About the importance of surface W species in WOx/Al2O3 during n-butene skeletal isomerization

WOx/Al2O3 is accepted as an active catalyst for the skeletal isomerization of n-butene. We have analyzed the effect of preparation conditions on the properties of WOx/Al2O3. Catalysts were prepared by an equilibrium-adsorption method followed by different drying procedures and they were characterized by TPR, laser Raman spectroscopy, NH3-TPD, XRD and catalytic activity and selectivity. The active catalysts present Raman bands and TPR profiles that indicate the presence of tetrahedrally coordinated WOx, species. The poorly active catalysts show, in addition, WO, species in octahedral coordination which decrease total acidity and disrupt the contiguous tetrahedral sites necessary for the bimolecular reaction mechanism. (C) 2002 Elsevier Science B.V. All rights reserved.