Catalyst composition comprising chromium and supported methylaluminoxane

Abstract

This invention relates to catalyst compositions for the selective oligomerization of ethylene, particularly for the tetramerization of ethylene into 1-octene, comprising: - 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 composition has a molar ratio of aluminum in the supported methylaluminoxane on the inorganic support to chromium in the metal precursor greater than 250, and a molar ratio of aluminum in the additive to chromium in the metal precursor greater than 200.

Description

Technical Field

[0001] This invention relates to catalyst compositions based on chromium and supported methylaluminoxane (MAO), and their use in the selective oligomerization of ethylene, particularly in the tetramerization of ethylene into 1-octene. Existing technology

[0002] Linear-chain alpha-olefins (LAOs), containing four to more than 20 carbon atoms, are important feedstocks for the manufacture 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 classes of ethylene oligomerization methods using homogeneous catalysts: methods producing broadly distributed olefins (typically from C4 to C30), and selective methods producing 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, substantial progress has been made in recent years in controlling product distribution, favoring shorter truncated alpha-olefin distributions, or even selectively producing only one alpha-olefin. In this field, the tetramerization of ethylene to 1-octene via chromium-based homogeneous catalysts has led to numerous developments in recent years (PWNM van Leeuwen et al., Coordination Chemistry Reviews 255 (2011) 1499-1517). Systems known to result in the selective production of 1-octene include those described, for example, in documents WO2004056477, WO2004056478, or WO2004056479. These catalysts utilize Cr(III)-based metal precursors associated with PNP ligands (e.g., Ph2PN(iPr)PPh2), activated in situ via aluminum oxanes (MAO: methylaluminoxane; MMAO: modified methylaluminoxane; etc.). They result in the “selective” production of 1-octene (selectivity exceeding 60%). Other Cr-based catalytic systems have subsequently been developed, such as those described in documents WO2010034102, WO2011156892, or WO2011108772.

[0003] A major drawback of chromium-based catalytic systems used for ethylene oligomerization is the formation of a large amount of polymer along with the target olefin (1-octene). This formation of a viscous polymer leads to rapid catalyst deactivation and increases the difficulty of operating the method. A preliminary approach adopted in this field by polymer experts (who are accustomed to handling large amounts of polymer in their methods) involves supporting a homogeneous catalyst on an inorganic support to specifically control the morphology of the resulting polymer. Applying this strategy to ethylene oligomerization has been specifically described by R. Duchateau, using a silica-supported MAO for the selective trimerization of ethylene to 1-hexene by complexes of titanium (ACS Catalysis, 2015, 5, 5068-5076). The polymer generated in this conversion is a non-viscous solid, which significantly reduces reactor fouling. Supported MAO refers to MAO 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 catalyst composition for ethylene tetramerization that avoids the problems of conventional catalyst compositions in the prior art (especially those containing homogeneous MAO cocatalysts).

[0005] The applicant has demonstrated that, unexpectedly, the use of a composition comprising a chromium-based metal precursor, a heteroatom ligand, a supported MAO on an inorganic support, and an additive in the form of an aluminum-based compound, enables the production of a catalyst composition that is active and selective in the oligomerization of ethylene (ethylene tetramerization into 1-octene), while simultaneously allowing control over the morphology of polymerization byproducts, thereby addressing the problem of reactor fouling. Invention Overview This invention relates to a catalyst composition for the selective oligomerization of ethylene, particularly for the tetramerization of ethylene to 1-octene, comprising: - Chromium-based metal precursors; - Heteroatom ligands; -Methylaluminoxane supported on an inorganic carrier; - Additives in the form of aluminum-based compounds; The composition has an aluminum-to-chromium molar ratio in the supported methylaluminoxane on an inorganic carrier greater than 250, and an aluminum-to-chromium molar ratio in the additive greater than 200.

[0007] One advantage of the catalyst composition according to the invention is particularly the control of the morphology of the polymer byproducts formed, thereby facilitating their removal from the reactor while maintaining a high degree of selectivity for 1-octene. Invention Details According to the present invention, the expressions "between... and..." and "between... and..." are equivalent, and are intended to mean that the limit values ​​of the interval are included within the said numerical range. If this is not the case, and the limit values ​​are not included in the said range, the present invention provides such a description.

[0009] For the purposes of this invention, various parameter ranges (e.g., pressure ranges and temperature ranges) for a given step 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 in the following text. They may be implemented individually or combined together when technically feasible, without limitation on the combination.

[0011] Metal precursor "Metal precursor" is understood to refer to a compound containing a metal center and a ligand of at least one stable precursor, which can be charged or neutral, organic or inorganic.

[0012] In this application, the terms "metal precursor" and "chromium-based metal precursor" will be used in a manner equivalent to each other.

[0013] 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, acetylacetonate groups, and alkoxy and aryloxy anions.

[0014] The halogen anion is preferably selected from chloride ions, bromide ions, fluoride ions or iodide ions.

[0015] Carboxylate anions are preferably selected from those having C3–C 20 C3–C is preferred. 15 C4–C is preferred. 12 C5-C is preferred. 10 A carboxylate group of a straight-chain or branched alkyl chain, wherein the alkyl chain is preferably unsubstituted or substituted by one or more fluorine, chlorine or bromine atoms.

[0016] Alkoxy anions are preferably selected from those having C1–C 20 C2–C is preferred. 15 C3–C is preferred. 12 C4–C is preferred. 10An alkoxy anion of a straight or branched alkyl chain that is cyclic or acyclic, wherein the alkyl chain is preferably unsubstituted or substituted with one or more fluorine, chlorine or bromine atoms.

[0017] The aryloxy anion is preferably selected from those having C5–C 30 C5-C is preferred. 20 C6-C is preferred. 15 C6-C is preferred. 12 The aryl group has an aryloxy anion, wherein the aryl group is preferably unsubstituted or substituted by one or more fluorine, chlorine or bromine atoms.

[0018] 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 applicable. 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, in pure or diluted form. Preferred Cr precursor derivatives are Cr(III) acetylacetone, Cr(III) 2-ethylhexanoate, and Cr(III) heptanoate, alone or in mixtures, in pure or diluted form. The chromium-based metal precursor is most preferably Cr(III) acetylacetone.

[0019] heteroatom ligands The compositions according to the invention contain heteroatom ligands.

[0020] "Heteroatom ligands" are understood to refer to ions or molecules with functional groups (heteroatoms) that bind to one or more atoms of a metal precursor in order to impart the electronic and structural properties required for the relevant chemical transformation.

[0021] The heteroatom ligands advantageously correspond to the following general formula: in R 1 R 2 R 3 R 4 and R 5 They may be the same or different from each other, optionally connected to each other, and selected from those having 1 to 15 carbon atoms (C1–C4). 15 A cyclic or acyclic alkyl group, optionally containing one or more heteroelements, and having 4 to 15 carbon atoms (C4–C5). 15 A substituted or unsubstituted aryl group, optionally containing one or more heteroelements.

[0022] The heteroelement is preferably selected from iodine, bromine, chlorine, fluorine, nitrogen, sulfur and / or oxygen.

[0023] Preferably, R 1 R 2 R 3 R 4 and R 5 Same or different, and selected from C1–C 10 Alkyl groups, C3–C 10 Cycloalkyl groups and C5–C 15 Aryl group.

[0024] Preferably, R 1 R 2 R 3 R 4 and R 5 Same or different, and selected from C1–C6 alkyl groups, C3–C6 cycloalkyl groups and C5–C6 alkyl groups. 12 Aryl group.

[0025] Group R 1 R 2 R 3 R 4 and R 5 Preferably, they are the same as or different from each other, optionally linked together, and selected from substituted or unsubstituted methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl and adamantyl groups; 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-bis(trifluoromethyl)phenyl, benzyl, naphthyl, bisnaphthyl, pyridyl, furanyl and thiophene groups.

[0026] 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.

[0027] The heteroatom ligands are very preferably selected from (phenyl)2PN(isopropyl)P(phenyl)2 and (2-fluorophenyl)2PN(isopropyl)P(2-fluorophenyl)2.

[0028] Preferably, the molar ratio (HL / Cr) of the heteroatom ligand to the chromium-based metal precursor is 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.

[0029] Supported MAO cocatalyst Supported MAO consists of methylaluminoxane (MAO) immobilized on a solid support. During the use of the catalyst composition, the supported MAO enables the formation of a catalyst via 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 on the surface or in the pores of the formed supported catalyst.

[0030] The catalyst composition according to the present invention comprises a supported methylaluminoxane (denoted as SMAO) on an inorganic support.

[0031] Descriptions of supported MAOs that can be used in catalyst compositions according to the present invention and methods for their production can be found in the book "Tailor-Made Polymers Via Immobilization of Alpha-Olefin Polymerization Catalysts", document US2015353658 of King Fahd University of Petroleum and Minerals, document US20180354870 of Saudi Arabian Oil Company, or document US6211311 of Equistar Chem LP.

[0032] In this application, the terms “loaded MAO”, “loaded MAO on an inorganic carrier” or “SMAO” will be used in a similar manner.

[0033] The MAO is advantageously obtained by the controlled hydrolysis of trimethylaluminum (TMA) in an organic solvent (e.g., toluene). The properties and composition of the MAO used in this invention can be found in the document "Methylalumoxane – History, Production, Properties, and Applications". Eur. J. Inorg. Chem Found in 2015, 19-43.

[0034] The MAO used in this invention advantageously comprises a polymer chain (PMAO) formed of Al and O atoms and methyl groups (-Me or -CH3), defined by the following formula: [Chemical Formula 2] Wherein n can advantageously take a value between 1 and 60, preferably between 10 and 50. MAO also advantageously contains associated trimethylaluminum in its structure, which is either free or interacts with the PMAO chain. The PMAO can have a linear, cyclic, or branched structure, provided that the polymer chain corresponds to the above formula.

[0035] In one embodiment, the MAO used in this invention contains a straight-chain and / or branched PMAO structure, but also contains cyclic fragments and residual molecules of solvents that interact with TMA (which is free or interacts with PMAO).

[0036] SMAO is advantageously obtained by the direct reaction of MAO solution with an inorganic carrier in an organic solvent.

[0037] Inorganic carriers are advantageously selected from silica, alumina, silica-alumina, zeolite and TiO2.

[0038] The support is preferably based on silicon dioxide, and more preferably SiO2. Silicon dioxide advantageously contains Si-OH or Si-O-Si groups.

[0039] 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.

[0040] In one embodiment, the SiO2 may have a crystalline, amorphous, or partially crystalline structure. Preferably, the SiO2 has an amorphous structure.

[0041] The inorganic carrier is advantageously in particulate form, which is defined by an average diameter of less than or equal to 200 μm, preferably less than or equal to 150 μm, preferably less than or equal to 100 μm, and most preferably less than or equal to 50 μm.

[0042] In a preferred embodiment, the inorganic support has a granular or spherical morphology. A spherical morphology is highly preferred for the inorganic support.

[0043] In a preferred embodiment, the inorganic carrier is in the form of particles, which are 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.

[0044] In one embodiment, the inorganic carrier is inherently 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.

[0045] In one embodiment, the inorganic carrier 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. The pore volume is understood to refer to the volume measured by the mercury intrusion pore method at a maximum pressure of 4000 bar (400 MPa) according to ASTM standard D4284-83, using a surface tension of 484 dynes / cm and a contact angle of 140°. Following the recommendations of "Techniques de l'ingénieur, traité analyze et caractérisation" [Techniques of the engineer, analytical and characterization treatise], pp. 1050-5, by authors Jean Charpin and Bernard Rasneur, a wetting angle of 140° is adopted.

[0046] 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 The concentration is between 300 and 350 m / g, and very preferably between 300 and 350 m / g. 2 The specific surface area is between / g. The specific surface area was calculated by the Brunauer-Emmett-Teller (BET) method and measured by nitrogen adsorption analysis.

[0047] The aluminum content of SMAO 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%, relative to the total weight of SMAO. This ensures that SMAO will have good properties, such as the ability to prevent catalyst leaching into the solution.

[0048] In the tetramerization of ethylene, the molar ratio of aluminum in the supported methylaluminoxane (SMAO) on the inorganic support to chromium in the metal precursor (denoted as Al) SMAO (Cr) may have a significant impact on catalyst productivity and the viscous properties of the resulting polymer.

[0049] The Al SMAO The / Cr molar ratio is preferably greater than 250 and less than 750. The Al SMAO The / Cr molar ratio is calculated as the ratio between the number of moles of aluminum in the SMAO and the number of moles of chromium in the precursor.

[0050] Surprisingly, the applicant has indicated that the Al value is greater than or equal to 750. SMAO The / Cr ratio leads to active species poisoning by reducing catalyst productivity. Productivity is defined as the weight of the product formed divided by the weight of Cr per hour. Furthermore, Al values ​​less than or equal to 250... SMAO The / Cr ratio leads to the leaching of active species and loss of polymer morphology control.

[0051] Additives in the form of aluminum-based compounds The compositions according to the invention contain additives in the form of aluminum-based compounds.

[0052] In this application, the terms “additive” or “additive in the form of an aluminum-based compound” will be used in a similar manner.

[0053] In one embodiment, the additive, in the form of an aluminum-based compound, is of the formula Al(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 comprises an alkyl and / or alkoxy group, selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, pentyl, hexyl, heptyl, and octyl, as well as the corresponding alkoxy group. 6 Preferably, the alkyl and / or alkoxy groups are selected from ethyl, propyl, isopropyl, n-butyl, and tert-butyl groups and the corresponding alkoxy groups.

[0054] The additives in the form of aluminum-based compounds are preferably selected from aluminum oxanes, such as methylaluminoxane (MAO), modified methylaluminoxanes (MMAOs), or ethylaluminoxane (EAO), 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 ethylaluminum sesquichloride.

[0055] Additives in the form of aluminum-based compounds are preferably selected from methylaluminoxanes (MAO) or modified methylaluminoxanes (MMAOs), alone or as a mixture.

[0056] 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 being loaded onto the inorganic carrier.

[0057] The additive, which is in the form of an aluminum-based compound, is very preferably selected from modified methylaluminoxanes (MMAOs). Non-limiting examples of alternative MMAOs include MMAO-3A, ​​MMAO-7, or MMAO-21.

[0058] In one embodiment, the additive, in the form of an aluminum-based compound, is MMAO mixed with a compound selected from TMA, TEA, methylaluminum dichloride, ethylaluminum dichloride, dimethylaluminum chloride, diethylaluminum chloride, or ethylaluminum sesquichloride.

[0059] In one embodiment, the additive, which is in the form of an aluminum-based compound, is MMAO mixed with TEA.

[0060] In a preferred embodiment, the additive is MMAO-3A. ​​Similar to MAO, MMAO-3A is advantageously obtained by controlled hydrolysis of TMA in the presence of triisobutylaluminum (TIBA), which imparts increased stability to the compound in alkane solvents (e.g., heptane or cyclohexane). MMAO-3A advantageously comprises a polyalkylaluminoxane (PAAO) polymer chain formed from Al and O atoms, as well as methyl groups (-Me or -CH3) and / or isobutyl (-iBu) groups, defined by the following formula: Wherein n and m can advantageously take values ​​between 1 and 60, preferably between 10 and 50. MMAO-3A also advantageously contains associated trimethylaluminum (which is free or interacts with the PAAO chain) and / or associated triisobutylaluminum (which is free or interacts with the PAAO chain) in its structure. PAAO can have a linear, cyclic, or branched structure, provided that the polymer chain corresponds to the above formula.

[0061] MMAO-3A, ​​used as an additive, consists of straight-chain and / or branched PAAO, as well as cyclic fragments and solvent residue molecules that interact with TMA or TIBA (which are free or interact with PAAO), as described above for MAO.

[0062] Advantageously, the molar ratio of aluminum in the additive to chromium in the metal precursor (denoted as Al) 添加剂 The Cr content is 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.

[0063] Al 添加剂The / Cr molar ratio is calculated as the ratio between the number of moles of aluminum in the additive and the number of moles of chromium in the precursor.

[0064] Without being bound by any particular theory, the presence of additives in the form of aluminum-based compounds is crucial for activating the metal precursor and generating the active species involved in the catalytic reaction. Supported MAO exhibits significantly less associated TMA compared to MAO or MMAO in solution. In this context, the presence of additives serves to achieve the alkylation of the metal complex and trigger the catalytic reaction. Furthermore, the additives allow for the protection of the catalytically active species from the formation of large amounts of polyethylene (PE). A minimum amount of additive is required to ensure the activation of the metal precursor in order to produce 1-octene as the major reaction product.

[0065] Optional solvents The catalyst composition according to the invention may further comprise a solvent. Solvents selected from organic solvents, and particularly from saturated or unsaturated, cyclic or acyclic hydrocarbons, may be used.

[0066] The solvent (one or more) 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.

[0067] 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 in pure form or as a mixture. More preferably, the solvent is selected from hexane, heptane, cyclohexane, methylcyclohexane, 2,2,4-trimethylpentane, and isobutane.

[0068] In one embodiment, the solvent is selected from supercritical solvents. The supercritical solvent is preferably selected from supercritical propane.

[0069] In one embodiment, the solvent is selected from the product of an oligomerization reaction.

[0070] oligomerization method The present invention also relates to a method for oligomerizing ethylene, preferably for tetramerizing ethylene into 1-octene, comprising contacting an ethylene-containing feedstock with a catalyst composition according to the invention in an oligomerization reactor.

[0071] Advantageously, the concentration of the metal precursor used in the oligomerization method according to the invention is between 0.01 and 10,000 µmol / l, more preferably between 0.1 and 1,000 µmol / l, and very preferably between 1 and 100 µmol / l.

[0072] The method can be advantageously carried out in the presence of the solvent described above.

[0073] Advantageously, the oligomerization method according to the invention is carried out at a total pressure of 0.1 to 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 15°C to 200°C, preferably between 20°C and 100°C, and very preferably between 25°C and 60°C.

[0074] The raw material used in the method is ethylene, preferably ethylene in gaseous form.

[0075] Advantageously, ethylene is injected into the reactor after the catalyst composition according to the invention.

[0076] Advantageously, the feedstock containing ethylene may also contain hydrogen to reduce selectivity for polyethylene (PE). Preferably, the volume percentage of hydrogen in the ethylene feedstock is between 0% and 10%, more preferably between 0.1% and 5%, and very preferably between 1% and 3%.

[0077] The heat generated by the reaction can be removed by any means known to those skilled in the art.

[0078] Advantageously, the oligomerization method according to the invention can be carried out continuously.

[0079] In one embodiment, at least four compounds of the catalyst composition according to the invention are injected into a reactor, which is advantageously stirred by conventional mechanical means or by external circulation, and in which ethylene reacts, preferably under temperature control.

[0080] In one embodiment, a first solution comprising a mixture of a chromium-based metal precursor and a heteroatom ligand, and a second solution comprising an additive in the form of an aluminum-based compound, are respectively injected into a reactor, which is advantageously stirred by conventional mechanical means or by external circulation, and in which ethylene reacts, preferably under temperature control, and SMAO is introduced last.

[0081] In a preferred embodiment, after the introduction of SMAO and before the introduction of the feedstock, the reactor is stirred at room temperature to immobilize the catalytically active species on the support. The stirring time is several minutes, for example, 5 minutes.

[0082] The catalyst composition present in the oligomer effluent downstream of the reactor can be neutralized in any manner known to those skilled in the art.

[0083] The following examples illustrate the invention but do not limit its scope.

[0084] List of Attachments Figure 1These are photographs of the agitator blades of the reactor at the end of the ethylene tetramerization process according to Examples 2, 8, and 9 (Comparative Examples). "Sticky" polymerization 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 polymerization byproducts. A "filamentous" structure, characteristic of uncontrolled or "viscous" polymer morphologies, was observed.

[0086] Figure 3 These are photographs of the agitator blades of the reactor at the end of the ethylene tetramerization process according to Examples 5, 6, 7, 10, 11, 12 and 13 (according to the present invention). Particulate polymerization 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 polymerization byproducts. A "granular" structure was observed, which is characteristic of morphology-controlled polymers. Example

[0088] Example 1: Method for preparing SMAO containing 10.1 wt% Al 3g of silica (average diameter = 33 µm; average pore size D) pre-dried under vacuum at 80°C for 2 h in a glove box for polymerization. P =21 nm; pore volume V P =1.56 ml / g; Specific surface area S BET =315 m 2 Weigh the contents (g) into a Schlenk flask.

[0089] Under an argon flow, silica was impregnated with 4.7 ml (corresponding to the total pore volume) of anhydrous toluene. Then, MAO (4.65 wt% Al, d = 0.895 g / ml, theoretically 0.54 g Al) in 13 ml of toluene was added. The mixture became a translucent liquid gel.

[0090] The mixture was heated at 80°C for 4 h, with manual stirring every 15 minutes. After 4 h, the toluene was evaporated, and the resulting white powder was dried under vacuum at 80°C for 1 h.

[0091] The Al content in SMAO was determined by ICP-AES: wt% Al = 10.1% ± 0.5%.

[0092] Example 2 (Comparative Example): A homogeneous solution of MMAO-3A in cyclohexane was used as a co-catalyst (relative to Cr). Method for ethylene tetramerization using 1100 equivalent Al) Weigh 14.0 mg Cr(acac)2 and 28.0 mg N,N-bis[di(2-fluorophenyl)]phosphinoisopropylamine (PNP heteroatom ligand) into a Schlenk flask 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 atmosphere.

[0093] 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 one 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 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 feed valve was then opened (30 bar (3 MPa) pressure), stirring was started, and the reactor heating setpoint was raised to 45°C.

[0094] At the end of the test, the ethylene supply was cut off, the medium 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. An organic phase sample was taken and filtered for analysis. The results are described in Table 1.

[0095] Example 3 (Comparative Example): Using a SMAO suspension in cyclohexane as a co-catalyst (relative to Cr of 1100 d). Methods for the tetramerization of ethylene (using Al) In a glove box, 588 mg SMAO containing 10.1% Al, or 59.4 mg Al (2.2 mmol Al), prepared according to Example 1, was weighed into a Schlenk flask. Then, 5.0 ml of cyclohexane was introduced to form a suspension.

[0096] 89 ml of cyclohexane was introduced into a 250 ml reactor, with the internal temperature preset to 25°C and the ethylene pressure preset 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 one 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), 5.0 ml of SMAO suspension in 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 min at 25°C and 2 bar (0.2 MPa) of ethylene pressure. The ethylene feed valve was then opened (30 bar (3 MPa) pressure), stirring was started, and the reactor heating setpoint was raised to 45°C.

[0097] At the end of the test, the ethylene supply was cut off, the medium 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. A sample of the organic phase was taken and filtered for analysis. The results are described in Table 1.

[0098] Example 4 (Comparative Example): Using a SMAO suspension in cyclohexane as a co-catalyst (relative to Cr of 250 ppm) A method for ethylene tetramerization using Al and MMAO-3A as additives (300 equivalent Al relative to Cr). In a glove box, 134 mg SMAO (13.5 mg Al, or 0.5 mmol Al) containing 10.1% Al, prepared according to Example 1, was weighed into a Schlenk flask. Then, 5 ml of cyclohexane was introduced to form a suspension.

[0099] Add 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 to another Schlenk flask under Ar conditions to form a 0.10 mol / L solution.

[0100] 83 ml of cyclohexane was introduced into a 250 ml reactor, with the internal temperature preset to 25 °C and the ethylene pressure preset 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 one 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), 6.0 ml of 0.1 mol / L MMAO-3A solution (i.e., 0.6 mmol), 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 mixture was stirred at 250 rpm for 5 min at 25 °C. The SMAO suspension in 5.0 ml of cyclohexane was then injected. Then, the reactor was stirred at 250 rpm for 5 min at 25°C and 2 bar (0.2 MPa) ethylene pressure. Then, the ethylene feed valve was opened (30 bar (3 MPa) pressure), stirring was started, and the reactor heating setpoint was raised to 45°C.

[0101] At the end of the test, the ethylene supply was cut off, the medium 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. A sample of the organic phase was taken and filtered for analysis. The results are described in Table 1.

[0102] Example 5 (according to the present invention): Using a SMAO suspension in cyclohexane as a co-catalyst (relative to Cr) A method for ethylene tetramerization using 500 equivalent Al and MMAO-3A as additives (300 equivalent Al relative to Cr). The test was performed under similar conditions to Example 4, but by introducing a suspension of 268 mg SMAO containing 10.1% Al, i.e., 1.0 mmol Al, in 5.0 ml cyclohexane. The results are described in Table 1.

[0103] Example 6 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr 750) A method for ethylene tetramerization using MMAO-3A as an additive (equivalent Al) and MMAO-3A (300 equivalent Al relative to Cr). The test was performed under similar conditions to Example 4, but by introducing a suspension of 402 mg SMAO containing 10.1% Al, i.e., 1.5 mmol Al, in 5.0 ml cyclohexane. The results are described in Table 1.

[0104] Example 7 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr of 1000) A method for ethylene tetramerization using MMAO-3A as an additive (equivalent Al) and MMAO-3A (300 equivalent Al relative to Cr). The test was performed under similar conditions to Example 4, but by introducing a suspension of 536 mg SMAO containing 10.1% Al, i.e., 2.0 mmol Al, in 5.0 ml cyclohexane. The results are described in Table 1.

[0105] The results of Examples 2 to 7 are described in Table 1.

[0106] Table 1 * indicates the percentage (selectivity) of 1-octene isomers in a molecule with 8 carbon atoms (C8).

[0107] Observed at constant Al 添加剂 At a Cr ratio, use Al greater than 250 SMAO The / Cr ratio allows for obtaining C8 content greater than 50% (with near 100% selectivity for 1-octene) and "controlled" morphology of the polymer (here, polyethylene PE). Al content greater than or equal to 750 SMAO The / Cr ratio reduces productivity to below 1 million. The “mixed” PE appearance indicates the coexistence of “controlled” and “viscous” PE.

[0108] Example 8 (Comparative Example): Using SMAO suspension in cyclohexane as a co-catalyst (500 equivalents relative to Cr) A method for ethylene tetramerization using Al and MMAO-3A as additives (100 equivalent Al relative to Cr). The test was performed under similar conditions to Example 5, but with the introduction of 2.0 ml of 0.1 mol / L MMAO-3A solution (i.e., 0.2 mmol). The results are described in Table 2.

[0109] Example 9 (Comparative Example): Using SMAO suspension in cyclohexane as a co-catalyst (500 equivalents relative to Cr) A method for ethylene tetramerization using Al and MMAO-3A as additives (200 equivalent Al relative to Cr). The test was performed under similar conditions to Example 5, but with the introduction of 4.0 ml of 0.1 mol / L MMAO-3A solution (i.e., 0.4 mmol). The results are described in Table 2.

[0110] Example 10 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr 500) A method for ethylene tetramerization using 400 equivalent Al and MMAO-3A as additives (relative to Cr, 400 equivalent Al). The test was performed under similar conditions to Example 5, but with the introduction of 8.0 ml of 0.1 mol / L MMAO-3A solution (i.e., 0.8 mmol). The results are described in Table 2.

[0111] Example 11 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr 500) A method for ethylene tetramerization using MMAO-3A as an additive (equivalent Al) and MMAO-3A (500 equivalent Al relative to Cr). The test was performed under similar conditions to Example 5, but with the introduction of 10.0 ml of 0.1 mol / L MMAO-3A solution (i.e., 1.0 mmol). The results are described in Table 2.

[0112] Example 12 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr 500) A method for ethylene tetramerization using MMAO-3A as an additive (600 equivalent Al relative to Cr). The test was performed under similar conditions to Example 5, but with the introduction of 12.0 ml of 0.1 mol / L MMAO-3A solution (i.e., 1.2 mmol). The results are described in Table 2.

[0113] Example 13 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr 500) A method for ethylene tetramerization using MMAO-3A as an additive (equivalent Al) and MMAO-3A (1000 equivalent Al relative to Cr). The test was performed under similar conditions to Example 5, but with the introduction of 20.0 ml of 0.1 mol / L MMAO-3A solution (i.e., 2.0 mmol). The results are described in Table 2.

[0114] Table 2 * indicates the percentage (selectivity) of 1-octene isomers in a molecule with 8 carbon atoms (C8).

[0115] Observed at constant Al SMAO At a Cr ratio, use Al greater than 200 添加剂 The / Cr ratio enables the production of more than 50% C8 (with 100% selectivity for 1-octene), productivity close to or greater than 1 million, and controlled morphology of PE.

[0116] Therefore, these examples demonstrate that the catalytic composition according to the invention exhibits good Al SMAO / Cr ratio and Al 添加剂 The / Cr ratio is functional and enables it to achieve high selectivity for the selected molecule (here, 1-octene), which is close to that of prior art homogeneous MMAO-based catalyst compositions. It also enables the production of polymerization byproducts (here, PE byproducts) with “controlled” morphology, which do not cause fouling in the oligomerization reactor and can be easily removed from the reactor, unlike “sticky” PE filaments.

[0117] Example 14 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr 500) A mixture of Al equivalents (1000 equivalents of Al) and MMAO-3A with TEA in a 4:1 ratio was used as an additive (relative to Cr). Methods of ethylene tetramerization The test was performed under similar conditions to Example 5, but with the introduction of 3.2 ml of 0.5 mol / L MMAO-3A solution (i.e., 1.6 mmol) and 0.4 ml of 1.0 mol / L TEA solution (i.e., 0.4 mmol). The results are described in Table 3.

[0118] Example 15 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr 500) A mixture of MMAO-3A and TEA in a 1:1 ratio as an additive (relative to Cr, 1000 equivalent Al) is used for... Methods of ethylene tetramerization The test was performed under similar conditions to Example 5, but with the introduction of 2.0 ml of 0.5 mol / L MMAO-3A solution (i.e., 1.0 mmol) and 1.0 ml of 1.0 mol / L TEA solution (i.e., 1.0 mmol). The results are described in Table 3.

[0119] Example 16 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr 500) A mixture of Al equivalents (1000 equivalents of Al) and MMAO-3A with TEA in a 1:4 ratio was used as an additive (relative to Cr). Methods of ethylene tetramerization The test was performed under similar conditions to Example 5, but with the introduction of 0.8 ml of 0.5 mol / L MMAO-3A solution (i.e., 0.4 mmol) and 1.6 ml of 1.0 mol / L TEA solution (i.e., 1.6 mmol). The results are described in Table 3.

[0120] Example 17 (according to the present invention): Using SMAO suspension in cyclohexane as a co-catalyst (relative to Cr 500) A method for ethylene tetramerization using (equivalent Al) and TEA as additives (1000 equivalent Al relative to Cr). The test was performed under similar conditions to that of Example 5, but with the introduction of 2.0 ml of 1.0 mol / L TEA solution (i.e., 2.0 mmol). The results are described in Table 3.

[0121] Table 3 Example MMAO / TEA Ratio Time (h) <![CDATA[Productivity (g / g Cr ·h)]]> C6(%) C8(%) 1-C8*(%) C10(%) C12+(%) PE (%) PE appearance 14 4:1 0.42 827 000 21.7 64.5 99.7 1.4 9.8 2.5 controlled 15 1:1 0.75 444 000 20.5 63.2 99.6 1.1 7.9 7.2 controlled 16 1: 4 1.0 289 000 18.7 48.4 99.5 1.0 5.8 26.0 controlled 17 standalone TEA 1.0 124 500 12.8 19.3 99 0.9 3.1 63.8 controlled * indicates the percentage (selectivity) of 1-octene isomers in a molecule with 8 carbon atoms (C8).

[0122] These examples demonstrate that using an additive in the form of a mixture of MMAO and alkylaluminum (here, TEA) or alkylaluminum alone (where the Al additive / Cr ratio is greater than 200) allows for control of the morphology of PE. When using a mixture of MMAO and alkylaluminum, it is shown that the presence of MMAO enables better productivity and better selectivity for the selected molecule (here, 1-octene) than using alkylaluminum alone.

Claims

1. A catalyst composition for the selective oligomerization of ethylene, particularly for the tetramerization of ethylene to 1-octene, comprising: - Chromium-based metal precursors; - Heteroatom ligands; -Methylaluminoxane supported on an inorganic carrier; - Additives in the form of aluminum-based compounds; The composition has an aluminum-to-chromium molar ratio in the supported methylaluminoxane on an inorganic carrier greater than 250, and an aluminum-to-chromium molar ratio in the additive greater than 200.

2. The composition according to claim 1, wherein the chromium-based metal precursor is acetylacetone Cr(III).

3. The composition according to claim 1 or 2, wherein the heteroatom ligand corresponds to the following general formula: in R 1 R 2 R 3 R 4 and R 5 They may be the same or different from each other, optionally connected to each other, and selected from cyclic or acyclic alkyl groups having 1 to 15 carbon atoms, optionally containing one or more heteroelements, and substituted or unsubstituted aryl groups having 4 to 15 carbon atoms, optionally containing one or more heteroelements.

4. The composition according to any one of the preceding claims, wherein the molar ratio of the heteroatom ligand to the chromium-based metal precursor is between 0.5 and 10, preferably between 0.8 and 6, more preferably between 1.0 and 4.0, and very preferably between 1.2 and 2.

0.

5. The composition according to any one of the preceding claims, wherein the inorganic carrier is selected from silica, alumina, silica-alumina, zeolite and TiO2.

6. The composition according to claim 5, wherein the support is based on silicon dioxide, preferably SiO2.

7. The composition according to any one of the preceding claims, wherein the inorganic carrier is in particulate form and is 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.

8. The composition according to any one of the preceding claims, wherein the aluminum content of the supported methylaluminoxane on the inorganic carrier is between 1% by weight and 25% by weight, preferably between 5% by weight and 15% by weight, more preferably between 8% by weight and 12% by weight, and very preferably between 9% by weight and 11% by weight, relative to the total weight of the supported methylaluminoxane on the inorganic carrier.

9. The composition according to any one of the preceding claims, wherein the molar ratio of aluminum in the supported methylaluminoxane on the inorganic carrier to chromium in the metal precursor is greater than 250 and less than 750.

10. The composition 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.

11. The composition according to claim 10, wherein the additive is MMAO-3A.

12. The composition according to any one of the preceding claims, wherein the molar ratio of aluminum in the additive to chromium in the metal precursor is 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.

13. The composition according to any one of the preceding claims further comprises a solvent selected from saturated or unsaturated, cyclic or acyclic hydrocarbons.

14. A method for oligomerizing ethylene, preferably for tetramerizing ethylene into 1-octene, comprising contacting a feedstock containing ethylene with a catalyst composition according to any one of claims 1 to 13 in an oligomerization reactor.

15. The method of claim 14, wherein the ethylene-containing feedstock further contains hydrogen, wherein 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%.

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