Compositions of alumina and ceria having a specific porosity distribution

Abstract

This invention relates to a composition based on Al and Ce in oxide form (composition C1); or based on Al, Ce, and La in oxide form (composition C2), the composition having the following proportions: - CeO2 proportion between 3.0 wt% and 35.0 wt%; - La2O3 proportion (for composition C2 only) between 0.1 wt% and 6.0 wt%; - the remainder being Al2O3; the composition exhibits the following porosity distribution: - pore volume in the range of pore size between 5 nm and 100 nm between 0.35 and 1.00 mL / g; and - pore volume less than or equal to 0.15 mL / g in the range of pore size between 10 nm and 5 nm. The pore volume in the range of 0 nm to 1000 nm, determined by mercury porosimetry; and the following characteristics: - an average crystallite size of less than 45.0 nm, preferably less than 40.0 nm, after calcination in air at 1100 °C for 5 hours (denoted as D1100 °C-5h); - an average crystallite size of less than 25.0 nm, preferably less than 20.0 nm, and even more preferably less than 15.0 nm, after calcination in air at 900 °C for 2 hours (denoted as D900 °C-2h); and - the increase in the average crystallite size of less than 30.0 nm, preferably less than 25.0 nm, ΔD, calculated by the following formula: ΔD = D 1100℃‑2h -D 900℃‑5h The average size of the crystallites was obtained by XRD from the diffraction peaks corresponding to the cubic phase of cerium oxide, which are typically present at 2Φ between 28.0 and 30.0 [111].

Description

[0001] This invention relates to a composition of alumina, cerium oxide, and optionally lanthanum oxide having a specific porosity distribution, which maintains a high specific surface area and low crystallite size even after calcination at high temperatures. The composition is also characterized by its high packing density. The invention further relates to a catalytic composition comprising the said composition and to the use of the composition. Technical Field

[0002] Currently, to meet the pollutant regulations in most parts of the world (e.g., Europe, the United States, Japan, China, South Korea, India, etc.), catalysts used to purify vehicle exhaust are almost mandatory. The function of a catalyst is to remove pollutants harmful to health and the environment, such as CO, unburned particulate matter (e.g., soot), unburned hydrocarbons (HC), nitrogen oxides (NO), and NO2 (also known as NO2). x ).

[0003] Regulations are becoming increasingly challenging and are expected to become even stricter in the near future: see Euro 7 in Europe, SULEV 20 in the US, or China VI b in China. Real-world emissions are now also regulated by RDE (Real Driving Emissions) limits, just like in Europe, adding another challenge as catalysts must be efficient under a wide range of driving conditions. Therefore, increasingly efficient catalysts are needed.

[0004] TWC catalyst

[0005] For gasoline vehicles, emission control is achieved using so-called 'three-way' catalysts (TWCs) that can simultaneously reduce the amounts of hydrocarbons, CO, and NOx. Natural gas vehicles can also typically rely on TWC catalysts when the engine is running in stoichiometric mode. However, they are expected to face the same challenges as gasoline engines. Furthermore, a higher fuel-to-air ratio is anticipated, which will require a greater oxygen storage capacity (OSC).

[0006] GPF

[0007] In many regions, gasoline vehicles are also equipped with gasoline particulate filters (GPFs), which function to reduce the release of particulate matter emissions, particularly, but not only, for gasoline direct injection engine technology. GPFs are based on TWC catalysts, which are coated onto the filter and have improved OSC (Oxygen Content Coefficient) to facilitate the combustion of particulate matter. Therefore, there is a general need for catalysts that exhibit improved OSC.

[0008] DOC and DPF

[0009] For diesel engines, various catalysts (such as diesel oxidation catalysts (DOC)) can be used to control the oxidation of CO and HC, and also to some extent the oxidation of particulate matter and NOx. Modern diesel engines are also typically equipped with diesel particulate filters (DPFs), which filter and burn particulate matter. Therefore, the oxidation function of both DOC and DPF is crucial, and maintaining this function after the thermal stress caused by soot oxidation during DPF regeneration is important. NOx emissions from diesel engines are managed through selective catalytic reduction (SCR) catalysts (where NOx is reduced through the reaction between NOx and NH3) or through NOx capture or adsorption on lean NOx traps (LNTs) or partial NOx absorbers (PNAs). In both cases, oxidation is required to efficiently remove NOx.

[0010] Technical issues

[0011] The catalysts disclosed above, in all cases except SCR, require the presence of at least one noble metal (e.g., Pt, Pd, and Rh), also known as platinum group metals (or PGMs). Rh and Pd are generally more expensive than Pt, so Pt tends to be more commonly used today. Due to the price of PGMs, there is a general need to minimize their content in the catalyst. PGMs (especially Pd and Pt) are dispersed on the surface of alumina and are known to be stabilized by cerium oxide.

[0012] All the catalysts disclosed above contain alumina, which is used to disperse PGM (TWC, GPF, DOC, DPF, LNT, PNA) or mixed with SCR catalysts (e.g., typically zeolite-based or vanadium oxide associated with titanium dioxide). They all also contain cerium dioxide-based materials, which provide oxygen storage capacity (OSC) or assist oxidation. Both alumina and cerium dioxide-based materials require thermal stability.

[0013] Therefore, there is a need for heat-resistant alumina-based supports that can be used to prepare catalysts containing at least one PGM and exhibit OSC, contributing to the stabilization of one or more PGMs present in the catalyst. In the context of this application, the term 'heat-resistant' is used to characterize supports that can maintain a high specific surface area and / or small particle size after heat treatment at high temperatures. A simple and common way to characterize the thermal stability of a support includes measuring its specific surface area after calcination in air at high temperatures. Another way is to measure the particle size by X-ray diffraction (XRD) after the same treatment. The expression 'high temperature' depends on the nature of the catalyst used: typically, the calcination temperature is up to about 900°C for diesel catalysts (like DOC, DPF, LNT, or SCR), and about 1100°C, or even sometimes 1200°C, for gasoline or natural gas catalysts (like TWC or GPF).

[0014] Furthermore, catalyst preparation typically involves coating a suspension of a catalytic composition made of inorganic materials onto a substrate or bulk material. Naturally, using a highly concentrated suspension exhibiting low viscosity is more convenient for preparation. Therefore, there is a need for a heat-resistant carrier that can be easily handled and used to prepare highly concentrated suspensions with low viscosity.

[0015] The compositions of the present invention are intended to solve these technical problems. Background Technology

[0016] WO 12067654 discloses a porous inorganic composite oxide comprising oxides of aluminum and cerium, or oxides of aluminum and zirconium, or oxides of aluminum, cerium, and zirconium, and optionally, oxides of one or more dopants selected from transition metals, rare earths, and mixtures thereof. No disclosure is made of the composition as in claim 1.

[0017] US 9,611,774 B2 discloses an emission treatment system comprising: a catalyst comprising a catalyst composition having cerium dioxide-alumina particles having a cerium dioxide phase present in a particle weight percentage ranging from about 20% to about 80% based on oxides; an alkaline earth metal component supported on the cerium dioxide-alumina particles; wherein the CeO2 is present in a hydrothermally stable microcrystalline form having an average crystallite size of less than 16 nm after aging at 950°C for 5 hours in N2 with 2% O2 and 10% steam. No disclosure of a composition as in claim 1 is provided.

[0018] Brief description of the invention (to be revised later)

[0019] This invention relates to compositions as defined in any one of claims 1 to 34. The composition is based on two main embodiments:

[0020] - Composition C1, which is based on Al and Ce in oxide form;

[0021] -Composition C2, which is based on Al, Ce, and La in oxide form,

[0022] It has the following proportions:

[0023] The proportion of -CeO2 is between 3.0 wt% and 35.0 wt%.

[0024] The proportion of La2O3 (for composition C2 only) is between 0.1 wt% and 6.0 wt%.

[0025] -The remaining part is Al2O3;

[0026] Furthermore, it exhibits the following porosity distribution:

[0027] - Pore volume in the range of pore size between 5 nm and 100 nm, between 0.35 and 1.00 mL / g; and

[0028] - Pore volume less than or equal to 0.15 mL / g in the range of pore size between 100 nm and 1000 nm.

[0029] These pore volumes were determined using the mercury porosimetry technique.

[0030] And the following characteristics:

[0031] - The average crystallite size (denoted as D) is less than 45.0 nm, preferably less than 40.0 nm, after calcination in air at 1100°C for 5 hours. 1100 ℃ -5h );

[0032] - The average crystallite size (denoted as D) is less than 25.0 nm, preferably less than 20.0 nm, and even more preferably less than 15.0 nm after calcination in air at 900°C for 2 hours. 900 ℃ -2h );as well as

[0033] - The increase in the average size of the crystallite, ΔD, which is less than 30.0 nm, preferably less than 25.0 nm, is calculated using the following formula: ΔD = D 1100 ℃ -5h -D 900 ℃ -2h ;

[0034] The average size of the crystallites was obtained by XRD from the diffraction peaks corresponding to the cubic phase of cerium oxide, which are typically present at 2θ between 28.0° and 30.0°

[111] .

[0035] The present invention also relates to a catalytic composition as defined in any one of claims 35 to 40, and further relates to the use of the composition as defined in claim 41 and the use of the catalytic composition as defined in claim 42. The present invention relates to a method for preparing the composition as defined in claim 43 or 44.

[0036] All these purposes will now be defined in more detail. Detailed Implementation

[0037] In this patent application, for the sake of continuity of this specification, it is specified that, unless otherwise stated, the limiting values ​​are included within the range of these values ​​given. It is also specified that calcination is carried out in air.

[0038] "wt%" means percentage by weight.

[0039] In the context of this invention, the term "particle" refers to an agglomeration formed from primary particles. Particle size is determined by a volumetric particle size distribution obtained using a laser particle size analyzer. The particle size distribution is characterized by parameters D10, D50, and D90. These parameters have their common meaning in the field of measurements performed by laser diffraction. Thus, Dx represents a value determined based on the volumetric particle size distribution, where x% of the particles have a size less than or equal to this value Dx. Therefore, D50 corresponds to the median of the distribution. D90 corresponds to a size where 90% of the particles have a size less than D90. D10 corresponds to a size where 10% of the particles have a size less than D10. This measurement is typically performed on a dispersion of particles in water.

[0040] In the context of this invention, rare earth elements refer to elements including yttrium and elements having atomic numbers between 57 and 71 (inclusive) in the periodic table.

[0041] Porosity data were obtained using the mercury porosimetry technique. This technique allows for the definition of pore volume (V) as a function of pore size (D). A Micromeritics Autopore 9520 machine equipped with a powder needle penetration meter can be used according to the manufacturer's recommended instructions. The procedure of ASTM D 4284-07 can be followed. These data allow for the determination of pore volume (expressed as PV) in the range of pores with sizes between 5 nm and 100 nm. 5-100 nm ), pore volume (denoted as PV) in the range of pore sizes between 100 nm and 1000 nm. 100-1000 nm ) and total pore volume (expressed as TPV).

[0042] The term "specific surface area" refers to the BET specific surface area determined by nitrogen adsorption using the Brunauer-Emmett-Teller method. This method was described in the journal *The Journal of the American Chemical Society*, 60, 309 (1938). The recommendations of standard ASTM D3663-03 may be followed. Unless otherwise specified, calcination at a given temperature and duration corresponds to calcination in air at an isothermal stage for a specified duration.

[0043] Furthermore, the concentration of the solution or the ratio of elements Al, Ce, and La (if any) in the composition is specified as a weight percentage of oxide equivalents. Therefore, the following oxides are retained for these concentration or ratio calculations: Al₂O₃ for Al, CeO₂ for Ce, and La₂O₃ for La. For example, an aqueous solution of aluminum sulfate with an aluminum concentration of 2.0 wt% corresponds to a solution containing 2.0 wt% Al₂O₃ equivalent. Similarly, a composition having 92.0 wt% Al and 8.0 wt% Ce corresponds to 92.0 wt% Al₂O₃ and 8.0 wt% CeO₂.

[0044] The composition is based on Al and Ce in oxide form (composition C1) or Al, Ce, and La in oxide form (composition C2). According to one embodiment, composition C1 consists of oxides of Ce and Al. According to another embodiment, composition C2 consists of oxides of Ce, Al, and La.

[0045] First, the composition is defined by the proportions of its components. These proportions are given by weight relative to the total weight of the composition. Therefore, for compositions C1 and C2, the proportion of CeO2 is between 3.0 wt% and 35.0 wt%, or between 5.0 wt% and 30.0 wt%, or even between 6.0 wt% and 25.0 wt%. This proportion can be between 10.0 wt% and 25.0 wt%, or even between 15.0 wt% and 25.0 wt%. The proportion of CeO2 can be less than 20.0 wt%.

[0046] For composition C2, the proportion of La is between 0.1 wt% and 6.0 wt%, or even between 0.5 wt% and 6.0 wt%, or even between 1.0 wt% and 5.0 wt%, expressed as the weight of La2O3 relative to the total weight of the composition.

[0047] The proportion of Al2O3 corresponds to up to 100% of the remainder. For composition C1, the proportion of Al2O3 is between 65.0 wt% and 97.0 wt%. For composition C2, the proportion of Al2O3 is between 59.0 wt% and 96.9 wt%. Al2O3 is the major component of the composition.

[0048] The composition is further defined by a trade-off between physicochemical properties. Typically, the thermal stability of alumina-based products is related to their pore volume fraction. Increasing the total pore volume generally increases thermal stability. However, increasing the total pore volume usually results in a significant decrease in bulk density and an increase in the viscosity of the product suspension in an aqueous medium. It has been found that by combining specific properties (such as specific porosity and high bulk density), thermally stable carriers that can be readily processed as powders and used to prepare highly loaded suspensions with low viscosity can be obtained. Therefore, the composition is characterized by the following porosity distribution:

[0049] - Pore volume in the range of pore size between 5 nm and 100 nm, between 0.35 and 1.00 mL / g, more particularly between 0.40 and 1.00 mL / g, and even more particularly between 0.40 and 0.80 mL / g; and

[0050] - Pore volume less than or equal to 0.15 mL / g, more particularly less than or equal to 0.10 mL / g, or even less than or equal to 0.07 mL / g, in the range of pore sizes between 100 nm and 1000 nm.

[0051] The composition can also be defined by the following porosity distribution:

[0052] - Pore volume in the range of pore size between 5 nm and 100 nm, between 0.40 and 1.00 mL / g; and

[0053] - Pore volume less than or equal to 0.07 mL / g in the range of pores between 100 nm and 1000 nm.

[0054] Furthermore, this composition can exhibit a high specific surface area. The composition can have a specific surface area between 80 and 300 m². 2 Between / g, and more specifically between 90 and 200m 2 BET specific surface area between / g. This specific surface area can be greater than or equal to 100m². 2 / g. This specific surface area can also be between 100 and 200m. 2 Between / g.

[0055] Furthermore, this composition exhibits high thermal stability. The composition can withstand calcination at 1100°C in air for 5 hours at 40m.2 / g and 110m 2 Between / g, preferably at 45m 2 / g and 110m 2 The BET specific surface area is between / g. This specific surface area is typically strictly less than 82.35×(Al2O3)+11.157m. 2 / g, where (Al2O3) corresponds to the proportion of Al2O3 in the composition, expressed in wt%. As an example, for an Al2O3 proportion of 80.0 wt%, the calculated value is: 82.35 × 80.0% + 11.157 = 77.037m 2 / g.

[0056] Furthermore, this composition exhibits high thermal stability. The composition can maintain its thermal stability at 25 and 60 m after calcination in air at 1200°C for 5 hours. 2 BET specific surface area between / g.

[0057] Typically, the composition has a total pore volume that is usually strictly greater than 0.70 mL / g. This total pore volume may advantageously be at least 0.80 mL / g, or even at least 0.90 mL / g. This total pore volume usually does not exceed 2.50 mL / g, or even does not exceed 2.00 mL / g.

[0058] The composition can have a concentration of 0.35 g / cm³. 3 With 0.90g / cm 3 Between, and more specifically at 0.40 g / cm 3 With 0.85g / cm 3 The bulk density of the powder. This bulk density of the powder corresponds to the weight of a certain amount of powder relative to the volume occupied by the powder:

[0059] Bulk density in g / mL = (mass of powder (g)) / (volume of powder (mL))

[0060] The bulk density can be determined as follows. First, accurately determine the volume of a graduated cylinder (approximately 25 mL) without a spout. To do this, weigh the empty graduated cylinder (tare weight T). Then pour distilled water into the graduated cylinder up to the rim, but not beyond the rim (without a meniscus). Weigh the graduated cylinder filled with distilled water (M). Therefore, the mass of water contained in the graduated cylinder is:

[0061] E=MT

[0062] The calibration volume of this graduated cylinder is equal to V. 量筒 = E / (density of water at the measurement temperature). For a measurement temperature of 20°C, the density of water is, for example, 0.99983 g / mL.

[0063] Using a funnel, carefully pour the powdered composition into an empty, dry graduated cylinder until it reaches the rim. Use a scraper to level any excess powder. Do not compact or tamp the powder during filling. Then weigh the graduated cylinder containing the powder.

[0064] Bulk density (g / mL) = (mass of graduated cylinder containing alumina powder - tare weight T (g)) / (V)

[0065] 量筒 (mL))

[0066] The composition may have a D50 between 2.0 μm and 80.0 μm. It may have a D90 of less than or equal to 150.0 μm, more particularly less than or equal to 100.0 μm. It may have a D10 of greater than or equal to 1.0 μm.

[0067] It will also be noted that the composition is crystalline. This can be confirmed by X-ray diffraction. The composition comprises an alumina-based crystalline phase. This phase can be a δ phase, θ phase, γ phase, or a mixture of at least two of these phases.

[0068] Composition C2 preferably does not contain a lanthanum-containing phase, particularly the following phases: LaAlO3 or LaAl 11 O 18 Any XRD diffraction pattern of any phase. These last two phases can be identified by the following corresponding index numbers from the International Data Center for Diffraction: ICDD 01-070-4111 and ICDD 00-033-0699.

[0069] The composition also comprises a cerium oxide-based crystalline phase. This phase may correspond to pure CeO2 or CeO2 containing lanthanum. This phase exhibits diffraction lines 2θ between 28.0° and 30.0°.

[0070] The average crystallite size can be determined from the diffraction peaks corresponding to the cubic phase of cerium oxide

[111] (which are present at 2θ between 28.0° and 30.0°). The composition indeed exhibits:

[0071] - The average crystallite size (denoted as D) is less than 45.0 nm, preferably less than 40.0 nm, after calcination in air at 1100°C for 5 hours. 1100 ℃ -5h );

[0072] - The average crystallite size (denoted as D) is less than 25.0 nm, preferably less than 20.0 nm, and even more preferably less than 15.0 nm after calcination in air at 900°C for 2 hours. 900 ℃ -2h );as well as

[0073] - The increase in the average size of the crystallite, ΔD, which is less than 30.0 nm, preferably less than 25.0 nm, is calculated using the following formula: ΔD = D 1100 ℃ -5h -D 900 ℃ -2h .

[0074] Average size D 1100 ℃ -5h Typically at least 8.0 nm. Similarly, the average size D 900 ℃ -2h Typically, it is at least 5.0nm.

[0075] The average crystallite size D was measured by X-ray diffraction. It corresponds to the size of the coherence domain calculated using the Scherrer equation, based on the width of the diffraction line 2θ between 28.0° and 30.0°. According to the Scherrer equation, D is given by formula (I):

[0076]

[0077] D: Average crystallite size;

[0078] k: a form factor equal to 0.9;

[0079] λ(lambda): the wavelength of the incident beam (for a CuKα1 source, λ = 1.5406 angstroms);

[0080] B: Spectral line broadening (in radians) measured at half the maximum intensity;

[0081] θ: Bragg angle (radians)

[0082] To determine B, instrument-induced widening is usually taken into account.

[0083] In formula (II), the instrument-induced widening is B. 仪器 and

[0084]

[0085] D: Average crystallite size;

[0086] k: a form factor equal to 0.9;

[0087] λ(lambda): the wavelength of the incident beam (for a CuKα1 source, λ = 1.5406 angstroms);

[0088] B 观测 Full width at half maximum (in radians) of a diffraction peak;

[0089] B 仪器 : Increased spectral line width (in radians);

[0090] θ: Bragg angle (radians).

[0091] B 仪器 It depends on the instrument used and the 2θ (theta) angle.

[0092] The composition is typically in powder form. As a powder, the composition can be characterized according to two specific embodiments:

[0093] According to a first embodiment, the composition has a D50 between 2.0 and 15.0 μm, or even between 4.0 and 12.0 μm. The D90 can be between 20.0 μm and 60.0 μm, or even between 25.0 μm and 50.0 μm. According to this first embodiment, when the D50 is between 2.0 and 15.0 μm, the bulk density is between 0.35 and 0.55 g / cm³. 3 between;

[0094] According to a second embodiment, the composition has a D50 between 15.0 and 80.0 μm, or even between 20.0 and 60.0 μm. The D90 can be between 40.0 μm and 150.0 μm, or even between 50.0 μm and 100.0 μm. According to this second embodiment, when the D50 is between 15.0 and 80.0 μm, the bulk density can be between 0.40 and 0.90 g / cm³. 3 between.

[0095] D50 and D90 are determined by volumetric particle size distribution using a laser particle size analyzer, which is performed on a dispersion of particles in water.

[0096] D10 is typically at least 0.5 μm.

[0097] The composition may also contain some residual components. The composition may contain residual sodium. The residual sodium content may be less than or equal to 0.50% by weight, or even less than or equal to 0.15% by weight. The sodium content may be greater than or equal to 50 ppm. This content may be between 50 and 900 ppm, or even between 100 and 800 ppm. This content is expressed as the weight of Na₂O relative to the total weight of the composition. Therefore, for a composition having a residual sodium content of 0.15%, it is considered that there are 0.15 g of Na₂O per 100 g of mixed oxides. Methods for determining the sodium content within this concentration range are known to those skilled in the art. For example, the composition may be digested under acidic conditions, optionally assisted by microwave, and once the composition is completely dissolved, the acidic solution may be titrated by inductively coupled plasma spectroscopy.

[0098] The composition may contain residual sulfate. The residual sulfate content may be less than or equal to 1.00 wt%, or even less than or equal to 0.50 wt%, or even less than or equal to 0.25 wt%. The sulfate content may be greater than or equal to 50 ppm. This content may be between 100 and 2500 ppm, or even between 400 and 1000 ppm. This content is expressed as the weight of sulfate relative to the total weight of the composition. Therefore, for a composition having a residual sulfate content of 0.50 wt%, it is considered that there is 0.50 g of SO4 per 100 g of the composition. Methods for determining the sulfate content within this concentration range are known to those skilled in the art. For example, the same method as sodium titration can be applied.

[0099] The composition may contain impurities other than sodium and sulfate, such as silicon-, titanium-, or iron-based impurities. The proportion of each impurity is typically less than 0.10 wt%, or even less than 0.05 wt%.

[0100] Use of the composition

[0101] The compositions of the present invention can be used in the field of catalysis, and particularly in the preparation of catalysts for purifying vehicle exhaust. The compositions according to the invention can be used to prepare catalytic converters for treating motor vehicle exhaust. The catalytic converter includes at least one catalytically active coating prepared from the composition and deposited on a support. The function of the catalytic converter is to convert certain pollutants in exhaust, particularly carbon monoxide, unburned hydrocarbons, and nitrogen oxides, into less harmful products through chemical reactions.

[0102] The compositions of the present invention can also be used to prepare catalytic compositions. A catalytic composition typically comprises:

[0103] (i) the compositions of the present invention; and

[0104] (ii) optionally at least one inorganic material other than the compositions of the present invention; and / or

[0105] (iii) Optionally at least one platinum group metal (PGM).

[0106] According to one embodiment, the catalytic composition is:

[0107] (i) the compositions of the present invention; and

[0108] (ii) at least one inorganic material other than the composition of the present invention; and

[0109] (iii) Optionally at least one platinum group metal (PGM).

[0110] According to another embodiment, the catalytic composition:

[0111] (i) the compositions of the present invention; and

[0112] (ii) at least one inorganic material other than the composition of the present invention; and

[0113] (iii) At least one platinum group metal (PGM).

[0114] Inorganic materials other than the compositions of the present invention are selected from the group consisting of: zeolites; alumina-based materials; cerium dioxide-based materials; zirconium oxide-based materials; mixed oxides comprising oxides of cerium and zirconium; mixed oxides comprising oxides of aluminum, cerium and zirconium; and combinations thereof.

[0115] The inorganic material can be zeolite. Zeolite can be selected from the group consisting of: AEI, AFT, AFV, AFX, AVL, CHA, DDR, EAB, EEI, ERI, IFY, IRN, KFI, LEV, LTA, LTN, MER, MWF, NPT, PAU, RHO, RTE, RTH, SAS, SAT, SAV, SFW, TSC, UFI, and combinations thereof. Zeolite can undergo ion exchange with at least one catalytic metal (such as Cu, Fe, Ce, and combinations thereof).

[0116] The inorganic material can be a cerium dioxide-based material. Cerium dioxide-based materials can be selected from the group consisting of: cerium oxide; mixed oxides of cerium and at least one rare earth element other than cerium; and composite oxides of cerium and at least one alkaline earth element. The proportion of the rare earth element or alkaline earth element is typically between 1.0 wt% and 30.0 wt%, expressed as relative to the oxide of the cerium dioxide-based material (as a whole). Examples of cerium dioxide-based materials can be found in the following references: EP 1435338 B1, US 8,435,919, EP 3218307 B1, EP 1435338.

[0117] The inorganic material can be an alumina-based material. The alumina-based material can be selected from the group consisting of: alumina; alumina stabilized by an oxide of at least one element selected from the group consisting of silicon, zirconium, rare earth metals, and alkaline earth metals; aluminum hydrate; and combinations thereof. The alumina-based material can more particularly be alumina or alumina stabilized by lanthanum oxide. The proportion of the stabilizing element is typically between 1.0 wt% and 10.0 wt%, expressed as a percentage of the oxide relative to the alumina-based material (as a whole). Examples of alumina-based materials can be found in the following references: US2017 / 0129781, US 4,301,037.

[0118] The inorganic material can be a zirconium oxide-based material. The zirconium oxide-based material can be selected from the group consisting of zirconium oxide and zirconium oxide stabilized by an oxide of at least one element selected from the group consisting of yttrium, lanthanum, praseodymium, cerium, and combinations thereof. Examples of zirconium oxide-based materials can be found in the following references: EP 1735242 B1, EP 1729883 B1 and EP 2646370 B1.

[0119] The inorganic material can be a mixed oxide comprising oxides of cerium and zirconium. The mixed oxide comprising oxides of cerium and zirconium can be selected from the group consisting of: mixed oxides of cerium and zirconium, and mixed oxides of cerium, zirconium, and at least one rare earth element other than cerium. Examples of mixed oxides comprising oxides of cerium and zirconium can be found in the following references: EP 1527018 B1, EP 3009403 B1, EP 0863846 B1, EP 2454196 B1, EP1603667B1, WO 2016037059.

[0120] The inorganic material can be a mixed oxide comprising oxides of aluminum, cerium, and zirconium. The mixed oxide comprising oxides of aluminum, cerium, and zirconium can be selected from the group consisting of: mixed oxides of aluminum, cerium, and zirconium, and mixed oxides of aluminum, cerium, zirconium, and at least one rare earth element other than cerium. Examples of such mixed oxides can be found in the following references: WO 2018 / 115436, US2013 / 0336864, US2013 / 0017947.

[0121] Platinum group metals (PGMs) are elements selected from groups in Group VIII of the periodic table. More specifically and generally, PGMs are selected from groups consisting of Pt, Pd, Rh, and combinations thereof.

[0122] The catalytic composition is prepared using conventional techniques known to those skilled in the art. For example, a method for preparing the catalytic composition includes the following steps: (a) preparing a suspension containing the composition of the present invention and inorganic materials other than the composition of the present invention in an aqueous medium; (b) wet milling the suspension from step (a); (c) optionally contacting the suspension with an aqueous solution of at least one PGM; (d) coating the obtained suspension onto a support (e.g., a bulk material or filter); and (e) drying and / or calcining in air. Alternatively, the method may exclude step (c) and apply the PGM to the composition of the present invention prior to step (a) using any known technique (such as initial wet impregnation).

[0123] An example of the preparation of the catalytic composition according to this method corresponds to Example 1 of EP 2969191: the composition of the present invention is impregnated with a Pd nitric acid solution using a standard initial wetting technique. The Pd-impregnated powder is placed in deionized water, and a Pt nitric acid solution is added. After lowering the pH to 4 by adding acid, the slurry is ground, and the ground slurry is dried and calcined in air at 450°C for 2 hours. Another example of preparation is provided in Example 1 of EP 3281697.

[0124] The catalytic composition may also contain at least one element selected from the group consisting of alkali metals and alkaline earth metals. This element is typically in the form of an oxide. The element may be an alkali metal such as sodium or potassium. The element may also be an alkaline earth metal such as magnesium, barium, or strontium. This element may exist in the catalytic composition in different forms:

[0125] -According to one embodiment, it is present on the composition of the invention, for example, by impregnation thereon. An example of an impregnation method includes the steps of: (a) contacting the composition of the invention with a salt of an alkali metal or alkaline earth metal, (b) drying the mixture, and (c) optionally calcining the dried mixture in air. An example of preparation corresponds to Example 1 of US 9,611,774 B2: impregnating the composition of the invention with a barium acetate solution, drying the mixture at 110°C and calcining it at 720°C for 2 hours;

[0126] -According to another embodiment, it can be present in inorganic materials other than the compositions of the present invention. Typically, it is present in alumina-based materials or cerium dioxide-based materials.

[0127] Examples of catalytic compositions are provided below as examples, not as limitations:

[0128] - A catalytic composition that can be used as a TWC or GPF catalyst, comprising the composition of the present invention; a mixed oxide of at least one cerium, zirconium and at least one rare earth element; at least one alumina; at least one PGM, for example, a combination of platinum + palladium + rhodium;

[0129] - A catalytic composition that can be used as a TWC or GPF catalyst, comprising the composition of the present invention; a mixed oxide of at least one aluminum, cerium, zirconium and at least one rare earth element other than cerium; at least one aluminum oxide; at least one PGM, for example, a combination of palladium and rhodium;

[0130] - A catalytic composition that can be used as a TWC or GPF catalyst, comprising the composition of the present invention; a mixed oxide of at least one cerium, zirconium and at least one rare earth element; at least one PGM, for example, a combination of palladium and rhodium;

[0131] - A catalytic composition that can be used as DOC, comprising the composition of the present invention; at least one alumina; at least one zeolite; at least one PGM, for example, a combination of platinum and palladium;

[0132] - A catalytic composition that can be used as a DOC, comprising the composition of the present invention; at least one zeolite; at least one PGM, for example, a combination of platinum and palladium;

[0133] - A catalytic composition that can be used as a DPF, comprising the composition of the present invention; at least one alumina; at least one PGM, such as platinum;

[0134] - A catalytic composition that can be used as an SCR, comprising the composition of the present invention; at least one zeolite containing copper oxide or iron oxide; boehmite;

[0135] - A catalytic composition that can be used as LNT comprises the composition of the present invention; at least one cerium and barium composite oxide; at least one aluminum oxide; at least one PGM, for example, a combination of platinum and palladium;

[0136] - A catalytic composition that can be used as LNT comprises the composition of the present invention; at least one cerium and barium composite oxide; at least one PGM, for example, a combination of platinum and palladium.

[0137] Preparation method

[0138] The present invention also relates to a method for preparing the composition of the present invention, the method comprising the following steps:

[0139] (a) With stirring, introduce the following into a tank initially containing an acidic aqueous solution with a pH between 0.5 and 4.0, or even between 0.5 and 3.5:

[0140] (a1)-Sodium aluminate aqueous solution until a pH of the reaction mixture between 8.0 and 10.0, or even between 8.5 and 9.5, is obtained;

[0141] (a2) - or simultaneously, (i) aqueous aluminum sulfate and (ii) aqueous 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;

[0142] Thus, at the end of step (a), the aluminum concentration of the reaction mixture is between 0.50% and 3.0% by weight;

[0143] (b) Subsequently, aqueous solutions of aluminum sulfate and sodium aluminate are introduced simultaneously at a rate such that the average pH of the reaction mixture is maintained within the target pH range of step (a);

[0144] The temperature of the reaction mixture in steps (a) and (b) is at least 60°C;

[0145] (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;

[0146] (d) The reaction mixture is then filtered, and the recovered solids are washed.

[0147] (e) subject the dispersion of the solid recovered in water at the end of step (d) to mechanical or ultrasonic crushing in order to reduce the particle size of the dispersion;

[0148] (f) Add at least one cerium salt to the dispersion obtained at the end of step (e);

[0149] (g) The dispersion obtained at the end of step (f) is dried;

[0150] (h) The solid obtained from step (g) is then calcined in air.

[0151] Its features are:

[0152] - For compositions C1 and C2, at least one cerium salt is added in step (f) and may also be added before step (d), wherein the proportion α of the cerium salt added in step (f) is between 20% and 100%, preferably between 50% and 100%, and α is calculated by the following formula: α = Amount added in step (f) / Total amount of cerium added × 100; and

[0153] - For composition C2, at least one lanthanum salt is added before step (d) or in step (f).

[0154] Step (a)

[0155] In step (a), the following is introduced into a tank initially containing an acidic aqueous solution with a pH between 0.5 and 4.0, or even between 0.5 and 3.5, while being stirred:

[0156] (a1)-Sodium aluminate aqueous solution until a pH of the reaction mixture between 8.0 and 10.0, or even between 8.5 and 9.5, is obtained;

[0157] (a2) - or simultaneously, (i) aqueous aluminum sulfate and (ii) aqueous 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;

[0158] This results in the aluminum concentration of the reaction mixture being between 0.50% and 3.0% by weight at the end of step (a).

[0159] The acidic aqueous solution initially contained in the container has a pH between 0.5 and 4.0, or even between 0.5 and 3.5. This solution may consist of a dilute aqueous solution of an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid.

[0160] The acidic aqueous solution can also consist of an aqueous solution of an acidic aluminum salt such as aluminum nitrate, aluminum chloride, or aluminum sulfate. Preferably, the aluminum concentration of the solution is between 0.01 wt% and 2.0 wt%, or even between 0.01 wt% and 1.0 wt%, or even even between 0.10 wt% and 1.0 wt%. Preferably, the acidic aqueous solution is an aqueous solution of aluminum sulfate. This solution is prepared by dissolving aluminum sulfate in water or by diluting one or more pre-formed aqueous solutions in water. The pH of the aqueous solution formed in the presence of aluminum sulfate is typically between 0.5 and 4.0, or even between 0.5 and 3.5.

[0161] Step (a) is performed according to either (a1) or (a2). According to Example (a1), an aqueous solution of sodium aluminate is introduced with stirring. According to Example (a2), (i) an aqueous solution of aluminum sulfate and (ii) an aqueous solution of sodium aluminate are introduced simultaneously with stirring.

[0162] Preferably, the aqueous sodium aluminate solution is free of any precipitated alumina. The sodium aluminate preferably has a Na₂O / Al₂O₃ ratio greater than or equal to 1.20, for example, between 1.20 and 1.40.

[0163] Sodium aluminate aqueous solutions can have an aluminum concentration between 15.0 wt% and 35.0 wt%, more particularly between 15.0 wt% and 30.0 wt%, or even between 20.0 wt% and 30.0 wt%. Aluminum sulfate aqueous solutions can have an aluminum concentration between 1.0 wt% and 15.0 wt%, more particularly between 5.0 wt% and 10.0 wt%.

[0164] At the end of step (a), the aluminum concentration of the reaction mixture is between 0.50 wt% and 3.0 wt%.

[0165] In step (a), the time for introducing one or more solutions is typically between 2 min and 30 min.

[0166] In step (a), the introduction of an aqueous sodium aluminate solution has the effect of increasing the pH of the reaction mixture.

[0167] Specifically, for Example (a1), an aqueous solution of sodium aluminate can be introduced directly into the reaction medium, for example, through at least one inlet sleeve. Specifically, for Example (a2), both solutions can be introduced directly into the reaction medium, for example, through at least two inlet sleeves. For both Examples (a1) and (a2), it is preferable to introduce one or more solutions into a well-stirred area of ​​the reactor, for example, into a region close to the stirring rotor, in order to achieve effective mixing of the one or more solutions introduced into the reaction mixture. For Example (a2), when solutions are introduced through at least two inlet sleeves, the injection points through which the two solutions are introduced into the reaction mixture are distributed such that these solutions are effectively diluted in the mixture. Therefore, for example, two sleeves can be arranged in a tank such that the injection points of the solutions to the reaction mixture are completely opposite.

[0168] Step (b)

[0169] In step (b), aqueous solutions of aluminum sulfate and sodium aluminate are introduced simultaneously, with the introduction rates of these solutions adjusted to maintain the average pH of the reaction mixture within the target pH range of step (a). Therefore, the target average pH value is:

[0170] - Between 8.0 and 10.0, or even between 8.5 and 9.5, for the case where embodiment (a1) is followed in step (a); or

[0171] - Between 6.5 and 10.0, or even between 7.0 and 8.0, or between 8.5 and 9.5, for the case of following embodiment (a2) in step (a).

[0172] The term “average pH” refers to the arithmetic mean of the pH values ​​of the reaction mixture recorded continuously during step (b).

[0173] Preferably, the sodium aluminate aqueous solution is introduced simultaneously with the aluminum sulfate aqueous solution at a flow rate adjusted such that the average pH of the reaction mixture equals the target value. During step (b), the flow rate of the sodium aluminate aqueous solution used to adjust the pH can fluctuate.

[0174] The introduction time of the two solutions can be between 10 minutes and 2 hours, or even between 30 minutes and 90 minutes. The flow rate of introducing one or both solutions can be constant.

[0175] It is necessary that the temperature of the reaction mixture in steps (a) and (b) be at least 60°C. This temperature can be between 60°C and 95°C. For this purpose, the solution initially contained in the tank in step (a) can be preheated before the introduction of the one or more solutions. The solutions introduced into the tank in steps (a) and (b) can also be preheated in advance.

[0176] Step (c)

[0177] 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 adding an alkaline or acidic aqueous solution.

[0178] Acidic aqueous solutions that can be used to adjust pH can consist of aqueous solutions of inorganic acids such as sulfuric acid, hydrochloric acid, or nitric acid. Acidic aqueous solutions can also consist of aqueous solutions of acidic aluminum salts such as aluminum nitrate, aluminum chloride, or aluminum sulfate.

[0179] Alkaline aqueous solutions that can be used to adjust pH can consist of aqueous solutions of inorganic bases such as sodium hydroxide, potassium hydroxide, or ammonia. Alkaline aqueous solutions can also consist of aqueous solutions of basic aluminum salts such as sodium aluminate. Sodium aluminate aqueous solutions are preferred.

[0180] Preferably, the pH is adjusted and stopped as follows:

[0181] (c1) Introduce an aqueous sulfate solution followed by an aqueous sodium aluminate solution until the target pH is reached; or alternatively...

[0182] (c2) Introduce sodium aluminate aqueous solution and continue to introduce aluminum sulfate aqueous solution until the target pH is reached.

[0183] According to one embodiment, the introduction of the aluminum sulfate aqueous solution is stopped while the introduction of the sodium aluminate aqueous solution continues until a target pH between 8.0 and 10.5, and preferably between 9.0 and 10.0, is reached. The duration of step (c) can be variable. This duration can be between 5 min and 30 min.

[0184] Step (d)

[0185] In step (d), the reaction mixture is filtered. This reaction mixture is typically in slurry form. The solids recovered on the filter can be washed with water. For this purpose, hot water at a temperature of at least 50°C can be used.

[0186] Step (e)

[0187] In step (e), the dispersion of solids recovered at the end of step (d) in water is subjected to mechanical or ultrasonic crushing to reduce the particle size of the dispersion. The pH of the dispersion can optionally be adjusted to between 5.0 and 8.0 prior to grinding. For this purpose, a nitric acid solution can be used, for example.

[0188] Prior to mechanical or ultrasonic fragmentation, the particle size distribution (D50) of the dispersion typically ranges from 10.0 μm to 40.0 μm, or even from 10.0 μm to 30.0 μm. After mechanical or ultrasonic fragmentation, the particle size distribution (D50) of the solid is preferably between 1.0 μm and 15.0 μm, or even from 2.0 μm to 10.0 μm.

[0189] Mechanical processing involves applying mechanical stress or shear force to the dispersion to classify the particles. Mechanical processing can be carried out, for example, by a ball mill, a high-pressure homogenizer, or a grinding system comprising a rotor and a stator. At a laboratory scale, Microcer or Labstar Zeta ball mills, both sold by Netzsch, can be used (see: [link to Netzsch product details]). https: / / www.netzsch-grinding.com / fr / produits-solutions / broyage- humide / broyeurs-de-laboratoire-serie-mini / A grinding system as described in the examples can be used. In the case of a ball mill, yttrium-stabilized zirconia beads can be used, for example. ZetaBeads Plus 0.2mm balls can be used.

[0190] Ultrasonic disruption, by its very nature, involves applying sound waves to a dispersion. Sound waves propagating through a liquid medium induce cavitation, which allows particles to be fractionated. On a laboratory scale, an ultrasonic disruption system with a Sonics Vibracell VC750 generator equipped with a 13mm probe can be used. The duration and applied power are adjusted to achieve the target D50.

[0191] Mechanical or ultrasonic crushing can be performed in intermittent or continuous mode.

[0192] Step (f)

[0193] In step (f), at least one cerium salt is added to the dispersion obtained at the end of step (e). It is also conceivable to add an aqueous ammonia solution in this step to raise the pH, preferably to a value between 5.0 and 8.0. The cerium salt can be selected from the group consisting of cerium chloride, cerium acetate, and cerium nitrate. The cerium salt is preferably a salt of Ce(III).

[0194] Alternatively, cerium salts can be added to a solution containing, for example, aluminum sulfate, before step (d), such as in step (a). The proportion α of cerium salt added in step (f) is between 20% and 100%, preferably between 50% and 100%, and α is calculated using the following formula: α = Amount added in step (f) / Total amount of cerium added × 100. Preferably, α = 100%, which means that cerium salts are added only in step (f) to the dispersion obtained at the end of step (e).

[0195] For composition C2, at least one lanthanum salt may also be added to the dispersion obtained at the end of step (e) before step (d) or in step (f).

[0196] Cerium and lanthanum salts can be conveniently introduced in the form of aqueous solutions.

[0197] Step (g)

[0198] In step (g), the dispersion from step (f) is dried, preferably by spraying.

[0199] Spray drying has the advantage of producing particles with a controlled particle size distribution. This drying method also provides good production efficiency. The drying method involves spraying a dispersion as a droplet mist into a hot gas stream (e.g., a hot air stream) circulating in a chamber. The quality of the spray controls the droplet size distribution, and thus the size distribution of the dried particles. This spraying can be performed using any sprayer known per se. There are two main types of spraying devices: turbines and nozzles. For details on various spraying techniques that can be implemented in the method of this invention, refer in particular to Masters' standard manual entitled "Spray-Drying" (2nd edition, 1976, published by George Godwin, London). Operating parameters that can be modified by those skilled in the art include, in particular, the flow rate and temperature of the dispersion entering the sprayer; the flow rate, pressure, humidity, and temperature of the hot gas. The inlet temperature of the gas is typically between 100°C and 800°C. The outlet temperature of the gas is typically between 80°C and 150°C.

[0200] The D50 of the recovered powder at the end of step (g) is typically between 2.0 μm and 80.0 μm. This size is related to the size distribution of the droplets leaving the atomizer. The evaporation capacity of the atomizer is generally related to the size of the chamber. Therefore, on a laboratory scale (Büchi B 290), D50 can be between 2.0 and 15.0 μm. On a larger scale, D50 can be between 15.0 and 80.0 μm.

[0201] Step (h)

[0202] In step (h), the solid obtained in step (g) is calcined in air. Calcination aims to convert the components added in the previous steps into oxides and to develop the crystallinity of the composition. The calcination temperature is typically between 500°C and 1000°C, more particularly between 800°C and 1000°C. The calcination time is typically between 1 and 10 hours.

[0203] Considering that excessively high calcination temperatures can negatively impact both specific surface area and average crystallite size, a balance should be struck between calcination temperature and calcination time to convert the components into oxides and improve the crystallinity of the composition. The calcination conditions given in Example 1 can be used, as they provide this favorable balance.

[0204] It is conceivable that these two steps (g) and (h) are carried out in the same apparatus, in which the dispersion obtained from step (f) undergoes both drying and calcination as heat treatments.

[0205] Preferably, the mixed oxide recovered at the end of step (h) (i.e., at the end of calcination) has a D50 typically between 2.0 μm and 80.0 μm. It typically has a D90 of less than or equal to 150.0 μm, and more particularly less than or equal to 100.0 μm.

[0206] According to the first embodiment, at the end of step (h), D50 can be between 2.0 and 15.0 μm, or even between 4.0 and 12.0 μm. D90 can be between 20.0 μm and 60.0 μm, or even between 25.0 μm and 50.0 μm. This embodiment is more likely to be performed on a laboratory scale using, for example, a Büchi B 290 atomizer.

[0207] According to the second embodiment, at the end of step (h), D50 can be between 15.0 and 80.0 μm, or even between 20.0 and 60.0 μm. D90 can be between 40.0 μm and 150.0 μm, or even between 50.0 μm and 100.0 μm. This embodiment is more likely to be implemented when step (f) is performed on a larger scale.

[0208] The method may also include a final step in which the solid obtained in the previous step is ground to adjust the particle size of the solid. A knife mill, air jet mill, hammer mill, or ball mill may be used. Preferably, the ground product has a D50 typically between 2.0 μm and 15.0 μm. D90 may be between 20.0 μm and 60.0 μm, or even between 25.0 μm and 50.0 μm.

[0209] The composition of the present invention is in powder form.

[0210] Further details regarding the preparation of the compositions of the present invention will be found in the following illustrative examples.

[0211] Example

[0212] Measurement of specific surface area :

[0213] For the sake of continuity in this specification, the term "specific surface area" refers to the BET specific surface area determined by nitrogen adsorption according to the standard ASTM D3663-03 established by the Bruno-Emmett-Teller method as described in the Journal of the American Chemical Society, 60, 309 (1938). The specific surface area is determined automatically using, for example, a Tristar II 3020 machine from Micromeritics, according to the manufacturer's recommended instructions. The sample is preheated at 250°C for 90 min under vacuum (e.g., pressure reaching 50 mmHg). This treatment allows for the removal of physically adsorbed volatile substances (e.g., H₂O, etc.) from the surface.

[0214] Porosity measurement using mercury (Hg porosity determination method)

[0215] This measurement was performed using a mercury porosimeter. In the present case, a Micromeritics Autopore IV 9520 machine equipped with a powder penetration meter was used, according to the manufacturer's recommended instructions. The following parameters were used: Penetration meter used: 3.2 ml (Micromeritics reference: Penetration meter model, number 8); Capillary volume: 0.412 ml; Maximum pressure (“indenter”): 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 mmHg was applied to the sample for 5 min. Equilibrium times were 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 sample was treated at 200°C for 120 min to remove physically adsorbed volatile substances (e.g., H₂O) from the surface. The pore volume can be derived from this measurement.

[0216] X-ray diffraction: The X'Pert Pro X-ray diffractometer with a copper source (CuKα1, λ = 1.5406 Å) was used.

[0217] Measurement of particle size (D10, D50, D90)

[0218] For particle size measurement, a Malvern Mastersizer 2000 or 3000 laser diffraction particle size analyzer was used (further details about this machine are given here: https: / / www.malvernpanalytical.com / fr / products / product-range / mastersize r-range / mastersizer-3000The laser diffraction technique used involves measuring the intensity of light scattered as a laser beam passes through a dispersed particulate sample. The laser beam passes through the sample, and the intensity of the scattered light is measured as a function of angle. The diffraction intensity is then analyzed to calculate the particle size using Mie scattering theory. This measurement allows for obtaining a volume-based size distribution, from which parameters D10, D50, and D90 are derived.

[0219] Example 1: According to embodiment (a1) and wherein α =100% preparation of alumina and cerium oxide according to the present invention Composition (80wt% Al2O3-20wt% CeO2)

[0220] 157 kg of deionized water was introduced into the stirred reactor and heated to 85 °C. This temperature was maintained throughout steps (a) to (c). 13.8 kg of an aluminum sulfate solution with a concentration of 8.3 wt% alumina (Al₂O₃) was introduced through an inlet sleeve near the stirring rotor at a flow rate of 920 g solution / min. At the end of the introduction, the pH in the reactor was close to 2.6 and the aluminum concentration was 0.7 wt% alumina (Al₂O₃). The introduction of the aluminum sulfate solution was then stopped.

[0221] Step (a): A sodium aluminate solution with a concentration of 24.9 wt% alumina (Al₂O₃) and a Na₂O / Al₂O₃ molar ratio of 1.27 was introduced through a second inlet sleeve near the stirring rotor at a flow rate of 690 g solution / min until the pH reached 9.0. The introduction was then stopped. The reaction mixture then had an aluminum concentration of 2.10 wt% alumina (Al₂O₃).

[0222] In step (b), aluminum sulfate solution is introduced again at a flow rate of 570 g solution / min, while sodium aluminate solution is introduced into the stirred reactor at an adjusted flow rate to maintain the pH at 9.0. This step lasts for 45 minutes.

[0223] In step (c), stop introducing the aluminum sulfate solution and continue adding sodium aluminate solution at a flow rate of 320 g solution / min until the pH reaches 9.5. Then stop adding the sodium aluminate solution.

[0224] In step (d), the reaction slurry is poured onto a vacuum filter. At the end of the filtration step, the filter cake is washed with deionized water at 65°C.

[0225] In step (e), the filter cake is redispersed in deionized water to obtain a suspension with a concentration of approximately 9 wt% oxides (Al₂O₃). A nitric acid solution with a concentration of 69% by weight is added to the suspension to obtain a pH close to 6. The suspension is then passed through a ball mill of the LME20 brand from the manufacturer Netzsch. The milling operating conditions are adjusted to obtain a D50 of 5 microns.

[0226] In step (f), a cerium nitrate solution with a concentration of approximately 29% by weight of oxide (CeO2) is prepared. This solution is added to the suspension obtained from step (e) with stirring to obtain a CeO2 / (CeO2+Al2O3) mass ratio of 20 wt%.

[0227] In step (g), the suspension obtained in step (f) is spray-dried to obtain a dry powder.

[0228] In step (h), the spray-dried powder was calcined in air at 940°C for 2 hours (temperature rise rate of 3°C / min). The observed mass loss during this calcination was 47% wt%.

[0229] Example 2: The alumina and cerium oxide mixture according to the present invention was prepared according to Example (a1) wherein α = 60%. Compound (80wt% Al2O3-20wt% CeO2)

[0230] 157 kg of deionized water was introduced into a stirred reactor and heated to 85 °C. This temperature was maintained throughout steps (a) to (c). An acid mixture was prepared consisting of 36.3 kg of an aluminum sulfate solution with a concentration of 8.3 wt% alumina (Al₂O₃) and 3.2 kg of a cerium nitrate solution with a concentration of 29.0 wt% cerium dioxide (CeO₂).

[0231] 13.8 kg of acid mixture was introduced into the reactor through an inlet sleeve near the stirring rotor at a flow rate of 920 g solution / min. At the end of the introduction, the pH in the reactor was close to 2.6 and the aluminum concentration was 0.62% alumina (Al₂O₃) by weight. The introduction of the acid mixture was then stopped.

[0232] Step (a): A sodium aluminate solution with a concentration of 24.9 wt% alumina (Al₂O₃) and a Na₂O / Al₂O₃ molar ratio of 1.27 is introduced through a second inlet sleeve near the stirring rotor at a flow rate of 690 g solution / min until the pH reaches 9.0. The introduction is then stopped.

[0233] In step (b), the acid mixture is again introduced into the stirred reactor at a flow rate of 570 g solution / min, while the sodium aluminate solution is introduced into the reactor at an adjusted flow rate to maintain the pH at 9.0. This step lasts for 45 minutes.

[0234] In step (c), stop introducing the acid mixture and continue adding sodium aluminate solution at a flow rate of 320 g solution / min until the pH reaches 9.5. Then stop adding sodium aluminate solution.

[0235] In step (d), the reaction slurry is poured onto a vacuum filter. At the end of the filtration step, the filter cake is washed with deionized water at 65°C.

[0236] In step (e), the filter cake is redispersed in deionized water to obtain a suspension with a concentration of approximately 9 wt% oxides (Al₂O₃). A nitric acid solution with a concentration of 69% by weight is added to the suspension to obtain a pH close to 6. The suspension is then passed through a ball mill of the LME20 brand from the manufacturer Netzsch. The milling operating conditions are adjusted to obtain a D50 of 5.1 microns.

[0237] In step (f), a cerium nitrate solution with a concentration of 29% by weight of oxide (CeO2) is prepared. This solution is added to the suspension obtained from step (e) with stirring to obtain a CeO2 / (CeO2+Al2O3) mass ratio of 20 wt%.

[0238] In step (g), the suspension obtained in step (f) is spray-dried to obtain a dry powder.

[0239] In step (h), the spray-dried powder is calcined in air at 940°C for 2 hours (temperature rise rate is 3°C / min).

[0240] Comparative Example 3: Preparation of cerium oxide containing 20% ​​(80% Al2O3-20% CeO2) and wherein α=0% cerium oxide Composition of aluminum and cerium oxide

[0241] 157 kg of deionized water was introduced into a stirred reactor and heated to 85 °C. This temperature was maintained throughout steps (a) to (c). An acid mixture was prepared consisting of 31.6 kg of an aluminum sulfate solution with a concentration of 8.3 wt% alumina (Al₂O₃) and 7.9 kg of a cerium nitrate solution with a concentration of 29.0 wt% cerium dioxide (CeO₂).

[0242] 13.8 kg of acid mixture was introduced into the reactor through an inlet sleeve near the stirring rotor at a flow rate of 920 g solution / min. At the end of the introduction, the pH in the reactor was close to 2.7 and the aluminum concentration was 0.54% alumina (Al₂O₃) by weight. The introduction of the acid mixture was then stopped.

[0243] Step (a): A sodium aluminate solution with a concentration of 24.9 wt% alumina (Al₂O₃) and a Na₂O / Al₂O₃ molar ratio of 1.27 was introduced through a second inlet sleeve near the stirring rotor at a flow rate of 690 g solution / min until the pH reached 9.0. The introduction was then stopped. The reaction mixture then had an aluminum concentration of 1.60 wt% alumina (Al₂O₃).

[0244] In step (b), the acid mixture is again introduced into the stirred reactor at a flow rate of 570 g solution / min, while the sodium aluminate solution is introduced into the reactor at an adjusted flow rate to maintain the pH at 9.0. This step lasts for 45 minutes.

[0245] In step (c), stop introducing the acid mixture and continue adding sodium aluminate solution at a flow rate of 320 g solution / min until the pH reaches 9.5. Then stop adding sodium aluminate solution.

[0246] In step (d), the reaction slurry is poured onto a vacuum filter. At the end of the filtration step, the filter cake is washed with deionized water at 65°C.

[0247] In step (e), the filter cake is redispersed in deionized water to obtain a suspension with a concentration of approximately 9 wt% oxides (Al₂O₃). A nitric acid solution with a concentration of 69% by weight is added to the suspension to obtain a pH close to 6. The suspension is then passed through a ball mill of the LME20 brand from the manufacturer Netzsch. The milling operating conditions are adjusted to obtain a D50 of 5.4 microns.

[0248] In the next step, the suspension obtained in step (e) will be spray-dried to obtain a dry powder.

[0249] In the next step, the spray-dried powder was calcined in air at 940°C for 2 hours (temperature rise rate of 3°C / min). The observed mass loss during this calcination was 46.3 wt%.

[0250] Table I

[0251]

[0252] Table II

[0253]

[0254]

[0255] As can be seen, the method of the present invention makes it possible to obtain compositions with low crystallite size at 900°C and 1100°C.

Claims

1. A composition, wherein the composition is - Based on the composition C1 of Al and Ce in oxide form; or - Based on the composition C2 of Al, Ce and La in oxide form; It has the following proportions: - The proportion of CeO2 is between 3.0 wt% and 35.0 wt%; - For composition C2, the proportion of La2O3 is between 0.1 wt% and 6.0 wt%; - The remaining part is Al2O3; The composition exhibits the following porosity distribution: - Pore volume in the range of pore size between 5 nm and 100 nm, between 0.35 and 1.00 mL / g; and - Pore volume less than or equal to 0.15 mL / g in the range of pore sizes between 100 nm and 1000 nm. These pore volumes were determined using the mercury porosimetry technique. And the following characteristics: - less than 45.0 nm after calcination in air at 1100 °C for 5 hours, expressed as D 1100°C-5h ; - a crystallite average size of less than 25.0 nm, expressed as D after calcination in air at 900°C for 2 hours 900°C-2h ; and - an increase in the average size of the crystallites, ΔD, of less than 30.0 nm, ΔD being calculated with the following formula: ΔD = D 1100°C-5h - D 900°C-2h ; The average size of the crystallites was obtained by XRD from the diffraction peaks corresponding to the cubic phase of cerium oxide at 2θ between 28.0° and 30.0° [111].

2. The composition according to claim 1, wherein, The composition, after calcination in air at 1100°C for 5 hours, exhibits an average crystallite size of less than 40.0 nm, denoted as D. 1100°C-5h .

3. The composition according to claim 1, wherein, The composition, after calcination in air at 900°C for 2 hours, exhibits an average crystallite size of less than 20.0 nm, denoted as D. 900°C-2h .

4. The composition according to claim 3, wherein, The composition, after calcination in air at 900°C for 2 hours, exhibits an average crystallite size of less than 15.0 nm, denoted as D. 900°C-2h .

5. The composition according to claim 1, wherein, The composition has an increase in the average crystallite size ΔD of less than 25.0 nm.

6. The composition according to claim 1, wherein the composition is composition C1 consisting of oxides of Ce and Al or composition C2 consisting of oxides of Ce, Al and La.

7. The composition according to claim 1 or 2, wherein, The proportion of CeO2 is between 5.0 wt% and 30.0 wt%.

8. The composition according to claim 3, wherein, The proportion of CeO2 is between 15.0 wt% and 25.0 wt%.

9. The composition according to any one of the preceding claims, wherein, The proportion of Al2O3 is: - For composition C1, between 65.0 wt% and 97.0 wt%; - For composition C2, the concentration is between 59.0 wt% and 96.9 wt%.

10. The composition according to any one of the preceding claims, comprising an alumina-based crystalline phase.

11. The composition according to any one of the preceding claims, comprising a cerium oxide-based crystalline phase.

12. The composition according to claim 7, wherein, The cerium oxide-based crystal phase corresponds to pure CeO2 or CeO2 containing lanthanum.

13. The composition according to any one of the preceding claims, wherein, D 1100°C-5h Less than 40.0 nm.

14. The composition according to any one of the preceding claims, wherein, D 900°C-2h Less than 25.0 nm.

15. The composition according to claim 14, wherein, D 900°C-2h Less than 20.0 nm.

16. The composition according to any one of the preceding claims, wherein, ΔD is less than 25 nm.

17. The composition according to any one of the preceding claims, wherein, D 1100°C-5h It is at least 8.0 nm.

18. The composition according to any one of the preceding claims, wherein, D 900°C-2h It is at least 5.0 nm.

19. The composition according to any one of the preceding claims, wherein, The pore volume for pores with sizes between 5 nm and 100 nm is between 0.40 and 1.00 mL / g.

20. The composition according to any one of the preceding claims, wherein, The pore volume for pores with sizes between 5 nm and 100 nm is between 0.40 and 0.80 mL / g.

21. The composition according to any one of the preceding claims, wherein, The pore volume is less than or equal to 0.10 mL / g for pores with sizes between 100 nm and 1000 nm.

22. The composition according to any one of the preceding claims, wherein, The pore volume is less than or equal to 0.07 mL / g for pores with sizes between 100 nm and 1000 nm.

23. The composition according to any one of the preceding claims, wherein the composition is defined by the following porosity distribution: - Pore volume in the range of pore size between 5 nm and 100 nm, between 0.40 and 1.00 mL / g; and - Pore volume less than or equal to 0.07 mL / g in the range of pores with dimensions between 100 nm and 1000 nm.

24. The composition according to any one of the preceding claims, exhibiting properties at 80 and 300 m 2 BET specific surface area between / g.

25. The composition according to claim 24, exhibiting a concentration at 90 and 200 m 2 BET specific surface area between / g.

26. The composition according to any one of the preceding claims, exhibiting a value greater than 40 μm after calcination in air at 1100°C for 5 hours. 2 / g BET specific surface area.

27. The composition according to claim 26, exhibiting a value greater than 45 m after calcination in air at 1100°C for 5 hours. 2 / g BET specific surface area.

28. The composition according to any one of the preceding claims, exhibiting a density strictly less than 82.35 × (Al₂O₃) + 11.157 m after calcination in air at 1100°C for 5 hours. 2 / g BET specific surface area, where (Al2O3) corresponds to the proportion of Al2O3 in the composition in wt%.

29. The composition according to any one of the preceding claims, exhibiting a temperature range of 25 and 60 m after calcination in air at 1200°C for 5 hours. 2 BET specific surface area between / g.

30. The composition according to any one of the preceding claims exhibits a total pore volume greater than 0.70 mL / g, the total pore volume being determined by mercury porosimetry.

31. The composition of claim 30, exhibiting a total pore volume of at least 0.80 mL / g, the total pore volume being determined by mercury porosimetry.

32. The composition of claim 30, exhibiting a total pore volume of at least 0.90 mL / g, the total pore volume being determined by mercury porosimetry.

33. The composition according to any one of the preceding claims exhibits a total pore volume of not more than 2.50 mL / g, the total pore volume being determined by mercury porosimetry.

34. The composition of claim 33, exhibiting a total pore volume of not more than 2.00 mL / g, the total pore volume being determined by mercury porosimetry.

35. The composition according to any one of the preceding claims, exhibiting a concentration of 0.35 g / cm³. 3 With 0.90 g / cm 3 The packing density between them.

36. The composition according to any one of the preceding claims, exhibiting a concentration of 0.40 g / cm³. 3 With 0.85 g / cm 3 The packing density between them.

37. The composition according to any one of the preceding claims exhibits the following properties: - D50 between 2.0 and 15.0 μm; - At 0.35 and 0.55 g / cm 3 The packing density between them.

38. The composition according to claim 37, having a D90 between 20.0 μm and 60.0 μm.

39. The composition according to any one of claims 1 to 36, exhibiting the following properties: - D50 between 15.0 and 80.0 μm; - At 0.40 and 0.90 g / cm 3 The packing density between them.

40. The composition according to claim 39, having a D90 between 40.0 μm and 150.0 μm.

41. The composition according to any one of the preceding claims, having a sodium content of less than or equal to 0.50% by weight, the sodium content being expressed as the weight of Na2O relative to the total weight of the composition.

42. The composition according to claim 41, having a sodium content of less than or equal to 0.15% by weight, the sodium content being expressed as the weight of Na2O relative to the total weight of the composition.

43. The composition according to any one of the preceding claims, having a sodium content of greater than or equal to 50 ppm, the sodium content being expressed as the weight of Na2O relative to the total weight of the composition.

44. The composition according to any one of the preceding claims, having a sulfate content of less than or equal to 1.00% by weight, the sulfate content being expressed as the weight of SO4 relative to the total weight of the composition.

45. The composition according to claim 44, having a sulfate content of less than or equal to 0.50% by weight, the sulfate content being expressed as the weight of SO4 relative to the total weight of the composition.

46. ​​The composition according to claim 44, having a sulfate content of less than or equal to 0.25% by weight, the sulfate content being expressed as the weight of SO4 relative to the total weight of the composition.

47. The composition according to any one of the preceding claims, having a sulfate content of 50 ppm or more, the sulfate content being expressed as the weight of SO4 relative to the total weight of the composition.

48. A catalytic composition comprising: (i) the composition according to any one of claims 1 to 42; and (ii) Optionally at least one inorganic material other than the composition according to any one of claims 1 to 47; and / or (iii) Optionally at least one platinum group metal PGM.

49. The catalytic composition according to claim 48, comprising: (i) the composition according to any one of claims 1 to 42; and (ii) at least one inorganic material other than the composition according to any one of claims 1 to 47; and (iii) Optionally at least one platinum group metal PGM.

50. The catalytic composition according to claim 48, comprising: (i) the composition according to any one of claims 1 to 42; and (ii) at least one inorganic material other than the composition according to any one of claims 1 to 47; and (iii) At least one platinum group metal PGM.

51. The catalytic composition according to any one of claims 48 to 50, wherein, The inorganic material (ii) is selected from the group consisting of: zeolites; alumina-based materials; Cerium dioxide-based materials; Zirconia-based materials; mixed oxides containing oxides of cerium and zirconium; mixed oxides containing oxides of aluminum, cerium and zirconium; and combinations thereof.

52. The catalytic composition according to any one of claims 48 to 51, wherein, The PGM is selected from the group consisting of Pt, Pd, Rh and their combinations.

53. The catalytic composition according to any one of claims 48 to 52, further comprising at least one element selected from the group consisting of alkali metals and alkaline earth metals.

54. Use of the composition according to any one of claims 1 to 47 in the preparation of a catalyst for purifying vehicle exhaust.

55. Use of the catalytic composition according to any one of claims 48 to 53 in the preparation of a catalytic converter.

56. A method for preparing a composition according to any one of claims 1 to 47, the method comprising the following steps: (a) Introduce the following into a tank initially containing an acidic aqueous solution with a pH between 0.5 and 4.0, while stirring: (a1)- Sodium aluminate aqueous solution until the pH of the reaction mixture is between 8.0 and 10.0; (a2) - or simultaneously, (i) aqueous aluminum sulfate and (ii) aqueous sodium aluminate, until a pH of the reaction mixture is obtained between 6.5 and 10.0; Thus, at the end of step (a), the aluminum concentration of the reaction mixture is between 0.50% and 3.0% by weight; (b) Subsequently, aqueous solutions of aluminum sulfate and sodium aluminate are introduced simultaneously at a rate that maintains the average pH of the reaction mixture within the target pH range of step (a). The temperature of the reaction mixture in steps (a) and (b) is at least 60°C; (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; (d) The reaction mixture is then filtered, and the recovered solids are washed. (e) subject the dispersion of the solid recovered in water at the end of step (d) to mechanical or ultrasonic crushing in order to reduce the particle size of the dispersion; (f) Add at least one cerium salt to the dispersion obtained at the end of step (e); (g) Dry the dispersion obtained at the end of step (f); (h) The solid obtained from step (g) is then calcined in air. Its features are: - For compositions C1 and C2, at least one cerium salt is added in step (f) and may also be added before step (d), wherein the proportion α of the cerium salt added in step (f) is between 20% and 100%, and α is calculated by the following formula: α = Amount added in step (f) / Total amount of cerium added × 100; and - For composition C2, at least one lanthanum salt is added before step (d) or in step (f).

57. The method according to claim 56, wherein, The pH of the acidic aqueous solution in step (a) is between 0.5 and 3.

5.

58. The method according to claim 56, wherein, Step (a) introduce an aqueous solution of sodium aluminate until the pH of the reaction mixture is between 8.5 and 9.

5.

59. The method according to claim 56, wherein, Step (a) involves simultaneously introducing (i) an aqueous solution of aluminum sulfate and (ii) an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 7.0 and 8.

0.

60. The method of claim 56, wherein, Step (a) involves simultaneously introducing (i) an aqueous solution of aluminum sulfate and (ii) an aqueous solution of sodium aluminate until a pH of the reaction mixture is obtained between 8.5 and 9.

5.

61. The method according to claim 56, wherein, Step (c) At the end of step (b), the pH of the reaction mixture is optionally adjusted to a value between 8.0 and 9.

0.

62. The method according to claim 56, wherein, Step (c) At the end of step (b), the pH of the reaction mixture is optionally adjusted to a value between 9.0 and 10.

0.

63. The method according to claim 56, wherein, The proportion α of cerium salt added in step (f) is between 50% and 100%.

64. The method according to claim 56, wherein, α = 100%。

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