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Spectroscopic, calorimetric, and catalytic evidences of hydrophobicity on Ti-MCM-41 silylated materials for olefin epoxidations

Paper ID Volume ID Publish Year Pages File Format Full-Text
39162 45810 2015 12 PDF Available
Title
Spectroscopic, calorimetric, and catalytic evidences of hydrophobicity on Ti-MCM-41 silylated materials for olefin epoxidations
Abstract

•Hydrophobic Ti-MCM-41-Sil. catalysts show high efficiency in olefins epoxidation with organic hydroperoxides.•Catalytic activities are correlated with adsorption properties measured by spectroscopic techniques and calorimetry.•Hydrophobicity level of samples is responsible for decreasing in water adsorption and catalyst deactivation by glycol poisoning.•Increased stability of Ti-MCM-41-Sil. catalysts leads to practically quantitative production of epoxides even from natural terpenes.

Hydrophobic Ti-MCM-41 samples prepared by post-synthesis silylation treatment demonstrate to be highly active and selective catalysts in olefins epoxidation by using organic hydroperoxides as oxidizing agents in liquid phase reaction systems. Epoxide yields show important enhancements with increased silylation degrees of the Ti-mesoporous samples. Catalytic studies are combined and correlated with spectroscopic techniques (e.g. XRD, XANES, UV-Visible, 29Si MAS-NMR) and calorimetric measurements to better understand the changes in the surface chemistry of Ti-MCM-41 samples due to the post-synthesis silylation treatment and to ascertain the role of these trimethylsilyl groups incorporated in olefin epoxidation. In such manner, the effect of the organic moieties on solids, and both water and glycol molecules contents on the catalytic activity and selectivity are analyzed in detail. Results show that the hydrophobicity level of the samples is responsible for the decrease in water adsorption and, consequently, the negligible formation of the non-desired glycol during the catalytic process. Thus, catalyst deactivation by glycol poisoning of Ti active sites is greatly diminished, this increasing catalyst stability and leading to practically quantitative production of the corresponding epoxide. The extended use of these hydrophobic Ti-MCM-41 catalysts together with organic hydroperoxides for the highly efficient and selective epoxidation of natural terpenes is also exemplified.

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Keywords
Hydrophobic materials; Ti-MCM-41 catalyst; Silylation treatment; Immersion calorimetry; Catalytic epoxidation
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Spectroscopic, calorimetric, and catalytic evidences of hydrophobicity on Ti-MCM-41 silylated materials for olefin epoxidations
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 507, 25 October 2015, Pages 14–25
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us