WO2024056416A1 - Method for preparing a silicon carbide catalyst for dehydrating hydroxypropanoic acid and the derivatives thereof - Google Patents

Abstract

The present invention relates to a method for preparing a catalyst comprising at least one compound of a phosphate salt, of the M1HxPOy type, x being a fractional number between [0-2] and y being a fractional number between [3-4], with M selected from the group formed by the metals of group I and group II of the periodic table, taken alone or as a mixture, and a substrate comprising porous silicon carbide SiC, said method comprising at least a step of adding said phosphate salt to the substrate comprising the silicon carbide.

Description

METHOD FOR PREPARING A CATALYST BASED ON SILICON CARBIDE FOR THE DEHYDRATION OF HYDROXYPROPANOIC ACID AND ITS DERIVATIVES

Technical area

The present invention relates to a process for preparing a catalyst comprising at least one compound of a phosphate salt, of type M1 HxPOy, x being a fractional number between [0-2] and y being a fractional number between [ 3-4] with M chosen from the group formed by the metals of group I and group II of the periodic table, taken alone or as a mixture and a support comprising porous silicon carbide SiC, said process comprising at least one step of adding said phosphate salt to the support comprising silicon carbide. Said catalyst thus prepared can advantageously be used in a process for dehydrating hydroxypropanoic acid and its derivatives.

Prior art

Patent US9849447 teaches the preparation of catalyst for the dehydration of hydroxypropanoic acid. The catalyst is composed of phosphate salts, chosen from the group consisting of Na+, K+, Rb+, Cs+ and comprises an inorganic oxide support, preferably amorphous silica SiO2.

Silicon carbide SiC, porous or non-porous, is a catalyst support used for example for the preparation of metal catalysts, as illustrated in the publication by Ledoux et al. (J. Catal 114 (1988)) and more recently in the review by Kulkarni et al. (Catalysis Reviews, 2022). We can cite patent WO14140973 which discloses the preparation of a catalyst containing cobalt on a support containing silicon carbide for the preparation of hydrocarbons from a mixture of hydrogen and carbon monoxide (Fisher-Tropsch synthesis).

There is no catalyst in the literature comprising at least one compound of a phosphate salt, a support comprising silicon carbide SiC, and its use for the dehydration of hydroxypropanoic acid and its derivatives.

SiC or silicon carbide is an inorganic material with particular properties (stability, conductivity, mechanical and chemical resistance) which make it interesting for catalysis applications.

Summary of the invention

The present invention relates to a process for preparing a catalyst comprising at least one compound of a phosphate salt, of type M1 HxPOy, x being a fractional number between [0-2] and y being a fractional number between [ 3-4] with M chosen in the group formed by the metals of Group I and Group II of the periodic table, taken alone or as a mixture and a support comprising porous silicon carbide SiC, said process comprising at least one step of adding said phosphate salt to the support comprising silicon carbide.

According to a preferred embodiment of the invention, another object of the invention may also relate to said catalyst comprising at least one compound of a phosphate salt, of the MI HxPOy type, x being a fractional number between [0- 2] and y being a fractional number between [3-4] with M chosen from the group formed by the metals of group I and group II of the periodic table, taken alone or in mixture and a support comprising silicon carbide Porous SiC and a process for dehydrating hydroxypropanoic acid and its derivatives using the catalyst prepared by the preparation process according to the invention.

An advantage of the present invention is to provide a process for the preparation of a stable catalyst under the conditions of the dehydration process of hydroxypropanoic acid and its derivatives, that is to say that its structure and its textural properties are not or only slightly modified. after its use in the process.

Description of embodiments

The present invention relates to a process for preparing a catalyst comprising at least one compound of a phosphate salt, of the MI HxPOy type, x being a fractional number between [0-2] and y being a fractional number between [ 3-4] with M chosen from the group formed by the metals of group I and group II of the periodic table, taken alone or as a mixture and a support comprising porous silicon carbide SiC, said process comprising at least one step of adding said phosphate salt to the support comprising silicon carbide.

The catalyst

In accordance with the invention, the catalyst prepared according to the invention comprises at least one phosphate salt, of the MI HxPOy type, x being a fractional number between [0-2] and y being a fractional number between [3-4 ] with M being at least one metal chosen from the group formed by the metals of group I and group II of the periodic table, taken alone or as a mixture and a support comprising silicon carbide SiC. Preferably, the phosphate salts may be present in the oxide form MPO3, fully hydrated MH2PO4 or partially hydrated MHxPOy with x being a fractional number between [0-2] and y being a fractional number between [3-4], The catalyst can be used indifferently in oxide, partially hydrated or fully hydrated form.

Preferably, the phosphate salts are chosen from the following compounds M1 H2PO4, M2HPO4, (MPO3)n with n>1, M2H2P2O7, M3P3O9, M4P4O12, M6P6O18, M8P8O24 alone or as a mixture.

Preferably, the phosphate salts are chosen from M1 H2PO4, M2HPO4, (MPO3)n, n> 1 alone or as a mixture.

Preferably, the metal(s) M are chosen from the metals Li, Na K, Cs, Rb, taken alone or in a mixture and very preferably from Na, K, Cs, Rb taken alone or in a mixture, and again most preferred among K and Cs and very preferably, the metal is potassium K.

In the case where several metals Ma and Mb are used, the phosphate salts are chosen from the following compounds MaH2PO4, MaMbHPO4, MaMbH2P2O7, MaMb2P3O9, Ma3MbP4O12, Ma3Mb3P6O18, with Ma and Mb chosen from the metals Li, Na K, Cs , Rb, taken alone or in a mixture and Ma + Mb = M and very preferably among Na K, Cs, Rb taken alone or in a mixture and even more preferably among K and Cs.

Preferably, the catalyst comprises a phosphate salt, of formula MPO3 with M chosen from the group formed by the metals of group I and group II of the periodic table, preferably chosen from the metals of group I, preferably chosen from Li, Na K, Cs, Rb and very preferably from Na, K, Cs, Rb taken alone or in a mixture and even more preferably from K and Cs and very preferably, the metal is potassium K.

The catalyst prepared according to the invention advantageously has a specific surface area greater than 5 m ² /g, preferably between 5 and 300 m ² /g, and more preferably between 10 and 250 m ² /g and a porous volume between 0.1 and 1.0 cm3/g, preferably between 0.15 and 0.8 cm3/g

The support

In accordance with the invention, the catalyst prepared according to the invention comprises a support comprising and preferably consisting of silicon carbide SiC.

Preferably, the support is a shaped silicon carbide. The catalyst support prepared according to the invention according to the invention has a crystallized phase of p-SiC, characterizable by X-ray diffraction.

The silicon carbide used in the catalyst prepared according to the invention has a specific surface area greater than 5 m ² /g, preferably between 5 and 300 m ² /g, and more preferably between 10 and 250 m ² /g. g.

The pore volume of the support is advantageously between 0.20 cm3/g and 1.5 cm3/g, preferably between 0.25 cm3/g and 1.4 cm3/g, and more preferably between 0. 25 cm3/g and 1.2 cm3/g.

The macroporous volume of the support, therefore the pores are greater than 50 nm, is advantageously between 0.01 cm3/g and 1 cm3/g, preferably between 0.05 cm3/g and 0.9 cm3/g, and still preferably between 0.10 cm3/g and 0.8 cm3/g.

The manufacture of silicon carbide type supports usable in heterogeneous catalysis is already known and taught in patents such as in particular patent EP 0440569 B1 or even patent US 6,184,178 B1, without this list being exhaustive.

Preferably, the support is in the form of powder, balls, cylinders, trilobes, quatrefoils, extrudates, pellets, or irregular and non-spherical agglomerates whose specific shape can result from a step of crushing. Very advantageously, said support is in the form of balls or extrudates. The size of the shaped objects is between 0.5 mm and 10 mm, preferably between 1 and 5 mm.

The specific surface area, pore volume, and macroporous volume values of the catalyst and support were determined by mercury intrusion porosimetry.

The catalyst thus prepared is advantageously in the form of powder, balls, cylinders, trilobes, quadrilobes of extrudates, pellets, or irregular and non-spherical agglomerates whose specific shape can result from a crushing step . Very advantageously, said catalyst is in the form of beads or extrudates. The size of the objects is between 0.5 mm and 10 mm, preferably between 1 and 5 mm.

Preferably, the catalyst prepared according to the invention comprises and is preferably constituted, in weight percentage, by:

- 40 to 95%, preferably 50 to 90% and very preferably 55 to 90%, even more preferably between 70% and 85% silicon carbide (SiC),

- 5 to 60%, preferably 10 to 50% and very preferably 10 to 45%, even more preferably between 15% and 30% oxide equivalent of the phosphate salt, noted Preparation of the catalyst

Method of preparation

Preferably, the step of adding the phosphate salt to the support comprising silicon carbide can be carried out by any method known to those skilled in the art, and preferably by moisture-based impregnation or dry impregnation, by excess impregnation, by ion exchange, by precipitation deposition, or by vapor phase deposition. Preferably, the addition of the phosphate salt to the support comprising silicon carbide is carried out by dry impregnation.

Preferably, the step of adding the phosphate salt to the support comprising silicon carbide, preferably produced by dry impregnation, comprises the following steps:

- a step a) of preparing a liquid solution of one or more phosphate salts in an aqueous or organic phase, the preparation temperature being advantageously between 5°C and 80°C, preferably between 10°C and 70 °C.

- a step b) of impregnation of said solution prepared in step a) on the support comprising silicon carbide, the volume of the solution being advantageously between 0.7 and 1.1, preferably between 0.8 and 1.05 times the pore volume of the support and the phosphate concentration of the solution is preferably between 50g/L to 2000g/L.

- a step c) of maturation of the impregnated support obtained in step b), for a period of between 5 min and 40 h, preferably between 10 min and 10 h and even more preferably between 30 min and 5 h, so even more preferred between 1 a.m. and 5 a.m. at a temperature preferably between 10°C and 40°C to obtain a catalyst precursor,

- a step d) of drying said catalyst precursor obtained in step c) to obtain a dried catalyst precursor, said drying step being carried out at a temperature between 70°C and 200°C, under air, for a period duration between 30 min and 12 hours preferably between 1 hour and 10 hours,

- Optionally a step e) of calcination in air of the dried catalyst precursor obtained in step d) to obtain a catalyst, said calcination step being carried out at a temperature between 300°C and 550°C, for a duration between 30 min and 12 hours, preferably between 1 hour and 10 hours.

- Optionally a step f) of heat treatment of the catalyst obtained in step e) optional, said step f) being carried out under inert gas, preferably nitrogen, helium, methane, or carbon dioxide , alone or in mixture, at a temperature between 500°C and 1200°C, preferably between 600°C and 1100°C and very preferably between 750°C and 1000°C, for a period of between 30min and 12h, preferably between 1h and 10h,

- Optionally a step g) of heat treatment under gas containing water vapor of the catalyst obtained in step d) and/in step f), at a temperature between 350°C and 1000°C, of preferably between 450°C and 950°C and very preferably between 450°C and 900°C at a pressure of between 0.1 and 2 MPa, preferably between 0.15 and 1.5 MPa and even more most preferred between 0.17 and 1.0 MPa.

The heat treatment steps e) f) and g) can be added or carried out independently.

The impregnation solution of step a) is preferably prepared by dissolution in the aqueous or organic phase of one or more phosphate and element M precursors.

The impregnation solution can advantageously be prepared by mixing phosphorous and alkaline elements introduced independently. In this case, the metal precursor M chosen from Li, Na, K, Cs, Rb is chosen for example from one or more of the salts of carbonate M2CO3, nitrate MNO3, sulfate, formate HCOOM, acetate CH3COOM, citrate, lactate, MCI chloride, MOH hydroxide, M2O oxide.

The phosphate precursor(s) may advantageously be chosen, for example from H3PO4, (NH4)H2PO4, (NH4)2HPO4, (NH4)3PO4, P2O5.

The phosphate concentration of the solution is preferably between 50g/L to 2000g/L.

Preferably, the impregnation step b) can be preceded by a heat treatment step carried out at a temperature between 80°C and 550°C.

Preferably, impregnation step b) can be followed, optionally by other impregnation steps. The impregnation steps following the first impregnation step b) can advantageously be carried out after the drying step d) or after the calcination step e) or after the treatment steps f), g) and h). thermal. Preferably an impregnation step following the first impregnation step b) is carried out after the calcination step e).

The preparation process according to the invention allows the preparation of a catalyst comprising at least one phosphate salt, of the MI HxPOy type, x being a fractional number between [0-2] and y being a fractional number between [3 -4] with M being at least one metal chosen from the group formed by the metals of group I and group II of the classification periodic, taken alone or as a mixture and a support comprising silicon carbide SiC, said catalyst being able to advantageously be used in a process for dehydrating hydroxypropanoic acid and its derivatives.

Transformation process

Said process for dehydrating hydroxypropanoic acid and its derivatives operates in the presence of the catalyst prepared according to the invention, and is advantageously carried out at a temperature between 180°C and 450°C, preferably between 190°C and 430°C. C, very preferably between 250°C and 420°C and very preferably between 270°C and 420°C, at a pressure of between 0.1 and 12 MPa, preferably between 0.1 1 MPa and 10 MPa, preferably between 0.13 MPa and 9 MPa and very preferably between 0.15 MPa and 8 MPa, and at a mass flow rate of charge to catalyst mass of between 0.01 h-1 and 100 h-1, preferably between 0.02 and 50 h-1, preferably between 0.03 h-1 to 30 h-1 and very preferably from 0.05 h-1 to 20h-1.

Said process makes it possible to selectively obtain a mixture of products comprising acrylic acid.

During the dehydration of hydroxypropanoic acid and its derivatives into acrylic acid, a mixture of different products, called by-products, is obtained, including in particular propanoic acid, carbon monoxide, carbon dioxide, acetaldehyde, heavy compounds containing more than 3 carbon atoms.

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

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

Charge

The feedstock supplying said process advantageously comprises at least one compound included in the list of hydroxypropanoic acid and its derivatives. Said filler advantageously comprises a hydroxypropanoic acid chosen from 2-hydroxypropanoic acid, 3-hydroxypropanoic acid. Preferably, said filler comprises 2-hydroxypropanoic acid. Said filler comprises between 1% and 99.9% by weight, preferably between 5% and 99.5% by weight, very preferably between 7% and 99% by weight and even more preferably between 8% and 98% by weight. hydroxypropanoic acid and its derivatives. Said filler may also include impurities linked, in particular, to the processes for obtaining hydroxypropanoic acid and its derivatives such as fermentation. The impurity content is preferably less than 10% of the weight of said filler. The acid(s) hydroxypropanoics and its derivatives included in said charge can be of any origin, chemical, petrochemical or biosourced.

Said filler comprises between 0.1% and 99% by weight, preferably between 0.5% and 90% by weight, very preferably between 1% and 80% by weight and even more preferably between 2% and 70% by weight. of water.

Said filler comprises between 0.1% and 99% by weight, preferably between 0.5% and 90% by weight, very preferably between 1% and 80% by weight and even more preferably between 2% and 70% by weight. organic solvent, such as for example an alcohol.

The main products obtained by said process are hydroxypropanoic acids and its unconverted derivatives, acrylic acid resulting from the dehydration reaction.

The examples illustrate the scope of the invention without limiting its scope.

Examples:

Example 1: Preparation of a catalyst C1 according to the invention

The S1 silicon carbide support in extruded form is supplied by the company SICAT, in the form of trilobals with a diameter of 1.6 mm. Its main characteristics are provided in Table 1 below.

Table 1: main characteristics of the S1 support.

100 grams of silicon carbide are calcined in air in a muffle furnace in a thin layer at 450°C for 2 hours.

17 grams of potassium dihydrogen phosphate (KH ₂ PO ₄ , M= 136 g/mol) with x = 2 and y = 4 are first dissolved in 60 ml of distilled water at room temperature. The concentration of the solution is 283g of KH2PO4/I. After complete dissolution, the mixture is added dropwise to the SiC extrudates. The solid is matured at room temperature for 40 minutes then dried for 10 hours at 120°C in air. The material is calcined in air at 450°C for 4 hours.

Compositional analysis by FX gives a weight content of K of 4.3% and P of 3.5%. The equivalent weight content of KPO3 with x = 0 and y = 3 of the catalyst after calcination is 13%. The catalyst presents in XRD the majority of diffraction peaks of p-SiC as well as diffraction peaks of the KPO3 metaphosphate phase.

The specific surface area (Hg porosimetry) of catalyst C1 is 35 m2/g, its total pore volume (Hg porosimetry) is 0.74 ml/g, its macroporous volume is 0.52 ml/g.

Example 2: Preparation of a C2 catalyst in accordance with the invention

100 grams of silicon carbide in the form of extrudates are calcined in air in a muffle furnace in a thin layer at 450°C for 2 hours.

29.2 grams of potassium acetate (CH3COOK M= 98 g/mol) are first dissolved in 60 ml of acetic acid at room temperature. The concentration of the solution is 483 g/l. After complete dissolution, the mixture is added dropwise to the SiC extrudates. The solid is matured at room temperature for 20 minutes then dried for 10 hours at 120°C in air. The material is calcined in air at 450°C for 4 hours.

14 mL of an 85% solution of phosphoric acid (H3PO4 M= 98 g/mol) are first dissolved in 40 ml of water at room temperature. After complete dissolution, the mixture is added drop by drop to the calcined material. The solid is matured at room temperature for 20 minutes then dried for 12 hours at 120°C in air. The material is calcined in air at 450°C for 4 hours.

Compositional analysis by FX gives a weight content of K of 8.35% and P of 6.5%. The average equivalent weight content of KPO3 with x = 0 and y = 3 of the catalyst after calcination is 26%.

The catalyst presents in XRD the majority of diffraction peaks of p-SiC as well as diffraction peaks of the KPO3 metaphosphate phase.

The specific surface area (Hg porosimetry) of catalyst C2 is 20 m2/g, its total pore volume (Hg porosimetry) is 0.60 ml/g, its macroporous volume is 0.40ml/g.

Example 3: Preparation of a C3 catalyst according to the invention

100 grams of silicon carbide are calcined in air in a muffle furnace in a thin layer at 450°C for 2 hours.

22 grams of diaminophosphate ((NH4)2HPO4 M= 132 g/mol) with x = 1 and y = 4 and 27 g of cesium carbonate (Cs2CO3 M=326 g/mol) are first dissolved in 60 ml of 'distilled water. After complete dissolution, the mixture is added dropwise to the SiC extrudates. The solid is matured at room temperature for 40 minutes then dried for 10 hours at 120°C in air. The material is calcined in air at 450°C for 4 hours. Compositional analysis by FX gives a weight content of Cs of 17.7% and P of 3.6%. The equivalent average weight content of CsPO3 with x = 0 and y = 3 of the catalyst after calcination is 26.5%.

The catalyst presents in XRD the majority diffraction peaks of p-SiC as well as diffraction peaks of the CsH2PO4 phases with x = 2 and y = 4 and Cs2H2P2O7 with x = 1 and y = 3.5.

The specific surface area (Hg porosimetry) of catalyst C3 is 18 m2/g, its total pore volume (Hg porosimetry) is 0.45 ml/g, its macroporous volume is 0.30ml/g.

Example 4: Preparation of a C4 catalyst (not in accordance with the invention)

The S2 support is a commercial silica in the form of beads with a diameter of less than 2 mm. Its main characteristics are provided in Table 2 below.

Table 2: main characteristics of S2 support.

17 grams of potassium dihydrogen phosphate (KH2PO4M= 136 g/mol) with x = 2 and y = 4 are first dissolved in 68 ml of distilled water at room temperature. The concentration of the solution is 250g of KH2PO4/I. After complete dissolution, the mixture is added dropwise to the SiO2 extrudates. The solid is matured at room temperature for 20 minutes then dried for 1 hour at 120°C in air. The material is calcined in air at 450°C for 4 hours.

Compositional analysis by FX gives a weight content of K of 4.1% and P of 3.6%. The equivalent average weight content of KPO3 with x = 0 and y = 3 of the catalyst after calcination is 13%.

The catalyst shows diffraction peaks of the KPO3 metaphosphate phase in XRD.

The specific surface area (Hg porosimetry) of catalyst 04 is 82 m2/g, its total pore volume (Hg porosimetry) is 0.72 mL/g, its macroporous volume is 0.01 mL/g and its mesoprous volume is 0.68 mL/g. .

Example 5: Use of catalysts C1, C2, C3, C4 for dehydration of lactic acid into acrylic acid.

The C1, C2, C3 and non-C4 compliant catalysts are used for the lactic acid dehydration reaction.

6 grams of shaped catalyst are loaded into a tubular reactor with a diameter of 1 cm. The solid is then heated under a flow of nitrogen at 6 NL/h to 365°C. The pressure in the reactor is 25 bar. After 2 hours of stabilization, a charge containing 10% by weight of lactic acid in 90% water is introduced into the reactor with a flow rate of 3g/h of charge. At the reactor outlet, the liquid effluent is condensed, then analyzed by liquid chromatography. After 100 hours of catalytic testing, the catalyst is unloaded and analyzed.

Conversion and yield

The conversion of lactic acid (LA) is calculated according to the following formula:

AL conversion (%) = 100 x ([AL]load - [AL]effluent) / [AL]load. We checked beforehand that the liquid material balance of the unit was more than 95% recovery mass. with [AL] = mass concentration of AL in g/L determined by high pressure liquid chromatography (HPLC).

The yield is deduced from the acrylic acid (AA) concentration of the liquid effluent relative to the injected load, calculated on a carbon basis only. AA yield (%C) = 100 x (0.5*([AA]effluent) / (0.4*([AL]load - [AL]effluent).

Table 3: Lactic acid conversion of catalysts C1 to C4.

Tableau 5 : Caractérisations par porosimétrie mercure des catalyseurs C1 à C4 avant et après 10Oh de test.

Table 4: XRD characterizations of catalysts C1 to C4 before and after 100 hours of testing.

Table 5: Characterizations by mercury porosimetry of catalysts C1 to C4 before and after 10 Oh of testing.

By catalyst before testing we mean the catalyst before its use in the process.

The catalysts according to the invention are active for the transformation of lactic acid (Table 3). The conversion to lactic acid is greater than or equal to 80%.

They are stable under reaction conditions. The beta-SiC crystal structure of the support is preserved after catalytic testing (Table 4). For catalyst C4, not in accordance with the invention, the structure is modified and diffraction lines of Opal CT are observed after testing which are characteristic of another form of silica than the commercial silica used in catalyst C4 ( Table 4). The textural properties are little modified. In fact, the specific surface area of the catalyst and its pore volume are maintained after testing. Their variation Ax =100* (X before test-X after test) / The macroporous volume decreases by less than 17% while it increases by 30% for catalyst C4. The catalysts of the invention have their textural properties little modified by the operating conditions of the reaction unlike the non-compliant catalyst C4.

Claims

1. Process for preparing a catalyst comprising at least one phosphate salt, of the MI HxPOy type, x being a fractional number between [0-2] and y being a fractional number between [3-4] with M being at least a metal chosen from the group formed by the metals of group I and group II of the periodic table, taken alone or as a mixture and a support comprising silicon carbide SiC, said process comprising at least one step of adding said salt of phosphate on the support comprising silicon carbide. 2. Method according to claim 1 in which the phosphate salts are chosen from the following compounds M1 H2PO4, M2HPO4, (MPO3)n with n>1, M2H2P2O7, M3P3O9, M4P4O12, M6P6O18, M8P8O24 alone or as a mixture. 3. Method according to one of claims 1 or 2 in which the metal(s) M are chosen from the metals Li, Na K, Cs, Rb, taken alone or as a mixture and very preferably from Na, K, Cs, Rb taken alone or in a mixture and even more preferably among K and Cs and very preferably, the metal is potassium K. 4. Method according to one of the preceding claims in which in the case where several metals Ma and Mb are used, the phosphate salts are chosen from the following compounds MaH2PO4, MaMbHPO4, MaMbH2P2O7, MaMb2P3O9, Ma3MbP4O12, Ma3Mb3P6O18, with Ma and Mb chosen from the metals Li, Na K, Cs, Rb, taken alone or in a mixture and Ma + Mb = M and very preferably from Na K, Cs, Rb taken alone or in a mixture and even more preferably from K and Cs. 5. Method according to one of the preceding claims in which said catalyst has a specific surface area greater than 5 m ² /g, preferably between 5 and 300 m ² /g, and more preferably between 10 and 250 m ² /g and a pore volume of between 0.1 and 1.0 cm3/g, preferably between 0.15 and 0.8 cm3/g. 6. Method according to one of the preceding claims in which the silicon carbide used in the catalyst has a specific surface area greater than 5 m ² /g, preferably between 5 and 300 m ² /g, and more preferably comprised between 10 and 250 m ² /g. 7. Method according to one of the preceding claims in which said support has a porous volume of between 0.20 cm3/g and 1.5 cm3/g, preferably between 0.25 cm3/g and 1.4 cm3/ g, and more preferably between 0.25 cm3/g and 1.2 cm3/g. 8. Method according to one of the preceding claims in which the catalyst comprises and is preferably constituted, in weight percentage, by: - 40 to 95%, preferably 50 to 90% and very preferably 55 to 90%, even more preferably between 70% and 85% silicon carbide (SiC), - 5 to 60%, preferably 10 to 50% and very preferably 10 to 45%, even more preferably between 15% and 30% of oxide equivalent of the phosphate salt, denoted MPO3. 9. Preparation process according to one of the preceding claims in which the step of adding the phosphate salt to the support comprising the porous silicon carbide can be carried out by moisture-based impregnation or dry impregnation, by impregnation in excess, by ion exchange, by precipitation deposition, or by vapor phase deposition and preferably by dry impregnation. 10. Preparation process according to one of the preceding claims in which the step of adding the phosphate salt to the support comprising silicon carbide preferably produced by dry impregnation comprises the following steps: - a step a) of preparing a liquid solution of one or more phosphate salts in an aqueous or organic phase, the preparation temperature being advantageously between 5°C and 80°C, preferably between 10°C and 70 °C. - a step b) of impregnation of said solution prepared in step a) on the support comprising silicon carbide, the volume of the solution being advantageously between 0.7 and 1.1, preferably between 0.8 and 1.05 times the pore volume of the support and the phosphate concentration of the solution is preferably between 50g/L to 2000g/L. - a step c) of maturation of the impregnated support obtained in step b), for a period of between 5 min and 40 h, preferably between 10 min and 10 h and even more preferably between 30 min and 5 h, so even more preferred between 1 a.m. and 5 a.m. at a temperature preferably between 10°C and 40°C to obtain a catalyst precursor, - a step d) of drying said catalyst precursor obtained in step c) to obtain a dried catalyst precursor, said drying step being carried out at a temperature between 70°C and 200°C, under air, for a period duration between 30 min and 12 hours, preferably between 1 hour and 10 hours, - Optionally a step e) of calcination in air of the dried catalyst precursor obtained in step d) to obtain a catalyst, said calcination step being carried out at a temperature between 300°C and 550°C, for a duration between 30min and 12h, preferably between 1h and 10h. - Optionally a step f) of heat treatment of the catalyst obtained in step e) optional, said step f) being carried out under inert gas, preferably nitrogen, helium, methane, or carbon dioxide , alone or in a mixture, at a temperature between 500°C and 1200°C, preferably between 600°C and 1100°C and very preferably between 750°C and 1000°C, for a period of between 30min and 12 p.m., preferably between 1 a.m. and 10 a.m., - Optionally a step g) of heat treatment under gas containing water vapor of the catalyst obtained in step d) and/in step f), at a temperature between 350°C and 1000°C, of preferably between 450°C and 950°C and very preferably between 450°C and 900°C at a pressure of between 0.1 and 2 MPa, preferably between 0.15 and 1.5 MPa and even more most preferred between 0.17 and 1.0 MPa.