Process for the preparation of a mixture of cyclohexylamine and dicyclohexylamine using a supported noble metal catalyst

Optionally substituted cyclohexylamine and optionally substituted dicyclohexylamine can be obtained by catalytic hydrogenation of optionally substituted aniline, a catalyst being employed which contains ruthenium, palladium or a mixture of both metals, which are applied to a support of niobic acid or tantalic acid or a mixture of both. The catalyst contains the noble metal(s) in a total amount from 0.05 to 5% by weight, relative to the total weight of the catalyst. In the case of the use of both noble metals, their weight ratio to one another is 1:9-9:1.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a supported catalyst which contains ruthenium, 
palladium or a mixture of both metals and has a support of niobic acid, 
tantalic acid or a mixture of both. The invention furthermore relates to a 
process for the preparation of such a catalyst and to a process for the 
preparation of a mixture of optionally substituted cyclohexylamine and 
optionally substituted dicyclohexylamine by catalytic hydrogenation of 
optionally substituted aniline using the catalyst according to the 
invention. 
2. Description of the Related Art 
It is known to prepare cyclohexylamine and other ring-hydrogenated amino 
compounds by catalytic hydrogenation of aniline and other aromatic amino 
compounds. Catalysts which are known for this purpose are: cobalt 
catalysts which contain a basic additive (GB 969,542), Raney-Kobalt (JP 
68/03180), ruthenium catalysts (German Auslegeschrift 1,106,319), 
ruthenium catalysts doped with alkali metal compounds (U.S. Pat. No. 
3,636,108) or nickel catalysts (German Patent Specification 805,518). 
Most of the processes mentioned are carried out under pressure and give 
mainly cyclohexylamine apart from only a little dicyclohexylamine. 
Dicyclohexylamine is therefore frequently prepared by other processes, for 
example by pressure hydrogenation of diphenylamine using a ruthenium 
catalyst (German Auslegeschrift 1,106,319). Dicyclohexylamine is 
additionally formed in the reaction of cyclohexanone with cyclohexylamine 
in the presence of a palladium/carbon catalyst under a hydrogen pressure 
of about 4 bar (FR 1,333,692). The process of German Patent Specification 
805,518 mentioned is mainly directed to the production of 
dicyclohexylamine, but is carried out with troublesome returns of 
by-product. 
Other disadvantages of the processes mentioned consist in some cases 
considerable amounts of cyclohexane waste products, as well as in the 
unsatisfactory working life of the catalysts employed. There was therefore 
the desire to develop a process which can be used on an industrial scale, 
in which the loss due to the formation of cyclohexane is decreased and the 
working life of the catalyst used is improved, and also to develop a 
process in which cyclohexylamine and dicyclohexylamine are jointly formed 
in amounts which are variable according to the demand for the two 
substances mentioned. 
Surprisingly, it has been found that the demands mentioned can be met by 
the use of the supported noble metal catalyst described in the following. 
SUMMARY OF THE INVENTION 
The invention accordingly relates to a catalyst containing ruthenium, 
palladium or a mixture of both on a support containing niobic acid, 
Nb.sub.2 O.sub.5.nH.sub.2 O, tantalic acid Ta.sub.2 O.sub.5.nH.sub.2 O or 
a mixture of both, which contains the noble metal(s) in a total amount 
from 0.05 to 5% by weight, preferably 0.1 to 4% by weight, particularly 
preferably 0.1 to 3% by weight and in the case of an Ru/Pd mixture 
contains both metals in a weight ratio of 1:9-9:1, preferably 2:8-8:2, 
particularly preferably 3:7-7:3, all percentages being based on the total 
weight of the catalyst.

DETAILED DESCRIPTION OF THE INVENTION 
The catalysts according to the invention are accordingly primarily 
distinguished by the combination of Pd and/or Ru with niobic acid and/or 
tantalic acid. Compared to the known supported catalysts, such catalysts 
give higher yields of dicyclohexylamine. 
It is particularly a feature of the catalyst according to the invention to 
employ niobic acid or tantalic acid as the catalyst support or as 
components of such supports. As is known, niobic acid is a niobium 
pentoxide hydrate (Nb.sub.2 O.sub.5.nH.sub.2 O) which can be obtained, for 
example, by treatment of aqueous solutions of niobic acid salts with 
strong mineral acids or by treatment of niobium alkoxides, niobic acid 
halides or niobic acid esters with water, acids or bases. Niobic acid 
precipitated in this way is dried and is then a poorly soluble solid 
compound whose residual water content is not defined, although a niobic 
acid prepared in this way is superficially a dry powder. The preparation 
of niobic acid (niobium pentoxide hydrate) is described, for example, in 
Gmelin's Handbuch der Anorg. Chemie (Gmelin/s Handbook of Inorganic 
Chemistry), 8th Edition, niobium, part B1, p. 49. 
Tantalum pentoxide hydrate (tantalic acid) for the preparation of the 
catalyst according to the invention can be prepared by hydrolysis of 
tantalum(V) salts, tantalum(V) alkoxides or other suitable hydrolysable 
tantalum(V) compounds. The hydrolysis can be performed in a manner 
analogous to that in the case of the niobium compounds. The carrying-out 
of such a hydrolysis is fundamentally known to the person skilled in the 
art, as for Nb, and is described, for example, in Gmelins-Handbuch der 
Anorg. Chemie (Gmelin's Handbook of Inorganic Chemistry), 8th Edition, 
tantalum, part B1, (1970), p. 53 and Chem. Lett. 1988, p. 1573. What is 
written for one of the two elements basically also applies to the other. 
The great chemical similarity of both elements and their compounds is also 
expressed in the fact that in their natural occurrence they are largely 
associated with one another. 
Niobic acid is preferentially employed as the support, or as component of 
such a support, in particular that which contains a content of tantalic 
acid of natural origin of 0.0001-10 Mol %, relative to the sum of the 
molar number of niobic and tantalic acid. 
In order that the niobic or tantalic acid can be brought into the lump form 
favourable for use as a solid bed catalyst, the moist precipitate, for 
example, from the hydrolysis is thoroughly kneaded in a kneader and 
processed in a granulating apparatus to give moulded articles. The moist 
moulded articles are then dried, for example, at 120.degree. C. and 
calcined for 0.5-5 hours at 200.degree.-400.degree. C. A BET surface area 
of 5-350 cm.sup.2 /g results in this process. To prepare granules, 
extrudates or spheres, niobic or tantalic acid can also be compressed with 
a binder and granulated. 
With regard to the catalyst according to the invention, niobic or tantalic 
acid is an active substance whose activity is also retained by mixing with 
other solids. Suitable solids are, for example, titanium dioxide, zinc 
oxide, magnesium oxide, iron oxide, silicon dioxide, graphite, Al.sub.2 
O.sub.3 and others. These solids can also be employed as binders in the 
manner described above. Mixtures of niobic or tantalic acid with these 
inert solids can be employed in a ratio of 5:95-99:1, preferably 
50:50-98:2. Preferentially, however, niobic or tantalic acid or a mixture 
of both is employed on its own as the support. Therewith in an inventive 
manner, also catalysts are at disposal in which niobic or tantalic acid or 
a mixture of both constitute only a part of the catalyst support. As such 
support may be especially mentioned Al.sub.2 O.sub.3 /niobic or tantalic 
acid-supports, which e.g. can be produced by mixing and compressing the 
components of such supports or by impregnation and precipitation of niob 
or tantalum compounds in the form of niobic or tantalic acid on Al.sub.2 
O.sub.3..gamma.-Al.sub.2 O.sub.3 in the preferred Al.sub. 2 O.sub.3. The 
contents of niobic and/or tantalic acid may be varied within broad limits, 
but is preferable of 1-10% by weight based on the support weight. 
The invention furthermore relates to a process for the preparation of the 
catalyst described, which is characterised in that a solution of a salt of 
ruthenium or palladium or, in the case of the use of both metals, 
solutions of both salts are impregnated into niobic acid, tantalic acid or 
a mixture of both, the catalyst is dried after impregnation, and the 
catalyst is employed in the form then present or after a treatment with 
hydrogen at 120.degree.-400.degree. C. 
The catalyst support is used for the preparation in the form of pills, 
spheres or fragments of about 1-10 mm. The impregnation of the noble metal 
salts is carried out in a manner fundamentally known to the person skilled 
in the art. The drying is performed, for example, at 
100.degree.-140.degree. C. and a reduced to normal pressure, for example 
at 1-1000 mbar, for example in a water pump vacuum. 
The noble metal salts can be dissolved in water or in suitable organic 
solvents. They are preferably dissolved in organic solvents, such as in 
simple alcohols, ketones, nitriles or cyclic ethers. Examples of such 
solvents are methanol, ethanol, acetone, acetonitrile and dioxane. 
Suitable salts of the noble metals are, for example, their chlorides, 
nitrates or acetates. 
After impregnation and subsequent drying, the catalyst according to the 
invention is fundamentally available. Preferentially, however, it is 
activated before use by treatment with hydrogen at elevated temperature. 
Such an elevated temperature is in the range from 120.degree.-400.degree. 
C., preferably in the range from 150.degree. to 340.degree. C. 
The catalysts according to the invention can be employed in an outstanding 
fashion for the ring hydrogenation of optionally substituted aniline. A 
mixture of cyclohexylamine and dicyclohexylamine which has the 
substitution pattern of the aniline employed is formed in this process. 
Particularly surprisingly, using the catalysts according to the invention 
the amount of dicyclohexylamine additionally formed compared to 
monocyclohexylamine can be altered as a function of the hydrogenation 
temperature, as a result of which controlled preparation of 
dicyclohexylamine is possible in relatively large amounts. 
The invention thus furthermore relates to the use of the inventive catalyst 
in a process for the preparation of a mixture of optionally substituted 
cyclohexylamine and optionally substituted dicyclohexylamine by catalytic 
hydrogenation of optionally substituted aniline on a supported noble metal 
catalyst, which is characterised in that the catalyst described above is 
employed and the reaction is carried out at a temperature in the range 
from 100.degree. to 340.degree. C., preferably 130.degree. to 240.degree. 
C., and at a pressure of 0.5 to 500 bar, preferably 2 to 400 bar, 
particularly preferably 100 to 400 bar and very particularly preferably 
150 to 350 bar. 
This process can therefore be carried out within a wide pressure range, 
which extends from a pressure close to normal pressure up to a very high 
pressure. Conceivable embodiments include, for example, working in the gas 
phase close to normal pressure, working in an autoclave at high pressure 
and working in the liquid phase, likewise at high pressure. 
The hydrogenation of the catalysts according to the invention can therefore 
be carried out both batchwise and continuously; for industrial purposes, 
it is preferentially carried out continuously. Advantageously, the process 
is carried out, as already mentioned, in the liquid phase on a fixed 
catalyst packing. The catalyst loading in this process is set at an amount 
from 0.05 to 3 kg, preferably 0.1 to 2 kg, particularly preferably 0.15 to 
1.5 kg, of optionally substituted aniline per liter of catalyst and per 
hour. A slight change in the amount of dicyclohexylamine obtained and also 
in the yield and selectivity due to the changing activity of the catalyst 
during the course of relatively long reaction periods can be compensated 
by a slight adjustment of the reaction temperature or the other 
parameters. These ratios can be monitored by the analysis of the reaction 
mixture. Possible starting materials within the meaning of the following 
reaction equation are aniline and substituted anilines, which are reacted 
to give the corresponding cyclohexylamines and dicyclohexylamines: 
##STR1## 
The radicals R.sup.1 and R.sup.2 independently of one another have the 
meaning hydrogen, C.sub.1 -C.sub.4 -alkyl or C.sub.1 -C.sub.4 -alkoxy. 
Examples of the alkyl and aloxy substituents mentioned are: methyl, ethyl, 
propyl, isopropyl, butyl, isobutyl, methoxy, ethoxy, propoxy, isopropoxy, 
butoxy or isobutyoxy. The substituents mentioned preferentially have 1-2 C 
atoms; they are particularly preferably methyl or methoxy. In a 
furthermore preferred manner, one of the substituents R.sup.1 and R.sup.2 
has the meaning hydrogen, while the other substituent denotes hydrogen or 
alkyl or alkoxy in the context mentioned. In a particularly preferred 
manner, the process according to the invention is directed to the ring 
hydrogenation of unsubstituted aniline. 
According to the invention, substituted aniline is furthermore to be 
understood as an aniline substituted on the nitrogen by the 
cyclohexylidene group, which can be prepared in a simple manner by 
condensation of aniline and cyclohexanone. Such a cyclohexylideneaniline 
can likewise be ring-substituted and then corresponds to the formula 
##STR2## 
in which R.sup.1 and R.sup.2 have the scope of meaning given. It is 
finally furthermore possible to employ such an optionally substituted 
cyclohexylideneaniline also in the form of a mixture of the optionally 
substituted cyclohexanone on which it is based with the optionally 
substituted aniline on which it is based. 
Cyclohexylamines and dicyclohexylamines of the scope of meaning mentioned 
are used for the preparation of antiageing agents for rubbers and 
plastics, as corrosion inhibitors, and as precursors for plant protection 
agents and textile auxiliaries. 
EXAMPLE 1 
75 g of niobic acid, Nb.sub.2 O.sub.5.nH.sub.2 O, which had been moulded 
with addition of 3.5% of graphite powder to give 5 mm tablets, were 
impregnated with a solution which had been prepared from 1.56 g of Pd 
acetate and 26.8 g of acetonitrile. The niobic acid tablets impregnated in 
this manner with 1% Pd were dried for 18 hours at 100.degree. C. in a 
water pump vacuum. The niobic acid was then again impregnated in the same 
manner with 1% Pd. 60 ml (61 g) of the catalyst prepared were brought into 
a vertically arranged pressure tube (diameter 14 mm, length 70 cm) which 
was heated using an oil thermostat. The volume between the particles was 
filled with fine sea sand (0.2-0.4 mm). The catalyst was first activated 
with hydrogen for 3 hours at 250.degree. C. and 270 bar, 40 l of hydrogen 
hourly being released at the lower end of the reaction tube. The 
hydrogenation of aniline was then started at 270 bar and 182.degree. C., 
aniline and hydrogen being passed into the catalyst from above. The liquid 
trickled downwards through the catalyst to a separator. 26 to 62 liters 
per hour of hydrogen were released at the top of the separator. The amount 
of aniline continuously fed in corresponded to a catalyst loading in the 
range from 0.23 to 0.28 g/ml of catalyst/h. Under stationary reaction 
conditions, the following product composition resulted depending on the 
hours of operation and the reaction temperatures (the remainder to 100% is 
by-products). 
______________________________________ 
Time Temperature DCHA*.sup.) 
CHA*.sup.) 
h .degree.C. % % 
______________________________________ 
47 181 82.0 17.8 
119 171 84.5 15.3 
263 150 88.5 11.4 
360 139 91.8 8.0 
______________________________________ 
*.sup.) DHA = dicyclohexylamine; 
CHA = cyclohexylamine 
EXAMPLE 2 
100 g of niobic acid tablets of the same type as in Example 1 were 
impregnated with a solution which had been prepared from 2.08 g of Pd 
acetate and 25 g of dioxane. The niobic acid tablets impregnated with 1% 
Pd were dried for 18 hours at 100.degree. C. 
Using 60 ml (59.7 g) of the catalyst prepared, the hydrogenation of aniline 
was performed in the same manner as in Example 1. The amount of aniline 
continuously employed corresponded to a catalyst loading of 0.25 g of 
aniline/ml of cat..times.h. Depending on the hours of operation of the 
catalyst and also the hydrogenation temperature, the following products 
composition resulted (the remainder to 100% is by-products); 
______________________________________ 
Time Temperature 
DCHA*.sup.) 
CHA*.sup.) 
Aniline 
h .degree.C. % % % 
______________________________________ 
98 179 84.2 15.6 -- 
219 179 83.8 16.0 0.05 
411 180 86.7 13.1 0.04 
578 189 85.7 13.9 -- 
748 189 86.5 13.3 -- 
895 189 86.4 13.5 -- 
940 170 92.2 7.5 0.13 
______________________________________ 
*.sup.) DCHA dicyclohexylamine; 
CHA cyclohexylamine 
EXAMPLE 3 
50 g of niobic acid tablets (d=5 mm) were impregnated with a solution which 
had been prepared from 3.13 g of Ru(NO.sub.3).sub.2 and 25 g of methanol. 
The niobic acid impregnated in this way with 2% Ru was dried for 18 hours 
at 100.degree. C. a water pump vacuum. 25 ml (24 g) of the catalyst thus 
prepared were used for the hydrogenation of aniline in a 250 ml shaking 
autoclave which was equipped inside with a sieve basket which was 
centrally supported and firmly connected to the autoclave and into which 
the catalyst was poured. Using this catalyst filling, in each case 50 g of 
aniline were hydrogenated at a hydrogen pressure of 260 to 280 bar at 
various temperatures. The hydrogenation time was 3 hours in each 
hydrogenation experiment. Depending on the reaction temperature, the 
reaction products had the following composition (remainder to 100% is 
by-products): 
______________________________________ 
Temperature (.degree.C.) 
110 200 
______________________________________ 
Aniline 0.4% 0.5% 
Cyclohexylamine 90.7% 48.2% 
Dicyclohexylamine 8.5% 50.0% 
______________________________________ 
Example 4 
80 g of Nb.sub.2 O.sub.5.nH.sub.2 O, which had been tabletted (d=5 mm) with 
the addition of 1.9% of graphite, were impregnated with a solution which 
was prepared from 0.83 g of Pd acetate and 17.2 g of acetonitrile. After 
an intermediate drying--18 hours at 100.degree. C. in the water pump 
vacuum--the niobic acid tablets were again impregnated with a solution 
which was prepared from 1.25 g of Ru(NO.sub.3).sub.2 and 17.2 g of 
methanol. After a fresh drying, the catalyst was ready of use for the 
hydrogenation. The niobic acid tablets contained 0.5% of Pd and 0.5% of 
Ru. 
25 ml (25.3 g) of the Pd-Ru catalyst thus prepared were used for the 
hydrogenation of aniline in a 0.25 l shaking autoclave. The autoclave was 
equipped inside with a sieve basket into which the catalyst was poured. 
Using this catalyst filling, 50 g of aniline were hydrogenated twice in 
succession at a hydrogen pressure of 260-280 bar and at various 
temperatures. After the individual hydrogenations, the autoclave was 
cooled to room temperature, the reaction product was removed and the 
autoclave was again charged with aniline. In this case, depending on the 
temperature, the following product composition resulted at a constant 
hydrogenation time of 3 hours (remainder to 100% is by-products): 
______________________________________ 
Temperature (.degree.C.) 
180 200 
______________________________________ 
Aniline 0.1% 0.5% 
Cyclohexylamine 69.8% 38.5% 
Dicyclohexylamine 29.4% 56.3% 
______________________________________ 
Example 5 
15 ml (15.5 g) of the catalyst prepared analogously to Example 1 were 
employed for the hydrogenation of aniline in the gas phase. The catalyst 
was first activated for one hour in a stream of hydrogen of 20 l/h at 
190.degree. C. 1.54 g of aniline together with 20 l of hydrogen were 
passed per hour through the activated catalyst, which was situated in a 
vertically arranged 17 mm wide reaction tube. The resulting reaction 
product was condensed and analyzed after various time intervals. In this 
case, depending on the hours of operation of the catalyst, the following 
composition of the reaction products was found (remainder to 100% is 
by-products): 
______________________________________ 
Duration of experiment 
116 h 238 h 303 h 
438 h 
______________________________________ 
Cyclohexylamine 22.5 22.1 18.8 18.5 
Dicyclohexylamine 
74.2 74.6 77.9 77.9 
N-Cyclohexylaniline 
1.2 1.2 1.2 1.4 
Aniline 0.4 0.6 1.2 0.7 
______________________________________ 
Example 6 
25 ml (24.8 g) of the catalyst prepared according to Example 2 were used 
for the hydrogenation of cyclohexylideneaniline in a 250 ml shaking 
autoclave which was equipped inside with a sieve basket which was 
centrally supported and firmly connected to the autoclave, and into which 
the catalyst was poured. Using this catalyst filling, 50 g of 
cyclohexylideneaniline in each case were hydrogenated at various 
temperatures at a hydrogen pressure of 280 bar. About 95% of 
cyclohexylideneaniline was contained in the starting product. The 
hydrogenation time was 3 hours in all experiments of this series. The 
hydrogenation products had the following composition (remainder to 100% 
are by-products): 
______________________________________ 
Temperature (.degree.C.) 
200 100 
______________________________________ 
Dicyclohexylamine % 89.1 89.9 
Cyclohexylamine % 0.9 1.25 
N-Cyclohexylaniline -- 3.5 
______________________________________ 
Example 7 
Reusing the apparatus described in Example 1 together with catalyst filling 
(2% Pd on Nb.sub.2 O.sub.5.nH.sub.2 O), a mixture of cyclohexanone and 
aniline in a molar ratio of 0.9:1 was employed instead of aniline. The 
amount of starting material continuously fed in corresponded to a catalyst 
loading of 0.26 g of mixture/ml of catalyst/h. About 50 liters of hydrogen 
per hour were released at the top of the separator. Under stationary 
reaction conditions, the following product composition resulted depending 
on the reaction temperature (the remainder to 100% is by-products). 
______________________________________ 
Temperature 180.degree. C. 
141.degree. C. 
Running time (.phi. from) 47 h 
(.phi. from) 24 h 
______________________________________ 
Dicyclohexylamine 
94.2 92.7 
Cyclohexylamine 3.7 2.8 
N-Cyclohexylaniline 
-- 2.8 
Cyclohexanol 1.9 1.7 
______________________________________ 
EXAMPLE 8 
400 g of bead-shaped .gamma.-Al.sub.2 O.sub.3 with a diameter of 2-5 mm and 
a specific surface of 350 m.sup.2 /g were impregnated with a solution of 
23.3 g of NbCl.sub.5 in 120 g of 37% strength hydrochloric acid, and 
thereafter dried at 120.degree. C. Thereafter the catalyst support was 
impregnated with 410 g of a 16.9% strength by weight aqueous solution of 
ammonia, and subsequent washed free of chloride with water and dried 
again. 150 g of the so produced catalyst support were impregnated with a 
solution which had been prepared from 3.13 g Pd acetate and 40 g of 
acetonitrile. After again drying at 120.degree. C. the catalyst was ready 
for use. 
With 60 ml (53 g) of the so produced catalyst the hydrogenation of aniline 
was carried out. For that purpose the catalyst was brought into an upright 
standing pressure tube (internal diameter =14 mm, length ca. 70 cm). The 
catalyst was first activated with hydrogen during 3 hours at 250.degree. 
C. and 276 bar, 60 l of hydrogen hourly being released at the lower end of 
the pressure tube. 
The temperature was then lowered to 200.degree. C., and at 275 bar aniline 
and hydrogen were passed into the catalyst from above. The liquid trickled 
downwards through the catalyst to a separator. 60 to 100 liters per hour 
of hydrogen were released at the top of the separator. The throughput of 
aniline corresponded to a catalyst loading in the range of 0.2 to 0.3 g of 
aniline/ml catalyst/h. The hydrogenation product was taken from the 
separator in regular intervals and analysed. The following product 
composition resulted depending on the hours of operation at a reaction 
temperature of 200.degree. C. (the remainder to 100% is by-products): 
______________________________________ 
Time Aniline DCHA* CHA* 
h % % % 
______________________________________ 
89 0.2 76.1 22.9 
137 -- 79.2 20.5 
212 -- 78.2 21.4 
255 -- 80.6 18.7 
326 0.1 74.3 24.6 
374 -- 77.1 22.6 
______________________________________ 
*DCHA = dicyclohexylamine; 
CHA = cyclohexylamine 
EXAMPLE 9 
400 g of .gamma.-Al.sub.2 O.sub.3 granulate of the same type as in Example 
8 were impregnated with a solution of niobium chloride which had been 
prepared from 11.64 g of NbCl.sub.5, 11.64 g of NaCl and 100 g of water. 
This impregnation was repeated four times after a drying between the 
impregnations each at 120.degree. C. Onto the dried catalyst support one 
had influenced for one hour 410 g of a 8.9% strength aqueous solution of 
ammonia; the support was then washed free of chloride with water and again 
dried. 100 g of the such prepared catalyst support were impregnated with a 
solution which had been prepared from 4.16 g of Pd acetate and 31 g of 
methylene chloride. After drying again, 60 ml (51.1 g) of the catalyst 
were employed for the hydrogenation of aniline in the same manner as in 
Example 8. 
At 200.degree. C. and 275 bar 368 g of aniline were passed through the 
catalyst in 21 hour. 220 l of hydrogen were released hourly at the top of 
the product separator. The gaschromatographic analysis resulted in 23% 
cyclohexylamine and 76.9% dicyclohexylamine. 
EXAMPLE 10 
4 g of TaCl.sub.5 were dissolved in 6.8 g of 37% strength hydrochloric acid 
and then diluted with 25 g of water. 100 g of .gamma.-Al.sub.2 O.sub.3 
granulate (diameter=2-5 mm, specific surface=350 m.sup.2 /g) were 
impregnated with the thus prepared tantalum chloride solution. After 
drying at 100.degree. C. under water jet vacuum the catalyst support was 
impregnated with 25 g of 19.3% strength aqueous solution of ammonia and 
then washed in fluent water until free of chloride. After a further 
drying, the catalyst support was impregnated with a solution which had 
been prepared from 4.16 g of Pd acetate and 35 g of methylene chloride. 
After subsequent drying the catalyst was ready for use. 60 ml (49.4 g) of 
the thus prepared catalyst were employed for the continuous hydrogenation 
of aniline according to Example 8. Under stationary conditions 935 g of 
aniline were passed through the catalyst in the course of 42 hours at 
196.degree. C. and a hydrogen pressure of 270 bar. 140 liters of hydrogen 
were released hourly from the product separator. The product collected in 
the separator contained 18.9% cyclohexylamine and 81% dicyclohexylamine.