Solubility-based gas separation with oligomer-modified inorganic membranes Part II. Mixed gas permeation of 5 nm alumina membranes modified with octadecyltrichlorosilane

Membrane technology can play a very influential role in the separation of the constituents of HFC refrigerant gas mixtures, which usually exhibit azeotropic or near-azeotropic behavior, with the goal of promoting the reuse of value-added compounds in the manufacture of new low-global warming potential (GWP) refrigerant mixtures that abide by the current F-gases regulations. In this context, the selective recovery of difluorometane (R32, GWP = 677) from the commercial blend R410A (GWP = 1924), an equimass mixture of R32 and pentafluoroethane (R125, GWP = 3170), is sought. To that end, this work explores for the first time the separation performance of novel mixed-matrix membranes (MMMs) functionalized with ioNanofluids (IoNFs) consisting in a stable suspension of exfoliated graphene nanoplatelets (xGnP) into a fluorinated ionic liquid (FIL), 1-ethyl-3-methylpyridinium perfluorobutanesulfonate ([C2C1py][C4F9SO3]). The results show that the presence of IoNF in the MMMs significantly enhances gas permeation, yet at the expense of slightly decreasing the selectivity of the base polymer. The best results were obtained with the MMM containing 40 wt% IoNF, which led to an improved permeability of the gas of interest (PR32 = 496 barrer) with respect to that of the neat polymer (PR32 = 279 barrer) with a mixed-gas separation factor of 3.0 at the highest feed R410A pressure tested. Overall, the newly fabricated IoNF-MMMs allowed the separation of the near-azeotropic R410A mixture to recover the low-GWP R32 gas, which is of great interest for the circular economy of the refrigeration sector.

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Pentiptycene-based ladder polymers with configurational free volume for enhanced gas separation performance and physical aging resistance

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2022204118 ◽

2021 ◽

Vol 118 (37) ◽

pp. e2022204118

Author(s):

Tanner J. Corrado ◽

Zihan Huang ◽

Dezhao Huang ◽

Noah Wamble ◽

Tengfei Luo ◽

...

Keyword(s):

Free Volume ◽

Gas Separation ◽

Physical Aging ◽

Gas Permeation ◽

Separation Performance ◽

Structure Property ◽

Mixed Gas ◽

Initial Separation ◽

Primary Advantage ◽

Polymers Of Intrinsic Microporosity

Polymers of intrinsic microporosity (PIMs) have shown promise in pushing the limits of gas separation membranes, recently redefining upper bounds for a variety of gas pair separations. However, many of these membranes still suffer from reductions in permeability over time, removing the primary advantage of this class of polymer. In this work, a series of pentiptycene-based PIMs incorporated into copolymers with PIM-1 are examined to identify fundamental structure–property relationships between the configuration of the pentiptycene backbone and its accompanying linear or branched substituent group. The incorporation of pentiptycene provides a route to instill a more permanent, configuration-based free volume, resistant to physical aging via traditional collapse of conformation-based free volume. PPIM-ip-C and PPIM-np-S, copolymers with C- and S-shape backbones and branched isopropoxy and linear n-propoxy substituent groups, respectively, each exhibited initial separation performance enhancements relative to PIM-1. Additionally, aging-enhanced gas permeabilities were observed, a stark departure from the typical permeability losses pure PIM-1 experiences with aging. Mixed-gas separation data showed enhanced CO2/CH4 selectivity relative to the pure-gas permeation results, with only ∼20% decreases in selectivity when moving from a CO2 partial pressure of ∼2.4 to ∼7.1 atm (atmospheric pressure) when utilizing a mixed-gas CO2/CH4 feed stream. These results highlight the potential of pentiptycene’s intrinsic, configurational free volume for simultaneously delivering size-sieving above the 2008 upper bound, along with exceptional resistance to physical aging that often plagues high free volume PIMs.

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Mixed gas separation technology using inorganic membranes

Membrane Technology ◽

10.1016/s0958-2118(00)88586-9 ◽

2000 ◽

Vol 2000 (120) ◽

pp. 9-13 ◽

Cited By ~ 4

Author(s):

Douglas E. Fain

Keyword(s):

Gas Separation ◽

Inorganic Membranes ◽

Mixed Gas ◽

Separation Technology

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A Molecular Simulation Study of Silica/Polysulfone Mixed Matrix Membrane for Mixed Gas Separation

Polymers ◽

10.3390/polym13132199 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2199

Author(s):

Khadija Asif ◽

Serene Sow Mun Lock ◽

Syed Ali Ammar Taqvi ◽

Norwahyu Jusoh ◽

Chung Loong Yiin ◽

...

Keyword(s):

Transport Properties ◽

Molecular Simulation ◽

Gas Separation ◽

Membrane Separation ◽

Gas Transport ◽

Mixed Matrix ◽

Mixed Gas ◽

Gas Transport Properties ◽

Simulation Results ◽

Mixed Gases

Polysulfone-based mixed matrix membranes (MMMs) incorporated with silica nanoparticles are a new generation material under ongoing research and development for gas separation. However, the attributes of a better-performing MMM cannot be precisely studied under experimental conditions. Thus, it requires an atomistic scale study to elucidate the separation performance of silica/polysulfone MMMs. As most of the research work and empirical models for gas transport properties have been limited to pure gas, a computational framework for molecular simulation is required to study the mixed gas transport properties in silica/polysulfone MMMs to reflect real membrane separation. In this work, Monte Carlo (MC) and molecular dynamics (MD) simulations were employed to study the solubility and diffusivity of CO2/CH4 with varying gas concentrations (i.e., 30% CO2/CH4, 50% CO2/CH4, and 70% CO2/CH4) and silica content (i.e., 15–30 wt.%). The accuracy of the simulated structures was validated with published literature, followed by the study of the gas transport properties at 308.15 K and 1 atm. Simulation results concluded an increase in the free volume with an increasing weight percentage of silica. It was also found that pure gas consistently exhibited higher gas transport properties when compared to mixed gas conditions. The results also showed a competitive gas transport performance for mixed gases, which is more apparent when CO2 increases. In this context, an increment in the permeation was observed for mixed gas with increasing gas concentrations (i.e., 70% CO2/CH4 > 50% CO2/CH4 > 30% CO2/CH4). The diffusivity, solubility, and permeability of the mixed gases were consistently increasing until 25 wt.%, followed by a decrease for 30 wt.% of silica. An empirical model based on a parallel resistance approach was developed by incorporating mathematical formulations for solubility and permeability. The model results were compared with simulation results to quantify the effect of mixed gas transport, which showed an 18% and 15% percentage error for the permeability and solubility, respectively, in comparison to the simulation data. This study provides a basis for future understanding of MMMs using molecular simulations and modeling techniques for mixed gas conditions that demonstrate real membrane separation.

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Optical, thermal and gas separation properties of acetate-containing copoly(ether-imide)s based on 6FDA and fluorenyl diamines

High Performance Polymers ◽

10.1177/0954008318822118 ◽

2019 ◽

Vol 31 (9-10) ◽

pp. 1101-1111 ◽

Cited By ~ 2

Author(s):

Yunhua Lu ◽

Jican Hao ◽

Guoyong Xiao ◽

Lin Li ◽

Zhizhi Hu ◽

...

Keyword(s):

Gas Separation ◽

Gas Permeation ◽

Light Transmittance ◽

Step Method ◽

Ether Linkage ◽

Nuclear Magnetic Resonance Spectrometer ◽

Thermogravimetric Analyzer ◽

Structures And Properties ◽

Infrared Spectrometer ◽

The Ideal

The diamine, 9,9-bis[4-(4-amino-3-hydroxylphenoxy)phenyl]fluorene (BAHPPF) was synthesized by the modified two-step method. Then, a series of acetate-containing copoly(ether-imide)s were prepared by the copolymerization of BAHPPF, 9,9-bis(4-aminophenyl)fluorene (BAF) and 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) followed by chemical imidization. The structures and properties of the BAHPPF and copoly(ether-imide)s were characterized by nuclear magnetic resonance spectrometer (NMR), Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), ultraviolet-visible spectrophotometer (UV-VIS), and tensile testing. Single gas permeation performances of these copoly(ether-imide)s were also studied for five representative gases of interest including H2, O2, N2, CO2, and CH4. The experimental results showed that the copoly(ether-imide)s showed excellent optical properties with high light transmittance above 80.2% at 450 nm. The glass transition temperature of these copolymers were higher than 333°C. Their tensile strength and Young’s module also increased, and the elongation decreased with the decrease of BAHPPF. High gas permeabilities of copoly(ether-imide)s were obtained, and the ideal selectivity of CO2/CH4 was improved due to the introduction of acetate group and flexible ether linkage. These copoly(ether-imide)s could be applied to the field of optics and gas separation.

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Maxwell–Stefan modeling of slowing-down effects in mixed gas permeation across porous membranes

Journal of Membrane Science ◽

10.1016/j.memsci.2011.08.067 ◽

2011 ◽

Vol 383 (1-2) ◽

pp. 289-300 ◽

Cited By ~ 55

Author(s):

Rajamani Krishna ◽

Jasper M. van Baten

Keyword(s):

Gas Permeation ◽

Porous Membranes ◽

Mixed Gas ◽

Slowing Down

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Gas Permeation Characteristics across Nano-Porous Inorganic Membranes

IIUM Engineering Journal ◽

10.31436/iiumej.v5i2.379 ◽

1970 ◽

Vol 5 (2) ◽

Cited By ~ 3

Author(s):

M.R Othman, H. Mukhtar ◽

A.L. Ahmad

Keyword(s):

Pore Size ◽

Membrane Surface ◽

Porous Ceramic ◽

Knudsen Diffusion ◽

Gas Permeation ◽

Physical Characteristics ◽

Inorganic Membrane ◽

Molecular Characteristics ◽

Inorganic Membranes ◽

Operational Parameters

An overview of parameters affecting gas permeation in inorganic membranes is presented. These factors include membrane physical characteristics, operational parameters and gas molecular characteristics. The membrane physical characteristics include membrane materials and surface area, porosity, pore size and pore size distribution and membrane morphology. The operational parameters include feed flow rate and concentration, stage cut, temperature and pressure. The gas molecular characteristics include gas molecular weight, diameter, critical temperature, critical pressure, Lennard-Jones parameters and diffusion volumes. The current techniques of material characterization may require complementary method in describing microscopic heterogeneity of the porous ceramic media. The method to be incorporated in the future will be to apply a stochastic model and/or fractal dimension. Keywords: Inorganic membrane, surface adsorption, Knudsen diffusion, Micro-porous membrane, permeation, gas separation.

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