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Abstract
A novel polysulfone/polyethylene oxide/silicone rubber (PSf/PEO/SR) multilayer composite membrane was fabricated by double coating polysulfone substrate membrane with polyethylene oxide and silicone rubber. Gas permeation experiments were performed at 30 °C for hydrogen and nitrogen. PSf/PEO/SR membrane displayed high and steady performance for H2/N2: permeances of H2 and N2 of 49.51 and 0.601 GPU, respectively, and H2/N2 ideal separation factor of 82.3. It was explained that layer interfaces due to the introduction of PEO layer act as the permselective media and are responsible for the higher H2/N2 ideal separation factor which has exceeded the intrinsic permselectivities of the three polymers used in this study.
... Multilayer thin film composite membranes are prepared for use to improve the gas separation efficiency of thin film composite membranes. Generally, the protective layer is coated on the surface of the selective layer to seal the existing defects and to protect the selective layer from abrasion or detrimental chemical attacks (Liang et al., 2018;Ye et al., 2005). The gutter layer is coated on the surface of substrate to improve the adhesion between substrate and selective layer. ...
... The gutter layer is coated on the surface of substrate to improve the adhesion between substrate and selective layer. Moreover, the gutter layer can minimize the mass transport resistance since it is usually made from highly permeable materials (Liang et al., 2018;Ye et al., 2005). ...
... The selectivities of H 2 /N 2 , CO 2 /CH 4 , and O 2 /N 2 were 100, 50, and 7, respectively (Chung et al., 1999). Ye et al. (Ye et al., 2005) prepared polysulfone/polyethylene oxide/silicone rubber (PSf/PEO/SR) multilayer composite membrane by using the dip-coating method. The PEO layer was selective and the SR layer was used as a protective layer. ...
Gas separation is an important separation process to many industries, and membrane separation using hollow fibre membranes (HFMs) has become one of the emerging technologies. In this article, the gas separation concepts, gas transport mechanism, and the fabrication and gas separation performance of HFMs including asymmetric HFMs, thin film composite hollow fibre membranes (TFC-HFMs), and mixed matrix hollow fibre membranes (MM-HFMs), are reviewed and discussed. Dope composition and spinning parameters directly influence the structure of HFMs and subsequently the gas separation performance of HFMs. The gas separation performance of TFC-HFMs can be improved by the design of the coating solution, surface modification, and the addition of both a gutter layer and a protective layer. Mixed matrix membranes (MMMs) have been intensively investigated in flat sheet membranes and the inspiring gas separation results have been obtained. Therefore, the incorporation of nanoparticles into hollow fibre membranes is a desirable solution to increase the gas permeability and selectivity simultaneously. The functionalization of nanoparticles and fabrication methods of MM-HFMs are also presented.
... Multilayer composite membrane has been reported for various applications especially for water filtration [15][16][17][18]. The multilayer composite membrane usually has three layers and can be divided into two types based on the membrane configuration: (selective layer)/(gutter layer)/(support substrate) and (sealing or protective layer)/ (selective layer)/(support substrate) [19][20][21]. In the former, the selective layer might be as thin as a few tens nanometers and slightly defective; the gutter layer is a permeable material which serves as a channelling and adhesive medium between the selective layer and the support substrate. ...
... The dipped membranes were then coated with a mixture of 3 wt.% of silicone (with curing agent) and 97% n-hexane for 30 minutes. This was to ensure that membrane surface has been completely covered by the mixture of silicone and curing agent [19]. The ratio of silicone to curing agent was fixed at 10:1.The silicone coated layer membranes were then cross-linked with each other by keeping the silicone coated membranes in an oven at 60 o C for 1 hour [21]. ...
In this study, silicone rubbers were used to achieve the desire absorbing properties of PANI onto polyvinylidene fluoride (PVDF) microporous support. Poly (methyl-vinyl ether-alt-maleic acid) (PMVEA) polymeric acid was used as acid dopant to enhance the membrane filtration performance. Initially PVDF micro-porous support was dip-coated with silicone rubber elastomer solution followed by deposition with PANI by in-situ chemical oxidative polymerisation techniques using two-compartment cell in presence of PMVEA and ammonium persulfate as the oxidizing agent. The PANI multilayer composite membranes were characterized by gravimetric for PANI content measurement namely Scanning Electron Microscope (SEM), Fourier-Transform Infrared (FTIR), Differential Scanning Calorimetry (DSC) and contact angle. The PANI content was found to be more than 30 %. SEM, FTIR and DSC analysis have confirmed the presence of PANI onto the multilayers membrane while the contact angle of the membrane in presence of high loading PANI was 0 ° indicating the super hydrophilicity than without the PANI presence of 78.8 °. The pressure filtration of PANI multilayer composite filtration membrane with a range of polyethylene glycols at different molecular weights was obtained based on the high flux up to 904.11 L/m2.h and reasonable molecular weight cut off of below 20,000 g/mol were obtained for the synthesized membrane. © 2016, Malaysian Society of Analytical Sciences. All rights reserved.
... High surface tension can cause pores wall collapse when water is removed and create a thick nonselective layer. Flat sheet composite membranes usually simply made by coating the second polymer onto the surface of the substrate polymer [6,7,8] and deposited the polymer for certain time while HF composite membranes made by dip-coating the substrate polymer [9,10,11] or co extrude spinning process [12,13]. ...
The world market for CO 2 /CH 4 separation using membrane technology is getting bigger and polysulfone (PSf) is one of the most widely investigated polymer membrane materials. However, the existing PSf membranes performances are insufficient to fully exploit these opportunities. Therefore, modification that would produce membrane that fit the needs of target separation performances is a main issue. Firstly, various manufacturing processes to achieve best CO 2 /CH 4 separation performance are discussed, including important post-treatments. The formulation of polymer solution and effects of manufacturing parameters on the resulting membranes are presented. Other modifications, which involved PSf structure modification, PSf-based copolymer, mixed matrix membrane and facilitated transport membrane, are also discussed. Performances of those modified membranes are compared with the Robeson's upper bound and some modifications give satisfying results. Finally, commercial application of PSf membranes for CO 2 /CH 4 separation is discussed.
... Hydrogen separation from carbon dioxide or natural gas is one of the most significant applications of membrane technology [1][2][3]. Enriched-hydrogen gas provides a potential opportunity to obtain clean, renewable and storable energy from abundant fossil fuel using steam reforming. In the gas separation processes with a membrane material, the permeability coefficient and separation factor are two major factors in deciding their permeation characteristics. ...
Novel polymer blend membranes of poly(bisphenol A-co-4-nitrophthalic anhydride-co-1,3-phenylenediamine) (PBNPI) and polyphenylsulfone (PPSU) in different weight ratios were prepared by a solution casting technique with N-methyl-2-pyrrolidone (NMP) as solvent. The effects of blend polymer composition on the membrane structure and the H2, CO2 and CH4 separation performance were investigated. The membranes appear macroscopically miscible but microscopically immiscible based on thin-film X-ray diffraction investigations. A remarkably and continuously enhanced permeability has been achieved for these gases with increasing PPSU content from 0 to 50%. The highest pure H2, CO2 and CH4 permeability are, respectively, equal to 40.4, 34.1 and 8.0barrer.
... Several studies focusing on single polymeric membranes, membrane blends, [5][6][7][8][9] or modification with a crosslinking agent 10,11 have been applied to the separation of gases with similar kinetic diameters to enhance their permeability and selectivity. Among these, crosslinking has been widely used to restrict the mobility of polymer chains by covalent bond formation. ...
A series of blend membranes of poly(phenyl sulfone) (PPSU) with poly(bisphenol A-co-4-nitrophthalic anhydride-co-1,3-phenylenediamine) (PBNPI) were prepared through a solution casting method. This was done to examine the permeation characteristics of oxygen and nitrogen. The effect of the PPSU/PBNPI ratio on the membrane structure and O2/N2 separation performance were investigated. The results show that the permeability increased remarkably with the content of PPSU, whereas the selectivity decreased slightly. To enhance the selectivity of O2/N2, the blend membranes were further crosslinked with a p-xylylenediamine agent via the immersion method. According to the Fourier transform infrared analysis, the NH group was formed on the imide group of PBNPI. Therefore, we suggest that during the crosslinking modification, the PBNPI served as a crosslinkable polymer; this resulted in increased crosslinking efficiency with PBNPI content. The high-resolution X-ray diffraction and melting point method results show that crosslinking modification improved the selectivity with an acceptable loss in permeability along with increased crystallinity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
In this study, fumed silica nanoparticles were functionalized using amine groups and used as inorganic modifiers for preparation of poly (ether-block-amide) based nanocomposite membranes. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and CHNO elemental analysis were used to characterize nanoparticles and nanocomposite membranes. The prepared membranes were applied for separation of carbon dioxide (CO2) from methane (CH4). The effects of nanoparticles loading, feed pressure and feed temperature on permeability and CO2/CH4 ideal selectivity of the nanocomposite membranes were investigated. The results indicated that addition of 15 wt % of amine-functionalized fumed silica nanoparticles in the casting solution enhances the membrane CO2 permeability and CO2/CH4 ideal selectivity 10% and 14%, respectively.
UniSim Design software was used to simulate the H2 recovery process from purge gas of gas-to-liquid plant. In different processes with different membrane modules namely polyimide (PI) with one-stage recovery process and polysulfone (PSf) with one-stage and two-stage recovery processes, effect of permeation pressure on mole fraction of H2 product, H2 recovery rate and economic benefit were discussed. The simulation results showed that in conditions of purge gas pressure (G) 3.0 MPa, temperature 45°C and feed flow rate 1.33 × 105 m3/h, choosing PI membrane module with one-stage recovery process can obtain higher economic benefit than choosing PSf membrane module when mole fraction of H2 product is not more than 94.0%. When mole fraction of H2 product is in the range of 90.0%-94.0%, economic benefit is the highest if permeation pressure is maintained in the range of 100-150 kPa (G).
Production of pure molecular hydrogen is essential to the realization of the proposed “hydrogen economy” that could ultimately provide hydrogen as a clean, renewable source of energy; eliminate the industrialized world's dependence on petroleum; and reduce the generation of greenhouse gases linked to global warming. A crucial step in obtaining pure hydrogen is separating it from other gaseous compounds—mainly CO 2 —that often accompany hydrogen in industrial chemical reactions. Advanced membrane technology may prove to be the key to the successful, economical production of molecular hydrogen.
Size-sieving glassy polymer membranes can separate H 2 on the basis of its small size. Alternatively, reverse-selective rubbery polymers can expedite the passage and, hence, removal of CO 2 due to its relatively high solubility in such membranes alone or in conjunction with dissociative chemical reactions. Transition-metal membranes and their alloys can adsorb H 2 molecules, dissociate the molecules into H atoms for transport through interstitial sites, and subsequently recombine the H atoms to form molecular H 2 again on the opposite membrane side. Microporous amorphous silica and zeolite membranes comprising thin films on a multilayer porous support exhibit good sorption selectivity and high diffusion mobilities for H 2 , leading to high H 2 fluxes. Finally, carbon-based membranes, including carbon nanotubes, may be viable for H 2 separation on the basis of selective surface flow and molecular sieving. A wide variety of materials challenges exist in hydrogen purification, and the objective of this issue of MRS Bulletin is to address those challenges and their potential solutions from basic principles.
Hydrogen separation on microporous methyltriethoxysilane-templating silica composite/α-alumina membranes (below MTES membrane) was studied using three binary gas mixtures: H2/N2, H2/CO2, and H2/CH4. The characteristics of unsteady and steady-state permeation/separation on the MTES membrane were compared to each other. Although permeation flux in the H2/N2 mixture was comparatively low, H2 selectivity was high (H2/N2 SF ≈ 30–60). On the contrary, the H2/CO2 mixture showed high permeation flux but low H2 selectivity (H2/CO2 SF ≈ 1.5–6.5). The H2/CH4 mixture showed a large difference between permselectivity (28–48) and separation factor (10–22). Results from this study revealed that it was difficult to predict the separation factor using the one-component permeation ratio (permselectivity) over the experimental range tested. These separation characteristics could be primarily ascribed to the molecular size and structure of each gas, which likely contributed to steric hindrance or molecular sieving within the membrane pore. In addition, the adsorption affinity of each molecule on the membrane surface acted as a key factor in separation performance because it significantly influenced surface diffusion. The generalized Maxwell-Stefan model incorporating the dust gas model, and the Langmuir model could successfully predict the transient and steady-state permeation/separation. © 2007 American Institute of Chemical Engineers AIChE J, 2007
A method has been developed by which a porous hollow fiber which cannot separate gases to a significant extent can be made to exhibit its intrinsic separation properties by coating with an appropriate material. A unique feature of this composited fiber is that the separation properties are determined by the porous support polymer rather than by the coating polymer. The hollow fibers produced by this method have extraordinarily high rates compared to earlier hollow fibers used for gas separations. In addition, they can function under extremely high pressure gradients. Gases such as He, H2, and CO2 can be separated from gases like CH4, CO, and N2, and the system is chemically and physically stable to a wide range of typical industrial contaminants. As a result, systems based on these fibers should be useful in a variety of processes, some of which include stream splitting, gas composition control, H2 upgrading, and purge gas recovery.
Cellulose nitrate (CN)-based composite hollow fiber membranes are prepared for gas separation. The membrane performance is studied in terms of the concentration of CN coating solution, polysulfone (PS) substrate, pre-wetting treatment, solvent used in CN solution, and the various substrate materials. In order to fabricate a useful multilayer composite membrane, the surface porosity of composite hollow fiber has to be reduced to a certain degree, before silicone rubber coating, by adjusting the CN coated layer and the PS substrate structure. The effect of pre-wetting treatment on the membrane performance is found to be minor, which may be due to the coating technique and the relatively highly permeable substrate used in this study. The solvent used in dissolving CN also affects the gas permselective property of the multilayer composite membranes and this effect may be attributed to the formation of different membrane morphology of CN layer caused by the different physical properties of solvents. The selection of substrate materials is important and this work suggests that a permeable material is more suitable to serve as the substrate. Besides, the substructure resistance in the substrate should be kept as low as possible in order not to deteriorate membrane performance of the resultant multilayer composite hollow fiber membranes.
An improved resistance model based on Henis-Tripodi's model for gas permeation in composite membranes has been established, in which the degree of penetration of the coating material into the defects or pores of the effective dense layer has been taken into account. The influences of the degree of penetration, the thickness of the coating layer and surface porosity of the dense layer on gas permeation resistance throughout the composite membrane and separation factor of the composite membrane have been calculated and analysed. Some experimental results have also been explained with this model. The model together with its corresponding coating method is useful for the improvement of membrane separation properties.
The kinetics of the aggregation of high molecular weight polyethylene oxide (PEO) at temperatures above the PEO–water cloud point temperature (CPT) was studied by monitoring the particle size profile with time using photometric dispersion analysis and light diffraction. Upon PEO–water phase separation, hydrophobic inter/intra molecular PEO–PEO interactions cause the random PEO coils to collapse to a compact configuration and aggregate with each other. The rate of aggregation was found to increase with increasing temperature deviation from the CPT, PEO concentration and molecular weight. Higher temperature and lower shear gave rise to larger equilibrium PEO aggregates. These aggregates can reach a size of 600 μm in diameter. Aggregation was also found to proceed until the aggregation rate is balanced out by the breakup rate. It was observed that the aggregation process could be reversed repeatedly by shifting across the phase boundary. It is suggested that the main mechanism for the breakup of the aggregates is surface erosion, which is caused by the shearing action of the water surrounding the aggregates.
A new resistance model for the transport of gases through composite membranes is proposed in this work. The new model is an analog of the Wheatstone bridge for an electric circuit. The resistance model proposed by Henis and Tripodi is considered as a special case of the new model, where the resistance of the cross flow between two vertical parallel flows is set equal to zero. The experimental data for the laminated polydimethylsiloxane (silicone rubber)/polyethersulfone membranes, however, have shown that the high permeation rate ration of hydrogen and nitrogen can not be explain by the Henis and Tripodi model. The parallel flow model, where the resistance of the cross flow is equal to infinity, explains the experimental data.
The effect of pressure on the solubility, diffusivity, and permeability of He, H2, O2, N2, CO2, CH4, C2H4, C2H6, C3H6 and C3H8 in poly(ethylene oxide) (PEO) is reported at 35 °C. Additionally, the temperature dependence of permeability is reported. The effect of polar ether linkages in PEO on gas transport is illustrated by comparing transport properties in PEO with those in polyethylene (PE). For example, at 35 °C and infinite dilution, semi-crystalline PEO exhibits CO2 permeability coefficient of 12 Barrers, and CO2/H2 and CO2/N2 pure gas selectivities of 6.7 and 48, respectively. In contrast, at similar conditions, the permeability of PE to CO2 is 13 Barrers, but the CO2/N2 selectivity is only 13. In addition to good separation properties for quadrupolar–nonpolar gas pairs, PEO also shows interestingly high selectivity for olefins over paraffins, which is ascribed to favorable interaction between the polar ether groups in PEO and olefins. For example, the infinite dilution permeability of PEO to propylene is 3.8 Barrers and pure gas propylene–propane selectivity is 2.7 at 35 °C. At similar conditions, PE exhibits propylene–propane selectivity of only 1.4.
Using multilayer composite hollow fiber membranes consisting of a sealing layer (silicone rubber), a selective layer (poly(4-vinylpyridine)), and a support substrate (polysulfone), we have determined the key parameters for fabricating high-performance multilayer hollow fiber composite membranes for gas separation. Surface roughness and surface porosity of the support substrate play two crucial roles in successful membrane fabrication. Substrates with smooth surfaces tend to reduce defects in the selective layer to yield composite membranes of better separation performance. Substrates with a high surface porosity can enhance the permeance of composite membranes. However, SEM micrographs show that, when preparing an asymmetric microporous membrane substrate using a phase-inversion process, the higher the surface porosity, the greater the surface roughness. How to optimize and compromise the effect of both factors with respect to permselectivity is a critical issue for the selection of support substrates to fabricate high-performance multilayer composite membranes. For a highly permeable support substrate, pre-wetting shows no significant improvement in membrane performance. Composite hollow fiber membranes made from a composition of silicone rubber/0.1–0.5 wt% poly(4-vinylpyridine)/25 wt% polysulfone show impressive separation performance. Gas permeances of around 100 GPU for H2, 40 GPU for CO2, and 8 GPU for O2 with selectivities of around 100 for H2/N2, 50 for CO2/CH4, and 7 for O2/N2 were obtained.
An exhaustive treatment of the past decade of intense activity in the membrane-based gas separation field would require an entire book and provide more detail than necessary to capture the essence of this dynamic field. This review seeks to define the current scientific, technological and commercial boundaries of the field of membrane-based gas separation and to project the position of these boundaries for the immediate future. The most understandable connection between these three areas lies in the material science and engineering achievements and limitations that dominate the application of the technology at the present time. Achievements over the past ten to fifteen have promoted the current strong interest in membrane-based gas separations, and the promise of steady progress toward removing remaining limitations suggests the likelihood of its long term growth as a field. Material selection, membrane formation, and trends in module and system characteristics are discussed in the context of the challenges and opportunities that exist for major commercial applications of the technology.
A simple mathematical model for facilitated mass transport with a fixed site carrier membrane was derived by assuming an instantaneous, microscopic concentration (activity) fluctuation in the membrane. The concentration fluctuation, developed due to the reversible chemical reaction between carrier and solute, could cause the higher chemical potential gradient and the facilitated transport. For mathematical formulation, the fluctuated concentration profile was assumed to be a sinusoidal, which is analogous to an alternating voltage in electric circuit. An analogy was employed between the mass transfer for the facilitated transport with fixed site carrier membrane and the electron transfer in a single parallel resistor-capacitor (RC) circuit. The current model showed that the facilitation factor, F, increased linearly with the extent of the pressure fluctuation, , the ratio of the time scales of diffusion to chemical reaction, , and the ratio of the total carrier concentration to the solute solubility in matrix, . F also increased logarithmically with one plus the combined driving force for facilitation, Δ (=Kp0), i.e. (1+Δ). The model was examined against experimental data on oxygen transport in poly(dimethyl siloxane), poly(butyl methacrylate) and poly(methyl methacrylate) with metallo-porphyrin carrier and the agreement was exceptional.
A model is developed to explain the behavior of composite gas separation membranes which consist of a porous asymmetric substrate of one polymer, and a coating of a second polymer. An analogy between gas permeation and electrical flow is made, and the various portions of the composite membrane are described in terms of their resistance to gas permeation. It is shown that substrate porosity can vary significantly without altering the separating properties of such a composite, and that substrate and coating properties can be matched to optimize the flux and separation factor. Several major problems previously associated with the development of useful hollow fibers for gas separation are discussed, and it is shown that the use of Resistance Model composites can help to resolve these problems.
The background of and commercial needs leading to the development of practical membrane systems for the separation of industrial gases are presented. The critical issues and fundamental technical limitations that delayed earlier development of such systems and the solutions of some of the major problems in the field are discussed. Particular attention is given to the methods by which high gas fluxes and high selectivities have been achieved in hollow fibers. The performance characteristics of various practical gas separation methods are compared, and the effects of parameters such as pressure and contaminant levels are illustrated with representative examples.
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