Accessibility and Location of Acid Sites in Zeolites as Probed by Fourier Transform Infrared Spectroscopy and Magic Angle Spinning Nuclear Magnetic Resonance(Article)(Open Access)

Johnson Matthey Technology ReviewOpen Access

Journal Article

The understanding of location and accessibility of zeolite acid sites is a key issue in heterogeneous catalysis. This paper provides a brief overview of Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) characterisation of acidity in zeolites based on the application of test molecules with a diverse range of basicity and kinetic diameters. Many zeolites, including ZSM-5 and BEA, have been characterised by monitoring the interaction between the zeolite acid sites and test molecules, such as 1,3,5-triisopropylbenzene, pyridine and alkylpyridines, to probe the location, accessibility and strength of the Brønsted acid sites. 1,3,5-triisopropylbenzene can be used to distinguish Brønsted acid sites located on the external and internal surface in most medium and large pore channel zeolites. Brønsted acid sites on the external surface of medium pore zeolites can also be quantified using 2,6-di-tert-butyl-pyridine and 2,4,6-trimethylpyridine. It is concluded that using a combination of probe molecules, including co-adsorption experiments, affords differentiation between acid sites located in channels and cavities of different sizes and on the external and internal surfaces of various zeolitic structures. © 2018 Johnson Matthey

N.S.b Barrow

V.a Zholobenko

Publication

Year of publication: 2018

Identifiers

ISSN: 20565135

Locators

DOI: 10.1595/205651318X696792

Alternative Titles