DE1933537A1 - Process for the preparation of alkenyl acetates - Google Patents

Description

1933537 FARBENFABRIKEN BAYER AG

UVIKUSIN-hnm * Pateat department

The

Process for the production of alkenyl acetates

The invention relates to a particularly advantageous method for the production of alkenyl acetates.

It has been found that in the production of alkenyl acetates by reaction of alkenes with 4-12 carbon atoms, oxygen and acetic acid in the presence of water in the gas phase at temperatures of 100 - economical 250 ⁰ C and in the presence of palladium catalysts particularly good results obtained when a ratio of 1-100 mol of water per mol of acetic acid is established in the feedstock.

Examples of alkenes having 4-12 carbon atoms are: n-butene-1, n-butene-2, isobutene, n-pentene-1, n-pentene-2, 2-methyl-butene-1,2-methyl ! buten-2, 3-methylbutene-1 ₉ n-hexenes, iso-hexene, n-heptenes, Isoheptene, n-octenes, isooctenes, Isododecene.

The reaction can be carried out in the absence or in the presence of inerts such as nitrogen, argon, carbon dioxide or saturated aliphatic hydrocarbons. The process according to the invention can be carried out under reduced pressure, under normal pressure or elevated pressure, for example at pressures of up to 25 atU. The amounts of acetic acid, water and alkenes are chosen so that the reactants are in the gas phase under the reaction conditions. The sour

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3toffzentration at the entrance to the reactor is advantageous chosen so that one is below the explosion limit of the in the reactor located gas mixture lies.

A preferred method of working is to use the following amounts per hour:

0.5 - 50 mol alkene / l per catalyst, 0.1 - 10 mol acetic acid / mol alkene and 1-100 mol water / mol acetic acid

The palladium contained in the catalyst can be used as metal or in the form of compounds, preferably essentially are free of halogens, sulfur and nitrogen, are present, e.g. as palladium oxide, palladium acetate, palladium benzoate, Palladium propionate, palladium acetylacetonate, palladium hydroxide.

The catalyst advantageously contains alkali compounds, which consist of alkali acetates or of alkali compounds which, under the reaction conditions, are at least partially in Transfer alkali acetates, e.g. formates, propionates, hydroxides, carbonates, phosphates, borates, citrates, tartrates, lactates. Suitable Alkali compounds are compounds of potassium, sodium, lithium, rubidium and cesium.

Metals or compounds which influence the activity and selectivity of the catalyst can also be added to the catalyst. Suitable additives are, for example, metals of groups V - VIII of the periodic table and / or gold and / or copper, it also being possible for the metals to be in the form of compounds which are essentially free of halogen, sulfur and nitrogen. Examples of additives are gold, platinum, iridium, ruthenium, rhodium as metal or oxide or hydroxide, as well as oxides, hydroxides, acetates, acetylacetonates, or decomposition or conversion products thereof, the elements iron, manganese, chromium, tungsten, Molybdenum. Preferably iron compounds that are essentially free from halo

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genes, sulfur and nitrogen are used as additives.

The catalysts are preferably on supports. The following can be used as a catalyst carrier, for example: silica, natural and synthetic silicates, activated carbon, aluminum oxide, spinels, pumice stone, titanium dioxide. Preferred are those carriers that have a high chemical resistance to water and acetic acid, such as silica.

The catalyst can e.g. in the form of pills, sausages or Balls can be used, e.g. in the form of balls with a diameter of 4 - 6 mm.

The catalysts can be prepared in a wide variety of ways. Palladium can be used in the form of soluble salts, e.g. as an aqueous sodium palladate solution, impregnate onto the carrier. Then you can the catalyst with aqueous reducing agents, e.g. hydrazine, and reduce the palladium to metal. But you can also reduce with gaseous Carry out reducing agents such as hydrogen. You can impregnate the palladium compounds on the carrier, then through a treatment with alkali hydroxides in water-insoluble palladium compounds, e.g. palladium hydroxide. The catalysts obtained after the treatment described are freed from inorganic salts such as alkali chlorides by washing and then dried. In case of Conversion of the palladium salts into palladium hydroxides can be done the catalyst before or after washing with aqueous or gaseous reducing agents such as hydrazine or hydrogen or reduce ethylene to metal.

Furthermore, organic palladium compounds and, if appropriate, iron compounds can be impregnated together in an organic solvent and dried, it being possible, for example, to use drying temperatures of 50-15O ⁰ C.

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Alkali acetates can then be impregnated from aqueous solutions onto the catalysts obtained by the most varied of methods. The catalyst can then be dried at temperatures of 50 200 ^{0 C.} A partial or complete decomposition or conversion of organic palladium and iron compounds can take place under the drying conditions.

The finished catalyst advantageously contains, calculated as metal, 1-10 g Pd and 1-50 g alkali acetate per liter of catalyst. In the event that other metals or metal compounds are used as additives, the finished catalyst can contain these metals - calculated as metal - in amounts of 0.1-10 g, for example. The substances required for the production of the alkenyl acetate should preferably be free of halogen, sulfur and nitrogen compounds.

While the alkali acetates gradually leave the catalyst when small amounts of water are used, this is the case with the method according to the invention Functioning largely not the case. Another Adding the alkali acetates is therefore i.a. not necessary or only at longer intervals. If required, The addition can take place, for example, by adding small amounts of alkali acetates to the hot gas stream before the reaction begins e.g. in the form of a dilute solution of alkali acetates in water and / or acetic acid. You can do this with the solution inject in the liquid phase directly into the hot gas stream and evaporate here.

According to the process of the invention, a gaseous mixture of alkene, oxygen, acetic acid, water and optionally Inerts passed over the catalyst, the starting product containing 1-100 mol of water / mol of acetic acid. the Isolation of the alkenyl acetates formed from the gaseous The reaction product can be carried out in such a way that the re-

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Action product is cooled to temperatures below 50 ° C under the reaction pressure. A liquid phase is then obtained which separates into an upper organic and a lower aqueous phase. The upper phase consists essentially of the alkenyl acetate formed and optionally of condensed, unreacted alkene. It can also contain small amounts of water and acetic acid. The lower aqueous phase consists essentially of water and the unreacted acetic acid. It can also contain small amounts of alkenyl acetate and alkene in solution. The remaining after the cooling to below 50 ⁰ C Gas phase consists of inerts, unreacted oxygen, and optionally non-condensed unreacted alkene. It can also contain small amounts of the alkenyl acetate formed. The alkenyl acetate can be obtained in pure form from the upper organic phase, for example by distillation. The following can be fed back into the reaction: the gas phase remaining after the condensation, the proportions of alkene and acetic acid contained in the upper organic phase and the lower aqueous phase. A small part can always be removed from the gas cycle in order to avoid excessive accumulation of the carbon dioxide formed as a by-product and of inerts. This part can be returned to the reaction after the carbon dioxide and the inerts have been removed. Part of the aqueous lower phase, which corresponds to the water of reaction, can be withdrawn from the circuit.

The reaction is advantageously carried out in tubular reactors. Suitable dimensions of the reaction tubes are, for example, lengths of 4-8 m and internal diameters of, for example, 20-50 mm. The heat of reaction can advantageously be dissipated by boiling cooling liquids which surround the reaction tubes on the shell side, such as, for example, pressurized water.

The reaction can be carried out, for example, in such a way that one essentially consists of inerts, such as carbon dioxide,

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Propane, nitrogen and argon and oxygen if necessary Cycle gas existing in alkene passes under pressure through an evaporator which contains acetic acid and water and optionally alkene, and that by suitable choice of the composition of the liquid product in the evaporator and the temperature in the Evaporate the cycle gas with the desired amount of acetic acid at the desired ratio of 1-100 mol water / mol acetic acid The gas mixture is then heated under pressure to the reaction temperature and the temperature required for the reaction Oxygen added. Alkenes can be in liquid or gaseous form from the vaporizer or the cycle gas after the vaporizer be admitted.

The inventive method allows in economically advantageous Way the production of alkenyl acetates by reacting alkenes with 4-12 C-atoms with oxygen and acetic acid. The alkenyl acetates are obtained with good space-time yields and good selectivities. As by-products are only small amounts of carbon dioxide are formed. The catalysts have a long service life under the conditions according to the invention. A decrease in their activity and selectivity is not noticeable even after several hundred hours.

example 1

H · About 1 liter of a catalyst which contains 3.3 g of Pd as metal and 30 g of potassium acetate on 1 liter of silica support with an inner surface of 120 m / g in the form of spheres 5 mm in diameter, and which is in a Reaction tube with a length of 2.5 m and an internal diameter of 25 mm are passed every hour in gaseous form at 150 ⁰ G and a pressure of 1 atm:

2 mol of 2,4,4-trimethylpentene-i 2 mol of acetic acid
20 mol of water 1.5 mol of oxygen 9 mol of nitrogen

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The gaseous reaction product yvird to 20 ⁰ C cooled and depressurized to atmospheric pressure. A gas phase consisting essentially of nitrogen and oxygen forms, which also contains small amounts of carbon dioxide and 2,4,4-trimethylpentene-1, and an upper organic phase essentially consisting of 2,4,4-trimethylpentene-1 and alkenyl acetate and a lower aqueous phase consisting essentially of water and acetic acid. It is determined by analysis that the alkenyl acetate formed consists of pure 1-acetoxy-2-methylene-4,4-dimethylpentane. The used 2,4,4-trimethyl-1 had implemented $ 24>, the unreacted 2,4,4-trimethyl-1 had $ 94> to 1-acetoxy-2-methylene-4,4-dimethyl-pentane and $ 6 converted to carbon dioxide.

Example 2

The procedure was as in Example 1, but the following starting products passed over the catalyst:

10 moles of isobutene

2 moles of acetic acid

20 moles of water

1.5 moles of oxygen.

The gaseous reaction product was ^{cooled to 20 °} C. and let down to normal pressure. A gas phase consisting essentially of isobutene and oxygen and containing small amounts of carbon dioxide was formed, an upper organic phase consisting essentially of alkenyl acetate and an aqueous lower phase consisting essentially of water and acetic acid; analysis showed that the alkenyl acetate is pure methallyl acetate. The used isobutene had implemented $ 8>, had the unconverted isobutene is 94 # to methallyl and 6 1 "converted to carbon dioxide.

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Claims (6)

Patent claims ** 1) J process for the preparation of alkenyl acetates by Umset- "iung of alkenes with 4 - 12 carbon atoms, oxygen and acetic acid in the presence of water in the gas phase at temperatures from 100 to 250 ⁰ C and in the presence of palladium catalysts, characterized in that a ratio of 1-100 mol of water per mol of acetic acid is used in the starting product. 2) Method according to claim 1), characterized in that the Catalyst Additions of alkali acetates or alkali compounds, which under reaction conditions are at least partially in Convert alkali acetates, contains. 3) Method according to claim 1) and 2), characterized in that the. Catalyst, calculated as metal, 1 - 10 g Pd, as well as Contains 1-5Og alkali acetate per liter of catalyst. 4) Method according to claim 1) to 3), characterized in that the catalyst has additions of metals or metal compounds from group V to VIII of the periodic table and / or gold and / or copper. 5) Method according to claim 1) to 4), characterized in that the catalyst contains additions of iron compounds. 6) Method according to claim 1) to 5), characterized in that the gaseous reaction product is ^{cooled under pressure to a temperature below 50 0} C and separated in a separator into a gaseous phase, a liquid upper phase and a "liquid lower phase . Le A 12 339 - 8 - 009883 / 2.206