The basic principle,material of gas separation membrane,and its applications in the separation and recovery of hydrogen and air as well as the treatment of sour gas were reviewed.Finally,the opinions about the prospected application of gas separation membrane were proposed.

简要介绍了有关气体膜分离的基本原理、材料及其在氢气分离回收、空气分离和酸性气处理中的应用,并对气体膜分离的发展前景提出了自己的见解。

Organic–inorganic polymer membranes were prepared by reacting 3-glycidoxypropyl trimethoxysilane with diamines containing polyether segments, followed by hydrolysis and condensation with acid catalysis. The films were characterized by nuclear magnetic resonance and by dynamic mechanical analysis. The rigidity of the films increased with increasing epoxy content and also with addition of tetraethoxy silane (TEOS) to the reacting medium. Water absorption experiments showed that the diffusivity is decreased with increasing TEOS content. Membranes were evaluated for nanofiltration giving cut offs down to 860 g/mol (with a water flux of 2.5 l/h m² bar). For gas separation, CO₂/N₂ selectivity values up to 89 were obtained with CO₂ permeability of 125 Barrer.

A new organic-inorganic hybrid microporous membrane was prepared via Sol-Gel method with bridged silsesquioxane (1, 2-bis(triethoxysilyl)ethane, BTESE) as a precursor. Macroporous α-Al₂O₃disk supported mesopo- rous γ-Al₂O₃ layer was used as support. Defect-free hybrid silica membrane was deposited on such support by using a stable nano-sized sol and subsequently calcining in pure nitrogen atmosphere. The hybrid SiO₂ membrane as well as the powder was characterized by TG/DSC, BET and gas permeation. The hybrid silica membranes exhibit molecular sieve properties for small gases like He, CO₂, O₂, N₂, CH₄, and SF₆  with helium permeance in the range of (1.0-3.5)´10^-7mol/(m²·s·Pa)(at 200℃, 0.3MPa). Considering the membrane calcined at 500℃, it is found that the permselectivity of the He (0.255nm) with respect to CO₂(0.33nm) is 47, which is much higher than the corresponding Knudsen value (He/CO₂=3.3). Effect of calcination temperature on hydrothermal stability of those microporous membranes was studied in detail. Results show that the performances of hybrid SiO₂ membranes calcined at 450℃, 500℃ and 550℃ deteriorate under a H₂O partial pressure of 200, 500 and 1000kPa, respectively.

以1, 2-二(三乙氧基硅基)乙烷为前驱体, 通过溶胶-凝胶法合成出稳定的纳米复合SiO₂溶胶, 采用浸浆法在具有g-Al₂O₃/α-Al₂O₃结构的片状载体上涂膜, 然后在N₂气氛下烧成得到完整无缺陷的有机-无机复合SiO₂膜. 以TG/DSC、BET和气体渗透性能测试等手段对复合SiO₂膜及粉体进行了表征. 该膜对小分子气体(He、CO₂、O₂、N₂、CH₄和SF₆)的分离表现出分子筛分效应, 对He的渗透通量为(1.0~3.5)´10^-7mol/(m²·s·Pa)(200℃, 0.3MPa). 500℃烧成的膜对He/CO₂的理想分离因子为47, 远远高于Knudsen扩散时He/CO₂的理想分离因子(3.3). 详细考察了烧成温度对膜水热稳定性的影响. 结果表明: 在450、500和550℃三个温度下烧成的膜水蒸气稳定条件(分压)分别为200、500和1000kPa.

This review discusses the state of the art on the synthesis, functionalization and emerging applications of mesoporous silica materials. Mesoporous silica materials can be synthesized as membranes or powders with controlled pore size and geometry depending on the synthesis conditions. Mesoporous membranes are generally grown on porous supports by solvent evaporation or hydrothermal synthesis techniques. Synthesis of powdered mesoporous silica materials with controlled pore sizes in the range 2–30 nm and various different pore geometries has been an active area of research over last 15 years. Functionalization of the pore channels of ordered mesoporous silica with organic groups provides new opportunities for fine-tuning the chemical, physical, mechanical, and dielectric properties of these intriguing materials. This has led to an interest in application of these materials as separation membranes for the removal of environmental pollutants, e.g. greenhouse CO₂ emissions, and the separation of bioethanol from water; heterogeneous catalysts; adsorbents for removal of environmental pollutants, such as Hg; as well as other advanced nanotechnological applications.

An incompletely condensed polyvinylsilsesquioxane (PVSQ) oligomer containing abundant silanol groups was synthesized and characterized by FTIR,¹H-NMR,²⁹Si-NMR, and MALDI-TOF-MS. Polystyrene/polyvinylsilsesquioxane (PS/PVSQ) hybrid composites were prepared by anin situ bulk polymerization. The hybrid composites showed higherT_g, T_d, and char yield than PS homopolymer and without mechanical loss. The improvements in the properties of PS/PVSQ hybrid composites can be ascribed to the crosslinking function of PVSQ by silanol condensation in later processing. The hybrids showed different morphology from discrete microstructure to continuous network depending on the concentration of PVSQ. Because of the surface enrichment, a PVSQ protection layer was formed, which made the hybrid surface more hydrophobic. The structure and the reaction mechanism of PS/PVSQ hybrid composites were also investigated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A simple approach has been developed to synthesize the carbon/zeolite T composite membrane materials with the high gas separation performance. The precursors of the composite membrane are composed of polyimide matrix and dispersed zeolite T particles. The composite membranes prepared by pyrolysis at 973 K show excellent gas (H₂, CO₂, O₂, N₂, and CH₄) permeability and selectivity (O₂/N₂, CO₂/CH₄) for both single gas and mixed-gas. The gas separation performance of the composite membranes can be controlled in a wide range by only changing the zeolite T particle size. The maximum selectivity of O₂ over N₂ (21/79 mol%) for the composite membranes with the least zeolite T particle (0.5 μm) is 15 with an O₂ permeability of 347 Barrers (1 Barrer = 7.5 × 10⁻¹⁸ m² s⁻¹ Pa⁻¹) and the selectivity of CO₂ over CH₄ (50/50 mol%) reaches a value of 179 with a CO₂ permeability of 1532 Barrers. It is believed that the increase of gas permeability is attributed to the ordered microchannels in the zeolite and the interfacial gaps formed between zeolite and carbon matrix in the composite membranes. And the gas selectivity is tuned by the size of interfacial gaps which are varied with the zeolite particle size. This technique will provide a simple and convenient route to efficiently improve the trade-off relationship between the permeability and the selectivity and enable the construction of carbon-based composite materials with novel functionalities in membrane science.

Abstract

The preparation of carbon membranes by pyrolysis of polyetherimide hollow fibers and the influence of process variables on the final membrane morphology using a statistical experimental design are described in this work. The characterization of polymers and membranes was carried out by thermal analysis and scanning electron microscopy (SEM). The carbonization process was accompanied by mass spectroscopy to monitor the products formed. Similar to carbonization of others polymers, H₂O, CO₂ and CO evolution from 420 to 680 °C, and hydrogen evolution from 450 to 800 °C, indicate the formation of crosslinking of polymeric chains and formation of a graphite-like structure. These experiments permitted the production of thermostable carbon hollow fibers and selection of best treatment conditions. The extent of membrane exposure under oxidizing atmosphere and the maximum temperature of stabilization were decisive in the final membrane morphologic characteristics and properties. When the stabilization temperature was above 500 °C an intensive degradation of the fiber was observed. An initial exposure to an oxidizing atmosphere seems to be fundamental in order to control the final membrane properties. In this atmosphere, heating rates as low as 1 °C min⁻¹ during stabilization reduce cracks in the surface of final membranes.

A new, highly porous silicon-based membrane was developed by pyrolyzing a silicon-rubber material (polydimethyl siloxane)in two steps. The first step was performed under an inert-gas environment below 800°C. The second step was performed in air below 950°C to oxidize and cross-link Si-O chains. The resulting silicon-based material was highly porous and had a fine pore structure (maximum porosity of 50%, BET surface area of I40m₂/g) suitable for hot industrial gas separation even in a highly oxidizing environment. Gas permeability studies were performed at several different temperatures using a material derived by the pyrolysis of commercial silicon-rubber tubes. The results indicated that the flow through the membrane could be adequately explained by the Knudsen diffusion mechanism. The average permeabilities were 10 to 50 times those of porous Vycor glass.

The partial pyrolysis of poly(dimethyl siloxane) is reported. Pyrolysis is completed in a two step process, inert pyrolysis in a nitrogen atmosphere followed by oxidative pyrolysis in air. Treatment temperatures were from 300–400°C for the inert processing and 260–300°C for oxidative treatment. This thermal processing required no solvents or bulky catalysts, whose transport into the matrix is diffusion controlled and thus limit product uniformity. Therefore, high sample uniformity was achieved. Hybrid materials with reduced carbon and hydrogen content and an increased oxygen/silicon ratio resulted. These composites were shown to be stronger than composites reported in the literature with similar elemental compositions, but prepared in such a way as to achieve only limited interphase interaction. At high oxidation temperatures, microporosity developed in the materials.

In this investigation, the preparation and characterization of partially pyrolyzed membranes based on poly(dimethylsiloxane) (PDMS) are described. These membranes were obtained by the crosslinking of silanol-terminated PDMS with multifunctional nanoclusters derived from the reaction of pentaerythritoltriacrylate with 2-aminoethyl-3-aminopropyltrimethoxysilane and thein situ polycondensation of tetraethylortosilicate, followed by the thermal treatment of the resulting membranes at different temperatures. The partially pyrolyzed membranes were characterized with infrared spectroscopy, thermogravimetry, elemental analyses, dynamic mechanical analysis, small-angle X-ray scattering, and scanning electron microscopy. The membranes exhibited improvements in the thermal stability and mechanical strength. Even with distinct compositions with respect to the Si/O and Si/C ratios, the flexibility of these materials was maintained. The flux rates of the gases through the membranes were measured for N₂, H₂, O₂, CH₄, and CO₂, at 25 °C. The permeability of the membranes changed with increases in the pyrolysis and oxidation temperatures. These membranes could be described as PDMS chains separated by inorganic clusters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 299–309, 2007.

Permeability, diffusivity and solubility of gases in polymer/inorganic composite membranes are reported. Membranes were prepared by covering a porous Vycor glass tube with polysilastyrene solution followed by pyrolysis at 382 and 470°C. The experimental data indicate that the gas separation properties of such a membrane are a combination of the transport characteristics of the polymer and the molecular-sieve material. Selectivity factor for H₂/SF₆ increases to 328 for the membrane pyrolyzed at 470°C whereas for the unpyrolyzed polymer it is merely 10.

A technique for the determination of the pore size distribution of molecular sieve materials is described. This method is based on the determination of the microporous volume accessible to molecular probes of different sizes. The method is used to follow the molecular sieve structure which develops during the pyrolysis of polysilastyrene (dimethylsilane-methylphenylsilane copolymer). A molecular sieve membrane is prepared by partially pyrolyzing a polysilastyrene solution-coated porous Vycor glass tube.

This study examines the use of a partial pyrolysis coupled with an oxidation technique for the formation of porous hybrid organic/inorganic composite structures. Partial pyrolysis of poly(dimethyl siloxane), followed by oxidation, results in the formation of a microporous sample with increased thermal stability and enhanced chemical resistance while maintaining the mechanical strength and some flexibility of the samples. Gas transport through these modified composites is examined as a function of temperature to 300°C. Flux rates through the composite are increased due to increasing pyrolysis and oxidative temperatures while the flexibility and strength of composite materials are slightly impaired. Systems with varying degrees of porosity and separating capabilities are formed, and several of these systems show promise as membrane materials.