烯烃/烷烃促进传递气体膜分离的发展状况

在总结烯烃/烷烃气体分离技术现状、描述过渡金属-烯烃配合作用原理的基础上,阐述了烯烃/烷烃促进传递气体膜法分离的分离原理、研究进展及存在的问题等.同时展望了膜技术应用于烯烃/烷烃气体分离的前景及研究方向.     

Mathematical Modeling of Facilitated Liquid Membrane Transport Systems Containing lonically Charged Species

Abstract

A numerical model is presented which solves the transient nonlinear system of partial differential equations governing the facilitated transport of ionically charged species through a liquid membrane. The mathematical model is derived in dimensionless form and solved numerically. Facilitation factors and electrical potentials across the membrane are computed and compared to experimental results. This model is useful in predicting transient concentration, flux, and electrical potential gradients provided that the values of the required physical constants are known. It was noticed that transient facilitation factors are not affected by the transient electrical potential buildup, which indicates that both the pure diffusion and the faciltated transport of permeate are affected equally by the electrical effects of the ionically charged species.     

A Single Stage Membrane Process for CO2 Capture from Flue Gas by a Facilitated Transport Membrane

Carbon dioxide is the most important anthropogenic greenhouse gas and it accounts for about 80% of all greenhouse gases (GHG). The global atmospheric CO₂ concentrations have been increased significantly and have become the major source responsible for global warming; the greatest environmental challenge the world is facing now. The efforts to control the GHG emissions include the recovery of CO₂ from flue gas. In this work, feasibility analysis, based on a single stage membrane process, has been carried out with an in-house membrane program interfaced within process simulation program (AspenHysys) to investigate the influence of process parameters on the energy demand and flue gas processing cost. A novel CO₂-selective membrane with the facilitated transport mechanism has been employed to capture CO₂ from the flue gas mixtures. The results show that a membrane process using the facilitated transport membrane can also be considered as an alternative CO₂ capture process and it is possible to achieve more than 90% CO₂ recovery and 90% CO₂ purity in the permeate with reasonable energy consumption compared to amine absorption and other capture techniques.     

固定白蛋白促进传递膜的制备及性能研究

以戊二醛作交联剂，固定白蛋白于常规的微波膜，制得固定白蛋白促进传递膜，并将该膜用于血浆中亲脂性毒物的消除，依据促进传递原理，建立了实验条件下的数学模型，实验结果表明，膜对亲脂性毒物有一定的消除效果，所建模型与实验结果较为吻合。     

Facilitated Transport of Gold through a Membrane via Complexation to Thiourea-Based Reagents

Abstract

The facilitated transport of Au(III) from hydrochloric acid solutions through double solid supported liquid membranes (SSLMs) is reported. The organic phase consisted of a chloroform solution of thiourea-based extraction reagents, dodecyl-thiourea (DTH) or nonylthiourea (NTH), physically absorbed onto microporous polypropylene films, Celgard 2500 or Celgard 2400 (Celanese Plastic Inc.). A cell composed of three compartments, including a reservoir of organic solution, with double SSLM was used in this study. Aqueous solutions of thiourea, KSCN, or Na₂S₂O₃ were used for removing Au(III) from the membrane phase. The permeability coefficient, P, of the SSLM was determined from the slope of Iog[Au]/[Au]_o or log A/A_o vs time plot. The influences of the stirring rate in aqueous feed and organic solutions, of the stripping reagents and their concentration, of the carrier concentration, and of the concentration of HCl in the aqueous feed on the permeability coefficient were determined. A model describing the transport mechanism consisting of diffusion through a feed aqueous diffusion layer, a fast interfacial chemical reaction, and diffusion through the membranes is reported. The study also demonstrates the suitability of the liquid membrane technique to use reagents with low solubility in organic solutions for the permeation of Au³⁺ without problem of solid-phase formation.

     

Separation of Propylene-Propane Mixture Using Immobilized Liquid Membrane via Facilitated Transport Mechanism

Abstract

Separation of propylene-propane mixtures using immobilized liquid membrane was investigated. A porous polymeric sheet was used as support to immobilize the liquid membrane. The effect of propylene partial pressure in feed stream, trans-membrane pressure, and carrier concentration on membrane separation performance was investigated and the results were evaluated in terms of separation factor, propylene permeability, and propane permeability. Propylene permeability ranged from 0.4 to 650 Barrer. Moreover, it was observed that for 30:70 (vol.%) propylene-propane mixture, at pressure 120 kPa and carrier concentration 20 wt.%, a separation factor of 480 was obtained.     

Facilitated Transport of Zinc Chloride through Hollow Fiber Supported Liquid Membrane. Part 2. Membrane Stability

Abstract

The stability of a hollow fiber supported liquid membrane of tri-n-octylamine diluted in n-dodecane with 2-ethylhexyl alcohol was examined for the facilitated transport of zinc chloride. The liquid membrane was unstable when the feed and the strip aqueous solutions were not saturated with the organic phase used as the liquid membrane. This was found to be due to the dissolution of relatively soluble 2-ethylhexyl alcohol to the aqueous phases. When both aqueous phases were presaturated with the organic phase used, a rather constant flux could be maintained for a long time by the reimpregnation of the organic phase approximately once a day. The continuous impregnation of the organic phase to the support membrane drastically increased the stability of the liquid membrane, even without presaturation of the two aqueous phases with the organic phase     

仿生促进杂化膜的制备及其性能研究

基于人工肺(ECMO)与血液直接接触,提出利用生物相容性良好的材料制备仿生促进杂化膜用于ECMO.在聚醚砜超滤膜上涂覆聚甲基丙烯酸甲酯作为分离层,氧栽体选用钴卟啉与咪唑配位的仿血红素结构,制备了一种仿生促进杂化膜,重点考察其在低压环境下对氧气/二氧化碳及氧气/氮气的分离性能.气体渗透性测试结果表明:当聚甲基丙烯酸甲酯(PMMA)质量分数为4.6％、四苯基钴卟啉质量分数为0.460％、压力为0.012 MPa时,制备的CoTPP-PMMA-PES复合膜分离性能较好,此时膜厚度为0.92 μm.与PMMA-PES复合膜相比,氧气渗透速率由8.05 GPU升至21.25 GPU,氧气/氮气选择性由1.28升至2.66,氧气/二氧化碳选择性由0.70升至0.92.     

Facilitated Transport of Zinc Chloride through Hollow Fiber Supported Liquid Membrane. Part 1. Transport Mechanism

Abstract

The facilitated transport of zinc chloride through a liquid membrane of tri-n-octylamine dissolved in n-dodecane with 2-ethylhexyl alcohol, supported on a microporous polyethylene hollow fiber, has been studied in a series of three papers. This first paper deals with the transport mechanism. The distribution of zinc chloride between the liquid membrane phase and the aqueous hydrochloric acid solution was clarified. The characteristics of the support membrane and of the flow system were examined through phenol transport experiments. The initial permeation rate of zinc chloride was explained by the sum of film resistances in the two aqueous phases and a membrane phase resistance     

Kinetic Efficiency Factors for Facilitated Transport Membranes

Abstract

A kinetic efficiency factor (η) is defined for facilitated transport membranes. η is defined as the actual facilitated flux divided by the facilitated flux under reaction equilibrium conditions. η is correlated with an inverse Damkohler number ε. A dimensionless equilibrium constant K and mobility ratio a also affect the value of η. η is shown to be useful in determining the operating regime of the system, comparing actual performance to maximum attainable, and providing a qualitative measure of the time to reach steady-state conditions.     

Two-Dimensional Permeate Transport with Facilitated Transport Membranes

Abstract

An analytical model has been developed for steady-state permeate transport with facilitated transport membranes. The model contains no adjustable parameters. The model accounts for both axial permeate transport parallel to the membrane and facilitated permeate transport through the membrane. The model predicts the fraction of permeate separated through the membrane as a function of physical properties and operating conditions. The model was derived for a cylindrical geometry but can be applied to a planar geometry. Also, the model could be used for the simple diffusion case when no facilitation is present. Reasonable agreement with experimental data is presented.     

Small-Scale Membrane Systems for the Recovery and Purification of Water

Abstract

The availability of high-quality membrane modules in a variety of configurations has expanded the range of potential applications for membrane systems. These expanded capabilities make it possible to use membrane systems to solve separation problems that previously could not have been addressed using membrane-based technology. This paper describes the development of three innovative membrane systems for water-recovery applications for the National Aeronautics and Space Administration and the U.S. military. For each membrane system, the separation problem is outlined, the technology and system are described, the operating data are reported, and potential spinoff applications are discussed.     

Off-Gas Purification by Means of Membrane Vapor Separation Systems

Abstract

The separation and recovery of volatile hydrocarbon vapors from gasoline tank farm off-gases can in Europe be considered to be a state-of-the-art technology (1). A new application in the treatment of gasoline vapors is the installation of a membrane module in vapor return lines from petrol dispensers to storage tanks at gasoline stations to enhance the vapor recovery efficiency of this system. For solvent vapor recovery, some membrane systems have been installed in the chemical and pharmaceutical industry (2). This paper deals with design features and operating experience.     

Preparation of a Facilitated Transport Membrane Composed of Carboxymethyl Chitosan and Polyethylenimine for CO2/N2 Separation

The miscibility of carboxymethyl chitosan/polyethylenimine (CMCS/PEI) blends was analyzed by FT-IR, TGA and SEM. Defect-free CMCS/PEI blend membranes were prepared with polysulfone (PSf) ultrafiltration membranes as support layer for the separation of CO₂/N₂ mixtures. The results demonstrate that the CMCS/PEI blend is miscible, due to the hydrogen bonding interaction between the two targeted polymers. For the blended membrane without water, the permeability of CO₂ gas is 3.6 × 10⁻⁷ cm³ cm⁻² s⁻¹ cmHg⁻¹ and the corresponding separation factor for CO₂ and N₂ gas is about 33 at the pressure of 15.2 cmHg. Meanwhile, the blended membrane with water has the better permselectivity. The blended membrane containing water with PEI content of 30 wt% has the permeance of 6.3 × 10⁻⁴ cm³ cm⁻² s⁻¹ cmHg⁻¹ for CO₂ gas and a separation factor of 325 for CO₂/N₂ mixtures at the same feed pressure. This indicates that the CO₂ separation performance of the CMCS/PEI blend membrane is higher than that of other facilitated transport membranes reported for CO₂/N₂ mixture separation.     

Facilitated Transport through a Liquid Surfactant Membrane with Continuous Phase Resistance: Role of Drop-Size Distribution

Abstract

An advancing reaction front model with drop-size distribution has been proposed for the case of facilitated transport through a liquid surfactant membrane. The model takes into account the continuous phase and outer liquid membrane phase resistances along with diffusion through a composite emulsion drop. The computed results are found to be in excellent agreement with the experimental data of Ho et al. The outer liquid membrane phase resistance seems to be an important parameter in controlling the overall extraction rate. Analytical solutions to model equations for uniform drop size are also presented in this study. The model is also capable of predicting the effect of various parameters on the overall extraction rate for the limiting cases of inverse Biot modulus tending to zero and infinity.     

金属离子固载膜及其有机物的渗透汽化分离

在简要介绍了金属离子固载促进传递膜制备方法的基础上，分析了金属离子和反离子的种类、分离体系的温度和膜厚度等对金属离子固载膜分离性能的影响；并对金属离子固载促进传递膜在烯烃／烷烃、苯／环己烷等有机物体系分离中的应用进行了综述。     

Selective Facilitated Transport of Uranium(VI) Across a Bulk Liquid Membrane Containing Benzoyltrifluoroacetone as Extractant-Carrier

Abstract

A study has been made on carrier-mediated transport of uranium(VI) using a bulk liquid membrane prepared by dissolving benzoyltrifluoroacetone (HBTA) in carbon tetrachloride. The source phase comprised of a solution of UO₂ ²⁺ or its binary mixture with other cations such as Th⁴⁺, Hf⁴⁺, Zr⁴⁺, Fe³⁺, La³⁺, Cu²⁺, Co²⁺, Mn²⁺, Ni²⁺, and Zn²⁺ in aqueous solutions of pH 6.0, while 0.1 M hydrochloric acid was serving as a stripping agent in the receiving compartment. The interference from Th⁴⁺ and a few other cations could be eliminated by using trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (DCTA) as a proper masking agent in the feed solution. Various factors influencing the transport process have been studied and an uphill transport (>99%) of uranium(VI) from the source phase could be accomplished under optimum conditions.     

Facilitated Transport of Zinc Chloride through Hollow Fiber Supported Liquid Membrane. Part 3. Module Operation

Abstract

The third paper of this series of three papers on the facilitated transport of zinc chloride through a hollow fiber supported liquid membrane of tri-n-octylamine diluted in n-dodecane with 2-ethylhexyl alcohol deals with module operation. The Type A module, in which 300 polyethylene fibers were simply bundled, revealed that only a fraction of the total surface was effective. The Type B module, with a sheet of glass fiber cloth as a spacer and a cross-flow arrangement of the outside strip solution, showed the same performance as with single fiber operation. The continuous impregnation discussed for a single fiber operation in the second paper was demonstrated to be effective by a Type C module     

Quantitative Description of Ion Transport in Donnan Ion Exchange Membrane Systems

Abstract

Presented are simplified mass transfer techniques describing the transfer of ions in continuous ion selective membrane systems in which the resistance to ion transport through the membrane is Small in relation to the resistance to ion transport in the solution phase. Methods are developed through the application of the transfer unit concept to the Donnan equilibrium. This equilibrium describes the equilibrium ion concentration on either side of an ion selective membrane. Data from one cation selection system is presented as evidence of the validity of these methods. Further techniques are shown that will allow the determination of ion transport given only equipment parameters and solution diffusivities. Supporting data are shewn.