Title of Invention

PRODUCTION OF CU/ZN/AI CATALYSTS VIA THE FORMATE ROUTE

Abstract The invention relates to a process for preparing Cu/Zn/Al catalysts. In this process, the metals are used in the form of their formates and are precipitated in a suitable form. Suitable precipitants are, for example, alkali metal carbonates. The invention further relates to a catalyst as can be obtained by the process according to the invention and to its use.
Full Text PATENT APPLICATION
PRODUCTION OF Cu/Zn/Al CATALYSTS
VIA THE FORMATE ROUTE
The invention relates to a process for preparing Cu/Zn/A1
catalysts, to a catalyst which can be obtained by the process,
and to its use for methanol synthesis and the reformation of
methanol and the low-temperature conversion of carbon monoxide.
Cu/Zn/A1 catalysts which catalyze the conversion of CO, CO2 and
H2 to methanol have been known for some time. The atomic ratios
between copper and zinc can vary in these known catalysts,
except that copper is generally present in excess. Moreover,
part of the zinc component can be replaced by calcium, magnesium
and/or manganese. The aluminum oxide used as a thermally
stabilizing substance can also be replaced partly by chromium
oxide.
For example, DE 1 965 007 discloses a catalyst for low-
temperature methanol synthesis. For the preparation of the
catalyst, the corresponding basic carbonates are first

precipitated from a solution of suitable zinc and copper salts
by adding alkali metal carbonates. The basic carbonates are
removed from the aqueous phase, dried and calcined in order to
obtain the corresponding oxides. The zinc oxides and copper
oxides are subsequently mixed with aluminum oxide to prepare a
suspension of the oxides which contains not more than 20%
solids. This is subsequently homogenized, the homogenization
being performed until the dispersed oxides do not settle out
over the course of 2 hours. After the homogenization, the
mixture is dried, tableted and calcined. In order to convert the
oxidic form to the catalyst, it is then reduced in a hydrogen
stream.
DE 2 302 658 A discloses a process for preparing a precursor for
a catalyst which can be used for methanol synthesis. To prepare
the catalyst precursor, a first precipitate which comprises a
divalent metal, for example zinc, and a trivalent metal, for
example aluminum, is first prepared in the form of a compound
which can be decomposed thermally to the corresponding oxides.
Suitable compounds are, for example, carbonates or bicarbonates.
In addition, a second precipitate which comprises copper
compounds which can be decomposed thermally to oxides is
prepared. The two precipitates are mixed. This is followed by
the customary stages of drying and calcination in order to
obtain the oxides from the metal compounds and possibly to bring
about the formation of a spinel structure. The solid is then
tableted. In order to convert the precursor to an active
catalyst, the tablets are reduced in a hydrogen stream.
DE 2 056 612 A describes a process for preparing methanol, the
conversion being effected over a catalyst which comprises zinc,
copper and aluminum. The catalyst belongs to a mixed crystal
series of the formula (CuxZny) Al2 (OH) 16.CO3.4H2O in which x and y
can assume numerical values from 0.5 to 5.5, and the sum of x
and y is equal to 6. The mixed crystal compound is precipitated


from an aqueous solution which comprises copper, zinc and
aluminum salts by adding alkali metal carbonates, alkali metal
bicarbonates or mixtures thereof. The atomic ratio of the sum of
the divalent metals copper and zinc to the trivalent aluminum in
the mixed crystal series is constant and is 6:2. For the
preparation, copper, zinc and aluminum are dissolved in water in
the form of suitable salts, preferably of the nitrates, in a
quantitative ratio which corresponds to the desired composition
of the catalyst. This solution is heated to temperatures of from
50 to 100°C, preferably from 70 to 100°C, and treated with an
aqueous solution of a precipitant, for example of an alkali
metal carbonate, at an appropriate temperature. The precipitate
formed is filtered off, washed and dried. The dried compound is
calcined at temperatures in the range from 200 to 500°C over
from 12 to 24 h. The calcined product is shaped to tablets and
then converted to the active form of the catalyst by reduction
in a hydrogen stream.
US 4,279,781 describes a catalyst for methanol synthesis, which
comprises copper oxide and zinc oxide and also a metal oxide for
the thermal stabilization, for example aluminum oxide. The ratio
of copper oxide and zinc oxide is, calculated as the weight of
the metals, from 2:1 to 3.5:1. The catalyst is prepared by
coprecipitation of soluble zinc, copper and aluminum salts, for
example of the nitrates. This achieves intimate mixing of the
catalyst constituents. In order to obtain the active form, the
catalyst precursor is reduced in a hydrogen stream.
EP 0 125 689 A2 discloses a catalyst for methanol synthesis,
which comprises, as catalytically active substances, copper
oxide and zinc oxide and, as a thermally stabilizing substance,
aluminum oxide. The catalyst features a particular pore radius
distribution, the proportion of the pores having a diameter of
from 20 to 75 A (mesopores) being at least 20% and the
proportion of the pores having a diameter of more than 75 A


(macropores) being at most 80%. The desired pore radius
distribution can be achieved by using colloidally distributed
aluminum oxide or hydroxide in the preparation of the catalyst.
For the preparation of these catalysts, the catalytically active
copper oxide-zinc oxide component is precipitated from aqueous
solutions of the corresponding salts, for example the nitrates,
sulfates, chlorides, acetates, with alkaline substances in the
presence of a colloidally distributed aluminum oxide or
hydroxide. The precipitation product can subsequently be dried,
calcined, compressed to shaped bodies and optionally reduced.
EP 0 152 809 A2 discloses a catalyst for synthesizing alcohol
mixtures comprising methanol and higher alcohols, said catalyst
comprising copper oxide and zinc oxide in the form of an oxidic
precursor which can be converted by a reduction of at least a
portion of the copper oxide to a catalytically active component,
and also aluminum oxide as a thermally stabilizing substance,
and at least one alkali metal carbonate or alkali metal oxide.
The oxidic precursor has a proportion of pores having a diameter
between 14 and 7.5 nm of from 20 to 70% of the total volume. The
alkali metal content is from 13 to 13 0 x 10~6 gram atom of
alkali metal per gram of the oxidic precursor. The aluminum
oxide component was obtained from a colloidally distributed
aluminum hydroxide. For the preparation of the catalyst,
generally solutions of the nitrates of copper and zinc are used,
and the precipitation is preferably performed with an aqueous
K2CO3 solution. The concentration of the solution is preferably
from 5 to 20% by weight. Instead of the nitrates, it is also
possible to proceed from the corresponding metal formates or
acetates. The precipitation can also be performed with the aid
of a potassium hydrogen carbonate solution. The precipitation
can be performed batchwise or continuously. Preference is given
to performing the precipitation by continuously combining the
solution of the nitrates of copper and zinc which comprises the
aluminum hydroxide distributed in colloidal form with aqueous


K2CO3 solution. After the precipitation, the washed precipitate
of the catalyst is calcined and alkalized by treatment with a
solution of an alkali metal compound. The alkalized catalyst
precursors are, after drying, compressed to shaped bodies in a
manner known per se, for which lubricants such as graphite can
be added. In order to convert the catalyst precursor to an
active form, it is reduced with hydrogen.
WO 03/053569 A1 discloses a catalyst for methanol synthesis,
which comprises copper oxide and zinc oxide as catalytically
active substances and aluminum oxide as a thermally stabilizing
substance. To prepare the catalyst, the corresponding
hydroxocarbonates or hydroxides are precipitated from a solution
which comprises the Cu and Zn salts and a portion of the Al
salts with an alkali metal carbonate or alkali metal aluminate
solution. Either the solution of the Cu and Zn salts or the
alkali metal carbonate or alkali metal aluminate solution
comprises an aluminum hydroxide sol. The precipitate obtained is
removed from the precipitation solution, washed, dried and
optionally calcined. In the preparation of the catalyst, the
starting materials are preferably the copper and zinc nitrates,
which are preferably precipitated with sodium carbonate or
sodium aluminate.
JP 2001-144779 describes a copper-zinc catalyst for the reaction
of carbon monoxide and water to give carbon dioxide and water,
which is prepared by mixing a solution which comprises copper
formate and zinc formate with an aqueous solution of an alkali
metal material. The resulting precipitate is subsequently
filtered, washed, dried and calcined. The calcined solid is
slurried by adding water and applied to the surface of a
honeycomb carrier. The binder used may be aluminum oxide sol or
zirconium oxide sol. These are added to the slurry of the
calcined precipitate. The aluminum oxide is therefore not
distributed homogeneously in the catalyst but rather arranged


merely between the catalyst particles. It thus merely has the
task of acting as a binder between the copper- and zinc-
containing catalyst particles and the honeycomb carrier, and is
not an active part of the catalyst.
For the preparation of Cu/Zn/A1 catalysts for the methanol
synthesis, copper nitrates and zinc nitrates are usually used in
industrial processes owing to their good water solubility. In
the precipitation, wastewaters which comprise large amounts of
sodium nitrate are therefore obtained. On introduction into
surface waters, this would lead to overfertilization. Before
introduction into surface waters, the content of water-soluble
nitrogen in the wastewater obtained in the preparation of the
methanol synthesis catalyst must therefore be reduced
drastically.
It is therefore an object of the invention to provide a process
for preparing Cu/Zn/Al catalysts which firstly enables a
significant reduction in the salt burden, especially of alkali
metal nitrates, in the wastewater, and which secondly provides
catalysts for the methanol synthesis which have at least a
comparable activity to a catalyst prepared from metal nitrates.
This object is achieved by a process having the features of
claim 1. Advantageous embodiments of the process form the
subject matter of the dependent claims.
In the process according to the invention for preparing Cu/Zn/Al
catalysts, a first aqueous solution which comprises at least
copper formate and zinc formate is first prepared. In addition,
a second solution which comprises a precipitant is prepared. A
precipitant is understood to be a reagent which directly or
indirectly provides ions, for example hydroxyl ions and/or
carbonate ions, with which the metals, especially copper, zinc
and aluminum, can be precipitated. The first solution and/or the
second solution comprises an aluminum hydroxide sol/gel mixture.


An aluminum hydroxide sol is understood to mean a finely
dispersed distribution of aluminum hydroxide in water, in which
polyacids have already formed by condensation of aluminum
hydroxide, but still no particles are perceptible with the naked
eye in the aqueous phase, i.e. a clear solution is present. An
aluminum hydroxide gel is understood to mean a dispersion of
aluminum hydroxide in water where relatively large agglomerates
of polyacids have already formed, such that particles can be
perceived even with the naked eye, for example as opacity of the
aqueous phase.
In a precipitation step, the first solution and the second
solution are combined to obtain a precipitate. The precipitate
is removed from the aqueous phase, and the aqueous phase forms
wastewater which is sent to a workup.
The precipitate is washed until it has an alkali metal content
of less than 500 ppm based on the catalyst calcined at 600°C.
Subsequently, the precipitate is dried, optionally calcined and
ground.
In the process according to the invention, no nitrate-containing
wastewaters are obtained. As a result of the use of copper
formate and zinc formate as water-soluble copper and zinc salts,
the wastewater comprises formate ions which can be worked up in
a simple manner. Through the use of formates, the contamination
of the wastewater with organic material is kept relatively low.
This is an advantage over the use of higher carboxylic acids,
such as acetic acid, since they increase the organic
contamination in the wastewater through the greater number of
C-H bonds. As a further advantage, formic acid, which is
required for the preparation of the copper formates and zinc
formates, can be prepared inexpensively, so that the process
according to the invention is also advantageous from cost
aspects.


For the process according to the invention, it is essential that
at least a portion of the aluminum is introduced into the
precipitation solution in the form of an aluminum hydroxide sol
and another portion as an aluminum hydroxide gel. When the
addition of the aluminum hydroxide sol/gel mixture into the
solution of the metal salts is dispensed with, the weight-time
yield falls (WTY, [kg of methanol/{kg of catalyst x hour}]).
After the removal, the precipitate is washed carefully, such
that its alkali metal content, based on the oxidic catalyst
calcined at 600°C, falls to values of less than 500 ppm,
preferably less than 400 ppm, especially to values in the range
from 100 to 300 ppm. The washing water obtained can be combined
with the formate-containing wastewater and optionally worked up.
After the washing, drying and optionally calcining, the oxidic
form of the catalyst still has a residual formate content of
less than 5% by weight, preferably from 0.5 to 4% by weight,
especially preferably 1 - 2% by weight. The formate content can
be determined, for example, by oxidative titration or by
quantitative chromatographic processes, for example HPLC.
As well as the copper formate and the zinc formate, the first
aqueous solution may also comprise customary promoters, for
example calcium, magnesium, manganese, cerium, lanthanum, and
also ruthenium or palladium. As well as the promoters mentioned,
it is also possible for other promoters to be used. The
promoters are preferably likewise introduced in the form of
their formates, preferably into the first aqueous solution.
Their proportion in the oxidic form of the catalyst is,
calculated as the oxide, preferably less than 10% by weight,
especially less than 5% by weight. When noble metals, such as
ruthenium or palladium, are used as promoters, they are present
preferably in amounts of less than 1% by weight.


As already mentioned, in the process according to the invention,
the first and/or the second solution comprises an aluminum
hydroxide sol/gel mixture. The starting material used for the
aluminum hydroxide sol /gel may, for example, be a commercially
available product. The aluminum hydroxide sol/gel mixture can,
though, also be obtained by adding a little ammonium hydroxide
to a dilute aluminum salt solution while avoiding heating in
order to delay the conversion to coarsely dispersed hydroxo
derivatives. In a further variant, a small amount of acid can be
added to an alkali metal aluminate solution to form the aluminum
hydroxide sol/gel. The aluminum hydroxide sol/gel is preferably
present in the first aqueous solution. The conversion products
formed from the aluminum hydroxide sol/gel serve both as
supports and as thermally stabilizing substances. Without being
bound to this theory, the inventors suspect that the aluminum
hydroxide sol/gel mixture, in the course of heating, forms a
three-dimensional network in whose gaps the copper crystals
which belong to the active species and are present after the
reduction are arranged. As a result, further growth of the
copper crystals during the methanol synthesis becomes more
difficult, which increases the stability of the catalyst and its
lifetime in industrial processes.
Zinc oxide is assumed firstly to exert an important influence on
the formation of the active species and secondly to contribute
to the stability of the catalyst through its partially
needlelike structure. Moreover, the zinc oxide acts as a
scavenger of poisons by reacting with any sulfur compounds which
occur.
The oxides of calcium, of magnesium, of manganese, of cerium and
of lanthanum which may be present as promoters likewise have a
stabilizing action.


The first solution, which comprises a mixture of different metal
salts, is preferably prepared by
preparing an aqueous copper formate solution by
dissolving a copper salt without residue by adding
formic acid,
preparing an aqueous dispersion or solution of a
zinc salt,
preparing an aqueous aluminum salt solution, and
combining the copper formate solution, the
dispersion or solution of the zinc salt and the
aluminum salt solution.
When the Cu/Zn/A1 catalyst is still to be modified by promoters,
they may, for example, be added to the first solution. The
promoters may be added in the form of suitable salts, for
example as carbonates, oxides or hydroxides. In principle, these
salts may be added at any time, i.e. to the copper formate
solution, to the dispersion or solution of the zinc salt, or
else after combination of the copper formate solution and of the
dispersion or solution of the zinc salt. Particularly expensive
promoters, such as noble metals, are preferably added to the
suspension in a later process step, for example before the spray
drying, or sprayed onto the dry powder in ultrafinely
distributed form after the spray-drying.
In the preparation of the copper-zinc formate solution,
preference is given to adding sufficient formic acid that, based
on the amount of copper salt and zinc salt used, taking account
of the stoichiometry, the formic acid is present in an excess of
at least 10 mol%, preferably from 10 to 20 mol%, especially
preferably from 14 to 16 mol%. After the addition of the formic
acid, the pH of the copper formate solution is preferably less
than 3, preferably less than 2.5.


In a preferred process version, the solution or dispersion of
the zinc salt is combined with the copper formate solution.
After the copper formate solution or dispersion and the zinc
salt solution or dispersion have been combined, both the copper
and the zinc are present in the form of their formates in
solution. The resulting solution preferably has a pH in the
range from 3.0 to 4.0, especially preferably from 3.5 to 3.7.
Subsequently, the aluminum salt solution is added to the
copper/zinc solution.
The aluminum salt solution is preferably added to the
copper/zinc solution in several portions. In this case, at least
one first portion of the aluminum salt solution is prepared by
dissolving at least a first portion of the aluminum salt in
water with addition of formic acid.
In the preparation of the first portion of the aluminum salt
solution, the procedure is preferably first to dissolve sodium
aluminate, for example, in water and then to add sufficient
formic acid that the pH is in the range of less than 5,
preferably from 4.5 to 2, especially from 4 to 3. Preferably
sufficient formic acid is added to obtain a clear solution.
Preference is given to preparing a second portion of the
aluminum salt solution by dissolving a second portion of the
aluminum salt in water. In this case, no formic acid is added to
the second portion of the aluminum salt solution. To complete
the first solution, which comprises the mixture of all metal
salts before the precipitation, the first portion of the
aluminum salt solution and the second portion of the aluminum
salt solution, preferably offset in time, are preferably added
to the aqueous copper/zinc solution.
The second portion of the aluminum salt solution is prepared,
for example, by dissolving NaAlO2 in water. The pH of the
aqueous NaAlO2 solution is, depending on the alkali excess in


the reactant, in the range from 11 to 14, preferably from 12 to
13.
The proportions of the first and second portion of the aluminum
salt solution may, based on the aluminum content, be selected
within the range from 0:100 to 100:0, preferably from 1:99 to
99:1, more preferably from 30:70 to 70:30 and especially
preferably at about 50:50.
The aluminum salt solutions are prepared preferably at
temperatures of less than 40°C, especially preferably less than
30°C. This temperature should also not be exceeded when the
aluminum salt solution is added to the copper/zinc solution or
to the copper formate solution or to the dispersion or solution
of the zinc salt. In this way, the formation of coarsely
dispersed polymeric aluminum compounds is suppressed. Coarsely
dispersed polymeric aluminum compounds are understood to mean
complex aluminum hydroxo compounds which form particles which
are visible to the eye and sink relatively rapidly. Preference
is therefore given to preparing the solutions in a tank which is
equipped with an appropriate cooling device.
Aluminum salts which can be used in a suitable manner in the
process according to the invention are, for example, aluminum
di- and triformate, Al(NO3)3 hydrates or NaAlO2. The aluminum
salt solutions preferably have an aluminum concentration in the
range from about 0.4 to about 1.1 mol/1, especially preferably
from about 0.9 to 1.1 mol/1. The upper value of the range
specified is determined by the solubility limit of the aluminum
salt, while the lower limit arises from economic considerations.
The copper salts used are preferably those salts whose anions
are oxides, hydroxides and carbonates or their derivatives
obtained by reduction, and can no longer be detected separately
by means of distinguishable elements in the first solution or in


the oxidic form of the catalyst. The copper salt is preferably
selected from CuO, Cu(OH)2 and Cu (OH)2.CuCO3 .
The zinc salt selected is preferably likewise a zinc compound
whose anion is not disruptive in the first solution or in the
oxidic precursor of the catalyst, and is preferably not
detectable as a distinguishable element. The zinc salt selected
is preferably ZnO.
The concentration of the copper formate solution is preferably
selected such that, after the copper formate solution and zinc
salt solution or dispersion have been combined, the
concentration of the copper is set within a range of from about
0.1 to about 0.5 mol/1, especially preferably from 0.3 to about
0.5 mol/1. The upper limit is determined by the solubility limit
of the copper salt, while the lower limit arises from economic
considerations, since the processing of dilute solutions gives
rise to relatively large volumes, which influences, for example,
the dimensioning of the apparatus in which the process according
to the invention is performed.
The concentration of the zinc salt is preferably selected such
that, after the copper formate solution and zinc salt solution
or dispersion have been combined, the concentration of the zinc
is preferably within the range from about 0.1 to about
0.2 mol/1, preferably from 0.15 to about 0.2 mol/1. The upper
limit arises here too from the solubility of the zinc salt, and
the lower limit from economic considerations.
The aluminum salt solution is preferably added to the
copper/zinc solution. The pH of the first solution, which
preferably comprises the total amount of Cu, Zn and Al, is then
preferably adjusted to a value in the range from 4.0 to 5.0,
more preferably from 4.2 to 4.4.

The precipitation reagent used is preferably an alkali metal
base. The alkali metal bases used are preferably alkali metal
carbonates, alkali metal hydrogencarbonates or alkali metal
aluminates. The alkali metal used is preferably sodium. When,
for example, a sodium carbonate solution is used as the
precipitation reagent, the sodium carbonate solution preferably
has a concentration of from 80 g/1 to 200 g/1, preferably from
170 to 180 g/1.
In a further embodiment of the process according to the
invention, the precipitation reagent used is hydrogen peroxide.
The hydrogen peroxide is added to the first solution or
dispersion, which comprises copper, zinc and aluminum in the
form of their formates or hydroxoformates. The hydrogen peroxide
oxidizes the formate to carbonate, so that the metals are
precipitated in the form of their hydroxocarbonates, carbonates
or hydroxides. In the oxidation of the formate anion, first the
hydrogencarbonate anion and then the carbonate anion are formed
with rising pH. The metal ions used are precipitated as
hydroxocarbonates in a sequential precipitation in the series of
Al-Cu-Zn. The use of a carbonate-containing alkali metal
solution can thus be dispensed with. In addition to hydrogen
peroxide, it is also possible to use other suitable oxidizing
agents, for example ozone.
To prepare the oxidic catalyst precursor, first and second
solution are first combined to obtain a precipitate. The
precipitation is preferably performed in such a way that, during
the precipitation, a pH in the range from 3.5 to 7.5, preferably
from 6.0 to 7.0, especially preferably 6.5 ± 0.1, is maintained.
The temperature during the precipitation is preferably kept
within a range from 2 5 to 95°C, especially preferably from 50 to
75°C.


After the mixing, the precipitate formed is preferably aged. To
this end, the suspension obtained in the mixing of first and
second solution can, for example, be transferred to an aging
vessel in which the suspension can be moved, for example, with a
suitable stirrer.
The aging is performed preferably over a period of from
10 minutes to 10 hours, especially preferably from 1 to 5 hours.
During the aging, the suspension is preferably heated, the aging
being effected especially at a temperature of more than 60°C,
especially preferably within the range from 65 to 80°C.
The combination of first and second solution is preferably
performed in such a way that the solutions are introduced in
parallel into a mixing vessel and mixed there. Rapid mixing is
effected therein, for example by means of a suitable stirrer.
However, preference is given to performing the precipitation as
a continuous precipitation. To this end, an appropriately
dimensioned mixing vessel is provided, into which first and
second solution are fed continuously and the resulting mixture
is removed continuously. The volume of the mixing vessel is
preferably selected such that first and second solution can be
fed continuously into the mixing vessel and the mixture can be
removed continuously, the residence time of the mixture being
preferably within the range from about 0.1 second to 10 minutes,
more preferably from about 1 to 120 seconds, especially
preferably from 1 to 20 seconds.
The residence time of the mixture in the mixing vessel depends
greatly upon the dimensioning of the mixing vessel and the flow
rate. The dimensioning of the mixing vessel and the feed and
removal rates of the solutions or suspension can be selected in
a suitable manner correspondingly by the person skilled in the
art.


After the precipitation and any aging step performed, the
precipitate is removed from the aqueous phase, for which
customary processes can be used, for example a filtration. The
precipitate is subsequently washed and dried. The precipitate is
preferably calcined after drying. Depending on the process used,
the calcination is effected at temperatures of preferably from
140°C to 1000°C, especially preferably from 170°C to 350°C, for
a period of at least 0.1 second, preferably at least 4 minutes,
more preferably from 20 minutes to 8 hours, especially
preferably from 30 minutes to 4 hours. Depending on the
calcination conditions selected, the formate remaining in the
filtercake, in the course of calcining, is largely eliminated
oxidatively under air or by an intramolecular redox reaction
under inert gas. In the latter case, the Cu (HCO2)2.H2O is
suspected to be decomposed first to H2 and CuC2O2. The copper
oxalate then reacts further to give CO2 and elemental copper.
The calcination can be performed in customary apparatus. In an
industrial manufacture, owing to the better heat transfer, both
pulsation reactors and fluidized bed reactors, such as the
commercially preferred rotary tube ovens, are used. Pulsation
dryers enable very short drying times in the region of less than
1 second, generally within the range from 0.1 second to
4 minutes, and very high temperatures of up to 1000°C may be
employed.
The calcined powder can optionally be ground and then processed
by means of customary tools, for example to tablets or
extrudates. However, it is also possible to slurry the powder,
to grind it to a very fine particle size and to coat suitable
support bodies, for example honeycombs, with the resulting
suspension. It is possible here to employ customary processes.
The particle size is suitably adjusted such that the mean
particle size D50 is in the range from 10 nm to 10 µm,
especially preferably from 100 nm to 5 µm. The mean particle


size can be determined, for example, by laser light scattering.
Suitable catalysts can be prepared, for example, with particle
sizes in which the D50 value is in the range of about 2-3 µm.
A particular advantage of the process according to the invention
is that the formate-containing wastewater obtained after the
removal of the precipitate can be worked up by comparatively
simple means. For this purpose, the formate-containing
wastewater is preferably subjected to an oxidative treatment,
which oxidizes the formate ions in the aqueous solution,
depending on the pH, essentially to carbonate,
hydrogencarbonate, carbon dioxide and water. The content in the
wastewater of formate, for example in the form of sodium
formate, in an industrial implementation of the process
according to the invention, is typically in the range from 0.2
to 1.5 mol/1, especially preferably from 0.8 to 1.0 mol/1,
although it is also possible for higher or lower formate
concentrations to be present. The oxidative treatment of the
wastewater allows the formate concentration to be lowered to
values of less than 0.1 mol/1, preferably from 0.01 to
0.075 mol/1, especially preferably from 0.02 to 0.04 mol/1. This
corresponds to a lowering in the amount of formate present in
the wastewater by more than 95%.
In a preferred embodiment, hydrogen peroxide is added to the
formate-containing wastewater for oxidative treatment. The
hydrogen peroxide is preferably added to the formate-containing
wastewater in the form of a solution whose hydrogen peroxide
concentration is in the range from about 9 to 20 mol/1 (up to
approx. 60% by weight). In the case that the relevant transport
regulations are complied with, the concentration of the hydrogen
peroxide solution used can be increased up to above 90% by
weight. Preference is given to adding the hydrogen peroxide in
excess, in which case the amount added, based on the formate
present in the wastewater, is selected within the range from 160


to 200 mol%, especially preferably from 160 to 170 mol%. As well
as hydrogen peroxide, it is also possible to use other oxidizing
agents, for example ozone or sodium hypochlorite solution. In
the selection of the oxidizing agents, for example, production
costs and environmental legislation play a role. Depending on
the legal limits and the further purification stages available,
it is under some circumstances not necessary to oxidize the
entire amount of the formate ions. It may actually be sufficient
to considerably reduce the concentration of the formate ions by
a chemical oxidative treatment and to feed the wastewater thus
treated optionally, for example, to a biological clarification
stage.
The treatment of the formate-containing wastewater with hydrogen
peroxide is performed preferably at from 20 to 95°C, especially
preferably at from 50 to 80°C, within a pH range of 4 - 8,
especially preferably from 5.0 to 6.5.
In one embodiment of the process according to the invention, the
oxidative treatment of the formate-containing wastewater is
effected actually before the removal of the precipitate. To this
end, after the aging step, for example, a suitable amount of
hydrogen peroxide can be added to the suspension and the
precipitate can be removed only after the substantial oxidative
degradation of the formate ions. Alternatively, in the course of
the process with time, the hydrogen peroxide solution can also
be added actually to the Cu-, Zn-, Al-containing formate
solution, in which case the precipitation reagent, carbonate
ions, is generated from formate ions by oxidation.
The oxidative workup of the wastewater by adding a suitable
oxidizing agent, such as hydrogen peroxide, is quite simple to
perform in apparatus terms and also enables the treatment of
wastewaters which have a relatively high concentration of
formate ions. However, it is also possible that the oxidative


treatment is effected solely by a biological treatment of the
formate-containing wastewater. If appropriate, the formate-
containing wastewater can be diluted to a suitable concentration
for this purpose.
The oxidative treatment of the formate-containing wastewater is
preferably performed in such a way that the formate
concentration in the wastewater after the oxidative treatment is
less than 0.1% by weight.
When the Cu/Zn/A1 catalyst obtained using the formates is
compared with catalysts which have been prepared starting from
the nitrates, the catalyst obtained by the process according to
the invention exhibits a better to comparable activity and a
comparable selectivity. The long-term stability of the catalyst
prepared using the formates, which has been determined in the
methanol synthesis test at 250°C, is also somewhat better than
or at least comparable with the stability of a catalyst which
has been prepared starting from the metal nitrates. The
invention therefore also provides a catalyst which can be
prepared by the above-described process.
The inventive catalyst contains, in its oxidic form, less than
5% by weight, preferably between 0.5 and 4% by weight,
especially preferably between 1 and 2% by weight of formate,
calculated as formic acid. Gentle calcination allows
preservation of the formate structure which, according to the
lock-and-key principle which is frequently encountered in
catalysis, can play an important role for the attainment of a
high activity. A gentle calcination at about 170°C for 4 minutes
forms a catalyst which exhibits a very high activity at 250°C.
The inventive catalyst features a high mesopore volume. The
proportion of mesopores having a radius of from 3.75 to 7.0 nm
in the total pore volume is preferably more than 30%, preferably
from 30 to 80%. The total pore volume includes the volume of the


pores having a radius of from 3.75 to 7500 nm. The pore volume
can be determined by the mercury intrusion method. The total
pore volume, determined on 6 x 4 mm tablets, is preferably
100 mm3/g - 700 mm3/g, preferably 250 mm3/g - 450 mm3/g.
The proportion of the copper, calculated as CuO and based on the
weight of the oxidic catalyst form, taking account of the
ignition loss at 600°C, is selected preferably between 55 and 69
by weight, especially preferably 60 and 63 by weight.
The proportion of the zinc, calculated as ZnO and based on the
weight of the oxidic catalyst form, taking account of the
ignition loss at 600°C, is selected preferably between 20 and
33% by weight, especially preferably between 25 and 31% by
weight.
The proportion of aluminum, calculated as Al2O3 and based on the
weight of the oxidic catalyst form, is selected preferably
between 5 and 20% by weight, especially preferably between 8 and
11% by weight.
The percentages for the proportions of the copper, zinc and
aluminum are based on a catalyst calcined at 600°C for three
hours.
The inventive catalyst also has, in the oxidic form, an alkali
metal ion content, especially sodium ion content, of preferably
less than 500 ppm, especially preferably less than 300 ppm,
especially from 100 ppm to 300 ppm.
In its oxidic form, the inventive catalyst preferably has a
specific surface area of more than 90 m2/g, especially
preferably more than 100 m2/g.
The inventive catalyst can in principle be molded as shaped
bodies with any shape. For example, it can be configured in the
form of rings, 3-20 hole shaped bodies, tablets with a smooth or


undulating surface, or honeycombs. The dimensioning of the
shaped bodies corresponds to the customary values. For the
preparation of the shaped bodies, the pulverulent catalyst,
optionally with addition of a lubricant, such as graphite, is
compressed, for example to tablets of, for example, 6x4 mm.
Before use, the catalyst is converted from the oxidic form to
the active form. To this end, the copper oxide is at least
partly reduced to elemental copper. For this purpose, the oxidic
form of the inventive catalyst is preferably reduced in a
hydrogen stream. The activation can be effected directly within
the synthesis reactor and is preferably done by reducing first
with the aid of an inert gas, such as nitrogen, comprising a
small amount of hydrogen. The nitrogen typically contains
initially about 2.0% by volume of H2. In this case, the
temperature is raised, for example, from 100 to 235°C over a
period of 16 hours. Thereafter, the hydrogen content is
increased, and reduction is effected, for example, with 20% by
volume of H2 (remainder N2) within the temperature range from
235 to 270°C over a period of 3 hours. The reductive treatment
can be completed with 99.9% H2 at from 270°C to 300°C over a
period of about 3 hours. Typically, activation is effected with
a superficial velocity of from about 3000 to 4000 liters of
reduction gas per hour and liter of catalyst.
In the reduced state, the size of the copper crystals is
preferably from about 4 to 12 nm, preferably from 5 to 7 nm.
The inventive catalyst is suitable especially for use in
methanol synthesis. The invention therefore also provides for
the use of the above-described catalyst for synthesizing
methanol from CO, CO2 and H2. The synthesis is typically
performed at a temperature of from about 200 to 320°C,
preferably at from 210°C to 280°C, at a pressure of from about
40 to 150 bar, preferably at from about 60 to 100 bar, and at a


superficial velocity of from about 2000 to 22 000, preferably
from 8000 to 12 000, liters of synthesis gas per hour and liter
of catalyst, and the synthesis gas may contain from about 5 to
25% by volume, preferably from 6 to 12% by volume, of CO, from
about 4 to 10% by volume of CO2, from about 10 to 30% by volume
of N2 plus CH4 (inert gases) and, as the remainder, H2.
The inventive catalyst is also suitable for use in methanol
reformation and in the low-temperature conversion of carbon
monoxide to carbon dioxide. The latter reaction, also referred
to as the low-temperature shift (LTS), is effected at
temperatures in the range from about 175 to 250°C, preferably
from 205 to 215°C, and steam/gas ratios in the range from about
0.4 to 1.5 (1 (STP)/1 (STP)). Typical feed gas mixtures contain
about 3% by volume of CO, 17% by volume of CO2, 2% by volume of
N2 and 7 8% by volume of H2, which are passed through the reactor
with superficial velocities of from about 2000 to 12 000 1 of
dry gas (i.e. without water) per liter of catalyst and hour.
Good catalysts achieve, at a superficial velocity of 11 200 h-1
and a ratio of steam to gas of about 1.5, CO conversions of from
70 to 85%.
The invention is illustrated in detail hereinafter with
reference to examples.
EXAMPLE
(a) Preparation of the copper solution
5054 g of a suspension of Cu(OH)2.CuCO3 (Cu content: 27.7% by
weight, corresponding to 1400 g of Cu) are dispersed in a 10 1
beaker and admixed in portions with a total of 2399 ml of 85%
formic acid (D = 1.1856 g/cm3) until the CO2 evolution has
ended. The copper solution has a pH of 2.35 and a temperature of
55°C.


(b) Preparation of the Cu/Zn solution (precursor to first
solution)
In a 5 1 beaker, a ZnO dispersion is prepared from 7 81 g of ZnO
and 4000 ml of H2O. The suspension is combined with the copper
solution obtained in (a) . With continued dispersion, a further
890 ml of formic acid and 33.6 1 of demineralized water are
added in portions. The blue, initially still slightly opal
solution is stirred until it is completely clear.
(c) Preparation of the sodium carbonate solution (second
solution)
24 000 ml of Na2CO3 solution which has a concentration of
approx. 180 g of CO3/100 ml are prepared, and the solution is
heated to 7 0°C.
(d) Preparation of the aluminum solution I
A 5 1 stirred apparatus provided with a cooling device is
initially charged with 2193 ml of demineralized water and
246.7 g of NaAlO2 are added. The solution is heated to a
temperature of not more than 30°C, and then 350 ml of formic
acid are added in portions. The milky solution has a pH of
approx.4.0.
(e) Preparation of the aluminum solution II
A stirred apparatus provided with a cooling device is initially
charged with 2193 ml of water, and 246.7 g of NaAlO2 are added
in portions. It is ensured that the temperature of the solution
does not exceed 30°C. The mixture is stirred until a clear
solution is obtained.
(f) Precipitation
The solution obtained in (b) is transferred to a first reservoir
tank of a mixing apparatus. Subsequently, the aluminum solution


I obtained in (d) is introduced into the tank and stirred there
at room temperature until the combined solutions are completely
clear. Water can optionally be added in order to eliminate the
opalescence of the solution. Before the start of precipitation,
the solution is heated to 70°C. Approx. 30 minutes before the
start of precipitation, the aluminum solution II obtained in (e)
is transferred into the tank, which forms a milky, white-bluish
suspension.
The Na2CO3 solution obtained in (c) is introduced into a second
reservoir tank and heated to 70°C.
The solutions present in the first and second tank are
simultaneously fed to a mixing apparatus and, after a residence
time of about 20 s, pass from there into an overflow vessel. The
pumping rates are adjusted such that the pH during the
precipitation is about 6.5 ± 0.1. From the mixing apparatus, the
mixture passes into an overflow vessel. From the overflow
vessel, the suspension formed passes into an aging vessel, where
it is kept at approx. 65°C with stirring. The precipitation has
ended after approx. 35 minutes. Subsequently, the unit is
flushed with approx. 600 ml of demineralized water and the
temperature in the aging vessel is increased to 70°C. After the
flushing operation has ended, the suspension is aged with
stirring. The commencement of the aging is defined by the end of
the flushing operation. The aging times employed in the examples
are specified in table 2.
After the aging has ended, the suspension is filtered and washed
with demineralized water until the residual content of sodium in
the filtercake has fallen to less than 350 ppm, and the
resulting solid is dried by spray-drying using a one-substance
nozzle in countercurrent. The feed established is a suspension
with a dry substance content of 30% by weight. The heating gas
entrance temperature is 330 - 350°C, the product exit


temperature 110 - 120°C. The dried powder is subsequently
calcined at about 320°C for 50 minutes either in porcelain
dishes in a staged oven or in a batchwise laboratory rotary tube
oven.
(g) Treatment of the wastewater
The wastewater obtained in the filtration and the washing is
treated by adding hydrogen peroxide, the pH being kept between 5
and 6.5 with sulfuric acid and the temperature of the wastewater
at approx. 7 0°C. The formate concentration of the wastewater is
adjusted to values between 2.8% by weight and 0.09% by weight.
The selectivity, defined as mol of formate converted/mol of
hydrogen peroxide used, is approx. 60%.
COMPARATIVE EXAMPLE
(a) Preparation of a copper/zinc nitrate solution
781.25 g of zinc oxide are added to 9.79 kg of a copper nitrate
solution which contains 1400 g of copper. 2 077 g of nitric acid
(58%) are then added and the mixture is stirred until the solids
have dissolved completely.
(b) Preparation of an aluminum nitrate solution
246.7 g of Na2AlO2 are dissolved in 1.5 1 of demineralized
water. 1365 g of nitric acid (58%) are then added and the
mixture is stirred until a clear solution is obtained. The
aluminum nitrate solution obtained is added to the copper/zinc
nitrate solution and the Cu/Zn/Al solution is heated to 60°C.
(c) Preparation of the aluminum sol
246.7 g of Na2AlO2 are dissolved in 1.5 1 of demineralized water
with stirring over 30 minutes. The resulting solution is added
to the Cu/Zn/Al solution and the mixture is heated to 60°C.

(d) Precipitation
The mixture obtained in (c) is introduced into the first
reservoir tank of a mixing apparatus. 25 1 of an aqueous
solution which contains 172 g of Na2CO3 per liter are introduced
into the second reservoir tank of the mixing apparatus. The two
solutions are pumped simultaneously into a mixing vessel and the
mixture is passed from there into an aging vessel.
After the end of precipitation, the mixing vessel is flushed
with demineralized water, the temperature in the aging vessel is
increased to 7 0°C and the precipitate is aged for 1 or 4 hours.
After the aging has ended, the suspension is filtered and washed
with demineralized water until the residual content of sodium in
the filtercake has fallen to less than 350 ppm, and the
resulting solid is dried in countercurrent by spray-drying using
a one-substance nozzle. The heating gas entrance temperature is
330 - 350°C, the product exit temperature 110 -120°C. The dried
powder is subsequently calcined at about 320°C for 50 minutes
either in porcelain dishes in a staged oven or in a batchwise
laboratory rotary tube oven.
The precipitation examples performed and the calcination
conditions employed thereafter are compiled in tables 2a + b.
Likewise included in these tables are the chemical compositions
and the physical parameters of the resulting oxidic catalyst
precursors.
The determination of the physical parameters is undertaken in
the following manner:
Determination of the Cu crystal size:
The size of the Cu crystals is determined by means of X-ray
powder diffractometry (XRD). The Cu (111) reflection in the
region of ~ 43.3°(2D) is analyzed. The half-height width and the
integral intensity of the reflection are calculated with the

pseudo-Voigt function. The Cu crystal size is calculated with
the aid of the Scherrer function on the basis of the calculated
half-height width.
For preparation for the X-ray determination of the crystal size,
the oxidic catalysts are reduced as follows:
2 - 5 g of tablets having a size of 6 x 4 mm are heated in a
tube reactor from room temperature to a maximum temperature at a
heating rate of 2°C/min with a reduction gas (98% N2, 2% H2) .
Catalysts which have been prepared from the formates are heated
to a maximum temperature of 80 - 120°C. Catalysts which have
been prepared using the nitrates are first heated to 175°C
overnight. Subsequently, within less than 2 hours, the maximum
temperature is established: 180°C for catalysts from a) the
formate/carbonate route; 240°C for catalysts from b) the
nitrate/carbonate route. While maintaining the maximum
temperature, the hydrogen content of the reduction gas is
finally increased to 100% within one hour and then the sample is
reduced for a further 3 hours.
Determination of the specific surface area
The BET surface area is determined by the one-point nitrogen
method on the pulverulent oxidic catalyst and on 6 x 4 mm
tablets on the basis of DIN 66132.
Determination of the ignition loss
When the ignition loss is to be determined on tablets, they are
first ground to a powder. The sample to be determined is weighed
into a weighed porcelain crucible which had been heated
beforehand at 600°C in a muffle furnace for 3 hours and then
cooled to room temperature in a desiccator. The crucible is
heated to 600°C in a muffle furnace for 3 hours and then cooled
to room temperature in a desiccator. The cooled crucible is


weighed again and the ignition loss at 600°C is determined from
the difference.
Determination of the side crushing strength
The side crushing strength is determined to DIN EN 1094-5, 1995-
09 edition, feuerfeste Erzeugnisse fur Isolationszwecke
[Refractory products for insulation purposes] - part 5:
Bestimmung der Kaltdruckfestigkeit geformter Erzeugnisse
[Determination of the cold compressive strength of molded
products] . The determination is performed with a commercial
instrument such as Schleuninger 6-D or ERWEKA TBH 310 MD
according to the instrument manufacturer's instructions.
For a representative sample amount of 100 tablets, the pressures
acting on their cylinder layer in the bursting operation are
determined and evaluated with the instrument's own statistics
program for mean, standard deviation and minimum and maximum
hardness. The distribution of the tablet hardness (N) is shown
in graphic form.
Determination of the pore volume
The pore volume is determined by the mercury intrusion method on
the basis of DIN 66133 on the pulverulent oxidic catalysts and
on 6 x 4 mm tablets.
Determination of the formate content
Approx. 10 to 20 g of the calcined catalyst powder are taken up
in 25 + x ml of H2SO4 (25%) and dissolved with heating to
approx. 70°C in a 300 ml Erlenmeyer flask. The amount x ml of
H2SO4 (25%) is determined by the minimum amount of sulfuric acid
which may be additionally required to achieve complete
dissolution of the amount weighed in. The mixture is made up to
approx. 100 ml with distilled water. Addition of approx. 2.5 to
25 ml of NaOH (30%) adjusts the solution to a pH of from 8 to


10. The solution is then heated to 70°C for at least a further
5 minutes. Subsequently, 20 ml of KMnO4 solution (0.2 N) are
added and the solution is heated to gentle boiling for at least
30 min. The hot solution is acidified with H2SO4 (25 - 50 ml)
and 20 ml of oxalic acid (0.2 N) are added in order to reduce
manganese dioxide and excess KMnO4 to Mh2+. The oxalic acid
solution added has to correspond exactly to the oxidation
equivalents of the permanganate solution in its content of
reduction equivalents. The clear solution is ultimately titrated
with 0.2 N KMnO4 until a slight pink coloration is observed.
Calculation:
Every ml of 0.2 N KMnO4 solution consumed corresponds to 4.5 mg
of formate. The percentage content of formate in the sample is
found to be:
[% formate] = [(ml of 0.2 N KMnO4 solution consumed) x (4.5 mg
of formate/ml of 0.2 N KMnO4 solution) x 100)/(weight of sample
in mg)]
The method affords verified results for formate concentrations
in the solution to be titrated between 0.08 and 0.5% by weight
with deviations of + /- 2% in the case of use of a 0.02 N permanganate solution.
Owing to the dependence of the method accuracy on the formate
concentration which is unknown per se, it may be necessary to
align the sample weight first to an expected value in order to,
after the first result is present, repeat the titration with an
adjusted sample weight, which then gives rise to formate
concentrations within the abovementioned range for the solution
to be titrated.
The formate contents of the samples from examples 3 and 5 are
reported in table 1.


The physical properties of the catalysts prepared are reported
in table 2. Table 2a is based on the pulverulent catalysts,
while the values from table 2b are based on catalysts which have
been compressed to tablets having the dimensions of 6 x 4 mm.





Methanol activity tests
The oxidized tablets are quartered, and a screen fraction of
from 2.5 to 3.5 mm is filled into a crude reactor and, after
activation, subjected to a standardized activity test with
periodically alternating temperatures. In the evaluation, the
weight-time yields (WTY) in kg (methanol)/(kg (catalyst) x h)
are determined as the mean for one period at constant
temperature in each case. In a test reactor system consisting of
6-16 individual tubes, in a test tube, the catalyst C79-7 from
Sud-Chemie AG, Munich, Germany is used as a standard and the WTY
determined for the other samples is in each case determined
relative to the value for the standard. This process has the
advantage that small variations, for example, in the synthesis
gas composition are the same for all specimens, and the results
from different test runs can thus be compared with one another.
By-products are determined with the aid of gas chromatography
analysis of condensate samples to which an internal standard has
been added in each case. The values determined are likewise
reported relative to the values which are obtained for the
standard.
The results of the methanol activity test are listed in table 3.



CLAIMS
1. A process for preparing Cu/Zn/Al catalysts, characterized
in that

a first aqueous solution which comprises at least
copper formate and zinc formate is prepared,
a second solution which comprises a precipitation
reagent is prepared,
the first solution and/or the second solution
comprising an aluminum hydroxide sol/gel mixture,
in a precipitation step, the first solution and the
second solution are combined to obtain a
precipitate,
the precipitate is removed from the aqueous phase,
which forms wastewater, and
the precipitate is washed until an alkali metal
content, based on the catalyst calcined at 600°C, of
less than 500 ppm is attained and
the precipitate is then dried.
2. A process as claimed in claim 1, characterized in that the
first solution is prepared by
preparing an aqueous copper formate solution by
dissolving a copper salt without residue by adding
formic acid,
preparing an aqueous dispersion or solution of a
zinc salt,

preparing an aqueous aluminum salt solution, and
combining the copper formate solution, the
dispersion or solution of the zinc salt and the
aluminum salt solution.
3. The process as claimed in claim 2, wherein the copper
formate solution has a pH of less than 3, preferably less
than 2.5.
4. The process as claimed in either of claims 2 and 3,
wherein the solution or dispersion of the zinc salt is
combined with the copper formate solution to give a
copper/zinc solution, the resulting copper/zinc solution
having a pH in the range from 3.0 to 4.0, preferably 3.5
to 3.7, and the aluminum salt solution is added to the
copper/zinc solution.
5. The process as claimed in claim 4, wherein the aluminum
salt solution is added in several part-solutions, at least
a first portion of the aluminum salt solution being
prepared by dissolving at least a first part of the
aluminum salt in water with addition of formic acid.
6. The process as claimed in claim 4 or 5, wherein a second
portion of the aluminum salt solution is prepared by
dissolving a second portion of the aluminum salt in water
and, to prepare the first solution, adding the first
portion of the aluminum salt solution and the second
portion of the aluminum salt solution, preferably offset
in time, to the copper/zinc solution.
7. The process as claimed in one of claims 2 to 6,
characterized in that the aqueous aluminum salt solution,
the first portion of the aluminum salt solution and/or the
second portion of the aluminum salt solution, before the

precipitation, is/are heated to temperatures of not more
than 40°C, especially not more than 30°C.
8. The process as claimed in one of the preceding claims,
wherein, during the precipitation step, a pH in the range
from 3.5 to 7.5, preferably from 6.0 to 7.0, especially
preferably of 6.5 ± 0.1, is maintained.
9. The process as claimed in one of the preceding claims,
characterized in that the copper salt is selected from
CuO, Cu(OH)2 and Cu (OH)2.CuCO3.
10. The process as claimed in one of the preceding claims,
characterized in that the zinc salt selected is ZnO.
11. The process as claimed in one of the preceding claims,
wherein the precipitation reagent is an alkali metal base,
preferably an alkali metal carbonate.
12. The process as claimed in one of claims 1 to 10, wherein
the precipitation reagent is hydrogen peroxide.
13. The process as claimed in one of the preceding claims,
characterized in that the precipitate is aged after the
precipitation.
14. The process as claimed in claim 13, characterized in that
the aging is effected over a period of from 10 minutes to
10 hours, preferably from 1 to 5 hours.
15. The process as claimed in claim 13 or 14, characterized in
that the aging is effected at a temperature of more than
60°C, especially in the range from 65 to 80°C.
16. The process as claimed in one of the preceding claims,
characterized in that the precipitation step is performed
as a continuous precipitation.

17. The process as claimed in one of the preceding claims,
characterized in that the first solution comprises copper
and zinc in a ratio which is selected between 1:99 and
99:1.
18. The process as claimed in one of the preceding claims,
characterized in that the precipitate is calcined after
drying.
19. The process as claimed in claim 18, wherein the
precipitate is calcined at temperatures in the range of
140 - 1000°C, preferably 170 - 350°C, for a period of at
least 0.1 second, preferably from 20 minutes to 8 hours,
especially preferably from 30 minutes to 4 hours.
20. The process as claimed in one of the preceding claims,
characterized in that the wastewater comprises formate
ions and the formate-containing wastewater is subjected to
an oxidative treatment, which oxidizes the formate ions
essentially to carbonate, hydrogencarbonate, carbon
dioxide and water.
21. The process as claimed in claim 20, characterized in that
hydrogen peroxide is added to the formate-containing
wastewater for the oxidative treatment.
22. The process as claimed in claim 20 or 21, characterized in
that the oxidative treatment of the formate-containing
wastewater is effected before the removal of the
precipitate.
23. The process as claimed in one of claims 20 to 22,
characterized in that the oxidative treatment is effected
by a biological treatment of the formate-containing
wastewater.

24. A catalyst which has been obtained by a process as claimed
in one of claims 1 to 2 3 and has a formate content, based on
the oxidic catalyst, of less that 5%, preferably 0.5 - 4%,
especially preferably 1-2%.
25. The catalyst as claimed in claim 24, characterized in that
the proportion of mesopores having a radius from 3.75
to 7.0 nm in the total pore volume is more than 30%.
26. The catalyst as claimed in claim 24 or 25, characterized
in that the proportion of copper, calculated as copper oxide
and based on the weight of the oxidic catalyst, is selected
between 55 and 69% by weight.
27. The catalyst as claimed in one of claims 24 to 26,
characterized in that the proportion of zinc, calculated as
zinc oxide and based on the weight of the oxidic catalyst, is
selected between 2 0 and 33% by weight.
28. The catalyst as claimed in one of claims 24 to 27,
characterized in that the proportion of aluminum, calculated as
aluminum oxide and based on the weight of the oxidic catalyst,
is selected between 5 and 20% by weight.
29. The catalyst as claimed in one of claims 24 to 28,
characterized in that the oxidic catalyst has a content of
alkali metal ions of less than 500 ppm.


The invention relates to a process for preparing Cu/Zn/Al
catalysts. In this process, the metals are used in the form of
their formates and are precipitated in a suitable form. Suitable
precipitants are, for example, alkali metal carbonates. The
invention further relates to a catalyst as can be obtained by
the process according to the invention and to its use.

Documents:

03577-kolnp-2007-abstract.pdf

03577-kolnp-2007-claims.pdf

03577-kolnp-2007-correspondence others.pdf

03577-kolnp-2007-description complete.pdf

03577-kolnp-2007-form 1.pdf

03577-kolnp-2007-form 3.pdf

03577-kolnp-2007-form 5.pdf

03577-kolnp-2007-gpa.pdf

03577-kolnp-2007-international publication.pdf

03577-kolnp-2007-pct priority document notification.pdf

03577-kolnp-2007-pct request form.pdf

3577-KOLNP-2007-(27-06-2012)-ASSIGNMENT.pdf

3577-KOLNP-2007-(27-06-2012)-CORRESPONDENCE.pdf

3577-KOLNP-2007-(27-06-2012)-FORM-16.pdf

3577-KOLNP-2007-(27-06-2012)-PA.pdf

3577-kolnp-2007-assignment-1.1.pdf

3577-KOLNP-2007-ASSIGNMENT.pdf

3577-KOLNP-2007-CORRESPONDENCE OTHERS 1.1.pdf

3577-kolnp-2007-correspondence-1.1.pdf

3577-KOLNP-2007-CORRESPONDENCE.pdf

3577-kolnp-2007-examination report.pdf

3577-kolnp-2007-form 18-1.1.pdf

3577-kolnp-2007-form 18.pdf

3577-kolnp-2007-form 3-1.1.pdf

3577-KOLNP-2007-FORM 3.pdf

3577-kolnp-2007-form 5.pdf

3577-KOLNP-2007-FORM-27.pdf

3577-kolnp-2007-gpa.pdf

3577-kolnp-2007-granted-abstract.pdf

3577-kolnp-2007-granted-claims.pdf

3577-kolnp-2007-granted-description (complete).pdf

3577-kolnp-2007-granted-form 1.pdf

3577-KOLNP-2007-GRANTED-FORM 2.pdf

3577-kolnp-2007-granted-specification.pdf

3577-kolnp-2007-others-1.1.pdf

3577-KOLNP-2007-OTHERS.pdf

3577-KOLNP-2007-PETITION UNDER RULE 137-1.1.pdf

3577-KOLNP-2007-PETITION UNDER RULE 137.pdf

3577-kolnp-2007-reply to examination report.pdf


Patent Number 249943
Indian Patent Application Number 3577/KOLNP/2007
PG Journal Number 47/2011
Publication Date 25-Nov-2011
Grant Date 23-Nov-2011
Date of Filing 21-Sep-2007
Name of Patentee SUD-CHEMIE AG
Applicant Address LENBACHPLATZ 6, D-80333 MUNCHEN
Inventors:
# Inventor's Name Inventor's Address
1 POLIER SIEGFRIED FRAUNHOFERSTR. 24, D-83052 BRUCKMUHL
2 HINZE DIETER HERMANN-LONS-STR. 7B , D-83059 KOLBERMOOR
3 HIEKE MARTIN SONNENWIECHSER STR. 21, D-83052 BRUCKMUHL
PCT International Classification Number C01B 3/32,B01J 23/80
PCT International Application Number PCT/EP2006/004091
PCT International Filing date 2006-05-02
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 102005020630.1 2005-05-03 Germany