scholarly journals Highly Permeable Matrimid®/PIM-EA(H2)-TB Blend Membrane for Gas Separation

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 46 ◽  
Author(s):  
Elisa Esposito ◽  
Irene Mazzei ◽  
Marcello Monteleone ◽  
Alessio Fuoco ◽  
Mariolino Carta ◽  
...  
Keyword(s):  
Diffusion Coefficients ◽  
Gas Transport ◽  
Gas Permeability ◽  
Time Lag ◽  
Gas Diffusion ◽  
Gas Permeation ◽  
Spectrometric Analysis ◽  
Competitive Sorption ◽  
Transport Parameters ◽  
Mixed Gas

The effect on the gas transport properties of Matrimid®5218 of blending with the polymer of intrinsic microporosity PIM-EA(H2)-TB was studied by pure and mixed gas permeation measurements. Membranes of the two neat polymers and their 50/50 wt % blend were prepared by solution casting from a dilute solution in dichloromethane. The pure gas permeability and diffusion coefficients of H2, He, O2, N2, CO2 and CH4 were determined by the time lag method in a traditional fixed volume gas permeation setup. Mixed gas permeability measurements with a 35/65 vol % CO2/CH4 mixture and a 15/85 vol % CO2/N2 mixture were performed on a novel variable volume setup with on-line mass spectrometric analysis of the permeate composition, with the unique feature that it is also able to determine the mixed gas diffusion coefficients. It was found that the permeability of Matrimid increased approximately 20-fold with the addition of 50 wt % PIM-EA(H2)-TB. Mixed gas permeation measurements showed a slightly stronger pressure dependence for selectivity of separation of the CO2/CH4 mixture as compared to the CO2/N2 mixture, particularly for both the blended membrane and the pure PIM. The mixed gas selectivity was slightly higher than for pure gases, and although N2 and CH4 diffusion coefficients strongly increase in the presence of CO2, their solubility is dramatically reduced as a result of competitive sorption. A full analysis is provided of the difference between the pure and mixed gas transport parameters of PIM-EA(H2)-TB, Matrimid®5218 and their 50:50 wt % blend, including unique mixed gas diffusion coefficients.

scholarly journals Gas Transport in Mixed Matrix Membranes: Two Methods for Time Lag Determination

Computation ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 28 ◽  
Author(s):  
Alessio Fuoco ◽  
Marcello Monteleone ◽  
Elisa Esposito ◽  
Rosaria Bruno ◽  
Jesús Ferrando-Soria ◽  
...  
Keyword(s):  
Transport Properties ◽  
Gas Transport ◽  
Time Lag ◽  
Effective Diffusion ◽  
Gas Permeation ◽  
Mixed Matrix Membranes ◽  
Mixed Matrix ◽  
Mixed Gas ◽  
Fitting Procedure ◽  
Matrix Membranes

The most widely used method to measure the transport properties of dense polymeric membranes is the time lag method in a constant volume/pressure increase instrument. Although simple and quick, this method provides only relatively superficial, averaged data of the permeability, diffusivity, and solubility of gas or vapor species in the membrane. The present manuscript discusses a more sophisticated computational method to determine the transport properties on the basis of a fit of the entire permeation curve, including the transient period. The traditional tangent method and the fitting procedure were compared for the transport of six light gases (H2, He, O2, N2, CH4, and CO2) and ethane and ethylene in mixed matrix membranes (MMM) based on Pebax®1657 and the metal–organic framework (MOF) CuII2(S,S)-hismox·5H2O. Deviations of the experimental data from the theoretical curve could be attributed to the particular MOF structure, with cavities of different sizes. The fitting procedure revealed two different effective diffusion coefficients for the same gas in the case of methane and ethylene, due to the unusual void morphology in the MOFs. The method was furthermore applied to mixed gas permeation in an innovative constant-pressure/variable-volume setup with continuous analysis of the permeate composition by an on-line mass-spectrometric residual gas analyzer. This method can provide the diffusion coefficient of individual gas species in a mixture, during mixed gas permeation experiments. Such information was previously inaccessible, and it will greatly enhance insight into the mixed gas transport in polymeric or mixed matrix membranes.

scholarly journals Experimental Mixed-Gas Permeability, Sorption and Diffusion of CO2-CH4 Mixtures in 6FDA-mPDA Polyimide Membrane: Unveiling the Effect of Competitive Sorption on Permeability Selectivity

Membranes ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 10 ◽  
Author(s):  
Giuseppe Genduso ◽  
Bader Ghanem ◽  
Ingo Pinnau
Keyword(s):  
Infinite Dilution ◽  
Gas Permeability ◽  
Diffusion Theory ◽  
Linear Trend ◽  
Effective Diffusion ◽  
Gas Diffusion ◽  
Competitive Sorption ◽  
Gas Solubility ◽  
Mixed Gas ◽  
Polyimide Membrane

The nonideal behavior of polymeric membranes during separation of gas mixtures can be quantified via the solution-diffusion theory from experimental mixed-gas solubility and permeability coefficients. In this study, CO2-CH4 mixtures were sorbed at 35 °C in 4,4′-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA)-m-phenylenediamine (mPDA)—a polyimide of remarkable performance. The existence of a linear trend for all data of mixed-gas CO2 versus CH4 solubility coefficients—regardless of mixture concentration—was observed for 6FDA-mPDA and other polymeric films; the slope of this trend was identified as the ratio of gas solubilities at infinite dilution. The CO2/CH4 mixed-gas solubility selectivity of 6FDA-mPDA and previously reported polymers was higher than the equimolar pure-gas value and increased with pressure from the infinite dilution value. The analysis of CO2-CH4 mixed-gas concentration-averaged effective diffusion coefficients of equimolar feeds showed that CO2 diffusivity was not affected by CH4. Our data indicate that the decrease of CO2/CH4 mixed-gas diffusion, and permeability selectivity from the pure-gas values, resulted from an increase in the methane diffusion coefficient in mixtures. This effect was the result of an alteration of the size sieving properties of 6FDA-mPDA as a consequence of CO2 presence in the 6FDA-mPDA film matrix.

scholarly journals Characterization of Gas Transport Properties of Compacted Solid Waste Materials

Environments ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 26
Author(s):  
Muhammad Rashid Iqbal ◽  
Hiniduma Liyanage Damith Nandika ◽  
Yugo Isobe ◽  
Ken Kawamoto
Keyword(s):  
Hydraulic Conductivity ◽  
Solid Waste ◽  
Gas Transport ◽  
Bottom Ash ◽  
Gas Diffusion ◽  
Saturated Hydraulic Conductivity ◽  
Dry Density ◽  
Transport Parameters ◽  
Functional Relations ◽  
Mixed Waste

Gas transport parameters such as gas diffusivity (Dp/D0), air permeability (ka), and their dependency on void space (air-filled porosity, ε) in a waste body govern convective air and gas diffusion at solid waste dumpsites and surface emission of various gases generated by microbial processes under aerobic and anaerobic decompositions. In this study, Dp/D0(ε) and ka(ε) were measured on dumping solid waste in Japan such as incinerated bottom ash and unburnable mixed waste as well as a buried waste sample (dumped for 20 years). Sieved samples with variable adjusted moistures were compacted by a standard proctor method and used for a series of laboratory tests for measuring compressibility, saturated hydraulic conductivity, and gas transport parameters. Results showed that incinerated bottom ash and unburnable mixed waste did not give the maximum dry density and optimum moisture content. Measured compressibility and saturated hydraulic conductivity of tested samples varied widely depending on the types of materials. Based on the previously proposed Dp/D0(ε) models, the diffusion-based tortuosity (T) was analyzed and unique power functional relations were found in T(ε) and could contribute to evaluating the gas diffusion process in the waste body compacted at different moisture conditions.

In-Plane Microstructure of Gas Diffusion Layers With Different Properties for PEFC

2013 ◽  
Author(s):  
Mehdi Mortazavi ◽  
Kazuya Tajiri
Keyword(s):  
Contact Angle ◽  
Fuel Cell ◽  
Pore Diameter ◽  
Gas Transport ◽  
Gas Permeability ◽  
Transport Phenomena ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cell ◽  
Diameter Distribution ◽  
Carbon Paper

Gas diffusion layer (GDL) is undoubtedly one of the most complicated components used in a polymer electrolyte fuel cell (PEFC) in terms of liquid and gas transport phenomena. An appropriate fuel cell design seeks a fundamental study of this tortuous porous component. Currently, porosity and gas permeability have been known as some of the key parameters affecting liquid and gas transport through GDL. Although these are dominant parameters defining mass transport through porous layers, there are still many other factors affecting transport phenomena as well as overall cell performance. In this work, microstructural properties of Toray carbon papers with different thicknesses and for polytetrafluoroethylene (PTFE) treated and untreated cases have been studied based on scanning electron microscopy (SEM) image analysis. Water droplet contact angle as a dominant macroscale property as well as mean pore diameter, pore diameter distribution, and pore roundness distribution as important microscale properties have been studied. It was observed that the mean pore diameter of Toray carbon paper does not change with its thickness and PTFE content. Mean pore diameter for Toray carbon papers was calculated to be around 26μm regardless of their thicknesses and PTFE content. It was also observed that droplet contact angle on GDL surface does not vary with GDL thickness. The average contact angle for 10 wt.% PTFE treated GDLs of different thicknesses was measured about 150°. Finally, the heterogeneous in-plane PTFE distribution on the GDL surface was observed to have no effect on mean pore diameter of GDLs.

scholarly journals Effect of Bridgehead Methyl Substituents on the Gas Permeability of Tröger’s-Base Derived Polymers of Intrinsic Microporosity

Membranes ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 62 ◽  
Author(s):  
Richard Malpass-Evans ◽  
Ian Rose ◽  
Alessio Fuoco ◽  
Paola Bernardo ◽  
Gabriele Clarizia ◽  
...  
Keyword(s):  
Gas Permeability ◽  
Time Lag ◽  
Composite Membranes ◽  
Detailed Comparison ◽  
Gas Diffusion ◽  
Size Selectivity ◽  
Surface Areas ◽  
Troger's Base ◽  
Polymers Of Intrinsic Microporosity ◽  
Intrinsic Microporosity

A detailed comparison of the gas permeability of four Polymers of Intrinsic Microporosity containing Tröger’s base (TB-PIMs) is reported. In particular, we present the results of a systematic study of the differences between four related polymers, highlighting the importance of the role of methyl groups positioned at the bridgehead of ethanoanthracene (EA) and triptycene (Trip) components. The PIMs show BET surface areas between 845–1028 m2 g−1 and complete solubility in chloroform, which allowed for the casting of robust films that provided excellent permselectivities for O2/N2, CO2/N2, CO2/CH4 and H2/CH4 gas pairs so that some data surpass the 2008 Robeson upper bounds. Their interesting gas transport properties were mostly ascribed to a combination of high permeability and very strong size-selectivity of the polymers. Time lag measurements and determination of the gas diffusion coefficient of all polymers revealed that physical ageing strongly increased the size-selectivity, making them suitable for the preparation of thin film composite membranes.

scholarly journals Synthesis and Gas-Permeation Characterization of a Novel High-Surface Area Polyamide Derived from 1,3,6,8-Tetramethyl-2,7-diaminotriptycene: Towards Polyamides of Intrinsic Microporosity (PIM-PAs)

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 361 ◽  
Author(s):  
Giuseppe Genduso ◽  
Bader Ghanem ◽  
Yingge Wang ◽  
Ingo Pinnau
Keyword(s):  
Surface Area ◽  
Gas Permeability ◽  
High Surface ◽  
High Surface Area ◽  
Gas Permeation ◽  
Bet Surface Area ◽  
Mixed Gas ◽  
Fractional Free Volume ◽  
Intrinsic Microporosity

A triptycene-based diamine, 1,3,6,8-tetramethyl-2,7-diamino-triptycene (TMDAT), was used for the synthesis of a novel solution-processable polyamide obtained via polycondensation reaction with 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (6FBBA). Molecular simulations confirmed that the tetrasubstitution with ortho-methyl groups in the triptycene building block reduced rotations around the C–N bond of the amide group leading to enhanced fractional free volume. Based on N2 sorption at 77 K, 6FBBA-TMDAT revealed microporosity with a Brunauer–Emmett–Teller (BET) surface area of 396 m2 g−1; to date, this is the highest value reported for a linear polyamide. The aged 6FBBA-TMDAT sample showed moderate pure-gas permeabilities (e.g., 198 barrer for H2, ~109 for CO2, and ~25 for O2) and permselectivities (e.g., αH2/CH4 of ~50) that position this polyamide close to the 2008 H2/CH4 and H2/N2 upper bounds. CO2–CH4 mixed-gas permeability experiments at 35 °C demonstrated poor plasticization resistance; mixed-gas permselectivity negatively deviated from the pure-gas values likely, due to the enhancement of CH4 diffusion induced by mixing effects.

In-Plane Microstructure of Gas Diffusion Layers With Different Properties for PEFC

2013 ◽  
Vol 11 (2) ◽  
Author(s):  
Mehdi Mortazavi ◽  
Kazuya Tajiri
Keyword(s):  
Contact Angle ◽  
Fuel Cell ◽  
Pore Diameter ◽  
Gas Transport ◽  
Gas Permeability ◽  
Transport Phenomena ◽  
Gas Diffusion ◽  
Polymer Electrolyte Fuel Cell ◽  
Carbon Paper ◽  
The Mean

The gas diffusion layer (GDL) is undoubtedly one of the most complicated components used in a polymer electrolyte fuel cell (PEFC) in terms of liquid and gas transport phenomena. An appropriate fuel cell design seeks a fundamental study of this tortuous porous component. Currently, porosity and gas permeability have been known as some of the key parameters affecting liquid and gas transport through the GDL. Although these are dominant parameters defining mass transport through porous layers, there are still many other factors affecting the transport phenomena and overall cell performance. In this work, the microstructural properties of Toray carbon papers with different thicknesses and for polytetrafluoroethylene (PTFE) treated and untreated cases have been studied based on scanning electron microscopy (SEM) image analysis. The water droplet contact angle, as a dominant macroscale property, along with the mean pore diameter, pore diameter distribution, and pore roundness distribution, as important microscale properties, have been studied. It was observed that the mean pore diameter of Toray carbon paper does not change with its thickness and PTFE content. Mean pore diameter for Toray carbon papers was calculated to be around 26μm, regardless of their thicknesses and PTFE content. It was also observed that the droplet contact angle on the GDL surface does not vary with the GDL thickness. The average contact angle for the 10 wt. % PTFE treated GDLs of different thicknesses was measured at about 150 deg. Finally, the heterogeneous in-plane PTFE distribution on the GDL surface was observed to have no effect on the mean pore diameter of GDLs.

scholarly journals Temperature-Dependent Gas Transport Behavior in Cross-Linked Liquid Crystalline Polyacrylate Membranes

Membranes ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 104 ◽  
Author(s):  
Feras Rabie ◽  
Lenka Poláková ◽  
Sebastian Fallas ◽  
Zdenka Sedlakova ◽  
Eva Marand ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Gas Transport ◽  
Gas Permeation ◽  
Isotropic Phase ◽  
Sorption Behavior ◽  
Phase Solubility ◽  
Cross Link ◽  
Mixed Gas ◽  
Transport Behavior ◽  
The Cross

Stable, cross-linked, liquid crystalline polymer (LCP) films for membrane separation applications have been fabricated from the mesogenic monomer 11-(4-cyanobiphenyl-4′-yloxy) undecyl methacrylate (CNBPh), non-mesogenic monomer 2-ethylhexyl acrylate (2-EHA), and cross-linker ethylene glycol dimethacrylate (EGDMA) using an in-situ free radical polymerization technique with UV initiation. The phase behavior of the LCP membranes was characterized using differential scanning calorimetry (DSC) and X-ray scattering, and indicated the formation of a nematic liquid crystalline (LC) phase above the glass transition temperature. The single gas transport behavior of CO2, CH4, propane, and propylene in the cross-linked LCP membranes was investigated for a range of temperatures in the LC mesophase and the isotropic phase. Solubility of the gases was dependent not only on the condensability in the LC mesophase, but also on favorable molecular interactions of penetrant gas molecules exhibiting a charge separation, such as CO2 and propylene, with the ordered polar mesogenic side chains of the LCP. Selectivities for various gas pairs generally decreased with increasing temperature and were discontinuous across the nematic–sotropic transition. Sorption behavior of CO2 and propylene exhibited a significant change due to a decrease in favorable intermolecular interactions in the disordered isotropic phase. Higher cross-link densities in the membrane generally led to decreased selectivity at low temperatures when the main chain motion was limited by the lack of mesogen mobility in the ordered nematic phase. However, at higher temperatures, increasing the cross-link density increased selectivity as the cross-links acted to limit chain mobility. Mixed gas permeation measurements for propylene and propane showed close agreement with the results of the single gas permeation experiments.

Gas transport properties of polyimide membranes based on triphenylamine unit

2016 ◽  
Vol 30 (1) ◽  
pp. 100-108 ◽  
Author(s):  
Guangliang Song ◽  
Lina Wang ◽  
Dandan Liu ◽  
Jianan Yao ◽  
Yiming Cao
Keyword(s):  
Transport Properties ◽  
Diffusion Coefficients ◽  
Gas Transport ◽  
Nitrogen Atmosphere ◽  
Gas Permeation ◽  
Gas Transport Properties ◽  
Thermal Imidization ◽  
Backbone Structure ◽  
Solubility Coefficients ◽  
Permeation Properties

A series of polyimide (PI) membranes were prepared based on three triphenylamine-based diamines, namely 4,4′-diaminotriphenylamine, 4,4′-diamino-3′′,5′′-dimethyltriphenylamine, and 4,4′-diamino-3′′,5′′-ditrifluoromethyltriphenylamine, via thermal imidization procedure. The PI membranes displayed good thermal properties, with glass transition temperatures of 279–341°C and 5% weight loss temperatures above 515°C under a nitrogen atmosphere. The gas permeation properties of the membranes were investigated and interpreted from the viewpoint of the PI backbone structure. The gas permeation coefficients increased as the substituent pendant groups at the 3′′,5′′ positions of the triphenylamine varied from –H to –CH3 and –CF3, and the permselectivity of gas pairs (including hydrogen/nitrogen (N2), oxygen/N2, carbon dioxide (CO2)/N2, and CO2/methane) decreased in this order. The diffusion coefficients and solubility coefficients were calculated, and the results revealed the variation of the substituted triphenylamine units principally influenced the diffusion coefficients, indicating that the substituted triphenylamine affected the gas transport properties by “diffusivity-controlled” modification.

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