EP1940764A1

EP1940764A1 - Mixed oxide catalysts for the catalytic gas-phase oxidation of olefins and processes for producing them

Info

Publication number: EP1940764A1
Application number: EP06793560A
Authority: EP
Inventors: Achim Fischer; Werner Burkhardt; Christoph Weckbecker; Klaus Huthmacher; Frank Wilz
Original assignee: Evonik Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2005-10-14
Filing date: 2006-09-15
Publication date: 2008-07-09
Also published as: CN101331103A; RU2396115C2; US20090030230A1; CA2625922A1; BRPI0617370A2; BRPI0617370B1; JP2009511256A; JP5227176B2; RU2008118490A; WO2007042369A1; US8008227B2; CN101331103B; DE102006015710A1

Abstract

The invention relates to mixed oxide catalysts for the catalytic gas-phase oxidation of olefins and methylated aromatics, processes for producing the catalysts and the reaction with air or oxygen in the presence of inert gases in various ratios at elevated temperatures and pressure to form aldehydes and carboxylic acids.

Description

Mixed oxide catalysts for the catalytic gas phase oxidation of olefins and process for their

manufacturing

The invention relates to mixed oxide catalysts for the catalytic gas phase oxidation of olefins or methylated aromatics, processes for preparing the catalysts and the reaction to aldehydes and carboxylic acids with air or oxygen in the presence of inert gases in different proportions, at elevated temperatures and pressures.

In particular, the catalyst can be used to convert the highly exothermic reaction of propene to acrolein and acrylic acid or isobutene to methacrolein and methacrylic acid. The highly exothermic reaction of the olefin on heterogeneous catalysts with an oxygen-containing gas leads in addition to the desired product acrolein and acrylic acid to a number of by-products: for example, to form CO2, CO, acetaldehyde or acetic acid.

It is known that by type of chemical

Composition of the mixed oxide (phase formation and formation of reaction centers) as well as the type of physical structure (eg porosity, surface area, shape of the catalyst), the type of heat removal, the product formation (selectivity) and the productivity (space - time yield) ) can be strongly influenced. In the case of olefin oxidation, mixed oxides are generally used as the catalyst, which have a complex structure in their chemical and physical structure. A variety of publications describe mixed oxides which are capable of being used as catalysts for the production of acrolein and acrylic acid from propene. These catalysts are usually made of molybdenum, vanadium and / or tungsten. To these basic components As a rule, at least one of bismuth, antimony, vanadium, tellurium, tin, iron, cobalt, nickel and / or copper is added.

The number of publications on the heterogeneously catalyzed gas phase oxidation of olefins to acrolein and acrylic acid has been numerous since the first development GB 821999 (1958) in the standard OiI Inc. Despite the long development time, improving the performance of the catalyst such as product yield, activity and lifetime is still a challenging task. For this purpose, various techniques for the preparation and formulations of the catalyst are claimed in the literature. As an example, the latest developments are shown here:

US 2005159621 describes a catalyst consisting of the basic elements Mo, Bi, Fe, Cs. In addition, as shown in the examples of the reaction of isobutene to methacrolein or propene to acrolein that the highly toxic antimony is required for this catalyst.

WO 2005/035115 uses the following production steps for the preparation of the catalyst: preparation of a suspension containing the metal components, drying of the suspension, comminution of the dried material, mixture of the material with a sublimable substance, in particular urea for pore formation, which is removed in the calcination. The removal of organic additives in the calcination, however, carries the danger of explosion, a controlled removal of the organic often does not succeed even with inert gas dilution. It must therefore be doubted whether such a procedure should be implemented on a production scale.

In DE 103 53 954 catalysts of the type Mθi2WbCocFedBieSifKgO _{x are used} as annular unsupported catalysts in which the task of reducing the maximum temperature increase at high propene load and thereby increasing the product selectivity is claimed. At a single throughput, the propene conversion should be greater than or equal to 90 mol% and therefore the associated acrolein formation should be more than 80 mol%. Yields of maximum 83.8% are shown in the examples.

WO 2005/063673, for example, describes a method by diluting the catalyst with an inert material in order to reduce the formation of heat in the reaction zone and thereby increase the product yield, by avoiding too high an excess temperature to reduce the total oxidation of the products. Despite the temperature modulation of the reaction by inert, the process described achieves only a cumulative yield of acrolein and acrylic acid of a maximum of 91.22%. However, it would be more useful to directly improve the yield of the catalyst. Thus, a time-consuming and costly Mehrzonenverfullen the reactor could be avoided.

Task and demarcation

It is generally accepted that highly specific local electronic structures of the catalytically active material are essential for catalytic performance. These structures are already determined by the manufacturing steps of the catalyst precursors and the way in which these production steps are carried out. Thus, even a small change of a manufacturing parameter (concentration,

Temperature, etc.) cause the catalyst to be more active and selective or inactive and unselective.

The object of the present invention is to improve the catalytic activity and selectivity of the catalyst over the prior art.

The invention is further based on the object to provide an improved process for the preparation of aldehydes and acids, wherein the acrolein and acrylic acid from Propene be prepared by oxidation with air or oxygen in the presence of inert gases, including steam or exhaust gases from the reaction at elevated temperatures and the presence of a heterogeneous mixed oxide catalyst. It is a mixed oxide catalyst can be provided, with the next Propenumsätzen greater than 95% and a high product selectivity of the same size is achieved 88%, so that improves the efficiency of the process.

The conversion of the olefin to the oxidation product aldehyde and acid takes place at higher temperatures and a ratio between olefin, air and inert gas (s) of preferably 1: 6-9: 3-18.

As inert gases, it is possible to use all gaseous compounds which are described below

Oxidizing conditions are inert. For example, these may be nitrogen, helium, ethane, propane, steam or mixtures of these. It is also possible to feed the "return gas" from the reactor again. The water vapor may originate from the reaction or be added.

The invention relates to mixed oxide catalysts of the general formula

(Mo ₁₂ Bi _a _b C (Co + Ni) _c D _d E _e F _f G _g H _h) O _x (I),

in which mean

C: Eggs,

D: at least one of the elements from W, P,

E: at least one of Li, K, Na, Rb, Cs,

Mg, Ca, Ba, Sr, F: at least one of the elements Ce, Mn, Cr, V,

G: at least one of Nb, Se, Te, Sm, Gd,

La, Y, Pd, Pt, Ru, Ag, Au,

H: at least one of the elements of Si, Al, Ti, Zr, and

a = 0 - 5, 0 b = 0, 5 - 5, 0 c = 2 - 15 d = 0, 01 - 5, 0 e = 0, 001 - 2 f = 0, 001 - 5 g = 0 - 1, 5 h = 0 - 800,

x = number determined by the valency and frequency of elements other than oxygen.

The use of the catalysts according to the invention leads to a significantly improved product selectivity of greater than (>) 88% at high propene conversions of greater than (95%).

The novel process for the preparation of the catalysts having the general formulas I, a particularly suitable catalytically active solid z. B. for the conversion of propene to acrolein and acrylic acid. The reaction is particularly advantageously carried out in reactors which allow the catalyst to be used as a fixed bed. However, it is also possible to apply the catalyst to the wall of the reaction space. It should be noted that catalysts of general formula I can also be used for the conversion of isobutene to methacrolein and methacrylic acid. It is also possible to convert toluene to benzaldehyde and benzoic acid.

The preparation of the catalysts of the invention can be carried out by producing a finely divided powder through the production steps: dissolving the metal salts, precipitation of the active components, drying and calcination. It is recommended to grind the dried or calcined powder. The calcined powder can be shaped become. This can be done by tableting, extrusion or by coating a carrier. The carrier type or carrier form is not limiting. For example, the carrier may be a pyramid, a cylinder or a sphere. But it can also represent a wall of the reactor. Particularly preferred is the extrusion and coating of a round carrier. The catalyst can be used as a fixed bed contact. The carrier material may be a metal alloy, a common steel, a high temperature plastic, a ceramic or

Be ceramic raw materials. If a shaping is necessary, then it is expedient to interrupt the calcination in the temperature range of 420 to 490 ⁰ C, then perform the shaping in order to then continue in the temperature range of 490 to 600 ⁰ C, the calcination. The catalyst thus prepared has excellent activity, selectivity and lifetime, and gives a very good product yield.

The catalysts to be used in the described gas phase oxidation process are obtained by combining the dissolved compounds with the desired concentrations of the catalytically active elements of formula I. The components are ideally used in the form of the compounds selected from the group consisting of ammonium or amine compounds, oxalates, carbonates, phosphates, acetates, carbonyls and / or nitrates, individually or together. Particular preference is given to carbonates, nitrates and phosphates or mixtures of these. It is also possible to use acids of the salts, for example nitric acid, phosphoric acid or carbonic acid.

The first stage of the catalyst preparation is, as already mentioned, a precipitate. It has been found that in a preferred embodiment, the concentration of the metal counterions during the precipitation and their molar ratios are of essential importance for the have catalytic efficiency of the oxidation catalyst.

Particularly active and selective catalysts of general formula I are obtained when the molar ratios of the counterions by

Rl = [NH _4] / [NCT] = 1/10 - 1/1, and / or

R2 = [NO ₃ ^"] / ([NO _^3"] + [CO ₃ ^{2 "]} + PO ₄ ^3" + [Y-COO ^"]) = 0.5

1.1

and Y can be any radical, especially methyl or ethyl, and the concentration of one or more of the ions, other than NO ₃ ^" and NH ₄ ⁺ , can also be zero.

Depending on the type of metal salts used in the precipitation, it may be necessary to add salts, acids or solutions thereof to the precipitation mixture to adjust the preferred ionic ratio R1 and / or R2. Ideally, this ammonia or ammonium salts, such as ammonium carbonate,

Ammonium heptamolybdate or metal nitrates, for example, iron nitrate, cobalt nitrate; It is also possible to use the corresponding acids, for example nitric acid, in the adjustment of the ionic ratio, which amounts are necessary. The pH during the precipitation is <8, in particular <7.

Also of importance is the temperature of the precipitation solution. So it may be that at too high a temperature, the activity of the catalyst is significantly reduced. The precipitation can be carried out in principle at temperatures of 5 to 90 ⁰ C. However, it has been found that a catalyst, whose precursor was precipitated at temperatures of 20 to 50 ⁰ C, is significantly more active.

The preparation of the coprecipitate can be carried out in a precipitation step. It is particularly preferred to carry out the precipitation in several stages by adding the individual components step by step or by mixtures of these. The number of precipitation stages is not limited in principle. However, one to three precipitation stages are preferred.

The suspension obtained can be further processed directly or allowed to mature for> 0 to 24 hours, preferably> 0 to 12 hours, more preferably 0 to 6 hours. It is understood that the precipitation suspension is homogenized prior to further processing, for example by stirring.

After maturation, the liquid of the suspension can be removed by evaporation, centrifugation or filtration. To evaporate the liquid and at the same time to dry the solid is also possible and can be done, for example, by spray-drying. The

Liquid should be evaporated at a temperature of 80 to 130 ⁰ C. The drying of the solid can be carried out with air, oxygen-containing inert gases or inert gases, for example nitrogen. If the drying is carried out in an oven, the temperature should be between 100 and 200 ^° C. In a spray dryer, the initial temperature of the dry medium of 200 and 500 ^° C and a temperature at deposition of the dried powder of 80 to 200 ⁰ C should provide. The resulting grain should preferably have a particle size distribution of 15 to 160 microns with a mean grain diameter between 15 and 80 microns.

The dried powder can in principle in a variety of furnace types such. Eg in one Convection oven, rotary kiln, tray furnace, shaft furnace or belt kiln are calcined. The quality of control or the quality of the temperature detection of the furnace should be as high as possible. The residence time of the powder in the oven should be between 0.25 and 13 h, depending on the type of oven.

It is also possible to carry out the calcination and the resulting thermal decomposition of the salts in one or more stages. In this case, temperatures of 200 to 600 ⁰ C, in particular 300 ° to 600 ° can be used. The thermal decomposition can with the addition of

Inert gas, from mixtures of oxygen with an inert gas.

As inert gas can be used, for. As nitrogen, helium, water vapor or mixtures of these gases.

It has been found that comminution of the powder after spray-drying or calcination is beneficial to the activity. The comminution can be achieved dry or as an aqueous suspension, for example by grinding. However, it is advantageous to perform the comminution after calcination or in a multi-stage calcination between individual calcination stages. The powder thus obtained can be used as a catalyst. The mean particle size distribution of the powder should be from 0.01 to 50 μm. Particularly preferred is an average particle size distribution of 0.1 to 30 microns. For industrial application, it is particularly useful to bring the powder into shape after the addition of commercially available molding and binding agents. This can be done by tableting, extrusion or by coating a carrier. The geometric shape of the carrier is not limiting. Rather, it is based on the specifications of the reactor (for example, pipe diameter, length of the

Catalyst bed). For example, the carrier may be a pyramid, a cylinder, a saddle, a ball or a But it can also be a wall of a reaction chamber.

As binders, various oils, celluloses, polyvinyl alcohols, saccharides, acrylates and alkyl derivatives, mixtures or condensates thereof can be used. Preference is given to acrylates, polyvinyl alcohols and celluloses. Particular preference is given to derivatives and condensates of acrylates and / or celluloses, and mixtures of these.

At a molding of the catalyst powder, the catalyst should preferably in the temperature range 490-600 ⁰ C are thermally treated, then the active material for use in industrial reactors that solidified.

The invention also relates to the oxidation of

Olefins to unsaturated aldehydes and corresponding acids in the presence of the catalysts of the invention.

The reaction for producing acrolein and acrylic acid is generally carried out at temperatures from 250 to 2.2 bara - 450 ⁰ C and a pressure of 1.0. The reactants olefin, air and inert gases are preferably fed in a ratio of 1: 6 to 9: 3 to 18 at a loading of 2 to 10 mol of olefin / dm ^{3 of} catalyst feed / h of the catalyst bed.

Propene is mainly used for the production of acrolein and acrylic acid as chemical grade or polymer grade, but you can also use refinery grade propene. Instead of inert gas, the exhaust gas can be used from the reaction, from which the condensable components were separated. Particularly good results are the use of

Rohrbundel, Platten (eg EP, 0 995 491, EP 1 147 807) or wall reactors (eg Redlingshoefer H., Fischer A., et al., Ind. Eng. Chem. Res. 2003, 42, 5482 -5488; EP 1 234 612) in which the catalyst is applied to the wall.

The inner diameter of the reaction tubes or the distance of the plates should be 18 to 28 mm, preferably 20 to 26 mm, the wall thickness of the ferrous steel should be between 1 and 3.5 mm. A typical reactor length is 3.00 to 4.00 m. The catalyst is preferably used uniformly on the reactor length without dilution with diluent bodies, of course, it may require the application, for example, to dilute with inert shaped bodies.

The catalysts according to the invention lead to improved activity and selectivity when used in the abovementioned oxidation processes, even under high specific loading.

The invention will be explained below with reference to exemplary embodiments. It is defined

the yield (%) of the product as

(mol / h product formed) / (mol / h reactant added) * 100

the turnover of the olefin (%) as

[1 - (mol / h leaving the reaction tube

Olefin) / (mol / h of olefin entering the reaction tube)] *

100

the selectivity (%) as

(Yield of the product / conversion) * 100

The illustrated invention will be described for the sake of understanding by the following examples, but it is not limited to these examples. EXAMPLES

example 1

A solution I was prepared by dissolving the nitrates of iron, cobalt, nickel, manganese, potassium in the proportions by weight 23.2: 47.26: 29.28: 0.0646: 0.2067 in 3.5 liters of water, under Stirring was heated to 40 ⁰ C and a nitric acid solution of 0.1 mol of Sm ³⁺ and 2 mol HNO3 was added.

For a solution II, a solution of 2118.6 g of ammonium heptamolybdate in 2.7 1 of water was prepared at 40 ⁰ C, to 4.4 g of phosphoric acid and 0.42 g Aerosil 200 (Degussa), 14 g of alumina in 1 1 water was added.

Solution II was added slowly to solution I with vigorous stirring. In a separate vessel, another solution III consisting of 790 g of bismuth nitrate and

0.72 mol HNO3 set. By adding this solution to the other active components, the coprecipitate was obtained for the preparation of the active catalyst phase.

The coprecipitate was stirred vigorously for 12 hours. The resulting suspension was dried in a spray dryer with a hub at a gas inlet temperature of 350 ⁰ C. The amount of air was adjusted so that an exit temperature of 110 +/- 10 ⁰ C was obtained.

The obtained average particle diameter of the thus prepared powder was 55 μm. This powder was treated in a circulating air oven at a temperature of 445 ° C for 1 hour until a mixed oxide formed, which was milled in the next step to a mean particle diameter of 1 micron. The mixed oxide was sprayed as an aqueous suspension through a two-fluid nozzle onto a ceramic spherical catalyst support and dried at 6O ⁰ C in a stream of air. To homogenize the pellets they were circulated in a drum. For consolidation the applied active material, the resulting material was heated to 540 ⁰ C for 1 hour.

The catalyst prepared in this way had the composition: (Mθi ₂ Bii, ₅ (Co + Ni) ₈ , ₀ Fei, ₈ Mn ₀ , oiK _o , oβ Po, 0 ₄ Al ₂₇ SS i ₀ , 6βSm ₀ , i) O _x

In game 2 a

The catalyst of Example 1 was charged with a mixture of the composition of 7.5 vol% chemical grade, 58 vol% air, and inert gas (100 vol% total). The total gas flow was 36.9 l / min. The temperature of the heat carrier was 340 ^° C. The propylene conversion was 94 mol%, the product selectivity for acrolein and acrylic acid being 96%.

Example 2b

The prepared catalyst of Example 1 was blended with a composition of 7.8 vol% propene

(chemical grade), 12.1 vol% oxygen, 3.9 vol% water and nitrogen fed. The total gas flow was 27.5 l / min. The temperature of the heat carrier was 334 ^° C. This resulted in formation of undesired by-products with a selectivity of 4%.

Example 2c

The prepared catalyst of Example 1 was charged with a mixture of composition of 4.6% by volume of chemical grade, 47% by volume of air and 47% by volume of inert gas. The total gas flow was 1100 l / h. The

Temperature of the heat carrier was chosen so that the conversion of the propene was 93 mol%, while the yield of acrolein was 88%.

Example 2d

The prepared catalyst of Example 1 was blended with a composition of 5.8 vol% propene (chemical grade), charged 51 vol% air, 46 vol% inert gas. The total gas flow was 20 l / min. The temperature of the heat carrier was chosen so that the conversion of the propene was 92 mol%, while the selectivity of acrolein was 92%.

Example 2e

The prepared catalyst of Example 1 was charged with a mixture of composition 6.2 vol% chemical grade, 55% air and nitrogen. The total gas flow was 22.2 l / min. The temperature of the heat carrier was 327 ° C, the propene conversion was 96 mol%, while the selectivity of acrolein was 91%.

Example 3

The calcined mixed oxide was prepared as described in Example 1. 1.6 kg of the mixed oxide powder are mixed with 0.4 kg of pentaerythritol (very finely ground). A 6% methyl cellulose solution was added into this mixture and kneaded until a homogeneous, plastic mass obtained under a constant pressure as a pellet with a diameter of 3 mm and extruded a length of 5 mm and was dried at 10 ⁰ C.

The extrudate was solidified in the rotary kiln. For this purpose, the inlet and speed of rotation is coordinated so that the residence time in the tube was 20 minutes. The peak temperature of the tube was 580 ⁰ C.

Example 4

The catalyst of Example 3 was charged with a mixture of the composition of 7.3 vol% chemical grade, 57 vol% air and inert gas. At a bath temperature of 308 ⁰ C and a contact time of 2.9s was obtained at a conversion of 90%, acrolein and acrylic acid with a selectivity of 94%. 5

A solution I was prepared by dissolving the nitrates of iron, cobalt, nickel, manganese, potassium in the proportions by mass 37.16: 31.24: 31.22: 0.06133: 0.3095 in 3.5 liters of water, heated with stirring to 40 ⁰ C and a nitric acid solution of 0.1 mol of Sm ³⁺ and 2 mol HNO3 admitted. For a solution II, a solution of 2119 g of ammonium heptamolybdate in 2.7 1 of water was prepared at 40 ⁰ C, to 4.4 g of phosphoric acid and 0.4 g of Aerosil 200 (Degussa), 14 g of alumina in 1 1 water was added.

Solution II was added slowly to solution I with vigorous stirring. In a separate vessel, another solution consisting of 776 g bismuth nitrate and 0.72 mol HNO3 was set. By adding this solution to the other active components, the coprecipitate was obtained.

The obtained average particle diameter of the thus prepared powder was 55 μm. The thus obtained powder was treated in a circulating air oven at a temperature of 445 ° C for 1 hour to form the mixed oxide.

The mixed oxide was sprayed as an aqueous suspension through a two-fluid nozzle on a ceramic spherical catalyst support and dried in a steady stream of air. To homogenize the pellets they were circulated in a drum. To solidify the applied active composition, the resulting material was heated to 540 ⁰ C for 2 hours. The catalyst thus prepared has the composition: (Mo i ₂ Bi, ₆ Cθ ₃ , ₄ Fe ₂ , ₉ Ni ₃ , ₄ Mn _O1O iKo _1I Po _1CM Al ₂₇₅ _Sig , ₃₅ Sm ₀ , i) O _x

Example 6

The catalyst of Example 5 was charged with a mixture of the composition of 7.3 vol% chemical grade, 57 vol% air and inert gas. At a bath temperature of 350 ⁰ C and a contact time of 2.7s was obtained at a conversion of 93%, acrolein and acrylic acid with a selectivity of 96%.

Example 7

A solution I was prepared by dissolving the nitrates of iron, cobalt, nickel, manganese, potassium in the proportions by weight 23.2: 47.26: 29.28: 0.0646: 0.2067 in 3.5 liters of water and heated with stirring to 40 ⁰ C and a nitric acid solution of 0.1 mol of Sm ³⁺ and 2 mol HNO3 admitted.

For a solution II, a solution of 2118.6 g of ammonium heptamolybdate in 2.7 1 of water was prepared at 40 ⁰ C, to 4.4 g of phosphoric acid was added.

Solution II was added slowly to solution I with vigorous stirring. In a separate vessel, another solution III consisting of 790 g of bismuth nitrate and 0.72 mol HNO3 was prepared. By adding this solution to the other active components, the coprecipitate was obtained for the preparation of the active catalyst phase.

The coprecipitate was stirred vigorously for 12 hours. The resulting suspension was dried in a spray dryer with a hub at a gas inlet temperature of 350 ⁰ C. The amount of air was adjusted so that an exit temperature of 110 +/- 10 ⁰ C was obtained. The obtained average particle diameter of the thus prepared powder was 55 μm. The thus obtained powder was treated in a circulating air oven at a temperature of 445 ° C for 1 hour to form the mixed oxide.

The mixed oxide was sprayed as an aqueous suspension whose solid has an average particle diameter (D50 value) of 1 μm through a two-substance nozzle onto a ceramic spherical catalyst support and dried in a steady stream of air. To homogenize the pellets they were circulated in a drum. To solidify the applied active composition, the resulting material was heated to 540 ⁰ C for 2 hours.

The catalyst thus prepared has the following composition: (Mθi2Bii, ₅ (Co + Ni) 8, Ofei, ₇ MnO, oiko, o6Po, θ4Smo, i) O _x

Example 8

The prepared catalyst of Example 5 was charged with a mixture of the composition of 7.3 vol% chemical grade, 57 vol% air and inert gas. At a bath temperature of 333 ° C and a contact time of 2.5s was obtained at a conversion of 92%, acrolein with a selectivity of 89%.

Example 9

The manufacturer's instructions for Example 1 have been changed so that the catalyst is the composition:

(Mθi ₂ Bii, ₆ (Co + Ni) ₈ , 1 ₂ Fe _x , ₈ Mn ₀ , oosK _o , oβPo, 004Al ₂₇₅ S i ₀ , 65Sm ₀ , i) O _{x contains} it.

At game 10

The prepared catalyst of Example 9 was blended with a composition composition of 3% by volume of chemical grade, 43% by volume of air, 5.2% by volume of water and Inert gas charged. The total gas flow was 16 l / min. The temperature of the heat carrier was chosen so that the conversion of the propene was 97 mol%, while the yield of acrolein was 87%.

Counterexample 1

The preparation of the catalyst was carried out as described in Example 1 at a solution temperature of 80 ⁰ C.

The catalyst thus prepared was charged with a mixture of the composition of 7.5 vol% chemical grade, 58 vol% air, and inert gases. The maximum possible total gas flow was only 28.2 l / min. The temperature of the heat carrier was 15 ° C higher than in Example 2a, yet a propene conversion of only 91% could be obtained, the acrolein yield was only 82%. The catalyst is thus significantly less active

Counterexample 2

In order to be able to adjust a propene conversion of 97% with the prepared catalyst of Counterexample 1, the total gas flow had to be reduced to 18.9 l / h and the volume fraction of propene to 4.5% by volume of propene (chemical grade). The catalyst consequently had a significantly lower activity.

Counterexample 3

The preparation of the catalyst is carried out as described in Example 1. However, solution II was submitted, then added the solution III and finally the solution II.

The catalyst thus prepared reached a maximum selectivity of acrolein of 85% (selectivity to acrolein and acrylic acid of 88%) at a propene conversion of 96%. The catalyst thus produced was thus significantly less selective.

Counterexample 4

The preparation of the catalyst is carried out as described in Example 1, but the average particle diameter in the coating suspension is 25 μm.

The testing of the catalyst is carried out under conditions of Example 2a. In this case, a 15 ° C higher bath temperature had to be set, but the resulting propene conversion was only 88 mol%. The catalyst was thus significantly less active.

Claims

claims

1. mixed oxide catalysts of the general formula

(Mo ₁₂ Bi _a _b C (Co + Ni) _c D _d E _e F _f G _g H _h) O _x (I),

in the mean

C: Eggs,

D: at least one of the elements from W, P,

E: at least one of the elements of Li, K, Na, Rb,

Cs, Mg, Ca, Ba, Sr,

F: at least one of Ce, Mn, Cr, V G elements: at least one of Nb, Se, Te, Sm,

Gd, La, Y, Pd, Pt, Ru, Ag, Au

H: at least one of Si, Al, Ti, Zr

and

a = 0 - 5.0 b = 0.5 - 5, 0 c = 2 - 15 d = 0.01 - 5.0 e = 0.001 - 2 f = 0, 001 - 5 g = 0 - 1.5 h = 0 - 800,

and

2. mixed catalysts according to claim 1, characterized in that the mixed oxides are supported on support materials.

3. A process for the preparation of mixed oxide catalysts according to the formula I, characterized in that Solutions of compounds of the metals contained in the mixed oxide catalysts according to formula I mixed, prepares coprecipitates, the resulting solid isolated, dried calcined and optionally deformed.

4. The method according to claim 3, characterized in that the pH during the precipitation of the (s) solids (s) <8.

5. The method according to claims 3 or 4, characterized in that metal compounds selected from the group consisting of ammonium or, amine compounds, oxalates, carbonates, phosphates, acetates, carbonyls and / or nitrates, individually or together, are used ,

6. Process according to claims 3 to 5, characterized in that carbonates, nitrates or phosphates or mixtures of these salts are used.

7. Process according to claims 3 to 6, characterized in that optionally the anions of the salts used corresponding acids are used.

8. Process according to claims 3 to 7, characterized in that the molar ratios of the metal counterions in the precipitation by

Rl = [NH ₄ ^+] / [NO ₃ ^"] = 1/10 - 1/1, and / or

R2 = [NO ₃ ^"] / ([NO _^3"] + [CO ₃ ^{2 "]} + [PO ₄ ^3"] + [Y-COO ^"]) = 0.5 - 1.1,

being represented, wherein Y is in particular CH ₃ or C ₂ H ₅ and [NO ₃ ^" ] and [NH ₄ ⁺ ]> 0 s ind.

9. Process according to claims 3 to 8, characterized in that ammonia or ammonium salts, in particular ammonium carbonate, ammonium heptamolybdate or metal nitrates, in particular iron nitrate, cobalt nitrate; and / or the corresponding acids, for example nitric acid for the preparation of the coprecipitate.

10. The method according to claims 3 to 9, characterized in that the precipitation is carried out at temperatures of 5 to 90 ° C.

11. The method according to claim 10, characterized in that the precipitation is carried out at temperatures of 20 to 50 ⁰ C.

12. The method according to claims 3 to 11, characterized in that the suspension obtained by precipitation for> 0 to 24 hours matures, preferably> 0 to 12 hours, more preferably _> 0 to 6 hours.

13. The method according to claims 3 to 12, characterized in that the dried powder prior to the calcination of spray grain with a particle size distribution of 15 to 160 microns.

14. The method according to claim 13, characterized in that the mean particle size distribution of the dried coprecipitate is between 15μm and 80μm.

15. The method according to claims 3-14, characterized in that the residence time of the dried powder in the calcination furnace between 0.25 and 13 h and while temperatures of 200 to 600 ⁰ C are set.

16. The method according to claims 3 to 15, characterized in that the calcination is carried out in one or more stages.

17. The method according to claims 15 and 16, characterized in that the calcination is carried out with the addition of inert gas, from mixtures of oxygen with an inert gas in the presence or absence of water vapor.

18. Process according to claims 15 to 17, characterized in that the calcined powder is fixed by tabletting, extrusion or coating of a carrier.

19. The method according to claims 15 to 18, characterized in that the particle size distribution of the calcined or partially calcined powder optionally by grinding is between 0.01 and 80μm.

20. Process according to claims 3 to 19, characterized in that the particle size distribution of the spray-dried powder is optionally between 0.1 and 50 μm by grinding.

21. The method according to claims 3 and 19, characterized in that the average particle size distribution of the calcined or partially calcined powder can optionally be adjusted by grinding to a distribution of 0.01 to 30 microns.

22. The method according to claims 3 and 21, characterized in that after a shaping of the

Catalyst powder, a temperature treatment in the temperature range of 450 to 600 ⁰ C takes place.

23. A process for the preparation of aldehydes and acids by oxidation of olefins or methylated aromatics with air or oxygen in the presence of inert gases, water vapor or exhaust gases from the reaction at elevated temperatures, characterized in that a catalyst of the general formula

(M0 ₁ 2 Bi _a _b C (Co + Ni) _c D _d E _e F _f G _G H _h) O _x (I):

in the mean

C: iron,

D: at least one of the elements from W, P,

E: at least one of the elements of Li, K, Na, Rb,

Cs, Mg, Ca, Ba, Sr,

F: at least one of Ce, Mn, Cr, V G elements: at least one of Nb, Se, Te, Sm,

Gd, La, Y, Pd, Pt, Ru, Ag, Au

H: at least one of the elements of Si, Al, Ti, Zr,

and

a = 0 - 5, 0 b = 0.5 - 5, 0 c = 2 - 15 d = 0.01 - 5.0 e = 0.001 - 2 f = 0, 001 - 5 g = 0 - 1.5 h = 0 - 800,

and

24. The method according to claim 23, characterized in that one obtains acrolein and acrylic acid from propene.

25. The method according to claim 23, characterized in that one obtains methacrolein and methacrylic acid from isobutene.

26. The method according to claim 23, characterized in that one wins benzaldehyde and benzoic acid from toluene.

27. The method according to claims 23 to 26, characterized in that the catalyst is acted upon by a reaction gas mixture containing olefin or methylated aromatics, air, inert gases in a ratio of 1: 6-9: 3-18.