Relation between acidity and local structure of dealuminated zeolites Y investigated by solid-state NMR spectroscopy

Leizhi Wang, Yijiao Jiang, Jun Huang, Michael Hunger

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contribution

Abstract

Multi-nuclear (²⁷Al, ²⁹Si, ¹H, ¹³C) solid-state NMR spectroscopy was carried out for investigating the relationship between acidity and local structure of a dealuminated zeolite Y. The generation of extra-framework aluminum species after mild steam treatment of a parent zeolite H,Na-Y was detected by ²⁷Al MAS NMR spectroscopy. An increase of the framework nSi/nAl ratio from 2.7 to 5.4 was determined by simulation of the ²⁹Si MAS NMR spectra. Via quantitative ¹H MAS NMR spectroscopy, the concentration of Brønsted acid sites of zeolite deH-Y was found to decrease with steaming. Furthermore, after loading of deuterated acetonitrile, the ¹H MAS NMR spectra show a significantly larger adsorbate-induced low-field shift Delta delta1H of the signal of bridging OH groups in zeolite deH-Y (5.6 ppm) in comparison with parent zeolite H,Na-Y (5.1 ppm). This larger low-field shift ∆δ₁H indicates an enhanced acid strength of Brønsted acid sites due to the decrease of the framework aluminum content. Finally, ¹³C MAS NMR spectroscopic studies gave hints for aldol reactions of 2-¹³C-acetone on zeolite deH-Y. However, no aldol reactions could be observed on zeolite H,Na-Y. This result indicates that dealumination enhances the reactivity of Y zeolites due to the stronger Brønsted acid sites and the formation of Lewis acid sites.
Original languageEnglish
Title of host publicationChemeca 2011
Subtitle of host publicationEngineering a Better World : proceedings
Place of PublicationBarton, ACT
PublisherEngineers Australia
Pages550-558
Number of pages9
ISBN (Print)9780858259676
Publication statusPublished - 2011
Externally publishedYes
EventChemeca (39th : 2011) - Sydney, Australia
Duration: 18 Sep 201121 Sep 2011

Conference

ConferenceChemeca (39th : 2011)
CitySydney, Australia
Period18/09/1121/09/11

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