Gas permeation properties of a composite membrane filled with poly(ethylene oxide) into a porous membrane

The permeability coefficients of O₂, N₂, and CO₂ gases at 25°C were examined for composite membranes that were prepared by filling poly(ethylene oxide)(PEO) with different molecular weights into a porous membrane. The permeability coefficients of O₂, N₂, and CO₂ were 2 × 10⁻¹⁰ – 4 × 10⁻¹⁰, 5 × 10⁻¹¹ – 9.5 × 10⁻¹¹, and 6 × 10⁻¹⁰ – 1 × 10⁻⁹ (cm³ STPcm/cm² s cmHg), respectively. The higher permeability coefficients of CO₂ are explained in terms of high solubility of CO₂ in filled PEO. The permeability coefficient of CO₂ was affected by the degree of crystallinity of PEO in the composite. On the other hand, there was little effect of crystallinity on O₂ and N₂ permeability coefficients. Some probable relationships between selectivities of O₂ to N₂ and CO₂ to N₂ and the degree of crystallinity of PEO were observed. The CO₂ gas permeability coefficients of the composite membrane for PEO50000 (M_w = 5 × 10⁴) showed a marked change due to melting or crystallization of PEO. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2733–2738, 1999     

Oxygen permeation of various archetypes of oxygen membranes based on BSCF

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3‐δ tubes, capillaries, capillary modules, and asymmetric membranes were prepared and tested for oxygen permeation in a dead‐end vacuum operation mode at temperatures up to 850^°C. The capillary module was built up by reactive air brazing using seven capillaries and a supply tube. Two machined discs were used as an end cap and as a connector plate. The oxygen permeation behaves according to Wagner at small driving forces, but significant negative deviations were observed for asymmetric membranes and single capillaries at higher ones. This is caused by pressure drops at the vacuum side for single capillaries. The highest oxygen flux was revealed for the capillary module with 175.5 mL(STP)/min at a low‐vacuum pressure of 0.042 bar at 850^°C, but the asymmetric membrane showing a little bit higher flux at moderate vacuum pressures above 0.07 bar. © 2012 American Institute of Chemical Engineers AIChE J, 58: 3195–3202, 2012     

Single- and dual-phase capillary membranes prepared through plastic extrusion method for oxygen permeation

Two capillary membranes, single-phase Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) and dual-phase 75 wt% Ce_0.85Sm_0.15O_1.925 - 25 wt% Sm_0.6Sr_0.4Cr_0.3Fe_0.7O_3-δ (SDC-SSCF), with dense cross section, were successfully prepared through the plastic extrusion method. The dual-phase capillary membrane shows higher strength compared to the BSCF counterpart, while the two capillary membranes exhibit much higher fracture strength than those of hollow fiber membranes. The oxygen permeation fluxes of both membranes increase with the increase of temperature and flow rate of sweep gas at the ambient pressure, and can be greatly improved by applying high pressures to the feed side. The oxygen permeation flux of BSCF capillary membrane is up to 19.5 mL cm^?2 min^?1 when 0.5 MPa air was applied to the feed side at 900 °C, which is one order of magnitude higher than that of SDC-SSCF capillary membrane. Thus, both capillary membranes have their own advantages and meet applications under different operation conditions.     

Swelling behavior of pervaporation membranes in ethanol–water mixtures

Novel hydrophobic composite membranes made of crosslinked poly(dimethylsiloxane) and poly(methyl hydrogen siloxane) (PDMS–PMHS) with various amounts of catalyst were prepared. Pervaporation experiments with water–ethanol mixtures revealed that an optimum ratio of catalyst to polymer base existed. Both swelling behavior and dynamic–mechanical properties of these silicone films were studied. The swelling experiments in different mixtures of ethanol and water determined that ethanol is preferentially sorbed and that the membranes are only capable to absorb a limited quantity of solvent. Equilibrium swelling data were also used in combination with the analysis of the viscoelastic relaxation of the swollen samples to obtain the dependence of the dynamic–mechanical properties of the silicone films on the quantity of permeants sorbed into the membrane. It was observed that the permselective parameters were related with the mobility of the chains and the free volume. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1424–1433, 2000     

Selective permeability of grafted nylon-6 membranes: 2. Potassium chloride permeation in acrylic acid grafted membranes

The permeation of potassium chloride through γ-irradicated nylon-6 membranes grafted with acrylic acid (AA) was investigated. The permeability of potassium chloride increases with increasing levels grafting in the membrane. It was found that the theory of permeation of electrolyte through ionic membranes (derived from the phenomenological equation) was applicable to the permeation of potassium chloride through AA-grafted membrane with high levels of grafting. The effective concentration of fixed charge determined by the Donnan membrane equilibrium exhibited almost the same value in the grafted membrane regardless of the levels of grafting. It was found that a tortuosity factor was dominant through affecting the permeation of KCI through the membrane. This may be considered as an interference factor in a homogeneous membrane.     

MQ硅树脂的制备及其对硅橡胶的补强作用

采用水玻璃法制备了MQ硅树脂；研究了不同溶剂在MQ硅树脂制备中的作用，并讨论了在MQ硅树脂制备过程中的一些影响因素。结果发现，以20mL乙醇作混配溶剂、六甲基二硅氧烷为萃取剂制备的MQ硅树脂性能较好；乙醇与六甲基二硅氧烷的体积比为1，nM／nQ值为0．78；较佳的水解温度是30～40℃；硅酸钠水解时间控制在1min，共水解时间控制在30～40min；制得的MQ硅树脂对硅橡胶的补强效果最好。     

用于离子迁移谱仪进样的纳米二氧化硅增强硅橡胶膜的制备

以六甲基二硅氮烷为改性剂,采用湿法工艺对纳米Si O2进行表面疏水化改性,制备了用于离子迁移谱仪进样的纳米Si O2增强硅橡胶膜,考察了加热温度与反应时间对纳米Si O2的改性效果,研究了改性纳米Si O2与硅橡胶的相容性、纳米Si O2掺杂硅橡胶膜的厚度及拉伸性能。结果表明,在疏水化改性反应中,随着加热温度的升高或反应时间的延长,纳米Si O2表面羟基数下降,比表面积减小,最佳加热温度为120℃,反应时间为4 h;随着反应时间的延长,改性纳米Si O2与硅橡胶的混合液透光度增大,说明纳米Si O2与硅橡胶的相容性提高;以聚苯乙烯为基底材料,采用溶剂挥发工艺制得纳米Si O2掺杂硅橡胶膜的拉伸强度随着纳米Si O2掺杂量的增加而增大,当纳米Si O2与硅橡胶掺杂质量比为30∶100时,可制得厚为2~5μm的最薄硅橡胶膜。     

Oxygen permeation study of perovskite hollow fiber membranes

The first oxygen permeation data of a dense hollow fiber perovskite membrane based on BaCo_xFe_yZr_zO_3 − δ are reported. The hollow fiber was prepared by a phase inversion process. Dense fibers were obtained with the following typical geometries: outer diameter, 800–900 μm; inner diameter, 500–600 μm; length, 30 cm. The O₂-permeation through the hollow fiber perovskite membrane was studied in a high-temperature gas permeation cell under different operation conditions. The increase of the helium gas flow rate reduces the oxygen partial pressure (p_O2) on the core side and a higher oxygen permeation flux is observed. High oxygen flux of 0.73 m³ (O₂)/(m² (membrane) h) was achieved at 850 °C under the operation parameters F_air (shell side) = 150 ml/min and F_He (core side) = 30 ml/min. The oxygen partial pressure dependence of the O₂ permeation flux indicated an interplay of both surface reaction and bulk diffusion as rate limiting steps. During 5 days of permeation a high and stable oxygen flux was observed. X-ray diffraction patterns of fresh and spent membranes after the permeation measurements revealed that no degradation after oxygen permeation appears.     

Oxygen permeation mechanism in polycrystalline mullite at high temperatures

The oxygen permeability of polycrystalline mullite wafers, serving as a model environmental barrier coating layer on SiC fiber‐reinforced SiC matrix composites, was evaluated at temperatures above 1673 h with an oxygen tracer gas (¹⁸O₂). Oxygen permeation occurred by grain‐boundary (GB) diffusion of oxygen from the high oxygen partial pressure (high‐Po ₂) surface to the low‐Po ₂ surface, with simultaneous GB diffusion of aluminum in the opposite direction. This GB interdiffusion of both oxygen and aluminum proceeded without acceleration or retardation, maintaining the Gibbs‐Duhem relationship. Oxygen permeation related to the GB diffusion of silicon was negligibly small compared to that generated by aluminum GB diffusion, resulting in decomposition of the mullite near the low‐Po ₂ surface. The GB diffusion coefficients for oxygen in the vicinity of the high‐Po ₂ surface were determined directly from the SIMS‐¹⁸O line profiles along individual GBs, as assessed from cross sections of the exposed wafer. The coefficients thus obtained were comparable to those determined in the absence of an oxygen potential gradient and those calculated from an oxygen permeation trial under the assumption of nearly ionic conductivity.     

有机硅纳米杂化改性环氧胶的研制和应用

通过溶胶-凝胶法制备了纳米有机硅溶胶。用透射电镜和红外光谱表征和分析了纳米粒子的形态和粒径,粒径为30－70nm。制备了用活性稀释剂糠醛和丙酮及有机硅纳米杂化改性的环氧胶。研究了胶液的初始黏度、渗透性、力学强度、弹性模量、粘接性、表面疏水性和防腐蚀性能。实验结果表明,环氧树脂含量、有机硅溶胶、硅烷偶联剂等对改性环氧胶的这些性能有显著影响,改性环氧胶双组分混合液的初始黏度可低至1.1mPa·s,渗透性强,固结体抗压强度高达40．8－81．5MPa,弹性模量为1．3－2．1×10^3MPa,剪切粘接强度5．1－11．9MPa,防水抗渗性及防腐蚀耐候性良好,可应用于灌浆防水加固补强、工业地坪涂料和防腐蚀涂料等多种用途。     

Preparation and gas permeation of immobilized fullerene membranes

Fullerene‐dispersed membranes were homogeneously prepared under the conditions in which a 10 wt % polystyrene solution containing 1 wt % fullerene was dried under a reduced pressure of 50 cmHg at room temperature. The fullerene membranes prepared with 1,2‐dichlorobenzene were found to have the darkest color, and showed no evidence of fullerene crystals in their photomicrographs. UV‐visible and infrared absorption spectra of the fullerene membranes showed fullerene bands, which indicated that the fullerene was homogeneously dispersed in the membranes. The permeability coefficients of pure nitrogen, oxygen, carbon dioxide, ethane, and ethylene were found to increase significantly in the fullerene membranes compared to those in the polystyrene membranes, although the ideal separation factors for oxygen/nitrogen and ethylene/ethane in the fullerene membranes (i.e., 4.3 and 1.7, respectively) were slightly less than the separation factors in the polystyrene membranes. The permeability increase originated from the increase in diffusion coefficients in the fullerene membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 529–537, 2000     

Oxygen permeation characteristics of sol‐gel derived barium‐substituted strontium ferrite membranes

The pervoskite‐type oxides have received attention due to their potential applications in catalysis, solid oxide fuel cells, gas sensors, and gas separable membranes. In view of their importance in oxygen separation from air, Ba_xSr_1?xFeO_3?δ (0≤x≤1.0) samples have been synthesized by sol‐gel process and investigated with regard to phase(s), oxygen permeation, and electrical conductivity. These compounds possess at room temperature, a perovskite‐type cubic, mixture of rhombohedral and hexagonal, and hexagonal phase(s) depending upon the composition 0≤x≤0.94, x=0.96‐0.98, and x=1.0, respectively. The barium incorporation causes initially enhancement but decrease in electrical conductivity above x=0.94. Above 800°C, all the compositions exhibit a stable cubic phase. The compacts made in the form of discs serve as stable oxygen permeable membranes displaying flux density () of ~2.45‐3.58 mL/cm².min at 1000°C. A good correlation has been demonstrated between the oxygen permeation and the electrical conductivity data. The maximum values of and conductivity correspond to Ba_xSr_1?xFeO_3?δ (x=0.94) with a perovskite‐type cubic structure. Hence, this membrane is quite suitable for oxygen separation technology.     

Separation and enrichment of carbon dioxide by capillary membrane module with permeation of carrier solution

A novel facilitated transport membrane for gas separation using a capillary membrane module is proposed in which a carrier solution is forced to permeate the membrane. Both a feed gas and a carrier solution are supplied to the lumen side (high pressure side, feed side) of the capillary ultrafiltration membrane and flow upward. Most of the carrier solution which contains dissolved solute gas, CO₂ in the present case, permeates the membrane to the permeate side (low pressure side, shell side), where the solution liberates dissolved gas to form a lean solution. The lean solution is circulated to the lumen side. This type of capillary membrane module was applied to the separation of CO₂ from model flue gases consisting of CO₂ and N₂. Monoethanolamine (MEA), diethanolamine (DEA) and 2-amino-2-methyl-1-propanol (AMP) were used as carriers or absorbents of CO₂. The feed side pressure was atmospheric and the permeate side was evacuated at about 10 kPa. CO₂ in the feed gas was successfully concentrated from 5–15% to more than 98%. The CO₂ permeance was as high as 2.7×10⁻⁴ mol m⁻² s⁻¹ kPa⁻¹ (8.0×10⁻⁴ cm³ cm⁻² s⁻¹ cmHg⁻¹) when the CO₂ mole fraction in the feed was 0.1 and temperature was 333 K. The selectivity of CO₂ over N₂ was in the range from 430 to 1790. The membrane was very stable over a discontinuous one-month testing period.     

水基硅橡胶固化膜的性能

以硅溶胶作增强剂,二月桂酸二丁基锡为催化剂,研究了增强剂、固化剂及催化剂对水基硅橡胶的乳液黏度、表干时间及固化膜性能的影响。结果表明,硅溶胶是水基硅橡胶有效的增强剂,硅溶胶和固化剂用量对水基硅橡胶的物理机械性能及固化速率有显著影响;二月桂酸二丁基锡可以明显改变水基硅橡胶的固化速率,但对固化物的物理机械性能不会产生明显的影响。当硅溶胶和固化剂的质量分数分别为20%和4.0%时,固化膜可具有拉伸强度3.11 MPa、扯断伸长率520%、邵尔A硬度55的良好性能。     

中空玻璃用低水蒸气渗透率有机硅密封胶的研制

以α，ω-二羟基聚二甲基硅氧烷为基胶，配合自制的改性石油树脂及碳酸钙等填料、复合固化剂，制得专用于中空玻璃粘接密封的低水蒸气渗透率有机硅密封胶；研究了改性石油树脂对产品性能的影响。结果表明，100份密封胶中，改性石油树脂的最佳用量为20份，A、B组分的质量比为11～13：1；该密封胶的水蒸气渗透率为1．8g／m^2．d，硫化后的邵尔A硬度为42度，拉伸粘接强度1．04MPa，粘接破坏面积0：70℃下加速贮存168h后性能没有变化，常态下的贮存期为9个月。     

Separation properties of alcohol–water mixture through silicalite-I-filled silicone rubber membranes by pervaporation

The structure and the adsorption–desorption properties of zeolite silicalite-I by different treatments after synthesis were studied. The pervaporation properties of the alcohol–water mixture through silicone rubber filled with zeolite silicalite-I by different treatments were also investigated. Treating silicalite-I by acid or/and under steam was found to eliminate the metallic impurities in the zeolite and to perfect the crystalline structure of the zeolite. After treatment, silicalite-I is more selective to alcohol and the desorption of the alcohol from the zeolite is also easier. The silicone rubber membrane filled with treated silicalite-I shows a high performance for alcohol extraction from the dilute aqueous solution by pervaporation. The separation factor of the poly(dimethyl siloxane) (PDMS) membrane filled with silicalite-I treated successively by acid and steam is about 30 when the ethanol content in the feed is 5 wt % at 50°C. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 629–636, 1998     

2005年国外有机硅进展

根据2005年公开发表的相关资料,对1年来国外有机硅的市场状况作了分析,重点介绍了1年来国外几大有机硅公司的动向及产品开发情况。     

国外有机硅的产品及消费构成

根据SRI Internationl的“2003年化学经济手册”提供的数据,分析了1998年世界有机硅产品的产量和消费量的地区分布,及美国、欧洲和日本的有机硅的产品和消费构成,以供同行借鉴和参考。     

Preparation of thermosensitive cellophane-graft-N-isopropylacrylamide copolymer membranes and permeation of solutes through the membranes

Thermosensitive membranes with high mechanical strength were prepared by heterogeneous graft copolymerization of N-isopropylacrylamide (NIPAAm) onto cellophane in a nitric acid solution using cerium ammonium nitrate as an initiator, and the permeation behavior of solutes such as lithium chloride and poly(ethylene glycol)s (PEGs) through the membranes at various temperatures was investigated. The degree of graft copolymerization of NIPAAm on cellophane depended on temperature, time, initiator concentration, and so on. The copolymer membranes having a high content of the NIPAAm moiety could be obtained at 25°C for 24 h. The permeation of Li⁺ through the membranes was affected by temperature, i.e., the permeation rate of Li⁺ increased with increasing temperature up to 32°C and then decreased rapidly above 35°C. The permeation rate of Li⁺ through the copolymer membranes at 40°C decreased considerably, but that at 20°C decreased slightly with an increasing amount of the NIPAAm moiety in the membranes. The permeation rate of PEGs with a molecular weight more than 1000 through the cellophane-g-NIPPAm copolymer membranes was considerably suppressed and only the permeation rate of PEG300 increased with increasing temperature up to 35°C and then decreased at 40°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 209–216, 1997     

Promotion of hydrogen permeation on metal-dispersed alumina membranes and its application to a membrane reactor for methane steam reforming

A mesoporous membrane for selective separation of hydrogen was prepared usingthe sol-gel method. Some metal salts such as RuCl₃, Pd(NH₃)₄Cl₂, RhCl₃,, and H ₂PtCl₆, were added to the boehmite sol and coated on a porous alumina substrate before firing at 500°C. It was foundthat the permeability of hydrogen and the separation factor for a hydrogen-nitrogen gaseous mixture of these metaldispersed membranes exceeded the limitations of the Knudsen diffusion mechanism. Although the gas permeation through a neat alumina membrane is governed by the Knudsen diffusion, the metals dispersed in alumina membranes were effective in promoting hydrogen permeation. These metaldispersed alumina membranes were also used in a membrane reactor for methane steam reforming at low temperature. In the temperature range of 300 to 500°C, the membrane reactor attained a methane conversion twice as high as the equilibrium value of the packed bed catalytic reactor system as a result of the selective removal of hydrogen from the reaction system.