EP1345689A2

EP1345689A2 - Method for producing a multi-metal oxide active material containing mo, bi, fe and ni and/or co

Info

Publication number: EP1345689A2
Application number: EP01991826A
Authority: EP
Inventors: Jochen Petzoldt; Heiko Arnold; Signe Unverricht
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2000-12-18
Filing date: 2001-12-12
Publication date: 2003-09-24
Also published as: WO2002049757A2; DE10063162A1; WO2002049757A3; JP2004516132A

Abstract

The invention relates to a method for producing a multi-metal oxide material containing Mo, Bi, Fe and Ni and/or Co. The invention is characterised in that the source of the Bi is added in portions during the production process.

Description

Process for producing a multimetal oxide active composition containing Mo, Bi, Fe and Ni and / or Co

description

The present invention relates to a method for producing a multimetal oxide active composition of the general formula I.

θι ₂ Bi _a Fe _b W _G X ¹ dX ² eX ³ fOy (1),

With

X ¹ _^ Co and / or Ni, X = Si and / or Al,

X ³ = Li, Na, K, Cs and / or Rb,

0.2 <a <2,

0.5 <b <10,

0 <c <4, 2 <d <10,

0 <e <10,

0 <f <0.5 and y = a number which is determined under the condition of charge neutrality by the valency and frequency of the elements in I other than oxygen,

in which a solution or suspension is produced from starting compounds of the elemental constituents of the multimetal oxide active composition I, the solution or suspension is dried to obtain a dry composition and the dry composition is thermally treated at elevated temperature.

Furthermore, the present invention relates to the use of multi-oxide active I as catalysts for the gas-phase catalytic oxidation of propene to acrolein.

The production of the important intermediate acrolein by heterogeneously catalyzed gas phase oxidation of propene is generally known (see e.g. DE-A 19855915).

Acrolein is used inter alia. for the production of acrylic acid, the alkyl esters of which are used in particular as monomers for the production of aqueous polymer dispersions.

It is also known to use multimetal oxide active compositions of the general formula I as catalysts for the catalyzed gas phase oxidation of propene to acrolein. For example, DE-A 19855913 recommends the use of rings formed exclusively from multimetal oxide active composition I (all-catalyst rings) and the use of multimetal oxide active composition I (shell catalysts) applied to supports as catalysts for the gas-phase catalytic oxidative production of acrolein from propene.

Corresponding recommendations can be found in DE-A 10049873.

According to the cited prior art, the multi-metal oxide active composition I is prepared in such a way that a solution or suspension is produced from starting compounds of the elemental constituents of the multimetal oxide active composition I, the solution or suspension is dried to give a dry mass and the dry mass is thermally treated at elevated temperature.

A disadvantage of multi-metal oxide active materials I produced in this way is that their long-term activity when used as catalysts for the gas-phase catalytic oxidation of propene to acrolein is not fully satisfactory.

The object of the present invention was therefore to provide an improved process for the preparation of multimetal oxide active compositions I which ensures increased long-term activity when using the resulting multimetal oxide compositions I as catalysts for the gas-phase catalytic oxidation of propene to acrolein.

Accordingly, a process for the preparation of a multimetal oxide active composition of the general formula I

Mθι ₂ Bi _a Fe _b W _c X ¹ _d X ² _e X ³ _f O _y (I),

With

X ^x = Co and / or Ni,

X ² = Si and / or AI,

X ³ = Li, Na, K, Cs and / or Rb,

0.2 <a <2, 0.5 <b <10,

0 <c <4,

2 <d <10,

0 <e <10,

0 <f <0.5 and y = a number provided that the charge is neutral is determined by the valency and frequency of the elements in I other than oxygen,

in which a solution or suspension is produced from starting compounds of the elementary constituents of the multimetal oxide active composition I, the solution or suspension is dried to obtain a dry matter and the dry matter is thermally treated at elevated temperature, which is characterized in that the solution to be dried or Suspension of the starting compounds contains the total amount of the elemental constituents different from Bi required for the preparation of the multimetal oxide active compound I, but only contains a partial amount of the Bi required for the preparation of the multimetal oxide active compound I, and the residual amount of Bi additionally required for the preparation of the multimetal oxide active compound I only subsequently and in advance of thermal treatment in the form of an initial compound of the Bi is incorporated into the dry matter.

According to the invention, the stoichiometric coefficient a is advantageously 0.4 a <2, preferably 0.4 a <1.5 and particularly preferably 0.6 a <1.5. According to the invention, the value for the variable b is advantageously in the range 1 <b <5 and with particular advantage in the range 2 <b <4. According to the invention, the stoichiometric coefficient c is frequently 1 to 3. The variable d is preferably in the range 4 <according to the invention d <8, and particularly preferably in the range 6 <Ξ d <8. According to the invention, the stoichiometric coefficient f is expediently> 0. Preferably 0.01 <f <0.5 and particularly preferably 0.05 f <0.2.

The value for the stoichiometric coefficient of oxygen, y, results from the valence and frequency of the cations under the condition of charge neutrality.

According to the invention, preference is given to those multimetal oxide active compositions I whose catalytically active oxide composition has only Co as X ¹ . Preferred X ² is Si and X ³ is preferably K, Na and / or Cs, particularly preferably X ³ = K.

Also advantageous according to the invention are those multimetal oxide compositions I whose molar ratio of Co / Ni is at least 2: 1, preferably at least 3: 1 and particularly preferably at least 4: 1. The best is only Co.

In particularly preferred multi-metal oxide masses I according to the invention, the value for 1.5 x (a + b) + d is in the range> 11 and <14, preferably in the range> 11.5 and <13. Values ^' for 1.5 x are particularly preferred (a + b) + d in the range> 11.8 and <12.5. In addition, those multimetal oxide actives I are suitable according to the invention whose stoichiometry corresponds to a catalytically active oxide mass specified in DE-A 19855913.

Based on the total amount of Bi contained in a multimetal oxide active composition I obtainable according to the invention, the amount of Bi subsequently incorporated into the dry matter in the process according to the invention is generally 20 to 80%, preferably 30 to 60% and particularly preferably 35 to 45% ,

The source for the Bi to be subsequently incorporated into the dry matter can either be bismuth oxide or bismuth compounds which can be converted into oxide by heating, at least in the presence of oxygen. Bismuth compounds suitable according to the invention for the aforementioned purpose are thus e.g. Bismuth nitrate, bismuth subcarbonate, bismuth salicylate and bismuth oxychloride and hydrates of these compounds. According to the invention, these bismuth starting compounds can of course also be used as sources for the proportion of bismuth to be incorporated into the dry matter beforehand.

To prepare the solution or suspension from starting compounds of the elementary constituents of the multimetal oxide active composition I, both water and an organic liquid, such as e.g. Methanol or ethanol or their mixture with water can be used. The use of water is preferred. As starting compounds (sources) of the elemental constituents of the multimetal oxide active composition I, as already described for the case of bismuth, are oxides of the elemental constituents or compounds containing the elemental constituents, which can be converted into oxides by heating, at least in the presence of oxygen are. In addition to the oxides, ammonium metallates, halides, nitrates, formates, oxalates, acetates, carbonates or hydroxides are therefore particularly suitable as starting compounds.

The drying of the solution or suspension from starting compounds of the elementary constituents of the multimetal oxide active composition I can be carried out in any manner per se. Ie, according to the invention, both the method of evaporation with stirring (for example at normal pressure and temperatures from 80 to 130 ° C., or else at reduced pressure), the method of freeze drying or the method of spray drying can be used. Drying is advantageously carried out by spray drying (the gas inlet temperature is generally 280 to 420 ° C., and the gas outlet temperature is typically 100 to 150 ° C).

In principle, the residual amount of bismuth required according to the invention can be incorporated directly into the solid obtained during drying. For this purpose, the mixture, if appropriate after prior comminution, is appropriately mixed homogeneously with a dry bismuth source and kneaded after adding 20 to 60% by weight of water or an organic liquid, such as methanol or ethanol, based on the total dry matter. After kneading, the kneaded material is appropriately roughly divided and dried (e.g. at temperatures of 100 to 150 ° C in a drying cabinet). Drying can then be followed by the thermal treatment at elevated temperature required according to the invention.

The thermal treatment required according to the invention can take place both under an oxidizing, under an inert or under a reducing atmosphere. It expediently takes place in air. Of course, it can also be carried out under vacuum. For generating an inert gas atmosphere, e.g. inert gases such as molecular nitrogen and / or noble gases such as He, Ar. For example, the thermal treatment can take place in a forced air oven.

The temperature of 600 ° C. is expediently not exceeded during the thermal treatment. Furthermore, it is advantageous according to the invention if the temperature of 400 ° C. is exceeded during the thermal treatment. The temperature of 550 ° C. is preferably not exceeded during the thermal treatment. However, it is advantageous according to the invention if the temperature of 430 ° C. is exceeded in the thermal treatment according to the invention. The thermal treatment can be carried out within a period of a few hours (typical time period is 2 h to 10 h), the required treatment time decreasing with increasing temperature.

After the thermal treatment has ended, the multimetal oxide active composition I obtained can be used as such, optionally after comminution, or shaped into geometric bodies as a catalyst for the gas-phase catalytic oxidation of the propene to acrolein.

For example, solid catalysts can be prepared from the powder form of the active composition by compression to the desired catalyst geometry (for example by tableting, extrusion or extrusion), with auxiliaries such as, for example, Graphite or stearic acid can be added as a lubricant and / or molding aid and reinforcing agent such as microfibers made of glass, asbestos, silicon carbide or potassium titanate. Suitable full catalyst geometries are, for example, full cylinders or hollow cylinders with an outer diameter and a length of 2 to 10 mm. The full catalyst can of course also have a spherical geometry, the spherical diameter being 2 to 10 mm.

Of course, the powdery active composition can also be shaped by application to preformed inert catalyst supports.

The coating of the support bodies for the production of the shell catalysts is usually carried out in a suitable rotatable container, as it is e.g. is known from DE-A 2909671, EP-A 293859, EP-A 714 700 and DE-A 4442346.

For coating the support bodies, the powder mass to be applied is expediently moistened and after application, e.g. using hot air, dried again. The layer thickness of the powder composition applied to the carrier body is expediently selected in the range from 10 to 1000 μm, preferably in the range from 100 to 700 μm and particularly preferably in the range from 300 to 500 μm. Possible shell thicknesses are also 10 to 500 μm or 200 to 300 μm.

Conventional porous or non-porous aluminum oxides, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide or silicates such as magnesium or aluminum silicate can be used as carrier materials. Particularly suitable silicates are clay, kaolin, steatite and pumice.

The surface of the carrier body can be both smooth and rough. The surface of the carrier body is advantageously rough, since an increased surface roughness generally results in an increased adhesive strength of the applied shell on oxidic active material. The surface roughness R _{z of} the support is often. body in the range of 40 to 200 microns, often in the range of 40 to 100 microns (determined according to DIN 4768 sheet 1 with a "Hommel Tester for DIN-ISO surface measurements" from Hommelwerke, DE).

The carrier material is expediently non-porous (total volume of the pores based on the volume of the carrier body <1% by volume). The fineness of the active composition to be applied to the surface of the carrier body is of course adapted to the desired thickness of the active oxide composition shell. For the range of a shell thickness of 100 to 500 μ, for example, powders are suitable, of which at least 50% of the powder particles pass through a sieve with a mesh size of 1 to 10 μm and their proportion of particles with a longitudinal expansion above 50 μm less than 1% (based on the total number of particles). As a rule, the distribution of the longest dimensions of the powder particles corresponds to a Gaussian distribution due to the manufacturing process.

The carrier bodies can be regularly or irregularly shaped, with regularly shaped carrier bodies, e.g. Balls or hollow cylinders are preferred.

Suitable according to the invention is e.g. the use of spherical supports, the diameter of which is 1 to 8 mm, preferably 4 to 5 mm.

However, it is also suitable to use cylinders as support bodies, the length of which is 2 to 10 mm and the outside diameter is 4 to 10 mm. In the case of rings suitable as support bodies according to the invention, the wall thickness is moreover usually 1 to 4 mm. Cylinder dimensions suitable according to the invention are also 3 to 6 mm (length), 4 to 8 mm (outside diameter) and, in the case of rings, 1 to 2 mm (wall thickness).

Of course, 2 to 4 mm (length), 4 to 8 mm (outer diameter) and 1 to 2 mm (wall thickness) are also suitable as the ring geometry suitable according to the invention.

Striking carrier ring geometries according to the invention are e.g. 7 mm x 3 mm x 1.5 mm (outside diameter x length x wall thickness) and 5 mm x 3 mm x 1.5 mm (outside diameter x length x wall thickness).

However, the thermal treatment required according to the invention to obtain the multimetal oxide active composition I can also be divided into several sections in ^{terms of} its timing.

For example, first a thermal treatment at a temperature of 150 to 350 ° C, preferably 220 to 280 ° C, and then a thermal treatment at a temperature of 400 to 600 ° C, preferably 430 to 550 ° C can be carried out.

In the manufacture of coated catalysts, it is generally expedient according to the invention, even after a first thermal treatment at a temperature of 150 to 350 ° C., preferably 220 to 280 ° C, multimetal oxide precursor mass to be used for coating the catalyst carrier body, as described in DE-A 10049873, and only the carrier body coated with multimetal oxide precursor mass of the thermal finishing treatment at 400 to 600 ° C, preferably 430 to Subject to 500 ° C.

It is also advantageous according to the invention to carry out the production of the dry matter, into which the additional amount of Bi additionally required is subsequently incorporated, as follows.

As already described, the solution or suspension to be dried is converted into a dry form by evaporation, freeze-drying and / or spray drying. This is then further dried at a temperature of 150 to 350 ° C, preferably 220 to 280 ° C, for a few hours (usually 2 to 6 h) (under reducing, oxidizing and / or under an inert gas atmosphere, or under vacuum) , Then, as already described, the bismuth-containing starting compound is worked in and after or before the geometry is thermally treated at temperatures of 400 to 600 ° C., preferably 430 to 550 ° C., as described.

The method according to the invention is particularly preferably carried out as follows. The solution or suspension of the starting compounds is produced in an aqueous medium, preferably in water.

The aqueous solution or suspension is then spray-dried (the gas inlet temperature is usually 280 to 420 ° C, and the gas outlet temperature is typically 100 to 150 ° C).

In many cases, the powder obtained during spray drying proves to be too finely divided for immediate further processing. In these cases, it is expediently kneaded with the addition of water. After kneading, the kneaded material is appropriately roughly divided and dried again (e.g. at temperatures from 100 to 150 ° C in a drying cabinet).

This drying step is followed by further drying at 150 to 350 ° C (e.g. in a convection oven; but also possible under other reducing, oxidizing or inert atmospheres and under vacuum).

The dry matter obtained is then mixed in fine particles with a bismuth starting compound (preferably bismuth subcarbonate and / or bismuth nitrate and or their hydrates). Then, based on the total dry matter, 20 to 60 wt .-% water added and kneaded. Following the kneading, the kneaded material is expediently roughly divided and dried (for example at temperatures from 100 to 150 ° C. in a drying cabinet).

Then either the geometric shaping (to give a full catalyst or coated catalyst) is carried out (this can be done as already described) and then thermally treated at 400 to 600 ° C, preferably 430 to 550 ° C, or first at 400 to 600 ° C, preferably 430 up to 550 ° C, thermally treated and then the geometric shaping (to full catalyst or coated catalyst) is carried out (this can be done as already described).

In particular, if first the geometric shaping to form a coated catalyst and then the thermal treatment is carried out, the coating of the support body and the thermal treatment are carried out as described in DE-A 10049873.

The catalysts obtainable according to the invention are suitable not only for the selective gas phase oxidation of propene to acrolein, but also for the partial gas phase oxidation of other organic compounds (other alkenes, alkanes, alkanones or alkenols) to give α, β-unsaturated aldehydes and / or carboxylic acids. The production of acrylic acid from acrolein and the production of methacrolein and methacrylic acid from isobutene, isobutane, tert. -Butanol or tert. -Butylmethyl- ether.

The general reaction conditions to be observed using the catalysts for the gas-phase catalytic oxidation of propene to acrolein obtainable according to the invention can be found e.g. in DE-A 4023239, DE-A 4431957 and in DE-A 19955176.

The multimetal oxide active compositions I obtainable according to the invention are particularly suitable for catalysts for carrying out the partial catalytic gas-phase oxidation of propene to acrolein using increased propene loads on the catalyst feed, as described, for example, in DE-A 19955168, DE-A 19948523 and DE-A 19948248 and is described in DE-A 19955176. Here, the present invention easteä-Ltliehen multimetal are distinguished by an improved life (improved long term activity) ^'. It is also essential according to the invention that the multimetal oxide active compositions I obtainable according to the invention, particularly in the case of increased propene load, have a completely satisfactory activity with regard to acrolein formation and an increased selectivity with acrolein formation.

A measure of the aforementioned activity is the reaction temperature required to achieve a given propene conversion. The lower the required reaction temperature, the higher the activity.

Finally, it should be noted that the catalysts according to the invention which are consumed in the course of a gas phase catalytically oxide-active propene oxidation to acrolein can be regenerated as described in EP-A 339119.

In addition, it should also be mentioned that the multimetal oxide active compositions obtainable according to the invention and the catalysts formed from and / or with them in this document also serve as catalysts for the gas-phase-catalytic partial oxidation of xylenes, in particular p-xylene and m-xylene, to form the corresponding mono- and Dialdehydes such as p-Tolylaldehyde, terephthalaldehyde, m-Tolylaldehyde and isophthalaldehyde are suitable.

The aforementioned partial oxidation of xylenes can e.g. be carried out in the tray reactor or in the tube bundle reactor. The reaction temperature is usually 350 to 500 ° C, preferably 400 to 450 ° C. Air or air enriched with molecular nitrogen is suitable as the source of the molecular oxygen required for the partial oxidation. The reaction gas starting mixture, based on the xylene to be oxidized and the reaction stoichiometry, generally contains at least a 10-fold excess of molecular oxygen. Normally, however, the aforementioned excess is <50. The proportion of the xylene to be oxidized in the reaction gas starting mixture is usually in the range from 0.1 to 1.5 vol. -%. The loading of the catalyst feed with reaction gas starting mixture is frequently chosen to be 10,000 to 20,000 Nl / l-h. This often corresponds to a corresponding xylene load of 20 to 40 Nl / l-h.

Of course, the gas-phase-catalytic partial oxidation of the xylenes can be carried out either on a mixture of the individual xylene isomers or on an individual xylene isomer. More detailed information on the conditions of the xylene partial oxidation to be used can be found in US-A 5324702 and in US-A 4017547. Examples and comparative examples

1. Production according to the invention of a dry mass of stoichiometry Mθι ₂ Bi ₀ , 6Fe ₃ Co ₇ Siι, _{6 0} , ₀ 8th

To 3530.05 g of an aqueous cobalt (II) nitrate solution (12.4% by weight Co) heated to 60 ° C., 1252.51 were added over a powder funnel with stirring within one minute while maintaining the 60 ° C. g of ice (III) nitrate (14.2% by weight Fe) was added. After the addition was complete, 30 min. stirred at 60 ° C. Finally, while maintaining the 60 ° C., 1198.99 g of an aqueous bismuth nitrate solution (11.1% by weight of Bi) were stirred in via a dropping funnel within two minutes. After stirring for a further 10 minutes at 60 ° C., a clear, red-colored aqueous solution A was obtained.

10.18 g of an aqueous KOH solution (46.8% by weight KOH) were stirred into 2500 g of water. The solution was then heated to 60 ° C. with stirring. Then, while maintaining the 60 ° C. with stirring, 2249.72 g were added in portions

Ammonium heptamolybdate was added and the mixture was stirred at 60 ° C. for another hour. A slightly cloudy, pale yellow aqueous solution B was obtained.

To the aqueous solution B having 60 ° C was using a

Pump with stirring within 15 min. given the aqueous solution A at 60 ° C. After the addition had ended, a further 5 min. stirred at 60 ° C. Then, while maintaining were 60 ° C, with stirring, 204.11 g of silica sol (Ludox ^® TM, Du Pont, 50 wt .-% Si0 _2, density: 1.39 g / ml, pH: 8.8,

Alkali content 0.5 wt .-%) added and stirred for a further five minutes at 60 ° C.

The aqueous mixture obtained was spray-dried in a spray dryer from Niro (spray dryer Niro A / S Atomizer Transportable Minor System, centrifugal atomizer from Niro, DK). The initial temperature was 60 ° C. The gas inlet temperature was 360 ± 10 ° C, the gas outlet temperature was 115 ± 5 ° C. The entire aqueous mixture was sprayed at a rate of 2 l / h through a two-fluid nozzle with an attached atomizer wheel with a spray nozzle pressure of 5.2 bar and air as carrier gas (40 m ³ / h) in cocurrent. After powder separation in a cyclone, a spray powder with a particle size of 20 to 25 μin was obtained. 400 g of the spray powder were kneaded in a 1 1 kneader from Werner & Pfleiderer, DE, type LUK 075 with the addition of 150 ml of water. The kneader had two counter-operated sigma plates. The kneading was carried out in three steps, which lasted 5, 10 and 15 minutes. Before the third kneading step, the kneaded material was cut up by hand, mixed and detached from the kneading blades to ensure uniform mixing.

Following the kneading, the kneaded material was roughly divided and dried for 17 hours in a drying cabinet from Binder, DE, type FD 53 (53 1 internal volume) at 120 ° C.

The dried kneaded material was further dried in a forced-air oven from Nabertherm, DE, type N60 / A (60 l internal volume). The oven was first heated to 240 ° C within one hour and 10 min. kept at this temperature. The mixture was then heated to 280 ° C. within 60 minutes. This temperature was kept constant for 2 h. A gas flow of 300 Nl / 1 air was passed through the circulating air oven during the entire time. A dry matter A according to the invention was thus obtained.

2. Incorporation of bismuth nitrate pentahydrate into dry matter A

400 g of dry matter A were ground to a particle size of> 0 to <0.12 mm (the grain size distribution corresponded to the grain size distribution given in this document under "6"). Then the 400 g of dry matter A were mixed with 27.89 g of bismuth nitrate pentahydrate (Merck, Darmstadt, DE, purity:> 98.5% by weight, particle size 0.25 mm to 1 mm) in a 1.4 liter laboratory mixer (ABC, DE, type 1000 CHA) and then kneaded in a 1 1 kneader from Werner & Pfleiderer type LUK 075 with the addition of 150 ml of water. The kneader had two sigma plates operated in opposite directions. The kneading was carried out in three steps, which lasted 5, 10 and 15 minutes. Before the third kneading step, the kneaded material was cut up by hand, mixed and detached from the kneading blades. to ensure uniform mixing. Following the kneading, the kneaded material was roughly divided and for 15 to 20 hours in a drying cabinet from Binder, DE, type FD 53 (53 1 internal volume) to obtain a precursor composition 1 according to the invention with the stoichiometry Mo ₁₂ Bi, oFe ₃ Co ₇ Siι _{/ 6} K _{0 /} o ₈ dried at 120 ° C. 3. Incorporation of bismuth subcarbonate (Bi C0s) into dry matter A

400 g of dry matter A were ground to a particle size of> 0 to <0.12 mm (the grain size distribution corresponded to the grain size distribution given in this document under "6"). The 400 g of dry matter A were then mixed with 14.64 g of bismuth subcarbonate (particle size 0.05 to 2 mm, from Fluka, DE, Bi content 80-82% by weight) in a 1.4 l laboratory mixer ( ABC, DE, type 1000 CHA) 2 min. mixed and then kneaded in a 1 1 kneader from Werner & Pfleiderer, DE, type LUK 0.75 with the addition of 150 ml of water. The kneader had two counter-rotating sigma blades. The kneading was carried out in three steps, which lasted 5, 10 and 15 minutes. Before the third kneading step, that was

Dough kneaded by hand, mixed and detached from the kneading blades to ensure uniform mixing.

Following the kneading, the kneaded material was roughly divided and dried for 17 hours in a drying cabinet from Binder, DE, type FD 53 (53 1 internal volume) at 120 ° C., a precursor composition ₂ according to the invention having the stoichiometry Mθι ₂ Biι, oF ^e 3Co ₇ Siι, 6 ^κ o, θ8 was obtained.

4. Production of a comparative precursor mass 1 with the stoichiometry Mo ₁₂ Bi _{/ 0} Fe ₃ Co ₇ Si 6, 6 Ko, θ8

Comparative precursor mass 1 was prepared in the same way as dry mass A, but in 1998.32 g of aqueous bismuth nitrate solution were stirred in.

5. Preparation of a 3 Vorlaufermasse inventive stoichiometry Mθι ₂ Bi !, ₀ Fe ₃ Co ₇ Siι, ₅ K _0, 08

The preparation was carried out in the same way as the dry mass A according to the invention. However, the 400 g of the spray powder were kneaded not only with the addition of 150 ml of water but also with the addition of 27.89 g of bismuth nitrate pentahydrate. Production of coated catalysts coated with multi-metal oxide active materials I and production of a comparison coated catalyst

General manufacturing instructions:

The precursor mass to be used for the coating of the inert catalyst carrier body was ground in a centrifugal mill (Retsch, DE, type ZM 100) to a grain size> 0 and <0.12 mm.

The following resulted in the following grain size distribution:

with D = diameter of the grain

X = the numerical percentage of the grains whose diameter is> D. Y = the numerical percentage of the grains whose diameter is <D.

116 g of the ground precursor mass were placed on 250 g spherical carrier bodies with a diameter of 2.5 to 3.5 mm (R ₂ = 45 μm, carrier material = steatite, total pore volume of the carrier <1% by volume based on total carrier volume ) applied. For this purpose, the carrier was placed in a coating drum (2 1 internal volume, angle of inclination of the drum center axis against the horizontal = 30 °). The drum was rotated at 25 revolutions per minute. An atomizer nozzle operated with 300 Nl / h of compressed air was used for 60 min. about 45 ml of water sprayed onto the carrier. The nozzle was installed in such a way that the spray cone wetted the carrier bodies in the drum, which were carried by driving plates to the uppermost point of the inclined drum, in the upper half of the rolling path.

The finely divided precursor mass was introduced into the drum via a powder screw, the point of the powder additions being within the unrolling section but below the spray cone. Through the periodic repetition of wetting and In the following period the powder-coated carrier body itself became the carrier body. After completion of the coating, the coated carrier body was dried for 15 to 20 hours at 120 ° C. in a drying cabinet (company Binder, DE, internal volume 53 l). The dried coated catalyst precursors were then thermally treated in a forced-air oven from Heraeus, DE (type K 750/2 S, internal volume 55 l) through which 800 Nl / h of air flowed, using the temperature program below:

Heating rate and final temperature Holding time at the final temperature first within 45 min li30 min near from 25 ° C to 240 ° C then linear within 10 min from 240 ° C 30 min to 280 ° C then linear over 180 min from 1 min 280 ° C to 450 ° C then within 30 min from 450 ° C to 360 min

470 ° C

The shell catalysts produced in this way had a multimetal oxide active mass layer thickness of 370 i 30 μ in all cases.

The following precursor masses were used for the production of shell catalysts:

a) Precursor mass 1 (shell catalyst 1 was obtained) b) Precursor mass 2 (shell catalyst 2 was obtained) c) Precursor mass 3 (shell catalyst 3 was obtained) d) Comparative precursor mass 1 (comparison shell catalyst 1 was obtained).

7. Testing the shell catalysts produced

A reaction tube made of V2A steel (outer diameter = 21 mm, inner diameter = 15 mm) was charged with the respective tray catalyst. The feed length was selected in all cases so that the fixed catalyst bed contained approximately 43 g of active composition.

The entire length of the reaction tube was heated with a salt bath flowing around it. A mixture of 5 vol .-% propene, 9.5 vol. -% mo- molecular oxygen and 85.5 vol .-% molecular nitrogen used.

The load on the reaction tube was chosen to be 10 Nl / h of propene. The salt bath temperature was adjusted in all cases so that a propene conversion U _p of 95 mol% was achieved in one pass through the reaction tube. After reaching the propene conversion of 95 mol%, the salt bath temperature required for this was maintained and it was examined how the propene conversion developed over the operating period t. In the product gas stream, the selectivity S _{A of} the value product formation on acrolein was additionally determined by gas chromatographic analysis.

The following table shows the results obtained depending on the coated catalyst used:

The salt bath temperature required in the case of the shell catalysts 1, 2 and 3 was below the salt bath temperature required in the case of the comparison shell catalyst 1.

Claims

claims

1. Process for the preparation of a multimetal oxide active composition of the general formula I

Mo ₁₂ Bi _a Fe _b W _c X ¹ _d X ² _e X ³ _f O _y (I),

With

X ^x = Co and / or Ni,

X ² = Si and / or AI,

X ³ = Li, Na, K, Cs and / or Rb,

0.2 <a <2, 0.5 <b <10,

0 <c <4,

2 <d <10,

0 <e <10

in which a solution or. from starting compounds of the elementary constituents of the multimetal oxide active composition I

Suspension produced, the solution or suspension is dried to obtain a dry matter and the dry matter is thermally treated at elevated temperature, which is characterized in that the solution or suspension to be dried ^'of the starting compounds is indeed the total amount required by Bi various elementary constituents, but only contains a subset of the Bi required for the preparation of the multimetal oxide active composition I, and the additional amount of Bi additionally required for the manufacture of the multimetal oxide active composition I only subsequently and in advance of the thermal treatment in the form of a starting compound of the Bi in the dry matter is incorporated.

2. The method according to claim 1, characterized in that 0.6 <a <1.5.

3. The method according to claim 1 or 2, characterized in that 2 <b <4.

4. The method according to any one of claims 1 to 3, characterized in that 4 <d <8.

5. The method according to any one of claims 1 to 4, characterized in that 0.05 <f <2nd

6. The method according to any one of claims 1 to 5, characterized in that X ^{1 is} only Co.

7. The method according to any one of claims 1 to 6, characterized in that X ^{2 is} only Si.

8. The method according to any one of claims 1 to 7, characterized in that X ^{3 is} only K.

9. The method according to any one of claims 1 to 8, characterized in that the amount of Bi subsequently incorporated into the dry matter, based on the total amount of Bi contained in the multimetal oxide active material I, is 20 to 80%.

10. The method according to any one of claims 1 to 9, characterized in that the amount of Bi subsequently incorporated into the dry matter in the form of the starting compound bismuth nitrate and / or in the form of a hydrate of bismuth nitrate is incorporated.

11. The method according to any one of claims 1 to 10, characterized in that water is used to prepare the solution or suspension from starting compounds of the elementary constituents of the multimetal oxide active composition.

12. The method according to any one of claims 1 to 11, characterized in that the thermal treatment of the dry mass comprises a thermal treatment at 400 to 600 ° C.

13. The method according to any one of claims 1 to 12, characterized in that the drying of the suspension or solution comprises spray drying.

14. Multimetal oxide active composition, obtainable by a process according to claims 1 to 13.

15. Use of a multimetal oxide active composition according to claim 14 as a catalyst for the gas-phase catalytic oxidation of

Propene to acrolein.

16. A process of gas phase catalytic oxidation of propene to acrolein, characterized in that a multimetal oxide active composition according to claim 14 is used as the catalyst.

17. A method of gas phase catalytic oxidation of propene to acrylic acid, characterized in that it comprises a method according to claim 16.