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Novel alkoxysilane pentacoordinate OV(IV) complexes as supported catalysts for cyclohexane oxidation with dioxygen

Paper ID Volume ID Publish Year Pages File Format Full-Text
41946 45905 2010 11 PDF Available
Title
Novel alkoxysilane pentacoordinate OV(IV) complexes as supported catalysts for cyclohexane oxidation with dioxygen
Abstract

A variety of newly synthesized and well characterized alkoxysilane pentacoordinate Oxovanadium(IV) complexes, VO[Sal(PMeOSi)DPTA] 3[a], VO[Cl-Sal(PMeOSi)DPTA] 3[b], VO[Sal(PMeOSi)DETA] 6[a] and VO[Cl-Sal(PMeOSi)DETA] 6[b], (Sal = salicylaldehyde, DPTA = bis(aminopropyl)amine, DETA = diaminoethylamine), have been anchored by covalent bond into the surface of SiO2 and/or Al2O3 via silicon-alkoxide route by a condensation process as supported catalysts. These solid supported catalysts (abbreviated as catalysts A to H) showed high catalytic efficiency in the selective oxidation reaction of cyclohexane using molecular oxygen under relatively mild condition in a micro-batch reactor. The Catalyst C (SiO2/3[a] complex) system exhibits best activity, overall yield 38.5% (TONs, ca. 5.0 × 103) as well as high selectivity 98% (cyclohexanol 74%, cyclohexanone 24%). Notably, cyclohexane shows significantly improved yield 44.0%, by the addition of pyrazinecarboxylic acid as a co-catalyst. The TGA indicates these catalysts are stable up to maximum reaction temperature, ca. 473 K and ICP analysis shows there is negligible vanadium loss from the supported catalyst after the reaction, allowing further use of the V-catalyst. The various factors influences (i.e. temperature, O2 pressure, reaction time, catalyst amount) were also investigated in the systematic way, to optimize the reaction processes. The impact of radical traps and detection of intermediate peroxy radical were also investigated to establish a radical mechanism.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (124 K)Download as PowerPoint slideResearch highlights▶ Synthesis and well characterization of newly alkoxysilane pentacoordinate Oxovanadium(IV) complexes. ▶ Covalently anchored Oxovanadium(IV) complexes on the surface of SiO2 and/or Al2O3 as supported catalysts. ▶ Supported V-catalysts showed high catalytic efficiency (high TONs, ca. 5.0 × 103) in the selective oxidation of cyclohexane with molecular O2. ▶ Significantly improved yield was obtained by pyrazinecarboxylic acid as a co-catalyst.

Keywords
V-complexes; Covalent bond anchoring; Supported catalysts; Cyclohexane; Oxygen
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Novel alkoxysilane pentacoordinate OV(IV) complexes as supported catalysts for cyclohexane oxidation with dioxygen
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 384, Issues 1–2, 20 August 2010, Pages 136–146
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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Any Questions? feel free to contact us