WO2002090468A1 - Method for desulphurization and/or denitrogenation of a hydrocarbon mixture - Google Patents

Abstract

The invention concerns a method for desulphurization and/or denitrogenation of a hydrocarbon mixture containing sulphur and/or nitrogenous compounds, comprising an oxidation step with hydrogen peroxide and a solid catalyst containing a metallosilicate having been subjected to a silylating treatment with at least a silylating agent.

Description

 Desulfurization and / or denitrogenation process for a mixture of hydrocarbons

The present invention relates to a process for desulfurization and / or denitrogenation of a mixture of hydrocarbons containing sulfur compounds and / or nitrogen compounds, comprising at least one oxidation step, in which, as oxidant, hydrogen peroxide in the presence of a solid catalyst, in order to oxidize the sulfur compounds and / or the nitrogen compounds.

On the one hand, for reasons related to certain catalytic refining operations, the presence of basic nitrogen compounds must be limited. It is indeed known that this type of compound can poison the catalysts used in these operations (hydrodesulfurization and catalytic cracking). On the other hand, for environmental reasons, the specifications on the sulfur content of fuels are becoming more and more strict. Since 2000, the maximum sulfur contents in petrol and diesel, authorized by the European Union, have been 150 and 350 ppm by weight respectively. From 2005, these limits will fall to 50 ppm by weight. Limitations are also expected for heating oil, for which the current specification is 2000 ppm by weight of sulfur.

The conventional process for removing sulfur from oils is based on the hydrodesulfurization reaction represented by RSR '+ 2 H ₂ → RH + R'H + H ₂ S where RSR' represents an aliphatic, alicyclic or aromatic sulfur compound.

This known method has certain drawbacks. For example, compliance with the new sulfur specifications requires more severe hydrodesulfurization conditions (excess hydrogen, higher temperature, higher pressure, etc.) and necessarily leads to an increase in the cost of fuels. In addition, certain sulfur compounds that are found in petroleum fractions, such as benzothiophenes and substituted dibenzothiophenes such as for example 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene, are very resistant to hydrodesulfurization. The sulfur present there is therefore difficult to remove by this route.

An alternative to the hydrodesulfurization process based on the oxidation of sulfur compounds is described in the publication entitled "Mild Oxidation with H ₂ O ₂ over Ti-Containing Molecular Sieves - A very Efficient Method for Removing Aromatic Sulfur Compounds from Fuels "which appeared in" Journal of Catalysis 198, 179-186 (2001) ". hydrogen peroxide in the presence of a solid catalyst such as titanosilicalite TS-1, zeolite Ti-beta or mesoporous hexagonal silica Ti-HMS, and optionally in the presence of a polar solvent such as acetonitrile or an alcohol.

This known alternative has certain drawbacks because it requires the addition of a polar organic solvent in order to lead to a higher conversion of the sulfur compounds into oxidized sulfur compounds.

In addition, the Applicant has found that, in certain cases, in the absence of added polar organic solvent, no oxidation occurs, in particular with the catalysts TS-1 and Ti-HMS. In addition, the Applicant has found that with Ti-beta in the absence of an added polar organic solvent, certain sulfur-containing compounds such as benzothiophenes and substituted dibenzothiophenes, for example 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene, are not oxidized.

The present invention aims to avoid the aforementioned drawbacks and to provide a new process for removing sulfur and / or nitrogen from hydrocarbon mixtures which makes it possible to significantly reduce the sulfur and / or nitrogen content, even in the absence of added polar organic solvent.

The invention therefore relates to a process for desulfurization and / or denitrogenation of a mixture of hydrocarbons containing sulfur compounds and / or nitrogen compounds, comprising a step of oxidation using hydrogen peroxide and a solid catalyst which contains a metallosilicate which has undergone a silylation treatment using at least one silylating agent.

A metallosilicate catalyst generally has active sites containing the metal on its outer surface and / or on the surface of the pores. When the hydrogen peroxide comes into contact with these active sites, the latter are activated so that, when they come into contact with the sulfur compounds and / or the nitrogen compounds, they oxidize the latter and return to their state initial. Therefore, in the process according to the invention, the hydrogen peroxide plays the role of activating the catalyst whose active sites, once activated, oxidize the sulfur compounds and / or the nitrogen compounds. Most often, the catalyst has on its outer surface and on the surface of the pores also [-Si - OH] groups which give the catalyst surfaces a character hydrophilic which can be more or less pronounced depending on the amount of these groups.

One of the characteristic elements of the invention resides in the use of a solid catalyst comprising a metallosilicate which has undergone a silylation treatment using a silylating agent. It has in fact been observed that such a catalyst makes it possible to avoid the use of an additional polar organic solvent and makes it possible to oxidize sulfur-containing compounds, in particular certain sulfur-containing compounds resistant to oxidation, such as benzothiophenes and substituted dibenzothiophenes such as for example 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. This catalyst also makes it possible to oxidize nitrogenous compounds.

The function of the silylation treatment carried out in the process according to the invention is to react the groups of formula [-Si - OH], which are present on the external surface and / or on the surface of the pores of the solid catalyst, for the silylated tran s of formula

- n = 1,2,3

- a + b + c = 4 - n - a, b, c = 0, 1, 2, 3

- R ¹ , R ² and R ³ are as defined below.

The surface of the catalyst is thus made less hydrophilic. Without wishing to be bound by a theoretical explanation, the Applicant thinks that the best performance in oxidation would be due to the reduced hydrophilicity of the catalyst, which would lead to a more favorable interaction of the molecules of sulfur compounds and / or of nitrogen compounds to be oxidized with ènvirδήnëmeήt from the active sites of the catalyst.

By "mixture of hydrocarbons" is meant any product containing predominantly hydrocarbons such as paraffins, olefins, naphthenic compounds and aromatic compounds. It may be crude oil or a petroleum derivative obtained by any known refining treatment. The mixture of hydrocarbons can be chosen from petroleum fractions which are used in the composition of any type of fuel and fuel. Among these, mention may be made of kerosene, motor fuels such as petrol or diesel, and domestic fuels such as heating oil. By "sulfur compounds" means all the compounds present in the mixture of hydrocarbons which contain sulfur. They are in particular benzothiophene, dibenzothiophene and their mono- or multisubstituted derivatives, more specifically 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene.

The term "desulphurization" means any treatment which makes it possible to reduce the sulfur content of the mixture of hydrocarbons.

The sulfur-containing compounds can be oxidized, for example to sulfoxides,

sulfones et acides sulfoniques correspondants. Dans le cas du 4,6-diméthyldibenzothiophène, le sulfoxyde correspondant présente la structure suivante

sulfones and corresponding sulfonic acids. In the case of 4,6-dimethyldibenzothiophene, the corresponding sulfoxide has the following structure

the corresponding sulfone has the following structure

and sulfonic acid has the following structure

By "nitrogen compounds" means all the compounds present in the mixture of hydrocarbons which contain nitrogen. These are in particular indole, carbazole, quinoline, acridin, aniline and their mono- or multisubstituted derivatives.

By "denitrogenation" is meant any treatment which makes it possible to reduce the nitrogen content of the mixture of hydrocarbons. The nitrogen compounds can be oxidized for example to amine oxides, acridones, indigo and nitroso or nitro compounds.

By "metallosilicate" is intended to denote any solid containing silicon oxide and an oxide of at least one metal capable of activating hydrogen peroxide. Metals that activate hydrogen peroxide include, for example, silver, cobalt, cerium, manganese, iron, copper, molybdenum, tungsten, vanadium, titanium, chromium, zirconium, hafnium, niobium, tantalum and their mixtures. Titanium is preferred.

The metallosilicate generally contains an amount of the metal such that the molar ratio of silicon and metal is greater than or equal to 1, in particular greater than or equal to 4, more particularly greater than or equal to 10 and preferably greater than or equal to 15. The amount of metal is such that the molar ratio of silicon and metal is usually less than or equal to 8000, more especially less than or equal to 1000, in particular less than or equal to 500, preferably less than or equal to 300, the values less than or equal to 55 being recommended.

The metallosilicate may optionally contain an oxide of another metal such as aluminum. The amount of the other metal in the metallosilicate is generally such that the molar ratio of the silicon and the other metal is greater than or equal to 2, in particular to 5 and preferably to 15. Alternatively, the metallosilicate may be free of this other metal.

The metallosilicates which can be used in the process according to the invention can be prepared by any suitable known means.

According to a first method, they can be prepared by reacting a source of silicon with a source of the metal, and optionally a source of the other metal, in the presence of a hydrolyzing agent and optionally a structuring agent, in order to obtain a solid matrix containing at the same time silicon oxide, the oxide of the metal and optionally the oxide of the other metal. This solid matrix corresponds to metallosilicate.

According to a second method, the source of silicon and possibly the source of the other metal are first hydrolyzed in the presence of a hydrolyzing agent and optionally a structuring agent to obtain a matrix. solid containing silicon oxide and optionally the oxide of the other metal. Then, a source of the metal is reacted with this matrix in order to graft the metal to the external and / or internal surface of the matrix and thus obtain the metallosilicate. This last grafting step may possibly be preceded by complete or partial elimination of the other metal by any suitable known means, for example a steam treatment or an acid extraction. In these two methods: the source of silicon can be chosen from silicon halides, silicas, alkali or alkaline earth metal silicates and silicon alcoholates. The latter are particularly suitable. Methanolates, ethanolates, propanolates, linear or branched butanolates give good results. Tetraethylorthosilicate is preferred.

the source of the metal can be chosen from halides, alcoholates and organometallic compounds of the metal. In the first method, the metal alcoholates are particularly suitable. Ethanolates, propanolates and linear or branched butanolates give good results. Butanolates, in particular titanium, are preferred. In the second method, the organometallic compounds are particularly suitable. By way of example, mention may be made of dichlorodicyclopentadienyltitanium. the source of the other metal can be chosen from the halides, oxides, hydroxides and alcoholates of the other metal. Oxides, hydroxides and alcoholates are well suited.

- The hydrolyzing agent can be chosen from aqueous solutions containing a base or an acid. The base and the acid can be organic or inorganic. As a basic example, there may be mentioned ammonia, alkali or alkaline earth hydroxides, amines and tetraalkylammonium hydroxides. The latter are preferred. As an example of an acid, mention may be made of mineral acids such as halogen acids and oxygenated acids, and organic sulfonic or carboxylic acids. Acids with a pKa in water less than or equal to -1.74 are preferred.

- the structuring agent can be chosen from those which lead to the desired structure. As examples of structuring agent, there may be mentioned amines, phosphines, quaternary ammonium salts and quaternary phosphonium salts. The metallosilicate used in the process of the invention can have a crystalline or amorphous structure. By "crystal structure" is meant a structure which has at least one X-ray diffraction line. By "amorphous structure" is meant a structure which has no X-ray diffraction line. It can for example s act of crystalline or amorphous silicas on which the metal is grafted, of zeolites containing the metal or of cogels containing of the oxides of silicon and of the metal. When the metal is titanium, mention may be made, as examples, of medium-pore zeolites such as TS-1 (described in the publication G. Perego et al, Studies in Surface Science and Catalysis, 1986, vol. 28, p. 129) and TS-2 (described in X Sudhakar Reddy et al, Zéolites, 1992, vol.12, p.95), wide-pore zeolites of the Ti-MOR type (described in P. Wu et al, Journal of Catalysis, 1997, vol. 168, p.400), Ti-beta (described in T. Blasco et al, Journal of Physical Chemistry B, 1998, vol. 102, p. 75) and Ti-Y (described in K. X Balkus et al, Studies in Surface Science and Catalysis, 1997, vol. 110, p. 999), zeolites with extra large pores such as Ti-UTD-1 (described in KJ Balkus et al, Studies in Surface Science and Catalysis, 1996, vol. 101, p. 1341), mesoporous solids of the Ti-MCM-41 type (described in A. Corma et al, Journal of Chemical Society, Chemical Communications, 1994, p.147) or Ti-HMS (described in M. Kruk, Microporous Materials, 1997, vol. 9, p.1 73), and amorphous cogels based on oxides of silicon and titanium (described in DCM Dutoit, Journal of Catalysis, 1995, vol.153, p.165). The Ti-beta and Ti-Y zeolites, the mesoporous silicas containing titanium and having the crystal structure of Ti-MCM-41, the mesoporous hexagonal silicas containing titanium and having the crystal structure of Ti-HMS, and cogels based oxides of silicon and titanium give good results.

The metallosilicate used in the process according to the invention generally has a specific surface greater than or equal to 1 m ² / g, in particular greater than or equal to 20 m ² / g, and preferably greater than or equal to 100 m / g, the values greater than or equal to 200 m ² / g being the most recommended. The specific surface is usually less than or equal to 1200 m ² / g, more especially less than or equal to 1000 m ² / g, preferably less than or equal to 800 m ² / g, values less than or equal to 600 m ² / g being the most common.

The metallosilicate used in the process according to the invention generally has a pore volume greater than or equal to 0.1 cm ³ / g, in particular greater than or equal to 0.2 cm ³ / g, and preferably greater than or equal to 0, 5 cm ³ / g. The pore volume is usually less than or equal to 5 cm ³ / g, more especially less than or equal to 3 cm ³ / g, values less than or equal to 1.5 cm ³ / g being the most common. The metallosilicate used in the process according to the invention can be non-porous.

According to a first variant of the method according to the invention, the silylation treatment is carried out during the manufacture of the metallosilicate. Three scenarios are possible.

In the first case, a source of silicon is reacted with a source of the metal in the presence of a hydrolyzing agent, possibly of a source of another metal, optionally of a structuring agent, and in the presence of the agent. silylation, in order to obtain in a single step a solid matrix which corresponds to the silylated metallosilicate.

In the second case, the source of silicon is first hydrolyzed, in a first step, in the presence of a hydrolyzing agent, optionally a structuring agent, optionally a source of another metal, and a silylating agent, to obtain a solid matrix based on silicon oxide containing silylated groups. Then, in a second step, a source of the metal is reacted with this matrix in order to graft the metal to the external and / or internal surface of the matrix and thus obtain the silylated metallosilicate.

In the third case, the silicon source is first, in a first step, hydrolyzed in the presence of a hydrolyzing agent and optionally a structuring agent and optionally a source of another metal to obtain a solid matrix based on silicon oxide. Then, in a second step, this solid matrix is reacted with the silylating agent, and finally, in a third step, with a source of the metal so as to obtain the silylated metallosilicate.

In these three cases, the sources of silicon, the sources of the metal, the sources of the other metal, the hydrolysing agents and the structuring agents are those defined before.

In the first and second cases of the first variant, the step in which the silylating agent is used is generally carried out at a temperature of 15 to 200 ° C. It is often carried out at a pressure of 1 to 30 bar. The duration of this stage is usually 1 hour to 10 days.

In the third case of the first variant, the silylation treatment can be carried out in various known ways. For example, the solid matrix can be mixed with a silylating agent, preferably liquid, and optionally in the presence of a solvent and a catalyst, most often at a temperature from 15 to 450 ° C, as described in KD Me Murtrey, Journal of Liquid Chromatography, 1988, vol.11, n ° 16, p. 3375. Alternatively, the solid matrix can be heated to a temperature of 100 to 450 ° C. before being brought into contact with the silylating agent, as described in patent FR 2305390. In the third case of the first variant , the silylation treatment can be carried out in batch or continuously. The time required for the silylating agent to react with the surface of the solid matrix depends on the temperature and the agent used. The lowest temperatures require the longest times. Times of 0.1 to 48 h are generally used. It is commonly operated at a pressure of 1 to 10 bar and preferably at atmospheric pressure.

According to a second variant of the method according to the invention, the silylation treatment is carried out in a step subsequent to the manufacture of the metallosilicate according to one of the two methods described above. In the second variant, the silylation treatment can be carried out as in the third case of the first variant as described above. The silylating agent used in the process according to the invention can be chosen from the compounds corresponding to the general formula R _a R bc - Si - X _x YyZ _z in which

- a + b + c + x + y + z = 4 a + b + c = 1, 2, 3 x + y + z = l, 2, 3 a, b, c, x, y, z = 0, 1, 2, 3 - R ¹ , R ² and R ³ are identical or different and chosen from hydrogen and organic radicals containing from 1 to 20 carbon atoms, aliphatic, alicyclic or aromatic, linear or branched, saturated or unsaturated , substituted or unsubstituted, which may optionally contain one or more heteroatoms chosen from halogens (preferably fluorine), nitrogen, oxygen, silicon, phosphorus and sulfur, R ¹ , R ² and R ³ not being simultaneously hydrogen,

- X, Y and Z are identical or different and chosen from (1) hydrogen, (2) a halogen atom, (3) a nitrile group, (4) an azide group, (5) a radical chosen from -OR ⁴ , -O-SO ₂ -R ⁴ , -O-SO ₂ -OR ⁴ , -SR ⁴ , -NR ⁴ R ⁵ , - Si ^ R ⁶ in which R ⁴ , R ⁵ and R ⁶ are identical or different and chosen from all the radicals mentioned in the definition of R ¹ , R ² and R ³ , (6) a heterocycle which may contain one or more heteroatoms chosen from halogens (preferably fluorine), nitrogen, oxygen and sulfur, and (7) hydrocarbon radicals containing up to 20 carbon atoms and which may optionally contain one or more several heteroatoms chosen from halogens (preferably fluorine), nitrogen and oxygen.

Mention may be made, by way of examples, of alkoxysilanes, halosilanes, disilazanes, siloxanes, mid-date silyls, silylamides, silylamines, silylated sulfonates, silylated sulfates, silylated carboxylates, silylureas, and their mixtures. Among the alkoxysilanes, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane and phenyltriethoxysilane are preferred. Among the halosilanes, chlorotrimethylsilane, bromotrimethylsilane, iodotrimethylsilane, chlorotriisopropylsilane, chloro-t-butyldimethylsilane, dichlorodimethylsilane and chlorodimethylphenylsilane are preferred. Among the disilazanes, hexamethyldisilazane is preferred. Among the siloxanes, hexamethyldisiloxane is preferred. Among the silylimidates, N, O-bis (trimethylsilyl) trifTuoroacetamide and N, O-bis (trimethylsilyl) acetamide are preferred. Among the silylamides, N-methyl-N-trimethylsilyltrifluoroacetamide and N-methyl-N-trimethylsilylacetamide are preferred. Among the silylamines, N-trimethylsilylimidazole is preferred. Among the silylated sulfonates, trimethylsilyl trifluoromethanesulfonate is preferred. Among the silylated sulfates, bis (trimethylsilyl) sulfate is preferred. Among the silylated carboxylates, trimethylsilyl trifluoroacetate is preferred. Among the silylureas, N, N'-bis (trimethylsilyl) urea is preferred. When the silylation treatment is carried out according to the first or the second case of the first variant described above, the silylation agent is preferably at least one alkoxysilane.

When the silylation treatment is carried out according to the third case of the first variant described above, or according to the second variant described above, the silylation agent is preferably chosen from halosilanes, disilazanes, siloxanes, silylimidates, silylamides, silylamines, silylated sulfonates, silylated sulfates, silylated carboxylates, silylureas, and mixtures thereof.

In the process according to the invention, three phases can be distinguished in the oxidation reaction medium: an organic phase consisting essentially of the mixture of hydrocarbons, an aqueous phase containing essentially water, hydrogen peroxide and optionally an added organic solvent, and a solid phase consisting of the solid catalyst. It is preferred to work in the absence of added organic solvent. It is also preferred to work in the absence of organic acid. The oxidation step of the process according to the invention consists in bringing the mixture of hydrocarbons, hydrogen peroxide, the solid catalyst and any added solvent into contact, by any known means ensuring intimate contact of the various phases.

The quantity of solid catalyst used in the process according to the invention must be sufficient to allow rapid oxidation of the sulfur-containing compounds and / or of the nitrogen-containing compounds. It depends on the metal content, the oxidation conditions and the type of reactor used. This quantity of catalyst is generally such that the number of moles of the metal used and related to the number of moles of hydrogen peroxide present in the oxidation reaction medium is greater than or equal to 0.00015, in particular 0, 00065 and preferably 0.0015. This ratio is usually less than or equal to 0.5, preferably 0.0465, more particularly 0.0075 and most often 0.0035. A ratio greater than or equal to 0.00015 and less than or equal to 0.5 is suitable. In the oxidation step of the process according to the invention, the catalyst is generally used in the form of particles, which can be obtained by any known process. One thinks of the most diverse forms of particles such as in particular powders, beads, pellets, extrudates or honeycomb structures. The catalyst can be used in suspension in the oxidation medium or in the form of a fixed bed. The average size of these particles depends on the type of implementation. For a process where the catalyst is in suspension, the average particle size is generally greater than or equal to 5 μm, more particularly to 10 μm and more particularly to 50 μm. The average particle size is usually less than or equal to 500 μm, more particularly to 250 μm and more particularly to 150 μm. Average sizes greater than or equal to 100 μm and less than or equal to 125 μm are particularly suitable. For a process where the catalyst is used in a fixed bed, the average particle size is generally greater than or equal to 0.5 mm, more particularly to 1 mm and very particularly to 2 mm. The average particle size is commonly less than or equal to 100 mm, more particularly 75 mm and very particularly 50 mm. Sizes averages greater than or equal to 5 mm and less than or equal to 30 mm are particularly suitable.

In the process according to the invention, the oxidation is generally carried out at a temperature greater than or equal to 0 ° C., in particular at 10 ° C. and preferably at 20 ° C. The temperature is usually less than or equal to 200 ° C, preferably 100 ° C, in particular 90 ° C and most particularly 80 ° C. Temperatures of 25 to 70 ° C are suitable.

In the process of the invention, hydrogen peroxide is generally used in the oxidation reaction in the form of an aqueous solution. This solution most often has a hydrogen peroxide concentration greater than or equal to 1% by weight, in particular 10% by weight. The hydrogen peroxide concentration is commonly less than or equal to 80%, in particular 70%. A concentration of 30 to 60% by weight is suitable. The amount of hydrogen peroxide present in the oxidation reaction medium depends on the amount of sulfur and / or nitrogen present in the mixture of hydrocarbons. The hydrogen peroxide / [sulfur and / or nitrogen present in the hydrocarbon mixture] molar ratio is generally greater than or equal to 1, in particular 2. This ratio is often less than or equal to 5,000, in particular particular to 3000. The ratios from 3 to 1500 are particularly suitable. The aqueous phase which comes into contact with the mixture of hydrocarbons is used in a volume such that the ratio of the volumes of this aqueous phase and of the mixture of hydrocarbons ensures optimum dispersion of the phases. This ratio is generally less than or equal to 0.5, in particular to 0.4. It is usually greater than or equal to 0.01, in particular 0.05. Values greater than or equal to 0.075 and less than or equal to 0.3 are preferred. In the process according to the invention, the oxidation can be carried out at atmospheric pressure or at an atmospheric pressure. We prefer to work at atmospheric pressure.

The oxidation can be preceded by one or more hydrodesulfurization steps. It can also be followed by one or more steps for the separation of the oxidized sulfur compounds and / or the oxidized nitrogen compounds. These separations can be carried out in any known manner, for example by distillation, by extraction by means of solvents, by adsorption on solids, by pyrolysis, by acid or basic hydrolysis or by precipitation. The process according to the invention can be carried out continuously or batchwise.

Examples 1 to 8: Preparation of Catalysts Example 1 - Synthesis of a Ti-β a zeolite. Removal of aluminum from a beta zeolite:

50 g of a commercial β zeolite (Zeolyst International, ZEOLYST ™ CP 811E-75, SiO ₂ / Al ₂ O ₃ = 75 mol / mol, 12 g) are introduced into a 1 liter erlenmeyer flask fitted with a magnetic bar. Ai / kg) and 200 ml of 14N HNO ₃ (65%).

The suspension was heated with stirring at 80 ° C for 4 h, then cooled, filtered and the collected solid was washed with demineralized water until neutral pH. This solid was dried for 16 h at 175 ° C in a ventilated oven. All of the above operations were repeated twice. The solid was then calcined in air for 10 h at 550 ° C.

The residual Al content was 0.7 g / kg (SiO ₂ / Al ₂ O ₃ = 1280 mol / mol). The crystallographic structure was not modified by the treatment. b. Ti grafting In a pyrex reaction tube of dimensions 28x25x90 mm closed at one end and extended by another tube of dimensions 18x15x95 mm, 4.00 g of the dealuminized zeolite-β were introduced according to the procedure described above. The system was brought to 120 ° C. and maintained under vacuum (3 mbar) for one hour, then cooled under nitrogen. 0.31 g of dichlorodicyclopentadienyltitanium (TiCp ₂ Cl ₂ ) was then introduced, under nitrogen, into the tube. The tube was evacuated (3 mbar) and sealed. It was then rotated at 60 rpm in a horizontal oven. It was then brought to 300 ° C in 1 h, kept at this temperature for 4 h, then heated to 310 ° C for 16 h. After cooling, the tube was opened and the solid obtained was calcined in air for 10 h at 550 ° C.

The β crystal structure was confirmed by X-ray diffraction. The Ti content was 16.2 g Ti / kg.

Example 2 Synthesis of a Ti-Y Zeolite

The synthesis procedure is identical to that of Example 1 except that the starting zeolite is a Y zeolite US commercial (CU Chemie Uetikon AG ZEOCAT ^® Z6-05-02, SiO ₂ / Al ₂ O ₃ = 6, 7 mol / mol, 107 g Ai / kg).

The crystal structure Y is confirmed by X-ray diffraction. The Ti content was 16.2 g Ti / kg. The Al content was 24 g Ai / kg. Example 3 - Synthesis of a Ti-MCM-41 Silicalite a. Synthesis of a MCM-41 type silicalite 41.5 g of tetraethylorthosilicate were introduced into a 500 ml polyethylene bottle. 100 g of a 5% by weight aqueous solution of tetramethylammonium hydroxide (hydrolyzing agent) were then added over 0.5 h. A solution consisting of 24.3 g of cetyltrimethylammonium bromide (structuring agent) previously dissolved in a mixture of 10 g of ethanol and 60 g of water was then introduced. The suspension obtained was stirred for 0.5 h and then transferred to a teflon-coated autoclave. The latter was brought to 135 ° C. for 24 h under autogenous pressure and without agitation. After cooling, the solid was collected by filtration and then washed once with 200 ml of deionized water and four times with 200 ml of ethanol. It was then dried for 12 hours in air at 135 ° C and then brought to 540 ° C in air at 1 ° C / min and calcined for 6 hours in air at this temperature.

The X-ray diffraction spectrum of the solid presented a single line corresponding to a reticular distance of 3.1 nm. b - Grafting of Ti

4.5 g of the sample obtained according to the procedure described above was introduced into a 500 ml Erlenmeyer flask fitted with a magnetic bar, surmounted by a 3-way stopcock and previously purged under dry nitrogen. The system was brought to 120 ° C. and maintained under vacuum (3 mbar) for 1 h and then cooled under nitrogen. Then 180 ml of dried CHCl ₃ was added over a 4A molecular sieve and the suspension was stirred at room temperature.

1.38 g of TiCp ₂ Cl ₂ were added to a 250 ml Erlenmeyer flask fitted with a magnetic bar, surmounted by a 3-way stopcock and previously purged under dry nitrogen, then 120 ml of dried CHC1 ₃ were added. on 4Â molecular sieve. We got a red solution. This solution was then added under nitrogen to the zeolite suspension and the mixture was stirred for 0.5 h at room temperature.

45.0 g of dried triethylamine was then added under nitrogen over a 4A molecular sieve and the system was stirred for 2 h at room temperature.

The suspension obtained was filtered under nitrogen and the collected solid was washed, under nitrogen, with 3 times 50 ml of CHC1 ₃ dried over 4A molecular sieve, then it was dried under vacuum at 120 ° C for 16 h then calcined under air for 10 h at 550 ° C. The Ti content was 14.9 g Ti / kg. Example 4 - Silylation of a Ti-beta zeolite with N, O-bis (trimethylsilyDtrifluoroacetamide (BSTFA) In a 250 ml Erlenmeyer flask fitted with a magnetic bar, surmounted by a 3-way tap and previously purged under dry nitrogen, 2.5 g of Ti-beta zeolite obtained in Example 1 were introduced. The system was brought to 120 ° C. and maintained under vacuum (3 mbar) for 1 h and then cooled under nitrogen. added under nitrogen, 40 g of a solution of BSTFA (silylating agent) obtained by dissolving 25 g of BSTFA in 205 g of toluene previously dried on a 4A molecular sieve The suspension was stirred for 2 h at room temperature.

The suspension obtained was filtered under nitrogen and the collected solid was washed, under nitrogen, with twice 50 ml of dried toluene on a 4A molecular sieve, then it was dried under vacuum at 25 ° C for 16 h.

Example 5 - Silylation of a Ti-Y zeolite by BSTFA The procedure of Example 4 was reproduced using the Ti-Y zeolite obtained by the procedure of Example 2.

Example 6 - Silylation of a Ti-MCM-41 Silicalite by BSTFA The procedure of Example 4 was reproduced using the Ti-MCM-41 Silicalite obtained by the procedure of Example 3. Example 7 - Silylation d a commercial Si-Ti cogel by the BSTFA

The procedure of Example 4 was reproduced using a commercial Si-Ti cogel (Crosfield Catalysts, EP 50 silica / titania cogel, 26 g Ti / kg). Example 8 Silylation of a Ti-MCM-41 Silicalite by the Chlorotrimethylsilane Mixture (TMCS / Hexamethyldisiloxane (ΗMDSO)

In a 250 ml Erlenmeyer flask fitted with a magnetic bar, surmounted by a 3-way stopcock and previously purged under dry nitrogen, 2.5 g of the Ti-MCM-41 silicalite obtained by the procedure of Example 3. The system was brought to 120 ° C and maintained under vacuum (3 mbar) for 1 h then cooled under nitrogen. 125 g of a mixture (silylating agent) consisting of 50 g of TMCS and 75 g of HMDSO were then added under nitrogen, then the system was brought to reflux under a stream of nitrogen for 16 h. The suspension was placed in a rotary evaporator and the excess reagents were removed at 80 ° C under a vacuum of 30 mbar. The solid collected was then washed with 4 times 200 ml of acetone and then dried under vacuum for 16 h at room temperature. Examples 9 to 17: Oxidation of Sulfur Compounds A synthetic solution of benzothiophene (BT) and dibenzothiophene (DBT) in toluene was used to simulate a mixture of hydrocarbons containing sulfur compounds. Compounds of the benzo- and dibenzothiophene type are difficult to remove by hydrodesulfurization and contribute mainly to the S content of certain petroleum products.

80 g of a solution of benzothiophene (BT, 5.249 g / kg) and dibenzothiophene (80 g / kg) in a pyrex double jacket reactor equipped with a paddle stirrer and surmounted by a cooler cooled to -20 ° C. DBT, 7, 188 g / kg) in toluene, which corresponded to an S content of 2500 ppm by weight, 1.0 g of Ti solid and 12.25 ml of a hydrogen peroxide solution at 37.8% by weight. The mixture was stirred for 1 h at 25 ° C and then for 4 h at 50 ° C.

The BT and DBT contents were determined by vapor phase chromatography after different reaction times. They make it possible to determine the conversion rate of sulfur compounds, defined as:

100 * (number of moles of sulfur compounds initially present - number of moles of non-oxidized sulfur compounds) / (number of moles of sulfur compounds initially present). The results are collated in Table 1. The conversion rates of the sulfur compounds are given after 2 and 5 h. Table 1

Examples 18 to 21: Oxidation of Sulfur Compounds The oxidation conditions are those of the previous examples except that the sulfur compound to be oxidized is 4,6-dimethyldibenzothiophene dissolved in an amount of 160 ppm of S in toluene.

The results are collated in Table 2. The conversion rates of the sulfur compound are given after 2 and 3 h of reaction at 50 ° C.

Table 2

Example 22 Oxidation of Sulfur Compounds and Nitrogen Compounds A synthetic solution of benzothiophene (BT), dibenzothiophene (DBT), quinoline (Q) and indole (I) was used in toluene to simulate a mixture of hydrocarbons containing sulfur compounds and nitrogen compounds.

80 g of a solution of benzothiophene (BT, 6.472 g / kg), of dibenzothiophene (DBT) were introduced into a pyrex double jacket reactor equipped with a paddle agitator surmounted by a cooler cooled to -20 ° C. , 9.350 g / kg), quinoline (Q, 1.085 g / kg) and indole (I, 1.084 g / kg) in toluene, which corresponded to an S content of 3,168 ppm by weight and a N content of 247 ppm by weight, 2.0 g of Ti solid as obtained in Example 5 and 12.25 mL of a 38.9% by weight hydrogen peroxide solution. The mixture was stirred for 1 h at 25 ° C and then for 3 h at 50 ° C.

The contents of BT, DBT, Q and I were determined by vapor phase chromatography. They make it possible to determine the conversion rates of sulfur compounds and of nitrogen compounds, defined as:. 100 * [number of moles of sulfur compounds (or nitrogen compounds) initially present - number of moles of sulfur compounds (or nitrogen compounds) not oxidized] / [number of moles of sulfur compounds (or nitrogen compounds) initially present]

After 4 h of reaction, the conversion rate of the sulfur compounds is 100 mol% and that of the nitrogen compounds is 100 mol%.

Claims

RENENDICATIONS 1 - Process for desulfurization and / or denitrogenation of a mixture of hydrocarbons containing sulfur compounds and / or nitrogen compounds, comprising an oxidation step using hydrogen peroxide and a solid catalyst which contains a metallosilicate having undergone a silylation treatment using at least one silylation agent. 2 - Process according to claim 1, in which the metallosilicate is chosen from Ti-beta and Ti-Y zeolites, mesoporous silicas containing titanium and having the crystal structure of Ti-MCM-41, hexagonal mesoporous silicas containing titanium and exhibiting the crystal structure of Ti-HMS, and the cogels based on oxides of silicon and titanium. 3 - Process according to claim 1 or 2, wherein the silylating agent corresponds to the general formula R'aR'bR'c - Si - X _x Y _y Z _z in which a + b + c + x + y + z = 4 a + b + c = 1, 2, 3 x + y + z = 1, 2, 3 a, b, c, x, y, z = 0, 1, 2, 3 - R ¹ , R ² and R ³ are identical or different and chosen from hydrogen and organic radicals containing from 1 to 20 carbon atoms, aliphatic, alicyclic or aromatic, linear or branched, saturated or unsaturated, substituted or unsubstituted , which may optionally contain one or more heteroatoms chosen from halogens, nitrogen, oxygen, silicon, phosphorus and sulfur, R ¹ , R ² and R ³ not being simultaneously hydrogen, X, Y and Z are identical or different and chosen from (1) hydrogen, (2) a halogen atom, (3) a nitrile group, (4) an azide group, (5) a radical chosen from - OR ⁴ , -O-SO ₂ -R ⁴ , -O-SO ₂ -OR ⁴ , -SR ⁴ , -NR ⁴ R ⁵ , - SiR ⁴ R ⁵ R ⁶ in which R ⁴ , R ⁵ and R ⁶ are identical or different and chosen from all the radicals mentioned in the definition of R ¹ , R ² and R ³ , (6) a heterocycle which may contain one or more heteroatoms chosen from halogens, nitrogen, oxygen and sulfur, and (7) hydrocarbon radicals containing up to 20 carbon atoms and possibly containing one or more heteroatoms chosen from halogens, nitrogen and oxygen. 4 - Method according to claim 3, wherein the silylating agent is chosen from alkoxysilanes, halosilanes, disilazanes, siloxanes, silylimidates, silylamides, silylamines, silyl sulfonates, silyl sulfates, silyl carboxylates, silylureas, and mixtures thereof. 5 - Process according to any one of claims 1 to 4, wherein the silylating agent is used during the preparation of the metallosilicate. 6 - Process according to any one of claims 1 to 4, wherein the silylating agent is used in a step subsequent to the preparation of the metallosilicate. 7 - Process according to any one of claims 1 to 6, wherein the oxidation is carried out in the absence of organic acid. 8 - Process according to any one of claims 1 to 7, wherein the oxidation is carried out in the absence of added solvent. 9 - Process according to any one of claims 1 to 8, in which the oxidation is carried out at a temperature of 0 to 200 ° C and using an amount of hydrogen peroxide such that, in the reaction medium d oxidation, the hydrogen peroxide / [sulfur and / or nitrogen (s) present in the hydrocarbon mixture] molar ratio is from 1 to 5000, and an amount of solid catalyst such as the number of moles of the metal work and related to the number of moles of hydrogen peroxide present in the oxidation reaction medium is greater than or equal to 0.00015 and less than or equal to 0.5. 10 - Process according to any one of claims 1 to 9, in which the oxidation is preceded by one or more hydrodesulfurization steps and followed by one or more steps for separating the oxidized sulfur compounds and or the oxidized nitrogen compounds .