DE1146056B - Process for the preparation of pyrrolidone - Google Patents

Description

Process for the preparation of pyrrolidone The invention relates to a Process for the preparation of pyrrolidone by treating a β-cyanopropionic acid alkyl ester with hydrogen in the presence of a nickel hydrogenation catalyst and an organic one Solvent at elevated temperature and under elevated pressure.

It is known that ß-cyanopropionic acid ethyl ester by hydrogenation in Pyrrolidone can be converted. At 70 to 90 ° C under a hydrogen pressure A yield of 50 to 200 kg / cm2 with Raney nickel and ether as the solvent is achieved of 38% (Journal of the American Chemical Society, vol. 55 [1933], p. 4167 to 4176).

The formation of by-products is increased by adding at least 2.0 moles, preferably 3.5 moles, of anhydrous ammonia per mole of ß-cyanopropionic acid ethyl ester pushed back. At a temperature of 90 to 130 ° C and a pressure of 70 kg / cm " yields of up to 910% are achieved in ethanol as a solvent (Journal of Organic Chemistry, Vol. 21 [1956], pp. 578 and 579). However, it can be a pretty violent one and uncontrolled reactions cannot be avoided even after this procedure. aside from that the use of such large amounts of ammonia is undesirable and uneconomical.

It has now been found that the disadvantages mentioned are avoided and pyrrolidone is obtained in very high yields when using the process for the production of pyrrolidone by treating an alkyl ß-cyanopropionate with hydrogen in the presence of a nickel hydrogenation catalyst and an organic one Solvent at elevated temperature and under elevated pressure, the ß-cyanopropionic acid alkyl ester into a slurry of the nickel hydrogenation catalyst in the organic solvent allowed to flow in with stirring at a temperature of 150 to 300 ° C.

The hydrogenation and cyclization take place under these conditions at great speed. The side reactions are strongly suppressed. Of the Catalyst remains effective and can be used repeatedly. There will be yields obtained from 90 to 95 ° / o. By adding a small amount of ammonia, the yield can be increased can be increased to 96 to 98 per cent. According to one embodiment of the Process according to the invention 0.1 to the reaction mixture in a manner known per se up to 0.5 moles of ammonia per mole of ß-cyanopropionic acid alkyl ester.

As an organic solvent, pyrrolidone itself or a reaction mixture, which contains pyrrolidone from a previous batch, an alkanol, especially a lower alkanol, or an ether such as butyl ether can be used. It needs to Start the reaction only as much solvent to be used that the mixture can be stirred well from solvent and catalyst. As the Reaction, the pyrrolidone formed serves as an additional solvent.

The catalyst used is a nickel catalyst suitable for hydrogenation, such as Raney nickel or reduced nickel which has been deposited on alumina or diatomaceous earth. The proportion of the catalyst is preferably 1 to 100/0, based on the total amount of the .beta.-cyanopropionic acid alkyl ester to be converted. At lower temperatures and pressures it is advisable to use a larger proportion of the catalyst than at higher temperatures. At 160 ° C. and 17.5 kg / cm 2, very good results are obtained with more than 5 % of the catalyst, while at 220 ° C. and a pressure of 56 kg / cm 2, 0.5% are sufficient.

The process according to the invention is carried out by charging a pressure vessel with the catalyst and the organic solvent. The vessel is flushed with an inert gas or with hydrogen, whereupon hydrogen is injected at a pressure of 2.1 to 21 kg / cm2 and this is topped up if necessary in order to maintain the partial pressure of the hydrogen. The mixture in the vessel is heated to at least 150 ° C and the contents are mixed well. The ß-cyanopropionic acid alkyl ester is then pressed into the vessel and the rate of addition is regulated in order to keep the temperature of the reaction mixture between 150 and 300.degree. There is a considerable heat of reaction e.g. B. dissipated through a cooling coil. After the supply of the .beta.-cyanopropionic acid alkyl ester has been terminated, the reaction mixture is cooled, filtered and distilled. If necessary, the gas can be blown out of the reaction vessel in order to remove some of the alkanol formed during the reaction with it.

The process can be carried out batchwise or continuously.

If ammonia @ is to be used, this can be put into the reaction vessel be pressed, or it can be in the mixture of the ß-Cyanpropionäurealkylester and of the solvent pumped into the vessel.

The invention is illustrated by the following examples. Unless otherwise indicated, all parts are parts by weight.

Example 1 An autoclave is used which has an effective Stirrer that can make 600 revolutions per minute, a cooling coil, an electric heater and an inlet. In the vessel will Hydrogen is introduced through a tube that is located below the stirring device is located. The raw materials are pumped into the plant.

The autoclave is filled with 250 parts of methanol and 30 parts of a nickel catalyst, which consists of 50% reduced nickel on diatomaceous earth is charged. The vessel will closed, flushed with hydrogen, with hydrogen to a pressure of 14 kg / cm2 brought and heated to 155 ° C. This increases the hydrogen pressure to 35 kg / cm2 elevated. Through the liquid line, which was originally filled with methanol, ß-cyanopropionic acid methyl ester is then pumped into the vessel. This inlet pipe is equipped with a preheater so that the flowing ester can be heated can. The initial inlet temperature is 155 ° C. After about 10 parts of this Esters have been introduced, a rise in temperature is recorded. Through the Water is then sent to the cooling coil at such a rate that the Reaction mixture is kept at 170 ° C, with about 9 parts of the ester per minute be pumped in. Through a reducing valve that is adjusted to about 35 kg / cm2 is, hydrogen is supplied. Pumping in continues until 565 parts of the ß-Cyanpropionic acid methyl ester have been initiated. The feed line will then rinsed with methanol. As soon as the addition of the ester is interrupted, a noticeable drop in the temperature of the reaction mixture.

The supply of hydrogen is interrupted and the reaction mixture is cooled. The reaction vessel is blown off. The reaction mixture is filtered and the vessel and filter are rinsed with methanol. The filtrate is a pale yellow liquid. It is heated under reduced pressure on a steam bath, the methanol is distilled off (final temperature at 30 mm 95 ° C.) and collected. The yield of crude pyrrolidone is 420 parts. It is purified by distilling under reduced pressure. A high reflux ratio is used initially. The boiling point of the pyrrolidone is reached quickly and the pure product is taken off at a low reflux ratio. The distillation is continued until the bath temperature is 40 to 50 ° C. above the boiling point of the pyrrolidone. Yield 400 parts (94 ° / 0). The residue is 15 parts. The product consists of at least 98.5% pure pyrrolidone. The boiling point is 122 ° C at 10 mm pressure. The refractive index is 1.4860 at 25 ° C. Infrared analysis shows a trace of butyrolactone but no methyl cyanopropionate.

If the above process is applied to ethyl β-cyanopropionate, a yield of 92 % of pyrrolidone is obtained. When using ß-cyanopropionic acid butyl ester as the starting material, the same yield of pyrrolidone is obtained.

If the process is carried out at reaction temperatures of 220 to 240 ° C, in this way the pyrrolidone is obtained in good purity and in equal yields. the higher temperature requires a larger cooling surface or requires a faster one Inflow of the cooling means with the same cooling surface. The residue when distilling is noticeably reduced.

Example 2 The same system is used as in Example 1, and the conditions and the proportions are kept almost the same, only become 15 parts of ammonia added to the original batch: the withdrawn crude pyrrolidone makes 423 parts, and the yield of distilled, practically pure pyrrolidone is 950 /, with a residue of 10 parts.

Example 3 The procedure given in Example 2 is carried out with the Repeated catalyst from a previous batch. It will be almost the same Achieved yield of practically pure pyrrolidone.

Example 4 The system described in Example 1 is modified, using a dip tube through which the reaction mixture is withdrawn can be. The lower end of the dip tube carries a micrometallic filter. The solution and gas can be drawn off through this filter and the tube and transferred to a high-pressure collection system be transferred. There is a cooling coil between the autoclave and the collecting system attached around the pipe. The collecting system contains valves for blowing off gases on the upper part of the collecting system and for liquids' on the bottom of the system.

The autoclave is charged with 160 parts of methanol and 45 parts of a hydrogenation catalyst which consists of reduced nickel (50 %) on a kieselguhr support (50010) . The autoclave is closed, flushed with hydrogen, brought to a pressure of 28 kg / cm2 with hydrogen and heated to 170 ° C. The heating is interrupted and the hydrogen pressure is steadily regulated to 56 kg / cm2.

A storage vessel for the starting material is charged with a solution which contains methyl β-cyanopropionate, methanol and ammonia in a weight ratio of 20: 5: 1. This solution is pumped into the heated reaction vessel, the temperature being allowed to rise to 180 ° C., whereupon water is pumped into the cooling coil at a rate such that the temperature remains the same and the feed rate of the solution is 12 parts per minute. After the hydrogen has been blown out of the collecting vessel, the reaction mixture begins to flow to the pressure receiving vessel, from which it is then drawn off. The reaction mixture is filtered using a filter aid to remove very small particles of the catalyst, freed from methanol and distilled. The yield of the purified product is 950 /, of theory.

If this process is carried out with a starting material of ß-cyanopropionic acid methyl ester, Methanol and ammonia in a weight ratio of 20: 2: 1 are repeated so achieved essentially the same results. The only purpose of the methanol is to bring the ammonia, which is sparingly soluble in the ester, into solution.

Claims (2)

PATENT CLAIMS: 1. A process for the preparation of Pyrrohdon by treating a ß-cyanopropionic acid alkyl ester with hydrogen in the presence of a nickel hydrogenation catalyst and an organic solvent at elevated temperature and under increased pressure, characterized in that the ß-cyanopropionic acid alkyl ester is in a slurry of the nickel Hydrogenation catalyst is allowed to flow into the organic solvent with stirring at a temperature of 150 to 300 ° C. 2. Procedure according to claim 1, characterized in that the reaction mixture in itself as is known, 0.1 to 0.5 mol of ammonia is added per mol of alkyl β-cyanopropionate. Papers considered: Journal of the American Chemical Society, Vol. 55 (1933), pp. 4167 to 4176; The Journal of Organic Chemistry, Vol. 21, p. 578 and 579 (May 1956).