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The performance of a given membrane in gas separation, nanofiltration and pervaporation is found to be interplay between the thickness of the top layer, steric hindrance during transport and is indirectly determined by effects of hydrophobicity/hydrophilicity. The results have shown that multifunctional membranes would rapidly gain importance in view of the flexibility of processes and the robustness of the separation.

A study was conducted on the differences on structure and transport mechanisms of nanofiltration (NF) and pervaporation (PV) membranes by measuring water and ethanol fluxes and raffinose rejections, water and ethanol fluxes and water/ethanol-n-propanol separation factors, and gas and vapor (water, ethanol) permeance with the same membrane sequence.

Metal-organic frameworks (MOFs) were supported on polymer membrane substrates for the fabrication of composite polymer membranes based on unmodified and modified polymer of intrinsic microporosity (PIM-1). Layers of two different MOFs, zeolitic imidazolate framework-8 (ZIF-8) and Copper benzene tricarboxylate ((HKUST-1), were grown onto neat PIM-1, amide surface-modified PIM-1 and hexamethylenediamine (HMDA) -modified PIM-1. The surface-grown crystalline MOFs were characterized by a combination of several techniques, including powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy to investigate the film morphology on the neat and modified PIM-1 membranes. The pure gas permeabilities of He, H2, O2, N2, CH4, CO2 were studied to understand the effect of the surface modification on the basic transport properties and evaluate the potential use of these membranes for industrially relevant gas separations. The pure gas transport was discussed in terms of permeability and selectivity, highlighting the effect of the MOF growth on the diffusion coefficients of the gas in the new composite polymer membranes. The results confirm that the growth of MOFs on polymer membranes can enhance the selectivity of the appropriately functionalized PIM-1, without a dramatic decrease of the permeability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Membrane-based gas separation has been recognized as one of the most promising and energy-efficient processes for CO 2 capture from industrial gas streams. Remarkably, commercial gas separation membranes typically contain conventional polymers with sub-optimal performance, necessitating the search for better-performing materials. In this work, we developed novel mixed matrix membranes (MMMs) based on the benchmark polyimide Matrimid® 9725 and a soluble poly (ether ether ketone) PEEK-WC. The addition of a zinc-based metal-organic cage (MOC) featuring two calixsalen macrocyclic units significantly improved the transport properties for various gas pairs with an up to 100 % increase in permeability and up to 10 % increase in selectivity at 30 % MOC. SEM and DSC analyses offered valuable insights into the compatibility between the polymer and MOC, revealing excellent dispersion of up to 30 % of MOC with almost complete phase separation from the matrix. The thermal properties and transport properties were successfully described using the Fox equation and the Maxwell model, respectively. Most interestingly, thin film composites (TFCs) performed much better at 3 times higher cage concentrations than the corresponding self-standing thick films because the faster solvent evaporation limited crystal growth to sub-micron size, favouring a fine homogeneous distribution of the MOC in the polymer matrix. Based on their pure and mixed gas permeation, the TFC-MMMs show promise for the future development of new-generation gas separation membranes. [Display omitted] • Metalorganic cages (MOC) as porous fillers in mixed matrix membranes for gas separation. • The soluble MOCs crystallize to sub-micron sized homogeneously dispersed crystals. • Thin film composites allow ≥3 times higher MOC loadings than thick self-standing films. • MOCs double the permeability, maintaining the good selectivity or increasing it up to 10 %. • Mixed gas separation shows promise for several industrially relevant gas pairs. [ABSTRACT FROM AUTHOR]

Abstract: A method for the sulfonation of PEEK-WC, a glassy poly(ether ether ketone) with sulphuric acid is presented. Depending on the reaction time, polymers with ion exchange capacity (IEC) from 0.30 to are obtained, as determined by titration with NaOH solutions. The thermal properties of the polymers were studied by differential scanning calorimetry, showing that the glass transition temperature increases with increasing degree of sulfonation, from 224°C for pure PEEK-WC to 246°C for the polymer having an IEC of . The sulfonated polymers were used to prepare proton exchange membranes for possible application in fuel cells. Dense membranes were prepared by solvent evaporation, using DMA as the solvent. The transport properties of the membranes were determined in terms of water uptake and permeability for hydrogen and oxygen. Electrochemical characterization was performed by measuring cell voltage and power density curves as a function of current density at different working temperatures and the results were compared with those of a commercial Nafion membrane. A power density of 284mW/cm2 was obtained for S-PEEK-WC membrane at 120°C in H2/air fuel cell, slightly above the corresponding value found for Nafion. [Copyright &y& Elsevier]

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.