WO2010043738A1 - Procedure for the selective hydrogenation of nitrocycloalkanes to obtain cyclic oximes - Google Patents

Abstract

The present invention relates to a procedure for the selective hydrogenation of nitrocycloalkanes, substituted or not, comprising carrying out a catalytic hydrogenation of said compounds utilising a catalyst comprising at least one metal, being Pt, supported on titanium oxide, iron oxide, cerium oxide, alumina, carbon, active carbon, magnesium oxide, zirconium oxide, silica, silicic acid, lanthanum oxide, zinc oxide, calcium carbonate, calcium phosphate, calcium sulphate, barium sulphate and combinations thereof. Furthermore said catalyst may comprise a modifier metal selected from one or more alkaline or alkaline earth metals.

Description

 SELECTIVE HYDROGENATION PROCEDURE OF

NiTROCICLOALCANOs TO OBTAIN CYCLIC OXIMES

FIELD OF THE TECHNIQUE The present invention relates to a process for the selective hydrogenation of nitrocycloalkanes in the presence or absence of other reducible functional groups, using supported metal catalysts that include alkali metals.

BACKGROUND

In recent years, the use of cyclic oximes as reaction intermediates in the production of polymers, resins, dyes, pesticides, etc., has aroused great industrial interest. The production of Nylon-6 has become an important reference in the industrial production of polymers, and its demand continues to expand today. Epsiloncaprolactam, precursor of Nylon-6, is obtained industrially from cyclohexanone, which is converted into cyclohexanone oxime and finally rearranged to form the lactam in a three-stage process. While great effort has been made in Beckmann's rearrangement of the cyclohexanone oxime (US5304643, US5264571, DE19608660), it should be taken into account that the aerobic oxidation of cyclohexane to cyclohexanone limits the total efficiency of the process, given the low yields achieved per stage (~ 5%) with homogeneous cobalt catalysts (US3644526, GB1315983). In addition, the need to use hydroxylamine to produce the cyclohexanone oxime or H ₂ O ₂ and ammonia hydroxide for

Ia production in situ of hydroxylamine (US5320819), introduces another sensitive reaction stage.

Other alternative processes for the production of epsiloncaprolactam have been raised without much success. In US4504681 the use of tungsten catalysts to produce cyclohexanone oxime by partial oxidation of cyclohexylamine is claimed.

However, low yields at the maximum (<7%) completely limit

The application of this procedure during the production sequence of epsilon-caprolactam. Recently (S. K. Klitgaard et al, Green Chemistry

10, 2008, 419) a reaction sequence has been proposed that involves the controlled oxidation of cyclohexylamine to cyclohexanone oxime using

TIO2 as catalyst. Despite the greater yield to oxime through this process (~ 60%), the selectivity obtained and the total duration of the reaction (10 days) clearly limit the interest of the process.

WO2007116112 claims the use of gold catalysts to produce cyclohexanone oxime by hydrogenation of 1-nitro-1-cyclohexene. The selectivity and activity of these catalysts is good, with yields greater than 90%, but requires 1-nitro-1-cyclohexene as raw material.

Unlike the hydrogenation process of 1-nitro-1-cyclohexene, the partial reduction of nitrocyclohexane to cyclohexanone oxime has an industrial background. GB860340 describes the hydrogenation of nitrocyclohexane to cyclohexanone oxime using a supported catalyst of Pd working at 35 bar, 413 K, and in the presence of a source of Pb. Unfortunately, to achieve moderate yields to oxime (~ 70%) this process requires high pressures and the use of environmentally toxic PbO salts.

On the other hand, to carry out a production of cyclohexanone oxime from nitrocyclohexane, this nitrocycloalkane must be previously produced, and industrial nitration, although economical, only entails a yield per step of 16% and under severe reaction conditions (523 - 673K). However, in US6468487 the possibility of nitrating cyclohexane under mild reaction conditions (343 K) and with selectivities is claimed to 70% nitrocyclohexane, which increases the outlook for an industrial production of cyclohexanone oxime from this substrate.

In the present invention, it has been found that certain catalysts based on Pt nanoparticles and containing one or more alkali metals are capable of selectively catalyzing the hydrogenation of nitro to oxime groups in cyclic nitroalkanes, using H ₂ or another hydrogen donor molecule as agent reducer, when supported on a suitable support and activated properly.

OBJECT OF THE INVENTION

The present invention relates to a process for the selective hydrogenation of nitrocycloalkanes, substituted or not, which comprises carrying out a catalytic hydrogenation of said compounds using a catalyst comprising, at least one metal that is Pt, supported on titanium oxide, iron oxide, cerium oxide, alumina, carbon, activated carbon, magnesium oxide, zirconium oxide, silica, silicic acid, lanthanum oxide, zinc oxide, calcium carbonate, calcium phosphate, calcium sulfate, barium sulfate and combinations thereof.

Pt, or modified Pt as explained later in this report, is supported in order to increase its dispersion and decrease the particle size on supports of inorganic or carbonaceous nature, as is known in the field of metal catalysts. .

Some of these metal oxides can play a role simply as physical supports of the Pt nanoparticles or a mechanistic role in the catalytic process of reducing nitro groups to oximes, so that It is possible to avoid the complete reduction of the nitro group to amino. Similarly, coals can be used as supports.

According to a preferred embodiment, the support is selected from iron and titanium oxides and combinations thereof, or activated carbon.

The catalyst used in the process of the present invention can comprise at least one other modifying metal selected from one or more alkali or alkaline earth metals, preferably Li, Na, K, Cs, Fr, Mg, Ca and combinations thereof. The modifying metal is preferably present in a weight percentage between 0.01% and 10% with respect to the support, more preferably between 0.05% and 4% depending on the content of the nature of the metal.

The supported Pt of the catalyst according to the process of the present invention is preferably in a weight percentage between 0.01% and 10% with respect to the support, more preferably between 0.05% and 4%. Said Pt can be applied in metallic or ionic form on the support. In either of the two ways, conventional procedures are known, known in the art.

It is important to note that, contrary to what happens with the Pd catalysts proposed by Dupont in GB860340, in our case we have found that with Pt the introduction of Pb is not required to avoid the complete hydrogenation of the nitro to amino group, as long as Use the appropriate support and catalyst activation.

This process for the selective hydrogenation of nitroalkanes can be carried out when the, or nitro groups, are in the presence of other reducible functional groups, such as for example aldehydes, ketones, olefins, nitriles, esters, amides, halogens, triple bonds , etc. The claimed catalysts are active and selective when properly supported and activated.

In general, nitrocycloalkane has a general formula

R-NO ₂ where R is a completely saturated or unsaturated ring conjugated with the nitro group to be hydrogenated, selected from unsubstituted rings and rings with one or more substituents. Said substituents are groups selected from C1 to C8 alkyl groups, C1 to C4 aromatic or aliphatic vinyl groups, C1 to C4 aromatic or aliphatic vinyl groups, C1 to C8 alkoxy groups, CeH ₅ to CioH ₈ aryloxy, fluorine groups, chlorine groups, groups bromine, iodine groups, hydroxy groups, groups with unsaturated carbon-carbon bonds, O- (CO) -alkyl groups, O- (CO) -aryl groups, COOH groups, OH groups, SH groups, CN groups, SO ₃ groups - , SO ₂ -alkyl groups, NH ₂ groups, NH-alkyl groups, NH ₂ SO ₂ groups, NSO ₂ - (alkyl) ₂ groups, SO ₂ -NH-alkyl groups, aromatic or aliphatic aldehyde groups C1 to C4, ketone groups aliphatic or aromatic, C1 to C6 group, C1 to C6 ether groups, thioester, sulfides and combinations thereof.

The term carbon-carbon unsaturated bond, according to the present invention, includes bonds of alkenes, alkynes and alenes.

The Pt / nitro molar ratio is between 0.0001 and 5%, preferably between 0.01 and 1%. Here the term "nitro" does not refer to the nitrocycloalkane compound as such but to the total number of "nitro group (s) present in the reaction medium, with more than one of these groups being possible per nitrocycloalkane molecule.

According to a particular embodiment of the process of the present invention, a second additional metal can be introduced as a modifier in the catalyst preferably selected from Au, Hg, Bi,

Ge, Cd, As, Sb, Mn, Co, Ti, Fe, Pd, Ru, Ni, Rh, Go, Cu, Cr and combinations of the same. The weight ratio of Pt to second modifying metal is preferably between 1: 0.01 and 1: 2.

In the process of the invention, hydrogenation is carried out with a hydrogen source that is a hydrogen donor molecule. Said hydrogen source is preferably selected from ammonium formate, formic acid, decaborane, cyclohexene, cyclohexadiene, phosphoric acid and combinations thereof. According to a particular embodiment, the source of hydrogen can be molecular hydrogen.

The process of the present invention can be carried out at a pressure selected from atmospheric pressure, a pressure between 1 and 100 bars, preferably between 2 and 15 bars and at a temperature between 2O ⁰ C and 25O ⁰ C, preferably between 8O ⁰ C and 15O ⁰ C.

According to a particular embodiment, the process of the present invention is carried out at atmospheric pressure and at a temperature between 2O ⁰ C and 25O ⁰ C. And preferably with molecular hydrogen as a source of hydrogen.

According to another additional particular embodiment, the process is carried out at a pressure between 1 and 100 bar and at a temperature between 2O ⁰ C and 25O ⁰ C, preferably between 5O ⁰ C and 200 ⁰ C, and preferably, with molecular hydrogen as a source of hydrogen.

According to another additional particular embodiment the process is carried out at a pressure between 1 and 50 bar and at a temperature between 2O ⁰ C and

15O ⁰ C, more preferably still between 2 and 20 bar and at a temperature between 100 ⁰ C and 15O ⁰ C, and, preferably with molecular hydrogen as a source of hydrogen. In the process according to the present invention, the hydrogenation reaction can be carried out in the presence or absence of solvent.

If the procedure is carried out with solvent, this can be water, alcohols, ethers, esters, ketones, carboxylic acids, aprotic dipole solvents, apolar solvents, chlorinated aromatic hydrocarbons, methylene chloride, C3-C7 alkanes, cyclohexane and combinations thereof.

In the case where the solvent is an alcohol, this may be selected from methanol, ethanol, n-propanol, isopropanol, n-butanol, isomeric butane, cyclohexanol and combinations thereof. In the case that it is an ether, it may be selected from diethyl ether, methyl tert-butyl ether, tetrahydrofuran, dioxane, dimethoxyethane and combinations thereof. In the case that it is an ester it may be selected from ethyl acetate, butyl acetate and combinations thereof. In the case that it is a ketone, it may be selected from butyrolactone, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and combinations thereof. In the event that the solvent is a carboxylic acid, it may be selected from acetic acid, propionic acid and combinations thereof. In the case of an aprotic dipolar solvent, it may be selected from dimethylformamide, N-methylpyrrolidine, dimethylacetamide, sulfolane, dimethyl sulfoxide, acetonitrile and combinations thereof. In the case of an apolar solvent, it may be selected from toluene, xylene and combinations thereof.

Preferably, said solvent is selected from toluene, xylene, tetrahydrofuran, dioxane, methyl ethyl ketone, methanol, ethanol and combinations thereof. The solvent may also be chlorinated aromatic hydrocarbons, methylene chloride, C3-C7 alkanes, cyclohexane and combinations thereof.

Said solvent serves as a means of dissolution or to facilitate separation processes.

The process can be performed according to particular embodiments in the presence of a solvent and one or more co-solvents. Said co-solvent may be ethanol, acetone, acetonitrile and combinations thereof.

According to other embodiments of the process of the present invention,

The reaction is carried out in the absence of solvent. According to this embodiment, the reagents that are hydrogenated during the process are preferably in the liquid, gas or coexistence phase of both.

In the process of the present invention, the hydrogenation reaction can be carried out in the gas-solid phase (catalyst), or in a gas-liquid-solid system (catalyst).

Furthermore, said process can be carried out in a reactor in discontinuous or continuous mode, and the recovery of the catalyst can be carried out by recirculation or regeneration.

The method of the present invention may further comprise a step of activating the catalyst under flowing hydrogen at temperatures between 100 ⁰ C and 600 ⁰ C, preferably between 35O ⁰ C and 55O ⁰ C. According to a particular embodiment of the present invention, the catalyst formed by Pt and the support is calcined at a temperature preferably between 350 and 55O ⁰ C. The calcination can be carried out in an atmosphere of air, oxygen or hydrogen, in one or several stages successive Preferably, the calcination is carried out under H ₂ flow.

For preventing the complete reduction of the corresponding compound nitrocicloalcano amino compound during the stage of reaction have special influence the temperature of activation of the catalyst, preferably between 350 and 550 ⁰ C under flow higrógeno; the percentage of supported metal, preferably a Pt to support molar ratio between 0.01% and 10%; and the type of support, preferably TiO ₂ . In addition, in order to avoid other secondary reactions of the oxime formed, such as its hydrolysis to cyclohexanone, it is very important to control the acidity of possible acid centers of the catalyst, for which a doping alkali metal or alkaline earth metal can be used, preferably Na, K or Cs with a ratio in dopant metal weight to support between 0.001 and 20%.

These facts are illustrated below by specific and non-limiting examples.

Example-1: Preparation of catalyst 0.2% PtTTiO ₂ reduced to 450 ⁰ C

The platinum catalyst supported on titanium oxide was prepared by the pore volume impregnation technique. Platinum deposition was carried out by adding an aqueous solution of H ₂ PtCIe containing the required amount of platinum on the support, so that it is impregnated with pore volume. To prepare 10 g of catalyst, 20 mL of an aqueous solution containing 53.1 mg of H ₂ PtCIe should be used. After homogenizing the resulting gel, the catalyst was dried in a conventional oven at 100 ⁰ C for 6 hours. Finally, the sample was reduced under H ₂ flow (50 mL / min) at

450 ⁰ C for 3 hours. Example-2: Preparation of cyclohexanone oxime with H ₂ using 0.2% PtTTiO ₂ catalyst reduced to 450 ⁰ C

In an autoclave, 150 mg of catalyst, prepared according to Example 1, are added to a solution of 418 mg of nitrocyclohexane in 0.55 ml_ of toluene, using 41 mg of o-xylene as the internal standard of the reaction. The air inside the autoclave is removed by cold purging the reactor with H ₂ at 10 bar. With the reactor at atmospheric pressure of H2, the contents of the autoclave are heated to 120 ° C and pressurized with 10 bars of hydrogen, setting a stirring level of 1000 rpm. The pressure inside the reactor was kept constant at 10 bars during The whole experiment, following the evolution of the reaction by analysis of the liquid phase by gas chromatography and mass spectrometry. After 80 minutes of reaction, cyclohexanone oxime was produced in 62% yield.

Example-3: Preparation of cyclohexanone oxime in the absence of solvent with H ₂ using the catalyst 0.2% PtTTiO ₂ reduced to 450 ⁰ C

In an autoclave, 200 mg of catalyst, prepared according to Example 1, are added to a solution of 1 g of nitrocyclohexane, using 41 mg of o-xylene as the internal standard of the reaction. The air inside the autoclave is removed by cold purging the reactor with H2 at 10 bar. With the reactor at atmospheric pressure of H2, the contents of the autoclave are heated to 110 ° C and pressurized with 4 bars of hydrogen, setting a stirring level of 1000 rpm. The pressure inside the reactor was kept constant at 4 bars during The whole experiment, following the evolution of the reaction by analysis of the liquid phase by gas chromatography and mass spectrometry. After 900 minutes of reaction, cyclohexanone oxime was produced in 69% yield. Example-4: Preparation of catalyst 0.2% PtTTiO ₂ reduced to 450 ⁰ C and doped with 1500 ppm Na

The platinum catalyst supported on titanium oxide doped Na was prepared from material Ptito 0.2% ₂ reduced to 450 ⁰ C indicated in Example 1 by impregnation pore volume with an aqueous sodium acetate solution. The deposition of Na on the 0.2% Pt / Tiθ2 material reduced to 450 ⁰ C was carried out by adding an aqueous solution of CHsCOONa containing the required amount of Na on the catalyst, so that it is impregnated with pore volume. To prepare 10 g of catalyst containing 1500 ppm of Na, 20 measures an aqueous solution containing 53.5 mg of anhydrous CH ₃ COONa must be used. After homogenizing the resulting gel, the catalyst was dried in a conventional oven at 100 ° C for 6 hours.

Example-5: Preparation of cyclohexanone oxime in the absence of solvent with H ₂ using 0.2% PtTTiO ₂ catalyst reduced to 450 ⁰ C and doped with 1500 ppm Na

In an autoclave, 200 mg of catalyst, prepared according to Example 4, are added to a solution of 1 g of nitrocyclohexane, using 41 mg of o-xylene as the internal standard of the reaction. The air inside the autoclave is removed by cold purging the reactor with H ₂ at 10 bar. With the reactor at atmospheric pressure of H ₂ , the contents of the autoclave are heated to 110 ° C and pressurized with 4 bars of hydrogen, setting a stirring level of 1000 rpm. The pressure inside the reactor was kept constant at 4 bars throughout the experiment, following the evolution of the reaction by analysis of the liquid phase by gas chromatography and mass spectrometry. After 900 minutes of reaction, cyclohexanone oxime was produced with a yield of 74%. Example-6: Preparation of catalyst 0.2% PtTTiO ₂ reduced to 450 ⁰ C and doped with 6000 ppm Na The platinum catalyst supported on titanium oxide doped Na was prepared from material Ptito 0.2% ₂ reduced to 450 ⁰ C indicated in Example 1 by impregnation pore volume with an aqueous sodium acetate solution. The deposition of Na on the 0.2% PtATiO _{2 material} reduced to 450 ⁰ C was carried out by adding an aqueous solution of CHsCOONa containing the required amount of Na on the catalyst, so that it is impregnated with pore volume. To prepare 10 g of catalyst containing 6000 ppm of Na, 20 measures an aqueous solution containing 214.1 mg of anhydrous CHsCOONa must be used. After homogenizing the resulting gel, the catalyst was dried in a conventional oven at 100 ° C for 6 hours.

Example-7: Preparation of cyclohexanone oxime in the absence of solvent with H ₂ using 0.2% PtZTiO ₂ catalyst reduced to 450 ⁰ C and doped with 6000 ppm Na

In an autoclave, 200 mg of catalyst, prepared according to Example 6, are added to a solution of 1 g of nitrocyclohexane, using 41 mg of o-xylene as the internal standard of the reaction. The air inside the autoclave is removed by cold purging the reactor with H ₂ at 10 bar. With the reactor at atmospheric pressure of H ₂ , the contents of the autoclave are heated to 110 ° C and pressurized with 4 bars of hydrogen, setting a stirring level of 1000 rpm. The pressure inside the reactor was kept constant at 4 bars throughout the experiment, following the evolution of the reaction by analysis of the liquid phase by gas chromatography and mass spectrometry. After 820 minutes of reaction, cyclohexanone oxime was produced in 85% yield.

Example-8 Preparation of Catalyst ₂ 0.2% PtTTiO reduced to 200 ⁰ C The platinum catalyst supported on titanium oxide was prepared by the technique of pore volume impregnation. Deposition Platinum was carried out by adding an aqueous solution of H ₂ PtCIe containing the required amount of platinum on the support, so that it is impregnated with pore volume. To prepare 10 g of catalyst, 20 ml of an aqueous solution containing 53.1 mg of H ₂ PtCI ₆ must be used. After homogenizing the resulting gel, the catalyst was dried in a conventional oven at 100 ⁰ C for 6 hours. Finally, the sample was reduced under pure _H2 stream (50 mL / min) at 200 ⁰ C for 3 hours.

Example-9: Preparation of cyclohexanone oxime with H ₂ using the catalyst 0.2% PtTTiO ₂ reduced to 200 ⁰ C

In an autoclave, 150 mg of catalyst, prepared according to Example 8, are added to a solution of 418 mg of nitrocyclohexane in 0.55 ml_ of toluene, using 41 mg of o-xylene as the internal standard of the reaction. The air inside the autoclave is removed by cold purging the reactor with H ₂ at 10 bar. With the reactor at atmospheric pressure of H ₂ , the contents of the autoclave are heated to 120 ° C and pressurized with 10 bars of hydrogen, setting a stirring level of 1000 rpm. The pressure inside the reactor was kept constant at 10 bars. throughout the experiment, following the evolution of the reaction by analysis of the liquid phase by gas chromatography and mass spectrometry. After 100 minutes of reaction, cyclohexanone oxime was produced with a yield of 5.4%.

Example-10: Preparation of catalyst 0.2% Pt / C reduced to 450 ⁰ C

The platinum catalyst supported on activated carbon was prepared by the pore volume impregnation technique. Platinum deposition was carried out by adding an aqueous solution of H ₂ PtCI ₆ containing the required amount of platinum on the support, so that it is impregnated with pore volume. To prepare 10 g of catalyst, 22 mL of an aqueous solution containing 53.1 mg of H ₂ PtCIe should be used. After homogenizing the resulting gel, the catalyst was dried in a conventional oven at 100 ⁰ C for 6 hours. Finally, the sample was reduced under pure _H2 stream (50 mL / min) at 450 ⁰ C for 3 hours.

Example-11: Preparation of cyclohexanone oxime with H ₂ using 0.2% Pt / C catalyst reduced to 450 ⁰ C

In an autoclave, 100 mg of catalyst, prepared according to Example 10, are added to a solution of 418 mg of nitrocyclohexane in 0.55 ml_ of toluene, using 41 mg of o-xylene as the internal standard of the reaction. The air inside the autoclave is removed by cold purging the reactor with H ₂ at 10 bar. With the reactor at atmospheric pressure of H ₂ , the contents of the autoclave are heated to 120 ° C and pressurized with 10 bars of hydrogen, setting a stirring level of 1000 rpm. The pressure inside the reactor was kept constant at 10 bars. throughout the experiment, following the evolution of the reaction by analysis of the liquid phase by gas chromatography and mass spectrometry. After 80 minutes of reaction, cyclohexanone oxime was produced with a yield of 18%.

Claims

1. A process for the selective hydrogenation of nitrocycloalkanes, substituted or not, characterized in that it comprises carrying out a catalytic hydrogenation of said compounds using a catalyst comprising, at least one metal that is Pt, supported on titanium oxide, oxide of iron, cerium oxide, alumina, carbon, active carbon, magnesium oxide, zirconium oxide, silica, silicic acid, lanthanum oxide, zinc oxide, calcium carbonate, calcium phosphate, calcium sulfate, barium sulfate and combinations of same. 2. A method according to claim 1, characterized in that the catalyst further comprises a modifying metal selected from one or more alkaline or alkaline earth metals. 3. A method according to claim 2, characterized in that the alkali or alkaline earth metals are selected from Li, Na, K, Cs, Fr, Mg, Ca and combinations thereof. 4. A method according to claim 2, characterized in that the modifying metal is present in a weight percentage between 0.01 and 10% with respect to the support. 5. A method according to claim 1, characterized in that the Pt is in a weight percentage between 0.01% and 10% with respect to the support. 6. A method according to claim 1, characterized in that the nitrocycloalkane has a general formula R-NO ₂ where R is a completely saturated ring or with installations not conjugated with the nitro group to be hydrogenated, selected from unsubstituted rings and rings with one or more substituents. 7. A method according to claim 6, characterized in that said substituents are groups selected from C1 to C8 alkyl groups, C1 to C4 aromatic or aliphatic vinyl groups, C1 to C4 aromatic or aliphatic vinyl groups, C1 to C8 alkoxy groups, aryloxy CeH ₅ to CioH ₈ , fluorine groups, chlorine groups, bromine groups, iodine groups, hydroxy groups, groups with unsaturated carbon-carbon bonds, O- (CO) -alkyl groups, O- (CO) -aryl groups, COOH groups, groups OH, SH groups, CN groups, SO3- groups, Sθ2-alkyl groups, NH ₂ groups, NH-alkyl groups, NH ₂ SO ₂ groups, NSO ₂ - (alkyl) ₂ groups, SO ₂ -NH-alkyl groups, groups C1 to C4 aromatic or aliphatic aldehyde, aliphatic or aromatic ketone groups, C1 to C6 group, C1 to C6 ether groups, thioester, sulphides and combinations thereof. 8. A method according to claim 1, characterized in that the Pt is applied in metallic or ionic form in the support. 9. A method according to one of the preceding claims, characterized in that an additional second metal is introduced as a modifier selected from Au, Hg, Bi, Ge, Cd, As, Sb, Mn, Co, Ti, Fe, Pd, Ru, Ni , Rh, Ir, Cu, Cr and combinations thereof. 10. A method according to claim 9, characterized in that the weight ratio of Pt to second modifying metal is in a ratio between 1: 0.01 and 1: 2. 11. A method according to claim 1, characterized in that the hydrogenation is carried out with a hydrogen source that is a hydrogen donor molecule. 12. A method according to claim 11, characterized in that the source of hydrogen is selected from ammonium formate, formic acid, decaborane, cyclohexene, cyclohexadiene, phosphoric acid and combinations thereof. 13. A method according to claim 11, characterized in that the source of hydrogen is molecular hydrogen. 14. A method according to one of the preceding claims, characterized in that it is carried out at atmospheric pressure. 15. A method according to one of the preceding claims, characterized in that it is carried out at a pressure between 1 and 100 bars. 16. A method according to one of the preceding claims, characterized in that it is carried out at a temperature between 2O ⁰ C and 25O ⁰ C. 17. A method according to one of the preceding claims, characterized in that it is carried out in the presence of a solvent selected from water, alcohols, ethers, esters, ketones, carboxylic acids, aprotic dipole solvents, apolar solvents, chlorinated aromatic hydrocarbons, chloride of methylene, C3-C7 alkanes, cyclohexane and combinations thereof. 18. A process according to one of the preceding claims, characterized in that it is carried out in the presence of a solvent and one or more co-solvents selected from ethanol, acetone, acetonitrile and combinations thereof. 19. A process according to one of the preceding claims, characterized in that the reaction is carried out in the absence of solvent. 20. A process according to one of the preceding claims, characterized in that the hydrogenation reaction is carried out in the gas-solid phase. 21. A process according to one of the preceding claims, characterized in that the hydrogenation reaction is carried out in a gas-liquid-solid system. 22. A method according to one of the preceding claims, characterized in that it is carried out in a reactor selected between reactor in discontinuous mode and reactor in continuous mode. 23. A method according to claim 1, characterized in that it further comprises a step of activating the catalyst under hydrogen flow at temperatures between 100 ⁰ C and 600 ⁰ C.