Concepts in Selective Oxidation of Small Alkane Molecules

Schlögl, Robert

doi:10.1002/9783527627547.ch1

Cited by 19 publications

(19 citation statements)

References 248 publications

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“…The electron delocalization is in contradiction with the concept of "isolated active site" often cited in the literature to explain the selectivity of catalysts toward partial oxidation reaction. Schlogl 43 has already discussed the accuracy of this concept for highly polymeric systems. The author reports that the concept of "isolated selective sites" for partial oxidation (in opposition to the concept of cooperative phase made by "multielement multiphase oxide") needs to be reconciled simultaneously with the geometric and the electronic structures of the catalyst.…”

Section: The Journal Of Physical Chemistry Cmentioning

confidence: 99%

Investigation of the Reducibility of Supported Oxomolybdate Species for Mapping of Active Centers of Partial Oxidation Reaction: In Situ Mo K-Edge XAS and DFT Study

Souza

Berrier

et al. 2019

J. Phys. Chem. C

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We have investigated the molecular and electronic structure of a TiO 2supported oxomolybdate phase upon reduction under methanol or dihydrogen atmosphere. In situ Mo K-edge X-ray absorption spectroscopy, supported by density functional theory (DFT) calculations and ab initio X-ray absorption spectroscopy (XAS) spectra simulation showed that the reducibility of supported molybdate species is closely related to the geometric environment of Mo atoms. Indeed, Mo atoms not involved in terminal oxo sites are easily reducible whereas Mo dioxo species are not under the conditions we have applied. Between those extreme cases, Mo atoms involved in monooxo terminal sites exhibit intermediate reducibility, which varies according to their local environment and their interaction with the support. Spin density calculations showed that under CH 3 OH flow, the surface of the catalyst is partially reduced. The structure of the reduced phase after reaction with methanol was compared to that afforded after reduction by dihydrogen. Our results show that the reduction under H 2 flow does not increase the number of reduced Mo atoms but causes a higher spin density per Mo atom. On the basis of the individual mapping of the electronic structure of Mo species as drawn by DFT and XAS spectra simulation, a model that details the structure of the Mo active sites in the selective oxidation of methanol is proposed.

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Section: The Journal Of Physical Chemistry Cmentioning

confidence: 99%

Investigation of the Reducibility of Supported Oxomolybdate Species for Mapping of Active Centers of Partial Oxidation Reaction: In Situ Mo K-Edge XAS and DFT Study

Souza

Berrier

et al. 2019

J. Phys. Chem. C

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“…This observation characterises element segregation or the formation of a sublayer of different composition than the bulk, as shown by Millet et al [25]. It was observed [26] that the surface composition of the M1 phase differs significantly from the bulk, implying that the catalytically active sites are not part of the M1 crystal structure and rather part of all terminating planes. It then appeared that the active sites are formed under propane oxidation conditions and are embedded in a thin layer enriched in V, Te, and Nb on the surface of the stable self-supporting M1 phase [23].…”

Section: Introduction To Metal Oxide Catalystsmentioning

confidence: 64%

Heterogeneous Catalysis on Metal Oxides

2017

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This review article contains a reminder of the fundamentals of heterogeneous catalysis and a description of the main domains of heterogeneous catalysis and main families of metal oxide catalysts, which cover acid-base reactions, selective partial oxidation reactions, total oxidation reactions, depollution, biomass conversion, green chemistry and photocatalysis. Metal oxide catalysts are essential components in most refining and petrochemical processes. These catalysts are also critical to improving environmental quality. This paper attempts to review the major current industrial applications of supported and unsupported metal oxide catalysts. Viewpoints for understanding the catalysts' action are given, while applications and several case studies from academia and industry are given. Emphases are on catalyst description from synthesis to reaction conditions, on main industrial applications in the different domains and on views for the future, mainly regulated by environmental issues. Following a review of the major types of metal oxide catalysts and the processes that use these catalysts, this paper considers current and prospective major applications, where recent advances in the science of metal oxide catalysts have major economic and environmental impacts.

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“…Its formation is likely connected to calcination in argon. The amorphous layer is intrinsically defective and the reactivity of oxygen in amorphous mixed metal oxides is higher than in any of its crystalline components [40]. Ruth et al [41], report that the amorphous part of the multiphase Mo-V-Nb oxide catalyst is particularly important during oxidative dehydrogenation and partial oxidation of ethane.…”

Section: Discussionmentioning

confidence: 99%

Role of CO2 During Oxidative Dehydrogenation of Propane Over Bulk and Activated-Carbon Supported Cerium and Vanadium Based Catalysts

et al. 2021

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CeO2, V2O5 and CeVO4 were synthesised as bulk oxides, or deposited over activated carbon, characterized by XRD, HRTEM, CO2-TPO, C3H8-TPR, DRIFTS and Raman techniques and tested in propane oxidative dehydrogenation using CO2. Complete oxidation of propane to CO and CO2 is favoured by lattice oxygen of CeO2. The temperature programmed experiments show the ~ 4 nm AC supported CeO2 crystallites become more susceptible to reduction by propane, but less prone to re-oxidation with CO2 compared to bulk CeO2. Catalytic activity of CeVO4/AC catalysts requires a 1–2 nm amorphous CeVO4 layer. During reaction, the amorphous CeVO4 layer crystallises and several atomic layers of carbon cover the CeVO4 surface, resulting in deactivation. During reaction, V2O5 is irreversibly reduced to V2O3. The lattice oxygen in bulk V2O5 favours catalytic activity and propene selectivity. Bulk V2O3 promotes only propane cracking with no propene selectivity. In VOx/AC materials, vanadium carbide is the catalytically active phase. Propane dehydrogenation over VC proceeds via chemisorbed oxygen species originating from the dissociated CO2. Graphic Abstract

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Concepts in Selective Oxidation of Small Alkane Molecules

Cited by 19 publications

References 248 publications

Investigation of the Reducibility of Supported Oxomolybdate Species for Mapping of Active Centers of Partial Oxidation Reaction: In Situ Mo K-Edge XAS and DFT Study

Investigation of the Reducibility of Supported Oxomolybdate Species for Mapping of Active Centers of Partial Oxidation Reaction: In Situ Mo K-Edge XAS and DFT Study

Heterogeneous Catalysis on Metal Oxides

Role of CO2 During Oxidative Dehydrogenation of Propane Over Bulk and Activated-Carbon Supported Cerium and Vanadium Based Catalysts

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