Selective hydrogenation catalyst containing a specific support in the form of aluminate

Abstract

Hydrotreating catalyst, which comprises an active phase containing at least one Group VIB metal and at least one Group VIII metal and a porous support containing alumina and at least one spinel MAl2O4, where M is selected from nickel and cobalt, characterized in that: - the molar ratio (r1) between the Group VIII metal and the Group VIB metal of the active phase is 1.0 - 3.0 mol / mol; - the molar ratio (r2) between the metal M of the porous support and the Group VIII metal of the active phase is 0.3 - 0.7 mol / mol; - the molar ratio (r3) between the sum of the contents of the metal M and the Group VIII metal and the content of the Group VIB metal is 2.2 - 3.0 mol / mol.

Description

Background Art

[0002] Producing gasoline that meets new environmental standards requires a significant reduction in its sulfur content to a value that generally does not exceed 50 ppm, preferably less than 10 ppm.

[0003] In addition, it is known that converted gasoline, more particularly converted gasoline resulting from catalytic cracking (which can account for 30% - 50% of the gasoline pool), has a high content of monoolefins and sulfur.

[0004] For this reason, nearly 90% of the sulfur present in gasoline is attributed to gasoline produced by the catalytic cracking process, which is hereinafter referred to as FCC (fluid catalytic cracking) gasoline. Thus, FCC gasoline constitutes a preferred feedstock for the process of the present invention. More generally, the process according to the present invention can be applied to any gasoline fraction containing a certain proportion of diolefins, and the gasoline fraction can also contain some lighter compounds belonging to the C3 and C4 fractions.

[0005] Gasoline from the cracking unit is usually rich in olefins and sulfur, but also rich in diolefins. For gasoline from catalytic cracking, the content of diolefins can be as high as 5 wt%. Diolefins are unstable compounds that can easily polymerize and generally must be removed before any treatment of these gasolines (such as hydrodesulfurization treatment aimed at meeting the sulfur content specification in gasoline). However, this hydrogenation must be selective for diolefins and must limit the hydrogenation of olefins to limit hydrogen consumption and the loss of octane number in gasoline. In addition, as described in patent application EP01077247 A1, it is advantageous to convert mercaptans by increasing the molecular weight before the desulfurization step, because this can produce a desulfurized gasoline fraction mainly composed of olefins with 5 carbon atoms by simple distillation without loss of octane number. After selective hydrogenation and an increase in the molecular weight of light sulfur-containing compounds, the amount of sulfur present in the feedstock does not change; only the nature of the sulfur changes due to the increase in the molecular weight of mercaptans.

[0006] In addition, the diolefin compounds present in the feedstock to be treated are unstable and tend to form gums by polymerization. This gum formation causes the gradual inactivation of the downstream hydrodesulfurization catalyst or the gradual blockage of the reactor. Therefore, for industrial applications, it is important to use a catalyst that limits polymer formation, that is, a catalyst with low acidity or whose porosity is optimized to promote the continuous extraction of polymers or gum precursors by the hydrocarbons in the feedstock to ensure the maximum cycle time of the catalyst.

[0007] The applicant's patent FR 2118309 proposed a method for preparing a catalyst on a support, the catalyst comprising at least one metal of Group VIB and at least one metal of Group VIII deposited on a specific support, the specific support comprising a metal aluminate of the MAl2O4 type, where the metal M is selected from nickel and cobalt.

[0008] Patent US2005 / 014639 proposes a method for preparing a catalyst on a support, said catalyst comprising at least one Group VIB metal and at least one Group VIII non-noble metal successively deposited on a specific support comprising a metal aluminate of the MAl2O4 type, wherein the metal M is selected from Group VIII metals.

[0009] The patent FR 2895415 of the present applicant proposes a selective hydrogenation method using a catalyst with a specific support. This method uses a catalyst on a support, said catalyst comprising at least one Group VIB metal and at least one Group VIII non-noble metal deposited on a specific support in a sulfided form, said specific support comprising a metal aluminate of the MAl2O4 type, wherein the metal M is selected from nickel and cobalt.

[0010] The patent FR 2935389 of the present applicant proposes a selective hydrogenation method using a sulfur-containing catalyst with a specific composition. This catalyst comprises at least one Group VIB metal and at least one Group VIII metal supported on alumina, wherein the content of the Group VIB metal oxide is 4 wt%-20 wt% relative to the total weight of the catalyst, the content of the Group VIII metal oxide is less than 15 wt% relative to the total weight of the catalyst, the molar ratio of the Group VIII metal to the Group VIB metal is 0.6 - 3.0 mol / mol, and the catalyst has a total pore volume of 0.4 - 1.4 cm 3 / g.

[0011] According to the solutions described in the literature, the present invention proposes a novel catalyst with a specific support, which can selectively hydrogenate polyunsaturated compounds, more particularly dienes, and can also increase the molecular weight of light sulfur-containing compounds, more particularly mercaptans.

[0012] Subject matter of the invention

[0013] The present invention relates to a hydrotreating catalyst, which comprises an active phase containing at least one Group VIB metal and at least one Group VIII metal and a porous support containing alumina and at least one spinel MAl2O4, wherein M is selected from nickel and cobalt, and is characterized in that:

[0014] - The molar ratio (r1) between the Group VIII metal of the active phase and the Group VIB metal of the active phase is 1.0 - 3.0 mol / mol;

[0015] - The molar ratio (r2) between the metal M of the porous support and the Group VIII metal of the active phase is 0.3 - 0.7 mol / mol;

[0016] - The molar ratio (r3) between the sum of the contents of metal M and the Group VIII metal of the active phase and the content of the Group VIB metal of the active phase is 2.2 - 3.0 mol / mol.

[0017] The Applicant has actually surprisingly found that a catalyst based on at least one Group VIII metal and at least one Group VIB metal deposited on a specific support has better activity and better selectivity in the hydrogenation of diolefins via a synergistic effect, while allowing light sulfur-containing compounds to be converted at least as well or even better than the catalysts disclosed in the prior art. The specific support at least partially contains nickel aluminate or cobalt aluminate and has a specific ratio between these different metals.

[0018] Without wishing to be bound by any theory, optimizing the content of metal M aluminate relative to the content of the Group VIB metal will allow for better dispersion of the active phase, resulting in improved catalytic performance. The presence of aluminate in a given amount can also limit or prevent the migration of the Group VIII metal within the porous support containing alumina during the activation stage of the catalyst before sulfidation, thereby maintaining the ratio between the Group VIII metal and the Group VIB metal optimally on the catalyst surface.

[0019] Advantageously, the molar ratio (r4) between the metal M of the porous support and the Group VIB metal of the active phase is 0.5 - 1.5 mol / mol.

[0020] Advantageously, the molar ratio (r4) is 0.7 - 1.5 mol / mol.

[0021] Advantageously, the content of the Group VIII metal of the active phase measured in oxide form is 1 - 20 wt% relative to the total weight of the catalyst.

[0022] Advantageously, the content of the Group VIB metal of the active phase measured in oxide form is 1 - 12 wt% relative to the total weight of the catalyst.

[0023] Advantageously, the content of metal M measured in oxide form is 0.5 - 10 wt% relative to the total weight of the catalyst.

[0024] Advantageously, the specific surface area of the catalyst is 110 - 190 m² / g.

[0025] Advantageously, the degree of sulfidation of the metals of the active phase is at least equal to 50%.

[0026] Preferably, the molar ratio (r3) is 2.3 - 3.0 mol / mol.

[0027] Preferably, the Group VIII metal is nickel and the Group VIB metal is molybdenum.

[0028] Preferably, the metal M is nickel.

[0029] Another subject according to the present invention relates to a method for preparing the catalyst according to the present invention, which comprises the following steps:

[0030] a) contacting a support with an aqueous or organic solution containing a salt of at least one metal M selected from nickel and cobalt;

[0031] b) aging the impregnated support at a temperature below 50 °C for a period of 0.5 hour to 24 hours at the end of step a);

[0032] c) drying the aged and impregnated support obtained at the end of step b) at a temperature of 50 °C to 200 °C;

[0033] d) calcining the solid obtained in step c) at a temperature of 500 °C to 1000 °C to obtain a spinel of the MAl2O4 type;

[0034] e) performing the following sub-steps:

[0035] i) contacting the solid obtained at the end of step d) with a solution containing at least one metal active phase precursor based on a Group VIII metal, and then aging the catalyst precursor at a temperature below 50 °C, preferably at ambient temperature, for a period of 0.5 hour to 12 hours, preferably 0.5 hour to 6 hours, more preferably 0.5 to 3 hours;

[0036] ii) contacting the solid obtained at the end of step d) with a solution containing at least one metal active phase precursor based on a Group VIB metal, and then aging the catalyst precursor at a temperature below 50 °C, preferably at ambient temperature, for a period of 0.5 hour to 12 hours, preferably 0.5 hour to 6 hours, more preferably 0.5 to 3 hours;

[0037] Step i) and step ii) are carried out separately or simultaneously in any order;

[0038] f) drying the catalyst precursor obtained in step e) at a temperature of 50 °C to 200 °C, preferably 70 °C to 180 °C, for a period generally of 0.5 to 12 hours, even more preferably 0.5 to 5 hours.

[0039] In one embodiment according to the present invention, the method further comprises step g), wherein the catalyst precursor obtained in step f) is calcined at a temperature of 200 °C to 550 °C for a period advantageously of 0.5 to 24 hours.

[0040] Another subject according to the present invention relates to a method for the selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds, wherein at a temperature of 80°C to 220°C, for 1 h -1 to 10 h -1 of the liquid hourly space velocity and at a pressure of 0.5 - 5 MPa, with a molar ratio of hydrogen to dienes to be hydrogenated greater than 1 and less than 10 mol / mol, the gasoline and hydrogen are brought into contact with a catalyst according to the present invention, or a catalyst obtained according to the preparation method of the present invention (in the form of sulfide).

[0041] Preferably, the gasoline is fluid catalytic cracking (FCC) gasoline and has a boiling point of 0°C to 280°C.

[0042] Another subject according to the present invention relates to a method for desulfurizing gasoline containing sulfur compounds, which comprises the following steps:

[0043] a) Performing the selective hydrogenation step of the method for the selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds according to the present invention;

[0044] b) Separating the gasoline obtained in step a) into at least two fractions, which respectively contain at least one light gasoline and at least one heavy gasoline;

[0045] c) Performing a hydrodesulfurization step on the heavy gasoline separated in step b) over a catalyst, which can decompose the sulfur compounds into H2S at least partially. Detailed description of the invention

[0047] Definition

[0048] Hereinafter, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, published by CRC Press, edited by D.R. 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.

[0049] The term "specific surface area" is understood to mean the BET specific surface area (S BET , unit: m 2 / g) determined by nitrogen adsorption according to the standard ASTM D 3663 - 78 established by the Brunauer - Emmett - Teller method described in the journal "The Journal of the American Chemical Society", 1938, 60, 309.

[0050] The total pore volume of the catalyst or the support used for preparing the catalyst is understood to mean the volume measured by mercury porosimetry under a maximum pressure of 4000 bar (400 MPa), using a surface tension of 484 dynes / cm and a contact angle of 140°, in accordance with standard ASTM D4284-83. According to the recommendations on pages 1050-1055 of the publication "Techniques de l'ingénieur, traité analyse et caractérisation" [Techniques of the Engineer, Analysis and Characterization Treatise] written by Jean Charpin and Bernard Rasneur, the wetting angle is taken to be 140°. For better accuracy, the value of the total pore volume corresponds to the value of the total pore volume measured by mercury porosimetry on the sample minus the value of the total pore volume measured by mercury porosimetry on the same sample for a pressure corresponding to 30 psi (about 0.2 MPa).

[0051] The content of metals from Group VIII and Group VIB is measured by X-ray fluorescence spectrometry.

[0052] Catalyst

[0053] The catalyst according to the invention comprises an active phase containing at least one metal from Group VIB and at least one metal from Group VIII (preferably consisting of them) and a porous support containing alumina and at least one spinel MAl2O4 (where M is selected from nickel and cobalt), preferably consisting of them, characterized in that:

[0054] - The molar ratio (r1) between the metal from Group VIII of the active phase and the metal from Group VIB of the active phase is 1.0 - 3.0 mol / mol, preferably 1.5 - 3.0 mol / mol, more preferably 1.6 - 3.0 mol / mol;

[0055] - The molar ratio (r2) between the metal M of the porous support and the metal from Group VIII of the active phase is 0.3 - 0.7 mol / mol, more preferably 0.5 - 0.7 mol / mol;

[0056] - The molar ratio (r3) between the sum of the contents of metal M and the metal from Group VIII of the active phase and the content of the metal from Group VIB of the active phase is 2.2 - 3.0 mol / mol, preferably 2.3 - 3.0 mol / mol, more preferably 2.5 - 3.0 mol / mol.

[0057] When the Group VIII metal of the active phase used is nickel or cobalt, the molar ratio is calculated without considering the nickel or cobalt involved in the spinel.

[0058] The content of the Group VIII metal of the active phase measured in oxide form is 1-20% by weight, preferably 2-15% by weight, even more preferably 4-13% by weight relative to the total weight of the catalyst. The Group VIII metal is preferably selected from nickel, cobalt, and iron. More preferably, the Group VIII metal is nickel.

[0059] The content of the Group VIB metal of the active phase measured in oxide form is advantageously 1-12% by weight, preferably 1-10% by weight, even more preferably 2-9% by weight relative to the total weight of the catalyst. The Group VIB metal is preferably selected from molybdenum and tungsten. More preferably, the Group VIB metal is molybdenum.

[0060] Preferably, the catalyst according to the present invention further has a molar ratio (r4) between the metal M of the porous support and the Group VIB metal of the active phase, which is 0.5-1.5 mol / mol, preferably 0.7-1.5 mol / mol, more preferably 0.8-1.5 mol / mol. Without wishing to be bound by any theory, optimizing the content of the metal M aluminate relative to the content of the Group VIB metal will allow for better dispersion of the active phase, resulting in improved catalytic performance.

[0061] Preferably, a catalyst having a total pore volume measured by mercury porosimetry of 0.3-1.1 cm 3 / g, very preferably 0.35-0.7 cm 3 / g is used. According to standard ASTM D4284-92, mercury porosimetry is measured with a wetting angle of 140° using an Autopore III device from the Micromeritics® brand.

[0062] The specific surface area of the catalyst is preferably less than 350 m 2 / g, more preferably 80 m 2 / g - 280 m 2 / g, preferably 100 m² / g - 250 m² / g, even more preferably 110 m² / g - 190 m² / g.

[0063] In addition, the pore volume of the catalyst (with a diameter greater than 0.05 μm) measured by mercury porosimetry is preferably 5%-50% of the total pore volume, preferably 10%-40% of the total pore volume.

[0064] The pore volume of the catalyst with a diameter greater than 0.1 μm is preferably 5% - 35% of the total pore volume, more preferably 10% - 30% of the total pore volume. The inventors have noticed that such a pore distribution makes it possible to limit the formation of gums in the catalyst.

[0065] Support

[0066] The support of the catalyst comprises alumina and an aluminate of metal M of the MAl2O4 type, preferably consisting of it, where M is selected from nickel and cobalt, and preferably M is nickel.

[0067] Advantageously, the content of metal M measured in oxide form is 0.5 - 10% by weight, preferably 0.7 - 8% by weight, even more preferably 1 - 5% by weight relative to the total weight of the catalyst.

[0068] The presence of spinel in the catalyst according to the invention is measured by temperature-programmed reduction (or TPR), as described, for example, 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 stream of reducing agent, for example in a hydrogen stream. Measuring the hydrogen consumption as a function of temperature gives quantitative information about the reducibility of the substances present. Thus, the presence of spinel in the catalyst is represented by the hydrogen consumption at a temperature above about 800 °C.

[0069] The alumina used is selected from the following aluminas: γ-alumina, δ-alumina, θ-alumina, η-alumina, ρ-alumina, χ-alumina, κ-alumina, either alone or as a mixture.

[0070] Preferably, a support with a total pore volume of 0.3 - 1.1 cm 3 / g, preferably 0.35 - 0.7 cm 3 / g is used.

[0071] Furthermore, the pore volume of the support (with a diameter greater than 0.05 μm) measured by mercury porosimetry is preferably 5% - 50% of the total pore volume, more preferably 10% - 40% of the total pore volume.

[0072] The pore volume of the support with a diameter greater than 0.1 μm is preferably 5% - 35% of the total pore volume, more preferably 5% - 30% of the total pore volume.

[0073] The specific surface area of the support is preferably less than 350 m 2 / g, more preferably 80 m 2 / g - 280 m 2 / g, preferably 100 m² / g - 250 m² / g, even more preferably 120 m² / g - 190 m² / g.

[0074] Synthesis of a support containing aluminate

[0075] The precursor of the support that can be used in the context of the present invention comprises alumina. The precursor of the support can also consist of a mixture of alumina and any other oxide (such as silica, titanium oxide, magnesium oxide, zinc oxide, zirconium oxide) known to those skilled in the art other than aluminates. The alumina used can incorporate a metal M selected from nickel and cobalt, preferably nickel. Preferably, the alumina is selected from γ-alumina, δ-alumina, θ-alumina, η-alumina, ρ-alumina, χ-alumina, κ-alumina, either alone or as a mixture.

[0076] The dry impregnation of the alumina as described above is advantageously carried out by dry impregnation of the alumina as described above (preferably comprising γ-alumina) with an aqueous solution containing an appropriate amount of metal nitrate (such as nickel nitrate or cobalt nitrate). The amount of metal nitrate corresponds to a metal content of 0.5 - 10 wt%, preferably 0.7 - 8 wt%, even more preferably 1 - 5 wt% relative to the total weight of the catalyst (calculated as the oxide equivalent MO, where M is selected from nickel and cobalt).

[0077] After impregnation, the solid is aged at a temperature below 50°C, preferably at ambient temperature, for 0.5 - 24 hours, preferably 0.5 - 12 hours, and then dried for a period advantageously of 1 - 48 hours, preferably 2 - 12 hours, at a temperature advantageously of 50°C - 200°C, preferably 70 - 180°C. Finally, the solid is calcined at a temperature of 500 - 1100°C, preferably 600 - 900°C, under a dry air stream or a moist air stream, preferably under a moist air stream, for a period advantageously of 1 - 12 hours, preferably 2 - 8 hours. This calcination enables the formation of spinel MAl2O4, where M is selected from nickel and cobalt. The resulting solid is subsequently denoted by the term AlNi or AlCo.

[0078] Preparation of the catalyst

[0079] The catalyst according to the present invention can be prepared by any technique known to those skilled in the art, in particular by impregnating Group VIII and Group VIB elements on the selected support. For example, the impregnation can be carried out according to the method known to those skilled in the art as dry impregnation, where only the amount of the desired elements in the form of soluble salts is introduced into the selected solvent (such as demineralized water) in order to fill the pores of the support as precisely as possible.

[0080] Precursors of the active phase based on Group VIII metals and precursors of the active phase of Group VIB metals can be introduced simultaneously or successively. The impregnation of each precursor can advantageously be carried out at least twice. Thus, the different precursors can advantageously be successively impregnated with different numbers of impregnation and aging steps. One precursor can also be impregnated several times.

[0081] The carrier thus filled with the solution is aged for a period of 0.5 h to 12 h, preferably 0.5 h to 6 h, even more preferably 0.5 - 3 h, at a temperature below 50°C, preferably at ambient temperature.

[0082] After the aging step, the obtained catalyst precursor is subjected to an activation treatment.

[0083] The purpose of this treatment is generally to convert the molecular precursors of the elements into oxide phases. In this case, it is an oxidation treatment, but simple drying of the catalyst can also be carried out.

[0084] In the case of drying, the catalyst precursor is dried at a temperature of 50°C - 200°C, preferably 70°C - 180°C, usually for a period of 0.5 - 12 h, even more preferably 0.5 - 5 h.

[0085] In the case of the oxidation treatment (also known as calcination), the treatment is generally carried out in dry or moist air or dilute oxygen, and the treatment temperature is generally 200°C - 550°C, preferably 300°C - 500°C, more preferably 325°C - 475°C, advantageously usually for 0.5 - 24 h, preferably 0.5 - 12 h, even more preferably 0.5 - 10 h. Salts of Group VIB and Group VIII metals that can be used in the method for preparing the catalyst are, for example, cobalt nitrate, nickel nitrate, ammonium heptamolybdate or ammonium metatungstate. Any other salts known to those skilled in the art with sufficient solubility and that can decompose during the activation treatment can also be used. Advantageously, both the drying and the oxidation treatment are carried out during the process of preparing the catalyst.

[0086] Preferably, the catalyst according to the invention is prepared according to the following steps:

[0087] a) contacting a support with an aqueous or organic solution containing a salt of at least one metal M selected from nickel and cobalt;

[0088] b) aging the impregnated support obtained at the end of step a) for a period of 0.5 h to 24 h, preferably 0.5 h to 12 h, at a temperature below 50°C, preferably at ambient temperature;

[0089] c) drying the aged and impregnated support obtained at the end of step b) at a temperature of 50°C - 200°C, preferably 70°C - 180°C, advantageously for a period of 1 - 48 h, preferably 2 - 12 h;

[0090] d) Calcining the solid obtained in step c) at a temperature of 500 °C - 1000 °C, preferably 600 °C - 900 °C, advantageously for a period of 1 - 12 hours, preferably 2 - 12 hours, to obtain a spinel of the MAl2O4 type;

[0091] e) Performing the following sub-steps:

[0092] i) Contacting the solid obtained at the end of step d) with a solution comprising at least one metal active phase precursor based on a Group VIII metal, and then aging the catalyst precursor at a temperature below 50 °C, preferably at ambient temperature, for a period of 0.5 hour - 12 hours, preferably 0.5 hour - 6 hours, even more preferably 0.5 hour - 3 hours;

[0093] ii) Contacting the solid obtained at the end of step d) with a solution comprising at least one metal active phase precursor based on a Group VIB metal, and then aging the catalyst precursor at a temperature below 50 °C, preferably at ambient temperature, for a period of 0.5 hour - 12 hours, preferably 0.5 hour - 6 hours, even more preferably 0.5 hour - 3 hours;

[0094] Steps i) and ii) are carried out separately or simultaneously in any order;

[0095] f) Drying the catalyst precursor obtained in step e) at a temperature of 50 °C - 200 °C, preferably 70 °C - 180 °C, generally for a period of 0.5 - 12 hours, even more preferably 0.5 - 5 hours;

[0096] g) Optionally, calcining the catalyst precursor obtained in step f) at a temperature of 200 °C - 550 °C, preferably 300 °C - 500 °C, more preferably 325 °C - 475 °C, advantageously for a period of 0.5 - 24 hours, preferably 0.5 - 12 hours, even more preferably 0.5 - 10 hours.

[0097] Step 3: Sulfurization of the catalyst

[0098] Before contacting the feedstock to be treated, the catalyst is subjected to a sulfiding step. The sulfiding is carried out in a sulfur-containing reducing medium, i.e., in the presence of H2S and hydrogen, in order to convert the metal oxides into sulfides, such as MoS2 and NiS. The sulfiding is carried out by injecting a stream containing H2S and hydrogen, or a sulfur-containing compound capable of decomposing in the presence of the catalyst and hydrogen to produce H2S, onto the catalyst. Polysulfides, such as dimethyldisulfide, are commonly used H2S precursors for sulfiding catalysts. The temperature is adjusted so that H2S reacts with the metal oxides or the dried (uncalcined) catalyst to form metal sulfides. The sulfiding can be carried out in situ or ex situ (inside or outside the reactor) of a hydrotreating reactor at a temperature of 200 - 600 °C, more preferably 250 - 500 °C. In order to maintain activity, the metal must be substantially sulfided. An element is considered to be substantially sulfided when the molar ratio of sulfur (S) present on the catalyst to the metal is at least equal to 50% of the theoretical molar ratio corresponding to complete sulfidation of the element considered. The overall degree of sulfidation is defined by the following equation:

[0099] (S / element) 催化剂 ≥ 0.5 × (S / element) 理论

[0100] where:

[0101] (S / element) 催化剂 is the molar ratio between sulfur (S) and the element present on the catalyst (excluding the metals (Ni or Co) present in the form of aluminates)

[0102] (S / element) 理论 is the molar ratio between sulfur and the element corresponding to complete sulfidation of the element to form a sulfide.

[0103] This theoretical molar ratio varies according to the element considered:

[0104] -(S / Fe) 理论 =1

[0105] -(S / Co) 理论 =8 / 9

[0106] -(S / Ni) 理论 =1 / 1

[0107] -(S / Mo) 理论 =2 / 1

[0108] -(S / W) 理论 =2 / 1.

[0109] Since the catalyst contains several metals, the molar ratio of S present on the catalyst to the elemental combination must also be at least equal to 50% of the theoretical molar ratio corresponding to the complete sulfidation of each element to form a sulfide, and this calculation is carried out proportionally to the relative molar fraction of each element, excluding the metals (Ni or Co) involved in the preparation of the support.

[0110] For example, for a catalyst containing molybdenum and nickel (with respective molar fractions of 0.7 and 0.3), the minimum molar ratio (S / Mo+Ni) is given by the following relationship:

[0111] (S / Mo+Ni) 催化剂 = 0.5 × [(0.7×2) + (0.3×1)].

[0112] Very preferably, the degree of sulfidation of the metal will be greater than 70%.

[0113] Sulfidation is carried out on the metal in oxide form without a prior metal reduction step. In fact, it is known that the sulfidation of reduced metals is more difficult than that of metals in oxide form.

[0114] Selective hydrogenation process

[0115] The present invention also relates to a method for treating gasoline, which contains any type of compound family, especially diolefins, monoolefins, and sulfur-containing compounds in the form of mercaptans and light sulfides. The present invention is particularly applicable to the conversion of gasoline, especially gasoline produced from catalytic cracking, fluid catalytic cracking (FCC), coking processes, visbreaking processes, or pyrolysis processes. The feedstock applicable to the present invention has a boiling point of 0 °C - 280 °C. The feedstock may also contain hydrocarbons having 3 or 4 carbon atoms.

[0116] For example, gasoline produced from a fluid catalytic cracking (FCC) unit typically contains 0.5 wt% - 5 wt% of diolefins, 20 wt% - 50 wt% of monoolefins, and 10 wt ppm - 0.5 wt% of sulfur, and usually contains less than 300 ppm of mercaptans. Mercaptans are usually concentrated in the light fractions of gasoline, more particularly in fractions with a boiling point below 120 °C.

[0117] The gasoline treatment described in the selective hydrogenation method of the present invention mainly includes:

[0118] - Selectively hydrogenating diolefins to monoolefins;

[0119] - Converting saturated light sulfur-containing compounds, mainly mercaptans, into heavier sulfides or mercaptans by reaction with monoolefins;

[0120] - Isomerizing monoolefin compounds having a C=C double bond at an external position to their isomers having a C=C double bond at an internal position.

[0121] The reaction of hydrogenating a diene to a monoolefin is illustrated below by the conversion of 1,3 - pentadiene (an unstable compound which can be readily hydrogenated to 2 - pentene). However, an attempt is made to limit the side reaction of hydrogenating the monoolefin, which in the following examples will result in the formation of n - pentane, thus leading to a decrease in the octane number.

[0122]

[0123] The sulfur - containing compounds to be converted are mainly thiols. The main reactions for converting thiols include the thioetherification reaction between a monoolefin and a thiol. The reaction is illustrated below by adding propan - 2 - thiol to 2 - pentene to form propyl pentyl sulfide.

[0124]

[0125] In the presence of hydrogen, the conversion of sulfur - containing compounds can also proceed through the formation of an H2S intermediate, which can then add to the unsaturated compounds present in the feedstock. However, under the preferred reaction conditions, this route is minor.

[0126] In addition to thiols, the compounds that can be converted in this way and become heavier are also sulfides, mainly CS2, COS, tetrahydrothiophene, and methyltetrahydrothiophene.

[0127] In some cases, reactions can be observed in which the molecular weight of light nitrogen - containing compounds (mainly nitriles, pyrroles, and their derivatives) increases.

[0128] According to the present invention, the catalyst can also isomerize a monoolefin compound having a C = C double bond at an external position to its isomer having a C = C double bond at an internal position.

[0129] The reaction is illustrated below by the isomerization of 1 - hexene to 2 - hexene or 3 - hexene:

[0130]

[0131] In the selective hydrogenation process according to the present invention, the feedstock to be treated is mixed with hydrogen before contacting with the catalyst. The amount of hydrogen injected is such that the molar ratio between hydrogen and the dienes to be hydrogenated is greater than 1 (stoichiometry) and less than 10, preferably 1 - 5 mol / mol. Excessive hydrogen will cause strong hydrogenation of monoolefins, thus reducing the octane number of gasoline. When the process is carried out in a fixed bed, usually all the feedstock is injected at the inlet of the reactor. However, in some cases, it may be advantageous to inject part or all of the feedstock between two consecutive catalytic beds placed in the reactor. If the inlet of the reactor is blocked by deposits of polymers, particles or gums present in the feedstock, this embodiment can particularly continue to operate the reactor.

[0132] A mixture consisting of gasoline and hydrogen is contacted with the catalyst at a temperature of 80 °C - 220 °C, preferably 90 °C - 200 °C, with a liquid hourly space velocity (LHSV) of 1 h -1 to 10 h -1 , and this liquid hourly space velocity is the number of liters of feedstock per hour per liter of catalyst (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 - 5 MPa, preferably 1 - 4 MPa.

[0133] The gasoline treated under the above conditions has a reduced content of dienes and mercaptans. Generally, the produced gasoline contains less than 1 wt% of dienes, preferably less than 0.5 wt% of dienes. Usually, more than 50% of the light sulfur-containing compounds with boiling points lower than the boiling point of thiophene (84 °C) are converted. Therefore, the light fraction can be separated from the gasoline by distillation and this fraction can be directly sent to the gasoline pool without additional treatment. The light fraction of gasoline generally has an end boiling point lower than 120 °C, preferably lower than 100 °C, and most preferably lower than 80 °C.

[0134] The selective hydrogenation process according to the present invention is particularly suitable for implementation in the context of the desulfurization process described in patent application EP 1 077 247.

[0135] The subject matter of the present invention also includes a method for desulfurizing gasoline containing sulfur compounds, which comprises at least the following steps:

[0136] a) Performing the selective hydrogenation step of the above method;

[0137] b) Separating the gasoline obtained in step a) into at least two fractions, said fractions respectively containing at least one light gasoline and at least one heavy gasoline;

[0138] c) Performing a hydrodesulfurization step on the heavy gasoline separated in step b) over a catalyst, which can decompose at least part of said sulfur compounds into H2S.

[0139] The separation step b) is preferably carried out in a conventional distillation column also known as a splitter. This fractionating column must be able to separate the light fraction of gasoline containing a small amount of sulfur and the heavy fraction preferably containing most of the sulfur initially present in the initial gasoline.

[0140] This column is typically operated at a pressure of 0.1 - 2 MPa, preferably 0.2 - 1 MPa. The number of theoretical plates of this separation column is usually 10 - 100, preferably 20 - 60. The reflux ratio is usually less than 1, preferably less than 0.8, and this reflux ratio is expressed as the ratio of the liquid flow rate in the column divided by the distillate flow rate (expressed in kg / h).

[0141] The light gasoline obtained at the end of the separation usually contains at least all of the C5 olefins (preferably C5 compounds) and at least 20% of the C6 olefins. Generally, the sulfur content of this light fraction is low, that is to say, it usually does not need to be treated before being used as a fuel.

[0142] The desulfurization step c) is preferably a hydrodesulfurization step in which the heavy gasoline is passed through a hydrodesulfurization catalyst containing at least one Group VIII element and / or at least one Group VIB element in at least partially sulfide form in the presence of hydrogen at a temperature of about 210 °C - about 350 °C, preferably 220 °C - 320 °C, and at a pressure of generally about 1 - about 4 MPa, preferably 1.5 - 3 MPa. The liquid hourly space velocity is about 1 to about 20 h -1 (expressed as the volume of liquid per volume of catalyst per hour), preferably 1 to 10 h -1 , very preferably 3 to 8 h -1 . The H2 / feed ratio is 100 - 600 Nl / l, preferably 300 - 600 N1 / l.

[0143] The content of the Group VIII metal expressed as an oxide is usually 0.5 - 15 wt% relative to the weight of the hydrodesulfurization catalyst, preferably 1 - 10 wt%. The content of the Group VIB metal expressed as an oxide is usually 1.5 - 60 wt% relative to the weight of the hydrodesulfurization catalyst, preferably 3 - 50 wt%.

[0144] The Group VIII element (when present) is preferably cobalt, and the Group VIB element (when present) is usually molybdenum or tungsten. Combinations such as cobalt-molybdenum are preferred. The support of the hydrodesulfurization catalyst is usually a porous solid, such as alumina, silica-alumina, or other porous solids, such as magnesia, silica, or titania, either alone or as a mixture with alumina or silica-alumina. To minimize the hydrogenation of olefins present in heavy gasoline, it is advantageous to use the following catalyst: wherein the density of molybdenum expressed as weight % of MoO3 (weight % based on the total weight of the catalyst) / unit specific surface area is greater than 0.07, preferably greater than 0.12. The specific surface area of the hydrodesulfurization catalyst according to step c) is preferably less than 250 m² / g, more preferably less than 230 m² / g, and very preferably less than 190 m² / g, more preferably 100 - 180 m² / g.

[0145] The deposition of the metal on the support is obtained by any method known to those skilled in the art, such as by dry impregnation, by an excess solution containing the metal precursor. The impregnation solution is chosen so as to be able to dissolve the metal precursor at the desired concentration. For example, in the case of synthesizing a CoMo catalyst, the molybdenum precursor can be molybdenum oxide, ammonium heptamolybdate, while the cobalt precursor can be, for example, cobalt nitrate, cobalt hydroxide, cobalt carbonate. The precursor is usually dissolved in a medium that dissolves it at the desired concentration.

[0146] After introducing one or more elements and optionally shaping the catalyst, the catalyst is activated in a first step. The activation can correspond to oxidation, then to reduction or direct reduction, or only to calcination. The calcination step is usually carried out under an air flow at a temperature of about 100 - about 600 °C, preferably 200 - 450 °C. The reduction step is carried out under conditions capable of converting at least a part of the oxidized form of the base metal into the metal. Usually, it consists of treating the catalyst under a hydrogen stream at a temperature preferably at least equal to 300 °C. The reduction can also be carried out partially by a chemical reducing agent.

[0147] The catalyst is preferably used at least in part in its sulfided form. The introduction of sulfur can be carried out before or after any activation step (i.e., calcination or reduction step). The sulfur or sulfur-containing compound 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., in the reactor used for the process according to the invention. In the first case, ex-situ sulfidation is characterized by a final passivation step. In fact, sulfides have a very high reactivity with respect to ambient air (self-heating property due to oxidation), prohibiting subsequent treatment without additional treatment aimed at limiting this reactivity. In commercial ex-situ sulfidation processes, mention is 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 second case (in-situ sulfidation), the catalyst is preferably reduced under the above conditions and then sulfided by passing a feedstock containing at least one sulfur-containing compound therethrough, which, once decomposed, will cause sulfur to be fixed on the catalyst. The feedstock can be gaseous or liquid, such as hydrogen containing H2S, or a liquid containing at least one sulfur-containing compound.

[0148] Preferably, the sulfur-containing compound is added to the catalyst ex-situ. For example, after the calcination step, the sulfur-containing compound can be introduced onto the catalyst, optionally in the presence of another compound. The catalyst is then dried and then transferred to the reactor in which the process according to the invention is carried out. In this reactor, the catalyst is subsequently treated under hydrogen in order to convert at least a part of the main metal into sulfide. Particularly suitable for the process of the invention are the processes described in patents FR-B-2708 596 and FR-B-2 70 8 597. Examples

[0149] The invention is subsequently described by the following examples, without limiting its scope.

[0150] Example 1: Preparation of catalyst A, catalyst B and catalyst D (not according to the invention) and catalyst C (according to the invention) Preparation

[0151] The support used is alumina (Al-1) with a pore volume of 0.7 ml / g and a high specific surface area provided by Axens. The characteristics of the catalysts thus prepared are given in Table 1 below. The catalysts prepared differ in their active phase content and their ratios r1, r2 and r3.

[0152] The dry impregnation of this alumina is carried out using an aqueous solution of nickel nitrate, and the volume of the aqueous solution is equal to the water absorption volume corresponding to the mass of the carrier to be impregnated (the total volume of water can penetrate into the pores). In this case, the amount of nickel nitrate impregnated corresponds to a nickel content of 4.7% by mass based on the solid (or the content of the oxide equivalent NiO). After impregnation, the solid is aged 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, and this solid is subsequently denoted by the term AlNi hereinafter.

[0153] Catalyst A is prepared by dry impregnation of the carrier Al-1 (spinel-free). Catalysts B, C, and D are prepared by dry impregnation of the AlNi carrier. The synthesis method includes dry impregnation using a solution of ammonium heptamolybdate and nickel nitrate, and the volume of the aqueous solution containing the metal precursor is equal to the water absorption volume corresponding to the mass of the carrier to be impregnated (the total volume of water can penetrate into the pores). The concentration of the precursor in the solution is adjusted to deposit the required weight content of metal oxide on the carrier. Then the solid is aged 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 an air stream with a flow rate of 1 l / g / h.

[0154] Table 1

[0155] Catalyst A B C D Support Al-1 AlNi AlNi AlNi <![CDATA[Weight percentage of MoO3]]> 7.0 3.5 7.0 7.0 Weight % of NiO* 6.6 6.6 6.6 3.3 (of NiO) Weight % of M 0 4.7 4.7 4.7 Ratio r1 1.80 3.60 1.80 0.90 Ratio r2 0 0.61 0.61 1.22 Ratio r3 1.80 5.80 2.90 2.00

[0156] Characteristics of catalysts A, B, C, and D in oxide form

[0157] * Does not include the nickel involved in the AlNi carrier.

[0158] Example 2: Evaluation of the catalyst

[0159] The activities of catalyst A, catalyst B, catalyst C, and catalyst D are evaluated by a selective hydrogenation test of a model molecule mixture carried out in a 500 ml stirred autoclave reactor. The catalyst is sulfided at atmospheric pressure in a bench containing an H2S / H2 mixture with 15% by volume of H2S at a rate of 1 l / g·h of catalyst and at 350 °C for 2 hours. The catalyst sulfided in this way is transferred to the reactor without air, and then contacted with 250 ml of the model feedstock at a total pressure of 1.5 MPa and a temperature of 130 °C. During the test, the pressure is kept constant by supplying hydrogen.

[0160] The feedstock for the activity test has the following composition in n-heptane: 1000 weight ppm of sulfur in the form of 3-methylthiophene, 500 weight ppm of sulfur in the form of 2-propanethiol, 10 weight % of olefins in the form of 1-hexene, and 1 weight % of diolefins in the form of isoprene.

[0161] The test time t = 0 corresponds to the contact of the catalyst with the feedstock. The duration of the test is set to 200 minutes, and gas chromatographic analysis of the obtained liquid effluent can evaluate the activity of various catalysts in the hydrogenation of isoprene (formation of methylbutene), the hydrogenation of 1-hexene (formation of n-hexane), and the increase in the molecular weight of light mercaptans (conversion of 2-propanethiol).

[0162] The activity of the catalyst for each reaction is defined relative to the rate constant obtained for each reaction normalized to per gram of catalyst. The rate constant is calculated assuming the order of the reaction is 1. The activity of catalyst C is normalized to 100%.

[0163] The selectivity of the catalyst for isoprene hydrogenation is equal to the ratio of the activity of the catalyst in the hydrogenation of isoprene and the activity in the hydrogenation of 1-hexene: A(isoprene) / A(1-hexene). The selectivity of catalyst C according to the present invention is normalized to 100%.

[0164] The results obtained on various catalysts are reported in Table 2 below.

[0165] Table 2

[0166] Catalyst A B C D A (isoprene) 79 67 100 95 A (1-hexene) 87 70 100 102 A (isoprene) / A (1-hexene) 91 96 100 93 A (2-propanethiol) 98 94 100 85

[0167] Performance of the catalyst in the model molecule test.

[0168] The catalyst C according to the present invention has better activity and better selectivity in the hydrogenation of diolefins via a synergistic effect, while allowing the light sulfur-containing compounds to be converted at least as well or even better compared to catalysts A, B, and D not according to the present invention.

Claims

1. A selective hydrogenation catalyst, which comprises an active phase containing at least one metal of Group VIB and at least one metal of Group VIII and a porous support containing alumina and at least one spinel MAl₂O₄, wherein M is selected from nickel and cobalt, the content of the metal of Group VIB in the active phase measured in oxide form is 1-12% by weight relative to the total weight of the catalyst, and the content of the metal of Group VIII in the active phase measured in oxide form is 1-20% by weight relative to the total weight of the catalyst, and it is characterized in that: - The molar ratio r1 between the metal of Group VIII and the metal of Group VIB in the active phase is 1.0-3.0 mol / mol; - The molar ratio r2 between the metal M in the porous support and the metal of Group VIII in the active phase is 0.3-0.7 mol / mol; - The molar ratio r3 between the sum of the contents of the metal M and the metal of Group VIII and the content of the metal of Group VIB is 2.2-3.0 mol / mol.

2. The catalyst according to claim 1, wherein The molar ratio r4 between the metal M in the porous support and the metal of Group VIB in the active phase is 0.5-1.5 mol / mol.

3. The catalyst according to claim 2, wherein The molar ratio r4 is 0.7-1.5 mol / mol.

4. The catalyst according to any one of claims 1-3, characterized in that, The content of the metal M measured in oxide form is 0.5-10% by weight relative to the total weight of the catalyst.

5. The catalyst according to any one of claims 1 to 3, characterized in that, The specific surface area of the catalyst is 110 m 2 / g - 190 m 2 / g.

6. The catalyst according to any one of claims 1-3, characterized in that, The degree of sulfidation of the metals in the active phase is at least equal to 50%.

7. The catalyst according to any one of claims 1-3, characterized in that, The molar ratio r3 is 2.3-3.0 mol / mol.

8. The catalyst according to any one of claims 1-3, characterized in that, The metal of Group VIII is nickel and the metal of Group VIB is molybdenum.

9. The catalyst according to any one of claims 1 to 3, characterized in that, The metal M is nickel.

10. A method for preparing the catalyst according to any one of claims 1-9, which comprises the following steps: a) contacting a support with an aqueous or organic solution containing a salt of at least one metal M selected from nickel and cobalt; b) aging the impregnated support at a temperature below 50 °C for a period of 0.5 hour to 24 hours at the end of step a); c) drying the aged impregnated support obtained at the end of step b) at a temperature of 50 °C to 200 °C; d) calcining the solid obtained in step c) at a temperature of 500 °C to 1000 °C to obtain a spinel of the MAl₂O₄ type; e) performing the following sub-steps: i) contacting the solid obtained at the end of step d) with a solution containing at least one metal active phase precursor based on a metal of Group VIII, and then aging the catalyst precursor at a temperature below 50 °C for a period of 0.5 hour to 12 hours; ii) contacting the solid obtained at the end of step d) with a solution containing at least one metal active phase precursor based on a metal of Group VIB, and then aging the catalyst precursor at a temperature below 50 °C for a period of 0.5 hour to 12 hours; Steps i) and ii) are carried out separately or simultaneously in any order; f) drying the catalyst precursor obtained in step e) at a temperature of 50 °C to 200 °C for a period of 0.5 to 12 hours.

11. The method according to claim 10, wherein step f) is carried out at a temperature of 70 °C to 180 °C for a period of 0.5 to 5 hours.

12. The method according to claim 10, further comprising step g), wherein the catalyst precursor obtained in step f) is calcined at a temperature of 200°C - 550°C for a period of 0.5 - 24 hours.

13. A method for the selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds, wherein at a temperature of 80°C to 220°C, at a liquid hourly space velocity of 1 h -1 to 10 h -1 and at a pressure of 0.5 - 5 MPa, with a molar ratio of hydrogen to dienes to be hydrogenated greater than 1 and less than 10 mol / mol, the gasoline and hydrogen are contacted with a catalyst in the form of a sulfide as described in any one of claims 1 - 9 or a catalyst obtained according to the preparation method described in any one of claims 10 to 12.

14. The method according to claim 13, wherein the gasoline is fluid catalytic cracking gasoline and has a boiling point of 0°C - 280°C.

15. A method for desulfurizing gasoline containing sulfur compounds, comprising the following steps: a) performing a selective hydrogenation step of the method according to claim 13 or 14; b) separating the gasoline obtained in step a) into at least two fractions, the fractions respectively containing at least one light gasoline and at least one heavy gasoline; c) performing a hydrodesulfurization step on the heavy gasoline separated in step b) over a catalyst to decompose the sulfur compounds into H2S at least partially.

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