WO2018114398A1

WO2018114398A1 - Selective hydrogenation method using a nickel-based catalyst produced using an additive comprising an alcohol function

Info

Publication number: WO2018114398A1
Application number: PCT/EP2017/082025
Authority: WO
Inventors: Anne-Claire Dubreuil; Agathe MARTEL
Original assignee: IFP Energies Nouvelles
Priority date: 2016-12-22
Filing date: 2017-12-08
Publication date: 2018-06-28
Also published as: FR3061196A1

Abstract

The invention relates to a method for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule, contained in a hydrocarbon feedstock having a final boiling point less than or equal to 300°C in the presence of a catalyst comprising an alumina substrate and an active phase consisting of nickel. The catalyst is produced using a method comprising at least: i) a step of bringing the substrate into contact with at least one solution containing at least one nickel precursor; ii) a step of bringing the substrate into contact with at least one solution containing at least one organic compound comprising at least one alcohol function, said organic compound comprising between 1 and 20 carbon atoms; iii) a step of drying the impregnated substrate at a temperature below 250°C; steps i) and ii) being carried out separately, in any order, or simultaneously.

Description

A SELECTIVE HYDROGENATION PROCESS USING A PREPARED NICKEL CATALYST USING AN ADDITIVE COMPRISING A

ALCOHOL FUNCTION

Field of the invention The subject of the invention is a process for the selective hydrogenation of polyunsaturated compounds in a hydrocarbon feedstock, in particular in steam-cracked C2-C5 cuts and steam-cracking gasolines, in the presence of a nickel-based catalyst. supported on an alumina support prepared using an organic additive comprising at least one alcohol-type function. State of the art

The catalysts for selective hydrogenation of polyunsaturated compounds are generally based on Group VIII metals of the periodic table of elements such as nickel. The metal is in the form of nanometric metal particles deposited on a support which may be a refractory oxide. The metal content of the group VIII, the possible presence of a second metal element, the size of the metal particles and the distribution of the active phase in the support as well as the nature and porous distribution of the support are parameters which may have a importance on the performance of the catalysts.

The speed of the hydrogenation reaction is governed by several criteria, such as the diffusion of the reactants towards the surface of the catalyst (external diffusional limitations), the diffusion of the reagents in the porosity of the support towards the active sites (internal diffusion limitations) and the intrinsic properties of the active phase such as the size of the metal particles and the distribution of the active phase within the support.

As regards the size of the metal particles, it is generally accepted that the catalyst is all the more active as the size of the metal particles is small. In addition, it is important to obtain a particle size distribution centered on the optimum value and a narrow distribution around this value.

In order to obtain better catalytic performances, in particular a better selectivity and / or activity, it is known in the state of the art to proceed with the use of additives of the organic compound type for the preparation of metal catalysts. selective hydrogenation. For example, the application FR2984761 discloses a process for the preparation of a selective hydrogenation catalyst comprising a support and an active phase comprising a group VIII metal, said catalyst being prepared by a process comprising a step of impregnating a solution containing a precursor of the metal group VIII and an organic additive, more particularly an organic compound having one to three carboxylic acid functions, a step of drying the impregnated support, and a step of calcination of the dried support to obtain the catalyst.

The patent FR2963344 teaches the use of very particular organic compounds comprising a cyclic oligosaccharide composed of at least 6 α- (1,4) -linked glucopyranose subunits.

In this context, one of the objectives of the present invention is to propose a process for the selective hydrogenation of polyunsaturated compounds such as diolefins and / or acetylenes and / or alkenylaromatics in the presence of a nickel-phase supported supported catalyst, prepared using a particular organic additive to obtain performance in hydrogenation in terms of activity at least as good or better than the processes of the prior art that known methods of the state of the art.

The Applicant has discovered that an alumina-supported nickel catalyst prepared using an organic alcohol additive comprising between 1 and 20 carbon atoms, when present in a hydrogenation process. selective, improved catalytic performance, in terms of catalytic activity. This results in a better conversion of the charge under identical operating conditions.

Objects of the Invention The present invention relates to a process for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule, such as diolefins and / or acetylenics and / or alkenylaromates, contained in a hydrocarbon feedstock. having a final boiling point less than or equal to 300 ° C, which process is carried out at a temperature between 0 and 300 ° C, at a pressure of between 0.1 and 10 MPa, at a molar ratio hydrogen / (compounds polyunsaturates to be hydrogenated) between 0.1 and 10 and at an hourly space velocity of between 0.1 and 200 h ^-1 when the process is carried out in the liquid phase, or at a molar ratio of hydrogen / (polyunsaturated compounds to be hydrogenated) included between 0.5 and 1000 and at an hourly space velocity between 100 and 40000 h ^-1 when the process is carried out in the gaseous phase, in the presence of a catalyst comprising an alumina support and a phase active ingredient made of nickel, said catalyst being prepared by a process comprising at least:

i) a step of bringing said support into contact with at least one solution containing at least one nickel precursor; ii) a step of bringing said support into contact with at least one solution containing at least one organic compound comprising at least one alcohol function, said organic compound comprising between 1 and 20 carbon atoms;

iii) a step of drying said impregnated support at a temperature below 250 ° C; steps i) and ii) being performed separately, in any order, or simultaneously.

According to one embodiment of the invention, the process may further comprise at least one step iv) of calcination of said dried catalyst obtained in step iii) at a temperature of between 250 and 1000 ° C.

In one embodiment of the invention, steps i) and ii) of the method according to the invention are carried out simultaneously.

In another embodiment according to the invention, step i) of the process according to the invention is carried out before step ii).

In yet another embodiment of the invention, step ii) of the method according to the invention is carried out before step i). Preferably, steps i) and / or ii) are (are) carried out by dry impregnation.

Advantageously, the nickel element content is between 10 and 35% by weight relative to the total weight of the catalyst.

According to one embodiment of the invention, said organic compound comprises a single alcohol function. According to one embodiment of the invention, said organic compound comprises at least two alcohol functions.

According to one embodiment of the invention, said organic compound is an aromatic organic compound comprising at least two alcohol functional groups.

According to one embodiment of the invention, said organic compound is chosen from diethylene glycol, triethylene glycol, tetraethylene glycol, or a polyethylene glycol corresponding to the formula Η (00 ₂ Η 4) _η ΟΗ with n greater than 4 and having an average molecular weight of less than 20000 g / mol.

According to one embodiment of the invention, said organic compound is a monosaccharide of formula C _n (H ₂ 0) _p with n between 3 and 12. According to one embodiment of the invention, said organic compound comprises at least one alcohol function, at least one ketone function and at least one unsaturated heterocyclic.

According to one embodiment of the invention, said organic compound is a disaccharide or a trisaccharide, or a derivative of a monosaccharide. In one embodiment according to the invention, the process according to the invention is carried out in the presence of a feedstock chosen from a C2 steam cracking cut or a C2-C3 steam cracking cut, and in which the molar ratio (hydrogen) process is used. (Polyunsaturated compounds to be hydrogenated) is between 0.5 and 1000, the temperature is between 0 and 300 ° C, the hourly volume velocity (VVH) is between 100 and 40000 h ^"1 , and the pressure is between 0.1 and 6.0 MPa.

In an embodiment according to the invention, the process according to the invention is carried out in the presence of a filler selected from steam cracking gasolines and in which the molar ratio (hydrogen) / (polyunsaturated compounds to be hydrogenated) is between 0.5 and 10, the temperature is between 0 and 200 ° C, the hourly volume velocity (VVH) is between 0.5 and 100 h ^"1 , and the pressure is between 0.3 and 8.0 MPa .

detailed description

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 DR Lide, 81 ^st 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 textural and structural properties of the support and the catalyst described below are determined by the characterization methods known to those skilled in the art. The total pore volume and the porous distribution are determined in the present invention by nitrogen porosimetry as described in the book "Adsorption by powders and porous solids. Principles, methodology and applications "written by F. Rouquérol, J. Rouquérol and K. Sing, Academy Press, 1999.

Specific surface area is understood to mean the BET specific surface area (S _B AND in m ² / g) 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 the American Society", 1938, 60, 309. The size of the nickel nanoparticles is understood to mean the average diameter of the nickel crystallites in oxide form. The average diameter of nickel crystallites in oxide form is determined by X-ray diffraction from the width of the diffraction line at the angle 2theta = 43 ° (i.e. in the crystallographic direction [ 200]) using Scherrer's relation. This method, used in X-ray diffraction on powders or polycrystalline samples which connects the half-height width of the diffraction peaks to the particle size, is described in detail in the reference: Appl. Cryst. (1978), 11, 102-1. "Scherrer after sixty years: A survey and some new results in the determination of crystallite size", JI Langford and AJC Wilson. Process description

The present invention relates to a process for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule, such as diolefins and / or acetylenics and / or alkenylaromatics, also called styrenics, contained in a hydrocarbon feed having a final boiling point less than or equal to 300 ° C., which process is carried out at a temperature of between 0 and 300 ° C., at a pressure of between 0.1 and 10 MPa, at a molar ratio of hydrogen / (polyunsaturated compounds) to hydrogenate) between 0.1 and 10 and at a hourly space velocity of between 0.1 and 200 h ^-1 when the process is carried out in the liquid phase, or at a molar ratio of hydrogen / (polyunsaturated compounds to be hydrogenated) between 0.5 and 1000 and at an hourly space velocity between 100 and 40000 h ^-1 when the process is carried out in the gas phase, in the presence of a catalyst comprising an alumina support and a an active phase consisting of nickel, said catalyst being prepared by a process comprising at least:

i) a step of bringing said support into contact with at least one solution containing at least one nickel precursor;

ii) a step of bringing said support into contact with at least one solution containing at least one organic compound comprising at least one alcohol function, said organic compound comprising between 1 and 20 carbon atoms;

iii) a step of drying said impregnated support at a temperature below 250 ° C, so as to obtain a dried catalyst; steps i) and ii) being performed separately, in any order, or simultaneously.

Monounsaturated organic compounds such as, for example, ethylene and propylene, are at the source of the manufacture of polymers, plastics and other products. value-added chemicals. These compounds are obtained from natural gas, naphtha or gas oil which have been treated by steam cracking or catalytic cracking processes. These processes are operated at high temperature and produce, in addition to the desired monounsaturated compounds, polyunsaturated organic compounds such as acetylene, propadiene and methylacetylene (or propyne), 1 -2-butadiene and 1 -3 butadiene, vinylacetylene and ethylacetylene, and other polyunsaturated compounds whose boiling point corresponds to the C5 + cut (hydrocarbon compounds having at least 5 carbon atoms), in particular diolefinic or styrenic or indenic compounds. These polyunsaturated compounds are very reactive and lead to spurious reactions in the polymerization units. It is therefore necessary to eliminate them before valuing these cuts.

Selective hydrogenation is the main treatment developed to specifically remove undesired polyunsaturated compounds from these hydrocarbon feeds. It allows the conversion of the polyunsaturated compounds to the corresponding alkenes or aromatics, avoiding their total saturation and thus the formation of the corresponding alkanes or naphthenes. In the case of steam cracking gasolines used as a filler, the selective hydrogenation also makes it possible to selectively hydrogenate alkenyl aromatics to aromatics by avoiding the hydrogenation of the aromatic rings.

The hydrocarbon feedstock treated in the selective hydrogenation process has a final boiling point less than or equal to 300 ° C and contains at least 2 carbon atoms per molecule and comprises at least one polyunsaturated compound. The term "polyunsaturated compounds" means compounds comprising at least one acetylenic function and / or at least one diene function and / or at least one alkenylaromatic function.

More particularly, the filler is selected from the group consisting of a C2 steam cracking cut, a C2-C3 steam cracking cut, a steam cracking C3 cut, a steam cracking C4 cut, a steam cracking C5 cut and a still called steam cracking gasoline. pyrolysis gasoline or C5 + cut.

The steam cracking section C2, advantageously used for carrying out the selective hydrogenation process according to the invention, has for example the following composition: between 40 and 95% by weight of ethylene, of the order of 0.1 to 5% by weight of acetylene, the remainder being essentially ethane and methane. In certain steam cracking sections, between 0.1 and 1% by weight of C 3 compounds may also be present.

The C3 steam-cracking cut, advantageously used for carrying out the selective hydrogenation process according to the invention, has, for example, the average composition next: of the order of 90% by weight of propylene, of the order of 1 to 8% by weight of propadiene and methylacetylene, the remainder being essentially propane. In some C3 cuts, between 0.1 and 2% by weight of C 2 compounds and C 4 compounds may also be present.

A C2 - C3 cut can also be advantageously used for the implementation of the selective hydrogenation process according to the invention. It has for example the following composition: of the order of 0.1 to 5% by weight of acetylene, of the order of 0.1 to 3% by weight of propadiene and methylacetylene, of the order of 30% by weight ethylene, of the order of 5% by weight of propylene, the remainder being essentially methane, ethane and propane. This filler may also contain between 0.1 and 2% by weight of C4 compounds. The C4 steam-cracking cut, advantageously used for the implementation of the selective hydrogenation process according to the invention, has for example the following average mass composition: 1% weight of butane, 46.5% weight of butene, 51% by weight butadiene, 1.3% by weight of vinylacetylene and 0.2% by weight of butyne. In some C4 cuts, between 0.1 and 2% by weight of C3 compounds and C5 compounds may also be present. The C5 steam-cracking cut, advantageously used for carrying out the selective hydrogenation process according to the invention, has, for example, the following composition: 21% by weight of pentanes, 45% by weight of pentenes and 34% by weight of pentadienes.

The steam cracking gasoline or pyrolysis gasoline, advantageously used for carrying out the selective hydrogenation process according to the invention, corresponds to a hydrocarbon fraction whose boiling point is generally between 0 and 300 ° C., preferably between 10 and 250 ° C. The polyunsaturated hydrocarbons to be hydrogenated present in said steam cracking gasoline are, in particular, diolefinic compounds (butadiene, isoprene, cyclopentadiene, etc.), styrenic compounds (styrene, alpha-methylstyrene, etc.) and indene compounds (indene). ). Steam cracking gasoline generally comprises the C5-C12 cut with traces of C3, C4, C13, C14, C15 (for example between 0.1 and 3% by weight for each of these cuts). For example, a charge formed of pyrolysis gasoline generally has the following composition: 5 to 30% by weight of saturated compounds (paraffins and naphthenes), 40 to 80% by weight of aromatic compounds, 5 to 20% by weight of mono-olefins, 5 to 40% by weight of diolefins, 1 to 20% by weight of alkenylaromatic compounds, all the compounds forming 100%. It also contains from 0 to 1000 ppm by weight of sulfur, preferably from 0 to 500 ppm by weight of sulfur.

Preferably, the polyunsaturated hydrocarbon feedstock treated according to the selective hydrogenation process according to the invention is a C2 steam cracking cut, or a C2-C3 steam cracking cut, or a steam cracking gasoline. The selective hydrogenation process according to the invention aims at eliminating said polyunsaturated hydrocarbons present in said feedstock to be hydrogenated without hydrogenating the monounsaturated hydrocarbons. For example, when said feed is a C2 cut, the selective hydrogenation process aims to selectively hydrogenate acetylene. When said feedstock is a C3 cut, the selective hydrogenation process aims to selectively hydrogenate propadiene and methylacetylene. In the case of a C4 cut, it is intended to remove butadiene, vinylacetylene (VAC) and butyne, in the case of a C5 cut, it is intended to eliminate pentadienes. When said feed is a steam cracking gasoline, the selective hydrogenation process aims to selectively hydrogenate said polyunsaturated hydrocarbons present in said feed to be treated so that the diolefinic compounds are partially hydrogenated to mono-olefins and that the styrenic and indene compounds are partially hydrogenated to corresponding aromatic compounds by avoiding the hydrogenation of aromatic rings.

The technological implementation of the selective hydrogenation process is carried out, for example, by injection, in ascending or descending current, of the polyunsaturated hydrocarbon feedstock and hydrogen in at least one fixed bed reactor. Said reactor may be of the isothermal or adiabatic type. An adiabatic reactor is preferred. The polyunsaturated hydrocarbon feedstock may advantageously be diluted by one or more reinjections of the effluent, coming from said reactor where the selective hydrogenation reaction occurs, at various points of the reactor, located between the inlet and the outlet of the reactor. in order to limit the temperature gradient in the reactor. The technological implementation of the selective hydrogenation process according to the invention may also be advantageously carried out by implanting at least one of said supported catalyst in a reactive distillation column or in reactor-exchangers or in a slurry-type reactor. . The flow of hydrogen can be introduced at the same time as the feedstock to be hydrogenated and / or at one or more different points of the reactor.

The selective hydrogenation of the steam-cracking cuts C2, C2-C3, C3, C4, C5 and C5 + can be carried out in the gaseous phase or in the liquid phase, preferably in the liquid phase for the C3, C4, C5 and C5 + cuts and in the phase gaseous for C2 and C2-C3 cuts. A reaction in the liquid phase makes it possible to lower the energy cost and to increase the catalyst cycle time.

In general, the selective hydrogenation of a hydrocarbon feed containing polyunsaturated compounds containing at least 2 carbon atoms per molecule and having a final boiling point of less than or equal to 300 ° C. temperature between 0 and 300 ° C, at a pressure of between 0.1 and 10 MPa, at a molar ratio hydrogen / (polyunsaturated compounds to be hydrogenated) between 0.1 and 10 and at an hourly space velocity VVH (defined as the ratio of the volume flow rate of charge to the volume of the catalyst) of between 0.1 and 200 h ^-1 for a process carried out in the liquid phase, or at a hydrogen / (polyunsaturated compounds to be hydrogenated) molar ratio of between 0.5 and 1000 and at a VVH hourly volume rate of between 100 and 40,000 h ^-1 for a process carried out in the gas phase.

In one embodiment according to the invention, when a selective hydrogenation process is carried out in which the feedstock is a steam cracking gasoline containing polyunsaturated compounds, the molar ratio (hydrogen) / (polyunsaturated compounds to be hydrogenated) is generally understood. between 0.5 and 10, preferably between 0.7 and 5.0 and even more preferably between 1.0 and 2.0, the temperature is between 0 and 200 ° C, preferably between 20 and 200 ° C and even more preferably between 30 and 180 ° C, the hourly volume velocity (VVH) is generally between 0.5 and 100 h ^"1 , preferably between 1 and 50 h ^{" 1} and the pressure is generally between 0.3 and 8.0 MPa, preferably between 1.0 and 7.0 MPa and even more preferably between 1.5 and 4.0 MPa.

More preferably, a selective hydrogenation process is carried out in which the feedstock is a steam cracking gasoline comprising polyunsaturated compounds, the molar ratio of hydrogen / (polyunsaturated compounds to be hydrogenated) is between 0.7 and 5.0, the temperature is between 20 and 200 ° C, the hourly volume velocity (VVH) is generally between 1 and 50 h ^-1 and the pressure is between 1.0 and 7.0 MPa.

Even more preferentially, a selective hydrogenation process is carried out in which the feedstock is a steam cracking gasoline comprising polyunsaturated compounds, the molar ratio of hydrogen / (polyunsaturated compounds to be hydrogenated) is between 1.0 and 2.0, the temperature is between 30 and 180 ° C, the hourly volume velocity (VVH) is generally between 1 and 50 h ^"1 and the pressure is between 1, 5 and 4.0 MPa.

The hydrogen flow rate is adjusted in order to dispose of it in sufficient quantity to theoretically hydrogenate all of the polyunsaturated compounds and to maintain an excess of hydrogen at the outlet of the reactor.

In another embodiment according to the invention, when a selective hydrogenation process is carried out in which the feedstock is a steam-cracking cross-section C2 and / or a C2-C3 steam-cracking cross-section comprising polyunsaturated compounds, the molar ratio ( hydrogen) / (polyunsaturated compounds to be hydrogenated) is generally between 0.5 and 1000, preferably between 0.7 and 800, the temperature is between 0 and 300 ° C, preferably between 15 and 280 ° C, the speed hourly volume (VVH) is included generally between 100 and 40000 h ^-1 , preferably between 500 and 30000 h ^-1 and the pressure is generally between 0.1 and 6.0 MPa, preferably between 0.2 and 5.0 MPa.

Description of the catalyst

The catalyst used for the implementation of the selective hydrogenation process according to the invention comprises an active phase deposited on a support comprising alumina, said active phase consisting of nickel. According to the invention, the nickel element content in the catalyst is between 10 and 35% by weight of the catalyst mass, preferably between 1 and 30% by weight, more preferably between 12 and 25% by weight, and more preferably between 12 and 23% by weight. The Ni content is measured by X-ray fluorescence.

The nickel is in the form of nanoparticles deposited on said support. The size of the nickel nanoparticles in the catalyst, measured in their oxide form, is less than or equal to 18 nm, preferably less than or equal to 15 nm, more preferably between 0.5 and 12 nm, and even more preferably between 1, 5 and 10 nm.

Said catalyst according to the invention is generally presented in all the forms known to those skilled in the art, for example in the form of balls, extrudates, tablets, pellets, hollow cylinders or irregular and non-spherical agglomerates which the specific shape can result from a crushing step. In a particular embodiment according to the invention, the catalyst consists of extrudates of diameter generally between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm and very preferably between 1.0 and 3.2 mm. and 2.5 mm. This may advantageously be in the form of cylindrical, multilobed, trilobed or quadrilobed 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.

In another particular embodiment according to the invention, the catalyst is in the form of beads having a diameter of between 1 and 8 mm, preferably between 2 and 7 mm.

The support on which said active phase is deposited comprises alumina (Al ₂ O ₃ ).

In a first variant embodiment, the alumina present in said support is a transition alumina such as gamma, delta, theta, chi, rho, eta or kappa alumina, alone or as a mixture. More preferably, the alumina is a gamma, delta or theta transition alumina, alone or as a mixture. In a second variant embodiment, the alumina present in said support is an alpha alumina.

The support may comprise another oxide other than alumina, such as silica (SiO ₂ ), titanium dioxide (TiO ₂ ), ceria (CeO ₂ ) and zirconia (ZrO ₂ ). The support can be a silica-alumina. Very preferably, said support consists solely of alumina.

The pore volume of the support is generally between 0.1 cm ³ / g and 1.5 cm ³ / g, preferably between 0.5 cm ³ / g and 1 0 cm ³ / g. The specific surface area of the support is generally greater than or equal to 5 m ² / g, preferably greater than or equal to 30 m ² / g, more preferably between 40 m ² / g and 250 m ² / g, and even more preferentially between 50 m ² / g and 200 m ² / g.

Description of the catalyst preparation process

In general, the catalyst used in the context of the selective hydrogenation process is prepared by a process comprising at least the following steps:

Step i) Contacting the nickel precursor with the support

The deposition of nickel on said support, in accordance with the implementation of said step i), can be carried out by any method well known to those skilled in the art. In particular, said step i) can be carried out by impregnation, dry or in excess, or by deposition - precipitation, according to methods well known to those skilled in the art.

Said step i) is preferably carried out by impregnation of the support consisting, for example, in bringing said support into contact with at least one aqueous or organic solution (for example methanol or ethanol or phenol or acetone or toluene or dimethylsulfoxide (DMSO)) or consists of a mixture of water and at least one organic solvent, containing at least one nickel precursor at least partially in the state dissolved, or in bringing said support into contact with at least one colloidal solution of at least one nickel precursor, in oxidized form (nanoparticles of oxide, oxy (hydroxide) or of nickel hydroxide) or under reduced form (metal nanoparticles of nickel in the reduced state). Preferably, the solution is aqueous. The pH of this solution can be modified by the possible addition of an acid or a base. According to another preferred variant, the aqueous solution may contain ammonia or ammonium ions NH ₄ ⁺ .

Preferably, said step i) is carried out by dry impregnation, which consists in bringing the catalyst support into contact with a solution containing at least one nickel precursor, the volume of the solution of which is between 0.25 and 1, 5 times the pore volume of the support to be impregnated.

When the nickel precursor is introduced in aqueous solution, it is advantageous to use a nickel precursor in the form of nitrate, carbonate, chloride, sulfate, hydroxide, hydroxycarbonate, formate, acetate, oxalate , complexes formed with acetylacetonates, or tetrammine or hexammine complexes, or any other soluble inorganic derivative in aqueous solution, which is brought into contact with said support. Nickel precursor, nickel nitrate, nickel carbonate, nickel chloride, nickel hydroxide and nickel hydroxycarbonate are advantageously used as nickel precursors. Very preferably, the nickel precursor is nickel nitrate, nickel carbonate or nickel hydroxide.

The quantities of the nickel precursor (s) introduced into the solution are chosen such that the total content of nickel element is between 10 and 35% by weight of the catalyst mass, preferably between 1 and 30% by weight, more preferably between 12 and 25% by weight, and even more preferably between 12 and 23% by weight. In the embodiment in which step i) is carried out by impregnation, dry or in excess, preferably dry, the impregnation of the nickel with the support can advantageously be carried out via at least two impregnation cycles, using identical or different nickel precursors at each cycle. In this case, each impregnation is advantageously followed by drying and optionally heat treatment.

Step ii) bringing the organic compound into contact with the support

Bringing said support into contact with at least one solution containing at least one organic compound comprising at least one alcohol function, in accordance with the implementation the work of said step ii) may be carried out by any method that is well known to those skilled in the art. In particular, said step ii) can be carried out by impregnation, dry or in excess according to methods well known to those skilled in the art. Preferably, said step ii) is carried out by dry impregnation, which consists in bringing the support of the catalyst into contact with a volume of said solution of between 0.25 and 1.5 times the pore volume of the support to be impregnated.

Said solution containing at least one organic compound comprising at least one alcohol function may be aqueous or organic (for example methanol or ethanol or phenol or acetone or toluene or dimethylsulfoxide (DMSO)) or 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 impregnating solution.

In the embodiment in which step ii) is carried out by impregnation, dry or in excess, preferably dry, the impregnation of the support can be carried out using one or more solutions, at least one of said solutions comprises at least one organic compound comprising at least one alcohol function. In the embodiment in which step ii) is carried out by impregnation, dry or in excess, preferably dry, the impregnation of the support can advantageously be carried out via at least two impregnation cycles, using compounds organic compounds, or mixtures of organic compounds of which at least one comprises at least one alcohol function, which are identical or different at each cycle. In this case, each impregnation is advantageously followed by drying and optionally heat treatment.

The molar ratio of said organic compound comprising at least one alcohol function introduced during step ii) relative to the nickel element introduced in step i) is between 0.01 and 5.0 mol / mol, preferably between 0.05 and 1.5 mol / mol, more preferably between 0.08 and 0.9 mol / mol. Said organic compound comprises between 1 and 20 carbon atoms, preferably between 1 and 12 carbon atoms, and even more preferably between 1 and 8 carbon atoms.

In one embodiment of the invention, the organic compound comprises a single alcohol function (mono-alcohol). Preferably, the organic compound is chosen from methanol, ethanol, propanol, butanol, pentanol, hexanol, 2-propyn-1-ol, geraniol, menthol, phenol, cresol, in any of their isomeric forms. More preferentially, said organic compound is selected from methanol, ethanol, phenol and the like.

In another embodiment of the invention, the organic compound comprises at least two alcohol functions (diol or more generally polyol). Preferably, the organic compound is selected from ethylene glycol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol , heptane-1,7-diol, octane-1,8-diol, propane-1,2-diol, butane-1,2-diol, butane-2,3-diol, butane 1,3-diol, pentane-1,2-diol, pentane-1,3-diol, pentane-2,3-diol, pentane-2,4-diol, 2-ethylhexane-1, 3-diol (hexhexadiol), p-menthane-3,8-diol, 2-methylpentane-2,4-diol, but-2-yn-1,4-diol, 2,3,4-trihydroxypentane , 2,2-dihydroxyhexane, 2,2,4-trihydroxyhexane, glycerol, erythritol, threitol, arabitol, xylitol, ribitol, mannitol, sorbitol, dulcitol, allitol, gluciotol, tolitol, fucitol, iditol, volemitol, inositol, in any of their isomeric forms. More preferably, said organic compound is chosen from ethylene glycol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol and hexane-1,6-diol. , glycerol, xylitol, mannitol, sorbitol, in any of their isomeric forms.

In another embodiment according to the invention, the organic compound is an aromatic organic compound comprising at least two alcohol functional groups. Preferably, the organic compound is selected from pyrocatechol, resorcinol, hydroquinol, pyrogallol, phloroglucinol, hydroxyquinol, tetrahydroxybenzene, benzenehexol, in any of their isomeric forms. More preferably, said organic compound is selected from pyrocatechol, resorcinol, hydroquinol.

In another embodiment of the invention, the organic compound may be selected from diethylene glycol, triethylene glycol, tetraethylene glycol, or more generally polyethylene glycol having the formula H (OC ₂ H ₄ ) _n OH with n greater than 4 and having an average molecular weight of less than 20,000 g / mol. More preferably, said organic compound is selected from diethylene glycol, triethylene glycol, polyethylene glycol having an average molecular weight of less than 600 g / mol.

In another embodiment according to the invention, the organic compound is a monosaccharide of formula C _n (H ₂ O) _p with n of between 3 and 12, preferably between 3 and 10. Preferably, the organic compound is selected from glyceraldehyde, dihydroxyacetone, erythrose, threose, erythrulose, lyxose, arabinose, xylose, ribose, ribulose, xylulose, glucose, mannose, sorbose, galactose, fructose, allose, altrose, gulose, idose, talose, psicosis, tagatose, sedoheptulose, mannoheptulose, in any of their isomeric forms. More preferably, said organic compound is selected from glucose, mannose, fructose, in any of their isomeric forms.

In another embodiment of the invention, the organic compound is a disaccharide or a trisaccharide, or a derivative of a monosaccharide, selected from sucrose, maltose, lactose, cellobiose, gentiobiose, inulobiosis, isomaltose, isomaltulose, kojibiose, lactulose, laminaribiose, leucrose, maltulose, melibiose, nigerose, robinose, rutinose, sophorose, trehalose, trehalulose, turanose, erlose , fucosyllactose, gentianose, inulotriose, kestose, maltotriose, mannotriose, melezitose, neokestose, panose, raffinose, rhamninose, maltitol, lactitol, isomaltitol, isomaltulose, any of their isomeric forms. More preferably, said organic compound is selected from sucrose, maltose, lactose, in any of their isomeric forms.

In another embodiment according to the invention, the organic compound comprises at least one alcohol function, at least one ketone functional group and at least one unsaturated heterocyclic functional group, preferably chosen from isomaltol, maltol, ethylmaltol and the acid. dehydroacetic acid, kojic acid, erythorbic acid, in any of their isomeric forms.

Among all the preceding embodiments, said organic compound comprising at least one alcohol function is preferably chosen from methanol, ethanol, propanol, butanol, pentanol, hexanol and 2-propyn-1-ol. , geraniol, menthol, phenol, cresol, ethylene glycol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1 , 6-diol, heptane-1,7-diol, octane-1,8-diol, propane-1,2-diol, butane-1,2-diol, 2,3-butane diol, butane-1,3-diol, pentane-1,2-diol, pentane-1,3-diol, pentane-2,3-diol, pentane-2,4-diol, 2- ethylhexane-1,3-diol, p-menthane-3,8-diol, 2-methylpentane-2,4-diol, but-2-yn-1,4-diol, 2,3,4-diol, trihydroxypentane, 2,2-dihydroxyhexane, 2,2,4-trihydroxyhexane, glycerol, erythritol, threitol, arabitol, xylitol, ribitol, mannitol, sorbitol, dulcitol, allitol , gluciotol, tolitol, fucitol, iditol, volemitol, inosito 1, pyrocatechol, resorcinol, hydroquinol, pyrogallol, phloroglucinol, hydroxyquinol, tetrahydroxybenzene, benzenehexol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol having the formula H (OC ₂ H ₄ ) _n OH with n greater than 4 and having an average molecular weight of less than 20000 g / mol, glyceraldehyde, dihydroxyacetone, erythrose, threose, erythrulose, lyxose, arabinose, xylose , ribose, ribulose, xylulose, glucose, mannose, sorbose, galactose, fructose, allose, altrose, gulose, idose, talose, psicose, tagatose, sedoheptulose, mannoheptulose, sucrose, maltose, lactose, cellobiose, gentiobiose, inulobiose, isomaltose, isomaltulose, kojibiose, lactulose, laminaribiose, leucrose, maltulose, melibiose, nigerose, robinose, rutinose, sophorose, trehalose, trehalulose, turanose, erlose, fucosyllactose, gentianose, inulotriose, kestose, maltotriose, mannotriose, melezitose, neokestose, panose, raffinose, rhamninose, maltitol, lactitol, isomaltitol, isomaltulose, isomaltol, maltol, ethylmaltol, dehydroacetic acid, kojic acid, erythorbic acid, in any of their isomeric forms.

More preferably, said organic compound is selected 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 glycol having a lower average molecular weight at 600 g / mol, glucose, mannose, fructose, sucrose, maltose, lactose, in any of their isomeric forms.

All the embodiments relating to the nature of said organic compound are combinable with each other so that step ii) can be carried out by placing said support in contact with at least one solution containing at least one organic compound comprising at least one alcohol function , in particular an organic compound comprising at least one alcohol function as mentioned above.

Implementation of Steps i) and ii) The process for preparing the nickel catalyst comprises several modes of implementation. They are distinguished in particular by the order of introduction of the organic compound and the nickel precursor, the contacting of the organic compound with the support can be performed either after contacting the nickel precursor with the support, or before the contacting the nickel precursor with the support, or at the same time as bringing the nickel into contact with the support.

A first mode of implementation consists in performing said step i) prior to said step ii).

A second mode of implementation consists in performing said step ii) prior to said step i). Each step i) and ii) bringing the support into contact with the nickel precursor (step i), and bringing the support into contact with at least one solution containing at least one organic compound comprising at least one alcohol function (step ii) ), is performed at least once and may advantageously be carried out several times, optionally in the presence of a nickel precursor and / or an identical or different organic compound at each step i) and / or ii) respectively, all possible combinations implementations of steps i) and ii) being included in the scope of the invention. A third mode of implementation consists in performing said step i) and said step ii) simultaneously (co-contacting). This embodiment may advantageously comprise the implementation of one or more steps i), possibly with a nickel precursor identical or different at each step i). In particular, one or more steps i) advantageously (nt) and / or follow (nt) said co-contacting step. This embodiment may also comprise several co-contacting steps: steps i) and ii) are carried out simultaneously several times, optionally in the presence of a nickel precursor and / or an identical organic compound (s) or different at each co-contact step.

Preferably, when said organic compound comprises at least two alcohol functional groups (diol or more generally polyol), with the exception of compounds of diethylene glycol, triethylene glycol, tetraethylene glycol, or more generally polyethylene glycol type, step i is carried out. before step ii), or step ii) is carried out before step i). More preferably, step i) is carried out before step ii).

Preferably, when said organic compound is an aromatic organic compound comprising at least two alcohol functional groups, step i) is carried out before step ii), or steps i) and ii) are carried out simultaneously.

Preferably, when said organic compound is a diethylene glycol, a triethylene glycol, a tetraethylene glycol, or more generally a polyethylene glycol having the formula H (OC ₂ H ₄ ) _n OI-1 with n greater than 4 and having a molar mass average less than 20000 g / mol, step i) is carried out before step ii) or step ii) before step i). More preferentially, step i) is carried out before step ii).

Preferably, when said organic compound is a monosaccharide of formula C _n (H ₂ 0) p with n of between 3 and 12, or a disaccharide or a trisaccharide, or a derivative of a monosaccharide, step ii is carried out ) before step i) or step i) before step ii). Preferably, when said organic compound comprises at least one alcohol function, at least one ketone and at least one unsaturated heterocyclic functional group, step i) is carried out before step ii) or step ii) before step i) . Each contacting step may preferably be followed by an intermediate drying step. The intermediate drying step is carried out at a temperature below 250 ° C., preferably between 15 and 240 ° C., more preferably between 30 and 220 ° C., still more preferably between 50 and 200 ° C., and still more preferably between more preferably between 70 and 180 ° C. Advantageously, when performing an intermediate drying step, an intermediate calcination step can be carried out. The intermediate calcination step is carried out at a temperature between 250 ° C and 1000 ° C, preferably between 250 and 750 ° C.

Advantageously, after each contacting step, whether it is a step of contacting the nickel precursor with the support, a step of contacting the organic compound with the support, or a step of contacting the precursor of the nickel and the organic compound simultaneously with the support, it is allowed to mature the impregnated support, possibly before an intermediate drying step. The maturation allows the solution to distribute itself homogeneously within the support. When a maturation step is carried out, said step is advantageously carried out at atmospheric pressure or under reduced pressure, under an inert atmosphere or under an atmosphere containing oxygen or under an atmosphere containing water, and at a temperature of 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. Longer durations are not excluded, but do not necessarily improve.

Step iii) - drying

According to the step of drying iii) the implementation of the preparation of the catalyst, prepared according to at least one embodiment described above, the drying step is carried out at a temperature below 250 ° C. preferably between 15 and 240 ° C, more preferably between 30 and 220 ° C, still more preferably between 50 and 200 ° C, and even more preferably between 70 and 180 ° C, for a period of time typically between 10 and 200 ° C. minutes and 24 hours. Longer durations are not excluded, but do not necessarily improve. The drying step may be performed by any technique known to those skilled in the art. It is advantageously carried out under an inert atmosphere or under an atmosphere containing oxygen or under a mixture of inert gas and oxygen. It is advantageously carried out at atmospheric pressure or under reduced pressure. Preferably, this step is carried out at atmospheric pressure and in the presence of air or nitrogen. Step iv) - calcination (optional)

Optionally, at the end of the drying step iii), a calcination step iv) is carried out at a temperature of between 250.degree. C. and 1000.degree. C., preferably between 250.degree. C. and 750.degree. inert atmosphere or under an atmosphere containing oxygen. The duration of this heat treatment is generally between 15 minutes and 10 hours. Longer durations are not excluded, but do not necessarily improve. After this treatment, the nickel of the active phase is thus in oxide form and the catalyst contains no more or very little organic compound introduced during its synthesis. Step v) - reducing treatment (optional)

Prior to the use of the catalyst in the catalytic reactor and the implementation of a hydrogenation process, advantageously at least one reducing treatment step v) is carried out in the presence of a reducing gas after steps iii) or iv ) to obtain a catalyst comprising nickel at least partially in metallic form.

This treatment makes it possible to activate the said catalyst and to form metal particles, in particular nickel in the zero state. Said reducing treatment can be carried out in situ or ex situ, that is to say after or before the catalyst is loaded into the hydrogenation reactor. Said step v) of reducing treatment can be carried out on the catalyst which has or has not been subjected to the passivation step vi), described hereinafter.

The reducing gas is preferably hydrogen. The hydrogen can be used pure or as a mixture (for example a hydrogen / nitrogen mixture, or hydrogen / argon, or hydrogen / methane). In the case where the hydrogen is used as a mixture, all proportions are possible. Said reducing treatment is carried out at a temperature between 120 and 500 ° C, preferably between 150 and 450 ° C. When the catalyst is not passivated, or undergoes a reducing treatment before passivation, the reducing treatment is carried out at a temperature between 180 and 500 ° C, preferably between 200 and 450 ° C, and even more preferably between 350 and 450 ° C. When the catalyst has been previously passivated, the reducing treatment is generally carried out at a temperature between 120 and 350 ° C, preferably between 150 and 350 ° C. The duration of the reducing treatment is generally between 2 and 40 hours, preferably between 3 and 30 hours. The rise in temperature to the desired reduction temperature is generally slow, for example set between 0.1 and 10 ° C / min, preferably between 0.3 and 7 ° C / min. The flow rate of hydrogen, expressed in L / hour / g of catalyst, is between 0.01 and 100 L / hour / g of catalyst, preferably between 0.05 and 10 L / hour / g of catalyst, moreover more preferably between 0.1 and 5 L / hour / gram of catalyst.

Step vi) - passivation (optional)

Prior to its implementation in the catalytic reactor, the catalyst according to the invention may optionally undergo a passivation step (step vi) with a sulfur or oxygen-containing compound or with CO ₂ before or after the reducing treatment step v) . This passivation step may be performed ex situ or in situ. The passivation step is carried out by the implementation of methods known to those skilled in the art.

The sulfur passivation step makes it possible to improve the selectivity of the catalysts and to avoid thermal runaways when starting new catalysts ("run away" according to the English terminology). Passivation generally consists in irreversibly poisoning with the sulfur compound the most virulent active sites of the nickel which exist on the new catalyst and thus in attenuating the activity of the catalyst in favor of its selectivity. The passivation step is carried out by the implementation of methods known to those skilled in the art and in particular, for example by the implementation of one of the methods described in patent documents EP0466567, US5153163, FR2676184, WO2004 / 098774, EP0707890. The sulfur compound is for example chosen from the following compounds: thiophene, thiophane, alkylmonosulfides such as dimethylsulfide, diethylsulfide, dipropylsulphide and propylmethylsulphide or an organic disulfide of formula HO-R SSR ₂ -OH such as di-thio-di-ethanol of formula HO-C ₂ H4-H4 SSC _2-OH (often called DEODS). The sulfur content is generally between 0.1 and 2% by weight of said element relative to the mass of the catalyst.

The passivation step with an oxygenated compound or with CO ₂ is generally carried out after a reducing treatment beforehand at elevated temperature, generally between 350 and 500 ° C., and makes it possible to preserve the metallic phase of the catalyst in the presence of air. . A second reducing treatment at a lower temperature, generally between 120 and 350 ° C., is then generally carried out. The oxygenated compound is generally air or any other stream containing oxygen. The catalyst prepared according to at least one of the embodiments described above, in association or not with said step iv) and / or said step v) and / or said step vi), is, before the implementation implementation of the selective hydrogenation process according to the invention, either entirely or at least partially free of said organic compound comprising at least one alcohol function. The introduction of the organic compound during its preparation has made it possible to increase the dispersion of the active phase thus leading to a more active and / or more selective catalyst.

The invention is illustrated by the following examples.

All the catalysts prepared in Examples 2 to 9 are prepared with nickel element isoteneur. The support used for the preparation of each of these catalysts is a delta alumina having a pore volume of 0.67 ml / g and a BET surface equal to 140 m ² / g.

Example 1 Preparation of aqueous solutions of Ni precursors

A first aqueous solution of Ni precursors (solution S1) used for the preparation of catalysts A, B and C is prepared at 25 ° C by dissolving 276 g of nickel nitrate Ni (N0 ₃ ) 2.6H ₂ O (supplier Strem Chemicals) ®) in a volume of 100 mL of demineralized water. The solution S1 is obtained whose NiO concentration is 19.0% by weight (relative to the mass of the solution).

A second aqueous solution of Ni precursors (solution S2) used for the preparation of catalysts D, E, F and G is prepared at 25 ° C. by dissolving 151 g of nickel nitrate Ni (N0 ₃ ) 2.6H ₂ O (supplier Strem Chemicals®) in a volume of 50 mL of demineralized water. Solution S2 is obtained whose NiO concentration is 19.3% by weight (relative to the mass of the solution).

Example 2 (Comparative) Preparation of Catalyst A by Impregnation of Nitrate of Nickel without Additive

The solution S1 prepared in Example 1 is impregnated dry on 10 g of said alumina support. The solid thus obtained is then dried in an oven overnight at 120 ° C, and then calcined under an air flow of 1 L / h / g of catalyst at 450 ° C for 2 hours.

The calcined catalyst thus prepared contains 13.8% by weight of the nickel element supported on alumina and has nickel oxide crystallites whose average diameter (determined by X-ray diffraction from the width of the diffraction at the angle 2theta = 43 °) is 15.2 nm. Example 3 (Invention): Preparation of a catalyst B by successive impregnation of nickel nitrate and then pentane-1,5-diol

Catalyst B is prepared by impregnating Ni nitrate on said alumina support and then impregnating pentane-1,5-diol using a molar ratio {pentane-1,5-diol / nickel} equal to 0.6.

To do this, the solution S1 prepared in Example 1 is impregnated dry on said alumina support. The solid B1 thus obtained is then dried in an oven overnight at 120 ° C. Then, an aqueous solution B 'is prepared by dissolving 4.81 g of pentane-1,5-diol (CAS 11 -29-5, supplier Sigma-Aldrich®, purity 97%) in 20 ml of water. demineralized. This solution B 'is then impregnated dry on 10 g of the solid B1 previously prepared. The solid thus obtained is then dried in an oven overnight at 120 ° C and calcined under an air flow of 1 L / g of catalyst at 450 ° C for 2 hours.

The calcined catalyst B thus prepared contains 13.8% by weight of the nickel element supported on alumina and has nickel oxide crystallites with an average diameter of 5.1 nm.

Example 4 (Invention): Preparation of a catalyst C by successive impregnation of nickel nitrate and then pentane-1,5-diol, without final calcination

Catalyst C is prepared by impregnating Ni nitrate on said alumina support and then impregnating pentane-1,5-diol using a molar ratio {pentane-1,5-diol / nickel} equal to 0.6.

To do this, the solution S1 prepared in Example 1 is impregnated dry on said alumina support. The solid B1 thus obtained is then dried in an oven overnight at 120 ° C. Then, an aqueous solution B 'is prepared by dissolving 4.81 g of pentane-1,5-diol (CAS 11 -29-5, supplier Sigma-Aldrich®, purity 97%) in 20 ml of water. demineralized. This solution B 'is then impregnated dry on 10 g of the solid B1 previously prepared. The solid thus obtained is then dried in an oven overnight at 120 ° C., without further heat treatment. Catalyst C is obtained.

To carry out the characterizations, a part of this catalyst C is calcined under an air flow of 1 L / hr / g of catalyst at 450 ° C. for 2 hours, in order to obtain calcined catalyst C_calci. The calcined calcined catalyst contains 13.8% by weight of the nickel element supported on alumina and has nickel oxide crystallites with an average diameter of 5.9 nm. Example 5 (Invention): Preparation of a catalyst D by successive impregnation of (D) - mannitol and then nickel nitrate

Catalyst D is prepared by impregnating (D) -mannitol on said alumina support and then impregnating Ni nitrate using a {(D) -mannitol / nickel} molar ratio equal to 0.6.

To do this, an aqueous solution D 'is prepared by dissolving 8.42 g of (D) -mannitol (CAS 69-65-8, supplier Sigma-Aldrich®, purity 98%) in 20 ml of demineralised water. This solution D 'is then impregnated dry on said alumina support. The solid D1 thus obtained is then dried in an oven overnight at 120 ° C. Then, the solution S2 prepared in Example 1 is impregnated to dryness on 10 g of the previously prepared solid D1. The solid thus obtained is then dried in an oven overnight at 120 ° C, and then calcined under an air flow of 1 L / h / g of catalyst at 450 ° C for 2 hours.

The calcined catalyst D thus prepared contains 13.8% by weight of the nickel element supported on alumina and has nickel oxide crystallites with an average diameter of 6.2 nm.

Example 6 (Invention): Preparation of a catalyst E by successive impregnation of (D) - mannitol and then nickel nitrate, with an additive molar ratio on nickel of 0.08

Catalyst E is prepared by impregnating (D) -mannitol on said alumina support and then impregnating Ni nitrate using a molar ratio {(D) -mannitol / nickel} equal to 0.08.

To do this, an aqueous solution E 'is prepared by dissolving 1.12 g of (D) -mannitol (CAS 69-65-8, supplier Sigma-Aldrich®, purity 98%) in 20 ml of demineralized water. This solution E 'is then impregnated dry on said alumina support. The solid E1 thus obtained is then dried in an oven overnight at 120 ° C. Then, the solution S2 prepared in Example 1 is impregnated dry on 10 g of the previously prepared solid E1. The solid thus obtained is then dried in an oven overnight at 120 ° C and calcined under an air flow of 1 L / g of catalyst at 450 ° C for 2 hours.

The calcined catalyst E thus prepared contains 13.8% by weight of the nickel element supported on alumina and has nickel oxide crystallites with an average diameter of 7.4 nm. EXAMPLE 7 (Invention) Preparation of a Catalyst F by Successive Impregnation of (D) -mannitol and then Nitrate of Nickel, with an Additive to Nickel Molar Ratio of 0.9

Catalyst F is prepared by impregnating (D) -mannitol on said alumina support and then impregnating Ni nitrate using a {(D) -mannitol / nickel} molar ratio equal to 0.08.

To do this, an aqueous solution F 'is prepared by dissolving 12.6 g of (D) -mannitol (CAS 69-65-8, supplier Sigma-Aldrich®, purity 98%) in 20 mL of demineralized water. This solution F 'is then impregnated dry on said alumina support. The solid F1 thus obtained is then dried in an oven overnight at 120 ° C. Then, the solution S2 prepared in Example 1 is impregnated dry on 10 g of the F1 solid prepared beforehand. The solid thus obtained is then dried in an oven overnight at 120 ° C, and then calcined under an air flow of 1 L / h / g of catalyst at 450 ° C for 2 hours.

The calcined catalyst F thus prepared contains 13.8% by weight of the nickel element supported on alumina and has nickel oxide crystallites with an average diameter of 5.9 nm.

Example 8 (Invention) Preparation of a catalyst G by successive impregnation of (D) - (+) - mannose and then nickel nitrate

Catalyst G is prepared by impregnation of (D) - (+) - mannose on said alumina support and then by impregnation of Ni nitrate using a molar ratio {(D) - (+) - mannose / nickel} equal to 0.6.

To do this, an aqueous solution G 'is prepared by dissolving 6.20 g of (D) - (+) - mannose (CAS 3458-28-4, supplier Sigma-Aldrich®, purity 99%) in 20 ml of water. 'Demineralized Water. This solution G 'is then impregnated dry on said alumina support. The solid G1 thus obtained is then dried in an oven overnight at 120 ° C. Then, the solution S2 prepared in Example 1 is impregnated to dryness on 10 g of the previously prepared solid G1. The solid thus obtained is then dried in an oven overnight at 120 ° C, and then calcined under an air flow of 1 L / h / g of catalyst at 450 ° C for 2 hours.

The calcined catalyst G thus prepared contains 13.8% by weight of the nickel element supported on alumina and has nickel oxide crystallites with an average diameter of 4.8 nm.

Example 9 (Invention): Preparation of a catalyst H by co-impregnation of nickel nitrate and (D) - (+) - mannose

Catalyst H is prepared by co-impregnation of nickel nitrate and (D) - (+) - mannose on said alumina support using a molar ratio {(D) - (+) - mannose / nickel} equal to 0.6. To do this, an aqueous solution H 'is prepared by dissolving 62.0 g of nickel nitrate Ni (N0 ₃ ) ₂ -6H ₂ O (supplier Strem Chemicals®) and 23.0 g of (D) - (+) -mannose (CAS 3458-28-4, supplier Sigma-Aldrich®, purity 99%) in 20 ml of demineralized water. This solution H 'is then impregnated dry on 10 g of said alumina support. The solid thus obtained is then dried in an oven overnight at 120 ° C, and then calcined under an air flow of 1 L / h / g of catalyst at 450 ° C for 2 hours.

The calcined catalyst H thus prepared contains 13.8% by weight of the nickel element supported on alumina and has nickel oxide crystallites with an average diameter of 6.3 nm.

Example 10 Evaluation of Catalytic Properties of Catalysts A to H in Selective Hydrogenation of a Mixture Containing Styrene and Isoprene

The catalysts A to H described in the above examples are tested for the selective hydrogenation reaction of a mixture containing styrene and isoprene.

The composition of the filler to be selectively hydrogenated is as follows: 8% by weight styrene (supplier Sigma Aldrich®, purity 99%), 8% by weight isoprene (supplier Sigma Aldrich®, purity 99%), 84% by weight n-heptane (solvent ) (VWR® supplier, purity> 99% chromanorm HPLC). This feed also contains sulfur compounds in very low content: 10 ppm wt of sulfur introduced in the form of pentanethiol (supplier Fluka®, purity> 97%) and 100 ppm wt of sulfur introduced in the form of thiophene (Merck® supplier, purity 99 %). This composition corresponds to the initial composition of the reaction mixture. This mixture of model molecules is representative of a pyrolysis species.

The selective hydrogenation reaction is carried out in a 500 ml autoclave made of stainless steel, equipped with magnetic stirring mechanical stirring and capable of operating at a maximum pressure of 100 bar (10 MPa) and temperatures of between 5 ° C. and 5 ° C. 200 ° C.

Prior to its introduction into the autoclave, a quantity of 3 ml of catalyst is reduced ex situ under a flow of hydrogen of 1 L / g of catalyst at 400 ° C. for 16 hours (temperature rise ramp of 1 ° C / min), then it is transferred to the autoclave, protected from the air. After addition of 214 mL of n-heptane (supplier VWR®, purity> 99% chromanorm HPLC), the autoclave is closed, purged, then pressurized under 35 bar (3.5 MPa) of hydrogen, and brought to temperature. test equal to 30 ° C. At time t = 0, about 30 g of a mixture containing styrene, isoprene, n-heptane, pentanethiol and thiophene are introduced into the autoclave. The reaction mixture then has the composition described above and stirring is started at 1600 rpm. The pressure is kept constant at 35 bar (3.5 MPa) in the autoclave using a reservoir bottle located upstream of the reactor.

The progress of the reaction is monitored by taking samples of the reaction medium at regular time intervals: the styrene is hydrogenated to ethylbenzene, without hydrogenation of the aromatic ring, and the isoprene is hydrogenated to methyl-butenes. If the reaction is prolonged longer than necessary, the methyl-butenes are in turn hydrogenated to isopentane. Hydrogen consumption is also monitored over time by the pressure decrease in a reservoir bottle located upstream of the reactor. The catalytic activity is expressed in moles of H ₂ consumed per minute and per gram of Ni.

The catalytic activities measured for catalysts A to H are reported in Table 1 below. They are related to the catalytic activity measured for catalyst A (A _HYD i) -

Table 1: Comparison of the performances in selective hydrogenation of a mixture containing styrene and isoprene.

The results in Table 1 demonstrate that catalysts B to H, prepared in the presence of an organic compound (having at least one alcohol type function and comprising between 1 and 20 carbon atoms), are more active than catalyst A prepared in the absence of this type of organic compound. This effect is related to the decrease in the size of the Ni particles.

Claims

Process for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule, such as diolefins and / or acetylenes and / or alkenyl aromatics, contained in a hydrocarbon feed having a lower or equal final boiling point at 300 ° C., which process is carried out at a temperature of between 0 and 300 ° C., at a pressure of between 0.1 and 10 MPa, at a molar ratio of hydrogen / (polyunsaturated compounds to be hydrogenated) of between 0.1 and 10 and at a hourly space velocity of between 0.1 and 200 h ^-1 when the process is carried out in the liquid phase, or at a molar ratio of hydrogen / (polyunsaturated compounds to be hydrogenated) of between 0.5 and 1000 and at a rate of between 100 and 40000 h ^-1 when the process is carried out in the gaseous phase, in the presence of a catalyst comprising an alumina support and an active phase consisting of nickel, said catalyst being dispersed by a process comprising at least:

Process according to claim 1, characterized in that it further comprises a step iv) of calcination of said dried catalyst obtained in step iii) at a temperature of between 250 and 1000 ° C.

Process according to claims 1 or 2, characterized in that steps i) and ii) are carried out simultaneously.

Process according to claims 1 or 2, characterized in that step i) is carried out before step ii).

Process according to claims 1 or 2, characterized in that step ii) is carried out before step i).

Process according to claims 1 or 2, characterized in that steps i) and / or ii) are (are) carried out by dry impregnation.

7. Method according to any one of the preceding claims, characterized in that the nickel element content is between 10 and 35% by weight relative to the total weight of the catalyst.

8. Process according to any one of claims 1 to 7, characterized in that said organic compound comprises a single alcohol function.

9. Method according to any one of claims 1 to 7, characterized in that said organic compound comprises at least two alcohol functions.

10. Process according to any one of claims 1 to 7, characterized in that said organic compound is an aromatic organic compound comprising at least two alcohol functional groups.

1 1. Process according to any one of Claims 1 to 7, characterized in that the said organic compound is 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 molecular weight of less than 20000 g / mol. 12. Method according to any one of claims 1 to 7, characterized in that said organic compound is a monosaccharide of formula C _n (H ₂ 0) _p with n between 3 and 12.

13. Method according to any one of claims 1 to 7, characterized in that said organic compound comprises at least one alcohol function, at least one ketone function and at least one unsaturated heterocyclic.

14. Process according to any one of Claims 1 to 7, characterized in that the said organic compound is a disaccharide or a trisaccharide, or a derivative of a monosaccharide.

15. Process according to any one of claims 1 to 14, characterized in that the filler is chosen from a C2 steam cracking cut or a C2-C3 steam cracking cut, and in which the molar ratio (hydrogen) / (compounds polyunsaturates to be hydrogenated) is between 0.5 and 1000, the temperature is between 0 and 300 ° C, the hourly volume velocity (VVH) is between 100 and 40000 h ^"1 , and the pressure is between 0.1 and 6.0 MPa.

16. Process according to any one of Claims 1 to 14, characterized in that the filler is chosen from steam cracking gasolines and in which the molar ratio (hydrogen) / (polyunsaturated compounds to be hydrogenated) is between 0.5 and 10, the temperature is between 0 and 200 ° C, the hourly volume velocity (VVH) is between 0.5 and 100 h ^"1 , and the pressure is between 0.3 and 8.0 MPa.