DE10235064A1 - Preparation of iron-doped ruthenium-on-carbon catalysts, used for selective liquid hydrogenation of carbonyls to corresponding alcohols, involves reducing in hydrogen stream and forming catalyst in difficultly-flammable liquid - Google Patents

Abstract

Two methods are claimed for the production of ruthenium/iron/carbon carrier catalysts containing 0.1-5 wt.% iron as well as 0.1-10 wt.% ruthenium on a carbon carrier. Two methods are claimed for the production of ruthenium/iron/carbon carrier catalysts containing 0.1-5 wt.% iron as well as 0.1-10 wt.% ruthenium on a carbon carrier. The first method involves: (i) addition of a base to a mixture in water of the carrier and a solution containing the catalytically-active ruthenium and iron components so as to effect simultaneous precipitation onto the carrier; (ii) separating the catalyst from the aqueous phase of the suspension; (iii) drying the catalyst; (iv) reducing in a hydrogen stream at 400-600 degreesC; and (v) forming the catalyst in a difficultly-flammable liquid or passivating it with a diluted air stream. The second method proceeds as per step (i) above but this is followed by: (iia) reduction of the catalyst by addition of an aqueous reductant; (iiia) separating from the aqueous phase of the suspension; and (iva) washing with water. An Independent claim is included for the use of the catalyst is in selective liquid hydrogenation of carbonyl compounds of formula R1C(O)R2 (I) to the corresponding alcohols of formula R1C(OH)HR2 (II). R1 and R2 = H, optionally mono- or poly-unsaturated, optionally substituted 1-20C alkyl, optionally substituted aryl or optionally substituted heterocyclic group.

Description

description

The present invention relates to a process for the production of iron-doped ruthenium / carbon supported catalysts as well their use for the selective liquid phase hydrogenation of carbonyl compounds to the corresponding alcohols, especially for the hydrogenation of Citral to geraniol or nerol or from citronellal to citronellol.

Various are from the prior art Processes for the preparation of catalysts known. The proceedings differ essentially in the precursors used of the active components or by the type of deposition of the active Components on the carbon carrier.

EP 071 787 discloses ruthenium / iron / coal hydrogenation catalysts and their preparation and use for the selective hydrogenation of unsaturated carbonyl compounds. The Ru / Fe / carbon catalyst used is produced by impregnating activated carbon powder with ruthenium chloride solution, drying and then mixing it with iron oxide. The catalyst is reduced with hydrogen at 500 ° C.

The use of chlorides prepares however, technical problems, since chloride is highly corrosive. So must when watering and drying the active components in expensive, corrosion-resistant equipment be worked. The reduction produces HCl, which is the reduction furnace damage can and can remain on the catalyst, the chloride Use of the catalyst in the hydrogenation to corrosion in the production reactor to lead can.

If the nitrate salts of ruthenium are used instead of the chlorides, this can lead to a safety problem, since nitrate / coal mixtures can be explosive. Another disadvantage of the described method is the sequential doping with Fe ₂ O ₃ , which requires an additional process step.

Are also from the prior art different hydrogenation processes for α, β-unsaturated carbonyl compounds known. With the described processes and the catalysts used however, it is difficult to achieve high selectivities of the corresponding alcohols to obtain. In the hydrogenation of citral, for example, in addition to Aldehyde group, the olefinic double bonds are hydrogenated or only the double bond conjugated to the aldehyde group, so that in addition to the unsaturated Alcohols geraniol or nerol also by-products such as citronellol or Citronellal can arise.

In M.M. Paulose et al, J. Oil Technol. Assoc. India 1974, 6, 88-91, becomes a continuous fixed bed process for the selective hydrogenation of citral. As catalysts copper / chromium / cadmium catalysts were used. To adequate Citral sales To achieve, must work at high temperatures of 170 to 250 ° C. become. There is a maximum geraniol / nerol yield of 66.4% at 225 to 235 ° C and almost Full sales of Citral achieved. The citronellol yield was 14.8%. Even with lower sales the yield of the undesired citronellol was still around 44% 7.6%, the citronellol selectivity thus around 17%. The Paulose et al. selectivities for citronellol are for an economical process for hydrogenating citral too high.

Object of the present invention was an improved process for making a ruthenium / iron / carbon supported catalyst, especially for the selective hydrogenation of olefinically unsaturated carbonyl compounds to the correspondingly unsaturated ones Develop alcohols without the disadvantages described above.

The catalyst should be improved catalyst activity and long-term stability have and also in particular in the hydrogenation of citral to geraniol / nerol to high citral conversions and low at the same time Citronellol selectivities to lead.

In the manufacture of the catalyst the use of corrosive ingredients such as chloride salts or explosive Intermediates such as nitrate soaked Coals should be avoided.

The object was achieved according to the invention by a process for producing a ruthenium / carbon supported catalyst, containing 0.1 to 10 wt .-% ruthenium on a carbon support 0.1 up to 5% by weight of iron

• a) placing the carrier in water
• b) Simultaneous addition of the catalytically active components in the form of solutions their metal salts
• c) simultaneous striking of the catalytically active components on the support by adding a base
• d) separating the catalyst from the aqueous phase of the carrier suspension
• e) drying the catalyst
• f) reduction of the catalyst in a hydrogen stream at 400 to 600 ° C
• g) Removal of the catalyst under flame-resistant liquids or passivating the catalyst with oxygen.

Steps (b) and (c) can be carried out in succession either in the process according to the invention can also be carried out simultaneously.

wobei
R¹, R² jeweils unabhängig voneinander gleich oder verschieden sein können und Wasserstoff oder einen gesättigten oder einen ein- oder mehrfach ungesättigten geradkettigen oder verzweigten gegebenenfalls substituierten C₁-C₂₀-Alkylrest, einen gegebenenfalls substituierten Arylrest oder eine gegebenenfalls substituierte heterocyclische Gruppe darstellen
zu den entsprechenden Alkoholen der allgemeinen Formel IIThe invention furthermore relates to the use of the ruthenium / iron / carbon support catalysts prepared by the process according to the invention for the selective liquid phase hydrogenation of carbonyl compounds of the general formula I,

in which
R ¹ , R ^{2 can} each independently be the same or different and represent hydrogen or a saturated or a mono- or polyunsaturated straight-chain or branched optionally substituted C ₁ -C ₂₀ -alkyl radical, an optionally substituted aryl radical or an optionally substituted heterocyclic group
to the corresponding alcohols of the general formula II

where R ¹ and R ^{2 have} the meaning given above.

As carbonyl compounds, both saturated as well as olefinically unsaturated Carbonyl compounds are used.

A saturated or mono- or polyunsaturated straight-chain or branched C ₁ -C ₂₀ -alkyl radical is, unless otherwise stated, a methyl, ethyl, propyl, isopropyl, n-butyl, i-butyl, t -Butyl, pennyl, hexyl, heptenyl, octyl, nonyl, decyl, 1-propenyl, 2-propenyl, 2-methyl-2-propenyl, 1-pentenyl, 1-methyl-2 -Pentenyl, isopropenyl, 1-butenyl, hexenyl, heptenyl, octenyl, nonenyl or a decenyl radical or the radicals corresponding to the compounds used below.

An aryl residue means a benzyl, phenyl or naphthyl radical.

Under a heterocyclic group one understands for example a pyridine, pyrimidine, pyridazine, Pyrazine, piperazine, imidazole, furan, oxazole, isothiazole, isoxazole, 1,2,3-triazole or 1,2,4-triazole, thiazole, thiophene or indole ring.

Substituents can be methyl, ethyl, propyl, i-propyl, butyl, t-butyl, fluorine, chlorine, bromine, iodine, nitro or amino residues.

As saturated carbonyl compounds For example, 3,7-dimethyloctan-1-al and its isomers, Tetrahydrogeranylacetone, hexahydrofarnesylacetone, 6-methylheptanone or isovaleraldehyde used.

As olefinically unsaturated carbonyl compounds can for example citronellal, H-geranylacetone, H-nerolidol, methyl vinyl ketone, Mesityl oxide, pseudoions, dihydrofarnesylacetone, lysmeral, methylhexenone, particularly preferably citronellal or else α, β-unsaturated carbonyl compounds, for example acrolein, methacrolein, crotonaldehyde, prenal, farnesal or citral, particularly preferably citral.

Under the step (g) of the method according to the invention Flame-retardant liquids are liquids with a flash point greater than 80 ° C, preferably greater than 100 ° C, for example Water, geraniol, pentanediol, ethylene glycol or nerol or mixtures thereof, particularly preferably geraniol or nerol or mixtures from that.

Surprisingly leads the simultaneous striking the metal salts of the active components ruthenium and iron to one improved catalyst activity, -selectivity and service life. By the precipitation of the metals in the form of their hydroxides are those in the prior art listed Problems of corrosion or the risk of explosion avoided.

As metal salts of the active components Ruthenium and iron can the chlorides, nitrates, nitrosyl nitrates, acetates, oxides, hydroxides, Acetylacetonates, preferably the chlorides and nitrates, are used become.

With the method according to the invention can the catalyst both as a fixed bed and as a suspension catalyst getting produced.

The carbon carrier materials are understood to mean, for example, graphite, carbon black or activated carbon, but preferably activated carbon, for example NORIT SX Plus ^® . Depending on whether the catalyst is to be produced as a suspension or fixed bed catalyst, the carbon support material is used in powder form or in the form of strands, spheres, grit etc. The carbon support can be pretreated before it is doped, for example by oxidation with nitric acid, oxygen, hydrogen peroxide, hydrochloric acid, etc.

The preparation of the catalyst according to the invention is carried out in detail as follows:
To produce a suspension catalyst, the carbon support is suspended in water (step (a)) and the support suspension prepared in this way is either with no further pretreatment, ie without setting a specific pH, or by setting a pH less than 6 with an acid , for example HNO ₃ , or greater than 8 with a base, for example NaOH, used for the further process.

In step (b), the active components ruthenium and iron are added simultaneously in the form of solutions of their metal salts. The addition is preferably carried out at an elevated temperature of the suspension, particularly preferably at a temperature between 50 and 95 ° C, particularly preferably at a temperature of 70 to 90 ° C. A base, for example Na ₂ CO ₃ , NaHCO ₃ , (NH ₄ ) ₂ CO ₃ , NH ₃ , urea, NaOH, KOH or LiOH, preferably NaOH, is then slowly added to precipitate the catalytically active components onto the support, and the pH -Value between 6 and 14, preferably to 8 to 12, particularly preferably to 9, increased ((c)). The base is preferably added at an elevated temperature, particularly preferably at a temperature between 50 and 95 ° C., preferably at a temperature of 70 to 90 ° C. The base can also be added simultaneously with the addition of the metal salt solution, for example in order to keep the pH of the suspension constant, preferably to a pH of 8 to 14, particularly preferably of 9. Since after the precipitation ruthenium and iron in Substantially present as hydroxides, chloride or nitrate anions are washed out to an unproblematically low content in the washing and separation of the catalyst from the aqueous phase ((d)) following the precipitation.

The filter cake is then under Vacuum or inert gas dried (e) and then the catalyst in a stream of hydrogen, possibly diluted with an inert gas such as Nitrogen, between 400 and 600 ° C reduced (f). Finally, the catalyst is opened after cooling Temperatures below 40 ° C e.g. under water or a flame-retardant liquid expanded or by overflowing one diluted Oxygen flow (about 1% oxygen in an inert gas such as nitrogen) passivated (g).

Alternatively to that described above Process variant with gas phase reduction, can depend on the precipitation of the catalytically active components (c) also a wet chemical reduction the catalyst by adding a reducing agent such as hydrazine, Sodium borohydride, sodium formate, sodium hydrophosphate or formaldehyde connect. The catalyst is filtered after the wet chemical reduction and washed and stored moist.

The production of fixed bed catalysts takes place in the same way as for the process described suspension catalyst, wherein in step (a) instead of the powdered support material strands, Balls, grit etc. are used. The characteristic lengths of these moldings (Diameter length etc.) are usually above 1 mm. Here too is instead the gas phase reduction is a wet chemical reduction, as described above, possible. When dispersing the strands in water care must be taken that their mechanical stress preferably is kept low to minimize abrasion. Advantageously the strands washed with water before use in catalyst synthesis in order to remove weakly adhering fine-particle carbon particles.

The catalysts of the invention contain generally 0.1 to 10 wt .-% ruthenium on a carbon support, preferably on activated carbon.

The BET surface area of the catalysts is, accordingly the carbon carrier used in the production, preferably about 100 to 1500, preferably about 800 to 1200 m2 / g. The particle size of the ruthenium crystallites is essentially below 10 nm and thus corresponds to the from the literature for Ruthenium / carbon catalysts known values.

The information about the contained in the catalyst % By weight of ruthenium and iron refer to the present Registration always on the dry weight of the catalyst.

The one produced according to the invention is of particular importance Catalyst for the selective hydrogenation of carbonyl compounds, preferably for the selective Hydrogenation of unsaturated Carbonyl compounds, particularly preferred for the hydrogenation of citral to geraniol or nerol or from citronellal to citronellol.

The catalyst produced according to the invention hydrated with surprising high selectivity the aldehyde group of the carbonyl compound.

The hydrogenation process can both continuously or discontinuously in suspension or in a fixed bed carried out become. Continuous driving is particularly advantageous.

For the suspension or fixed bed variants offer common reactor concepts how they e.g. in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, 2000 Electronic Release.

The continuous or discontinuous suspension process can, for example, as in EP 947 943 respectively. US 5,939,589 described. The catalyst is used both in the batchwise and in the continuous suspension mode in finely divided form, the particle size being less than 1 mm, preferably between 1 and 100 μm.

For the fixed bed variant, the catalyst is used in the forms customary for fixed bed catalysts, for example in the form of extrudates, chips, tablets or spheres. Typical strand diameters are between 1 and 5 mm, the strand lengths are between 1 and 20 mm. The reactor can run in trickle or bottoms operate.

The reaction is both in the Suspension procedure as well as with the fixed bed variant without pressure or under a pressure of 1 to 200 bar, preferably 10 to 100 bar, in particular preferably carried out at 20 to 50 bar. The temperatures are between 25 and 200 ° C, preferably between 60 and 100 ° C. The reaction can be carried out either with or without a solvent. As a solvent can lower alcohols such as methanol, ethanol or isopropyl alcohol are used become. An organic base such as trimethylamine can also be used if necessary be added.

The hydrogenation of the carbonyl compound on the manufactured according to the invention Catalysts are preferably in the presence of a tertiary amine carried out.

In principle, any tertiary amines suitable so that it is based on their chemical nature, provided they are functional groups not otherwise with the reactants can react does not arrive.

As amines, for example, come in EP 071 787 mentioned in question.

The amount of amines is preferably 1 to 5 wt .-% of the amount of carbonyl compound used.

The following examples are intended the invention closer explain, but without restricting it to that.

Manufacture of suspension catalysts

example 1

• A) 100 g of activated carbon were concentrated with 500 ml. HNO _{3 was} added and the mixture was stirred in a 1 L flask at 80 ° C. for 6 h. After cooling, it was filtered and the filter cake with 10 l of dist. Washed water. The moist coal was returned to the stirred tank, suspended with 2.5 l of water and heated to 80 ° C. under reflux. A solution of 13.11 g of ruthenium chloride and 5.15 g of iron chloride in 375 ml of water was then added dropwise with stirring over the course of 120 minutes. The pH of the suspension was 1.4 after adding the metal salt solution. By adding 1 M sodium hydroxide solution, the pH was then raised to 9 by slow dropping; about 400 ml of NaOH were used for this. The mixture was then stirred for 1 h and then cooled. The catalyst was transferred to a glass suction filter, washed with a total of 40 l of water and dried in a vacuum drying cabinet at 80 ° C. for 6 h. The dried powder was then reduced in a rotary kiln in a stream of 70% H ₂ and 30% N ₂ at 500 ° C for 3 h. After the end of the reduction, the mixture was cooled under nitrogen and passivated with a gas mixture of 1% oxygen in nitrogen. The finished catalyst had a chloride content of less than 0.05% by weight. The following contents (% by weight) are also determined: Na: 2.8, Ru: 5.2, Fe: 1.1.
• B) The procedure was as described in A, but instead of of ruthenium and iron chloride, ruthenium nitrosyl nitrate and iron (III) nitrate used. The finished catalyst had a ruthenium content of 5.1% by weight, an iron content of 1.1% by weight, a nitrate content <0.01% by weight and a Na content of 2.1% by weight.
• C) The procedure was as described in A, but fewer were Ruthenium and iron contents applied to the activated carbon. The finished catalyst had a ruthenium content of 2.8 wt .-%, an iron content of 0.54% by weight, a chloride content of 0.02% by weight and one Na content of 3.8% by weight.
• D) 110 g of the activated carbon Norit SX Plus ^® were placed in a stirred flask with 2 l of water without further pretreatment, suspended and heated to 80 ° C. under reflux. Then the pH was raised to 9 by adding aqueous NaOH (1 mol / l). 300 ml of a solution of ruthenium nitrosyl nitrate and iron nitrate (concentration corresponding to 5.85 g Ru and 1.17 g Fe) were then added dropwise at 80 ° C. At the same time, the pH was brought to approx 9 held. The mixture was stirred at 80 ° C for one hour and then cooled. The cold suspension was filtered and washed with 40 l of water, then dried in a vacuum drying cabinet at 80 ° C. for 16 h and reduced and passivated as described under A. The catalyst had an Ru content of 5.0% by weight, an Fe content of 1.0% by weight and a Na content of 0.036% by weight.
• E) Comparative example: A catalyst according to the in EP 0071787 Specification specified by impregnating the activated carbon with Ru chloride solution, drying, mixing with iron red, reduction at 500 ° C and expansion under water.

Testing the under A to D manufactured catalysts

a) Continuous suspension hydrogenation

The continuous suspension hydrogenation was carried out in a packed bubble column reactor with Pro Duct recirculation and hydrogen cycle gas (accordingly EP 947 493 ) carried out.

A liquid mixture of 70% by volume Citral (E / Z ≈ 1), 27 vol .-% methanol and 3 vol .-% trimethylamine hydrogenated. liquid and gas were over a packed bubble column (Pack volume: 143 ml, pack diameter: 27 mm) with one Flow rate of approx. 120 l / h each. Citral sales could by varying the parameters pressure, temperature or educt inflow rate can be set. The pressure was between 20 and 40 bar and the Temperature between 80 and 100 ° C varied.

b) discontinuous hydrogenation

The discontinuous hydrogenation was carried out in an autoclave from Medimex. The liquid Educt (250 ml of a mixture of 70 vol .-% citral (E / Z ≈ 1), 27 vol .-% Methanol and 3% by volume trimethylamine) and the catalyst (2.5 g) were transferred to the autoclave before the start of the experiment. Then was flushed with nitrogen at normal pressure. After complete removal The air supply from the reaction chamber was stopped, the autoclave is relaxed and switched to hydrogen. Then was Hydrogen passed into the autoclave and the desired reaction pressure set. Meanwhile, the required reaction temperature was reached regulated. After reaching the temperature and the pressure the Stirrer switched on and started the reaction. During the reaction, over a Riser pipe samples are taken from the reaction space. It was at a temperature of 100 ° C and hydrogenated to a hydrogen pressure of 50 bar.

Result

The results shown in Table 1 show that the catalysts of the invention A to D are much more active and selective than the comparison contact. Especially with high sales becomes significantly more geraniol / nerol and significantly less citronellol educated. Across from the comparative catalyst needs less dry matter to achieve high sales catalyst can be used (examples A and B) or it can a lower load with precious metal can be set (example C). Moreover deactivate the catalysts of the invention slower than the comparison contact.

Table 2 is the activity comparison of the catalyst of the invention A with the comparative catalyst from a batch hydrogenation test shown. After 50 minutes, the catalyst A has almost reached full conversion, while the contact according to the invention only implemented 50% of the citral.

• F) A catalyst prepared according to Example 1A) was used for the continuous suspension hydrogenation of Citronellal (3,7-dimethyloct-7-en-1-al) to citronellol (3,7-dimethyloct-7-en-1-ol) used. Here is the formation of the fully hydrogenated product Avoid 3,7-dimethyloctan-l-ol as much as possible. As a starting material was a mixture of 70% citronellal, 27% methanol and 3% trimethylamine used. At a reaction temperature of 80 ° C, a pressure of 20 bar, one Educt feed of 2.2 ml / min, a catalyst amount of 40 g (dry) became Citronellal sales after 142 hours of 94%, a citronellol selectivity of 97.3% and a selectivity to 3,7-dimethyloctan-l-ol received by only 1.4%. The catalyst was characterized by a high activity and long-term stability and high selectivity to Citronellol even with high Citronellal sales.

Table 1

Table 2

Manufacture of fixed bed catalysts

Example 2

62 g of activated carbon strands (Supersorbon SX 30 from Lurgi, diameter 3 mm, surface area approx. 1000 m ² g-1) were placed in a stirred tank with 400 ml of demineralized water and heated to 80 ° C. with gentle stirring and reflux cooling. A solution of 8.13 g of ruthenium chloride and 3.19 g of iron chloride was added dropwise at 80 ° C. in the course of 60 min. Then the pH was raised to 9 by adding 1 M sodium hydroxide solution and stirring was continued for one hour. The catalyst was transferred to a glass suction filter, washed with 10 l of demineralized water and then in a vacuum drying cabinet 6 Dried at 80 ° C for hours. The mixture was then reduced in a reduction oven for 3 hours at 500 ° C. in a gas mixture of hydrogen and nitrogen (50/4), cooled to room temperature and passivated with a gas mixture of 1% oxygen in nitrogen.

Testing the catalysts

See also 1

description

Citral and a methanol trimethylamine solution separately pumped in by piston pumps with scale control. The ratio of citral / methanol / trimethylamine is about 70/27/3. The hydrogen feed is via a mass flow controller dosed. The reactor is operated in a liquid phase mode at 50 to 70 ° C. 80% of the reactor discharge is from the separator sump by means of a piston pump returned and by a variable area flow meter controlled. The rest Product share is about a pressure maintaining valve is discharged.

General implementation

The catalyst is in the reactor built in and reduced. The contact is depressurized at 13 Nl / h Hydrogen to 120 ° C heated. After 1 hour it is cooled. Then be Citral and trimethylamine / methanol mixture separately fed to the reactor. The Parameters can be found in the individual tests. The analytics is carried out with a 30 m DBWAX 0.32 mm 0.25 μm column (80 ° C - 3 ° C / min - 230 ° C - 20 min).

Example 3

Fixed bed catalyst from example 2 with return: 100 ml (41.1 g) of catalyst were installed in the reactor and after the general rule activated. At a hydrogen pressure of 40 bar (24 N1 / h) the inlets were set as follows: Citral (2.60 g / h, purity 98%), methanol + 10% TMA (3.25.5 g / h), reverse current (6, 240 g / h). At a reactor temperature of 75 ° C with a conversion of 95.61% (runtime: 713 h) a selectivity to nerol / geraniol of 95.22% reached (ratio Ger / Ner: 1.20). By-products: selectivity citronellol: 1.80%, selectivity nerol isomers: 1.70%.

Claims (14)

Process for the preparation of a ruthenium / iron / carbon supported catalyst, containing 0.1 to 10 wt .-% ruthenium on a carbon support 0.1 up to 5% by weight of iron a) Introducing a carrier into water b) Simultaneous addition of the catalytically active components Ruthenium and iron in the form of solutions of their metal salts c) simultaneous conspicuousness the catalytically active components on the support by adding a base d) Separating the catalyst from the aqueous phase of the carrier suspension e) Drying the catalyst f) reduction of the catalyst in Hydrogen flow at 400 to 600 ° C G) Removal of the catalyst under flame-retardant liquids or passivate the catalyst with a dilute stream of oxygen Process for the preparation of a ruthenium / iron / carbon supported catalyst, containing 0.1 to 10 wt .-% ruthenium on a carbon carrier 0.1 up to 5% by weight of iron a) Introducing a carrier into water b) Simultaneous addition of the catalytically active components Ruthenium and iron in the form of solutions of their metal salts c) simultaneous conspicuousness the catalytically active components on the support by adding a base d) Reduction of the catalyst by adding an aqueous reducing agent e) Separating the catalyst from the aqueous phase of the carrier suspension f) Wash the catalyst with water Procedure according to a of claims 1 or 2, characterized in that the catalyst produced is a suspension catalyst. Procedure according to a of claims 1 or 2, characterized in that the catalyst produced is a fixed bed catalyst. Procedure according to a of claims 1 to 4, characterized in that steps (b) and (c) at a temperature of 50 to 95 ° C carried out become. Procedure according to a of claims 1 to 5, characterized in that steps (b) and (c) both can be done simultaneously as well as one after the other. Procedure according to a of claims 1 to 5, characterized in that the catalytically active components in the form of their chlorides, nitrates, nitrosyl nitrates, acetates, oxides, Hydroxides or acetylacetonates are used. Method according to one of claims 1 to 6, characterized in that the carbon carrier can be pretreated by oxidation with HNO ₃ , oxygen, hydrogen peroxide or hydrochloric acid. Method according to one of claims 1 to 7, characterized in that to precipitate the catalytically active components on the support as the base Na ₂ CO ₃ , NaHCO ₃ , (NH ₄ ) ₂ CO ₃ , NH ₃ , urea, NaOH, KOH or LiOH is used. Procedure according to a of claims 1 to 9, characterized in that to precipitate the catalytically active Components NaOH is used. Use of the catalyst prepared by a process according to one of Claims 1 to 10 for the selective liquid phase hydrogenation of carbonyl compounds of the general formula I.

where R ¹ , R ^{2 can} each independently be the same or different and hydrogen or a saturated or a mono- or polyunsaturated straight-chain or branched optionally substituted C ₁ -C ₂₀ alkyl radical, an optionally substituted aryl radical or an optionally substituted heterocyclic group represent the corresponding alcohols of the general formula II

where R1 and R2 have the meaning given above. Use according to claim 11, characterized in that the carbonyl compound is an α, β-unsaturated carbonyl compound is. Use according to a of claims 11 or 12, characterized in that the carbonyl compound Citral is. Use according to a of claims 11 to 13, characterized in that the carbonyl compound Citronellal is.