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-001995nas a2200193   4500008004100000022001400041245009800055210006900153260011000222300001400332490000600346520120600352100002201558700002101580700002001601700001901621700002901640856013201669       2011                        eng d  a2044-475300aOxidative dehydrogenation of ethylbenzene using nitrous oxide over vanadia-magnesia catalysts0 aOxidative dehydrogenation of ethylbenzene using nitrous oxide ov  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcAUG  a1262-12700 v13 a<p>A series of V-Mg-O catalysts with different loadings of vanadia were prepared by the wet impregnation method and the effect of the local structure of these catalysts on the oxidative dehydrogenation of ethylbenzene with N(2)O was investigated. High styrene selectivity (similar to 97%) was obtained at 773 K. The characterization of catalysts with methods such as XRD, FTIR, UV-visible, TPR, NMR and Laser Raman spectroscopy suggested that magnesium orthovanadate is the predominant vanadium containing phase and the size of the orthovanadate domains increases with increasing vanadia loading. The rate of ODH of ethylbenzene per V atom increases with vanadia loading and reaches a maximum at 10 wt%. The specific activity, i.e. the conversion of ethylbenzene per unit surface area of the catalysts, also exhibited a maximum at a vanadia loading of 10 wt% leading to the conclusion that activity of these catalysts is due to the presence of very small domains of Mg(3)(VO(4))(2) on the surface of MgO rather than crystallites of bulk Mg(3)(VO(4))(2). The higher styrene yield in the presence of N(2)O can be ascribed to the ability of N(2)O to keep vanadium species at a higher oxidation state.</p>1 aShiju, Raveendran1 aAnilkumar, Mettu1 aGokhale, S., P.1 aRao, Seshagiri1 aSatyanarayana, C., V. V.  uhttps://library.ncl.res.in/content/oxidative-dehydrogenation-ethylbenzene-using-nitrous-oxide-over-vanadia-magnesia-catalysts-0