Classifications

• • 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
  • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
• • 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
  • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
• • 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
  • 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
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
  • B01J37/0027—Powdering
  • B01J37/0045—Drying a slurry, e.g. spray drying
• • 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
  • B01J37/0201—Impregnation
• • 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
  • B01J37/0201—Impregnation
  • B01J37/0203—Impregnation the impregnation liquid containing organic compounds
• • 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
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/03—Precipitation; Co-precipitation
  • B01J37/031—Precipitation
  • B01J37/033—Using Hydrolysis
• • 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
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
• • 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

Definitions

• the present invention refers to compositions based on ceria (oxide of cerium), zirconia (oxide of zirconium) and alumina (oxide of aluminium) with enhanced thermal stability.
• compositions may be used as washcoats in the application of exhaust gas aftertreatment of combustion engines such as fuel- and dieselengines, e.g. as components of catalysts (mainly Three Way Catalysts, TWC), but also in other parts integrated into the exhaust stream such as NOx traps, Diesel Oxidation Catalysts (DOC) and Diesel Particulate Filters (DPF).
• catalysts mainly Three Way Catalysts, TWC
• DOC Diesel Oxidation Catalysts
• DPF Diesel Particulate Filters
• Ceria-Zirconia based mixed oxides and alumina are widely used in automotive application for catalyst preparation.
• WO 2008/113457 the preparation of washcoats introducing separateley mixed oxides of ceria / zirconia and alumina (lanthanum doped aluminium oxide) is described and thus is a well established process.
• composition materials consisting of Al 2 O 3 with the balance typically being CeO 2 , ZrO 2 , and optionally stabilizers such as rare earth metal oxides or non rare earth metal oxides.
• such types of composition materials are described paying attention also to the surface stability of such compounds.
• surface stability of Ce-Zr- Alumina based materials amongst other properties is important to be effective as a catalyst.
• example 1 of US 5,883,037 refers to a composition of 50%
• composition oxide exhibits a specific surface area of 52 m /g after being heat treated at 600°C for 2 hours and after additional heat treatment for 2 hours at 1050°C. No values on specific surface area are reported for heat treatment at higher temperatures and/or for a longer period of time.
• EP 1 172 139 there is reported the preparation and the thermal stability of several Al-Ce- Zr-Y-La composition oxides and various compositions consisting of Al 2 O 3 /CeO 2 /ZrO 2 /Y 2 O 3 La 2 0 3 with different ratios of the oxides are disclosed.
• the materials are described to be prepared via co-precipitation starting from the corresponding metal salt solutions.
• As intermediates suspensions of Al-Ce-Zr-Y-La hydroxides are formed which after calcination were transferred into the corresponding oxides (see page 8, lines 1 to 6).
• the surface area of such composition oxides is described to be dependent on the amount of A1 2 0 3 being present in the composition.
• examples 10 to 22 in which the A1 2 0 3 content is in the range between 21 and 25 weight % (calculated from the molar ratios disclosed in table 2) the specific surface area is less than 15 m /g after the compounds have been subjected to heat treatment at 1100°C for 20 hours (see table 2 page 14). Higher values of the surface area are indicated after heat treatment at 1100°C / 20 hours in case that the A1 2 0 3 content is increased as disclosed in the examples 24, 27 and 31.
• example 24 corresponding to a composition with an A1 2 0 3 content of 57% weight, there is disclosed a surface area of 27 m /g after calcination at 1100°C / 20 hours, and in examples 27 and 31 which correspond to an A1 2 0 3 content of 63%, surface areas of 31 m /g and 30 m /g, respectively, after calcination at 1100°C / 20 hours are indicated.
• WO 2006/070201 there is reported an improved method for the formation of composition hydroxides or oxides comprising, on an oxide basis, alumina (A1 2 0 3 ) and Zirconia (Zr0 2 ), and optionally including at least one member selected from Ce0 2 , La 2 0 3 , Nd 2 0 3 , ⁇ 6 ⁇ , Sm 2 0 3 .Y 2 0 3 and optionally other rare earth metal oxides.
• the compounds are described to be made by co-precipitation starting from a metal salt solution using caustic alkali as a precipitation agent.
• a strict narrow pH range is to be kept: According to WO 2006/070201 the deviation of the pH during precipitation must not be more than +/- 1.
• a Al/Ce/Zr-composition oxide is reported consisting of 51% A1 2 0 3 , 14.2%
• the precipitate formed by co-precipitation from the mixed metal- solution (Al, Ce, Zr) requires an extensive washing and re- slurrying for proper removal of the caustic alkali which was used for precipitating the metal composition.
• a hydrothermal treatment at 120°C of the material obtained prior to final calcination of the hydroxides (wet cake) is described to be required to get material with reasonable stability in surface area.
• the materials are described to be re-slurried and subjected to extensive washing the final products still contains Na in a range of up to 100 ppm.
• Na is an undesired impurity in materials for automotive application since it might be detrimental to the action of rhodium which for example is part of a three way catalyst for the removal of NOx (see e.g. Norman Macleod et al. in Applied Catalysis B: Environmental, Volume 33, Issue 4, October 25, 2001, Pages 335-343).
• the use of huge amounts of caustic alkali in the precipitation step generates heavily contaminated nitrate containing waste water causing environmental concerns.
• Hyroxides of cerium and zirconiumn are not water soluble and are thus not present in a salt solution of cerium/zirconium.
• the present invention is aimed to solve disadvantages related with the limited thermal stability of Al/Ce/Zr compositions and to improve the manufacturing process of such compounds/compositions; in particular to avoid co-precipitation with formation of huge amount of waste water and hydrothermal treatment steps and moreover, to provide compositions with enhanced surface stability, particularly after long term ageing.
• the present invention provides a process for the preparation of a calcined mixed oxide comprising A1-, Ce- and Zr-oxides, comprising the steps of
• step (d) calcining the solid composition of step (c) at a temperature from 450°C to 1200°C for at least 1 hour to obtain a calcined mixed oxide.
• the Al/Ce/Zr-oxides according to the present invention preferably have surface areas (BET) exceeding 20 m 2 /g or even 30 m 27g when treated for 4 h at 1200°C.
• a process provided by the present invention is herein also designated as sawA process of (according to) the present invention.
• the aqueous slurry in step (a) comprises cerium calculated as cerium oxide (Ce0 2 ) in the range of 5% to 90% by weight based on the total oxide content (TO) of the calcined mixed oxide.
• the calcined mixed oxide in step (d) comprises cerium from 5 to 90 % by weight, preferably 5 to 50 % by weight, aluminium from 20 to 80 % by weight, preferably 40 to 70 % by weight, zirconium from 5 to 80 % by weight, preferably 5 to 40 % by weight, and optionally rare earth metals (RE) from 0 to 12 % by weight, preferably 0,1 bis 9 % by weight; wherein cerium, zirconium, and rare earth metals (RE) are calculated as Ce0 2 , Zr0 2 , A1 2 0 3 , or RE 2 0 3 , respectively.
• the present invention provides a process according to the present invention, wherein the calcined mixed oxide comprises
• - zirconium from 5 to 80 % by weight, preferably 5 to 40 % by weight, and optionally
• RE rare earth metals
• cerium, zirconium, and rare earth metals are calculated as Ce0 2 , Zr0 2 , A1 2 0 3 , or RE 2 0 3 , respectively.
• Ce/Zr-hydroxides used according to step (a) contain at least one rare earth metal element, preferably selected from Y, La, Pr, Nd, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.
• the present invention provides a process according to the present invention, wherein the aqueous slurry in step (a) further comprises one or more hydroxides of rare earth metals other than cerium.
• An aqueous slurry as defined in step (a) in a process of the present invention includes either an aqueous slurry 1, or an aqueous slurry 2.
• An aqueous slurry 1 is a suspension of hydroxides of cerium and zirconium, optionally comprising further rare earth metal salts which was treated with ammonium hydroxide, and optionally with H 2 0 2 and/or a surfactant.
• An aqueous slurry 2 is an aqueous slurry 1 isolated (e.g. filtrated) as a solid (Wet Cake) and re-suspended in water, optionally further treated, e.g. with ammonia and/or a surfactant.
• Step (a) may be carried out by providing an aqueous solution of cerium and zirconium salts, optionally in combination with other rare earth metal salts and treating the aqueous solution with aqueous ammonium hydroxide.
• a treatment with H 2 0 2 is carried out, either before ammonium hydroxide treatment, or after ammonium hydroxide treatment.
• a pH of 7 and higher, e.g. 7 to 10 of the aqueous slurry is adjusted.
• a precipitate forms and aqueous slurry 1 is obtained.
• Aqueous slurry 1 may be used in a step (b) as such, or the solid from aqueous slurry 1 may be isolated (Wet Cake), e.g.
• Step (a) preferably is carried out at temperatures from 10 to 40°C, preferably at room temperature.
• Step (b) may be carried out by mixing the aqueous slurry of step (a), or the isolated solids from the aqueous slurry of step (a) with an alumina precursor, e.g. aluminium hydroxide, e.g. a Boehmite, in aqueous suspension.
• Step (b) preferably is carried out at temperatures from 10 to 40°C, preferably at room temperature.
• An aqueous suspension of solids is obtained.
• a treatment with a surfactant is carried out in step (b) by adding a surfactant to the aqueous suspension.
• the alumina precursor may be treated with a surfactant before mixing with the aqueous suspension of step (a).
• step (c) the solids from the aqueous suspension are isolated, e.g. by filtration,
• centrifugation preferably filtration and are dried. Drying preferably is carried out at temperatures from 90 to 150°C, optionally under vacuum.
• the solid composition is contacted, e.g. impregnated with a surfactant. A solid composition is obtained which is subjected to step (d).
• step (c) The solid composition obtained in step (c) is subjected to calcination in step (d), i.e. heat treated at temperatures from 450 °C to 1200°C, preferably 600 to 1000°C, e.g. 800 to 900°C, for at least 1 hour, e.g. for several hours, e.g. 1 to 10 hours, such as 2 to 6 hours.
• calcination in step (d) i.e. heat treated at temperatures from 450 °C to 1200°C, preferably 600 to 1000°C, e.g. 800 to 900°C, for at least 1 hour, e.g. for several hours, e.g. 1 to 10 hours, such as 2 to 6 hours.
• a surfactant in a process of the present invention may influence, e.g. may increase the stability of the surface area of the final Al/Ce/Zr composition.
• a surfactant is used in a process according to the present invention, preferably either the starting mixture of step (a) comprises a surfactant, e.g. a surfactant is added in step (a), or a surfactant is added in step (b); or a surfactant is added in step (d).
• the present invention provides a process according to the present invention comprising using a surfactant; e.g.
• the aqueous slurry of step (a) comprises a surfactant, e.g. a surfactant is added in step (a); and/or
• the aqueous suspension of solids in step (b) comprises a surfactant, e.g. a surfactant is added in step (b); and/or
• step (d) comprising a surfactant, e.g. a surfactant is added to the solid compostion in step (d).
• a surfactant e.g. a surfactant
• the aqueous slurry in step (a) and/or the aqueous suspension of solids in step (b) comprises a surfactant, e.g. wherein the surfactant is added before the solid component is added.
• surfactants for use in a process of the present invention include compounds which lower the interfacial tension of a liquid and a solid, e.g. including organic compounds, e.g. such which are amphiphilic and contain both hydrophobic groups and hydrophilic groups.
• Preferred surfactants include nonionic surfactants, e.g. nonionic surfactants comprising ethylene oxide / propylene oxide units, such as Triton ® , Tergitol ® , e.g. including ethyl phenol ethoxylates and ethylene oxide / propylene oxide copolymers, or lauric acid.
• step (c) comprises
• filtration and air drying e.g. drying at elevated temperatures and/or
• the enhanced stability of surface area of the Al/Ce/Zr compositions may be influenced by the chemical nature of the alumina precursor used.
• the alumina precursor in step (b) comprises Boehmite of formula (A10(OH)xH 2 0) and optionally aluminium hydroxide, optionally the alumina precursor in step (b) consists of Boehmite.
• a preferred Boehmite in a process of the present invention has pore volumes of 0.4 to 1.2 ml/g and/or crystallite sizes of 4 to 40 nm, preferably 4 to 16 nm, measured at the (120) reflection.
• Boehmite in a process of the present invention preferably has a purity as follows: Contents of
• a Boehmite according to the present invention is a compound of formula AIO(OH) x H 2 0.
• Preferred is a Boehmite obtainable by hydrolysis of aluminium alcoholate, e.g. obtainable via a process as disclosed in US 5,055,019 Extractor Aluminas").
• boehmitic alumina with a purity of at least 99,95% A1 2 0 3 is obtained having defined pore radii in the range of 3 to 100 nm by salt-free hydrolysis of aluminium alcoholates in water, whereby the Boehmite slurry obtained is aged in a autoclave at a water vapour pressure of 1 to 30 bar corresponding to a temperature of 100 to 235°C over a period of time of 0.5 to 20 h and by stirring with a circumferential speed of 1.0 to 6.0 m/s.
• aluminium alcoholates are used as starting material to obtain a Boehmite of high purity.
• the aluminuim alcoholates can be produced by the so called Ziegler-Process preferably comprising a filtration step as a cleaning step.
• C - to C 24 -alcohols, or mixtures thereof may be used to form the aluminium alcoholates.
• a Boehmite or Boehmite slurry used comprise lanthanum or barium compounds, preferably such which are soluble in water under the reaction conditions, in order to obtain a Boehmite, comprising 1 to 10 % by weight of lanthanum and/or barium, calculated as La 2 0 3 or BaO, respectively,
• the process of the present invention is useful for the preparation of a catalyst composition with outstanding favorable and surprising properties as described herein.
• comparative example 1 of the present application it is shown that, in case that the co- precipitation process as disclosed in EP 1 172 139 is applied to a composition being different from the compositions disclosed therein, a material with significant lower surface stability in comparison with a composition prepared according to the present invention is obtained.
• a composition consisting of 50% A1 2 0 3 , 10% Ce0 2 , 36.5% Zr0 2 , 1% La 2 0 3 and
• comparative example 2 For the purpose of investigating the surface stability at more severe ageing conditions (higher temperatures and longer ageing time) comparative example 2 is provided in the present application. It is shown that a composition consisting exactly of the same
• the present invention provides a composition, e.g. a catalyst composition obtainable, e.g. obtained, according to a process of the present invention.
• a calcined mixed oxide obtainable, e.g. obtained, according to a process of the present invention preferably is a composite material comprising aluminium oxide and a solid solution of cerium oxide and zirconium oxide, optionally further comprising rare earth metal oxides.
• Boehmite may improve the stability of surface area of Al/Ce/Zr- oxide compositions.
• the present invention provides the use of a Boehmite for improving the stability of surface area of Al/Ce/Zr- oxide compositions.
• a solid solution of cerium oxide and zirconium oxide, optionally further comprising rare earth metal oxides may be obtained as appropriate, e.g. according, e.g. analogously, to a known process.
• BET BET theory aims to explain the physical adsorption of gas molecules on a solid
• the percent indication of the oxides as indicated herein are indications in nominal by weight”.
• Surface area (BET) analysis was performed with Quantachrome NOVA 4000 according to DIN (Deutsche Industrie Norm) 66131 under use of N 2 .
• An aqueous slurry as referred to herein is either an aqueous slurry 1, or an aqueous slurry 2.
• An aqueous slurry 1 is a suspension of hydroxides of cerium and zirconium, optionally comprising further rare earth metal salts which was treated with ammonium hydroxide, and optionally with H 2 0 2 and/or a surfactant.
• An aqueous slurry 2 is an aqueous slurry 1 isolated as a solid (Wet Cake) and re- suspended in water, optionally further treated, e.g. with ammonia and/or a surfactant.
• Ce0 2 (29%) Zr0 2 (62%) La 2 0 3 (9%) / TO was obtained in the form of a solid and was washed with deionised water to obtain Wet Cake A: CeO 2 (29%) ZrO 2 (62%) La 2 O 3 (9%) / TO.
• Yield approximately 500 kg of Wet Cake A corresponding to 120 kg of TO.
• An aluminium alkoxide mixture such as obtained as an intermediate during the synthesis of the Ziegler/Alfol process, was hydrolyzed at 90°C in a stirring vessel with deionized water. Two immiscible phases were obtained, i.e. an upper alcohol phase and a lower
• alumina/water phase contained Boehmite with an Al 2 O 3 content of 10-11%.
• 500g of this alumina/water phase (pH 9) were separated and added to a reactor in batch wise operation, at ambient reactor pressure and at 98°C. After setting the reactor conditions, ageing took place for 16 hours using a conventional stirrer with a peripheral speed of 1.6 m/s corresponding to a stirring rate of 500 rpm.
• the crystallite size of the spray dried material, measured at the (120) reflection was 13.5 nm.
• DISPERAL HP 14 was obtained.
• An aluminium alkoxide mixture such as obtained as an intermediate during the synthesis of the Ziegler/Alfol process, was hydrolyzed at 90°C in a stirring vessel with deionized water. Two immiscible phases were obtained, i.e. an upper alcohol phase and a lower
• alumina/water phase contained Boehmite and the alumina/water phase was separated.
• the crystallite size of the spray dried material, measured at the (120) reflection, 2 was 5.0 nm. PURAL SB was obtained.
• the aqueous suspension obtained was stirred vigorously using an external stirrer for 30 minutes, was filtered and the solid obtained was dried at 120°C overnight.
• the solid composition obtained was calcined at 850°C / 4 hours. Approximately 50 g of Ce0 2 (14.5%) Zr0 2 (31%) La 2 0 3 (4.5%) Al 2 O 3 (50%) were obtained. BET after 850°C / 4 hours (Fresh material) : 76 m 2 /g
• the aqueous suspension obtained was vigorously stirred using an external stirrer for 2 hours, filtered, and the solid obtained was dried at 120°C overnight (approximately 20 hours).
• the solid composition obtained was calcined at 850°C / 4 hours.
• the aqueous suspension obtained was vigorously stirred using an external stirrer for 2 hours and was filtered.
• the solid obtained was dried at 120°C overnight (approx imately 20 hours).
• the solid composition obtained was calcined at 850°C / 4 hours to obtain 50 g of CeO 2 (10%) Zr0 2 (36.5%) La 2 0 3 (l%) Nd 2 0 3 (2.5%) Al 2 O 3 (50%).
• the mixture obtained was vigorously stirred using an external stirrer for 2 hours, filtered, and the solid obtained was dried at 120°C overnight and calcined at 850°C / 4 hours.
• 100 g of Ce0 2 (13%) Zr0 2 (47.5%) La 2 0 3 (1.3%) Nd 2 0 3 (3.25%) Al 2 0 3 (35%) were obtained.
• the aqueous suspension obtained was vigorously stirred using an external stirrer for 2 hours and filtered.
• the solid obtained was dried at 120°C overnight (approx. 20 hours) and the solid composition obtained was calcined at 850°C / 4 hours.
• the aqueous suspension obtained was vigorously stirred using an external stirrer for 2 hours and was filtered.
• the solid obtained was dried at 120°C overnight and the solid composition obtained was calcined at 850°C / 4 hours.
• the aqueous suspension obtained was vigorously stirred using an external stirrer for 2 hours and filtered.
• the solid obtained was dried at 120°C overnight and the solid composition obtained was calcined at 850°C / 4 hours. 100 g of Ce0 2 (24.1%) Zr0 2 (17.3%) La 2 O 3 (0.5%) Y 2 O 3 (0.9%) Al 2 0 3 (57.2) were obtained.
• composition of the composite material obtained according to Example 13 corresponds exactly to the composition disclosed in example 24 of EP 1 172 139.
• the following BET values are reported in EP 1 172 139:
• the aqueous suspension obtained was vigorously stirred using an external stirrer for 2 hours and spray dried.
• the solid composition obtained was calcined at 850°C / 4 hours.
• composition of the composite material obtained according to Example 14 corresponds exactly to the composition disclosed in example 24 of EP 1 172 139.
• the following BET values are reported in EP 1 172 139:
• the aqueous suspension obtained was vigorously stirred using an external stirrer for 2 hours and filtered.
• the solid obtained was dried at 120°C overnight and the solid composition obtained was calcined at 850°C / 4 hours.
• the title composition correponds to a composition of 50% Al 2 0 3 /La 2 0 3 (97% / 3%) and 50% Ce0 2 / Zr0 2 / Pr 6 On / Fe 2 0 3 (56% / 30% / 7% / 7%).
• the mixture obtained was stirred for 1 hour and the pH of the mixture obtained was adjusted to 8 using 30% nitric acid.
• the slurry obtained was maintained at 60°C for 1 hour.
• the mixture obtained was filtered and the solid obtained was washed with deionized water at 60°C until the electrical conductivity of the filtrate was less than 0.5 S-m -1 .
• the Wet Cake 3COMP obtained was isolated and resuspended in 850 mL of water, the pH of the slurry obtained was adjusted to 10 and the mixture obtained was autoclaved at 120°C for 6 hours.
• the slurry obtained was cooled down and the pH of the mixture obtained was adjusted to 8 using 30% nitric acid.
• the mixture obtained was stirred for 30 minutes.
• the slurry obtained was maintained at 60°C for 1 hour and filtered.
• the solid obtained was washed with deionised water and directly calcined at 850°C. BET was measured at different ageing temperatures.

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