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ABSTRACT: Making use of the preferred adsorption affinity and capacity to CO(2) as well as the highly porous structure with huge cavities of 2.4 nm, a highly permeable and selective ZIF-95 molecular sieve membrane was developed for the separation of H(2) from CO(2).
Chemical Communications 10/2012; 48(89):10981-3. · 6.17 Impact Factor
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ABSTRACT: A clear separation: A post-synthetic functionalization method is reported to obtain a highly permselective zeolitic imidazolate framework (ZIF-90) membrane. The intercrystalline defects of the ZIF-90 membrane are minimized to enhance the separation selectivity while a high permeance is maintained.
Angewandte Chemie International Edition 09/2012; 51(42):10551-5. · 13.45 Impact Factor
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ABSTRACT: Micro-imaging is employed to monitor the evolution of intra-crystalline guest profiles during molecular adsorption and desorption in cation-free zeolites AlPO-LTA. The measurements are shown to provide direct evidence on the rate of intra-crystalline diffusion and surface permeation and their inter-relation. Complemented by PFG NMR and integral IR measurements, a comprehensive overview of the diffusivities of light hydrocarbons in this important type of host materials is provided.
Journal of the American Chemical Society 04/2012; 134(18):7725-32. · 9.91 Impact Factor
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ABSTRACT: Sandwich-structured composite zeolite membranes with enhanced hydrogen selectivity were prepared on porous α-Al(2)O(3) supports by using 3-aminopropyltriethoxysilane as an interlayer.
Chemical Communications 03/2012; 48(29):3542-4. · 6.17 Impact Factor
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ABSTRACT: CO2-stable oxygen-permeable Fe2O3 (FO) - Ce0.9Gd0.1O2-δ (CGO) dual phase composite membranes of the composition χ wt % FO - (100 – χ) wt % CGO with χ = 25, 40, 50 were successfully prepared via a one-pot single-step method. X-ray diffraction (XRD) demonstrated that all FO - CGO composite membranes after sintering at 1300 °C for 5 h represent a microscale mixture of only the two pure phases FO and CGO. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), and oxygen permeation revealed that the microstructure of the composition of the χ FO - (100 – χ) CGO dual phase membranes has a great influence on the oxygen permeability including its time-dependence. It was found that the composition of 40FO - 60CGO displays the highest oxygen permeability. An oxygen permeation flux of 0.18 mL/min·cm2 was obtained through the uncoated 40FO - 60CGO membrane with a thickness of 0.5 mm under an air/He oxygen gradient at 1000 °C. In situ XRD demonstrates that the 40FO - 60CGO material possesses a good phase stability not only in an atmosphere of 50 vol % CO2/50 vol % Ar but also in other atmospheres with a low oxygen partial pressure like reduced pressure (vacuum) and 5 vol % H2/95 vol % He. After coating the 40FO - 60CGO dual phase membrane with a porous La0.6Sr0.4CoO3-δ (LSC) layer of a few μm thicknesses on the air side, the oxygen permeation flux reaches the steady state immediately. This steady oxygen permeation flux of the LSC coated membrane was found to be 0.20 mL/min·cm2 unchanged for more than 150 h even when pure CO2 was used as the sweep gas, which indicates that the coated 40FO - 60CGO dual phase membrane is CO2 stable.
11/2011;
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ABSTRACT: An oriented, neutral and cation-free AlPO(4) LTA molecular sieve membrane with high hydrogen selectivity was prepared on porous α-Al(2)O(3) supports through secondary growth of a highly oriented AlPO(4) LTA monolayer.
Chemical Communications 03/2011; 47(14):4201-3. · 6.17 Impact Factor
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Angewandte Chemie International Edition 03/2011; 50(21):4979-82. · 13.45 Impact Factor
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Angewandte Chemie International Edition 01/2011; 50(3):759-63. · 13.45 Impact Factor
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ABSTRACT: Pore-space homogeneity of zeolite NaX was probed by pulsed field gradient (PFG) NMR diffusion studies with n-butane as a guest molecule. At a loading of 0.75 molecules per supercage, a wide spectrum of diffusivities was observed. Guest molecules in the (well-shaped) zeolite crystallites were thus found to experience pore spaces of quite different properties. After loading enhancement to 3 molecules per supercage, however, molecular propagation ideally followed the laws of normal diffusion in homogeneous media. At sufficiently high guest concentrations, sample heterogeneity was thus found to be of no perceptible influence on the guest mobilities anymore.
Langmuir 01/2011; 27(1):416-9. · 4.19 Impact Factor
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Angewandte Chemie International Edition 12/2010; · 13.45 Impact Factor
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Advanced Materials 11/2010; 22(42):4741-3. · 13.88 Impact Factor
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ABSTRACT: A neutral framework cation-free hydrophobic ITQ-29 molecular sieve membrane with hydrogen selectivity was prepared on porous α-Al(2)O(3) supports by using Kryptofix 222 as organic structure directing agent through secondary growth method.
Chemical Communications 11/2010; 46(41):7748-50. · 6.17 Impact Factor
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ABSTRACT: A novel covalent functionalization strategy was developed to prepare reproducible ZIF-90 molecular sieve membranes by using 3-aminopropyltriethoxysilane as a covalent linker between the ZIF-90 layer and Al(2)O(3) support via imines condensation. The ZIF-90 membranes show high thermal and hydrothermal stabilities, and they allow the separation of hydrogen from larger gases by molecular sieving.
Journal of the American Chemical Society 10/2010; 132(44):15562-4. · 9.91 Impact Factor
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Advanced Materials 08/2010; 22(30):3322-6. · 13.88 Impact Factor
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Angewandte Chemie International Edition 08/2010; 49(33):5656-60. · 13.45 Impact Factor
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Angewandte Chemie International Edition 07/2010; 49(29):4958-61. · 13.45 Impact Factor
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ABSTRACT: A porous perovskite BaCo(x)Fe(y)Zr(0.9-x-y)Pd(0.1)O(3-delta) (BCFZ-Pd) coating was deposited onto the outer surface of a BaCo(x)Fe(y)Zr(1-x-y)O(3-delta) (BCFZ) perovskite hollow-fiber membrane. The surface morphology of the modified BCFZ fiber was characterized by scanning electron microscopy (SEM), indicating the formation of a BCFZ-Pd porous layer on the outer surface of a dense BCFZ hollow-fiber membrane. The oxygen permeation flux of the BCFZ membrane with a BCFZ-Pd porous layer increased 3.5 times more than that of the blank BCFZ membrane when feeding reactive CH(4) onto the permeation side of the membrane. The blank BCFZ membrane and surface-modified BCFZ membrane were used as reactors to shift the equilibrium of thermal water dissociation for hydrogen production because they allow the selective removal of the produced oxygen from the water dissociation system. It was found that the hydrogen production rate increased from 0.7 to 2.1 mL H(2) min(-1) cm(-2) at 950 degrees C after depositing a BCFZ-Pd porous layer onto the BCFZ membrane.
Chemistry 05/2010; 16(26):7898-903. · 5.93 Impact Factor
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ABSTRACT: A novel neutral and cation-free LTA-type AlPO(4) membrane has been prepared on porous asymmetric ceramic supports. Hydrogen can be effectively separated from other gases by molecular sieving.
Journal of the American Chemical Society 02/2010; 132(7):2140-1. · 9.91 Impact Factor
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ABSTRACT: Diffusion is known to be quantified by measuring the rate of molecular fluxes in the direction of falling concentration. In contrast with intuition, considering methanol diffusion in a novel type of nanoporous material (MOF ZIF-8), this rate has now been found to be enhanced rather than slowed down by an opposing flux of labeled molecules. In terms of the key quantities of random particle movement, this result means that the self-diffusivity exceeds the transport diffusivity. It is rationalized by considering the strong intermolecular interaction and the dominating role of intercage hopping in mass transfer in the systems under study.
Physical Review Letters 02/2010; 104(8):085902. · 7.37 Impact Factor
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ABSTRACT: A membrane reactor incorporating a hollow fiber with successive parts of oxygen permeable and passivated surface segments has been developed and was used for the oxidative dehydrogenation (DH) of propane. This membrane geometry allows a controlled oxygen feeding into the reactor over its axial length. In the oxidative DH, the thermodynamic limitation of propane DH can be overcome. By using this novel hollow fiber membrane reactor with a Pt/Sn/K DH catalyst, oxygen separation and propene formation could be established even at temperatures as low as 625°C with long-term stability. Combining the hollow fiber membrane and the DH catalyst, the highest propene selectivity of 75% was observed at a propane conversion of 26% and 625°C whereas the best propene yield of 36% was obtained at 675°C (48% propene selectivity). The performance of this reactor is evaluated by applying various reaction conditions. © 2010 American Institute of Chemical Engineers AIChE J, 2010
AIChE Journal 01/2010; 56(9):2390 - 2396. · 2.26 Impact Factor
