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.     

Enhanced CO2 separation performance by PVA/PEG/silica mixed matrix membrane

This article focused on segregation of low concentration CO₂ from CO₂/N₂ mixture gas by implementing high‐performance facilitated transport mixed matrix membranes (MMMs) in large‐scale carbon capture techniques. These advanced, novel CO₂‐selective membrane materials were developed by embedding silica nanoparticles at different loading into the poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) matrix using solution casting. In situ sol–gel technique was applied for the synthesis of the hydrophilic SiO₂ nanoparticles. The compatibility of filler‐polymer matrix plays a crucial role in the optimization of the membrane performance. The dispersion and interaction of the filler into the polymer matrix were confirmed by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy, contact angle tests, and swelling ratio analysis. Field emission scanning electron microscopy analysis of the synthesized MMMs established the homogeneous dispersion of the fillers in the polymer matrix. Owing to its good compatibility with PVA/PEG matrix, the inclusion of fillers significantly increased the overall separation efficiency of CO₂ within the membrane. Compared to pristine PVA/PEG membrane, PVA/PEG/silica membrane with 3.34 wt % silica loading showed pronounced improvement in its gas separation properties with 78% augmentation in CO₂ permeability and 45% enhancement in CO₂/N₂ selectivity for fixed conditions pertaining to sweep side water flow rate of 0.04 mL/min and 100 °C temperature. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46481.     

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.     

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.     

Changes in free volume and gas permeation properties of poly(vinyl alcohol) nanocomposite membranes modified using cage-structured polyhedral oligomeric silsesquioxane

The present work reports the effect of various organically functionalized polyhedral oligomeric silsesquioxane (POSS) particles on the gas transport properties (N₂, O₂, and CO₂ molecules) in poly(vinyl alcohol) (PVA) membranes. The incorporation of polyethylene glycol-POSS (PEG-POSS), octa-tetramethylammonium-POSS (Octa-TMA-POSS) and m-POSS (Octa-TMA-POSS molecule was modified using cetyltrimethyl ammonium bromide) led to the enhancement in CO₂ separation performance of PVA, among which, PEG-POSS exhibited highest CO₂ separation due to the dipole-quadrupolar interaction of CO₂ with ethylene oxide group in POSS. Octa-TMA-POSS and m-POSS reduced the O₂ and N₂ permeability of the PVA membrane due to the reduction in the number of permeating pathways as compared to pure PVA. Free volume of the membranes was evaluated by positron annihilation lifetime spectroscopic (PALS) and coincidence Doppler broadening measurements. PALS confirms the increase in polymer free volume in PVA/POSS system due to the presence of rigid and spherical POSS molecule, which could enter in the polymer chain and provide viable pathway for molecular transport. Maxwel–Wagner–Sillar and Higuchi models were applied for the theoretical prediction of permeability of the fabricated membranes.     

Preparation and characterization of CO2-selective Pebax/NaY mixed matrix membranes

CO₂-selective Pebax/NaY mixed matrix membranes (MMMs) were prepared by incorporating NaY zeolite into Pebax matrix. The morphology, chemical groups, thermal stability, and microstructure of the MMMs were investigated by scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction, respectively. The effects of zeolite loading amount, permeation temperature and pressure on the CO₂/N₂ separation performance of the resultant membranes were studied. The as-prepared MMMs are much superior to the pristine Pebax membranes in terms of permeability and selectivity. The CO₂ permeability and CO₂/N₂ selectivity can respectively reach to 131.8 Barrer and 130.8 for MMMs made by the starting materials containing 40 wt % NaY. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48398.     

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     

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.     

The morphology and gas‐separation performance of membranes comprising multiwalled carbon nanotubes/polysulfone–Kapton

The development of desirable chemical structures and properties in nanocomposite membranes involve steps that need to be carefully designed and controlled. This study investigates the effect of adding multiwalled nanotubes (MWNT) on a Kapton–polysulfone composite membrane on the separation of various gas pairs. Data from Fourier transform infrared spectroscopy and scanning electron microscopy confirm that some studies on the Kapton–polysulfone blends are miscible on the molecular level. In fact, the results indicate that the chemical structure of the blend components, the Kapton–polysulfone blend compositions, and the carbon nanotubes play important roles in the transport properties of the resulting membranes. The results of gas permeability tests for the synthesized membranes specify that using a higher percentage of polysulfone (PSF) in blends resulted in membranes with higher ideal selectivity and permeability. Although the addition of nanotubes can increase the permeability of gases, it decreases gas pair selectivity. Furthermore, these outcomes suggest that Kapton–PSF membranes with higher PSF are special candidates for CO₂/CH₄ separation compared to CO₂/N₂ and O₂/N₂ separation. High CH₄, CO₂, N₂, and O₂ permeabilities of 0.35, 6.2, 0.34, and 1.15 bar, respectively, are obtained for the developed Kapton–PSF membranes (25/75%) with the highest percentage of carbon nanotubes (8%), whose values are the highest among all the resultant membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43839.     

Facile CO2 Separation in Composite Membranes

CO₂ emission from anthropogenic sources has raised worldwide environmental concerns and hence proficient energy paradigm has tilted towards CO₂ capture. Membrane technology is one of the efficient technologies for CO₂ separation since it is environmentally friendly, inexpensive, and offers high surface areas. Various approaches are discussed to improve membrane performance focusing mainly on permeability and selectivity parameters. Different types of fillers are incorporated to reach the Robeson's upper bound curve. In this review, polymer‐inorganic nanocomposite membranes for the separation of CO₂, CH₄, and N₂ from various gas mixtures are comprehensively discussed. Metal organic frameworks (MOFs) and ionic liquid (ILs) mixed‐matrix membranes are also considered.     

Phosphorylated nanocellulose fibrils/PVA nanocomposite membranes for biogas upgrading at higher pressure

ABSTRACT

High moisture uptake and excellent mechanical properties of cellulose nano-fibril (CNF) make it an interesting material to use as an additive in facilitated transport membranes. The objective of this work is to develop novel phosphorylated nanocellulose fibrils (PCNF)/polyvinyl alcohol (PVA) nanocomposite membranes for biogas upgrading. Results showed that the thickness of membrane increases with increasing concentration of PCNF. The addition of PCNF to pristine PVA membranes has beneficial effect for CO₂/CH₄ separation. However, maximum performance was achieved with 1 wt.% PCNF in 2% PVA at pH 12. Furthermore, increasing feed pressure caused a decrease in both permeability and selectivity.     

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     

Development of CO2-Philic Blended Membranes Using PIM–PI and PIM–PEG/PPG

Blending is a simple method through which one can effectively tailor new polymers exhibiting the properties of their parent ones. Because the original properties of polymers are maintained after blending, various studies have used these films as gas separation membranes. In this study, a new CO₂ separation membrane is developed by physically mixing a polymer of intrinsic microporosity (PIM) with high gas permeability, polyimide (PIM-PI), as the hard segment and CO₂-philic PIM-poly(ethylene glycol)/poly(propylene glycol), or PIM-PEG/PPG, as the soft segment. Prepared by adding 5 mol.% of PIM-PEG/PPG to PIM-PI, the blended membrane PPB-5, with a tensile strength of 54 MPa and 35.5% elongation at break, shows better mechanical properties than commercial high-performance polymer membranes developed for gas separation, PEG-based blended membranes, and corresponding copolymer membranes with similar compositions developed in a previous study. In addition, it shows high CO₂ permeability (1552.6 Barrer) and CO₂/N₂ selectivity (29.3) due to the well-developed microphase separation characteristics originating from the optimal two-component composition, and the gas separation performance is close to the Robeson (2008) upper bound.     

Mixed matrix metal–organic framework membranes for efficient CO2/N2 separation under humid conditions

Mixed matrix metal–organic framework (MOF) membranes show excellent application prospects in gas separation. However, their stability in various practical application scenarios is poor, especially under humid conditions. Herein, we encapsulated a hydrophobic ionic liquid (IL) into the cavity of MOFs, which effectively mitigated the competition between H₂O and CO₂ in humid gas mixtures, leading to stable and high-performance gas separation. For this reason, the resulting membranes using polymer of intrinsic miroporosity-1 (PIM-1) as a polymer matrix show good CO₂/N₂ separation performance and long-term test stability under humid environment. In particular, the 20 wt% IL-UiO/PIM-1 shows a high permeability of 13,778 Barrer and competitive CO₂/N₂ separation factor of ~35.2, transcending the latest upper bound. Besides, the according membrane module exhibits slightly decreased CO₂ permeability and selectivity, promoting the application of self-supporting membranes. This work provides a reliable strategy for the rational design of MOF-based hybrid membranes under extreme conditions.     

Polyurethane/polyethersulfone dual-layer anisotropic membranes for CO2 removal from flue gas

Removing CO₂ from flue gas streams has been a permanent challenge regarding environmental issues. Membrane technology is a solution for this problem but more efficient membranes are required. The fabrication of dual-layer polyurethane/polyethersulfone membrane by the co-casting technique is undertaken and the effects of previous evaporation time and coagulation water bath temperature on membrane morphology are explored. Uniform layers with excellent adhesion are obtained. The effect of feed pressure and temperature on membrane permeability and selectivity for CO₂, N₂, and O₂ are studied. Increasing the pressure from 1 to 8 bar results in a reduction of CO₂ permeability and CO₂/N₂ ideal selectivity from 19.6 to 13.0 barrer, and from 66 to 60, respectively. Temperature in the range of 25–45°C enhances CO₂ permeability from 19.6 to 28.9 barrer, although CO₂/N₂ selectivity decreases from 66 to 43, yet showing good potential for applications.     

Size effects of graphene oxide on mixed matrix membranes for CO2 separation

Graphene oxide (GO)‐polyether block amide (PEBA) mixed matrix membranes were fabricated and the effects of GO lateral size on membranes morphologies, microstructures, physicochemical properties, and gas separation performances were systematically investigated. By varying the GO lateral sizes (100–200 nm, 1–2 μm, and 5–10 μm), the polymer chains mobility, as well as the length of the gas channels could be effectively manipulated. Among the as‐prepared membranes, a GO‐PEBA mixed matrix membrane (GO‐M‐PEBA) containing 0.1 wt % medium‐lateral sized (1–2 μm) GO sheets showed the highest CO₂ permeation performance (CO₂ permeability of 110 Barrer and CO₂/N₂ mixed gas selectivity of 80), which transcends the Robeson upper bound. Also, this GO‐PEBA mixed matrix membrane exhibited high stability during long‐term operation testing. Optimized by GO lateral size, the developed GO‐PEBA mixed matrix membrane shows promising potential for industrial implementation of efficient CO₂ capture. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2843–2852, 2016     

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.     

Preparation of poly(acrylic acid)/poly(vinyl alcohol) membrane for the facilitated transport of CO2

Poly(acrylic acid) (PAA)/poly(vinyl alcohol) (PVA) membrane was prepared for the facilitated transport of CO₂. The carrier of CO₂ was monoprotonated ethylenediamine and was introduced in the membrane by ion exchange. The ion‐exchange capacity of the membrane was 4.5 meq/g, which was much higher than that of the Nafion 117 membrane. The membrane was highly swollen by the aqueous solution. Much higher selectivity of CO₂ over N₂ and higher CO₂ permeability were obtained in the PAA/PVA membrane than in the Nafion membrane because of the higher ion‐exchange capacity and solvent content. The highest selectivity was more than 1900 when the CO₂ partial pressure in the feed gas was 0.061 atm. Effects of ion‐exchange capacity, membrane thickness, and annealing temperature in conditions of membrane preparation on membrane performance were investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 936–942, 2001     

Separability of SO2 from SO2/N2 mixture through sulfoxide-modified poly(vinyl alcohol) and cellulose membranes

Separability of SO₂ from mixtures of SO₂ and N₂ gases was studied for membranes of poly(vinyl alcohol) (PVA) and cellulose modified with methyl, ethyl, t-butyl, and phenyl vinyl sulfoxides. Of these sulfoxide-modified polymers, the phenyl vinyl sulfoxide-modified PVA membranes were found to give the best separation of SO₂. In the phenyl vinyl sulfoxide modified PVA membranes, the permeability coefficient of SO₂ increased with sulfoxide content while separability of SO₂ was maximum at a sulfoxide content of 23.5 mol %; the separation factor of SO₂ was about 170 at this sulfoxide content. © 1993 John Wiley & Sons, Inc.     

CO2-facilitated transport membranes prepared by blending polyvinyl alcohol and various water-absorbing agents

This study describes the production of a membrane by blending polyvinyl alcohol (PVA) and water-absorbing agents for the selective permeation of CO₂ by optimizing the type of water-absorbing agent and its ratio to PVA. A CO₂-facilitated transport membrane is prepared by adding an aqueous cesium carbonate solution to a coated polymer blend matrix. When sodium polyacrylate (PAANa) is blended with PVA as a water-absorbing agent, the resulting membrane shows promising heat and pressure resistances and a relatively high CO₂/He separation performance. Particularly, the CO₂/He selectivity of the membrane composed of PVA, PAANa, and another water-absorbing agent exceeds 400 under a total pressure of 0.1 MPa and a CO₂ partial pressure of 0.08 MPa at 85°C. Moreover, the CO₂/He selectivity is approximately 100 even under a total pressure of 0.7 MPa and a CO₂ partial pressure of 0.56 MPa. Thus, a high-performance CO₂ separation membrane at 85°C is produced.