FR3150966A1 - HYDROGENATION PROCESS USING A CATALYST COMPRISING COPPER AND AN ELEMENT FROM COLUMN IIIA - Google Patents

Abstract

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 of less than or equal to 300°C, in the presence of a catalyst comprising an active phase comprising copper and an element from column IIIA, and an alumina support, the copper content being between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, the atomic ratio between copper and the element from column IIIA being between 1 and 50 mol/mol, said catalyst being in the form of a powder with a particle size of between 20 µm and 500 µm.

Description

HYDROGENATION PROCESS USING A CATALYST COMPRISING COPPER AND AN ELEMENT FROM COLUMN IIIA

The subject of the invention is a process for the hydrogenation of unsaturated hydrocarbons, and more particularly, for the selective hydrogenation of polyunsaturated compounds carried out in the presence of a metal catalyst in the form of powder based on copper and an element from column IIIA, chosen from indium and gallium.

State of the art

Monounsaturated organic compounds such as ethylene and propylene are the source of polymers, plastics and other value-added chemicals. These compounds are obtained from natural gas, naphtha or diesel fuel that has been treated by steam cracking or catalytic cracking processes. These processes are operated at high temperatures and produce, in addition to the desired monounsaturated compounds, polyunsaturated organic compounds such as acetylene, propadiene and methylacetylene (or propyne), 1,2-butadiene and 1,3-butadiene, vinylacetylene and ethylacetylene, and other polyunsaturated compounds whose boiling point corresponds to the C5+ gasoline fraction (gasoline containing hydrocarbon compounds with 5 or more carbon atoms), in particular styrene or indene compounds. These polyunsaturated compounds are very reactive and lead to parasitic reactions in the polymerization units. It is therefore necessary to eliminate them before valorizing these cuts.

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

Selective hydrogenation catalysts are usually 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 that have an importance on the activity and selectivity of the catalysts.

Palladium-based catalysts are widely used in selective hydrogenation reactions of C2-C4 light fractions.

Typically, the palladium content is low, generally less than 1% by weight of palladium relative to the catalyst. The palladium is distributed in a crust on the periphery of the catalyst (egg-shell catalyst according to the Anglo-Saxon terminology, for example described in FR2922784 or US2010/217052).

Recent years have seen an increase in the price of noble metals, particularly gold, ruthenium, platinum and palladium, and have led to the search for metallic or multimetallic catalysts containing non-noble metals for the hydrogenation of acetylenics and diolefins.

Thus, the publication of Wang et al. (Chem. Commun., 2021,57, 7031-7034) describes the use of a catalyst comprising iron supported on a titanium oxide for the selective hydrogenation of butadiene to alkenes at 175°C.

Patent application CN110433813A (2019) discloses the use of catalyst containing CuIn/ _ZrO2 alloy for hydrogenation of _CO2 to methanol. The catalyst is prepared by coprecipitation of precursors of the three elements.

Patent application CN114054024A (2021) discloses the preparation of a catalyst for the hydrogenation of dimethyl oxalate containing an active phase based on Cu added by another metal (or in oxide form) chosen from Ni, In, Mo, W, Fe and Zn with a ratio of 0.2-1.5 based on the metal on a SiO ₂ support.

The publication of Onyestyák et al. (Catalysis Communications, 2012, 26, 19–24) describes the use of a CuIn on Al ₂ O ₃ gamma catalyst comprising 3–20% Cu and 3–20% In introduced by mechanical mixing for the hydrogenation of organic acids. The catalyst is in powder form. The specific surface area of the support is 203 m ² /g.

The publication of Zhang et al. (Chinese Journal of Catalysis, 2018, 39, 99–108) describes the use of a CuIn catalyst on SiO ₂ for the hydrogenation of methyl acetate to ethanol. The addition of 0.2–2% indium is carried out on a catalyst comprising 30% Cu/SiO ₂ corresponding to a Cu/In molar ratio greater than 66 mol/mol.

The publication of Dong et al. (Applied Catalysis B: Environmental, 2018, 244) describes the use of a catalyst comprising 10% Cu on a silica type SBA15 and indium such that the Cu/In ratio is between 0.01 and 15 to hydrogenate acetic acid into ethanol.

Surprisingly, the Applicant has discovered that a catalyst comprising copper and an element selected from column III A, preferably selected from indium and gallium, and an alumina support in powder form makes it possible to obtain performances in terms of activity in selective hydrogenation of polyunsaturated compounds at least as good, or even better than the processes known from the state of the art.

Objects of the invention

A first subject of 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 of less than or equal to 300°C, which process is carried out at a temperature of between 0 and 300°C, at a pressure of between 0.1 MPa and 10 MPa, at a hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio of between 0.1 and 10 and at an hourly volumetric flow rate of between 0.1 and 200 h ^-1 when the process is carried out in the liquid phase, or at a hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio of between 0.5 and 1000 and at an hourly volumetric flow rate of between 100 and 40000 h ^-1 when the process is carried out in the gas phase, in the presence of a catalyst comprising an active phase comprising copper and an element of the column IIIA, and an alumina support, the copper content being between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, the atomic ratio between the copper and the element of column IIIA being between 1 and 50 mol/mol, said catalyst being in the form of a powder with a particle size of between 20 µm and 500 µm.

According to one or more embodiments of the invention, the element of column III A is chosen from indium or gallium.

According to one or more embodiments according to the invention, when the element IIIA is indium, the indium content is between 0.02% and 25% by weight of indium element relative to the total weight of the catalyst.

According to one or more embodiments according to the invention, when the element IIIA is gallium, the gallium content is between 0.5% and 25% by weight of gallium element relative to the total weight of the catalyst.

According to one or more embodiments according to the invention, the specific surface area of the catalyst used is between 80 and 200 m²/g.

Another subject matter according to the invention relates to a process according to the invention in which said catalyst is obtained by a preparation process comprising the following steps:

a) a catalyst precursor is formed by carrying out the following sequence:

a1) an alumina powder is brought into contact with a solution comprising at least one precursor of the active copper phase;

a2) the alumina powder is brought into contact with at least one solution comprising at least one precursor of the active phase based on an element from column IIIA;

steps a1) and a2) being carried out separately, in any order, or simultaneously;

b) the catalyst precursor obtained at the end of step a) is dried at a temperature below 250°C to obtain a dried catalyst precursor.

According to one or more embodiments according to the invention, when steps a1) and a2) are carried out separately, an intermediate drying step is carried out between steps a1) and a2), or between steps a2) and a1), in which the catalyst precursor obtained at the end of step a1), or of step a2), is dried at a temperature below 250°C.

According to one or more embodiments according to the invention, the catalyst precursor obtained at the end of the intermediate drying step is subjected to a heat treatment at a temperature between 250°C and 1000°C.

According to one or more embodiments of the invention, steps a1) and a2) are carried out simultaneously.

According to one or more embodiments according to the invention, the precursor of the active copper phase is chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide or copper fluoride.

According to one or more embodiments according to the invention, the element IIIA of the active phase is indium, and in which the indium precursor is chosen from indium acetate, indium acetylacetonate, indium nitrate, indium sulfate, indium sulfide, indium chloride, indium mercaptoacetate, indium bromide, indium iodide, indium fluoride, indium oxide, indium phosphide, indium hydroxide.

According to one or more embodiments according to the invention, the element IIIA of the active phase is gallium, and in which the gallium precursor is chosen from gallium acetylacetonate, gallium nitrate, gallium sulfate, gallium sulfide, gallium chloride, gallium bromide, gallium iodide, gallium oxide, gallium nitride, gallium phosphide, gallium perchlorate, organics such as gallium triethyl and gallium trimethyl.

Detailed description of the invention Definitions

In the following, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief D.R. Lide, 81st edition, 2000-2001). For example, group IIIA according to the CAS classification corresponds to the metals of column 13 according to the new IUPAC classification.

BET specific surface area is measured by nitrogen physisorption. BET specific surface area is measured by nitrogen physisorption according to ASTM D3663-03 as described in Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academic Press, 1999.

The total pore volume is measured by mercury porosimetry according to ASTM D4284-92 with a wetting angle of 140°, for example using an Autopore® III model device from Microméritics®.

The size of the support and/or catalyst grains is measured by the laser scattering particle size analysis technique. This analysis method uses the principle of light scattering (Mie theory) and/or diffraction (Fraunhoffer theory and Mie theory). Particles illuminated by laser light deflect the light from its main axis. The amount of deflected light and the magnitude of the deflection angle allow the particle size to be measured accurately.

Copper, indium and gallium contents are measured by X-ray fluorescence.

Catalyst Active phase of the catalyst

The catalyst comprises an active phase comprising copper and an element from column IIIA, an alumina support in powder form, the copper content being between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, the atomic ratio between copper and the element from column IIIA being between 1 and 50 mol/mol.

The copper content in the catalyst is between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, preferably between 1 and 20% by weight, more preferably between 2 and 18% by weight, more preferably between 3 and 15% by weight, even more preferably between 5 and 15% by weight.

Preferably the element of column IIIA is chosen from indium or gallium.

The content of element from column III A in the catalyst is preferably between 0.02% and 25% by weight of element from column III A relative to the total weight of the catalyst, preferably between 0.05% and 20% by weight, and even more preferably between 0.1% and 15% by weight.

When the element IIIA is indium, the indium content is preferably between 0.02% and 25% by weight of indium element relative to the total weight of the catalyst, more preferably between 0.05% and 20% by weight, and even more preferably between 0.1% and 15% by weight.

When the element IIIA is gallium, the gallium content is preferably between 0.5% and 25% by weight of gallium element relative to the total weight of the catalyst, more preferably between 0.5 and 20% by weight, and even more preferably between 1 and 15% by weight.

The atomic ratio between copper and the element of column III A is between 1 and 50 mol/mol, preferably between 10 and 45 mol/mol, and more preferably between 15 and 45 mol/mol, and even more particularly between 18 and 40 mol/mol.

The catalyst may preferably contain the presence of an alloy containing copper and indium.

The catalyst is in the form of powder with a particle size of between 20 microns and 500 µm, preferably 25 and 350 µm.

The average particle size (in size) of the metal crystallites comprising copper and indium is advantageously between 3.5 and 100 nm, preferably between 4 and 50 nm.

The specific surface area of the catalyst is advantageously between 80 m ² /g and 200 m ² /g, preferably between 90 m ² /g and 180 m ² /g, more preferably between 100 m ² /g and 170 m ² /g, more preferably between 110 m ² /g and 170 m²/g, more preferably between 120 m ² /g and 160 m²/g.

The total pore volume (TPV) of the catalyst is advantageously between 0.1 cm ³ /g and 1.5 cm ³ /g, preferably between 0.2 cm ³ /g and 1.4 cm ³ /g, and even more preferably between 0.25 cm ³ /g and 1.3 cm ³ /g.

Catalyst support

The catalyst support is alumina in powder form, i.e. the support comprises at least 95%, preferably at least 98%, and particularly preferably at least 99% by weight of alumina relative to the weight of the support. The alumina generally has a crystallographic structure of the delta, gamma or theta alumina type, alone or as a mixture.

Preferably, alumina is present mainly in gamma form.

According to the invention, the alumina support may comprise impurities such as metal oxides from groups IIA, IIIB, IVB, IIB, IIIA, IVA according to the CAS classification, preferably silica, titanium dioxide, zirconium dioxide, zinc oxide, magnesium oxide and calcium oxide, or alkali metals, preferably lithium, sodium or potassium, and/or alkaline earths, preferably magnesium, calcium, strontium or barium or sulfur.

The specific surface area of the support is between 80 m ² /g and 200 m ² /g, preferably between 90 m ² /g and 180 m ² /g, more preferably between 100 m ² /g and 170 m ² /g, more preferably between 110 m ² /g and 170 m²/g, more preferably between 120 m ² /g and 160 m²/g.

The total pore volume (TPV) of the porous support is advantageously between 0.1 cm ³ /g and 1.5 cm ³ /g, preferably between 0.2 cm ³ /g and 1.4 cm ³ /g, and even more preferably between 0.25 cm ³ /g and 1.3 cm ³ /g.

The porous support is in the form of powder with a particle size of between 20 µm and 500 µm, preferably 25 µm and 350 µm.

Catalyst preparation

According to the invention, the process for preparing the catalyst comprises the following steps:

a) a catalyst precursor is formed by carrying out the following sequence:

a1) an alumina powder is brought into contact with a solution comprising at least one precursor of the active copper phase;

a2) an alumina powder is brought into contact with at least one solution comprising at least one precursor of the active phase based on an element from column IIIA;

steps a1) and a2) being carried out separately, in any order, or simultaneously;

b) the catalyst precursor obtained at the end of step a) is dried at a temperature below 250°C to obtain a dried catalyst precursor.

The different steps are explained in detail below.

Step a) – Contacting the support with a precursor of the active copper phase and a precursor based on element from column IIIA.

In step a), a catalyst precursor is formed by carrying out the following sequence:

a1) an alumina powder is brought into contact with a solution comprising at least one precursor of the active copper phase;

a2) an alumina powder is brought into contact with at least one solution comprising at least one precursor of the active phase based on an element from column IIIA;

steps a1) and a2) being carried out separately, in any order, or simultaneously;

Said step a1) is characterized in that the contacting of the alumina powder with a solution containing a precursor of the active copper phase 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. The pH of said solution can be modified by the possible addition of an acid or a base.

Said step a1) is preferably carried out by impregnation of the support consisting for example of bringing the alumina powder into contact with at least one aqueous solution containing a copper precursor.

Preferably, said step a1) is carried out by dry impregnation, which consists of bringing the alumina powder into contact with at least one solution, containing, preferably consisting of, at least one copper precursor, the volume of the solution of which is between 0.25 and 1.5 times the pore volume of the support to be impregnated.

The copper precursor salt is preferably selected from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide or copper fluoride.

Preferably, the copper precursor salt is selected from copper nitrate, copper sulfate or copper chloride.

The concentration of copper in solution is adjusted according to the type of impregnation (dry or excess impregnation) and the pore volume of the support so as to obtain for the supported catalyst, a copper content of between 0.5% and 25% by weight in copper element relative to the total weight of the catalyst, preferably between 1 and 20% by weight, more preferably between 2 and 18% by weight, more preferably between 3 and 15% by weight, even more preferably between 5 and 15% by weight.

Said step a2) is characterized in that the contacting of the alumina powder with a solution containing a precursor of at least one precursor of an element from column III A, preferably chosen from indium and gallium, in accordance with the implementation of step b2), 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 a2) is preferably carried out by impregnation of the alumina powder consisting for example in bringing the powder into contact with at least one aqueous solution containing a precursor of an element from column III A, preferably chosen from indium and gallium. The pH of said solution can be modified by the possible addition of an acid or a base.

Preferably, said step a2) is carried out by dry impregnation, which consists of bringing the alumina powder into contact with at least one solution, containing, preferably consisting of, at least one precursor of an element from column III A, preferably chosen from indium and gallium, the volume of the solution of which is between 0.25 and 1.5 times the pore volume of the support to be impregnated.

The indium precursor is preferably chosen from indium acetate, indium acetylacetonate, indium nitrate, indium sulfate, indium sulfide, indium chloride, indium mercaptoacetate, indium bromide, indium iodide, indium fluoride, indium oxide, indium phosphide, indium hydroxide.

The gallium precursor is selected from gallium acetylacetonate, gallium nitrate, gallium sulfate, gallium sulfide, gallium chloride, gallium bromide, gallium iodide, gallium oxide, gallium nitride, gallium phosphide, gallium perchlorate, organic precursors such as gallium triethyl and gallium trimethyl.

The concentration in solution of the element of column III A, preferably chosen from indium and gallium, is adjusted according to the type of impregnation (dry or excess impregnation) and the pore volume of the support so as to obtain for the supported catalyst, a content of element of column III A, preferably chosen from indium and gallium of between 0.02% and 25% by weight element of column III A, preferably chosen from indium and gallium relative to the total weight of the catalyst, preferably between 0.05 and 20% by weight, more preferably between 0.1 and 15% by weight.

Similarly, the concentration of element of column III A, preferably chosen from indium and gallium in solution is supplied so that the atomic ratio between copper and element of column III A, preferably chosen from indium and gallium, is between 0.5 and 100 mol/mol, preferably between 1 and 80 mol/mol, and more preferably between 1 and 70 mol/mol, and even more particularly between 1 and 50 mol/mol.

When steps a1) and a2) are carried out separately, an intermediate drying step is carried out between steps a1) and a2), or between steps a2) and a1), in which the catalyst precursor obtained at the end of step b1), or step a2), is dried at a temperature below 250°C, preferably between 70°C and 200°C. The drying time is generally between 0.5 hours and 20 hours. Longer times are not excluded, but do not necessarily provide an improvement.

Drying is generally carried out under combustion air of a hydrocarbon, preferably methane, or under heated air comprising between 0 and 80 grams of water per kilogram of combustion air, an oxygen level of between 5% and 25% by volume and a carbon dioxide level of between 0% and 10% by volume.

Optionally, the catalyst precursor obtained at the end of the intermediate drying step is subjected to a heat treatment in air, preferably combustion air, and more preferably methane combustion air, comprising between 40 and 80 grams of water per kg of air, an oxygen content of between 5% and 15% by volume and a CO ₂ content of between 4% and 10% by volume. The calcination temperature is generally between 250°C and 900°C, preferably between approximately 300°C and approximately 500°C. The calcination time is generally between 0.5 hours and 5 hours. The hourly volumetric speed (HVS) is generally between 150 and 3000, preferably between 300 and 1500 liters of combustion air per hour and per liter of catalyst.

In another embodiment, steps a1) and a2) are carried out simultaneously. In this case, the impregnated support can be dried during step b).

Step b) Drying the impregnated support

Step b) of drying the catalyst precursor obtained at the end of step a) 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 periods are not excluded, but do not necessarily provide an 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.

Heat treatment of dried catalyst (optional)

Optionally, after drying (step b), the catalyst is calcined in air, preferably combustion air, and more preferably methane combustion air, comprising between 40 and 80 grams of water per kg of air, an oxygen content of between 5% and 15% by volume and a CO ₂ content of between 4% and 10% by volume. The calcination temperature is generally between 250°C and 900°C, preferably between approximately 300°C and approximately 500°C. The calcination time is generally between 0.5 hours and 5 hours. The hourly volumetric speed (HVS) is generally between 150 and 3000, preferably between 300 and 1500 liters of combustion air per hour and per liter of catalyst.

Reduction by a reducing gas (optional)

Optionally, the catalyst is reduced. This step is preferably carried out in the presence of a reducing gas, either in situ, i.e. in the reactor where the catalytic transformation is carried out, or ex situ. Preferably, this step is carried out at a temperature between 100°C and 600°C, even more preferably between 120°C and 500°C.

The reduction is carried out in the presence of a reducing gas comprising between 25 vol% and 100 vol% hydrogen, preferably 100% volume hydrogen. The hydrogen is optionally supplemented by an inert gas for the reduction, preferably argon, nitrogen or methane.

The reduction generally includes a temperature increase phase followed by a plateau.

The duration of the reduction stage is generally between 1 hour and 10 hours, preferably between 2 hours and 8 hours.

The Hourly Volumetric Velocity (HVV) is generally between 150 and 3000, preferably between 300 and 1500 liters of reducing gas per hour and per liter of catalyst.

Selective hydrogenation process

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

Monounsaturated organic compounds such as ethylene and propylene are the source of polymers, plastics and other value-added chemicals. These compounds are obtained from natural gas, naphtha or diesel that has been treated by steam cracking or catalytic cracking processes. These processes are operated at high temperatures 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 with a boiling point corresponding to the C5+ cut (hydrocarbon compounds with at least 5 carbon atoms), in particular diolefinic or styrenic or indenic compounds. These polyunsaturated compounds are very reactive and lead to parasitic reactions in the polymerization units. It is therefore necessary to eliminate them before valorizing these cuts.

Selective hydrogenation is the main treatment developed to specifically remove undesirable polyunsaturated compounds from these hydrocarbon feedstocks. It allows the conversion of polyunsaturated compounds to the corresponding alkenes or aromatics while avoiding their total saturation and therefore the formation of the corresponding alkanes or naphthenes. In the case of steam cracked gasolines used as feedstock, selective hydrogenation also allows the selective hydrogenation of alkenyl aromatics to aromatics while avoiding the hydrogenation of the aromatic nuclei.

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

More specifically, the charge used is a steam cracking gasoline also called pyrolysis gasoline or C5+ cut.

The steam cracking gasoline or pyrolysis gasoline, advantageously used for implementing the selective hydrogenation process according to the invention, corresponds to a hydrocarbon fraction whose boiling point is generally between 0 and 300°C, preferably between 10 and 250°C. The polyunsaturated hydrocarbons to be hydrogenated present in said steam cracking gasoline are in particular diolefinic compounds (butadiene, isoprene, cyclopentadiene, etc.), styrenic compounds (styrene, alpha-methylstyrene, etc.) and indenic compounds (indene, etc.). The steam cracking gasoline generally comprises the C5-C12 fraction with traces of C3, C4, C13, C14, C15 (for example between 0.1 and 3% by weight for each of these fractions). 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 monoolefins, 5 to 40% by weight of diolefins, 1 to 20% by weight of alkenyl aromatic compounds, all of the compounds forming 100%. It also contains from 0 to 1000 ppm by weight of sulfur, preferably from 0 to 500 ppm by weight of sulfur.

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

In an embodiment according to the invention, when a selective hydrogenation process is carried out in which the feedstock is a steam cracking gasoline comprising polyunsaturated compounds, the molar ratio (hydrogen)/(polyunsaturated compounds to be hydrogenated) is generally 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 volumetric speed (HVS) is generally between 0.5 and 100 h ^-1 , preferably between 1 and 50 h ^-1 and the pressure is generally between 0.3 MPa and 8.0 MPa, preferably between 1.0 MPa and 7.0 MPa and even more preferably between 1.5 MPa and 4.0 MPa.

More preferably, a selective hydrogenation process is carried out in which the feedstock is a steam cracking gasoline comprising polyunsaturated compounds, the 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 volumetric velocity (HVV) is generally between 1 and 50 h ^-1 and the pressure is between 1.0 and 7.0 Mpa.

Even more preferably, a selective hydrogenation process is carried out in which the feedstock is a steam cracking 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 volumetric velocity (HVV) 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 to provide sufficient quantity to theoretically hydrogenate all the polyunsaturated compounds and to maintain an excess of hydrogen at the reactor outlet.

The invention will now be illustrated by means of the following examples which are in no way limiting.

Examples

Example 1: preparation of a 10% Cu/Al catalyst ₂ O ₃ (non-compliant)

4.1 g of hydrated copper nitrate (Cu(NO ₃ ) ₂ ; 2.5 H ₂ O, M = 232.6 g / mol, 1.75 mmol) are dissolved in 10 mL of deionized water at room temperature. The solution is then added dropwise to 10 g of commercial Puralox TH100 alumina powder (Sasol, diameter 80 µm) in a 100 mL beaker. The mixture is then stirred until the solution is completely absorbed. The material is dried for 12 hours in air at 60 ° C and then calcined for 2 hours at 400 ° C under air flow. The material is reduced under hydrogen at 450 ° C for 2 hours.

Catalyst A comprises a copper element content of 10% by weight relative to the weight of the catalyst.

Example 2: preparation of a 6.1% In/Al catalyst ₂ O ₃ (non-compliant)

2.2 g of hydrated indium nitrate (In(NO ₃ ) ₃ ; 5 H ₂ O, M = 391 g / mol, 0.57 mmol) are dissolved in 10 mL of deionized water at room temperature. The solution is then added dropwise to 10 g of commercial Puralox TH100 alumina powder (Sasol, diameter 80 µm) in a 100 mL beaker. The mixture is then stirred until the solution is completely absorbed. The material is dried for 12 hours in air at 60 ° C and then calcined for 2 hours at 400 ° C under air flow. The material is reduced under hydrogen at 450 ° C for 2 hours.

Catalyst B comprises an indium element content of 6.1% by weight relative to the weight of the catalyst.

Example 3: preparation of a 9.4%Cu 5.6% In/Al catalyst ₂ O ₃ (mol/mol ratio Cu/In = 3.1, compliant) by co-impregnation

2.2 g of hydrated indium nitrate (In(NO ₃ ) ₃ ;5 H ₂ O, M = 391 g/mol, 0.57 mmol) and 4.1 g of hydrated copper nitrate (Cu(NO ₃ ) ₂ ; 2.5 H ₂ O, M = 232.6 g/mol, 1.75 mmol) are dissolved in 10 mL of deionized water at room temperature. The solution is then added dropwise to 10 g of commercial Puralox TH100 alumina powder (Sasol, diameter 80 µm) in a 100 mL beaker. The mixture is then stirred until the solution is completely absorbed. The material is dried for 12 hours in air at 60 ° C and then calcined for 2 hours at 400 ° C in air flow. The material is reduced under hydrogen at 450°C for 2 hours.

Catalyst C comprises a copper element content of 9.4 wt% relative to the catalyst weight and an indium content of 5.6 wt% relative to the catalyst weight. The Cu/In molar ratio is 3.1 mol/mol. Alloy peaks containing copper and indium are noted in XRD.

Example 4: preparation of a 9.4%Cu 5.6% In/Al catalyst ₂ O ₃ (mol/mol Cu/In ratio = 3.1, compliant) by successive impregnation.

4.1 g of hydrated copper nitrate (Cu( _NO3 ) ₂ ; _2.5H2O , M=232.6 g/mol, 1.75 mmol) are dissolved in 10 mL of deionized water at room temperature. The solution is then added dropwise to 10 g of commercial Puralox TH100 alumina powder (Sasol, diameter 80 µm) in a 100 mL beaker. The mixture is then stirred until the solution is completely absorbed. The material is dried for 12 hours in air at 60°C.

2.2 g of hydrated indium nitrate (In(NO ₃ ) ₃ ; 5 H ₂ O, M = 391 g / mol, 0.57 mmol) are dissolved in 10 mL of deionized water at room temperature. The solution is then added dropwise to the dried material in a 100 mL beaker. The mixture is then stirred until the solution is completely absorbed. The material is dried for 12 hours in air at 60 ° C and then calcined for 2 hours at 400 ° C under air flow. The material is reduced under hydrogen at 450 ° C for 2 hours.

Catalyst D comprises a copper element content of 9.4 wt% relative to the catalyst weight and an indium content of 5.6 wt% relative to the catalyst weight. The Cu/In molar ratio is 3.1 mol/mol. Peaks of alloys containing copper and indium are noted in XRD.

Example 5: preparation of a 9.7%Cu 3.5% In/Al catalyst ₂ O ₃ (mol/mol ratio Cu/In = 5, compliant) by co-impregnation

1.36 g of hydrated indium nitrate (In(NO ₃ ) ₃ ; 5 H ₂ O, M = 391 g / mol, 0.35 mmol) and 4.1 g of hydrated copper nitrate (Cu(NO ₃ ) ₂ ; 2.5 H ₂ O, M = 232.6 g / mol, 1.75 mmol) are dissolved in 10 mL of deionized water at room temperature. The solution is then added dropwise to 10 g of commercial Puralox TH100 alumina powder (Sasol, diameter 80 µm) in a 100 mL beaker. The mixture is then stirred until the solution is completely absorbed. The material is dried for 12 hours in air at 60 ° C and then calcined for 2 hours at 400 ° C in air flow. The material is reduced under hydrogen at 450°C for 2 hours.

Catalyst E comprises a copper element content of 9.7% by weight relative to the weight of the catalyst and an indium content of 3.5% by weight relative to the weight of the catalyst. The Cu/In molar ratio is 5 mol/mol. Peaks of alloys containing copper and indium are noted in XRD.

Example 6: preparation of a 9.7% Cu 2.5% In/Al catalyst ₂ O ₃ (mol/mol ratio Cu/In = 33, compliant) by co-impregnation

0.97 g of hydrated indium nitrate (In(NO ₃ ) ₃ ;5 H ₂ O, M = 391 g / mol, 0.25 mmol) and 4.1 g of hydrated copper nitrate (Cu(NO ₃ ) ₂ ; 2.5 H ₂ O, M = 232.6 g / mol, 1.75 mmol) are dissolved in 10 mL of deionized water at room temperature. The solution is then added dropwise to 10 g of commercial Puralox TH100 alumina powder (Sasol, diameter 80 µm) in a 100 mL beaker. The mixture is then stirred until the solution is completely absorbed. The material is dried for 12 hours in air at 60 ° C and then calcined for 2 hours at 400 ° C in air flow. The material is reduced under hydrogen at 450°C for 2 hours.

Catalyst F comprises a copper element content of 9.7% by weight relative to the weight of the catalyst and an indium content of 2.5% by weight relative to the weight of the catalyst. The Cu/In molar ratio is 7 mol/mol. Peaks of alloys containing copper and indium are noted in XRD.

Example 7: preparation of a 9.7%Cu 2.5% Ga/Al catalyst ₂ O ₃ (mol/mol ratio Cu/In = 7.1, compliant) by co-impregnation

1.027 g of hydrated gallium nitrate (Ga(NO ₃ ) ₃ ; 9 H ₂ O, M = 418 g/mol, 0.25 mmol) and 4.1 g of hydrated copper nitrate (Cu(NO ₃ ) ₂ ; 2.5 H ₂ O, M = 232.6 g/mol, 1.75 mmol) are dissolved in 10 mL of deionized water at room temperature. The solution is then added dropwise to 10 g of commercial Puralox TH100 alumina powder (Sasol, diameter 80 µm) in a 100 mL beaker. The mixture is then stirred until the solution is completely absorbed. The material is dried for 12 hours in air at 60 ° C and then calcined for 2 hours at 400 ° C in air flow. The material is reduced under hydrogen at 450°C for 2 hours.

Catalyst G comprises a copper element content of 9.7% by weight relative to the weight of the catalyst and a gallium content of 1.5% by weight relative to the weight of the catalyst. The Cu/In molar ratio is 7 mol/mol.

Example 8: Catalytic tests (performance in selective hydrogenation of butadiene)

Catalysts A to G described in the above examples are tested for the selective hydrogenation reaction of butadiene in the gas phase.

The composition of the charge to be selectively hydrogenated is as follows: 0.3% butadiene, 30% propene and 20% hydrogen in helium.

The selective hydrogenation reaction is carried out in a pyrex plug flow reactor (inner diameter of 4 mm) operating at atmospheric pressure and temperatures between 5°C and 200°C.

Prior to its introduction into the reactor, 50 mg of calcined catalyst powder (fraction 125 – 250 µm) are mixed with 200 mg of silicon carbide powder of the same particle size.

The catalyst is activated in situ under a pure hydrogen flow of 2 L/h/g of catalyst, at 450 °C for 2 hours (temperature rise ramp of 3 °C/min). The reactor is cooled to 90 °C under hydrogen flow, then the reaction mixture is introduced.

Depending on the catalyst activity, the reactor temperature or feed flow rate are modified to achieve 99% butadiene conversion. The reaction products are analyzed over time online by gas chromatography.

The conversion of butadiene is calculated according to the following formula:

Conversion (%) = 100*[1- (butadiene out/butadiene in)]

The butadiene activity normalized by the copper content is expressed in moles of butadiene converted per second and per mole of copper. The catalytic activities are measured at 90°C for catalysts A to G. They are reported in Table 1 below.

Selectivity is represented by the selectivity to alkenes and the amount of alkane formed:

Alkane formation (ppm) = (propane out - propane in) + butane

The selectivity of the catalysts is compared to 99% conversion of butadiene.

Catalyst Cu content (%wt) In content (%wt) or Ga Cu/In or Cu/Ga (mol/mol) Method
of preparation _Initial A (10 ^-3
mol butadiene/second/mol copper) at 90°C Alkanes
formed (ppm wt) at 99% conversion Deactivation A (non-compliant) 10 0 - I 2.7 180 Yes B (non-compliant) 0 6.1 - I 0 0 - C (compliant) 9.4 5.6 3.1 CI 0.070 38 No D (compliant) 9.4 5.6 3.1 IS 0.15 35 No E (compliant) 9.7 3.5 5 CI 0.73 40 No F (compliant) 9.7 2.5 7 CI 1.35 90 No G (compliant) 9.7 1.5 7 CI 2.3 130 No

I: Impregnation, CI: Co-Impregnancy, IS: Successive Impregnation.

Table 1: Comparison of the performances of catalysts A to G in selective hydrogenation of a mixture containing butadiene.

Monometallic catalyst B (non-compliant) comprising only indium is inactive for the reaction.

Catalysts C to G, in accordance with the invention, are active for the hydrogenation of butadiene. The selectivity of the catalysts of the invention is improved compared to the non-compliant catalyst A. Indeed, the addition of indium makes it possible to reduce the quantity of alkene formed at iso-conversion of butadiene, from 180 ppm by weight for catalyst A (non-compliant) to 35 and 38 ppm by weight (catalysts C and D, compliant, Cu/In ratio = 3.1), 40 ppm by weight (catalyst E, compliant Cu/In ratio = 5) and 90 ppm by weight (catalyst F, compliant Cu/In ratio = 7).

In addition, the addition to copper of an element from column IIIA, chosen from indium and gallium, makes it possible to have a stable catalyst. The deactivation over time of the catalytic activity of catalysts C to G is very low compared to catalyst A (Cu only, non-compliant).

Claims (12)

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 of less than or equal to 300°C, which process is carried out at a temperature of between 0 and 300°C, at a pressure of between 0.1 MPa and 10 MPa, at a hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio of between 0.1 and 10 and at an hourly volumetric flow rate of between 0.1 and 200 h ^-1 when the process is carried out in the liquid phase, or at a hydrogen/(polyunsaturated compounds to be hydrogenated) molar ratio of between 0.5 and 1000 and at an hourly volumetric flow rate of between 100 and 40000 h ^-1 when the process is carried out in the gas phase, in the presence of a catalyst comprising an active phase comprising copper and an element from column IIIA, and a support of alumina, the copper content being between 0.5% and 25% by weight of copper element relative to the total weight of the catalyst, the atomic ratio between copper and the element of column IIIA being between 1 and 50 mol/mol, said catalyst being in the form of a powder with a particle size of between 20 µm and 500 µm. The method of claim 1, wherein the element of column III A is selected from indium or gallium. A process according to any one of claims 1 to 2, wherein when the element IIIA is indium, the indium content is between 0.02% and 25% by weight of indium element relative to the total weight of the catalyst. Process according to any one of claims 1 to 2, in which when the element IIIA is gallium, the gallium content is between 0.5% and 25% by weight of gallium element relative to the total weight of the catalyst. Process according to any one of the preceding claims, characterized in that the specific surface area of the catalyst used is between 80 and 200 m²/g. A process according to any preceding claim wherein said catalyst is obtained by a preparation process comprising the following steps:
a) a catalyst precursor is formed by carrying out the following sequence:
a1) an alumina powder is brought into contact with a solution comprising at least one precursor of the active copper phase;
a2) the alumina powder is brought into contact with at least one solution comprising at least one precursor of the active phase based on an element from column IIIA;
steps a1) and a2) being carried out separately, in any order, or simultaneously;
b) drying the catalyst precursor obtained at the end of step a) at a temperature below 250°C to obtain a dried catalyst precursor. Process according to claim 6, in which when steps a1) and a2) are carried out separately, an intermediate drying step is carried out between steps a1) and a2), or between steps a2) and a1), in which the catalyst precursor obtained at the end of step a1), or of step a2), is dried at a temperature below 250°C. Process according to claim 7, in which the catalyst precursor obtained at the end of the intermediate drying step is subjected to a heat treatment at a temperature between 250°C and 1000°C. Method according to claim 6, wherein steps a1) and a2) are carried out simultaneously. A method according to any one of claims 6 to 9, wherein the precursor of the active copper phase is selected from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide or copper fluoride. A method according to any preceding claim, wherein the element IIIA of the active phase is indium, and wherein the indium precursor is selected from indium acetate, indium acetylacetonate, indium nitrate, indium sulfate, indium sulfide, indium chloride, indium mercaptoacetate, indium bromide, indium iodide, indium fluoride, indium oxide, indium phosphide, indium hydroxide. A process according to any one of claims 1 to 10, wherein the element IIIA of the active phase is gallium, and wherein the gallium precursor is selected from gallium acetylacetonate, gallium nitrate, gallium sulfate, gallium sulfide, gallium chloride, gallium bromide, gallium iodide, gallium oxide, gallium nitride, gallium phosphide, gallium perchlorate, organics such as gallium triethyl and gallium trimethyl.