Active centers in Mo–V–Nb–Te–O (amm)oxidation catalysts

Grasselli, Robert K.; Buttrey, Douglas J.; DeSanto, Peter; Burrington, James D.; Lugmair, Claus G.; Volpe, Anthony F.; Weingand, Thomas

doi:10.1016/j.cattod.2004.03.060

Cited by 169 publications

(171 citation statements)

References 18 publications

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“…This part would require a trimeric unit for the most difficult step of allylic oxidation plus storage sites for three additional redox equivalents. We know from the original concept [15,96] and from the analysis of the dynamics of reactive surfaces by in situ spectroscopy [13] that vanadium is essential in the active site. From the correlation of Fig.…”

Section: Size and Functions Of Active Sitesmentioning

confidence: 99%

“…As the complete conversion of propane to AA requires the exchange of eight redox equivalents, the active site ensemble should be able to store these eight equivalents. The suggested pentameric unit [15] within the a-b plane of the M1 structure may store five redox equivalents; as the pentameric units also coordinate two tellurate anions, these may complete the electron storage capacity if we assume that the surface tellurate are hexa-valent.…”

Section: Size and Functions Of Active Sitesmentioning

confidence: 99%

“…The variation of the site occupation [16,45,46] as an ingredient or reactivity leading to metastability controls the formation and abundance of isolated nanodomains with the correct chemical composition [13,26,49,53] yielding the active catalyst. The cation composition of the pentameric site is of a mixture of V and Mo according to the original literature [15] with highly specific requirements for assumed catalytic function; not all V x Mo Y combinations would be active based upon assumptions of rigid oxidation states and neglecting the concept of adaptive sites. The model of essential cation occupation statistics achieving site isolation would be equivalent in its consequences to the statements in the literature based, however, on quite different arguments.…”

Section: Termination Of the M1 Phasementioning

confidence: 99%

“…For the case of propane oxidation a proposal has been made [14,15] that can well serve as discussion basis. A highlight in the development process [16][17][18][19][20][21][22] of selective oxidation catalysis was the discovery of the orthorhombic M1 phase MoVNbTeOx.…”

Section: Introductionmentioning

confidence: 99%

“…not under vacuum [13,42]. The undeniable fact [15] that a pure rigid V 5? active phase would be over-oxidizing but that a redox change between V 5?…”

Section: Termination Of the M1 Phasementioning

confidence: 99%

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Active Sites for Propane Oxidation: Some Generic Considerations

Schlögl

2011

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Based on experimental observations about structure and dynamics of the reactive surface of the M1 phase some considerations are made about the nature and size of active sites. In analyzing the stoichiometry of the reactions following activation of propane it occurs that for dehydrogenation small sites are desirable being just sufficient to re-activate oxygen without kinetic hindrance. For deeper oxidation to acrylic acid (AA) the sites should be larger to accommodate all redox equivalents and oxygen species required for one transformation. A qualitative model for size and composition of the active site is made. It is likely that the active site consists on a VxOy species of strictly 2-D nature. This follows the structural suggestion for the active site on the a-b-plane of the M1 structure. The role of Te in moderating the active site is discussed. The suggestions are discussed in comparing requirements for oxidative dehydrogenation of propane (ODP) with those for AA synthesis.

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Section: Size and Functions Of Active Sitesmentioning

confidence: 99%

Section: Size and Functions Of Active Sitesmentioning

confidence: 99%

Section: Termination Of the M1 Phasementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…not under vacuum [13,42]. The undeniable fact [15] that a pure rigid V 5? active phase would be over-oxidizing but that a redox change between V 5?…”

Section: Termination Of the M1 Phasementioning

confidence: 99%

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Active Sites for Propane Oxidation: Some Generic Considerations

Schlögl

2011

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Application of Ambient‐Pressure X‐ray Photoelectron Spectroscopy for the In‐situ Investigation of Heterogeneous Catalytic Reactions

Starr

Bluhm

et al. 2013

In‐situ Characterization of Heterogeneous Catalysts

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Heterogeneous chemical reactions at vapor/solid interfaces play an important role in many processes in the environment and technology. Ambient pressure X-ray photoelectron spectroscopy (APXPS) is a valuable tool to investigate the elemental composition and chemical specificity of surfaces and adsorbates on the molecular scale at pressures of up to 130 mbar. In this review we summarize the historical development of APXPS since its introduction over forty years ago, discuss different approaches to minimize scattering of electrons by gas molecules, and give a comprehensive overview about the experimental systems (vapor/solid interfaces) that have been studied so far. We also present several examples for the application of APXPS to environmental science, heterogeneous catalysis, and electrochemistry.

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