Magnetic material comprising iron, an oxide matrix and silicon carbide.

Abstract

The invention relates to a magnetic material comprising at least iron, in metallic form and / or in oxide form, at least one oxide matrix, the iron content being between 15% and 70% by weight in element iron relative to the total weight of said material, and at least silicon carbide in its alpha crystallographic form (α-SiC), characterized in that said material comprises at most 25% by weight of hematite relative to the total weight of said material, said material being in the form of beads or extrudates.

Description

Title of the invention: Magnetic material comprising iron, an oxide matrix and silicon carbide. Scope of the invention

[0001] The invention relates to a novel composite magnetic material containing metallic iron and / or iron oxide, an oxide matrix, and silicon carbide in its alpha crystallographic form (also referred to herein as alpha-SiC or a-SiC). The magnetic material is capable of providing induced heating in response to an applied alternating magnetic field. The material can advantageously be used as a heating material in a catalytic reactor, as a catalyst support, or as a catalyst in catalytic processes, particularly processes for the conversion of bio-based molecules and carbon dioxide. Previous art

[0002] Electromagnetic induction heating technology is used in numerous fields of application, such as metallurgy, biomedical applications, and more recently, catalytic oxidation reactions. This technology allows for significant, locally targeted heating, very close to the active sites. It is therefore particularly advantageous for endothermic reactions of heat-sensitive compounds with a short lifetime in the reactor, such as bio-based oxygenated products.

[0003] This heating technology generally employs magnetic materials (superparamagnetic, ferromagnetic, ferrimagnetic) as a heating agent. Magnetic materials generally consist of a magnetic core comprising one or more metals or oxides. Examples include iron, cobalt, nickel, copper, and the alloys FeCo, NiCo, NiFe, CuNi, and CuCo.

[0004] Such a material can be used pure or incorporated into an oxide matrix, for example by impregnating a powder or a previously shaped oxide matrix. By this preparation method, the quantity of magnetic material incorporated is small, generally less than 20% by weight, and distributed exclusively on the surface of the oxide matrix. The heating, being inhomogeneous, does not occur at the core of the oxide grain.

[0005] Exxon patents US4,252,679 and US4,255,289 disclose a magnetic catalyst composed of an iron or cobalt alloy dispersed in an alumina oxide matrix by spray-drying with the addition of phosphoric acid. The grain size of the magnetic catalyst is less than 800 pm.

[0006] US patent application 2023 / 0356198 describes the use of a catalytic composition consisting of a magnetic material containing ferrite and a catalytic agent, in powder form coated on ceramics in particular for NOx oxidation reactions.

[0007] Patent application WO2017 / 186608 discloses a porous ferromagnetic material, in powder form, with a spinel, inverted spinel, or perovskite-type structure for the vapor reforming reaction with induction heating. Patent application WO2020 / 254184 describes a ceramic-type catalyst support comprising particles with a ferromagnetic core and an oxide shell, said particles being dispersed in an oxide matrix. The particle size is less than 500 pm, preferably less than 10 pm. The support has a specific surface area greater than 1 m² / g, preferably between 5 and 50 m² / g.

[0008] Patents FR3100990 and FR3100988 disclose a methanation process in presence of a ferromagnetic material in the form of micrometric powder and / or wires based on iron or an iron alloy, said material being suitable for heating by magnetic induction using a magnetic field inductor.

[0009] Silicon carbide (also referred to here as SiC) is an inorganic material possessing particular properties in terms of stability, conductivity, mechanical and chemical resistance which make it interesting for applications in catalysis.

[0010] There is therefore still a strong interest in developing new magnetic materials that can be used as a heating material for energy-intensive endothermic catalytic reactions.

[0011] The Applicant has developed a new shaped magnetic material with good mechanical strength, capable of providing induced heating in response to an applied alternating magnetic field. This material can be used as a heating material for the dehydration reaction of a charge comprising an alcohol, and as both a heating material and a catalyst for the CO2 reduction reaction. The material according to the invention is also stable under hydrothermal conditions, i.e., conditions combining water pressure and temperature. Its textural and magnetic properties are preserved. Objects of the invention

[0012] The present invention relates to a magnetic material comprising at least iron, in metallic form and / or in oxide form, at least one oxide matrix, the iron content being between 15% and 70% by weight as elemental iron relative to the total weight of said material, and at least silicon carbide in its alpha crystallographic form (α-SiC), characterized in that said material comprises at most 25% by weight of hematite relative to the total weight of said material, said material being in the form of beads or extrudates.

[0013] According to one or more embodiments of the invention, the oxide matrix is ​​chosen from aluminium, zirconium, titanium oxides, and clays.

[0014] According to one or more embodiments of the invention, the silicon carbide content is between 1% and 50% by weight relative to the total weight of the material.

[0015] According to one or more embodiments of the invention, said material has a mechanical resistance value measured by grain-by-grain crushing greater than 0.65 daN / mm.

[0016] According to one or more embodiments of the invention, said material has a specific absorption rate of between 2 W / g and 120 W / g after activation by a magnetic field of amplitude between 1 mT and 50 mT at a frequency between 90 kHz and 300 kHz.

[0017] Another object according to the invention relates to a method for preparing a magnetic material according to the invention comprising at least the following steps:

[0018] a) at least one source of iron in metallic or oxide or oxyhydroxide form, an oxide matrix source, a silicon carbide source in its alpha crystallographic form (a-SiC) and at least one solvent are brought into contact to obtain a paste, said iron source being in the form of a powder with a grain size between 1 pm and 500 pm;

[0019] b) the paste obtained at the end of step a) is shaped to obtain a precursor of material;

[0020] c) the precursor material obtained at the end of step b) is dried at a temperature below 250°C to obtain a dried precursor material;

[0021] d) the dried material precursor obtained at the end of step c) is calcined at a temperature between 250°C and 1000°C.

[0022] According to one or more embodiments of the invention, said process includes a step e) in which the material obtained at the end of step d) is reduced to a temperature between 200°C and 600°C and for a period between 1 hour and 10 hours in the presence of a reducing gas.

[0023] According to one or more embodiments of the invention, said material obtained at the end of step d) is subjected to hydrothermal treatment at a temperature between 100°C and 1100°C.

[0024] According to one or more embodiments of the invention, step e) is carried out in the presence of a reducing gas comprising between 25 vol% and 100 vol% of hydrogen, the hydrogen flow rate being between 0.01 and 100 NL / hour / gram of material.

[0025] According to one or more embodiments of the invention, the iron source is chosen from metallic iron, magnetite, maghemite, goethite, lepidocrocite and hematite, taken alone or in mixture.

[0026] According to one or more embodiments of the invention, when the oxide matrix is ​​an aluminum oxide, the source of said oxide matrix is ​​a boehmite.

[0027] According to one or more embodiments of the invention, when the oxide matrix is ​​a clay, the source of said oxide matrix is ​​chosen from kaolin, kaolinite, metakaolin, and montmorillonite, taken alone or in mixture.

[0028] Another object according to the invention relates to a catalyst comprising an active phase based on at least one metal chosen from groups 6 to 11 of the periodic table, preferably chosen from Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt, Re, Au, Ag, Mo, W, Cr, taken alone or in mixture, and a support in the form of a magnetic material according to the invention or prepared by the material preparation process according to the invention.

[0029] According to one or more embodiments of the invention, said metal is chosen from Co, Ni, and Cu, and in which the content of said metal is between 0.5% and 30% by weight of the element of said metal relative to the total weight of the catalyst.

[0030] According to one or more embodiments of the invention, said metal is chosen from Pt, Pd, Au, Ag, Ru, and in which the content of said metal is between 0.01% and 10% by weight of the element of said metal relative to the total weight of the catalyst.

[0031] Another object according to the invention relates to a method for preparing a catalyst according to the invention comprising at least the following steps:

[0032] fl) a liquid solution is prepared in aqueous or organic phase comprising at least one precursor of the active phase based on at least one metal chosen from groups 6 to 11 of the periodic table, preferably chosen from Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt, Re, Au, Ag, Mo, W, Cr, taken alone or in mixture, preferably at a temperature between 5°C and 80°C, more preferably between 10°C and 70°C;

[0033] f2) the solution prepared in step fl) is impregnated onto the material according to the invention or prepared according to the invention, the volume of the solution being advantageously between 0.9 and 1.1 times the porous volume of said material;

[0034] f3) Optionally, the catalyst precursor obtained in step f2) is subjected to a maturation in order to obtain a catalyst precursor;

[0035] f4) the catalyst precursor obtained in step f2), optionally f3), is dried at a temperature greater than or equal to 15°C and less than 250°C;

[0036] f5) the catalyst precursor obtained in step f4) is calcined at a temperature between 250°C and 600°C.

[0037] Another object relates to a process for hydrogenating CO2 carried out at a temperature between 180°C and 800°C, at a pressure between 0.1 MPa and 13 MPa, at a hydrogen / CO2 molar ratio between 0.1 and 10 and at an hourly volumetric rate between 100 h 1 and 40000 h 1 in the presence of a catalyst according to the invention, said process being carried out under the action of a magnetic field of amplitude between 1 mT and 50 mT at a frequency between 90 kHz and 300 kHz.

[0038] Another object relates to a process for dehydrating a charge comprising at least one alcohol carried out at a temperature between 180°C and 450°C, at a pressure between 0.1 MPa and 12 MPa, at a mass flow rate ratio of charge divided by the total mass of the material and the catalyst between 0.01 h 1 and 100 h 1 in the presence of a dehydration catalyst and a magnetic material according to the invention, said process being carried out under the action of a magnetic field of amplitude between 1 mT and 50 mT at a frequency between 90 kHz and 300 kHz. Detailed description of the invention

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

[0040] Mass percentages are expressed relative to the anhydrous mass of the final composite material. This anhydrous mass is determined by a measurement known as Loss on Ignition (LOI), which corresponds to the mass change resulting from heating the sample at 1000°C for 2 hours. The loss on ignition is expressed as a percentage by mass of the dry matter.

[0041] The specific surface area BET is measured by nitrogen physisorption according to ASTM D3663-03, a method described in the book Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academy Press, 1999.

[0042] In the present description, according to the IUP AC convention, micropores are pores with a diameter less than 2 nm, i.e. 0.002 pm; mesopores are pores with a diameter greater than or equal to 2 nm, i.e. 0.002 pm and less than or equal to 50 nm, i.e. 0.05 pm; and macropores are pores with a diameter greater than 50 nm, i.e. 0.05 pm.

[0043] The total pore volume is measured by mercury porosimetry according to ASTM D4284-92 with a wetting angle of 140°, for example using an Autopore III™ device from Microméritics™.

[0044] In order to obtain better accuracy, the value of the total pore volume corresponds to the value of the total pore volume measured by intrusion with the mercury porosimeter measured on the sample less the value of the total pore volume measured by intrusion with the mercury porosimeter measured on the same sample for a pressure corresponding to 30 psi (approximately 0.2 MPa).

[0045] The volume of macropores and mesopores is measured by mercury intrusion porosimetry according to ASTM D4284-83 at a maximum pressure of 4000 bars (400 MPa), using a surface tension of 484 dyne / cm and a contact angle of 140°. The value at which mercury fills all intergranular voids is set at 0.2 MPa, and beyond this value, mercury is considered to penetrate the pores of the sample.

[0046] The macroporous volume of the material according to the invention is defined as the cumulative volume of mercury introduced at a pressure between 0.2 MPa and 30 MPa, corresponding to the volume contained in pores with an apparent diameter greater than 50 nm.

[0047] The mesoporous volume of the material according to the invention is defined as the cumulative volume of mercury introduced at a pressure between 30 MPa and 400 MPa, corresponding to the volume contained in the pores with an apparent diameter between 2 nm and 50 nm.

[0048] The median mesoporous diameter is also defined as the diameter such that all the pores, among all the pores constituting the mesoporous volume, of a size less than this diameter constitute 50% of the total mesoporous volume determined by intrusion with a mercury porosimeter.

[0049] The metal content is measured by X-ray fluorescence or by inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0050] The crystallographic structure of metallic iron or oxide is determined by the X-ray diffraction (XRD) technique. More specifically, in the case of a copper source, the 20 lines at 44.69° and 65.05° are associated with the crystallographic form of metallic iron, the 20 lines at 30.08°, 35.43°, 56.94°, and 62.53° are associated with the magnetite crystallographic form, the 20 lines at 30.26°, 35.65°, 43.33°, 57.31°, and 62.95° are associated with the maghemite crystallographic form, and the 20 lines at 33.16°, 35.64°, and 49.47° are associated with the maghemite crystallographic form. 54.08° and 62.95° are associated with the hematite crystallographic form. In the case of SiC, the diffraction lines are 34.09°; 35.65°; 38.13° and 59.99° are associated with the a-SiC crystallographic form (polytype 6H, hexagonal).

[0051] Throughout this text, lateral crush resistance refers to the mechanical resistance of the material according to the invention as determined by the grain-by-grain crush (GBC) test. This is a standardized test (ASTM D4179-01) which consists of subjecting a material in the form of a millimeter-sized object, such as a ball, pellet, or extrudate, to a compressive force that causes it to break. This test is therefore a measure of the tensile strength of the material. The analysis is repeated on a number of individual solids, typically between 10 and 200. The average of the measured lateral breaking forces constitutes the average GBC, which is expressed in units of force (N) for granules and in units of force per unit length (daN / mm or decaNewton per millimeter of extrudate length) for extrudates.

[0052] In the following text, the grain size or particle size distribution of the constituents of the materials obtained according to the invention is measured by laser scattering particle size analysis. This indirect measurement technique makes it possible to determine the particle size distribution (on the micron to millimeter scale). This analytical method uses the principle of light scattering (Mie theory) and / or diffraction (Fraunhofer theory and Mie theory). Particles illuminated by the laser light deflect the light from its principal axis. The amount of light deflected and the magnitude of the deflection angle allow for the precise measurement of the particle size. The powder is conveyed by a solvent (water, isopropanol) or by air before passing in front of the laser beam. Two paths are thus distinguished: the wet path and the dry path.

[0053] The wet method allows for the characterization of dispersions (elementary particle size distribution after dispersion) or suspended solids (aggregate particle size distribution). The measured particles are in the range of 0.02 pm to 2000 pm.

[0054] Dry particle size analysis allows for the characterization of powders without disrupting their initial aggregation. The measurement range extends from 0.2 µm to 2000 µm. In the present invention, dry particle size analysis is used to measure the grain size of the constituents of the material of the invention.

[0055] The heating capacity of the material is defined by its specific absorption rate, also called SAR (Specific Absorption Rate) in Anglo-Saxon terminology. It corresponds to the amount of energy absorbed per unit mass as a function of the intensity of the applied alternating magnetic field and is expressed in watts per gram of material. The SAR is measured by calorimetry. More precisely, it involves measuring the temperature rise per unit time when the sample is heated by magnetic induction. To do this, a quantity of material is weighed and placed in a tube in the presence of water and a thermocouple. The tube is then placed at the center of a coil to apply an alternating magnetic field of 47.1 mT at a frequency of 93 kHz. The SAR value is then determined by the following equation:

[0056] [Math.l]

[0057] with Cp; and m; representing respectively the specific heat capacities and the masses introduced of the elements of the system.

[0058] By hourly volumetric velocity “PPH”, we mean the mass flow rate of the feed at the reactor inlet in kg / h at 15°C and 0.1MPa divided by the mass of material in kg contained in the reactor. Magnetic material

[0059] A first object of the invention relates to a magnetic material comprising at least iron, in metallic form and / or in oxide form, at least one oxide matrix, the iron content being between 15% and 70% by weight in element iron relative to the total weight of said material, and at least silicon carbide in its alpha crystallographic form (a-SiC), characterized in that said material comprises at most 25% by weight of hematite relative to the total weight of said material, said material being in the form of beads or extrudates and in that said material.

[0060] The presence of silicon carbide improves heat transfer within the material. The presence of silicon carbide also improves the mechanical strength properties of the material. Finally, the material according to the invention exhibits good crush resistance (EGG) compared to an oxide-based support lacking silicon carbide.

[0061] The magnetic material according to the invention is capable of providing induced heating in response to an applied alternating magnetic field. Heating is thus initiated within a reaction chamber itself, rapidly and with minimal energy input, resulting in significant energy cost savings.

[0062] Said material has an iron content of between 15% and 70% by weight, preferably between 20% and 65% by weight, and even more preferably between 25% and 60% by weight in iron element relative to the total weight of the material.

[0063] According to an essential feature of the invention, the magnetic material comprises at most 25% by weight of hematite relative to the total weight of said material, preferably at most 10% by weight, more preferably at most 5% by weight, and even more preferably at most 3% by weight relative to the total weight of the material. In one embodiment of the invention, said magnetic material does not comprise hematite. In another embodiment of the invention, said material comprises between 0.1 and 25% by weight of hematite relative to the total weight of said material, preferably between 0.5% and 10% by weight, and even more preferably between 1 and 5% by weight. Above 25% by weight, the magnetic properties of the material are degraded, making it impossible to provide effective heating when an alternating magnetic field is applied.

[0064] The oxide matrix may be chosen from aluminium oxides, zirconium oxides, titanium oxides, clays.

[0065] In an embodiment according to the invention, the oxide matrix is ​​alumina, which can be present in all possible crystallographic forms: alpha, delta, theta, chi, gamma, etc., alone or in mixtures. Preferably, the alumina is chosen from delta, theta, or gamma alumina, and even more preferably gamma alumina.

[0066] In another embodiment of the invention, the oxide matrix is ​​a clay, that is to say, an oxide matrix comprising one or more silicate-based or aluminosilicate materials, which may, for example, be in the form of kaolin, kaolinite, metakaolin, or montmorillonite, without limitation. Preferably, the oxide matrix comprises kaolin, kaolinite, metakaolin, or montmorillonite, alone or in mixtures.

[0067] The material advantageously has between 1% and 50% by weight of silicon carbide relative to the total weight of the material, preferably between 2% and 40% by weight, preferably from 3% to 30% by weight, and most preferably from 5% to 25% by weight, and more preferably between 5% and 18% by weight.

[0068] Preferably, said material has a total pore volume (TPV) between 0.05 and 1 cm3 / g, more preferably between 0.1 and 0.90 cm3 / g, even more preferably between 0.1 and 0.70 cm3 / g, and even more preferably between 0.1 and 0.6 cm3 / g.

[0069] Preferably said material has a macroporous volume between 0.01 and 0.1 cm3 / g, more preferably between 0.01 and 0.08 cm3 / g, even more preferably between 0.02 and 0.07 cm3 / g, and even more preferably between 0.02 and 0.06 cm3 / g.

[0070] Said material advantageously has a specific surface area between 1 m2 / g and 300 m2 / g, preferably between 1 m2 / g and 250 m2 / g, more preferably between 1 m2 / g and 200 m2 / g, even more preferably between 1 and 100 m2 / g, and even more preferably between 1 and 50 m2 / g.

[0071] Advantageously, said material has a mechanical resistance value measured by grain-by-grain crushing greater than 0.65 daN / mm, preferably greater than 0.85 daN / mm, more preferably greater than 0.9 daN / mm.

[0072] According to one or more embodiments, said material exhibits a SAR between 2 W / g and 120 W / g after activation by a magnetic field of amplitude between 1 mT and 50 mT at a frequency between 90 kHz and 300 kHz.

[0073] Said material is in the form of beads or extrudates.

[0074] When the material is in the form of beads, the diameter of the beads is generally between 0.5 mm and 10 mm, preferably between 1 mm and 5 mm.

[0075] When the material is in the form of an extrudate, the length of the extrudate is generally between 2 mm and 10 mm, preferably between 2 mm and 8 mm, and more preferably between 3 mm and 6 mm.

[0076] When the material is in the form of an extrudate, the extrudates generally have a diameter between 0.5 mm and 10 mm, preferably between 1.0 mm and 2.5 mm and a length between 1.0 mm and 2.0 mm.

[0077] The aspect ratio of an object is defined as the ratio between its length and width. Preferably, the material has an aspect ratio greater than 2. Material preparation process

[0078] In accordance with the invention, the present invention relates to a method for preparing a magnetic material according to the invention comprising at least the following steps:

[0079] a) at least one source of iron in metallic or oxide or oxyhydroxide form, an oxide matrix source, a silicon carbide source in its alpha crystallographic form (a-SiC) and at least one solvent are brought into contact to obtain a paste, said iron source being in the form of a powder with a grain size between 1 pm and 500 pm;

[0080] b) the paste obtained at the end of step a) is shaped to obtain a precursor of material;

[0081] c) the precursor material obtained at the end of step b) is dried at a temperature below 250°C to obtain a dried precursor material;

[0082] d) the dried material precursor obtained at the end of step c) is calcined at a temperature between 250°C and 1000°C.

[0083] Steps a) to d) are described in detail below. Additional optional steps may be performed. These optional steps are also described below. Step a)

[0084] According to the invention, the process includes a step a) of bringing into contact at least one source of iron in metallic or oxide or oxyhydroxide form, an oxide matrix source, a silicon carbide source in its alpha crystallographic form (a-SiC) and at least one solvent to obtain a paste.

[0085] Advantageously, the iron source is chosen from metallic iron, magnetite, maghemite, goethite, lepidocrocite, and hematite, taken alone or in mixtures. Preferably, the iron source is metallic iron, magnetite, maghemite, and goethite, taken alone or in mixtures.

[0086] The iron source in metallic, oxide, or oxyhydroxide form added in step a) advantageously has a grain size between 1 µm and 50 µm, preferably between 1 µm and 40 µm, and even more preferably between 1 µm and 10 µm. The grain size of the metallic iron, oxide, or oxyhydroxide is advantageously measured by dry laser granulometry.

[0087] When the oxide matrix is ​​aluminous, the oxide matrix source is chosen from aluminum oxide or boehmite. Preferably, the oxide matrix source is boehmite. Preferably, the aluminum oxide or oxyhydroxide source added in step a) is chosen, without restriction, from the following commercial sources: Pural SB 1 (Sasol), Pural SB3 (Sasol), CT800FG (Almatis), Apyral AOH60 (Nabaltec).

[0088] When the oxide matrix is ​​clay-based, the oxide matrix source is chosen from kaolin, kaolinite, metakaolin, or montmorillonite. Preferably, the oxide matrix source is kaolin. Preferably, the clay source added in step a) is chosen, without restriction, from the following commercial sources: ARGICALTM M1000 (Imerys), ARGICALTM M1200S (Imerys), MetaStar® 501 (Imerys), MetaStar® 501HP (Imerys), Sorbix® (Imerys).

[0089] The silicon carbide source in its alpha crystallographic form advantageously has a grain size of less than 20 pm, preferably less than 15 pm, even more preferably less than 10 pm, and even more preferably less than 5 pm. The silicon carbide grain size is advantageously measured by dry laser granulometry.

[0090] Preferably, the source of silicon carbide in its alpha crystallographic form may be chosen, without restriction, from the following commercial sources: superfine silicon carbide powder, 600, in grain from Thermo Scientific Chemicals®; alpha-phase silicon carbide, 99.8% from Thermo Scientific Chemicals®, taken alone or in mixture.

[0091] In a particularly preferred manner, silicon carbide in its alpha crystallographic form has a hexagonal crystal structure. Within the scope of the invention, it is entirely possible to carry out mixtures of several different iron powders and / or different oxide matrix source powders and / or different silicon carbide powders.

[0092] According to the invention, at least one solvent is added in step a). Said solvent is advantageously chosen from water, ethanol, alcohols and amines. Preferably, said solvent is water.

[0093] In an embodiment according to the invention, at least one organic adjuvant is also added during step a). Said organic adjuvant may be chosen from all additives known to those skilled in the art. Preferably, said organic adjuvant is chosen from cellulose derivatives, polyethylene glycols, monocarboxylic aliphatic acids, alkylated aromatic compounds, sulfonic acid salts, fatty acids, polyvinylpyrrolidone, polyvinyl alcohol, methylcellulose, polyacrylates, polymethacrylates, polyisobutene, polytetrahydrofuran, starch, polysaccharide-type polymers (such as xanthan gum), scleroglucan, hydroxyethylated cellulose-type derivatives, carboxymethylcellulose, lignosulfonates, and galactomannan derivatives, taken alone or in mixtures.

[0094] Preferably, said organic adjuvant may be mixed in powder form or in solution in said solvent.

[0095] Preferably, said step a) is carried out by mixing, continuously (batch according to Anglo-Saxon terminology) or continuously.

[0096] In the case where said step a) is carried out discontinuously, said step a) is preferably carried out in a mixer equipped with Z-arms, or cams, or in any other type of mixer such as, for example, a planetary mixer. Said mixing step a) makes it possible to obtain a paste or a homogeneous mixture of the constituents.

[0097] In the case of the implementation of a "Z-arm" type mixer, the rotation speed of the mixer arms is advantageously between 10 and 75 revolutions / minute, preferably between 25 and 50 revolutions / minute.

[0098] In the case of implementation in a centrifugal planetary mixer, the rotation speed is advantageously between 300 and 2000 revolutions per minute, preferably between 1500 and 2000 revolutions per minute in order to obtain a paste.

[0099] Preferably, the following quantities are introduced in step a):

[0100] - 10% to 90% by weight, preferably 20% to 80% by weight, preferably 30% at 70% by weight, and very preferably from 35% to 65% by weight and even more preferably from 40% to 60% by weight of at least one metallic iron powder or oxide;

[0101] - 10% to 90% by weight, preferably 20% to 80% by weight, preferably 30% at 70% by weight, and very preferably from 35% to 65% by weight and even more preferably from 40% to 60% by weight of at least one oxide matrix source powder;

[0102] - 1% to 90% by weight, preferably 2% to 80% by weight, preferably 3% to 70% by weight, and most preferably from 5% to 65% by weight and even more preferably from 4% to 60% by weight of at least one silicon carbide source powder;

[0103] - 0% to 20% by weight, preferably from 1% to 15% by weight, preferably from 1% at 10% by weight, and most preferably from 1% to 7% by weight of at least one organic additive, the percentages by weight being expressed in relation to the total weight of said material and the sum of the contents of each of the compounds of said material being equal to 100%. Step b)

[0104] According to the invention, said process includes a step b) of shaping the dough obtained at the end of step a).

[0105] Preferably, the paste obtained at the end of step a) is advantageously shaped by extrusion.

[0106] If the shaping of the mixture from step a) is carried out by extrusion, step b) is advantageously performed in a piston, single-screw, or twin-screw extruder. In this case, an organic additive may optionally be added in step a) as described above. The presence of said organic additive facilitates shaping by extrusion. This organic additive is described above and is introduced in step a) in the proportions indicated above.

[0107] Extrusion can be carried out either by extruding directly from the end of a continuous mixer, such as a twin-screw mixer, or by connecting one or more batch mixers to an extruder. The geometry of the die, which gives the extrudates their shape, can be chosen from among the dies well known to those skilled in the art. They can thus be, for example, cylindrical or multilobed (e.g., trilobed or quadrilobed).

[0108] In the case where the shaping of the mixture from step a) is carried out by extrusion, the quantity of solvent added in step a) of mixing is adjusted so as to obtain, at the end of this step and whatever the variant implemented, a mixture or paste which does not flow but which is not too dry either in order to allow its extrusion under suitable pressure conditions well known to the person skilled in the art and dependent on the extrusion equipment used.

[0109] Preferably, said step b) of shaping by extrusion is carried out at an extrusion pressure greater than 1 MPa and preferably between 3 MPa and 10 MPa. Step c)

[0110] The preparation process according to the invention comprises a step c) of drying the precursor material obtained at the end of step b). Said drying step is advantageously carried out at a temperature below 250°C, preferably between 20°C and 200°C, and preferably between 20°C and 150°C, for a duration advantageously between 1 minute and 72 hours, preferably between 30 minutes and 72 hours, preferably between 1 hour and 48 hours, and more preferably between 1 hour and 24 hours.

[0111] Preferably, said drying step is carried out in air and preferably in humid air with a relative humidity between 20% and 100%, and preferably between 70% and 100%. This step allows for good hydration of the material, necessary to limit the appearance of cracks that are detrimental to mechanical strength. Step d)

[0112] According to the invention, the dried material precursor obtained at the end of step c) undergoes a calcination step d) at a temperature between 250°C and 1000°C, preferably between 300°C and 900°C, and even more preferably between 400°C and 600°C. Step d) is carried out for a duration advantageously between 1 and 12 hours, and preferably between 1 and 4 hours. This calcination step is particularly useful for removing the organic additives used to facilitate shaping the material.

[0113] Said calcination step d) is advantageously carried out under a gas stream comprising oxygen; for example, preferably the material precursor is calcined under dry air or with varying humidity levels, or alternatively, treated at temperature in the presence of a gas mixture comprising an inert gas, preferably nitrogen, and oxygen. The gas mixture used preferably comprises at least 5% by volume, or even more preferably at least 10% by volume, oxygen.

[0114] At the end of step d), a material is obtained according to an embodiment of the invention. However, the preparation process may include additional steps which are described in detail below. Hydrothermal treatment stage (optional)

[0115] In one embodiment according to the invention, the process includes a hydrothermal treatment step in the presence of steam. The hydrothermal treatment is carried out by any technique known to those skilled in the art. Hydrothermal treatment means contacting the material or material precursor with water in vapor or liquid phase at any stage of its preparation. Hydrothermal treatment may include, in particular, curing, steam treatment or steaming (according to Anglo-Saxon terminology), autoclaving, calcination under humid air, and rehydration.

[0116] Preferably, the hydrothermal treatment step is carried out between step d) calcination and optional step e) reduction. In a preferred embodiment, said hydrothermal treatment step may, where appropriate, totally or partially replace step d) of calcination.

[0117] In a highly preferred embodiment, the hydrothermal treatment step is carried out at atmospheric pressure, at a temperature between 200°C and 1100°C, preferably between 400°C and 1000°C, for a period of between 30 minutes and 5 hours. The water content in the gas is between 5% and 100%, preferably between 10% and 90%.

[0118] In another highly preferred embodiment, the hydrothermal treatment step is carried out under partial water pressure. The material or material precursor can thus advantageously be subjected to hydrothermal treatment in a confined atmosphere or by autoclaving. Hydrothermal treatment in a confined atmosphere is understood to mean treatment by passing through an autoclave in the presence of water at a temperature above ambient temperature.

[0119] According to this highly preferred embodiment of the invention, the hydrothermal treatment is a treatment under a flow containing water vapor and a gas, at a specific temperature and pressure. The gas is advantageously air or nitrogen. The water volume composition in the gas is between 5% and 100%, preferably between 10% and 90%. The temperature during the hydrothermal treatment can be between 100°C and 1100°C, and preferably between 100°C and 450°C, and preferably between 200°C and 450°C, for a period of between 30 minutes and 24 hours, and preferably between 30 minutes and 4 hours. The partial pressure of water is between 0.1 MPa and 10 MPa, preferably between 0.11 MPa and 7.5 MPa, and even more preferably between 0.1 and 5 MPa. Step e) reduction (optional)

[0120] The calcination, or hydrothermal treatment, step is advantageously followed by a temperature reduction treatment. The reduction heat treatment is advantageously carried out at a temperature between 200°C and 600°C, preferably between 220°C and 500°C, and even more preferably between 250°C and 475°C, under a flow or atmosphere containing hydrogen. The reduction process allows, in particular, the reduction of iron oxide to metallic iron.

[0121] The reduction is carried out in the presence of a reducing gas advantageously comprising between 25 vol% and 100 vol% of hydrogen, preferably 100 vol% hydrogen. The hydrogen is optionally supplemented by an inert gas for the reduction, preferably argon, nitrogen, or methane.

[0122] The duration of the reduction treatment is between 1 hour and 10 hours, preferably between 2 hours and 8 hours.

[0123] The hydrogen flow rate, expressed in NL / hour / gram of material, is between 0.01 and 100 NL / hour / gram of material, preferably between 0.05 and 10 NL / hour / gram of material, preferably between 0.1 and 5 NL / hour / gram of material. Catalyst

[0124] Another object according to the invention relates to a catalyst comprising an active phase based on at least one metal chosen from groups 6 to 11 of the periodic table, preferably chosen from Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt, Re, Au, Ag, Mo, W, Cr, taken alone or in mixture, and a support in the form of a material according to the invention.

[0125] In an embodiment according to the invention, said metal is chosen from the metals Co, Ni, Cu, taken alone or in mixture.

[0126] The content of metal chosen from Co, Ni, Cu is preferably between 0.5% and 30% by weight, preferably between 1% and 20% by weight, even more preferably between 2% and 15% by weight and even more preferably between 3% and 12% by weight of the element of said metal in relation to the total weight of the catalyst.

[0127] In another embodiment according to the invention, said metal is chosen from the metals Pt, Pd, Au, Ag, Ru, taken alone or in mixture.

[0128] The content of metal chosen from Pt, Pd, Au, Ag, Ru is preferably between 0.01% and 10% by weight, preferably between 0.05% and 5% by weight of the element of said metal relative to the total weight of the catalyst. Catalyst preparation process

[0129] Another object of the invention relates to a method for preparing a catalyst according to the invention. In one embodiment of the invention, the preparation method comprises at least the following steps:

[0130] fl) a liquid solution is prepared in aqueous or organic phase comprising at least one precursor of the active phase based on at least one metal chosen from groups 6 to 11 of the periodic table, preferably chosen from Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt, Re, Au, Ag, Mo, W, Cr, taken alone or in mixture, preferably at a temperature between 5°C and 80°C, more preferably between 10°C and 70°C;

[0131] f2) the solution prepared in step fl) is impregnated onto the material according to the invention or obtained according to the material preparation process according to the invention, the volume of the solution being advantageously between 0.9 and 1.1, preferably between 0.8 and 1.05 times the porous volume of the material;

[0132] f3) Optionally, the catalyst precursor obtained in step f2) is subjected to a maturation in order to obtain a catalyst precursor;

[0133] f4) the catalyst precursor obtained in step f2), optionally f3), is dried at a temperature greater than or equal to 15°C and less than 250°C;

[0134] f5) the catalyst precursor obtained in step f4) is calcined at a temperature between 250°C and 600°C;

[0135] f6) Optionally, the catalyst obtained at the end of step 15) is reduced to a temperature between 200°C and 600°C and for 1 hour and 10 hours in the presence of a reducing gas.

[0136] The impregnation solution of step 11) is preferably prepared by dissolving in aqueous or organic phase one or more precursors of the active phase based on at least one metal selected from groups 6 to 11 of the periodic table, preferably chosen from Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt, Re, Au, Ag, Mo, W, Cr, taken alone or in mixtures. The precursors are preferably chosen from salts of carbonate, nitrate, sulfate, formate, acetate, citrate, lactate, chloride, hydroxide, oxide, and metal organic complexes.

[0137] Preferably, a maturation step f3) is carried out for a duration of between 1 minute and 72 hours, preferably between 30 minutes and 72 hours, most preferably between 1 hour and 48 hours, and even more preferably between 1 hour and 24 hours. Advantageously, step f3) is carried out at atmospheric pressure, in a water-saturated atmosphere and at a temperature between 17°C and 50°C, preferably at ambient temperature.

[0138] Preferably, drying step f4) is advantageously carried out at a temperature greater than or equal to 15°C and less than 250°C, preferably between 15°C and 180°C, more preferably between 30°C and 160°C, even more preferably between 50°C and 150°C, and even more preferably between 70°C and 140°C, for a duration typically between 0.5 hours and 12 hours, and even more preferably for a duration of 0.5 hours to 5 hours. Longer durations are not excluded, but do not necessarily provide any improvement.

[0139] The drying step can be carried out by any technique known to those skilled in the art. It is advantageously carried out under an inert atmosphere or under an atmosphere containing oxygen or under a mixture of inert gas and oxygen. It is advantageously carried out at atmospheric pressure or at reduced pressure. Preferably, this step is carried out at atmospheric pressure and in the presence of air or nitrogen.

[0140] Preferably, the calcination step f5) is carried out at a temperature between 250°C and 600°C, preferably between 350°C and 550°C, for a period typically between 0.5 hours and 24 hours, preferably between 0.5 hours and 12 hours, and even more preferably between 0.5 hours and 10 hours, preferably under an inert atmosphere or an atmosphere containing oxygen. Longer durations are not excluded, but do not necessarily provide any improvement.

[0141] The calcination step (f5) can optionally be followed by a temperature reduction treatment (step (f6)). The reduction heat treatment is advantageously carried out at a temperature between 200°C and 600°C, preferably between 220°C and 500°C, and even more preferably between 250°C and 475°C, under a flow or atmosphere containing hydrogen. The reduction allows, in particular, the reduction of iron oxide to metallic iron.

[0142] The reduction is carried out in the presence of a reducing gas advantageously comprising between 25 vol% and 100 vol% of hydrogen, preferably 100 vol% hydrogen. The hydrogen is optionally supplemented by an inert gas for the reduction, preferably argon, nitrogen, or methane.

[0143] The duration of the reduction treatment is between 1 hour and 10 hours, preferably between 2 hours and 8 hours.

[0144] The hydrogen flow rate, expressed in NL / hour / gram of material, is between 0.01 and 100 NL / hour / gram of material, preferably between 0.05 and 10 NL / hour / gram of material, even more preferably between 0.1 and 5 NL / hour / gram of material. CO2 conversion process using hydrogenation

[0145] The catalyst according to the invention can advantageously be used in a CO2 hydrogenation process.

[0146] The CO2 hydrogenation process, which operates in the presence of the catalyst according to the invention, is advantageously carried out at a temperature between 180°C and 800°C, preferably between 190°C and 750°C, most preferably between 250°C and 700°C, and most preferably between 250°C and 600°C, at a pressure between 0.1 MPa and 12 MPa, preferably between 0.11 MPa and 10 MPa, most preferably between 0.13 MPa and 9 MPa, and most preferably between 0.15 MPa and 8 MPa, at a hydrogen / (carbon dioxide) molar ratio between 0.1 and 10, and at an hourly volumetric rate between 100 h₁ and 40,000 h₁ in the presence of the catalyst according to the invention or prepared by the process according to the invention described above.

[0147] The heat required for the catalytic reaction is supplied by radiation from the material according to the invention induced in response to an applied alternating magnetic field. The magnetic field may, in particular, be generated by a field inductor and have an amplitude between 1 mT and 80 mT, preferably between 1 mT and 50 mT, with a frequency between 30 kHz and 500 kHz, preferably between 90 and 300 kHz.

[0148] In the process according to the invention, carbon dioxide is hydrogenated to carbon monoxide, methane or methanol depending on the operating conditions.

[0149] The effluents consist mainly of carbon monoxide, water, hydrogen, methanol, methane, and unconverted carbon dioxide. By-products of the reaction, such as alcohols, alkenes, ethers, and alkanes, may also be observed.

[0150] The carbon dioxide contained in the gas mixture feed can come from various sources. Preferably, the CO2 comes from process exhaust gases or the environment. The hydrogen / (carbon dioxide) molar ratio is between 0.1 and 10, preferably between 0.5 and 5, and even more preferably between 1 and 3.

[0151] The gaseous mixture constituting the charge may contain, in addition to carbon dioxide and hydrogen, other gaseous elements such as water vapor, alkanes such as methane, propane, isobutane.

[0152] Said process is preferably operated continuously, in a fixed bed, preferably at a pressure adjusted so that the products and reactants are in gas phase.

[0153] Preferably, the catalyst is heat-treated in the reactor under a reducing atmosphere, before the injection of the feed, at a temperature between 100°C and 600°C, preferably between 150°C and 500°C and for a duration of between 30 minutes and 12 hours. Dehydration process for an alcoholic load

[0154] The material according to the invention can advantageously be used in a mixture with a dehydration catalyst in a process for dehydrating a feed comprising at least one alcohol.

[0155] The dehydration catalyst is chosen from materials known to those skilled in the art. Preferably, the catalyst is chosen from acidic solids such as amorphous or crystalline aluminosilicates, zeolites such as, for example, ZSM-5, Y, Mordenite, Ferrierite, and Beta, aluminas, phosphorus-modified aluminas, solid or oxide-supported heteropolyacids, modified silicas, resins.

[0156] The dehydration process operates in the presence of the material prepared according to the invention and a dehydration catalyst, and is advantageously carried out at a temperature between 180°C and 450°C, preferably between 190°C and 430°C, most preferably between 250°C and 420°C and most preferably between 270°C and 420°C, at a pressure between 0.1 MPa and 12 MPa, preferably between 0.11 MPa and 10 MPa, most preferably between 0.13 MPa and 9 MPa and most preferably between 0.15 MPa and 8 MPa, and at a mass flow rate ratio of feed to total mass of the material and catalyst between 0.01 h₁ and 100 h₂', preferably between 0.02 h 1 and 50 h 1, more preferably between 0.03 h ' and 30 h 1 and very preferably between 0.05 h ' and 20 h '.

[0157] The mass ratio [mass of dehydration catalyst: mass of material according to the invention] is preferably between 90:10 and 35:55, preferably between 80:20 and 40:60 and even more preferably between 75:25 and 45:55.

[0158] The loading of the reactor between the dehydration catalyst and the material according to the invention is either homogeneous or by stacking of beds of variable thickness between the catalyst and the material according to the invention.

[0159] The heat required for the catalytic reaction is supplied by radiation from the material according to the invention induced in response to an applied alternating magnetic field. The magnetic field may, in particular, be generated by a field inductor and have an amplitude between 1 mT and 80 mT, preferably between 1 mT and 50 mT, with a frequency between 30 kHz and 500 kHz, preferably between 90 kHz and 300 kHz.

[0160] Said process makes it possible to selectively obtain a mixture of products comprising established compounds such as ethylene, propylene, or butadiene.

[0161] Said process can advantageously be carried out under a neutral or oxidizing atmosphere.

[0162] Said process is preferably operated continuously, in a fixed bed, preferably at a pressure adjusted so that the products and reactants are in gas phase, the liquid feed being injected into the process preferentially in liquid phase.

[0163] The feedstock for the dehydration process comprises at least one molecule with at least one alcohol functional group such as ethanol, propanol, isopropanol, butanol, propylene glycol, butane diols, or hydroxypropanoic acids. Preferably, said feedstock comprises ethanol.

[0164] Said charge advantageously comprises between 1% and 99.9% by weight, preferably between 5% and 99.5% by weight, most preferably between 7% and 99% by weight and even more preferably between 8% and 98% of a molecule with at least one alcohol function.

[0165] Said charge may also include impurities related, in particular, to the processes of obtaining molecules with at least one alcohol function.

[0166] The molecules with at least one alcohol function included in said charge may be of any origin, chemical, petrochemical or bio-based.

[0167] Said charge advantageously comprises between 0.1% and 99% by weight, preferably between 0.5% and 90% by weight, most preferably between 1% and 80% by weight and even more preferably between 2% and 70% by weight of water.

[0168] Said charge advantageously comprises between 0.1% and 99% by weight, preferably between 0.5% and 90% by weight, most preferably between 1% and 80% by weight and even more preferably between 2% and 70% by weight of organic solvent.

[0169] The main products obtained by said process are molecules with at least one unconverted alcohol function, unsaturated compounds resulting from the dehydration reaction.

[0170] The examples below illustrate the invention without limiting its scope. Examples Example 1: Preparation of materials Ax Non-compliant A0 material (without SiC)

[0171] A powdered iron source and kaolin are introduced and mixed in the bowl of a Thinky™ brand centrifugal planetary mixer (see Table 1 for the iron sources used and the target Fe and alumina contents of the material). The rotation speed is set at 1500 rpm for 30 seconds. Water is gradually added until a paste is obtained. The rotation speed is set at 2000 rpm for 30 seconds. The resulting paste is then extruded on an MTS brand piston extruder using a 1.6 mm diameter cylindrical die. The extrudates are dried for 16 h at 120°C in a ventilated oven and then calcined for 4 h at 550°C.

[0172] Al (SiC 5%) and A2 (10% SiC) materials according to the invention

[0173] A powdered source of iron and kaolin, and alpha silicon carbide, are introduced and mixed in the bowl of a Thinky™ brand centrifugal planetary mixer (see Table 1 for the iron sources used and the target Fe and alumina contents of the material). The rotation speed is set at 1500 rpm for 30 seconds. Water is gradually added until a paste is obtained. The rotation speed is then set at 2000 rpm for 30 seconds. The resulting paste is then extruded on an MTS brand piston extruder using a 1.6 mm diameter cylindrical die. The extrudates are dried for 16 h at 120°C in a ventilated oven and then calcined for 4 h at 550°C.

[0174] Material A3 according to the invention (additional reduction step)

[0175] A powdered source of iron and kaolin, and alpha silicon carbide are introduced and mixed in the bowl of a Thinky™ brand centrifugal planetary mixer (see Table 1 for the iron sources used and the target Fe and alumina contents of the material). The rotation speed is set at 1500 rpm for 30 seconds. Water is added dropwise until a paste is obtained. The rotation speed is then set at 2000 rpm for 30 seconds. The resulting paste is then extruded on an MTS brand piston extruder using a 1.6 mm diameter cylindrical die. The extrudates are dried for 16 h at 120°C in a ventilated oven, then The material is calcined for 4 hours at 550°C. Following calcination, the extruded material undergoes a reduction step under pure hydrogen at atmospheric pressure for 4 hours at a temperature of 450°C with a ramp rate of 5°C / min. The reducing gas flow rate is 11 h / g of catalyst. The cooling step is carried out under nitrogen.

[0176] Material A4 according to the invention (additional hydrothermal treatment step)

[0177] A powdered source of iron and kaolin, and alpha silicon carbide are introduced and mixed in the tank of a Thinky™ brand centrifugal planetary mixer (see Table 1 for the iron sources used and the target Fe and alumina contents of the material). The rotation speed is set at 1500 rpm for 30 seconds. Water is added dropwise until a paste is obtained. The rotation speed is set at 2000 rpm for 30 seconds. The resulting paste is then extruded on an MTS brand piston extruder using a cylindrical die with a diameter of 1.6 mm. The extrudates are dried for 16 h at 120°C in a ventilated oven and then calcined for 4 h at 550°C. After calcination, the extrudates are subjected to a hydrothermal treatment step at atmospheric pressure for 4 hours at a temperature of 450°C.The volumetric composition of water in the air for hydrothermal treatment is 50%.

[0178] [Tables] Material A0 Al A2 A3 A4 Source Iron Fe Fe Fe Fe Fe Fe Fe % weight 50 50 50 50 50 Kaolin % weight 50 45 40 40 40 SiC % weight 0 5 10 10 10 Hematite % weight 10 10 11 0 11 VPT mL / g 0.13 0.13 0.1 0.15 0.11 Sbet m2 / g 10 10 8 13 8 EGG dN / mm 0.5 0.7 0.93 0.95 1.2 SAR W / g 14 15 18 20 17

[0179] Example 2: Use of Ax materials for the dehydration of ethanol.

[0180] The experimental setup for carrying out such a reaction consists of a fixed-bed reactor whose walls are permeable to magnetic fields. The reactor is surrounded by a coil with a helical winding and is connected to an alternating current generator, which generates the alternating magnetic field necessary for induction heating. The coil is cooled by a water circuit to prevent overheating.

[0181] Materials A2, A3, A4 are mixed with zeolitic dehydration catalyst D at iso mass (for example, 50% weight of material A2 and 50% weight of dehydration catalyst).

[0182] The mixture is active and stable for gas-phase dehydration with a water:ethanol gas mixture at a volumetric hourly rate (PPH) of 10 h

[0183] [Tables2] % weight of dehydrating catalyst D % weight of magnetic material Ethanol conversion (%) Ethylene selectivity (%) 50 50 (A2) 98 95 50 50 (A3) 100 95 50 50 (A4) 98 95

Claims

Demands

1. Magnetic material comprising at least iron, in metallic form and / or in oxide form, at least one oxide matrix, the iron content being between 15% and 70% by weight as elemental iron relative to the total weight of said material, and at least silicon carbide in its alpha crystallographic form (a-SiC), characterized in that said material comprises at most 25% by weight of hematite relative to the total weight of said material, said material being in the form of beads or extrudates.

2. Material according to claim 1, characterized in that the oxide matrix is ​​selected from aluminium, zirconium, titanium oxides, and clays.

3. Material according to any one of claims 1 or 2, characterized in that the silicon carbide content is between 1% and 50% by weight relative to the total weight of the material.

4. Material according to any one of the preceding claims, characterized in that said material has a mechanical strength value measured by grain-by-grain crushing greater than 0.65 daN / mm.

5. Material according to any one of the preceding claims, characterized in that said material has a specific absorption rate of between 2 W / g and 120 W / g after activation by a magnetic field of amplitude between 1 mT and 50 mT at a frequency between 90 kHz and 300 kHz.

6. A method for preparing a magnetic material according to any one of claims 1 to 5, comprising at least the following steps: a) contacting at least one iron source in metallic or oxide or oxyhydroxide form, an oxide matrix source, a silicon carbide source in its alpha crystallographic form (a-SiC) and at least one solvent to obtain a paste, said iron source being in the form of a powder with a grain size between 1 pm and 500 pm; b) shaping the paste obtained at the end of step a) to obtain a material precursor; c) the precursor material obtained at the end of step b) is dried at a temperature below 250°C to obtain a dried precursor material; d) the dried precursor material obtained at the end of step c) is calcined at a temperature between 250°C and 1000°C.

7. A process according to claim 6, wherein said material obtained at the end of step d) is subjected to hydrothermal treatment at a temperature between 100°C and 1100°C.

8. A process according to any one of claims 6 or 7, comprising a step e) in which the material obtained at the end of step d) is reduced at a temperature between 200°C and 600°C and for a period of between 1 hour and 10 hours in the presence of a reducing gas.

9. A process according to claim 8, wherein step e) is carried out in the presence of a reducing gas comprising between 25 vol% and 100 vol% of hydrogen, the hydrogen flow rate being between 0.01 and 100 NL / hour / gram of material.

10. A method according to any one of claims 6 to 9, wherein the iron source is chosen from metallic iron, magnetite, maghemite, goethite, lepidocrocite and hematite, taken alone or in mixtures.

11. A method according to any one of claims 6 to 10, wherein where the oxide matrix is ​​an aluminum oxide, the source of said oxide matrix is ​​a boehmite.

12. A method according to any one of claims 6 to 10, wherein when the oxide matrix is ​​a clay, the source of said oxide matrix is ​​selected from kaolin, kaolinite, metakaolin, and montmorillonite, taken alone or in mixture.

13. Catalyst comprising an active phase based on at least one metal selected from groups 6 to 11 of the periodic table, preferably selected from Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt, Re, Au, Ag, Mo, W, Cr, taken alone or in mixture, and a support in the form of a magnetic material according to any one of claims 1 to 5 or prepared according to any one of claims 6 to 12.

14. Catalyst according to claim 13, characterized in that said metal is selected from Co, Ni, and Cu, and in which the content of said metal is between 0.5% and 30% by weight in element of said metal relative to the total weight of the catalyst.

15. Catalyst according to claim 13, characterized in that said metal is selected from Pt, Pd, Au, Ag, Ru, and in which the content of said metal is between 0.01% and 10% by weight in element of said metal relative to the total weight of the catalyst.

16. A process for preparing a catalyst according to any one of claims 13 to 15 comprising at least the following steps: (f1) a liquid solution in aqueous or organic phase is prepared comprising at least one precursor of the active phase based on at least one metal selected from groups 6 to 11 of the periodic table, preferably selected from Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Pt, Re, Au, Ag, Mo, W, Cr, taken alone or in mixture, preferably at a temperature between 5°C and 80°C, more preferably between 10°C and 70°C; (f2) the solution prepared in step (f1) is impregnated onto the material according to any one of claims 1 to 5 or prepared according to any one of claims 6 to 12, the volume of the solution advantageously being between 0.9 and 1.1 times the porous volume of said material; f3) optionally, the catalyst precursor obtained in step f2) is subjected to maturation in order to obtain a catalyst precursor;f4) the catalyst precursor obtained in step f2), optionally f3), is dried at a temperature greater than or equal to 15°C and less than 250°C; f5) the catalyst precursor obtained in step f4) is calcined at a temperature between 250°C and 600°C.

17. A process for hydrogenating CO2 carried out at a temperature between 180°C and 800°C, at a pressure between 0.1 MPa and 13 MPa, at a hydrogen / CO2 molar ratio between 0.1 and 10 and at an hourly volumetric rate between 100 h 1 and 40000 h 1 in the presence of a catalyst according to any one of claims 13 to 15, said process being carried out under the action of a magnetic field of amplitude between 1 mT and 50 mT at a frequency between 90 kHz and 300 kHz.

18. A process for dehydrating a feed comprising at least one alcohol, carried out at a temperature between 180°C and 450°C, at a pressure between 0.1 MPa and 12 MPa, at a mass flow rate ratio of charge divided by the total mass of the material and catalyst between 0.01 h 1 and 100 h 1 in the presence of a dehydration catalyst and a magnetic material according to any one of claims 1 to 5, said process being carried out under the action of a magnetic field of amplitude between 1 mT and 50 mT at a frequency between 90 kHz and 300 kHz.