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Selective oxidation and ammoxidation of propene on bismuth molybdates, ab initio calculations

Jang, Yun Hee and Goddard, William A., III (2001) Selective oxidation and ammoxidation of propene on bismuth molybdates, ab initio calculations. Topics in Catalysis, 15 (2). pp. 273-289. ISSN 1022-5528. https://resolver.caltech.edu/CaltechAUTHORS:20170408-150859177

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Abstract

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 BiMoOxcatalysts. 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 while 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. Since 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 coworkers that imido sites (Mo=NH) 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 (Mo=NH) than on oxo groups (Mo=O) 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.


Item Type:Article
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http://dx.doi.org/10.1023/A:1016631100417DOIArticle
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ORCID:
AuthorORCID
Goddard, William A., III0000-0003-0097-5716
Additional Information:© Plenum Publishing Corporation 2001. We thank Asahi Chemical Ind. Co., Ltd., Fuji, Shizuoka 416–8501, Japan for providing funding for this project and Dr. Terumasa Yamasaki of Asahi Chemical for helpful comments. We also thank Dr. Bob Grasselli and Dr. Jim Burrington for many helpful discussions over the year. The facilities of the MSC are also supported by grants from NSF-MRI, DOE-ASCI, ARO/MURI, Chevron, 3M, Beckman Institute, Seiko-Epson, Dow, Avery-Dennison, Kellogg, NSF-CHE, NIH, and ARO/DURIP.
Funders:
Funding AgencyGrant Number
Asahi ChemicalUNSPECIFIED
NSFUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Army Research Office (ARO)UNSPECIFIED
Chevron CorporationUNSPECIFIED
3MUNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Seiko-EpsonUNSPECIFIED
Dow Chemical CompanyUNSPECIFIED
Avery-DennisonUNSPECIFIED
KelloggUNSPECIFIED
NIHUNSPECIFIED
Subject Keywords:: selective oxidation; ammoxidation mechanism; bismuth molybdates; density functional theory; cluster model
Issue or Number:2
Record Number:CaltechAUTHORS:20170408-150859177
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170408-150859177
Official Citation:Jang, Y.H. & Goddard III, W.A. Topics in Catalysis (2001) 15: 273. doi:10.1023/A:1016631100417
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76030
Collection:CaltechAUTHORS
Deposited By: 1Science Import
Deposited On:05 May 2017 22:50
Last Modified:03 Oct 2019 16:56

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