Gas Permeation Properties Research Articles

Methoxy poly (ethylene glycol) methacrylate-TiO2/poly (methyl methacrylate) nanocomposite: an efficient membrane for gas separation

ABSTRACTPolymer/nanoparticle mixed matrix membranes (MMMs) is one of the most important topics in gas separation field. In this study, to improve gas separation efficiency, methoxy poly(ethylene glycol) methacrylate (MPEG) was grafted on TiO2 surface and was used for synthesis of poly (methyl methacrylate) (PMMA) MMMs. Gas permeation and separation properties of PMMA/PMPEG-TiO2 MMMs were studied for CO2, CH4, O2, and N2 gases. The results showed that the MMM filled with 5 wt% PMPEG-TiO2 nanoparticle exhibited optimal separation performance with CO2 permeability of 32.48 Barrer and CO2/N2 selectivity of 56.98, which are higher than pure polymer (2.75 Barrer and 36.71).

Poly(1-trimethylsilyl-1-propyne)-Based Hybrid Membranes: Effects of Various Nanofillers and Feed Gas Humidity on CO₂ Permeation.

Poly(1-trimethylsilyl-1-propyne) (PTMSP) is a high free volume polymer with exceptionally high gas permeation rate but the serious aging problem and low selectivity have limited its application as CO2 separation membrane material. Incorporating inorganic nanoparticles in polymeric membranes has been a common approach to improve the separation performance of membranes, which has also been used in PTMSP based membrane but mostly with respect to tackling the aging issues. Aiming at increasing the CO2 selectivity, in this work, hybrid membranes containing four types of selected nanofillers (from 0 to 3D) were fabricated using PTMSP as the polymer matrix. The effects of the various types of nanofillers on the CO2 separation performance of the resultant membranes were systematically investigated in humid conditions. The thermal, chemical and morphologic properties of the hybrid membranes were characterized using TGA, FTIR and SEM. The gas permeation properties of the hybrid membranes were evaluated using mixed gas permeation test with the presence of water vapour to simulate the flue gas conditions. Experiments show that the addition of different fillers results in significantly different separation performances; The addition of ZIF-L porous 2D filler improves the CO2/N2 selectivity at the expenses of CO2 permeability, while the addition of TiO2, ZIF-7 and ZIF-8 increases the CO2 permeability but the CO2/N2 selectivity decreases.

Effect of heating rates on the microstructure and gas permeation properties of carbon membranes

High performance tubular carbon membrane (TCM’s) for CO2 separation were prepared by controlling the carbonization heating rates in range of 1-7 oC/min carbonized at 800 oC under Argon environment. A single permeation apparatus was used to determine the gas permeation properties of the membrane at room temperature. Fine turning of the carbonization condition was necessary to obtain the desired permeation properties. The preparation of PI/NCC-based TCM at low heating rate caused the gas permeance for the examined gas N2 and CO2 decreased whereas the selectivity of CO2/N2 increased. It was also identified that the gas permeation properties of the resultant TCM and its structure was highly affected by the heating rate. The best carbonization heating rate was found at 3oC/min for the fabrication of TCM derived via polymer blending of PI/NCC for CO2/N2 separation.

Synthesis and Gas Permeation Properties of STT-type Zeolite Membranes

Synthesis and Gas Permeation Properties of STT-type Zeolite Membranes

Exploiting pyrolysis protocols on BTDA‐TDI/MDI (P84) polyimide/nanocrystalline cellulose carbon membrane for gas separations

ABSTRACTTubular carbon membranes were fabricated by the blending of BTDA‐TDI/MDI (P84) polyimide with nanocrystalline cellulose in a controlled pyrolysis process, specifically the pyrolysis environment (He, Ar, and N2) and the thermal soak time (30–120 min). The carbon membrane layer on a tubular support is converted to carbon matrix at 800 °C with a heating rate of 3 °C min−1. The effects of these controlled pyrolysis conditions on the gas permeation properties have been investigated. The results revealed that the pyrolysis under Ar gas environment at 120 min of thermal soak time have the best gas permeation performance with the highest CO2/CH4 selectivity of 68.2 ± 3.3 and CO2 permeance of 213.6 ± 2.2 GPU. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46901.

Gas Permeation and Hemocompatibility of Novel Perfluorinated Polymers for Blood Oxygenation

Gas permeation properties of three highly permeable perfluorinated polymers (polyhexafluoropropylene (PHFP), amorphous Teflon AF2400, and polyperfluoro(2-methyl-2-ethyl-dioxole-1,3) (PPFMED)), which are promising materials for the dense thin layer of hollow fiber membranes for extracorporeal membrane oxygenation have been studied using nitrogen, oxygen, and carbon dioxide. Hemocompatibility of the polymeric films has also been investigated on whole blood from healthy donors. Gas permeation of the polymers increases in the order PHFP PPFMED > AF2400, with the most permeable polymer AF2400 exhibiting the worst hemocompatibility among the other polymers studied. Polyperfluoro(2-methyl-2-ethyl-dioxole-1,3) is shown to be the most appropriate polymer to fabricate hollow fiber membranes for blood oxygenation.

Gas transport and mechanical properties of PDMS-TFS/LDPE nanocomposite membranes

This study investigates the effect of trimethylsiloxy fumed silica (TFS) on the mechanical and gas permeation properties of polymer nano-composite membranes. The membranes were produced by coating TFS incorporated polydimethylsiloxane (PDMS) at different loadings (5, 10 and 15 wt.%) on a porous low density polyethylene (LDPE) substrate which was formed by a melt-extrusion/salt leaching technique. The PDMS-TFS/LDPE membranes were characterized by SEM, TGA and DMTA. The results showed that good affinity between the PDMS treated TFS particles and PDMS matrix was obtained leading to improved mechanical and thermal properties. For gas permeation, CH4 and C3H8 at different upstream pressure (50 to 80 psig) and temperature (27 to 55 °C) were investigated. The results showed that the C3H8/CH4 ideal selectivity (17.6) and C3H8 permeability (1.89 × 104 Barrer) through 10 wt.% TFS loaded membranes (PDMS-TFS10%/LDPE) were 41 and 14% higher than the neat membranes (PDMS-TFS0%/LDPE), respectively. The permeation results also indicate that the performance stability under the conditions investigated makes PDMS-TFS/LDPE membranes interesting for industrial applications.

Novel semi-alicyclic polyimide membranes: Synthesis, characterization, and gas separation properties

To develop membrane materials for gas separation, a series of semi-alicyclic polyimides was synthesized using one-step thermal solution imidization from an alicyclic dianhydride with non-planar twisted structure, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA). All synthesized polyimides exhibited amorphous structures and superior thermal stability, with high glass transition temperatures (242–288 °C) withstanding high operation temperature and pressure. They also showed excellent solubility in many polar organic solvents commonly used in the fabrication of gas separation membranes. The gas permeation properties of the polyimide membranes were measured for six representative gases (H2, CO2, O2, CO, N2, and CH4). The gas permeabilities and selectivities of polyimide membranes were significantly influenced by the chemical structure of the diamines, which could be explained reasonably by the kinetic diameter of gases, the fractional free volumes, and d-spacing values of the polyimides. Two DOCDA-based polyimides showed very high selectivities for H2/CH4 and CO2/CH4 and slightly low permeabilities for H2 and CO2, which performances were comparable to the commercial polyimide materials such as P84® and Matrimid® used in gas separation field.

Experimental and modeling investigations towards tailoring cellulose triacetate membranes for high performance helium separation

In this study, novel membranes are designed and fabricated using CTA as the main matrix with contributions of PEG and as-synthesized ZIF-8 nanoparticles. Gas permeation properties of blend membranes containing 25–45wt.% PEG and MMMs containing 2–20wt.% ZIF-8 crystals are evaluated for the separation of He from N2 and CH4 at various temperatures and pressures. The properties of synthesized ZIF-8 nanoparticles as well as membranes are well characterized. Among all the prepared membranes, the MMMs membrane with composition of CTA/PEG/ZIF-8 (60/20/20wt.%) exhibits the best performance (PH2=73.25 Barrer) for He/N2 (α=43) and He/CH4 (α=40) separations. In addition, various predictive permeation models are investigated in order to gain more insights about the systems and for validation of the experimental results. The %AAREs of the models are high, while the best value is obtained by applying the Maxwell model (5.98). Also, by choosing Lewis–Nielsen model and taking into account some of the non-ideal effects such as particle pore blockage, polymer chains rigidification as well as the effect of particles size on the rigidified layer thickness, a new while accurate model is proposed. Finally, the accuracy of the newly developed model is examined utilizing several experimental data.

Preparation and characterization of graphene oxide as a candidate filler material for the preparation of mixed matrix polyimide membranes

In this study three polyimide-based flat sheet membranes were prepared, characterized and investigated regarding gas permeability properties. For the membranes' preparation Matrimid® 5218 was used as polymer matrix whereas graphene oxide (GO) was used as filler material. The thickness of the membranes ranged from 40 to 300 μm. The size of the GO material varied from 200 to 500 nm in length, according to the TEM images. Furthermore, the structural characteristics of the GO fillers were investigated by using N2 adsorption at 77 K, X-ray diffraction (XRD), small angle X-ray scattering (SAXS), Raman spectroscopy and scanning electron microscopy (SEM). The three prepared membranes were also characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and gas permeability measurements at ambient temperature. The findings led to the possible explanation regarding the GO nanoflakes' anchoring which seems to be strongly dependent on the preparation method.

Design, synthesis, and gas permeation properties of polyimides containing pendent imidazolium groups

ABSTRACTFilm‐forming polymers containing ionic groups have attracted considerable attention as emerging materials for gas separation applications. The aim of this article was to synthesize new film‐forming polyimides containing imidazolium groups (PI‐IMs) and establish their structure–performance relationship. In this context, a new aromatic diamine, namely, N1‐(4‐aminophenyl)‐N1‐(4‐(2‐phenyl‐1H‐imidazol‐1‐yl)phenyl)benzene‐1,4‐diamine (ImTPADA), was synthesized and polycondensed with three aromatic dianhydrides, namely, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, 4,4‐(4,4‐isopropylidenediphenoxy) bis(phthalic anhydride), and 4,4′‐oxydiphthalic anhydride to form the corresponding polyimides containing pendent 2‐phenylimidazole groups (PI‐IEs). Next, PI‐IMs were prepared by N‐quaternization of pendent 2‐phenylimidazole groups present in PI‐6FDA using methyl iodide followed by anion exchange with bis(trifluoromethane)sulfonimide lithium salt (LiTf2N). PI‐IEs and PI‐IMs exhibited reasonably high molecular weights, amorphous nature, good solubility, and could be cast into self‐standing films from their DMAc solutions. Thermogravimetric analysis showed that 10% weight loss temperature of PI‐IEs and PI‐IMs were in the range 545–475 °C and 303–306 °C, respectively. Gas permeability analysis of films of PI‐IEs and PI‐IMs was investigated by variable‐volume method and it was observed that incorporation of ionic groups into PI‐6FDA resulted in increased permeability while maintaining selectivity. In particular, polymer bearing Tf2N− anion exhibited high CO2 permeability (33.3 Barr) and high selectivity for CO2/CH4 (41.1) and CO2/N2 (35.4). © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1721–1729

Gas Separation Membrane Composed of Polyimide and Surface-modified Nanoparticles: Influence of Surface-modification Structures on Gas Permeation Properties

Gas Separation Membrane Composed of Polyimide and Surface-modified Nanoparticles: Influence of Surface-modification Structures on Gas Permeation Properties

Gas permeability of Ti6Al4V foams prepared via gelcasting, experiments and modelling

The use of light components possessing tailored functional properties will represent one of the main issues for the development of new products. Open cells foams, where porosity is engineered in order to grant for lightness, high geometrical surface, interconnectivity and permeability, can be shaped using various techniques and possess regular or irregular structure. In this work, Ti6Al4V foams were produced using the gelcasting route, a technique usually employed for ceramics. Numerical simulations were carried out directly on 3D images of the foam’s microstructure obtained by X-ray 3D µCT in order to predict the gas permeability properties of the produced samples. The obtained results were compared to experimental measurements of gas permeability. This approach could be useful for the prediction of Newtonian fluids permeability behavior of non-periodic and complex porous structures.

Diethylenedioxane-bridged microporous organosilica membrane for gas and water separation

Abstract A new dioxane-bridged alkoxysilane, 2,5-bis[2-(triethoxysilyl)ethyl]-1,4-dioxane (BTES-ED), was synthesized as a precursor of organically bridged silica membrane to investigate the effects of the 1,4-dioxane ring as a rigid and polar spacer. The monomer was polymerized by the sol-gel process to give the gels in film, powder, and membrane forms. Nitrogen adsorption measurement of the gel powder showed the type-I adsorption/desorption isotherm, suggesting that the gel possessed a microporous structure with pore size distribution ranging from approximately 0.8 to 1.6 nm. Reflecting microporosity, the membrane exhibited selective gas permeation properties (H2/SF6 permeance ratio = ca. 1900) based on molecular sieving effects. Reverse osmosis experiments were conducted using a 2000 ppm NaCl aqueous solution at an operation pressure of 1.0 MPa, revealing water desalination properties with the water permeance of 1.84 × 10−13 m3/m2·s·Pa and the NaCl rejection of 98.5%. These results are discussed in comparison with the results of other bridged silica membranes reported previously. The 2,5-diethylene-1,4-dioxane bridging unit is rigid and polar, thereby contributing to improving gas and water separation performance.

Mixed Matrix Membranes Based on Metal–Organic Frameworks with Tunable Pore Size for CO2 Separation

Two isomorphous MOFs (Ni2(l-asp)2bipy and Ni2(l-asp)2pz) with different pore sizes were incorporated into poly(ether-block-amide) (Pebax-1657) to prepare the mixed matrix membranes (MMMs) with gas permeation properties for CO2, H2, N2, and CH4. Different loading ratios of MOFs with mass percentage from 10% to 30% were studied. Compared with the pure polymer membrane, the as-synthesized two series of MMMs showed improved CO2 permeability and CO2/H2 selectivity. The highest CO2 permeation property was achieved by Ni2(l-asp)2bipy@Pebax-20 of 120.2 barrers with an enhanced CO2/H2 selectivity of 32.88 compared with 55.85 barrers and 1.729 of the pure polymer membrane, respectively, which makes it a potential candidate for future applications in CO2 capturing.

Tailoring a Thermally Stable Amorphous SiOC Structure for the Separation of Large Molecules: The Effect of Calcination Temperature on SiOC Structures and Gas Permeation Properties

A SiOC membrane with high oxidative stability for gas separation was tailored by utilizing vinyltrimethoxysilane, triethoxysilane, and 1,1,3,3-tetramethyldisiloxane as Si precursors. Amorphous SiOC networks were formed via the condensation of Si–OH groups, the hydrosilylation of Si–H and Si–CH=CH2 groups, and a crosslinking reaction of Si–CH3 groups, respectively. The crosslinking of Si–CH3 groups at temperatures ranging from 600 to 700 °C under a N2 atmosphere was quite effective in constructing a Si–CH2–Si unit without the formation of mesopores, which was confirmed by the results of N2 adsorption and by the gas permeation properties. The network pore size of the SiOC membrane calcined at 700 °C under N2 showed high oxidative stability at 500 °C and was appropriate for the separation of large molecules (H2/CF4 selectivity: 640, H2/SF6: 2900, N2/CF4: 98). A SiOC membrane calcined at 800 °C showed H2/N2 selectivity of 62, which was approximately 10 times higher than that calcined at 700 °C because the SiOC networks were densified by the cleavage and redistribution reactions of Si–C and Si–O groups.

Effect of substrate curvature on microstructure and gas permeability of hollow fiber MFI zeolite membranes

Literature data show that gas permeability of MFI zeolite membrane varies depending on the geometry of supports. The present work investigates the effects of the surface curvature of substrates on the microstructure and the gas permeation property of supported zeolite membranes. MFI zeolite membranes were grown on porous alumina hollow fibers with different diameters (surface curvature) by the secondary growth method. Single gas permeation and H2/CO2 binary gas separation from 25 to 300 were conducted to study the membrane quality. The zeolite membranes on supports of larger surface curvature have higher permeability and lower selectivity due to the presence of more inter‐crystalline gaps in the zeolite layer formed during the template removal step. The effects of the support surface curvature (and geometry) on zeolite membrane microstructure and gas permeation characteristics are semi‐quantitatively analyzed by a transport model considering both structural change and gas diffusion in micropores. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3419–3428, 2018

Effects of sub-Tg cross-linking of triptycene-based polyimides on gas permeation, plasticization resistance and physical aging properties

Two triptycene-based diamines, 2,6-diaminotriptycene and 2,6-diaminotriptycene- 14-carboxylic acid, were synthesized and reacted with 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) to form three polyimides, denoted as 6FDA-DAT, 6FDA-DAT/DATCA (9:1) and 6FDA-DAT/DATCA (8:2). The last two carboxylic acid containing polyimides were further heated at a temperature range of 200–450 °C to induce decarboxylation crosslinking. Properties including solubility, thermal stabilities, glass transition temperature (Tg), d-spacing, physical aging and gas permeation were measured. Since Tg of 6FDA-DAT/DATCA (9:1) and 6FDA-DAT/DATCA (8:2) were not observable at temperature up to 450 °C, all decarboxylation crosslinking reactions were carried out below their Tgs. Gas permeabilities of 6FDA-DAT/DATCA (9:1) and 6FDA-DAT/DATCA (8:2) increased with decreased selectivities after crosslinking. No plasticization were observed for crosslinked 6FDA-DAT/DATCA (9:1) and 6FDA-DAT/DATCA (8:2) at a CO2 pressure up to 30 atm for pure gas and a partial CO2 pressure up to 20 atm for (CO2:CH4 1:1) mixed gases. In addition, crosslinked polymers exhibited significantly reduced physical aging rate. Therefore, the sub-Tg decarboxylation crosslinked polyimides had great potential for natural gas separation.

Gas Permeation Properties, Physical Aging, and Its Mitigation in High Free Volume Glassy Polymers.

Hundreds of polymers have been evaluated as membrane materials for gas separations, but fewer than 10 have made it into current commercial applications, mainly due to the effects of physical aging and plasticization. Efforts to overcome these two problems are a significant focus in gas separation membrane research, in conjunction with improving membrane separation performance to surpass the Robeson upper bounds of selectivity versus permeability for commercially important gas pairs. While there has been extensive research, ranging from manipulating the chemistry of existing polymers (e.g., thermally rearranged or cross-linked polyimides) to synthesizing new polymers such as polymers of intrinsic microporosity (PIMs), there have been three major oversights that this review addresses: (1) the need to compare the approaches to achieving the best performance in order to identify their effectiveness in improving gas transport properties and in mitigating aging, (2) a common standardized aging protocol that allows rapid determination of the success (or not) of these approaches, and (3) standard techniques that can be used to characterize aging and plasticization across all studies to enable them to be robustly and equally compared. In this review, we also provide our perspectives on a few key aspects of research related to high free volume polymer membranes: (1) the importance of Robeson plots for membrane aging studies, (2) eliminating thermal history, (3) measurement and reporting of gas permeability and aging rate, (4) aging and storing conditions, and (5) promising approaches to mitigate aging.

Role of quaternary ammonium compound immobilized metallic graphene oxide in PMMA/PEG membrane for antibacterial, antifouling and selective gas permeability properties

Recently, there is a high demand for development of polymeric membrane for their widespread technological applications. Polymer blends incorporation with inorganic composite particles is the most effective strategy for obtaining antifouling, antibacterial, gas and water permeable membrane materials. However, their biological and surface properties are always hindered by the inefficient interaction of filler into polymer matrix because it is distributed into the bulk membrane matrix. In this study, graphene oxide nanosheets are incorporated with metal (Ag)/metal oxide (ZnO) composite filler (MGO) followed by surface modification with quaternary cetyltrimethylammonium bromide (CTAB) to enhance non-covalent interactions between filler and poly methyl methacrylate (PMMA)/polyethylene glycol (PEG) blend membrane. The membrane was utilized for improving antifouling, antibacterial and gas permeability of membrane. Our results indicated that CTAB-modified filler (CTAB@MGO) was bonded to the polymer blend membrane without affecting the membranes’ physicochemical properties. The prepared CTAB@MGO–PMMA/PEG membrane showed excellent antibacterial property against model Escherichia coli bacteria. The antifouling activity and CTAB stability results of modified blend membrane ensured reduced bovine serum albumin adsorption and slow dissociation of surfactant molecules, respectively. The CTAB@MGO–PMMA/PEG blend membrane also showed promising gas permeability results with hydrogen (H2), nitrogen (N2) and carbon dioxide (CO2). The presented approach highlights the potential of surface modification of filler and introduces them in polymeric membrane as a simple, easy and cost-effective strategy for preparing antifouling and gas/water permeable polymeric membranes.