Preparation of vanadium phosphorus catalysts using a mixed phosphorus source and use thereof in oxidation of C4-hydro-carbons to maleic anhydride.

摘要

A process for the preparation of oxidation catalysts containing mixed oxides of vanadium and phosphorus comprises
a) introducing a pentavalent vanadium-containing compound into a liquid medium capable of reducing the valence state of said vanadium;
b) effecting reduction of at least a portion of said vanadium to a valence state of approximately +4;
c) adding a mixed phosphorus component comprising orthophosphoric acid and pyrophosphoric acid to said medium prior to or subsequent to effecting said reduction to form a catalyst precursor;
d) recovering the catalyst precursor;
e) drying the catalyst precursor;
f) calcining the catalyst precursor;

<??>Improved results are obtained by the use as the mixed phosphorus of component one containing orthophosphoric and pyrophosphoric acid.
<??>The catalyst are useful in the oxidation of C4 hydrocarbons to maleic anhydride.