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The acid properties of H-ZSM-5 as studied by NH3-TPD and 27Al-MAS-NMR spectroscopy

Paper ID Volume ID Publish Year Pages File Format Full-Text
43546 45976 2007 9 PDF Available
Title
The acid properties of H-ZSM-5 as studied by NH3-TPD and 27Al-MAS-NMR spectroscopy
Abstract

The acid properties of H-ZSM-5 zeolites with different SiO2/Al2O3 ratios (30, 50, 80, 150, 280 and 1000) were examined by means of the temperature programmed desorption of ammonia (NH3-TPD). Different pretreatments together with a comparison of different curve-fitting methods after desorption of ammonia were used to differentiate between different adsorption sites. 27Al-MAS-NMR spectroscopy was applied to distinguish the framework (AlF) from the extra-framework aluminum (AlEF). Both techniques reveal that the concentration of Brønsted acid sites is lower than expected when considering the aluminum content. The strength of the Brønsted acid sites, determined by a theoretical model assuming the free readsorption of ammonia, is found to be in the range of ΔH = 129–161 kJ mol−1 and shows variations in the acid strength to be less than σ = 12 kJ mol−1.

Graphical abstractThe acid properties of H-ZSM-5 zeolites with different SiO2/Al2O3 ratios (30, 50, 80, 150, 280 and 1000) were examined by means of the temperature programmed desorption of ammonia (NH3-TPD). The strength of the Brønsted acid sites, determined by a theoretical model assuming the free readsorption of ammonia, is found to be in the range of ΔH = 129–161 kJ mol−1 and shows variations in the acid strength to be less than σ = 12 kJ mol−1. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
NH3-TPD; H-ZSM-5; 27Al-MAS-NMR; Brønsted acidity; Zeolite
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The acid properties of H-ZSM-5 as studied by NH3-TPD and 27Al-MAS-NMR spectroscopy
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 328, Issue 2, 10 September 2007, Pages 174–182
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
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