OXIDATIVE DEHYDROGENATION CATALYSTS CONSISTING ESSENTIALLY OF PHOSPHORUS, TIN, A METAL SELECTD FROM THE GROUP CONSISTING OF GROUP IA METALS AND GROUP IIA METALS, AND OXYGEN, WHEREIN THE PHOSPHORUS IS PRESENT IN THE RANGE OF 0.1 TO 16 WEIGHT PERCENT, THE TIN IS PRESENT IN THE RANGE OF 15 TO 75 WEIGHT PERCENT, THE GROUP IA OR GROUP IIA METAL IS PRESENT IN THE RANGE OF 0.1 TO 10 WEIGHT PERCENT AND THE OXYGEN IS PRESENT IN SUFFICENT QUANTITY TO PRODUCE THE REMAINING TOTAL CATALYST COMPOSITION, ARE ACTIVATED BY CONTACTING THE FORMED PARTICLES OF CATALYST WITH WATER.