Insights into Brønsted acid sites in the zeolite mordenite

Dmitry B. Lukyanov, Tanya Vazhnova, Nikolay Cherkasov, John L. Casci, John J. Birtill

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The unique feature of the zeolite catalysts is the presence of catalytically active acidic hydroxyls, also known as Brønsted acid sites (BAS), in the zeolite micropores of molecular dimensions. The accessibility and catalytic properties of BAS depend on their local environment, and it is therefore important to know the exact locations of BAS and the number of BAS in these locations. This paper reports a detailed FT-IR investigation into BAS present in the acidic and partially Na-exchanged samples of industrially important mordenite (MOR) zeolite. Our results demonstrate the existence of (at least) six distinct BAS that can be visualized by six single bands in Fourier self-deconvolution traces of the IR spectra. The quantitative estimates for the amounts of these distinct BAS were obtained using the six-band deconvolution method developed in this work. These estimates show that in the purely acidic H-MOR sample about 25% of BAS are located in eight-membered ring (8-MR) channels (O1-H and O9-H hydroxyls), ∼13% of BAS are at the intersections between the side pockets and 12-MR channels (O5-H hydroxyls), and ∼62% of BAS are located in 12-MR channels (∼39% correspond to O2-H and/or O10-H hydroxyls and the remaining 23% to O3-H and O7-H hydroxyls). These quantitative data demonstrate that the acid sites are distributed quite evenly between oxygen atoms in different crystallographic positions, thus revealing the complexity of the experimental identification of distinct BAS in mordenites and explaining the variety of the earlier suggestions regarding their positions in these zeolites.

Original languageEnglish
Pages (from-to)23918-23929
Number of pages12
JournalJournal of Physical Chemistry C
Volume118
Issue number41
DOIs
Publication statusPublished - 16 Oct 2014

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Zeolites
acids
Acids
Hydroxyl Radical
Deconvolution
mordenite
estimates
zeolites
intersections
suggestion
oxygen atoms

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Lukyanov, D. B., Vazhnova, T., Cherkasov, N., Casci, J. L., & Birtill, J. J. (2014). Insights into Brønsted acid sites in the zeolite mordenite. Journal of Physical Chemistry C, 118(41), 23918-23929. https://doi.org/10.1021/jp5086334

Insights into Brønsted acid sites in the zeolite mordenite. / Lukyanov, Dmitry B.; Vazhnova, Tanya; Cherkasov, Nikolay; Casci, John L.; Birtill, John J.

In: Journal of Physical Chemistry C, Vol. 118, No. 41, 16.10.2014, p. 23918-23929.

Research output: Contribution to journalArticle

Lukyanov, DB, Vazhnova, T, Cherkasov, N, Casci, JL & Birtill, JJ 2014, 'Insights into Brønsted acid sites in the zeolite mordenite', Journal of Physical Chemistry C, vol. 118, no. 41, pp. 23918-23929. https://doi.org/10.1021/jp5086334
Lukyanov, Dmitry B. ; Vazhnova, Tanya ; Cherkasov, Nikolay ; Casci, John L. ; Birtill, John J. / Insights into Brønsted acid sites in the zeolite mordenite. In: Journal of Physical Chemistry C. 2014 ; Vol. 118, No. 41. pp. 23918-23929.
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