Catalyst for methacrylic acid production and process for producing methacrylic acid

A catalyst for methacrylic acid production used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen,

• the catalyst having a composition represented by the following general formula:
• MoaPbVcCudYeZfZ′fOg
• wherein Mo, P, V, Cu and O represent molybdenum, phosphorus, vanadium, copper and oxygen, respectively;
• Y represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium;
• Z represents ammonium;
• Z′ represents antimony;
• a, b, c, d, e, f, f′ and g represent each an atomic ratio of each element and, when a is 10, b is 0.1 or more and 4 or less, c is 0.01 or more and 4 or less, d is 0.01 or more and 1 or less, e is 0.5 or more and 1.0 or less, f is greater than 0 to 3 or less, f′ is 0 or more and 3 or less and g is a numerical value determined depending on oxidation states of individual elements,
• wherein a proton that is a counter cation is replaced by an alkali metal ion so as to satisfy conditions:
• α=A+(B×C)
• 0.5≦α≦1.4
• when an atomic ratio of the alkali metal atom relative to 10 atoms of molybdenum in a hetero polyacid and hetero polyacid salt containing molybdenum, phosphorus, vanadium and copper as essential ingredients is taken as A and an atomic ratio of copper atom relative to 10 atoms of molybdenum in the hetero polyacid and hetero polyacid salt is taken as B, and a valence number is taken as C.