NL7905987A - PROCESS FOR THE PURIFICATION OF TERTIARY AMINES. - Google Patents

Description

y - 1 - IT. 0. 27,874 CHEMICAL WEEKS HULS AKTIMGESELLSCEAFB, in Marl,

Federal Republic of Germany

Method for the purification of tertiary amines.

The invention relates to a process for the purification of tertiary amines.

Unwanted by-products generally occur both from the preparation of tertiary amines and from their thermal load in some engineering processes. Complete separation thereof by preparative methods is complicated or impossible.

The problem of the invention was therefore to provide a process which makes it possible to purify tertiary amines in a simple and economical manner. 10

The process according to the invention is characterized in that the amine to be purified is optionally passed over adsorbents in an organic solvent and, if appropriate, the pure tertiary amine is isolated from the eluate.

Tertiary amines to be purified are, for example, jej tertiary amines which contain impurities from the preparation or the tertiary amines used in the thermolysis of tertiary amine hydrochlorides, such as, for example, according to German Offenlegungsschrift 2,633 ° 40 and German patent application. P 28 05 933 · 8 have been obtained 20

Namely, it has been established by the thermal cleavage of amine hydrochlorides that tertiary amines are formed in a more or less short time, inter alia, by the formation of interfering primary and secondary amines, which are also the main part of the impurities in general by the preparation of tertiary amines. dissected. These decomposition products or the hydrochlorides thereof obtained from the amines therefore also serve with -1- 7905987. 2 in view of the economic efficiency of the processes to be removed before the tertiary amines are recycled.

In general, the process according to the invention is carried out such that the tertiary amine to be purified is preferably passed over the adsorbent dissolved in a suitable organic solvent.

Suitable solvents are those which are totally or substantially non-polar, such as, for example, straight or branched aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbons. Typical examples of these solvents are hexane, heptane, octane, iso-octane, nonane, decane, undecane, dodecane, tetradecane, cyclohexane, methylcyclohexane, decalene, tetralien, benzene, toluene, cumene, xylenes, cumenes, ethylbenzene , p-tert-butyltoluene, trimethylbenzenan, 1,2,4-triethylbenzene, 1,3,5-triethylbenzene, tert-butyl-m-xylene, 1.2.3.4-tetramethylbenzene, 1.2.3.5-tetramethylbenzene, 3-phenylpentane and dodecylbenzene.

The effective concentration of the tertiary amine in the solution is selected depending on the nature of the amine and the amount of the impurities to be separated, and can be easily determined by some preliminary tests. Generally, a ratio of the amine to the solvent of 1: 1-1.1 is used. In addition, another solvent can be used as an eluent. At large concentrations of impurities, it is also possible to partially separate the feather cleanings in advance using the different solubilities in the selected solvent.

Suitable adsorbents for the process according to the invention are aluminum oxides with a high specific surface area (100-400 m 2 / g) in granular, tableted or broken form. It has been found that the basicity of the alumina is not decisive, basic, neutral or acidic alumina can be used on the surface. However, the activity level is important. The activity steps 1 to 3 may be useful, preferably the activity steps 1 and 2. 35

Aluminum oxide used as a chromatographic adsorbent is subdivided into 5 activity steps according to the Brockmann scale. The aluminum oxides standardized according to Brockmann are distinguished by the water contents (in weight percent): 1 (0 wt.%), 2 (3 wt.%), 3 (4.5 wt.%), 4 (9.5 wt.%) .5 (15 wt.%) (OA Heumüller, Hömpps Chemie- 5

Lexikon, hl, 427 C1972); further literature is also indicated).

Other suitable adsorbents are silica gels with 2 specific surfaces of 500 to 700 m / g, silanized 2 silica gels (300-400 τα. / G) and molecular sieves of the calcium-zeolite type (500-600 m / g). In the silica gels the -jq silicic acid is present in the form of highly condensed polysilicic acids with leaf structure which is rich in surface. Silica gels whose hydrophilic surfaces have been rendered hydrophobic by reaction with chlorosilanes are referred to as silanized silica gels. The surface area is determined according to the BET method (S. Brunauer, P.H. Emmett, T. Teller, J. Am. Chem. Soc.

£ 0,309 (1938)).

In general, the process according to the invention is carried out at room temperature (15-30 ° C), but it may also be expedient to use higher temperatures. 20

The eluate obtained can be used either directly or after a concentration with complete removal of the solvent, the concentration being carried out in any desired manner.

The adsorbent can be regenerated without difficulty using polar solvents.

According to the process of the invention, tertiary amines with a total of 6 to 54 carbon atoms in the alkyl groups are preferably purified, which originate from the thermolysis of tertiary amine hydrochlorides and which are then recycled without separation of the solvent. ird. The purity of the purified tertiary amine should be greater than 99%, preferably greater than 99.5%, especially greater than 99.9%

The method according to the invention is illustrated by the following examples.

7905987 er \ 4 é

Example I

A mixture of 45 S t: d- (2-ethylhexyl) -amine and 5 g of di (2-ethylhexyl) -amine hydrochloride, dissolved in 50 g of xylene, was passed through an adsorption column (diameter 22 mm), containing 225 ml of acid alumina (activity step 1, surface area 200 m / g) was filled. 250 ml of xylene were used as the eluent. The eluate discharged contained 44.5 g of gas chromatographically pure tert-amine. 4.6 g of the secondary amine hydrochloride were washed by washing the adsorbent "with a mixture of acetone and methanol in a ratio of 1: 1.

isolated. The polar solvent mixture was exchanged again for xylene; a new separation of an amine mixture was then possible without further regeneration of the adsorbent. Example II

A mixture of -1492.5 g of tri- (2-ethylhexyl) -amine and 7.5 g of di- (2-ethylhexyl) -amine hydrochloride dissolved in 1500 g of xylene was mixed with 225 ml of acid alumina (activity step 1.0 specific surface area 200 m yg) in an adsorption column according to Example 1, without the use of an additional eluent. 1270 g of pure gas tert-amine 20 were obtained.

Example III

A mixture of 90 g of tri- (2-ethylhexyl) -amine, 10 g of di- (2-ethylhexyl) -amine and 1 g of 2-ethylhexylamine dissolved in 100 g of xylene was separated according to the procedure of Example II. 25

Until the occurrence of secondary and primary amine in the eluate, 81 g of gas chromatographically pure tertamine was isolated.

Example IV

A mixture of 200 g of tri- (2-ethylhexyl) -amine and 4 g of di- (2-ethylhexyl) -amine, dissolved in 200 g of xylene, was mixed with 225 ml of silanized silica gel (surface area 535 m / g) according to the method of Example II separated. 115 g of gas chromatographically pure tert-amine were obtained until secamine developed in the eluate.

7905987 35 5

Example V

A mixture of 200 g of tri- (2-ethylhexyl) -amine and 4 g of di- (2-ethylhexyl) -amine, dissolved in 200 g of xylene, was mixed with 225 ml of silica gel with a surface area of 700 m / g according to the method separated from example II. 100 g of gas chromatography were purified until 5 seconds of amine had occurred in the elate. received.

Example VI

A mixture of 200 g of tri- (2-ethylhexyl) -amine and 4 g of di- (2-ethylhexyl) -amine, dissolved in 200 g of xylene, was mixed with 225 ml of 10 2 silica gel with a surface area of 500 m / g according to separate the method of Example II. 60 g of gas chromatographically pure tert-amine were obtained until secamine appeared in the eluate.

Example VII 45

A mixture of 500 g of tri- (2-ethylhexyl) -amine and 5 g of di- (2-ethylhexyl) -amine, dissolved in 500 g of xylene, was added with 225 ml of 2 calcium zeolite with a surface area of 550 m / g according to the method of Example II separated. Until secamine occurred in the eluate, 250 g of pure tertamine was chromatographed.

Example VIII

A mixture of 1492.5 g of trioctylamine and 7.55 g of dioctylamine dissolved in 1500 g of xylene was separated with 225 ml of acidic alumina (activity step 1, surface area 200 ml / g) according to the procedure of Example II. Until the occurrence of sec. amine in the eluate, 1190 g of gas chromatographically pure tert. amine isolated.

Example IX

A mixture of 180 g of triethylamine and 20 g of diethylamine, dissolved in 200 g of xylene, was separated with 225 ml of acid alumina 2 (activity step 1, surface area 200 m / g) according to the procedure of Example II. Until secondary amine appeared in the eluate, 110 g of gas chromatographically pure tertamine was isolated. 35 790 5 9 87 ir 6

Example X.

A mixture of 180 g of trioctylamine and 20 g of dioctylamine was separated with 225 ml of acidic alumina (activity step 1, surface area 200 m / g) according to the procedure of Example II. Until sec.amine occurred at the exit of the adsorption column, 105 g of gas chromatography was pure tert. amine isolated.

Examples XI and XII

A mixture of 100 trilaurylamine and 500 g dilaurylamine or 100 g tristearylamine and 500 g distearylamine was pre-separated by slurrying in xylene. The tert-amines dissolved quantitatively, while the sec. amines dissolved in an amount of up to 5 wt.

For the complete separation of the secamines, the filtrate was treated on 225 ml of acid alumina with a surface area of 200 m / g as described. The eluate obtained contained the tert-amines which, according to the thin layer chromatographic analysis, were free of secamines.

Example XIII

A mixture of 150 g of trioctylamine and 0.5 g of dioctylamine was dissolved in an hour continuously through an adsorption column (diameter 100 mm), filled with 8 kg of acid alumina (activity step 1, surface area 2 200 m / g). 600 g of dodecane from a thermal cleavage test of amine hydrochlorides was passed. The drained eluate remained free from secamine for about 800 hours.

7905987

Claims (3)

Process for the purification of tertiary amines, characterized in that the amine to be purified is optionally passed in an organic solvent over adsorbents and, if appropriate, the pure tertiary amine is isolated from the eluate. 5 2. Process according to claim 1, characterized in that a tertiary amine from the thermolysis of tertiary amine hydrochloride is used as the tertiary amine to be purified. 3. Process according to claims 1 and 2, characterized in that the adsorbent is aluminum oxide with a 2 specific surface area of 100 - 400 m / g, silica gel with a 2 specific surface area of 500 - 7 ° 0 m / g, silanized pebble 2 gel. with a specific surface area of 300-400 m / g or ealeium zeolite with a specific surface area of 500-600 m / g determined by the BET method. 7905987