EP1073518A1 - Multi-metal oxide compounds - Google Patents

Abstract

The invention relates to multi-metal oxide compounds with a multi-component structure, containing molybdenum, vanadium, copper and antimony, as well as one or more certain other metals. The invention also relates to the use of said compounds for producing acrylic acid from acrolein by gas phase catalytic oxidation.

Description

Multimetal oxide materials

description

The invention relates to multimetal oxide compositions of the general formula I.

[A] _p [B] _q [C] _r (I),

in which the variables have the following meaning:

A = Mθι ₂ V _a X ¹ X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁵ gO _x ,

B = X ⁷ ιCu _h HiO _y , C = X ⁸ ιSbjH _k O _z ,

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

X ² = Cu, Ni, Co, Fe, Mn and / or Zn, preferably Cu, Ni, Co and / or Fe, X ³ = Sb and / or Bi, preferably Sb,

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

X ⁵ = Mg, Ca, Sr and / or Ba, preferably Ca, Sr and / or Ba,

X ⁶ = Si, Al, Ti and / or Zr, preferably Si, Al and / or Ti,

X ⁷ = Mo,, V, Nb and / or Ta, preferably Mo and / or W, X ⁸ = Cu, Ni, Zn, Co, Fe, Cd, Mn, Mg, Ca, Sr and / or Ba, preferably Cu and / or Zn, particularly preferably Cu, a = 1 to 8, preferably 2 to 6, b = 0.2 to 5, preferably 0.5 to 2.5, c = 0 to 23, preferably 0 to 4, d = 0 to 50, preferably 0 to 3, e = 0 to 2, preferably 0 to 0.3, f = 0 to 5, preferably 0 to 2, g = 0 to 50, preferably 0 to 20, h = 0.3 to 2.5, preferably 0.5 to 2, particularly preferably 0.75 to 1.5, i = 0 to 2, preferably 0 to 1, j = 0.1 to 50, preferably 0.2 to 20, particularly preferably 0 , 2 to 5, k = 0 to 50, preferably 0 to 20, particularly preferably 0 to 12,

x, y, z = numbers which are determined by the valency and frequency of the elements other than oxygen in (I) and 2 p, q, r = numbers other than zero, with the proviso that the

Ratio p / (q + r) = 20: 1 to 1:20, preferably 5: 1 to 1:14 and particularly preferably 2: 1 to 1: 8 and the ratio q / r = 20: 1 to 1:20, is preferably 2: 1 to 1: 2 and particularly preferably 1: 1,

which the portion [A] _p in the form of three-dimensionally extended areas A of the chemical composition

A Mθι ₂ V _a χ ⁱ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ gO _x ,

the proportion [B] _q in the form of three-dimensionally extended areas B of the chemical composition

BX ⁷ ιCu _h HiO _y and

the proportion [C] _r in the form of three-dimensionally extended areas C of the chemical composition

CX ⁸ ιSbjHO _z

included, areas A, B, C being distributed relative to one another as in a mixture of finely divided A, finely divided B and finely divided C.

Furthermore, the present invention relates to the use of multimetal oxide compositions (I) for catalytic gas phase oxidations of low molecular weight organic compounds, in particular from acrolein to acrylic acid, and to processes for the preparation of multimetal oxide compositions (I).

DE-A 44 05 514, DE-A 44 40 891, DE-A 19 528 646 and DE-A 19 740 493 relate to multimetal oxide compositions which have a two-component structure [A '] _p . [B '] _g . have, where the gross element compositions of component A 'and component B' match the gross element compositions of component A and component B of the multimetal oxide compositions (I) of the present invention.

A disadvantage of the aforementioned multimetal oxide compositions of the prior art, however, is that when they are used as catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid, the selectivity of acrylic acid formation cannot be fully satisfied for a given conversion. 3

WO 96/27437 relates to multimetal oxide compositions which contain the elements Mo, V, Cu and Sb as essential components and whose X-ray diffraction pattern has the highest intensity line at a 2θ value of 22.2 + 0.3 °. WO 96/27437 recommends these multimetal oxide compositions as suitable catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid. Furthermore, WO 96/27437 recommends using Sb0 ₃ as an antimony source for the production of these multimetal oxide materials. WO 96/27437 does not teach a preliminary preparation of an Sb-containing component.

EP-B 235 760 relates to a process for the preparation of Sb, Mo, V and / or Nb-containing multimetal oxide compositions which are suitable as catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid. EP-B 235 760 recommends using a previously prepared antimonate as the antimony source for the production of these multimetal oxide materials. EP-B 235 760 does not teach the preliminary production of a Cu-containing component.

A disadvantage of the multimetal oxide compositions of WO 96/27437 and EP-B 235 760 is that when they are used as catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid, their activity and the selectivity of acrylic acid formation are likewise not fully satisfactory.

The object of the present invention was therefore to provide new multimetal oxide compositions which, when used as catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid, at most still have the disadvantages of the catalysts of the prior art to a reduced extent.

Accordingly, the multimetal oxide materials (I) defined at the outset were found.

Preferred multimetal oxide compositions I are those whose regions A have a composition of the general formula II below

Mo ₁₂ V _a .X ¹ .X ² _c .X ⁵ _f .X ⁶ _g .O _x - (II),

With

X ¹ = W and / or Nb, X ² = Cu and / or Ni,

X ⁵ = Ca and / or Sr,

X ⁶ = Si and / or AI, 4 a '= 2 to 6, b' = 1 to 2, c '= 1 to 3, f = 0 to 0.75, g' = 0 to 10 and x '= a number determined by the value and frequency of the elements other than oxygen is determined in II.

It is also advantageous if the proportions [B] _q , [C] _{r of} the multimetal oxide compositions (I) according to the invention are contained in the latter in the form of three-dimensionally extended areas of the chemical composition B, C, the largest diameter d (longest by the Center of gravity of the area connecting line of two points on the surface (interface) of the area)> 0 to 300 μm, preferably 0.01 to 100 μm and particularly preferably 0.05 to 20 μm. Of course, the size diameters can also be 0.01 to 150 μm or 75 to 125 μm (the experimental determination of the size diameters allows, for example, a microstructure analysis using a scanning electron microscope (SEM)).

The fraction [A] _p can be amorphous and / or crystalline in the multimetal oxide compositions (I) according to the invention.

In principle, the proportions B, C in the multimetal oxide compositions (I) according to the invention can also be amorphous and / or crystalline.

It is favorable according to the invention if the promoter phase B consists of crystallites of oxometalates B or contains those oxometalate crystallites B which have the X-ray diffraction pattern and thus the crystal structure type of at least one of the following copper molybdate (the expression in brackets gives the source for the associated X-ray diffraction fingerprint again) or if the promoter phase B consists of crystallites of these copper molybdates or contains such copper molybdate crystallites:

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

Cu ₄ Mo ₅ 0ι ₇ [index card 39-181 of the ICPDS-ICDD index (1991)],

α-CuMo0 ₄ [index card 22-242 of the JCPDS-ICDD index (1991)],

Cu ₆ Mo ₅ 0i ₈ [index card 40-865 of the JCPDS-ICDD index (1991)], Cu ₄ _ _x Mo ₃ 0ι ₂ with x = 0 to 0.25 [index cards 24-56 and 26-547 of the JCPDS-ICDD index (1991)],

Cu ₆ Mo0i ₅ [index card 35-17 of the JCPDS-ICDD index (1991)],

Cu ₃ (Mo0 ₄ ) ₂ (OH) ₂ [index card 36-405 of the JCPDS-ICDD index (1991)],

Cu ₃ Mo ₂ 0 ₉ [index cards 24-55 and 34-637 of the JCPDS-ICDD index (1991)],

Cu ₂ Mo0 ₅ [index card 22-607 of the JCPDS-ICDD index (1991)].

According to the invention, portions B which contain or consist of oxometalates B, which have the X-ray diffraction pattern and thus the crystal structure type of the subsequent copper molybdate, or which themselves contain or consist of copper molybdate are advantageous:

CUM0O ₄ -III with a tungsten structure according to Russian Journal of Inorganic Chemistry 36 (7) (1991) 927 - 928, Table 1.

Among these are those with the following stoichiometry III

CuMo _A W _B V _c Nb _D Ta _E Oγ • (H ₂ 0) _F : ni)

With

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

0 to 1,

B + C + D + E: 0 to 1, preferably 0 to 0.7, and

a number determined by the valency and frequency of the elements other than oxygen,

prefers .

Among these, those of stoichiometries IV, V or VI are particularly preferred: 6

CuMo _A W _B V _c O _y (IV),

With

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

B + C: 0 to 1, preferably 0 to 0.7, and

Y is a number determined by the valency and frequency of the elements other than oxygen;

CuMo _A W _B O _y (V), with

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

A, B: 0 to 1 and

Y is a number determined by the valency and frequency of the elements other than oxygen;

CuMo _A V _c O _y (VI),

With

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

A, C: 0 to 1 and

Y: a number determined by the valency and frequency of the elements other than oxygen.

The production of such oxometalates B is disclosed, for example, in EP-A 668 104.

Suitable promoter phases B are also those which contain oxometalates B of the following stoichiometry VII CuMo _A W _B V _c Nb _D Ta _E Oy (VII),

With

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

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

a number determined by the valency and frequency of the elements other than oxygen,

contain or consist of a structure type, which is referred to as HT copper molybdate structure and subsequently defined by its X-ray diffraction pattern (fingerprint), reproduced by its most characteristic and most intense diffraction lines in the form of network plane spacings d [Ä] which are independent of the wavelength of the X-ray radiation used becomes:

6.79 + 0.3

3.56 + 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

1.70 + 0.2

1.64 + 0.2

1.59 + 0.2

1.57 + 0.2

1.55 + 0.2

1.51 + 0.2 1.44 + 0.2 8th

In the event that the promoter phase B contains a mixture of different oxometalates B or consists of such, a mixture of oxometalates with a tungsten and HT copper molybdate structure is preferred. The weight ratio of crystallites with HT copper molybdate structure to crystallites with tungsten structure can be 0.01 to 100, 0.1 to 10, 0.25 to 4 and 0.5 to 2.

The production of oxometalates VII or compositions containing them discloses e.g. DE-A 19 528 646.

In particular, those multimetal oxide compositions according to the invention are preferred whose regions C essentially consist of crystallites which have the trirutile structure type of the α- and / or β-copper antimony CuSb ₂ θ ₆ . α-CuSb0 ₆ crystallizes in a tetrahedral trirutile structure (E. -O. Giere et al., J. Solid State Chem. 131 (1997) 263-274), while β-CuSb ₂ 0 _{6 is} a monoclinically distorted trirutile Structure (A. Nakua et al., J. Solid State Chem. 91 (1991) 105-112 or comparative diffractogram in index card 17-284 in the 1989 JCPDS-ICDD index). Moreover, areas C are preferred, the structure of the mineral Pyrochlore- Partzite, a copper-antimony oxide hydroxide with a variable composition Cu _y Sb _-x (0, OH, H0) ₆ - ₇ (y <2.0 < x <1) (B. Mason et al., Mineral. Mag. 30 (1953) 100-112 or comparison diagram in index card 7-303 of the JCPDS-ICDD index 1996).

Furthermore, the areas C may consist of crystallites. Acta the structure of the copper antimonate CugSb ₄ 0i ₉ (S. Shimada et al., Chem. Lett., 1983, 1875-1876 or S. Shimada et al., Thermochim 133 (1988 ) 73-77 or comparison diagram in index card 45-54 of the JCPDS-ICDD register) and / or the structure of Cu ₄ Sbθ _4.5 (S. Shimada et al., Thermochim. Acta 56 (1982) 73-82 or S Shimada et al., Thermochim. Acta 133 (1988) 73-77 or comparison diagram in index card 36-1106 of the JCPDS-ICDD index).

Of course, the areas C can also consist of crystallites, which represent a mixture of the aforementioned structures.

The multimetal oxide compositions (I) according to the invention are easily e.g. obtainable by having a multimetal oxide mass

X ⁷ ιCu _h HiO _y (B)

as starting mass 1 and a multimetal oxide mass 9 χ ⁸ iSbjH _k 0 _z (C)

as the starting mass 2 either separated from one another or associated with one another in a finely divided form and then the starting masses 1, 2 with suitable sources of the elementary constituents of the multimetal oxide mass A

Mθι ₂ V _a χi _b X ² _c χ3 _d χ _e χ5 _f χ6 _g0χ (A)

brings into intimate contact in the desired proportions and a resulting dry mixture is calcined at a temperature of 250 to 500 ° C, the calcination under inert gas (eg N ₂ ), a mixture of inert gas and oxygen (eg air), reducing gases such as hydrocarbons (For example methane), aldehydes (for example acrolein) or ammonia, but also under a mixture of 0 and reducing gases (for example all of the above) can be carried out, as described for example in DE-A 43 35 973. When calcining under reducing conditions it should be noted that the metallic constituents are not reduced to the element.

The calcination time usually extends over a period of a few minutes to a few hours and usually decreases with increasing calcination temperature. What is essential for the sources of the elementary constituents of the multimetal oxide composition A, as is generally known, is only that they are either already oxides or those compounds which can be converted into oxides by heating, at least in the presence of oxygen. In addition to the oxides, halides, nitrates, formates, oxalates, citrates, acetates, carbonates or hydroxides are particularly suitable as starting compounds.

Suitable starting compounds for Mo, V, W and Nb are also their oxo compounds (molybdates, vanadates, tungstates and niobates) and the acids derived from them. This applies in particular to the corresponding ammonium compounds (ammonium molybdate, ammonium vanadate, ammonium tungstate).

According to the invention, the finely divided starting materials 1, 2 advantageously consist of particles whose size diameter d (longest connecting section through the center of gravity of the particles of two points located on the surface of the particles)> 0 to 300 μm, preferably 0.01 to 100 μm and particularly preferably Is 0.05 to 20 μm. Of course, the particle diameter d can also be 0.01 to 150 μm or 75 to 125 μm. 10

It is possible that the starting aces 1, 2 to be used according to the invention have a specific surface area 0 (determined according to DIN 66131 by gas adsorption (N) according to Brunauer-Emmet-Teller (BET)), which is often <80 m ² / g <50 m ² / g or <10 m ² / g and sometimes <1 m ² / g. As a rule, 0> 0.1 m ² / g.

In principle, the starting materials 1, 2 can be used according to the invention both amorphously and / or in crystalline form.

It is favorable if the starting materials 1, 2 consist of crystallites of oxometalates B (e.g. those of the general formulas III to VII) and crystallates of oxometalates C, as described above. As already mentioned, such oxometalates B are e.g. Available according to the procedures of EP-A 668 104 and DE-A 19 528 646. However, the manufacturing processes of DE-A 44 05 514 and DE-A 44 40 891 can also be used.

In principle, multimetal oxide masses B containing oxometalates B or consisting of oxometalates B can be produced in a simple manner by generating an intimate, preferably finely divided, dry mixture of stoichiometry which is composed of suitable elementary constituents and at temperatures of 200 to 1000 ° C, preferably 250 to 900 ° C or 700 to 850 ° C for several hours under inert gas or preferably calcined in air, the calcination time can be from a few minutes to a few hours. The calcination atmosphere can additionally contain water vapor. Suitable sources for the elemental constituents of the multimetal oxide mass B are those compounds which are already oxides and / or those compounds which can be converted into oxides by heating, at least in the presence of oxygen. In addition to the oxides, such starting compounds are, above all, halides, nitrates, formates, oxalates, citrates, acetates, carbonates, amine complex salts, ammonium salts and / or hydroxides (compounds such as NH ₄ OH, (NH ₄ ) ₂ CO ₃ , NH ₄ NO ₃ , NH ₄ CHO ₂ , CH ₃ COOH, NH ₄ CH ₃ C0 or ammonium oxalate, which can decompose and / or decompose later at the later calcination to form gaseous compounds, can also be incorporated).

The intimate mixing of the starting compounds for the production of multimetal oxide compositions B can be carried out in dry form or in wet form. If it is carried out in dry form, the starting compounds are expediently used as finely divided powders and after mixing and, if appropriate, compacting the 11

Subjected to calcination. However, the intimate mixing is preferably carried out in wet form. The _A are in this case normally usgangsverbindungen in the form of an aqueous solution and / or suspension mixed. In the dry process described, particularly intimate dry mixtures are obtained if only sources of the elementary constituents present in dissolved form are used. Water is preferably used as the solvent. The aqueous composition obtained is then dried, the drying process preferably being carried out by spray drying the aqueous mixture at exit temperatures of 100 to 150 ° C. The dried mass is then calcined as described above.

A preferred way of producing oxometalates B (X ⁷ ιCu _h HiO _y with X = Mo u./o. W) is to use an aqueous solution of ammonium heptamolybolate and ammonium paratungstate with an aqueous ammoniacal solution of copper carbonate (for example the composition Cu (OH) ₂ CO ₃ ) to dry the resulting mixture, e.g. B. spray drying, and calcining the resulting dry mixture, optionally after a subsequent kneading and extrusion and drying, as described.

In another production variant of multimetal oxide compositions B, the mixture of the starting compounds used is thermally treated in an overpressure vessel (autoclave) in the presence of superatmospheric water vapor at temperatures in the range from> 100 to 600 ° C. The pressure range typically extends up to 500 atm, preferably up to 250 atm. This hydrothermal treatment is particularly advantageously carried out in the temperature range from> 100 to 374.15 ° C. (critical temperature of the water), in which water vapor and liquid water coexist under the resulting pressures.

The multimetal oxide compositions B obtainable as described here, which can contain oxometalates B of a single structure type or a mixture of oxometalates B of different structure types, or consist exclusively of oxometalates B of a single structure type or of a mixture of oxometalates of different structure types, can now, if appropriate, be used Grinding and / or classification to desired sizes can be used as the starting material 1 required according to the invention.

In principle, the multimetal oxide compositions C can be produced in the same way as the multimetal oxide compositions B. In the case of the multimetal oxide composition C, the intimate dry mixture is advantageously calculated at temperatures from 250 to 1200 ° C., preferably from 250 to 850 ° C. The calcination can be done under 12

Inert gas, but also under a mixture of inert gas and oxygen, e.g. Air or under pure oxygen. Calcination under a reducing atmosphere is also possible. As a rule, the required calcination time also decreases with increasing calcination temperature.

According to the invention, preference is given to using multimetal oxide compositions C which are obtainable by preparing a dry mixture from sources of the elementary constituents of the multimetal oxide composition C which contain at least part, preferably the total amount, of the antimone in the oxidation state +5, and this at temperatures of 200 calcined to 1200 ° C, preferably from 200 to 850 ° C and particularly preferably from 300 to 850 ° C. Such multimetal oxide compositions C can be obtained, for example, by the production methods described in detail in DE-A 24 07 677. Among these, the procedure is preferred in which antimony trioxide or Sb0 ₄ in aqueous medium by means of hydrogen peroxide in an amount which is below or equal to or exceeds the stoichiometric, at temperatures between 40 and 100 ° C. to form antimony (V. ) oxidized oxide hydroxide, even before this oxidation, during this oxidation and / or after this oxidation, aqueous solutions and / or suspensions of combined starting compounds of the other elemental constituents of the multimetal oxide mass C are added, then the resulting aqueous mixture dries (preferably spray-dried, inlet temperature: 250 to 600 ° C, starting temperature: 80 to 130 ° C) and then calcined the intimate dry mixture as described.

In the process as just described, aqueous hydrogen peroxide solutions with an H ₂ O content of 5 to 33% by weight can be used, for example. Subsequent addition of suitable starting compounds of the other elemental constituents of oxometalate C is particularly recommended if they are capable of catalytically decomposing the hydrogen peroxide. Of course, one could also isolate the antimony (V) oxide hydroxide from the aqueous medium and, for example, mix it intimately with suitable finely divided starting compounds of the other elemental constituents of oxometallate C and, if appropriate, further Sb starting compounds, and then calcine this intimate mixture as described.

It is essential that the element sources of oxometalates C are either already oxides, or those compounds which can be converted into oxides by heating, if appropriate in the presence of oxygen. In addition to the oxides, the main starting compounds are halides, nitrates, 13

Formates, oxalates, acetates, carbonates and / or hydroxides into consideration (compounds such as NH ₄ OH, (NH ₄ ) ₂ CO ₃ , NH ₄ NO ₃ , NH ₄ CHO ₂ , CH ₃ COOH, NHCH ₃ CO ₂ or ammonium oxalate, the can decompose and / or be decomposed at the latest during the later calcination to form gaseous compounds, can also be incorporated).

In general, the intimate mixing of the starting compounds can also be carried out in dry or wet form for the preparation of oxometalates C. If it is in dry form, the starting compounds are expediently used as finely divided powders. However, the intimate mixing is preferably carried out in wet form. Usually, the starting compounds are mixed together in the form of an aqueous solution and / or suspension. After the mixing process is complete, the fluid mass is dried and, after drying, calcined. Here, too, drying is preferably carried out by spray drying. After the calcination, the oxometalates C can be comminuted again (for example by wet or dry milling, for example in a ball mill or by jet milling) and the powder, which generally consists of essentially spherical particles, can be used to give the particle size class with an im for the invention Multimetallic oxide (I) desired large diameter range lying grain size diameter by separating in a conventional manner to be carried out (eg wet or dry sieving). A preferred way of producing oxometallates C of the general formula (Cu, Zn) iSb _h HiO _y consists in first dissolving antimony trioxide and / or Sbθ in an aqueous medium using hydrogen peroxide in a, preferably finely divided, Sb (V) compound, for example Sb (V) oxide hydroxide hydrate, to transfer the resulting aqueous suspension with an oniakalisehen aqueous solution of Zn and / or Cu carbonate (which may have the composition Cu ₂ (OH) ₂ C0 ₃ ), drying the resulting aqueous mixture, for example spray-drying as described, and calcining the powder obtained, if appropriate after subsequent kneading with water and subsequent extrusion and drying, as described. Under favorable circumstances, the oxometalates B and the oxometalates C can be produced in a socialized form. In these cases, a mixture of crystallites of oxometalates B and crystallites of oxometalates C is obtained, which can be used directly as starting material 1 + 2.

The intimate contacting of the constituents of the starting materials 1, 2 with the sources of the multimetal oxide material A (starting material 3) can take place both dry and wet. In the latter case, care must only be taken that the preformed crystallite B and crystallite C do not go into solution. In an aqueous medium 14 dium is usually guaranteed at pH values that do not deviate too much from 7 and at temperatures that are not too high. If the intimate contact is wet, it is then normally dried to a dry mass (preferably by spray drying). Such a dry mass is automatically obtained during dry mixing. Of course, the intimate contacting of the constituents of the starting materials 1, 2 with the sources of the multimetal oxide composition A (starting composition 3) can also be carried out by first bringing the oxometalates B and then the oxometalates C, or vice versa, into contact. Of course, the multimetal oxide compositions B and C can also be brought into intimate contact with the constituents of the starting composition 3 as a premixed starting composition 1 + 2.

Possible mixture variants are e.g. considered:

a) Mix a dry, finely divided, preformed starting mass 1 + 2 with dry, finely divided starting compounds of the elemental constituents of the desired multimetal oxide A in the desired ratio in a mixer, kneader or in a mill;

b) pre-form a finely divided multimetal oxide A by intimately mixing suitable starting compounds of its elemental constituents (dry or wet) and then calcining the resulting intimate dry mixture at temperatures of 250 to 500 ° C .; Shape the pre-formed multimetal oxide A into fine particles and mix with the fine-particle starting materials 1, 2 in the desired ratio as in a); With this mixture variant, a final calcination of the resulting mixture is not essential;

c) in an aqueous solution and / or suspension of starting compounds of the elemental constituents of the desired multimetal oxide A, the required amounts of preformed

Stir in starting materials 1, 2 and then spray dry; Of course, instead of the starting compounds of the elementary constituents of the desired multimetal oxide A, a multimetal oxide A which has already been preformed in accordance with b) can itself be used. Further, in the aqueous mixture in addition to the starting materials 1, 2 and the output - mass 3 compounds such as NH ₄ OH, (H ₄₎ C0 _3, NHHC0 _3, NH ₄ N0 _3, NH ₄ CH0, CH ₃ COOH or NH ₄ CH ₃ C0 ₂ , which disintegrate and / or decompose at the latest during the later calcination to form completely gaseous compounds, can also be incorporated. 15

To produce an aqueous solution required as starting material 3, starting from the above-mentioned sources of the elemental constituents, it is generally necessary to use elevated temperatures. As a rule, temperatures> 60 ° C, usually> 70 ° C, but normally <100 ° C are used. The latter and the following applies in particular if the ammonium heptamolybdate tetrahydrate [AHM = (NH ₄ ) ₆ Mo ₇ 0 ₄ • 4 H0] and / or the vanadium source ammonium metavanadate [AMV = NH ₄ V0 ₃ ] is used as the Mo element source. The situation is particularly difficult when the element W is part of the aqueous starting mass 3 and ammonium paratungstate heptahydrate [APW = (NH ₄ ) ιo ι ₂ 0 ₄ ι • 7 H ₂ 0] in addition to at least one of the two aforementioned element sources as Initial connection of the relevant aqueous solution is used.

It has now surprisingly been found that aqueous solutions prepared as starting material 3 at elevated temperatures during and after the subsequent cooling to below the dissolving temperature, even when the Mo element is> 10% by weight and cooling temperatures of up to 20 ° C. or below ( usually not <0 ° C), based on the aqueous solution, are normally stable. That , no solid precipitates during or after cooling of the aqueous solution. As a rule, the above statement also applies to corresponding Mo contents of up to 20% by weight.

The Mo content of such aqueous solutions, which are cooled to temperatures of up to 20 ° C. or below (usually not below 0 ° C.) and are suitable as starting material 3, based on the solution, is not more than 35% by weight.

The above finding is attributed to the fact that, when dissolved at elevated temperature, compounds of the relevant elements are evidently formed which have an increased solubility in water. This idea is supported by the fact that the residue obtainable by drying from such an aqueous solution (e.g. spray drying) has a correspondingly increased solubility in water (even at the corresponding low temperatures).

It is therefore expedient to proceed as follows. At a temperature T _L > 60 ° C (for example up to 65 ° C, or up to 75 ° C, or up to 85 ° C, or up to 95 ° C or <100 ° C) as a starting mass 3 suitable aqueous solution. After cooling to a temperature T _E <T, the finely divided solid starting materials 1, 2 are then incorporated into this aqueous solution. Often T _{L will be} > 70 ° C and T _E <70 ° C. When buying 16 T somewhat lower dissolving speeds and lower solids contents, T _L <60 ° C is also possible.

The preparation of the prepared solid starting materials 1, 2 5 into the aqueous starting material 3 is usually carried out by adding the starting materials 1, 2 into the, as already mentioned, cooled aqueous starting material 3 and subsequent mechanical mixing, e.g. using stirring or dispersing agents over a period of a few minutes or hours to

10 several days, preferably over a period of several hours. As already stated, it is particularly advantageous according to the invention if the incorporation of the solid starting materials 1, 2 into the aqueous starting material 3 at temperatures <70 ° C., preferably at temperatures <60 ° C. and particularly preferably at temperatures <

15 40 ° C takes place. As a rule, the incorporation temperature will be> 0 ° C.

Furthermore, it is advantageous if the solid starting materials 1, 2 are incorporated into an aqueous starting material 3,

20 whose pH at 25 ° C is 4 to 7, preferably 5 to 6.5. The latter can e.g. can be achieved by adding one or more pH buffer systems to the aqueous starting mass 3. As such, an addition of ammonia and acetic acid and / or formic acid or an addition of ammonium

25 acetate and / or onium formate. Of course, ammonium carbonate can also be used with regard to the aforementioned purpose.

The drying of the aqueous mixture obtained when the starting materials 1, 2 are incorporated into the 30 aqueous starting material 3 is usually carried out by spray drying. Outlet temperatures of 100 to 150 ° C. are expediently set. It can be spray dried both in cocurrent and in countercurrent. 35

Of course, all mixture variants lying between a), b) and / or c) can also be used. The resulting intimate dry mixture can then be calcined as described and then shaped to the desired catalyst geometry or vice versa. In principle, the calcined (or, if using mixture variant b) optionally uncalcined) dry mixture can also be used as a powder catalyst.

Our own investigations have shown that when calcining the dry mixture comprising the 5 starting materials 1, 2 and the starting material 3, the structure type of the crystallites contained in the starting materials 1, 2 is essentially retained, or al 17 if necessary converted into other structure types. However, there is essentially no fusion (dissolving) of the constituents of the starting materials 1, 2 with one another or with those of the starting material 3.

As already indicated above, this opens up the possibility, after grinding the pre-formed starting materials 1, 2, of the grain size with a grain size diameter in the size range desired for the multimetal oxide material (I) (generally> 0 to 300 μm, preferably 0 , 01 to 100 μm and particularly preferably 0.05 to 20 μm) by classifying them in a manner known per se (for example wet or dry sieving) and thus using them to produce the desired multimetal oxide mass in a tailored manner.

When the multimetal oxide compositions (I) according to the invention are used as catalysts for the gas-phase catalytic oxidation of acrolein to acrylic acid, the shaping to the desired catalyst geometry is preferably carried out by application to preformed inert catalyst supports, it being possible to apply the catalyst before or after the final calcination. The usual carrier materials such as 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. The carrier bodies can have a regular or irregular shape, with regularly shaped carrier bodies with a clearly formed surface roughness, e.g. Balls or hollow cylinders are preferred. Again, balls are particularly advantageous among these. Of particular advantage is the use of essentially non-porous, rough-surface, spherical supports made of steatite, the diameter of which is 1 to 8 mm, preferably 4 to 5 mm. The layer thickness of the active composition is expediently chosen to be in the range from 50 to 500 μm, preferably in the range from 150 to 250 μm. At this point it should be pointed out that in the production of such coated catalysts for coating the support bodies, the powder mass to be applied is generally moistened and after application, e.g. by means of hot air.

The coating of the carrier body is used to manufacture the

Shell catalysts are generally carried out in a suitable rotatable container, as is known, for example, from DE-A 29 096 71 or from EP-A 293 859. As a rule, the relevant mass is calcined before the carrier coating. 18th

In a suitable manner, the coating and calcination process according to EP-A 293 859 can be used in a manner known per se such that the resulting multimetal oxide active compositions (I) have a specific surface area of 0.50 to 150 m ² / g, a speci - Fish pore volume of 0.10 to 0, 90 cm ³ / g and such a pore diameter distribution that at least 0.1 to <1 microns, 1.0 to <10 microns and 10 microns to 100 microns in the diameter ranges 10% of the total pore volume is eliminated. The pore diameter distributions mentioned as preferred in EP-A 293 859 can also be set.

Of course, the multimetal oxide compositions (I) according to the invention can also be operated as full catalysts. In this regard, the intimate dry mixture comprising the starting materials 1, 2 and 3 is preferably compacted directly to the desired catalyst geometry (e.g. by means of tableting, extrusion or extrusion), where appropriate conventional aids, e.g. 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, and calcined. In general, calcination can also be carried out here before shaping. Preferred all-catalyst geometry are hollow cylinders with an outside diameter and a length of 2 to 10 mm or 3 to 8 mm and a wall thickness of 1 to 3 mm.

The multimetal oxide compositions (I) according to the invention are particularly suitable as catalysts with increased activity and selectivity (for a given conversion) for the gas-phase catalytic oxidation of acrolein to acrylic acid. Typically, the process uses acrolein that was generated by the catalytic gas phase oxidation of propene. As a rule, the reaction gases of this propene oxidation containing acrolein are used without intermediate purification. The gas-phase catalytic oxidation of acrolein in tube bundle reactors is usually carried out as a heterogeneous fixed bed oxidation. Oxygen, expediently diluted with inert gases (for example in the form of air), is used as the oxidizing agent in a manner known per se. Suitable diluent gases are, for example, N, C0 ₂ , hydrocarbon, recycled reaction gases and / or water vapor. In acrolein oxidation, an acrolein: oxygen: water vapor: inert gas volume ratio of 1: (1 to 3) :( 0 to 20) :( 3 to 30), preferably 1: (1 to 3): (0 , 5 to 10): (7 to 18) set. The reaction pressure is generally 1 to 3 bar and the total space load is preferably 1000 to 3500 Nl / l / h. Typical multi-tube fixed bed reactors are described, for example, in the documents DE-A 28 30 765, DE-A 22 01 528 or US-A 3 147 084. The reaction temperature is usually chosen so that the 19

Acrolein conversion in a single pass is above 90%, preferably above 98%. Normally, reaction temperatures of 230 to 330 ° C are required.

In addition to the gas-phase catalytic oxidation of acrolein to acrylic acid, the process products according to the invention are also capable of gas-phase catalytic oxidation of other organic compounds, such as, in particular, other alkanes, alkanols, alkanals, alkenes and alkanes (eg propylene, methacrolein, tert-butanol, methyl ether of tert-butanol, isobutene, isobutane or isobutyraldehyde) to give olefinically unsaturated aldehydes and / or carboxylic acids, and the corresponding nitriles (ammoxidation, especially from propene to acrylonitrile and from iso- Butene or tert-butanol to catalyze methacrylonitrile). The production of acrolein, methacrolein and methacrylic acid may be mentioned by way of example. However, they are also suitable for the oxidative dehydrogenation of olefinic compounds.

Unless otherwise stated, turnover, selectivity and retention time are defined in this document as follows:

Mole number of converted acrolein

U conversion to acrolein (%) = ^x OK ⁰ » ^*

Mole number of acrolein used

Number of moles of acrolein converted selectivity S to acrylic acid x 100;

Acrylic acid formation (% ⁾ total number of moles of acrolein converted

Empty volume of the reactor filled with catalyst (1)

Dwell time (sec) = x 3600. Synthesis gas flow (Nl / h)

20th

Examples

a) Production of multimetal oxide compositions M according to the invention and multimetal oxide compositions MV for comparison and coated catalysts produced from these multimetal oxide compositions

example 1

Production of starting mass 1:

10

219.9 g of onium heptamolybdate tetrahydrate (81.8% by weight of MoO ₃ ) and 325.6 g of ammonium paratungstate heptahydrate (89.0% by weight of W0 ₃ ) were dissolved in succession in 5000 g of water with stirring at 95 ° C. (solution a) . 445.0 g of 25% by weight were added to 3000 g of water at 25 ° C

15 aqueous ammonia solution and then 497.2 g of copper acetate hydrate (40.0% by weight CuO) dissolved therein, resulting in a deep blue solution (solution b). Solution b was then stirred into solution a at 95 ° C., the temperature of the overall mixture not falling below 80 ° C. The resulting aqueous

20 suspension c was stirred at 80 ° C. for 1 h and then spray-dried (inlet temperature: 330 ° C., outlet temperature: 110 ° C.). The resulting light green spray powder was kneaded with water in a LUK 2.5 kneader from Werner & Pfleiderer, Stuttgart, (200 g water per 1 kg spray powder) and on a

25 extrusion press from Werner & Pfleiderer, Stuttgart, with 50 bar into 6 mm thick strands (approx. 1 cm long). These strands were dried in air at 110 ° C for 16 hours. The strands were then calcined in air. For this purpose, the calcined material (150 g) was placed in an air flow (50 Nl / h air)

30 muffle furnace (internal volume: 3.0 l) are given, heated to 300 ° C. within 1 h, left at this temperature for 30 min, heated to 750 ° C. within 2 h and at this temperature for 1 h leave. The resulting product had a red-brown color and after grinding in a centrifugal mill

35 Retsch, DE, a specific BET surface area according to DIN 66131 of 0.6 + 0.2 m ² / g and the composition CuMθo, so, sO _y . Using Cu-Kα radiation (Siemens diffractometer D-5000, 40 kV, 30 mA, with automatic divergence-scattered beam and counter tube diaphragm and Peltier detector) showed the obtained

40 crystalline powders of the composition CuMθo, ₅ W ₀ , ₅ θ _y (y <4) an X-ray powder diffraction gram with a superposition of the Wolfra fingerprint and the HT copper molybdate fingerprint, ie it had a two-phase structure. According to the line intensities, the two structure types were approximately in the molar frequency ratio 90 (tungsten structure): 10 (HT copper molybdate structure). 21

Production of starting mass 2:

With stirring, 946.0 g of Sb0 ₃ with an Sb content of 83.0% by weight were suspended in 4000 g of water. At room temperature (25 ° C) 822.4 g of a 30 wt. -.Aqueous H ₂ 0 ₂ solution added. The aqueous suspension was then heated to 100 ° C. in the course of 1 hour with further stirring and kept at this temperature under reflux for 5 hours. A solution of 595.6 g of copper acetate hydrate (32.0% by weight of Cu) in 4000 g of water was then added to the 100 ° C. hot aqueous suspension over the course of 30 minutes, the temperature of the suspension decreasing to 60 ° C. 407.9 g of a 25% strength by weight aqueous ammonia solution were then added at this temperature. The aqueous suspension was then stirred at 80 ° C. for 2 hours and cooled to room temperature (25 ° C.). Finally, the aqueous suspension was spray-dried (inlet temperature: 350 ° C, outlet temperature: 110 ° C). Part of the resulting spray powder (150 g) was gradually in a rotary tube oven (1.5 l internal volume) while passing 50 Nl / h of air to 150 ° C. in the course of 1 h, then to 200 ° C. in the course of 4 h then heated to 300 ° C. within 2 h and held at the latter temperature for 1 h. The powder was then heated to 800 ° C. in the course of 2 hours and held at this temperature for 2 hours. The resulting powder had a specific BET surface area of 0.6 m ² / g and the composition CuSb ₂ , i ₅ θ _z (z <0.6375). The powder X-ray diagram of the powder obtained essentially showed the diffraction reflections of CuSb ₂ 0 ₆ (comparison spectrum 17-0284 from the JCPDS-ICDD file).

Production of starting mass 3:

703.6 g of ammonium heptamolybdate tetrahydrate (81.8% by weight of MoO ₃ ), 135.72 g of ammonium metavanadate (77.3% by weight of V ₂ 0 ₅ ) and 120 were in succession in 5170 g of water at 95 ° C. , 3 g of ammonium paratungstate heptahydrate (89.0% by weight WO ₃ ). The aqueous solution

(Starting mass 3) was based on the following element stoichiometry:

θ Vι, i5 ₀ , 4 ₆ ^ (Mθι ₂ V3, ₄₆ Wι ₃₈ ) o, 33.

Production of the multimetal oxide mass Ml and the coated catalyst SM1:

The clear, orange-colored aqueous solution obtained above (starting mass 3) was cooled to 25 ° C. and then 116.9 g of 100% strength by weight acetic acid and 132.3 g of 25% strength by weight aqueous ammonia solution were added in succession. From the starting mass 1 were 82.3 g 22 stirred into the cooled to 25 ° C, the starting mass 3 containing aqueous solution, so that the molar ratio of the aforementioned stoichiometric units was 0.31 (starting mass 1) to 0.33 (starting mass 3). Subsequently, 129.7 g of the starting mass 2 were added to the aqueous suspension containing the starting masses 1 and 3, so that the molar ratio of the aforementioned stoichiometric units was 0.30 (starting mass 2) to 0.33 (starting mass 3). The resulting aqueous suspension was stirred at 25 ° C. for 1 h and then the aqueous mixture was spray-dried (inlet temperature:

350 ° C, initial temperature: 110 ° C). The spray powder was then mixed with a mixture of 70% by weight of water and 30% by weight of acetic acid

(0.35 kg liquid / kg spray powder) kneaded (kneader LUK 2.5 from Werner & Pfleiderer, Stuttgart). The kneaded material obtained was dried in a forced air oven at 110 ° C. for 16 hours. The comminuted kneaded material was calcined in a cylindrical rotary tube through which air flows (10 Nl / h) (inner diameter 12.5 cm, heated length 51 cm). 700 g of calcined material were introduced into the heated zone of the rotary tube. In the course of the calcination, the modeling clay was first heated to 210 ° C. in 30 minutes, then the temperature was raised to 310 ° C. in the course of 2.5 hours and then to 395 ° C. in the course of 2.5 hours, and this temperature was maintained for 3 h held. The resulting catalytically active multimetal oxide mass Ml had the following gross stoichiometry:

Mθ _{4 /} ι ₆ V _{1 (1} 5Wo, 6lCUo, 6lSb ₀ , 64θχ = [Mθ ₁₂ V ₃ , 4 ^ 3., ₃₈ 0 _x ] ₀ , 33 - θ ₀ , _{5 0} , sCUjOy] ₀ , _3l

[CuSb ₂ , ₅ O _z ] 0.3.

The X-ray diffractogram of the multimetal oxide mass Ml contained the superposition of HT copper molybdate structure type,

Wolframite structure type and CuSb ₂ 0g structure type. After the calcined mass Ml had been ground, it was used to rotate non-porous and surface-rough steatite balls with a diameter of 4 to 5 mm in a quantity of 60 g active mass per 400 g steatite balls with simultaneous addition of water (coating method according to DE-A 4,442,346) coated. The shell catalyst SM1 obtained was then dried with hot air at 110 ° C. 23

Example 2

Production of starting material 1: as in example 1.

5 Production of starting mass 2:

With stirring, 946.0 g of Sb ₂ 0 ₃ with an Sb content of

83.0% by weight suspended in 4 l of water. 822.4 g of a 30% strength by weight aqueous H ₂ O ₂ solution were added at room temperature (25 ° C.)

10 ben. The suspension was then heated to 100.degree. C. over the course of 1 h and kept at this temperature under reflux for 5 h. A solution of 595.6 g of Cu (CH ₃ COO) -H ₂ O having a Cu content of 32.0% by weight in 4 l of water was then added to the 100 ° C. hot aqueous suspension within 30 minutes

15 added, the temperature of the total aqueous mixture lowered to 60 ° C. 407.9 g of a 25% strength by weight aqueous ammonia solution were then added at this temperature. The aqueous suspension was then stirred at 80 ° C. for 2 hours and then cooled to room temperature (25 ° C.). Finally was

20 spray-dried the aqueous suspension (inlet temperature: 350 ° C, outlet temperature: 110 ° C). The resulting spray powder was gradually in a rotary kiln (1.5 l internal volume) while passing 50 Nl / h of air first to 150 ° C. within 1 h, then to 200 ° C. within 4 h and finally within 2 h

25 300 ° C heated and held at the latter temperature for 1 h. The powder obtained was then heated to 400 ° C. in the course of 1.5 h and tempered at this temperature for 1 h. The powder obtained had a specific BET surface area of 48.5 m ² / g and the composition CuSb _2j i ₅ θ _z . The powder X-ray

30 diagram of the powder obtained showed the diffraction reflections of the mineral Partzite and thus corresponded to the comparison spectrum 7-0303 of the JCPDS-ICDD file.

Production of starting mass 3:

35

633.8 g ammonium heptamolbdate tetrahydrate (81.8% by weight M0O ₃ ), 122.25 g ammonium etavanadate (77.3% by weight V ₂ Os) and 107.0 g ammonium paratungstate heptahydrate (89.0% by weight WO ₃ ) dissolved. The aqueous solution (starting

40 mass 3) was based on the following element stoichiometry:

Mθ _3/6 θ, ₀ Where, 4i = (Mθι ₂ V _{3 (47} W _{1/37) 0 / 30th}

45 24

Production of the multimetal oxide mass M2 and the coated catalyst SM2:

The clear, orange-colored solution obtained above (starting mass 5) was cooled to 25 ° C. and 105.3 g in succession

100% by weight acetic acid and 119.2 g of a 25% by weight aqueous ammonia solution were added. 74.1 g of the starting mass 1 were then stirred into the aqueous solution which had cooled to 25 ° C. and contained the starting mass 3, so that the molar ratio of the above

10 stoichiometric units mentioned was 0.277 (starting mass 1) to 0.30 (starting mass 3). Subsequently 116.86 g of the starting mass 2 were added to the aqueous suspension which contained the starting masses 1 and 3, so that the molar ratio of the aforementioned stoichiometric units was 0.273

15 (starting mass 2) to 0.30 (starting mass 3). The resulting aqueous suspension was stirred at 25 ° C. for 1 hour and then spray-dried (inlet temperature: 350 ° C., outlet temperature: 110 ° C.). The spray powder was then mixed with a mixture of 70% by weight of water and 30% by weight of acetic acid

20 (0.35 kg liquid / kg spray powder) kneaded (kneader LUK 2.5 from Werner & Pfleiderer, Stuttgart). The kneaded material obtained was dried in a forced air oven at 110 ° C. for 16 hours. The comminuted kneaded material was then mixed in an air / nitrogen mixture (40 Nl / h air and 500 Nl / h nitrogen) in the rotary tube (inside

25 diameter 2.5 cm, heated length 51 cm) calcined. 700 g of calcined material were introduced into the heated length of the rotary tube. In the course of the calcination, the kneading material was first heated to 325 ° C. in the course of 60 min, this temperature was then held for 4 h, then within

30 heated to 400 ° C for 10 min and maintained at this temperature for 1 h. The resulting multimetal oxide mass M2 had the following gross stoichiometry:

Mθ3, ₇ 4V _1/04 Wo, 5sCUo, 55Sbo, 59 ° x = 35 [Mθι ₂ V ₃ , ₄₇ Wι, ₃₇ O _x ] o, ₃ 0 [Moo.sWo.δCuxOylo ^ - ?? [CuSb _2, ι ₅ O _{z] 0, 273rd}

The X-ray diffractogram of the active composition obtained contained the superposition of the HT copper molybdate structure type, the tungsten structure type and the CuSb ₂ θ6 structure type. After grinding the

40 calcined active materials were coated with this non-porous and surface-rough steatite balls with a diameter of 4 to 5 mm in a volume of 60 g active powder per 400 g steatite balls with simultaneous addition of water (coating method according to DE-A 4 442 346). Then was

45 the shell catalyst SM2 obtained was dried with hot air at 110 ° C. 25th

In game 3

Associated production of starting mass 1 and starting mass 2 5

366.2 g of Sb0 ₃ (Sb content: 83.0% by weight) were suspended in 4000 g of water with stirring. 421.6 g of a 30% strength by weight aqueous H ₂ O ₂ solution were added at room temperature (25 ° C.). Then the suspension was opened with further stirring within 1 h

10 100 ° C heated and held at this temperature for 5 hours under reflux. A solution of 496.3 g of Cu (CH ₃ COO) ₂ -H ₂ O (32.3% by weight of Cu) in 4000 g of water was then added to the 100 ° C. hot aqueous suspension over the course of 30 minutes, during which time the temperature of the aqueous mixture as a whole was reduced to 60.degree. at

15 of this temperature were then 340.0 g of a 25 wt. -.Aqueous ammonia solution added. The aqueous suspension was then stirred at 80 ° C. for 2 hours. Then 110.3 g (NH ₄ ) ₆ Mo ₇ 0 ₂ -4H ₂ 0 (81.5% by weight M0O ₃ ) and 161.8 g (NH ₄ ) ι ₀ Wι ₂ O ₁ -7H ₂ O ( 89.5 wt .-% W0 ₃ ) added. The resulting aqueous suspension

20 was stirred for a further 20 h at 80 ° C and then spray dried (inlet temperature: 350 ° C, outlet temperature: 110 ° C). A portion of the spray powder obtained (approx. 200 g) was gradually in a rotary tube oven (1 1 internal volume) while passing 20 Nl / h of air at 150 ° C. in the course of 1 h, then

25 heated within 4 h to 200 ° C and then within 2 h to 300 ° C and held at the latter temperature for 1 h. The mixture was then heated to 850 ° C. in the course of 2 h and this temperature was maintained for 2 h. The resulting powder had a specific BET surface area of 0.6 m ² / g and the composition

30 CuMoo, ₂₅ weeks, ₂₅ SbιO _x (x <5). The powder X-ray diagram of the powder obtained showed the diffraction reflections of CuSb ₂ 0 ₆ (comparison spectrum 17-0284 of the JCPDS-ICDD file) and the diffraction reflections of CuW0 ₄ (comparison spectrum 21-0307 of the JCPDS-ICDD file).

35

Production of starting mass 3:

790.4 g ammonium heptamolbdate tetrahydrate (81.8% by weight M0O ₃ ), 152.3 g ammonium meta- 40 vanadate (77.3% by weight V ₂ Os) and 128.4 g of ammonium paratungstate heptahydrate (89.0% by weight WO ₃ ) dissolved. The aqueous solution (starting mass 3) was therefore based on the following element oechiometry:

Mθ ₄ , 4 ₉ Vι _r29 Wo, ₄₉ = (Mθ ₁₂ V _{3> 45!, 32} ) ₀ , ₃₇₄ • 5 26

Production of the multimetal oxide mass M3 and the coated catalyst SM3:

The clear, orange-colored solution obtained above (starting mass 3) was cooled to 25 ° C. and 150.0 g of ammonium acetate were added. 115.8 g of the starting mass (1 + 2) were stirred into the aqueous solution containing the starting mass 3 and cooled to 25 ° C., so that the molar ratio of the aforementioned stoichiometric units 0.345 (starting mass (1 + 2)) to 0.374 (Starting mass 3). The resulting aqueous suspension was stirred at 25 ° C. for 1 hour and then the aqueous mixture was spray-dried (inlet temperature: 350 ° C., outlet temperature: 110 ° C.). The spray powder was then kneaded with a mixture of 70% by weight of water and 30% by weight of acetic acid (0.35 kg of liquid / kg of spray powder) (kneader LUK 2.5 from Werner & Pfleiderer, Stuttgart). The kneaded material obtained was dried in a forced air drying cabinet at 110 ° C. for 16 hours. The comminuted kneaded material was calcined in a rotary tube (6.3 l internal volume) through which an air / nitrogen mixture (15 Nl / h air and 200 Nl / h nitrogen) flowed. 700 g of calcined material were introduced into the rotary tube. In the course of the calcination, the kneading material was first heated to 325 ° C. in 60 minutes, this temperature was held for 4 hours, then heated to 400 ° C. within 20 minutes and this temperature was maintained for 1 hour. The resulting catalytically active material had the following gross stoichiometry:

θ ₄ , 5 ₇ V _{lr 29} weeks, 5 ₈ CUo, ₃ 45Sbo, 3 5θχ

≤ [V Mθι _{2 3/45} Wι, 32θ _x] o, 374 [CuMθ _{0, 5} W _{0, 5} O _y] 0, 1725 [CuSb ₂ 0 _z] o, ι ₇₂ 5 -

The X-ray diffractogram of the multi-metal oxide mass obtained contained the superposition of the HT copper molybdate structure type, the Cu antimonate and the tungsten structure type. After the calcined multimetal oxide mass had been ground, this was used to coat non-porous and surface-rough steatite balls with a diameter of 4 to 5 mm in a quantity of 60 g active powder per 400 g steatite balls with simultaneous addition of water (coating method according to DE-A 4,442,346). The shell catalyst SM3 obtained was then dried with hot air at 110 ° C. 27

Example 4

Associated production of starting mass 1 and starting mass 2

The starting mass (1 + 2) was produced as in Example 3.

Production of starting mass 3:

435.6 g ammonium heptamolybdate tetrahydrate (81.8% by weight M0O ₃ ), 83.6 g ammonium metavanadate (77.3% by weight V ₂ O ₅ ) and 73.1 g of ammonium paratungstate heptahydrate (89.0% by weight WO ₃ ) were dissolved. The aqueous solution (starting mass 3) was therefore based on the following element stoichiometry:

Mθ2.48 ^v O, 7lWo, 28 = (Mθι ₂ V, 43W1, 35) 0, 207 •

Production of the multimetal oxide mass M4 and the shell catalyst SM4:

The clear, orange-colored solution obtained above (starting mass 3) was cooled to 25 ° C. and then 108.4 g of ammonium acetate were added. From the starting mass (1 + 2) 127.2 g were cooled to 25 ° C. in the aqueous containing the starting mass 3

Solution stirred in so that the molar ratio of the aforementioned stoichiometric units was 0.379 (starting mass (1 + 2)) to 0.207 (starting mass 3). The resulting aqueous suspension was stirred at 25 ° C. for 1 hour and then the aqueous mixture was spray-dried (inlet temperature: 350 ° C.,

Initial temperature: 110 ° C). The spray powder was then kneaded with a mixture of 70% by weight water and 30% by weight acetic acid (0.35 kg liquid / kg spray powder) (kneader LUK 2.5 from Werner & Pfleiderer, Stuttgart). The kneaded material obtained was dried at 110 ° C. in a circulating air drying cabinet for 16 hours. 700 g of a kneaded material produced and dried in this way were comminuted and calcined in a rotary tube (6.3 l internal volume) through which an air / nitrogen mixture (15 Nl / h air and 200 Nl / h nitrogen) flowed. In the course of the calcination, the kneading mass was first heated to 325 ° C. in 60 minutes, this temperature was then held for 4 hours, then increased to 400 ° C. within 20 minutes and this temperature was maintained for 1 hour. The resulting catalytically active multimetal oxide mass M4 had the following gross stoichiometry: 28 θ ₂ , 58V ₀ , lW ₀ , 3 ₇ CUo, 379SbO _x = [Mθι ₂ V ₃ , 43W1, ₃₅ O _x ] ₀ , 207 [CuMθ ₀ , 5 ^ 0, _δ Oy] 0, 189

[CuSb ₂ O _z ] 0.189 -

The X-ray diffractogram of the M4 5 multi-metal oxide mass obtained contained the superposition of the HT copper molybdate structure type, the Cu antimonate and the Wolfrmait structure type. After grinding the calcined multimetal oxide mass M4, this was used to coat non-porous and surface-rough steatite spheres with a diameter of 4 to 5 mm in an amount of 60 g active powder per 400 g steatite spheres with simultaneous addition of water in a rotary drum (coating method according to DE-A 4 442 346). The shell catalyst SM4 obtained was then dried with hot air at 110 ° C.

15 Example 5

Production of starting mass 1:

The preparation of starting material 1 as in Example 1. 20

Production of starting mass 2:

946.05 g of Sb ₂ 0 ₃ (Sb content: of 83.0% by weight) were suspended in 4000 g of water with stirring. At room temperature, 822.4 g

25 of a 30% by weight aqueous H ₂ 0 ₂ solution are added. The resulting aqueous suspension was heated to 100 ° C. in the course of 1 h with further stirring and kept at this temperature under reflux for 5 h. Subsequently, a solution of was in the 100 ° C hot aqueous suspension within 30 min

30 748.8 g of Ni (CH ₃ COO) ₂ -4H ₂ 0 (Ni content: 23.6% by weight) in 4000 g of water were added, the temperature of the resulting aqueous mixture decreasing to 60 ° C. 407.9 g of a 25% strength by weight aqueous ammonia solution were then added at this temperature. Thereafter, the suspension was post-treated at 80 ° C. for 2 hours.

35 stirred and then cooled to room temperature (25 ° C). The resulting aqueous suspension was then spray dried (inlet temperature: 350 ° C, outlet temperature: 110 ° C). 150 g of the spray powder obtained were gradually added in a rotary tube oven (1 l internal volume) while passing air (20 Nl / h).

40 next heated to 150 ° C within 1 h, then to 200 ° C within 4 h and then to 300 ° C within 2 h and held at the latter temperature for 1 h. The mixture was then heated to 800 ° C. within 2 h and this temperature was maintained for 2 h. The resulting powder had a specific BET

45 surface area of 0.9 m ² / g and had the composition NiSb _{2 /} i ₅ θ _x (x <0.6375). The powder X-ray diagram of the powder obtained 29 essentially showed the diffraction reflections of NiSb 0 ₆ (comparison spectrum 38-1083 of the JCPDS-ICDD file).

Preparation of the initial mass 3: 5

704.1 g of ammonium heptamolybdate tetrahydrate (81.8% by weight of M0O ₃ ), 135.7 g of ammonium metavanadate (77.3% by weight of V ₂ Os) and 118 , 77 g ammonium paratungstate heptahydrate (89.0 wt .-% W0 ₃ ) dissolved. The aqueous solution 10 (starting mass 3) was therefore based on the following element stoichiometry:

(Mθ ₄ , oo ^v l, 15 ^w 0, 456) = (MθιV ₃ , ₅ W _{lt 37} ) ₀ _ ₃₃₃ .

15 Production of the multimetal oxide mass M5 and the coated catalyst SM5:

The clear, orange-colored solution obtained above (starting mass 3) was cooled to 25 ° C. and 116.9 g in succession

20 100% acetic acid and 132.3 g 25% ammonia solution added. 82.3 g of the starting mass 1 were stirred into the aqueous solution containing the starting mass 3 and cooled to 25.degree. C., so that the molar ratio of the aforementioned stoichiometric units was 0.308 (starting mass 1) to 0.333 (starting mass 3).

25 130.0 g of the starting mass 2 were then added to the aqueous suspension, which contained starting masses 1 and 3, so that the molar ratio of the aforementioned stoichiometric units was 0.308 (starting mass 2) to 0.333 (starting mass 3). The resulting aqueous suspension was at

30 25 ° C stirred for 1 h and then the aqueous mixture was spray dried (inlet temperature: 350 ° C, outlet temperature: 110 ° C). The spray powder was then kneaded with a mixture of 70% by weight water and 30% by weight acetic acid (0.35 kg liquid / kg spray powder) (kneader LUK 2.5 from Werner &

35 Pfleiderer, Stuttgart). The kneaded material obtained was dried at 110 ° C. in a circulating air drying cabinet for 16 hours. The comminuted kneaded material was calcined in a rotary tube (6.3 l internal volume) through which an air / nitrogen mixture (15 Nl / h air and 200 Nl / h nitrogen) flowed. 700 g of calcining

40 well introduced. In the course of the calcination, the kneading material was first heated to 325 ° C. in 60 minutes, this temperature was held for 4 hours, then heated to 400 ° C. within 20 minutes and this temperature was maintained for 1 hour. The resulting catalytically active multimetal oxide mass M5 5 had the following gross stoichiometry: 30th

Mθ, 15 ^v l, 15 ^W 0.6lCUo, 308Niθ, ₃ 08Sb ₀ , 662θ = tMθι ₂ V _{3 # 5} Wι, 3 ₇ O _x ] o, ₃₃₃ [CuMθ ₀ , 5Wo, 5θ _y ] 0.308 [NiSb _{2 /} ι ₅ O _z ] 0.308-

The X-ray diffractogram of the resulting multi-metal mass M5 5 contained the superposition of the HT copper molybdate structure type, the Ni antimonate and the tungsten structure type. After grinding the calcined multimetal oxide mass M5, this was used to coat non-porous and surface-rough steatite balls with a diameter of 4 to 5 mm in a rotary drum in a quantity of 60 g active powder and 400 g steatite balls with the simultaneous addition of water (coating method according to DE-A 4 442 346). The shell catalyst SM5 obtained was then dried with hot air at 110 ° C.

15 Comparative Example 1

According to the following one-pot production method, a comparison multi-time oxide mass VM1 was produced, which had the same gross stoichiometry as the multi-metal oxide mass M1:

20th

730.7 g ammonium heptamolybdate tetrahydrate (81.8% by weight M0O ₃ ), 135.7 g ammonium metavanadate (77.3% by weight V ₂ Os) and 160 , 3 g of ammonium paratungstate heptahydrate (89.0% by weight WO ₃ ). The clear, orange

25 colored aqueous solution was cooled to 25 ° C and with 116.5 g 100 wt. -% acetic acid and 132.3 g of 25 wt .-% aqueous ammonia solution. 94.6 g of Sb ₂ θ ₃ with an Sb content of 83.0% by weight were stirred into the solution obtained. A solution of 120.8 g of copper acetate hydrate (32.0% by weight of Cu) was then

30 in a mixture of 800 g of water and 95.6 g of a 25 wt. -% aqueous ammonia solution added.

The aqueous suspension obtained was stirred at 25 ° C. for 1 hour and then spray-dried (inlet temperature: 35 350 ° C., outlet temperature: 110 ° C.). The spray powder was then kneaded with dilute acetic acid, as in Example 1, dried and calcined.

A coated catalyst SVM1 was then produced from the reference multimetal oxide mass VM1 as 40 in Example 1.

Comparative Example 2

Production of the starting mass 1: 5

Starting mass 1 was prepared as in Example 1. 31

Preparation of a starting mass (2 + 3):

For the combined preparation of a starting mass (2 + 3), 703.6 g of ammonium heptamolybdate tetrahydrate (81.8% by weight - M0O ₃ ), 135.7 g of ammonium metavanadate (77.3% by weight) % V ₂ Os) and 120.3 g ammonium paratungstate heptahydrate (89.0% by weight WO ₃ ) dissolved. The aqueous solution was cooled to 25 ° C and successively with 116.9 g 100 wt. -% acetic acid and 132.3 g 25 wt. -% aqueous ammonia solution added. 94.6 g of Sb ₂ 0 ₃ with an Sb content of 83.0% by weight were suspended in 4000 g of water in the solution obtained. A solution of 59.6 g of copper acetethydrate (32.0% by weight of Cu) in a mixture of 400 g of water and 40.8 g of 25% by weight aqueous ammonia solution was added to the aqueous mixture obtained.

Production of the comparison multimetal oxide mass VM2 and the comparison shell catalyst SVM2:

A comparison multimetal oxide mass VM2 was produced from the starting mass 1 and the starting mass (2 + 3) as follows:

82.3 g of the starting material 1 prepared in Example 1 were stirred into the aqueous mixture obtained above. The suspension obtained was stirred at 25 ° C. for 1 h and then spray-dried (inlet temperature: 350 ° C., outlet temperature: 110 ° C.). The spray powder was then kneaded with dilute acetic acid, as in Example 1, dried and calcined to VM2, and this was processed into a coated catalyst SVM2.

Comparative Example 3

Production of starting mass 2:

Starting mass 2 was prepared as in Example 1.

Preparation of a starting mass (1 + 3):

For the combined preparation of a starting mass (1 + 3), 730.7 g ammonium heptamolybdate tetrahydrate (81.8% by weight M0O ₃ ), 135.7 g ammonium metavanadate (77.3% by weight) were added in succession in 5800 g water at 95 ° C. - V0 ₅ ) and 160.4 g ammonium paratungstate heptahydrate (89.0 wt.% WO ₃ ) dissolved. The aqueous solution was cooled to 25 ° C and then 116.9 g of 100 wt. -% acetic acid and 132.3 g 25 wt. -% aqueous ammonia solution added. A solution of 61.2 g of copper acetate hydrate (40.0% by weight of CuO) in a mixture of 400 g was then added to the aqueous mixture obtained 32

Water and 54.8 g of a 25 wt. -% aqueous ammonia solution added.

Production of the comparison multimetal oxide mass VM3 and the comparison shell catalyst SVM3:

A comparative multimetal oxide mass VM3 was produced from the starting mass 2 and the starting mass (1 + 3) as follows:

10 129.7 g of the starting material 2 prepared in Example 1 were stirred into the aqueous mixture obtained above. The suspension obtained was stirred at 25 ° C. for 1 hour and then spray-dried (inlet temperature: 350 ° C., outlet temperature: 110 ° C.). The spray powder was then as in Example 1

15 kneaded with dilute acetic acid, dried and calcined to VM3, and a coated catalyst SVM3 was produced therefrom.

b) Use of the coated catalysts from a) as catalysts for the gas phase oxidation of acrolein to acrylic acid

20th

The coated catalysts were placed in a tubular reactor (V2A steel, 25 mm inside diameter, 2000 g catalyst bed, salt bath temperature control) and at reaction temperatures in the range from 250 to 280 ° C. using a residence time of 2.0 seconds

25 a gaseous mixture of the composition

5 vol.% Acrolein, 7 vol.% Oxygen, 10 vol.% Water vapor and 30 78 vol.% Nitrogen

loaded. The salt bath temperature was set in all cases so that, after formation, a single pass resulted in a uniform acrolein conversion U of 99%. The product gas mixture flowing out of the reactor was analyzed by gas chromatography. The results for the selectivity S of acrylic acid formation using the various catalysts are shown in the table below.

40

5 33

Table

Catalyst salt bath temperature [° C] S%

SM1 270 96

SM2 273 96

SM3 281 93.8

SM4 254 94.6

SM5 267 95.0

SVM1 268 93.7

SVM2 266 95.5

SVM3 266 94.8

Claims

34 patent claims

1. Multimetal oxide compositions of the general formula I

[A] _p [B] g [C] _r (I),

in which the variables have the following meaning:

A Mθι ₂ V _a χl _b X ² _c X ³ _d X ⁴ eX ⁵ fX ⁶ gO _x ,

B = X ⁷ ιCu _h HiO _y ,

C = ^ Sb H _k Oz,

X ¹ = W, Nb, Ta, Cr and / or Ce,

X ² = Cu, Ni, Co, Fe, Mn and / or Zn, X ³ = Sb and / or Bi,

X ⁴ = Li, Na, K, Rb, Cs and / or H,

X ⁵ = Mg, Ca, Sr and / or Ba,

X ⁶ = Si, Al, Ti and / or Zr,

X ⁷ = Mo, W, V, Nb and / or Ta, X ⁸ = Cu, Ni, Zn, Co, Fe, Cd, Mn, Mg, Ca, Sr and / or Ba, a = 1 to 8, b = 0.2 to 5, c = 0 to 23, d = 0 to 50, e = 0 to 2, f = 0 to 5, g = 0 to 50, h = 0.3 to 2.5, i = 0 to 2, j = 0.05 to 50, k = 0 to 50,

x, y, z = numbers which are determined by the valency and frequency of the elements other than oxygen in (I) and

p, q, r = non-zero numbers, with the proviso that the ratio p / (q + r) = 20: 1 to 1:20 and the ratio q / r = 20: 1 to 1:20,

which the portion [A] _p in the form of three-dimensionally extended areas A of the chemical composition

A Mθι ₂ V _a χl _b X ² _c X ³ _d X ⁴ _e X ⁵ _f χ6 O _x , 35 the proportion [B] _q in the form of three-dimensionally extended regions B of the chemical composition

BX ⁷ ιCu _h HιO _y and

the proportion [C] _r in the form of three-dimensionally extended areas C of the chemical composition

CX ⁸ ιSbjH ⁿ k _k O "z

included, areas A, B, C being distributed relative to one another as in a mixture of finely divided A, finely divided B and finely divided C.

2. A process for the preparation of multimetal oxide compositions according to claim 1, characterized in that a multimetal oxide composition B

X ⁷ ιCu _h HiO _y (B)

as starting mass 1 and a multimetal oxide mass C

X ⁸ _l SbH _k O _z (C)

as starting mass 2 either separately or in association with one another in finely divided form and then starting masses 1 and 2 with suitable sources of the elementary constituents of multimetal oxide mass A.

Mθι ₂ V _a X ¹ _b X ² _c ^X3 _d ^X _e ^X5 fX ⁶ g ° x ⁽ A ⁾ brings into intimate contact in the desired ratio and a resulting dry mixture is calcined at a temperature of 250 to 500 ° C.

3. A process for the gas-phase catalytic oxidative production of acrylic acid from acrolein, characterized in that a multimetal oxide according to claim 1 is used as the catalyst.

4. Process for the preparation of an oxometalate B of the general formula

X ⁷ ιCu _h HιO _y ,

in which the variables have the following meaning: 36 χ7 _ Mo and / or W, h = 0.3 to 2.5, i = 0 to 2 and y = a number which is determined by the valency and frequency of the elements in the general formula other than oxygen,

characterized in that an aqueous solution of ammonium heptamolybdate and ammonium paratungstate is mixed with an aqueous ammoniacal solution of copper carbonate, the resulting aqueous mixture is dried and calcined at a temperature of 200 to 1000 ° C.

5. Oxometalate B obtainable by a process according to claim 4.