WO2021018601A1

WO2021018601A1 - Catalyst comprising an active nickel phase distributed in a shell as well as a nickel-copper alloy

Info

Publication number: WO2021018601A1
Application number: PCT/EP2020/070079
Authority: WO
Inventors: Anne-Claire Dubreuil; Vincent Coupard; Malika Boualleg
Original assignee: IFP Energies Nouvelles
Priority date: 2019-07-31
Filing date: 2020-07-16
Publication date: 2021-02-04
Also published as: FR3099386A1; FR3099386B1

Abstract

Disclosed is a catalyst comprising nickel, copper and an alumina support, said catalyst being characterized in that: - the nickel is distributed both in a shell at the periphery of the support and in the core of the support, the thickness of the shell being between 2% and 15% of the diameter of the catalyst; - the nickel density ratio of the shell to the core is strictly greater than 3; - the shell comprises more than 25% by weight of nickel element relative to the total weight of nickel contained in the catalyst; - the molar ratio of nickel to copper is between 0.5 and 5; - at least some of the nickel and copper is in the form of a nickel-copper alloy; - the nickel content in the nickel-copper alloy is between 0.5 and 15 wt % of nickel element relative to the total weight of the catalyst; - the size of the nickel particles, measured in oxide form, in the catalyst is between 7 and 25 nm. Fig. 1 AA%%%dshell BB%%%shell CC%%%dcore DD%%%core ep%%%thickness

Description

CATALYST INCLUDING AN ACTIVE PHASE OF NICKEL DISTRIBUTED IN

CRUST AND A NICKEL COPPER ALLOY

Technical area

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

State of the art

Monounsaturated organic compounds, such as ethylene and propylene, 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 (gasolines containing hydrocarbon compounds having 5 or more carbon atoms), in particular styrenic or indene compounds . These polyunsaturated compounds are very reactive and lead to side reactions in the polymerization units. It is therefore necessary to eliminate them before upgrading these cuts.

Selective hydrogenation is the main treatment developed to specifically remove unwanted polyunsaturated compounds from these hydrocarbon feeds. It enables the conversion of the polyunsaturated compounds to the corresponding alkenes or aromatics while avoiding their total saturation and therefore the formation of the corresponding alkanes or naphthenes.

The 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 metal 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 metal particles in the support constitutes an important criterion, mainly in the context of rapid and consecutive reactions such as selective hydrogenations. It is generally desirable that these elements be located in a crust at the periphery of the support in order to avoid problems of intragranular material transfer which can lead to defects in activity and loss of selectivity. Such catalysts are also called “eggshell” catalysts according to English terminology.

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

It is often proposed to replace palladium with nickel, a less active metal than palladium which it is therefore necessary to have in a larger quantity in the catalyst. Thus, nickel-based catalysts generally have a metal content of 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 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 Pat. No. 4,519,951 describes an “eggshell” type catalyst with nickel on a porous support having a pore volume of the pores the size of which is less than 11.7 nm of at least 0.2 ml / g and a pore volume of at least 0.2 ml / g. porous pores larger than 11.7nm in size of at least 0.1ml / g. More than 50% of nickel is found in a crust 0.15 times the radius of the support thickness. This catalyst is used for the hydrogenation of fat.

CN 101890351 describes a supported nickel catalyst in which more than 90% of the nickel is found in a 700 µm thick crust. The catalyst is prepared using an ammoniacal solution to dissolve the nickel salt. These catalysts are used in a selective hydrogenation application.

Document U S2012 / 0065442 describes a supported nickel catalyst in which the size distribution of the nickel crystallites is bimodal with 30 to 70% of the nickel crystallites having an average size (diameter) of 1.0 to 2.5 nm , the remaining nickel crystallites having an average size (diameter) of 3.0-4.5 nm. The nickel is distributed both on 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. At least 75% of the pore volume is in pores having a size greater than 5.0 nm. Objects of the invention

Surprisingly, the Applicant has discovered that by applying a specific hydrothermal treatment after the addition of a particular organic additive to a catalyst based on nickel and copper (and in which an alloy based on nickel and copper is formed. copper on the support) comprising an alumina support obtained according to a very specific method, a catalyst is obtained in which at least part of the nickel is distributed over a crust at the periphery of the support, the other part of the nickel being distributed in catalyst core. Without wishing to be bound by any theory, the hydrothermal treatment carried out after the step of bringing a specific organic additive into contact with the nickel and copper-based catalyst on a particular alumina support, which has undergone a hydrothermal treatment in the presence of an acid solution, seems to cause the nickel to migrate at least in part from the interior of the support to the periphery of the support, thus forming a nickel crust. In addition, it has been observed by the Applicant that during the preparation of the catalyst, carrying out a step of bringing the support into contact with a solution simultaneously containing a metallic precursor based on copper and a metallic precursor based on nickel. followed by a drying and reduction step in the presence of a reducing gas at low temperature (between 150 ° C and 250 ° C) makes it possible to obtain a nickel-copper alloy (in reduced form) which allows unexpectedly greatly improve the reducibility of the active phase of nickel on the support. Furthermore, the presence of copper in the catalyst makes it possible to maintain good activity and a longer lifetime of the catalyst when the latter is brought into contact with a hydrocarbon feed comprising sulfur. In fact, compared to nickel, the copper present in the catalyst more easily captures the sulfur compounds included in the feed, which limits the irreversible poisoning of the active sites.

The present invention thus relates to a new type of catalyst which, by virtue of its specific preparation process, 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 the reactions. selective hydrogenation of polyunsaturated compounds or hydrogenation of polyunsaturated aromatics, while using a lower quantity of nickel phase than 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 reagents.

A first object according to the invention relates to 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 of a second metallic element of copper, at a rate of 0.5 to 15% by weight of element copper relative to the total weight of the catalyst, and an alumina support, said catalyst being characterized in that:

the nickel is distributed both over a crust at the periphery of the support, and at the heart of the support, the thickness of said crust being between 2% and 15% of the diameter of the catalyst;

the nickel density ratio between the crust and the core is strictly greater than 3; said crust comprises more than 25% by weight of the element nickel relative to the total weight of nickel contained in the catalyst;

the molar ratio between nickel and copper is between 0.5 and 5;

at least part of the nickel and copper is in the form of a nickel-copper alloy;

the nickel content in the nickel-copper alloy is between 0.5 and 15% by weight of nickel element relative to the total weight of the catalyst,

the size of the nickel particles, measured in oxide form, in the catalyst is between 7 and 25 nm.

Advantageously, the nickel density ratio between the crust and the core is greater than or equal to 3.5.

Advantageously, said crust comprises more than 40% by weight of the nickel element relative to the total weight of nickel contained in the catalyst.

Advantageously, the transition interval between the core and the crust of the catalyst is between 0.05% and 3% of the diameter of the catalyst.

Advantageously, the size of the nickel particles in the catalyst is between 8 and 23 nm.

Advantageously, the sulfur content of the alumina support is between 0.001% and 2% by weight relative to the total weight of the alumina support, and the sodium content of said alumina support is between 0.001% and 2% by weight. relative to the total weight of said alumina gel.

Advantageously, the thickness of said crust is between 2.5% and 12% of the diameter of the catalyst;

Advantageously, the nickel density ratio between the crust and the core is between 3.8 and 15. Another object according to the invention relates to a process for preparing a catalyst according to the invention, said process being characterized in that:

a) an alumina gel is supplied;

b) shaping the alumina gel from step a);

c) the shaped alumina gel obtained at the end of step b) is subjected to a heat treatment comprising at least one hydrothermal treatment step in an autoclave in the presence of an acid solution, at a temperature of between 100 and 800 ° C, and at least one calcination step, at a temperature between 400 and 1500 ° C, carried out after the hydrothermal treatment step, to obtain an alumina support;

d) the sequence of the following sub-steps is carried out:

d1) the alumina support is brought into contact with at least one nickel precursor to obtain a catalyst precursor,

d2) the catalyst precursor obtained at the end of step d1) is dried at a temperature below 250 ° C;

d3) the dried catalyst precursor obtained at the end of step d2) is brought into contact with at least one solution containing at least one organic additive chosen from aldehydes containing 1 to 14 carbon atoms per molecule, ketones or polyketones containing 3 to 18 carbon atoms per molecule, ethers and esters containing 2 to 14 carbon atoms per molecule, alcohols or polyalcohols containing 1 to 14 carbon atoms per molecule and carboxylic acids or polycarboxylic acids containing 1 to 14 carbon atoms per molecule, the molar ratio between the organic additive and the nickel being greater than 0.05 mol / mol;

d4) a hydrothermal treatment of the catalyst precursor obtained at the end of step d3) is carried out at a temperature between 100 and 200 ° C for a period of between 30 minutes and 5 hours under a gas flow comprising between 5 and 650 grams of water per kg of dry gas;

e) the sequence of the following sub-steps is carried out:

e1) the alumina support is brought into contact with at least one solution containing at least one copper precursor and one nickel precursor at a desired nickel concentration in order to obtain a content of between 0.5 and 15% on the final catalyst weight of nickel element relative to the total weight of the final catalyst; e2) at least one step of drying the catalyst precursor obtained at the end of step e1) is carried out at a temperature below 250 ° C;

steps d) and e) being carried out separately in any order, f) the catalyst precursor resulting from steps d) and e), or e) and d) is reduced by bringing said catalyst precursor into contact with a reducing gas at a temperature greater than or equal to 150 ° C and less than 250 ° C.

Advantageously, the copper precursor is chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide or fluoride. copper.

Advantageously, the method further comprises a calcination step d2 ′) of the dried catalyst precursor obtained at the end of step d2), under a gas stream comprising a quantity of water strictly less than 150 grams of water per kg. of dry gas at a temperature between 250 ° C and 1000 ° C.

Advantageously, in step d3), the organic additive is chosen from formic acid, formaldehyde, acetic acid, citric acid, oxalic acid, glycolic acid, malonic acid, l ethanol, methanol, ethyl formate, methyl formate, paraldehyde, acetaldehyde, gamma-valerolactone acid, glucose, sorbitol and trioxane.

Advantageously, the molar ratio between the organic additive and the nickel is between 0.1 and 5 mol / mol.

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 hydrocarbon feedstock having a final boiling point less than or equal to 300 ° C, which process being 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 of between 0.1 and 10 and at an hourly volume 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 speed between 100 and 40,000 h ¹ when the process is carried out in the gas phase, in the presence of a catalyst 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 hydrocarbon feedstock having a final boiling point less than or equal to 650 ° C, said process being carried out in phase gas or in 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 speed (VVH) of between 0.05 and 50 h ¹ , in the presence of a catalyst according to the invention. Description of figure

FIG. 1 is a diagram showing 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 y-axis corresponds to the nickel density (in grams of Ni / mm ³ ). 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 density of nickel on the crust _cr0 ute is greater than the nickel density in the heart of the _core of carrier - The transition interval between the heart 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, editor 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, ie 0.002 μm; by mesopores the 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 the 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 device used is a CAMECA XS100, equipped with four monochromator crystals allowing the simultaneous analysis of four elements. The Castaing microprobe analysis technique consists of the detection of X radiation emitted by a solid after excitation of its elements by a beam of high energy electrons. For the purposes of this characterization, the catalyst grains are coated in pads of epoxy resin. These pads are polished until they reach the cut to the diameter of the balls or extruded and then metallized by depositing carbon in a metallic evaporator. The electronic 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 establishes 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 standard ASTM D4284-92 with a wetting angle of 140 °, for example by means of an Autopore III ™ model device from the Microméritics ™ brand.

The BET specific surface is measured by physisorption with nitrogen according to the ASTM D3663-03 standard, method described in the work Rouquerol F .; Rouquerol J .; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academie Press, 1999.

The mesoporous median 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” is understood to mean the diameter of the crystallites of nickel in oxide form. The diameter of the crystallites of nickel in oxide form is determined by X-ray diffraction, from the width of the diffraction line located at the angle 2theta = 43 ° (that is to say according to the crystallographic direction [200 ]) using the Scherrer relation. This method, used in X-ray diffraction on powders or polycrystalline samples which relates the width at mid-height of the diffraction peaks to the size of the particles, is described in detail in the reference: Appl. Cryst. (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

The invention relates to 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 a second metallic element of copper, in an amount of 0.5. at 15% by weight of copper element relative to the total weight of the catalyst, and an alumina support, said catalyst being characterized in that: the nickel is distributed both on a crust at the periphery of the support, and at the heart of the support, the crust thickness (also called ep1) being between 2% and 15% of the diameter of the catalyst, preferably between 2.5 % and 12% of the diameter of the catalyst, even 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;

the nickel density ratio between the crust and the core (also referred to here as _crust / core) is strictly greater than 3, preferably greater than 3.5 and preferably between 3.8 and 15;

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;

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;

at least 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 ranging between 0.1 and 0.9 and including between 0.1 and 0.9;

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 between 7 and 25 nm, preferably between 8 and 23 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 in FIG. 1), linked to the variation in the density of nickel 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 according to the invention 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% by 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, so preferred between 0.75 and 10% by weight, and even more preferably between 1 and 9% by weight.

The catalyst according to the invention 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 m ² / g and 200 m ² / g, preferably between 25 m ² / g and 110 m ² / g, more preferably between 40 m ² / g and 100 m ² / 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 0.7 ml / g.

The active phase of the catalyst does not contain a metal from group VIB. 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 all the shapes known to those skilled in the art, for example the shape of balls (preferably having a diameter of between 1 and 8 mm), of extrudates, of tablets, of 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 circumscribing the cross section of these extrudates. The catalyst can advantageously be presented in the form of cylindrical, multilobed, trilobal or quadrilobed extrudates. Preferably its shape will be trilobed or quadrilobed. The shape of the lobes can be adjusted according to all the methods known from the prior art.

3. Support

The characteristics of alumina, mentioned in this section, correspond to the characteristics of the alumina before impregnation of the active phase with nickel, ie the alumina support obtained at the end of step c) of the process for preparing the catalyst according to the invention. 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 particularly preferably at least 99% by weight of alumina relative to the weight support. The alumina generally has a crystallographic structure of the delta, gamma or theta alumina type, alone or as a mixture. According to the invention, the alumina support may comprise impurities such as oxides of metals from groups MA, INB, IVB, NB, NIA, IVA according to the CAS classification, preferably silica, titanium dioxide, zirconium dioxide, zinc oxide, magnesium oxide and calcium oxide, or even alkali metals, preferably lithium, sodium or potassium, and / or alkaline earth metals, preferably magnesium, calcium, strontium or barium or even sulfur.

The specific surface of the alumina is generally between 10 m ² / g and 250 m ² / g, preferably between 30 m ² / g and 200 m ² / g, more preferably between 50 m ² / g and 150 m 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 0.5 ml / g and 0.9 ml / g.

Process for preparing the catalyst

Another object according to the invention relates to a process for preparing a catalyst according to the invention comprising at least the following steps:

a) an alumina gel is supplied;

b) shaping the alumina gel from step a);

d) the sequence of the following sub-steps is carried out:

d1) the alumina support is brought into contact with at least one nickel precursor to obtain a catalyst precursor, d2) the catalyst precursor obtained at the end of step d1) is dried at a temperature below 250 ° C .;

d2 ’) optionally, a heat treatment of the dried catalyst precursor obtained at the end of step d2) is carried out at a temperature between 250 and 1000 ° C to obtain a calcined catalyst precursor;

d3) the dried catalyst precursor obtained at the end of step d2) (optionally calcined obtained at the end of step d2 ') is brought into contact with at least one solution containing at least one organic additive chosen from among aldehydes containing 1 to 14 carbon atoms per molecule, ketones or polyketones containing 3 to 18 carbon atoms per molecule, ethers and esters containing 2 to 14 carbon atoms per molecule, alcohols or polyalcohols containing 1 to 14 atoms carbon per molecule and the carboxylic acids or polycarboxylic acids containing 1 to 14 carbon atoms per molecule, the molar ratio between the organic additive and the nickel being greater than 0.05 mol / mol;

d5) optionally, a drying step is carried out between 50 and 200 ° C of the catalyst precursor obtained at the end of step d4) under a gas flow comprising a quantity of water strictly less than 5 grams of water per kilogram dry gas; e) the sequence of the following sub-steps is carried out:

e1) the alumina support is brought into contact with at least one solution containing at least one copper precursor and one nickel precursor at a desired nickel concentration in order to obtain a content of between 0.5 and 15% on the final catalyst weight of nickel element relative to the total weight of the final catalyst;

e2) at least one step of drying the catalyst precursor obtained at the end of step e1) is carried out at a temperature below 250 ° C;

e3) optionally, a heat treatment of the catalyst precursor obtained at the end of step e2) is carried out at a temperature between 250 and 1000 ° C, in the presence or absence of water;

steps d) and e) being carried out separately in any order,

f) the catalyst precursor resulting from steps d) and e), or e) and d) is reduced by bringing said catalyst precursor into contact with a reducing gas at a temperature greater than or equal to 150 ° C and less than 250 ° C. The order of steps a) to f) is not permutable, with the exception of the 2 steps d) and e) which are permutable between them.

Intermediate steps can be inserted (in particular additional drying steps) and some steps can be carried out several times in a row (for example step d1). Finally, it is possible to add additional steps before using the catalyst at the end of step f).

Preferably, a drying step is carried out followed by a calcination step at the end of step b) of shaping (but before carrying out step c).

Preferably, steps d2 ′) and d5) are not optional.

Preferably step d) and carried out before step e).

Steps a) to f) of said preparation process are described in detail below.

Step a) - Alumina gel

The catalyst according to the invention comprises an alumina support which is obtained from an alumina gel (or alumina gel) which essentially comprises a precursor of the aluminum oxy (hydroxide) type (AIO (OH)) - also called boehmite.

According to the invention, the alumina gel (or otherwise called boehmite gel) is synthesized by precipitation of basic and / or acidic solutions of aluminum salts induced by change in pH or any other method known to those skilled in the art. (P. Euzen, P. Raybaud, X. Krokidis, H. Toulhoat, JL Le Loarer, JP Jolivet, C. Froidefond, Alumina, in Handbook of Porous Solids, Eds F. Schüth, KSW Sing, J. Weitkamp, Wiley- VCH, Weinheim, Germany, 2002, pp. 1591-1677).

Generally the precipitation reaction is carried out at a temperature between 5 ° C and 80 ° C and at a pH between 6 and 10. Preferably the temperature is between 35 ° C and 70 ° C and the pH is between 6 and 10.

According to one embodiment, the alumina gel is obtained by bringing an aqueous solution of an acidic aluminum salt into contact with a basic solution. For example, the acidic aluminum salt is chosen from the group consisting of aluminum sulphate, aluminum nitrate or aluminum chloride and preferably said acid salt is aluminum sulphate. The basic solution is preferably chosen from soda or potash. Alternatively, an alkaline solution of aluminum salts which can be chosen from the group consisting of sodium aluminate and potassium aluminate can be brought into contact with an acid solution. In a very preferred variant, the gel is obtained by bringing a solution of sodium aluminate into contact with nitric acid. The solution of sodium aluminate advantageously has a concentration of between 10 ⁵ and 10 ¹ mol.L ¹ and preferably this concentration is between 10 ⁴ and 10 ² mol.L ¹ . According to another embodiment, the alumina gel is obtained by bringing an aqueous solution of acidic aluminum salts into contact with an alkaline solution of aluminum salts.

The support can advantageously be shaped by any technique known to those skilled in the art. The shaping can be carried out for example by kneading-extrusion, by pelletizing, by the drop coagulation method (oil-drop), by granulation on a turntable or by any other method well known to those skilled in the art. The catalysts according to the invention can optionally be manufactured and used in the form of extrudates, tablets or beads. The advantageous shaping method according to the invention is extrusion and the preferred extrudate shapes are cylindrical, twisted cylindrical or multilobed (2, 3, 4 or 5 lobes for example).

In a particular embodiment, the alumina gel obtained at the end of step a) is subjected to a mixing step, preferably in an acidic medium. The acid used can be, for example, nitric acid. This step is carried out by means of known tools such as Z-arm mixers, grindstone mixers, continuous mono or twin screws allowing the transformation of the gel into a product having the consistency of a paste. According to an advantageous embodiment, one or more compounds called “pore-forming agents” are introduced into the mixing medium. These compounds have the property of degrading on heating and thus creating porosity in the support. For example, wood flour, charcoal, tars and plastics can be used as pore-forming compounds. The paste thus obtained after kneading is passed through an extrusion die. Generally the extrudates have a diameter of 0.5 and 10 mm, preferably between 0.8 and 3.2 mm and very preferably between 1.0 and 2.5 mm and a length of between 0.5 and 20 mm . These extrudates can be cylindrical, multilobed (for example trilobed or quadrilobed).

After its shaping, the support is optionally dried before undergoing the hydrothermal treatment according to step c) of the process. For example, drying is carried out at a temperature between 50 and 200 ° C. The dried support is optionally calcined before undergoing the hydrothermal treatment according to step c) of the process. For example, the calcination is carried out at a temperature between 200 and 1000 ° C., in the presence or absence of an air flow containing up to 150 water per kilogram of dry air. Step c) - Heat treatment

The support obtained at the end of step b) then undergoes a heat treatment step which allows it to give it physical properties corresponding to the envisaged application.

The term “hydrothermal treatment” denotes a treatment by passage in an autoclave in the presence of water at a temperature above ambient temperature.

During this hydrothermal treatment, the shaped alumina can be treated in different ways. Thus, the alumina can be impregnated with an acid solution, prior to its passage in the autoclave, the hydrothermal treatment of the alumina being able to be carried out either in the vapor phase or in the liquid phase, this vapor or liquid phase of the liquid. autoclave which may or may not be acidic. This impregnation, before the hydrothermal treatment, can be carried out dry or by immersing the alumina in an acidic aqueous solution. The term “dry impregnation” is understood to mean bringing the alumina into contact with a volume of solution less than or equal to the total pore volume of the alumina treated. Preferably, the impregnation is carried out dry.

The extruded support can also be treated without prior impregnation with an acid solution, the acidity in this case being provided by the aqueous liquid in the autoclave.

The acidic aqueous solution comprises at least one acidic compound making it possible to dissolve at least part of the alumina of the extrudates. The term “acidic compound making it possible to dissolve at least part of the alumina of the extrudates” is understood to mean any acid compound which, brought into contact with the alumina extrudates, brings about the dissolution of at least part of the aluminum ions. . The acid should preferably dissolve at least 0.5% by weight of the alumina of the alumina extrudates.

Preferably, this acid is chosen from strong acids such as nitric acid, hydrochloric acid, perchloric acid, sulfuric acid or a weak acid used at a concentration such that its aqueous solution has a pH less than 4, such as acetic acid, or a mixture of these acids.

According to a preferred embodiment, the hydrothermal treatment is carried out in the presence of nitric acid and acetic acid taken alone or as a mixture. The autoclave is preferably an autoclave with a rotary basket such as that defined in patent application EP-A-0 387 109.

The hydrothermal treatment can also be carried out under saturating vapor pressure or under a partial pressure of water vapor at least equal to 70% of the saturated vapor pressure corresponding to the treatment temperature.

Preferably the hydrothermal treatment is carried out at a temperature of between 100 and 800 ° C, preferably between 200 and 700 ° C, preferably between 30 minutes and 8 hours, more preferably between 30 minutes and 3 hours.

Preferably, the calcination step which takes place after the hydrothermal treatment by autoclaving takes place at a temperature generally between 400 and 1500 ° C, preferably between 800 and 1300 ° C, preferably for 1 and 5 hours in air, the water content of which is generally between 0 and 700 g of water per kilogram of dry air.

At the end of step c), the alumina obtained exhibits the specific textural properties as described above.

Step d)

Step d) includes the following substeps.

Step d1) - Bringing the support into contact with a precursor of the active phase of nickel

The contacting of the support with a solution containing a precursor of the active phase of nickel, in accordance with the implementation of step d1), can be carried out by impregnation, dry or in excess, or by deposition - precipitation. , according to methods well known to those skilled in the art.

Said step d1) is preferably carried out by impregnation of the support consisting, for example, of bringing the support into contact with at least one aqueous solution containing a nickel precursor. The pH of said solution can be modified by the possible addition of an acid or a base.

Preferably, said step d1) is carried out by dry impregnation, which consists in bringing the support into contact with at least one solution, containing, preferably consisting of, at least one precursor of nickel, the volume of the solution of which is between 0.25 and 1.5 times the pore volume of the support to be impregnated.

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, of complexes formed with acetylacetonates, or of any other inorganic derivative soluble in aqueous solution, which is brought into contact with said support. Preferably, nickel precursor, nickel nitrate, nickel chloride, nickel acetate or nickel hydroxycarbonate are advantageously used. Very preferably, the nickel precursor is nickel nitrate.

According to another variant, the aqueous solution may contain ammonia or NH ₄ ⁺ ammonium ions.

The nickel concentration in solution is adjusted according to the type of impregnation (dry impregnation or in excess) and the pore volume of the support so as to obtain, for the supported catalyst, a nickel content of between 1 and 50% by weight of nickel element per report to the total weight of the catalyst, more preferably between 2 and 45% by weight and even more preferably between 3 and 35% by weight and even more preferably 5 and 25% by weight.

Step d2) - Séchaae

The drying step is carried out under a gas flow comprising a quantity of water less than 150 grams of water per kilogram of dry gas, preferably less than 50 g of water per kilogram of dry gas, at a temperature below 250 ° C, preferably between 15 and 240 ° C, more preferably between 30 and 220 ° C, even more preferably between 50 and 200 ° C, and even more preferably between 70 and 180 ° C, for a period typically between between 10 minutes and 24 hours. Longer durations are not excluded, but do not necessarily bring improvement.

The gas can contain oxygen, nitrogen or an inert gas and preferably the gas is air.

The optional calcination step is carried out under a gas stream comprising a quantity of water less than 150 grams of water per kilogram of dry gas, preferably less than 50 g of water per kilogram of dry gas, at a temperature between 250 ° C and 1000 ° C, preferably between 250 and 750 ° C. The duration of this heat treatment is generally between 15 minutes and 10 hours. Longer durations are not excluded, but do not necessarily bring improvement.

The gas may contain oxygen, nitrogen or an inert gas and preferably the gas is air.

At the end of steps d2) or d2 ’), the nickel is distributed homogeneously on the support.

Step d3) - Addendum

According to step d3) of the process for preparing the catalyst, the catalyst precursor obtained at the end of step d2), optionally at the end of step d2 ′), is brought into contact with at least one solution comprising at least one organic additive chosen from aldehydes containing from 1 to 14 carbon atoms per molecule (preferably from 2 to 12), ketones or polyketones containing from 3 to 18 (preferably from 3 to 12) carbon atoms per molecule, ethers or esters containing from 2 to 14 (preferably from 3 to 12) carbon atoms per molecule, alcohols or polyalcohols containing from 1 to 14 (preferably from 2 to 12) carbon atoms per molecule and carboxylic acids or polycarboxylic acids containing from 1 to 14 (preferably from 1 to 12) carbon atoms per molecule. The organic additive can be composed of a combination of the various functional groups mentioned above.

Preferably, the organic additive is chosen from formic acid HCOOH, formaldehyde CH ₂ 0, acetic acid CH ₃ COOH, citric acid, oxalic acid, glycolic acid (HOOC-CH2-OH ), malonic acid (HOOC-CH ₂ -COOH), ethanol, methanol, ethyl formate HCOOC ₂ H ₅ , methyl formate HCOOCH ₃ , paraldehyde (CH ₃ -CHO) ₃ , l acetaldehyde C ₂ H ₄ 0, gamma-valerolactone acid (C ₅ H ₈ 0 ₂ ), glucose, sorbitol and trioxane.

Most preferably, the organic additive is formic acid.

It is essential that the step of adding the organic additive to the catalyst (step d3)) is carried out after the step of bringing the support into contact with the precursor of the active phase of nickel.

Preferably, said step d3) is carried out by impregnating the catalyst precursor obtained at the end of the implementation of step d2) or of step d2 ′), with a solution comprising at least one organic additive as mentioned above. Impregnation is generally carried out in aqueous solution or in organic solution or in suspension in aqueous or organic solution, preferably in aqueous solution. When the operation is carried out in an organic solution or suspension, an alcohol or polyalcohol, glycol or polyglycol will preferably be used as organic solvent.

Preferably, said step d3) is carried out by dry impregnation, which consists in bringing the catalyst precursor obtained at the end of the implementation of step d2) or of step d2 ′) into contact, with a solution comprising at least one organic additive as mentioned above, the volume of the solution of which is between 0.25 and 1.5 times the pore volume of the catalyst precursor to be impregnated.

The impregnation is generally carried out at a temperature between 0 and 50 ° C, preferably between 10 and 40 ° C, and particularly preferably at room temperature.

According to the invention, the molar ratio between the organic additive and the nickel is greater than 0.05 mol / mol, preferably between 0.1 and 5 mol / mol, more preferably between 0.12 and 3 mol / mol, and even more preferably between 0.15 and 2.5 mol / mol.

Step d4) Hydrothermal treatment

According to step d4) of the process for preparing the catalyst according to the invention, a hydrothermal treatment of the product from step d3) is carried out at a temperature of between 100 ° C and 200 ° C, preferably between 130 ° C. and 170 ° C, and more particularly around of 150 ° C, under a gas flow comprising between 5 and 650 grams of water per kilogram of dry gas, preferably between 7 and 150 grams of water per kilogram of dry gas, even more preferably between 10 and 50 grams of water per kilogram of dry gas. The gas may contain oxygen, nitrogen or an inert gas and preferably the gas is air.

The duration of the hydrothermal treatment is generally between 30 minutes and 5 hours, preferably between 1 and 3 hours.

Step d5) - Drying (optional)

Step d4) can be followed by a step d5) of drying between 50 and 200 ° C under a gas flow comprising a quantity of water strictly less than 5 grams of water per kilogram of dry gas, advantageously for a period of time between between 30 minutes and 5 hours, preferably between 1 and 3 hours.

At the end of step d4) or optionally of step d5), a "semi egg-shell" catalyst is obtained as shown schematically in Figure 1 and whose characteristics are described above.

Step e)

Step e) comprises the following sub-steps.

Step e 1) Contacting a nickel precursor and a copper precursor

The deposition of nickel and copper on the alumina support can be carried out by impregnation, dry or in excess, or by deposition - precipitation, according to methods well known to those skilled in the art.

Said step e1) is preferably carried out by impregnation of the catalyst precursor consisting, for example, of bringing said support into contact with at least one solution, aqueous or organic (for example methanol or ethanol or phenol or acetone or toluene or dimethylsulfoxide (DMSO)) or else consisting of a mixture of water and at least one organic solvent, comprising, preferably consisting of, at least one nickel precursor and at least one copper precursor at least partially in the dissolved state, or alternatively by bringing said catalyst precursor into contact with at least one colloidal solution comprising, preferably consisting of, at least one nickel precursor and one copper precursor in oxidized form (nanoparticles oxide, oxy (hydroxide) or hydroxide of nickel and copper) or in reduced form (metallic nanoparticles of nickel and copper in the reduced state). Preferably, the solution is aqueous. The pH of this solution can be modified by the optional addition of an acid or a base.

Preferably, said step e1) is carried out by dry impregnation, which consists in bringing the support of the catalyst precursor into contact with a solution, preferably comprising at least one precursor of nickel and at least one precursor of nickel. copper, the volume of the solution of which is between 0.25 and 1.5 times the pore volume of the support to be impregnated.

When the nickel precursor is introduced in aqueous solution, a nickel precursor is advantageously used in the form of nitrate, carbonate, acetate, chloride, hydroxide, hydroxycarbonate, oxalate, sulfate, 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 even of any other inorganic derivative soluble in aqueous solution, which is brought into contact with said precursor of catalyst. Preferably, nickel precursor, nickel nitrate, nickel hydroxide, nickel carbonate, nickel chloride or nickel hydroxycarbonate are advantageously used. 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 sulfate, copper chloride, copper bromide, copper iodide or copper fluoride. Very preferably, the copper precursor salt is copper nitrate.

According to the invention, the nickel precursor is supplied to step e1) at a desired concentration to obtain on the final catalyst (ie obtained at the end of step f) reduction or step g) of passivation if the latter is carried out) a content of between 0.5 and 10% by weight of nickel element relative to the total weight of the final catalyst, preferably between 0.5 and 8% by weight, more preferably between 1 and 7% by weight weight, even more preferably between 1 and 5% by weight.

The quantities of the copper precursor (s) introduced into the solution according to step e1) 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 (ie obtained at the end of step f) of reduction or of step g) of passivation if the latter is carried out), of 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 e2) Drying of the impregnated support

Step e2) of drying the impregnated support is 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 preferably between 70 and 140 ° C, typically for a period of between 10 minutes and 24 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.

The dried catalyst precursor can undergo an additional heat treatment step, before reduction step f), at a temperature between 250 and 1000 ° C and preferably between 250 and 750 ° C, typically for a period of between 15 minutes and 10 hours, under an inert atmosphere or under an atmosphere containing oxygen, in the presence of water or not. Longer durations of treatment are not excluded, but do not necessarily bring improvement.

The term “heat treatment” is understood to mean treatment at temperature respectively without the presence or in the presence of water. In the latter case, the contact with the water vapor can take place at atmospheric pressure or at autogenous pressure. Several combined cycles without the presence or with the presence of water can be carried out. After this or these treatment (s), the catalyst precursor comprises nickel in oxide form, that is to say in NiO form.

In the event of the presence of water, the water content is preferably between 150 and 900 grams per kilogram of dry air, and even more preferably, between 250 and 650 grams per kilogram of dry air. Step f) Reduction by reducing gas

Prior to the use of the catalyst in the catalytic reactor and the implementation of a hydrogenation process, a reducing treatment step f) is carried out in the presence of a reducing gas so as to obtain a catalyst comprising nickel in less 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 metal particles, in particular nickel in the zero valent state. Carrying out in situ the reducing treatment of the catalyst eliminates the need for an additional step of passivation of the catalyst with an oxygenated compound or with C0 ₂ , which is necessarily the case when the catalyst is prepared by performing a reducing 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 the operations of transporting and loading the catalyst into the reactor d. '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 as a mixture (for example a mixture of hydrogen / nitrogen, hydrogen / argon, hydrogen / methane). In the case where the hydrogen is used as a mixture, all the proportions can be envisaged.

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 operating conditions for reducing the active phase of nickel which are less severe than in the prior art and thus makes it possible to carry out the reduction step directly. within the reactor in which it is desired to carry out the hydrogenation of unsaturated or aromatic compounds.

Moreover, the presence of copper in the catalyst makes it possible to maintain good activity of the catalyst and a good lifetime of the catalyst when the latter is brought into contact with a hydrocarbon feed comprising sulfur. Indeed, compared to nickel, the copper present in the catalyst more easily captures the sulfur compounds included in the feed, which limits the irreversible poisoning of the active sites. The rise in temperature to the desired reduction temperature is generally slow, for example set between 0.1 and 10 ° C / min, preferably between 0.3 and 7 ° C / min.

The hydrogen flow rate, 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 Q) 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, alkylmonosulphides such as dimethylsulphide, diethylsulphide, dipropylsulphide and propylmethylsulphide or else an organic disulphide of formula HO-R 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 process for the selective hydrogenation or hydrogenation of aromatics.

Selective hydrogenation process

A subject of the present invention is also 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 at 300 ° C, which process being 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 of between 0.1 and 10 and at an hourly volume speed 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 1000 and at a volume speed hourly 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 description.

Monounsaturated organic compounds, such as ethylene and propylene, 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 indene compounds. These polyunsaturated compounds are very reactive and lead to side reactions in the polymerization units. It is therefore necessary to eliminate them before upgrading these cuts.

Selective hydrogenation is the main treatment developed to specifically remove unwanted polyunsaturated compounds from these hydrocarbon feeds. It enables the conversion of the 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 allows the alkenylaromatics to be selectively hydrogenated to aromatics by avoiding the hydrogenation of the aromatic rings.

The hydrocarbon feed treated in the selective hydrogenation process has a final boiling point of 300 ° C or less and contains at least 2 carbon atoms per molecule and comprises at least one polyunsaturated compound. The term “polyunsaturated compounds” means compounds comprising at least one acetylenic function and / or at least one diene function and / or at least one alkenylaromatic function. More particularly, the feed 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 steam cracking cut, advantageously used for carrying out the selective hydrogenation process according to the invention, has for example the following composition: between 40 and 95% by weight of ethylene, of the order of 0.1 to 5% by weight of acetylene, the remainder being essentially ethane and methane. In certain steam cracking C2 cuts, between 0.1 and 1% by weight of C3 compounds can also be present.

The C3 steam cracking cut, advantageously used for carrying out the selective hydrogenation process according to the invention, has for example the following average composition: of the order of 90% by weight of propylene, of the order of 1 to 8% by weight of propadiene and methyl acetylene, the remainder being essentially propane. In some C3 cuts, between 0.1 and 2% by weight of C2 compounds and C4 compounds can also be present.

A C2 - C3 cut can also be advantageously used for carrying out the selective hydrogenation process according to the invention. It has for example the following composition: of the order of 0.1 to 5% by weight of acetylene, of the order of 0.1 to 3% by weight of propadiene and methylacetylene, of the order of 30% by weight ethylene, of the order of 5% by weight of propylene, the remainder being essentially methane, ethane and propane. This charge can also contain between 0.1 and 2% by weight of C4 compounds.

The C4 steam cracking cut, advantageously used for carrying out the selective hydrogenation process according to the invention, has for example the following average composition by weight: 1% by weight of butane, 46.5% by weight of butene, 51% by 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 can also be present.

The C5 steam cracking cut, advantageously used for carrying out the selective hydrogenation process according to the invention, has for example the following composition: 21% by weight of pentanes, 45% by weight of pentenes, 34% by weight of pentadienes.

Steam cracking gasoline or pyrolysis gasoline, advantageously used for carrying out 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. Polyunsaturated hydrocarbons to be hydrogenated present in said steam cracking gasoline are in particular diolefinic compounds (butadiene, isoprene, cyclopentadiene, etc.), styrene compounds (styrene, alpha-methylstyrene, etc.) and indene compounds (indene, etc.). Steam cracking gasoline generally comprises the C5-C12 cut with traces of C3, C4, C13, C14, C15 (for example between 0.1 and 3% by weight for each of these cuts). For example, a charge formed 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 of the compounds forming 100%. It also contains 0 to 1000 ppm by weight of sulfur, preferably 0 to 500 ppm by weight of sulfur.

Preferably, the polyunsaturated hydrocarbon feed treated in accordance with the selective hydrogenation process according to the invention is a C2 steam cracking cut, or a C2-C3 steam cracking cut, or a steam cracked gasoline.

The selective hydrogenation process according to the invention aims to eliminate said polyunsaturated hydrocarbons present in said feedstock to be hydrogenated without hydrogenating the monounsaturated hydrocarbons. For example, when said feedstock is a C2 cut, the selective hydrogenation process aims to selectively hydrogenate acetylene. When said feedstock is a C3 cut, the selective hydrogenation process aims to selectively hydrogenate propadiene and methylacetylene. In the case of a C4 cut, the aim is to eliminate the butadiene, vinylacetylene (VAC) and 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 diolefin compounds are partially hydrogenated to mono-olefins and that the styrenic and indene compounds are partially hydrogenated to the corresponding aromatic compounds while avoiding the hydrogenation of the aromatic rings.

The technological implementation of the selective hydrogenation process is for example carried out by injection, in an ascending or descending current, of the feed of polyunsaturated hydrocarbons and of hydrogen in at least one fixed bed reactor. Said reactor may be of the isothermal type or of the adiabatic type. An adiabatic reactor is preferred. The polyunsaturated hydrocarbon feedstock can advantageously be diluted by one or more re-injections of the effluent, coming 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. 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 implanting at least said supported catalyst in a reactive distillation column or in reactors - exchangers or in a slurry type reactor. The hydrogen stream can be introduced at the same time as the feed 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 gas phase or in the liquid phase, preferably in the liquid phase for the C3, C4, C5 and C5 + cuts and in the carbonated for cuts C2 and C2-C3. A liquid phase reaction lowers the energy cost and increases the cycle time of the catalyst.

In general, the selective hydrogenation of a hydrocarbon feed containing polyunsaturated compounds containing at least 2 carbon atoms per molecule and having a final boiling point 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 of between 0.1 and 10 and at an hourly volume speed (defined as ratio of the volume flow rate of feed 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 speed 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 carrying out a selective hydrogenation process in which the feed is a steam cracked gasoline comprising polyunsaturated compounds, the molar ratio (hydrogen) / (polyunsaturated compounds to be hydrogenated) is generally included 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 speed (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 feed is a steam cracking 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 speed (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 feed 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 speed (VVH) is generally between 1 and 50 h ¹ and the pressure is between 1, 5 and 4.0 MPa.

The hydrogen flow rate is adjusted in order to have enough 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 carrying out a selective hydrogenation process in which the feed is a C2 steam cracking cut and / or a C2-C3 steam cracking cut 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 .

Aromatics hydrogenation process

A subject of the present invention is also a process for the hydrogenation of at least one aromatic or polyaromatic compound contained in a hydrocarbon feedstock 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 feedstock containing at least one aromatic or polyaromatic compound can be chosen from the following petroleum or petrochemical cuts: reformate from catalytic reforming, kerosene, light gas oil, heavy gas oil, cracked distillates, such as recycle oil from FCC, gas oil from coking unit, hydrocracking distillates.

The content of aromatic or polyaromatic compounds contained in the hydrocarbon feed 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 feed. The aromatic compounds present in said hydrocarbon feed are, for example, benzene or alkylaromatics such as toluene, ethylbenzene, o-xylene, m-xylene, or p-xylene, or else aromatics having several aromatic (polyaromatic) rings such as naphthalene. The sulfur or chlorine content of the feed is generally less than 5000 ppm by weight of sulfur or chlorine, preferably less than 100 ppm by weight, and particularly preferably 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 feed and hydrogen in at least one fixed bed reactor. Said reactor may be of the isothermal type or of the adiabatic type. An adiabatic reactor is preferred. The hydrocarbon feedstock can advantageously be diluted by one or more re-injection (s) of the effluent, coming from said reactor where the aromatic hydrogenation reaction takes place, at various points of the reactor, located between the inlet and the reactor. the outlet of the reactor in order to limit the temperature gradient in the reactor. The technological implementation of the aromatics hydrogenation process according to the invention can also be advantageously carried out by implanting at least said supported catalyst in a reactive distillation column or in reactors - exchangers or in a reactor of the type. slurry. The hydrogen stream can be introduced at the same time as the feed 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 speed of between 0.05 and 50 h ¹ , preferably between 0.1 and 10 h ¹ of a hydrocarbon feed 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 ° C .

The hydrogen flow rate is adjusted in order to have it in sufficient quantity 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 mol%, preferably greater than 40 mol%, more preferably greater than 80 mol%, and particularly preferably greater than 90 mol% of the aromatic compounds. or polyaromatics contained in the hydrocarbon feed. 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 produced by the total moles of 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 feed, such as the reformate obtained from a catalytic reforming unit. The benzene content in said hydrocarbon feedstock 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 oil charge.

The sulfur or chlorine content of the feed 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 feed can be carried out in the gas 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 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 speed of between 0.05 and 50 h ¹ , of 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

Example 1: Preparation of AL-1 alumina

An alumina gel is synthesized using a mixture of sodium aluminate and aluminum sulfate. The precipitation reaction is carried out at a temperature of 60 ° C., at a pH of 9, for 60 minutes and with stirring at 200 rpm.

The gel thus obtained undergoes mixing on a Z-arm mixer to provide the paste. The extrusion is carried out by passing the paste through a die provided with orifices of diameter 1.6 mm in the shape of a trilobe. The extrudates thus obtained are dried under a flow of dry air at 150 ° C. for 12 hours and then calcined at 450 ° C. under a flow of dry air for 5 hours. The extrude undergoes a hydrothermal treatment at 650 ° C in the presence of an aqueous solution containing acetic acid at 6.5% by weight relative to the weight of alumina for 3 hours. in an autoclave, then calcined in dry air at 1000 ° C. for 2 hours in a tubular reactor. AL-1 alumina is obtained.

AL-1 alumina has a specific surface area of 80 m ² / g, a pore volume (determined by Hg porosimetry) of 0.85 mL / g and a mesoporous diameter of 35 nm.

The sodium content is 0.0350% by weight based on the total weight of the alumina and the sulfur content is 0.15% by weight based on the total weight of the alumina.

Example 1a: Preparation of AL-2 alumina

The gel thus obtained undergoes mixing on a Z-arm mixer to provide the paste. The extrusion is carried out by passing the paste through a die provided with orifices of 1.6 mm diameter in the shape of a trilobe. The extrudates thus obtained are dried under a flow of dry air at 150 ° C for 12 hours and then calcined at 450 ° C under a flow of dry air for 5 hours.

The AL-2 alumina is obtained.

AL-2 alumina has a specific surface area of 250 m ² / g, a pore volume (determined by Hg porosimetry) of 0.7 mL / g and a median mesoporous diameter of 12 nm.

The sodium content is 0.0350% by weight relative to the total weight of the alumina and the sulfur content is 0.15% by weight relative to the total weight of the alumina.

The aqueous solution of Ni precursors (solution S1) used for the preparation of catalyst A is prepared by dissolving 43.5 grams (g) of nickel nitrate (NiN0 ₃ , supplier Strem Chemicals®) in a volume of 13 mL of distilled water. The solution S1 is obtained, the Ni concentration of which is 350 g of Ni per liter of solution.

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

The aqueous solution of Ni precursors (solution S2) is prepared by dissolving 14.5 g of nickel nitrate (NiN0 ₃ , supplier Strem Chemicals®) in a volume of 13 mL of distilled water. Solution S2 is obtained, the Ni concentration of which is 116.6 g of Ni per liter of solution. The copper nitrate precursor is then added in order to have an Ni / Cu molar ratio within the range claimed according to the invention and in particular a Ni / Cu molar ratio of 3 and 1 according to the examples. Example 3: Preparation of a catalyst A according to the invention (in accordance)

The S1 solution prepared in Example 2 is dry impregnated, by adding it dropwise, onto 10 g of AL-1 alumina obtained according to Example 1.

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 dry air used in this example and all of the examples below contains less than 5 grams of water per kilogram of air. Catalyst A 'precursor is obtained.

The catalyst precursor thus obtained is dry impregnated with an aqueous solution containing formic acid with the HCOOH / Ni molar ratio equal to 1 mol / mol.

At the end of the impregnation of the aqueous solution containing formic acid, the catalyst precursor undergoes a heat treatment at 150 ° C. for 2 hours under a flow of air containing 50 grams of water per kilogram of dry air with a flow rate of 1 L / h / g of catalyst, then for 1 hour at 120 ° C. under a flow of dry air.

Then solution S2, prepared in Example 2a, is added to the catalyst precursor. The Ni content targeted in this step is 5% by weight of Ni relative to the weight of the final catalyst. The solid thus obtained is then dried in an oven overnight 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 precursor is then reduced under the conditions as described in Example 9 below.

Catalyst A is obtained, the characteristics of which are shown in Tables 1 and 2 below.

Example 4: Preparation of a catalyst B according to the invention (in accordance)

Solution S2, prepared in Example 2a, is dry impregnated, by adding it dropwise, onto 10 g of AL-1 alumina obtained according to Example 1. The Ni content referred to in this step is 5% by weight of Ni relative to the weight of the final catalyst. The solid thus obtained is then dried in an oven overnight 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 B 'precursor is obtained.

Then, the S1 solution prepared in Example 2 is dry impregnated, adding it dropwise, to the catalyst precursor B '.

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 precursor thus obtained is then dry impregnated with an aqueous solution containing formic acid with the HCOOH / Ni molar ratio equal to 1 mol / mol. At the end of the impregnation of the aqueous solution containing formic acid, the catalyst precursor undergoes a heat treatment at 150 ° C. for 2 hours under a flow of air containing 50 grams of water per kilogram of dry air with a flow rate of 1 L / h / g of catalyst, then for 1 hour at 120 ° C. under a flow of dry air.

Catalyst B is obtained, the characteristics of which are shown in Tables 1 and 2 below.

Example 5: Preparation of a catalyst C not in accordance with the invention

Solution S2, prepared in Example 2 bis, is dry impregnated, by adding it dropwise, onto 10 g of AL-2 alumina obtained according to Example 1 bis. The Ni content targeted in this step is 5% by weight of Ni relative to the weight of the final catalyst. The solid thus obtained is then dried in an oven overnight 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 precursor C 'is obtained.

Then, the S1 solution prepared in Example 2 is dry impregnated, adding it dropwise, the final catalyst precursor.

The catalyst precursor thus obtained is then dry impregnated with an aqueous solution containing formic acid with the HCOOH / Ni molar ratio equal to 1 mol / mol.

Catalyst C is obtained, the characteristics of which are shown in Tables 1 and 2 below.

Example 6: Preparation of a catalyst D (non-compliant)

Solution S2, prepared in Example 2a, is dry impregnated, by adding it dropwise, onto 10 g of AL-1 alumina obtained according to Example 1. The Ni content referred to in this step is 5% by weight of Ni relative to the weight of the final catalyst. The solid thus obtained is then dried in an oven overnight 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 precursor D 'is obtained.

Then, the S1 solution prepared in Example 2 is dry impregnated, adding it dropwise, the final catalyst precursor. 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 is obtained, the characteristics of which are shown in Tables 1 and 2 below.

Example 7: Preparation of a catalyst E (non-compliant)

Solution S2, prepared in Example 2a, is dry impregnated, by adding it dropwise, onto 10 g of AL-1 alumina obtained according to Example 1. The Ni content referred to in this step is 5% by weight of Ni relative to the weight of the final catalyst. The solid thus obtained is then dried in an oven overnight 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 precursor E 'is obtained.

Then the S1 solution prepared in Example 2 is impregnated to dryness, adding it dropwise, the precursor E ’. 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 E is obtained, the characteristics of which are shown in Tables 1 and 2 below.

Example 8: Preparation of a catalyst F (non-compliant)

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 precursor F 'is obtained. The catalyst precursor thus obtained is dry impregnated with an aqueous solution containing formic acid with the HCOOH / Ni molar ratio equal to 1 mol / mol.

The catalyst precursor is then reduced under the conditions as described in Example 9 below. Catalyst F is obtained, the characteristics of which are shown in Tables 1 and 2 below.

Example 9: Characterization

All the catalysts contain the target contents during the impregnation, i.e. 15% of nickel element (characterized by Fluorescence X) relative to the total weight of the catalyst, and the% of added copper (characterized by Fluorescence X) .

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

The amount of metallic nickel obtained after the reduction step was determined by X-ray diffraction (XRD) analysis on samples of the catalyst in powder form. Between the reduction step and throughout the duration of the XRD characterization, the catalysts are never vented. The diffraction patterns are obtained by radiocrystallographic analysis using a diffractometer using the classical powder method with the Ka1 radiation of copper (l = 1, 5406

AT).

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

Table 1 below collates the reduction rates or even the metallic nickel content Ni ° (expressed in% by weight relative to the total weight of active Ni, ie without taking into account the nickel which makes up the alloy) for all catalysts A to F characterized by DRX 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 F (Ni alone) after a conventional reduction step (that is to say at a temperature of 400 ° C. for 16 hours under a flow of hydrogen). At room temperature on all the 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 NÎO, 76CUO, 24.

In order to evaluate the rate of reducibility and therefore the formation of Ni ⁰ , the area of the Ni ^{0 line} located around 52 ° 2Q is measured, on all the diffractograms, by subtracting the signal present from ambient 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 reduction. Table 1 below recapitulates the reducibility rates or else the Ni ° content for all the catalysts characterized by DRX after reduction at 170 ° C. for 90 minutes under a flow of hydrogen. These values were also compared with the reduction rate obtained for catalyst F (Ni alone) after a conventional reduction step (that is to say at a temperature of 400 ° C. for 15 hours under a flow of hydrogen).

Table 1: Characteristics of catalysts A to F

* The particles of the 15% of Nickel which do not make up the alloy. Table 2: Characteristics of catalysts A to F Example 10: Catalytic tests: performance in selective hydrogenation of a mixture containing styrene and isoprene (A _y m)

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

The composition of the feed to be selectively hydrogenated is as follows: 8% wt styrene (supplier Sigma Aldrich®, purity 99%), 8% wt isoprene (supplier Sigma Aldrich®, purity 99%), 84% wt 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 essence.

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

214 mL of n-heptane (supplier VWR®, purity> 99% chromanorm HPLC) and a quantity of 3 mL of catalyst are added in an autoclave. 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 F ( which corresponds here to step f) 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, about 30 g of a mixture containing styrene, isoprene, n-heptane are introduced into the autoclave. The reaction mixture then has the composition described above and the 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 performed for catalyst F, but with a catalyst reduction temperature of 400 ° C for 16 hours in an ex situ cross-flow reactor.

The progress of the reaction is followed by taking samples of the reaction medium at regular time intervals: the styrene is hydrogenated to ethylbenzene, without hydrogenation of the aromatic ring, and isoprene is hydrogenated to methyl-butenes. If the reaction is prolonged longer than necessary, the methyl-butenes are in turn hydrogenated to isopentane. The 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 F are reported in Table 3 below. They are related to the catalytic activity (AHYD1) measured for catalyst E. For comparison, catalyst F prepared without the presence of NiCu, was tested prepared under conventional reduction conditions (at a temperature of 400 ° C for 16 hours under hydrogen flow).

Example 11: Catalytic tests: performance in hydrogenation of toluene

Catalysts A to F described in the examples above are also tested against the reaction of hydrogenation of toluene.

The selective hydrogenation reaction is carried out in the same autoclave as that described in Example 10.

214 mL of n-heptane (supplier VWR®, purity> 99% chromanorm HPLC) and a quantity of 3 mL of catalyst are added in an autoclave. 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 F ( which corresponds here to step f) of the preparation process according to the invention according to one embodiment). After the addition of 216 mL of n-heptane (supplier VWR®, purity> 99% chromanorm HPLC), the autoclave is closed, purged, then pressurized under 35 bar (3.5 MPa) of hydrogen, and brought to the test temperature equal to 80 ° C. At time t = 0, approximately 26 g of toluene (supplier SDS®, purity> 99.8%) are introduced into the autoclave (the initial composition of the reaction mixture is then toluene 6% wt / n-heptane 94% wt) and agitation 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 followed by taking samples of the reaction medium at regular time intervals: the toluene is completely hydrogenated to methylcyclohexane. The hydrogen consumption is also monitored over time by the decrease in pressure in a reservoir bottle located upstream of the reactor. Catalytic activity is expressed in moles of H2 consumed per minute and per gram of Ni.

The catalytic activities measured for catalysts A to F are reported in Table 3 below. They are related to the catalytic activity (AHYD2) measured for catalyst E. For comparison, catalyst F prepared without the presence of NiCu, was tested, prepared under conventional reduction conditions (at a temperature of 400 ° C. for 16 hours under hydrogen flow).

containing styrene and isoprene (A _H YDI) and hydrogenating toluene (A _H YD2)

This clearly shows the improved performance of catalysts A and B according to the invention, compared to catalysts C to F which do not conform. Catalysts A and B due to the crust distribution of Ni and the presence of the NiCu alloy, which makes it possible to have approximately 90% of the Ni in its reduced form from 170 ° C, exhibit activities of the same order of magnitude that catalyst F reduced at 400 ° C for 16h.

Catalyst F reduced at 170 ° C is not at all active because it does not have Ni in its reduced form. Catalysts C, D and E have a homogeneous distribution of Ni throughout the grain (use of AL-2 alumina not in accordance with the invention for C and steps of the preparation process not in accordance with D and E) and present from during an activity well behind catalysts A and B in AHYD1 and AHYD2.

Claims

1. 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 of a second metallic element of copper, in an amount of 0.5 to 15% in weight of copper element relative to the total weight of the catalyst, and an alumina support, said catalyst being characterized in that:

the nickel is distributed both over a crust at the periphery of the support, and at the core of the support, the thickness of said crust being between 2% and 15% of the diameter of the catalyst;

- the nickel density ratio between the crust and the core is strictly greater than 3;

- Said crust comprises more than 25% by weight of the nickel element relative to the total weight of nickel contained in the catalyst;

- the molar ratio between nickel and copper is between 0.5 and 5 mol / mol;

- at least part of the nickel and copper is in the form of a nickel-copper alloy;

- the nickel content in the nickel-copper alloy is between 0.5 and 15% by weight of nickel element relative to the total weight of the catalyst,

2. Catalyst according to claim 1, in which the nickel density ratio between the crust and the core is greater than or equal to 3.5.

3. Catalyst according to one of claims 1 or 2, wherein said crust comprises more than 40% by weight of the element nickel relative to the total weight of nickel contained in the catalyst.

4. Catalyst according to any one of claims 1 to 3, wherein the transition interval between the core and the catalyst crust is between 0.05% and 3% of the diameter of the catalyst.

5. Catalyst according to any one of claims 1 to 4, characterized in that the size of the nickel particles in the catalyst is between 8 and 23 nm.

6. Catalyst according to any one of claims 1 to 5, wherein the sulfur content of the alumina support is between 0.001% and 2% by weight relative to the total weight of the alumina support, and the sodium content. of said alumina support is between 0.001% and 2% by weight relative to the total weight of said alumina gel.

7. Catalyst according to any one of claims 1 to 6, characterized in that the thickness of said crust is between 2.5% and 12% of the diameter of the catalyst;

8. Catalyst according to any one of claims 1 to 7, characterized in that the nickel density ratio between the crust and the core is between 3.8 and 15.

9. Process for preparing a catalyst according to any one of claims 1 to 8, said process being characterized in that:

a) an alumina gel is supplied;

b) shaping the alumina gel from step a);

d) the sequence of the following sub-steps is carried out:

e) the sequence of the following sub-steps is carried out: e1) the alumina support is brought into contact with at least one solution containing at least one copper precursor and one nickel precursor at a desired nickel concentration in order to obtain a content of between 0.5 and 15% on the final catalyst weight of nickel element relative to the total weight of the final catalyst;

steps d) and e) being carried out separately in any order,

f) the catalyst precursor resulting from steps d) and e), or e) and d) is reduced by bringing said catalyst precursor into contact with a reducing gas at a temperature greater than or equal to 150 ° C and less than 250 ° C.

10. The method of claim 9, wherein the copper precursor is selected from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, l copper iodide or copper fluoride.

11. Method according to one of claims 9 or 11, which method further comprising a calcination step d2 ′) of the dried catalyst precursor obtained at the end of step d2), under a gas stream comprising a quantity of water strictly less than 150 grams of water per kg of dry gas at a temperature between 250 ° C and 1000 ° C.

12. Method according to any one of claims 9 to 11, wherein in step d3) the organic additive is chosen from formic acid, formaldehyde, acetic acid, citric acid, acid. oxalic acid, glycolic acid, malonic acid, ethanol, methanol, ethyl formate, methyl formate, paraldehyde, acetaldehyde, gamma-valerolactone acid, glucose, sorbitol and trioxane.

13. A method according to any one of claims 9 to 12, wherein the molar ratio between the organic additive and the nickel is between 0.1 and 5 mol / mol.

14. Process for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule contained in a hydrocarbon feedstock having a final boiling point less than or equal to 300 ° C, which process being 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 of between 0.1 and 10 and at an hourly volume 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 speed between 100 and 40,000 h ¹ when the process is carried out in phase gas, in the presence of a catalyst according to any one of claims 1 to 8.

15. Process for the hydrogenation of at least one aromatic or polyaromatic compound contained in a hydrocarbon feedstock having a final boiling point less than or equal to 650 ° C, said process being carried out in gas phase or in 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 speed between 0, 05 and 50 h ¹ , in the presence of a catalyst according to any one of claims 1 to 8.