In Situ Raman Spectroscopy of Supported Transition Metal Oxide Catalysts:  ¹⁸O₂−¹⁶O₂ Isotopic Labeling Studies

Abstract

The isothermal isotopic exchange reaction of 18 reoxidation cycles at relatively high temperatures. The Raman spectroscopy data reveal that all the supported transition metal oxides are present as a monooxo species on ZrO 2 . This finding is consistent with the shifts calculated from the isotopic ratios for a simple diatomic oscillator, with the corresponding infrared spectra of the same catalysts and with the vibrational frequencies of several monooxo reference compounds. On this basis, coordination models of the molecular structures are proposed for

Molecular Structure of a Supported VO4 Cluster and Its Interfacial Geometry as a Function of the SiO2, Nb2O5, and ZrO2 Support

“…At dehydrated conditions and low loadingsbelow the monomeric monolayer (2.3 VO x /nm 2 ) as defined by Khodakov 7 sthe vanadium oxide species on the surface will be present only as a monomeric VO 4 cluster with one VdO bond. 17,18 EXAFS data analysis showed that for all supports the VO 4 cluster is attached to the surface with only one V-O b -M support bond under the applied measurement conditions. Both the V-O b bond distance and the V‚‚‚ M support distance depend on the structure of the support surface.…”

Chemistry, Spectroscopy and the Role of Supported Vanadium Oxides in Heterogeneous Catalysis

“…At low surface vanadium oxide loading the supported vanadium oxides are isolated VO 4 units, containing one terminal mono-oxo V=O bond and three bridging vanadium-oxygen-support bond with symmetry C 3v . The mono-oxo nature of this species has been concluded from O-18 isotopic labeling experiments in conjunction with Raman spectroscopy [189]. In addition, the frequency of the V=O bond has the same value in IR and Raman spectroscopy.…”

Catalytic upgrading of refinery cracked products by trans-hydrogenation: a review

“…Chromia catalysts have been subject to extensive characterisation using a variety of techniques such as electron spin resonance (ESR) [40,41], infrared spectroscopy (IR) [42,43], diffuse reflectance spectroscopy (DRS) [44,45], photon electron spectroscopy (XPS) [46,47], X-ray diffraction (XRD) [48][49][50], thermo-gravimetric analysis (TGA) [49,50] and Raman spectroscopy [51,52]. Although in the as-prepared catalyst chromia is often in a 6?…”