Preparation of amines

Details Preparation of amines Preparation of amines

2002-09-05

2004-02-10

Davis, Brian (Department: 1621)

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

Organic compounds

Amino nitrogen containing

C564S397000, C564S398000, C564S401000, C564S472000, C564S473000, C564S479000

Reexamination Certificate

active

06689914

ABSTRACT:

The invention relates to a process for the preparation of amines by catalytic reductive amination of carbonyl compounds or alcohols which comprise halogen-containing impurities.
The reductive amination of carbonyl compounds with ammonia or primary or secondary amines is a standard process for the preparation of amines. The reaction is usually carried out in the presence of metallic catalysts, Raney-Ni, Raney-Co, Pt/activated carbon, Pd/activated carbon, Pd/BaSO
4
, Rh/Al
2
O
3
, for example, being used as catalysts.
If the carbonyl compound to be aminated comprises, as a result of preparation, significant amounts of chlorine (for example >50 ppm), this leads to problems during reductive amination. Thus, for example, lower selectivities and space-time yields result, as does premature deactivation or destruction of the catalyst. In many cases, only partial conversion can be achieved, which hinders work-up. In particular, fixed-bed hydrogenations cannot be carried out economically in the presence of halogens or halogen-containing impurities due to disintegration of the catalyst.
In these cases, the carbonyl compound has to be purified prior to the amination in a complex manner. In many cases this is not economically feasible.
DE-A-100 53 380, which has an earlier priority date but was unpublished at the priority date of the present application, relates to a process for the preparation of amines by catalytic reductive amination of carbonyl compounds or alcohols which have at least one aromatic ring substituted by halogen which is not changed during the reductive amination. The hydrogenation is carried out in the presence of Co- and/or Ni-containing catalysts and solid acidic cocatalysts and in the absence of organic sulfur compounds.
It is an object of the present invention to provide a process for the simple and cost-effective preparation of amines by reductive amination of corresponding carbonyl compounds or alcohols which have a significant content of halogen (at least 50 ppm, in particular organically bonded), and which leads to the desired products with high space-time yields with low catalyst consumption.
We have found that this object is achieved according to the invention by a process for the preparation of amines of the formula (I):
R
1
R
2
CH—N R
3
R
4
  (I)
in which R
1
, R
2
, R
3
and R
4
, independently of one another, are hydrogen, straight-chain or branched C
1
-C
2
-alkyl, C
3
-C
12
-cycloalkyl, C
6
-C
10
-aryl or C
7
-C
11
-aralkyl, where at least one of the radicals R
1
and R
2
is aryl or aralkyl, by catalytic, reductive amination of mixtures comprising carbonyl compounds of the formula (II) or alcohols of the formula (III):
R
1
—C(═O)—R
2
  (II)
R
1
—CH(OH)—R
2
  (III)
which also comprise at least 50 ppm, based on the mixtures, of halogen, with nitrogen compounds of the formula (IV):
H N R
3
R
4
  (IV)
with the abovementioned meanings for R
1
to R
4
in the presence of Co- and/or Ni-containing catalysts, where the reductive amination is additionally carried out in the presence of solid acidic cocatalysts and optionally in the absence of organic sulfur compounds.
It has been found according to the invention that during the reductive amination of ketones, aldehydes or alcohols which are contaminated by significant amounts of halogen, it is possible to achieve very good amine yields if, during the reaction, the Co- and/or Ni-containing catalysts are used in combination with solid acidic cocatalysts.
The Co- and/or Ni-containing catalysts are preferably chosen from Raney-Co, Raney-Ni, Raney-Co—Ni, Raney-Ni—Fe, Raney-Ni—Fe—Co, Ni—Co mixed oxides, Ni/Co mixed oxides or mixtures thereof, which may also be on inorganic supports.
In addition, the Co and/or Ni catalysts can additionally comprise 0 to 80% by weight of Cu and 0 to 10% by weight, preferably 0 to 5% by weight, of further metals, calculated as metal and based on the total weight of the catalyst.
In the process according to the invention, the Co- and/or Ni-containing catalysts are preferably used in the form of elemental Co and/or Ni sponge, Raney-cobalt or Raney-nickel, Co or Ni or Co oxide or Ni oxide on supports (supported catalysts). They can also be used mixed in any weight ratios. Supports therefor are, for example, Al
2
O
3
, SiO
2
, TiO
2
, ZrO
2
, activated carbon and other catalyst supports known to the person skilled in the art.
Of the Raney catalysts, preference is given to using Raney catalysts such as Raney-cobalt, Raney-cobalt-nickel, Raney-cobalt-nickel-iron, Raney-cobalt-nickel-iron-chromium or Raney-cobalt or Raney-nickel with dopings of other transition metals in anhydrous or else water-moist or solvent-moist form. Particular preference is given to using Raney-cobalt which comprises in each case 0 or 0.1 to 10% by weight; preferably up to 5% by weight of Al, Ni, Fe, Cr. The Co- or Ni-containing catalyst is used in an amount of from 0.01 to 20% by weight, preferably 0.1 to 10% by weight and particularly preferably 0.3 to 5% by weight, based on the carbonyl compound to be aminated.
According to the invention, it may also be preferred to use an Ni or Co-Ni catalyst which is supported on ZrO
2
and comprises 0 to 50% by weight of CuO, calculated as CuO and based on the total weight of the catalyst.
According to the invention, the solid acidic cocatalysts are preferably chosen from metal oxides or metal mixed oxides, zeolites, metal or ammonium salts of mineral acids or organic acids, acidic ion exchangers or mixtures thereof.
Preferred solid acidic cocatalysts in the process according to the invention are metal oxides, such as oxides or mixed oxides of the elements Zr, Ti, Cr, Mo, W, Mn, Fe, B, Al, Si, zeolites of natural and synthetic origin, metal or ammonium salts of strong mineral acids, such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and of strong organic acids, such as formic acid, acetic acid, propionic acid and sulfonic acid, acidic ion exchangers, such as Nafion etc. In particular, ZrO
2
is used. The use amounts of the acidic cocatalysts are preferably between 0.1 and 20% by weight, preferably between 1-10% by weight, based on the carbonyl compound to be aminated.
If Co- or Ni-containing supported catalysts are used, the support materials such as Al
2
O
3
, SiO
2
, TiO
2
, ZrO
2
etc., may function as acidic cocatalysts. In this case, the addition of an additional acidic cocatalyst is not necessary. If the ammonium salts are used as acidic cocatalysts, then the conventional acid can be used directly instead of the ammonium salts. The ammonium salts then form as a result of the reaction of the acid with ammonia or amines.
In the process according to the invention, the acidic cocatalysts used are preferably metal oxides or mixtures thereof. Particular preference is given to ZrO
2
.
The reductive amination can be carried out in a suspension operation or fixed-bed operation.
The carbonyl compounds or alcohols used according to the invention can be chosen with a large degree of freedom.
The aryl radicals and phenyl radicals and the aralkyl radicals are particularly preferably benzyl radicals. The alkyl radicals are preferably C
1-6
-alkyl radicals, and the cycloalkyl radicals are preferably c
3-6
-cycloalkyl radicals. It is particularly preferred that in the compounds of the formula (II) and (III), none of the radicals is hydrogen. In particular, the carbonyl compound is pinacolone or a derivative thereof.
The carbonyl compounds or alcohols to be aminated and used according to the invention comprise at least 50 ppm, particularly preferably 50 ppm to 10% by weight, in particular 100 ppm to 10% by weight, of halogen. The quantitative data refer here to a mixture of the carbonyl compounds or alcohols and to the halogen or halogen-containing compounds. The expression “halogen” and the quantitative data refer to halogen atoms present in the mixture, which may be in chemically bonded form or in the form of ions or salts. In particular, the halogen is organically bonded, i.e. the organic compounds contain the halogen atom

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