Aromatic hydrogenation catalysts obtained from molten salts and organic additives

Abstract

Disclosed is a catalyst for hydrogenating aromatic compounds obtainable by a process comprising at least the following steps: a) contacting an alumina support with at least one organic additive; b) contacting the alumina support with at least one nickel metal salt, the melting temperature of which is between 20°C and 150°C; c) heating the solid mixture obtained at the end of steps a) and b) with stirring; d) drying the catalyst precursor at the end of step c); and e) performing a heat treatment step on the dried catalyst precursor obtained at the end of step d).

Description

[Technical Field]

[0001] The present invention relates to a catalyst that is particularly directed to the hydrogenation of unsaturated hydrocarbons, and more particularly to the hydrogenation of aromatic compounds. [Background technology]

[0002] The most active catalysts for hydrogenation reactions are usually based on precious metals such as palladium or platinum. These catalysts are used industrially in refining and petrochemistry for the purification of certain petroleum fractions by hydrogenation, especially in reactions for the selective hydrogenation of polyunsaturated molecules, such as diolefins, acetylenes, or alkenylaromatic compounds, or for the hydrogenation of aromatic compounds. It is often proposed to replace palladium with nickel, a metal that is less active than palladium and therefore needs to be present in greater amounts in the catalyst. Therefore, nickel-based catalysts generally have a metal content of 5% to 60% by weight of nickel relative to the catalyst.

[0003] The rate of the hydrogenation reaction is governed by several criteria, such as the diffusion of reactants at the surface of the catalyst (external diffusion limit), the diffusion of reactants through the porosity of the support towards the active sites (internal diffusion limit) and the intrinsic properties of the active phase, such as the size of the metal particles and the distribution of the active phase within the support.

[0004] With respect to internal diffusion limitations, it is important that the pore distribution of macropores and mesopores is appropriate for the desired reaction to provide for diffusion of reactants within the porosity of the support towards the active sites and diffusion of formed products towards the outside.

[0005] Catalysts for the hydrogenation of aromatic compounds are generally based on metals from group VIII of the periodic table, preferably palladium or nickel. The metal is provided 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 affect the activity and selectivity of the catalyst. With regard to the size of the metal particles, it is generally accepted that the smaller the size of the metal particles, the more active the catalyst. Furthermore, it is important to obtain a particle size distribution centered on an optimum value and also a narrow distribution around this value.

[0006] The often high nickel content in hydrogenation catalysts requires specific synthetic routes.

[0007] The most common route for preparing these catalysts is to impregnate the support with an aqueous solution of nickel precursor, typically followed by drying and calcination. Before they are used for hydrogenation reactions, they are typically reduced to obtain the active phase in the metallic form (i.e., the zero-valent state). Nickel-based catalysts on alumina prepared by a single impregnation step generally allow nickel contents of about 12% to 15% by weight to be achieved, depending on the pore volume of the alumina used. If it is desired to prepare catalysts with higher nickel contents, several successive impregnations are often required to obtain the desired nickel content, followed by at least one drying step between each impregnation and, optionally, a calcination step.

[0008] Thus, Patent Document 1 describes a nickel-based catalyst on activated alumina for hydrogenation, in particular for the hydrogenation of aromatic compounds, which has a nickel content of more than 35% by weight relative to the total weight of the catalyst and a high dispersion of metallic nickel on the surface of alumina with large open porosity and a high specific surface area. The catalyst is prepared by at least four successive impregnations. The preparation of nickel catalysts with high nickel contents by the impregnation route therefore involves a series of multiple steps, which increase the associated production costs.

[0009] Another preparation route that can also be used to obtain catalysts with high nickel contents is coprecipitation. Coprecipitation generally consists of simultaneously pouring both an aluminum salt (e.g., aluminum nitrate) and a nickel salt (e.g., nickel nitrate) into a batch reactor. The two salts precipitate simultaneously. High-temperature calcination is then required to cause the transformation of the alumina gel (e.g., boehmite) into alumina. Nickel contents of up to 70 wt. % have been achieved by this preparation route. Catalysts prepared by coprecipitation are described, for example, in Patent Documents 2 to 4.

[0010] Finally, a preparation route by co-kneading is also known. Co-kneading generally consists of mixing a nickel salt with an alumina gel such as boehmite, and the resulting mixture is then shaped, generally by extrusion, followed by drying and calcination. Patent document 5 describes a nickel-on-alumina-based catalyst having a nickel content of 10% to 60% by weight and a nickel particle size of 15 to 60 nm, which is prepared by co-kneading a nickel compound with an alumina gel, followed by shaping, drying and reduction.

[0011] Furthermore, it is known in the art to promote the use of additives of organic compound type in the preparation of metal-selective hydrogenation catalysts or metal catalysts for the hydrogenation of aromatic compounds, with the aim of obtaining better catalytic performance qualities, in particular better selectivity and / or activity.

[0012] For example, Patent Document 6 discloses a method for preparing a selective hydrogenation catalyst comprising a support and an active phase containing a metal from Group VIII, and the catalyst is prepared by a method comprising the steps of impregnating the support with a solution containing a precursor of the metal from Group VIII and an organic additive, more specifically an organic compound exhibiting 1 to 3 carboxylic acid functional groups, drying the impregnated support, and calcining the dried support to obtain the catalyst.

[0013] Patent document 7 discloses a method for hydrogenating aromatic compounds of the benzenepolycarboxylic acid type in the presence of a catalyst comprising an active phase containing at least one metal from group VIII, the catalyst being prepared by a process comprising the steps of impregnating the catalyst with a solution containing a precursor of a metal from group VIII and impregnating an organic additive of the amine or amino acid type, the step of impregnating the organic additive being carried out before or after the step of impregnating the active phase, or even simultaneously.

[0014] Furthermore, the use of molten salts as precursors of the active phase of catalysts or traps is also known from the literature.

[0015] For example, Patent Document 8 discloses a method for preparing a cobalt-based supported catalyst by contacting a support in a batch of molten cobalt nitrate salt (on the order of tens of seconds), followed by drying and reduction, without intermediate calcination. This method allows for preferential localization of the cobalt phase around the support. However, this method does not allow for precise control of the amount of active phase (in this example, cobalt) deposited due to the very short contact time. Furthermore, the absence of a calcination step is dangerous because the reaction between the reducing element and the nitrate in the solid is highly exothermic. Finally, this method requires handling large amounts of (toxic) cobalt nitrate in liquid form and at a temperature of approximately 4 grams of active phase precursor per gram of support. Catalysts obtained by this preparation route are used in the Fischer-Tropsch synthesis of hydrocarbons.

[0016] It is known from Non-Patent Document 1 to prepare mixed phosphates via a molten salt-type route. The reaction mixture contains a metal precursor salt (in particular Ni(NO3)2 or Co(NO3)2), a phosphorus source (NH4H2PO4), and an alkali metal (Na or K) nitrate. These preparations are carried out at high temperatures of around 400-450°C. Mixed phosphate-type solids are obtained, such as Na3Ni2(PO7)PO4, K2Ni4(PO4)2P2O7, or Na9CO3(PO4)5. These solids can find applications in ion exchange, high-temperature ionic conduction, or catalysis.

[0017] Patent Document 9 discloses a method for synthesizing bulk catalysts based on nickel or cobalt for the production of hydrogen by steam reforming. These catalysts can be obtained by liquefying metal salts at moderate temperatures and then pouring them into molds before a calcination heat treatment.

[0018] Non-Patent Document 2 proposes the use of CoCl-NaCl mixtures in molten salt form at high temperatures (450-580 °C) for intercalation between graphite sheets. These graphite intercalation compounds find application in catalysis for the reduction of oxygen in polymer electrolyte fuel cells. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] International Publication No. 2011 / 080515 [Patent Document 2] U.S. Patent No. 4,273,680 [Patent Document 3] U.S. Patent No. 8,518,851 [Patent Document 4] US Patent Application Publication No. 2010 / 0116717 [Patent Document 5] U.S. Patent No. 5,478,791 [Patent Document 6] French Patent Application Publication No. 2984761 [Patent Document 7] US Patent Application Publication No. 2006 / 0149097 [Patent Document 8] U.S. Patent No. 5,036,032 [Patent Document 9] British Patent No. 191308864 [Non-patent literature]

[0020] [Non-Patent Document 1] Chem. Mater., 1999, Vol. 11, pp. 1999-2007 [Non-patent document 2] J. -Y. Tilquin, "Intercalation of CoCl2 into Graphite: Mix Method vs Molten Salt Method", published in Carbon, 1997, Vol. 35, No. 2, pp. 299-30 Summary of the Invention [Means for solving the problem]

[0021] (Subject of the Invention) The present invention therefore relates to a new type of catalyst, which, due to its specific preparation method, makes it possible to obtain a catalyst with at least equally good, and in fact even better, performance qualities in terms of activity in the context of reactions for the hydrogenation of aromatic compounds, while using amounts of nickel-based active phase equal to, and in fact lower than, those normally used in the art. In addition, this preparation method results in a catalyst exhibiting nickel particle sizes of less than 18 nm, imparting a high intrinsic activity of the nickel active phase. The preparation method employed here makes it possible to obtain a catalyst with catalytic performance qualities superior to those of conventional catalysts, without the addition of solvents and therefore in a very limited number of steps, particularly fewer than those of conventional (impregnation) preparation methods (in particular, without upstream preparation of solutions containing Ni and / or additives and without intermediate drying).

[0022] The subject of the present invention is a catalyst for the hydrogenation of aromatic or polyaromatic compounds, comprising a nickel-based active phase and an alumina support, said active phase being free of metals from group VIB, said catalyst comprising 20% ​​to 60% by weight of elemental nickel relative to the total weight of said catalyst, the size of the nickel particles in said catalyst being less than 18 nm, measured in oxide form, said catalyst being at least in the following stage: a) contacting the alumina support with at least one organic additive comprising oxygen and / or nitrogen, wherein the molar ratio of the organic additive to the nickel is greater than 0.05 mol / mol; b) contacting an alumina support with at least one nickel metal salt at a temperature below the melting point of the nickel metal salt to form a solid mixture, wherein the weight ratio of the metal salt to the alumina support is 0.1 to 2.3; Steps a) and b) are carried out sequentially in this order or simultaneously; c) heating the solid mixture obtained at the end of steps a) and b) with stirring to a temperature between the melting point of the metal salt and 200°C to obtain a catalyst precursor; d) drying the catalyst precursor obtained at the end of step c) at a temperature below 250°C to obtain a dried catalyst precursor; e) heat treatment of the dried catalyst precursor obtained at the end of step d) at a temperature of 250-1000 ° C. The present invention relates to a catalyst obtainable by a process comprising:

[0023] Preferably, the size of the nickel particles in the catalyst is between 0.5 and 12 nm, more preferentially between 1 and 5 nm, measured in oxide form.

[0024] Another subject of the present invention is a method for preparing a catalyst for the hydrogenation of aromatic or polyaromatic compounds, comprising a nickel-based active phase and an alumina support, said active phase being free of metals from group VIB, said catalyst comprising 20% ​​to 60% by weight of elemental nickel relative to the total weight of said catalyst, the size of the nickel particles in said catalyst being less than 18 nm, measured in oxide form, comprising the following steps: a) contacting an alumina support with at least one organic additive containing oxygen and / or nitrogen, wherein the molar ratio of organic additive to nickel is greater than 0.05 mol / mol; b) contacting an alumina support with at least one nickel metal salt at a temperature below the melting point of the nickel metal salt to form a solid mixture, wherein the weight ratio of the metal salt to the alumina support is 0.1 to 2.3; Steps a) and b) are carried out either sequentially in that order or simultaneously; c) heating the solid mixture obtained at the end of steps a) and b) with stirring to a temperature between the melting point of the metal salt and 200°C to obtain a catalyst precursor; d) drying the catalyst precursor obtained at the end of step c) at a temperature below 250°C to obtain a dried catalyst precursor; e) heat treatment of the dried catalyst precursor obtained at the end of step d) at a temperature of 250-1000 ° C. The present invention relates to a method, comprising:

[0025] Preferably, the melting point of the metal salt is 20°C to 150°C.

[0026] Preferably, step e) of heat treatment of the dried catalyst precursor obtained in step d) is carried out at a temperature between 250°C and 1000°C.

[0027] Preferably, the molar ratio of said organic additive introduced in step a) to elemental nickel introduced in step b) is between 0.1 and 5.0 mol / mol.

[0028] In one embodiment according to the invention, steps a) and b) are carried out simultaneously.

[0029] Preferably, the organic additive is 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, or a combination of the various functional groups mentioned above.

[0030] More preferentially, said organic additive of step a) is chosen from formic acid, formaldehyde, acetic acid, citric acid, oxalic acid, glycolic acid, malonic acid, levulinic acid, ethanol, methanol, ethyl formate, methyl formate, paraldehyde, acetaldehyde, gamma-valerolactone, glucose and sorbitol.

[0031] More preferentially, the organic additive is chosen from citric acid, formic acid, glycolic acid, levulinic acid and oxalic acid.

[0032] Preferably, step c) is carried out by means of a pan operating at a speed of between 4 and 70 revolutions per minute.

[0033] Preferably, in step b), the weight ratio of said metal salt to alumina support is between 0.2 and 2.

[0034] Another subject of the present invention is a process for the hydrogenation of at least one aromatic or polyaromatic compound present in a hydrocarbon feedstock having a final boiling point of less than or equal to 650 ° C, in the gas or liquid phase, at a temperature of 30 to 350 ° C, a pressure of 0.1 to 20 MPa, a hydrogen / (aromatic compound to be hydrogenated) molar ratio of 0.1 to 10 and an hourly space velocity HSV of 0.05 to 50 h -1 in the presence of a catalyst according to the invention or a catalyst prepared according to the preparation process according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] (Detailed Description of the Invention) (definition) The groups of chemical elements are then given according to the CAS classification (CRC Handbook of Chemistry and Physics, published by CRC Press, editor in chief DRLide, 81st edition, 2000-2001). For example, group VIII according to the CAS classification corresponds to metals in groups 8, 9 and 10 according to the new IUPAC classification.

[0036] The specific surface area of ​​the catalyst or of the support used for the preparation of the catalyst according to the invention is understood to mean the BET specific surface area determined by nitrogen adsorption according to standard ASTM D 3663-78, which is derived from the Brunauer-Emmett-Teller method described in the journal "The Journal of the American Chemical Society", 60, 309 (1938).

[0037] In this patent application, the term "to comprise" is synonymous with (meaning the same as) "to include" and "to contain" and is inclusive or open and does not exclude other elements not stated. The term "to comprise" is understood to include the exclusive and closed term "to consist."

[0038] The term "macropores" is understood to mean pores with openings greater than 50 nm.

[0039] The term "mesopores" is understood to mean pores with an opening between 2 nm and 50 nm, both limits included.

[0040] The term "micropore" is understood to mean a pore with an opening of less than 2 nm.

[0041] The total pore volume of the catalyst or of the support used to prepare the catalyst according to the invention is understood to mean the volume measured by mercury intrusion porosimetry according to standard ASTM D4284-83 at a maximum pressure of 4000 bar (400 MPa), using a surface tension of 484 dynes / cm and a contact angle of 140°. The wetting angle was taken to be equal to 140° according to the recommendation of the publication "Techniques de l'ingenieur, traite analyze et caracterisation" [Techniques of the Engineer, Analysis and Characterisation Treatise] written by Jean Charpin and Bernard Rasneur, pages 1050-1055.

[0042] For better accuracy, the value of the total pore volume corresponds to the value of the total pore volume measured by mercury intrusion porosimetry on a sample minus the value of the total pore volume measured by mercury intrusion porosimetry on the same sample for a pressure equivalent to 30 psi (about 0.2 MPa).

[0043] The macropore and mesopore volumes are measured by mercury intrusion porosimetry according to standard ASTM D4284-83, using a maximum pressure of 4000 bar (400 MPa), a surface tension of 484 dynes / cm, and a contact angle of 140°. The value at which mercury fills all intergranular voids is set at 0.2 MPa, above which mercury is considered to penetrate into the pores of the sample.

[0044] The macropore volume of the catalyst or of the support used to prepare the catalyst according to the invention is defined as the cumulative volume of mercury introduced at a pressure between 0.2 MPa and 30 MPa, which corresponds to the volume present in pores with an apparent diameter of more than 50 nm.

[0045] The mesopore volume of the catalyst or of the support used for preparing the catalyst according to the invention is defined as the cumulative volume of mercury introduced at a pressure of 30 MPa to 400 MPa, and corresponds to the volume present in pores with an apparent diameter of 2 to 50 nm.

[0046] The micropore volume is measured by nitrogen porosimetry. The quantitative analysis of the microporosity is carried out starting from the "t" method (method of Lippens-De Boer, 1965), which corresponds to the transformation of the starting adsorption isotherm as described in the study "Adsorption by Powders and Porous Solids. Principles, Methodology and Applications" by F. Rouquerol, J. Rouquerol and K. Sing, Academic Press, 1999.

[0047] The median mesopore diameter is also defined as the diameter such that all pores with a size less than this diameter, of the combined pores that make up the mesopore volume, make up 50% of the total mesopore volume as determined by mercury intrusion porosimetry.

[0048] The median macropore diameter is also defined as the diameter such that all pores having a size less than this diameter, of the combined pores that make up the macropore volume, make up 50% of the total macropore volume as determined by mercury intrusion porosimetry.

[0049] The term "nickel particle size" is understood to mean the diameter of nickel crystallites in the oxide form. The diameter of nickel crystallites in the oxide form is determined by X-ray diffraction from the width of the diffraction line located at an angle 2θ=43° (i.e., along the crystallographic direction 0200) using the Scherrer relationship. This method, used in the X-ray diffraction of polycrystalline samples or powders, relates the full width at half maximum of the diffraction peak to the size of the particle and is described in detail in the 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.

[0050] The nickel content is measured by X-ray fluorescence.

[0051] (catalyst) The nickel content in said catalyst according to the invention is advantageously between 20% and 60% by weight, more preferentially between 20% and 50% by weight, and even more preferentially between 20% and 45% by weight of elemental nickel relative to the total weight of the catalyst.

[0052] The active phase of the catalyst does not contain any metal from group VIB. In particular, it does not contain molybdenum or tungsten. Preferably, the catalyst consists of an active phase consisting solely of nickel and an alumina support.

[0053] The size of the nickel particles in the catalyst, measured in oxide form, is less than 18 nm, preferably less than 15 nm, more preferentially between 0.5 and 12 nm, suitably between 1 and 8 nm, even more preferably between 1 and 6 nm, and even more preferentially between 1 and 5 nm.

[0054] The catalyst is generally provided in any form known to those skilled in the art, such as beads (generally having a diameter of 1 to 8 mm), extrudates, blocks, or hollow cylinders. Preferably, it consists of extrudates, which generally have a diameter of 0.5 to 10 mm, preferably 0.8 to 3.2 mm, and highly preferably 1.0 to 2.5 mm, and an average length of 0.5 to 20 mm. The term "average diameter" of the extrudates is understood to mean the average diameter of the circle circumscribing the cross section of these extrudates. The catalyst can advantageously be presented in the form of cylindrical, multilobed, trilobed, or tetralobed extrudates. Preferably, the form will be trilobed or tetralobed. The shape of the lobes can be adjusted according to any known method in the prior art.

[0055] The specific surface area of ​​the catalyst is generally 30m 2 / g or more, preferably 50m 2 / g or more, more preferentially 60m 2 / g~500m 2 / g, and even more preferentially 70m 2 / g~400m 2 / g.

[0056] The total pore volume of the catalyst is generally 0.1 to 1.5 cm 3 / g, preferably 0.35 to 1.2 cm 3 / g, more preferentially 0.4-1.0 cm 3 / g, more preferentially 0.45-0.9 cm 3 / g.

[0057] The catalyst advantageously has a macropore volume of less than or equal to 0.6 mL / g, preferably less than or equal to 0.5 mL / g, more preferentially less than or equal to 0.4 mL / g and even more preferentially less than or equal to 0.3 mL / g.

[0058] The mesopore volume of the catalyst is generally at least 0.10 mL / g, preferably at least 0.20 mL / g, suitably 0.25 mL / g to 0.80 mL / g, more suitably 0.30 to 0.65 mL / g.

[0059] The median mesopore diameter of the catalyst is advantageously between 3 and 25 nm, preferably between 6 and 20 nm, particularly preferably between 8 and 18 nm.

[0060] The catalyst has a median macropore diameter advantageously between 50 and 1500 nm, preferably between 80 and 1000 nm, and even more preferably between 250 and 800 nm.

[0061] Preferably, the catalyst exhibits low microporosity; highly preferably, it does not exhibit any microporosity.

[0062] (Carrier) 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 alumina generally exhibits a crystallographic structure of the δ-, γ- or θ-alumina type, alone or as a mixture.

[0063] According to the invention, the alumina support may contain impurities, such as oxides of metals from groups IIA, IIIB, IVB, IIB, IIIA and IVA according to the CAS classification, preferably silica, titanium dioxide, zirconium dioxide, zinc oxide, magnesium oxide and calcium oxide, or else alkali metals, preferably lithium, sodium or potassium, and / or alkaline earth metals, preferably magnesium, calcium, strontium or barium, or also sulfur.

[0064] The specific surface area of ​​the carrier is generally 30m 2 / g or more, preferably 50m 2 / g or more, more preferentially 60m 2 / g~500m 2 / g, and even more preferentially 70m2 / g~400m 2 / g.

[0065] The total pore volume of the support is generally 0.1 to 1.5 cm 3 / g, preferably 0.35 to 1.2 cm 3 / g, more preferentially 0.4-1.0 cm 3 / g, more preferentially 0.45-0.9 cm 3 / g.

[0066] The support advantageously has a macropore volume of less than or equal to 0.6 mL / g, preferably less than or equal to 0.5 mL / g, more preferentially less than or equal to 0.4 mL / g and even more preferentially less than or equal to 0.3 mL / g.

[0067] The mesopore volume of the support is generally at least 0.10 mL / g, preferably at least 0.20 mL / g, suitably 0.25 mL / g to 0.80 mL / g, more suitably 0.30 to 0.65 mL / g.

[0068] The median mesopore diameter of the support is advantageously 3 to 25 nm, preferably 6 to 20 nm, particularly preferably 8 to 18 nm.

[0069] The support has a median macropore diameter of advantageously between 50 and 1500 nm, preferably between 80 and 1000 nm, and even more preferably between 250 and 800 nm.

[0070] Preferably, the support exhibits low microporosity; highly preferably, it does not exhibit any microporosity.

[0071] (Preparation method) The steps of the catalyst preparation process are described in detail below.

[0072] (Step a) According to step a) of the catalyst preparation process, the support is contacted with at least one organic additive containing oxygen and / or nitrogen, preferably 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 (preferably 1 to 12) carbon atoms per molecule. The organic additive may consist of a combination of the various functional groups mentioned above.

[0073] Preferably, the organic additive is selected from formic acid (HCOOH), formaldehyde (CHO), acetic acid (CHCOOH), citric acid, oxalic acid, glycolic acid (HOOC-CH-OH), malonic acid (HOOC-CH-COOH), levulinic acid (CHCCHCHCOH), ethanol, methanol, ethyl formate (HCOOCH), methyl formate (HCOOCH), paraldehyde (CH-CHO), acetaldehyde (CHO), γ-valerolactone (CHO), glucose, and sorbitol.

[0074] Particularly preferably, the organic additive is selected from citric acid, formic acid, glycolic acid, levulinic acid and oxalic acid.

[0075] In one embodiment according to the invention, said step a) is carried out by contacting the support with at least one organic additive in the form of a powder.

[0076] In another embodiment according to the invention, step a) is carried out by contacting the support with at least one organic additive in the form of a powder dissolved in a minimum amount of water. A minimum amount of water is understood to mean an amount of water that allows at least partial dissolution of the organic additive in water. This minimum amount of water may not be compatible with the solvent. In this case, if the step of introducing the additive is carried out separately from the introduction of the precursor of the active phase of the catalyst (i.e., steps a) and b) are carried out separately), the support is advantageously dried after each step of contacting with the organic additive at a temperature below 250°C, preferably between 15 and 240°C, more preferentially between 30 and 220°C.

[0077] The contacting operation is generally carried out at a temperature of 0 to 70°C, preferably 10 to 60°C, particularly preferably at ambient temperature.

[0078] According to step a), the contacting of the porous carrier with the organic additive can be carried out by any method known to those skilled in the art. Preferably, a convection mixer, a drum mixer or a static mixer can be used. Step a) is advantageously carried out for a period of 5 minutes to 5 hours, preferably 10 minutes to 4 hours, depending on the type of mixer used.

[0079] According to the invention, the molar ratio of organic additive to nickel is greater than 0.05 mol / mol, preferably between 0.1 and 5 mol / mol, more preferentially between 0.12 and 3 mol / mol, even more preferably between 0.15 and 2.5 mol / mol.

[0080] (Step b) According to step b), the alumina support is contacted with at least one nickel metal salt, advantageously for a period of 5 minutes to 5 hours, to form a solid mixture, said metal salt having a melting point between 20°C and 150°C, and said metal salt to alumina support weight ratio being between 0.1 and 2.3, preferably between 0.2 and 2.

[0081] Preferably, the metal salt is hydrated. Preferably, the metal salt is nickel nitrate hexahydrate (Ni(NO3)2·6H2O, Tmelting =56.7℃).

[0082] According to step b), the contacting of the porous oxide support with the nickel metal salt can be carried out by any method known to those skilled in the art. Preferably, a convection mixer, a drum mixer or a static mixer can be used. Step b) is advantageously carried out for a period of 5 minutes to 5 hours, preferably 10 minutes to 4 hours, depending on the type of mixer used.

[0083] Compared to the prior art, described in document US 5 036 032 and based on contacting the support in a batch of molten salt, step b) of the process according to the invention makes it possible to: - Optimized control of the amount of metal deposited on the catalyst; and - Controlled risk and controlled cost of the preparation process by minimizing the amount of metal precursor employed, so as not to exceed 1 gram of metal precursor per gram of support.

[0084] (Implementation of steps a) and b) According to the present invention: - steps a) and b) are carried out consecutively in this order, or - Steps a) and b) are carried out simultaneously.

[0085] In a preferred embodiment, step a) is performed before step b) is performed.

[0086] (Step c) According to step c), the mixture obtained at the end of steps a) and b) is heated, with stirring, to a temperature between the melting point of the metal salt and 200° C., advantageously at atmospheric pressure. Preferably, the temperature is between 50 and 180° C., more preferentially between 60 and 160° C.

[0087] Advantageously, step c) is carried out over a period of between 5 minutes and 12 hours, preferably between 5 minutes and 4 hours.

[0088] According to step c), the mechanical homogenization of the mixture can be carried out by any method known to those skilled in the art. Preferably, a convection mixer, a drum mixer or a static mixer can be used. Even more preferentially, step c) is carried out by a drum mixer, the rotation speed of which is between 4 and 70 rpm, preferably between 10 and 60 rpm. This is because if the rotation speed of the drum is too high, the active phase of the catalyst will not be distributed as a crust around the support, but will be distributed homogeneously throughout the support, which is undesirable.

[0089] (Step d): Drying of the catalyst precursor) Step d) of drying the catalyst precursor obtained at the end of step c) is carried out at a temperature below 250°C, preferably between 15 and 180°C, more preferentially between 30 and 160°C, even more preferentially between 50 and 150°C, and even more preferentially between 70 and 140°C, typically for a period of between 10 minutes and 24 hours. Longer periods are not excluded, but do not necessarily contribute to improvements. The drying temperature in step d) is generally higher than the heating temperature in step c). Preferably, the drying temperature in step d) is at least 10°C higher than the heating temperature in step c).

[0090] The drying step can be carried out by any technique known to those skilled in the art. It is advantageously carried out under an inert atmosphere or an oxygen-containing atmosphere or a mixture of an inert gas and oxygen. It is advantageously carried out at atmospheric pressure or under reduced pressure. Preferably, this step is carried out at atmospheric pressure in the presence of air or nitrogen.

[0091] (Step e): Heat treatment of the dried catalyst) The dried catalyst precursor undergoes, before the optional reduction step f), an additional heat treatment step at a temperature of 250 to 1000° C., preferably 250 to 750° C., for a period typically of 15 minutes to 10 hours, in an inert or oxygen-containing atmosphere, in the presence or absence of water. Longer treatment times are not excluded, but do not necessarily contribute to improvements.

[0092] The term "thermal treatment" is understood to mean a temperature treatment in the absence or presence of water, respectively. In the latter case, contact with water vapor can be carried out at atmospheric pressure or under autogenous pressure. Several combined cycles in the absence or presence of water can be carried out. After this or these treatments, the catalyst precursor contains nickel in the form of an oxide, i.e., NiO.

[0093] If water is present, the water content is preferably between 150 and 900 grams per kilogram of dry air, more preferably between 250 and 650 grams per kilogram of dry air.

[0094] (Step f): Reduction with reducing gas (optional step) Prior to use of the catalyst in the catalytic reactor and implementation of the hydrogenation process, at least one reduction treatment step f) is advantageously carried out after step e) in the presence of a reducing gas to obtain a catalyst comprising nickel at least partly in metallic form.

[0095] This treatment makes it possible to activate the catalyst and form metal particles, in particular nickel metal particles, in the zero valent state. The reduction treatment can be carried out in situ or ex situ, i.e., after or before the catalyst is loaded into the hydrogenation reactor.

[0096] 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 possible.

[0097] The reduction treatment is carried out at a temperature of 120 to 500° C., preferably 150 to 450° C. If the catalyst is not passivated or is subjected to a reduction treatment before passivation, the reduction treatment is carried out at a temperature of 180 to 500° C., preferably 200 to 450° C., more preferentially 350 to 450° C. If the catalyst has been passivated beforehand, the reduction treatment is generally carried out at a temperature of 120 to 350° C., preferably 150 to 350° C.

[0098] The duration of the reduction treatment is generally 2 to 40 hours, preferably 3 to 30 hours. The temperature is generally raised to the desired reduction temperature slowly, for example, at 0.1 to 10°C / min, preferably 0.3 to 7°C / min.

[0099] The hydrogen flow rate is expressed in L / hour / g catalyst and is 0.01 to 100 L / hour / g catalyst, preferably 0.05 to 10 L / hour / g catalyst, and more preferably 0.1 to 5 L / hour / g catalyst.

[0100] (Step g): Passivation (optional) The catalyst prepared according to the method of the invention can advantageously undergo a passivation step with sulfur-containing compounds, which makes it possible to improve the selectivity of the catalyst and prevent thermal runaway during the start-up of the fresh catalyst. Passivation generally consists in irreversibly poisoning the most toxic active sites of nickel present on the fresh catalyst with sulfur-containing compounds, thus weakening the activity of the catalyst and favoring its selectivity. The passivation step can be carried out by using methods known to those skilled in the art.

[0101] The passivation step with sulfur-containing compounds is generally carried out at temperatures between 20 and 350°C, preferably between 40 and 200°C, for 10 to 240 minutes. 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 propylmethyl sulfide, or also organic disulfides of the formula HO-R1-SS-R2-OH, such as dithiodiethanol of the formula HO-C2H4-SS-C2H4-OH (often called DEODS). The sulfur content is generally between 0.1% and 2% by weight of said element relative to the total weight of the catalyst.

[0102] (Method for hydrogenating aromatic compounds) Another subject of the present 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 and 650° C., preferably between 20 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, cracked distillates such as fluid catalytic cracking (FCC) cycle oils, gas oils from coking units or hydrocracking distillates.

[0103] The content of aromatic or polyaromatic compounds contained in the hydrocarbon feedstock to be treated in the hydrogenation process according to the invention is generally 0.1% to 80% by weight, preferably 1% to 50% by weight, particularly preferably 2% to 35% by weight, the percentages being based on the total weight of the hydrocarbon feedstock. Aromatic compounds present in the hydrocarbon feedstock are, for example, benzene alkyl aromatic compounds such as toluene, ethylbenzene, o-xylene, m-xylene or p-xylene, or also aromatic compounds with several aromatic rings (polyaromatic compounds), such as naphthalene.

[0104] 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, and particularly preferably less than 10 ppm by weight.

[0105] The technical implementation of the process for the hydrogenation of aromatic or polyaromatic compounds is carried out, for example, by injecting the hydrocarbon feedstock and hydrogen into at least one fixed-bed reactor as an upflow or downflow. The reactor can be isothermal or adiabatic. Adiabatic reactors are preferred. The hydrocarbon feedstock can be advantageously diluted by reinjecting the effluent from the reactor in which the reaction of aromatic compound hydrogenation is carried out one or more times into various points of the reactor located between the inlet and outlet of the reactor, thereby limiting the temperature gradient within the reactor. The technical implementation of the process for the hydrogenation of aromatic compounds according to the invention can also be advantageously carried out by embedding at least the supported catalyst in a reactive distillation column, a reactor-exchanger, or a reactor in which the catalyst is in suspension (slurry). The hydrogen flow can be introduced simultaneously with the feedstock to be hydrogenated and / or at one or more different points of the reactor.

[0106] The hydrogenation of aromatic or polyaromatic compounds can be carried out in the gas phase or in the liquid phase, preferably in the liquid phase. Generally, the temperature during the hydrogenation of aromatic or polyaromatic compounds is 30 to 350°C, preferably 50 to 325°C, the pressure is 0.1 to 20 MPa, preferably 0.5 to 10 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 , preferably 0.1 to 10 hours -1 and the hydrocarbon feedstock contains aromatic or polyaromatic compounds and has a final boiling point of up to 650°C, generally between 20 and 650°C, and preferably between 20 and 450°C.

[0107] The hydrogen flow rate is adjusted to make available enough hydrogen to theoretically hydrogenate all of the aromatics and to maintain an excess of hydrogen at the reactor outlet.

[0108] The conversion of aromatic or polyaromatic compounds is generally greater than 20 mol%, preferably greater than 40 mol%, more preferably greater than 80 mol%, and 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 number of moles of aromatic or polyaromatic compounds in the hydrocarbon feedstock and the total number of moles of aromatic or polyaromatic compounds in the product by the total number of moles of aromatic or polyaromatic compounds in the hydrocarbon feedstock.

[0109] According to a specific alternative embodiment of the process according to the invention, a process for hydrogenating benzene from a hydrocarbon feedstock, for example a reformate derived from a catalytic reforming unit, is carried out, wherein the benzene content in the hydrocarbon feedstock is generally between 0.1% and 40% by weight, preferably between 0.5% and 35% by weight, particularly preferably between 2% and 30% by weight, the percentages by weight being based on the total weight of the hydrocarbon feedstock.

[0110] The sulfur or chlorine content of the feedstock is generally less than 10 ppm by weight, and preferably less than 2 ppm by weight of sulfur or chlorine, respectively.

[0111] The hydrogenation of benzene contained in the hydrocarbon feedstock can be carried out in the gas phase or the liquid phase, preferably in the liquid phase. When carried out in the liquid phase, a solvent such as cyclohexane, heptane, or octane may be present. Generally, the temperature during the hydrogenation of benzene is 30 to 250°C, preferably 50 to 200°C, more preferably 80 to 180°C, the pressure during the hydrogenation is 0.1 to 10 MPa, preferably 0.5 to 4 MPa, the hydrogen / (benzene) molar ratio during the hydrogenation is 0.1 to 10, and the hourly space velocity (HSV) during the hydrogenation is 0.05 to 50 h -1 , preferably 0.5 to 10 hours -1 is.

[0112] 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 %.

[0113] The present invention will now be illustrated by way of the following examples, which are not intended to be limiting in any way.

[0114] (Example) For all catalysts mentioned in the examples below, the support is alumina AL-1, with a specific surface area of ​​80 m 2 / g, pore volume 0.7 mL / g and mesopore median diameter 12 nm.

[0115] Example 1: Matching 10 g of alumina AL-1 support is contacted with 1.96 g of citric acid dissolved in 5.4 g of water, and the solid thus obtained is subsequently dried in an oven at 60° C. for 2 hours and then at 120° C. for 12 hours.

[0116] The support is then contacted with 9.47 g of nickel nitrate hexahydrate in a pan at 25°C rotating at 40-50 rpm. The pan is then heated to 62°C and rotated at 40-50 rpm for 15 minutes. The molar ratio of citric acid to nickel is 0.2.

[0117] The targeted nickel content for this stage is 25 wt.% Ni based on the weight of the final catalyst. The solid thus obtained is subsequently dried in an oven at 120°C overnight and then calcined at 450°C for 2 hours under a flow of air at 1 L / h / g catalyst.

[0118] Catalyst A is obtained containing 28% by weight of elemental nickel relative to the total weight of the catalyst. The characteristics of catalyst A thus obtained are shown in Table 1 below.

[0119] Example 2: Matching 10 g of alumina AL-1 support is contacted with 3.96 g of citric acid dissolved in 10 g of water. The solid thus obtained is then dried in an oven at 60°C for 2 hours and then at 120°C for 12 hours. The support is then contacted with 9.47 g of nickel nitrate hexahydrate in a pan at 25°C rotating at a speed of 40-50 rpm. The pan is then heated to 62°C and rotated at a speed of 40-50 rpm for 15 minutes. The molar ratio of citric acid to Ni is 0.4.

[0120] The targeted nickel content for this stage is 25 wt.% Ni based on the weight of the final catalyst. The solid thus obtained is subsequently dried in an oven at 120°C overnight and then calcined at 450°C for 2 hours under a flow of air at 1 L / h / g catalyst.

[0121] Catalyst B is obtained containing 25% by weight of elemental nickel relative to the total weight of the catalyst. The characteristics of catalyst B thus obtained are given in Table 1 below.

[0122] Example 3: Matching 10 g of alumina AL-1 support is contacted with 0.77 g of glycolic acid dissolved in 5.4 g of water, and the solid thus obtained is subsequently dried in an oven at 60° C. for 2 hours and then at 120° C. for 12 hours.

[0123] The support is then contacted with 9.47 g of nickel nitrate hexahydrate in a pan at 25°C rotating at 40-50 rpm. The pan is then heated to 62°C and rotated at 40-50 rpm for 15 minutes. The mole ratio of glycolic acid to Ni is 0.2.

[0124] The targeted Ni content for this stage is 25 wt.% Ni based on the weight of the final catalyst. The solid thus obtained is subsequently dried in an oven at 120°C overnight and then calcined at 450°C for 2 hours under a flow of air at 1 L / h / g catalyst.

[0125] Catalyst C is obtained, containing 25% by weight of elemental nickel relative to the total weight of the catalyst. The characteristics of catalyst C thus obtained are given in Table 1 below.

[0126] Example 4: Non-match 10 g of alumina AL-1 support is dry-impregnated with 15.78 g of nickel nitrate hexahydrate in a pan rotating at 40-50 rpm at 25°C. The pan is then heated to 62°C and rotated at 40-50 rpm for 15 min.

[0127] The targeted Ni content for this stage is 25 wt.% Ni based on the weight of the final catalyst. The solid thus obtained is subsequently dried in an oven at 120°C overnight and then calcined at 450°C for 2 hours under a flow of air at 1 L / h / g catalyst.

[0128] Catalyst D is obtained containing 25% by weight of elemental nickel relative to the total weight of the catalyst. The characteristics of catalyst D thus obtained are given in Table 1 below.

[0129] Example 5: Characterization All catalysts contained the NiO content targeted during impregnation, i.e., 25% (characterized by X-ray fluorescence) relative to the total weight of the catalyst. The size of the NiO particles obtained after the calcination step was determined by X-ray diffraction (XRD) analysis on samples of the catalysts in powder form. The characteristics of catalysts A to D are listed in Table 1 below.

[0130] [Table 1]

[0131] Example 6: Catalysts A to D described in the above examples are tested in the reaction for the hydrogenation of toluene. The toluene hydrogenation reaction was carried out in a 500 mL stainless steel autoclave equipped with a magnetically driven mechanical stirrer and capable of operating at pressures up to 100 bar (10 MPa) and temperatures between 5°C and 200°C.

[0132] Before being introduced into the autoclave, a quantity of 2 mL of catalyst is reduced ex situ at 400 °C for 16 hours (temperature ramp rate 1 °C / min) under a hydrogen flow of 1 L / h / g catalyst, then transferred to the autoclave and air-purged. 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 to a test temperature equal to 80 °C. At time t = 0, approximately 26 g of toluene (supplier SDS®, purity >99.8%) is introduced into the autoclave (initial composition of the reaction mixture is 6% by weight toluene / 94% by weight n-heptane), and stirring is initiated at 1600 rpm. The pressure in the autoclave is kept constant at 35 bar (3.5 MPa) using a storage cylinder located upstream of the reactor.

[0133] 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 decrease in pressure in a storage cylinder located upstream of the reactor. The catalytic activity is expressed in moles of H2 consumed per minute and per gram of Ni weight.

[0134] The catalytic activities measured for catalysts A to D are shown in Table 2 below. HYD ) is the standard.

[0135] [Table 2]

[0136] Catalysts A, B and C in accordance with the present invention provide very high selective hydrogenation activity. In Example 4, no additive was added, which results in catalyst D having significantly reduced activity due to the nickel particle size of 20 nm, i.e., 10 times larger than the catalyst in accordance with the present invention.

Claims

1. 1. A process for the preparation of a catalyst for the hydrogenation of aromatic or polyaromatic compounds, comprising a nickel-based active phase and an alumina support, said active phase being free of metals from group VIB, said catalyst comprising 20% ​​to 60% by weight of elemental nickel relative to the total weight of said catalyst, the size of the nickel particles in the catalyst being less than 18 nm, measured in the form of the oxide, comprising the following steps: a) contacting an alumina support with at least one organic additive containing oxygen and / or nitrogen, wherein the molar ratio of organic additive to nickel is greater than 0.05 mol / mol; The organic additives are 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, or combinations of the various functional groups mentioned above; b) contacting an alumina support with at least one nickel metal salt at a temperature below the melting point of said nickel metal salt to form a solid mixture, wherein said metal salt has a melting point of 20°C to 150°C and the weight ratio of said metal salt to said alumina support is 0.1 to 2.3; Steps a) and b) are carried out either sequentially in that order or simultaneously; c) heating the solid mixture obtained at the end of steps a) and b) to a temperature between the melting point of the metal salt and 200°C with stirring to obtain a catalyst precursor; d) drying the catalyst precursor obtained at the end of step c) at a temperature below 250°C to obtain a dried catalyst precursor; e) heat treatment of the dried catalyst precursor obtained at the end of step d) at a temperature between 250 and 1000° C. A method comprising:

2. 2. The method of claim 1, wherein the molar ratio of the organic additive introduced in step a) to elemental nickel introduced in step b) is 0.1 to 5.0 mol / mol.

3. 3. The method of claim 1 or 2, wherein steps a) and b) are carried out simultaneously.

4. 4. The method according to any one of claims 1 to 3, wherein the organic additive in step a) is selected from formic acid, formaldehyde, acetic acid, citric acid, oxalic acid, glycolic acid, malonic acid, levulinic acid, ethanol, methanol, ethyl formate, methyl formate, paraldehyde, acetaldehyde, gamma-valerolactone, glucose and sorbitol.

5. 5. The method of claim 4, wherein the organic additive is selected from citric acid, formic acid, glycolic acid, levulinic acid and oxalic acid.

6. 6. The method according to any one of claims 1 to 5, wherein step c) is carried out by means of a pan operating at a speed of between 4 and 70 revolutions per minute.

7. 7. The method according to claim 1, wherein in step b) the weight ratio of the metal salt to the alumina support is between 0.2 and 2.

8. A process for the hydrogenation of at least one aromatic or polyaromatic compound present in a hydrocarbon feedstock having a final boiling point of not more than 650°C, which is carried out in the gas or liquid phase in the presence of a catalyst prepared by the process according to any one of claims 1 to 7, wherein the temperature is from 30 to 350°C, the pressure is from 0.1 to 20 MPa, the hydrogen / aromatic compound to be hydrogenated molar ratio is from 0.1 to 10, and the hourly space velocity HSV is from 0.05 to 50 h －１ That's the method.

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