Transport properties of gases through integrally skinned asymmetric composite membranes prepared from date pit powder and polysulfone

Studies were conducted on transport properties and separation performance of date pit/polysulfone composite membranes for CO₂, CH₄, N₂, He, and H₂ gases. Date seeds were obtained and processed into powder. Asymmetric flat sheet membrane was prepared by solvent casting method with 2–10 wt % date pit powder. Membrane characterization was done using high pressure gas permeation, X‐ray diffraction, thermogravimetric, and scanning electron microscope analyses. The separation performance and the plasticization resistance property were evaluated in terms of gas permeability, selectivity, and plasticization pressure, respectively. Time dependent performance properties were evaluated up to a pressure of 40 bar for 75 days. Results obtained showed the highest selectivity values of 1.54 (He/H₂), 3.637 (He/N₂), 2.538 (He/CO₂), 2.779 (He/CH₄), 3.179 (H₂/N₂), 3.907 (H₂/CO₂), 1.519 (CH₄/N₂), 1.650 (CO₂/N₂), and 1.261 (CO₂/CH₄) at 10 bar and 35 °C feed pressure and temperature, respectively. The resulting composite membrane showed about 39.50 and 66.94% increase in the selectivity of He/N₂ and CO₂/CH₄, respectively, as compared to the pure polysulfone membrane. Thus, the membrane composites possess some potentials in membrane gas separation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43606.     

Enhanced gas separation properties by using nanostructured PES‐Zeolite 4A mixed matrix membranes

The polymer–zeolite mixed matrix membranes were fabricated by incorporating nanosized or microsized zeolite 4A into polyethersulfone. A comparison of zeolite 4A nanocrystals and microcrystals was made by using SEM, XRD, N₂ adsorption–desorption measurements. Zeolite particles were well‐distributed in the polymer phase, as reflected by the SEM images. The effects of the zeolite 4A particle size on the gas permeation performance were studied. Experimental results demonstrate that mixed matrix membranes exhibit decreased gas permeabilities due to the barrier effect of zeolite particles. The obtained permselectivity is greatly enhanced for He/N₂, H₂/N₂, He/CO₂, and H₂/CO₂ gas pairs, especially for nanosized zeolite 4A mixed matrix membranes. The gas permeation performance difference is observed between the nanostructured and microstructured membranes, which is attributed to a combined effect of different zeolite composition and different particle size. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3800–3805, 2006     

Mixed matrix membranes based on 6FDA polyimide with silica and zeolite microsphere dispersed phases

Mixed matrix membranes (MMMs) prepared with 6FDA‐DAM polymer using ordered mesoporous silica MCM‐41 spheres (MSSs), Grignard surface functionalized MSSs (Mg‐MSSs) and hollow zeolite spheres are studied to evaluate the effects of surface modification on performance. Performance near or above the so‐called permeability‐selectivity trade‐off curve was achieved for the H₂/CH₄, CO₂/N₂, CO₂/CH_4, and O₂/N₂ systems. Two loadings (8 wt % and 16 wt %) of MSSs were tested using both constant volume and Wicke–Kallenbach sweep gas permeation systems. Besides single gas H₂, CO₂, O₂, N₂, and CH₄ tests, mixed gas (50/50 vol %) selectivities were obtained for H₂/CH₄, CO₂/N₂, CO₂/CH₄, and O₂/N₂ and found to show enhancements vs. single gases for CO₂ including cases. Mg‐MSS/6FDA‐DAM was the best performing MMM with H₂/CH₄, CO₂/N₂, CO₂/CH₄, and O₂/N₂ separation selectivities of 21.8 (794 Barrer of H₂), 24.4 (1214 Barrer of CO₂), 31.5 (1245 Barrer of CO₂), and 4.3 (178 Barrer of O₂), respectively. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4481–4490, 2015     

Gas permeation performance of cellulose hollow fiber membranes made from the cellulose/N‐methylmorpholine‐N‐oxide/H2O system

Cellulose hollow fiber membranes (CHFM) were prepared using a spinning solution containing N‐methylmorpholine‐N‐oxide as solvent and water as a nonsolvent additive. Water was also used as both the internal and external coagulant. It was demonstrated that the phase separation mechanism of this system was delayed demixing. The CHFM was revealed to be homogeneously dense structure after desiccation. The gas permeation properties of CO₂, N₂, CH₄, and H₂ through CHFM were investigated as a function of membrane water content and operation pressure. The water content of CHFM had crucial influence on gas permeation performance, and the permeation rates of all gases increased sharply with the increase of membrane water content. The permeation rate of CO₂ increased with the increase of operation pressure, which has no significant effect on N₂, H₂, and CH₄. At the end of this article a detailed comparison of gas permeation performance and mechanism between the CHFM and cellulose acetate flat membrane was given. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1873–1880, 2004     

Impact of H+ ion beam irradiation on Matrimid®. II. Evolution in gas transport properties

Ion beam irradiation is an easily controlled method to modify the chemical structure and microstructure of polymers including the fractional free volume, free volume distribution and chain mobility, thus altering the gas transport properties of the irradiated polymers. The previous paper focused on the impact of H⁺ ion beam irradiation on chemical structural evolution of the polyimide Matrimid®. This paper focuses on the impact of H⁺ ion beam irradiation on microstructure and gas permeation properties of Matrimid®. Irradiation at low ion fluence resulted in slight decreases in permeabilities for five gases (i.e., He, CO₂, O₂, N₂, and CH₄) with increases in permselectivities for some gas pairs (e.g., He/CH₄ and He/N₂). In contrast, irradiation at relatively high ion fluences resulted in simultaneous increases in permeabilities and permselectivities for most gas pairs (e.g., He/CH₄, He/N₂, O₂/N₂, and CO₂/CH₄). While Matrimid® has bulk gas permeation properties that are below the range of commercially interesting polymers, samples irradiated at high ion fluences exhibited significant improvement in gas separation performances. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1670–1680, 2007     

Enhancing the CO2 Separation Performance of Matrimid 5218 Membranes for CO2/CH4 Binary Mixtures

The effect of CO₂‐philic additive polyethylene glycol (PEG) 200 in Matrimid 5218 on the separation performance of prepared membranes was evaluated in a binary gas mixture. Matrimid/PEG 200 flat‐sheet blended membranes with low PEG concentrations were prepared by the dense film‐casting method. Pure Matrimid and blended membranes were characterized by FTIR spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and permeation measurements. The addition of 4–5 % of PEG enhanced considerably the CO₂ permeability of the Matrimid matrix. The best formulation, Matrimid/PEG 200 (96/4), showed in comparison to pure Matrimid a more than threefold increase in CO₂ permeability and an increase in separation factor of about 40 %.     

A high CO2 permselective mesoporous silica/carbon composite membrane for CO2 separation

Ordered mesoporous silica/carbon composite membranes with a high CO₂ permeability and selectivity were designed and prepared by incorporating SBA-15 or MCM-48 particles into polymeric precursors followed by heat treatment. The as-made composite membranes were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and N₂ adsorption, of which the gas separation performance in terms of gas permeability and selectivity were evaluated using the single gas (CO₂, N₂, CH₄) and gas mixtures (CO₂/N₂ and CO₂/CH₄, 50/50 mol.%). In comparison to the pure carbon membranes and microporous zeolite/C composite membranes, the as-made mesoporous silica/C composite membranes, and the MCM-48/C composite membrane in particular, exhibit an outstanding CO₂ gas permeability and selectivity for the separation of CO₂/CH₄ and CO₂/N₂ gas pairs owing to the smaller gas diffusive resistance through the membrane and additional gas permeation channels created by the incorporation of mesoporous silicas in carbon membrane matrix. The channel shape and dimension of mesoporous silicas are key parameters for governing the gas permeability of the as-made composite membranes. The gas separation mechanism and the functions of porous materials incorporated inside the composite membranes are addressed.     

Fabrication and characterization of PEI/PVP‐based carbon hollow fiber membranes for CO2/CH4 and CO2/N2 separation

Carbon hollow fiber membranes derived from polymer blend of polyetherimide and polyvinylpyrrolidone (PVP) were extensively prepared through stabilization under air atmosphere followed by carbonization under N₂ atmosphere. The effects of the PVP compositions on the thermal behavior, structure, and gas permeation properties were investigated thoroughly by means of differential scanning calorimetry, thermogravimetric analysis, X‐ray diffraction, and pure gas permeation apparatus. The experimental results indicate that the transport mechanism of small gas molecules of N₂, CO₂, and CH₄ is dominated by the molecular sieving effect. The gas permeation properties of the prepared carbon membranes have a strong dependency on PVP composition. The carbon membranes prepared from polymer blends with 6 wt % PVP demonstrated the highest CO₂/CH₄ and CO₂/N₂ selectivities of 55.33 and 41.50, respectively. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3167–3175, 2012     

Dual-layer hollow carbon fiber membranes for gas separation consisting of carbon and mixed matrix layers

Hollow carbon fiber membranes for gas separation have been successfully fabricated for the first time by a special type of precursor. This precursor is dual-layer hollow fiber composed of a polysulfone-beta zeolite (PSF-beta) mixed matrix outer layer and a Matrimid inner layer. Pure gas permeation measurements show that the resultant hollow carbon fiber has O₂/N₂ and CO₂/CH₄ selectivities of 9.3 and 150, respectively; this performance is much better than that of the hollow carbon fiber derived from single-layer Matrimid hollow fiber. Mixed gas measurements show the CO₂/CH₄ selectivity of 128. After pyrolysis, the PSF-beta layer in the dual-layer precursor evolves into a continuous structure of closely packed zeolite particles embedded in the PSF carbon residue. TGA spectra suggest that the possible reason for the above observation is that the PSF-beta outer layer and Matrimid inner layer has significantly changed each other’s pyrolysis dynamics and thermal degradation process.     

Untersuchungen zum Hochdruck‐Permeationsverhalten reiner Gase durch mikroporöse keramische Membranen Teil 1. Messmethode und Einfluss der Adsorption auf den Permeatfluss

The permeation behaviour of single gases (He, H₂, N₂, Ar, CH₄, CO₂) through meso (ZrO₂) and micro (TiO₂) porous ceramic membranes was measured within a pressure range of 1 to 10 MPa and a temperature range of 293 to 373 K, using steady state and dynamic experimental methods. The TiO₂‐membrane shows by adsorption affected permeation, whereas the ZrO₂‐membrane is not influenced by these effects.     

CO2‐facilitated transport through poly(N‐vinyl‐γ‐sodium aminobutyrate‐co‐sodium acrylate)/polysulfone composite membranes

Poly(N‐vinyl‐γ‐sodium aminobutyrate‐co‐sodium acrylate) (VSA–SA)/polysulfone (PS) composite membranes were prepared for the separation of CO₂. VSA–SA contained secondary amines and carboxylate ions that could act as carriers for CO₂. At 20°C and 1.06 atm of feed pressure, a VSA–SA/PS composite membrane displayed a pure CO₂ permeation rate of 6.12 × 10^?6 cm³(STP)/cm² s cmHg and a CO₂/CH₄ ideal selectivity of 524.5. In experiments with a mixed gas of 50 vol % CO₂ and 50 vol % CH₄, at 20°C and 1.04 atm of feed pressure, the CO₂ permeation rate was 9.2 × 10^?6 cm³ (STP)/cm² s cmHg, and the selectivity of CO₂/CH₄ was 46.8. Crosslinkages with metal ions were effective for increasing the selectivity. Both the selectivity of CO₂ over CH₄ and the CO₂ permeation rate had a maximum against the carrier concentration. The high CO₂ permeation rate originated from the facilitated transport mechanism, which was confirmed by Fourier transform infrared with attenuated total reflectance techniques. The performance of the membranes prepared in this work had good stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 275–282, 2006     

Carbon dioxide separation and dry reforming of methane for synthesis of syngas by a dual‐phase membrane reactor

High‐temperature CO₂ selective membranes offer potential for use to separate flue gas and produce a warm, pure CO₂ stream as a chemical feedstock. The coupling of separation of CO₂ by a ceramic–carbonate dual‐phase membrane with dry reforming of CH₄ to produce syngas is reported. CO₂ permeation and the dry reforming reaction performance of the membrane reactor were experimentally studied with a CO₂–N₂ mixture as the feed and CH₄ as the sweep gas passing through either an empty permeation chamber or one that was packed with a solid catalyst. CO₂ permeation flux through the membrane matches the rate of dry reforming of methane using a 10% Ni/γ‐alumina catalyst at temperatures above 750°C. At 850°C under the reaction conditions, the membrane reactor gives a CO₂ permeation flux of 0.17 mL min^?1 cm^?2, hydrogen production rate of 0.3 mL min^?1 cm^?2 with a H₂ to CO formation ratio of about 1, and conversion of CO₂ and CH₄, respectively, of 88.5 and 8.1%. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2207–2218, 2013     

The permeation resistance of interface and the directional dependence of permeation in plasma-grafted composite membranes

Composite membranes were prepared by grafting plasma-polymerized films onto the surface of nonporous poly (dimethylsiloxane) films. Gas permeabilities of the composite membranes were measured at 35°C, 1 atm for N₂, 0₂, CO₂ and CH₄. The permeation properties of the composite membrane was analyzed using the series resistance model. There was a great interfacial resistance to CH₄ permeation through the composite membrane. The interfacial resistance was negligible for the other gases. The interfacial resistance seems to be a result of an interfacial layer caused by the interaction between the bulk two layers. For CH₄ gas, the permeation rate through the composite membrane was affected by the direction of flow. The directional dependence was negligible for the other gases.     

Preparation of C/CMS composite membranes derived from Poly(furfuryl alcohol) polymerized by iodine catalyst

C/CMS composite membranes derived from poly(furfuryl alcohol) (PFA) polymerized by iodine catalyst were prepared. Gas separation performance was investigated by molecular probe study with pure gases (H₂, CO₂, O₂, N₂, and CH₄) at 25 °C. The pyrolysis behaviour of PFA was studied by TG and DTG. The surface morphology of C/CMS composite membranes was observed by SEM and HRTEM. The results show a C/CMS composite membrane with uniform and defect-free thin top layer can be prepared by the PFA liquid in only one coating step. The C/CMS composite membranes have excellent gas separation properties for the gas pairs such as H₂/N₂, CO₂/N₂, O₂/N₂ and CO₂/CH₄, the permselectivities for above gas pairs in same sequence were 124.72, 12.74, 9.12 and 15.91 respectively. Compared to carbon membranes derived from PFA polymerized by acid catalyst, the carbon membranes obtained from PFA polymerized by iodine catalyst have slightly lower permselectivity, but higher permeance.     

A study of gas transport through interfacially formed poly(N,N-dimethylaminoethyl methacrylate) membranes

Gas transport through interfacially formed poly(N,N-dimethylaminoethyl methacrylate) membranes was investigated. The membrane performance for the separation of binary CO₂/N₂, CO₂/CH₄ and CO₂/H₂ mixtures was studied, and the coupling effects between the permeating species were evaluated by comparing the permeance of individual components in the mixture with their pure gas permeance. For the permeation of these binary gas mixtures, the presence of CO₂ was shown to influence the permeation of the other components (i.e., N₂, H₂ and CH₄), whereas the permeation of CO₂ was not affected by these components. In consideration that water vapor is often encountered in applications involving CO₂ separation, the presence of water vapor on the membrane permselectivity was also studied. When hydrated, the membrane was shown to be more permeable to CO₂, while the membrane selectivity did not change significantly. Unlike membranes based on size-sieving of penetrant molecules, the present membranes exploit the favorable interactions between the hydrophilic quaternary amines in the membrane and CO₂, especially in the presence of water vapor in the feed.     

Preparation of polyvinylamine/polysulfone composite hollow‐fiber membranes and their CO2/CH4 separation performance

Fixed‐carrier composite hollow‐fiber membranes were prepared with polyvinylamine (PVAm) as the selective layer and a polysulfone ultrafiltration membrane as the substrate. The effects of the PVAm concentration in the coating solution, the number of coatings, and the crosslinking of glutaraldehyde and sulfuric acid on the CO₂ permeation rate and CO₂/CH₄ selectivity of the composite membranes were investigated. As the PVAm concentration and the number of coatings increased, the CO₂/CH₄ selectivity increased, but the CO₂ permeation rate decreased. The membranes crosslinked by glutaraldehyde or sulfuric acid possessed higher CO₂/CH₄ selectivities but lower CO₂ permeation rates. For the pure feed gas, a composite hollow‐fiber membrane coated with a 2 wt % PVAm solution two times and then crosslinked with glutaraldehyde and an acid solution in sequence had a CO₂ permeation rate of 3.99 × 10^?6 cm³ cm^?2 s^?1 cmHg^?1 and an ideal CO₂/CH₄ selectivity of 206 at a feed gas pressure of 96 cmHg and 298 K. The effect of time on the performance of the membranes was also investigated. The performance stability of the membranes was good during 6 days of testing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1885–1891, 2006     

Matrimid‐based carbon tubular membranes: The effect of the polymer composition

In this article, we present a development study of new membrane materials and enhancements of productive membranes to improve the current performance of polymeric membranes. Carbon membranes are a promising material for this matter as they offer an improvement in the gas‐separation performance and exhibit a good combination of permeability and selectivity. Carbon membranes produced from the carbonization of polymeric materials have been reported to be effective for gas separation because of their ability to separate gases with almost similar molecular sizes. In this study, a carbon support membrane was prepared with Matrimid 5218 as a polymeric precursor. The polymer solution was coated on the surface of a tubular support with the dip‐coating method. The polymer tubular membrane was then carbonized under a nitrogen atmosphere with different polymer compositions of 5–18 wt %. The carbonization process was performed at 850°C at a heating rate of 2°C/min. Matrimid‐based carbon tubular membranes were fabricated and characterized in terms of their structural morphology, thermal stability, and gas‐permeation properties with scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and a pure‐gas‐permeation system, respectively. Pure‐gas‐permeation tests were performed with the pure gases carbon dioxide (CO₂) and N₂ at room temperature at a pressure of 8 bar. On the basis of the results, the highest CO₂/N₂ selectivity of 75.73 was obtained for the carbon membrane prepared with a 15 wt % polymer composition. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42394.     

Preparation,characterization, and applicability of novel calix[4]arene‐based cellulose acetate membranes in gas permeation

Cellulose acetate (CA) is well known glassy polymer used in the fabrication of gas‐separation membranes. In this study, 5,11,17,23‐tetrakis(N‐morpholinomethyl)‐25,26,27,28‐tetrahydroxycalix[4]arene (CL) was blended with CA to study the gas‐permeation behavior for CO₂, N₂, and CH₄ gases. We prepared the pure CA and CA/CL blended membranes by following a diffusion‐induced phase‐separation method. Three different concentrations of CL (3, 10, and 30 wt %) were selected for membrane preparation. The CA/CL blended membranes were then characterized via Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X‐ray diffraction analysis. The homogeneous blending of CL and CA was confirmed in the CA/CL blended membranes by both SEM and AFM analysis. In addition to this, the surface roughness of the CA/CL blended membranes also increased with increasing CL concentration. FTIR analysis described the structural modification in the CA polymer after it was blended with CL too. Furthermore, CL improved the tensile strength of the CA membrane appreciably from 0.160 to 1.28 MPa, but this trend was not linear with the increase in the CL concentration. CO₂, CH₄, and N₂ gases were used for gas‐permeation experiments at 4 bars. With the permeation experiments, we concluded that permeability of N₂ was higher in comparison to those of CO₂ and CH₄ through the CA/CL blended membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39985.     

Effect of graphene oxide on the behavior of poly(amide‐6‐b‐ethylene oxide)/graphene oxide mixed‐matrix membranes in the permeation process

Polyether‐block‐amide (Pebax)/graphene oxide (GO) mixed‐matrix membranes (MMMs) were prepared with a solution casting method, and their gas‐separation performance and mechanical properties were investigated. Compared with the pristine Pebax membrane, the crystallinity of the Pebax/GO MMMs showed a little increase. The incorporation of GO induced an increase in the elastic modulus, whereas the strain at break and tensile strength decreased. The apparent activation energies (E_p) of CO₂, N₂, H₂, and CH₄ permeation through the Pebax/GO MMMs increased because of the greater difficulty of polymer chain rotation. The E_p value of CO₂ changed from 16.5 kJ/mol of the pristine Pebax to 23.7 kJ/mol of the Pebax/GO MMMs with 3.85 vol % GO. Because of the impermeable nature of GO, the gas permeabilities of the Pebax/GO MMMs decreased remarkably with increasing GO content, in particular for the larger gases. The CO₂ permeability of the Pebax/GO MMMs with 3.85 vol % GO decreased by about 70% of that of the pristine Pebax membrane. Rather than the Maxwell model, the permeation properties of the Pebax/GO MMMs could be described successfully with the Lape model, which considered the influence of the geometrical shape and arrangement pattern of GO on the gas transport. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42624.     

Effect of air gap on gas permeance/selectivity performance of BTDA‐TDI/MDI copolyimide hollow fiber membranes

Fabrication, morphology evaluation , and permeance/selectivity properties of three asymmetric BTDA‐TDI/MDI copolyimide hollow fiber membranes (HFM s ) are reported. The asymmetric HFM s were spun using the dry/wet phase inversion process. The effect of one of the major spinning parameters, the air gap, on the permeance/selectivity properties of the produced HFM was investigated. Scanning e lectron m icroscopy was used to evaluate the morphological characteristics and the macroscopic structure of the developed HFM. The permeance values of He, H₂, CH₄, CO₂, O₂, and N₂ gases were measured by the variable pressure method at different feed pressures and temperatures and the permselectivity coefficients were calculated. The higher selectivity values were evaluated for the Μ1 membrane and were found to be 49.33, 2.99, 5.13, 5.57 , and 9.61 for H₂/CH₄, O₂/N₂, CO₂/CH₄, CO₂/N₂ , and H₂/CO₂ gas mixtures , respectively. The selectivity experiments of H₂/CH₄, CO₂/CH₄ , and O₂/N₂ mixtures were performed at 25 ° C. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4490–4499, 2013