JPS59219253A - Production of hexamethylenediamine - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a raw material for the polymerization of polyamide, in high yield and purity, suppressing the side reactions, by hydrogenating aminocapronitrile under specific condition. CONSTITUTION:The objective compound can be produced by reacting aminocapronitrile with hydrogen under hydrogen-pressure of 1-50kg/cm<2> at 50-140 deg.C in the presence of a cobalt/alumina catalyst and 0.2-4, preferably 0.5-2pts.wt. of water, based on 100pts.wt. of the nitrile. Preferably, the reaction is carried out by adding 0.01-1pts.wt., based on 100pts.wt. of the nitrile, of a caustic alkali, e.g. caustic soda, etc. to the reaction system. EFFECT:The catalytic activity can be remarkably increased by the presence of water in the reaction system, and the rate of reaction can be doubled compared with the anhydrous reaction system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hexamethylene diamine by hydrogenating aminocapronitrile,
More specifically, the present invention relates to a method for efficiently producing high-purity hexamethylene diamine by accelerating the reaction rate of the water-added knife and suppressing side reactions.

Aliphatic nitrile, especially aminocapronitrile, is an important precursor for the production of hexamethylene diamine as a raw material for polyamide polymerization, and this aminocapronitrile is generally hydrogenated with molecular hydrogen in the presence of a hydrogenation catalyst. be synthesized. Since the reductive hydrogenation of nitrile groups is a reaction via aldimine as shown in the formula below, in parallel with the main reaction of reduction to primary amines, intramolecular and intermolecular deamination reactions are induced to convert secondary amines into secondary amines. may occur (first side reaction).

R-C=N + H2→ R-CH=NH (aldimine)...(1) R-CH=NH+ H2→ R-CH
2-NH2←-class amicyamine (2) In addition, the second side reaction is the production of acid amide, aldehyde, or carboxylic acid by hydrolysis of the nitrile group or intermediate, and in order to prevent this side reaction, it is desirable to The reaction system should be kept in an anhydrous state.

Furthermore, products resulting from the third side reaction include cyclic diamines, cyclic imines, amino acids, lactams, etc., which are produced through complex reaction routes.

In order to reduce these side reactions and increase the yield of -class amines, it is important to accelerate the main reaction, and a catalyst with high hydrogenation activity and good selectivity is required. From this point of view, nickel-based catalysts, especially Raney nickel, are highly active as hydrogenation catalysts, and cobalt-based catalysts are preferred from the viewpoint of selectivity to -class amines.

In addition, a method of adding ammonia (liquid ammonia is often used as a solvent) or caustic alkali is known to suppress the formation of secondary amines according to equation (3), but the presence of water can be avoided according to equation (4). It is difficult to avoid the loss of nitrile and nitrile.

Furthermore, methods have been proposed in which hydrocarbons, alcohols, or ethers are used alone or in combination with ammonia, caustic alkali, or water. However, in these methods of adding hydrocarbons, alcohols, etc., the type of catalyst used is specified and is not a general method. For example, German Patent No. 848.654 uses a mixture of ammonia and toluene as a solvent, but the catalyst is cobalt-zinc. Furthermore, methods using ammonia or organic solvents other than water are not economical because they require a large amount of equipment for recovering the product after the reaction.

Furthermore, a method for producing a cobalt/alumina catalyst is known, in which hexamethylene diamine is produced by hydrogenating aminocapronitrile with molecular hydrogen in the presence of a cobalt-aluminum alloy together with water, alcohol, or an alkaline solution thereof. (Special Public Interest Publication 43-1.505
9, Japanese Patent Publication No. 13484/1984),
The role of water and alcohol in these known methods is to develop cobalt-aluminum alloy to produce cobalt-alumina, which becomes a hydrogenation catalyst, and therefore, the amount of water and alcohol added is sufficient for the development of the alloy, that is, the elution of aluminum. Because of this necessity, water and alcohol were used in large quantities, at least 10% by weight based on aminocapronitrile. When the hydrogenation reaction of aminocapronitrile was carried out using a cobalt/alumina catalyst in the presence of such large amounts of water and alcohol, the yield was low due to the large amount of side reaction products. Therefore, in the hydrogenation reaction of aminocapronitrile using a cobalt/alumina catalyst, we investigated a method for achieving even higher activity and higher selectivity.As a result, we found that a small amount of water (4 parts by weight or less) was added to 100 parts by weight of aminocapronitrile. The present invention was achieved based on the discovery that when water is present, side reactions due to water are so small that they do not pose a problem, and in fact, the effect of enhancing the catalytic activity is significantly large. Its feature is that the catalytic activity is significantly enhanced by the presence of 0.2 to 4 parts of water, most preferably 0.5 to 2 parts by weight of water, in the reaction system per 100 parts by weight of nitrile. It is in. This effect of increasing the catalytic activity by water is such that the reaction rate is doubled compared to an anhydrous reaction system. Due to this effect, the hydrogen pressure is 50kq/d or less, for example, 1okq/cA, 120℃
For example, it reacts in a short time even at 110℃! Since the process can be carried out completely, it is also possible to significantly reduce nitrile hydrolysis and other side reactions.

If the amount of water present in the system is less than 0.2 parts by weight per 2 liters/100 tons of water, the above effect is not observed;
When the amount exceeds 1 part by weight, the amount of side reaction products increases significantly and the yield decreases. The most preferable addition amount is 0.5 to 2 parts by weight.

There are no particular restrictions on the method of adding water into the system. For example, it may be added to water alone or as an aqueous caustic solution, or it may be included in aminocapronitrile and the catalyst in advance.

In addition, when there is no need to accelerate the reaction rate, the reaction rate may be adjusted by reducing the amount of catalyst used or lowering the hydrogen pressure to match the reaction acceleration by water.

Further, it is preferable that a caustic alkali such as a caustic sorter be present in the system in order to improve the quality of hexamethylene diamine. The caustic alkali is preferably used in an amount of 0.0 l to 1 ffiffi part per 100 parts by weight of aminocapronitrile. Furthermore, the hydrogen pressure in the system i, t 1-50 kq
/cA, temperature i, i50- ], about 40 parts is sufficient.

In addition to aminocapronitrile, other compounds that can be converted into hexamethylenediamine by hydrogenation may be used in combination as starting materials for hydrogenation; In order to facilitate purification by reducing the number of dishes, it is preferable not to use other compounds in combination. Further, it is preferable not to use an alcohol such as methanol in combination.

The present invention will be specifically described below with examples, but the present invention is not limited thereto.

Example 1 A 500 ml autoclave was charged with 22.5 f/ of cobalt-alumina catalyst, 150 g of aminocapronitrile, and 0.3 F of a 25% aqueous solution of caustic soda. Further, as shown in Tables 52 to 8 in Table 1, water was added in the required amount to give a moisture content of 0.15 to 10.15 parts per 100 parts by weight of nitrile. Comparative experiments were also carried out in the case where 0.075 g of solid caustic hoop was added instead of the aqueous caustic soda solution (41) and in the case where no caustic soda or water was added at all (A9). The autoclave is equipped with a pressure sensor and is heated under a constant hydrogen pressure of 10 kq/c- with sufficient stirring.
The hydrogen absorption rate at 30°C was followed. After confirming that hydrogen absorption had completely stopped, the catalyst was separated from the reaction mixture and vacuum distilled (5**HQ) to determine the gas chromatography purity and high boiling point residue ratio (residue amount/charged amount) of the fraction. .

From this result, it is clear that if the moisture content is too low, the catalyst activity cannot be sufficiently increased and the reaction rate is low.
It can be seen that when the amount exceeds t%, there is almost no increase in the reaction rate, and the cruelty rate increases rapidly, resulting in a decrease in yield.

Example 2 Example 11 Regarding experiment names 2 and 56 in Table 1, the reaction was carried out in the same manner as in Example 1 except that the amount of cobalt-alumina catalyst added was changed, and Example 1 except that the hydrogen pressure was changed. Tables 2 and 3 show the results of an experiment similar to 1.

Table 2: Catalyst addition amount and relative reaction rate Table 3: Hydrogen pressure and relative reaction rate These results show that the water content of the reaction system controls the reaction rate more than the reaction pressure and catalyst addition rate.

Claims (1)

[Claims] In a method for producing hexamethylene diamine by hydrogenating aminocapronitrile in the presence of a cobalt/alumina catalyst, 0% is added to the hydrogenation reaction system based on 100 parts by weight of the aminocapronitrile.
, a method for producing hexamethylene diamine, characterized in that 2 to 4 parts by weight of water is present.