NL1039868C2 - Process for producing an oligo(alpha-olefin) and the use of a particular form of methylaluminoxane in such process. - Google Patents
Process for producing an oligo(alpha-olefin) and the use of a particular form of methylaluminoxane in such process. Download PDFInfo
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- C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
- C07C2/02—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons
- C07C2/04—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons by oligomerisation of well-defined unsaturated hydrocarbons without ring formation
- C07C2/06—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons by oligomerisation of well-defined unsaturated hydrocarbons without ring formation of alkenes, i.e. acyclic hydrocarbons having only one carbon-to-carbon double bond
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- C07C2/32—Catalytic processes with hydrides or organic compounds as complexes, e.g. acetyl-acetonates
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- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
- B01J31/12—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing organo-metallic compounds or metal hydrides
- B01J31/14—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing organo-metallic compounds or metal hydrides of aluminium or boron
- B01J31/143—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing organo-metallic compounds or metal hydrides of aluminium or boron of aluminium
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- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
- B01J31/18—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms
- B01J31/1805—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms the ligands containing nitrogen
- B01J31/181—Cyclic ligands, including e.g. non-condensed polycyclic ligands, comprising at least one complexing nitrogen atom as ring member, e.g. pyridine
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- C08F4/00—Polymerisation catalysts
- C08F4/42—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
- C08F4/72—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from metals not provided for in group C08F4/44
- C08F4/74—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from metals not provided for in group C08F4/44 selected from refractory metals
- C08F4/78—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from metals not provided for in group C08F4/44 selected from refractory metals selected from chromium, molybdenum or tungsten
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Abstract
The invention relates to a process for producing an oligo(alpha-olefin), comprising preparing a mixture of at least a chromium complex comprising one or more ligands comprising a deprotonated pyrrole moiety; methylaluminoxane; an aluminum alkyl compound; an alpha-olefin; and a solvent; wherein the methylaluminoxane is a substance that is obtained by removing essentially all volatiles from a mixture that is obtained when trimethylaluminum is partly · hydrolyzed in a solvent.
Description
Process for producing an oligo(alpha-olefin) and the use of a particular form of methylaluminoxane in such process
The invention relates to a process for producing an oligo(alpha-olefin) 5 and to the use of a particular form of methylaluminoxane in an alpha-olefin oligomerization process.
The oligomerization of olefins, in particular alpha-olefins, has been extensively studied. Among oligomerizations of olefins, the trimerization of ethylene to 1-hexene is of particular importance. A major industrial application 10 of 1-hexene is its use as a comonomer in copolymerization with ethylene to produce linear low-density polyethylene (LLDPE), wherein approximately 1-10 mol% of 1-hexene comonomers are incorporated. Further, 1-hexene is used in the production of heptanal via hydroformylation.
Many catalytic systems for the oligomerization of olefins produce a 15 mixture of oligomers (for example a Flory-Shultz or poisson distribution), wherein 1-hexene forms a minor portion of the many oligomers formed. Also, significant amounts of polyethylene are formed in many of such systems.
More recently, however, there have been developed catalytic trimerization systems that are capable of producing 1-hexene in a more selective way.
20 Such systems are described in e.g. US5856257 (known as the Phillips trimerization system), W00204119 (known as the BP MeO-PNP trimerization system), EP1456152 (known as the Sasol SNS trimerization system), EP0611743 and US5856612 (both known as a Mitsubishi trimerization system). However, although these catalytic systems have an increased 25 selectivity towards 1-hexene, they still produce small but significant amounts of polyethylene by-products. Such high molecular weight by-products can cause severe problems during the process operation, because they accumulate in systems wherein the oligomerization is carried out in a continuous process. This leads to fouling of the equipment and to down-time 30 of the reactor when it needs to be disposed of the polyethylene. A further disadvantage of the formation of polyethylene by-product is that a lower yield of the desired trimer is obtained, which makes the process less efficient.
1039868 2
Further, the Mitsubishi trimerization system described in US5856612 is one of the most active and selective catalytic trimerization systems. However, these performances can only be achieved when the trimerizations are performed in the presence of a chlorinated organic solvent such as 5 hexachloroethane, which is undesired from an environmental point of view.
It is therefore an object of the invention to provide a catalytic process for alpha-olefin oligomerization wherein the catalyst has a higher activity than that in known oligomerization systems. It is also an object of the invention to provide a catalytic process for alpha-olefin oligomerization wherein the 10 catalyst has a higher selectivity towards 1-hexene than that in known oligomerization systems. It is in particular an object that the catalyst has both a higher activity and a higher selectivity.
It is a further object of the invention to provide a catalytic process for alpha-olefin oligomerization wherein no halogenated, in particular no 15 chlorinated (co-)solvent or reagent, is used. It is in particular an object that such process without a chlorinated (co-)solvent or reagent also has an activity and/or a selectivity comparable to or higher than that of known oligomerization systems wherein no chlorinated (co-)solvent or reagent is used.
20 It is a further object of the invention to provide a catalytic process for alpha-olefin oligomerization wherein less polyolefin formation occurs as a side reaction to the oligomerization, i.e. less reactor fouling takes place or at least less reactor fouling that is disadvantageous to running the oligomerization process.
25 It is a further object of the invention to provide a catalytic process for alpha-olefin oligomerization wherein milder conditions are used than in known oligomerization systems, in particular wherein a lower temperature and/or pressure are used. More in particular, it is an object that a process can be carried out under mild conditions wherein an activity and/or selectivity is 30 reached at least comparable to that of known oligomerization systems.
It has been found that one or more of these objects can be reached by using a specific activator for the catalyst in the catalytic process.
3
Accordingly, the invention relates to a process for producing an oligo(alpha-olefin), comprising preparing a mixture of at least - a chromium complex comprising one or more ligands comprising a deprotonated pyrrole moiety; 5 - methylaluminoxane; - an aluminum alkyl compound; - an alpha-olefin; - a solvent; wherein the methylaluminoxane is a substance that is obtained by removing 10 essentially all volatiles from a mixture that is obtained when trimethylaluminum is partly hydrolyzed in a solvent.
The chromium complex is usually a Cr(lll) complex wherein one or more ligands formally bear a negative charge. A ligand may be monoanionic, dianionic or trianionic to compensate for the positive charge on the chromium. 15 The chromium may also contain one or more neutral ligands, in particular neutral ligands that co-ordinate to the chromium via a lone pair of electrons such as diethyl ether, tetrahydrofuran (THF) or pyridine. An anionic ligand may however also comprise moieties that co-ordinate to the chromium via a lone pair of electrons, e.g. an ether group, a tertiary amine group, a pyridinyl 20 group, a phosphine group or a thioether group. An anionic ligand may however also comprise moieties that are non-coordinating anions, e.g. tetrakis(pentafluorophenyl)borate.
The chromium complex comprises one or more ligands comprising a deprotonated pyrrole moiety. Such moiety is therefore in principle anionic.
25 The deprotonation of a pyrrole moiety usually occurs during the reaction of the uncomplexed ligand with a chromium precursor to form the chromium complex. The abstracted proton is usually the proton on the nitrogen in the pyrrole ring, whereby the nitrogen in the pyrrole ring is capable of binding to a metal center, in particular to a chromium or an aluminum metal center.
30 For the purpose of the invention, a pyrrole moiety capable of losing a proton is termed ΊΗ-pyrrole moiety”. A pyrrole moiety that is not capable of losing a proton is an A/-substituted pyrrole moiety, and is termed “1R-pyrrole moiety”. The substituent on the nitrogen is e.g. an alkyl or an aryl group.
4 A ligand (before it is deprotonated) contains one or more 1H-pyrrole moieties, and may, in addition thereto, contain one or more 1R-pyrrole moieties as well.
As an example, it contains one 1H-pyrrole moiety, such as a 5 dialkylpyrrole moiety. A particular example is a 2,5-dialkyl pyrrole, more in particular 2,5-dimethylpyrrole (where the nitrogen atom is occupying the 1-position of the pyrrole ring).
Another particular example of a ligand having one 1H-pyrrole moiety is the class of pyridinyl pyrroles, in particular pyrroles having a (pyridin-2-yl)-10 substituent on the 2-position of the pyrrole ring (i.e. 2-(pyridin-2-yl)pyrroles) or on the 3-position of the pyrrole ring (i.e. 3-(pyridin-2-yl)pyrroles). Examples of the latter pyrroles are 3,5-dialkylated-2-(pyridin-2-yl)pyrroles and 2.5- dialkylated-3-(pyridin-2-yl)pyrroles, respectively. Specific examples are 3.5- di-(f-butyl)-2-(pyridin-2-yl)pyrrole and 2,5-di-(f-butyl)-3-(pyridin-2- 15 yl)pyrrole, respectively.
As a further example, a ligand may contain two pyrrole moieties, i.e. it is a bis-pyrrole. In a bis-pyrrole, the two pyrrole moieties are usually connected to each other via a bridge. Such bridge is for example an alkyl or aryl unit having 1-10 carbon atoms. In particular, the bridge is a methylene 20 bridge or an ethylene bridge. Such bridge may contain one or more further substituents on the methylene or ethylene, e.g. an alkyl or an aryl group.
A bis-pyrrole may for example comprise one 1 H-pyrrole moiety and one 1R-pyrrole moiety, such as (1H-pyrrol-2-yl)-(1Me-pyrrol-2-yl)methane or dihydrocarbyl-(1H-pyrrol-2-yl)-(1Me-pyrrol-2-yl)methane. A particular example 25 is diphenyl-(1 H-pyrrol-2-yl)-(1 Me-pyrrol-2-yl)methane.
As a further example, a bis-pyrrole may contain two 1 H-pyrrole moieties and no 1R-pyrrole moieties, such as a di-(1H-pyrrol-2-yl)methane. A particular example is diphenyl-di-(1H-pyrrol-2-yl)methane.
The chromium complex may also comprise one or more anionic 30 ligands that lack a pyrrole moiety, such as a halide (e.g. chloride, bromide, iodide), a hydride or a hydrocarbyl (e.g. alkyl, vinyl, allyl, alkynyl, aryl).
The chromium complex is typically formed from the reaction of a chromium(ll) or chromium(lll) precursor with a compound comprising a 1H- 5 pyrrole moiety capable of being deprotoned. The proton abstraction of the 1H proton usually occurs by a base, e.g. potassium hydride. The base may also be a deprotonated ligand present on the chromium(ll) or chromium(lll) precursor, e.g. acetylacetonate. The precursor may for example be Cr(acac)3.
5 In case the precursor is a chromium halide, e.g. CrCl2(THF)x (x=0-2), CrCI3 or CrCI3(THF)3, the halide is usually not capable of acting as a base, which necessitates the use of an additional compound that acts as a base. The deprotonation may also occur by methylaluminoxane or by an aluminum alkyl compound such as trimethylaluminum ortriethylaluminum. In a process of the 10 invention, this may for example be the case when a mixture of uncomplexed ligand and chromium precursor in a solvent (which mixture may be a solution or a suspension) is added to a reactor comprising methylaluminoxane, an aluminum alkyl compound and an alpha-olefin. In this case, the chromium complex of a process of the invention is regarded as being prepared in situ, 15 because the chromium complex generated is not isolated prior to its application as a catalyst in the catalytic process for the production of oligo(alpha-olefin).
Accordingly, in a particular embodiment of the invention, the preparation of the mixture of the process of the invention comprises 20 introducing a mixture comprising - the chromium precursor; - a compound comprising a pyrrole moiety which pyrrole moiety is capable of being deprotonated; into a mixture comprising 25 - the solvent; - the methylaluminoxane; - the aluminum alkyl compound;
Alternatively, the chromium complex is first synthesized and isolated in essentially pure form, optionally by crystallization. Secondly, the isolated 30 chromium complex can be used as such to prepare the mixture of a process of the invention.
6
Accordingly, in a particular embodiment of the invention, the preparation of the mixture comprises introducing the chromium complex into a mixture comprising - the solvent; 5 - methylaluminoxane; - the aluminum alkyl compound; - the alpha-olefin.
The chromium complex may be added as such (i.e. as a solid), but it may also be added as a solution or a suspension thereof.
10 The methylaluminoxane (MAO) is an essential component of the mixture that is prepared in a process of the invention. MAO is known to the person skilled in the art. It is a poorly-defined material, and is thought to adopt a number of structures in solution, at least some of which exist in dynamic equilibria. It is usually produced by a (controlled) partial hydrolysis of 15 trimethylaluminum, wherein water and trimethylaluminum are reacted in a solvent in a molar ratio in a range typically of from 0.1:1 to 1.2:1, in particular in a range of from 0.5:1 to 1.5:1. Most commonly, MAO is commercially available and used as a solution in an organic solvent, in particular toluene. However, it may also be present in similar solvents such as xylene, cumene 20 or mesitylene.
The MAO that is applied in a process of the invention is, however, not present in such a solution. This means that it is not used as a solution that is obtained by partially hydrolyzing trimethylaluminum in the presence of a solvent. Instead, the MAO that is applied in a process of the invention is 25 obtained by removing essentially all volatiles from a mixture (in particular a solution) that is obtained when trimethylaluminum is partly hydrolyzed in a solvent.
The hydrolysis of trimethylaluminum to form methylaluminoxane is usually performed by using a mixture of water and trimethylaluminium in a 30 molar ratio of at least 0.4:1, at least 0.5:1, at least 0.6:1, at least 0.8:1 or at least 1:1. The molar ratio is usually less than 2.5:1, less than 2.2:1, less than 2:1, less than 1.8:1 or less than 1.5:1. It may for example be in the range of 7 from 0.4:1 to 2.2:1, in the range of from 0.5:1 to 2:1 or 0.6:1 to 1.2:1. In particular it is in the range of from 0.65:1 to 0.75:1.
Besides the MAO thus obtained, an amount of unreacted trimethylaluminum is usually also still present. This amount may for example 5 be in the range of 20-40 wt%, based on the total mass of the unreacted trimethylaluminum and the MAO. The amount may for example be around 30 wt%. Further, when the mixture of the trimethylaluminum and the MAO is present as a solution, e.g. as a toluene solution, the amount of MAO present is usually in the range of 5-15 wt%, based on the total mass of the solution 10 containing the unreacted trimethylaluminum and the MAO. In particular, the amount is 10 wt%. When the amount is 10 wt%, the amount of unreacted trimethylaluminum is for example 2-4 wt%.
In a process of the invention, essentially all volatiles are removed from a mixture that is obtained when trimethylaluminum is partly hydrolyzed. 15 By doing so, MAO is usually obtained as a white solid. To achieve the removal of the last traces of volatiles, the MAO residue may be stripped one or more times with a solvent, in particular with a low-boiling aliphatic hydrocarbon, e.g. petroleum ether. The MAO thus obtained may be used as such in a process of the invention, but it may also be suspended in a solvent 20 before it is used to prepare the mixture of a process of the invention, in particular in an aliphatic hydrocarbon solvent. Thus, in such case, a suspension of pre-dried MAO in a solvent is applied in a process of the invention.
It has been found that using the MAO as defined hereinabove in the 25 present invention, instead of a conventional form of MAO, has advantageous effects. First, an increase of the selectivity of oligo(alpha-olefin)-formation towards the tri(alpha-olefin) is observed. This means that there is a higher selectivity towards a trimer of the alpha-olefin monomer, such as 1-hexene in case ethylene is used as a monomer. Further, it has been observed that in a 30 process of the invention less polyethylene by-product is formed. An advantage of the higher selectivity is that alpha-olefin trimers can be obtained in a more efficient way from the respective alpha-olefins and that less purification of the trimer is required. An advantage of the lower amount of 8 polyolefins in a product obtained by a process of the invention is that the process operation is easier and more energy-efficient, since less reactor fouling takes place or at least less reactor fouling that is disadvantageous to running the oligomerization process.
5 In addition, it is an advantage that no halogenated solvent is used, while the activity of the catalyst in a process of the invention is at least comparable to or higher than that in conventional processes wherein no halogenated solvent is used.
The aluminum alkyl compound is an essential component in a 10 process of the invention. In conventional catalytic systems wherein an aluminum alkyl compound is present, at least a part of the amount of aluminum alkyl compound is trimethylaluminum that is introduced together with the MAO. This is because the trimethylaluminum is a constituent of the MAO solution that is added in such conventional process. In the present 15 invention, if any trimethylaluminum is present in the mixture of the invention, the trimethylaluminum does not originate from the mixture wherein the MAO has been formed from trimethylaluminum. Instead, if present, the trimethylaluminum is introduced to the mixture from another source, e.g. it is added as such.
20 The aluminum alkyl compound may in principle be any aluminum alkyl compound. An aluminum alkyl compound may comprise one, two or three alkyl groups attached to the aluminum. The number of carbon atoms in an alkyl group is usually in the range of 1-50,1-25, or 1-10. An alkyl group may for example be an octyl group, in particular an n-octyl group. In 25 particular, an alkyl group comprises 1-5 carbon atoms. It may for example be selected from the group of a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an /7-butyl group, a sec-butyl group, an isobutyl group and a ferf-butyl group. In case more than one alkyl group is attached to the aluminum, the more than one alkyl groups may be selected independently 30 from each other. In particular, the aluminum alkyl compound is selected from the group of trialkylaluminum (R3AI, where R is an alkyl group), dialkylaluminum halide (R2AIX, where R is an alkyl group and X is a halide) and alkylaluminum dihalide (RAIX2, where R is an alkyl group and X is a 9 halide). A trialkylaluminum is in particular selected from the group of trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylalumuinum and (tris(n-octyl)aluminum). A dialkylaluminum halide is in particular selected from the group of dimethylaluminum chloride, 5 diethylaluminum chloride, diisopropylaluminum chloride and diisobutylaluminum chloride. An alkylaluminum dihalide is in particular selected from the group of methylaluminum dichloride and ethylaluminum dichloride. An aluminum alkyl compound may also be selected from the group of aluminum hydrides of the formula R3.XAIHX (x =1,2).
10 In a process of the invention, the chromium and the aluminum are usually present in a molar ratio of at least 1:50, at least 1:250, at least 1:500 or at least 1:800. The molar ratio is usually less than 1:3000, less than 1:2000, less than 1:1200, or less than 1:800. It may for example be in the range of from 1:50 to 1:3000, in particular in the range of 1:200 to 1:1500, 15 more in particular in the range of from 1:500 to 1:800.
In a process of the invention, the methylaluminoxane and the aluminum alkyl compound are usually present in a molar ratio of at least 1:1, at least 1:1.2, at least 1:1.5 or at least 1:1.8. The molar ratio is usually less than 1:4, less than 1:3, less than 1:2.5, or less than 1:2. It may for example be 20 in the range of from 1:1 to 1:4, in particular in the range of 1:1.5 to 1:2.5, more in particular in the range of from 1:1.8 to 1:2.2. More in particular, the ratio is 1:2.
The alpha-olefin may in principle be any alpha-olefin. Preferably, however, the alpha-olefin is ethylene.
25 The solvent usually is a hydrocarbon, preferably it is an aliphatic hydrocarbon, in particular an alicyclic hydrocarbon. A preferred solvent is methylcyclohexane.
In case the alpha-olefin is ethylene, the pressure of ethylene applied during the oligomerization may be 60 bar or less, 40 bar or less, or 30 bar or 30 less. It may be 10 bar or more, 20 bar or more or 25 bar or more. Usually it is in the range of 10-60 bar, in particular in the range of 15-40 bar.
In case the alpha-olefin is a higher alpha-olefin than ethylene (/.e. it contains 3 or more carbon atoms), the pressure is usually lower. In case the 10 alpha-olefin is a liquid under the reaction conditions, it can act as a solvent in the mixture of the invention. Eventually, the formed product can also act as a solvent.
The temperature during the oligomerization may be 100°C or less, 5 85°C or less, 75°C or less or 65°C or less. It may be 30 °C or more, 40 °C or more, 50 °C or more or 60°C or more. Usually it is in the range of from 40-80°C, in particular in range of from 50-75°C.
In particular, a process of the invention wherein ethylene is used, is performed at an ethylene pressure in the range of from 35-45 bar and at a 10 temperature in the range of from 75-85°C.
It is an advantage of the invention that the process can be performed at milder conditions (i.e. at a lower temperature and/or at a lower ethylene pressure) than processes known in the art are performed, while a comparable or even higher activity and/or selectivity is reached.
15 In a particular in mixture of a process of the invention, the deprotonated pyrrole moiety is a deprotonated 2,5-dimethylpyrrole, the aluminum alkyl compound is triisobutylaluminum, the alpha-olefin is ethylene and the solvent is an aliphatic solvent such as methylcyclohexane.
The invention further relates to the use of methylaluminoxane in an 20 alpha-olefin oligomerization process to increase the selectivity of the process towards the formation of a trimer of the alpha-olefin, wherein the methylaluminoxane is a substance that is obtained by removing essentially all volatiles from a mixture that is obtained when trimethylaluminum is partly hydrolyzed in a solvent.
25
EXAMPLES
General Procedures:
All air and/or water sensitive reactions were performed under a nitrogen atmosphere, in oven dried flasks using standard Schlenk type techniques. Anhydrous reaction solvents were obtained by means of a multiple column 30 11 purification system. CrCI2(THF)2 and CrCI3(THF)3 were prepared according to a known literature procedure. Cr(acac)3 was purchased from Alfa Aeasr and was used as such. Ligand 1 was obtained from Aldrich. Ligands 2 and 3 were synthesised according to known literature procedures ((a) Berube, C. D.; 5 Yazdanbakhsh, M.; Gambarotta, S.; Yap, G. P. A. Organometallics 2003, 22, 3742. (b) Freckmann, D. Μ. M.; Dube, T; Berube, C. D.; Gambarotta, S.; Yap, G. P. A. Organometallics 2002, 21, 1240. (c) Athimoolam, A.; Korobkov, I.; Gambarotta, S. Can. J. Chem. 2005, 83, 832. (d) Athimoolam, A.; Crewdson, P.; Korobkov, I.; Gambarotta, S. Organometallics 2006, 25, 3856). Molecular 10 weights and molecular weight distributions of the polyethylenes were determined by means of high temperature SEC on a PL-GPC210, equipped with refractive index and viscosity detectors and a 3 χ PLgel 10 pm MIXED-B column set, at 160 °C with 1,2,4-trichlorobenzene as solvent. BHT and Irganox have been used as antioxidants. The molecular weights of the polyethylenes 15 produced were referenced to linear polyethylene standards. Results of the oligomerization reactions were assessed by 1H NMR spectroscopy for activity and by GC-MS for reaction mixture composition. Gas chromatography of oligomerization products was conducted on a Varian 450-GC equipped with an auto sampler. Preparation of MAO according to a process of the invention: 20 Commercial grade MAO (100 mL, 10 wt% in toluene) obtained from Sigma Aldrich) was dried under vacuum to remove the toluene and free AIMe3 present in the MAO solution. The resulting white powder was then heated to 60 eC under vacuum for 6 hours to obtain a white crystalline powder. The MAO thus obtained is referred to as “dried MAO”, which is hereinbelow indicated with the 25 abbreviation “DMAO”.
General Oligomerization Procedure:
All oligomerizations were performed in a 250 mL Biichi reactor. The 30 reactor was dried in an oven at 120 °C for two hours prior to each run and then evacuated for half an hour and rinsed with argon three times. After that, the reactor was charged with toluene and the desired amount of co-catalyst. After the solution was stirred for 10 minutes it was saturated with ethylene. The 12 reactor was temporarily depressurised to allow injection of the catalyst solution into the reactor under argon flow, after which the reactor was immediately repressurised to the desired set point. The temperature of the reactor was kept as constant as possible by a thermostat bath. After 30 minutes reaction time 5 and cooling to 0 °C, the reaction mixture was depressurised and a mixture of ethanol and diluted hydrochloric acid was subsequently injected to quench the reaction. The polymer was separated by filtration and dried at 60 °C for 18 hours under reduced pressure before the molecular weight was determined.
10 Results and discussion:
Three different pyrrole-based ligands 1, 2 and 3 were provided. The corresponding chromium catalysts based on these ligands were tested in the catalytic oligomerization of ethylene in a process according to the invention, and 15 compared to conventional oligomerization processes.
Π Λ Ph^^Ph Ph^^Ph H \-NH \-N HN-^y 1 2 X 3 20 Table 1 provides an overview of the effects of different co-catalysts on the activity and selectivity of the trimerization systems 1-3/Cr(acac)3. The selectivity towards the formation of oligomers significantly increases when TIBA or TEA is used in combination with DMAO (as compared to the use of only MAO or only DMAO), i.e. there is less PE formation relative to oligomer 25 formation. Further, when TEA is used, the 1-hexene selectivity remains nearly the same, i.e. the mol% of 1-hexene in the total amount of oligomers remains nearly the same. Moreover, when TIBA is used, a significant increase of selectivity towards the formation of 1-hexene is observed. Thus, in the latter case, the selectivity towards the formation of oligomers as well as the 30 selectivity towards the formation of 1-hexene have both increased. Most spectacular is the case where ligand 1 is used in combination with DMAO and TIBA: essentially no PE has been formed, the selectivity towards the 13 formation of 1-hexene is significantly higher, and the activity increases with one order of magnitude.
Table 1: effects of different co-catalysts on the activity and selectivity of the 5 trimerization systems l-3/Cr(acac)3.
Ligand Co-catalyst Oligomers PE Mass ratio Amount C6 Activity (equiv) (g) (g) oligomers/ (mol% of (g/(mmol _ PE (g/g) oligomers)_Cr.h)) 2 MAO (250) 1.0 - 53 2 DMAO (250) 1.6 1.1 1.45 95.4 175 2 DMAO/TIBA 7.1 2.3 3.09 98.6 625 10 (250)/(500) 2 DMAO/TEA 3.2 0.6 5.33 95.1 253 (250)/(500) 3 MAO (250) - 3 DMAO (250) 0.80 10.5 0.08 95.2 2260 3 DMAO/TIBA 8.7 2.4 3.63 99.2 2226 (250)/(500) 3 DMAO/TEA 3.7 2.2 1.68 92.1 1182 (250)/(500) 1 MAO (250) 2.2 6.6 0.33 83.6 1760 1 DMAO (250) 8.4 3.8 2.21 93.1 2446 1 DMAO/TIBA 9.68 - °° 96.1 19360 20 (250)/(500)
Solvent = 100 mL of methylcyclohexane, ethylene pressure = 30 bar, reaction time = 30 min, reaction temperature = 60 °C, Crfacacyiigand = 1/1. Catalyst loading adjusted according to the exotherm.
Ligand 1 is also known from the Phillips trimerization system and the Mitsubishi trimerization system. A comparison of a process of the invention with 25 the Phillips and Mitsubishi processes is summarized in Figure 1.
The process wherein the complex 1/Cr(acac)3 is used in combination with TIBA and DMAO surpasses the process of the Phillips trimerization system in a couple of aspects. First, the activity is more than two times higher than the values reported in the Phillips patent publications US5563312 and US 5856257.
30 Secondly, there is a significant improvement in the selectivity towards 1-hexene. Further, the higher activity and selectivity were obtained at a lower ethylene pressure and at a lower temperature (30 bar, 60 °C), than in the commercial Phillips trimerization proces (50-100 bar).
14
The process wherein the complex 1/Cr(acac)3 is used in combination with TIBA and DMAO also surpasses the process of the Mitsubishi trimerization system as reported in EP0611743. The process of the invention has an activity that is more than 2.5 times higher, and the selectivity towards 1-hexene is also 5 significantly higher. Moreover, these results are obtained at a lower ethylene pressure and a lower temperature than in the commercial lower ethylene pressure trimerization process.
The Mitsubishi trimerization system as reported in US5856612 makes use of hexachloroethane (HCE) as a solvent, which is not necessary in a 10 process of the invention. A process of the invention reaches a selectivity towards 1-hexene that is comparable to that of the Mitsubishi process.
1039868
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| NL1039868A NL1039868C2 (en) | 2012-11-01 | 2012-11-01 | Process for producing an oligo(alpha-olefin) and the use of a particular form of methylaluminoxane in such process. |
| PCT/NL2013/000050 WO2014069989A1 (en) | 2012-11-01 | 2013-10-31 | Process for producing an oligo(alpha-olefin) and the use of a particular form of methylaluminoxane in such process |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5427992A (en) * | 1990-02-14 | 1995-06-27 | Witco Gmbh | Process for preparing solutions of oligomeric methylaluminoxanes |
| US5856257A (en) * | 1997-05-16 | 1999-01-05 | Phillips Petroleum Company | Olefin production |
| US5856612A (en) * | 1996-02-02 | 1999-01-05 | Mitsubishi Chemical Corporation | Process for producing α-olefin oligomer |
| US20050119516A1 (en) * | 2001-12-20 | 2005-06-02 | Dixon John T. | Trimerisation and oligomerisation of olefins using a chromium based catalyst |
| US20070043181A1 (en) * | 2005-08-19 | 2007-02-22 | Knudsen Ronald D | Methods of preparation of an olefin oligomerization catalyst |
| US20100240847A1 (en) * | 2007-05-28 | 2010-09-23 | John Thomas Dixon | Two stage activation of oligomerisation catalyst and oligomerisation of olefinic compounds in the presence of an oligomerisation catalyst so activated |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5206199A (en) * | 1987-04-20 | 1993-04-27 | Mitsui Petrochemical Industries, Ltd. | Catalyst for polymerizing an olefin and process for polymerizing an olefin |
| TW354300B (en) | 1993-02-17 | 1999-03-11 | Mitsubishi Chem Corp | Process for producing <alpha>-olefin oligomers |
| US5543375A (en) | 1994-02-18 | 1996-08-06 | Phillips Petroleum Company | Olefin production |
| US5663394A (en) * | 1996-07-15 | 1997-09-02 | Albemarle Corporation | High yield aluminoxane synthesis process |
| GB0016895D0 (en) | 2000-07-11 | 2000-08-30 | Bp Chem Int Ltd | Olefin oligomerisation |
| BRPI0215088B1 (en) | 2001-12-20 | 2015-12-22 | Sasol Tech Pty Ltd | trimerization catalyst system and process for olefin oligomerization |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5427992A (en) * | 1990-02-14 | 1995-06-27 | Witco Gmbh | Process for preparing solutions of oligomeric methylaluminoxanes |
| US5856612A (en) * | 1996-02-02 | 1999-01-05 | Mitsubishi Chemical Corporation | Process for producing α-olefin oligomer |
| US5856257A (en) * | 1997-05-16 | 1999-01-05 | Phillips Petroleum Company | Olefin production |
| US20050119516A1 (en) * | 2001-12-20 | 2005-06-02 | Dixon John T. | Trimerisation and oligomerisation of olefins using a chromium based catalyst |
| US20070043181A1 (en) * | 2005-08-19 | 2007-02-22 | Knudsen Ronald D | Methods of preparation of an olefin oligomerization catalyst |
| US20100240847A1 (en) * | 2007-05-28 | 2010-09-23 | John Thomas Dixon | Two stage activation of oligomerisation catalyst and oligomerisation of olefinic compounds in the presence of an oligomerisation catalyst so activated |
Non-Patent Citations (2)
| Title |
|---|
| DIXON J T ET AL: "Advances in selective ethylene trimerisation - a critical overview", JOURNAL OF ORGANOMETALLIC CHEMISTRY, ELSEVIER-SEQUOIA S.A. LAUSANNE, CH, vol. 689, no. 23, 15 November 2004 (2004-11-15), pages 3641 - 3668, XP004629409, ISSN: 0022-328X, DOI: 10.1016/J.JORGANCHEM.2004.06.008 * |
| PATRICK CREWDSON ET AL: "Switchable Chromium(II) Ethylene Oligomerization/Polymerization Catalyst", ORGANOMETALLICS, vol. 24, no. 22, 1 October 2005 (2005-10-01), pages 5214 - 5216, XP055021328, ISSN: 0276-7333, DOI: 10.1021/om050699n * |
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