ChemInform Abstract: MECHANISM OF NITROGEN INSERTION IN AMMOXIDATION CATALYSIS

Burrington, James D.; KARTISEK, C. T.; Grasselli, Robert K.

doi:10.1002/chin.198337074

Cited by 45 publications

(93 citation statements)

References 1 publication

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“…49 They assumed that N insertion is favored over O insertion. Considering that the allyl adsorption is the major part of the O-or N-insertion process, the lower energy cost for the allyl adsorption on an imido group [case (b); -4.0 kcal/mol] than on an oxo group [case (c); 12.8 kcal/mol] confirms this assumption.…”

Section: Ammoxidationmentioning

confidence: 99%

Mechanism of Selective Oxidation and Ammoxidation of Propene on Bismuth Molybdates from DFT Calculations on Model Clusters

Jang

Goddard

2002

J. Phys. Chem. B

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In this paper, we use first principles quantum mechanical methods (B3LYP flavor of Density Functional Theory) to examine the mechanism of selective oxidation and ammoxidation of propene by BiMoO x catalysts. To do this, we use finite clusters chosen to mimic likely sites on the heterogeneous surfaces of the catalysts. We conclude that activation of the propene requires a Bi(V) site, whereas all subsequent reactions involve di-oxo Mo(VI) sites adjacent to the Bi. We find that two such Mo sites are required for the most favorable reactions. These results are compatible with current experimental data. For ammoxidation, we conclude that ammonia activation would be easier on Mo(IV) rather than on Mo(VI). Ammonia would be activated more easily for more reducing condition. Because ammonia and propene are reducing agents, higher partial pressures of them could accelerate the ammonia activation. This is consistent with the kinetic model of ammoxidation proposed by Grasselli and co-workers that imido sites (ModNH) are more abundant in higher partial pressures of feed. Our calculations also indicate that allyl groups produced as a result of the hydrogen abstraction from propenes would be adsorbed more easily on imido groups (ModNH) than on oxo groups (ModO) and that the spectator oxo effect is larger than spectator imido effect. Thus, we propose that the best site for ammoxidation (at least for allyl adsorption) is the imido group of the "oxo-imido" species.

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Section: Ammoxidationmentioning

confidence: 99%

Mechanism of Selective Oxidation and Ammoxidation of Propene on Bismuth Molybdates from DFT Calculations on Model Clusters

Jang

Goddard

2002

J. Phys. Chem. B

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“…Previously, it has been reported [27,28] that the high activity of bismuth molybdate compounds forming acrolein was due to the presence of active sites including both Mo and Bi atoms. These complex active sites are indeed available in the structure of bismuth molybdate compounds.…”

Section: Characterizationmentioning

confidence: 99%

Synergy effects in mixed Bi2O3, MoO3 and V2O5 catalysts for selective oxidation of propylene

Truong

Fehrmann

et al. 2011

Res Chem Intermed

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In this work, the possible synergy effects between Bi2O3, MoO3 and V2O5, and between Bi2Mo3O12 and BiVO4, were investigated. The catalytic activity of the "mechanical mixture" of these compounds was measured. The mixture containing 36.96 mol% Bi2O3, 39.13 mol% MoO3 and 23.91 mol% V2O5 (21.43 mol% Bi2Mo3O12 and 78.57 mol% BiVO4), corresponding to the compound Bi1-x/3V1-xMoxO4 with x = 0.45 (Bi0.85V0.55Mo0.45O4), exhibited the highest activity for the selective oxidation of propylene to acrolein. The mixed sample prepared chemically by a sol-gel method possessed higher activity than that of mechanical mixtures

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“…(19)(20)(21)(22) , demonstrated that after the first hydrogen abstraction, insertion of oxygen takes place, and only then the second hydrogen is abstracted resulting in the formation of the acrolein precursor.…”

Section: Activation Of Organic Moleculementioning

confidence: 99%

Catalysis by Transition Metal Oxides

Haber

1985

Solid State Chemistry in Catalysis

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Catalytic oxidation reactions are divided into two groups:electrophilic oxidation proceeding through activation of oxygen and nucleophilic oxidation in which activation of the hydrocarbon molecule is the first step, followed by consecutive hydrogen abstraction and nucleophilic oxygen insertion. Properties of individual cations and their coordination polyhedra determine their behaviour as active centers responsible for activation of hydrocarbon molecules. A facile route for nucleophilic insertion of oxygen into such molecules by group V, VI and VII transition metal oxides is provided by the crystallographic shear mechanism, catalytic properties are thus dependent upon the geometry of the surface. The catalyst surface is in dynamic interaction with the gas phase, and changes of the latter may thus result in surface transformations and appearance of surface phases, which influence the selectivity of catalytic reactions.The vast majority of catalysts used in modern chemical industry are oxides. Because of their ability to take part in the exchange of electrons, as well as in the exchange of protons or oxide ions, oxides are used as catalysts in both redox and acid-base reactions. They constitute the active phase not only in oxide catalysts but also in the case of many metal catalysts, which in the conditions of catalytic reaction are covered by a surface layer of a reactive oxide.Properties of oxides are also important in the case of preparation of many metal and sulphide catalysts, which are obtained from an oxide precursor.Very often, highly dispersed metals are prepared by reduction of an appropriate oxide phase, and sulphide catalysts are formed from the oxide precursor in the course of the hydrodesulphurization by interaction with the reaction medium.Finally, oxides play an important role in carriers for active metal or oxide phases, very often modifying strongly their catalytic properties. The present paper concerns

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ChemInform Abstract: MECHANISM OF NITROGEN INSERTION IN AMMOXIDATION CATALYSIS

Cited by 45 publications

References 1 publication

Mechanism of Selective Oxidation and Ammoxidation of Propene on Bismuth Molybdates from DFT Calculations on Model Clusters

Mechanism of Selective Oxidation and Ammoxidation of Propene on Bismuth Molybdates from DFT Calculations on Model Clusters

Synergy effects in mixed Bi2O3, MoO3 and V2O5 catalysts for selective oxidation of propylene

Catalysis by Transition Metal Oxides

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