Reaction of aldehydes with the H5PV2Mo10O40 polyoxometalate and cooxidation of alkanes with molecular oxygen

Alexander M. Khenkin, Avi Rosenberger, Ronny Neumann

Research output: Contribution to journalArticle

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Abstract

The oxidation of alkanes with molecular oxygen using aldehydes as reducing agents (aldehydes are cooxidized) was studied using the α-H5PV2Mo10O40 polyoxometalate as catalyst. Emphasis was placed on the initiation of the radical chain reaction by investigation of the aldehyde-polyoxometalate interaction. Using 31P NMR and ESR spectroscopy one could differentiate between the reactivity of the five inseparable isomers of α-H5PV2Mo10O40. Contrary to previous belief, the 1,11 isomer with vanadium in distal positions is the most abundant. The 31P NMR and ESR spectra supported by UV-vis absorption-time profiles of the reduction of α-H5PV2Mo10O40 indicated that isomers with vanadium in vicinal positions were most kinetically viable in the alkane oxidation. Addition of isobutyraldehyde to α-H5PV2Mo10O40 gave in the 51V NMR spectrum a new downfield peak attributed to the formation of an aldehyde-polyoxometalate intermediate. The alkane/aldehyde/02 oxidizing system was found to be quite effective and selective for ketone formation. Reaction probes indicated that acyl peroxo radicals were the active oxidizing intermediates. Five pathways for its reaction were identified: chain propagation, alkane oxidation, decomposition to form oxygen, decomposition to acyl oxo radicals leading to CO2 and ketone, and capture and inhibition by the polyoxometalate.

Original languageEnglish
Pages (from-to)82-91
Number of pages10
JournalJournal of Catalysis
Volume182
Issue number1
Publication statusPublished - 1999

Fingerprint

Alkanes
Molecular oxygen
Aldehydes
aldehydes
Paraffins
alkanes
Isomers
oxygen
Vanadium
isomers
Nuclear magnetic resonance
Ketones
ketones
Oxidation
vanadium
nuclear magnetic resonance
oxidation
Paramagnetic resonance
Decomposition
decomposition

Keywords

  • Aldehyde
  • Alkane oxidation
  • Oxygen
  • Polyoxometalate

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

Reaction of aldehydes with the H5PV2Mo10O40 polyoxometalate and cooxidation of alkanes with molecular oxygen. / Khenkin, Alexander M.; Rosenberger, Avi; Neumann, Ronny.

In: Journal of Catalysis, Vol. 182, No. 1, 1999, p. 82-91.

Research output: Contribution to journalArticle

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