PL68719B1 - - Google Patents

Description

Priority: 30.111.1966 France Published: 20.VIII.1973 68719 IC. 12o, 7/03 MKP C07c 47/20 UKD Inventor: Louis Alheritiere Patent proprietor: Melle-Bezons SA, Melle (Deux-Sevres) (France) Process for the treatment of butyraldehyde condensation products 1 The invention relates to a method of treating condensation products formed during condensation butyl aldehyde to ethylpropylacroleine (or α-ethyl-O-propylacroleine or ethyl-2-hexen-2-al).

It is known that during the condensation of butyraldehyde into ethylpropylacroleine, especially under the influence of an alkaline catalyst, e.g. an aqueous solution of sodium hydroxide, a small amount of high-boiling by-products are formed, which are obtained during the separation of the reaction products in the form of a mixture O-hydroxybutyric aldehyde (or ethyl-2-hexanol-3-aldehyde) and complexes derived from p-hydroxybutyric aldehyde and butyraldehyde and containing acetal groups.

Thus, during the industrial production of ethylpropyl acrolein according to the method described in French patent No. 1,091,824, about 2% of the mixture of high-boiling by-products in the weight ratio to the introduced butyraldehyde is produced, which reduces the yield of ethylpropylacrolein, respectively.

High-boiling by-products are decomposed by stronger alkalis, when hot, especially in an aqueous solution, preferably in sodium hydroxide or potassium hydroxide solution. By decomposition, an additional amount of ethylpropylacrolein is obtained and in the process some butyraldehyde is regenerated.

In conventional processes, the decomposition of high-boiling by-products is usually carried out in a crude mixture obtained by condensation reactions of butyraldehyde. This is the case, for example, in the process described in French Patent No. 1,036,156.

According to this patent, the action of the alkaline solution which serves as a catalyst for the condensation of butyraldehyde is extended to the crude reaction mixture obtained from the condensation. For this purpose, the operations are carried out in a plate column of suitable dimensions, preferably under pressure. Partial decomposition of high-boiling by-products is obtained and thus an increase in the overall efficiency of the processing operation.

The process described in French patent No. 1,036,156 does not provide optimal possibilities of using the by-products, because in the best industrial operating conditions, 2% of high-boiling by-products still remain undecomposed, which is the same as according to the process of the earlier French patent No. 1,091,824.

It has surprisingly been found that the decomposition of the high-boiling by-products occurs faster if, after the separation of the ethylpropylacrolein, these products are added at an elevated temperature with strong alkali, preferably remaining after the butyraldehyde condensation process, ie an aqueous alkaline solution. Thus, the loss in yield is 0.5% instead of 2% in the form of high-boiling by-products.

The decomposition of the high-boiling by-products according to the invention is carried out with the aid of conventional means, that is, with more concentrated alkaline solutions, especially in aqueous solutions, preferably with sodium hydroxide or potassium hydroxide solution. As in conventional processes, the decomposition of these by-products yields ethylpropylacroleine and butyraldehyde. After that, it is easy to recover the two compounds by known methods. The recovery of ethylpropylacrolein directly increases the efficiency of the reaction, while the recovered butyraldehyde can be fed to the reactor where the butyraldehyde is condensed into ethylpropylacrolinc. The treatment of high-boiling by-products with an alkaline solution is preferably carried out at a temperature of 100-105 ° C, but when working under pressure, much higher temperatures, up to 200 ° C, can be used, which allows for a significant reduction in the contact time of the reactants and thus to increase the production capacity of the reactor .

The method according to the invention is preferably carried out as follows. High-boiling by-products are treated with an aqueous solution of alkali, continuously while hot, in a reaction column with trays designated as deep plates. On the other hand, when the condensation of butyraldehyde is carried out with a basic catalyst, in particular as described in French Patent 1,091,824 mentioned above, it is preferable to use for the treatment of by-products according to the invention a sodium hydroxide solution which leaves the apparatus after condensation. and would not be used, it would be discharged into the sewage. Butyraldehyde and ethylpropyl acroleine recovered by the alkaline treatment of high-boiling by-products can be isolated in the same column by stripping the two products with water vapor directly introduced into the bottom of the column, condensation of the vapors escaping from the top of the column and liquid stratification, to separate water from organic products.

Example: In an industrial plant with a daily production capacity of 48 tons of ethylpropylacrolein according to the method described in French Patent No. 1 091 824, within an hour from the bottom of the ethylpropyl acrolein column about 100 kg of a mixture containing approximately 60 kg of ethylpropylacroleine and 40 kg of high ¬ boiling by-products.

In order to decompose the by-products according to the invention, they are introduced continuously into a normal steel reaction column with 12 trays, total capacity of about 1000 liters. At the same time, 350 liters / hour of water are introduced into the reaction column. 20 g / l of aqueous sodium hydroxide solution derived from the decantation of the liquid mixture obtained by the basic condensation of butyraldehyde into ethyl propyl acrolein. The reaction column is heated to 150 kg / h with steam, the temperature is 100-105 ° C.

The contact time of the high-boiling by-products with the sodium hydroxide solution is about 2 hours.

The vapor escaping from the top of the reaction column condenses and the condensed liquid is decanted. 84 kg / h of ethylpropylacrolein and 8 kg / h of butyraldehyde are collected in the upper organic layer. In addition to the 60 kg / hour of ethylpropylacrolein fed in the organic mixture fed to the reaction column, approximately 40 kg / hour of high-boiling by-products are obtained by decomposing an additional 24 kg / hour. ethylpropylacrolein and 8 kg / h of butyraldehyde, ie 32 kg / h in total of useful products, representing a gain of about 1.5% of theoretical yield with respect to the initially introduced butyric aldehyde. Moreover, the daily production of ethylpropylacrolein increases by half a ton.

At the bottom of the reaction column, about 40 kg / h of very high boiling point, water-insoluble, non-recoverable, non-recoverable by-products are collected and drained.

For comparative purposes, in an earlier process, 100 kg / h of a mixture containing high-boiling by-products was continuously distilled with 120 kg / h of direct steam in a distillation column filled with Raschig rings. 60 kg of recovered ethylpropyl acrolein and 40 kg of high-boiling by-products were obtained within an hour, after decanting, which were recycled to the bottom of the column and then drained to the waste water, so completely lost.

The method according to the invention entails in this case only an additional expenditure of 30 kg / hour direct steam.

The sodium hydroxide solution which is used to treat the by-products is not included in the calculation, otherwise it would be rejected directly into the waste water. A normal steel reaction column represents only a slightly higher investment than a conventional steam distillation column used in earlier process processes.

Ultimately, it is apparent that the yield of ethylpropyl aciolein can be increased by the invention by about 1.5% at the cost of very little extra pair and very moderate investment costs.

The process of processing the condensation products of butyraldehyde into ethylpropylacroleine in an alkaline environment, characterized by the fact that the ethylpropylacroleine formed is separated from the reaction environment, and the by-products of the odorless molecular weight, those remaining after separation are treated at an elevated temperature with strong alkali, preferably with an aqueous alkaline solution remaining after the condensation process, and then the ethylpropylacroleine and butyraldehyde are separated from the resulting mixture. io 2. The method according to p. The method of claim 1, wherein the alkali is sodium or potassium hydroxide. 3. The method according to p. A process as claimed in any one of the preceding claims, characterized in that the by-products with high molecular weight are treated with an alkali solution at a temperature of 100-200 ° C, preferably 100-105 ° C, under atmospheric pressure.

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