A catalyst comprising an active nickel phase in the form of small particles distributed in a shell and a nickel-copper alloy.

Abstract

Disclosed is a catalyst comprising nickel, copper and an alumina support, said catalyst being characterized in that: the nickel is distributed both in a shell around the support and in the core of the support, the thickness of the shell being 2% to 15% of the diameter of the catalyst; the nickel density ratio of the shell to the core is strictly greater than 3; the shell contains more than 25% by weight of elemental nickel relative to the total weight of nickel contained in the catalyst; the molar ratio of nickel to copper is 0.5 to 5; at least a portion of the nickel and copper is in the form of a nickel-copper alloy; the nickel content in the nickel-copper alloy is 0.5 to 15% by weight, in terms of the weight of elemental nickel relative to the total weight of the catalyst; the size of the nickel particles in the catalyst is less than 7 nm.

Description

[Technical field]

[0001] The present invention relates to supported metal catalysts based on nickel and copper that are particularly intended for the hydrogenation of unsaturated hydrocarbons, and more particularly for the selective hydrogenation of polyunsaturated compounds or the hydrogenation of aromatic compounds. [Background technology]

[0002] Monounsaturated organic compounds, such as ethylene and propylene, are at the root of the production of polymers, plastics and other chemical products with added value. These compounds are obtained from natural gas, naphtha or gas oils that have been treated by steam cracking or catalytic cracking methods. These processes are carried out at high temperatures and produce, in addition to the desired monounsaturated compounds, polyunsaturated organic compounds, such as acetylene, propadiene and methylacetylene (or propyne), 1,2-butadiene and 1,3-butadiene, vinylacetylene and ethylacetylene, and other polyunsaturated compounds whose boiling points correspond to the C5+ gasoline fraction (gasoline containing hydrocarbon compounds with 5 or more carbon atoms), especially styrene or indene compounds. These polyunsaturated compounds are very reactive and bring about side reactions in the polymerization unit. It is therefore necessary to remove them before making economical use of these fractions.

[0003] Selective hydrogenation is the primary process that has been developed to specifically remove undesired polyunsaturated compounds from these hydrocarbon feedstocks, allowing their conversion to the corresponding alkenes or aromatics while avoiding their complete saturation, and therefore the formation of the corresponding alkanes or naphthenes.

[0004] Selective hydrogenation catalysts are generally based on metals from group VIII of the periodic table, preferably palladium or nickel. The metal is in the form of metal particles deposited on a support. The metal content, the size of the metal particles and the distribution of the active phase in the support are among the criteria that have an influence on the activity and selectivity of the catalyst.

[0005] The macroscopic distribution of metal particles in the support constitutes an important criterion, mainly in terms of rapid and continuous reactions, such as selective hydrogenation. It is generally desirable to arrange these elements in a crust at the periphery of the support to avoid intraparticle mass transfer problems that may result in activity defects and selectivity losses. Such catalysts are also called "eggshell" catalysts.

[0006] Such catalysts are widely known in the case of palladium-based selective hydrogenation catalysts. Indeed, due to the low palladium content (generally less than 1% by weight of palladium relative to the catalyst) and suitable preparation methods, a thin crust of palladium can be obtained around the support grains (Patent Documents 1 and 2).

[0007] It is often proposed to replace palladium with nickel. This metal is less active than palladium and therefore needs to be present in larger amounts in the catalyst. Nickel-based catalysts therefore generally have a metal content of between 5% and 50% by weight of nickel relative to the catalyst. In these catalysts, the nickel is generally distributed homogeneously in the support. One possible way to improve these catalysts in terms of activity and selectivity is to control the distribution of nickel in the support by depositing it more intensively on a crust at the periphery of the support. Such catalysts are known from the prior art.

[0008] The document (US Pat. No. 5,399,433) describes an "eggshell" catalyst with nickel on a porous support, the porous support having a pore volume of at least 0.2 mL / g for pores with a size of less than 11.7 nm and a pore volume of at least 0.1 mL / g for pores with a size of 11.7 nm or more. More than 50% of the nickel is found in a crust, the thickness of which is equal to 0.15 times the radius of the support. This catalyst is used for the hydrogenation of fats.

[0009] The literature (US Pat. No. 5,399,433) describes supported nickel catalysts in which more than 90% of the nickel is found in a crust 700 μm thick. The catalysts are prepared using a solution of ammonia to dissolve the nickel salts. These catalysts are used in selective hydrogenation applications.

[0010] The literature (Patent Document 5) describes a supported nickel catalyst in which the nickel crystallite size distribution is bimodal, with 30%-70% of the nickel crystallites having an average size (diameter) of 1.0-2.5 nm and the remaining nickel crystallites having an average size (diameter) of 3.0-4.5 nm. Nickel is distributed on a crust with a thickness of 3%-15% of the diameter and at the core, with the nickel concentration ratio between the crust and the core being 3.0:1-1.3:1. At least 75% of the pore volume is found in pores having a size of more than 5.0 nm. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] French Patent Application Publication No. 2922784 (Patent Publication No. 2011-500327) [Patent Document 2] US Patent Application Publication No. 2010 / 217052 [Patent Document 3] U.S. Pat. No. 4,519,951 [Patent Document 4] China Patent Application Publication No. 101890351 [Patent Document 5] US Patent Application Publication No. 2012 / 0065442 Summary of the Invention [Means for solving the problem]

[0012] (Objective of the Invention) Surprisingly, the applicant has discovered that by adding a special organic additive to a catalyst based on nickel and copper (and the nickel and copper based alloy formed on the support) and including an alumina support obtained by a very special method, followed by a special hydrothermal treatment, a catalyst is obtained in which at least a part of the nickel is distributed on a crust at the periphery of the support, and another part of the nickel is distributed in the core of the catalyst. Without wishing to be bound by any theory, it appears that the hydrothermal treatment, which is carried out after the step of contacting the special organic additive with the nickel and copper based catalyst on the special alumina support that has been subjected to a hydrothermal treatment in the presence of an acid solution, causes the nickel to at least partially migrate from the interior of the support to the periphery of the support, thus forming a nickel crust. Furthermore, the Applicant has observed that during the preparation of the catalyst, a step of contacting the support with a solution containing simultaneously a copper-based metal precursor and a nickel-based metal precursor, followed by a step of drying and reducing in the presence of a reducing gas at low temperature (150°C to 250°C), makes it possible to obtain a nickel-copper alloy (in reduced form), which unexpectedly makes it possible to significantly improve the reducibility of the nickel active phase on the support. Furthermore, the presence of copper in the catalyst makes it possible to maintain a good activity and a longer service life of the catalyst when it comes into contact with a sulfur-containing hydrocarbon feedstock. Indeed, compared to nickel, the copper present in the catalyst more easily captures the sulfur-containing compounds contained in the feedstock, thereby limiting the irreversible poisoning of the active sites.

[0013] The present invention therefore relates to a new type of catalyst, which, due to its particular preparation method, makes it possible to obtain catalysts that contain at least equally good, and even better, performance qualities in terms of activity and selectivity in the context of the selective hydrogenation of polyunsaturated compounds or the hydrogenation of polyunsaturated aromatic compounds, while using lower amounts of nickel phase than typically used in the prior art, due to a better distribution of the nickel active phase in the support, making it more accessible to the reagents and even nickel particles with a size of less than 7 nm, giving a greater intrinsic activity than that of nickel. The presence of the NiCu alloy also makes it possible to carry out the step of reducing the metal element in the presence of a reducing gas at lower temperatures and shorter reaction times than are generally used in the prior art. Advantageously, by using less severe operating conditions than in the prior art, it becomes possible to carry out the reduction step directly in the reactor in which it is desired to carry out the selective hydrogenation of the polyunsaturated fraction.

[0014] The first subject of the present invention is a catalyst comprising nickel, copper, and an alumina carrier, the nickel being present in an amount of 1% by weight to 50% by weight of elemental nickel relative to the total weight of the catalyst, and the second metallic element copper being present in an amount of 0.5% by weight to 15% by weight of elemental copper relative to the total weight of the catalyst, and having the following properties: - the nickel is distributed both on a crust at the periphery of the support and in the core of the support, the thickness of said crust being between 2% and 15% of the diameter of the catalyst; - The nickel density ratio between the crust and the core is strictly greater than 3; - the crust comprises more than 25% by weight of elemental nickel relative to the total weight of nickel contained in the catalyst; - the molar ratio between nickel and copper is 0.5-5; - at least a portion of the nickel and copper is in the form of a nickel-copper alloy; - the nickel content in the nickel-copper alloy is between 0.5% and 15% by weight of elemental nickel relative to the total weight of the catalyst; - The size of the nickel particles in the catalyst is less than 7 nm The present invention relates to a catalyst characterized by:

[0015] Advantageously, the nickel density ratio between the crust and the core is between 3.8 and 15.

[0016] Advantageously, said crust comprises more than 40% by weight of elemental nickel relative to the total weight of nickel contained in the catalyst.

[0017] Advantageously, the transition interval between the catalyst core and the crust is between 0.05 and 3% of the catalyst diameter.

[0018] Advantageously, the sulphur content of the alumina support is between 0.001 and 2% by weight relative to the total weight of the alumina support and the sodium content of said alumina support is between 0.001 and 2% by weight relative to the total weight of said alumina gel.

[0019] Advantageously, the thickness of said crust is between 2.5% and 12% of the diameter of the catalyst.

[0020] Advantageously, the nickel density ratio between the crust and the core is greater than 3.5.

[0021] Another subject of the invention relates to a method for preparing a catalyst according to the invention, said method comprising the steps of: a) providing an alumina gel; b) shaping the alumina gel from step a); c) subjecting the shaped alumina gel obtained at the end of step b) to a heat treatment to obtain an alumina support, said heat treatment comprising at least one hydrothermal treatment step at a temperature between 100 and 800°C in the presence of an acid solution in an autoclave and at least one calcination step carried out after the hydrothermal treatment step at a temperature between 400 and 1500°C; d) Perform the following sub-step sequence; d1) contacting an alumina support with at least one nickel precursor to obtain a catalyst precursor; d2) drying the catalyst precursor obtained at the end of step d1) at a temperature below 250° C.; d3) contacting the dried catalyst precursor obtained at the end of step d2) with at least one solution containing at least one organic additive selected from aldehydes containing 1 to 14 carbon atoms per molecule, ketones or polyketones containing 3 to 18 carbon atoms per molecule, ethers and esters containing 2 to 14 carbon atoms per molecule, alcohols or polyalcohols containing 1 to 14 carbon atoms per molecule and carboxylic acids or polycarboxylic acids containing 1 to 14 carbon atoms per molecule, the molar ratio of organic additive to nickel being greater than 0.05 mol / mol; d4) hydrothermal treatment of the catalyst precursor obtained at the end of step d3) at a temperature between 100° C. and 200° C. for a period between 30 minutes and 5 hours under a gas flow containing 5 to 650 grams of water per kg of dry gas; e) The following sequence of sub-steps is carried out; e1) contacting the alumina support with at least one solution containing at least one copper precursor and at least one nickel precursor, said solution being in the desired nickel concentration so as to obtain, on the final catalyst, a content of elemental nickel of between 0.5% and 15% by weight relative to the total weight of the final catalyst; e2) at least one step of drying the catalyst precursor obtained at the end of step e1) is carried out at a temperature below 250° C.; Steps d) and e) are carried out separately in any order f) contacting the alumina support with at least one solution containing at least one organic compound containing at least one carboxylic acid group, or at least one alcohol group, or at least one ester group, or at least one amide group, or at least one amine group; It is understood that step f) is carried out simultaneously with sub-step d1) of step d) or before or after step d), but before step g), and in case step f) is carried out before or after step d), said step f) comprises drying of the catalyst precursor at a temperature below 250° C. after contacting the support with said solution comprising at least one organic compound; g) reducing the catalyst precursor from steps a) to f) by contacting said catalyst precursor with a reducing gas at a temperature of 150° C. or more and less than 250° C. It is characterized by:

[0022] Advantageously, the molar ratio between said organic compound introduced in step f) and elemental nickel introduced in step d1) is between 0.01 and 5.0 mol / mol.

[0023] Advantageously, steps d1) and f) are carried out simultaneously.

[0024] Advantageously, the organic compound of step f) is chosen from oxalic acid, malonic acid, glycolic acid, lactic acid, tartronic acid, citric acid, tartaric acid, pyruvic acid, levulinic acid, ethylene glycol, propane-1,3-diol, butane-1,4-diol, glycerol, xylitol, mannitol, sorbitol, glycol, glucose, dimethyl carbonate, diethyl carbonate, formamide, N-methylformamide, acetamide, N-methylacetamide, N,N-dimethylmethanamide, 2-pyrrolidone, γ-lactam, lactamide, urea, alanine, arginine, lysine, proline, serine, EDTA. Advantageously, the copper precursor is chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide or copper fluoride.

[0025] Advantageously, in step d3), the organic additive is chosen from formic acid, formaldehyde, acetic acid, citric acid, oxalic acid, glycolic acid, malonic acid, ethanol, methanol, ethyl formate, methyl formate, paraldehyde, acetaldehyde, gamma-valerolactone, glucose, sorbitol and trioxane.

[0026] Advantageously, the molar ratio between the organic additive introduced in step d2) and nickel is 0.1 to 5 mol / mol.

[0027] Advantageously, the organic compound in step f) is different from the organic additive in step d2).

[0028] Another subject according to the present invention relates to a method for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule, which are contained in a hydrocarbon feedstock having a boiling point of 300 °C or lower. The method is carried out in the presence of a catalyst according to the present invention, wherein the temperature is 0 °C to 300 °C, the pressure is 0.1 to 10 MPa, and when the method is carried out in the liquid phase, the molar ratio of hydrogen / (polyunsaturated compound to be hydrogenated) is 0.1 to 10, and the hourly space velocity is 0.1 to 200 h -1 -1, or when the method is carried out in the gas phase, the molar ratio of hydrogen / (polyunsaturated compound to be hydrogenated) is 0.5 to 1000, and the hourly space velocity is 100 to 40000 h -1 -1.

[0029] Another subject according to the present invention relates to a method for the hydrogenation of at least one aromatic or polyaromatic compound contained in a hydrocarbon feedstock having a final boiling point of 650 °C or lower. The method is carried out in the gas phase or the liquid phase in the presence of a catalyst according to the present invention, wherein the temperature is 30 °C to 350 °C, the pressure is 0.1 to 20 MPa, the molar ratio of hydrogen / (aromatic compound to be hydrogenated) is 0.1 to 10, and the hourly space velocity (HSV) is 0.05 to 50 h -1 -1.

Embodiments for Carrying Out the Invention

[0030] (Description of the Drawings) Figure 1 is a diagram showing the distribution of nickel in the catalyst. The x-axis corresponds to the thickness (μm) of the catalyst measured from the edge of the catalyst. The y-axis is the nickel density (grams of Ni / mm 3) The nickel is distributed on a crust at the periphery of the support with a thickness of ep1 and in the core of the support. The nickel density on the crust d crust is the nickel density in the support core, d core The transition interval between the catalyst core and the crust has a thickness denoted ep2-ep1.

[0031] Detailed Description of the Invention (1.Definition) Hereinafter, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, Press, Editor in Chief DR Lide, 81st edition, 2000-2001). For example, group VIII according to the CAS classification corresponds to the metals in columns 8, 9 and 10 according to the new IUPAC classification.

[0032] In this specification, in accordance with the IUPAC convention, "micropores" is understood to mean pores with a diameter of less than 2 nm, i.e. less than 0.002 μm; "mesopores" is understood to mean pores with a diameter of 2 nm or more, i.e. 0.002 μm or more, and 50 nm or less, i.e. 0.05 μm or less, and "macropores" is understood to mean pores with a diameter of more than 50 nm, i.e. more than 0.05 μm.

[0033] To analyze the distribution of metallic phases on the support, the crust thickness is measured by Castaing microprobe (or electron microprobe microanalysis). The device used is a CAMECA XS100, equipped with four monochromator crystals, allowing the simultaneous analysis of four elements. The Castaing microprobe analysis technique consists of the detection of X-rays emitted by a solid after excitation of the elements of that solid by a high-energy electron beam. For the purpose of this characterization, the catalyst grains are coated on blocks of epoxy resin. These blocks are polished until a cross section through the diameter of the bead or extrudate is produced, then metallized by carbon deposition in a metal evaporator. The electron probe is scanned along the diameter of five beads or extrudates, and an average distribution profile of the constituent elements of the solid is obtained. This method is well known to the skilled person and is defined in the publication "Measurement of palladium crust thickness on catalyst by EPMA" by L. Sorbier et al., Materials Science and Engineering 32 (2012). It is then possible to establish the distribution profile within the grain of a given element, here nickel. Furthermore, the Ni concentration is defined for each measurement and therefore for each analytical step. The density of Ni within the grain is therefore given by the volume (mm 3 ) is defined as the concentration of Ni per unit area.

[0034] The total pore volume is measured by mercury porosimetry according to standard ASTM D4284-92 at a wetting angle of 140°, for example using an Autopore III® model device from the brand Micromeritics®.

[0035] The BET specific surface area is measured by nitrogen physical adsorption according to standard ASTM D3663-03, as described in the study by Rouquerol F., Rouquerol J. and Singh K. "Adsorption by Powders & Porous Solids: Principles, Methodology and Applications, Academic Press, 1999."

[0036] The median mesopore diameter is also defined as the diameter such that, among the combined pores making up the mesopore volume, all pores having a size less than this diameter make up 50% of the total mesopore volume as determined by mercury porosimetry intrusion.

[0037] "Size of nickel particles" is understood to mean the diameter of nickel crystallites in the form of oxide. The diameter of nickel crystallites in the form of oxide is determined by X-ray diffraction from the width of the diffraction line located at the angle 2θ=43° (i.e. along the crystallographic direction

[0200] ) using the Scherrer relation. This method, used in X-ray diffraction on polycrystalline samples or powders, connects the full width at half maximum of the diffraction peak to the size of the particles, and is described in detail in the following reference: Appl. Cryst. (1978), 11, 102-113, "Scherrer after sixty years: A survey and some new results in the determination of crystallite size", JI Langford and AJC Wilson.

[0038] The nickel and copper content is measured by X-ray fluorescence.

[0039] (2. Catalyst) The present invention relates to a catalyst based on nickel and copper, with a proportion by weight of elemental nickel between 1% and 50% by weight relative to the total weight of the catalyst and a proportion by weight of elemental copper between 0.5% and 15% by weight relative to the total weight of the catalyst, comprising an alumina support, said catalyst having the following characteristics: - the nickel is distributed both on a crust at the periphery of the support and in the core of the support, the crust thickness (also called ep1) being between 2% and 15% of the diameter of the catalyst, preferably between 2.5% and 12% of the diameter of the catalyst, even more preferably between 3% and 10% of the diameter of the catalyst, even more preferably between 3% and 7.5% of the diameter of the catalyst; - Nickel density ratio between the crust and the core (d crust / d core (also referred to as ) is strictly greater than 3, preferably greater than 3.5, preferably between 3.8 and 15; - said crust comprises more than 25% by weight, preferably more than 40% by weight, more preferentially between 45% and 90% by weight and even more preferably between 60% and 90% by weight of elemental nickel relative to the total weight of nickel contained in the catalyst; the molar ratio between nickel and copper is between 0.5 and 5 mol / mol, preferably between 0.7 and 4.5 mol / mol and more preferentially between 0.9 and 4 mol / mol; at least a portion of the nickel and copper is in the form of a nickel-copper alloy, advantageously of the formula Ni x Cu y , where x is between 0.1 and 0.9 and y is between 0.1 and 0.9; the nickel content in the copper-nickel alloy is between 0.5% and 15% by weight, preferably between 1% and 12% by weight and more preferentially between 1% and 10% by weight, of elemental nickel relative to the total weight of the catalyst; the size of the nickel particles, measured in the oxide form in the catalyst, is less than 7 nm, preferably less than 5 nm, more preferentially less than 4 nm and even more preferentially less than 3 nm; It is characterized by:

[0040] Advantageously, the transition interval between the core and crust of the catalyst (also referred to herein as the core / crust transition interval, or ep2-ep1 according to the notation in Figure 1), which is associated with the variation in nickel density measured across the thickness of the catalyst from the edge of the catalyst to the center of the catalyst, is very abrupt. Preferably, the core / crust transition interval is between 0.05% and 3% of the catalyst diameter, preferably between 0.5% and 2.5% of the catalyst diameter.

[0041] The nickel content in the catalyst according to the invention is advantageously between 1% and 50% by weight relative to the total weight of the catalyst, more preferentially between 2% and 40% by weight relative to the total weight of the catalyst, more preferentially between 3% and 35% by weight relative to the total weight of the catalyst and more preferentially between 5% and 25% by weight relative to the total weight of the catalyst.

[0042] The copper content is 0.5% to 15% by weight, preferably 0.5% to 12% by weight, preferably 0.75% to 10% by weight, and more preferably 1% to 9% by weight, of elemental copper relative to the total weight of the catalyst.

[0043] The catalyst according to the invention may be described as a "semi-eggshell" catalyst in that the concentration of nickel is higher at the periphery of the support than in the core of the support, the concentration of said nickel in the core of the support being non-zero.

[0044] The specific surface area of ​​a catalyst is generally 10 m 2 / g~200m 2 / g, preferably 25m 2 / g~110m 2 / g, more preferably 40m 2 / g~100m 2 / g.

[0045] The total pore volume of the catalyst is generally 0.1 mL / g to 1 mL / g, preferably 0.2 mL / g to 0.8 mL / g, and particularly preferably 0.3 mL / g to 0.7 mL / g.

[0046] The active phase of the catalyst does not contain any metal from group VIB, in particular it does not contain molybdenum or tungsten.

[0047] The catalyst (and the support used for the preparation of the catalyst) is in the form of grains, advantageously having a diameter between 0.5 and 10 mm. The grains may have any form known to the person skilled in the art, for example in the form of beads (preferably having a diameter between 1 and 8 mm), in the form of extrudates, in the form of tablets or in the form of hollow cylinders. Preferably, the catalyst (and the support used for the preparation of the catalyst) is in the form of extrudates, which have a diameter between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm, highly preferably between 1.0 and 2.5 mm, and which have a length between 0.5 and 20 mm. The "diameter" of the extrudates is intended to mean the diameter of the circle circumscribing the cross section of these extrudates. The catalyst may advantageously be presented in the form of cylindrical, multilobal, trilobal or tetralobal extrudates. Preferably, its shape will be trilobal or tetralobal. The shape of the lobes may be adjusted by all methods known from the prior art.

[0048] (3. Carrier) The characteristics of the alumina mentioned in this section correspond to the characteristics of the alumina before impregnation with the nickel active phase, i.e. the alumina support obtained at the end of step c) of the process for preparing a catalyst according to the invention.

[0049] According to the invention, the support is an alumina, i.e. it comprises at least 95% by weight, preferably at least 98% by weight, particularly preferably at least 99% by weight, of alumina relative to the weight of the support. The crystallographic structure which the alumina has is generally of the delta, gamma or theta alumina type, used alone or in mixtures.

[0050] According to the invention, the alumina support may also contain impurities, such as oxides of metals from 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.

[0051] Advantageously, the sulphur content of the alumina support is between 0.001% and 2% by weight relative to the total weight of the alumina support and the sodium content of said alumina support is between 0.001% and 2% by weight relative to the total weight of said alumina gel.

[0052] The specific surface area of ​​alumina is generally 10m 2 / g~250m 2 / g, preferably 30m 2 / g~200m 2 / g, more preferably 50m 2 / g~150m 2 / g.

[0053] The pore volume of the alumina is generally from 0.1 mL / g to 1.2 mL / g, preferably from 0.3 mL / g to 0.9 mL / g, and highly preferably from 0.5 mL / g to 0.9 mL / g.

[0054] Methods for preparing the catalyst Another subject of the invention is a process for preparing a catalyst according to the invention, comprising at least the following steps: a) providing an alumina gel; b) shaping the alumina gel from step a); c) subjecting the shaped alumina gel obtained at the end of step b) to a heat treatment to obtain an alumina support, said heat treatment comprising at least one hydrothermal treatment step at a temperature between 100° C. and 800° C. in the presence of an acid solution in an autoclave and at least one calcination step carried out after the hydrothermal treatment step at a temperature between 400° C. and 1500° C.; d) performing the following sequence of substeps: d1) contacting an alumina support with at least one precursor of a nickel active phase to obtain a catalyst precursor; d2) drying the catalyst precursor obtained at the end of step d1) at a temperature below 250° C.; d2') optional heat treatment of the dried catalyst precursor obtained at the end of step d2) at a temperature between 250°C and 1000°C to obtain a calcined catalyst precursor; d3) contacting the dried catalyst precursor obtained at the end of step d2) (optionally step d2')) with at least one solution containing at least one organic additive selected from aldehydes containing 1 to 14 carbon atoms per molecule, ketones or polyketones containing 3 to 18 carbon atoms per molecule, ethers and esters containing 2 to 14 carbon atoms per molecule, alcohols or polyalcohols containing 1 to 14 carbon atoms per molecule and carboxylic acids or polycarboxylic acids containing 1 to 14 carbon atoms per molecule, wherein the molar ratio between the organic additive and nickel is greater than 0.05 mol / mol; d4) hydrothermal treatment of the catalyst precursor obtained at the end of step d3) at a temperature between 100° C. and 200° C. for a period between 30 minutes and 5 hours under a gas flow containing 5 to 650 grams of water per kg of dry gas; d5) optional drying of the catalyst precursor obtained at the end of step d4) at between 50° C. and 200° C. under a gas stream containing water in an amount strictly less than 5 grams of water per kg of dry gas; e) performing the following sequence of substeps: e1) contacting an alumina support with at least one solution containing at least one copper precursor and at least one nickel precursor at a desired nickel concentration such that, on the final catalyst, the content of nickel element relative to the total weight of the final catalyst is from 0.5 wt% to 15 wt%; e2) performing at least one step of drying the catalyst precursor obtained at the end of step e1) at a temperature below 250 °C; e3) optionally, heat-treating the catalyst precursor obtained at the end of step e2) at a temperature of 250 °C to 1000 °C, in the presence or absence of water; Steps d) and e) are carried out separately in any order; f) contacting an alumina support with at least one solution containing at least one organic compound containing at least one carboxylic acid group, or at least one alcohol group, or at least one ester group, or at least one amide group, or at least one amine group; Step f) is carried out simultaneously with sub-step d1) of step d), or before or after step d), but before step g). When step f) is carried out before or after step d), it is understood that said step f) includes drying the catalyst precursor at a temperature below 250 °C after contacting the support with said solution containing at least one organic compound; g) reducing the catalyst precursor obtained from steps a) to f) by contacting it with a reducing gas at a temperature of 150 °C or higher and lower than 250 °C relates to a method comprising.

[0055] Intermediate steps may be inserted (in particular additional drying steps), and a given step may be carried out a plurality of times in succession (for example step d1)). Finally, it is possible to add additional steps before using the catalyst at the end of step g).

[0056] Preferably, the drying step and the subsequent calcination step are carried out at the end of shaping step b) (but before carrying out step c).

[0057] Preferably, steps d2') and d5) are not optional.

[0058] Steps a) to g) of said preparation process are described in detail below.

[0059] (Step a)-Alumina gel) The alumina support which the catalyst according to the invention comprises is obtained from an alumina gel which essentially comprises a precursor of the aluminium oxy(hydroxide) (AlO(OH)) type, also known as boehmite.

[0060] According to the invention, the synthesis of alumina gel (or otherwise known as boehmite gel) is carried out by precipitation of basic and / or acidic solutions of aluminum salts induced by a change in pH or any other method known to the skilled person (P. Euzen, P. Raybaud, X. Krokidis, H. Toulhoat, JL Le Loarer, JP Jolivet and C. Froidefond, Alumina, in "Handbook of Porous Solids", edited by F. Schuth, KSW Sing and J. Weitkamp, ​​Wiley-VCH, Weinheim, Germany, 2002, pp. 1591-1677).

[0061] In general, the temperature during the precipitation reaction is 5° C. to 80° C., and the pH during the reaction is 6 to 10. Preferably, the temperature is 35° C. to 70° C., and the pH is 6 to 10.

[0062] According to one embodiment, the alumina gel is obtained by contacting an aqueous solution of an aluminium salt with a basic solution, for example the aluminium salt is selected from the group consisting of aluminium sulfate, aluminium nitrate or aluminium chloride, preferably said aluminium salt is aluminium sulfate, and the basic solution is preferentially selected from sodium hydroxide or potassium hydroxide.

[0063] Alternatively, an alkaline solution of an aluminium salt, which may be selected from the group consisting of sodium aluminate and potassium aluminate, may be contacted with an acidic solution. In a highly preferred variant, the gel is obtained by contacting a sodium aluminate solution with nitric acid. The sodium aluminate solution is advantageously in the range of 10 -5 ~10 -1 mol L -1 and preferably, this concentration is 10 -4 ~10 -2 mol L -1 It is.

[0064] According to another embodiment, the alumina gel is obtained by contacting an aqueous solution of an aluminium salt with an alkaline solution of an aluminium salt.

[0065] (Step b) - Shaping of the carrier) The support may advantageously be shaped by any technique known to those skilled in the art. Shaping may be carried out, for example, by kneading-extrusion, pelleting, the drop solidification (oil drop) method, granulation on a rotating plate or any other method known to those skilled in the art. The catalyst according to the invention may be produced and used, if appropriate, in the form of extrudates, tablets, beads. An advantageous shaping method according to the invention is extrusion, with preferred extrusion shapes being cylindrical, twisted cylindrical or multilobed (for example 2, 3, 4 or 5 lobes).

[0066] In a particular embodiment, the alumina gel obtained at the end of step a) is subjected to a kneading step. The kneading step is preferably carried out in an acidic medium. The acid used may be, for example, nitric acid. This step is carried out by known tools capable of converting the gel into a viscous paste, such as Z-arm mixers, grinding mixers, continuous single or twin screws. According to one advantageous embodiment, one or more compounds, called "pore-forming agents", are introduced into the kneading medium. These compounds have the property that they degrade on heating and therefore create porosity in the carrier. For example, wood flour, charcoal, tar and plastics can be used as pore-forming compounds. The paste thus obtained after kneading is passed into an extrusion die. Generally, the extrudates have a diameter of 0.5 to 10 mm, preferably 0.8 to 3.2 mm, highly preferably 1.0 to 2.5 mm, and a length of 0.5 to 20 mm. The extrudates may be cylindrical, multilobal (eg, trilobal or tetralobal).

[0067] After the shaping, the support is optionally dried before undergoing hydrothermal treatment according to step c) of the method. For example, the temperature at which the drying is carried out is between 50° C. and 200° C. The dried support is optionally calcined before undergoing hydrothermal treatment according to step c) of the method. For example, the calcination is carried out at a temperature between 200° C. and 1000° C. in the presence or absence of a current of air containing up to 150 grams of water per kilogram of dry air by weight.

[0068] (Step c)-Heat treatment) The support obtained at the end of step b) then undergoes a heat treatment step which makes it possible to give it physical properties that satisfy the application envisaged.

[0069] The term "hydrothermal treatment" means treatment by passage through an autoclave in the presence of water at a temperature above room temperature.

[0070] During this hydrothermal treatment, the shaped alumina can be treated in different ways. Thus, the alumina can be impregnated with an acid solution before passing into the autoclave, and the hydrothermal treatment of the alumina can be carried out either in the vapour or in the liquid phase, the vapour or liquid phase of the autoclave being acidic or non-acidic. This impregnation, which precedes the hydrothermal treatment, can be carried out dry or by immersing the alumina in an acidic aqueous solution. The term "dry impregnation" means that the alumina is placed in contact with a volume of solution less than or equal to the total pore volume of the alumina to be treated. Preferably, the impregnation is carried out dry.

[0071] It is also possible to treat the extruded support without prior impregnation with an acidic solution, the acidity in this case being provided by the aqueous liquid of the autoclave.

[0072] The aqueous acidic solution comprises at least one acidic compound for dissolving at least a portion of the alumina of the extrudates. The term "acidic compound for dissolving at least a portion of the alumina of the extrudates" is understood to mean any acidic compound which, when in contact with the alumina extrudates, dissolves at least a portion of the aluminum ions. The acid should preferably dissolve a minimum of 0.5% by weight of the alumina of the alumina extrudates.

[0073] Preferably, the acid is selected from strong acids such as nitric acid, hydrochloric acid, perchloric acid, sulfuric acid or weak acids such as acetic acid used in a concentration such that an aqueous solution thereof has a pH of less than 4, or mixtures of these acids.

[0074] According to a preferred embodiment, the hydrothermal treatment is carried out in the presence of nitric acid and acetic acid, employed alone or as a mixture. The autoclave is preferably a rotating basket autoclave, such as those defined in patent application EP-A-0 387 109.

[0075] The hydrothermal treatment may be carried out under the saturated steam pressure corresponding to the treatment temperature or under a partial pressure of water vapor at least equal to 70% of the saturated steam pressure.

[0076] Preferably, the hydrothermal treatment is carried out at a temperature between 100° C. and 800° C., preferably between 200° C. and 700° C., preferably for a period between 30 minutes and 8 hours, more preferentially between 30 minutes and 3 hours.

[0077] The calcination step, preferably carried out in an autoclave after the hydrothermal treatment, is generally carried out at a temperature between 400°C and 1500°C, preferably between 800°C and 1300°C, generally for 1 to 5 hours, in air, the water content of which is generally between 0 and 700 g water per kilogram of dry air.

[0078] At the end of step c), the alumina obtained exhibits the specific textural properties as described above.

[0079] (Step d)) Step d) comprises the following sub-steps:

[0080] (Step d1)--Contacting the support with a precursor of the nickel active phase) According to the impregnation of step d1), the support may be contacted with the solution containing the precursors of the nickel active phase by dry impregnation or excess impregnation or else by deposition-precipitation, by methods well known to those skilled in the art.

[0081] Said step d1) is preferentially carried out by impregnation of the support, which consists, for example, in contacting the support with at least one aqueous solution containing the nickel precursor, the pH of said solution being capable of being modified by the optional addition of an acid or a base.

[0082] Preferably, said step d1) is carried out by dry impregnation, which consists of contacting the support with at least one solution containing, preferably consisting of, at least one nickel precursor, the volume of which is between 0.25 and 1.5 times the pore volume of the support to be impregnated.

[0083] Preferably, the nickel precursor is introduced into an aqueous solution, for example in the form of a nitrate, carbonate, acetate, chloride or oxalate, in the form of a complex formed with a polyacid or an acid alcohol and its salt, in the form of a complex formed with an acetylacetonate or in the form of any other inorganic derivative soluble in an aqueous solution, which is brought into contact with the support. Preferably, as nickel precursor, the use of nickel nitrate, nickel chloride, nickel acetate or nickel hydroxycarbonate is advantageously made. Highly preferably, the nickel precursor is nickel nitrate.

[0084] According to another variant, the aqueous solution is aqueous ammonia or ammonium NH 4 + It may contain ions.

[0085] The concentration of nickel in the solution is adjusted, depending on the type of impregnation (dry impregnation or excess impregnation) and the pore volume of the support, to obtain a nickel content of 1% to 50% by weight, more preferentially 2% to 40% by weight, more preferentially 3% to 35% by weight, more preferentially 5% to 25% by weight for supported catalysts, by weight of elemental nickel relative to the total weight of the catalyst.

[0086] (Step d2)-Drying) The drying step is carried out under a gas flow containing water in an amount of less than 150 grams of water per kilogram of dry gas, preferably less than 50 g of water per kilogram of dry gas, at a temperature of less than 250° C., preferably between 15° C. and 240° C., more preferentially between 30° C. and 220° C., even more preferentially between 50° C. and 200° C., even more preferentially between 70° C. and 180° C., typically for a period of between 10 minutes and 24 hours. Longer periods of time are not unspecified but do not necessarily offer any improvement.

[0087] The gas may contain oxygen, nitrogen or an inert gas, preferably the gas is air.

[0088] (Step d2') - Firing (optional)) The optional calcination step is carried out at temperatures between 250° C. and 1000° C., preferably between 250° C. and 750° C., under a gas flow containing water in an amount of less than 150 grams of water per kilogram of dry gas, preferably less than 50 grams of water per kilogram of dry gas. The duration of this heat treatment is generally between 15 minutes and 10 hours. Longer periods of time are not excluded, but do not necessarily provide any improvement.

[0089] The gas may contain oxygen, nitrogen or an inert gas, preferably the gas is air.

[0090] At the end of step d2) or d2'), the nickel is uniformly distributed on the support.

[0091] (Step d3) - Additives) According to step d3) of the method for preparing the catalyst, at the end of step d2), and optionally at the end of step d2'), the catalyst precursor obtained is contacted with at least one solution containing at least one organic additive selected from aldehydes containing 1 to 14 (preferably 2 to 12) carbon atoms per molecule, ketones or polyketones containing 3 to 18 (preferably 3 to 12) carbon atoms per molecule, ethers or esters containing 2 to 14 (preferably 3 to 12) carbon atoms per molecule, alcohols or polyalcohols containing 1 to 14 (preferably 2 to 12) carbon atoms per molecule and carboxylic acids or polycarboxylic acids containing 1 to 14 (1 to 12) carbon atoms per molecule. The organic additive may consist of a combination of the various functional groups mentioned above.

[0092] Preferably, the organic additive is formic acid HCOOH, formaldehyde CH 2 O, CH Acetate 3 COOH, citric acid, oxalic acid, glycolic acid (HOOC-CH 2 -OH), malonic acid (HOOC-CH 2 -COOH), ethanol, methanol, ethyl formate HCOOC 2 H 5 , Methyl formate HCOOCH 3 , paraldehyde (CH 3 -CHO) 3 , Acetaldehyde C 2 H 4 O, gamma-valerolactone (C 5 H 8 O 2 ), glucose, sorbitol, and trioxane.

[0093] Particularly preferably, the organic additive is formic acid.

[0094] It is essential that the step of adding the organic additive to the catalyst (step d3)) is carried out after the step of contacting the support with the precursor of the nickel active phase.

[0095] Preferably, the step d3) is carried out by impregnating the catalyst precursor obtained at the end of the implementation of step d2) or step d2’) with a solution containing at least one of the above organic additives. The impregnation is generally carried out in an aqueous solution, an organic solution, or a suspension in an aqueous or organic solution, preferably in an aqueous solution. When the operation is carried out in an organic solution or suspension, alcohol or polyalcohol, glycol or polyglycol is preferably used as the organic solvent.

[0096] Preferably, the step d3) is carried out by dry impregnation, which consists of contacting the catalyst precursor obtained at the end of the implementation of step d2) or step d2’) with a solution containing at least one organic additive as described above, and the volume of the solution is 0.25 to 1.5 times the pore volume of the catalyst precursor to be impregnated.

[0097] The temperature at which the impregnation is carried out is generally from 0 °C to 50 °C, preferably from 10 °C to 40 °C, particularly preferably at room temperature.

[0098] According to the present invention, the molar ratio between the organic additive and nickel is more than 0.05 mol / mol, preferably from 0.1 to 5 mol / mol, more preferentially from 0.12 to 3 mol / mol, and even more preferably from 0.15 to 2.5 mol / mol.

[0099] (Step d4) - Hydrothermal treatment) According to step d4) of the method for preparing the catalyst according to the present invention, the hydrothermal treatment of the product derived from step d3) is carried out at a temperature of 100 °C to 200 °C, preferably 130 °C to 170 °C, more specifically about 150 °C, under a gas flow containing 5 to 650 grams of water, preferably 7 to 150 grams of water, and even more preferably 10 to 50 grams of water per kilogram of the weight of the dry gas. The gas may contain oxygen, nitrogen or an inert gas, and preferably, the gas is air.

[0100] The duration of the hydrothermal treatment is generally 30 minutes to 5 hours, preferably 1 to 3 hours.

[0101] (Step d5) - Drying (optional)) Step d4) may be followed by a step d5) of drying under a gas stream containing water in an amount strictly less than 5 grams of water per kilogram of weight of drying gas at between 50° C. and 200° C., advantageously for a period of between 30 minutes and 5 hours, preferably between 1 and 3 hours.

[0102] The gas may contain oxygen, nitrogen or an inert gas, preferably the gas is air.

[0103] At the end of step d4), or possibly step d5), a "semi-eggshell" catalyst is obtained as shown diagrammatically in FIG. 1 and whose characteristics are described above.

[0104] (Step e)) Step e) comprises the following sub-steps:

[0105] (Step e1) Contacting copper and nickel precursors with a support) The deposition of nickel and copper on the alumina support may be carried out by dry impregnation or excess impregnation, or else by deposition-precipitation, according to methods well known to those skilled in the art.

[0106] Said step e1) is preferentially carried out by impregnation of the catalyst precursor, which impregnation consists, for example, of contacting said support with at least one solution, aqueous or organic (for example methanol or ethanol or phenol or acetone or toluene or dimethylsulfoxide (DMSO)) or else of a mixture of water and at least one organic solvent, which comprises, and preferably consists of, at least one nickel precursor and at least one copper precursor at least partially dissolved, or else of contacting said catalyst precursor with at least one colloidal solution, which comprises, and preferably consists of, at least one nickel precursor and at least one copper precursor in oxidized form (nickel and copper oxide, oxy(hydroxide) or hydroxide nanoparticles) or in reduced form (nickel and copper metallic nanoparticles in reduced state). Preferably, the solution is aqueous. The pH of this solution may be modified by the optional addition of an acid or a base.

[0107] Preferably, said step e1) is carried out by dry impregnation, which consists in contacting the catalyst precursor support with a solution containing, preferably consisting of, at least one nickel precursor and at least one copper precursor, the volume of the solution being between 0.25 and 1.5 times the pore volume of the support to be impregnated.

[0108] When the nickel precursor is introduced into the aqueous solution, it is advantageous to use a nickel precursor in the form of a nitrate, carbonate, acetate, chloride, hydroxide, hydroxycarbonate, oxalate, sulfate or formate, in the form of a complex formed with a polyacid or an acid alcohol and its salt, in the form of a complex formed with an acetylacetonate, in the form of a complex with tetramine or hexamine, or in the form of any other inorganic derivative soluble in the aqueous solution, and to bring it into contact with said catalyst precursor. Preferably, nickel nitrate, nickel hydroxide, nickel carbonate, nickel chloride or nickel hydroxycarbonate are advantageously used as nickel precursor. Highly preferably, the nickel precursor is nickel nitrate, nickel carbonate or nickel hydroxide.

[0109] When the copper precursor is introduced into the aqueous solution, a copper precursor in mineral or organic form is advantageously used. In mineral form, the copper precursor may be selected from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide or copper fluoride. Highly preferably, the copper precursor salt is copper nitrate.

[0110] According to the invention, the nickel precursor is provided in step e1) in the desired concentration so as to obtain, on the final catalyst (i.e. the catalyst obtained at the end of the reduction step f) or, if a passivation step g) is performed, a content of 0.5% to 10% by weight, preferably 0.5% to 8% by weight, more preferentially 1% to 7% by weight and even more preferentially 1% to 5% by weight, by weight of elemental nickel relative to the total weight of the final catalyst.

[0111] The amount of copper precursor(s) introduced into the solution according to step e1) is chosen so that the total copper content is between 0.5% and 15% by weight, preferably between 0.5% and 12% by weight, preferably between 0.75% and 10% by weight and even more preferentially between 1% and 9% by weight, of elemental copper relative to the total weight of the final catalyst (i.e. the catalyst obtained at the end of reduction step f) or passivation step g) if a passivation step g) is performed).

[0112] (Step e2) Drying the impregnated carrier) Step e2) of drying the impregnated support is typically carried out at a temperature below 250° C., preferably between 15° C. and 180° C., more preferentially between 30° C. and 160° C., even more preferentially between 50° C. and 150° C., even more preferentially between 70° C. and 140° C., for a period typically between 10 minutes and 24 hours. Longer periods are not unconventional, but do not necessarily result in any improvement.

[0113] The drying step can be carried out by any technique known to the person skilled in the art. It is advantageously carried out under an inert atmosphere or under an oxygen-containing atmosphere 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 in the presence of air or nitrogen at atmospheric pressure.

[0114] ((Step e3) Heat treatment of the dried catalyst (optional step)) The dried catalyst precursor may undergo a further heat treatment step prior to the reduction step f) at temperatures between 250° C. and 1000° C., preferably between 250° C. and 750° C., typically for a period of 15 minutes to 10 hours, under an inert or oxygen-containing atmosphere, optionally in the presence of water. Longer treatment times are not unconventional but do not necessarily give an improvement.

[0115] The term "thermal treatment" is intended to mean a temperature treatment in the absence or presence of water, respectively. In the latter case, the contact with water vapor can be carried out at atmospheric pressure or under autogenous pressure. Multiple combined cycles can be carried out in the absence or presence of water. After this or these treatments, the catalyst precursor contains nickel in the form of an oxide, i.e., NiO.

[0116] When water is present, the water content is preferably between 150 and 900 grams per kg of dry air, even more preferably between 250 and 650 grams per kg of dry air.

[0117] (Implementation of step e) in relation to other steps of the preparation method) The method for the preparation of the nickel catalyst comprises several embodiments, which differ in particular by the order of introduction of the nickel and copper precursors constituting the NiCu alloy. It is possible to contact the nickel and copper precursors with the support either after or before contacting the nickel precursor with the support.

[0118] A first embodiment consists in carrying out said step e) before said step d).

[0119] A second embodiment consists in carrying out said step d) before said step e).

[0120] When step e) is performed before or after step d), said step e) comprises drying the catalyst precursor at a temperature below 250° C. after contacting the support with said solution containing at least one organic compound.

[0121] (Step f) Addition of organic compound) The support may be contacted by any method known to those skilled in the art with at least one solution containing at least one organic compound comprising at least one carboxylic acid group, or at least one alcohol group, or at least one ester group, or at least one amide group, or at least one amine group, by carrying out said step f), since it has further been noted that the catalyst according to the invention prepared in the presence of an organic compound is more active than the catalyst prepared in the absence of this type of organic compound. This effect is related to the reduction in the size of the nickel particles.

[0122] In particular, said step f) may be carried out by dry impregnation or by excess impregnation, according to methods known to those skilled in the art. Preferably, said step f) is carried out by dry impregnation, which consists in contacting the catalyst support with said solution in a volume between 0.25 and 1.5 times the pore volume of the support to be impregnated.

[0123] The solution containing at least one organic compound comprising at least one carboxylic acid group, or at least one alcohol group, or at least one ester group, or at least one amide group, or at least one amine group, may be aqueous or organic (e.g. methanol or ethanol or phenol or acetone or toluene or dimethylsulfoxide (DMSO)) or may otherwise consist of a mixture of water and at least one organic solvent. The organic compound is at least partially dissolved in the solution beforehand at the desired concentration. Preferably, the solution is aqueous or contains ethanol. Even more preferably, the solution is aqueous. The pH of the solution could be modified by the optional addition of an acid or a base. In another possible embodiment, no solvent may be present in the impregnation solution.

[0124] In the embodiment in which step f) is carried out by dry impregnation or excess impregnation, preferably dry impregnation, the impregnation of the support with at least one solution containing at least said organic compound may advantageously be carried out via at least two impregnation cycles, with the same or different organic compound in each cycle, where each impregnation is advantageously followed by drying and optionally a heat treatment.

[0125] Advantageously, the molar ratio of said organic compound introduced in step f) to elemental nickel introduced in step d1) is between 0.01 and 5.0 mol / mol, preferably between 0.05 and 2.0 mol / mol, more preferentially between 0.1 and 1.5 mol / mol and even more preferentially between 0.3 and 1.2 mol / mol.

[0126] The organic compound according to step f) may contain multiple identical or different carboxylic acid, alcohol, ester, amide or amine organic groups in the same molecule. The organic compound according to step f) may contain a combination of multiple types of organic groups selected from carboxylic acid, alcohol, ester, amide or amine organic groups.

[0127] Preferably, the organic compound of step f) is different from the organic additive of step d2).

[0128] (A) an organic compound containing at least one carboxylic acid group) In one embodiment according to the invention, the organic compound comprises at least one carboxylic acid group.

[0129] The organic compound comprising at least one carboxylic acid group may be a saturated or unsaturated aliphatic organic compound or an aromatic organic compound. Preferably, the saturated or unsaturated aliphatic organic compound comprises 1 to 9 carbon atoms, preferably 2 to 7 carbon atoms. Preferably, the aromatic organic compound comprises 7 to 10 carbon atoms, preferably 7 to 9 carbon atoms.

[0130] The saturated or unsaturated aliphatic organic compound or the aromatic organic compound containing at least one carboxylic acid group may be selected from monocarboxylic acids, dicarboxylic acids, tricarboxylic acids or tetracarboxylic acids.

[0131] Advantageously, the organic compound comprising at least one carboxylic acid group is chosen from ethanedioic acid (oxalic acid), propanedioic acid (malonic acid), pentanedioic acid (glutaric acid), hydroxyacetic acid (glycolic acid), 2-hydroxypropanoic acid (lactic acid), 2-hydroxypropanedioic acid (tartronic acid), 2-hydroxypropane-1,2,3-tricarboxylic acid (citric acid), 2,3-dihydroxybutanedioic acid (tartaric acid), 2-oxopropanoic acid (pyruvic acid) or 4-oxopentanoic acid (levulinic acid).

[0132] (B) an organic compound containing at least one alcohol group) In another embodiment according to the present invention, the organic compound comprises at least one alcohol group.

[0133] Preferably, said organic compound comprises from 2 to 20 carbon atoms, preferably from 2 to 12 carbon atoms, even more preferably from 2 to 8 carbon atoms.

[0134] Advantageously, the organic compound is chosen from methanol, ethanol, phenol, ethylene glycol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, glycerol, xylitol, mannitol, sorbitol, pyrocatechol, resorcinol, hydroquinone, diethylene glycol, triethylene glycol, polyethylene glycols with an average molar mass of less than 600 g / mol, glucose, mannose, fructose, sucrose, maltose or lactose, in any one of the isomeric forms.

[0135] (C) An organic compound containing at least one ester group In another embodiment according to the invention, the organic compound comprises at least one ester group. Preferably, said organic compound comprises from 2 to 20 carbon atoms, preferably from 3 to 14 carbon atoms, even more preferentially from 3 to 8 carbon atoms.

[0136] The organic compound may be chosen from linear or cyclic or unsaturated cyclic carboxylic acid esters, or cyclic or linear carbonate esters, or else linear carbonic acid diesters. In the case of cyclic carboxylic acid esters, the compound is γ-valerolactone.

[0137] In the case of carboxylic acid unsaturated cyclic esters (containing unsaturation in the ring), the compound can be a furan or a pyrone or any one of their derivatives, for example 6-pentyl-α-pyrone.

[0138] In the case of linear carboxylic acid esters, the compound may be a compound containing a single ester group corresponding to the empirical formula RCOOR', where R and R' are linear, branched or cyclic alkyl groups, or alkyl groups containing unsaturation, or alkyl groups substituted by one or more aromatic rings, or aryl groups, each containing 1 to 15 carbon atoms, and may be the same or different. The R group may also be a hydrogen atom H. The organic compound is preferably methyl laurate.

[0139] In another embodiment according to the present invention, the organic compound may be a compound containing at least two carboxylic acid ester groups. Preferably, said compound is dimethyl succinate.

[0140] In another embodiment according to the present invention, the organic compound may be a compound containing at least one carboxylic acid ester group and at least one second functional group selected from an alcohol, an ether, a ketone or an aldehyde.

[0141] Preferably, the compound is dimethyl malate.

[0142] Advantageously, said organic compound comprises at least one carbonate group and at least one ketone or aldehyde group. In the case of cyclic carbonates, the compound is propylene carbonate. In the case of linear carbonates, the compound is chosen from dimethyl carbonate, diethyl carbonate or diphenyl carbonate. In the case of linear carbonates, the compound is chosen from dimethyl dicarbonate, diethyl dicarbonate or di(tert-butyl) dicarbonate.

[0143] (D) An organic compound containing at least one amide group In another embodiment according to the invention, the organic compound comprises at least one amide group selected from acyclic amide groups or cyclic amide groups which may contain alkyl, aryl or alkyl substituents containing unsaturation. The amide group may be selected from primary, secondary or tertiary amides.

[0144] Advantageously, the organic compound containing at least one amide group is chosen from formamide, N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylmethanamide, N,N-diethylacetamide, N,N-dimethylpropionamide, propanamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, γ-lactam, caprolactam, acetylleucine, N-acetylaspartic acid, aminohippuric acid, N-acetylglutamic acid, 4-acetamidobenzoic acid, lactamide and glycolamide, urea, N-methylurea, N,N′-dimethylurea, 1,1-dimethylurea and tetramethylurea, or any one of its isomers.

[0145] (E) an organic compound containing at least one amine group In another embodiment according to the invention, the organic compound comprises at least one amine group, said organic compound comprising from 1 to 20 carbon atoms, preferably from 1 to 14 carbon atoms, even more preferably from 2 to 8 carbon atoms.

[0146] In one embodiment according to the invention, the organic compound has the empirical formula C x N y H z where 1≦x≦20, 1≦y≦x, and 2≦z≦2x+2. More particularly, the organic compound is selected from ethylenediamine, diaminohexane, tetramethylenediamine, hexamethylenediamine, tetramethylethylenediamine, tetraethylethylenediamine, diethylenetriamine, and triethylenetetramine.

[0147] In one embodiment according to the invention, the organic compound comprises at least one amine group and at least one carboxylic acid group (amino acid). When the compound is an amino acid, it is preferably selected from alanine, arginine, lysine, proline, serine, threonine or EDTA.

[0148] In all of the above embodiments, the organic compound is selected from oxalic acid, malonic acid, glycolic acid, lactic acid, tartronic acid, citric acid, tartaric acid, pyruvic acid, levulinic acid, ethylene glycol, propane-1,3-diol, butane-1,4-diol, glycerol, xylitol, mannitol, sorbitol, diethylene glycol, glucose, gamma-valerolactone, dimethyl carbonate, diethyl carbonate, formamide, N-methylformamide, acetamide, N-methylacetamide, N,N-dimethylmethanamide, 2-pyrrolidone, γ-lactam, lactamide, urea, alanine, arginine, lysine, proline, serine, and EDTA.

[0149] (Implementation of step f) in relation to other steps of the preparation method) The method for the preparation of the nickel catalyst includes several embodiments, which differ in particular in the order of introduction of the organic compound and the nickel precursor, which can be contacted with the support either after the nickel precursor is contacted with the support, or before the nickel precursor is contacted with the support, or at the same time as the nickel is contacted with the support.

[0150] A first embodiment consists in carrying out said step f) after said step d).

[0151] A second embodiment consists in carrying out said step d) after said step f).

[0152] When step f) is performed before or after step d), said step f) comprises drying the catalyst precursor at a temperature below 250° C. after contacting the support with said solution containing at least one organic compound.

[0153] The step of contacting the carrier with a nickel precursor (step d1)), and the step of contacting the carrier with at least one solution containing at least one organic compound containing at least one carboxylic acid group, or at least one alcohol group, or at least one ester group, or at least one amide group, or at least one amine group (step f) are each carried out at least once, and preferably, a plurality of times, and in some cases, may be carried out in the presence of a nickel precursor and / or the same or different organic compounds in each of steps d1) and / or f).

[0154] The third embodiment consists of carrying out the said step d1) and the said step f) simultaneously (simultaneous contact). This embodiment can advantageously include the implementation of one or more steps d), and in some cases, involves the same or different nickel precursors in each step d1). In particular, one or more steps d1) precede the said simultaneous contact step and / or advantageously follow the said simultaneous contact step, and in some cases, involve the same or different nickel precursors in each step. This embodiment may include a plurality of simultaneous contact steps: steps d1) and f) are carried out simultaneously a plurality of times, and in some cases, in the presence of the same or different nickel precursors and / or organic compounds in each simultaneous contact step.

[0155] After each contact step, preferably, an intermediate drying step is carried out. The temperature at which the intermediate drying step is carried out is less than 250 °C, preferably 15 - 240 °C, more preferably 30 - 220 °C, even more preferably 50 - 200 °C, and still more preferably 70 - 180 °C. Advantageously, when the intermediate drying step is carried out, an intermediate firing step may be carried out. The temperature at which the intermediate firing step is carried out is 250 - 1000 °C, preferably 250 - 750 °C.

[0156] Advantageously, after each contacting step, regardless of whether this is a step of contacting a nickel precursor with a support, a step of contacting an organic compound with a support, or a step of simultaneously contacting a nickel precursor and an organic compound with a support, in some cases, it is possible to age and leave the impregnated support standing before the intermediate drying step. Aging enables the solution to be uniformly distributed within the support. When the aging step is carried out, the step is preferably carried out at a temperature of 10-50 °C, preferably at ambient temperature, under an inert atmosphere or an oxygen-containing atmosphere or a water-containing atmosphere, at atmospheric pressure or reduced pressure. Generally, an aging time of less than 48 hours, preferably 5 minutes to 5 hours, is sufficient. Longer periods are not excluded but do not necessarily provide any improvement.

[0157] (Step g) Reduction with reducing gas) Prior to the use of the catalyst in the contact reactor and the implementation of the hydrogenation process, a reduction treatment step g) is carried out in the presence of a reducing gas, and a catalyst containing nickel in at least partially metallic form is obtained. This step is preferably carried out in situ, i.e., after the loading of the catalyst into the hydrogenation reactor. This treatment activates the catalyst and enables the formation of metal particles, particularly nickel particles in the zero-valent state. The in-situ implementation of the catalyst reduction treatment enables the omission of an additional step of passivating the catalyst with an oxygen-bearing compound or CO 2 This is the case where the catalyst is prepared by carrying out the reduction treatment ex situ, i.e., outside the reactor used for the hydrogenation of aromatic or polyaromatic compounds. In fact, when the reduction treatment is carried out ex situ, it is necessary to carry out a passivation step to protect the metallic phase of the catalyst in the presence of air (during the operations of transporting the catalyst and loading it into the hydrogenation reactor), and then to carry out a new step of reducing the catalyst.

[0158] The reducing gas is preferably hydrogen. Hydrogen can be used in high purity or as a mixture (for example, a mixture of hydrogen / nitrogen, hydrogen / argon or hydrogen / methane). When hydrogen is used as a mixture, all proportions are conceivable.

[0159] According to an essential aspect of the preparation method according to the present invention, the temperature at which the reduction treatment is carried out is equal to or higher than 150° C. and lower than 250° C., preferably 160° C. to 230° C., and more preferentially 170° C. to 220° C. The duration of the reduction treatment is between 5 minutes and less than 5 hours, preferably 10 minutes to 4 hours, and more preferentially 10 minutes to 110 minutes.

[0160] The presence of the nickel-copper alloy in at least partially reduced form makes it possible to use less severe operating conditions for reducing the nickel active phase than in the prior art, and therefore makes it possible to carry out the reduction step directly in the reactor in which it is desired to carry out the hydrogenation of aromatic unsaturated compounds.

[0161] Furthermore, the presence of copper in the catalyst makes it possible to protect the good activity and good service life of the catalyst when it is placed in contact with a hydrocarbon feedstock containing sulfur. Indeed, compared to nickel, the copper present in the catalyst more easily captures the sulfur-containing compounds contained in the feedstock, which limits the irreversible poisoning of the active sites. The temperature increase to the desired reduction temperature is generally set slow, for example between 0.1 and 10°C / min, preferably between 0.3 and 7°C / min.

[0162] The hydrogen flow rate is expressed in L / h / gram of catalyst precursor and is between 0.01 and 100 L / h / gram of catalyst precursor, preferably between 0.05 and 10 L / h / gram of catalyst precursor, and even more preferably between 0.1 and 5 L / h / gram of catalyst precursor.

[0163] (Step h) Passivation (optional) The catalyst prepared by the method according to the invention can advantageously undergo a passivation step with sulfur-containing compounds, which makes it possible to improve the selectivity of the catalyst and to avoid thermal runaway during the start-up of the new catalyst. Passivation generally consists in irreversibly poisoning the most toxic active sites of nickel present on the new catalyst with sulfur-containing compounds, thus weakening the activity of the catalyst that benefits its selectivity. The passivation step is carried out using methods known to those skilled in the art.

[0164] The passivation step with sulfur-containing compounds is generally carried out for 10 to 240 minutes at temperatures between 20° C. and 350° C., preferably between 40 and 200° C. The sulfur-containing compounds are, for example, chosen from the following compounds: thiophenes, thiophanes, alkyl monosulfides, such as dimethyl sulfide, diethyl sulfide, dipropyl sulfide and propyl methyl sulfide, or also compounds of the formula HO-R 1 -SSR 2 Organic disulfides of -OH, such as those of the formula HO-C 2 H 4 -SSC 2 H 4 -OH dithiodiethanol (often referred to as DEODS). The sulfur content is generally between 0.1% and 2% by weight of said element relative to the total weight of the catalyst.

[0165] In one embodiment according to the invention, the preparation of the catalyst is carried out ex situ, i.e. before loading the catalyst into the reaction unit of the process for the selective hydrogenation or hydrogenation of aromatics.

[0166] (Selective Hydrogenation Method) Another subject of the invention is a process for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule, for example diolefinic and / or acetylenic and / or alkenyl aromatic compounds (also known as styrenic compounds), contained in a hydrocarbon feedstock having a final boiling point below 300° C., said process being carried out in the presence of a catalyst obtained by the preparation process as described above in the present description, wherein the temperature is between 0° C. and 300° C., wherein the pressure is between 0.1 and 10 MPa, and, if the process is carried out in the liquid phase, wherein the hydrogen / polyunsaturated compound to be hydrogenated molar ratio is between 0.1 and 10, and wherein the hourly space velocity is between 0.1 and 200 h -1 or, if the process is carried out in the gas phase, the hydrogen / (polyunsaturated compound to be hydrogenated) molar ratio is 0.5 to 1000, and the hourly space velocity is 100 to 40,000 h -1 It is.

[0167] Monounsaturated organic compounds, such as ethylene and propylene, are at the root of the production of polymers, plastics and other chemical products with added value. These compounds are obtained from natural gas, naphtha or gas oils, which are processed by the methods of steam cracking or catalytic cracking. These processes are carried out at high temperatures and give rise to polyunsaturated organic compounds, such as acetylene, propadiene and methylacetylene (or propyne), 1,2-butadiene and 1,3-butadiene, vinylacetylene and ethylacetylene, and other polyunsaturated compounds whose boiling points correspond to the C5+ fraction (hydrocarbon-based compounds having at least 5 carbon atoms), in particular diolefins or styrene or indene compounds. These polyunsaturated compounds are highly reactive and lead to side reactions in the polymerization unit. It is therefore necessary to remove them before making an economical use of these fractions.

[0168] Selective hydrogenation is a major process developed to specifically remove unwanted polyunsaturated compounds from these hydrocarbon feedstocks. Thereby, it becomes possible to convert polyunsaturated compounds into the corresponding alkenes or aromatic compounds while avoiding complete saturation of the polyunsaturated compounds and thus the formation of the corresponding alkanes or naphthenes. In the case of steam-cracked gasoline used as a feedstock, selective hydrogenation also makes it possible to selectively hydrogenate alkenyl aromatic compounds to give aromatic compounds while avoiding hydrogenation of the aromatic rings.

[0169] The hydrocarbon feedstock treated in the selective hydrogenation process has a final boiling point of 300 °C or lower, contains at least 2 carbon atoms per molecule, and contains at least one polyunsaturated compound. The term "polyunsaturated compounds" is intended to mean a compound containing at least one acetylene group and / or at least one diene group and / or at least one alkenyl aromatic group.

[0170] More specifically, the feedstock is selected from the group consisting of steam-cracked C2 fraction, steam-cracked C2-C3 fraction, steam-cracked C3 fraction, steam-cracked C4 fraction, steam-cracked C5 fraction, and steam-cracked gasoline also known as the pyrolysis gasoline or C5+ fraction.

[0171] The steam-cracked C2 fraction is advantageously used for the implementation of the selective hydrogenation process according to the invention, which has, for example, the following composition: 40% to 95% by weight of ethylene and about 0.1% to 5% by weight of acetylene, the balance being essentially ethane and methane. In some steam-cracked C2 fractions, 0.1% to 1% by weight of C3 compounds may be present.

[0172] The steam cracked C3 fractions, which are advantageously used for the implementation of the selective hydrogenation process according to the invention, have, for example, the following average composition: about 90% by weight of propylene and about 1% to 8% by weight of propadiene and methylacetylene, the remainder being essentially propane. In some C3 fractions, 0.1% to 2% by weight of C2 and C4 compounds may also be present.

[0173] The C2-C3 fraction may also be advantageously used for the implementation of the selective hydrogenation process according to the invention. It has, for example, the following composition: acetylene in the order of 0.1% to 5% by weight, propadiene and methylacetylene in the order of 0.1% to 3% by weight, ethylene in the order of 30% by weight and propylene in the order of 5% by weight, the remainder being essentially methane, ethane and propane. This feedstock may contain C4 compounds in the order of 0.1% to 2% by weight.

[0174] The steam cracked C4 fraction, which is advantageously used for the implementation of the selective hydrogenation process according to the invention, has, for example, the following average composition by weight: 1% by weight of butane, 46.5% by weight of butene, 51% by weight of butadiene, 1.3% by weight of vinylacetylene and 0.2% by weight of butyne. In some C4 fractions, 0.1% to 2% by weight of C3 and C5 compounds may be present.

[0175] The steam cracked C5 fraction, which is advantageously used for the implementation of the selective hydrogenation process according to the invention, has, for example, the following composition: 21% by weight of pentane, 45% by weight of pentene and 34% by weight of pentadiene.

[0176] Steam cracked gasoline or pyrolysis gasoline, which is advantageously used for the implementation of the selective hydrogenation process according to the invention, corresponds to a hydrocarbon fraction whose boiling point is generally between 0 and 300° C., preferably between 10 and 250° C. The polyunsaturated hydrocarbons to be hydrogenated present in said steam cracked gasoline are in particular diolefin compounds (butadiene, isoprene, cyclopentadiene, etc.), styrene compounds (styrene, α-methylstyrene, etc.) and indenic compounds (indene, etc.). Steam cracked gasoline generally contains C5-C12 fractions together with traces of C3, C4, C13, C14 and C15 (for example 0.1% by weight to 3% by weight for each of these fractions). For example, a feedstock formed from pyrolysis gasoline generally has the following composition: 5% to 30% by weight of saturates (paraffins and naphthenes), 40% to 80% by weight of aromatics, 5% to 20% by weight of monoolefins, 5% to 40% by weight of diolefins, and 1% to 20% by weight of alkenyl aromatics, which together make up 100%. It also contains 0 to 1000 ppm by weight of sulfur, preferably 0 to 500 ppm by weight of sulfur.

[0177] Preferably, the polyunsaturated hydrocarbon feedstock treated by the selective hydrogenation process according to the invention is a steam cracked C2 fraction or a steam cracked C2-C3 fraction or a steam cracked gasoline.

[0178] The selective hydrogenation process according to the invention is aimed at removing the polyunsaturated hydrocarbons present in the feedstock to be hydrogenated, without hydrogenating the monounsaturated hydrocarbons. For example, when the feedstock is a C2 fraction, the selective hydrogenation process is aimed at selectively hydrogenating acetylene. When the feedstock is a C3 fraction, the selective hydrogenation process is aimed at selectively hydrogenating propadiene and methylacetylene. In the case of the C4 fraction, the objective is to remove butadiene, vinylacetylene (VAC) and butyne; in the case of the C5 fraction, the objective is to remove pentadiene. When the feedstock is steam cracked gasoline, the selective hydrogenation process is aimed at selectively hydrogenating the polyunsaturated hydrocarbons present in the feedstock to be treated, so that diolefinic compounds are particularly hydrogenated to give monoolefins and styrene and indene compounds are particularly hydrogenated to give the corresponding aromatic compounds, avoiding the hydrogenation of aromatic rings.

[0179] The technical implementation of the selective hydrogenation process is, for example, carried out by injection of the polyunsaturated hydrocarbon feedstock and hydrogen as an upflow or downflow into at least one fixed-bed reactor. The reactor may be of isothermal or adiabatic type. Adiabatic reactors are preferred. The polyunsaturated hydrocarbon feedstock may advantageously be diluted by reinjecting the effluent from the reactor in which the selective hydrogenation reaction has been carried out one or more times at various points of the reactor located between the inlet and the outlet of the reactor, limiting the temperature gradient in the reactor. The technical implementation of the selective hydrogenation process according to the invention may also advantageously be carried out by implantation of at least the supported catalyst in a reactive distillation column or a reactor-exchanger or a slurry type reactor. The hydrogen flow may be introduced simultaneously with the feedstock to be hydrogenated and / or at one or several different points of the reactor.

[0180] The selective hydrogenation of the steam cracked C2, C2-C3, C3, C4, C5 and C5+ fractions can be carried out in the gas or liquid phase, preferably in the liquid phase for the C3, C4, C5 and C5+ fractions and in the gas phase for the C2 and C2-C3 fractions. The liquid phase reaction allows to reduce the energy costs and increase the cycle period of the catalyst.

[0181] In general, the selective hydrogenation of a hydrocarbon feedstock containing polyunsaturated compounds containing at least two carbon atoms per molecule and having a final boiling point of 300° C. or less is carried out at a temperature between 0° C. and 300° C., at a pressure between 0.1 and 10 MPa, and for processes carried out in the liquid phase, the hydrogen / (polyunsaturated compounds to be hydrogenated) molar ratio is between 0.1 and 10, and the hourly space velocity HSV (defined as the ratio of the flow rate by the volume of the feedstock to the volume of the catalyst) is between 0.1 and 200 h . -1 or for processes carried out in the gas phase, in which the hydrogen / (polyunsaturated compound to be hydrogenated) molar ratio is 0.5 to 1000, and the hourly space velocity HSV is 100 to 40,000 h -1 It is.

[0182] In one embodiment of the present invention, when a selective hydrogenation process is carried out and the feedstock is a steam cracked gasoline containing polyunsaturated compounds, the molar ratio of (hydrogen) / (polyunsaturated compounds to be hydrogenated) is generally 0.5-10, preferably 0.7-5.0, more preferably 1.0-2.0, the temperature is 0° C.-200° C., preferably 20° C.-200° C., more preferably 30° C.-180° C., the hourly space velocity (HSV) is generally 0.5-100 h -1 , preferably 1 to 50 hours -1 and the pressure is generally 0.3 to 8.0 MPa, preferably 1.0 to 7.0 MPa, and even more preferably 1.5 to 4.0 MPa.

[0183] More preferentially, when the selective hydrogenation process is carried out and the feedstock is steam cracked gasoline containing polyunsaturated compounds, the hydrogen / polyunsaturated compounds to be hydrogenated molar ratio is 0.7-5.0, the temperature is 20°C-200°C, and the hourly space velocity (HSV) is generally 1-50 h -1 and the pressure is 1.0 to 7.0 MPa.

[0184] Even more preferentially, when a selective hydrogenation process is carried out and the feedstock is steam cracked gasoline containing polyunsaturated compounds, the hydrogen / polyunsaturated compounds to be hydrogenated molar ratio is between 1.0 and 2.0, the temperature is between 30°C and 180°C, and the hourly space velocity (HSV) is generally between 1 and 50 h -1 and the pressure is 1.5 to 4.0 MPa.

[0185] The hydrogen flow rate is adjusted so that a sufficient amount is available to theoretically hydrogenate all of the polyunsaturated compounds and maintain an excess of hydrogen at the reactor outlet.

[0186] In another embodiment of the present invention, when a selective hydrogenation process is carried out and the feedstock is a steam cracked C2 fraction and / or a steam cracked C2-C3 fraction containing polyunsaturated compounds, the molar ratio of (hydrogen) / (polyunsaturated compounds to be hydrogenated) is generally 0.5-1000, preferably 0.7-800, the temperature is 0° C.-300° C., preferably 15° C.-280° C., the hourly space velocity (HSV) is generally 100-40000 h -1 , preferably 500 to 30,000 h -1 The pressure is generally 0.1 to 6.0 MPa, and preferably 0.2 to 5.0 MPa.

[0187] (Method for hydrogenating aromatic compounds) Another subject of the invention is a process for the hydrogenation of at least one aromatic or polyaromatic compound contained in a hydrocarbon feedstock having a final boiling point below 650° C., generally between 20° C. and 650° C., preferably between 20° C. and 450° C. Said hydrocarbon feedstock containing at least one aromatic or polyaromatic compound may be chosen from the following petroleum or petrochemical fractions: reformates from catalytic reforming, kerosene, light gas oils, heavy gas oils, cracking distillates, such as FCC recycle oils, coking unit gas oils or hydrocracking distillates.

[0188] The content of aromatic or polyaromatic compounds contained in the hydrocarbon feedstock treated in the hydrogenation process according to the invention is generally between 0.1 and 80% by weight, preferably between 1 and 50% by weight and particularly preferably between 2 and 35% by weight, the percentages being based on the total weight of the hydrocarbon feedstock. The aromatic compounds present in the hydrocarbon feedstock are, for example, benzene or alkylaromatics, such as toluene, ethylbenzene, o-xylene, m-xylene or p-xylene, or also aromatic compounds having several aromatic rings (polyaromatics), such as naphthalene.

[0189] The sulfur or chlorine content of the feedstock is generally less than 5000 ppm by weight of sulfur or chlorine, preferably less than 100 ppm by weight, particularly preferably less than 10 ppm by weight.

[0190] The technical implementation of the process for the hydrogenation of aromatic or polyaromatic compounds is carried out, for example, by injection of the hydrocarbon feedstock and hydrogen as upflow or downflow into at least one fixed-bed reactor. The reactor may be of isothermal or adiabatic type. Adiabatic reactors are preferred. The hydrocarbon feedstock may advantageously be diluted by one or more reinjections of the effluent from the reactor in which the reaction for the hydrogenation of aromatic compounds was carried out at various points of the reactor, located between the inlet and the outlet of the reactor, so that the temperature gradient in the reactor is limited. The technical implementation of the process for the hydrogenation of aromatic compounds according to the invention may advantageously be carried out by implantation of at least the supported catalyst in a reactive distillation column or in a reactor-exchanger or in a slurry-type reactor. The hydrogen flow may be introduced simultaneously with the feedstock to be hydrogenated and / or at one or more different points of the reactor.

[0191] The hydrogenation of aromatic or polyunsaturated compounds may be carried out in gas phase or liquid phase, and is preferably carried out in liquid phase. In general, the temperature during hydrogenation of aromatic or polyaromatic compounds is 30°C to 350°C, preferably 50°C to 325°C, the pressure during hydrogenation is 0.1 to 20MPa, preferably 0.5 to 10MPa, the molar ratio of hydrogen / (aromatic compound to be hydrogenated) is 0.1 to 10, and the hourly space velocity HSV during hydrogenation is 0.05 to 50h -1 , preferably 0.1 to 10 hours -1 and the hydrocarbon feedstock contains aromatic or polyaromatic compounds and has a final boiling point below 650°C, typically between 20°C and 650°C, preferably between 20°C and 450°C.

[0192] The hydrogen flow rate is adjusted so that a sufficient amount is available to theoretically hydrogenate all of the aromatics and maintain an excess of hydrogen at the reactor exit.

[0193] The conversion of aromatic or polyaromatic compounds is generally greater than 20 mol%, preferably greater than 40 mol%, more preferably greater than 80 mol%, particularly preferably greater than 90 mol% of the aromatic or polyaromatic compounds contained in the hydrocarbon feedstock. The conversion is calculated by dividing the difference between the total moles of aromatic or polyaromatic compounds in the hydrocarbon feedstock and in the product by the total moles of aromatic or polyaromatic compounds in the hydrocarbon feedstock.

[0194] According to a specific alternative embodiment of the process according to the invention, a process for hydrogenation of benzene from a hydrocarbon feedstock, for example a reformate derived from a catalytic reforming unit, is carried out, the benzene content in said hydrocarbon feedstock generally being between 0.1 and 40% by weight, preferably between 0.5 and 35% by weight, particularly preferably between 2 and 30% by weight, the weight percentages being based on the total weight of the hydrocarbon feedstock.

[0195] The sulfur or chlorine content of the feedstock is generally less than 10 ppm by weight, preferably less than 2 ppm by weight of sulfur or chlorine, respectively.

[0196] The hydrogenation of benzene contained in the hydrocarbon feedstock may be carried out in the gas phase or liquid phase, but is preferably carried out in the liquid phase. When it is carried out in the liquid phase, a solvent may be present, for example, cyclohexane, heptane or octane. In general, the temperature at which the hydrogenation of benzene is carried out is 30°C to 250°C, preferably 50°C to 200°C, more preferably 80°C to 180°C, the pressure at which it is carried out is 0.1 to 10 MPa, preferably 0.5 to 4 MPa, the molar ratio of hydrogen / (benzene) at which it is carried out is 0.1 to 10, and the hourly space velocity HSV at which it is carried out is 0.05 to 50 h -1 , preferably 0.5 to 10 hours -1 It is.

[0197] The benzene conversion is generally greater than 50 mol %, preferably greater than 80 mol %, more preferably greater than 90 mol %, particularly preferably greater than 98 mol %.

[0198] The present invention will now be illustrated by the following examples, which are not intended to be limiting in any way.

[0199] (Example) Example 1: Preparation of AL-1 alumina The synthesis of alumina gel is carried out via a mixture of sodium aluminate and aluminum sulfate. The precipitation reaction is carried out at a temperature of 60° C., pH 9, and with stirring at 200 rpm for 60 minutes.

[0200] The gel thus obtained is kneaded in a Z-arm mixer to give a paste. Extrusion is carried out by passing the paste through a die equipped with a trilobal orifice having a diameter of 1.6 mm. The extrudates thus obtained are dried at 150° C. for 12 hours under a stream of dry air and then calcined at 450° C. for 5 hours under a stream of dry air.

[0201] The extrudates undergo hydrothermal treatment in an autoclave in the presence of an aqueous solution containing acetic acid at 6.5% by weight relative to the weight of the alumina at 650° C. for 3 hours, then calcined in a tubular reactor in dry air at 1000° C. for 2 hours. AL-1 alumina is obtained.

[0202] The specific surface area of ​​AL-1 alumina is 80m 2 / g, the pore volume (determined by Hg porosimetry) is 0.85 mL / g and the mesopore diameter is 35 nm.

[0203] The sodium content is 0.0350% by weight relative to the total weight of the alumina, and the sulfur content is 0.15% by weight relative to the total weight of the alumina.

[0204] Example 1a: Preparation of AL-2 Alumina The synthesis of alumina gel is carried out via a mixture of sodium aluminate and aluminum sulfate. The precipitation reaction is carried out at a temperature of 60° C., pH 9, and with stirring at 200 rpm for 60 minutes.

[0205] The gel thus obtained is kneaded in a Z-arm mixer to give a paste. Extrusion is carried out by passing the paste through a die equipped with a trilobal orifice of 1.6 mm diameter. The extrudates thus obtained are dried at 150° C. for 12 hours under a stream of dry air and then calcined at 450° C. for 5 hours under a stream of dry air. AL-2 alumina is obtained.

[0206] The specific surface area of ​​AL-2 alumina is 255m 2 / g, the pore volume (determined by Hg porosimetry) is 0.7 mL / g and the mesopore diameter is 12 nm.

[0207] The sodium content is 0.0350% by weight relative to the total weight of the alumina, and the sulfur content is 0.15% by weight relative to the total weight of the alumina.

[0208] Example 2: Preparation of an aqueous solution of Ni precursor The aqueous solution of Ni precursor (solution S1) used for the preparation of catalyst A was prepared using nickel nitrate (NiNO 3 This is done by dissolving 43.5 g of NiCl, supplier Strem Chemicals®, in a volume of 13 mL of distilled water. A solution S1 is obtained, the Ni concentration of which is 350 g Ni per liter of solution volume.

[0209] Example 3: Preparation of an aqueous solution of Ni precursor with organic compounds The aqueous solution of the Ni precursor (solution S2) used for the preparation of catalysts B to G was prepared using nickel nitrate (NiNO 3 This is done by dissolving 43.5 g of dimethylformamide (CAS 141-82-2; supplier Strem Chemicals®) and malonic acid (CAS 141-82-2; supplier Fluka®) in a volume of 13 mL of distilled water. The additive / Ni molar ratio is 0.5. A solution S2 is obtained, the Ni concentration of which is 350 g Ni per liter of solution volume.

[0210] Example 4: Preparation of an aqueous solution of a precursor of NiCu alloy (5% Ni) The aqueous solution of Ni precursor (solution S3) used for the preparation of catalysts C, D, E, and G was prepared using nickel nitrate (NiNO 3 This is done by dissolving 14.5 g of NiCl, supplier Strem Chemicals®, in a volume of 13 mL of distilled water. A solution is obtained whose Ni concentration is 116.6 g Ni per liter of solution volume. Copper nitrate precursor is then added, in particular having a Ni / Cu molar ratio of 3 (catalyst C / F). A solution S3 is obtained, which makes it possible to introduce the precursor of the NiCu alloy, the weight content of Ni relative to the final catalyst being approximately 5% by weight.

[0211] Example 5: Preparation of Catalyst A Dry impregnation of solution S2 prepared in example 3 is carried out on 10 g of AL-1 alumina obtained according to example 1 by adding it dropwise.

[0212] The solid thus obtained is subsequently dried in an oven at 120° C. for 12 hours and then calcined at 450° C. for 2 hours under a flow of dry air of 1 L / h / g (catalyst).

[0213] The dry air used in this and all following examples contains less than 5 grams of water per kilogram of dry air weight.

[0214] The catalyst precursor thus obtained is dry impregnated with an aqueous solution containing formic acid in a molar ratio HCOOH / Ni equal to 1 mol / mol.

[0215] At the end of the impregnation with the aqueous solution containing formic acid, the catalyst precursor undergoes a heat treatment at 150° C. for 2 hours under a flow of air containing 50 grams of water per kilogram of weight of dry air at a flow rate of 1 L / h / g (catalyst), then at 120° C. for 1 hour under a flow of dry air.

[0216] Solution S3 is then dry-impregnated onto the catalyst precursor. The Ni content targeted in this step is 5 wt.% Ni relative to the weight of the final catalyst. The solid thus obtained is then dried overnight in an oven at 120°C, then calcined at 450°C for 2 hours under an air flow of 1 L / h / g (catalyst).

[0217] The catalyst precursor is then reduced under the conditions described in Example 12 below.

[0218] Catalyst A is obtained, the characteristics of which are reported in Tables 1 and 2 below.

[0219] Example 6: Preparation of Catalyst B in Accordance with the Invention Solution S3 is dry-impregnated dropwise onto 10 g of AL-1 support. The Ni content targeted in this step is 5 wt. % Ni weight relative to the weight of the final catalyst. The solid thus obtained is subsequently dried overnight at 120° C. in an oven and then calcined at 450° C. for 2 h under an air flow of 1 L / h / g (catalyst). Precursor B' of the final catalyst is obtained.

[0220] The final catalyst precursor B' is then dry impregnated with the solution S2 prepared in example 3 by adding it dropwise.

[0221] The solid thus obtained is subsequently dried in an oven at 120° C. for 12 hours and then calcined at 450° C. for 2 hours under a flow of dry air of 1 L / h / g (catalyst).

[0222] The obtained catalyst precursor is dry impregnated with an aqueous solution containing formic acid in a HCOOH / Ni molar ratio equal to 1 mol / mol.

[0223] At the end of the impregnation with the aqueous solution containing formic acid, the catalyst precursor undergoes a heat treatment under a flow of air containing 50 grams of water per kilogram of weight of dry air at a flow rate of 1 L / h / g (catalyst) for 2 hours at 150° C., then under a flow of dry air for 1 hour at 120° C. The catalyst precursor is then reduced under the conditions described in Example 12 below.

[0224] Catalyst B is obtained, the characteristics of which are reported in Tables 1 and 2 below.

[0225] Example 7: Preparation of Catalyst C (not in accordance with the present invention) Solution S3 is dry-impregnated dropwise onto 10 g of AL-1 support. The Ni content targeted in this step is 5 wt. % Ni relative to the weight of the final catalyst. The solid thus obtained is subsequently dried overnight at 120° C. in an oven and then calcined at 450° C. for 2 h under an air flow of 1 L / h / g (catalyst).

[0226] The precursor C' of the final catalyst is obtained.

[0227] The final catalyst precursor C' is then dry impregnated with the solution S1 prepared in example 2 by adding it dropwise.

[0228] The solid thus obtained is subsequently dried in an oven at 120° C. for 12 hours and then calcined at 450° C. for 2 hours under a flow of dry air of 1 L / h / g (catalyst).

[0229] The catalyst precursor thus obtained is dry impregnated with an aqueous solution containing formic acid in a HCOOH / Ni molar ratio equal to 1 mol / mol.

[0230] At the end of the impregnation with the aqueous solution containing formic acid, the catalyst precursor undergoes a heat treatment under a flow of air containing 50 grams of water per kilogram of weight of dry air at a flow rate of 1 L / h / g (catalyst) for 2 hours at 150° C., then under a flow of dry air for 1 hour at 120° C. The catalyst precursor is then reduced under the conditions described in Example 12 below.

[0231] Catalyst C is obtained, the characteristics of which are reported in Tables 1 and 2 below.

[0232] Example 8: Preparation of Catalyst D (not in accordance with the present invention) The solution of S3 is dry-impregnated dropwise onto 10 g of AL-2 support. The Ni content targeted in this step is 5 wt. % Ni relative to the weight of the final catalyst. The solid thus obtained is subsequently dried overnight at 120° C. in an oven and then calcined at 450° C. for 2 h under an air flow of 1 L / h / g (catalyst).

[0233] A precursor D' of the final catalyst is obtained.

[0234] Dry impregnation of the solution S2 prepared in example 3 is then carried out onto the final catalyst precursor D' by adding it dropwise.

[0235] The solid thus obtained is subsequently dried in an oven at 120° C. for 12 hours and then calcined at 450° C. for 2 hours under a flow of dry air of 1 L / h / g (catalyst).

[0236] The catalyst precursor thus obtained is dry impregnated with an aqueous solution containing formic acid in a HCOOH / Ni molar ratio equal to 1 mol / mol.

[0237] At the end of the impregnation with the aqueous solution containing formic acid, the catalyst precursor undergoes a heat treatment under a flow of air containing 50 grams of water per kilogram of weight of dry air at a flow rate of 1 L / h / g (catalyst) for 2 hours at 150° C., then under a flow of dry air for 1 hour at 120° C. The catalyst precursor is then reduced under the conditions described in Example 12 below.

[0238] Catalyst D is obtained, the characteristics of which are reported in Tables 1 and 2 below.

[0239] Example 9: Preparation of Catalyst E (not in accordance with the invention) Dry impregnation of solution S2 prepared in example 3 is carried out onto 10 g of AL-1 support obtained according to example 1 by adding it dropwise.

[0240] The solid thus obtained is subsequently dried in an oven at 120° C. for 12 hours and then calcined at 450° C. for 2 hours under a flow of dry air of 1 L / h / g (catalyst).

[0241] The dry air used in this and all following examples contains less than 5 grams of water per kilogram of air weight.

[0242] The catalyst precursor E' thus obtained is dry impregnated with an aqueous solution containing formic acid in a HCOOH / Ni molar ratio equal to 1 mol / mol.

[0243] At the end of the impregnation with the aqueous solution containing formic acid, the catalyst precursor undergoes a heat treatment under a flow of air containing 50 grams of water per kilogram of weight of dry air at a flow rate of 1 L / h / g (catalyst) at 150° C. for 2 hours, then under a flow of dry air at 120° C. for 1 hour.

[0244] Catalyst E is obtained, the characteristics of which are reported in Tables 1 and 2 below.

[0245] The catalyst precursor is then reduced under the conditions described in Example 12 below.

[0246] Example 10: Preparation of Catalyst F (not in accordance with the invention) The solution of S3 is dry-impregnated dropwise onto 10 g of AL-1 support. The Ni content targeted in this step is 5 wt. % Ni relative to the weight of the final catalyst. The solid thus obtained is subsequently dried overnight at 120° C. in an oven and then calcined at 450° C. for 2 h under a flow of air at 1 L / h / g (catalyst).

[0247] The precursor F' of the final catalyst is obtained.

[0248] Dry impregnation of the solution S2 prepared in example 3 is then carried out onto the catalyst precursor F' by dropping it dropwise.

[0249] The solid thus obtained is subsequently dried in an oven at 120° C. for 12 hours and then calcined at 450° C. for 2 hours under a flow of dry air of 1 L / h / g (catalyst).

[0250] Catalyst F is obtained, the characteristics of which are reported in Tables 1 and 2 below.

[0251] The catalyst precursor is then reduced under the conditions described in Example 12 below.

[0252] Example 11: Preparation of Catalyst G (not in accordance with the invention) Dry impregnation of solution S2 prepared in example 3 is carried out onto 10 g of AL-1 support obtained according to example 1 by adding it dropwise.

[0253] The solid thus obtained is subsequently dried in an oven at 120° C. for 12 hours and then calcined at 450° C. for 2 hours under a flow of dry air of 1 L / h / g (catalyst). The catalyst precursor is then reduced under the conditions described in Example 9 below.

[0254] Catalyst G is obtained, the characteristics of which are reported in Tables 1 and 2 below.

[0255] The catalyst precursor is then reduced under the conditions described in Example 12 below.

[0256] Example 12: Characterization All catalysts contain the contents targeted during impregnation, i.e. 15% elemental nickel (characterized by X-ray fluorescence) relative to the total weight of the catalyst, and % of copper (characterized by X-ray fluorescence) added.

[0257] The amount of alloy obtained after calcination and subsequent reduction steps was determined by X-ray diffraction (XRD) analysis on a sample of the powdered catalyst.

[0258] The amount of nickel in metallic form obtained after the reduction step was determined by X-ray diffraction (XRD) analysis on a powdered catalyst sample. During the reduction step and the duration of the XRD characterization, the catalyst was never returned to the open air. The diffraction patterns were obtained by radiation crystallographic analysis on a diffractometer using conventional powder techniques with copper Kα1 radiation (λ=1.5406 Å).

[0259] The degree of reduction was calculated by calculating the area of ​​the Ni line located near 52° 2θ on all of the diffractograms of each sample of catalyst analyzed, and then subtracting the signal due to alumina that is present below the line at 52° and reaches ambient temperature as quickly as possible.

[0260] Table 1 below collates the degree of reduction of nickel metal Ni° and / or the content of nickel metal Ni° (expressed as weight % relative to the total weight of "active" nickel, i.e. without taking into account the nickel constituting the alloy) for all catalysts A to G characterized by XRD after a reduction step under flowing hydrogen for 90 minutes at 170° C. These values ​​were also compared with the degree of reduction obtained for catalyst G (Ni alone) after a conventional reduction step (i.e. reduction under flowing hydrogen for 15 hours at a temperature of 400° C.).

[0261] Alumina in the delta and theta forms, as well as large CuO and NiO lines, are detected at ambient temperature on all copper-nickel containing catalysts after calcination.

[0262] After reduction, Ni 0.76 Cu 0.24 A line corresponding to the alloy in the form of is further detected after reduction.

[0263] The degree of reducing power and therefore Ni 0 To evaluate the formation of 0 The area of ​​the line of is measured by subtracting the signal due to alumina present on all diffractograms below the line at 52° as soon as possible after reaching ambient temperature. Therefore, the area of ​​the Ni crystallized after reduction is 0 It is possible to determine the relative percentages of

[0264] Table 1 below shows the reduction power or Ni for all catalysts characterized by XRD after reduction under hydrogen flow at 170° C. for 90 minutes. 0 The contents are summarized below. These values ​​were also compared with the degree of reduction obtained for catalyst G (Ni alone) after a conventional reduction step (i.e. reduction under a flow of hydrogen at a temperature of 400° C. for 15 hours).

[0265] [Table 1]

[0266] [Table 2]

[0267] Example 13: Catalytic testing: Performance in selective hydrogenation of mixtures containing styrene and isoprene (A HYD1 )) Catalysts A to G described in the above examples are tested in a reaction for the selective hydrogenation of a mixture containing styrene and isoprene.

[0268] The composition of the feedstock to be selectively hydrogenated is as follows: 8% by weight of styrene (supplied by Sigma Aldrich®, purity 99%), 8% by weight of isoprene (supplied by Sigma Aldrich®, purity 99%) and 84% by weight of n-heptane (solvent) (supplied by VWR®, purity >99% Chromanorm® HPLC). This composition corresponds to the initial composition of the reaction mixture. This mixture of model molecules is typical of pyrolysis gasoline.

[0269] The selective hydrogenation reaction is carried out in a 500 mL stainless steel autoclave equipped with a magnetically driven mechanical stirrer and capable of operating at a maximum pressure of 100 bar (10 MPa) and temperatures between 5°C and 200°C.

[0270] 214 mL of n-heptane (supplier VWR®, purity >99% Chromanorm HPLC) and a quantity of 3 mL of catalyst are added to the autoclave. The autoclave is closed and purged. The autoclave is then pressurized under 35 bar (3.5 MPa) of hydrogen. The catalyst is first reduced in situ for catalysts A to G (here corresponding to step g) of the preparation method according to the invention according to one embodiment) at 170° C. for 90 minutes under a hydrogen flow of 1 L / h / g (temperature increase gradient is 1° C. / min). The autoclave is then brought to a test temperature equal to 30° C. At time t=0, about 30 g of a mixture containing styrene, isoprene and n-heptane are introduced into the autoclave. The reaction mixture then has the composition described above and stirring is started at 1600 rpm. In the autoclave, the pressure is kept constant at 35 bar (3.5 MPa) by means of a storage cylinder placed upstream of the reactor.

[0271] Another test was run on Catalyst A, where the catalyst reduction temperature was 400° C. for 15 hours.

[0272] The progress of the reaction is monitored by taking samples at regular intervals from the reaction medium: styrene is hydrogenated to give ethylbenzene, there is no hydrogenation of the aromatic ring, and isoprene is hydrogenated to give methylbutenes. If the reaction is extended longer than necessary, the methylbutenes are then themselves hydrogenated to give isopentane. Hydrogen consumption is also monitored over time by the reduction in pressure in a storage cylinder located upstream of the reactor. The catalytic activity is expressed as consumed H per minute and per weight (gram) of Ni. 2 It is expressed in moles.

[0273] The catalytic activities measured for catalysts A to G are recorded in Table 3 below. They are compared with the catalytic activities measured for catalyst A prepared under conventional reduction conditions (under hydrogen flow at a temperature of 400° C. for 16 hours) (A HYD1 )

[0274] Example 14: Catalytic testing: performance in hydrogenation of toluene (A HYD2 )) Catalysts A to G described in the above examples are also tested for the reaction for the hydrogenation of toluene. The selective hydrogenation reaction is carried out in the same autoclave as described in Example 13.

[0275] 214 mL of n-heptane (supplier VWR®, purity >99% Chromanorm HPLC) and a quantity of 3 mL of catalyst are added to the autoclave. The autoclave is closed and purged. It is then pressurized under 35 bar (3.5 MPa) of hydrogen. The catalyst is first reduced in situ for catalysts A to G (here corresponding to step g) of the preparation method according to the invention according to one embodiment) at 170° C. for 90 minutes under a hydrogen flow of 1 L / h / g (temperature increase gradient is 1° C. / min). After the addition of 216 mL of n-heptane (supplier VWR®, purity >99% Chromanorm HPLC), the autoclave is closed, purged and then pressurized under 35 bar (3.5 MPa) of hydrogen and a test temperature equal to 80° C. At time t=0, about 26 g of toluene (supplier SDS®, purity >99.8%) are introduced into the autoclave (initial composition of the reaction mixture is 6% by weight toluene / 94% by weight n-heptane) and stirring is started at 1600 rpm. The pressure in the autoclave is kept constant at 35 bar (3.5 MPa) by means of a storage cylinder located upstream of the reactor.

[0276] The progress of the reaction is monitored by taking samples from the reaction medium at regular time intervals: toluene is completely hydrogenated to give methylcyclohexane. Hydrogen consumption is also monitored over time by the drop in pressure in a storage cylinder located upstream of the reactor. The consumed H per minute and per weight (gram) of Ni is 2 The catalytic activity is expressed in moles.

[0277] The catalytic activities measured for catalysts A to G are recorded in Table 2 below. They are the catalytic activities measured for catalyst C (A HYD2 For comparison, catalyst G was also prepared under conventional reduction conditions (in an ex situ flow-through reactor under hydrogen flow at a temperature of 400° C. for 16 hours).

[0278] [Table 3]

[0279] This shows the improved A of catalysts A and B according to the invention compared to catalysts C to G not according to the invention. HYD1 and A HYD2 The results clearly show the performance of catalysts A and B, which are reduced to a level of at least 90% at 170° C., have small size particles and are distributed in the “eggshell”. Catalyst C, due to the use of solution S2 without additives, has large particles. Its catalytic activity is still favorable due to the presence of 100% of reduced Ni due to the addition of NiCu. Catalysts D and F, in fact, have small particles reduced to a level of 90%, but they are not distributed in the crust and therefore the activity is reduced. Catalysts E and G, despite the small particles, are not active. The absence of NiCu does not make it possible to obtain reduced Ni, which is the active phase in hydrogenation, at 170° C. [Brief description of the drawings]

[0280] [Figure 1] FIG. 2 shows the distribution of nickel in the catalyst.

Claims

1. A catalyst for selective hydrogenation of polyunsaturated compounds or hydrogenation of polyunsaturated aromatic compounds, comprising nickel and copper, the nickel content being 1% to 50% by weight relative to the total weight of the catalyst, and a second metallic element, copper, being 0.5% to 15% by weight relative to the total weight of the catalyst, the catalyst comprising an alumina carrier; the nickel is distributed both on a crust at the periphery of the support and in the core of the support, the thickness of said crust being between 2% and 15% of the diameter of the catalyst; - the nickel density ratio between the crust and the core is strictly greater than 3; - said crust comprises more than 25% by weight of elemental nickel relative to the total weight of nickel contained in the catalyst; the molar ratio between nickel and copper is between 0.5 and 5; at least a portion of the nickel and copper is in the form of a nickel-copper alloy; the nickel content in the nickel-copper alloy is between 0.5% and 15% by weight of elemental nickel relative to the total weight of the catalyst; The size of the nickel particles, measured in the form of oxide in the catalyst, is less than 7 nm. A catalyst characterized by:

2. 2. The catalyst of claim 1, wherein the nickel density ratio between the crust and the core is 3.5 or greater.

3. 3. The catalyst according to claim 1, wherein the crust comprises more than 40% by weight of elemental nickel relative to the total weight of nickel contained in the catalyst.

4. 4. The catalyst according to claim 1, wherein the transition spacing between the catalyst core and the crust is between 0.05% and 3% of the catalyst diameter as measured by Castaing microprobe.

5. 5. The catalyst according to claim 1, wherein the size of the nickel particles in the catalyst is less than 5 nm.

6. 6. A catalyst according to any one of claims 1 to 5, wherein the sulphur content of the alumina support is between 0.001% and 2% by weight relative to the total weight of the alumina support and the sodium content of the alumina support is between 0.001% and 2% by weight relative to the total weight of the alumina.

7. 7. The catalyst according to claim 1, wherein the thickness of the crust is 2.5% to 12% of the diameter of the catalyst.

8. 8. The catalyst according to claim 1, wherein the nickel density ratio between the crust and the core is between 3.8 and 15.

9. A method for preparing the catalyst according to any one of claims 1 to 8, comprising the steps of: a) providing an alumina gel; b) shaping the alumina gel from step a); c) subjecting the shaped alumina gel obtained at the end of step b) to a heat treatment to obtain an alumina support, said heat treatment comprising at least one hydrothermal treatment step at a temperature between 100° C. and 800° C. in the presence of an acid solution in an autoclave and at least one calcination step carried out after the hydrothermal treatment at a temperature between 400° C. and 1500° C.; d) performing the following sequence of substeps: d1) contacting an alumina support with at least one nickel precursor to obtain a catalyst precursor; d2) drying the catalyst precursor obtained at the end of step d1) at a temperature below 250° C.; d3) contacting the dried catalyst precursor obtained at the end of step d2) with at least one solution containing at least one organic additive selected from formic acid, formaldehyde, acetic acid, citric acid, oxalic acid, glycolic acid, malonic acid, ethanol, methanol, ethyl formate, methyl formate, paraldehyde, acetaldehyde, gamma-valerolactone, glucose, sorbitol and trioxane; the molar ratio between the organic additive and nickel is greater than 0.05 mol / mol; d4) hydrothermal treatment of the catalyst precursor obtained at the end of step d3) at a temperature between 100° C. and 200° C. for a period between 30 minutes and 5 hours under a gas flow containing 5 to 650 grams of water per kg of dry gas; e) performing the following sequence of substeps: e1) contacting the alumina support with at least one solution containing at least one copper precursor and at least one nickel precursor, said solution being in the desired nickel concentration so as to obtain, on the final catalyst, a content of 0.5% to 15% by weight of elemental nickel relative to the total weight of the final catalyst; e2) carrying out at least one step of drying the catalyst precursor obtained at the end of step e1) at a temperature below 250° C.; Steps d) and e) are carried out separately in any order; f) contacting the alumina support with at least one solution containing at least one organic compound selected from oxalic acid, malonic acid, glycolic acid, lactic acid, tartronic acid, citric acid, tartaric acid, pyruvic acid, levulinic acid, ethylene glycol, propane-1,3-diol, butane-1,4-diol, glycerol, xylitol, mannitol, sorbitol, diethylene glycol, glucose, gamma-valerolactone, dimethyl carbonate, diethyl carbonate, formamide, N-methylformamide, acetamide, N-methylacetamide, N,N-dimethylmethanamide, 2-pyrrolidone, gamma-lactam, lactamide, urea, alanine, arginine, lysine, proline, serine, EDTA; Step f) is carried out either simultaneously with sub-step d1) of step d) or before or after step d), but before step g), it being understood that when step f) is carried out before or after step d), said step f) comprises, after contacting the support with said solution comprising at least one organic compound, drying the catalyst precursor at a temperature below 250° C.; g) reducing the catalyst precursor from steps a)-f) by contacting the catalyst precursor with a reducing gas at a temperature of at least 150° C. and less than 250° C. A method comprising:

10. 10. The method according to claim 9, wherein the molar ratio between the organic compound introduced in step f) and elemental nickel also introduced in step d1) is between 0.01 and 5.0 mol / mol.

11. The method according to claim 9 or 10, wherein step d1) and step f) are carried out simultaneously.

12. The method according to any one of claims 9 to 11, wherein the copper precursor is selected from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide or copper fluoride.

13. 13. The method according to any one of claims 9 to 12, wherein the molar ratio between the organic additive introduced in step d2) and nickel is between 0.1 and 5 mol / mol.

14. The method according to any one of claims 9 to 13, wherein the organic compound of step f) is different from the organic additive of step d2).

15. A process for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule, which are contained in a hydrocarbon feedstock having a final boiling point of less than or equal to 300° C., which is carried out in the presence of a catalyst according to any one of claims 1 to 8, wherein the temperature is from 0° C. to 300° C., the pressure is from 0.1 to 10 MPa, and, if the process is carried out in the liquid phase, the hydrogen / polyunsaturated compound to be hydrogenated molar ratio is from 0.1 to 10 and the hourly space velocity is from 0.1 to 200 h －１ or, if the process is carried out in the gas phase, the hydrogen / polyunsaturated compound to be hydrogenated molar ratio is from 0.5 to 1000, the hourly space velocity being from 100 to 40,000 h －１ That is, the method.

16. A process for the hydrogenation of at least one aromatic or polyaromatic compound contained in a hydrocarbon feedstock having a final boiling point of less than or equal to 650° C., which is carried out in the gas or liquid phase in the presence of a catalyst according to any one of claims 1 to 8, wherein the temperature is between 30° C. and 350° C., the pressure is between 0.1 and 20 MPa, the hydrogen / aromatic compound to be hydrogenated molar ratio is between 0.1 and 10, and the hourly space velocity HSV is between 0.05 and 50 h －１ That is, the method.

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