Heteroatoms Increase the Selectivity in Oxidative Dehydrogenation Reactions on Nanocarbons

Frank, Benjamin; Zhang, Jian; Blume, Raoul; Schlögl, Robert; Su, Dang Sheng

doi:10.1002/anie.200901826

Cited by 307 publications

(223 citation statements)

References 30 publications

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“…In addition, carbon nanotubes without any transition metal in the active site are also included in the comparison. The latter catalyst is of interest as it allows studying oxygen species in the form of nucleophilic and electrophilic species [117,118] without having to analyze the large background of lattice oxygen [119] being the most abundant surface species on oxide catalysts.…”

Section: Active Sites For Odpmentioning

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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Section: Active Sites For Odpmentioning

confidence: 99%

Active Sites for Propane Oxidation: Some Generic Considerations

Schlögl

2011

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“…[4] The fact that the surface modification of CNTs can increase the selectivity to alkene has also been reported for the ODH of propane to propene. [5] CNTs doped with B or P provided selectivities to propene higher than that of pristine or oxidised CNTs. B-CNTs afforded a high selectivity to propene, that is, 60 % selectivity at 5 % conversion.…”

Section: Introductionmentioning

confidence: 78%

“…A 39 % selectivity to propene at 42 % conversion along with enhanced stability to oxidation compared to that of undoped carbon nanofibres (CNFs) have been reported if P-CNFs are used. [6] The higher selectivities achieved using P-or B-doped CNTs have been explained in terms of P or B reaction with CNT sidewall defects that would suppress the formation of electrophilic O species, which are the cause of the decrease in selectivity [5] Recently, N-CNTs have shown an enhanced performance in the ODH of propane. [7] Unlike CNTs, which expose graphitic planes to the gas reactants, CNFs expose the basal plane edges.…”

Section: Introductionmentioning

confidence: 99%

“…The selective sites are reported to be quinone or dicarbonyl groups on the carbon surface, while carboxylic acids are unselective to propene and favour the complete oxidation of its double bond. [5,8,9] CNFs have been used as a catalyst for the ODH of ethylbenzene, in which the graphitic platelet orientation has a significant effect on the catalyst activity and selectivity. [10] In that case, the conversion was promoted by enhanced p-p interactions of the ethylbenzene phenyl ring with the carbon basal planes.…”

Section: Introductionmentioning

confidence: 99%

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Carbon Nanofibers Modified with Heteroatoms as Metal‐Free Catalysts for the Oxidative Dehydrogenation of Propane

et al. 2014

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Carbon nanofibres (CNFs) were modified with B and P by an ex situ approach. In addition, CNFs doped with N were prepared in situ using ethylenediamine as the N and C source. After calcination, the doped CNFs were used as catalysts for the oxidative dehydrogenation of propane. For B-CNFs, the effects of boron loading and calcination temperature on B speciation and catalytic conversion were studied. For the same reaction temperatures and conversions, B- and P-doped CNFs exhibited higher selectivities to propene than pristine CNFs. The N-CNFs were the most active but the least selective of the catalysts tested here. Our results also show that the type of P precursor affects the selectivity to propene and that CNFs modified using triphenylphosphine as the precursor provided the highest selectivity at isoconversion.

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“…In the present work highly ordered CNFs were used as model catalyst to determine and interpret the evolution the catalytic performance and get some additional information regarding the active sites and the catalyst activation during the reaction. Using elemental carbon as a catalyst for oxidation reactions, a pronounced initial (de)activation profile is generally observed, which is related to coke deposition in micropores [13], surface restructuring [9], and equilibration of surface oxygen groups [14][15][16][17]. The present study focuses on different methods of surface treatment, which are expected to result in different states of activated surfaces with different catalytic performances.…”

Section: Introductionmentioning

confidence: 96%

Activation processes of highly ordered carbon nanofibers in the oxidative dehydrogenation of ethylbenzene

et al. 2012

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Highly graphitized multiwalled carbon nanofibers (CNFs) were used as a carbon-based model catalyst to study the oxidative dehydrogenation (ODH) of ethylbenzene. Their stability as well as the evolution of catalytic performance as well as structural and textural properties under robust operation conditions were studied. The catalyst was characterized by TEM, TPO, XPS, and N2 physisorption techniques. Highly ordered CNFs provide a low initial catalytic activity owing to the low degree of surface functionalization. The rate of ethylbenzene conversion increases by factor of 5 as the catalyst is exposed to the reaction conditions at 475°C for a period of 30h time on stream. A similar catalytic performance is obtained after short-term oxidation treatment of the pristine CNFs. The in-situ formation of surface defects is attributed to the activation of the catalyst, whereas the generation of an active carbonaceous deposit on the catalyst surface is found to be less relevant.

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Heteroatoms Increase the Selectivity in Oxidative Dehydrogenation Reactions on Nanocarbons

Cited by 307 publications

References 30 publications

Active Sites for Propane Oxidation: Some Generic Considerations

Active Sites for Propane Oxidation: Some Generic Considerations

Carbon Nanofibers Modified with Heteroatoms as Metal‐Free Catalysts for the Oxidative Dehydrogenation of Propane

Activation processes of highly ordered carbon nanofibers in the oxidative dehydrogenation of ethylbenzene

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