Catalyst for the hydrogenation and dehydrogenation of organic liquid hydrogen carriers

Abstract

Catalyst for the hydrogenation and dehydrogenation of organic liquid hydrogen carriers Catalyst comprising copper, zinc oxide, magnesium oxide and aluminium oxide, the catalyst comprising, relative to its total mass: - from 10% to 30% by mass of copper; - from 0.5% to 42.4% by mass of zinc; - from 12.5% ​​to 30% by mass of magnesium; and - from 1% to 20% by mass of aluminium; with the ratio of the mass of magnesium to the mass of zinc Mg / Zn being greater than or equal to 0.5, and the ratio of the mass of magnesium to the mass of aluminium Mg / Al being greater than or equal to 1.3. Figure for abstract: None

Description

Title of the invention: Catalyst for the hydrogenation and dehydrogenation of organic liquid hydrogen carriers Technical field

[0001] The present invention relates to the field of catalysts for the hydrogenation and dehydrogenation of liquid organic hydrogen carriers (more commonly referred to as LOHC according to the English terminology "Liquid Organic Hydrogen Carrier"), in particular for the hydrogenation of γ-butyrolactone to 1,4-butanediol and for the dehydrogenation of 1,4-butanediol to γ-butyrolactone. It also relates to a process for the synthesis of such catalysts. Finally, it relates to the use of such catalysts in one or more hydrogenation / dehydrogenation cycles of dehydrogenated LOHC / hydrogenated LOHC pairs, in particular of the γ-butyrolactone / 1,4-butanediol pair, in particular for generating hydrogen. Prior art

[0002] LOHCs are molecules used as liquid carriers for hydrogen that can be hydrogenated or dehydrogenated. They can be used to transport and / or store hydrogen, particularly as an alternative to pressurized or liquefied hydrogen.

[0003] In principle, hydrogen is fixed on the hydrogen-poor organic liquid (dehydrogenated LOHC) by means of a catalytic hydrogenation reaction to produce a hydrogen-rich organic liquid (hydrogenated LOHC) which is stable under ambient conditions and therefore transportable and storable. The hydrogen-rich organic liquid is then dehydrogenated in a second catalytic dehydrogenation reaction in order to regenerate the hydrogen and the hydrogen-poor organic liquid. Thanks to their high volumetric density (50-70 g of hydrogen per liter of hydrogenated LOHC), their mass content (5-7% by mass of hydrogen in the hydrogenated LOHC) and their stability under ambient conditions, it is possible to transport and store them in simple tanks, cisterns or pipelines.

[0004] Advantageously, these LOHCs are therefore capable of being reversibly hydrogenated and dehydrogenated in the presence of a catalyst. The catalyst is generally chosen independently for the hydrogenation and dehydrogenation so as to obtain a high conversion rate and high selectivity respectively for the hydrogenation or dehydrogenation reaction.

[0005] An example of a dehydrogenated LOHC / hydrogenated LOHC pair is the y-butyrolactone / 1,4-butanediol pair, described in particular in FR3095203, the hydrogenation and dehydrogenation reactions of which are as follows:

[0006] [Chem.l] hydrogenation ) + 2 H2 ---------* 1,4-butanediol y-butyrolactone 1,4-butanedio dehydrogenation ---------► y-butyrolactone

[0007]

[0008]

[0009]

[0010]

[0011] Various catalysts have been proposed for the dehydrogenation of 1,4-butanediol. Copper-based catalysts boosted by metals or oxides, such as Cu-Cr / SiO2 (US 5,110,954), Cu-Cr-Mn (US 5,210,229) or Cu-CaO-Na2O / SiO2 (US 6,093,677), were first proposed. Since the active site for the dehydrogenation of 1,4-butanediol (BDO) has been identified as copper, catalysts have been developed by optimizing the synergy between copper and its support, such as CuOZnOZrO2Al2O3 (Ichikawa et al. J. Mol. Catal. A Chem., 2004), Cu / SiO2 (Hwang et al. Green Chem., 2011), Cu-Ba / SiO2 (Zhang et al. Appl. Catal. A, 2012), Cu / MgO (Reddy et al. Catal. Commun., 2017), Co-Cu / MgO (Kannapu et al. Catal. Sci. Technol., 2016), Cux / Zn3o.^Mg; 0.5XAl2O <J x (Liu et al. J. Ind. Eng. Chem., 2021) et CuO / Al2O3 / MnO2 (US 8,828,903 B2). As for the hydrogenation of γ-butyrolactone, generally studied as an intermediate reaction of the hydrogenation of succinic acid or maleic anhydride, it can use homogeneous catalysts such as ruthenium complexes (Li et al., Green Chem., 2014) or heterogeneous catalysts such as palladium or copper catalysts different from those used in dehydrogenation, for example PdRe / SiO2 (Costa et al., J. Supercrit. Fluids, 2023) or CuCo / TiO2 (Huang et al. ACS Catal., 2017) in the presence of a solvent such as an organic solvent, water or supercritical CO2. However, for LOHC applications, hydrogenation and dehydrogenation are advantageously carried out without solvents in order to maximize the percentage of hydrogen transported and minimize production costs. In addition, many catalysts contain toxic metals such as chromium and / or which are poorly available, particularly from the platinum group (known as PGM according to the Anglo-Saxon terminology "platinum group metal"). Furthermore, the aforementioned catalysts are generally described to catalyze only hydrogenation, or only dehydrogenation. Thus, there is a need for new efficient catalysts, including having a high conversion rate and selectivity, both for the hydrogenation reaction and for the dehydrogenation reaction of a dehydrogenated LOHC / hydrogenated LOHC couple, in particular the y-buty-rolactone / l,4-butanediol couple, which can be used without the use of solvent and which are stable over several hydrogenation / dehydrogenation cycles.

[0012] There is further a need for new low-cost catalysts for the hydrogenation and dehydrogenation of a dehydrogenated LOHC / hydrogenated LOHC pair, in particular the γ-butyrolactone / 1,4-butanediol pair, which do not contain toxic metals such as chromium or platinum group metals, while exhibiting good efficiency. Statement of the invention

[0013] The invention relates to a catalyst comprising, or even consisting of, copper, zinc oxide, magnesium oxide and aluminum oxide, the catalyst comprising, relative to its total mass: - from 10% to 30% by mass of copper; - from 0.5% to 42.4% by mass of zinc; - from 12.5% ​​to 30% by mass of magnesium; and - from 1% to 20% by mass of aluminum; with the ratio of the mass of magnesium to the mass of zinc Mg / Zn being greater than or equal to 0.5, and the ratio of the mass of magnesium to the mass of aluminum Mg / Al being greater than or equal to 1.3.

[0014] The invention also relates to a process for synthesizing a catalyst, in particular according to the invention, comprising copper, zinc oxide, magnesium oxide and aluminum oxide, the method comprising at least the steps of: (a) having an aqueous solution A comprising magnesium nitrate, zinc nitrate and aluminium nitrate, the ratio of the mass of magnesium to the mass of zinc Mg / Zn being greater than or equal to 0.5 and the ratio of the mass of magnesium to the mass of aluminium Mg / Al being greater than or equal to 1.3; b) introducing solution A into a basic solution B with a pH greater than or equal to 11, in particular greater than or equal to 12, comprising carbonate ions to form a solid material by coprecipitation, the pH of solution B supplemented with solution A being maintained at a value greater than or equal to 11 during step b); c) impregnate the solid material, possibly after calcination, with copper nitrate; (d) calcining and reducing the impregnated solid material; and e) optionally recovering the catalyst obtained at the end of step d).

[0015] The invention provides a catalyst effective both for catalyzing the hydrogenation reaction of a dehydrogenated LOHC and for catalyzing the dehydrogenation reaction of hydrogenated LOHC, in particular for catalyzing the hydrogenation reaction of γ-butyrolactone to 1,4-butanediol, and for catalyzing the dehydrogenation reaction of 1,4-butanediol to γ-butyrolactone.

[0016] More particularly, the catalyst makes it possible both to hydrogenate γ-butyrolactone to 1,4-butanediol, and to dehydrogenate 1,4-butanediol to γ-butyrolactone, with a good conversion rate and good selectivity.

[0017] It also makes it possible to carry out the hydrogenation / dehydrogenation cycles of the γ-butyrolactone / 1,4-butanediol couple without using a solvent.

[0018] Advantageously, the catalyst does not contain toxic and / or poorly available metals, and has a low cost.

[0019] The invention also relates to a method for generating hydrogen comprising at least one cycle comprising: - the hydrogenation of a dehydrogenated liquid organic hydrogen (LOHC) carrier into hydrogenated LOHC; and - the dehydrogenation of hydrogenated LOHC into dehydrogenated LOHC; the hydrogenation and dehydrogenation being carried out in the presence of the catalyst according to the invention or obtained by the process according to the invention.

[0020] In particular, the invention relates to a method for generating hydrogen comprising at least one cycle comprising: - hydrogenation of γ-butyrolactone to 1,4-butanediol; and - dehydrogenation of 1,4-butanediol to y-butyrolactone; the hydrogenation and dehydrogenation being carried out in the presence of the catalyst according to the invention or obtained by the process according to the invention.

[0021] The invention also relates to the use of the catalyst according to the invention or obtained by the process according to the invention for generating hydrogen by catalytic dehydrogenation of a hydrogenated LOHC into the dehydrogenated LOHC, and for regenerating the dehydrogenated LOHC into the hydrogenated LOHC, the dehydrogenated LOHC / hydrogenated LOHC pair being chosen in particular from the γ-butyrolactone / 1,4-butanediol pair, the dimethyl oxalate / mixture of ethylene glycol and methanol pair, and the ethanol / ethyl acetate pair.

[0022] In particular, the invention also relates to the use of the catalyst according to the invention or obtained by the process according to the invention for generating hydrogen by catalytic dehydrogenation of 1,4-butanediol to γ-butyrolactone, and for regenerating 1,4-butanediol by catalytic hydrogenation of γ-butyrolactone.

[0023] In particular, it relates to the use of the catalyst according to the invention or obtained by the process according to the invention for dehydrogenating a hydrogenated LOHC into the dehydrogenated LOHC following its transport, and preferably for regenerating the hydrogenated LOHC by catalytic hydrogenation of the dehydrogenated LOHC thus formed, in particular following its transport.

[0024] It also relates to the use of the catalyst according to the invention or obtained by the process according to the invention for dehydrogenating a hydrogenated LOHC into the dehydrogenated LOHC within a vehicle, in particular a maritime vehicle, and preferably for regenerating the hydrogenated LOHC by catalytic hydrogenation of the dehydrogenated LOHC thus formed.

[0025] It also relates to the use of the catalyst according to the invention or obtained by the process according to the invention for dehydrogenating a hydrogenated LOHC into dehydrogenated LOHC for a stationary application, in particular in the field of construction or energy storage, and preferably for regenerating the hydrogenated LOHC by catalytic hydrogenation of the dehydrogenated LOHC thus formed.

[0026] In particular, in the uses described above, the dehydrogenated LOHC / hydrogenated LOHC pair may be chosen from the γ-butyrolactone / 1,4-butanediol pair, the dimethyl oxalate / mixture of ethylene glycol and methanol pair, and the ethanol / ethyl acetate pair, in particular may be the γ-butyrolactone / 1,4-butanediol pair.

[0027] In this text, unless otherwise indicated, the term hydrogen is used to refer to dihydrogen, unless it is specified that it is the hydrogen atom. Detailed description Catalyst

[0028] The catalyst may comprise, relative to its total mass, at least 15% by mass, in particular at least 20% by mass, of copper.

[0029] The catalyst may comprise, relative to its total mass, at most 28% by mass, in particular at most 25% by mass, of copper.

[0030] In particular, the catalyst may comprise, relative to its total mass, from 10% to 28% by mass, in particular from 15% to 25% by mass, in particular from 20% to 25% by mass, of copper.

[0031] The catalyst may comprise, relative to its total mass, at least 1% by mass, in particular at least 3% by mass, more particularly at least 5% by mass of zinc, in particular at least 7% by mass of zinc.

[0032] The catalyst may comprise, relative to its total mass, at most 40% by mass, in particular at most 30% by mass, more particularly at most 25% by mass, in particular at most 15% by mass, or even at most 12% by mass, of zinc.

[0033] In particular, the catalyst may comprise, relative to its total mass, from 1% to 40% by mass, in particular from 5% to 40% by mass, more particularly from 5% to 30% by mass, in particular from 5% to 25% by mass, or even from 5 to 15% by mass, of zinc.

[0034] The catalyst may comprise, relative to its total mass, at least 13% by mass, in particular at least 15% by mass, more particularly at least 20% by mass, in particular at least 23% by mass, of magnesium.

[0035] The catalyst may comprise, relative to its total mass, at most 28% by mass of magnesium.

[0036] In particular, the catalyst may comprise, relative to its total mass, from 15% to 30% by mass, in particular from 20% to 30% by mass, more particularly from 23% to 28% by mass, of magnesium.

[0037] The catalyst may comprise, relative to its total mass, at least 5% by mass, in particular at least 6% by mass, more particularly at least 10% by mass of aluminum.

[0038] The catalyst may comprise, relative to its total mass, at most 15% by mass of aluminum.

[0039] In particular, the catalyst may comprise, relative to its total mass, from 5% to 20% by mass, in particular from 6% to 15% by mass, in particular from 10% to 15% by mass of aluminum.

[0040] In particular, the catalyst may comprise, relative to its total mass:

[0041] - from 15% to 30% by mass of copper, in particular from 20% to 25% by mass of copper; - from 3% to 40% by mass of zinc, in particular from 5% to 15% by mass of zinc; - from 15% to 30% by mass of magnesium, in particular from 20% to 30% by mass of magnesium; and - from 5% to 20% by mass of aluminum, in particular from 6% to 15% by mass of aluminum.

[0042] In particular, the catalyst may comprise, relative to its total mass:

[0043] - from 15% to 30% by mass of copper, in particular from 20% to 25% by mass of copper; - from 4.5% to 27% by mass of zinc, in particular from 7% to 13% by mass of zinc; - from 17% to 30% by mass of magnesium, in particular from 21.5% to 30% by mass of magnesium; and - from 5% to 20% by mass of aluminum, in particular from 10% to 15% by mass of aluminum; with the ratio of the mass of magnesium to the mass of zinc Mg / Zn being between 1 and 5, in particular between 2 and 3.5 and the ratio of the mass of magnesium to the mass of aluminium Mg / Al being between 1.5 and 5, in particular between 1.5 and 3.

[0044] The ratio of the mass of magnesium to the mass of zinc Mg / Zn may be greater than or equal to 1, in particular greater than or equal to 1.5, more particularly greater than or equal to 2, in particular greater than or equal to 2.5.

[0045] The ratio of the mass of magnesium to the mass of zinc Mg / Zn may be less than or equal to 10, in particular less than or equal to 5, more particularly less than or equal to 3.5, in particular less than or equal to 3.

[0046] In particular, the ratio of the mass of magnesium to the mass of zinc Mg / Zn may be between 1.5 and 10, more particularly between 2 and 5, in particular between 2.5 and 3.5.

[0047] The ratio of the mass of magnesium to the mass of aluminum Mg / Al may be greater than or equal to 1.5, in particular greater than or equal to 1.6, more particularly greater than or equal to 1.8, in particular greater than or equal to 2.

[0048] The ratio of the mass of magnesium to the mass of aluminum Mg / Al may be less than or equal to 10, in particular less than or equal to 5, more particularly less than or equal to 3, in particular less than or equal to 2.5.

[0049] In particular, the ratio of the mass of magnesium to the mass of aluminum Mg / Al may be between 1.6 and 10, more particularly between 1.8 and 5, in particular between 2 and 2.5.

[0050] The ratio of the mass of aluminum to the mass of zinc Al / Zn may be greater than or equal to 1, in particular greater than or equal to 1.2.

[0051] The ratio of the mass of aluminum to the mass of zinc Al / Zn may be less than or equal to 5, in particular less than or equal to 2, more particularly less than or equal to 1.75.

[0052] In particular, the ratio of the mass of aluminum to the mass of zinc Al / Zn may be between 1 and 5, more particularly between 1 and 2, in particular between 1.2 and 1.5.

[0053] The ratio of the mass of copper to the total mass of zinc, magnesium and aluminum Cu / (Zn+Mg+Al) may be greater than or equal to 0.05, in particular greater than or equal to 0.1, more particularly greater than or equal to 0.3.

[0054] The ratio of the mass of copper to the total mass of zinc, magnesium and aluminum Cu / (Zn+Mg+Al) may be less than or equal to 5, in particular less than or equal to 2, more particularly less than or equal to 1.

[0055] In particular, the ratio of the mass of copper to the total mass of zinc, magnesium and aluminum Cu / (Zn+Mg+Al) may be between 0.05 and 5, more particularly between 0.1 and 2, in particular between 0.3 and 1.

[0056] Copper may be in the zero oxidation state or in the form of copper (II) oxide of formula CuO, in particular in the zero oxidation state.

[0057] Zinc oxide may be of the formula ZnO.

[0058] Magnesium oxide may be of the formula MgO.

[0059] The aluminum oxide may be alumina of formula A12O3.

[0060] The catalyst may consist of at least 95% by mass, in particular at least 99% by mass, more particularly at least 99.9% by mass, or even 100% by mass, relative to its total mass, of copper atoms, zinc atoms, magnesium atoms, aluminum atoms and oxygen atoms.

[0061] In particular, the catalyst may consist of at least 95% by mass, in particular at least 99% by mass, more particularly at least 99.9% by mass, or even 100% by mass, relative to its total mass, of copper and / or copper (II) oxide, in particular copper in the zero oxidation state, zinc oxide, magnesium oxide and aluminum oxide.

[0062] Preferably, the catalyst is free of metals selected from chromium and platinum group metals such as ruthenium, rhodium, palladium, osmium, iridium, platinum and rhenium.

[0063] Copper may be present in a support comprising zinc oxide, magnesium oxide and aluminum oxide. The support may be in the form of particles. In particular, the support may consist of at least 95% by mass, in particular at least 99% by mass, more particularly at least 99.9% by mass, or even 100% by mass, relative to its total mass, zinc oxide, magnesium oxide and aluminum oxide.

[0064] In particular, the catalyst may be of formula Cu / (ZnO)x(MgO)y(Al2O3)z or of formula CuO / (ZnO)x(MgO)y(Al2O3)z, with x, y and z being the stoichiometric coefficients of the different oxides, more particularly the catalyst may be of formula Cu / (ZnO)x(MgO)y(Al2O3)z.

[0065] The coefficient x can be between 0.1 and 0.6.

[0066] The coefficient y can be between 2.1 and 3.3.

[0067] The coefficient z can be between 0.3 and 0.9.

[0068] The ratio y / x may be greater than or equal to 1.4, in particular greater than or equal to 4.

[0069] The y / z ratio may be greater than or equal to 2.9, in particular greater than or equal to 3.6.

[0070] The catalyst may be in the form of a powder, granules, or extrudates, in particular in the form of a powder.

[0071] In particular, the catalyst can be obtained by the process for synthesizing a catalyst according to the invention, in particular as described below. Process for synthesizing a catalyst

[0072] The synthesis process makes it possible to synthesize the catalyst according to the invention.

[0073] The total nitrate content, including magnesium nitrate, zinc nitrate and aluminium nitrate, in solution A may be between 0.1 and 2 mol / L, in particular between 0.5 mol / L and 1.5 mol / L.

[0074] The zinc nitrate content in solution A may be between 0.01 and 1 mol / L, in particular between 0.04 mol / L and 0.6 mol / L, more particularly between 0.05 and 0.2 mol / L, or even between 0.06 and 0.1 mol / L.

[0075] The magnesium nitrate content in solution A may be between 0.01 and 1.5 mol / L, in particular between 0.15 mol / L and 0.8 mol / L, more particularly between 0.3 and 0.8 mol / L, or even between 0.5 and 0.7 mol / L.

[0076] The content of aluminum nitrate in solution A may be between 0.01 and 1 mol / L, in particular between 0.1 mol / L and 0.4 mol / L.

[0077] The ratio of the mass of magnesium to the mass of zinc in solution A may be greater than or equal to 1, in particular between 1.5 and 10, more particularly between 2 and 5, in particular between 2.5 and 3.5.

[0078] The molar ratio of magnesium nitrate to zinc nitrate in solution A may be greater than or equal to 1.4, in particular greater than or equal to 2.7, in particular between 4 and 26, more particularly between 5 and 13, in particular between 7 and 10.

[0079] The ratio of the mass of magnesium to the mass of aluminum in solution A may be greater than or equal to 1.5, in particular between 1.6 and 10, more particularly between 1.8 and 5, in particular between 2 and 2.5.

[0080] The molar ratio of magnesium nitrate to aluminum nitrate in solution A may be greater than or equal to 1.4, in particular greater than or equal to 1.6, in particular between 1.7 and 11, more particularly between 2 and 5.5, in particular between 2.2 and 2.8.

[0081] Solution B may have a pH between 11 and 14, in particular between 12 and 13.

[0082] Solution B may comprise an alkali or alkaline earth metal carbonate, in particular sodium carbonate, and an alkali or alkaline earth metal hydroxide, in particular sodium hydroxide.

[0083] The total content of carbonate and hydroxide in solution B may be between 0.1 and 5 mol / L, in particular between 2 mol / L and 3 mol / L.

[0084] The content of alkali or alkaline earth metal carbonate, in particular sodium carbonate, in solution B may be between 0.01 and 2 mol / L, in particular between 0.1 mol / L and 1 mol / L.

[0085] The content of alkali or alkaline earth metal hydroxide, in particular sodium hydroxide, in solution B may be between 0.01 and 5 mol / L, in particular between 1.5 mol / L and 2.5 mol / L.

[0086] The molar ratio of the number of moles of carbonate ions in solution B to the total number of moles of zinc, magnesium and aluminum atoms in solution A, named n(CO32 ) / n(Zn+Mg+Al), can be between 0.05 and 2, in par- particular between 0.5 and 1.

[0087] The molar ratio of the number of moles of sodium hydroxide in solution B to the total number of moles of zinc, magnesium and aluminum atoms in solution A, called n(NaOH) / n(Zn+Mg+Al), may be between 0.1 and 5, in particular between 1 and 2.

[0088] In particular, the total nitrate content in aqueous solution A may be between 0.5 and 1.5 mol / L, the total carbonate and hydroxide content in basic solution B being between 2 and 3 mol / L, the molar ratio n(CO32) / n(Zn+Mg+Al) being between 0.5 and 1 and the molar ratio n(NaOH) / n(Zn+Mg+Al) being between 1 and 2.

[0089] In step b), solution A can be introduced into solution B at a flow rate of between 0.01 mL / min and 20 mL / min, in particular between 1 mL / min and 10 mL / min.

[0090] In step b), solution A may be introduced into solution B at a flow rate of solution A divided by the volume of solution B of between 0.001 min 1 and 0.1 min *. In particular, solution A may be introduced into solution B at a flow rate of between 4 mL / min and 6 mL / min.

[0091] The introduction can be carried out with stirring, in particular using magnetic stirring such as a cross-shaped magnetic bar, for example at a rotation speed of between 200 and 400 revolutions per minute (more commonly called RPM according to the Anglo-Saxon terminology “rounds per minute”).

[0092] In step b), the pH can vary from 13 to 11.

[0093] The pH may be maintained at a value greater than or equal to 11 during step b) by introducing into the mixture of solutions B and A a basic solution C having a pH greater than or equal to 12, in particular greater than or equal to 13. In particular, solution C may comprise an alkali or alkaline-earth metal hydroxide, in particular sodium hydroxide, in particular at a content of between 0.5 mol / L and 5 mol / L.

[0094] Step b) may comprise stirring the mixture obtained after the introduction of solution A into solution B, in particular using magnetic stirring such as a cross-shaped magnetic bar, for example at a rotation speed of between 200 and 400 revolutions per minute. In particular, stirring may be carried out for at least 2 hours, in particular for 3 hours to 5 hours.

[0095] At the end of step b), and before step c), the solid material can be recovered, in particular by centrifugation or filtration, in particular by centrifugation.

[0096] The recovered solid material may be washed with water, in particular distilled water. The solid material may be separated from the water by centrifugation or filtration. In particular, the washing of the solid material may comprise at least 3 washing steps with water, in particular distilled water, the solid material being recovered at least twice by centrifugation and at least once by filtration.

[0097] In particular, the recovered solid material, possibly after washing, can be dried at a temperature ranging from 80°C to 150°C.

[0098] In particular, the solid material, preferably obtained after washing and drying, can be calcined at a temperature of at least 400°C, in particular at a temperature between 400°C and 500°C, in particular for at least 2 hours, for example for 3 hours to 5 hours.

[0099] In particular, step c) can bring together the copper nitrate and the solid material in a ratio of the mass of the solid material to the number of moles of the copper nitrate of between 10 g(material) / mol(nitrate) and 600 g(material) / mol(nitrate), in particular between 150 g(material) / mol(nitrate) and 350 g(material) / mol(nitrate).

[0100] Step c) may be carried out by wet impregnation, i.e. in the presence of water. In particular, the impregnation in step c) may be carried out by bringing the solid material into contact with an aqueous solution of copper nitrate. In particular, an aqueous dispersion comprising from 10 g / L to 140 g / L of solid material and from 0.05 mol / L to 1 mol / L of copper nitrate may be formed.

[0101] In particular, copper nitrate, especially in aqueous solution, can be introduced into an aqueous dispersion of the solid material.

[0102] The copper nitrate may be introduced in the form of an aqueous solution, in particular at a copper nitrate concentration of between 0.05 mol / L and 3 mol / L, in particular between 0.1 mol / L and 0.9 mol / L, into an aqueous dispersion of the solid material, in particular at a solid material concentration of between 1 g / L and 300 g / L, in particular between 100 g / L and 200 g / L. The introduction may be carried out with stirring, in particular using magnetic stirring such as a magnetic bar, for example at a rotation speed of between 10 and 1000 revolutions per minute. In particular, the introduction may be carried out dropwise.

[0103] Alternatively, the copper nitrate may be solubilized directly in an aqueous dispersion of the solid material or the solid material may be dispersed in an aqueous solution of copper nitrate.

[0104] Step c) may comprise stirring the mixture obtained by wet impregnation, in particular using magnetic stirring such as a magnetic bar, for example at a rotation speed of between 200 and 1400 revolutions per minute. In particular, stirring may be carried out for at least 12 hours, in particular for 20 hours to 2 days.

[0105] At the end of step c), and before step d), the impregnated solid material can be recovered, in particular by centrifugation or filtration, in particular by filtration.

[0106] The impregnated solid material can be washed with water, in particular distilled water, and recovered by centrifugation or filtration, in particular by filtration.

[0107] In particular, the impregnated solid material, possibly after washing, can be dried at a temperature ranging from 80°C to 150°C for at least 12 hours, especially at least 20 hours.

[0108] In step d), the impregnated solid material, preferably obtained after washing and drying, may be calcined at a temperature of at least 400°C, in particular at a temperature of between 400°C and 500°C, in particular for at least 2 hours, or even at least 5 hours, for example for 5 hours to 12 hours.

[0109] The calcined solid material can be reduced by contacting with a reducing agent, in particular with hydrogen at a temperature between 250°C and 350°C, in particular for 2 hours to 12 hours.

[0110] The catalyst is obtained after the reduction of the calcined solid material. Method for generating hydrogen

[0111] The method for generating hydrogen may comprise one or more cycles comprising hydrogenation of a dehydrogenated liquid organic hydrogen (LOHC) carrier to the hydrogenated LOHC and dehydrogenation of the hydrogenated LOHC to the dehydrogenated LOHC, referred to as hydrogenation / dehydrogenation cycles.

[0112] Dehydrogenated LOHC and hydrogenated LOHC form a pair called dehydrogenated LOHC / hydrogenated LOHC pair.

[0113] In particular, the dehydrogenated LOHC / hydrogenated LOHC pair may be chosen from the y-butyrolactone / 1,4-butanediol pair, the dimethyl oxalate / mixture of ethylene glycol and methanol pair, and the ethanol / ethyl acetate pair. Preferably, the dehydrogenated LOHC / hydrogenated LOHC pair is the y-butyrolactone / 1,4-butanediol pair.

[0114] The method may comprise repeating the hydrogenation / dehydrogenation cycle. In particular, the method may comprise at least two repetitions of the hydrogenation / dehydrogenation cycle, more particularly at least 5, in particular at least 10, or even at least 50 repetitions of the cycle.

[0115] The hydrogenation reaction is carried out in the presence of the catalyst according to the invention or obtained by the process according to the invention, in particular as described above. The hydrogenation can be carried out in the presence of at least 4% by mass, in particular from 8% to 40% by mass, more particularly from 12% to 30% by mass, in particular from 17% to 25% by mass, of the catalyst relative to the total mass of the dehydrogenated LOHC, in particular chosen from γ-butyrolactone, dimethyl oxalate and ethanol, in particular γ-butyrolactone.

[0116] In particular, the hydrogenation can be carried out in the presence of at least 1% by mass, in particular from 2% to 10% by mass, more particularly from 3% to 7% by mass, of copper, in particular present at the catalyst, relative to the total mass of the dehydrogenated LOHC, in particular chosen from γ-butyrolactone, dimethyl oxalate and ethanol, in particular γ-butyrolactone.

[0117] The hydrogenation may be carried out at a pressure of between 1 MPa and 28 MPa (10 to 280 bar), in particular between 3 MPa and 10 MPa (30 to 100 bar). It may be carried out at a temperature of between 100°C and 300°C, in particular between 140°C and 260°C. The temperature and pressure conditions for the hydrogenation reaction may be maintained for at least 6 hours, in particular at least 12 hours, more particularly for 18 hours to 2 days.

[0118] For example, the dehydrogenated LOHC, in particular chosen from γ-butyrolactone, dimethyl oxalate and ethanol, in particular γ-butyrolactone, is preheated within a reactor, to a temperature between 100°C and 260°C, then mixed with hydrogen at the reaction pressure, the mixture formed then being able to be injected into a fixed bed reactor, loaded with catalyst. The hydrogen and the dehydrogenated LOHC can also be fed directly separately into the reactor.

[0119] In particular, the hydrogenation can be carried out in an isothermal reactor.

[0120] At the end of the hydrogenation, the compounds present can be separated from each other. In particular, the hydrogen and the hydrogenated LOHC produced, in particular in a mixture with other liquids, can be separated at the end of the hydrogenation reaction by gas / liquid separation.

[0121] The method can be operated in batch or semi-batch reactors or even continuously in a “slurry”, “trickle bed”, fluidized bed or fixed bed type reactor.

[0122] The dehydrogenation reaction is carried out in the presence of the catalyst according to the invention or obtained by the process according to the invention, in particular as described above. The dehydrogenation can be carried out in the presence of at least 4% by mass, in particular from 8% to 40% by mass, more particularly from 12% to 30% by mass, in particular from 17% to 25% by mass, of the catalyst relative to the total mass of hydrogenated LOHC, in particular chosen from 1,4-butanediol, a mixture of ethylene glycol and methanol, and ethyl acetate, in particular 1,4-butanediol.

[0123] In particular, the dehydrogenation can be carried out in the presence of at least 1% by mass, in particular from 2% to 10% by mass, more particularly from 3% to 7% by mass, of copper, in particular present at the catalyst, relative to the total mass of hydrogenated LOHC, in particular chosen from 1,4-butanediol, a mixture of ethylene glycol and methanol, and ethyl acetate, in particular 1,4-butanediol.

[0124] The dehydrogenation may be carried out at a pressure of between 0.1 MPa and 1 MPa (1 to 10 bar). It may be carried out at a temperature of between 110°C and 320°C, in particular of between 140°C and 260°C. The temperature and pressure conditions for the hydrogenation reaction may be maintained for at least 1 h, in particular for 4 h to 10 h.

[0125] For example, hydrogenated LOHC, in particular chosen from 1,4-butanediol, a mixture of ethylene glycol and methanol, and ethyl acetate, in particular 1,4-butanediol, is preheated to the reaction temperature and injected into a fixed bed reactor, loaded with catalyst.

[0126] The method can be operated in a batch, semi-batch or continuous reactor.

[0127] At the end of the dehydrogenation, the reaction products can be separated from each other. In particular, the dehydrogenated LOHC produced, especially in a mixture with other liquids, can be separated from the hydrogen by gas / liquid separation.

[0128] Preferably, the method does not use a solvent.

[0129] The hydrogenation and dehydrogenation can be carried out with only the catalyst according to the invention or obtained according to the invention as catalyst.

[0130] The hydrogenation can be carried out from a mixture consisting of the catalyst, hydrogen, and dehydrogenated LOHC, in particular chosen from γ-butyrolactone, dimethyl oxalate and ethanol, in particular γ-butyrolactone.

[0131] The dehydrogenation can be carried out from a mixture consisting of the catalyst and the hydrogenated LOHC, in particular chosen from 1,4-butanediol, a mixture of ethylene glycol and methanol, and ethyl acetate, in particular 1,4-butanediol.

[0132] The step of dehydrogenating hydrogenated LOHC to dehydrogenated LOHC, in particular 1,4-butanediol to y-butyrolactone, a mixture of ethylene glycol and methanol to dimethyl oxalate, and ethyl acetate to ethanol, in particular 1,4-butanediol to y-butyrolactone, may comprise the generation of hydrogen.

[0133] The cycle may further include the use of the generated hydrogen as an energy source or as a reactant in industrial processes.

[0134] According to a particular embodiment, the method comprises the hydrogenation of γ-butyrolactone to 1,4-butanediol and the dehydrogenation of 1,4-butanediol to γ-butyrolactone, the hydrogenation and the dehydrogenation being carried out in the presence of the catalyst.

[0135] The conversion rate of γ-butyrolactone from the hydrogenation reaction may be greater than or equal to 80%, in particular greater than or equal to 84%. The selectivity to 1,4-butanediol from the hydrogenation reaction may be greater than or equal to 80%, in particular greater than or equal to 85%, or even greater than or equal to 90%.

[0136] The conversion rate of γ-butyrolactone from the hydrogenation reaction corresponds to the number of moles of γ-butyrolactone reacted divided by the number of moles of γ-butyrolactone initially present. The selectivity to 1,4-butanediol from the hydrogenation reaction corresponds to the number of moles of 1,4-butanediol formed divided by the number of moles of γ-butyrolactone reacted.

[0137] The conversion rate of 1,4-butanediol from the dehydrogenation reaction may be greater than or equal to 95%, in particular greater than or equal to 99%. The selectivity to y- butyrolactone of the dehydrogenation reaction may be greater than or equal to 75%, in particular greater than or equal to 85%, or even greater than or equal to 95%.

[0138] The conversion rate of 1,4-butanediol from the dehydrogenation reaction corresponds to the number of moles of 1,4-butanediol reacted divided by the number of moles of 1,4-butanediol initially present. The selectivity to γ-butyrolactone from the dehydrogenation reaction corresponds to the number of moles of γ-butyrolactone formed divided by the number of moles of 1,4-butanediol reacted. Applications

[0139] The hydrogen generated by the method or use according to the invention can be used for applications in the field of transport, in particular rail, maritime or road, in particular maritime, of construction, in particular for heating, or of energy storage. The hydrogen generated can be exploited as a source of decarbonized energy, in particular by combustion or in electrochemical energy conversion devices, or as a reactant in industrial processes, in particular in industrial methanation processes or in processes for hydrogenating petroleum fractions.

[0140] The hydrogen generated can be used as a reactant in an industrial process (hydrodesulfurization, hydrogenation of different compounds, recovery of CO2 into gaseous or liquid fuels, etc.). In particular, the hydrogen generated can be used in hydrogenation processes. It can, for example, be used in chemical reduction reactions, particularly in catalytic chemical reduction reactions.

[0141] Advantageously, the hydrogen generated can be used in a process for hydrogenating petroleum fractions, in particular heavy petroleum fractions, to transform them into fuels such as diesel or kerosene. This type of process is generally operated in hydrocracking units.

[0142] Advantageously, the hydrogen from hydrogenated LOHC can also be used in an industrial methanation process, in particular catalytic or biological, to generate methane by hydrogenation reaction of carbon monoxide or carbon dioxide.

[0143] Among the methanation processes suitable for such use, mention may be made of processes for converting electricity into gas (PtG or P2G, "power to gas") or into liquid (PtL or P2L, "power to liquid"). Such use has the advantage of being able to generate hydrogen from hydrogenated LOHC directly on a CO2-emitting site in order to transform it into methane, and reduce CO2 emissions on the site without requiring intermediate storage and transport of the emitted CO2 or the installation of a hydrogen production unit on the same site.

[0144] The hydrogen produced can also be used as an energy vector decarbonized either by combustion or by powering an electrochemical energy conversion device.

[0145] An electrochemical energy conversion device makes it possible to convert chemical energy into electrical energy. These may be fuel cells, in particular proton exchange membrane or solid oxide fuel cells.

[0146] A combustion energy conversion device converts chemical energy into thermal energy (and then possibly into mechanical or electrical energy). These may be thermal engines powered by hydrogen such as hydrogen car engines, jet engines such as rocket engines, boilers powered by hydrogen or even power plants based on hydrogen combustion. Examples

[0147] Example 1: Synthesis of a catalyst according to the invention

[0148] - An aqueous solution A containing 11.7360g of Zn(NO3)2,6H2O, 84.3461g of Mg(NO3)2.6H2O and 49.3484g of A1(NO3)3.9H2O in 500mL of distilled water is prepared. Solution A has a pH of 2.34.

[0149] An aqueous solution B containing 37.0961g of Na2CO3 and 35.9973g of NaOH in 500mL of distilled water is prepared. Solution B has a pH of 12.88.

[0150] A third solution C of sodium hydroxide in distilled water at a concentration of 3 mol / L is prepared.

[0151] Solution A is added to solution B with a peristaltic pump at a flow rate of 5 mL / min while stirring using a magnetic stirrer such as a cross-shaped magnetic bar at a rotation speed of 300 RPM. Throughout the addition of solution A, the pH is controlled and maintained at a value greater than 11 by dropwise addition of solution C. A solid material forms in the reaction mixture during the addition. At the end of the addition, the resulting mixture is stirred for 4 hours.

[0152] The solid material is recovered by centrifugation. It is then washed 3 times with distilled water, its recovery being carried out 2 times by centrifugation and 1 time by filtration on a Buchner frit.

[0153] The solid material, once recovered and washed, is dried at 100°C overnight and then calcined at 450°C for 4 hours. Analysis by inductively coupled plasma spectrometry (more commonly called ICP according to the English terminology "inductively coupled plasma") of the solid material obtained makes it possible to determine a zinc (Zn) content of 19% by mass, an aluminum (Al) content of 25% by mass and a magnesium (Mg) content of 55% by mass relative to the total mass of the solid material.

[0154] - The catalyst is then synthesized by wet impregnation of the solid material obtained previously. To do this, a solution D containing 31.3618g of Cu(NO3)2, 3H2O in 247mL of distilled water is prepared. 33g of the previously obtained solid material is dispersed in 220mL of distilled water and the dispersion obtained is stirred using a magnetic stirrer equipped with a magnetic bar at 750 RPM for 1h to form a dispersion E.

[0155] Solution D is then added dropwise into dispersion E over a period of 1 hour. After addition, the mixture obtained is stirred using a magnetic stirrer equipped with a magnetic bar at 750 RPM for 1 night.

[0156] The solid material is recovered by filtration. It is then washed with distilled water once and recovered by filtration, then the solid material is dried overnight at 100°C.

[0157] The solid material is then calcined at 450°C for 1 night and then reduced under hydrogen at 280°C for 6 hours to obtain the catalyst.

[0158] The ICP analysis of the catalyst obtained makes it possible to determine a mass content of copper (Cu) of 24% by mass, of zinc (Zn) of 9% by mass, of aluminum (Al) of 12% by mass and of magnesium (Mg) of 26% by mass, relative to the total mass of the catalyst.

[0159] Example 2: Hydrogenation and dehydrogenation of the y-butyrolactone / 1,4-butanediol couple catalyzed by a catalyst according to the invention

[0160] The catalyst synthesized in Example 1 is used to carry out a hydrogenation / dehydrogenation cycle of the LOHC y-butyrolactone (GBL) / 1,4-butanediol (BDO) couple.

[0161] 25g of GBL and a mass of catalyst corresponding to 5% by mass of Cu per relative to the mass of GBL are introduced into a closed Parr reactor.

[0162] A hydrogenation / dehydrogenation cycle was then carried out in batch mode, keeping the same catalyst during the hydrogenation and dehydrogenation reactions. In other words, the catalyst is introduced only before the hydrogenation reaction. The hydrogenation reaction is carried out in the reactor by applying a pressure of 50 bar of H2 and at a temperature of 200°C in batch mode for 24 hours. The dehydrogenation reaction is then carried out in the reactor under atmospheric pressure and at a temperature of 205°C in batch mode for 6 hours. The products obtained at the end of the hydrogenation reaction and at the end of the dehydrogenation reaction are quantitatively analyzed by gas chromatography coupled with mass spectrometry (more commonly called GC-MS according to the English terminology "gas chromatography-mass spectrometry").

[0163] The conversion rate and selectivity measured by GC-MS at the end of each hydrogenation or dehydrogenation reaction are summarized in Table 1.

[0164] [Tables 1] Cycle Reaction Conversion (m%) Selectivity (ni%) EDO GBL 1 Hydrogenation 89.8 yy 9 Dehydrogenation 99.4 73.0

[0165] The results obtained show that the catalyst can be used to carry out a complete hydrogenation / dehydrogenation cycle of the GBL / BDO couple with a good conversion rate of the starting product, greater than 85%, and good selectivity towards the desired product, greater than 73%.

Claims

Claims

1. A catalyst comprising copper, zinc oxide, magnesium oxide and aluminum oxide, the catalyst comprising, relative to its total mass: - from 10% to 30% by mass of copper; - from 0.5% to 42.4% by mass of zinc; - from 12.5% ​​to 30% by mass of magnesium; and - from 1% to 20% by mass of aluminum; with the ratio of the mass of magnesium to the mass of zinc Mg / Zn being greater than or equal to 0.5, and the ratio of the mass of magnesium to the mass of aluminum Mg / Al being greater than or equal to 1.

3.

2. Catalyst according to the preceding claim, in which the ratio of the mass of magnesium to the mass of zinc Mg / Zn is greater than or equal to 1, in particular between 1.5 and 10, more particularly between 2 and 5, in particular between 2.5 and 3.

5.

3. Catalyst according to claim 1 or 2, in which the ratio of the mass of magnesium to the mass of aluminum Mg / Al is greater than or equal to 1.5, in particular between 1.6 and 10, more particularly between 1.8 and 5, in particular between 2 and 2.

5.

4. Catalyst according to any one of the preceding claims, the catalyst comprising, relative to its total mass, from 10% to 28% by mass, in particular from 15% to 25% by mass, in particular from 20% to 25% by mass, of copper.

5. Catalyst according to any one of the preceding claims, the catalyst comprising, relative to its total mass, from 1% to 40% by mass, in particular from 5% to 40% by mass, more particularly from 5% to 30% by mass, in particular from 5% to 25% by mass, or even from 5% to 15% by mass, of zinc.

6. Catalyst according to any one of the preceding claims, the catalyst comprising, relative to its total mass, from 15% to 30% by mass, in particular from 20% to 30% by mass, more particularly from 23% to 28% by mass of magnesium.

7. Catalyst according to any one of the preceding claims, the catalyst comprising, relative to its total mass, from 5% to 20% by mass, in particular from 6% to 15% by mass, in particular from 10% to 15% by mass of aluminum.

8. Catalyst according to any one of the preceding claims, the catalyst being made up of at least 95% by mass, in particular at least 99% by mass, more particularly at least 99.9% by mass, or even 100% by mass, relative to its total mass, of copper and / or copper (II) oxide, zinc oxide, magnesium oxide and aluminium oxide.

9. A catalyst according to any preceding claim, wherein the copper is present on a support comprising zinc oxide, magnesium oxide and aluminium oxide, the support being in particular in the form of particles.

10. A catalyst according to any preceding claim, wherein the copper is in the zero oxidation state or in the form of copper (II) oxide, in particular in the zero oxidation state.

11. A method for synthesizing a catalyst, in particular according to any one of the preceding claims, comprising copper, zinc oxide, magnesium oxide and aluminum oxide, the method comprising at least the steps of: a) providing an aqueous solution A comprising magnesium nitrate, zinc nitrate and aluminum nitrate, the ratio of the mass of magnesium to the mass of zinc Mg / Zn being greater than or equal to 0.5 and the ratio of the mass of magnesium to the mass of aluminum Mg / Al being greater than or equal to 1.3; b) introducing solution A into a basic solution B of pH greater than or equal to 11, in particular greater than or equal to 12, comprising carbonate ions to form a solid material by coprecipitation, the pH of solution B supplemented with solution A being maintained at a value greater than or equal to 11 during step b);c) impregnating the solid material, optionally after calcination, with copper nitrate; d) calcining and reducing the impregnated solid material; and e) optionally recovering the catalyst obtained at the end of step d).;

12. Method according to the preceding claim, according to which the impregnation in step c) is carried out by bringing the solid material into contact with an aqueous solution of copper nitrate, the copper nitrate, in particular in aqueous solution, being in particular introduced into an aqueous dispersion of the solid material.

13. Method for generating hydrogen comprising at least one cycle comprising: - the hydrogenation of a dehydrogenated liquid organic hydrogen (LOHC) vector into hydrogenated LOHC; and - the dehydrogenation of hydrogenated LOHC into dehydrogenated LOHC; the hydrogenation and dehydrogenation being carried out in the presence of the catalyst according to any one of claims 1 to 10 or obtained by the process according to any one of claims 11 or 12.

14. Method according to the preceding claim, the dehydrogenated LOHC / hydrogenated LOHC pair being chosen from the y-butyrolactone / l,4-butanediol pair, the dimethyl oxalate / mixture of ethylene glycol and methanol pair, and the ethanol / ethyl acetate pair, preferably being the y-butyrolactone / l,4-butanediol pair.

15. A method according to claim 13 or 14, comprising repeating the cycle, in particular at least two repetitions of the cycle, more particularly at least 5, in particular at least 10, or even at least 50 repetitions of the cycle.

16. Method according to any one of claims 13 to 15, the hydrogenation being carried out in the presence of at least 1% by mass, in particular from 2% to 10% by mass, more particularly from 3% to 7% by mass, of copper, in particular present at the catalyst level, relative to the total mass of the dehydrogenated LOHC, in particular of the γ-butyrolactone.

17. Method according to any one of claims 13 to 16, the hydrogenation being carried out at a pressure of between 1 MPa and 28 MPa, in particular between 3 MPa and 10 MPa, and at a temperature of between 100°C and 300°C, in particular between 140°C and 260°C.

18. Method according to any one of claims 13 to 17, the dehydrogenation being carried out in the presence of at least 1% by mass, in particular 2% to 10% by mass, in particular 3% to 7% by mass, of copper, in particular present at the catalyst, relative to the total mass of hydrogenated LOHC, in particular 1,4-butanediol.

19. Method according to any one of claims 13 to 18, the dehydrogenation being carried out at a pressure of between 0.1 MPa and 1 MPa and at a temperature of between 110°C and 320°C, in particular of between 140°C and 260°C.

20. Use of the catalyst according to any one of claims 1 to 10 or obtained by the process according to any one of claims 11 or 12 for generating hydrogen by catalytic dehydrogenation of a hydrogenated LOHC into the dehydrogenated LOHC, and for regenerating the dehydrogenated LOHC into the hydrogenated LOHC, the dehydrogenated LOHC / hydrogenated LOHC pair being chosen in particular from the γ-butyrolactone / 1,4-butanediol pair, the dimethyl oxalate / mixture of ethylene glycol and methanol pair, and the ethanol / ethyl acetate pair, in particular for generating hydrogen by catalytic dehydrogenation of 1,4-butanediol into γ-butyrolactone, and for regenerating 1,4-butanediol by catalytic hydrogenation of γ-butyrolactone.