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.     

炭分子筛膜的制备与改性

炭分子筛膜足近年来发展起来的高效、新型气体分离膜,具有良好的气体分离选择性,高的热和化学稳定性,但其气体分离选择性与气体渗透通量却不能同时达到很高的要求.综述了炭分子筛膜的制备材料,重点讨论了化学方法和物理方法对制备炭膜的前驱体进行改性,展望了炭分子筛膜的未来发展方向.     

分子筛膜的研究进展

分子筛膜是近些年发展起来的一种新型无机膜,具有很好的筛分效应、极高的耐热稳定性及良好的催化作用等优异性能。本文简单介绍了分子筛膜制备技术和分子筛膜反应器种类,分析了近年来分子筛膜在脱氢反应、酯化反应和氧化反应催化反应中的初步应用,发现其可实现催化与分离的很好结合,并对分子筛膜的应用前景进行了展望。     

分子筛膜的研究进展

分子筛膜是近些年发展起来的一种新型无机膜,具有很好的筛分效应、极高的耐热稳定性及良好的催化作用等优异性能。本文简单介绍了分子筛膜制备技术和分子筛膜反应器种类,分析了近年来分子筛膜在脱氢反应、酯化反应和氧化反应催化反应中的初步应用,发现其可实现催化与分离的很好结合,并对分子筛膜的应用前景进行了展望。     

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。     

炭分子筛膜研究的新进展

炭分子筛膜是一种用于气体分离的高效，节能的新型材料，具有好的气体分离选择性，高的热和化学稳定性，近年来得到国内外广泛的重视和发展，本文从制备炭分子筛膜的原料，制备工艺及其在气体分离应用等方面综合了国内外近年来炭分子筛膜的研究进展，并指出了目前存在的问题。     

CVD法制备微纤复合Cu分子筛膜催化氧化异丙醇

采用化学气相沉积法(CVD)制备了微纤复合Cu-5A/PSSF和Cu-ZSM-5/PSSF分子筛膜催化剂,研究了异丙醇在两种微纤复合分子筛膜催化剂上的催化氧化性能。采用湿法造纸和现代烧结工艺制备了不锈钢微纤预载体,分别采用二次生长法和原位水热合成法在经过表面改性后的不锈钢微纤表面合成ZSM-5和5A分子筛膜,通过化学气相沉积法分子筛膜表面负载Cu元素,得到微纤复合Cu-ZSM-5/PSSF和Cu-5A/PSSF分子筛膜催化剂。N2吸脱附曲线、XRD、SEM和XPS等表征结果表明:所制备的不锈钢微纤预载体形成了发达的三维网状结构,分子筛膜致密均匀地分布在不锈钢微纤载体表面,厚度分别为1.2和1.5μm,Cu O活性组分被均匀的分散在分子筛膜上,实际负载量约为(3.2~3.7)%(wt)。结合异丙醇催化氧化反应的T90看,催化活性为:Cu-ZSM-5/PSSFCu-ZSM-5Cu-5ACu-5A/PSSF,其中Cu-ZSM-5/PSSF的T90比Cu-ZSM-5降低了20℃,T50降低了40℃,表明分子筛膜材料的三维网状结构加强了传热与传质;Cu-ZSM-5分子筛催化剂的活性要好于Cu-5A分子筛催化剂,表明ZSM-5比5A分子筛的孔道结构更有利于异丙醇的催化氧化。     

我国研制出世界最薄分子筛膜

<正>12月12日,中国化工报记者从中国科学院大连化学物理研究所获悉,该所杨维慎研究员和李砚硕研究员带领的研究团队,成功制备出一种由1nm厚的纳米片构成的分子筛膜,其厚度仅为蝉翼厚度的千分之一,而且具有如筛眼般高度规整的孔道,可以精确筛分尺寸差异仅为0.04nm的氢气和二氧化碳分子。该纳米片分子筛膜的渗透通量和分离选择性远远超过目前所有氢气、二氧化碳分离膜。该项研究成果被美国无机膜科学家林跃生教授,德国分子筛膜和膜催化科学家卡     

分子筛膜在石油化工领域应用的研究进展

分子筛膜因其独特的吸附性能、规整孔道及择形性和优异的酸催化活性,在石油化工领域有着广阔的应用前景。简述了分子筛膜的结构与合成方法,指出未来研究的方向是降低合成成本、以及通过新型合成方法制备具有高渗透性能的分子筛膜材料。介绍了分子筛膜及膜反应器在石油化工原料与产品分离提纯(包括天然气中CO2及水蒸气分离、H2净化和醇类脱水)以及催化反应(包括酯化与酯交换反应、合成醚反应、CO2加氢制甲醇、脱氢反应和合成对二甲苯等)中应用的研究进展。目前分子筛膜已在醇类脱水领域实现20多年的工业应用,具有高渗透性、高择形性、化学稳定性和水热稳定性的分子筛膜反应器在接近工业条件下的H2分离及催化反应等过程中也表现出良好的实验结果。未来需进一步研究分子筛膜合成机理,加快工业规模膜组件制备技术的开发,以更好地推动石油化工高效可持续性发展。     

合成次数及硅铝比调控SAPO-34分子筛膜的乙醇脱水性能

SAPO-34分子筛膜因其独特的孔道结构和优异的稳定性被广大学者所青睐,目前的研究大多集中在催化、吸附和气体分离等方面,而关于其在液体分离中的研究鲜少报道。本文在Al₂O₃中空纤维支撑体表面分别一次和二次合成制备了SAPO-34分子筛膜,考察了四种不同硅铝比对SAPO-34分子筛膜结构形貌和性能的影响,并用于乙醇溶液的渗透汽化脱水,考察了操作温度、原料液中乙醇浓度以及分子筛合成次数对分离效果的影响。研究结果表明,硅铝比为0.5的二次合成的SAPO-34分子筛膜具有连续而致密的分离层和良好的渗透汽化分离性能,60℃下对乙醇（90%）-水（10%）的分离因子可以达到1170,渗透通量为0.9 kg/(m²·h)。     

Growth and characterization of highly oriented CuBr thin films through room temperature electrochemical route

A simple electrochemical process has been demonstrated to grow highly oriented copper(I) bromide thin films on indium-doped tin oxide (ITO) glass through reducing CuBr₂ in aqueous solutions at room temperature. The copper(I) bromide thin films grow preferential orientation along the 〈1 1 1〉 crystal axis from the X-ray diffraction patterns. The orientation growth of the CuBr thin films is little affected by the solution pH and applied potentials. The possible mechanism of the orientation growth has been discussed, and the surface energy of different crystal plane of CuBr crystal is believed to play an important role to control the orientation growth of the CuBr thin films. The oriented films exhibit intense free-exciton photoluminescence at room temperature.     

Synthesis of radially aligned single-walled carbon nanotubes on a SiO2/Si substrate by introducing sodium chloride

Radially aligned single-walled carbon nanotubes (SWCNTs) were synthesized on a SiO₂/Si substrate with thermal chemical vapor deposition by introducing sodium chloride (NaCl) onto the substrate surface. The growth of such SWCNTs was sensitive to the thickness of the SiO₂ layer on the Si substrate and the speed of the reactive gas flow. Cristobalite crystals were found to be formed on the substrate after the SWCNT growth process and were significant for the growth of radially aligned SWCNTs. The SWCNTs were assumed to be directed by the cristobalite crystals along a certain crystal direction on the (1 0 1) crystal face.     

Fabrication of Blanket-Like Assembled ZnO Nanowhiskers Using an Aqueous Solution

Blanket-like assembled ZnO nanowhiskers were fabricated using a freestanding ZnO nanoparticle layer by an aqueous solution deposition. X-ray diffraction and field emission scanning electron microscopy clarified the crystalline phase, orientation, morphology, and microstructure. Thermal treatment of the zinc acetate dihydrate layer resulted in the formation and delamination of the ZnO nanoparticle layer on the glass substrate. The growth habits of ZnO crystals resulted in the growth of ZnO nanowhiskers preferentially orientated along the direction of the c -axis on the whole surface of the freestanding ZnO nanoparticle layer by heterogeneorous nucleation and growth. The hierarchical-structured blanket-like ZnO nanowhisker assemblies can be utilized for dye-sensitive solar cells and gas sensors because of their high surface-to-volume ratio.     

Microstructure of SiC Prepared by Chemical Vapor Deposition

Silicon carbide prepared by chemical vapor deposition at a substrate temperature of ∼1400425-429°C was investigated. Optical microscopy showed that the growth characteristic is dendritic; the deposits consist of columnar blocks within each of which the orientation of crystals is approximately the same. Small pores occur along the boundaries of these blocks. Transmission electron microscopy revealed finer details of the growth characteristics. The crystals were mostly 3 C in structure, but crystals with 2H and one-dimensionally-disordered structures were also found. The 3 C crystals are mostly dendritic, but some columnar growth with alternating twin bands occurs. Both 2 H and one-dimensionallydisordered crystals exhibit a columnar habit, reflecting the difference in crystal symmetry from 3 C . In all these crystals, the c axis (or one of the <111> axes in 3 C crystals) lies perpendicular to the substrate.     

Control of the Preferred Orientation in MFI Films Synthesized by Seeding

Single crystal silicon and quartz wafers were seeded with colloidal TPA-silicalite-1 crystals. Hydrothermal treatment of the seeded substrates was used to grow dense MFI films. The preferred orientation of the crystals constituting the films as a function of the amount and size of seeds, film thickness and hydrothermal treatment conditions was investigated. In thin films, most of the crystalline material was found to be oriented with the b-axes close to perpendicular to the substrate surface. In thick films, the a- or c-axes were close to perpendicular to the substrate surface depending on the conditions used for hydrothermal treatment. The seed size and amount was found to affect the rate of change in preferred orientation as a function of film thickness. A film growth mechanism which is able to explain the experimental results is proposed.     

Electrodeposition and optical properties of highly oriented γ-CuI thin films

A simple electrochemical process has been demonstrated to grow highly oriented γ-CuI thin films on indium doped tin oxide (ITO) glass through reducing Cu(II)-ethylene diamine tetraacetic acid disodium (EDTA) complex in aqueous solutions at or near room temperature. The CuI thin films grow preferential orientation along the 〈1 1 1〉 crystal axis from the X-ray diffraction patterns. The oriented growth of the CuI thin films is not affected by the solution pH and the applied potentials. The possible mechanism of the oriented growth is discussed, and the surface energy of different crystal planes of CuI crystal is believed to play an important role to control the oriented growth of the CuI thin films. The bandgap of the electrodeposited CuI films is 2.98 eV and the photoluminescence spectra of the CuI thin films exhibit relative intense exciton band luminescence at room temperature.     

Ir coating prepared on Mo substrate by double glow plasma

Dense and adherent Ir coating was obtained on the surface of the Mo substrate by double glow plasma, which had a deposition chamber and two cathodes. Argon gas was used as the working gas. The bias voltage of Ir target and Mo substrate were −800 and −300 V, respectively. The chamber pressure was 35 Pa. Microstructure of the Ir coating was observed by scanning electron microscopy. The Ir coating had a polycrystalline structure with preferential growth orientation of (220) crystal plane. The deposition rate was ~3.5 μm/h. The good adhesion resulted from the buffer layer between the Mo substrate and the Ir coating. The buffer layer, a combined Ir and Mo, was formed at the beginning of the deposition. The Mo concentration distributed gradiently along the depth of the buffer layer.     

溶胶组分对AZO薄膜晶体结构的影响

采用溶胶-凝胶法在玻璃基底上制备得到了AZO薄膜,研究了溶胶组分对AZO薄膜晶体结构的影响。结果表明:溶剂、稳定剂和铝掺杂量不仅可以改变晶体生长取向,而且影响晶体的尺寸;以乙二醇独甲醚为溶剂,乙醇胺为稳定剂能够得到(002)晶面优先生长,且粒径较大的晶体;而铝掺杂量的增加虽然能够增强晶体的优先生长趋势,但抑制了晶体的长大。     

Structural and optical studies of CdS and CdS:Ag nano needles prepared by a SILAR method

Nano-crystalline CdS and Ag-doped CdS films are deposited on glass substrate by a SILAR technique at room temperature with cationic precursors of cadmium nitrate and silver nitrate, and anionic precursor of sodium sulfide with different S:Cd ratio in starting solutions. In order to fabricate samples, substrates were taken in the solutions with determined duration and immersion cycles. To investigate the structural and morphological characteristics of the samples XRD analysis and SEM were used. The X-ray diffraction patterns show that the CdS samples have cubic crystal structure with preferential orientation along the (111) plane and CdS:Ag samples have hexagonal crystal structure with preferential orientation along the (002) plane. Also the peak intensity of XRD patterns of CdS increases with increasing the number of immersion cycles. Optical reflection of the layers is measured with a spectrophotometer and their optical absorption coefficient and band gaps are calculated. The band gap energy of Ag-doped samples decreases respect to CdS samples. It seems that silver doping creates intermediate levels in the energy gap and this causes decreasing of energy gap. Making samples with different S:Cd ratio demonstrates that the sample with 3:1 ratio has highest peak intensity in the XRD pattern and best stoichiometry. It is also observed that with increasing S:Cd ratio, the band gap energy of the samples decreases.     

Growth of Devitrite,Na2Ca3Si6O16, in Soda–Lime–Silica Glass

The morphology and crystal growth of devitrite crystals nucleated heterogeneously on glass surfaces have been studied. The crystals grow as fans of needles, with each needle having a characteristic [100] growth direction with respect to the centrosymmetric triclinic unit cell. An analysis of crystal growth data reported here and a reappraisal of crystal growth data reported in prior studies suggests a best estimate of 260 kJ/mol for the activation enthalpy for the crystal growth of devitrite along [100], higher than the values previously reported.