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 language | English |
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Title of host publication | Chemeca 2011 |
Subtitle of host publication | Engineering a Better World : proceedings |
Place of Publication | Barton, ACT |
Publisher | Engineers Australia |
Pages | 550-558 |
Number of pages | 9 |
ISBN (Print) | 9780858259676 |
Publication status | Published - 2011 |
Externally published | Yes |
Event | Chemeca (39th : 2011) - Sydney, Australia Duration: 18 Sept 2011 → 21 Sept 2011 |
Conference
Conference | Chemeca (39th : 2011) |
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City | Sydney, Australia |
Period | 18/09/11 → 21/09/11 |