Process for the preparation of catalysts by organic methods in the presence of additives

Abstract

The present invention relates to a process for the preparation of a catalyst, said process comprising: a) a step of preparing an organic solution comprising: a metal precursor of a metal element selected from the elements of groups 3, 4 and 5 of the periodic table, such as tantalum and zirconium, and an additive, wherein said metal precursor and said additive are present in the organic solution in such amounts that the additive / metal molar ratio is greater than 2; b) a step of depositing said metal precursor onto an oxide substrate by contacting said organic solution with said oxide substrate; followed by c) a heat treatment step. The present invention also relates to the catalyst obtained and its use for the conversion of a feedstock comprising ethanol into butadiene.

Description

Technical Field

[0001] This invention relates to a method for manufacturing supported metal oxide catalysts of Group 3, 4, and / or 5 elements with improved properties. More particularly, this invention relates to a method for preparing a heterogeneous catalyst comprising at least one metal element selected from Group 3, 4, and 5 elements of the periodic table deposited on an oxide matrix by contacting the oxide matrix with an organic solution containing at least one precursor of the metal element, wherein the organic solution further contains additives. This invention also relates to the catalyst obtained by the preparation method and the use of the catalyst for converting a feedstock containing at least ethanol into butadiene. This invention further relates to a method for converting a feedstock containing at least ethanol into butadiene, which particularly includes steps corresponding to the method for preparing a heterogeneous catalyst according to the invention. Existing technology

[0002] Supported metal oxides are a class of heterogeneous catalysts comprising one or more types of charged metal oxides deposited on the surface of a support material, such as silica (SiO2), alumina (Al2O3), titanium dioxide (TiO2), zirconium oxide (ZrO2), magnesium oxide (MgO), and mixtures thereof. Examples of commonly used metal oxides include those from groups 3 to 10, as they are capable of forming numerous catalysts for the synthesis of a wide variety of chemicals. For example, supported tantalum oxide catalysts possess diverse active sites (acid-base and redox), and are therefore capable of catalyzing many industrially relevant chemical reactions, including the production of 1,3-butadiene (also referred to as butadiene in this specification) from ethanol, the decomposition of methyl tert-butyl ether into isobutene and methanol, the Beckmann rearrangement, and olefin epoxidation. Similarly, they can be used for photocatalysis and electrocatalysis.

[0003] For example, US Patent 2,421,361 describes the use of niobium-based or tantalum-based catalysts in a method for converting a mixture of ethanol and acetaldehyde into butadiene, the catalysts being prepared, in particular, by contacting silica with an aqueous solution of citric acid containing niobium or tantalum precursors.

[0004] For any catalyst composed of metal elements deposited on a support, a specific dispersion and distribution of the metal element, such as tantalum, can be pursued as a characteristic of the catalyst. The atomic-level dispersion of metal elements is known to influence the selectivity and activity of the catalyst by modulating the properties of the active sites. Completely independently, controlling the distribution of metal elements within the support particles is another parameter explored to manage intraparticle diffusion limitations in the presence of such limitations. In the absence of interparticle diffusion limitations, it is generally known to utilize the entire available surface area and volume, especially for catalytic performance considerations.

[0005] There is still a need to improve the catalytic performance, such as selectivity, of heterogeneous catalysts, especially those containing metals selected from Groups 3, 4 and / or 5.

[0006] In the preparation of catalysts containing elemental tantalum, the use of commercial tantalum precursors soluble in organic media, such as tantalum alkoxides or tantalum halides, is widely described, for example in patent application WO 2017 / 009107 or in Corson's 1950 article (BB Corson et al., Butadiene from Ethyl Alcohol. Catalysis in the One- and Two-Step Processes). Industrial and Engineering Chemistry. In 1950, 42 (2), 359-373. However, tantalum alkoxide or halide precursors may have the disadvantage of being extremely sensitive to hydrolysis. The formation of tantalum hydroxide functionality leads to the formation of tantalum clusters, and may therefore lead to alterations or even limitations in catalytic performance (see Ambreen, S. et al., Characterization and photocatalytic study of tantalum oxide nanoparticles prepared by the hydrolysis of tantalum oxo-ethoxide Ta8(μ3-O)2(μ-O)8(μ-OEt)6(OEt)). 14 . Beilstein J. Nanotechnol. 2014, 5, 1082–1090).

[0007] To limit hydrolysis, it appears necessary to limit the amount of water present in the support, for example, by rigorous drying of the support, especially at temperatures above 100°C, preferably at 150°C for several hours. To further limit the hydrolysis of the tantalum or niobium precursor (which is a Group 5 element), the precursor can be modified by adding additives.

[0008] The literature contains a wide range of complexing agents, with varying degrees of success. For example, studies have been conducted on the reactions of Group 5 elements, particularly tantalum and niobium, with the following compounds: - Diketones, such as acetylacetone (see Kapoor PN, Mehrotra RC, Organic Compounds of Niobium and Tantalum. IV. Reactions of niobium and tantalum pentaethoxides with β-diketones). J. Less-Common Metals , 8 (1965) 339-346). - Keto ester (see Mehrotra RC, Kapoor PN, Organic Compounds of Tantalum. Reactions of tantalum pentaethoxide with β-ketoesters. J. Less-Common Metals , 7 (1964) 453-457). - Hydroxy esters (see Narula AK et al., Some Aliphatic and Aromatic Hydroxy Ester Derivatives of Niobium and Tantalum). Transition Met. Chem. 7 (1982) 325-330). - Glycols (see Mehrotra RC, Kapoor PN, Organic Compounds of Tantalum.I. Reactions of tantalum pentaethoxide with glycols. J. Less-Common Metals , 10(1965) 237-245). - Acyl halides (see R Mehrotra RC, Kapoor PN, Organic Compounds of Niobium. I. Reactions of niobium penta-alkoxides with acyl halides). J. Less- Common Metals , 10 (1966) 348-353).

[0009] While these documents detail the reactions and properties of the formed complexes, they do not specify the effects and uses of such Ta or Nb complexes in the preparation of heterogeneous catalysts. Patent application WO 2022 / 165190 describes the use of acetylacetone in the preparation of tantalum-based catalysts deposited on silica. Patent application CN115364844 describes the preparation of tantalum-silica catalysts by contacting silica with an organic solution containing a tantalum precursor and anhydrous citric acid.

[0010] The object of the present invention is to prepare heterogeneous catalysts containing at least one metal element, particularly metal elements selected from Groups 3, 4 and 5, which exhibit good catalytic performance, or even performance gains compared with prior art catalysts, particularly in terms of selectivity and productivity, and especially in the conversion of ethanol-containing feedstocks into butadiene. Invention Overview This invention therefore relates to a method for preparing a catalyst, comprising: a) The step of preparing at least one organic solution, said organic solution comprising: At least one metallic precursor selected from at least one metallic element in Groups 3, 4, and 5 of the periodic table. At least one additive, wherein the at least one additive is a polyfunctional ketone compound, a polyfunctional organic acid compound, a β-polyfunctional ester compound, a hydrogen halide, a hydrogen halide precursor, or a mixture thereof. The at least one metal precursor and the at least one additive are present in an organic solution such that the additive / metal molar ratio between the number of moles of the at least one additive and the number of moles of the metal element from the at least one metal precursor is greater than 2. b) A step of depositing the at least one metal precursor onto the oxide matrix by contacting the organic solution prepared in step a) with the oxide matrix to obtain a solid. c) The step of heat treatment of the solid obtained in step b).

[0012] This method allows for the production of catalysts with satisfactory or even improved catalytic performance (particularly in terms of selectivity and productivity) during the conversion of ethanol-containing feedstocks to butadiene, compared to prior art catalysts (especially those prepared using organic methods). The present invention therefore has the advantage of allowing the simple preparation of catalysts with satisfactory or even improved performance at a reasonable production cost. Another advantage of the method according to the invention is that the preparation of catalysts with good catalytic performance does not require extensive drying of the support and / or the compounds involved (such as additives and / or organic solvents). Therefore, the method according to the invention has the advantage of mitigating processing limitations during catalyst preparation that would relate to the need for a dried product or a product with low residual water content.

[0013] The present invention also relates to a catalyst obtained by the preparation method according to the invention, and comprising elements selected from Groups 3, 4 and 5 of the periodic table, preferably selected from yttrium, zirconium, hafnium, niobium, tantalum and mixtures thereof, preferably selected from element tantalum, element niobium and / or element zirconium, preferably at least one metallic element of element tantalum, and preferably an oxide matrix based on silica.

[0014] The present invention also relates to the use of the catalyst for converting a feedstock containing ethanol into butadiene at a temperature between 250 and 450°C and a pressure between 0.05 and 2.00 MPa.

[0015] Finally, according to another aspect, the present invention relates to a method for converting a feedstock containing at least ethanol into butadiene, comprising: The step of converting a feedstock containing ethanol into butadiene is carried out in the presence of a catalyst prepared according to the preparation method, at a temperature between 250 and 450°C, and at a pressure between 0.05 and 2.00 MPa.

[0016] Description of the implementation plan According to the present invention, the expressions "of between ... and ..." and "...to ..." are equivalent and refer to the fact that the limit values ​​of the interval are included within the described numerical range. If this is not the case and if the limit values ​​are not included within the described range, this will be indicated in this specification.

[0017] In this specification, various ranges of parameters for a given step, such as pressure ranges and temperature ranges, can be used individually or in combination. For example, in this specification, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0018] Specific embodiments of the invention are described below. They may be implemented individually or in combination, and there is no limitation on the combination where technically feasible.

[0019] According to the present invention, the pressure is absolute pressure and is given in absolute MPa (or MPa abs).

[0020] According to the present invention, time and duration are expressed in hours (h), minutes (min) and / or seconds (sec).

[0021] In this specification, the term "room temperature (T)" is used. 室"" corresponds to a temperature of 20°C ± 5°C (the abbreviation "±" means "addition or subtraction", and "20°C ± 5°C" means between 15°C and 25°C), and the term "atmospheric pressure" refers to a pressure of about 0.1 MPa, that is, between 0.05 MPa and 0.15 MPa, preferably between 0.08 MPa and 0.12 MPa, and usually 0.101325 MPa.

[0022] The terms “upstream” and “downstream” should be understood in accordance with the general flow of the fluid or material flow considered in this method.

[0023] According to the present invention, the term "hydroxy acid" refers to any compound, or a derivative thereof, preferably containing carboxylic acid and hydroxyl functional groups at the α, β, or γ position (very preferably at the α or β position), and the term "derivative" herein refers to its oligomers, particularly containing 2 to 20 repeating units, optionally in a cyclic form (i.e., lactone form). Specifically, hydroxy acids are known to have an oligomerization tendency, i.e., to condense into linear or cyclic oligomers, particularly when they are in concentrated solutions. For example, as the concentration of lactic acid in aqueous solution increases, lactic acid oligomers form lactic acid oligomers containing 2 to 20 repeating units, and more particularly 2 to 10 repeating units (see Vu DT et al., Oligomer distribution in concentrated lactic acid solutions, Fluid Phase Equilibria , 236 (2005) 125–135). Lactic acid can also dimerize and cyclize to form dilactides. Therefore, hydroxy acids that can be conceived as additives in the method according to the invention can be in the form of monomeric compounds of hydroxy acids whose hydroxyl functionalization is preferably at the α, β, or γ positions, or in the form of oligomers of said hydroxy acids in cyclic (e.g., dilactides) or linear forms. In this specification, the terms “hydroxy acid,” “α-hydroxy acid,” “β-hydroxy acid,” and “γ-hydroxy acid” should therefore be understood as “hydroxy acid and its derivatives,” “α-hydroxy acid and its derivatives,” “β-hydroxy acid and its derivatives,” and “γ-hydroxy acid and its derivatives,” respectively. Similarly, the various specific hydroxy acids mentioned in this specification, such as lactic acid, tartaric acid, malic acid, and mandelic acid, correspond to said specific acids in the form of monomers and their oligomer derivatives, such as lactic acid and its derivatives, tartaric acid and its derivatives, malic acid and its derivatives, and mandelic acid and its derivatives, respectively.

[0024] The present invention relates to a method for preparing a catalyst (referred to as a heterogeneous catalyst), the catalyst comprising at least one metallic element selected from elements of Groups 3, 4 and 5 of the periodic table, preferably selected from yttrium, zirconium, hafnium, niobium, tantalum and mixtures thereof, more preferably zirconium, niobium, tantalum and mixtures thereof, very preferably tantalum, and an oxide matrix, preferably a silica-based matrix.

[0025] The preparation method according to the present invention comprises the following steps, and very specifically consists of the following steps: a) The step of preparing at least one organic solution, the organic solution comprising at least one metallic precursor of at least one metallic element selected from Groups 3, 4 and 5 of the periodic table, at least one additive, and optionally an organic solvent. The at least one additive is advantageously a polyfunctional ketone compound, a polyfunctional organic acid compound, a β-polyfunctional ester compound, a hydrogen halide, a hydrogen halide precursor, or a mixture thereof, and is preferably selected from hydroxy ketones, diketones, hydroxy acids and their anhydrides, keto acids and their anhydrides, polybasic acids (e.g., diacids and tricids) and their anhydrides, β-hydroxy esters, β-keto esters, hydrogen halides, hydrogen halide precursors, or mixtures thereof. The at least one metal precursor and the at least one additive are present in an organic solution such that the molar ratio (additive / metal) between the number of moles of the at least one additive and the number of moles of the metal element contributed by the at least one metal precursor is greater than, preferably between 2.1 and 30, more preferably between 2.5 and 20, and even more preferably between 5 and 15. b) A step of depositing the at least one metal precursor onto the oxide matrix by contacting the organic solution prepared in step a) with the oxide matrix to obtain a solid. b') Optionally, the maturation step of the solid obtained in step b) c) A heat treatment step of the solid obtained in deposition step b) or optionally aging step b'), preferably including drying or drying followed by calcination. Drying is advantageously carried out at a temperature between 50°C and 200°C, preferably between 80°C and 150°C, for a time between 1 and 24 hours, advantageously in a gaseous stream, preferably in an air stream; Calcination, when integrated into step c), is advantageously carried out in a gaseous stream, preferably an oxygen-containing gaseous stream, at a temperature between 350 and 700°C, preferably between 450 and 600°C, for a time between 1 and 6 hours, preferably between 2 and 4 hours; and d) Optionally repeat the sequence of deposition step b) and heat treatment step c), or optionally repeat the sequence of deposition step b), followed by ripening step b'), and then heat treatment step c).

[0026] Advantageously, step a) of the preparation method enables the preparation of at least one organic solution containing at least one metal precursor, preferably one or two metal precursors, and very particularly one metal precursor containing at least one metal element selected from Groups 3, 4, and 5 of the periodic table, i.e., at least one metal precursor of at least one metal element selected from Groups 3, 4, and 5 of the periodic table, preferably one or two of at least Group 3, Group 4, and / or Group 5 elements, and very particularly one metal precursor. Preferably, the metal precursor or each metal precursor contains a metal element selected from Groups 3, 4, and 5 of the periodic table. The metal precursor or each metal precursor may optionally contain another element selected from groups other than Groups 3, 4, and 5 of the periodic table.

[0027] The at least one metallic precursor selected from at least one metallic element of Group 3, Group 4 and / or Group 5 of the periodic table is advantageously selected particularly from yttrium (Y), zirconium (Zr), hafnium (Hf), niobium (Nb), tantalum (Ta) and mixtures thereof, preferably from zirconium (Zr), niobium (Nb), tantalum (Ta) and mixtures thereof, and very preferably from at least one metallic element of tantalum. According to a very preferred embodiment of the invention, the at least one metallic precursor is a metallic precursor of element tantalum, optionally combined with a metallic precursor of element niobium and / or a metallic precursor of element zirconium.

[0028] Advantageously, the metal precursor selected from at least one metal element of Groups 3, 4, and / or 5, such as the metal precursor of tantalum, is any compound containing at least one element of Groups 3, 4, and / or 5, such as tantalum, and capable of releasing the element in a reactive form in solution. The metal precursor used is therefore an organic or inorganic compound containing the metal element of Groups 3, 4, and / or 5, and is advantageously at least partially, and preferably completely, soluble in an organic solution under the temperature and pressure conditions used particularly in steps a) and b) of the preparation method, and particularly soluble in an organic solvent when an organic solvent is used. The organic or inorganic compound is particularly selected from halides, nitrates, sulfates, phosphates, hydroxides, carbonates, carboxylates, alkoxides, diketoates, amines, and cyclopentadienyl groups of the metal element of Groups 3, 4, and / or 5, and combinations of two or more thereof, more preferably from chlorides, nitrates, carboxylates, alkoxides, and diketoates of the metal element of Groups 3, 4, and / or 5, and combinations of two or more thereof. For example, alkoxide precursors have the formula M(OR). nIn this formula, M is a metallic element from group n of the periodic table, where n is an integer equal to 3, 4, or 5. Preferably, M is Ta, Nb, or Zr, with Ta being very preferred. R is a group selected from alkyl groups, such as ethyl, isopropyl, n-butyl, sec-butyl, or tert-butyl. For example, preferred tantalum metal precursors are tantalum pentachloride (TaCl5) and tantalum pentaethoxy (Ta(OC2H5)5 or Ta(OEt)5), which can be used with most organic solvents. Niobium metal precursors can be selected from niobium pentachloride (NbCl5) and niobium pentaethoxy (Nb(OC2H5)5 or Nb(OEt)5). Zirconium metal precursors can be selected from zirconium tetrachloride (ZrCl4) and zirconium tetraethoxy (Zr(OC2H5)4 or Zr(OEt)4). According to a highly preferred embodiment of the invention, the at least one metal precursor is tantalum pentachloride (TaCl5) or tantalum pentaethoxylate (Ta(OC2H5)5 or Ta(OEt)5), optionally in combination with a metal precursor of element niobium and / or a metal precursor of element zirconium.

[0029] The organic solution prepared in step a) of the method according to the invention contains, in addition to the at least one metal precursor of at least one element of groups 3, 4 and / or 5 of the periodic table, at least one additive and optional organic solvent.

[0030] The additive may be a polyfunctionalized ketone compound, a polyfunctionalized organic acid compound, a β-polyfunctionalized ester compound, a hydrogen halide, a hydrogen halide precursor, or a mixture thereof. According to the invention, the polyfunctionalized ketone compound is an organic compound comprising a ketone function and at least one second chemical function, wherein the second chemical function is advantageously oxygen-containing (e.g., carbonyl or hydroxyl), nitrogen-containing (e.g., amino or amide), or sulfur-containing, preferably located at position 1 (α-position, i.e., the carbon directly adjacent to the carbon of the ketone function), position 2 (β-position, i.e., the second carbon adjacent to the carbon of the ketone function), or position 3 (γ-position, i.e., the third carbon adjacent to the carbon of the ketone function). Polyfunctionalized organic acid compounds are organic compounds comprising a carboxylic acid or carboxylic acid-forming function (i.e., an anhydride capable of forming an acid, particularly an acid-forming anhydride in an alcoholic medium) and at least one second chemical function, wherein the second chemical function is advantageously oxygen-containing (e.g., carbonyl or hydroxyl), nitrogen-containing (e.g., amino or amide), or sulfur-containing, preferably located at the 1 position (α position, i.e., the carbon directly adjacent to the acid-functionalized carbon), the 2 position (β position, i.e., the second carbon adjacent to the acid-functionalized carbon), or the 3 position (γ position, i.e., the third carbon adjacent to the acid-functionalized carbon). Finally, β-polyfunctionalized ester compounds are organic compounds comprising an ester function and at least one second chemical function, wherein the second chemical function is advantageously oxygen-containing (e.g., carbonyl or hydroxyl), nitrogen-containing (e.g., amino or amide), or sulfur-containing, located at the 2 position (β position, i.e., the second carbon adjacent to the ester-functionalized carbon). Preferably, the at least one additive is selected from hydroxy acids and their anhydrides, keto acids and their anhydrides, polybasic acids (e.g., diacids and triacids) and their anhydrides, hydroxy ketones, diketones, β-hydroxy esters, β-keto esters, hydrogen halides, hydrogen halide precursors and mixtures thereof.

[0031] Preferably, the hydroxy ketone and diketone are selected from α-hydroxy ketone, β-hydroxy ketone, β-diketone and mixtures thereof, for example selected from 3-hydroxybutanone (or acetoin), pentane-2,4-dione (or acetylacetone) and mixtures thereof.

[0032] Preferably, the hydroxy acid, keto acid, and polybasic acid are selected from α-hydroxy acids, β-hydroxy acids, α-keto acids, β-keto acids, α-diacids, β-diacids, their anhydrides, and mixtures thereof, and more particularly from pyruvate, lactic acid, tartaric acid, malic acid, citric acid, oxalic acid, glycolic acid, salicylic acid, mandelic acid, α-ketoglutaric acid, and β-ketoglutaric acid, their anhydrides, and mixtures thereof. Preferably, the hydroxy acid, keto acid, and polybasic acid are selected from α-hydroxy acids, α-keto acids, and α-diacids, such as pyruvate, lactic acid, tartaric acid, malic acid, citric acid, oxalic acid, glycolic acid, mandelic acid, their anhydrides, and mixtures thereof.

[0033] Preferably, the β-hydroxy ester and β-keto ester are selected from ethyl acetoacetate, ethyl 2-oxocyclopentanecarbamate, diethyl malonate and mixtures thereof, and more preferably ethyl acetoacetate, ethyl 2-oxocyclopentanecarbamate and mixtures thereof.

[0034] Preferably, the hydrogen halide is selected from hydrogen chloride, hydrogen bromide, hydrogen iodide, and mixtures thereof, with hydrogen chloride being the most preferred. It can be introduced into the organic solvent, for example, by sparging gaseous hydrogen halide into the organic solvent, or introduced into the organic solvent prior to step a); at least a portion of the gaseous hydrogen halide is then advantageously dissolved in the organic solvent.

[0035] Advantageously, the hydrogen halide precursor is a compound comprising at least one halide, wherein said at least one halide is unstable. Therefore, the hydrogen halide precursor advantageously releases at least one halide ion, which can react with an organic solvent to form hydrogen halide. Preferably, the hydrogen halide precursor is selected from acyl halides (R-COHa, where Ha is a halide ion, i.e., fluoride, chloride, bromide, or iodide ion), alcohol hydrogen halides (ROH-HHa, where Ha is a halide ion, i.e., fluoride, chloride, bromide, or iodide ion, and ROH, wherein the alcohol is preferably selected from methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, and mixtures thereof), and mixtures thereof. Most preferably, the hydrogen halide precursor is selected from acyl halides, such as formyl chloride, acetyl chloride, propionyl chloride, butyryl chloride, and mixtures thereof, and most preferably acetyl chloride.

[0036] Preferably, the at least one additive is selected from hydroxy ketones and diketones, such as 3-hydroxybutanone, pentane-2,4-dione and mixtures thereof; selected from hydroxy acids, keto acids and polyacids, such as pyruvic acid, lactic acid, tartaric acid, malic acid, citric acid, oxalic acid, glycolic acid, mandelic acid and their anhydrides, and mixtures thereof; selected from β-hydroxy esters and β-keto esters, such as ethyl acetoacetate, ethyl 2-oxocyclopentanecarbamate, diethyl malonate and mixtures thereof; selected from hydrogen chloride, hydrogen bromide and hydrogen iodide, preferably hydrogen chloride; and / or selected from hydrogen halide precursors, such as formyl chloride, acetyl chloride, propionyl chloride, butyryl chloride and mixtures thereof.

[0037] Preferably, the organic solution prepared in step a) contains one or two additives, preferably one additive as defined above in this specification.

[0038] The organic solution may also contain an organic solvent to provide a “homogeneous” organic solution as explained below in this specification. Preferably, the organic solution contains an organic solvent, preferably at least 5% by weight, or even at least 20% by weight, and for example at most 90% by weight or 75% by weight, the percentages being given by weight of the organic solvent relative to the total weight of the organic solution. When the organic solvent is present in the organic solution, it is very advantageously selected from organic compounds soluble in said at least one additive and said at least one metal precursor. Advantageously, when present, the organic solvent of the organic solution prepared in step a) contains at least one organic compound, and preferably an oxygen- or hydrocarbon-based organic compound, preferably composed of such compounds. The organic solvent may also optionally contain water. More particularly, the organic solvent is selected from alcohols, carboxylic acids, ethers, esters, ketones, hydrocarbon compounds, and mixtures thereof. Preferably, the organic solvent comprises at least one alcohol, preferably at least 10% by weight (and at most 100% by weight), particularly at least 50% by weight (and at most 100% by weight), or even at least 90% by weight (and at most 100% by weight), the percentage being given relative to the total weight of the organic solvent in the organic solution. Alcohols that can be used as organic solvents are preferably monohydric alcohols containing 1 to 6 carbon atoms (i.e., C1-C6), preferably 1 to 4 carbon atoms (i.e., C1-C4), and particularly containing 1, 2, 3, or 4 carbon atoms, especially straight-chain, branched, or cyclic, advantageously non-aromatic alcohols. Alcohols that can be used as organic solvents are, for example, selected from methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, and mixtures thereof. Preferably, carboxylic acids that can be used as organic solvents are preferably carboxylic acids containing 2 to 4 carbon atoms (i.e., C2-C4), especially straight-chain, branched, or cyclic, advantageously non-aromatic carboxylic acids. Carboxylic acids that can be used as organic solvents are, for example, selected from acetic acid, propionic acid, and butyric acid. Ethers optionally used as organic solvents are preferably C4-C8 ethers, particularly straight-chain, branched, or cyclic, advantageously non-aromatic ethers, such as tetrahydrofuran (THF), diethyl ether, or diisopropyl ether. Esters that can be used as organic solvents are preferably C2-C6, preferably C2-C4 carboxylic acids and C1-C6, preferably C1-C4 alcohols, particularly straight-chain, branched, or cyclic, advantageously non-aromatic esters, such as methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, or ethyl propionate. Ketones optionally used as organic solvents are selected from diketones, such as acetylacetone. Hydrocarbon compounds that can be used as organic solvents are preferably aliphatic, cyclic, or aromatic hydrocarbon compounds containing 5 to 10 carbon atoms (i.e., C5-C10), preferably 6 to 8 carbon atoms (i.e., C6-C8), and particularly containing 6, 7, or 8 carbon atoms, such as hexadecane isomers, heptane isomers, octane isomers, and mixtures thereof.For example, the organic solvent comprises at least one organic compound selected from methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, acetic acid, propionic acid, butyric acid, tetrahydrofuran (THF), diethyl ether, diisopropyl ether, methyl acetate, ethyl acetate, isopropyl acetate, ethyl propionate, acetylacetone, hexane, heptane, and mixtures thereof, particularly selected from methanol, ethanol, propanol, isopropanol, isobutanol, tert-butanol, acetic acid, propionic acid, isopropyl acetate, hexane, heptane, and mixtures thereof, preferably composed of such organic compounds. According to a highly preferred embodiment, the organic solvent comprises at least one alcohol, preferably consisting of at least one alcohol, preferably at least 10% by weight (and at most 100% by weight), particularly at least 50% by weight (and at most 100% by weight), or even at least 90% by weight (and at most 100% by weight) of at least one alcohol, said alcohol preferably selected from methanol, ethanol, propanol, isopropanol, butanol, isobutanol and tert-butanol or mixtures thereof, and particularly selected from ethanol, isopropanol and tert-butanol and mixtures thereof, said percentage being given relative to the total weight of the organic solvent in the organic solution, said at least one alcohol optionally being mixed with acetic acid and / or propionic acid.

[0039] The metal precursor and additive of at least one element from Groups 3, 4, and / or 5 are present in an organic solution such that the molar ratio of the additive to the metal element contributed by the metal precursor (i.e., the total molar number of Group 3, 4, and 5 elements (e.g., tantalum)) is greater than 2 (i.e., strictly greater than 2), preferably between 2.1 and 30, more preferably between 2.5 and 20, and more preferably between 5 and 15. When the additive / metal molar ratio is less than or equal to 2, the catalytic performance of the obtained catalyst (particularly in terms of selectivity and productivity, especially when converting ethanol-containing feedstocks to butadiene) is not improved or only slightly improved compared to prior art catalysts (particularly those prepared without additives). Above a certain additive to metal molar ratio, for example between 10 and 15, the catalytic performance of the obtained catalyst (particularly in terms of selectivity and productivity, especially when converting ethanol-containing feedstocks to butadiene) is significantly improved and appears to have reached a plateau (it no longer changes or changes very little). Therefore, an additive-to-metal molar ratio higher than 30 may lead to excessive consumption of the additive without any additional impact on the catalytic performance of the obtained catalyst.

[0040] The metal precursors and additives can be dissolved, diluted, and / or suspended (advantageously in colloidal form) in the organic solution prepared in step a). Regardless of their form, the metal precursors and additives are uniformly distributed in the organic solution in step a). This organic solution can then be referred to as homogeneous.

[0041] During step a), multiple organic solutions, such as two or three organic solutions, can be prepared. Each of the organic solutions prepared may advantageously contain the same or different metal precursors of Group 3, Group 4, and / or Group 5 elements among the prepared organic solutions, and at least one additive among them. In the case of preparing multiple organic solutions, the method of preparing the catalyst advantageously includes repeating step d) of at least deposition step b) and heat treatment step c) in such a way that each prepared organic solution is contacted with the oxide matrix (or support) at least once.

[0042] Preferably, step a) of preparing the organic solution is carried out at a temperature between room temperature and 80°C and at a pressure between atmospheric pressure and 3.0 MPa. Step a) of preparing the organic solution advantageously includes mixing the at least one metal precursor and the at least one additive optionally with an organic solvent.

[0043] Step a) thus allows the preparation of at least one organic solution, which optionally, particularly in an oxygen-containing organic solvent, contains at least one metal precursor of at least one element of Group 3, Group 4 and / or Group 5 of the periodic table and at least one additive, very advantageously selected from hydrogen ketones, diketones, hydroxy acids and their anhydrides, keto acids and their anhydrides, β-hydroxy esters, β-keto esters, hydrogen halides, hydrogen halide precursors and mixtures thereof.

[0044] The organic solution obtained in step a) can then be contacted with the oxide matrix to obtain a solid. This contact step corresponds to step b) of the preparation method according to the invention, which is the step of depositing the metal precursor onto the oxide matrix.

[0045] The oxide matrix can also be referred to as a carrier and is typically in particle form. Preferably, the oxide matrix comprises silica; the oxide matrix is ​​thus referred to as a silica-based oxide matrix. It preferably contains at least 90% by weight (i.e., between 90% and 100% by weight), more preferably at least 95% by weight (i.e., 95% to 100%), more preferably at least 98% by weight (i.e., 98% to 100%), and even more preferably at least 99.5% by weight (i.e., 99.5% to 100%) silica relative to the total mass of the oxide matrix. The oxide matrix advantageously contains pores, particularly mesopores. The average pore size (or pore size) of the silica-based oxide matrix is ​​preferably at least 4 nm, preferably between 4.5 and 50 nm, and even more preferably between 4.5 and 20 nm. Preferably, the pore volume of the oxide matrix, particularly the silica-based matrix, is between 0.4 and 1.8 ml / g, and especially between 0.5 and 1.5 ml / g. Preferably, the oxide matrix has an S content of at least 250 m² / g, more preferably between 250 m² / g and 700 m² / g, and even more preferably between 400 m² / g and 600 m² / g. BET Specific surface area.

[0046] The aforementioned textural parameters were determined using an analytical technique known as "nitrogen volumetry," which corresponds to the physical adsorption of nitrogen molecules into the pores of the material via a gradual increase in pressure at a constant temperature. According to the invention, in particular, the specific surface area of ​​the oxide matrix corresponds to the parameters specified in the journal "..." The Journal of the American Chemical Society The standard ASTM D 3663-78, established by the Brunauer-Emmett-Teller method described in 1938, 60, 309, measures the BET specific surface area (in m²) by nitrogen adsorption, as determined by nitrogen adsorption. 2 S in g BET The pore distribution, representing the mesoporous population, was determined using the Barrett-Joyner-Halenda (BJH) model. Nitrogen adsorption-desorption isotherms derived from the obtained BJH model are described in the journal "..." by EP Barrett, LG Joyner, and PP Halenda. The Journal of the American Chemical Society In 1951, 73, 373, the pore volume V was defined as the partial pressure P / P corresponding to the nitrogen adsorption-desorption isotherm. 0 最大 The observed volume value. Nitrogen adsorption volume is at P / P 0 最大= 0.99, the volume measured at this pressure, under which nitrogen is considered to have filled all pores. The mesopore diameter ϕ of the tested material, particularly the oxide matrix, is determined by the formula 4000.V / S BET Measurement.

[0047] The oxide matrix may optionally contain trace amounts of water, for example, a content greater than or equal to 0.5% by weight relative to the total weight of the oxide matrix. The presence of trace amounts of water in the support does not appear to affect the quality of the resulting heterogeneous catalyst, particularly its catalytic performance, such as selectivity and productivity, especially during the reaction converting a feedstock containing ethanol to butadiene. Therefore, operational limitations can be mitigated by relaxing the requirement to operate with dry materials, for example: pre-drying of the oxide matrix can be avoided or lightened (e.g., drying the oxide matrix at 100°C for 2 hours may be sufficient); storage of the oxide matrix can be considered, in particular, without any specific humidity conditions; handling the oxide matrix in a dry atmosphere can be avoided; drying of the organic solvent is not necessary. Therefore, the method according to the invention allows for reductions in energy consumption and cost of the preparation process.

[0048] Optionally, the oxide matrix may be dried, for example, in a stationary or circulating furnace at a temperature typically less than or equal to 500°C, more particularly between 100 and 300°C, or even between 100 and 250°C, for 1 to 24 hours, particularly 2 to 16 hours, prior to step b). Advantageously, the oxide matrix in contact with the organic solution in step b) has a water content preferably less than or equal to 5% by weight, preferably less than or equal to 2.5% by weight, or even between 0.5% and 2.5% by weight, relative to the total weight of the oxide matrix.

[0049] The oxide matrix, particularly the silica-based matrix, can be commercially available or synthesized according to methods known to those skilled in the art. The oxide matrix, particularly the silica-based matrix, can be used directly in powder form or has been shaped, particularly granulated, crushed, and sieved powders, beads, pellets, granules, or extrusions (hollow or filled cylinders, multi-leaved cylinders with, for example, 2, 3, 4, or 5 leaves, twisted cylinders), or rings, etc., these shaping operations being performed using conventional techniques known to those skilled in the art. For example, the oxide matrix, particularly the silica-based matrix, may be in the form of optionally spherical beads or extrusions, preferably having a size between 0.5 and 10 mm, preferably between 1.0 and 5 mm.

[0050] The contact in step b), i.e., the deposition of the at least one metal precursor onto the oxide matrix, can be performed using any method known to those skilled in the art. For example, and not exhaustively, methods known as dry impregnation, over-impregnation, CVD (chemical vapor deposition), CLD (chemical liquid deposition), etc., can be used. For example, step b) of the method for preparing a catalyst according to the invention preferably includes: contacting a certain volume of the organic solution prepared in step a) with the oxide matrix such that the volume of the organic solution corresponds to all or part of the pore volume of the oxide matrix, and impregnating the organic solution onto the surface of the oxide matrix to ensure that the at least one metal precursor is dispersed across the entire surface of the oxide matrix. Most advantageously, the contact and impregnation are performed at a temperature between room temperature and 80°C and at a pressure between atmospheric pressure and 3.0 MPa.

[0051] Optionally, a step b') of aging the obtained solid can be performed after deposition step b) to further promote the dispersion and distribution of the at least one metal precursor on the entire surface of the oxide matrix. For example, the aging step can be carried out at a temperature between room temperature and 80°C and a pressure between atmospheric pressure and 3.0 MPa for a duration between 1 and 5 hours, particularly 2 hours.

[0052] The method for preparing the catalyst according to the invention further includes step c) of heat treatment of the solid obtained in deposition step b) or optionally aging step b').

[0053] Preferably, heat treatment step c) includes, and preferably comprises: drying or drying followed by calcination, more preferably drying followed by calcination. Drying is very advantageously carried out at a temperature between 50 and 200°C, and more preferably between 80 and 150°C, for a period of 1 to 24 hours, advantageously in a gaseous stream, preferably in an air stream, for example in an oven. Calcination, when carried out in step c) of the catalyst preparation method, is advantageously carried out in a gaseous stream, preferably in a gaseous stream containing oxygen, for example in an air stream, at a temperature between 350 and 700°C, preferably between 450 and 600°C, for a period of 1 to 6 hours, preferably between 2 and 4 hours.

[0054] Optionally, the deposition step b) and the heat treatment step c), or optionally steps b), b'), and then c), can be repeated n times, where n is an integer between 1 and 10, preferably between 1 and 5. Therefore, the catalyst preparation method may include repeated step d), for example, where the target catalyst contains multiple Group 3, Group 4, and / or Group 5 metal elements, such as element Nb and element Ta, or element Ta and element Zr; or to achieve a target content of metal elements in the prepared catalyst; or in the case of preparing multiple organic solutions in step a), as explained above in this specification, etc. When the preparation method includes repeated step d), the organic solution is then contacted with the solid heat-treated in step c) during the first repetition, or with the solid heat-treated in the (i-1)th heat treatment step during the i-th repetition, where i is an integer between 2 and n. When it includes repeated step d), i.e., repeated steps b) and c), or optionally b), b'), and c), the catalyst preparation method therefore includes: - At least one step a) for preparing the organic solution (step a) may be repeated if necessary); - Deposition step b), optionally followed by ripening step b'), and then - Heat treatment step c), which advantageously includes drying or drying followed by calcination; Then the following sequence is repeated n times: deposition step b), optionally followed by ripening step b'), followed by heat treatment step c), which advantageously includes drying or drying followed by calcination, and a final heat treatment (i.e. the nth heat treatment), which preferably includes drying followed by calcination.

[0055] The catalyst obtained in step c) or optionally in step d) is a heterogeneous catalyst containing at least one metal element from Group 3, Group 4 and / or Group 5 deposited on a support (or oxide matrix) particularly based on silica.

[0056] The preparation method may optionally include a step of shaping the obtained catalyst, possibly followed by a heat treatment, particularly when the oxide matrix used in step b) is in unshaped powder form. Thus, during this optional shaping step, at the end of step c) or possibly in step d), the catalyst may be shaped into granulated, crushed, sieved powders, beads, pellets, granules, or extrusions (hollow or filled cylinders, multi-lobed cylinders with, for example, 2, 3, 4, or 5 lobes, twisted cylinders), or rings, etc., using conventional techniques known to those skilled in the art. Preferably, the catalyst is shaped into extrusions with dimensions between 1 and 10 mm, optionally sphericalized. During this optional shaping step, the catalyst may optionally be mixed with at least one porous oxide material acting as a binder to produce suitable physical properties of the catalyst (mechanical strength, abrasion resistance, etc.). The porous oxide material serving as the binder is preferably selected from silica, magnesium oxide, clay (such as kaolinite, serpentine, chrysotile, montmorillonite, bedecitex, vermiculite, talc, hydropyrite, soapstone, lithium soapstone), titanium oxide, titanates (e.g., zinc, nickel, or cobalt titanates), lanthanum oxide, cerium oxide, boron phosphate, and mixtures thereof. Very preferably, the binder used is siliceous in nature and preferably comprises between 5% and 60% by weight, more preferably between 10% and 30% by weight, relative to the total mass of the catalyst after final molding and optional post-heat treatment. When post-heat treatment is performed, it exhibits properties similar to the heat treatment in step c) and follows its operating conditions.

[0057] The catalyst obtained in step c), or possibly in step d), or even in an optional molding step, comprises elements selected from Group 3, Group 4, and Group 5, preferably yttrium, zirconium, hafnium, niobium, tantalum, and mixtures thereof, preferably elemental tantalum, elemental niobium, elemental zirconium, and mixtures thereof, very preferably at least one metallic element of elemental tantalum, and preferably between 0.1 wt% and 30 wt% relative to the oxide matrix, preferably between 0.3 wt% and 10 wt%, preferably between 0.5 wt% and 5 wt%.

[0058] Advantageously, the obtained catalyst can be loaded into any type of catalytic reactor known to those skilled in the art, particularly axial, radial, or tubular reactors, with or without heat exchange, and with or without multiple injections.

[0059] The present invention also relates to a catalyst obtained by the preparation method according to the invention, comprising at least one metallic element selected from Groups 3, 4, and 5 of the periodic table, preferably selected from yttrium, zirconium, hafnium, niobium, tantalum, and mixtures thereof, preferably selected from elemental tantalum, elemental niobium, elemental zirconium, and mixtures thereof, very preferably elemental tantalum, and an oxide matrix, preferably a silica-based matrix. Preferably, the metallic element is present in an amount between 0.1 wt% and 30 wt%, preferably between 0.3 wt% and 10 wt%, more preferably between 0.5 wt% and 5 wt% relative to the oxide matrix. According to a highly preferred embodiment, the catalyst comprises a silica-based oxide matrix and tantalum in an amount between 0.5 wt% and 5 wt% relative to the oxide matrix. According to another embodiment, the catalyst comprises a silica-based oxide matrix and zirconium in an amount between 0.3 wt% and 10 wt% relative to the oxide matrix, particularly between 0.5 wt% and 5 wt%. According to another embodiment, the catalyst comprises a silica-based oxide matrix and niobium in an amount between 0.3 wt% and 10 wt% relative to the oxide matrix, particularly between 0.5 wt% and 5 wt%.

[0060] The method for preparing the catalyst according to the invention advantageously enables the simple and inexpensive acquisition of a heterogeneous catalyst comprising at least one metal element from Group 3, Group 4 and / or Group 5, particularly elements Nb and / or Ta and / or Zr, with Ta being very preferred. Compared with prior art organically prepared catalysts, this method provides very satisfactory or even improved catalytic performance, particularly in selectivity and productivity, during the reaction of converting a feedstock containing ethanol into butadiene.

[0061] The present invention also relates to the use of a catalyst obtained by the preparation method according to the invention for converting a feedstock containing at least ethanol into butadiene, wherein the catalyst comprises at least one metallic element selected from elements of Groups 3, 4, and 5 of the periodic table, preferably selected from yttrium, zirconium, hafnium, niobium, tantalum, and mixtures thereof, preferably selected from elemental tantalum, elemental niobium, elemental zirconium, and mixtures thereof, preferably elemental tantalum, and preferably a silica-based matrix, preferably between 0.1 wt% and 30 wt% relative to the oxide matrix, more preferably between 0.3 wt% and 10 wt%, and more preferably between 0.5 wt% and 5 wt% of the metallic element. According to a preferred embodiment, the catalyst used comprises a silica-based oxide matrix and tantalum between 0.5 wt% and 5 wt% relative to the oxide matrix. The use of the obtained catalyst for converting a feedstock containing at least ethanol into butadiene subsequently reflects improvements in catalytic performance, particularly in selectivity and productivity. The preferred operating conditions for this conversion reaction are a temperature between 250 and 450°C, more preferably between 270 and 380°C, and more preferably between 300 and 360°C; a pressure between 0.05 and 2.00 MPa, more preferably between 0.05 and 1.50 MPa, and more preferably between 0.08 and 1.00 MPa; and a duration of 0.2 to 10 h⁻¹. -1 Between 0.5 and 5 h is preferred. -1 Between, and preferably between 1 and 4 hours -1 The space velocity is defined as the flow rate ratio between the mass of the feedstock and the mass of the catalyst. When the feedstock also contains acetaldehyde, the ethanol / acetaldehyde molar ratio is between 1 and 5, preferably between 2 and 4.

[0062] According to another aspect, the present invention also relates to a method for converting a feedstock comprising ethanol and optionally acetaldehyde into butadiene, comprising at least: The step of converting a feedstock containing ethanol, preferably ethanol and acetaldehyde, into butadiene, preferably with a molar ratio of ethanol to acetaldehyde between 1 and 5, more preferably between 2 and 4, wherein the conversion step is carried out in the presence of a catalyst prepared according to the above preparation method and at a temperature between 250 and 450°C, preferably between 270 and 380°C, more preferably between 300 and 360°C, at a pressure between 0.05 and 2.00 MPa, more preferably between 0.05 and 1.50 MPa, more preferably between 0.08 and 1.00 MPa, and preferably for 0.2 to 10 h. -1 Between 0.5 and 5 h is preferred. -1 Between, preferably 1 to 4 hours -1 The process is carried out at airspeeds between these intervals.

[0063] When the feedstock contains ethanol and acetaldehyde, the catalyst preferably contains elemental tantalum and a silica-based oxide matrix, wherein the tantalum content in the catalyst is preferably between 0.3% by weight and 10% by weight, and particularly between 0.5% by weight and 5% by weight, relative to the silica-based oxide matrix.

[0064] The following examples illustrate the present invention, particularly specific embodiments thereof, but do not limit its scope. Example

[0065] Catalysts were prepared according to the method described in Example 1. The catalysts were then tested: they were used to convert feedstocks containing ethanol and acetaldehyde, as described in Example 2.

[0066] Example 1: Preparation of 3% Ta / SiO2 catalyst Catalysts containing 3% by weight tantalum were prepared on silica beads (also known as silica supports), where the percentage of tantalum is given as the weight of elemental tantalum relative to the weight of the silica beads. The preparation methods for each catalyst are as follows: The silica support used in the impregnation step has the following characteristics: [Table 1] ( The average bead size corresponds to the number-average diameter of the silica beads.

[0067] Before impregnation, the carrier was dried at 100°C for 2 hours. After drying, the water content in the silica beads was 1.5% by weight (determined by weight loss of a 50 g silica bead sample).

[0068] In some cases, the additive is introduced into volume V EtOH In ethanol (which may contain up to 1% water by volume), to form an ethanol solution. In other cases, no water is added to the volume V. EtOH Additives are introduced into ethanol. The volume V of ethanol... EtOH It is proportional to the pore volume of the silica carrier and equal to the total pore volume of the silica carrier used.

[0069] Then, the tantalum precursor, pentaethoxytantalum (Ta(OEt)5), was introduced and diluted in volume V at a concentration corresponding to the target additive / Ta molar ratio. EtOH The organic solution is then homogenized with stirring in ethanol (reference) or in an ethanol solution containing additives.

[0070] The obtained organic solution was rapidly added dropwise and mixed with the silica support until wettability of the support surface was observed (dry impregnation). The solid was then placed in an ethanol-saturated atmosphere for 3 hours. The solid was then dried in an oven at 100°C for 24 hours, and then calcined in air at 550°C for 4 hours to obtain the catalyst.

[0071] The prepared catalysts and preparation parameters are shown in Table 2.

[0072] [Table 2] .

[0073] Example 2: Application of the prepared catalyst in converting ethanol-acetaldehyde feedstock into butadiene. Description of the catalytic testing unit The reactor used consisted of stainless steel tubes 20 cm long and 10 mm in diameter. The reactor was first filled with silicon carbide, then with catalyst diluted in the silicon carbide, and finally with silicon carbide again. Silicon carbide is inert to the feedstock and does not affect the catalytic results; it allows the catalyst to be positioned within the isothermal zone of the reactor and limits the risk of heat and material transfer problems. A tubular furnace with three heating zones was used to control the reactor temperature.

[0074] The liquid feedstock (a mixture of ethanol and acetaldehyde) is injected via a dual-piston HPLC pump. The liquid stream is vaporized in a tracer-heated line before entering the reactor and homogenized by passing through a static mixer.

[0075] At the reactor outlet, the products formed during the reaction are retained in the gas phase for online analysis by gas chromatography (PONA capillary column), allowing for the most accurate identification of the hundreds of products formed. The catalyst is activated in situ under nitrogen at the test temperature.

[0076] For each test, the ethanol / acetaldehyde ratio of the raw material was set to 2.6 (mol / mol), the temperature was set to 350°C, and the pressure was set to 0.15 MPa.

[0077] For each catalyst tested, the carbon productivity value was obtained at an equivalent feed flow rate (250 g / g Ta / h at a constant pph, i.e., 7.5 h). -1The carbon productivity (usually expressed as weight / weight / percentage per hour) is measured at the reactor outlet at a feed pph of 250 g / g Ta / h, while the butadiene selectivity is determined at an equivalent conversion rate (40% feed conversion). The carbon productivity (usually expressed as weight / weight / percentage per hour) corresponds to the butadiene mass flow rate (in g / h) / unit mass of elemental Ta measured at the reactor outlet. The measured butadiene selectivity (expressed as weight / weight percentage) is the carbon selectivity and corresponds to the butadiene flow rate measured at the reactor outlet relative to the total flow rate of the carbon-based products formed (unconverted ethanol and acetaldehyde are not considered in the selectivity calculation).

[0078] The results obtained with respect to butadiene selectivity and carbon productivity using catalysts A to M prepared as described in Example 1 are shown in Table 3 as the butadiene selectivity gain relative to reference catalyst A (i.e., selectivity gain = [selectivity obtained with this catalyst] - [selectivity obtained with catalyst A], expressed as a gain in points or weight / weight percentage) and as the carbon productivity gain relative to the productivity measured against the corresponding reference catalyst A (i.e., productivity gain = ([productivity obtained with this catalyst] - [productivity obtained with catalyst A]) / [productivity obtained with catalyst A], expressed as a weight / weight percentage).

[0079] [Table 3] .

[0080] Table 3 shows that when the conversion reaction is carried out in the presence of a catalyst according to the invention (i.e., a catalyst prepared in the presence of sufficient additives, particularly such as keto acids, hydroxy acids, hydroxy ketones, diketones, β-polyfunctional esters, or hydrogen halide types), the butadiene selectivity and carbon productivity are significantly improved (i.e., exceeding the uncertainty) compared to the conversion carried out in the presence of a non-compliant catalyst (catalyst A) prepared without additives or a catalyst with insufficient additives (catalysts B, E, and I).

[0081] Example 3: Preparation and Use of Zr / Silica Catalyst A catalyst with 3% zirconium by weight on silica beads was prepared in the same manner as the catalyst in Example 1, using the same silica beads as in Example 1, except that the precursor used was tetraethoxyzirconium (Zr(OEt)4). Catalyst N was prepared without additives, while catalyst O was prepared in the presence of acetylacetone, wherein the additive / Zr molar ratio was 7.

[0082] The prepared catalyst with 3% zirconium by weight on silica was tested in the same catalytic unit as described in Example 2 and under the same operating conditions as described in Example 2.

[0083] The results obtained in terms of butadiene selectivity and carbon productivity are presented in Table 4. They are expressed in the same manner as in Example 2, with catalyst N as the reference catalyst. In other words, the results are expressed as the gain in butadiene selectivity relative to the reference catalyst P (i.e., selectivity gain = [selectivity obtained with this catalyst] - [selectivity obtained with the reference catalyst], expressed as a gain in points or weight / weight percentage) and as the gain in carbon productivity relative to the productivity measured against the reference catalyst P (i.e., productivity gain = ([productivity obtained with this catalyst] - [productivity obtained with the reference catalyst]) / [productivity obtained with the reference catalyst], expressed as a weight / weight percentage).

[0084] [Table 4] .

[0085] Table 4 clearly shows that when the zirconium-based catalyst is the catalyst according to the invention (i.e., prepared in the presence of acetylacetone at a molar ratio of 7) (catalyst O), the butadiene selectivity and carbon productivity are significantly improved compared with the catalyst not according to the invention prepared without additives (catalyst N).

Claims

1. A method for preparing a catalyst, comprising: a) The step of preparing at least one organic solution, said organic solution comprising: At least one metallic precursor selected from at least one metallic element in Groups 3, 4, and 5 of the periodic table. At least one additive, wherein the at least one additive is a polyfunctional ketone compound, a polyfunctional organic acid compound, a β-polyfunctional ester compound, a hydrogen halide, a hydrogen halide precursor, or a mixture thereof. The at least one metal precursor and the at least one additive are present in an organic solution such that the additive / metal molar ratio between the number of moles of the at least one additive and the number of moles of the metal element from the at least one metal precursor is greater than 2. b) A step of depositing the at least one metal precursor onto the oxide matrix by contacting the organic solution prepared in step a) with the oxide matrix to obtain a solid; c) The step of heat treatment of the solid obtained in step b).

2. The method according to claim 1, wherein the additive / metal molar ratio in step a) is between 2.1 and 30, preferably between 2.5 and 20, and more preferably between 5 and 15.

3. The method according to claim 1 or 2, wherein the metallic element is selected from yttrium, zirconium, hafnium, niobium, tantalum and mixtures thereof, preferably selected from tantalum, niobium, zirconium and mixtures thereof, and preferably tantalum.

4. The method according to any one of claims 1 to 3, wherein the at least one metal precursor is tantalum pentachloride or tantalum pentaethoxychloride, which is optionally combined with a metal precursor of element niobium and / or a metal precursor of element zirconium.

5. The method according to any one of claims 1 to 4, wherein the additive is a polyfunctional ketone compound, a polyfunctional organic acid compound, a β-polyfunctional ester compound, a hydrogen halide, a hydrogen halide precursor, or a mixture thereof.

6. The method according to claim 5, wherein the additive is selected from hydroxy ketones and diketones, such as 3-hydroxybutanone, pentane-2,4-dione and mixtures thereof; selected from hydroxy acids, keto acids and polyacids, such as pyruvic acid, lactic acid, tartaric acid, malic acid, citric acid, oxalic acid, glycolic acid, mandelic acid and their anhydrides, and mixtures thereof; selected from β-hydroxy esters and β-keto esters, such as ethyl acetoacetate, ethyl 2-oxocyclopentanecarbamate and diethyl malonate; selected from hydrogen chloride, hydrogen bromide and hydrogen iodide, preferably hydrogen chloride; and / or selected from hydrogen halide precursors, such as formyl chloride, acetyl chloride, propionyl chloride, butyryl chloride and mixtures thereof.

7. The method according to any one of claims 1 to 6, wherein the organic solution in step a) comprises an organic solvent.

8. The method according to any one of claims 1 to 7, wherein the oxide matrix comprises silicon dioxide, preferably at least 90% by weight of silicon dioxide relative to the total mass of the oxide matrix.

9. The method according to any one of claims 1 to 8, wherein the heat treatment step c) comprises drying, the drying preferably being carried out at a temperature between 50 and 200°C for a time between 1 and 24 hours, preferably under a gaseous flow.

10. The method of claim 9, wherein the heat treatment step c) comprises calcination after the drying, the calcination being carried out under a gaseous flow at a temperature between 350 and 700°C for a period between 1 and 6 hours.

11. A catalyst obtained by the preparation method according to any one of claims 1 to 10, comprising elements selected from Groups 3, 4 and 5 of the periodic table, preferably selected from yttrium, zirconium, hafnium, niobium, tantalum and mixtures thereof, preferably selected from elemental tantalum, elemental niobium and / or elemental zirconium, preferably at least one metallic element of elemental tantalum, and preferably an oxide matrix based on silica.

12. The catalyst according to claim 11, wherein the at least one metal element is present in a metal element content between 0.1 wt% and 30 wt%, preferably between 0.3 wt% and 10 wt%, more preferably between 0.5 wt% and 5 wt%, relative to the weight of the oxide matrix.

13. The catalyst according to claim 11 or 12 is used for converting a feedstock containing ethanol into butadiene at a temperature between 250 and 450°C and a pressure between 0.05 and 2.00 MPa.

14. A method for converting a feedstock containing ethanol into butadiene, comprising: The step of converting a feedstock containing ethanol into butadiene is carried out in the presence of a catalyst prepared by any one of claims 1 to 10, at a temperature between 250 and 450°C, and at a pressure between 0.05 and 2.00 MPa.

15. The conversion method according to claim 14, wherein the raw materials comprise ethanol and acetaldehyde, preferably at a molar ratio of ethanol to acetaldehyde between 1 and 5.

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