Stable Stoichiometry of Gas-Phase Cerium Oxide Cluster Ions and Their Reactions with CO

Nagata, Toshiaki; Miyajima, Ken; Mafuné, Fumitaka

doi:10.1021/jp509592a

Cited by 45 publications

(90 citation statements)

References 27 publications

(79 reference statements)

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“…CO) + , was not identified during the reaction 32. In contrast, the Langmuir−Hinshelwood mechanism can describe the NO oxidation (reaction 6) in the present study, because the intermediate complex, Ce n O 2n (NO) + , was observed.…”

contrasting

confidence: 78%

“…Moreover, the activation energy of NO 2 release (reaction 5) was estimated from the gas-phase TPD plots. 32,33,42 The rate constant of unimolecular dissociation can be described as a function of temperature, k(T), using the Arrhenius equation,…”

Section: Resultsmentioning

confidence: 99%

“…32 By contrast, both the rate constant of NO adsorption (Figure 2b) and the activation energy of NO 2 desorption (Figure 4b) were less size dependent. These differences were likely related to the location of the highest activation barrier in the reaction pathway, as mentioned above, which were the Ce n O 2n + CO → Ce n O 2n−1 + CO 2 step for CO oxidation and the Ce n O 2n−1 + NO 2 → Ce n O 2n−1 + + NO 2 step for NO oxidation.…”

Section: Comparison With Collision-induced Dissociationmentioning

confidence: 90%

“…The redox activity of cerium oxide clusters for the oxidation of CO has been reported. 27,28,32,34 Figure 8 with "NO" replaced with "CO" and "NO 2 " replaced with "CO 2 ". It remains unclear why NO oxidation ceased at the intermediate complex at room temperature, while CO oxidation reached completion without thermal excitation.…”

Section: Comparison With Collision-induced Dissociationmentioning

confidence: 99%

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Oxidation of Nitric Oxide on Gas-Phase Cerium Oxide Clusters via Reactant Adsorption and Product Desorption Processes

2015

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The reactivity of cerium oxide cluster cations, CenO2n+x(+) (n = 2-9, x = -1 to +2), with NO was investigated using gas-phase temperature-programmed desorption (TPD) combined with mass spectrometry. Target clusters were prepared in the gas phase via the laser ablation of a cerium oxide rod in the presence of oxygen, which was diluted using helium as a carrier gas. NO adsorbed onto stoichiometric and oxygen-rich clusters of CenO2n+x(+) (x = 0-2), forming CenO2n+x(NO)(+) (x = 0-2) species. Gas-phase TPD was measured for the NO-adsorbed clusters, revealing that CenO2n(NO)(+) released NO2 at 600-900 K, forming CenO2n-1(+). Therefore, the overall reaction was the oxidation of NO by the CenO2n(+) clusters, which was explained in terms of a Langmuir-Hinshelwood type reaction. An activation barrier existed between the initial complex (CenO2n(NO)(+)) and the final oxidation products (CenO2n-1(+) + NO2). To determine the nature of the intermediates and the activation barrier, TPD was also performed on CenO2n-1(NO2)(+), which had been prepared through the adsorption of NO2 on CenO2n-1(+) for comparison. The activation barrier was associated with the release of NO2 from the intermediate complex (CenO2n-1(+)-NO2 → CenO2n-1(+) + NO2) rather than the structural rearrangement that formed NO2 in the other intermediate complex (CenO2n(+)-NO → CenO2n-1(+)-NO2).

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contrasting

confidence: 78%

Section: Resultsmentioning

confidence: 99%

Section: Comparison With Collision-induced Dissociationmentioning

confidence: 90%

Section: Comparison With Collision-induced Dissociationmentioning

confidence: 99%

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Oxidation of Nitric Oxide on Gas-Phase Cerium Oxide Clusters via Reactant Adsorption and Product Desorption Processes

2015

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“…18,19 Rh n + cluster ions were prepared using pulse laser ablation in a cluster source. A Rh (99.9%) metal rod was vaporized using the focused second harmonic of an Nd:YAG pulse laser at a typical pulse energy of 10 mJ and a repetition rate of 10 Hz.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Thermal Desorption and Reaction of NO Adsorbed on Rhodium Cluster Ions Studied by Thermal Desorption Spectroscopy

et al. 2015

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Cationic rhodium clusters, Rh(n)(+) (n = 4-8), were prepared in the gas phase by the laser ablation of a Rh rod. The Rh(n)(+) clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He, where they were subjected to collisions with NO and He in a thermal equilibrium at 300 K. The NO molecules were found to adsorb sequentially on the Rh(n)(+) clusters forming Rh(n)(+)(NO)m. To examine the adsorption form and the reaction of NO, we heated Rh(n)(+)(NO)m in an extension tube located after the reaction gas cell and the thermal response of the clusters, desorption of the fragments, was recorded as a function of temperature (300-1000 K). The desorption of NO molecules was predominantly observed below 500 K, giving either Rh(n)(+)(NO)n+1 or Rh(n)(+)(NO)n+2, which indicates that there were NO molecules loosely adsorbed on the Rhn(+) clusters. Further desorption was found to proceed at higher temperatures (500-1000 K), whereby NO was released from the smaller clusters, Rh(n)(+) (n ≤ 5). In contrast, for the larger clusters (n ≥ 6), N2 release was clearly observed at high temperatures (>800 K). Thus, the reduction of NO occurred for larger clusters at higher temperatures.

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Ursachen der unterschiedlichen Reaktivität von [AlCeO_x]⁺ (x=2–4) gegenüber Methan in Abhängigkeit vom Sauerstoffgehalt

Zhou

Schlangen

et al. 2016

Angewandte Chemie

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Die thermischen Gasphasenreaktionen der geschlossenschaligen heteronuklearen Metalloxidcluster [AlCeO x ] + (x = 2-4) mit Methan wurden mittels FT-ICR-Massenspektrometrie und quantenchemischer Rechnungen untersucht. Während [AlCeO 2 ] + und [AlCeO 4 ] + unter thermischen Bedingungen gegenüber Methan inert sind, reagiert [AlCeO 3 ] + spontan unter Wasserstoffatomabstraktion. Unter Berücksichtigung mechanistischer Aspekte konnten die Ursachen dieser deutlich unterschiedlichen Eigenschaften der [AlCeO x ] + /CH 4 -Paare aufgedeckt werden;d ie elektronische Grundlage der beispiellosen, einfachen Wasserstoffatomabstraktion von Methan durchd en geschlossenschaligen Cluster [AlCeO 3 ] + wird diskutiert.Aluminiumund cerhaltige Metalloxide stehen wegen ihrer katalytischen Funktion in vielen großtechnischen Umwandlungsprozessen von Kohlenwasserstoffen nach wie vor im Fokus der chemischen Forschung. [1] Um Einblicke in diese Prozesse zu gewinnen, wurden zahlreiche Gasphasenuntersuchungen durchgeführt, mit denen die Reaktionsmechanismen auf strikt molekularer Ebene aufgeklärt werden konnten. [2] So kann in Modellstudien zur Methanaktivierung das aktive Zentrum eines Katalysators nachgebildet und damit die katalytische Umsetzung von Methan in der kondensierten Phase verbessert werden. Während eine Reihe von alumini-) n ]C + (n = 3-5) [10] und [Al 2 TaO 5 ] + , [11] zur thermischen Aktivierung von Methan in der Lage ist, sind nur zwei Arten von cerhaltigen Clustern, nämlich [(CeO 2 ) n ]C + (n = 2-4) [12] und [(CeO 2 ) m (V 2 O 5 ) n ] + (m = 1, 2, n = 1-5; m = 3, n = 1-4), [13] bekannt, die unter thermischen Bedingungen spontan mit Methan reagieren. Darüber hinaus gibt es unseres Wissens keine Studien zur thermischen Methanaktivierung durch heteronukleare Al/Ce-Cluster in der Gasphase;ind er konden-sierten Phase dagegen werden Al/Ce-haltige Katalysatoren fürdie Methanaktivierung bereits genutzt. [14] Hier berichten wir, dass das geschlossenschalige Oxid [AlCeO 3 ] + unter thermischen Bedingungen ein Wasserstoffatom von Methan abstrahieren kann;i mU nterschied dazu sind die beiden Kationen [AlCeO 2 ] + und [AlCeO 4 ] + gegenüber diesem Substrat inert. Darüber hinaus ist das Verhalten von [AlCeO 3 ] + auch deutlich verschieden von dem anderer geschlossenschaliger Spezies wie [OTiH] + , [15] [AuCH 2 ] + , [16] [AuC] + , [17] [OSiOH] + , [18] [XHfO] + (X = F, Cl, Br), [19] [TaO 2 ] + , [20] [TaO 3 ] + , [21] [Al 2 TaO 5 ] + , [11] [AuTi 3 O x ] À (x = 7, 8) [22] und [AuV 2 O 6 ] + . [23] Zwar kçnnen auch diese Ionen Methan unter thermischen Bedingungen aktivieren, zur einfachen Wasserstoffatomabstraktion unter Verlust eines Methylradikals sind sie jedoch nicht in der Lage.D ie Ursachen der unterschiedlichen Reaktivitäten von [AlCeO x ] + (x = 2-4) gegenüber Methan sowie die besonderen Eigenschaften von [AlCeO 3 ] + werden hier diskutiert. Setzt man massenselektierte und thermalisierte [AlCeO x ] + -Ionen (x = 2-4) der Gegenwart von CH 4 aus, reagiert nur [AlCeO 3 ] + unter Bildung von [AlCeO 3 H]C + [Abbildung 1a und Gl. (1) (t...

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Stable Stoichiometry of Gas-Phase Cerium Oxide Cluster Ions and Their Reactions with CO

Cited by 45 publications

References 27 publications

Oxidation of Nitric Oxide on Gas-Phase Cerium Oxide Clusters via Reactant Adsorption and Product Desorption Processes

Oxidation of Nitric Oxide on Gas-Phase Cerium Oxide Clusters via Reactant Adsorption and Product Desorption Processes

Thermal Desorption and Reaction of NO Adsorbed on Rhodium Cluster Ions Studied by Thermal Desorption Spectroscopy

Ursachen der unterschiedlichen Reaktivität von [AlCeO_x]⁺ (x=2–4) gegenüber Methan in Abhängigkeit vom Sauerstoffgehalt

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Stable Stoichiometry of Gas-Phase Cerium Oxide Cluster Ions and Their Reactions with CO

Cited by 45 publications

References 27 publications

Oxidation of Nitric Oxide on Gas-Phase Cerium Oxide Clusters via Reactant Adsorption and Product Desorption Processes

Oxidation of Nitric Oxide on Gas-Phase Cerium Oxide Clusters via Reactant Adsorption and Product Desorption Processes

Thermal Desorption and Reaction of NO Adsorbed on Rhodium Cluster Ions Studied by Thermal Desorption Spectroscopy

Ursachen der unterschiedlichen Reaktivität von [AlCeOx]+ (x=2–4) gegenüber Methan in Abhängigkeit vom Sauerstoffgehalt

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Ursachen der unterschiedlichen Reaktivität von [AlCeO_x]⁺ (x=2–4) gegenüber Methan in Abhängigkeit vom Sauerstoffgehalt