FR3110865A1 - PROCESS FOR PREPARING A CATALYST COMPRISING AN ACTIVE PHASE OF NICKEL IN THE FORM OF SMALL PARTICLES DISTRIBUTED INTO A CRUST AND A NICKEL COPPER ALLOY - Google Patents

Abstract

Process for preparing a catalyst comprising nickel and copper comprising the following steps: - impregnation of the porous support with a volume of a butanol solution of between 0.2 and 0.8 times the total pore volume of the support; - maturation of the impregnated porous support for 0.5 to 40 hours; - impregnation of the matured impregnated support with a solution comprising a precursor of the active phase of nickel; - impregnation of the support with a solution containing an organic compound comprising a carboxylic acid function; - impregnation of the support with a solution containing a copper precursor and a nickel precursor.

Description

METHOD FOR PREPARING A CATALYST COMPRISING AN ACTIVE PHASE OF NICKEL IN THE FORM OF SMALL PARTICLES DISTRIBUTED IN A CRUST AND A NICKEL COPPER ALLOY

The present invention relates to a process for the preparation of a supported metal catalyst based on nickel intended particularly for the hydrogenation of unsaturated hydrocarbons, and more particularly, for the selective hydrogenation of polyunsaturated compounds or for the hydrogenation of aromatics.

State of the art

Monounsaturated organic compounds such as ethylene and propylene, for example, are the source of the manufacture of polymers, plastics and other 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+ gasoline fraction (gasoline containing hydrocarbon compounds having 5 or more carbon atoms), in particular styrenic or indenic compounds . These polyunsaturated compounds are very reactive and lead to side reactions in the polymerization units. It is therefore necessary to eliminate them before recovering these cuts. Selective hydrogenation is the main treatment developed to specifically remove unwanted polyunsaturated compounds from these hydrocarbon feedstocks. It allows the conversion of polyunsaturated compounds to the corresponding alkenes or aromatics while avoiding their total saturation and therefore the formation of the corresponding alkanes or naphthenes.

Selective hydrogenation catalysts are generally based on metals from group VIII of the periodic table, preferably palladium or nickel. The metal is in the form of metallic particles deposited on a support. The metal content, the size of the metal particles and the distribution of the active phase in the support are among the criteria which have an importance on the activity and the selectivity of the catalysts.

The macroscopic distribution of the metallic particles in the support constitutes an important criterion, mainly within the framework of rapid and consecutive reactions such as selective hydrogenations. It is generally desirable for these elements to be located in a crust at the periphery of the support in order to avoid intragranular material transfer problems which can lead to activity defects and a loss of selectivity. Such catalysts are also called "eggshell" catalysts according to Anglo-Saxon terminology.

Such catalysts are widely known in the case of selective hydrogenation catalysts based on palladium. Indeed, thanks to the low palladium content (generally less than 1% by weight (1% wt) of palladium relative to the catalyst) and the appropriate preparation processes, a fine crust of palladium at the periphery of the support grains can be obtained (FR2922784, US2010/217052).

It is often proposed to substitute palladium with nickel, a metal less active than palladium which it is therefore necessary to have in greater quantity in the catalyst. Thus, nickel-based catalysts generally have a metal content between 5 and 50% by weight of nickel relative to the catalyst. In these catalysts, the nickel is generally distributed homogeneously within the support. One of the possible ways of improving these catalysts in terms of activity and selectivity is to control the distribution of the nickel within the support by depositing the nickel in a more concentrated manner on a crust, at the periphery of the support. Such catalysts are known from the state of the art.

Document US 4,519,951 describes an "eggshell" type catalyst with nickel on a porous support having a porous volume of the pores whose size is less than 11.7 nm of at least 0.2 ml/g and a volume porous pores larger than 11.7 nm of at least 0.1 ml/g. More than 50% by weight of the nickel is in a crust whose thickness is equal to 0.15 times the radius of the support. This catalyst is used for the hydrogenation of fats.

Document CN101890351 describes a nickel-supported catalyst in which more than 90% by weight of the nickel is found in a crust 700 μm thick. The catalyst is prepared using an ammoniacal solution to dissolve the nickel salt. These catalysts are used in a selective hydrogenation application.

Document US2012/0065442 describes a supported nickel catalyst distributed both over a crust with a thickness of 3 to 15% of the diameter and at the core, the nickel concentration ratio between the crust and the core being between 3, 0:1 and 1.3:1. The deposition of the active nickel phase is carried out by spraying (“ spray coating ” according to English terminology) of an ammoniacal solution of a nickel salt on the support.

Document FR19/08.719 describes a method for preparing a catalyst based on nickel on an alumina support obtained according to a very specific method, the nickel being distributed both on a crust on the periphery of the support, and in the heart of the support, the thickness of said crust being between 2% and 15% of the diameter of the catalyst. The process for preparing such a catalyst requires, on the one hand, the use of a specific alumina support which has undergone a hydrothermal treatment in the presence of an acid solution, and, on the other hand, the performance of a step of hydrothermal treatment after adding a specific organic additive to the catalyst precursor.

Objects of the invention

The present invention thus relates to a new process for the preparation of a catalyst which makes it possible to obtain a catalyst comprising performance at least as good, or even better, in terms of activity and selectivity in the context of hydrogenation reactions. selective polyunsaturated compounds or hydrogenation of aromatics, while using a lower effective quantity of nickel phase (that is to say a quantity of nickel found in-fine in the crust on the periphery of the support allowing the realization of the reactions hydrogenation or hydrogenation of aromatics) to that typically used in the state of the art, which is due to a better distribution of the active phase of nickel in the support, making the latter more accessible to the reactants as well as to a Ni particle size of less than 7 nm through the use of an organic compound, giving even greater intrinsic nickel activity.

The subject of the present invention is a method for preparing a catalyst comprising nickel and copper, in an amount of 1 and 50% by weight of nickel element relative to the total weight of the catalyst, and in an amount of 0.5 to 15 % by weight of copper element relative to the total weight of the catalyst, and a porous alumina support, the nickel being distributed both over a crust on the periphery of the support, and in the heart of the support, the thickness of said crust being between 2% and 15% of the diameter of the catalyst, the size of the nickel particles in the catalyst, measured in oxide form, being less than 7 nm, which method comprises the following steps:

a) the porous support is impregnated with a volume (V1) of a butanol solution of between 0.2 and 0.8 times the total pore volume (TPV) of said support to obtain an impregnated support;

b) the impregnated porous support obtained at the end of step a) is allowed to mature for 0.5 to 40 hours;

c) the sequence of the following sub-steps is carried out:
c1) either the matured impregnated porous support obtained at the end of step b), or the catalyst precursor obtained at the end of step d), is impregnated with a solution comprising at least one precursor of the phase active nickel;
c2) either the matured impregnated porous support obtained at the end of step b), or the catalyst precursor obtained at the end of step d), is impregnated with at least one solution containing at least one organic compound comprising at least one carboxylic acid function;
steps c1) and c2) being carried out simultaneously, or separately in any order;
c3) optionally, the catalyst precursor obtained at the end of the sequence of steps c1) and c2) is dried at a temperature below 250° C.;

d) the sequence of the following sub-steps is carried out:
d1) either the porous support, or the matured impregnated porous support obtained at the end of step b), or the catalyst precursor obtained at the end of step c), is impregnated with at least one solution containing at least one copper precursor and one nickel precursor at a desired copper concentration to obtain on the final catalyst a content of between 0.5 and 15% by weight of copper element relative to the total weight of the final catalyst;
d2) optionally, the catalyst precursor obtained at the end of step d1) is dried at a temperature below 250° C.;

said step d) being carried out either before step a), or between steps b) and c), or after step c), it being understood that:

i) when performing step d) before step a), then sub-steps c3) and d2) are mandatory;

ii) when performing step d) between steps b) and c), then sub-step c3) is mandatory;

iii) when performing step d) after step c), then sub-step d2) is mandatory.

Surprisingly, the Applicant has discovered that carrying out a particular step of impregnating a butanol solution on a porous alumina support, whatever its origin, followed by a maturation step before the step addition of the precursor of the active phase of nickel on said impregnated matured support, and this without carrying out an intermediate drying step between the impregnation of the butanol and the impregnation of the precursor of the active phase of nickel, makes it possible to obtain a catalyst in which at least a part of the nickel is distributed over a crust at the periphery of the support, the other part of the nickel being distributed in the heart of the catalyst. Without wishing to be bound by any theory, the presence of butanol makes it possible to limit the migration of the active phase of nickel to the core of the support. Indeed, only part of the porosity is occupied by the butanol. The maturation step allows the butanol solution to migrate to the core of the support and to release a "crown of free pores" at the periphery of the support accessible by the nickel during the step of impregnation of the precursor of the active phase . In addition, butanol and water being poorly miscible, the butanol layer constitutes a barrier limiting the diffusion of nickel to the core of the support. Furthermore, the presence on the catalyst of a NiCu alloy allows these catalysts to be reduced in situ in the reactor before hydrogenation and this at very low temperatures compared to the conventional reduction temperature which thus takes place ex situ and which therefore requires an additional passivation step.

Preferably, step b) is carried out at a temperature less than or equal to 60°C.

Preferably, in step a) a solution of n-butanol is used.

Preferably, the copper precursor is chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulphate, copper chloride, copper bromide, copper iodide and fluoride. of copper.

Preferably, the precursor of the nickel active phase is nickel nitrate, nickel chloride, nickel acetate or nickel hydroxycarbonate.

Preferably, the molar ratio between said organic compound introduced in step c2) and the nickel element introduced in step c1) is between 0.01 and 5.0 mol/mol.

Preferably, the organic compound of step c2) is chosen from oxalic acid, malonic acid, glycolic acid, lactic acid, tartronic acid, citric acid, tartaric acid , pyruvic acid and levulinic acid.

Preferably, steps c1) and c2) are carried out simultaneously.

In one embodiment according to the invention, when step d) is carried out before step a), the volume V2' of the solution comprising at least one precursor of the active phase of nickel and at least one organic compound comprising at least one carboxylic acid function supplied in step c) is such that the V2' = VPT – V1.

In one embodiment according to the invention, in which when step d) is carried out between steps b) and c), or after step c), the volume V2' of the solution comprising at least one precursor of the active nickel phase and at least one organic compound comprising at least one carboxylic acid function supplied in step c) and the volume V4 of the solution comprising a nickel precursor and a copper precursor supplied in step d) are such that V2' + V4 = VPT – V1.

In one embodiment according to the invention, said method further comprises a step c3′) of calcining the dried catalyst precursor obtained at the end of step c3) at a temperature between 250°C and 600°C .

Preferably, in step a) said volume (V1) of said butanol solution is between 0.25 and 0.75 times the total pore volume (TPV) of said support.

Preferably, the sub-steps c3) and/or d2) are carried out for a time comprised between 0.5 hours and 12 hours.

In one embodiment according to the invention, said method further comprises a step e) in which the catalyst precursor obtained at the end of the sequence of steps a) to d) is reduced by bringing said precursor of catalyst with a reducing gas at a temperature greater than or equal to 150°C and less than 250°C.

Another object according to the invention relates to a catalyst capable of being obtained by the process according to the invention.

Another object according to the invention relates to a process for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule contained in a charge of hydrocarbons having a final boiling point less than or equal to 300° C., which process being carried out at a temperature of between 0 and 300°C, at a pressure of between 0.1 and 10 MPa, at a hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio of between 0.1 and 10 and at an hourly volumetric speed between 0.1 and 200 h ^-1 when the process is 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 an hourly volume rate between 100 and 40000 h ^-1 when the process is carried out in the gas phase, in the presence of a catalyst according to the invention or obtained according to the preparation process according to the invention.

Another object according to the invention relates to a process for the hydrogenation of at least one aromatic or polyaromatic compound contained in a charge of hydrocarbons having a final boiling point less than or equal to 650° C., said process being carried out in phase gaseous or in the liquid phase, at a temperature between 30 and 350°C, at a pressure between 0.1 and 20 MPa, at a hydrogen/(aromatic compounds to be hydrogenated) molar ratio between 0.1 and 10 and at a hourly volume rate of between 0.05 and 50 h ^-1 , in the presence of a catalyst according to the invention or obtained according to the preparation process according to the invention.

Description of figure

There is a diagram representing the distribution of nickel in the catalyst. The abscissa axis corresponds to the thickness of the catalyst, measured from the edge of the catalyst (in µm). The ordinate axis corresponds to the nickel density (in grams of Ni/mm3). The nickel is distributed both on a crust at the periphery of the support, of thickness ep1, and at the heart of the support. The nickel density on the crust crust is greater than the nickel density at the core of the core support. The transition interval between the core and the crust of the catalyst has a thickness denoted ep2-ep1.

Detailed description of the invention

1. 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.

In the present description, according to the IUPAC convention, micropores are understood to mean pores whose diameter is less than 2 nm, that is to say 0.002 μm; by mesopores pores whose diameter is greater than or equal to 2 nm, i.e. 0.002 µm and less than or equal to 50 nm, i.e. 0.05 µm and by macropores pores whose diameter is greater than 50 nm, i.e. 0.05 µm.

In order to analyze the distribution of the metallic phase on the support, a crust thickness is measured by Castaing microprobe (or microanalysis by electron microprobe). The apparatus used is a CAMECA XS100, equipped with four monochromator crystals allowing the simultaneous analysis of four elements. Castaing's microprobe analysis technique consists of detecting X-rays emitted by a solid after its elements have been excited by a high-energy electron beam. For the purposes of this characterization, the catalyst grains are coated in epoxy resin pads. These studs are polished until they reach the cut to the diameter of the balls or extruded then metallized by depositing carbon in a metal evaporator. The electron probe is scanned along the diameter of five balls or extrudates to obtain the average distribution profile of the constituent elements of the solids. This method, well known to those skilled in the art, is defined in the publication by L. Sorbier et al. “ Measurement of palladium crust thickness on catalyst by EPMA” Materials Science and Engineering 32 (2012). It makes it possible to establish the distribution profile of a given element, here Nickel, within the grain. Furthermore, the Ni concentration is defined for each measurement and therefore for each analysis step. The density of Ni within the grain is therefore defined as the concentration of Ni per mm ³ .

The total pore volume is measured by mercury porosimetry according to the ASTM D4284-92 standard with a wetting angle of 140°, for example by means of an Autopore III™ model device from the Micromeritics™ brand.

The BET specific surface is measured by physisorption with nitrogen according to standard ASTM D3663-03, method described in the work Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, 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 term “size of the nickel particles” means the diameter of the crystallites of nickel in oxide form. The diameter of nickel crystallites in oxide form is determined by X-ray diffraction, from the width of the diffraction line located at the angle 2theta=43° (i.e. along the crystallographic direction [200 ]) using the Scherrer relation. 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: 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 nickel and copper content is measured by X-ray fluorescence.

2. Catalyst preparation process

The steps of said preparation process are described in detail below.

Step a)

According to step a) of the process, the alumina support is impregnated with a volume V1 of a butanol solution of between 0.2 and 0.8 times the total pore volume (also called here VPT) of said support to be impregnated. , preferably between 0.25 and 0.75.

By butanol is meant organic compounds comprising an alcohol function corresponding to the chemical formula C ₄ H ₁₀ O. By butanol is thus meant the family of the following organic compounds: butan-1-ol (or n-butanol), butan-2-ol, isobutanol, and tert-butanol. Preferably step a) is carried out in the presence of butan-1-ol.

Step b)

After step a), the impregnated support is matured in the wet state for 0.5 hour to 40 hours, preferably for 1 hour to 30 hours. Maturation step b) is preferably carried out at a temperature less than or equal to 60° C., and more preferably at room temperature. This step allows the migration of the butanol solution to the core of the support.

Step c)

Step c1)

During step c1) of the process, the matured impregnated porous alumina support obtained at the end of step b), or the catalyst precursor obtained at the end of step d), is impregnated with a solution comprising at least one precursor of the active nickel phase to obtain a catalyst precursor. The impregnation step can be carried out according to methods well known to those skilled in the art.

The pH of said solution comprising at least one precursor of the active phase of impregnated nickel may be modified by the possible addition of an acid or a base.

Preferably, said nickel precursor is introduced in aqueous solution, for example in the form of nitrate, carbonate, acetate, chloride, oxalate, complexes formed by a polyacid or an acid-alcohol and its salts, complexes formed with acetylacetonates, or any other inorganic derivative soluble in aqueous solution, which is brought into contact with said support. Preferably, nickel nitrate, nickel chloride, nickel acetate or nickel hydroxycarbonate are advantageously used as nickel precursor. Very preferably, the nickel precursor is nickel nitrate.

The nickel concentration in solution is adjusted according to the pore volume of the support still available so as to obtain for the supported catalyst, a nickel content of between 1 and 50% by weight of nickel element relative to the total weight of the catalyst, more preferably between 2 and 40% by weight and even more preferably between 3 and 35% by weight and even more preferably 5 and 25% by weight.

Step c2)

During step c2) of the process, the matured impregnated porous alumina support obtained at the end of step b), or the catalyst precursor obtained at the end of step d), is impregnated with a solution containing at least one organic compound comprising at least one carboxylic acid function. The impregnation step can be carried out by dry or excess impregnation according to methods well known to those skilled in the art. Indeed, it has also been noticed that the catalysts prepared in the presence of an organic compound (cited below) are more active than the catalysts prepared in the absence of this type of organic compound. This effect is linked to the decrease in the size of the nickel particles.

Said solution containing at least one organic compound comprising at least one carboxylic acid function is preferably aqueous. Said organic compound is previously at least partially dissolved in said solution at the desired concentration. The pH of said solution may be modified by the possible addition of an acid or a base.

Advantageously, the molar ratio between said organic compound introduced in step c2) and the nickel element also introduced in step c1) is between 0.01 and 5.0 mol/mol, preferably between 0.05 and 2.0 mol/mol, more preferably between 0.1 and 1.5 mol/mol and even more preferably between 0.3 and 1.2 mol/mol.

Said organic compound comprising at least one carboxylic acid function can be an aliphatic, saturated or unsaturated organic compound, or an aromatic organic compound. Preferably, the aliphatic organic compound, saturated or unsaturated, comprises between 1 and 9 carbon atoms, preferably between 2 and 7 carbon atoms. Preferably, the aromatic organic compound comprises between 7 and 10 carbon atoms, preferably between 7 and 9 carbon atoms.

Said aliphatic organic compound, saturated or unsaturated, or said aromatic organic compound, comprising at least one carboxylic acid function can be chosen from monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids.

Advantageously, the organic compound comprising at least one carboxylic acid function is chosen from ethanedioic acid (oxalic acid), propanedioic acid (malonic acid), pentanedioic acid (glutaric acid), hydroxyacetic acid (glycolic acid) , 2-hydroxypropanoic acid (lactic acid), 2-hydroxypropanedioic acid (tartronic acid), 2-hydroxypropane-1,2,3-tricarboxylic acid (citric acid), 2,3-dihydroxybutanedioic acid (tartaric acid), 2-oxopropanoic acid (pyruvic acid), 4-oxopentanoic acid (levulinic acid).

Implementation of steps c1) and c2)

The method for preparing the nickel catalyst comprises several modes of implementation. They are distinguished in particular by the order in which the organic compound and the nickel precursor are introduced, it being possible for the organic compound to come into contact with the support either after the nickel precursor has been brought into contact with the support, or before the bringing the nickel precursor into contact with the support, or either at the same time as bringing the nickel into contact with the support.

A first mode of implementation consists in performing said step c1) prior to said step c2) (post-impregnation).

A second mode of implementation consists in carrying out said step c2) prior to said step c1) (pre-impregnation).

Each step c1) and c2) of impregnation of the matured impregnated support with the nickel precursor (step c1), and of impregnation of the matured impregnated support with at least one solution containing at least one organic compound comprising at least one carboxylic acid function is carried out at least once and can advantageously be carried out several times, optionally in the presence of a nickel precursor and/or of an identical or different organic compound at each stage c1) and/or c2) respectively, all possible combinations of implementations of steps c1) and c2) being included within the scope of the invention.

Preferably, the volume V2 of the solution comprising at least one precursor of the active phase of nickel and the volume V3 of the solution comprising at least one organic compound impregnated on the matured impregnated support obtained at the end of step b) are such that V2 + V3 = VPT – V1.

A third mode of implementation consists in carrying out said step c1) and said step c2) simultaneously (co-impregnation). This mode of implementation can advantageously comprise the implementation of one or more steps c1), possibly with an identical or different nickel precursor at each step c1). In particular, one or more steps c1) advantageously precede(s) and/or follow(s) said co-impregnation step, optionally with an identical or different nickel precursor at each step. This mode of implementation can also comprise several co-impregnation steps: steps c1) and c2) are carried out simultaneously on several occasions, optionally in the presence of a nickel precursor and/or of an identical organic compound (s) or different (s) at each co-impregnation step.

Preferably, steps c1) and c2) are carried out simultaneously. Preferably, the volume V2' of the solution comprising at least one precursor of the active nickel phase and at least one organic compound impregnated on the matured impregnated support obtained at the end of step b) is such that V2' = TPV – V1.

Each impregnation step can preferably be followed by an intermediate drying step. The intermediate drying step is carried out at a temperature below 100° C., preferably below 80° C. and even more preferably below 70° C. for a duration typically between 0.5 hour and 12 hours, and in such a way even more preferred for a period of 0.5 hour to 5 hours.

Step c3)

In one embodiment according to the invention, a step c3) of drying the catalyst precursor obtained at the end of the sequence of sub-steps c1) and c2) is carried out. Step c3) of drying is advantageously carried out at a temperature below 250° C., preferably between 15 and 180° C., more preferably between 30 and 160° C., even more preferably between 50 and 150° C., and even more preferentially between 70 and 140° C., for a duration typically comprised between 0.5 hour and 12 hours, and even more preferably for a duration of 0.5 hour to 5 hours. Longer durations are not excluded, but do not necessarily bring improvement.

The drying step can be carried out 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 at reduced pressure. Preferably, this step is carried out at atmospheric pressure and in the presence of air or nitrogen.

Step c3) is no longer optional when step d) is performed before step a) or between steps a) and b). In these cases, at the end of step c3), the total, partial presence or absence of the butanol solution in the catalyst has no effect on the activity and/or the selectivity of the catalyst in the context of the selective hydrogenation of polyunsaturated compounds or the hydrogenation of aromatic compounds.

Step c3’)

In one embodiment according to the invention, a step c3′) of calcining the catalyst precursor obtained at the end of step c3) is carried out at a temperature between 250°C and 600°C. Calcination step c3′) can be carried out at a temperature between 250° C. and 600° C., preferably between 350° C. and 550° C., for a period typically between 0.5 and 24 hours, so as to preferably for a period of 0.5 to 12 hours, and even more preferably for a period of 0.5 to 10 hours, preferably under an inert atmosphere or under an atmosphere containing oxygen. Longer durations are not excluded, but do not necessarily bring improvement.

At the end of step c3′), the total, partial presence or absence of the butanol solution in the catalyst has no effect on the activity and/or the selectivity of the catalyst in the part of the selective hydrogenation of polyunsaturated compounds or the hydrogenation of aromatic compounds.

Step d)

Step d1)

During step d1) of the process, either the porous support, or the matured impregnated porous support obtained at the end of step b), or the catalyst precursor obtained at the end of step c is impregnated. ), with at least one solution containing at least one copper precursor and one nickel precursor at a desired copper concentration to obtain on the final catalyst a content of between 0.5 and 15% by weight of copper element relative to the total weight of the final catalyst.

The pH of said solution comprising at least one precursor of nickel and an impregnated copper precursor may be modified by the possible addition of an acid or a base.

Preferably, said nickel precursor and the copper precursor are introduced in aqueous solution.

When the nickel precursor is introduced in aqueous solution, a nickel precursor is advantageously used in the form of nitrate, carbonate, acetate, chloride, hydroxide, hydroxycarbonate, oxalate, sulphate, formate , of complexes formed by a polyacid or an acid-alcohol and its salts, of complexes formed with acetylacetonates, of tetrammine or hexammine complexes, or of any other inorganic derivative which is soluble in aqueous solution, which is brought into contact with the said precursor of catalyst. Preferably, the nickel precursor used is advantageously nickel nitrate, nickel hydroxide, nickel carbonate, nickel chloride, or nickel hydroxycarbonate. Very preferably, the nickel precursor is nickel nitrate, nickel carbonate or nickel hydroxide.

When the copper precursor is introduced in aqueous solution, a copper precursor in mineral or organic form is advantageously used. In mineral form, the copper precursor can be chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulphate, copper chloride, copper bromide, copper iodide or copper fluoride. Very preferably, the copper precursor salt is copper nitrate.

Preferably, the nickel precursor is supplied to step d1) at a desired concentration to obtain on the final catalyst (i.e. obtained at the end of step f) of reduction) a nickel content included in the alloy copper-nickel between 0.5 and 15% by weight of nickel element relative to the total weight of the catalyst, preferably between 1 and 12% by weight, and more preferably between 1 and 10% by weight.

The quantities of the copper precursor(s) introduced into the solution according to step d1) are chosen such that the total copper content is between 0.5 and 15% by weight of copper element relative to the total weight of the catalyst. final (i.e. obtained at the end of step f), preferably between 0.5 and 12% by weight, preferably between 0.75 and 10% by weight, and even more preferably between 1 and 9% by weight.

Step d2)

In one embodiment according to the invention, a step d2) of drying the catalyst precursor obtained at the end of step d1) is carried out. Step d2) of drying is advantageously carried out at a temperature below 250° C., preferably between 15 and 180° C., more preferably between 30 and 160° C., even more preferably between 50 and 150° C., and even more preferentially between 70 and 140° C., for a duration typically comprised between 0.5 hour and 12 hours, and even more preferably for a duration of 0.5 hour to 5 hours. Longer durations are not excluded, but do not necessarily bring improvement.

The drying step can be carried out 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 at reduced pressure. Preferably, this step is carried out at atmospheric pressure and in the presence of air or nitrogen.

Sub-step d2) is no longer optional when step d) is performed before step a) or after step c). When step d) is carried out after step c), then at the end of sub-step d2), the total, partial presence, or absence of the butanol solution in the catalyst has not of incidence on the activity and/or the selectivity of the catalyst within the framework of the selective hydrogenation of polyunsaturated compounds or the hydrogenation of aromatic compounds.

Step d2’)

In one embodiment according to the invention, a step d2′) of calcining the catalyst precursor obtained at the end of step d2) is carried out at a temperature of between 250°C and 600°C. Step d2′) of calcination can be carried out at a temperature of between 250° C. and 600° C., preferably between 350° C. and 550° C., for a duration typically of between 0.5 and 24 hours, so as to preferably for a period of 0.5 to 12 hours, and even more preferably for a period of 0.5 to 10 hours, preferably under an inert atmosphere or under an atmosphere containing oxygen. Longer durations are not excluded, but do not necessarily bring improvement.

Implementation of steps c) and d)

The process for preparing the catalyst comprises several modes of implementation. They are distinguished in particular by the order of introduction of the solution comprising the precursor of the active phase of nickel, of the solution comprising at least one organic compound comprising at least one carboxylic acid function, and of the solution based on nickel and of copper to obtain the NiCu alloy.

Step d) can be carried out either before step a), or between steps b) and c), or after step c) of the preparation process.

When performing step d) before step a), then sub-steps c3) and d2) are mandatory. Preferably, steps c3′) and/or d2′) are also carried out.

In this case, the volume V2 of the solution comprising at least one precursor of the active nickel phase supplied in step c1) and the volume V3 of the solution comprising at least one organic compound comprising at least one carboxylic acid function are preferably such that V2 + V3 = VPT – V1.

Still in this case, and when steps c1) and c2) are carried out simultaneously, the volume V2' of the solution comprising at least one precursor of the active phase of nickel and at least one organic compound is such that V2' = VPT – V1.

When performing step d) between steps b) and c), then sub-step c3) is mandatory. When performing step d) after step c), then sub-step d2) is mandatory.

For these two cases, preferably, the volume V2 of the solution comprising at least one precursor of the active nickel phase, the volume V3 of the solution comprising at least one organic compound comprising at least one carboxylic acid function and the volume V4 of the solution based on nickel and copper are such that V2 + V3 + V4 = VPT – V1.

Still in this case, and when steps c1) and c2) are carried out simultaneously, the volume V2' of the solution comprising at least one precursor of the active phase of nickel and at least one organic compound is such that V2' + V4 = TPV – V1.

In one embodiment according to the invention, steps a) to d) are advantageously carried out in the following order: a); b); c) then d).

In another embodiment according to the invention, steps a) to d) are advantageously carried out in the following order: d); To) ; b) then c).

Step e) Reduction with a reducing gas (optional)

In one embodiment according to the invention, prior to the use of the catalyst in the catalytic reactor and the implementation of a hydrogenation process, a reducing treatment step e) is carried out in the presence of a reducing gas so as to obtain a catalyst comprising nickel at least partially in metallic form. This step is advantageously carried out in situ, that is to say after loading the catalyst into a hydrogenation reactor. This treatment makes it possible to activate said catalyst and to form metallic particles, in particular nickel in the zero valent state. Performing the catalyst reduction treatment in situ makes it possible to dispense with an additional step of passivation of the catalyst by an oxygenated compound or by CO ₂ , which is necessarily the case when the catalyst is prepared by carrying out a reduction treatment. ex-situ, that is to say outside the reactor used for the hydrogenation of aromatic or polyaromatic compounds. Indeed, when the reducing treatment is carried out ex-situ, it is necessary to carry out a passivation step in order to preserve the metallic phase of the catalyst in the presence of air (during transport and loading operations of the catalyst in the reactor of hydrogenation), then to carry out a new step of reduction of the catalyst.

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.

According to an essential aspect of the preparation process according to the invention, said reducing treatment is carried out at a temperature greater than or equal to 150° C. and less than 250° C., preferably between 160 and 230° C., and more preferably between 170 and 220°C. The duration of the reducing treatment is between 5 minutes and less than 5 hours, preferably between 10 minutes and 4 hours, and even more preferably between 10 minutes and 110 minutes.

The presence of the nickel-copper alloy at least partially in reduced form makes it possible to use less severe operating conditions for reducing the active phase of nickel than in the prior art and thus makes it possible to directly carry out the reduction step within the reactor in which it is desired to carry out the hydrogenation of unsaturated or aromatic compounds.

Furthermore, the presence of copper in the catalyst makes it possible to maintain good activity of the catalyst and good life of the catalyst when the latter is brought into contact with a hydrocarbon feedstock comprising sulfur. Indeed, compared to nickel, the copper present in the catalyst more easily captures the sulfur compounds included in the charge, which limits the irreversible poisoning of the active sites. 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.

The hydrogen flow, expressed in L/hour/gram of catalyst precursor is between 0.01 and 100 L/hour/gram of catalyst, preferably between 0.05 and 10 L/hour/gram of catalyst precursor , even more preferably between 0.1 and 5 L/hour/gram of catalyst precursor.

Step f) Passivation (optional)

The catalyst prepared according to the process according to the invention can advantageously undergo a step of passivation by a sulfur compound which makes it possible to improve the selectivity of the catalysts and to avoid thermal runaways during the start-up of new catalysts (" run-away " according to Anglo-Saxon terminology). Passivation generally consists in irreversibly poisoning with the sulfur compound the most virulent active sites of nickel which exist on the new catalyst and therefore in attenuating the activity of the catalyst in favor of its selectivity. The passivation step is carried out by implementing methods known to those skilled in the art

The passivation step with a sulfur compound is generally carried out at a temperature of between 20 and 350° C., preferably between 40 and 200° C., for 10 to 240 minutes. The sulfur compound is for example chosen from the following compounds: thiophene, thiophane, alkylmonosulfides such as dimethylsulfide, diethylsulfide, dipropylsulfide and propylmethylsulfide or else an organic disulfide of formula HO-R ₁ -SSR ₂ -OH such as di-thio-di -ethanol of formula HO-C ₂ H ₄ -SSC ₂ H ₄ -OH (often called DEODS). The sulfur content is generally between 0.1 and 2% by weight of said element relative to the total weight of the catalyst.

In one embodiment according to the invention, the preparation of the catalyst is carried out ex-situ, that is to say before loading the catalyst into the reaction unit of the selective hydrogenation or aromatics hydrogenation process.

3. Catalyst

The preparation process according to the invention makes it possible to obtain on a catalyst comprising nickel and copper, at a rate of 1 and 50% by weight of nickel element relative to the total weight of the catalyst, and at a rate of 0.5 to 15% by weight of copper element relative to the total weight of the catalyst, and a porous alumina support, the nickel being distributed both over a crust at the periphery of the support, and in the heart of the support, the thickness of said crust being between 2% and 15% of the diameter of the catalyst, the size of the nickel particles in the catalyst, measured in oxide form, is less than 7 nm.

Preferably, the nickel is distributed both on a crust on the periphery of the support, and in the heart of the support, the thickness of the crust (also called ep1) being 2.5% and 12% of the diameter of the catalyst, so as still more preferably between 3% and 10% of the diameter of the catalyst and even more preferably between 3% and 7.5% of the diameter of the catalyst.

Preferably, the nickel density ratio between the crust and the core (also called here d _crust /d _core ) is strictly greater than 3, preferably greater than 3.5 and preferably between 3.8 and 15.

Preferably, said crust comprises more than 25% by weight of nickel element relative to the total weight of nickel contained in the catalyst, preferably more than 40% by weight, more preferably between 45% and 90% by weight, and even more preferably between 60% and 90% by weight.

Preferably, the molar ratio between nickel and copper is between 0.5 and 5 mol/mol, preferably between 0.7 and 4.5 mol/mol, more preferably between 0.9 and 4 mol/mol .

Preferably, at least a part of the nickel and the copper is in the form of a nickel-copper alloy, advantageously corresponding to the formula Ni _x Cu _y with x between 0.1 and 0.9 and including between 0.1 and 0.9.

Preferably, the nickel content included in the copper-nickel alloy is between 0.5 and 15% by weight of nickel element relative to the total weight of the catalyst, preferably between 1 and 12% by weight, and more preferably between 1 and 10% by weight.

The size of the nickel particles, measured in oxide form, in the catalyst is less than 7 nm, preferably less than 5 nm, more preferably less than 4 nm, and even more preferably less than 3 nm.

Advantageously, the transition interval between the core and the crust of the catalyst (also called here the core/crust transition interval, or ep2-ep1 according to the notations of the ), related to the variation of the nickel density measured over the thickness of the catalyst from the edge of the catalyst to the center of the catalyst, is very steep. Preferably, the core/crust transition interval is between 0.05% and 3% of the diameter of the catalyst, preferably between 0.5% and 2.5% of the diameter of the catalyst.

The nickel content in said catalyst is advantageously between 1 and 50% by weight relative to the total weight of the catalyst, more preferably between 2 and 40% by weight and even more preferably between 3 and 35% by weight and even more preferably 5 and 25% weight relative to the total weight of the catalyst

The copper content is between 0.5 and 15% by weight of copper element relative to the total weight of the catalyst, preferably between 0.5 and 12% by weight, preferably between 0.75 and 10% by weight , and even more preferably between 1 and 9% by weight.

The catalyst can be qualified as a “semi-egg-shell” catalyst in which the concentration of nickel is higher at the periphery of the support than in the core of the support, said concentration of nickel in the core of the support being non-zero.

The specific surface of the catalyst is generally between 10 m²/g and 350 m²/g, preferably between 25 m²/g and 300 m²/g, more preferably between 40 m²/g and 250 m²/g.

The total pore volume of the catalyst is generally between 0.1 and 1 ml/g, preferably between 0.2 ml/g and 0.8 ml/g, and particularly preferably between 0.3 ml/g and 0.7ml/g.

The active phase of the catalyst does not include any Group VIB metal. In particular, it does not include molybdenum or tungsten.

Said catalyst (and the support used for the preparation of the catalyst) is in the form of grains advantageously having a 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 8 mm), extrudates, tablets, hollow cylinders. Preferably, the catalyst (and the support used for the preparation of the catalyst) are in the form of extrudates with a diameter of between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm and very preferably between 1.0 and 2.5 mm and length between 0.5 and 20 mm. The term “diameter” of the extrudates is understood to mean the diameter of the circle circumscribed to the cross section of these extrudates. The catalyst 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.

4. Support

The characteristics of the alumina, mentioned in this section, correspond to the characteristics of the alumina before carrying out step a) of the preparation process according to the invention.

The support is an alumina, that is to say that the support comprises at least 95%, preferably at least 98%, and in a particularly preferred manner at least 99% by weight of alumina relative to the weight of the support. Alumina generally has a crystallographic structure of the delta, gamma or theta alumina type, alone or in a mixture.

The alumina carrier may include impurities such as group IIA, IIIB, IVB, IIB, IIIA, IVA metal oxides according to CAS classification, preferably silica, titanium dioxide, zirconium dioxide, zinc oxide, magnesium oxide and calcium oxide, or alternatively alkali metals, preferably lithium, sodium or potassium, and/or alkaline earth metals, preferably magnesium, calcium, strontium or barium or sulfur.

The specific surface of the alumina is generally between 10 m ² /g and 400m ² /g, preferably between 30 m ² /g and 350 m ² /g, more preferably between 50 m ² /g and 300m ² /g.

The pore volume of the alumina is generally between 0.1 ml/g and 1.2 ml/g, preferably between 0.3 ml/g and 0.9 ml/g, and very preferably between 0.5ml/g and 0.9ml/g.

5. Selective hydrogenation process

The present invention also 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 charge of hydrocarbons having a final boiling point of 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 hydrogen/ (polyunsaturated compounds to be hydrogenated) of between 0.1 and 10 and at an hourly volume rate of between 0.1 and 200 h ^-1 when the process is carried out in the liquid phase, or at a molar hydrogen/(polyunsaturated compounds to be hydrogenated ) between 0.5 and 1000 and at an hourly volume rate between 100 and 40,000 h ^-1 when the process is carried out in the gas phase, in the presence of a catalyst obtained by the preparation process as described above in the describe option.

Monounsaturated organic compounds such as ethylene and propylene, for example, are the source of the manufacture of polymers, plastics and other 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 side reactions in the polymerization units. It is therefore necessary to eliminate them before recovering these cuts.

Selective hydrogenation is the main treatment developed to specifically remove unwanted polyunsaturated compounds from these hydrocarbon feedstocks. It allows the conversion of polyunsaturated compounds to the corresponding alkenes or aromatics while avoiding their total saturation and therefore the formation of the corresponding alkanes or naphthenes. In the case of steam cracked gasolines used as feed, selective hydrogenation also makes it possible to selectively hydrogenate alkenylaromatics into aromatics by avoiding the hydrogenation of aromatic rings.

The hydrocarbon feed 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 includes 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 feedstock is selected from the group consisting of a C2 steam cracking cut, a C2-C3 steam cracking cut, a C3 steam cracking cut, a C4 steam cracking cut, a C5 steam cracking cut and a steam cracking gasoline also called pyrolysis gasoline or C5+ cut.

The C2 cut from steam cracking, advantageously used for the implementation of 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 C2 cuts from steam cracking, between 0.1 and 1% by weight of C3 compounds may also be present.

The C3 steam cracking cut, advantageously used for the implementation of the selective hydrogenation process according to the invention, has for example the following average composition: 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 C2 compounds and C4 compounds may also be present.

A C2-C3 cut can also be advantageously used for implementing 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 of 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 cut from steam cracking, 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% weight of 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 cut from steam cracking, 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, 34% by weight of pentadienes.

The steam cracking gasoline or pyrolysis gasoline, advantageously used for the implementation of the selective hydrogenation process according to the invention, corresponds to a hydrocarbon cut whose boiling point is generally between 0 and 300° C., from preferably between 10 and 250°C. The polyunsaturated hydrocarbons to be hydrogenated present in said steam cracked gasoline are in particular diolefinic compounds (butadiene, isoprene, cyclopentadiene, etc.), styrenic compounds (styrene, alpha-methylstyrene, etc.) and indene compounds (indene, etc.). ). Steam cracked 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 from 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 sulphur, preferably from 0 to 500 ppm by weight of sulphur.

Preferably, the charge of polyunsaturated hydrocarbons treated in accordance with the selective hydrogenation process according to the invention is a C2 cut from steam cracking, or a C2-C3 cut from steam cracking, or a gasoline from steam cracking.

The selective hydrogenation process according to the invention aims to eliminate said polyunsaturated hydrocarbons present in said charge 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 feed is a C3 cut, the selective hydrogenation process aims to selectively hydrogenate propadiene and methylacetylene. In the case of a C4 cut, the aim is to eliminate the butadiene, vinylacetylene (VAC) and the butyne, in the case of a C5 cut, the aim is to eliminate the pentadienes. When said feed is a steam cracked 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 into mono-olefins and that the styrenic and indenic compounds are partially hydrogenated to the corresponding aromatic compounds avoiding the hydrogenation of the aromatic rings.

The technological implementation of the selective hydrogenation process is for example carried out by injection, in ascending or descending current, of the charge of polyunsaturated hydrocarbons and hydrogen into at least one fixed-bed reactor. Said reactor can be of the isothermal type or of the adiabatic type. An adiabatic reactor is preferred. The charge of polyunsaturated hydrocarbons can advantageously be diluted by one or more re-injection(s) of the effluent, from said reactor where the selective hydrogenation reaction takes place, 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 can also be advantageously carried out by the implantation of at least said supported catalyst in a reactive distillation column or in reactors – exchangers or in a reactor of the slurry type. . The hydrogen flow can be introduced at the same time as the charge to be hydrogenated and/or at one or more different points of the reactor.

The selective hydrogenation of the C2, C2-C3, C3, C4, C5 and C5+ cuts from steam cracking 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 carbonated for C2 and C2-C3 cuts. A reaction in the liquid phase makes it possible to lower the energy cost and to increase the cycle time of the catalyst.

In general, the selective hydrogenation of a hydrocarbon charge containing polyunsaturated compounds containing at least 2 carbon atoms per molecule and having a final boiling point less than or equal to 300°C is carried out at a temperature between 0 and 300°C, at a pressure between 0.1 and 10 MPa, at a hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio between 0.1 and 10 and at an hourly volumetric speed (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 an 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 cracked gasoline comprising polyunsaturated compounds, the molar ratio (hydrogen)/(polyunsaturated compounds to be hydrogenated) is generally comprised 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 cracked gasoline comprising polyunsaturated compounds, the hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio 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 preferably, a selective hydrogenation process is carried out in which the feedstock is a steam cracked gasoline comprising polyunsaturated compounds, the hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio 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 is adjusted in order to have a sufficient quantity of it to theoretically hydrogenate all the polyunsaturated compounds and to maintain an excess of hydrogen at the reactor outlet.

In another embodiment according to the invention, when a selective hydrogenation process is carried out in which the feed is a C2 cut from steam cracking and/or a C2-C3 cut from steam cracking 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 generally between 100 and 40,000 h ^-1 , preferably between 500 and 30,000 h ^-1 and the pressure is generally between 0.1 and 6.0 MPa, preferably between 0.2 and 5, 0 MPa.

6. Aromatic hydrogenation process

The present invention also relates to a process for the hydrogenation of at least one aromatic or polyaromatic compound contained in a charge of hydrocarbons having a final boiling point less than or equal to 650° C., generally between 20 and 650° C. , and preferably between 20 and 450°C. Said hydrocarbon charge containing at least one aromatic or polyaromatic compound can be chosen from the following petroleum or petrochemical fractions: catalytic reforming reformate, kerosene, light gas oil, heavy gas oil, cracking distillates, such as FCC recycle oil, coker diesel, hydrocracking distillates.

The content of aromatic or polyaromatic compounds contained in the hydrocarbon charge treated in the hydrogenation process according to the invention is generally between 0.1 and 80% by weight, preferably between 1 and 50% by weight, and particularly preferably between 2 and 35% by weight, the percentage being based on the total weight of the hydrocarbon charge. The aromatic compounds present in said hydrocarbon charge are, for example, benzene or alkylaromatics such as toluene, ethylbenzene, o-xylene, m-xylene, or p-xylene, or alternatively aromatics having several aromatic (polyaromatic) rings such as naphthalene.

The sulfur or chlorine content of the charge is generally less than 5000 ppm by weight of sulfur or chlorine, preferably less than 100 ppm by weight, and in a particularly preferred manner less than 10 ppm by weight.

The technological implementation of the process for the hydrogenation of aromatic or polyaromatic compounds is for example carried out by injection, in ascending or descending current, of the hydrocarbon charge and hydrogen into at least one fixed-bed reactor. Said reactor can be of the isothermal type or of the adiabatic type. An adiabatic reactor is preferred. The hydrocarbon charge can advantageously be diluted by one or more re-injection(s) of the effluent, from said reactor where the hydrogenation reaction of the aromatics takes place, 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 process for the hydrogenation of aromatics according to the invention can also be advantageously carried out by the implantation of at least said supported catalyst in a reactive distillation column or in reactors-exchangers or in a reactor of the slurries. The hydrogen flow can be introduced at the same time as the charge to be hydrogenated and/or at one or more different points of the reactor.

The hydrogenation of the aromatic or polyaromatic compounds can be carried out in the gas phase or in the liquid phase, preferably in the liquid phase. In general, the hydrogenation of aromatic or polyaromatic compounds is carried out at a temperature between 30 and 350° C., preferably between 50 and 325° C., at a pressure between 0.1 and 20 MPa, from preferably between 0.5 and 10 MPa, at a hydrogen/(aromatic compounds to be hydrogenated) molar ratio between 0.1 and 10 and at an hourly volume rate of between 0.05 and 50 h ^-1 , preferably between 0.1 and 10 h ^-1 of a hydrocarbon charge containing aromatic or polyaromatic compounds and having a final boiling point less than or equal to 650°C, generally between 20 and 650°C, and preferably between 20 and 450° vs.

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

The conversion of the aromatic or polyaromatic compounds is generally greater than 20% by mole, preferably greater than 40% by mole, more preferably greater than 80% by mole, and in a particularly preferred manner greater than 90% by mole of the aromatic compounds or polyaromatics contained in the hydrocarbon charge. The conversion is calculated by dividing the difference between the total moles of the aromatic or polyaromatic compounds in the hydrocarbon feed and in the product by the total moles of the aromatic or polyaromatic compounds in the hydrocarbon feed.

According to a particular variant of the process according to the invention, a process is carried out for the hydrogenation of benzene from a hydrocarbon charge, such as the reformate from a catalytic reforming unit. The benzene content in said hydrocarbon charge is generally between 0.1 and 40% by weight, preferably between 0.5 and 35% by weight, and particularly preferably between 2 and 30% by weight, the percentage by weight being based on the total weight of the hydrocarbon charge.

The sulfur or chlorine content of the charge is generally less than 10 ppm by weight of sulfur or chlorine respectively, and preferably less than 2 ppm by weight.

The hydrogenation of the benzene contained in the hydrocarbon charge can be carried out in the gaseous phase or in the liquid phase, preferably in the liquid phase. When it is carried out in the liquid phase, a solvent may be present, such as cyclohexane, heptane, octane. In general, the hydrogenation of benzene is carried out at a temperature of between 30 and 250° C., preferably between 50 and 200° C., and more preferably between 80 and 180° C., at a pressure of between 0.1 and 10 MPa, preferably between 0.5 and 4 MPa, at a hydrogen/(benzene) molar ratio between 0.1 and 10 and at an hourly volume rate of between 0.05 and 50 h ^-1 , preferably between 0.5 and 10 h ^-1 .

The conversion of benzene is generally greater than 50 mol%, preferably greater than 80 mol%, more preferably greater than 90 mol% and particularly preferably greater than 98 mol%.

The invention will now be illustrated via the examples below which are in no way limiting.

Examples

For all the catalysts mentioned in the examples mentioned below, the support is an alumina A having a specific surface area of 80 m²/g, a pore volume of 0.7 mL/g and a median mesoporous diameter of 12 nm.

Example 1: Preparation of an aqueous solution of Ni precursors with an organic additive

The aqueous solution S1 used for the preparation of catalysts A to H is prepared by dissolving 43.5 g of nickel nitrate (NiNO ₃ , supplier Strem Chemicals®) and 7.69 g of malonic acid (CAS 141-82-2 ; Fluka® supplier) in a volume of 13 mL of distilled water. The additive/Ni molar ratio is set at 0.5. The solution S1 is obtained, the Ni concentration of which is 350 g of Ni per liter of solution.

Example 2: Preparation of an aqueous solution of the precursors of the NiCu alloy (5% Ni)

The aqueous solution of precursors of the NiCu alloy (solution S2) used for the preparation of the catalysts containing NiCu is prepared by dissolving 14.5 g of nickel nitrate (NiNO ₃ , supplier Strem Chemicals®) in a volume of 13 mL of distilled water. A solution is obtained whose Ni concentration is 116.6 g of Ni per liter of solution. The copper nitrate precursor is then added in order to have a Ni/Cu molar ratio of 1.

We obtain the solution S2. It makes it possible to introduce the precursors of the NiCu alloy with a mass content of Ni relative to the final catalyst of 5% by weight relative to the total weight of the catalyst.

Example 3: Preparation of a catalyst A according to the invention

10 g of alumina are impregnated with 2.4 ml of butanol added dropwise. The impregnated support is then left to mature for 30 min at 60°C. Then 7.1 ml of solution S1 is impregnated dry by adding it drop by drop to the matured impregnated support obtained above. The catalyst precursor obtained is then dried in an oven for 12 hours at 120°C. Then 10 ml of the solution S2 prepared in example 2 is impregnated dry by adding it drop by drop. The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L/h/g of catalyst at 450°C for 2 hours.

Catalyst A containing 15% by weight of the nickel element relative to the total weight of the catalyst is obtained (including 5% by weight of the nickel element included in the NiCu alloy). The characteristics of catalyst A thus obtained are reported in Table 1 below.

Example 4: Preparation of a catalyst B according to the invention

10 g of alumina are impregnated with 2.4 ml of butanol added dropwise. The impregnated support is then left to mature for 30 min at 60°C. 7.1 ml of solution S1 diluted by two (3.35 ml of solution S1 diluted with water to obtain 7.1 ml of final solution, half as concentrated as for example 3) is impregnated dry by adding it drop by drop, on the matured impregnated support obtained above. The catalyst precursor thus obtained is then dried in an oven for 12 hours at 120°C. Then 10 ml of the solution S2 prepared in example 2 is impregnated dry by adding it drop by drop. The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L/h/g of catalyst at 450°C for 2 hours.

Catalyst B containing 10% by weight of the nickel element relative to the total weight of the catalyst is obtained (including 5% by weight of the nickel element included in the NiCu alloy). The characteristics of catalyst B thus obtained are reported in Table 1 below.

Example 5: Preparation of a catalyst C according to the invention

10 g of alumina are impregnated with 7.2 ml of butanol added dropwise. The impregnated support is then left to mature for 30 min at 60°C. Then 2.4 ml of solution S1 is impregnated by adding it drop by drop to the matured impregnated support obtained above. The catalyst precursor thus obtained is then dried in an oven for 12 hours at 120°C. Then 10 ml of the solution S2 prepared in example 2 is impregnated dry by adding it drop by drop. The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L/h/g of catalyst at 450°C for 2 hours.

Catalyst C containing 15% by weight of the nickel element relative to the total weight of the catalyst is obtained (including 5% by weight of the nickel element included in the NiCu alloy). The characteristics of catalyst C thus obtained are reported in Table 1 below.

Example 6: Preparation of a catalyst D not in accordance with the invention

10 ml of solution S1 is impregnated dry by adding it drop by drop to the alumina support A. The impregnated support thus obtained is then dried in an oven for 12 hours at 120°C. Then 10 ml of the solution S2 prepared in example 2 is impregnated dry by adding it drop by drop. The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L/h/g of catalyst at 450°C for 2 hours.

Catalyst D containing 15% by weight of the nickel element relative to the total weight of the catalyst is obtained (including 5% by weight of the nickel element included in the NiCu alloy). The characteristics of catalyst D thus obtained are reported in Table 1 below.

Example 7: Preparation of a catalyst E not in accordance with the invention

10 g of alumina are impregnated with 2.4 ml of butanol added dropwise. The impregnated support is then left to mature for 30 min at 60°C. 7.1 ml of the solution S1 prepared in Example 1 is impregnated dry, by adding it drop by drop, to the matured impregnated support obtained above.

The catalyst precursor thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a stream of dry air of 1 L/h/g of catalyst at 450°C for 2 hours.

Catalyst E containing 10% by weight of the element nickel relative to the total weight of the catalyst is obtained. The characteristics of catalyst E thus obtained are reported in Table 1 below.

Example 8: Preparation of a Non-Compliant Catalyst F

7.1 ml of solution S1 is impregnated dry by adding it drop by drop to the alumina support A. The catalyst precursor thus obtained is then dried in an oven for 12 hours at 120°C. Then 10 ml of the solution S2 prepared in Example 2 is impregnated dry by adding it drop by drop to the catalyst precursor obtained above.

The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L/h/g of catalyst at 450°C for 2 hours. 2.4 ml of butanol are then impregnated. The solid is then left to mature for 30 min at 60°C. The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L/h/g of catalyst at 450°C for 2 hours.

The catalyst F containing 15% by weight of the nickel element relative to the total weight of the catalyst is obtained (including 5% by weight of the nickel element included in the NiCu alloy). The characteristics of catalyst F thus obtained are reported in Table 1 below.

Example 9: Preparation of a Non-Compliant Catalyst G

10 g of alumina impregnated with 2.4 ml of toluene added dropwise. The impregnated support is then left to mature for 30 min at 60°C. Then 7.1 ml of solution S1 is impregnated dry by adding it drop by drop to the matured impregnated support obtained above. The catalyst precursor thus obtained is then dried in an oven for 12 hours at 120°C. Then 10 ml of the solution S2 prepared in example 2 is impregnated dry by adding it drop by drop. The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L/h/g of catalyst at 450°C for 2 hours.

The catalyst G is obtained, containing 15% by weight of the nickel element relative to the total weight of the catalyst (including 5% by weight of the nickel element included in the NiCu alloy). The characteristics of catalyst G thus obtained are reported in Table 1 below.

Example 10: Preparation of a Non-Compliant Catalyst H

10 g of alumina A are impregnated with 2.4 ml of n-propanol added dropwise. The impregnated support is then left to mature for 30 min at 60°C. Then, 7.1 ml of solution S1 is impregnated dry by adding it drop by drop to the matured impregnated support obtained above. The catalyst precursor thus obtained is then dried in an oven for 12 hours at 120°C. Then 10 ml of solution S2 prepared in example 2 is impregnated dry by adding it drop by drop. The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L/h/g of catalyst at 450°C for 2 hours.

Catalyst H containing 15% by weight of the nickel element relative to the total weight of the catalyst is obtained (including 5% by weight of the nickel element included in the NiCu alloy). The characteristics of catalyst H thus obtained are reported in Table 1 below.

Example 11: Preparation of a Non-Compliant Catalyst I

10 g of alumina are impregnated with 2.4 ml of butanol added dropwise. The impregnated support is then left to mature for 30 min at 60°C. Then 7.1 ml of an aqueous solution S prepared by dissolving 43.5 g of nickel nitrate (NiNO ₃ , supplier Strem Chemicals®) in a volume of 13 ml of distilled water is impregnated dry by adding it drop -by drop, on the impregnated matured support obtained above. The catalyst precursor obtained is then dried in an oven for 12 hours at 120°C. Then 10 ml of the solution S2 prepared in example 2 is impregnated dry by adding it drop by drop. The solid thus obtained is then dried in an oven for 12 hours at 120° C., then calcined under a stream of dry air of 1 L/h/g of catalyst at 450° C. for 2 hours.

The catalyst I is obtained, containing 15% by weight of the nickel element relative to the total weight of the catalyst (including 5% by weight of the nickel element included in the NiCu alloy). The characteristics of catalyst I thus obtained are reported in Table 1 below.

Example 12: Characterization

The amount of alloy obtained after the calcination then reduction step was determined by X-ray diffraction (XRD) analysis on catalyst samples in powder form.

The amount of nickel in metallic form obtained after the reduction step was determined by X-ray diffraction (XRD) analysis on catalyst samples in powder form. Between the reduction stage and throughout the duration of characterization by XRD, the catalysts are never released into the open air. The diffraction diagrams are obtained by X-ray crystallographic analysis using a diffractometer using the conventional powder method with Kα1 radiation from copper (λ=1.5406 Å).

The reduction rate was calculated by calculating the area of the Ni ⁰ line located around 52°2θ, on all the diffractograms of each sample of catalyst analyzed, then by subtracting the signal present from room temperature under the line at 52° and which is due to the alumina.

Table 1 below summarizes the reduction rates or even the metallic nickel content Ni° (expressed in % by weight relative to the total weight of "active" Ni which does not make up the alloy) for all catalysts A to I characterized by XRD after a reduction step at 170° C. for 90 minutes under a flow of hydrogen. These values were also compared with the reduction rate obtained for catalyst E (Ni alone) after a conventional reduction step (i.e. at a temperature of 400°C for 15 hours under a flow of hydrogen) .

At room temperature on all catalysts, after calcination, containing copper and nickel, we detect alumina in delta and theta form, and large lines of NiO and CuO.

We also detect after reduction a line corresponding to the alloy in the form of Ni _0.76 Cu _0.24.

In order to evaluate the rate of reducibility and therefore the formation of Ni ⁰ , we measure the area of the Ni ⁰ line located around 52°2θ, on all the diffractograms, by subtracting the signal present from room temperature under the line at 52° and which is due to the alumina. It is thus possible to determine the relative percentage of Ni ⁰ crystallized after the reduction.

Table 1 below summarizes the reducibility rates or the Ni° content for all the catalysts characterized by XRD after reduction at 170°C for 90 minutes under a hydrogen flow. These values were also compared with the reduction rate obtained for catalyst E (Ni alone) after a conventional reduction step (i.e. at a temperature of 400°C for 15 hours under a flow of hydrogen) .

Catalyst Solvent
(% by volume relative to the VPT of the medium)
Ni (% wt) Particle size (nm) Crust thickness /
grain diameter
(%) d _crust /
of _heart Ni content in the crust / total Ni (%) A (compliant) 25%BuTOH in pre-impregnation 15 4 6.8 5 66 B (compliant) 25%BuTOH in pre-impregnation 10 4 3.8 12 71 C (compliant) 75%BuTOH in pre-impregnation 15 4 4.7 10 70 D
(improper) - 15 4 Homogeneous distribution - - E
(improper) 25%BuTOH in pre-impregnation 10 4 6.8 5 66 F
(improper) 25%BuTOH in post-impregnation 15 4 Homogeneous distribution - - G
(improper) 25% toluene in pre-impregnation 15 4 Homogeneous distribution - - H
(improper) 25% n-propanol in pre-impregnation 15 4 Homogeneous distribution - - I
(improper) 25%BuTOH in pre-impregnation 15 12 6.8 5 66

Catalyst Final reduction Ni/Cu Particle size
(m) Percentage of Ni° alone (DRX) after reduction (%) A (compliant) 170°C, 90 mins Yes 4 90 B (compliant) 170°C, 90 mins Yes 4 92 C (compliant) 170°C, 90 mins Yes 4 90 D (non-compliant) 170°C, 90 mins Yes 4 90 E (not compliant) 170°C, 90 mins No 4 0* E (not compliant) 400°C, 3 p.m. No 4 80 F (non-compliant) 170°C, 90 mins Yes 4 90 G (non-compliant) 170°C, 90 mins Yes 4 95 H (non-compliant) 170°C, 90 mins Yes 4 95 I (non-compliant) 170°C, 90 mins Yes 12 90

*Nickel as NiO

For catalyst E (10% Ni alone/alumina), the nickel reducibility rate is 0% after exactly the same reduction treatment under hydrogen as for catalysts A, B, C, D, F, G, H and I. The catalyst E must be reduced to 400° C. in order to have a reduction of the nickel oxide to Ni° of the order of 80%.

Example 13: Catalytic tests: performance in selective hydrogenation of a mixture containing styrene and isoprene (A _HYD1 )

Catalysts A to I described in the examples above are tested against the selective hydrogenation reaction of a mixture containing styrene and isoprene.

The composition of the charge to be selectively hydrogenated is as follows: 8% by weight styrene (Sigma Aldrich® supplier, purity 99%), 8% by weight isoprene (Sigma Aldrich® supplier, purity 99%), 84% by weight n-heptane (solvent ) (VWR® supplier, purity > 99% chromanorm HPLC). This composition corresponds to the initial composition of the reaction mixture. This mixture of model molecules is representative of a pyrolysis gasoline.

The selective hydrogenation reaction is carried out in a 500 mL stainless steel autoclave, equipped with mechanical stirring with magnetic drive and able to operate under a maximum pressure of 100 bar (10 MPa) and temperatures between 5°C and 200°C.

In an autoclave are added 214 mL of n-heptane (supplier VWR®, purity> 99% chromanorm HPLC) and a quantity of 3 mL of catalyst. The autoclave is closed and purged. Then the autoclave is pressurized under 35 bar (3.5 MPa) of hydrogen. The catalyst is first reduced in situ , at 170°C for 90 minutes under a hydrogen flow of 1 L/h/g (temperature rise ramp of 1°C/min) for catalysts A to I ( which here corresponds to step e) of the preparation process according to the invention according to one embodiment). Then the autoclave is brought to the test temperature equal to 30°C. At time t=0, approximately 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.

Another test was carried out for catalyst E, but with a catalyst reduction temperature of 400° C. for 15 hours.

The progress of the reaction is monitored by taking samples from 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 decrease in pressure 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 I are reported in Table 3 below. They are related to the catalytic activity (A _HYD1 ) measured for catalyst E prepared under conventional reduction conditions (at a temperature of 400° C. for 16 hours under a flow of hydrogen).

Example 14: Catalytic tests: performance in hydrogenation of toluene (A _HYD2 )

Catalysts A to I described in the examples above are also tested with respect to the hydrogenation reaction of toluene. The selective hydrogenation reaction is carried out in the same autoclave as that described in Example 13.

In an autoclave are added 214 mL of n-heptane (supplier VWR®, purity> 99% chromanorm HPLC) and a quantity of 3 mL of catalyst. The autoclave is closed and purged. Then the autoclave is pressurized under 35 bar (3.5 MPa) of hydrogen. The catalyst is first reduced in situ , at 170°C for 90 minutes under a hydrogen flow of 1 L/h/g (temperature rise ramp of 1°C/min) for catalysts A to I ( which here corresponds to step e) of the preparation process according to the invention according to one embodiment). After adding 216 mL of n-heptane (VWR® supplier, purity > 99% chromanorm HPLC), the autoclave is closed, purged, then pressurized under 35 bar (3.5 MPa) of hydrogen, and brought to the test temperature equal to 80°C. At time t=0, approximately 26 g of toluene (SDS® supplier, purity > 99.8%) are introduced into the autoclave (the initial composition of the reaction mixture is then toluene 6% by weight / n-heptane 94% by weight) 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 toluene is completely hydrogenated to methylcyclohexane. Hydrogen consumption is also monitored over time by the decrease in pressure 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 I are reported in Table 3 below. They are related to the catalytic activity (A _HYD2 ) measured for catalyst E prepared under conventional reduction conditions (at a temperature of 400° C. for 16 hours under a flow of hydrogen).

Catalyst Reduction
(°C) Ni° content (%) A _HYD1 (%) A _HYD2 (%) A (compliant) 170°C, 16h 15 180 175 B (compliant) 170°C, 16h 10 150 155 C (compliant) 170°C, 16h 15 181 190 D (non-compliant) 170°C, 16h 15 60 70 E (not compliant) 170°C, 16h 15 <1 <1 E (not compliant) 400°C, 4 p.m. 15 100 100 F (non-compliant) 170°C, 16h 15 55 45 G (non-compliant) 170°C, 16h 15 93 102 H (non-compliant) 170°C, 16h 15 95 98 I (non-compliant) 170°C, 16h 15 95 98

This clearly shows the improved performances in A _HYD1 and AH _YD2 of catalysts A, B and C obtained by the preparation process according to the invention, compared with catalysts B to I which do not comply. For catalysts A, B and C, the nickel oxide is reduced by 90% at 170° C. and presents particles distributed in a “semi-egg-shell”. Catalyst E is down in activity from the absence of NiCu and therefore from a reducibility of NiO at 170° C. which is almost zero. Catalyst F has undergone post-impregnation with butanol, which does not allow an egg-shell distribution of the nickel. Catalyst G and H is prepared with a step of pre-impregnation of toluene and propanol respectively. In these two cases, the nickel is distributed homogeneously throughout the catalyst grain. Catalysts G and H therefore have an activity well behind catalyst A in A _HYD1 . Catalyst I is set back due to the size of its much larger particles than catalyst A to H due to the absence of organic additive. This is explained by the distribution of Ni in “semi egg-shell” on catalysts A, B, and C, which gives them a markedly improved activity, particularly in rapid hydrogenation reactions. Catalyst E is down in activity due to the absence of NiCu, which does not make it possible to obtain reduced Ni, the active phase in hydrogenation, at 170°C.

Claims (17)

Process for the preparation of a catalyst comprising nickel and copper, in an amount of 1 and 50% by weight in element nickel relative to the total weight of the catalyst, and in an amount of 0.5 to 15% by weight in element copper per relative to the total weight of the catalyst, and a porous alumina support, the nickel being distributed both over a crust around the periphery of the support, and in the heart of the support, the thickness of said crust being between 2% and 15% of the diameter of the catalyst, the size of the particles of nickel in the catalyst, measured in oxide form, being less than 7 nm, which method comprises the following steps:
a) either the porous support or the catalyst precursor obtained at the end of step d) is impregnated with a volume (V1) of a butanol solution of between 0.2 and 0.8 times the total pore volume (VPT) of said support to obtain an impregnated support;
b) the impregnated porous support obtained at the end of step a) is allowed to mature for 0.5 to 40 hours;
c) the sequence of the following sub-steps is carried out:
c1) either the matured impregnated porous support obtained at the end of step b), or the catalyst precursor obtained at the end of step d), is impregnated with a solution comprising at least one precursor of the phase active nickel;
c2) either the matured impregnated porous support obtained at the end of step b), or the catalyst precursor obtained at the end of step d), is impregnated with at least one solution containing at least one organic compound comprising at least one carboxylic acid function;
steps c1) and c2) being carried out simultaneously, or separately in any order;
c3) optionally, the catalyst precursor obtained at the end of the sequence of steps c1) and c2) is dried at a temperature below 250° C.;
d) the sequence of the following sub-steps is carried out:
d1) either the porous support, or the matured impregnated porous support obtained at the end of step b), or the catalyst precursor obtained at the end of step c), is impregnated with at least one solution containing at least one copper precursor and one nickel precursor at a desired copper concentration to obtain on the final catalyst a content of between 0.5 and 15% by weight of copper element relative to the total weight of the final catalyst;
d2) optionally, the catalyst precursor obtained at the end of step d1) is dried at a temperature below 250° C.;
said step d) being carried out either before step a), or between steps b) and c), or after step c), it being understood that:
i) when step d) is carried out before step a), then sub-steps c3) and d2) are mandatory;
ii) when step d) is performed between steps b) and c), then sub-step c3) is mandatory;
iii) when performing step d) after step c), then sub-step d2) is mandatory. Process according to Claim 1, in which step b) is carried out at a temperature lower than or equal to 60°C. Process according to one of Claims 1 or 2, in which in step a) an n-butanol solution is used. Process according to any one of Claims 1 to 3, in which the copper precursor is chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulphate, copper chloride, bromide copper, copper iodide or copper fluoride. Process according to any one of Claims 1 to 4, in which the precursor of the nickel active phase is nickel nitrate, nickel chloride, nickel acetate or nickel hydroxycarbonate. Process according to any one of Claims 1 to 5, in which the molar ratio between the said organic compound introduced in step c2) and the nickel element also introduced in step c1) is between 0.01 and 5, 0 mol/mol. Process according to any one of Claims 1 to 6, in which the organic compound of step c2) is chosen from oxalic acid, malonic acid, glycolic acid, lactic acid, tartronic, citric acid, tartaric acid, pyruvic acid, levulinic acid. Process according to any one of Claims 1 to 7, in which steps c1) and c2) are carried out simultaneously. Process according to claim 8, in which when step d) is carried out before step a), the volume V2' of the solution comprising at least one precursor of the active phase of nickel and at least one organic compound comprising at least one carboxylic acid function is such that the V2' = VPT – V1. Process according to claim 8, in which when step d) is carried out between steps b) and c), or after step c), the volume V2' of the solution comprising at least one precursor of the active phase of nickel and at least one organic compound comprising at least one carboxylic acid function supplied in stage c) and the volume V4 of the solution comprising a nickel precursor and a copper precursor supplied in stage d) are such that V2 ' + V4 = TPV – V1. Process according to any one of Claims 1 to 10, which process additionally comprises a step of calcining c3') the dried catalyst precursor obtained at the end of step c3) at a temperature of between 250°C and 600 °C. Process according to any one of claims 1 to 11, in which in step a) said volume (V1) of said butanol solution is between 0.25 and 0.75 times the total pore volume (TPV) of said support . Process according to any one of Claims 1 to 12, in which the substeps c3) and/or d2) are carried out for a time comprised between 0.5 hours and 12 hours. Process according to any one of Claims 1 to 13, further comprising a step e) in which the catalyst precursor obtained at the end of the sequence of steps a) to d) is reduced by bringing the said precursor of catalyst with a reducing gas at a temperature greater than or equal to 150°C and less than 250°C. Catalyst comprising nickel and copper, in an amount of 1 and 50% by weight in element nickel relative to the total weight of the catalyst, and in an amount of 0.5 to 15% by weight in element copper relative to the total weight of the catalyst , and a porous alumina support, the nickel being distributed both over a crust on the periphery of the support, and in the heart of the support, the thickness of said crust being between 2% and 15% of the diameter of the catalyst, the size particles of nickel in the catalyst, measured in oxide form, being less than 7 nm, said catalyst being obtained by the process according to any one of Claims 1 to 14. Process for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule contained in a charge of hydrocarbons 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 hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio of between 0.1 and 10 and at an hourly volume rate of between 0.1 and 200 h ^{- 1} when the process is carried out in the liquid phase, or at a hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio of between 0.5 and 1,000 and at an hourly volume rate between 100 and 40,000 h ^-1 when the process is carried out in the gas, in the presence of a catalyst according to claim 15 or obtained according to the preparation process according to any one of claims 1 to 14. Process for the hydrogenation of at least one aromatic or polyaromatic compound contained in a charge of hydrocarbons having a final boiling point less than or equal to 650°C, said process being carried out in the gaseous phase or in the liquid phase, at a temperature between 30 and 350°C, at a pressure between 0.1 and 20 MPa, at a hydrogen/(aromatic compounds to be hydrogenated) molar ratio between 0.1 and 10 and at an hourly volume rate between 0.05 and 50 h ^-1 , in the presence of a catalyst according to claim 15 or obtained according to the preparation process according to any one of claims 1 to 14.