CA2303137A1 - Composition based on an organic sol of tetravalent metal oxide and an organic alkaline-earth compound - Google Patents

Abstract

The invention concerns a composition comprising an organic sol of particles of at least one tetravalent metal oxide, and at least an organic compound of at least one alkaline-earth. The composition may further contain at least an organic compound of at least an alkaline. The tetravalent metal is more particularly cerium. The invention also concerns the use of said composition as additive of hydrocarbon compounds.

Description

COMPOSITION BASED ON ORGANIC METAL OXIDE SOL
TETRAVALENT AND AN ORGANIC ALKALINE EARTH COMPOUND
The subject of the present invention is a composition based on at least one compound organic of at least one alkaline earth and one self of at least one oxide of minus one tetravalent metal.
The present invention also relates to a process for obtaining these compositions and their use.
We know that when diesel fuel is burned in the diesel engine, the products carbonaceous tends to form soot, which is said to be novice both for the environment only for health. He's been wanted for a long time techniques that reduce (emission of these carbonaceous particles, which we will designate in the continuation of the description under the expression "soot".
This research is concomitant with the need not to increase the emission of carbon monoxide and gases known to be toxic and mutagenic, such as nitrogen oxides.
Many solutions have been proposed to reduce these emissions carbonaceous.
However, we are moving more and more towards adaptation in the circuits exhaust of a filter capable of stopping the whole; or a very strong proportion (at minus 80% by mass) of the carbonaceous particles generated by the combustion of various fuels.
This technique is however limited by the storage capacity of the filter, that need either empty or burn the soot contained. This so-called operation regeneration is extremely expensive to plan and implement. One of the solutions more commonly proposed is the combustion of this soot, induced combustion of intermittently either by electric heating or by use of a fossil igniter fuel.
However, this technique has many drawbacks, the least of which is not the risk of thermal shock leading to a fracture or a cracking of ceramic filter, or a fusion of the metal filter.
One solution which would be satisfactory consists in introducing soot catalysts that allow frequent self-ignition of soot collected in the filtered. For that, it is necessary that these soot present a temperature of auto inflammation low enough to be reached frequently during normal walking of engine.
We realized that rare earths in general, and cerium in particular, could be a good element to reduce the auto-ignition temperature of soot.
However, there has been a need for a product which, after introduction in

2 diesel, then after combustion, gives good self-ignition of soot to one even lower temperature.
For this purpose, the composition of the invention is characterized in that it understands an organic soil of particles of at least one oxide of at least one metal tetravalent and at at least one organic compound of at least one alkaline earth.
For the purposes of the invention, the term “soil” is intended to denote a colloidal suspension organic of particles of at least one oxide of at least one tetravalent metal.
The tetravalent metal can be chosen from rare earths which can form of tetravalent metal oxides. By rare earth we mean the elements of the group consisting of (yttrium and the elements of the periodic table atomic number between 57 and 71. The periodic classification of the elements to which it's done reference is that published in the Supplement to the Chemical Bulletin of France # 1 (January 1966). As such, we can cite cerium, praseodymium, and terbium. In the special case of rare earth mixtures, it is preferable that cerium be present.
The tetravalent metal is more particularly cerium.
The alkaline earth can be chosen from magnesium, calcium, strontium, or barium. More specifically, falcalino-earth is calcium, or strontium.
According to a preferred variant of the invention, the composition comprises a sol organic of cerium oxide particles and at least one organic compound of strontium.
The composition of the invention can, in addition, comprise at least one compound organic of at least one alkaline.
The alkali will then be chosen from sodium, potassium, or cesium.
Also suitable in the context of the present invention, the compositions which include one or more organic compounds of one or more alkaline earthy, and, where appropriate, one or more) organic) compounds of one or more many alkaline.
The organic compound of alkaline earth or alkaline is a complex organometallic of the type described in patent application WO 96/34074 whose teaching on this subject is incorporated here.
It may very particularly be the complex defined in this WO application 96/34074 by the formula M (R) mnL in which M is alkaline earth and possibly alkaline, R is the residue of an organic compound of formula RH in which H
represents an active hydrogen atom reactive with the metal M and attached either has a heteroatom chosen from O, S and N in the organic group R, or to an atom of carbon, this heteroatom or carbon atom being located in the group organic R near an electron-attracting group, for example a heteroatom or

3 a group consisting of or containing O, S or N, or an aromatic ring, by phenyl example, n is a number indicating the number of organic electron-donor molecules (Lewis bases) forming dative bonds with the metal cation in the complex, usually up to 5 in number, especially a number integer from 1 to 4, and L is one or more electron donor ligands (Lewis bases).
R can include one or more functional groups capable of acting as Electro-donor organic ligand.
The whole teaching of WO 96/34074 concerning the complex of The above formula is incorporated here by reference.
According to a particular embodiment, the aforementioned organic soil comprises particles of at least one oxide of at least one tetravalent metal, an amphiphilic acid system, and ~ a thinner, and it is further characterized by the fact that said particles have a d9a at most equal to 20 nanometers and it has at least one of the following characteristics ~ said particles of metal oxide (s) tetravalent (s) are in the form of crystallite agglomerates, including d9o, measured by photometric counting (high resolution transmission electron microscopy), is at most equal to 5 nanometers, 90% by mass of agglomerates comprising from 1 to 5, preferably 1 to 3 crystallites, ~ said amphiphilic acid system comprises at least one acid from 10 to 50 atoms of carbon, having at least one branching in alpha, beta, gamma or delta of the atom carrying acid hydrogen.
The aforementioned tetravalent metal oxide particles are advantageously cerium dioxide.
In the rest of the presentation, what will be described for the particular case of cerium, can also apply to the other rare earth mixtures mentioned above (in which the cerium is always present).
The soil characteristics of this particular embodiment will be developed below.
In the present description, the particle size characteristics make often reference to notations of the type d ~ where n is a number from 1 to 99. This scoring represents the particle size such that n% by weight of said particles has a size less than or equal to said size. For example, a 5 nanometer d9p means that 90 by weight of the particles have a size less than or equal to 5 nanometers.

4 These more stringent conditions and how to respond to them are set out below.
after.
Advantageously, at least 50% by mass of the agglomerates are monocrystalline, that is, they consist of only one crystallite (or at least appear consist of only one crystallite when examining the soil by METHR
(High Resolution Transmission Electron Microscopy).
In addition, by playing on the technique and the conditions of hydrolysis, one can do in so that 80%, preferably 90% by mass of the crystallites are of size understood in the range 2 to 5 nanometers.
Advantageously, the molar ratio between said amphiphilic acid and the elements metal of the soil is at most equal to 0.5, advantageously at most equal to 0.4, of preferably at most equal to 0.3. Here the molar ratio must be taken in (acceptance of a functional molar ratio, that is to say that one counts as mole of acid amphiphilic, the number of moles multiplied by the number of useful acid functions.
It is desirable that in the soil, the ratio between the content of cerium (III) and the cerium (IV) content, as low as possible, usually less than 1.5%, advantageously at most equal to 1% preferably to 0.5%.
Advantageously, the soil has a concentration such as the content of dioxide of cerium content, ie between 10 and 60%, preferably 30 to 50% by mass.
Cerium, therefore, is essentially in the form of an oxide agglomerate metallic, possibly hydrated dioxide, which agglomerate of oxide (s) is returned fat soluble using an amphiphilic organic acid.
In the soil, the cerium can possibly be accompanied by impurities. In the In the context of the present invention, the purity of the cerium is not critical.
Soils of this type and their methods of preparation are known to man of career. However, as an example of preparing a soil based on cerium, we can describe the following preparation process.
This process comprises the following stages consisting a) subjecting an aqueous ceriferous phase to a hydrolysis operation of so as to precipitate a cerium dioxide, b) to bring into contact, simultaneously or consecutively, a suspension of cerium dioxide from step (a) with an organic phase comprising a acid organic and preferably an organic compound or mixture playing the role of solvent then c) recovering the organic phase.
Which phase constitutes a soil.
The soil preparation process will now be developed in more detail.

Advantageously, one can proceed between step (a) and step (b), to a separation of solid particles from the mother liquors, possibly with drying of preferably by atomization, then plumping solid particles in phase watery which will then be subject to (step (b).

5 The plumping is carried out in such a way that the content of cerium dioxide in the aqueous phase is between 100 and 400 g / I.
According to an advantageous implementation of the present invention, advantageously drying (between steps (a) and (b)] is carried out by atomization, i.e. by spraying the soil mixture into a warm atmosphere (spray-drying). The atomization can be carried out using any known sprayer in itself, by example by a spray nozzle of the apple type watering can or other. We can also use so-called turbine atomizers. On the various techniques of spray which can be used in the present process, will be able refer in particular to the MASTERS basic work entitled "SPRAY-DRYING"
(second edition, 1976, Editions Gerge Godwin - London).
Note that we can also implement the atomization operation -drying by means of a "flash" reactor, for example of the type developed by the Applicant and described in particular in French patent applications numbers 257 326, 2 419 754 and 2 431 321. In this case, the treating gases (hot gases) are animated by a helical movement and flow in a whirlpool. The mix with drying is injected along a path coincident with the axis of symmetry of helical trajectories of said gases, which makes it possible to transfer perfectly the quantity movement of gases to the mixture to be treated. The gases thus actually provide a double function: on the one hand the spraying, i.e. the transformation into fine droplets, of the initial mixture, and on the other hand fe drying of the droplets obtained. Through elsewhere, the extremely short dwell time (usually less than 1/10 of a second about) particles in the reactor have the advantage, among other things, of limit unlikely risks of overheating as a result of prolonged contact with gas hot.
It should be noted here that this atomization treatment makes it possible to improve significantly the suitability of thermohydrolysed soil at "low" temperatures at form stable soils and even when the gas temperature is at least equal to 200 ° C, preferably between 200 and 300 ° C, to obtain results similar to those who are obtained by thermohydrolysis at "high" temperature (150 ° C), and therefore soils according the present invention which are optimal.
The temperature of the drying atmosphere can vary within wide limits, and it depends in particular on the average residence time that one wishes or that fon can impose on the atomized product once in said atmosphere. In a way general, WO 99/1302

6 PCT / FR98 / 01849 drying conditions (temperatures and / or time of stay) are determined conventionally so as to at least obtain a total elimination or almost total of the residual water contained in the product, that is to say, overall, up to obtaining a constant weight for the latter.
The solid particles will then be repulped in the aqueous phase.
Mention may in particular be made, as water-soluble compounds of cerium, of cerium (IV} salts such as nitrates or cerium ammonium nitrates by example who are particularly suitable here. Preferably, nitrate is used ceric.
The cerium (IV) salt solution can contain cerium without disadvantage.
the state serous but it is desirable that it contains at least 85% of cerium (IV).
A
aqueous serum nitrate solution can for example be obtained by reaction acid nitric on a hydrated serum oxide prepacked in a conventional manner by reaction of a solution of a serous salt, for example serous carbonate, and a solution of ammonia in the presence of hydrogen peroxide. It is also possible, preferably, use a serum nitrate solution obtained by the oxidation process electrolytic serous nitrate solution as described in document FR 2 570 087, and who constitutes here a raw material of choice.
It should be noted here that the aqueous solution of cerium (IV) salts may have a some initial free acidity, for example a normality varying between 0.1 and 4 N.
According to the present invention, it is as much possible to implement a solution initial cerium (IV) salts actually showing some acidity free as mentioned above, that a solution which has been previously neutralized way more or less advanced by adding a base, such as for example a solution of ammonia or of alkali hydroxides, in particular sodium, or potassium, but preferably an ammonia solution, so as to limit this acidity. We can then, in the latter case, practically define a rate of neutralization (r) of the initial solution of cerium by the following equation r = n3 -n2 n1 in which n1 represents the total number of moles of Ce (IV) present in the solution after neutralization; n2 represents the total number of moles of ions OH-actually necessary to neutralize the initial free acidity provided by the solution aqueous cerium salt. (IV); and n3 represents the total number of moles OH- ions brought by the addition of the base.
When the "neutralization" variant is implemented, it is used in all cases a quantity of base which must imperatively be less than the quantity of base which would be necessary to obtain the total precipitation of the hydroxide species Ce (OH) 4

7 (r = 4). In practice, this is limited to neutralization rates not exceeding 1, and preferably not exceeding 0.5.
The following operation consists in carrying out a hydrolysis so as to rush a cerium dioxide. Cerium dioxide is precipitated by a treatment thermal, also called thermohydrolysis.
The temperature at which thermohydrolysis is carried out can be understood Between 80 ° C and the critical temperature of the reaction medium, in particular between 80 and 350 ° C, preferably between 90 and 200 ° C.
This treatment can be carried out, depending on the temperature conditions retained, either under normal atmospheric pressure, or under pressure such as for example the saturated vapor pressure corresponding substantially to the temperature of the treatment thermal.
When, as preferred, the treatment temperature is chosen higher than the reflux temperature (under ordinary pressure) of the mixture reactive (i.e. generally higher than 10 ° C), for example chosen between 120 plus often between 150 and 350 ° C, the operation is then carried out in a closed enclosure which is more particularly a closed reactor more commonly called an autoclave. We introduced the aqueous mixture containing the aforementioned species in this enclosure, the pressure necessary result only from the heating of the reaction medium (pressure autogenous).
Under the temperature conditions given above, and in aqueous media, we can thus specify, by way of illustration, that the pressure in the closed reactor varies between value greater than 1 Bar (105 Pa) and 200 Bar (20.10 Pa), preferably between 5 Bar (5.105 Pa) and 150 Bar (1.5.10 Pa). It is of course also possible to exercise a external pressure which is then added to that following heating.
Heating can be carried out either under an air atmosphere or under atmosphere of inert gas, preferably (nitrogen.
The duration of treatment is not critical, and can therefore vary widely.
limits, for example between 1 and 48 hours, preferably between 2 and 24 hours.
Likewise,) the temperature rise takes place at a speed which is not critical, and we can reach the reaction temperature set by heating the medium for example between 30 minutes and 4 hours, these values being given completely indicative.
At the end of the thermohydrolysis step (step (a)), a precipitate is recovered solid which can be separated from its environment by any conventional separation technique solid liquid such as, for example, elutriation, filtration, decantation, spinning or centrifugation.
Note that it is of course possible to repeat one or more times, the same or not, a heating step (thermohydrolysis) I precipitation as.

8 above defined, then implementing for example cycles of treatments thermal.
As an indication, it can be used as a starting solution for thermolysis of cerium (IV) solutions, generally nitrate, meeting the following features FeaturesPossible Advantageous Zone Crumble content 1 g / I la between 40 and 120 between 60 and g / I limit 100 gll solubility Acidity (r) at the most equal (r) included 1 between 0.5 and -0.5 Counter ion of all ion weakly oxygen and nitrate non complexing crium The characteristic of step (b) of the process of the invention is to obtain a ground organic, expression which designates the dispersion of the cerium dioxide, eventually impure, in an organic medium, by transferring said cerium dioxide in phase organic, to from an aqueous phase consisting of the ceric compound which is found form colloidal in aqueous soil. The aqueous dispersion denotes the dispersion colloidal cerium dioxide in an aqueous medium which constitutes the basic raw material of the stage (b).
In order to conduct the process of the invention satisfactorily, it is desirable that the starting aqueous soil meet the following requirements ~ the rate of metal (aux) in the form of colloidal oxide (s)) must be very Student, advantageously 90%, preferably greater than or equal to 95%, and in good standing general as high as possible;
~ the concentration of the aqueous soil in colloidal oxide must be sufficient and To be situated preferably between 0.1 and 3 moles / liter;
~ ie aqueous soil must have good thermal stability properties and do not flocculate at the reaction temperature which is higher than 60 ° C and varies the most often between 80 ° C and boiling (variable depending on the pressure).
The organic liquid medium used in (step (b) of the process can be a inert aliphatic, cycloaliphatic hydrocarbon, or their mixture, such as for example mineral or petroleum spirits, mineral or petroleum ethers which may contain also aromatic components. Mention may be made, as an indication, of fhexane, heptane, octane, nonane, Bécane, cyclohexane, cyclopentane, cycloheptane and liquid naphthenes. Aromatic solvents such as benzene, the toluene, ethylbenzene and xylenes are also suitable as well as cuts petroleum type ISOPAR or SOLVESSO (trademarks registered by the company EXXON),

9 in particular the SOLVESSO 100 which essentially contains a mixture of methylethyl and trimethylbenzene, and SOLVESSO 150 which contains a mixture of alkylbenzenes in particular of dimethylethylbenzene and tetramethylbenzene.
It is also possible to use chlorinated hydrocarbons such as chloro or dichlorobenzene, chlorotoluene, as well as aliphatic ethers and cycloaliphatics such as düsopropyl ether, (dibutyl ether and ketones aliphatics and cycloaliphatics such as methyl isobutyl ketone, dobosyl ketone, mesityl oxide.
Esters can be considered, but they have the disadvantage of risk to be hydrolyzed. Mention may be made, as esters capable of being used, those from acids cited in the present application with C1 to C8 alcohols and in particular the secondary alcohol palmitates such as fisopropanol.
We will choose the organic liquid or solvent system taking into account acid organic solubilizer used, heating temperature and the final application of the colloidal solution or dispersion. In some cases it is better to employ a mixture of solvents. The amount of liquid or solvents obviously determines the final concentration. It is more economical and more convenient to prepare more concentrated dispersions which can be diluted later when employment.
It is for this reason that the amount of solvent is not critical.
It may be advantageous to add an agent to the organic phase promoter whose function is to accelerate the transfer of colloids from the phase aqueous phase organic and to improve the stability of the organic soils obtained. As agents promoters, the alcohol-functional compounds can be used, and any particularly linear or branched aliphatic alcohols having from 6 to 12 carbon atoms.
As specific examples, mention may be made of 2-ethyl hexanoi, decanol, dodecanol, where their mixture.
The proportion of said agent in the organic phase is not critical and can vary within wide limits.
However, a proportion of between 2 and 15% by weight is suitable generally fine.
If the field of usable acids is very large, the total number of carbon in the molecule to obtain a good dissolution, is a little more restrictive.
The total number (average if the acid used is a mixture) of carbon acids is advantageously greater than 6 preferably 10, it is also desirable that he is less than about 60.
If you want high concentrations of cerium, or equivalent it is desirable to choose acids as short as possible.

These acids can be linear or branched. It is preferable, however, that the ramifications are either far from the carboxylic function, or little numerous and numerous by different carbons. Carboxylic acids usable for the present invention can be aryl, aliphatic or arylaliphatic acids.
They can 5 carry other functions provided that these functions are stable in the environments where it is desired to use the cerium compounds according to the present invention.
To keep the soil usable at low temperatures, below (ambient, or even below 0 ° C, it is preferable that the melting point of acid, or acid mixture is at most equal to 50 ° C., advantageously at room temperature, preferably

10 to 0 ° C.
So we can easily use carboxylic acids whose chain carbonaceous carries ketone functions such as alpha substituted pyruvic acids of the ketone function. It can also be alpha-halo acids carboxylic or alpha-hydroxy carboxylic acids.
The chain attached to the carboxylic group can carry unsaturations.
However, in general we tend to avoid too many double bonds because the cerium catalyzes the crosslinking of double bonds. The chain can be interrupted by ether or ester functions provided that they do not alter the chain lipophilicity carrier of the carboxylic group.
Thus, it is possible to use aliphatic carboxylic acids, acids aliphatic sulfonic, aliphatic phosphonic acid, acid alkylarylsulfonic, and alkylarylphosphonic acids having about from 10 to about 40 carbon atoms, whether natural or synthetic. We can use them alone or mixed with each other.
By way of example, mention may be made of tall oil fatty acids, coconut oil, soy, tallow, linseed oil, oleic acid, (linoleic acid, stearic acid and its isomers, (pelargonic acid, capric acid, lauric acid, myristic acid, acid dodecylbenzenesulfonic, 2-ethylhexanoic acid, (naphthenic acid, acid hexoic, toluene sulfonic acid, toluene phosphonic acid, acid lauryl-sulfonic,! lauryl-phosphonic acid, palmityl-sulfonic acid, and palmityl- acid phosphonic. Preferably, oleic acid or the acids alkylarylsulfonic.
The amount of amphiphilic organic acid used expressed in number of moles of acid per mole of oxide can vary within wide limits between 1/10 and 1 mole of cerium dioxide. The upper bound is not critical but he no more acid is needed. In a way preferential, organic acid is used at a rate of 1/5 to 4/5 mole per mole of dioxide cerium.

11 In the organic phase, the proportion between the organic solvent and the acid organic is not critical. The weight ratio between the organic solvent and acid organic is preferably chosen between 0.3 and 2.0.
The order of introduction of the different reagents is indifferent. We can perform the simultaneous mixing of the colloidal aqueous dispersion (s), of the acid organic, organic solvent, and optionally the promoter. We can also do the premix of organic acid, organic solvent and optionally the agent promoter which constitute the organic phase.
The temperature of the reaction medium is preferably chosen from a range from 60 to 150 ° C.
In some cases, due to the volatility of the organic solvent, it is necessary of condensing its vapors by cooling to a temperature inside its point of boiling.
Advantageously, one works at a temperature between 60 and 120 ° C, from preferably between 90 and 110 ° C.
The reaction mixture is kept under stirring for the entire duration of the heating which can be from less than an hour to about a day, from preference between 2 hours and a half day.
At the end of the above heating time, the heating is stopped. We note the presence of two phases: an organic phase containing in dispersion, the complex metal oxide - organic acid and a residual aqueous phase.
The organic phase and the aqueous phase are then separated according to the techniques separation classics: decantation, centrifugation, etc ...
In accordance with the present invention, organic dispersions are obtained colloids of metal oxides) the size of the colloids may be very variable and can be controlled by playing on certain parameters, in particular the diameter of starting colloidal aqueous dispersions in step (b), which depends respect thermohydrolysis conditions in step (a).
For certain applications, it is possible to use the reaction mixture as is but sometimes it is desirable to eliminate the water which can represent from 1 to 3 % in weight of the organic phase. To this end, well known means are used through a person skilled in the art, for example passing over a drying agent (including a filter to hydrophobic membrane) or the addition of a third inert solvent relative to the dioxide cerium, preferably having a boiling point below 100 ° C
and forming a azeotrope with water then distillation of the azeotrope obtained. As a third party solvents suitable for the invention, there may be mentioned aliphatic hydrocarbons, such that fhexane, heptane, cycloaliphatic hydrocarbons: aromatic, or alcohols such as by example, ethanol, ethylene glycol, diethylene glycol etc ...

12 I! is preferable, especially for applications as a diesel additive than the water content is at most equal to 1%, advantageously 1000 ppm, of preference at 100 ppm.
We will now examine the amphiphilic acid system.
As already mentioned, the amphiphilic acid system has at least one acid of 10 to 50 carbon atoms, having at least one branching alpha, beta, gamma or delta of (atom carrying acid hydrogen.
Advantageously, the amphilphile acid system comprises at least one acid of 11 to 25 carbon atoms. The preferred range is 15 to 25 carbon atoms for the acids of said amphiphilic system.
For best results, especially when the chain length is low (less than 14 carbon atoms), when the branching is single and mostly when it is located in the gamma or delta position of the atom carrying hydrogen acid, it is very desirable that this branching is at least two atoms of carbon, advantageously three.
To explain the nomenclature of positions, we will find below the examples of di (2-ethylhexyl) acid phosphate and 2-ethyl octanoic acid position alpha bta gamma delta (function - (atom) - (atom) - (atom) - (atom) H) HO -P (C8H '~) -O -CH2 -CH (C2H5) -CH2 (C3H ~) HO -CO -CH (C2H5) CHZ CH2 CHZ (C3H ~) It is preferred that the longest linear part is at least 6, of preference 8 carbon atoms.
It is advantageous for the pKa of at least one of the acids to be at least equal to 5, of preferably 4.5.
It is also advantageous that the side chain (s) of the acids branched have at least two atoms, preferably three carbon atoms.
It is preferable, in particular when the acids are carboxylic acids, than the amphiphilic acid system is a mixture of acids.
In this case the conditions on the branching must play on at least the half, advantageously two-thirds, preferably four-fifths by mole of acids constitutive of said amphiphilic acid system.
Among the acids giving very good results, mention may be made of acids containing phosphorus, such as phosphoric acids, especially diesters of acid phosphonic, and their monoesters, and phosphinic acids.

13 Among the carboxylic acids giving good results, it is worth mentioning the constituent acids of the acid mixture known as acid isostearic. The The acid system is advantageously isostearic acid itself.
The starting melting point of the amphiphilic acid (s) system is advantageously less than 50 ° C, more advantageously less than or equal to 20 ° C, from preferably at most equal to 0 ° C.
For good stability and for good extraction it is desirable that the molar ratio between the extradant and the metal (s) tétravrav (s), de preferably cerium, is between 1.1 and 0.6, preferably between 0.2 and 0.4. This report grows when the particle size decreases.
To obtain particularly stable soils, it is preferable that at most 5 %, advantageously at most 1%, preferably at most 0.5% by mass of the particles tetravalent metal oxide (s), at most equal to 100 nm, advantageously to 50 nanometer, preferably 20 nanometer.
Any diluent leading to a stable soil is part of this invention.
The floors according to the present invention can be used according to numerous implemented. Depending on the desired implementation, choose a compromise taking into account the technical data below - for synthesis and stability it is desirable to avoid very hydrocarbons apolar, such as non-cyclic aliphatic hydrocarbons, - diluents, such as esters or ethers, having a polar function give good results, but for certain uses may be to be avoided as far as possible possible.
The mixture of diluents can provide a solution by compensating for the non polarity certain diluents by the addition of polar compounds, generally solvents.
According to a particularly advantageous implementation of ia present invention, the soil is used to form a soil diluted in diesel.
The initial soil is generally very concentrated.
Furthermore, for reasons of compatibility with diesel, and its numerous additives, the diluents are preferably not very polar. As an element constituting a diluent, aromatic or aliphatic compounds are preferable to compounds having a polar function, such as for example the ester functions or ethers.
It is preferable that the diluents have a Kauri Butanol index (measured according to ASTM D 11 33) less than 105, advantageously less than 90.
For use as an on-board additive, it is preferable that the point of fusion thinners, or mixture of thinners, are low and meet the constraints from point to fusion described in this title about the amphiphilic acid system.

14 It is also preferable that these diluents have a solubility in the water very low, preferably less than 5% by mass, preferably at most 1%, more preferably at most equal to 0.5% by mass.
Symmetrically, it is also preferable for the water to be soluble at more 5%, preferably at most 1%, more preferably at most 0.5% in the ~
diluent.
Among the preferred diluents, it comes to mention the hydrocarbon compounds aromatics and their mixtures, as well as aliphatic compounds and their mixed containing less than 50%, preferably 25%, or more preferably 1% of aromatic compounds.
Metal oxides (tetravalent) may contain proportions relatively reduced metals with other valencies. In general, the proportion of addition elements, or impurities, contained in the particles of metal (s) tetravalent (s), does not exceed 10% by mass, more particularly 5% in mass.
The tetravalent metal content of the soil according to the invention is advantageously at most 2/3 by mass, preferably between 30 and 40% by mass. For use as an additive for on-board diesel, it is preferable that the grade of descent not in below 1/6, preferably 1/5.
The organic soils according to the present invention are generally prepared from known manner by heating an aqueous soil containing said oxide (s) of tetravalent metal (s), in the presence of said diluent and said acid system amphiphilic.
According to one of the particularly advantageous features of the invention, it care should be taken that there are no excessively coarse particles in the aqueous soil and so in the final soil.
The coarsest-sized particles can be removed by all technique for selectively removing the most coarse. This elimination can be carried out on aqueous soil, on organic soil, or of them.
However, it is preferred that there is at least one separation on the aqueous soil.
The preferred technique is centrifugation.
A centrifugation of the aqueous soil corresponding to 1000 to 10 000 G during one hour generally gives good results. We can, however, go as far as of centrifugations corresponding to 50,000 G.
It should be noted that the centrifugation prior to the stage of constitution of the ground organic, often called the extraction step, promotes the latter.
The aqueous soils are advantageously produced by hydrolysis, preferably by thermohydrolysis. Among the techniques which can be used for the present invention, we can cite the techniques disclosed in the published European patent application under the number 97563 in the name of the Claimant. We can also cite the request for European patent published under number 206907.
Said soils obtained according to the invention have a concentration of compound of cerium (IV) which can be very high since it can go up to 3.5 M to 4 M of Ce02.
5 It is found that the yield of extraction of cerium in the organic phase East very good since it can reach 90 to 95 ° ~.
The organic soils thus produced have excellent stability. We does not observe decantation after several months.
According to one of the preferred characteristics of the present invention, the soil is Phone 10 that, adjusted to a concentration of cerium metal content of 30%, the soil viscosity at 25 ° C is at most equal to 20 mPa.s, advantageously 15 mPa.s, of preferably 10 mPa.s. This viscosity can be measured by Contraves brand "low shear"
in varying the speed gradient from 0.01 to 1 s- ~.
It is also preferable that the counter anions of the cerium solution source

15 of the soil, are no longer present in the various soils according to this invention that at a content at most equal to 0.1, advantageously 0.05, preferably 0.03 equivalents per 100 grams of cerium dioxide.
The organic soils thus obtained can be diluted to obtain concentrations of 10 to 500 ppm, preferably 50 to 200 ppm of metal (aux) tetravalent (s).
The diluent is advantageously a fuel for an internal combustion engine of preferably diesel. Thus, the invention also relates to soils whose phase organic is essentially consisting of diesel fuel and its additives.
Another object of the present invention is the process for preparing the aforementioned composition. This preparation process is characterized by the fact that one mixture of at least one organic compound of at least one alkaline earth and, the case if necessary, at least one organic compound of at least one alkaline, with the soil organic cited above.
Generally, the atomic proportion of metal (s) tetravalent (s) / sum of tetravalent metal (s), alkaline earth elements, and possibly alkaline, is at least minus 50%, more particularly at least 70%.
The invention also relates to the use of said compositions.
The compositions of the invention can be used as driers in the paint and varnish industry to speed up the drying of oils unsaturated.
They can also be used as combustion aids in fuels or liquid fuels from energy generators such as motors to explosion, oil burners, or jet engines.

16 The compositions of the invention are more particularly suitable as adjuvant diesel fuel for diesel engines.
Concrete but non-limiting examples will now be given.
EXAMPLES
Reagents Unless otherwise stated the reagents used in the examples are - a pre-neutralized ceric nitrate at r = + 0.5 (cf. European patent in the name of the Applicant published under No. 153227) - an oleic acid extracting agent, which can be replaced without modification with olein (70% oleic acid + 30% linoleic acid) - a solvent, SOLVESSO 150, which is not specific and can be replaced through fISOPAR L, fhexane or even diesel.
General procedure The procedure for the examples is as follows - the first step consists in the synthesis of the precursor which is a soil watery from colloids of Ce02 whose size (MET) is between 3 and 5 mm.
The serum nitrate solution at r = + 0.5 is placed in an autoclave covered with tantalum. The concentration of the solution used is 60 g / I expressed in Ce02.
Autoclaving is carried out at 180 ° C for 4 hours, with a rise in temperature in 1 hour. Agitation is maintained throughout the operation.
At the end of the shouldoclaving, the product is decanted and then separated (filtered and wrung out) mother liquors. It is then redispersed in water, which makes it possible to obtain a aqueous soil stable.
The concentration of this soil of 150 g / l.
Example 1 Reagents - a pre-neutralized serum nitrate at r = + 0.5 and at a concentration of 60 g / I in cerium.
- an oleic acid extracting agent, First stage The serum nitrate solution at r = + 0.5 is placed in an autoclave covered with tantalum. The concentration of the solution used is 80 g / l expressed in Ce02.
Autoclaving is carried out at 180 ° C for 4 hours, with a rise in temperature in 1 hour.
Agitation is maintained throughout the operation.

17 The solution obtained is filtered through a No. 4 frit.
The product is then redispersed in water, which makes it possible to obtain a soil aqueous stable. The concentration of this soil is 150 g / I.
Second step The second stage of preparation is the transfer of colloids from the phase aqueous to the organic phase.
A metered amount of Ce02 aqueous soil is placed in a flask, to which we add the organic mixture which is such that the acid molar ratio oleic / cerium either 0.3 and the SOLVESSO 150 / oleic acid ratio is 3.75.
In (example consider, this leads to using - 24.8 g of Ce02 (i.e. 0.165 I of soil at 150 g / I), -12.2 g of oleic acid, - 45.7 g of SOLVESSO 150.
The mixture is then heated at 100 ° C at reflux for about 10 hours After cooling, the organic phase is separated from the aqueous phase and then filtered on hydrophobic filter.
The exact soil title is then measured by calcination (dry extract after 6 hours at 950 ° C).
This gives a soil with measured stability greater than 4 months (duration of the sample), whose Ce02 concentration is 29.1% (mass), and whose the size of colloids (measured by TEM) is between 3 and 5 nm.
Example 2 Mixture of an organic cerium sof and a strontium salt according to the invention A strontium salt of polyisobutylene succinic anhydride is prepared.
molecular weight 420 Sr-PISSA 420, as described in Examples 13 and 14 of the patent WO 96/34074 from the company OCTEL.
Next, a mixture of the organic cerium sol described in the example is mixed.

with r-PISSA 420 salt in the following proportions: 90 mol% of cerium and 10 % molar of Sr.
Example 3 Mixture of a sol or4anipue of cerium and a strontium salt according to the invention the procedure is as in Example 2, using the organic cerium soil and the salt to Sr-PISSA 420 in the following proportions: 75 mol% of cerium and 25 molar of Sr.

18 Performance: measurement of the ignition temperature of soot We proceed as follows Carbon black which we know can be produced productively (ref.
ELFTEX 125 n ° 137 from) has been selected for these properties in size term of particle and specific surfaces. These respectively 60 nm and 30 m2 / g are due same order of magnitude as the carbonaceous particles emitted from a diesel engine exhaust.
This carbon black is impregnated with additive so as to obtain a content final 15% by weight metal equivalent (Ce + Sr). This content is representative of what can be obtained in the particles emitted from an engine exhaust diesel, when using an additive in diesel fuel. The impregnation is carried out from the same way as the catalysts supported by the so-called technique are prepared dry impregnation.
Carbon black and the desired amount of additive are thoroughly mixed in a glass container until a homogeneous paste is obtained. Then, (together is dried overnight at 95 ° C. Monitoring in Thermo Gravimetric Analysis (ATG) of the combustion in fact of this impregnated carbon black allows to set evidence the more or less great catalytic effect thus generated by the presence of (additive. The additive will be considered all the more active as the corresponding temperature of the start carbon combustion during fATG will be low.
A test carried out with carbon black not impregnated with an additive serves to reference.
ATG is performed with a load of 20 to 25 mg of carbon black, in a debit air flow of 3.5 Nl / h and with a temperature programming between the temperature ambient and 900 ° C at a rate of 10 ° C / min.
For the mixtures prepared according to Examples 1 to 3, the temperatures of inflammation are listed in the table below Results by ATG
T ignition additives (C) without 580 This (example 1) 305 Ce-Sr (example 2) 230 Ce-Sr (example 3) 210 The results obtained show without ambiguity that the temperature inflammation soot is dropped significantly when the carbon particles are impregnated with an additive consisting of the mixture of an organic soil of cerium and a strontium salt.

Claims (14)

1. Composition characterized in that it comprises an organic soil of water particles at least one oxide of at least one tetravalent metal and at least one compound organic water least one alkaline earth. 2. Composition according to claim 1, characterized in that the metal tetravalent is the cerium, praseodymium, terbium; in the particular case of mixtures of rare earth, it is preferable that cerium is present. 3. Composition according to one of claims 1 or 2, characterized in that metal tetravalent is cerium. 4. Composition according to any one of claims 1 to 3, characterized in that the alkaline earth metal is magnesium, calcium, strontium or barium. 5. Composition according to any one of claims 1 to 4, characterized in this that it comprises an organic sol of cerium oxide particles and at least a organic strontium compound. 6. Composition according to any one of claims 1 to 5, characterized in this that it comprises at least one organic compound of at least one alkali. 7. Composition according to any one of claims 1 to 6, characterized in that the alkali is chosen from sodium, potassium and cesium. 8. Composition according to any one of the preceding claims, characterized in what the floor has:
~ particles of at least one oxide of at least one tetravalent metal, ~ an amphiphilic acid system, and ~ a thinner, and it is further characterized by said particles having a d90 at most equal to 20 nanometers and has at least one of the following characteristics:
~ said particles of oxide (s) of tetravalent metal (s) are in the form of crystallite agglomerates, including the d90, measured by photometric counting (high-resolution transmission electron microscopy), is at most equal to 5 nanometers, 90% by mass of agglomerates comprising from 1 to 5, preferably 1 to 3 crystallites, ~ said amphiphilic acid system comprises at least one acid of 10 to 50 atoms of carbon, having at least one branch in alpha, beta, gamma or delta of the carrier atom of acidic hydrogen. 9. Composition according to claim 8, characterized in that the particles oxide tetravalent metal are cerium dioxide. 10. Composition according to any one of the preceding claims, characterized by the fact that the diluent essentially consists of diesel fuel and its additives. 11. Composition according to any one of the preceding claims, characterized in what the atomic proportion tetravalent metal(s) / sum of the elements tetravalent, alkaline-earth metal(s), and possibly alkali metal(s), is at least 50 %, more particularly at least 70%. 12. Process for the preparation of a composition according to one of claims 1 at 11, characterized in that at least one organic compound of at least one minus one alkaline-earth, and where appropriate at least one organic compound of at least a alkaline, with organic soil. 13. Fuel for an internal combustion engine, characterized by the fact that it is obtained by mixing with a usual fuel a composition according to any one of claims 1 to 11. 14. Use of the compositions according to any one of claims 1 to as a diesel fuel additive.