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Support Effect on the Structure and Reactivity of VSbO4 Catalysts for Propane Ammoxidation to Acrylonitrile

“…2,20,26 The dynamic states of V and Sb appear to be more flexible if segregated Sb oxide species are present along with VSbO 4 phases. 2,26,48 Our XPS results agree with previous literature on the oxidation states in VSbO 4 , V 3+ and Sb 5+ . 49,50 Operando Raman-GC studies provide experimental evidence of the dynamic character of VSbO 4 interacting with dispersed vanadium oxide species and with segregated Sb oxides.…”

“…There is an important difference with such alumina-supported series: XPS, XRD, and Raman spectroscopy show that there is no segregated Sb oxide phase . Segregated Sb oxides show no activity for propane ammoxidation, , but they couple with VSbO 4 into an efficient catalytic system for propane ammoxidation. ,,,,, It has been proposed that a segregated antimony phase participates in the redox cycle on vanadium species in VSbO 4 . ,, The dynamic states of V and Sb appear to be more flexible if segregated Sb oxide species are present along with VSbO 4 phases. ,, Our XPS results agree with previous literature on the oxidation states in VSbO 4 , V 3+ and Sb 5+ . , Operando Raman−GC studies provide experimental evidence of the dynamic character of VSbO 4 interacting with dispersed vanadium oxide species and with segregated Sb oxides. ,, The redox cycle of vanadia species between surface V 5+ and V 3+ in VSbO 4 appears facilitated by the presence of segregated Sb 2 O 3 that hosts migrating Sb 5+ species from VSbO 4 , forming α-Sb 2 O 4 (mixed-valence oxide) to compensate for V 3+ species that leave the VSbO 4 lattice as a result of their oxidation toward surface V 5+ species . Such migration is reversible upon reduction of surface V 5+ to V 3+ into VSbO 4 .…”

Dissecting the role of Bi and Ba in the catalytic efficiency of VSbBiBa/Al2O3 catalysts in oxidative dehydrogenation and oxidation of propane

“…9–11 Substitutions of vanadium and antimony inside this phase by elements such as Al, Ga, Fe, Sn Ti, or W have been studied and were shown to change either its activity or selectivity. 12–16 Three main effects of these simple or multiple substitutions were proposed in the literature: (i) the isolation of active vanadium sites on the surface of the catalyst, (ii) the formation or suppression of unselective strong acid sites, and (iii) the participation in the re-oxidation of the phase through redox couples other than those of vanadium. 17–19 Interestingly, bismuth had never been considered as a possible substituent.…”

“…This explanation would account for the higher rate of alkane conversion but no details were given on how this might occur. 13…”