Matrix Membranes For Gas Separation Research Articles

Exfoliated zeolite Nu-6(2) as filler for 6FDA-based copolyimide mixed matrix membranes

► Exfoliated zeolite Nu-6(2)-6FDA-based copolyimide mixed matrix membranes for gas separation. ► Copolyimides were prepared with different DABA carboxyl group concentrations. ► Exfoliated zeolite Nu-6(2) with 300 m 2 /g surface area as the filler. ► Evidence for the formation of hydrogen bonds between the zeolite and the DABA group. ► Gas separation experiments for H 2 /CH 4 and O 2 /N 2 mixtures. Exfoliated zeolite Nu-6(2)-6FDA-4MPD/6FDA-DABA copolyimide mixed matrix membranes (MMMs) were prepared and used for gas separation. The interaction of the polymer and the filler was investigated for copolyimides with different carboxyl group concentrations and hydrogen bonding was found to take place between the hydroxyl groups on the surface of the zeolite and the carboxylic groups of the polymer. Exfoliated zeolite Nu-6(2) with 300 m 2 /g surface area was chosen as the filler due to its small pore size, appropriate chemical composition and high aspect ratio. The morphology and nature of the membranes were investigated using chromatography, 1 H NMR, ATR-FTIR, TGA, SEM and TEM. Gas separation experiments were performed for H 2 /CH 4 and O 2 /N 2 mixtures. With MMMs containing a 4MPD:DABA molar ratio of 4:1, a maximum value of H 2 /CH 4 selectivity of 37.9 (with 500 Barrer of H 2 permeability) was achieved with a 5.3 wt.% of zeolite, while a maximum O 2 permeability of 147 Barrer (with a O 2 /N 2 selectivity of 4.0) was obtained with a 9.7 wt.% of zeolite.

Metal Organic Framework Containing Mixed Matrix Membranes for Gas Separation: A Different Approach to Mmm Preparation Methods

Metal Organic Framework Containing Mixed Matrix Membranes for Gas Separation: A Different Approach to Mmm Preparation Methods

High activated carbon loading mixed matrix membranes for gas separations

Mixed matrix membranes (MMMs) containing highest amounts of activated carbon (AC) reported to date were prepared for gas separation. A polymeric phase of semicrystalline polyvinyl chloride (PVC) was loaded with different amounts (from 23 to 60 wt%) of AC, and then was crosslinked using an aromatic diamine. Thermal treatment was used to complete the crosslinking reaction. Uncrosslinked MMMs were also prepared. FT-IR, SEM microscopy, X-ray diffraction, thermal degradation, and differential scanning calorimetry characterization techniques were used to verify the extent of crosslinking, crystalline structure, and the thermal resistance of the membranes. Crosslinked PVC membrane has higher both permeation flux and selectivity than the uncrosslinked one. It was observed the crosslinking process favored the formation of a less permeable porous structure in all MMMs. A decrease in the polymer crystallinity as the carbon content increased was also observed. This effect was more pronounced in absent of crosslinking. Crosslinked MMMs showed higher thermal resistance than uncrosslinked ones and pure PVC. Permeation tests showed crosslinked MMMs were more selective; i.e., the gas pair H2/CH4 selectivities varied from diffusion to Knudsen mechanisms (\( \alpha_{{{\text{H}}_{ 2} /{\text{CH}}_{ 4} }} \) 11.87–2.25), whereas the selectivity of uncrosslinked MMMs varied from Knudsen to viscous mechanisms (\( \alpha_{{{\text{H}}_{ 2} /{\text{CH}}_{ 4} }} \) 2.42–1.89). High AC content MMMs possessed permeability values comparable to those of pyrolytic carbon membranes.

Carbon Nanotubes Based Mixed Matrix Membrane for Gas Separation

Mixed matrix membranes (MMM) combine useful molecular sieving properties of inorganic fillers with the desirable mechanical and processing properties of polymers. The current trend in polymeric membranes is the incorporation of filler-like nanoparticles to improve the separation performance. Most MMM have shown higher gas permeabilities and improved gas selectivities compared to the corresponding pure polymer membranes. Carbon nanotubes based mixed matrix membrane was prepared by the solution casting method in which the functionalized multiwalled carbon nanotubes (f-MWNTs) were embedded into the polyimide membrane and the resulting membranes were characterized. The effect of nominal MWNTs content between 0.5 and 1.0 wt% on the gas separation properties were looked into. The as-prepared membranes were characterized for their morphology using field emission scanning electron microscopy (FESEM) and Transmission Electron Microscopy (TEM). The morphologies of the MMM also indicated that at 0.7 % loading of f-MWNTs, the structures of the MMM showed uniform finger-like structures which have facilitated the fast gas transport through the polymer matrix. It may also be concluded that addition of open ended and shortened MWNTs to the polymer matrix can improve its permeability by increasing diffusivity through the MWNTs smooth cavity.

Facilitated transport effect of Ag + ion exchanged halloysite nanotubes on the performance of polyetherimide mixed matrix membrane for gas separation

This study investigated the facilitated transport effect of Ag + ion exchanged halloysite nanotubes (HNTs) as filler on the gas separation performance of asymmetric mixed matrix membranes (MMMs). The polymer matrix employed in this study was commercial polyetherimide (PEI) Ultem 1000. The modified HNTs were prepared by treating HNTs with N-β-(aminoethyl)-γ-aminopropyltrimethoxy silane (AEAPTMS) and silver nitrate. FESEM, XRD, FTIR, TGA, DSC, EDX and pure gas permeation testing were used to characterise the modified HNTs and the fabricated MMMs. Three protocols were performed: (i) S-HNT MMM (no Ag + ion exchange treatment), (ii) S-Ag-HNT MMM (first Ag + ion exchanging and then silylation of HNTs), and (iii) Ag-S-HNT MMM (first silylation and then Ag + ion exchanging of HNTs). FTIR and TGA showed that silylation occurred successfully. From XRD we found out that, the Ag + ion exchanging did not affect the HNT crystalline structure. EDX revealed that, Ag + ion exchanging after silylation of HNTs resulted in much higher concentration of Ag + ions in the Ag-S-HNT product. This in turn showed that AEAPTMS could successfully enhance the HNTs cation exchange capacity (CEC), which resulted in higher concentration of Ag + ions in the modified HNTs. DSC disclosed depression in the glass transition temperature ( T g) of MMMs possessed Ag + ions. Three major factors were discussed: (i) facilitated transport affect of Ag + ions, (ii) Knudsen diffusion and (iii) T g depression. By increasing the fillers loading, all of the factors exhibited an additive influence on the permeability. The order of closeness of the resultant MMMs to the ideal morphology was as follows: Ag-S-HNT MMM > S-Ag-HNT MMM > S-HNT MMM. Ag-S-HNT MMM exhibited outstanding performance among the three protocols.

Fabrication and characterization of polysulfone/polyimide–zeolite mixed matrix membrane for gas separation

In this study the gas separation performance of polyimide/polysulfone (PI/PSF) mixed matrix membranes filled with zeolite ZSM-5 particles is investigated. The membranes are prepared by solution-casting method and utilized to determine the permeation rates of N 2, O 2, CO 2 and CH 4 through pure polymers as well as composite membranes. The membranes are characterized by SEM, TGA and FTIR. The effects of polymers ratio and weight fraction of zeolite on permeation and selectivity of the gases are discussed. Polymers ratio in the mixed matrix have assumed values of 100% PSF, 70/30 (PSF/PI), 50/50, 30/70 and 100% PI while ZSM-5 loadings are varied between 0 and 20 wt.%. SEM results showed that fabricated membranes have homogeneous structure. With pure polyimide membrane, O 2 permeability increased from 0.69 Barrer for membrane without zeolite up to 0.73 and 0.89 Barrer for membranes with 10% and 20% zeolite, respectively. Within blended matrices, the minimum permeability (maximum selectivity) and the most homogeneous matrix structure were related to the matrix with 50/50 weight percent of two polymers.

Mixed matrix membranes for gas separation with special nanoporous fillers

Special nanoporous fi llers for enhancing the gas separation performance of mixed matrix membranes (MMMs) are addressed in this work. The incorporation of small amounts of ordered mesoporous silica spheres (MSS) or exfoliated layered microporous titanosilicate UZAR-S1 (obtained from layered material JDF-L1) into a commercial polysulfone (PSF) membrane matrix was successfully carried out. The obtained results in terms of the separation of H2/CH4 and CO2/N2 mixtures were compared to those achieved with special fillers in the literature, such as mesoporous molecular sieves, lamellar zeolites and metal-organic frameworks. 8 wt.% MSS–PSF MMMs gave rise to H2/CH4 and CO2/N2 selectivities of 79.2 and 36.0 with H2 and CO2 permeabilities of 26.5 and 12.6 Barrer, respectively. 4 wt.% UZAR-S1-PSF MMM gave rise to H2/CH4 selectivity of 69.2 with H2 permeability of 11.5 Barrer.

Fabrication and characterization of poly(phenylene oxide)/SBA-15/carbon molecule sieve multilayer mixed matrix membrane for gas separation

Abstract A novel multilayer mixed matrix membrane (MMM), consisting of poly(phenylene oxide) (PPO), large-pore mesoporous silica molecular sieve zeolite SBA-15, and a carbon molecular sieve (CMS)/Al 2 O 3 substrate, was successfully fabricated using the procedure outlined in this paper. The membranes were cast by spin coating and exposed to different gases for the purpose of determining and comparing the permeability and selectivity of PPO/SBA-15 membranes to H 2 , CO 2 , N 2 , and CH 4 . PPO/SBA-15/CMS/Al 2 O 3 MMMs with different loading weights of zeolite SBA-15 were also studied. This new class of PPO/SBA-15/CMS/Al 2 O 3 multilayer MMMs showed higher levels of gas permeability compared to PPO/SBA-15 membranes. The permselectivity of H 2 /N 2 and H 2 /CH 4 combinations increased remarkably, with values at 38.9 and 50.9, respectively, at 10 wt% zeolite loading. Field emission scanning electron microscopy results showed that the interface between the polymer and the zeolite in MMMs was better at a 10 wt% loading than other loading levels. The increments of the glass transition temperature of MMMs with zeolite confirm that zeolite causes polymer chains to become rigid.

Polysulfone and functionalized carbon nanotube mixed matrix membranes for gas separation: Theory and experiment

Novel nanocomposite membranes containing single walled carbon nanotubes inside a polysulfone matrix have been prepared and characterized. The carbon nanotubes were functionalized with long chain alkyl amines to facilitate dispersion in the polymer. Both permeabilities and diffusivities of the membranes increased with increasing weight fraction of carbon nanotubes at 4 atm. Experimental sorption isotherms of H 2, O 2, CH 4 and CO 2 were consistent with isotherms predicted by atomistic simulations. Comparison of CO 2 adsorption of closed and open nanotubes with simulations of closed and partially open carbon nanotube bundles suggests that HiPco nanotubes are approximately 47% open.

Fabrication and characterization of polyimide–zeolite L mixed matrix membranes for gas separations

Mixed matrix membranes composed of zeolite L dispersed in a 6FDA-6FpDA-DABA polyimide matrix were fabricated and characterized for gas separation performance. The interfacial contact between the two phases relied on introducing amine functional groups on the zeolite surface and covalently linking them with carboxylic acid groups present along the polyimide backbone. While certain gas permeabilities in the membranes increased with the addition of zeolite L, overall these mixed matrix membranes did not offer substantial selectivity improvements. Separate gravimetric sorption measurements indicated that the sorption capacity of zeolites modified with silane coupling agents is substantially lower than the gas sorption in unmodified zeolites.