New unsupported [100]-oriented MoO 3 catalysts : I. Preparation and characterization

Abstract

In the general frame of the structure-sensitive character of the oxidation reactions of olefins and alcohols on oxide catalysts, a new method of preparation of unsupported, [100]-oriented, MoO 3 catalysts is described. Diffraction techniques and SEM observations showed that the oxidation of Mo sheets leads to MoO 3 oxide plates with a preferential [100]orientation of the crystallites, this feature being most likely in relation with the special texture of the starting material. Moreover, evidence is presented that MoO 3 (100) planes, which are believed to be active in the mild oxidation of olefins, are actually truncated to (110), (120), or (130) surface planes. A structural model indicates that such (1k0) planes should have a dual-site character and the consequences have been discussed in relation with the mechanism of the mild oxidation of propene on MoO 3 catalysts.