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Gas transport in mixed matrix membranes: Two methods for time lag determination

DOI: 10.3390/computation8020028 DOI Help

Authors: Alessio Fuoco (CNR-ITM) , Marcello Monteleone (CNR-ITM) , Elisa Esposito (CNR-ITM) , Rosaria Bruno (Università della Calabria) , Jesus Ferrando-soria (Universidad de Valencia) , Emilio Pardo (Universidad de Valencia) , Donatella Armentano (Università della Calabria) , Johannes Carolus Jansen (CNR-ITM)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Computation , VOL 8(2) , PAGES 28

State: Published (Approved)
Published: April 2020
Diamond Proposal Number(s): 18768

Open Access Open Access

Abstract: The most widely used method to measure the transport properties of dense polymeric membranes is the time lag method in a constant volume/pressure increase instrument. Although simple and quick, this method provides only relatively superficial, averaged data of the permeability, diffusivity, and solubility of gas or vapor species in the membrane. The present manuscript discusses a more sophisticated computational method to determine the transport properties on the basis of a fit of the entire permeation curve, including the transient period. The traditional tangent method and the fitting procedure were compared for the transport of six light gases (H2, He, O2, N2, CH4, and CO2) and ethane and ethylene in mixed matrix membranes (MMM) based on Pebax®1657 and the metal–organic framework (MOF) CuII2(S,S)-hismox·5H2O. Deviations of the experimental data from the theoretical curve could be attributed to the particular MOF structure, with cavities of different sizes. The fitting procedure revealed two different effective diffusion coefficients for the same gas in the case of methane and ethylene, due to the unusual void morphology in the MOFs. The method was furthermore applied to mixed gas permeation in an innovative constant-pressure/variable-volume setup with continuous analysis of the permeate composition by an on-line mass-spectrometric residual gas analyzer. This method can provide the diffusion coefficient of individual gas species in a mixture, during mixed gas permeation experiments. Such information was previously inaccessible, and it will greatly enhance insight into the mixed gas transport in polymeric or mixed matrix membranes.

Journal Keywords: gas separation; transport phenomena; diffusion; mixed gas diffusion; mixed matrix membranes; MOF; time lag method; on-line mass spectrometry

Subject Areas: Materials, Physics, Technique Development

Instruments: I19-Small Molecule Single Crystal Diffraction


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