FR2839661A1 - Fluid bed catalytic cracking compound comprises mesostructured material with nanometric particles based on cerium oxide in mineral matrix - Google Patents

Abstract

The compound comprises a mesostructured material containing particles of nanometric dimensions, at least partly crystalline and based on cerium oxide, bound in a mineral matrix based on silica or aluminum. It contains at least one compound of an element selected from the group comprising elements with atomic numbers 21 to 31 in the Periodic Table, plus molybdenum and tungsten, combined with the mesostructured material. Preferred Features: The element can be zinc or vanadium, and the matrix is mainly of silica, while the crystalline content of the mesostructured material is preferably at least 40 per cent. The particles have a spherical or isotropic morphology, with at least 50 per cent having a diameter of 1 - 10 nm and monodispersed distribution.

Description

COMPOSITION COMPRISING A BASIC MESOSTRUCTURE MATERIAL

  SILICA OR ALUMINA AND POSSIBLY A SELECTED ELEMENT

  AMONG ATOMIC NUMBER 21 TO 31, MOLYBDENUM AND

  TUNGSTEN, USEFUL AS CATALYST FOR CRACKING

CATALYST

  The present invention relates to a composition comprising a mesostructure material based on silica or alumina that can be used as catalyst for catalytic cracking, in particular for cracking.

catalytic fluid bed.

  The catalytic cracking process, in particular the fluid catalytic cracking (FCC) process, is an important refining process whose main objective is the production of gasoline and diesel fuel from heavy loads. More specifically, this process leads to gasolines or gas oils which contain relatively high amounts of sulfur. However, in the context of environmental protection, the legislative measures of many countries impose a significant reduction in the sulfur content of

  motor vehicle fuels.

  There is therefore a need for an FCC process leading to low sulfur products. Various methods have been studied such as hydrotreatment of FCC feeds, post-treatment of gasoline or reduction of sulfur content of the gasoline during cracking. In the latter case, the results obtained so far are not yet fully satisfactory. There is also a need to improve the cracking performance of

FCC processes.

  The object of the invention is to meet these needs and in particular to provide a catalytic system for FCC with improved properties and

usable during cracking.

  The invention firstly relates to a first composition which is characterized in that it comprises: at least one compound of an element E chosen from the group comprising the elements of the atomic numbers 21 to 31 of the periodic classification and the molybdenum and tungsten; a mesostructure material comprising particles of nanometric dimensions, at least partially crystalline, based on a cerium oxide, said particles being bonded to one another by a mineral matrix;

silica or alumina base.

  The invention also relates to a second composition which is characterized in that it comprises: a catalytic cracking catalyst in a fluid bed; a mesostructure material comprising particles of nanometric dimensions, at least partially crystalline, based on an oxide of cerium, said particles being bonded to one another by a mineral matrix;

silica or alumina base.

  The invention also relates to a third composition which is characterized in that it comprises: a catalyst for catalytic cracking in a fluid bed; a mesostructure material comprising particles of nanometric dimensions, at least partially crystalline, based on an oxide of cerium, said particles being bonded together by a silica or alumina-based mineral matrix; at least one compound of an element E selected from the group consisting of the elements of the atomic numbers 21 to 31 of the periodic classification and the

  molybdenum and tungsten, in combination with said mesostructure material.

  The compositions of the invention may be used especially in the catalytic cracking process and may offer one or more of the following advantages. Elies allow first of all to reduce the content of

  sulfur in both gasoline (C5-221 C) and light diesel fuel.

  Wiles may also allow the cracking of heavy sulfur compounds such as long-chain alkyl thiofenes, benzothiophene and alkyl benzothiofenes, the known catalysts being less effective with respect to these heavy sulfur compounds. These compositions also have the advantage of being more selective for obtaining olefins C3 and C4. Finally, the compositions

  of the invention can also improve the cracking yield.

  Other features, details and advantages of the invention will be apparent.

  even more fully on reading the description which will follow, as well as

  various concrete but non-limiting examples intended to illustrate it.

  For the rest of the description, the term "specific surface" means the

  specific surface B.E.T. determined by nitrogen adsorption according to ASTM D 3663-78 established from the method BRUNAUER EMMETTTELLER described in the periodical "The Journal of the American

Chemical Society, 60, 309 (1938).

  On the other hand, rare earth means the elements of the group constituted by yttrium and the elements of the periodic classification of atomic number.

  inclusive between 57 and 71.

  As has been seen above, the compositions of the invention all comprise a mesostructure or mesoporous material ordered. This material will be described more specifically below in a first step and the

  Compositions of the invention will be described in a second step.

  The mesostructure material In the strict sense of the term, the so-called mesoporous compounds wind solids having, within their structure, pores having an intermediate size between that of micropores of zeolite type materials and

this is macroscopic pores.

  Specifically, the term "myoporous compounds" originally refers to a compound which specifically comprises pores of

  average between 2 and 50 nm, designated by the term "mesopores".

  Typically, these compounds are amorphous or paracrystalline silica compounds in which the pores are generally distributed

  randomly, with a very wide distribution of pore size.

  With regard to the description of composite teds, it will be possible

  in particular see Science, Vol. 220, pp. 365-371 (1983) or the Journal of Chemical Society, Faraday Transactions, 1, vol. 81, pp. 545548

(1985).

  On the other hand, so-called structured compounds are compounds having an organized structure and characterized in a more precise manner by having at least one scattering peak in a diffusion pattern. diffusion-type radiation by X-rays or neutrons. Such diffusion diagrams as well as their method of obtaining wind are particularly described in Small Angle X-Rays Scattering.

  (Glatter and Kratky - Academic Press London - 1982).

  The scattering peak observed in this type of diagram can be associated with a characteristic repetition distance of the considered compound, which will be

  designated in the remainder of this description by the term of a period

  space of repetition >> of the system structure.

  On the basis of these definitions, a compound mesostructure is understood to mean a structure compound having a repetition period including

between 2 and 50 nm.

  The ordered mesoporous compounds constitute in their case a particular case of mesostructure compounds. They are in fact mesoporous compounds which present an organized spatial arrangement of mesopores present in their structure, and which thus effectively possess a repetition space period associated with the appearance of a peak in a

diffusion diagram.

  In the remainder of the description and unless otherwise indicated the term

  << mesostructure should be understood as applying both to

  mesostructure materials and prescribed mesoporous materials.

  The mesostructure material which is part of the composition of the invention is of the type comprising particles of nanometric dimensions, at least partially crystalline, based on a cerium oxide, said particles being bonded together by a silica-based mineral matrix. or alumina. Materials of this type wind described in the patent application WO 01/32558 to the teaching of which we can refer. We remind you

  below the main features of this material.

  For particles of nanometric dimensions, for the purpose of the present invention, particles of preferably spherical or isotropic morphology, of which at least 50% of the population have a mean diameter of between 1 and 10 nm, advantageously less than 6 nm, with a

  granulometric distribution of these particles preferably monodisperse.

  In particular, the term "particles of nanometric dimensions" can also designate according to the invention anisotropic particles, rod-type, provided that for at least 50% of the population of these particles, the diameter average transverse is between 1 and 10 nm and the length does not exceed 100 nm, with a distribution

  granulometric of these particles preferably monodisperse.

  These particles of nanometric dimensions which are present in the material of the invention wind particles at least partially crystalline, that is to say that they have a degree of crystallinity ranging from 30 to 100% by volume. This degree of crystallinity can be calculated by the ratio of the area of a diffraction peak measured by X-ray diffraction for a sample of the material according to the invention to the area of the same measured diffraction peak for a sample sample in which constitutive element of the particle is in the state

  crystal reads and corrects absorption coefficients of corresponding oxides.

  The presence of these partially crystallized particles within the mineral matrix gives the mesostructure materials of the invention, in addition to an ordered arrangement of their pore network, an overall crystallinity level generally at least 10% by volume, and more particularly at least 30% by volume, this total crystallinite volume ratio being calculated by multiplying the volume crystallinity determined experimentally for the particles, according to the method described above, by

  the fraction of volume of the material which is occupied by said particles.

  The compound according to the present invention advantageously has an overall crystallinite content by volume of at least 40%. By "crystallinite ratio" in the sense of the invention is meant the rate of crystallinity inherent to the walls of the structure, which takes into account at the same time the possible crystal in the event of the matrix of the mother or binding matrix and the crystallinity of particles of nanometric dimensions included in this binder matrix. In this respect, it must be pointed out that the "crystallinity" of the material, in the sense of the invention, corresponds to a microscopic organization detectable in particular by diffraction (for example by X-ray diffraction at large angles), which is to distinguish in particular from "the order" presented,

  a more macroscopic level, by the mesostructure of the material.

  The mineral matrix of the material structure of the present invention incorporating the particles of nanometric dimensions defined above constitutes an inorganic, partially crystalline, amorphous matrix which, in the case of the present invention, is based on silica or alumina. For the purpose of the present invention, the matrix may be based on a mixture of alumina and silica. It should be noted that the particles can be completely dispersed within the mineral matrix but that, preferably, this mineral matrix does not completely cover the particles of nanometric dimensions that it contains. In this case, the mineral matrix plays a role of binder between the particles of which at least a part of the surface is thus accessible and cleared of the mineral matrix. Thus, at least a part of the particles is in contact with the porous parts constitute the internal space

  material accessible by a gas phase in particular.

  The mineral matrix is most often constituted mainly by silicon dioxide or alumina, ie the mineral matrix is generally made up of at least 60% by weight, and preferably at least 60% by weight.

  at least 70% by weight of silica eVou alumina.

  The molar ratio (silica eVou alumina) / cerium oxide is generally between 20:80 and 99.5: 0.5, preferably between 40:60 and 5: 4.5. Even more preferably, this molar ratio is from 40:60 to 92:8. It appears that the stability of the structure can no longer be ensured when the molar matrix / particle ratio is less than

the proportion of 20:80.

  The material which forms part of the constitution of the compositions of the invention may advantageously have, at least at a local level, one or more mesostructure (s) chosen from mesoporous mesostructures of hexagonal symmetry three-dimensional P63 / mmc, of hexagonal symmetry. two-dimensional, of cubic three-dimensional symmetry la3d, Im3m or Pn3m; among mesostructures of vesicular or lamellar type, or among

  vermicular type mesostructures.

  As regards the structure of the mesostructure material, it has mineral walls which can be described as constituting discrete domains of binding matrix and particles of nanometric dimensions. The overall thickness of the walls of the mesoporous structure, which integrate particles of nanometric dimensions, is preferably between 2 and 12 nm, more particularly between 3 and nm. The material according to the invention advantageously has a mesoporous structure with pores between 2 and 12 nm in size, preferably between 3 and 9 nm. In the case of a mesoporous structure

  ordered, the diameter of the pores is generally between 2 and 8 nm.

  However, this diameter can be further increased, in particular by the use of solvents, by known techniques of the state of the art. On the other hand, the mesostructure materials have a surface

  high BET specific, preferably between 400 and 2400 m2 / cm3.

  The mesostructure materials may have a particle size of between 0.1 μm and 50 μm, preferably between 0.1 μm and 10 μm,

  advantageously between 0.1'um and 5.um.

  The mesostructure material according to a first variant of the invention According to a first variant of the invention, the cerium oxide on which the nanometric particles are based comprises at least one metal element

  Mi in solid solution within the crystal lattice of this oxide.

  This element M 'is chosen from zirconium and rare earths other

  than cerium. M 'may be more particularly lanthanum or zirconium.

  Characteristically for this variant, particles of nanometric dimensions integrated in the mineral matrix wind based on a cerium oxide which comprises at least one metal M, in the cationic state, called "doping" element, which is present in solid solution, usually in solid solution

  insertion eVou substitution, within the crystalline structure of the oxide.

  By "cations present in solid solution within a cerium oxide" is meant cations present, as substitution eVou insertion cations, within the crystalline cerium oxide playing in a characteristic manner. a crystal network, said cations generally representing less than 50 mol% of the total amount of metal cations present in the oxide, i.e. the solid solution integrated cations preferentially carry minority cations; relative to the constitutive cations of the cerium oxide, or they are integrated in solid solution, the content of said cations can however reach 50% in some cast Cerium crystalline oxide integrating cations in solid solution retains the structure of the oxide crystalline cerium in the pure state, slight changes in the mesh parameters can however be observed, for example in accordance with the law of Vegard. Thus, a crystalline oxide incorporating solid solution cations generally exhibits an X-ray diffraction pattern similar to that of pure oxide, with

  more or less important shift of the magpies.

  Preferably, within the cerium oxide particles included in the materials of the invention, the amount of cations of the "doping" element "M" in solid solution (or the total of solid solution dopant cations, when more than one dopant is present) is at least 0.2 mol% of the total amount of metal cation present in the oxide, preferably at least 0.5 mol%, and still more preferably at least 1 mol%. In general, it is most often preferred that the content of "doping" cations be as high as possible. Thus, when this is conceivable, particularly in view of the nature of the doping element (s) and of the oxide within which they are introduced in solid solution, it is preferred that the content of "doping" cations be at least 5%, preferably at least 20%, and still more preferably at least 30%, or even at least 40%. The quantity of cations of metal M that can be integrated in solid solution can represent up to 50 mol% of the total quantity of metal cations present in the doped cerium oxide, this all

  particularly in the case where the metal M, dopant represents zirconium.

  The material of this first variant can be prepared by a method which comprises three steps. In a first step (a), a mesostructure material is formed comprising particles of nanometric dimensions, at least partially crystalline, based on an oxide of cerium, said particles being bonded together by a silica-based or silica-based mineral matrix. alumina by implementing for example the method of preparation described in patent application WO 01/32558. In a second step (b), a compound based on said element M '(preferably said metal M' in cationic form, possibly complexed, or even an alkoxide metal M ') is introduced into the mesoporous structure obtained. ), the total content of element M 'introduced into the structure, relative to the total surface developed by the mesostructure, being less than 5 micromoles of cation per m2 of surface. In a third step (c), the mesostructure thus carried out is subjected to a temperature at least equal to 300 ° C., and not higher than 1000 ° C., whereby at least a portion of the solution M 'is in the form of cations in solution. solid within the oxide present in the particles of nanometric dimensions introduced in step (a), which leads to obtaining a material according to this principle

variant of the invention.

  The second step (b) consists more precisely in impregnating at least a portion of the porous zones of the mesostructure realized in step (a) with a component of element M, which it is desired to introduce as " dopant "in solid solution within the particles of cerium oxide integrated within the walls of the mesostructure. Generally, this impregnation is carried out by introducing said cations of the element M into the mesostructure by dispersing them in a liquid or gaseous vector phase, this vector phase being preferably a liquid medium, generally a medium. aqueous or hydro-alcoholic, or else an organic solvent medium. Thus, step (b) most often involves impregnating at least a portion of the porous zones of the mesostructure made in step (a) with a solution, generally aqueous, of a salt of a cation of the metal M ', preferably of a nitrate, oxy-nitrate, oxalate, eVou acetate of the metal M4, or with an aqueous or aqueous-alcoholic solution comprising cations of the metal M' in the complex state, or even with a solution, generally in an anhydrous organic solvent medium, comprising a

metal alkoxide M4.

  However, according to particular implementation modes, it is also possible to envisage in step (b) the use of metal-based cluster dispersions (in particular oxide-based clusters of metal oxide hydroxides). ), or else a gaseous phase comprising a metal compound (this gas phase being preferentially constituted by it composed in the gaseous state). In step (b) it is necessary that the overall cation concentration of the M element introduced into the porous zones be relatively low, especially so that a too great reduction in the specific surface area is not observed. material, or even clogging of the pores, following the heat treatment of step (c). This overall concentration is such that the total content of cations at said element M4, relative to the total surface area developed by the mesostructure, remains, as a rule, less than 5 micromoles of cation per m 2 of surface area. Preferably, this content remains at least equal to 1 micromole of cation per m 2 of surface. The "total surface of the mesostructure material" referred to herein is calculated by multiplying the BET specific surface, measured in m2 / g for the mesostructure material obtained at the end of step (a), by the mass materieu. It is generally preferred that, in step (b), the compounds based on the metal M, are introduced into the mesostructure in the form of a solution, in aqueous or hydroalcoholic medium, or else in within an organic solvent. In this context, to be placed in the aforementioned concentration conditions, the overall concentration C in Mi cations within the medium which is found incorporated in the mesostructure at the end of step (b) is in general less than 2 mol / L and it is preferably between 0.1 mol / L and 1.5 mol / l, this concentration being advantageously less than or equal to 1 mol / L. It should be noted that, in the context of the present process, it is possible to impregnate with relatively concentrated solutions, the concentration C may be greater than 0.5 mol / L, or even 0.7 mol / L in the Most cast to achieve incorporation of a solution having such a concentration C within the mesostructure material from step (a), step (b) can be conducted in several possible ways. Thus, according to a first variant that can be envisaged, step (b) can be carried out by immersing the material or mesostructure obtained at the end of step (a) in a solution comprising the element Mi at a concentration of order of the concentration C (generally between 0.1 and 1.5 mol / L, and advantageously between 0.2 and 1 mol / L), then filtering the medium obtained. The impregnated solid collected after filtration then effectively comprises, within its porous zones, a solution comprising a metal compound M4, with the desired content of

metal M '.

  According to another possible variant, step (b) can also be carried out by immersing the mesostructure material obtained at the end of step (a) in a solution comprising element M, at a concentration close to the concentration. C (in general at a concentration advantageously between 0.2 and 1.5 mol / l, and preferably between 0.4 and 1.2 mol / l), then subjecting the medium obtained to centrifugation. Provided that centrifugation is not carried out under conditions that are too severe (typically centrifugation is carried out at 2000 to 5000 rpm, for a duration not generally exceeding 30 minutes), the centrifugation pellet obtained is solid impregnated which includes, within its porous zones,

  a solution comprising the element M at the desired concentration.

  According to yet another conceivable variant, step (b) can also be carried out by adding to the mesostructure material obtained at the end of step (a) a volume V of a solution comprising ['element M', said volume V being of the order of the pore volume developed by the material, whereby we obtain a paste. The mixing is usually done by mixing. The resulting paste is then evaporated from the solvent, preferably slowly. In this case, the quasi-totality of the element M initially introduced is found within the mesostructure. In this context, it is generally preferred to conduct step (b) by adding to the mattric mesostructure obtained at the end of step (a) a volume of solution representing between 0.2 and 3 times the volume of the material (and preferably representing at most 2 times the volume of the material), said solution comprising ['element M' has a concentration generally between 0.1 and 2 mol / L, then evaporating the solvent in

the mixture obtained.

  Whatever the exact method of covering step (b), the impregnated solid obtained at the end of this step is then subjected to a step (c) heat treatment. This step (c) is essentially intended to achieve at least partial integration of solid solution (M ') cations within the oxide-based particles included in the walls of the mesostructure. For this purpose, it comprises a treatment of the material at a temperature at least equal to 300 ° C., this temperature being preferably at least equal to 350 ° C., higher temperatures being generally not required with respect to the integration of the materials. cations of the M element, within the oxide-based particles. In this connection, it should be emphasized that the method described here makes it possible, surprisingly, to disintegrate doping metal cations in solid solution for insertion and / or substitution within the cerium oxide of particles of nanometric dimensions. low temperatures, which allows in particular to obtain functionalized mesostructure materials having very large specific surfaces. However, in certain cases, it may be advantageous to carry out the heat treatment of step (c) at a temperature at least equal to 400 C, or even at least equal to 500 C, especially in order to improve certain physical characteristics. eVou chemical material (concentrations of active catalytic sites, specific catalytic activities ...), which generally does not excessive effect the specific surface of the material. However, in order not to jeopardize the stability of the mesostructure, the temperature of the heat treatment should generally not exceed 1000 C, and preferably it remains below 950 C, advantageously less than or equal to 900 C, and again

  more preferentially less than or equal to 850 C.

  Optionally, especially in the case where the metal M is introduced in step (b) in the form of a solution, the step (c) may comprise a drying step, prior to the heat treatment. In this case, this preliminary drying is generally carried out as slowly as possible, especially so as to promote ion exchange. For this purpose, the drying is most often conducted at a temperature of between 15 and 80 ° C., preferably at a temperature below 50 ° C., or even at 40 ° C., and advantageously at room temperature. This drying can be carried out under an inert atmosphere (nitrogen, argon) or under an oxidizing atmosphere (air, oxygen) depending on the compounds present in the material. In the case where the metal M 'is introduced into the material in the form of an alkoxide, the

  Drying is advantageously carried out under a water-free atmosphere.

  In a particularly advantageous manner, step (c) can be carried out by subjecting the solid to a temperature gradient, with an initial temperature of between 15 and 95 ° C., at a final temperature of between 350 ° C. and 1000 ° C. advantageously with an increase in temperature between 0.5 C per minute and 2 C per minute, and with one or more successive stages of maintenance at intermediate temperatures, preferably between 350 and 600 C, for varying periods, generally

  between 1 hour and 24 hours. According to a particularly advantageous embodiment, the method of

  The invention may comprise, following the impregnation / heat treatment process of steps (b) and (c), one or more subsequent cycles of impregnation / heat treatment using steps of type (b) and (c). , conducted on the solid obtained at the end of the previous cycle. By covering this type of process with several cycles successive impregnation / heat treatment, it is possible to achieve a very good incorporation of the element Mi in solid solution within the oxide particles integrated with the walls during the step ( at). It is also possible to envisage the implementation of several impregnation / heat treatment cycles using discrete type-III doping elements, whereby materials which integrate particles of cerium oxide that are doped with several elements can be obtained.

  metallic elements in solid solution.

  It should also be noted that the impregnation process or processes that are poorly heat-treated can lead, parallel to an integration of the solid solution element M in the oxide particles, to an integration of this element in the form of cationic or clustered within eVou at the surface of the binder mineral phase of the mesostructure, particularly when this binder phase or matrix is at least partially made of silica. Moreover, after a heat treatment step of type (c), the formation of crystallites based on a metal compound Mi, in particular of oxide, hydroxide, oxyhydroxide, carbonate or hydroxycarbonate, at the surface of the binder phase, eVou at least partially integrated therein. We can also observe the formation of the clusters or crystallites mentioned above.

  eVou surface within the particles of cerium oxide.

  According to a second variant of the invention, it is possible to use as material mesostructure a material of the type which has been described above in the

  part preceding the description of the first variant with the

  characteristics mentioned and whose matrix is based on silica, or mainly consists of sil ice in the sense given above, and contains cations of a metal M2 selected from aluminum or titanium. These cations of a metal M2 may be more particularly in the tetracdric position within the silica. Of course, in this variant, the material can

  understand both in combination with aluminum and titanium cations.

  By "cations of a metal M2 in the tetrahedral position within a silica", it is emend, within the meaning of the present invention, cations of metal M2 in coordination 4 within a silica phase, namely integrated in M2O4 type tetrahedra, with oxygen atoms as nearest neighbors, the M2O4 tetrahedra being able to be considered as analogs of the SiO4 tetrahedra present elsewhere in the silica, and where the silicon is substituted by the M2 metal. These metal cations integrated in the tetrahedral position within the silica of the mineral matrix advantageously represent at least 15%, and preferably at least 20% of the total amount of M2 metal element present in the material. Preferably, this total amount of metal element M2 present in a material according to this variant of the invention is such that the overall molar ratio M2 / Si within the material is greater than or equal to 10%, this ratio being

  advantageously at least 15%.

  The specific presence of aluminum cations in the tetrahedral position within the mineral matrix can be demonstrated in particular by subjecting said materials to a nuclear magnetic resonance (NMR) analysis of aluminum (27AI). The presence of aluminum cations in the tetrahedral position is then reflected on the spectrum obtained by the appearance of a peak at a chemical displacement around 50 ppm. A 27AI NMR analysis on a material according to the invention also makes it possible to demonstrate the possible presence of other types of aluminum cations. Thus, on the 27 A NMR spectrum of a material according to this variant of the invention having aluminum cations in the tetrahedral position within the silica of its mineral matrix, there are generally other magpies than the peak at 50 ppm. to know, most often, a peak around 25 ppm, correspond to aluminum cations called "a pentaedric environment", and a peak around 0 ppm, correspond to aluminum cations called "a

octeedric environment ".

  In general, the aluminum element is present in the form of cations distributed in the three populations of cations with tetrahedric, inclined or octahedral environments mentioned above. In a material according to this variation of the invention incorporating aluminum cations in the tetrahedral position, the molar ratio of the quantity of aluminum cations to the tetraedric position relative to the total quantity of aluminum cations present in the material is most often at least equal. at 20 mol%. Preferably, this ratio is at least 25 mol%, and it is advantageously greater than or equal to 30 mol%, this ratio possibly reaching, in certain cases, higher values or

  equal to 35%. This ratio is usually less than or equal to 80%.

  Within a material according to this second variant of the invention comprising aluminum cations, in particular in the tetrahedral position, in its mineral matrix, the Al / Si molar ratio of the total amount of aluminum present, is related to the total quantity. present silicon is generally between 5% and 50%. Preferably, this ratio is higher

  at 10%, and more preferably at 15%.

  Furthermore, the presence, within a material according to this variant of the invention, of titanium cations in the tetrasdrique position can in particular be demonstrated by an analysis of the material by X-ray spectroabsorption.

(spectrometry quoted EXAFS).

  In these materials which comprise the titanium element, titanium is generally present in the form of cations of which only a part is found integrated in tetrahedral form within the silica of the matrix. Most often, the molar ratio of the amount of titanium cations to the tetraedric position relative to the total amount of titanium cations present in the material is greater than or equal to 10 mol%, this ratio being preferably at least 15% by weight. mole. In a material according to this variant of the invention, this ratio remains as a rule less than or equal to 80%. In a material according to this variant of the invention comprising titanium cations in the tetrahedral position within its mineral matrix, the Ti / Si molar ratio of the total amount of titanium present relative to the total amount of silicon present is generally between 5% and 80%. Of

  preferably, this ratio is greater than 10%.

  It is generally advantageous that a material according to this variant of the invention comprises, in the tetrahedral position within the silica of the matrix, both aluminum cations and titanium cations. Indeed, it has been found that in most cases7 the combined presence of both types of cations within the matrix results in improved stability.

thermal of the mesostructure.

  The material according to the variant which has just been described can be obtained by impregnation of a silica-based matrix mesostructure material as described previously from, for example, a solution of a compound of

Aluminum or titanium.

  Furthermore, the mesostructure material used for the compositions of the invention and comprising aluminum titanium cations according to the second variant which has just been studied can also be presented according to a method of

  particular achievement that will be described now.

  The mesostructure material comprising aluminum and / or titanium according to a first particular embodiment of the second variant As has been said above with regard to the material comprising cations of a metal M2, this applies to this mode. of particular embodiment, unless indicated

  contrary in the following description. More specifically, this material can

  have a BET specific surface greater than or equal to 400 m 2 / cm 3 and it comprises particles (p) of nanometric dimensions of cerium oxide, said particles (p) being linked together by a mineral matrix (m), said matrix being based on a silica containing cations of a metal M2, at least a portion of these cations being integrated in the tetrahedral position within said silica. The material is characterized in that furthermore: - (i) the amount of metal M2 present in the cation state in the tetrahedral position within the silica is at least 10 mol% of the total amount of M2 metal present in the material, with a total amount of M2 metal present in the material such that the overall M2 / Si molar ratio of the material is greater than or equal to 5%; (ii) the M2 metal cations present within the silica vent distributed in the mineral matrix with a gradient of decreasing concentration of the surface towards the heart; - (iii) the particles present within the material have a surface

partially accessible.

  The mesostructure material according to this particular embodiment of the invention typically has a relatively high BET specific surface area, namely generally between 400 and 2300 m 2 per cm 3 of material, this BET specific surface being preferably at least equal to to 600 m2 per cm3 of material, advantageously at least equal to 1000 m2 per cm3 of material and even more preferentially at least equal to 1500 m2 per cm3 of material. Expressed as a unit area by mass unit, this BET specific surface is. as a rule, between 600 and 600 m 2 / g, preferably at least 150 m 2 / g and more

  advantageously at least equal to 200 m 2 / g.

  Characteristically, in the mesostructure material according to this particular embodiment, the M2 metal cations which are present within the matrix (m) are distributed within said matrix with a gradient of decreasing concentration from the surface to the the heart, and these cations are thus mostly located on the surface of the matrix, that is to say near the porous areas of the mesostructure. In this context, it is preferred that at least 50%, preferably at least 60%, of M2 metal cations that are integrated within the matrix (m) are located in the zones located less than 2 nm below the level of the area. Cations specifically present in the tetrahedral position generally have the same type of distribution within the matrix (m), with a gradient of decreasing concentration from the surface to the cosur. In this respect, it is preferable that these tetrasdric species be present in substantial quantities on the surface of the material. More generally, it is advantageous that at least 10% of the tetracrylated M2 cation species within the matrix (m) (preferably at least 20% of these species, advantageously at least 30% of these species). and even more preferably at least 40% or at least 50% of these species) is accessible, which gives the material of the invention an effective acidic character and / or redox properties. This particular embodiment makes it possible to supply materials with a

improved temperature stability.

  This material according to this particular embodiment can also present, at least at a local level, the mesostructure or structures described above. It should be emphasized that the mineral matrix (m) present in the materials according to this embodiment plays a characteristic role of binding between particles of nanometric dimensions (p). Thus, the particles (p) are specifically localized within this binding phase (m), ie within the walls of the mesoporous structure. It should therefore be emphasized that the materials according to the invention are particularly distinguished from materials

  mesoporous including particles in the internal space of their pores.

  Furthermore, in the materials according to this embodiment, at least a portion of the particles (p) incorporated in the binder mineral phase are in contact with the porous parts constituting the accessible internal space of the material. As a result, the material according to the invention is in particular a material where the mineral phase plays an effective role of interparticle binder, but where said matrix (m) does not completely cover the

  particles of nanometric dimensions that it contains.

  Characteristically, in a material according to this embodiment, the particles (p) based on cerium oxide which are connected together by the matrix (m) wind particles of which at least a portion of the surface is accessible. It is understood that in the material in this embodiment, some of the particles (p) (preferably at least 20%, and preferably at least 40%, or even at least 50% of these particles) have a portion of their surface in direct contact with the porous space of the mesostructure, so that their constituent oxide (cerium oxide) can react with reactive chemical species (molecules (in particular in the form of gas or in solution), ions , radicals ...) of sufficient size

  weak to penetrate inside the mesostructure of the material.

  Thus, it is particularly emphasized that, in a material according to this embodiment, the particles (p) can not all be continuously covered by a layer of one or more materials other than cerium oxide. Therefore, it is in particular excluded that the particles (p) are all completely encapsulated by the matrix (m), and it is preferable, in general, that the free surfaces of the particles (p) are that is, surfaces which do not come into contact with the matrix (m), are not covered by a layer of one or more materials other than cerium oxide or only partially so, and preference of fa, con discontinuous if necessary. In any case, continuous coverage of the free surfaces of particles (p) by a layer of one or more materials other than oxide

of cerium is prohibited.

  The accessible character of said particles (p) can in particular be demonstrated by the fact that the materials have a reducible character, that is to say that they have an ability to reduce in reductive atmosphere (especially in the presence of hydrogen) and reoxidize in an oxidizing atmosphere. More precisely, this "reducibility" of a material according to this particular embodiment can be demonstrated by treating the material with hydrogen and analyzing the degree of conversion of the cerium to the state of IV oxidation initially present, in cerium to the oxidation state lil in the material obtained after the treatment, according to the overall reaction below: 2CeO2 + H2 Ce2O3 + H2O The reducible character of a material according to this embodiment incorporating particles (p ) based on cerium oxide can thus notably be quantified by the conversion rate measured at the end of the diode according to the so-called "TPR" protocol, set out below: - In an AMI-1 Altamira type apparatus equipped with a silica reactor is placed at room temperature (generally between 15 C and 25 C) a 100 mg sample of the solid to be tested, under a gaseous flow of a hydrogen / argon mixture with 10% hydrogen by volume, a a flow rate of 30 mL per minute. - A rise in temperature up to 900 C is carried out at the rate of a constant temperature rise gradient of 10 C per minute. Using a thermal conductivity detector at 70 mA, the amount of hydrogen captured by the material is determined from the missing surface of the baseline hydrogen signal at room temperature at baseline.

at 900 C.

  At the end of such a test, a conversion rate of the initially present cerium IV species which is at least 20% is generally measured, this conversion rate being advantageously at least 30%, more preferably at least equal to 40%, and even more

  50% or more. In general, this conversion rate remains below 90%.

  According to a second particular embodiment of the second variant which has just been described, the integrated material, in addition to the cations of the metal M2, compounds of an element M3 selected from rare earths and zirconium. This compound is preferably at least in the form of cations,

  clusters or crystallites based on the M3 element, these forms being able to

  to exist. This compound M3 may be present within the matrix (m), on the surface of this matrix (m) or within the particles of cerium oxide with the formation of solid solutions, it being understood that the element M3 may be they are held together in two or three of these places. "Cluster" based on the metal M3 is understood to mean a polyatomic entity of dimension less than 2 nm, preferably less than 1 nm, comprising at least atoms of the metal M3, in the oxidation state 0 or has a higher oxidation state (typically, it is clusters based on oxides species eVou hydroxides metal M3, for example polyatomic entities in which several atoms of metal M3 wind connected to each other by poets -O- or -OH-, each of the atoms of the metal M2 may be relic to one or more

-O- or -OH groups).

  The element M3 may be more particularly lanthanum or zirconium.

  The materisux of this variant and especially those integrating a

  M3 element often have increased thermal stability.

  In general, when this material is subjected to a heat treatment of 6 hours at temperatures of, for example, between 400 ° C. and 900 ° C., in addition to preserving the mesostructure character, a relatively good maintenance of the specific surface is observed, that is to say, following this type of heat treatment, the specific surface BET said material does not generally vary by a factor exceeding 60%, this restart factor preferably less than or equal to 50%, advantageously lower or equal to 40%, and even more preferentially less than 30%. The variation factor of the BET surface to which reference is made is calculated by the ratio (Si-Sf) / (Si), or "Si" designates the specific surface BET measured before heat treatment and or "Sf" designates the specific surface BET measured after heat treatment. A material according to this embodiment is generally such that, if treated at 400 ° C. for 6 hours, and then treated again for 6 hours at a temperature of 500 ° C., the specific surface S400 measured after the treatment temperature at 400 C and the specific surface ST measured after heat treatment at 500 C wind such that the ratio (S400 ST) / S400 is less than or equal to 60%, preferably less than or equal to 50%, and advantageously less than or equal to at 40%. Preferably, this ratio remains below the above values if the second heat treatment is carried out at a temperature T of 600 ° C., preferably even when T = 700 ° C., advantageously even when T = 800 ° C., or even when T =

900 C.

  Most often, a material according to this second embodiment is such that, following a heat treatment of 6 hours at 400 C, its BET specific surface remains at least equal to 900 m2 per cm3 of material, this BET specific surface being typically between 1000 and 2300 m2 per cm3 of material (and most often between 200 and 400 m2 / g), this specific surface being advantageously at least equal to 1200 m2 per cm3 of material. Moreover, if a material according to this embodiment is subjected to a heat treatment of 6 hours at 800.degree. C., its BET specific surface area generally remains at least equal to 400 m.sup.2 per cm.sup.3 of material.

  specific BET restart preferably at least equal to 750 m2 per cm3.

  A specific process will be detailed below for the material preparation according to the particular embodiment described above, a

  matrix containing cations of a metal M2 in tetrahedral form.

  This method is characterized in that it comprises the successive steps consisting in: (a ') producing a mineral mesostructure integrating, within its walls, particles of nanometric dimensions based on an oxide of cerium, connected together by a silica-based mineral matrix, said matrix not completely covering said particles; (b ') introducing within the mesoporous structure thus obtained a compound of a metal M2 (preferably said metal M2 being in cationic form, possibly complexed, or even an alkoxide metal M2), the total content of metal M2 introduced into the structure, relative to the total surface developed by the mesostructure, being less than 5 micromoles of cation per m 2 of surface; and (c ') subjecting the mesostructure thus produced to a temperature at least equal to 300 C, and not higher than 1000 C, whereby at least a portion of the metal M2 is integrated in the form of cations in the tetrahedral position

  in the mineral phase based on silica.

  Step (a ') of the method of the invention may be conducted by any means known to those skilled in the art. However, this step (a ') is preferably carried out by implementing the method which is the subject of the patent application WO 01/32558, ie by implementing the steps consisting in: (a' 1) forming an initial medium, preferably an aqueous or aqueous-alcoholic medium, advantageously having a pH of less than 4, comprising a texturizing agent, namely an amphiphilic compound of surfactant type, in particular a copolymer, preferably a non-filler under the conditions of implementation. process, and capable of forming micelles in the reaction medium (especially a non-ionic surfactant of block copolymer type), and more preferably a triblock copolymer poly (ethylene oxide) -poly (propylene oxide) -poly (oxide of ethylene; (a'2) add in the middle of step (a'1) a colloidal dispersion of particles of nanometric dimensions, based on a cerium oxide, advantageously in the crystalline state, preferably with a hydrodynamic diameter at least 50% of the population colloidal particles of between 1 and 15 nm, and a preferentially monodisperse granulometric distribution of these colloidal particles; (a'3) forming, by adding to the medium of a mineral precursor alkali silicate type (sodium silicate for example) or silicon alkoxide, a mesostructure mineral phase, at least partially (preferably substantially) silica said mineral phase then integrating, within its mesostructured walls, at least a part of the particles of nanometric dimensions introduced during step (a'2); and (a'4) removing the texturizing agent, in particular by heat treatment or by a solvent, these steps possibly being followed by one or more stages of ravage, drying, eVou calcination, possibly followed by partial chemical etching control of the mineral phase (for example by NH 4 OH, NaOH or HF), in particular in the case where, in the structure obtained at the end of step (a'4), the binding matrix covers

totally the oxide particles.

  In any case, it is generally preferred that the mesoporous structure obtained from stage (a ') has the highest BET specific surface area possible, this area being most often at least equal to 1500 m2 per cm3. of material, preferably at least equal to 1600 m2 per cm3 of material, and still more preferably of the order of 2100 m2 per cm3 of material, that is to say, in general, between 1800 and 2500 m2 per cm3 of materisu. It is also preferred that this mesostructure produced in step (a ') has a pore volume at least equal to 0.2 cm 3 / g for its

  pores with dimensions less than or equal to 20 nm.

  Characteristically, in the material obtained from step (a ') it is necessary that the ceria-based particles are not completely covered by the silica-based binder matrix. In other words, these particles must be at least partially in contact with the internal space of the pores of the mesostructure. This property can be verified by realizing for the material mesostructure a curve of evolution of the electrophoretic potential as a function of the pH (in particular by zetametrie). Another means of verifying the accessible character of the oxide particles within the material of step (a ') is to establish the reducible character of the material by a hydrogen treatment and to measure the conversion rate of the cerium IV cerium lil, especially according to the operating mode "TPR" accurate. It is preferred that the degree of conversion of cerium IV cerium lil measures according to the TPR operating mode is at least 25%, preferably at least 35%, this conversion rate being advantageously at least equal to%. In all cases, if it is desired to improve the accessibility of the oxide particles, it is possible to carry out a partial etching of the silica-based mineral phase, for example by NH 4 OH, NaOH or HF. In this context, it is of course necessary to carry out this partial chemical attack in

  controlled conditions, so as not to affect the stability of the material.

  Whatever the exact mode of implementation of step (a '), the particles of nanometric size which are immobilized within the mineral mesostructure preferably wind particles of cerium oxide of the type described in particular in patent applications

  FR 2 416 867, EP 0 206 906 or EP 208 580.

  More generally, the particles may also be any particles based on cerium oxide obtained in particular by acid treatment, ravage or by dispersion of ultrafine powders obtained for example by high temperature synthesis methods of the combustion type. metal chlorides in a flame known to man

of career.

  Step (b ') of the process consists in impregnating at least a part of the porous zones of the mesostructure realized in step (a') with a compound of the element M2. Generally, this impregnation is carried out by introducing said compound of the element M2 into the mesostructure, by dispersing it in a liquid or gaseous vector phase, this vector phase being preferably a liquid medium, generally a medium. aqueous or hydro-alcoholic, or else an organic solvent medium. Thus, step (b ') most often involves impregnating at least a portion of the porous zones of the mesostructure made in step (a') with a solution, generally aqueous, of a sodium salt. a metal cation M2, or with an aqueous or hydro-alcoholic solution comprising metal cations M2 in the complex state, or else with a solution, generally in an anhydrous organic solvent medium, comprising a metal alkoxide M2. However, according to the particular covering modes, it is also possible to envisage in step (b ') the use of dispersions of clusters based on metal M2 (in particular oxide-based clusters of metal hydroxide eVou). M2), or else a gaseous phase comprising a metal compound (this gas phase being then generally constituted by said

compound in the gaseous state).

  Preferably in the case where the element M2 is aluminum, the aluminum compound of stage (b ') is introduced either: in the form of an aqueous solution (or optionally hydroalcoholic) comprising at least one salt aluminum, preferably an aluminum salt having a tendency to sthydrate the more falble possible. In this context, the aluminum can be introduced in the form of a solution comprising an aluminum nitrate, an aluminum acetate, an aluminum sulphate, or a mixture of these salts, and advantageously in the form of a solution comprising an aluminum nitrate or acetate, or an aluminum acetate / aluminum nitrate mixture; in the form of a solution, generally aqueous or hydroalcoholic, comprising aluminum cations in complexed form, for example in the form of polynuclear aluminum complexes, of the Al (OH) X (NO 3) 3 X (or x va from 1 to 2.5); in the form of an aqueous dispersion comprising clusters based on an aluminum compound, preferably eVou oxide clusters

  aluminum hydroxide, in particular Al'3 type clusters.

  In this context, it is generally preferred that aluminum be introduced in the form of species having a positive overall charge. Thus, according to a particularly preferred embodiment, the introduction of aluminum in step (b ') is carried out by impregnating the structure of step (a') with an aqueous solution comprising an aluminum salt (preferably a nitrate and an acetate) has a pH of between 1 and 6, and preferably less than or

equal to 5.5.

  The introduction of aluminum is of course not limited to the introduction of the solutions and dispersions envisaged above, the covering of which constitutes only a preferential mode of realization. Thus, this introduction of aluminum can alternatively be carried out with the aid of a solution, generally in an organic solvent medium, of an aluminum alkoxide, such as, for example, aluminum butylate Al (OBu) 3. According to another variant, the introduction of aluminum into the mesostructure obtained at the end of step (a ') can also be carried out by subjecting said mesostructure to

a flow of AlCl 3 in a gaseous medium.

  In the specific case where the metal M2 designates titanium, the compound based on the metal M2 of step (b ') is generally introduced either: in the form of an aqueous (or possibly hydroalcoholic) solution comprising at least a titanium salt, preferably selected from titanium acetate, or TiOC12; in the form of a solution of a titanium alkoxide, said titanium alkoxide preferably having the general formula Ti (OR) 4, or R denotes a hydrocarbon group, linear or branched, saturates or unsaturated, and

  preferably an alkyl group having 1 to 6 carbon atoms.

  In this context, it is also preferred, as a rule, that titanium be

  introduced as species with a positive overall burden.

  Thus, according to a particularly preferred embodiment, the introduction of titanium in step (b ') is carried out by impregnating the structure of step (a') with a hydroalcoholic solution, preferably concentrated, comprising a titanium alkoxide in combination with an acid with a H + / Ti ratio in the

  hydroalcoholic medium generally ranging from 0.1 to 4.

  Generally, in step (b '), the metal M2 designates aluminum or titanium, it is necessary that the overall concentration of M2 metal introduced into the porous zones is relatively low, especially in not to observe an excessive reduction of the specific surface of the material, or even clogging of the pores, following the heat treatment of step (c '). This overall concentration is such that the total cation content of metal M2, relative to the total surface area developed by the mesostructure, remains, as a rule, less than 5 micromoles of cation per m 2 of surface area. Preferably, this content remains at least equal to 1 micromole of cation per m 2 of surface. The "total surface of the mesostructure material" referred to herein is calculated by multiplying the BET specific surface area measured in m2 / g for the mesostructure material obtained at the end of

  step (a '), by the mass to said material.

  In most cases, it is preferred that, in step (b '), the compounds of the metal M2 are introduced into the mesostructure in the form of a solution, in an aqueous or aqueous-alcoholic medium, or else at within an organic solvent. In this context, so as to be placed under the above-mentioned concentration conditions, the global cation C concentration of the metal M2 within the medium which is incorporated in the mesostructure at the end of step (b ') is in general less than 2 mol / L and it is preferably between 0.1 mol / L and 1.5 mol / L, this concentration being advantageously less than or equal to 1 mol / L. It should be noted that, in the context of the present process, it is possible to impregnate with relatively concentrated solutions, the concentration C may be greater than 0.5 mol / L, or even 0.7 mol / L in the Most of the cast to achieve incorporation of a solution having such a concentration C within the material mesostructure from step (a '), step (b') can be

  conduct different routes possible.

  Thus, according to a first conceivable variant, step (b ') can be carried out by immersing the mesostructure material obtained at the end of step (a') in a solution comprising [the element M2 at a concentration of the order of the concentration C (generally between 0.1 and 1.5 mol / L, and advantageously between 0.2 and 1 mol / L), then filtering the medium obtained. The impregnated solid collected after the filtration then effectively comprises within its porous zones a solution comprising a metal compound

  M2, with the desired content in metal M2.

  According to another possible variant, step (b ') can also be carried out by immersing the mesostructure material obtained at the end of step (a') in a solution comprising [element M2 at a concentration close to concentration C (generally at a concentration advantageously of between 0.2 and 1.5 mol / l, and preferably between 0.4 and 1.2 mol / l), and then subjecting the medium obtained to centrifugation. Provided that centrifugation is not carried out under conditions that are too severe (typically centrifugation is carried out at 2000 to 5000 rpm, for a duration not generally exceeding 30 minutes), the centrifugation pellet obtained is impregnated solid which comprises, within its porous zones, a solution comprising the element

M2 has the sought concentration.

  According to another conceivable variant, step (b ') can also be carried out by adding to the mesostructure material obtained at the end of step (a') a volume V of a solution comprising the element M2, said volume V being of the order of the pore volume developed by the material, whereby a paste is obtained. The mixing is usually done by mixing. The resulting paste is then evaporated from the solvent, preferably slowly. In this case, the quasi-totality of the element M2 introduced initially is found within the mesostructure. In this context, it is generally preferred to conduct step (b ') by adding to the mesostructure material obtained at the end of step (a') a volume of solution representing between 0.2 and 3 times the volume of the material (and preferably representing at most 2 times the volume of the material), said solution comprising [the element M2 has a concentration generally of between 0.1 and 2 mol / L and then evaporating the solvent in

the mixture obtained.

  Whatever the exact mode of implementation of step (b '), the impregnated solid obtained at the end of this step is then subjected to a step (c') of heat treatment. This step (c ') generally comprises a treatment of the material at a temperature at least equal to 300 ° C., this temperature being preferably at least equal to 350 ° C., higher temperatures being generally not required with respect to integration of the elements of the element M2 in tetrahedral form within the silica of the mineral matrix

  of the mesostructure realized in step (a ').

  However, in certain cases, it may be advantageous to carry out the heat treatment of step (c ') at a temperature at least equal to 400 C, or even at least equal to 500 C, in particular so as to improve certain physical and chemical properties of the material (concentrations of active catalytic sites, specific catalytic activities, etc.), which generally does not affect the surface area of the material excessively. Nevertheless, so as not to call into question the stability of the mesostructure, the temperature of the heat treatment should generally not exceed 1000 ° C., and preferably it remains below 950 ° C., advantageously less than or equal to 900 C, and again

  more preferentially less than or equal to 850 C.

  Of course, especially in the case where element M2 is introduced in step (b ') in the form of a solution, step (c') can

  include a drying step, prior to heat treatment.

  In this case, this preliminary drying is generally carried out as slowly as possible, in particular so as to promote ion exchange. For this purpose, the drying is most often conducted at a temperature of between 15 and 80 ° C., preferably at a temperature below 50 ° C., or even at a temperature of C, and advantageously at room temperature. This drying can be carried out under an inert atmosphere (nitrogen, argon) or under an oxidizing atmosphere (air, oxygen) depending on the compounds present in the material. In the case where the element M2 is introduced into the material in the form of an alkoxide, the drying is advantageously carried out under a water-free atmosphere. In a particularly advantageous manner, step (c ') can be carried out by subjecting the solid to a temperature gradient, from an initial temperature of between 15 and 95 ° C., at a final temperature of between 350 ° C. and 1000 ° C. , advantageously with an increase in temperature between 0.5 C per minute and 2 C per minute, and with one or more successive stages of maintenance at intermediate temperatures, preferably between 350 and 600 C, for variable periods, generally

  between 1 hour and 24 hours.

  According to a particularly advantageous embodiment, the method of the invention may comprise, following the process of impregnation / heat treatment steps (b ') and (c'), one or more subsequent cycles of impregnation / heat treatment putting in steps of type (b ') and (c'), conducted on the solid obtained at the end of the previous cycle. By placing this type of process in the process of several cycles of successive impregnation / heat treatment, it is possible to achieve a very good incorporation of the element M2 into the silica of the matrix binding of the mesostructure.

performed in step (a ').

  It should be noted that the process or processes of impregnation / heat treatment implemented can lead, parallel to an integration of the element M2 in the tetrahedral position within the matrix, to the formation of crystallites based on a compound metal M2, in particular of the oxide, hydroxide, oxyhydroxide, carbonate or hydroxycarbonate type, at the surface of the binder phase, eVou at least partially integrated therein. We can also observe in some cases the formation of clusters or crystallites on the surface

  eVou within the particles of cerium oxides.

  According to an embodiment that is even more specific, the material obtained at the end of the impregnation / heat treatment cycle (s) implementing steps of type (b ') and (c') can be further modified. . In this context, the preparation process can thus include, in an additional manner, one or more subsequent cycles of impregnation / heat treatment similar to the steps of type (b ') and (c') previously described, but implementing an impregnation by a compound of another metal than the metal M2. The method then generally comprises steps (b ") and (c"), subsequent to steps (b ') and (c'), and consist of: (b ") introducing, within at least a part porous areas of the material, a compound of a metal M3 as defined above (generally said metal M3 in cationic form, possibly complexed, or an alkoxide metal M3 said), the content of said element M3 introduced into the structure relative to the total surface area developed by the mesostructure, being less than 5 micromoles of cation per m 2 of surface, and (c ") subjecting the impregnated material to a temperature at least equal to

300 C, and not more than 1000 C.

  In the most general case, steps (b ") and (c") can advantageously be conducted under the conditions described above for steps (b ') and (c'), subject to any adjustments that may be necessary. , especially if the compound based on the metal M3 used in step (b ") had a specific physico-chemical nature.In most cases, the various impregnation modes envisaged for the aluminum metal compounds wind in general transposable to the impregnation of a compound of a metal M3, particularly with regard to the concentrations to be covered.The conditions of the heat treatment to implement for stage (c ") are, as a rule , the same as

  those used in step (c) defined above.

According to a particularly advantageous embodiment, the impregnation / heat treatment cycle of stages (b ") and (c") can be implemented when it is desired to integrate compounds of element M3 within the material, in particular in the form of cations eVou clusters based on i'element M3 within its matrix eVou the surface of this matrix, which leads in particular to an increase in the thermal stability of the material obtained. As a rule, the compound of the element M3 covered in step (b) is preferably a salt of the element M3, for example the nitrate or acetate of the element M3, and the Step (b ") can typically consist in impregnating the material with a solution of the salt M3, the pH of said solution being preferably less than 8 and advantageously less than 7. In general, it is also possible to observe more than one integration of the element M3 in the form of cations eVou of clusters based on this element within its matrix eVou on the surface thereof, the formation of crystallites based on the element M3, which are generally located on the surface of the material. Most often, part of the M3 element is also integrated within

particles of cerium oxides.

  It should also be emphasized that, surprisingly, in spite of the impregnation / heat treatment steps imposed during the process described, the solids obtained in the most general case have a BET specific surface which remains relatively high. and which generally represents at least%, advantageously at least 60%, and even more preferably at least 75% of the BET specific surface area of the mesostructure material obtained by

['outcome of step (a').

  It should also be noted that the various impregnation / heat treatment steps imposed during the process described do not induce a consequent reduction in the accessibility of the particles with respect to the accessibility to the particles presented in the mesostructure realized in the process. step (a '). Thus, the reducibility of the material obtained following the different stages of impregnation / heat treatment is generally similar to that of the mesostructure obtained at the end of step (a '). Thus, if the conversion rate of the cerium IV to cerium is defined by the procedure of "TPR" specified for the mesostructure carried out in step (a '), and by tf the degree of conversion of the cerium IV to According to the precise "TPR" operating method for the material obtained at the end of the different impregnation / heat treatment stages imposed during the process, the ratio tf / ta remains generally greater than or equal to 40%, this ratio being most often at least 50%, advantageously at least equal to

  %, and preferably at least 80%.

  The mesostructure material having been described, the compositions of

  The invention will now be studied.

  The compositions of the invention The invention firstly relates to a first compositio based on at least one compound of an element E selected from the group consisting of the elements of atomic numbers 21 to 31 inclusive of the periodic classification and molybdenum and tungsten and a mesostructure material of the type described above. It will be understood that, of course, the invention covers the case where the composition comprises several elements E in combination, the respective proportions of these different elements E possibly being arbitrary. This remark applies, of course, not only to the first composition of the invention but to all other compositions according to the invention containing the element E. The element E is therefore a metal selected from the group consisting of the elements which go from scandium to gallium in the fourth period of the table of periodic classification of elements, group to which they add

molybdenum and tungsten.

  The element E may be more particularly zinc or vanadium.

  The E element proportions of this composition may vary over a wide range. Wiles can thus be understood for example between 0.5% and 50%, proportions expressed by weight of metal E with respect to the material mesostructure. However, for zinc, these proportions are preferably between 2% and 50%, more particularly between 5% and 25% and even more particularly between 10% and 15%, proportions expressed as

p reced em me nt ..

  The proportion of vanadium is preferably between 0.5% and 7%, more particularly between 0.5% and 5% and even more particularly between

  0.5% and 2.5%, proportions expressed as before.

  The compounds of the elements E, in particular of Zn and V, may be of various nature. It can be hydroxides or oxides (ZnO, V2O5 for example). In the case of vanadium, this compound can also be a mixed oxide (CeVO3), in this case the cerium can be present at the valence lilt

  These hydroxides or oxides can be amorphous or crystallized.

  The composition of the invention based on the element E and the material mesostructure can be obtained from this element and the material by

  any suitable means of bringing this element into contact with the material.

  The contacting can be done by immersing the starting mesostructure material in a solution comprising E element and then subjecting the obtained medium to centrifugation. The solution of the element E used in the case of the process according to the invention is usually an aqueous solution of salts of this element. The salts of inorganic acids such as nitrates, sulphates or chlorides can be chosen. It is also possible to use the salts of organic acids and in particular the salts of acids

  saturated aliphatic carboxylic acids or salts of hydroxycarboxylic acids.

  As vanadium salts it is preferable to use VO (SO 4), Na 3 (VO 4),

N H4VO3.

  According to a particular embodiment, the contacting is done by dry impregnation. Dry impregnation consists in adding to the product to impregnate a volume of an aqueous solution of element E which is equal to

  porous volume of the material to impregnate.

  After contacting, the obtained material is dried and then calcined so as to obtain a composition in which the element E, for example zinc or vanadium, is present in the oxide state. This calcination can be

  for example at a temperature of 600 C.

  It is also possible to prepare this first composition by solid flow by mixing an ultrafine size E-element precursor (nanometric size) with the mesostructure material and then calcining the mixture at a temperature sufficient to obtain the compound of E element in the form desired for example in the oxide form. The invention also relates to a second composition which comprises a fluid bed catalytic cracking catalyst and a mesostructure material.

  of the type just described above.

  Fluid catalytic cracking catalysts are well known.

  They are generally understood to include one or more zeolites and one or more matrices. The zeolite may be, for example, of type Y of faujasite structure, X, beta, ZSM-5; it can also be a product obtained from a heat treatment of these zeolites or by total or partial exchange with rare earths thereof. The zeolites used have specific surfaces generally between 100 and 300 m 2 / g, preferably between 120 and 200 m 2 / g. The matrix in which the zeolite (s) is dispersed may for example be based on silica, alumina or silica gel alumina and usually further comprises an inert compound such as kaolin. The zeolite content may vary in particular between 10% and 80% by

  weight and that of the matrix can be between 20% and 90% by weight.

  In a known manner, the catalytic cracking catalyst may further comprise additives such as those intended for example to increase the production of olefins, to trap vanadium or to eliminate NOx or SOx. As another type of additive, mention may also be made of those based on ZnO, supported on Al 2 O 3 alumina, or on hydrotalcites, nickel-based and vanadium-based additives supported on Al 2 O 3 alumina or on a zeolite. or based on zinc on a support based on alumina and titanium or on a hydrotalcite support. The additives may also be based on zinc and cobalt on a hydrotalcite support, or based on

  zinc, manganese and zirconium on an alumina support.

  These additives may be present in an amount of, for example, between 1% and 30% by weight, more particularly between 5% and 20% by weight.

  weight with respect to the cracking catalyst.

  The third composition of the invention is close to the second insofar as it also comprises a catalytic cracking catalyst in a fluid bed with a mesostructure material but with in addition at least one element E in combination with said mesostructure material. This third composition is in fact the combination of a catalytic cracking catalyst

  in a fluid bed with the first composition of the invention.

  The amounts of the mesostructure material in the second composition of the invention generally vary from 3% to 40% by weight, preferably from 5% to 30% by weight, based on the cracking catalyst. These proportions are identical for the third composition but eiles this time apply to the assembly materos mesostructure + element E. According to a particular embodiment of the invention, the second or third composition of the invention may comprise a catalyst catalytic cracking of the type which has just been described and which further comprises as a specific additive a Lewis acid supported on an alumina. Such a type of catalyst is described in the patent application EP-A609971 to the

  description of which we can refer. Lewis acid can be chosen

  in the group comprising the elements, or compounds thereof, Ni, Cu. Zn, Ag, Cd, In, Sn, Hg, Tl, Pb, Bi, B. Al (other than Al2O3) and Ga. Particularly zinc or a zinc compound may be mentioned. An alumina having a large specific surface is preferably used, the surface of this alumina can thus be stabilized by an additive such as a lanthanum or barium oxide, for example. The deposition of the Lewis acid on the alumina can be done by any suitable means for example by impregnation. The amount of Lewis acid is generally from 1 to 50% by weight, more preferably from 10 to 40% by weight of the Lewis acid and alumina complex. The amount of Lewis acid and alumina can be between 1 and 50% by weight relative to the whole of the

catalytic cracking catalyst.

  The second and third compositions can be formed by physical mixing of the constituents. By "constituents" is meant all the components and compounds which constitute the compositions, ie, in particular the FCC type catalyst as described above, the mesostructure compound with optionally E. Wiles may also be prepared. by atomization of an aqueous suspension with the various r:

constituents of the composition.

  The compositions of the invention may optionally be shaped to be in the form of granules, beads, cylinders or honeycombs of varying sizes. For the second and third compositions which additionally contain a cracking catalyst, the constituents of these compositions may be present either in juxtapose form, for example in the form of granules, balls or blended rolls and arranged next to one another and each consisting of one constituting either a more intimate mixture, ie in the form for example of granules, balls or cylinders, each of these granules, balls or cylinders being constituted of a

mixture of said constituents.

  The compositions of the invention, in particular those comprising an FCC catalyst, and which have been described above, are particularly suitable for use as catalysts in catalytic cracking processes operating without the addition of hydrogen and especially in a conventional process.

FCC type.

  Consequently, the invention also relates to a catalytic cracking process operating without the addition of hydrogen and in particular to a process

  FCC using as catalyst system these compositions.

  These compositions of the invention may be added to all catalytic particles circulating in the cracking process, at the start of the process or during the process. These compositions can be added directly to the cracking zone, in the regeneration zone of the cracking reactor or at any suitable place to obtain the reduction.

desired level of sulfur.

  In the case of an FCC process, the catalytic cracking process is carried out in a conventional FCC installation in which reaction temperatures which can vary between 400 ° C. and 700 ° C. and regeneration temperatures of between 500 ° C. and 500 ° C. are used. and 850 C in particular. The baking time in the riser is usually from 2s to 10s and the residence time of the catalyst in the regenerator varies from 5 minutes to 15 minutes. The process can be used for various heavy loads of fluid bed catalytic cracking. By way of example, distillate boiling in the range between 350 ° C. and 550 ° C. (or 380 ° C.-550 ° C.) may be mentioned. These distillate under pressure can be mixed with light atmospheric distillate (380 C-410 C), coking distillate or residues under asphalts deputy. The process of the invention is particularly suitable for high sulfur content feeds, for example 0.1 to 4 wt% sulfur. It can in particular be used to recover liquid products,

  especially gasoline and diesel fractions, reduced sulfur content.

  On the other hand, the amount of catalyst relative to the amount of charge can usually vary between 4 g / g and 14 g / g, preferably between 6 and 12 g / g. The yield MAT is between 40 and 80%, preferably between 50

and 75%.

  The MAT conversion rate is the conversion rate in% by weight of the gasoline + coke + gas combination and the total yield TOT

  conversion into% by weight of gas + gasoline + gas oil + coke together.

  In the implementation of the catalytic cracking process, the compositions of the invention have advantages which will be described more

precisely below. Thus, the second composition of the invention makes it possible to obtain for

  MAT yields ranging from 50% to 80%, more particularly between 60% and% and TOT yields ranging from 60% to 98%, more particularly between 80% and 95%, better desulfurization of gasoline and light diesel. An advantage of the use of the second composition of the invention is the reduction in the gasolines and light gas oils of heavy sulfur compounds of alkyl-thiofenes type, especially the alkylthiofenes in Cn for which n is equal to or greater than 3, of benzothiofenes and alkyl type

Benzo thiofenes.

  By alkyl compound is meant methyl methyl thiofen ethyl thiofen, butyl thiofene, pentyl thiofene. By alkyl-benzo thiofenes compound, is meant in particular methyl-benzo-thiofene, ethyl-benzo

  thiofene, propyl-benzothiofene and butyl-benzothiofene.

  The reduction in gasolines and light gasolines of the benzothiofenes content is greater than 15%, more particularly greater than 20% and advantageously greater than 25% compared to the content observed for operation with a basic FCC catalyst without addition of

composes mesostructure.

  The third composition of the invention provides the same advantages as those just described for the second. In addition, this composition provides a reduction in gasolines and light gas oils of an even wider range of sulfur compounds including mercaptans. For yields MAT ranging from 50 to 80%, it provides a decrease in gasoline and light gas on the one hand mercaptan content greater than 40%, preferably greater than 50% and preferably greater than 60% and on the other hand, the benzo thiofen content greater than 15%, preferably greater than 20%, advantageously greater than 25%, compared to the content observed for operation with a base catalyst without the addition of a mesostructure compound. The third composition according to the particular embodiment described above, that is to say the one whose FCC catalyst comprises an additive of the type described in EP-A-609971 has the same advantages as those just described here. above for the two preceding compositions in particular with regard to the reduction of sulfur compounds. Wile also offers the additional advantage of minimizing the quantities of mesostructure compounds, in combination with compounds of an element E, especially zinc or vanadium, to be used when this compound

  Mesostructure is in combination with another FCC catalyst additive.

  Another feature of the various compositions of the invention is the improvement of the overall conversion efficiency of FCC charges. Thus, the second and third compositions of the invention, for the content of mesostructure compounds, optionally based on compounds of an element E, especially zinc and vanadium, ranging from 5 to 40%, are characterized by an improvement of from at least 2.5%, preferably at least 4% and advantageously above 5%, with MAT yields ranging from 60 to 80% and TOT yields ranging from 80 to 95% for MAT operating conditions corresponding to amounts of catalyst ranging from 2.5 to 4g per g of FCC charge. For compositions of the invention with the additive based on a Lewis acid of the type described above and for contents of mesostructure compounds, optionally based on a compound E, in particular Zn and V, ranging from 2% to 20%, there is an improvement of at least 2.5%, preferably at least 4% and advantageously greater than 5%, MAT yields ranging from 60 to 75% and TOT yields ranging from 80 to 95% for MAT operating conditions

  has catalyst levels ranging from 2.5 to 4 g per g of FCC charge.

  Another feature of the compositions of the invention is their good aging behavior. This good aging behavior can be demonstrated by the substantially identical desulfurization characteristics obtained after an accelerated aging test. The accelerated aging test carried out is a hydrothermal treatment of the compositions of the invention carried out at 750 ° C. for 5 hours under a

atmosphere 100% water vapor.

  Another feature of the compositions of the invention is a better selectivity of the conversion to olefins. Thus, the second and third compositions of the invention, for example with% of mesostructure compounds varying from 10 to 35% by weight, are characterized, under operating conditions corresponding to MAT yields varying from 50% to gains in% of C3 and C4 olefins expressed by molar ratios "olefinic compound / compound saturates with identical carbon number" in the

  gases greater than 3%, preferably greater than 5%.

  Examples will now be given.

EXEM PLES

  The following will be given below (1) the compositions used, (2) the test used to measure the catalytic activity of these compositions and (3) the

results obtained.

  1 Compositions Used 1-1 Example 1 (Composition 1) This composition corresponds to an FCC catalyst referred to hereafter as a base catalyst. The catalyst employed is a Millenium commercial FCC catalyst from Engelhard Company which contains 1% rare earth weight (TR), with a BET specific surface area of 170 m2 / g and a zeolite with a mesh size of 2.455 nm. The commercial catalyst was hydrotreated at 816 C for 11 hours in a 90% water vapor atmosphere. In addition, it was subjected to another hydrotreatment at 750 C for 5 hours in a 100% atmosphere of water vapor in a second time. This second treatment did not modify the specific surface or the size of the mesh. 1-2 Example 2 (Composition 2) This composition corresponds to a mesostructure material of the type of that of Example 3 of the patent application WO 01/32558. It is therefore a mesostructure compound whose matrix is silica and having a ratio

  molar silica / cerium oxide 50/50.

  Example 3 (composition 3 according to the invention) The material of Example 2, after calcination at 500 ° C., was impregnated with 10% by weight of Zn using an aqueous solution of Zn (NO 3) 2. The dry impregnation technique was used. The impregnated material was dried at 100 ° C. for 6 hours and then calcined for 3 hours at 600 ° C. Example 4 (composition 4 according to the invention) The material of Example 2, after calcination at 500 ° C. was impregnated at different levels of V using an aqueous solution of VO (SO4). The dry impregnation technique was used. The amounts of V impregnated were 0.5, 0.75 and 1.5% by weight of V. The material was dried at 100 ° C.

  for 6 hours and then calcine for 3 hours at 600 C.

  Example 5 (Composition 5) A zinc-based composition supported on alumina (Zn / Al2O3) was prepared according to the teaching of EP-A0609971. The product was granulated, crushed and screened to a particle size of 0.25-0.42 mm. It was hydrothermally treated at 750 ° C. for 5 hours in a 100% water vapor atmosphere. The zinc content is 8% by weight of the

  composition. It has a BET surface area of 110m2 / g.

  Example 6 (Composition 6 according to the invention) The material of Example 2 was granulated, crushed and screened to a particle size of 0.25-0.42 mm. 30% by weight of this material was mixed with

  the basic catalyst described in Example 1.

  Example 7 (composition 7 according to the invention) The material of Example 3 was granulated, crushed and screened to a particle size of 0.25-0.42 mm. 30% by weight of this material was mixed with

  the basic catalyst described in Example 1.

  Example 8 (Composition 8 according to the invention) The material of Example 4 to 0.75% by weight of vanadium was granulated, crushed and screened to a particle size of 0.25-0.42 mm. It was then hydrothermally treated at 750 ° C for 5 hours in a steam atmosphere. 30% by weight of this material was mixed with the

  base catalyst described in Example 1.

  Example 9 (Composition 9 according to the invention) The material of Example 5 and that of the material of Example 4 were mixed with the base catalyst of Example 1 in a proportion by weight of 10%. each relative to the amount of base catalyst. Before mixing, the materials were hydrotreated at 750 ° C. for 5 hours in

  an atmosphere with 100% water vapor.

  2 Test 2-1 Charge The charge used for the catalytic test is an Arabian light distillate diesel oil, whose characteristics are given in Table 1 below:

Table 1

  Density 288 K (g / cm3) 0.9072 Aniline point (wt.%) 91.2 Sulfur (wt.%) 1.4 N2 (ppm) 890 Average Molecular Weight 438 Viscosity (cs at 373 K) 6, 29 Refractive index at 340 K 1.488 CCR (% by weight) 0.32

K (UOP) 12.03

  Distillation curve Dn D-1160 in% by weight (K) IBP (boiling point 5 10 30 50 70 90

552 604 633 690 721 751 812

  2-2 Requirements For testing an automated micro-activity test (MAT) test unit was used in accordance with ASTM D3907. This unit can be programmed to perform cyclic experiments (reaction, stripping and regendration) by varying the experimental conditions. The reaction conditions used were: Reaction: T = 510 ° C, residence time: 30s, catalyst / feed ratio: 2-5 g / g; Stripping: 15 minutes in a stream of nitrogen;

  Regeneration: T = 540 C, 3 h in column of air.

  2-3 Analyzes Sulfur compounds in gasoline and light diesel fraction up to a boiling point of 286.8 C were analyzed by gas chromatography using a specific sulfur detector (PFPD, Detector

Photometric Pulse Flame).

3 Results

  The results of the wind tests given in the tables that follow.

  The amount of sulfur in gasoline, given in ppm by weight of sulfur in gasoline, includes benzothiofen (Tb = 221 C). The alkyl benzothiofenes (C1-, C2- and C3-benzothiofenes) produce the sulfur compounds present

in the light diesel cut.

  To present the results of these alkyl benzothiofenes, the concentration of sulfur from the different compounds in the C5-286,8 C liquid cut is also given in the tables: CB stands for the base catalyst, CaVcharge is the ratio of the amount of catalyst the quantity of feedstock, these quantities being expressed in grams, LPG means liquefied gas, O is olefins, P is parafines.

Table 2

  Test carried out with a MAT conversion rate of 60% by weight The values given in the table wind sulfur contents in ppm CB catalyst Composition 6 Composition 7 CaVcharge (g / g) 3,2 2,2 2,9 Gas yield 16 , 15.6 14.7 Petrol 39.5 38.5 39.6 Coke 4.3 5.9 5.7 O / P in GPL 1.3 1.5 1.4 Distribution of sulfur in gasoline ( ppm) Mercaptans 68 45 16 Thiofene 64 63 46

THT 70 48 33

  C1-thiofene 211 187 153 C2-thiofene 145 133 109 C3-thiofene 66 48 47 C4thiofene 165 56 98 Benzothiofene 774 663 585

TOTAL 1564 1243 1087

  Separation of sulfur in the liquid fraction C5-286.8 C Tb <221 C 523 386 334 Benzothiofen 513 441 390 C1-benzothiofen 2548 2159 2252 C2benzothiofen 4538 3580 3215 C3-benzothiofen 5017 4014 3812

TOTAL 13139 10580 10003

Table 3

  Test carried out with a MAT conversion rate of 70% by weight The values given in the table wind the sulfur contents in ppm CB catalyst Composition 6 Composition 7 Caticharge (g / g) 4.2 3.3 4.5 Gas yield 20 , 19.7 19.4 Petrol 43.8 41.7 42.1 Coke 6.0 8.6 8.5 O / P in GPL 1.2 1, 2 1.2 Sulfur distribution in gasoline (pp rn) Mercaptans 83 37 Thiofene 74 70 57

THT 55 33 26

  C1-Thiofene 236 221 205 C2-thiofene 114 99 100 C3-Thiofene 63 33 42 C4thiofene 168 51 76 Benzothiofen 820 749 676

TOTAL 1613 1350 1219

  Sulfur distribution in the C 5-286.8 C cut Tb <221 C 543 410 370 Benzothiofen 562 510 460 C1-benzothiofen 2727 2406 2569 C2benzothiofen 4516 3623 3529 C3-benzothiofen 4862 3992 3965

TOTAL 13210 10941 10893

  TABLE 4 Test carried out with a MAT conversion rate of 60% by weight The values given in the table show the sulfur contents in ppm Distribution of sulfur in gasoline (ppm) Catalyst CB Composition 8 Composition 9 Mercaptans 68 60 39 Thiofene 64 39 36

THT 70 36 3

  C1-thiofene 211 140 87 C2-thiofene 145 105 36 C3-thiofene66 43 28 C4thiofene165 40 26 Benzothiofene774 588 734

TOTAL1564 1051 988

  Distribution of Sulfur in the Liquid Cut C5-286.8 C Tb <221 C523 305 254 Benzothiofene513 387 505 C1-benzothiofen2548 1947 2478 C2benzothiofene4538 3263 4127 C3-benzothiofene5017 3716 4593

TOTAL13139 9618 11957

Table 5

  Test carried out with a MAT conversion rate of 70% by weight The values given in the table wind the sulfur contents in ppm Distribution of sulfur in gasoline (pp m) Catalyst CB Composition 8 Composition 9 Mercaptans 83 116 83 Thiofene 74 48 41

THT 55 23 1

  C1-thiofene 236 163 91 C2-thiofene 114 77 33 C3-thiofene 63 26 16 C4thiofene 168 27 22 Benzothiofen 820 663 814

TOTAL 1613 1144 1102

  Separation of sulfur in the liquid section C5-286.8 C Tb <221 C 543 327 287 Benzothiofen 562 452 573 C1-benzothiofen 2727 2183 2802 C2benzothiofen 4516 3593 4437 C3-benzothiophene 4862 3875 4854

TOTAL 13210 10431 12954

Claims (20)

  1- Composition characterized in that it comprises: a catalytic cracking catalyst in a fluid bed; a mesostructure material comprising particles of nanometric dimensions, at least partially crystalline, based on a cerium oxide, said particles being bonded to one another by a mineral matrix; silica or alumina base.   2- Composition, characterized in that it comprises: a catalytic cracking catalyst in a fluid bed; a mesostructure material comprising particles of nanometric dimensions, at least partially crystalline, based on an oxide of cerium, said particles being bonded together by a silica or alumina-based mineral matrix; at least one compound of an element E selected from the group consisting of the elements of the atomic numbers 21 to 31 of the periodic classification and the   molybdenum and tungsten, in combination with said mesostructure material.   3- Composition according to claim 2, characterized in that the element E is zinc or vanadium.   4- Composition according to one of the preceding claims, characterized in that   that the matrix consists mainly of silica   - Composition according to one of the preceding claims, characterized in that   that the overall crystallinity level of said mesostructure material is at least   % by volume, more particularly by at least 40%.   6. Composition according to one of the preceding claims, characterized in that   that the above-mentioned particles of nanometric dimensions wind particles of spherical or isotropic morphology of which at least 50% of the population has a mean diameter of between 1 and 10 nm, the distribution   granulometric of said particles being monodisperse.   7- Composition according to one of the preceding claims, characterized in that   that the mesostructure material has a specific BET surface area between 400 m2 / cm3 and 2400m2 / cm3.   8- Composition according to any one of the preceding claims,   characterized in that the precise mesostructure material has, at least at a local level, one or more mesostructure (s) selected from mesoporous three-dimensional hexagonal symmetry P63 / mmc, of two-dimensional hexagonal symmetry, of three-dimensional cubic symmetry la3d , Im3m or Pn3m; among the type mesostructures   vesicular or lamellar, or among vermicular mesostructures.   9- Composition according to any one of the preceding claims,   characterized in that in the mesostructure material the molar ratio (silica eVou alumina) / cerium oxide is between 20:80 and   99.5: 0.5, preferably between 40:60 and 95.5: 4.5.   - Composition according to any one of the preceding claims,   characterized in that the cerium oxide of the mesostructure material comprises at least one metal element M, in solid solution within the crystal lattice of said oxide, M 'being selected from zirconium and earths rare other than cerium.   11- Composition according to any one of the preceding claims,   characterized in that the matrix of the mesostructure material is based on it contains cations of a metal M2 selected from aluminum or titanium.   especially in the tetrahedral position within the silica.   12. Composition according to claim 11, characterized in that the mesostructure material has a BET specific surface greater than or equal to 400 m 2 / cm 3 and in that: (i) the quantity of M2 metal present in the cation state in The tetrahedral position within the silica represents at least 10 mol% of the total amount of M2 metal present in the material, with a total amount of M2 metal present in the material such that the overall molar ratio M2 / Si of the material is greater. or equal to 5%; (ii) the cations of the M2 metal present within the silica wind distributed in the mineral matrix with a gradient of decreasing concentration from the surface to the cosur; - (iii) the particles present in the material have a partially accessible surface. 13Composition according to claim 11 or 12, characterized in that the total amount of M2 element present in the mesostru ctu re material is such that   that the overall molar ratio M2 / Si of the material is greater than or equal to 10%.   14- Composition according to one of claims 11 to 13, characterized in that   that the molar ratio of the quantity of M2 element cations to the tetrahedral position relates to the total quantity of M2 element cations present in the   within said material is at least 10 mol%.   - Composition according to one of claims 11 to 14, characterized in that   that the metallic element M2 is aluminum and the Al / Si molar ratio of the total quantity of aluminum present, relative to the total amount of silicon.   present is between 10% and 50%.   16- Composition according to one of claims 11 to 15, characterized in that   that the metal element M2 is titanium and the Ti / Si molar ratio of the total amount of titanium present relative to the total amount of silicon present is between 10% and 80%.   17- Composition according to one of claims 2 to 16, characterized in that   E precise element is zinc in a proportion by weight relative to the mesostructure material between 2% and 50%, more particularly between% and 25%. ;   18- Composition according to one of claims 2 to 16, characterized in that   The precise E element is vanadium in a proportion by weight relative to the mesostructure material of between 0.5% and 7%, more particularly between 0.5% and 5%.   19- Composition according to one of claims 1 to 18, characterized in that   the proportion by weight material possibly mesostructure with the element E / catalytic cracking catalytic fluid bed is between 3% and   % by weight, preferably between 5% and 30% by weight.   - Composition according to one of claims 1 to 19, characterized in that   the fluid bed catalytic cracking catalyst comprises one or more   zeolites and one or more matrices.   21. Composition according to claim 20, characterized in that the fluid-bed catalytic cracking catalyst further comprises an additive chosen from: ZnO additives, supported on alumina Al2O3, or on hydrotalcites; the nickel and vanadium additives supported on alumina or on a zeolite; zinc-based additives on a support based on alumina and titanium or on a hydrotalcite support; - additives based on zinc and cobalt on a hydrotalcite support; additives based on zinc, manganese and zirconium on an alumina support. 22. Composition according to claim 20, characterized in that the fluid-bed catalytic cracking catlyseur further comprises an additive which is a   Lewis acid supports on an alumina.   23. Composition according to claim 22, characterized in that the acid of   Lewis is zinc or a compound of zinc.   24- Catalytic cracking process operating without the addition of hydrogen, characterized in that a composition according to the invention is used as catalyst One of claims 1 to 23.   - Process for catalytic cracking in a fluid bed, characterized in that one   uses as catalyst a composition according to one of claims 1 to   23. 26- Method according to claim 25, characterized in that it is used on   a high content of sulfur compounds.   27- Solon process claim 25 or 26, characterized in that recupere   gasoline and diesel fractions with reduced sulfur content.   28- Method according to one of claims 24 to 27, characterized in that the   composition is added in the cracking zone or in the zone of