Preparation of primary and secondary amines from nitriles

Details Preparation of primary and secondary amines from nitriles Preparation of primary and secondary amines from nitriles

2002-01-03

2004-09-14

Davis, Brian (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Amino nitrogen containing

C564S493000

Reexamination Certificate

active

06790995

ABSTRACT:

The present invention relates to a process for preparing mixtures of primary and secondary amines from nitrites over a palladium catalyst.
Processes for preparing amines from nitrites over particular palladium catalysts are known.
DEA-39 35 641 describes the preparation of amines from 3-(dimethylamino)propionitrile (DMAPN). Products formed are bis(3-(dimethylamino)propyl)amine (bis-DMAPA) and tris(3-(dimethylamino)propyl)amine (tris-DMAPA). The reaction is carried out over palladium on aluminum oxide as catalyst. The proportion of bis-DMAPA is not more than 32%.
EP-A-0 869 113 relates to a process for preparing tertiary amines from nitrites and secondary amines. Here, secondary amines are reacted in the presence of hydrogen over a catalyst comprising 0.9% of Pd and 0.1% of Pd on zirconium oxide as support.
WO 99/32429 relates to a process for preparing secondary amines from nitrites and primary amines. The reaction is carried out in the presence of hydrogen likewise over the abovementioned catalyst comprising 0.9% of Pd and 0.1% of Pt on zirconium oxide.
It is an object of the present invention to provide a process for preparing mixtures of primary amines and secondary amines by reaction of nitriles with hydrogen in the presence of catalysts.
In particular, mixtures of primary and symmetrical secondary amines are to be prepared.
We have found that this object is achieved by a process for preparing mixtures of primary amines of the formula (I)
X—CH
2
—NH
2
  (I)
and secondary amines of the formula (II)
(X—CH
2
—)
2
NH  (II)
where
X is C
1-20
-alkyl, C
2-20
-alkenyl or C
3-8
-cycloalkyl which may be unsubstituted or substituted by C
1-20
-alkyl, C
3-8
-cycloalkyl, C
4-20
-alkylcycloalkyl, C
4-20
-cycloalkylalkyl, C
2-20
-alkoxyalkyl, C
6-14
-aryl, C
7-20
-alkylaryl, C
7-20
-aralkyl, C
1-20
-alkoxy, hydroxy, C
1-20
-hydroxyalkyl, amino, C
1-20
-alkylamino, C
2-20
-dialkylamino, C
2-12
-alkenylamino, C
3-8
-cycloalkylamino, arylamino, diarylamino, aryl-C
1-8
-alkylamino, halogen, mercapto, C
2-20
-alkenyloxy, C
3-8
-cycloalkoxy, aryloxy and/or C
2-8
-alkoxycarbonyl
by reacting nitrites of the formula (III)
X—CN  (III)
with hydrogen at from 50 to 250° C. and pressures of from 5 to 350 bar in the presence of a Pd-containing catalyst comprising, based on the total weight of the catalyst, from 0.1 to 10% by weight of Pd on a support.
The catalyst preferably further comprises from 0.1 to 10% by weight of at least one additional metal selected from among groups IB and VIII of the Periodic Table, cerium and lanthanum.
According to the present invention, it has been found that the use of a catalyst as defined above for reacting nitriles with hydrogen to give mixtures of primary and secondary amines can lead to an increased operating life or long-term stability of the catalyst.
The catalysts used according to the present invention contain, based on the total weight of the catalyst, from 0.1 to 10% by weight, preferably from 0.1 to 5% by weight, particularly preferably from 0.2 to 1% by weight, of palladium.
In addition, they may farther comprise, based on the total weight of the catalyst, from 0.1 to 10% by weight, preferably from 0.1 to 5% by weight, particularly preferably from 0.2 to 1% by weight, of at least one additional metal selected from among groups IB and VIII of the Periodic Table of the Elements, cerium and lanthanum. One further metal or a mixture of a plurality of further metals can be used. Preference is given to using copper, platinum and mixtures thereof, particularly preferably platinum. Particular preference is given to a catalyst containing from 0.2 to 1% by weight of palladium and from 0.2 to 1% by weight of platinum, in particular from 0.3 to 0.5% by weight of palladium and from 0.3 to 0.5% by weight of platinum, based on the total weight of the catalyst.
Particular preference is given to a catalyst comprising about 0.4% by weight of Pd and about 0.4% by weight of Pt, based on the total weight of the catalyst, on ZrO
2
as support.
The catalyst preferably comprises Pd and Pt as only active components. The catalyst particularly preferably consists of Pd and Pt on the support. Here, Pd and Pt are preferably present in approximately or exactly equal amounts, based on the weight.
All known, suitable supports can be used as supports. For example, the support is selected from among activated carbon, silicon carbide and metal oxides. Preferred metal oxides are aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, magnesium oxide or mixtures thereof, which may optionally be doped with alkali metal oxides and/or alkaline earth metal oxides. Particular preference is given to using &ggr;-aluminum oxide, silicon dioxide, zirconium dioxide or titanium oxide or mixtures thereof, in particular ZrO
2
. The supports used can have any shape; for example they can be used as extrudates, pellets or tablets. The catalysts can be produced by generally known methods, for example by impregnating the support with solutions of compounds of the metals used. Palladium can be applied, for example, by impregnating the support with solutions of PdCl
2
or Pd(NO
3
)
2
.
The supports can, for example, be coated with metal precursors. Suitable metal precursors are metal salts such as nitrates, nitrosyl nitrates, halides, carbonates, carboxylates, acetylacetates, chloro complexes, nitrito complexes and amine complexes. Preference is given to nitrates, chlorides, chloro complexes and amine complexes. Application is preferably carried out by coprecipitation or joint impregnation. The metal precursors can be applied simultaneously or in succession. The order in which the active components are applied can be chosen freely.
Further methods of producing the catalysts used according to the present invention are known to those skilled in the art and include vapor deposition, sputtering and coprecipitation.
The surface area, the pore volume and the pore size distribution of the catalyst are not critical within wide ranges.
The process of the present invention is carried out at from 50 to 200° C., preferably from 90 to 170° C. particularly preferably from 120 to 160° C., and pressures of from 5 to 300 bar, preferably from 50 to 250 bar, particularly preferably from 70 to 210 bar, batchwise or preferably continuously in pressure apparatuses such as autoclaves or preferably in a tube reactor. The pressure is preferably the hydrogen pressure in the reactor. When using a tube reactor, the catalyst employed can also be present as a fixed-bed catalyst.
The reaction is preferably carried out in the liquid phase in the upflow or downflow mode, particularly preferably in the upflow mode. In particular, preference is given to carrying out the reaction without the use of ammonia.
The space velocity over the catalyst, based on the nitrile used, is preferably from 0.1 to 2 kg/(l·h), in particular about 0.1 kg/(l·h). Part of the liquid output from the reactor can be recirculated to the reaction. The reaction is preferably carried out with recirculation of liquid output from the reactor in an amount of from 1 to 20 kg/(l
cat
·h), in particular from 5 to 10 kg/(l
cat
·h).
The process of the present invention can be carried out in the absence of solvents or in solvents such as water, methanol, ethanol, tetrahydrofuran methyl tert-butyl ether or N-methylpyrrolidone, The nitrile of the formula (III) may be dissolved in the solvent. The solvent can also be fed separately into the reactor at any point. Preference is given to candying out the reaction in the absence of solvents.
The amines of the formulae (I) and (II) obtained in the process of the present invention can be separated from the reaction mixture and purified in a manner known per se, for example by distillation.
It is, for example, possible to obtain a stream comprising pure secondary amine and a stream comprising primary amine by rectification, with the stream comprising the primary amine being returned to the synthesis.
According to the present invention, the primary amines of the formula (I) and the secondary

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