Process for producing composite oxide catalyst

1. 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):

Fe 10 Sb a A b Te c D d E e O x .(SiO 2 ) 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.

2. The process of claim 1 , wherein

the proportion of the precipitated particles having the particle size of not less than 1 μm but less than 10 μm is from 45 to 85% by volume as measured after the particle size reduction treatment, and

the proportion of the precipitated particles having the particle size of not less than 10 μm but less than 150 μm is from 15 to 55% by volume as measured after the particle size reduction treatment.

3. The process of claim 1 , wherein the dried material comprises particles having a particle size of from 5 to 200 μm.

4. The process of claim 1 , wherein the dried material comprises particles having a particle size of from 10 to 180 μm.

5. The process of claim 1 , wherein the calcining (iv) comprises a preliminary calcination and a final calcination.

6. The process of claim 5 , wherein a temperature of the preliminary calcination is 50 to 400° C. lower than a temperature of the final calcination.

7. The process of claim 5 , wherein a temperature of the preliminary calcination is from 180 to 500° C.

8. The process of claim 5 , wherein a time of the preliminary calcination is at least 0.5 hours.

9. The process of claim 5 , wherein a temperature of the final calcination is from 570 to 1,000° C.

10. The process of claim 5 , wherein a time of the final calcination is at least 0.5 hours.

11. The process of claim 1 , wherein the measuring a particle size of precipitated particles in the aqueous slurry is conducted in accordance with laser diffraction methods, dynamic scattering methods, centrifugation methods, or electrical detection methods.

12. The process of claim 1 , wherein the aqueous slurry comprises precipitated particles having a particle size of 150 μm or more is not more than 5% by volume, relative to the volume of the precipitated particles having a particle size of not less than 1 μm but less than 150 μm.