SU1088304A1 - Method of producing 2,2,6,6-tetramethyl-4-aminopiperidine - Google Patents

Abstract

1. THE METHOD OF OBTAINING 2,2,6,6 TETRAMETHIL-4-AMINOPIPERIDANE by reductive amiation with 2,2,6,6 tetramethyl-4-oxopiperidine with ammonia and hydrogen at a temperature and pressure in the presence of a hydrogenation catalyst, characterized in that, in order to simplify the process and increasing labor productivity, Raney nickel is used as a hydrogenation catalyst; the process is carried out at a pressure of 10-25 atm in an aqueous medium in the presence of a cocatalyst of alkaline or alkaline earth metal oxide hydrochloride. 2. The POP.1 method, characterized in that the cocatalyst takes 1-2% by weight of Rene nickel.

Description

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The invention relates to an improved process for the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine, which is used as an intermediate product for the synthesis of non-staining light-heat stabilizers of polymeric materials.

Electrochemical methods for the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine are known, consisting in the reduction of a mixture of 2,2,6,6-tetramethyl-4-oxopiperidine (triacetonamine) and nitric acid or a mixture of 2,2,6,6-tetramethyl-4-oxopiperidine and mineral salts of hydroxylamine in an aqueous acid medium at room temperature. The yield of the target product is 96-99%.

The disadvantage of these methods is their high energy consumption and the need to carry out the process in special equipment.

The closest in technical essence and the obtained result is the method of obtaining the target product, which consists in the reductive amination of 2,2,6,6-tetramethyl-4-oxopiperidine (triacetonamine) with hydrogen and ammonia in the presence of a hydrogenation catalyst.

The process is carried out at 120-220 ° C, a pressure of 150-500 bar in the presence or absence of an organic solvent. Yield 90-95%, calculated on triacetonamine.

The disadvantage of this method is the need to use large pressures, a significant (up to 50 mol) excess of ammonia, a relatively small productivity of the process, as it lasts 1-4 hours. The purpose of the invention is to simplify the technology and improve the productivity of labor. This goal is achieved by the described method for the preparation of 2,2,6,6 tetramethyl-4-aminopiperidine, which consists in the fact that 2,2., 6,6-tetramethyl 1-4-oxopiperidine is subjected to reductive amination in the presence of a catalyst for the hydrogenation of René nickel at 100-135 ° C, pressure of 10-25 atm in an aqueous medium in the presence of a cocatalyst of an alkali or alkaline-earth metal hydroxide.

A distinctive feature of the process is that nickel is used as a hydrogenation catalyst.

Rene, the process is carried out at 100135 ° C, a pressure of 10-25 atm in an aqueous medium in the presence of a cocatalyst

alkali or alkaline earth metal hydroxides.

Preferably the cocatalyst takes 1-2% by weight of Rene nickel. The process is as follows.

in a way.

Triacetonamine, a 25% aqueous solution of ammonia, and Rene's bottle in an amount of 5-10% by weight of triacetonamine are loaded into the autoclave. and alkaline cocatalyst in the amount of 1-2% by weight of Rene nickel. The contents of the autoclave are sealed, purged with nitrogen, then with hydrogen, and heated to 100-135 ° C with the stirrer running. Wherein,

The pressure in the autoclave first rises to 10–17 atm, and then begins to fall in connection with the beginning of the process of reductive amination. Using a hydrogen reducer, the pressure of hydrogen in the autoclave is maintained from 10 to 25 atm, depending on the temperature. The end of the reaction is determined by stopping the uptake of hydrogen. The processing time is 15-20 minutes. At the end of the reaction, the contents are cooled to 20-25 ° C with water in the jacket of the autoclave and the pressure is released. The hydrogenate is decanted from the catalyst and accelerated,

collecting the fraction boiling at 78-79 ° C (7 mm Hg). The yield of the target product is 90-95%.

Example 1 .. In an autoclave with a capacity of 5 liters, equipped with a mixing device. The autoclave is sealed, twice purged with nitrogen, then with hydrogen, and a hydrogen pressure of 10 atm is created in it. When the stirrer is operating, the supply of steam whose steam in the autoclave shirt raises the temperature to 130-135 C. At the same time, the pressure in the autoclave first increases to 10 atm, and then begins to fall due to the onset of the reaction

gg reductive amination. With the help of a hydrogen reducer, the pressure of hydrogen in an autoclave is 10-15 atm. Over the course of the reaction, pressure drop in the reactor is observed at 4 ° with a jacket for heating and cooling, 1.27 kg (8.0 g-mol) of triacetonamine, 1.51 l (20.0 g-mol) of 25% aqueous ammonia solution, 63.5 g of 50% aqueous paste, 45 Rene nickel and 6.25 g of hydroxide after the termination of the supply of hydrogen to it. The end of the reaction is determined by stopping the uptake of hydrogen. The duration of the reductive amination reaction is 15-20 minutes. At the end of the reaction, the supply of water into the jacket of the autoclave is cooled to 20-25 ° C and depressurized. The hydrogenate is decanted from the catalyst and dispersed, collecting the fraction boiling at 7879 ° C / 7 mm Hg. The yield is 1.17 kg (93.6% of the theoretical, calculated as triacetonamine), 1.4700, d4 0.8963. Example 2. The process is carried out under the conditions of example 1 with a pressure in the autoclave of 15-25 atm and a temperature of 10–25 atm. The yield of the target product is 1.1 9 kg (95.2% of the theoretical value for triacetonamine), p 1.4710, d 0.8966. Example 3. The process is carried out under the conditions of Example 1 using potassium hydroxide as a cocatalyst. , The yield of the target product is 1.18 kg (94.7% of the theoretical, calculated as triacetonamine). EXAMPLE 4 The process is carried out under the conditions of Example 1 using calcium hydroxide as the cocatalyst. The yield of the target product is 1.13 kg (90.4% of theoretical, calculated on triacetonamine) Pd 1.4699, d 0.8961. The proposed method allows the process to be carried out at lower, compared with the prototype, pressures, which increases its safety; reduce the process time from 1-4 hours to 1520 minutes, which increases the removal of the target product per unit time, reduce the excess ammonia, thereby significantly reducing its consumption and eliminating the complex system of its capture to return to the process; eliminate the use of flammable and toxic. solvents.

Claims (2)

1. METHOD FOR PRODUCING 2,2,6,6TETRAMETHYL-4-AMIN0PIPERIDINE by reductive amination of 2,2,6,6tetramethyl-4-oxopiperidine with ammonia and hydrogen at elevated temperature and pressure in the presence of a hydrogenation catalyst, characterized in that, in order to simplify the technology and increase labor productivity, Raney nickel is used as a hydrogenation catalyst, the process is carried out at 100135 ° C, a pressure of 10-25 atm · in an aqueous medium in the presence of an alkali metal or alkaline earth metal hydroxide cocatalyst. 2. The method according to π.1, with the exception of the fact that the cocatalyst take 1-2% of the weight of Raney nickel.