DE1046608B - Process for the production of acrylic acid amide by splitting off alcohol from low molecular weight ª ‰ -alkoxypropionic acid amides - Google Patents

Description

There are different methods of making. Acrylsäureamtd known. Acrylic amide can for example, by reacting acrylic acid chloride with amides in a benzene solution. Acrylic acid amide is also obtained through partial saponification of acrylonitrile. However, this arises an aqueous acrylic acid amide solution, and the amide must in most cases before further processing, for example, if it is to be copolymerized with other monomers, from the aqueous Solution to be separated. In addition, the resulting acrylic acid amide is not pure enough to be without a special cleaning process to be polymerized.

Also by splitting off hydrogen halide from / I-halopropionic acid amides with the help of acrylic acid amide is obtained from equivalent amounts of strong alkalis. Another method is used from / 7-oxypropionamide water under reduced Cleaved under pressure and at temperatures above 160 ° C., anhydrous sodium carbonate as a catalyst is used. It is also known to produce from / 3-alkoxypropionic acid amides by splitting off Alcohols to produce acrylic acid amide. The elimination of alcohol from / I-methoxypropionic acid amide is z. B. with acidic compounds such as sulfuric acid, sulfur trioxide, hydrogen halides and sulfuric acid esters, or carried out with lithium phosphate and titanium oxide. It is also possible to go out / r-Alkoxypropionäureamiden with the help of inorganic alkaline catalysts to split off the alcohol. The yields based on the converted Starting materials and the degree of purification of the resulting acrylic acid amide are known for these However, the method is not yet satisfactory.

It is also known to use N-alkylacrylic acid amide Passing over of N-alkyl-alkoxypropionic acid amides to be made via aluminum oxide. The acrylic acid amides alkylated on the nitrogen differ, however considerably different from the acrylic acid amide, which is not substituted on the nitrogen, and are much more stable than this.

It has now been found that acrylic acid amide cannot be obtained by splitting off alcohol from nitrogen substituted low molecular weight / i-alkoxypropionic acid amides obtained in the gas state and under reduced pressure, if you split the alcohol in In the presence of aluminum oxide at temperatures of about 160 to 260 ° C.

It was surprising that in this reaction, in the presence of aluminum oxide, alcohol is split off from the low molecular weight / I-alkoxypropionic acid amides without any dehydration taking place at the acidic acid group. Alu method of manufacture
of acrylic acid amide by elimination of alcohol from low molecular weight
ß-alkoxypropionic acid amides

Applicant:

Aniline & Soda Factory in Baden

Aktiengesellschaft,

Ludwigshafen / Rhine

Dr. Manfred Minsinger, Ludwigshafen / Rhine,

and Dr. Herbert Friederich, Worms / Rhine,

have been named as inventors

miniutnoxyd is known to be a very powerful means of splitting off water.

Compared to the known process for the production of acrylic acid amide which is not substituted on the nitrogen the inventive method has the advantages that you work at lower temperatures can and very good yields, based on the reacted / J-alkoxypropionic acid amide obtained. Under the reaction conditions in the process of the invention is the polymerization of the self-polymerization inclined acrylic acid amide completely prevented; also arises from the / 5-alkoxypropionic acid amide only acrylic acid amide, without any by-products being formed. One therefore receives a very pure acrylic acid amide, which is particularly suitable for polymerisation purposes.

The aluminum oxide used as a catalyst should be in the y-form; it is represented, for example, by briefly heating boehmite, which may contain some bayerite, to 450 ° C. The surface of the aluminum oxide should be at least 150 m ² / g, but preferably 250 to 350 m ² / g of catalyst. The commercially available j'-aluminum oxide complies with these conditions.

The aluminum oxide used as a catalyst has an unlimited shelf life; if necessary, it can go through can be revived simply by heating. With the strongly acidic or strongly basic ones used so far Catalysts also always polymerized the formed under the respective reaction conditions

809 699/557

Acrylic acid amide. As a result, the surface of the solid catalyst used was blocked, i.e. made ineffective. In the method according to the invention on the other hand, no polymerization occurs during the cleavage of the alcohol.

The method can e.g. B. be carried out so that the vapors of /? ~ Methoxypropionamide at temperatures between about 160 and 260 ° C at a pressure of 0.1 to 10OTorr by an outside heated pipe that is filled with the catalyst passes. The escaping vapors are liquefied. the end the reaction mixture, the pure acrylic acid amide z. B. by fractional distillation or recrystallization be separated. The unreacted starting materials are returned to the reaction vessel fed. The degree of conversion can be changed by changing the reaction temperature, the pressure and the length the catalyst layer up to. a very high degree of conversion of the / J-methoxypropionic acid amide used be steered. Under certain circumstances it is advantageous to use the / 3-alkoxypropionic acid amide used with an inert gas, e.g. B. with nitrogen to dilute. Other alkoxypropionic acid amides, which according to are useful in the process of the invention are e.g. B. /? - ethoxypropionic acid amide and /? - propoxypropionic acid amide.

example 1

A vertical tube, 25 mm in diameter and 800 mm in length, which is filled with aluminum strands 4 mm in length and the surface area of which is 250 m ² / g, is heated from the outside. At the lower end of the reaction tube there is a receiver heated with water at 85 ° C., in which the higher-boiling reaction products are liquefied. Behind this receiver is a receiver cooled with a dry ice-acetone mixture, in which the low-boiling components are liquefied. At a pressure of 1 Torr and a reaction temperature of 190 ° C, 50 g /? - Methoxypropionamide per hour are passed over the abovementioned catalyst. After a total of 350 g of ^ methoxypropionic acid amide has been passed through, 254 g of a reaction mixture consisting of 189 g of acrylic acid amide and 65 g of methoxypropionic acid amide are obtained in the first receiver. In the second template, 80 g of methanol are obtained. This corresponds to a yield of 96% of theory, based on the converted yo-methoxypropionsaupeamide.

Example 2

A vertical tube, 25 mm in diameter and 800 mm in length, which is filled with aluminum oxide strands 4 mm in length, the surface area of which is 250 m ² / g, is heated from the outside. At the lower end of the reaction tube there is a receiver heated with water at 85 ° C., in which the higher-boiling reaction products are liquefied.

Behind this template is one with a dry ice-acetone mixture Cooled receiver switched in which the low-boiling components are liquefied. at a pressure of 1.4 Torr and a reaction temperature of 195 ° C are now 50 g /? - Ethoxy every hour propionic acid amide passed over the above catalyst. After passing through a total of 350 g /? - ethoxypropionic acid amide is obtained in the first template 212 g of a reaction mixture consisting of 182 g of acrylic acid amide and 28 g / I-ethoxypropionic acid amide consists. In the second template, 128 g of ethanol are obtained. This corresponds to a yield of 93% of theory.

Claims (1)

Claim = Process for the production of acrylic acid amide by splitting off alcohol from nitrogen does not substituted low molecular weight / J-alkoxypropionic acid amides in the gas state and under reduced pressure, characterized in that the elimination of alcohol is carried out in the presence of aluminum oxide carried out at temperatures of about 160 to 260 ° C. Considered publications:
German Patent Nos. 752 481, 851 186; U.S. Patent Nos. 2,508,279, 2,534,585, 2,702,822, 2,719,178, 2,749,355; British Patent Nos. 728 955, 723 006, 743 302.