Mixed oxide catalysts for the catalytic gas-phase oxidation of olefins and processes for producing them

1. A mixed oxide catalyst of the formula

(Mo 12 Bi a C b (Co+Ni) c D d E e F f G g H h )O x   (I)

in which

C: iron,

D: at least one of the elements selected from the group consisting of W and P,

E: at least one of the elements selected from the groups consisting of Li, K, Na, Rb, Cs, Mg, Ca, Ba and Sr,

F: at least one of the elements selected from Ce, Mn, Cr and V

G: at least one of the elements selected from the groups consisting of Nb, Se, Te, Sm, Gd, La, Y, Pd, Pt, Ru, Ag and Au

H: at least one of the elements selected from the groups consisting of Si, Al, Ti and Zr

and

a=0-5.0

b=0.5-5.0

c=2-15

d=0.01-5.0

e=0.001-2

f=0.001-5

g=0-1.5

h=0-800,

and

x=number which is determined by the valency and frequency of the elements other than oxygen, and g+h>0.

2. A mixed catalyst according to claim 1 , wherein the mixed oxides have been applied to support materials.

3. Process for preparing a mixed oxide catalyst of the formula I, according to claim 1 wherein solutions of compounds of the metals present in the mixed oxide catalysts of the formula I are mixed, coprecipitates are prepared, and the resulting solid is isolated, dry-calcined and optionally reshaped.

4. Process according to claim 3 , wherein the pH during the precipitation of the solid(s) is <8.

5. Process according to claim 3 , wherein metal compounds selected from the group consisting of ammonium or amine compounds, oxalates, carbonates, phosphates, acetates, carbonyls, nitrates and mixtures thereof are used individually or together.

6. Process according to claim 3 , wherein carbonates, nitrates or phosphates, or mixtures of these salts are used.

7. Process according to claim 3 , wherein acids corresponding to the anions of the salts used are optionally used.

8. Process according to claim 3 , wherein the molar ratios of the metal counterions in the precipitation are represented by

R1=[NH 4 + ]/[NO 3 − ]=1/10−1/1 and/or

R2=[NO 3 − ]/([NO 3 − ]+[CO 3 2− ]+[PO 4 3− ]+[Y−COO − ])=0.5−1/1

where Y

is CH 3 or C 2 H 5 , and [NO 3 − ] and [NH 4 + ] are each >0.

9. Process according to claim 3 , wherein ammonia or ammonium salts, or metal nitrates, and/or the corresponding acids, are used to prepare the coprecipitate.

10. Process according to claim 3 , wherein the precipitation is carried out at temperatures of 5 to 90° C.

11. Process according to claim 10 , wherein the precipitation is carried out at temperatures of 20 to 50° C.

12. Process according to claim 3 , wherein the suspension obtained by precipitation matures for 0 to 24 hours.

13. Process according to claim 3 , wherein the dried powder, before the calcination, consists of spray-dried particles having a particle size distribution of 15 to 160 μm.

14. Process according to claim 13 , wherein the mean particle size distribution of the dried coprecipitate is between 15 μm and 80 μm.

15. Process according to claim 3 , wherein the residence time of the dried powder in the oven for calcination is between 0.25 and 13 h, in the course of which temperatures of 200 to 600° C. are established.

16. Process according to claim 3 , wherein the calcination is carried out in one or more stages.

17. Process according to claim 15 , wherein the calcination is carried out with addition of inert gas, from mixtures of oxygen with an inert gas in the presence or absence of steam.

18. Process according to claim 15 , wherein the calcined powder is fixed by tabletting, extrusion or coating of a support.

19. Process according to claim 15 , wherein the particle size distribution of the calcined or partly calcined powder, is between 0.01 and 80 μm.

20. Process according to claim 3 , wherein the particle size distribution of the spray-dried powder, if appropriate by virtue of grinding, is between 0.1 and 50 μm.

21. Process according to claim 3 , wherein the mean particle size distribution of the calcined or partly calcined powder, can be adjusted to a distribution of 0.01 to 30 μm.

22. Process according to claim 3 , wherein shaping of the catalyst powder is followed by a thermal treatment in the temperature range of 450 to 600° C.

23. Process for preparing aldehydes and acids by oxidizing olefins or methylated aromatics with air or oxygen in the presence of inert gases, steam or offgases from the reaction at elevated temperatures, characterized in that a catalyst of the general formula

(Mo 12 Bi a C b (Co+Ni) c D d E e F f G G H h )O x   (I) is used,

in which

C: iron,

D: at least one of the elements selected from the groups consisting of W and P,

E: at least one of the elements selected from the groups consisting of Li, K, Na, Rb, Cs, Mg, Ca, Ba and Sr,

F: at least one of the elements selected from the groups consisting of Ce, Mn, Cr and V

G: at least one of the elements selected from the groups consisting of Nb, Se, Te, Sm, Gd, La, Y, Pd, Pt, Ru, Ag and Au

H: at least one of the elements selected from the groups consisting of Si, Al, Ti and Zr

and

a=0-5.0

b=0.5-5.0

c=2-15

d=0.01-5.0

e=0.001-2

f=0.001-5

g=0-1.5

h=0-800,

and

x=number which is determined by the valency and frequency of the elements other than oxygen, and g+h>0.

24. Process according to claim 23 , wherein acrolein and acrylic acid are obtained from propene.

25. Process according to claim 23 , wherein methacrolein and methacrylic acid are obtained from isobutene.

26. Process according to claim 23 , wherein benzaldehyde and benzoic acid are obtained from toluene.

27. Process according to claim 23 , wherein the catalyst is contacted with a reaction gas mixture which comprises olefin or methylated aromatics, air, inert gases in a ratio of 1:6-9:3-18.

28. Process according to claim 3 wherein ammonium carbonate, ammonium heptamolybdate, iron nitrate or cobalt nitrate are used to prepare the coprecipitate.

29. Process according to claim 3 wherein the suspension obtained by precipitation matures for ≧0 to 12 hours.

30. Process according to claim 3 wherein the suspension obtained by precipitation matures for ≧0 to 6 hours.