Process for preparing a material comprising cristobalite silica, a lithium salt, and a potassium and / or cesium phosphate salt

Abstract

The invention relates to a process for preparing a macroporous material comprising an active phase comprising at least one potassium and / or cesium phosphate salt, at least one lithium salt, and a support comprising silica in the crystalline form cristobalite, comprising the following steps: a) at least one silica source is contacted with at least one phosphate precursor, at least one potassium and / or cesium precursor, and at least one lithium precursor to obtain a material precursor; b) the material precursor obtained at the end of step a) is allowed to mature for a period of between 1 minute and 72 hours to obtain a matured material precursor; c) the matured material precursor obtained at the end of step b) is calcined at a temperature of between 800°C and 1200°C to obtain said material.

Description

Title of the invention: Process for preparing a material comprising cristobalite silica, a lithium salt, and a potassium and / or cesium phosphate salt Scope of the invention

[0001] The invention relates to a process for preparing a new macroporous material comprising an active phase including at least one potassium and / or cesium phosphate salt, at least one lithium salt, and a silica-based support in the crystalline form of cristobalite. The material obtained by the process according to the invention can advantageously be used as a support or as a catalyst in catalytic processes. State of the art

[0002] Silica is an interesting compound for use as a catalyst support. However, silica cannot be extruded like other materials in conventional extrusion equipment to produce products sufficiently robust for use in catalytic processes. Indeed, from its manufacture to its implementation, the catalyst incorporating such a support is subjected to numerous steps that can impact its physical integrity. In particular, it must be resistant to crushing, attrition, and pressure variations related to the operating conditions of the catalytic reactor in which it is used. Thus, there is a continuous need to supply catalysts with improved mechanical and physical properties.

[0003] Patent application WO2003 / 026795 discloses a process for producing a catalyst comprising a silica support, which consists of impregnating a silica constituent with a catalytic metal using an aqueous alkaline bath before drying in order to improve its mechanical strength. More specifically, the preparation process consists of forming and washing a silica constituent, such as a silica gel or cogel, for example, a silica-zirconia cogel. The washed silica constituent is then contacted with an alkaline bath to impregnate the catalytic metal, such as cesium, and to form an activated silica constituent. The activated silica constituent is then dried to form the catalyst without a calcination step.

[0004] Patent application WO17040383 discloses a plurality of catalysts comprising at least one mixture of alkali phosphates, some of which have the formula M xPOy (with M = K or Cs or Li), and a non-porous silica binder. The catalysts are prepared by mechanical mixing, using a planetary mill, of an amorphous fused silica, which is a The catalyst precursor is a dense material with no surface or porosity properties, and potassium phosphate precursors. It is then calcined under air at 450°C to obtain a material composed of a LiPO3 / (LiPO3 + SiO2) mixture with a mass ratio of 13 to 26% LiPO3 by weight relative to the total weight of the material. This document also discloses a catalyst in the form of a powder with variable particle size, sieved between 106 and 212 µm. The silica in the final material is in its amorphous form.

[0005] However, none of the prior art documents disclose a macroporous material formed from a lithium phosphate salt, and a potassium and / or cesium phosphate salt, and silica occurring at least partially in the crystalline form cristobalite. Objects of the invention

[0006] The present invention relates to a process for preparing a macroporous material comprising an active phase comprising at least one potassium phosphate salt and / or at least one cesium phosphate salt, at least one lithium salt, and a support comprising silica in at least partial crystalline form cristobalite, comprising at least the following steps:

[0007] a) at least one silica source is brought into contact with at least one phosphate precursor, at least one potassium and / or cesium precursor, and at least one lithium precursor to obtain a material precursor;

[0008] b) the precursor of material obtained at the end of step a) is allowed to mature for a period of between 1 minute and 72 hours to obtain a matured precursor of material;

[0009] c) the precursor of matured material obtained at the end of step b) is calcined at a temperature between 800°C and 1200°C to obtain said material.

[0010] According to one or more embodiments of the invention, in step a) said phosphate, potassium and / or cesium precursors are supplied in the form of at least one potassium phosphate salt and / or at least one cesium phosphate salt.

[0011] According to one or more embodiments of the invention, said potassium phosphate salt is selected from: KH2PO4, KH2P2O2, K6P6O7, K3H2P3O10, K4H2P4O13, K3P3O9, IQP.O12, K6P6O18, K8P8O24, K10P1O03O, potassium phosphate (tripotassium) (PO43,3K+), alone or in mixture.

[0012] According to one or more embodiments of the invention, said cesium phosphate salt is selected from: CsH2PO4, Cs2H2P3O10, Cs4H2P4013, Cs3P3O9, Cs4P4012, Cs6P6O18, Cs8P8O24, (CsPO3), alone or in mixture.

[0013] According to one or more embodiments of the invention, in step a) said lithium precursor is supplied in the form of at least one lithium salt chosen from the phosphate, sulfate, nitrate, carbonate or lithium hydroxide salts, in amorphous or crystalline oxide form, taken alone or in mixture.

[0014] According to one or more embodiments of the invention, said lithium salt is chosen from the lithium phosphate, sulfate, nitrate, carbonate or hydroxide salts of the following list: LiH2PO4, Li2H2P2O7 Li3P3O9, Li4P40i2, Li6P60i8, Li8P8O24, Li2SO4, LiNO3, Li2CO3 LiOH, taken alone or in mixture.

[0015] According to one or more embodiments of the invention, said lithium salt is chosen from lithium nitrate (LiNO3), lithium hydroxide (LiOH), or lithium carbonate (Li2CO3).

[0016] According to one or more embodiments of the invention, said potassium phosphate salt and / or said cesium phosphate salt and said lithium salt are supplied in step a) in powder form.

[0017] According to one or more embodiments of the invention, said powder of at least one potassium and / or cesium phosphate salt and / or said powder of at least one lithium salt are ground and sieved to a grain size of less than 100 µm prior to their introduction into step a).

[0018] According to one or more embodiments of the invention, in which step a) comprises the following substeps:

[0019] i) at least one precipitated silica powder, silica gel or zeolite with a Si / Al ratio >100, at least one colloidal silica sol, at least one powder of at least one potassium and / or cesium phosphate salt and at least one powder of at least one lithium salt are mixed in at least one solvent to obtain a mixture;

[0020] ii) the mixture obtained at the end of step i) is shaped.

[0021] According to one or more embodiments of the invention, step a) comprises the next sub-steps:

[0022] i') at least one colloidal silica sol is mixed with at least one water powder minus a potassium and / or cesium phosphate salt to obtain a suspension;

[0023] ii') a powder of at least one precipitated silica, a silica gel, or a zeolite with a Si / Al ratio >100, at least one powder of at least one lithium salt, and at least one solvent are added to said suspension obtained at the end of step i');

[0024] iii') the dough obtained at the end of step ii' is shaped.

[0025] According to one or more embodiments of the invention, step a) comprises the following substeps:

[0026] i”) a liquid solution in aqueous or organic phase is supplied including at least one phosphate precursor, at least one potassium and / or cesium precursor, and at least one lithium precursor;

[0027] ii”) said solution obtained at the end of step i”) is impregnated onto a shaped support containing silica as a silica source.

[0028] According to one or more embodiments of the invention, the impregnation solution of step i”) comprises a mixture of alkali metal precursors Ml and M2, with Ml selected from K and / or Cs, and M2 being lithium.

[0029] According to one or more embodiments of the invention, said alkali metal precursors M1 and M2 are chosen from carbonate salts M2CO3, nitrate MN03, sulfate, formate HCOOM, acetate CH2COOM, citrate, lactate, chloride MCl, hydroxide MOH and oxide M2O, with M = M1 and / or M2.

[0030] According to one or more embodiments of the invention, said phosphate precursor is chosen from H3PO4, (NH4)H2PO4, (NH4)2HPO4, (NH4)PO4, and P2O5.

[0031] According to one or more embodiments of the invention, said method further comprises the following steps:

[0032] d) said material obtained at the end of step c) is brought into contact with at least a second phosphate precursor, and at least a second potassium and / or cesium precursor to obtain a second material precursor;

[0033] e) the second precursor of material obtained at the end of step d) is calcined at a temperature between 300°C and 600°C. Detailed description 1. Definitions

[0034] In the sense of the present invention, the different embodiments presented can be used alone or in combination with each other, without limitation of combination.

[0035] In the sense of the present invention, the different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the sense of the present invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0036] By "macropores" we mean pores whose opening is greater than 50 nm.

[0037] By "mesopores", we mean pores whose opening is between 2 nm and 50 nm, inclusive.

[0038] The total pore volume (TPV) of the material according to the invention is defined as the volume measured by intrusion with a mercury porosimeter 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 wetting angle was taken to be 140° following the recommendations of the book "Techniques de l'ingénieur, traité analyse et caractérisation", pages 1050-1055, written by Jean Charpin and Bernard Rasneur.

[0039] In order to obtain greater accuracy, the value of the total pore volume corresponds to the value of the total pore volume measured by intrusion with a mercury porosimeter measured on the sample less the value of the total pore volume measured by intrusion with a mercury porosimeter measured on the same sample for a pressure corresponding to 30 psi (approximately 0.2 MPa).

[0040] The volume of macropores and mesopores is measured by mercury intrusion porosimetry according to ASTM D4284-83 at a maximum pressure of 4000 bar (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.

[0041] 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.

[0042] 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.

[0043] The median diameter of macropores (Dmacro in nm) is also defined as a diameter such that all pores smaller than this diameter constitute 50% of the macroporous volume, measured by mercury porosimetry.

[0044] 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.

[0045] 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 laser light deviate the light from its principal axis. The amount of light deviated and The importance of the deflection angle allows for precise measurement of particle size. The powder is conveyed either 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.

[0046] 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 microns to 2000 microns.

[0047] Dry particle size analysis allows for the characterization of powders without disrupting their initial aggregation. The measurement range extends from 0.2 microns to 2000 microns. In the present invention, dry particle size analysis is used to measure the grain size of the constituents of the material of the invention.

[0048] By hourly volumetric velocity “PPH”, we mean the mass flow rate of the feed at the reactor inlet in kg / h at 15°C, 0.1MPa divided by the mass of material in kg contained in the reactor. 2. Detailed Description Material

[0049] An object according to the invention relates to a macroporous material comprising an active phase comprising at least one potassium and / or cesium phosphate salt, at least one lithium salt, and a silica-based support, it being understood that the silica is at least partially in the form of cristobalite crystals.

[0050] Indeed, the Applicant has surprisingly discovered that the use of such a macroporous material as a dehydration catalyst for hydroxypropanoic acid significantly increases its stability under load compared to a catalyst obtained by conventional preparation processes in which the silica is in amorphous form. The macroporous structure of the material and the particular crystallinity of the silica contained therein were obtained by carrying out a specific preparation process comprising a step in which a calcination step is performed at a temperature greater than or equal to 800°C based on a material precursor comprising at least one silica source, at least one potassium and / or cesium precursor, and at least one lithium precursor.

[0051] X-ray diffraction makes it possible to verify that the material according to the invention does indeed contain silica that is totally or partially crystallized in its cristobalite form by comparing the diffractogram obtained with those existing in a database such as the ICDD® (International Centre for Diffraction Data) PDF4+ 2020 crystallographic database. The X-ray diffraction pattern is obtained by X-ray crystallographic analysis using a diffractometer with the classical powder method and copper Kal radiation (X = 1.54060 Å). Starting from the position of the diffraction peaks represented by angle 20, the characteristic interplanar spacings dhkl of the sample are calculated using Bragg's relation. The measurement error A(dhkl) on dhkl is calculated using Bragg's relation as a function of the absolute error A(20) assigned to the measurement of 20. An absolute error A(20) equal to ±0.02° is commonly accepted.

[0052] More specifically, the 21.8° line 20 is primarily associated with the cristobalite crystallographic form. The 28.3°, 31.3°, and 36° lines are also attributed to the formation of cristobalite.

[0053] Advantageously, said potassium phosphate and / or cesium phosphate salt is potassium metaphosphate (KPO3) and / or cesium metaphosphate (CsPO3).

[0054] Advantageously, said lithium salt is selected from lithium metaphosphate (LiPO3), preferably of monoclinic structure, tripotassium lithium diphosphate (LiK3P2O7), preferably of orthorhombic structure, or lithiophosphate (Li3PO4), preferably of orthorhombic structure, taken alone or in mixture.

[0055] Advantageously, said material has a mass ratio MPO3 / (MPO3+SiO2 +Li2O) of between 13 and 50, preferably between 15 and 45, and even more preferably between 17 and 40, and even more preferably between 20 and 40, with M being chosen from potassium and / or cesium (M = K and / or Cs). Preferably, M is potassium.

[0056] Advantageously, said material has a Li / M molar ratio (M = K or Cs) between 0 and 2, preferably between 0.1 and 1.5, most preferably between 0.2 and 1.

[0057] Preferably said material has a total porous volume between 0.01 and 0.6 cmVg, more preferably between 0.04 and 0.5 cmVg, even more preferably between 0.10 and 0.40 cmVg, and even more preferably between 0.14 and 0.39 cmVg.

[0058] Preferably, said material has a macroporous volume between 0.01 and 0.6 cmVg, more preferably between 0.04 and 0.5 cmVg, even more preferably between 0.1 and 0.4 cmVg, and even more preferably between 0.14 and 0.39 cmVg.

[0059] Preferably, the macroporous volume of the material represents between 50% and 100% of the total porous volume of said material, preferably between 60% and 100% and even more preferably between 80% and 100%.

[0060] In an embodiment according to the invention, said material has a specific surface area of ​​less than 1 m2 / g.

[0061] In another embodiment according to the invention, said material has a specific surface area greater than or equal to 1 m² / g and less than 50 m² / g, preferably between 1 and 20 m2 / g, and more preferably between 1 and 18 m2 / g, even more preferred between 1 and 15 m2 / g.

[0062] Advantageously, said material has a mechanical resistance value measured by grain-by-grain crushing greater than 0.5 daN / mm, preferably greater than 0.7 daN / mm, more preferably greater than 0.9 daN / mm and preferably greater than 1.2 daN / mm.

[0063] The material advantageously comprises between 1% and 99% by weight, preferably between 5% and 99% by weight, preferably from 10% to 95% by weight, and most preferably from 20% to 75% by weight of at least one potassium and / or cesium phosphate salt.

[0064] The material advantageously comprises between 1% and 30% by weight, preferably between 3% and 25% by weight, preferably from 5% to 20% by weight, of at least one lithium phosphate salt.

[0065] The material advantageously has between 50% and 90% by weight, preferably between 55% and 85% by weight, preferably from 60% to 85% by weight, and most preferably from 60% to 80% by weight of silica, relative to the total weight of said material.

[0066] Said material according to the invention advantageously has a macroporous median diameter between 80 nm and 7000 nm, preferably between 200 nm and 6500 nm, and more preferably between 500 nm and 4000 nm.

[0067] Said material is advantageously in the form of beads, extrudates, pellets, or irregular and non-spherical agglomerates. Preparation process

[0068] According to the invention, the present invention relates to a process for preparing a macroporous material comprising an active phase comprising at least one potassium phosphate salt and / or at least one cesium phosphate salt, at least one lithium salt, and a support comprising silica in at least partial crystalline form cristobalite, comprising at least the following steps:

[0069] a) at least one silica source is brought into contact with at least one phosphate precursor, at least one potassium and / or cesium precursor, and at least one lithium precursor to obtain a material precursor;

[0070] b) the precursor of material obtained at the end of step a) is allowed to mature for a period of between 1 minute and 72 hours to obtain a matured precursor of material;

[0071] c) the precursor of matured material obtained at the end of step b) is calcined at a temperature between 800°C and 1200°C to obtain said material.

[0072] All steps a) to c) are detailed below. Optional steps d) and e) may also be considered to obtain the material according to the invention. Step a)

[0073] Step a) can be carried out according to several embodiments. Implementation method 1

[0074] In a first embodiment according to the invention, step a) comprises the following substeps:

[0075] i) at least one precipitated silica powder, silica gel or zeolite with a Si / Al ratio >100, at least one colloidal silica sol, at least one powder of at least one potassium and / or cesium phosphate salt and at least one powder of at least one lithium salt are mixed in at least one solvent to obtain a mixture;

[0076] ii) the mixture obtained at the end of step i) is shaped.

[0077] According to this embodiment, said step i) consists of mixing at least one precipitated silica powder, silica gel or zeolite with a Si / Al ratio >100 with at least one colloidal silica sol, at least one powder of at least one potassium phosphate salt and / or at least one cesium salt and at least one powder of at least one lithium salt in at least one solvent to obtain a mixture.

[0078] Preferably, precipitated silica powder, silica gel or zeolite with a Si / Al ratio >100 is selected, without restriction, from the following commercial sources: Nyasil20 (Nyacol ®), Siliaflash P60 (Silicycle ®), Siliaflash C60 (Silicycle ®), Ultrasil VN3 GR, EXP4232 (Evonik ®), ZSM-5 (CBV 28014 ; Zeolyst®), HY (CBV780 ; Zeolyst®) taken alone or in mixture.

[0079] Preferably, precipitated silica powder, silica gel or zeolite with a Si / Al ratio >100 has a grain size of less than 10 pm, and preferably less than 5 pm, even more preferably less than 1 pm.

[0080] Preferably, colloidal silica sols are chosen, without restriction, from the following commercial sources: Ludox (WR Grâce Davison®), Nyacol (Nyacol Nano Technologies®, Inc. or PQ Corp®.), Nalco (Nalco Chemical Company®), Ultra-Sol (RESI Inc®), NexSil (NNTI®), Levasil (Nouryon) taken alone or in mixture.

[0081] Most colloidal silica sols are prepared from sodium silicate and inevitably contain sodium. Since the presence of sodium can be detrimental to catalytic activity, an ion exchange step may be necessary to reduce or even eliminate residual sodium. To avoid this step, the use of low-sodium colloidal silica sols is preferable; examples include Ludox AS40 stabilized with an ammonium counterion, or Nyacol 2034DI, Nalco 1034A, Ultra-Sol 7H, or NexSil 20A.

[0082] The silica source(s) used in the process according to the present invention are advantageously synthetic amorphous silicas or zeolites with Si / Al ratios >100.

[0083] The potassium phosphate salt(s) used in step i) are advantageously chosen from potassium phosphate salts in amorphous or crystalline oxide form taken alone or in mixture.

[0084] The potassium phosphate salt(s) are advantageously chosen from the following list: KH2PO4, KH2P2O2, K6P6O7, K3H2P3O1, K4H2P4O3, K3P3O9, K4P4O2, K6P6O18, K8P8O24, K10P10O3, potassium phosphate (tripotassium) (PO43,3K+), alone or in a mixture. Preferably, the preferred potassium phosphate salt is chosen from potassium phosphate (tripotassium) (PO43,3K+) and KH2PO4, alone or in a mixture.

[0085] The cesium phosphate salt(s) are advantageously chosen from the following list: CsH2PO4, Cs2H2P3O10, Cs4H2P4O13, Cs3P3O9, Cs4P4O12, Cs6P6O18, Cs8P8O24, (CsPO3), alone or in mixtures. Preferably, the preferred cesium phosphate salt is CsH2PO4.

[0086] Preferably, the potassium phosphate or cesium phosphate salt(s) are chosen from potassium phosphate (tripotassium) (PO43,3K+), KH2PO4, CsH2 PO4 in their hydrated or non-hydrated form.

[0087] The lithium salt(s) used in step i) are advantageously chosen from lithium phosphate, sulfate, nitrate, carbonate or hydroxide salts, in amorphous or crystalline oxide form, taken alone or in mixture.

[0088] Preferably, the lithium salt(s) are chosen from lithium phosphate, sulfate, nitrate, carbonate or hydroxide salts from the following list: LiH 2PO4, Li2H2P2O7 Li3P3O9, Li4P4O12, Li6P6O18, Li8P8O24, Li2SO4, LiNO3, Li2CO3jLiOH, taken alone or in mixture.

[0089] Preferably, the lithium salt(s) are chosen from the following list: lithium nitrate (LiNO3), lithium hydroxide (LiOH), or lithium carbonate Li2CO3, in their hydrated or non-hydrated form, taken alone or in mixture.

[0090] Even more preferably, the lithium salt is lithium nitrate (LiNO3), in its hydrated or non-hydrated form. Preferably, at least one organic adjuvant is also mixed in during step i).

[0091] Said organic adjuvant may also be selected from any additives known to those skilled in the art. In the case where at least one organic adjuvant is added in step i), said organic adjuvant is advantageously selected 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.

[0092] Preferably, said organic adjuvant may be mixed in powder form or in solution in said solvent.

[0093] Said solvent is advantageously chosen from water, ethanol, alcohols and amines. Preferably, said solvent is water.

[0094] Within the framework of the invention, it is entirely possible to proceed with mixtures of several different silica powders and / or different silica sols and / or different potassium or cesium phosphate powders, and / or different lithium salt powders.

[0095] The order in which the mixture of powders of at least the silica sources, at least one powder of potassium and / or cesium phosphate salt, at least one powder of lithium salt, and possibly at least one organic adjuvant in the case where these are mixed in powder form, with at least one solvent is carried out is indifferent.

[0096] The mixing of said powders and said solvent can advantageously be carried out in a single step.

[0097] The addition of powders and solvent can also advantageously be alternated.

[0098] The potassium phosphate and / or cesium phosphate salt(s) used in step i) are advantageously presented in powder form.

[0099] Preferably, the potassium and / or cesium phosphate salt(s), when mixed in powder form, can advantageously be ground and sieved to a particle size of less than 100 pm.

[0100] The lithium salt(s) used in step i) are advantageously in powder form.

[0101] Preferably, said lithium salt, when mixed in powder form, can advantageously be ground and sieved to a particle size of less than 100 µm. Preferably, the silica source used in step i) has a grain size of less than 60 µm, and preferably less than 25 µm, even more preferably less than 5 µm, and most preferably less than 2 µm.

[0102] In a particularly preferred embodiment, the use of a silica source used in step i) having a grain size of less than 60 pm, and preferably less than 25 pm, even more preferably less than 5 pm, most preferably less than 2 pm, combined with the use of a powder of at least one potassium and / or cesium phosphate salt ground and sieved to a grain size of less than 100 pm, allows a significant improvement in the mechanical strength of the materials obtained according to the invention.

[0103] Preferably, said powders of at least one source of silica, of at least one potassium and / or cesium phosphate salt, of lithium salt, and possibly of less an organic adjuvant, in the case where these are mixed in powder form, are first premixed, dry, before the introduction of the solvent. Said premixed powders are then advantageously brought into contact with said solvent.

[0104] In another embodiment, at least said silica sources and at least said organic adjuvant may be pre-in solution or suspension in said solvent when said solvent is brought into contact with potassium and / or cesium phosphate powders and lithium salt powder. Contact with said solvent leads to the formation of a mixture which is then advantageously kneaded.

[0105] In the case where at least one cesium phosphate salt powder is used, ammonia is advantageously added to the mixture to obtain an extrudable mixture.

[0106] Preferably, said mixing step i) is carried out by kneading, either batch (according to Anglo-Saxon terminology) or continuously.

[0107] In the case where said step i) is carried out discontinuously, said step i) is advantageously carried out in a mixer preferably equipped with Z-arms, or cams, or in any other type of mixer such as, for example, a planetary mixer. Said mixing step i) makes it possible to obtain a homogeneous mixture of the powdered constituents.

[0108] Preferably, said step i) is carried out at a temperature between 13 and 25°C, for a duration between 5 and 60 minutes, and preferably between 10 and 50 minutes. The rotation speed of the mixer arms is advantageously between 10 and 75 rpm, preferably between 25 and 50 rpm.

[0109] Preferably, the following quantities are introduced in step i) of mixing of the process according to the invention:

[0110] - 1% to 99% by weight, preferably 5% to 99% by weight, preferably 10% at 95% by weight, and most preferably from 15% to 65% by weight of at least one precipitated silica, silica gel or zeolite with a Si / Al ratio>100; [YES] - 1% to 99% by weight, preferably 5% to 99% by weight, preferably 10% to 95% by weight, and most preferably 5% to 50% by weight of at least one colloidal silica sol;

[0112] - 1% to 99% by weight, preferably 5% to 99% by weight, preferably 10% at 95% by weight, and most preferably from 20% to 75% by weight of at least one powder of potassium or cesium phosphate salt;

[0113] - 1% to 30% by weight, preferably 3% to 25% by weight, preferably 5% to 20% by weight of at least one lithium salt powder;

[0114] - 0% to 20% by weight, preferably from 1% to 15% by weight, preferably from 1% to 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 (i.e. the final material obtained at the end of step c) and the sum of the contents of each of the compounds of said material being equal to 100%.

[0115] According to the invention, said step ii) consists of shaping the mixture obtained at the end of step i). Preferably, the mixture obtained at the end of step i) is advantageously shaped by extrusion.

[0116] If the shaping of the mixture from step i) is carried out by extrusion, said step ii) is advantageously performed in a piston, single-screw, or twin-screw extruder. In this case, an organic additive may optionally be added in mixing step i). The presence of said organic additive facilitates shaping by extrusion. Said organic additive is described above and is introduced in step i) in the proportions indicated above.

[0117] In the case where said preparation process is implemented continuously, said step i) of mixing can be coupled with step ii) of shaping by extrusion in the same equipment. According to this implementation, the extrusion of the mixture, also called "mixed paste," can be carried out either by extruding directly from the end of a continuous mixer of the twin-screw type, for example, 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, and more preferably trilobed or quadrilobed.

[0118] In the case where the shaping of the mixture from step i) is carried out by extrusion, the quantity of solvent added in step i) 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.

[0119] Preferably, said extrusion shaping step ii) is carried out at an extrusion pressure greater than 1 MPa and preferably between 3 MPa and 10 MPa. Implementation method 2

[0120] In a second embodiment according to the invention, step a) comprises the following substeps:

[0121] i') at least one colloidal silica sol is mixed with at least one water powder minus a potassium and / or cesium phosphate salt to obtain a suspension;

[0122] ii') a powder of at least one precipitated silica, silica gel, or zeolite with a Si / Al ratio >100, at least one powder of at least one lithium salt, and is added to minus a solvent in said suspension obtained at the end of step i');

[0123] iii') the dough obtained at the end of step ii' is shaped.

[0124] According to the second embodiment, said step i') consists of mixing at least one colloidal silica sol with at least one powder of at least one potassium and / or cesium phosphate salt to obtain a suspension.

[0125] A solvent, preferably water, can advantageously be added in step i').

[0126] Preferably, colloidal silicas or silica sols are chosen, without restriction, from the following commercial sources and are in liquid form: Ludox (WR Grâce Davison®), Nyacol (Nyacol Nano Technologies®, Inc. or PQ Corp®), Nalco (Nalco Chemical Company®), Ultra-Sol (RESI Inc®), NexSil (NNTI®), taken alone or in mixtures.

[0127] The source or sources of colloidal silica soil used in the process according to the present invention are advantageously synthetic amorphous silicas.

[0128] The potassium phosphate and / or cesium phosphate salt(s) used in step a) are advantageously chosen from potassium or cesium phosphate salts in amorphous or crystalline oxide form taken alone or in mixture.

[0129] The potassium phosphate salt(s) are advantageously chosen from the following list: KH2PO4, KH2P2O12, K6P6O7, K3H2P3O10, K4H2P4O13, K3P3O9, K4P4O12, K6P6O18, K8P8O24, K10P10O30, potassium phosphate (tripotassium) (PO43,3K+), alone or in mixtures. Preferably, the preferred potassium phosphate salt is KH2PO4.

[0130] The cesium phosphate salt(s) are advantageously chosen from the following list: CsH2PO4, CS2H2P3O10, CS4H2P4O13, CS3P3O9, Cs4P4O12, Cs6P6O18, Cs8P8O24, (CsPO3), alone or in mixtures. Preferably, the preferred cesium phosphate salt is CsH2PO4.

[0131] Preferably, the potassium phosphate or cesium phosphate salt(s) are chosen from KH2PO4, CsH2PO4 in their hydrated or non-hydrated form.

[0132] Preferably, said powders of at least one potassium and / or cesium phosphate salt can advantageously be ground and sieved to a grain size of less than 100 µm prior to their introduction in step i'). The grain size of the potassium and / or cesium phosphate salts is advantageously measured by dry laser granulometry.

[0133] Most preferably, said step i') is advantageously carried out in a centrifugal planetary mixer. Said powders of at least one potassium and / or cesium phosphate salt, preferably ground and sieved to a particle size of less than 100 µm, are pre-dispersed by means of a centrifugal planetary mixer in the presence of the colloidal silica soil source so as to obtain said suspension.

[0134] Said step i') is advantageously carried out at a mixing speed applied to the centrifugal planetary mixer, between 100 and 2000 revolutions per minute, preferably between 200 and 500 revolutions per minute.

[0135] Preferably, said step i') is carried out for a duration of between 5 seconds and 60 seconds and preferably between 20 seconds and 60 seconds.

[0136] The additions of powders, colloidal silica sol and solvent can also advantageously be alternated.

[0137] According to the second embodiment, the process includes a step ii') of adding a powder of at least one precipitated silica, a silica gel, or a zeolite of Si / Al ratio >100, at least one powder of at least one lithium salt, and at least one solvent into said suspension obtained at the end of step i').

[0138] Preferably, precipitated silicas, silica gels, or zeolites with a Si / Al ratio >100 added in step ii') are chosen without restriction from the following commercial sources: Nyasil20 (Nyacol ®), Siliaflash P60 (Silicycle ®), Siliaflash C60 (Silicycle ®), Ultrasil VN3 GR (Evonik ®), ZSM-5 (CBV 28014; Zeolyst®), HY (CBV780; Zeolyst®) taken alone or in mixture.

[0139] Preferably, the powder of at least one precipitated silica or silica gel or zeolite with a Si / Al ratio >100 added in step ii') has a grain size of less than 60 pm, and preferably less than 25 pm, even more preferably less than 5 pm, most preferably less than 2 pm.

[0140] The grain size of precipitated silica or silica gel or zeolite with a Si / Al ratio >100 is advantageously measured by dry laser granulometry.

[0141] Preferably, the precipitated silica or silica gel is in amorphous form.

[0142] The lithium salt(s) added in step ii') are advantageously chosen from lithium phosphate, sulfate, nitrate, carbonate or hydroxide salts, in amorphous or crystalline oxide form taken alone or in mixture.

[0143] Preferably, the lithium salt(s) are chosen from lithium phosphate, sulfate, nitrate, carbonate or hydroxide salts from the following list: LiH 2PO4, Li2H2P2O7 Li3P3O9, Li4P4O12, Li6P6O18, Li8P8O24, Li2SO4, LiNO3, Li2CO3jLiOH, taken alone or in mixture.

[0144] Preferably, the lithium salt(s) are chosen from lithium nitrate (LiNO3), lithium hydroxide (LiOH), or lithium carbonate (Li2CO3) in their hydrated or non-hydrated form.

[0145] Even more preferably, the lithium salt is lithium nitrate (LiNO3), in its hydrated or non-hydrated form.

[0146] In a variant of the second embodiment of the preparation process according to the invention, the introduction of the lithium salt can be carried out in step i') instead of step ii) under the same conditions as mentioned above.

[0147] Furthermore, within the scope of the invention, it is entirely possible to proceed to mixtures of several different silica powders and / or different silica sols and / or different potassium and / or cesium phosphate salt powders and / or different lithium salt powders.

[0148] According to the invention, at least one solvent is added in step ii'). Said solvent is advantageously chosen from water, ethanol, alcohols and amines. Preferably, said solvent is water.

[0149] Preferably, at least one organic adjuvant may also be added during step ii').

[0150] Said organic adjuvant may also be chosen from among all additives known to the person skilled in the art.

[0151] In the case where at least one organic adjuvant is added in step ii'), said organic adjuvant is advantageously selected 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 mixture.

[0152] Preferably, said organic adjuvant may be mixed in powder form or in solution in said solvent.

[0153] Step i') and step ii') can advantageously be carried out in the same equipment and preferably in a centrifugal planetary mixer.

[0154] In another embodiment, steps i') and ii') can advantageously be carried out in different equipment. In this case, step i') is preferably carried out in a centrifugal planetary mixer and then the suspension obtained at the end of step i') is then transferred to a Z-arm type batch mixer in which are added to said suspension a powder of at least one precipitated silica or silica gel, a powder of at least one lithium salt and at least one solvent, according to step ii').

[0155] In the case where step i') and step ii') are not carried out in the same equipment, preferably, the source of precipitated silica, silica gel or zeolite with a Si / Al ratio > 100, a powder of at least one lithium salt, at least one solvent and optionally at least one organic adjuvant are added first, preferably in the Z-arm type batch mixer, before the introduction of the suspension obtained in step i').

[0156] In the case where a cesium phosphate salt powder is used, ammonia may be added to obtain an extrudable mixture in step ii').

[0157] Preferably, said mixing step ii') is carried out by kneading, either discontinuously or continuously.

[0158] In the case where said step ii') is carried out discontinuously, said step ii') is advantageously carried out in a mixer preferably equipped with Z-arms, or cams, or in any other type of mixer such as, for example, a planetary mixer. Said mixing step ii') makes it possible to obtain a paste or a homogeneous mixture of the constituents.

[0159] In the case of the implementation of a "Z-arm" type mixer in step ii'), the rotation speed of the mixer arms is advantageously between 10 and 75 revolutions / minute, preferably between 25 and 50 revolutions / minute.

[0160] In the case of implementing step ii') in a centrifugal planetary mixer, the rotation speed is advantageously between 300 and 2000 rpm, preferably between 1500 and 2000 rpm in order to obtain a paste.

[0161] In a particularly preferred embodiment, the use of a powder of at least one salt of potassium and / or cesium phosphate ground and sieved to a particle size of less than 100 pm in step i') associated with the use of a source of precipitated silica or silica gel, or zeolite of Si / Al ratio>100 having a reduced size and preferably less than 10 pm, more preferably less than 5 pm, more preferably less than 1 pm, in step ii') allows a significant improvement in the mechanical strength of the materials obtained according to the invention.

[0162] Preferably, the following quantities are introduced in steps i') and ii'):

[0163] - 1% to 99% by weight, preferably 5% to 99% by weight, preferably 5% to 95% by weight, and most preferably 5% to 40% by weight and even more preferably 5% to 20% by weight of at least one colloidal silica sol;

[0164] - 1% to 99% by weight, preferably 5% to 99% by weight, preferably 10% at 95% by weight, and most preferably from 10% to 60% by weight of at least one potassium and / or cesium phosphate salt;

[0165] - 1% to 99% by weight, preferably 5% to 99% by weight, preferably 10% at 95% by weight, and very preferably from 30% to 80% by weight of at least one precipitated silica, silica gel or zeolite with a Si / Al ratio > 100;

[0166] - 1% to 30% by weight, preferably 3% to 25% by weight, preferably 5% to 20% by weight of at least one lithium salt powder;

[0167] - 0% to 20% by weight, preferably from 1% to 15% by weight, preferably from 1% to 10% by weight, and 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%.

[0168] According to the second embodiment, said process includes a step iii') of shaping the dough obtained at the end of step ii') of mixing.

[0169] Preferably, the paste obtained at the end of step ii') is advantageously shaped by extrusion.

[0170] In the case where the shaping of the mixture from step ii') is carried out by extrusion, said step ii') is advantageously carried out in a piston, single screw or twin screw extruder.

[0171] In this case, an organic additive may optionally be added in mixing step ii'). The presence of said organic additive facilitates shaping by extrusion. Said organic additive is described above and is introduced in step ii' in the proportions indicated above.

[0172] The extrusion of the mixture, also called "kneaded paste," can be carried out either by extruding directly from the end of a continuous twin-screw mixer, for example, 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, multilobed, grooved, or slotted.

[0173] In the case where the shaping of the mixture from step ii') is carried out by extrusion, the quantity of solvent added in step ii') 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.

[0174] Preferably, said extrusion shaping step iii') is carried out at an extrusion pressure greater than 1 MPa and preferably between 3 MPa and 10 MPa. Implementation method 3

[0175] In a third embodiment according to the invention, step a) comprises the following substeps:

[0176] i”) a liquid solution in aqueous or organic phase is supplied comprising at least one phosphate precursor, and at least one potassium and / or cesium precursor, and at least one lithium precursor, the preparation temperature being advantageously between 5°C and 80°C, preferably between 10°C and 70°C, the phosphate concentration of the solution being preferably between 50 g / L and 2000 g / L;

[0177] ii”) the solution obtained at the end of step i”) is impregnated onto a support containing silica (as a silica source), the volume of the solution being avan typically between 0.9 and 1.1, preferably between 0.8 and 1.05 times the porous volume of the support.

[0178] The impregnation solution of step i”) is preferably prepared by dissolving one or more phosphate, potassium (K) and / or cesium (Cs), and lithium (Li) precursors in an aqueous or organic phase. The impregnation solution may advantageously be prepared by mixing phosphorus and alkali metals introduced independently. In this case, the alkali metal precursors M1 and M2 are, on the one hand, K and / or Cs for metal M1 and Li for metal M2. For example, said alkali metal precursors M1 and M2 may be selected from carbonate salts M2CO3, nitrate salts MN03, sulfate salts, formate salts HCOOM, acetate salts CH2COOM, citrate salts, lactate salts, chloride salts MCl, hydroxide salts MOH, and oxide salts M2O, with M = M1 and / or M2.

[0179] The phosphate precursor(s) may advantageously be chosen, for example, from H3PO4, (NH4)H2PO4, (NH4)2HPO4, (NH4)PO4, P2O5.

[0180] The support supplied in step ii”) advantageously comprises an amorphous SiO2 phase, characterizable by X-ray diffraction. Said support preferably has a specific surface area greater than 5 m2 / g, preferably between 5 and 500 m2 / g, and even more preferably between 10 and 450 m2 / g.

[0181] The porous volume of the support is advantageously between 0.05 cmVg and 1.5 cmVg, preferably between 0.2 cmVg and 1.2 cmVg, and even more preferably between 0.25 cmVg and 1.1 cmVg.

[0182] The macroporous volume of the support is advantageously between 0.01 cmVg and 0.5 cmVg, preferably between 0.01 cmVg and 0.4 cmVg, and even more preferably between 0.01 cmVg and 0.3 cmVg.

[0183] The manufacture of amorphous silicon oxide type supports and their shaping is well known and taught in the art, for example in the Handbook of Porous Solids, Wiley-VCH (Volume 3, pages 1543-1590).

[0184] Preferably, the support supplied in step ii”) is in the form of beads, extrudates (preferably cylindrical, trilobed or quadrilobed), pellets, or irregular and non-spherical agglomerates.

[0185] Most advantageously, said support is in the form of beads or extrudates.

[0186] When the support 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. When the support 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. When the support 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 of length between 1.0 mm and 2.0 mm.

[0187] Preferably, the impregnation step ii”) can be preceded by a heat treatment step carried out at a temperature between 80°C and 550°C.

[0188] Preferably, the impregnation step ii”) can be followed, optionally, by other impregnation steps. The impregnation steps following the first can advantageously be carried out after the maturation step b). Step b)

[0189] The preparation process according to the invention includes a step b) of maturing the material obtained at the end of step a). Said maturation step is advantageously carried out at a temperature between 0°C and 300°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.

[0190] Preferably, this maturation 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 ensures good hydration of the material, limiting the appearance of cracks that are detrimental to mechanical strength. At the end of step b), a precursor of the matured material is obtained. Step c)

[0191] According to an essential step in the preparation process, the matured material precursor from step b) undergoes a calcination step c) at a temperature between 800°C and 1200°C, preferably between 800°C and 1100°C, and most preferably between 800°C and 900°C. Step c) is carried out for a duration advantageously between 1 and 12 hours, preferably between 1 and 4 hours. This step is essential for the formation of the cristobalite crystallographic phase. This step also allows for the removal of the organic additives used to facilitate shaping the material.

[0192] Said calcination step c) is advantageously carried out under a gas stream comprising oxygen, for example preferably the precursor of mature material obtained at the end of step b) is calcined under dry air or with different humidity levels or 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 preferably at least 10% by volume, of oxygen relative to the total volume of said gas mixture.

[0193] At the end of step c) a material is obtained according to an embodiment according to the invention. However, the preparation process may also include two additional steps (d) and (e) to obtain a material according to another embodiment of the invention. Steps (d) and (e) are described in detail below. Step d) (optional)

[0194] In an embodiment according to the invention, the material obtained at the end of step c) is contacted with at least one second phosphate precursor, and at least one second potassium and / or cesium precursor to obtain a second material precursor.

[0195] Advantageously, step d) comprises the following substeps:

[0196] dl) a liquid solution in aqueous or organic phase is prepared comprising at least one second precursor of phosphate, and at least one second precursor of potassium and / or cesium, at a temperature preferably between 5°C and 80°C, more preferably between 10°C and 70°C;

[0197] d2) the solution prepared in step d1) is impregnated onto the material obtained at the end of step c), 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 obtained at the end of step c);

[0198] d3) optionally, a maturation step of the second material precursor obtained at the end of step d2),

[0199] d4) optionally, a drying step of the second material precursor matured obtained at the end of step d3).

[0200] Preferably, the phosphate concentration of the solution supplied in step dl) is between either 50 g / L and 2000 g / L.

[0201] The impregnation solution of step d1) is preferably prepared by dissolving one or more phosphate precursors and potassium (K) or cesium (Cs) in an aqueous or organic phase. The impregnation solution can advantageously be prepared by mixing phosphorus and alkali metals introduced independently. In this case, the alkali metal precursor M, chosen from K or Cs, is selected, for example, from one or more of the following salts: carbonate M2CO3, nitrate MNO3, sulfate, formate HCOOM, acetate CH2COOM, citrate, lactate, chloride MCl, hydroxide MOH, or oxide M2O.

[0202] The phosphate precursor(s) may advantageously be chosen, for example, from H3PO4, (NH4)H2PO4, (NH4)2HPO4, (NH4)PO4, P2O5.

[0203] Preferably, a maturation step d3) is carried out, advantageously at a temperature between 0°C and 300°C, preferably between 20°C and 200°C and preferably between 20°C and 150°C, preferably for a duration 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.

[0204] Preferably, said maturation 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 good hydration of the material, limiting the appearance of cracks that are detrimental to mechanical strength.

[0205] Preferably, after the maturation step d3), a drying step is carried out at a temperature below 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 more preferably between 0.5 hours and 5 hours. Longer durations are not excluded, but do not necessarily provide any improvement.

[0206] Preferably, the impregnation step d) can be followed, optionally, by other impregnation steps. Step e) (optional)

[0207] In an embodiment according to the invention, the second precursor of material obtained at the end of step d) of impregnation, undergoes a step e) of calcination at a temperature between 300°C and 600°C, preferably between 300°C and 550°C, and most preferably between 300°C and 525°C for a duration advantageously between 1 hour and 12 hours, preferably between 1 hour and 4 hours.

[0208] Said calcination step e) is advantageously carried out under a gas stream comprising oxygen; for example, preferably the extrudates are calcined under dry air or with different humidity levels, or 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, of oxygen.

[0209] At the end of step e) the material is obtained according to another embodiment according to the invention. Transformation process

[0210] The material according to the invention can advantageously be used as a catalyst in a process for the dehydration of hydroxypropanoic acid and its derivatives.

[0211] The process for dehydrating hydroxypropanoic acid and its derivatives operates in the presence of the material prepared according to the invention, which is advantageously used as a catalyst 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 material mass load between 0.01 h 1 and 100 h *, preferably between 0.02 and 50 h1, more preferably between 0.03 and 30 h 1 and very preferably between 0.05 and 20 h1.

[0212] Said process makes it possible to selectively obtain a mixture of products comprising acrylic acid.

[0213] 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.

[0214] Said process can advantageously be carried out under a neutral or oxidizing atmosphere.

[0215] 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 feed being injected into the process preferentially in liquid phase. Charge

[0216] The feedstock for said process advantageously comprises at least one compound included in the list of hydroxypropanoic acid and its derivatives. Said feedstock advantageously comprises a hydroxypropanoic acid selected from 2-hydroxypropanoic acid, 3-hydroxypropanoic acid. Preferably, said feedstock comprises 2-hydroxypropanoic acid. Said feedstock 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% by weight of hydroxypropanoic acid and its derivatives.

[0217] Said feedstock may also include impurities related, 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 feedstock. The hydroxypropanoic acid(s) and its derivatives included in said feedstock may be of any origin, chemical, petrochemical, or bio-based.

[0218] Said charge 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.

[0219] Said charge 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, such as an alcohol.

[0220] The main products obtained by said process are hydroxypropanoic acids and its unconverted derivatives, acrylic acid from the dehydration reaction.

[0221] The examples below illustrate the invention without limiting its scope. Examples

[0222] To exemplify the invention, several methods of preparing materials are described. The contents are expressed as mass percentages.

[0223] Example 1: Preparation of extrudates A based on embodiment 1 in presence of precipitated silica powder (% Li2O = 8.1)

[0224] Precipitated silica powder (Nyasil20; Nyacol®) (41.1%), colloidal silica sol source (12.8%), potassium phosphate (KPO3, Aldrich) (27.5%), lithium nitrate (LiNO3, Aldrich) (18.6%), and Methocel™ (K15M) (3%) are introduced and premixed in a Brabender brand mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The resulting paste is then extruded on an MTS brand piston extruder using a 1.6 mm diameter cylindrical die. The resulting extrudates (extruded A) are then dried for 16 hours at 120°C in a ventilated oven. Finally, the extrudates A are subjected to different calcination temperatures (450°C and 800°C) in a muffle furnace for 3 hours. The extrudates calcined at 450°C are named materials Al (not according to the invention) and the extrudates calcined at 800°C are named materials A2 (according to the invention) [see Table 1 below].

[0225] Example 2: Preparation of extrudates B based on embodiment 2 in presence of a colloidal silica soil (% Li2O = 7.8)

[0226] A source of colloidal silica soil (12.3%) and a source of ground and sieved potassium dihydrogen phosphate (KH2PO4; Aldrich) powder (30.4%) at 100 µm are introduced and mixed in the bowl of a Thinky brand centrifugal planetary mixer. The rotation speed is set at 1500 rpm for 30 seconds. Then, the resulting suspension, Methocel™ (K15M) powder (3%), lithium nitrate (LiNO3; Aldrich) powder (17.9%), and precipitated silica powder (Nyasil20; Nyacol®) (39.4%) are introduced and premixed in a Brabender brand mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The resulting paste is then extruded using an MTS piston extruder with a 1.6 mm diameter cylindrical die. The extruded products (extruded product B) are dried for 16 hours at 120°C in a ventilated oven.Finally, the B extrudates are subjected to different calcination temperatures (450°C and 800°C) in a muffle furnace for 3 hours. The extrudates calcined at 450°C are designated material B1 (not in accordance with the invention), the extrudates calcined at 800°C are designated material B2 (in accordance with the invention) [see Table 1 below].

[0227] Example 3: Preparation of extrudates B' based on embodiment 2 in presence of a colloidal silica soil (% Li2O = 5.5)

[0228] A source of colloidal silica soil (13.9%), a source of dihydrogen- powder Ground and sieved 100 µm potassium phosphate (KH2PO4; Aldrich) (31.5%) is introduced and mixed in the bowl of a Thinky centrifugal planetary mixer. The rotation speed is set at 1500 rpm for 30 seconds. The resulting suspension, Methocel™ (K15M) powder (3%), lithium nitrate (LiNO3; Aldrich) powder (12.8%), and precipitated silica powder (Nyasil20; Nyacol®) (41.8%) are then introduced and premixed in a Brabender mixer. Water is added dropwise until a paste is formed, and mixing is continued for 20 minutes. The resulting paste is then extruded on an MTS piston extruder using a 1.6 mm diameter cylindrical die. The resulting extrudates (extruded B') are dried for 16 hours at 120°C in a ventilated oven. Finally, the extruded B' are subjected to different calcination temperatures (450°C and 800°C) in a muffle furnace for 3 hours.Extruded materials calcined at 450°C are designated B3 materials (not in accordance with the invention), extruded materials calcined at 800°C are designated B4 materials (in accordance with the invention) [see Table 1 below].

[0229] Example 4: Preparation of extrudates B” based on embodiment 2 in the presence of a colloidal silica sol (% Li2O = 3.9)

[0230] A source of colloidal silica soil (14.5%) and a source of ground and sieved potassium dihydrogen phosphate (KH2PO4; Aldrich) powder (32.9%) (100 µm) are introduced and mixed in the bowl of a Thinky brand centrifugal planetary mixer. The rotation speed is set at 1500 rpm for 30 seconds. Then, the resulting suspension, Methocel™ (K15M) powder (3%), lithium nitrate (LiNO3; Aldrich) powder (8.9%), and precipitated silica powder (Nyasil20; Nyacol®) (43.6%) are introduced and premixed in a Brabender brand mixer. Water is added dropwise until a paste is obtained, and mixing is continued for 20 minutes. The resulting paste is then extruded using an MTS piston extruder with a 1.6 mm diameter cylindrical die. The extruded products (B” extrudates) are dried for 16 hours at 120°C in a ventilated oven.Finally, the extrudates B” are subjected to different calcination temperatures (450°C and 800°C) in a muffle furnace for 3 hours. The extrudates calcined at 450°C are designated B5 materials (not in accordance with the invention), the extrudates calcined at 800°C are designated B6 materials (in accordance with the invention) [see Table 1 below].

[0231] Example 5: Preparation of extruded B”' based on embodiment 2 in presence of a colloidal silica soil (% Li2O = 2.04)

[0232] A source of colloidal silica soil (15.2%) and a source of ground and sieved potassium dihydrogen phosphate (KH2PO4; Aldrich) powder (34.5%) (100 µm) are introduced and mixed in the bowl of a Thinky brand centrifugal planetary mixer. The rotation speed is set at 1500 rpm for 30 seconds. Then, the resulting suspension is mixed with Methocel™ (K15M) powder (3%) and nitrate powder. Lithium (LiNO3, Aldrich) (4.7%) and precipitated silica powder (Nyasil20; Nyacol®) (45.6%) are introduced and premixed in a Brabender mixer. Water is added dropwise until a paste is formed, and mixing is continued for 20 minutes. The resulting paste is then extruded on an MTS piston extruder using a 1.6 mm diameter cylindrical die. The resulting extrudates (B”' extrudates) are dried for 16 hours at 120°C in a ventilated oven. Finally, the extrudates B'” are subjected to different calcination temperatures (450°C and 800°C) in a muffle furnace for 3 hours. The extrudates calcined at 450°C are designated material B7 (not in accordance with the invention), the extrudates calcined at 800°C are designated material B8 (in accordance with the invention) [see Table 1 below].

[0233] Example 6: Preparation of extrudates C based on embodiment 2 in the presence of a zeolite powder (e.g., %Li2O = 7.9)

[0234] A source of colloidal silica soil (12.3%) and a source of ground and sieved potassium dihydrogen phosphate (KH2PO4; Aldrich) powder (30.4%) (100 µm) are introduced and mixed in the bowl of a Thinky centrifugal planetary mixer. The rotation speed is set at 1500 rpm for 30 seconds. The resulting suspension, along with methocel (K15M) powder (3%), lithium nitrate (LiNO3; Aldrich) powder (18.2%), and ZSM-5 zeolite powder (CBV28014; Zeolyst) (38.6%), are introduced and pre-mixed in a Brabender mixer. Water is added dropwise until a paste is formed, and mixing is continued for 20 minutes. The resulting paste is then extruded using an MTS piston extruder with a 1.6 mm diameter cylindrical die. The extruded products are dried for 16 hours at 120°C in a ventilated oven.Finally, the extrudates obtained (extrudes C) are subjected to different calcination temperatures (450°C and 800°C) in a muffle furnace for 3 hours. The extrudates calcined at 450°C are designated Cl materials (not in accordance with the invention) and the extrudates calcined at 800°C are designated C2 materials (in accordance with the invention) [see Table 1 below].

[0235] For each of the materials obtained (conforming or non-conforming), the structural characteristics (Total pore volume, macroporous volume, macroporous median diameter, specific surface area, EGG) and the crystalline phases observed by XRD are indicated in Table 1 below.

[0236] [Tables 1] Calcination temperature (°C) Li (% weight measured as Li2O) Total volume (cm3 / g) Macro volume (cmVg) Macro density (nm) Sbet (m2 / g) EGG (daN / mm) XRD Al (non-compliant) 450 8.1 0.28 0.28 500 55 Monoclinic KPO3 Amorphous silicic phase Quartz and tridymite A2 (compliant) 800 8.1 0.27 0.17 639 18 4 LiK3P2O7, Lithium tripotassium diphosphate with orthorhombic structure Li3PO4, Lithiophosphate with orthorhombic structure SiO2 of the cristobalite type with tetragonal structure B1 (non-compliant) 450 7.8 0.3 0.3 800 Monoclinic KPO3 Amorphous silicic phase Quartz and tridymite B2 (conforming) 800 7.8 0.26 0.26 2930 <1 1.28 LiK3P2O7, Lithium tripotassium diphosphate with orthorhombic structure Li3PO4, Lithiophosphate with orthorhombic structure SiO2 of the cristobalite type with tetragonal structure B3 (nonconforming) 450 5.5 0.28 0.28 789 <1 Monoclinic KPO3 Amorphous silicic phase Quartz and tridymite B4 (conforming) 800 5.5 0.16 0.16 3396 <1 1.2 LiK3P2O7, Lithium tripotassium diphosphate with orthorhombic structure Monoclinic KPO3 SiO2 of the cristobalite type with tetragonal structure B5 (nonconforming) 450 3.9 0.21 0.17 492 <1 Monoclinic KPO3 Amorphous silicic phase Quartz and Tridymite B6 (conforming) 800 3.9 0.3 0.3 2101 <1 1.2 LiK3P2O7, Lithium tripotassium diphosphate, orthorhombic structure LiPO3, orthorhombic structure SiO2, cristobalite type, tetragonal structure B7 (nonconforming) 450 2.1 0.24 0.18 422 16 - Monoclinic KPO3, Amorphous silicic phase B8 (conforming) 800 2.1 0.14 0.14 3923 <1 1.1 Monoclinic KPO3, orthorhombic structure SiO2, cristobalite type, tetragonal structure Cl (nonconforming) 450 1.9 0.16 0.16 450 22 2.2 Zeolite type ZSM-5 + quartz + tridymite KPO3 monoclinic C2 (compliant) 800 1.9 0.04 0.04 2500 <1 2.8 LiK3P2O7, Lithium tri-potassium di-phosphate orthorhombic structure Li3PO4, Lithio-phosphate with an orthorhombic structure SiO2 of the cristobalite type with a te-tragonal structure

[0237] Example 7: Preparation of PL extrades by impregnation of material B6

[0238] 1.6 grams of potassium hydrogen phosphate (K2HPO4, M= 174 g / mol) and 1.2 g Ammonium hydrogen phosphate ((NH4)2HPO4, M = 132 g / mol) is first dissolved in 4.9 mL of distilled water at room temperature. After complete dissolution, the mixture is added dropwise to 20 grams of material B6. The solid is matured at room temperature for 40 minutes and then dried for 10 hours at 120°C in air. It is then calcined in air at 450°C for 4 hours to obtain material DI (according to the invention).

[0239] Compositional analysis of the DI material by FX gives a K content of 12 wt% relative to the total weight of the material and a P content of 9.5 wt% relative to the total weight of the material. The equivalent average KPO3 content of the D3 material after calcination is 36 wt% relative to the total weight of the material.

[0240] Example 8: Use of catalysts B3, B4, B5, B6, B7, B8 and DI as catalysts for the dehydration of lactic acid to acrylic acid in the gas phase

[0241] The catalysts are tested in extruded form using an Avantium® unit comprising 16 reactors, with an internal diameter of 2 mm and a length of 560 mm. The reaction is carried out in the gas phase at 375°C and a total pressure of 10 barg (1 MPa). The feed contains 12 wt% lactic acid and 88 wt% water. The gas (N2) and the liquid feed are co-injected and mixed upstream of the reactor head. Evaporation of the feed is carried out in the first part of the reactor using a pull cord. The PPH of lactic acid is 0.2 h1. The mass of catalyst introduced is approximately 220 mg. At the unit outlet, all products are analyzed by gas chromatography. The results are presented in Table 2 below.

[0242] [Tables2] Catalyst KPO3 / (KPO3+SiO2 + Li2O) Li2O / (KPO3+SiO2 + Li2O) Li / K mol / mol Calcination temperature (°C) Bed height (mm) Yield Acrylic Acid (% molC) B3 (non-compliant) 28 5.5 0.55 450 110 80 B4 (compliant) 28 5.5 0.55 800 93 78 B5 (non-compliant) 30 3.9 0.31 450 96 71 B6 (compliant) 30 3.9 0.31 800 84 66 B7 (non-compliant) 31 2.1 0.17 450 87 70 B8 (compliant) 31 2.1 0.17 800 80 65 DI (Compliant) 36 3.5 0.19 800 80 70 Conversion

[0243] The conversion of lactic acid (LA) is calculated according to the following formula:

[0244] LA conversion (%) = 100 x ([LA]C feed - [LA]C effluent) / [LA]C feed

[0245] with [AL]C = carbon concentration in AL in gC / L determined by HPLC.

[0246] The carbon yield of acrylic acid (AA) is determined according to the following formula:

[0247] AA yield (%) = 100 x [AA]C effluent / [AL]C load

[0248] with [AA]C carbon concentration in AA in gC / L determined by HPLC.

[0249] Catalysts B3, B4, B5, B6, B7, B8, and DI convert a lactic acid feedstock to acrylic acid with a carbon yield exceeding 60%. After 150 hours under load, unloading catalysts B4, B6, B8, and DI is easier than unloading catalysts B3, B5, and B7, which adhere to the reactor walls. Shaped catalysts, calcined at a temperature above 800°C to obtain a cristobalite phase, are more stable under operating conditions and, after a time under load exceeding 100 hours, can be easily unloaded.

Claims

Demands

1. A process for preparing a macroporous material comprising an active phase comprising at least one potassium phosphate salt and / or at least one cesium phosphate salt, at least one lithium salt, and a support comprising silica in at least partial crystalline form cristobalite, comprising at least the following steps: a) contacting at least one silica source with at least one phosphate precursor, at least one potassium and / or cesium precursor, and at least one lithium precursor to obtain a material precursor; b) allowing the material precursor obtained at the end of step a) to mature for a period of between 1 minute and 72 hours to obtain a matured material precursor; c) calcining the matured material precursor obtained at the end of step b) at a temperature of between 800°C and 1200°C to obtain said material.

2. A method according to claim 1, wherein in step a) said phosphate, potassium and / or cesium precursors are supplied in the form of at least one potassium phosphate salt and / or at least one cesium phosphate salt.

3. A process according to claim 2, wherein said potassium phosphate salt is selected from: KH2PO4, KH2P2O2, K6P6O7, K3H2P3O10, K4 H2P4O13, K3P3O1, K4P4O12, K6P6O18, KxP3O24, KioPioO30, potassium phosphate (tripotassium) (PO43,3K+), alone or in mixture.

4. A process according to any one of claims 2 or 3, wherein said cesium phosphate salt is selected from: CsH2PO4, Cs2H2P3O10, Cs4H2P4O13, Cs3P3O9, Cs4P4O12, Cs6P6O18, Cs8P8O24, (CsPO3), alone or in mixture.

5. A method according to any one of claims 2 to 4, wherein in step a) said lithium precursor is supplied in the form of at least one lithium salt selected from lithium phosphate, sulfate, nitrate, carbonate or hydroxide salts, in amorphous or crystalline oxide form, taken alone or in mixture.

6. A method according to claim 5, wherein said lithium salt is selected from the following list of lithium phosphate, sulfate, nitrate, carbonate, or hydroxide salts: LiH2PO4, Li2H2P2O7, Li3P3O9, Li4P4O2, Li6P6O18, Li8P8O24, Li2SO4, LiNO3, Li2CO3, LiOH, taken alone or in a mixture.

7. A method according to any one of claims 5 or 6, wherein said lithium salt is selected from lithium nitrate (LiNO3), lithium hydroxide (LiOH), or lithium carbonate (Li2CO3).

8. A method according to any one of claims 5 to 7, wherein said potassium phosphate salt and / or said cesium phosphate salt, and said lithium salt, are supplied at step a) in powder form.

9. A method according to claim 8, wherein prior to their introduction in step a), said powder of at least one potassium and / or cesium phosphate salt and / or said powder of at least one lithium salt are ground and sieved to a grain size of less than 100 pm.

10. A method according to any one of claims 1 to 9, wherein step a) comprises the following substeps: i) at least one precipitated silica powder, silica gel or zeolite with a Si / Al ratio >100, at least one colloidal silica sol, at least one powder of at least one potassium and / or cesium phosphate salt and at least one powder of at least one lithium salt are mixed in at least one solvent to obtain a mixture; ii) the mixture obtained at the end of step i) is shaped.

11. A method according to any one of claims 1 to 9, wherein step a) comprises the following substeps: i') at least one colloidal silica sol is mixed with at least one powder of at least one potassium and / or cesium phosphate salt to obtain a suspension; ii') at least one precipitated silica powder, silica gel, or zeolite with a Si / Al ratio >100, at least one lithium salt powder, and at least one solvent are added to said suspension obtained at the end of step i'); iii') the paste obtained at the end of step ii' is shaped.

12. A method according to claim 1, wherein step a) comprises the following substeps: i) supplying a liquid solution in aqueous or organic phase comprising at least one phosphate precursor, at least one potassium and / or cesium precursor, and at least one lithium precursor; ii) impregnating said solution obtained at the end of step i) onto a shaped support containing silica as a silica source.

13. A process according to claim 12, wherein the impregnation solution of step i”) comprises a mixture of alkali metal precursors M1 and M2, with M1 selected from K and / or Cs, and M2 being lithium.

14. A process according to claim 13, wherein said alkali metal precursors M1 and M2 are selected from carbonate salts M2CO3, nitrate salts MNO3, sulfate salts, formate salts HCOOM, acetate salts CH2COOM, citrate salts, lactate salts, chloride salts MCl, hydroxide salts MOH and oxide salts M2O, with M = M1 and / or M2.

15. A process according to any one of claims 12 to 14, wherein said phosphate precursor is selected from H3PO4, (NH4)H2PO4, (NH4)2HPO4, (NH4)PO4, and P2O5.

16. A process according to any one of claims 1 to 15, further comprising the following steps: d) contacting said material obtained at the end of step c) with at least a second phosphate precursor, and at least a second potassium and / or cesium precursor to obtain a second material precursor; e) calcining the second material precursor obtained at the end of step d) at a temperature between 300°C and 600°C.