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Xu Y, Nelson ML, Seymour JD, Mason TG. Signatures of nanoemulsion jamming and unjamming in stimulated-echo NMR. Phys Rev E 2023; 107:024605. [PMID: 36932564 DOI: 10.1103/physreve.107.024605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 01/20/2023] [Indexed: 02/11/2023]
Abstract
The unjamming of elastic concentrated nanoemulsions into viscous dilute nanoemulsions, through dilution with the continuous phase, offers interesting opportunities for a pulsed-field gradient (PFG) NMR, particularly if the nanoemulsion is designed to take advantage of the nuclear specificity offered by NMR. Here, we make and study size-fractionated oil-in-water nanoemulsions using a perfluorinated copolymer silicone oil that is highly insoluble in the aqueous continuous phase. By studying these nanoemulsions using ^{19}F stimulated-echo PFG-NMR, we avoid any contribution from the aqueous continuous phase, which contains a nonfluorinated ionic surfactant. We find a dramatic change in the ^{19}F PFG-NMR decays at high field-gradient strengths as the droplet volume fraction, ϕ, is lowered through dilution. At high ϕ, observed decays as a function of field-gradient strength exhibit decay-to-plateau behavior indicating the jamming of nanodroplets, which contain ^{19}F probe molecules, in an elastic material reminiscent of a nanoporous solid. In contrast, at lower ϕ, only a simple decay is observed, indicating that the nanodroplets have unjammed and can diffuse over much larger distances. Through a comparison with bulk mechanical rheometry, we show that this dramatic change coincides with the loss of low-frequency shear elasticity of the nanoemulsion.
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Affiliation(s)
- Yixuan Xu
- Department of Materials Science and Engineering, University of California-Los Angeles, Los Angeles, California 90095, USA
| | - Madison L Nelson
- Department of Physics, Montana State University, Bozeman, Montana 59717-3920, USA
| | - Joseph D Seymour
- Department of Chemical and Biological Engineering, Montana State University, Bozeman, Montana 59717-3920, USA
| | - Thomas G Mason
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, USA.,Department of Physics and Astronomy, University of California-Los Angeles, Los Angeles, California 90095, USA
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2
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Quantifying diffusion of organic liquids in a MOF component of MOF/Polymer mixed-matrix membranes by high field NMR. J Memb Sci 2021. [DOI: 10.1016/j.memsci.2021.119786] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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3
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Abstract
AbstractLabeling in diffusion measurements by pulsed field gradient (PFG) NMR is based on the observation of the phase of nuclear spins acquired in a constant magnetic field with purposefully superimposed field gradients. This labeling does in no way affect microdynamics and provides information about the probability distribution of molecular displacements as a function of time. An introduction of the measuring principle is followed by a detailed description of the ranges of measurements and their limitation. Particular emphasis is given to an explanation of possible pitfalls in the measurements and the ways to circumvent them. Showcases presented for illustrating the wealth of information provided by PFG NMR include a survey on the various patterns of concentration dependence of intra-particle diffusion and examples of transport inhibition by additional transport resistances within the nanoporous particles and on their external surface. The latter information is attained by combination with the outcome of tracer exchange experiments, which are shown to become possible via a special formalism of PFG NMR data analysis. Further evidence provided by PFG NMR concerns diffusion enhancement in pore hierarchies, diffusion anisotropy and the impact of diffusion on chemical conversion in porous catalysts. A compilation of the specifics of PFG NMR and of the parallels with other measurement techniques concludes the paper.
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Ruthven DM, Kärger J, Brandani S, Mangano E. Sorption kinetics: measurement of surface resistance. ADSORPTION 2020. [DOI: 10.1007/s10450-020-00257-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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5
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Abstract
AbstractMeasurement of molecular diffusion in nanoporous host materials, which are typically inhomogeneous and anisotropic, often involves an intricate web of factors and relations to be taken into account since the associated diffusivities are a function of the diffusion path of the guest molecules during a given observation time. Depending on the observation time, therefore, the result of the experimental measurement can point to completely different conclusions about the underlying diffusion phenomena. The risk of misinterpretation of the experimental data, by correlating them with irrelevant phenomena, may be reduced if there is an option to compare the data with the results of totally independent measurements. The present communication addresses this issue with reference to the particular potentials of pulsed field gradient NMR and microimaging by infrared microscopy as techniques of microscopic diffusion measurement.
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Forman EM, Baniani A, Fan L, Ziegler KJ, Zhou E, Zhang F, Lively RP, Vasenkov S. Relationship between Ethane and Ethylene Diffusion inside ZIF-11 Crystals Confined in Polymers to Form Mixed-Matrix Membranes. J Memb Sci 2020; 593:117440. [PMID: 32863548 PMCID: PMC7449132 DOI: 10.1016/j.memsci.2019.117440] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Self-diffusivities of ethane were measured by multinuclear pulsed field gradient (PFG) NMR inside zeolitic imidazolate framework-11 (ZIF-11) crystals dispersed in several selected polymers to form mixed-matrix membranes (MMMs). These diffusivities were compared with the corresponding intracrystalline self-diffusivities in ZIF-11 crystal beds. It was observed that the confinement of ZIF-11 crystals in ZIF-11 / Torlon MMM can lead to a decrease in the ethane intracrystalline self-diffusivity. Such diffusivity decrease was observed at different temperatures used in this work. PFG NMR measurements of the temperature dependence of the intracrystalline self-diffusivity of ethylene in the same ZIF-11 / Torlon MMM revealed similar diffusivity decrease as well as an increase in the diffusion activation energy in comparison to those in unconfined ZIF-11 crystals in a crystal bed. These observations for ethane and ethylene were attributed to the reduction of the flexibility of the ZIF-11 framework due to the confinement in Torlon leading to a smaller effective aperture size of ZIF-11 crystals. Surprisingly, the intra-ZIF diffusion selectivity for ethane and ethylene was not changed appreciably by the confinement of ZIF-11 crystals in Torlon in comparison to the selectivity in a bed of ZIF-11 crystals. No ZIF-11 confinement effects leading to a reduction in the intracrystalline self-diffusivity of ethane and ethylene were observed for the other two studied MMM systems: ZIF-11 / Matrimid and ZIF-11 / 6FDA-DAM. The absence of the confinement effect in the latter MMMs can be related to the lower values of the polymer bulk modulus in these MMMs in comparison to that in ZIF-11 / Torlon MMM. In addition, there may be a contribution from possible differences in the ZIF-11/polymer adhesion in different MMM types.
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Affiliation(s)
- Evan M. Forman
- Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA
| | - Amineh Baniani
- Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA
| | - Lei Fan
- Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA
| | - Kirk J. Ziegler
- Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA
| | - Erkang Zhou
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Fengyi Zhang
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Ryan P. Lively
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Sergey Vasenkov
- Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA
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Bingre R, Losch P, Megías-Sayago C, Vincent B, Pale P, Nguyen P, Louis B. PFG-NMR as a Tool for Determining Self-Diffusivities of Various Probe Molecules through H-ZSM-5 Zeolites. Chemphyschem 2019; 20:2874-2880. [PMID: 31502391 DOI: 10.1002/cphc.201900672] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 08/26/2019] [Indexed: 11/06/2022]
Abstract
The understanding of major zeolite applications is partially based on diffusion of molecules inside or outside microporous networks. However, it is still a challenge to measure such phenomena. The diffusion ordered nuclear magnetic resonance spectroscopy (DOSY) technique has been reported to measure a probe molecule's diffusion inside porous solids. Pulsed-field gradient (PFG)-NMR has been used herein to measure the self-diffusivity of different probe molecules, such as neopentane, benzene, toluene and 1-dodecene with increasing dynamic diameter, respectively, on a series of H-ZSM-5 zeolites. The latter materials exhibit different crystal sizes, Si/Al ratios and the presence (or absence) of crystalline defects. In addition, shaped zeolite bodies representing industrial catalysts were compared with the afore-mentioned samples.
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Affiliation(s)
- Rogéria Bingre
- Energy and Fuels for a Sustainable Environment Team Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé, UMR 7515 CNRS - ECPM, Université de Strasbourg, 25 rue Becquerel, F-67087, Strasbourg cedex, France
| | - Pit Losch
- Max-Planck-Institut für Kohlenforschung, D-45470, Mülheim an der Ruhr, Germany
| | - Cristina Megías-Sayago
- Energy and Fuels for a Sustainable Environment Team Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé, UMR 7515 CNRS - ECPM, Université de Strasbourg, 25 rue Becquerel, F-67087, Strasbourg cedex, France
| | - Bruno Vincent
- Institut de Chimie - UMR 7177, Université de Strasbourg, 1 rue Blaise Pascal, 67000, Strasbourg cedex, France
| | - Patrick Pale
- Institut de Chimie - UMR 7177, Université de Strasbourg, 1 rue Blaise Pascal, 67000, Strasbourg cedex, France
| | - Patrick Nguyen
- Saint-Gobain C.R.E.E., 550 Avenue Alphonse Jauffret, BP 224, 84306, Cavaillon cedex, France
| | - Benoît Louis
- Energy and Fuels for a Sustainable Environment Team Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé, UMR 7515 CNRS - ECPM, Université de Strasbourg, 25 rue Becquerel, F-67087, Strasbourg cedex, France
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Hedin N, Rzepka P, Jasso-Salcedo AB, Church TL, Bernin D. Intracrystalline Transport Barriers Affecting the Self-Diffusion of CH 4 in Zeolites |Na 12|-A and |Na 12-xK x|-A. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:12971-12978. [PMID: 31510744 DOI: 10.1021/acs.langmuir.9b02574] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Carbon dioxide must be removed from biogas or natural gas to obtain compressed or liquefied methane, and adsorption-driven isolation of CO2 could be improved by developing new adsorbents. Zeolite adsorbents can select CO2 over CH4, and the adsorption of CH4 on zeolite |Na12-xKx|-A is significantly lower for samples with a high K+ content, i.e., x > 2. Nevertheless, we show, using 1H NMR experiments, that these zeolites adsorb CH4 after long equilibration times. Pulsed-field gradient NMR experiments indicated that in large crystals of zeolites |Na12-xKx|-A, the long-time diffusion coefficients of CH4 did not vary with x, and the upper limit of the mean-square displacement was about 1.5 μm, irrespective of the diffusion time. Also for zeolite |Na12|-A samples of three different particle sizes (∼0.44, ∼2.9, and ∼10.6 μm), the upper limit of the mean-square displacement of CH4 was 1.5 μm and largely independent of the diffusion time. This similarity provided further evidence for an intracrystalline diffusion restriction for CH4 within the medium- and large-sized zeolite A crystals and possibly of clustering and close contact among the small zeolite A crystals. The upper limit of the long-time diffusion coefficient of adsorbed CH4 was (at 1 atm and 298 K) about 10-10 m2/s irrespective of the size of the zeolite particle or the studied content of K+ in zeolites |Na12-xKx|-A and |Na12|-A. The T1 relaxation time for adsorbed CH4 on zeolites |Na12-xKx|-A with x > 2 was smaller than for those with x < 2, indicating that the short-time diffusion of CH4 was hindered.
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Affiliation(s)
- Niklas Hedin
- Department of Materials and Environmental Chemistry , Stockholm University , SE-106 91 Stockholm , Sweden
| | - Przemyslaw Rzepka
- Department of Materials and Environmental Chemistry , Stockholm University , SE-106 91 Stockholm , Sweden
| | | | - Tamara L Church
- Department of Materials and Environmental Chemistry , Stockholm University , SE-106 91 Stockholm , Sweden
| | - Diana Bernin
- Swedish NMR Centre , University of Gothenburg , SE-405 30 Göteborg , Sweden
- Department of Chemistry and Chemical Engineering , Chalmers University of Technology , SE-412 96 Göteborg , Sweden
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9
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Hwang S, Kärger J. NMR diffusometry with guest molecules in nanoporous materials. Magn Reson Imaging 2019; 56:3-13. [DOI: 10.1016/j.mri.2018.08.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 08/20/2018] [Accepted: 08/23/2018] [Indexed: 01/22/2023]
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10
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Schneider D, Mehlhorn D, Zeigermann P, Kärger J, Valiullin R. Transport properties of hierarchical micro–mesoporous materials. Chem Soc Rev 2016; 45:3439-67. [DOI: 10.1039/c5cs00715a] [Citation(s) in RCA: 167] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This work provides an overview of different experimental techniques of diffusion measurements in porous materials and discusses transport properties of several classes of hierarchically organized micro-mesoporous materials.
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Affiliation(s)
- Daniel Schneider
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
| | - Dirk Mehlhorn
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
| | - Philipp Zeigermann
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
| | - Jörg Kärger
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
| | - Rustem Valiullin
- Faculty of Physics and Earth Sciences
- University of Leipzig
- Leipzig
- Germany
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11
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Mueller R, Zhang S, Zhang C, Lively R, Vasenkov S. Relationship between long-range diffusion and diffusion in the ZIF-8 and polymer phases of a mixed-matrix membrane by high field NMR diffusometry. J Memb Sci 2015. [DOI: 10.1016/j.memsci.2014.12.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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12
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13
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Mehlhorn D, Inayat A, Schwieger W, Valiullin R, Kärger J. Probing Mass Transfer in Mesoporous Faujasite-Type Zeolite Nanosheet Assemblies. Chemphyschem 2014; 15:1681-6. [DOI: 10.1002/cphc.201301133] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Indexed: 11/10/2022]
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14
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Willis SA, Dennis GR, Zheng G, Price WS. Preparation and physical properties of a macroscopically aligned lyotropic hexagonal phase templated hydrogel. REACT FUNCT POLYM 2013. [DOI: 10.1016/j.reactfunctpolym.2013.02.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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15
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Lopez MG, Canepa P, Thonhauser T. NMR study of small molecule adsorption in MOF-74-Mg. J Chem Phys 2013; 138:154704. [DOI: 10.1063/1.4800952] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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16
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Roldughin V, Zhdanov V. Asymmetric gas mixture transport in composite membranes. Adv Colloid Interface Sci 2011; 168:223-46. [PMID: 21596363 DOI: 10.1016/j.cis.2011.04.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 04/13/2011] [Accepted: 04/13/2011] [Indexed: 11/24/2022]
Abstract
The asymmetry effects in gas and electrolyte transport through composite membranes are considered. The interrelation between the kinetic theory and non-equilibrium thermodynamics description of gas mixture transport in channels is discussed. The kinetic expressions for transport and slip coefficients are given. The effect of surface forces on gas transport is discussed. A set of general equations related to gas mixture flows in capillaries and porous media is deduced. The nano-size effects in gas flows are outlined. The theoretical analysis of one-way flow effect and asymmetric separation properties of a two-layer porous membrane is given.
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17
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Adem Z, Caro J, Furtado F, Galvosas P, Krause CB, Kärger J. Tracing pore-space heterogeneities in X-type zeolites by diffusion studies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:416-419. [PMID: 21117674 DOI: 10.1021/la103816r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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.
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Affiliation(s)
- Ziad Adem
- Department of Interface Physics, University of Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany
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18
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Webber JBW. Studies of nano-structured liquids in confined geometries and at surfaces. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2010; 56:78-93. [PMID: 20633349 DOI: 10.1016/j.pnmrs.2009.09.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Accepted: 09/12/2009] [Indexed: 05/29/2023]
Affiliation(s)
- J Beau W Webber
- Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, UK.
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19
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Zhao Q, Snurr RQ. Self-Diffusion Studies of Binary Mixtures in NaX Zeolites Using Pulsed Field Gradient NMR and a Maxwell−Stefan Model. J Phys Chem A 2009; 113:3904-10. [DOI: 10.1021/jp810058z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Qi Zhao
- Department of Chemical and Biological Engineering and Institute for Catalysis in Energy Processes, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208
| | - Randall Q. Snurr
- Department of Chemical and Biological Engineering and Institute for Catalysis in Energy Processes, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208
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Krutyeva M, Yang X, Vasenkov S, Kärger J. Exploring the surface permeability of nanoporous particles by pulsed field gradient NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 185:300-7. [PMID: 17270475 DOI: 10.1016/j.jmr.2007.01.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Revised: 01/08/2007] [Accepted: 01/10/2007] [Indexed: 05/13/2023]
Abstract
A new method to determine the surface permeability of nanoporous particles is proposed. It is based on the comparison of experimental data on tracer exchange and intracrystalline molecular mean square displacements as obtained by the PFG NMR tracer desorption technique with the corresponding solutions of the diffusion equation via dynamical Monte Carlo simulations. The method is found to be particularly sensitive in the "intermediate" regime, when the influence of intracrystalline diffusion and surface resistances of the nanoporous crystal on molecular transport are comparable and the conventional method fails. As an example, the surface permeabilities of two samples of zeolite NaCaA with different crystal sizes are determined with methane, as a probe molecule, at room temperature.
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Affiliation(s)
- M Krutyeva
- Department of Interface Physics, University of Leipzig, Linnéstrasse 5, D-04103 Leipzig, Germany.
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Stallmach F, Gröger S, Künzel V, Kärger J, Yaghi OM, Hesse M, Müller U. NMR-Untersuchungen zur Diffusion von Kohlenwasserstoffen im metall-organischen Netzwerk MOF-5. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200502553] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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23
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Stallmach F, Gröger S, Künzel V, Kärger J, Yaghi OM, Hesse M, Müller U. NMR Studies on the Diffusion of Hydrocarbons on the Metal-Organic Framework Material MOF-5. Angew Chem Int Ed Engl 2006; 45:2123-6. [PMID: 16498688 DOI: 10.1002/anie.200502553] [Citation(s) in RCA: 197] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Frank Stallmach
- Fakultät für Physik und Geowissenschaften, Universität Leipzig, Linnèstrasse 5, 04103 Leipzig, Germany.
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Gutsze A, Masierak W, Geil B, Kruk D, Pahlke H, Fujara F. On the problem of field-gradient NMR measurements of intracrystalline diffusion in small crystallites--water in NaA zeolites as an example. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2005; 28:244-9. [PMID: 16316747 DOI: 10.1016/j.ssnmr.2005.10.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Indexed: 05/05/2023]
Abstract
Necessary conditions for measuring intracrystalline diffusion in small crystal size systems via field-gradient NMR are discussed. As an illustrative case self-diffusion coefficients of water adsorbed in NaA zeolites (average crystal diameter about 1 microm) have been measured by 1H-NMR stimulated echoes in static magnetic field gradients of up to 180 T/m in the temperature range of 254-344 K. Obtaining intracrystalline diffusion coefficients necessitates a sufficiently high spatial resolution only provided by such large field gradients.
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Affiliation(s)
- Aleksander Gutsze
- Medical Academy of Bydgoszcz, Department of Biophysics, ul. Jagiellonska 13, PL-85-067 Bydgoszcz, Poland
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Takaba H, Yamamoto A, Hayamizu K, Nakao SI. Gas Diffusion in Polycrystalline Silicalite Membranes Investigated by 1H Pulse Field-Gradient NMR. J Phys Chem B 2005; 109:13871-6. [PMID: 16852740 DOI: 10.1021/jp044966z] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1H pulse field-gradient (PFG) spin-echo NMR was performed to measure the diffusivity of methane in a polycrystalline MFI-type silicalite membrane. Measured diffusivities decreased with an increase in the diffusion distance and converged to the constant value. This result suggests the presence of a transport barrier in the membrane. The long-time diffusivity in the membrane was 3.7 x 10(-9) m2/s, which was a factor of 3 smaller than reported values in a single crystal. The distance between the transport barriers was estimated to be much larger than 6 mum from the relationship of diffusivity with displacement. It should be noted that the estimated distances were larger than the smallest dimension of the crystals appearing in the membrane surface. Gas permeation and pervaporation tests were carried out on the same sample for which NMR measurements were taken. The estimated methane flux using measured long-time diffusivity by the permeation theory overestimated the experimental value, although it is closer to the experimental value than the value estimated using the short-time diffusivity. These results mean that the methane diffusivity in a silicalite membrane is much smaller than that in a single crystal.
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Affiliation(s)
- Hiromitsu Takaba
- Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo Bunkyo-ku, Tokyo 113-8685, Japan.
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