Process for treating gasoline containing sulfur compounds

Abstract

A method for treating gasoline containing sulfur compounds, olefins and diolefins, the method comprising at least the following steps: a) bringing gasoline, hydrogen and a hydrodesulfurization catalyst comprising an oxide support and an active phase comprising a group VIB metal and a group VIII metal into contact in at least one reactor; b) bringing the effluent from step a) into contact with hydrogen and a hydrodesulfurization catalyst comprising an oxide support and an active phase consisting of at least one group VIII metal; c) sending the effluent from step b) into a separation tank operating at a pressure of between 1.0 and 2.0 MPa to obtain a gaseous fraction containing H2S and hydrogen and a liquid fraction containing the desulfurized gasoline and a dissolved H2S fraction;d) said liquid fraction obtained in step c) is sent to a stabilization column to obtain at the top a flow comprising the residual H2S and C4- hydrocarbon compounds and at the bottom a stabilized gasoline; e) at least part of the gaseous fraction obtained at the end of step c) is recycled to at least one of steps a) and / or b).;

Description

Title of the invention: Method for treating gasoline containing sulfur compounds Field of the invention

[0001] The present invention relates to a process for producing gasoline with low sulfur and mercaptan content. State of the art

[0002] The production of gasolines meeting new environmental standards requires a significant reduction in their sulfur content.

[0003] It is also known that conversion gasolines, and more particularly those from catalytic cracking, which can represent 30 to 50% of the gasoline pool, have high mono-olefin and sulfur contents.

[0004] The sulfur present in gasolines is for this reason attributable, at nearly 90%, to gasolines resulting from catalytic cracking processes, which will be called in the following FCC gasolines (Fluid Catalytic Cracking according to the English terminology, which can be translated as fluidized bed catalytic cracking). FCC gasolines therefore constitute the preferred feedstock for the process of the present invention.

[0005] Among the possible ways to produce low-sulfur fuels, the one that has been very widely adopted consists of specifically treating sulfur-rich gasoline bases by catalytic hydrodesulfurization processes in the presence of hydrogen. Traditional processes desulfurize gasolines non-selectively by hydrogenating a large portion of the mono-olefins, which results in a high loss in octane number and high hydrogen consumption. The most recent processes, such as the Prime G+ process (trademark), make it possible to desulfurize olefin-rich cracked gasolines, while limiting the hydrogenation of the mono-olefins and consequently the loss of octane and the resulting high hydrogen consumption. Such processes are for example described in patent applications EP1077247 and EPI 174485.

[0006] The residual sulfur compounds generally present in desulfurized gasoline can be separated into two distinct families: the unconverted refractory sulfur compounds present in the feedstock on the one hand, and the sulfur compounds formed in the reactor by secondary reactions called recombination. Among this latter family of sulfur compounds, the majority compounds are the mercaptans resulting from the addition of the H2S formed in the reactor to the mono-olefins present in the feedstock.

[0007] Mercaptans, of chemical formula R-SH, where R is an alkyl group, are also called recombinant mercaptans. Their formation or decomposition obeys the thermodynamic equilibrium of the reaction between monoolefins and hydrogen sulfide to form recombinant mercaptans. An example is illustrated according to the following reaction:

[0008] [Chem.l] V'\ / \ + H2s *........................> Y'\zz\ SH

[0009] The sulfur contained in recombinant mercaptans generally represents between 20% and 80% by weight of the residual sulfur in desulfurized gasolines.

[0010] The formation of recombinant mercaptans is in particular described in patent US6231754 and patent application WO01 / 40409 which teach various combinations of operating conditions and catalysts making it possible to limit the formation of recombinant mercaptans.

[0011] Other solutions to the problem of the formation of recombinant mercaptans are based on a treatment of partially desulfurized gasolines to extract said recombinant mercaptans. Some of these solutions are described in patent applications WO02 / 28988 or WO01 / 79391.

[0012] Still other solutions are described in the literature for desulfurizing cracked gasolines using a combination of hydrodesulfurization steps and elimination of recombinant mercaptans by reaction into thioethers or disulfides (also called sweetening or "sweetening" according to English terminology) (see for example US7799210, US6960291, US2007 / 114156, EP2861094).

[0013] Finally, patent application US2006 / 278567 discloses a process for hydrodesulfurization of a cracked gasoline in two stages comprising intermediate separation stages making it possible in particular to limit the formation of mercaptans. Objects of the invention

[0014] The subject of the present invention is a process for treating a gasoline containing sulfur compounds, olefins and diolefins, the process comprising at least the following steps:

[0015] a) gasoline, hydrogen and a hydrodesulfurization catalyst comprising an oxide support and an active phase comprising a metal from group VIB and a metal from group VIII are brought into contact in at least one reactor, at a temperature of between 210 and 320°C, at a pressure of between 1.5 and 3 MPa, with a space velocity of between 1 and 10 h 1 and a ratio between the hydrogen flow rate expressed in normal m3 per hour and the flow rate of feedstock to be treated expressed in m3 per hour under standard conditions of between 100 and 600 Nm3 / m3, so as to convert at least some of the sulfur compounds into H2S;

[0016] b) the effluent from step a) without elimination of the H2S formed, hydrogen and a hydrodesulfurization catalyst comprising an oxide support and an active phase consisting of at least one metal from group VIII are brought into contact in at least one reactor at a temperature of between 280 and 400°C, at a pressure of between 1.0 and 3 MPa, with a space velocity of between 1 and 10 h 1 and a ratio between the hydrogen flow rate expressed in normal m3 per hour and the feed flow rate to be treated expressed in m3 per hour under standard conditions of between 100 and 600 Nm3 / m3;

[0017] c) the effluent from step b) is sent to at least one separation tank operating at a pressure of between 1.0 and 2.0 MPa to obtain a gaseous fraction containing H2S and hydrogen and a liquid fraction containing the desulfurized gasoline and a fraction of dissolved H2S;

[0018] d) said liquid fraction obtained in step c) is sent to a stabilization column to obtain at the top a flow comprising the residual H2S and C4- hydrocarbon compounds and at the bottom a stabilized gasoline;

[0019] e) at least part of the gaseous fraction obtained at the end of step c) is recycled to at least one of steps a) and / or b).

[0020] The Applicant has surprisingly identified that in order to maintain a mercaptan and sulfur content in the hydrodesulfurized gasoline of less than 10 ppm by weight while limiting octane loss, the pressure in the hydrodesulfurization section (step a) of the process) must be between 1.5 and 3 MPa and the pressure of the separation drum must be within a specific range of between 1.0 and 2.0 MPa. Indeed, if the pressure of the separation drum is less than 1.0 MPa, the purity of the hydrogen contained in the recycle gas fraction will decrease, thus leading to a decrease in the ratio between the hydrogen flow rate and the flow rate of feedstock to be treated. Thus, to maintain a mercaptan and sulfur content of 10 ppm by weight, it is necessary to increase the temperature of the hydrodesulfurization stages, which has the effect of increasing the hydrogenation of the olefins in the gasoline cut, which will have the effect of increasing the loss of octane.Furthermore, if the pressure of the separation tank is higher than 2.0 MPa, the purity of the hydrogen contained in the recycled gas fraction will certainly increase, but this leads to an increase in the pressure at the inlet of the hydrodesulfurization reactors, and therefore, in addition to an overconsumption of hydrogen, will lead to an increase in the mercaptan content in the hydrodesulfurized gasoline and an increase in octane loss.

[0021] According to one or more embodiments, the pressure of the separation tank of step c) is between 1.2 and 1.8 MPa.

[0022] According to one or more embodiments, the catalyst of step a) comprises a Group VIII metal content of between 0.1 and 10% by weight of Group VIII metal oxide relative to the total weight of the catalyst, and a Group VIB metal content of between 1 and 20% by weight of Group VIB metal oxide relative to the total weight of the catalyst.

[0023] According to one or more embodiments, the catalyst of step a) comprises a molar ratio of group VIII metal to group VIB metal of the catalyst of between 0.1 and 0.8.

[0024] According to one or more embodiments, the catalyst of step a) comprises a specific surface area of ​​between 5 and 400 m2 / g.

[0025] According to one or more embodiments, the catalyst of step a) comprises alumina and an active phase comprising cobalt, molybdenum and optionally phosphorus, 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%, a content by weight relative to the total weight of catalyst of molybdenum oxide, in MoO3 form, of between 1 and 20%, a cobalt / molybdenum molar ratio of between 0.1 and 0.8, a content by weight relative to the total weight of catalyst of phosphorus oxide in P2O5 form of between 0.3 and 10% when phosphorus is present, said catalyst having a specific surface area of ​​between 50 and 250 m2 / g.

[0026] According to one or more embodiments, the catalyst of step b) comprises a group VIII metal content of between 1 and 60% by weight of group VIII metal oxide relative to the total weight of the catalyst.

[0027] According to one or more embodiments, the catalyst of step b) comprises a specific surface area of ​​between 5 and 400 m2 / g.

[0028] According to one or more embodiments, the catalyst of step b) consists of alumina and nickel, said catalyst containing a content by weight relative to the total weight of catalyst of nickel oxide, in NiO form, of between 5 and 20%, said catalyst having a specific surface area of ​​between 30 and 180 m2 / g.

[0029] According to one or more embodiments, the temperature of step b) is higher than the temperature of step a).

[0030] According to one or more embodiments, the temperature of step b) is at least 5°C higher than the temperature of step a).

[0031] According to one or more embodiments, before step a), a step of distillation of the gasoline is carried out so as to fractionate said gasoline into at least two light and heavy gasoline cuts and the heavy gasoline cut is treated in steps a), b), c), d) and e).

[0032] According to one or more embodiments, before step a) and before any possible distillation step, the gasoline is brought into contact with hydrogen and a selective hydrogenation catalyst to selectively hydrogenate the diolefins contained in said gasoline into olefins.

[0033] According to one or more embodiments, the gasoline is a catalytic cracking gasoline. List of figures

[0034] [Fig-1] [Fig.l] is a schematic representation of an embodiment according to the invention.

[0035] [Fig.2] [Fig.2] is a schematic representation of a process not in accordance with the invention. Detailed Description Definitions

[0036] 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 according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUP AC classification.

[0037] Specific surface area means the BET specific surface area (SBet in m2 / g) determined by nitrogen adsorption in accordance with ASTM D 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of American Society", 1938, 60, 309.

[0038] The total pore volume of the catalyst or support used for the preparation of the catalyst is understood to mean the volume measured by intrusion with a mercury porosimeter according to standard ASTM D4284 at a maximum pressure of 4000 bar (400 MPa), using a surface tension of 484 dyne / cm and a contact angle of 140°, for example with an Autopore III model device from the Microméritics® brand.

[0039] The wetting angle was taken equal to 140° following the recommendations of the work "Techniques de l'ingénieur, traité analyse et caractérisation", pages 1050-1055, written by Jean Charpin and Bernard Rasneur. In order to obtain better precision, the value of the total pore volume corresponds to the value of the total pore volume measured by intrusion with a mercury porosimeter measured on the sample minus the value of the total pore volume measured by intrusion with a mercury porosimeter measured on the same sample for a pressure corresponding to 30 psi (approximately 0.2 MPa).

[0040] The contents of elements of group VIII, group VIB and phosphorus are measured by X-ray fluorescence. Description of the load

[0041] The process according to the invention makes it possible to treat any type of gasoline cut containing sulfur compounds and olefins, such as for example a cut from a coking unit (coking according to English terminology), visbreaking (visbreaking), steam cracking or fluid catalytic cracking (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 conversion processes (coking or steam cracking gasoline). Said feedstock preferably consists of a gasoline cut from a catalytic cracking unit.

[0042] 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.

[0043] The sulfur content of gasoline cuts produced by 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, as well as the end point of the cut. Generally, the sulfur contents of the entire gasoline cut, in particular those originating from the FCC, are greater than 100 ppm by weight and most of the time greater than 500 ppm by weight. For gasolines having end points 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.

[0044] The feedstock treated by the process according to the invention may be a feedstock containing sulfur compounds in a content greater than 1000 ppm by weight of sulfur, and often greater than 1500 ppm.

[0045] 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. Step a): Hydrodesulfurization

[0046] The hydrodesulfurization step a) is carried out to reduce the sulfur content of the gasoline to be treated by converting the sulfur compounds into H2S which is then eliminated in step c).

[0047] The hydrodesulfurization step a) consists of bringing the gasoline to be treated into contact with hydrogen, in one or more hydrodesulfurization reactors, containing one or several catalysts suitable for carrying out hydrodesulfurization.

[0048] According to a preferred embodiment of the invention, step a) is carried out with the aim of carrying out hydrodesulfurization selectively, that is to say with a hydrogenation rate of the mono-olefins of less than 80%, preferably less than 70% and very preferably less than 60%.

[0049] The temperature is generally between 210 and 320°C and preferably between 220 and 290°C. The temperature used must be sufficient to maintain the gasoline to be treated in the vapor phase in the reactor. In the case where the hydrodesulfurization step a) is carried out in several reactors in series, the temperature of each reactor is generally at least 5°C higher, preferably at least 10°C higher and very preferably at least 30°C higher than the temperature of the reactor preceding it.

[0050] The operating pressure of this step is generally between 1.5 and 3 MPa.

[0051] The quantity of catalyst used in each reactor is generally such that the ratio between the flow rate of gasoline to be treated expressed in m3 per hour at standard conditions, per m3 of catalyst (also called space velocity) is between 1 and 10 h 1 and preferably between 2 and 8 h1.

[0052] The hydrogen flow rate is generally such that the ratio between the hydrogen flow rate expressed in normal m3 per hour (Nm3 / h) and the flow rate of feedstock to be treated expressed in m3 per hour at standard conditions (15°C, 0.1 MPa) is between 100 and 600 Nm3 / m3, preferably between 200 and 500 Nm3 / m3. Normal m3 means the quantity of gas in a volume of 1 m3 at 0°C and 0.1 MPa.

[0053] The hydrogen required for this step may be fresh hydrogen or recycled hydrogen, preferably freed from H2S, or a mixture of fresh hydrogen and recycled hydrogen. Preferably, fresh hydrogen will be used.

[0054] 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 100 ppm by weight of sulfur and preferably less than 50 ppm by weight of sulfur.

[0055] The catalyst used in step a) must have good selectivity towards hydrodesulfurization reactions compared to the olefin hydrogenation reaction.

[0056] The hydrodesulfurization catalyst of step a) comprises an oxide support and an active phase comprising a group VIB metal and a group VIII metal and optionally phosphorus and / or an organic compound as described below.

[0057] The group VIB 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 elements. The active phase of the catalyst is chosen from preferably in the group formed by the combination of the elements nickel-molybdenum, cobalt-molybdenum and nickel-cobalt-molybdenum and very preferably the active phase consists of cobalt and molybdenum.

[0058] The content of group VIII metal is between 0.1 and 10% by weight of group VIII metal oxide relative to the total weight of the catalyst, preferably between 0.6 and 8% by weight, preferably between 0.6 and 7% by weight, very preferably between 1 and 6% by weight.

[0059] The content of group VIB metal is between 1 and 20% by weight of group VIB metal oxide relative to the total weight of the catalyst, preferably between 2 and 18% by weight, very preferably between 3 and 16% by weight.

[0060] The molar ratio of group VIII metal to group VIB metal of the catalyst is generally between 0.1 and 0.8, preferably between 0.2 and 0.6.

[0061] Optionally, the catalyst may further 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. For example, the phosphorus present in the catalyst is combined with the metal from group VIB and optionally also with the metal from group VIII in the form of heteropolyanions.

[0062] Furthermore, the phosphorus / (group VIB metal) molar ratio is generally between 0.1 and 0.7, preferably between 0.2 and 0.6, when phosphorus is present.

[0063] Preferably, the catalyst is characterized by a specific surface area of ​​between 5 and 400 m2 / g, preferably between 10 and 250 m2 / g, preferably between 50 and 250 m2 / g. The specific surface area is determined in the present invention by the BET method according to standard ASTM D3663, as described in the work Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academie Press, 1999, for example using an Autopore III™ model device from the Microméritics™ brand.

[0064] The total pore volume of the catalyst is generally between 0.4 cmVg and 1.3 cmVg, preferably between 0.6 cmVg and 1.1 cmVg. The total pore volume is measured by mercury porosimetry according to ASTM D4284 with a wetting angle of 140°, as described in the same work.

[0065] The packed filling density (DRT) of the catalyst is generally between 0.4 and 0.8 g / mL, preferably between 0.4 and 0.7 g / mL. The DRT measurement consists of introducing the catalyst into a test tube whose volume has been previously determined and then, by vibration, packing it until a constant volume is obtained. The apparent density of the packed product is calculated by comparing the mass introduced and the volume occupied after packing.

[0066] The catalyst can be in the form of small diameter extrudates, cylindrical or multi-lobed (tri-lobed, quadri-lobed, etc.), or spheres.

[0067] The oxide support of the catalyst is usually a porous solid chosen from the group consisting of: aluminas, silica, silica-aluminas or even titanium or magnesium oxides used alone or in a mixture with alumina or silica-alumina. It is preferably chosen from the group consisting of silica, the family of transition aluminas and silica-aluminas, very preferably, the oxide support is essentially made of alumina, that is to say that 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. It is preferably made solely of alumina. Preferably, the oxide support of the catalyst is a “high temperature” alumina, i.e. which contains aluminas of theta, delta, kappa or alpha phase, alone or in a mixture and a quantity of less than 20% of alumina of gamma, chi or eta phase.

[0068] The catalyst may also further comprise at least one organic compound containing oxygen and / or nitrogen and / or sulfur before sulfurization.

[0069] A very preferred embodiment of the invention corresponds to the use for step a) of a catalyst comprising alumina and an active phase comprising cobalt, molybdenum and optionally phosphorus, 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%, a content by weight relative to the total weight of catalyst of molybdenum oxide, in MoO3 form, of between 1 and 20%, a cobalt / molybdenum molar ratio of between 0.1 and 0.8, a content by weight relative to the total weight of catalyst of phosphorus oxide in P2O5 form of between 0.3 and 10% when phosphorus is present, said catalyst having a specific surface area of ​​between 50 and 250 m2 / g. According to one embodiment, the active phase consists of cobalt and molybdenum. According to another embodiment, the active phase consists of cobalt, molybdenum and phosphorus. Step b): Finishing hydrodesulfurization

[0070] During 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 the recombinant mercaptans resulting from the addition of the H2S formed in step a) to the mono-olefins present in the feedstock.

[0071] The so-called finishing hydrodesulfurization step is mainly implemented to reduce the content of recombinant mercaptans. 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 olefins and H2S will be favored by the thermodynamic equilibrium. Step b) also makes it possible to hydrodesulfurize the more refractory sulfur compounds.

[0072] The hydrodesulfurization step b) consists of bringing the effluent from step a) into contact, optionally with the addition of hydrogen, in one or more hydrodesulfurization reactors, containing one or more catalysts suitable for carrying out the hydrodesulfurization.

[0073] The hydrodesulfurization step b) is carried out without significant hydrogenation of the olefins. The hydrogenation rate of the olefins of the catalyst of the hydrodesulfurization step b) is generally less than 5% and even more generally less than 2%.

[0074] The temperature of this step is generally between 280 and 400°C, more preferably between 290 and 380°C, and very preferably between 300 and 360°C. The temperature of this step b) is generally higher by at least 5°C, preferably by at least 10°C and very preferably by at least 30°C than the temperature of step a).

[0075] The operating pressure of this step is generally between 1.0 and 3 MPa and preferably between 1.5 and 3 MPa.

[0076] The quantity of catalyst used in each reactor is generally such that the ratio between the flow rate of gasoline to be treated expressed in m3 per hour at standard conditions, per m3 of catalyst (also called space velocity) is between 1 and 10 h 1 and preferably between 2 and 8 h 1.

[0077] Preferably, the hydrogen flow rate is constant and equal to the quantity injected in step a) less the hydrogen consumed in step a). The hydrogen flow rate is generally such that the ratio between the hydrogen flow rate expressed in normal m3 per hour (Nm3 / h) and the flow rate of feedstock to be treated expressed in m3 per hour at standard conditions (15°C, 0.1 MPa) is between 100 and 600 Nm3 / m3, preferably between 200 and 500 Nm3 / m3.

[0078] The 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 60 ppm by weight of sulfur, preferably less than 40 ppm by weight of sulfur, and very preferably less than 20 ppm by weight of sulfur.

[0079] The hydrodesulfurization steps a) and b) can be carried out either in a single reactor containing the two catalysts, or in at least two different reactors. When steps a) and b) are carried out using two reactors, the latter two are placed in series, the second reactor treating all of the effluent at the outlet of the first reactor (without separation of the liquid and gas between the first and second reactors).

[0080] The catalyst of step b) is of a different nature and / or composition from that used in step a). The catalyst in step b) is in particular a very selective hydrodesulfurization catalyst: it allows hydrodesulfurization without hydrogenating the olefins and therefore maintains the octane number.

[0081] The catalyst which may be suitable for this step b) of the process according to the invention, without this list being limiting, is a catalyst comprising an oxide support and an active phase consisting of at least one metal from group VIII, and preferably chosen from the group formed by nickel, cobalt, iron. These metals can be used alone or in combination. Preferably, the active phase consists of a metal from group VIII, preferably nickel. Particularly preferably, the active phase consists of nickel.

[0082] The content of group VIII metal is between 1 and 60% by weight of group VIII metal oxide relative to the total weight of the catalyst, preferably between 5 and 30% by weight, very preferably between 5 and 20% by weight.

[0083] Preferably, the catalyst is characterized by a specific surface area of ​​between 5 and 400 m2 / g, preferably of between 10 and 250 m2 / g, preferably of between 20 and 200 m2 / g, very preferably of between 30 and 180 m2 / g. The specific surface area is determined in the present invention by the BET method according to the ASTM D3663 standard, as described in the work Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academie Press, 1999, for example using an Autopore III™ model device from the Microméritics™ brand.

[0084] The pore volume of the catalyst is generally between 0.4 cmVg and 1.3 cm3 / g, preferably between 0.6 cmVg and 1.1 cmVg. The total pore volume is measured by mercury porosimetry according to ASTM D4284 with a wetting angle of 140°, as described in the same work.

[0085] The packed filling density (DRT) of the catalyst is generally between 0.4 and 0.8 g / mL, preferably between 0.4 and 0.7 g / mL.

[0086] The DRT measurement consists of introducing the catalyst into a test tube whose volume has been previously determined and then, by vibration, tamping it until a constant volume is obtained. The apparent density of the tamped product is calculated by comparing the mass introduced and the volume occupied after tamping.

[0087] The catalyst can be in the form of small diameter extrudates, cylindrical or multi-lobed (tri-lobed, quadri-lobed, etc.), or spheres.

[0088] The oxide support of the catalyst is usually a porous solid chosen from the group consisting of: aluminas, silica, silica-aluminas or even titanium or magnesium oxides used alone or in a mixture with alumina or silica-alumina. It is preferably chosen from the group consisting of silica, the family of transition aluminas and silica-aluminas, very preferably, the support oxide support is essentially made up 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. It preferably consists solely of alumina. Preferably, the oxide support of the catalyst is a “high temperature” alumina, that is to say which contains aluminas of theta, delta, kappa or alpha phase, alone or in a mixture and a quantity of less than 20% of alumina of gamma, chi or eta phase.

[0089] A very preferred embodiment of the invention corresponds to the use for step b) of a catalyst consisting of alumina and nickel, said catalyst containing a content by weight relative to the total weight of catalyst of nickel oxide, in NiO form, of between 5 and 20%, said catalyst having a specific surface area of ​​between 30 and 180 m2 / g.

[0090] The catalyst of the hydrodesulfurization step b) is characterized by a catalytic hydrodesulfurization activity generally between 1% and 90%, preferably between 1% and 70%, and very preferably between 1% and 50% of the catalytic activity of the catalyst of the hydrodesulfurization step a). Step c): Separation section

[0091] This step is implemented in order to separate the excess hydrogen as well as the H2S formed during steps a) and b) and to extract the desulfurized gasoline meeting the sulfur and recombinant mercaptan specifications while reducing the losses of C5+ hydrocarbon compounds (octane).

[0092] According to step c) of the process according to the invention, the effluent from step b) is fractionated so as to produce a gaseous phase comprising hydrogen from steps a) and b), H2S formed during steps a) and b) and light compounds C1 to C4, and desulfurized gasoline.

[0093] More particularly, after the hydrodesulfurization step b), the gasoline is advantageously cooled to a temperature generally below 80°C, preferably below 60°C in order to condense the hydrocarbons. The gas and liquid phases are then separated in a separation tank. The temperature of the separation tank is generally between 20 and 80°C, preferably between 25 and 65°C. The pressure of the separation tank is set between 1.0 and 2.0 MPa, preferably between 1.2 and 1.8 MPa.

[0094] Step c) is preferably carried out so that the sulfur in the form of H2S remaining in the effluent from step b) represents less than 30%, preferably less than 20% and more preferably less than 10% of the total sulfur present in the treated hydrocarbon fraction. Step d): Stabilization

[0095] 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 (C4-) and a bottom cut freed from H2S which corresponds to the desulfurized and stabilized gasoline containing the compounds having a boiling point higher than that of butane.

[0096] Using a separator drum advantageously operating at low temperature to remove H2, H2S and light gases, followed by a stabilization column to remove dissolved H2S and produce stabilized desulfurized gasoline makes it possible to reduce the temperature at the bottom of the stabilization column compared to separating H2 and H2S directly in a stabilization column.

[0097] The stabilization column generally operates at a pressure between 0.1 and 2 MPa and preferably between 0.2 and 1 MPa.

[0098] The number of theoretical plates of this separation column is generally between 10 and 50 and preferably between 20 and 40.

[0099] The reflux ratio, expressed as the ratio of the liquid traffic in the column divided by the distillate flow rate expressed in kg / h, is generally less than unity and preferably less than 0.5.

[0100] The desulfurized and stabilized heavy gasoline produced by the process according to the invention is advantageously used as a base for the formulation of a gasoline fuel. Step e): Recycling

[0101] According to the invention, at least a portion of the gaseous fraction separated by the separator drum in step c) is recycled to steps a) and / or b), preferably to step b). Advantageously, said gaseous fraction is first sent to an amine absorber or a washing column operating at low pressure (typically 1.5 MPa), in order to remove at least a portion of the H2S.

[0102] Description of the preparation of catalysts and sulfurization

[0103] The preparation of the catalysts of steps a) and b) is known and generally comprises a step of impregnation of the metals of group VIII and group VIB when present, and optionally of the phosphorus and / or of the organic compound on the oxide support, followed by drying, then by an optional calcination making it possible to obtain the active phase in their oxide forms. Before its use in a process for hydrodesulfurization of an olefinic gasoline cut containing sulfur, the catalysts are generally subjected to sulfurization in order to form the active species as described below.

[0104] The impregnation step can be carried out either by slurry impregnation, or by excess impregnation, or by dry impregnation, or by any other means known to the person skilled in the art. The impregnation solution is chosen so as to be able to solubilize the metal precursors in the desired concentrations.

[0105] 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 (H3PMoi204o), and their salts, and possibly silicomolybdic acid (H4 SiMoi204o) 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.

[0106] The tungsten precursors that can be used are also well known to those skilled in the art. For example, among the sources of tungsten, it is possible to use oxides and hydroxides, tungstic acids and their salts, in particular ammonium salts such as ammonium tungstate, ammonium metatungstate, phosphotungstic acid and their salts, and possibly silicotungstic acid (H4SiWi2O40) and its salts. The sources of tungsten can also be any heteropolycompound of the Keggin, vacated Keggin, substituted Keggin, Dawson type, for example. Preferably, ammonium oxides and salts such as ammonium metatungstate or heteropolyanions of the Keggin, vacated Keggin or substituted Keggin type are used.

[0107] The cobalt precursors which can be used are advantageously chosen from oxides, hydroxides, hydroxycarbonates, carbonates and nitrates, for example. Cobalt hydroxide and cobalt carbonate are preferably used.

[0108] The nickel precursors which can be used are advantageously chosen from oxides, hydroxides, hydroxycarbonates, carbonates and nitrates, for example.

[0109] The preferred phosphorus precursor is orthophosphoric acid H3PO4, but its salts and esters such as ammonium phosphates are also suitable. Phosphorus may also be introduced together with the group VIB element(s) in the form of Keggin, vacated Keggin, substituted Keggin or Strandberg-type heteropolyanions.

[0110] After the impregnation step, the catalyst is generally subjected to a drying step at a temperature below 200°C, advantageously between 50°C and 180°C, preferably between 70°C and 150°C, very preferably between 75°C and 130°C. The drying step is preferably carried out under an inert atmosphere or under an atmosphere containing oxygen. The drying step can be carried out by any technique known to those skilled in the art. It is advantageously carried out at atmospheric pressure or at reduced pressure. Preferably, this step is carried out at atmospheric pressure. It is advantageously carried out in a traversed bed using air or any other hot gas. Preferably, when drying is carried out in a fixed bed, the gas used is either air or an inert gas such as argon or nitrogen. Very preferably, drying is carried out in a traversed bed in the presence of nitrogen and / or air. Preferably, the drying step lasts between 5 minutes and 15 hours, preferably between 30 minutes and 12 hours.

[0111] According to a variant of the invention, the catalyst has not undergone calcination during its preparation, that is to say that the impregnated catalytic precursor has not been subjected to a heat treatment step at a temperature above 200°C under an inert atmosphere or under an atmosphere containing oxygen, in the presence of water or not.

[0112] According to another preferred variant of the invention, the catalyst has undergone a calcination step during its preparation, that is to say that the impregnated catalytic precursor has been subjected to a heat treatment step at a temperature of between 250 and 1000°C and preferably between 200 and 750°C, for a duration typically of between 15 minutes and 10 hours, under an inert atmosphere or under an atmosphere containing oxygen, in the presence of water or not.

[0113] Before contacting with the feedstock to be treated in a gasoline hydrodesulfurization process, the catalysts of the process according to the invention generally undergo a sulfurization step. The sulfurization is preferably carried out in a sulforeducing medium, that is to say in the presence of H2S and hydrogen, in order to transform the metal oxides into sulfides such as, for example, MoS2, Co9S8 or Ni3S2. The sulfurization is carried out by injecting onto the catalyst a stream containing H2S and hydrogen, or a sulfur compound capable of decomposing into H2S in the presence of the catalyst and hydrogen. Polysulfides such as dimethyl disulfide (DMDS) are H2S precursors commonly used to sulfurize catalysts. The 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.

[0114] The sulfurization rate of the metals constituting the catalysts is at least equal to 60%, preferably at least equal to 80%. 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:

[0115]

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126] (S / metal)cataiy seur > 0.6 x (S / metal) theoretical in which: (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. This theoretical molar ratio varies depending on the metal considered: (S / Fe)theoretical 1 (S / Co)theoretical 1 (S / Ni)theoretical 1 - (S / Mo)theoretical=2 / 1 - (S / W)theoretical=2 / 1 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. Schemes that can be implemented within the scope of the invention Different schemes can be implemented to produce, at a lower cost, desulfurized gasoline with a reduced mercaptan content. The choice of the optimal scheme actually depends on the characteristics of the gasolines to be processed and produced as well as the constraints specific to each refinery. The diagrams described below are given for illustration purposes only and are not intended to be exhaustive. According to a first variant, a distillation step of the gasoline to be treated is carried out in order to separate two cuts (or fractions), namely a light cut and a heavy cut, and the heavy cut is treated according to the process of the invention. The light cut generally has a boiling temperature range below 100°C and the heavy cut a temperature range above 65°C. This first variant has the advantage of not hydrotreating the light cut, which is rich in olefins and generally low in sulfur, which makes it possible to limit the loss of octane by hydrogenation of the olefins. According to a second variant, the gasoline to be treated is subjected before the process according to the invention to a preliminary step consisting of selective hydrogenation of the diolefins present in the feed, as described in patent application EP 1077247. The gasoline to be treated is previously treated 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 make part of the light mercaptan compounds (RSH) present in the charge heavier in thioethers, by reaction with olefins.

[0127] 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 element from group VIII and optionally at least one element from group VIB and an oxide support. The element from group VIII is preferably chosen from nickel and cobalt and in particular nickel. The element from group VIB, when present, is preferably chosen from molybdenum and tungsten and very preferably molybdenum.

[0128] 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 MoO3 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%.

[0129] During the optional selective hydrogenation step, the gasoline is brought into contact 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 a liquid space velocity between 0.5 h 1 and 20 h1, the unit of the liquid space velocity being the liter of feed per liter of catalyst and per hour (L / L / h). The pressure is between 0.4 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 m3 per hour and the flow rate of feedstock to be treated expressed in m3 per hour under standard conditions of between 2 and 100 Nm3 / m3, preferably between 3 and 30 Nm3 / m3.

[0130] After selective hydrogenation, the diolefin content, determined by means of the maleic anhydride index (MAV or "Maleic Anhydride Value" according to the English terminology), 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 certain cases, less than 1 mg may be obtained AM / g.

[0131] The selectively hydrogenated gasoline is then distilled into at least two cuts, a light cut and a heavy cut and optionally an intermediate cut. In the case of fractionation into two cuts, the heavy cut is treated according to the process of the invention. In the case of fractionation into three cuts, the intermediate and heavy cuts can be treated separately by the process according to the invention.

[0132] It should be noted that it is possible to carry out the steps of hydrogenation of the 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.

[0133] Other characteristics and advantages of the invention will now appear on reading the description which follows, given solely for illustrative and non-limiting purposes, and with reference to the appended [Fig.l].

[0134] With reference to [Fig.l] and according to an embodiment of the method according to the invention, the gasoline to be treated is sent via line 1 and hydrogen via line 3 to a selective hydrogenation unit 2 (optional step) in order to selectively hydrogenate the diolefins and to make the light mercaptans heavier. The effluent with a low diolefin and mercaptan content is withdrawn from the reactor 2 via line 4 and is sent to a fractionation column 5 (or splitter according to the English terminology) configured to separate the gasoline into two cuts: a light gasoline cut 6 (or light gasoline) and a (first) heavy gasoline cut 7 which is constituted by the complementary heavy fraction of the light gasoline. The cutting point of light cutting is generally performed at a temperature below 100°C, and the cutting point of heavy cutting is generally performed at a temperature above 65°C.The final boiling point of the light cut is chosen to provide a low sulfur light gasoline cut (total sulfur content typically less than 30 ppm by weight and preferably less than 10 ppm by weight) without requiring a subsequent hydrodesulfurization step.

[0135] The heavy gasoline fraction and hydrogen are then sent via line 7 and recycle gas via line 8 and recycle gas via line 14a to the hydrodesulfurization unit 9 of step a). The hydrodesulfurization unit 9 of step a) is for example a reactor containing a supported hydrodesulfurization catalyst based on a metal from group VIII and VIB in a fixed bed or in a fluidized bed, preferably a fixed bed reactor is used. The reactor is operated under operating conditions and in the presence of a hydrodesulfurization catalyst, as described above to decompose the sulfur compounds and form hydrogen sulfide (H2S). During the hydrodesulfurization in step a), recombinant mercaptans are formed by addition of H2S formed on the olefins. The effluent from the hydrodesulfurization unit 9 is then introduced into the unit of so-called finishing hydrodesulfurization 11 via line 10 without elimination of the H2S formed. The recycle gas obtained after the separation step via line 14b is optionally sent to the finishing hydrodesulfurization unit 11. The hydrodesulfurization unit 11 of step b) is for example a reactor containing a fixed-bed or fluidized-bed hydrodesulfurization catalyst, preferably a fixed-bed reactor is used. Unit 11 is operated at a higher temperature than unit 9 and in the presence of a selective catalyst comprising an oxide support and an active phase consisting of at least one group VIII metal to decompose at least partially the recombinant mercaptans into olefins and H2S. It also makes it possible to hydrodesulfurize more refractory sulfur compounds.

[0136] According to one or more embodiments, recycle gas is sent via line 14b into the so-called finishing hydrodesulfurization unit 11, and recycle gas is optionally sent via line 14a into the hydrodesulfurization unit 9.

[0137] An effluent (gasoline) containing H2S is withdrawn from said hydrodesulfurization reactor 11 via line 12. The effluent then undergoes a step of removing the H2S (step c) which consists, in the embodiment of [Fig.l], in treating the effluent by condensation by introducing the effluent from step b) via line 12 into a separation tank 13 whose pressure is set so as to guarantee a mercaptan and sulfur content in the effluent of less than 10 ppm by weight while maintaining an optimal cycle time on the HDS catalyst. This separation tank 13 makes it possible to obtain a gaseous fraction containing H2S and hydrogen via line 14 and to withdraw a liquid fraction. The gaseous fraction, after removal of H2S, is recycled to hydrodesulfurization units 9 and / or 11 via lines 14a and / or 14b.The liquid fraction which contains the desulfurized gasoline as well as a fraction of the dissolved H2S is sent via line 15 to a stabilization column or debutanizer 16 in order to separate at the top of the column via line 17 a flow containing C4- hydrocarbons and the residual H2S and at the bottom of the column via line 18 a so-called stabilized gasoline containing the compounds having a boiling temperature higher than that of butane and which has mercaptan and total sulfur contents of less than 10 ppm by weight.

[0138] With the sequences proposed for the process according to the invention, it is possible to achieve high hydrodesulfurization rates while limiting the loss of olefins and consequently the reduction in the octane number. The process according to the invention also makes it possible to reduce losses of C5+ hydrocarbon compounds.

[0139] The following examples illustrate the invention without limiting its scope. Examples

[0140] The analysis methods used to characterize the loads and effluents are as follows:

[0141] - density according to the NF EN ISO 12185 method;

[0142] - sulfur content according to ASTM D2622 method for contents above 10 ppm S and ISO 20846 for contents below 10 ppm S;

[0143] - distillation according to the CSD method simulated distillation "CSD according to the method ASTM2887;

[0144] - diolefin content, determined via the anhydride index maleic (MAV or “Maleic Anhydride Value” according to Anglo-Saxon terminology), according to the UOP 326 method. Example 1 (non-compliant)

[0145] This example refers to [Fig.2].

[0146] Table 1 gives the characteristics of an FCC essence treated by the process according to [Fig.2].

[0147] The FCC gasoline (line 1) is treated in the selective hydrogenation reactor 2 in the presence of a catalyst A. Catalyst A is a NiMo on alumina type catalyst. The metal contents are respectively 7% by weight NiO and 11% by weight MoO 3 relative to the total weight of the catalyst, i.e. a Ni / Mo molar ratio of 1.2. The specific surface area of ​​the catalyst is 230 m2 / g. Prior to its use, catalyst A is sulfurized at atmospheric pressure in a sulfurization bench under a H2 S / H2 mixture consisting of 15% by volume of H2S at 1 L / gh of catalyst and at 400°C for two hours. This protocol makes it possible to obtain a sulfurization rate greater than 80%.

[0148] Gasoline (line 1) is brought into contact with hydrogen (line 3) in a reactor containing catalyst A. This step of the process carries out the selective hydrogenation of diolefins and the conversion (heaviness) of a portion of the light mercaptan compounds (RSH) present in the feedstock. The diolefin content is directly proportional to the MAV value (maleic anhydride index or Maleic Anhydrid Value according to English terminology). Diolefins are undesirable compounds because they are precursors of gums in gasoline.

[0149] The operating conditions implemented in the selective hydrogenation reactor are: Temperature: 140°C, Total pressure: 2.5 MPa, volume ratio of added H2 / gasoline charge: 5 normal liters of hydrogen per liter of gasoline at standard conditions (vol / vol), liquid space velocity: 3 h1.

[0150] [Tables 1] Line 1 Feed Line 4 Selective Hydrogenation Effluent Organic Sulfur Content (ppm wt S) 438 435 MAV (mg / g) 12 0.6 Olefin Content (% wt) 31% 31% Simulated Distillation (ASTM D2887) 5% Distilled Mass (°C) 23 23 50% Distilled Mass (°C) 95 95 95% Distilled Mass (°C) 180 180

[0151] Table 1: Characteristics of feedstock 1 and selective hydrogenation effluent 4.

[0152] The effluent from the selective hydrogenation step (line 4) with a low content of conjugated diolefins (MAV=0.6 mg / g) and a low content of light sulfur compounds (made heavier in the selective hydrogenation step) is sent to a fractionation column 5 in order to separate a light gasoline at the top (line 6) and a first heavy gasoline cut (line 7) at the bottom of the column. The characteristics of the light gasoline and the first heavy gasoline cut are indicated in Table 2. As indicated in Table 2, the light gasoline obtained (line 6) has a low sulfur content (10 ppm by weight). The first heavy gasoline cut, which corresponds to approximately 72% by mass of the gasoline, has a high sulfur content (600 ppm) and requires additional treatment before being incorporated into the gasoline pool.

[0153] [Tables2] Line 6 Light gasoline Line 7 Heavy gasoline Mass percentage of the cut % 28 72 Organic sulfur content (ppm weight S) 10 600 Olefin content (% weight) 46% 25%

[0154] Table 2: Characteristics of the cuts: Light gasoline and first cut heavy gasoline

[0155] The first heavy gasoline cut (line 7) is mixed with hydrogen (line 8) and treated in a selective hydrodesulfurization unit (9) which corresponds to a first hydrodesulfurization step. The first hydrodesulfurization step is carried out in the presence of a CoMo type catalyst supported on alumina, the metal contents being respectively 3% by weight of CoO and 10% by weight of MoO3, the specific surface area of ​​the catalyst is 135 m2 / g. Prior to its use, the catalyst is sulfurized at atmospheric pressure in a sulfurization bench under a H2S / H2 mixture consisting of 15% by volume of H2S at 1 L / gh of catalyst and at 400°C for two hours. This protocol makes it possible to obtain a sulfurization rate greater than 80%.The temperature is 270°C, the pressure is 2.1 MPa, the liquid space velocity (expressed as volume of liquid per volume of catalyst per hour) is 3 h1, the ratio between the hydrogen flow rate and the feed flow rate is 250 normal m3 per m3 under standard conditions. The reactor effluent (line 10) is then reheated in a furnace (not shown in the figure) and then introduced into a second reactor (11) containing a so-called finishing catalyst. This finishing step is carried out in the presence of a Ni catalyst supported on alumina. The temperature is 324°C, the pressure is 1.8 MPa, the liquid space velocity (expressed as volume of liquid per volume of catalyst per hour) is 3 h1.

[0156] The effluent from reactor 11 (line 12) is sent to a stabilization column or debutanizer (16) operating at a pressure of 1.6 MPa, in order to separate at the top of the column via line 17 a stream containing H2S, hydrogen, C4- hydrocarbons and at the bottom of the column, via line 18, a heavy gasoline called stabilized and whose characteristics are illustrated in table 3. The loss in gasoline yield is presented in table 4.

[0157] [Tables3] Line 10 Hydrodesulfurized Heavy Gasoline First Stage Line 18 Hydrodesulfurized Heavy Gasoline Second Stage Stabilized Organic Sulfur Content (ppm S) 13 10 Olefin Content (% wt) 16.6 16.5

[0158] Table 3: Characteristics of heavy gasoline after the first and second stages of hydrodesulfurization

[0159] [Tables4] Stabilization column bottom temperature (°C) 234 Loss of C5+ (% mol) 5.75

[0160] Table 4: Loss of C5+ compounds between the first heavy gasoline cut (line 7) and the gasoline obtained after the second hydrodesulfurization stage and after the stabilization stage (line 18)

[0161] The process as described in Example 1 makes it possible to obtain a heavy gasoline with a low sulfur content (10 ppm by weight). The loss of olefins between the first heavy gasoline cut and the stabilized heavy gasoline obtained after the second hydrodesulfurization step is 35.7% by mass (relative). Example 2 (compliant)

[0162] This example refers to the present invention according to [Fig.l].

[0163] Unless otherwise described below, the same feedstock as in Example 1 is sent under the same operating conditions as Example 1 to the selective hydrogenation, hydrodesulfurization and finishing hydrodesulfurization sections.

[0164] The effluent from reactor 11 (line 12) is sent to a separation tank (13) after condensation at a temperature of 65°C and a pressure of 1.6 MPa, in order to produce a liquid fraction which contains the desulfurized gasoline as well as a fraction of the dissolved H2S (line 15) and a gaseous fraction (line 14) containing essentially the hydrogen and the H2S formed during steps a) and b), optionally with light hydrocarbons C1 to C4. The liquid fraction (line 15) is then sent to a stabilization column (16) operating at a pressure of 0.7 MPa, in order to separate at the top of the column a cut of light compounds from the liquid fraction as well as the H2S (line 17) and a bottom cut free of H2S, called stabilized gasoline (line 18).

[0165] The gas stream (line 14) is recycled to the first hydrodesulfurization stage (stage a), via line 14a.

[0166] The characteristics of the gaseous fraction obtained after gas / liquid separation (line 14) of the reaction effluent (line 12) are illustrated in Table 5 below.

[0167] [Tables5] Line 14 Gas fraction Operating pressure separator drum (MPa) 1.6 h2 (% mol) 96.8 C5+ content (% mol) 2.03

[0168] Table 5: Characteristics of gas fraction (line 14) after gas / liquid separation of reaction effluent 12

[0169] The characteristics of the gasoline cut obtained after stabilization (line 18) of the present invention are illustrated in Tables 6 and 7.

[0170] [Tableauxô] Line 10 Hydrodesulfurized Heavy Gasoline First Stage Line 18 Hydrodesulfurized Heavy Gasoline Second Stage Stabilized Organic Sulfur Content (ppm S) 13 10 Olefin Content (% wt) 16.6 16.3

[0171] Table 6: Characteristics of heavy gasoline after the first and second stages of hydrodesulfurization

[0172] [Tables7] Stabilization column bottom temperature (°C) 184 Loss of C5+ (% mol) 3.04

[0173] Table 7: Loss of C5+ compounds between the first heavy gasoline cut (line 7) and the gasoline obtained after the second hydrodesulfurization stage and after the stabilization stage (line 18)

[0174] The process according to Example 2 makes it possible to obtain a heavy gasoline with a low sulfur content (10 ppm by weight). The loss of olefins between the first heavy gasoline cut and the stabilized heavy gasoline obtained after the second hydrodesulfurization stage is 34.7% by mass (relative). Example 3 (non-compliant)

[0175] Unless otherwise described below, the same feedstock as in Example 1 is sent under the same operating conditions as Example 1 to the selective hydrogenation, hydrodesulfurization and finishing hydrodesulfurization sections.

[0176] The volume flow rate of the recycle gas loop is kept constant compared to example 2, the ratio between the hydrogen flow rate and the feed flow rate is therefore a consequence and is 125 normal m3 per m3 of feed under standard conditions, the average temperature of the hydrodesulfurization reactor defined as being the average between the inlet and outlet temperature of the reactor is 283°C, the pressure is 2.2 MPa, the space velocity of the liquid (expressed in volume of liquid per volume of catalyst and per hour) is 3 h1.

[0177] The reactor effluent (line 10) is reheated in a furnace (not shown in the figure) and then introduced into a second reactor (11) containing a so-called finishing catalyst. This finishing step is carried out at an average temperature of 338°C, a pressure of 1.9 MPa, and a liquid space velocity (expressed as volume of liquid per volume of catalyst per hour) of 3 h1.

[0178] The effluent from reactor 11 (line 12) is sent to a separation tank (13) after condensation at a temperature of 65°C and a pressure of 0.8 MPa, in order to produce a liquid fraction which contains the desulfurized gasoline as well as a fraction of the dissolved H2S (line 15) and a gaseous fraction (line 14) containing essentially the hydrogen and the H2S formed during step b), optionally with light hydrocarbons C1 to C4 and C5+ hydrocarbons. The gaseous fraction is sent to an H2S separation section in an amine washing column (19) in order to obtain a recycle gas containing 10 ppm mol of H2S. The recycle gas is returned via line 14a, mixed with fresh hydrogen (line 8) to the selective hydrodesulfurization unit (9) after compression.

[0179] The liquid fraction (line 15) from the separator operating at 0.8 MPa is then sent to a stabilization column (16) operating at a pressure of 0.7 MPa, in order to separate at the top of the column a cut of light compounds from the liquid fraction as well as the H2S (line 17) and a bottom cut freed from the H2S, called stabilized gasoline (line 18).

[0180] The characteristics of the gaseous fraction obtained after separation (line 14) gas / liquid from the reaction effluent (line 12) are illustrated in Table 8 below.

[0181] [Tables8] Line 14 Gas fraction Operating pressure separator drum (MPa) 0.8 h2 (% mol) 93.9 C5+ content (% mol) 3.90

[0182] Table 8: Characteristics of gas fraction (line 14) after gas / liquid separation of reaction effluent 12

[0183] The characteristics of the gasoline cut obtained after stabilization (line 18) are illustrated in Table 9.

[0184] [Tables9] Line 10 Hydrodesulfurized Heavy Gasoline First Stage Line 18 Hydrodesulfurized Heavy Gasoline Second Stage Stabilized Organic Sulfur Content (ppm S) 13 10 Olefin Content (% wt) 15.8 15.7

[0185] Table 9: Characteristics of heavy gasoline after the first and second stages of hydrodesulfurization

[0186] The loss of C5+ compounds in the gaseous fraction obtained after the separation step (line 14) and in the gaseous cut after stabilization of the gasoline (line 17) is given in Table 10.

[0187] [TableauxlO] Loss of C5+ (mol%) 2.71

[0188] Table 10: Loss of C5+ compounds between the gasoline obtained after the second hydrodesulfurization stage (line 12) and after the stabilization stage (line 18)

[0189] The process according to Example 3 makes it possible to obtain a heavy gasoline with a low sulfur content (10 ppm by weight). The loss of olefins between the first heavy gasoline cut and the stabilized heavy gasoline obtained after the second hydrodesulfurization step is 37.4% by mass (relative). This loss of octane is greater than in the example according to the invention. This also increases the consumption of hydrogen in the hydrodesulfurization reactors. Example 4 (non-compliant)

[0190] Unless otherwise described below, the same feedstock as in Example 1 is fed under the same operating conditions as Example 1 to the selective hydrogenation, hydrodesulfurization, and finishing hydrodesulfurization sections.

[0191] The volume flow rate of the recycle gas loop is kept constant compared to example 2, the ratio between the hydrogen flow rate and the feed flow rate is therefore a consequence and is 330 normal m3 per m3 of feed under standard conditions, the average temperature of the hydrodesulfurization reactor defined as being the average between the inlet and outlet temperature of the reactor is 268°C, the pressure is 2.7 MPa, the space velocity of the liquid (expressed in volume of liquid per volume of catalyst and per hour) is 3 h1.

[0192] The reactor effluent (line 10) is reheated in a furnace (not shown in the figure) and then introduced into a second reactor (11) containing a so-called finishing catalyst. This finishing step is carried out at an average temperature of 320°C, a pressure of 2.4 MPa, and a liquid space velocity (expressed as volume of liquid per volume of catalyst per hour) of 3 h1.

[0193] The effluent from reactor 11 (line 12) is sent to a separation tank (13) after condensation at a temperature of 65°C and a pressure of 2.1 MPa, in order to produce a liquid fraction which contains the desulfurized gasoline as well as a fraction of the dissolved H2S (line 15) and a gaseous fraction (line 14) containing essentially the hydrogen and the H2S formed during step b), optionally with light hydrocarbons C1 to C4 and C5+ hydrocarbons. The gaseous fraction is sent to an H2S separation section in an amine washing column (19) in order to obtain a recycle gas containing 10 ppm mol of H2S. The recycle gas is returned via line 14a, mixed with fresh hydrogen (line 8) to the selective hydrodesulfurization unit (9) after compression.

[0194] The liquid fraction (line 15) from the separator operating at 2.1 MPa is then sent to a stabilization column (16) operating at a pressure of 0.7 MPa, in order to separate at the top of the column a cut of light compounds from the liquid fraction as well as the H2S (line 17) and a bottom cut freed from the H2S, called stabilized gasoline (line 18).

[0195] The characteristics of the gaseous fraction obtained after separation (line 14) gas / liquid from the reaction effluent (line 12) are illustrated in Table 11.

[0196] [Tableauxll] Line 14 Gas fraction Operating pressure separator drum (MPa) 2.1 h2 (mol%) 97.5 C5+ content (mol%) 1.58

[0197] Table 11: Characteristics of gas fraction (line 14) after gas / liquid separation of reaction effluent 12

[0198] The characteristics of the gasoline cut obtained after stabilization (line 18) are illustrated in Table 12.

[0199] [Tablesl2] Line 10 Hydrodesulfurized Heavy Gasoline First Stage Line 18 Hydrodesulfurized Heavy Gasoline Second Stage Stabilized Organic Sulfur Content (ppm S) 13 10 Olefin Content (% wt) 15.6 15.6

[0200] Table 12: Characteristics of heavy gasoline after the first and second stages of hydrodesulfurization

[0201] The loss of C5+ compounds in the gaseous fraction obtained after the separation step (line 14) and in the gaseous cut after stabilization of the gasoline (line 17) is given in Table 13.

[0202] [Tables 13] Loss of C5+ (mol%) 3.15

[0203] Table 13: Loss of C5+ compounds between the gasoline obtained after the second hydrodesulfurization step (line 12) and the gasoline obtained after the stabilization step (line 18)

[0204] The process according to Example 4 makes it possible to obtain a heavy gasoline with a low sulfur content (10 ppm by weight). The loss of olefins between the first heavy gasoline cut and the stabilized heavy gasoline obtained after the second hydrodesulfurization step is 37.8% by mass (relative). This loss of octane is greater than in the example according to the invention. This also increases the consumption of hydrogen. in hydrodesulfurization reactors. Example 5 (non-compliant)

[0205] Unless otherwise described below, the same feedstock as in Example 1 is sent under the same operating conditions as Example 1 to the selective hydrogenation, hydrodesulfurization and finishing hydrodesulfurization sections.

[0206] The volume flow rate of the recycle gas loop is kept constant compared to example 1, the ratio between the hydrogen flow rate and the feed flow rate is therefore 250 normal m3 per m3 of feed under standard conditions, the average temperature of the hydrodesulfurization reactor is 272°C, the pressure is 3.6 MPa, the space velocity of the liquid (expressed as volume of liquid per volume of catalyst and per hour) is 3 h1.

[0207] The reactor effluent (line 10) is then reheated in a furnace (not shown in the figure) and then introduced into a second reactor (11) containing a so-called finishing catalyst. This finishing step is carried out at an average temperature of 330°C, a pressure of 3.3 MPa, and a liquid space velocity (expressed as volume of liquid per volume of catalyst per hour) of 3 h1.

[0208] The effluent from reactor 11 (line 12) is sent to a separation tank (13) after condensation at a temperature of 65°C and a pressure of 1.6 MPa, in order to produce a liquid fraction which contains the desulfurized gasoline as well as a fraction of the dissolved H2S (line 15) and a gaseous fraction (line 14) containing essentially the hydrogen and the H2S formed during step b), optionally with light hydrocarbons C1 to C4 and C5+ hydrocarbons. The gaseous fraction is sent to an H2S separation section in an amine washing column (19) in order to obtain a recycle gas containing 10 ppm mol of H2S. The recycle gas is returned via line 14a, mixed with fresh hydrogen (line 8) to the selective hydrodesulfurization unit (9) after compression.

[0209] The liquid fraction (line 15) from the separator operating at 1.6 MPa is then sent to a stabilization column (16) operating at a pressure of 0.7 MPa, in order to separate at the top of the column a cut of light compounds from the liquid fraction as well as the H2S (line 17) and a bottom cut freed from the H2S, called stabilized gasoline (line 18).

[0210] The characteristics of the gaseous fraction obtained after gas / liquid separation (line 14) of the reaction effluent (line 12) are illustrated in Table 14.

[0211] [Tables 14] Line 14 Gas fraction Operating pressure separator drum (MPa) 1.6 h2 (mol%) 96.8 C5+ content (mol%) 2.0

[0212] Table 14: Characteristics of gas fraction (line 14) after gas / liquid separation of reaction effluent 12

[0213] The characteristics of the gasoline cut obtained after stabilization (line 18) are illustrated in Table 15.

[0214] [Tables 15] Line 10 Hydrodesulfurized Heavy Gasoline First Stage Line 18 Hydrodesulfurized Heavy Gasoline Second Stage Stabilized Organic Sulfur Content (ppm S) 14 10 Olefin Content (% wt) 13.7 13.4

[0215] Table 15: Characteristics of heavy gasoline after the first and second stages of hydrodesulfurization

[0216] The loss of C5+ compounds in the gaseous fraction obtained after the separation step (line 14) and in the gaseous cut after stabilization of the gasoline (line 17) is given in Table 16.

[0217] [Tableauxlô] Loss of C5+ (mol%) 2.95

[0218] Table 16: Loss of C5+ compounds between the gasoline obtained after the second hydrodesulfurization step (line 12) and the gasoline obtained after the stabilization step (line 18)

[0219] The process according to Example 5 makes it possible to obtain a heavy gasoline with a low sulfur content (10 ppm by weight). The loss of olefins between the first heavy gasoline cut and the stabilized heavy gasoline obtained after the second hydrodesulfurization step is 46.6% by mass (relative). This loss of octane is greater than in the example according to the invention.

[0220] All the results are compared in Table 17 below, presenting the olefin contents in the gasoline and losses of C5+ compounds in the gas purges after the stabilization step. Carrying out the process according to the invention presents itself as the best compromise for maximizing the olefin content in the gasoline obtained on the one hand, and for limiting the loss of recoverable C5+ compounds in a gasoline cut.

[0221] [Tablesl7] Example 1 Non-compliant Example 2 Compliant Example 3 Non-compliant Example 4 Non-compliant Example 5 Non-compliant Pressure stage a) (MPa) 2.2 2.2 2.2 2.7 3.6 Pressure stage b) (MPa) 1.9 1.9 1.9 2.4 3.3 Pressure stage c) (MPa) - 1.6 0.8 2.1 1.6 Olefin content in the gasoline cut (line 18) (% weight) 16.5 16.3 15.7 15.6 13.4 Loss of C5+ in the gaseous fraction from the separator drum (line 14) and the stabilization column (line 17) compared to the reaction effluent (line 12) (% mol) 5.75 3.03 2.71 3.15 2.95 H2 content in the gaseous fraction from the separator flask (line 14 (%mol) 96.8 93.9 97.5 96.8

Claims

1.

2.

3. Claims A method of treating gasoline containing sulfur compounds, olefins and diolefins, the method comprising at least the following steps: a) bringing into contact in at least one reactor, gasoline, hydrogen and a hydrodesulfurization catalyst comprising an oxide support and an active phase comprising a metal from group VIB and a metal from group VIII, at a temperature of between 210 and 320°C, at a pressure of between 1.5 and 3 MPa, with a space velocity of between 1 and 10 h 1 and a ratio between the hydrogen flow rate expressed in normal m3 per hour and the flow rate of feed to be treated expressed in m3 per hour under standard conditions of between 100 and 600 Nm3 / m3, so as to convert at least part of the sulfur compounds into H2S; b) the effluent from step a) without elimination of the H2S formed, hydrogen, and a hydrodesulfurization catalyst comprising an oxide support and an active phase consisting of at least one metal from group VIII are brought into contact in at least one reactor at a temperature of between 280 and 400°C, at a pressure of between 1.0 and 3 MPa, with a space velocity of between 1 and 10 h 1 and a ratio between the hydrogen flow rate expressed in normal m3 per hour and the feed flow rate to be treated expressed in m3 per hour under standard conditions of between 100 and 600 Nm3 / m3; c) the effluent from step b) is sent to at least one separation tank operating at a pressure of between 1.0 and 2.0 MPa to obtain a gaseous fraction containing H2S and hydrogen and a liquid fraction containing the desulfurized gasoline and a fraction of residual H2S; d) said liquid fraction obtained in step c) is sent to a stabilization column to obtain at the top a flow comprising the residual H2S and C4- hydrocarbon compounds and at the bottom a stabilized gasoline; e) at least part of the gaseous fraction obtained at the end of step c) is recycled to at least one of steps a) and / or b). The method of claim 1, wherein the pressure of the separation tank of step c) is between 1.2 and 1.8 MPa. A method according to any one of claims 1 and 2, wherein the catalyst of step a) comprises a group VIII metal content of between 0.1 and 10% by weight of group VIII metal oxide relative to the total weight of the catalyst, and a group VIB metal content of between 1 and 20% by weight of group VIB metal oxide relative to the total weight of the catalyst.

4. A process according to any one of claims 1 to 3, wherein the catalyst of step a) comprises a molar ratio of Group VIII metal to Group VIB metal of the catalyst of between 0.1 and 0.

8.

5. A process according to any one of claims 1 to 4, wherein the catalyst of step a) comprises a specific surface area of ​​between 5 and 400 m2 / g.

6. A process according to any one of claims 1 to 5, wherein the catalyst of step a) comprises alumina and an active phase comprising cobalt, molybdenum and optionally phosphorus, said catalyst containing a content by weight relative to the total catalyst weight of cobalt oxide, in CoO form, of between 0.1 and 10%, a content by weight relative to the total catalyst weight of molybdenum oxide, in MoO3 form, of between 1 and 20%, a cobalt / molybdenum molar ratio of between 0.1 and 0.8, a content by weight relative to the total catalyst weight of phosphorus oxide in P2O5 form of between 0.3 and 10% when phosphorus is present, said catalyst having a specific surface area of ​​between 50 and 250 m2 / g.

7. A process according to any one of claims 1 to 6, wherein the catalyst of step b) comprises a group VIII metal content of between 1 and 60% by weight of group VIII metal oxide relative to the total weight of the catalyst.

8. A process according to any one of claims 1 to 7, wherein the catalyst of step b) comprises a specific surface area of ​​between 5 and 400 m2 / g.

9. A process according to any one of claims 1 to 8, wherein the catalyst of step b) consists of alumina and nickel, said catalyst containing a content by weight relative to the total weight of catalyst of nickel oxide, in NiO form, of between 5 and 20%, said catalyst having a specific surface area of ​​between 30 and 180 m2 / g.

10. A method according to any one of claims 1 to 9, wherein the temperature of step b) is higher than the temperature of step a).

11. A method according to claim 10, wherein the temperature of step b) is at least 5°C higher than the temperature of step a).

12. Process according to any one of claims 1 to 11, in which before step a) a step of distillation of the gasoline is carried out so as to fractionate said gasoline into at least two light and heavy gasoline cuts and the heavy gasoline cut is treated in steps a), b), c), d) and e).

13. A process according to any one of claims 1 to 12, wherein before step a) and before any possible distillation step, the gasoline is brought into contact with hydrogen and a selective hydrogenation catalyst to selectively hydrogenate the diolefins contained in said gasoline into olefins.

14. A process according to any one of claims 1 to 13, wherein the gasoline is a catalytic cracked gasoline.

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