Oxidative dehydrogenation of ethylbenzene over vanadia-alumina catalysts in the presence of nitrous oxide: structure-activity relationship

Shiju, N. R. ; Anilkumar, M. ; Mirajkar, S. P. ; Gopinath, C. S. ; Rao, B. S. ; Satyanarayana, C. V. (2005) Oxidative dehydrogenation of ethylbenzene over vanadia-alumina catalysts in the presence of nitrous oxide: structure-activity relationship Journal of Catalysis, 230 (2). pp. 484-492. ISSN 0021-9517

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/j.jcat.2005.01.010

Abstract

A series of vanadia-alumina catalysts with different vanadia contents were prepared by a wet impregnation method. The influence of the local structure of vanadia in these catalysts on the oxidative dehydrogenation of ethylbenzene with nitrous oxide was investigated. The use of N2O as a co-feed remarkably enhanced the styrene yield compared with the use of N2. Characterization of these vanadia catalysts by XRD, FTIR, UV-vis, TPR, XPS, and 51V NMR techniques suggests that the nature of the VOx species depends on the vanadia loading; the predominant species are monomeric vanadia at lower loadings, two-dimensional polyvanadates at intermediate loadings, and bulk-like V2O5 and AlVO4 at higher loadings. The rate of oxidative dehydrogenation (ODH) of ethylbenzene per vanadium atom increases with vanadia loading and reaches a maximum at 10 wt%, the loading at which the surface predominantly contains polyvanadate species. The observed variation in the selectivity of products with vanadium loading indicates that the monomeric V5+ species favors dehydrogenation, whereas bulk-like V2O5 preferentially participates in the dealkylation of ethylbenzene. The vanadium species remains at a higher oxidation state in the presence of N2O, leading to a higher styrene yield, than in a N2 atmosphere. The ODH turnover rates increased with decreasing energy of the absorption edge in the UV-vis spectrum, at low VOx coverages of less than one monolayer on the Al2O3 surface.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Oxidative Dehydrogenation; Ethylbenzene; Nitrous Oxide; Styrene; Alumina; Vanadia; Polyvanadates; Absorption Edge Energy
ID Code:61866
Deposited On:15 Sep 2011 12:13
Last Modified:15 Sep 2011 12:13

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