DEMERCURISATION PROCESS USING SEVERAL TYPES OF CAPTURE MASSES

Abstract

The present invention relates to a method for capturing at least one heavy metal, preferably said heavy metal is mercury, present in a hydrocarbon feedstock, said method comprising bringing said feedstock into contact with at least: - a first capture mass comprising, preferably consisting of, at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt, or zinc, preferably copper, iron or zinc, preferably M is copper, - a second capture mass comprising, preferably consisting of, a porous support based on at least one refractory oxide, and at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt ... molybdenum, nickel,cobalt or zinc, preferably M is copper.,

Description

Title of the invention: DEMERCURISATION METHOD USING SEVERAL TYPES OF CAPTURE MASSES Technical field

[0001] The present invention lies in the field of the treatment of liquid or gaseous feedstocks containing heavy metals, in particular effluents of petroleum origin and their derivatives such as gases of industrial origin such as synthesis gas, natural gas and liquid hydrocarbons. More specifically, the invention relates to the capture of heavy metals, and in particular mercury, present in a gaseous or liquid feedstock.

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

[0003] It is known that certain natural feedstocks such as natural gas condensates, crude oils or cuts from its distillation, natural gas can contain a certain number 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 Gulf of Niger, South America, North Africa or the Asia-Pacific region.

[0004] The elimination of mercury from hydrocarbons is desired at the industrial level for several reasons. On the one hand, the presence of mercury in these hydrocarbons poses risks to operators working in contact with these products because mercury is toxic. In elemental form, mercury is volatile and presents serious risks of neurotoxicity by inhalation. In organic form, mercury presents similar risks of neurotoxicity by skin contact.

[0005] On the other hand, the presence of mercury in hydrocarbons is detrimental to conventional processing operations used to recover these hydrocarbons. Conventionally, hydrocarbons are subjected to catalytic reactions such as the selective hydrogenation of olefins produced by steam cracking or the catalytic cracking of liquid hydrocarbons. However, the catalysts used generally comprising noble metals such as platinum and palladium can be deactivated by mercury. Indeed, mercury induces sintering of the catalysts by amalgamation of the noble metal nanoparticles. The reduction in the specific surface area of ​​the catalysts leads to a very significant loss of their catalytic activity.

[0006] Among other reasons, for these reasons, it is desired to eliminate or at least reduce the concentration of mercury in gaseous or liquid hydrocarbon effluents.

[0007] Industrially, the removal of mercury from gaseous or liquid effluents is carried out by circulating the effluent to be treated through guard beds filled with adsorbent materials, otherwise known as capture masses. The impurity to be removed, here mercury, is then irreversibly retained, preferably by chemisorption, within or on the surface of the capture mass and the effluent discharged from the capture mass bed is then purified.

[0008] Mercury capture can be achieved by reacting, in a capture mass, the mercury with an active phase based on elemental sulfur. In fact, elemental sulfur, S, reacts irreversibly with elemental mercury, Hg°, in the following way:

[0009] Hg° (g / 1) + S (s) HgS (s) (1)

[0010] By "Hg° (g / 1)" is meant that the mercury is dissolved in a gaseous (g) or liquid (1) fluid phase. In contrast, "(s)" designates the solid phases consisting of the active phase of the capture mass and the reaction product.

[0011] Reaction (1) is spontaneous and has a negative free energy AG (kJ / mol) over a wide temperature range, typically from 0 to 150°C. The product formed, HgS, called cinnabar or metacinnabar, is a chemically inert mineral phase that is solid over a wide temperature range. The mercury is thus trapped in the capture mass and the effluent to be treated is purified.

[0012] Conventionally, capture masses based on elemental sulfur are obtained by a method of impregnating elemental sulfur on an activated carbon type support.

[0013] However, capture masses based on elemental sulfur deposited on activated carbon very often have stability problems when the effluent to be treated is liquid or when the effluent to be treated is gaseous and humid because the active phase can be entrained by water or another liquid. This phenomenon, linked to the weak energetic interaction between the active phase and the surface of the activated carbon, to the oxidation of the active phase or to the solubility of sulfur in these media, leads to a drastic drop in the lifetime of the capture masses.

[0014] To overcome these disadvantages, it is possible to use capture masses based on metal sulfides. Copper sulfide is used in particular because of its stability and low manufacturing cost. Patent document US 7645306 describes the fact that elemental mercury, Hg° (g / l), reduces copper (II) sulfide, CuS (s), irreversibly to form copper (I) sulfide, Cu2S (s), and mercury (II) sulfide, HgS (s). This is a gas / solid or liquid / solid reaction which is all the more favored from a kinetic point of view as the specific surface area of ​​the active phase, in this case CuS, is important.

[0015] This metal sulfide can be implemented in bulk or supported form. In this second option, the role of the support consists of dispersing the active phase. So-called bulk solids are for example described in patent EP 0480603. Patents for example FR 2980722, FR 2764214 and US 7,560,413 describe the use of capture masses of the CuS type deposited on a support based essentially on alumina.

[0016] These capture masses are implemented in non-regenerative processes. Consequently, when the Hg content at the outlet of the demercurization unit exceeds the imposed specification, the unit is stopped, the used capture mass is discharged and it is replaced by a load of new capture mass. Indeed, given the serious consequences of the presence of mercury in gaseous or liquid hydrocarbon streams, the mercury specifications at the outlet of the demercurization unit are particularly severe. The significant capture capacity is therefore that known as the piercing capacity and not the saturation capacity. The piercing capacity is that determined at the moment when the mercury concentration detected at the outlet of the demercurization unit exceeds the specification set for mercury at the outlet of the unit.The saturation capacity is that determined when the capture mass is entirely saturated, that is to say when all the mercury which enters the demercurization unit leaves it.

[0017] As soon as the mercury content at the outlet of the demercurization unit exceeds the set specification, it is necessary to change the capture mass. These capture mass change operations have a cost. There is therefore always a need to improve the masses and / or the process to increase the capture capacities during drilling in Hg to extend the operating time of the demercurization unit and space out the capture mass change operations.

[0018] The applicant has surprisingly discovered that bringing a hydrocarbon feedstock comprising a heavy metal, preferably mercury, into contact with at least two capture masses of different natures makes it possible to increase the capture capacity upon drilling of the demercurization unit beyond the capture capacity upon drilling estimated from the capture capacities upon drilling of the two capture masses taken separately. Such an implementation according to the invention therefore makes it possible to space out the operations of loading and unloading the capture masses, which makes it possible to reduce operational costs. Summary of the invention

[0019] The present invention relates to a method for capturing at least one heavy metal, preferably said heavy metal is mercury, present in a hydrocarbon feedstock, said method comprising bringing said feedstock into contact with at least:

[0020] - a first capture mass comprising, preferably consisting of, at at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt, or zinc, preferably copper, iron or zinc, preferably M is copper,

[0021] - a second capture mass comprising, preferably consisting of, a porous support based on at least one refractory oxide, and at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt or zinc, preferably copper, molybdenum, nickel, cobalt or zinc, preferably M is copper.

[0022] “Based on” means comprising more than 50% by weight of the compound. DETAILED DESCRIPTION OF THE INVENTION

[0023] According to the present invention, the expression "between ... and ..." and "between .... and ..." are equivalent and mean that the limit values ​​of the interval are included in the range of values ​​described. If this is not the case and the limit values ​​are not included in the range described, such precision will be provided by the present invention.

[0024] In the sense of the present invention, the different parameter ranges for a given step such as pressure ranges and temperature ranges may be used alone or in combination. For example, in the sense of the present invention, a preferred pressure value range may be combined with a more preferred temperature value range.

[0025] In the following, particular embodiments of the invention may be described. They may be implemented separately or combined with each other, without limitation of combinations when this is technically feasible.

[0026] Embodiments of the invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0027] The textural and structural properties of the capture masses according to the invention are determined by the characterization methods known to those skilled in the art. In the following description of the invention, the term specific surface area means the BET specific surface area determined by nitrogen adsorption in accordance with the ASTM D 3663-78 standard established from the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of American Society", 60, 309, (1938).

[0028] The pore volume, the grain density and the pore distribution are determined by mercury porosimetry (cf. Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academie Press, 1999). More particularly, the pore volume is measured by mercury porosimetry according to the ASTM D4284-92 standard with a wetting angle of 140°, for example using an Autopore III™ model device from the Microméritics™ brand.

[0029] In the technique of mercury porosimetry, Kelvin's law is applied, which gives the relationship between the pressure, the diameter of the smallest pore into which the mercury penetrates at said pressure, the wetting angle and the surface tension according to the following formula in which 0 represents the diameter of the pore (nm); t the surface tension (48.5 Pa); 0 the contact angle (0 = 140 degrees); and P the pressure (Mpa): 0 = (4t cos 0).10 / P.

[0030] In the present application, the term "comprise" is synonymous with (means the same as) "include" and "contain", and is inclusive or open and does not exclude other elements not recited. It is understood that the term "comprise" includes the exclusive and closed term "consist". Charge

[0031] The feedstock treated by the process according to the invention is a hydrocarbon feedstock.

[0032] Said feedstock may be in liquid or gaseous form.

[0033] Said feed contains at least one heavy metal, for example mercury, arsenic or lead, in different forms. Preferably, the at least one heavy metal is mercury. For example, mercury may be found in a form called Hg°, corresponding to elemental or atomic mercury, in molecular form, and / or in ionic form, for example Hg2+ and its complexes. The concentration of heavy metals in the feed may be variable. In one embodiment, the feed in gaseous form to be treated may preferably contain between 10 ng and 1 g of mercury per Nm 3 of gas. In one embodiment, the feed in liquid form to be treated may preferably contain between 10 ng and 1 g of mercury per m3 of liquid.

[0034] Furthermore, the feedstock may contain arsenic and / or lead in different forms. In one embodiment, the feedstock in gaseous form to be treated may contain between 1 ng and 100 mg of lead per Nm3 of gas and between 100 ng and 100 pg of arsenic per Nm3 of gas. In one embodiment, the feedstock in liquid form to be treated may contain between 1 ng and 100 mg of lead per m3 of liquid and between 100 ng and 100 pg of arsenic per m3 of liquid. Since these heavy metals are harmful for safety reasons and for reasons of efficiency in the treatment of hydrocarbon feedstocks, they can advantageously be eliminated using the method according to the invention, or at least their content can be reduced.

[0035] Finally, in one embodiment, the hydrocarbon feedstock to be treated may contain other elements such as sulfur and nitrogen in different forms. In particular, sulfur may be present in the form of hydrogen sulfide, mercaptans, organic sulfur or thiophene. In one embodiment, the feed in gaseous form to be treated may contain between 1 ng and 1000 mg of sulfur per Nm3 of gas and between 1 ng and 100 mg of nitrogen per Nm3 of gas. In one embodiment, the feed in liquid form to be treated may contain between 1 ng and 1000 mg of sulfur per m3 of liquid and between 1 ng and 100 mg of nitrogen per m3 of liquid. Advantageously, neither the nitrogen nor the sulfur that may be present in the feed to be treated causes any loss of performance of the capture masses used in the method according to the invention.

[0036] In one embodiment, the feedstock according to the invention may be a humid gas or one containing vapors of condensable compounds, without this significantly reducing the lifetime of the capture masses used in the method according to the invention. The hygrometry rate of the gaseous feedstock, defined as the ratio of the partial pressure of water to the saturated vapor pressure of water at a given temperature, may be between 0% and 100%, preferably between 1% and 95%, and more preferably between 2% and 90%.

[0037] The hydrocarbon feedstock to be treated in the process according to the invention may advantageously be chosen from the group consisting of combustion fumes, synthesis gas, natural gas, natural gas condensates, oil, liquid or gaseous petroleum cuts, petrochemical intermediates and mixtures thereof. Preferably, the hydrocarbon feedstock treated in the process according to the invention is advantageously chosen from the group consisting of combustion fumes, synthesis gas, natural gas, natural gas condensates, crude oil and liquid hydrocarbon cuts from refineries or petrochemical plants.

[0038] Combustion fumes are advantageously produced by the combustion of hydrocarbons, biogas and coal in a boiler or by a combustion gas turbine, for example for the purpose of producing electricity. These fumes have a temperature generally between 20°C and 60°C, a pressure generally between 0.1 and 0.5 MPa and may comprise, by volume, between 50% and 80% nitrogen, between 5% and 40% carbon dioxide, between 1% and 20% oxygen, and impurities such as SOX and NOX if these impurities have not been eliminated downstream by a deacidification process.

[0039] The synthesis gas is advantageously a gas containing carbon monoxide CO, hydrogen H2 in a molar ratio H2 / CO generally equal to approximately 2, water vapor generally at saturation and carbon dioxide CO2 at a content generally of approximately 10% by volume. The pressure of the synthesis gases most frequently encountered in industry is generally between 2 and 3 MPa, but it can reach 7 MPa. The synthesis gas may also contain sulfur impurities (H2S, COS, etc.), nitrogen impurities (NH3, HCN, etc.) and halogenated impurities.

[0040] Natural gas is advantageously composed mainly of gaseous hydrocarbons, but may contain several of the following acidic compounds: carbon dioxide CO2, hydrogen sulfide H2S, mercaptans, carbon oxysulfide COS and carbon sulfide CS2. The content of these acidic compounds in natural gas is very variable and can be up to 40% by volume for CO2 and H2S. The temperature of natural gas most frequently encountered in industry can be between 20°C and 100°C and its pressure can be between 1 and 20 MPa.

[0041] Natural gas condensates are advantageously composed of liquid hydrocarbons whose production is associated with the production of natural gas. These complex liquid mixtures are very similar to crude oil.

[0042] Advantageously, the liquid refinery hydrocarbons are chosen from LPGs (C3-C4 cut), naphthas (C5-C8 cut), kerosenes and diesels.

[0043] Advantageously, the liquid hydrocarbons from petrochemical plants are chosen from LPGs (C3-C4 cut) and cracked gasolines (or “Pyrolysis Gasoline” also called “PyGas” according to English terminology). Operating conditions

[0044] The process according to the present invention comprises bringing the hydrocarbon feedstock into contact with at least:

[0045] - a first capture mass comprising, preferably consisting of, at at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt, or zinc, preferably copper, iron or zinc, preferably M is copper,

[0046] - a second capture mass comprising, preferably consisting of, a porous support based on at least one refractory oxide, and at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt or zinc, preferably copper, molybdenum, nickel, cobalt or zinc, preferably M is copper.

[0047] In a preferred embodiment according to the invention, the first capture mass constitutes at least in part a first adsorption bed crossed by the hydrocarbon feedstock, then the hydrocarbon feedstock leaving the first adsorption bed is sent to a second adsorption bed constituted at least in part by the second capture mass. Advantageously, the two adsorption beds can be implemented in a single reactor or in two separate reactors arranged in series. In this embodiment, the first and / or the second adsorption bed can further comprise any other capture mass known to those skilled in the art to be effective in mercury capture.

[0048] According to a variant of the present invention, the hydrocarbon feed passes through 3 or more adsorption beds. According to this variant, the first adsorption beds always consist at least in part of the first capture mass, and the last adsorption bed passed through always consists at least in part of the second capture mass.

[0049] In a particular embodiment, the contacting of the hydrocarbon feedstock is carried out with at least the first capture mass and the second capture mass simultaneously. In this embodiment, the first capture mass and the second capture mass constitute the same adsorption bed crossed by the hydrocarbon feedstock. In this embodiment, the adsorption bed may further comprise any other capture mass known to those skilled in the art to be effective in capturing mercury.

[0050] Advantageously, the adsorption bed(s) have a volume distribution of the first capture mass, denoted M1, and of the second capture mass, denoted M2, between 95% vol M1 / 5% vol M2 and 5% vol M1 / 95% vol M2 relative to the total volume occupied by the two capture masses.

[0051] In one embodiment, the adsorption bed(s) have a volume distribution of the first capture mass, denoted M1, and of the second capture mass, denoted M2, between 75% vol M1 / 35% vol M2 and 35% vol M1 / 75% vol M2 relative to the total volume occupied by the two capture masses.

[0052] In one embodiment, the adsorption bed(s) have a volume distribution of the first capture mass, denoted M1, and of the second capture mass, denoted M2, between 55% vol M1 / 45% vol M2 and 45% vol M1 / 55% vol M2 relative to the total volume occupied by the two capture masses.

[0053] Advantageously, the adsorption bed(s) are arranged in one or more fixed bed reactors.

[0054] The contacting of the 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. In addition, 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.

[0055] In addition, the contacting can be carried out with a VVH of between 0.1 h 1 and 50,000 h1. The term "VVH" means the Hourly Volume Velocity of the gaseous or liquid hydrocarbon feedstock in the capture mass, i.e. the volume of the gaseous or liquid hydrocarbon feedstock per reactor volume and per hour. For a gaseous hydrocarbon feedstock to be treated, the VVH can preferably be understood initially between 50 h 1 and 500 h 1. For a hydrocarbon feedstock to be treated in liquid form, the VVH can be between 0.1 h 1 and 50 h 1. First capture mass

[0056] According to the invention, the first capture mass comprises, preferably consists of, at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt, or zinc, preferably copper, iron or zinc, preferably M is copper.

[0057] According to a variant of the invention, the first capture mass contains several metals chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt, or zinc, for example copper and zinc or copper and iron.

[0058] Advantageously, the metal M content of the first capture mass is between 30 and 80% by weight, preferably from 35 to 75% by weight, preferably from 40 to 70% by weight, and more preferably between 45 and 70% by weight.

[0059] In one embodiment, the metal M is present in the first capture mass in addition in a form other than sulfide chosen from carbonates, hydroxides, oxides, oxycarbonates, hydroxycarbonates, oxyhydroxycarbonates, alone or as a mixture.

[0060] Advantageously, the first capture mass preferably has at least 70% (mol / mol) of metal M in the sulfide form MxSy, preferably at least 80% (mol / mol) of metal M in the sulfide form MxSy. Advantageously, the fraction of metal contained in the sulfide form MxSy constituting the active phase preferably verifies x<2, more preferably x <l, de manière très préférée x=l. Avantageusement, la fraction de soufre contenue dans la forme sulfure MxSy vérifie de préférence y<2. Avantageusement, lorsque le métal est le cuivre, la fraction de soufre contenue dans la forme sulfure MxSy vérifie de préférence y<2, de manière plus préférée y<l, de manière très préférée y=l. Plus avantageusement, lorsque le métal est le cuivre, la première masse de captation est telle que la fraction de cuivre et la fraction de soufre dans la forme sulfure obéit aux égalités x=l et y=l.In the context of the present invention, the expression "copper sulfide" designates chemical compounds of the CuxSy type, with 0.5 < x; y < 2, preferably x = 1 and y = 1. Preferably, the expression "copper sulfide" designates CuS.

[0061] Advantageously, the first capture mass comprises 50 to 100% by weight, preferably 55 to 95% by weight, and more preferably 60 to 90% by weight of compounds comprising the metal M relative to the total weight of the first capture mass.

[0062] The term “compound comprising the metal M” means the metal M when it is in a particular form, for example in the form of sulfide, carbonate, etc.

[0063] When the compounds comprising the metal M do not represent 100% of the first capture mass, the latter may further comprise at least one mineral filler serving as a binder, in order to facilitate its shaping and / or to give it good mechanical resistance.

[0064] Advantageously, this mineral filler is an alumina or an alumina precursor, silica, a silica-alumina, a clay (bentonite, kaolinite, montmorillonite, smectite), a zirconia, a titanium oxide or their combinations. Preferably, the mineral filler is a clay.

[0065] Advantageously, the mineral filler is present in the first capture mass at a content of between 0.1 and 50% by weight, preferably between 5 and 45% by weight and more preferably between 10 and 40% by weight.

[0066] Advantageously, the first capture mass has a specific surface area, S BET, of at least 5 m2 / g, preferably at least 10 m2 / g and even more preferably at least 15 m2 / g.

[0067] Advantageously, the first capture mass has a pore volume measured by mercury porosimetry of between 0.01 and 0.4 cmVg, preferably between 0.05 and 0.3 cmVg and even more preferably between 0.05 and 0.25 cmVg.

[0068] Advantageously, the first capture mass is in the form of a ball, extruded cylinder or multi-lobe type materials, a cartwheel, a hollow cylinder or any other geometric shape used by those skilled in the art.

[0069] In one embodiment, the first capture mass is in the form of cylindrical, trilobed or multilobed extrudates. In this embodiment, said first capture mass has a diameter of between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm, and a length of between 1 mm and 20 mm, preferably between 1 and 10 mm, in particular when said first capture mass is used in a fixed bed.

[0070] In another embodiment according to the invention, the first capture mass is in the form of a ball. In this embodiment, said first capture mass has a diameter of between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm.

[0071] Advantageously, the first capture mass has a grain-to-grain crushing (EGG) of at least 0.6 daN / mm for extrudates with a diameter of 1.6 mm, preferably at least 1 mm, and a crushing strength (ESH) of at least 1 MPa.

[0072] The method for measuring grain-to-grain crushing (EGG) consists of measuring the maximum compression shape that an extrudate can withstand before breaking, when the product is placed between two planes moving at a constant speed of 5 cm / min. The compression is applied perpendicular to one of the generatrices of the extrudate, and the grain-to-grain crushing is expressed as the ratio of the force to the length of the extruded generator.

[0073] The method for measuring crushing strength (ESH) consists of subjecting a certain quantity of extrudates to increasing pressure above a sieve and recovering the fines resulting from the crushing of the extrudates. The crushing strength corresponds to the force exerted to obtain a rate of fines representing 0.5% of the weight of the extrudates subjected to the test.

[0074] The first capture mass can advantageously be prepared by any method known to those skilled in the art, for example by granulation, kneading-extrusion, precipitation, pelletizing, atomization and more particularly according to the methods described below. For example, it is possible to prepare the first capture mass by means of a preparation method comprising the following steps:

[0075] a) mixing the solid precursor(s) of the metal(s) M chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt or zinc;

[0076] b) optionally, a mineral filler is added to the mixture resulting from step a), for example chosen from aluminas, clays, silicas, titanium oxides, at a content of between 0.1 and 60% by weight, preferably between 5 and 55% by weight and more preferably between 10 and 50% by weight;

[0077] c) a paste is prepared by bringing the mixture from step a) or optionally from step b) into contact with a solution containing an acidic or basic peptizing agent, resulting in a paste being obtained (peptization);

[0078] d) kneading the dough obtained in step c);

[0079] e) extruding the kneaded paste from step d) at a pressure ranging from 3 to 10 MPa;

[0080] f) optionally, the extrudates obtained in step e) are dried at a temperature between 70 and 160°C for a period of 1 to 24 hours;

[0081] g) the extrudates from step e) or optionally the dried extrudates from step f) are calcined at a temperature of between 200 and 800°C, for a period of between 0.5 h and 8 h, under a gas flow comprising oxygen and optionally water;

[0082] h) the solid obtained at the end of step g) is sulfurized.

[0083] In one embodiment, the sulfurization step h) can be carried out by any method leading to the formation of metal sulfide and preferably to the CuS phase in the case of the use of copper. The sulfur supply is generally carried out by hydrogen sulfide or any organosulfur precursor known to those skilled in the art. The sulfurization step is advantageously carried out in the gas phase ex-situ or in-situ, preferably it is carried out in the gas phase ex-situ, that is to say outside the capture unit. Preferably, the sulfurization is carried out at atmospheric pressure.

[0084] Advantageously, the sulfurization step h) is carried out using a gaseous mixture of nitrogen and hydrogen sulfide where the molar concentration of hydrogen sulfide is between 1000 ppm and 10% and preferably between 0.5 and 6% at a temperature between 25 and 400°C, preferably between 50 and 250°C.

[0085] Advantageously, the sulfurization rate of the first capture mass defined as the ratio of the number of moles of sulfur contained in the first capture mass to the number of moles of metal contained in the first capture mass in the 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. Advantageously, the sulfurization rate is equal to 1.

[0086] Advantageously, an organic adjuvant may be used during step c) of preparation (removed during the step of calcination of the first capture mass during its manufacture) such as cellulose derivatives, polyethylene glycols, aliphatic monocarboxylic acids, alkylated aromatic compounds, sulfonic acid salts, fatty acids, polyvinyl pyridine, polyvinyl alcohol, methylcellulose and other additives known to those skilled in the art.

[0087] According to a variant, it is possible to prepare the first capture mass by means of a preparation process where one or more precursors of the metal(s) M are added not in powder form but after dispersion or solubilization in the solution used in step c). Second capture mass

[0088] According to the invention, the second capture mass comprises, preferably consists of, a porous support based on at least one refractory oxide, and at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt or zinc, preferably copper, molybdenum, nickel, cobalt or zinc, preferably M is copper.

[0089] According to a variant of the invention, the second capture mass contains several metals chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt, or zinc, for example copper and zinc or copper and iron.

[0090] The porous support is advantageously based on a compound chosen from alumina, silica, silica-alumina, titanium or their combination. Preferably, the porous support is based on alumina.

[0091] The porous support used in the second capture mass is advantageously made up of a plurality of juxtaposed agglomerates.

[0092] Advantageously, the alumina(s) of the porous support used in the second capture mass according to are of type y, q, y or ô. Preferably, they are of type y or ô.

[0093] Advantageously, the content of metal M in the second capture mass is between 1 and 50% by weight, preferably from 3 to 45% by weight, preferably from 5 to 40% by weight, and more preferably between 10 and 35% by weight.

[0094] In one embodiment, the metal M is present in the second capture mass in addition in a form other than sulfide chosen from carbonates, hydroxides, oxides, oxycarbonates, hydroxycarbonates, oxyhydroxycarbonates, alone or as a mixture.

[0095] Advantageously, the second capture mass according to the invention preferably has at least 90% (mol / mol) of metal M in the sulfide form MxSy, preferably at least 95% (mol / mol) of metal M in the sulfide form MxSy. The fraction of metal contained in the sulfide form MxSy constituting the active phase preferably verifies x<2, more preferably x <l, de manière très préférée x=l. La fraction de soufre contenue dans la forme sulfure MxSy vérifie de préférence y<2. Lorsque le métal est le cuivre, la fraction de soufre contenue dans la forme sulfure MXS y vérifie de préférence y<2, de manière plus préférée y<l, de manière très préférée y=l. Plus avantageusement, lorsque le métal est le cuivre, la deuxième masse de captation est telle que la fraction de cuivre et la fraction de soufre dans la forme sulfure obéit aux égalités x=l et y=l.

[0096] Advantageously, the second capture mass has a specific surface area, S BET, of at least 50 m2 / g, preferably at least 70 m2 / g and even more preferably at least 90 m2 / g.

[0097] Advantageously, the second capture mass has a pore volume measured by mercury porosimetry of between 0.2 cmVg and 1.5 cmVg, preferably between 0.2 cmVg and 1.3 cmVg and even more preferably between 0.3 cm 3 / g and 1.1 cmVg,

[0098] Advantageously, the second capture mass is in the form of balls, extrudates of the cylinder or multi-lobe type, cartwheel, hollow cylinder or any other geometric shape used by those skilled in the art.

[0099] In one embodiment according to the invention, the second capture mass is in the form of extrudates of cylindrical, trilobed or multilobed shape. In this embodiment, said second capture mass has a diameter of between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm, and a length of between 1 mm and 20 mm, preferably between 1 and 10 mm, in particular when said second capture mass is used in a fixed bed.

[0100] In another embodiment according to the invention, the second capture mass is in the form of a ball. In this embodiment, said second capture mass has a diameter of between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm.

[0101] Advantageously, the second capture mass has a grain-to-grain crushing (EGG) of at least 0.68 daN / mm for extrudates with a diameter of 1.6 mm, preferably at least 1 mm, and a crushing strength (ESH) of at least 1 MPa.

[0102] The second capture mass may be prepared by any method known to those skilled in the art, for example by co-granulation, co-kneading, co-precipitation, impregnation and more particularly according to the methods described below. For example, it is possible to prepare the second capture mass by means of a preparation method comprising the following steps:

[0103] A step a) of preparing a porous support based on alumina;

[0104] A step b) of preparing an aqueous solution containing at least one solubilized precursor of metal M chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel or cobalt;

[0105] A step c) of impregnation of the solution obtained at the end of step b) on the alumina support resulting from step a);

[0106] A step d) of maturation of the impregnated support resulting from step c) in a closed enclosure saturated with water at a temperature between 20°C and 60°C, preferably between 25 and 50°C, for a duration between 0.5 h and 8 h, preferably between 1 and 4 h;

[0107] A step e) of drying the matured solid from step d) between 70°C and 250°C, preferably between 70°C and 130°C and more preferably between 70°C and 110°C;

[0108] and / or a step f) of calcining the matured solid obtained at the end of step d) or the dried solid obtained in step e) in air, preferably in dry or humid air, preferably in air containing a relative humidity at 25°C of between 10 and 80%, preferably between 15 and 50%, at a temperature of between 300 and 800°C, preferably at a temperature of between 350°C and 600°C;

[0109] A step g) of sulfurization of the solid obtained at the end of step e) or f).

[0110] In one embodiment, the sulfurization step g) can be carried out by any method leading to the formation of metal sulfide and preferably to the CuS phase in the case of the use of copper. The sulfur supply is generally carried out by hydrogen sulfide or any organosulfur precursor known to those skilled in the art. The sulfurization step is advantageously carried out in the gas phase ex-situ or in-situ, preferably it is carried out in the gas phase ex-situ, that is to say outside the capture unit. Preferably, the sulfurization is carried out at atmospheric pressure.

[0111] Advantageously, the sulfurization step g) is carried out using a gaseous mixture of nitrogen and hydrogen sulfide where the molar concentration of hydrogen sulfide is between 1000 ppm mol and 10% mol and preferably between 0.5 mol% and 6 mol% at a temperature between 25 and 400°C, preferably between 50 and 250°C.

[0112] Advantageously, the sulfurization rate of the second capture mass defined as the ratio of the number of moles of sulfur contained in the second capture mass to the number of moles of metal contained in the second capture mass in the 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 sulfurization rate is equal to 1.

[0113] In step a), the alumina-based porous support can be synthesized by different methods known to those skilled in the art.

[0114] Advantageously, a first method for synthesizing the alumina support is as follows: A precursor of the aluminum trihydroxide type A1(OH)3, otherwise called hydrargillite or gibbsite, for example derived from the process commonly called "Bayer", is rapidly dehydrated. This dehydrated precursor is shaped, for example by granulation, then it is subjected to a hydrothermal treatment and finally to calcination to obtain the desired alumina. This method is described in more detail for example in the part entitled "Alumina" by P. Euzen, P. Raybaud, X. Krokidis, H. Toulhoat, JL Le Loarer, JP Jolivet and C. Froidefond, in "Handbook of Porous Solids" (F. Schüth, KSW Sing and J. Weitkamp, ​​Wiley-VCH, Weinheim, Germany, 2002). This method makes it possible to produce an alumina commonly called "flash alumina".

[0115] Advantageously, a second method of synthesizing the alumina support is as follows: A gel is first obtained from a precursor of the aluminum gamma-oxy(hydroxide) type AIO(OH), otherwise called boehmite, having specific surfaces of between 150 and 600 m2 / g. The boehmite gel can for example be obtained by precipitation of basic and / or acid solutions of aluminum salts induced by pH change or any other method known to those skilled in the art. This gel is then shaped, for example by kneading-extrusion. Then a series of thermal or hydrothermal treatments of the product are carried out leading to the production of the desired alumina. This method is also described in the section entitled “Alumina” by P. Euzen, P. Raybaud, X. Krokidis, H. Toulhoat, JL Le Loarer, JP Jolivet and C. Froidefond, in “Handbook of Porous Solids” (F. Schüth, KSW Sing and J. Weitkamp, ​​Wiley-VCH, Weinheim, Germany, 2002).This method makes it possible to produce an alumina commonly called “alumina gel”.

[0116] In one embodiment, the porous support may comprise 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.

[0117] Advantageously, step b) is carried out by adjusting the quantities of precursors according to the quantity of metal desired in the mass in the final state. In the case where the metal is copper, the precursors are chosen from the group consisting of copper carbonate, copper hydroxide, copper nitrate, copper hydroxy-nitrate, copper chloride, copper acetate and copper citrate. Preferably, the copper precursor is copper nitrate.Advantageously, it is possible to add to step b) of preparation, an organic adjuvant (removed during step e) and / or to step f) of calcination of the second capture mass during its manufacture) such as cellulose derivatives, polyethylene glycols, aliphatic monocarboxylic acids, alkylated aromatic compounds, sulfonic acid salts, fatty acids, polyvinyl pyridine, polyvinyl alcohol, methylcellulose and other additives known to those skilled in the art.

[0118] In a preferred variant of the preparation process, during step c), the metal precursor solution is introduced by dry impregnation. EXAMPLES

[0119] Example 1: Preparation of a first capture mass according to an embodiment of the invention - M1

[0120] A capture mass Ml is prepared by extrusion-kneading of a mixture of powders containing copper. The protocol is as follows:

[0121] a) 8 g of Cu2(OH)2CO3 powder are mixed with 8 g of CuO powder and with 14 g of bentonite clay;

[0122] b) a paste is prepared by adding additive water to the mixture from step a);

[0123] c) the dough obtained in step b) is kneaded at room temperature for 2 hours;

[0124] d) extruding the paste from step c) at 5 MPa;

[0125] e) the extrudates from step d) are calcined in humid air at 300°C;

[0126] f) the solid obtained at the end of step d) is sulfurized at atmospheric pressure under a nitrogen stream containing 5 mol% H2S diluted in nitrogen at a temperature of 250°C.

[0127] The first capture mass obtained contains 36.0% by weight of Cu and 17.8% by weight of S. The Cu content is determined by X-ray fluorescence on an Axios mAX device from PANanalytical. The sulfur content was measured using a CHNS / O Flash 2000 analyzer from ThermoFisherScientific.

[0128] It has a specific surface area measured by the BET method of 62 m2 / g and a pore volume measured by mercury porosimetry of 0.18 mL / g.

[0129] Example 2: Preparation of a second capture mass according to an embodiment of the invention - M2

[0130] A capture mass M2 is prepared by impregnation of a support S based on alumina with a pore volume measured by mercury porosimetry of 0.98 mL / g, with a solution of Cu(NO3).3H20 then sulfurization. The protocol followed is as follows:

[0131] a) an impregnation solution is prepared by dissolving Cu(NO3)2.3H2O in a volume of water making it possible to obtain the volume necessary to fill the entire porous volume of the aluminum support (concentration of the solution: 2.04.106 mol / L of Cu2+);

[0132] b) 30 g of porous support are impregnated by slow spraying with said solution prepared in the previous step;

[0133] c) the product obtained in the previous step is left to mature in a closed container for 3 hours at room temperature;

[0134] d) the material obtained in the previous step is dried at 90°C for 3 hours;

[0135] e) the material obtained in the previous step is calcined at 450°C under an atmosphere wet for 45 min in a tubular oven;

[0136] f) the product obtained in the previous step is sulphurized at atmospheric pressure under a flow of nitrogen containing 5 mol% of H2S diluted in nitrogen at a temperature of 250°C.

[0137] The second capture mass obtained contains 13.5% by weight of Cu and 5.8% by weight of S. The Cu content is determined by X-ray fluorescence on an Axios mAX device from PANanalytical. The sulfur content was measured using a CHNS / O Flash 2000 analyzer from ThermoFisherScientific.

[0138] It has a specific surface area measured by the BET method of 103 m2 / g and a pore volume measured by mercury porosimetry of 0.76 mL / g.

[0139] Example 3: Mercury capture test of masses Ml and M2 implemented separately (non-compliant) and successively (compliant)

[0140] These capture masses are brought into contact with a gaseous charge containing 3400 pg / Nm3 of Hg at 50°C under 20 bars (2 MPa) under a flow of 0.3 Nm3 / h in a fixed bed reactor (18 cm3 column). In a first case, mass Ml is used alone, in a second case, mass M2 is used alone and in a third case, mass Ml followed by mass M2 are used. In the latter case, the reactor is filled with 50% by volume of mass Ml and 50% by volume of mass M2. The test is stopped as soon as the Hg content exceeds 50 pg / Nm3 of Hg and the quantity of Hg captured is calculated.

[0141] [Tables 1] Quantity Hg captured (g) Ml 1.34 M2 0.59 50% vol Ml + 50% vol M2 1.52

[0142] In the third test, as the reactor is filled with 50% by volume of the mass Ml followed by 50% by volume of the mass M2, 0.5 x 1.34 + 0.59 x 0.5 = 0.97 g Hg should be captured. However, the reactor filled half with the mass Ml and half with the mass M2 captures 1.52 g of Hg, i.e. 56% more than expected and 13% more than the mass Ml taken separately. The sequence of the 2 capture masses therefore induces a synergistic effect because it allows more mercury to be captured than what is expected from their respective content and the quantity of mercury that they capture separately.

Claims

Claims

1. A method for capturing at least one heavy metal, preferably said heavy metal is mercury, present in a hydrocarbon feedstock, said method comprising bringing said feedstock into contact with at least: - a first capture mass comprising, preferably consisting of, at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt, or zinc, preferably copper, iron or zinc, preferably M is copper, - a second capture mass comprising, preferably consisting of, a porous support based on at least one refractory oxide, and at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt or zinc, preferably copper, iron or zinc, preferably M is copper, - a second capture mass comprising, preferably consisting of, a porous support based on at least one refractory oxide, and at least one metal M present at least partly in a sulfide form MxSy, M being chosen from the group consisting of copper, molybdenum, tungsten, iron, nickel, cobalt or zinc, preferably copper, iron or zinc, preferably M is copper, molybdenum, nickel,cobalt or zinc, preferably M is copper.,

2. Method according to claim 1 in which the first capture mass constitutes at least in part a first adsorption bed crossed by the hydrocarbon feed, then the hydrocarbon feed leaving the first adsorption bed is sent to a second adsorption bed constituted at least in part by the second capture mass.

3. Method according to claim 2 in which the adsorption beds have a volume distribution of the first capture mass, denoted Ml, and of the second capture mass, denoted M2, between 95% vol Ml / 5% vol M2 and 5% vol Ml / 95% vol M2 relative to the total volume occupied by the two capture masses.

4. Method according to any one of the preceding claims, in which the metal M content of the first capture mass is between 30 and 80% by weight, preferably from 35 to 75% by weight, preferably from 40 to 70% by weight, and more preferably between 45 and 70% by weight.

5. Method according to any one of the preceding claims in which the metal M is present in the first capture mass in addition in a form other than sulfide chosen from carbonates, hydroxides, oxides, oxycarbonates, hydroxycarbonates, oxyhydroxy- carbonates, alone or in mixture.

6. Method according to any one of the preceding claims in which the first capture mass comprises 50 to 100% by weight, preferably 55 to 95% by weight, and more preferably 60 to 90% by weight of compounds comprising the metal M relative to the total weight of the first capture mass.

7. Method according to any one of the preceding claims in which the first capture mass further comprises at least one mineral filler.

8. Method according to claim 7 in which the mineral filler is present in the first capture mass at a content of between 0.1 and 50% by weight, preferably between 5 and 45% by weight and more preferably between 10 and 40% by weight.

9. Method according to any one of the preceding claims, in which the first capture mass has a specific surface area, S bet, of at least 5 m2 / g, preferably at least 10 m2 / g and even more preferably at least 15 m2 / g.

10. Method according to any one of the preceding claims, in which the first capture mass has a pore volume measured by mercury porosimetry of between 0.01 and 0.4 cmVg, preferably between 0.05 and 0.3 cmVg and even more preferably between 0.05 and 0.25 cmVg.

11. Method according to any one of the preceding claims, in which the porous support of the second capture mass is based on a compound chosen from alumina, silica, silica-alumina, titanium or their combination, preferably the porous support is based on alumina.

12. Method according to any one of the preceding claims, in which the content of metal M in the second capture mass is between 1 and 50% by weight, preferably from 3 to 45% by weight, more preferably from 5 to 40% by weight, and more preferably between 10 and 35% by weight.

13. Method according to any one of the preceding claims in which the metal M is present in the second capture mass in addition in a form other than sulfide chosen from carbonates, hydroxides, oxides, oxycarbonates, hydroxycarbonates, oxyhydroxy-carbonates, alone or in a mixture.

14. A method according to any preceding claim in wherein the second capture mass has a specific surface area, SBET, of at least 50 m2 / g, preferably at least 70 m2 / g and even more preferably at least 90 m2 / g.

15. Method according to any one of the preceding claims, in which the second capture mass has a pore volume measured by mercury porosimetry of between 0.2 cmVg and 1.5 cm3 / g, preferably between 0.2 cmVg and 1.3 cmVg and even more preferably between 0.3 cmVg and 1.1 cmVg.