Novel titanium-based catalytic composition for the selective trimerization of ethylene to 1-hexene

Abstract

The present invention relates to a catalytic composition for the selective oligomerization of ethylene, preferably for the trimerization of ethylene to 1-hexene, comprising:- a titanium-based metal precursor corresponding to the formula below:  - and an activator of aluminoxane type.The invention also concerns a process for the oligomerization of ethylene, preferably for the selective trimerization of ethylene to 1-hexene, using the catalytic composition according to the invention.

Description

NOVEL TITANIUM-BASED CATALYTIC COMPOSITION FOR THE SELECTIVE TRIMERIZATION OF ETHYLENE TO 1-HEXENE TECHNICAL FIELDThe present invention concerns a novel titanium-based catalytic composition and the use thereof for the selective oligomerization of ethylene, in particular for the trimerization of ethylene to 1-hexene.The invention also concerns a process for the oligomerization of ethylene, preferably for the selective trimerization of ethylene to 1-hexene, using the catalytic composition according to the invention.PRIOR ART1-Hexene plays a very important role as a reaction intermediate in the chemical and petrochemical industries. Its main use is the production of various grades of polyethylene in which it is used as a comonomer. This compound is mainly obtained by oligomerization of ethylene. Systems that are capable of selectively trimerizing ethylene to 1-hexene are currently essentially chromium-based (D.S. McGuinness, Chem. Rev. 2011, 111, 2321). Among the known systems leading to the selective production of 1-hexene, mention may be made of the systems described, for example, in US5198563, US5288823, US5382738, EP608447, EP611743 and EP614865. These catalysts are prepared from a chromium salt and a metal amide, in particular a pyrrolide. Other catalysts involve an aluminoxane and a chromium complex in combination with phosphorus ligands, as described in US5550305.Recent studies have demonstrated the potential of titanium (Ti)-based systems for selectively producing 1-hexene. Since the discovery by Deckers et al. in 2001 (Angew. Chem. Int. Ed. 2001, 40, 2516-2519), systems derived from cyclopentadienyl (Cp) ligands activated with methylaluminoxane (MAO) have been very widely described in the literature ([(η5-CpCMe2Ph)TiCl3] / MAO) (Organometallics, 2002, 21, 5122; Organometallics 2002, 21, 5122-5135; J. Am. Chem. Soc. 2009, 131, 5298–5312; Chem. Commun., 2003, 2816-2817; J. Mol. Cat. A.: Chem., 2004, 214, 227-229; WO 2012 / 133928; WO 2012 / 133929).The company Mitsui has also proposed a novel titanium-based system for the selective trimerization of ethylene to 1-hexene (EP2174928; Organometallics 2010, 29, 2394-2396). This catalytic system, when activated with MAO (300-10 000 eq. / Ti), leads to a C6 selectivity of about 92% (of which 99.5% 1-hexene).The aim of the present invention is to provide a novel titanium-based catalytic composition for the selective trimerization of ethylene to 1-hexene.SUMMARY OF THE INVENTIONThe present invention relates to a catalytic composition for the selective oligomerization of ethylene, preferably for the trimerization of ethylene to 1-hexene, comprising:- a titanium-based metal precursor corresponding to the formula below:  in which: L is at least one bond linking Rx with x chosen between 1 and 12 and Rx with x chosen between 14 and 25, L being a cyclic or non-cyclic, aromatic or non-aromatic hydrocarbon-based group containing from 1 to 20 carbon atoms (C1-C20), which may or may not contain a heteroelement, or L being a covalent bond, R1 to R12, on the one hand, and R14 to R25, on the other hand, when they are not linked together, are each chosen from a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted aryl group, a cyclic or non-cyclic alkyl group and a cyclic or non-cyclic aralkyl group, said groups containing from 1 to 15 carbon atoms (C1-C15) and containing or not containing a heteroelement, R13 and R26 are each chosen from a substituted or unsubstituted aryl group, a cyclic or non-cyclic alkyl group and a cyclic or non-cyclic aralkyl group, said groups containing from 1 to 15 carbon atoms (C1-C15) and containing or not containing a heteroelement, X1 and X2 are each an identical or different heteroatom, and X3 and X4 are each an identical or different ligand X,- and an activator of aluminoxane type.DETAILED DESCRIPTION OF THE INVENTIONAccording to the present invention, the expressions “of between ... and ...” and “between ... and ...” are equivalent and mean that the limit values of the interval are included in the described range of values. If this is not the case and the limit values are not included in the described range, such a clarification will be provided by the present invention.For the purposes of the present invention, the various ranges of parameters for a given step, such as the pressure ranges and the temperature ranges, can be used alone or in combination. For example, for the purposes of the present invention, a preferred pressure value range may be combined with a more preferred temperature value range.In the text hereinbelow, particular embodiments of the invention may be described. They may be implemented separately or combined together without limitation of combinations when this is technically feasible.Titanium-based metal precursorA “metal precursor” is understood as meaning a compound comprising a metal centre and at least one ligand stabilizing the precursor, which may be charged or neutral, organic or inorganic.The composition according to the present invention comprises a titanium-based metal precursor corresponding to the formula below: in which: L is at least one bond linking Rx with x chosen between 1 and 12 and Rx with x chosen between 14 and 25, L being a cyclic or non-cyclic, aromatic or non-aromatic hydrocarbon-based group containing from 1 to 20 carbon atoms (C1-C20), which may or may not contain a heteroelement, or L being a covalent bond, R1 to R12, on the one hand, and R14 to R25, on the other hand, when they are not linked together, are each chosen from a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted aryl group, a cyclic or non-cyclic alkyl group and a cyclic or non-cyclic aralkyl group, said groups containing from 1 to 15 carbon atoms (C1-C15) and containing or not containing a heteroelement, R13 and R26 are each chosen from a substituted or unsubstituted aryl group, a cyclic or non-cyclic alkyl group and a cyclic or non-cyclic aralkyl group, said groups containing from 1 to 15 carbon atoms (C1-C15) and containing or not containing a heteroelement, X1 and X2 are each an identical or different heteroatom, and X3 and X4 are each an identical or different ligand X.Advantageously, R2, R4, R5, R6, R7, R8, R9, R10, R11, R12, R15, R17, R18, R19, R20, R21, R22, R23, R24 and R25, when they are not connected together, are each a hydrogen atom.Advantageously, R13 and R26 are each chosen from an alkyl group containing from 1 to 6 carbon atoms (C1-C6), which may or may not contain a heteroelement, a cycloalkyl group containing from 3 to 6 carbon atoms (C3-C6), which may or may not contain a heteroelement, and a substituted or unsubstituted aryl group containing from 6 to 15 carbon atoms (C6-C15), which may or may not contain a heteroelement. Preferably, R13 and R26 are each a methyl group.Advantageously, R1, R3, R14 and R16, when they are not linked together, are each chosen from an alkyl group containing from 1 to 10 carbon atoms (C1-C10), which may or may not contain a heteroelement, a cycloalkyl group containing from 3 to 10 carbon atoms (C3-C10), which may or may not contain a heteroelement, and a substituted or unsubstituted aryl group containing from 4 to 15 carbon atoms (C4-C15), which may or may not contain a heteroelement. Preferably, R1, R3, R14 and R16, when they are not linked together, are each chosen from a methyl, tert-butyl or adamantyl group.Advantageously, X1 and X2 are each an oxygen atom.The term “ligand X” means a ligand that has a formal negative charge in the ionic electron counting model. The metal-ligand assembly is described as a ligand X− interacting with a metal cation M+, thus giving a purely ionic description of the metal-ligand bond. The ligands X are described, for example, in the book “The Organometallic Chemistry of the Transition Metals”, Sixth Edition, Robert H. Crabtree. The ligands X are also well known to those skilled in the art in the field of organometallic chemistry.Advantageously, X3 and X4 are each chosen from fluoride, chloride, bromide, iodide, hydroxide, methyl, n-ethyl, n-propyl, i-propyl, n-butyl, i-butyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, methoxy, ethoxy, propoxy, isopropoxy, butoxy, tert-butoxy, formate, acetate, propionate and carbonate. Preferably, X3 and X4 are each an identical ligand X chosen from chloride, bromide and iodide. Very preferably, X3 and X4 are each a chloride.As non-limiting examples, some titanium-based metal precursor structures according to the invention are described below:In this titanium-based metal precursor structure, L is a phenylene group linking R3 and R16. In this titanium-based metal precursor structure, L is a methylene group linking R7 and R20.          In this titanium-based metal precursor structure, L is a covalent bond linking R10 and R23. In this titanium-based metal precursor structure, L is a covalent bond linking R2 and R20.Activator of aluminoxane typeThe composition according to the present invention comprises an activator of aluminoxane type.The term “activator of aluminoxane type” means either a soluble aluminoxane compound, or an aluminoxane compound which has been immobilized on a solid support, or a solid aluminoxane compound, or a mixture of these three compounds.Soluble aluminoxaneIn one embodiment, the activator of aluminoxane type is a soluble aluminoxane compound. Preferably, the soluble aluminoxane is chosen from methylaluminoxane (MAO), modified methylaluminoxane (MMAO) and ethylaluminoxane (EAO), alone or as a mixture.A description of a soluble aluminoxane that may be used in the catalytic composition according to the invention can be found in the document Eur. J. Inorg. Chem. 2015, 2015, 19-43.Preferably, the mole ratio of the aluminium of the soluble aluminoxane to the titanium of the metal precursor, denoted AlMAO / Ti, is between 1 and 15 000, preferably between 50 and 10 000, more preferably between 250 and 5000 and very preferably between 1000 and 3000.The AlMAO / Ti mole ratio is calculated as the ratio between the number of moles of aluminium contained in the soluble aluminoxane and the number of moles of titanium in the metal precursor.Supported aluminoxaneIn one embodiment, the activator of aluminoxane type is an aluminoxane compound which has been immobilized on a solid support, also known as a supported aluminoxane.The supported aluminoxane allows the catalyst to be formed, during the use of the catalytic composition, via ionic interactions between the titanium-based metal precursor and the supported aluminoxane; a catalytic structure of this kind may be referred to as a floating cation. The catalytic reaction takes place at the surface or in the pores of the catalyst formed.Advantageously, the supported aluminoxane is a methylaluminoxane immobilized on an inorganic support (denoted SMAO). The description of an SMAO which can be used in the catalytic composition according to the invention and the process for the production thereof can be found in the book Tailor-Made Polymers Via Immobilization of Alpha-Olefin Polymerization Catalysts, the document US2015 / 353658 in the name of King Fahd University of Petroleum and Minerals, the document US2018 / 0354870 in the name of Saudi Arabian Oil Company or the document US6211311 in the name of the company Equistar Chem LP.The SMAO is advantageously obtained by direct reaction of a solution of MAO with an inorganic support in an organic solvent.Advantageously, the inorganic support is chosen from silica, alumina, silica-alumina, zeolites, titanium dioxide (TiO2), etc. Preferably, the support is silica. The silica advantageously contains Si-OH or Si-O-Si groups.In one embodiment, the silica is chosen from high-purity silicas that do not contain any traces of metals. The silica preferably contains less than 10 ppm of Fe, Na, Al and / or Ti.In one embodiment, the silica may have a crystalline, amorphous or partially crystalline structure. The silica preferably has an amorphous structure.The inorganic support is advantageously in the form of particles defined by a mean diameter of less than or equal to 200 μm, preferably less than or equal to 150 μm, more preferably less than or equal to 100 μm, and very preferably less than or equal to 50 μm.In a preferred embodiment, the inorganic support has a granular or spherical morphology. The inorganic support very preferably has a spherical morphology.In a preferred embodiment, the inorganic support is in the form of particles defined by a mean diameter of between 1 and 100 μm, preferably between 10 and 50 μm, preferably between 20 and 40 μm, preferably between 30 and 35 μm.In one embodiment, the inorganic support is mesoporous in nature. It has a mean pore diameter of between 2 and 50 nm, preferably between 10 and 40 nm, more preferably between 15 and 30 nm, and very preferably between 20 and 25 nm. The pore diameter is calculated by the Barrett-Joyner-Halenda (BJH) method and measured by nitrogen adsorption analysis.In one embodiment, the inorganic support has a pore volume of between 0.5 and 2.5 ml / g, preferably between 1 and 2 ml / g, more preferably between 1.25 and 1.75 ml / g and very preferably between 1.4 and 1.6 ml / g. The pore volume is calculated by the Barrett-Joyner-Halenda (BJH) method and measured by nitrogen adsorption analysis.In one embodiment, the inorganic support has a specific surface area of between 1 and 600 m2 / g, preferably between 100 and 500 m2 / g, more preferably between 200 and 400 m2 / g, and very preferably between 300 and 350 m2 / g. The specific surface area is calculated by the Brunauer-Emmett-Teller (BET) method and measured by nitrogen adsorption analysis.The aluminium content of the SMAO is advantageously between 1% and 25% by mass, preferably between 5% and 15% by mass, more preferably between 8% and 12% by mass, very preferably between 9% and 11% by mass, relative to the total mass of the SMAO. This ensures that the SMAO will have good properties such as the ability to avoid leaching of the catalyst into the solution.Advantageously, the mole ratio of the aluminium of the SMAO to the titanium of the metal precursor, denoted AlSMAO / Ti, is between 50 and 5000, preferably between 100 and 2500, very preferably between 100 and 1000.The AlSMAO / Ti mole ratio is calculated as the ratio between the number of moles of aluminium contained in the SMAO and the number of moles of titanium in the metal precursor.Solid aluminoxaneIn one embodiment, the activator of aluminoxane type is a solid aluminoxane compound.Advantageously, the solid aluminoxane compound is a solid methylaluminoxane, also known as solid MAO.The description of a solid MAO that may be used in the catalytic composition according to the invention, and a process for manufacturing same, may be found in US2011 / 0282017, US2015 / 057418 or US2018 / 355077 in the name of the company Tosoh Finechem Corporation, or in US6518445 in the name of the company Albemarle Corporation.The solid MAO by definition is a particulate compound which at ambient temperature (30°C or below) is in the form of a solid suspension in hydrocarbon (aromatic or paraffinic) solvents, for instance toluene, cyclohexane, pentane, heptane, etc. Any solid MAO which is insoluble in a hydrocarbon solvent may act as an activator according to the invention.The solid MAO advantageously comprises polymeric chains (PMAO) formed by atoms of Al, O and methyl groups (-Me or -CH3) defined by the formula below:-[(Me)AlO]n-where n can advantageously take a value between 1 and 60, preferably between 10 and 50.The solid MAO essentially comprises PMAO chains according to the above formula, although its structure may also comprise associated trimethylaluminium (denoted TMA), free or in interaction with the PMAO chains. The PMAO may have a linear, cyclic or branched structure, provided that the polymer chains correspond to the above formula.The solid MAO used in this invention may contain PMAO of linear and / or branched structure, but also cyclic fragments and residual molecules of the solvent in interaction with the TMA.The mass content of aluminium in the solid MAO is advantageously between 36% and 52% by mass. This ensures that the solid MAO has good properties such as an optimum size and fragmentation resistance during the various synthetic steps.The solid MAO is preferably defined by an aluminium content of between 38% and 43% by mass. The solid MAO more preferably has an aluminium content of between 40% and 42% by mass. The solid MAO very preferably has an aluminum content of between 40.5% and 41.5% by mass.The solid MAO is advantageously in the form of particles defined by a mean diameter of less than or equal to 200 μm, preferably less than or equal to 150 μm, more preferably less than or equal to 100 μm, and very preferably less than or equal to 50 μm.In a preferred embodiment, the solid MAO is in the form of particles defined by a mean diameter of between 1 and 50 μm, preferably between 5 and 40 μm, preferably between 10 and 30 μm, preferably between 15 and 25 μm.Advantageously, the mole ratio of the solid MAO to the titanium-based metal precursor, denoted AlSMAO / Ti, is between 1 and 10 000, preferably between 25 and 5000, more preferably between 50 and 2500 and very preferably between 100 and 1500.The AlSMAO / Ti mole ratio is calculated as the ratio between the number of moles of aluminium contained in the solid MAO and the number of moles of titanium contained in the metal precursor.Optional additive in the form of an aluminium-based compoundIn one embodiment, the composition according to the present invention also comprises an additive in the form of an aluminium-based compound.In one embodiment, the additive in the form of an aluminium-based compound is a compound of formula AIR(3-a)R’a, where R and R’ are independently chosen from C1-C12 alkyl, C1-C12 alkoxy and halogen. Advantageously, a can take the value 0 or 1. Preferably, R and R’ are independently chosen from C1-C10 alkyl, C1-C10 alkoxy, preferably C1-C6 alkyl, C1-C6 alkoxy and a chlorine or bromine atom. Preferably, a takes the value 0. R is preferably an alkyl and / or alkoxy group chosen from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, pentyl, hexyl, heptyl and octyl and the corresponding alkyloxy groups. R is preferably an alkyl and / or alkoxy group chosen from ethyl, propyl, isopropyl, n-butyl and tert-butyl and the corresponding alkyloxy groups.The additive in the form of an aluminium-based compound is preferably chosen from trimethylaluminium (TMA), triethylaluminium (TEA), triisopropylaluminium, tri-n-butylaluminium, triisobutylaluminium, tri-tert-butylaluminium, trihexylaluminium, trioctylaluminium, diethylethoxyaluminium, dimethylethoxyaluminium, methylaluminium dichloride, ethylaluminium dichloride, dimethylaluminium chloride, diethylaluminium chloride and ethylaluminium sesquichloride, alone or as a mixture.Preferably, the additive in the form of an aluminium-based compound is chosen from trimethylaluminium (TMA), triethylaluminium (TEA), and triisobutylaluminium, alone or as a mixture.Preferably, the mole ratio of the aluminium of the additive in the form of an aluminium-based compound to the titanium of the metal precursor, denoted Aladd / Ti, is between 1 and 1500, preferably between 10 and 1000, more preferably between 20 and 500 and very preferably between 50 and 300.The Aladd / Ti mole ratio is calculated as the ratio between the number of moles of aluminium contained in the additive in the form of an aluminium-based compound and the number of moles of titanium contained in the metal precursor.Optional solventThe catalytic composition according to the invention may also comprise a solvent. A solvent that may be used is one chosen from organic solvents and in particular from saturated or unsaturated, cyclic or acyclic hydrocarbons.The solvent(s) are advantageously chosen from halogenated solvents and saturated or unsaturated, cyclic or acyclic hydrocarbons comprising between 1 and 20 carbon atoms, preferably between 1 and 15 carbon atoms and preferably between 4 and 15 carbon atoms.The solvent is preferably chosen from butane, isobutane, pentane, hexane, cyclohexane, heptane, methylcyclohexane, dichloromethane, toluene, xylene, dichloroethane, chlorobenzene and dichlorobenzene, pure or as a mixture. More preferably, the solvent is chosen from butane, isobutane, cyclohexane, methylcyclohexane, toluene and xylene. Very preferably, the solvent is cyclohexane.In a preferred embodiment, the solvent may be advantageously chosen from the products of the oligomerization reaction.Formulation of the catalytic compositionThe catalytic composition according to the invention can be formulated by preparing a mixture comprising the titanium-based metal precursor, the activator of aluminoxane type and optionally the aluminium-based compound used as additive in any order.Use of the composition in an oligomerization processAnother subject of the invention concerns a process for the oligomerization of ethylene, preferably for the selective trimerization of ethylene to 1-hexene, using the catalytic composition according to the invention.The feedstock employed in the oligomerization process is advantageously gaseous ethylene.In one embodiment, the gaseous ethylene may contain up to 5% dihydrogen, preferably less than 3% dihydrogen, very preferably less than 1% dihydrogen.The concentration of the titanium-based metal precursor used in the oligomerization process is advantageously between 0.01 and 10 000 µmol / L, preferably between 0.1 and 1000 µmol / L, very preferably between 1 and 100 µmol / L.The process may advantageously be performed in the presence of a solvent as described previously.Advantageously, the oligomerization process is performed at a total pressure of between 0.1 and 20.0 MPa, preferably between 0.1 and 15.0 MPa and more preferably between 0.5 and 8.0 MPa, and at a temperature of between 15 and 200°C, preferably between 20°C and 100°C and very preferably between 25°C and 80°C.The heat generated by the reaction may be removed via any means known to those skilled in the art.Advantageously, the process for the oligomerization and in particular for the trimerization of ethylene to 1-hexene may be performed continuously.In a first embodiment, the constituents of the catalytic composition according to the invention are injected into a reactor stirred by conventional mechanical means or by external recirculation, in which the ethylene reacts, preferably with temperature control.In another embodiment, a solution comprising a mixture of the titanium-based metal precursor and the activator of aluminoxane type, and a solution comprising the optional additive in the form of an aluminium-based compound, are injected separately into a reactor stirred by conventional mechanical means or by external recirculation, in which the ethylene reacts, preferably with temperature control.The catalytic composition may be neutralized downstream of the reactor via any means known to those skilled in the art.The examples that follow illustrate the invention without limiting the scope thereof.EXAMPLESExample 1: Synthesis of the titanium-based metal precursor C1 according to the invention:The synthesis of C1 requires the following steps to be performed:a) Synthesis of 3-tert-butylsalicylaldehyde:6.36 g (211.8 mmol, 6 eq) of paraformaldehyde and 5.00 g (52.5 mmol, 1.5 eq) of ultra dry MgCl2 (supplied in vials) are weighed out in a 250 mL round-bottomed flask. 70 mL of tetrahydrofuran (THF) and 5.26 g (35.0 mmol) of 2-tert-butylphenol are introduced. The mixture is stirred and 18.5 mL (132.7 mmol, 3.75 eq) of triethylamine are added. The mixture is heated at 85°C for 4h. It is allowed to cool to room temperature (25°C) and 270 mL of dichloromethane are then added. The solution is neutralized by adding 60 mL of 1M HCl in a separating funnel. The organic phase is washed with 2x100 mL of salt-saturated water and 100 mL of deionized water. The organic phase is dried over Na2SO4, and the volatiles are then evaporated off. A yellow oil is obtained. The product is purified on a silica column (80 / 20 nC5 / CH2Cl2, Rf (retention factor) = 0.55). 4.70 g of a slightly yellow oil are obtained (η (yield) ≈ 75%).The NMR characterization of the compound 3-tert-butylsalicylaldehyde obtained is as follows:1H NMR (300 MHz, CDCl3): δ = 11.8 (s, 1H), 9.9 (s, 1H), 7.54 (dd, 1H), 7.40 (dd, 1H), 6.95 (t, 1H), 1.43 (s, 9H).13C NMR {1H} (75 MHz, CDCl3): δ = 197.2; 161.3; 138.4; 134.2; 132.1; 120.8; 119.3; 35.0; 29.3.(b) Synthesis of 5-bromo-3-tert-butylsalicylaldehyde:2.5 g (14.0 mmol, 1 eq) of the 3-tert-butylsalicylaldehyde obtained in step a) and 5 mL of acetic acid are introduced into a 50 mL round-bottomed flask. A solution containing 4 mL (78.1 mmol, 5.5 eq) of dibromine and 4 mL of acetic acid is then added dropwise. The mixture is stirred at room temperature for 3h. 100 mL of dichloromethane are then added. The organic phase is washed with 3x50 mL of saturated sodium metabisulfite solution (Na2S2O5), 3x50 mL of saturated NaHCO3 solution and 3x50 mL of saturated salt solution. The organic phase is dried over Na2SO4. The solvent is evaporated off. 3.0 g of a pale yellow solid (η ≈ 83%) are obtained.The NMR characterization of the compound 5-bromo-3-tert-butylsalicylaldehyde obtained is as follows:1H NMR (300 MHz, CDCl3): δ = 11.7 (s,1H), 9.8 (s,1H), 7.58 (d,1H), 7.52 (d, 1H), 1.40 (s,9H).13C NMR {1H} (75 MHz, CDCl3): δ = 196.15; 160.35; 141.29; 137.14; 133.75; 121.83; 111.28; 35.29; 29.15.c) Synthesis of 5,5'-bis(3-tert-butyl-2-hydroxybenzaldehyde)-1,4-phenyl1.5 g (5.8 mmol, 1 eq) of 5-bromo-3-tert-butylsalicylaldehyde obtained in step b), 0.86 g (2.61 mmol, 0.45 eq) of 2-methoxyphenylboronic acid and 0.81 g (5.8 mmol, 1 eq) of K2CO3 are weighed out in a 100 mL round-bottomed flask. 337 mg (0.29 mmol, 0.05 eq) of Pd[P(Ph)3]4 are weighed out in a glove box. A 17 / 5 mL dimethoxyethane (DME) / H2O mixture degassed for 0.5h with argon is added. The resulting mixture is heated at 100°C for 24h. 30 mL of water are added and the mixture is then extracted with dichloromethane (DCM). The organic phase is dried over MgSO4 and the volatiles are evaporated off. The product is purified on a silica column (5 / 95 EtOAc / nC5). 350 mg of a slightly yellow product (η ≈ 14%) are obtained.The NMR characterization of the 5,5'-bis(3-tert-butyl-2-hydroxybenzaldehyde)-1,4-phenyl compound obtained is as follows:1H NMR (300 MHz, CDCl3): δ = 11.81 (s, 2H); 10.00 (s, 2H); 7.81 (d, 2H); 7.65 (m, 6H); 1.50 (s, 18H).13C NMR {1H} (75 MHz, CDCl3): δ = 197.3; 160.9; 139.14; 139.09; 133.14; 131.97; 130.05; 127.35; 120.97; 35.23; 29.41.d) Synthesis of 2-(2-methoxyphenyl)aniline6.09 g (35.4 mmol) of aniline and 34 mL of N,N-dimethylformamide (DMF) are introduced into a schlenk tube. 11 mL of saturated Na2CO3 solution are added. The mixture is stirred for 10 min and 5.38 g of boronic acid (35.4 mmol) are then added. 0.675 g (3.8 mmol) of PdCl2 and 2.00 g (7.6 mmol) of triphenylphosphine are weighed out in another schlenk tube. The tube is purged by performing three vacuum / argon cycles and 5.5 mL of dry DMF are then added. The solution is stirred for 10 min and is then added by cannula into the first schlenk tube. The mixture is maintained at 90°C overnight. The mixture is cooled and then extracted with 3x40 mL of EtOAc. The volatiles are evaporated off and the product is then purified on a silica column (90 / 10 nC5 / EtOAc). 3.75 g of a white solid are obtained (η ≈ 53%).The NMR characterization of the 2-(2-methoxyphenyl)aniline compound obtained is as follows:1H NMR (CH2Cl2): 7.38 (td, 1H), 7.23 (dd, 1H), 7.15 (td, 1H), 7.10-7.00 (m, 3H), 6.83-6.72 (m, 2H), 3.81 (s, 3H), 3.68 (br s, 2H).13C NMR {1H} (CH2Cl2): 157.2; 145.2; 132.1; 131.5; 129.4; 128.8; 128.7; 125.4; 121.4; 118.5; 115.8; 111.6; 55.9.e) Synthesis of the intermediate compound 1 having the following formula: 316.3 mg (0.73 mmol; 1 eq) of 5,5'-bis(3-tert-butyl-2-hydroxybenzaldehyde)-1,4-phenyl obtained in step c), 324.6 mg (1.62 mmol; 2.2 eq) of 2-(2-methoxyphenyl)aniline obtained in step d), a spatula tip of para-toluenesulfonic acid and 15 mL of EtOH are weighed out in a schlenk tube. The mixture is heated at 95°C for two days. The product is filtered off and washed with nC5. 378.7 mg of an orange / red solid are obtained (η ≈ 65%).The NMR characterization of the intermediate compound 1 obtained is as follows:1H NMR (300 MHz, CD2Cl2): δ = 13.69 (br s; 2H); 8.66 (s; 2H); 7.67 (d; 2H); 7.63 (s; 4H); 7.53-7.43 (m,4H); 7.43-7.33 (m,6H); 7.30 (d; 2H); 7.25 (dd; 2H); 7.04 (td; 2H); 6.98 (d; 2H); 3.74 (s; 6H); 1.43 (s; 18H).f) Synthesis of the titanium-based metal precursor C1 having the following formula: 300.0 mg (0.38 mmol) of the intermediate compound 1 obtained in step e), 4 mL of toluene and 4 mL of dichloromethane are introduced into a schlenk tube. This solution is added by cannula to a solution containing 9 mL of toluene and 0.9 mL of 1M TiCl4 in CH2Cl2 (0.9 mmol) cooled to -78°C. The resulting mixture is allowed to warm to room temperature. After stirring for 2h, the volatiles are evaporated off. The complex is washed with 3x10 mL of nC5. The solid is dried under vacuum at 45°C for 2h. 335 mg of a red-brown solid (η ≈ 80%) are obtained.The NMR characterization of the titanium-based metal precursor C1 obtained is as follows:1H NMR (300 MHz, CD2Cl2): δ = 8.27 (s, 2H); 7.90 (d, 2H); 7.62 (s, 4H); 7.59 (d, 2H); 7.56-7.50 (m, 4H); 7.45-7.36 (m, 6H); 7.36-7.27 (m, 4H); 7.25-7.10 (m, 2H); 4.36 (s, 6H); 1.57 (s,18H).13C NMR {1H} NMR (75 MHz, CD2Cl2): δ = 169.2; 163.2; 158.5; 151.9; 139.1; 137.7; 136.5; 133.4; 131.7; 131.6; 131.3; 131.0; 130.5; 130.3; 129.6; 129.4; 128.9; 128.6; 127.9; 127.85; 127.8; 126.1; 125.7; 123.4; 72.7; 35.7; 29.9.Example 2: Synthesis of the titanium-based metal precursor C2 according to the invention:The synthesis of C2 requires the following steps to be performed:a) Synthesis of 3,3'-dibromo-4,4'-diméthoxybiphenyl1.17 g (5.46 mmol, 1 eq) of 4,4'-dimethoxybiphenyl are weighed out in a 100 mL round-bottomed flask. 29 mL of glacial acetic acid are added. 0.6 mL (11.7 mmol, 2.15 eq) of dibromine is added. The mixture is heated for 1h at 120°C. It is allowed to cool to room temperature and the product formed is then filtered off. It is washed with 2x2 mL of glacial acetic acid. 1.1 g of a white solid are obtained (η ≈ 54%).The NMR characterization of the 3,3‘-dibromo-4,4’-dimethoxybiphenyl obtained is as follows:1H NMR (300 MHz, CDCl3): δ = 7.68 (d, 1H); 7.37 (dd, 2H); 6.90 (d, 2H); 3.90 (s, 6H).13C NMR {1H} NMR (75 MHz, CDCl3): δ = 155.3; 133.4; 131.5; 126.7; 112.2; 112.1; 56.4.b) Synthesis of 3,3‘-bis(2-aminophenyl)-4,4’-dimethoxybiphenyl0.60 g (1.61 mmol, 0.45 eq) of 3,3’-dibromo-4,4’-dimethoxybiphenyl obtained in step a), 0.78 g (3.56 mmol, 1 eq) of aminobenzeneboronic acid 2-pinacol ester and 0.49 g (3.56 mmol, 1 eq) of K2CO3 are weighed out in a 100 mL round-bottomed flask. 207 mg (0.179 mmol, 0.05 eq) of Pd[P(Ph)3]4 are weighed out in a glove box. A DME / H2O mixture (10 / 3 mL) degassed for 0.5h with argon is added. The resulting mixture is maintained at 100°C overnight. 20 mL of water are added, and the resulting mixture is then extracted with DCM. The organic phase is dried over MgSO4 and the volatiles are evaporated off. The product is purified on a silica column (nC5 / DCM). 400 mg of an orange-white solid are obtained (η ≈ 62%).The NMR characterization of the 3,3’-bis(2-aminophenyl)-4,4’-dimethoxybiphenyl obtained is as follows:1H NMR (300 MHz, CD2Cl2): δ = 7.60 (dd, 2H), 7.47 (d, 2H), 7.15 (td, 2H), 7.10 (dd, 2H), 7.08 (d, 2H), 6.79 (td, 2H), 6.75 (dd, 2H), 3.84 (s, 6H), 3.73 (br s, 4H).13C NMR {1H} NMR (75 MHz, CD2Cl2): δ = 156.4; 145.2; 133.7; 131.5; 130.4; 129.0; 128.9; 127.3; 125.3; 118.5; 115.8; 112.0; 56.2.c) Synthesis of the intermediate compound 2 having the following formula: 319 mg (0.80 mmol, 1eq) of 3,3’-bis(2-aminophenyl)-4,4’-dimethoxybiphenyl obtained in step b), 415 mg (1.77 mmol, 2.2 eq) of 3,5-di-tert-butyl-2-hydroxybenzaldehyde and 15 mL of dry ethanol are introduced into a schlenk tube. The mixture is maintained at 95°C overnight. The product is filtered off and washed with 3 mL of ethanol and 3 mL of nC5. It is dried under vacuum at 40°C. 510 mg of an orange solid (η ≈ 76%) are obtained.The NMR characterization of the intermediate compound 2 obtained is as follows:1H NMR (300 MHz, CD2Cl2): δ = 13.4 (br s; 2H); 8.54 (s; 2H); 7.57 (dd; 2H); 7.50-7.28 (m; 10H); 7.24 (d; 2H); 7.18 (d; 2H); 7.00 (d; 2H); 3.77 (s; 6H); 1.32 (s; 18H) 1.29 (s; 18H).13C NMR {1H} NMR (75 MHz, CD2Cl2): δ = 163.9; 158.5; 156.2; 147.8; 140.7; 137.1; 134.5; 133.4; 131.7; 130.3; 129.1; 129.0; 128.1; 127.5; 127.1; 126.7; 118.8; 118.4; 111.3; 55.7; 35.3; 34.4; 31.6; 29.5.d) Synthesis of the titanium-based metal precursor C2 having the following formula: 250 mg (0.30 mmol) of the intermediate compound 2 obtained in step c) and 5 mL of toluene are introduced into a schlenk tube. This solution is added by cannula to a solution containing 8 mL of toluene and 0.75 mL of 1M TiCl4 in CH2Cl2 (0.75 mmol) cooled to -78°C. The mixture is allowed to warm to room temperature. After stirring for 2h, the volatiles are evaporated off. The complex is washed with 3x10 mL of nC5. The solid is dried under vacuum at 45°C for 2h. 280 mg of an orange-brown solid (η ≈ 82%) are obtained.The NMR characterization of the titanium-based metal precursor C2 obtained is as follows:1H NMR (300 MHz, CDCl3): δ = 8.21 (s, 2H); 7.72 (d, 2H); 7.68-7.59 (m, 2H); 7.59-7.38 (m, 10H); 7.37-7.29 (m, 2H); 7.19-7.09 (m, 2H); 4.40 (s, 6H); 1.51 (s, 18H); 1.29 (s, 18H).Example 3: Process for preparing an SMAO containing 10.1 wt% Al3 g of silica for polymerization (average diameter = 33 µm; average pore diameter DP = 21 nm; pore volume VP = 1.56 ml / g; specific surface area SBET = 315 m2 / g) predried at 80°C under vacuum for 2 h are weighed out in a Schlenk tube in a glove box.Under a stream of argon, the silica is impregnated with 4.7 ml (corresponding to the total pore volume) of dry toluene. 13 ml of MAO in toluene are then added (4.65 wt% Al, d = 0.895 g / ml, theoretically 0.54 g Al). The mixture becomes a translucent liquid gel.The mixture is heated at 80°C for 4 h with manual stirring every 15 minutes. After 4 h, the toluene is evaporated off and the resulting white powder is dried under vacuum at 80°C for 1 h.The Al content in the SMAO is determined by ICP-AES: wt% Al = 10.1% ± 0.5%.Example 4: Process for the trimerization of ethylene, using the titanium-based metal precursor C1 activated with a soluble MAO (3000 eq. / Ti)43 mL of toluene and 5 mL of a solution of soluble MAO at 1.2 mol / L in toluene obtained from a 10% by weight solution in toluene are introduced into a 100 mL reactor previously purged with argon. Next, 2 mL of a solution of the titanium-based metal precursor C1 of Example 1, previously diluted in toluene to 1 mmol Ti / L (AlMAO / Ti mole ratio = 3000), are introduced. The reactor is pressurized under 0.5 MPa of ethylene and the temperature is raised to 30°C with gentle stirring (≈ 250 rpm). When the temperature reaches 28°C, the reactor pressure is adjusted to the desired pressure of 1 MPa and the stirring speed is increased to 1000 rpm marking the start of the catalytic test.The reaction temperature is maintained at 30°C and the pressure at a constant value of 1 MPa. After 30 minutes of reaction, the reactor is cooled to 15°C before being slowly depressurized. The contents of the reactor are collected in a bottle and weighed. The organic phase is neutralized with a 10% by weight aqueous solution of H2SO4 and then analysed by gas chromatography (GC). The solid (polyethylene) is dried at 100°C overnight and then weighed.Example 5: Process for the trimerization of ethylene, using the titanium-based metal precursor C2 activated with soluble MAO (3000 eq. / Ti)This test is performed under the same conditions as those described in Example 4, except that 2 mol of the titanium-based metal precursor C2 from Example 2 are introduced in place of C1.Example 6: Process for the trimerization of ethylene, using C1 activated with an SMAO (AlSMAO / Ti mole ratio = 171) with TEA as additive (Aladd / Ti mole ratio = 50)200 mg of SMAO containing 9.2% by weight of Al (0.68 mmol Al) are introduced into a Schlenk tube under argon. 2.00 mL of a 2.0 mM solution of C1 (4 µmol) are added to the Schlenk tube containing the SMAO. An orange gel forms at the bottom of the Schlenk tube. The mixture is heated at 50°C for 1 h with manual stirring every 15 min.The nominal temperature of the thermostatic bath of the reactor is set at 25°C. Subsequently, 92.0 ml of cyclohexane solvent are introduced into the reactor, which has been conditioned beforehand by introduction of an atmosphere of 0.05 MPa of ethylene. Subsequently, the solvent is saturated with ethylene after introduction of 0.5 MPa of gaseous ethylene with stirring at 1500 rpm for one minute. The pressure of the reactor is lowered to 0.05 MPa and stirring is halted. 5 ml of nonane dried over molecular sieves (3.6 g) and 1.00 ml of a 0.20M solution of TEA (0.2 mmol) are introduced. Lastly, the entirety of the oligomerization catalyst prepared previously is introduced, the catalyst being in suspension in toluene. The ethylene inlet valve is opened (3 MPa of pressure), stirring is commenced and the nominal temperature of the reactor is then raised to 28°C.At the end of the test, the ethylene supply is cut off, the medium is cooled to 20°C and the gas phase is then vented. The reactor is then opened. The liquid is transferred into a flask containing 1.00 ml of 10% H2SO4 solution. A sample of the organic phase is taken and filtered for analysis.The results of Examples 4 to 6 are described in the table below.Table 1ExampleTime (h)Productivity (g / gTi·h)C6(%)1-C6 (% in C6)C10 (%)C10+ (%)PE (%)40.5161 96886.199.811.60.61.750.5182 64982.799.915.70.70.961.0103 50974.899.919.61.33.7These examples show that the catalytic compositions according to the invention are functional for the selective production of 1-hexene (obtaining more than 70% of C6 molecules, including virtually 100% of 1-hexene), whether with a soluble aluminoxane activator or with an aluminoxane activator immobilized on a solid support.CLAIMS1. Catalytic composition for the selective oligomerization of ethylene, preferably for the tetramerization of ethylene to 1-hexene, comprising:- a titanium-based metal precursor corresponding to the formula below:  in which: L is at least one bond linking Rx with x chosen between 1 and 12 and Rx with x chosen between 14 and 25, L being a cyclic or non-cyclic, aromatic or non-aromatic hydrocarbon-based group, which may or may not contain a heteroelement, or L being a covalent bond, R1 to R12, on the one hand, and R14 to R25, on the other hand, when they are not linked together, are each chosen from a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted aryl group, a cyclic or non-cyclic alkyl group and a cyclic or non-cyclic aralkyl group, said groups containing from 1 to 15 carbon atoms (C1-C15) and containing or not containing a heteroelement, R13 and R26 are each chosen from a substituted or unsubstituted aryl group, a cyclic or non-cyclic alkyl group and a cyclic or non-cyclic aralkyl group, said groups containing from 1 to 15 carbon atoms and containing or not containing a heteroelement, X1 and X2 are each an identical or different heteroatom, and X3 and X4 are each an identical or different ligand X,- and an activator of aluminoxane type.2. Catalytic composition according to Claim 1, in which R2, R4, R5, R6, R7, R8, R9, R10, R11, R12, R15, R17, R18, R19, R20, R21, R22, R23, R24 and R25, when they are not linked together, are each a hydrogen atom.3. Catalytic composition according to Claim 1 or 2, in which R13 and R26 are each chosen from an alkyl group containing from 1 to 6 carbon atoms, which may or may not contain a heteroelement, a cycloalkyl group containing from 3 to 6 carbon atoms, which may or may not contain a heteroelement, and a substituted or unsubstituted aryl group containing from 6 to 15 carbon atoms, which may or may not contain a heteroelement.4. Catalytic composition according to Claim 3, in which R13 and R26 are each a methyl group.5. Catalytic composition according to any one of the preceding claims, in which R1, R3, R14 and R16, when they are not linked together, are each chosen from an alkyl group containing from 1 to 10 carbon atoms, which may or may not contain a heteroelement, a cycloalkyl group containing from 3 to 10 carbon atoms, which may or may not contain a heteroelement, and a substituted or unsubstituted aryl group containing from 4 to 15 carbon atoms, which may or may not contain a heteroelement.6. Catalytic composition according to Claim 5, in which R1, R3, R14 and R16, when they are not linked together, are each chosen from a methyl, tert-butyl or adamantyl group.7. Catalytic composition according to any one of the preceding claims, in which X1 and X2 are each an oxygen atom.8. Catalytic composition according to any one of the preceding claims, in which X3 and X4 are each an identical ligand X chosen from chloride, bromide and iodide.9. Catalytic composition according to any one of the preceding claims, in which the activator of aluminoxane type is a soluble aluminoxane compound chosen from methylaluminoxane, modified methylaluminoxane and ethylaluminoxane, alone or as a mixture.10. Catalytic composition according to Claim 9, in which the mole ratio of the aluminium of the soluble aluminoxane to the titanium of the metal precursor is between 1000 and 3000.11. Catalytic composition according to any one of Claims 1 to 8, in which the activator of aluminoxane type is a methylaluminoxane immobilized on an inorganic support.12. Catalytic composition according to Claim 11, in which the mole ratio of the aluminium of the methylaluminoxane immobilized on an inorganic support to the titanium of the metal precursor is between 100 and 1000.13. Catalytic composition according to Claim 11 or 12, also comprising an additive in the form of an aluminium-based compound chosen from trimethylaluminium, triethylaluminium and triisobutylaluminium, alone or as a mixture.14. Catalytic composition according to Claim 13, in which the mole ratio of the aluminium of the additive in the form of an aluminium-based compound to the titanium of the metal precursor is between 50 and 300.15. Process for the selective trimerization of ethylene to 1-hexene, using the catalytic composition according to any one of the preceding claims. ABSTRACTThe present invention relates to a catalytic composition for the selective oligomerization of ethylene, preferably for the trimerization of ethylene to 1-hexene, comprising:- a titanium-based metal precursor corresponding to the formula below:  - and an activator of aluminoxane type.The invention also concerns a process for the oligomerization of ethylene, preferably for the selective trimerization of ethylene to 1-hexene, using the catalytic composition according to the invention.

Claims

Claim 1. Catalytic composition for the selective oligomerization of ethylene, preferably for the tetramerization of ethylene to 1-hexene, comprising:- a titanium-based metal precursor corresponding to the formula below:  in which: L is at least one bond linking Rx with x chosen between 1 and 12 and Rx with x chosen between 14 and 25, L being a cyclic or non-cyclic, aromatic or non-aromatic hydrocarbon-based group, which may or may not contain a heteroelement, or L being a covalent bond,  R1 to R12, on the one hand, and R14 to R25, on the other hand, when they are not linked together, are each chosen from a hydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, a substituted or unsubstituted aryl group, a cyclic or non-cyclic alkyl group and a cyclic or non-cyclic aralkyl group, said groups containing from 1 to 15 carbon atoms (C1-C15) and containing or not containing a heteroelement, R13 and R26 are each chosen from a substituted or unsubstituted aryl group, a cyclic or non-cyclic alkyl group and a cyclic or non-cyclic aralkyl group, said groups containing from 1 to 15 carbon atoms and containing or not containing a heteroelement, X1 and X2 are each an identical or different heteroatom, and X3 and X4 are each an identical or different ligand X,- and an activator of aluminoxane type. Claim 2. Catalytic composition according to Claim 1, in which R2, R4, R5, R6, R7, R8, R9, R10, R11, R12, R15, R17, R18, R19, R20, R21, R22, R23, R24 and R25, when they are not linked together, are each a hydrogen atom. Claim 3. Catalytic composition according to Claim 1 or 2, in which R13 and R26 are each chosen from an alkyl group containing from 1 to 6 carbon atoms, which may or may not contain a heteroelement, a cycloalkyl group containing from 3 to 6 carbon atoms, which may or may not contain a heteroelement, and a substituted or unsubstituted aryl group containing from 6 to 15 carbon atoms, which may or may not contain a heteroelement. Claim 4. Catalytic composition according to Claim 3, in which R13 and R26 are each a methyl group. Claim 5. Catalytic composition according to any one of the preceding claims, in which R1, R3, R14 and R16, when they are not linked together, are each chosen from an alkyl group containing from 1 to 10 carbon atoms, which may or may not contain a heteroelement, a cycloalkyl group containing from 3 to 10 carbon atoms, which may or may not contain a heteroelement, and a substituted or unsubstituted aryl group containing from 4 to 15 carbon atoms, which may or may not contain a heteroelement. Claim 6. Catalytic composition according to Claim 5, in which R1, R3, R14 and R16, when they are not linked together, are each chosen from a methyl, tert-butyl or adamantyl group. Claim 7. Catalytic composition according to any one of the preceding claims, in which X1 and X2 are each an oxygen atom. Claim 8. Catalytic composition according to any one of the preceding claims, in which X3 and X4 are each an identical ligand X chosen from chloride, bromide and iodide. Claim 9. Catalytic composition according to any one of the preceding claims, in which the activator of aluminoxane type is a soluble aluminoxane compound chosen from methylaluminoxane, modified methylaluminoxane and ethylaluminoxane, alone or as a mixture. Claim 10. Catalytic composition according to Claim 9, in which the mole ratio of the aluminium of the soluble aluminoxane to the titanium of the metal precursor is between 1000 and 3000. Claim 11. Catalytic composition according to any one of Claims 1 to 8, in which the activator of aluminoxane type is a methylaluminoxane immobilized on an inorganic support. Claim 12. Catalytic composition according to Claim 11, in which the mole ratio of the aluminium of the methylaluminoxane immobilized on an inorganic support to the titanium of the metal precursor is between 100 and 1000. Claim 13. Catalytic composition according to Claim 11 or 12, also comprising an additive in the form of an aluminium-based compound chosen from trimethylaluminium, triethylaluminium and triisobutylaluminium, alone or as a mixture. Claim 14. Catalytic composition according to Claim 13, in which the mole ratio of the aluminium of the additive in the form of an aluminium-based compound to the titanium of the metal precursor is between 50 and 300. Claim 15. Process for the selective trimerization of ethylene to 1-hexene, using the catalytic composition according to any one of the preceding claims. 

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