Supported molybdenum or tungsten oxides treated with organoaluminum compounds as catalysts

As a composition of matter, a catalyst consisting essentially of an admixture of a composite of (a) molybdenum oxide or tungsten oxide associated with a suitable support material, said composite having been activated in flowing air at a temperature of from about 500.degree.F to about 1600.degree.F, and (b) at least one organoaluminum compound of the formula R.sub.a AlX.sub.b wherein R is a saturated aliphatic or aromatic hydrocarbon having up to 20 carbon atoms;

• X is chlorine, bromine, iodine or fluorine, a is an integer of at least 1;
• b is 0, 1 or 2;
• and the total of a and b is 3, wherein the (a) component of the catalyst is contacted with excess nitric oxide or nitrosyl halide, or with a sufficient amount of an alkali or alkaline earth metal hydroxide or carbonate to provide from about 0.005 to about 5 weight percent of said alkali or alkaline earth metal hydroxide or carbonate prior to contact with (b) and subsequent to being subjected to high temperature;
• and wherein the molar ratio of (b) to (a) is in the range of from about 0.005:1 to 20:1 mols of (b) per mol of molybdenum or tungsten oxide present in (a).