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Membranes 2018, 8(3), 73; https://doi.org/10.3390/membranes8030073

A Novel Time Lag Method for the Analysis of Mixed Gas Diffusion in Polymeric Membranes by On-Line Mass Spectrometry: Pressure Dependence of Transport Parameters

1
Institute on Membrane Technology (ITM-CNR), Via P. Bucci 17/C, 87036 Rende (CS), Italy
2
Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, 166 28 Prague, Czech Republic
3
EastChem, School of Chemistry, University of Edinburgh, David Brewster Road, EH9 3FJ Edinburgh, UK
4
Department of Chemistry, College of Science, Swansea University, Grove Building, Singleton Park, SA2 8PP Swansea, UK
Current address: School of Chemistry, Cardiff University, CF10 3AT Cardiff, UK.
*
Author to whom correspondence should be addressed.
Received: 19 July 2018 / Revised: 27 August 2018 / Accepted: 29 August 2018 / Published: 3 September 2018
(This article belongs to the Special Issue Polymeric Membranes for Gas Separation)
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Abstract

This paper presents a novel method for transient and steady state mixed gas permeation measurements, using a quadrupole residual gas analyser for the on-line determination of the permeate composition. The on-line analysis provides sufficiently quick response times to follow even fast transient phenomena, enabling the unique determination of the diffusion coefficient of the individual gases in a gas mixture. Following earlier work, the method is further optimised for higher gas pressures, using a thin film composite and a thick dense styrene-butadiene-styrene (SBS) block copolymer membrane. Finally, the method is used to calculate the CO2/CH4 mixed gas diffusion coefficients of the spirobisfluorene-based polymer of intrinsic microporosity, PIM-SBF-1. It is shown that the modest pressure dependence of the PIM-SBF-1 permeability can be ascribed to a much stronger pressure dependence of the diffusion coefficient, which partially compensates the decreasing solubility of CO2 with increasing pressure, typical for the strong sorption behaviour in PIMs. The characteristics of the instrument are discussed and suggestions are given for even more versatile measurements under stepwise increasing pressure conditions. This is the first report on mixed gas diffusion coefficients at different pressures in a polymer of intrinsic microporosity. View Full-Text
Keywords: Time lag; diffusion coefficient; mixed gas permeation; membrane; gas mixture; on-line mass spectrometry; polymer of intrinsic microporosity; PIM Time lag; diffusion coefficient; mixed gas permeation; membrane; gas mixture; on-line mass spectrometry; polymer of intrinsic microporosity; PIM
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Monteleone, M.; Esposito, E.; Fuoco, A.; Lanč, M.; Pilnáček, K.; Friess, K.; Bezzu, C.G.; Carta, M.; McKeown, N.B.; Jansen, J.C. A Novel Time Lag Method for the Analysis of Mixed Gas Diffusion in Polymeric Membranes by On-Line Mass Spectrometry: Pressure Dependence of Transport Parameters. Membranes 2018, 8, 73.

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