Note: Descriptions are shown in the official language in which they were submitted.
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Mo3612
LeA 27,775
PROCESS FOR THE PRODUCTION OF DI-(4-AMINOCYCLOHEXYL)-METHANE
CONTAINING 15 TO 25% BY WEIGHT OF THE TRAMS-TRAMS ISOMER
,~,ACKGROUND OF THE INVENTION
The present invention relates to an improved process for
the production of a liquid mixture of the isomers of
di-(4-aminocyclohexyl)-methane by hydrogenation of
di-(4-aminophenyl)-methane ("MDA"). The liquid isomer mixture
obtainable in accordance with the invention contains from 15 to '
25% by weight and preferably from 18 to 23.5% by weight of the
to traps-traps isomer.
A liquid isomer mixture of the type noted above is
generally required for the production of an isocyanate
derivative which in turn is liquid at room temperature
(approximately 10 to 25°C).
i5 In general, the hydrogenation of MDA leads to an isomer
mixture in which the cis-cis isomer, the cis-traps isomer and
the traps-traps isomer occur together and in which the
traps-traps content approaches the equilibrium concentration of
around 50% by weight. An isomer composition with the
2o relatively low traps-traps isomer content mentioned above
(i.e., from 15 to 25% by weight) can be produced by the
complicated conversion process described in German
Auslegungschrift 1,593,293. There are other known processes
which allow for the preparation of an isomer mixture of
25 di-(4-aminocyclohexyl)-methane containing a specific amount of
the traps-traps Isomer (see, e.g., U.S. patents 3,766,272,
3,644,522, 3,155,724, and 3,153,088). European Patent 324,190
describes a hydrogenation process for MDA which produces
hydrogenation products wherein the traps-traps content
3o corresponds to the desired value. The process requires the use
of special catalysts and the maintenance of certain reaction
conditions. However, this process has the disadvantage that
the overall yield of di-(4-aminocyclohexyl)-methane is
unsatisfactory. In addition, some of the hydrogenation or
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conversion processes mentioned must be carried out in the
presence of ammonia or high-grade solvents.
Accordingly, the problem addressed by the present
invention was to provide a new, simplified and industrially
workable process in which the traps-traps isomer content would
be in the desired range mentioned above with a high overall
conversion. This problem has been solved by the process
according to the invention.
DESCRIPTION OF THE INVENTION
zo The present invention is directed to a process for the
production of di-(4-aminocyclohexyl)-methane containing from
to 25% by weight of the traps-traps isomer by the catalytic
hydrogenation of di-(4-aminophenyl)-methane at elevated
temperature and elevated hydrogen pressure in the presence of a
i5 ruthenium-containing supported catalyst. The process of the
invention is characterized by the use of a ruthenium catalyst
on an A1203~support which has been treated with compounds of
' rare earth metals and manganese. The ruthenium content of the
catalyst used herein is from 0.05 to 5% by weight, preferably
2o from 0.05 to 3% by weight and most preferably from 0.1 to 2% by
weight, based on the total weight of the catalyst.
Accordingly, the process of the invention is characterized
by the use of a special ruthenium supported catalyst wherein
the support, A1203, contains compounds of rare earth metals and
z5 manganese. An addition of basic alkali compounds produces
further improvements.
The A120a is preferably a- or ~-A1203 and, most
preferably, is ~-A1203.
The combined content of rare earth metal and manganese is
so from 0.05 to 8% by weight and preferably from 0.2 to 59o by
weight, based an the total weight of the catalyst. The weight
ratio of rare earth metal to manganese is from 5:1 to 1:5 and
preferably from 2:1 to 1:2.
The rare earth metals are the elements of the IIIb group
ss of the Periodic system. These include materials such as
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scandium, yttrium, lanthanum and the lanthanides. Either one
or a mixture of two or more of the rare earth metals may be
used. Crude mixtures of rare earth metals of the type which
are commercially available and in which only one or two of the
s rare earth metals is/are initially enriched can also be used.
It is preferred to use one or more of the elements selected
from the group consisting of yttrium, lanthanum, cerium,
praseodymium, neodymium and dysprosium. In a particularly
preferred embodiment, cerium, lanthanum or a mixture thereof is
io used. In an especially preferred embodiment, cerium, which may
be in the form of a cerium-enriched mixture, is used. The rare
earth metals and manganese are present in the form of their
compounds, preferably in oxide form, for treating the A1203
support.
i5 The oxides, hydroxides or carbonates of the alkali metals,
preferably NaOH and KOH, may be used as basic additives. The
basic additives may be applied to the catalyst support before
or after the treatment with the rare earth metals and
manganese. The alkali metal addition is preferably between 0.1
2o and l0fo and more preferably between 0.2 to 5%, based on the
weight of the catalyst.
The catalyst useable in accordance with the invention may
be prepared, for example, by applying compounds of the rare
earth metals and manganese to an A1203 in the form of
z5 extrudates, pellets or spheres of between about 2 and 10 mm in
size. The support thus treated is dried and then further
treated with a ruthenium salt, followed by another drying step.
In a preferred embodiment, the catalyst support initially
treated with rare earth metals and manganese is heated to a
so temperature of 200 to 450'C before the ruthenium is applied.
Compounds of the rare earth metals and manganese may be
applied, for example, by impregnation or spraying with suitable
salts of the elements mentioned. The salts of the rare earth
metals and manganese are converted into compounds which adhere
35 firmly to the catalyst support by a suitable drying temperature
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and, in a preferred embodiment, by heating to between 200 and
450°C. However, compounds of the rare earth metals and
manganese may also be applied by co-precipitation of a rare
earth metal/manganese hydroxide mixture from rare earth metal
and manganese salts onto the impregnated support with alkali
hydroxide or ammonia, optionally followed by removal of the
soluble components by washing with water. Suitable salts of
the rare earth metals and manganese are, in particular, the
sulfates, chlorides, acetates and/or nitrates. The support
to treated with rare earth metals and manganese is first dried and
then heated, preferably for 1 to 120 hours at 200 to 450°C and
preferably at 250 to 430°C. The temperature may be increased
from lower to higher values within these ranges over the period
of time mentioned.
i5 The support thus treated may be subsequently impregnated
with ruthenium by applying the ruthenium to the support, for
example in the form of an aqueous solution of the chloride,
nitrate, acetate or any other suitable salt, by impregnation or
spraying, again followed by drying. Before drying, however,
2o the ruthenium-impregnated support may also be treated with a
solution of the basic compounds mentioned above, the ruthenium
precipitating in the form of the oxide or hydroxide. The
water-soluble components may then be removed by washing,
followed by drying. Thereafter a catalyst suitable for use in
2s accordance with the invention is available. In a preferred
embodiment, however, the catalyst is activated before use,
preferably after arrangement in the hydrogenation reactor, by
treatment with hydrogen at a temperature in the range from 150
to 350°C. After activation, it may again be desirable to
so remove anions, such as chloride, nitrate, acetate or others,
and optionally the cations of the basic compounds used for
precipitation by washing with water. However, the catalyst
support treated with compounds of the rare earth metals and
manganese may also first be impregnated with a solution of one
35 of the basic compounds mentioned, and subsequently dried.
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Solutions of ruthenium salts may then be applied to the
basified catalyst support, the ruthenium being precipitated in
the form of its oxide or hydroxide at the moment of
impregnation. In this case, too, the catalyst is ready for use
s after drying, although it is preferably first activated with
hydrogen in the manner described above. In this variant, too,
the ruthenium supported catalyst is ready for use despite the
presence of the residues of such alkaline compounds. In a
preferred embodiment, however, it is washed with water as
io described above.
The application of the various substances to the A1203
support by impregnation or spraying and the apparatus required
for this purpose are known in the art. It is also known that
the required degree of application can be adjusted through the
~5 choice of the quantity and concentration of the solutions of
the elements mentioned.
The hydrogenation reaction according to the invention
takes place at a temperature in the range from 80 to 160°C and
preferably at a temperature in the range from 90 to 140°C. The
2o choice of the temperature is determined by the required
reaction rate and also by the desired composition of the isomer
mixture. The reaction rate increases with increasing
temperature, as does the traps-traps content of the isomer
mixture formed. The catalyst has an isomerizing effect on the
2s hydrogenation product, particularly at relatively high
temperatures, so that the traps-traps content can increase even
further in the event of prolonged contact. Accordingly, it is
generally preferable to remove the hydrogenation product from
the catalyst after the uptake of hydrogen has stopped.
so According to the invention, the hydrogen pressure applied
is in the range from 20 to 500 bar and preferably in the range
from 200 to 400 bar. The higher the hydrogen pressure, the
faster the hydrogenation reaction. By applying a relatively
high hydrogen pressure, therefore, it is possible to keep to a
35 relatively low hydrogenation temperature and/or a relatively
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short contact time with the catalyst in order to reduce the
traps-traps content of the hydrogenation product.
Where hydrogenation is carried out discontinuously in an
autoclave, the course of the reaction can be followed and,
s thus, the end of the hydrogenation time can be determined from
the amount of hydrogen taken up. The hydrogenation time is
generally between 2 and 5 hours, depending on the quantity of
catalyst and the temperature applied.
In a particularly advantageous embodiment, the process is
io . conducted continuously. The catalyst can be introduced in the
form of granules into a vertical pressure tube. The MDA to be
hydrogenated, optionally together with an inert solvent for
dilution, and the hydrogen are passed through the catalyst bed
from above. The hydrogen removed from the reaction product
discharged may be reused for the reaction. Under given
reaction conditions, the most favorable throughput rate can be
established and followed by gas-chromatographic analysis ("GC"
analysis) of the hydrogenation product. A catalyst load of
0.05 to 0.5 kg MDA per liter catalyst per hour has proven to be
2o particularly advantageous.
Suitable inert diluents are liquid compounds, such as
dioxane, tetrahydrofuran, isobutanol or tert-butanol, which are
known to the art as being inert to hydrogenation. In a
preferred embodiment, however, part of the hydrogenation
25 product may be used for dilution, eliminating the need to
introduce a diluent from outside the system. Where an inert
diluent/solvent or the hydrogenation product formed is used for
dilution, the weight ratio of MDA to diluent is generally from
1:0.2 to 1:2 and preferably from 1:0.5 to 1:1.
so Compared with known processes, the process according to
the invention has the advantage of a higher yield in
conjunction with the direct establishment of the desired isomer
ratio and the use of a ruthenium catalyst which is easy to
produce.
s5 In the following Examples, all percentages are by weight.
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EXAMPLES
Examgle 1
200 g of a commercially available ~-A1203 having a
specific surface of 350 m2/g and a bead diameter of 2 to 6 mm
s were impregnated with a solution which had been prepared from
12.4 g Ce(N03)3 ' 6H20, 18.28 g Mn(N03)2 ' 4H20 and 50 g water.
The impregnated A1203 was dried for 18 hours at 120°C in a
water jet vacuum and then heated for 3 hours at 400°C. The
catalyst support thus produced was impregnated with 70 g of an
to aqueous RuCl3 solution containing 2 g Ru. The moist catalyst
was dried for 18 hours at 120°C in a water jet vacuum and
activated for 3 hours at 350°C in a stream of hydrogen (100
liters H2/hour).
ExamPl e~
is 25 ml (19 g) of the Ru-Ce-Mn-A1203 catalyst prepared in
accordance with Example 1 containing 1% Ru, 2fo Ce and 2% Mn
were used for the hydrogenation of di-(4-aminophenyl)-methane
.(MDA) in a 0.25 liter shaker autoclave. A sieve basket filled
with the catalyst was arranged inside the autoclave. 40 g MDA
2o dissolved in 40 g tert-butanol were hydrogenated six times in
succession with this catalyst filling. The hydrogen pressure
was 260 to 300 bar and the reaction temperature was 140°C. The
necessary hydrogenation time was between 240 and 300 minutes.
After each hydrogenation, the autoclave was cooled to room
2s temperature; the reaction product was removed and the autoclave
was refilled with a solution of MDA in tert-butanol. The
reaction products were analyzed for their content of
traps-traps isomer and di-(4-aminocyclohexyl)-methane ("HMDA").
The results obtained are shown in the following Table (the
so amount of traps-traps isomer is based on the amount of the
HMDA):
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Hydrogenation Trans-trans 3- and 4-Nuclear HMDA
time (rains.) isomer (%) compounds (%) (%)
300 22.5 2.8 96.5
s 265 19.8 2.6 96.9
240 19.0 1.7 97.9
270 21.0 1.5 98.3
260 20.6 1.9 97.7
Example 3
io 150 g of the catalyst prepared in accordance with Example
l were aftertreated by impregnation with a solution which had
been prepared from 54 g water and 6 g NaOH. The quantity of
sodium hydroxide used corresponded to the absorption capacity
of the catalyst. The impregnated catalyst was dried for 20
15 hours at 100°C. 60 ml (53 g) of the catalyst thus produced
were arranged in a vertical pressure tube (diameter 14 mm,
. length 70 cm) which was heated by an oil thermostat. The
spaces in the catalyst layer were filled with fine sea sand
(0.2 to 0.3 mm).
2o A mixture of 1 part by weight MDA and 1 part by weight
tert-butanol was introduced onto the catalyst from above
together with hydrogen at 270 bar/112°C. The liquid trickled
downwards through the catalyst into a separator. 30 to 50
liters hydrogen/hour were removed at the head of the separator.
2s The MDA throughput corresponded to a catalyst load of 0.11 to '
0.13 g MDA/ml cat. per hour and was kept in this range.
After 333 hours, the reaction product had the following
camposition according to analysis by gas chromatography:
Trans-trans isomer: 18.2%
30 . 3- and 4-nuclear compounds: 0.25%
Di-(4-aminocyclohexyl)-methane 98.9%
Secondary products 0.85%
Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be
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understood that such detail is solely for that purpose and that
variations can be made therein by those skilled in the art
without departing from the spirit and scope of the invention
except as it may be limited by the claims.
Mo3612
