CS235833B1 - A method for increasing the selectivity of copper catalysts used in reductive alkylation of aromatic amines by ketones - Google Patents

Abstract

The invention relates to a method for increasing the selectivity of copper catalysts active for the hydrogenation of ketimines in the reductive alkylation of primary aromatic amines with ketones in the liquid phase at 130 to 220 °C and a pressure of 2 to 10'MPa. The essence of the invention consists in adding 0.3 to 2% by weight of an organic acid with a number of carbon atoms of 1 to 4, based on the catalyst, to the reaction mixture.

Description

The invention relates to a process for increasing the selectivity of copper catalysts used in the preparation of the N-secalkylaromatic amines and diamines of formulas I, II, III, IV shown in the accompanying drawing, wherein:

R is alkyl, at least methyl and

R 1 is an alkyl or aryl group.

N-sec-alkylanilines are intermediates in the production of herbicides, N-phenyl-N-sec-alkyl-p-phenylenediamines are widespread antiozonants for rubber.

Catalytic reductive alkylation of aromatic amines with ketones takes place in the two reaction stages illustrated by Equations A, B in the accompanying drawing. The metal catalyst accelerates the second, i.e. hydrogenation, stage, and to some extent the ketimine formation rate is also affected by the catalyst composition. The use of various hydrogenation catalysts such as Pt, Pd, Ni, Gu, etc. is described in the literature. However, in the reductive alkylation of aromatic amines, the first three metals always catalyze to some extent hydrogenation of the benzene ring to form a variety of by-products. Most patents deal with various ways to increase the selectivity of these metals in terms of reducing the hydrogenation of the benzene ring. A simple solution to this problem is the use of copper catalysts, which are known not to catalyze the hydrogenation of the benzene ring.

The secondary alcohol is formed on all catalysts in parallel by the hydrogenation of the ketone and therefore the ketone is always used in an excess of 1.5 to 50 moles per mole of amine. On most copper catalysts differing in the support, respectively. with other additives, the ketone is hydrogenated before it can be reacted with an amine. The selectivity of the 2,235,833 catalyst with respect to the reduction of alcohol production is determined by two factors:

And / or the ability of the catalyst to accelerate ketimine formation. b) the relationship between the activity of the bond hydrogenation catalyst

C = N and the hydrogenation activity of the G = O bond.

The few copper catalysts offered by the market can be used for alkylation, especially when high conversion of the primary amine is desired. The individual catalysts differ significantly in

either in one or the other property, even if they have almost the same composition. For example, in Adkins-type chromium-chromium catalysts, the extent of alcohol formation depends on small amounts of impurities. For example, on an unprotected catalyst, ketone is rapidly hydrogenated to alcohol and ketimine formation is slow, while ketimine is formed rapidly on barium salt catalyst and its concentration is practically equilibrium, the hydrogenation rate of the G = N bond is much slower than the hydrogenation rate of G = 0. However, it is difficult to unequivocally account for the various catalytic properties of the promoter, as we have found that these properties are also largely influenced by the catalyst preparation process.

The selectivity of copper catalysts for the reductive alkylation of aromatic amines with ketones is solved by using an acidic carrier or by adding an adsorbent having acidic properties to a conventional non-selective catalyst (s). AO 179 110 /. Another way of addressing this issue is to add substances containing organically bound chlorine / MS. AO 209,731 /. A good effect is achieved by mixing two kinds of copper catalysts, one of which accelerates the formation of ketimine, although it does not satisfy the hydrogenation rate of the C = N bond and the other has at least a reasonable relation between the hydrogenation rate of the CN and G = 0 bond. little catalyzes the formation of ketimuiu.

A simple solution to the problem of selectivity of copper catalysts active for ketimine hydrogenation in the reductive liquid phase alkylation of aromatic amines at 130 to 220 ° C and a pressure of 2 to 10 MPa according to the invention is that

0.335 to 2 wt. organic acids having a carbon number of 1 to 4 based on the copper catalyst.

Poor selectivity of copper catalysts is in most cases due to insufficient ketimine formation activity. However, there are copper catalysts which accelerate the formation of ketimine well while being non-selective and in such cases the addition of organic acid does not help (see Example 4). Thus, the process for preparing the alkyl aromatic amines of the invention requires catalysts to be evaluated by a laboratory test.

A particularly advantageous solution to the selectivity of copper catalysts in the alkylation of aromatic amines with ketones is the addition of acetic acid, which gives a particularly pronounced catalytic effect, is easy to handle, and the required amount of 0.01 to 0.03% based on amine does not affect processing of the reaction mixture.

Example 1

A 150 ml autoclave was charged with 25 g of 4-aminodiphenyl amine (ADFA) and 0.5 g of a small iron oxide industrial chromium catalyst and 30 ml of acetone. The reductive alkylation was conducted at 160 ° C and 6 MPa. In the same way, two experiments were carried out with the addition of acetic acid.

Addition of acetic acid /% per cat./ Reakčni time / min / ADFA ¹ Composition of reaction mixture wt. ketiminl acetone 0 60 9.6 1,2 14.4 1.65 80 5.1 0.51 86.1 0.85 60 1.7 0.39 87.4

¹ content is calculated only for ADFA derivatives, the remainder up to 100% is the product, ie N-isopropyl-N-phenyl-p-phenylenediamine sum of acetone and isopropyl alcohol content is 100%

Thus, the addition of acetic acid strongly limits the formation of isopropyl alcohol and in this case even increases the rate of product formation.

- 4 Example 2

235 833

In the same manner as in Example 1, an experiment was performed with a copper-chromium catalyst promoted by manganese dioxide.

Acid admixture Reaction time /% to cat./min

Composition of reaction mixture wt. ADFA ketimine acetone

60 36,2

0.85 120 20

24.7 68.7

3,4 90

The addition of acid in this case somewhat reduced the rate of alkylation, however, the proportion of acetone hydrogenated to isopropyl alcohol is again lower. ,

Example 3

Under the conditions of Example 1, an experiment was conducted with a copper-on-silica gel catalyst.

Addition of acetic acid /% on cat./

Reaction composition of the reaction mixture wt.

ADFA ketimine acetone / min /

60 20,9

0.85 60 17.6

1,8 45,7

2,0 75

Example 4

Under the conditions of Example 1, alkylation of 4-aminodiphenylamine was performed with barium-activated copper chromium catalyst.

Addition of acetic acid /% on cat./

Reaction time (min)

ADFA

Composition of reaction mixture wt. ketimin acetone

30 51,4

1.65 60 47.6

43.3 5.7

43,6 15,8

In the case of this catalyst, the acid has no effect on selectivity. Even without the addition of acid, the rate of ketimine formation is high and its concentration is practically equilibrium. While achieving the same conversion of 4-aminodiphenylamine in the presence of acetic acid, the unreacted acetone content is somewhat higher, but this small difference is more likely to be attributed to a longer reaction time, i.e. a general reduction in the hydrogenation activity of the catalyst.

- 5 235 833

Example 5

Under the conditions of Example 1 including the catalyst, the effect of oxalic acid admixture was investigated. At an acid content of 0.6% per catalyst and a reaction time of 60 minutes, the composition of the reaction mixture was 6.1% ADPA, 0.4% ketimine and 52.4% acetone. The beneficial effect of oxalic acid on the selectivity of reductive alkylation is evident, but not as pronounced as acetic acid.

Example 6

A 150 ml autoclave was charged with 25 g of aniline, g of methyl isobutyl ketone and 1 g of a copper-chromium catalyst mixed with iron oxide. Again, two experiments were carried out, one without the acid, the other with the addition of acetic acid.

Acid admixture Reaction composition of the reaction mixture wt.

acetic acid /% to cat./min / aniline ketimin methylisobutylket on

60 15.5 2.1 20

0.85 60 2.0 0.4 60

Claims (2)

SUBJECT OF THE INVENTION 235 833 A process for increasing the selectivity of copper catalysts active for the hydrogenation of ketimines in the reductive liquid-phase alkylation of primary aromatic amines at 130 to 220 ° C and a pressure of 2 to 10 MPa, characterized in that 0.3 to 2 wt. . organic acids having carbon numbers 1 to 4, based on the catalyst. 2. A process according to claim 1, wherein 0.5 to 1.5% acetic acid / catalyst is added to the reaction mixture.