KR20010023081A - Method for Producing Multi-Metal Oxide Masses Containing Mo, V and Cu - Google Patents

Abstract

The present invention relates to a process for producing a composite metal oxide material containing Mo, V, Cu, and at least one of the elements W, Nb, Cr, and Ce. In this method, a solid component in particulate form is produced and incorporated at an low temperature in an aqueous solution of the parent compound of the residual composite metal oxide component. The mixture is dried and then calcined.

Description

Method for Producing Multi-Metal Oxide Materials Containing MO, VIII and Cu {Method for Producing Multi-Metal Oxide Masses Containing Mo, V and Cu}

The present invention firstly forms a finely divided composite metal oxide material B (X ⁷ ₁₂ Cu _h H _i O _y , starting material 1) separately, and the preformed solid phase starting material 1 is Mo ₁₂ V _a X ¹ _b X ² _c Aqueous solutions of sources of elements Mo, V, X ¹ , X ² , X ³ , X ⁴ , X ⁵ and X ⁶ contained in stoichiometric formula (A) of X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g (starting Incorporation in the desired molar ratio p: q in material 2), drying the resulting aqueous mixture, and before or after shaping the resulting precursor material to provide the desired catalytic geometry, preferably from 300 to 600 ° C. It relates to a process for preparing a composite metal oxide material of formula (I), which is calcined at 450 ° C.

[A] _p [B] _q

Where

A is Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _x ;

B is X ⁷ ₁₂ Cu _h H _i O _y ;

X ¹ is W, Nb, Ta, Cr and / or Ce, preferably W, Nb and / or Cr;

X ² is Cu, Ni, Co, Fe, Mn and / or Zn, preferably Cu, Ni, Co and / or Fe;

X ³ is Sb and / or Bi, preferably Sb;

X ⁴ is Li, Na, K, Rb, Cs and / or H, preferably Na and / or K;

X ⁵ is Mg, Ca, Sr and / or Ba, preferably Ca, Sr and / or Ba;

X ⁶ is Si, Al, Ti and / or Zr, preferably Si, Al and / or Ti;

X ⁷ is Mo, W, V, Nb and / or Ta, preferably Mo and / or W;

a is 1 to 8, preferably 2 to 6;

b is 0.2 to 5, preferably 0.5 to 2.5;

c is 0 to 23, preferably 0 to 4;

d is 0 to 50, preferably 0 to 3;

e is 0 to 2, preferably 0 to 0.3;

f is 0 to 5, preferably 0 to 2;

g is 0 to 50, preferably 0 to 20;

h is 4 to 30, preferably 6 to 24, particularly preferably 8 to 18;

i is 0 to 20, preferably 0 to 10;

x and y are numbers determined according to the valence and the frequency of elements other than oxygen in formula (I);

p and q are numbers other than 0, and their ratio p / q is 160: 1 to 1: 1, preferably 20: 1 to 1: 1, particularly preferably 15: 1 to 3: 1.

Multimetal oxide materials of formula (I) are for example disclosed in DE-A 19528646, for example alkanes, alkanols, alkanal, alkenes and alkenols having preferably 3 to 6 carbon atoms (eg For example, an organic compound such as propylene, acrolein, methacrolein, methyl ether of t-butanol, t-butanol, isobutene, isobutane or isobutyraldehyde) is subjected to gas phase catalytic oxidation to olefinically unsaturated aldehyde and / or carboxyl. Acid, and the corresponding nitrile (in particular, ammoxidation of propene to acrylonitrile or isobutene or t-butanol to methacrylonitrile) is used as catalyst.

DE-A 19528646 proposes to prepare a composite metal oxide material in the manner described in the introduction, in which the step of incorporating solid starting material 1 into aqueous starting material 2 is specifically carried out at ≥80 ° C in all cases. . DE-A 19528646 also does not contain information on the temperature at the time of incorporation.

A disadvantage of the production process mentioned in DE-A 19528646 is that the selectivity of acrylic acid formation is not entirely satisfactory when the resulting composite metal oxide material of formula (I) is used as a catalyst for the gas phase catalytic oxidation of acrolein to acrylic acid.

The preparation of the composite metal oxide materials of formula I is also disclosed in EP-A 668 104.

The preparation method in EP-A 668 104 is as described in DE-A 19528646. EP-A 668104 essentially does not mention the temperature when incorporating solid starting material 1 into aqueous starting material 2.

It is an object of the present invention to provide an improved process for the preparation of the composite metal oxide materials of formula (I) which does not have the disadvantages mentioned above.

The inventors have found that this object is achieved by the process for the preparation of the composite metal oxide material of formula (I) described above, in which the incorporation of solid starting material 1 into aqueous starting material 2 is carried out at ≦ 70 ° C. The mixing temperature is preferably ≦ 60 ° C., particularly preferably ≦ 40 ° C. Usually, the mixing is carried out at room temperature so that the mixing temperature is generally?

According to the invention, the finely divided starting material of the formula (I) advantageously has a maximum diameter d _B (the longest line connecting two points on the surface of the particle and passing through the particle's center of gravity)> 0 to 300 μm, preferably Is composed of particles of 0.1 to 200 μm, particularly preferably 0.5 to 50 μm, very particularly preferably 1 to 30 μm. However, the particle size d _B may of course be 10 to 80 μm or 75 to 125 μm.

The specific surface area A _B (measured according to DIN 66131 by gas adsorption (N ₂ ) by the Brunauer-Emmet-Teller (BET) method) of the starting material 1 used according to the invention It is also advantageous if ≦ 20 m 2 / g, preferably ≦ 5 m 2 / g, very particularly preferably ≦ 1 m 2 / g. Usually, A _B is> 0.1 m 2 / g.

In principle, starting material 1 can be used according to the invention in amorphous and / or crystalline form.

X-ray diffraction pattern of starting material 1 consisting of crystallites of oxometallate or of at least one copper molybdate (described in square brackets [] is the source of the associated X-ray diffraction fingerprint) And when such a metal oxide (oxometal) microcrystal having a crystal structure form thereof, or starting material 1 consists of a microcrystal of these copper molybdate or contains such a copper molybdate microcrystal The case is advantageous:

Cu ₄ Mo ₆ O ₂₀ [A. Moini et al., Inorg. Chem. 25 (21) (1986), 3782-3785;

Cu ₄ Mo ₅ O ₁₇ [Index card 39-181 of the JCPDS-ICDD index (1991)],

α-CuMoO ₄ [index cards 22-242 of the JCPDS-ICDD index (1991)],

Cu ₆ Mo ₅ O ₁₈ [Index cards 40-865 of the JCPDS-ICDD Index (1991)],

Cu _4-x Mo ₃ O ₁₂ , where x is 0 to 0.25 (index cards 24-56 and 26-547 of the JCPDS-ICDD index (1991)),

Cu ₆ Mo ₄ O ₁₅ [Index card 35-17 of JCPDS-ICDD Index (1991)],

Cu ₃ (MoO ₄ ) ₂ (OH) ₂ [index cards 36-405 of JCPDS-ICDD index (1991)],

Cu ₃ Mo ₂ O ₉ [indexcards 24-55 and 34-637 of JCPDS-ICDD Index (1991)], and

Cu ₂ MoO ₅ [Index card 22-607 of JCPDS-ICDD Index (1991)].

X-ray diffraction pattern of the following copper molybdate and thus oxometallate having a crystal structure form thereof, or composed of such oxometallate, or contains this copper molybdate itself or copper mol Composite metal oxide materials consisting of ribdate are advantageous in the present invention:

CuMoO ₄ -III with a wolframite structure according to the Russian Journal of Inorganic Chemistry 36 (7) (1991), 927-928, Table 1.

Among them, materials having a stoichiometric formula of the following formula (II) are preferred.

CuMo _A W _B V _C Nb _D Ta _E O _y ㆍ (H ₂ O) _F

Where

1 / (A + B + C + D + E) is 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05, very particularly preferably 1;

F is 0 to 1;

B + C + D + E is 0 to 1, preferably 0 to 0.7;

y is a number determined by the valence and the frequency of elements other than oxygen.

Particularly preferred among these are those having a stoichiometry of the formula (III), (IV) or (V) below.

CuMo _A W _B V _C O _y

Where

1 / (A + B + C) is 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05, very particularly preferably 1;

B + C is 0 to 1, preferably 0 to 0.7;

y is a number determined by the valence and the frequency of elements other than oxygen.

CuMo _A W _B O _y

Where

1 / (A + B) is 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05, very particularly preferably 1;

A and B are each 0 to 1;

y is a number determined by the valence and the frequency of elements other than oxygen.

CuMo _A V _C O _y

Where

1 / (A + C) is 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05, very particularly preferably 1;

A and C are each 0 to 1;

y is a number determined by the valence and the frequency of elements other than oxygen.

The preparation of such oxometallates or starting material B is described, for example, in EP-A 668 104.

Another suitable metal oxide material B has a stoichiometry of the formula VI and is called HT copper molybdate structure and is 6.79 ± 0.3, 3.56 in the form of lattice spacing d (Å) regardless of the wavelength of the X-rays used. ± 0.3, 3.54 ± 0.3, 3.40 ± 0.3, 3.04 ± 0.3, 2.96 ± 0.3, 2.67 ± 0.2, 2.66 ± 0.2, 2.56 ± 0.2, 2.36 ± 0.2, 2.35 ± 0.2, 2.27 ± 0.2, 2.00 ± 0.2, 1.87 ± 0.2 , His X-ray diffraction pattern (finger) showing the most characteristic and strongest diffraction lines at 1.70 ± 0.2, 1.64 ± 0.2, 1.59 ± 0.2, 1.57 ± 0.2, 1.57 ± 0.2, 1.55 ± 0.2, 1.51 ± 0.2, 1.44 ± 0.2 It is a material which is oxometallate having a structural form defined by print).

CuMo _A W _B V _C Nb _D Ta _E O _y

Where

1 / (A + B + C + D + E) is 0.7 to 1.3, preferably 0.85 to 1.15, particularly preferably 0.95 to 1.05, very particularly preferably 1;

(B + C + D + E) / A is 0.01 to 1, preferably 0.05 to 0.3, particularly preferably 0.075 to 0.15 and very particularly preferably 0.11;

y is a number determined by the valence and the frequency of elements other than oxygen.

When the multimetal oxide material B contains or consists of a mixture of different oxometallates, a mixture of iron manganese and oxometallates having an HT copper molybdate structure is preferred. The weight ratio of the microcrystals having the HT copper molybdate structure to the microcrystals having the iron manganese feldspar structure may be 0.01 to 100, 0.1 to 10, 0.25 to 4, or 0.5 to 2.

Oxometallates of formula VI and methods for preparing starting material B containing them are disclosed, for example, in DE-A 19528646.

In principle, suitable metal oxide materials B according to the invention produce very homogeneous, preferably finely divided, dry blends having a composition corresponding to their stoichiometry from a suitable source of their elemental constituents, and making the dry mixture inert It can be prepared in a simple manner by calcination at 200 to 1000 ° C., preferably at 250 to 800 ° C. under gas, or preferably in air for several hours, wherein the calcination period can be from several minutes to several hours. The calcining atmosphere may further contain steam. Suitable sources for the elemental constituents of the multimetal oxide material B are compounds which are already oxides and / or compounds which can be converted to oxides by heating at least in the presence of oxygen. In addition to the oxides, halides, nitrates, formates, oxalates, citrates, acetates, carbonates, amine complexes, ammonium salts and / or hydroxides are particularly suitable (decomposable and / or later) NH ₄ OH, (NH ₄ ) ₂ CO ₃ , NH ₄ NO ₃ , NH ₄ CHO ₂ , CH ₃ COOH, NH ₄ CH ₃ CO ₂ or ammonium oxal, which can be decomposed into compounds released in complete gaseous form during the calcination step Compounds such as late may be further incorporated). Complete mixing of the starting compounds for preparing the composite metal oxide material B can be carried out in dry or wet form. When carried out in dry form, the starting materials are advantageously used in the form of finely divided powders, which are subjected to the calcination step after mixing and compression as necessary. However, complete mixing is preferably carried out in wet form. Typically, the starting compounds are mixed with each other in the form of aqueous solutions and / or suspensions. Particularly homogeneous dry blends are obtained in the described dry process when using a source in which only the above elemental components are dissolved as starting material. Preferably the solvent used is water. The aqueous material obtained is then dried, which drying step is preferably carried out by spray drying the aqueous mixture at an outlet temperature of 100 to 150 ° C. The dried material is then calcined as described above.

In another method for preparing the composite metal oxide material B, the heat treatment of the mixture of starting compounds used is carried out in an autoclave in the presence of steam at superatmospheric pressure at> 100 to 600 ° C. The pressure range typically extends to 500 atmospheres, preferably 250 atmospheres. This hydrothermal treatment is carried out particularly advantageously in the temperature range of> 100 to 374.15 ° C. (critical water temperature) in which steam and liquid water coexist under the generated pressure.

It can be obtained as described above and may contain oxometallates of individual structures or mixtures of oxometalates of different structures, or of oxometallates of different structures only or with oxometallates of individual structures The multimetal oxide material B, which may be composed of a mixture, may be used as solid starting material 1, for example, after grinding and / or sorting to the desired size as needed.

Suitable sources of elemental components for the preparation of the aqueous starting material 2 required according to the invention are also compounds which are already oxides and / or compounds which can be converted into oxides by heating in the presence of at least oxygen. In addition to oxides, halides, nitrates, formates, oxalates, citrates, acetates, carbonates and / or hydroxides are particularly suitable (decomposable and / or complete gas phase at later stages of calcination). Compounds such as NH ₄ OH, (NH ₄ ) ₂ CO ₃ , NH ₄ HCO ₃ , NH ₄ NO ₃ , NH ₄ CHO ₂ , CH ₃ COOH or NH ₄ CH ₃ CO ₂ , which can be broken down into compounds released in form May be incorporated in addition). Particularly suitable starting compounds of Mo, V, W and Nb are also their oxo compounds (molybdate, vanadate, tungstate and niobate) or acids derived from them. This applies in particular for the corresponding ammonium compounds (ammonium molybdate, ammonium vanadate and ammonium tungstate).

For the preparation of the aqueous solutions required as starting material 2 according to the invention, it is generally necessary to apply elevated temperatures with the above-mentioned sources of elemental constituents as starting materials. As a rule, temperatures of ≧ 60 ° C., generally ≧ 70 ° C., typically ≦ 100 ° C. are used. The above and below conditions indicate that ammonium heptamolybdate tetrahydrate [AHM = (NH ₄ ) ₆ Mo ₇ O ₂₄ ㆍ 4H ₂ O] is used as the Mo element source and / or ammonium metavanadate [AMV = NH ₄ VO ₃ ] is used when used as a vanadium source. In addition to at least one of the two elemental sources described above, element W is part of aqueous starting material 2 and ammonium paratungstate heptahydrate [APW = (NH ₄ ) ₁₀ W ₁₂ O ₄₁ .7H ₂ O] is the starting material of the aqueous solution. These conditions are particularly demanding when used as.

Surprisingly, the inventors have found that aqueous solutions prepared at elevated temperatures as starting material 2 typically have an element Mo content of ≧ 10% by weight based on the aqueous solution and a cooling temperature of 20 ° C. or less (generally not <0 ° C.), It was found that during and after subsequent cooling below the dissolution temperature, that is, no solids precipitated during or after cooling of the aqueous solution. In general, the above also applies when the Mo content is 20% by weight or less based on the aqueous solution.

Typically, the Mo content of the aqueous solution cooled to 20 ° C. or less (generally not below 0 ° C.) and suitable as starting material 2 is 35% by weight or less based on the solution.

The above finding, which first recognized the novel process, is due to the fact that a compound of the element having a high water solubility is apparently formed upon dissolution at elevated temperature. This concept is supported by the fact that residues obtainable by drying (eg spray drying) from such aqueous solutions have correspondingly high solubility in water (even at corresponding low temperatures).

The inventors also surprisingly find that the composite metal oxide materials of the formula (I) prepared according to the invention (if prepared by incorporating finely divided starting material 1 at low temperature), in particular by using an aqueous solution prepared as starting material 2, in particular acrolein to acrylic acid It has been found that when partial gas phase oxidation has a high acrylic acid selectivity.

Therefore, according to the present invention, it is advantageous to carry out the process as follows. Aqueous solutions suitable as starting material 2 are produced at T _L ≧ 60 ° C. (eg, at 65 ° C. or below, or at 75 ° C. or below, or at 85 ° C. or below, or at 95 ° C. or below ≦ 100 ° C.). Subsequently, the finely divided solid starting material 1 is mixed into this aqueous solution after cooling to a temperature T _E <T _L. Often, T _L is> 70 ° C and T _E is <70 ° C. However, it may be T _L ≧ 60 ° C. if slightly lower dissolution rates and lower solids are allowed.

The incorporation of the solid starting material 1 prepared in advance into the aqueous starting material 2 is typically carried out by adding starting material 1 to the cooled aqueous starting material 2 as described above, followed by a period of several hours to several days, preferably several hours. Over, for example by mechanical mixing using agitation or dispersion aids. As mentioned above, according to the invention it is particularly advantageous if the solid starting material 1 is incorporated in the aqueous starting material 2 at ≦ 70 ° C., preferably ≦ 60 ° C., particularly preferably ≦ 40 ° C. In general, the incorporation temperature is ≧ 0 ° C.

Furthermore, according to the invention it is particularly advantageous if the solid starting material 1 is incorporated into the aqueous starting material 2 having a pH of 4 to 7, preferably 5 to 6.5, at 25 ° C. The latter case can be achieved, for example, by adding one or more pH buffer systems to aqueous starting material 2. Suitable for this are, for example, the addition of ammonia and acetic acid and / or formic acid or the addition of ammonium acetate and / or ammonium formate. In connection with the above-mentioned intended use, it is of course also possible to use ammonium carbonate simultaneously.

The aqueous mixture obtained upon incorporation of starting material 1 into aqueous starting material 2 is typically dried by spray-drying. Advantageously, an outlet temperature of 100 to 150 ° C. is set. Spray drying can be carried out by cocurrent or countercurrent methods.

In the case where the precursor material obtained in the above spray drying is used to prepare a catalyst for gas phase catalytic oxidation of acrolein to acrylic acid, shaping to the desired catalyst geometry is preferably carried out by application to a preformed inert catalyst carrier. This application here may take place either before or after the final calcination. As a rule, the corresponding precursor material is calcined prior to coating with the carrier. As a rule, the coating of the carrier for the production of the coated catalyst is carried out in a suitable rotary container as described, for example, in DE-A 2909671 or EP-A 293859. In order to coat the carrier, the powder material to be applied is advantageously wetted and then dried again using, for example, hot air. The coating thickness of the powder material applied to the carrier is advantageously 50 to 500 mu m, preferably 150 to 250 mu m.

The carrier material used may be conventional porous or nonporous alumina, such as magnesium silicate or aluminum silicate, silica, thorium dioxide, ceriumium dioxide, silicon carbide or silicate. The carrier may have a regular or irregular shape, with a carrier having a regular shape and well-developed surface roughness, for example a spherical or hollow cylinder. Among them, spherical shapes are particularly advantageous. It is particularly advantageous to use spherical steatite carriers having a rough surface and having a diameter of 1 to 8 mm, preferably 4 to 5 mm and are substantially nonporous.

Precursor materials obtained in the spray drying step during the course of the new process can also be used to prepare unsupported catalysts. In this regard, the precursor material is compressed before or after calcination (for example by pelleting or extrusion) to provide the desired catalytic geometry and, where necessary, conventional auxiliaries such as lubricants and / or As the release agent, reinforcing agents such as graphite or stearic acid and fine fibers of glass, asbestos, silicon carbide or potassium titanate can be added. Preferred unsupported catalyst geometries are hollow cylinders with an outer diameter and a length of 2 to 10 mm and a wall thickness of 1 to 3 mm.

The step of calcining the precursor material prepared according to the invention in the spray drying step described above to produce the substantially catalytically active composite metal oxide material is carried out before or after the forming step, from 250 to 600 ° C., preferably 300 To 450 ° C. Calcining can be carried out by inert gas (eg N ₂ ), mixture of inert gas and oxygen (eg air), hydrocarbon (eg methane), as described, for example, in DE-A 4335973, It may be carried out under a reducing gas such as aldehyde (eg acrolein) or ammonia, or a mixture of O ₂ and a reducing gas (eg all of the foregoing). However, when calcining under reducing conditions, it must be ensured that the metallic components are not reduced to elements. Therefore, calcination is advantageously carried out in an oxidizing atmosphere. The duration of calcination is usually several hours and generally decreases with increasing calcination temperature.

The composite metal oxide materials of the formula (I) obtainable according to the invention are particularly suitable as catalysts with high selectivity (with a certain conversion) for the gas phase catalytic oxidation of acrolein to acrylic acid. Typically, the process uses acrolein produced by gas phase catalytic oxidation of propene. In general, the acrolein-containing reactor of this propene oxidation reaction is used without intermediate purification steps. Typically, gas phase catalytic oxidation of acrolein is carried out by heterogeneous fixed bed oxidation in a tube-bundle reactor. Advantageously, oxygen (for example in the form of air) diluted with an inert gas is used as oxidant in a manner known per se. Suitable diluent gases are, for example, N ₂ , CO ₂ , hydrocarbons, recycle reaction offgases and / or steam. Generally, the acrolein: oxygen: steam: inert gas volume ratio is 1: (1 to 3): (0 to 20): (3 to 30), preferably 1: (1 to 3): (0.5 in the acrolein oxidation reaction. To 10): (7 to 18). The reaction pressure is generally 1 to 3 bar so that the total space velocity is preferably 1000 to 3500 l (stp) / (l · h). Typical multi-tubular fixed bed reactors are described, for example, in DE-A 28 30 765, DE-A 22 01 528 or US-A 3 147 084. The reaction temperature is generally selected so that the acrolein conversion in one pass is at least 90%, preferably at least 98%. Typically, this requires a reaction temperature of 230 to 330 ° C.

However, in addition to the gas phase catalytic oxidation of acrolein to acrylic acid, the novel products also contain other organic compounds, particularly preferably other alkanes, alkanols, alkanal, alkenes and alkenols having 3 to 6 carbon atoms (e.g. propylene , Methacrolein, t-butanol, methylether of t-butanol, asobutene, isobutane or isobutyraldehyde) to olefinically unsaturated aldehydes and / or carboxylic acids, and the corresponding nitrile (especially propene to acryl It may also act as a catalyst in the process of catalytic oxidation in the gas phase with nitrile or isobutene or t-butanol with methacrylonitrile). For example, mention may be made of the production of acrolein, methacrolein and methacrylic acid. However, they are also suitable for oxidative dehydrogenation of olefinic compounds.

In this specification, conversion, selectivity and residence time are defined as follows unless otherwise stated:

Comparative Example 1

732.7 g of ammoniumheptamolybdate tetrahydrate (MoO ₃ 82.5 wt%) and 146.5 g of ammonium metavanadate (V ₂ O ₅ 75.2 wt%) were dissolved in 5430 g of water for several minutes with stirring at 50 ° C. Then 126.3 g of ammonium paratungstate heptahydrate (W0 ₃ 89.0 wt.%) Were added and the suspension was stirred at 50 ° C. for an additional 3 days. Full dissolution could not be achieved after 3 days.

Example 1

732.7 g ammonium heptamolybdate tetrahydrate (MoO ₃ 82.5 wt%), 146.5 g ammonium metavanadate (V ₂ O ₅ 75.2 wt%) and 126.3 g ammonium paratungstate heptahydrate (WO ₃ 89.0 wt%) It was continuously dissolved in 5430 g of water with stirring at &lt; 0 &gt; C. After only 1 hour complete dissolution occurred. The clear orange solution obtained was stirred at 95 ° C. for a further 24 hours and remained unchanged. The clear orange solution obtained was then cooled to 25 ° C. The orange solution was kept without precipitate at 25 ° C. for 24 hours and was clear.

Example 2

126.3 g of ammonium paratungstate heptahydrate (WO ₃ 89.0 wt%), 146.5 g of ammonium metavanadate (V ₂ O ₅ 75.2 wt%) and 732.7 g of ammonium heptamolybdate tetrahydrate (MoO ₃ 82.5 wt%) 95 It was continuously dissolved in 5430 g of water with stirring at &lt; 0 &gt; C. Only 0.5 hours later complete dissolution was achieved.

Then, the temperature of the solution was lowered to 40 ° C. The solution was clear and kept free of precipitate.

Example 3

Starting material 1

219.8 g of ammoniumheptamolybdate tetrahydrate (MoO ₃ 82.5 wt%) and 328.25 g of ammonium paratungstate heptahydrate (89.0 wt% WO ₃ ) were dissolved in 5 L of water with stirring at 95 ° C. (solution A). 3 L of water and 445.0 g of an aqueous ammonia solution at a concentration of 25% by weight were added to 482.34 g of copper acetate hydrate (41.6% by weight of CuO), and stirred at 25 ° C. for 15 minutes to give a dark blue solution (solution B). Then solution B was added with stirring in solution A at 95 ° C., at which time the temperature of solution A did not drop below 80 ° C. The resulting suspension C was stirred for further 1 h at 80 ° C., and the pH (glass electrode) was 8.5. Suspension C was spray dried at an inlet temperature of 310 ° C. and an outlet temperature of 110 ° C. The resulting pale green spray powder was kneaded with water (200 g of water per kg of spray powder) and molded in an extruder under 50 bar to give a 6 mm thick extrudate (about 1 cm length). These extrudates were dried in air at 110 ° C. for 16 hours. Subsequently, calcination of the extrudate was carried out in air. The material to be calcined was introduced into a furnace at 300 ° C. and held at this temperature for 30 minutes, then heated to 750 ° C. over 1 hour and held at this temperature of 750 ° C. for 1 hour. The product obtained was reddish brown and had a specific surface area and composition Cu ₁₂ Mo ₆ W ₆ O ₄₈ according to DIN 66 131 of 0.8 m 2 / g after grinding in a centrifugal mill (manufactured by Retsch, Germany). Generation of composition Cu ₁₂ Mo ₆ W ₆ O ₄₈ using CuKα radiation (Siemens D-5000 diffractometer, 40 kV, 30 mA, equipped with automatic scattering and counting aperture and Peltier detectors) The crystalline powder thus obtained exhibited a powder X-ray diffraction pattern in which the iron manganese solid structure was superimposed on the HT copper molybdate fingerprint, ie, it had a two-phase structure. According to the line strength, the two structural forms existed at a ratio of about 90 (iron manganese barbed structure): 10 (HT copper molybdate structure).

Starting material 2

732.7 g ammonium heptamolybdate tetrahydrate (MoO ₃ 82.5 wt%), 146.5 g ammonium metavanadate (V ₂ O ₅ 75.2 wt%) and 126.3 g ammonium paratungstate heptahydrate (WO ₃ 89.0 wt%) It was continuously dissolved in 5430 g of water at &lt; RTI ID = 0.0 &gt; The aqueous solution (starting material 2) was thus based on the following elemental stoichiometry: Mo ₁₂ V _3.46 W _1.39 .

Active substance:

The clear orange solution (Active 2) obtained was then cooled to 25 ° C. 172.7 g of starting material 1 was added to starting material 2 cooled to 25 ° C. with stirring to bring the molar ratio of the stoichiometric units described above to 1 (starting material 1) to 6.5 (starting material 2). Thereafter, 150.0 g of ammonium acetate was added to the aqueous suspension with further stirring, the resulting suspension was further stirred at 25 ° C. for 1 hour, and then the aqueous mixture was spray dried. The spray powder was kneaded with a mixture of 70% by weight of water and 30% by weight of acetic acid (per kg of spray powder, 0.35 kg of liquid). The resulting kneaded material was dried at 110 ° C. in air for 16 hours. The ground kneaded material was calcined in a rotary tube fed with an oxygen / nitrogen mixture. 700 g of material to be calcined were introduced into a cylindrical calcination chamber (length: 51 cm, internal diameter: 12.5 cm) of the rotary tube. During the entire calcination process, a mixture containing 10 l (stp) / h of air and 200 l / (stp) of nitrogen and preheated to the calcination temperature was passed through the calcination chamber of the rotary tube. During calcination, the kneading material was first heated to 210 ° C. for 20 minutes, then to 400 ° C. for 5 hours, and then held at this temperature for 3 hours. The resulting catalytically active substance had the following total stoichiometry: [Mo ₁₂ V _3,46 W _1.39 O _x ] _6.5 [Cu ₁₂ Mo ₆ W ₆ O ₄₈ ].

As described above, the X-ray diffraction pattern of the obtained active material included the superposition of the iron manganese barbed structure form and the HT copper molybdate structure form. After milling the calcined active material, it was used in an amount of 50 g of active powder per 200 g of steatite sphere, adding 18 g of water at the same time with a non-porous stear having a rough surface and a diameter of 4 to 5 mm in a rotary drum. Tight spheres were coated. The coated catalyst obtained was then air dried at 110 ° C.

Example 4

Starting material 1:

As starting material 1, starting material 1 from Example 3 was used.

Starting material 2:

732.7 g ammonium heptamolybdate tetrahydrate (MoO ₃ 82.5 wt%), 146.5 g ammonium metavanadate (V ₂ O ₅ 75.2 wt%) and 126.3 g ammonium paratungstate heptahydrate (WO ₃ 89.0 wt%) It was continuously dissolved in 5430 g of water at &lt; RTI ID = 0.0 &gt; The aqueous solution (starting material 2) was thus based on the following elemental stoichiometry: Mo ₁₂ V _3.46 W _1.39 .

Active substance:

The resulting clear orange solution (starting material 2) was then cooled to 25 ° C., to which 116.9 g of acetic acid and 132.3 g of ammonia solution (25% by weight ammonia in water) were successively added. 172.7 g of starting material 1 was added to the buffered starting material 2 cooled to 25 ° C. with stirring to bring the molar ratio of the stoichiometric units described above to 1 (starting material 1) to 6.5 (starting material 2). The resulting suspension was stirred for further 1 h at 25 ° C. The aqueous mixture obtained was then spray dried and further treated as in Example 3.

Comparative Example 2

The procedure was the same as in Example 3. However, unlike Example 3, starting material 1 was added to aqueous starting material 2 with stirring at 95 ° C., and the resulting suspension was further stirred at 95 ° C. for 1 hour after the addition of ammonium acetate.

Example 5

The composite metal oxide catalysts prepared in Examples 3 and 4 and Example 2 were introduced into a tubular reactor (V2A stainless steel, 25 mm inner diameter, 2000 g catalyst bed, salt bath heating) and 5% by volume of acrolein, 7% by volume of oxygen, steam 10 A gaseous mixture having a composition of volume% and 78 volume% nitrogen was fed at a reaction temperature of 250 to 270 ° C., and the residence time was 2.0 seconds. In all cases, the salt bath temperature was set to give a uniform acrolein conversion C of 99% by one pass after the end of molding. The product gas mixture exiting the reactor was analyzed by gas chromatography. The results for selectivity of acrylic acid formation with various catalysts were as follows:

Catalyst S%

Example 3 96.3

Example 4 96.4

Comparative Example 2 96.0

Claims (10)

A finely divided composite metal oxide material B (X ⁷ ₁₂ Cu _h H _i O _y , starting material 1) was first formed separately, and this preformed solid starting material 1 was formed at Mo ₁₂ V _a X ¹ _b X at ≤70 ° C. An aqueous solution of a source of elements Mo, V, X ¹ , X ² , X ³ , X ⁴ , X ⁵ and X ⁶ contained in stoichiometric formula (A) of ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g ( Incorporation into starting material 2) in the desired molar ratio p: q, drying the resulting aqueous mixture and calcining the resulting precursor material at 250 to 600 ° C. before or after shaping to provide the desired catalytic geometry Process for the preparation of the composite metal oxide material of formula (I). <Formula I> [A] _p [B] _q Where A is Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _x ; B is X ⁷ ₁₂ Cu _h H _i O _y ; X ¹ is W, Nb, Ta, Cr or Ce; X ² is Cu, Ni, Co, Fe, Mn or Zn; X ³ is Sb and / or Bi; X ⁴ is Li, Na, K, Rb, Cs or H; X ⁵ is Mg, Ca, Sr or Ba; X ⁶ is Si, Al, Ti or Zr; X ⁷ is Mo, W, V, Nb or Ta; a is 1 to 8; b is 0.2 to 5; c is 0 to 23; d is 0 to 50; e is 0 to 2; f is 0 to 5; g is 0 to 50; h is 4 to 30; i is 0 to 20; x and y are numbers determined according to the valence and the frequency of elements other than oxygen in formula (I); p and q are numbers other than 0, and their ratio p / q is 160: 1 to 1: 1. The process of claim 1, wherein the preformed solid starting material 1 is incorporated into the aqueous starting material 2 at ≦ 60 ° C. 3. The process of claim 1, wherein the preformed solid starting material 1 is incorporated into the aqueous starting material 2 at ≦ 40 ° C. 3. A composite metal oxide material obtainable by the method according to claim 1. Obtained by dissolving the sources of the elements Mo, V, X ¹ , X ² , X ³ , X ⁴ , X ⁵ and X ⁶ in water of T _L ≧ ⁶⁰ ° C. and then cooling the aqueous solution to a temperature T _E <T _L In the solution, the stoichiometric Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g (where the variables have the meanings defined in claim 1). An aqueous solution containing X ¹ , X ² , X ³ , X ⁴ , X ⁵ and X ⁶ . The aqueous solution of claim 5 wherein T _L is> 70 ° C. and T _E is ≦ 70 ° C. 7. The aqueous solution of claim 5 wherein T _L is> 80 ° C. and T _E is ≦ 80 ° C. 7. The aqueous solution according to any one of claims 5 to 7, wherein the Mo content is 10 to 35% by weight based on the aqueous solution. A solid obtainable by drying the aqueous solution as claimed in claim 5. A process for producing acrylic acid via gas phase catalytic oxidation of acrolein, using the composite metal oxide material as claimed in claim 4 as a catalyst.