Note: Descriptions are shown in the official language in which they were submitted.
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1
CATALYST AND METHOD FOR HYDROGENATING
CARBONYL COMPOUNDS
The present invention relates to a process for hydrogenating organic compounds
which
have at least one carbonyl group using a catalyst which, among other features,
con-
sists of copper oxide, aluminum oxide and at least one of the oxides of iron,
lanthanum,
tungsten, molybdenum, titanium, zirconium, tin or manganese, and treatment
with boil-
ing water and/or steam gives rise to a catalyst with high selectivity and
simultaneously
high stability. In the course of its production, copper powder, copper flakes
or cement
may additionally be added.
The catalytic hydrogenation of carbonyl compounds, for example carboxylic
acids or
carboxylic esters, is assuming an important position in the production streams
of the
commodity chemicals industry.
The catalytic hydrogenation of carbonyl compounds, for example carboxylic
esters, is
carried out almost exclusively in fixed bed reactors in industrial processes.
The fixed
bed catalysts used, in addition to catalysts of the Raney type, are in
particular sup-
ported catalysts, for example copper, nickel or noble metal catalysts.
US 3,923,694 describes, for example, a catalyst of the copper oxide/zinc ox-
ide/aluminum oxide type. The disadvantage of this catalyst is that it is not
sufficiently
mechanically stable during the reaction and therefore decomposes relatively
rapidly.
This results in a loss of activity and a buildup of differential pressure over
the reactor as
a result of the decomposing shaped catalyst bodies. The consequence is that
the plant
has to be shut down prematurely.
DE 198 09 418.3 describes a process for catalytically hydrogenating a carbonyl
com-
pound in the presence of a catalyst which comprises a support which comprises
pri-
marily titanium dioxide, and, as the active component, copper or a mixture of
copper
with at least one of the metals selected from the group of zinc, aluminum,
cerium, a
noble metal and a metal of transition group VIII, the copper surface area
being not
more than 10 m2/g. Preferred support materials are mixtures of titanium
dioxide with
aluminum oxide or zirconium oxide or aluminum oxide and zirconium oxide. In a
pre-
ferred embodiment, the catalyst material is shaped with addition of metallic
copper
powder or copper flakes.
DE-A 195 05 347 describes, in quite general terms, a process of catalyst
tablets with
high mechanical strength, in which a metal powder or a powder of a metal alloy
is
added to the material to be tableted. The metal powders added include aluminum
pow-
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2
der or copper powder or copper flakes. In the case of the addition of aluminum
powder,
however, a shaped body obtained with a copper oxide/zinc oxide/aluminum oxide
cata-
lyst has a worse side crushing strength than a shaped body which was prepared
with-
out addition of aluminum powder, and the inventive shaped body exhibited, when
it was
used as a catalyst, a poorer conversion activity than catalysts which were
produced
without addition of aluminum powder. Likewise disclosed there is a
hydrogenation cata-
lyst composed of NiO, Zr02, MoO3 and CuO, to which materials including copper
pow-
der have been added in the course of production. However, this document does
not
make any statements on the selectivity or the activity.
DE 256 515 describes a process for preparing alcohols from synthesis gas, in
which
catalysts based on Cu / Al / Zn are used, which are obtained by joint grinding
and pill-
ing of metallic copper powder or copper flakes. The main emphasis in the
process de-
scribed is on the preparation of mixtures of C, to C5 alcohols, a process
being selected
in which the reaction reactor comprises, in the upper third of the bed, a
catalyst which
has a higher proportion of copper powder or copper flakes, and, in the lower
third,
comprises a catalyst which has a lower proportion of copper powder or copper
flakes.
JP-A 50-99987 describes the increase in the mechanical stability of specific
Raney
catalysts which may be copper-based by water or steam treatment. SU-A 728 908
dis-
closes the hardening of aluminum-coppper-zinc catalysts for methanol synthesis
by
water treatment. Neither document makes any statements on the selectivity or
activity.
It was an object of the present invention to provide a process and a catalyst
which do
not have the disadvantages of the prior art and provide processes for
catalytically hy-
drogenating carbonyl compounds and also catalysts, the catalysts having both
high
mechanical stability and high hydrogenation activity and selectivity.
It has been found that the simultaneous precipitation of copper and of an
aluminum
compound and also, if appropriate, additionally a compound of iron, lanthanum,
tung-
sten, molybdenum, titanium, zirconium, tin and/or manganese, and the
subsequent
drying, calcining, tableting, and the addition of metallic copper powder,
copper flakes or
cement powder or graphite or a mixture affords a catalyst which leads, by
virtue of a
water and/or steam treatment, both to high activities and selectivities, and
to a high
stability of the shaped body which is used as a catalyst.
Accordingly, the present invention relates to a process for hydrogenating an
organic
compound having at least one carbonyl group, in which the organic compound is
con-
tacted, in the presence of hydrogen, with a shaped body which is producible in
a proc-
ess in which
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3
(i) an oxidic material comprising copper oxide and aluminum oxide and at least
one
of the oxides of iron, lanthanum, tungsten, molybdenum, titanium, zirconium,
tin
or manganese is provided,
(ii) pulverulent metallic copper, copper flakes, pulverulent cement, graphite
or a mix-
ture thereof may be added to the oxidic material,
(iii) the mixture resulting from (ii) is shaped to a shaped body and
(iv) the shaped body is treated with boiling water and/or steam.
Iron oxide is understood to mean iron(III) oxide.
In preferred embodiments, the inventive shaped bodies are used in the form of
unsup-
ported catalysts, impregnated catalysts, coated catalysts and precipitation
catalysts.
The catalyst used in the process according to the invention has the feature
that the
copper active component, the aluminum component and the component of at least
one
of the oxides of iron, lanthanum, tungsten, molybdenum, titanium, zirconium,
tin or
manganese are preferably precipitated with a sodium carbonate solution
simultane-
ously or successively, subsequently dried, calcined, tableted and calcined
once more.
In particular, the following precipitation method is useful:
A) A copper salt solution, an aluminum salt solution and a solution of a salt
of iron,
lanthanum, tungsten, molybdenum, titanium, zirconium, tin or manganese, or a
solution comprising copper, aluminum and a salt of iron, lanthanum, tungsten,
molybdenum, titanium, zirconium, tin or manganese, is precipitated with a
sodium
carbonate solution in parallel or successively. The precipitated material is
subse-
quently dried and, if appropriate, calcined.
B) Precipitation of a copper salt solution and of a solution of a salt of
iron, lantha-
num, tungsten, molybdenum, titanium, zirconium, tin or manganese, or of a solu-
tion comprising copper salt and at least one salt of iron, onto a
prefabricated
aluminum oxide support. In a particularly preferred embodiment, this is
present in
the form of a powder in an aqueous suspension. However, the support material
may also be present in the form of spheres, extrudates, spall or tablets.
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131) In one embodiment (I), a copper salt solution and a solution of a salt of
iron, lan-
thanum, tungsten, molybdenum, titanium, zirconium, tin or manganese, or a solu-
tion comprising copper salt and a salt of iron, lanthanum, tungsten,
molybdenum,
titanium, zirconium, tin or manganese, is preferably precipitated with sodium
car-
bonate solution. The initial charge used is an aqueous suspension of the alumi-
num oxide support material.
Precipitated solids which result from A) or B) are typically filtered and
preferably
washed to free them of alkali, as described, for example, in DE 198 09 418.3.
Both the end products from A) and from B) are dried at temperatures of from 50
to
150 C, preferably at 120 C, and subsequently, if appropriate, calcined
preferably for
2 hours at generally from 200 to 600 C, in particular at from 300 to 500 C.
The starting substances used for A) and/or B) may in principle be all Cu(l)
and/or Cu(II)
salts soluble in the solvents used in the application, for example nitrates,
carbonates,
acetates, oxalates or ammonium complexes, analogous aluminum salts and salts
of
iron. For processes according to A) and B), particular preference is given to
using cop-
per nitrate.
In the process according to the invention, the above-described dried and, if
appropri-
ate, calcined powder is processed preferably to tablets, rings, ring tablets,
extrudates,
honeycombs or similar shaped bodies. For this purpose, all suitable processes
from the
prior art are conceivable. Particular preference is given to using a shaped
catalyst body
or a catalyst extrudate with a diameter d and a height h < 5 mm, catalyst
spheres with
a diameter d of < 6 mm or catalyst honeycombs with a cell diameter rZ < 5 mm.
The composition of the oxidic material is generally such that the proportion
of copper
oxide is in the range from 40 to 90% by weight, the proportion of oxides of
iron, lantha-
num, tungsten, molybdenum, titanium, zirconium, tin or manganese is in the
range from
0 to 50% by weight, and the proportion of aluminum oxide is in the range of up
to 50%
by weight, based in each case on the total weight of the sum of the
abovementioned
oxidic constituents, these three oxides together constituting at least 80% by
weight of
the oxidic material after calcination, cement not being included in the oxidic
material in
the above sense.
In a preferred embodiment, the present invention therefore relates to a
process as de-
scribed above, wherein the oxidic material comprises
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(a) copper oxide with a proportion in the range of 50 <_ x<_ 80% by weight,
preferably
55 <_ x<_ 75% by weight,
(b) aluminum oxide with a proportion in the range of 15 <_ y<_ 35% by weight,
pref-
5 erably 20 <_ y<_ 30% by weight and
(c) at least one of the oxides of iron, lanthanum, tungsten, molybdenum,
titanium,
zirconium, tin or manganese with a proportion in the range of 1:5 z<_ 30% by
weight, preferably 2:5 z<_ 25% by weight,
based in each case on the total weight of the oxidic material after
calcination, where:
80 <_ x + y + z<_ 100, especially 95 <_ + y + z<_ 100.
The inventive process and the inventive catalysts are notable in that, by
virtue of the
treatment of the shaped body with boiling water and/or steam, a high stability
of the
shaped body which is used as a catalyst is achieved, and the hydrogenation
activity
and selectivity of the catalyst is simultaneously increased.
For the water treatment, the shaped body which has been dried and calcined as
de-
scribed above is covered in an amount of water or of an aqueous-alcoholic
solution
with a C,- to C4 alcohol such as methanol, ethanol or butanol which is
sufficient to fully
cover the catalyst. The aqueous-alcoholic solutions have a maximum alcohol
concen-
tration of 30% by weight. When water is used, the pH is adjusted to from 4 to
9, pref-
erably to from 6 to 8.5, with the aid of mineral acids such as nitric acid,
sulfuric acid or
hydrochloric acid or sodium carbonate or sodium hydroxide solution. The
catalysts are
treated with water or the aqueous-alcoholic solution at from 100 to 140 C and
a pres-
sure of from 1 to 30 bar, preferably at from 1 to 3 bar, for from 1 to 48 h,
preferably
from 5 to 20 h.
The steam treatment may be carried out with 100% steam, with vapor mixtures
com-
posed of steam and inert gases, for example nitrogen, with a proportion of the
inert gas
of up to 90% by weight, and/or with vapors of compounds in which water is
formed un-
der the reaction conditions of the steam treatment, for example the C, to C4
alcohols
such as methanol, ethanol or butanol, with an alcohol proportion of not more
than 90%
by weight. Preference is given to carrying out the steam treatment with pure
steam.
The catalyst bodies are treated with steam at from 100 to 300 C, preferably at
from 100
to 150 C, generally at standard pressure, but an elevated pressure of from 1
to 20 bar,
preferably from 1 to 2 bar, is also possible. The steam treatment will
generally proceed
for at least 1 h; preference is given to from 10 to 48 h of treatment time.
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After the water and/or steam treatment, the shaped catalyst body is dried
again at tem-
peratures of 1200C, preferably for 2 h at generally from 5 to 3000C, and
calcined if ap-
propriate.
In general, pulverulent copper, copper flakes or pulveruient cement or
graphite or a
mixture thereof is added to the oxidic material in the range from 1 to 40% by
weight,
preferably in the range from 2 to 20% by weight and more preferably in the
range from
3 to 10% by weight, based in each case on the total weight of the oxidic
material.
The cement used is preferably an alumina cement. The alumina cement more
prefera-
bly consists substantially of aluminum oxide and calcium oxide, and more
preferably
consists of from about 75 to 85% by weight of aluminum oxide and from about 15
to
25% by weight of calcium oxide. In addition, it is also possible to use a
cement based
on magnesium oxide/aluminum oxide, calcium oxide/silicon oxide and calcium ox-
ide/aluminum oxide/iron oxide.
In particular, the oxidic material may have, in a proportion of at most 10% by
weight,
preferably at most 5% by weight, based on the total weight of the oxidic
material, of at
least one further component which is selected from the group consisting of the
ele-
ments Re, Fe, Ru, Co, Rh, Ir, Ni, Pd and Pt.
In a further preferred embodiment of the process according to the invention,
graphite is
added to the oxidic material before the shaping to the shaped body in addition
to the
copper powder, the copper flakes or the cement powder or the mixture thereof.
Prefer-
ence is given to adding sufficient graphite that the shaping to a shaped body
can be
carried out better. In a preferred embodiment, from 0.5 to 5% by weight of
graphite,
based on the total weight of the oxidic material, are added. It is immaterial
whether
graphite is added to the oxidic material before or after or simultaneously
with the cop-
per powder, the copper flakes or the cement powder or the mixture thereof.
Accordingly, the present invention also relates to a process as described
above,
wherein graphite is added to the oxidic material or to the mixture resulting
from (ii) in a
proportion in the range from 0.5 to 5% by weight based on the total weight of
the oxidic
material.
In a preferred embodiment, the present invention therefore also relates to a
shaped
body, treated with boiling water and/or steam and comprising
an oxidic material which comprises
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7
(a) copper oxide with a proportion in the range of 50 <_ x<_ 80% by weight,
preferably
55 <_ x<_ 75% by weight,
(b) aluminum oxide with a proportion in the range of 15 _ y<_35% by weight,
prefera-
bly 20 <_ y<_ 30% by weight and
(c) at least one of the oxides of iron, lanthanum, tungsten, molybdenum,
titanium,
zirconium, tin or manganese with a proportion in the range of 1 s z< 30% by
weight, preferably from 2 to 25% by weight,
based in each case on the total weight of the oxidic material after
calcination, where:
80 <_ x+ y+ z<_ 100, especially 95 <_ x+ y+ z<_ 100,
metallic copper powder, copper flakes or cement powder or a mixture thereof
with a
proportion in the range from 1 to 40% by weight based on the total weight of
the oxidic
material and
graphite with a proportion of from 0.5 to 5% by weight based on the total
weight of the
oxidic material,
the sum of the proportions of oxidic material, metallic copper powder, copper
flakes or
cement powder or a mixture thereof and graphite adding up to at least 95% by
weight
of the shaped body.
After addition of the copper powder, of the copper flakes or of the cement
powder or of
the mixture thereof and, if appropriate, graphite to the oxidic material, the
shaped body
obtained after the shaping is, if appropriate, calcined at least once over a
period of
generally from 0.5 to 10 h, preferably from 0.5 to 2 hours. The temperature in
this at
least one calcination step is generally in the range from 200 to 600 C,
preferably in the
range from 250 to 500 C and more preferably in the range from 270 to 400 C.
In the case of shaping with cement powder, it may be advantageous to moisten
the
shaped body obtained before the calcination with water and subsequently to dry
it.
In the case of use as a catalyst in the oxidic form, the shaped body, before
charging
with the hydrogenation solution, is pre-reduced with reducing gases, for
example hy-
drogen, preferably hydrogen-inert gas mixtures, especially hydrogen/nitrogen
mixtures,
at temperatures in the range from 100 to 500 C, preferably in the range from
150 to
350 C and in particular in the range from 180 to 200 C. Preference is given to
using a
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8
mixture having a hydrogen content in the range from 1 to 100% by volume, more
pref-
erably in the range from 1 to 50% by volume.
In a preferred embodiment, the inventive shaped body, before use as a
catalyst, is ac-
tivated in a manner known per se by treatment with reducing media. The
activation is
effected either beforehand in a reduction oven or after installation in the
reactor. When
the reactor has been activated beforehand in the reduction oven, it is
installed into the
reactor and charged with the hydrogenation solution directly under hydrogen
pressure.
The preferred field of use of the shaped bodies prepared by the process
according to
the invention is the hydrogenation of organic compounds having carbonyl groups
in a
fixed bed. Other embodiments, for example the fluidized reaction with catalyst
material
in upward and downward motion, are, however, likewise possible. The
hydrogenation
may be carried out in the gas phase or in the liquid phase. Preference is
given to carry-
ing out the hydrogenation in the liquid phase, for example in trickle mode or
liquid
phase mode.
Working in trickle mode allows the liquid reactant comprising the carbonyl
compound to
be hydrogenated, in the reactor which is under hydrogen pressure, to trickle
over the
catalyst bed arranged therein, a thin liquid film being formed on the
catalyst. In con-
trast, when working in liquid phase mode, hydrogen gas is introduced into the
reactor
flooded with the liquid reaction mixture, the hydrogen passing through the
catalyst bed
in ascending gas bubbles.
In one embodiment, the solution to be hydrogenated is pumped in straight pass
through the catalyst bed. In another embodiment of the process according to
the inven-
tion, a portion of the product is drawn off continuously as a product stream
after pass-
ing through the reactor and, if appropriate, passed through a second reactor
as defined
above. The other portion of the product is fed back to the reactor together
with fresh
reactant comprising the carbonyl compound. This procedure is referred to below
as
circulation mode.
When, as an embodiment of the process according to the invention, trickle mode
is
selected, preference is given here to circulation mode. Preference is further
given to
working in circulation mode with use of a main reactor and postreactor.
The process according to the invention is suitable for hydrogenating carbonyl
com-
pounds, for example aldehydes and ketones, carboxylic acids, carboxylic esters
or car-
boxylic anhydrides, to the corresponding alcohols, preference being given to
alipatic
and cycloaliphatic, saturated and unsaturated carbonyl compounds. In the case
of
CA 02614520 2008-01-08
PF 56895
9
aromatic carbonyl compounds, undesired by-products may be formed by hydrogena-
tion of the aromatic ring. The carbonyl compounds may bear further functional
groups
such as hydroxyl or amino groups. Unsaturated carbonyl compounds are generally
hydrogenated to the corresponding saturated alcohols. The term "carbonyl com-
pounds" as used in the context of the invention comprises all compounds which
have a
C=O group, including carboxylic acids and their derivatives. It will be
appreciated that it
is also possible to hydrogenate mixtures of two or more than two carbonyl
compounds
together. It is also possible for the individual carbonyl compound to be
hydrogenated to
comprise more than one carbonyl group.
Preference is given to using the process according to the invention for
hydrogenating
aliphatic aldehydes, hydroxy aldehydes, ketones, acids, esters, anhydrides,
lactones
and sugars.
Preferred aliphatic aldehydes are branched and unbranched, saturated and/or
unsatu-
rated aliphatic C2-C3o aldehydes, as are obtainable, for example, by oxo
synthesis from
linear or branched olefins with internal or terminal double bonds. It is also
possible to
hydrogenate oligomeric compounds which also comprise more than 30 carbonyl
groups.
Examples of aliphatic aldehydes include:
formaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde,
valeraldehyde,
2-methylbutyraldehyde, 3-methylbutyraldehyde (isovaleraldehyde), 2,2-dimethyl-
propionaldehyde (pivalaldehyde), caproaldehyde, 2-methylvaleraldehyde, 3-
methylvaleraldehyde, 4-methylvaleraldehyde, 2-ethylbutyraldehyde, 2,2-dimethyl-
butyraidehyde, 3,3-dimethylbutyraldehyde, caprylaldehyde, capraldehyde,
glutaralde-
hyde.
In addition to the short-chain aldehydes mentioned, long-chain aliphatic
aldehydes are
also especially suitable, as can be obtained, for example, by oxo synthesis
from linear
a-olefins.
Particular preference is given to enalization products, for example 2-
ethylhexenal, 2-
methylpentenal, 2,4-diethyloctenal or 2,4-dimethylheptenal.
Preferred hydroxy aldehydes are C3-C12 hydroxy aldehydes, as are obtainable,
for ex-
ample, by aldol reaction from aliphatic and cycloaliphatic aldehydes and
ketones with
themselves or formaldehyde. Examples are 3-hydroxypropanal, dimethylolethanal,
trimethylolethanal (pentaerythrital), 3-hydroxybutanal (acetaldol), 3-hydroxy-
2-
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PF 56895
ethylhexanal (butylaldol), 3-hydroxy-2-methylpentanal (propionaldol), 2-
methylol-
propanal, 2,2-dimethylolpropanal, 3-hydroxy-2-methylbutanal, 3-
hydroxypentanal, 2-
methylolbutanal, 2,2-dimethylolbutanal, hydroxypivalaldehyde. Particular
preference is
given to hydroxypivalaldehyde (HPA) and dimethylolbutanal (DMB).
5
Preferred ketones are acetone, butanone, 2-pentanone, 3-pentanone, 2-hexanone,
3-
hexanone, cyclohexanone, isophorone, methyl isobutyl ketone, mesityl oxide,
aceto-
phenone, propiophenone, benzophenone, benzalacetone, dibenzalacetone,
benzalace-
tophenone, 2,3-butanedione, 2,4-pentanedione, 2,5-hexanedione and methyl vinyl
ke-
10 tone.
It is also possible to convert carboxylic acids and derivatives thereof,
preferably those
having 1-20 carbon atoms. The following should be mentioned in particular:
carboxylic acids, for example formic acid, acetic acid, propionic acid,
butyric acid, iso-
butyric acid, n-valeric acid, trimethylacetic acid ("pivalic acid"), caproic
acid, enanthic
acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid,
stearic acid,
acrylic acid, methacrylic acid, oleic acid, elaidic acid, linoleic acid,
linolenic acid, cyclo-
hexanecarboxylic acid, benzoic acid, phenylacetic acid, o-toluic acid, m-
toluic acid, p-
toluic acid, o-chlorobenzoic acid, p-chlorobenzoic acid, o-nitrobenzoic acid,
p-
nitrobenzoic acid, salicylic acid, p-hydroxybenzoic acid, anthranilic acid, p-
amino-
benzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic
acid, pimelic
acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid,
phthalic acid,
isophthalic acid, terephthalic acid;
carboxylic esters, for example the C,-C,o-alkyl esters of the abovementioned
carboxylic
acids, especially methyl formate, ethyl acetate, butyl butyrate, dialkyl
phthalates, dialkyl
isophthalates, dialkyl terephthalates, dialkyl adipates, dialkyl maleates, for
example the
dimethyl esters of these acids, methyl (meth)acrylate, butyrolactone,
caprolactone and
polycarboxylic esters, for example polyacrylic and polymethacrylic esters and
their co-
polymers and polyesters, for example polymethyl methacrylate, terephthalic
esters and
other industrial plastics, in which case hydrogenolyses, i.e. the conversion
of esters to
the corresponding acids and alcohols, are carried out in particular;
fats;
carboxylic anhydrides, for example the anhydrides of the abovementioned
carboxylic
acids, especially acetic anhydride, propionic anhydride, benzoic anhydride and
maleic
anhydride;
CA 02614520 2008-01-08
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11
carboxamides, for example formamide, acetamide, propionamide, stearamide,
terephthalamide.
It is also possible to convert hydroxy carboxylic acids, for example lactic
acid, malic
acid, tartaric acid or citric acid, or amino acids, for example glycine,
alanine, proline
and arginine, and peptides.
Particularly preferred organic compounds to be hydrogenated are saturated or
unsatu-
rated carboxylic acids, carboxylic esters, carboxylic anhydrides or lactones
or mixtures
of two or more thereof.
Accordingly, the present invention also relates to a process as described
above,
wherein the organic compound is a carboxylic acid, a carboxylic ester, a
carboxylic
anhydride or a lactone.
Examples of these compounds include maleic acid, maleic anhydride, succinic
acid,
succinic anhydride, adipic acid, 6-hydroxycaproic acid, 2-
cyclododecylpropionic acid,
the esters of the aforementioned acids, for example methyl, ethyl, propyl or
butyl
esters. Further examples are y-butyrolactone and caprolactone.
In a very particularly preferred embodiment, the present invention relates to
a process
as described above, wherein the organic compound is adipic acid or an adipic
ester.
The carbonyl compound to be hydrogenated can be fed to the hydrogenation
reactor
alone or as mixture with the product of the hydrogenation reaction, in which
case this
can take place in undiluted form or with use of additional solvent. Suitable
additional
solvents are in particular water, alcohols such as methanol, ethanol and the
alcohol
formed under the reaction conditions. Preferred solvents are water, THF, and
NMP;
particular preference is given to water.
The hydrogenation both in trickle and liquid phase mode, each preferably being
carried
out in circulation mode, is generally carried out at a temperature in the
range from 50 to
350 C, preferably in the range from 70 to 300 C, more preferably in the range
from 100
to 270 C, and a pressure in the range from 3 to 350 bar, preferably in the
range from 5
to 330 bar, more preferably in the range from 10 to 300 bar.
In a very particularly preferred embodiment, the catalysts of the invention
are employed
in processes for preparing hexanediol and/or caprolactone, as described in
DE 196 07 954, DE 196 07 955, DE 196 47 348 and DE 196 47 349.
= CA 02614520 2008-01-08
PF 56895
12
The process according to the invention achieves high conversions and
selectivities
using the catalysts of the invention. At the same time, the catalysts of the
invention
have high chemical and mechanical stability.
The present invention therefore relates quite generally to the use of a
treatment with
boiling water and/or steam in the preparation of a catalyst to increase both
the me-
chanical stability and the activity and selectivity of the catalyst.
In a preferred embodiment, the present invention relates to a use as described
above,
wherein the catalyst comprises copper as active component.
The mechanical stability of the solid-state catalysts and specifically of the
catalysts of
the invention is described by the side crushing strength parameter in various
states
(oxidic, reduced, reduced and suspended under water).
The side crushing strength was determined for the purposes of the present
application
using an apparatus of the "Z 2.5/T 919" type supplied by Zwick Roll (Ulm).
Both for the
reduced and for the used catalysts, the measurements were carried out in
methanol
under nitrogen atmosphere in order to prevent reoxidation of the catalysts.
Examples
Example 1: Preparation of catalyst 1
A mixture of 12.41 kg of a 57% copper nitrate solution and 12.78 kg of a 33%
alumi-
num nitrate solution and 0.48 kg of a 40% lanthanum nitrate = 6H20 solution
was dis-
solved in 2 I of water (solution 1). Solution 2 contains 60 kg of a 20%
anhydrous
Na2CO3. Solution 1 and solution 2 were passed via separate lines into a
precipitation
vessel which is equipped with a stirrer and comprises 10 I of water heated to
80 C. In
the course of this, the pH was brought to 6.2 by appropriate adjustment of the
feed
rates of solution 1 and solution 2.
While keeping the pH constant at 6.2 and the temperature at 60 C, the entire
solution 1
was reacted with sodium carbonate. The suspension thus formed was subsequently
stirred for a further 1 hour, in the course of which the pH is run at 7.2 by
occasionally
adding dilute nitric acid or soda solution 2. The suspension is filtered and
washed with
distilled water until the nitrate content of the washing water was < 10 ppm.
The filtercake was dried at 120 C for 16 h and subsequently calcined at 600 C
for 2 h.
The catalyst powder thus obtained is precompacted with 1 % by weight of
graphite. The
CA 02614520 2008-01-08
PF 56895
13
resulting compacted material is mixed with 5% by weight of Unicoat copper
flakes and
subsequently with 2% by weight of graphite and compressed to tablets of
diameter
3 mm and height 3 mm. The tablets were finally calcined at 350 C for 2 h.
The catalyst thus prepared has the the chemical composition
58% CuO / 22 % AI203 / 5% La2Os/ 15 % Cu.
The side crushing strength was 25 N as specified in Table 1.
Example 2: Water treatment for catalyst 2
20 g of the catalyst according to Example 1 were mixed with 50 ml of water and
heated
at 140 C and a pressure of 2 bar for 24 h. After the removal of the water, the
catalyst
was dried at 120 C for 4 h.
Example 3: Steam treatment for catalyst 3
g of the catalyst according to Example 1 were treated at 140 C at 1.3 bar with
100%
steam for 20 h. The catalyst was then dried at 120 C for 4 h.
Example 4:
Catalyst T4489 of composition 60% CuO / 30% A1203 / 10 Mn02, sold by
Sudchemie.
Example 5: Steam treatment
The commercial catalyst of composition 60% Cu0 / 30% AI203 / 10 Mn02 (trade
name
T4489 from Sudchemie) was treated with 100% steam at a pressure of 1.3 bar for
20 h
and then dried at 120 C for 4 h.
Example 6: Hydrogenation of methyl adipate over catalysts 1, 2, 3, 4 or 5
Dimethyl adipate was hydrogenated continuously in trickle mode with recycling
(feed/recycle ratio = 10/1) at an hourly space velocity of 0.3 kg/(I*h), a
pressure of
200 bar and reaction temperatures of 210 bar and 190 C in a vertical tubular
reactor
which had been charged in each case with 200 ml of catalysts 1, 2, 3, 4 or 5.
The ex-
perimental duration was a total of 7 days. GC analysis detected, in the
reactor effluent
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14
at 190 C, ester conversions of 99.9%, a hexanediol selectivity of 97.5%. After
deinstal-
lation, the catalyst was still fully preserved and had a high mechanical
stability. The
experimental results are compiled in Table 1.
The data in Table 1 which follows show that the inventive catalysts have
significantly
higher hydrogenation activities, i.e. higher conversions of dimethyl adipate
at 190 C
than the comparative catalyst, and also higher product-of-value selectivities,
i.e. con-
tents of the hexanediol target products in the effluent.
Table 1
Catalyst Reaction Dimethyl adipate Hexanediol Side crushing
example temperature conversion selectivity strength (N)
[ C] [%] N
Catalyst 1
210 98.09 96.46 25
(untreated)
Catalyst 2
210 99.57 97.34 54
(water)
Catalyst 3
210 99.52 97.82 41
(steam)
Catalyst 4
190 90.05 96.66 22
(untreated)
Catalyst 5
190 92.8 97.1 34
(steam)
