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(11) EP 2 540 391 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: (51) Int Cl.: 02.01.2013 Bulletin 2013/01 B01J 23/10 (2006.01) B01J 37/00 (2006.01) B01J 37/03 (2006.01) C01F 17/00 (2006.01) (2006.01) (2006.01) (21) Application number: 11005382.4 C01G 25/00 B01J 35/10

(22) Date of filing: 01.07.2011

(84) Designated Contracting States: (72) Inventors: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB •Schermanz,Karl GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO 9314 Launsdorf (AT) PL PT RO RS SE SI SK SM TR •Sagar,Amod Designated Extension States: 9330 Althofen (AT) BA ME (74) Representative: Schwarz & Partner (71) Applicant: Treibacher Industrie AG Patentanwälte 9330 Treibach-Althofen (AT) Wipplingerstraße 30 1010 Wien (AT)

(54) Ceria zirconia alumina composition with enhanced thermal stability

(57) A process for the preparation of a composition (c) optionally isolating the precipitate obtained in step (b), comprising Al-, Ce- and Zr-oxides, comprising (d) treating the aqueous suspension obtained in step (b) (a) preparing an aqueous solution of a mixture of metal or the isolated precipitate obtained in step (c) with a sur- salts of cerium, zirconium and aluminium, wich aqueous factant, and solution optionally comprises one or more salts of the (e) isolating the precipitate obtained in step (d) and treat- Rare Earth Metals other than cerium, ing said precipitate at a temperature from 450°C to (b) adding to the solution obtained in step (a) a base at 1200°C; temperatures from 0°C to 95°C and precipitating the and a composition obtainable or obtained by such proc- mixed metal salts in the form of hydroxides or oxy-hy- ess. droxides, EP 2 540 391 A1

Printed by Jouve, 75001 PARIS (FR) 1 EP 2 540 391 A1 2

Description least one member selected from CeO2, La2O3, Nd2O3, Pr6O11, Sm 2O3,Y2O3 and optionally other rare earth met- [0001] The present invention refers to compositions al oxides. The compositions are described to be made based on ceria (oxide of cerium), zirconia (oxide of zir- by co-precipitation starting from a metal salt solution us- conium) andalumina (oxide ofaluminium) with enhanced 5 ing caustic alkali as a precipitation agent. A strict small thermal stability. pH range is to be kept: According to WO 2006/070201 [0002] Such compositions may be used as washcoats the deviation of the pH during precipitation must not be in the application of exhaust gas aftertreatment of com- more than 6 1. Furthermore the process requires an bustion engines such as fuel- and dieselengines e.g. as autoclaving step of the isolated precipitate at 120°C prior components of catalysts (mainly Three Way Catalysts, 10 to the final calcination of the material establishing a dis- TWC) but also in other parts integrated into the exhaust advantage of said preparation process. stream such as NOx traps, Diesel Oxidation Catalysts [0007] In example 6 in WO 2006/070201 an Al/Ce/Zr-

(DOC) and Diesel Particulate Filters (DPF). composition oxide is reported consisting of 51% Al2O3, [0003] Ceria-Zirconiabased mixedoxides andalumina 14.2% CeO2 and 34.8% ZrO2 exhibiting a surface area are widely used in automotive application for the catalyst 15 of 43 m2/g after being heat treated at 850°C / 4 hours preparation. For example, in WO 2008/113457 the prep- and at 1100°C / 2 hours. After more severe ageing (heat aration of washcoats introducing separateley mixed ox- treatment at 850°C / 4 hours and 1200°C / 2 hours) the ides of ceria / zirconia and alumina (lanthanum doped composition exhibits a surface area of 16 m2/g only. No aluminium oxide) is described and thus is a well estab- information on the surface areas are disclosed for the lished process. 20 case that the composition is heat treated for a longer [0004] However, there is also drawn attention to other period of time, e.g 850°C / 4 hours + 1150°C / 36 hours. types of composition materials consisting of Al2O3 with [0008] To investigate the properties of heat stability af- the balance typically being CeO2, ZrO2 and perhaps ter ageing for a longer period of time the compound was some stabilizers such as rare earth metal oxides. synthesized as disclosed in comparative example 2 of [0005] For example in EP 1 172 139 there is reported 25 the present application according to the method of ex- on the preparation and the thermal stability of several Al- ample 6 of WO 2006/070201. The surface area values Ce-Zr-Y-La oxide compositions. There are disclosed var- found after heat treatment at 850°C / 4 hours +1050°C / ious compositions consisting of 2O Al3/ CeO2/ZrO2 36 hours and after heat treatment at 850°C / 4 hours + 2 2 /Y2O3/La2O3 with different ratios of the oxides being 1150°C/ 36 hourswere 50 m /gand 19 m /g,respectively present in the compositions. The materials are described 30 and the disadvantage of a rather high drop in surface to be prepared via co-precipiation starting from the cor- area arises. responding metal salt solutions (including the Alumina in [0009] In spite of the fact that oxides of alumina and form of Al-Nitrate). As intermediates after conducting the oxides of ceria/zirconia as well as composition oxides of co-precipitation process suspensions of Al-Ce-Zr-Y-La Al/Ce/Zr are already used worldwide in automotive ap- hydroxidesare yielded which aftercalcination were trans- 35 plications, there is still the need to improve production ferred into the corresponding oxides (see page 8, lines routes and the performance of such materials, especially 1 to 6). The surface area of such composition oxides is in terms of their thermal stability to avoid a rather high described to be dependent on the amount of Al 2O3 being drop of surface area when exposing such materials to present in the composition. In examples 10 to 22 in which higher temperatures and to enhance the life time of such 40 the Al2O3 content is in the range between 21 and 25 catalysts. weight % (calculated from the molar ratios disclosed in [0010] In particular, the present invention is aimed to table 2) the specific surface area is less than 15 2m/g solve disadvantages related with the limited thermal sta- after the compounds have been subjected to heat treat- bility of Al/Ce/Zr compositions and to provide composi- ment at 1100°C for 20 hours (see table 2 page 14). Higher tions with enhanced surface stability, particularly after values of the surface area are indicated after heat treat- 45 long term ageing. ment at 1100°C / 20 hours in case that the Al 2O3 content [0011] It is known from prior art such as EP 2 223 905 is increased as disclosed in the examples 24, 27 and 31. that the surface stability of Ceria/Zirconia Mixed Oxides More in detail, in example 24 corresponding to a compo- can be enhanced by a treatment of the precipitated met- sition with an Al2O3 content of 57% weight, there is dis- als with a surfactant. This is outlined in several examples, closed a surface area of 27 2 m/g after calcination at 50 in which a precipitate of the metals is treated e.g. by lauric 1100°C / 20 hours, and in examples 27 and 31 which acid followed by converting the treated precipitate into correspond to an Al 2O3 content of 63% surface areas of mixed oxides. The surface area after heat treatment of 31 m2/g and 30 m2/g, respectively, after calcination at the Ceria/Zirconia mixed oxides at 1100°C / 4 hours ex- 1100°C / 20 hours are indicated. hibits values up to approximately 22 m 2/g. [0006] In WO 2006/070201 there is reported an im- 55 [0012] In comparative example 3 of the present appli- proved method for the formation of composition hydrox- cation it is shown that a ceria/zirconia mixed oxide con- ides or oxides comprising, on an oxide basis, alumina sisting of exact the same element ratio (based on Rare (Al2O3) and Zirconia (ZrO2) and optionally including at earths) as used in example 1 according to the invention

2 3 EP 2 540 391 A1 4 exhibits a surface area of 18 m2/g after heat treatment arate precipitation of the Ceria/ Zirconia and the Alumina at 1100°C/ 4 hours when a surfactant treatmentis applied may be attributed to the stabilization of a porous system in the process. The increase of the surface stability after in a Ceria Zirconia system by Alumina. Such a stabiliza- heat treating the compound at 1100°C / 4 hours of the tion of a Ceria-Zirconia for example is described by mixed ceria-zirconia oxide even after surface treatment 5 Tadashi Suzuki et.al, R&D Review of Toyota CRDL, Vol. is relatively low compared to other mixed ceria/zirconia 37 Nr.4, page 28 ff. mixed oxides known from prior art. For example, in WO [0016] Now it was surprisingly found that a synergistic 2007/093593 there are disclosed ceria/zirconia mixed effect on thermostability, yielding Ceria Zirconia Alumina oxides exhibiting surface areas up to 32 m 2/g after heat Composite Oxides with significant higher thermostability treatment 1100°C / 10 hours. In addition it is shown in 10 after heat treatment at 1100°C / 20 hours may be comparative example 4 and 5 of the present application achieved when preparing the composite oxide according that Aluminium Oxides prepared from Aluminium- Nitrate to the process according to the present invention. Nona Hydrate, the same starting material as used in ex- [0017] In one aspect the present invention provides a ample 1 according to the present invention, exhibits ex- process for the preparation of a composition comprising tremley low surface areas after being subjected to pre- 15 Al-, Ce- and Zr-oxides, which process comprises the cipitation and conversion into the corresponding oxides, steps of even after treatment with a surfactant. Thus the Alumina prepared by precipitation and conversion into the Oxide (a) preparing an aqueous solution of a mixture of exhibits a surface area of 1 m2/g only after being heat metal salts of cerium, zirconium and aluminium, treated at 1100°C / 4 hours. A surfactant treatment of the 20 which aqueous solution optionally comprises one or precipitate, as shown in comparative example 5, exhibits more salts of the Rare Earth Metals other than ceri- a surface area of 6.1 m2/g only after a heat treatment of um, the precipitate at 1100°C / 4 hours. Therefore a mixture e.g. either by dissolving water soluble salts such as of a 50% Ceria/ Zirconia and 50% Alumina, both prepared a nitrate, halogenide, e.g. chloride, or dissolving wa- by a separate precipitation process and additionally ap- 25 ter insoluble metal salts, such as a carbonate, hy- plying a surfactant as known to prior art will yield a Com- droxide, by acid treatment, such as by treatment with 2 posite oxide with a surface area of < 15 m /g only. HNO3, HCl, [0013] From the data disclosed in EP 2 223 905 and (b) adding to the solution of obtained in step (a) a out of the performed experiments as mentioned above it base, suchas an inorganic base,preferably aqueous 30 may be concluded that a composition made from Metal ammonia, optionally in the presence of H 2O2, at tem- Nitrate Solutions based on Ce/Zr and Alumina made via peratures from 0°C to 95°C, preferably at room tem- precipitation and using a surfactant will lead to a product perature; with low surface stability only. The examples demon- and precipitating the mixed metal salts in the form strates that is impossible to prepare a thermostable com- of hydroxides or oxy-hydroxides, position based on Ceria Zirconia-Alumina even with the 35 (c)optionally isolating the precipitate obtained instep help of a surfactant. (b), [0014] From examples outlined in EP 1 172 139, e.g. (d) treating the aqueous suspension obtained in step fromexample 24 (a Ce/Zr compound containing 57% Alu- (b), or the isolated precipitate obtained in step (c) mina) and example 26 (a Ceria /Zirconia compound con- with a surfactant, and taining 46% Alumina) it may be concluded that a co- pre- 40 (e) isolating the precipitate obtained in step (d) and cipitation process might contribute moderately to the sur- treating said precipitate at a temperature from 450°C face stability of the yielded composite oxide, however, to 1200°C; preferably from 600°C to 1200°C; compounds showing an Alumina content up to 60% ex- hibit in fact a moderate surface stability only, not exceed- e.g. such that the cerium content obtained, calculated as ing values of 32 m 2/g after calcination of the compounds 45 cerium oxide is in the range from 5 to 70% by weight, at 1100°C / 20 hours. This conclusion was confirmed also preferably 5 to 50% by weight, more preferably 5 to 30% by the experiment as described in comparative example by weight, most preferably 5 to 15 % by weight of the 1 in the present application. In case that the co-precipi- composition, tation process is performed according to the process dis- e.g. such that the zirconium content obtained, calculated closed in EP 1 172 139 with a compound relating to the 50 as zirconium oxide is in the range from 5 to 70% by same composition as disclosed in example 1 of the weight, preferably 10 to 60% by weight, more preferably present invention (and resulting in a composition of the 20 to 50 % by weight, most preferably 30 to 40 % by present invention) in fact leads to a material showing a weight, of the composition obtained, surface area of 30.7 m 2/g after ageing 1100°C / 20 hours e.g. such that Alumina content, calculated as aluminium only. 55 oxide obtained is in the range from 20 to 80% by weight, [0015] The moderate increase of the surface area in a preferably 25 to 75% by weight, more preferably 35 to Alumina-Ceria-Zirconia Mixed Oxide (prepared via co- 65 % by weight, most preferably 45 to 55 % by weight, precipitation) after heat treatment in comparison to a sep- of the composition,

3 5 EP 2 540 391 A1 6 e.g. the remainder being any other Rare Earth Metal Ox- in degree Celsius (°C) and are uncorrected. ide, or mixtures thereof. [0032] Surface area (BET) analysis was performed [0018] Cerium oxide as used herein includes Ce2O3 with Quantachrome NOVA 4000 according to DIN (Deut- and CeO2, preferably CeO2. sche Industrie Norm) 66131. 5 [0019] Aluminiumoxide as usedherein includes Al 2O3. [0020] Zirconium oxide as used herein includes ZrO 2. Preparation of Compositions according to the [0021] In a composition obtained according to a proc- present invention ess of the present invention Ce, Zr- oxides may optionally being present in the form of a solid-solid solution. Example 1 [0022] A process provided by the present invention is 10 herein also designated as "A process of (according to) [0033] CeO2(10%) ZrO2(36.5%) La2O3(1%) Nd2O3 the present invention". (2.5%) Al2O3(50%) [0023] An advantageous embodiment of a process of [0034] 92.8 g of an aqueous solution of zirconium ni- the present invention is characterized in that the Ce/Zr/Al trate (ZrO2 content = 29.5%), 26.32 g of of an aqueous 15 metal salt solution used according to step (a) contains at solution of cerium nitrate (CeO2 content = 28.5%), 1.99 least one rare earth metal element, preferably selected g of lanthanum nitrate in crystal form (La2O3 content = from Y, La, Pr, Nd, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb 37.7%), 4.91 g of neodymium nitrate in crystal form and Lu, e.g. La, Nd. (Nd2O3 content = 38.2%) and 275.74 g of aluminium ni- [0024] According to the present invention it was sur- trate nonahydrate (Al2O3 content = 13.6%) were treated prisingly found that the use of a surfactant in the process 20 with 600 mL of deionised water, the mixture obtained was of the present invention may significantly increase the stirred for a few minutes and a clear solution was ob- stability of the surface area of the composition obtained. tained. To the mixture obtained 74.6 mL of aqueous 35%

[0025] Appropriate surfactants for use in a process of H2O2 cooled to 10°C was added and the mixture obtained the present invention include compounds which lower was stirred for approximately 45 minutes. To the mixture the interfacial tension of a liquid and a solid, e.g. including 25 obtained aqueous 24% ammonia solution cooled to 10°C organic compounds, e.g. such which are amphiphilic and was added until a pH = 9.5 was reached. The mixture contain both, hydrophobic groups and hydrophilic obtained was stirredfor 15 minutes. The mixture obtained groups. Preferred surfactants include nonionic sur- was filtered and the precipitate obtained was washed with factants, e.g. nonionic surfactants comprising ethylene deionised water and afterwards impregnated with 22.7 g oxide / propylene oxide units, such as Triton ®, Tergitol®, 30 of Triton X-100. The wet cake obtained was dried at e.g. including ethyl phenol ethoxylates and ethylene ox- 120°C and calcined at 850°C / 4 hours to yield 75 g of ide / propylene oxide copolymers, or lauric acid. composite oxide. [0026] A process of the present invention is useful for the preparation of a composition with outstanding favo- BET after 850°C / 4 hours (Fresh material) : 162 m 2/g rable and surprising properties as described herein, e.g. 35 BET after 950°C / 5 hours: 127.5 m2/g useful as a catalyst composition, e.g.for exhaust gas af- BET after 1000°C / 4 hours: 116.5 m2/g tertreatment of combustion engines. BET after 1100°C / 2 hours: 66.2 m2/g [0027] Thus, in a further aspect the present invention BET after 1100°C / 20 hours: 45.2 m2/g provides a composition, e.g. a catalyst composition, ob- tainable, e.g. obtained, according to a process of the40 Example 2 present invention.

[0028] The increase of the surface area of a composi- [0035] CeO2(25%) ZrO2(20%) La2O3(2.5%) Nd2O3 tion obtainable or obtained according to the present in- (2.5%) Al2O3(50%) vention compared to a material prepared without a sur- [0036] 44.58 g ofan aqueous solution of zirconyl nitrate 45 factant treatment, is at least 10 %, preferably 20%, more (ZrO2 content = 22.43%), 42.44 g of an aqueous solution preferably 30%, most preferably 40 -50% after heat treat- of cerium nitrate (CeO 2 content = 29.45%), 3.32 g of lan- ing the material at 1100°C / 2 hours and 1100°C / 20 thanum nitrate in crystal form (La2O3 content = 37.7%), hours respectively. 3.3 g of neodymium nitrate in crystal form (Nd 2O3 content [0029] A composition obtained or obtainable according = 37.93%) and 183.82 g of aluminium nitrate nona hy- 50 to the present invention with an Alumina content of 40 to drate (Al2O3 content = 13.6%) were treated with 600 mL 60% by weight the BET measured after calcining for 2 of deionized water, the mixture obtained was stirred for hours at 1100°C is from about, e.g. from, 55 to 80 m 2/g, a few minutes until a clear solution was obtained. To the 2 2 such as from 55 to 75 m /g, e.g. 55 to 70 m /g, e.g. 60 mixture obtained42.78 mL ofaqueous 35% H 2O2(cooled to 70 m2/g. to 10°C) was added and the mixture obtained was stirred [0030] The percentage (%) of the metal salts as indi- 55 for approximately 45 minutes. To the mixture obtained, cated herein, including the examples, are percents by aqueous 24% ammonia solution (cooled to 10°C) was weight. added until a pH = 9.5 was reached. The mixture obtained [0031] In the following examples all temperatures are was stirred for 10 minutes. To this slurry was added

4 7 EP 2 540 391 A1 8

20.71g of lauric acid and the mixture was further stirred water 14.77 g of an aqueous solution of cerium nitrate vigorously for 1h at room temperature. Finally the mixture (CeO2 content = 28.85%) and 43.02 g of an aqueous wasfiltered and theprecipitate obtained was washed with solution of zirconyl nitrate (ZrO 2 content = 24.27%) were deionized water. The wet cake obtained was dried at added. The mixture obtained was stirred for 15 minutes. 120°C and calcined at 850°C / 4 hours to yield 50 g of 5 To the mixture obtained a 25% aqueous solution of NaOH composite oxide. BET was measured after ageing the were added whereupon a precipitate formed. The pH val- composite oxide 1100°C/20h. ue was kept close to 10 during precipitation. To the slurry 2 BET after 1100°C / 20 hours: 49.5 m /g. obtained 5 g of 35 % H 2O2 were added and the pH of the [0037] From example 1 and 2 when compared with pri- mixture obtained was adjusted to 10. The mixture ob- or art results it is evident that the BET values of the com- 10 tained was stirred for 1 hour and the pH of the mixture position prepared according to the present invention sur- obtained was adjusted to 8 using 30% HNO 3. The slurry prisingly are much higher than the BET values of the obtained was maintained at 60°C for 1 hour. The mixture compositions prepared according to prior art, e.g. which obtained was filtered and the solid obtained was washed can be seen from the comparative examples below. with deionized water at 60°C until the electrical conduc- 15 tivity of the filtrate did not change. The wet cake obtained Comparative Examples was isolated and resuspended in 850 mL of water, the pH of the slurry obtained was adjusted to 10 and the Comparative example 1 mixture obtained was autoclaved at 120°C for 6 hours. The slurry obtained was cooled down and the pH of the 20 [0038] CeO2(10%) ZrO2(36.5%) La2O3(1%) Nd2O3 mixture obtained was adjusted to 8 using 30% nitric acid. (2.5%) Al2O3(50%) The mixture obtained was stirred for 30 minutes. The [0039] Preparation according to the process dis- slurry obtained was maintained at 60°C for 1 hour and closed in example 1 of EP1 172 139 filtered. The solid obtained was washed with deionised [0040] 92.8 g of an aqueous solution of zirconium ni- water and directly calcined at 850°C. BET was measured 25 trate (ZrO2 content = 29.5%), 26.32 g of an aqueous so- at different ageing temperatures. lution of cerium nitrate (CeO2 content = 28.5%), 1.99 g 2 of lanthanum nitrate in crystal form (La2O3 content = BET after 850°C / 4 hours (Fresh material): 107 m /g 37.7%), 4.91 g of neodymium nitrate in crystal form BET after 1000°C / 4 hours: 77 m2/g 2 (Nd2O3 content = 38.2%) and 275.74 g of aluminium ni- BET after 1100°C / 4 hours: 49 m /g 30 2 trate nonahydrate (Al2O3 content = 13.6%) were treated BET after 1150°C / 36 hours: 19m /g with 600 mL of deionised water, the mixture obtained was stirred for a few minutes and a clear solution was ob- Comparative example 3 tained. To the mixture obtained 4.62 mL of aqueous 35% H2O2 cooled to 10°C were added and the mixture ob- ZrO2(73%) Ce02(20%) La203(2%) Nd2O3(5%) pre- tained was stirred for approximately 20 minutes. To the 35 pared via surfactant treatment mixture obtained aqueous 24% ammonia solution cooled to 10°C was added until a pH = 7 was achieved. The [0044] A mixed metal solution corresponding to the mixture obtained was stirred for 15 minutes. The mixture composition given above was prepared by mixing 27.33 obtained was filtered and the precipitate obtained was ml of zirconyl nitrate solution (ZrO 2: 22.8%) with 121 mL 40 washed with deionised water. The wet cake obtained was of deionised water, 5.045 g cerium III nitrate (CeO2: dried at 120°C and heat treated at 300°C / 5 hours and 39.6%) with 59 mL of deionoised water, 0.53 g of lantha- afterwards calcined at 700°C / 5 hours to yield 75 g of num nitrate (La2O3: 37.4%) in 12 mL of deionised water, composite oxide. 1.302 g neodymium nitrate (Nd2O3: 38%) in 7 mL of deionised water and combining the solutions. After stir- BET after 300°C / 5 hours + 700°C / 5 hours (Fresh 45 ring for a few minutes there was yielded a clear solution. 2 material) : 148 m /g [0045] To the solution obtained 23.2 mL of H 2O2 (30%, BET after 950°C / 5 hours: 101 m 2/g Sigma Aldrich, cooled to 5-10°C) were added. The mix- BET after 1000°C / 4 hours: 92 m 2/g ture obtained was stirred at room temperature for about BET after 1100°C / 2 hours: 47 m 2/g 45 minutes and to the mixture obtained 24% aqueous BET after 1100°C / 20 hours: 31 m 2/g 50 ammonia solution (cooled to 5-10°C) were added at room temperature with a dropping rate of 40 ml/min to obtain Comparative example 2 pH 9.5. The mixture obtained was kept stirring for a few minutes. During precipitation the temperature of the mix-

[0041] CeO2(14.2%) ZrO2(34.8%), Al2O3(51%) ture raised up to 60°C. Impregnation of the precipitates [0042] Preparation according to example 6 of WO 55 in the reaction mixture was done by adding 3.77 g of 2006/070201 lauric acid to the reaction mixture. The slurry so obtained [0043] To 112.5 g of aluminium nitrate nonahydrate was kept at vigorous stirring for at least 4h. The reaction (Al2O3 content = 13.6%) dissolved in 1.5 L of deionised mixture was then filtered and washed extensively with

5 9 EP 2 540 391 A1 10 deionised water. The filter cake was then dried in an oven a few minutes and a clear solution was obtained. To the at 100°C overnight (16 h) and calcined at 500°C for 4 mixture obtained42.78 mL ofaqueous 35% H 2O2(cooled hours to yield 10 g of composite oxide. to 10°C) was added and the mixture obtained was stirred for approximately 45 minutes. To the mixture obtained BET after 500°C/4 hours (fresh): 110 m2/g 5 aqueous 24% ammonia solution (cooled to 10°C) was BET 1100°C / 4 hours (aged): 18 m 2/g added until a pH = 7.5 was reached. The mixture obtained was stirred for 15 minutes. Finally the mixture was filtered Comparative example 4 and the precipitate obtained was washed with deionized water. The wet cake obtained was dried at 120°C and 10 Synthesis of Aluminium oxide (Al 2O3) out of Alumin- calcined at 850°C / 4 hours to yield 50 g of composite ium Nitrate Nonahydrate oxide. BET was measured after ageing the composite oxide 1100°C/20h. [0046] 100 g of Aluminium nitrate nonahydrate were dissolved in 500 ml of deionized water and 18% aqueous BET after 1100°C / 2 hours: 39 m2/g. ammonia solution (cooled at 10°C) were added until pH 15 BET after 1100°C / 20 hours: 32.5 m2/g. 7.5. The mixture obtained was stirred further for 15 min, filtered and the solid obtained was washed with deionized water. The wet cake so obtained was dried overnight at Claims 120°C and the dried material obtained was calcined at 500°C / 4 hours to yield 13.6 g of Aluminium oxide. BET 20 1. Process for the preparation of a composition com- was measured after calcining the material 1100°C / 4 prising Al-, Ce- and Zr-oxides, which process com- hours. prises the steps of

BET after 500°C / 4 hours: 138 m 2/g (a) preparing an aqueous solution of a mixture BET after 1100°C / 4 hours: 1 m 2/g 25 of metal salts of cerium, zirconium and alumin- ium,wich aqueoussolution optionally comprises Comparative example 5 one or more salts of the Rare Earth Metals other than cerium, Synthesis of Aluminium oxide (Al 2O3) out of Alumin- (b) adding to the solution of obtained in step (a) 30 ium Nitrate Nonahydrate using a surfactant a base, optionally in the presence of H2O2, at temperatures from 0°C to 95°C and precipitating [0047] 100 g of Aluminium nitrate nonahydrate were the mixed metal salts in the form of hydroxides dissolved in 500 ml of deionized water and 18% aqueous or oxy-hydroxides, ammonia solution (cooled at 10°C) was added until pH (c) optionally isolating the precipitate obtained 7.5. The mixture obtained was stirred further for 15 min- 35 in step (b), utes and then filtered and washed with deionized water. (d) treating the aqueous suspension obtained in The wet cake so obtained was impregnated with 9.34 g step (b), or the isolated precipitate obtained in of Triton X-100 and then dried overnight at 120°C. The step (c) with a surfactant, and dried material obtained was calcined at 500°C / 4 hours (e) isolating the precipitate obtained in step (d) to yield 13.6g of Aluminium oxide. BET was measured 40 and treating said precipitate at a temperature after calcining the material 1100°C / 4 hours. from 450°C to 1200°C.

BET after 500°C / 4 hours: 222 m 2/g 2. A process according to claim 1, wherein an aqueous BET after 1100°C / 4 hours: 6.1 m 2/g solution of a mixture of metal salts in step (a) is pre- 45 pared either by dissolving water soluble metal salts, Comparative Example 6 or by dissolving water insoluble metal salts by acid treatment.

CeO2(25%) ZrO2(20%) La2O3(2.5%) Nd2O3(2.5%) Al2O3(50%) 3. A process according to claim 2, wherein water sol- 50 uble metal salts comprise nitrates, halogenides, and [0048] 44.58g of anaqueous solution of zirconyl nitrate water insoluble metal salts comprise carbonates, hy- (ZrO2 content = 22.43%), 42.44 g of an aqueous solution droxides. of cerium nitrate (CeO 2 content = 29.45%), 3.32 g of lan- thanum nitrate in crystal form (La2O3 content = 37.7%), 4. A process according to any one of claims 1 to 3, 55 3.3 g of neodymium nitrate in crystal form (Nd 2O3 content wherein the temperature in step (b) is room temper- = 37.93%) and 183.82 g of aluminium nitrate nona hy- ature. drate (Al2O3 content = 13.6%) were treated with 600 mL of deionized water, the mixture obtained was stirred for 5. A process according to any one of claims 1 to 4,

6 11 EP 2 540 391 A1 12

wherein the temperature in step (e) is from 600°C to 1200°C

6. A process according to any one of claims 1 to 5, wherein the cerium content, calculated as cerium ox- 5 ide, of the composition obtained is in the range from 5 to 70% by weight; and the remainder comprising aluminium oxide, zir- conium oxide and optionally oxides of the Rare Earth metals other than cerium oxide. 10

7. A process according to any one of claims 1 to 6, wherein the zirconium content, calculated as zirco- nium oxide, of the composition obtained is is in the range from 5 to 70% by weight and the remainder 15 comprising cerium oxide, aluminium oxide and op- tionally oxides of the Rare Earth metals other than zirconium oxide.

8. A process according to any one of claims 1 to 7,20 wherein the aluminium content, calculated as alu- minium oxide, of the composition obtained is in the range from 20 to 80%, and the remainder comprising cerium oxide, zirconium oxide and optionally oxides of the Rare Earth metals other than cerium oxide or 25 zirconium oxide.

9. A process according to any one of claims 1 to 8, wherein a surfactant is an organic surfactant. 30 10. A process according to claim 9, wherein the sur- factant is Triton®.

11. A composition obtainable according to a process ac- cording to any one of claims 1 to 10. 35

12. A composition obtained according to a process ac- cording to any one of claims 1 to 10.

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• WO 2008113457 A [0003] • EP 2223905 A [0011] [0013] • EP 1172139 A [0005] [0014] [0039] • WO 2007093593 A [0012] • WO 2006070201 A [0006] [0007] [0008] [0042]

Non-patent literature cited in the description

• TADASHI SUZUKI. R&D Review of Toyota CRDL, vol. 37 (4), 28 ff [0015]

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