Journal Article10.1039/B915590B
Oxidation reactions on neutral cobalt oxide clusters: experimental and theoretical studies
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TL;DR: A catalytic cycle for these oxidation reactions on a condensed phase cobalt oxide catalyst is proposed, and the experimental cluster observations are in good agreement with condensed phase Co(3)O(4) behavior.
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Abstract: Reactions of neutral cobalt oxide clusters (ComOn, m = 3–9, n = 3–13) with CO, NO, C2H2, and C2H4 in a fast flow reactor are investigated by time of flight mass spectrometry employing 118 nm (10.5 eV) single photon ionization. Strong cluster size dependent behavior is observed for all the oxidation reactions; the Co3O4 cluster has the highest reactivity for reactions with CO and NO. Cluster reactivity is also highly correlated with either one or more following factors: cluster size, Co(III) concentration, the number of the cobalt atoms with high oxidation states, and the presence of an oxygen molecular moiety (an O–O bond) in the ComOn clusters. The experimental cluster observations are in good agreement with condensed phase Co3O4 behavior. Density functional theory calculations at the BPW91/TZVP level are carried out to explore the geometric and electronic structures of the Co3O4 cluster, reaction intermediates, transition states, as well as reaction mechanisms. CO, NO, C2H2, and C2H4 are predicted to be adsorbed on the Co(II) site, and react with one of the parallel bridge oxygen atoms between two Co(III) atoms in the Co3O4 cluster. Oxidation reactions with CO, NO, and C2H2 on the Co3O4 cluster are estimated as thermodynamically favorable and overall barrierless processes at room temperature. The oxidation reaction with C2H4 is predicted to have a very small overall barrier (<0.23 eV). The oxygen bridge between two Co(III) sites in the Co3O4 cluster is responsible for the oxidation reactions with CO, NO, C2H2, and C2H4. Based on the gas phase experimental and theoretical cluster studies, a catalytic cycle for these oxidation reactions on a condensed phase cobalt oxide catalyst is proposed.
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Citations
Structures of cobalt oxide cluster cations studied by ion mobility mass spectrometry
TL;DR: In this paper, collision cross sections of cobalt oxide cluster cations have been determined for (CoO ) 2 - 7 + and Co n O n - 1 + (n ǫ = 5 − 7) orientation-averaged collision crosssections were calculated for optimized structures of these ions obtained in quantum chemical calculations.
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Double C–H Bond Activation of Hydrocarbons by a Gas Phase Neutral Oxide Cluster: The Importance of Spin State
TL;DR: Experimental results show clearly that neutral V2O5 can react with n-butane (C4H10) to generate V 2O5H2, indicating double hydrogen atom transfer from C 4H10 to V2 O5 to produce C4H8, and density functional theory studies show that the lowest energy triplet state of V1O5 is reactive toward C4h10, whereas the ground state singlet V2o5 is inert.
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Formaldehyde and methanol formation from reaction of carbon monoxide and hydrogen on neutral Fe2S2 clusters in the gas phase
TL;DR: Catalytic cycles for formaldehyde and methanol formation from CO and H2 on a Fe2S2 cluster are proposed based on experimental and theoretical investigations and various reaction mechanisms explored are in good agreement with the experimental results.
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Synthesis of highly active Cobalt catalysts for low temperature CO oxidation
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