Composite membranes containing metal-organic polymers: Morphology and gas transport properties

Metal-organic framework compounds used in gas separation membranes based on polyimides with different chemical structures have been surveyed. According to analysis of published data, a metal-organic framework compound composed of MIL-101 and two polyimides with different chemical structures has been selected. Samples of gas separation membranes containing the additive in an amount of 2.5–20 wt % have been prepared to analyze the gas transport characteristics. A significant difference in the permeability and selectivity for a wide range of gases has been shown. The morphological structure of the polymer composites with additive different contents has been analyzed, a the differences in the gas transport properties have been explained.     

Investigation of gas transport properties of poly(2-methyl-5-vinyltetrazole) membranes

In recent years, progressively increasing attention of researchers has been given to vinyltetrazoles and their polymeric derivatives. However, despite the variety of properties revealed, a limited number of studies focus on the possibility of their practical application and there is no published data on the gas permeability of these polymers. This paper presents the results of study of the gas transport properties of polymeric membranes based on poly(2-methyl-5-vinyltetrazole) for helium, oxygen, nitrogen, and methane. It has been found that these properties depend on the membrane thickness. The permeability and diffusion coefficients increase with the decreasing kinetic diameter of penetrant molecules or the increasing temperature. Poly(2-methyl-5-vinyltetrazole) exhibits behavior typical of most of the known polymers.     

Synthesis and gas transport properties of polypentafluorostyrene

Polypentafluorostyrene (PPFS) (M _w = 1.7 × 10⁵ Da, M _w /M _n = 1.6, and Т _g = 110°С) has been synthesized by radical polymerization of pentafluorostyrene. The chemical structure of the polymer has been confirmed by ¹H and ¹⁹F NMR data. The permeability and diffusion coefficients of gases (He, H₂, O₂, N₂, CO₂, and CH₄) have been measured on a barometric setup. The permeability, diffusion, and solubility coefficients of gases have been shown to increase with the increases in the fluorine content in the repeat unit of the polymer in the polystyrene–poly(p-fluorostyrene)–PPFS series. Such behavior of transport parameters in the polymer series is associated with the growth in the fractional free volume and decrease in the cohesive energy density. The investigated polymers on the basis of styrene and its derivatives including PPFS are located in the middle of clouds of Robeson diagrams for N₂/CH₄, CO₂/CH₄, and O₂/N₂ and are not of interest for their separation.     

填料塔离子液体气相内脱水实验研究

以1-丁基-3-甲基咪唑醋酸盐([BMim][Ac])离子液体为吸收剂,用空气和水蒸气的混合气模拟含水湿气,在θ金属网环填料塔中进行脱水实验。探究了离子液体流量、液体含水量、液体温度、空气流量以及进气含水量对脱水效果的影响,获得了最佳实验参数条件。实验结果表明,气体露点降随液体流量和进气含水量的增加而增大,随液体含水量、液体温度和空气流量的增加而减小。在液体流量9L/h、气体流量1m~3/h、液体中水质量分数1%、湿气中水质量浓度18.26g/m~3、温度20℃的条件下,气体露点降在40℃以上,干气露点低于-20℃,取得了良好的脱水效果,在工业气体脱水、室内空气干燥等领域展现出良好的应用前景。     

Noble gases as indicators of molecular-selective gas transport in polymeric membranes

Methods of estimation of molecular-selective gas transport parameters in polymeric membranes and explanation of separation selectivity evolution for ‘small’ and ‘large’ molecules up to inversed selectivity are proposed based on comparative analysis of diffusion and solubility of noble gases as isotropic diffusion probes in different classes of polymers and block copolymers on their basis. Two approaches are considered in this work: (1) analysis of diffusional migration of permanent gases, lower hydrocarbons, and alcohols (vapor) in glassy polymers and rubbers relative to the diffusion of noble gases including radon; (2) adaptation of the ‘hard sphere’ theory developed for gas solubility in liquids to the calculation of the solubility of gases in the polymer matrix. In the latter case, noble gases as isotropic probes are used for calculating the required fitting parameters of the polymer medium.     

Porous hollow fiber membranes with varying hydrophobic–hydrophilic surface properties for gas–liquid membrane contactors

In relation to the demand for asymmetric porous hollow fiber membranes to be used in gas–liquid membrane contactors designed for operation in organic media, polysulfone membranes of this type have been prepared and subsequently modified to impart oleophobic properties to their surface. The structure and properties of the membranes have been characterized using various techniques, such as optical and scanning electron microscopy, and by measuring contact angles and the permeability of helium, carbon dioxide, and hexane. The surface properties of the membranes have been modified by etching with a mixture of hydrogen peroxide and sulfuric acid or coating with a perfluorinated acrylic copolymer. In the latter case, modified membrane samples have shown a significant reduction in wettability with both water and organic liquids. The hexane permeability data indicate the absence of hexane flow through the membrane modified with perfluorinated acrylic copolymer until a gauge pressure of about 1 atm. The results of the study lead to the conclusion that these membranes can find use in gas–liquid membrane contactors, e.g., for the removal of dissolved gases from liquid hydrocarbons.     

Sorption properties and transport parameters of membranes based on polybenzoxazinoneimide and its prepolymer

A comparative study of physicochemical parameters and transport properties of the heteroaromatic polymer polybenzoxazinoneimide (PBOI) and its hydrolytically stable prepolymer, imide-containing polyamic acid (PI-PAA), has been performed. The process of thermal conversion of PI-PAA into PBOI has been studied using thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry. The conversion of PI-PAA into PBOI increases the glass transition temperature and the density of the polymer, resulting in a reduction of fractional free volume. Both of the test polymers have been examined as membrane materials in pervaporation dehydration of aqueous isopropyl alcohol. It has been shown that PBOI is more effective in this process compared with the prepolymer. The transport properties of the PBOI membrane have been compared with published data on other polymers used in the pervaporative separation of the water–isopropanol azeotrope.     

焙烧温度对负载型Mo基催化剂结构与甲烷化性能的影响

以浸渍法制备得到的CeO2-Al2O3复合氧化物载体于500℃或700℃焙烧处理,浸渍Co和Mo物种后得到Co-Mo/(CeO2-Al2O3)催化剂前驱体,再于500℃或700℃进行焙烧处理得到催化剂。采用N2物理吸附、H2程序升温还原、X射线衍射及扫描电子显微镜对催化剂进行了表征,在固定床上于550℃,3MPa,5000h-1,n(H2)/n(CO)为1.0且含有H2S的合成气中对催化剂的甲烷化性能进行了测试。结果表明CeO2-Al2O3载体的焙烧温度对催化剂比表面积有较大影响,而催化剂表面Co与Mo物种的分散度主要受催化剂前驱体焙烧温度的影响。当CeO2-Al2O3载体于500℃焙烧催化剂前驱体于700℃焙烧后,Co与Mo物种的分散度最好,催化剂甲烷化活性最高。     

Effect of chromium compounds on the properties of ion-exchange membranes

The transport properties of ion-exchange membranes MK-40 and MF-4SK, MA-40, and MA-41 in solutions of sodium chloride, chromium(III) chloride, and chromium(VI) oxide have been studied. It has been found that the MA-40 and MA-41 membranes retain their transport properties in chromium chloride(III) solutions, whereas the anion-exchange membranes in chromium(VI) oxide solutions undergo partial or complete degradation. The oxidative impact of chromate ions on both the hydrocarbon matrix of the MK-40 membranes and the chemically resistant perfluorocarbon matrix of the MF-4SK membrane has been revealed.     

Synthesis,ion exchange,and transport properties of membranes based on sulfonated polycarbonatemethacrylate

Products with ion-exchange properties have been obtained by heterogeneous sulfonation of polycarbonatemethacrylate (PCM). The resulting polymer and membranes based on it have been studied by means of elemental analysis, titrimetry, and IR spectroscopy. It has been shown that the ion-exchange capacity of the resulting products is 6 mEq/g. Therefore, together with relatively high ionic conductivity and ionexchange capacity, the products hold promise for use as ion-exchange membranes and modified coatings with ion-exchange properties.     

Effect of temperature on deactivation models of alumina supported iron catalyst during Fischer-Tropsch synthesis

Determination of catalyst deactivation model plays prominent role in process controlling. The aim of this study is to investigate deactivation models of Fe/Al₂O₃ catalyst at different temperature during the Fischer-Tropsch synthesis. Data analysis determined the suitability of second-order GPLE model to describe deactivation behavior of the catalyst. Comparing model parameters at different conditions demonstrated that the catalyst deactivation rate increased by temperature elevation. Analysis of the models also revealed that the catalyst deactivation involves two stages, the first stage occurs at high temperatures while the next step happens at low temperatures, and the deactivation energy of both stages was calculated.     

致密砂岩气藏润湿性对液相圈闭损害的影响

致密砂岩储层易因外来工作液入侵造成严重的液相圈闭损害,岩石表面润湿性对于液相圈闭损害程度具有重要影响。使用氟碳表面活性剂Zonyl8740处理岩心,降低岩心表面能,制得不同润湿程度的岩心。通过岩心驱替和毛管自发渗吸实验分别研究了气湿岩心和液湿岩心的束缚水饱和度、自吸油水动态;建立初始含水饱和度岩心流动实验,对比了钻井液加入气湿反转剂前后液相圈闭损害率。实验表明,致密砂岩表面由液湿反转为优先气湿可大幅度减弱毛管自吸效应、降低自吸液量和最终滞留饱和度。气湿反转剂可有效减少钻井液对储层液相圈闭损害。对预防致密砂岩储层液相圈闭损害具有一定指导意义。     

聚合温度对聚丙烯性能的影响

采用连续釜式预聚和卧式釜气相串联聚合工艺,利用BCM催化剂,二乙氨基三乙氧基硅烷外给电子体进行了丙烯聚合,考察了聚合温度对聚丙烯性能的影响。实验结果表明,随聚合温度的升高,催化剂的聚合活性降低,聚丙烯的相对分子质量分布变窄、等规度先增大后减小、结晶温度和熔点逐渐降低。聚丙烯的热变形温度、拉伸强度、弯曲强度和弯曲模量与等规度的变化趋势相同,即先增大后减小,在95℃时为最大值。当聚合温度在85~95℃时,催化剂的氢调敏感性比较好,聚丙烯的相对分子质量分布较窄、等规度高、热性能较好、力学性能优异。     

高温下高矿化度对泡沫性能的影响

考察了一价阳离子Na~+和二价阳离子Ca~(2+),Mg~(2+)对非离子起泡剂烷基糖苷(WT)、两性离子起泡剂甜菜碱(YX)泡沫性能的影响,测定了WT和YX的临界胶束浓度(CMC)及YX在含Ca~(2+),Mg~(2+)溶液中的透射率,采用SEM表征了泡沫微观结构,分析了矿化度对泡沫稳定性的影响机理。表征结果显示,随矿化度增大,形成的泡沫液膜厚度和黏弹性均增加。实验结果表明,矿化度大于3×104 mg/L时,随矿化度的增大,CMC降低,泡沫液膜厚度增加,包裹在液膜上的无机盐增多,泡沫稳定性增强,表现出一定的盐增效性;Na~+主要通过改变泡沫体系的CMC和电荷作用来影响泡沫的稳定性,而Ca~(2+)与Mg~(2+)则是通过离子与离子之间的化学反应、水化作用及电荷作用共同影响泡沫的稳定性,Ca~(2+)将与YX中阴离子基团反应生成不溶物,降低泡沫的起泡性与稳定性;Mg~(2+)则对YX泡沫性能影响不大。     

Structure and transport properties of pervaporation membranes based on polyphenylene oxide and heteroarm star polymers

Thin-film membranes based on polyphenylene oxide composites with a varying concentration of heteroarm star-shaped polymers (1, 3, and 5 wt %) comprising arms of polystyrene and poly(2-vinylpyridine)- block-poly(tert-butylmethacrylate) diblock copolymer grafted onto a common fullerene C₆₀ core have been developed. The transport properties of the membranes have been studied in the pervaporation separation of a methanol–ethylene glycol mixture. An increase in the star-shaped polymer content in the membrane leads to an increase in the flux and separation factor of the membranes. Sorption studies have revealed that the sorption activity of methanol in the membranes is higher than that of ethylene glycol. The introduction of star-shaped polymer additives into the membrane composition leads to an increase in the degree of equilibrium sorption of the two components of the mixture subjected to separation. The formation of transport channels in pervaporation membranes during sorption in deuterated methanol has been first studied using the small-angle neutron scattering method. Comparative analysis of the data on neutron scattering on the original dry samples, the samples saturated with deuterated methanol, and the samples dried after sorption has shown that the structural uniformity of the composite membranes is higher than that of the matrix polymer. According to scanning electron microscopy, the morphology of the composite membranes is a system of closed cells.     

甲醇生产中循环气冷后温度对产量的影响

格尔木30万吨/年甲醇装置在实际生产中,由于装置化学结蜡和环境气温的影响,装置冷后温度每年有长达6个月的时间持续超出设计指标运行,温度最高时超过设计温度33℃,对甲醇合成效率、甲醇产量以及装置能耗均造成严重影响。介绍了装置冷后温度超标对甲醇产量的实际影响并在理论上进行了计算分析,提出相应整改措施,并对甲醇回收量和预期收益进行评价。