Note: Descriptions are shown in the official language in which they were submitted.
- 1 -
The invention relates to a process for the
preparation of 1-naphthylamine by the catalytic hydro-
genation of 1-nitronaphthalene at elevated temperature
and elevated pressure, in the presence of inert organic
solvents miscible with water.
Conventionally, 1-naphthylamine is prepared on
the industrial scale by the reduction of 1-nitronaphthalene
with iron in dilute hydrochloric acid (Béchamp reduction)
or catalytically with hydrogen in the presence of nickel
catalysts (for example Raney nickel3 or by the reaction
of 1-naphthol with ammonia and ammonium bisulphite
(Bucherer reaction) (cf., for example, Kirk-~thmer,
volume 4, 1st edition, pages 258-260). Thus, for example,
the yield of the reduction with iron is about 90X of
theory (cf. Kirk-Othmer, volume I, 1st Edition, page 260); for
catalytic hydrogenation with nickel catalysts, yields of
over 90%, for example 96.4~, are indicated (cf., U.S.
Patent 2,105,321, J. Chem. Soc. Japan, 54, 371 to 373
(1951), and C.A~ 48, 1979d).
The catalytic reduction processes have the dis-
advantage that they cannot successfully be applied also
to the reduction of purified 1-nitronaphthalene which is
virtually free of sulphur compounds and the 2-nitro-
naphthalene isomer. As shown by our own experiments
with purified 1-nitronaphthalene, the desired naphthyL-
amine is only wormed as a by-product in the catalytic
hydrogenation with Raney nickel under the usual reaction
conditions. Attack by the hydrogen takes place simul-
taneously and predominantly on the aromatic nucleus and
the main products obtained are the undesired amino com-
pounds hydrogenated on the nucleus (cf. Example 2 in the
examples section).
The hydrogenation of nitronaphthalenes at
elevated temperature and elevated pressure, in the
Le A 23 116
-- 2
presence of, for example, nobLe metaL catalysts which
may be supported, has also been described (cf., for
example, German Offenlegungsschriften 2,456,308 and Z,519,
838). However, the hydrogenations of nitro compounds
described in the said German ~ffenlegungsschrif~er, require
special conditions which entail some disadvantages for a
large-sca~e process. Thus, the hydrogenation according
to German Offenlegungsschrift 2,456,308 is carried out
with the addition of special diluents in which the nitro
10 compound to be hydrogenated is soluble and the hydrogena-
tion product, consisting essentially of amino compound
and water, is virtually insoluble. The process described
in German Offenlegungsschrift 2,519,838 takes place in the
trickle phase on fixed catalysts. disadvantages of the
15 process of German Offenlegungsschrift 2,456,308 are the
addition of special diluents,~ the high dilution of the
reactants with the resulting low throughputs, and the
industrially expensive recovery of the solvents, which
detract from the economy of the process.
In the process of German Offenlegungsschrift 2,
519,838, the trickle phase is of little advantage because
this reaction is also carried out at high dilution,
permitting only low throughputs, which again detracts
from the economy of the process. Moreover, deposits on
25 the fixed-bed catalyst are to be expected, which can lead
to high pressure losses in the unit and even to blockages
in some cases.
A process has now been found for the preparation
of 1-naphthylamine by the catalytic hydrogenation of 1-
30 nitronaphthalene at elevated temperature and elevated
pressure, in the presence of inert organic solvents
miscible with water, which is characterized in that
purified 1-nitronaphthalene~ which is virtually free of
sulphur compounds and the 2-nitronaphthalene isomer, is
35 hydrogenated at temperatures of 150 to 250C and pressures
of 50 to 300 bar, in the presence of platinum/activated
Le A 23 116
Lo
- 3 -
charcoaL, the average residence time of the reaction
mixture in the reactor being 3 to 30 minutes.
According to the invention, purified 1-nitro-
naphthalene which is virtually free of sulphur compounds,
such as nitrobenzothiophenes, and free of the 2-nitro-
naphthalene isomer is used in the process.
The purified 1-nitronaphthalene usually contains
less than 10 ppm of sulphur, preferably 3 to 5 ppm of
sulphur, in the form of sulphur compounds, and less than
10 ppm, preferably 1 to 3 ppm, of 2-nitronaphthalene~
The hydrogenation of the purified 1-nitro-
naphthalene is preferably carried out at temperatures of
160 to 200C and at pressures (H2) of 80 to 150 bar.
The hydrogenation catalyst used in the process
according to the invention is a platinum/activated char-
coal catalyst in which the platinum is applied to the
activated charcoal support in quantities of 0.3 to 7X by
weight, preferably 0.5 Jo 2% by weight, based on the
finished catalyst. The hydrogenation catalyst is pre-
~0 pared in a known manner by soaking or spraying the acti-
vated charcoal support with an aqueous platinum salt
solution, for example a hexachloroplatinic acid SGlution
~H2PtCl6). The platinum compound applied to the
support is then reduced to the metal in a customary manner,
for example with formaldehyde and hydrazine in alkaline
sGlution or with hydrogen
In the circuit of the continuous process, there
are 1 to 2% by weight of the Pttactivated charcoal catalyst,
based on the liquid contents of the hydrogenating unit.
The quantity of fresh catalyst used is generally about 2
to 20 9, preferably 4 to 8 9, based on 1 kmol of the 1-
nitronaphthalene used.
According to the invention, the reduction of the
purified 1-nitronaphthalene is carried out in the presence
of inert organic solvents miscible with water, such as
lower aliphatic and/or cycloaliphatic alcohols Examples
Le A 23 116
of lower alcohols which may be mentioned are methanol,
ethanol, n-propanol, isopropanol, n-butanol, isobutanol
and/or tert.-butanol, preferably isopropanol.
The quantity ox organic solvent used is not
criticaL and Jan easily be determined by means of pre-
~iminary experiments Usually, about 1 to 5 parts by
weight, preferabLy 1.5 to 3 parts by weight, ox soLvent
are used, based on 1 part by weight of 1~nitronaphthalene.
The process according to the invention is carried
out in such a way that the average residence time of the
reaction mixture in the reactor is 3 to 30, preferabLy 5
to 20 and particularly preferabLy 8 to 12 minutes
The process according to the invention can be
carried out either batch~ise or continuously. It is
preferably carried out continuously.
The 1-nitronaphthalene is obtained in high purity
(I 99.5%) and in high yields (> 99~) by the process
according to the invention.
The process according to the invention also turns
out to be so advantageous industrially because no special
solvent systems are used (cf. German Offenlegungsschrift
2,456,308 in this respect), which, inter alia, have to be
worked up in an industrially expensive manner, and no
special catalysts, for example catalysts provided with
specific additives (metal doping agents), or partially
poisoned catalysts are used, which detract from the
economy of the process on account of the high manufacturing
costs.
Furthermore, it is particularly surprising that
not all noble metal catalysts are equally suitable for
the process according to the invention, but only the
platinum-on-activated charcoal catalyst described above
(cf., in this context, Comparative Example 3 in the
examples section).
Example_1
2000 kg of purified 1-nitronaphthalene containing
Le A 23 116
3 ppm of sulphur in the form of sulphur compounds and
containing 3 ppm of 2-nitronaphthalene, 4200 kg of iso-
propanol/water mixture containing about 15% by weight
ot water and 3000 kg of finished product solution con-
taining the catalyst are pumped continuously, per hour,into the reactors of a system consisting of two main
reactors and one follow-up reactor each having a capacity
of 450 litres. In the circuit there are 1 to 2X by
weight of catalyst l platinum-on-activated charcoal).
Approx. 0.05 to 0~1 kg of spent catalyst is replaced per
hour. The hydrogen pressure is kept at 100 bar and the
temperature is kept at 160 to 195C by means of cooling
water. After a residence time of about minutes, the
product, which is completely converted and virtually free
of nitro compounds, it withdrawn from the reactor.
The pH of the solution containing the diamine
compound is about 9 to 12. The isopropanol/water mixture
recovered by distillation can be used again directly in
the reaction without further purification. The crude,
almost colourless 1-naphthylamine substantially freed of
water has a solidification point of 48.4C; the yield is
99.5% of theory; the purity of the product is 99.7X.
Example 2
In the abovementioned apparatus, 2000 kg of
purified 1-nitronaphthalene were hydrogenated per hour,
under the same conditions as described in Example 1, in
the presence of Raney nickel (doped with 15X of iron)
(catalyst concentration in the circuit: approx. 3%).
1-Naphthylamine was formed n only 48.1% yield and various
amino compounds partially and completely hydrogenated on
the nucleus (aminodecalin and aminotetralins) were formed
in 51.9X yield.
Example 3
1-Nitronaphthalene was hydrogenated in the
presence of 1Z palladium-on-activated charcoal under con-
ditions comparable to those described in Example 1. A
Le A 23 116
mixture consisting of only 90X of 1 naphthylamine and 10X
of amino compounds hydrogenated on the nucleus was
formed in quantitative yield
Le A 23 116
