DE1180364B - Process for the continuous production of acrylic acid alkyl esters from acrylic acid nitrile - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C 07 c

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German class: 12 ο - 21

C16475 IVb / 12 ο
March 14, 1958
October 29, 1964

The production of acrylic acid esters from acrylonitrile can be carried out in such a way that the obtained by acidic saponification of acrylonitrile is obtained Acrylic acid esterified with alcohols. The method is cumbersome and has the further disadvantage that Losses due to polymerization can hardly be avoided.

You can also produce esters of acrylic acid from acrylonitrile by attaching to this Alcohols accumulate, whereby the corresponding / J-alkoxypropionic acid nitriles are formed, which then converted into the corresponding acrylic esters with sulfuric acid, expediently at elevated temperature will.

It is also possible to obtain acrylic acid esters from acrylonitrile by converting this first with stoichiometric amounts of water and sulfuric acid into the acidic sulfate of the hydracrylic acid amide transferred and this reacts with alcohol, whereby the corresponding acrylic acid ester is formed will. In this process, too, the yields are poor, since it does not succeed in the formation of / 8-alkoxypropionic acid esters as far as possible.

It has now been found that acrylic acid alkyl esters of monohydric aliphatic alcohols with a boiling point lower than 150 ^° C. are obtained in excellent yields if the reaction of acrylonitrile with the alcohol, water and sulfuric acid is carried out in such a way that one on the head is carried out 100 to 150 ⁰ C, especially 130 to 140 ⁰ C heated distillation column is a mixture of 1 mol each of sulfuric acid and water and small amounts of the polymerization inhibitor, at the bottom of the column the vapor of 1 mol of acrylonitrile and 1 to 2 mol of the aliphatic alcohol, its Boiling point is below 150 ⁰ C, introduced separately or in a mixture with one another and the acrylic acid alkyl ester is distilled off at the top of the column.

If low molecular weight alcohols such as methyl and ethyl alcohol are used, the mixture of acrylonitrile and alcohol can be evaporated together, provided that a molar ratio of acrylonitrile to alcohol of at least 1: 1.1 is maintained in the mixture. The temperature of the distillation column may vary between 100 and 150 ⁰ C, but should be suitably maintained at 130 to 140 ⁰ C. At the top of the column, the resulting acrylic acid alkyl ester is distilled off in great purity and excellent yield, while a melt from processes for the continuous production of is in the bottom of the column
Acrylic acid alkyl esters from acrylonitrile

Applicant:

Chemical factory Stockhausen & Cie.,

Krefeld, Bäkerpfad 25

Named as inventor:

Dr. Eduard Barthell, Krefeld,

Herbert Schmidt, Tampere-Rahola (Finland)

Ammonium sulfate or hydrogen sulfate accumulates, which is withdrawn from time to time or continuously will. The acrylic esters produced by this process are generally in one yield gained by 90% and only have to continue in the case of using a larger excess of alcohol, z. B. by distillation cleaned.

There are numerous processes in the literature, including continuous ones, for the production of acrylic acid esters described. In the US patent specification 2759016, in the corresponding French patent specification 1 099 469 and the corresponding German Auslegeschrift 1 065 840 described method for However, the continuous production of acrylic acid esters from acrylonitrile must be acrylonitrile converted into the acrylic acid amide in another vessel with aqueous acid. The amide is reacted in two devices with alcohol vapor. Compared to the method of the invention this method has the disadvantage of additional devices. It is clearly still a two-step process. In the first stage, the acrylonitrile is reacted with aqueous acid to form the acrylamide, this is in the second stage in two vessels with alcohol or alcohol vapor in the Acrylic acid ester converted.

The method according to German patent specification 883 600 is in contrast to the method of the invention also characterized in that not acrylonitrile with aqueous acid and alcohol or alcohol vapor is reacted in a reaction column, but that acrylonitrile in one separate process with aqueous sulfuric acid is converted into the hydracrylic acid amide sulfate and only this in the second stage in a distillation column with alcohol or alcohol vapor to form the acrylic acid ester is implemented.

409 709 39

The procedure of the French patent specification

1 129 080 also relates to a process for the preparation of acrylic acid esters from the hydrolysis products of acrylonitrile, those made of acrylonitrile with dilute sulfuric acid in separate process must be obtained. Only those produced in the separate process Hydrolysis products of acrylonitrile, consisting of acrylic acid or acrylic acid amide and diluted Sulfuric acid, are added to the top of a column and the vapor of a mixture of methanol and water is directed towards it. The process of this patent specification is clearly two-stage.

According to the method of the USA patent specification

2,526,310 is used to manufacture acrylic acid esters carried out on a rudimentary basis. It should be noted that the acrylonitrile with aqueous sulfuric acid can also be converted continuously to the sulfate of the hydracrylic acid amide. From a continuous Production of acrylic acid esters is out of the question. It also goes from the claims This patent clearly shows that the hydrolysis of the acrylonitrile and the esterification of the hydrolysis product are to be carried out in two stages.

U.S. Patent 2,666,782 also deals with the manufacture of acrylic acid esters in one two-step process. According to this process, acrylonitrile, sulfuric acid and Water produced the hydrolysis product, which reacted with the alcohol in the second stage will. The method of this patent specification thus offers nothing new compared to the method of the USA patent specification 2,526,310.

The acrylic acid esters obtained by the process of the invention have a purity of 98 to 99%. The process has the advantage that the esters arise in the specified purity and not as azeotropic mixtures with the alcohols used, as in the known processes; the separation of the Azeotropic mixtures are difficult and require additional equipment or process steps.

example 1

At the top of an approximately 1 m long packed column heated to 140 ° C., 1 mol of an 84% sulfuric acid containing some copper sulfate and preheated to the same temperature is added per hour. The water content is 1 mol. Simultaneously, 1 mol of acrylonitrile and 1.1 mol of methanol are blown into the lower end or through the bottom of the column, regardless of whether the acrylonitrile and the methanol are evaporated separately or as a mixture. At the top of the column, 79 g of methyl acrylate distill over per hour at a temperature of about 110 ^° C., which can be reused as such or after working up by distillation. Instead of a packed column, a bubble tray column can also be used, which corresponds to the effectiveness of at least twenty theoretical trays. The yield is 92%, based on the acrylonitrile used. The saponification number of the methyl acrylate obtained is 640.5, which corresponds to a purity of 98.2%.

Example 2

The procedure given in Example 1 is followed, but acrylonitrile is used per mole 1.3 moles of ethanol are used. The ethyl acrylate is obtained as a mixture with a little ethanol. After distillation, 96 g of ethyl acrylate are obtained, corresponding to a yield of 96%.

Example 3

The process is carried out as in Example 1 and 2 moles of n-butyl alcohol are used per mole of acrylonitrile. After the crude ester formed has been distilled off as in Example 2, 110 g of n-butyl acrylate are obtained, corresponding to a yield of 86% of theory.

If you carry out the production of butyl acrylate by using acrylonitrile and n-butyl alcohol introduced separately in vapor form at the bottom of the column, you only need a molar ratio of Acrylonitrile to butanol is 1: 1.4. As a result, the crude ester formed contains less butanol. the Working up by distillation as in Example 2 is therefore more economical. The yields in this The procedure is also 86% butyl acrylate.

Claims (2)

Patent claims: 1. A process for the continuous production of acrylic acid alkyl esters by reacting acrylonitrile with water, sulfuric acid and monohydric aliphatic alcohols in the presence of a polymerization inhibitor at an elevated temperature, characterized in that a mixture of 1 mol of water and sulfuric acid and small amounts of the polymerization inhibitor are applied to the head a distillation column heated to 100 to 150 ^° C., especially 130 to 140 ^° C., the vapor of 1 mol of acrylonitrile and 1 to 2 mol of the aliphatic alcohol, whose boiling point is below 150 ^° C., separately or in a mixture with one another, is added at the bottom of the column introduces and the acrylic acid alkyl ester is distilled off at the top of the column. 2. The method according to claim 1, characterized in that the acrylonitrile and the alcohol evaporates either together or separately. Considered publications:
German Patent Nos. 883 600, 966 955;
French Patent Specification No. 1099469,1129080; U.S. Patent Nos. 2,526,310, 2,666,782, 2,759,016.