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Defect‐engineered metal–organic frameworks (MOFs) with outstanding structural and chemical features have become excellent candidates for specific separation applications. The introduction of structural defects in MOFs as an efficient approach to manipulate their functionality provides excellent opportunities for the preparation of MOF‐based mixed matrix membranes (MMMs). However, the use of this strategy to adjust the properties and develop the separation performance of gas separation membranes is still in its early stages. Here, a novel defect‐engineered MOF (quasi ZrFum or Q‐ZrFum) was synthesized via a controlled thermal deligandation process and incorporated into a CO2‐philic 6FDA‐durene polyimide (PI) matrix to form Q‐ZrFum loaded MMMs. Defect‐engineered MOFs and fabricated MMMs were investigated regarding their characteristic properties and separation performance. The incorporation of defects into the MOF structure increases the pore size and provides unsaturated active metal sites that positively affect CO2 molecule transport. The interfacial compatibility between the Q‐ZrFum particles and the PI matrix increases via the deligandation process, which improves the mechanical strength of Q‐ZrFum loaded membranes. MMM containing 5 wt.% of defect‐engineered Q‐ZrFum exhibits excellent CO2 permeability of 1308 Barrer, which increased by 99 % compared to the pure PI membrane (656 Barrer) at a feed pressure of 2 bar. CO2/CH4 and CO2/N2 selectivity reached 44 and 26.6 which increased by about 70 and 16 %, respectively. This study emphasizes that defect‐engineered MOFs can be promising candidates for use as fillers in the preparation of MMMs for the future development of membrane‐based gas separation applications. [ABSTRACT FROM AUTHOR]

The drive toward greater application of membrane has resulted in its rapid development in natural gas processing industry. In this work, amine-mediated membranes were tailored for C02 removal from C02/CH4 stream. The effects of various parameters such as amine concentration, microporous support, feed pressure and composition were examined to study the permeation behavior of pure and mixed gases. Generally, C02 transport through the DEA-PVA membranes was higher than that of MEA-PVA membranes for approximately 70%. The membrane containing 15 wt% DEA and 35 wt% MEA revealed higher permselectivity. C02 permeance enhancement of amine-PVA membranes in comparison with neat PVA membrane, confirmed that C02-amine reaction was the dominant transport mechanism. Additionally, with increasing feed pressure, C02/CH4 permselectivity decreased due to carrier saturation. However, lower partial pressure of C02 was in favor of reaction mechanism in pure and mixed gas tests. On the other hand, CH4 is not significantly affected by feed pressure confirming that solution-diffusion is the governing transport mechanism. Additionally, PTFE support with higher wettability showed better performance (+8%) regardless of amine type, concentration and feed pressure. DEA-PVA membrane has exhibited good stability during 2 weeks, unlike MEA-impregnated membrane, which was probably due to carrier degradation over time. POLYM. ENG. SCI., 54:1268-1279, 2014. © 2013 Society of Plastics Engineers, INTRODUCTION C[O.sub.2] removal from gas mixtures plays an important role in industries such as C[O.sub.2]/[N.sub.2] separation (C[O.sub.2] capturing from off-gas or flue gases for greenhouse gas emissions control) and C[O.sub.2]/C[H.sub.4] [...]

Polyethylene glycols have received worldwide attention as a highly permeable CO2-philic polymer in carbon dioxide separation applications. In this study, we investigated the influence of a low molecular weight polyethylene glycol (PEG 200) on physicochemical, morphological, and gas separation properties of Matrimid®5218 as a novel polymer blend. Both symmetric and asymmetric Matrimid flat sheet membranes with 0-20 wt.% PEG were prepared via a dense film-casting method. The miscibility of blends at low PEG concentrations (3-5 wt.%) was confirmed by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Moreover, the blends were partially miscible at higher PEG concentrations (10-20 wt.%). Matrimid/PEG molecular interactions were further studied by FTIR and XRD analysis. SEM images indicated an impressive influence of PEG on the symmetric structure of Matrimid membrane. An asymmetric structure with a dense thin skin layer and a highly porous sub-layer was observed for the blends containing 10-20 wt.% PEG. The CO2 permeability and CO2/CH4 selectivity of the best-yield CO2-selective blend membrane (Matrimid/PEG (95:5)) incvreased about 25% (from 7.68 to 9.62 Barrer) and 15% (from 35 to 40) compared to pure Matrimid, respectively. Furthermore studying the plasticization pressures of the membranes revealed that the more PEG content in blend the less the plasticization pressure obtained. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

The drive toward greater application of membrane has resulted in its rapid development in natural gas processing industry. In this work, amine-mediated membranes were tailored for CO2 removal from CO2/CH4 stream. The effects of various parameters such as amine concentration, microporous support, feed pressure and composition were examined to study the permeation behavior of pure and mixed gases. Generally, CO2 transport through the DEA-PVA membranes was higher than that of MEA-PVA membranes for approximately 70%. The membrane containing 15 wt% DEA and 35 wt% MEA revealed higher permselectivity. CO2 permeance enhancement of amine-PVA membranes in comparison with neat PVA membrane, confirmed that CO2-amine reaction was the dominant transport mechanism. Additionally, with increasing feed pressure, CO2/CH4 permselectivity decreased due to carrier saturation. However, lower partial pressure of CO2 was in favor of reaction mechanism in pure and mixed gas tests. On the other hand, CH4 is not significantly affected by feed pressure confirming that solution-diffusion is the governing transport mechanism. Additionally, PTFE support with higher wettability showed better performance (+8%) regardless of amine type, concentration and feed pressure. DEA-PVA membrane has exhibited good stability during 2 weeks, unlike MEA-impregnated membrane, which was probably due to carrier degradation over time. POLYM. ENG. SCI., 54:1268-1279, 2014. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this paper, polyvinyl alcohol (PVA) membranes impregnated with amines (monoethanolamine and diethanolamine) were prepared for CO2/N2 separation. The cross-linking of DEA impregnated PVA by glutaraldehyde (GA) with different mass ratios (GA/PVA: 0.5, 1, 3, 5, 7%) were investigated with no use of acid catalyst or organic solvents. The effects of the amine type-concentration, cross-linking agent content, and feed pressure as well as stability were examined in both pure and mixed gases. Generally, CO2/N2 performance through the DEA-PVA membranes was higher than that of MEA-PVA membranes. The fabricated membranes were characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The cross-linked membranes showed reasonable CO2/N2 permselectivities in comparison with uncross-linked membranes and these are recommended for high performance membrane for CO2/N2 separation. The best-yielding membranes (DEA-PVA/GA(1 wt%)/PTFE) represented the greatest CO2/N2 selectivity of 122.04 and 907.06 for pure and mixed gas experiments, respectively. [ABSTRACT FROM AUTHOR]

Abstract: CO2 removal from different gas streams via the polymeric membranes has been propounded as an important issue in greenhouse gas emissions control, natural gas upgrading, and enhanced oil recovery. Here, polymeric blend membranes were prepared from acrylonitrile–butadiene–styrene (ABS) and poly vinyl acetate (PVAc), and their CO2/N2 and CO2/CH4 separation characteristics were investigated. The influence of different PVAc contents on gas separation performance and the effect of pressure, ranging from 1 to 8bar, on CO2 permeability were studied. Furthermore, the morphology of the membranes was analyzed by FTIR, XRD, DSC and SEM. It was shown that the highest CO2 permeability of 5.72 Barrer for the membrane containing 10wt.% PVAc, the highest CO2/CH4 selectivity was 29 in 20wt.% PVAc and CO2/N2 was 40.41 in 30wt.% PVAc contents. These results comprised from different effective factors such as PVAc acetate polar groups, compactness in polymer matrix at the presence of high molecular weight PVAc, and the acrylonitrile and flexible butadiene contents of ABS. Furthermore, in the transmembrane pressure of 2–8bar the CO2 permeability approximately descended with the pressure increase for PVAc content of 0–40wt.%, and it ascended for 50–60wt.%. Generally, the prepared membranes can be taken into account as better membranes for CO2/N2 separation than CO2/CH4. [Copyright &y& Elsevier]

Fluorinated metal–organic frameworks (F-MOFs) as fast-growing porous materials have revolutionized the field of gas separation due to their tunable pore apertures, appealing chemical features, and excellent stability. A deep understanding of their structure–performance relationships is critical for the synthesis and development of new F-MOFs. This critical review has focused on several strategies for the precise design and synthesis of new F-MOFs with structures tuned for specific gas separation purposes. First, the basic principles and concepts of F-MOFs as well as their structure, synthesis and modification and their structure to property relationships are studied. Then, applications of F-MOFs in adsorption and membrane gas separation are discussed. A detailed account of the design and capabilities of F-MOFs for the adsorption of various gases and the governing principles is provided. In addition, the exceptional characteristics of highly stable F-MOFs with engineered pore size and tuned structures are put into perspective to fabricate selective membranes for gas separation. Systematic analysis of the position of F-MOFs in gas separation revealed that F-MOFs are benchmark materials in most of the challenging gas separations. The outlook and future directions of the science and engineering of F-MOFs and their challenges are highlighted to tackle the issues of overcoming the trade-off between capacity/permeability and selectivity for a serious move towards industrialization. [ABSTRACT FROM AUTHOR]