FR3104460A1 - Organometallic impurity capture mass prepared by the molten salt route - Google Patents

Abstract

The invention describes a mass for capturing organometallic compounds of arsenic and other heavy metals which is particularly suitable for the treatment of olefinic gasoline cuts loaded with sulfur, such as gasolines resulting from catalytic cracking. The capture mass comprises an active phase based on particles of group VIII metal sulphide prepared by a step of bringing a porous support into contact with a metal salt of said group VIII metal and a step of heating the mixture obtained at a temperature higher than the temperature of said metal salt. The invention also relates to a method of using said collection mass.

Description

Mass for capturing organometallic impurities prepared by the molten salt method

Field of the invention

The present invention relates to the field of hydrotreating gasoline cuts, in particular gasoline cuts from fluidized bed catalytic cracking units. More particularly, the present invention relates to a mass for capturing organometallic impurities such as organometallic impurities of heavy metals, silicon or phosphorus, and more particularly arsenic in hydrocarbon fractions of gasoline type rich in olefins and sulfur , as well as a method implementing said capture mass. The invention applies most particularly to the treatment of gasoline cuts containing olefins and sulfur, such as gasolines resulting from catalytic cracking, for which it is sought to extract the arsenic, without hydrogenating the olefins and the aromatics.

State of the art

The specifications for automotive fuels provide for a sharp reduction in the sulfur content in these fuels, and in particular in gasolines. This reduction is intended to limit, in particular, the sulfur and nitrogen oxide content in automobile exhaust gases. The specifications currently in force in Europe since 2009 for gasoline fuels set a maximum sulfur content of 10 ppm by weight (parts per million). Such specifications are also in force in other countries such as the United States and China, for example, where the same maximum sulfur content has been required since January 2017. To achieve these specifications, it is necessary to treat gasoline with desulfurization processes.

The main sources of sulfur in gasoline bases are so-called cracked gasolines, and mainly the gasoline fraction resulting from a catalytic cracking process of a residue from the atmospheric or vacuum distillation of a crude oil. The fraction of gasoline resulting from catalytic cracking, which represents on average 40% of the gasoline bases, in fact contributes for more than 90% to the contribution of sulfur in gasolines. Consequently, the production of low-sulphur gasolines requires a stage of desulphurization of catalytic cracking gasolines. Other sources of gasoline that may contain sulfur include coker and visbreaker gasoline or, to a lesser extent, gasoline from atmospheric distillation or steam cracked gasoline.

The elimination of sulfur in gasoline cuts consists of specifically treating these sulfur-rich gasolines by desulfurization processes in the presence of hydrogen. This is referred to as hydrodesulphurization (HDS) processes. However, these gasoline cuts and more particularly the gasolines from the FCC contain a significant proportion of unsaturated compounds in the form of mono-olefins (approximately 20 to 50% by weight) which contribute to a good octane number, diolefins (0.5 at 5% by weight) and aromatics. These unsaturated compounds are unstable and react during the hydrodesulfurization treatment. Diolefins form gums by polymerization during hydrodesulfurization treatments. This formation of gums leads to progressive deactivation of the hydrodesulphurization catalysts or progressive clogging of the reactor. Consequently, the diolefins must be eliminated by hydrogenation before any treatment of these gasolines. Traditional treatment processes desulphurize gasoline in a non-selective manner by hydrogenating a large part of the mono-olefins, which leads to a high loss in octane number and high hydrogen consumption. The most recent hydrodesulphurization processes make it possible to desulphurize cracked gasolines rich in mono-olefins, while limiting the hydrogenation of mono-olefins and consequently the loss of octane. Such methods are for example described in the documents EP-A-1077247 and EP-A-1174485.

The hydrodesulfurization processes are operated continuously over periods of at least 3 to 5 years. The catalysts used to carry out the hydrodesulfurization of sulfur-containing gasolines must therefore have good activity, good selectivity and good stability over time in order to be operated continuously for several years. However, the presence of heavy metals such as mercury or arsenic, or of contaminants such as phosphorus and silicon in the form of organometallics in the hydrocarbon feedstocks to be desulphurized leads to rapid deactivation of the hydrotreating catalysts. It is therefore necessary to remove these contaminants from the charge before bringing it into contact with these hydrodesulphurization catalysts.

Different solutions are proposed in the literature for extracting these compounds and more particularly arsenic in hydrocarbon fractions. However, there is still a need to have more efficient capture masses for the selective extraction of heavy metals such as arsenic, in the presence of olefins, with the aim of limiting the hydrogenation reactions responsible in this context for a decrease in the octane number of the gasolines concerned.

Numerous patents describe arsenic capture masses using different active phases based on transition metals, generally partially in sulphide form.

Thus, US patent 4046674 describes a process for eliminating arsenic using a capture mass containing at least one nickel compound in sulphide form in an amount of between 30% and 70% by weight (relative to the NiO form), and at least one molybdenum compound, also in sulphide form, in an amount of between 2% and 20% by weight (relative to the MoO ₃ form). Patent CN107011939A also describes a process for eliminating arsenic using a capture mass comprising nickel and molybdenum but in an amount respectively between 2% and 20% by weight of NiO and between 2% and 10% by weight of MoO ₃ .

Patent FR 2617497 describes a process for removing arsenic from hydrocarbon cuts by contacting them with a capture mass containing nickel, of which at least 50% by weight is in metal form. A person skilled in the art is well aware of the hydrogenating properties of Ni and therefore expects that the direct application of such a capture mass will lead to a more or less significant hydrogenation of a large part of the olefins present in the cut. hydrocarbon to be treated, which does not answer the problem that the present invention seeks to solve.

Patent EP 0 611 182 B1 describes a method for removing arsenic using a capture mass containing at least one metal from the nickel, cobalt, molybdenum, tungsten, chromium and palladium group, 5 to 50% by weight of said or said metals being in sulphide form.

Patent FR2876113 describes a process for eliminating arsenic using a capture mass comprising at least one metallic element chosen from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), lead (Pb) or zinc (Zn) deposited on a porous support chosen from the group consisting of aluminas, silica, silica aluminas, or titanium or magnesium oxides used alone or in a mixture with alumina or silica alumina, the metallic element being in sulphide form with a sulphidation rate at least equal to 60%, and preferably greater than 70%.

US patent 5024683 describes a process for at least partial elimination of trialkyl-arsines contained in a charge containing them comprising the step of bringing this charge into contact with a solid collection mass comprising at least one copper sulphide and a material of inorganic support.

US patent 6,759,364 and patent application US2016008795 describe catalysts suitable for capturing arsenic in hydrocarbon cuts containing nickel, molybdenum and phosphorus.

Patent application CN105562000 describes an arsenic capture agent based on copper and nickel, the metals being in oxide form.

The Applicant has surprisingly discovered that it is possible to improve the capture performance of organometallic compounds, in particular arsenic, by implementing a new capture mass. Furthermore, the process for preparing said capture mass makes it possible, without adding solvent and therefore in a very limited number of steps and above all less than the conventional preparation process (i.e. by impregnation), to obtain a mass of capture whose performance in retention of organometallic impurities is higher than those obtained by capture masses according to the prior art.

Objects of the invention

A first object according to the invention relates to a capture mass comprising an active phase based on at least one group VIII metal, said active phase being in sulphide form, and a porous oxide support chosen from the group consisting of alumina , silica, silica-alumina, or even titanium or magnesium oxide, used alone or as a mixture with alumina or silica-alumina, said capture mass being capable of being obtained by the preparation process comprising at least the following steps:

a) said porous support is brought into contact with at least one metal salt comprising at least one group VIII metal whose melting point of said metal salt is between 20 and 150° C., to form a solid mixture, the mass ratio between said metal salt and said porous support being between 0.1 and 2.5;

b) the solid mixture obtained at the end of step a) is heated with stirring to a temperature between the melting temperature of said metallic salt and 200° C. to obtain a precursor of capture mass;

c) optionally, the solid obtained at the end of step b) is dried at a temperature below 200° C. to obtain a dried capture mass precursor;

d) optionally, the solid obtained at the end of step b) or c) is calcined at a temperature greater than 200° C. and less than or equal to 1100° C. under an inert atmosphere or under an atmosphere containing oxygen to obtaining a calcined capture mass precursor;

e) optionally, the capture mass precursor obtained at the end of step c) or d) is reduced to obtain a reduced capture mass precursor;

f) the capture mass precursor obtained at the end of step b), optionally c), d) or e), is sulphided to obtain said capture mass.

It has indeed been surprisingly discovered that the implementation of this capture mass makes it possible to effectively capture organometallic impurities, and in particular organometallic impurities comprising arsenic, contained in a gasoline containing olefins and sulfur, while by limiting the degree of hydrogenation of the olefins to values generally below 30%, preferably below 20%, and even more preferably below 10%.

Preferably, said group VIII metal is chosen from nickel, iron and cobalt.

Preferably, the active phase consists of group VIII metal sulphide particles of size less than or equal to 20 nm.

Preferably, the group VIII metal content, expressed as group VIII element, is between 5 and 65% by weight relative to the total weight of the capture mass.

Another object according to the invention relates to a method for preparing a capture mass comprising an active phase based on at least one group VIII metal, said active phase being in sulphide form, and a porous oxide support chosen from the group group consisting of alumina, silica, silica-alumina, or even titanium or magnesium oxide used alone or in a mixture with alumina or silica-alumina, said process comprising the following steps:

a) said porous support is brought into contact with at least one metal salt comprising at least one group VIII metal whose melting point of said metal salt is between 20 and 150° C., to form a solid mixture, the mass ratio between said metal salt and said porous support being between 0.1 and 2.5;

b) the solid mixture obtained at the end of step a) is heated with stirring to a temperature between the melting point of said metallic salt and 200° C. to obtain a capture mass precursor;

c) optionally, the solid obtained at the end of step b) is dried at a temperature below 200° C. to obtain a dried capture mass precursor;

d) optionally, the solid obtained at the end of step b) or c) is calcined at a temperature greater than 200° C. and less than or equal to 1100° C. under an inert atmosphere or under an atmosphere containing oxygen to obtaining a calcined capture mass precursor;

e) optionally, the capture mass precursor obtained at the end of step c) or d) is reduced to obtain a reduced capture mass precursor;

f) the capture mass precursor obtained at the end of step b), optionally c), d) or e), is sulphided to obtain said capture mass.

Preferably, said metal salt is a hydrated nitrate salt.

Preferably, said metal salt is chosen from nickel nitrate hexahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate, taken alone or as a mixture.

Preferably, step b) is carried out by means of a drum operating at a speed of between 4 and 70 revolutions per minute.

Preferably, step a) is carried out for 5 minutes to 12 hours.

In one embodiment according to the invention, a step a′) of bringing the porous support into contact with an organic compound comprising oxygen and/or nitrogen and/or sulfur is carried out.

In a variant embodiment according to the invention, steps a) and a′) are carried out simultaneously, said organic compound being in solid form to form a solid mixture.

In a variant embodiment according to the invention, step a′) is carried out after the sequence of steps a) and b).

Another object according to the invention relates to a process for capturing organometallic impurities contained in a hydrocarbon feedstock implementing the capture mass according to the invention or prepared according to the preparation process according to the invention, in which said capture mass is brought into contact with the feed to be treated and a flow of hydrogen at a temperature of between 200 and 400°C, a pressure of between 0.2 and 5 MPa and a ratio of the flow rate of hydrogen to the flow rate of hydrocarbon feed between 50 and 800 Nm ³ /m ³ .

Advantageously, the organometallic impurities are chosen from organometallic impurities of heavy metals, silicon, phosphorus and arsenic.

Preferably, the feed to be treated is a catalytic cracking gasoline containing between 5% and 60% by weight of olefins relative to the total weight of the feed, 50 ppm to 6000 ppm by weight of sulfur relative to the total weight of the feed, as well as traces of arsenic in contents between 10 ppb and 1000 ppb by weight relative to the total weight of the charge.

Description of figures

Figure 1 is a schematic representation of a process for preparing a capture mass according to the invention.

Detailed description of the invention

Definitions

In the following, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief D.R. Lide, 81st edition, 2000-2001). For example, group VIII according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUPAC classification.

The specific surface of the capture mass or of the support used for the preparation of the capture mass according to the invention is understood to mean the B.E.T. determined by nitrogen adsorption in accordance with standard ASTM D 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the periodical “The Journal of American Society”, 60, 309, (1938).

In this application, the term "comprise" is synonymous with (means the same as) "include" and "contain", and is inclusive or open-ended and does not exclude other non-recited material. It is understood that the term “include” includes the exclusive and closed term “consist”.

By “macropores”, we mean pores whose opening is greater than 50 nm.

By "mesopores", we mean pores whose opening is between 2 nm and 50 nm, limits included.

By “micropores”, we mean pores whose opening is less than 2 nm.

The term “size of the group VIII metal sulphide (nano)particles” is understood to mean the size of the coherence domain of the crystallites of the group VIII metals in sulphide form. This coherence domain size of group VIII metal crystallites in sulphide form is determined by X-ray diffraction, from the width of the most intense diffraction line using the Scherrer relationship. This method, used in X-ray diffraction on powders or polycrystalline samples which links the width at mid-height of the diffraction peaks to the size of the particles, is described in detail in the reference: J. Appl. Crystal. (1978), 11, 102-113 "Scherrer after sixty years: A survey and some new results in the determination of crystallite size", J. I. Langford and A. J. C. Wilson. The size measurement of each species of nickel sulphide present is carried out by decomposition of the line of interest using functions of the Pseudo-Voigt type with a contribution of the Gaussian and Lorentzian forms equal to 0.5. This treatment is conventionally used by those skilled in the art.

Where multiple Group VIII sulfide species are present, "Group VIII metal sulfide particle size" is the weighted average of the sizes of each Group VIII sulfide species, the amount of each of the phases being determined by refinement of structure by the Rietveld method.

By total pore volume of the capture mass or of the support used for the preparation of the capture mass according to the invention is meant the volume measured by intrusion with a mercury porosimeter according to the ASTM D4284-83 standard at a maximum pressure of 4000 bar. (400 MPa), using a surface tension of 484 dyne/cm and a contact angle of 140°. The wetting angle was taken as equal to 140° by following the recommendations of the work “Engineering techniques, treatise on analysis and characterization”, pages 1050-1055, written by Jean Charpin and Bernard Rasneur.

In order to obtain better precision, the value of the total pore volume corresponds to the value of the total pore volume measured by intrusion with a mercury porosimeter measured on the sample minus the value of the total pore volume measured by intrusion with a mercury porosimeter measured on the same sample for a pressure corresponding to 30 psi (about 0.2 MPa).

The volume of macropores and mesopores is measured by mercury intrusion porosimetry according to ASTM D4284-83 at a maximum pressure of 4000 bar (400 MPa), using a surface tension of 484 dyne/cm and a contact angle of 140°. The value from which the mercury fills all the intergranular voids is fixed at 0.2 MPa, and it is considered that beyond that the mercury penetrates into the pores of the sample.

The macroporous volume of the capture mass or of the support used for the preparation of the capture mass according to the invention is defined as being the cumulative volume of mercury introduced at a pressure of between 0.2 MPa and 30 MPa, corresponding to the volume contained in pores with an apparent diameter greater than 50 nm.

The mesoporous volume of the capture mass or of the support used for the preparation of the capture mass according to the invention is defined as being the cumulative volume of mercury introduced at a pressure of between 30 MPa and 400 MPa, corresponding to the volume contained in pores with an apparent diameter between 2 and 50 nm.

The volume of the micropores is measured by nitrogen porosimetry. The quantitative analysis of the microporosity is carried out using the "t" method (method of Lippens-De Boer, 1965) which corresponds to a transformation of the initial adsorption isotherm as described in the work "Adsorption by powders and porous solids. Principles, methodology and applications” written by F. Rouquérol, J. Rouquérol and K. Sing, Academic Press, 1999.

The median mesoporous diameter is also defined as being the diameter such that all the pores, among all the pores constituting the mesoporous volume, of size less than this diameter constitute 50% of the total mesoporous volume determined by intrusion with a mercury porosimeter.

The median macroporous diameter is also defined as being the diameter such that all the pores, among all the pores constituting the macroporous volume, of size less than this diameter constitute 50% of the total macroporous volume determined by intrusion with a mercury porosimeter.

Group VIII metal content is measured by X-ray fluorescence.

Capture mass

The capture mass capable of being obtained by the preparation process as described below is in the form of a capture mass comprising, preferably consisting of, an active phase based on at least one metal of group VIII, said active phase being in sulfurized form, and a porous oxide support chosen from the group consisting of alumina, silica, silica-alumina, or even titanium or magnesium oxides used alone or mixed with the alumina or silica-alumina. Preferably, the capture mass that can be obtained by the preparation process consists of an active phase of sulfurized nickel and an alumina support.

Preferably, said group VIII metal is chosen from nickel (Ni), iron (Fe), cobalt (Co).

Preferably, said active phase does not comprise any group VIB metal.

When the Group VIII metal is nickel, the phase diagram of nickel sulfide exhibits a large number of sulfur-rich and nickel-rich phases at low temperatures. Different phases and stoichiometries of nickel sulphide are therefore possible, ranging from nickel-rich compounds such as Ni ₃ S ₂ , Ni ₆ S ₅ , Ni ₇ S ₆ , Ni ₉ S ₈ and NiS to sulfur-rich compounds such as Ni ₃ S ₄ and NiS ₂ . Note that NiS is also known to exist in two main phases, namely the hexagonal α-NiS, which is stable at high temperatures, and the rhombohedral β-NiS which is stable at low temperatures. The existence of these numerous phases makes the synthesis of nickel sulphide in the form of a single phase complex, the products therefore often being mixtures of two or more phases.

The active phase of at least one group VIII metal in sulphide form designates in the present application chemical compounds of the M _x S _y type, where M is a group VIII metal with 0.5 ≤ x/y ≤ 2 , preferably x = 1 and y = 1 or else x= 3 and y = 2. When the group VIII metal is nickel, the compounds most present are NiS in hexagonal or rhombohedral form or else Ni ₃ S ₂ .

Advantageously, the active phase of the group VIII metal in sulphide form is in the form of group VIII sulphide nanoparticles deposited on the oxide support. The size of the group VIII sulfide nanoparticles in the capture mass is preferably less than or equal to 20 nm, preferably less than or equal to 15 nm, more preferably between 1 and 12 nm.

The group VIII metal content, expressed as group VIII element, is preferably between 5 and 65% by weight relative to the total weight of the capture mass, preferably between 8 and 55% by weight, even more preferably between 12 and 40% by weight, and particularly preferably between 12 and 34% by weight.

The capture mass preferably has a total pore volume greater than or equal to 0.45 mL/g, preferably greater than or equal to 0.48 mL/g, and particularly preferably between 0.55 and 0.95 mL /g.

The capture mass has a BET specific surface of at least 40 m ² /g, preferably at least 50 m ² /g, and even more preferably between 55 and 250 m ² /g, preferably comprised between 60 and 225 m ² /g.

Said capture mass is advantageously in the form of grains having an average diameter of between 0.5 and 10 mm. The grains can have any shape known to those skilled in the art, for example the shape of beads (preferably having a diameter of between 1 and 6 mm), extrudates, tablets, hollow cylinders. Preferably, the capture mass (and the support used for the preparation of the capture mass) are either in the form of extrudates with an average diameter of between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm and with an average length of between 0.5 and 20 mm, or in the form of beads with an average diameter of between 0.5 and 10 mm, preferably between 1.4 and 4 mm. “Average diameter” of the extrudates is understood to mean the average diameter of the circle circumscribed to the cross section of these extrudates. The capture mass can advantageously be presented in the form of cylindrical, multi-lobed, tri-lobed or quadri-lobed extrudates. Preferably, its shape will be trilobed or quadrilobed. The shape of the lobes can be adjusted according to all known methods of the prior art.

The support for the capture mass is a mineral support selected from the group consisting of aluminas, silica, silica-aluminas, titanium oxides alone or mixed with alumina or silica alumina, magnesium oxides alone or mixed with alumina or silica alumina. Preferably, the support is selected from the group consisting of aluminas, silica and silica-aluminas. Very preferably, the support consists essentially of at least one alumina, that is to say it comprises at least 51% by weight, preferably at least 60% by weight, very preferably at least 80% by weight , or even at least 90% by weight of alumina relative to the total weight of said support. Preferably, said support has an alumina content greater than or equal to 90% by weight relative to the total weight of said support, optionally supplemented by silica and/or phosphorus at a total content of at most 10% by weight in equivalent SiO ₂ and/or P ₂ O ₅ , preferably less than 5% by weight, and very preferably less than 2% by weight relative to the total weight of the support. The silica and/or the phosphorus can be introduced by any technique known to those skilled in the art, during the synthesis of the alumina gel or by impregnation of the support used for the preparation of the capture mass.

Even more preferably, the support consists of alumina. Preferably, the alumina present in said support is a transition alumina such as a gamma, delta, theta, chi, rho or eta alumina, alone or as a mixture. More preferably, the alumina is a gamma, delta or theta transition alumina, alone or as a mixture.

The following characteristics of the support correspond to the characteristics of the support used for the preparation of the capture mass before the addition of the active phase.

The support used for the preparation of the capture mass preferably has a total pore volume greater than or equal to 0.68 mL/g, preferably greater than or equal to 0.70 mL/g, and in a particularly preferred manner comprised between 0 .70 and 1.0 mL/g.

The support used for the preparation of the capture mass has a BET specific surface of at least 40 m²/g, preferably at least 50 m²/g, and even more preferably between 60 and 300 m ² / g, preferably between 80 and 250 m ² /g.

Process for preparing the capture mass

The present invention also relates to a method for preparing a capture mass comprising at least the following steps:

a) said porous support is brought into contact with at least one metal salt comprising at least one group VIII metal whose melting point of said metal salt is between 20 and 150° C., to form a solid mixture, the mass ratio between said metal salt and said porous support being between 0.1 and 2.5;

b) the solid mixture obtained at the end of step a) is heated with stirring to a temperature between the melting temperature of said metallic salt and 200° C. to obtain a precursor of capture mass;

c) optionally, the solid obtained at the end of step b) is dried at a temperature below 200° C. to obtain a dried capture mass precursor;

d) optionally, the solid obtained at the end of step b) or c) is calcined at a temperature greater than 200° C. and less than or equal to 1100° C. under an inert atmosphere or under an atmosphere containing oxygen to obtaining a calcined capture mass precursor;

e) optionally, the capture mass precursor obtained at the end of step c) or d) is reduced to obtain a reduced capture mass precursor;

f) the capture mass precursor obtained at the end of step b), optionally c), d) or e), is sulphided to obtain said capture mass.

The process for preparing the capture mass according to the invention may also comprise a step a') of bringing the support into contact with an organic compound, optionally followed by a step a'') of drying said impregnated support at a temperature below 250°C.

The steps of the process for preparing the capture mass according to the invention are described in detail below.

Step a)

Step a) of the method according to the invention allows in particular an optimized control of the quantity of metal deposited on the capture mass. According to step a), a porous oxide support is brought into contact with at least one metal salt comprising at least one group VIII metal to form a solid mixture. According to the invention, the melting point of said metal salt is between 20 and 150°C.

The mass ratio between said metal salt and said porous oxide support is between 0.1 and 2.5, preferably between 0.3 and 2.0.

In this step, the metal salt is in solid form, that is to say that the bringing into contact between said porous support and said metal salt is carried out at a temperature below the melting temperature of said metal salt.

According to step a), at least one metal salt comprising at least one metal belonging to group VIII is provided. The melting point of said metal salt is between 20 and 150°C. Preferably, the metals are chosen from Ni, Fe, Co, taken alone or as a mixture. Preferably the metal salt is hydrated. Preferably, the metal salt is a hydrated nitrate salt. Preferably, the metal salt is chosen from nickel nitrate hexahydrate (Ni(NO ₃ ) ₂ .6H ₂ O, T _melting = 56.7° C.), iron nitrate nonahydrate (Fe(NO ₃ ) ₃ , 9H ₂ O, T _melting = 47.2° C.), cobalt nitrate hexahydrate (Co(NO ₃ ) ₂ .6H ₂ O, T _melting = 55.0° C.), taken alone or as a mixture.

According to step a), the bringing into contact of said porous oxide support and of the metal salt of group VIII can be done by any method known to those skilled in the art. Preferably, the bringing into contact of said porous support and of the metal salt is carried out with contact means chosen from among convective mixers, drum mixers or static mixers. Step a) is preferably carried out for a period of between 5 minutes and 12 hours depending on the type of mixer used, preferably between 10 minutes and 4 hours, and even more preferably between 15 minutes and 3 hours.

Step b)

According to step b), the mixture obtained at the end of step a) is heated with stirring to a temperature above the melting point of the metal salt. The temperature is between the melting temperature of the metal salt and 200° C., very preferably between the melting temperature of the metal salt and 150° C., and at atmospheric pressure. The residence time is generally between 5 minutes and 12 hours, preferably between 5 minutes and 4 hours.

According to step b), the mechanical homogenization of the mixture can be done by any method known to those skilled in the art. Preferably, convective mixers, drum mixers or static mixers can be used. Even more preferably, step b) is carried out by means of a drum mixer whose speed of rotation is between 4 and 70 revolutions/minute, preferably between 10 and 60 revolutions/minute.

At the end of step b), a capture mass precursor is obtained.

Step c) (optional step)

According to optional step c), the drying of the solid obtained in step b) is carried out at a temperature below 200° C., advantageously between 50 and 180° C., preferably between 70 and 150° C., so very preferred between 75 and 130°C.

The drying step is preferably carried out for a maximum duration of 4 hours, preferably under an inert atmosphere or under an atmosphere containing oxygen.

The optional drying step can be carried out by any technique known to those skilled in the art. It is advantageously carried out at atmospheric pressure or at reduced pressure. Preferably, this step is carried out at atmospheric pressure. It is advantageously carried out using air or any other hot gas. Preferably, the gas used is either air or an inert gas such as argon or nitrogen. Very preferably, the drying is carried out in the presence of nitrogen and/or air. Unlike step b), the drying step c) is preferably not carried out with stirring. A dried capture mass precursor is obtained. The drying temperature in step c) is generally higher than the heating temperature in step b). Preferably, the drying temperature of step c) is at least 10°C higher than the heating temperature of step b).

Step d) (optional step)

According to step d), the solid obtained in step b) or c) undergoes a calcination treatment at a temperature above 200° C. and less than or equal to 1100° C., preferably between 250° C. and 650° C. ° C, and very preferably between 300° C. and 500° C., under an inert atmosphere (nitrogen for example) or under an atmosphere containing oxygen (air for example). The duration of this heat treatment is generally less than 16 hours, preferably less than 5 hours. After this treatment, the group VIII element is in oxide form and the solid no longer contains or contains very few counterions and water of crystallization initially present in the metallic salt. The calcination step can be carried out by any technique known to those skilled in the art. It is advantageously carried out in a traversed bed or in a fluidized bed using air or any other hot gas. A calcined capture mass precursor is obtained.

Stage e ) ( stage optional)

Prior to the sulfurization of the capture mass, at least one step of reducing treatment is optionally carried out in the presence of a reducing gas after steps b), c) or d) so as to obtain a capture mass comprising at least one Group VIII metal at least partially in metallic form. This treatment makes it possible to form metallic particles, in particular of group VIII in the zero valent state. The reducing gas is preferably hydrogen. The hydrogen can be used pure or in a mixture (for example a hydrogen/nitrogen, hydrogen/argon, hydrogen/methane mixture). In the case where the hydrogen is used as a mixture, all the proportions are possible.

Said reducing treatment is preferably carried out at a temperature of between 120 and 500°C, preferably between 150 and 450°C. The duration of the reducing treatment is generally between 2 and 40 hours, preferably between 3 and 30 hours. The rise in temperature up to the desired reduction temperature is generally slow, for example fixed between 0.1 and 10° C./min, preferably between 0.3 and 7° C./min. A reduced capture mass precursor is obtained.

Stage f )

After stage b), or after optional stages c), d) or e), the product obtained (precursor of capture mass, dried, calcined or reduced) is sulfurized so as to form the group VIII sulphide. This sulfurization is carried out by methods well known to those skilled in the art, and advantageously under a sulfo-reducing atmosphere in the presence of hydrogen and hydrogen sulfide. Sulfurization is carried out by injecting onto the capture mass a flow containing H ₂ S and hydrogen, or else a sulfur compound capable of decomposing into H ₂ S in the presence of the capture mass and the hydrogen. Polysulfides such as dimethyl disulfide are H ₂ S precursors commonly used to sulfur capture masses. The temperature is adjusted so that the H ₂ S reacts with group VIII to form group VIII sulfide. This sulfurization can be carried out in situ or ex situ (inside or outside the reactor of the capture process). Advantageously, it is carried out ex-situ. Generally it is carried out at temperatures between 200 and 600°C and more preferably between 250 and 500°C. To be active, Group VIII should preferably be substantially sulfurized. The operating conditions of the sulfurization, in particular the nature of the sulfurizing agent, the H ₂ S/hydrogen ratio, the temperature and the duration of the sulfurization will preferably be adapted according to the product obtained after step b) or after the optional steps c) d) or e), so as to obtain a good sulphidation of the metal of group VIII, that is to say that the metal of group VIII is largely and preferably entirely sulphurized.

The degree of sulfurization of the metals constituting the active phase of the capture mass is advantageously at least equal to 60%, preferably at least equal to 80%. The sulfur content in the sulphide material is measured by elemental analysis according to ASTM D5373. A metal is considered sulphurized when the overall sulphidation rate defined by the molar ratio between the sulfur (S) present on the capture mass and said metal is at least equal to 60% of the theoretical molar ratio corresponding to the total sulphidation of ( of the metal(s) considered. The overall sulfurization rate is defined by the following equation:

in which :

(S/metal) _{capture mass} is the molar ratio between the sulfur (S) and the metal present on the capture mass;

(S/metal) _theoretical is the molar ratio between the sulfur and the metal corresponding to the total sulphidation of the metal in sulphide.

This theoretical molar ratio varies according to the metal considered:

(S/Fe) _theoretical = 1

(S/Co) _theoretical = 8/9

(S/Ni) _theoretical = 2/3

After sulfurization, the capture mass according to the invention is ready to be used, for example, in a process for the adsorption of organometallic arsenic compounds and for the hydrodesulfurization of a hydrocarbon charge comprising unsaturated compounds.

V ariante of achievement: P repair of the capture mass using an organic compound

The process for preparing the capture mass according to the invention may also optionally comprise a step a′) of bringing the support into contact with an organic compound comprising oxygen and/or nitrogen and/or sulfur, optionally followed by a step a'') of drying said impregnated support at a temperature below 250°C. According to this variant, during step a′), said support is brought into contact with at least one solution containing at least one organic compound comprising oxygen and/or nitrogen and/or sulfur. The introduction of an organic compound comprising oxygen and/or nitrogen and/or sulfur makes it possible to increase the dispersion of the active phase, thus leading to small size group VIII sulfide particles after sulfurization .

Generally, the organic compound comprising oxygen and/or nitrogen and/or sulfur is chosen from a compound comprising one or more chemical functions chosen from a carboxylic acid, alcohol, thiol, thioether, sulphone, sulphoxide, ether function. , aldehyde, ketone, ester, carbonate, amine, nitrile, imide, oxime, urea and amide.

Preferably, the organic compound is chosen from a compound comprising at least one carboxylic acid function, or at least one alcohol function, or at least one ester function, or at least one amide function.

The molar ratio of said organic compound introduced during step a′) relative to the group VIII element introduced in step a) is between 0.01 and 5.0 mol/mol, preferably between 0. 05 and 2.0 mol/mol.

In one embodiment according to the invention, said organic compound comprises at least one carboxylic acid function. Preferably, said organic compound is chosen from monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids. In this case, the organic compound is more preferably chosen from oxalic acid, malonic acid, glutaric acid, glycolic acid, lactic acid, tartronic acid, citric acid, acid tartaric acid, pyruvic acid and γ-ketovaleric acid.

In one embodiment according to the invention, said organic compound comprises at least one alcohol function. Preferably, said organic compound is chosen from:

- organic compounds comprising a single alcohol function;

- organic compounds comprising two alcohol functions;

- organic compounds chosen from diethylene glycol, triethylene glycol, tetraethylene glycol, or a polyethylene glycol corresponding to the formula H(OC ₂ H ₄ ) _n OH with n greater than 4 and having an average molar mass of less than 20,000 g /mol;

- monosaccharides of molecular formula C _n (H ₂ O) _p with n between 3 and 12;

- disaccharides, trisaccharides, or monosaccharide derivatives.

In this case, the organic compound is more preferably chosen from methanol, ethanol, phenol, ethylene glycol, propane-1,3-diol, butane-1,4-diol, pentane-1, 5-diol, hexane-1,6-diol, glycerol, xylitol, mannitol, sorbitol, pyrocatechol, resorcinol, hydroquinol, diethylene glycol, triethylene glycol, polyethylene glycols having a mass average molar less than 600 g/mol, glucose, mannose, fructose, sucrose, maltose, lactose, in any one of their isomeric forms.

In one embodiment according to the invention, said organic compound comprises at least one ester function.

Preferably, said organic compound is chosen from:

- linear or cyclic or cyclic unsaturated carboxylic acid esters;

- organic compounds comprising at least two carboxylic acid ester functions;

- organic compounds comprising at least one carboxylic acid ester function and at least one second functional group chosen from alcohols, ethers, ketones, aldehydes;

- cyclic or linear esters of carbonic acid;

- linear carbonic acid diesters.

In this case, the organic compound is more preferably chosen from γ-valerolactone, methyl laurate, C1-C4 dialkyl succinate and more particularly dimethyl succinate, dimethyl malate, an acetoacid and propylene carbonate.

In one embodiment according to the invention, said organic compound comprises at least one amide function. Preferably, said organic compound is chosen from:

- acyclic amides comprising one or two amide functions;

- cyclic amides or lactams;

- organic compounds comprising at least one amide function and one carboxylic acid function or one alcohol function;

- organic compounds comprising at least one amide function and one additional nitrogen heteroatom.

In this case, the organic compound is more preferably chosen from formamide, N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N ,N-dimethylmethanamide, N,N-diethylacetamide, N,N-dimethylpropionamide, propanamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, γ-lactam, caprolactam, acetylleucine, N-acetylaspartic acid, aminohippuric acid, N-acetylglutamic acid, 4-acetamidobenzoic acid, lactamide, glycolamide, urea, N-methylurea, N,N′-dimethylurea, 1,1- dimethylurea, tetramethylurea according to any of their isomeric forms.

The organic compound containing sulfur can be one or more chosen from compounds comprising one or more chemical functions chosen from a thiol, thioether, sulphone or sulphoxide function. By way of example, the organic compound containing sulfur can be one or more selected from the group consisting of thioglycolic acid, 2-hydroxy-4-methylthiobutanoic acid, a sulfonated derivative of a benzothiophene or a sulfoxide derivative of a benzothiophene.

Mode of introduction of the organic compound

The variant of the process for preparing the capture mass implementing step a′), possibly a′′) comprises several modes of implementation when it is desired to add the organic compound. They are distinguished in particular by the order in which the organic compound and the group VIII metal precursor are introduced, it being possible for the organic compound to come into contact with the support either after the group VIII metal precursor has been brought into contact with the support, or during contacting of the Group VIII metal precursor with the support.

In one embodiment according to the invention, step a′) is carried out at the same time as step a), that is to say that the contacting of the support is carried out in the presence of at least a metal salt comprising at least one Group VIII metal and at least one organic compound to form a solid mixture. In this variant embodiment, the organic additive must be in solid form to form a solid mixture.

In another embodiment according to the invention, step a′) is carried out after the sequence of steps a) and b). In this embodiment, step a′) can be carried out by impregnation, according to methods well known to those skilled in the art. Preferably, said step a′) is carried out by dry impregnation, which consists in bringing the support of the capture mass into contact with a volume of said solution of between 0.25 and 1.5 times the pore volume of the support. . Said solution containing at least one organic compound may be aqueous or organic (for example methanol or ethanol or phenol or acetone or toluene or dimethyl sulfoxide (DMSO)) or else consist of a mixture of water and at least one organic solvent. Said organic compound is previously at least partially dissolved in said solution at the desired concentration. Preferably, said solution is aqueous or contains ethanol. Even more preferably, said solution is aqueous. The pH of said solution may be modified by the possible addition of an acid or a base. In another possible embodiment, the solvent may be absent from the impregnation solution. In the embodiment in which step a′) is carried out by impregnation, dry or in excess, preferably dry, the impregnation of the support with at least one solution containing at least said organic compound can be advantageously carried out via at least two impregnation cycles, using identical or different organic compounds for each cycle. In this case, each impregnation is advantageously followed by drying and possibly by heat treatment. In this variant embodiment, after the step of bringing the organic compound into contact with the support, the impregnated support can advantageously be allowed to mature, optionally before an intermediate drying step. When a maturation step is carried out, said step is advantageously carried out at atmospheric pressure or at reduced pressure, under an inert atmosphere or under an atmosphere containing oxygen or under an atmosphere containing water, and at a temperature between between 10°C and 50°C, and preferably at room temperature. Generally, a maturation period of less than forty-eight hours and preferably between five minutes and five hours is sufficient.

In the embodiment in which step a') is carried out after the sequence of steps a) and b), step a') is followed by a step a'') of drying at a temperature below 250°C, preferably between 15 and 240°C, more preferably between 30 and 220°C, even more preferably between 50 and 200°C, and even more preferably between 70 and 180°C.

Each step a), b) and a') (optionally a'') can be carried out several times, optionally in the presence of a group VIII precursor and/or an identical or different organic compound(s). at each step a) and b) and/or a') respectively, all possible combinations of implementations of steps a) and b) and/or a') being included within the scope of the invention.

Process capture organometallic impurities

Another object of the invention is a process for capturing organometallic impurities of heavy metals, such as organometallic impurities of phosphorus silicon, and more particularly arsenic, contained in a hydrocarbon charge implementing the capture mass previously defined, wherein said capture mass is brought into contact with the hydrocarbon charge in the presence of hydrogen. Within the meaning of the present invention, the capture process according to the invention is a process for at least partial capture of arsenic and optionally of silicon from the hydrocarbon feedstock in the presence of hydrogen to produce an effluent with a heavy metal content. and especially reduced arsenic, with limited loss of octane rating. The capture process according to the invention makes it possible to eliminate the arsenic and also to limit the rate of hydrogenation of the mono-olefins. The degree of hydrogenation of the olefins is advantageously less than 50%, preferably less than 30%, and even more preferably less than 20%.

The hydrocarbon feedstock to be treated is catalytic cracking gasoline from catalytic cracking, thermal cracking or steam cracking units. The method can also be applied to the treatment of mixtures of straight run gasolines which may contain heavy metals from the crude with cracked gasolines comprising mono-olefins and diolefins. Preferably, the hydrocarbon feed to be treated is a catalytic cracking gasoline comprising between 5% and 60% by weight of mono-olefins relative to the total weight of the feed, between 50 ppm and 6000 ppm by weight of sulfur compounds and between 10 and 1000 ppb weight of arsenic. The sulfur compounds contained in the hydrocarbon feedstock to be treated can be organic sulfur compounds such as, for example, mercaptans, thiophenic, benzothiophenic compounds and other aromatic sulfur compounds, disulphide compounds, etc. The arsenic compounds contained in the hydrocarbon feedstock to be treated can be organic arsenic compounds such as, for example, trimethylarsine or triethylarsine. Mono-olefins designate hydrocarbon molecules having a single carbon-carbon double bond and diolefins are hydrocarbon molecules comprising at least two carbon-carbon double bonds. Mono-olefins and diolefins can be linear, branched and/or cyclic hydrocarbon molecules.

The capture mass according to the invention is advantageously implemented under operating conditions such that the rate of capture of arsenic is maximized, while limiting the rate of hydrogenation of the olefins. The contacting is generally carried out at a temperature between 200 and 400° C., at a pressure between 0.2 and 5 MPa and with a ratio of the hydrogen flow rate to the hydrocarbon feed flow rate of between 50 and 800 Nm3/m3. The hydrogen used can come from any source of hydrogen. Preferably, fresh hydrogen from the refinery and/or hydrogen recycled from a hydrodesulfurization unit, preferably from the hydrodesulfurization unit of the hydrocarbon cut to be purified, is used.

Several reactor technologies can be envisaged for carrying out the capture of arsenic from a hydrocarbon charge in the presence of the capture mass according to the invention. The most classic and widespread technology is the fixed bed technology. In this case, a reactor is charged with the capture mass according to the invention and a hydrodesulphurization catalyst, operating in adsorption of arsenic and in hydrodesulphurization, in principle until the appearance of arsenic in the effluent output (phenomenon known to those skilled in the art as drilling). In some cases the total amount of poisoned catchment mass can be replaced by an equivalent amount of fresh catchment mass. The choice of a technology for replacing the capture mass according to the invention is not considered within the scope of the present invention as a limiting element. The capture mass can be implemented in a moving bed reactor, that is to say that the used capture mass is continuously withdrawn and replaced by fresh capture mass. This type of technology makes it possible to maintain the capture of arsenic by the capture mass and to avoid the penetration of the latter in the effluents produced. Among other solutions, let us mention the implementation of expanded bed reactors which also allows continuous withdrawal and make-up of the capture mass in order to maintain the hydrodesulphurization activity of the capture mass.

The capture process according to the invention is preferably coupled with at least one additional catalytic hydrodesulphurization or selective hydrogenation stage which is carried out on the effluent resulting from the contact with the capture mass according to the invention. Thus the stage of treatment of the hydrocarbon charge by the capture mass is considered as a pre-treatment which makes it possible in particular to preserve the catalytic activity of the catalyst used in the subsequent hydrodesulphurization or selective hydrogenation stage. Thus, the capture process according to the invention comprises one or more other complementary stages of hydrodesulphurization or selective hydrogenation in which the effluent resulting from the contacting of the charge hydrocarbon with the capture mass according to the invention, with at least one other catalyst for hydrodesulphurization or selective hydrogenation of the diolefins present in the olefin feed. Said complementary hydrodesulfurization step(s) makes it possible to eliminate the residual sulfur compounds contained in the effluent depleted in arsenic and with a lower sulfur content. Some of these residual sulfur compounds may result from the addition of H ₂ S to the olefins present in the charge. The H ₂ S can form during the contacting of the hydrocarbon charge with the capture mass, that is to say, during the capture of the arsenic. Said complementary hydrodesulphurization stage(s) is (are) implemented when the effluent resulting from the contacting of the hydrocarbon charge with the capture mass generally has a sulfur content greater than 10 ppm and that it is necessary to produce gasolines with low sulfur content meeting the current specifications which are in many countries lower than 10 ppm. The effluent freed from arsenic and from a part of the sulfur compounds is then treated in at least one of said complementary stages of selective hydrodesulphurization. In said step(s), said effluent is brought into contact with at least one other hydrodesulphurization catalyst under operating conditions which may be identical to or different from those for bringing the hydrocarbon feedstock into contact with the mass. of capture.

The catalyst(s) used in the said additional hydrodesulphurization stage(s) is (are) protected from deactivation by the arsenic present in the charge thanks to the capture mass according to the invention. Thus very selective hydrodesulphurization catalysts which are sensitive to the presence of arsenic can be implemented in the said complementary hydrodesulphurization step(s). Any hydrodesulphurization catalyst can be used in said complementary hydrodesulphurization step(s). Preferably, catalysts are used which exhibit a high selectivity with respect to hydrodesulphurization reactions relative to the hydrogenation reactions of olefins. Such catalysts comprise at least one amorphous and porous mineral support, a group VIB metal, a group VIII metal. The group VIB metal is preferably molybdenum or tungsten and the group VIII metal is preferably nickel or cobalt. The support is generally selected from the group consisting of aluminas, silica, silica-aluminas, silicon carbide, titanium oxides alone or mixed with alumina or silica alumina, magnesium oxides alone or as a mixture with alumina or silica alumina. Preferably, the support is selected from the group consisting of aluminas, silica and silica-aluminas. Preferably, the hydrodesulphurization catalyst used in the additional hydrodesulphurization stage or stages has the following characteristics:

- the content of group VIB elements is between 1 and 20% by weight of oxides of group VIB elements;

- the content of group VIII elements is between 0.1 and 20% by weight of oxides of group VIII elements;

- the molar ratio (group VIII elements/group VIB elements) is between 0.1 and 0.8.

A very preferred hydrodesulfurization catalyst comprises cobalt and molybdenum and has the characteristics mentioned above. Furthermore, the hydrodesulphurization catalyst may comprise phosphorus. In this case, the phosphorus content is preferably between 0.1 and 10% by weight of P ₂ O ₅ relative to the total weight of catalyst and the phosphorus to group VIB elements molar ratio is greater than or equal to 0.25 , preferably greater than or equal to 0.27.

In the said complementary hydrodesulphurization step(s), the arsenic-depleted effluent resulting from the contacting of the hydrocarbon charge with the capture mass according to the invention is brought into contact with at least one other selective hydrodesulfurization catalyst under the following operating conditions:

- a temperature between about 210°C and about 410°C, preferably between 240 and 360°C;

- a total pressure between 0.2 and 5 MPa and more preferably between 0.5 and about 3 MPa;

- a volume ratio of hydrogen per volume of hydrocarbon charge, between 50 and 800 Nm ³ /m ³ and more preferably between 60 and 600 Nm ³ /m ³ .

In a variant of the process according to the invention, the operating conditions for bringing the hydrocarbon feedstock into contact with the capture mass according to the invention are identical to those implemented in the said step(s). ) additional hydrodesulfurization(s).

According to another embodiment, the step of hydrotreating the effluent from the capture step by means of the capture mass according to the invention is a selective hydrogenation which allows the hydrogenation of the diolefins into olefins and optionally unsaturated sulfur compounds but also the transformation (heaviness) of light sulfur compounds (i.e. having a temperature lower than that of thiophene) into sulfur compounds whose temperature is higher than that of thiophene, for example by adding mercaptans to olefins. This hydrogenation step is carried out in the presence of hydrogen and of a catalyst containing at least one metal from group VIb and at least one non-noble metal from group VIII deposited on a porous support. Preferably, a catalyst is used of which:

- the content by weight of oxide of the element of group VIb is between 6 and 18% relative to the weight of the catalyst;

- the content by weight of oxide of the element of group VIII is between 4 and 12% relative to the weight of the catalyst;

- the specific surface of the catalyst is between 200 and 270 m²/g;

- the density of the element of group VIb, expressed as being the ratio between the said content by weight of oxide of the element of group VIb and the specific surface of the catalyst, is between 4 and 6.10-4 g/m²;

- the molar ratio between the group VIII metal and the group VIb metal is between 0.6 and 3 mol/mol.

The group VIb metal is preferably chosen from molybdenum and tungsten, very preferably the group VIb metal is molybdenum. The group VIII metal is preferably nickel and/or cobalt, very preferably nicekl. The hydrogen is generally introduced in slight excess, up to 5 moles per mole, relative to the stoichiometry necessary to hydrogenate the diolefins (one mole of hydrogen per mole of diolefin). The mixture consisting of gasoline and hydrogen is brought into contact with the catalyst under a pressure of between 0.5 and 5 MPa, a temperature of between 80 and 220°C, with a liquid space velocity (LHSV) of between 1 and 10 h ^-1 , the liquid space velocity being expressed in liter of charge per liter of catalyst and per hour (L/Lh).

In a variant of the process according to the invention, the capture mass according to the invention can be placed in the guard bed position of one or more reactor(s) containing the catalyst(s) used in the (are) said (s) stage (s) complementary hydrodesulphurization and / or selective hydrogenation. In another variant of the method according to the invention, the capture mass according to the invention is placed in a so-called capture reactor. This reactor is separate and is placed upstream of the reactor(s) containing the catalyst(s) used in said complementary hydrodesulphurization step(s) and / or selective hydrogenation. In all the variants of the process according to the invention, implementing at least one additional step of hydrodesulphurization and/or selective hydrogenation, the volume ratio of the capture mass according to the invention relative to the volume of (of ) catalyst(s) used in said additional hydrodesulphurization and/or selective hydrogenation step(s) is advantageously between 4 and 50%, preferably between 5 and 40 %, more preferably between 5 and 35%.

The invention is illustrated by the examples which follow without being limiting.

Examples

Example 1: Mass prepared by impregnation according to the state of the art ( vs omparative)

In this example, solid A is prepared by double dry impregnation of the alumina support via an aqueous solution of nickel nitrate. Drying at 120° C. followed by calcination at 450° C. is carried out after each impregnation. The solid is then sulfurized ex situ under a flow of an H ₂ /H ₂ S mixture at 15% vol of H ₂ S and at a temperature of 350° C. for 2 hours, then cooled under pure hydrogen with a plateau of 2 hours at 200°C.

Example 2: Prepared mass by (according to the invention)

In this example, solid B is prepared by the preparation process according to the invention. Referring to Figure 1, is supplied to a homogenization step 3 an alumina support stored in a storage unit 1 via line 7 and a hexahydrated nickel nitrate salt (Aldrich®,> 98%, ~ 20% weight of Ni) stored in a storage unit 2 via line 8. The homogenization stage is a drum mixer inclined at 45° and equipped with counter-blades to ensure a cascading movement when mixing the powders . The mixer is stirred at 60 revolutions per minute for 1 hour at ambient temperature and pressure. The solid mixture obtained is then sent via line 9 to a heating capacity 4 (hot impregnator) in which the temperature is increased at 5° C./min up to 80° C. and left for 1 hour. The solid obtained is then sent to a calcining furnace 5 via line 10 operating at 400° C. for 4 hours in a traversed bed. The capture mass obtained, containing 20% by weight of Ni relative to the weight of the capture mass, is sent to a storage unit 6 via line 11. The solid is then sulfurized ex situ under a flow of a mixture of H ₂ / H ₂ S at 15% vol of H ₂ S and at a temperature of 350°C for 2 hours, then cooled under pure hydrogen with a plateau of 2 hours at 200°C.

Example 3 : Evaluation of the performances of the capture masses with respect to the capture of To rsenic

The performance of a nickel-based capture mass is measured by following the rate of disappearance of an arsenic compound dissolved in a model charge brought into contact with the solid, after sulphurization, during a reaction carried out in static mode in a stirred and closed autoclave reactor, at a temperature of 210° C., in the presence of hydrogen and under a total pressure of 35 bar (3.5 MPa).

A model load is used for all tests. It is composed of a volume of 250 cm ³ of toluene, i.e. 217 g, and triphenyl-arsine (AsPh ₃ ), at a content of 500 ppm mas in "As" equivalent, i.e. approximately 1.45 mmol of As . The mass of solid used is adjusted so as to obtain an initial Ni/As molar ratio of 5 in order to take account of the differences in nickel content on the various solids.

The results of the relative rate of disappearance of arsenic for the two capture masses A and B are grouped together in Table 1 below.

Solid AT
(comparative)
B
(according to the invention) Preparation Classic impregnation Molten salt route S _BET support (m ² .g ^-1 ) 152 152 Ni content (wt%) 20 20 Relative speed of disappearance of the Ace 100 112

Example 4 : Evaluation of olefin hydrogenation performance

A catalytic cracking gasoline (FCC or Fluid Catalytic Cracking according to the Anglo-Saxon terminology) whose characteristics are collated in Table 2 below, is brought into contact with the various capture masses. The reaction is carried out in a reactor of the traversed bed type under the following conditions: P=2 MPa, H ₂ /HC=360 litres/litres of hydrocarbon feed, Hourly volume velocity (VVH) =10 h ^-1 , the temperature being set at 250 °C. The effluents are analyzed by gas phase chromatography to determine the hydrocarbon concentrations.

Sppm 392 Aromatics %wt 41.3 Paraffins % wt 27.2 Naphthenics % wt 11.0 Olefins %wt 20.5 T ₅ °C (ASTM D-2887) 62 T ₉₅ °C (ASTM D-2887) 225

For all the masses tested, the hydrogenation of the olefins is extremely low and less than 2% by weight relative to the total weight of the olefins.

Claims (15)

Capture mass comprising an active phase based on at least one group VIII metal, said active phase being in sulphide form, and a porous oxide support chosen from the group consisting of alumina, silica, silica-alumina, or even titanium or magnesium oxide, used alone or in a mixture with alumina or silica alumina, said capture mass being capable of being obtained by the preparation process comprising at least the following steps:
a) said porous support is brought into contact with at least one metal salt comprising at least one group VIII metal whose melting point of said metal salt is between 20 and 150° C., to form a solid mixture, the mass ratio between said metal salt and said porous support being between 0.1 and 2.5;
b) the solid mixture obtained at the end of step a) is heated with stirring to a temperature between the melting point of said metal salt and 200° C. to obtain a precursor of capture mass;
c) optionally, the solid obtained at the end of step b) is dried at a temperature below 200° C. to obtain a dried capture mass precursor;
d) optionally, the solid obtained at the end of step b) or c) is calcined at a temperature greater than 200° C. and less than or equal to 1100° C. under an inert atmosphere or under an atmosphere containing oxygen to obtaining a calcined capture mass precursor;
e) optionally, the capture mass precursor obtained at the end of step c) or d) is reduced to obtain a reduced capture mass precursor;
f) the capture mass precursor obtained at the end of step b), optionally c), d) or e), is sulphided to obtain said capture mass. Capture mass according to Claim 1, in which the said Group VIII metal is chosen from nickel, iron and cobalt. Capture mass according to one of Claims 1 or 2, in which the active phase consists of group VIII metal sulphide particles of a size less than or equal to 20 nm. Capture mass according to any one of Claims 1 to 3, in which the group VIII metal content, expressed as group VIII element, is between 5 and 65% by weight relative to the total weight of the capture mass. Process for preparing a capture mass comprising an active phase based on at least one group VIII metal, said active phase being in sulphide form, and a porous oxide support chosen from the group consisting of alumina, silica , silica-alumina, or even titanium or magnesium oxide used alone or in a mixture with alumina or silica-alumina, said process comprising the following steps:
a) said porous support is brought into contact with at least one metal salt comprising at least one group VIII metal whose melting point of said metal salt is between 20 and 150° C., to form a solid mixture, the mass ratio between said metal salt and said porous support being between 0.1 and 2.5;
b) the solid mixture obtained at the end of step a) is heated, with stirring, to a temperature between the melting point of said metal salt and 200° C. to obtain a capture mass precursor;
c) optionally, the solid obtained at the end of step b) is dried at a temperature below 200° C. to obtain a dried capture mass precursor;
d) optionally, the solid obtained at the end of step b) or c) is calcined at a temperature greater than 200° C. and less than or equal to 1100° C. under an inert atmosphere or under an atmosphere containing oxygen to obtaining a calcined capture mass precursor;
e) optionally, the capture mass precursor obtained at the end of step c) or d) is reduced to obtain a reduced capture mass precursor;
f) the capture mass precursor obtained at the end of step b), optionally c), d) or e), is sulphided to obtain said capture mass. A method according to claim 5, wherein said metal salt is a hydrated nitrate salt. Process according to Claim 6, in which the said metal salt is chosen from nickel nitrate hexahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate, taken alone or as a mixture. Process according to any one of Claims 5 to 7, in which step b) is carried out by means of a drum operating at a speed of between 4 and 70 revolutions per minute. Process according to any one of claims 5 to 8, in which step a) is carried out for 5 minutes to 12 hours. Process according to any one of Claims 5 to 9, in which a step a′) of bringing the porous support into contact with an organic compound comprising oxygen and/or nitrogen and/or sulfur is carried out. Process according to claim 10, in which steps a) and a') are carried out simultaneously, said organic compound being in solid form to form a solid mixture. Process according to Claim 10, in which step a') is carried out after the sequence of steps a) and b). 13. Process for capturing organometallic impurities contained in a hydrocarbon feedstock implementing the capture mass according to claims 1 to 4 or prepared according to claims 5 to 12, in which said capture mass is brought into contact with the feedstock at process and a flow of hydrogen at a temperature of between 200 and 400°C, a pressure of between 0.2 and 5 MPa and a ratio of the flow rate of hydrogen to the flow rate of hydrocarbon feed of between 50 and 800 Nm ³ / m ³ . 14. Capture process according to claim 13, in which the organometallic impurities are chosen from organometallic impurities of heavy metals, silicon, phosphorus and arsenic. 15. Capture process according to one of Claims 13 or 14, in which the feedstock to be treated is a catalytic cracking gasoline containing between 5% and 60% by weight of olefins relative to the total weight of the feedstock, 50 ppm to 6000 ppm by weight of sulfur relative to the total weight of the charge, as well as traces of arsenic in contents between 10 ppb and 1000 ppb by weight relative to the total weight of the charge.