Note: Descriptions are shown in the official language in which they were submitted.
~127666
l Background of the Invention
1,
This invention relates to a process for the preparation
of para-amino diphenylamine by means of the catalytic hydrogena-
tion of para-nitroso diphenylhydroxylamine.
5 1¦ The hydrogenation of para-nitroso diphenylhydroxylamine
to para-amino diphenylamine is well known. According to a process
, described in German patent application disclosure no. 1,9~1,008,
the nitroso compound may be hydrogenated either in a liquid mix-
l ture with a hydroxylic solvent, such as water, or a primary or
10 llsecondary alcohol, or in the gaseous phase. The catalysts used in
the process are combinations of two or more of the heavy metals,
iron, manganese, cobalt, copper, nickel, silver, cerium and lead,
in the form of their oxides, hydroxides or carbonates. Hydrogena-
'~ion may be carried out at temperatures from 100 to 250C, prefer-
ably under elevated pressure, and is indicated to result in thedesired para-amino diphenylamine, with a yield of 74 to 93%. How-
¦ ever, the yield is not of analytically pure product, but of crude
product, after removal of the solvent. Therefore, one must assume
that by-products, such as products formed by hydrogenation of the
20 nucleus, are included in the product yield.
According to the process of British Patent No.
1,296,211, the para-nitroso diphenylhydroxylamine may be charged
as its alkali derivative and hydrogenated at temperatures between
room temperature and 120C, i n an aqueous medium, in the presence
of a hydrogenation catalyst. Metals of Group VIII of the periodic
system, for example, nickel, cobalt, ruthenium, palladium, or
platinum, may be used as catalysts, which, if desired, rmay be
applied to an inert carrier. The quantity of catalyst is from 0.1
to 10, preferably 0.1 to 2~, by weight. Hydrogenation may be
carried out in the usllal manner, at temperatures between room
!l ~
112766~i
¦temperature and 120C, and preferably under elevated pressure.
Also, it is desirable to utilize an inert, organic solvent, which
is partly or completely miscible with water, as such methanol,
, ethanol, n-butanol, or dioxane, or an inert, organic solvent which
5 is not miscible with water, such as toluene, xylene or monochloro-
benzene. In the process of the British patent as well, the yields
of para-amino diphenylamine are in ttle range from 40 to 88% (crude
product). According to British Patent No- 1~304~525~ when alco-
~'hols are used as solvents, good yields are obtained only in the
case of propanol, isopropanol, n-butanol, and isobutanol (71 or
83% of theoretical crude product), whereas in the case of other
alcohols, such as ethanol, n-amyl alcohol, and isoamyl alcohol,
the yields are substantially lower (32~5~ 45~8 or 41~6% of
theoretical crude product).
The reduction of para-nitroso diphenylhydroxylamine to
para~amino diphenylamine by means of the catalytic transfer hydro-
llgenation is known from German patent application disclosure no.
¦ 2,715,785. Hydrogenation may be carried out in the presence of a
llcatalyst based on a noble metal of Group VIII of the periodic
20 l~system. Forrnic acid or a formate, a phosphorus compound with at
least one hydrogen atom bonded immediately to the phosphorus, or
hydrazine, which may contain up to two methyl groups, serve as
hydrogen donors. The catalyst is used in quantities of up to 25%
by weight, preferably up to 10% by weight of precious metal, based
25 on the substrate. Preferably, the reduction is carried out in a
mixture of water and tetrahydrofuran. The high quantity of cata-
lyst notwithstanding, the yield of para-amino diphenylamine is
only between 70 and 90%.
From the foregoing it is quite apparent that there
30 exists a need for an improved proccss for the production of para-
_z_
1~27666
Il .
l amino diphenylamine which provides for the production of such a
I compound in relatively high yields.
~ummary of the Invention
Ij
,1
~1l An improved process for the preparation of para-amino
5 ldiphenylamine in which para-nitroso diphenylhydroxylamine is
¦catalytically hydrogenated in the presence of an organic solvent
¦and one or more metal components selected from the group consist-
ing of ruthenium, rhodium, palladium, osmium, iridium, and plati-
num, and their sulfidic compounds, at temperatures from 20 to
10 200C, is provided. The irnprovement comprises utilizing as the
organic solvent one or more members of the group consisting of
aniline, aniline derivatives having ring-alkyl groups, containing
a total of 1 to 6 carbon atoms, aniline derivatives having N-alkyl
'Igroups which contain from 1 to 6 carbon atoms, and aniline deriva-
15 ! tives having a combination of ring-alkyl and N-alkyl groups where-
in the total number of ring-alkyl carbon atoms is from 1 to 6 and
the N-alkyl groups contain from 1 to 6 carbon atoms.
Detailed Description of thè Preferred Embodiments
Para-nitroso diphenylhydroxylamine is a compound which
is easily obtained by the catalytic dimerization of nitrosoben-
zene. According to a more recent, especially advantageous
process, it is obtainable with practically quantitative yield, if
a sulfonic acid with a PKa value < 1, for example, methane-,
l ethane-, or trifluoromethanesulfonic acid, perchloric acid, or
25 ¦ trifluoroacetic dcid are used as the catalyst, in accordance with
the teachings of German patent application no. P 27 03 919. The
nitrosobenzene required for the prepardtion of para-nitroso
Il .
jl l~Z76~;6
diphenylhydroxylamine is also easily obtainable, as through the
catalytic reduction of nitrobenzene. The reduction will proceed
with high yield and high selectivity if, according to another
llrecent process, an aliphatic, cycloaliphatic, olefinic, or aromat-
ic hydrocarbon is used as the reducing agent, as taught in Germanpatent application no. P 27 13 602.
It has now been surprisingly discovered that the amines
,to be used as solvents pursuant to the present invention are far
Isuperior to the customary solvents, such as water, alcohols, hy-
10 Idrocarbons~ and acetones, with respect to the conversion, as wellas the selectivity. The foregoing is even more surprising, in
view of the ~act that it is known from the literature that
aromatic nitroso compounds easily react with primary aromatic
amines to form azo compounds and water, or to form diphenylamine
derivatives, through condensation reactions in the para position.
Furthermore, nitroso-hydroxy-aromatic compounds present in the
quinoidal form can produce phenylinnines (anilines) with aryl-
j amines, instead of azo compounds. From the literature it is also
I known that especially the para-nitroso diphenylhydroxylalnine can
20 ~easily produce a quinoidal hybrid form and, based thereon, can
~enter into reactions such as methylation. In this connection,
reference may be made to the following literature:
W. Seidenfaden in Houben-Weyl, Methods of Organic Chem-
istry, 4th edition (1971), Georg Thieme Publishing
House, Stuttgart, vo1 X/1, p. 1077; H. Feuer, The Chem-
istry of Nitro and Nitroso Groups, in the series The
Chemistry of Functional Groups, of S. Patai, parts I and
II, Interscierlce Publishers, New York, 1969, pp~ 252 to
2~7; P.A.S. Smith, The Chemistry of Open Chain Nitrogen
Compounds, vol. 1 and 2, W.A. Benjamin, Inc., New York -
Amsterdam, 1966, pp. 361 to 36~.
,1 .
112~666
Il :
~¦ In the process pursuant to the invention, all metals of
the platinum and palladium group, or their sulfidic compounds, may
be used as catalysts. Thus, ruthenium, rhodium, palladium, osmi-
um, iridium, and platinum, and their sulfidic compounds, are use-
ful as catalysts in the present invention. The term "sulfidic
,compounds" is used to mean the commercial catalysts obtained whenthe referenced metals are sulfidized. Although specific, uniform
metal sulfides are not involved here, such catalysts are, for the
Isake of simplicity, referred to in industry as palladium sulfide,
10 ~platinum sulfide, and the like (cf. Robert I. Peterson, Hydrogena-
tion Catalysts, Noyes Data Corporation, Parkridge, N.J., USA 1977,
pp. 256 to 261).
Typically, the quantity of catalysts utilized in the
process of the present invention is from about 0.0005 to about
1.0%, by weight, of metal, and preferably from about 0.001 to
about 0.5%, by weight, of metal. Most preferably the quantity of
¦catalyst is from about 0.005 to about 0.02%, by weight, of metal,
¦all based on the charged para-nitroso diphenylhydroxylamine.
, Thereby, the endowment of the metal on the carrier, in particular
on the activated carbon, may be from about 15 to about 0.170, by
~weight, preferably from about 5 to about 1%, by weight.
The solvents used in the process of the present inven-
tion are aniline, or arnines of a benzene homologue with 7 to 12
carbon atoms, or their mixtures. The latter amines are aniline
derivatives carrying one or several alkyl groups in the benzene
ring (ring-alkyl groups), with the total number of carbon atoms in
the alkyl groups amounting to from 1 to about 6. Examples of such
compounds are tlle aniline homologues ortho-, meta-, and para-tolu-
idine; ortho-, meta-, and para-xylidine; 2,~,6-trimethyl aniline
(mesidine); 2,3,5-trinlethyl aniline (pseudocunlidine); n-propyl
aniline; orthopropyl aniline; para-isopropyl aniline (cumidine);
_5
i ;
2~6
para-tertiary butyl aniline, 2-isopropyl-5-methyl aniline (thymyl
amine), 5-isopropyl-2-methyl aniline (carvacryl amine) and
2,3,4,5-tetramethyl aniline. Suitable solvents are also the
'N-monoalkyl and N-dialkyl derivatives of aniline and the above-
mentioned aniline homologues, with the N-alkyl groups possessing 1
to 6 carbon atoms in each case. This may involve monomethyl,
monoethyl, monopropyl, monobutyl, monopentyl, monohexyl, dimethyl,
diethyl and dipropyl derivatives, or compounds with mixed alkyl
groups. Examples of such compounds are dimethyl, diethyl and
dipropyl aniline, as well as the corresponding N-substituted
toluidines and xylidines. Some of the mentioned aromatic amines
are solid substances under the conditions of the process pursuant
to the invention and are therefore only used in mixture with other
amines, that are liquid between 20 and 60C. Preference is given
to those aniline homologues and N-substituted derivatives of
aniline and its homologues, whose melting and/or boiling points
are sufficiently far below the melting and boiling point of para-
¦amino diphenylamine (66-67C, or 354C in H2), so that a simple
¦separation by means of distillation antl/or crystallization ls
possible. For economic reasons, aniline, ortho-toluidine and
meta-toluidine are preferred as solvents.
The quantity of solvent is not critical. Iligh conver-
sion rates and selectivities during hydrogenation can also be
obtained in a heterogeneous phase. The quantity of solvent should
be proportioned in such a way, that the suspension can be stirred
well. Furthermore, in order to achieve an economically favorable
separation of the catalyst from the formed para-amino diphenyl-
amine, it makes sense to select the concentration of para-nitroso-
diphenylhydroxylamine in such a way, that at the end of the reac-
tion the formed para-amino diphenylamine is completely dissolved.
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` ~127~66
!
A concentration of 10 to 25% by weight of para-anlino diphenylamine
in the solvent has thus been found to be favorable. A greater
~excess of solvent is of course not harmful but, because of the
dilution effect, is economically unfavorable.
5 l, The reaction pressure and temperature are also not crit-
ical. The process of the present invention may be performed at
normal pressure and room temperature. However, because of the
,influence of pressure and temperature on the reaction rate, it is
Idesirable to operate at elevated pressure and elevated tempera-
10 Iture. It is thus preferable to work in a temperature range fromabout 20 to about 150C, most preferably from about 30 to about
125C. It is possible to exceed such an upper temperature limita-
tion, but in general, such an elevated temperature does not bring
any advantages, as the reaction proceeds exothermically and,
because of the necessity of removing larger quantities of heat,
difficulties may then occur which can only be overcome with
greater technGlogical expenditures. Additionally, there is then a
greater danger that the reaction will become uncontrollable. As
'¦far as the hydrogen pressure is concerned, it is possible to work
20 1 ` within a wide range, beginning with 1 bar, up to about 150
bar, preferably in the range frorn about 5 to about 30 bar, most
preferably from about 7 to about 15 bar.
As is the case for all reactions involving mass transi-
1 tion, the reaction time in the present case is also pressure-
dependent, and a shorter reaction time may be achieved withincreasing hydrogen pressure. Generally, however, higher hydrogen
pressure results in difficulties witl-l the equipment and higher
investments are thus required, so that the resulting advantages
l again are minimal.
30l It is not absolutely necessary t~ use pure hydrogen, and
l carrier gases, such as nitro9en "nay also be utilized. It is also;
; l~Z7~i66
possible to use gas mixtures which, in addition to hydrogen, also
~contain carbon rnonoxide, for example, water gas and generator gas.
In such instances, the carbon monoxide also participates in the
!reduction, but enough hydrogen must be present so that a complete
5 Ireduction is assured.
A general statement regarding the reaction time is dif-
ficult to make as it depends upon a number of factors, such as the
kind and quantity of the selected solvent and catalyst, the hydro-
gen pressure, the reaction temperature and the stirring velocity.
10 ITypically, however, the reaction time is from about 15 to about 45
minutes. Termination of the reaction may be determined by known
means, such as by the cessation of hydrogen uptake. In the pres-
ent case, determination of the ~act that the para-nitroso diphen-
ylhydroxylamine has been completely transferred can be accom-
plished by subjecting a sample to thin-layer chromatography. The
process pursuant to the invention may be carried out continuously,
as well as discontinuously.
¦ Generally, the process may be carried out as follows:
~In d reaction vessel chosen in keepin~J with the size of the batch,
para-nitroso diphenylhydroxylamine and the catalyst are suspended
in an appropriate quantity of the selected solvent. After
exhausting, the air is displaced by venting with nitrogen and
thorough mixing, as by stirring, is provided under the selected
l hydrogen pressure. The reaction mixture is subsequently heated
25' until suitable self-heating occurs, due to the exothermic reac-
tion. Then, the reaction temperature is maintained by cooling and
after the heat of reaction drops, the reaction is allowed to con-
tinue briefly at an elevated temperature. Typically, the
Icatalyst is use~d wetted down with water, in order to exclude ca-
30 Italysis of the detonating gas reaction by the catalyst duringIcharging an;i filling of the equipme,lt with hydrogen. It is also
'I !
;1 llZ'-~66~
advisable to use para-nitroso diphenylhydroxylamine wetted down
with water. The quantities of water introduced in this matter do
as little harm as the forming water reaction. Thus, it is unim-
portant whether one phase is present in the course of the reac-
tion, or a second, aqueous phase forms as a result of the formingwater of reaction. After termination of the reaction (as a rule
with quantitative conversion), the reaction mixture is processed
in the usual manner. First, the contents of the reactor are
'cooled, the reaction vessel pressure removed, and the catalyst
filtered off at temperatures between ahout 20 and about 60C. The
formed water of reaction can then be separated in the usual man-
ner, but it can also be removed together with the solvent, when
the reaction products are separated, if necessary by distilla-
tion.
The process pursuant to the invention makes possible the
catalytic hydrogenation of para-nitroso diphenylhydroxylamine to
para-amino diphenylamine in an advantageous manner, by which it is
particularly possible to work with very small quantities of pre~
Icious metal catalysts. It was not expected that solely by the
20 Iselection of the solvents to be used pursuant to the present
~linvention, it would be possible to obtain higher conversion rates
i and selectivities, than with the customary solvents, such as
toluene, methanol, isopropanol, and acetone. Furthermore, the
l process pursuant to the present invention is distinguished by its
25 ¦ relatively short reaction time of about 15 to about 45 minutes,
whereas in the known processes, even after a reaction time of 6
¦hours, and in the most favorable prior art case, less than
9% of the theoretical yield of para-amino diphenylamirle is
l obtained.
30 ¦ The para-amino diphenylamine obtainable pursuant to the
present invention is an intermediate product in the manufactu,e of
.1 ,
2~66
¦~dyestuffs, and is in particu1ar required in the manufacture of
asymmetrical phenylene diamine derivatives, which are used as
~antidecredants in rubber mixtures.
Examples 1 to 5
The reactions are carried out in a 1 liter glass auto-
clave, equipped with a bottom outlet valve, a gas supply tube, a
flow breaker, a vaned stirrer, and a manometer. The reaction is
carried out between about 40 and about 150C, with hydrogen pres-
sure between about 5 and about 30 bar, for a reaction time of
about 30 minutes, and with a stirring velocity of 1500 rpm.
First, the autoclave is evacuated, then vented with hydrogen, and
subsequently, halF the solvent is added. The para-nitroso
diphenylhydroxylamine, together with the catalyst, is suspended in
the second half of the reaction medium and added through an inlet
valve by means of hydrogen pressure. After that, the autoclave is
put under hydrogen pressure and heated carefully. Depending upon
the other reaction parameters, the reaction begins between about
20 and about 70C. Additional heat is applied after the heat of
l reaction drops, so that the total reaction time is 30 minutesn
Subsequently, the pressure is removed from the autoclave and the
,catalyst filtered off at a somewhat elevated temperature (about 30
to about 50C). If the catalyst is to be used for additional
~¦cycles, the catalyst is flushed back into the reaction space while
IIstill moist with solvent. If the catalyst is to be used only
25 l'once, the still adhering solvent is washing out with a more
volatile solvent, such as methanol or methylene chloride.
First the water of reaction, then the solvent, and
finally the para-amino dipllenylamine are obtained separately from
the filtrate by rmeans of fractional distillation. When larger
quantities of para-amino diphenylamine are made, it is advisable
to connect d flaker to the distillation column and in such an
- llZ ~66~ I
il
¦instance, the para-amino diphenylamine is obtained in the form of
white flakes with a faintly beige cast.
The processing conditions as well as the resulting
l yields of para-amino diphenylamine are compiled in the following
5 IlTable I. In each case, 20 grams (93.2 mmol) of para-nitroso
¦diphenylhydroxylamine are utilized. The following catalysts
;obtained from the fi~^m ~egussa are employe~:
¦I A: ElOR, palladium on carbon, palladium endowment 1% by
I¦ weight.
10 , B: ElOR, palladium on carbon, palladium endowment 5% by
weight.
C: F103RS, platinum sulfide on carbon, platinum
endowment 5% by weight.
I D: ElOlRS, palladium sulfide on carbon, palladium
endowment 4.88% by weight.
j E: FlOlR, patinum on carbon, platinum endowment 1% by
i weight.
, The following abbreviations are used in the Table: NDHA = para-
~ nitroso diphenylhydroxylamine; ADA - para-amino diphenylamine;
20 IICPPD = N-cyclohexyl-para-phenylene dianline.
Examples 6 to 15
The following examples, or comparative examples, are
carried out in the manner described for Examples 1 through 5. The
examples show the superiority of the process pursuant to the
present invention, which is considerable, especially with respect
to the use of catalysts with a low metal content. As palladium
catalyst, use is made of the palladium-carbon catalyst ElOR of the
firm Degussa, with a 1%, by weight, palladium endowment, while the
nickel catalyst was Raney nickel.
From the data contained in Tables I and II, it is
apparent that the process of the present invcntion is capable of
-`- llZ76~i6
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producing yields from about 91 to about 99% of the theoretical
yield of para-amino diphenylamine. This in contrast to the yields
obtained with the same process utilizing different solvents such
llas acetone, methanol, isopropanol, toluene, and ethanol, which
5 llproduced yields in the range from about 30 to about 80% of the
theoretica1 yie1d of para-amino diphenyl Inine.
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