Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Patent
1996-04-19
1997-06-10
Caldarola, Glenn A.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
502311, B01J 2322
Patent
active
056375468
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of catalytically active poly-metal oxide materials which contain the elements V and Mo in oxide form as basic components, in which an intimate dry mixture is prepared from starting compounds which contain the elemental constituents of the poly-metal oxide materials and said mixture is calcined at from 300.degree. to 450.degree. C. in a gas atmosphere consisting of oxygen, ammonia and, as a residual amount, steam and/or inert gas.
Zesz. Nauk.-Politech. Lodz., Chem. 616 (43) (1991), 95-106, discloses that poly-metal oxide materials which contain the elements V and Mo in oxide form as basic components are suitable as catalysts for the catalytic gas-phase oxidation of acrolein to acrylic acid. Furthermore, the abovementioned publication discloses that such catalytically active poly-metal oxide materials can be produced by a method in which catalyst intermediates are calcined first in the presence of air and then in the presence of a gas mixture consisting of acrolein, oxygen and inert gases. Catal. Rev.-Sci. Eng. 35 (2) (1993), 213-259, recommends a corresponding preparation process. However, the disadvantage of this procedure is that acrolein-containing calcination atmospheres cannot be handled in conventional calcination ovens.
DE-31 19 586 C2 discloses that a catalytically active poly-metal oxide material which contains the elements V and Mo in oxide form as basic components can be produced by preparing an intimate dry mixture containing ammonium ions from starting compounds which contain the elemental constituents of the poly-metal oxide materials and calcining said mixture at 380.degree. C. in a gas stream which contains 1% by volume of oxygen in addition to steam and inert gases. The resulting poly-metal oxide material is recommended in DE-31 19 586 C2 as a catalyst for the catalytic gas-phase oxidation of acrolein to acrylic acid.
Owing to the content of ammonium ions in the material to be calcined, the calcination atmosphere according to DE-31 19 586 C2 does of course contain ammonia. DE-31 19 586 C2 does not envisage any effect of the ammonia content of the calcination atmosphere on the catalyst activity and selectivity.
The present invention is based on the surprising discovery that, in the case of poly-metal oxide materials containing V and Mo as basic components in oxide form, a defined NH.sub.3 content of the calcination atmosphere in combination with a defined O.sub.2 content thereof leads to catalytically active materials which have higher catalyst activity and selectivity when used as catalysts for obtaining acrylic acid from acrolein by catalytic gas-phase oxidation.
Accordingly, we have found a process for the preparation of catalytically active poly-metal oxide materials which contain the elements V and Mo in oxide form as basic components, in which an intimate dry mixture is prepared from starting compounds which contain the elemental constituents of the poly-metal oxide materials and said mixture is calcined at from 300.degree. to 450.degree. C., with the proviso that the gas atmosphere in which the calcination is carried out is composed of
from 0.5 to 4, preferably from 1 to 2, % by volume of O.sub.2 throughout the calcination,
from 1 to 8% by volume, averaged over the total duration of the calcination, of NH.sub.3 and
steam and/or inert gas as the remaining amount.
The NH.sub.3 content of the calcination atmosphere, averaged over the total duration of the calcination, is from 1 to 6, particularly preferably from 4 to 6, % by volume.
The calcination is particularly preferably carried out at a calcination temperature of from 300.degree. to 350.degree. C. (calcination stage I) for from 50 to 95% of the total calcination time (as a rule from 3 to 15 hours) and at a calcination temperature of from 380.degree. to 450.degree. C. for from 5 to 50% of the total calcination time in a subsequent calcination stage II.
It is advantageous if the NH.sub.3 content of the calcination atmosphere, averaged over the total duration of calcination
REFERENCES:
patent: 4062885 (1977-12-01), Mekhtiev et al.
patent: 4075283 (1978-02-01), Shiraishi et al.
patent: 4356114 (1982-10-01), Kadowaki et al.
Catal. Rev.-Sci. Eng., vol. 35, No. 2, pp. 213-259, 1993, T.V. Andrushkevich, "Heterogeneous Catalytic Oxidation of Acrolein to Acrylic Acid: Mechanism and Catalysts".
Chem., vol. 616, No. 43, pp. 95-106, 1991, J. Tichy, et al., "Active Component of Mo-V-O Catalysts in the Process of Acrolein Oxidation".
Hammon Ulrich
Tenten Andreas
Weidlich Peter
BASF - Aktiengesellschaft
Caldarola Glenn A.
Ghyka Alexander G.
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