Process for the preparation of asymmetrical N-phenyl-N'-substituted para-phenylene diamines

An improved process for the preparation of asymmetrical N-phenyl-N'-substituted para-phenylene diamines by the reductive alkylation of para-nitroso-diphenylhydroxylamine with an aldehyde or a ketone in the presence of hydrogen and a hydrogenation catalyst is disclosed. The improvement comprises utilizing as the hydrogenation catalyst (1) one member selected the group consisting of palladium and platinum sulfide, in an amount less than 1%, by weight, based on the weight of para-nitroso-diphenylhydroxylamine, and (2) activated carbon with a specific surface area of at least 700 square meters per gram and an ash content of less than 7.5%, by weight.

BACKGROUND OF THE INVENTION 
This invention relates to a process for the preparation of asymmetrical 
N-phenyl-N'-substituted para-phenylene diamines by the reductive 
alkylation of para-nitroso-diphenylhydroxylamines with an aldehyde or a 
ketone in the presence of hydrogen and a hydrogenation catalyst. 
The reductive alkylation of nitroso compounds by reaction with an aldehyde 
or a ketone in the presence of hydrogen and an hydrogenation catalyst is 
known in the art. Thus, use of certain metal compounds as hydrogenation 
catalysts, such as copper chromite (British Patent No. 804,113 and Russian 
Patent No. 230,828), nickel sulfide (East German Published Patent 
Applciation No. 1,542,171), a selenide, a telluride, or a nickel chromium 
catalyst (Czecholslovakian Patent No. 119,336), or mixtures of two or more 
heavy metals, iron, manganese, copper, chromium, nickel, silver, cerium or 
lead, in the form of their oxides, hydroxides, or carbonates (East German 
Patent Disclosure No. 1,941,009) is known. However, all of the catalysts 
used in accordance with the foregoing prior art procedures produce side 
reactions, in particular, reduction of the aldehyde or ketone to the 
corresponding alcohol. 
According to the process for the preparation of 
N-phenyl-N'-alkyl-para-phenylene diamines disclosed in British Patent No. 
1,295,672, para-nitroso-diphenylhydroxylamine is reacted with hydrogen and 
an aldehyde or a ketone in the presence of a hydrogenation catalyst at 
temperatures in the range from room temperature to 200.degree. C. The 
hydrogenation catalyst utilized is made of a metal from Group VIII of the 
periodic system, such as nickel, cobalt, ruthenium, palladium, or 
platinum, which, if desired, may have been deposited on an inert carrier 
material, such as carbon, aluminum oxide, or silica gel. Yields of 
N-phenyl-N'-alkyl- and N-phenyl-N'-cycloalkyl-para-phenylene diamines of 
about 95% of theoretical are indeed obtained by the foregoing process, but 
for an industrial scale preparation of such products, the yield and 
selectivity achieved thus far are inadequate. Furthermore, the required 
catalyst quantities are too large and the losses of catalyst are thus 
considerable. 
Therefore, an object of the present invention is to provide a process for 
the preparation of asymmetrical N-phenyl-N'-substituted para-phenylene 
diamines by reductive alkylation of para- nitroso-diphenylhydroxylamines 
with an aldehyde or a ketone in the presence of a hydrogenation catalyst, 
which process does not suffer from the foregoing drawbacks and results in 
the production of the desired compounds in high yields. 
SUMMARY OF THE INVENTION 
An improved process for the preparation of asymmetrical 
N-phenyl-N'-substituted para-phenylene diamines by the reductive 
alkylation of para-nitroso-diphenylhydroxylamine with an aldehyde or a 
ketone in the presence of hydrogen and a hydrogenation catalyst is thus 
provided. The improvement comprises utilizing as the hydrogenation 
catalyst (1) one member selected from the group consisting of palladium 
and platinum sulfide, in an amount less than 1%, based on the weight of 
para-nitroso-diphenylhydroxylamine, and (2) an activated carbon with a 
specific surface area of at least 700 square meters per gram and an ash 
content of less than 7.5%, by weight. Optionally, the process may be 
preformed in the presence of an inert solvent. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Para-nitroso-diphenylhydroxylamine is a compound which may be readily 
obtained by means of the catalytic dimerization of nitrosobenzene. 
According to a recent, especially advantageous process, the foregoing 
compound may be obtained with practically quantitative yield, if a 
sulfonic acid with a pK.sub.a .ltoreq.1, for example methane-, ethane-, or 
trifluoromethanesulfonic acid, or perchloric or trifluoroacetic acid is 
used as a catalyst (German Patent Application No. P 27 03 919). The 
nitrosobenzene required for the preparation of 
para-nitroso-diphenylhydroxylamine is likewise easily accessible and may 
be obtained by the catalytic reduction of nitrobenzene. The reduction will 
proceed with a high conversion rate and high selectivity if, pursuant to 
another recent process, an aliphatic, cycloaliphatic, olefinic, or 
aromatic hydrocarbon is used as the reducing agent (German Patent 
Application No. P 27 13 602). 
In each instance, the compounds obtainable pursuant to the present 
invention have a phenyl radical as a substituent on the N atom, whereas 
the N' atom carries one or two aliphatic, cycloaliphatic, or aromatic 
substituents. In the latter instance, the substituents may be the same or 
different. Selection of the aldehyde or ketone to be utilized depends, of 
course, upon the desired para-phenylene diamine derivative. For the 
preparation of N-phenyl-N'-monosubstituted para-phenylene diamines, one 
may utilize an aldehyde in the reaction and for the preparation of 
N-phenyl-N'-disubstituted para-phenylene diamines one may utilize a 
ketone. Examples of suitable carbonyl compounds are: aliphatic aldehydes, 
such as formaldehyde; alkyl-alkyl ketones, such as acetone; cyclic 
ketones, such as cyclobutanone; aryl-aryl ketones, such as benzophenone; 
alkyl-aryl ketones, such as acetophenone and methylbenzyl ketone; 
alkyl-cycloalkyl ketones, such as methylcyclohexyl ketone; aryl-cycloalkyl 
ketones, such as phenylcyclohexyl ketone; aromatic aldehydes, such as 
benzaldehyde; cyclic aldehydes, such as cyclohexyl aldehyde; and 
diketones, such as 2,4-pentanedione. 
The process pursuant to the present invention is preferably utilized for 
the preparation of N-phenyl-N'-monoalkyl-para-phenylene diamines, 
N-phenyl-N'-dialkyl-para-phenylene diamines and 
N-phenyl-N'-cycloalkyl-para-phenylene diamines. In such instances, 
aldehydes, alkyl-alkyl ketones, and cyclic ketones are utilized. 
Examples of suitable aldehydes are: formaldehyde, acetaldehyde, 
propionaldehyde, butyraldehyde, and valeraldehyde. Examples of suitable 
alkyl-alkyl ketones are: acetone, methylethyl ketone, methyl-propyl 
ketone, methyl-butyl ketone, methylisobutyl ketone, methyl-amyl ketone, 
methyl-isoamyl ketone, methyl-hexyl ketone, methyl-heptyl ketone, 
methyl-octyl ketone, diethyl ketone, ethyl-propyl ketone, ethyl-butyl 
ketone, ethylamyl ketone, ethyl-hexyl ketone, ethyl-heptyl ketone, 
5-methylheptanone-(3), dipropyl ketone, dibutyl ketone, diisobutyl ketone, 
diamyl ketone, dihexyl ketone, diheptyl ketone, and diisodecyl ketone. 
Examples of suitable cyclic ketones are: cyclobutanone, cyclopentanone, 
cyclohexanone, and cyclooctanone. 
In the process of the present invention it is not absolutely necessary to 
use pure hydrogen. Thus, one may use carrier gases, such as nitrogen, and 
gas mixtures, which, in addition to hydrogen, also contain carbon 
monoxide, such as water gas and generator gas. In such instances, the 
carbon monoxide also participates in the reaction, however, enough 
hydrogen should be present, so that a complete reduction is guaranteed. 
The customary palladium or platinum sulfide catalyst is used as the 
hydrogenation catalyst, such as catalysts with the usual types of carbon 
as carrier, such as coal, lamp black, and activated carbon. The term 
"platinum sulfide" is utilized herein to mean commercially available 
"sulfidized platinum", obtained by sulfidizing platinum. Although a 
specific platinum sulfide is not involved here, such catalysts are, for 
the sake of simplicity, referred to as platinum sulfide in the industry 
(cf. Robert I. Peterson, Hydrogenation Catalysts, Noyes Data Corporation, 
Parkridge, N.J., USA, 1977, pp. 256-261). In contrast to the kind of 
activated carbon to be additionally used as catalyst, the kind of carrier 
material is of only nominal importance. Preferably, however, an activated 
carbon with a specific surface area of at least 700 m.sup.2 /g and an ash 
content of less than 7.5%, by weight, is likewise utilized as the carrier 
material. 
Reductive alkylation of the para-nitroso-diphenylhydroxylamine will largely 
proceed without problems if, as in the customary processes, catalyst 
quantities of more than one percent, by weight, of palladium sulfide or 
platinum sulfide, based on the initial material, are utilized. However, 
such large catalyst quantities substantially increase the cost of 
synthesis, especially since the losses of catalyst are also considerable. 
Furthermore, excessive hydrogenation will result in the formation of 
products which are hydrogenated in the nucleus, the separation of which, 
from the desired N-phenyl-N'- substituted para-phenylene diamines, is 
difficult. In addition, there is the possibility of hydrogenation of the 
excess carbonyl compound which may be present as solvent, to an 
undesirable alcohol (cf. comparative example). 
In the process pursuant to the present invention, the hydrogenation 
catalyst is used in a quantity corresponding to less than 1%, by weight, 
of palladium, or platinum sulfide, based on the 
para-nitroso-diphenylhydroxylamine, preferably in quantities of from about 
0.05 to about 0.2%, by weight, of palladium or platinum sulfide. The 
formation of alcohol by hydrogenation of excess carbonyl compound, if any, 
is thus almost completely eliminated. Under such conditions, there is 
likewise no hydrogenation of the nucleus of the desired 
N-phenyl-N'-substituted para-phenylene diamines. 
The hydrogenation catalyst consisting of palladium or platinum sulfide 
typically on a carbon carrier material may contain from about 0.05 to 
about 10%, by weight, of palladium or platinum sulfide. Preferably, the 
catalyst is endowed with from about 0.5 to about 5%, by weight, of 
palladium or platinum sulfide. In particular, use may be made of the 
commercially available precious metal/carbon catalysts, which contain from 
about 1 to about 5%, by weight, of palladium or platinum sulfide. 
Consequently, depending upon the endowment with precious metal, the 
quantity of hydrogenation catalyst based on 
para-nitroso-diphenylhydroxylamine at most amounts to from about 0.1%, by 
weight (with 10% precious metal endowment), to about 20%, by weight (with 
0.05% precious metal endowment). 
Surprisingly, it has been found that, pursuant to the present invention, 
the concomitant use of activated carbon as catalyst in conjunction with 
the palladium or platinum sulfide catalyst, considerably increases the 
selectivity, as well as the yield of the reductive alkylation and, in a 
continuous operation, results in considerable lengthening of the life of 
the catalyst system. It is peculiar, that this effect is pronounced only 
with palladium and platinum sulfide catalysts, whereas it is barely 
noticeable with other catalyst metals. 
The nature of the activated carbon to be used as the additional catalyst is 
essential to the invention. It has thus been found that the catalytic 
effectiveness occurs only with highly active types of activated carbon. 
The specific surface area of the activated carbon has to be at least about 
700 m.sup.2 /g. The ash content, which as to be less than about 7.5%, by 
weight, is also decisive for the catalytic effectiveness of the activated 
carbon. The term "ash content" as used herein means the insoluble, as well 
as the soluble, ash constituents. As a rule, activated carbon types 
obtained from natural initial materials, such as lignite, peat, wood, 
bones, and the like, contain substantially greater quantities of ash and 
are therefore not suitable without further processing for use in the 
process pursuant to the present invention. However, if the ash content is 
reduced to less than 7.5%, by weight, by careful washing with acids, and 
if the required large specific surface area is present, such activated 
carbon types may be utilized. 
Trace elements evidently have no, or perhaps only a subordinate, influence 
on the effectiveness of the carbon catalyst. The selection of suitable 
carbon types is therefore governed by the two above-mentioned criteria. 
Although all activated carbons with a specific surface area of more than 
about 700 m.sup.2 g and an ash content of less than about 7.5%, display 
catalytic activity in the process pursuant to the present invention, 
activated carbons prepared from petroleum, natural gas, anthracite, or 
cellulose are preferred because of their purity. 
The quantity of activated carbon catalyst to be used is from about 10 to 
about 200%, by weight, based on the weight of 
para-nitroso-diphenylhydroxylamine. The exact quantity depends upon the 
quantity of precious metal based upon the 
para-nitroso-diphenylhydroxylamine and upon the endowment with precious 
metal in the hydrogenation catalyst, that is upon the quantity ratio of 
precious metal:carrier carbon. In order to obtain the same yield level, a 
reduction in precious metal quantity requires an increase in activated 
carbon catalyst quantity. The following correlation exists between the 
endowment of the hydrogenation catalyst with precious metal and the 
required quantity of activated carbon catalyst: In the range of a precious 
metal endowment of the hydrogenation catalyst of about 1 to about 10%, by 
weight, the quantity of activated carbon catalyst required for the same 
level of conversion declines with declining endowment of precious metal. 
In the range of endowment with precious metal of about 0.05 to about 1%, 
by weight, a declining endowment with precious metal requires increasing 
quantities of activated carbon catalyst, in order to obtain the same level 
of conversion. 
In the preferred version of the process pursuant to the present invention 
use is made of from about 0.01 to about 20%, by weight, of the palladium, 
or platinum sulfide catalyst, on a carbon carrier (with from about 0.05 to 
about 0.2%, by weight, of the metal) and from about 10 to about 200%, by 
weight, of activated carbon as additional catalyst, all based on the 
weight of para-nitroso-diphenylhydroxylamine. 
The quantity of aldehyde or ketone typically amounts to from about 1 to 
about 10 equivalents, per equivalent of 
para-nitroso-diphenylhydroxylamine, preferably to from about 2 to about 10 
equivalents. It is also possible to use greater quantities of aldehyde or 
ketone, in which instance the excess serves as solvent. 
If desired, other inert solvents (co-solvents) may also be used, for 
example, aliphatic or aromatic hydrocarbons, their halogen derivatives or 
ethers, such as toluene, monochlorobenzene, dichlorobenzene, 
1,2,4-trichlorobenzene, or 1,1,2-trifluoro-1,1,2-trichloroethane. 
Especially suitable inert solvents are the lower alcohols, such as 
methanol, ethanol, isopropanol, propanol, butanol, pentanols, 
isopentanols, and 4-methylpentanol-2. The use of inert solvents is 
particularly advantageous when the water of reaction formed in the course 
of the reaction is not, or is only slightly, soluble in the ketone or 
aldehyde utilized, so that an aqueous phase is formed in addition to the 
organic one. In cases in which the aldehyde or ketone is miscible with 
water to such an extent that a second phase will not form, it is 
preferable not to use an additional solvent. 
In the process pursuant to the present invention one may also use 
para-nitroso-diphenylhydroxylamine wetted with water, which contains up to 
100%, by weight, of water. Here, the water is also a co-solvent. It is 
also not necessary that the para-nitroso-diphenylhydroxylamine be present 
in dissolved form, so that the reaction takes place in a homogeneous 
phase. Preferably, the conversion is carried out in a heterogeneous phase. 
This is advantageous in that the reaction volume is relatively small and 
the processing of the reaction mixture is expedited. 
The process pursuant to the present invention can be carried out batchwise, 
as well as continuously. The reaction temperature and the reaction 
pressure are not critical. The process pursuant to the present invention 
may be performed at normal pressure and room temperature, but, because of 
the influence of pressure and temperature on the reaction rate, it is 
expedient to perform the reaction at elevated temperatures and elevated 
pressures. Generally, it is advisable to work within a temperature range 
from about 20.degree. to about 150.degree. C. The preferred reaction 
temperature is from about 25.degree. to about 125.degree. C., most 
preferably from about 40.degree. to about 100.degree. C. The hydrogen 
pressure may be anywhere within a wide range, as from about 1 to about 150 
bar. Preferably the hydrogen pressure is from about 5 to about 15 bar, 
most preferably from about 7 to about 12 bar. As a general rule, the 
reaction time is typically from about 15 minutes to about 5 hours, 
preferably from about 0.05 to about 3 hours. 
The reaction mixture may be processed in a typical manner. First, the 
catalyst may be filtered off, then the solvent siphoned off, if necessary, 
and subsequently the amine may either be distilled or crystallized. The 
method suitable in the particular case depends upon the physical 
characteristics of the amine and the solvent utilized. The solvent may be 
circulated, if desired. In a classical prior art process, the catalyst is 
partially contaminated after the reductive alkylation has been carried out 
and when re-used, the catalyst displays a reduced activity, so that in 
practice it must be supplemented by a certain quantity of fresh catalyst. 
In contrast thereto it has been found from the process pursuant to the 
present invention that, due to the addition of the activated carbon 
catalyst, the used hydrogenation catalyst retains its activity for a 
lengthy period of time so that when it is re-used, none, or comparatively 
small quantity of fresh hydrogenation catalyst must be added in order to 
reach the original activity. For example, if a catalyst with 0.2%, by 
weight, of palladium, based on the para-nitroso-diphenylhydroxylamine, is 
used in a reductive alkylation process pursuant to the present invention, 
only an additional 0.01%, by weight, of palladium, is required in the 
second reaction cycle. After a few additional reaction cycles, the 
quantity of supplementary, fresh catalyst required for some of the 
catalyst activity declines to only 0.005%, by weight. Finally, several 
additional reaction cycles can even be carried out without any further 
fresh hydrogenation catalyst. 
It is not necessary to supply fresh activated carbon catalyst in every new 
reaction cycle. On the average, the consumption of hydrogenation catalyst 
per reaction cycle is thus less than 0.01%, by weight, of palladium, based 
on the charged para-nitroso-diphenylhydroxylamine. If, for example, in the 
case of methylisobutyl ketone, a catalyst with 0.2%, by weight, of 
platinum sulfide and 100%, by weight, of activated carbon within the scope 
of the present invention, based on the para-nitroso-diphenylhydroxylamine 
are utilized, 15 additional reaction cycles can be carried out without any 
loss in activity of the catalyst system. When the same series is performed 
without activated carbon, the yield of 
N-(1,3-dimethylbutyl)-N'-phenyl-para- phenylene diamine (DBPPD) is only 
60% of theoretical in the first cycle (vs. 95% of theoretical with 
activated carbon present), while in the second cycle it immediately drops 
to 38% of theoretical (vs. an unchanged yield of 95% of theoretical in the 
presence of activated carbon). 
Compared with the prior art process of British Patent No. 1,295,672, the 
process pursuant to the present invention is substantially more 
advantageous. For example, according to Example 1 of the British patent, 
N-isopropyl-N'-phenyl-para-phenylene diamine (IPPD) is allegedly 
obtainable with a 93% yield. However, a true yield of a desired 
substituted para-phenylene diamine apparently in reality, was not 
achieved, as the amount of reaction product remaining after distillation 
of the solvent was improperly assumed to consist entirely of the desired 
substance. As is discovered when the example is reproduced, the initial 
material is indeed converted quantitatively, but the reaction product is a 
mixture of substances with a share of only about 78% of 
N-isopropyl-N'-phenyl-para-phenylene diamine (IPPD). In addition, the 
large quantity of 0.3%, by weight, of palladium, based on the 
para-nitroso-diphenylhydroxylamine, as well as the long reaction time, are 
required and the reaction is performed under a pressure of 50 bar. As a 
result, one gets not only higher losses of 
N-isopropyl-N'-phenyl-para-phenylene diamine (IPPD), but the excess ketone 
is also substantially reduced to an undesirable alcohol. 
The process pursuant to the present invention, on the other hand, requires 
lower pressures and temperatures, smaller quantities of precious metal 
catalysts, and substantially shorter reaction times. Furthermore, the 
selectivity, with respect to the formation of the desired substituted 
para-phenylene diamine, is substantially higher and the formation of 
alcohol by reduction of the carbonyl compound does not occur. When the 
process of the British patent is carried out at lower temperatures, for 
example, at less than 150.degree. C., and with lower pressures, for 
example below 50 bar, the reaction proceeds much less selectively than 
under the more drastic conditions. The reason is that one obtains about 25 
to about 50% of the non-alkylated reaction product and about 2.5 to about 
10% of the ketimine, as by-products. The yield of the desired substituted 
para-phenylene diamine is only from about 12 to about 70%, the remainder 
consisting of unreacted initial compound and the aforementioned 
by-products. The process pursuant to the present invention is thus 
distinguished by the fact that it is performed at a comparatively low 
pressure and temperature with low consumption of precious metal, leading 
to the formation of the desired product within short reaction times and 
producing a high conversion rate with associated high selectivity. 
Large quantities of compounds obtainable by the process pursuant to the 
present invention are useful industrially for the antioxidation and 
ozonation of rubber.

COMATIVE EXAMPLES NOS. 1 to 9 
The reactions are carried out in a 1 liter glass autoclave equipped with a 
bottom drain valve, a gas supply tube, a flow breaker, and a vaned stirrer 
(magnetic stirring). 20 g (93.2 mmol) of 
para-nitroso-diphenylhydroxylamine (NDHA) and 200 ml of acetone are 
charged and the reaction is carried out between 30.degree. and 75.degree. 
C., with hydrogen pressure between 9 and 10 bar. The reaction lasts for 
approximately one hour and the stirring velocity is 1,500 rpm. The 
autoclave is first evacuated, then vented with hydrogen. Subsequently, the 
autoclave is charged with half of the reaction medium, and finally the 
para-nitroso-diphenylhydroxylamine (NDHA), together with the 
palladium/carbon catalyst (E10R of the firm Degussa), is suspended in the 
remainder of the reaction medium and fed in via the inlet valve. 
Subsequently, the autoclave is placed under a pressure of 9 to 10 bar of 
hydrogen, and heated carefully. Depending upon the quantity of palladium, 
the reaction commences between 20.degree. and 70.degree. C. After the heat 
of reaction declines, heating to 75.degree. C. is continued, so that the 
total reaction time amounts to approximately 1 hour. 
Table I shows the influence of the quantity of precious metal on the yield 
of N-isopropyl-N'-phenyl-para-phenylene diamine (IPPD). The composition of 
the palladium/carbon catalyst, the quantity of metal based on the charged 
para-nitroso-diphenylhydroxylamine, as well as the yields of asymmetrical 
N-phenyl-N'-substituted-para-phenylene diamine and the quantity of 
ketimines formed as by-product and non-alkylated para-phenylene diamine 
derivatives are compiled in Table I. 
The following abbreviations are used in the Table: 
NDHA=para-nitroso-diphenylhydroxylamine 
ADA=4-amino-diphenylamine 
IPPD=N-isopropyl-N'-phenyl-para-phenylene diamine 
ketimine=N-isopropylidene-N'-phenyl-para-phenylene diamine. 
The results contained in Table I show, in an impressive manner, that with 
the use of a catalyst quantity corresponding to 1%, by weight, based on 
the para-nitroso-diphenylhydroxylamine, the reductive alkylation to the 
desired N-isopropyl-N'-phenyl-para-phenylene diamine still proceeds with 
relatively high selectivity. However, when smaller catalyst quantities are 
utilized, the selectivity, with respect to the formation of 
N-isopropyl-N'-phenyl-para-phenylene diamine declines rapidly. With 
catalyst quantities of 0.20%, by weight, of palladium, the selectivity is 
already considerably below 10%. 
Table I 
__________________________________________________________________________ 
Hydrogenation Catalyst E10R 
Endow- 
Solvent ment % by Wt. 
Example 
NDHA Acetone % by Wt. 
Pd. Ref. 
Reaction Products in % by Weight 
No. g m.mol 
ml g of Pd to NDHA 
IPPD 
ADA Ketimine 
NDHA 
__________________________________________________________________________ 
1 20.0 
93.2 
200 4.0 
5 1.0 94.3 
&lt;0.1 
&lt;0.2 &lt;0.1 
2 20.0 
93.2 
200 3.0 
5 0.75 92.6 
1.1 0.65 &lt;0.1 
3 20.0 
93.2 
200 2.0 
5 0.50 86.3 
2.2 3.6 &lt;0.1 
4 20.0 
93.2 
200 1.0 
5 0.25 68.2 
26.7 
2.4 1-2 
5 20.0 
93.2 
200 0.80 
5 0.20 58.1 
48.4 
3.2 .about.5 
6 20.0 
93.2 
200 0.50 
5 0.125 40.2 
50.2 
3.5 .about.7 
7 20.0 
93.2 
200 0.40 
5 0.10 12.7 
76.8 
7.6 .about.10 
8 20.0 
93.2 
200 0.20 
5 0.05 7.1 48.3 
28.7 .about.15 
9 20.0 
93.2 
200 0.040 
5 0.01 2.8 28.9 
49.8 .about.20 
__________________________________________________________________________ 
EXAMPLES 10 through 21 
The conversion rate, as well as the selectivity, obtained pursuant to the 
process of the present invention, by the addition of of activated carbon 
with a surface area of at least 700 m.sup.2 /g and an ash content less 
than 7.5%, by weight, is easily recognizable from these examples, and the 
comparative examples contained in Table II. For this purpose, Example 7 of 
Table I was repeated once with, and once without, the addition of 
activated carbon, and the conversion rate, as well as the yield were 
determined quantitatively after different reaction times. 
In each case, 60 g (280 mmol) of para-nitroso-diphenylhydroxylamine and 600 
ml of acetone are reacted in the manner described for Examples 1 through 9 
in the presence of 6.0 g of a palladium/carbon catalyst (E10R of the firm 
Degussa) with a palladium endowment of 1.01%, by weight, a specific 
surface area of 1100 m.sup.2 /g and an ash content of .ltoreq.0.5%, by 
weight. In the cases of Examples 17, 19, and 21, the yield of 
N-isopropyl-N'-phenylpara-phenylene diamine is lower than, for example, in 
the case of Example 15, since, because of the long reaction times, 
reduction of part of the desired product has to be continued to form 
N-isopropyl-N'-cyclohexyl-para-phenylene diamine. 
Table II 
__________________________________________________________________________ 
A. Carbon 
Solvent 
Hydrogenation Catalyst 
React. 
% by Wt. 
Example 
NDHA Acetone Pd Ref. 
Time 
Ref. to 
Reaction Products in % by Wt. 
No. g mmol 
ml % by Wt. 
to NDHA 
Min. 
NDHA IPPD 
ADA Ketimine 
NDHA 
__________________________________________________________________________ 
10* 60 
280 600 6.0 0.1 15 -- 2.2 43.5 
23.2 25 
11 60 
280 600 6.0 0.1 15 100 90.0 
6.4 1.8 &lt;1 
12* 60 
280 600 6.0 0.1 30 -- 7.8 50.2 
15.2 18 
13 60 
280 600 6.0 0.1 30 100 95.0 
0.95 
0.5 &lt;0.1 
14* 60 
280 600 6.0 0.1 60 -- 12.7 
76.0 
7.6 10 
15 60 
280 600 6.0 0.1 60 100 96.5 
0.1 0.2 &lt;0.1 
16* 60 
280 600 6.0 0.1 120 -- 17.7 
58.0 
18.5 5 
17 60 
280 600 6.0 0.1 120 100 95.5 
0.1 0.1 &lt;0.1 
18* 60 
280 600 6.0 0.1 180 -- 24.2 
50.5 
12.8 .about. 
19 60 
280 600 6.0 0.1 180 100 91.5 
0.1 0.1 &lt;0.1 
20* 60 
280 600 6.0 0.1 300 -- 22.5 
68.5 
5.5 &lt;1 
21 60 
280 600 6.0 0.1 300 100 89.5 
0.1 0.1 &lt;0.1 
__________________________________________________________________________ 
*Comparative Example 
EXAMPLES 22 THROUGH 32 
To a 1.5 liter glass autoclave, equipped with vaned stirrer, thermometer, 
gas supply tube, manometer, flow breaker, gas outlet valve, bottom 
discharge valve, and filter candle, there is charged a suspension of 20 g 
of para-nitroso-diphenylhydroxylamine and 0.8 g of palladium/carbon 
catalyst (E10R of the firm Degussa) with an endowment of 5% of palladium 
(0.20%, palladium, based on the para-nitroso-diphenylhydroxylamine), as 
well as 25 g of activated carbon (Merck, in powder form, dried, with a 
specific surface area of 1050 m.sup.2 /g, ash content less than 5%, by 
weight) and 200 ml of methylisobutyl ketone. After repeated evacuation and 
venting with hydrogen, the reaction was started under a hydrogen pressure 
of 9 to 10 bar. The reductive alkylation is started at about 40.degree. C. 
and, after cooling of the exothermic reaction, heating to 75.degree. C. is 
continued for a total of 1 hour, with a stirring velocity of 1500 rpm. 
After termination of the reaction, the substrate is separated from the 
hydrogenation catalyst and the activated carbon catalyst, which afterwards 
are flushed back into the autoclave with methylisobutyl ketone, via the 
filter candle under hydrogen pressure. Subsequently, the following batch, 
consisting of 20 g of para-nitroso-diphenylhydroxylamine and a total of 
200 g of methylisobutyl ketone are mixed with activated carbon catalyst 
and, if necessary, fresh hydrogenation catalyst, and again reacted for 1 
hour at 75.degree. to 80.degree. C. and a hydrogen pressure of 9 to 10 
bar. These experiments were carried out for a total of 10 cycles, so that 
at the end of the conversion a total of 220 g of 
para-nitroso-diphenylhydroxylamine are subjected to reductive alkylation. 
The quantities of hydrogenation catalyst, as well as the quantity of 
activated carbon catalyst, indicated in %, by weight, of palladium, based 
on the total par-nitroso-diphenylhydroxylamine charged, as well as the 
resulting yield of N-(1,3-dimethylbutyl)-N'-phenyl-para-phenylene diamine 
(DBPPD), para-amino-diphenylamine (ADA), and ketimine are lised in Table 
III. The results clearly show that after a few reaction cycles, the 
quantity of fresh hydrogenation catalyst to be added declines 
considerably. 
Table III 
__________________________________________________________________________ 
Hydrogenation Catalyst 
% by Wt. 
Example 
NDHA Solvent Pd Ref. Act. Carbon 
Reaction Products in % by Wt. 
No. g mmol 
MIBK ml 
g to NDHA g % by Wt. 
DBPPD 
ADA Ketimine 
NDHA 
__________________________________________________________________________ 
22 20 93.2 
200 0.8 0.20 25 
120 95 0.1 0.5 &lt;0.1 
23 40 186.4 
400 1.2 0.15 25 
62.5 93 0.5 1.0 .about.0.5 
24 60 279.6 
600 1.2 0.10 30 
50 95 0.1 0.5 &lt;0.1 
25 80 372.8 
800 1.2 0.075 30 
37.5 86 1.7 2.8 .about.1 
26 100 
466 1000 1.5 0.075 40 
40 95 0.3 0.5 &lt;0.1 
27 120 
599.2 
1200 1.5 0.0625 40 
33.3 88 2.8 4.5 &lt;1 
28 140 
652.4 
1400 1.5 0.0536 50 
35.7 92.5 0.6 1.2 &lt;0.1 
29 160 
745.6 
1600 1.5 0.047 50 
31.25 83 3.6 5.9 .about.2 
30 180 
838.8 
1800 1.5 0.0416 65 
36 91 1.0 1.3 .about.0.5 
31 200 
932.0 
2000 1.5 0.0375 65 
32.5 44 18.0 
33.0 .about.5 
32 220 
1025.2 
2200 1.5 0.034 85 
38.6 78.5 3.5 2.5 .about.1 
__________________________________________________________________________ 
EXAMPLES 33 THROUGH 45 
In these examples, and comparative examples, the influence of the quantity 
of added activated carbon (Examples 33 to 36), as well as the influence of 
the type of activated carbon (Examples 37 to 45) on the progress of 
reductive alkylation is demonstrated. 
The reactions are carried out in the manner described for Examples 1 
through 9 and in each case, 20 g of para-nitrosodiphenylhydroxylamine 
(NDHA) and 150 ml methylisobutyl ketone (MIBK) are charged. The 
hydrogenation catalyst is a palladium/carbon catalyst (E106R of the firm 
Degussa) with 1.02%, by weight, of palladium endowment. The types of 
activated carbon are synthetic carbons of the firms Degussa and Merck, 
with different specific surfaces and ash contents, as well as various 
activated carbons from natural raw materials. 
Comparative examples 42 through 45 clearly show that in the case of too 
small of a specific surface area, as well as in the case of too high of an 
ash content of the activated carbons, the yields of 
N-(1,3-dimethylbutyl)-N'-phenyl-para-phenylene diamine (DBPPD) are low. 
Table IV 
__________________________________________________________________________ 
Hydrog. Catal. 
Exam- % by Wt. 
% by Wt. 
ple NDHA 
MIBK Pd Ref. 
Ref. To Spec. Sur- 
No. g ml g to NDHA 
NDHA Type face m.sup.2 /g 
Ash, % 
DBPPD 
ADA Ketimine 
NDHA 
__________________________________________________________________________ 
33* 20 150 2.0 
0.1 -- -- -- -- 63.0 15.5 
16.0 .about.2 
34 20 150 2.0 
0.1 50 R10 900-950 
0.7-0.75 
86.5 4.65 
4.5 &lt;0.1 
35 20 150 2.0 
0.1 100 R10 900-950 
0.7-0.75 
94.0 1.29 
1.1 &lt;0.1 
36 20 150 2.0 
0.1 150 R10 900-950 
0.7-0.75 
95.5 1.12 
0.9 &lt;0.1 
37 20 150 2.0 
0.1 50 R101 1100 1.0 92.5 2.4 2.7 &lt;0.1 
38 20 150 2.0 
0.1 50 R102 900 4.7 73.2 14.2 
9.9 &lt;0.1 
39 20 150 2.0 
0.1 50 R103 1000 0.72 89.5 4.5 3.28 &lt;0.1 
40 20 150 2.0 
0.1 50 R106 950 0.53 86.5 5.6 5.4 &lt;0.1 
41 20 150 2.0 
0.1 50 R106 1000 0.44 85.5 6.65 
4.8 &lt;0.1 
42* 20 150 2.0 
0.1 50 Merck Purest 
1000-1050 
0.63 88.5 4.5 4.0 &lt;0.1 
43* 20 150 2.0 
0.1 50 Animal Carbon 
150 78.5 57.0 22.7 
17.5 .about.5 
44* 20 150 2.0 
0.1 50 Linden Wood 
300 3.65 29.5 26.9 
40.0 .about.2 
Carbon 
45* 20 150 2.0 
0.1 50 Beech Wood 
450 4.78 51.5 19.9 
25.5 .about.5 
Carbon 
__________________________________________________________________________ 
*Comparative Example 
EXAMPLES 46 THROUGH 55 
In these examples, the results of which are compiled in Table V, it is 
demonstrated that in the process pursuant to the present invention the 
used hydrogenation catalyst retains its activity for an extended period of 
time when activated carbon catalyst is added, even in the presence of 
larger quantities of N-phenyl-N'-substituted para-phenylene diamines (end 
product) so that when it is used again, no, or comparatively small 
quantities of fresh hydrogenation catalyst must be added, to reach the 
original activity again. Furthermore, the favorable influence is shown 
which an additional inert solvent (cosolvent) exerts in those instances 
where the formed water of reaction is not, or is only slightly soluble, in 
the ketone used for the reductive alkylation, and a second, aqueous phase 
would be formed without addition of the cosolvent. 
The reactions are carried out in a 1.5 liter apparatus already described in 
conjunction with Examples 22 through 32. The reaction temperatures are 
from 75.degree. to 100.degree. C., the hydrogen pressure is from 9 to 10 
bar, the duration of the reaction is 1.5 hours, and the stirring velocity 
is 1000 to 1500 rpm. After each cycle, a small sample is taken for an 
analytical determination of the reaction mixture, whereupon in each 
instance the following batch consisting of 10 g of 
para-nitroso-diphenylhydroxylamine (NDHA), 50 ml each of cyclohexanone, 
and cosolvent, and, depending upon the experiment, an additional quantity 
of activated carbon catalyst, or fresh palladium/carbon catalyst, is added 
through the inlet valve to the already complete reaction mixture under 
hydrogen pressure. The experiments are continued through a total of 10 
cycles, so that at the end of the reactions, a total of 100 g of 
para-nitroso-diphenylhydroxylamine (NDHA) with cyclohexanone have been 
subjected to reductive alkylation. 
Table V 
__________________________________________________________________________ 
Hydrogenation Cat. 
Activated Carbon 
Cyclo- % by Wt. % by Wt. 
Example 
NDHA 
hexanone 
Cosolvent Ref. to Ref. to 
Reaction Products in % by Wt. 
No. g ml ml Type g to NDHA 
g to NDHA 
CPPD 
ADA Ketimine 
NDHA 
__________________________________________________________________________ 
46 10 50 50 
Methanol 
0.6 0.3 -- -- 25.2 
25.6 
48.5 .about.3 
47 20 100 100 
Methanol 
0.6 0.15 10 50 94.5 
0.8 1.5 &lt;0.1 
48 30 150 150 
Methanol 
1.8 0.30 10 33 96.5 
&lt;0.1 
&lt;0.2 &lt;0.1 
49 40 200 200 
Methanol 
1.8 0.225 10 25 87.1 
1.6 2.6 .about.1 
50 50 250 250 
Methanol 
1.8 0.18 20 40 95.8 
0.2 0.5 &lt;0.1 
51 60 300 250 
Methanol 
2.16 
0.18 20 33 90.1 
2.9 4.8 .about.0.5 
52 70 350 250 
Methanol 
2.16 
0.15 35 50 93.5 
0.6 0.95 &lt;0.1 
100 
Ethanol 
53 80 400 250 
Methanol 
2.16 
0.135 35 43.7 83.5 
3.9 5.8 .about.1 
150 
Ethanol 
54 90 450 250 
Methanol 
2.16 
0.12 50 55 91.5 
0.9 1.2 .about.0.5 
200 
Ethanol 
55 100 500 250 
Methanol 
2.16 
0.108 100 
100 93.5 
.about.0.5 
0.7 &lt;0.1 
250 
Ethanol 
__________________________________________________________________________ 
CPPD = Nphenyl-N'-cyclohexyl-para-phenylene diamine 
COMATIVE EXAMPLE 56 
This example is a reproduction of Example 1 of British Patent No. 1,295, 
672. 
50 g of para-nitroso-diphenylhydroxylamine (NDHA), together with 5 g of 
catalyst consisting of 3% of palladium on activated carbon (E10R, 
Degussa), corresponding to 0.3% palladium, based on the NDHA in 790 ml of 
acetone are suspended in a 2 liter autoclave of refined steel, equipped 
with a horsehoe mixer, a gas supply tube, a manometer, a high-pressure 
relief valve, and a bottom discharge valve. After the autoclave has been 
carefully freed of traces of oxygen, a hydrogen pressure of 50 bar was 
applied and the reaction commenced by heating to 60.degree. C. (heat-up 
time 15 min.). After the temperature is maintained at 60.degree. C. for 1 
hour, it is raised to 150.degree. C. within 30 minutes, then reduced to 
95.degree. C. (15 min.) and left at 95.degree. C. for 6 hours. 
Subsequently, the reactor is cooled down and the catalyst separated from 
the content by filtration under hydrogen as protective gas. After the 
solvent is distilled off, 93.25% (based on the desired 
N-isopropyl-N'-phenyl-para-phenylene diamine (IPPD)) of a grayish brown 
solid substance remains. The reaction mixture is subjected to a 
quantitative analysis and determined to contain the following components: 
______________________________________ 
N-isopropyl-N'-phenyl-para-phenylene diamine 
77.90% 
N-isopropyl-N'-cyclohexyl-para-phenylene diamine 
6.95% 
4-amino-diphenylamine 2.10% 
N,N'-diisopropyl-para-phenylene diamine 
0.96% 
N-phenyl-N,N'-diisopropyl-para-phenylene diamine 
0.95% 
N-phenyl-N'-diisopropyl-para-phenylene diamine 
0.65% 
para-anilinocyclohexanone 0.65% 
______________________________________ 
In addition, the mixture is found to contain 2.84% of polymeric compounds, 
which are comprised predominately of 4-isopropylamino-diphenylamine units. 
Special mention must be made of the compounds which are hydrogenated in 
the nucleus, formed under the high pressure and temperature, the 
separation of which from the desire N-isopropyl-N'-phenyl-para-phenylene 
diamine is very difficult. Furthermore, about 18% of the charged acetone 
is converted to isopropanol. 
EXAMPLES 57 THROUGH 68 
In the manner described for Examples 1 through 9, 20 g (93.2 mmol) of 
para-nitroso-diphenylhydroxylamine (NDHA) are reacted with methylisobutyl 
ketone (MIBK) in the presence of a sulfidized platinum catalyst (F103RS of 
the firm Degussa, platinum sulfide endowment of 5%, by weight) at a 
temperature of no more than 100.degree. C. and under a hydrogen pressure 
of 9 to 10 bar. The stirring velocity is 1500 rpm and the reaction time is 
45 minutes. The activated carbon has a specific surface area of 1050 
m.sup.2 /g and an ash content of 0.6% ("purest" activated carbon of the 
firm Merck). 
Pressure is removed from the autoclave after cooling to 40.degree. to 
50.degree. C. and the catalyst, and, if necessary, the activated carbon 
are filtered off under a slight nitrogen pressure. The other process 
parameters and the quantitative composition of the resulting reaction 
mixtures, as obtained by gas chromatography, are compiled in Table VI. 
Table VI 
__________________________________________________________________________ 
Cosolvent Platinum Cat. 
Act. Carbon 
Example 
MIBK % Ref. to % Pt Ref. 
Ref. to 
Conversion 
ADA Ketimine 
DBPPD 
No. ml. g NDHA g to NDHA 
g NDHA 
NDHA % by Wt. 
% by 
% by 
__________________________________________________________________________ 
Wt. 
water 
57 200 20 100 0.20 
0.05 20 
100 100 2.4 1.0 91.5 
water 
58 200 20 100 0.40 
0.10 10 
50 100 0.6 1.2 92.5 
water 
59 200 20 200 0.80 
0.20 5 
25 100 0.05 0.6 93.5 
water 
60* 200 20 100 0.20 
0.05 -- 
-- 95 56.8 4.0 33.1 
water 
61* 200 20 100 0.40 
0.10 -- 
-- 100 48.9 1.8 44.0 
water 
62* 200 20 100 0.80 
0.20 -- 
-- 100 33.7 1.5 59.4 
63* 200 -- -- 0.20 
0.05 -- 
-- 100 56.5 9.8 28.8 
methanol 
64* 120 80 400 0.20 
0.05 -- 
-- 100 41.3 7.7 44.2 
3-methylpentanol-2 
65* 150 50 250 0.20 
0.05 -- 
-- 90 63.1 8.2 21.2 
66 200 -- -- 0.20 
0.05 20 
100 100 0.65 0.9 92.9 
methanol 
67 120 80 400 0.20 
0.05 20 
100 100 1.9 2.3 89.1 
3-methylpentanol-2 
68 150 50 250 0.20 
0.05 20 
100 100 2.2 2.8 88.6 
__________________________________________________________________________ 
*Comparative Examples 
ADA = 4aminodiphenyl, 
DBPPD = N(1,3-dimethylbutyl)-N'-phenyl-para-phenylene diamine