Dependence of selectivity on surface structure of MoO3 catalysts

Abstract

The mild oxidation of propylene has been studied on oriented and non-oriented supported MoO₃ catalysts. In the case of the oriented MoO₃–graphite catalysts, the orientation of the MoO₃ crystallites and catalytic properties are strongly dependent on preparation conditions.

Reaction specificity of the MoO₃ crystalline faces has been observed. By radiocrystallographic and electron-microscopy studies it has been possible to identify the reactive faces. Catalytic studies have allowed us to suggest that, at low conversion, acrolein and carbon dioxide issue from different catalytic sites; these are situated on the (100) MoO₃ faces for acrolein and on the (010) MoO₃ faces for carbon dioxide.

On the basis of stereochemical and electronic considerations, a mechanism for the oxidation of propylene to acrolein on the (100) MoO₃ face has been proposed.