FR2750976A1 - Treatment of aqueous solution or suspension of organic compounds - Google Patents

Abstract

Process for treating an aqueous solution or suspension of organic compounds at elevated temperature and pressure by oxidation of the organic compounds by an oxygen-containing gas in the presence of an oxidation catalyst to reduce the chemical oxygen demand of the solution/suspension to a predetermined level, where the catalyst comprises a catalytically active phase on a support comprising a composition of a cerium oxide and a zirconium oxide in atomic ratio Ce/Zr \-1, having a specific surface area after calcination for 6 hours at 900 deg C of at least 35 m<2>/g and oxygen storage capacity at 400 deg C of at least 1.5ml O2/g.

Description

PROCESS FOR TREATING A SOLUTION OR SUSPENSION OF COMPOUNDS
ORGANIC BY WET OXIDATION
The present invention relates to a process for the wet oxidation of a solution or suspension of organic compounds to reduce the chemical oxygen demand (COD) to a determined level.

It relates more particularly to the use of a particular catalytic system for carrying out this wet oxidation.

Wet oxidation of organic compounds in an aqueous medium has been used to reduce the chemical oxygen demand (COD) of aqueous effluents to an environmentally acceptable level.

Different processes are used. By way of example, we can cite the process
ZIMPRO which uses an oxidizing gas (air or oxygen) with a temperature between 175-320 "C under a pressure of 20-210 bar. In this process the reaction is carried out in the absence of catalyst.

The company CIBA-GEIGY has developed a wet oxidation process using air as oxidant, the temperature range is 250-300 "C, the pressure being between 50 and 200 bars. This oxidation is carried out. in the presence of a catalyst composed of copper salts.

On the basis of this catalyzed process, many companies have proposed new catalytic systems making it possible to decrease the reaction times and 'or to lower the temperature or pressure conditions.

Thus, the company OSAKA GAS describes in French patent 2361308 the use of ruthenium oxide as the catalytically active phase. This active phase is deposited on a support conventionally used in heterogeneous catalysis, such as alumina silica or activated carbon. The reaction is carried out under a pressure of between 70 and 90 bars and a temperature of between 250-280 ° C., the reaction times are then between 1 and 3 hours.

The company NIPPON SHOKUBAI has also proposed catalysts comprising as active phase metals such as palladium or platinum supported on supports comprising in particular rare earth oxides such as cerium oxide.

In Japanese patent J4100595 this company describes a catalyst comprising a support consisting of a mixture of zirconium oxide and a rare earth oxide such as cerium oxide in combination with a catalytically active phase consisting of a metal chosen from the group comprising Mn, Fe, Co, Ni, W, Cu, Ag, Au,
Pt, Pd, Rh, Ru, and Ir. The reaction conditions are for the pressure between 30 and 70 bars, for the temperature between 200 and 250 ° C., the reaction time being between 10 minutes and one hour.

These processes are used industrially all over the world. However,
The improvement of the reaction conditions is a constant problem which requires the development of new devices to promote the gas / liquid reaction, or to reduce the reaction times.

One of the aims of the present invention is to provide a novel catalytic system making it possible to accelerate the reaction under pressure and temperature conditions similar to those used in the known processes.

To this end, the invention provides a process for treating an aqueous solution or suspension of organic compounds at an elevated temperature and pressure by oxidation of the organic compounds with a gas containing oxygen in the presence of an oxidation catalyst in order to reduce. the chemical oxygen demand of said solution or suspension at a predetermined level characterized in that the catalyst comprises a catalytically active phase present on a support consisting of a composition based on a cerium oxide and a zirconium oxide in a atomic cerium / zirconium ratio of at least 1, exhibiting a specific surface area after calcination for 6 hours at 900 "C of at least 35m2 / g and an oxygen storage capacity at 400" C of at least 1, 5 ml of O2 / g.

The particular characteristics of the ceriumlzirconium support lead to the production of a wet oxidation catalyst exhibiting an activity markedly greater than the known catalysts comprising similar catalytically active phases.

According to a preferred characteristic of the invention, the catalytically active phase consists of ruthenium or iridium in metal form or in oxide form.

The oxidation reaction is carried out by using, as oxidizing gas, a gas containing oxygen, such as, for example, pure oxygen, air, air enriched with oxygen, waste gases containing oxygen. oxygen.

The quantity of gas supplied is determined from the COD of the solution to be treated. Usually, the oxygen-containing gas is used in an amount 1 to 1.5 times the theoretical amount of oxygen.

Advantageously, the oxygen pressure is between 1 and 50 bars, the total pressure of the gases being sufficiently high to maintain the solution or suspension in the liquid state at the reaction temperature.

This reaction temperature is advantageously between 100 ° C. and 400 "C, preferably between 1200 ° C. and 200" C. This temperature depends in particular on the nature of the organic compounds present in the effluents to be treated.

The aqueous solutions or suspensions which can be treated by the process of the invention are waters which preferably contain oxidizable organic substances such as aqueous effluents exhibiting a moderately concentrated chemical oxygen demand, advantageously less than 200 girls.

Examples of waste water are, for example, waste water from industrial installations such as chemical or petroleum industries, municipal effluents, waste water containing oils, waste water from gas purification processes or activated sludge process.

Advantageously, to avoid clogging of the installations and of the catalyst, this water can be filtered before being treated by the process of the invention.

The catalyst of the invention can be in various forms such as a cylinder in the shape of a honeycomb, balls, pellets, extruded granules or powders.

Generally, the catalyst is used in the form of a fixed bed in a reactor of sufficient capacity to ensure a solution / gas contact for a determined period of time of the order of a few minutes to several hours.

It is also possible to use the catalyst in the form of a fluidized bed, or to introduce the catalyst in suspension in the solution to be treated. The catalyst is recovered at the end of the reaction by any known means of solid / liquid separation.

The catalyst support in accordance with the invention is described in French patent application No. 96, a document included by reference in the present application.

The composition of this support can vary within very wide limits. Thus, the molar concentration expressed in Ce relative to the Ce + Zr mixture is between 0.5 and 0.9, preferably between 0.6 and 0.8, the Zr concentration being the complement to 1, in the absence of 'other compounds. In the presence of other compounds, the Ce / Zr ratio will advantageously be between 1 and 19, preferably between 1 and 9.

Thus, this support is prepared according to a process of the type in which a mixture is prepared in a liquid medium containing a cerium compound, a zirconium compound; said mixture is heated; the precipitate obtained is recovered and this precipitate is calcined, and it is characterized in that the aforementioned mixture is prepared using a zirconium solution which is such that the amount of base necessary to reach the equivalent point during an acid determination -base of this solution verifies the condition OH- / Zr molar ratio <1.65.

The catalytically active phase is then deposited or impregnated on this support by conventional methods, for example by suspending the support in an aqueous solution of a soluble compound of the catalytically active metal. The impregnated support is then recovered and then dried. The catalyst is then heated to a temperature of between about 250 and 400 ° C under a reducing atmosphere, eg, hydrogen, to reduce the catalytically active metal compound.

Advantageously, the catalyst can be passivated by treatment under nitrogen.

According to a preferred characteristic of the invention, the compositions of the support phase have a specific surface area after calcination for 6 hours at 900 ° C. in air of at least 35 m 2 / g. This surface can more particularly be at least 40 m 2 / g. It can still more particularly be at least 45 m 2 / g.

For the remainder of the description, the term “specific surface area” means the specific surface area B.E.T. determined by nitrogen adsorption in accordance with the ASTM D 3663-78 standard established from the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of the American Society, 60, 309 (1938)".

According to another characteristic of the invention, the support compositions may also have areas which still remain large even after calcination for 6 hours at 1000 ° C. These areas may be at least 14 m 2 / g, more particularly at least 20 m 2 / g and even more particularly at least 30 m 2 / g.

The compositions used as a catalyst support in the process of the invention can also comprise another compound associated with cerium oxide and zirconium oxide.

Thus, the presence of an element such as yttrium, rare earths and scandium makes it possible to obtain the compositions having the highest specific surfaces.

By rare earth is meant the elements of the group consisting of the elements of the periodic table of number. atomic included between 57 and 71.

Another characteristic of the compositions used as a catalyst support in the process of the invention is their capacity for storing oxygen. This capacity measured at 400 "C is at least 1.5 ml of O2 / g. It can more particularly be at least 1.8 ml of O2 / g and even more particularly at least 2 ml of O2. / g.

These compositions can advantageously be in the form of a solid solution. The X-ray diffraction spectra of these compositions in fact reveal, within the latter, the existence of a single homogeneous phase. For the compositions richest in cerium, this phase corresponds in fact to that of a crystallized ceric oxide CeO2 and whose mesh parameters are more or less offset with respect to a pure ceric oxide, thus reflecting the incorporation of zirconium in the crystal lattice of cerium oxide, and therefore obtaining a true solid solution.

The process for preparing these compositions will now be described.

The first step of the process consists in preparing a mixture in a liquid medium, generally in an aqueous phase, containing at least one cerium compound, at least one zirconium compound and, where appropriate, another compound such as an yttrium compound, scandium or rare earth. This mixture is prepared using a zirconium solution.

This zirconium solution can come from the acid attack of a reagent comprising zirconium. As suitable reagent, mention may be made of carbonate,
Zirconium hydroxide or oxide. The attack can be done with an inorganic acid like nitric acid, hydrochloric acid or sulfuric acid. Nitric acid is the preferred acid, and the use of a zirconyl nitrate originating from the nitric attack of a zirconium carbonate can thus be mentioned very particularly. It can also be an organic acid such as acetic acid or citric acid.

This zirconium solution must have the following characteristic. The quantity of base necessary to reach the equivalent point during an acid-base dosage of this solution must verify the condition OH- / Zr molar ratio <1.65. More particularly, this ratio can be at most 1.5 and even more particularly at most 1.3. Generally, the specific surface of the composition obtained tends to increase when this ratio decreases.

The acid-base dosage is carried out in a known manner. To carry it out under optimum conditions, a solution can be assayed which has been brought to a concentration of approximately 3.10-2 moles per liter expressed as the element zirconium. A 1N sodium hydroxide solution is added thereto with stirring. Under these conditions, the determination of the equivalent point (change in the pH of the solution) is done in a clear manner. This equivalent point is expressed by the OH- / Zr molar ratio.

As cerium compounds, mention may in particular be made of cerium salts such as cerium IV salts such as cerium-ammoniacal nitrates or nitrates, for example, which are particularly suitable here. Preferably, ceric nitrate is used. The cerium IV salt solution may contain cerium in the cerous state, but it is preferable that it contains at least 85% cerium IV. An aqueous solution of ceric nitrate can, for example, be obtained by reacting nitric acid with a hydrated ceric oxide prepared in a conventional manner by reacting a solution of a cerous salt, for example cerous nitrate, and an ammonia solution in the presence of hydrogen peroxide. It is also possible to use a ceric nitrate solution obtained by the electrolytic oxidation process of a cerous nitrate solution as described in document FR-A-2 570 087, and which can constitute an advantageous raw material.

The amounts of cerium, zirconium and optionally other compounds present in the mixture must correspond to the stoichiometric proportions required to obtain the desired final composition.

The initial mixture being thus obtained, one then proceeds, in accordance with the second step of the process according to the invention, to its heating.

The temperature at which this heat treatment, also called thermohydrolysis, is carried out, can be 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 adopted, either under normal atmospheric pressure, or under pressure such as for example the saturated vapor pressure corresponding to the temperature of the heat treatment.

When the treatment temperature is chosen to be greater than the reflux temperature of the reaction mixture (that is to say generally greater than 100 "C), for example chosen between 150 and 350" C, the operation is then carried out by introducing the mixture. aqueous containing the aforementioned species in a closed chamber (closed reactor more commonly called an autoclave), the necessary pressure then resulting only from heating the reaction medium (autogenous pressure). Under the temperature conditions given above, and in aqueous media, it is thus possible to specify, by way of illustration, that the pressure in the closed reactor varies between a value greater than 1
Bar (105 Pa) and 165 Bar (165. 105 Pa), preferably between 5 Bar (5. 105 Pa) and 165 Bar (165. 105 Pa). It is of course also possible to exert an external pressure which is then added to that resulting from the heating.

The heating can be carried out either under an air atmosphere or under an inert gas atmosphere, preferably nitrogen.

The duration of the treatment is not critical, and can thus vary within wide limits, for example between 1 and 48 hours, preferably between 2 and 24 hours.

At the end of the heating step, a solid precipitate is recovered which can be separated from its medium by any conventional solid-liquid separation technique such as, for example, filtration, decantation, draining or centrifugation.

It may be advantageous to introduce, after the heating step, a base such as, for example, an ammonia solution, into the precipitation medium. This makes it possible to increase the recovery yields in the precipitated species.

It is also possible to add hydrogen peroxide in the same way, after the heating step.

The product as recovered can then be subjected to washings with water and / or with ammonia, at a temperature between room temperature and the boiling point. To remove the residual water, the washed product can finally, optionally, be dried, for example in air, and this at a temperature which can vary between 80 and 300 "C, preferably between 100 and 1500C, the drying being continued until a constant weight was obtained.

It will of course be noted that it is of course possible to repeat one or more times, identically or not, after recovery of the product and possible addition of the base or of the hydrogen peroxide, a heating step as described above. , then returning the product to a liquid medium, in particular in water, and for example by carrying out heat treatment cycles.

In a final step of the process, the precipitate recovered, optionally after washing and / or drying, is then calcined. According to a particular embodiment, it is possible after the thermohydrolysis treatment and optionally after returning the product to a liquid medium and an additional treatment, to directly dry the reaction medium obtained by atomization.

The calcination is carried out at a temperature generally between 200 and 1200 "C and preferably between 300 and 900" C. This calcination temperature must be sufficient to transform the precursors into oxides, and it is also chosen according to the temperature of subsequent use of the catalytic composition and taking into account the fact that the specific surface of the product is all the lower. that the calcination temperature used is higher. The duration of the calcination can for its part vary within wide limits, for example between 1 and 24 hours, preferably between 4 and 10 hours. The calcination is generally carried out in air, but calcination carried out for example under inert gas is obviously not excluded.

The compositions of the invention as described above or as obtained in the processes mentioned above are in the form of powders but they can optionally be shaped to be in the form of granules, beads, cylinders or nests. bee of variable dimensions.

This support is then impregnated with a catalytically active phase, such as ruthenium in the preferred embodiment of the invention as described above.

The examples given below only by way of indication, will illustrate the characteristics of the catalysts used in the process of the invention as well as their activity in the wet oxidation processes of organic compounds.

Examples of the preparation of several catalysts in accordance with the invention and catalysts illustrating the prior art will be described.

The catalytic activity of these catalysts will be determined by carrying out a wet oxidation of an aqueous solution of acetic acid. This organic compound was chosen as the test compound because its oxidation is more difficult than that of most oxidizable organic compounds present in the aqueous effluents to be treated.
Example 1: Prenaration of a catalyst A in accordance with the invention:
First, a mixed oxide of formula Ca0.62Zr0.38O2 is prepared.

In the stoichiometric proportions required for obtaining the above mixed oxide, a solution of ceric nitrate and a solution of zirconyl nitrate are mixed. The latter was obtained by attacking a carbonate using concentrated nitric acid. The solution responds, in the sense defined above, to the OH- / Zr molar ratio condition = 0.94.

The concentration of this mixture (expressed as oxide of the different elements) is adjusted to 80 g / l. This mixture is then brought to 1500C for 4 hours.

An ammonia solution is then added to the reaction medium so that the pH is greater than 8.5. The reaction medium thus obtained is brought to the boil for 2 hours. After decantation and then withdrawal, the solid product is resuspended and the medium thus obtained is treated for 1 hour at 100 ° C. The product is then filtered and then calcined at a temperature of 900 ° C.

Secondly, the catalyst is prepared by impregnation of the composition prepared above with a catalytically active phase, namely ruthenium.

For this, 8 g of support prepared above are suspended in 13.1 cm3 of an aqueous solution of hydrochloric acid at 11 g / l containing 0.190 g of RuCl3.

After stirring at 25 "C for 20 hours, the solution is filtered. The precursor is slowly evaporated in an oven at 1200C. The dried precursor is then reduced under hydrogen by heating the catalyst to 350" C with a temperature rise of 10. C / min., Then hold at this temperature for 3 hours. The catalyst is then cooled, still under a hydrogen atmosphere, then passivated under nitrogen.

Catalyst A according to the invention has the following composition by mass 4%
Ru on oxide Ce0.62 - Zr0.38O2.

Example 2 Preparation of a catalyst B in accordance with the invention:
In a first step, a mixed oxide of formula Ce0.65Zr0.31Nd0 Nd0.04O2 is prepared.

In the stoichiometric proportions required for obtaining the above mixed oxide, a preneutralized solution of ceric nitrate is mixed by adding
NH40H such that r = - 0.22 (r being as defined above), a solution of neodymium nitrate and a solution of zirconyl nitrate which meets, in the sense defined above, the condition OH- / Zr = molar ratio = 1.17.

The operating mode then followed is identical to that of Example 1 up to the treatment step for 1 hour at 100 ° C. The reaction medium thus obtained is dried by atomization and then calcined at a temperature of 900 ° C.

The synthesis of catalyst B is carried out according to the same protocol as that described in Example 1 except for the nature of the support.

Catalyst B according to the invention has the composition by mass: 4% Ru on Ce0.65Zr0.31 NdO.0402
Example 3 Preparation of a catalyst C in accordance with the invention:
First, a mixed oxide of formula Ce0.65Zr0.31 La0.04O2 is prepared.

The mixing of the solutions and the procedure are the same as in Example 2, the neodymium nitrate being replaced by lanthanum nitrate.

The synthesis of catalyst C is carried out according to the procedure described in Example 1 with the exception of the nature of the support.

Catalyst C according to the invention has the composition by mass of 4% Ru on Ce0.65Zr0.3La0.04O2.

Example 4 Preparation of a catalyst D in accordance with the invention:
First, a mixed oxide of formula Ce0.65Zr0.31 LaO, 0402 is prepared.
The mixture of the solutions and the procedure are the same as in Example 2, the neodymium nitrate being replaced by lanthanum nitrate, and the solution of RuCL3 by a solution of IrCl3.

The synthesis of catalyst D is carried out according to the procedure described in Example 1 with the exception of the nature of the support.

Catalyst D according to the invention has the composition by mass of 4% Ir on Ca0.65Zr0.3La0.04O2.

Example 5 Preparation of a catalyst E in accordance with the invention:
First, a mixed oxide of formula Ca0.66Zr0.30Pr0.04O2 is prepared.

The mixing of the solutions and the procedure are the same as in Example 2, the neodymium nitrate being replaced by praseodymium nitrate.

The synthesis of catalyst E is carried out according to the procedure described in Example 1 except for the nature of the support.

Catalyst E according to the invention has the composition by mass of 4% Ru on Ce0.65Zr0.30Pr0.04O2.

Example 6 Preparation of a catalyst F according to the prior art
In a first step, according to the prior art, a mixed oxide of cerium and of zirconium of formula Ce0.765Zr0.23502 is prepared.

In the stoichiometric proportions required for obtaining the above mixed oxide, a solution of cerous nitrate and a solution of zirconyl nitrate are mixed. The latter has an NO3 / Zr ratio of 2. The oxide concentration of the elements is adjusted to 172 g / l.

This mixture thus obtained is added over 30 minutes to a solution containing ammonia, water and hydrogen peroxide. The product thus obtained is washed several times with demineralized water by a series of decantations and eliminations of the washing water. The product is then filtered and then dried at 100 ° C. for 2 hours.

The synthesis of catalyst F is carried out as follows: 8 g of support are calcined according to the following protocol: rise to 700 ° C. at 10 ° C. / min., Then hold at this temperature for 3 h. The support is then cooled under the same current of air.

The support is suspended in 6.56 cm3 of an aqueous solution containing 0.100 g of RuCl3.

After stirring at 25 "C for 20 h, the solution is slowly evaporated on a sand bath at 1200 ° C. The dried precursor is then calcined in air (20 cm3 / min.) According to the following protocol: rise to 400 ° C. at 10 ° C. / min., then maintained at this temperature for 3 h, it is then cooled under the same air stream.

Catalyst F according to the prior art has the composition by mass of 4% Ru on Ca0.765Zr0.23502.

Example 7: Preparation of a catalyst G according to the prior art
The synthesis protocol of catalyst G is identical to that described in Example 5 except for the final treatment of catalyst G which consists, after the calcination treatment in air at 400 ° C. in reducing the ruthenium precursor under hydrogen (20 cm3 / min.) according to the protocol described in Example 1.

Catalyst G according to the prior art has the composition by mass of 4% Ru on Ca0.765Zr0.23502.

Example 8: Preparation of an H catalyst according to the prior art
The synthesis of catalyst H is carried out as follows: 8 g of TiO2 support with a specific surface area of 120 m2 / g are suspended in 13.1 cm3 of an aqueous solution of HCl (11 g / l) containing 0.190 g of RuCI3.

After stirring at 25 ° C. for 20 h, the solution is filtered. The precursor is slowly evaporated in an oven at 1200 ° C. The dried precursor is then reduced under hydrogen (20 cm3 / min.) According to the following protocol: rise to 350 "C at 10 C / min., Then maintained at this temperature for 3 h, it is then cooled under the same stream of hydrogen and passivated under nitrogen.

Catalyst H according to the prior art has the composition by weight of 4% Ru on TiO 2.

Example 9:
Performance measurement of catalysts A to H described in examples 1 to 9
The oxidation performance of acetic acid is measured according to the following protocol: 0.88 g of catalyst is placed in a 440 cm3 autoclave containing 220 cm3 of an aqueous solution containing 5 g / l of acetic acid. . Then the mixture is heated under nitrogen (3 bar) to the reaction temperature (200 ° C.), with stirring (120 revolutions / min.)
When the temperature is stabilized, we add 20 bar of pure oxygen (zero reaction time) and we follow the evolution of the disappearance of acetic acid and the appearance of CO2 (CO2 in gas phase + dissolved CO2) . At t = 0, the conversion of acetic acid (during the rise in temperature) is less than 0.5%.

The performances of the catalysts are expressed: either by the initial rate of conversion of acetic acid into CO2 expressed in
millimole of acetic acid converted per liter of solution, per hour and per gram of
catalyst, or in percentage of conversion of the acetic acid converted after 1 hour of
reaction.

The results reported in Table 1 for catalysts A to H clearly demonstrate the superiority of the catalysts of the invention over those of the prior art.

Table 1

<tb><SEP> Invention <SEP> Art <SEP> Previous
<tb> Example <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <SEP> 8
<tb> Catalyst <SEP> | <SEP> A <SEP> B <SEP> | <SEP> C <SEP> D <SEP> E <SEP> F <SEP> G <SEP> H
<tb> Initial <SEP> speed <SEP> mmolell.hg <SEP> 58 <SEP> 93 <SEP> 111 <SEP> 79 <SEP> 34 <SEP> l <SEP> 2X5 <SEP> 2.5511.4 <SEP>
<tb> Rate <SEP> of <SEP> conversion <SEP> to <SEP> 1 <SEP> h <SEP> 61 <SEP> 91 <SEP> 100 <SEP> 81 <SEP> 30 <SEP> 3,4 <SEP> 4.412 <SEP>
<tb> to <SEP>% <SEP> of <SEP> conversion
<tb>

Claims (12)

1 - A method of treating an aqueous solution or suspension of organic compounds at a high temperature and pressure by oxidation of the organic compounds with a gas containing oxygen in the presence of an oxidation catalyst to reduce the chemical oxygen demand of said solution or suspension at a predetermined level characterized in that the catalyst comprises a catalytically active phase present on a support consisting of a composition based on a cerium oxide and a zirconium oxide in a cerium / zirconium atomic proportion of at least 1, exhibiting a specific surface area after calcination for 6 hours at 900 "C of at least 35m2 / g and an oxygen storage capacity at 400" C of at least 1.5 ml of O2 / g . 2 -Procédé according to claim 1, characterized in that the support composition based on a cerium oxide and a zirconium oxide has a specific surface area after calcination for 6 hours at 1000 "C of at least 14 m 2 / g and more particularly at least 20 m 2 / g and even more particularly at least 30 m 2 / g. 3-A method according to claim 1 or 2, characterized in that the support composition based on a cerium oxide and a zirconium oxide has an oxygen storage capacity at 400 "C of at least 1 , 8 ml of O2 / g, more particularly at least 2 ml of O2 / g. 4 - Process according to claim 3, characterized in that the support composition based on a cerium oxide and a zirconium oxide has an oxygen storage capacity at 400 "C of at least 2.5 ml of O2 / g. 5 - Method according to one of claims 1 to 4, characterized in that the support composition based on a cerium oxide and a zirconium oxide is in the form of a solid solution. 6 - Method according to one of claims 1 to 6, characterized in that the active phase of the catalyst comprises ruthenium or iridium in the form of metal or of compounds. 7 - Process according to claim 6, characterized in that the catalyst comprises at least 0.5% by weight expressed as ruthenium or iridium metal, preferably between 0.5% and 10%. 8 - Method according to one of claims 6 to 7, characterized in that the ruthenium or iridium compound is an oxide of these metals. 9 - Method according to one of the preceding claims, characterized in that the treatment is carried out at a pressure sufficient to maintain the solution or suspension of organic compounds in the liquid state. 10 - Method according to one of the preceding claims, characterized in that the treatment is carried out at a temperature between 100 "C and 400" C, preferably between 1200C and 200 "C. 11 - Method according to one of the preceding claims, characterized in that the treatment is carried out under an oxygen pressure of between 1 and 50 bar. 12 - Method according to one of the preceding claims, characterized in that the solution or suspension of organic compounds to be treated has a maximum chemical oxygen demand of 200 g / l.