DD238043A1 - PROCESS FOR THE PREPARATION OF DIPROPYLENEDRIAMINE - Google Patents

Abstract

The invention relates to a process for the hydrogenation of iminobispropionitrile and / or predominantly iminobispropionitrile-containing cyanoethylation products of ammonia, which gives high yields of dipropylenetriamine. The simultaneous addition of propane-1,3-diamine, ammonia and water during the hydrogenation avoids a cleavage of the iminobispropionitrile to aminopropionitrile and acrylonitrile and thus the deposition of polymers on the surface of the hydrogenation catalysts.

Description

-Z- MO UtO

Cyanethylation of ammonia-produced, predominantly IBPN-containing mixtures of hydrogenation catalysts at elevated temperature and elevated pressure and in the presence of ammonia according to the invention achieved in that the hydrogenation of IBPN and / or predominantly IBPN containing cyantylation of ammonia in the presence of both propane-1,3- diamine, ammonia and water in the molar ratio N H3 / IBPN of 0.5 to 1.5, preferably 0.6 to 1.4, DPA / IBPN of 0.3 to 0.8, preferably 0.4 to 0.7 and H ₂ (VIBPN from 0.05 to 0.5, preferably 0.1 to 0.3 is carried out, wherein all components are merged intensively mixed at the latest immediately before the catalyst layer and

These happen in the trickle phase.

For the process according to the invention, it is possible to use directly both IBPN purified by distillation and a cyanoethylation product of ammonia prepared by a known process. The PDPN obtained by distillation both PDA and liquid ammonia and water are added before entering the hydrogenation reactor, while only a PDA must be added to a Cyanethylierungsprodukt produced by a known method of ammonia, because it is necessary for the hydrogenation by the novel process Ammonia and water already contains as the high IBPN formation favoring additives from the cyanoethylation ago.

As hydrogenation catalysts for the process according to the invention, it is possible to use all catalysts suitable for hydrogenating nitriles, preferably those containing Co and other hydrogenation-active additives on an acid-free support

contain.

The hydrogenation by the process according to the invention is carried out in the temperature range from 335 to 395K, preferably 355 to 375 K, wherein a heating jacket divided into several heating zones of the high pressure reaction tube preferably used for hydrogenation despite the exothermic hydrogenation almost isothermal operation over the entire

Catalyst layer allowed to reach.

The hydrogenation by the process according to the invention is carried out with a hydrogen excess of at least 20 moles per mole of nitrile group to be hydrogenated at a pressure of 6 to 25 MPa, preferably 20 to 22 MPa. The excess

Hydrogen can be recycled.

A preferred embodiment of the process according to the invention is the continuous hydrogenation in the trickle phase.

However, this does not exclude that the process can also be carried out batchwise in an autoclave.

The amine mixture obtained by the process according to the invention is worked up by known procedures, for example by distillation, to PDA, DPTA and possibly also propylamine, wherein the PDA is predominantly recycled.

The hydrogenation results are monitored by gas chromatography. The hydrogenation by the novel process is virtually quantitative, so that aminopropionitriles are detectable only in traces or very small amounts.

embodiment

In a high-pressure reaction tube (length 1500 mm, diameter 28 mm) over a length of 1 200 mm, a bed of a pre-reduced hydrogenation catalyst (24Ma .-% CoO impregnated on silicate and acid-free Al ₂ O ₃ strands) introduced, each after top and bottom, symmetrically distributed, through porcelain caliper body (diameter 3 mm) to the lower and upper end of the reaction tube is completed.

At the upper end of the reaction tube, the task of iminobispropionitrile, water, liquid ammonia (or cyanoethylation product) and propane-1,3-damin (amounts see table) via a Cenics mixer is carried out via piston metering pumps. The hydrogen is introduced into the high-pressure reaction tube parallel to the liquid feed products and flows through them in cocurrent with the catalyst layer.

The catalyst layer is separated by a heating jacket divided into 3 separate heating zones with independent Heizbzw. Cooling circuits kept at the required temperature. The temperature is controlled over the length of the catalyst layer via 3 centrally arranged thermocouples (diameter of the thermocouple sleeve 4 mm). The hydrogenation products, including the hydrogen, are withdrawn at the lower end of the reaction tube and separated in a high-pressure separator into liquid and gaseous segregation products, the relaxation of which takes place separately. The hydrogenation results are determined by gas chromatography on the reaction product which is liquid under normal pressure.

table

2 3 4 5 6

IBPN 'cyanoethylation product of NH ₃

240 65 80 110 150 5 000 5000 5000 5000 5000

77.0 11.5 1.7

22 24 24 24 24 375 375 355 375 376 394

Middle I

example 1 feedstock IBPN Amounts used g / h IBPN98% strength 500 water 15 Ammoniakfl. 60 PDA 150 Hydrogen N l / h 5,000 Cyanethylation product g / h with IBPN APN NTPN VCN reaction conditions Pressure MPa 22 Temperature K 370 above (200 mm) 370

below (900 mm) 371 374 Composition of the liquid 45.8 50.4 mol 0.51 0.81 354 373 375 393 catalyst loading Hydrogenation product in% by mass 38.4 35.2 0.88 0.59 IBPNg / mlxh 0.54 0.54 DPTA 0.2 0.3 0.21 0.21 0.20 0.20 0.35 0.35. hydrogenation result PDA 1.7 2.3 propylamine 0.1 0.2 66.2 79.7 IBPN 2.2 1.9 = / 3-aminopropionitrile APN 10.2 8.4 = Iminobispropionitrile 45.8 47.2 54.2 43.8 ammonia = Nitrilotrispropionitrile 40.2 31.4 28.4 30.1 polymers = Acrylonitrile 0.3 0.5 0.4 0.4 Use product ratios = Dipropylenetriamine 0.8 2.0 1.7 0.2 DPA / IBPN = Propane-1,3-diamine 0.2 0.7 0.6 <0.1 NH3 / IBPN 3.5 3.2 3.3 2.8 H ₂ O / IBPN 16.4 12.4 8.6 14.2 Yield DPTA mol% based on IBPN 0.58 0.41 0.56 0.77 Notes: APN 0.66 0.66 0.66 0.66 IBPN 0.23 0.23 0.23 0.23 NTPN VCN 74.2 71.8 87.2 75.5 DPTA DPA polymers = All hydrogenation products with a boiling point of> 420 K / 2 Torr, ie including tripropylenetetraamine

Claims (3)

Invention claim: 1. A process for the preparation of dipropylenetriamine by hydrogenation of iminobispropionitrile and / or produced by cyanoethylation of ammonia, predominantly iminobispropionitrile-containing mixtures of hydrogenation catalysts at elevated temperature and elevated pressure and in the presence of ammonia, characterized in that the hydrogenation of iminobispropionitrile and / or predominantly iminobispropionitrile containing cyanethylation of ammonia in the presence of both propane-1,3-diamine, ammonia and water in the molar ratio NH3 / IBPN of 0.5 to 1.5, DPA / IBPN of 0.3 to 0.8 and H ₂ CVIBPN is carried out from 0.05 to 0.5, wherein all components are merged intensively mixed at least immediately before the catalyst layer and these happen in the trickle phase. 2. The method according to item 1, characterized in that the necessary for the hydrogenation additives of ammonia and water are supplied together with the predominantly iminobispropionitrile containing Cyanethylierungsprodukt of ammonia. 3. The method according to item 1 and 2, characterized in that the hydrogenation is carried out almost isothermally over the entire catalyst layer. Field of application of the invention The invention relates to a process for the preparation of dipropylenetriamine (DPTA) by hydrogenation of iminobispropionitrile (IBPN) and / or products of cyanoethylation of ammonia, which contain predominantly IBPN. DPTA is an important intermediate, for example for the production of epoxy resins. Characteristic of the known technical solutions The hydrogenation of nitriles is a well-known, industrially used possibility for the synthesis of amines which, in order to suppress side reactions for the formation of secondary and tertiary amines, is carried out in the presence of considerable amounts of ammonia and preferably of co-catalysts. In the hydrogenation of aminopropionitrile to di- and polyamines come as additional difficulties nor the shift of the equilibrium between the Aminopropionitrilen by the high ammonia excess, the thermal instability of Aminopropionitrilen and the occurrence of free acrylonitrile added. The control of the exothermic hydrogenation of aminopropionitriles, especially on a continuous scale, therefore requires special measures. It is known, for example, to reduce mixtures of aminopropionitriles prepared from excess ammonia and acrylonitrile, to powdered CoO (DE-AS 1034184), to manganese-doped catalysts (DE-AS 1543337) and to cobalt catalysts on a silicate-free support (DE-AS 1593763) hydrogenate. Furthermore, was also ready? worked in the hydrogenation with a partial conversion (DE-AS 1493465) or with an addition of water (DE-OS 2004405). The aim of all these measures should be to significantly extend the useful life of the same, which is limited to a few days by the deposition of polymers on the catalysts, while at the same time reducing the proportion of non-recyclable polymeric products. Despite the substantial ammonia addition of up to 45 moles of NH ₃ per mole of acrylonitrile in the hydrogenation and accepting of low space-time yields by carrying out the hydrogenation at low temperatures to limit polymerization, no substantial catalyst life extension could be achieved become. It is also known to stabilize Ni / Cu / Cr catalysts by the addition of sodium hydroxide or sodium methylate in the hydrogenation of IBPN (US-PS 3384666), so that the operating time of the catalysts is extended to 200 h. It is also known to hydrogenate IBPN discontinuously with Raney-Ni in alcoholic solution saturated with ammonia. These possibilities can satisfy neither technically nor economically. Object of the invention The aim of the invention is to hydrogenate IBPN and / or Cyanethylierungsprodukte of ammonia with high levels of IBPN under such conditions that DPTA is the main product of the hydrogenation and the hydrogenation can be carried out technically simple and economical. Explanation of the essence of the invention It was therefore an object to provide such conditions for the hydrogenation of IBPN and / or ammonia and acrylonitrile, mainly containing IBPN mixtures such that a cleavage of the IBPN is largely suppressed and the formation of free acrylonitrile and its polymerization is avoided at the catalyst surface , The object is achieved by a process for the preparation of dipropylenetriamine by hydrogenation of IBPN and / or by