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Gas Separation (gas + separation)
Selected AbstractsSynthesis and Properties of 6FDA-MDA Copolyimide Membranes: Effects of Diamines and Dianhydrides on Gas Separation and Pervaporation PropertiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 24 2007Shude Xiao Abstract 6FDA-MDA-based polyimides were synthesized from a one-step polycondensation of 6FDA and MDA with other diamines and dianhydrides. The polyimides were characterized by GPC, FT-IR and NMR, and dense membranes were prepared from their solutions for gas separation and pervaporation. Gas separation and pervaporation properties were investigated using the linear moiety contribution method. The moiety contribution factors were used to analyze the effects of the dianhydride and diamine monomers on gas permselectivity and pervaporation permeation flux. It was shown that the steric effects and flexibility of the monomers and the interactions between the membrane and the penetrants accounted for the differences in separation properties. [source] A Microporous Metal,Organic Framework with Immobilized ,OH Functional Groups within the Pore Surfaces for Selective Gas SorptionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2010Zhenxia Chen Abstract A new two-dimensional microporous metal,organic framework Cu(BDC-OH)(H2O)·0.5DEF [abbreviation: Cu(BDC-OH); H2BDC-OH = 2-hydroxybenzene-1,4-dicarboxylic acid; DEF = diethylformamide] with functional OH groups on the pore surfaces was solvothermally synthesized and structurally characterized. The activated Cu(BDC-OH) exhibits a moderate Langmuir surface of 584 m2,g,1, a pore volume of 0.214 cm3,g,1, and C2H2/CH4 and CO2/CH4 selectivity of 6.7 and 9.3, respectively, at 296 K, thereby highlighting the promise for its application in gas separation. [source] Microporous Metal,Organic Frameworks with High Gas Sorption and Separation Capacity,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007Y. Lee Abstract The design, synthesis, and structural characterization of two microporous metal,organic framework structures, [M(bdc)(ted)0.5]·2,DMF·0.2,H2O (M,=,Zn (1), Cu (2); H2bdc,=,1,4-benzenedicarboxylic acid; ted,=,triethylenediamine; DMF: N,N -dimethylformamide) is reported. The pore characteristics and gas sorption properties of these compounds are investigated at cryogenic temperatures, room temperature, and higher temperatures by experimentally measuring argon, hydrogen, and selected hydrocarbon adsorption/desorption isotherms. These studies show that both compounds are highly porous with a pore volume of 0.65 (1) and 0.52,cm3,g,,1 (2). The amount of the hydrogen uptake, 2.1,wt,% (1) and 1.8,wt,% (2) at 77,K (1,atm; 1,atm,=,101,325,Pa), places them among the group of metal,organic frameworks (MOFs) having the highest H2 sorption capacity. [Zn(bdc)(ted)0.5]·2,DMF·0.2,H2O adsorbs a very large amount of hydrocarbons, including methanol, ethanol, dimethylether (DME), n -hexane, cyclohexane, and benzene, giving the highest sorption values among all metal,organic based porous materials reported to date. In addition, these materials hold great promise for gas separation. [source] Simulation and optimal design of multiple-bed pressure swing adsorption systemsAICHE JOURNAL, Issue 11 2004Ling Jiang Abstract Pressure swing adsorption (PSA) is a very versatile technology for gas separation and purification. The widespread industrial application of PSA has called for an efficient set of simulation, design, and optimization methodologies. In previous work by Jiang and co-workers, we used a Newton-based approach to quickly converge the cyclic steady state and design constraints, and a simultaneous tailored approach with the state-of-art nonlinear optimization strategy to design optimal PSA processes. In this work we extend the simulation and optimization strategies to multiple bed systems. Both unibed and multibed frameworks are adopted to describe bed behaviors. The unibed framework models only one bed over a cycle and uses storage buffers to mimic the bed interactions. The multibed framework simultaneously solves all beds but only for a portion of the cycle. Challenges and implementation details of both frameworks are discussed. A five-bed, 11-step hydrocarbon separation process, which separates H2 from a mixture of H2, N2, CO2, CO, and CH4, is used for illustration. By manipulating valve constants, step times, flow rates, and bed geometry, the optimizer successfully maximizes H2 recovery, while meeting product purity and pressure specifications. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2904,2917, 2004 [source] Equilibrium theory analysis of rectifying PSA for heavy component productionAICHE JOURNAL, Issue 8 2002Armin D. Ebner An isothermal equilibrium theory analysis, based on linear isotherms and a binary feed stream, was carried out to evaluate the feasibility of a rectifying PSA process for producing a pure heavy component at high recovery. Analytic expressions were derived to describe the performance of this process at the periodic state. The performance was also analyzed in terms of the different concentration and velocity profiles exhibited during various cycle steps that included the analysis of complex shock and simple wave interactions. Based on a parametric study, periodic behavior was established for a wide range of process conditions; and a design study with the PCB activated carbon,H2,CH4 system at 25°C further demonstrated the feasibility of a rectifying PSA cycle for producing a 100% CH4 stream from a dilute feed stream (y = 0.01) with a respectable recovery (80%), and reasonable process conditions. It also demonstrated the potential usefulness of an actual rectifying PSA process for bulk gas separation and purification. [source] Synthesis and Properties of 6FDA-MDA Copolyimide Membranes: Effects of Diamines and Dianhydrides on Gas Separation and Pervaporation PropertiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 24 2007Shude Xiao Abstract 6FDA-MDA-based polyimides were synthesized from a one-step polycondensation of 6FDA and MDA with other diamines and dianhydrides. The polyimides were characterized by GPC, FT-IR and NMR, and dense membranes were prepared from their solutions for gas separation and pervaporation. Gas separation and pervaporation properties were investigated using the linear moiety contribution method. The moiety contribution factors were used to analyze the effects of the dianhydride and diamine monomers on gas permselectivity and pervaporation permeation flux. It was shown that the steric effects and flexibility of the monomers and the interactions between the membrane and the penetrants accounted for the differences in separation properties. [source] Electroactive composite systems containing high conductive polymer layers on poly(ethylene) porous films,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9-10 2006G. K. Elyashevich Abstract New composite electroactive materials containing conducting polymers were elaborated by oxidative polymerization of aniline and pyrrole onto porous poly(ethylene) films. The morphology of the conducting phase on the surface of the composites was investigated by scanning electron microscopy. The influence of preparation method and porous support structure on electric and mechanical properties of the composite materials was studied. The correlation between the composites electroconductivity and the absorbance of electromagnetic radiation in the IR region was observed. It was found that gas separation and ion-exchange membrane properties of the composites strongly depend on their conductivity and content of conducting component. Copyright © 2006 John Wiley & Sons, Ltd. [source] Membrane reactor modelling, validation and simulation for the WGS reaction using metal doped silica membranesASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010S. Battersby Abstract In this work, a Matlab Simulink© model was developed to analyse and predict the performance of a metal doped silica membrane reactor for H2 production via both the high and low temperature water gas shift reaction. An activated transport model for mixed gas separation with combined reaction was developed to model the effects within a membrane reactor unit. The membrane reactor was modelled as a number of perfectly mixed compartments containing a catalyst bed and a gas selective membrane. The combined model provided a good fit to experimentally measured results for higher conversions up to equilibrium, which is generally the case for industrial applications. Simulation results showed that H2 separation and H2 recovery improved with pressure, due to the H2 concentration driving force across the membrane. For a single stage membrane reactor unit, a maximum conversion of 93% could be achieved with a H2 recovery rate of 95%. In addition, the membrane reactor efficiency increased at higher temperatures and lower H2O:CO feed ratios, allowing for CO conversion improvements by the membrane reactor. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] State of the art of carbon molecular sieves supported on tubular ceramics for gas separation applicationsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010Kelly Briceño Abstract During recent years, research into alternative power generation and less polluting vehicles has been directed towards the fabrication of compact and efficient devices using hydrogen fuel cells. As a compact viable proposal, membrane reactors (MR) have been studied as means of providing a fuel cell with an on-board supply device for pure hydrogen streams obtained by reforming hydrocarbons. However, the development of MRs is strongly dependant on the membrane having high permeation flux and high selectivity ratios towards H2 in a mixture of gases. To meet this need, carbon membranes are proposed materials, which have pores that are the same size as the kinetic diameters of syngases. These would provide an alternative to polymers, metals and ceramics in MR applications. Moreover, a tubular shape is a highly recommended configuration for achieving a compact and large reaction surface area. However, it is not easy to obtain a supported and amorphous carbon layer from polymer pyrolysis because the fabrication methods, the type of precursor material, characteristics of the support and pyrolysis conditions are all closely connected. The combination of all these factors and the stability problems of carbon membranes have limited the use of carbon molecular sieves (CMS) in large-scale applications. This review attempts to provide an overview of the use of carbon membranes in MRs for gas separation. It also reviews the advances in the materials, fabrication methods and characterisation techniques of specific supported carbon molecular sieve membranes that have been supported on tubular carriers so they can take advantage of the high permeation and selectivity values previously reported for unsupported CMS. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Accessibility of simple gases in disordered carbons: theory and simulationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009T. X. Nguyen Abstract We present a review of our recent studies on the accessibility of simple gases (Ar, N2, CH4 and CO2) in disordered microporous carbons using transition state theory (TST) and molecular simulation techniques. A realistic carbon model rather than the slit-pore approximation is utilised, providing more accurate understanding of complex adsorption equilibrium and dynamics behaviour at the molecular level in porous carbons, especially kinetic restriction of adsorbate molecules through highly constricted pore mouths of coals and molecular sieve carbons (MSC). This kinetic restriction leads to a molecular sieving effect which plays a vital role in gas separation using the MSCs. In particular, the realistic carbon model of a saccharose char used in a recent study was obtained by hybrid reverse Monte Carlo simulation. The time of adsorption or desorption of the single gas molecule between two neighbouring pores through a highly constricted window of the realistic saccharose char model was determined using TST. Finally, the validation of TST calculated results of adsorption and desorption times against experimental measurements as well as molecular dynamics simulation is also presented in this article. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] A New Numerical Approach for a Detailed Multicomponent Gas Separation Membrane Model and AspenPlus SimulationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2005M. H. Murad Chowdhury Abstract A new numerical solution approach for a widely accepted model developed earlier by Pan [1] for multicomponent gas separation by high-flux asymmetric membranes is presented. The advantage of the new technique is that it can easily be incorporated into commercial process simulators such as AspenPlusTM [2] as a user-model for an overall membrane process study and for the design and simulation of hybrid processes (i.e., membrane plus chemical absorption or membrane plus physical absorption). The proposed technique does not require initial estimates of the pressure, flow and concentration profiles inside the fiber as does in Pan's original approach, thus allowing faster execution of the model equations. The numerical solution was formulated as an initial value problem (IVP). Either Adams-Moulton's or Gear's backward differentiation formulas (BDF) method was used for solving the non-linear differential equations, and a modified Powell hybrid algorithm with a finite-difference approximation of the Jacobian was used to solve the non-linear algebraic equations. The model predictions were validated with experimental data reported in the literature for different types of membrane gas separation systems with or without purge streams. The robustness of the new numerical technique was also tested by simulating the stiff type of problems such as air dehydration. This demonstrates the potential of the new solution technique to handle different membrane systems conveniently. As an illustration, a multi-stage membrane plant with recycle and purge streams has been designed and simulated for CO2 capture from a 500,MW power plant flue gas as a first step to build hybrid processes and also to make an economic comparison among different existing separation technologies available for CO2 separation from flue gas. [source] Physicochemical Properties of Ionic Clathrate HydratesCHEMISTRY - AN ASIAN JOURNAL, Issue 1 2010Kyuchul Shin Abstract Ionic clathrate hydrates are known to be formed by the enclathration of hydrophobic cations or anions into confined cages and the incorporation of counterions into the water framework. As the ionic clathrate hydrates are considered for their potential applicability in various fields, including those that involve solid electrolytes, gas separation, and gas storage, numerous studies of the ionic clathrate hydrates have been reported. This review concentrates on the physicochemical properties of the ionic clathrate hydrates and the notable characteristics of these materials regarding their potential application are addressed. [source] Separation of light gas mixtures using SAPO-34 membranesAICHE JOURNAL, Issue 4 2000Joseph C. Poshusta Continuous SAPO-34 membranes were prepared on porous alumina tubular supports, and shown to be useful for light gas separations at low and high temperatures. Single-gas permeances of CO2, N2 and CH4 decreased with increasing kinetic diameter. For the best membrane at 300 K, the He and H2 permeances were less than that of CO2, because He, H2, and CO2 were small compared to the SAPO-34 pore, and differences in the heat of adsorption determined the permeance order. The smaller component permeated the fastest in CO2/CH4, CO2/N2, N2/CH4, H2/CH4 and H2/N2 mixtures between 300 and 470 K. For H2/CO2 mixtures, which were separated by competitive adsorption at room temperature, the larger component permeated faster below 400 K. The CO2/CH4 selectivity at room temperature was 36 and decreased with temperature. The H2/CH4 mixture selectivity was 8 and constant with temperature up to 480 K. Calcination, slow temperature cycles, and exposure to water vapor had no permanent effect on membrane performance, but temperature changes of approximately 30 K/min decreased the membrane's effectiveness. [source] Mixed matrix membrane materials with glassy polymers.POLYMER ENGINEERING & SCIENCE, Issue 7 2002Part Mixed matrix materials comprising molecular sieve entities embedded in a polymer matrix can economically increase membrane permselectivity, thereby addressing a key challenge hindering the widespread use of membrane-based gas separations. Prior work has clarified the importance of proper selection of the dispersed sieve phase and the continuous matrix phase based on their intrinsic transport properties. Proper material selection for the two components, while necessary, is not sufficient since the interfacial contact zone appears to be equally important to achieve optimum transport properties. Specifically, it was found that chemical coupling of the sieve to the polymer can lead to better macroscopic adhesion but to even poorer transport properties than in the absence of the adhesion promoter. This counterintuitive behavior may be attributed to a nanometric region of disturbed packing at the polymer sieve interphase. The poor properties are believed to result from "leakage" of gas molecules along this nanometric interface. The Maxwell model was modified to take into account these complexities and to provide a first order quantification of the nanometric interphase. The analysis indicates that optimization of the transport properties of the interfacial region is key to the formation of ideal mixed matrix materials. This approach is used in the second part of this paper to form successful mixed matrix membrane materials. [source] | |||||||||||||