Synthesis of a moVNbTe catalyst from low-cost metal oxides
A novel catalyst and process for producing a mixed oxide material containing molybdenum, vanadium, tellurium and niobium is disclosed. The material can be used as a catalyst for the oxidative dehydrogenation of ethane to ethene or the oxidation of propane to acrylic acid.
1. A process for producing a mixed oxide material, comprising the steps:
a) production of a mixture of starting compounds, which contains starting compounds comprising molybdenum, vanadium, niobium, and tellurium, and also contains oxalic acid, a first chelating oxo ligand, and a second chelating oxo ligand,
b) hydrothermal treatment of the mixture of starting compounds at a temperature of from 100° C. to 300° C. to give a product suspension,
c) isolation and drying of the solid present in the product suspension resulting from step b), and
d) activation of the solid obtained from step c) in an inert gas,
wherein the mixture of starting compounds contains
tellurium dioxide or a compound of the formula M x n+ TeO 3 where n=1 or 2 and x=2/n, where M is an alkali metal or alkaline earth metal, and
at least one of molybdenum trioxide, vanadium pentoxide, and niobium pentoxide.
2. The process as claimed in claim 1 , wherein the activation in step d) is carried out at a temperature in the range from 450° C. to 700° C.
3. The process as claimed in claim 1 , wherein the mixture of starting compounds contains molybdenum trioxide.
4. The process as claimed in claim 1 , wherein the mixture of starting compounds contains vanadium pentoxide.
5. The process as claimed in claim 1 , wherein the mixture of starting compounds contains niobium pentoxide.
6. The process as claimed in claim 5 , wherein the niobium pentoxide has a particle size D 90 of less than 100 μm.
7. The process as claimed in claim 1 , wherein the mixture of starting compounds contains tellurium dioxide having a particle size D 90 of less than 100 μm.
8. The process as claimed in claim 1 , wherein the first chelating oxo ligand or the second chelating oxo ligand is ethylene glycol, present in a molar ratio to molybdenum of 0.01:1 to 1:1.
9. The process as claimed in claim 1 , wherein the first chelating oxo ligand or the second chelating oxo ligand is citric acid.
10. A mixed oxide material for the oxidation of ethane, which comprises the elements molybdenum, vanadium, niobium and tellurium and has the following stoichiometry:
Mo 1 V a Nb b Te c O x
where 0.27<a<0.31; 0.08<b<0.12; 0.08<c<0.12,
and which in the XRD, when using Cu-Kα radiation, has diffraction reflections h, i, k and l whose peaks are approximately at the diffraction angles (2θ) 26.2°±0.5° (h), 27.0°±0.5° (i), 7.8°±0.5° (k) and 28.0°±0.5° (l).
11. The use of the mixed oxide material as claimed in claim 10 for the oxidative dehydrogenation of ethane to ethene.
12. The use of the mixed oxide material as claimed in claim 10 for the oxidation of propane.
13. The process as claimed in claim 1 , wherein each chelating oxo ligand is independently present in the mixture of starting compounds in a molar ratio to molybdenum of 0.08:1 to 0.4:1.
14. The process as claimed in claim 1 , wherein the product suspension resulting from step b) includes the mixed oxide material, having the following stoichiometry:
Mo 1 V a Nb b Te c O x
where 0.27<a<0.31; 0.08<b<0.12; 0.08<c<0.12,
and which in the XRD, when using Cu-Kα radiation, has diffraction reflections h, i, k and l whose peaks are approximately at the diffraction angles (2θ) 26.2°±0.5° (h), 27.0°±0.5° (i), 7.8°±0.5° (k) and 28.0°±0.5° (l).
15. The process as claimed in claim 1 , wherein the product suspension resulting from step b) comprises a mother liquor including less than 100 ppm of a combined amount of molybdenum, vanadium, niobium, and tellurium.
16. The process as claimed in claim 1 , wherein each chelating oxo ligand is independently present in the mixture of starting compounds in a molar ratio to molybdenum of 0.08:1 to 0.4:1.
17. A process for producing a mixed oxide material, comprising the steps:
a) production of a mixture of starting compounds, which contains starting compounds comprising molybdenum, vanadium, niobium, and tellurium, and also contains oxalic acid a first chelating oxo ligand and a second chelating oxo ligand, wherein molybdenum is present in the mixture
in an atomic ratio to vanadium of 1:0.22 to 1:0.3,
in an atomic ratio to niobium of 1:0.1 to 1:0.17, and
in an atomic ratio to tellurium of 1:0.1 to 1:0.17,
b) hydrothermal treatment of the mixture of starting compounds at a temperature of from 100° C. to 300° C. to give a product suspension,
c) isolation and drying of the solid present in the product suspension resulting from step b), and
d) activation of the solid obtained from step c) in an inert gas,
wherein the mixture contains tellurium dioxide or a compound of the formula M x n+ TeO 3 where n=1 or 2 and x=2/n, where M is an alkali metal or alkaline earth metal.
18. The process as claimed in claim 17 , wherein the mixture of starting compounds includes at least one of molybdenum trioxide, vanadium pentoxide, and niobium pentoxide.
19. The process as claimed in claim 17 , wherein the product suspension resulting from step b) includes the mixed oxide material, having the following stoichiometry:
Mo 1 V a Nb b Te c O x
where 0.27<a<0.31; 0.08<b<0.12; 0.08<c<0.12,
and which in the XRD, when using Cu-Kα radiation, has diffraction reflections h, i, k and l whose peaks are approximately at the diffraction angles (2θ) 26.2°±0.5° (h), 27.0°±0.5° (i), 7.8°±0.5° (k) and 28.0°±0.5° (l).
20. The process as claimed in claim 17 , wherein the product suspension resulting from step b) comprises a mother liquor including less than 100 ppm of a combined amount of molybdenum, vanadium, niobium, and tellurium.