Structural study of VOx doped aluminium fluoride and aluminium oxide catalysts

摘要

The structural properties of vanadium doped aluminium oxyfluorides and aluminium oxides, prepared by a modified sol-get synthesis route, were thoroughly investigated. The influence of the preparation technique and the calcination temperature on the coordination of vanadium, aluminium and fluorine was analysed by different spectroscopic methods such as Raman, MAS NMR and ESR spectroscopy. In all samples calcined at low temperatures (350 degrees C), vanadium coexists in two oxidation states V-IV and V-V, with V-IV as dominating species in the vanadium doped aluminium oxyfluorides. In the fluoride containing solids aluminium as well as vanadium are coordinated by fluorine and oxygen. Thermal annealing of 800 degrees C leads to an extensive reorganisation of the original matrices and to the oxidation of V-IV to V-V in both systems. (c) 2006 Elsevier Inc. All rights reserved.