Composition based on cerium oxide and zirconium oxide having specific porosity, method of production and use in catalysis. RU patent 2509725.

FIELD: chemistry.

SUBSTANCE: invention relates to a composition based on cerium oxide and zirconium oxide having special porosity, which can be used in catalyst systems for treating exhaust gases. The composition is based on cerium oxide and zirconium oxide containing at least 30 wt % cerium oxide which, after calcination at temperature of 900°C for 4 hours, has two types of pore distribution, the diameters of which, for the first type of distribution, lie in the range from 5 nm to 15 nm for a composition having cerium oxide content of 30% to 65%, or from 10 nm to 20 nm for a composition having cerium oxide content higher than 65% and, for the second type of distribution, in the range from 45 nm to 65 nm for a composition having a cerium oxide content of 30% to 65% or from 60 nm to 100 nm for a composition having cerium oxide content higher than 65%. The method of producing the composition includes steps of: forming a first liquid medium containing a zirconium compound, a cerium (III) compound, sulphate ions, an oxidising agent and, optimally, a compound of a rare-earth element other than cerium; bringing the medium into contact with a base, whereby a precipitate is formed; separating and washing the precipitate; suspending the precipitate in water and heat treatment of the obtained medium at temperature of 90°C; and separating and calcining the precipitate.

EFFECT: composition has high specific surface area and provides good diffusion of gases.

17 cl, 2 dwg, 2 tbl, 2 ex

The present invention relates to a composition based on cerium oxide and zirconium oxide with a specific porosity, to its preparation and to its use in catalysis.

Now for purification of exhaust gases of internal combustion engines (catalytic afterburning in cars) are applied catalysts, known as multi-functional. Under multifunction understood catalysts, able not only to carry out the oxidation, in particular of carbon monoxide and hydrocarbons present in the exhaust gases, but also the restoration, in particular, oxides of nitrogen, are present in these gases ("three-way" catalysts). Zirconium oxide and cerium oxide are two particularly important and interesting components for catalysts of this type.

Products of this type must have a porosity that is appropriate for their application. So, they must have pores large enough to ensure good diffusion of gases.

However, these products should also contain pores of small size, as these pores contribute to the provision of products sufficiently high specific surface area, so that they can be used in catalysis.

Thus, it would be interesting to find a good compromise between a large surface area introduced by then small size, ilusha the diffusion of gases, made pores of large size.

Object of the invention is to offer a product that implements this compromise.

To this end, the composition according to the invention is based on the cerium oxide and the zirconium oxide containing cerium oxide, at least 30 wt.%, and it is different because, after firing at a temperature of 900°C for 4 hours it has two types of pore distribution, the respective diameters which are distributed around the values lying in the interval, for the first distribution, from 5 nm to 15 nm for the composition, the content of cerium oxide is from 30% to 65%, or from 10 nm to 20 nm for the composition, the content of cerium oxide which is above 65%, and for the second type of distribution near the values lying in the range from 45 nm to 65 nm for the composition the content of cerium oxide is from 30% to 65%, or in the range from 60 nm to 100 nm for the composition, the content of cerium oxide which is above 65%.

As will be seen hereinafter, the composition of the invention have significant distribution of pores of small size, which contribute to the formation of high specific surface area even at high temperatures.

In addition, as another advantage, the composition according to the invention are in the form of particles, which can easily disagglomerated and which can lead to particles significantly smaller h is about making these compositions are particularly interesting for applications in catalysis.

Other characteristics, details and advantages of the invention will appear more fully in the study of the following description, carried out with reference to the attached figures, in which:

- figure 1 is a distribution curve of pore size for the composition according to the invention after firing at 900°C;

- figure 2 is the distribution curve of pore size for the composition according to the invention after firing at 1000°C.

Check also for further description that, unless otherwise stated, all given ranges or limits of values included boundary values thus defined so the ranges or limits of values encompass any value at least equal to and longer than the bottom border and/or at most equal to or less than the bottom border.

For the present description under rare earths are elements of the group consisting of yttrium and elements with atomic numbers from 57 to 71, inclusive, of the periodic system of elements.

Under the specific surface area refers to the specific surface according to BET, determined by nitrogen adsorption according to ASTM D3663-78, developed on the basis of the brunauer-Emmett-teller described in the journal "The Journal of the American Chemical Society, 60, 309 (1938)".

In addition, firing, after which the values of a surface and the air.

Content,unless otherwise noted, given the weight of the oxide to the total weight of the composition. The cerium oxide is in the form of an oxide of tetravalent cerium, oxides of other rare earth metals are in the form Ln₂O₃where Ln indicates a rare earth element, except praseodymium, expressed in the form Pr₆O₁₁.

Particle size distribution obtained by the measurement using laser diffraction and conducted on the apparatus of the Coulter type.

The composition of the invention presents two options for implementation, which differ by the nature of their components.

According to the first embodiment, these compositions based on cerium oxide and zirconium oxide. More precisely, we can talk about the songs that comprise or essentially consist of cerium oxide and zirconium oxide. This means that the composition does not contain another oxide of another element, which could be the main element of this composition and/or stabilizer of its surface, as, for example, rare earth element. On the contrary, the composition may contain impurities usually present with cerium and zirconium.

In the case of the second variant of the invention, compositions are based on a cerium oxide, zirconium oxide and at least one oxide of rare earth element other than cerium. Thus, in this case we are talking about the songs containing the at least three oxide. Non-cerium rare-earth element may be selected in particular from yttrium, lanthanum, neodymium and praseodymium. So, as the compositions according to this second variant can be called, more specifically, a composition based on cerium oxide, zirconium oxide, lanthanum oxide and praseodymium oxide based on cerium oxide, zirconium oxide, lanthanum oxide and neodymium oxide based on cerium oxide, zirconium oxide, lanthanum oxide and yttrium oxide.

For the second option, you should always understand that the invention applies to the case when the composition comprises or essentially consists of cerium oxide, zirconium oxide and at least one other oxide, other than rare earth, and that the composition in this case does not contain oxide no other element besides the three mentioned above, which could be an integral element of this composition and/or stabilizer of its surface. In this case, again, the composition may contain impurities usually present with zirconium and rare earth elements.

In addition, for both the above-mentioned embodiments of the composition according to the invention do not contain the type of precious metal or precious metal as the main element. In the context of the present invention and for this type of metal under "component" means that testwuide metal could be present in the composition, in the form of a homogeneous mixture with other elements: cerium, zirconium, and optionally a rare earth element other than cerium, and this homogeneous mixture is obtained, for example, when a noble or precious metal is used at the receiving composition. In contrast, the term "composite element" as applied to the specified noble or precious metal, not used, in the spirit of the present invention, in the case, which will be described later and in which, for example, for use in the field of catalysis, noble or precious metal is used in a mixture with the composition according to the invention, which was prepared in advance.

The content of cerium and zirconium in the compositions according to the invention, whatever the variant of their implementation may vary within wide ranges, and it is understood that the content of cerium oxide is at least about 30%. Generally speaking, this content is such that the ratio of Ce/Zr, expressed in mass of oxides of these elements, ranging from 3/10 to 9/10, in particular from 2.5/2 to 8/2.

In the case of the second variant implementation, the content of the oxide of rare earth element other than cerium, may be, in particular at most 20 wt.%. This content can be, in particular, not more than 15% and even, in particular, not more than 10%. Usually she is at mere%, in particular, at least 5%.

Depending on the variants of the invention, the content of cerium oxide can be, in particular, at least 40%, especially in the case of compositions according to the second variant implementation, and, in particular, at least 50%.

As was shown above, the main characteristic of the compositions according to the invention is their porosity.

So, after firing at 900°C for 4 hours compositions according to the invention have two distinct distribution of pores, which are concentrated near the specified values.

Here and throughout the description indicates that the porosity measured by the method of Parametrii the indentation of mercury, according to the standard ASTM D4284-83 (Standard method for determining pore volume distribution of catalysts by mercury intrusion porosimetry).

The above method of measuring the porosity allows a known manner to determine the distribution curves then gives pore volume depending on the size of the pores (V=f(d), where V denotes the pore volume and d is the diameter of pores). Based on this distribution curve of the pore, it is always possible in a known manner to obtain a curve (C), which gives the derivative of V as a function of d. This curve can have peaks depending on the diameter of the pores.

In the spirit of the invention under the "pore distribution, concentrated near the specified value" means the presence on the curve (C) peak, the maximum of which is which and it the specified value.

One interesting characteristic of the compositions according to the invention is that they retain these two types of pore distribution and, consequently, with all the associated benefits, even at a high temperature, for example, even at temperatures above 900°C.

Thus, the composition of the invention after firing at 1000°C for 4 hours always have two types of pore distribution: small size and larger. For the first distribution of the pore diameters are concentrated near the average of from 8 to 20 nm, and the second type of distribution of diameters are concentrated near the value from 30 nm to 70 nm for the compositions, the content of cerium oxide is from 30% to 50%, or from 70 nm to 80 nm for the compositions, the content of cerium oxide in which more than 50%.

The second type of pore distribution is narrow or monodisperse distribution, as most of the pores of this type of distribution has a size, which remains very close to the value near which there is a corresponding peak. This characteristic can be measured by the ratio of the width I of the peak at its half-height to the width L of the peak at its zero line. So, this is the ratio I/L, measured from the curves of pore distribution after calcination at 900°C or 1000°C, usually at least 30%, in particular at least 40%.

The composition according to the invention have, besides a large total pore volume. Thus, the composition after four hours ' calcination at 900°C have a total pore volume of at least 0.6 ml Hg/g This pore volume can be, in particular at least 0.7 ml Hg/g At this temperature can be achieved pore size approximately 0.90 ml Hg/g

This total pore volume is still significant at higher temperatures. For example, after firing at 1000°C for 4 hours composition may have a total pore volume of at least 0.5 ml Hg/g, in particular at least 0,65 ml Hg/g At the same temperature can be achieved pore size of about 0,70 ml Hg/g

Mentioned here the total pore volume is formed by pores whose diameter is from 3 nm to 100 μm.

Another interesting characteristic of the invention is that the pores of small size, i.e. the pores of the above-mentioned first type of distribution, make a fairly large contribution to the total pore volume. Their share depends on the temperature at which the fired composition, it is higher for songs that are fired at lower temperatures, and can typically range from 5 to 20%.

So, in the case of a four-hour calcination at 900°C this percentage may range from 8 to 12%.

The particular porosity of the compositions according to the invention leads to their high specific surface area.

Thus, the composition of the invention can have after a four-hour calcination at 900°C specific p is the surface at least 30 m ²/g, in particular at least 45 m²/g for the compositions according to the second variant of implementation. After firing at the same temperature for the compositions according to the first and second variants of the implementation can be obtained surface values up to about 35 m²/g and up to about 55 m²/g, respectively.

Surface values can be maintained high at higher temperatures. After firing at 1000°C for 4 hours, the specific surface can be at least 15 m²/g for the first variant of implementation and at least 30 m²/g for the compositions according to the second variant of implementation. After firing at the same temperature for the compositions according to the first and second variants of the implementation can be obtained surface values up to about 17 m²/g and up to about 45 m²/g, respectively.

The specific surface compositions according to the invention can be at least 5 m²/g for the first variant of implementation and at least 15 m²/g for the compositions according to the second variant of implementation after firing the same duration, but at 1100°C.

Finally, after firing at 1200°C for 10 hours can be obtained specific surface area of at least 5 m²/year

Another particularly interesting feature of compositio invention is the ease they disagglomerated.

Indeed, immediately after receiving the composition according to the invention are usually in the form of particles, the average size (d₅₀) is usually from 7 μm to 20 μm.

In fact, these particles are agglomerates that are easily collapse on units with a significantly smaller average size, in particular not more than 3 μm, in particular not more than 2 μm, which consist of crystallites, concatenated with each other.

Under "easy desagglomeration" means that to move from agglomerates to the aggregates by processing that does not require much energy, in contrast to the crushing type micronisation or, for example, type wet crushing. This treatment may be, for example, desagglomeration ultrasound or by suspension.

Ease of access units, i.e. with a low expenditure of energy, is advantageous characteristic of the compositions according to the invention. Thus, when used in catalysis, it is important to be able to easily get at the disposal of small products, in order to mould them, for example, for coatings (washcoat coating of a porous oxide), for deposition on the monoliths.

It can be noted, moreover, that the composition according to the invention have good phase purity. Thus, these compositions can be in the form of solid solutions up to high the temperature is, that is, even after firing at 1100°C, in particular, to compositions according to the second variant implementation.

Under the solid solution is understood that x-ray analysis of these compositions after firing at a predetermined temperature reveal the existence of a single clearly identifiable phases. The nature of this single phase depends on the respective percentages of the different elements in the composition. For songs that are quite rich in cerium, this phase actually corresponds to the crystal structure of fluorite type, like the crystallized oxide of cerium(IV) CeO₂parameters crystal cells which are more or less offset from pure cerium oxide(IV), which reflects the introduction of zirconium and, if necessary, another rare earth element in the crystal lattice of the cerium oxide and, consequently, to gain a true solid solution. In the case of compositions with relatively high zirconium content this phase corresponds to the phase of zirconium oxide crystallized in the tetragonal system, the unit cell parameters of which are also shifted, which also reflects the introduction of cerium and possibly other element in the crystal lattice of the zirconium oxide.

Now will be described a method of producing compositions according to the invention.

This method includes the following steps:

- form the first fluid is th Wednesday, which contains a compound of zirconium, a compound of cerium(III), sulfate ions, an oxidizing agent and, if necessary, the compound of rare earth element other than cerium;

- the above environment is brought into contact with the ground, resulting in a precipitate;

- the precipitate is isolated and washed;

- the precipitate obtained in the previous step is suspended in water and the environment is subjected to heat treatment at a temperature of at least 90°C;

- the precipitate is isolated and fired.

The first step of the method consists in the formation of a liquid medium, which preferably is water, and in which the required quantities are the connections of the various elements forming part of the song you want. Thus, it comes to compounds of zirconium, of cerium and, in the case of obtaining the composition according to the second variant implementation, rare earth element or elements other than cerium.

These compounds preferably are soluble compounds. They can be, in particular, salts of these elements.

In respect of these compounds must be adhered to certain conditions.

The compound of cerium is the connection in which this element has a valence III. More specifically there can be mentioned halides and, in particular, chloride, and nitrate.

For zirconium can use the th nitrate Zirconia or chloride Zirconia, sulfate of zirconium, in particular, articulate zirconium, or basic sulfate of zirconium.

Rare earth element or elements other than cerium, the compounds can be selected from nitrates, sulfates, acetates, chlorides.

The original liquid medium should also contain an oxidizing agent, which may be, for example, hydrogen peroxide.

The original liquid medium should also contain sulfate ions. These sulfate ions must be present in such quantity that the atomic ratio of sulfate ions/Zr is at least 0.5, and preferably at least 2.

These sulfate ions may be, for example, sulfuric acid. They may also be made, at least in part, by the connection of zirconium, when it is the connection type sulfate.

The second step of the method consists in the contact liquid medium obtained at the first stage, to the base. As a basis you can use products such as hydroxides. You can call hydroxides of alkaline or alkaline earth metals. You can also use a secondary, tertiary or Quaternary amines. However, amines and ammonia may be preferred to the extent that they reduce the risk of contamination of the cations of the alkaline or alkaline earth metals. You can also mention urea. The base can be used, in particular, as p is the target.

According to one private variant of the invention, the bringing into contact of the first liquid medium and substrate can be accomplished by introducing the medium into the base, for example, by introducing the medium into the reactor, which contains the basis in the original mixture.

The contact or reaction between the first liquid medium and the substrate can be carried out at once, gradually or continuously, preferably they are carried out under stirring. The contact or reaction is preferably conducted at a temperature of at least 45°C.

Reaction with base leads to the formation of a precipitate. This precipitate was separated from the reaction medium in which it was received, by any known method, for example, by filtering.

The separated precipitate is washed with water to remove sulfates, still existing in the sediment. This washing can be carried out with water at ambient temperature or hot water, for example, at a temperature at least 50°C.

The next step of the method is the step of heat treatment of sediment in the aquatic environment.

This heat treatment is carried out on a suspension obtained after the introduction of water-washed precipitate. The temperature to which the heat medium is at least 90°C, in particular at least 100°C and even more specifically at least 150°C, and it can range from 150°C to 200°C. thermal Process about what abode can spend introducing fluid into the closed chamber (closed-type reactor of the autoclave). For the above temperature conditions and the aquatic environment can be updated, as an illustration, that the pressure in the closed reactor can range from the upper value of 1 bar (10⁵PA) and 165 bar (1,65·10⁷PA), preferably between 5 bar (5·10⁵PA) and 165 bar (1,65·10⁷PA). Heat treatment may be carried out either in air or in an atmosphere of inert gas, preferably nitrogen.

The duration of the heat treatment may vary within wide limits, for example, from 1 to 48 hours, preferably from 1 to 24 hours. In addition, the rate of temperature rise is not critical, and thus it is possible to achieve a fixed reaction temperature, warming the environment, for example, during the period from 30 minutes to 4 hours, and these values are given only as a guide.

At the last step of the method according to the invention the extracted residue is separated from the environment in which heat treatment was carried out in any suitable way, for example, by filtration, and then calcined. This roasting allows you to develop crystallinity la formed product and it can also be adjusted and/or selected depending on the temperature of the subsequent use intended for the composition according to the invention, bearing in mind that the compulsory product surface the less, the higher the temperature of the ongoing firing. Such calcination is usually carried out in air, but, of course, cannot be ruled out conducting firing in an atmosphere of inert gas or in a controlled atmosphere (oxidizing or reducing).

In practice, the firing temperature limit is usually an interval of values from 500 to 900°C, in particular from 600°C to 800°C.

According to one variant, the sediment can be distinguished by spraying a liquid medium in which it had been cooked.

Under spray drying refers to drying by spraying the mixture in a hot atmosphere (spray-drying is spray drying). Spraying can be implemented using any known spray, for example, spray nozzle type irrigation nozzle or the other. You can also use the spray, called a turbine. With respect to the various spraying techniques that can be used in this way, you can refer, in particular, on the fundamental work of the MASTERS called "SPRAY-DRYING" (second edition, 1976, publisher George Godwin, London).

After spraying the obtained dry residue is subjected to calcination under conditions that were stated previously.

The composition of the invention which have been described above or which are obtained as described above are in powder form, but if necessary, can be molded, getting f the RMU granules, balls, cylinders or honeycomb structures of various sizes.

The composition of the invention can be used as catalysts or catalyst substrates. Thus, the invention relates to catalytic systems containing compositions according to the invention. For such systems, these compositions can be applied to any substrate commonly used in the field of catalysis, that is, in particular, thermally inert substrate. This substrate may be selected from aluminum oxide, titanium oxide, cerium oxide, zirconium oxide, silicon oxide, spinels, zeolites, silicates, crystalline phosphates of silicoaluminate, crystalline aluminum phosphate.

The composition can also be used in catalytic systems containing coating (washcoat) on the basis of these compositions possessing catalytic properties, on the bottom layer of the type, for example, metal or ceramic monolith. The coating may contain a substrate of the type mentioned above. This coverage receive, mixing the composition with a substrate, to obtain a suspension, which can then be applied to the bottom layer.

These catalytic systems and, in particular, the composition according to the invention can find many applications. Thus, they are particularly suitable and, therefore, can be used in the catalysis of various reactions, such as, for example, ka is dehydration, hydrosulfate, hydrodenitrification, sulfur removal, hydrodesulfurized, dehydrohalogenation, reforming, steam reforming, cracking, hydrocracking, hydrogenation, dehydrogenation, isomerization, disproportionation process, oxychlorination process, dehydrocyclization hydrocarbons or other organic compounds, oxidation and/or recovery, the Claus reaction, the purification of exhaust gases of internal combustion engines, demeterova, mahanirvana, the reaction of water gas, the catalytic oxidation of soot emitted by internal combustion engines, as diesel or gasoline engines, or engines operating lean mixture. Finally, catalytic systems and compositions according to the invention can be used as traps for NOx or to facilitate the reduction of NOx even in an oxidizing atmosphere, or as catalysts in the decomposition of N₂O, for example, in a plant for the production of nitric acid or in a residential installation.

In the case of their application in catalysis, the compositions according to the invention are used in combination with noble metals, however, they play the role of substrate for these metals. The nature of these metals and methods for their introduction in the composition of the substrate to a specialist well known. For example, these metals can be platinum, rhodium, palladium or and the of IDI, and they can be introduced into the composition, in particular by impregnation.

Among these applications are particularly interesting application is the purification of exhaust gases of internal combustion engines (catalytic afterburning in cars). Therefore, the invention relates also to a method for purification of exhaust gases of internal combustion engines, which is characterized in that it as the catalyst used for the catalytic system, which is described above, or a composition according to the invention, which is described previously.

The following are examples.

In these examples, the porosity measured above-mentioned method according to the above standard, in particular, in the following measuring conditions:

The samples, which is measured, is subjected to degassing for 10 hours at 100°C in a ventilated drying chamber. They have a mass of about 300 mg.

- Use the penetrometer No. 14 for powders, the cell which has a size of 3.28 cm³with capillary 0,413 cm³.

The measurement is performed at an angle of wetting 130°, using a table of pressures pushing and squeezing.

Example 1

This example relates to the preparation of a composition based on zirconium oxide and cerium oxide in the corresponding fractions, the mass of the oxide, 20% and 80%.

Used compound of zirconium is articulat zirconium, RA the creators, obtained by dissolving a basic zirconium sulfate with sulfuric acid at ambient temperature, a concentration equal to 253,5 g/l, and the density 1,478, the compound oxide is cerium nitrate Ce(NO₃)₃in solution, the concentration of which is equal to 496 g/l, and the density of 1,716.

Mixing the above compounds is carried out in quantities suitable to obtain the final oxide in the desired composition; then to this mixture was added 140 ml of 35%H₂O₂.

The resulting solution is diluted to a concentration of 100 g/l, then with constant stirring dropwise introduced into the main source mixture consisting of 1500 ml of NH₄OH concentration of 5 mol/l). After semi-continuous deposition by overflow into the second reactor, continuously stirring, the precipitate is filtered, then washed twice with repeated suspendirovanie.

Concentration in the precipitation reactor is 100 g/l in the whole reaction.

The precipitate obtained in perelivom reactor, suspended in water at a concentration of 100 g/l, then it is introduced into the autoclave for 1 hour at 200°C with stirring. Then the precipitate is fired in air at 850°C for two hours.

Thus obtained composition has the following characteristics:

After firing at 1100°C for 4 hours, the composition is in the form of a purely cubic crystallographic phase of fluorite.

Example 2

This example relates to the preparation of a composition based on zirconium oxide, cerium oxide, lanthanum oxide and praseodymium oxide in the relevant shares and, in many oxides, 30%, 60%, 3% and 7%.

Used the same compounds of zirconium and cerium, as in example 1. Connection lanthanum is (NO₃)₃in the solution concentration of 454 g/l and the density 1,687, and connection praseodymium has the form Pr(NO₃)₃in the solution to what centrala 500 g/l and the density of 1,732.

Mixing the above compounds is carried out in quantities suitable to obtain the final oxide in the desired composition; then to this mixture 107 ml of H₂O₂(concentration of 11.6 mol/l and the density 1,132).

The resulting solution is diluted to a concentration of 100 g/l, then with constant stirring dropwise introduced into the main source mixture consisting of 1500 ml of NH₄OH concentration of 5 mol/l). After deposition and mixing for one hour at 50°C the precipitate was filtered, then washed twice with repeated suspendirovanie.

The precipitate is suspended in water at a concentration of 100 g/l, to enter into the autoclave for 1 hour at 200°C with stirring. Then the precipitate is fired in air at 850°C for two hours.

Thus obtained composition has the following characteristics:

After firing at 1100°C for 4 hours, the composition has the appearance of a purely cubic crystallographic phase of fluorite.

Figure 1 shows the distribution curve of pore size for the composition of example 2 after four hours ' calcination at 900°C. is visible first, if you go to the right of the curve, the peak, the maximum of which is 10 nm and the second peak with maximum is 45 nm. Figure 2 shows a graph of pore distribution for the same song, but after firing at 1000°C for 4 hours. Found the same peaks as on the previous curve, but shifted them to the left, the first with a maximum at 15 nm and the second at 60 nm.

1. Composition based on cerium oxide and zirconium oxide containing cerium oxide, at least 30 wt.%, characterized in that after firing at a temperature of 900°C for 4 hours it has two types of pore distribution, the respective diameters of which are concentrated near the value for the first type of distribution lies in the range from 5 nm to 15 nm for the composition, the content of cerium oxide is from 30% to 65%, or from 10 nm to 20 nm for the composition, the content of cerium oxide which is above 65%, and for the second species distribution in the range from 45 nm to 65 nm for the composition, the content of cerium oxide which is from 30% to 65%, or from 60 nm to 100 nm for the composition, the content of cerium oxide which is above 65%.

2. Composition based on cerium oxide and zirconium oxide containing cerium oxide, at least 30 wt.%, characterized in that after firing at 1000°C for 4 hours it has two types of pore distribution, the respective diameters of which are concentrated near the value, which for the first distribution of pores lies in the range from 8 nm to 20 nm, and the La of the second kind distribution in the range from 30 nm to 70 nm for the composition, the content of cerium oxide is from 30% to 50%, or from 70 nm to 80 nm for the composition, the content of cerium oxide in which more than 50%.

3. The composition according to claim 1, characterized in that it has a total pore volume of at least 0.6 ml Hg/g

4. The composition according to claim 2, characterized in that it has a total pore volume of at least 0.5 ml Hg/g

5. Composition according to one of claims 1 or 2, characterized in that the pores of the first distributions form a pore volume average of the share from 8% to 12% of the total pore volume.

6. Composition according to one of claims 1 to 4, characterized in that it contains at least one oxide of rare earth element other than cerium, which can be selected, in particular, of yttrium, of lanthanum, neodymium and praseodymium.

7. Composition according to one of claims 1 to 4, characterized in that it is the content of cerium and zirconium, which is the ratio of Ce/Zr, expressed in mass of oxides of these elements, ranging from 3/10 to 9/10, in particular from 2.5/4 to 8/2.

8. The composition according to claim 6, characterized in that it has a content of rare earth element other than cerium, expressed as weight of oxide, not more than 20%.

9. The composition according to claim 7, characterized in that it has a content of rare earth element other than cerium, expressed as weight of oxide, not more than 20%.

10. Composition according to one of claims 1 to 4, characterized in that it after firing at 900°C in those who tell 4 hours has a specific surface area of at least 30 m ²/year

11. Composition according to one of claims 1 to 4, characterized in that it after firing at 1200°C for 10 hours has a specific surface area of at least 5 m²/so

12. Composition according to one of claims 1 to 4, characterized in that it is in the form of particles with an average size of 7 μm and 20 μm, which can disagglomerated with an average size of not more than 3 μm.

13. The method of obtaining the composition according to one of the preceding paragraphs, characterized in that it comprises the following stages:
- form a first liquid medium, which contains a compound of zirconium, a compound of cerium(III), sulfate ions, an oxidizing agent and, if necessary, the compound of rare earth element other than cerium;
- the above environment is brought into contact with the ground, resulting in a precipitate;
- the precipitate was separated and washed;
- the precipitate obtained in the previous step is suspended in water and the thus obtained medium is subjected to heat treatment at a temperature of at least 90°C;
- the precipitate is isolated and fired.

14. The method according to item 13, characterized in that zirconium compounds used articulat Zirconia.

15. The method according to PP or 14, characterized in that the bringing into contact of the above first liquid medium with base is carried out in a reactor containing a specified basis in the original mixture, by introducing a decree which authorized the environment in the reactor.

16. The catalytic system, characterized in that it contains a composition according to one of claims 1 to 12.

17. Method of treatment of exhaust gases of internal combustion engines, characterized in that the catalyst used for the catalytic system according to clause 16 or a composition according to one of claims 1 to 12.