Mechanically stable hollow cylindrical shaped catalyst bodies for gas phase oxidation of an alkene to an unsaturated aldehyde and/or an unsaturated carboxylic acid
A hollow cylindrical shaped catalyst body for gas phase oxidation of an alkene to an α,β-unsaturated aldehyde and/or an α,β-unsaturated carboxylic acid comprises a compacted multimetal oxide having an external diameter ED, an internal diameter ID and a height H, wherein ED is in the range from 3.5 to 4.5 mm; the ratio q=ID/ED is in the range from 0.4 to 0.55; and the ratio p=H/ED is in the range from 0.5 to 1. The shaped catalyst body is mechanically stable and catalyzes the partial oxidation of an alkene to the products of value with high selectivity. It provides a sufficiently high catalyst mass density of the catalyst bed and good long-term stability with acceptable pressure drop.
1. A hollow cylindrical shaped catalyst body, comprising a compacted multimetal oxide comprising the elements molybdenum, iron and bismuth having an external diameter ED, an internal diameter ID and a height H, wherein
(i) ED is from 3.5 to 4.5 mm;
(ii) a ratio q according to the following equation
q
=
ID
ED
is from 0.45 to 0.55;
and
(iii) a ratio p according to the following equation
p
=
H
ED
is from 0.5 to 0.95
wherein a ratio of the geometric surface area of the shaped catalyst body to a geometric volume of the shaped catalyst body is from 26 to 30.01 cm −1 .
2. The catalyst body according to claim 1 , wherein ED from 3.7 to 4.3 mm.
3. The catalyst body according to claim 1 , wherein p is from 0.65 to 0.9.
4. The catalyst body according to claim 1 , wherein a geometric volume of the shaped catalyst body is from 22 to 34 mm 3 .
5. The catalyst body according to claim 1 , wherein a density of the shaped catalyst body is from 1.2 to 2.0 g/cm 3 .
6. The catalyst body according to claim 1 , wherein a value WT according to the following equation
WT
=
ED
-
ID
2
is from 0.8 to 1.2 mm.
7. The catalyst body according to claim 1 , wherein ED is from 3.7 to 4.3 mm, H is from 2.8 to 3.2 mm and ID is from 1.8 to 2.2 mm.
8. The catalyst body according to claim 1 , obtained by a process comprising:
(i) producing an intimate dry mixture of sources of the elemental constituents of the multimetal oxide,
(ii) compacting the intimate dry mixture to obtain a hollow cylindrical shaped precursor body,
(iii) and calcining at a temperature of from 350 to 650° C.
9. The catalyst body according to claim 8 , wherein the intimate dry mixture is compacted to the hollow cylindrical shaped precursor body by tableting.
10. The catalyst body according to claim 8 , obtained by thermally pretreating the hollow cylindrical shaped precursor body prior to the calcination under conditions under which a maximum relative decrease in mass of the shaped catalyst precursor body does not exceed a value of 1% per minute.
11. A process for preparing an α,β-unsaturated aldehyde an α,β-unsaturated carboxylic acid, or both, comprising contacting an alkene with molecular oxygen over a fixed catalyst bed comprising a bed of hollow cylindrical shaped catalyst bodies according to claim 1 .
12. The process according to claim 11 , wherein the process obtains acrolein by gas phase oxidation of propene.
13. The process according to claim 11 , wherein
the fixed catalyst bed comprises a bed having a plurality of reaction zones,
the bed comprises inert shaped diluent bodies in a reaction zone, and
a proportion of inert shaped diluent bodies in at least two reaction zones is different.
14. The process according to claim 13 , wherein a bed in the reaction zone which comprises the lowest proportion of inert shaped diluent bodies, if any inert shaped diluent bodies, comprises the hollow cylindrical shaped catalyst bodies.
15. The process according to claim 13 , wherein a bed in the reaction zone in which the highest local temperature in the fixed catalyst bed occurs, comprises the hollow cylindrical shaped catalyst bodies.
16. The process according to claim 11 , wherein the bed further comprises other shaped catalyst bodies which are not in accordance with the hollow cylindrical shaped catalyst bodies.