminum in the preparation of ZSM-5 crystals, was placed vertically in Teflon-lined stainless-steel autoclaves with a high H2O/SiO2 ratio aqueous solution. The results showed that a layer of well-intergrown ZSM-5 crystals was formed on anodized alumina and the adhesion between zeolite and anodized alumina was excellent. The morphology and crystallization of the ZSM-5 zeolite membrane were characterized by using SEM and XRD.     

Preparation and characterization of a thin continuous faujasite membrane on tubular porous mullite support

The progressive increase of VOC emissions, the growing information of their hazardous nature, and the resulting increasingly more restrictive environmental regulations in the industrialized countries have induced the development of different methods for VOCs abatement. Membrane separation process is a good alternative to gain this purpose. In this paper, a high quality faujasite membrane was prepared. Tubular porous mullite supports were fabricated from Kaolin clay by a temperature-programmed calcination treatment, following a leaching treatment. As observed in SEM photographs, the porosity of the support increased during the leaching treatment. The NaX zeolite powders were prepared hydrothermally and characterized with XRD and SEM. The best crystalline powder and the corresponding starting gel were respectively used for seeding treatment and hydrothermal crystallization of a thin, continuous and fully covering X-type zeolitic top layer on outer surface of the cylindrical support. The membrane was characterized with XRD and SEM.     

二次水热合成法制备ZSM-5分子筛膜及其渗透汽化性能

采用二次水热合成法在管状多孔莫来石支撑体上制备高耐酸性ZSM-5分子筛膜,系统地研究分子筛晶种和合成溶胶中H₂O/SiO₂摩尔比率对ZSM-5分子筛膜生长与渗透汽化性能的影响,采用X射线衍射、冷场扫描电子显微镜和电子能谱等表征技术分别对制备的ZSM-5分子筛及其ZSM-5分子筛膜的结构、形貌和Si/Al比进行表征。针对分离75℃、90% HAc/H₂O的水溶液,最优化条件下制备的ZSM-5分子筛膜表现出优良的渗透汽化性能,渗透通量和分离因子分别为0.98kg/(m²·h)和890。此外,本研究所采用制备耐酸性ZSM-5分子筛膜的方法表现出良好的重现性,重复制备的12根ZSM-5分子筛膜在75℃下分离90% HAc/H₂O的水溶液时,平均通量和分离系数分别为（0.85±0.15）kg/(m²·h)和650±290。再者,ZSM-5分子筛膜在45～75℃的温度范围内分离50%～95% HAc/H₂O水溶液时都表现出优良的渗透汽化性能。     

COBALT-EXCHANGED MORDENITE ONTO A CORDIERITE HONEYCOMB FOR SCR-NO

Structured catalysts were prepared by deposition of cobalt-exchanged mordenite films on the walls of cordierite monolith channels either by wash coating or by hydrothermal synthesis. The aim of this work is to analyze different deposition techniques and their influence on the catalytic activity. The catalytic activity of the structured materials is compared with that of zeolite powder. The hydrothermal synthesis was performed in situ in a pressured autoclave reactor varying the reaction conditions (time, stirring degree). This technique consists in the crystallization of mordenite on the cordierite honeycombs employed as a substrate. In order to analyze the stirring effect, some of the samples were synthesized by stirring while others were treated in a stagnant medium. The influence of time on reaction was estimated by sampling at regular time intervals. Deposition by impregnation (wash coating) was also performed by immersing the monolith into a suspension (20-40 wt.%) with Co-exchanged mordenite. The wash coating was performed under different conditions (suspension concentration, incorporation of agglutinants, number of immersions) to obtain a zeolite coating active and selective as catalyst for nitric oxide selective reduction with hydrocarbons. The samples obtained by either method were characterized by scanning microscopy, TPR, XRD, and catalytic activity for the SCR of NO_x with propane.     

PEA-NaA /α-Al2OPEA-NaA /α-Al2O3复合支撑分子筛膜的微波水热合成

采用微波水热合成法在聚醚酰亚胺(PEI)-NaA分子筛/α-Al2O3复合载体表面合成了具有高选择性的致密NaA型分子筛膜,重点考察了微波辐射时间对成膜的影响。采用X射线衍射图谱(XRD)和扫描电子显微镜(SEM)对NaA型分子筛膜进行了表征。XRD结果表明,复合载体表面生成的膜中只有NaA分子筛的晶相;SEM结果表明,复合载体基膜表面覆盖了一层致密连续的NaA型分子筛膜。合成的NaA型分子筛膜在不同质量分数乙醇中的渗透汽化性能结果表明,渗透通量随乙醇质量分数增大而减小,分离因子则反之,当乙醇质量分数为95%时,渗透通量仅0.05 kg/(m2.h),而分离因子高达13 000。     

Preparation of high‐performance zeolite NaA membranes in clear solution by adding SiO2 into Al2O3 hollow‐fiber precursor

Zeolite NaA membranes were prepared in a clear synthesis solution without the aid of nanoseeds. To improve the properties of the membranes formed in a clear solution, alumina hollow fibers were fabricated by adding silica powder to the conventional spinning slurry, resulting in hollow fibers with a mullite phase. Prior to the membrane synthesis, the hollow fibers were pretreated by dipping in an aged synthesis solution diluted with isopropanol. Dense zeolite NaA membranes on mullite‐containing alumina hollow fibers were successfully obtained at 100°C for 2 h without the aid of nanoseeds. The membranes have a good pervaporation performance with a high flux of 10.8 kg m^?2 h^?1 and a separation factor of over 10,000. The abundant mullite‐phase hydroxyl groups on the support surface promote the nucleation and growth of zeolite crystals on the support, resulting in dense membranes. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2679–2688, 2018     

Preparation and Characterization of Mordenite Thin Films via Pulsed Laser Deposition

Zeolite thin films are interesting for their potential application in membrane based separations, catalysis, and molecular sensing. Mordenite is a one-dimensional channel type zeolite that has been used in alcohol/water separations. Pulsed-laser deposition has been used to prepare partially oriented, crystalline mordenite thin films on stainless steel foil, and frits as well as carbon fibers and DAM-1 particles. Preliminary results for pervaporation of isopropanol/H₂O mixtures using mordenite membranes indicate separation factors of 133 and 459 at room temperature and 76°C, respectively.     

二次生长法合成SAPO-34沸石膜及其气体渗透性能

以四乙基氢氧化铵(TEAOH)为模板剂,采用二次生长法在α-Al_2O_3多孔陶瓷管上合成了SAPO-34沸石膜.利用X射线衍射(XRD)、扫描电镜(SEM)以及气体渗透对合成的膜进行了表征.XRD结果表明合成的膜具有典型的CHA型沸石特征峰,无其它杂相存在.SEM显示膜厚大约为5 μm,膜表面晶粒交织共生完好,且连续、致密,没有发现明显的针孔和裂纹.室温下, 当膜两侧压降为0.1 MPa时,CO_2/CH_4的理想选择性和混合气体分离选择性分别为7和40.     

Enhancement of NaA zeolite membrane properties through organic cation addition

Thin NaA zeolite membranes, with uniform and small crystals, were prepared on the tubular -Al₂O₃ support by adding a small amount of tetramethylammonium hydroxide (TMAOH) in the clear synthesis solution. The as-synthesized NaA zeolite membranes were characterized by XRD and SEM. The permeation properties of the membranes were evaluated by pervaporation and gas permeation. The effects of TMAOH amount on membrane formation and permeation properties were investigated. By addition of suitable amount of TMAOH in the clear synthesis solution, the crystals size of NaA zeolite could be remarkably reduced from about 10 μm to 3–4 μm, and the membrane thickness correspondingly reduced from about 16 μm to 5 μm. The thinner membrane prepared by adding TMAOH in the clear synthesis solution, with uniform and small crystal, displayed higher perm-selective properties than that without adding TMAOH. For the as-synthesized NaA zeolite membrane prepared with adding suitable amount of TMAOH (x = 1), the separation factor (water/isopropanol) was 4700 and the flux was 1.67 kg/(m² h), which were higher than that without adding TMAOH of 339 and 1.08 kg/(m² h), respectively. The ideal separation factor of H₂/N₂ was 6.60, higher than that without adding TMAOH of 3.41.     

Synthesis and Characterization of Ceramic Membranes (W‐Type Zeolite Membranes)

In this article, effects of synthesis parameters (synthesis temperature, synthesis time, and number of layers) on W‐type zeolite membranes synthesized over flat SUS supports for O₂/SF₆ gas separation were experimentally investigated. Experiments were carried out at these levels of synthesis temperature: 165°C, 185°C, and 200°C; synthesis time: 6, 12, and 18 h and number of layers: 1 and 2. Permeation measurements, XRD and SEM analysis were used for characterization of the synthesized membranes. The results showed that increasing synthesis temperature from 165°C up to 185°C increases separation factor of O₂/SF₆, however, further increasing decreases the separation performance. The same trend was observed for synthesis time for the single layer synthesized zeolite W membrane, although for the double layer synthesized zeolite W membrane, separation factor increased with increasing synthesis time. Repetition of layering has a net positive effect on separation factor of O₂/SF₆, and negative effect on permeation flux through the membranes. This behavior was attributed to the dual effect of synthesis temperature and synthesis time on selectivity. More zeolite crystals are deposited and larger crystals are formed at higher synthesis temperatures and longer synthesis times. Well W‐type zeolite membrane was synthesized at 185°C for 18 h with two repeating layers with a high separation factor of 20.1.     

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。     

Synthesis of zeolite L membranes with sub-micron to micron thicknesses

The growth of zeolite membranes with controlled thicknesses in the sub-micron to micron region is examined, using zeolite L as the example. It was demonstrated that by controlling the concentration of the zeolite solid load and suspension viscosity, dip-coating provided a method to prepare zeolite seed layers of controlled thicknesses. Disk-shaped zeolite L crystals, with size distribution of 0.5–2 μm in diameter, were used as seed crystals for the growth of 2–7 μm thick membranes. By choosing the composition of the secondary growth medium, as well as time and temperature, crystal growth primarily occurred along the xy-plane in these micron plus-thickness membranes, with eventual thickness similar to the originally deposited seed layer. For the synthesis of sub-micron-sized membranes, seed crystals from 20 to 60 nm were used and growth was observed along the z-axis. The optimum secondary growth conditions was found to occur at 60 h of growth time (40 h for sub-micron membranes) using a temperature of 110 °C with a solution composition of 10K₂O:1Al₂O₃:20SiO₂:2000H₂O. Membranes were characterized by electron microscopy and single gas permeation studies, providing confirmation of membrane densification.     

管式支撑体内表面NaA分子筛膜的合成与表征

采用转动合成方式通过二次生长法在管式α-Al₂O₃支撑体内表面合成了NaA分子筛膜,采用X射线衍射仪（XRD）、场发射扫描式电子显微镜（FE-SEM）和渗透汽化分离技术对所合成的膜进行了系统表征。考察了合成釜转速对分子筛膜合成的影响,结果表明合成釜转速的提高有利于分子筛膜合成。在转速为4 r·min^-1时所合成NaA分子筛膜分离因子高达2370,渗透通量1.86 kg·h^-1·m^-2左右（乙醇/相似文献   

The change of the unit cell dimension of different zeolite types by heating and its influence on supported membrane layers

In comparison with the well-known swelling of organic polymer membranes, zeolite membranes have been considered for a long time as relatively stiff. The problem of the different thermal expansion coefficients of the α-Al₂O₃ support and the zeolite layer was usually reduced on a possible crack formation during the template removal of MFI membranes. However, the crack formation could be avoided by an extremely slow heating rate and by membrane layers formed of small and non-oriented zeolite crystallites. Several papers have shown that the isomorphous incorporation of Al into the MFI structure (silicalite → ZSM-5) results in an increase of the non-selective intercrystalline transport and – as a consequence – the separation selectivity drops. In accordance with this observation, no shape-selective gas separation is reported for the Al-rich zeolite membranes MOR, FAU and LTA. On the other hand, these membranes allow the highly selective separation of water from organic mixtures due to hydrophilic interactions. In the present paper the change of the unit cell dimension (UCD) for zeolites LTA, FAU, MOR and MFI was studied as a function of temperature and water content using Rietveld refinement. Parallel to the determination of the linear and volume expansion coefficients by in situ-heating XRD, the de-watering and de-templating was studied by thermogravimetry (TGA). A strong UCD-change was found for all Al-rich zeolite types as a result of the de-watering. In contrast, the smallest changes of the UCD in the temperature range 50–450 °C were found for MFI crystals. Nevertheless, also for MFI membrane layers with rising temperature an increasing tension between the expanding α-Al₂O₃ support and the slightly shrinking membrane layer takes place. Zeolite layers of small crystals with either a random or a preferential crystal orientation relative to the support and an only partial de-watering in the case of Al-rich zeolite layers can minimize the tension in the support-membrane system. Thus, the irreversible formation of macroscopic cracks can be avoided and the formation of small intercrystalline pores in the mesopore region becomes reversible.     

Improvement of Zeolite T Membrane via Clear Solution Gel in Dehydration of Methanol,Ethanol, and 2-Propanol

Using of clear gel solution on synthesis of zeolite membrane can potentially have many benefits. In this research, zeolite T membrane on home-made α-Alumina disc-shaped MF support was successfully synthesized in 120°C for 24 h via secondary growth hydrothermal method using high alkalinity clear gel solution in molar ratio formulation (SiO₂:Al₂O₃:Na₂O:K₂O:H₂O = 55:1:122.7:42.3:2000). The synthesized membrane showed elevated selectivity in dehydration of ethanol/water and 2-propanol/water solutions (between 1000 to more than 10000) and high-water permeation fluxes (between 1.2 to 2.4 kg/m²h at 40°C for 10 wt.% water content). The synthesized MF alumina supports, zeolite T membranes, and crystals used for seeding were characterized by XRD and SEM analyses. These analyses indicated 10 μm dense and defect-free well-intergrowth zeolite T as active layers were formed on the porous media support.     

Preparation of zeolite NaA membranes on the inner side of tubular supports by means of a controlled seeding technique

Zeolite NaA membranes have been reproducibly prepared by seeded hydrothermal synthesis on the internal surface of porous -alumina tubular supports. A cross-flow filtration technique has been developed to allow a controlled seeding of zeolite NaA crystals from a suspension according to transmembrane pressure, pH, seed suspension flow rate, crystal size and concentration. The optimal seeding weight gain was found to be around 0.40 mg cm⁻² of membrane area. With this procedure, zeolite membranes with selectivities up to 600 at fluxes of 0.50 kg m⁻² h⁻¹ were obtained in the pervaporation of 92:8 wt.% ethanol/water mixtures at 323 K.     

Synthesis at several length scales of zeolite A membranes using a continuous flow method

Zeolite A membranes were synthesized in the inner side of porous TiO₂ and α-Al₂O₃ tubular supports by a continuous method. The methodology was then used at several scales for preparing membranes on TiO₂ and α-Al₂O₃ supports with lengths of 6, 12 and 25 cm. Formation of an homogeneous zeolite film was confirmed by XRD and SEM in all supports. Single-gas permeation experiments (He, H₂, N₂ and n-C₃H₈) indicated that Knudsen diffusion was the predominant mechanism in both supports. All the synthesized membranes present high flux and moderate selectivity to water in water–ethanol mixtures.