DE965237C - Process for cleaning acrylic acid ester mixtures - Google Patents

Description

When converting organic compounds with carbon oxide in the presence of carbonyl-forming metals, especially cobalt or nickel or their compounds, the so-called "carbonylations", is the reaction product by the corresponding metal carbonyls or the metal carbonyl hydrogen contaminated. It is true that during the work-up of the reaction product Distillation decomposes some of these metal compounds, but a part is usually still found thereof or their decomposition products in the distillates.

So one observes z. B. in the production of acrylic acid esters by reacting acetylene, Carbon oxide and alcohols in the presence of halogen compounds of nickel or cobalt that the distillates are sometimes heavily contaminated by carbonyl compounds, which in the case of Nickel can be recognized by an initially greenish coloration of the distillate.

It has now been found that d) the acrylic acid ester mixtures were eaten Obtained in pure form if the reaction products are low before the distillation Amounts of halogen, especially Brqm or iodine, add and thereby the metal carbonyl compounds decomposed in a manner known per se to the corresponding metal halides. Surprisingly the halogens react so quickly

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with the metal carbonyl compounds that the present Acrylic acid esters are not attacked with addition or substitution.

The method also offers the advantage that Loss of catalyst metal due to volatilization of the metal carbonyl compounds largely prevented and it is obtained in the form of the 'stable metal halide.

The process is expediently carried out in such a way that the raw material to be distilled is used A halogen is added to the ester mixture, the reaction can be carried out and then with the distillation begins. To accelerate the reaction, the mixture can be added after the halogen has been added short time, e.g. B. to reflux, heat or, if the crude ester mixture was still hot, do without intermediate cooling and then, if necessary, with increased or reduced pressure, distill. Contains the ester mixture to be freed from the metal If catalyst metal is already used as a halogen compound, it is expedient to use the halogen compounds underlying halogen or one with a higher atomic weight. The amount of halogen to be supplied depends on the amount of carbonyl compounds to be destroyed; it can easily be determined by means of a preliminary experiment and is generally 0.05 to 0.5%. You can also do the implementation continuously perform, for example by adding a solution of the halogen, e.g. B. in alcohols, carboxylic acids, Ethers or esters, expediently continuously in a liquid compound involved in the process the ester mixture after it has left the pressure device and after releasing the pressure of the pressure.

It has long been known that metal carbonyls can be converted into metal carbonyls by adding halogen Can decompose metal halides and carbon oxides. It is surprising, however, that this is also the case in the present of reactive esters per se, such as acrylic acid esters, is possible, especially since the Carries out reaction with halogen with prolonged exposure and at a slightly elevated temperature.

It is also known that crude acrylonitrile can be purified by treatment with chlorine to remove the divinylacetylene without attacking the acrylonitrile ¹ . However, this implementation takes place very quickly. It has now been shown, surprisingly, that the removal of metal carbonyls from acrylic acid ester mixtures by treatment with halogen is possible without the acrylic acid esters being attacked, even if the above-mentioned conditions are used.

The parts given in the following example are parts by weight.

example

An ester mixture obtained by catalytic conversion between n-butanol, carbon oxide and acetylene, which consists of 650 parts of n-butyl acrylate, 350 parts of butanol, 120 parts of higher-boiling by-products and ^{1 to} 20 parts of a complex compound composed of triphenylbutylphosphonium bromide, pyridinium butyl bromide and nickel bromide, is 1 Part of bromine was added and held ^{at 35 0 for 15 minutes.} In the subsequent distillation of the ester mixture, a completely nickel-free distillate is obtained.

If, on the other hand, the distillation of the crude ester mixture is carried out without treatment with bromine by, a distillate is obtained which contains 0.04% nickel.

Claims (1)

PATENT CLAIM: Process for cleaning acrylic acid ester mixtures, by reacting acetylene with carbon oxide! and alcohols in the presence of carbonyl-forming metals, especially cobalt or nickel or their compounds, were obtained, characterized in that one in the crude Estergemiechen metal carbonyl compounds still present prior to the distillation by treating decomposed with halogens, especially with bromine or iodine. Considered publications: German Patent Specifications Nos. 512223, 851 341.