Role of Ceria in Oxidative Dehydrogenation on Supported Vanadia Catalysts

Ganduglia‐Pirovano, M. V.; Popa, Cristina; Sauer, Joachim; Abbott, Heather; Uhl, Alexander; Baron, Martín; Stacchiola, Darı́o; Bondarchuk, Oleksandr; Shaikhutdinov, Shamil K.; Freund, Hans‐Joachim

doi:10.1021/ja910574h

Cited by 191 publications

(308 citation statements)

References 47 publications

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“…The calculations [29] indicate a rather high diffusion barrier for vanadia monomers, which turns out to be of key importance to understand the temperature programmed reaction data presented in Fig. 5 for the oxidation of methanol to formaldehyde [13]. The traces from top to bottom refer to pure CeO 2 (111) followed by increasing vanadia coverage.…”

Section: Resultsmentioning

confidence: 92%

“…Recently, further concepts have been introduced. A concept, relating oxidation reaction energetics to partial reaction descriptors, was recently introduced by Joachim Sauer, and we will make use of it when we discuss methanol oxidation on ceria supported vanadia catalysts [12,13]. Another, even more general concept on acid-base pair formation through modified oxide surfaces was proposed by Horia Metiu, enabling also a more systematic approach of the influence of dopants [14].…”

Section: Introductionmentioning

confidence: 99%

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Model Studies on Heterogeneous Catalysts at the Atomic Scale

2014

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Thin single crystalline oxide films comprise perfect supports to grow nanoparticles of metals and other catalytically relevant materials. The model systems thus created can be thoroughly investigated with respect to structure and/or chemical activity applying both, the techniques of surface science under ultrahigh vacuum conditions as well as the traditional techniques applied in catalysis to study chemical kinetics under ambient conditions. We discuss here in particular the oxidation of methanol to formaldehyde on ceria supported vanadia nanoclusters as well as the effect of transition-metal dopants in single crystalline oxides, such as CaO, on the activation of molecular oxygen

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Model Studies on Heterogeneous Catalysts at the Atomic Scale

2014

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“…The combined STM and infrared reflection absorption spectroscopy (IRAS) study, supported by DFT calculations, allowed us to establish a direct structure-spectroscopy relationship [55]. Furthermore, using the energies of hydrogenation and oxygen defect formation as descriptors for reactivity of oxidation catalysts, DFT calculations were shown to be consistent with the experimentally observed higher reactivity of vanadia/ceria systems towards methanol compared with that of vanadia and ceria surfaces [56].…”

Section: Introductionmentioning

confidence: 92%

Relating methanol oxidation to the structure of ceria-supported vanadia monolayer catalysts

Abbott

Uhl

Baron

et al. 2010

Journal of Catalysis

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Abstract.Vanadia "monolayer"-type catalysts supported on reducible oxides such as ceria previously have shown high activity for the selective oxidation of alcohols. Here, a model system consisting of vanadia particles deposited on well-ordered CeO 2 (111) thin films has been employed. Scanning tunneling microscopy (STM), photoelectron spectroscopy (PES), and infrared reflection absorption spectroscopy (IRAS) were used to characterize the VO x /CeO 2 surface as a function of vanadia loading. The formation of isolated monomeric species as well as two-dimensional vanadia islands that wet the ceria support was directly observed by STM. The vanadia species exhibit V in a +5 oxidation state and expose vanadyl (V=O) groups with stretching vibrations that blue -shift from ~1005 cm -1 , to ~1040 cm -1 with increasing coverage.Temperature programmed desorption (TPD) of methanol revealed three peaks for formaldehyde production. One is correlated with reactivity on the ceria support (565-590 K). Another is correlated with reactivity on large vanadia particles (475-505 K) similar to that previously observed on vanadia/silica and vanadia/alumina model systems. A low temperature reaction pathway (~370 K) is observed at low coverage, which is assigned to the reactivity of isolated vanadia species surrounded by a reduced ceria surface. It is concluded that strong support effects reported in the literature for the real catalysts are likely related to the stabilization of small vanadia clusters by reducible oxide supports.

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“…Surface-science approaches work only with activated molecules such as methanol [5,6] and theory [5,7,8] is confined to simplified yet highly valuable model systems [6,9,10]. It is still a great challenge to construct concepts of active sites [11,12] for selective oxidation that are based upon experimental observations [13] of reacting surfaces.…”

Section: Introductionmentioning

confidence: 99%

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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Role of Ceria in Oxidative Dehydrogenation on Supported Vanadia Catalysts

Cited by 191 publications

References 47 publications

Model Studies on Heterogeneous Catalysts at the Atomic Scale

Model Studies on Heterogeneous Catalysts at the Atomic Scale

Relating methanol oxidation to the structure of ceria-supported vanadia monolayer catalysts

Active Sites for Propane Oxidation: Some Generic Considerations

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