EFFECT OF ANIONS ON THE CATALYTIC PROPERTIES OF FERRIC MOLYBDATE IN THE SELECTIVE OXIDATION OF METHANOL

The amorphous precursor method was used to prepare ferric molybdate ca talysts containing superstoichiometric molybdate, sulfate, and phospha te ions. The introduction of sulfate or phosphate ions into stoichiome tric ferric molybdate leads to the formation of double salts and the a ppearance of a proportional amount of molybdenum oxide, as indicated b y IR spectroscopy and x-ray phase analysis. The dependence of the cata lytic properties of these compounds derived from double salts on their composition is analogous to those characteristic for iron-molybdenum systems and the maximum activity is observed upon the introduction of these anions up to 2 mass % superstoichiometric composition. These res ults may be explained assuming that stoichiometric ferric molybdate is the active component in the iron-molybdenum catalyst, while double sa lts also with stoichiometric composition are the active component upon the introduction of sulfate and phosphate ions. A slight excess of mo lybdenum oxide is presumably necessary for maintaining the stoichiomet ry of the surface during catalyst preparation.