Selective hydrogenation of alkynes to alkenes using a nickel / / palladium catalyst

Abstract

The present invention relates to the selective hydrogenations of alkynes to alkenes. It has been surprisingly found that a catalyst based on Ni and Pd on a solid carrier observed achieves very high selectivities and high yield in the desired alkene.

Description

[0001] - 1 - 34790-WO-PCT[2]

[0002] SELECTIVE HYDROGENATION OF ALKYNES TO ALKENES USING A NICKEL / / PALLADIUM CATALYST

[0003] Technical Field

[0004] The present invention relates to the field of selective hydrogenation of alkynes to alkenes.

[0005] Background of the invention

[0006] The hydrogenation of alkynes is known. When aiming to form the respective alkenes from alkynes, one encounters the problem of overhydrogenation, i.e. that typically the hydrogenation cannot be stopped at the alkene stage, but continues to form the corresponding alkane, at least in considerable amounts.

[0007] The person skilled in the art knows that this problem can be solved by using Lindlar catalyst. Such Lindlar catalysts are heterogeneous catalysts consisting of palladium deposited on calcium carbonate or barium sulfate then poisoned with various forms of lead and are named after Herbert Lindlar.

[0008] These Lindlar catalysts are used in large scale particularly in the production of intermediates for vitamins E, A and aroma compounds.

[0009] However, the use of lead containing compounds should be minimized from an environmental point of view. Furthermore, there is a large demand for different types of catalysts allowing a selective hydrogenation of alkynes to alkenes, i.e. without the formation of considerable amounts of the respective alkane. It is particularly desired to have lead-free hydrogenation catalysts for this purpose.

[0010] Different approaches have been tried to solve this problem.

[0011] A particular promising attempt has been disclosed by McNeice et al., in Green. Chem, 2022, 24, 6912 in which a cobalt-based hydrogenation catalyst is suggested to be used for selective hydrogenations. However, the use of cobalt catalysts requires relatively harsh reaction conditions and, particularly, is very disadvantageous in view of toxicity. In addition, harsh reaction conditions generally lead to lower selectivities. - 2 - 34790-WO-PCT[2]

[0012] Summary of the invention

[0013] Therefore, the problem to be solved by the present invention is to offer a process for the hydrogenation of alkynes to yield selectively the corresponding alkenes, i.e. without the formation of considerable amounts of the respective alkanes.

[0014] Surprisingly, it has been found that the process according to claim 1 offers a solution to this problem.

[0015] It has been found that a catalyst based on Ni and Pd can be used for the selective hydrogenation at particularly high conversion, yield and selectivity.

[0016] Further aspects of the invention are subject of further independent claims. Particularly preferred embodiments are subject of dependent claims.

[0017] Detailed description of the invention

[0018] In a first aspect the present invention relates to a process of preparing an alkene from an alkyne by selectively hydrogenating the carbon-carbon triple bond to a carbon-carbon double bond by using a hydrogen source, and a hydrogenation catalyst which comprises at least the two transition metals Ni and Pd and a solid carrier material which contains nitrogen and carbon atoms on its surface.

[0019] For sake of clarity, some terms used in the present document are defined as follows:

[0020] In the present document, a “Cx-y-alkyl” group is an alkyl group comprising x to y carbon atoms, i.e., for example, a Ci-3-alkyl group is an alkyl group comprising 1 to 3 carbon atoms. The alkyl group can be linear or branched. For example -CH(CH3)-CH2-CH3 is considered as a C4-alkyl group.

[0021] In case identical labels for symbols or groups are present in several formulae, in the present document, the definition of said group or symbol made in the context of one specific formula applies also to other formulae which comprises the same said label. - 3 - 34790-WO-PCT[2]

[0022] The term “independently from each other” in this document means, in the context of substituents, moieties, or groups, that identically designated substituents, moieties, or groups can occur simultaneously with a different meaning in the same molecule.

[0023] Any single dotted line in any formulae represents the bond by which said substituent is bound to the rest of a molecule.

[0024] In the present document, any wavy line represents independently from each other a carbon-carbon bond which when linked to the carbon-carbon double bond is either in the Z or in the E-configuration.

[0025] In the present document, “aralkyl” group is an alkyl group of which at least one H is substituted by an aryl group. Hence, for example, benzyl (=CeH5-CH2-) is a Cyaralkyl group.

[0026] The term “a linear or branched or cyclic C1-25 alkyl group” as used in this document clearly is to be understood as a short term for embracing linear C1-25 alkyl groups, branched C3-25 alkyl groups and cyclic C3-25 alkyl groups as there exist no branched or cyclic Ci and C2 groups.

[0027] Hydrogenation catalyst

[0028] Said hydrogenation catalyst which comprises preferably a support material, often also referred as carrier material, being carbon, SiO2 or AI2O3.

[0029] The AI2O3 can be of different crystal phases or polymorphs. Particularly suitable as AI2O3 is a -AI2O3, -AI2O3 or y -AI2O3.

[0030] The hydrogenation catalyst comprises least the two transition metals Ni and Pd. Therefore, any suitable hydrogenation catalyst comprises mandatorily at least palladium and nickel.

[0031] Next to Ni and Pd, there might be also some further transition metals present. It is, however, preferred that the amount of such additional transition metals is lower, particularly significantly lower, typically less than half, than the amount of Ni and Pd, particularly less than the combined weight of Ni and Pd. - 4 - 34790-WO-PCT[2]

[0032] As the present hydrogenation catalyst is suitable for selectively hydrogenating the carbon-carbon triple bond of an alkyne to a carbon-carbon double bond of an alkene even in the absence of lead, it is preferred that the hydrogenation catalyst is free of Pb.

[0033] In view of the weight ratio of Pd versus Ni, it is preferred that Ni is in excess in relation to the Pd.

[0034] It is particularly preferred that the weight ratio of Ni to Pd is in the range of between 500:1 and 10:1 , preferably of between 300:1 and 20:1 , particularly preferred between 200:1 and 50:1.

[0035] The Ni and Pd atoms of the hydrogenation catalyst can be either present as separate metal particles or in an agglomerated or in alloyed form.

[0036] In one of the embodiments the Ni and Pd particles are agglomerated. Typically, the size of the transition metal particles on the surface of the carrier are in the range of 5 to 30 nm, particularly of between 8 and 15 nm.

[0037] The agglomeration can be detected for example by Scanning Transmission Microscopy (STEM), particularly by High-Angle Annular Dark-Field imaging (HAADF).

[0038] In another, preferred, embodiment, the Ni and Pd particles are not agglomerated. In this embodiment the transition metal particles are essentially present as single metal atoms. Typically for this embodiment more than 80 %, preferably more than 90 %, of Ni and Pd are present as single, i.e. not agglomerated, metal atoms.

[0039] It is preferred that that particle size, determined by transmission electron microscopy (TEM) of the hydrogenation catalyst is between 1 nm and 1 u m, particularly between 1 nm and 300 nm, preferably between 5 nm and 200 nm.

[0040] Furthermore, the solid carrier material of the hydrogenation catalyst contains nitrogen and carbon atoms on its surface. There are different methods - 5 - 34790-WO-PCT[2] possible how the carbon and nitrogen atoms can be brought on to the carrier surface.

[0041] It has been found that said hydrogenation catalyst can be prepared particularly suitably by a method of preparing comprising the steps a) coating the surface of the solid carrier material at least partially, preferably completely, by an organic coating, particularly by a polymer coating which comprises significant amounts of nitrogen and carbon atoms; b) subsequently exposing said coating exposed to high temperature under respective conditions to pyrolyze said coating, leaving nitrogen and carbon atoms at the surface of the carrier material forming a carbon / nitrogen modified carrier material; c) subsequently exposing said carbon / nitrogen modified carrier material with Ni and Pd, particularly with a Ni and Pd salt or complex solution; forming a precursor hydrogenation catalyst; and d) exposing the precursor hydrogenation catalyst to temperatures lower than those used in step b) to stabilize the surface of the hydrogenation catalyst and yielding the final hydrogenation catalyst.

[0042] In a preferred embodiment, the hydrogenation catalyst is particularly prepared by a process comprising the following steps i) coating the surface of AI2O3 by a polymer prepared from a polyamine, preferably a diamine or a triamine; ii) adding ammonia or urea to the mixture after step i); iii) heating the mixture obtained by step ii) under an inert gas at a temperature of between 600°C and 1000°C, particularly between 700 °C and 900°C, preferably between 750°C and 850°C, for at least 1 hour, preferably between 1 hour and 8 hours, to yield a solid (N / C@AI2O3), iv) mixing a solution, particularly an aqueous solution, of a Ni salt and Pd salt with the solid (N / C@AhO3) obtained in step iii); - 6 - 34790-WO-PCT[2] v) treating the mixture obtained by step iv) under an inert gas at a temperature of between 150°C and 300°C for at least 1 hour, preferably between 1 hour and 8 hours, to yield the hydrogenation catalyst (PdNi-N / C@AI2O3).

[0043] The term “polyamine” as used in the present document refer to substances formally containing amino groups, particularly two or more NH2 groups per molecule.

[0044] Preferred polyamines are polyamines of the group consisting of dicyandiamide, melamine, mono- and di-aminopyridines, diaminobenzenes, ureas, bipyridines, phenanthrolines, phthalocyanines, preferably 2,6-diaminopyridine, 2 ,2’-bipyridine, phenanthroline, phthalocyanine and urea, or derivatives thereof. Most preferably the polyamine is 2,6-diaminopyridine.

[0045] Said polyamines are forming a polymer. This polymer can be prepared directly from said polyamines or by a reaction of the polyamines with another suitable molecule. The polymerization is typically performed by a condensation or addition reaction or by free radical polymerization.

[0046] Particularly, the polymer is prepared from the polyamine by free radical polymerization using particularly persulfate salts as initiator. Typically said radical polymerization is performed in aqueous solution.

[0047] The Ni and Pd source is typically a salt or a complex, preferably a salt, of Ni or Pd. It is preferred that said Ni or Pd salt or complex is used as solution or dispersion preferable as a solution in a suitable solvent or solvent mixture, particularly as an aqueous solution.

[0048] It is further preferred that the salt or complex is a salt or complex of Ni(ll) and / or Pd(ll). Accordingly, it is preferred that the Ni or Pd salt has suitable ligands and / or anions allowing good solubility in the selected solvent, particularly in water. Particularly suitable as Ni and Pd salts are Ni(ll) or Pd(ll) nitrates, sulfates, hydrogen sulfates, carboxylates, particularly benzoates or acetates, halogenated carboxylates, particularly trifluoracetates and halides, particularly chlorides. - 7 - 34790-WO-PCT[2]

[0049] The person skilled in the art knows that certain of the above-mentioned salts exist also in the form of hydrates which may be preferably used allowing a better solubility of the Pd respectively the Ni source.

[0050] Examples of Pd or Ni complexes are Ni(ll)acetylacetonate (Ni(acac)2) nickel acetate, nickel benzoate and Pd(ll)acetylacetonate (Pd(acac)2), palladium acetate palladium benzoate.

[0051] Most preferred source of Ni and Pd are selected from the group consisting of Ni(ll) diacetate, Pd(ll) diacetate, Pd(benzoate) Ni(NO3)2, NiC , Pd(NO3)2, PdC , H2PdCl4 and their respective hydrates, particularly Ni(NO3)2'6H2O or Pd(NO3)2'2H2O.

[0052] It has been observed that the above catalyst is, compared to a cobalt hydrogenation catalyst, is not only advantageous in view of toxicity but also shows milder reaction conditions in the hydrogenation reaction, such as temperature and pressure, and yield the desired product in a higher selectivity.

[0053] Hydrogen source

[0054] The selective hydrogenation process requires a hydrogen source.

[0055] The required hydrogen source is particularly either molecular hydrogen or a gas containing molecular hydrogen or a hydrogen donor or a transfer hydrogenation agent.

[0056] The hydrogenation can also be carried out in the presence of a reductant or hydrogen donor or a transfer hydrogenation agent, in place of molecular hydrogen. Suitable hydrogen donors or transfer hydrogenation agents are particularly formic acid, formate salts, hydrazine, and alcohols such as 2-propanol.

[0057] The preferred hydrogen source is molecular hydrogen.

[0058] Alkyne

[0059] The alkyne which is selectively hydrogenated to alkene is particularly of the formula (I). The resulting alkene is accordingly preferably an alkene of the formula (II)

[0060] R1- - R2(I) - 8 - 34790-WO-PCT[2]

[0061] Herein R1represents a linear or branched or cyclic C1-25 alkyl group, which optionally is substituted by OH OR, NHR, NRRa, NH2, C(=O)Ra; or a linear or branched or cyclic C1-42 alkenyl group, which optionally is substituted by OH, NHR, NRRa, NH2, C(=O)Ra; or a Ce-15 aryl group, which optionally is substituted by OH, OR, C(=O)Ra, halide, NO2, or a linear or branched C1-3 alkyl group, and

[0062] R2represents

[0063] H; or a linear or branched, or cyclic C1-20 alkyl group, which optionally is substituted by OH, NHR, NRRa, NH2, C(=O)Ra; or a linear or branched or cyclic C1-20 alkenyl group, which optionally is substituted by OH, NHR, NRRa, NH2, C(=O)Ra; or a Ce-15 aryl group, which optionally is substituted by OH, OR, C(=O)Ra, halide, NO2, or a linear or branched C1-3 alkyl group wherein

[0064] R represents a linear or branched or cyclic C1-25 alkyl group; and

[0065] Rarepresents H or a linear or branched or cyclic C1-25 alkyl group or a C7-16 aralkyl group; and wherein any wavy line represents independently from each other a carboncarbon bond which when linked to the carbon-carbon double bond is either in the Z or in the E-configuration.

[0066] In one of the preferred embodiments, the alkyne is a compound of the formula - 9 - 34790-WO-PCT[2] in which Rxand Ryindependently from each represent

[0067] H; or a linear or branched or cyclic C1-25 alkyl group; or a halogenated linear or branched or cyclic C1-25 alkyl group, particularly a perfluorinated linear C1-25 alkyl group, preferably a trifluoromethyl group; or a C1-25 alkyoxy group, particularly a methoxy group; or an electron withdrawing group particularly an electron with drawing group selected from the group consisting of NO2, CN and C(O)RZwherein Rzrepresents H or a a linear or branched or cyclic C1-25 alkyl group or an aryl group, particularly a phenyl group. with the proviso that at least one of the substituents Rxand Ryis different from H; and x1 and y1 represent an integer of 1 to 4 with the proviso that the sum of x1 and y1 is 5;

[0068] In another preferred embodiment, the alkyne is an alkynol, particularly an alkyne having a terminal alkynol group of the formula wherein

[0069] R3represents a methyl or ethyl group, preferably a methyl group;

[0070] R’ represents H or COR”, preferably H; - 10 - 34790-WO-PCT[2] wherein R” represents a C1-6 alkyl group, preferably a methyl group; and the dotted line represents the bond by which said group is bound to the rest of the molecule. It is preferred that the alkyne is selected from the group consisting of alkynol having a having a terminal alkynol group of the formula as described above.

[0071] Most preferably, alkyne is an alkynol having a terminal alkynol group of the formula as described above. In a very preferred embodiment, the alkyne is alkyne of the formula (l-A) and the alkene is an alkene of the formula ( I l-A)

[0072] (l-A) (ll-A) wherein

[0073] R3represents a methyl or ethyl group, preferably a methyl group;

[0074] R4represents a saturated or unsaturated linear or branched or cyclic hydrocarbyl group with 1 to 46 C atoms, preferably with 1 to 21 C atoms;

[0075] R’ represents H or COR”, preferably H; wherein R” represents a C1-6 alkyl group, preferably a methyl group.

[0076] It is further preferred, that the substituent R4is selected from the group wherein the dotted line represents the bond by which the substituent of the formula (R4-I), (R4-II), (R4-III) or (R4-IV) is bound to the rest of the compound of the formula (l-A) or formula (ll-A); and wherein any double bond having dotted line ( ) represents independently from each other either a single carbon-carbon bond or a carbon-carbon double bond; and wherein any wavy line represents independently from each other a carbon-carbon bond which when linked to the carbon-carbon double bond is either in the Z or in the E-configuration; and wherein n represents 1 , 2, 3 or 4, particularly 1 or 2. - 12 - 34790-WO-PCT[2]

[0077] It is mostly preferred that the alkyne is an alkynol selected from the group consisting of preferably selected from the group consisting of - 13 - 34790-WO-PCT[2]

[0078] It has been found that the above-described process is particularly suitable for hydrogenate alkynes selectively to an alkenes in particularly high conversion, yield and selectivity.

[0079] In a further aspect, the invention relates to a composition comprising a) an alkyne; particularly an alkynol, preferably an alkynol having terminal ormula wherein R’ represents H or COR”, preferably H; wherein R” represents a C1-6 alkyl group, preferably a methyl group; and wherein the dotted line represents the bond by which said group is bound to the rest of the molecule;

[0080] P) a hydrogen source, particularly molecular hydrogen or a gas containing molecular hydrogen or a hydrogen donor or a transfer hydrogenation agent, preferably molecular hydrogen; y) a hydrogenation catalyst comprising at least the two transition metals Ni and Pd and a support material which contains nitrogen and carbon atoms on its surface,

[0081] As described above in great detail, said composition is suitable to be reacted to yield the corresponding alkene, particularly alkenol, preferably alkenol - 14 - 34790-WO-PCT[2] having terminal alkenol group of the formula high conversion, yields and selectivity.

[0082] It has been found that after the selective hydrogenation particular low amounts, preferably none, of the respective alkane, respectively alkanol, anols with the terminal alkanol group of the formula have been observed in the reaction product.

[0083] Examples

[0084] The following examples are provided to further illustrate the compositions and effects of the present invention. These examples are illustrative only and are not intended to limit the scope of the invention in any way.

[0085] Example preparation of PdNi-N / C&A Os

[0086] 5.5 g 2,6-diaminopyridine and 5.5 g AI2O3 (Aldrich, Aluminum oxide nanopowder, <50nm particle size (TEM)) were firstly mixed in 250 mL H2O under vigorous stirring for 10 min. Then 0.75 g NaOH was added into the solution above under agitation for another 10 min. Next, 18 g / 50 ml (NH4)2S20s aqueous solution was quickly dropped into the resultant solution with successive stir for 16 h in ice bath for sufficient polymerization. The polymerized product was collected by filtration with water alternatively several times, and then dried in an oven 80°C overnight. Subsequently, 2 g of the as-prepared solid was mixed with 2 g of urea and milled to powder. Then solid mixture was heated at 800°C for 2 h with a ramping rate of 5°C / min. 1 .3 g of the solid N / C@AhO3 was obtained.

[0087] 10 mg Pd(NO3)2'2H2O was first dissolved in 100 mL water and stored overnight. Desired amount (to obtain the Ni / Pd) of Pd(NOs)2 aqueous solution and Ni(NO3)2'6H2O were dissolved in 16 mL water. Then N / C@AhO3 powder was dispersed into the above solution under sonication for 5 min. Subsequently, the - 15 - 34790-WO-PCT[2] mixed solution was stirred for 16 h at 50°C. Afterwards, the mixed solution was filtered and washed repeatedly using water. The resulted sample was dried in an oven at 80°C overnight and then heated in Ar at 200°C with a heating rate of 5°C / min for 2 h to obtain the final catalyst PdNi-N / C@AhO3

[0088] Semi-hydrogenation of dehydroisophytol (DIP).

[0089] All of the prepared materials were tested as catalysts without any further treatment. For the following experiments the general reaction procedure was used (unless given different conditions):

[0090] 100 mg of catalyst, 1000 mg of substrate were added in a 4 mL vial with magnetic stirring bar and septum cap. Then, a needle was inserted in the septum, allowing H2 to enter the vial. The vials (up to eight) were set in an alloy plate and placed in a 300 mL steel Parr autoclave. The autoclave was flushed with H2 3 times at 10 bar and finally pressurized to 10 bar. Then, it was placed into an aluminium block and kept at 100 °C for 24 h. When the reaction was complete, the autoclave was vented. Finally, the samples were removed from the autoclave with the addition of 80 pL of n-dodecane as internal standard and pentane to the crude mixture, followed by centrifugation to separate the catalyst and product.

[0091] Different transition metals in the catalyst

[0092] In a first series of experiments, different catalysts have been prepared and used for the semi-hydrogenation of dehydroisophytol (DIP). For these experiments the respective transition metal salts have been used in the preparation of the catalyst of table 1 instead. In example Ref.0, the metal free catalyst N / C@AhO3 as described above, was used as such. The respective conversions and yields obtained have been compiled in table 1 . - 16 - 34790-WO-PCT[2]

[0093] Table 1. Selective hydrogenation of 3,7,11 , 15-tetram ethyl hexadec-1 -yn- 3-ol using different catalysts. Conditions: 10 bar, 60°C, 16 h.

[0094] 1Loading in Pd, Pt or Ru is set as 0.02 wt.% and loading in Ni, Co, Cu or Fe is 2 wt.%.

[0095] Table 1 clearly shows that the combined use of both Pd and Ni is essential to obtain the desired product, i.e. IP in a high yield and selectivity. Different carriers in the catalyst

[0096] In a second series of experiments, different carriers have been prepared and used for the semi-hydrogenation of dehydroisophytol (DIP). The respective conversions and yields obtained have been compiled in table 2.

[0097] Table 2. Selective hydrogenation of 3,7,11 ,15-tetramethylhexadec-1 -yn-3-ol using different carrier for the catalyst.

[0098] Conditions: 10 bar, 60°C, 16 h.

[0099] 1Pd loading is set as 0.02 wt.% and Ni loading is 2 wt.%.

[0100] - 17 - 34790-WO-PCT[2]

[0101] Different Pd precursors

[0102] In a third series of experiments, different Pd salts have been used for the synthesis of the catalysts which then have been used for the semi-hydrogenation of dehydroisophytol (DIP). The respective conversions and yields obtained have been compiled in table 3.

[0103] Conditions: 10 bar, 120°C, 16 h.

[0104] Pd loading is set as 0.02 wt.% and Ni loading is 2 wt.%.

[0105] Different ratios of metals in the catalyst

[0106] In a fourth series of experiments, ratio of Ni and Pd has been varied in the catalyst PdNi-N / C@Al2O3 used in in the semi-hydrogenation of dehydroisophytol (DIP). The respective conversions and yields obtained have been compiled in table 4.

[0107] Table 4. Selective hydrogenation of 3,7,11 ,15-tetramethylhexadec-1-yn-3-ol using different Ni / Pd wt. / wt. ratio in PdNi-N / C@Al2O3. Conditions: 10 bar, 120°C, 16 h.

[0108] Different substrates used for the semi-hydogenation

[0109] In a fifth series of experiments, the following substrates, i.e. alkynes, have been used in the semi-hydrogenation to get the desired alkenes and the undesired alkanes: - 18 - 34790-WO-PCT[2] - 19 - 34790-WO-PCT[2]

[0110] The respective conversions and yields obtained have been compiled in table 5.

[0111] N / C@AI2O3.

[0112] Conditions: 10 bar, 100°C, 24 h.110 bar, 120°C, 16h.

[0113] Pd loading is set as 0.02 wt.% and Ni loading is 2 wt.%. - 20 - 34790-WO-PCT[2]

[0114] Selectivity of catalyst

[0115] In a final experiment a hydrogenation of isophytol (IP) has been attempted using the catalyst PdNi-N / C@Al2O3. The results have been reported in table 6.

[0116] The comparison of the results of these experiments with those shown previously clearly shows that the catalyst is very selective for the hydrogenation of alkyne to the respective alkene. Further hydrogenation of alkene to the respective alkane is observed to occur only to a very small amount.

Claims

- 21 - 34790-WO-PCT[2]Claims1 . A process of preparing an alkene from an alkyne by selectively hydrogenating the carbon-carbon triple bond to a carbon-carbon double bond by using a hydrogen source, and a hydrogenation catalyst which comprises at least the two transition metals Ni and Pd and a solid carrier material which contains nitrogen and carbon atoms on its surface.

2. The process according to claim 1 , characterized in that the hydrogenation catalyst comprises a solid carrier material being carbon, SiCh or AI2O3.

3. The process according to claim 1 or 2, characterized in that the solid carrier material is a -AI2O3, -AI2O3 or y -AI2O3.

4. The process according to any of the preceding claims, characterized in that the weight ratio of Ni to Pd is in the range of between 500:1 and 10:1 , preferably of between 300:1 and 20:1 , particularly preferred between 200:1 and 50:1 .

5. The process according to any of the preceding claims, characterized in that particle size, determined by transmission electron microscopy (TEM) of the hydrogenation catalyst is between 1 nm and 1 u rn, particularly between 1 nm and 300 nm, preferably between 5 nm and 200 nm.

6. The process according to any of the preceding claims, characterized in that the size of the transition metal particles on the surface of the carrier are in the range of 5 to 30 nm, particularly of between 8 and 15 nm.

7. The process according to claim 6, characterized in that the particles of Ni and Pd are agglomerated.- 22 - 34790-WO-PCT[2]8. The process according to claim 6, characterized in that the metal particles are not agglomerated.

9. The process according to any of the preceding claims 3 to 8, characterized in that the hydrogenation catalyst is prepared by a process comprising the steps: i) coating the surface of AI2O3 by a polymer prepared from a polyamine, preferably a diamine or a triamine; ii) adding ammonia or urea to the mixture after step i); iii) heating the mixture obtained by step ii) under an inert gas at a temperature of between 600°C and 1000°C, particularly between 700 °C and 900°C, preferably between 750°C and 850°C, for at least 1 hour, preferably between 1 hour and 8 hours, to yield a solid N / C@AI2O3iv) mixing a solution, particularly an aqueous solution, of a Ni salt and Pd salt with the solid N / C@AI2O3obtained in step iii); v) treating the mixture obtained by step iv) under an inert gas at a temperature of between 150°C and 300°C for at least 1 hour, preferably between 1 hour and 8 hours, to yield the hydrogenation catalyst PdNi-N / C@AI2O3.

10. The process according to any of the preceding claims, characterized in that the hydrogenation catalyst is free of Pb.11 . The process according to any of the preceding claims, characterized in that the alkyne is an alkyne of the formula (I) and the alkene is an alkene of the formula (II)whereinR1represents a linear or branched or cyclic C1-25 alkyl group,- 23 - 34790-WO-PCT[2] which optionally is substituted by OH OR, NHR, NRRa, NH2, C(=O)Ra; or a linear or branched or cyclic C1-42 alkenyl group, which optionally is substituted by OH, NHR, NRRa, NH2, C(=O)Ra; or a Ce-15 aryl group, which optionally is substituted by OH, OR, C(=O)Ra, halide, NO2, or a linear or branched C1-3 alkyl group, andR2representsH; or a linear or branched, or cyclic C1-20 alkyl group, which optionally is substituted by OH, NHR, NRRa, NH2, C(=O)Ra; or a linear or branched or cyclic C1-20 alkenyl group, which optionally is substituted by OH, NHR, NRRa, NH2, C(=O)Ra; or a Ce-15 aryl group, which optionally is substituted by OH, OR, C(=O)Ra, halide, NO2, or a linear or branched C1-3 alkyl group whereinR represents a linear or branched or cyclic C1-25 alkyl group; andRarepresents H or a linear or branched or cyclic C1-25 alkyl group or a C7-16 aralkyl group; and wherein any wavy line represents independently from each other a carboncarbon bond which when linked to the carbon-carbon double bond is either in the Z or in the E-configuration.

12. The process according to any of the preceding claims, characterized in that the alkyne is an alkynol, particularly an alkyne having a terminal alkynol group of the formulawhereinR3represents a methyl or ethyl group, preferably a methyl group;R’ represents H or COR”, preferably H; wherein R” represents a C1-6 alkyl group, preferably a methyl group; and the dotted line represents the bond by which said group is bound to the rest of the molecule.

13. The process according to any of the preceding claims, characterized in that the alkyne is alkyne of the formula (l-A) and the alkene is an alkene of the formula (I l-A)whereinR3represents a methyl or ethyl group, preferably a methyl group;R4represents a saturated or unsaturated linear or branched or cyclic hydrocarbyl group with 1 to 46 C atoms, preferably with 1 to 21 C atoms;R’ represents H or COR”, preferably H; wherein R” represents a C1-6 alkyl group, preferably a methyl group.

14. The process according to claim 13, characterized in that the substituent R4is selected from the group consisting of formula (R4-I), (R4-II), (R4-III) and (R4-IV)- 25 - 34790-WO-PCT[2]wherein the dotted line represents the bond by which the substituent of the formula (R4-I), (R4-II), (R4-III) or (R4-IV) is bound to the rest of the compound of the formula (l-A) or formula (ll-A); and wherein any double bond having dotted line ( - ) represents independently from each other either a single carbon-carbon bond or a double carbon-carbon bond; and wherein any wavy line represents independently from each other a carbon-carbon bond which when linked to the carbon-carbon double bond is either in the Z or in the E-configuration; and wherein n represents 1 , 2, 3 or 4, particularly 1 or 2.

15. A composition comprising a) an alkyne; particularly an alkynol, preferably an alkynol having terminal alkynol group of the formulawherein R’ represents H or COR”, preferably H; wherein R” represents a C1-6 alkyl group, preferably a methyl group; and wherein the dotted line represents the bond by which said group is bound to the rest of the molecule;P) a hydrogen source, particularly molecular hydrogen or a gas comprising molecular hydrogen or a hydrogen donor or a transfer hydrogenation agent, preferably molecular hydrogen; y) a hydrogenation catalyst comprising at least the two transition metals Ni and Pd and a support material which contains nitrogen and carbon atoms on its surface.