NO773568L - PROCEDURE FOR THE PREPARATION OF UNSaturated Acids - Google Patents

Description

Procedure for the production of unsaturated acids.

Methacrylic acid or acrylic acid is produced according to the invention by oxidation of methacrolein, respectively. acrolein, with molecular oxygen in vapor phase in the presence of a catalytic oxide of molybdenum, phosphorus, arsenic, oxygen and the following constituents specified in three groups I to III: (I) a rare earth element or mixture thereof, and possibly at least one of Ag, Tl, Rh, Pd, Ru, Pt, Cd, Al, Au, Cu, alkaline earth metal. Cl and NH 3 ; or (II) at least one element selected from the group consisting of U, Ti, Nb, Re, Pb, Zn and Ga, and optionally at least one of Cu, a rare earth element, Ag, Ta, In, Th, Cd, Tl, alkaline earth metal , NH 3 , Cl, Ni, Al and Ge; or (III) at least one element selected from the group consisting of Ag, Rh, Ru and Au, and optionally at least one of Cd, Pt, Tl, Pd, Al, Ge, Cu, Ni, alkaline earth metal, NH^ and Cl.

A number of catalysts are known to be effective for the oxidation of acrolein or methacrolein to acrylic acid, respectively. methacrylic acid. However, the yields obtained using the catalysts for the production of methacrylic acid are low. DT patent 2 048 620 relates to catalysts containing the oxides of molybdenum, phosphorus and arsenic for the oxidation of methacrolein and acrolein to methacrylic acid, respectively. acrylic acid. U.S. patent no. 3 76l 5l6 relates to catalysts containing oxides of molybdenum, arsenic and phosphorus on a support, in particular A1„0, with external macro-pores and a surface not greater than 2 m 2 /g.

The present invention is the result of an investigation into more effective and desirable catalysts for the production of acrylic acid and methacrylic acid. Unexpectedly higher yields of and selectivities for acrylic acid and methacrylic acid are obtained by vapor phase oxidation of acrolein, resp. methacrolein, with molecular oxygen in the presence of the new and useful catalysts according to the present invention.

It has been shown that according to the present invention in the method for the production of acrylic acid or methacrylic acid by oxidation of acrolein, resp. methacrolein, with molecular oxygen in the vapor phase, with a reaction time of from approx. 2(J0°C to approx. 500°C in the presence of an oxide catalyst, and optionally in the presence

of steam, the improvement characterized by the use of a ca L a lysa L oi: with the formula:

where X is a rare earth element or a mixture thereof; U is at least one of Ag, Tl, Rh, Pd, Ru, Pt, Cd, Al, Au, Cu, alkaline earth metal, Cl and NH^; where a is 0.001 to 10; b is 0 to 10; c is 0.01 to 5; d is 0.01 to 5; x is the number of oxygen atoms required to satisfy the valence states of the other elements present; or that a catalyst with the formula is used: where X is at least one element selected from the group consisting of U, Ti, Nb, Re, Pb, Zn and GA; Y is Cu, a rare earth element, Ag, Ta, In, Th, Cd, Tl, an alkaline earth metal, NH^, Cl, Ni, Al and Ge; and where a is 0.001 to 10; b is 0 to 10; c is 0.01 to 5; d is 0.01 to 5; x is the number of oxygen atoms required to satisfy the valence states of the other elements present; or a catalyst with the formula is used:

wherein X is at least one element selected from the group consisting of Ag, Rh, Ru and Au;

Y is at least one of Cd, Tl, Pd, Al, Ge, Cu, Pt, Ni, alkaline earth metal, NH^ and Cl;

and where a is 0.001 to 10;

b is 0 to 10;

c is 0.01 to 5;

d is 0.01 to 5;

x is the number of oxygen atoms required to satisfy the valence states of the other elements present.

The surprisingly advantageous catalysts according to the invention provide improved yields of acrylic acid and methacrylic acid from acrolein, respectively .. methacrolein, in an efficient, convenient and economical way at a relatively low temperature. The exotherm of the reaction is low, which enables easy reaction control.

The most significant feature of the present invention is the catalyst used. The catalyst may be any of the catalysts indicated by formulas I to III. The catalysts can be prepared by a number of different known methods, such as coprecipitation of soluble salts and calcination of the product formed. The catalysts according to the invention have preferred restrictions on their composition.

When catalysts of formula I are used, preferred catalysts are those where a is 0.001 to 3>catalysts where b is 0.001 to 3j and catalysts where b is 0. Particularly preferred are catalysts where X is cerium, erbium or a mixture of rare earth elements consisting of the essential of Ce, La, Nd and Pr. Catalysts of particular interest are those where Y is silver, thallium or copper.

When catalysts of formula II are used, catalysts where a is 0.001 to 3, catalysts where b is 0.001 to 3> and catalysts where b is 0 are preferred. Particularly preferred are catalysts where each of the elements denoted by X is incorporated separately into the catalyst. This is conveniently achieved by setting X independently equal to the various elements. Catalysts of particular interest are those where Y is at least one element selected from the group consisting of a rare earth element, Al, Ag and Cu.

When catalysts of formula III are used, preferred catalysts are those where a is 0.001 to 3, catalysts where b is 0.001 to 3, and catalysts where b is 0. Particularly preferred are catalysts where each of the elements indicated by X is incorporated separately into the catalyst. This is conveniently achieved by setting X independently equal to the various elements. Also preferred are catalysts where Y is at least one of Cd, Tl, Cu, NH 4 and Cl.

In catalyst production, the different elements of the catalyst are combined, and the final product is calcined to obtain the catalyst. A number of methods for combining the elements of the catalyst and calcining the resulting product are known to those skilled in the art. For the broad idea of the invention, the particular method for producing the catalysts is not critical.

There are, however, methods for producing the catalysts which have been shown to be preferred. A preferred method involves preparing the catalysts in an aqueous slurry or solution of molybdenum, arsenic and/or phosphorus containing ingredients, and adding the remaining ingredients; evaporate this aqueous mixture and calcine the catalysts obtained. Suitable molybdenum compounds which can be used in the production of the catalysts indicated by the above formulas include molybdenum trioxide, phosphormolybdic acid, molybdic acid, ammonium heptamolybdate and the like. Suitable phosphorus compounds which can be used in the preparation of the catalysts include orthophosphoric acid, metaphosphoric acid, triphosphoric acid and phosphorus halides or -oxyhalides. The remaining components of the catalysts can be added as oxide, acetate, formate, sulphate, nitrate, carbonate, oxyhalide or halide and the like.

Excellent results are obtained by refluxing phosphoric acid, an arsenic-containing compound and molybdenum trioxide or ammonium heptamolybdate in water for approx. half an hour to 3 hours, but commercial phosphormolybdic acid can be used effectively; adding the remaining ingredients to the aqueous slurry and boiling to a thick paste; drying at 110 - 120°C in air;

and calcination of the obtained catalysts.

The calcination of the catalyst is usually carried out by heating the dry catalytic components at a temperature of approx. 200 C to approx. 700 C. The preferred method according to the invention is the one where the catalyst is calcined at a temperature of 325 - 425°C

The reactants in the reaction according to the invention are methacrolein or acrolein and oxygen. Molecular oxygen is usually supplied to the reaction in the form of air, but oxygen gas can also be used. About. 0.5 to approx. 4 moles of oxygen are usually added per moles of methacrolein.

The reaction temperature can vary according to which different catalysts are used. A temperature of approx. 200 to approx. 500°C, with a temperature of 250 - 370°C being preferred.

The catalyst may be used alone, or a carrier may be used. Suitable carriers include silicon oxide, aluminum oxide, "Alundum", silicon carbide, boron phosphate, zirconium dioxide and titanium dioxide. The catalysts are often used in a fixed bed reactor as tablets, pellets or the like, or in a fluidized bed reactor using a catalyst with a particle size of less than approx. 300 µm. When a fluidized bed reactor is used,

are the preferred catalysts in the form of microspherical particles. The contact time can be as low as a fraction of a second or as high as 20 seconds or more. The reaction can be carried out at atmospheric pressure, overpressure or underpressure, with absolute pressures of approx. 0.5 to approx. 4 ata is preferred.

Excellent results are obtained using a coated catalyst consisting essentially of an inert support material with a diameter of at least 20 µm and having an outer surface and a continuous coating of the active catalyst on the inert support strongly adhering to the outer surface of the support. The special coated catalyst consists of an internal support material with an external surface and a coating of active catalytic material on this external surface. These catalysts can be prepared by a number of different methods.

The support material for the catalyst forms the inner core of the catalyst. This is a substantially inert carrier and may have virtually any particle size although a diameter greater than 20 µm is preferred. Particularly preferred according to the present invention for use in a commercial reactor are the carriers which are spherical and have a diameter of from approx. 0.2 cm to approx. 2 cm. Suitable examples of substantially inert carrier materials include: "Alundum", silicon oxide, aluminum oxide, aluminum oxide-silicon oxide, silicon carbide, titanium dioxide and zirconium dioxide. Particularly preferred among these carriers are "Alundum", silicon oxide, aluminum oxide and aluminum oxide-silicon oxide.

The catalysts can contain virtually any ratio of carrier and catalytically active material. The limits of this relationship are set only by the relative ability of the catalyst and the support material to adapt to each other. Preferred catalysts contain approx. 10 to approx. 100% by weight catalytically active material calculated on the weight of the carrier.

The production of these coated catalysts can be carried out by different methods. The basic method for producing these catalysts is by partially wetting the carrier material with a liquid and then bringing the carrier material into contact with a powder of the catalytically active material and gently shaking the mixture until the catalyst is formed. The gentle shaking is most conveniently accomplished by placing the partially wet support in a rotating drum or jar and adding the powdered active catalytic material.

When using the catalysts according to the invention in the production of methacrylic acid or acrylic acid, excellent yields are obtained in a convenient reaction with low amounts of by-products.

Specific embodiments

Comparative examples A to D and examples 1 to 80: Comparison of catalysts containing promoters according to the invention with basic catalyst in the production of methacrylic acid.

A 20 cm<J>fixed bed reactor was constructed from a 1.3 cm stainless steel tube. Catalysts prepared as described above were introduced into the reactor and heated to the reaction temperature under an air stream and a feed of methacrolein/air/nitrogen/steam in the ratio 1:5.7=4.6:8.7 was fed over the catalyst with an apparent contact time of 2 - 4 seconds. The reactor was run under the reaction conditions for 1-6 hours, and the product was collected and analyzed.

Comparative example A

25% Moi2PlAs0 5°x + 7-^ ° "Alundum"

A solution was prepared consisting of 211.88 g of ammonium heptamolybdate , (NH^) ^MoyDg^ • 4^0 , (1.2 mol Mo), 500 ml of distilled water of 6o°C and 7.94 g of ammonium arsenate, NH ^H2AsO^ (0.05 mol As) as a solution in 25 ml of distilled water. A white precipitate was formed which was heated to approx. 100°C for 2 hours. 11.53985% phosphoric acid (0.10 mol P) was added to this mixture. Half an hour later, 5.0 g of hydrazine hydrate was added. The slurry was evaporated to a thick paste, dried overnight in an oven at 110 - 120°C and ground and screened to less than 80 mesh. This powder was coated on "Norton 3.2 mm SA 5223" "Alundum" beads by wetting 50 g of "Alundum" partially with 1.8 g of water and adding 16.7 g of active catalyst prepared above in five equal portions. During and after each addition, the "Alundum" balls were rolled in a glass jar. The powder was uniformly coated on the surface of the "Alundum" balls and the final product was dried. A hard, uniform material was obtained which consisted of an inner core of the "Alundum" carrier with a continuous, highly adherent coating of the powder on the outer surface of the carrier. The material was then calcined for 1 hour at 370°C in 40 ml/min air to form the active catalyst.

Examples 1 to 9

Various catalysts of formula I were prepared as follows:

Example 1

25% (rare earth mixture) Mo P As JD + 75% "Alundum"

A solution was determined consisting of 105.9 g of ammonium heptamolybdate , (NH^) ^MoyD,^ • 4^0 , (0.6 mol Mo), 700 ml of distilled water of 6o°C and 4.0 g of ammonium arsenate, NH^ H2AsO^, (0.025 mol As) as a solution in 25 ml of water. A white precipitate was formed which was heated at 100°C for half an hour. To this mixture was added 4.49 Moly Corp. rare earth chloride mixture (product code no. 4700) consisting of 48% CeO , 33% La„0_, 13% Nd_0o, L\, y% > Pt^ O-^ and 1.5% other rare earth elements are calculated as oxides. To this solution was added 5.8 g of 85% phosphoric acid, H3P04(°'°-5 mo1 p) • Half an hour later, 2.5 g of hydrazine hydrate was added. The slurry was evaporated to a thick paste,

dried overnight in an oven at 110 - 120°C and ground and sieved to below 80 mesh size. The catalyst was then coated to an active thickness of 25% on 3.2 mm "SA 5223" "Alundum" beads. The calcination was the same as in Comparative Example A.

Example 2 to 7

Preparation of the catalysts

25% X Y.Mo., _P.. As^ c0 + 75% "Alundum"

ab 121 Q , 5x

Various catalysts according to the invention were prepared. The catalysts were prepared according to the procedure in example 1 using 105.9 g of ammonium molybdate, 700 ml of 6o°C distilled water and 4.0 g of ammonium arsenate dissolved in 25 nil of water. The catalytic components indicated by X and/or Y were added immediately before the addition of 5.8 g of 85% phosphoric acid and 2.59 hydrazine hydrate. To prepare the catalysts, the following compounds and quantities were used:

Example 8

25% rare earth metal mixture ocCu^ ^cMonoPnAs^ c0

o ><0 o ,o>LZ1 o.5 x

<+>75% "Alundum"

This catalyst was prepared in the same manner as described in Example 1, except that 34.25 g of ammonium heptamolybdate, 1.28 g of ammonium arsenate, 1.43 g of rare earth chloride mixture,

0.161 g of copper acetate, 1.88 g of 85% phosphoric acid and 0.8 g of hydrazine hydrate were used.

Example 9

25% rare earth metal mixtureQ 25Ago lM°12PlAs0 5°x + 75% "Alundum"

This catalyst was prepared in the same manner as described in Example 8, except that 0.269 g of silver acetate was used.

Comparative examples B, C and examples 10 to 20

The results of the experiments using catalysts of formula I in the oxidation of methacrolein to produce methacrylic acid are shown in Table I. The following definitions are used to measure the carbon atoms in the feed and products.

Examples 21 to 43

Various catalysts of formula II were prepared as follows:

Example 21

25% --Mo^P.As- c0 + 75% "Alundum."

0.25 12 1 O ,Dx

A solution was prepared consisting of 105.99 ammonium heptamolybdate, (NH^)^MoyD^-4H2O, (0.6 mol Mo),. 700 ml of distilled water of 6o°C and 4.0 g of ammonium arsenate, NH^H2AsO^ (0.025 mol As) dissolved in 25 ml of water. A white precipitate was formed which was heated at 100°C for approx. half hour. To this mixture was added 5.3 g uranyl acetate (0.0125 mol U), followed by the addition of 5.8 g 85% phosphoric acid (0.05 mol P). Half an hour later, 2.5 g of hydrazine hydrate was added. The slurry was evaporated to a thick paste, dried overnight in an oven at 110 - 120°C and ground and sieved to below 80 mesh size. The catalyst was then coated to a 25% activity level on 3.2 mm "SA 5223" "Alundum" beads. The calcification was the same as in comparative ex-

pile A.

Example 22

25% TiQ 2Mol2PlAs0 5°x + 75% "Alundum"

This catalyst is prepared in the same way as described in example 21, except that 7.72 g of a 20% titanium trichloride solution was used and hydrazine hydrate was looped at catalyst progress 11-ing.

Example 23

25% (rare earth metal mixture) 0Ti0 Mo.. 0Pn As~ c0

+ 75% "Alundum" Q, 2 Q, l 12 1 0, 5 x

This catalyst was prepared in the same way as described

in Example 21, except that 3.54 g of rare earth chloride mixture, 0.5 g of hydrazine hydrate were used, and 3.85 g of 20% titanium trichloride solution was added.

Examples 24 to 39

Preparation of the catalysts 25% X ^ Y.o Mol .. 0P 1 As 0.5 c0 x+75% "Alundum"

Various catalysts according to the invention were prepared. The catalysts were prepared by the method in example 21, using 105.9 g of ammonium molybdate, 700 ml of distilled water at 60°C and 4.0 g of ammonium arsenate dissolved in 25 ml of water. The catalyst components indicated by X and/or Y were added immediately before the addition of 5.8985% phosphoric acid. 2.5 g of hydrazine hydrate was added in all preparations, except that no hydrazine was added in examples 28, 30, 32 and 38; and 1.0 g of hydrazine was added in example 14- To prepare the catalysts, the following compounds and amounts were used:

Example 40

25% Mo12P1As0;5N<b>0?25Ago?o5<O>x<+>75%" Alundum-

This catalyst was prepared in the same manner as described in Example 21, except that 34.25 g of ammonium molybdate, 150 ml of water, 1.28 g of ammonium arsenate, 0.537 g of niobium chloride, 0.134 g of silver acetate, 1.86 g of 85% phosphoric acid and 0 .89 hydrazine hydrate was used.

Example 4l

25% Mo10P,As0,Nb. ocCu„ -.O + 75% "Alundum"

12 1 O.5 0.25 Q, l x

This catalyst was prepared in the same way as described in example 24, except that 0.322 g of copper acetate was added in addition to the niobium chloride.

Example 42

25% Zn0>2Al0) 08Cu0>Q5Mo12P1) 32As0) 5Ox<+>75% "Alundum"

This catalyst was prepared in the same way as described in example 37, except that 0.96 g of aluminum chloride hydrate and 7.6 g of 85% phosphoric acid were used.

Example 43

25<%>^ o>1A10>oq1Cu0>o5Mo12P;L) 32ASo>5Ox<+>75% "Alundum"

This catalyst was prepared in the same manner as described in Example 42, except that 1.1 g of aluminum chloride hydrate and 1.21 g of Re 2 Oy were used.

Comparative Examples B to D and Examples 44 to 67

The results of the experiments using catalysts of formula II in the oxidation of methacrolein to methacrylic acid are shown in Table II. The same definitions as described above,

is used when measuring the carbon atoms in the feed and the products.

In the same way as described above, the catalysts according to the invention can be effectively used in the production of acrylic acid from acrolein.

Examples 68 to 73

Various catalysts of formula III were prepared

as follows:

Oak sample 68

<25%>AgQ 25M°12P1AS0 5°x<+>75% "Alundura"

A solution was prepared consisting of 105.99 ammonium heptamol<y>bdate, (NH^) gMoyD^ .4H20 , (0.6 mol Mo), 700 ml of distilled water of 6o°C and 4.0 g of ammonium arsenate, NH^ H^AsO^, (0.025 mol As), as a solution in 25 ml of water. A white precipitate was formed which was heated at 100°C for approx. half hour. To this mixture was added 2.08 g of silver acetate (0.0125 mol Ag), followed by the addition of 5.8 g of 85% phosphoric acid (0.05 mol P). Half an hour later, 2.5 g of hydrazine hydrate was added. The slurry was evaporated to a thick paste, dried overnight in an oven at 110 - 120°C, and ground and sieved to less than 80 mesh size. The catalyst was then coated to 25% active level on 3.2 mm "SA 5223" "Alundum" beads. The calcination was the same as in Comparative Example A.

Example 69

25% Au0 OI-Cd_ 0Mon JP- _As„ c0<+>75% "Alundum"

0.05 0 .2 12 1 .0 0 .5 x

This catalyst was prepared in the same manner as described in Example 68, except that 150 ml of water, 34.25 g of ammonium molybdate, 1.28 g of ammonium arsenate, 0.862 g of cadmium acetate, 0.318 g of gold chloride, 1.86 g of 85% phosphoric acid and 0.8 g of hydrazine hydrate was used.

Example 70

25% RuQ 2Moi2PlAsO 5°x + 75% "Alundum"

This catalyst was prepared in the same manner as described in Example 68, except that 500 ml water, 70.6 g ammonium molybdate, 2.64 g ammonium arsenate, 1.74 g ruthenium chloride, RuCl3 _.3H2o0, (0.006 mol Ru), 3.849 phosphoric acid and 1.6 g of hydrazine hydrate were used.

Examples 71 to 73

Preparation of the catalysts 25% x Y, Mo P As 0

<+>75% "Alundum" a b 12 1 0.5 x

Various catalysts according to the invention were prepared. The catalysts were prepared by the method in Example 68, using 105.9 g of ammonium molybdate, 700 ml of distilled water at 60°C and 4.0 g of ammonium arsenate dissolved in 25 ml of water. The catalytic components denoted by X and/or Y were added immediately before the addition of 5.8985% phosphoric acid and 2.5 g of hydrazine hydrate. To prepare the catalysts, the following compounds and quantities were used:

Comparative examples B to D and examples 74 to 80

The results of the experiments using catalysts of formula III in the oxidation of methacrolein to methacrylic acid are shown in Table III. The same definitions as described above were used to measure the carbon atoms in the feed and in the products.

In the same way as described above, the catalysts according to the invention can be effectively used in the production of acrylic acid from acrolein.

Claims (1)

1. Catalyst, characterized by the formula: where X is a rare earth element or a mixture thereof; Y is at least one element selected from the group consisting of Ag, Tl, Rh, Pd, Ru, Pt, Cd, Al, Au, Cu, alkaline earth metal, Cl and NH^ ; where a is 0.001 to 10; b is 0 to 10; c is 0.01 to 5; d is 0.01 to 5; x is the number of oxygen atoms required to satisfy the valence states of the other elements present; or in that the catalyst has formula I, where X is at least one element selected from the group consisting of U, Ti, Nb, Re, Pb, Zn and Ga; Y is at least one element selected from the group consisting of Cu, a rare earth element, Ag, Ta, In, Th, Cd, Tl, alkaline earth metal, NH^ , Cl, Ni, Se and Ge; and where a, b, c, d and x are as above, or the catalyst has formula I, where X is at least one element selected from the group consisting of Ag, Rh, Au and Ru; Y is at least one element selected from the group consisting of Cd, Tl, Pd, Al, Ge, Cu, Pt, Ni, alkaline earth metal, NH₂ and Cl; and where a, b, c, d and x are as above. 2. Catalyst according to claim 1, characterized in that it has formula I where X is a rare earth element or a mixture thereof; Y is at least one of Ag, Tl, Rh, Pd, Ru, Pt, Cd, Al, Au, Cu, alkaline earth metal, Cl and NH^ ; and a, b, c, d and x are as indicated above. 3- Catalyst according to claim 2, characterized in that X is cerium, erbium or a mixture of rare earth elements consisting essentially of Ce, La, Nd and Pr. 4. Catalyst according to claim 2, characterized in that X is a mixture of rare earth elements, consisting essentially of Ce, La, Nd and Pr. 5. Catalyst according to claim 2, characterized in that X is cerium. 6. Catalyst according to claim 2, characterized in that X is erbium. 7. Catalyst according to claim 2, characterized by having at least one of the metals silver, thallium and copper. 8. Catalyst according to claim 2, characterized by atYer silver. 9. Catalyst according to claim 2, characterized by atYer thallium. 10. Catalyst according to claim 2, characterized by atYer copper. 11. Catalyst according to claim 2, characterized by atber zero. 12. Catalyst according to claim 2, characterized in that a is 0.001 to 3-13- Catalyst according to claim 2, characterized by atber 0.001 to 3. 14- Catalyst according to claims 1 - 13, characterized in that it is coated on an inert support. 15- Catalyst according to claim 14, characterized in that it consists essentially of an inert carrier material with a diameter of at least 20 µm and an outer surface and a continuous coating of the active catalyst adhering strongly to the outer surface of the carrier. l6. Catalyst according to claim 15, characterized in that the active catalyst constitutes 10 - 100% by weight calculated on the inert carrier. 17- Catalyst according to claims 14 - 16, characterized in that the carrier is selected from the group consisting of silicon oxide, aluminum oxide, "Alundum", aluminum oxide-silicon oxide, silicon carbide, titanium dioxide and zirconium dioxide. 18- Catalyst according to claims 15 - 17, characterized in that the particle size of the inert carrier is 0.2 - 2 cm. 19. Procedure for the production of acrylic acid and methacrylic acid by oxidation of acrolein, respectively. methacrolein, with molecular oxygen in the vapor phase at a reaction temperature of 200 - 500°C in the presence of a catalyst, and optionally in the presence of steam, characterized in that a catalyst according to claims 1 - 18 is used as catalyst 20. Catalyst according to claim 1, characterized in that it has formula I where X is at least one element selected from the group consisting of U, Ti, Nb, Re, Pb, Zn and Ga; Y is at least one element selected from the group consisting of Cu, a rare earth element, Ag, Ta, In, Th, Cd, Tl, alkaline earth metal, NH^ , Cl, Ni, Al and Ge; and where a, b, c, d and x are as above. 21. Catalyst according to claim 20, characterized in that a is 0.001 to 3. 22. Catalyst according to claim 20, characterized by atber 0.001 to 3. 23. Catalyst according to claim 20, characterized by atber zero. 24. Catalyst according to claim 20, characterized in that X is uranium. 25. Catalyst according to claim 20, characterized in that X is titanium. 26. Catalyst according to claim 20, characterized in that X is lead. 27. Catalyst according to claim 20, characterized in that X is niobium. 28. Catalyst according to claim 20, characterized in that X is rhenium. 29. Catalyst according to claim 20, characterized in that X is zinc. 30. Catalyst according to claim 20, characterized in that X is gallium. 31. Catalyst according to claim 20, characterized in that X is titanium and niobium. 32. Catalyst according to claim 20, characterized in that X is titanium and zinc. 33. Catalyst according to claim 20, characterized by having at least one element selected from the group consisting of Cu, a rare earth element, Al and Ag. 34. Catalyst according to claim 20, characterized in that X is rhenium and Y is copper. 35. Catalyst according to claims 20-34, characterized in that it is coated on an inert support. 36. Catalyst according to claim 35, characterized in that it essentially consists of an inert carrier material with a particle diameter of at least 20 µm and an outer surface and a continuous coating of the active catalyst adhering strongly to the outer surface of the carrier. 37. Catalyst according to claim 35 or 36, characterized in that the active catalyst constitutes 10 - 100% by weight of the inert carrier. 38- Catalyst according to claims 35 - 37, characterized in that the carrier is selected from the group consisting of silicon oxide, aluminum oxide, "Alundum", aluminum oxide-silicon oxide, silicon carbide, titanium dioxide and zirconium dioxide. 39. Catalyst according to claims 35 - 38, characterized in that the particle size of the inert carrier is 0.2 - 2 cm. 40. Procedure for the production of acrylic acid and methacrylic acid by oxidation of acrolein, respectively. methacrolein, with molecular oxygen in vapor phase at a reaction temperature of 200 - 500°C in the presence of a catalyst, and optionally in the presence of steam, characterized in that a catalyst according to claims 20 - 39 is used as catalyst 41. Catalyst according to claim 1, characterized in that it has formula I where X is at least one element selected from the group consisting of Ag, Rh, Au and Ru; Y is at least one of Cd, Tl, Pd, Al, Ge, Cu, Pt, Ni, alkaline earth metal, NH^ and Cl; and a, b, c, d and x are as above. 42. Catalyst according to claim 4l, characterized in that a is 0.001 to 3. 43« Catalyst according to claim 4l, characterized by atber 0.001 to 3. 44- Catalyst according to claim 41, characterized by atber zero. 45. Catalyst according to claim 4l, characterized in that X is silver. 46. Catalyst according to claim 4l, characterized in that X is rhodium. 47.. Catalyst according to claim 4l, characterized in that X is ruthenium. 48. Catalyst according to claim 4l, characterized by X being gold. 49- Catalyst according to claim 4l, characterized by atYer cadmium. 50. Catalyst according to claim 4l, characterized in that it is coated on an inert carrier. 51. Catalyst according to claim 50, characterized in that it consists essentially of an inert carrier material with a diameter of at least 20 µm and an outer surface and a continuous coating of the active catalyst adhering strongly to the outer surface of the carrier, the coated catalyst being produced by partially wetting the carrier with water and roll the partially wet carrier in a powder of active catalyst. 52. Catalyst according to claim 51, characterized in that the active catalyst constitutes 10 - 100% by weight of the weight of the inert carrier. 53» Catalyst according to claim 51 or 52, characterized in that the carrier is selected from the group consisting of silicon oxide, aluminum oxide, "Alundum", aluminum oxide-silicon oxide, silicon carbide, titanium dioxide and zirconium dioxide. 54- Catalyst according to claims 51 - 53, characterized in that the particle size of the inert carrier is 0.2 - 2 cm. 55. Procedure for the production of acrylic acid and methacrylic acid by oxidation of acrolein, respectively. methacrolein, with molecular oxygen in the vapor phase at a reaction temperature of 200 - 500°C in the presence of steam, characterized in that a catalyst according to claims 4l - 54 is used as catalyst