EP1346009B1 - Method for desulphurising hydrocarbons containing thiophene derivatives - Google Patents

Abstract

The invention relates to a selective desulphurisation method for thiophene derivatives contained in the hydrocarbons emitted from the distillation of crude oil, refined or not, consisting in oxidising the atoms of thiophene sulphur in sulphone in the presence of an oxidising agent and separating the sulphonated compounds from said hydrocarbons. This inventive method comprises at least one first stage involving the oxidation/absorption by heterogeneous catalysis of the sulphurous compounds in an organic environment, at a temperature of at least 40?C, at atmospheric pressure in the presence of an organic oxidiser from the family of peroxides and peracids, in the presence of a catalyst having a specific surface area greater than 100 m2/g and a porosity varying from 0.2 to 4 ml/g, and a second stage wherein the used catalyst is regenerated.

Description

The present invention relates to a desulfurization process hydrocarbons, in particular desulfurization of the bases of fuels for diesel, kerosene and gasoline. It concerns in particular the desulfurization of the fuel bases loaded with dibenzothiophenic compounds.

The presence of sulfur in fuels constitutes a problem considered today as major for the environment. Indeed, by combustion, the sulfur is converted into various oxides of sulfur, which can turn into acids thus contributing to the formation of acid rain.

Generally, refineries use processes catalytic hydrodesulfurization to lower the sulfur content of fuels.

Thus, the gas oils coming directly from the distillation are hydrotreated between 300 and 400 ° C, under a hydrogen pressure varying between 30 and 100 bars (30 to 100.10 ⁵ Pa), in the presence of a catalyst placed in a fixed bed and constituted metal sulfides of groups VIb and VIII deposited on alumina, for example cobalt and molybdenum sulfides or nickel and molybdenum sulfides. Given the operating conditions and the consumption of hydrogen, these processes can be costly in investment and in operation, in particular if it is sought to produce fuels with a very low sulfur content. Thus, to desulfurize a fuel initially containing 1% by weight of sulfur, up to a sulfur content of between 0.05 and 0.005% by weight, the size of the reactor can be multiplied by 4 and the quantity of hydrogen necessary for the reaction should be increased by about 20%. It is particularly difficult, by such methods, to remove traces of sulfur, especially if the sulfur belongs to refractory molecules such as dibenzothiophene alkylated in position 4, and and 6.

In some countries like Sweden, the United States, especially in California, and others, the total sulfur content of diesel is already limited to 0.005% by weight. This limitation could be generalize over time in OECD countries. For Europe, this goal 0.005% by weight of total sulfur should be reached in 2005.

Unlike gas oils, gasolines do not come from only from the direct distillation of crude oil, these essences being then weakly sulfur, but can also be obtained by several processes such as naphtha reforming, isomerization light naphthas, butane or propane alkylation producing isooctane, methoxylation of isobutene and catalytic cracking vacuum distillates or atmospheric residues. In particular, catalytic cracking provides between 20 and 60% by weight of the petrol final. These essences contain up to 0.1% by weight of sulfur. he It is therefore common to desulfurize gasolines from cracking catalytic by processes similar to those described for hydrodesulfurization of gas oils, for which the conditions are more severe in hydrogen pressure, space velocity and temperature. These processes, although expensive, do not allow however not in the conventional way to reach total sulfur contents, in these cracked essences, between 0.005 and 0.03% by weight. Although, to reduce this sulfur content, refiners have imagined adding decomposing additives to the cracking catalyst sulfur compounds formed during the process, especially mercaptans and sulfides, these additives have only a limited effect, even zero, on benzothiophenic derivatives, even when the mercaptans and the sulfides were removed before cracking.

In the case of generating catalytic cracking gasolines of sulfur in gasolines, hydrodesulfurization is not only ineffective with respect to thiophene compounds, but it is also destructive to the octane number of gasoline. Indeed, during of the hydrodesulfurization reaction, there is partial hydrogenation of olefins contained in these cracked essences, their disappearance resulting in a drop in the octane number of gasoline and therefore a deterioration in the quality of petrol. To compensate for this loss, there it is possible to introduce other constituents to improve this index or to reprocess the essence itself to increase this index. Adding additive or reprocessing to improve the quality of petrol strikes its cost price all the more, and it is therefore advantageous to have a treatment process allowing direct elimination refractory sulfur compounds, such as derivatives benzothiophenics, limiting the use of hydrogen.

Selective oxidation processes for sulfur compounds make part of the treatment processes likely to achieve this goal. Among methods and processes developed to reduce the amount of sulfur present in fuels in the form of thiophene derivatives, oxidation with organic peroxides, hydroperoxides organic, hydrogen peroxide and organic peracids, has been considered either without catalyst or by homogeneous catalysis in the presence of catalysts based on organometallic compounds or oxides metallic in the aqueous phase (see US 3,668,117, US 3,565,793, EP 0 565 324 and the publications of T.A. KOCH, K.R. KRAUSE, L. EMANZER, H. MEHDIZADEH, J.M. ODOM, S.K. SENGUPTA, New J. Chem., 1996, 20, 163-173 and F.M. COLLINS, A.R. LUCY, C. SHARP, J. of Molecular Catalysis A: Chemical 117 (1997) 397-403).

For processes using catalysts metals based on molybdenum and tungsten in the presence of hydrogen peroxide in aqueous solution (heterogeneous catalysis), operates at temperatures above 60 ° C and there is overconsumption of hydrogen peroxide, part of this oxidant being broken down by the catalyst used. The peracids used, very powerful oxidants, obtained by reaction of hydrogen peroxide and an acid carboxylic such as formic acid or acetic acid, are generally less effective than hydrogen peroxide and less selective with regard to sulfur compounds and can in particular oxidize olefins.

Other organic oxidesulfurization processes have been proposed: they consist of putting in contact in powder form metal oxides or to form metal compounds containing peroxo groups in aqueous solutions or organic with hydrocarbons containing these sulfur compounds refractory, in the presence or absence of organic or aqueous peroxides, these being introduced with an alcohol type solvent or into water (see US 3,816,301, US 4,956,578, US 5,958,224).

Another method, described in US Patent 3,945,914, consists of producing a desulfurized hydrocarbon material in three processing steps. The first step is to oxidize at least partially the sulfur compounds by contacting with peroxides, in the presence of metal catalysts containing metals of the group including titanium, zirconium, molybdenum, tungsten, vanadium, tantalum, chromium and their mixtures, under liquid or solid form possibly supported, the supports not being not essential for the reaction. The second step is to put in contact the hydrocarbonaceous material containing these oxidized compounds with another metallic component, metallic oxide or peroxide (metals from the group comprising nickel, molybdenum, cobalt, tungsten, iron, zinc, vanadium, copper, manganese, mercury and their mixtures), at a temperature varying from 250 to 730 ° C, under pressure hydrogen. The third step is to recover the material desulfurized hydrocarbon

In all these methods and processes, we transform the thiophene derivatives in their sulfonated and / or sulfonic form. However, for some of these compounds, even if we work at high temperature, the reaction is relatively slow and the total conversion is not reached in less than an hour, otherwise using very strong oxidant concentrations, often much higher than the quantities necessary for the oxidation of sulfur derivatives. In other cases, it is possible to work in several stages, but which are expensive in time and unit tracking.

The present invention therefore aims to propose a method of desulfurization of hydrocarbons, especially those used as fuel bases containing thiophenic derivatives, without decrease in the octane number or cetane number index, sometimes even with an increase in these indices. It relates to particularly the finishing treatment of hydrotreated gas oils, kerosene and gasoline from catalytic cracking, strongly concentrated in thiophenic derivatives refractory to hydrogenations.

The invention further aims to propose such a method which allows to reach identical oxidation levels, otherwise superior to known methods, while limiting reaction times and separation of oxidized sulfur compounds from hydrocarbons desulphurized.

The present invention therefore relates to a process for the selective desulfurization of thiophenic compounds contained in hydrocarbons obtained from the distillation of crude oil, refined or not, consisting in oxidizing thiophenic sulfur atoms to sulfones in the presence of an oxidizing agent and d 'a catalyst, and to separate the sulfonated compounds obtained from said hydrocarbons, this process being characterized in that it comprises at least a first oxidation / adsorption step by heterogeneous catalysis of the sulfur-containing compounds, in organic medium, at a temperature d '' at least 40 ° C, in the presence of an organic oxidant from the family of peroxides and peracids and in the presence of a catalyst with a specific surface greater than 100 m ² / g and a porosity varying from 0.2 to 4 ml / g, and a second stage of regeneration of the spent catalyst, the regeneration stage always succeeding the oxidation / adsorption stage.

In the context of the present invention, the term “derivatives” thiophene benzothiophenic, polybenzothiophenic compounds and their alkylated derivatives, among which the alkyldibenzothiophenes, particularly refractory to the processes of conversion usually used by refiners.

The method according to the invention has the advantage, on the one hand, to ensure at atmospheric pressure an oxidation of the entire sulfur contained in hydrocarbons and more selectively a conversion of thiophene derivatives into sulfones, and this in the context of a simple industrial process, and, on the other hand, to adsorb simultaneously these sulfoxidized compounds on the catalyst. Indeed, the separation of hydrocarbons from most of the sulfones and sulfoxides formed is immediate, the latter being found under solid form deposited on the catalyst or in the form of filterable deposit by means known per se, in the treated hydrocarbons. This catalyst, on which these sulfoxidized compounds have been absorbed, constitutes the "spent catalyst". We can extract sulfones possibly dissolved in the treated hydrocarbons. Otherwise, this oxidation / adsorption has no effect on olefins, which does not not modify, in catalytic cracking gasolines, the index octane, nor the content of non-sulfur aromatic compounds. The process oxidation according to the invention further improves the cetane number of gas oils.

Without being limited by theory, it appeared that the more the the greater the specific surface of the catalyst, the more active it is long time. In addition, the sulfone and sulfoxide type compounds having strongly polar in character, they are maintained on the surface of catalyst, probably at the Lewis acid sites of catalyst. Similarly, the larger the pore size, the less the catalyst pores may clog quickly, and the lower the longevity of the catalyst during the oxidation cycle is ensured. For the present invention, it is a question of selecting the catalyst which exhibits the best compromise in specific surface and pore size for get enough activity for as long as possible to be most effective in oxidation / adsorption.

When the process is carried out continuously so intermittent, the oxidation / adsorption and regeneration stages can be carried out in the same reactor or simultaneously in reactors arranged in parallel and operating alternately for one or other of the stages in a fixed bed, or in at least two moving bed reactors connected to each other by the catalytic bed, one being dedicated to oxidation / adsorption, the other to regeneration.

In a fixed bed, the first reactor containing a fixed bed of catalyst receives the flows of hydrocarbons and oxidant and the second receives, for the regeneration of the catalyst, liquid effluents, for example a washing solvent, or oxidizing gaseous effluents , like air or an air / N ₂ mixture, the temperature of the catalytic bed being raised. These reactors change function when the efficiency of the catalyst in the oxidation / adsorption reactor is no longer sufficient for oxidation and / or adsorption.

In a moving bed, the hydrocarbons are brought into the first oxidation reactor, the catalyst being gradually pushed to the second reactor, where it is regenerated before being returned in the oxidation / adsorption reactor. Mobile bed reactors, well known in particular in the field of reforming, can be used in this device. In this embodiment, a third reactor, arranged between the first two reactors and to remove the hydrocarbons from the used catalyst before wash it or perform the combustion of sulfone compounds and trapped sulfoxides.

The catalysts used according to the present invention are chosen from the supports of the group made up of silicas, aluminas, zirconia, amorphous or crystalline aluminosilicates, aluminophosphates, silicic and silicoaluminous mesoporous solids, activated carbon and clay, these supports being used alone or in combination mixed. In the catalysts of the invention, these supports can be advantageously used as group metal supports consisting of titanium, zirconium, vanadium, chromium, molybdenum, iron, manganese, cerium and tungsten, these metals in the form of oxides which can be introduced into the support network or deposited on the surface of the support. Indeed, there was an effect synergistic of the metal with the support, i.e. an increase unexpected activity of the catalyst with regard to the oxidation of thiophenic compounds and, in parallel, an increase in trapping of sulfone and sulfoxide compounds in the pores of the catalyst, without any of them being subsequently desorbed.

In the process according to the invention, the catalyst contains from 0 to 30% by weight of metal in the form of oxide on at least one support. Of preferably, the catalyst contains from 0 to 20% of metal in the form oxide.

Among the supports consisting of refractory oxides, it is preferred gamma aluminas, silicas, silicic mesoporous solids and silicoaluminés.

Among the supported catalysts, the catalysts are preferred. containing tungsten or titanium in the form of oxide deposited on a support or introduced into the network, this support being chosen from among the silicas, aluminas and aluminosilicates, alone or as a mixture.

In a preferred embodiment of the method, the total oxidant / sulfur molar ratio in hydrocarbons is between 2 and 20, and preferably between 2 and 6.

According to the invention, the oxidants are chosen from the compounds of general formula R ₁ OOR ₂ , in which R ₁ and R ₂ are identical or different, chosen from hydrogen, linear or branched alkyl groups, comprising from 1 to 30 carbon atoms and aryl or alkylaryl groups, the aryl unit of which is optionally substituted by alkyl groups, R ₁ and R ₂ which cannot simultaneously be hydrogen.

In a preferred embodiment, the oxidant of formula R ₁ OOR ₂ is chosen from the group consisting of tert-butyl hydropcroxide and ditertiobutylperoxide.

Other oxidants of the invention, the peracids of formula R ₃ COOOH, are chosen such that R ₃ is hydrogen or a linear or branched alkyl group comprising from 1 to 30 carbon atoms. They are preferably chosen from the group consisting of peracetic acid, performic acid and perbenzoic acid.

In the process of the invention, the step of regenerating the catalyst consists in washing away or burning deposits trained

For washing, a preferably polar solvent is used. group consisting of water, linear or branched alkanols comprising from 1 to 30 carbon atoms, alone or in admixture with water, alkylnitriles comprising from 1 to 6 carbon atoms. The water, acetonitrile, methanol and mixtures thereof are preferred.

By combustion, the catalyst is brought to a temperature of at most 800 ° C, preferably to a temperature less than or equal to 650 ° C, under a pressure varying from 10 ⁵ Pa to 10 ° Pa, and preferably from 10 ⁵ Pa at 2.10 ⁵ Pa, in the presence of an oxidizing gas. By oxidizing gas is meant pure oxygen and all mixtures of gases containing oxygen, in particular mixtures of oxygen and nitrogen and the air itself. The quantity of oxygen in the nitrogen is adjusted so as to limit the formation of water vapor, an excessively large quantity of water vapor having the secondary effect of modifying the structure of the pores of the catalyst with reduction in their volume, especially when it contains crystalline aluminosilicates as support, such as zeolites or aluminophosphates. This adjustment also makes it possible to control the temperature variations linked to the exothermicity of the combustion.

For the implementation of the process defined above, it is possible to use a device comprising at least a first reactor containing an oxidation catalyst and comprising pipes of hydrocarbons and oxidant and an outlet pipe desulfurized hydrocarbons, and possibly a second reactor comprising inlet pipes for solvent or oxidizing gas from catalyst, in order to regenerate it, and an outlet pipe for combustion gases. By oxidizing gas is meant here the mixtures oxygen / air, air / nitrogen and oxygen / nitrogen.

When the device comprises two reactors, the reactors can operate in fixed bed or mobile bed.

Another object of the invention is the application of the defined method above to the specific finishing treatment of essences from catalytic cracking or the treatment of diesel fuel that has been previously hydrotreated and kerosene, for better economy of the process.

La figure 1 est un schéma d'un dispositif à deux réacteurs fonctionnant alternativement en oxydation et en régénération du catalyseur ;

La figure 2 est un schéma d'un dispositif comprenant deux réacteurs à lit mobile, le premier correspondant à l'étape d'oxydation, le second à l'étape de régénération du catalyseur, un conduite de retour du catalyseur régénéré étant adjointe au système ;

Les figures 3-1 et 3-2 représentent des courbes fllustrant la teneur en soufre total, en fonction du temps, des hydrocarbures traités scion l'invention dans l'Exemple III ci-après.

The invention will be described below in more detail with reference to the accompanying drawings. In these drawings:

FIG. 1 is a diagram of a device with two reactors operating alternately in oxidation and in regeneration of the catalyst;

FIG. 2 is a diagram of a device comprising two moving bed reactors, the first corresponding to the oxidation step, the second to the catalyst regeneration step, a return line of the regenerated catalyst being added to the system ;

Figures 3-1 and 3-2 show curves showing the total sulfur content, as a function of time, of the hydrocarbons treated according to the invention in Example III below.

The device of Figure 1 comprises two reactors 1 and 2 loaded with a catalyst arranged in a fixed bed. When the reactor 1 operates in oxidation and the reactor 2 operates in regeneration, the line 3 brings to the reactor 1 the sulfur-containing hydrocarbon charge, into which the oxidant has been introduced via the line 4, the three-way valve 6 a and the line 8 a . The desulfurized hydrocarbon stream leaves the reactor 1 through line 9 to and joins the pipe 10 to discharge the hydrocarbon desulfurized via the three way valve 7 a.

At the same time, line 5 brings to reactor 2 either a suitable solvent or an oxidizing gas, via the three-way valve 6 b and line 8 b . When the reactor is operating in combustion, the temperature of the catalytic bed is maintained at 500 ° C. The solvent containing the sulfones recovered from the catalyst or the combustion gases, mainly SO ₂ , CO and CO ₂ , are evacuated via line 9 b , the three-way valve 7 b and line 11 b in line 11 a .

When the regeneration of the catalyst is done and the activity of the catalyst of reactor 1 becomes insufficient, there is a permutation of the function of the two reactors. Thus, the hydrocarbon / oxidant mixture takes the line 3 a and the valve 6 b to enter the reactor 2. The desulphurized hydrocarbons are evacuated through the line 9 b and are directed to the evacuation line 10 a via the valve 7 b and driving 10 b .

At the same time, the solvent or the oxidizing gas arriving via line 5 is directed into reactor 1 via line 3 a , valve 6 a and line 8 a . The solvent or the oxidation gases are brought back into the discharge line 11 a via the line 9 a and the valve 7 a .

The valves 6 a , 6 b , 7 a and 7 b can be swapped according to a common process to allow the circulation of the proposed flows.

One can advantageously place on one of the lines 9 a or 9 b , or else 10 a or 10 b , a filter for recovering the solid sulfones formed during the oxidation, which remain in suspension in the hydrocarbons. One can advantageously add on these same pipes, downstream of these filters, sulfur traps equipped with absorbents of the silica or activated alumina type, to trap the sulfones still dissolved in the treated hydrocarbons.

The device of FIG. 2 comprises two reactors 20 a and 20 b , arranged in series, each containing a movable bed of catalyst, the reactor 20 a operating in oxidation mode and the reactor 20 b operating in regenerative mode, and a propulsion device 30 to the reactor catalyst back to the reactor 20 b 20 a.

The hydrocarbons are brought via line 40 into reactor 20 a , after having been doped by the oxidant via line 50. For example, reactor 20 a can be chosen from reactors with funnels, the moving bed of the catalyst moving by gravity to the lower part of the reactor. Thus, while the desulphurized hydrocarbons are evacuated via line 60, the catalyst is pushed by gravity into reactor 20 b via line 70. The solvent or the combustion gas is introduced via line 80 into reactor 20 b . To perform regeneration by combustion, the temperature is increased and maintained at 500 ° C. The solvent loaded with sulfones or the combustion gases are evacuated via line 100.

As, generally, these moving beds operate intermittently, the catalyst not moving continuously, it is advantageous to have on the reactor 20 b a solvent or nitrogen purge allowing the elimination of the hydrocarbons before washing, and / or the elimination of combustion gases by nitrogen stripping.

At the outlet of the reactor 20 b , the regenerated catalyst is led via the line 110 to the device 30. This device can be a device powered by gas under pressure or a worm. It brings the regenerated catalyst via line 120 to reactor 20 a .

In certain particular embodiments of these mobile reactors, the reactors 20 a and 20 b can be part of the same unit having two separate stages.

The examples below are intended to illustrate the effectiveness of the process of the invention, without limiting its scope.

EXAMPLE I

This example aims to describe the efficiency of the process according to the invention with regard to the elimination of dibenzothiophene derivatives present in bases for partially desulphurized fuels.

The samples of catalysts used are of two types, catalysts formed from a single support and those with one or more metals deposited by impregnation. Table 1 below gives the specific surface and porosity characteristics of each of them. Sample
of
catalyst Nature of
support Area
specific
(m ² / g) Size of
pore
(Angstroms) oxides
metal C ₁ SiO ₂ 160 252 - C ₂ SiO ₂ 140 300 WO ₃ K ₃ Al ₂ O ₃ gamma 245 104 WO ₃ C ₄ Beta zeolite 470 30 TiO ₂ C ₅ mesoporous 1000 85 C ₆ mesoporous 830 70 MoO ₃ K ₇ Al ₂ O ₃ γ 210 95 WO ₃

Catalysts C ₂ , C ₃ and C ₆ were obtained by wet impregnation of a metal salt, ammonium metatungstate and ammonium hexamolybdate, respectively, at a content of 140 mg of metal per gram of support, then dried and finally calcined at a temperature of 500 ° C.

Catalyst C ₄ was obtained by treatment of a commercial titanium beta zeolite according to the procedure described in patent EP 0 842 114.

To test the activity of these catalysts in oxidation as a function of time, 20 ml of catalyst were introduced into a 150 ml micropilot. A charge of middle distillates is circulated on the catalyst after hydrotreatment, containing 212 ppm of residual sulfur refractory to hydrotreatment, doped with 1800 ppm of tert-butyl hydroperoxide (tBHP), at an hourly space speed (VVH) of 1 h ^-1, under atmospheric pressure, at a temperature of 70 ° C. Samples are taken regularly during the oxidation to measure the activity of the catalyst over time. A comparative sample called T ₁ , corresponding to the use of catalyst alone without peroxide, is also followed.

In Table II below are given the results of efficiency of these catalysts over time. Sample Catalyst Total sulfur (ppm) after different
operating periods. 2 hours 4h 5 a.m. 6h T ₁ C ₁ 121 185 196 202 X ₁ This 49 46 48 49 X ₂ C ₂ 28 14 9 16 X ₃ K ₃ 30 28 23 27 X ₄ C ₄ 18 16 11 11 X ₅ C ₅ 35 32 38 35 X ₆ C ₆ 23 20 17 22 X ₇ K ₇ 34 31 25 31

After two hours of operation, these results confirm that, apart from the effect due to the nature of the catalyst, the larger the size the higher the pore size of the catalyst and the specific surface, sulfur content of the treated hydrocarbons is low. We see in besides that the activity of the catalyst increases, when it consists of a metal oxide with support. However, after 24 hours, what whatever the catalyst, there is a slight increase in the content sulfur of desulfurized hydrocarbons, which may correspond to a start of clogging of catalyst pores, sulfones and sulfoxides settling there.

By this process, it is clear that the choice of a catalyst for the process of the invention is the result of a compromise between the nature of the catalyst, its specific surface and the pore size thereof.

EXAMPLE II

In this example, the efficiency of the catalyst is measured by function of the oxidation of the compounds.

The procedure is as in Example I, with the catalysts C ₁ -C ₆ and the formation of sulfones and sulfoxides is monitored with respect to the dibenzothiophene compounds, in particular benzothiophene (BT), dibenzothiophene (DBT) and 4.6 dimethyldibenzothiophene (DMBT), by gas chromatography equipped with a specific sulfur detector (SIEVERS method).

Table III below collates the results obtained. Catalyst Concentration
oxidant (eqS) % Sulfone oxidation BT DBT DMBT C ₁ 3 80 78 81 C ₂ 3 90 95 93 K ₃ 3 88 92 89 C ₄ 3 96 99 95 C ₅ 3 85 87 88 C ₆ 3 92 94 93

These results show that there is at least 80% conversion thiophene derivatives refractory to sulfones, with catalysts consist of the only support, and more than 90%, with catalysts consisting of supports and at least one metal in the form of oxide metal inserted into the support network or deposited on the support.

Example III

This example aims to show, in addition to oxidation, the time-dependent effect of the adsorption of the sulfone compounds and sulfoxides on the oxidation / adsorption and regeneration sequences, and the efficiency of the regeneration operation compared to oxidation / adsorption.

The operation is carried out with catalyst C ₃ under the operating conditions described in Example I on a middle distillate containing 44 ppm of sulfur after hydrotreatment, and in the presence of 600 ppm of tBHP.

The results of the oxidation / adsorption are given in the Figure 3-1, when the catalyst is fresh. After two days, the content of total sulfur in hydrocarbons goes up significantly in value initial, in the absence of the treatment according to the invention.

The results in Figure 3-2 correspond to the monitoring of the sulfur content of these same hydrocarbons when this same catalyst C ₃ regenerated by combustion was used. The results obtained on a fresh catalyst are almost identical to those obtained on this same regenerated catalyst.

These two curves show the advantage of the process of the invention which offers alternative operation of the same catalyst in oxidation / adsorption or regeneration, the time of oxidation / adsorption must naturally be adapted to the rate of sulfur.

Claims (17)

1. A process for the selective desulphurisation of the thiophenic derivatives contained in refined or unrefined hydrocarbons originating from the distillation of crude petroleum, comprising oxidising the atoms of thiophenic sulphur into sulphones in the presence of an oxidising agent and separating the sulphonated compounds of said hydrocarbons, said process being characterised in that it comprises at least one first oxidation/adsorption step by heterogeneous catalysis of the sulphur compounds, in an organic medium, at a temperature of at least 40°C, in the presence of an organic oxidant of the family of the peroxides and peracids and in the presence of a catalyst with a specific surface greater than 100 m²/g and of a porosity varying from 0.2 to 4 ml/g, and a second step for regeneration of the spent catalyst, the regeneration step always succeeding the oxidation/adsorption step.
2. A process according to claim 1, characterised in that the oxidation/adsorption and regeneration steps are carried out successively in the same reactor on the same catalyst.
3. A process according to claim 1, characterised in that the oxidation/adsorption and regeneration steps are carried out simultaneously in the reactors (1,2) disposed in parallel and operating alternately for either of the steps.
4. A process according to claim 1, characterised in that the oxidation/adsorption and regeneration steps are carried out in two reactors with moving beds (20a,20b) connected to one another by the catalytic bed, one bed being dedicated to the oxidation and the other bed to the regeneration.
5. A process according to any one of claims 1 to 4, characterised in that the oxidising agent is chosen from the group comprising the organic peroxides, the organic hydroperoxides and the peracids.
6. A process according to either one of claims 1 and 2, characterised in that the catalyst comprises a support chosen from the group comprising the silicas, the aluminas, the zircons, the amorphous or crystalline aluminosilicates, the aluminophosphates, the mesoporous solids, the activated charcoals, the clays and mixtures thereof.
7. A process according to claim 6, characterised in that the catalyst contains at least one metal chosen from the group comprising titanium, vanadium, chromium, molybdenum, iron, manganese and tungsten, said metal being introduced into the network of the support or deposited on the support in the form of oxide.
8. A process according to any one of claims 1 to 7, characterised in that the catalyst contains from 0 to 30 % by weight and, preferably, from 0 to 20 % by weight of metal in the form of oxide.
9. A process according to any one of claims 1 to 8, characterised in that the catalyst is composed of at least one support chosen from gamma alumina, silica and the silicic and silicoaluminous mesoporous solids.
10. A process according to any one of claims 1 to 9, characterised in that the supported catalyst is chosen from the catalysts containing tungsten on a support chosen from the silicas and the aluminas, alone or mixed.
11. A process according to any one of claims 1 to 10, characterised in that the total oxidant/sulphur molar ratio in the hydrocarbons varies from 2 to 20 and, preferably, from 2 to 6.
12. A process according to any one of claims 1 to 11, characterised in that the oxidant is a compound having the general formula R₁OOR₂, in which R₁ and R₂ are chosen to be identical or different in the group formed by the hydrogen atom and the linear or branched alkyl groups, comprising from 1 to 30 carbon atoms, it not being possible for R₁ and R₂ simultaneously to be hydrogen.
13. A process according to claim 12, characterised in that the oxidant is chosen from the group comprising tertiobutyl hydroperoxide and ditertiobutyl peroxide.
14. A process according to any one of claims 1 to 13, characterised in that the oxidant is a peracid of the formula R₃COOOH, in which R₃ is hydrogen or a linear or branched alkyl group comprising from 1 to 30 carbon atoms.
15. A process according to claim 14, characterised in that the oxidant is chosen from the group comprising peracetic acid, performic acid and perbenzoic acid.
16. A process according to any one of claims 1 to 15, characterised in that the catalyst regeneration step comprises eliminating the deposits formed by washing or by combustion.
17. Application of the process according to any one of claims 1 to 16 to the desulphurisation of hydrotreated gas oils, kerosenes and gasolines, in particular gasolines originating from catalytic cracking.

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