Process for producing composite oxide catalyst

A process for producing a composite oxide catalyst, the process comprising:

• (i) preparing an aqueous slurry comprising iron and antimony,
• (ii) subjecting the aqueous slurry to a particle size reduction treatment while measuring particle size of precipitated particles in the aqueous slurry,
• (iii) drying the aqueous slurry to obtain a dried material, and
• (iv) calcining the dried material, thereby obtaining the composite oxide catalyst,
• wherein
• the aqueous slurry comprises precipitated particles having a particle size of not less than 1 μm but less than 150 μm,
• a proportion of precipitated particles having a particle size of not less than 1 μm but less than 10 μm in the aqueous slurry is from 40 to 90% by volume as measured after the particle size reduction treatment,
• a proportion of precipitated particles having a particle size of not less than 10 μm but less than 150 μm in the aqueous slurry is from 10 to 60% by volume as measured after the particle size reduction treatment, and
• the composite oxide catalyst comprises a composition of formula (I):
• Fe10SbaAbTecDdEeOx.(SiO2)y (I),
• wherein:
• A is at least one element selected from the group consisting of vanadium, molybdenum and tungsten;
• D is at least one element selected from the group consisting of magnesium, calcium, strontium, barium, titanium, zirconium, niobium, chromium, manganese, cobalt, nickel, copper, silver, zinc, boron, aluminum, gallium, indium, thallium, germanium, tin, lead, phosphorus, arsenic and bismuth;
• E is at least one element selected from the group consisting of lithium, sodium, potassium, rubidium and cesium;
• and
• a, b, c, d, e, x and y are atomic ratios, wherein a is 3 to 100, b is 0.1 to 1, c is 0.2 to 12, d is 0 to 50, e is 0 to 5, y is 10 to 200;
• and x is an atomic ratio for an amount of oxygen required to satisfy valency of other components excluding silica.