A hydrogenation catalyst comprising a carrier and a specific nickel-molybdenum ratio

Abstract

A selective hydrogenation catalyst, which comprises an active phase based on nickel and molybdenum and a porous support composed of alumina and / or nickel aluminate, characterized in that the molar ratio of nickel to molybdenum is greater than 2.5 mol / mol and less than 3.0 mol / mol.

Description

BACKGROUND OF THE INVENTION

[0002] Producing gasoline meeting new environmental standards requires a significant reduction in its sulfur content to a value generally not exceeding 50 ppm, preferably below 10 ppm.

[0003] Furthermore, it is known that reformed gasoline, and more particularly reformed gasoline resulting from catalytic cracking (which can represent 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 attributable 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 generally rich in olefins and sulfur, but also rich in diolefins, and for gasoline from catalytic cracking, the diolefin content can be as high as 5% by weight. 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 specifications 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. Furthermore, 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 consisting mainly of olefins having 5 carbon atoms by simple distillation without loss of octane number. After selective hydrogenation and an increase in the molecular weight of the 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 the light sulfur-containing compounds.

[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 hydrodesulfurization reactor. Therefore, for industrial applications, it is important to use a catalyst that limits polymer formation, i.e., 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 patent FR2118309 of the present applicant proposes 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, wherein the metal M is selected from nickel and cobalt.

[0008] The patent FR2895415 of the present applicant proposes a selective hydrogenation method using a catalyst with a specific support. This method uses a catalyst comprising at least one metal of Group VIB and at least one non-noble metal of Group VIII deposited on a specific support in the sulfided form, the specific support comprising a metal aluminate of the MAl2O4 type, wherein the metal M is selected from nickel and cobalt.

[0009] The patent FR2935389 of the present applicant proposes a method for selective hydrogenation using a sulfur-containing catalyst with a specific composition. The catalyst comprises at least one metal of Group VIB and at least one metal of Group VIII supported on alumina, wherein the content of the metal oxide of Group VIB is 4 wt% - 20 wt% relative to the total weight of the catalyst, the content of the metal oxide of Group VIII is less than 15 wt% relative to the total weight of the catalyst, the molar ratio of the metal of Group VIII to the metal of Group VIB is 0.6 - 3.0 mol / mol, and the catalyst has a total pore volume of 0.4 - 1.4 cm 3 / g.

[0010] Patent US2003 / 111391 proposes a catalyst for removing arsenic from petroleum feedstocks, which comprises a porous high-melting-point support impregnated with at least 8 wt% of a metal of Group VIB and a certain amount of a metal of Group VIII such that the atomic ratio of the metal of Group VIII to the metal of Group VIB is 1.5 - 2.5. A method for producing such a catalyst and a method for using the catalyst to remove arsenic metals from petroleum fractions are also described.

[0011] Application CN101869839 discloses a selective hydrogenation catalyst, which comprises 10 - 20 wt% of nickel measured in oxide form and 5 - 12 wt% of molybdenum measured in oxide form deposited on an alumina-titania-based support.

[0012] Application US2015 / 290626 discloses a selective hydrogenation catalyst, which comprises an active phase comprising 6 - 15 wt% of a metal of Group VIII and 4 - 10 wt% of a metal of Group VIB measured in oxide form and an alumina-based oxide support, and the molar ratio of the metal of Group VIII to the metal of Group VIB is greater than 3 mol / mol and less than or equal to 5 mol / mol.

[0013] Based on the solutions described in the literature, the present invention proposes a novel catalyst with a specific active phase, which can selectively hydrogenate polyunsaturated compounds, more particularly dienes, and can also increase the molecular weight of light sulfur-containing compounds, more particularly mercaptans.

[0014] Subject matter of the invention

[0015] The present invention relates to a hydrotreating catalyst comprising an active phase based on nickel and molybdenum and a porous support composed of alumina and / or nickel aluminate of the NiAl2O4 type, characterized in that the molar ratio of nickel contained in the active phase and the support to molybdenum of the active phase is greater than 2.5 mol / mol and less than 3.0 mol / mol.

[0016] In fact, the Applicant has surprisingly found that a catalyst comprising an active phase based on nickel and molybdenum (with a specific ratio between nickel and molybdenum) has better activity and better selectivity in the hydrogenation of dienes, while allowing light sulfur-containing compounds to be converted at least as well or even better than the catalysts disclosed in the prior art.

[0017] Without wishing to be bound by any theory, formulating the catalyst within the specific range claimed makes it possible to ensure strong dedienization activity, better stability of the catalyst against polymer formation, good selectivity for the hydrogenation of dienes, and good activity for the conversion of mercaptans and other light sulfur-containing compounds. In particular, at an equal molybdenum content, an increase in the Ni / Mo molar ratio makes it possible to generate a NiS active phase with thioetherification activity and without dedienization activity. Beyond a certain amount, the NiS phase covers the dedienization-active NiMoS phase, thus resulting in a loss of dedienization activity. In addition, at the same active phase content, an increase in the catalyst specific surface area makes it possible to adjust the respective dispersion of the NiS phase and the NiMoS phase to a specific surface area threshold, which results in a loss of selectivity for the selective hydrogenation of dienes relative to the hydrogenation of olefins. Therefore, there is an optimum value between the amounts of the NiMoS phase and the NiS phase introduced onto the catalyst and the specific surface area of the catalyst, yielding a catalyst that is optimum for thioetherification and dedienization.

[0018] Preferably, the specific surface area of the catalyst is less than 200 m 2 / g.

[0019] Preferably, the nickel content of the active phase measured in oxide form is 1-20% by weight relative to the total weight of the catalyst.

[0020] Preferably, the molybdenum content of the active phase measured in oxide form is 1-12% by weight relative to the total weight of the catalyst.

[0021] Preferably, the porous support is composed of alumina and nickel aluminate.

[0022] Preferably, the molar ratio between nickel of the porous support and molybdenum of the active phase is 0.5 - 1.5 mol / mol.

[0023] Preferably, the molar ratio between nickel of the porous support and nickel of the active phase is 0.3 - 0.7 mol / mol.

[0024] Preferably, the nickel content of the support measured in oxide form is 0.5 - 10% by weight relative to the total weight of the catalyst.

[0025] Preferably, the nickel content of the active phase measured in oxide form is 1 - 12% by weight relative to the total weight of the catalyst.

[0026] Preferably, the specific surface area of the catalyst is 120 - 160 m 2 / g.

[0027] Preferably, the degree of sulfidation of the metal of the active phase is at least equal to 50%.

[0028] Preferably, the total pore volume of the catalyst is 0.3 - 0.7 cm 3 / g.

[0029] According to another subject of the present invention, it relates to a method for the selective hydrogenation of gasoline containing polyunsaturated compounds and light sulfur compounds, wherein at a temperature of 80°C - 220°C, at a liquid hourly space velocity of 1 h -1 to 10 h -1 and a pressure of 0.5 - 5 MPa, with a molar ratio of hydrogen to diene to be hydrogenated greater than 1 and less than 10 mol / mol, the gasoline and hydrogen are brought into contact with the catalyst according to the present invention (in the form of sulfide).

[0030] Preferably, the gasoline is fluid catalytic cracking (FCC) gasoline and has a boiling point of 0°C - 280°C.

[0031] The method for desulfurizing gasoline containing sulfur compounds comprises the following steps:

[0032] 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;

[0033] 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;

[0034] c) Performing the hydrodesulfurization step of the heavy gasoline separated in step b) on a catalyst, which can decompose the sulfur compounds into H2S at least partially. Detailed Description of the Invention

[0036] Definition

[0037] In the following text, 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.

[0038] The term "specific surface area" is understood to mean the BET specific surface area (S BET , unit: m 2 / g) determined by nitrogen adsorption in accordance with the standard ASTM D 3663 - 78 established according to the Brunauer - Emmett - Teller method described in the journal "The Journal of the American Chemical Society", 1938, 60, 309.

[0039] The total pore volume of a catalyst or the support used for preparing the catalyst is understood to mean the volume measured by mercury porosimetry according to the standard ASTM D4284 - 83 at a maximum pressure of 4000 bar (400 MPa), using a surface tension of 484 dynes / cm and a contact angle of 140°. According to the recommendation 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 at a pressure corresponding to 30 psi (about 0.2 MPa).

[0040] The contents of molybdenum and nickel are measured by X - ray fluorescence spectrometry.

[0041] Catalyst

[0042] The catalyst according to the present invention comprises an active phase containing nickel and molybdenum and a porous support composed of alumina and / or nickel aluminate, with a molar ratio between nickel and molybdenum greater than 2.5 mol / mol and less than 3.0 mol / mol, preferably 2.6 - 2.9 mol / mol. Preferably, the catalyst consists of an active phase of nickel and molybdenum and a porous support composed of alumina and / or nickel aluminate.

[0043] The nickel content of the active phase measured in oxide form is advantageously 1 - 20 wt%, preferably 2 - 15 wt%, even more preferably 4 - 13 wt% relative to the total weight of the catalyst.

[0044] The molybdenum content of the active phase measured in oxide form is advantageously 1 - 12 wt%, preferably 1 - 10 wt%, even more preferably 2 - 9 wt% relative to the total weight of the catalyst.

[0045] Preferably, a catalyst with a total pore volume measured by mercury intrusion porosimetry of 0.3 - 0.7 cm 3 / g, very preferably 0.35 - 0.65 cm 3 / g is used. Mercury porosimetry is measured with a wetting angle of 140° using an Autopore III device from the Micromeritics® brand according to standard ASTM D4284 - 92.

[0046] The specific surface area of the catalyst is preferably less than 300 m 2 / g, preferably less than 200 m 2 / g, even more preferably 120 m 2 / g - 190 m 2 / g, more preferably 120 m² / g - 180 m² / g, more preferably 120 m² / g - 170 m² / g, even more preferably 120 m 2 / g - 160 m 2 / g.

[0047] In a preferred embodiment, the catalyst comprises an active phase based on nickel and molybdenum and a porous support composed of alumina, preferably consisting of it, the catalyst has a molar ratio between nickel and molybdenum greater than 2.5 mol / mol and less than 3.0 mol / mol, preferably 2.6 - 2.9 mol / mol, and the catalyst has a specific surface area less than 200 m 2 / g, even more preferably 120 m 2 / g - 190 m 2 / g, more preferably 120 - 180 m 2 / g, and more preferably 120 - 170 m 2 / g, and even more preferably 120 - 160 m 2 / g.

[0048] In another preferred embodiment, the catalyst comprises an active phase based on nickel and molybdenum and a porous support consisting of nickel aluminate, preferably consisting thereof, the catalyst having a molar ratio between nickel and molybdenum greater than 2.5 mol / mol and less than 3.0 mol / mol, preferably 2.6 - 2.9 mol / mol, and the catalyst having a specific surface area of less than 200 m 2 / g, even more preferably 120 m 2 / g - 190 m 2 / g, more preferably 120 - 180 m 2 / g, and more preferably 120 - 170 m 2 / g, and even more preferably 120 - 160 m 2 / g.

[0049] In another preferred embodiment, the catalyst comprises an active phase based on nickel and molybdenum and a porous support consisting of alumina and nickel aluminate, preferably consisting thereof, the catalyst having a molar ratio between nickel and molybdenum greater than 2.5 mol / mol and less than 3.0 mol / mol, preferably 2.6 - 2.9 mol / mol, and the catalyst having a specific surface area of less than 200 m 2 / g, even more preferably 120 m 2 / g - 190 m 2 / g, more preferably 120 - 180 m 2 / g, and more preferably 120 - 170 m 2 / g, and even more preferably 120 - 160 m 2 / g.

[0050] In fact, for these three preferred embodiments, at equal active phase contents, the increase in the catalyst specific surface area makes it possible to adjust the respective dispersions of the NiS phase and the NiMoS phase to a specific surface area threshold, which causes a selectivity loss of the selective hydrogenation of diolefins relative to the hydrogenation of olefins. Thus, there is an optimum value between the amounts of NiMoS phase and NiS phase introduced onto the catalyst and the specific surface area of said catalyst, thus obtaining a catalyst that is optimal for sulfidization and dearomatization.

[0051] Furthermore, 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.

[0052] 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 noted that such a pore distribution makes it possible to limit the formation of gums in the catalyst.

[0053] Support

[0054] The porous supports that can be used in the context of the present invention comprise alumina, preferably 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. Preferably, the porous support is based on η-alumina, θ-alumina, δ-alumina, χ-alumina, either alone or as a mixture. When the porous support further comprises nickel aluminate, the method for preparing said support advantageously proceeds by dry impregnation of an alumina comprising γ-alumina.

[0055] In one embodiment according to the present invention, the porous support further comprises nickel aluminate of the NiAl2O4 type. The presence of spinel in the catalyst according to the present 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 a reducing agent, for example in a stream of hydrogen. 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 expressed by the hydrogen consumption at a temperature above about 800 °C.

[0056] When the porous support comprises nickel aluminate, the nickel content in the support measured in oxide form is advantageously 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.

[0057] 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 0.5-1.5 mol / mol, preferably 0.7-1.5 mol / mol, even more preferably 0.8-1.5 mol / mol. Without wishing to be bound by any theory, the optimization of the nickel aluminate content relative to the molybdenum content will result in a better dispersion of the active phase, leading to an improvement in catalytic performance.

[0058] When the porous support comprises nickel aluminate, the molar ratio between the nickel of the porous support and the nickel of the active phase is advantageously 0.3-0.7 mol / mol, more preferably 0.5-0.7 mol / mol.

[0059] Preferably, the porous support has a total pore volume of 0.3-0.7 cm 3 / g, preferably 0.35-0.65 cm 3 / g measured by mercury porosimetry.

[0060] In addition, the pore volume of the porous support measured by mercury intrusion (with a diameter greater than 0.05 μm) is preferably 5% - 50% of the total pore volume, more preferably 10% - 40% of the total pore volume.

[0061] The pore volume of the porous 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.

[0062] The pore volume of the porous support with a diameter of 0.004 - 0.009 μm is preferably 5% - 12% of the total pore volume, preferably 8% - 10% of the total pore volume.

[0063] The specific surface area of the support is preferably less than 300 m 2 / g, preferably less than 260 m 2 / g, preferably less than 220 m 2 / g, even more preferably less than 200 m 2 / g, even more preferably 120 m 2 / g - 190 m 2 / g, more preferably 120 m² / g - 180 m² / g, more preferably 120 m² / g - 170 m² / g, even more preferably 120 m² / g - 160 m² / g.

[0064] Synthesis of an aluminates (optional) based support

[0065] The porous support usable in the context of the present invention comprises alumina, preferably selected from the following aluminas: γ-alumina, δ-alumina, θ-alumina, η-alumina, ρ-alumina, χ-alumina, κ-alumina, individually or as a mixture. Preferably, the porous support is based on η-alumina, θ-alumina, δ-alumina, χ-alumina, individually or as a mixture.

[0066] When the porous support further contains nickel aluminate, the method for preparing the support is advantageously carried out by dry impregnation of the above-described alumina (preferably including γ-alumina) with an aqueous solution containing an appropriate amount of metal nitrate (such as nickel nitrate). The amount of metal nitrate corresponds to a metal content (calculated as the oxide equivalent NiO) of 0.5 - 10 wt%, preferably 0.7 - 8 wt%, even more preferably 1 - 5 wt% relative to the total weight of the catalyst.

[0067] After impregnation, the solid is cured 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 of advantageously 1 - 48 hours, preferably 2 - 12 hours, at a temperature of advantageously 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 of advantageously 1 - 12 hours, preferably 2 - 8 hours. This calcination enables the formation of nickel aluminate. The resulting solid is subsequently denoted by the term AlNi.

[0068] Preparation of the catalyst

[0069] The catalyst according to the invention can then be prepared by any technique known to those skilled in the art, in particular by impregnating nickel and molybdenum on a selected support. For example, this impregnation can be carried out according to the method known to those skilled in the art as dry impregnation, in which only the amount of the desired elements in the form of soluble salts is introduced into a selected solvent (such as demineralized water) in order to fill the pores of the support as precisely as possible.

[0070] The precursors of the active phase based on nickel and the precursors of the active phase of molybdenum 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 curing times. One precursor can also be impregnated several times.

[0071] The support thus filled with the solution is cured at a temperature below 50 °C, preferably at ambient temperature, for a period of 0.5 hours - 12 hours, preferably 0.5 hours - 6 hours, even more preferably 0.5 - 3 hours.

[0072] After introducing nickel and molybdenum, the support is subjected to an activation treatment.

[0073] 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.

[0074] In the case of drying, the catalyst precursor is dried at a temperature of 50 °C - 200 °C, preferably 70 °C - 180 °C, for a period generally of 0.5 - 12 hours, even more preferably 0.5 - 5 hours.

[0075] In the case of an oxidation treatment (also known as calcination), the treatment is typically carried out in air or dilute oxygen, and the treatment temperature is typically 200 °C - 550 °C, preferably 300 °C - 500 °C, and advantageously is typically 0.5 - 24 hours, preferably 0.5 - 12 hours, and even more preferably 0.5 - 10 hours. Salts of molybdenum and nickel metals that can be used in the method for preparing the catalyst are, for example, nickel nitrate and ammonium heptamolybdate. Any other salts known to those skilled in the art that have sufficient solubility and can decompose during the activation treatment can also be used. Advantageously, both the drying and oxidation treatments are carried out during the process of preparing the catalyst.

[0076] In one embodiment, the catalyst according to the present invention is prepared according to the following steps:

[0077] a) contacting a support with an aqueous or organic solution containing at least one nickel salt;

[0078] b) aging the impregnated support obtained at the end of step a) for a period of 0.5 hours - 24 hours, preferably 0.5 hours - 12 hours, at a temperature below 50 °C, preferably at ambient temperature;

[0079] 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, for a period of advantageously 1 - 48 hours, preferably 2 - 12 hours;

[0080] d) calcining the solid obtained in step c) at a temperature of 500 °C - 1000 °C, preferably 600 °C - 900 °C, for a period of advantageously 1 - 12 hours, preferably 2 - 12 hours, to obtain a spinel of the NiAl2O4 type;

[0081] e) performing the following sub - steps:

[0082] i) contacting the solid obtained at the end of step d) with a solution containing at least one nickel active phase precursor, and then aging the catalyst precursor for a period of 0.5 hours - 12 hours, preferably 0.5 hours - 6 hours, even more preferably 0.5 hours - 3 hours, at a temperature below 50 °C, preferably at ambient temperature;

[0083] ii) contacting the solid obtained at the end of step d) with a solution containing at least one molybdenum active phase precursor, and then aging the catalyst precursor for a period of 0.5 hours - 12 hours, preferably 0.5 hours - 6 hours, even more preferably 0.5 hours - 3 hours, at a temperature below 50 °C, preferably at ambient temperature;

[0084] Steps i) and ii) are carried out separately or simultaneously in any order;

[0085] f) The catalyst precursor obtained in step e) is dried at a temperature of 50 °C to 200 °C, preferably 70 °C to 180 °C, for a period typically of 0.5 to 12 hours, even more preferably 0.5 to 5 hours;

[0086] g) Optionally, the catalyst precursor obtained in step f) is calcined at a temperature of from 200 °C to 550 °C, preferably 300 °C to 500 °C, for a period advantageously of 0.5 to 24 hours, preferably 0.5 to 12 hours, even more preferably 0.5 to 10 hours.

[0087] Sulfiding of the catalyst

[0088] Before contacting with the feedstock to be treated, the catalyst is subjected to a sulfidation step. The sulfidation 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 sulfidation 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, into 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 to form metal sulfides. This sulfidation can be carried out at a temperature of 200 - 600 °C, more preferably 250 - 500 °C, in situ or ex situ (inside or outside the reactor) in a hydrotreating reactor. 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) to the metal present on the catalyst 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:

[0089] (S / element) 催化剂 ≥ 0.5 × (S / element) 理论

[0090] where:

[0091] (S / element) 催化剂 is the molar ratio between sulfur (S) and the element present on the catalyst (excluding the metal (Ni or Co) present in the form of aluminate)

[0092] (S / element) 理论 is the molar ratio between sulfur and the element corresponding to complete sulfidation of the element to form the sulfide.

[0093] This theoretical molar ratio varies according to the element considered:

[0094] -(S / Fe) 理论 = 1

[0095] -(S / Co) 理论 = 8 / 9

[0096] -(S / Ni) 理论 =1 / 1

[0097] -(S / Mo) 理论 =2 / 1

[0098] -(S / W) 理论 =2 / 1。

[0099] 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 fractions of each element, excluding the metals (Ni or Co) involved in the support preparation process.

[0100] 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:

[0101] (S / Mo + Ni) 催化剂 = 0.5 × [(0.7×2) + (0.3×1)].

[0102] Very preferably, the degree of sulfidation of the metal will be greater than 70%.

[0103] The 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.

[0104] Selective hydrogenation process

[0105] The present invention also relates to a method for treating gasoline, which contains any type of compound family, especially sulfur-containing compounds in the form of diolefins, monoolefins, mercaptans and light sulfides. The present invention is particularly applicable to the conversion of gasoline, especially the conversion of gasoline produced from catalytic cracking, fluid catalytic cracking (FCC), coking process, visbreaking process or pyrolysis process. 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.

[0106] 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.

[0107] The gasoline treatment described in the selective hydrogenation method of the present invention mainly includes:

[0108] - Selectively hydrogenating dienes to monoolefins;

[0109] - Converting saturated light sulfur-containing compounds, mainly mercaptans, into heavier sulfides or mercaptans by reaction with monoolefins;

[0110] - Isomerizing monoolefin compounds having a C=C double bond in an external position into their isomers having a C=C double bond in an internal position.

[0111] The reaction of hydrogenating dienes to monoolefins is illustrated below by the conversion of 1,3-pentadiene (an unstable compound that can be easily hydrogenated to 2-pentene). However, an attempt is made to limit this side reaction of hydrogenating monoolefins, which in the following examples would lead to the formation of n-pentane, thereby causing a decrease in the octane number.

[0112]

[0113] The sulfur-containing compounds to be converted are mainly mercaptans. The main reactions for converting mercaptans include the thioetherification reaction between monoolefins and mercaptans. This reaction is illustrated below by adding propan-2-thiol to 2-pentene to form propyl pentyl sulfide.

[0114]

[0115] 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.

[0116] In addition to mercaptans, compounds that can be converted in this way and become heavier include sulfides, mainly CS2, COS, tetrahydrothiophene, and methyltetrahydrothiophene.

[0117] In some cases, reactions can be observed in which the molecular weight of light nitrogen-containing compounds (mainly nitriles, pyrroles, and their derivatives) increases.

[0118] According to the present invention, the catalyst can also isomerize monoolefin compounds having a C=C double bond in an external position into their isomers having a C=C double bond in an internal position.

[0119] This reaction is illustrated below by the isomerization of 1-hexene to 2-hexene or 3-hexene:

[0120]

[0121] 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 (stoichiometric) 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 catalyst 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.

[0122] A mixture composed of gasoline and hydrogen is contacted with the catalyst at a temperature of 80°C - 220°C, preferably 90°C - 200°C, and the liquid hourly space velocity (LHSV) is 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.

[0123] 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 the gasoline usually has an end boiling point lower than 120°C, preferably lower than 100°C, and most preferably lower than 80°C.

[0124] 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.

[0125] The subject matter of the present invention also includes a method for desulfurizing gasoline containing sulfur compounds, which includes at least the following steps:

[0126] a) Implementing the selective hydrogenation step of the above method;

[0127] 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;

[0128] c) Carrying out a hydrodesulfurization step on the heavy gasoline separated in step b) over a catalyst, which can decompose the sulfur-containing compounds into H2S at least partially.

[0129] The separation step b) is preferably carried out in a conventional distillation column, also known as a splitter. This fractionation 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.

[0130] 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 typically 10 - 100, preferably 20 - 60. The reflux ratio is typically 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).

[0131] 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 fuel.

[0132] 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 and very preferably 3 to 8 h -1 . The H2 / feed ratio is 100 - 600 Nl / l, preferably 300 - 600 N1 / l.

[0133] The content of the Group VIII metal expressed as an oxide is generally 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 generally 1.5 - 60 wt% relative to the weight of the hydrodesulfurization catalyst, preferably 3 - 50 wt%.

[0134] 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 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 weight percentage of the Group VIB metal in oxide form (weight percentage expressed relative to the total weight of the catalyst) / the density of the Group VIB metal expressed per unit specific surface area is greater than 0.07, preferably greater than 0.12. The specific surface area of the 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.

[0135] 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 selected 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.

[0136] After introducing one or more elements and optionally shaping the catalyst, the catalyst is activated in a first step. This 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 stream 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 portion of the oxidized form of the base metal to the metal. Usually, it involves 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.

[0137] The catalyst is preferably used at least partially in its sulfided form. The introduction of sulfur can be carried out before or after any activation step (i.e., calcination or reduction step). Sulfur or sulfur-containing 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., in the reactor used for the process according to the invention. In the first case, these ex-situ sulfidations are 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 processing 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.

[0138] Preferably, the sulfur-containing compound is added to the catalyst ex-situ. For example, after the calcination step, the sulfur-containing compound can optionally be introduced onto the catalyst in the presence of another compound. The catalyst is then dried and subsequently 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

[0139] The invention is subsequently described by the following examples, without limiting its scope.

[0140] Example 1: Preparation of catalysts A, D and F (not according to the invention) and B, C and E (according to the invention)

[0141] The characteristics of the support used for preparing the catalyst are listed in Table 1. A support containing nickel aluminate is prepared by dry impregnation of alumina Al-2 with an aqueous solution of nickel nitrate, the volume of the aqueous solution being equal to the water absorption volume corresponding to the mass of the support to be impregnated (the total volume of water capable of infiltrating the pores). In this case, the amount of nickel nitrate impregnated corresponds to a nickel content of 4.65% by weight based on the solid (or the content of the oxide equivalent NiO). After impregnation, the solid is aged for 12 hours at ambient temperature and then dried for 2 hours at 120 °C in a ventilated oven. Finally, the solid is calcined for two hours at 750 °C in a muffle furnace; this solid is subsequently designated as AlNi.

[0142] Table 1

[0143] Support Al-1 Al-2 AlNi <![CDATA[S BET (square meters per gram)]]> 155 296 150 <![CDATA[Total pore volume (cm 3 / g)]]> 1.07 0.63 0.54 NiO (wt%) 0 0 4.65

[0144] Characteristics of the support.

[0145] Catalysts A and B were prepared by dry impregnation of the support Al-1. For Ni / Mo molar ratios greater than 3 and molybdenum contents greater than 4 wt%, it is difficult to dissolve the substances to prepare the impregnation solution. Catalyst C was prepared by dry impregnation of the Al-2 support. Catalysts D, E and F were prepared by dry impregnation of the AlNi support. The synthesis method involves 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 support to be impregnated (the total volume of water can penetrate into the pores). The concentration of the precursor in the solution was adjusted to deposit the desired weight content of metal oxide on the support. The solid was then aged at ambient temperature for 6 hours and then dried in a ventilated oven at 120 °C for 2 hours. Finally, the solid was calcined in a flow-through fixed bed reactor at 450 °C for two hours under an air stream with a flow rate of 1 l / g / h. The characteristics of the catalysts thus prepared are given in Table 2.

[0146] Table 2

[0147] A B C D E F Support Al-1 Al-1 Al-2 AlNi AlNi AlNi NiO* (wt%) 3.1 12.1 12.1 6.9 11.6 14.7 <![CDATA[MoO3 (wt%)]]> 8.3 8.1 8.1 8.2 8.3 8.2 <![CDATA[S BET (m 2 / g)]]> 136 125 236 138 128 121 Ni / Mo ratio 0.72 2.88 2.88 1.62 2.69 3.45

[0148] Characteristics of catalysts A, B, C, D, E and F in oxide form

[0149] * Considering the nickel involved in the support.

[0150] Example 2: Evaluation of catalysts A, B and C

[0151] The activities of catalysts A, B and C were evaluated by a selective hydrogenation test of a model molecule mixture carried out in a 500 ml stirred autoclave reactor. The catalysts were sulfided at atmospheric pressure in a sulfidation bench under an H2S / H2 mixture containing 15 vol% H2S at 1 l / g·h catalyst and at 350 °C for 2 hours. The thus-sulfided catalysts were 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 was kept constant by supplying hydrogen.

[0152] The feedstock for the activity test had the following composition in n-heptane: 1000 wt ppm of sulfur in the form of 3-methylthiophene, 500 wt ppm of sulfur in the form of 2-propanethiol, 10 wt% of olefins in the form of 1-hexene, and 1 wt% of diolefins in the form of isoprene.

[0153] The test time t = 0 corresponds to bringing the catalyst into contact with the feedstock. The duration of the test was set at 200 minutes, and the resulting liquid effluent was analyzed by gas chromatography to evaluate the activity of the various catalysts in the hydrogenation of isoprene (to form methylbutenes), the hydrogenation of 1 - hexene (to form n - hexane), and the increase in the molecular weight of light mercaptans (conversion of 2 - propanethiol).

[0154] 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 was calculated assuming the order of the reaction to be 1. The activity of catalyst A was normalized to 100%.

[0155] The selectivity of the catalyst for isoprene hydrogenation is equal to the ratio of the activity of the catalyst in the hydrogenation of isoprene to its activity in the hydrogenation of 1 - hexene: A(isoprene) / A(1 - hexene). The selectivity of catalyst A according to the present invention was normalized to 100%.

[0156] The results obtained on the various catalysts are reported in Table 3 below.

[0157] Table 3

[0158] Catalyst A B C A(isoprene) 100 123 122 A(1 - hexene) 100 103 118 A(isoprene) / A(1 - hexene) 100 120 103 A(2 - propanethiol) 100 137 132

[0159] Performance of the catalysts in the model molecule test.

[0160] Catalysts B and C according to the present invention have better activity and better selectivity in the hydrogenation of dienes, while allowing the light sulfur - containing compounds to be converted at least as well or even better than catalyst A which is not according to the present invention. Furthermore, compared to catalyst C, catalyst B shows excellent results in terms of activity and selectivity for selective hydrogenation and for the conversion of light sulfur - containing compounds.

[0161] Example 3: Evaluation of catalysts D, E, and F

[0162] The activities of catalysts D, E, and F were evaluated under the test conditions described in Example 2.

[0163] The activity of the catalyst for each reaction is defined relative to the rate constant of each reaction normalized to per gram of catalyst. The rate constant was calculated assuming the order of the reaction to be 1. The activity of catalyst D was normalized to 100%.

[0164] 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 1 - hexene: A(isoprene) / A(1 - hexene). The selectivity of catalyst D according to the present invention was normalized to 100%.

[0165] The results obtained on the various catalysts are reported in Table 4 below.

[0166] Table 4

[0167] Catalyst D E F A(isoprene) 100 118 107 A(1 - hexene) 100 108 105 A(isoprene) / A(1 - hexene) 100 109 102 A(2 - propanethiol) 100 109 98

[0168] Performance of the catalyst in the model molecule test.

[0169] The catalyst E according to the invention has better activity and better selectivity in the hydrogenation of diolefins, while allowing the conversion of light sulfur-containing compounds to be at least as good or even better compared to the catalysts D and F not according to the invention.

Claims

1. A selective hydrogenation catalyst, which comprises an active phase based on nickel and molybdenum and a porous support composed of alumina and nickel aluminate, characterized in that The molar ratio of nickel to molybdenum is greater than 2.6 mol / mol and less than 2.9 mol / mol, and the specific surface area of the catalyst is 120 - 160 m 2 / g. The molar ratio between nickel of the porous support and molybdenum of the active phase is 0.5 - 1.5 mol / mol, and the molar ratio between nickel of the porous support and nickel of the active phase is 0.5 - 0.7 mol / mol.

2. The catalyst according to claim 1, characterized in that, The nickel content of the active phase measured in oxide form is 1-20% by weight relative to the total weight of the catalyst.

3. The catalyst according to claim 1 or 2, characterized in that, The molybdenum content of the active phase measured in oxide form is 1-12% by weight relative to the total weight of the catalyst.

4. The catalyst according to any one of claims 1-2, characterized in that, The nickel content of the support 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 1-2, characterized in that, The nickel content of the active phase measured in oxide form is 1-12% by weight relative to the total weight of the catalyst.

6. The catalyst according to any one of claims 1-2, 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 1-2, characterized in that, The total pore volume of the catalyst is 0.3 - 0.7 cm 3 / g.

8. 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 a pressure of 0.5 - 5 MPa, with a molar ratio of hydrogen to diolefins 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 - 7.

9. The method according to claim 8, wherein the gasoline is fluid catalytic cracking (FCC) gasoline and has a boiling point of 0°C - 280°C.

10. A method for desulfurizing gasoline containing sulfur compounds, comprising the following steps: a) Performing the selective hydrogenation step of the method according to claim 8 or 9; b) Separating the gasoline obtained in step a) into at least two fractions, the fractions containing at least one light gasoline and at least one heavy gasoline respectively; 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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