JPS6133169A - Preparation of 4-amino-2,2,6,6-tetramethylpiperidine - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as an important intermediate of a hindered piperidine stabilizer, economically, in an industrial scale, at a low cost, by reducing and aminating triacetoneamine with ammonia and hydrogen in the presence of a cobalt-based catalyst at specific temperature and pressure. CONSTITUTION:4-Amino-2,2,6,6-tetramethylpiperidine of formula II is produced by the reductive amination of triacetoneamine of formula I with ammonia and hydrogen. The reaction is carried out at 80-200 deg.C, preferably 100-150 deg.C under a pressure of <150kg/cm<2>G, usually 50-180kg/cm<2>G, in the presence of a cobalt- based catalyst (especially Raney-cobalt).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing 4-amino-2,2,6,6-tetramethylpiperidine.

4-Amino-2,2,6,6-tetramethylbiveridine (hereinafter abbreviated as TAM) is an important intermediate for hindered piperidine stabilizers used in plastics, rubber, and the like.

An object of the present invention is to provide a method for manufacturing such TAM at low cost and industrially advantageously.

As a method for producing TAM, it is known that it is produced according to the following formula. Namely Liebigs Ann.

d, Chemie, Vol. 417, pp. 118-119 Oyohi Izv, Akad, Nauk, 5SSRSer
, Khim, 1966, 1477] has a holon (I
) and ammonia to form triacetonamine (m
A method is described in which the oxime (m) is obtained by reacting with hydroxylamine and then reduced with zinc or metallic sodium to obtain T A M (rv) with a yield of about 80%.

Furthermore, JP-A-50-126674 discloses a method for obtaining TAM at a yield of 71% by reductive amination of folon.

However, all of the above methods use holon as a starting material, and the yield of holon itself is 7 (approximately 80% from F ton).
Because of the extremely low 0, there was a big problem in terms of raw materials industrially.

In addition to these problems, the former method requires a three-step complicated process and has an extremely low yield, while the latter method is not satisfactory in terms of yield. Furthermore, there are problems in that it requires a large amount of catalyst, 20 W t% based on holon, and in addition, acetic acid is required to prevent the formation of alcohol. There were also problems in that it needed to be press-fitted and special equipment was required.

On the other hand, a method using triacetonamine obtained in good yield from acetone and ammonia as a starting material is disclosed in JP-A-56-122852.

However, this method requires special catalysts (RCH < 45/
This method uses as much as 10 wt% of 2o> based on triacetone amine, and is carried out at high temperatures and pressures of 180 to 200° C1 and 800 Kf/CIA, which is an industrially unfavorable method in terms of catalysts and equipment. . In addition, as a result of conducting additional tests on this method, T
The reaction yield of AM was at most 70%, and the method required improvement in this respect as well.

As mentioned above, all the known methods have drawbacks and are not suitable for industrial use.
It was hard to say that it was manufactured using a model.

In view of this current situation, the present inventors have conducted intensive studies on an industrial method for producing TAM by reductive amination of triacetonamine, and have found that if reductive amination is carried out using a specific catalyst and under specific reaction conditions They discovered that TAM can be obtained almost quantitatively and completed the present invention.

That is, the present invention provides an industrially superior method characterized in that the reductive amination of triacetonamine is carried out in the presence of a cobalt-based catalyst at a reaction temperature of 80 to 200°C and a pressure of less than 150 Kt/dG. A method for manufacturing TAM is provided.

The present invention is represented by the following reaction formula.

In the present invention, ammonia is used in a stoichiometrically 1-fold molar amount relative to triacetonamine, but 1. It is preferable to use excess amount, usually in the range of 1 to 80 moles, especially 5
(preferably 10 moles).

Furthermore, hydrogen may be used in a theoretical amount, but an excess amount will not adversely affect the reaction (usually the amount of hydrogen is determined to match the pressure range selected for the reaction.

Further, the reductive amination catalyst used in the present invention is limited to Kobal N medium. When other catalysts such as nickel, palladium, platinum, rhodium catalysts, etc. are used, they may be supported on a carrier such as earth, alumina, silica gel, or activated carbon, which provide a remarkable yield of the target product, or they may be supported on a carrier such as earth, alumina, silica gel, or activated carbon. Even if you don't have one. Among them, Raney cobalt is most preferred.

The amount of catalyst used is usually 0.2 to triacetonamine.
10% by weight, preferably 0.5-2% by weight.

The reaction temperature is 80-200°C, preferably 100-150°C.
Perform at °C. The reaction pressure is selected to be less than 150 Kp/ff1G, but is usually 50 to 180 Kf/dG.

Temperature and pressure ranges other than these are undesirable because they require a long reaction time, the yield is low, or a large amount of by-products are produced.

As mentioned above, the method of the present invention uses a specific cobalt catalyst and is carried out under specific reaction conditions, but the reaction solvent may or may not be used.

If a solvent is used, cyclic or acyclic aliphatic hydrocarbons such as hexane, isooctane, cyclopentane, cyclohexane, cyclic or acyclic aliphatic ethers such as propyl ether, butyl ether, amyl ether, tetrahydrofuran, dioxane, benzene, toluene, etc. , aromatic hydrocarbons such as xylene, propylbenzene,
Lower alcohols such as methanol, ethanol, propatool, isopropanol, butanol, and isobutanol can be used, and among them, methanol is preferred.

Further, the method of the present invention can be carried out in either a batch method or a continuous method. In the case of a batch method, triacetone amine, a catalyst, ammonia, and in some cases a solvent are added to the autoclave, and finally hydrogen is injected to a predetermined pressure, and then heated to a predetermined temperature. The reaction is usually complete in 1 to 5 hours, with the end point indicated by the absence of hydrogen absorption.

In the case of a continuous method, raw materials are introduced into a reactor filled with a catalyst in advance and adjusted to a predetermined reaction temperature and pressure, and reacted. The catalyst bed in this case may be either a fixed bed or a fluidized bed.

Thus, according to the method of the present invention, TAM can be obtained under much milder conditions than in known methods and with a high reaction yield of 98% or more.

The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these in any way.

Example 1 In an 800-autoclave, 46% of triacetonamine was added.
7(f), methanol 98.1 (IF) 50% hydrated cobalt x, o (l), liquid ammonia 40
．． Enclose 9(f).

Thereafter, hydrogen was injected to gQKp/dG, the temperature was raised to 180°C, and this temperature was maintained.

The pressure rose to a maximum of 1soKf/dlG, but decreased over time and reached a constant value of 85 about 2 hours after the temperature was raised.
Since it became Kf/-G, it was cooled.

After cooling, the liquid in the pot was bubbled with N2 to remove excess ammonia, and then filtered to remove the reaction catalyst and obtain a reaction mass.

Analysis of the reaction mass by gas chromatography revealed that the triacetonamine conversion rate was 100 (%) and the TAM selectivity was 99 (%).

To remove TAM from the reaction mass, the solvent was recovered by simple distillation and then rectified to obtain 98% TAM45.4F (
yield 95%).

B, P 114°C 150 Torr Example-2 In an autoclave, triacetonamine as, 7(f)
, methanol 74(f), 60% hydrated Raney cobalt 0
．． Prepare 98(f).

Liquid ammonia 4o and 9(f) are sealed. After that, hydrogen was injected to 80Kr/cdG, and the temperature was raised to 180°.
It was set as C. The reaction was completed in 2 hours. The extraction was carried out in the same manner as in Experimental Example-1, and the reaction mass was analyzed and found to be triacetone amine Yabu #, Ka11111 France-TAM Kaisakakimoto QQ.
I wrote it in Buddha.

Comparative Example-1 Same charge composition as Example-1, reaction temperature 190℃
The temperature rose to . The pressure at this time was 180Kf/dG,
Although the temperature was maintained at 190° C. thereafter, the pressure gradually increased and reached 200 Kt/cIAG after 4 hours of incubation.

At this point it was cooled and the reaction mass was removed and analyzed in the same manner as in Example i. Triacetonamine conversion rate 100 (%)
, the TAM selectivity was 60 (%).

Comparative Example-2 Triacetonamine 49.7 (g), methanol 74.
5 (f), 50% water-containing pt-C0,5 (f), and ammonia 40.9 (f) were charged into an autoclave, and hydrogen was added to 8
It was press-fitted to 0Kt/dG. When the reactor was heated to 180 ("0)" and reacted, a maximum pressure of 150 Kt/cdG was exhibited, and hydrogen absorption was completed within 4 hours.

After cooling, the reaction mass was taken out and analyzed in the same manner as in Example 1, and it was found that the triacetone conversion rate was 100 (%), the TAM selectivity was 44 (%), and there were many side reaction products.

Comparative Example-8 49.7 (g) of triacetonamine in an autoclave
, commercial name: RCH45/20 catalyst (manufactured by Hoechst) 51'
), liquid ammonia 109(f) was charged, and hydrogen was charged 109(f).
It was press-fitted to 0-/jG. The reactor was heated to 190 ('C) and further hydrogen was injected under pressure to 800 Kf/cjG, and the reaction was carried out until no more H2 was absorbed. When the reaction mass was taken out and analyzed in the same manner as in Example 1, the triacetone amine conversion rate was 1.
00 (%), and TAM selectivity was 70 (%).

Claims (1)

[Claims] A 4-amino amine characterized in that the reductive amination of triacetonamine with ammonia and hydrogen is carried out in the presence of a cobalt-based catalyst at a reaction temperature of 80 to 200°C and a pressure of less than 150 kg/cm^2G. -2
, 2,6,6-tetramethylpiperidine manufacturing method.