Enhanced CO2 selectivity of polyimide membranes through dispersion of polyethyleneimine decorated UiO-66 particles

Branched polyethyleneimine (PEI) functionalized UiO-66 were synthesized and used as fillers to fabricated mixed-matrix membranes (MMMs) for CO₂/CH₄ separation. The purpose of introducing amino-functional groups in the filler is to improve the interfacial compatibility of the filler with the polymer through the formation of hydrogen bonds with the carbonyl group of 6FDA-ODA. Additionally, the amino group can facilitate CO₂ transport through a reversible reaction, enhancing the CO₂/CH₄ separation properties of MMM. The chemical structure and morphology of fillers and membranes were characterized by employing X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), thermogravimetric (TGA), Derivative thermogravimetry (DTG) and scanning electron microscope (SEM). Furthermore, the effects of filler loading and feed pressure on CO₂ permeability and CO₂/CH₄ selectivity have been investigated. MMMs present higher gas separation performance than pure 6FDA-ODA due to the presence of amino groups and the improvement of interface morphology. In particular, the MMM with 15 wt% loading of UiO-66-PEI shows optimum CO₂ permeability of 28.23 Barrer and CO₂/CH₄ selectivity of 56.49. Therefore, post-synthetic modification of UiO-66 particle with PEI is a promising alternative to improved membrane performance.     

Mixed matrix membranes of Pebax1657 loaded with iron benzene‐1,3,5‐tricarboxylate for gas separation

Mixed matrix membranes offer major advantages in gas separation processes due to desirable properties found in both organic and inorganic membranes. In this study, a novel mixed matrix membrane was prepared for such application by incorporating iron benzene‐1,3,5‐tricarboxylate (Fe‐BTC) into the poly(amide‐6‐b‐ethylene oxide) (Pebax1657) polymer. Membranes with various loadings of 5, 10, and 20 wt% Fe‐BTC in the polymer matrix were fabricated to investigate the effect of filler loading on the membrane performance. Membranes, prepared by solution‐casting were characterized by scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared, X‐ray diffraction, and tensile test. Pure gas separation of CO₂, CH₄, and N₂ and ideal gas selectivity of CO₂/CH₄ and CO₂/N₂ were performed and permeation tests were carried out under 4, 8, and 12 bar pressures. Results show that adding Fe‐BTC into the Pebax1657 matrix improved both permeability and selectivity of the filled membranes. For instance, 10 wt% loading of Fe‐BTC into the Pebax1657 matrix led to CO₂ permeability increase of 49% as well as CO₂/CH₄ and CO₂/N₂ selectivities enhancements of about 36% and 16%, respectively. POLYM. COMPOS., 38:1363–1370, 2017. © 2015 Society of Plastics Engineers     

Polyurethane-SAPO-34 mixed matrix membrane for CO2/CH4 and CO2/N2 separation

SAPO-34 nanocrystals (inorganic filler) were incorporated in polyurethane membranes and the permeation properties of CO₂, CH_4, and N₂ gases were explored. In this regard, the synthesized PU-SAPO-34 mixed matrix membranes (MMMs) were characterized via SEM, AFM, TGA, XRD and FTIR analyses. Gas permeation properties of PU-SAPO-34 MMMs with SAPO-34 contents of 5 wt%, 10 wt% and 20 wt% were investigated. The permeation results revealed that the presence of 20 wt% SAPO-34 resulted in 4.45%, 18.24% and 40.2% reductions in permeability of CO_2, CH_4, and N₂, respectively, as compared to the permeability of neat polyurethane membrane. Also, the findings showed that at the pressure of 1.2 MPa, the incorporation of 20 wt% SAPO-34 into the polyurethane membranes enhanced the selectivity of CO₂/CH₄ and CO₂/N₂, 14.43 and 37.46%, respectively. In this research, PU containing 20 wt% SAPO-34 showed the best separation performance. For the first time, polynomial regression (PR) as a simple yet accurate tool yielded a mathematical equation for the prediction of permeabilities with high accuracy (R² > 99%).     

Poly(ether-b-amide)/Tween20 Gel Membranes for CO2/N2 Separation

Poly(ether-b-amide) (PEBA)/Tween20 gel membranes containing from 0 wt% to 65 wt% of Tween20 in PEBA2533, PEBA3533, and PEBA4033 were prepared by solvent casting method for CO₂/N₂ separation. The gas separation properties of the polymeric gel membranes were tested for single gases of CO₂ and N₂ at 25°C with the feed pressure of 0.6 atm. For all pure PEBA membranes, CO₂ and N₂ permeability decreased as the amount of polyamide block increased, but CO₂/N₂ selectivity increased. For PEBA/Tween20 gel membranes, both the CO₂ permeability and CO₂/N₂ selectivity were greatly enhanced with the increase of Tween20 content. For the membrane of PEBA4033/Tween20-65, CO₂/N₂ selectivity, and CO₂ permeability reached 54 and 146 Barrer, respectively, which is very interesting for potential application in CO₂ removal from flue gas.     

Fabrication of Pebax/SAPO mixed matrix membranes for CO2/N2 separation

Mixed matrix membranes (MMMs) were prepared by solvent evaporation method using Pebax-1074 polymer as matrix and inorganic zeolite SAPO-23 as dopant. The morphology, surface functional groups, microstructure, thermal stability, and separation performance of MMMs were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and gas permeation, respectively. The effects of dopant loading amount, permeation temperature, and permeation pressure on the structure and properties of MMMs were investigated. The results showed that the introduction of SAPO zeolite reduced the crystallinity of the MMMs and improved the CO₂/N₂ selectivity. Under the conditions of 30°C and 0.15 MPa, the MMMs prepared by incorporating with 5% SAPO zeolite in content exhibited the highest CO₂/N₂ selectivity of 72.0 together with the CO₂ permeability of 98.2 Barrer.     

Fabrication and modification of cellulose acetate based mixed matrix membrane: Gas separation and physical properties

[Cellulose acetate (CA)-blend-multi walled carbon nano tubes (MWCNTs)] mixed matrix membranes (MMMs), [CA/polyethylene glycol (PEG)/MWCNTs] and [CA/styrene butadiene rubber (SBR)/MWCNTs] blend MMMs were prepared by solution casting method for gas separation applications using Tetrahydrofuran (THF) as solvent. Both raw-MWCNTs (R-MWCNTs) and functionalized carboxylic-MWCNTs (C-MWCNTs) were used in membrane preparation. The MWCNTs loading ratio and pressure effects on the gas separation performance of prepared membranes were investigated for pure He, N₂, CH₄ and CO₂ gases. Results indicated that utilizing C-MWCNT instead of R-MWCNTs in membrane fabrication has better performance and (CO₂/CH₄) and (CO₂/N₂) selectivity reached to 21.81 and 13.74 from 13.41 and 9.33 at 0.65 wt% of MWCNTs loading respectively. The effects of PEG and SBR on the gas transport performance and mechanical properties were also investigated. The highest CO₂/CH₄ selectivity at 2 bar pressure was reached to 53.98 for [CA/PEG/C-MWCNT] and 43.91 for [CA/SBR/C-MWCNT] blend MMMs at 0.5 wt% and 2 wt% MWCNTs loading ratio respectively. Moreover, increase of feed pressure led to membrane gas permeability and gas pair selectivity improvement for almost all prepared membranes. The mechanical properties analysis exhibited tensile modules improvement with increasing MWCNTs loading ratio and utilizing polymer blending.     

Recent advances on mixed-matrix membranes for gas separation: Opportunities and engineering challenges

In the past decades, gas separation using polymeric membranes has received considerable attention and become one of the fastest growing research areas. However, existing polymeric membranes may not be able to keep up with the increasing separation needs for challenging gas mixtures such as N₂/CH₄ and light olefin/paraffin pairs on industrial scale due to their so-called permeability-selectivity bound. On the other hand, scaling-up issues poise huge challenges for highly permeable and highly selective inorganic membranes. Mixed-matrix membranes, composite membranes, provide an evolutionary solution to debottleneck the permeability-selectivity and scale-up issues currently faced by polymeric and inorganic membranes, respectively. Inorganic fillers in mixed-matrix membranes improve gas permeability and/or selectivity, outperforming polymeric membranes. Combined with relatively economical and simple scaling-up compared to inorganic membranes, mixed-matrix membranes could potentially be a next-generation membrane concept for gas separation applications. This review provides a brief summary on the recent progress in both flat sheet and hollow fiber mixed-matrix membranes with an emphasis on those made over the last five years. A separate section is dedicated to discussing engineering challenges transitioning from laboratory-scale to large-scale synthesis of mixed-matrix membranes. Finally, future prospects and perspectives in mixed-matrix membranes research are briefly outlined.     

Optimizing membrane synthesis parameters via Taguchi method: An approach to prepare high performance mixed-matrix membranes for carbon capture applications

Mixed-matrix membranes (MMMs) comprising polysulfone (PSF) and zeolite 4A (Z4A) were prepared for carbon capture applications. Membranes of varying compositions were fabricated by solution casting technique. Viscous solutions of dissolved ingredients were cast on a clean glass plate followed by evaporation and drying of prepared membrane. Fabricated composite membranes were subjected to morphological, structural, and permeation analyzes. The morphological results showed a uniform dispersal of zeolite nanoparticles with agglomerates formation at higher nanofiller loadings. The structural analysis corroborated the noninteractive behaviour of organic polymer and inorganic zeolite phases. Permeation results suggested that the fabricated membranes were more permeable to CO₂ gas, which can be described by higher diffusivity and structural affinity for CO₂. Taguchi statistical analysis was employed to optimize carbon capture performance of developed hybrid membranes by carefully controlling the membrane casting parameters such as loading levels of functional nanofiller, sonication time, and drying time of casting solution. The statistical investigation of permeation results suggested the sensitivity of casting parameters on membrane performance in the following manner: zeolite loading > sonication time > drying time. The optimized membrane casting parameters obtained from signal-to-noise ratio analysis performed on Minitab led to synthesis of a composite membrane with both high CO₂/N₂ selectivity and CO₂ permeability. The chosen technique also assisted in justifying the dependence of permeation results on various membrane casting parameters, associating it with the morphological results. The technique also facilitated the optimization of the membrane characteristics and is recommended for future study based on membrane separation processes.     

Improved gas transport properties of polyurethane–urea membranes through incorporating a cadmium-based metal organic framework

The increasing need for more efficient separation processes has motivated the development of polymer membranes that can provide fast and selective transport. In this work, cadmium-based metal–organic framework (MOF) nanoparticles and a polyurethane–urea (PUU) elastomer were synthesized. New mixed-matrix membranes (MMMs) were then fabricated from the nanoparticles and the PUU. SEM images verified that embedding the nanoparticles changes the morphology of the PUU and the nanoparticles disperse well in the PUU due to satisfactory compatibility of the polymer and nanoparticles. Fourier transform infrared spectroscopy and X-ray diffraction analysis confirmed the dispersion of the nanoparticles in the soft segment of the PUU. With increased temperature, gas permeabilities of the MMMs improved but their sieving ability deteriorated. An MMM incorporating 2.5 wt % of the MOF showed a CO₂ permeability of ~140 barrer and a CO₂/N₂ selectivity of ~30, which are 89 and 38% higher than those of the pristine membrane. Gas permeation tests showed that the higher CO₂/N₂ selectivity of the MMMs was due to improved solubility selectivity and the higher CO₂ permeability was a result of improved CO₂ diffusivity and solubility coefficients. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48704.     

High oxygen permeable Zeolite-4A poly(dimethylsiloxane) membrane for air separation

High oxygen permeability with optimal selectivity of the membrane is required for advancement in air separation membrane technology. Zeolite 4A-PDMS composite membranes were prepared by incorporation of Zeolite 4A nanoscale crystals during the polymerization process of PDMS membrane using toluene and n-heptane solvents, and their oxygen gas permeability and selectivity were explored. Small angle neutron scattering (SANS) technique was further used to study the polymer chain conformation and structure of membranes influenced by Zeolite 4A loading. The intersegmental distance between polymer chains and polymer chain aggregation or clustering were found to be increased on increasing the Zeolite 4A content in the membranes. Increment in the O₂ permeability and O₂/N₂ selectivity were observed for both type of membranes (toluene and n-heptane) with 1 wt% Zeolite 4A loading. The best performance result with O₂/N₂ selectivity of 2.6, and O₂ permeability of 1052 Barrer was exhibited by PDMS/toluene membrane loaded with 1 wt% Zeolite 4A. The PDMS/toluene membranes with 10 wt% Zeolite 4A loading exhibited increased O₂ permeability of 1245 Barrer with a fair O₂/N₂selectivity of ~1.7, while the PDMS/n-heptane membrane with the same loading exhibited excellent O₂ permeability of 6773 Barrer but lesser O₂/N₂ selectivity of ~1.2. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48047.     

Effect of coating method on gas separation by PDMS/PES membrane

In this study, polydimethylsiloxane (PDMS)‐coated polyethersulfone (PES) composite membrane was prepared for gas separation. “Film casting” and “dip‐coating” techniques were used for producing selective PDMS layer on the surface of the PES support. The effects of coating technique and conditions including coating solution concentration and curing temperature on permselectivity of CO₂, CH₄, and N₂ were investigated. The prepared PES support did not provide any selectivity to the gases. When the concentration of PDMS coating solution was increased, initially permeability of CO₂ was rapidly dropped and then gradually reached to an almost constant value. The optimum concentration of coating solution was 5 wt%. Curing temperature showed no pronounced effect on the CO₂ permeability and selectivity. In “film casting” method, double coating showed superior permeability and selectivity. However, triple “dip‐coating” was promising. The selectivity of composite membrane prepared by “dip‐coating” was higher than “film casting” method. CO₂/N₂ and CO₂/CH₄ selectivity of five sequential dip‐coated composite membranes was 45.5 and 9.3, respectively. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Selective permeation of sour gases through polymeric membranes modified by sulfolanes. I. Study of selective permeation of CO2 through modified polymeric membranes determined on different systems

Several sulfolanes such as 3-methylsulfolane, sulfolane, and 3-sulfolene were tested as modifiers in poly(trimethylsilyl methyl methacrylate) (PTMSMMA) and poly(trimethylsilyl propyne) (PMSP) to improve the selectivity of CO₂. The gas permeabilities for the PTMSMMA-blend membranes containing high 3-methylsulfolane content were determined on a nonvacuum system in which the membranes started to be measured at their steady states at 30°C; those for all the other membranes were determined in a vacuum system in which those membranes were measured after they reached their unsteady states at 30°C. The PTMSMMA-blend membrane containing 40% 3-methylsulfolane was found to give the best separation of CO₂ under the conditions in this study compared to all the PTMSMMA-blend membranes and the others prepared in our work; its ideal separation factors for CO₂ over N₂ were above 40 and its permeability coefficients of CO₂ increased to above 250 Barrer. The modifications of PMSP membranes by impregnating with sulfolane and blending with sulfolene were found to be effective in improving the selectivity for CO₂ over N₂ for the PMSP membrane. The ideal separation factors for CO₂ over N₂ for the modified PMSP membranes impregnated with 30% sulfolane and blended with 25% 3-sulfolene were improved to above 10 and 13, respectively. © 1996 John Wiley & Sons, Inc.     

Dialdehyde polyethylene glycol cross-linked poly(vinyl alcohol) membranes with enhanced CO2/N2 separation performance

The development of carbon dioxide (CO₂) separation technology is crucial for mitigating global climate change and promoting sustainable development. In this study, we successfully synthesized an array of cross-linked poly(vinyl alcohol) (PVA) membranes, xALD-PEG-ALD-c-PVA, with enhanced CO₂/N₂ separation performance by employing dialdehyde polyethylene glycol (ALD-PEG-ALD) as a cross-linker. The formation of the cross-linked network structure not only inhibits the crystallization of PVA but also disrupts hydrogen bonding and thus increases fractional free volume of PVA chains. Under the synergistic effect of these multiple factors, the cross-linked PVA membranes exhibit a significantly improved CO₂ permeability. Moreover, they maintain high CO₂/N₂ selectivity, attributing to the CO₂-philic characteristic of ethylene oxide groups in the cross-linked structure. At the ALD-PEG-ALD content of 1.6 mmol g⁻¹, the xALD-PEG-ALD-c-PVA membrane demonstrates a CO₂ permeability of 41.4 barrer and a CO₂/N₂ selectivity of 57.4 at 2 bar and 25°C. Furthermore, compared with the pristine PVA membrane, xALD-PEG-ALD-c-PVA membranes manifest superior mechanical properties and outstanding separation performance for a CO₂/N₂ (15/85, vol%) gas mixture. The excellent combination of permeability and selectivity makes xALD-PEG-ALD-c-PVA membranes highly promising for various CO₂ separation applications.     

Membranes for CO2 /CH4 and CO2/N2 Gas Separation

Membrane technology has emerged as a leading tool worldwide for effective CO₂ separation because of its well-known advantages, including high surface area, compact design, ease of maintenance, environmentally friendly nature, and cost-effectiveness. Polymeric and inorganic membranes are generally utilized for the separation of gas mixtures. The mixed-matrix membrane (MMM) utilizes the advantages of both polymeric and inorganic membranes to surpass the trade-off limits. The high permeability and selectivity of MMMs by incorporating different types of fillers exhibit the best performance for CO₂ separation from natural gas and other flue gases. The recent progress made in the field of MMMs having different types of fillers is emphasized. Specifically, CO₂/CH₄ and CO₂/N₂ separation from various types of MMMs are comprehensively reviewed that are closely relevant to natural gas purification and compositional flue gas treatment     

Pseudopeptide bioconjugate additives for CO2 separation membranes

1:1[α/α‐N^α‐Bn‐hydrazino] pseudopeptide?polymer bioconjugates were synthesized and investigated as additives in a reference gas separation membrane (Pebax®) for CO₂ capture. Pebax® is a polyether block amide thermoplastic elastomer provided by Arkema and is already well known for its good performance for CO₂ separations. First, dimer and tetramer pseudopeptides were synthesized and their terminal amine was modified into a ‘clickable’ alkyne group in view of coupling. Second, an α‐azido acrylic poly(ethylene glycol)‐based oligomer was obtained by single‐electron transfer living radical polymerization and the two partners were coupled using copper(I) catalyzed alkyne‐azide cycloaddition (CuAAC) ‘click’ chemistry. The pseudopeptides and their bioconjugates were then assessed as original additives in Pebax® membranes for CO₂/CH₄ and CO₂/N₂ separations. The permeation data were analyzed according to the solution‐diffusion model. Compared to pseudopeptides, the pseudopeptide?polymer bioconjugates enabled the membrane properties to be greatly improved with better permeability (×1.5) and a good constant selectivity for CO₂ capture. The best membrane properties were obtained with 3 eq. wt% of the tetramer‐based bioconjugate with a CO₂ permeability of 194 Barrer (+46% compared to that of Pebax®) and constant selectivity (αCO₂/N₂ = 44 and αCO₂/CH₄ = 13). © 2016 Society of Chemical Industry     

Fabrication and characterization of polyetherimide/polyvinyl acetate polymer blend membranes for CO2/CH4 separation

This article presents fabrication, characterization, and performance evaluation of polyetherimide (PEI)/polyvinyl acetate (PVAc) blend membranes. Polymer blend membranes with various blend ratios of PEI/PVAc were prepared by solution casting and evaporation technique. Morphology and miscibility of polymer blend membranes were characterized by field emission scanning electron microscope (FESEM) and differential scanning calorimetry (DSC), respectively. The interaction between blend polymers was analyzed by FTIR analysis. Gas separation performance was evaluated in terms of permeability and selectivity. FESEM results revealed that pure polymer and blend membranes were homogeneous and dense in structure. A single glass transition temperature of polymer blend membranes was found in DSC analysis which indicated the miscibility of PEI/PVAc blend. FTIR analysis confirmed the presence of molecular interaction between blend polymers. The permeation results showed that the presence of PVAc (3 wt%) in blend membranes has improved CO₂ permeability up to 95% compared to pure PEI membrane. In addition, CO₂/CH₄ selectivity was found to be 40% higher than pure PEI membrane. This study shows that blending a small fraction of PVAc can improve the gas separation performance of PEI/PVAc blend membranes. POLYM. ENG. SCI., 59:E293–E301, 2019. © 2018 Society of Plastics Engineers     

Preparation and Characterization of Polycarbonate-Blend-Raw/Functionalized Multi-Walled Carbon Nano Tubes Mixed Matrix Membrane for CO2 Separation

Membrane composed of PC as base of polymer matrix with different ratio of multiwall carbon nano tubes (MWCNTs) as nanofillers and poly ethylene glycol (PEG) as second polymer was prepared by solution casting method. Both raw-MWCNTs (R-MWCNTs) and functionalized carboxyle-MWCNTs (C-MWCNTs) were used in membrane preparation. The MWCNTs loading ratio and pressure effects on the gas transport properties of membranes were examined in relation to pure He, N₂, CH₄, and CO₂ gases. Results showed that the use of C-MWCNT instead of R-MWCNTs in mixed matrix membranes (MMMs) fabrication with base of PC provides better performance and also it increases (CO₂/CH₄) and (CO₂/N₂) selectivities to 27.38 and 25.42 from 25.45 and 19.24, respectively (at 5 wt% of MWCNTs). PEG as the second rubbery polymer was utilized to improve the separation performance and mechanical properties. In blend MMMs, highest (CO₂/CH₄) selectivity at 2 bar pressure increased to 35.64 for PC/PEG/C-MWCNT blend MMMs which was 27.28 for PC/MWCNTs MMMs at 10 wt%. Increase of feed pressure led to gas permeability and gas pair selectivity improvement in approximately all of membranes. Analysis of mechanical properties showed improvement in tensile modules with the increase of MWCNTs loading ratio and use of PEG in prepared MMMs.     

Application of poly (amide-<Emphasis Type="Italic">b</Emphasis>-ethylene oxide)/zeolitic imidazolate framework nanocomposite membrane in gas separation

Mixed matrix membranes (MMMs) are gaining increasing interest in academic and industrial research due to their combined, desirable properties of both polymers and organic/inorganic filler as important materials. In this work, synthesized zeolitic imidazolate framework (ZIF-8) suspension (10–50 wt%) was directly incorporated into a [poly (amide-b-ethylene oxide) Pebax^® 1657] matrix in order to improve the gas separation performance of the membrane. Dynamic light scattering (DLS) analysis showed an average diameter of 77.4 nm for the prepared nanoparticles. The transparent membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffractometry (XRD). These indicated excellent dispersion of nanoparticles, which was achieved by ultrasonication before casting the solution. Incorporation of ZIF-8 as filler in the polymer matrix led to improved thermal and mechanical stability of the membranes. This was confirmed by TGA and tensile analyses, indicating good contacts provided at the polymer/filler interfaces. The effect of ZIF-8 loading (up to 50 wt%) on membrane performance was investigated and it showed an optimum loading of 30 %. Single gas (CO₂, N₂ and CH₄) permeation tests revealed rapid, enhanced permeability of the nanocomposite membranes without significant changes in selectivity (compared to those of the pristine polymeric membrane). The permeability increases for CO₂, CH₄ and N₂ in the optimum Pebax^® 1657/ZIF-8 (30 wt%) membrane were found in the stated order as 111, 88 and 99 %. The study revealed that Pebax^® 1657/ZIF-8 membranes displayed better gas permeation properties compared to those of Pebax^® 1657.     

Effect of preparation parameters on performance of dense homogeneous polycarbonate gas separation membranes

The aim of this study is to determine the effect of preparation parameters on the membrane permeation mechanism and separation performances of dense homogeneous poly(bisphenol A carbonate) (PC) membranes. Blade‐casting and drop‐casting techniques are used for casting films from solutions with varying concentrations. Chloroform and methylene chloride are used to determine the effect of the properties of the casting solvent. Permeation measurements are done with Ar, N₂, O₂, CH₄, CO₂, and H₂ gases. The selectivity values of dense homogeneous membranes with a PC composition of 7% (w/v chloroform) are 1.7 for Ar/N₂, 1.1. for CH₄/N₂, 18 for CO₂/N₂, 26 for H₂/N₂, and 9.7 for O₂/N₂. These values with a PC composition of 15% (w/v methylene chloride) are 2.7, 1.3, 25, 44, and 13 for the same gases, respectively. In addition to the importance of the solvent type and composition, the casting type and thermal history also affects the performance of the membrane. Increasing the annealing period enhances the selectivity while decreasing the permeability for both casting solvents, yet this thermal history effect strongly depends on the solvent type because of solvent–polymer interactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 776–785, 2003     

Preparation and characterization of SAPO-34 – Matrimid 5218 mixed matrix membranes for CO2/CH4 separation

Different SAPO-34 zeolite loaded Matrimid^® 5218 mixed matrix membranes (MMMs) were prepared by solution casting method and characterized using XRD and SEM analysis. Findings showed that semi crystalline neat polymer becomes more crystalline after thermal treatment at higher temperatures close to Matrimid^® 5218 glass transition temperature. Furthermore, incorporation of crystalline filler particles of SAPO-34 zeolite resulted in more and more crystallinity of the MMMs. SEM images also exhibited acceptable contacts between the filler particles and the polymer chains. Permeation measurement showed that CO₂ permeabilities and CO₂/CH₄ selectivities of the MMM with 20 wt% loading of SAPO-34 zeolite particles up to 6.9 (Barrer) and 67, respectively. This can be attributed to size discrimination of SAPO-34 pores that falls between CO₂ and CH₄ kinetic diameters.