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Acidity and defect sites in titanium silicalite catalyst

Paper ID Volume ID Publish Year Pages File Format Full-Text
43637 45980 2008 8 PDF Available
Title
Acidity and defect sites in titanium silicalite catalyst
Abstract

With density functional calculations and in situ 29Si and 31P MAS NMR experiments, a novel defect site (defect site II, dsII) was identified in titanium silicalite molecular sieve (TS-1 zeolite), supported by the previous experimental results. The conversion from Q3 species [(SiO)3Si(OH)] into Q4-like species [Si(OSi)4] due to TMP adsorption indicated the presence of Brönsted acidity in TS-1 zeolite. The thermodynamic analysis and Ti/Si substitution energies further confirmed that the proton transferring process of defect site II is much facilitated in TS-1 zeolite whereas on the contrary in silicalite-1. With the proton-affinity calculations, the Brönsted acidities of several cation-doped zeolites were found to decrease in the order of Al-ZSM-5 > Fe-ZSM-5 > B-ZSM-5 > TS-1. The Brönsted acidity of TS-1 zeolite is even weaker than that of B-ZSM-5 zeolite, suggesting the potential role as a new acid catalyst. As to silicalite-1, its acidity is even weaker than that of defect site I (dsI) in TS-1 zeolite.

Graphical abstractIn situ MAS NMR experiments and density functional calculations were performed to identify a novel defect site in TS-1 zeolite. It was explained why TS-1 zeolite shows Brönsted acidity whereas silicalite-1 not. Moreover, it was found that the Brönsted acidity of TS-1 zeolite is the weakest to best of our knowledge, suggesting potential roles as new acid catalysts. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Acidity; Defect sites; Density functional calculations; MAS NMR; Proton transfer
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 337, Issue 1, 15 March 2008, Pages 58–65
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
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