PREPARATION OF ACRYLIC ACID OR METHACRYLIC ACID

PURPOSE:To obtain the titled substance in high selectivity with a long life of a catalyst, by using the catalyst comprising a combination of specific component elements in a composition ratio, by reacting acrolein or methacrolein with molecular oxygen at high-temperature gas phase. CONSTITUTION:Using a composition shown by the formula (Mo is molybdenum; P is phosphorus, Ca is calcium; Ta is tantalum; B is boron; X is potassium and/ or cesium; V is vanadium; Cu is copper; As is arsenic; O is oxygen; added letters a, b, c, d, e, f, g, h, i, and j show numbers of atoms, when a is 12, b=0.5-5; c=0.005-5; d=0.005-5; e=0.005-5; f=0.01-4; g=0.05-3; h=0.005-5; i=0.05- 3; j is a value automatically fixed depending upon the valences of the component elements and usually 38-89) as a catalyst, acrolein or methacrolein is reacted with molecular oxygen in high-temperature gas phase, to give the desired compound.