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Effect of the support on the surface composition of vanadium phosphate catalysts in the oxidative dehydrogenation of ethane
Author(s) -
Casaletto M. P.,
Lisi L.,
Mattogno G.,
Patrono P.,
Ruoppolo G.
Publication year - 2004
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.1751
Subject(s) - dehydrogenation , calcination , x ray photoelectron spectroscopy , catalysis , vanadium , chemistry , oxidizing agent , vanadium oxide , inorganic chemistry , phosphate , dispersion (optics) , chemical engineering , organic chemistry , physics , optics , engineering
Vanadyl phosphate catalysts supported on different oxides (γ‐Al 2 O 3 , TiO 2 , SiO 2 ) have been investigated by x‐ray photoelectron spectroscopy (XPS). The surface chemical composition has been studied as a function of the thermal treatment under oxidizing (calcination) or reaction conditions in the oxidative dehydrogenation of ethane. Dispersion of vanadyl phosphates on γ‐Al 2 O 3 and TiO 2 results in the formation of vanadium species in different oxidation states, i.e. V 5+ phosphate, V 5+ and V 4+ oxide species, whose relative fraction depends both on the support and on the reaction temperature. A progressive reduction of vanadium species occurs in the samples as an effect of the temperature. Vanadyl phosphates exhibit a stronger interaction with the titania support, which undergoes surface modifications after impregnation, thermal treatments and catalysis runs. A noticeable interaction of the alumina support and a poor dispersion of the active phase on silica are also revealed by XPS. Copyright © 2004 John Wiley & Sons, Ltd.