DE2238452A1 - PROCESS FOR THE CONTINUOUS MANUFACTURING OF HEXAMETHYLENEDIAMINE BY HYDROGENATION OF ADIPONITRILE - Google Patents

Description

PATENT ADVOCATE MS OFFENBACH (MAIN) · KAISBRSTRASSE 9 · TBLEFON (»ill) USSIC · KABEL EWOPAT

August 3, 1972 1/7134

Zimmer Aktiengesellschaft Planning and construction of industrial plants 6 Frankfurt (Main) 60

Process for the continuous production of hexamethylenediamine by hydrogenating adiponitrile

The invention relates to a process for the continuous production of hexamethylenediamine by hydrogenation of adiponitrile at a hydrogen partial pressure of more than 25 atu, preferably between 180 and 300 atu, in the presence of ammonia over catalysts with contents of cobalt and its compounds and of compounds of alkali - And alkaline earth metals at temperatures between 80 and 250 ⁰ C, preferably between 100 and 150 C.

<a> 2 · »

409807/1098

Hexamethylene diamine is an important mass product for the production of polyamides, especially polyhexamethylene adipamide and polyhexamethylene sebacic acid diamide. It will preferably prepared in the manner described above by a hydrogenation process on special catalysts. For A number of catalysts have become known about the hydrogenation process. So are z. B. in DT-OS 1 518 118 a Cobalt catalyst and a process for its preparation are described in which the presence of magnesium oxide plays a special role. However, the form in which the known catalyst is to be used is not specified. It is only run as an example that the Catalyst components can be precipitated and deposited on carriers. Have supported catalysts but in many cases they do not have long idle times or do not tolerate heavy loads. It was also found that the presence of acidic carriers such as silicon dioxide leads to the formation of by-products such as hexamethyleneimine, Diaminocyclohexane-1,2, aniline and secondary amines increased. These by-products not only interfere with further processing, they also reduce the yield. In the cited publication, a yield of between 88 and 97% is stated to be achievable.

For a mass product such as hexamethylenediamine, technical progress is already given if the yield or the purity can only be increased slightly. It should not be overlooked that even small amounts of by-products have given way to costly cleaning and treatment processes, which can significantly worsen the competitiveness of the product. In connection with supported catalyst

409807/1098

not only the disadvantages listed above with regard to by-product formation were found, it has also been shown that supported catalysts are unable to achieve the desirable high space-time To achieve sales with the highest selectivity.

The invention is based on the object of avoiding the disadvantages inherent in the known catalyst systems and of specifying a catalyst which guarantees a high degree of selectivity or yield at high loads and at the same time has a long service life. It has now been found, surprisingly, that the object set can be achieved according to the invention in the method described at the beginning by the use of catalysts which are composed of a homogeneous mixture of oxides and / or carbonates of cobalt and compounds, preferably hydroxides of alkali and alkaline earth metals, be prepared by using a binder, by granulating or pelletizing and subsequent thermal treatment of the catalyst green bodies in a hydrogen atmosphere at temperatures of 80-350 ⁰ C to at least partial reduction of the cobalt compound to cobalt metal if necessary.

Such an unsupported catalyst is different basically of the supported catalysts, namely by the fact that they have the same, has a homogeneous composition. This is linked to a long service life on the one hand, and otherwise with the carrier material eliminated possible side reactions. In the present case it is possible with the one according to the invention Catalyst in particular, the formation of diaminocyclohexane-1,2, a highly undesirable by-product to

409807/1098

reduce by at least a factor of 2. While the content of this by-product when using supported catalysts is on average 2500 ppm, it is possible when using the catalyst according to the invention, not only this

in part to less than 1300 ppm, but also secondary amine formation, e.g. B. of bis-hexamethylene triamine, to suppress.

As a result of the specified treatment of the green catalyst pieces in a hydrogen atmosphere at temperatures between 80 and 350 ^° C., the oxides and / or carbonates of cobalt are wholly or partially reduced to cobalt.

The result found is also surprising insofar as it was stated in DT-OS 2 101 911 with regard to adiponitrile hydrogenation that the alkali or alkaline earth hydroxide content of cobalt contacts must not exceed a very low value, otherwise back on Increase in undesirable, yield-reducing by-products such as diaminocyclohexylamine and aminomethylcyclopentylamine would take place. In contrast, it was found that the cobalt catalyst according to the invention also at higher Base or alkali contents of up to 55% by weight not only do not reduce the hexamethylenediamine yield and also none Loss of catalytic effectiveness brings with it, but rather noticeable in terms of selectivity and reaction rate of the conventional catalysts is superior.

The proportion of cobalt oxide in the catalyst can be in spread wide boundaries. After the thermal treatment, calculated as cobalt metal, it can range between 10 and

409807/1098

75% by weight, preferably between 30 and 65% by weight. Also, the content of hydroxides of the alkali and alkaline earth kalimetalle ¹ can vary within wide limits and, for example, between 1 and 55 wt .-%, but preferably between 5 and 45 wt .-%, based on the finished catalyst amount. Finally, the degree of reduction of the cobalt content can also be varied over a wide range without influencing the effectiveness of the catalyst. It is possible to carry out the thermal treatment of the green catalyst compact under a hydrogen atmosphere until the degree of reduction of the cobalt contained in the catalyst is between 20 and 100%, preferably between 35 and 70%.

Another advantage of the catalyst according to the invention is his broad area of work. It has been shown that the hydrogenation selectivity is within a temperature deviation of 40 C is hardly temperature-dependent. Within this range, the reaction product contains at least 99% Hexamethylenediamine. There are no particular purity requirements for the adiponitrile used for the hydrogenation to deliver. However, the proportion of by-products should generally not exceed 0.8%. Besides, it doesn't matter which manufacturing process the adiponitrile comes from. Adiponitrile, which after the amalgam or hydrodimerization process was obtained, is suitable for carrying out the method according to the invention in the same way.

Details with regard to the preparation of the inventive Catalyst with different percentages of its constituents can have the following two

409807/1098

2238A52

play 1 to 4 can be taken. The mode of action of the catalysts is illustrated in the same examples shown hydrogenation process described.

The one necessary for the catalyst according to the invention basic content can be achieved in various ways in the manufacture of the catalyst.

Either the hydroxidic form is advantageously added in advance or the hydroxidic form is formed only when reducing the catalyst by using oxidic forms of the alkali and alkaline earth metals with water vapor reacts at a slightly elevated temperature.

So you can also solutions, preferably of chloride or nitrate »of the metals cobalt and z. B. Precipitate calcium in the required ratio with sodium hydroxide solution, the precipitate Separate from cobalt hydroxide and calcium hydroxide and dry washed or unwashed and to the appropriate Process shapes by machine. With this procedure, it is easy to bring in further promoters.

Corresponding alkali metal or alkaline earth metal carbonates can also be used which, after mixing with the cobalt compound, are thermally decomposed and then, at low temperatures, as discussed, largely converted to hydroxide Form can be converted. A certain amount of oxide and / or carbonate does not have a disruptive effect.

409807/1098

-Y-

Example 1:

54.9 parts (parts by weight) of basic cobalt carbonate / 5 parts of sodium hydroxide, 21 parts of water glass (density - 1.37) and approx. 8 parts of water were successively made into a thick paste in a mixer and then into strand sections (green compacts) with a diameter Deformed 4.5 mm and approx. 6 mm in length. The so-called green catalyst bodies were ^{slowly dried at 120 °} C. and slowly treated with hydrogen in a shaft furnace as a loose bed at a temperature of 350 ^{° C.}

The treatment was discontinued after a period of 36 hours and the catalyst cooled. An analysis showed the following composition:

Components:

Cobalt, total. 61.2% by weight

Sodium hydroxide (free) 7.0% by weight

Sodium silicate (from water glass) approx. 22.0% by weight

Degree of reduction 64%

2000 ml of the catalyst prepared as described were placed as a loose bed in a vessel equipped with heating jacket · pressure-resistant reaction tube of 3.0 cm diameter and 600 cm in height and heated to a temperature of 100 ⁰ C. A trickle device installed in the upper part of the reaction tube was used to feed in 1.04 kg of adiponitrile per hour. In addition, 1.4 kg of ammonia and 22.0 Nm of hydrogen per hour were fed in and the process parameters were controlled so that a pressure of 265 atm prevailed in the reaction tube. The temperatures were at the entrance of the

40980 7 / ro 9.3 -. :

Reaction tube, 85 ° C, in the middle of 95 ⁰ C and at the outlet 120 ⁰ C. An analysis of the product gave the following results:

Hexamethylenediamine 99.4 %

Hexamethyleneimine 0.17%

Diaminocyclohexane-1,2 0.16%

secondary amines 0.18 %

2-aminomethylcyclopentylamine 600 ppm

Aniline not detectable

The feedstock was chemically purified adiponitrile from the catalytic exhaustive AmmonoIyse Adi pinsäre at temperatures from 270 to 320 ⁰ C. The content of 2-aminomethylcyclopentylamine corresponded only contained in the inserted adiponitrile 2-cyano-cyclopenten-1-ylamine (550 to 600 ppm ). There was therefore no increase in the 2-aminomethylcyclopentylamine content as a result of the hydrogenation process. E-aminocapronitrile and adiponitrile could not be detected, which corresponds to complete conversion of the adiponitrile. After throughput of 71 kg of adiponitrile, no reduction in the catalyst activity was found. A space velocity over the catalyst is calculated from the above figures

3
of 0.52 kg of adiponitrile per dm of catalyst and hour.

Example 2:

The catalyst prepared according to Example 1 was used in the same amount and in the same reaction device hourly now with 1.4 kg adiponitrile, 3.3 kg

409807/1098

Ammonia and 24.0 Nm of hydrogen are applied. The pressure in the reaction tube was 265 atm. The temperatures were at the following values:

at the entrance: - 95 ⁰ C

in the middle: 105 ⁰ C

at the exit: 135 C.

An average analysis of this product produced the following result:

Hexamethylenediamine 99.6%

Hexamethyleneimine 0.03%

Diaminocyclohexane-1,2 0.18%

secondary amines 0.08%

2-aminomethylcyclopentylamine 600 ppm

The space velocity over the catalyst was 0.7 kg of adiponitrile per dm of catalyst and hour.

Example 3:

Basic cobalt carbonate was intensively mixed with powdered calcium hydroxide with the addition of so much water / water to the consistency of a crumbly mass and then processed in an extrusion device to form shapes with a diameter of 5.5 mm and an average length of 8-10 mm . The green catalyst was: and had the following composition:

is working. The green catalyst was dried at 120 ⁰ C

Cobalt 36.8 % by weight

Calcium hydroxide 35.6% by weight Residual moisture approx. 1% by weight

- 10 -

409807/1098

Subsequently, was performed in a tube furnace further heating under nitrogen stream up to 350 ⁰ C. The nitrogen was slowly admixed with hydrogen in accordance with the temperature up to 30 h of nitrogen by pure hydrogen was replaced.

After a further 4 hours of hydrogen treatment, the mixture was cooled and the catalyst is partially stabilized with an air / nitrogen mixture. The analysis showed the following composition:

Cobalt, total 44.0% by weight

Calcium hydroxide 40.7% by weight

Degree of reduction 45%

In a pressure-tight reaction tube, 300 parts by volume of the catalyst were mixed hourly with 300 parts by weight of adiponitrile, 1000 parts by weight of ammonia and 10600 normal parts by volume Reacted hydrogen at a pressure of 270 atm.

The temperature at the inlet of the reaction tube was 85 ^° C. and at the outlet 116 ^° C. An analysis of the product gave the following result:

Hexamethylenediamine 99.9% by weight

Hexamethyleneimine 0.03% by weight

Diaminocyclohexane-1,2 0.06 % by weight

secondary amines traces

2-aminomethylcyclopentylamine 600 ppm

The space velocity over the catalyst was calculated as 1.0 kg of adiponitrile per d * 3 of catalyst.

- 11 -

409807/1098

2238A52

Example 4:

Fine cobalt oxide was intensively mechanically mixed with calcium hydroxide, made by slaking pure quicklime with the required amount of water, and with graphite as a lubricant. By means of a tablet press, this mixture was compressed into tablets of dimension 4 mm in diameter and 4.8 mm length, and then dried at 120 ⁰ C. The green contact obtained in this way had the following composition:

Cobalt 41.6% by weight

Calcium hydroxide 39.8% by weight

Graphite approx. 2.0% by weight

This green contact was introduced into a conventional, pressure-resistant reactor tube with a volume of 300 ml as a loose bed and charged with 0.3 kg of adiponitrile, 0.85 kg of liquid ammonia and 10.8 Nm ^{3 of} hydrogen. The working pressure was 270 atm. The temperature at the inlet was 79 ⁰ C ₁ in the middle of 121 ⁰ C and at the outlet 133 ⁰ C. An analysis of the product showed folgendeis Result:

Hexamethylenediamine 99.3% by weight

Hexamethyleneimine 0.02% by weight

Diaminocyclohexane-1,2 0.12% by weight

sec. Amine traces

2-aminomethylcyclopentylamine 600 ppm

The space velocity over the catalyst was 1 kg of adiponitrile per dm ^{3 of} catalyst and hour.

- Expectations -

409807/109

Claims (6)

- 12 claims ίl. \ Process for the continuous production of hexawexhylenediamine by hydrogenation of adiponitrile at a hydrogen partial pressure of more than 25 atmospheres, preferably between 180 and 300 atmospheres, in the presence of ammonia over catalysts with contents of cobalt and its compounds and of compounds of alkali and alkaline earth metals at temperatures between 80 and 250 ⁰ C, preferably between 100 and 150 ° C, characterized by the use of catalysts consisting of a homogeneous mixture of oxides and / or carbonates of cobalt and compounds preferably hydroxides of the alkali and alkaline earth metals, possibly be prepared by using a binder, by granulating or pelletizing and subsequent thermal treatment of the catalyst green bodies in a hydrogen atmosphere at temperatures of 80-350 ⁰ C to at least partial reduction of the cobalt compound to cobalt metal. 2. The method according to claim 1, characterized in that the proportion of cobalt oxide in the catalyst after the thermal treatment, calculated as cobalt metal, is between 10 and 75% by weight, preferably between 30 and 65% by weight. 3. The method according to claims 1 and 2, characterized in that the content of compounds, preferably hydroxides of the alkali and alkaline earth metals between 1 and 55 wt .-%, preferably between 5 and 45 wt .-%, based on the finished catalyst , amounts to. - 13 - 409807/1098 4. The method according to claims 1 to 3, characterized in that the thermal treatment of the catalyst, green compacts under a hydrogen atmosphere, if necessary under pressure, is carried out until the degree of reduction of the cobalt contained in the catalyst is between 20 and 100%, preferably between 35 and 70%, lies. 5. The method according to claims 1 to 4, characterized in that the hydrogenation with a molar excess of ammonia over the adiponitrile of 2 to 100, preferably from 10 to 60, is carried out. 6. The method according to claims 1 to 5, characterized in that the amount of hydrogen in the hydrogenation in relation to the adiponitrile throughput is between 20 to 200 times, preferably between 50 to 150 times, molar. 40980 7/1098