DE2110876A1 - Process for the production of acetic acid by the catalytic oxidation of olefins in the gas phase - Google Patents

Description

? 11 Π8 7fi

PATENT LAWYERS ^ '' ^UO 'O

dr. W.Schalk dipl.-ing.P. Wirth dipl.-ing.G. Dannenberg DR. V. SCHMIED-ICOWARZIK · DR. P. WEINHOLD · DR. D. GUDEL

6 FRANKFURT AM MAIN CR. ESCHENHEIMER STRASSE 39

Case B 1267 + B 1270
Wd / CW

MONTECATINI EDISON SpA
Foro Buonaparte, 31
20100 Milan (Italy)

Process for the production of acetic acid by catalytic oxidation of olefins in the gas phase.

The present invention relates to a process for the production of acetic acid by catalytic oxidation in the vapor phase with molecular oxygen or oxygen-containing gases from unsaturated hydrocarbons with four carbon atoms .

Acetic acid is generally obtained either by the carbonylation of methanol or by the oxidation of acetaldehyde, butane and higher carbons. ^r asserstoffen prepared.

It is also known that it is possible to oxidize lower olefins catalytically in the gas phase to acetic acid. In in this case, however, generally unsatisfactory results are obtained because a high percentage of the converted Hydrocarbons are lost in the form of carbon oxides.

It has now been found that, surprisingly, using of the catalysts by the process according to the invention

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is possible unsaturated hydrocarbons with four carbon atoms to oxidize in a very selective manner to acetic acid, the combustion is kept within narrow limits.

The present invention now relates to a process for the preparation of acetic acid from one or more unsaturated acids Hydrocarbon oil with four carbon atoms by oxidation with oxygen or oxygen-containing gases, which thereby is characterized in that the reaction in the presence of a catalyst, the molybdenum, tin, oxygen and optionally Contains vanadium, is carried out, the amount of hydrocarbon between about 0.5 and 10 Vol .- ^, based on the Reaction mixture, and the amount of oxygen about 5 to 40 vol .-? 4 based on the reaction mixture, is and at a temperature of about 150 ° to 400 ° C and a contact time of about 0.1 to 20 seconds is worked.

In the process according to the invention, butene and isobutene, but also mixtures of these hydrocarbons, can be used of mixtures that are by-products in thermal cracking processes are obtained, can be used as starting compounds, the results obtained being particularly advantageous are.

The catalysts used in the process according to the invention contain mixtures of molybdenum, tin and optionally Vanadium oxides or, more generally, compounds of molybdenum, tin, oxygen and optionally vanadium, where The atomic ratios between molybdenum, tin and vanadium correspond to the following empirical formula:

^Mo a ^Sn b ^V c

a + b + c = 100, and

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a from 5 to 90

b from 5 to 80

c varies from 0 to 90.

Various processes can be used to produce the catalyst, which are already known per se, which lead to mixtures of molybdenum, tin and vanadium oxides or, more generally, lead to compounds of molybdenum, tin, oxygen and optionally vanadium, the atomic ratios of Mo / Sn / V correspond to the values given above.

For example, in the case of catalysts containing only molybdenum, tin and oxygen, a concentrated aqueous solution of ammonium paramolybdate (NI-L ·) g Mo ~ Op. · 4HpO with heating of an aqueous solution of Sn Clr. 5HpO mixed in with ground. The solution thus obtained is then neutralized with ammonia and slowly evaporated to dryness with continued stirring. On the other hand, in the case of the catalyst, which contains molybdenum, tin, vanadium and oxygen, concentrated aqueous solutions containing ammonium paramolybdate and ammonium metavanadate can be mixed together in suitable proportions with heating, for which purpose an aqueous solution of SnCl ^ .5HpO is then added. The solution thus obtained is neutralized with ammonia and slowly evaporated to dryness with stirring.

In any case, the resulting dry residue at a temperature of about 110 C vird dried, and then in the air or in a nitrogen stream for about 4 to 20 hours at temperatures between about 350 and 600 ⁰ C, preferably calcined between about 450 and 55O ⁰ C .

An alternative method of making the catalyst is to generate a precipitate of molybdenum (and Vanadium acids from an aqueous solution of ammonium paramolybdate (or of paramolybdate + metavanadate) with nitric acid and a precipitate of tin hydroxides from tin

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Ammonia. The precipitates obtained are after filtering and washing thoroughly with cold water in water suspended and slowly evaporated to dryness with vigorous stirring. The dry residue is then treated in the same way as in the previous embodiment.

The catalyst can be either unsupported or with a suitable one Carriers such as silicon oxide ("silica") »aluminum oxide, silicon oxide-aluminum oxide, silicon carbide, pumice stone, be used.

The process according to the invention can be carried out in any type of reaction vessel which is used for carrying out the oxidation is suitable in the gas phase. Both reaction vessels with a fixed bed and with a fluidized or fluidized bed can be used · The reaction temperature is preferably between about 180 ° and 350 ° C.

The reaction can be carried out at atmospheric pressure or with the application of pressure (e.g. up to about 15 kg / cm abs.) to specifically increase the production of acetic acid.

The contact time, which is defined as the ratio of the bulk catalyst volume to the volume of gas which is supplied per unit of time under reaction conditions, is preferably between about 0.5 and 15 seconds.

The starting amount of the unsaturated hydrocarbon or hydrocarbons is preferably not more than about 5 % by volume, based on the reaction mixture.

The oxygen required for the hydrocarbon oxidation process according to the invention can be 100 percent pure Form, but if there are no reasons for a specific concentration, the use of air is preferred .

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_ 5 -

The amount of oxygen is preferably about 7 to 30% by volume based on the reaction mixture.

The oxidation is preferably carried out in the presence of one or more diluents, such as nitrogen, carbon dioxide, water vapor, saturated hydrocarbons and the like. In particular, when a high percentage of steam is present, it is possible to work with highly concentrated oxygen, without the risk of explosion.

The inventive method is particularly advantageous that one fractions of unsaturated hydrocarbons with four Carbon atoms obtained in both refining cracking processes and steam cracking processes, and which are known to be obtained are available in considerable quantities, can be used directly to obtain such a sought-after product as acetic acid .

The following examples serve to illustrate the invention without restricting it. The terms "conversion" used and "selectivity" each express:

Olefin conversion in % -

Moles of olefin feed - moles of unreacted olefin ^

Moles of olefin feed

Selectivity d ^ -s product in % =
Gram atoms of carbon in the product
Gram atoms of carbon in the converted olefin

χ 100

In the examples below, the catalysts were used examined in reaction vessels with a fixed bed, and the reaction products were analyzed by direct gas chromatography with the exception of maleic acid, which was determined by potentiometric titration in the condensed fraction.

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The reaction products obtained according to the invention can in addition to acetic acid, butadiene, formaldehyde, acetaldehyde, propionaldehyde, Acrolein, methacrolein, acetone, propionic, acrylic, methacrylic and maleic acids include.

In the following examples, compounds with a selectivity below i% are not listed.

example 1

200 g of ammonium paramolybdate and 138 g (NIL) ₂ SnClg were dissolved in water while heating. After adding dilute ammonia (10 $), the solution was slowly evaporated to dryness with vigorous stirring. The residue was dried at 110 ° C. and then heated to 450 ° C. for eight hours in a stream of air.

The catalyst obtained in this way, with a Mo / Sn atom ratio of 75:25, was charged with a feed mixture of 1.1% by volume of 2-butene, 14% by volume of oxygen, 34.9% by volume of nitrogen and 50% by volume .-Jo steam at a temperature of 210 ⁰ C, a pressure of. 1.2 kg / cm abs. and a contact time of six seconds. The following results were obtained:

Butene conversion = 95.2 %

Acetic acid selectivity = 54.9 %

Acetaldehyde selectivity = 10.6 %

Acetone selectivity = 1.9 %

CO + CO ₂ selectivity = 31.2 %

Example 2

An aqueous solution of 240 g of SnCl ^. 5H ₂ O was mixed with an aqueous solution containing 240 g of ammonium paramolybdate while heating. After addition of diluted ammonia (10? 0 the solution was slowly evaporated with stirring to dryness. The residue was heated for four hours in an oven at 130 ⁰ C getrock · »· net and in an air stream at 450 ° C.

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The gaseous mixed breed of 4 vol .-% 2-butene, 52 vol .-% air and 44 vol 9i steam was thus obtained catalyst having a Mo / Sn atomic ratio of 50: 50 at a temperature of 350 ⁰ C. , a pressure of 1.2 kg / cm abs. and a contact time of two seconds.

The following results were obtained:

Butene conversion = 100 %

Acetic acid selectivity = 49.5 %

Acetaldehyde selectivity = 1.0 %

Maleic acid selectivity = 4.5 %

CO + C0 ₂ selectivity = 44.2 % i

Example 3

An aqueous solution containing 25 g of ammonium paramolybdate and 155.5 g of (NH _{4) 2} SnClg was added to 281 g of silica sol after mixing with dilute ammonia.

After the solution had been slowly evaporated to dryness with vigorous stirring, the residue was ^{dried in an oven at 130 ° C. and heated to 450 °} C. for eight hours in a stream of air. . <

The gaseous mixture of 1 vol .-? S 2-butene, 14 vol .-% oxygen g material, 35 vol 5ό nitrogen and 50 vol .-% of steam was thus obtained catalyst having a Mo / Sn atomic ratio of 25 ί 75 at a temperature of 300 C, a pressure of 1.2 kg / cm abs. and a contact time of Man, the following results were obtained:

ρ.

kg / cm abs. and a contact time of four seconds.

Butene conversion = 88.6 %

Acetic acid selectivity = 53.7 %

Acetaldehyde selectivity 8.5 %

Acetone selectivity = 1.8 %

Maleic acid selectivity = 1.4 %

CO + CO ₂ selectivity = 33.1 %

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Example 4

An aqueous, 99.2 g of SnCl ^. 5H ₂ O containing solution was mixed with an aqueous solution containing 50 g of ammonium paramolybdate and 33 g of ammonium metavanadate. After 364 g of silica sol (30%) had been added , ammonia (10%) was added until a basic pH was obtained. The solution was then slowly evaporated to dryness with vigorous stirring. After drying at 11O ⁰ C in an oven the RH
heated for a long time in a stream of air.

at 11O ⁰ C in an oven, the residue was at 500 ⁰ C for eight hours

The catalyst thus obtained, with a Mo / Sn / V atomic ratio of 33.3: 33.3: 33.3, was fed with a feed mixture of 33.9% by volume # 2-butene, 10% by volume oxygen, 43 % , 1% by volume nitrogen and 43% by volume steam were investigated. The reaction temperature was 320 ° C. and the pressure was 1.2 kg / cm abs. and the contact time three seconds.
The following results were obtained:

Butene conversion = 97.0 %

Acetic acid selectivity = 49.3 %

Acetaldehyde selectivity = 10.8 %

Maleic acid selectivity = 2.8 %

CO + COg selectivity = 34.6 %

Example 5

35 g SnCl. . 5H ₂ O, 61.5 g of tartaric acid and 9.1 g of ^v p ^ 5 were dissolved in 65 ecm of water while warming. Separately, 17 g of ammonium paramolybdate were dissolved in 20 ecm of water. These solutions were mixed together and reduced in volume to impregnate 115.5 grams of silica in microsphere form. After drying for ^{12 hours at 90 °} C. and a further 12 hours at 200 ^° C., the catalyst was activated in a stream of air ^{at 450 ° C. for eight hours.} The catalyst thus obtained had the following atomic ratio: Mo / Sn / V = 33.3: 33.3: 33.3.

The experiment was carried out by adding a gaseous mixture of 1.1 YpI .-% 2-butene, 14 vol.-56 oxygen, 34.9 vol .-%

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Nitrogen and 50 vol .-% steam at a temperature of 270 ° C and a contact time of four seconds over the catalyst.

The following results were obtained:

Butene conversion = 99.0 %

Acetic acid selectivity = 56.1 %

Acetaldehyde selectivity = 7.0 % .

Acrylic acid selectivity = 1.4 %

Maleic acid selectivity = 4.5 %

CO + CO ₂ selectivity = 29.3 %

Example 6

20 g of ammonium paramolybdate and 123 g of ammonium metavanadate were dissolved in boiling water. An aqueous, 122 g of SnCT ^. The solution containing 5H ₂ O was mixed with the solution thus obtained. After ammonia had been added until a basic pH was reached, the solution was slowly evaporated to dryness and the product obtained ^{was activated at 500 °} C. in a stream of air for eight hours. The Mo / Sn / V atomic ratio of the catalyst obtained was: 7.7: 23.1: 69.2.

The experiment was carried out with a feed mixture of 3.4 vol .- ^ 2-butene, 11 vol .-% O ₂ , 34.6 vol .-% nitrogen and 51 vol .-% steam at a temperature of 300 C, a Pressure of 1.2 kg / cm l abs. and a contact time of four seconds.

The following results were obtained:

Butene conversion - 93.3 %

Acetic acid selectivity = 51.5 %

Acetaldehyde selectivity = 6.3 %

Maleic acid selectivity = 3.5 %

CO +. C0 ₂ selectivity = 36.2 %

Example 7

An aqueous, 11 g ammonium paramolybdate, 22 g ammonium metavanadate and 197 g SnCl ^. 5H _o 0 containing solution was 184 g

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Silica sol ($ 30) mixed in and made basic by adding ammonia. After the solution had been slowly evaporated to dryness, the residue was activated in a stream of air ^{at 450 ° C. for eight hours.}

A gaseous mixture of 2 % by volume of 2-butene, 10% by volume of oxygen, 38% by volume of nitrogen and 50% by volume of steam was passed over the catalyst prepared in this way with a Mo / Sn / V ratio = 7 , 7: 64.2: 23.1 at a temperature of 240 ⁰ C, a pressure of 1.2 kg / cm abs. and · a contact time of six seconds.
The following results were obtained:

Butene conversion = 92.6 %

Acetic acid selectivity - = 61.4% acetaldehyde selectivity = 6.2% CO + C0 ₂ selectivity = 29.7 %

The same catalyst was with a gaseous mixture of 1 vol .-% 6 2-butene, 20 vol .-% oxygen, 29 vol .-% nitrogen and 50 vol .-% steam at a temperature of 210 ⁰ C, a pressure

2
of 1.2 kg / cm abs. and a contact time of six seconds.

The following results were obtained:

Butene conversion = 46.1 %

Acetic acid selectivity - 66.5 %

Acetaldehyde selectivity = 7.4 % .

CO + C0 ₂ selectivity = 25.0 %

Example 8

After an aqueous, 17 g ammonium pararaolybdate, 199 g ammonium metavanadate and 33 g SnCl ^. 5H ₂ O containing solution was made basic with ammonia, the solution was slowly evaporated to dryness and the residue was then ^{activated at 450 0} C for eight hours in a stream of air. The catalyst obtained in this way with a Mo / Sn / V ratio of 5: 5: 90 was with a loading

10 9 8 4 1/19 4 1

Schickungsmischüng of 4.1 vol % 2-butene, 10.6 vol .-% oxygen, 40.3 vol .-% nitrogen and 45 vol .-% steam at 300 C, a pressure of 1.2 kg / cm abs. and a contact time of four seconds.
The following results were obtained:

Butene conversion «92.5% Acetic acid selectivity = 51.6 % Acetaldehyde selectivity = 5.6 % Acrylic acid selectivity = 1.6 % CO + CO ₂ selectivity = 39.2 % Example 9

An aqueous 100 g ammonium paramolybdate, 66 g ammonium metavanadate and 66 g SnCl. . Solution containing 5HpO was basified by the addition of ammonia and slowly evaporated to dryness. The residue was heated for eight hours, after drying in an oven at 110 ° C in a stream of air at 450 ⁰ C. The catalyst thus obtained had a Mo / Sn / V atomic ratio of 42.8: 14.3: 42.9.

A gaseous mixture of 4.5 vol -.% 2-butene, 13.5 vol .- o oxygen, 32'Vol .- o nitrogen and 50 vol JS vapor was passed over the catalyst at a temperature of 310 ^0? C, a pressure of 1.2 kg / cm and a contact time of four seconds. The following results were obtained:

Butene conversion = 91.7 %

Acetic acid selectivity = 44.9 %

Acetaldehyde selectivity = 6.3 %

Methacrolein selectivity = 2.1 %

Acrylic acid selectivity = 3.3 %

Maleic acid selectivity = 7.1 %

CO + C0 ₂ selectivity = 34.0 %

A catalyst identical to the above-mentioned composition

m stick 41/19

but which in a nitrogen stream at 450 C for eight hours

activated for a long time was examined under the same conditions • and the following results were obtained:

Butene conversion = 84.7 %

Acetic acid selectivity = 48.5%

Acetaldehyde selectivity = 7.4%

Methacrolein selectivity = 2.5%

Acrylic acid selectivity = 1.6%

Maleic acid selectivity = 3.4%

CO + C0 ₂ selectivity = 33.8%

Example 10

An aqueous, 66.5 g ammonium paramolybdate, 14.7 g ammonium metavanadate and 395 g SnCl ^. Solution containing 5H ₂ O was basified by the addition of ammonia (10%) and slowly evaporated. The residue, which had been dried once in an oven at 110 ° C., was ^{heated to 500 °} C. in a stream of air for eight hours. The Mo / Sn / V atomic ratio of the catalyst obtained was 23.1: 69.2 × 7.7.

About the thus prepared catalyst, a gaseous mixture of 1 vol .-% 2-butene, 14 parts by volume of 96 oxygen, 35 vol .-% nitrogen and 50 vol .-% steam at a temperature of 210 ⁰ C.

a pressure of 1.2 kg / cm abs. and a contact time of six Seconds, with the following results:

Butene conversion = 99.0%

Acetic acid selectivity = 65.0%

Acetaldehyde selectivity = 11.1%

Acetone selectivity = 1.0%

CO + C0 ₂ selectivity = 22.0%

Example 11

Using 200 g of ammonium pararaolybdate, 7.4 g of ammonium, metavanadate and 22 g of SnCl ^. 5H ₂ O, a catalyst was prepared according to the procedure described in Example 6.

109841

The catalyst thus obtained, having a Mo / Sn / V atomic ratio of 90: 5: 5, was fed with a feed mixture comprising 3.1 vol. # 2-butene, 31 vol. # 2 air, 13.9 vol Containing nitrogen and 52% by volume of steam, " ^{examined at a temperature of 3A-O 0} C, a pressure of 1.2 kg / cm abs. And a contact time of four seconds.
The following results were obtained:

Butene conversion = 68.1 %

Acetic acid selectivity = 46.0 %

Acetaldehyde selectivity = 7.2 % *

Acetone selectivity = 1.6 % λ

Methacrolein selectivity - 3.2 %

Acrylic acid selectivity = 2.0%

Maleic acid electivity = 4.4 %

Butadiene selectivity = 1.9 %

CO + CQ ₂ selectivity = 32.7 % ■

Example 12 . ·

By mixing an aqueous, 67 g ammonium paramolybdate and 15 g ammonium metavanadate containing solution, and an aqueous, 133 g SnCl ^. Containing 5H ^ O and 410 g SJUkasol (30%) Solution, a catalyst was prepared according to the method described in Example 4.

The Mo / Sn / V catalyst obtained in this way had the following atomic ratio: 42.7: 43: 14.3.

The experiment was carried out by adding a gaseous mixture of 4% by volume of 2-butene, 12% by volume of oxygen, 29% by volume of nitrogen and 55% by volume of steam at a temperature of 290 ° C, a Pressure of 1.2 kg / cm abs. and passed over the catalyst for a contact time of six seconds. The following results were obtained.

Butene conversion = 90.0 %

Acetic acid selectivity = 46.7 %

1 0 9 8 A 1/1 9 U 1

2110878

Acetaldehyde selectivity = 14.2 %

Maleic acid selectivity = 2.3 %

CO + CO selectivity = 35.3 %

Example 13

An aqueous solution containing 25 g of ammonium paramolybdate and 49.5 g of ammonium metavanadate was mixed with a solution containing 149.2 g of SnCl, ^ 5HpO. Dilute ammonia (10%) was added and the solution was evaporated to dryness. The residue, which had been dried in an oven at 110 ° C once, "was activated for 16 hours at 400 ⁰ C in an air stream.

For the catalyst prepared in this way with a Mo / Sn / V atomic ratio of 14.3: 43 ": 42.7 was a gaseous mixture containing 1.1 vol .- $ 2-butene, 14 vol .- # oxygen , 34.9 vol .- # nitrogen and 59 vol .-? O steam, at a temperature of 190 ^° C., a pressure of 1.3 kg / cm abs. And a contact time of six seconds Results.

Butene conversion = 98.0 %

Acetic acid selectivity = 62.6 %

Acetaldehyde selectivity = 10.6 %

Acetone selectivity = 1.4 %

CO + CO ₂ selectivity = 24.5 %

During another experiment, a gaseous mixture of 1 vol .-% 2-butene, 30 vol .-% oxygen, 39 vol .-% nitrogen and 30 vol .-? 6 steam passed into the reaction vessel and at a temperature of 180 ° C, a pressure of 1.2 kg / cm abs. and a contact time of eight seconds. The following results were obtained.

Butene conversion = 97.0 %

Acetic acid selectivity = 61.4 %

Acetaldehyde selectivity "= 11.3 %

1 0 9 8 A 1/1 9 4 1

Acetone selectivity = 1.5 %

CO + C0 ₂ selectivity = 22.4 %

Example 14

A catalyst identical to the composition described in Example 4 ^{was activated at 58O 0} C in a stream of air for eight hours. It was with a feed mixture of 4 vol. 96 isobutene, 52 vol .-? Air and 44 vol. 96 steam at a temperature of 350 ° C., a pressure of 1.2 kg / cm · abs. and a contact time of about two seconds. The following results were obtained:

Isobutene conversion = 89.0 %

Acetic acid selectivity = 33.8 %

Acetaldehyde selectivity = 2.2%

Acetone selectivity = 5.3 %

Methacrolein selectivity = 10.2 %

Maleic acid selectivity = 1.8 %

CO + CO ₂ selectivity h 46.3 %

Example 15

A catalyst prepared according to the method described in Example 3 was investigated with a mixture of air, steam and 2-butene at 34-0 ^° C. and a contact time of 4 seconds, the following results being obtained.

Butene conversion = 71.4 %

Acetic acid selectivity = 46.1 %

Acetaldehyde selectivity 7.4 %

Acetone selectivity = * 2.0%

Acroleinselßktivität = 1, 6%

Methyl ethyl ketone selectivity = 1.2 96

Butadiene selectivity = 2.3 %

CO + C0 ₂ selectivity = 38.3%

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Example 16

The catalyst, as it was described in Example 12, was examined with a mixture of 2-butene, oxygen, nitrogen and steam at 290 ^° C. and a contact time of six seconds, the following results being obtained;

Butene conversion = 90 %

Acetic acid selectivity = 46.7 %

Acetaldehyde selectivity - 14.2 %

Maleic acid selectivity = 2.3 %

CO + COg selectivity = 35.3 ⁰ A

Example 17

The catalyst described in Example 13 was examined with a mixture of 2-butene, oxygen, nitrogen and steam at 220 ^° C. and a contact time of twelve seconds. The following results were obtained:

Butene conversion == 90 %

Acetic acid selectivity = 50 %

Acetaldehyde selectivity = 12.2 %

Acetone selectivity = 1.8 %

CO + eOg selectivity = 35.0 %

1Θ9841 / 1

Claims (11)

Claims 1. Process for the production of acetic acid by oxidation one or more unsaturated hydrocarbons with 4 carbon atoms with oxygen or oxygen-containing gases, characterized in that the reaction with an amount of hydrocarbon between about 0.5 and 10% by volume and with an amount of oxygen between about 5 and 40% by volume, each based on the reaction mixture, at a temperature between etv / a 0.1 and 20 seconds and in the presence of a catalyst made of molybdenum, tin, oxygen and optionally vanadium, which has ^{been activated by heating at a temperature between about 350 and 600 0} C ', the atomic ratio of. ... Mo / Sn / V corresponds to the sum formula Mo ₀ Sn-μ, V -, where a + b + C- = 100 ^: and a from about 5 to 90, b from about 5 to 80, and £ vary from about 0 to 90. '· 2. The method according to claim 1, characterized in that a catalyst is used on a carrier. 3. The method according to claim 1 and 2, characterized in 'that 1-butene, 2-butene or isobutene is used as the unsaturated hydrocarbon ■. - - "-" ■ 4. The method according to claim 1 to 3, characterized in that a mixture of unsaturated hydrocarbons is used, which consists of a fraction of unsaturated hydrocarbons with about 4 carbon atoms, which obtained as a by-product of chemical and petrochemical processes. 5. The method according to claim 1 to 4, characterized in that e
will. that a temperature between about 180 and 35O ⁰ O is applied 6. 'The method according to claim 1 to 5, characterized in that that a contact time between about 0.5 and 15 seconds is used. 7. The method according to claim 1 to 6, characterized in that it is either at atmospheric] pressure or higher Pressing is carried out. 8. The method according to claim 1 to 7, characterized in that air is used as the oxygen-containing gas. 9. The method according to claim 1 to 8, characterized in that an amount of oxygen in the reaction mixture between about 7.7 and 30 vol. $ Is used. 10. The method according to claim 1 to 9 »characterized in that it is in the presence of one or more diluents is carried out. 11. The method according to claim 1 to 10, characterized in that that nitrogen, carbon dioxide, steam and / or a saturated hydrocarbon are used as inert diluents will. 109841/1941