Ethylene oligomerization process using a catalytic composition containing chromium, supported methylaluminoxane and an additive

Abstract

This invention relates to an oligomerization method, preferably for the tetramerization of ethylene into 1-octene, the method comprising the step of injecting at least four compounds into an oligomerization reactor: - a chromium-based metal precursor; - a heteroatom ligand; - a supported methylaluminoxane on an inorganic support; - an additive in the form of an aluminum-based compound; wherein the chromium-based metal precursor and the heteroatom ligand are never in contact with the supported methylaluminoxane on the inorganic support in the absence of the additive in the form of an aluminum-based compound.

Description

Technical Field

[0001] This invention relates to a method for ethylene oligomerization using a chromium-based catalytic composition, supported methylaluminoxane (MAO), and additives, preferably a method for ethylene tetramerization into 1-octene. Existing technology

[0002] Linear alpha-olefins (LAOs) containing four to more than 20 carbon atoms are important feedstocks for the production of petrochemical intermediates. Despite their wide range of applications, global demand for LAOs is primarily driven by short-chain alpha-olefins such as 1-butene, 1-hexene, and 1-octene, which serve as comonomers in the polymer industry. The global supply of LAOs is largely covered by two types of ethylene oligomerization methods using homogeneous catalysts: methods that produce a broad olefin profile (typically C4 to C30) and selective methods that produce only one alpha-olefin (1-butene, 1-hexene, or 1-octene) as the main product. However, due to the faster growth in demand for short-chain C4 to C10 LAOs compared to the C10+ range, significant progress has recently been made towards shorter alpha-olefin profiles to control product distribution or even selectively produce only one alpha-olefin. In this field, the tetramerization of ethylene to 1-octene via chromium-based homogeneous catalysts has seen significant development in recent years (PWNM van Leeuwen et al., Coordination Chemistry Reviews 255 (2011) 1499-1517). Systems known to lead to the selective production of 1-octene include those described, for example, in documents WO2004056477, WO2004056478, or WO2004056479. These catalysts utilize a combination of a Cr(III)-based metal precursor and a PNP ligand (e.g., Ph2PN(iPr)PPh2) activated in situ via an aluminum oxane (MAO: methylaluminoxane; MMAO: modified methylaluminoxane; etc.). They result in “selective” production of 1-octene (more than 60% selectivity). Other Cr-based catalytic systems were subsequently developed, examples of which are those in literature WO2010034102, WO2011156892, or WO2011108772.

[0003] A major drawback of chromium-based catalytic systems used for ethylene oligomerization is the formation of significant amounts of polymer along with the target olefin (1-octene). This formation of polymers in a sticky form can lead to rapid catalyst deactivation and increase the operational complexity of the method. In this field, initial approaches from polymer experts (who are accustomed to managing large amounts of polymer in their methods) involve supporting homogeneous catalysts on inorganic supports to specifically control the morphology of the resulting polymer. R. Duchateau specifically describes transferring this strategy to ethylene oligomerization using silica-supported MAO for the selective trimerization of ethylene to 1-hexene via titanium complexes (ACS Catalysis, 2015, 5, 5068-5076). The polymer produced in this conversion is in the form of a non-sticky solid, which significantly reduces reactor fouling. Supported MAO is MAO that has already been immobilized on an inorganic support. It is generally insoluble in common organic solvents and can be used directly for catalyst formation. Such load-type MAOs are described, for example, in documents US2015353658, US20180354870, or US6211311.

[0004] The object of this invention is to provide a novel method for ethylene oligomerization, particularly ethylene tetramerization, which uses a catalytic composition that overcomes the problems of conventional catalytic compositions of the prior art, particularly catalytic compositions containing homogeneous MAO cocatalysts.

[0005] The applicant has surprisingly demonstrated that the use of compositions comprising chromium-based metal precursors, heteroatom ligands, supported MAO on an inorganic support, and additives in the form of aluminum-based compounds provides a method for selectively (tetramerizing ethylene into 1-octene) and controlling the morphology of polymer byproducts, thus addressing the problem of reactor fouling. The applicant has also surprisingly demonstrated that the order in which components are added to the catalytic reactor affects the productivity of the catalyst. Invention Overview This invention relates to an oligomerization method, preferably for the tetramerization of ethylene into 1-octene, carried out at a total pressure between 0.1 and 20.0 MPa, preferably between 0.1 and 15.0 MPa, more preferably between 0.5 and 8.0 MPa, and at a temperature between 15 and 200°C, preferably between 20 and 100°C, and most preferably between 25 and 80°C. The method comprises the following steps: a) Inject at least four of the following compounds into the oligomerization reactor: - Chromium-based metal precursors, - Heteroatom ligands, - Supported methylaluminoxanes on inorganic supports - Additives in the form of aluminum-based compounds, The chromium-based metal precursors and heteroatom ligands were never in contact with the supported methylaluminoxane on the inorganic support in the absence of additives in the form of aluminum-based compounds. b) Inject the feedstock containing ethylene into the oligomer reactor.

[0007] One advantage of the method according to the invention is particularly the control of the morphology of the polymer byproducts formed, thereby making them easy to remove from the reactor while maintaining a high level of 1-octene selectivity and high productivity. Invention Details According to the present invention, the expressions "of between ... and ..." and "...to ..." are equivalent and refer to the fact that the limit values ​​of the interval are included within the described numerical range. If this is not the case and if the limit values ​​are not included within the described range, the present invention provides such a statement.

[0009] For the purposes of this invention, various ranges of parameters for a given step, such as pressure ranges and temperature ranges, can be used individually or in combination. For example, for the purposes of this invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0010] Specific embodiments of the invention may be described below. They may be implemented individually or in combination, and there is no limitation on the combination where technically feasible.

[0011] Operating conditions and performance The oligomerization method according to the invention is carried out at a total pressure 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 between 15 and 200°C, preferably between 20 and 100°C, and very preferably between 25 and 80°C.

[0012] Ethylene is preferably injected into the reactor in gaseous form.

[0013] The ethylene-containing feedstock may advantageously also contain hydrogen to reduce selectivity for polyethylene (PE). Preferably, the volume percentage of hydrogen in the ethylene-containing feedstock is between 0% and 10%, more preferably between 0.1% and 5%, and very preferably between 1% and 3%.

[0014] The heat released by the reaction can be advantageously removed by any means known to those skilled in the art.

[0015] The oligomerization method according to the invention can advantageously be carried out in a discontinuous mode (also known as a batch mode) or a continuous mode.

[0016] In one embodiment, the at least four compounds are injected into a reactor, which is advantageously stirred by conventional mechanical means or by external recirculation, and wherein the ethylene is preferably reacted under temperature control.

[0017] In a preferred embodiment, the reactor is stirred at ambient temperature before the introduction of the ethylene-containing feedstock and after the introduction of the supported methylaluminoxane (SMAO) on the inorganic support, so as to immobilize the catalytically active compounds on the support. The stirring time is several minutes, for example, 5 minutes.

[0018] In one embodiment, the oligomerization method according to the invention further includes step c) of a catalytic composition present in the downstream of the reactor and in the oligomer effluent. This step can be performed by any means known to those skilled in the art.

[0019] Inject at least four compounds into the reactor The method according to the invention includes the step of injecting at least four of the following compounds into an oligomer reactor: - Chromium-based metal precursors; - Heteroatom ligands; - Supported methylaluminoxane (SMAO) on an inorganic carrier; - Additives in the form of aluminum-based compounds.

[0020] The injection of at least four compounds advantageously enables the formation of a catalytic composition to activate the oligomerization reaction.

[0021] Metal precursor "Metal precursor" is understood to refer to a compound containing a metal center and at least one ligand that stabilizes the precursor, said ligand being either charged or neutral, organic or inorganic.

[0022] In this application, the terms "metal precursor" or "chromium-based metal precursor" are used equivalently.

[0023] The compositions according to the invention comprise a chromium-based metal precursor, preferably selected from chromium(II) or chromium(III) salts. The chromium-based metal precursor preferably comprises one or more identical or different anions, selected from halide ions, carboxyl groups, acetylacetone, and alkoxy and aryloxy anions.

[0024] The halogen anion is preferably selected from chloride ions, bromide ions, fluoride ions or iodide ions.

[0025] The carboxylate anion is preferably selected from C3-C atoms with straight or branched chains. 20 C3-C is preferred. 15 C4-C is preferred. 12 C5-C is preferred. 10The alkyl chain contains a carboxylate group, wherein the alkyl chain is preferably unsubstituted or substituted with one or more fluorine, chlorine, or bromine atoms.

[0026] The alkoxy anion is preferably selected from C1-C atoms that have straight or branched chains and are cyclic or acyclic. 20 C2-C is preferred. 15 C3-C is preferred. 12 C4-C is preferred. 10 An alkoxy anion of an alkyl chain, wherein the alkyl chain is preferably unsubstituted or substituted with one or more fluorine, chlorine or bromine atoms.

[0027] The aryloxy anion is preferably selected from those having C5-C6 groups. 30 C5-C is preferred. 20 C6-C is preferred. 15 C6-C is preferred. 12 The aryl group is an aryloxy anion, wherein the aryl group is preferably unsubstituted or substituted with one or more fluorine, chlorine or bromine atoms.

[0028] In one embodiment, the chromium-based metal precursor used in this invention is a chromium(III) compound, but chromium(I) or chromium(II) compounds may also be suitable. Non-limiting examples include Cr(III) acetylacetone, Cr(III) trifluoroacetylacetone, Cr(III) hexafluoroacetylacetone, Cr(III) acetate, Cr(III) 2-ethylhexanoate, Cr(III) heptanoate, Cr(III) naphthenic acid, Cr(III) chloride, and Cr(III) bromide, alone or in mixtures, pure or diluted. Preferred Cr precursor derivatives are Cr(III) acetylacetone, Cr(III) 2-ethylhexanoate, and Cr(III) heptanoate, alone or in mixtures, pure or diluted. The chromium-based metal precursor is very preferably Cr(III) acetylacetone.

[0029] The concentration of the chromium-based metal precursor used in this oligomerization method is advantageously between 0.01 and 10,000 µmol / L, preferably between 0.1 and 1,000 µmol / L, and most preferably between 1 and 100 µmol / L.

[0030] heteroatom ligands "Heteroatom ligands" are understood to refer to ions or molecules that have functional groups (heteroatoms) that enable them to bind with one or more atoms of a metal precursor to impart the electronic and structural properties required for its relevant chemical transformation.

[0031] Heteroatom ligands advantageously conform to the following general formula: in R 1 R2 R 3 R 4 and R 5 They may be the same or different from each other and connected or unconnected to each other, and are selected from those having 1 to 15 carbon atoms (C1-C1). 15 ) and containing or not containing one or more heteroelements, cyclic or acycloalkyl groups and having 4 to 15 carbon atoms (C4-C5). 15 It contains or does not contain substituted or unsubstituted aryl groups of one or more heteroelements.

[0032] The heteroelement is preferably selected from iodine, bromine, chlorine, fluorine, nitrogen, sulfur and / or oxygen.

[0033] R 1 R 2 R 3 R 4 and R 5 Preferably the same or different, and selected from C1-C 10 Alkyl, C3-C 10 cycloalkyl and C5-C 15 Aryl.

[0034] R 1 R 2 R 3 R 4 and R 5 Preferably the same or different, and selected from C1-C6 alkyl, C3-C6 cycloalkyl and C5-C6 alkyl groups. 12 Aryl.

[0035] Group R 1 R 2 R 3 R 4 and R 5 Preferably, they are the same or different from each other, connected or not connected to each other, and selected from substituted or unsubstituted methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl and adamantyl; and / or phenyl, o-tolyl, m-tolyl, p-tolyl, mesitylene, 3,5-dimethylphenyl, 4-n-butylphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 2-isopropylphenyl, 4-methoxy-3,5-dimethylphenyl, 3,5-di-tert-butyl-4-methoxyphenyl, 2-chlorophenyl, 3-chlorophenyl, 4-chlorophenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 4-trifluoromethylphenyl, 3,5-di(trifluoromethyl)phenyl, benzyl, naphthyl, bisnaphthyl, pyridyl, furanyl or thiophene.

[0036] The heteroatom ligand is preferably selected from: (phenyl)2PN(methyl)P(phenyl)2, (phenyl)2PN(isopropyl)P(phenyl)2, (phenyl)2PN(phenyl)P(phenyl)2, (2-methoxyphenyl)2PN(isopropyl)P(phenyl)2, (2-methoxyphenyl)2PN(isopropyl)P(2-methoxyphenyl)2, (4-methoxyphenyl)2PN(isopropyl)P(4-methoxyphenyl)2, (2-fluorophenyl)2PN(isopropyl)P(2-fluorophenyl)2, (2-fluorophenyl)(phenyl)PN(isopropyl)P(2-fluorophenyl)2, (2-fluorophenyl)(phenyl)PN(isopropyl)P(2-fluorophenyl)(phenyl), (2-fluorophenyl)(phenyl)PN(isopropyl)P(2-fluorophenyl)(phenyl), (2-fluorophenyl)(phenyl)PN(isopropyl)P(phenyl)2.

[0037] The heteroatom ligands are very preferably selected from (phenyl)2PN(isopropyl)P(phenyl)2 and (2-fluorophenyl)2PN(isopropyl)P(2-fluorophenyl)2.

[0038] The molar ratio (expressed as HL / Cr) of the heteroatom ligand to the chromium-based metal precursor injected into the reactor is preferably between 0.5 and 10, more preferably between 0.8 and 6, more preferably between 1.0 and 4.0, and very preferably between 1.2 and 2.0.

[0039] SMAO loaded on an inorganic carrier SMAO consists of methylaluminoxane (MAO) immobilized on a solid support. The supported MAO enables the formation of a catalyst through ionic interactions between the metal complex and the supported MAO; this catalyst structure can be referred to as a floating cation. The catalytic reaction occurs at the surface or within the pores of the formed supported catalyst.

[0040] A description of the loaded MAO that can be used in the method according to the present invention and its production method can be found in Tailor-Made Polymers Via Immobilization ofΑ-Olefin Polymerization Catalysts, Documents under the name of King Fahd University of Petroleum and Minerals (US2015353658), Saudi Arabian Oil Company (US20180354870), or Equistar Chem LP (US6211311) are also mentioned.

[0041] In this application, the terms “loaded MAO” or “loaded MAO on an inorganic carrier” or “SMAO” are used in an equivalent manner.

[0042] MAO is advantageously obtained by controlled hydrolysis of trimethylaluminum (TMA) in an organic solvent such as toluene. The properties and composition of MAO used in this invention can be found in the literature. Methylalumoxane–History, Production, Properties, and Applications. Eur. J. Inorg. Chem. 2015, 19-43.

[0043] The MAO used in this invention advantageously comprises a polymer chain (PMAO) formed of Al and O atoms and methyl groups (-Me or -CH3) as defined by formula (ii): Wherein n can advantageously take a value between 1 and 60, preferably between 10 and 50. MAO advantageously also contains, in its structure, free or associated trimethylaluminum interacting with the PMAO chain. PMAO can have a linear, cyclic, or branched structure, as long as the polymer chain corresponds to the above formula.

[0044] In one embodiment, the MAO used in this invention contains a straight-chain and / or branched PMAO, as well as cyclic fragments and solvent residue molecules that interact with TMA (which is free or interacts with PMAO).

[0045] SMAO is advantageously obtained by the direct reaction of a solution of MAO with an inorganic support in an organic solvent.

[0046] The inorganic support is advantageously selected from silica, alumina, silica-alumina, zeolite, and TiO2. The support is preferably based on silica, and more preferably on SiO2. The silica advantageously contains Si-OH or Si-O-Si groups.

[0047] In one embodiment, the SiO2 is selected from high-purity silicon dioxide free of trace metals. The SiO2 preferably contains less than 10 ppm of Fe, Na, Al, and / or Ti.

[0048] In one embodiment, SiO2 may have a crystalline, amorphous, or partially crystalline structure. SiO2 preferably has an amorphous structure.

[0049] The inorganic carrier is advantageously a particle form defined by an average 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.

[0050] In a preferred embodiment, the inorganic carrier has a particulate or spherical shape. The inorganic carrier is very preferably spherical.

[0051] In a preferred embodiment, the inorganic carrier is in the form of particles defined by an average diameter between 1 and 100 μm, preferably between 10 and 50 μm, preferably between 20 and 40 μm, and preferably between 30 and 35 μm.

[0052] In one embodiment, the inorganic carrier is mesoporous. It has an average pore size preferably between 2 and 50 nm, more preferably between 10 and 40 nm, more preferably between 15 and 30 nm, and very preferably between 20 and 25 nm.

[0053] In one embodiment, the inorganic support has a pore volume 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. Pore volume is understood to refer to the volume measured by mercury porosimetry according to ASTM standard D4284-83 at a maximum pressure of 4000 bar (400 MPa) using a surface tension of 484 dynes / cm and a contact angle of 140°. Following the recommendation of the authors Jean Charpin and Bernard Rasneur in "Techniques de l'ingénieur, traité analyze et caractérisation" [Techniques of the engineer, analytical and characterization treatment], pages 1050-5, a wetting angle of 140° is taken.

[0054] In one embodiment, the inorganic carrier has a range of 1 to 600 m 2 Between / g, preferably between 100 and 500 m 2 Between / g, more preferably between 200 and 400 m 2 Between / g, and very preferably between 300 and 350 m 2 Specific surface area between / g. Specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method and measured by nitrogen adsorption analysis.

[0055] The aluminum content of SMAO, relative to its total mass, is advantageously between 1 wt% and 25 wt%, preferably between 5 wt% and 15 wt%, more preferably between 8 wt% and 12 wt%, and very preferably between 9 wt% and 11 wt%. This ensures that SMAO possesses good properties, such as the ability to prevent catalyst leaching into the solution.

[0056] The molar ratio of aluminum to chromium of the chromium-based metal precursor of the supported methylaluminoxane on an inorganic carrier injected into the reactor (expressed as Al) SMAO / Cr) is advantageously greater than 250.

[0057] Al SMAO The preferred Al / Cr molar ratio is greater than 250 and less than 750. SMAO The / Cr molar ratio is calculated as the ratio between the number of moles of aluminum contained in SMAO and the number of moles of chromium contained in the precursor.

[0058] Additives in the form of aluminum-based compounds In this application, the terms “additive” or “additive in the form of aluminum-based compounds” are used in an equivalent manner.

[0059] In one embodiment, the additive in the form of an aluminum-based compound is of formula AI(R) 6 Compounds of 3, wherein R 6 Independently selected from C1-C 12 Alkyl, C1-C 12 Alkyl groups and halogens. R 6 Preferably selected independently from C1-C 10 Alkyl, C1-C 10 Alkoxy group, preferably C1-C6 alkyl, C1-C6 alkoxy group and chlorine or bromine atom. R 6 Preferably, it is an alkyl and / or alkoxy group selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl and the corresponding alkoxy group. 6 Preferably, the alkyl and / or alkoxy groups are selected from ethyl, propyl, isopropyl, n-butyl, and tert-butyl and the corresponding alkoxy groups.

[0060] The additives in the form of aluminum-based compounds are preferably selected from aluminum oxanes, such as methylaluminoxane (MAO), modified methylaluminoxane (MMAO), or ethylaluminoxane (EAO), alone or in mixtures, or alkylaluminum, such as trimethylaluminum (TMA), triethylaluminum (TEA), triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-tert-butylaluminum, trihexylaluminum, trioctylaluminum, diethylethoxyaluminum and dimethylethoxyaluminum, methylaluminum dichloride, ethylaluminum dichloride, dimethylaluminum chloride, diethylaluminum chloride, or ethylsesquichloride.

[0061] Additives in the form of aluminum-based compounds are more preferably selected from methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), alone or as a mixture.

[0062] In one embodiment, the composition of the MAO that can be used as an additive is equivalent to the composition of the MAO as described above before it is loaded onto the inorganic carrier.

[0063] Additives in the form of aluminum-based compounds are very preferably selected from modified methylaluminoxanes (MMAO). Non-limiting examples of alternative MMAOs include MMAO-3A, ​​MMAO-7, or MMAO-21.

[0064] In a preferred embodiment, the additive is MMAO-3A. ​​MMAO-3A is advantageously obtained via controlled hydrolysis of TMA in the presence of triisobutylaluminum (TIBA) in a manner similar to MAO, which imparts improved stability of the compound in alkane solvents such as heptane or cyclohexane. MMAO-3A advantageously comprises Al and O atoms and a methyl group (-Me or -CH3) and / or an isobutyl group (-...) as defined by the following formula. i The polyalkylaluminoxane (PAAO) polymer chain formed by Bu: Wherein n and m can advantageously take values ​​between 1 and 60, preferably between 10 and 50. MMAO-3A advantageously also contains, in its structure, free or associated trimethylaluminum interacting with the PAAO chain, and / or free or associated triisobutylaluminum interacting with the PAAO chain. PAAO can have a linear, cyclic, or branched structure, as long as the polymer chain corresponds to the above formula.

[0065] As described above for MAO, MMAO-3A used as an additive consists of straight-chain and / or branched PAAO, as well as cyclic fragments and solvent residues that interact with TMA or TIBA (which are free or interact with PAAO).

[0066] The molar ratio of aluminum to chromium in the chromium-based metal precursor of the additive in the form of aluminum-based compounds injected into the reactor (expressed as Al) 添加剂 / Cr) is advantageously greater than 200.

[0067] Al 添加剂 The / Cr molar ratio is advantageously greater than 200 and less than or equal to 10,000, preferably between 275 and 5,000, more preferably between 300 and 3,000, and very preferably between 325 and 2,000.

[0068] Al 添加剂 The / Cr molar ratio is calculated as the ratio between the number of moles of aluminum contained in the additive and the number of moles of chromium contained in the precursor.

[0069] Optional solvents In one embodiment, a solvent is additionally injected into the reactor. Solvents selected from organic solvents, particularly those selected from saturated or unsaturated, cyclic or acyclic hydrocarbons, can be used.

[0070] The solvent is advantageously selected from halogenated solvents and saturated or unsaturated, cyclic or acyclic hydrocarbons containing 1 to 20 carbon atoms, preferably 1 to 15 carbon atoms, and more preferably 4 to 15 carbon atoms.

[0071] The solvent is preferably selected from butane, isobutane, pentane, hexane, heptane, cyclohexane, methylcyclohexane, 2,2,4-trimethylpentane, dichloromethane, toluene, xylene, dichloroethane, chlorobenzene, and dichlorobenzene, either pure or as a mixture. More preferably, the solvent is hexane, heptane, cyclohexane, methylcyclohexane, 2,2,4-trimethylpentane, and isobutane.

[0072] In one embodiment, the solvent is selected from supercritical solvents. Supercritical solvents are preferably selected from supercritical propane.

[0073] In a preferred embodiment, the solvent may be selected from the product of the oligomerization reaction.

[0074] The at least four compounds are used in the reactor. In the method according to the invention, the chromium-based metal precursor and heteroatom ligand are never contacted with the supported methylaluminoxane on the inorganic support in the absence of additives in the form of aluminum-based compounds.

[0075] In one embodiment, the method is carried out in a discontinuous mode in a reactor, wherein the at least four compounds are injected into the reactor in a specific order to avoid contact between the metal precursor and heteroatom ligand and SMAO in the absence of additives, the injection being carried out in the following order: i) Metal precursors and heteroatom ligands, ii) Additives, iii) SMAO; or i) additives, ii) metal precursors and heteroatom ligands, (iii) SMAO; Or i) additives, ii) SMAO, iii) metal precursors and heteroatom ligands; Or i) SMAO, ii) additives, iii) metal precursors and heteroatom ligands.

[0076] This implementation plan is, for example, in Figure 5 and 6 As shown in the image.

[0077] In another embodiment where the method is carried out in a discontinuous mode in the reactor, two or three of the at least four compounds are co-injected into the reactor in a specific order to avoid contact between the metal precursor and heteroatom ligand and SMAO in the absence of additives. This injection is carried out in the following order: i) Metal precursors, heteroatom ligands and additives; ii) SMAO; Or i) SMAO, ii) metal precursors, heteroatom ligands and additives; Or i) additives and SMAO, ii) metal precursors and heteroatom ligands; Or i) metal precursors and heteroatom ligands, ii) additives and SMAO.

[0078] In one embodiment, the method is carried out in a continuous mode in a reactor, wherein the at least four compounds are mixed upstream of the reactor in a specific order using any technique known to those skilled in the art to avoid contact between the metal precursor and heteroatom ligand and SMAO in the absence of additives. As a non-limiting example, the injection includes the following steps: i) Mix the metal precursor, heteroatom ligand and additive in mixer 1; ii) Mix the solution exiting mixer 1 and SMAO in mixer 2; iii) Inject the solution exiting mixer 2 into the reactor. Alternatively, i) mix SMAO and additives in mixer 1, ii) mix the solution leaving mixer 1, the metal precursor and heteroatom ligand in mixer 2, and iii) inject the solution leaving mixer 2 into the reactor.

[0079] These implementation schemes, for example, are in Figure 8 and 9 As shown in the image.

[0080] In another embodiment where the method is carried out in a continuous mode in a reactor, one or more of the at least four compounds are directly injected into the reactor using any technique known to those skilled in the art, to avoid contact between the metal precursor and heteroatom ligand and SMAO in the absence of additives. As a non-limiting example, this injection includes the following steps: i) Mix the metal precursor, heteroatom ligand and additive in mixer 1; ii) Inject the solution leaving mixer 1 into the reactor; iii) Inject SMAO directly into the reactor. Alternatively, i) mix SMAO and additives in mixer 1, ii) inject the solution leaving mixer 1 into the reactor, or iii) inject the metal precursor and ligand directly into the reactor.

[0081] These implementation schemes, for example, are in Figure 10 and 11 As shown in the image.

[0082] The applicant has surprisingly demonstrated that the presence of additives during contact between SMAO and the metal precursor / heteroatom ligand pair enables high productivity, expressed in terms of product quality in chromium mass per hour.

[0083] The applicant has surprisingly demonstrated that the presence of additives during contact between SMAO and the metal precursor / heteroatom ligand pair enables improved productivity, expressed as product mass per unit mass of chromium per hour.

[0084] List of Attached Figures Figure 1 This is a photograph of the agitator blades in the reactor at the end of the ethylene tetramerization process according to Example 2. "Sticky" polymer byproducts were observed on the agitator, which were difficult to remove and caused fouling in the reactor.

[0085] Figure 2 It comes from Figure 1 Scanning electron microscopy images of the morphology of polymer byproducts. Uncontrolled morphology of the polymer exhibits "filamentous" structural features.

[0086] Figure 3 This is a photograph of the agitator blades of the reactor at the end of the ethylene tetramerization process according to Examples 3, 4, 5, 6, and 7. Particulate polymer byproducts were observed on the agitator, which were easily removed and did not cause fouling in the reactor.

[0087] Figure 4 It comes from Figure 3 Scanning electron microscopy images of the morphology of polymer byproducts. The controlled morphology of the polymer exhibits a “particulate” structural characteristic.

[0088] Figure 5 A method according to one embodiment of the invention is described in a discontinuous mode, wherein the at least four compounds are injected into reactor R1 in the following order: i) metal precursor and heteroatom ligand, ii) additive, iii) SMAO.

[0089] Figure 6 A method according to one embodiment of the invention is described in a discontinuous mode, wherein the at least four compounds are injected into reactor R1 in the following order: i) additives, ii) SMAO, iii) metal precursors and heteroatom ligands.

[0090] Figure 7 A method according to an embodiment of the invention in a discontinuous mode is described, wherein the at least four compounds are injected into reactor R1 in the following order: i) metal precursor and heteroatom ligand, ii) SMAO, iii) additive.

[0091] Figure 8A method according to one embodiment of the invention in continuous mode is described, comprising the steps of: i) mixing a metal precursor, a heteroatom ligand and an additive in a mixer M1; ii) mixing a solution exiting mixer M1 and SMAO in a mixer M2; and iii) injecting the solution exiting mixer M2 into a reactor R1.

[0092] Figure 9 A method according to one embodiment of the invention in continuous mode is described, comprising the steps of: i) mixing SMAO and additives in mixer M1, ii) mixing the solution exiting mixer M1, the metal precursor and the heteroatom ligand in mixer M2, and iii) injecting the solution exiting mixer M2 into reactor R1.

[0093] Figure 10 A method according to one embodiment of the invention in continuous mode is described, comprising the steps of: i) mixing a metal precursor, a heteroatom ligand and an additive in a mixer M1; ii) injecting the solution exiting the mixer M1 into a reactor R1; and iii) injecting SMAO directly into the reactor.

[0094] Figure 11 A method according to one embodiment of the invention in continuous mode is described, comprising the steps of: i) mixing SMAO and additives in mixer M1, ii) injecting the solution exiting mixer M1 into a reactor, and iii) directly injecting the metal precursor and ligand into the reactor.

[0095] Figure 12 A method according to an embodiment of the invention in continuous mode is described, comprising the steps of: i) mixing an additive and SMAO in a mixer M1, ii) mixing a solution exiting mixer M1, a metal precursor, and a heteroatom ligand in a mixer M2, and iii) injecting the solution exiting mixer M2 into a reactor R1.

[0096] Reference numerals: R = reactor; M = mixer; P = chromium-based metal precursor; L = heteroatom ligand; A = additive in the form of aluminum-based compound. Example

[0097] Example 1: Method for preparing SMAO containing 10.1% by weight Al 3 g of silica (average diameter = 33 µm; average pore size D) to be pre-dried at 80 °C for 2 hours under reduced pressure for polymerization. P = 21 nm; pore volume V P = 1.56 mL / g; specific surface area S BET = 315 m 2Weigh (g) into Schlenk in the glove box.

[0098] Under an argon gas flow, the silica was impregnated with 4.7 mL (corresponding to the total pore volume) of anhydrous toluene. Then, 13 mL of a solution of MAO in toluene (4.65 wt% Al, d = 0.895 g / mL, theoretical value 0.54 g Al) was added. The mixture became a translucent liquid gel.

[0099] The mixture was heated at 80°C for 4 hours with manual stirring every 15 minutes. After 4 hours, toluene was evaporated and the resulting white powder was dried at 80°C for 1 hour under reduced pressure.

[0100] The Al content in SMAO was determined by ICP-AES: wt% Al = 10.1 ± 0.5%.

[0101] Example 2 (Comparative): A homogeneous solution of MMAO-3A in cyclohexane was used as a cocatalyst (relative to Cr, Ethylene tetramerization method with 1100 equivalent Al) Weigh 14.0 mg Cr(acac)2 and 28.0 mg N,N-bis[di(2-fluorophenyl)]phosphine isopropylamine (heteroatom ligand PNP) into a Schlenk container in a glove box. Add 20.0 mL of toluene (Cr concentration = 2 mmol / L; PNP concentration = 2.8 mmol / L; PNP / Cr ratio = 1.4) under an argon flow.

[0102] 93 mL of cyclohexane was introduced into a 250 mL reactor, with the internal temperature pre-set to 25 °C and the ethylene pressure pre-set to 0.5 bar (0.05 MPa). After introducing 5 bar (0.5 MPa) of ethylene gas, the solvent was saturated with ethylene by stirring at 1500 rpm for 1 minute. The reactor pressure was then reduced again to 0.5 bar (0.05 MPa) and stirring was stopped. Then, 5 mL of molecularly sieved dried nonane (3.6 g, internal standard), 1.2 mL of MMAO-3A solution in cyclohexane (7 wt% Al; d = 0.803 g / mL, approximately 2.2 mmol Al), and 1.0 mL of Cr / PNP solution (2 µmol Cr, 2.8 µmol PNP) were introduced. The ethylene inlet valve was then opened (pressure 30 bar (3 MPa), stirring was started, and the reactor heating setpoint was raised to 45 °C.

[0103] At the end of the experiment, the ethylene supply was cut off, the mixture was cooled to 20°C, and then the gas phase was vented. The reactor was then opened. The liquid was transferred to a bottle containing 1.00 mL of 10% H₂SO₄ solution. The organic phase sample was removed and filtered for analysis. The results are described in Table 1.

[0104] Example 3 (Comparative): Using a suspension of SMAO in cyclohexane as a co-catalyst (relative to Cr, 1100 when Ethylene tetramerization method of (amount of Al) 588 mg of SMAO containing 10.1% Al, prepared according to Example 1 (i.e., 59.4 mg Al (2.2 mmol Al), was weighed into a Schlenk container in a glove box. Then 5.0 mL of cyclohexane was introduced to form a suspension.

[0105] 89 mL of cyclohexane was introduced into a 250 mL reactor, with the internal temperature pre-set to 25 °C and the ethylene pressure pre-set to 0.5 bar (0.05 MPa). After introducing 5 bar (0.5 MPa) of ethylene gas, the solvent was saturated with ethylene by stirring at 1500 rpm for 1 minute. The reactor pressure was then reduced again to 0.5 bar (0.05 MPa) and stirring was stopped. Then, 5.0 mL of molecularly sieved dried nonane (3.6 g, internal standard), a suspension of SMAO in 5.0 mL of cyclohexane, and 1.0 mL of a Cr / PNP solution containing 2 mmol / L Cr with a PNP / Cr ratio of 1.4 (2 µmol Cr, 2.8 µmol PNP) were introduced. The reactor was then stirred at 250 rpm for 5 minutes at 25 °C under an ethylene pressure of 2 bar (0.2 MPa). The ethylene inlet valve was then opened (pressure 30 bar (3 MPa), stirring was started, and the reactor heating setpoint was raised to 45 °C.

[0106] At the end of the experiment, the ethylene supply was cut off, the mixture was cooled to 20°C, and then the gas phase was vented. The reactor was then opened. The liquid was transferred to a bottle containing 1.00 mL of 10% H₂SO₄ solution. The organic phase sample was removed and filtered for analysis. The results are described in Table 1.

[0107] Example 4 (Invention): Using a suspension of SMAO in cyclohexane as a co-catalyst (relative to Cr, 400 ppm) Ethylene tetramerization method using Al and MMAO-3A as additives (1000 equivalents of Al relative to Cr). Order of addition: i) MMAO-3A, ​​ii) Cr / PNP, iii) SMAO 107 mg of SMAO containing 10.1% Al, prepared according to Example 1 (i.e., 10.8 mg Al (0.4 mmol Al), was weighed into a Schlenk container in a glove box. Then 5.0 mL of cyclohexane was introduced to form a suspension.

[0108] 1.0 mL of MMAO-3A (7 wt% Al, d = 0.803 g / mL, approximately 2.1 mmol Al) in cyclohexane and 20 mL of anhydrous cyclohexane were added to a second Schlenk under Ar conditions to form a 0.10 mol / L solution.

[0109] 80 mL of cyclohexane was introduced into a 250 mL reactor, with the internal temperature pre-set to 25 °C and the ethylene pressure pre-set to 0.5 bar (0.05 MPa). After introducing 5 bar (0.5 MPa) of ethylene gas, the solvent was saturated with ethylene by stirring at 1500 rpm for 1 minute. The reactor pressure was then reduced again to 0.5 bar (0.05 MPa) and stirring was stopped. Then, 5.0 mL of molecularly sieved nonane (3.6 g, internal standard), 10.0 mL of 0.1 mol / L MMAO-3A solution (i.e., 1.0 mmol), and 1.0 mL of a Cr / PNP solution containing 1 mmol / L Cr with a PNP / Cr ratio of 1.4 (1 µmol Cr, 1.4 µmol PNP) were introduced. The mixture was stirred at 250 rpm for 5 minutes at 25 °C. The SMAO suspension was then injected into 5.0 mL of cyclohexane. The reactor was then stirred for 5 minutes at 250 rpm at 25°C under an ethylene pressure of 2 bar (0.2 MPa). The ethylene inlet valve was then opened (pressure 30 bar (3 MPa)), stirring was started, and the reactor heating setpoint was raised to 45°C.

[0110] At the end of the experiment, the ethylene supply was cut off, the mixture was cooled to 20°C, and then the gas phase was vented. The reactor was then opened. The liquid was transferred to a bottle containing 1.00 mL of 10% H₂SO₄ solution. The organic phase sample was removed and filtered for analysis. The results are described in Table 1.

[0111] Example 5 (Invention): Using a suspension of SMAO in cyclohexane as a co-catalyst (relative to Cr, 400 ppm) Ethylene tetramerization method using Al and MMAO-3A as additives (1000 equivalents of Al relative to Cr). Order of addition: i) Cr / PNP, ii) MMAO-3A, ​​iii) SMAO This experiment was conducted under conditions similar to Example 4, but with the order of component addition modified: i) 1.0 mL of a Cr / PNP solution containing 1 mmol / L Cr and having a PNP / Cr ratio of 1.4 (1 µmol Cr, 1.4 µmol PNP), ii) 10.0 mL of a 0.1 mol / L MMAO-3A solution (i.e., 1.0 mmol), and then stirred at 250 rpm and 25°C for 5 minutes, and iii) a suspension containing 107 mg SMAO in 5.0 mL of cyclohexane was injected, and the mixture was stirred at 250 rpm for 5 minutes at 25°C under an ethylene pressure of 2 bar (0.2 MPa).

[0112] Example 6 (Invention): Using a suspension of SMAO in cyclohexane as a co-catalyst (relative to Cr, 400 ppm) Ethylene tetramerization method using Al and MMAO-3A as additives (1000 equivalents of Al relative to Cr). Order of addition: i) MMAO-3A, ​​ii) SMAO, iii) Cr / PNP This experiment was conducted under conditions similar to Example 4, but with the order of component addition modified: i) 10.0 mL of 0.1 mol / L MMAO-3A solution (i.e., 1.0 mmol) was added; ii) a suspension containing 107 mg SMAO in 5.0 mL of cyclohexane was injected and stirred at 250 rpm for 5 minutes at 25°C under an ethylene pressure of 2 bar (0.2 MPa); and iii) 1.0 mL of a Cr / PNP solution containing 1 mmol / L Cr and having a PNP / Cr ratio of 1.4 (1 µmol Cr, 1.4 µmol PNP) was added, and the mixture was then stirred at 250 rpm and 25°C for 5 minutes.

[0113] Example 7 (Comparative): Using a suspension of SMAO in cyclohexane as a co-catalyst (400 equivalents relative to Cr). Ethylene tetramerization method using Al) and MMAO-3A as additives (1000 equivalents of Al relative to Cr). Order of addition: i) SMAO, ii) Cr / PNP, iii) MMAO-3A This experiment was conducted under conditions similar to Example 2, but with a modified order of component addition: i) a suspension containing 107 mg SMAO in 5.0 mL of cyclohexane was injected; ii) 1.0 mL of a Cr / PNP solution containing 1 mmol / L Cr and having a PNP / Cr ratio of 1.4 (1 µmol Cr, 1.4 µmol PNP) was added, and the mixture was stirred at 250 rpm for 5 minutes at 25°C under an ethylene pressure of 2 bar (0.2 MPa); and iii) 10.0 mL of a 0.1 mol / L MMAO-3A solution (i.e., 1.0 mmol) was added, and the mixture was stirred at 250 rpm and 25°C for 5 minutes.

[0114] Table 1 Example Time (h) The product formed (g) <![CDATA[Productivity (g / g Cr / h)]]> C6(%) C8(%) 1-C8*(%) C10(%) C12+(%) PE (%) PE appearance 2 0.27 36.7 1 307 500 31.2 60.2 99.8 1.6 6.9 0.1 viscosity 3 1.0 18.6 179 000 6.5 7.0 100 0.5 1.6 84.4 controlled 4 0.36 44.6 2 393 500 24.4 62.2 99.7 1.8 10.9 0.7 controlled 5 0.25 37.9 2 914 500 28.0 62.1 99.8 1.3 7.4 1.1 controlled 6 0.33 37.3 2 152 000 26.1 63.8 99.7 1.2 8.0 0.8 controlled 7 0.66 34.4 993 000 22.3 68.1 99.8 1.0 7.9 0.6 controlled * Represents the percentage (selectivity) of 1-octene isomers in molecules with 8 carbon atoms (C8).

[0115] It was observed that the method according to the invention enables the acquisition of C8 in amounts greater than 50%, with near 100% selectivity for 1-octene, similar to prior art methods using homogeneous MAO, while obtaining a controlled polymer morphology (in this case, polyethylene, PE), which, unlike "sticky" PE filaments, does not clog the oligomerization reactor and can be easily removed from the reactor. It was also observed that contacting the metal precursor and heteroatom ligand with SMAO in the absence of additives resulted in a significant decrease in productivity to below 1 million.

Claims

1. An oligomerization method, preferably for the tetramerization of ethylene into 1-octene, carried out at a total pressure 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 between 15 and 200°C, preferably between 20 and 100°C, and most preferably between 25 and 80°C, the method comprising the following steps: a) Inject at least four of the following compounds into the oligomerization reactor: - Chromium-based metal precursors, - Heteroatom ligands, - Supported methylaluminoxanes on inorganic supports - Additives in the form of aluminum-based compounds, The chromium-based metal precursors and heteroatom ligands were never in contact with the supported methylaluminoxane on the inorganic support in the absence of additives in the form of aluminum-based compounds. b) Inject the feedstock containing ethylene into the oligomerization reactor.

2. The method of claim 1, wherein ethylene is injected into the reactor in gaseous form.

3. The method according to claim 1 or 2, wherein the ethylene-containing feedstock further contains hydrogen, and the volume percentage of hydrogen in the feedstock is between 0% and 10%, preferably between 0.1% and 5%, and most preferably between 1% and 3%.

4. The method according to any one of the preceding claims, wherein the at least four compounds are injected into a reactor, the reactor being stirred by conventional mechanical means or by external recirculation, and wherein the ethylene is preferably reacted under temperature control.

5. The method according to any one of the preceding claims, further comprising step c) of a catalytic composition present in the downstream of the reactor and in the oligomer effluent.

6. The method according to any one of the preceding claims, wherein the chromium-based metal precursor is acetylacetone Cr(III).

7. The method according to any one of the preceding claims, wherein the concentration of the chromium-based metal precursor used in the oligomerization method is between 0.01 and 10,000 µmol / L, preferably between 0.1 and 1,000 µmol / L, and most preferably between 1 and 100 µmol / L.

8. The method according to any one of the preceding claims, wherein the heteroatom ligand conforms to the following general formula: in R1, R2, R3, R4, and R5 may be the same as or different from each other and may be connected to each other or not, and are selected from cyclic or acyclic alkyl groups having 1 to 15 carbon atoms and containing or not containing one or more heteroelements, and substituted or unsubstituted aryl groups having 4 to 15 carbon atoms and containing or not containing one or more heteroelements.

9. The method according to any one of the preceding claims, wherein the carrier is based on silicon dioxide, and preferably SiO2.

10. The method according to any one of the preceding claims, wherein the aluminum content of the supported methylaluminoxane on the inorganic support is between 1 wt% and 25 wt%, preferably between 5 wt% and 15 wt%, more preferably between 8 wt% and 12 wt%, and very preferably between 9 wt% and 11 wt%, relative to the total mass of the supported methylaluminoxane on the inorganic support.

11. The method according to any one of the preceding claims, wherein the molar ratio of aluminum to chromium of the chromium-based metal precursor of the supported methylaluminoxane injected into the reactor on the inorganic carrier is greater than 250.

12. The method according to any one of the preceding claims, wherein the additive in the form of an aluminum-based compound is selected from methylaluminoxane or modified methylaluminoxane, alone or as a mixture.

13. The method of claim 12, wherein the additive is MMAO-3A.

14. The method according to any one of the preceding claims, wherein the molar ratio of aluminum in the aluminum-based compound form of the additive injected into the reactor to chromium in the chromium-based metal precursor is greater than 200.

15. The method according to any one of the preceding claims, wherein a solvent selected from saturated or unsaturated, cyclic or acyclic hydrocarbons is further injected into the reactor.

Images