Molecular-scale hybrid membranes: Metal-oxo cluster crosslinked benzimidazole-linked polymer membranes for superior H2 purification

Hydrogen (H₂) purification requires separation membranes with excellent performance and high stability. Here, a few nanometer-sized Zr-oxygen clusters (CP-2) abundant in amino groups were incorporated in benzimidazole-linked polymers (BILPs) by interfacial polymerization (IP) to fabricate molecular-scale hybrid membranes for efficient H₂/CO₂ separation. The amino groups in CP-2 engage in IP. The structure of the BILPs polymer chains is regulated and more H₂ selective channels are created. The hybrid membranes provide an H₂/CO₂ selectivity of up to 75.2 (with a corresponding H₂ permeance of 318 GPU) and a high H₂ permeance of up to 1470 GPU (with a corresponding H₂/CO₂ selectivity of 23.6). In addition, the membranes exhibit satisfactory separation performance and durability under industry-relevant conditions (573 K, 11 bar, or steam treatment).     

CH4-Selective Mixed-Matrix Membranes Containing Functionalized Silica for Natural Gas Purification

Mixed-matrix membranes were prepared by incorporating functionalized silica nanoparticles (SNPs) into the poly(ether-block-amide). The gas permeation properties of membranes were investigated for the separation of N₂ and CO₂ from CH₄. Results revealed that chemical modification of SNPs and incorporation of the carboxylic groups on its surface had a strong interaction with the polymer matrix and improved the distribution of the nanofiller in the membrane matrix. According to the gas permeation experiments at various SNPs loadings and feed pressures, different trends were observed for the permeability and selectivity. Incorporation of the modified-SNPs nanofiller into the membrane enhanced the CH₄ permeability, as well as the CH₄/N₂ and CO₂/N₂ selectivities.     

High-speed CO2 transport channel containing carboxymethyl chitosan/hydrotalcite membrane for CO2 separation

A comprehensive understanding of carboxymethyl chitosan (CMC)-based mixed matrix membrane (MMM) has been critically investigated. The present work elaborates the compatibility of hydrotalcite (HT) and CMC in terms of CO₂ separation application. Various spectroscopic and microscopic techniques have been utilized to characterize the respective properties of the prepared membrane. The temperature stability and moisture retention behavior of the membrane recognized itself as the flue gas separation membrane. The CO₂/N₂ separation experiment was performed on the MMM at different temperature (60–110 °C) and sweep/feed water flow to the saturator ratio (0.33 to 3). The membrane exhibited the optimum CO₂ permeance of 70 GPU at 90°C pertaining to water flow ratio of 2.33 (sweep/feed). The CO₂/N₂ selectivity observed at that same operating condition was 13. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48715.     

一种引入CO2选择性吸附硅纳米颗粒提高固定载体膜性能的方法（英文）

Fixed carrier membrane exhibits attractive CO2 permeance and selectivity due to its transport mecha-nism of reaction selectivity (facilitated transport). However, its performance needs improvement to meet cost targets for CO2 capture. This study attempts to develop membranes with multiple permselective mechanisms in order to enhance CO2 separation performance of fixed carrier membrane. In this study, a novel membrane with multiple permselective mechanisms of solubility selectivity and reaction selectivity was developed by incorporating CO2-selective adsorptive silica nanoparticles in situ into the tertiary amine containing polyamide membrane formed by interfacial polymerization (IP). Various techniques were employed to characterize the polyamide and polyam-ide-silica composite membranes. The TGA result shows that nanocomposite membranes exhibit superior thermal stability than pure polyamide membranes. In addition, gas permeation experiments show that both nanocomposite membranes have larger CO2 permeance than pure polyamide membranes. The enhanced CO2/N2 separation per-formance for nanocomposite membranes is mainly due to the thin film thickness, and multiple permselective mechanisms of solubility selectivity and reaction selectivity.     

Influence of solvent and nanoparticles on the morphology and gas separation properties of copolyimide membranes

In this study, the effect of solvent type and nanoparticles of silica and zeolite 4A on the gas separation properties of polyimide (PI) membranes were investigated. Gas separation of the membranes based on pure solvents of dimethylformamide (DMF), n-methyl-2-pirrolidone (NMP), dimethylacetamide (DMAc), and dimethylsulfoxide (DMSO) were studied. The prepared PI membranes using DMAc and DMSO showed the highest selectivity and permeability, respectively. In this regard, the influence of their mixing on transport properties of the PI was evaluated. The prepared membrane using the mixture of DMSO/DMAc with the volume ratio of 1:3 showed the best gas separation performance in comparison to the Robeson's upper bound. Incorporation of 20 wt% of silica and zeolite 4A nanoparticles into the PI membrane indicated that the selectivity of CO₂/CH₄ increased from 39.4 to 57.6 and 68.5, respectively. Besides, gas transport properties of the PI-based mixed matrix membranes were satisfactory predicted by modified Maxwell model. Furthermore, characteristic parameters of the encapsulated particles by interfacial layer were determined.     

Effects of preparation parameters on CO2/N2 gas permselectivity of polyether thin film composite membrane

In this work, ether oxide (EO)-based multilayer composite membranes were prepared via interfacial polymerization (IP) of trimesoyl chloride (TMC) and polyetheramine (PEA) on polydimethylsiloxane precoated polysulfone support membrane. The effects of preparation parameters, such as monomer concentrations, reaction time, and heat-treatment temperature on the membrane performance were investigated. The optimal preparation parameters have been concluded. The results showed the increasing monomers concentration of both PEA and TMC can lead to the decrease of CO₂ permeance and increase of CO₂/N₂ selectivity. The optimal monomers concentration was found. When monomer concentrations are higher than the optimal values, the CO₂ permeance decreases continually while CO₂/N₂ selectivity only shows a very limited improvement with the further increase of monomers concentration. The reaction time has similar effects on membrane performance as the monomers concentration. The effect of heat-treatment temperature was also studied. With the increasing heat-treatment temperature, the CO₂ permeance shows a decrease tendency, while the CO₂/N₂ selectivity shows a maximum at 80 °C. When PEA is 0.013 mol L⁻¹, TMC is 0.020 mol L⁻¹, reaction time is 3 min, and heat-treatment temperature is 80 °C, the optimum preparation conditions are achieved with CO₂ permeance of 378.3 gas permeation unit (GPU) and CO₂/N₂ selectivity of 51.7 at 0.03 MPa. This work may help to design and fabricate gas separation membranes with desired performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47755.     

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.     

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     

A novel ternary mixed-matrix membrane comprising Pebax-1657, [HMIM][NTf2] IL,and Al2O3 nanoparticles for efficient CO2 separation

An innovative technique to efficiently remove CO₂ involves introducing a third component with a positive affinity with CO₂ into a binary mixed-matrix membrane (MMM) and eliminating interfacial defects in its structure. In this research, novel ternary MMMs (TMMMs) were synthesized by embedding 1–Hexyl–3–methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf₂]) ionic liquid (IL) and aluminum oxide (γ–Al₂O₃) nanoparticles into poly (ether-block-amide) (Pebax-1657) matrix for enhancing CO₂ removal from light gases. FESEM, DSC, ATR-FTIR, and XRD analyses were used to evaluate the fabricated MMMs structurally. The permeation tests of gases (CH₄, N₂, and CO₂) through prepared membranes were conducted at 25°C and 4, 6, 8, and 10 bar pressures. In accordance with the permeation outcomes, the ternary MMMs exhibited enhanced CO₂ separation performances compared to the unloaded polymeric membrane. Also, the optimized MMM comprising 10 wt.% of the IL and 6 wt.% of the nanoparticles obtained a CO₂ permeability of 173.90 Barrer, as well as CO₂/N₂ and CO₂/CH₄ selectivities of 77.98 and 24.29 at 10 bar and 25°C, which are higher by about 51%, 23%, and 22%, respectively than those of the pristine polymeric membrane. Based on these results, the prepared membrane appears to be a promising choice for separating CO₂ from light gases.     

Preparation and characterization of dimethyldichlorosilane modified SiO2/PSf nanocomposite membrane

Investigations on nanocomposite membranes imply that these hybrid materials recommend promising newgeneration membranes for gas separation in future. In this study, to investigate the effects of preparation parameters on the morphology and gas transport, various parameters including nanofiller content, surface modification and polymer concentration were considered. Two types of fumed silica nanoparticles (nonmodified and modified) were used to study the surface modification effect on agglomeration, void formation and gas separation properties of prepared membranes. Prepared nanocomposite membranes were characterized by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and tensile strength techniques. The gas permeabilities of hydrogen, methane, and carbon dioxide through pure PSf and nanocomposites were measured as a function of silica volume fraction, and permeability coefficients were determined using a variable pressure/constant volume experimental setup. Results showed that gas permeabilities increase with silica content, and proper H₂/CH₄ and H₂/CO₂ selectivities can be achieved with modified type of silica nanoparticles due to inhibition of particle agglomeration and bonding with polymer network. Hydrogen selectivity was improved by using 15 wt% polymer content instead of 9 wt% in preparation of nanocomposite membrane with same silica content. Gas permeation results indicated that increasing of feed pressure from 3 bar to 6 bar has a positive effect on selectivity of H₂/CH₄ but negligible effect on that of H₂/CO₂ for modified silica/PSf membrane.     

Interfacial polymerization of facilitated transport polyamide membrane prepared from PIP and IPC for gas separation applications

A facilitated transport polyamide (PA) membrane was developed for gas separation by interfacial polymerization reaction of piperazine (PIP) and isophthaloyl chloride (IPC) supported on polysulfone (PSF) membrane previously prepared by dry/wet phase inversion method. The properties of the prepared membranes were characterized by SEM, FT-IR, TGA, and XRD. SEM images showed that a defect-free PSF, and rough PA membranes were fabricated, while the FT-IR spectra confirmed the formation of PA layer on top of the PSF support. The separation performance of the thin film PA and PSF membranes was evaluated using four gasses (CO₂, CH₄, N₂, and O₂). Compared to the PSF membrane, the PA membrane demonstrated an increased selectivity of CO₂/CH₄ and CO₂/N₂ by 178%, 169%, respectively. This improvement was attributed to the presence of amine functional groups, which acted as a fixed carrier to facilitate the transport of CO₂ gas across the membrane. However, building the PA layer on top of PSF support reduced the membrane permeance of CO₂ from 2.41 to 2.12 GPU as a result of the increased mass transfer resistance. Furthermore, the effect of operating temperature and pressure on the separation performance of the membranes was investigated.     

Covalent Attachment of Monochlorosilanes to Mesoporous Silica Membranes using Supercritical Fluid Deposition

Abstract

We have prepared and characterized organically-modified mesoporous silica membranes using supercritical CO₂ fluid deposition. Supercritical CO₂ fluid deposition has the potential to increase both diffusion and concentration of the reactants at the reaction site, a particular advantage when the reaction site is inside a small pore, where access can be limited. The unmodified mesoporous silica membranes were prepared by surfactant-templated synthesis on α-alumina disk-shaped supports. These mesoporous silica supports had a mean pore diameter of 5 nm. The alkyl modification of the silica membranes was achieved by the covalent attachment of octadecyldimethylchlorosilane (ODMCS) using triethylamine (TEA) as a catalyst in supercritical-CO₂. Successful attachment was confirmed through infrared spectroscopic identification of the removal of the band due to isolated silanols accompanied by the appearance of bands due to methyl and methylene groups. We also directly measured a ～90% reduction in permeance of light gases through the modified membrane. The synthesis process did not degrade the support membrane, was relatively efficient, and was free of organic solvents required for traditional synthesis. The dominant transport mode in the membranes was Knudsen flow.

Ideal separation factors for methane and propane over nitrogen were not increased relative to the bare support, indicating that neither the surface flow was enhanced nor the size selectivity improved for the membrane system studied. Supercritical CO₂ fluid deposition was demonstrated as an effective technique for the reaction of the functionalized silanes on the surface of the silica membrane.     

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.     

Study on CO2 facilitated separation of mixed matrix membranes containing surface modified MWCNTs

Mixed matrix membranes (MMMs) for CO₂-facilitated separation were prepared by incorporating different surface-modified multiwalled carbon nanotubes (MWCNTs) in a fixed carrier membrane material. Polymer containing amino groups, poly(vinylalcohol-co-vinylamine) (VA-co-VAm) was synthesized as polymeric matrix. MWCNTs as well as MWCNTs surface-modified with  OH and  NH₂ were applied as nanofillers. The physical property, chemical structure, and membrane morphology were characterized by FT-IR, TG, XRD, DSC, CA, XPS, and SEM. The effects of content, functional group, temperature, and pressure on gas permselectivity were studied. Results show that the incorporation of nanofillers can effectively restrict the polymer chain packing and lead to low crystallinity. The MMMs exhibited higher CO₂ permselectivity than the pure polymeric membrane. For all the MMMs, the CO₂ permeance and selectivity increased with MWCNTs contents to a maximum and then decreased. MWCNT-NH₂ can be regarded as the most effective nanofiller. MMMs with 2.0 wt % MWCNT-NH₂ displayed the highest CO₂ permeance of 132 GPU and CO₂/N₂ selectivity of 74. Both CO₂ permeance and selectivity were decreased with feed gas pressure and temperature. The membrane exhibited good stability in the testing with the binary gas mixtures of CO₂/N₂ for 110 h under 0.54 MPa. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47848.     

Gas permeation properties of silica membranes with uniform pore sizes derived from polyhedral oligomeric silsesquioxane

The sol‐gel method was applied in the fabrication of homogenous polyhedral oligomeric silsesquioxane (HOMO‐POSS)‐derived silica membranes. Single gas permeation characteristics in a temperature range of 100–500^°C were examined to discuss the effect of silica precursor on amorphous silica networks. HOMO‐POSS‐derived membranes showed a CO₂ permeance of 1.1 × 10^?7 mol m^?2 s^?1 Pa^?1 with a CO₂/CH₄ permeance ratio of 131 at 100^°C, which is a superior CO₂/CH₄ separation performance by comparison with tetraethoxysilane (TEOS)‐derived silica membranes. Normalized Knudsen‐based permeance (NKP) was applied for quantitative evaluation of pore size. HOMO‐POSS‐derived membranes had loose amorphous silica structures compared to TEOS‐derived membranes and pore size was successfully tuned by changing the calcination temperatures. The activation energy for a HOMO‐POSS‐derived membrane fired at 550^°C with a uniform pore size of ～ 0.42 nm increased linearly with the ratio of the kinetic diameter of the gas molecule to the pore diameter, λ (=d_k/d_p), and showed a trend similar to that of DDR‐type zeolite membranes. © 2011 American Institute of Chemical Engineers AIChE J, 58: 1733–1743, 2012     

Modification of PES/PU membrane by supercritical CO2 to enhance CO2/CH4 selectivity: Fabrication and correlation approach using RSM

Integrally skinned asymmetric gas separation membranes of polyethersulfone (PES)/polyurethane (PU) blend were prepared using supercritical CO₂ (SC-CO₂) as a nonsolvent for the polymer solution. The membrane consisted of a dense and a porous layer, which were conjoined to separate CO₂ from CH₄. The FTIR, DSC, tensile and SEM tests were performed to study and characterize the membranes. The results revealed that an increase in SC-CO₂ temperature causes an increment in permeance and a decrease in membrane selectivity. Furthermore, by raising the pressure, both permeance and selectivity increased. The modified membrane with SC-CO₂ had much higher selectivity, about 5.5 times superior to the non-modified membrane. This higher selectivity performance compared to previous works was obtained by taking the advantages of both using partial miscible blend polymer due to the strong polar–polar interaction between PU PES and SC-CO₂ to fabricate the membrane. The response surface methodology (RSM) was applied to find the relationships between several explanatory variables and CO₂ and CH₄ permeance and CO₂/CH₄ selectivity as responses. Finally, the results were validated with the experimental data, which the model results were in good agreement with the available experimental data.     

Quest for high performance carbon capture membranes: Fabrication of SAPO-34 and CNTs-doped polyethersulfone-based mixed-matrix membranes

Gas separation process is an effective method for capturing and removing CO₂ from post-combustion flue gases. Due to their various essential properties such as ability to improve process efficiency, polymeric membranes are known to dominate the market. Trade-off between gas permeability and selectivity through membranes limits their separation performance. In this study, solution casting cum phase separation method was utilized to create polyethersulfone-based composite membranes doped with carbon nanotubes (CNTs) and silico aluminophosphate (SAPO-34) as nanofiller materials. Membrane properties were then examined by performing gas permeation test, chemical structural analysis and optical microscopy. While enhancing membranes CO₂ permeance, SAPO-34 and CNTs mixture improved their CO₂/N₂ selectivity. By carefully adjusting membrane casting factors such as filler loadings. Using Taguchi statistical analysis, their carbon capture efficiency was improved. The improved mixed-matrix membrane with loading of 5 wt% CNTs and 10 wt% SAPO-34 in PES showed highly promising separation performance with a CO₂ permeability of 319 Barrer and an ideal CO₂/N₂ selectivity of 12, both of which are within the 2008 Robeson upper bound. A better mixed-matrix membrane with outstanding CO₂/N₂ selectivity and CO₂ permeability was produced as a result of the synergistic effect of adding two types of fillers in optimized loading.     

Development of ethanolamine‐based ionic liquid membranes for efficient CO2/CH4 separation

This study is focused on the development of ionic liquids (ILs) based polymeric membranes for the separation of carbon dioxide (CO₂) from methane (CH₄). The advantage of ILs in selective CO₂ absorption is that it enhances the CO₂ selective separation for the ionic liquid membranes (ILMs). ILMs are developed and characterized with two different ILs using the solution‐casting method. Three different blend compositions of ILs and polysulfone (PSF) are selected for each ILMs 10, 20, and 30 wt %. Effect of the different types of ILs such as triethanolamine formate (TEAF) and triethanolamine acetate (TEAA) are investigated on PSF‐based ILMs. Field emission scanning electron microscopy analysis of the membranes showed reasonable homogeneity between the ILs and PSF. Thermogravimetric analysis showed that by increasing the ILs loading thermal stability of the membranes improved. Mechanical analysis on developed membranes showed that ILs phase reduced the amount of plastic flow of the PSF phase and therefore, fracture takes place at gradually lower strains with increasing ILs content. Gas permeation evaluation was carried out on the developed membranes for CO₂/CH₄ separation between 2 bar to 10 bar feed pressure. Results showed that CO₂ permeance increases with the addition of ILs 10–30 wt % in ILMs. With 20–30 wt % TEAF‐ILMs and TEAA‐ILMs, the highest selectivity of a CO₂/CH₄ 53.96 ± 0.3, 37.64 ± 0.2 and CO₂ permeance 69.5 ± 0.6, 55.21 ± 0.3 is observed for treated membrane at 2–10 bar. The selectivity using mixed gas test at various CO₂/CH₄ compositions shows consistent results with the ideal gas selectivity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45395.     

Optimization of CO2–CH4 separation performance of integrally skinned asymmetric membranes prepared from poly(2,6‐dimethyl‐1,4‐phenylene oxide) by factorial design

Integrally skinned asymmetric flat sheet membranes were prepared from poly(2,6‐dimethyl 1,4‐phenylene oxide)(PPO) for CO₂–CH₄ separation. Various experiments were carried out to identify PPO membranes, which have good mechanical strength and gas separation abilities. Membrane strength and selectivity depend on the interplay of the rate of precipitation and the rate of crystallization of the PPO. The effects of major variables involved in the membrane formation and performance, including the concentration of the polymer, solvent, and additive, the casting thickness, the evaporation time before gelation, and the temperature of the polymer solution, were investigated. Factorial design experiments were carried out to identify the factor effects. The membrane performance was modelled and optimized to approach preset values for high CO₂ permeance and a high CO₂ : CH₄ permeance ratio. Membranes were prepared based on the optimum conditions identified by the model. Essentially, defect‐free membranes were prepared at these conditions, which resulted in a pure gas permeance of 9.2 × 10⁻⁹ mol/m² s Pa for CO₂ and a permeance ratio of 19.2 for CO₂ : CH₄. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1601–1610, 1999     

Preparation and characterization of polysulfone mixed matrix membrane incorporated with palladium nanoparticles in the inversed microemulsion for hydrogen separation

Polysulfone (PSf) membrane shows acceptable gas separation performance, but its application is limited by the “trade-off” between selectivity and permeability. In this study, PSf mixed matrix membranes (MMMs) incorporated with palladium (Pd) nanoparticles in the inversed microemulsion were proposed for hydrogen (H₂) separation. Pd nanoparticles can be kinetically stabilized and dispersed using electrostatic and/or steric forces of a stabilizer which is typically introduced during the formation of Pd nanoparticles in the inversed microemulsion. Pd nanoparticles were synthesized by loading (PdCl₂) into the polymeric matrix, polyethylene glycol (PEG) which acts as reducing agent and stabilizer. The dry–wet phase inversion method was applied for the preparation of asymmetric PSf MMMs. The effects of Pd (0–4 wt%) on the membrane characteristics and separation performance were studied. Experimental findings verified that the MMMs are able to achieved a high H₂/N₂ selectivity of 21.69 and a satisfactory H₂ permeance of 46.24 GPU due to the changes in membrane structure from fully developed finger-like structure to closed cell structure besides the growth of dense layer. However, the selectivity of H₂/CO₂ decreased due to the addition of PEG.