Zholobenko, VL (2020) Probing the acid sites of zeolites with pyridine: quantitative AGIR measurements of the molar absorption coefficients. Journal of Catalysis, 385. pp. 52-60. ISSN 0021-9517

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This study presents a detailed methodology, which combines high-precision thermogravimetry and FTIR spectroscopy, aiming to establish the most accurate and reliable means of measuring the molar absorption coefficients of adsorbed species. As the integrated molar absorption coefficients of Py complexes with Brønsted and Lewis acid sites, ɛ(Py-B) and ɛ(Py-L), are determined and the validity of the Beer-Lambert-Bouguer law for IR characterisation of solid acids is demonstrated, this work is setting a benchmark for the quantitative acidity measurements in zeolites and related materials. The following values of ɛ(Py-B) have been obtained at 150°C (band at ~1545 cm-1): 1.09±0.08 cm μmol-1 for ZSM-5; 1.12±0.16 cm μmol-1 for BEA; 1.29±0.04 cm μmol-1 18 for MOR and 1.54±0.15 cm μmol-1 for FAU. The value of ɛ(Py-L) (band at ~1455 cm-1 19 , which refers to different cations) measured at the same temperature is 1.71±0.1 cm μmol-1 20 . Values of ɛ(Py-B) depend on the zeolite structure, in contrast to that for ɛ(Py-L). Clear correlations are presented between the temperature of the FTIR measurements and ɛ values for Py complexes and other species, which decrease by ~10% as the temperature increases by 100oC. In addition, the effects of key experimental procedures, instrumentation design and sample preparation are established and quantified.

Item Type: Article
Uncontrolled Keywords: zeolites; acid sites; FTIR; pyridine; molar absorption coefficients
Subjects: Q Science > Q Science (General)
Q Science > QD Chemistry
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Depositing User: Symplectic
Date Deposited: 09 Mar 2020 11:20
Last Modified: 20 Mar 2021 01:30
URI: https://eprints.keele.ac.uk/id/eprint/7762

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