Method for selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds

Abstract

To provide a method for selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds.SOLUTION: Provided is a method for applying a selective hydrotreatment catalyst comprising an active phase based on nickel and molybdenum, and a porous carrier made of alumina and / or nickel aluminate, characterized in that the molar ratio of nickel to molybdenum is more than 2.5 mol / mol and less than 3.0 mol / mol.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a process for the selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds.

[0002] The present invention relates to a catalyst for the selective hydrogenation of gasoline and the increase in molecular weight of light thiols, and to a method which makes it possible to both selectively hydrogenate polyunsaturated compounds contained in gasoline to monounsaturated compounds and increase the molecular weight of light sulfur compounds by reaction with the unsaturated compounds. [Background technology]

[0003] To produce gasoline that meets the new environmental standards, the sulfur content must be significantly reduced, generally to a value not exceeding 50 ppm, and preferentially to a value below 10 ppm.

[0004] Furthermore, conversion gasoline, especially gasoline derived from catalytic cracking, can account for 30% to 50% of the gasoline pool and is known to have high monoolefin and sulfur contents.

[0005] For this reason, nearly 90% of the sulfur present in gasoline comes from gasoline resulting from the catalytic cracking process, which will hereinafter be referred to as FCC (Fluid Catalytic Cracking) gasoline. FCC gasoline therefore constitutes a suitable feedstock for the process of the present invention. More generally, the process according to the invention is applicable to any gasoline fraction containing a certain proportion of diolefins, which may also contain some lighter compounds belonging to the C3 and C4 fractions.

[0006] Gasoline from cracking units is generally rich in olefins and sulfur, but also in diolefins, the content of which can reach 5% by weight in gasoline from catalytic cracking. Diolefins are unstable compounds that can easily polymerize and generally must be removed before any processing of these gasolines, such as hydrodesulfurization, intended to meet specifications for the sulfur content in gasoline. However, this hydrogenation must be selective for diolefins and limit the hydrogenation of olefins to limit hydrogen consumption and the loss of octane from the gasoline. Furthermore, as described in U.S. Patent No. 5,949,999, it is advantageous to convert thiols by increasing their molecular weight before the desulfurization step, because this makes it possible to produce a desulfurized gasoline fraction consisting mainly of olefins with five carbon atoms by simple distillation without losing octane. After selective hydrogenation and increasing the molecular weight of light sulfur compounds, the amount of sulfur present in the feedstock is not altered; only the nature of the sulfur is altered by increasing the molecular weight of the light sulfur compounds.

[0007] In addition, diene compounds present in the feedstock to be treated are unstable and tend to polymerize to form gums, which can lead to the gradual deactivation of downstream hydrodesulfurization catalysts or to the gradual plugging of hydrodesulfurization reactors. For industrial applications, it is therefore important to use catalysts that limit polymer formation, i.e., catalysts with low acidity or porosity optimized to promote the continuous extraction of polymer or gum precursors by hydrocarbons in the feedstock, thereby ensuring maximum catalyst cycle time.

[0008] Patent document 2, filed by the applicant, proposes a method for preparing a catalyst on a support, which comprises at least one metal of group VIB and at least one metal from group VIII, supported on a specific support comprising a metal aluminate of the MAl2O4 type, where the metal M is selected from nickel and cobalt.

[0009] In Patent Document 3, filed by the applicant, a selective hydrogenation process is proposed using a catalyst with a specific support, which comprises at least one metal of Group VIB and at least one non-noble metal from Group VIII, used in sulfided form, deposited on a specific support comprising a metal aluminate of the MAl2O4 type (wherein the metal M is selected from nickel and cobalt).

[0010] Patent Document 4, filed by the applicant, proposes a selective hydrogenation method using a sulfur-containing catalyst of a specific composition. The catalyst comprises at least one Group VIB metal and at least one Group VIII metal supported on alumina, the content of the Group VIB metal oxide being 4% to 20% by weight relative to the total weight of the catalyst, the content of the Group VIII metal oxide being less than 15% by weight relative to the total weight of the catalyst, the molar ratio of the Group VIII metal to the Group VIB metal being 0.6 to 3.0 mol / mol, and the total pore volume of the catalyst being 0.4 to 1.4 cm. 3 / g.

[0011] Patent Document 5 proposes a catalyst for removing arsenic from petroleum feedstocks. The catalyst comprises a porous refractory support impregnated with at least 8 wt. % of a Group VIB metal and an amount of a Group VIII metal such that the atomic ratio of the Group VIII metal to the Group VIB metal is approximately 1.5 to 2.5. A method for producing such a catalyst and a method for removing arsenic metals from petroleum fractions using the catalyst are also described.

[0012] Patent Document 6 discloses a selective hydrogenation catalyst comprising 10 to 20% by weight of nickel, measured in the form of oxides, and 5 to 12% by weight of molybdenum, measured in the form of oxides, deposited on an alumina-titanium-based support.

[0013] Patent Document 7 discloses a selective hydrogenation catalyst comprising an active phase and an oxide support, wherein the active phase comprises, measured in the form of oxide, 6 to 15 wt % of a Group VIII metal and 4 to 10 wt % of a Group VIB metal, measured in the form of oxide, the oxide support is alumina-based, and the molar ratio of the Group VIII metal to the Group VIB metal is greater than 3 mol / mol and not greater than 5 mol / mol.

[0014] In view of the solutions described in the literature, the present invention proposes a new catalyst with a specific active phase, which allows both the selective hydrogenation of polyunsaturated compounds, in particular diolefins, and the increase in the molecular weight of light sulfur compounds, in particular thiols. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] European Patent Application Publication No. 01077247 [Patent Document 2] French Patent Application Publication No. 2118309 (Japanese Patent Publication No. 54-9595) [Patent Document 3] French Patent Application Publication No. 2895415 (JP 2007-182567 A) [Patent Document 4] French Patent Application Publication No. 2935389 (JP 2010-90366 A) [Patent Document 5] US Patent Application Publication No. 2003 / 111391 [Patent Document 6] Chinese Patent Application Publication No. 101869839 [Patent Document 7] US Patent Application Publication No. 2015 / 290626 Summary of the Invention [Means for solving the problem]

[0016] (Subject of the Invention) The present invention relates to a hydrotreating catalyst comprising an active phase based on nickel and molybdenum and a porous support made of alumina and / or nickel aluminate of the NiAl2O4 type, characterized in that the molar ratio between the nickel contained in the active phase and in the support and the molybdenum of the active phase is greater than 2.5 mol / mol and less than 3.0 mol / mol.

[0017] In fact, the Applicant has surprisingly discovered that catalysts comprising an active phase based on nickel and molybdenum, with a specific ratio between nickel and molybdenum, have a better activity and a better selectivity for the hydrogenation of diolefins compared to catalysts disclosed in the prior art, while at the same time allowing at least an equally good, or even better, conversion of light sulfur compounds.

[0018] Without wishing to be bound by any theory, the catalyst formulation within the claimed specific ranges can ensure strong de-diene activity, better catalyst stability against polymer formation, good selectivity for diolefin hydrogenation, and good activity for the conversion of thiols and other light sulfur compounds. In particular, at an equal molybdenum content, increasing the Ni / Mo molar ratio can produce a NiS active phase that is active in thioetherification and inactive in de-diene. Above a certain amount, the NiS phase will cover the NiMoS phase active in de-diene, thus resulting in a loss of de-diene activity. Furthermore, at an equal active phase content, increasing the specific surface area of ​​the catalyst can adjust the dispersion of the NiS and NiMoS phases to a specific surface area threshold that induces a loss of selectivity for the selective hydrogenation of diolefins relative to the hydrogenation of olefins. Therefore, there is an optimum between the amount of NiMoS and NiS phases introduced onto the catalyst and the specific surface area of ​​said catalyst, which leads to an optimum catalyst for thioetherification and de-dienation.

[0019] Preferably, the specific surface area of ​​the catalyst is 200 m 2 / g.

[0020] Preferably, the nickel content of the active phase, measured in the form of the oxide, is between 1 and 20% by weight relative to the total weight of the catalyst.

[0021] Preferably, the molybdenum content of the active phase, measured in the form of the oxide, is between 1 and 12% by weight relative to the total weight of the catalyst.

[0022] Preferably, the porous support is made of alumina and nickel aluminate.

[0023] Preferably, the molar ratio between the nickel of the porous support and the molybdenum of the active phase is between 0.5 and 1.5 mol / mol.

[0024] Preferably, the molar ratio between the nickel of the porous support and the nickel of the active phase is between 0.3 and 0.7 mol / mol.

[0025] Preferably, the nickel content in the support, measured in the form of the oxide, is between 0.5 and 10% by weight relative to the total weight of the catalyst.

[0026] Preferably, the nickel content of the active phase, measured in the form of the oxide, is between 1 and 12% by weight relative to the total weight of the catalyst.

[0027] Preferably, the specific surface area of ​​the catalyst is 120 to 160 m 2 / g.

[0028] Preferably, the sulfidity of the metal of the active phase is at least equal to 50%.

[0029] Preferably, the total pore volume of the catalyst is 0.3 to 0.7 cm 3 / g.

[0030] Another subject of the present invention relates to a method for selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds, in which gasoline and hydrogen are contacted with the catalyst according to the present invention, which is in the form of a sulfide, and the temperature during contact is between 80 ° C and 220 ° C, and the liquid hourly space velocity is 1 h -1 ~10h -1 the pressure is between 0.5 and 5 MPa and the molar ratio between hydrogen and the diolefin to be hydrogenated is greater than 1 mol / mol and less than 10 mol / mol.

[0031] Preferably, the gasoline is a fluid catalytic cracking (FCC) gasoline and has a boiling point between 0°C and 280°C.

[0032] The method for desulfurizing gasoline containing sulfur compounds comprises the following steps: a) a step of selective hydrogenation; carrying out the method of the present invention for selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds; b) a step of separating the gasoline obtained in step a) into at least two fractions, each of the fractions comprising at least one light gasoline and at least one heavy gasoline; and c) A step of hydrodesulfurization of the heavy gasoline separated in step b) over a catalyst making it possible to at least partially decompose the sulfur compounds into H2S. DETAILED DESCRIPTION OF THE INVENTION

[0033] (Detailed Description of the Invention) (definition) Hereinafter, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, published by CRC Press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group VIII according to the CAS classification corresponds to the metals in columns 8, 9, and 10 according to the new IUPAC classification.

[0034] The term "specific surface area" refers to the BET specific surface area (S) determined by nitrogen adsorption according to standard ASTM D 3663-78, which was established from the Brunauer-Emmett-Teller method described in the academic journal "The Journal of the American Chemical Society", 1938, 60, 309. BET , unit is m 2 / g).

[0035] The total pore volume of the catalyst or of the support used to prepare the catalyst is understood to mean the volume measured by mercury porosimetry intrusion according to standard 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° according to the recommendation of the publication "Techniques de l'ingenieur, traite analyze et caracterisation" (Techniques of the Engineer, Analysis and Characterisation Treatise), pages 1050-1055, by Jean Charpin and Bernard Rasneur. For greater accuracy, the value of the total pore volume corresponds to the value of the total pore volume measured by mercury intrusion porosimetry on a sample minus the value of the total pore volume measured by mercury intrusion porosimetry on the same sample at a pressure equivalent to 30 psi (approximately 0.2 MPa).

[0036] The molybdenum and nickel contents are measured by X-ray fluorescence.

[0037] (catalyst) The catalyst according to the present invention comprises an active phase containing nickel and molybdenum and a porous support made of alumina and / or nickel aluminate, wherein the molar ratio between nickel and molybdenum is greater than 2.5 mol / mol and less than 3.0 mol / mol, preferably 2.6 to 2.9 mol / mol. Preferably, the catalyst comprises an active phase of nickel and molybdenum and a support made of alumina and / or nickel aluminate.

[0038] The nickel content of the active phase, measured in the form of the oxide, is advantageously between 1 and 20% by weight, preferably between 2 and 15% by weight and even more preferentially between 4 and 13% by weight relative to the total weight of the catalyst.

[0039] The molybdenum content of the active phase, measured in the form of the oxide, is advantageously between 1 and 12% by weight, preferably between 1 and 10% by weight and even more preferentially between 2 and 9% by weight, relative to the total weight of the catalyst.

[0040] Preferably, the total pore volume measured by mercury porosimetry is 0.3 to 0.7 cm 3 / g, very preferably 0.35 to 0.65 cm 3 A catalyst having a mercury porosimetry of 140° / g is used. Mercury porosimetry is measured according to standard ASTM D4284-92 with a wetting angle of 140° using an Autopore III model device from the Micromeritics® brand.

[0041] The specific surface area of ​​the catalyst is preferably 300 m 2 / g, preferably less than 200m 2 / g, and even more preferably less than 120m 2 / g~190m 2 / g, more preferentially 120-180m 2 / g, more preferentially 120-170m 2 / g, and even more preferentially 120-160m 2 / g.

[0042] In one preferred embodiment, the catalyst comprises, preferably consists of, an active phase based on nickel and molybdenum and a porous support made of alumina, the molar ratio between nickel and molybdenum contained in said catalyst being greater than 2.5 mol / mol and less than 3.0 mol / mol, preferably between 2.6 and 2.9 mol / mol, and the specific surface area of ​​said catalyst being less than 200 m 2 / g, and even more preferably less than 120m 2 / g~190m 2 / g, more preferentially 120-180m 2 / g, more preferentially 120-170m 2 / g, and even more preferentially 120-160m 2 / g.

[0043] In another preferred embodiment, the catalyst comprises, preferably consists of, an active phase based on nickel and molybdenum and a porous support made of nickel aluminate, the catalyst comprising a molar ratio between nickel and molybdenum of more than 2.5 mol / mol and less than 3.0 mol / mol, preferably between 2.6 and 2.9 mol / mol, and the catalyst comprising a specific surface area of ​​200 m 2 / g, and even more preferably less than 120m 2 / g~190m 2 / g, more preferentially 120-180m 2 / g, more preferentially 120-170m 2 / g, and even more preferentially 120-160m 2 / g.

[0044] In another preferred embodiment, the catalyst comprises, preferably consists of, an active phase based on nickel and molybdenum and a porous support made of alumina and nickel aluminate, the catalyst comprising a molar ratio between nickel and molybdenum of more than 2.5 mol / mol and less than 3.0 mol / mol, preferably between 2.6 and 2.9 mol / mol, and the catalyst comprising a specific surface area of ​​200 m 2 / g, and even more preferably less than 120m 2 / g~190m 2 / g, more preferentially 120-180m 2 / g, more preferentially 120-170m 2 / g, and even more preferentially 120-160m 2 / g.

[0045] In fact, in these three preferred embodiments, for an equal content of active phases, the increase in the specific surface area of ​​the catalyst makes it possible to adjust the dispersion of the NiS and NiMoS phases, respectively, up to a specific surface threshold at which a loss of selectivity for the selective hydrogenation of diolefins relative to the hydrogenation of olefins is initiated. Thus, there exists an optimum between the amount of NiMoS and NiS phases introduced on the catalyst and the specific surface area of ​​said catalyst, which, when met, leads to the obtaining of an optimal catalyst for thioetherification and de-dienation.

[0046] In addition, the volume of pores of the catalyst having a diameter of more than 0.05 μm, as measured by mercury porosimetry, is preferably from 5 to 50% of the total pore volume, preferably from 10 to 40% of the total pore volume.

[0047] The volume of pores in the catalyst having a diameter of more than 0.1 μm is preferably 5 to 35% of the total pore volume, more preferably 10 to 30% of the total pore volume. This pore distribution has been significantly observed by the inventors to make it possible to limit the formation of gum in the catalyst.

[0048] (Carrier) The porous supports that can be used in the context of the present invention comprise alumina, preferably chosen from the following aluminas: gamma-, delta-, theta-, eta-, rho-, chi-, kappa-alumina, used alone or in mixtures. Preferably, the porous supports are based on eta-, theta-, delta-, chi-alumina, used alone or in mixtures. When the porous support also comprises nickel aluminate, the process for preparing said support is advantageously carried out by dry impregnation of the alumina with gamma-alumina.

[0049] In one embodiment of the present invention, the porous support also contains nickel aluminate of the NiAl2O4 type. The presence of spinel in the catalyst of the present invention is measured by temperature-programmed reduction (TPR), for example, as described in Oil & Gas Science and Technology, Rev. IFP, Vol. 64 (2009), No. 1, pp. 11-12. According to this technique, the catalyst is heated in a flow of a reducing agent, for example, a flow of dihydrogen. Measuring the dihydrogen consumption as a function of temperature provides quantitative information about the reducibility of the species present. The presence of spinel in the catalyst is therefore indicated by the consumption of dihydrogen at temperatures above around 800°C.

[0050] When the porous support comprises nickel aluminate, the nickel content in said support, measured in oxide form, is advantageously between 0.5 and 10% by weight, preferably between 0.7 and 8% by weight and even more preferentially between 1 and 5% by weight relative to the total weight of the catalyst.

[0051] When the porous support comprises nickel aluminate, the molar ratio between the nickel of the porous support and the molybdenum of the active phase is advantageously between 0.5 and 1.5 mol / mol, preferably between 0.7 and 1.5 mol / mol, and even more preferentially between 0.8 and 1.5 mol / mol. Without wishing to be bound by any theory, optimizing the nickel aluminate content relative to the molybdenum content will allow a better dispersion of the active phase, which will result in improved catalytic performance.

[0052] When the porous support comprises nickel aluminate, the molar ratio between the nickel of the porous support and said nickel of the active phase is advantageously between 0.3 and 0.7 mol / mol, more preferentially between 0.5 and 0.7 mol / mol.

[0053] Preferably, the total pore volume of the porous support is 0.3 to 0.7 cm as measured by mercury porosimetry. 3 / g, preferentially 0.35-0.65 cm 3 / g.

[0054] In addition, the volume of pores in the porous support having a diameter of more than 0.05 μm, as measured by mercury porosimetry, is preferably 5 to 50% of the total pore volume, more preferably 10 to 40% of the total pore volume.

[0055] In the porous support, the volume of pores having a diameter of more than 0.1 μm is preferably 5 to 35% of the total pore volume, and more preferably 5 to 30% of the total pore volume.

[0056] The volume of pores in the porous support having a diameter of 0.004 to 0.009 μm preferably corresponds to 5 to 12% of the total pore volume, and more preferably 8 to 10% of the total pore volume.

[0057] The specific surface area of ​​the support is preferably 300 m 2 / g, preferably less than 260m 2 / g, preferably less than 220m 2 / g, and even more preferably less than 200m 2 / g, and even more preferably less than 120m 2 / g~190m 2 / g, more preferentially 120-180m 2 / g, more preferentially 120-170m 2 / g, and even more preferentially 120-160m 2 / g.

[0058] (Synthesis of nickel aluminate-based supports (optional)) Supports that can be used in the context of the present invention include aluminas, preferably selected from the following aluminas: gamma-, delta-, theta-, eta-, rho-, chi-, kappa-alumina, used alone or in mixtures. Preferably, the porous support is based on eta-, theta-, delta-, chi-alumina, used alone or in mixtures.

[0059] When the porous support also comprises nickel aluminate, the preparation of said support is advantageously carried out by dry impregnation of an alumina as described above, preferably comprising gamma-alumina, with an aqueous solution containing a suitable amount of metal nitrate, such as nickel nitrate, which corresponds to a metal content (oxide equivalent, NiO) of 0.5 to 10% by weight, preferably 0.7 to 8% by weight, and even more preferably 1 to 5% by weight, relative to the total weight of the catalyst, on the solid.

[0060] After impregnation, the solid is left to age at a temperature below 50°C, preferably at ambient temperature, for 0.5 to 24 hours, preferably 0.5 to 12 hours, and then dried advantageously at a temperature of 50 to 200°C, preferably 70 to 180°C, advantageously for a period of 1 to 48 hours, preferably 2 to 12 hours. Finally, the solid is calcined under a stream of dry or moist air, preferably moist air, at a temperature of 500 to 1100°C, preferably 600 to 900°C, advantageously for a period of 1 to 12 hours, preferably 2 to 8 hours. This calcination makes it possible to form nickel aluminate. The solid obtained will hereinafter be referred to by the term AlNi.

[0061] (Catalyst Preparation) The catalyst according to the invention can be prepared by any technique known to those skilled in the art, in particular by impregnation of nickel and molybdenum on the selected support, which can be carried out, for example, by methods known to those skilled in the art under the term dry impregnation, in which the exact amount of the desired element in the form of a soluble salt is introduced into a chosen solvent, for example demineralized water, so that the porosity of the support is filled as closely as possible.

[0062] The nickel-based precursor of the active phase and the molybdenum precursor of the active phase can be introduced simultaneously or successively. The impregnation of each precursor can advantageously be carried out at least twice. Different precursors can therefore advantageously be impregnated successively with different impregnation and aging times. One of the precursors can be impregnated several times. The support thus filled with the solution is left to age at a temperature below 50°C, preferably at ambient temperature, for a period of 0.5 to 12 hours, preferably 0.5 to 6 hours, and even more preferentially 0.5 to 3 hours.

[0063] Following the introduction of nickel and molybdenum, the support is subjected to an activation treatment, the purpose of which is generally to convert the molecular precursors of the elements into oxide phases. In this case, the treatment is an oxidation treatment, although simple drying of the catalyst can also be performed.

[0064] In the case of drying, the catalyst precursor is dried at a temperature of 50 to 200° C., preferably 70 to 180° C., typically for a period of 0.5 to 12 hours, even more preferably for a period of 0.5 to 5 hours.

[0065] In the case of the oxidation treatment (also called calcination), the treatment is generally carried out under air or diluted oxygen at a treatment temperature generally between 200°C and 550°C, preferably between 300°C and 500°C, advantageously for a period of typically between 0.5 and 24 hours, preferably between 0.5 and 12 hours, and even more preferably between 0.5 and 10 hours. Salts of molybdenum and nickel metals that can be used in the catalyst preparation method are, for example, nickel nitrate and ammonium heptamolybdate. Any other salt known to those skilled in the art that has sufficient solubility and can be decomposed during the activation treatment can also be used. Advantageously, both drying and oxidation treatment are carried out during the catalyst preparation method.

[0066] In one embodiment, the catalyst according to the present invention is prepared by the following steps: a) contacting the support with an aqueous or organic solution containing at least one nickel salt; b) allowing the support impregnated at the end of step a) to age at a temperature below 50°C, preferably at ambient temperature, for a period of between 0.5 hours and 24 hours, preferably between 0.5 hours and 12 hours; c) drying the impregnated and aged support obtained at the end of step b) at a temperature between 50°C and 200°C, preferably between 70°C and 180°C, advantageously for a period of 1 to 48 hours, preferably 2 to 12 hours; d) calcining the solid obtained in step c) at a temperature between 500°C and 1000°C, preferably between 600 and 900°C, advantageously for a period of 1 to 12 hours, preferably between 2 and 12 hours, to obtain a spinel of NiAl2O4 type; e) performing the following sub-steps: i) a substep of contacting the solid obtained at the end of step d) with a solution containing a precursor of at least one active phase of nickel, followed by static aging of the catalyst precursor at a temperature below 50°C, preferably at ambient temperature, for a period of between 0.5 and 12 hours, preferably between 0.5 and 6 hours, and even more preferentially between 0.5 and 3 hours; ii) a substep of contacting the solid obtained at the end of step d) with a solution containing a precursor of at least one active phase of molybdenum, followed by static maturation of the catalyst precursor at a temperature below 50°C, preferably at ambient temperature, for a period of between 0.5 and 12 hours, preferably between 0.5 and 6 hours, and even more preferentially between 0.5 and 3 hours; Sub-steps i) and ii) are carried out separately, in any order, or simultaneously; f) drying the catalyst precursor obtained in step e) at a temperature of 50°C to 200°C, preferably 70 to 180°C, typically for a period of 0.5 to 12 hours, even more preferably for a period of 0.5 to 5 hours; g) optionally calcining the catalyst precursor obtained in step f) at a temperature between 200°C and 550°C, preferably between 300 and 500°C, advantageously for a period of between 0.5 and 24 hours, preferably for a period of between 0.5 and 12 hours, even more preferably for a period of between 0.5 and 10 hours.

[0067] (Catalyst sulfurization) Before contacting the feedstock to be treated, the catalyst undergoes a sulfurization step. Sulfurization is carried out in a sulfur-reducing medium, i.e., in the presence of HS and hydrogen, to convert metal oxides to sulfides, such as MoS and NiS. Sulfurization is carried out by injecting onto the catalyst a stream containing HS and hydrogen, or alternatively, a stream containing other sulfur compounds capable of decomposing in the presence of the catalyst and hydrogen to give HS. Polysulfides, such as dimethyl disulfide, are commonly used HS precursors for sulfurizing catalysts. The temperature is adjusted so that HS reacts with the metal oxides to form metal sulfides. This sulfurization can be carried out in situ in the hydrotreating reactor or ex situ (inside or outside the reactor) at temperatures between 200 and 600°C, more preferentially between 250 and 500°C. To be active, the metals must be substantially sulfurized. A metal is considered to be substantially sulfided when the molar ratio of sulfur (S) to said element present on the catalyst is at least equal to 50% of the theoretical molar ratio corresponding to complete sulfidation of the element under consideration. The total sulfidity is defined by the following formula:

[0068]

number

[0069] During the ceremony: (S / element) catalyst is the molar ratio between sulfur (S) and the elements present on the catalyst, excluding metals (Ni or Co) present in the form of aluminates. (S / element) theoreticalis the molar ratio between sulfur and the element corresponding to the total sulfidation of the element giving the sulfide.

[0070] This theoretical molar ratio varies depending on the elements under consideration: - (S / Fe) theoretical =1 - (S / Co) theoretical =8 / 9 - (S / Ni) theoretical =1 / 1 - (S / Mo) theoretical =2 / 1 - (S / W) theoretical =2 / 1

[0071] Since the catalyst contains several types of metals, the molar ratio of S to the combined elements present on the catalyst must also be at least equal to 50% of the theoretical molar ratio corresponding to the complete sulfidation of each element to give the sulfide, this calculation being made according to the relative mole fraction of each element, except for the metal involved during the preparation of the support (Ni or Co).

[0072] For example, for a catalyst containing molybdenum and nickel in mole fractions of 0.7 and 0.3, respectively, the minimum molar ratio (S / Mo+Ni) is given by the following relationship:

[0073]

number

[0074] Highly preferably, the sulfidity of the metal will be greater than 70%.

[0075] The sulfurization is carried out on the metal in the oxide form without a prior metal reduction step, and in fact, the sulfurization of reduced metals is known to be more difficult than the sulfurization of metals in the oxide form.

[0076] (Selective hydrogenation method) The present invention also relates to a method for treating gasoline containing sulfur compounds of any type of chemical family, especially diolefins, monoolefins, and sulfur compounds in the form of thiols and light sulfides. The present invention finds particular application in the conversion of converted gasoline, especially gasoline derived from catalytic cracking, fluid catalytic cracking (FCC), coking, visbreaking, or thermal cracking processes. The feedstock to which the present invention is applicable has a boiling point between 0°C and 280°C. The feedstock may also contain hydrocarbons with 3 or 4 carbon atoms.

[0077] For example, gasoline derived from a catalytic cracking (FCC) unit contains, on average, 0.5% to 5% by weight of diolefins, 20% to 50% by weight of monoolefins, 10 ppm to 0.5% by weight of sulfur, and generally less than 300 ppm by weight of thiols, which are generally concentrated in the light fractions of gasoline, more particularly in the fractions boiling below 120°C.

[0078] The gasoline treatment described in this selective hydrogenation process mainly consists of: - selective hydrogenation of diolefins to monoolefins; - conversion of saturated light sulfur compounds, mainly thiols, into heavier sulfides or thiols by reaction with monoolefins; - isomerizing monoolefinic compounds with the C=C double bond in the external position to those isomers with the C=C double bond in the internal position.

[0079] The hydrogenation reaction of diolefins to monoolefins is exemplified below by the conversion of 1,3-pentadiene, an unstable compound that can easily be hydrogenated to 2-pentene. However, in the following example, it is desired to limit the side reaction of the hydrogenation of monoolefins, which would lead to the formation of n-pentane and thus to a drop in the octane number.

[0080] [ka]

[0081] The sulfur compounds to be converted are primarily thiols. The main reaction for converting thiols consists of the thioetherification reaction between monoolefins and thiols. This reaction is exemplified below by the addition of propane-2-thiol to 2-pentene to form pentyl sulfide.

[0082] [ka]

[0083] In the presence of hydrogen, the conversion of sulfur compounds can also go through the intermediate formation of H2S, which can then add to unsaturated compounds present in the feedstock, however, this route is in the minority under suitable reaction conditions.

[0084] In addition to thiols, compounds that are prone to be converted in this way and to heavier forms are sulfides, primarily CS2, COS, thiophanes and methylthiophanes.

[0085] In some cases it is possible to observe reactions in which the molecular weight of light nitrogen compounds, mainly nitriles, pyrroles and their derivatives, is increased.

[0086] According to the invention, the catalyst also makes it possible to carry out the isomerization of monoolefinic compounds having a C=C double bond in the external position to their isomers having a C=C double bond in the internal position.

[0087] This reaction is exemplified below by the isomerization of 1-hexene to 2-hexene or 3-hexene:

[0088] [ka]

[0089] In the selective hydrogenation process according to the present invention, the feedstock to be treated is mixed with hydrogen before being brought into contact with the catalyst. The amount of hydrogen injected is such that the molar ratio between hydrogen and the diolefins to be hydrogenated is greater than 1 (stoichiometric) and less than 10, preferably 1 to 5 mol / mol. If an excessive amount of hydrogen is present, the hydrogenation of monoolefins becomes strong, resulting in a decrease in the octane number of gasoline. When the process is carried out in a fixed bed, the entire feedstock is generally injected into the inlet of the reactor. However, in certain cases, it may be advantageous to inject part or all of the feedstock between two consecutive catalyst beds placed in the reactor. This embodiment makes it possible to continue operating the reactor even if the inlet of the reactor is blocked by deposits of polymers, particles, or gums present in the feedstock.

[0090] The temperature at which the mixture of gasoline and hydrogen is brought into contact with the catalyst is 80°C to 220°C, preferably 90°C to 200°C, and the associated liquid hourly space velocity (LHSV) is 1h -1 ~10h -1 where the liquid hourly space velocity is the volume (liters) of feedstock per volume (liters) of catalyst per hour (L / L·h). The pressure is adjusted so that the reaction mixture is mainly in liquid form in the reactor. The pressure is 0.5 MPa to 5 MPa, preferably 1 to 4 MPa.

[0091] The gasoline processed under the above conditions has a reduced content of diolefins and thiols. Generally, the resulting gasoline contains less than 1 wt. % of diolefins, preferably less than 0.5 wt. % of diolefins. Light sulfur compounds with boiling points lower than the boiling point of thiophene (84°C) are generally converted by more than 50%. Therefore, it is possible to separate the light fraction from gasoline by distillation and send this fraction directly to the gasoline pool without further treatment. The end point of the light fraction of gasoline is generally below 120°C, preferably below 100°C, and most preferably below 80°C.

[0092] The selective hydrogenation process according to the invention is particularly suitable to be carried out in connection with the desulfurization process described in patent application EP 1 077 247.

[0093] The subject of the present invention is also a process for desulfurizing gasoline containing sulfur compounds, comprising at least the following steps: a) selective hydrogenation step; carrying out the above method; b) a step of separating the gasoline obtained in step a) into at least two fractions, each of which contains at least one light gasoline and at least one heavy gasoline; c) a hydrodesulfurization step of the heavy gasoline separated in step b) over a catalyst making it possible to decompose the sulfur compounds at least partially into H2S.

[0094] The separation step b) is preferably carried out by means of a conventional distillation column, also called a splitter, which must be able to separate a light fraction of the gasoline containing a small amount of sulfur from a heavy fraction which preferably contains most of the sulfur originally present in the initial gasoline.

[0095] The column generally operates at a pressure of 0.1 to 2 MPa, preferably 0.2 to 1 MPa. The number of theoretical plates in the separation column is generally 10 to 100, preferably 20 to 60. The reflux ratio, expressed as the ratio of the liquid flow rate in the column divided by the distillate flow rate, expressed in kg / h, is generally less than 1, preferably less than 0.8.

[0096] The light gasoline obtained at the end of the separation generally contains at least all of the C5 olefins, preferably C5 compounds, and a minimum of 20% of the C6 olefins. The sulfur content of this light fraction is generally low, i.e., it is generally not necessary to treat this light fraction before using it as a fuel.

[0097] The desulfurization step c) is preferably a hydrodesulfurization step, which is carried out by passing heavy gasoline over a hydrodesulfurization catalyst containing at least one Group VIII element and / or at least one Group VIB element, at least partially in the form of a sulfide, in the presence of hydrogen at a temperature of about 210°C to about 350°C, preferably 220°C to 320°C, and at a pressure of generally about 1 to about 4 MPa, preferably 1.5 to 3 MPa. The liquid hourly space velocity (expressed as volume of liquid per hour and volume of catalyst) is about 1 to about 20 h -1 , preferably 1 to 10 hours -1 , very preferably 3 to 8 hours -1 The H2 / feedstock ratio is 100-600 NL / L, preferentially 300-600 NL / L.

[0098] The content of Group VIII metals, expressed as oxides, is generally 0.5 to 15% by weight, preferentially 1 to 10% by weight, relative to the weight of the hydrodesulfurization catalyst, and the content of Group VIB metals, expressed as oxides, is generally 1.5 to 60% by weight, preferentially 3 to 50% by weight, relative to the weight of the hydrodesulfurization catalyst.

[0099] The Group VIII element, if present, is preferably cobalt, and the Group VIB element, if present, is generally molybdenum or tungsten. Combinations such as cobalt-molybdenum are preferred. The support of the catalyst is usually a porous solid, such as alumina, silica-alumina, or other porous solids, such as magnesia, silica, or titanium oxide, used alone or in a mixture with alumina or silica-alumina. In order to minimize the hydrogenation of olefins present in heavy gasoline, it is advantageous to preferentially use catalysts in which the density of the Group VIB metal, expressed as the weight percent of the Group VIB metal in the form of oxide per unit of specific surface area (weight percent expressed relative to the total weight of the catalyst), is greater than 0.07, preferably greater than 0.12. The catalyst according to step c) preferably has a specific surface area of ​​250 m 2 / g, more preferably less than 230m 2 / g, very preferably less than 190m 2 / g.

[0100] The deposition of metals on the support can be achieved by any method known to those skilled in the art, such as dry impregnation, using an excess solution containing the metal precursor. The impregnation solution is selected so as to be able to dissolve the metal precursor at the desired concentration. For example, in the synthesis of a CoMo catalyst, the molybdenum precursor can be molybdenum oxide or ammonium heptamolybdate, while the cobalt precursor can be, for example, cobalt nitrate, cobalt hydroxide, or cobalt carbonate. The precursors are generally dissolved in a medium that allows solubilization at the desired concentration.

[0101] After the introduction of the element(s) and optional shaping of the catalyst, the catalyst is activated in a first step. This activation can correspond either to oxidation followed by reduction, or to direct reduction, or to a calcination treatment alone. The calcination step is generally carried out in a stream of air at a temperature ranging from about 100 to about 600°C, preferably from 200 to 450°C. The reduction step is carried out under conditions making it possible to convert at least a portion of the base metal in oxidized form into metal. Generally, it consists of treating the catalyst in a stream of hydrogen, preferably at a temperature at least equal to 300°C. The reduction can also be carried out in part by means of chemical reducing agents.

[0102] The catalyst is preferably used at least partially in its sulfurized form. The introduction of sulfur can be carried out before or after any activation step, i.e., calcination or reduction step. Sulfur or sulfur compounds can be introduced ex situ, i.e., outside the reactor in which the process according to the invention is carried out, or in situ, i.e., into the reactor used in the process according to the invention. In the former case, these ex situ sulfurizations are characterized by a final passivation step. In fact, the sulfide phase has a very high reactivity with ambient air (oxidative self-heating), which prevents subsequent handling without additional treatments aimed at limiting this reactivity. Among commercial ex situ sulfurization procedures, mention may be made of the Totsucat® process from Eurecat (EP 0 564 317 B1 and EP 0 707 890 B1) and the XpresS® process from Tricat (Patent US-A-5 958 816). In the latter case (in situ sulfiding), the catalyst is preferably reduced under the conditions described above and then sulfided by passing a feed containing at least one sulfur compound through it, which, upon decomposition, leads to the fixation of sulfur on the catalyst. This feed may be in gaseous or liquid form, for example hydrogen containing H2S, or a liquid containing at least one sulfur compound.

[0103] Preferably, the sulfur compound is added to the catalyst ex situ. For example, after the calcination step, the sulfur compound can be introduced onto the catalyst, optionally in the presence of another compound. The catalyst is subsequently dried and then transferred to a reactor that serves to carry out the process according to the invention. In this reactor, the catalyst is then treated under hydrogen to convert at least a portion of the main metals into sulfides. Particularly suitable procedures for use in the present invention are those described in patents FR-B-2 708 596 and FR-B-2 708 597.

[0104] (Example) The present invention will now be described through the following examples, which should not be construed as limiting the scope of the invention.

[0105] Example 1: Preparation of catalysts A, D and F (not in accordance with the invention) and catalysts B, C and E (in accordance with the invention) The characteristics of the supports used to prepare the catalysts are shown in Table 1. The preparation of the support containing nickel aluminate is carried out by dry impregnation of alumina Al-2 with an aqueous solution of nickel nitrate. The volume of the aqueous solution is equal to the water uptake volume (total volume of water that can penetrate into the porosity) corresponding to the mass of the support to be impregnated. In this case, the amount of nickel nitrate impregnated corresponds to a nickel content (or oxide equivalent NiO content) of 4.65% by weight, based on the solid. After impregnation, the solid is left to age at ambient temperature for 12 hours and then dried in a ventilated oven at 120°C for 2 hours. Finally, the solid is calcined in a muffle furnace at 750°C for 2 hours; this solid will hereafter be referred to as AlNi.

[0106] [Table 1]

[0107] Catalysts A and B are prepared by dry impregnation of support AI-1. When the Ni / Mo molar ratio exceeds 3 and the molybdenum content exceeds 4% by weight, it is difficult to dissolve the seeds and prepare the impregnation solution. Catalyst C is prepared by dry impregnation of support AI-2. Catalysts D, E, and F are prepared by dry impregnation of AlNi supports. The synthesis procedure involves dry impregnation with a solution of ammonium heptamolybdate and nickel nitrate. The volume of the aqueous solution containing the metal precursors is equal to the water uptake volume corresponding to the mass of the support to be impregnated (the total volume of water can penetrate into the porosity). The concentration of the precursors in the solution is adjusted to achieve the desired weight content of metal oxide on the support. The solid is then left to age at ambient temperature for 6 hours and then dried in a ventilated oven at 120 °C for 2 hours. Finally, the solid is calcined in a flow-through fixed-bed reactor at 450° C. for 2 hours under air flow at a rate of 1 L / g / h. The characteristics of the catalyst thus prepared are shown in Table 2.

[0108] [Table 2]

[0109] Example 2: Evaluation of Catalysts A, B, and C The activity of catalysts A, B, and C was evaluated by a test for the selective hydrogenation of a mixture of model molecules in a 500 mL stirred autoclave reactor. Three grams of catalyst were sulfided at atmospheric pressure in a sulfidation bench under an H2S / H2 mixture consisting of 15% by volume of H2S at 1 L / g h of catalyst for 2 hours at 350 °C. The sulfided catalyst was then transferred to a reactor in the absence of air and contacted with 250 mL of model feedstock at a total pressure of 1.5 MPa and a temperature of 130 °C. The pressure was maintained constant throughout the test by feeding hydrogen.

[0110] The feedstock used in the activity tests had the following composition: 1000 ppm by weight of sulfur in the form of 3-methylthiophene, 500 ppm by weight of sulfur in the form of 2-propanethiol, 10% by weight of olefins in the form of 1-hexene, and 1% by weight of diolefins in the form of isoprene in n-heptane.

[0111] The time t=0 of the test corresponds to the contact of the catalyst and the feedstock. The duration of the test is set to 200 min, and the gas chromatographic analysis of the liquid effluent obtained makes it possible to evaluate the activity of the different catalysts in the hydrogenation of isoprene (formation of methylbutenes), 1-hexene (formation of n-hexane) and in the increase in the molecular weight of light thiols (conversion of 2-propanethiol).

[0112] The activity of the catalyst for each reaction is specified relative to the rate constant obtained for each reaction normalized per gram of catalyst. Rate constants are calculated assuming first order for the reaction. These activities are normalized to 100% of catalyst A.

[0113] The selectivity of a catalyst for the hydrogenation of isoprene is equal to the ratio of the activity of the catalyst in the hydrogenation of isoprene and 1-hexene: A(isoprene) / A(1-hexene). The selectivity is normalized to 100% for catalyst A according to the invention.

[0114] The results obtained for the various catalysts are reported in Table 3 below. ●

[0115] [Table 3]

[0116] Catalysts B and C in accordance with the present invention have better activity and better selectivity for the hydrogenation of diolefins, while at the same time enabling at least equally good, or even better, conversion of light sulfur compounds, compared to Catalyst A, which is not in accordance with the present invention. Furthermore, Catalyst B exhibits better activity and selectivity for selective hydrogenation and better results for the conversion of light sulfur compounds, compared to Catalyst C.

[0117] Example 3: Evaluation of Catalysts D, E and F The activities of catalysts D, E and F are evaluated under the test conditions described in Example 2.

[0118] The activity of the catalyst for each reaction is specified relative to the rate constant obtained for each reaction normalized per gram of catalyst. The rate constants are calculated assuming first order for the reaction. These activities are normalized to 100% for catalyst D.

[0119] The selectivity of the catalyst for the hydrogenation of isoprene is equal to the ratio of the activity of the catalyst in the hydrogenation of isoprene and 1-hexene: A(isoprene) / A(1-hexene). The selectivity is normalized to 100% for catalyst D according to the invention.

[0120] The results obtained for the various catalysts are reported in Table 4 below.

[0121] [Table 4]

[0122] Catalyst E in accordance with the present invention has better activity and better selectivity for the hydrogenation of diolefins compared to catalysts D and F not in accordance with the present invention, while allowing at least as good, or even better, conversion of light sulfur compounds.

Claims

1. A process for selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds, comprising contacting gasoline and hydrogen with a catalyst comprising an active phase based on nickel and molybdenum and a porous support made of alumina and / or nickel aluminate, the catalyst being in the form of a sulfide, the catalyst being characterized in that the molar ratio between nickel and molybdenum is greater than 2.5 mol / mol and less than 3.0 mol / mol, the temperature during contact being between 80°C and 220°C, and the liquid hourly space velocity being less than 1 h －１ ~10 hours －１ wherein the pressure is between 0.5 and 5 MPa and the molar ratio between hydrogen and the diolefin to be hydrogenated is greater than 1 mol / mol and less than 10 mol / mol.

2. 2. The method of claim 1, wherein the gasoline is a fluid catalytic cracking (FCC) gasoline and has a boiling point between 0°C and 280°C.

3. The specific surface area of ​​the catalyst is 200 m 2 3. The method according to claim 1, wherein the solubility is less than 1 / g.

4. 4. The process according to claim 1, wherein the nickel content of the active phase, measured in the form of the oxide, is between 1 and 20% by weight relative to the total weight of the catalyst.

5. 5. The process according to claim 1, wherein the molybdenum content of the active phase, measured in the form of oxide, is between 1 and 12% by weight relative to the total weight of the catalyst.

6. 6. The method according to claim 1, wherein the porous support is made of alumina and nickel aluminate.

7. 7. The process according to claim 6, wherein the molar ratio between the nickel of the porous support and the molybdenum of the active phase is between 0.5 and 1.5 mol / mol.

8. 8. The method according to claim 6, wherein the molar ratio between the nickel of the porous support and the nickel of the active phase is between 0.3 and 0.7 mol / mol.

9. 9. A process according to claim 6, wherein the content of nickel in the support, measured in the form of the oxide, is between 0.5 and 10% by weight relative to the total weight of the catalyst.

10. 10. The process according to claim 1, wherein the nickel content of the active phase, measured in the form of the oxide, is between 1 and 12% by weight relative to the total weight of the catalyst.

11. The specific surface area of ​​the catalyst is 120 to 160 m 2 The method according to any one of claims 1 to 10, wherein the hydroxyl group is 0.15 to 0.25g.

12. 12. A method according to claim 1, wherein the sulphidity of the metal of the active phase is at least equal to 50%.

13. The total pore volume of the catalyst is 0.3 to 0.7 cm ３ 13. The method according to claim 1, wherein the hydroxyl group is 0.15 or 1.

0.

14. 1. A method for desulfurizing gasoline containing sulfur compounds, comprising the steps of: a) a step of selective hydrogenation; carrying out the method according to any one of claims 1 to 13; b) separating the gasoline obtained in step a) into at least two fractions, each of said fractions comprising at least one light gasoline and at least one heavy gasoline; c) Sulfur compounds are converted to H ２ 2. A step for hydrodesulfurization of the heavy gasoline separated in step b) over a catalyst capable of at least partially decomposing it into S.

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