Hydrogenation of an aromatic compound in the presence of a supported catalyst

In a process for hydrogenating an aromatic compound in which at least one hydroxyl group is bonded to an aromatic ring or an aromatic compound in which at least one amino group is bonded to an aromatic ring, in the presence of a catalyst comprising as catalytically active component at least one metal of transition group I, VII or VIII of the Periodic Table applied to a support, the catalyst is obtainable by PA1 a) dissolving the catalytically active component or a precursor compound thereof in a solvent, PA1 b) admixing the solution thus obtained with an organic polymer which is able to bind at least ten times its own weight of water, giving a swollen polymer, PA1 c) subsequently mixing the swollen polymer with a catalyst support material and PA1 d) shaping, drying and calcining the composition obtained in this way.

The present invention relates to a process for hydrogenating an aromatic 
compound in which at least one hydroxyl group is bonded to an aromatic 
ring or an aromatic compound in which at least one amino group is bonded 
to an aromatic ring, in the presence of a catalyst comprising as 
catalytically active component at least one metal of transition group I, 
VII or VIII of the Periodic Table applied to a support. 
In one embodiment, the present invention relates to a process for 
hydrogenating an aromatic compound in which at least one hydroxyl group is 
bonded to an aromatic ring and preferably, in addition to at least one 
hydroxyl group, at least one unsubstituted or substituted C.sub.1 
-C.sub.10 -alkyl group and/or at least one C.sub.1 -C.sub.10 -alkoxy group 
is bonded to an aromatic ring. Furthermore, preference is given to using 
monoalkyl-substituted phenols in the process of the present invention. 
The monocyclic or polycyclic aromatic compounds are hydrogenated in the 
presence of the catalyst described herein to give the corresponding 
cycloaliphatic compounds, with the hydroxyl group being retained. 
Cycloaliphatic alcohols, in particular alkylcyclohexanols, are important 
intermediates for the preparation of various fragrances, drugs and other 
organic fine chemicals. The abovementioned cycloaliphatic alcohols are 
conveniently obtained by catalytic hydrogenation of the corresponding 
aromatic precursors. 
The process for preparing alkylcyclohexanols by catalytic hydrogenation of 
the corresponding alkylphenols is known. The hydrogenation of alkylphenols 
to give the corresponding alkylcyclohexanols in the presence of 
hydrogenation catalysts, in particular catalysts applied to supports, has 
been described many times. 
Catalysts used are, for example, metallic rhodium, rhodium-platinum alloys, 
rhodium-ruthenium alloys and also ruthenium, palladium or nickel on 
catalyst supports. Catalyst supports used are carbon, barium carbonate and 
in particular aluminum oxide. 
PL 137 526 describes the hydrogenation of p-tert-butylphenol to give 
p-tert-butylcyclohexanol using a nickel catalyst. 
DE-A-34 01 343 and EP 0 141 054 describe a process for preparing 2- and 
4-tert-butylcyclohexanol from 2- and 4-tert-butylphenol by catalytic 
hydrogenation. The hydrogenation is carried out in two stages, using a 
palladium catalyst on an Al.sub.2 O.sub.3 support in the first stage and 
using a ruthenium catalyst on an Al.sub.2 O.sub.3 support in the second 
stage. The metal content on the support is here from 0.1 to 5% by weight. 
The supports are not specified further. The reaction is carried out at a 
pressure of 300 bar with recirculation of product, and the 
cis-tert-butylcyclohexanols are obtained preferentially, with from 0.1 to 
0.5% of by-products being formed. 
U.S. Pat. No. 2,927,127 describes a process for preparing 
p-tert-butylcyclohexanol and esters thereof by catalytic hydrogenation of 
p-tert-butylphenol. Catalysts used are 5% rhodium on carbon, 5% palladium 
on barium carbonate and 5% ruthenium on carbon. When using ruthenium on 
carbon, the reaction was carried out at from 74.degree. to 93.degree. C. 
and a pressure of from 70 to 120 bar. 66% of the cis isomer were obtained 
as hydrogenation product. 
DE-A-29 09 663 describes a process for preparing cis-alkylcyclohexanols by 
catalytic hydrogenation of the corresponding alkylphenols. The catalyst 
used was ruthenium on an Al.sub.2 O.sub.3 support and the reaction was 
carried out at a pressure of 40, 60 or 80 bar. The products obtained were 
predominantly cis-alkylcyclohexanols, with from 0.1 to 1% of alkylbenzenes 
being formed as by-product. 
In a further embodiment, the present invention relates to a process for 
hydrogenating an aromatic compound in which at least one amino group is 
bonded to an aromatic ring and preferably, in addition to at least one 
amino group, at least one unsubstituted or substituted C.sub.1 -C.sub.10 
-alkyl group and/or at least one C.sub.1 -C.sub.10 -alkoxy group is bonded 
to an aromatic ring. Particular preference is given to using 
monoalkyl-substituted amines. 
The monocyclic or polycyclic aromatic compounds are hydrogenated in the 
presence of the catalyst described herein to give the corresponding 
cycloaliphatic compounds, with the amino group being retained. 
Cycloaliphatic amines, in particular unsubstituted or substituted 
cyclohexylamines and dicyclohexylamines, are used for preparing ageing 
inhibitors for rubbers and plastics, as corrosion inhibitors and also as 
precursors for crop protection agents and textile auxiliaries. 
Cycloaliphatic diamines are additionally employed in the production of 
polyamide and polyurethane resins and are also used as hardeners for epoxy 
resins. 
It is known that cycloaliphatic amines can be prepared by catalytic 
hydrogenation of the corresponding monocyclic or polycyclic aromatic 
amines. The hydrogenation of aromatic amines to give the corresponding 
cycloaliphatic amines in the presence of hydrogenation catalysts, 
particularly catalysts applied to supports, has been described many times. 
Catalysts used are, for example, Raney cobalt with additions of basic 
compounds (JP 43/3180), nickel catalysts (U.S. Pat. No. 4,914,239, DE 80 
55 18), rhodium catalysts (BE 73 93 76, JP 70 19 901, JP 72 35 424) and 
palladium catalysts (U.S. Pat. No. 3,520,928, EP 501 265, EP 53 818, JP 
59/196 843). However, ruthenium-containing catalysts are used in the 
majority of cases. 
DE 21 32 547 discloses a process for hydrogenating monocyclic or polycyclic 
aromatic diamines in the presence of a suspended ruthenium catalyst to 
give the corresponding cycloaliphatic amines. 
EP 67 058 describes a process for preparing cyclohexylamine by catalytic 
hydrogenation of the corresponding aromatic amine. The catalyst used is 
ruthenium metal in finely divided form on activated aluminum pellets. 
After four recirculations, the catalyst began to lose its effectiveness. 
EP 324 984 relates to a process for preparing a mixture of unsubstituted or 
substituted cyclohexylamine and unsubstituted or substituted 
dicyclohexylamine by hydrogenation of unsubstituted or substituted aniline 
using a catalyst comprising ruthenium and palladium on a support and 
further comprising an alkaline alkali metal compound as modifier. A 
process which is similar in principle is described in EP 501 265 where the 
catalyst contains niobic acid, tantalic acid or a mixture of the two as 
modifier. 
U.S. Pat. No. 2,606,925 describes a process for preparing an 
aminocyclohexyl compound by hydrogenating a corresponding aromatic 
compound using a ruthenium catalyst whose active catalytic component is 
selected from among elemental ruthenium, ruthenium oxides and ruthenium 
salts in which the ruthenium is present in the anion or in the cation. As 
the examples of this process show, here too, the catalyst is prepared in a 
separate step, dried and after a prolonged drying time introduced into the 
reaction vessel. 
A further process for preparing cyclohexylamine is described in U.S. Pat. 
No. 2,822,392. This patent mainly addresses the use of a specific reactor 
in which the aniline and the hydrogen as starting materials are reacted 
with one another in countercurrent. 
U.S. Pat. No. 3,636,108 and U.S. Pat. No. 3,697,449 concern the catalytic 
hydrogenation of aromatic, nitrogen-containing compounds using a ruthenium 
catalyst which further comprises an alkali metal compound as modifier. 
In many of the above-described processes, it has been found to be a 
disadvantage that these reactions not infrequently resulted in relatively 
large amounts of alkylbenzenes as well as further, unidentifiable 
compounds which are formed in the hydrogenation as decomposition products 
or by-products. These by-products make the work-up and purification of the 
reaction product more difficult, particularly when, for example, 
alkylcyclohexanols are to be used as fragrances or for the preparation of 
fragrances. Furthermore, the activity of many of the catalysts used in the 
processes described above decreases quickly, particularly when the 
hydrogenation is carried out at relatively high reaction temperatures to 
accelerate the reaction rate. 
The Applicant itself has submitted a series of recent Patent Applications, 
DE 196 04 791.9, DE 195 33 718.2, DE 196 24 484.6, DE 196 24 485.4, DE 196 
16 822.8, DE 196 22 705.4, which all concern processes of the type being 
considered here for using specific supported catalysts comprising 
ruthenium and possibly further metals of transition groups I, VII and VIII 
of the Periodic Table. These processes for hydrogenating aromatic 
compounds as defined above make it possible to obtain the corresponding 
hydrogenated aromatic compounds in very high yield or at virtually 
complete conversion with a simultaneously only minimal proportion of 
by-products. 
It is an object of the present invention to provide a further process for 
hydrogenating an aromatic compound as defined in the introduction which 
enables very high yields or virtually complete conversion to be achieved. 
Furthermore, this process should make it possible to obtain the desired 
products with an only minimal proportion of by-products or decomposition 
products and the process should be carried out at high throughputs over 
the catalyst and long operating lives with an extremely high turnover 
number. 
We have found that these objects are achieved by a process for 
hydrogenating an aromatic compound in which at least one hydroxyl group is 
bonded to an aromatic ring or an aromatic compound in which at least one 
amino group is bonded to an aromatic ring, in the presence of a catalyst 
comprising as catalytically active component at least one metal of 
transition group I, VII or VIII of the Periodic Table applied to a 
support, wherein the catalyst is obtainable by 
a) dissolving the catalytically active component or a precursor compound 
thereof in a solvent, 
b) admixing the solution thus obtained with an organic polymer which is 
able to bind at least ten times its own weight of water, giving a swollen 
polymer, 
c) subsequently mixing the swollen polymer with a catalyst support material 
and 
d) shaping, drying and calcining the composition obtained in this way. 
We have also found that these objects and possibly further objects are 
achieved by hydrogenation processes as are described in the subclaims. The 
process of the present invention is notable for the fact that the active 
component is, owing to the above-defined method of preparation, 
predominantly located in the macropores of the support, which leads to 
satisfactory activity and high selectivity. For the purposes of the 
present invention, macropores are pores whose diameter is above 50 nm and 
mesopores are pores whose diameter is from 2 to 50 nm, corresponding to 
the definition in Pure Applied Chem. 45 (1976), 79. 
The term "aromatic compound in which at least one hydroxyl group is bonded 
to an aromatic ring" or "aromatic compound in which at least one amino 
group is bonded to an aromatic ring" refers to all compounds which contain 
a unit of the following structure (I): 
##STR1## 
where R is a hydroxyl or amino group. 
If, for the purposes of the present invention, use is made of aromatic 
compounds in which at least one hydroxyl group and also at least one 
unsubstituted or substituted C.sub.1 -C.sub.10 -alkyl radical and/or 
C.sub.1 -C.sub.10 -alkoxy radical is bonded to an aromatic ring, the 
resulting ratio of cis to trans isomers can be varied within a wide range 
as a function of the reaction conditions (temperature, solvent). 
Furthermore, the compounds obtained can be further processed without 
further purification steps. The formation of alkylbenzenes is virtually 
completely avoided. 
As in the case of the above-described compounds in which at least one 
hydroxyl group is bonded to an aromatic ring, the process of the present 
invention can also be used to hydrogenate aromatic compounds in which at 
least one amino group is bonded to an aromatic ring with high selectivity 
to give the corresponding cycloaliphatic compounds. What has been said 
above regarding the cis and trans isomers also applies to the amines which 
are additionally substituted by a C.sub.1 -C.sub.10 -alkyl radical and/or 
C.sub.1 -C.sub.10 -alkoxy radical. 
In particular, the formation of deamination products, for example 
cyclohexanes or partially hydrogenated dimerization products such as 
phenylcyclohexylamines, is virtually completely avoided in this 
embodiment. 
Furthermore, the process of the present invention gives high turnover 
numbers at high throughputs over the catalyst and for long catalyst 
operating lives. The throughput over the catalyst is here the space-time 
yield of the process, i.e. the amount of starting material reacted per 
unit time and per amount of catalyst present. Operating life is the time 
or the amount of reacted starting material which a catalyst copes with 
without its properties deteriorating and without the product properties 
changing significantly. 
Compounds 
Aromatic compounds in which at least one hydroxyl group is bonded to an 
aromatic ring 
The process of the present invention enables aromatic compounds in which at 
least one hydroxyl group and preferably also at least one unsubstituted or 
substituted C.sub.1 -C.sub.10 -alkyl radical and/or alkoxy radical is 
bonded to an aromatic ring to be hydrogenated to give the corresponding 
cycloaliphatic compounds. Mixtures of two or more of these compounds can 
also be used and the aromatic compounds can be monocyclic or polycyclic 
aromatic compounds. The aromatic compounds contain at least one hydroxyl 
group which is bonded to an aromatic ring. The simplest compound of this 
group is phenol. The aromatic compounds preferably have one hydroxyl group 
per aromatic ring and can be substituted on the aromatic ring or rings by 
one or more alkyl and/or alkoxy radicals, preferably C.sub.1 -C.sub.10 
-alkyl and/or alkoxy radicals, particularly preferably C.sub.1 -C.sub.10 
-alkyl radicals, in particular methyl, ethyl, propyl, isopropyl, butyl, 
isobutyl or tert-butyl radicals; among the alkoxy radicals, preference is 
given to the C.sub.1 -C.sub.8 -alkoxy radicals such as methoxy, ethoxy, 
propoxy, isopropoxy, butoxy, isobutoxy or tert-butoxy radicals. The 
aromatic ring or rings and also the alkyl and alkoxy radicals may be 
substituted by halogen atoms, in particular fluorine atoms, or bear other 
suitable inert substituents. 
Preferably, the compounds which can be hydrogenated according to the 
present invention contain at least one, preferably from one to four, in 
particular one, C.sub.1 -C.sub.10 -alkyl radical which is preferably 
located on the same aromatic ring as the hydroxyl group or groups. 
Preferred compounds are (mono) alkylphenols in which the alkyl radical can 
be in the o, m or p position to the hydroxyl group. Particular preference 
is given to para-alkylphenols, also known as 4-alkylphenols, where the 
alkyl radical preferably has from 1 to 10 carbon atoms and, in particular, 
is a tert-butyl radical. Preference is given to 4-tert-butylphenol. 
Polycyclic aromatic compounds which can be used according to the present 
invention are, for example, .beta.-naphthol and .alpha.-naphthol. 
The aromatic compounds in which at least one hydroxyl group and preferably 
also at least one unsubstituted or substituted C.sub.1 -C.sub.10 -alkyl 
radical and/or alkoxy radical is bonded to an aromatic ring can also 
contain a plurality of aromatic rings which are linked via an alkylene 
radical, preferably a methylene group. The linking alkylene group, 
preferably methylene group, can bear one or more alkyl substituents which 
can be C.sub.1 -C.sub.20 -alkyl radicals and are preferably C.sub.1 
-C.sub.10 -alkyl radicals, particularly preferably methyl, ethyl, propyl, 
isopropyl, butyl or tert-butyl radicals. 
In these compounds, each of the aromatic rings can contain at least one 
bonded hydroxyl group. Examples of such compounds are bisphenols which are 
linked in the 4 position via an alkylene radical, preferably a methylene 
radical. 
In the process of the present invention, particular preference is given to 
reacting a phenol substituted by a C.sub.1 -C.sub.10 -alkyl radical, 
preferably C.sub.1 -C.sub.6 -alkyl radical, where the alkyl radical may be 
substituted by an aromatic radical, or mixtures of two or more of these 
compounds. 
In a further preferred embodiment of this process, p-tert-butylphenol, 
bis(p-hydroxyphenyl)dimethylmethane or a mixture thereof is reacted. 
Aromatic compounds in which at least one amino group is bonded to an 
aromatic ring 
The process of the present invention also enables aromatic compounds in 
which at least one amino group is bonded to an aromatic ring to be 
hydrogenated to give the corresponding cycloaliphatic compounds. Mixtures 
of two or more of these compounds can also be used. The aromatic compounds 
can be monocyclic or polycyclic aromatic compounds and contain at least 
one amino group which is bonded to an aromatic ring. The aromatic 
compounds are preferably aromatic amines or diamines. The aromatic 
compounds can be substituted on the aromatic ring or rings or on the amino 
group by one or more alkyl and/or alkoxy radicals, preferably C.sub.1 
-C.sub.20 -alkyl radicals, in particular methyl, ethyl, propyl, isopropyl, 
butyl, isobutyl or tert-butyl radicals; among the alkoxy radicals, 
preference is given to the C.sub.1 -C.sub.8 -alkoxy radicals such as 
methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy or tert-butoxy 
radicals. The aromatic ring or rings and also the alkyl and alkoxy 
radicals may be substituted by halogen atoms, in particular fluorine 
atoms, or bear other suitable inert substituents. 
The aromatic compound in which at least one amino group is bonded to an 
aromatic ring can also contain a plurality of aromatic rings which are 
linked via an alkylene group, preferably a methylene group. The linking 
alkylene group, preferably methylene group, can bear one or more alkyl 
substituents which can be C.sub.1 -C.sub.20 -alkyl radicals and are 
preferably C.sub.1 -C.sub.10 -alkyl radicals, particularly preferably 
methyl, ethyl, propyl, isopropyl, butyl, sec-butyl or tert-butyl radicals. 
The amino group bonded to the aromatic ring can likewise be substituted by 
one or two of the above-described alkyl radicals. 
Particularly preferred compounds are aniline, naphthylamine, 
diaminobenzenes, diaminotoluenes, bis(p-aminophenyl)dimethylmethane and 
bis(p-aminophenyl)methane or mixtures thereof. 
Catalysts 
The catalysts used according to the present invention and their preparation 
are known per se and are described in detail in EP-A-0 653 243, the full 
scope of which in respect of the catalyst used and its preparation is 
incorporated by reference in the present application. 
Nevertheless, the principal process steps a) to d) for preparing the 
catalyst used according to the present invention will be described in 
general terms below. 
The supported catalysts used according to the present invention are 
prepared by the following process steps: 
Process step a): 
The catalytically active components or their precursor compounds, i.e. the 
metals of transition group I, VII or VIII of the Periodic Table or 
mixtures of two or more of these metals, preferably ruthenium, rhodium, 
platinum, palladium, copper, rhenium, cobalt, nickel or a mixture of two 
or more thereof, in particular ruthenium alone or together with at least 
one metal of transition group I, VII or VIII of the Periodic Table, or 
their precursor compounds which are only converted into catalytically 
active components during further processing or activation steps, are 
dissolved in a solvent. 
The solvent to be used is preferably water or a polar, water-miscible 
solvent such as an alcohol, ether or amine. Preference is given to using 
water or an ammonia/water mixture. 
The catalytically active component is generally used in the form of a 
water-soluble metal salt such as a nitrate, nitrosyl nitrate or halide, or 
as a chloro, nitrito or amine complex. Such compounds are commercially 
available. 
Also suitable are sols of the above-described metals, e.g. sols of the 
metals palladium, platinum, silver and copper as are obtainable, for 
example, by methods described in Angew. Chem. 103 (1991), 852 or sometimes 
commercially. 
Furthermore, the catalyst used according to the present invention can 
further comprise, in addition to the catalytically active component 
defined above, promoters or moderators which can influence the catalytic 
activity or selectivity and are different from the active metal or metals. 
These are added directly or likewise in the form of their precursor 
compounds to the solution of the abovementioned metal salts of metals of 
transition groups I, VII and VIII of the Periodic Table or their sols. 
The concentration of the above-described metals of transition groups I, VII 
and VIII of the Periodic Table is subject to no particular restrictions 
and depends on the solubility of the corresponding compound in the solvent 
selected. It is generally in a range from at least about 0.1 g/l to the 
saturation concentration of the solution. Furthermore, the amount of the 
active component depends on the desired concentration used in the 
supported catalyst used according to the present invention. The 
above-described solutions are generally prepared at room temperature. 
Further details and preferred embodiments of process step a) may be found 
in EP-A-0 653 234 in the section "Process step a)". 
Process step b): 
The above-described solutions of the catalytically active components or 
their precursor compounds are admixed with an organic polymer. The 
solution can either be added to the polymer or the polymer can be added to 
the solution. 
The organic polymer used is capable of binding at least ten times its own 
weight of water. Such compounds are described as hydrogels (cf. B. D. 
Rathmer et al., in "Hydrogels for medical and related applications", ACS 
Symposium Series No. 31 (1976)). These are crosslinked polymeric compounds 
in which the crosslinking can be by means of ionic interactions or 
hydrogen bonds or by means of chemical crosslinking. 
Suitable polymers are, for example, graft copolymers of starch and acrylic 
acid, (e.g. G. F. Fanta et al., in Starch 34 (1982), 95), starch and 
acrylic acid (EP-A 83 022), polysaccharides and acrylic acid (DE-A 41 05 
000), copolymers of polyvinyl alcohol and sodium acrylates (U.S. Pat. No. 
4,155,893), copolymers of acrylamide and acrylic acid (EP-A 72 214), 
crosslinked polyethylene oxide (U.S. Pat. No. 3,264,202), crosslinked 
polyacrylamide (U.S. Pat. No. 3,669,103), crosslinked 
poly-N-vinylpyrrolidone (U.S. Pat. No. 3,669,103), crosslinked 
polyvinylalcohol (Walter et al., Biomaterials 9 (1988), 150), crosslinked 
carboxycellulose fibers (U.S. Pat. No. 3,826,711), hydrolysates of 
polyvinyl acetate-acrylic acid copolymers (GB 20 30 990) and hydrolysates 
of polyacrylonitrile (U.S. Pat. No. 4,366,206). 
Preference is given to using crosslinked polymers of acrylic acid, acrylic 
acid and acrylamide and also of acrylamide, with particular preference 
being given to using partially neutralized sodium polyacrylates which are 
weakly crosslinked, these can be crosslinked using known crosslinkers as 
are described in EP-A-0 653 243 under "process step b)". 
In general, the polymer is admixed with as much solution of the active 
component as it can completely absorb. This process is generally complete 
in 60 minutes; the swelling of the polymer is usually carried out at room 
temperature. When swelling polyacrylates, the pH should be at least 6 
since otherwise only insufficient absorption of solution occurs. 
Further details regarding process step b) may be found in EP-A-0 653 243 
under "process step b)". 
Process step c): 
The swollen polymer is mixed with a pulverulent catalyst support material. 
The order in which the components are added to one another is of no 
consequence. Suitable support materials are materials which are inert 
under the reaction conditions of the reaction to be catalyzed, with 
preference being given to using aluminum oxide, silicon dioxide, 
kieselguhr, a silica gel, an alumina, a silicate, a zeolite in admixture 
with an aluminum oxide, a zirconium oxide, a titanium oxide or a mixture 
of two or more thereof. Particular preference is given to aluminum oxides 
and silicon dioxide. 
It is also possible to use oxides of Mg, Ca, Sr, Ba, sulfates of Ca, Ba, 
Sr, Pb, carbonates of Mg, Ca, Sr, Ba, Ni, Co, Mn, Fe, Cu, sulfides of Mo, 
W, Co, Ni, Fe, Pb, Ag, Cr, Cu, Cd, Sn, Zn, carbides of B, Si, W and 
nitrides of B and Si. 
The amount of the support material is generally from about 10 to about 100 
times, preferably from about 20 to about 200 times, that of the 
non-swollen polymer. 
Customary peptizing agents can be added to the solution to improve the 
mechanical stability of the shaped bodies obtained, for example ammonia 
for aluminum oxide support materials and sodium hydroxide for silicon 
dioxide. The amount of these substances is generally from about 0.1 to 
about 5% by weight, based on the total weight of the support material. 
The above-described components are mixed, which can be carried out using 
customary kneaders or compounders. 
Process step d): 
The composition obtained after process step c) is shaped, e.g. by extrusion 
in an extruder or by shaping in a ram extruder to form extrudates having 
the desired dimensions. 
The shaped bodies obtained in this way are subsequently dried, generally at 
from about 100.degree. C. to about 150.degree. C. for from about 2 to 
about 24 hours. 
The shaped bodies are subsequently calcined, generally for more than 2 up 
to about 24 hours at from about 300.degree. C. to about 800.degree. C., 
preferably from about 300.degree. C. to 550.degree. C. Depending on the 
active component, this can be followed by an activation step in which the 
catalytically active component is formed. 
The resulting supported catalysts can also be applied in a manner known per 
se to nonporous supports of, for example, steatite, to glass rings, quartz 
rings or highly sintered aluminum oxide rings. 
Further details regarding process step d) may be found in EP-A-0 653 241 
under "process step d)". 
The catalysts are activated by treatment in a gas stream comprising from 50 
to 100% by volume of H.sub.2 and from 0 to 50% by volume of N.sub.2 at 
from about 30.degree. C. to about 600.degree. C., preferably from about 
150.degree. C. to about 450.degree. C. 
The resulting supported catalysts are highly porous and have a low bulk 
density. It can clearly be seen from electron micrographs that the major 
part, in general more than 80%, of the active component is located in the 
macropores. The proportion of the active component which is located in the 
macropores can be determined only by examining a plurality of 
representative sections through the catalyst extrudate by scanning 
electron microscopy using backscattering of electrons to reveal the heavy 
elements. 
In the catalysts of the present invention, the reactants can easily reach 
the active centers and the reaction products can easily leave them. 
Locating the catalytically active components in the macropores makes it 
possible to prepare catalysts which, compared with conventional catalysts 
having the same activity, only require a fraction of the amount of active 
component. The amount of catalytically active component is preferably from 
about 0.01 to about 30% by weight, more preferably from about 0.05 to 
about 5% by weight and in particular from about 0.1 to about 3% by weight. 
The catalyst used according to the present invention has a high reactivity, 
selectivity and operating life. 
The process of the present invention gives the corresponding hydrogenation 
product in high yield and purity. 
Hydrogenation 
The hydrogenation is carried out at suitable pressures and temperatures. 
Preference is given to pressures above about 5.times.10.sup.6 Pa, 
preferably from about 1.times.10.sup.7 to 3.times.10.sup.7 Pa. Preferred 
temperatures are in the range from about 50.degree. C. to about 
300.degree. C., preferably from about 100.degree. C. to about 270.degree. 
C. and particularly preferably from about 150.degree. C. to about 
220.degree. C. 
The hydrogenation can be carried out continuously or batchwise, either in 
the downflow mode or the upflow mode. In a continuous process, part of the 
hydrogenation product leaving the reactor can be recirculated to the 
reactor feed upstream of the reactor. The amount of any such hydrogenation 
product leaving the reactor which is recirculated as solvent is such that 
the ratios indicated in the section "solvents and diluents" are achieved. 
The remaining amount of hydrogenation product is taken off. 
When the process is carried out continuously, the amount of compound or 
compounds to be hydrogenated is preferably from about 0.05 to about 3 kg 
per liter of catalyst per hour, more preferably from about 0.1 to about 1 
kg per liter of catalyst per hour. 
Hydrogenation gases used can be any gases which comprise free hydrogen and 
do not contain any harmful amounts of catalyst poisons such as CO. For 
example, reformer off-gases can be used. Preference is given to using pure 
hydrogen as hydrogenation gas. 
In the case of phenols and amines which are additionally substituted by at 
least one unsubstituted or substituted C.sub.1 -C.sub.10 -alkyl and/or 
C.sub.1 -C.sub.10 -alkoxy radical, the resulting ratio of cis to trans 
isomers can be varied within a wide range as a function of the reaction 
conditions (temperature, solvent). 
If an aromatic compound in which at least one amino group is bonded to an 
aromatic ring is to be hydrogenated by means of the catalyst of the 
present invention, the hydrogenation can also be carried out in the 
presence of ammonia or alkylamines, for example methylamine, ethylamine, 
propylamine or dimethylamine, diethylamine or dipropylamine. In this case, 
appropriate amounts of ammonia, monoalkylamine or dialkylamine are used, 
preferably from about 0.5 to about 50 parts by weight, particularly 
preferably from about 1 to about 20 parts by weight, in each case based on 
100 parts by weight of the compound or compounds to be hydrogenated. 
Particular preference is given to using anhydrous ammonia or anhydrous 
amines. 
Solvents or Diluents 
In the process of the present invention, the hydrogenation can be carried 
out in the absence of a solvent or diluent, i.e. the hydrogenation does 
not have to be carried out in solution. 
If a solvent or diluent is employed, any suitable solvent or diluent can be 
used. The selection is not critical. For example, the solvents or diluents 
can also contain small amounts of water. 
In the hydrogenation of an aromatic compound in which at least one hydroxyl 
group is bonded to an aromatic ring, examples of suitable solvents or 
diluents include the following: 
Straight-chain or cyclic ethers such as tetrahydrofuran or dioxane, and 
also aliphatic alcohols in which the alkyl radical preferably has from 1 
to 10 carbon atoms, in particular from 3 to 6 carbon atoms. 
Examples of preferred alcohols are i-propanol, n-butanol, i-butanol and 
n-hexanol. 
Mixtures of these or other solvents or diluents can likewise be used. 
In the hydrogenation of an aromatic compound in which at least one amino 
group is bonded to an aromatic ring, examples of suitable solvents or 
diluents include the following: 
Straight-chain or cyclic ethers such as tetrahydrofuran or dioxane, and 
also ammonia and monoalkylamines or dialkylamines in which the alkyl 
radical preferably has from 1 to 3 carbon atoms, for example methylamine, 
ethylamine, propylamine or the corresponding dialkylamines. 
Mixtures of these or other solvents or diluents can likewise be used. 
In both the above embodiments, the amount of solvent or diluent used is not 
subject to any particular restriction and can be freely selected according 
to requirements, although preference is given to amounts which lead to a 
10-80% strength by weight solution of the compound to be hydrogenated. 
In the process of the present invention, particular preference is given to 
using the product formed in the hydrogenation of this process as solvent, 
if desired together with other solvents or diluents. In this case, part of 
the product formed in the hydrogenation process can be mixed into the 
compounds to be hydrogenated. The amount of hydrogenation product mixed in 
as solvent or diluent is preferably from 1 to 30 times, particularly 
preferably from 5 to 20 times, in particular from 5 to 10 times, the 
weight of the aromatic compounds to be hydrogenated. 
The invention is illustrated below by means of some examples.

EXAMPLES 
Preparation of catalyst A 
(1 % by weight Ru/Al.sub.2 O.sub.3) 
14.2 g of a nitric acid solution of ruthenium nitrosyl nitrate (14% by 
weight of Ru) were admixed with 150 ml of water and 6 g of a high 
molecular weight sodium polyacrylate (90% of the acid groups neutralized, 
crosslinked with 0.4 mol % of polyethylene glycol having a molar mass of 
1,500) which can bind 300 times its own weight of water. After 30 minutes, 
the gel-like mass was kneaded with 280 g of Al.sub.2 O.sub.3 
(pseudo-boehmite, BET surface area after calcination at 600.degree. C.: 
300 m.sup.2 /g). After addition of 200 ml of ammonia solution (containing 
50 ml of concentrated ammonia), the mixture was kneaded for 1 hour. The 
mixture was shaped at 6.5.times.10.sup.6 Pa (65 bar) in a ram extruder to 
form 3.8 mm extrudates, dried for 16 hours at 120.degree. C. and calcined 
for 6 hours at 300.degree. C. 
The resulting catalyst had the following properties: 
______________________________________ 
Bulk density: 425 g/l 
BET surface area: 294 m.sup.2 /g 
Pore volume (DIN 66 132) 
0.81 ml/g 
Mean diameter of the 1,000 
macropores nm!: 
Mean diameter of the 6 
mesopores nm!: 
Proportion of macropores 
35 
% by volume! 
______________________________________ 
The pore volume was determined in accordance with DIN 66 132 by mercury 
porosimetry as per the teachings of J. V. Brakel et al., Powder Technology 
29 (1991), 1. 
Example 1 
1.2 l of the above-described catalyst were placed in an electrically heated 
flow reactor. The hydrogenation of aniline was then commenced at 
2.times.10.sup.7 Pa (200 bar) and 160.degree. C. without prior activation. 
The hydrogenation was carried out continuously in the upflow mode, with 
part of the hydrogenation product being recirculated via a circulation 
pump and mixed into the feed upstream of the reactor. In this way, an 
amount of hydrogenation product which was 10 times the amount of aniline 
was added as solvent. At the top of the separator, 500 l/h to 600 l/h of 
hydrogen were depressurized. The amount of aniline which was fed 
continuously to the reactor corresponded to a throughput over the catalyst 
of 1.0 kg/l.multidot.h. 
Depending on the reaction temperatures, the following product compositions 
were obtained under steady-state reaction conditions (both here and in the 
following tables "%" refers to the gas chromatographic percentage areas of 
the respective product peaks): 
TABLE 1 
______________________________________ 
Temperature 
CHA.sup.1) 
DCHA.sup.2) Cyclohexane + 
.degree.C. 
% % Aniline % 
Cyclohexene % 
______________________________________ 
160 99.1 0.45 0.10 0.04 
180 97.0 2.75 0.06 0.06 
200 95.9 3.9 -- 0.09 
______________________________________ 
.sup.1) CHA = Cyclohexylamine; 
.sup.2) DCHA = Dicyclohexylamine 
Example 2 
A hydrogenation was carried out as described in Example 1, but, in 
addition, anhydrous ammonia was metered in continuously. 10 parts by 
weight of ammonia were added per 100 parts by weight of aniline. Depending 
on the reaction temperatures, the following product compositions were 
obtained under steady-state reaction conditions: 
TABLE 2 
______________________________________ 
Temperature 
CHA.sup.1) 
DCHA.sup.2) Cyclohexane + 
.degree.C. 
% % Aniline % 
Cyclohexene % 
______________________________________ 
180 99.3 0.08 -- 0.07 
200 98.4 0.8 -- 0.09 
______________________________________ 
.sup.1) CHA = Cyclohexylamine; 
.sup.2) DCHA = Dicyclohexylamine 
Example 3 
2 kg of a solution of 50% by weight of tolylenediamine (2,4- and 
2,6-diaminotoluene isomer mixture) in tetrahydrofuran and 500 ml of the 
above-described catalyst were introduced into a 3.5 l pressure autoclave. 
Hydrogenation was subsequently carried out batchwise at 150.degree. C. and 
2.times.10.sup.7 Pa (200 bar) for 5 hours. The conversion to the desired 
cycloaliphatic diamine isomer mixture was quantitative and the residual 
aromatics content was less than 0.01% by weight. 
Example 4 
150 ml of a solution of 50% of p-tert-butylphenol in butanol and 15 ml of 
the above-described catalyst were placed in a 0.3 l stirring autoclave. 
Hydrogenation was subsequently carried out at 200.degree. C. for 6 hours. 
The conversion to 4-tert-butylcyclohexanol was quantitative, the 
selectivity was 99.2% at a cis/trans ratio of 48/52. 
Example 5 
150ml of a solution of 50% of bisphenol A in butanol and 15 ml of the 
above-described catalyst were placed in a 0.3 l stirring autoclave. 
Hydrogenation was subsequently carried out at 200.degree. C. for 6 hours. 
The conversion was quantitative, the selectivity to 
2,2-bis(4-hydroxycyclohexyl)propane was 98.7%.