02623nas a2200301   4500008004100000022001400041245014300055210006900198260009500267300001200362490000800374520152800382653002701910653001201937653001701949653001801966653003001984653001802014653001202032653001202044100001802056700002102074700002602095700003002121700001602151700002602167856012802193       2005                        eng d  a0021-951700aOxidative dehydrogenation of ethylbenzene over vanadia-alumina catalysts in the presence of nitrous oxide: structure-activity relationship0 aOxidative dehydrogenation of ethylbenzene over vanadiaalumina ca  a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcMAR  a484-4920 v2303 a<p>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 N-2. Characterization of these vanadia catalysts by XRD, FTIR, UV-vis, TPR, XPS, and V-51 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 N-2 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. (c) 2005 Elsevier Inc. All rights reserved.</p>10aabsorption edge energy10aAlumina10aethylbenzene10aNitrous oxide10aoxidative dehydrogenation10apolyvanadates10astyrene10avanadia1 aShiju, N., R.1 aAnilkumar, Mettu1 aMirajkar, Subhash, P.1 aGopinath, Chinnakonda, S.1 aRao, B., S.1 aSatyanarayana, C., V.  uhttps://library.ncl.res.in/content/oxidative-dehydrogenation-ethylbenzene-over-vanadia-alumina-catalysts-presence-nitrous-0