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Issue 17, 2017
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Simple quantification of zeolite acid site density by reactive gas chromatography

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Abstract

The Brønsted acid site densities of ZSM-5, BEA and single unit cell self-pillared pentasil (SPP) zeolites of varying Si/Al ratios were measured using a new technique, reactive gas chromatography (RGC), which utilizes alkylamine decomposition to selectively count Brønsted acid sites. Reactive gas chromatography condenses the conventional temperature-programmed desorption mass spectrometer (TPD-MS) setup into a single, fully-automated gas chromatograph (GC). Alkylamine decomposition reactions were conducted in a microcatalytic reactor placed within a temperature-controlled GC inlet liner. Products were then separated in a GC column and quantified with a flame ionization detector. A comparison between reactive gas chromatography measurements and conventional temperature programmed desorption methods showed agreement; RGC acid site density measurements were further confirmed by comparison with in situ pyridine titration of isopropanol dehydration. Reactive gas chromatography measurements performed using multiple alkylamines, were found to yield identical Brønsted acid site densities. The method of reactive gas chromatography was found to be highly sensitive, where siliceous materials with Brønsted acid site densities as low as ∼1.0 μmol gcat−1 could be reliably measured.

Graphical abstract: Simple quantification of zeolite acid site density by reactive gas chromatography

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Publication details

The article was received on 26 May 2017, accepted on 05 Aug 2017 and first published on 07 Aug 2017


Article type: Paper
DOI: 10.1039/C7CY01068K
Citation: Catal. Sci. Technol., 2017,7, 3831-3841
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    Simple quantification of zeolite acid site density by reactive gas chromatography

    O. A. Abdelrahman, K. P. Vinter, L. Ren, D. Xu, R. J. Gorte, M. Tsapatsis and P. J. Dauenhauer, Catal. Sci. Technol., 2017, 7, 3831
    DOI: 10.1039/C7CY01068K

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