Finishing hydrodesulfurization catalyst comprising a group vib metal, a group viii metal and phosphorus on an alpha alumina support

Abstract

Finishing hydrodesulfurization catalyst comprising an active phase comprising at least one group VIB metal and at least one group VIII metal, phosphorus, and a porous support comprising alpha alumina, the content of group VIB metal, measured in oxide form, being between 1 and 8% by weight relative to the total weight of the catalyst, the content of group VIII metal, measured in oxide form, being between 0.2 and 5% by weight relative to the total weight of the catalyst, and the content of phosphorus, measured in its P2O5 form, being between 0.1 and 3% by weight relative to the total weight of the catalyst, said catalyst having a specific surface area greater than or equal to 1 m2 / g and less than 20 m2 / g. The catalyst of one example contains oxides of Co, Mo and P on alpha alumina.

Description

[0001] FINISHING HYDRODESULFURIZATION CATALYST COMPRISING A GROUP VIB METAL, A GROUP VIII METAL AND PHOSPHORUS ON AN ALPHA ALUMINA SUPPORT

[0002] Field of invention

[0003] The present invention relates to the field of hydrotreatment of gasoline cuts, in particular gasoline cuts from fluidized bed catalytic cracking units. More particularly, the present invention relates to the use of catalysts in a process for producing low-sulfur gasoline. The invention applies particularly to the treatment of gasoline cuts containing olefins and sulfur, such as gasolines from catalytic cracking, for which it is sought to reduce the content of sulfur compounds, without hydrogenating the olefins and aromatics.

[0004] State of the art

[0005] Automotive fuel specifications require a significant reduction in sulfur content in these fuels, particularly in gasoline. This reduction is intended to limit, in particular, the sulfur and nitrogen oxide content in automobile exhaust gases. The specifications currently in force in Europe since 2009 for gasoline fuels set a maximum sulfur content of 10 ppm by weight (parts per million). Similar specifications are also in force in other countries such as the United States and China, where the same maximum sulfur content has been required since January 2017. To achieve these specifications, it is necessary to treat gasoline using desulfurization processes.

[0006] The main sources of sulfur in gasoline bases are so-called cracked gasolines, and primarily the gasoline fraction resulting from a catalytic cracking process of a vacuum distillate or a residue from the atmospheric or vacuum distillation of crude oil. The gasoline fraction resulting from catalytic cracking, which represents on average 40% of gasoline bases, contributes more than 90% of the sulfur content in gasolines. Consequently, the production of low-sulfur gasolines requires a desulfurization step for catalytic cracked gasolines. Other sources of gasoline that may contain sulfur include coker gasolines, visbreaker gasolines, or, to a lesser extent, gasolines resulting from atmospheric distillation or steam-cracking gasolines.

[0007] Sulfur removal from gasoline cuts involves specifically treating these sulfur-rich gasolines using desulfurization processes in the presence of hydrogen. These are called hydrodesulfurization (HDS) processes. However, these gasoline cuts, and more specifically those produced by fluidized catalytic cracking (FCC), contain a significant proportion of unsaturated compounds in the form of monoolefins (approximately 20 to 50% by weight), which contribute to a good octane rating, diolefins (0.5 to 5% by weight), and aromatics. These unsaturated compounds are unstable and react during the hydrodesulfurization treatment. Diolefins form gums through polymerization during hydrodesulfurization treatments. This gum formation leads to progressive deactivation of the hydrodesulfurization catalysts or progressive clogging of the reactor.Consequently, diolefins must be removed by hydrogenation before any treatment of these gasolines. Traditional treatment processes desulfurize gasolines non-selectively by hydrogenating a large proportion of the monoolefins, which results in a high loss of octane number and high hydrogen consumption. The most recent hydrodesulfurization processes make it possible to desulfurize cracked gasolines rich in monoolefins, while limiting the hydrogenation of monoolefins and consequently the loss of octane. Such processes are for example described in documents EP-A-1077247 and EP-A-1174485.

[0008] However, in the case where cracked gasolines must be desulfurized very deeply, a portion of the olefins present in the cracked gasolines is hydrogenated on the one hand and recombines with F^S to form mercaptans on the other hand. This family of compounds, with the chemical formula R-SH where R is an alkyl group, are generally called recombinant mercaptans, and generally represent between 20% by weight and 80% by weight of the residual sulfur in desulfurized gasolines. Reducing the content of recombinant mercaptans can be achieved by catalytic hydrodesulfurization, but this leads to the hydrogenation of a significant portion of the mono-olefins present in the gasoline, which then leads to a significant reduction in the octane number of the gasoline as well as excessive hydrogen consumption.It is also known that the loss of octane linked to the hydrogenation of mono-olefins during the hydrodesulfurization stage is all the greater when the targeted sulfur content is low, that is to say when the aim is to thoroughly eliminate the sulfur compounds present in the feed.

[0009] It is thus possible to treat gasoline by a sequence of two reactors as described in document EP1077247, the first stage, also called the selective HDS stage, generally aims to achieve deep desulfurization of the gasoline with minimal olefin saturation (and no aromatic loss) leading to maximum octane retention. The catalyst used is generally a CoMo type catalyst. During this stage, new sulfur compounds are formed by recombination of the H2S resulting from the desulfurization with the olefins: the recombinant mercaptans. The second stage generally has the role of minimizing the quantity of recombinant mercaptans. The temperature is generally higher in the second stage in order to thermodynamically favor the elimination of the mercaptans.In practice, a furnace is therefore placed between the two reactors in order to raise the temperature of the second reactor to a temperature higher than that of the first.

[0010] The catalyst used in the finishing process must be particularly selective so as not to induce saturation of the olefins (and no aromatic loss) leading to a loss of octane. It must therefore make it possible to reduce the total sulfur and mercaptan contents of hydrocarbon cuts, preferably gasoline cuts, to very low contents, minimizing the reduction in the octane number. Usually, the catalyst used is nickel-based.

[0011] It is known from patent FR 3,023,184 to propose a hydrotreatment catalyst on an alumina-based support comprising at least one metal from group VI B, one metal from group VIII and phosphorus, having a specific surface area of ​​between 20 and 150 m 2 / g and a high density of group VI B metal per unit area of ​​the catalyst between 7 and 30 metal atoms per nm 2 of catalyst.

[0012] It is also known from patent FR 2,840,315 to propose the use of a catalyst comprising at least one metal from group VI B, one metal from group VIII and a support with a specific surface area of ​​less than 200 m 2 / g in which the density of group VIB metal per unit area of ​​the support is between 4.10 -4 and 36.10 -4 g of group VIB metal oxides per m 2 of support.

[0013] Nevertheless, there is still a need to maximize performance in the hydrotreatment of gasoline cuts to achieve sulfur specifications.

[0014] Surprisingly, the Applicant has discovered that a catalyst based on at least one metal from group VIII, at least one metal from group VIB and phosphorus on an alpha alumina support allows an improvement in the performance in gasoline hydrotreatment when it is implemented in a finishing hydrodesulfurization (FNS) section located downstream of the selective hydrodesulfurization (HDS) section. Without being bound by any theory, the use of such a catalyst in the finishing hydrodesulfurization section makes it possible to eliminate a portion of the refractory sulfur compounds in the finishing section while preserving the olefins induced by a high selectivity enabled by a specific interaction between the active phase and the surface of the alpha alumina support, thus overall on the selective and finishing hydrodesulfurization sections to better control the hydrogenation reactions of the olefins while promoting the conversion of the sulfur compounds.

[0015] Objects of the invention

[0016] The present invention relates to a finishing hydrodesulfurization catalyst comprising an active phase containing at least one metal from group VIB and at least one metal from group VIII, phosphorus, and a porous support comprising alpha alumina. The content of metal from group VIB, measured in oxide form, is between 1 and 8% by weight relative to the total weight of the catalyst, the content of metal from group VIII, measured in oxide form, is between 0.2 and 5% by weight relative to the total weight of the catalyst, and the content of phosphorus, measured in its P2O5 form, is between 0.1 and 3% by weight relative to the total weight of the catalyst, said catalyst having a specific surface area greater than or equal to 1 and 20 m 2 / g.

[0017] According to one or more embodiments, the molar ratio between the group VIII metal and the group VIB metal is between 0.1 and 2.0 mol / mol.

[0018] According to one or more embodiments, the molar ratio between phosphorus and the group VIB metal is between 0.1 and 2.0 mol / mol.

[0019] According to one or more embodiments, the specific surface area of ​​the catalyst is between 1 and 16 m 2 / g.

[0020] According to one or more embodiments, the surface density of group VIB metal expressed as weight of group VIB metal oxides per unit area of ​​the catalyst is between 33.10' 4 and 130.10' 4 g / m 2 .

[0021] According to one or more embodiments, the Group VIII metal is cobalt and the Group VIB metal is molybdenum.

[0022] According to one or more embodiments, the support is in the form of balls.

[0023] According to one or more embodiments, said catalyst comprises an active phase consisting of molybdenum and cobalt, phosphorus, and a porous support consisting of alpha alumina, the cobalt content being between 0.5 and 3% by weight, measured in the oxide form CoO, relative to the total weight of the catalyst, the molybdenum content being between 3 and 7% by weight, measured in the oxide form MoOs, relative to the total weight of the catalyst, a phosphorus content of between 0.3 and 1.5% by weight, measured in the oxide form P2O5, relative to the total weight of the catalyst, the molar ratio between cobalt and molybdenum being between 0.3 and 1.0 mol / mol, the molar ratio between phosphorus and molybdenum being between 0.2 and 0.5 mol / mol, the surface density of molybdenum, expressed in the oxide form MoOs, being between 40.10-4 and 90.10 -4 g / m 2 , the specific surface area of ​​the catalyst being between 1 and 16 m 2 / g.

[0024] Another subject matter of the invention relates to a method for treating gasoline containing sulfur compounds and olefins, the method comprising at least the following steps: a) gasoline, hydrogen and a hydrodesulfurization catalyst comprising an active phase comprising a metal from group VI B and a metal from group VIII at least partly in sulfurized form, and an oxide support are brought into contact in a first reaction section, at a temperature of between 200°C and 350°C, at a pressure of between 0.2 MPa and 5 MPa, with an hourly volumetric flow rate of between 1 h' 1 and 8 p.m. 1 and a ratio between the hydrogen flow rate expressed in normal m 3 per hour and the flow rate of load to be treated expressed in m 3 per hour under standard conditions between 10 Nm3 / m 3 and 1000 Nm 3 / m 3 , to obtain a partially desulfurized effluent; b) without separation of the H2S formed in step a), the partially desulfurized effluent obtained at the end of step a) is brought directly into contact in a second reaction section with a finishing hydrodesulfurization catalyst according to the invention at least partly in sulfurized form, at a temperature between 250°C and 400°C, at a pressure between 0.2 MPa and 5 MPa, with an hourly volumetric flow rate between 1 h -1 and 8 p.m. 1 , to obtain a desulfurized effluent.

[0025] According to one or more embodiments, the temperature of step b) is higher than the temperature of step a).

[0026] According to one or more embodiments, the gasoline is a catalytic cracked gasoline.

[0027] Detailed description

[0028] Definitions

[0029] In the following, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group VIII (or VIIIB) according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUPAC classification. The BET specific surface area is measured by nitrogen physisorption according to ASTM D3663-03, a method described in the book Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academic Press, 1999.

[0030] In the following description of the invention, the total pore volume of the oxide support or catalyst is understood to mean the volume measured by intrusion with a mercury porosimeter according to ASTM D4284-83 at a maximum pressure of 4000 bar (400 MPa), using a surface tension of 484 dyne / cm and a contact angle of 140°. The wetting angle was taken to be equal to 140° following the recommendations of the work “Techniques de l'ingénieur, traité analyse et caractérisation”, p.1050-5, written by Jean Charpin and Bernard Rasneur.

[0031] To obtain better accuracy, the value of the total pore volume in ml / g or cm 3 / g given in the following text corresponds to the value of the total mercury volume (total pore volume measured by intrusion with a mercury porosimeter) in ml / g or cm 3 / g measured on the sample minus the value of the mercury volume in ml / g or cm 3 / g measured on the same sample for a pressure corresponding to 30 psi (approximately 0.2 MPa).

[0032] The contents of group VIII metal, group VI B metal and phosphorus are measured by X-ray fluorescence.

[0033] The contents of Group VI B metal, Group VIII metal, and phosphorus in the catalyst are expressed as oxides after correction for the loss on ignition of the catalyst sample at 550°C for two hours in a muffle furnace. The loss on ignition is due to moisture loss. It is determined according to ASTM D7348.

[0034] Finishing hydrodesulfurization catalyst

[0035] The catalyst according to the invention comprises, preferably consists of, an active phase comprising at least one metal from group VI B and at least one metal from group VIII, phosphorus, and a porous support comprising, preferably consisting of, alpha alumina, the content of metal from group VI B, measured in oxide form, is between 1 and 8% by weight relative to the total weight of the catalyst, the content of metal from group VIII, measured in oxide form, being between 0.2 and 5% by weight relative to the total weight of the catalyst, and the content of phosphorus, measured in its oxide form P2O5, being between 0.1 and 3% by weight relative to the total weight of the catalyst, said catalyst having a specific surface area greater than or equal to 1 m 2 / g and less than 20 m 2 / g.

[0036] The Group VI B metal content of the active phase, measured in oxide form, is between 1 and 8% by weight relative to the total weight of the catalyst, preferably between 2 and 7% by weight, and even more preferably between 3 and 7% by weight. The Group VI B metal is preferably molybdenum. When the metal is molybdenum, the metal content is expressed as MoOs.

[0037] The Group VIII metal content of the active phase, measured in oxide form, is between 0.2 and 5% by weight relative to the total weight of the catalyst, preferably between 0.5 and 4% by weight, and even more preferably between 0.5 and 3% by weight. The Group VIII metal is preferably cobalt. When the metal is cobalt, the cobalt content is expressed as CoO.

[0038] The phosphorus content, measured in its oxide form P2O5, is between 0.1 and 3% by weight relative to the total weight of the catalyst, preferably between 0.2 and 2% by weight, and even more preferably between 0.3 and 1.5% by weight.

[0039] Preferably, the molar ratio between the group VIII metal of the active phase and the group VIB metal of the active phase is between 0.1 and 2.0 mol / mol, preferably between 0.3 and 1.0 mol / mol.

[0040] Preferably, the molar ratio between phosphorus and the group VIB metal of the active phase is between 0.1 and 2.0 mol / mol, preferably between 0.2 and 1.0 mol / mol, more preferably between 0.2 and 0.5 mol / mol.

[0041] The specific surface area of ​​the catalyst is greater than or equal to 1 m 2 / g and less than 20 m 2 / g, preferably between 1 m 2 / g and 16 m 2 / g, and even more preferably between 5 m 2 / g and 15 m 2 / g.

[0042] The catalyst advantageously has a total pore volume measured by mercury porosimetry of between 0.3 cm 3 / g and 0.9 cm 3 / g, preferably between 0.35 cm 3 / g and 0.8 cm 3 / g, and very preferably between 0.4 cm 3 / g and 0.7 cm 3 / g.

[0043] The surface density of group VIB metal expressed as weight of group VIB oxides per unit area of ​​the catalyst is between 33.10 -4 and 130.10 -4 g / m 2 , preferably between 37.10 -4 and 120.10 -4 g / m 2 , more preferably between 40.10 -4 and 90.10 -4 g / m 2 .

[0044] Finishing hydrodesulfurization catalyst support

[0045] The support of the finishing hydrodesulfurization catalyst according to the invention may be in the form of beads, extrudates of any geometry, platelets, pellets, compressed cylinders, crushed solids or any other shape. Preferably, the support is in the form of beads of 0.5 to 6 mm in diameter or in the form of cylindrical, trilobal or quadrilobal extrudates of 0.8 to 3 mm in circumscribed diameter. More preferably, the support is in the form of beads.

[0046] The support of said catalyst according to the invention comprises alpha alumina, preferably the support is mainly composed of alpha alumina, that is to say that it comprises at least 51% by weight of alpha alumina, preferably at least 60% by weight, very preferably at least 80% by weight, or even at least 90% by weight of alpha alumina relative to the total weight of said support. Even more preferably, the support is made of alpha alumina.

[0047] The specific surface area of ​​the support is greater than or equal to 1 m 2 / g and less than 20 m 2 / g, preferably between 1 m 2 / g and 16 m 2 / g, and even more preferably between 5 m 2 / g and 15 m 2 / g.

[0048] The support advantageously has a total pore volume measured by mercury porosimetry of between 0.3 cm 3 / g and 0.9 cm 3 / g, preferably between 0.35 cm 3 / g and 0.8 cm 3 / g, and very preferably between 0.4 cm 3 / g and 0.7 cm 3 / g.

[0049] Preparation of the finishing hydrodesulfurization catalyst

[0050] The catalyst according to the invention can be prepared by means of any technique known to those skilled in the art, and in particular by impregnation of the metals of groups VIII and VIB and of phosphorus on the selected porous support. The impregnation can for example be carried out according to the method known to those skilled in the art under the terminology of dry impregnation, in which just the quantity of precursors of desired elements in the form of salts soluble in the chosen solvent, for example demineralized water, is introduced so as to fill the porosity of the support as exactly as possible. Preferably, the aqueous impregnation solution when it contains cobalt, molybdenum and phosphorus is prepared under pH conditions favoring the formation of heteropolyanions in solution. For example, the pH of such an aqueous solution is between 1 and 5.Preferably, the preparation of the catalyst is carried out without adding organic agent in a mixture with the precursors of the metals of group VIII, group VIB and phosphorus.

[0051] For example, among the sources of molybdenum, it is possible to use oxides and hydroxides, molybdic acids and their salts, in particular ammonium salts such as ammonium molybdate, ammonium heptamolybdate, phosphomolybdic acid (H3PM012O40), and their salts, and possibly silicomolybdic acid (hLSiMo^C o) and its salts. The sources of molybdenum can also be any heteropolycompound of the Keggin, lacunar Keggin, substituted Keggin, Dawson, Anderson, Strandberg type, for example. Molybdenum trioxide and heteropolycompounds of the Keggin, lacunar Keggin, substituted Keggin and Strandberg type are preferably used. The cobalt precursors that can be used are advantageously chosen from oxides, hydroxides, hydroxycarbonates, carbonates and nitrates, for example. Cobalt hydroxide and cobalt carbonate are preferably used.

[0052] Phosphorus may advantageously be introduced alone or in a mixture with at least one of the metals of groups VI B and VIII. Phosphorus is preferably introduced in a mixture with the precursors of the metals of group VI B and of group VIII by dry impregnation of said porous support using a solution containing the precursors of the metals and the precursor of phosphorus. The preferred source of phosphorus is orthophosphoric acid H3PO4, but its salts and esters such as ammonium phosphates or mixtures thereof are also suitable. Phosphorus may also be introduced at the same time as the metal(s) of group VI B in the form of, for example, Keggin, vacated Keggin, substituted Keggin or Strandberg type heteropolyanions.

[0053] The support thus filled with the solution can be left to mature at a temperature below 50°C, preferably at room temperature, for a time not exceeding 12 hours, preferably not exceeding 6 hours.

[0054] Following the maturation stage, the resulting catalyst precursor can undergo heat treatment. This treatment generally aims to transform the molecular precursors of the elements into the oxide phase. In this case, it is an oxidizing treatment, but simple drying of the catalyst can also be carried out.

[0055] In the case of drying, the catalyst precursor is dried at a temperature of between 50°C and less than 200°C, preferably between 70°C and 180°C, for a period of time typically between 0.5 hours and 12 hours, and even more preferably for a period of time between 0.5 hours and 5 hours.

[0056] In the case of an oxidizing treatment, also called calcination, this is generally carried out in air or diluted oxygen, and the treatment temperature is generally between 200°C and 550°C, preferably between 300°C and 500°C, and advantageously for a duration typically between 0.5 hours and 24 hours, preferably for a duration of 0.5 hours to 12 hours, and even more preferably for a duration of 0.5 hours to 10 hours.

[0057] Before its use as a hydrotreatment catalyst, it is advantageous to subject the optionally dried or calcined catalyst to a sulfurization activation step. This activation phase is carried out by methods well known to those skilled in the art, and advantageously under a sulfide-reducing atmosphere in the presence of hydrogen and hydrogen sulfide. The hydrogen sulfide can be used directly or generated by a sulfide agent (such as dimethyl disulfide).

[0058] Gasoline hydrodesulfurization process

[0059] Another subject of the invention relates to a process for treating a gasoline containing sulfur compounds and olefins, the process comprising at least the following steps: a) bringing into contact in a first reaction section the gasoline, hydrogen and a hydrodesulfurization catalyst comprising an active phase comprising a metal from group VI B and a metal from group VIII at least partly in sulfurized form, and an oxide support, at a temperature between 200°C and 350°C, at a pressure between 0.2 MPa and 5 MPa, with an hourly volumetric flow rate between 1 h -1 and 8 p.m. -1 and a ratio between the hydrogen flow rate expressed in normal m 3 per hour and the flow rate of load to be treated expressed in m 3 per hour under standard conditions between 10 Nm 3 / m 3 and 1000 Nm 3 / m 3, to obtain a partially desulfurized effluent; b) without separation of the H2S formed in step a), the partially desulfurized effluent obtained at the end of step a) is brought directly into contact in a second reaction section with a finishing hydrodesulfurization catalyst as described above at a temperature between 250°C and 400°C, at a pressure between 0.2 MPa and 5 MPa, with an hourly volumetric flow rate between 1 h' 1 and 8 p.m. 1 , to obtain a desulfurized effluent.

[0060] Description of the load

[0061] The process according to the invention makes it possible to treat any type of gasoline cut containing sulfur compounds and olefins, alone or in a mixture such as, for example, a cut from a coking unit, visbreaking unit, steam cracking unit or fluid catalytic cracking unit (FCC). This gasoline may optionally be composed of a significant fraction of gasoline from other production processes such as atmospheric distillation (gasoline from direct distillation (or straight run gasoline)) or from conversion processes (coking or steam cracking gasoline). Said feedstock preferably consists of a gasoline cut from a catalytic cracking unit.

[0062] The feedstock is a gasoline cut containing sulfur compounds and olefins whose boiling point range typically extends from the boiling points of hydrocarbons with 2 or 3 carbon atoms (C2 or C3) up to 260°C, preferably from the boiling points of hydrocarbons with 2 or 3 carbon atoms (C2 or C3) up to 220°C, more preferably from the boiling points of hydrocarbons with 5 carbon atoms up to 220°C. The process according to the invention can also treat feedstocks having end points lower than those mentioned above, such as for example a C5-180°C cut.

[0063] The sulfur content of gasoline cuts produced by fuel catalytic cracking (FCC) depends on the sulfur content of the feedstock treated by the FCC, the presence or absence of pretreatment of the FCC feedstock, and the endpoint of the cut. Generally, the sulfur contents of an entire gasoline cut, especially those from FCC, are greater than 100 ppm by weight and most of the time greater than 500 ppm by weight. For gasolines with endpoints above 200°C, the sulfur contents are often greater than 1000 ppm by weight, and in some cases they can even reach values ​​of the order of 4000 to 5000 ppm by weight.

[0064] The feedstock treated by the process according to the invention may be a feedstock containing sulfur compounds in a content greater than 200 ppm by weight of sulfur, and often greater than 500 ppm.

[0065] Furthermore, gasolines from catalytic cracking units (FCC) contain, on average, between 0.5% and 5% by weight of diolefins, between 20% and 50% by weight of olefins, between 10 ppm and 0.5% by weight of sulfur, of which generally less than 300 ppm of mercaptans.

[0066] Depending on the type of gasoline to be treated, it may be advantageous to pre-treat the gasoline in the presence of hydrogen and a selective hydrogenation catalyst so as to at least partially hydrogenate the diolefins and carry out a reaction to increase the weight of part of the light mercaptans (RSH) present in the charge in thioethers, by reaction with olefins.

[0067] For this purpose, the gasoline to be treated is sent to a selective hydrogenation catalytic reactor containing at least one fixed or mobile bed of catalyst for selective hydrogenation of diolefins and for weighting of light mercaptans. The reaction for selective hydrogenation of diolefins and weighting of light mercaptans is preferably carried out on a sulfurized catalyst comprising at least one metal from group VIII and optionally at least one metal from group VI B and an oxide support. The metal from group VIII is preferably chosen from nickel and cobalt and in particular nickel. The metal from group VI B, when present, is preferably chosen from molybdenum and tungsten and very preferably molybdenum. The oxide support of the catalyst is preferably chosen from alumina, nickel aluminate, silica, silicon carbide, or a mixture of these oxides.Preferably, alumina is used, and even more preferably, high-purity alumina. According to a preferred embodiment, the selective hydrogenation catalyst contains nickel with a content by weight of nickel oxide, in NiO form, of between 1 and 12%, and molybdenum with a content by weight of molybdenum oxide, in MoOs form, of between 6% and 18% and a nickel / molybdenum molar ratio of between 0.3 and 2.5, the metals being deposited on a support consisting of alumina. The sulfurization rate of the metals constituting the catalyst is, preferably, greater than 60%.

[0068] In the optional selective hydrogenation step, the gasoline is contacted with the catalyst at a temperature between 50 and 250°C, and preferably between 80 and 220°C, and even more preferably between 90 and 200°C, with an hourly volumetric flow rate (WH) between 0.5 h -1 and 8 p.m. 1, the unit of the hourly volumetric flow rate being the volumetric flow rate of feed at 15°C per volume of catalytic bed and per hour (L / L / h). The pressure is between 0.2 and 5 MPa, preferably between 0.6 and 4 MPa and even more preferably between 1 and 3 MPa. The optional selective hydrogenation step is typically carried out with a ratio between the hydrogen flow rate expressed in normal m 3 per hour and the volume flow rate of the load to be treated expressed in m 3 per hour at standard conditions (15°C, 0.1 MPa) between 2 and 100 Nm 3 / m 3 , preferably between 3 and 30 Nm 3 / m 3 .

[0069] After selective hydrogenation, the diolefin content, determined by means of the maleic anhydride value (MAV), according to the UOP 326 method, is generally reduced to less than 6 mg maleic anhydride / g, or even less than 4 mg AM / g and more preferably less than 2 mg AM / g. In some cases, less than 1 mg AM / g may be obtained.

[0070] The selectively hydrogenated gasoline can then be distilled into at least two fractions, a light fraction and a heavy fraction and optionally an intermediate fraction. In the case of fractionation into two fractions, the heavy fraction is treated according to the process of the invention. In the case of fractionation into three fractions, the intermediate and heavy fractions can be treated separately by the process according to the invention.

[0071] It should be noted that it is possible to carry out the stages of hydrogenation of diolefins and fractionation into two or three cuts simultaneously by means of a catalytic distillation column which includes a distillation column equipped with at least one catalytic bed.

[0072] The hydrodesulfurization step a) is implemented to reduce the sulfur content of the gasoline to be treated by converting the sulfur compounds into H2S.

[0073] The temperature is generally between 200°C and 350°C, and preferably between 220°C and 320°C. The temperature used must be sufficient to keep the gasoline to be treated in the gas phase in the reactor.

[0074] The operating pressure of this step is generally between 0.2 MPa and 5 MPa, preferably between 1 MPa and 3 MPa.

[0075] The quantity of catalyst used in each reactor of the first reaction section is generally such that the ratio between the volume flow rate at 15°C of gasoline to be treated expressed in m 3 per hour at standard conditions, per m 3 catalytic bed velocity (also called hourly volumetric flow rate - WH) is between 1 and 20 h -1 and preferably between 2 and 10 a.m. 1 .

[0076] The hydrogen flow rate is generally such that the ratio between the hydrogen flow rate expressed in normal m 3 per hour (Nm 3 / h) and the volume flow rate of the load to be treated expressed in m 3 per hour at standard conditions (15°C, 0.1 MPa) is between 10 and 1000 Nm 3 / m 3 , preferably between 50 and 600 Nm 3 / m 3 . We mean by normal m 3 the volume of 1 m 3 of gas at 0°C and 0.1 MPa.

[0077] The hydrogen required for this step can be fresh hydrogen or recycled hydrogen, preferably freed from H2S, or a mixture of fresh and recycled hydrogen. Preferably, a mixture of fresh and recycled hydrogen will be used.

[0078] The desulfurization rate of step a), which depends on the sulfur content of the feed to be treated, is generally greater than 50% and preferably greater than 70% so that the product from step a) contains less than 200 ppm by weight of sulfur and preferably less than 100 ppm by weight of sulfur.

[0079] In the process according to the invention the hydrogenation rate of the olefins is preferably less than 50%, more preferably less than 40% during this step.

[0080] According to the invention, the hydrodesulfurization catalyst of step a) comprises an active phase comprising, preferably consisting of, at least one metal from group VI B and at least one metal from group VIII, optionally phosphorus, and an oxide support, as described below.

[0081] The group VI B metal present in the active phase of the catalyst is preferably chosen from molybdenum and tungsten. The group VIII metal present in the active phase of the catalyst is preferably chosen from cobalt, nickel and the mixture of these two metals.

[0082] The active phase of the catalyst is preferably chosen from the group formed by the combination of the metals nickel-molybdenum, cobalt-molybdenum and nickel-cobalt-molybdenum and very preferably the active phase consists of cobalt and molybdenum.

[0083] The content of group VIII metal is preferably between 0.1 and 10% by weight of group VIII metal oxide relative to the total weight of the catalyst, more preferably between 0.6 and 8% by weight, even more preferably between 0.6 and 7% by weight, and very preferably between 1 and 6% by weight of group VIII metal oxide relative to the total weight of the catalyst. When the metal is cobalt or nickel, the metal content is expressed as CoO or NiO.

[0084] The content of group VI B metal is preferably between 1 and 20% by weight of group VI B metal oxide relative to the total weight of the catalyst, more preferably between 2 and 18% by weight, and very preferably between 3 and 16% by weight of group VI B metal oxide relative to the total weight of the catalyst. When the metal is molybdenum or tungsten, the metal content is expressed as MoOs or WO3.

[0085] Preferably, the molar ratio of group VIII metal to group VI B metal of the catalyst is generally between 0.1 and 0.8 mol / mol, preferably between 0.2 and 0.6 mol / mol.

[0086] Optionally, the catalyst may also have a phosphorus content generally between 0.3 and 10% by weight of P2O5 relative to the total weight of catalyst, preferably between 0.3 and 5% by weight, very preferably between 0.5 and 3% by weight.

[0087] Furthermore, when phosphorus is present, the phosphorus / (group VI B metal) molar ratio is generally between 0.1 and 0.7 mol / mol, preferably between 0.2 and 0.6 mol / mol.

[0088] Preferably, the catalyst of step a) comprises a specific surface area of ​​between 60 and 250 m 2 / g, preferably between 60 and 200 m 2 / g, and even more preferably between 65 and 180 m 2 / g, and even more preferably between 70 and 130 m 2 / g.

[0089] The total pore volume of the catalyst from step a) is generally between 0.3 cm 3 / g and 1.3 cm 3 / g, preferably between 0.4 cm 3 / g and 1.1 cm 3 / g. The oxide support of the hydrodesulfurization catalyst is typically a porous solid selected from the group consisting of: aluminas, silica, silica-alumina or titanium or magnesium oxides used alone or in a mixture with alumina or silica-alumina. It is preferably selected from the group consisting of silica, alumina, and silica-alumina. Very preferably, the oxide support is essentially composed of alumina, that is to say it comprises at least 51% by weight, preferably at least 60% by weight, very preferably at least 80% by weight, or even at least 90% by weight of alumina relative to the total weight of said oxide support. It is preferably composed solely of alumina.

[0090] In a preferred embodiment, the catalyst of step a) comprises an alumina support and an active phase comprising, preferably consisting of, cobalt and molybdenum, said catalyst containing a content by weight relative to the total weight of catalyst of cobalt oxide, in CoO form, of between 0.1 and 10% by weight, preferably between 0.6 and 8% by weight, more preferably between 0.6 and 7% by weight and even more preferably between 1 and 6% by weight, and a content by weight relative to the total weight of catalyst of molybdenum oxide, in MoOs form, of between 1 and 20% by weight, preferably between 2 and 18% by weight, and very preferably between 3 and 16% by weight, with a cobalt / molybdenum molar ratio of between 0.1 and 0.8 mol / mol, preferably between 0.2 and 0.6 mol / mol.

[0091] Preferably, the support of the hydrodesulfurization catalyst comprises a specific surface area of ​​between 60 and 250 m 2 / g, preferably between 60 and 200 m 2 / g, and even more preferably between 65 and 180 m 2 / g, and even more preferably between 70 and 130 m 2 / g.

[0092] The total pore volume of the hydrodesulfurization catalyst support is typically between 0.3 cm 3 / g and 1.3 cm 3 / g, preferably between 0.4 cm 3 / g and 1.1 cm 3 / g.

[0093] The support for the hydrodesulfurization catalyst may be in the form of beads, extrudates of any geometry, platelets, pellets, compressed cylinders, crushed solids or any other shape. Preferably, the support is in the form of beads with a diameter of 0.5 to 6 mm or in the form of cylindrical, trilobal or quadrilobal extrudates with a circumscribed diameter of 0.8 to 3 mm. More preferably, the support is in the form of beads.

[0094] The first partially desulfurized effluent obtained at the end of step a) is then sent directly and without separation to step b) of the process according to the invention.

[0095] In the hydrodesulfurization step a), a large part of the sulfur compounds is transformed into H2S. The remaining sulfur compounds are essentially refractory sulfur compounds and recombinant mercaptans resulting from the addition of the H2S formed in step a) to the olefins present in the feedstock.

[0096] Step b) of the process according to the invention consists of transforming at least a portion of the recombinant mercaptans contained in the first effluent from step a) into olefins and H2S as well as at least a portion of the sulfur compounds contained in the first effluent from step a) such as thiophene compounds, into saturated compounds, for example thiophanes (or thiacyclopentanes) or mercaptans, then at least partially hydrogenolyzing these sulfur compounds to form H2S.

[0097] Preferably, step b) is carried out at a higher temperature than that of step a). Indeed, by using a higher temperature in this step compared to the temperature of step a), the formation of mercaptans will be disadvantaged by shifting the thermodynamic equilibrium. Step b) also allows the hydrodesulfurization of the residual sulfur compounds to continue.

[0098] The temperature is generally between 250°C and 400°C, preferably between 270°C and 390°C. The temperature used must be sufficient to keep the gasoline to be treated in the gas phase in the reactor.

[0099] The operating pressure of this step is generally between 0.2 MPa and 5 MPa and preferably between 1.5 MPa and 3 MPa.

[0100] The quantity of catalyst used in each reactor is generally such that the ratio between the volume flow rate of gasoline to be treated expressed in m 3 per hour at standard conditions (15°C, 0.1 MPa), per m 3 catalytic bed (hourly volumetric flow rate - WH) is between 1 and 20 h -1 and preferably between 2 and 10 a.m. -1 .

[0101] The finishing hydrodesulfurization catalyst as described above is used in finishing hydrodesulfurization step b).

[0102] In the process according to the invention, the total olefin hydrogenation rate of step b) is preferably less than 30%, more preferably less than 20%, and very preferably less than 15%, during this step. The total desulfurization rate of step b), which depends on the sulfur content of the feedstock to be treated, is generally greater than 50% and preferably greater than 70% so that the product from step b) contains less than 50 ppm by weight of sulfur and preferably less than 20 ppm by weight of sulfur, and even more preferably less than 10 ppm by weight of sulfur.

[0103] Step c): H2S separation step [optional!

[0104] Separation step c) is carried out in order to separate the excess hydrogen as well as the h S formed during steps a) and b). Any method known to those skilled in the art can be considered.

[0105] According to a first embodiment, after steps a) and b), the effluent is cooled to a temperature generally below 80°C in order to condense the hydrocarbons. The gas and liquid phases are then separated in a separation tank. The liquid fraction which contains the desulfurized gasoline as well as a fraction of the dissolved H2S is sent to a stabilization column or debutanizer. This column separates a top cut essentially consisting of residual H2S and hydrocarbon compounds having a boiling point less than or equal to that of butane and a bottom cut freed from H^S, called stabilized gasoline, containing the compounds having a boiling point higher than that of n-butane.

[0106] According to a second embodiment, after the condensation step, the liquid fraction which contains the desulfurized gasoline as well as a fraction of the dissolved h^S is sent to a stripping section, while the gaseous fraction consisting mainly of hydrogen and H2S is sent to a purification section. The stripping can be carried out by heating the hydrocarbon fraction alone or with an injection of hydrogen or water vapor, in a distillation column in order to extract at the top, the light compounds which have been entrained by dissolution in the liquid fraction as well as the dissolved residual h^S. The temperature of the stripped gasoline recovered at the bottom of the column is generally between 120°C and 250°C.

[0107] Preferably, separation step c) is carried out in a stabilization column or debutanizer. Indeed, a stabilization column allows H2S to be separated more efficiently than a stripping section.

[0108] Step c) is preferably carried out so that the sulfur in the form of H2S remaining in the desulfurized gasoline represents less than 30%, preferably less than 20% and more preferably less than 10% of the total sulfur present in the treated hydrocarbon fraction. Sulphurization of

[0109] Before contacting with the feedstock to be treated in a gasoline hydrodesulfurization process, the catalysts used in the process according to the invention generally undergo a sulfurization step. Sulfurization is preferably carried out in a sulforeducing medium, i.e. in the presence of H2S and hydrogen, in order to transform the metal oxides into sulfides. Sulfurization is carried out by injecting a stream containing H2S and hydrogen onto the catalyst, or a sulfur compound capable of decomposing into H2S in the presence of the catalyst and hydrogen. Polysulfides such as dimethyl disulfide (DM DS) are H2S precursors commonly used to sulfurize catalysts. Sulfur can also come from the feedstock. The temperature is adjusted so that the H2S reacts with the metal oxides to form metal sulfides.This sulfurization can be carried out in situ or ex situ (inside or outside the reactor) of the reactor of the process according to the invention at temperatures between 200 and 600°C, and more preferably between 300 and 500°C.

[0110] The sulfurization rate of the metals constituting the catalysts is at least equal to 60%, preferably at least equal to 70%. The sulfur content in the sulfurized catalyst is measured by elemental analysis according to ASTM D5373. A metal is considered to be sulfurized when the overall sulfurization rate defined by the molar ratio between the sulfur (S) present on the catalyst and said metal is at least equal to 60% of the theoretical molar ratio corresponding to the total sulfurization of the metal(s) considered. The overall sulfurization rate is defined by the following equation:

[0111] (S / metal)catalyst — 0.6 X (S / metal)theoretical in which:

[0112] (S / metal)catalyst is the molar ratio between sulfur (S) and metal present on the catalyst (S / metal)theoretical is the molar ratio between sulfur and metal corresponding to the total sulfurization of the metal into sulfide.

[0113] This theoretical molar ratio varies depending on the metal considered:

[0114] - (S / Co)theoretical — 1

[0115] - (S / Ni)theoretical — 1

[0116] - (S / Mo)theoretical — 2 / 1

[0117] - (S / W)theoretical = 2 / 1

[0118] When the catalyst comprises several metals, the molar ratio between the S present on the catalyst and all the metals must also be at least equal to 60% of the theoretical molar ratio corresponding to the total sulfurization of each metal into sulfide, the calculation being carried out in proportion to the relative molar fractions of each metal. The examples below illustrate the invention without limiting its scope.

[0119] Examples

[0120] The analysis methods used to characterize loads and effluents are as follows:

[0121] - sulfur content according to ASTM D2622 method for contents above 10 ppm S and ISO 20846 for contents below 10 ppm S;

[0122] - mercaptan content according to ASTM D3227 method

[0123] - olefin content based on gas chromatography analysis according to ASTM D6733 method.

[0124] Example 1: Preparation of catalyst A (compliant)

[0125] A support A' is provided, mainly composed of alpha alumina in the form of balls with a particle size between 2 and 4 mm, and having a specific surface area of ​​12 m 2 / g and a pore volume of 0.51 mL / g.

[0126] Cobalt, molybdenum and phosphorus are then added. The impregnation solution is prepared by dissolving at 100°C molybdenum oxide (2.56 g, >99.5%, Sigma-Aldrich®), cobalt hydroxide (0.73 g, 96%, Alfa Aesar®), 85% phosphoric acid by weight (0.49 g, 99.99%, Sigma-Aldrich®) in 15 mL of demineralized water. After dry impregnation of 40 grams of support A', the impregnated alumina is left to mature in a water-saturated atmosphere for 4 hours at room temperature, then dried at 120°C for 4 hours. The catalyst thus obtained is denoted A.

[0127] The final composition of elements in catalyst A, expressed in the form of oxides and relative to the weight of the dry catalyst is then as follows: MoOs = 5.9 + / - 0.2% by weight, CoO = 1.3 + / - 0.1% by weight and P2O5 = 0.7 + / - 0.1% by weight.

[0128] The Co / Mo and P / Mo molar ratios are 0.39 and 0.24, respectively.

[0129] The specific surface area of ​​catalyst A is 12 m2 / g. The surface density of molybdenum is 49.2.10 -4 gMoos / m 2 .

[0130] A support B' is provided, mainly composed of gamma alumina in the form of beads with a particle size between 2 and 4 mm, and having a specific surface area of ​​139 m 2 / g and a pore volume of 0.97 mL / g.

[0131] Nickel is then added. The impregnation solution is prepared by dissolving nickel nitrate hexahydrate (34.36 g, >99.5%, Sigma-Aldrich®) at room temperature in 25 mL of demineralized water. After dry impregnation of 40 grams of support B', the impregnated alumina is left to mature in a water-saturated atmosphere for 4 hours at room temperature, then dried at 120°C for 4 hours, and finally calcined under an air flow rate of 1 L / h / g at 450°C for 4 hours. The catalyst thus obtained is denoted B.

[0132] The final composition of elements in catalyst B, expressed in the form of oxides and relative to the weight of the dry catalyst is then as follows: NiO = 17.9 + / - 0.3% by weight.

[0133] The specific surface area of ​​catalyst B is 114 m 2 / g.

[0134] Example 3: Preparation of catalyst C (non-compliant)

[0135] We provide a support C' identical to support B'.

[0136] Cobalt, molybdenum and phosphorus are then added. The impregnation solution is prepared by dissolving at 100°C molybdenum oxide (4.62 g, >99.5%, Sigma-Aldrich®), cobalt hydroxide (1.19 g, 96%, Alfa Aesar®), 85% phosphoric acid by weight (1.05 g, 99.99%, Sigma-Aldrich®) in 28 mL of demineralized water. After dry impregnation of 40 grams of support C', the impregnated alumina is left to mature in a water-saturated atmosphere for 4 hours at room temperature, then dried at 120°C for 4 hours. The catalyst thus obtained is denoted C.

[0137] The final composition of elements in catalyst C, expressed in the form of oxides and relative to the weight of the dry catalyst, is then as follows: MoOs = 10.0 + / - 0.2% by weight, CoO = 2.1 + / - 0.1% by weight and P2O5 = 1.4 + / - 0.1% by weight.

[0138] The Co / Mo and P / Mo molar ratios are 0.42 and 0.29, respectively. The specific surface area of ​​catalyst C is 118 m 2 / g.

[0139] The surface density of molybdenum is 8.5.10 -4 gwoos / m 2 .

[0140] We provide a support D' identical to support B'.

[0141] Cobalt and molybdenum are then added. The impregnation solution is prepared by dissolving ammonium heptamolybdate tetrahydrate (5.64 g, >99.5%, Sigma-Aldrich®), cobalt nitrate hexahydrate (5.36 g, >99.5%, Alfa Aesar®), at room temperature in 28 mL of demineralized water. After dry impregnation of 40 grams of support D', the impregnated alumina is left to mature in a water-saturated atmosphere for 4 hours at room temperature, then dried at 120°C for 4 hours, and finally calcined under an air flow rate of 1 L / h / g at 450°C for 4 hours. The catalyst thus obtained is denoted D.

[0142] The final element composition of catalyst D, expressed in the form of oxides and relative to the weight of the dry catalyst, is then as follows: MoOs = 10.0 + / - 0.2% by weight and CoO = 3.0 + / - 0.1% by weight. The Co / Mo and P / Mo molar ratios are 0.60 and 0, respectively.

[0143] The specific surface area of ​​catalyst D is 124 m 2 / g. The surface density of molybdenum is 8.1 .10 -4 gwoos / m 2 .

[0144] A support E' is provided, mainly composed of gamma alumina in the form of beads with a particle size between 2 and 4 mm, and having a specific surface area of ​​194 m 2 / g and a pore volume of 0.60 mL / g.

[0145] Cobalt, molybdenum and phosphorus are then added. The impregnation solution is prepared by dissolving at 100°C molybdenum oxide (2.24 g, >99.5%, Sigma-Aldrich®), cobalt hydroxide (0.61 g, 96%, Alfa Aesar®), 85% phosphoric acid by weight (0.49 g, 99.99%, Sigma-Aldrich®) in 17 mL of demineralized water. After dry impregnation of 40 grams of support E', the impregnated alumina is left to mature in a water-saturated atmosphere for 4 hours at room temperature, then dried at 120°C for 4 hours. The catalyst thus obtained is denoted E.

[0146] The final composition of elements in catalyst E, expressed in the form of oxides and relative to the weight of the dry catalyst is then as follows: MoOs = 5.2 + / - 0.2% by weight, CoO = 1.1 + / - 0.1% by weight and P2O5 = 0.7 + / - 0.1% by weight.

[0147] The Co / Mo and P / Mo molar ratios are 0.42 and 0.27, respectively. The specific surface area of ​​catalyst E is 189 m 2 / g.

[0148] The surface density of molybdenum is 2.7.10 -4 gwoos / m 2 .

[0149] A support F' is provided, mainly composed of delta and theta alumina in the form of cylindrical extrudates of 1.6 mm diameter, and having a specific surface area of ​​78 m 2 / g and a pore volume of 0.84 mL / g.

[0150] Cobalt, molybdenum and phosphorus are then added. The impregnation solution is prepared by dissolving at 100°C molybdenum oxide (3.67 g, >99.5%, Sigma-Aldrich®), cobalt hydroxide (0.87 g, 96%, Alfa Aesar®), 85% phosphoric acid by weight (0.73 g, 99.99%, Sigma-Aldrich®) in 24 mL of demineralized water. After dry impregnation of 40 grams of support F', the impregnated alumina is left to mature in a water-saturated atmosphere for 4 hours at room temperature, then dried at 120°C for 4 hours. The catalyst thus obtained is noted F. The final composition in elements of catalyst F, expressed in the form of oxides and related to the weight of the dry catalyst is then as follows: MoOs = 8.2 + / - 0.2% by weight, CoO = 1.5 + / - 0.1% by weight and P2O5 = 1.0 + / - 0.1% by weight.

[0151] The Co / Mo and P / Mo molar ratios are 0.36 and 0.25, respectively. The specific surface area of ​​catalyst F is 75 m 2 / g.

[0152] The surface density of molybdenum is 10.9.10 -4 gwoos / m 2 .

[0153] Example 7: Implementation of catalysts in a gasoline desulfurization process Gasoline from a catalytic cracking unit composed of 25% by weight of olefins and 600 ppmS in total sulfur is subjected to a 2-stage treatment:

[0154] - a first stage of selective hydrodesulfurization (H DS) in an adiabatic reactor using catalyst D. The operating conditions of the single-stage hydrodesulfurization stage of the gasoline feedstock are as follows: WH = 3 h' 1 , P = 2.0 MPa. A pure hydrogen stream is added to the reactor inlet feed such that H2 / HC = 250 Nm 3 / m 3 The effluent is sent directly to the second stage reactor;

[0155] - a second finishing hydrodesulfurization (FNS) stage in an adiabatic reactor using catalysts A to F. Only the effluent from the first stage is treated in this second stage. The operating conditions of the finishing stage are as follows: WH = 3 h' 1 , P = 2.0 Mpa. The reactor inlet temperature is always set at 35°C higher than the effluent temperature at the outlet of the first selective hydrodesulfurization stage.

[0156] The inlet temperature into the reactor of the first stage of selective hydrodesulfurization is set to obtain an effluent containing 10 ppm wt S in total sulfur (i.e. more than 98% conversion into total sulfur)

[0157] Prior to use, the catalysts used in the selective hydrodesulfurization (H DS) and finishing (FNS) reactors are sulfurized by treatment for 4 hours under a pressure of 3.4 Mpa at 350°C, in contact with a charge consisting of 2% by weight of sulfur in the form of dimethyl disulfide in n-heptane.

[0158] The properties of the catalysts are presented in Table 1. The performances in gasoline desulfurization process are presented in Table 2.

[0159] The results illustrate that the use of the catalyst according to the invention in a finishing step of a gasoline hydrodesulfurization process makes it possible to obtain the best performances compared to the use of catalysts known from the prior art, in particular in terms of selectivity in hydrogenation of olefins for the same specification in sulfur content at the process outlet.

[0160] Table 1

[0161] Table 2

Claims

CLAIMS 1. Finishing hydrodesulfurization catalyst comprising an active phase comprising at least one metal from group VIB and at least one metal from group VIII, phosphorus, and a porous support comprising alpha alumina, the content of metal from group VIB, measured in oxide form, being between 1 and 8% by weight relative to the total weight of the catalyst, the content of metal from group VIII, measured in oxide form, being between 0.2 and 5% by weight relative to the total weight of the catalyst, and the content of phosphorus, measured in its P2O5 form, being between 0.1 and 3% by weight relative to the total weight of the catalyst, said catalyst having a specific surface area greater than or equal to 1 m 2 / g and less than 20 m 2 / g.

2. Catalyst according to claim 1, characterized in that the molar ratio between the metal of group VIII and the metal of group VIB is between 0.1 and 2.0 mol / mol.

3. Catalyst according to one of claims 1 or 2, characterized in that the molar ratio between phosphorus and the metal of group VIB is between 0.1 and 2.0 mol / mol.

4. Catalyst according to any one of the preceding claims, characterized in that the specific surface area of ​​the catalyst is between 1 and 16 m 2 / g.

5. Catalyst according to any one of the preceding claims, characterized in that the surface density of group VIB metal expressed in weight of group VIB metal oxides per unit surface area of ​​the catalyst is between 33.10 -4 and 130.10 -4 g / m 2 .

6. Catalyst according to any one of the preceding claims, characterized in that the group VIII metal is cobalt and the group VIB metal is molybdenum.

7. Catalyst according to any one of the preceding claims, characterized in that the support is in the form of beads.

8. Catalyst according to any one of the preceding claims, comprising an active phase consisting of molybdenum and cobalt, phosphorus, and a porous support consisting of alpha alumina, the cobalt content being between 0.5 and 3% by weight, measured in the oxide form CoO, relative to the total weight of the catalyst, the molybdenum content being between 3 and 7% by weight, measured in the oxide form MoOs, relative to the total weight of the catalyst, a phosphorus content of between 0.3 and 1.5% by weight, measured in the oxide form P2O5, relative to the total weight of the catalyst, the molar ratio between cobalt and molybdenum being between 0.3 and 1.0 mol / mol, the molar ratio between phosphorus and molybdenum being between 0.2 and 0.5 mol / mol, the surface density of molybdenum, expressed in the form of MoOs oxide, being between 40.10' 4 and 90.10' 4 g / m 2, the specific surface area of ​​the catalyst being between 1 and 16 m 2 / g.

9. A method of treating a gasoline containing sulfur compounds and olefins, the method comprising at least the following steps: a) bringing into contact in a first reaction section the gasoline, hydrogen and a hydrodesulfurization catalyst comprising an active phase comprising a metal from group VI B and a metal from group VIII at least partly in sulfurized form, and an oxide support, at a temperature of between 200°C and 350°C, at a pressure of between 0.2 Mpa and 5 Mpa, with an hourly volumetric flow rate of between 1 h -1 and 8 p.m. -1 and a ratio between the hydrogen flow rate expressed in normal m 3 per hour and the volume flow rate of the load to be treated expressed in m 3 per hour at standard conditions between 10 Nm 3 / m 3 and 1000 Nm 3 / m 3, to obtain a partially desulfurized effluent; b) without separation of the H2S formed in step a), the partially desulfurized effluent obtained at the end of step a) is brought directly into contact in a second reaction section with a finishing hydrodesulfurization catalyst according to any one of claims 1 to 8 at least partly in sulfurized form, at a temperature between 250°C and 400°C, at a pressure between 0.2 MPa and 5 MPa, with an hourly volumetric flow rate between 1 h' 1 and 8 p.m. 1 , to obtain a desulfurized effluent.

10. Process according to claim 9, in which the catalyst of step a) comprises an alumina support and an active phase comprising cobalt and molybdenum, said catalyst containing a content by weight relative to the total weight of catalyst of cobalt oxide, in CoO form, of between 0.1 and 10% by weight, and a content by weight relative to the total weight of catalyst of molybdenum oxide, in MoOs form, of between 1 and 20% by weight, with a cobalt / molybdenum molar ratio of between 0.1 and 0.8 mol / mol.

11. Process according to one of claims 9 or 10, in which the catalyst of step a) comprises a specific surface area of ​​between 60 and 250 m 2 / g.

12. Method according to any one of claims 9 to 11, in which the temperature of step b) is higher than the temperature of step a).

13. A process according to any one of claims 9 to 12, wherein the gasoline is a catalytic cracked gasoline.

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