NO773570L - METHOD OF PREPARING MALEIC ACID ANHYDRID - Google Patents

Description

The present invention relates to a method for the production of maleic anhydride by oxidation of n-butane, n-butenes, 1,3-butadiene with molecular oxygen in the vapor phase in the presence of a catalyst.

Belgian patent no. 828-074 relates to the use of a catalyst containing phosphorus, molybdenum, bismuth, copper, at least one of Fe, Ni, Co and K, and optionally Li, Na, Rb, Cs, Be, Mg, Ca, Sr or Ba in the preparation of maleic anhydride from butene-1, butene-2, butadiene, pentane, pentadiene, cyclopentadiene and benzene. Comparative example 4 on pages 20 and 21 of the aforementioned patent exemplifies the use of a catalyst with the formula P.^ 0QMo12Bi0 g6Cu0 54°39 6 in the oxidation of butene-1 gave a 27.9% yield of maleic anhydride, calculated on the amount of fed butene-1. French patent No. 1,601,955 relates to the use of a catalyst with the composition AO^~B2°5~M2°5-Nx°~R2° where A is Cr, Mo, W or U; B is V or Nb; M is P, As, Sb or Bi;

N is Cu, Ag, Fe, Co or Ni; R is Li, Na, K, Cs or Rb. Pre-drawn composition is 15-55 atomic %, 30-70% B, 0-15% M,

0.1-20% N and 0-15% R.

The present invention is the result of an investigation into more effective catalysts for use in the oxidation of n-butane, n-butenes and 1,3-butadiene.

The catalysts used according to the present invention are unexpectedly advantageous in the production of maleic anhydride from n-butane, n-butenes and 1,3-butadiene. Particularly advantageous yields are obtained from 1,3-butadiene or n-butenes using the catalysts according to the invention.

The present invention relates to a method for the production of maleic anhydride by oxidation of n-butane, n-butenes, 1,3-butadiene or mixtures thereof, with molecular oxygen in the vapor phase at a reaction temperature of from approx. 250°C to approx. 600°C in the presence of a catalyst, and possibly in the presence of steam, as the improvement includes the use of a catalyst with the formula:

where X is one of the halogens chlorine, bromine or iodine; and where a, b and c are numbers from 0.001 to 10; d is from 0.001 to 5; f is a positive number of oxygen atoms required to satisfy the valence states of the other elements present; that where a catalyst is used with the formula: where X is at least one element selected from the group consisting of Sn, rare earth metals, Zr, Rh, Mn, Re, Ru, Cu, Pb, Zn, Ti, Cr, Nb, Al, Ga and alkaline earth metals; and where a is a positive number below approx. 20; b and c are numbers from 0.001 to 10; x is the number of oxygen atoms required by the valence states of the other elements present; or that a catalyst with the formula is used as catalyst: where X is at least one element selected from the group consisting of As, Rb, Pd, Cd, Cs, Tl and In; and where a is a positive number below approx. 10; b is a positive number below approx. 3; 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 as catalyst:

wherein X is at least one element selected from the group consisting of Sn, rare earth metals, Ni, Zr, Ba, Fe, Rh, Mn, Re, Ru, Co and Cu; and where a is a positive number below approx. 20;

b and c are numbers from 0.001 to 10;

x is the number of oxygen atoms required by the valence steps of the other elements present.

Particularly high yields and selectivities of maleic anhydride are obtained from hydrocarbons with 4 carbon atoms in an efficient, convenient and economical way at a relatively low temperature. The exotherm of the reaction is low, allowing 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 - IV. The catalysts according to the invention have preferred limitations on their composition.

When catalysts of formula I are used, catalysts are preferred where a, b and c are numbers from 0.01 to 5> and d is from 0.001 to 1.0. Also preferred are catalysts where a is 0.5 to 1.5", catalysts where b is 0.1 to 1.0, catalysts where c is 0.1 to 1.0 and catalysts where d is 0.01 to 0.5 - Catalysts of particular interest are described where d is 0.005 to 0.1. Particularly preferred are catalysts where X is chlorine.

When catalysts of formula II are used, preferred catalysts are described where a is a positive number below approx. 12, catalysts where b is 0.01 to 5, and catalysts where c is 0.01 to 5-Very desirable results are obtained when b is 0.5 to 1.5 and c is 0.1 to 1.0. Preferred catalysts are described where each element denoted by X is separately incorporated into the catalyst. Particularly preferred catalysts are described where X is copper in combination with at least one of the remaining elements also denoted by X.

When catalysts of formula III are used, preferred catalysts are described where a is a positive number below approx. 7, and catalysts where b is a positive number below approx. 2. Highly desirable. results are obtained when a is 0.01 to 3 and b is 0.0.1 to 1.0. Catalysts of particular interest are described where X is at least one element selected from the group consisting of rubidium, cesium, thallium and indium. Excellent results are obtained1 where each element denoted by X in the catalyst formula is separately incorporated into the catalyst.

When catalysts of formula IV are used, preferred catalysts are described where a is a positive number below approx. 12;

catalysts where b is 0.01 to 5; and catalysts where c is 0.01 to 5- Particularly preferred catalysts are described where b is 0.5 to 1.5 and c is 0.1 to 1.0. Particularly desirable catalysts

is described where X is at least one element selected from the group consisting of Ni, Cu, Sn and a rare earth element.

The methods for producing the catalysts according to the invention can vary greatly. A number of methods are known to those skilled in the art. Methods for catalyst preparation such as coprecipitation, evaporative drying or oxide mixing, followed by calcination of the catalysts formed, can be successfully used.

The preferred method of preparing catalysts of formulas I to IV involves preparing the catalysts in an aqueous slurry or solution of compounds containing molybdenum and phosphorus, adding the other ingredients; and evaporating this aqueous mixture. However, when catalysts of formula II are prepared, the preferred method involves preparing the catalysts in an aqueous slurry or solution of compounds containing molybdenum, arsenic and/or phosphorus and then adding the remaining compounds. Suitable molybdenum compounds which can be used in the production of the catalysts indicated by the formulas I to IV include molybdenum trioxide, phosphormolybdic acid, molybdic acid and ammonium heptamolybdate • Excellent results have been obtained using catalysts according to the invention where at least part of the molybdenum used in the production of the catalysts is supplied in the form of molybdenum trioxide. Suitable phosphorus compounds which can be used in the preparation of the catalysts include ortho-phosphoric acid, metaphosphoric acid, triphosphoric acid, phosphorus halides and -oxyhalides. The remaining components of the catalysts can be added as oxide, acetate, formate, sulphate, nitrate, carbonate, halide or oxyhalide.

It is important to note that when catalysts of formula I are prepared, particularly preferred catalysts are those where bismuth is added in the form of a bismuth halide or -oxyhalide. It is not clearly understood where the halogen atom is located in the catalytic structure. Infrared analysis shows that the catalysts

is mostly phosphormolybdate-based and that the halogen is most likely present as a molybdenum oxyhalide.

Excellent results have been obtained by boiling phosphoric acid and molybdenum trioxide in water under reflux for approx. 1.5 to 3 hours, but commercial phosphormolybdic acid can be used effectively; wherein the remaining ingredients are added to the aqueous slurry and boiled to a thick paste, where at least one of the ingredients is added as a halide or oxyhalide; and dried at 110° to 120°C in air. However, when catalysts of formula II are prepared, the best results are obtained when the catalysts are calcined after the drying step. The catalysts with the formulas III

and IV can also be prepared by mixing the catalyst components in an aqueous slurry or solution, heating the aqueous mixture to dryness and calcining the catalysts formed.

With the exception of catalysts under catalyst II, in the preferred method according to the invention, calcination is not generally necessary to obtain the desired catalysts. However, the ca ley ring can be carried out by heating the dry catalyst components at a temperature of approx. 300°C to approx. 700°C, the calcination preferably being carried out at a temperature of 325° to 450°C. The converted hydrocarbon can be n-butane, n-butenes, 1,3_butadiene or a mixture thereof. Preferably, 1,3-butadiene, n-butenes or a mixture of hydrocarbons produced in refining streams are used. The molecular oxygen is most conveniently added as air, but synthetic streams containing molecular oxygen are also suitable. Besides the hydrocarbon and molecular oxygen, other gases can be added to the reactant feed. For example, steam or nitrogen can be added to the reactants.

The ratio between the reactants can vary greatly and is not critical. The ratio of the hydrocarbon to molecular oxygen can vary from approx. 2 to approx. 30 moles of oxygen per moles of hydrocarbon. Preferred oxygen conditions are approx. 4 to approx. 20 moles per moles of hydro-ca rbon.

The reaction temperature can vary widely and is dependent on the particular hydrocarbon and catalyst used. Normally, temperatures from approx. 250°C to approx. 600°C, with temperatures of 250° to 450°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 oxide and titanium dioxide. The catalysts are conveniently used in a fixed bed reactor using tablets, pellets or the like, or in a fluidized bed reactor using a catalyst which preferably has a particle size of less than approx. 300 |im. The contact time can be as low as a fraction of a second or so

high as 20 seconds or more. The reaction can be carried out at atmospheric pressure, positive pressure or negative pressure.

Excellent results are obtained using a coated catalyst consisting essentially of an inert support material with a diameter of at least 20 [mu]m and an outer surface and a continuous coating of said active catalyst on said inert support and which strongly adheres to the outer surface of the carrier.

When using these coated catalysts in the reaction for the production of maleic anhydride, a very low exotherm is obtained which allows better regulation of the reaction. High yields are obtained with one-off implementation, and unwanted by-products are avoided.

A special coated catalyst consists of an internal support material with an external surface and a coating of the 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 which can be of virtually any particle size and shape although a diameter greater than 20 µm is preferred. Particularly preferred in the present invention for use in a commercial reactor are the carriers which are spherical and which have a diameter of 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 to this ratio are given only by the relative ability of the catalyst and support material to make room for 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 main method for producing these catalysts is to partially wet the carrier material with a liquid. The carrier should not be wet on the outer surface of the entire mass. It should feel dry to the touch. If the support is wet, the active catalytic material may agglomerate into separate aggregates when attempting to apply the coating to the support. These partially wet supports are then brought into contact with a powder of catalytically active material, and the mixture is gently stirred until the catalyst is formed. The gentle movement is most conveniently accomplished by placing the partially wet carrier in a rotating drum or jar and adding the active catalytic material. This is done very economically.

Using the catalysts according to the invention in the production of maleic anhydride, excellent yields are obtained in a convenient reaction with low amounts of by-products.

Special embodiments

Examples 1 to 6o: Preparation of maleic anhydride using different catalysts according to the invention.

Examples 1 to 5 'Preparation of maleic anhydride using catalysts within formula I

Example 1

A catalyst with the formula Mo10Pn 00Bi^ cCu. OI-Cl,, ^/-G\-

i. ,3<£ 0,DO, 25 O,0o f was prepared as follows: A slurry was prepared from 86.49 (0.60 mol Mo) molybdenum trioxide and 7.6 g (0 .067 mol P) of 85% phosphoric acid in 500 ml distilled water, boiling with stirring for 3 hours to form phosphormolybdic acid which was yellowish-green in colour. To this slurry was added 2.5 g (0.0125 mol cu ) of copper acetate; no color change, followed by addition of 7.9 g (0.025 mol Bi) of bismuth chloride dissolved in 4.0 ml of concentrated hydrochloric acid. The mixture was boiled to dryness; dried overnight at 110°C in air. The catalyst was ground and aim for a 10/30 mesh fraction.

A portion of the catalytic particles was introduced into a

20 cm3 fixed bed reactor fitted with a 1.02 cm internal diameter stainless steel tube.

The reactor was heated to reaction temperature under a stream of air and a feed of 1,3-butadiene/air, as indicated below, was fed over the catalyst with an apparent contact time of 3 to /f seconds and the effect was assessed by collecting and analyzing the products.

The results of these tests appear in Table I. The following definitions are used when measuring the carbon atoms in the feed and in the product: Examples 2 to 5

In the same way, catalysts containing different amounts of phosphorus, bismuth, copper and chlorine are used to produce maleic anhydride from 1,3-butadiene.

In addition, different catalysts according to the invention are prepared in the same way with elements such as Mn, Rh, Ru, Ti, Zn, Re, Pb, rare earth elements, In, Sn, Zr, Cr, Pd or mixtures thereof to give desired yields of maleic anhydride from n-butane, n-butenes, 1,3-butadiene or mixtures thereof.

Examples 6 to 23: Preparation of maleic anhydride using catalysts of formula II

Oak samples 6 to 8

Various catalysts of formula II were prepared as follows:

Example 6

Mon „P, OQAs_ OK0

12 1 , 32 0 , 5 0 , 25x

A slurry consisting of 317.89 ammonium heptamolybdate, (NH 2 ) 6 Mo 2 O 2 /+.4H 2 O and 1500 ml of distilled water was boiled with stirring. To this slurry was added 11.919 ammonium arsenate, NH^H2AsO^, and the heating continued for 20 minutes; the color was white. On addition of 7.5 g of copper acetate, the color changed to light blue. To this mixture was added 22.89. phosphoric acid, H^PO^ (85% solution), and 10 minutes later 7.5 g of hydrazine was added, whereby a dark blue solution was obtained which was evaporated to a thick paste, dried overnight at 100° 120°C and ground and sieved to less than 50 mesh. The catalyst formed was calcined for 1 hour at 371°C in 40 ml/min air.

Example 7

MQ12Pl, 32AS0, 5CU0, 20Cr4°x

A slurry was prepared consisting of 105.99 ammonium heptamolybdate, 700 ml of distilled water of 60°C and 3.979 ammonium arsenate as a solution in 25 ml of water. A white precipitate formed which was heated to boiling for 45 minutes. To this mixture was added 15.2 g of chromium oxide, 15 minutes later 2.49 copper acetate was added, and half an hour later 7.6 g of 85% phosphoric acid was added. The solution was boiled to a thick paste, dried in an oven overnight at 110°-120°C and ground and sieved to below 50 mesh size. The calcination was the same as described in Example 2.

Example 8

<2>5%<Mo>12<P>i,32<A>sO,5CuO,20Cr4°x+ 75% "Alundum" (coated)

This catalyst was prepared in the same manner as described in Example 3 except that the dry catalytic particles were coated on 3.2 mm SA5223 "Alundum" beads by taking 50 g of "Alundum", partially wetting the "Alundum" with 1.8 g water and add 16.7 g of active catalyst prepared above in five equal portions. During and after each addition, the "Alundum" particles were rolled in a glass jar. The powder was evenly coated on the surface of the "Alundum" balls and the final product was dried. A hard uniformly coated catalyst was obtained which consisted of the "Alundum" support with a continuous, strongly adherent coating of the active catalyst. The catalyst was then calcined for 2 hours at 371°C in 40 ml/min of air.

Examples 9 to 23

Preparation of maleic anhydride from 1,3-butadiene

A portion of the catalytic particles prepared according to Examples 6-8 was introduced into a 20 cm<3> fixed bed reactor fitted with a 1.02 cm inside diameter stainless steel tube.

The reactor was heated to reaction temperature under a stream of air, and a feed of 1,3-butadiene/air as indicated below was fed over the catalyst with an apparent contact time of 3 to 4 seconds, and the efficiency was assessed by collecting and analyzing the products.

The results of these tests appear in table II.

Examples 24 to 50: Preparation of maleic anhydride below

use of catalysts of formula III

Examples 24 to 27

Various catalysts of formula III were prepared as follows:

Example 24

Rb_ cMo„P_ ' 0

0.5 3 Q) 33 x

An aqueous slurry was prepared by adding 55.39 molybdenum trioxide to 1 liter of boiling distilled water while stirring and boiling the slurry for approx. 2 hours. To this aqueous slurry was added 4>9985% phosphoric acid, and the color of the slurry changed to yellow. About. 200 ml of distilled water was. added to maintain a solution amount of approx. 800 ml. To this aqueous mixture was added 7.59 rubidium carbonate; the color of the slurry became bright yellow; after approx. After 30 minutes, 25 ml of distilled water was added. The catalyst was heated with stirring; boiled to dryness, and dried in air at approx. 110°C. The catalyst was ground and sieved, whereby one was obtained

10 to 30 mesh fraction.

Examples 25 to 27

Various catalysts according to the invention were prepared. These catalysts had the general formula X0 5M°3P0 33°x'<K>the catalysts were prepared by the method in example 1, except that 86.2 g of MoO3„ and 7.7 g of 85% H^PO^ were used . The element denoted by X was added after the addition of phosphoric acid. To prepare the catalysts, the following compounds and quantities were used:

After the addition of the element, x, the catalysts were boiled to dryness, dried in air, ground and sieved in the same way as described in example 1.

Examples 28 to 46

Production of maleic acid anhydride from butene-2

A portion of the catalyst particles prepared according to Examples 25-27 was introduced into a 20 cm fixed bed reactor fitted with a 1.02 cm inside diameter stainless steel tube.

The reactor was heated to reaction temperature under a stream of air and a feed of air/butene^/H^O, as indicated below, was fed over the catalyst with an apparent contact time of 1.0 to 1.5 seconds, and the efficiency was determined by collection and analysis of the products. The results of these tests appear in table III.

Examples 47 to 50

Preparation of maleic anhydride from butene-2 using supported catalysts

Various catalysts were prepared using the catalyst from Example 2 of the formula Cs^ rMo„P^ „„0 for-0.5 3 0.33 x thinned with 30% by weight of low surface area supports (ie up to 20 m /g) . These catalysts were reacted with butene-2 and air in the same manner as described above. The results of these tests appear in table IV.

Examples 51 to 60: Preparation of Maleic Anhydride Using Cata]^s£t_o£e^_ji^

Example 51

A catalyst with the formula NiQ 2Cuo 25Mo12Pl 32Rb2°x was prepared as follows: A slurry was prepared from 86.49 (0.6 mol) molybdenum trioxide and 7.7 g (0.067 mol) 85% phosphoric acid in 800 ml distilled water, was boiled with stirring for 2 hours and was yellowish-green in colour. 0.749 (0.01 mole) of nickel oxide was added to the slurry; no change in color, followed by addition of 2.499

(0.0125 mole) of copper acetate hydrate, and no change in color was observed. Boiling was continued for an additional 1.5 hours, heating was discontinued, distilled water was added to the mixture to bring the volume up to 800 mL, and the slurry was stirred overnight. The next day, 14.4 g (0.1 mol) of rubidium acetate was added, and a heavy, yellow precipitate immediately formed there. This mixture was boiled to a thick paste and dried in an oven at 110-120°C overnight. The catalyst was ground and sieved to 20/30 mesh size.

The reactor was constructed of a stainless steel tube with a 1.02 cm internal diameter. A portion of the catalyst fraction was introduced into the 20 craJ reaction zone in the reactor.

The reactor was heated to reaction temperature and a feed of air/butene-2, as indicated below, was fed over the catalyst with an apparent contact time of 1.0 to 1.5 seconds, and performance was determined by collecting and analyzing the products.

The results from the experiments appear in table V in ex-

empel 53 to 60.

Example 52

Production of maleic anhydride from 1,3-butadiene

In the same way as described above, the catalyst NiO,2CuO,25Mo12Pl,32Rb20x was reacted with air and 1,3-butadiene. An air/1,3-butadiene feed (84/1) was passed over the catalyst at a reaction temperature of 285°C with an apparent contact time of 1.5 seconds. The results from this experiment showed a yield of total acid in a simple review of 17.8%.

Claims (41)

1. Process for the production of maleic anhydride by oxidation of n-butane, n-butenes, 1,3-butadiene or mixtures thereof with molecular oxygen in the vapor phase at a reaction temperature of 2.50 to 600°C in the presence of a catalyst, characterized in that there as a catalyst, a catalyst with the formula is used: where X is one of the halogens chlorine, bromine or iodine; and where a ,. b and c are numbers from 0.001 to 10; d is a number from 0.001 to 5; f is a positive number of oxygen atoms required to satisfy the valence ratios of the other elements present; or by using as a catalyst a catalyst with the formula: wherein X is at least one element selected from the group consisting of Sn, rare earth metals, Zr, Rh, Mn, Re, Ru, Cu, Pb, Zn, Ti, Cr, Nb, Al, Ga and alkaline earth metals; and where a is a positive number below 20; b and c are numbers from 0.001 to 10; x is the number of oxygen atoms required by the valence states of the other elements present; or that a catalyst with the formula is used as catalyst: wherein X is at least one element selected from the group consisting of As, Rb, Pd, Cd, Cs, Tl and In; and where a is a positive number less than 10; b is a positive number less than 3; 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 as catalyst: wherein X is at least one element selected from the group consisting of Sn, rare earth elements, Ni, Zr, Ba, Fe, Rh, Mn, Re, Ru, Co and Cu; and where a is a positive number below 20; b and c are numbers from 0.001 to 10; x is the number of oxygen atoms required by the valence states of the other elements present. 2. Method according to claim 1, characterized in that a catalyst with the formula is used". where X is one of the halogens chlorine, bromine or iodine; and where a, b and c are numbers from 0.001 to 10; d is a number from 0.001 to 5; and f is a positive number of oxygen atoms required to satisfy the valence states of the other elements present. 3- Method according to claim 2, characterized in that a, b and c are numbers from 0.01 to 5, and d is a number from 0.001 to 1.0. 4- Method according to claim 2, characterized in that a is a number from 0.5 to 1.5. 5. Method according to claim 2, characterized in that b is a number from 0.1 to 1.0. 6. Method according to claim 2, characterized in that c is a number from 0.1 to 1^0. 7 • Method according to claim 2, characterized in that d is a number from 0.005 to 0.1. 8. Method according to claim 2, characterized in that d is a number from 0.01 to 0.5. 9. Method according to claim 2, characterized in that X is chlorine. 10. Method according to claim 2, characterized in that a catalyst with the formula is used 11. Method according to claim 2, characterized in that 1,3-butadiene is used as starting material. 12. Method according to claim 1, characterized in that a catalyst with the formula is used: wherein X is at least one element selected from the group consisting of Sn, rare earth metals, Zr, Rh, Mn, Re, Ru, Cu, Pb, Zn, Ti, Cr, Nb, Al, Ga and alkaline earth metals; and where a is a positive number below 20; b and c are numbers from 0.001 to 10; and x is the number of oxygen atoms required by the valence states of the other elements present. 13• Method according to claim 12, characterized in that a is a positive number below 12. 14- Method according to claim 12, characterized in that b is a number from 0.01 to 5- 15. Method according to claim 12, characterized in that c is a number from 0.01 to 5. 16. Method according to claim 12, characterized in that b is a number from 0.5 to 1.5, and c is a number from 0.1 to 1.0. 17- Method according to claim 12, characterized in that X is copper. 18- Method according to claim 12, characterized in that X is copper and chromium. 19- Method according to claim 12, characterized in that 1,3-butadiene is used as starting material. 20. Method according to claim 12, characterized in that the catalyst is coated on an inert carrier. 21. Method according to claim 20, characterized in that the catalyst 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 strongly adhering to the outer surface of the carrier. 22. Method according to claim 21, characterized in that the active catalyst constitutes 10 - 100% by weight of the inert carrier. 23- Method according to claim 21, characterized in that the inert carrier is selected from the group consisting of silicon oxide, aluminum oxide, aluminum oxide-silicon oxide, silicon carbide, titanium dioxide and zirconium dioxide. 24- Method according to claim 21, characterized in that the particle size of the inert carrier is 0.2 - 2 cm. 25. Method according to claim 1, characterized in that a catalyst with the formula is used: wherein X is at least one element selected from the group consisting of As, Rb, Pd, Cd, Cs, Tl and In; and where a is a positive number below 10; b is a positive number below 3; and x is the number of oxygen atoms required to satisfy the valence states of the other elements present. 26. Method according to claim 25, characterized in that a is a positive number below 7. 27- Method according to claim 25, characterized by b being a positive number less than 2. . 28- Method according to claim 25, characterized in that a is a number from 0.01 to 3, and b is a number from 0.01 to 1. 29. Method according to claim 25, characterized in that X is at least one element selected from the group consisting of Rb, Cs, Tl and In. 30. Method according to claim 25, characterized in that X is rubidium. 31. Method according to claim 25, characterized in that X is cesium. 32. Method according to claim 25, characterized in that X is indium. 33- Method according to claim 25, characterized in that X is thallium. 34- Method according to claim 25, • characterized in that the active catalytic material is placed on titanium dioxide, zirconium dioxide, aluminum oxide or silicon oxide. 35- Method according to claim 25, characterized in that n-butenes are used as starting material. 36. Method according to claim 1, characterized in that a catalyst with the formula is used: wherein X is at least one element selected from the group consisting of Sn, rare earth elements, Ni, Zr, Ba, Fe, Rh, Mn, Re, Ru, Co and Cu; and where a is a positive number below 20; b and c are numbers from 0.001 to 10; and x is the number of oxygen atoms required by the valence states of the other elements present. 37. Method according to claim 3°, characterized in that a is an integer below 12. 38. Method according to claim 36, characterized in that b is a number from 0.01 to 5. 39- Method according to claim 36, characterized in that c is a number from 0.01 to 5. 40. Method according to claim 36, characterized in that b is a number from 0.5 to 1.5, and c is a number from 0.1 to 1.0. 41. Method according to claim 36, characterized in that X is at least one element selected from the group consisting of Ni, Cu, Sn and a rare earth element.