EP4065269A1 - Alumina having a particular pore profile - Google Patents

Alumina having a particular pore profile

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Publication number
EP4065269A1
EP4065269A1 EP20810988.4A EP20810988A EP4065269A1 EP 4065269 A1 EP4065269 A1 EP 4065269A1 EP 20810988 A EP20810988 A EP 20810988A EP 4065269 A1 EP4065269 A1 EP 4065269A1
Authority
EP
European Patent Office
Prior art keywords
alumina
pore volume
alumina according
equal
less
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20810988.4A
Other languages
German (de)
French (fr)
Inventor
Julien Hernandez
Virginie Harle
Oguzhan Yaglidere
Andrew D Allerton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rhodia Operations SAS
Original Assignee
Rhodia Operations SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rhodia Operations SAS filed Critical Rhodia Operations SAS
Publication of EP4065269A1 publication Critical patent/EP4065269A1/en
Pending legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04—Alumina
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/31—Density
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/613—10-100 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/615—100-500 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/63—Pore volume
    • B01J35/633—Pore volume less than 0.5 ml/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/63—Pore volume
    • B01J35/635—0.5-1.0 ml/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/63—Pore volume
    • B01J35/638—Pore volume more than 1.0 ml/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/64—Pore diameter
    • B01J35/647—2-50 nm
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/64—Pore diameter
    • B01J35/651—50-500 nm
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/64—Pore diameter
    • B01J35/653—500-1000 nm
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/031—Precipitation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/04—Mixing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/06—Washing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/34—Preparation of aluminium hydroxide by precipitation from solutions containing aluminium salts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
    • C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2006/11—Powder tap density
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    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C01P2006/13—Surface area thermal stability thereof at high temperatures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/14—Pore volume
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • C01P2006/17—Pore diameter distribution
    • C—CHEMISTRY; METALLURGY
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    • C01P2006/80—Compositional purity
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the present invention relates to an alumina exhibiting a particular porous profile and good thermal stability.
  • This alumina is also characterized by the fact that it has a high bulk density.
  • Alumina is used as a support for precious metals, in particular platinum, palladium and / or rhodium. It can also be associated with other components of the catalyst, components which will depend on the catalyst and the intended application (diesel or gasoline pollution control).
  • oxides based on rare earths such as cerium oxides or mixed oxides of cerium and zirconium used as oxygen mobility materials for gasoline engine catalysts ( so-called three-way catalyst (TWC in English) or gasoline particulate filters (GPF)).
  • the alumina can also be combined with a zeolite used for example as a hydrocarbon trap for diesel catalysts or else with a zeolite exchanged with copper and / or iron for catalysts for the catalytic reduction of nitrogen oxides with ammonia ( SCR) for the reduction of NO x emitted by diesel engines.
  • a zeolite used for example as a hydrocarbon trap for diesel catalysts or else with a zeolite exchanged with copper and / or iron for catalysts for the catalytic reduction of nitrogen oxides with ammonia ( SCR) for the reduction of NO x emitted by diesel engines.
  • thermal stability of the alumina is required to be high because this makes it possible to maintain the efficiency of the catalyst over time, that is to say to maintain a good conversion of gaseous pollutants.
  • thermal stability is understood to mean the fact of maintaining a high specific surface area after heat treatments at high temperature.
  • a simple and common way to characterize the thermal stability of an alumina is to measure its specific surface area after heat treatment at high temperature, for example at 1200 ° C for 5 hours in air.
  • the preparation of an automotive pollution control catalyst generally involves the deposition or coating of an alumina-based suspension on a substrate or on a monolith.
  • the alumina of the invention is suitable for the preparation of a suspension having a low viscosity, which makes it possible to prepare a suspension having a high proportion of alumina. Furthermore, the high density of the alumina of the invention facilitates the handling of the alumina powder.
  • thermal stability of aluminas is generally partly linked to the pore volume of the alumina. By increasing this pore volume, thermal stability is generally increased. This increase in pore volume, however, leads to a lowering significant in the density of the alumina and an increase in the viscosity of the alumina slurry during the catalyst preparation process.
  • the specific porosity of the alumina of the invention makes it possible to obtain both high thermal stability as well as high bulk density.
  • Fig. 1/1 represents a diffractogram of the alumina of the example of the invention. It can be seen that this alumina exhibits the peaks characteristic of a crystallized alumina.
  • the invention relates to an alumina as defined in one of claims 1 to 41.
  • ⁇ 1 st profile a pore volume in the area of the pores, the size of which is between 5 nm and 100 nm which is between 0.60 and 0.85 mL / g, more particularly between 0.60 and 0.80 mL / g; and a pore volume in the area of the pores, the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 ml / g, more particularly less than or equal to 0.15 ml / g, or even less than or equal at 0.10 ml / g, or even less than or equal to 0.05 ml / g; and or
  • a pore volume in the area of pores having a size between 5 nm and 100 nm is between 0.50 and 0.75 mL / g , more particularly between 0.50 and 0.70 mL / g; and a pore volume in the area of the pores, the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 ml / g, more particularly less than or equal to 0.15 ml / g, or even less than or equal at 0.10 ml / g, or even less than or equal to 0.05 ml / g; these pore volumes being determined using the mercury porosimetry technique.
  • This alumina is generally represented by the general formula Al 2 O 3 . It can include sodium and sulfate as well as impurities.
  • the invention also relates to a catalytic composition as described in claim 42 as well as to the use of alumina as described in claim 43.
  • the invention also relates to a process for preparing alumina as described in one of claims 44 to 51. All these objects will be described in more detail.
  • concentrations of the solutions or the proportions in alumina are given in% by weight in oxide equivalents.
  • the formula AI 2 O 3 is used for the calculations of these concentrations or proportions.
  • an aqueous solution of aluminum sulphate having an aluminum concentration of 2.0% by weight corresponds to a solution containing 2.0% by weight in Al 2 O 3 equivalent.
  • Particle is understood to mean an agglomerate formed from primary particles.
  • Particle size is determined from a volume distribution of particle sizes obtained using a laser particle sizer.
  • the particle size distribution is characterized using parameters D10, D50 and D90. These parameters have the usual meaning in the field of measurements by laser diffraction.
  • Dx is denoted the value which is determined on the volume distribution of the sizes of the particles for which x% of the particles have a size less than or equal to this value Dx.
  • D50 therefore corresponds to the median value of the distribution.
  • D90 corresponds to the size for which 90% of the particles have a size which is less than D90.
  • D10 corresponds to the size for which 10% of the particles have a size which is less than D10.
  • the measurement is generally made on a dispersion of the particles in water.
  • the porosity data are obtained by the mercury porosimetry technique. This technique makes it possible to define the pore volume (V) as a function of the pore diameter (D).
  • a Micromeritics Autopore 9520 device fitted with a powder penetrometer can be used, complying with the instructions recommended by the manufacturer.
  • the ASTM D 4284-07 procedure can be followed.
  • specific surface area means the BET specific surface area determined by nitrogen adsorption determined using the Brunauer-Emmett-Teller method. This method has been described in the periodical "The Journal of the American Chemical Society, 60, 309 (1938)". The recommendations of the standard ASTM D3663 - 03 can be complied with. The calcinations for a given temperature and time correspond, unless otherwise indicated, to calcinations in air at a temperature plateau over the indicated time.
  • the alumina of the invention can be represented by the general formula Al 2 O 3 .
  • the alumina can include residual sodium.
  • the residual sodium level may be less than or equal to 0.50% by weight, or even less than or equal to 0.15% by weight.
  • the sodium level can be greater than or equal to 50 ppm. This rate can be between 50 and 900 ppm, or even between 100 and 800 ppm. This rate is expressed as the weight of Na2O relative to the total weight of the alumina.
  • alumina having a residual sodium level of 0.15% it is considered that there is per 100 g of alumina, 0.15 g of Na 2 0.
  • the method for determining the sodium level in this range of concentrations is known to those skilled in the art. For example, the technique of inductively coupled plasma spectroscopy can be used.
  • the alumina can include residual sulfate.
  • the level of residual sulphate may be less than or equal to 1.00% by weight, or even less than or equal to 0.20% by weight, or even less than or equal to 0.10% by weight.
  • the sulphate level can be greater than or equal to 50 ppm. This rate can be between 100 and 1500 ppm, or even between 400 and 1000 ppm. This rate is expressed in weight of sulphate relative to the total weight of alumina. Thus, for an alumina having a residual sulphate level of 0.50%, it is considered that there is per 100 g of alumina, 0.50 g of SO 4 .
  • the method for determining the level of sulphate in this range of concentrations is known to those skilled in the art such as, for example, the technique of inductively coupled plasma spectroscopy. Microanalysis techniques can also be used. A Horiba EMIA 320-V2 type microanalysis device could be suitable.
  • Alumina can also contain impurities other than sodium and sulphate, for example impurities based on silicon, titanium or iron.
  • the proportion of each impurity is generally less than 0.07% by weight (£ 0.07%), or even less than 0.05% by weight (£ 0.05%).
  • the alumina of the invention is characterized by a particular porosity.
  • this alumina has at least one of the following two porosity profiles:
  • 1 st profile a pore volume in the area of the pores, the size of which is between 5 nm and 100 nm which is between 0.60 and 0.85 mL / g, more particularly between 0.60 and 0.80 mL / g; and a pore volume in the area of the pores, the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g, more particularly less than or equal to 0.15 mL / g, or even less than or equal at 0.10 mL / g, or even less than or equal to 0.05 mL / g.
  • 2 nd profile after calcination in air at 1100 ° C for 5 hours: a pore volume in the area of the pores the size of which is between 5 nm and 100 nm which is between 0.50 and 0.75 mL / g, more particularly between 0.50 and 0.70 mL / g; and a pore volume in the area of the pores, the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g, more particularly less than or equal to 0.15 mL / g, or even less than or equal at 0.10 mL / g, or even less than or equal to 0.05 mL / g.
  • Alumina can also be defined by at least one of the following two porosity profiles:
  • ⁇ 1 st profile a pore volume in the region of the pores, the size of which is between 5 nm and 100 nm which is between 0.60 and 0.85 mL / g; and a pore volume in the area of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g; and or
  • ⁇ 2 nd profile after calcination in air at 1100 ° C for 5 hours: a pore volume in the area of pores having a size between 5 nm and 100 nm is between 0.50 and 0.75 mL / g ; and a pore volume in the region of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g.
  • the alumina which is described in the present application can have at least one of the two aforementioned profiles, it being understood that it can have both profiles at the same time.
  • the alumina can have a high specific surface. It may have a BET specific surface area of between 100 and 200 m 2 / g, more particularly between 150 and 200 m 2 / g. This specific surface can be greater than or equal to 120 m 2 / g, preferably greater than or equal to 140 m 2 / g. This specific surface can also be between 100 and 140 m 2 / g, or even between 100 and 120 m 2 / g.
  • the alumina also has high thermal stability. It can have a BET specific surface after calcination in air at 1100 ° C. for 5 hours of between 70 and 100 m 2 / g.
  • the alumina generally has a total pore volume which is generally strictly greater than 1.05 mL / g.
  • This total pore volume can advantageously be at least 1.10 mL / g, or even at least 1.20 mL / g, or even at least 1.30 mL / g or at least 1.40 mL / g or at least 1.50 mL / g.
  • This total pore volume is generally at most 2.40 mL / g.
  • the alumina retains a large total pore volume even after calcination at 1100 ° C. for 5 hours.
  • the alumina after calcination at 1100 ° C. for 5 hours, the alumina generally exhibits a total pore volume which is at least 0.90 mL / g.
  • This total pore volume is preferably at least 1.00 mL / g, or even at least 1.10 mL / g, or even more advantageously at least 1.20 mL / g.
  • This total pore volume is generally at most 1.80 mL / g.
  • the alumina is crystallized. This can be demonstrated using an X-ray diffractogram.
  • the alumina can comprise a delta phase, a theta phase, a gamma phase or a mixture of at least two of these phases.
  • the alumina can have an apparent density of between 0.25 g / cm 3 and 0.55 g / cm 3 , more particularly between 0.40 g / cm 3 and 0.55 g / cm 3 .
  • This bulk density can be determined by the method described below. First, the volume of a cylindrical-shaped test tube of approximately 25 mL is precisely determined. To do this, the empty specimen is weighed (tare T). Distilled water is then poured into the test tube to the edge but without going over the edge (no meniscus). Weigh the test tube filled with distilled water (M). The mass of water contained in the test tube is therefore:
  • the density of the water is for example equal to 0.99983 g / mL for a measurement temperature of 20 ° C.
  • the alumina powder is gently poured using a funnel until it reaches the edge of the test tube. The excess powder is leveled off using a spatula. The powder should not be compacted or packed when filling.
  • the test tube containing the powder is then weighed.
  • apparent density (g / mL) (mass of the test piece containing the alumina powder - Tare
  • Alumina can have an D50 between 2.0 ⁇ m and 80.0 ⁇ m. It may have a D90 less than or equal to 150.0 ⁇ m, more particularly less than or equal to 100.0 ⁇ m. It may have a D10 greater than or equal to 1.0 ⁇ m.
  • the alumina has a D50 of between 2.0 and 15.0 ⁇ m, or even between 4.0 and 12.0 ⁇ m.
  • the D90 can be between 20.0 pm and 60.0 pm, or even between 25.0 pm and 50.0 pm.
  • the apparent density is between 0.25 and 0.40 g / cm 3 ; and / or - the total pore volume is between 1.40 and 2.40 mL / g.
  • the alumina has a D50 of between 15.0 and 80.0 ⁇ m, or even between 20.0 and 60.0 ⁇ m.
  • the D90 can be between 40.0 pm and 150.0 pm, or even between 50.0 pm and 100.0 pm.
  • the bulk density can be between 0.40 and 0.55 g / cm 3 ;
  • the total pore volume is between 1.05 (excluded value) and 1.80 mL / g.
  • This total pore volume can be more advantageously between 1, 20 and 1, 80 ml / g.
  • the alumina of the invention may more particularly exhibit at least one of the following two porosity profiles:
  • 1 st profile - a pore volume in the area of the pores, the size of which is between 5 nm and 100 nm which is between 0.60 and 0.85 mL / g, more particularly between 0.60 and 0.80 mL / g; and a pore volume in the region of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.05 mL / g; and or
  • 2 nd profile after calcination in air at 1100 ° C for 5 hours: a pore volume in the area of the pores the size of which is between 5 nm and 100 nm which is between 0.50 and 0.75 mL / g, more particularly between 0.50 and 0.70 mL / g; and a pore volume in the area of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.05 mL / g.
  • this particular alumina can have at least one of the two aforementioned profiles, it being understood that it can have both profiles at the same time. It can also have the following characteristics:
  • this particular alumina can also exhibit the characteristics of total pore volume as described above.
  • it generally has a total pore volume which is generally strictly greater than 1.05 mL / g.
  • This total pore volume can advantageously be at least 1.10 mL / g, or even at least 1. 20 mL / g, or even at least 1.30 mL / g or at least 1.40 mL / g or at least 1.50 mL / g.
  • This total pore volume is generally at most 2.40 mL / g.
  • This particular alumina retains a large total pore volume even after calcination at 1100 ° C. for 5 hours.
  • the alumina after calcination at 1100 ° C. for 5 hours, the alumina generally exhibits a total pore volume which is at least 0.90 mL / g.
  • This total pore volume is preferably at least 1.00 mL / g, or even at least 1.10 mL / g, or even more advantageously at least 1.20 mL / g.
  • This total pore volume is generally at most 1.80 mL / g.
  • the sodium and sulfate levels are for that particular alumina as previously described.
  • the alumina of the invention can be used in the field of catalysis for the depollution of the exhaust gases of gasoline or diesel heat engines.
  • a catalytic composition comprising the alumina of the invention and at least one oxide based on cerium and optionally at least one rare earth other than cerium is used in this field.
  • This oxide can be, for example, cerium oxide (generally represented by the formula Ce0 2 ), a mixed oxide based on cerium, on zirconium and optionally on at least one rare earth other than cerium.
  • the rare earth other than cerium can be chosen from the group formed by yttrium, praseodymium or neodymium. Preparation process
  • the invention also relates to a process for preparing an alumina, in particular alumina as described above or as described in one of claims 1 to 39, comprising the following steps:
  • step (a2) either simultaneously (i) an aqueous solution of aluminum sulphate and (ii) an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 6.5 and 10, or even between 7, 0 and 8.0 or between 8.5 and 9.5; so that at the end of step (a), the aluminum concentration of the reaction mixture is between 0.50% and 3.0% by weight;
  • the pH of the reaction mixture is optionally adjusted to a value between 7.5 and 10.5, or even between 8.0 and 9.0 or between 9.0 and 10.0;
  • step (e) a dispersion in water of the solid recovered at the end of step (d) undergoes mechanical or ultrasonic treatment so as to reduce the size of the particles of the dispersion;
  • step (f) the dispersion obtained at the end of step (e) is dried;
  • step (g) the solid resulting from step (f) is then calcined in air. step (a)
  • step (a) the following are introduced with stirring into a tank initially containing an acidic aqueous solution, the pH of which is between 0.5 and 4.0, or even between 0.5 and 3.5:
  • step (a2) either simultaneously (i) an aqueous solution of aluminum sulphate and (ii) an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 6.5 and 10.0, or even between 7.0 and 8.0 or between 8.5 and 9.5; so that at the end of step (a), the aluminum concentration of the reaction mixture is between 0.50% and 3.0% by weight.
  • the acidic aqueous solution initially contained in the tank has a pH of between 0.5 and 4.0, or even between 0.5 and 3.5.
  • This solution may consist of a dilute aqueous solution of a mineral acid such as, for example, sulfuric acid, hydrochloric acid or nitric acid.
  • the acidic aqueous solution can also consist of an aqueous solution of an acidic aluminum salt such as aluminum nitrate, chloride or sulfate.
  • an acidic aluminum salt such as aluminum nitrate, chloride or sulfate.
  • the aluminum concentration of this solution is between 0.01% and 2.0% by weight, or even between 0.01% and 1.0% by weight, or even between 0.10% and 1.0% by weight.
  • the acidic aqueous solution is an aqueous solution of aluminum sulfate. This solution is prepared by dissolving aluminum sulphate in water or else by diluting preformed aqueous solution (s) in water.
  • the pH of the aqueous solution developed by the presence of aluminum sulfate is generally between 0.5 and 4.0, or even between 0.5 and 3.5.
  • Step (a) is implemented according to two embodiments (a1) or (a2).
  • an aqueous solution of sodium aluminate is introduced with stirring.
  • an aqueous solution of aluminum sulphate and (ii) an aqueous solution of sodium aluminate are simultaneously introduced with stirring.
  • the aqueous solution of sodium aluminate does not have precipitated alumina.
  • the sodium aluminate preferably has an Na 2 0 / Al 2 C> 3 ratio greater than or equal to 1. 20, for example between 1. 20 and 1. 40.
  • the aqueous solution of sodium aluminate may have an aluminum concentration of between 15.0% and 35.0% by weight, more particularly between 15.0% and 30.0% by weight, or even between 20.0% and 30.0% by weight. , 0%.
  • the aqueous solution of aluminum sulphate can have an aluminum concentration of between 1.0% and 15.0% by weight, more particularly between 5.0% and 10.0% by weight.
  • the aluminum concentration of the reaction mixture is between 0.50% and 3.0% by weight.
  • the duration of introduction of the solution (s) is generally between 2 min and 30 min.
  • step (a) the introduction of the aqueous solution of sodium aluminate has the effect of increasing the pH of the reaction mixture.
  • the aqueous solution of sodium aluminate can be introduced directly into the reaction medium, for example by means of at least one introduction pipe.
  • the two solutions can be introduced directly into the reaction medium, for example by means of at least two introduction pipes.
  • the solution (s) is / are preferably introduced into a well-stirred zone of the reactor, for example in a zone close to the stirring wheel, so as to obtain an effective mixture of the solution (s) introduced into the reaction mixture.
  • the solutions are introduced via at least two introduction pipes, the injection points through which the two solutions are introduced into the reaction mixture are distributed so as to that the solutions dilute effectively in said mixture.
  • step (b) In step (b), an aqueous solution of aluminum sulphate and an aqueous solution of sodium aluminate are introduced simultaneously, the introduction rates of which are regulated so as to maintain the average pH of the reaction mixture in the range of pH referred to in step (a).
  • the target value of the mean pH is between: between 8.0 and 10.0, or even between 8.5 and 9.5, for the case where the embodiment (a1) has been followed in step (a ); or else between 6.5 and 10.0, or even between 7.0 and 8.0 or between 8.5 and 9.5, for the case where the embodiment (a2) has been followed in step (a ).
  • the aqueous solution of sodium aluminate is introduced at the same time as the aqueous solution of aluminum sulphate at a rate which is regulated so that the average pH of the reaction mixture is equal to the target value.
  • the flow rate of the aqueous sodium aluminate solution used to regulate the pH may fluctuate during step (b).
  • the duration of introduction of the two solutions may be between 10 minutes and 2 hours, or even between 30 minutes and 90 minutes.
  • the rate of introduction of the or both solutions can be constant.
  • the temperature of the reaction mixture for steps (a) and (b) is at least 60 ° C. This temperature can be between 60 ° C and 95 ° C.
  • the solution initially contained in the tank in step (a) may have been preheated before the start of the introduction of the solution (s). It is also possible to preheat the solutions which are introduced into the tank in steps (a) and (b) beforehand. step (cl
  • step (c) the pH of the reaction mixture is optionally adjusted to a value between 7.5 and 10.5, or even between 8.0 and 9.0 or between 9.0 and 10.0, by l addition of a basic or acidic aqueous solution.
  • the acidic aqueous solution which can be used to adjust the pH may consist of an aqueous solution of a mineral acid such as, for example, sulfuric acid, hydrochloric acid or nitric acid.
  • the aqueous acidic solution can also consist of an aqueous solution of an acidic aluminum salt such as aluminum nitrate, chloride or sulfate.
  • the basic aqueous solution which can be used to adjust the pH may consist of an aqueous solution of a mineral base such as, for example, soda, potassium hydroxide, ammonia.
  • the basic aqueous solution can also consist of an aqueous solution of a basic aluminum salt such as sodium aluminate.
  • aqueous solution of sodium aluminate is used.
  • the pH is adjusted by stopping:
  • the introduction of the aqueous solution of aluminum sulphate is stopped and the aqueous solution of sodium aluminate is continued to be introduced until a target pH of between 8.0 and 10.5 is reached. , preferably between 9.0 and 10.0.
  • the duration of step (c) can be variable. This duration can be between 5 min and 30 min. step (d)
  • step (d) the reaction mixture is filtered.
  • the reaction mixture is generally in the form of a slurry.
  • the solid collected on the filter can be washed with water. To do this, you can use hot water with a temperature of at least 50 ° C. step (e)
  • step (e) a dispersion in water of the solid recovered at the end of step (d) undergoes mechanical or ultrasonic treatment so as to reduce the size of the particles of the dispersion.
  • the pH of this dispersion before grinding can optionally be adjusted between 5.0 and 8.0. You can use a nitric acid solution, for example.
  • the D50 of the particles of the dispersion before the mechanical or ultrasonic treatment is generally between 10.0 pm and 40.0 pm, or even between 10.0 pm and 30.0 pm.
  • the D50 of the particles of the solid after the mechanical or ultrasonic treatment is preferably between 1.0 ⁇ m and 15.0 ⁇ m, or even between 2.0 ⁇ m and 10.0 ⁇ m.
  • Mechanical treatment involves applying mechanical stress or shear forces to the dispersion so as to split the particles.
  • the mechanical treatment can, for example, be carried out using a ball mill, a high pressure homogenizer or a grinding system comprising a rotor and a stator.
  • a Microcer ball mill or a Labstar Zêta both marketed by the company Netzsch (for more details, see: https://www.netzsch-qrindinq.com/ en / products-solutions / wet-brovaqe / mini-series-laboratory-grinders / j.
  • a grinding system as described in the examples can be used.
  • a ball mill it is possible to use example of beads of zirconium oxide stabilized with yttrium It is possible, for example, to use 0.2 mm ZetaBeads Plus beads.
  • Ultrasound treatment consists of applying a sound wave to the dispersion.
  • the sound wave which propagates in the liquid medium induces a phenomenon of cavitation allowing the particles to be split.
  • an ultrasound system with a Vibracell VC750 type sound generator equipped with a 13 mm probe. The duration and the power applied are adjusted so as to reach the target D50.
  • step (f) The mechanical or ultrasonic treatment can be carried out in batch mode or else continuously. step (f)
  • step (f) the dispersion from step (e) is dried, preferably by atomization.
  • Spray drying has the advantage of resulting in particles with a controlled particle size distribution.
  • This drying method also has good productivity. It involves spraying the dispersion into a cloud of droplets in a stream of hot gas (eg a stream of hot air) circulating in an enclosure.
  • the quality of the spray controls the size distribution of the droplets and hence the size distribution of the dried particles.
  • Spraying can be carried out using any sprayer known per se. There are two main types of spray devices: turbines and nozzles.
  • turbines and nozzles There are two main types of spray devices.
  • the flow rate and the temperature of the dispersion entering the sprayer are in particular the following: the flow rate and the temperature of the dispersion entering the sprayer; the flow rate, the pressure, the humidity and the temperature of the hot gas. of the gas is generally between 100 ° C. and 800 ° C.
  • the gas outlet temperature is generally between 80 ° C. and 150 ° C.
  • the D50 of the powder recovered at the end of step (g) is generally between 2.0 ⁇ m and 80.0 ⁇ m. This size is linked to the size distribution of the droplets at the outlet of the sprayer.
  • the vaporizer capacity of the atomizer is generally related to the size of the enclosure. Thus, at the laboratory scale (Büchi B 290), the D50 can be between 2.0 and 15.0 ⁇ m. On a larger scale, the D50 can be between 15.0 and 80.0 ⁇ m. step (g)
  • step (g) the solid resulting from step (f) is calcined in air.
  • the calcination temperature is generally between 500 ° C and 1000 ° C, more particularly between 800 ° C and 1000 ° C.
  • the duration of the calcination is generally between 1 and 10 h. It is possible to use the calcination conditions given in the examples.
  • step (f) it is possible to carry out the two steps (f) and (g) in the same equipment in which the dispersion resulting from step (e) undergoes a heat treatment allowing both drying and calcination to be carried out.
  • the alumina which is recovered at the end of step (g) (that is to say at the end of the calcination) has a D50 generally between 2.0 ⁇ m and 80.0. pm. It generally has a D90 less than or equal to 150.0 ⁇ m, more particularly less than or equal to 100.0 ⁇ m.
  • the D50 can be between 2.0 and 15.0 pm, or even between 4.0 and 12.0 pm.
  • the D90 can be between 20.0 pm and 60.0 pm, or even between 25.0 pm and 50.0 pm.
  • This embodiment can instead be implemented when step (f) is carried out on a laboratory scale using, for example, a Büchi B 290 atomizer.
  • the D50 can be between 15.0 and 80.0 pm, or even between 20.0 and 60.0 pm.
  • the D90 can be between 40.0 pm and 150.0 pm, or even between 50.0 pm and 100.0 pm. This embodiment can rather be implemented when step (f) is carried out on a larger scale.
  • the process can also include a final step whereby the solid obtained in the previous step undergoes grinding in order to adjust the particle size of the solid.
  • You can use a knife, air jet, hammer or ball mill.
  • the ground product has an OD generally between 2.0 ⁇ m and 15.0 ⁇ m.
  • the D90 can be between 20.0 pm and 60.0 pm, or even between 25.0 pm and 50.0 pm.
  • the alumina of the invention is in the form of a powder.
  • the term “specific surface area” means the specific surface area B.E.T. determined by nitrogen adsorption in accordance with the ASTM D 3663-03 standard established from the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of the American Chemical Society, 60, 309 (1938)".
  • the specific surface is determined automatically using an apparatus, for example of the T ristar II 3020 type from Micromeritics, in accordance with the indications recommended by the manufacturer.
  • the samples are pretreated at 250 ° C. for 90 min under vacuum (for example to reach a pressure of 50 mm of mercury). This treatment makes it possible to eliminate volatile species that are physisorbed on the surface (such as for example H2O, ).
  • the measurement is carried out using a mercury porosimetry measuring device.
  • a Micromeritics Autopore IV 9520 device fitted with a powder penetrometer was used, complying with the instructions recommended by the manufacturer.
  • the following parameters were used: penetrometer used: 3.2 ml (Micromeritics reference: type No. 8 penetrometer); capillary volume: 0.412 ml; max pressure ("head pressure"): 4.68 psi; contact angle: 130 °; surface tension of mercury: 485 dynes / cm; density of mercury: 13.5335 g / ml.
  • a vacuum of 50 mm Hg is applied to the sample for 5 min.
  • the equilibrium times are as follows: low pressure range (1, 3-30 psi): 20 s - high pressure range (30-60,000 psi): 20 s.
  • the samples Prior to the measurement, the samples are treated at 200 ° C. for 120 min to eliminate the volatile species physisorbed on the surface (such as for example H2O, etc.).
  • a MALVERN Mastersizer 2000 or 3000 laser diffraction particle size analyzer is used (more details on this device given here: https://www.malvernpanalvtical.com/fr/products/product-ranqe/mastersizer - ranqe / mastersizer-3000).
  • the laser diffraction technique used consists in measuring the intensity of the light scattered during the passage of a laser beam through a sample of dispersed particles. The laser beam passes through the sample and the intensity of the scattered light is measured as a function of the angle. The diffracted intensities are then analyzed to calculate the particle size using the Mie diffusion theory. The measurement makes it possible to obtain a volume distribution of sizes from which the parameters D10, D50 and D90 are deduced.
  • the introduction is then stopped.
  • the aluminum concentration of the reaction mixture is then 2.10%.
  • step (b) the introduction of the aluminum sulphate solution is again started at a flow rate of 570 g of solution / min and the sodium aluminate solution is simultaneously introduced into the stirred reactor at a flow rate regulated so as to maintain the pH at a value of 9.0. This stage lasts 45 minutes,
  • step (c) the introduction of the aluminum sulphate solution is stopped and the sodium aluminate solution is continued to be added with a flow rate of 320 g of solution / min until a pH of 9.5. The addition of the sodium aluminate solution is stopped.
  • step (d) the reaction slurry is poured onto a vacuum filter. After filtration, the cake is washed with deionized water at 65 ° C.
  • step (e) the cake is redispersed in deionized water to obtain a suspension with a concentration of around 10% by weight of oxide (Al2O3).
  • a nitric acid solution with a concentration of 69% by weight is added to the suspension so as to obtain a pH close to 6.
  • the suspension is passed through a ball mill of the LME20 brand from the manufacturer Netzsch. The operating conditions of the mill are adjusted so as to obtain a D50 of 3.5 microns.
  • step (f) the suspension from step (e) is atomized to obtain a dry powder of aluminum hydrate doped with lanthanum.
  • step (g) the atomized powder is calcined at 940 ° C for 2 hours (temperature rise rate of 3 ° C / min). The mass loss observed during this calcination is 26.9%.
  • - pore volume in the field of pores the size of which is between 100 nm and 1000 nm: 0.02 mL / g; - total pore volume: 1.51 ml / g;

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Abstract

The present invention relates to an alumina having a particular pore profile and good thermal stability. This alumina is also characterised by the fact that it has a high apparent density. The alumina has, after calcination in air at 1100°C for 5 hours: - a pore volume, in the pore size range of between 5 nm and 100 nm, that is between 0.50 and 0.75 ml/g, more particularly between 0.50 and 0.70 ml/g; and - a pore volume, in the pore size range of between 100 nm and 1000 nm, that is less than or equal to 0.20 ml/g, more particularly less than or equal to 0.15 ml/g, or even less than or equal to 0.10 ml/g.

Description

Alumine présentant un profil poreux particulier Alumina with a particular porous profile
La présente demande revendique la priorité des demandes de brevet européen N°19315153.7 et 19315155.2 et déposées toutes deux le 29 novembre 2019 et dont le contenu est intégralement incorporé par référence. En cas d'incohérence entre le texte de la présente demande et le texte de la demande de brevet français qui affecterait la clarté d'un terme ou d'une expression, il sera fait référence à la présente demande uniquement.The present application claims the priority of European patent applications Nos. 19315153.7 and 19315155.2 and both filed on November 29, 2019 and the contents of which are fully incorporated by reference. In the event of an inconsistency between the text of the present application and the text of the French patent application which would affect the clarity of a term or an expression, reference will be made to the present application only.
La présente invention est relative à une alumine présentant un profil poreux particulier et une bonne stabilité thermique. Cette alumine se caractérise également par le fait qu’elle présente une densité apparente élevée. The present invention relates to an alumina exhibiting a particular porous profile and good thermal stability. This alumina is also characterized by the fact that it has a high bulk density.
Domaine technique Technical area
Il est connu d’utiliser une alumine pour la préparation d’un catalyseur de dépollution automobile pour convertir les polluants émis par les moteurs thermiques essence ou diesel. L’alumine est utilisée comme support de métaux précieux, notamment le platine, le palladium et/ou le rhodium. Elle peut aussi être associée à d’autres composants du catalyseur, composants qui vont dépendre du catalyseur et de l’application visée (dépollution diesel ou essence). Parmi les autres composants usuels présents dans le catalyseur, on peut citer les oxydes à base de terres rares comme les oxydes de cérium ou les oxydes mixtes de cérium et de zirconium utilisés comme matériaux à mobilité d’oxygène pour les catalyseurs des moteurs à essence (catalyseur dits trois voies (TWC en Anglais) ou des filtres à particules essence (GPF)). L’alumine peut également être associée à une zéolithe utilisée par exemple comme piège à hydrocarbures pour les catalyseurs diesel ou bien à une zéolithe échangée au cuivre et/ou au fer pour les catalyseurs de réduction catalytique des oxydes d’azote avec l’ammoniac (SCR) pour la réduction des NOx émis par les moteurs diesel. It is known to use an alumina for the preparation of an automobile pollution control catalyst to convert the pollutants emitted by gasoline or diesel heat engines. Alumina is used as a support for precious metals, in particular platinum, palladium and / or rhodium. It can also be associated with other components of the catalyst, components which will depend on the catalyst and the intended application (diesel or gasoline pollution control). Among the other usual components present in the catalyst, mention may be made of oxides based on rare earths such as cerium oxides or mixed oxides of cerium and zirconium used as oxygen mobility materials for gasoline engine catalysts ( so-called three-way catalyst (TWC in English) or gasoline particulate filters (GPF)). The alumina can also be combined with a zeolite used for example as a hydrocarbon trap for diesel catalysts or else with a zeolite exchanged with copper and / or iron for catalysts for the catalytic reduction of nitrogen oxides with ammonia ( SCR) for the reduction of NO x emitted by diesel engines.
Problème technique Technical problem
Pour toutes ces applications de dépollution automobile, il est requis que la stabilité thermique de l’alumine soit élevée car cela permet de maintenir l’efficacité du catalyseur au cours du temps c’est-à-dire de maintenir une bonne conversion des polluants gazeux. On entend par stabilité thermique le fait de maintenir une surface spécifique élevée après des traitements thermiques à haute température. Une façon simple et courante de caractériser la stabilité thermique d’une alumine consiste à mesurer sa surface spécifique après un traitement thermique à haute température, par exemple à 1200°C pendant 5 heures sous air. For all these automotive pollution control applications, the thermal stability of the alumina is required to be high because this makes it possible to maintain the efficiency of the catalyst over time, that is to say to maintain a good conversion of gaseous pollutants. . The term thermal stability is understood to mean the fact of maintaining a high specific surface area after heat treatments at high temperature. A simple and common way to characterize the thermal stability of an alumina is to measure its specific surface area after heat treatment at high temperature, for example at 1200 ° C for 5 hours in air.
La préparation d’un catalyseur de dépollution automobile met généralement en oeuvre le dépôt ou l’enduction d’une suspension à base d’alumine sur un substrat ou sur un monolithe. L’alumine de l’invention est adaptée à la préparation d’une suspension présentant une viscosité faible, ce qui permet de préparer une suspension présentant une proportion élevée en alumine. Par ailleurs, la densité élevée de l’alumine de l’invention facilite la manipulation de la poudre d’alumine. The preparation of an automotive pollution control catalyst generally involves the deposition or coating of an alumina-based suspension on a substrate or on a monolith. The alumina of the invention is suitable for the preparation of a suspension having a low viscosity, which makes it possible to prepare a suspension having a high proportion of alumina. Furthermore, the high density of the alumina of the invention facilitates the handling of the alumina powder.
La stabilité thermique des alumines est généralement pour partie liée au volume poreux de l’alumine. En augmentant ce volume poreux, la stabilité thermique est généralement augmentée. Cette augmentation de volume poreux entraîne toutefois un abaissement significatif de la densité de l’alumine et une augmentation de la viscosité de la suspension d’alumine au cours du procédé de préparation du catalyseur. The thermal stability of aluminas is generally partly linked to the pore volume of the alumina. By increasing this pore volume, thermal stability is generally increased. This increase in pore volume, however, leads to a lowering significant in the density of the alumina and an increase in the viscosity of the alumina slurry during the catalyst preparation process.
Afin de résoudre ce problème, il a été observé que la porosité spécifique de l’alumine de l’invention permet d’obtenir à la fois une stabilité thermique élevée ainsi qu’une densité apparente élevée. In order to solve this problem, it has been observed that the specific porosity of the alumina of the invention makes it possible to obtain both high thermal stability as well as high bulk density.
Arrière plan technique Technical background
US 4,154,812 décrit un procédé de préparation d’une alumine. Ce procédé ne comprend pas d’étape (e). US 4,154,812 describes a process for preparing an alumina. This process does not include step (e).
Figures Figures
Fig. 1/1 représente un diffractogramme de l'alumine de l'exemple de l'invention. On peut constater que cette alumine présente les pics caractéristiques d'une alumine cristallisée. Fig. 1/1 represents a diffractogram of the alumina of the example of the invention. It can be seen that this alumina exhibits the peaks characteristic of a crystallized alumina.
Brève description de l'invention Brief description of the invention
L'invention est relative à une alumine telle que définie à l'une des revendications 1 à 41.The invention relates to an alumina as defined in one of claims 1 to 41.
Celle-ci est caractérisée par au moins l'un des deux profils de porosité suivants : This is characterized by at least one of the following two porosity profiles:
■ 1er profil : un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,60 et 0,85 mL/g, plus particulièrement entre 0,60 et 0,80 mL/g ; et un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,20 ml_/g, plus particulièrement inférieur ou égal à 0,15 ml_/g, voire inférieur ou égal à 0,10 mL/g, voire encore inférieur ou égal à 0,05 ml_/g ; et/ou ■ 1 st profile: a pore volume in the area of the pores, the size of which is between 5 nm and 100 nm which is between 0.60 and 0.85 mL / g, more particularly between 0.60 and 0.80 mL / g; and a pore volume in the area of the pores, the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 ml / g, more particularly less than or equal to 0.15 ml / g, or even less than or equal at 0.10 ml / g, or even less than or equal to 0.05 ml / g; and or
■ 2nd profil : après calcination sous air à 1100°C pendant 5 heures : un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,50 et 0,75 ml_/g, plus particulièrement entre 0,50 et 0,70 mL/g ; et un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,20 ml_/g, plus particulièrement inférieur ou égal à 0,15 ml_/g, voire inférieur ou égal à 0,10 mL/g, voire encore inférieur ou égal à 0,05 ml_/g ; ces volumes poreux étant déterminés à l'aide de la technique de porosimétrie au mercure. ■ 2 nd profile: after calcination in air at 1100 ° C for 5 hours: a pore volume in the area of pores having a size between 5 nm and 100 nm is between 0.50 and 0.75 mL / g , more particularly between 0.50 and 0.70 mL / g; and a pore volume in the area of the pores, the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 ml / g, more particularly less than or equal to 0.15 ml / g, or even less than or equal at 0.10 ml / g, or even less than or equal to 0.05 ml / g; these pore volumes being determined using the mercury porosimetry technique.
Cette alumine est généralement représentée par la formule générale AI2O3. Elle peut comprendre du sodium et du sulfate ainsi que des impuretés. This alumina is generally represented by the general formula Al 2 O 3 . It can include sodium and sulfate as well as impurities.
L'invention est aussi relative à une composition catalytique telle que décrite à la revendication 42 ainsi qu'à l'utilisation de l'alumine telle que décrite à la revendication 43.The invention also relates to a catalytic composition as described in claim 42 as well as to the use of alumina as described in claim 43.
L'invention est aussi relative à un procédé de préparation d'alumine tel que décrit à l'une des revendications 44 à 51. Tous ces objets vont être décrits plus en détails. The invention also relates to a process for preparing alumina as described in one of claims 44 to 51. All these objects will be described in more detail.
Description de l'invention Description of the invention
Dans la présente demande, on précise pour la suite de la description que, sauf indication contraire, dans les fourchettes de valeurs qui sont données, les valeurs aux bornes sont incluses. De plus, les concentrations des solutions ou les proportions dans l’alumine sont données en % en poids en équivalents oxydes. On retient la formule AI2O3 pour les calculs de ces concentrations ou proportions. Par exemple, une solution aqueuse de sulfate d’aluminium présentant une concentration en aluminium de 2,0% poids correspond à solution renfermant 2,0% en poids en équivalent AI2O3. In the present application, it is specified for the remainder of the description that, unless otherwise indicated, in the ranges of values which are given, the values at the limits are included. In addition, the concentrations of the solutions or the proportions in alumina are given in% by weight in oxide equivalents. The formula AI 2 O 3 is used for the calculations of these concentrations or proportions. For example, an aqueous solution of aluminum sulphate having an aluminum concentration of 2.0% by weight corresponds to a solution containing 2.0% by weight in Al 2 O 3 equivalent.
On entend par “particule” un agglomérat formé de particules primaires. On détermine la taille des particules à partir d'une distribution en volume des tailles de particules obtenue à l’aide d’un granulomètre laser. On caractérise la distribution de tailles des particules à l’aide des paramètres D10, D50 et D90. Ces paramètres ont le sens habituel dans le domaine des mesures par diffraction laser. Ainsi, on note Dx la valeur qui est déterminée sur la distribution en volume des tailles des particules pour laquelle x% des particules ont une taille inférieure ou égale à cette valeur Dx. D50 correspond donc à la valeur médiane de la distribution. D90 correspond à la taille pour laquelle 90% des particules ont une taille qui est inférieure à D90. D10 correspond à la taille pour laquelle 10% des particules ont une taille qui est inférieure à D10. La mesure se fait généralement sur une dispersion des particules dans l'eau. The term “particle” is understood to mean an agglomerate formed from primary particles. Particle size is determined from a volume distribution of particle sizes obtained using a laser particle sizer. The particle size distribution is characterized using parameters D10, D50 and D90. These parameters have the usual meaning in the field of measurements by laser diffraction. Thus, Dx is denoted the value which is determined on the volume distribution of the sizes of the particles for which x% of the particles have a size less than or equal to this value Dx. D50 therefore corresponds to the median value of the distribution. D90 corresponds to the size for which 90% of the particles have a size which is less than D90. D10 corresponds to the size for which 10% of the particles have a size which is less than D10. The measurement is generally made on a dispersion of the particles in water.
Les données de porosité sont obtenues par la technique de porosimétrie mercure. Cette technique permet de définir le volume poreux (V) en fonction du diamètre de pore (D). On peut utiliser un appareil Micromeritics Autopore 9520 muni d’un pénétromètre à poudre en se conformant aux indications préconisées par le constructeur. On peut suivre la procédure ASTM D 4284-07. The porosity data are obtained by the mercury porosimetry technique. This technique makes it possible to define the pore volume (V) as a function of the pore diameter (D). A Micromeritics Autopore 9520 device fitted with a powder penetrometer can be used, complying with the instructions recommended by the manufacturer. The ASTM D 4284-07 procedure can be followed.
On entend par surface spécifique, la surface spécifique BET déterminée par adsorption d'azote déterminée à partir de la méthode Brunauer-Emmett-Teller. Cette méthode a été décrite dans le périodique "The Journal of the American Chemical Society, 60, 309 (1938)". On peut se conformer aux recommandations de la norme norme ASTM D3663 - 03. Les calcinations pour une température et une durée données correspondent, sauf indication contraire, à des calcinations sous air à un palier de température sur la durée indiquée. The term “specific surface area” means the BET specific surface area determined by nitrogen adsorption determined using the Brunauer-Emmett-Teller method. This method has been described in the periodical "The Journal of the American Chemical Society, 60, 309 (1938)". The recommendations of the standard ASTM D3663 - 03 can be complied with. The calcinations for a given temperature and time correspond, unless otherwise indicated, to calcinations in air at a temperature plateau over the indicated time.
L'alumine de l'invention peut être représentée par la formule générale AI2O3. The alumina of the invention can be represented by the general formula Al 2 O 3 .
L'alumine peut comprendre du sodium résiduel. Le taux de sodium résiduel peut être inférieur ou égal à 0,50% en poids, voire inférieur ou égal à 0,15% en poids. Le taux de sodium peut être supérieur ou égal à 50 ppm. Ce taux peut être compris entre 50 et 900 ppm, voire entre 100 et 800 ppm. Ce taux est exprimé en poids de Na2Û par rapport au poids total de l'alumine. Ainsi, pour une alumine ayant un taux de sodium résiduel de 0,15%, on considère qu'il y a pour 100 g d'alumine, 0,15 g de Na20. La méthode de détermination du taux de sodium dans cette gamme de concentrations est connue de l'homme du métier. On peut par exemple utiliser la technique de spectroscopie plasma à couplage inductif. L'alumine peut comprendre du sulfate résiduel. Le taux de sulfate résiduel peut être inférieur ou égal à 1 ,00% en poids, voire inférieur ou égal à 0,20% en poids, voire encore inférieur ou égal à 0,10% en poids. Le taux de sulfate peut être supérieur ou égal à 50 ppm. Ce taux peut être compris entre 100 et 1500 ppm, voire entre 400 et 1000 ppm. Ce taux est exprimé en poids de sulfate par rapport au poids total de l'alumine. Ainsi, pour une alumine ayant un taux de sulfate résiduel de 0,50%, on considère qu'il y a pour 100 g d'alumine, 0,50 g de SO4. La méthode de détermination du taux de sulfate dans cette gamme de concentrations est connue de l'homme du métier comme par exemple la technique de spectroscopie plasma à couplage inductif. On peut aussi utiliser des techniques de microanalyse. Un appareil de microanalyse de type Horiba EMIA 320-V2 pourrait convenir. The alumina can include residual sodium. The residual sodium level may be less than or equal to 0.50% by weight, or even less than or equal to 0.15% by weight. The sodium level can be greater than or equal to 50 ppm. This rate can be between 50 and 900 ppm, or even between 100 and 800 ppm. This rate is expressed as the weight of Na2O relative to the total weight of the alumina. Thus, for an alumina having a residual sodium level of 0.15%, it is considered that there is per 100 g of alumina, 0.15 g of Na 2 0. The method for determining the sodium level in this range of concentrations is known to those skilled in the art. For example, the technique of inductively coupled plasma spectroscopy can be used. The alumina can include residual sulfate. The level of residual sulphate may be less than or equal to 1.00% by weight, or even less than or equal to 0.20% by weight, or even less than or equal to 0.10% by weight. The sulphate level can be greater than or equal to 50 ppm. This rate can be between 100 and 1500 ppm, or even between 400 and 1000 ppm. This rate is expressed in weight of sulphate relative to the total weight of alumina. Thus, for an alumina having a residual sulphate level of 0.50%, it is considered that there is per 100 g of alumina, 0.50 g of SO 4 . The method for determining the level of sulphate in this range of concentrations is known to those skilled in the art such as, for example, the technique of inductively coupled plasma spectroscopy. Microanalysis techniques can also be used. A Horiba EMIA 320-V2 type microanalysis device could be suitable.
L’alumine peut également contenir des impuretés autres que le sodium et le sulfate, par exemple des impuretés à base de silicium, de titane ou de fer. La proportion de chaque impureté est généralement inférieure à 0,07% en poids (£ 0,07%), voire inférieure à 0,05% en poids (£ 0,05%). Alumina can also contain impurities other than sodium and sulphate, for example impurities based on silicon, titanium or iron. The proportion of each impurity is generally less than 0.07% by weight (£ 0.07%), or even less than 0.05% by weight (£ 0.05%).
L’alumine de l'invention se caractérise par une porosité particulière. Ainsi, cette alumine présente au moins l'un des deux profils de porosité suivants : The alumina of the invention is characterized by a particular porosity. Thus, this alumina has at least one of the following two porosity profiles:
1er profil : un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,60 et 0,85 mL/g, plus particulièrement entre 0,60 et 0,80 mL/g ; et un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,20 mL/g, plus particulièrement inférieur ou égal à 0,15 mL/g, voire inférieur ou égal à 0,10 mL/g, voire encore inférieur ou égal à 0,05 mL/g. 1 st profile: a pore volume in the area of the pores, the size of which is between 5 nm and 100 nm which is between 0.60 and 0.85 mL / g, more particularly between 0.60 and 0.80 mL / g; and a pore volume in the area of the pores, the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g, more particularly less than or equal to 0.15 mL / g, or even less than or equal at 0.10 mL / g, or even less than or equal to 0.05 mL / g.
2nd profil : après calcination sous air à 1100°C pendant 5 heures : un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,50 et 0,75 mL/g, plus particulièrement entre 0,50 et 0,70 mL/g ; et un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,20 mL/g, plus particulièrement inférieur ou égal à 0,15 mL/g, voire inférieur ou égal à 0,10 mL/g, voire encore inférieur ou égal à 0,05 mL/g. 2 nd profile: after calcination in air at 1100 ° C for 5 hours: a pore volume in the area of the pores the size of which is between 5 nm and 100 nm which is between 0.50 and 0.75 mL / g, more particularly between 0.50 and 0.70 mL / g; and a pore volume in the area of the pores, the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g, more particularly less than or equal to 0.15 mL / g, or even less than or equal at 0.10 mL / g, or even less than or equal to 0.05 mL / g.
L'alumine peut aussi être définie par au moins l'un des deux profils de porosité suivants : Alumina can also be defined by at least one of the following two porosity profiles:
■ 1er profil : un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,60 et 0,85 mL/g; et un volume poreux dans le domaine des pores dont la taille est compris entre 100 nm et 1000 nm qui est inférieur ou égal à 0,20 mL/g; et/ou ■ 1 st profile: a pore volume in the region of the pores, the size of which is between 5 nm and 100 nm which is between 0.60 and 0.85 mL / g; and a pore volume in the area of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g; and or
■ 2nd profil : après calcination sous air à 1100°C pendant 5 heures : un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,50 et 0,75 mL/g; et un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,20 mL/g. ■ 2 nd profile: after calcination in air at 1100 ° C for 5 hours: a pore volume in the area of pores having a size between 5 nm and 100 nm is between 0.50 and 0.75 mL / g ; and a pore volume in the region of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g.
L'alumine qui est décrite dans la présente demande peut présenter au moins l'un des deux profils précités, étant entendu qu'elle peut présenter les deux profils en même temps.The alumina which is described in the present application can have at least one of the two aforementioned profiles, it being understood that it can have both profiles at the same time.
Par ailleurs, l’alumine peut présenter une surface spécifique élevée. Elle peut présenter une surface spécifique BET comprise entre 100 et 200 m2/g, plus particulièrement entre 150 et 200 m2/g. Cette surface spécifique peut être supérieure ou égale à 120 m2/g, de préférence, supérieure ou égale à 140 m2/g. Cette surface spécifique peut être aussi comprise entre 100 et 140 m2/g, voire entre 100 et 120 m2/g. Furthermore, the alumina can have a high specific surface. It may have a BET specific surface area of between 100 and 200 m 2 / g, more particularly between 150 and 200 m 2 / g. This specific surface can be greater than or equal to 120 m 2 / g, preferably greater than or equal to 140 m 2 / g. This specific surface can also be between 100 and 140 m 2 / g, or even between 100 and 120 m 2 / g.
L'alumine présente par ailleurs une stabilité thermique élevée. Elle peut présenter une surface spécifique BET après calcination sous air à 1100°C pendant 5 heures comprise entre 70 et 100 m2/g. The alumina also has high thermal stability. It can have a BET specific surface after calcination in air at 1100 ° C. for 5 hours of between 70 and 100 m 2 / g.
L'alumine présente généralement un volume poreux total qui est généralement strictement supérieur à 1,05 mL/g. Ce volume poreux total peut être avantageusement d'au moins 1 ,10 mL/g, voire d'au moins 1,20 mL/g, voire encore d'au moins 1 ,30 mL/g ou d'au moins 1 ,40 mL/g ou d'au moins 1 ,50 mL/g. Ce volume poreux total est généralement d'au plus 2,40 mL/g. The alumina generally has a total pore volume which is generally strictly greater than 1.05 mL / g. This total pore volume can advantageously be at least 1.10 mL / g, or even at least 1.20 mL / g, or even at least 1.30 mL / g or at least 1.40 mL / g or at least 1.50 mL / g. This total pore volume is generally at most 2.40 mL / g.
L'alumine conserve un volume poreux total important même après calcination à 1100°C pendant 5 heures. Ainsi, après calcination à 1100°C pendant 5 heures, l'alumine présente généralement un volume poreux total qui est d'au moins 0,90 mL/g. Ce volume poreux total est de préférence d'au moins 1 ,00 mL/g, voire d'au moins 1,10 mL/g, voire encore plus avantageusement d'au moins 1,20 mL/g. Ce volume poreux total est généralement d'au plus 1 ,80 mL/g. The alumina retains a large total pore volume even after calcination at 1100 ° C. for 5 hours. Thus, after calcination at 1100 ° C. for 5 hours, the alumina generally exhibits a total pore volume which is at least 0.90 mL / g. This total pore volume is preferably at least 1.00 mL / g, or even at least 1.10 mL / g, or even more advantageously at least 1.20 mL / g. This total pore volume is generally at most 1.80 mL / g.
On notera également que l'alumine est cristallisée. Ceci peut être mis en évidence à l'aide d'un diffractogramme des rayons X. L'alumine peut comprendre une phase delta, une phase thêta, une phase gamma ou un mélange d'au moins deux de ces phases. It will also be noted that the alumina is crystallized. This can be demonstrated using an X-ray diffractogram. The alumina can comprise a delta phase, a theta phase, a gamma phase or a mixture of at least two of these phases.
L’alumine peut présenter une densité apparente comprise entre 0,25 g/cm3 et 0,55 g/cm3, plus particulièrement entre 0,40 g/cm3 et 0,55 g/cm3. Cette densité apparente de la poudre d’alumine correspond au poids d’une certaine quantité de poudre rapporté au volume occupé par cette poudre : densité apparente en g/mL = (masse de la poudre (g) )/(volume de la poudre (mL))The alumina can have an apparent density of between 0.25 g / cm 3 and 0.55 g / cm 3 , more particularly between 0.40 g / cm 3 and 0.55 g / cm 3 . This bulk density of the alumina powder corresponds to the weight of a certain quantity of powder relative to the volume occupied by this powder: bulk density in g / mL = (mass of the powder (g)) / (volume of the powder ( mL))
Cette densité apparente peut être déterminée par la méthode décrite ci-après. On détermine tout d’abord précisément le volume d’une éprouvette sans bec verseur de forme cylindrique d’environ 25 mL. Pour ce faire, on pèse l’éprouvette vide (tare T). On verse ensuite de l’eau distillée dans l’éprouvette jusqu’au bord mais sans dépasser le bord (pas de ménisque). On pèse l’éprouvette remplie d’eau distillée (M). La masse d’eau contenue dans l’éprouvette est donc : This bulk density can be determined by the method described below. First, the volume of a cylindrical-shaped test tube of approximately 25 mL is precisely determined. To do this, the empty specimen is weighed (tare T). Distilled water is then poured into the test tube to the edge but without going over the edge (no meniscus). Weigh the test tube filled with distilled water (M). The mass of water contained in the test tube is therefore:
E = M - T Le volume calibré de l’éprouvette est égal à Vépr0uvette = E/(masse volumique de l'eau à la température de mesure). La masse volumique de l’eau est par exemple égale à 0,99983 g/mL pour une température de mesure de 20°C. Dans l’éprouvette vide et sèche, on verse délicatement la poudre d’alumine à l’aide d’un entonnoir jusqu’à atteindre le bord de l’éprouvette. L’excès de poudre est arasé à l’aide d’une spatule. La poudre ne doit pas être compactée ou tassée lors du remplissage. On pèse ensuite l’éprouvette contenant la poudre. densité apparente (g/mL) = (masse de l'éprouvette contenant la poudre d’alumine - TareE = M - T The calibrated volume of the test piece is equal to V test tube = E / (density of water at the measurement temperature). The density of the water is for example equal to 0.99983 g / mL for a measurement temperature of 20 ° C. In the empty and dry test tube, the alumina powder is gently poured using a funnel until it reaches the edge of the test tube. The excess powder is leveled off using a spatula. The powder should not be compacted or packed when filling. The test tube containing the powder is then weighed. apparent density (g / mL) = (mass of the test piece containing the alumina powder - Tare
T (9) )/(Véprouvette (mL)) T (9)) / (V-tube (mL))
L’alumine peut présenter un D50 compris entre 2,0 pm et 80,0 pm. Elle peut présenter un D90 inférieur ou égal à 150,0 pm, plus particulièrement inférieur ou égal à 100,0 pm. Elle peut présenter un D10 supérieur ou égal à 1 ,0 pm. Alumina can have an D50 between 2.0 µm and 80.0 µm. It may have a D90 less than or equal to 150.0 μm, more particularly less than or equal to 100.0 μm. It may have a D10 greater than or equal to 1.0 μm.
Premier mode de réalisation First embodiment
Selon un premier mode de réalisation, l'alumine présente un D50 compris entre 2,0 et 15,0 pm, voire entre 4,0 et 12,0 pm. Le D90 peut être compris entre 20,0 pm et 60,0 pm, voire entre 25,0 pm et 50,0 pm. According to a first embodiment, the alumina has a D50 of between 2.0 and 15.0 μm, or even between 4.0 and 12.0 μm. The D90 can be between 20.0 pm and 60.0 pm, or even between 25.0 pm and 50.0 pm.
Selon le premier mode de réalisation, lorsque le D50 est compris entre 2,0 et 15,0 pm,According to the first embodiment, when the D50 is between 2.0 and 15.0 pm,
- la densité apparente est comprise entre 0,25 et 0,40 g/cm3 ; et/ou - le volume poreux total est compris entre 1 ,40 et 2,40 mL/g. - the apparent density is between 0.25 and 0.40 g / cm 3 ; and / or - the total pore volume is between 1.40 and 2.40 mL / g.
Ce volume poreux total peut être plus avantageusement compris entre 1 ,50 et 2,40 mL/g. Second mode de réalisation Selon un second mode de réalisation, l'alumine présente un D50 compris entre 15,0 et 80,0 pm, voire entre 20,0 et 60,0 pm. Le D90 peut être compris entre 40,0 pm et 150,0 pm, voire entre 50,0 pm et 100,0 pm. This total pore volume can be more advantageously between 1.50 and 2.40 mL / g. Second embodiment According to a second embodiment, the alumina has a D50 of between 15.0 and 80.0 μm, or even between 20.0 and 60.0 μm. The D90 can be between 40.0 pm and 150.0 pm, or even between 50.0 pm and 100.0 pm.
Selon le second mode de réalisation, lorsque D50 est compris entre 15,0 et 80,0 pm, - la densité apparente peut être comprise entre 0,40 et 0,55 g/cm3 ; et/ou According to the second embodiment, when D50 is between 15.0 and 80.0 μm, - the bulk density can be between 0.40 and 0.55 g / cm 3 ; and or
- le volume poreux total est compris entre 1,05 (valeur exclue) et 1,80 mL/g. - the total pore volume is between 1.05 (excluded value) and 1.80 mL / g.
Ce volume poreux total peut être plus avantageusement compris entre 1 ,20 et 1 ,80 mL/g. This total pore volume can be more advantageously between 1, 20 and 1, 80 ml / g.
Alumine particulière Special alumina
L'alumine de l'invention peut présenter plus particulièrement au moins l'un des deux profils de porosité suivants : The alumina of the invention may more particularly exhibit at least one of the following two porosity profiles:
1er profil : - un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,60 et 0,85 mL/g, plus particulièrement entre 0,60 et 0,80 mL/g ; et un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,05 mL/g ; et/ou 1 st profile: - a pore volume in the area of the pores, the size of which is between 5 nm and 100 nm which is between 0.60 and 0.85 mL / g, more particularly between 0.60 and 0.80 mL / g; and a pore volume in the region of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.05 mL / g; and or
2nd profil : après calcination sous air à 1100°C pendant 5 heures : un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,50 et 0,75 mL/g, plus particulièrement entre 0,50 et 0,70 mL/g ; et un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,05 mL/g. 2 nd profile: after calcination in air at 1100 ° C for 5 hours: a pore volume in the area of the pores the size of which is between 5 nm and 100 nm which is between 0.50 and 0.75 mL / g, more particularly between 0.50 and 0.70 mL / g; and a pore volume in the area of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.05 mL / g.
Comme précédemment, cette alumine particulière peut présenter au moins l'un des deux profils précités, étant entendu qu'elle peut présenter les deux profils en même temps. Elle peut également présenter les caractéristiques suivantes : As previously, this particular alumina can have at least one of the two aforementioned profiles, it being understood that it can have both profiles at the same time. It can also have the following characteristics:
- une surface spécifique BET comprise entre 150 et 200 m2/g ; et - a BET specific surface area of between 150 and 200 m 2 / g; and
- une surface spécifique BET après calcination sous air à 1100°C pendant 5 heures comprise entre 70 et 100 m2/g ; et a BET specific surface area after calcination in air at 1100 ° C. for 5 hours of between 70 and 100 m 2 / g; and
- une densité apparente comprise entre 0,40 g/cm3 et 0,55 g/cm3 ; et - an apparent density of between 0.40 g / cm 3 and 0.55 g / cm 3 ; and
- un D50 compris entre 15,0 et 80,0 pm ; et - a D50 of between 15.0 and 80.0 pm; and
- un D90 compris entre 40,0 pm et 150,0 pm. - a D90 of between 40.0 pm and 150.0 pm.
Par ailleurs, cette alumine particulière peut aussi présenter les caractéristiques de volume poreux total telles que décrites plus haut. Ainsi, elle présente généralement un volume poreux total qui est généralement strictement supérieur à 1 ,05 mL/g. Ce volume poreux total peut avantageusement être d'au moins 1 ,10 mL/g, voire d'au moins 1 ,20 mL/g, voire encore d'au moins 1 ,30 mL/g ou d'au moins 1 ,40 mL/g ou d'au moins 1 ,50 mL/g. Ce volume poreux total est généralement d'au plus 2,40 mL/g. Moreover, this particular alumina can also exhibit the characteristics of total pore volume as described above. Thus, it generally has a total pore volume which is generally strictly greater than 1.05 mL / g. This total pore volume can advantageously be at least 1.10 mL / g, or even at least 1. 20 mL / g, or even at least 1.30 mL / g or at least 1.40 mL / g or at least 1.50 mL / g. This total pore volume is generally at most 2.40 mL / g.
Cette alumine particulière conserve un volume poreux total important même après calcination à 1100°C pendant 5 heures. Ainsi, après calcination à 1100°C pendant 5 heures, l'alumine présente généralement un volume poreux total qui est d'au moins 0,90 mL/g. Ce volume poreux total est de préférence d'au moins 1 ,00 mL/g, voire d'au moiins 1,10 mL/g, voire encore plus avantageusement d'au moins 1,20 mL/g. Ce volume poreux total est généralement d'au plus 1 ,80 mL/g. This particular alumina retains a large total pore volume even after calcination at 1100 ° C. for 5 hours. Thus, after calcination at 1100 ° C. for 5 hours, the alumina generally exhibits a total pore volume which is at least 0.90 mL / g. This total pore volume is preferably at least 1.00 mL / g, or even at least 1.10 mL / g, or even more advantageously at least 1.20 mL / g. This total pore volume is generally at most 1.80 mL / g.
Les taux de sodium et de sulfate sont pour cette alumine particulière tels que décrits précédemment. The sodium and sulfate levels are for that particular alumina as previously described.
Utilisation de l'alumine Use of alumina
L'alumine de l'invention est utilisable dans le domaine de la catalyse de dépollution des gaz d'échappement des moteurs thermiques essence ou diesel. On utilise dans ce domaine une composition catalytique comprenant l'alumine de l'invention et au moins un oxyde à base de cérium et éventuellement d'au moins une terre rare autre que le cérium. Cet oxyde peut être par exemple l'oxyde de cérium (généralement représenté par la formule Ce02), un oxyde mixte à base de cérium, de zirconium et éventuellement d'au moins une terre rare autre que le cérium. La terre rare autre que le cérium peut être choisie dans le groupe formée par l'yttrium, le praséodyme ou le néodyme. Procédé de préparation The alumina of the invention can be used in the field of catalysis for the depollution of the exhaust gases of gasoline or diesel heat engines. A catalytic composition comprising the alumina of the invention and at least one oxide based on cerium and optionally at least one rare earth other than cerium is used in this field. This oxide can be, for example, cerium oxide (generally represented by the formula Ce0 2 ), a mixed oxide based on cerium, on zirconium and optionally on at least one rare earth other than cerium. The rare earth other than cerium can be chosen from the group formed by yttrium, praseodymium or neodymium. Preparation process
L'invention est aussi relative à un procédé de préparation d’une alumine, notamment l'alumine telle que décrite précédemment ou telle que décrite à l'une des revendications 1 à 39, comprenant les étapes suivantes : The invention also relates to a process for preparing an alumina, in particular alumina as described above or as described in one of claims 1 to 39, comprising the following steps:
(a) dans une cuve contenant initialement une solution aqueuse acide dont le pH est compris entre 0,5 et 4,0, voire entre 0,5 et 3,5, on introduit sous agitation : (a) in a tank initially containing an acidic aqueous solution the pH of which is between 0.5 and 4.0, or even between 0.5 and 3.5, the following are introduced with stirring:
(a1)- soit une solution aqueuse d'aluminate de sodium jusqu'à obtenir un pH du mélange réactionnel compris entre 8,0 et 10,0, voire entre 8,5 et 9,5 ; (a1) - either an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 8.0 and 10.0, or even between 8.5 and 9.5;
(a2)- soit simultanément (i) une solution aqueuse de sulfate d'aluminium et (ii) une solution aqueuse d'aluminate de sodium jusqu'à obtenir un pH du mélange réactionnel compris entre 6,5 et 10, voire entre 7,0 et 8,0 ou entre 8,5 et 9,5 ; de façon à ce qu’à la fin de l’étape (a), la concentration en aluminium du mélange réactionnel soit comprise entre 0,50% et 3,0% poids ; (a2) - either simultaneously (i) an aqueous solution of aluminum sulphate and (ii) an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 6.5 and 10, or even between 7, 0 and 8.0 or between 8.5 and 9.5; so that at the end of step (a), the aluminum concentration of the reaction mixture is between 0.50% and 3.0% by weight;
(b) puis on introduit ensuite simultanément une solution aqueuse de sulfate d'aluminium et une solution aqueuse d'aluminate de sodium dont les débits d'introduction sont tels que le pH moyen du mélange réactionnel est maintenu dans la gamme de pH visée à l'étape (a) ; la température du mélange réactionnel pour les étapes (a) et (b) étant d'au moins 60°C ;(b) then an aqueous solution of aluminum sulphate and an aqueous solution of sodium aluminate are then introduced simultaneously, the introduction rates of which are such that the average pH of the reaction mixture is maintained in the pH range referred to in 1 'step (a); the temperature of the reaction mixture for steps (a) and (b) being at least 60 ° C;
(c) à l'issue de l'étape (b), on ajuste éventuellement le pH du mélange réactionnel à une valeur comprise entre 7,5 et 10,5, voire entre 8,0 et 9,0 ou entre 9,0 et 10,0 ; (c) at the end of step (b), the pH of the reaction mixture is optionally adjusted to a value between 7.5 and 10.5, or even between 8.0 and 9.0 or between 9.0 and 10.0;
(d) le mélange réactionnel est ensuite filtré et le solide récupéré est lavé ; (d) the reaction mixture is then filtered and the solid recovered is washed;
(e) une dispersion dans l’eau du solide récupéré à l’issue de l'étape (d) subit un traitement mécanique ou par ultrasons de façon à réduire la taille des particules de la dispersion ;(e) a dispersion in water of the solid recovered at the end of step (d) undergoes mechanical or ultrasonic treatment so as to reduce the size of the particles of the dispersion;
(f) la dispersion obtenue à l’issue de l'étape (e) est séchée ; (f) the dispersion obtained at the end of step (e) is dried;
(g) le solide issu de l'étape (f) est ensuite calciné sous air. étape (a) (g) the solid resulting from step (f) is then calcined in air. step (a)
A l'étape (a), on introduit sous agitation dans une cuve contenant initialement une solution aqueuse acide dont le pH est compris entre 0,5 et 4,0, voire entre 0,5 et 3,5 : In step (a), the following are introduced with stirring into a tank initially containing an acidic aqueous solution, the pH of which is between 0.5 and 4.0, or even between 0.5 and 3.5:
(a1 )- soit une solution aqueuse d'aluminate de sodium jusqu'à obtenir un pH du mélange réactionnel compris entre 8,0 et 10,0, voire entre 8,5 et 9,5 ; (a1) - either an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 8.0 and 10.0, or even between 8.5 and 9.5;
(a2)- soit simultanément (i) une solution aqueuse de sulfate d'aluminium et (ii) une solution aqueuse d'aluminate de sodium jusqu'à obtenir un pH du mélange réactionnel compris entre 6,5 et 10,0, voire entre 7,0 et 8,0 ou entre 8,5 et 9,5 ; de façon à ce qu’à la fin de l’étape (a), la concentration en aluminium du mélange réactionnel soit comprise entre 0,50% et 3,0% en poids. (a2) - either simultaneously (i) an aqueous solution of aluminum sulphate and (ii) an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 6.5 and 10.0, or even between 7.0 and 8.0 or between 8.5 and 9.5; so that at the end of step (a), the aluminum concentration of the reaction mixture is between 0.50% and 3.0% by weight.
La solution aqueuse acide initialement contenue dans la cuve présente un pH compris entre 0,5 et 4,0, voire entre 0,5 et 3,5. Cette solution peut être constituée d’une solution aqueuse diluée d’un acide minéral comme par exemple l’acide sulfurique, l’acide chlorhydrique ou l’acide nitrique. The acidic aqueous solution initially contained in the tank has a pH of between 0.5 and 4.0, or even between 0.5 and 3.5. This solution may consist of a dilute aqueous solution of a mineral acid such as, for example, sulfuric acid, hydrochloric acid or nitric acid.
La solution aqueuse acide peut être aussi constituée d’une solution aqueuse d’un sel acide d’aluminium comme le nitrate, le chlorure ou le sulfate d’aluminium. De préférence, la concentration en aluminium de cette solution est comprise entre 0,01% et 2,0% poids, voire entre 0,01% et 1,0% poids, voire encore entre 0,10% et 1 ,0% poids. De préférence, la solution aqueuse acide est une solution aqueuse de sulfate d’aluminium. On prépare cette solution par dissolution du sulfate d’aluminium dans l’eau ou bien par dilution dans de l'eau de solution(s) aqueuses préformées. Le pH de la solution aqueuse développé par la présence du sulfate d’aluminium est généralement compris entre 0,5 et 4,0, voire entre 0,5 et 3,5. The acidic aqueous solution can also consist of an aqueous solution of an acidic aluminum salt such as aluminum nitrate, chloride or sulfate. Preferably, the aluminum concentration of this solution is between 0.01% and 2.0% by weight, or even between 0.01% and 1.0% by weight, or even between 0.10% and 1.0% by weight. . Preferably the acidic aqueous solution is an aqueous solution of aluminum sulfate. This solution is prepared by dissolving aluminum sulphate in water or else by diluting preformed aqueous solution (s) in water. The pH of the aqueous solution developed by the presence of aluminum sulfate is generally between 0.5 and 4.0, or even between 0.5 and 3.5.
L’étape (a) est mise en oeuvre selon deux modes de réalisation (a1) ou (a2). Selon le mode de réalisation (a1), on introduit sous agitation une solution aqueuse d’aluminate de sodium. Selon le mode de réalisation (a2), on introduit sous agitation simultanément (i) une solution aqueuse de sulfate d'aluminium et (ii) une solution aqueuse d'aluminate de sodium. Step (a) is implemented according to two embodiments (a1) or (a2). According to embodiment (a1), an aqueous solution of sodium aluminate is introduced with stirring. According to embodiment (a2), (i) an aqueous solution of aluminum sulphate and (ii) an aqueous solution of sodium aluminate are simultaneously introduced with stirring.
De préférence, la solution aqueuse d’aluminate de sodium ne présente pas d'alumine précipitée. L'aluminate de sodium présente de préférence un rapport Na20/AI2C>3 supérieur ou égal à 1 ,20, par exemple compris entre 1 ,20 et 1 ,40. Preferably, the aqueous solution of sodium aluminate does not have precipitated alumina. The sodium aluminate preferably has an Na 2 0 / Al 2 C> 3 ratio greater than or equal to 1. 20, for example between 1. 20 and 1. 40.
La solution aqueuse d’aluminate de sodium peut présenter une concentration en aluminium comprise entre 15,0% et 35,0% en poids, plus particulièrement entre 15,0% et 30,0% poids, voire entre 20,0% et 30,0%. La solution aqueuse de sulfate d'aluminium peut présenter une concentration en aluminium comprise entre 1 ,0% et 15,0% en poids, plus particulièrement entre 5,0% et 10,0% poids. The aqueous solution of sodium aluminate may have an aluminum concentration of between 15.0% and 35.0% by weight, more particularly between 15.0% and 30.0% by weight, or even between 20.0% and 30.0% by weight. , 0%. The aqueous solution of aluminum sulphate can have an aluminum concentration of between 1.0% and 15.0% by weight, more particularly between 5.0% and 10.0% by weight.
A l’issue de l’étape (a), la concentration en aluminium du mélange réactionnel est comprise entre 0,50% et 3,0% poids. At the end of step (a), the aluminum concentration of the reaction mixture is between 0.50% and 3.0% by weight.
A cette étape (a), la durée d'introduction de la ou des solutions est généralement comprise entre 2 min et 30 min. In this step (a), the duration of introduction of the solution (s) is generally between 2 min and 30 min.
A l'étape (a), l'introduction de la solution aqueuse d’aluminate de sodium a pour effet de faire augmenter le pH du mélange réactionnel. In step (a), the introduction of the aqueous solution of sodium aluminate has the effect of increasing the pH of the reaction mixture.
De façon particulière pour le mode de réalisation (a1), la solution aqueuse d’aluminate de sodium peut être introduite directement au sein du milieu réactionnel, par exemple par l'intermédiaire d’au moins une canne d'introduction. De façon particulière pour le mode de réalisation (a2), les deux solutions peuvent être introduites directement au sein du milieu réactionnel, par exemple par l'intermédiaire d’au moins deux cannes d'introduction. Pour ces deux modes de réalisation (a1) et (a2), la ou les solution(s) est/sont introduite(s) de préférence dans une zone bien agitée du réacteur, par exemple dans une zone proche du mobile d'agitation, de façon à obtenir un mélange efficace de la ou des solution(s) introduite(s) dans le mélange réactionnel. Pour le mode de réalisation (a2), lorsque les solutions sont introduites par l’intermédiaire d’au moins deux cannes d’introduction, les points d'injection par lesquels les deux solutions sont introduites au sein du mélange réactionnel sont répartis de façon à ce que les solutions se diluent efficacement dans ledit mélange. Ainsi, par exemple, on peut disposer deux cannes dans la cuve de façon à ce que les points d’injection des solutions dans le mélange réactionnel soient diamétralement opposés. étape (b) A l’étape (b), on introduit simultanément une solution aqueuse de sulfate d'aluminium et une solution aqueuse d'aluminate de sodium dont les débits d'introduction sont régulés de façon à maintenir le pH moyen du mélange réactionnel dans la gamme de pH visée à l'étape (a). Ainsi, la valeur cible du pH moyen est comprise: entre 8,0 et 10,0, voire entre 8,5 et 9,5, pour le cas où le mode de réalisation (a1) a été suivi à l’étape (a) ; ou bien entre 6,5 et 10,0, voire entre 7,0 et 8,0 ou entre 8,5 et 9,5, pour le cas où le mode de réalisation (a2) a été suivi à l’étape (a). In particular for embodiment (a1), the aqueous solution of sodium aluminate can be introduced directly into the reaction medium, for example by means of at least one introduction pipe. In particular for embodiment (a2), the two solutions can be introduced directly into the reaction medium, for example by means of at least two introduction pipes. For these two embodiments (a1) and (a2), the solution (s) is / are preferably introduced into a well-stirred zone of the reactor, for example in a zone close to the stirring wheel, so as to obtain an effective mixture of the solution (s) introduced into the reaction mixture. For embodiment (a2), when the solutions are introduced via at least two introduction pipes, the injection points through which the two solutions are introduced into the reaction mixture are distributed so as to that the solutions dilute effectively in said mixture. Thus, for example, it is possible to place two rods in the tank so that the points of injection of the solutions into the reaction mixture are diametrically opposed. step (b) In step (b), an aqueous solution of aluminum sulphate and an aqueous solution of sodium aluminate are introduced simultaneously, the introduction rates of which are regulated so as to maintain the average pH of the reaction mixture in the range of pH referred to in step (a). Thus, the target value of the mean pH is between: between 8.0 and 10.0, or even between 8.5 and 9.5, for the case where the embodiment (a1) has been followed in step (a ); or else between 6.5 and 10.0, or even between 7.0 and 8.0 or between 8.5 and 9.5, for the case where the embodiment (a2) has been followed in step (a ).
On entend par "pH moyen" la moyenne arithmétique des valeurs de pH du mélange réactionnel qui sont enregistrées en continu au cours de l'étape (b). The term “mean pH” is understood to mean the arithmetic mean of the pH values of the reaction mixture which are recorded continuously during step (b).
De préférence, la solution aqueuse d’aluminate de sodium est introduite en même temps que la solution aqueuse de sulfate d'aluminium à un débit qui est régulé de façon à ce que le pH moyen du mélange réactionnel soit égal à la valeur cible. Le débit de la solution aqueuse d'aluminate de sodium servant à réguler le pH peut fluctuer au cours de l’étape (b). Preferably, the aqueous solution of sodium aluminate is introduced at the same time as the aqueous solution of aluminum sulphate at a rate which is regulated so that the average pH of the reaction mixture is equal to the target value. The flow rate of the aqueous sodium aluminate solution used to regulate the pH may fluctuate during step (b).
La durée d'introduction des deux solutions peut être comprise entre 10 minutes et 2 heures, voire entre 30 minutes et 90 minutes. Le débit d’introduction de la ou des deux solutions peut être constant. The duration of introduction of the two solutions may be between 10 minutes and 2 hours, or even between 30 minutes and 90 minutes. The rate of introduction of the or both solutions can be constant.
Il est nécessaire que la température du mélange réactionnel pour les étapes (a) et (b) soit d'au moins 60°C. Cette température peut être comprise entre 60°C et 95°C. Pour ce faire, la solution contenue initialement dans la cuve à l’étape (a) peut avoir été préchauffée avant le début de l’introduction de la ou des solutions. On peut aussi préalablement préchauffer les solutions qui sont introduites dans la cuve aux étapes (a) et (b). étape (cl It is necessary that the temperature of the reaction mixture for steps (a) and (b) is at least 60 ° C. This temperature can be between 60 ° C and 95 ° C. To do this, the solution initially contained in the tank in step (a) may have been preheated before the start of the introduction of the solution (s). It is also possible to preheat the solutions which are introduced into the tank in steps (a) and (b) beforehand. step (cl
A l'étape (c), on ajuste éventuellement le pH du mélange réactionnel à une valeur comprise entre 7,5 et 10,5, voire entre 8,0 et 9,0 ou entre 9,0 et 10,0, par l’ajout d’une solution aqueuse basique ou acide. In step (c), the pH of the reaction mixture is optionally adjusted to a value between 7.5 and 10.5, or even between 8.0 and 9.0 or between 9.0 and 10.0, by l addition of a basic or acidic aqueous solution.
La solution aqueuse acide utilisable pour ajuster le pH peut être constituée d’une solution aqueuse d’un acide minéral comme par exemple l’acide sulfurique, l’acide chlorhydrique ou l’acide nitrique. La solution aqueuse acide peut être aussi constituée d’une solution aqueuse d’un sel acide d’aluminium comme le nitrate, le chlorure ou le sulfate d’aluminium. The acidic aqueous solution which can be used to adjust the pH may consist of an aqueous solution of a mineral acid such as, for example, sulfuric acid, hydrochloric acid or nitric acid. The aqueous acidic solution can also consist of an aqueous solution of an acidic aluminum salt such as aluminum nitrate, chloride or sulfate.
La solution aqueuse basique utilisable pour ajuster le pH peut être constituée d’une solution aqueuse d’une base minérale comme par exemple la soude, la potasse, l’ammoniaque. La solution aqueuse basique peut être aussi constituée d’une solution aqueuse d’un sel basique d’aluminium comme l’aluminate de sodium. De préférence, on utilise une solution aqueuse d’aluminate de sodium. The basic aqueous solution which can be used to adjust the pH may consist of an aqueous solution of a mineral base such as, for example, soda, potassium hydroxide, ammonia. The basic aqueous solution can also consist of an aqueous solution of a basic aluminum salt such as sodium aluminate. Preferably, an aqueous solution of sodium aluminate is used.
De préférence, on ajuste le pH en arrêtant : Preferably, the pH is adjusted by stopping:
(c1)- l'introduction de la solution aqueuse de sulfate et on continue d'introduire la solution aqueuse d'aluminate de sodium jusqu'à atteindre le pH cible ; ou bien (c2)-l'introduction de la solution aqueuse d'aluminate de sodium et on continue d'introduire la solution aqueuse de sulfate d'aluminium jusqu'à atteindre le pH cible. (c1) - the introduction of the aqueous sulphate solution and the introduction of the aqueous sodium aluminate solution is continued until the target pH is reached; or (c2) - the introduction of the aqueous solution of sodium aluminate and the introduction of the aqueous solution of aluminum sulphate is continued until the target pH is reached.
Selon un mode de réalisation, on arrête l’introduction de la solution aqueuse de sulfate d’aluminium et on continue d'introduire la solution aqueuse d’aluminate de sodium jusqu'à atteindre un pH cible compris entre 8,0 et 10,5, de préférence compris entre 9,0 et 10,0. La durée de l'étape (c) peut être variable. Cette durée peut être comprise entre 5 min et 30 min. étape (d) According to one embodiment, the introduction of the aqueous solution of aluminum sulphate is stopped and the aqueous solution of sodium aluminate is continued to be introduced until a target pH of between 8.0 and 10.5 is reached. , preferably between 9.0 and 10.0. The duration of step (c) can be variable. This duration can be between 5 min and 30 min. step (d)
A l'étape (d), le mélange réactionnel est filtré. Le mélange réactionnel se présente généralement sous la forme d’une bouillie. Le solide récupéré sur le filtre peut être lavé avec de l'eau. Pour ce faire, on peut utiliser de l'eau chaude dont la température est d'au moins 50°C. étape (e) In step (d), the reaction mixture is filtered. The reaction mixture is generally in the form of a slurry. The solid collected on the filter can be washed with water. To do this, you can use hot water with a temperature of at least 50 ° C. step (e)
A l’étape (e), une dispersion dans l’eau du solide récupéré à l’issue de l’étape (d) subit un traitement mécanique ou par ultrasons de façon à réduire la taille des particules de la dispersion. Le pH de cette dispersion avant broyage peut être éventuellement ajusté entre 5,0 et 8,0. On peut pour cela utiliser par exemple une solution d’acide nitrique. In step (e), a dispersion in water of the solid recovered at the end of step (d) undergoes mechanical or ultrasonic treatment so as to reduce the size of the particles of the dispersion. The pH of this dispersion before grinding can optionally be adjusted between 5.0 and 8.0. You can use a nitric acid solution, for example.
Le D50 des particules de la dispersion avant le traitement mécanique ou par ultrasons est généralement compris entre 10,0 pm et 40,0 pm, voire entre 10,0 pm et 30,0 pm. Le D50 des particules du solide après le traitement mécanique ou par ultrasons est de préférence compris entre 1,0 pm et 15,0 pm, voire entre 2,0 pm et 10,0 pm. The D50 of the particles of the dispersion before the mechanical or ultrasonic treatment is generally between 10.0 pm and 40.0 pm, or even between 10.0 pm and 30.0 pm. The D50 of the particles of the solid after the mechanical or ultrasonic treatment is preferably between 1.0 μm and 15.0 μm, or even between 2.0 μm and 10.0 μm.
Le traitement mécanique consiste à appliquer une contrainte mécanique ou des forces de cisaillement à la dispersion de façon à fractionner les particules. Le traitement mécanique peut être par exemple opéré à l’aide d’un broyeur à billes, d’un homogénéisateur haute pression ou d’un système de broyage comprenant un rotor et un stator. A l’échelle du laboratoire, il est possible d’utiliser un broyeur à billes Microcer ou bien Labstar Zêta, tous deux commercialisés par la société Netzsch (pour plus de détails, voir : https://www.netzsch-qrindinq.com/fr/produits-solutions/brovaqe-humide/broveurs-de- laboratoire-serie-mini/j. On pourra utiliser un système de broyage tel que décrit dans les exemples. Dans le cas d’un broyeur à billes, on peut utiliser par exemple des billes en oxyde de zirconium stabilisé à l’yttrium. On peut par exemple utiliser des billes ZetaBeads Plus 0,2 mm. Mechanical treatment involves applying mechanical stress or shear forces to the dispersion so as to split the particles. The mechanical treatment can, for example, be carried out using a ball mill, a high pressure homogenizer or a grinding system comprising a rotor and a stator. On a laboratory scale, it is possible to use a Microcer ball mill or a Labstar Zêta, both marketed by the company Netzsch (for more details, see: https://www.netzsch-qrindinq.com/ en / products-solutions / wet-brovaqe / mini-series-laboratory-grinders / j. A grinding system as described in the examples can be used. In the case of a ball mill, it is possible to use example of beads of zirconium oxide stabilized with yttrium It is possible, for example, to use 0.2 mm ZetaBeads Plus beads.
Le traitement par ultrasons consiste quant à lui à appliquer une onde sonore à la dispersion. L’onde sonore qui se propage dans le milieu liquide induit un phénomène de cavitation permettant de fractionner les particules. A l’échelle du laboratoire, il est possible d’utiliser un système ultrasons avec un générateur de type Sonies Vibracell VC750 équipé d'une sonde de 13 mm. La durée et la puissance appliquée sont ajustées de manière à atteindre le D50 visé. Ultrasound treatment consists of applying a sound wave to the dispersion. The sound wave which propagates in the liquid medium induces a phenomenon of cavitation allowing the particles to be split. On a laboratory scale, it is possible to use an ultrasound system with a Vibracell VC750 type sound generator equipped with a 13 mm probe. The duration and the power applied are adjusted so as to reach the target D50.
Le traitement mécanique ou par ultrasons peut être réalisé en mode batch ou bien en continu. étape (f) The mechanical or ultrasonic treatment can be carried out in batch mode or else continuously. step (f)
A l’étape (f), la dispersion de l’étape (e) est séchée, de préférence par atomisation. In step (f), the dispersion from step (e) is dried, preferably by atomization.
Le séchage par atomisation présente l’avantage de conduire à des particules dont la distribution granulométrique est contrôlée. Ce mode de séchage présente aussi une bonne productivité. Il consiste à pulvériser la dispersion en un nuage de gouttelettes dans un courant de gaz chaud (par ex. un courant d’air chaud) circulant dans une enceinte. La qualité de la pulvérisation contrôle la distribution de tailles des gouttelettes et partant, la distribution de tailles des particules séchées. La pulvérisation peut être réalisée au moyen de tout pulvérisateur connu en soi. Il existe deux principaux types de dispositifs de pulvérisation : turbines et buses. Sur les diverses techniques de pulvérisation susceptibles d'être mises en oeuvre dans le présent procédé, on pourra se référer notamment à l'ouvrage de base de MASTERS intitulé “SPRAY-DRYING" (deuxième édition, 1976, Editions George Godwin London). Les paramètres opératoires sur lesquels l’homme du métier peut agir sont notamment les suivants : le débit et la température de la dispersion entrant dans le pulvérisateur ; le débit, la pression, l’humidité et la température du gaz chaud. La température d’entrée du gaz est généralement comprise entre 100°C et 800°C. La température de sortie du gaz est généralement comprise entre 80°C et 150°C. Spray drying has the advantage of resulting in particles with a controlled particle size distribution. This drying method also has good productivity. It involves spraying the dispersion into a cloud of droplets in a stream of hot gas (eg a stream of hot air) circulating in an enclosure. The quality of the spray controls the size distribution of the droplets and hence the size distribution of the dried particles. Spraying can be carried out using any sprayer known per se. There are two main types of spray devices: turbines and nozzles. On the various spraying techniques that may be used in the present process, reference may be made in particular to the basic work by MASTERS entitled “SPRAY-DRYING” (second edition, 1976, Editions George Godwin London). operating parameters on which a person skilled in the art can act are in particular the following: the flow rate and the temperature of the dispersion entering the sprayer; the flow rate, the pressure, the humidity and the temperature of the hot gas. of the gas is generally between 100 ° C. and 800 ° C. The gas outlet temperature is generally between 80 ° C. and 150 ° C.
Le D50 de la poudre récupérée à l’issue de l’étape (g) est généralement compris entre 2,0 pm et 80,0 pm. Cette taille est liée à la distribution de tailles des gouttelettes en sortie du pulvérisateur. La capacité d’évaporation de l’atomiseur est généralement liée à la taille de l’enceinte. Ainsi, à l’échelle du laboratoire (Büchi B 290), le D50 peut être compris entre 2,0 et 15,0 pm. A plus grande échelle, le D50 peut être compris entre 15,0 et 80,0 pm. étape (g) The D50 of the powder recovered at the end of step (g) is generally between 2.0 µm and 80.0 µm. This size is linked to the size distribution of the droplets at the outlet of the sprayer. The vaporizer capacity of the atomizer is generally related to the size of the enclosure. Thus, at the laboratory scale (Büchi B 290), the D50 can be between 2.0 and 15.0 µm. On a larger scale, the D50 can be between 15.0 and 80.0 µm. step (g)
A l’étape (g), le solide issu de l’étape (f) est calciné sous air. La température de calcination est généralement comprise entre 500°C et 1000°C, plus particulièrement entre 800°C et 1000°C. La durée de la calcination est généralement comprise entre 1 et 10 h. On pourra utiliser les conditions de calcination données dans les exemples. In step (g), the solid resulting from step (f) is calcined in air. The calcination temperature is generally between 500 ° C and 1000 ° C, more particularly between 800 ° C and 1000 ° C. The duration of the calcination is generally between 1 and 10 h. It is possible to use the calcination conditions given in the examples.
Il est envisageable de réaliser les deux étapes (f) et (g) dans un même équipement au sein duquel la dispersion issue de l’étape (e) subit un traitement thermique permettant de réaliser à la fois le séchage et la calcination. It is possible to carry out the two steps (f) and (g) in the same equipment in which the dispersion resulting from step (e) undergoes a heat treatment allowing both drying and calcination to be carried out.
De préférence, l’alumine qui est récupérée à l’issue de l’étape (g) (c’est-à-dire à l’issue de la calcination) présente un D50 généralement compris entre 2,0 pm et 80,0 pm. Elle présente généralement un D90 inférieur ou égal à 150,0 pm, plus particulièrement inférieur ou égal à 100,0 pm. Preferably, the alumina which is recovered at the end of step (g) (that is to say at the end of the calcination) has a D50 generally between 2.0 μm and 80.0. pm. It generally has a D90 less than or equal to 150.0 μm, more particularly less than or equal to 100.0 μm.
Selon un premier mode de réalisation, à l’issue de l’étape (g), le D50 peut être compris entre 2,0 et 15,0 pm, voire entre 4,0 et 12,0 pm. Le D90 peut être compris entre 20,0 pm et 60,0 pm, voire entre 25,0 pm et 50,0 pm. Ce mode de réalisation peut être plutôt mis en oeuvre lorsque l’étape (f) est conduite à l’échelle du laboratoire à l’aide par exemple d’un atomiseur Büchi B 290. According to a first embodiment, at the end of step (g), the D50 can be between 2.0 and 15.0 pm, or even between 4.0 and 12.0 pm. The D90 can be between 20.0 pm and 60.0 pm, or even between 25.0 pm and 50.0 pm. This embodiment can instead be implemented when step (f) is carried out on a laboratory scale using, for example, a Büchi B 290 atomizer.
Selon un second mode de réalisation, à l’issue de l’étape (g), le D50 peut être compris entre 15,0 et 80,0 pm, voire entre 20,0 et 60,0 pm. Le D90 peut être compris entre 40,0 pm et 150,0 pm, voire entre 50,0 pm et 100,0 pm. Ce mode de réalisation peut être plutôt mis en oeuvre lorsque l’étape (f) est conduite à plus grande échelle. According to a second embodiment, at the end of step (g), the D50 can be between 15.0 and 80.0 pm, or even between 20.0 and 60.0 pm. The D90 can be between 40.0 pm and 150.0 pm, or even between 50.0 pm and 100.0 pm. This embodiment can rather be implemented when step (f) is carried out on a larger scale.
Le procédé peut aussi comprendre une étape ultime par laquelle le solide obtenu à l’étape précédente subit un broyage afin d’ajuster la taille de particules du solide. On peut utiliser un broyeur à couteaux, à jet d’air, à marteaux ou à boulets. De préférence, le produit broyé présente un D50 généralement compris entre 2,0 pm et 15,0 pm. Le D90 peut être compris entre 20,0 pm et 60,0 pm, voire entre 25,0 pm et 50,0 pm. The process can also include a final step whereby the solid obtained in the previous step undergoes grinding in order to adjust the particle size of the solid. You can use a knife, air jet, hammer or ball mill. Preferably, the ground product has an OD generally between 2.0 µm and 15.0 µm. The D90 can be between 20.0 pm and 60.0 pm, or even between 25.0 pm and 50.0 pm.
L'alumine de l'invention se présente sous la forme d'une poudre. The alumina of the invention is in the form of a powder.
On trouvera plus de détails pour la préparation de l'alumine de l'invention dans l'exemple ilustratif suivant. More details for the preparation of the alumina of the invention will be found in the following illustrative example.
Exemple Example
Mesure de la surface spécifique : Measurement of the specific surface:
Pour la suite de la description, on entend par surface spécifique, la surface spécifique B.E.T. déterminée par adsorption d'azote conformément à la norme ASTM D 3663-03 établie à partir de la méthode BRUNAUER-EMMETT-TELLER décrite dans le périodique "The Journal of the American Chemical Society, 60, 309 (1938)". La surface spécifique est déterminée automatiquement à l'aide d'un appareil par exemple de type T ristar II 3020 de Micromeritics en se conformant aux indications préconisées par le constructeur. Les échantillons sont préalablement traités à 250°C pendant 90 min sous vide (par exemple pour atteindre une pression de 50 mm de mercure). Ce traitement permet d’éliminer les espèces volatiles physisorbées en surface (telles que par exemple H2O,...). For the remainder of the description, the term “specific surface area” means the specific surface area B.E.T. determined by nitrogen adsorption in accordance with the ASTM D 3663-03 standard established from the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of the American Chemical Society, 60, 309 (1938)". The specific surface is determined automatically using an apparatus, for example of the T ristar II 3020 type from Micromeritics, in accordance with the indications recommended by the manufacturer. The samples are pretreated at 250 ° C. for 90 min under vacuum (for example to reach a pressure of 50 mm of mercury). This treatment makes it possible to eliminate volatile species that are physisorbed on the surface (such as for example H2O, ...).
Mesure de la porosité au mercure Measurement of mercury porosity
La mesure est réalisée à l’aide d’un appareil de mesure de porosimétrie au mercure. Dans notre cas, on a utilisé un appareil Micromeritics Autopore IV 9520 muni d’un pénétromètre à poudre en se conformant aux indications préconisées par le constructeur. On a utilisé les paramètres suivants : pénétromètre utilisé : 3,2 ml (référence Micromeritics : pénétromètre type n°8) ; volume du capillaire : 0,412 ml ; pression max ("head pressure") : 4,68 psi ; angle de contact : 130°; tension superficielle du mercure : 485 dynes/cm ; densité du mercure : 13,5335 g/ml. On applique à l’échantillon au début de la mesure un vide de 50 mm Hg pendant 5 min. Les temps d’équilibre sont les suivants : domaine des basses pressions (1 ,3-30 psi) : 20 s - domaine des hautes pressions (30-60 000 psi) : 20 s. Préalablement à la mesure, les échantillons sont traités à 200°C pendant 120 min pour éliminer les espèces volatiles physisorbées en surface (telles que par exemple H2O,...). The measurement is carried out using a mercury porosimetry measuring device. In our case, a Micromeritics Autopore IV 9520 device fitted with a powder penetrometer was used, complying with the instructions recommended by the manufacturer. The following parameters were used: penetrometer used: 3.2 ml (Micromeritics reference: type No. 8 penetrometer); capillary volume: 0.412 ml; max pressure ("head pressure"): 4.68 psi; contact angle: 130 °; surface tension of mercury: 485 dynes / cm; density of mercury: 13.5335 g / ml. At the start of the measurement, a vacuum of 50 mm Hg is applied to the sample for 5 min. The equilibrium times are as follows: low pressure range (1, 3-30 psi): 20 s - high pressure range (30-60,000 psi): 20 s. Prior to the measurement, the samples are treated at 200 ° C. for 120 min to eliminate the volatile species physisorbed on the surface (such as for example H2O, etc.).
Mesure de la granulométrie (D10, D50, D90) Particle size measurement (D10, D50, D90)
Pour réaliser les mesures de taille de particules, on utilise un granulomètre à diffraction laser MALVERN Mastersizer 2000 ou 3000 (plus de détails sur cet appareil donnés ici: https://www.malvernpanalvtical.com/fr/products/product-ranqe/mastersizer- ranqe/mastersizer-3000). La technique de diffraction laser utilisée consiste à mesurer l'intensité de la lumière diffusée lors du passage d'un faisceau laser à travers un échantillon de particules dispersées. Le faisceau laser passe à travers l’échantillon et l’intensité de la lumière diffusée est mesurée en fonction de l’angle. Les intensités diffractées sont ensuite analysées pour calculer la taille des particules en utilisant la théorie de diffusion de Mie. La mesure permet d’obtenir une distribution de tailles en volume de laquelle on déduit les paramètres D10, D50 et D90. To carry out the particle size measurements, a MALVERN Mastersizer 2000 or 3000 laser diffraction particle size analyzer is used (more details on this device given here: https://www.malvernpanalvtical.com/fr/products/product-ranqe/mastersizer - ranqe / mastersizer-3000). The laser diffraction technique used consists in measuring the intensity of the light scattered during the passage of a laser beam through a sample of dispersed particles. The laser beam passes through the sample and the intensity of the scattered light is measured as a function of the angle. The diffracted intensities are then analyzed to calculate the particle size using the Mie diffusion theory. The measurement makes it possible to obtain a volume distribution of sizes from which the parameters D10, D50 and D90 are deduced.
Exemple : préparation d'un oxyde d’aluminium selon l'invention Example: preparation of an aluminum oxide according to the invention
Dans une cuve agitée à l’aide d’un mobile d’agitation à pâles inclinées, munie d'une sonde de pH située dans la partie supérieure du liquide, on introduit 157 kg d’eau désionisée que l’on chauffe jusqu’à 85°C. Cette température sera maintenue tout au long des étapes (a) à (c). Par une canne d’introduction proche du mobile d’agitation, on introduit 13,8 kg d’une solution de sulfate d’aluminium de concentration 8,3% en poids d’alumine (AI2O3) à un débit de 920 g de solution/min. A l’issue de l’introduction, le pH du pied de cuve est proche de 2,6 et la concentration en aluminium est de 0,7% en poids. L’introduction de la solution de sulfate d’aluminium est alors arrêtée. étape (a) : par une seconde canne d’introduction proche du mobile d’agitation, on introduit une solution d’aluminate de sodium de concentration 24,9% en poids d’alumine (AI2O3) et de ratio molaire Na20/Al2C>3 de 1,27 à un débit de 690 g de solution/min jusqu’à atteindre un pH de 9,0. L’introduction est alors arrêtée. La concentration en aluminium du mélange réactionnel est alors de 2,10%. 157 kg of deionized water are introduced into a tank stirred using a mobile stirrer with inclined blades, fitted with a pH probe located in the upper part of the liquid, which is heated to 85 ° C. This temperature will be maintained throughout steps (a) to (c). 13.8 kg of an aluminum sulphate solution with a concentration of 8.3% by weight of alumina (AI2O3) are introduced via an introduction rod close to the stirring unit, at a flow rate of 920 g of solution. / min. At the end of the introduction, the pH of the starter is close to 2.6 and the aluminum concentration is 0.7% by weight. The introduction of the aluminum sulphate solution is then stopped. step (a): using a second introduction rod close to the stirring unit, a sodium aluminate solution with a concentration of 24.9% by weight of alumina (AI2O3) and a molar ratio Na 2 0 / Al 2 C> 3 from 1.27 at a flow rate of 690 g of solution / min until a pH of 9.0 is reached. The introduction is then stopped. The aluminum concentration of the reaction mixture is then 2.10%.
A l’étape (b), l’introduction de la solution de sulfate d’aluminium est à nouveau démarrée à un débit de 570 g de solution/min et la solution d’aluminate de sodium est simultanément introduite dans le réacteur agité à un débit régulé de manière à maintenir le pH à une valeur de 9,0. Cette étape dure 45 minutes, In step (b), the introduction of the aluminum sulphate solution is again started at a flow rate of 570 g of solution / min and the sodium aluminate solution is simultaneously introduced into the stirred reactor at a flow rate regulated so as to maintain the pH at a value of 9.0. This stage lasts 45 minutes,
A l’étape (c), on arrête l’introduction de la solution de sulfate d’aluminium et on continue à ajouter la solution d’aluminate de sodium avec un débit de 320 g de solution/min jusqu’à atteindre un pH de 9,5. L’addition de la solution d’aluminate de sodium est stoppée.In step (c), the introduction of the aluminum sulphate solution is stopped and the sodium aluminate solution is continued to be added with a flow rate of 320 g of solution / min until a pH of 9.5. The addition of the sodium aluminate solution is stopped.
A l'étape (d), la bouillie réactionnelle est déversée sur un filtre sous vide. A l’issue de la filtration, le gâteau est lavé par de l’eau désionisée à 65°C. In step (d), the reaction slurry is poured onto a vacuum filter. After filtration, the cake is washed with deionized water at 65 ° C.
A l’étape (e), le gâteau est redispersé dans de l’eau désionisée pour obtenir une suspension de concentration voisine de 10% en poids d’oxyde (AI2O3). Une solution d’acide nitrique de concentration 69% en poids est ajoutée à la suspension de manière à obtenir un pH proche de 6. La suspension est passée dans un broyeur à billes de marque LME20 du fabricant Netzsch. Les conditions de fonctionnement du broyeur sont ajustées de manière à obtenir un D50 de 3,5 microns. In step (e), the cake is redispersed in deionized water to obtain a suspension with a concentration of around 10% by weight of oxide (Al2O3). A nitric acid solution with a concentration of 69% by weight is added to the suspension so as to obtain a pH close to 6. The suspension is passed through a ball mill of the LME20 brand from the manufacturer Netzsch. The operating conditions of the mill are adjusted so as to obtain a D50 of 3.5 microns.
A l'étape (f), la suspension issue de l’étape (e) est atomisée pour obtenir une poudre sèche d’hydrate d’aluminium dopé au lanthane. In step (f), the suspension from step (e) is atomized to obtain a dry powder of aluminum hydrate doped with lanthanum.
A l’étape (g), la poudre atomisée est calcinée à 940°C pendant 2 heures (vitesse de montée en température de 3°C/min). La perte de masse observée pendant cette calcination est de 26,9%. In step (g), the atomized powder is calcined at 940 ° C for 2 hours (temperature rise rate of 3 ° C / min). The mass loss observed during this calcination is 26.9%.
On obtient alors une alumine qui présente les caractéristiques suivantes : An alumina is then obtained which has the following characteristics:
- surface spécifique : 174 m2/g ; - specific surface: 174 m 2 / g;
- surface spécifique après calcination sous air à 1100°C / 5 h : 81 m2/g ; - volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm : 0,69 mL/g ; - specific surface after calcination in air at 1100 ° C / 5 h: 81 m 2 / g; - pore volume in the field of pores, the size of which is between 5 nm and 100 nm: 0.69 mL / g;
- volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm : 0,02 mL/g ; - volume poreux total : 1,51 ml_/g ; - pore volume in the field of pores, the size of which is between 100 nm and 1000 nm: 0.02 mL / g; - total pore volume: 1.51 ml / g;
- après calcination sous air à 1100°C / 5 h, volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm : 0,55 ml_/g ; - after calcination in air at 1100 ° C / 5 h, pore volume in the range of pores, the size of which is between 5 nm and 100 nm: 0.55 ml / g;
- après calcination sous air à 1100°C / 5 h, volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm : 0,01 mL/g : - après calcination sous air à 1100°C / 5 h, volume poreux total : 1,15 mL/g. autres caractéristiques de l'alumine - after calcination in air at 1100 ° C / 5 h, pore volume in the range of pores whose size is between 100 nm and 1000 nm: 0.01 mL / g: - after calcination in air at 1100 ° C / 5 h, total pore volume: 1.15 mL / g. other characteristics of alumina

Claims

REVENDICATIONS
1. Alumine caractérisée par au moins l'un des deux profils de porosité suivants : 1. Alumina characterized by at least one of the following two porosity profiles:
■ 1er profil : - un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,60 et 0,85 mL/g ; et un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,20 mL/g ; et/ou ■ 2nd profil : après calcination sous air à 1100°C pendant 5 heures : un volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm qui est compris entre 0,50 et 0,75 mL/g ; et un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,20 mL/g ; ces volumes poreux étant déterminés à l'aide de la technique de porosimétrie au mercure. ■ 1 st profile: - a pore volume in the area of the pores, the size of which is between 5 nm and 100 nm which is between 0.60 and 0.85 mL / g; and a pore volume in the area of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g; and / or ■ 2 nd profile: after calcination in air at 1100 ° C for 5 hours: a pore volume in the area of pores having a size between 5 nm and 100 nm is between 0.50 and 0.75 mL / g; and a pore volume in the area of the pores the size of which is between 100 nm and 1000 nm which is less than or equal to 0.20 mL / g; these pore volumes being determined using the mercury porosimetry technique.
2. Alumine selon la revendication 1 caractérisée en ce que pour le 1er profil, le volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm est compris entre 0,60 et 0,80 mL/g. 2. Alumina according to claim 1 characterized in that for the 1 st profile, the pore volume in the region of the pores, the size of which is between 5 nm and 100 nm, is between 0.60 and 0.80 mL / g.
3. Alumine selon la revendication 1 ou 2 caractérisée en ce que pour le 2nd profil, le volume poreux dans le domaine des pores dont la taille est comprise entre 5 nm et 100 nm est compris entre 0,50 et 0,70 mL/g. 3. Alumina according to claim 1 or 2 characterized in that for the 2 nd profile, the pore volume in the range of pores whose size is between 5 nm and 100 nm is between 0.50 and 0.70 mL / g.
4. Alumine selon l'une des revendications précédentes caractérisée en ce que pour le 1er profil le volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm est inférieur ou égal à 0,15 mL/g, voire inférieur ou égal à 0,10 mL/g, voire encore inférieur ou égal à 0,05 mL/g. 4. Alumina according to one of the preceding claims, characterized in that for the 1 st profile, the pore volume in the region of the pores, the size of which is between 100 nm and 1000 nm, is less than or equal to 0.15 mL / g, or even less than or equal to 0.10 mL / g, or even less than or equal to 0.05 mL / g.
5. Alumine selon l'une des revendications précédentes caractérisée en ce que pour le 2nd profil le volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm est inférieur ou égal à 0,15 mL/g, voire inférieur ou égal à 0,10 mL/g, voire encore inférieur ou égal à 0,05 mL/g. 5. Alumina according to one of the preceding claims, characterized in that for the 2 nd profile the pore volume in the region of the pores, the size of which is between 100 nm and 1000 nm, is less than or equal to 0.15 mL / g, or even less than or equal to 0.10 mL / g, or even less than or equal to 0.05 mL / g.
6. Alumine selon l'une des revendications précédentes présentant une surface spécifique BET comprise entre 100 et 200 m2/g, plus particulièrement entre 150 et 200 m2/g. 6. Alumina according to one of the preceding claims having a BET specific surface area of between 100 and 200 m 2 / g, more particularly between 150 and 200 m 2 / g.
7. Alumine selon l'une des revendications précédentes présentant une surface spécifique BET qui est supérieure ou égale à 120 m2/g. 7. Alumina according to one of the preceding claims having a BET specific surface which is greater than or equal to 120 m 2 / g.
8. Alumine selon l'une des revendications précédentes présentant une surface spécifique BET qui est supérieure ou égale à 140 m2/g. 8. Alumina according to one of the preceding claims having a BET specific surface which is greater than or equal to 140 m 2 / g.
9. Alumine selon l'une des revendications précédentes présentant une surface spécifique9. Alumina according to one of the preceding claims having a specific surface.
BET après calcination sous air à 1100°C pendant 5 heures comprise entre 70 et 100 m2/g. BET after calcination in air at 1100 ° C for 5 hours between 70 and 100 m 2 / g.
10. Alumine selon l'une des revendications précédentes présentant une densité apparente comprise entre 0,25 g/cm3 et 0,55 g/cm3, plus particulièrement entre 0,40 g/cm3 et 0,55 g/cm3. 10. Alumina according to one of the preceding claims having an apparent density of between 0.25 g / cm 3 and 0.55 g / cm 3 , more particularly between 0.40 g / cm 3 and 0.55 g / cm 3. .
11. Alumine selon l'une des revendications précédentes présentant un volume poreux total qui est strictement supérieur à 1 ,05 mL/g, ce volume poreux étant déterminé à l'aide de la technique de porosimétrie au mercure. 11. Alumina according to one of the preceding claims having a total pore volume which is strictly greater than 1.05 mL / g, this pore volume being determined using the mercury porosimetry technique.
12. Alumine selon l'une des revendications précédentes présentant un volume poreux total qui est d'au moins 1,10 mL/g, ce volume poreux étant déterminé à l'aide de la technique de porosimétrie au mercure. 12. Alumina according to one of the preceding claims having a total pore volume which is at least 1.10 mL / g, this pore volume being determined using the mercury porosimetry technique.
13. Alumine selon l'une des revendications précédentes présentant un volume poreux total qui est d'au moins 1,20 mL/g, ce volume poreux étant déterminé à l'aide de la technique de porosimétrie au mercure. 13. Alumina according to one of the preceding claims having a total pore volume which is at least 1.20 mL / g, this pore volume being determined using the mercury porosimetry technique.
14. Alumine selon l'une des revendications précédentes présentant un volume poreux total qui est d'au d'au plus 2,40 mL/g, ce volume poreux étant déterminé à l'aide de la technique de porosimétrie au mercure. 14. Alumina according to one of the preceding claims having a total pore volume which is at most 2.40 mL / g, this pore volume being determined using the mercury porosimetry technique.
15. Alumine selon l'une des revendications précédentes présentant après calcination à 1100°C pendant 5 heures, un volume poreux total qui est d'au moins 0,90 mL/g, ce volume poreux étant déterminé à l'aide de la technique de porosimétrie au mercure. 15. Alumina according to one of the preceding claims having, after calcination at 1100 ° C for 5 hours, a total pore volume which is at least 0.90 mL / g, this pore volume being determined using the technique. mercury porosimetry.
16. Alumine selon l'une des revendications précédentes présentant après calcination à 1100°C pendant 5 heures, un volume poreux total qui est d'au moins 1,10 mL/g, ce volume poreux étant déterminé à l'aide de la technique de porosimétrie au mercure. 16. Alumina according to one of the preceding claims having, after calcination at 1100 ° C for 5 hours, a total pore volume which is at least 1.10 mL / g, this pore volume being determined using the technique. mercury porosimetry.
17. Alumine selon l'une des revendications précédentes présentant après calcination à 1100°C pendant 5 heures, un volume poreux total qui est d'au moins 1,20 mL/g, ce volume poreux étant déterminé à l'aide de la technique de porosimétrie au mercure. 17. Alumina according to one of the preceding claims having, after calcination at 1100 ° C for 5 hours, a total pore volume which is at least 1.20 mL / g, this pore volume being determined using the technique. mercury porosimetry.
18. Alumine selon l'une des revendications précédentes présentant après calcination à 1100°C pendant 5 heures, un volume poreux total qui est d'au plus 1 ,80 mL/g, ce volume poreux étant déterminé à l'aide de la technique de porosimétrie au mercure. 18. Alumina according to one of the preceding claims having, after calcination at 1100 ° C for 5 hours, a total pore volume which is at most 1.80 mL / g, this pore volume being determined using the technique. mercury porosimetry.
19. Alumine selon l'une des revendications précédentes caractérisée pour le 1er profil, par un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,05 mL/g. 19. Alumina according to one of the preceding claims, characterized for the 1 st profile, by a pore volume in the region of the pores, the size of which is between 100 nm and 1000 nm, which is less than or equal to 0.05 mL / g.
20. Alumine selon l'une des revendications précédentes caractérisée pour le 2nd profil, par un volume poreux dans le domaine des pores dont la taille est comprise entre 100 nm et 1000 nm qui est inférieur ou égal à 0,05 mL/g, ce volume poreux étant déterminé après calcination sous air à 1100°C pendant 5 heures. 20. Alumina according to one of the preceding claims, characterized for the 2 nd profile, by a pore volume in the region of the pores, the size of which is between 100 nm and 1000 nm which is less than or equal to 0.05 mL / g, this pore volume being determined after calcination in air at 1100 ° C. for 5 hours.
21. Alumine selon l'une des revendications précédentes caractérisée par un D50 compris entre 2,0 pm et 80,0 pm, D50 désignant la médiane d'une distribution en volume des tailles de particules obtenue à l’aide d’un granulomètre laser. 21. Alumina according to one of the preceding claims, characterized by a D50 of between 2.0 μm and 80.0 μm, D50 denoting the median of a volume distribution of the particle sizes obtained using a laser particle size analyzer. .
22. Alumine selon l'une des revendications précédentes caractérisée par un D90 inférieur ou égal à 150,0 pm, plus particulièrement inférieur ou égal à 100,0 pm, D90 désignant la taille pour laquelle 90% des particules ont une taille qui est inférieure à D90, D90 étant déterminé à partir d'une distribution en volume des tailles de particules obtenue à l’aide d’un granulomètre laser. 22. Alumina according to one of the preceding claims, characterized by a D90 less than or equal to 150.0 pm, more particularly less than or equal to 100.0 pm, D90 designating the size for which 90% of the particles have a size which is less. at D90, D90 being determined from a volume distribution of the particle sizes obtained using a laser particle size analyzer.
23. Alumine selon la revendication 21 caractérisée par un D50 compris entre 15,0 et 80,0 pm, voire entre 20,0 et 60,0 pm. 23. Alumina according to claim 21 characterized by a D50 of between 15.0 and 80.0 pm, or even between 20.0 and 60.0 pm.
24. Alumine selon la revendication 23 caractérisée par un D90 compris entre 40,0 pm et 150,0 pm, voire entre 50,0 pm et 100,0 pm, D90 désignant la taille pour laquelle 90% des particules ont une taille qui est inférieure à D90, D90 étant déterminé à partir d'une distribution en volume des tailles de particules obtenue à l’aide d’un granulomètre laser. 24. Alumina according to claim 23 characterized by a D90 of between 40.0 pm and 150.0 pm, or even between 50.0 pm and 100.0 pm, D90 designating the size for which 90% of the particles have a size which is. less than D90, D90 being determined from a volume distribution of the particle sizes obtained using a laser particle size analyzer.
25. Alumine selon la revendication 23 ou 24 caractérisée par une densité apparente comprise entre 0,40 et 0,55 g/cm3. 25. Alumina according to claim 23 or 24, characterized by an apparent density of between 0.40 and 0.55 g / cm 3 .
26. Alumine selon l'une des revendications 23 à 25 caractérisée par un volume poreux total compris entre 1 ,05 (valeur exclue) et 1 ,80 mL/g. 26. Alumina according to one of claims 23 to 25, characterized by a total pore volume of between 1.05 (excluded value) and 1.80 mL / g.
27. Alumine selon la revendication 26 caractérisée par un volume poreux total compris entre 1,20 et 1 ,80 mL/g. 27. Alumina according to claim 26 characterized by a total pore volume of between 1.20 and 1.80 mL / g.
28. Alumine selon la revendication 21 caractérisée par un D50 compris entre 2,0 et 15,0 pm, voire entre 4,0 et 12,0 pm. 28. Alumina according to claim 21 characterized by a D50 of between 2.0 and 15.0 pm, or even between 4.0 and 12.0 pm.
29. Alumine selon la revendication 28 caractérisée par un D90 compris entre 20,0 pm et 60,0 pm, voire entre 25,0 pm et 50,0 pm, D90 désignant la taille pour laquelle 90% des particules ont une taille qui est inférieure à D90, D90 étant déterminé à partir d'une distribution en volume des tailles de particules obtenue à l’aide d’un granulomètre laser. 29. Alumina according to claim 28 characterized by a D90 of between 20.0 pm and 60.0 pm, or even between 25.0 pm and 50.0 pm, D90 designating the size for which 90% of the particles have a size which is less than D90, D90 being determined from a volume distribution of the particle sizes obtained using a laser particle size analyzer.
30. Alumine selon la revendication 28 ou 29 caractérisée par une densité apparente comprise entre 0,25 et 0,40 g/cm3. 30. Alumina according to claim 28 or 29, characterized by an apparent density of between 0.25 and 0.40 g / cm 3 .
31. Alumine selon la revendication 28 à 30 caractérisée par un volume poreux total compris entre 1,40 et 2,40 mL/g. 31. Alumina according to claim 28 to 30, characterized by a total pore volume of between 1.40 and 2.40 mL / g.
32. Alumine selon la revendication 31 caractérisée par un volume poreux total compris entre 1,50 et 2,40 mL/g. 32. Alumina according to claim 31, characterized by a total pore volume of between 1.50 and 2.40 mL / g.
33. Alumine selon l'une des revendications précédentes présentant un taux de sodium inférieur ou égal à 0,50% en poids, voire inférieur ou égal à 0,15% en poids, ce taux de sodium étant exprimé en poids de Na20 par rapport au poids total de l'alumine. 33. Alumina according to one of the preceding claims having a sodium level less than or equal to 0.50% by weight, or even less than or equal to 0.15% by weight, this sodium level being expressed by weight of Na 2 0 relative to the total weight of the alumina.
34. Alumine selon l'une des revendications précédentes présentant un taux de sodium supérieur ou égal à 50 ppm, ce taux de sodium étant exprimé en poids de Na20 par rapport au poids total de l'alumine. 34. Alumina according to one of the preceding claims having a sodium level greater than or equal to 50 ppm, this sodium level being expressed by weight of Na 2 0 relative to the total weight of the alumina.
35. Alumine selon l'une des revendications précédentes présentant un taux de sodium compris entre 50 et 900 ppm, voire entre 100 et 800 ppm, ce taux de sodium étant exprimé en poids de Na20 par rapport au poids total de l'alumine. 35. Alumina according to one of the preceding claims having a sodium level of between 50 and 900 ppm, or even between 100 and 800 ppm, this sodium level being expressed by weight of Na 2 0 relative to the total weight of the alumina. .
36. Alumine selon l'une des revendications précédentes présentant un taux de sulfate inférieur ou égal à 1 ,00% en poids, voire inférieur ou égal à 0,20% en poids, voire encore inférieur ou égal à 0,10% en poids, ce taux de sulfate étant exprimé en poids de SO4 par rapport au poids total de l'alumine. 36. Alumina according to one of the preceding claims having a sulphate content less than or equal to 1.00% by weight, or even less than or equal to 0.20% by weight, or even less than or equal to 0.10% by weight. , this sulphate level being expressed by weight of SO 4 relative to the total weight of the alumina.
37. Alumine selon l'une des revendications précédentes présentant un taux de sulfate supérieur ou égal à 50 ppm, ce taux de sulfate étant exprimé en poids de SO4 par rapport au poids total de l'alumine. 37. Alumina according to one of the preceding claims having a sulphate level greater than or equal to 50 ppm, this sulphate level being expressed by weight of SO 4 relative to the total weight of the alumina.
38. Alumine selon l'une des revendications précédentes présentant un taux de sulfate compris entre 100 et 1500 ppm, voire entre 400 et 1000 ppm, ce taux de sulfate étant exprimé en poids de SO4 par rapport au poids total de l'alumine. 38. Alumina according to one of the preceding claims having a sulphate level of between 100 and 1500 ppm, or even between 400 and 1000 ppm, this sulphate level being expressed by weight of SO 4 relative to the total weight of the alumina.
39. Alumine selon l'une des revendications précédentes caractérisée en ce qu'elle est cristallisée. 39. Alumina according to one of the preceding claims, characterized in that it is crystallized.
40. Alumine selon l'une des revendications précédentes de formule générale AI2O3.40. Alumina according to one of the preceding claims of general formula Al 2 O 3 .
41. Alumine selon l'une des revendications précédentes présentant le 1er et le 2nd profil de porosité. 41. Alumina according to one of the preceding claims exhibiting the 1 st and the 2 nd porosity profile.
42. Composition catalytique comprenant l'alumine selon l'une des revendications 1 à 41 et au moins un oxyde à base de cérium et éventuellement d'au moins une terre rare autre que le cérium. 42. Catalytic composition comprising the alumina according to one of claims 1 to 41 and at least one oxide based on cerium and optionally on at least one rare earth other than cerium.
43. Utilisation d'une alumine selon l'une des revendications 1 à 41 dans la préparation d'un catalyseur de dépollution des gaz d'échappement des moteurs thermiques essence ou diesel. 43. Use of an alumina according to one of claims 1 to 41 in the preparation of a catalyst for depolluting the exhaust gases of gasoline or diesel heat engines.
44. Procédé de préparation d’une alumine, notamment une alumine telle que décrite à l'une des revendications 1 à 41 , comprenant les étapes suivantes : 44. Process for preparing an alumina, in particular an alumina as described in one of claims 1 to 41, comprising the following steps:
(a) dans une cuve contenant initialement une solution aqueuse acide dont le pH est compris entre 0,5 et 4,0, voire entre 0,5 et 3,5, on introduit sous agitation : (a) in a tank initially containing an acidic aqueous solution the pH of which is between 0.5 and 4.0, or even between 0.5 and 3.5, the following are introduced with stirring:
(a1)- soit une solution aqueuse d'aluminate de sodium jusqu'à obtenir un pH du mélange réactionnel compris entre 8,0 et 10,0, voire entre 8,5 et 9,5 ; (a1) - either an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 8.0 and 10.0, or even between 8.5 and 9.5;
(a2)- soit simultanément (i) une solution aqueuse de sulfate d'aluminium et (ii) une solution aqueuse d'aluminate de sodium jusqu'à obtenir un pH du mélange réactionnel compris entre 6,5 et 10, voire entre 7,0 et 8,0 ou entre 8,5 et 9,5 ; de façon à ce qu’à la fin de l’étape (a), la concentration en aluminium du mélange réactionnel soit comprise entre 0,50% et 3,0% poids ; (b) puis on introduit ensuite simultanément une solution aqueuse de sulfate d'aluminium et une solution aqueuse d'aluminate de sodium dont les débits d'introduction sont tels que le pH moyen du mélange réactionnel est maintenu dans la gamme de pH visée à l'étape (a) ; la température du mélange réactionnel pour les étapes (a) et (b) étant d'au moins 60°C ;(a2) - either simultaneously (i) an aqueous solution of aluminum sulphate and (ii) an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 6.5 and 10, or even between 7, 0 and 8.0 or between 8.5 and 9.5; so that at the end of step (a), the aluminum concentration in the reaction mixture is between 0.50% and 3.0% by weight; (b) then an aqueous solution of aluminum sulphate and an aqueous solution of sodium aluminate are then introduced simultaneously, the introduction rates of which are such that the average pH of the reaction mixture is maintained in the pH range referred to in 1 'step (a); the temperature of the reaction mixture for steps (a) and (b) being at least 60 ° C;
(c) à l'issue de l'étape (b), on ajuste éventuellement le pH du mélange réactionnel à une valeur comprise entre 7,5 et 10,5, voire entre 8,0 et 9,0 ou entre 9,0 et 10,0 ; (c) at the end of step (b), the pH of the reaction mixture is optionally adjusted to a value between 7.5 and 10.5, or even between 8.0 and 9.0 or between 9.0 and 10.0;
(d) le mélange réactionnel est ensuite filtré et le solide récupéré est lavé ; (d) the reaction mixture is then filtered and the solid recovered is washed;
(e) une dispersion dans l’eau du solide récupéré à l’issue de l'étape (d) subit un traitement mécanique ou par ultrasons de façon à réduire la taille des particules de la dispersion ;(e) a dispersion in water of the solid recovered at the end of step (d) undergoes mechanical or ultrasonic treatment so as to reduce the size of the particles of the dispersion;
(f) la dispersion obtenue à l’issue de l'étape (e) est séchée ; (f) the dispersion obtained at the end of step (e) is dried;
(g) le solide issu de l'étape (f) est ensuite calciné sous air. (g) the solid resulting from step (f) is then calcined in air.
45. Procédé selon la revendication 44 caractérisé en ce que la solution aqueuse acide contenue initialement dans la cuve est une solution aqueuse d’un acide minéral ou une solution aqueuse d’un sel acide d’aluminium. 45. The method of claim 44 characterized in that the acidic aqueous solution initially contained in the tank is an aqueous solution of a mineral acid or an aqueous solution of an acid salt of aluminum.
46. Procédé selon la revendication 44 ou 45 dans lequel pour le mode de réalisation (a1), la solution aqueuse d’aluminate de sodium est introduite directement au sein du mélange réactionnel, notamment par l'intermédiaire d'au moins une canne d'introduction. 46. The method of claim 44 or 45 wherein for embodiment (a1), the aqueous solution of sodium aluminate is introduced directly into the reaction mixture, in particular via at least one cane of sodium aluminate. introduction.
47. Procédé selon l’une des revendications 44 à 46 dans lequel pour le mode de réalisation (a2), les deux solutions sont introduites directement au sein du mélange réactionnel, notamment par l'intermédiaire d’au moins deux cannes d'introduction. 47. Method according to one of claims 44 to 46 wherein for embodiment (a2), the two solutions are introduced directly into the reaction mixture, in particular via at least two introduction pipes.
48. Procédé selon l’une des revendications 44 à 47 dans lequel la valeur cible visée à l’étape (b) est comprise: entre 8,0 et 10,0, voire entre 8,5 et 9,5, pour le cas où le mode de réalisation (a1) a été suivi à l’étape (a) ; ou bien entre 6,5 et 8,5, voire entre 7,0 et 8,0, pour le cas où le mode de réalisation (a2) a été suivi à l’étape (a). 48. Method according to one of claims 44 to 47 wherein the target value referred to in step (b) is: between 8.0 and 10.0, or even between 8.5 and 9.5, for the case where the embodiment (a1) has been followed in step (a); or else between 6.5 and 8.5, or even between 7.0 and 8.0, for the case where the embodiment (a2) has been followed in step (a).
49. Procédé selon l’une des revendications 44 à 48 dans lequel le D50 des particules de la dispersion avant le traitement mécanique ou par ultrasons est compris entre 10,0 pm et 40,0 pm, voire entre 10,0 pm et 30,0 pm. 49. Method according to one of claims 44 to 48 wherein the D50 of the particles of the dispersion before the mechanical or ultrasonic treatment is between 10.0 pm and 40.0 pm, or even between 10.0 pm and 30, 0 pm.
50. Procédé selon l’une des revendications 44 à 49 dans lequel les particules du solide après le traitement mécanique ou par ultrasons est compris entre 1 ,0 pm et 15,0 pm, voire entre 2,0 pm et 10,0 pm. 50. Method according to one of claims 44 to 49 wherein the particles of the solid after the mechanical or ultrasonic treatment is between 1.0 pm and 15.0 pm, or even between 2.0 pm and 10.0 pm.
51. Procédé selon l’une des revendications 44 à 50 dans lequel le traitement mécanique de l’étape (e) est opéré à l’aide d’un broyeur à billes, d’un homogénéisateur haute pression ou d’un système de broyage comprenant un rotor et un stator. 51. Method according to one of claims 44 to 50 wherein the mechanical treatment of step (e) is carried out using a ball mill, a high pressure homogenizer or a grinding system. comprising a rotor and a stator.
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