Catalytic system of bimetallic nanoparticles based on group VIII and / or IB metal

Abstract

The present invention relates to a catalytic system in the form of a colloidal suspension comprising a plurality of bimetallic nanoparticles based on at least one metal from group VIII and / or a metal from group IB, characterized in that said nanoparticles have a number average diameter of less than 10 nm, and in that the standard deviation relative to the size of said nanoparticles is less than or equal to 50% of said average diameter.

Description

Title of the invention: Catalytic system of bimetallic nanoparticles based on metal from group VIII and / or IB Field of the invention

[0001] The invention relates to the synthesis of a catalytic system in the form of a colloidal suspension based on bimetallic nanoparticles based on metals from group VIII and / or IB, as well as a supported catalyst obtained by bringing such a suspension into contact with a support comprising at least one refractory oxide. State of the art

[0002] It is known to prepare catalysts comprising an active phase based on at least one transition metal for their use in various fields of chemistry, in particular in the field of catalytic transformations such as hydrogenation, dehydrogenation, or the activation of carbon-hydrogen CH bonds. The metal is in the form of nanometric metal particles deposited on a support which may be a refractory oxide. The metal content, the possible presence of a second metallic element, the size of the metal particles and the distribution of the active phase in the support as well as the nature and porous distribution of the support are parameters which have an importance on the performance of the catalysts. With regard to the size of the metal particles, it is generally accepted that the catalyst is all the more active as the size of the metal particles is small.Furthermore, it is important to obtain a particle size distribution centered on the optimal value as well as a narrow distribution around this value.

[0003] The synthesis of such catalysts can be carried out in several ways. Typically, a first way consists of the impregnation on a porous support of metal salts, for example nickel and cobalt salts, or nickel and copper salts, as described for example in the scientific publication by Chen et al. entitled "Carbon dioxide reforming of methane reaction catalyzed by stable nickel copper catalysts", Catalysis Today 97 (2004), 173-180. However, such a preparation route does not allow the size and distribution of the nanoparticles of the metals constituting the active phase of the catalyst, as well as their chemical composition, to be controlled.

[0004] Another synthesis route consists of the preparation in a first stage of nanoparticles of metals of the active phase in suspension in a solution in the presence of stabilizing agents and under hydrogen pressure, then in a second time of impregnation of said nanoparticles in suspension on a porous support. Such a process is described in particular in the scientific publication by Chaudret et al. entitled “Tuning the Composition of FeCo Nanoparticle Heating Agents for Magnetically Induced Catalysis”, Applied Nano Materials, 3, 2020, 3, 3767-3778. Such a preparation process makes it possible to obtain catalysts comprising bimetallic nanoparticles of well-defined composition. However, the size of the nanoparticles obtained is much too large (10 nm or more).

[0005] The Applicant in its research has developed a new process for preparing a catalytic system in the form of a colloidal suspension comprising a plurality of small bimetallic nanoparticles, more specifically less than 10 nm, with a very narrow particle size distribution, and of well-defined chemical composition. Subject of the invention

[0006] An object according to the invention relates to a catalytic system in the form of a colloidal suspension comprising a plurality of bimetallic nanoparticles based on at least one metal from group VIII and / or one metal from group IB, characterized in that said nanoparticles have a number average diameter of less than 10 nm, measured by transmission electron microscopy, and in that the standard deviation relative to the size of said nanoparticles is less than or equal to 50% of said average diameter.

[0007] Surprisingly, the Applicant has developed a new process for preparing a catalytic system in the form of a colloidal suspension comprising a plurality of bimetallic nanoparticles comprising at least one metal from group VIII and / or at least one metal from group IB, said process making it possible to obtain nanoparticles of very small diameter, i.e. having a number average diameter of less than 10 nm, with a very narrow particle size distribution, and of very precise composition, i.e. all of the bimetallic nanoparticles all have the same atomic ratio between the two constituent metals of said nanoparticles. In addition, such a preparation process makes it possible to obtain bimetallic nanoparticles whose constituent metals are already in reduced form, which makes it possible to save an additional step of reducing the catalyst before its use.This catalytic system can be supported on refractory oxides, such as silica, silica-alumina, or alumina, for use in various heterogeneous catalysis applications.

[0008] According to one or more embodiments, said bimetallic nanoparticles are based on nickel and cobalt.

[0009] According to one or more embodiments, said bimetallic nanoparticles correspond to the formula NixCoy with x and y integers between 1 and 20, preferably between 1 and 5, and more preferably between 1 and 4.

[0010] According to one or more embodiments, x = 1 and y is between 1 and 4.

[0011] According to one or more embodiments, said bimetallic nanoparticles are based on nickel and copper.

[0012] According to one or more embodiments, said bimetallic nanoparticles correspond to the formula Nix Cuy- with x' and y' integers between 1 and 20, preferably between 1 and 5, and more preferably between 1 and 3.

[0013] According to one or more embodiments, x' = 1 and y' is between 1 and 3.

[0014] According to one or more embodiments, said nanoparticles have a diameter average number less than 7 nm, and the standard deviation relative to the size of said nanoparticles is between 20% and 50% of said average diameter.

[0015] According to one or more embodiments, said nanoparticles are in reduced form.

[0016] Another object according to the invention relates to a process for preparing a catalytic system according to the invention comprising at least the following steps:

[0017] a) at least one organometallic precursor based on at least one metal from group VIII and / or at least one organometallic precursor based on at least one metal from group IB is supplied separately;

[0018] b) said organometallic precursors supplied at the end of step a) are brought into contact in the presence of a solvent, at least one first stabilizing agent and at least one second stabilizing agent to obtain a colloidal suspension, said step b) comprising the following sub-steps:

[0019] bl) said organometallic precursors supplied at the end of step a) are brought into contact in the presence of the solvent to obtain a first solution;

[0020] b2) the first solution obtained at the end of step b1) is brought into contact with at least minus a first stabilizing agent to obtain a second solution;

[0021] b3) the second solution obtained at the end of step b2) is brought into contact with at least at least one second stabilizing agent, different from the first stabilizing agent, to obtain the colloidal suspension;

[0022] c) said colloidal suspension obtained at the end of step b) is heated to a temperature between 25°C and 180°C under a hydrogen pressure between 0.01 MPa and 1 MPa to obtain said catalytic system.

[0023] According to one or more embodiments according to the invention, said metal precursors supplied in step a) are chosen from transition metal complexes of nickel, cobalt and / or copper, neutral or charged, containing one or more organic or inorganic ligands.

[0024] According to one or more embodiments according to the invention:

[0025] - when said metal precursor is chosen from metal complexes of nickel transition, the oxidation state of nickel in the complex is 0, 1, 2, 3 or 4;

[0026] - when said metal precursor is chosen from metal complexes of cobalt transition, the oxidation state of cobalt in the complex is 0, 1, 2 or 3;

[0027] - when said metal precursor is chosen from metal complexes of copper transition, the oxidation state of copper in the complex is 0, 1, 2 or 3.

[0028] According to one or more embodiments according to the invention, said transition metal complexes comprise several ligands, identical or different from each other, linked or not to each other, and chosen from a hydride, fluoride, chloride, bromide, iodide group, an organic compound, preferably an alkyl, cyclic or not, having from 1 to 15 carbon atoms (in C1-C15) comprising or not one or more heteroelements and / or one or more multiple bonds, and / or an organic compound, preferably a substituted or unsubstituted aryl, having between 4 and 15 carbon atoms (in C4-C15) comprising or not one or more heteroelements, or a substituted or unsubstituted aryl having between 4 and 15 carbon atoms (in C4-C15) comprising or not one or more heteroelements.

[0029] According to one or more embodiments according to the invention, when said organometallic precursor is nickel-based, said precursor is chosen from nickel(II) bis-(hexamethyldisilazane) [Ni[iPrNC(CH3)NiPr]2]; nickel(II) bis-[N,N'-di(isopropyl)methylcarbodiimide] [Ni[iPrNC(CH2CH2CH2CH3)NiPr]2]; nickel(II) bis-[N,N'-di(cyclohexyl)methylcarbodiimide] [Ni[CyNC(CH3 )NCy]2]; nickel(II) bis-(1,5-cyclooctadiene)nickel(0), Ni(q4-C8Hi2)2.

[0030] According to one or more embodiments according to the invention, when said organometallic precursor is based on copper, said precursor is chosen from copper(II) bis-(hexamethyldisilazane) [Cu(hmds)2]; copper(I) bis-[N,N'-di(isopropyl)methylcarbodiimide] {Cu[iPrNC(CH3)NiPr]}2; copper(I) bis-[N,N'-di(isopropyl)n-butylcarbodiimide] {Cu[iPrNC(CH2CH2CH2CH3)Ni Pr]}2; copper(I) bis-[N,N'-di(cyclohexyl)methylcarbodiimide] {Cu[CyNC(CH3 )Cy]}2.

[0031] According to one or more embodiments according to the invention, when said organometallic precursor is based on cobalt, said precursor is chosen from bis-(hexamethyldisilazane)tetrahydrofuran cobalt(II) |Co( / 2w / .s)2(tiif)]; bis-[N,N'-di(isopropyl)methylcarbodiimide] of cobalt(II), [Co[iPrNC(CH3)NiPr]2]; bis-[N,N'-di(isopropyl)n-butylcarbodiimide] of cobalt(II), [Co[iPrNC(CH2CH2CH2CH3)Ni Pr]2]; bis-[N,N'-di(cyclohexyl)methylcarbodiimide] of cobalt(II), [Co[CyNC(CH3 )NCy]2]; (1,5-cyclooctadiene)(cyclooctadienyl) cobalt (I), Co(q3-C8Hi3)(q4-C8Hi2).

[0032] According to one or more embodiments according to the invention, said first stabilizing agent and / or said second stabilizing agent are chosen from carboxylic acids, carboxylate anions, primary, secondary or tertiary amines, primary, secondary, tertiary or quaternary ammonium cations, amides, esters, alcohols, alcoholates, thiols, thiolates, saturated or unsaturated, having between 1 and 30 carbon atoms.

[0033] According to one or more embodiments according to the invention, the first stabilizing agent is palmitic acid and the second stabilizing agent is hexadecylamine.

[0034] Another subject according to the invention relates to a process for preparing a catalyst comprising an active phase based on at least one metal from group VIII and / or at least one metal from group IB and a support comprising at least one refractory oxide, comprising the following steps:

[0035] i) said catalytic system according to the invention is brought into contact with a support comprising at least one refractory oxide to obtain a catalyst precursor;

[0036] ii) the catalyst precursor obtained at the end of step i) is dried at a temperature below 250°C to obtain a dried catalyst precursor;

[0037] iii) optionally, the dried catalyst precursor obtained in step ii) is calcined at a temperature between 250°C and 500°C.

[0038] Another subject according to the invention relates to a catalyst comprising a bimetallic active phase based on at least one metal from group VIII and / or at least one metal from group IB and a support comprising at least one refractory oxide obtained according to the process for preparing a catalyst according to the invention. Detailed description of the invention 1. Definitions

[0039] In the following, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group VIII (or VIIIB) according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUP AC classification.

[0040] In the present description, according to the IUP AC convention, micropores are understood to mean pores whose diameter is less than 2 nm, i.e. 0.002 pm; mesopores are understood to mean pores whose diameter is greater than or equal to 2 nm, i.e. 0.002 pm and less than or equal to 50 nm, i.e. 0.05 pm and macropores are understood to mean pores whose diameter is greater than 50 nm, i.e. 0.05 pm.

[0041] The total pore volume is measured by mercury porosimetry according to ASTM D4284-92 with a wetting angle of 140°, for example using an Autopore III™ model device from Microméritics™.

[0042] The BET specific surface area is measured by nitrogen physisorption according to the ASTM D3663-03 standard, a method described in the work Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academie Press, 1999.

[0043] The metal content is measured by X-ray fluorescence and / or by induction plasma spectroscopy (ICP).

[0044] In the present description, the term "comprise" is synonymous with (means the same as) "include" and "contain", and is inclusive or open and does not exclude other elements not recited. It is understood that the term "comprise" includes the exclusive and closed term "consist". Furthermore, in the present description, the term "substantially" corresponds to an approximation of ± 10%, preferably ± 5%, very preferably ± 2%, of a reference value such as a distance, a speed, a flow rate, a compound content, a temperature, a pressure, etc. 2. Catalytic system

[0045] An object according to the invention relates to a catalytic system in the form of a colloidal suspension comprising, preferably consisting of, a plurality of bimetallic nanoparticles based on at least one metal from group VIII and / or one metal from group IB, characterized in that said nanoparticles have a number average diameter of less than 10 nm, measured by transmission electron microscopy, preferably less than 9 nm, preferably less than 7 nm, more preferably less than 5 nm, even more preferably less than 4 nm, and even more preferably less than or equal to 3 nm, and in that the standard deviation relative to the size of said nanoparticles is less than or equal to 50% of said average diameter, preferably between 20% and 50%, more preferably between 20% and 35%, and even more preferably between 22% and 28%.

[0046] The person skilled in the art knows the techniques suitable for determining the average particle diameter and also knows the degree of uncertainty existing in these measurements. For example, the average particle diameter of a set, the standard deviation and the size distribution can be determined by statistical studies from microscopy images, and in particular by transmission electron microscopy (TEM). The number average diameter is calculated on at least 250 nanoparticles. The standard deviation is calculated as the square root of the variance.

[0047] According to one or more embodiments, said bimetallic nanoparticles are based on nickel and cobalt.

[0048] According to one or more embodiments, said bimetallic nanoparticles correspond to the formula NixCoy with x and y integers between 1 and 20, preferably between 1 and 5, and more preferably between 1 and 4.

[0049] Preferably, x = 1 and y is between 1 and 4. Even more preferably x = 1 and y = 1 or 4.

[0050] According to one or more embodiments, said bimetallic nanoparticles are based on nickel and copper.

[0051] According to one or more embodiments, said bimetallic nanoparticles correspond to the formula Nix Cuy- with x' and y' being integers between 1 and 20, preferably between 1 and 5, and more preferably between 1 and 3.

[0052] Preferably, x' = 1 and y' is between 1 and 3. Even more preferably x' = 1 and y' = 1 or 3.

[0053] Preferably, said nanoparticles are in reduced form, and more particularly said bimetallic nanoparticles of nickel and cobalt, or of nickel and copper are in the reduced state, that is to say in the zero valence state. 3. Process for preparing the catalytic system

[0054] The catalytic system according to the invention is prepared according to a particular preparation process, comprising at least the following steps:

[0055] a) at least one organometallic precursor based on at least one metal from group VIII and / or at least one organometallic precursor based on at least one metal from group IB is supplied separately;

[0056] b) said organometallic precursors supplied at the end of step a) are brought into contact in the presence of a solvent, at least one first stabilizing agent and at least one second stabilizing agent to obtain a colloidal suspension, said step b) comprising the following sub-steps:

[0057] bl) said organometallic precursors supplied at the end of step a) are brought into contact in the presence of the solvent to obtain a first solution;

[0058] b2) the first solution obtained at the end of step b1) is brought into contact with at least minus a first stabilizing agent to obtain a second solution;

[0059] b3) the second solution obtained at the end of step b2) is brought into contact with at at least one second stabilizing agent, different from the first stabilizing agent, to obtain the colloidal suspension;

[0060] c) said colloidal suspension obtained at the end of step b) is heated to a temperature between 25°C and 180°C under a hydrogen pressure between 0.01 MPa and 1 MPa to obtain said catalytic system.

[0061] Steps a) to c) are described in more detail below. Step a)

[0062] According to step a) of the process for preparing a catalytic system according to the invention, at least one organometallic precursor based on at least one metal from group VIII and / or at least one organometallic precursor based on at least one metal from group IB is supplied separately.

[0063] More particularly, said organometallic precursors supplied in step a) are chosen from transition metal complexes of nickel, cobalt and / or copper, neutral or charged, containing one or more organic or inorganic ligands.

[0064] When said organometallic precursor is selected from nickel transition metal complexes, the oxidation state of nickel in the complex is 0, 1, 2, 3 or 4. Preferably the oxidation state of nickel in the complex is 2.

[0065] When said organometallic precursor is selected from cobalt transition metal complexes, the oxidation state of cobalt in the complex is 0, 1, 2 or 3. Preferably the oxidation state of cobalt in the complex is 2.

[0066] When said organometallic precursor is selected from copper transition metal complexes, the oxidation state of copper in the complex is 0, 1, 2 or 3. Preferably the oxidation state of copper in the complex is 1.

[0067] Advantageously, the transition metal complexes may contain neutral, anionic or cationic ligands. The ligands may form single, double or triple bonds with the metal center. The ligands may be identical or different from each other, bonded or not to each other, and are preferably chosen from a hydride, fluoride, chloride, bromide, iodide group, an organic compound, preferably an alkyl, cyclic or not, having from 1 to 15 carbon atoms (C1-C15) comprising or not one or more heteroelements and / or one or more multiple bonds, and / or an organic compound, preferably a substituted or unsubstituted aryl, having between 4 and 15 carbon atoms (C4-C15) comprising or not one or more heteroelements, or a substituted or unsubstituted aryl having between 4 and 15 carbon atoms (C4-C15) comprising or not one or more heteroelements.

[0068] The donor atom, that is to say the one which forms the bonds with the metal center, can be chosen from the elements H, C, N, O, Si, P, S, F, Cl, Br, I. Preferably, the donor atom is chosen from N or O.

[0069] In a particular non-limiting case, the metal complex may be chosen from multinucleated coordination complexes containing 2 or more metals, which may be identical or different. The multinucleated complexes may be linked together by one or more bridging ligands, and / or by the formation of metal-metal type chemical bonds.

[0070] In one embodiment according to the invention, when said organometallic precursor is nickel-based, said precursor is chosen from nickel(II) bis-(hexamethyldisilazane) [Ni[iPrNC(CH3)NiPr]2]; nickel(II) bis-[N,N'-di(isopropyl)methylcarbodiimide] [Ni[iPrNC(CH2CH2CH2CH3)NiPr]2]; nickel(II) bis-[N,N'-di(isopropyl)n-butylcarbodiimide], [Ni[iPrNC(CH2CH2CH2CH3)NiPr]2]; nickel(II) bis-[N,N'-di(cyclohexyl)methylcarbodiimide], [Ni[CyNC(CH3 )NCy]2]; nickel(II) bis-(1,5-cyclooctadiene)nickel(0), Ni(q4-C8Hi2)2. Preferably, said nickel-based organometallic precursor is the bis- complex Nickel(II) [N,N'-di(isopropyl)methylcarbodümide] [Ni[iPrNC(CH3)NiPr]2] whose chemical structure is shown below:

[0071] [Chem.l]

[0072] In one embodiment according to the invention, when said organometallic precursor is based on copper, said precursor is chosen from copper(II) bis-(hexamethyldisilazane) [Cu(hmds)2]; copper(I) bis-[N,N'-di(isopropyl)methylcarbodiimide] {Cu[iPrNC(CH3)NiPr]}2; copper(I) bis-[N,N'-di(isopropyl)n-butylcarbodiimidc] {Cu| PrNC(CH2CH2CH2CH3)N' Pr]}2; copper(I) bis-[N,N'-di(cyclohexyl)methylcarbodiimide] {Cu[CyNC(CH3 )Cy]}2. Preferably, said copper-based organometallic precursor is the bis-[N,N'-di(isopropyl)methylcarbodiimide copper(I)] complex {Cu|PrNC(CH3)N' Pr]}2 whose chemical structure is represented below:

[0073] [Chem.2] N" t..

[0074] In one embodiment according to the invention, when said organometallic precursor is cobalt-based, said precursor is chosen from bis-(hexamethyldisilazane)tetrahydrofuran cobalt(II) [Co( / zm6?5)2(thf)]; bis-[N,N'-di(isopropyl)methylcarbodiimide] of cobalt(II), [Co[iPrNC(CH3)NiPr]2]; bis-[N,N'-di(isopropyl)n-butylcarbodiimide] of cobalt(II), [Co[iPrNC(CH2CH2CH2CH3)Ni Pr]2]; bis-[N,N'-di(cyclohexyl)methylcarbodiimide] of cobalt(II), [Co[CyNC(CH3 )NCy]2]; (1,5-cyclooctadiene)(cyclooctadienyl) cobalt(I), Co(q3-C8Hi3)(q4-C8Hi2). Preferably, said cobalt-based organometallic precursor is the cobalt(II) bis-(hexamethyldisilazane)tetrahydrofuran complex [Co( / zm6?5)2(thf)] whose chemical structure is represented below:

[0075] [Chem.3]

[0076] In step a), the organometallic precursors based on at least one metal from group VIII and / or based on at least one metal from group IB may be in the presence or absence of a solvent, identical or different, preferably identical.

[0077] The solvent may be chosen from organic solvents and in particular from ethers, alcohols, chlorinated solvents and saturated, unsaturated, aromatic or non-aromatic, cyclic or non-cyclic hydrocarbons. Preferably, the solvent is chosen from hexane, cyclohexane, methylcyclohexane, heptane, butane or isobutane, mono-olefins or diolefins preferably comprising 4 to 20 carbon atoms, cycloocta-1,5-diene, benzene, toluene, orthoxylene, mesitylene, ethylbenzene, dichloromethane, chlorobenzene, methanol, ethanol, pure or as a mixture, and ionic liquids. In the case where the solvent is an ionic liquid, it is advantageously chosen from the ionic liquids described in patents US 6,951,831 B2 and FR 2895406 B1. Step b)

[0078] According to step b) of the preparation process according to the invention, said organometallic precursors based on at least one metal from group VIII and / or based on at least one metal from group IB supplied at the end of step a) are brought into contact in the presence of a solvent, at least one first stabilizing agent and at least one second stabilizing agent to obtain a colloidal suspension.

[0079] The role of the first stabilizing agent is to form a stabilizing complex before the nucleation phase but also to stabilize the suspended nanoparticles obtained after the nucleation phase.

[0080] The role of the second stabilizing agent is to initiate the nucleation phase allowing the formation of the suspended bimetallic nanoparticles while playing a stabilizing role once the suspended nanoparticles have been formed.

[0081] More particularly, step b) comprises the following sub-steps:

[0082] bl) said organometallic precursors supplied at the end of step a) are brought into contact in the presence of a solvent to obtain a first solution;

[0083] b2) the first solution obtained at the end of step b1) is brought into contact with a first stabilizing agent to obtain a second solution;

[0084] b3) the second solution obtained at the end of step b2) is brought into contact with a second stabilizing agent, different from the first stabilizing agent, to obtain a colloidal suspension.

[0085] In step b1) the solvent may be identical or different, preferably identical, to the solvent(s) optionally used in step a). The solvent may be chosen from organic solvents and in particular from ethers, alcohols, chlorinated solvents and saturated, unsaturated, aromatic or non-aromatic, cyclic or non-cyclic hydrocarbons. Preferably, the solvent is chosen from hexane, cyclohexane, methylcyclohexane, heptane, butane or isobutane, monoolefins or diolefins preferably comprising 4 to 20 carbon atoms, cycloocta-1,5-diene, benzene, toluene, orthoxylene, mesitylene, ethylbenzene, dichloromethane, chlorobenzene, methanol, ethanol, pure or as a mixture, and ionic liquids. Preferably, the solvent is mesitylene. In the case where the solvent is an ionic liquid, it is advantageously chosen from the ionic liquids described in patents US 6,951,831 B2 and FR 2895406 B1.

[0086] In step b2) the first stabilizing agent may be chosen from carboxylic acids, carboxylate anions, primary, secondary or tertiary amines, primary, secondary, tertiary or quaternary ammonium cations, amides, esters, alcohols, alcoholates, thiols, thiolates, saturated or unsaturated, having between 1 and 30 carbon atoms.

[0087] Preferably, said first stabilizing agent is palmitic acid.

[0088] In step b3), the second stabilizing agent may be chosen from carboxylic acids, carboxylate anions, primary, secondary or tertiary amines, primary, secondary, tertiary or quaternary ammonium cations, amides, esters, alcohols, alcoholates, thiols, thiolates, saturated or unsaturated, having between 1 and 30 carbon atoms.

[0089] Preferably, the second stabilizing agent is hexadecylamine.

[0090] Preferably, the molar ratio between the stabilizing agents supplied in step b) and said organometallic precursors supplied in step a) is greater than 0 and less than or equal to 10, preferably between 0.05 and 5, and even more preferably between 0.05 and 1.5.

[0091] Preferably, the molar ratio between the first stabilizing agent and said organometallic precursors supplied in step a) is less than 0.5, more preferably between 0.1 and 0.3.

[0092] Preferably, the molar ratio between the second stabilizing agent and said organometallic precursors supplied in step a) is less than 1.5, more preferably between 0.8 and 1.2. Step c)

[0093] After step b) of contacting, said colloidal suspension obtained at the end of step b) is heated to a temperature of between 25°C and 180°C, preferably between 30°C and 170°C, under a hydrogen pressure of between 0.01 MPa and 1 MPa, preferably between 0.1 MPa and 0.3 MPa, to obtain said catalytic system, preferably for a period of between 1 and 24 hours, preferably between 2 and 20 hours.

[0094] The concentration of said organometallic precursors contained in the solution obtained at the end of step c) is less than or equal to 1 mol / L, preferably between 0.001 mol / L and 0.1 mol / L, and very preferably between 0.025 mol / L and 0.75 mol / L. 4. Process for preparing a catalyst

[0095] Another subject according to the invention relates to a process for preparing a catalyst comprising an active phase based on at least one metal from group VIII and / or at least one metal from group IB and a support comprising at least one refractory oxide, comprising the following steps:

[0096] i) a catalytic system according to the invention is brought into contact with a support comprising at least one refractory oxide to obtain a catalyst precursor;

[0097] ii) the catalyst precursor obtained at the end of step i) is dried at a temperature below 250°C and preferably at a pressure below 0.001 MPa, to obtain a catalyst;

[0098] iii) optionally, the catalyst obtained in step ii) is calcined at a temperature between 250°C and 500°C to obtain a calcined catalyst,

[0099] iv) optionally, the calcined catalyst obtained at the end of step iii) is reduced by contacting with a reducing gas to obtain a reduced catalyst.

[0100] Preferably, step i) of contacting is carried out by impregnating the support with a volume of colloidal suspension of between 0.25 and 1.5 times the pore volume of the support to be impregnated.

[0101] The catalyst precursor obtained at the end of step i) is then dried at a temperature below 250°C, preferably between 15°C and 180°C, more preferably between 30°C and 160°C, even more preferably between 50°C and 150°C, and even more preferably between 70°C and 140°C, for a duration typically between 0.5 hours and 12 hours, and more preferably for a duration between 0.5 hours and 5 hours. Longer durations are not excluded, but do not necessarily provide an improvement.

[0102] The drying step can be carried out by any technique known to those skilled in the art. It is advantageously carried out under an inert atmosphere or under an atmosphere containing oxygen or under a mixture of inert gas and oxygen. It is advantageously carried out at atmospheric pressure or at reduced pressure. Preferably, this step is carried out at a pressure of less than 0.001 MPa.

[0103] After drying, the catalyst obtained at the end of step ü) can be calcined at a temperature of between 250°C and 600°C, preferably between 350°C and 550°C, for a period typically of between 0.5 and 24 hours, preferably for a period of between 0.5 and 12 hours, and even more preferably for a period of between 0.5 and 10 hours, preferably under an inert atmosphere or under an atmosphere containing oxygen. Longer periods are not excluded, but do not necessarily provide an improvement. A calcined catalyst is obtained.

[0104] The calcined catalyst obtained at the end of step iii) (optional) is generally reduced. This step is preferably carried out in the presence of a reducing gas, either in-situ, i.e. in the reactor where the catalytic transformation is carried out, or ex-situ. Preferably, this step is carried out at a temperature between 80°C and 450°C, even more preferably between 100°C and 400°C.

[0105] The reduction is carried out in the presence of a reducing gas comprising between 25 vol% and 100 vol% of hydrogen, preferably 100% volume of hydrogen. The hydrogen is optionally supplemented by an inert gas for the reduction, preferably argon, nitrogen or methane.

[0106] The reduction generally includes a temperature increase phase followed by a plateau.

[0107] The duration of the reduction stage is generally between 1 hour and 40 hours, preferably between 2 hours and 20 hours.

[0108] The Hourly Volumetric Velocity (HVV) is generally between 150 and 3000, preferably between 300 and 1500 liters of reducing gas per hour and per liter of catalyst. 5. Catalyst

[0109] The process for preparing the catalyst according to the invention makes it possible to obtain a bimetallic catalyst comprising an active phase based on at least one metal from group VIII and / or at least one metal from group IB and a support comprising at least one refractory oxide.

[0110] Preferably, the active phase comprises, preferably consists of, nickel and copper, or nickel and cobalt.

[0111] When the group VIII metal is nickel, the nickel content is between 0.1 and 15% by weight of nickel element relative to the total weight of the catalyst, preferably between 0.5 and 10% by weight, and even more preferably between 1 and 7.5% by weight.

[0112] When the metal from group VIII is cobalt, the cobalt content is between 0.1 and 15% by weight of cobalt element relative to the total weight of the catalyst, preferably between 0.5 and 10% by weight, and even more preferably between 1 and 7.5% weight.

[0113] When the metal from group IB is copper, the copper content is between 0.1 and 15% by weight of copper element relative to the total weight of the catalyst, preferably between 0.5 and 10% by weight, and even more preferably between 1 and 7.5% by weight.

[0114] The number-average diameter of the bimetallic nanoparticles based on at least one metal from group VIII and / or one metal from group IB, measured in oxide form, is less than 10 nm, preferably less than 9 nm, preferentially less than 7 nm, more preferentially less than 5 nm, even more preferentially less than 4 nm, and even more preferably less than or equal to 3 nm.

[0115] The specific surface area of ​​the catalyst is generally between 10 m2 / g and 350 m2 / g, preferably between 25 m2 / g and 300 m2 / g, more preferably between 40 m2 / g and 250 m2 / g.

[0116] The total pore volume of the catalyst is generally between 0.1 ml / g and 1 ml / g, preferably between 0.2 ml / g and 0.8 ml / g, and particularly preferably between 0.3 ml / g and 0.7 ml / g.

[0117] Said catalyst (and the support used for the preparation of the catalyst) is in the form of grains advantageously having a diameter of between 0.5 mm and 10 mm. The grains may have any shape known to those skilled in the art, for example the shape of balls (preferably having a diameter of between 1 mm and 8 mm), extrudates, tablets, hollow cylinders. Preferably, the catalyst (and the support used for the preparation of the catalyst) are in the form of extrudates with a diameter of between 0.5 mm and 10 mm, preferably between 0.8 mm and 3.2 mm and very preferably between 1.0 mm and 2.5 mm and a length of between 0.5 mm and 20 mm. The term "diameter" of the extrudates is understood to mean the diameter of the circle circumscribed to the cross section of these extrudates. The catalyst may advantageously be presented in the form of cylindrical, multi-lobed, tri-lobed or quadri-lobed extrudates. Preferably its shape is trilobed or quadrilobed.The shape of the lobes can be adjusted according to any method known in the prior art. 6. Support

[0118] The support generally comprises at least one refractory oxide preferably selected from the group consisting of magnesium, titanium, zirconium, aluminum, silicon oxides. Preferably, the support comprises silica, alumina or silica-alumina, and very preferably alumina. Preferably, the support is made of alumina. The alumina generally has a crystallographic structure of the delta, gamma or theta alumina type, alone or as a mixture.

[0119] The characteristics of the support, mentioned in this section, correspond to the characteristics of the support before carrying out step i) of the catalyst preparation process according to the invention.

[0120] When the support is an alumina, said alumina support may comprise impurities such as metal oxides of groups IIA, IIIB, IVB, IIB, IIIA, IVA according to the CAS classification, preferably silica, titanium dioxide, zirconium dioxide, zinc oxide, magnesium oxide and calcium oxide, or alkali metals, preferably lithium, sodium or potassium, and / or alkaline earth metals, preferably magnesium, calcium, strontium or barium or sulfur.

[0121] The specific surface area of ​​the support is generally between 10 m2 / g and 400 m2 / g, preferably between 30 m2 / g and 350 m2 / g, more preferably between 50 m2 / g and 300 m2 / g.

[0122] The pore volume of the support is generally between 0.1 ml / g and 1.2 ml / g, preferably between 0.3 ml / g and 0.9 ml / g, and very preferably between 0.5 ml / g and 0.9 ml / g.

[0123] The mesoporous median diameter of the support is advantageously between 3 nm and 25 nm, and preferably between 6 nm and 20 nm, and particularly preferably between 8 nm and 18 nm. 7. Examples

[0124] The following examples illustrate the invention without limiting its scope.

[0125] Example 1 (non-compliant): NhCu^prcparc catalytic system by impregnation of Ni and Cu metal salts (5% by weight Ni and molar ratio Ni / Cu=L5)

[0126] An aqueous solution of nickel and copper precursors is prepared by dissolving nickel nitrate (NiNO3, supplier Strem Chemicals®) and copper nitrate (CuNO3, supplier Strem Chemicals®) in a volume of 13 mL of distilled water.

[0127] This solution is prepared so as to finally obtain a Ni / Cu ratio=1.5 on the final catalyst. The solution obtained is dry impregnated on 10 grams of alumina A. The solid thus obtained is then dried in an oven overnight at 120°C, then calcined under an air flow of 1 L / h / g of catalyst at 450°C for 2 hours.

[0128] The content of metallic elements, i.e. nickel plus copper, is 5% by weight relative to the weight of the final catalyst.

[0129] The average diameter of the bimetallic nanoparticles determined, on the solid obtained, by Transmission Microscopy (TEM) on 250 measured nanoparticles is 14 nm with a standard deviation of 4.18 (60.6%).

[0130] Furthermore, the theoretically targeted ratio of Ni / Cu is 1.5. Out of 250 nanoparticles counted, 55 are composed only of nickel, and the molar ratio Ni / Cu measured by EDS (energy dispersive X-ray spectroscopy) allowing analysis of the composition of the measured particles varies between 2 and 12.

[0131] Example 2 (compliant): NiCo bimetallic catalytic system by colloidal route (Ni / Co molar ratio=1)

[0132] In the glove box, a solution of 171 mg (0.5 mmol Ni) of the complex [Ni[' PrNC(CH3)NiPr]2] in 4 mL of mesitylene and a solution of 226 mg (0.5 mmol Co) of the complex [Co( / zmt / 5)2(thf)] in 4 mL of mesitylene are prepared. These two solutions are introduced into a Fisher-Porter bottle of 120 mL capacity while stirring. Then, 51 mg (0.2 mmol) of palmitic acid dissolved in 8 mL of mesitylene are added to the medium while stirring. Finally, a solution of 241 mg (1 mmol) of 1-hexadecylamine dissolved in 4 mL of mesitylene is introduced into the Fisher-Porter. The bottle is then closed and removed from the glove box, pressurized to 0.2 MPa of H2, and the reaction medium is heated to 150°C for 18 hours with stirring.

[0133] At the end of the reaction, a drop of the colloidal solution is placed on a grid for analysis by Transmission Microscopy.

[0134] The average diameter of bimetallic nanoparticles determined by Transmission Microscopy (TEM) on 250 measured nanoparticles is 2.3 nm with a standard deviation of 0.8 (34.8%).

[0135] The theoretically targeted Ni / Co ratio is 1. Out of 10 particles counted, the Ni / Co ratio measured by EDS (energy dispersive X-ray spectroscopy, which allows analysis of the composition of the measured particles) fluctuates from 0.8 to 1.2.

[0136] Example 3 (compliant): NLCo bimetallic catalytic system by colloidal route (Ni / Co molar ratio=4)

[0137] This synthesis is identical to that described in Example 3, except that a solution of 276 mg (0.8 mmol Ni) of the complex [Ni[iPrNC(CH3)NiPr]2] in 4 mL of mesitylene and a solution of 90 mg (0.2 mmol Co) of the complex [Co( / zmtA)2(thf)] in 4 mL of mesitylene are used instead.

[0138] The average diameter of bimetallic nanoparticles determined by Transmission Microscopy (TEM) on 250 measured nanoparticles is 3.9 nm with a standard deviation of 1.0 (25.6%).

[0139] The theoretically targeted Ni / Co ratio is 4. Out of 10 particles counted, the Ni / Co ratio measured by EDS (energy dispersive X-ray spectroscopy, which allows analysis of the composition of the measured particles) fluctuates from 3 to 5.

[0140] Example 4 (compliant): Bimetallic catalytic system Ni2Cur by colloidal route (molar ratio Ni / Cu=L5)

[0141] In the glove box, a solution of 257 mg (0.75 mmol Ni) of the complex [Ni[' PrNC(CH3)N'Pr]2] in 4 mL of mesitylene and a solution of 102 mg (0.5 mmol Cu) of the complex {Cu[iPrNC(CH3)NiPr]}2 in 4 mL of mesitylene are prepared. These two solutions are introduced into a Fisher-Porter bottle of 120 mL capacity with stirring. Then, 51 mg (0.2 mmol) of palmitic acid dissolved in 8 mL of mesitylene is added to the medium with stirring. Finally, 241 mg (1 mmol) of 1-hexadec y lamine dissolved in 4 mL of mesitylene is introduced into the Fisher-Porter. The bottle is removed from the glove box and pressurized to 0.2 MPa of H2 and heated to 120 °C for 18 hours with stirring.

[0142] The average diameter of bimetallic nanoparticles determined by Transmission Microscopy (TEM) on 250 measured nanoparticles is 6.9 nm with a standard deviation of 1.7 (24.6%).

[0143] The theoretically targeted Ni / Cu ratio is 1.5. Out of 10 particles counted, the Ni / Cu ratio measured by EDS (energy dispersive X-ray spectroscopy, which allows analysis of the composition of the measured particles) fluctuates from 1 to 2.

[0144] Example 5 (compliant): Impregnation of a compliant catalytic system on an alumina support

[0145] In a Schlenk® tube under argon, a solution containing the catalytic system according to the invention obtained according to examples 2, 3 or 4 is brought into contact with a support comprising at least one refractory oxide, aiming for a theoretical mass content of 5% by weight of metals of the active phase based on at least one metal from group VIII and / or IB relative to the total weight of the catalyst. In a typical experiment, a solution containing 50 mg of precursors of the active phase based on at least one metal from group VIII and / or IB is brought into contact with 950 mg of alumina support having a specific surface area of ​​80 m2 / g, a pore volume of 0.7 mL / g and a median mesoporous diameter of 12 nm. The suspension is soaked in an ultrasonic bath for 20 minutes at room temperature. Then, the solvent is evaporated under vacuum at 150°C. The solid obtained is washed twice with 5 mL of toluene and then dried under vacuum at room temperature for at least one hour.

Claims

Claims

1. Catalytic system in the form of a colloidal suspension comprising a plurality of bimetallic nanoparticles based on at least one metal from group VIII and / or one metal from group IB, characterized in that said nanoparticles have a number average diameter of less than 10 nm, measured by transmission electron microscopy, and in that the standard deviation relative to the size of said nanoparticles is less than or equal to 50% of said average diameter.

2. System according to claim 1, characterized in that said bimetallic nanoparticles are based on nickel and cobalt.

3. System according to claim 2, characterized in that said bimetallic nanoparticles correspond to the formula NixCoy with x and y integers between 1 and 20.

4. The system of claim 3, wherein x = 1 and y is between 1 and 4.

5. System according to claim 1, characterized in that said bimetallic nanoparticles are based on nickel and copper.

6. System according to claim 5, characterized in that said bimetallic nanoparticles correspond to the formula Nix Cuy- with x' and y' integers between 1 and 20.

7. The system of claim 6, wherein x' = 1 and y' is between 1 and 3.

8. Catalytic system according to any one of the preceding claims, characterized in that said nanoparticles have a number average diameter of less than 7 nm, and in that the standard deviation relative to the size of said nanoparticles is between 20% and 50% of said average diameter.

9. Catalytic system according to any one of the preceding claims, characterized in that said nanoparticles are in reduced form.

10. Process for preparing a catalytic system according to any one of claims 1 to 9 comprising at least the following steps: a) at least one organometallic precursor based on at least one metal from group VIII and / or at least one organometallic precursor based on at least one metal from group IB is supplied separately; b) said organometallic precursors supplied at the end of step a) are brought into contact in the presence of a solvent, at least one first stabilizing agent and at least one second stabilizing agent to obtain a colloidal suspension, said step b) comprising the following sub-steps: bl) bringing said organometallic precursors supplied at the end of step a) into contact in the presence of the solvent to obtain a first solution; b2) bringing the first solution obtained at the end of step bl) into contact with at least one first stabilizing agent to obtain a second solution; b3) bringing the second solution obtained at the end of step b2) into contact with at least one second stabilizing agent, different from the first stabilizing agent, to obtain the colloidal suspension; c) heating said colloidal suspension obtained at the end of step b) to a temperature between 25°C and 180°C under a hydrogen pressure between 0.01 MPa and 1 MPa to obtain said catalytic system.

11. A method according to claim 10, wherein said organometallic precursors supplied in step a) are selected from transition metal complexes of nickel, cobalt and / or copper, neutral or charged, containing one or more organic or inorganic ligands.

12. The method of claim 11, wherein: - when said organometallic precursor is selected from nickel transition metal complexes, the oxidation state of nickel in the complex is 0, 1, 2, 3 or 4; - when said organometallic precursor is selected from cobalt transition metal complexes, the oxidation state of cobalt in the complex is 0, 1, 2 or 3; - when said organometallic precursor is selected from copper transition metal complexes, the oxidation state of copper in the complex is 0, 1, 2 or 3.

13. Process according to any one of claims 11 or 12, in which said transition metal complexes comprise several ligands, identical or different from each other, linked or not to each other, and chosen from a hydride, fluoride, chloride, bromide, iodide group, an organic compound, preferably an alkyl, cyclic or not, having from 1 to 15 carbon atoms (in Cl-Cl 5) comprising or not one or more heteroelements and / or one or more multiple bonds, and / or an organic compound, preferably a substituted or unsubstituted aryl, having between 4 and 15 carbon atoms (C4-C15) including or not one or more heteroelements, or a substituted or unsubstituted aryl having between 4 and 15 carbon atoms (C4-C15) including or not one or more heteroelements.

14. A method according to any one of claims 10 to 13, wherein when said organometallic precursor is nickel-based, said precursor is selected from nickel(II) bis-(hexamethyldisilazane) [Ni^mds^]; nickel(II) bis-[N,N'-di(isopropyl)methylcarbodiimide] [Ni[iPrNC(CH3)NiPr]2]; nickel(II) bis-[N,N'-di(isopropyl)n-butylcarbodiimide], [Ni[iPrNC(CH2CH2CH2CH3)NiPr]2]; nickel(II) bis-[N,N'-di(cyclohexyl)methylcarbodiimide], [Ni[CyNC(CH3)NCy]2]; bis-(1,5-cyclooctadiene)nickel(0), Ni(q4-C8 H12)2.

15. A method according to any one of claims 10 to 13, characterized in that when said organometallic precursor is based on copper, said precursor is chosen from copper(II) bis-(hexamethyldisilazane) [Cuihmds')^; copper(I) bis-[N,N'-di(isopropyl)methylcarbodiimide] {Cu[iPrNC(CH3)NiPr]}2; copper(I) bis-[N,N'-di(isopropyl)n-butylcarbodiimide] {Cu[iPrNC(CH2CH2CH2CH3)NiPr]}2; copper(I) bis-[N,N'-di(cyclohexyl)methylcarbodiimide] {Cu[CyNC(CH3)Cy]}2.

16. A method according to any one of claims 10 to 13, characterized in that when said organometallic precursor is cobalt-based, said precursor is chosen from bis-(hexamethyldisilazane)tetrahydrofuran cobalt(II) [Co( / zm6?5)2(thf)]; bis-[N,N'-di(isopropyl)methylcarbodiimide] of cobalt(II), [Cop PrNC(CH3)NiPr]2]; bis-[N,N'-di(isopropyl)n-butylcarbodiimide] of cobalt(II), [Co[iPrNC(CH2CH2CH2CH3)NiPr]2]; bis-[N,N'-di(cyclohexyl)methylcarbodiimide] of cobalt(II), [Co[CyNC(CH3 )NCy]2]; (l,5-cyclooctadiene)(cyclooctadienyl) cobalt (I), Co(q3-C8H 13)(q4-C8H12).

17. A method according to any one of claims 10 to 16, wherein said first stabilizing agent and / or said second stabilizing agent are selected from carboxylic acids, carboxylate anions, primary, secondary or tertiary amines, primary, secondary, tertiary or quaternary ammonium cations, amides, esters, alcohols, alcoholates, thiols, thiolates, saturated or unsaturated, having between 1 and 30 carbon atonies.

18. A method according to claim 17, characterized in that the first stabilizing agent is palmitic acid and the second stabilizing agent is hexadecylamine.

19. Process for preparing a catalyst comprising an active phase based on at least one metal from group VIII and / or at least one metal from group IB and a support comprising at least one refractory oxide, comprising the following steps: i) bringing said catalytic system according to any one of claims 1 to 9 into contact with a support comprising at least one refractory oxide to obtain a catalyst precursor; ii) drying the catalyst precursor obtained at the end of step i) at a temperature below 250°C to obtain a dried catalyst precursor; iii) optionally, calcining the dried catalyst precursor obtained in step ii) at a temperature between 250°C and 500°C.

20. Catalyst comprising a bimetallic active phase based on at least one metal from group VIII and / or at least one metal from group IB and a support comprising at least one refractory oxide obtained according to the process according to claim 19.