Oxide catalyst and method for producing the same, and methods for producing unsaturated aldehyde, diolefin, and unsaturated nitrile

1. An oxide catalyst for use in the production of unsaturated aldehyde, diolefin, or unsaturated nitrile from olefin and/or alcohol, the oxide catalyst satisfying the following (1) to (3):

(1) the oxide catalyst comprises molybdenum, bismuth, iron, cobalt, and an element A having an ion radius larger than 0.96 Å (except for potassium, cesium, and rubidium);

(2) an atomic ratio a of the bismuth to 12 atoms of the molybdenum is 1≦a≦5, an atomic ratio b of the iron to 12 atoms of the molybdenum is 1.5≦b≦6, an atomic ratio c of the element A to 12 atoms of the molybdenum is 1≦c≦5, and an atomic ratio d of the cobalt to 12 atoms of the molybdenum is 1≦d≦8; and

(3) the oxide catalyst comprises a disordered phase consisting of a crystal system comprising the molybdenum, the bismuth, the iron, and the element A.

2. The oxide catalyst according to claim 1 , wherein the oxide catalyst has a single peak in each range of diffraction angles (2θ) of 18.30°±0.2°, 28.20°±0.2°, 33.65°±0.2°, and 46.15°±0.2° in X-ray diffraction, and

an intensity ratio (Ia/Ib) of intensity (Ia) of peak a at 2θ=33.65°±0.2° to intensity (Ib) of peak b at 2θ=34.10°±0.2° is 2.0 or larger.

3. The oxide catalyst according to claim 1 , wherein the oxide catalyst has a composition represented by the following composition formula (1):

Mo 12 Bi a Fe b A c Co d B e C f O g   (1)

wherein Mo represents molybdenum; Bi represents bismuth; Fe represents iron; the element A represents an element having an ion radius larger than 0.96 Å(except for potassium, cesium, and rubidium); Co represents cobalt; an element B represents at least one element selected from the group consisting of magnesium, zinc, copper, nickel, manganese, chromium, and tin; an element C represents at least one element selected from the group consisting of potassium, cesium, and rubidium; a to g each represent the atomic ratio of each element to 12 Mo atoms wherein the atomic ratio a of Bi is 1≦a≦5, the atomic ratio b of Fe is 1.5≦b≦6, the atomic ratio c of the element A is 1≦c≦5, and the atomic ratio d of Co is 1≦d≦8, an atomic ratio e of the element B is 0≦e<3, an atomic ratio f of the element C is 0≦f≦2, and an ratio of Fe/Co is 0.8≦b/d; and g represents an atomicity of oxygen determined by an valences of constituent elements other than oxygen.

4. The oxide catalyst according to claim 1 , further comprising at least one selected from the group consisting of silica, alumina, titania, and zirconia as a carrier.

5. A method for producing an oxide catalyst, comprising:

a mixing step of mixing a starting material constituting the catalyst, comprising molybdenum, bismuth, iron, cobalt, and an element A having an ion radius larger than 0.96 Å(except for potassium, cesium, and rubidium), to obtain a slurry;

a drying step of drying the slurry thus obtained to obtain a dried product; and

a calcination step of calcining the dried product thus obtained, wherein

the calcination step comprises a heating step of gradually heating the dried product from 100° C. to 200° C. over 1 hour or longer.

6. The method for producing the oxide catalyst according to claim 5 , wherein the slurry has a pH of 8 or lower.

7. The method for producing the oxide catalyst according to claim 5 , wherein the calcination step comprises:

a preliminary calcination step of preliminarily calcining the dried product at a temperature of 200 to 300° C. to obtain a preliminarily calcined product; and

a final calcination step of finally calcining the preliminarily calcined product thus obtained at a temperature of 300° C. or higher to obtain the catalyst.

8. A method for producing unsaturated aldehyde, comprising an unsaturated aldehyde production step of oxidizing olefin and/or alcohol using the oxide catalyst according to claim 1 to obtain the unsaturated aldehyde.

9. The method for producing unsaturated aldehyde according to claim 8 , wherein the olefin and/or the alcohol is at least one selected from the group consisting of propylene, isobutylene, propanol, isopropanol, isobutanol, and t-butyl alcohol.

10. The method for producing unsaturated aldehyde according to claim 8 , wherein the unsaturated aldehyde production step comprises a discharging step of discharging a product gas comprising the unsaturated aldehyde from a fluidized-bed reactor through the gas-phase catalytic oxidation reaction of the olefin and/or the alcohol with an oxygen source in the fluidized-bed reactor.

11. The method for producing unsaturated aldehyde according to claim 8 , wherein

the gas-phase catalytic oxidation reaction is performed at a reaction temperature of 400 to 500° C., and

the product gas discharged from the fluidized-bed reactor has an oxygen concentration of 0.03 to 0.5% by volume.

12. A method for producing diolefin, comprising a diolefin production step of oxidizing monoolefin having 4 or more carbon atoms using the oxide catalyst according to claim 1 to obtain the diolefin.

13. A method for producing unsaturated nitrile, comprising an unsaturated nitrile production step of reacting at least one selected from the group consisting of propylene, isobutylene, propanol, isopropanol, isobutanol, and t-butyl alcohol, with molecular oxygen and ammonia in a fluidized-bed reactor using the oxide catalyst according to claim 1 to obtain the unsaturated nitrile.