DE1443906B2 - Process for the preparation of alkenyl esters - Google Patents

Description

A process for the preparation of alkenyl esters has been found which is characterized in that one monoolefins with oxygen and higher organic acids than acetic acid in the presence of a palladium metal catalyst, which is applied to supports containing silica or aluminum oxide, is converted at an elevated temperature.

Suitable olefins for the process according to the invention are aliphatic monoolefins, such as ethylene and propylene or butylenes. It is advantageous to use the olefins in high concentration, e.g. B. ethylene as 99% ethylene, but they can also z. B. used in a mixture with paraffinic hydrocarbons with which they often arise in petroleum refining processes.

Mono- or polybasic acids can be used as acids for the process according to the invention, z. B. propionic acid, butyric acids, adipic acid, but also aromatic acids such as benzoic acid or Phthalic acids, such as o-, m- or p-phthalic acid. Here too it is advisable to use the acids in concentrated form. The molar ratio of the acids to the Olefins or the alkylbenzenes is advantageously about 0.2 to 3.0: K ''

Examples of the organic esters obtained according to the invention are: vinyl propionate, vinyl butyrate, vinyl benzoate, Divinyl adipate, divinyl o-phthalate, divinyl pphthalate, Allyl propionate, allyl butyrate, allyl benzoate, Di-allyl-m-phthalate, methallyl propionate, methallyl butyrate or di-methallyl-o-phthalate.

The palladium-metal catalyst used according to the invention is applied to a carrier. An aluminum oxide carrier is used as the carrier, expediently those in which the aluminum oxide is partially or completely in the form of spinel. Aluminum silicates or silicas can also be used as carriers. If aluminum oxide itself is used as a carrier, it is advisable to use carriers which have been produced from active aluminum oxide by thermal treatment and have internal surfaces between 1 and 100 m ² / g, preferably 10 and 80 m 2 / g. In the spinel catalysts, the aluminum oxide is advantageously at least 20%, if possible 40% and more, as spinel.
Such carriers have proven to be very suitable,

ίο in which the aluminum oxide is practically completely present as spinel and which preferably have internal surfaces of 10 to 80 m ² / g. Lithium, beryllium and magnesium in particular have proven themselves as spinel-forming metals. Zinc, manganese, iron, cobalt and nickel, with lithium in the monovalent form and all others in the divalent form. The spinel catalysts can be produced in various ways. One can, for example, start from highly active aluminum oxide in lump form, which has an internal surface area of 200 to 350 m ² / g. This lumpy aluminum oxide, for example in the form of sausages, pills or balls, can be impregnated with an aqueous salt solution of the spinel-forming metal to be used or, in the case of lithium, with an aqueous hydroxide solution and the impregnated catalyst can be dried. As far as one has impregnated with salts, it is expedient to perform this above by heating at 250 to 650 ⁰ C, if appropriate with addition of oxygen-containing or water vapor-containing gases into oxides. Then, heating is performed to effect the Spinellbildung'eine at 900 to 1300 ⁰ C, z. B. for a period of 2 to 20 hours. If lithium is used as the spinel-forming metal, it is possible to soak several times with the hydroxide solution to bring about complete spinel formation with intermediate drying. If you have made the soaking with salts, you can also soak several times with the interposition of the decomposition stage for the salt. Another way of working is to start from fine-grain aluminum oxide with a large internal surface and to add the solution of the metal compound to this, whereby you can add as much solution of the metal compound as the intended degree of conversion into spinels. After drying, the mass can be deformed by suitable means, e.g. B. pressed into strands or pills, optionally with the addition of lubricants and - if salts were used - glow as described above with the interposition of the decomposition stage. Another production possibility consists in precipitating the 'metal aluminates from aqueous solutions of aluminum salts, for example sodium aluminate, by adding compounds of the spinel-forming metals, removing them from adhering soluble salts by washing and the spinel precursor obtained by thermal treatment in spinel convict. It is also possible to make mixing spindles by using several spinel-forming metal compounds. The level of the annealing temperatures and the duration of the annealing process are different for the individual spinel precursors, but it is easy to determine by means of preliminary tests which conditions must be met in order to obtain the desired porosity of the finished catalyst carrier.

When using silica or aluminum silicates as a catalyst support, it is more advantageous to

wise from preliminary products with a large internal surface (above 200 m ² / g) and converts them through thermal treatment into products with internal surfaces between 20 and 80 m ² / g.

The palladium can be on the support in amounts of e.g. B. 0.1 to 10 percent by weight, advantageously 0.5 to 5 percent by weight. The palladium can be applied to the carrier, by z. B. soaked with an aqueous palladium salt solution and by reduction, for example with hydrazine hydrate, in alkaline solution the palladium precipitates on the carrier. But you can also the palladium, for example the nitrate, or the organic salts, for example the acetate, through Conversion of reduction with hydrogen at elevated temperature into the metal.

In a particularly preferred embodiment, the reaction in the presence of alkali or Carry out alkaline earth salts of the relevant organic acids used. Mainly the lithium, sodium and potassium salts of organic acids are suitable. As far as one can see the reaction in carries out the liquid phase, it is appropriate to apply the mentioned organic salts in the organic acid to dissolve. 0.2 to 2 molar solutions of the organic salts in the to be used are suitable Acids. As far as one works in the gas phase, one brings the salts to the done with palladium provided catalysts in amounts of 0.5 to 10 percent by weight, advantageously 1 to 5 percent by weight, related to the carrier. It is advisable to apply the salts in aqueous solution to the noble metal to impregnate the catalyst provided and then to dry it.

If you use the catalysts in a fixed arrangement in the reaction space, you can get pills, sausages or use balls in a size of 2 to 8 mm, advantageously 3 to 5 mm. When using the Catalyst in the moving bed is advantageously chosen the spherical shape of the catalyst when working in Fluidized bed can, for. B. the microsphere shape with sizes from 20 to 80 μ can be used. So much for If the process according to the invention works in the liquid phase, the catalyst can be solid in the reaction space and the reactants can be disposed up or down through the catalyst bed are passed through, the gaseous components - so z. B. Ethylene and the Oxygen - can be conducted in cocurrent or in countercurrent with the liquid products. Man but can also suspend the catalyst finely divided in the liquid products and after the end Separate the reaction from the reaction product and return it to the reaction chamber. So far if you work in the gas phase, the use of a fixed catalyst is particularly advantageous. The reactants can be passed up or down through the catalyst bed. But it can z. B. can also be worked with a moving lump catalyst, d. That is, the catalyst can be passed through the reaction space in the form of a moving bed, or a fluidized bed can also be used, with the reactants in gaseous form be passed through a bed in which the catalyst is in a fluidized state.

The oxygen can be supplied in the form of air. Especially when the reactants are circulated but it is more advantageous to work with concentrated oxygen, expediently over 99%. If one works in the liquid phase, one uses advantageously 0.5 to 30 mol Oxygen per 100 moles of olefins used. When working in the gas phase, the oxygen content in the gaseous mixture of olefins, acids and oxygen e.g. B. 1 to 40 parts by volume, advantageously 2 to 30 parts by volume. Since in a single pass only some of the gases, especially the olefins, is implemented, it may be advisable to put the gases after separation from the reaction products in the Recirculated.

The reaction temperatures are expediently in the range from 50 to 250 ^° C., advantageously 100 to 180 ^° C. The reaction can be carried out under normal pressure or elevated pressure. When working in the liquid phase you can, for. B. Total pressures from 2 to 80 atm. use. When working in the gas phase, it is expedient to work at normal or slightly increased pressure.

When working in the liquid phase, you can work up the reaction products in the following How to proceed: If no salts are dissolved in the reaction material, the reaction material is separated by distillation into unreacted reactants into the esters formed and any by-products formed. If dissolved salts were present in the reaction, the low-boiling products can be used first Separate by distillation, if necessary with the aid of steam or other carrier gases, and can separate the salt and higher-boiling products in the residue by extraction with an organic solvent such as hydrocarbons. When working in the gas phase you can cool the products leaving the reactor, so that most of the Säuien and the reaction products are liquefied. The non-condensed portions of the reaction products, For example the esters, can be obtained from the gases leaving the condensation with suitable means, for example acids, higher-boiling esters, glycols, Glycol ethers, wash out or liquefy by compressing the gases. The application of compression the gas has the advantage of separating the carbonic acid formed as a by-product from the To facilitate reaction gases. From the condensates obtained through cooling or compression the reaction products, i.e. the organic esters, can be removed from the water by distillation on the one hand and separated from the acids on the other hand. The acid can evaporate and vaporize be returned to the reaction chamber.

example 1

The preparation of the catalyst support was carried out in the following way: spheres with a diameter of 4 mm made of active aluminum oxide with an internal surface area of 288 m ² / g were soaked at ordinary temperature with such an amount of saturated aqueous solution of zinc nitrate that a 40% formation of Zinc spinel corresponds. The zinc nitrate decomposed to the oxide by heating the impregnated and dried balls to 500 ⁰ C. This product was then heated to 1050 ° C. for 12 hours, during which the spinel formation took place. The carrier obtained in this way has an inner surface of

36 m ² / g. To produce the catalyst, it was impregnated with palladium chloride solution. The palladium was then finely dispersed onto the support using an alkaline hadrazine hydrate solution. The palladium content of the finished catalyst was

2 percent by weight. 4.7 parts by weight of sodium propionate per 100 cm ^{3 of} the finished catalyst were impregnated as an aqueous solution on this catalyst. It was then ^{dried at 110 °} C. in vacuo. 500 cm ^{3 of} this catalyst were introduced into a tube of 22 mm inside diameter and 1500 mm in length. A mixture of 4.5 moles of ethylene, 1.45 moles of propionic acid and 0.85 moles of oxygen was passed hourly in a downward flow over this catalyst, which was fixedly arranged in the reaction space. The reaction temperature was 145 ° C. Work was carried out at ordinary pressure. 8.8% of the carbon used as ethylene was converted. From the implemented. Carbon was obtained 80.6% as vinyl propionate and 19.4% as carbon dioxide.

Example 2

For the preparation of the catalyst, one obtained by heating active alumina was obtained Aluminum oxide with an inner surface of

3 m ² / g used. This carrier was impregnated with palladium chloride, then the palladium was finely dispersed on the carrier using an alkaline hydrazine hydrate solution. The palladium content of the finished catalyst was 2 percent by weight. A horizontal autoclave was used, in which 250 cm ^{3 of} the described catalyst were placed in a wire mesh. When the wire mesh was rotating in the autoclave, the catalyst was alternately in the liquid and gas phase, corresponding to the continuous operation in the trickle phase. 99 g of propionic acid and 34 g of propylene (94.5 g) ^{were used in the 700 cm 3 autoclave} Then 49 atmospheres of air were injected, corresponding to 5.0 g of oxygen. While the wire mesh was rotating, the autoclave was ^{heated to 120 °} C. and left at this temperature for 12 minutes. 18% of the carbon used as propylene had reacted converted carbon were obtained 66.2% as allyl propionate, 17.6% as acetone and 5.5% as carbon dioxide.

Example 3

Tn the same arrangement as in Example 2 and with the same catalyst were in the autoclave introduced 98 g of butyric acid, 35 g of ethylene, and pressurized air to a total pressure of f: i { 50 atm., Corresponding to 5.7 g oxygen. The autoclave was heated to 122 ° C. while the wire mesh was rotating and leave at this temperature for 10 minutes. Of the carbon introduced as ethylene 4.6% implemented. 48.9% of the converted carbon was obtained as vinyl butyrate and 48.3% as carbon dioxide.

Claims (5)

Patent claims: 1. Process for the preparation of alkenyl esters, characterized in that one Monoolefins with oxygen and organic acids higher than acetic acid in the presence of a Palladium metal catalyst applied to supports containing silica or aluminum oxide is, reacted at elevated temperature. 2. The method according to claim 1, characterized in that the catalyst supports to be used have internal surfaces of 1 to 100 m ² / g, preferably 10 to 80 m ² / g. 3. The method according to claim 1 and 2, characterized in that there is an aluminum oxide Carrier used in which the alumina partially or completely as spinel is present. 4. The method according to claim 1 to 3, characterized in that the reaction is carried out in the presence of alkali or alkaline earth salts of the organic acids used. 5. The method according to claim 1 to 4, characterized in that the method in the liquid Phase or in the gas phase.