Mercury abatement method using multiple types of trapping materials

Abstract

This invention relates to a method for capturing at least one heavy metal, preferably mercury, present in a hydrocarbon feedstock, the method comprising contacting the feedstock with at least: - a first capturing substance comprising, preferably, at least one of, at least partially in the form of M x S y A metal M existing in the form of a sulfide, M being selected from copper, molybdenum, tungsten, iron, nickel, cobalt, and zinc, preferably copper, iron, and zinc; preferably, M is copper; a second trapping material comprising, preferably consisting of: a porous support based on at least one refractory oxide, and at least one element at least partially composed of M. x S y The metal M exists in the form of a sulfide, and M is selected from copper, molybdenum, tungsten, iron, nickel, cobalt and zinc, preferably copper, molybdenum, nickel, cobalt and zinc; preferably, M is copper.

Description

Technical Field

[0001] This invention pertains to the field of processing liquid or gaseous feedstocks containing heavy metals, particularly petroleum-derived effluents and their derivatives, such as industrial gases like syngas, natural gas, and liquid hydrocarbons. More specifically, this invention relates to the capture of heavy metals, and in particular mercury, present in gaseous or liquid feedstocks.

[0002] More specifically, the present invention relates to an improved method for capturing heavy metals present in gaseous or liquid hydrocarbon feedstocks by linking several types of capturing substances together. Existing technology

[0003] It is known that certain natural feedstocks (such as natural gas condensate, crude oil or fractions produced by their distillation, and natural gas) can contain amounts of heavy metals. In particular, mercury is a metallic contaminant found in gaseous or liquid hydrocarbons produced in many regions of the world, such as the Niger Gulf, South America, North Africa, or the Asia-Pacific region.

[0004] For several reasons, it is desirable to remove mercury from hydrocarbons at the industrial level. On the one hand, the presence of mercury in these hydrocarbons spreads the risk to workers exposed to these products, as mercury is toxic. Mercury in its elemental form is volatile and presents a serious neurotoxic risk through inhalation. In its organic form, mercury presents a similar neurotoxic risk through skin contact.

[0005] Furthermore, the presence of mercury in hydrocarbons is detrimental to conventional processing operations used to upgrade these hydrocarbons. Hydrocarbons typically undergo catalytic reactions, such as the selective hydrogenation of olefins produced by steam cracking or catalytic cracking of liquid hydrocarbons. In fact, catalysts commonly used, which often contain noble metals (e.g., platinum and palladium), can be deactivated by mercury. This is because mercury induces sintering of the catalyst by binding noble metal nanoparticles. The reduction in the specific surface area of ​​the catalyst leads to a very significant loss of its catalytic activity.

[0006] In particular, for these reasons, it is desirable to remove mercury or at least reduce its concentration from gaseous or liquid hydrocarbon effluents.

[0007] In industry, the removal of mercury from gaseous or liquid effluents is carried out by circulating the effluent to be treated through a protective bed filled with an adsorbent material (also known as a trapping substance). The impurity to be removed (in this case, mercury) is then irreversibly retained, preferably by chemisorption, in or on the surface of the trapping substance, and the effluent discharged from the trapping substance bed is then purified.

[0008] Mercury can be captured by reacting it with an elemental sulfur-based active phase in the capturing material. This is because elemental sulfur (S) reacts irreversibly with elemental mercury (Hg) in the following manner: Hg (g / l) + S (s) → HgS (s) (1) The term "Hg (g / l)" should be understood as mercury dissolved in a gaseous (g) or liquid (l) fluid phase. In contrast, "(s)" indicates a solid phase formed by the active phase of the trapping substance and the reaction products.

[0009] Reaction (1) is spontaneous and exhibits a negative free energy ΔG (kJ / mol) over a wide temperature range (typically 0°C to 150°C). The resulting product, HgS, known as cinnabar or metacinnabar, is a chemically inert and solid inorganic phase over a wide temperature range. Mercury is thus trapped in the trapping material, and the effluent to be treated is purified.

[0010] Typically, elemental sulfur-based traps are obtained by impregnating elemental sulfur onto a carrier of activated carbon.

[0011] However, when the effluent to be treated is liquid, or when the effluent to be treated is gaseous and moist, elemental sulfur-based traps deposited on activated carbon often exhibit stability problems because the active phase can be entrained by water or other liquids. This phenomenon is related to the weak energy interactions between the active phase and the activated carbon surface, the oxidation of the active phase, or the solubility of sulfur in these media, leading to a sharp decline in the trap lifetime.

[0012] To overcome these drawbacks, trapping materials based on metal sulfides can be used. Copper sulfide is particularly favored due to its stability and low manufacturing cost. Patent document US 7,645,306 describes the irreversible reduction of copper(II)CuS(s) by elemental mercury (Hg) (g / l) to form copper(I)Cu2S(s) and mercury(II)HgS(s). This is a gas / solid or liquid / solid reaction, which is kinetically more favorable due to the higher specific surface area of ​​the active phase (CuS in this case).

[0013] This metal sulfide can be used in bulk or supported form. In the second option, the support serves to disperse the active phase. Solids referred to as bulk solids are described, for example, in patent EP 0 480 603. Patents such as FR 2 980 722, FR 2 764 214, and US 7 560 413 describe the use of CuS-type trapping materials deposited on substantially alumina-based supports.

[0014] These captured materials are used in non-renewable processes. Therefore, when the mercury concentration at the mercury removal unit outlet exceeds specified limits, the unit is shut down, the waste captured material is discharged, and new captured material is loaded. This is because the mercury limits at the mercury removal unit outlet are particularly stringent due to the serious consequences of the presence of mercury in gaseous or liquid hydrocarbon streams. Therefore, the important capture capacity is known as the breakthrough capacity, not the saturation capacity. The breakthrough capacity is the capacity determined when the mercury concentration detected at the mercury removal unit outlet exceeds the mercury limit set at that unit outlet. The saturation capacity is the capacity determined when the captured material is completely saturated, i.e., when all the mercury entering the mercury removal unit has been discharged.

[0015] Once the mercury content at the mercury removal unit outlet exceeds the set specification, the trapping material must be replaced. These trapping material replacement operations are costly. Therefore, there is always a need to improve the material and / or method to increase Hg penetration trapping capacity, extend the operating time of the mercury removal unit, and space out trapping material replacement operations.

[0016] The applicant company has surprisingly discovered that contacting a hydrocarbon feedstock containing heavy metals (preferably mercury) with at least two trapping substances of different properties allows the penetration trapping capacity of the mercury removal unit to be increased beyond the penetration trapping capacity estimated from the penetration trapping capacities of the two trapping substances obtained separately. Therefore, this embodiment of the invention allows for the separation of the loading and unloading of trapping substances, which reduces operating costs. Invention Overview This invention relates to a method for capturing at least one heavy metal, preferably mercury, present in a hydrocarbon feedstock, the method comprising contacting the feedstock with at least the following: - A first trapping substance, comprising, preferably, of the following: at least one at least partially composed of M x S y The metal M exists in sulfide form, and M is selected from copper, molybdenum, tungsten, iron, nickel, cobalt, and zinc, preferably copper, iron, and zinc; preferably, M is copper. - A second trapping material comprising, preferably, the following: a porous support based on at least one refractory oxide, and at least one component at least partially composed of M x S y The metal M exists in the form of a sulfide, and M is selected from copper, molybdenum, tungsten, iron, nickel, cobalt and zinc, preferably copper, molybdenum, nickel, cobalt and zinc; preferably, M is copper.

[0018] The term “based on” should be understood to mean that the compound comprises more than 50% by weight. Invention Details According to the present invention, the expressions "between... and..." and "between... and..." are equivalent, and mean that the limit value of the interval is included within the range of values ​​described. If this is not the case and the limit value is not included within the range described, the present invention will provide such information.

[0020] Within the scope of this invention, the parameter ranges for a given stage, such as pressure and temperature ranges, can be used individually or in combination. For example, within the scope of this invention, a pressure range is preferably combined with a more preferred temperature range.

[0021] Specific embodiments of the invention may then be described. They may be implemented individually or in combination, and there are no limitations on the combination when this is technically feasible.

[0022] Embodiments of the invention will now be described in detail. Numerous specific details are presented in the following detailed description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0023] The texture and structural properties of the trapping material according to the invention were determined by characterization methods known to those skilled in the art. In the following description of the invention, specific surface area should be understood to mean the BET specific surface area determined by nitrogen adsorption according to standard ASTM D 3663-78, which was drafted from the Brunauer-Emmett-Teller method described in the journal “The Journal of the American Chemical Society”, 60, 309 (1938).

[0024] Pore ​​volume, particle density, and pore distribution were determined by mercury porosimetry (see Rouquerol F., Rouquerol J., and Sing K., “Adsorption by Powders and Porous Solids: Principles, Methodology, and Applications”, Academic Press, 1999). More specifically, pore volume was measured by mercury porosimetry according to standard ASTM D4284-92, at a wetting angle of 140°, for example, using an Autopore III™ model instrument from Micromeritics™.

[0025] In mercury porosity measurement techniques, the Kelvin equation is applied, which gives the relationship between pressure, the diameter of the smallest pore into which mercury can penetrate under said pressure, the wetting angle, and the surface tension, according to the following formula, where Ø represents the pore diameter (nm), t represents the surface tension (48.5 Pa), θ represents the contact angle (θ = 140 degrees), and P represents the pressure (MPa): Ø = (4tcosθ).10 / P.

[0026] In this patent application, the term “comprising” is synonymous with “including” and “containing” (meaning the same thing) and is inclusive or open-ended, not excluding other elements not mentioned. It should be understood that the verb “comprising” includes the exclusive and closed term “consisting of”.

[0027] raw material The raw material processed by the method according to the present invention is a hydrocarbon raw material.

[0028] The raw materials can be in liquid or gaseous form.

[0029] The raw material contains at least one heavy metal, such as mercury, arsenic, or lead, in various forms. Preferably, the at least one heavy metal is mercury. For example, mercury can be found in the form of "Hg," corresponding to elemental mercury or atomic mercury, in molecular and / or ionic forms, such as Hg. 2+ and its complexes. The concentration of heavy metals in the feedstock can be variable. In one embodiment, the gaseous feedstock to be treated preferably contains 1 Sm 3 The gaseous material contains between 10 ng and 1 g of mercury. In one embodiment, the liquid feedstock to be processed preferably contains mercury per m³. 3 Liquid mercury, ranging from 10 ng to 1 g.

[0030] Furthermore, the raw material may contain arsenic and / or lead in various forms. In one embodiment, the gaseous raw material to be treated may contain per Sm 3 Lead gas from 1 ng to 100 mg and per Sm 3 The gaseous arsenic contains 100 ng to 100 µg. In one embodiment, the liquid feedstock to be treated may contain arsenic per m³. 3 Liquid lead between 1 ng and 100 mg and per m 3 Arsenic in liquid form, ranging from 100 ng to 100 µg. Since these heavy metals are harmful for safety reasons and for the effectiveness of hydrocarbon feedstock processing, they can be advantageously removed, or at least their concentration reduced, by the method according to the invention.

[0031] Finally, in one embodiment, the hydrocarbon feedstock to be treated may contain other elements, such as sulfur and nitrogen, in various forms. In particular, sulfur may exist as hydrogen sulfide, thiols, organic sulfur, or also thiophene. In one embodiment, the gaseous feedstock to be treated may contain per Sm 3 Sulfur in gases ranging from 1 ng to 1000 mg and per Sm 3 The nitrogen content is between 1 ng and 100 mg. In one embodiment, the liquid feedstock to be processed may contain nitrogen per m³. 3 Liquid sulfur ranging from 1 ng to 1000 mg and per m 3 The nitrogen content is between 1 ng and 100 mg in liquid form. Advantageously, neither nitrogen nor sulfur, which may be present in the raw material to be treated, will cause a loss of performance quality of the trapping material used in the method according to the invention.

[0032] In one embodiment, the feedstock according to the invention can be a wet gas or a gas containing vapors of condensable compounds without significantly reducing the lifetime of the trapping material used in the method according to the invention. The relative humidity of the gaseous feedstock, defined as the ratio of water pressure to saturated water vapor pressure at a given temperature, can be between 0% and 100%, preferably between 1% and 95%, and more preferably between 2% and 90%.

[0033] In the method according to the invention, the hydrocarbon feedstock to be processed can advantageously be selected from combustion flue gas, syngas, natural gas, natural gas condensate, oil, liquid or gaseous petroleum fractions, petrochemical intermediates, and mixtures thereof. Preferably, the hydrocarbon feedstock to be processed in the method according to the invention is advantageously selected from combustion flue gas, syngas, natural gas, natural gas condensate, crude oil, and liquid hydrocarbon fractions from refineries or petrochemical plants.

[0034] Combustion flue gas is advantageously produced by burning hydrocarbons, biogas, and coal in a boiler or by a gas turbine, for example, for power generation. These flue gases typically have temperatures between 20°C and 60°C and pressures typically between 0.1 and 0.5 MPa, and by volume may contain 50% to 80% nitrogen, 5% to 40% carbon dioxide, 1% to 20% oxygen, and other gases such as SO₂. x and NO x Impurities, if these impurities are not removed downstream by deacidification methods.

[0035] Syngas advantageously contains the following gases: carbon monoxide (CO) and hydrogen (H2) (the H2 / CO molar ratio is typically about 2), usually saturated water vapor, and carbon dioxide (CO2) typically present in a concentration of about 10% by volume. The pressure of syngas most commonly encountered in industry is typically between 2 and 3 MPa, but can reach 7 MPa. Syngas may also contain sulfur-containing impurities (H2S, COS, etc.), nitrogen-containing impurities (NH3, HCN, etc.), and halogenated impurities.

[0036] Natural gas is advantageously composed primarily of gaseous hydrocarbons, but may contain several acidic compounds, including carbon dioxide (CO2), hydrogen sulfide (H2S), thiols, carbon oxysulfide (COS), and carbon disulfide (CS2). The content of these acidic compounds in natural gas varies considerably, reaching up to 40% by volume for CO2 and H2S. The most commonly encountered industrial natural gas temperatures range from 20°C to 100°C, and its pressures range from 1 to 20 MPa.

[0037] Natural gas condensate is advantageously composed of liquid hydrocarbons, and its production is linked to natural gas production. These complex liquid mixtures are very similar to crude oil.

[0038] Advantageously, the liquid hydrocarbons from the refinery are selected from LPGs (C3-C4 fractions), naphtha (C5-C8 fractions), kerosene, and diesel.

[0039] Advantageously, the liquid hydrocarbons from petrochemical plants are selected from LPGs (C3-C4 fractions) and gasoline from cracking (or Pyrolysis Gasoline, also known as PyGas).

[0040] Operating conditions The method according to the invention includes contacting the hydrocarbon feedstock with at least the following substances: - A first trapping substance, comprising, preferably, of the following: at least one at least partially composed of M x S y The metal M exists in sulfide form, and M is selected from copper, molybdenum, tungsten, iron, nickel, cobalt, and zinc, preferably copper, iron, and zinc; preferably, M is copper. - A second trapping material comprising, preferably, the following: a porous support based on at least one refractory oxide, and at least one component at least partially composed of M x S y The metal M exists in the form of a sulfide, and M is selected from copper, molybdenum, tungsten, iron, nickel, cobalt and zinc, preferably copper, molybdenum, nickel, cobalt and zinc; preferably, M is copper.

[0041] In a preferred embodiment of the invention, a first trapping material at least partially forms a first adsorption bed through which the hydrocarbon feedstock passes, and the hydrocarbon feedstock exiting the first adsorption bed is then fed to a second adsorption bed at least partially formed by a second trapping material. Advantageously, the two adsorption beds can be used in a single reactor or in two separate reactors arranged in series. In this embodiment, the first and / or second adsorption beds may additionally contain any other trapping materials known to those skilled in the art that are effective in trapping mercury.

[0042] According to an alternative form of the invention, the hydrocarbon feedstock passes through three or more adsorption beds. According to this alternative form, the first adsorption bed is always at least partially formed by a first trapping material, and the last adsorption bed passed through is always at least partially formed by a second trapping material.

[0043] In a particular embodiment, the operation of contacting the hydrocarbon feedstock with at least a first trapping substance and a second trapping substance is performed simultaneously. In this embodiment, the first trapping substance and the second trapping substance form a single adsorption bed through which the hydrocarbon feedstock passes. In this embodiment, the adsorption bed may additionally contain any other trapping substances known to those skilled in the art that are effective in trapping mercury.

[0044] Advantageously, the adsorption bed(s) exhibits a volumetric distribution of the first trapped substance (denoted as M1) and the second trapped substance (denoted as M2) between 95% M1 / 5% M2 and 5% M1 / 95% M2 relative to the total volume occupied by the two trapped substances.

[0045] In one embodiment, the adsorption bed(s) exhibits a volumetric distribution of a first trapped substance (denoted as M1) and a second trapped substance (denoted as M2) between 75% M1 / 35% M2 and 35% M1 / 75% M2 relative to the total volume occupied by the two trapped substances.

[0046] In one embodiment, the adsorption bed(s) exhibits a volumetric distribution of a first trapped substance (denoted as M1) and a second trapped substance (denoted as M2) between 55% M1 / 45% M2 and 45% M1 / 55% M2 relative to the total volume occupied by the two trapped substances.

[0047] Advantageously, the adsorption bed(s) are arranged in one or more fixed-bed reactors.

[0048] The operation of contacting a hydrocarbon feedstock containing at least one heavy metal, preferably mercury, can be carried out at a temperature between -50°C and 150°C, preferably between 0°C and 110°C, and more preferably between 20°C and 100°C. Furthermore, it can be carried out at an absolute pressure between 0.01 and 20 MPa, preferably between 0.1 and 15 MPa, and more preferably between 0.1 and 12 MPa.

[0049] In addition, contact operation can be performed at an HSV of 0.1h. -1 Up to 50,000 h -1 The process is carried out below. The term "HSV" is understood to refer to the space-time velocity of gaseous or liquid hydrocarbon feedstock in the trapping material, i.e., the volume of gaseous or liquid hydrocarbon feedstock per reactor volume and per hour. For the gaseous hydrocarbon feedstock to be treated, an HSV of 50 h⁻¹ is preferably preferred. -1 Up to 500 h -1 Between. For the liquid hydrocarbon feedstock to be processed, the HSV can be between 0.1 h. -1 Up to 50 h -1 between.

[0050] First trap material According to the present invention, the first trapping substance comprises, preferably, the following: at least one of which is at least partially composed of M x S y The metal M exists in the form of a sulfide, and M is selected from copper, molybdenum, tungsten, iron, nickel, cobalt and zinc, preferably copper, iron and zinc; preferably, M is copper.

[0051] According to an alternative embodiment of the invention, the first trapping material contains several metals selected from copper, molybdenum, tungsten, iron, nickel, cobalt, and zinc, such as copper and zinc or copper and iron.

[0052] Advantageously, the content of metal M in the first captured substance is between 30% by weight and 80% by weight, preferably between 35% by weight and 75% by weight, preferably between 40% by weight and 70% by weight, and more preferably between 45% by weight and 70% by weight.

[0053] In one embodiment, metal M is present in the first trapping substance in a form other than a sulfide, the form being selected from carbonates, hydroxides, oxides, oxycarbonates, hydroxycarbonates, or oxyhydroxycarbonates, alone or as a mixture.

[0054] Advantageously, the first trapping material preferably exhibits at least 70% (mol / mol) of metal M as M x S y In the form of sulfides, preferably at least 80% (mol / mol) of metal M is in the form of M. x S ySulfide form. Advantageously, M constitutes the active phase. x S y The metallic portion contained in the sulfide form preferably has x ≤ 2, more preferably x ≤ 1, and very preferably x = 1. Advantageously, M x S y The sulfur content in the sulfide form preferably confirms y ≤ 2. Advantageously, when the metal is copper, with M x S y The sulfur portion contained in the sulfide form is preferably confirmed to be y ≤ 2, more preferably y ≤ 1, and very preferably y = 1. More advantageously, when the metal is copper, the first trapping substance causes the copper portion and sulfur portion in the sulfide form to follow the equations x = 1 and y = 1. In the context of this invention, the expression "copper sulfide" means Cu x S y A chemical compound of the type wherein 0.5 ≤ x; y ≤ 2, preferably x = 1 and y = 1. Preferably, the expression "copper sulfide" refers to CuS.

[0055] Advantageously, the first trapping substance comprises 50% to 100% by weight, preferably 55% to 95% by weight, and more preferably 60% to 90% by weight, of a compound containing metal M, relative to the total weight of the first trapping substance.

[0056] The term "compound containing metal M" is understood to mean metal M when it is in a specific form, such as a sulfide, carbonate, etc.

[0057] When the compound containing metal M does not constitute 100% of the first trapping material, the latter may additionally contain at least one inorganic filler that acts as a binder to facilitate its formation and / or impart good mechanical strength.

[0058] Advantageously, the inorganic filler is alumina or alumina precursor, silica, silica-alumina, clay (bentonite, kaolinite, montmorillonite, smectite), zirconium oxide, titanium oxide, or combinations thereof. Preferably, the inorganic filler is clay.

[0059] Advantageously, the inorganic filler is present in the first trapping material in an amount between 0.1% by weight and 50% by weight, preferably between 5% by weight and 45% by weight, and more preferably between 10% by weight and 40% by weight.

[0060] Advantageously, the first captured substance exhibits a specific surface area S of at least 5 m² / g, preferably at least 10 m² / g, and even more preferably at least 15 m² / g. BET .

[0061] Advantageously, the first trapping material exhibits a pore volume between 0.01 and 0.4 cm³ / g, preferably between 0.05 and 0.3 cm³ / g, and even more preferably between 0.05 and 0.25 cm³ / g, as measured by mercury porosimetry.

[0062] Advantageously, the first trapping material is provided in the form of beads, cylindrical or multi-leaf type extrusions, wheel-shaped, hollow cylinders or any other geometry used by those skilled in the art.

[0063] In one embodiment, the first trapping material is provided in the form of an extrusion in a cylindrical, trilobal, or multilobal shape. In this embodiment, the first trapping material exhibits a diameter between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm, and a length between 1 mm and 20 mm, preferably between 1 and 10 mm, particularly when the first trapping material is used in a fixed bed.

[0064] In another embodiment of the invention, the first trapping material is provided in the form of beads. According to this embodiment, the first trapping material exhibits a diameter between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm.

[0065] Advantageously, the first trapping material exhibits a single pellet crushing (SPC) of at least 0.6 daN / mm and a crushing strength (CS) of at least 1 MPa for extrudates having a diameter of 1.6 mm, preferably at least 1 mm.

[0066] The method for measuring single-particle crushing (SPC) involves measuring the maximum form of compression that a product can withstand before it breaks when placed between two planes moving at a constant speed of 5 cm / min. The compression is applied perpendicular to a generatrix of the extrudate, and single-particle crushing is expressed as the ratio of force to the length of the extrudate generatrix.

[0067] Crushing strength (CS) is measured by applying gradually increasing pressure to a given amount of extrudate above a sieve and recovering the fine particles produced by crushing the extrudate. Crushing strength corresponds to the force applied to obtain a fine particle level of 0.5% of the weight of the extrudate being tested.

[0068] The first trapping material can advantageously be prepared by any method known to those skilled in the art, such as by granulation, kneading-extrusion, precipitation, pelletizing, atomization, and more specifically by the following methods. For example, the first trapping material can be prepared by means of a preparation method comprising the following stages: a) Mix one or more solid precursors of one or more metals M selected from copper, molybdenum, tungsten, iron, nickel, cobalt and zinc; b) Optionally, an inorganic filler, such as selected from alumina, clay, silica or titanium oxide, is added to the mixture produced from stage a) in an amount between 0.1% by weight and 60% by weight, preferably between 5% by weight and 55% by weight, and more preferably between 10% by weight and 50% by weight. c) A paste is prepared by contacting a mixture produced from stage a) or optionally from stage b) with a solution containing an acidic or basic peptizing agent, resulting in a paste (peptide). d) Knead the paste obtained in stage c); e) The kneaded paste produced in stage d) will be extruded under a pressure of 3 to 10 MPa; f) Optionally, the extrudate obtained in stage e) is dried at a temperature between 70°C and 160°C for a period of 1 to 24 hours; g) The extrudate produced in stage e) or optionally the dried extrudate produced in stage f) is calcined in a gas stream containing oxygen and optionally water at a temperature between 200°C and 800°C for a period of time between 0.5 hours and 8 hours. h) Sulfide the solid obtained at the end of stage g).

[0069] In one embodiment, the sulfidation stage (h) can be carried out by any method that leads to the formation of metal sulfides, and preferably in the case of copper, in the presence of the CuS phase. Sulfur is typically supplied by hydrogen sulfide or any organic sulfur precursor known to those skilled in the art. The sulfidation stage is advantageously carried out in the gas phase, either in situ or ex-situ; preferably, it is carried out in the gas phase, i.e., outside the trapping unit. Preferably, the sulfidation is carried out at atmospheric pressure.

[0070] Advantageously, the sulfidation stage h) is carried out by a gaseous mixture of nitrogen and hydrogen sulfide, wherein the molar concentration of hydrogen sulfide is between 1000 ppm and 10%, and preferably between 0.5% and 6%, at a temperature between 25°C and 400°C, preferably between 50°C and 250°C.

[0071] Advantageously, the degree of sulfidation of the first trapping material (defined as the ratio of the number of moles of sulfur contained in the first trapping material to the number of moles of metal contained in the first trapping material in oxide state) is greater than or equal to 0.50, preferably greater than or equal to 0.70, and very preferably greater than 0.90.

[0072] Advantageously, the degree of sulfidation is equal to 1.

[0073] Advantageously, organic auxiliaries (which are removed during the calcination stage of the first trapping substance during its manufacture) may be used during preparation stage c), such as cellulose derivatives, polyethylene glycol, aliphatic monocarboxylic acids, alkylated aromatic compounds, sulfonates, fatty acids, polyvinylpyridine, polyvinyl alcohol, methylcellulose, and other additives known to those skilled in the art.

[0074] According to an alternative approach, the first trapping substance can be prepared by means of a preparation method in which one or more metal M precursors are not added in powder form, but are added after being dispersed or dissolved in the solution used in stage c).

[0075] Second trapping material According to the present invention, the second trapping material comprises, preferably, the following: a porous support based on at least one refractory oxide, and at least one component at least partially composed of M x S y The metal M exists in the form of a sulfide, and M is selected from copper, molybdenum, tungsten, iron, nickel, cobalt and zinc, preferably copper, molybdenum, nickel, cobalt and zinc; preferably, M is copper.

[0076] According to an alternative embodiment of the invention, the second trapping material contains several metals selected from copper, molybdenum, tungsten, iron, nickel, cobalt, and zinc, such as copper and zinc or copper and iron.

[0077] The porous support is advantageously based on a compound selected from alumina, silica, silica-alumina, titanium, or combinations thereof. Preferably, the porous support is based on alumina.

[0078] The porous carrier used for the second trapping material is advantageously composed of multiple juxtaposed aggregates.

[0079] Advantageously, the alumina(one or more) used as the porous support for the second trapping material is of the χ, η, γ, or δ type. Preferably, they are of the γ or δ type.

[0080] Advantageously, the content of metal M in the second trapping material is between 1 wt% and 50 wt%, preferably between 3 wt% and 45 wt%, more preferably between 5 wt% and 40 wt%, and even more preferably between 10 wt% and 35 wt%.

[0081] In one embodiment, metal M is also present in the second trapping substance in a form other than sulfides, said form being selected from carbonates, hydroxides, oxides, oxycarbonates, hydroxycarbonates, or oxyhydroxycarbonates, alone or as a mixture.

[0082] Advantageously, the second trapping material according to the invention preferably exhibits at least 90% (mol / mol) of metal M in the form of M. x S yIn the form of sulfides, preferably at least 95% (mol / mol) of metal M is in the form of M. x S y Sulfide form. M, constituting the active phase. x S y The metallic portion contained in the sulfide form preferably has x ≤ 2, more preferably x ≤ 1, and very preferably x = 1. M x S y The sulfur content in the sulfide form preferably confirms y ≤ 2. When the metal is copper, M x S y The sulfur portion contained in the sulfide form preferably has y ≤ 2, more preferably y ≤ 1, and very preferably y = 1. More advantageously, when the metal is copper, the second trapping substance causes the copper portion and the sulfur portion in the sulfide form to follow the equations x = 1 and y = 1.

[0083] Advantageously, the second trapping substance exhibits a specific surface area S of at least 50 m² / g, preferably at least 70 m² / g, and even more preferably at least 90 m² / g. BET .

[0084] Advantageously, the second trapping material exhibits a pore volume between 0.2 cm³ / g and 1.5 cm³ / g, preferably between 0.2 cm³ / g and 1.3 cm³ / g, and even more preferably between 0.3 cm³ / g and 1.1 cm³ / g, as measured by mercury porosity determination.

[0085] Advantageously, the second trapping material is provided in the form of beads, cylindrical or multi-leaf type extrusions, wheel-shaped, hollow cylinders or any other geometry used by those skilled in the art.

[0086] In one embodiment of the invention, the second trapping material is provided in the form of a cylindrical, trilobal, or multilobal extrusion. In this embodiment, the second trapping material exhibits a diameter between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm, and a length between 1 mm and 20 mm, preferably between 1 and 10 mm, particularly when the second trapping material is used in a fixed bed.

[0087] In another embodiment of the invention, the second trapping material is provided in the form of beads. According to this embodiment, the second trapping material exhibits a diameter between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm.

[0088] Advantageously, the second trapping material exhibits a single-particle crushing (SPC) of at least 0.68 daN / mm and a crushing strength (CS) of at least 1 MPa for extrudates having a diameter of 1.6 mm, preferably at least 1 mm.

[0089] The second trapping material can be prepared by any method known to those skilled in the art, such as by co-granulation, co-kneading, co-precipitation, impregnation, and more specifically according to the methods described below. For example, the second trapping material can be prepared by means of a preparation method comprising the following stages: Stage a): Preparation of a support based on porous alumina; Stage b): Prepare an aqueous solution containing at least one dissolved metal M precursor, wherein the metal M is selected from copper, molybdenum, tungsten, iron, nickel and cobalt; Stage c): The solution obtained at the end of stage b) is impregnated onto the alumina support produced in stage a); Stage d): In a closed, water-saturated container, the impregnated carrier produced in stage c) is aged for a period of 0.5 hours to 8 hours, preferably 1 hour to 4 hours, at a temperature between 20°C and 60°C, preferably between 25°C and 50°C. Stage e): Drying the cured solid produced from stage d) at a temperature between 70°C and 250°C, preferably between 70°C and 130°C, and more preferably between 70°C and 110°C; And / or stage f): calcining the cured solid obtained at the end of stage d) or the dried solid obtained in stage e) in air, preferably in dry or humid air, preferably in air containing a relative humidity between 10% and 80% at 25°C, preferably between 15% and 50%, at a temperature between 300°C and 800°C, preferably between 350°C and 600°C; Stage g): Sulfurize the solid obtained at the end of stage e) or f).

[0090] In one embodiment, the sulfidation stage (g) can be carried out by any method that results in the formation of a metal sulfide, and preferably a CuS phase when copper is used. Sulfur is typically supplied by hydrogen sulfide or any organic sulfur precursor known to those skilled in the art. The sulfidation stage is advantageously carried out in the gas phase, either in situ or ex-situ; preferably, it is carried out in the gas phase, i.e., outside the trapping unit. Preferably, the sulfidation is carried out at atmospheric pressure.

[0091] Advantageously, the sulfidation stage g) is carried out by a gaseous mixture of nitrogen and hydrogen sulfide (wherein the molar concentration of hydrogen sulfide is between 1000 mol ppm and 10 mol%, and preferably between 0.5 mol% and 6 mol%) at a temperature of 25°C to 400°C, preferably 50°C to 250°C.

[0092] Advantageously, the degree of sulfidation of the second trapping material (defined as the ratio of the number of moles of sulfur contained in the second trapping material to the number of moles of metal contained in the second trapping material in oxide state) is greater than or equal to 0.70, preferably greater than or equal to 0.90, and very preferably greater than 0.95. Advantageously, the degree of sulfidation is equal to 1.

[0093] In stage a), the porous alumina-based support can be synthesized by various methods known to those skilled in the art.

[0094] Advantageously, a first method for synthesizing a support for alumina is as follows: a precursor of aluminum hydroxide Al(OH)3 type (also known as gibbsite or trihydrate) (e.g., produced by a method commonly known as the “Bayer” process) is rapidly dehydrated. This dehydrated precursor is shaped, for example by granulation, then hydrothermally treated, and finally calcined to obtain the desired alumina. This method is described in more detail, for example, in the section entitled “Alumina” in “Handbook of Porous Solids” (F. Schüth, KSW Sing and J. Weitkamp, ​​Wiley-VCH, Weinheim, Germany, 2002). This method enables the production of alumina commonly known as “flashalumina”.

[0095] Advantageously, a second method for synthesizing a support made of alumina is as follows: First, a gel is obtained from a precursor of γ-hydroxyalumina AlO(OH) type (also known as boehmite), which exhibits a specific surface area between 150 and 600 m² / g. The boehmite gel can be obtained, for example, by precipitation of aluminum salts in alkaline and / or acidic solutions induced by pH changes, or by any other method known to those skilled in the art. The gel is then shaped, for example, by kneading-extrusion. The product is then subjected to a series of heat or hydrothermal treatments to produce the desired alumina. This method is also described in the section entitled "Alumina" in “Handbook of Porous Solids” (F. Schüth, KSW Sing and J. Weitkamp, ​​Wiley-VCH, Weinheim, Germany, 2002). This method enables the production of alumina commonly referred to as “gel alumina”.

[0096] In one embodiment, the porous support may contain sodium. The sodium oxide (Na2O) content of the porous support may be between 0 and 5000 ppm by weight, preferably between 100 and 5000 ppm by weight, and more preferably between 500 and 5000 ppm by weight.

[0097] Advantageously, stage b) is carried out by adjusting the amount of the precursor according to the desired amount of metal on the final substance in this form. In the case of copper, the precursor is selected from copper carbonate, copper hydroxide, copper nitrate, copper hydroxynitrate, copper chloride, copper acetate, and copper citrate. Preferably, the copper precursor is copper nitrate. Advantageously, organic auxiliaries (removed during stage e) and / or during the calcination of the second trapping substance in stage f) can be added in preparation stage b), such as cellulose derivatives, polyethylene glycol, aliphatic monocarboxylic acids, alkylated aromatic compounds, sulfonates, fatty acids, polyvinylpyridine, polyvinyl alcohol, methylcellulose, and other additives known to those skilled in the art.

[0098] In a preferred alternative to the preparation method, the metal precursor solution is introduced by dry impregnation during stage c). Example

[0099] Example 1: Preparation of a first trapping substance according to an embodiment of the present invention – M1 The trapping substance M1 was prepared by extrusion-kneading a mixture of copper-containing powders. The procedure is as follows: a) Mix 8 g of Cu2(OH)2CO3 powder with 8 g of CuO powder and 14 g of bentonite clay; b) Prepare a paste by adding water with additives to the mixture obtained from stage a); c) Knead the paste obtained in stage b) at ambient temperature for 2 hours; d) Extrude the paste obtained from stage c) at 5 MPa; e) Calcine the extrudate obtained from stage d) at 300°C in humid air; f) The solid obtained at the end of stage d) is vulcanized at atmospheric pressure and at 250°C in a nitrogen stream (containing 5 mol% H2S diluted in nitrogen).

[0100] The first trap obtained contained 36.0 wt% Cu and 17.8 wt% S. The Cu content was determined by X-ray fluorescence analysis on an Axios-mAX instrument from PANalytical. The sulfur content was measured using a CHNS / O Flash 2000 analyzer from Thermo Fisher Scientific.

[0101] It has a specific surface area of ​​62 m² / g as measured by the BET method and a pore volume of 0.18 ml / g as measured by the mercury porosity assay.

[0102] Example 2: Preparation of a second trapping substance according to an embodiment of the present invention – M2 The trapping substance M2 was prepared by impregnating an alumina-based support S (with a pore volume of 0.98 ml / g as measured by mercury porosimetry) with a Cu(NO3)2·3H2O solution, followed by sulfidation. The protocol followed is as follows: a) An impregnation solution was prepared by dissolving Cu(NO3)2·3H2O in a certain volume of water, which resulted in the volume necessary to fill the full pore volume of the alumina support (solution concentration: 2.04 x 10⁻⁶). -6 Cu mol / L 2+ ); b) Impregnate 30 g of porous carrier by slow spraying with the solution prepared in the previous stage; c) The product obtained in the previous stage is aged in a sealed container at ambient temperature for 3 hours; d) Dry the material obtained in the previous stage at 90°C for 3 hours; e) Calcine the material obtained in the previous stage in a tube furnace at 450°C in a humid atmosphere for 45 minutes; f) The product obtained in the previous stage is vulcanized under atmospheric pressure and at a temperature of 250°C in a nitrogen stream (containing 5 mol% H2S diluted in nitrogen).

[0103] The second trap obtained contained 13.5 wt% Cu and 5.8 wt% S. The Cu content was determined by X-ray fluorescence analysis on an Axios-mAX instrument from PANalytical. The sulfur content was measured using a CHNS / O Flash 2000 analyzer from Thermo Fisher Scientific.

[0104] It has a specific surface area of ​​103 m² / g as measured by the BET method and a pore volume of 0.76 ml / g as measured by the mercury porosity determination method.

[0105] Example 3: Separate (not in accordance with the present invention) and continuous (in accordance with the present invention) mercury capture on substances M1 and M2 test These captured substances were contacted with a gaseous feedstock containing 3400 µg / Sm³ Hg in a fixed-bed reactor (18 cm³ column) at 50 °C, 20 bar (2 MPa), and a feed flow rate of 0.3 Sm³ / h. In the first case, substance M1 was used alone; in the second case, substance M2 was used alone; and in the third case, substance M1 was used followed by substance M2. In the last case, the reactor was filled with 50 vol% substance M1 and 50 vol% substance M2. The test was stopped once the Hg content exceeded 50 µg / Sm³ Hg, and the amount of Hg captured was calculated. Amount of Hg captured (g) M1 1.34 M2 0.59 50% by volume M1 + 50% by volume M2 1.52

[0106] In the third test, with the reactor filled with 50% by volume of substance M1 followed by 50% by volume of substance M2, 0.5 × 1.34 + 0.59 × 0.5 = 0.97 g of Hg should have been captured. In fact, the reactor, filled with half substance M1 and half substance M2, captured 1.52 g of Hg, 56% more than expected and 13% more than substance M1 used separately. Therefore, the combination of these two capturing substances triggered a synergistic effect, enabling the capture of more mercury than expected from their individual contents and the amount of mercury captured by them individually.

Claims

1. A method for capturing at least one heavy metal, preferably mercury, present in a hydrocarbon feedstock, the method comprising contacting the feedstock with at least the following: -The first trapping substance comprises, preferably, the following: At least one metal M present at least partially in the form of MxSy sulfide, M being selected from copper, molybdenum, tungsten, iron, nickel, cobalt, and zinc, preferably copper, iron, and zinc; preferably, M is copper. - A second trapping material comprising, preferably, the following: a porous support based on at least one refractory oxide, and at least one component at least partially composed of M x S y The metal M exists in the form of a sulfide, and M is selected from copper, molybdenum, tungsten, iron, nickel, cobalt and zinc, preferably copper, molybdenum, nickel, cobalt and zinc; preferably, M is copper.

2. The method of claim 1, wherein the first trapping material at least partially forms a first adsorption bed through which the hydrocarbon feedstock passes, and the hydrocarbon feedstock leaving the first adsorption bed is then fed to a second adsorption bed at least partially formed by a second trapping material.

3. The method of claim 2, wherein the adsorption bed exhibits a volume distribution of the first trapped substance, denoted as M1, and the second trapped substance, denoted as M2, between 95% M1 / 5% M2 and 5% M1 / 95% M2 relative to the total volume occupied by the two trapped substances.

4. The method according to any one of the preceding claims, wherein the content of metal M in the first trapping substance is between 30% by weight and 80% by weight, preferably between 35% by weight and 75% by weight, preferably between 40% by weight and 70% by weight, and more preferably between 45% by weight and 70% by weight.

5. The method according to any one of the preceding claims, wherein the metal M is present in the first trapping substance in a form other than a sulfide, the form being selected from carbonates, hydroxides, oxides, oxycarbonates, hydroxycarbonates or oxyhydroxycarbonates, alone or as a mixture.

6. The method according to any one of the preceding claims, wherein the first trapping substance comprises 50% to 100% by weight, preferably 55% to 95% by weight, and more preferably 60% to 90% by weight, of a compound containing metal M, relative to the total weight of the first trapping substance.

7. The method according to any one of the preceding claims, wherein the first trapping substance further comprises at least one inorganic filler.

8. The method according to claim 7, wherein the inorganic filler is present in the first trapping material in an amount between 0.1% by weight and 50% by weight, preferably between 5% by weight and 45% by weight, and more preferably between 10% by weight and 40% by weight.

9. The method according to any one of the preceding claims, wherein the first trapping substance exhibits a specific surface area S of at least 5 m² / g, preferably at least 10 m² / g, and even more preferably at least 15 m² / g. BET .

10. The method according to any one of the preceding claims, wherein the first trapping substance exhibits a pore volume, as measured by mercury porosimetry, between 0.01 and 0.4 cm³ / g, preferably between 0.05 and 0.3 cm³ / g, and even more preferably between 0.05 and 0.25 cm³ / g.

11. The method according to any one of the preceding claims, wherein the porous carrier of the second trapping material is based on a compound selected from alumina, silica, silica-alumina, titanium, or combinations thereof; preferably, the porous carrier is based on alumina.

12. The method according to any one of the preceding claims, wherein the content of metal M in the second trapping substance is between 1 wt% and 50 wt%, preferably between 3 wt% and 45 wt%, preferably between 5 wt% and 40 wt%, and more preferably between 10 wt% and 35 wt%.

13. The method according to any one of the preceding claims, wherein the metal M is additionally present in the second trapping substance in a form other than a sulfide, the form being selected from carbonates, hydroxides, oxides, oxycarbonates, hydroxycarbonates or oxyhydroxycarbonates, alone or as a mixture.

14. The method according to any one of the preceding claims, wherein the second trapping substance exhibits a specific surface area S of at least 50 m² / g, preferably at least 70 m² / g, and even more preferably at least 90 m² / g. BET .

15. The method according to any one of the preceding claims, wherein the second trapping substance exhibits a pore volume, as measured by mercury porosimetry, between 0.2 cm³ / g and 1.5 cm³ / g, preferably between 0.2 cm³ / g and 1.3 cm³ / g, and even more preferably between 0.3 cm³ / g and 1.1 cm³ / g.