Mo-, Bi- and Fe-comprising multimetal oxide compositions
Mo-, Bi- and Fe-comprising multimetal oxide compositions of the general stoichiometry I, Mo 12 Bi a Co b Fe c K d Si e O x (I), where a=0.5 to 1, b=7 to 8.5, c=1.5 to 3.0, d=0 to 0.15, e=0 to 2.5 and x=the stoichiometric coefficient of O 2− which guarantees the electric neutrality of the multimetal oxide, and 12− b −1.5· c=A and 0.5≦ A ≦1.5, 0.2≦ a/A ≦1.3, and 2.5≦ b/c ≦9, and the use thereof.
1. An Mo-, Bi- and Fe-comprising multimetal oxide composition of the general stoichiometry I,
Mo 12 Bi a Co b Fe c K d Si e O x (I),
where the variables have the following meanings:
a=0.5 to 1,
b=7 to 8.5,
c=1.5 to 3.0,
d=0 to 0.15,
e=0 to 2.5 and
x=a number which is determined by the valence and abundance of the elements other than oxygen in I and fulfil the following conditions:
12 −b− 1.5 ·c=A,
and
0.5 ≦A≦ 1.5; condition 1
0.2 ≦a/A≦ 1.3; and condition 2
2.5 ≦b/c≦ 9. condition 3
2. The multimetal oxide composition according to claim 1 whose stoichiometric coefficient d is from 0.04 to 0.1.
3. The multimetal oxide composition according to any of claims 1 and 2 whose stoichiometric coefficient e is from 0.5 to 2.
4. The multimetal oxide composition according to claim 1 , which fulfils the condition 1, 0.5≦A≦1.25.
5. The multimetal oxide composition according to claim 1 , which fulfils the condition 2, 0.3≦a/A≦1.2.
6. The multimetal oxide composition according to claim 1 , which fulfils the condition 3, 3≦b/c≦9.
7. A coated catalyst comprising a shaped support body and a coating of at least one multimetal oxide composition according to claim 1 present on the outer surface of the shaped support body.
8. An all-active shaped catalyst body whose active composition is at least one multimetal oxide according to claim 1 .
9. The all-active shaped catalyst body according to claim 8 which has the geometry of a ring having a wall thickness of from 1 to 3 mm, a length of from 2 to 10 mm and an external diameter of from 2 to 10 mm.
10. A process for preparing a multimetal oxide composition according to claim 1 , wherein a finely divided dry mix is produced from sources of elemental constituents of the multimetal oxide composition and this mixture is calcined at temperatures in the range from 350 to 650° C.
11. A process, comprising oxidizing an alkane, alkanol, alkanal, alkene and/or alkenal having from 3 to 6 carbon atoms over a catalyst bed, wherein the catalyst bed comprises at least one multimetal oxide composition according to claim 1 .
12. The process according to claim 11 , which is a process for the heterogeneously catalyzed partial gas-phase oxidation of propene to acrolein.
13. A process, comprising oxidizing an alkane, alkanol, alkanal, alkene and/or alkenal having from 3 to 6 carbon atoms over a catalyst bed, wherein the catalyst bed comprises at least one catalyst according to claim 7 .
14. A process, comprising oxidizing an alkane, alkanol, alkanal, alkene and/or alkenal having from 3 to 6 carbon atoms over a catalyst bed, wherein the catalyst bed comprises at least one multimetal oxide composition obtained by the process according to claim 10 .