Effect of dehydration of VOPO₄·2H₂O on the preparation and reactivity of vanadium phosphate catalyst for the oxidation of n-butane

The effect of drying of VOPO4.2H(2)O on the preparation of vanadium phosphate catalysts for the selective oxidation of n-butane to maleic anhydride is described and discussed. It is found that partially dehydrated samples of the dihydrate containing small amounts of alpha(I)-VOPO4 are formed when the material is initially dried. The presence of this impurity leads to a final catalyst containing trace amounts of alpha(I)-VOPO4 in combination with (VO)(2)P2O7 and this combination leads to a catalyst with a higher activity but with a lower selectivity to maleic anhydride. The drying stage is also found to influence the surface area and intrinsic activity of the activated catalyst.