JPH0912627A - Method for producing α-olefin low polymer - Google Patents

Abstract

(57) [Abstract] [Purpose] A catalyst which is low in cost and in which decomposition of halogen-containing compounds is suppressed is used, and it is industrially advantageous to reduce the weight of α-olefin such as 1-hexene without complicated operations. Provided is a method for producing an α-olefin low polymer capable of producing a combined product in a high yield and a high selectivity. A method for producing an α-olefin low polymer using a chromium-based catalyst, wherein the chromium-based catalyst comprises at least a combination of a chromium compound, a nitrogen-containing compound, an alkylaluminum compound, and an allyl halide compound. Is used, and the α-olefin and the chromium-based catalyst are brought into contact with each other in a solvent in such a manner that the chromium compound and the alkylaluminum compound do not come into contact with each other in advance, so that the low polymerization of the α-olefin is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an α-olefin low polymer, and more specifically, it is industrially advantageous in a high yield and a high selectivity by using a catalyst whose deterioration with time is improved. And a method for producing an α-olefin low polymer.

[0002]

2. Description of the Related Art Heretofore, as a method for low-polymerizing an α-olefin such as ethylene, there has been known a method using a chromium-based catalyst comprising a combination of a specific chromium compound and a specific organic aluminum compound. For example, JP-A-3-128
Japanese Patent Publication 904 describes a method of trimerizing an α-olefin using a catalyst obtained by previously reacting a chromium-containing compound having a chromium-pyrrolyl bond with a metal alkyl or a Lewis acid.

US Pat. No. 5,376,612 also uses a catalyst system obtained by mixing a chromium compound, a pyrrole-containing compound, a metal alkyl compound and a halide source in a common solvent. A method for low polymerizing α-olefins is described. Some of the inventors of the present invention previously disclosed in Japanese Patent Application No. 6-139024, by contacting a chromium compound, an amine or metal amide, an alkylaluminum compound, and a halogen-containing compound with an α-olefin in a specific mode, -Proposed a method to carry out low polymerization reaction of olefins.

Some of the inventors of the present invention have filed Japanese Patent Application No. 6-2.
No. 18477 and Japanese Patent Application No. 6-295073, by using a specific chromium-based catalyst containing a specific halogenated hydrocarbon in a specific contact mode, an α-olefin such as 1-hexene can be produced at a high yield. A method of obtaining with high selectivity was proposed.

[0005]

However, the method described in US Pat. No. 5,376,612 has the drawback that the cost of the halogen compound used is very high. In addition, in the method using a halogen-containing compound, the halogen-containing compound used is decomposed in the reaction step and the purification step to generate a halogen-containing decomposition product that is difficult to separate and purify. There is a problem that the product purity may be reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to industrially advantageously use a catalyst that is low in cost and suppresses decomposition of a halogen-containing compound, and does not require complicated operations. -To provide a method for producing an α-olefin low polymer capable of producing an α-olefin low polymer such as hexene with high yield and high selectivity.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that if a specific chromium-based catalyst containing a specific halogen-containing compound is used in a specific contact mode. In this case, the catalyst cost is kept low, and the decomposition of the halogen-containing compound that is the catalyst component is suppressed, and α-
A low polymerization reaction of an olefin, in particular, a low polymerization reaction mainly consisting of trimerization of ethylene is advanced to a high activity to obtain a high purity 1-
We have found that hexene can be produced.

The present invention has been completed based on the above findings, and the gist thereof is, in a method for producing an α-olefin low polymer using a chromium-based catalyst, at least chromium as a chromium-based catalyst. Compound (a), at least one nitrogen-containing compound (b) selected from the group consisting of amine, amide and imide, alkylaluminum compound (c)
And a catalyst system comprising a combination of an allyl halide compound (d) represented by the following general formula (I), wherein each of the components (a) to (d) and the α-olefin are present in the reaction solvent at the same time. Before the low polymerization reaction is started, the chromium compound (a) and the alkylaluminum compound (c)
The above-mentioned components (a) to (d) are supplied to the reaction system and contacted with the α-olefin to perform low polymerization of the α-olefin, in a mode that does not contact with the α-olefin. The manufacturing method of the coalescence.

[0009]

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(In the formula, X _{1 to} X ₃ represent a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, X _{4 to} X ₆ represent a hydrogen atom,
An alkyl group having 1 to 30 carbon atoms or a halogen atom,
One or two of X _{4 to} X ₆ are halogen atoms. )

The present invention will be described in more detail below. In the present invention, the chromium-based catalyst comprises at least a combination of a chromium compound (a), a specific nitrogen-containing compound (b), an alkylaluminum compound (c) and an allyl halide compound (d) having a specific structure. A catalyst system is used. Chromium compound (a) used in the present invention
Is represented by the general formula CrXn. However, in the general formula, X
Is any organic or inorganic group or negative atom, n
Represents an integer of 1 to 6, and when n is 2 or more,
X's may be the same or different from each other. The valence of chromium is 0 to 6, and n in the above general formula is 2
The above is preferred.

The above organic group usually has 1 to 3 carbon atoms.
Various groups of 0 are mentioned. Specifically, a hydrocarbon group,
Examples thereof include a carbonyl group, an alkoxy group, a carboxyl group, a β-diketonate group, a β-ketocarboxyl group, a β-ketoester group and an amide group. Examples of the hydrocarbon group include an alkyl group, a cycloalkyl group, an aryl group, an alkylaryl group, an aralkyl group and a cyclopentadienyl group. Examples of the inorganic group include chromium salt-forming groups such as nitrate group and sulfate group, and examples of the negative atom include:
Oxygen, halogen and the like can be mentioned.

A preferred chromium compound is an alkoxy salt,
A carboxyl salt, a β-diketonate salt, a salt with an anion of a β-ketoester, or a chromium halide, and specifically, chromium (IV) -t-butoxide, chromium (III) acetylacetonate, chromium (III) Trifluoroacetylacetonate, chromium (III) Hexafluoroacetylacetonate, chromium (III) (2,2,6
6-tetramethyl-3,5-heptanedionate), C
r (PhCOCHCOPh) ₃ (where Ph represents a phenyl group), chromium (II) acetate, chromium (III)
Acetate, chromium (III)-2-ethylhexanoate, chromium (III) benzoate, chromium (III) _{naphthenate, Cr (CH 3 COCHCOOCH 3)} 3, a first chromium chloride, chromic chloride, bromide first chromium , Chromium bromide, chromium iodide, chromium iodide, chromium fluoride, chromium fluoride and the like.

Further, a complex composed of the above-mentioned chromium compound and an electron donor can also be preferably used. The electron donor is selected, for example, from compounds containing nitrogen, oxygen, phosphorus or sulfur. Examples of the nitrogen-containing compound include nitrile, amine, and amide. Specifically, acetonitrile, pyridine, dimethylpyridine, dimethylformamide, N-methylformamide, aniline, nitrobenzene, tetramethylethylenediamine,
Examples thereof include diethylamine, isopropylamine, hexamethyldisilazane, pyrrolidone and the like.

Examples of oxygen-containing compounds include esters, ethers, ketones, alcohols, aldehydes,
Specific examples include ethyl acetate, methyl acetate, tetrahydrofuran, dioxane, diethyl ether, dimethoxyethane, diglyme, triglyme, acetone, methyl ethyl ketone, methanol, ethanol, acetaldehyde and the like.

Examples of the phosphorus-containing compound include hexamethylphosphoramide, hexamethylphosphorus triamide, triethylphosphite, tributylphosphine oxide, triethylphosphine and the like. On the other hand, examples of the sulfur-containing compound include carbon disulfide, dimethyl sulfoxide, tetramethylene sulfone, thiophene and dimethyl sulfide.

Therefore, from the chromium compound and the electron donor,
An example of the complex is a chromium halide ether complex.
Body, ester complex, ketone complex, aldehyde complex,
Cole complex, amine complex, nitrile complex, phosphine complex
Body, thioether complex and the like. Specifically, C
rCl_Three・ 3THF (where THF is tetrahydrofuran
Indicate the ), CrCl_Three・ 3dioxane, CrC
l_Three・ (CH_ThreeCO_Two-N-C_FourH₉), CrCl_Three・
(CH_ThreeCO_TwoC_TwoH_Five), CrCl_Three・ 3 (i-C_Three
H₇OH), CrCl_Three.3 [CH_Three(CH_Two)_ThreeCH
(C_TwoH_Five) CH _TwoOH], CrCl_Three・ 3pyrid
ine, CrCl_Three・ 2 (i-C_ThreeH₇NH_Two), [C
rCl_Three・ 3CH_ThreeCN] ・ CH_ThreeCN, CrCl_Three・
3PPh_Three, CrCl_Two・ 2THF, CrCl_Two・ 2p
yridine, CrCl_Two・ 2 [(C_TwoH_Five)_TwoN
H], CrCl_Two・ 2CH_ThreeCN, CrCl_Two・ 2 [P
(CH _Three)_TwoPh] and the like.

The chromium compound can be used in a hydrocarbon solvent.
Soluble compounds are preferred, β-diketonate salts of chromium,
Carboxylates, salts of β-ketoesters with anions, β
-Ketocarboxylates, amide complexes, carbonyl complexes,
Ruben complex, various cyclopentadienyl complexes, alkyl
Examples thereof include complexes and phenyl complexes. Various cals of chrome
Bonyl complex, carbene complex, cyclopentadienyl complex
As a compound, an alkyl complex, a phenyl complex, etc., Cr (C
O)₆, (C₆H₆) Cr (CO)_Three, (CO) _FiveCr
(= CCH_Three(OCH_Three)), (CO)_FiveCr (= CC
₆H_Five(OCH_Three)), CpCrCl_Two(Where Cp is
Indicates a cyclopentadienyl group. ), (Cp * CrCl
CH_Three)_Two(Where Cp * is pentamethylcyclopenta
Indicates a dienyl group. ), (CH_Three)_TwoExamples include CrCl
Is done.

The chromium compound can be used by being supported on a carrier such as an inorganic oxide. However, it is preferable to use the chromium compound in combination with another catalyst component without supporting the carrier. That is, in the present invention, the chromium-based catalyst is used in a specific contact mode to be described later, but according to such a mode, high catalytic activity can be obtained without supporting the chromium compound on the carrier. When the chromium compound is used without being loaded on the carrier, the loading on the carrier which involves complicated operations can be omitted, and the total amount of the catalyst used (the total amount of the carrier and the catalyst component) is increased by the use of the carrier. It is possible to avoid the problem.

Nitrogen-containing compound (b) used in the present invention
Is one or more compounds selected from the group consisting of amines, amides and imides. The amine used in the present invention is
It is a primary or secondary amine, or a mixture thereof. Examples of primary amines include ammonia, ethylamine, isopropylamine, cyclohexylamine, benzylamine, aniline, and naphthylamine, and secondary amines include diethylamine, diisopropylamine, dicyclohexylamine, dibenzylamine, bis (trimethylsilyl) amine, Morpholine, imidazole, indoline, indole, pyrrole, 2,5-dimethylpyrrole, 3,4-dimethylpyrrole, 3,4-diethylpyrrole, 2,3,4-trimethylpyrrole,
3,4-dichloropyrrole, 2,3,4,5-tetrachloropyrrole, 2-acetylpyrrole, 3,3 ', 4
Examples include 4'-tetramethyldipyrrolomethane, pyrazole, pyrrolidine and the like.

One of the amides used in the present invention is a metal amide derived from a primary or secondary amine, or a mixture thereof, and specifically, a primary or secondary amine and a group IA. An amide obtained by reaction with a metal selected from Group IIA, Group IIIA, and Group IVB. Specific examples of such metal amides include lithium amide, sodium ethylamide, calcium diethylamide, lithium diisopropylamide, potassium benzylamide, sodium bis (trimethylsilyl) amide, lithium indolide, sodium pyrrolide, lithium pyrrolide, potassium pyrrolide. , Potassium pyrrolidide, aluminum diethylpyrrolid, ethylaluminum dipyrrolide, aluminum tripyrrolid, lithium (2,5-dimethylpyrrolid) and the like.

In the present invention, a secondary amine, an amide derived from a secondary amine, or a mixture thereof is more preferably used. As secondary amines, pyrrole, 2,5-dimethylpyrrole, 3,4-dimethylpyrrole, 2,3,4-trimethylpyrrole, 3,4-dichloropyrrole, 2,3,4,5-tetrachloropyrrole, 2-Acetylpyrrole and 3,3 ', 4,4'-tetramethyldipyrrolomethane are preferable, and pyrrole or 2,5-dimethylpyrrole is particularly preferable. In addition, examples of the metal amide derived from a secondary amine include aluminum pyrrolide, ethylaluminum dipyrrolide, aluminum tripyrolide, sodium pyrrolide, lithium pyrrolide, potassium pyrrolide, and aluminum (2,5-dimethylpyrrolidone. De), ethyl aluminum bis (2,5-
Dimethylpyrrolide), aluminum tris (2,5-dimethylpyrrolide), sodium (2,5-dimethylpyrrolide), lithium (2,5-dimethylpyrrolide), potassium (2,5-dimethylpyrrolide) It is suitable. Among the pyrrole derivatives, those having a hydrocarbon group on the pyrrole ring are preferable.

Another one of the amides used in the present invention is an acid amide. Examples of the acid amide used in the present invention include compounds represented by the following general formulas (1) to (3). In addition, for convenience, the following general formulas (1) to (3) also include imide which is another nitrogen-containing compound used in the present invention. Examples of the acid amide or imide compound used in the present invention include compounds represented by the following general formulas (1) to (3).

[0024]

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In the general formula (1), M ¹ is a hydrogen atom or a metal element selected from Group IA, IIA, IB or IIIA of the periodic table, and R ¹ is a hydrogen atom or a carbon number of 1 to 3
0 represents an alkyl group, an alkenyl group, an aralkyl group, an aryl group which may have a substituent, or an aryl group which may contain a hetero element, and R ² represents a hydrogen atom or a carbon number of 1 to 30. , An alkyl group, an alkenyl group, an aralkyl group, an aryl group which may have a substituent, an aryl group which may contain a hetero element, or an acyl group C (═O) R ³ (where R ³ is defined as Same as R ¹ , but
R ¹ may be different) and R ¹ and R ² may form a ring.

[0026]

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In the general formula (2), M ² and M ³ are hydrogen atoms or metal elements selected from the group IA, IIA, IB or IIIA of the periodic table, R ⁴ and R ⁵ are hydrogen atoms, Represents an alkyl group having 1 to 30 carbon atoms, an alkenyl group, an aralkyl group, an aryl group which may have a substituent, or an aryl group which may contain a hetero element,
R ⁴ and R ⁵ may form a ring, and A represents an alkylene group which may contain an unsaturated bond.

Examples of the acid amides represented by the general formula (1) or the general formula (2) include acetamide, N-methylhexanamide, succinamide, maleamide and N-.
Methylbenzamide, imidazole-2-carboxamide, di-2-thenoylamine, β-lactam, δ-lactam, ε-caprolactam, and salts thereof with metals of Group IA, IIA, IB or IIIA of the Periodic Table. To be

Examples of the imides include 1,2-cyclohexanedicarboximide, succinimide, phthalimide, maleimide, 2,4,6-piperidinetrione, perhydroazecin-2,10-dione, and
Salts thereof with salts of Group IA, IIA, IB or IIIA of the Periodic Table can be mentioned.

[0030]

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In the general formula (3), M ⁴ is a hydrogen atom or a metal element selected from Group IA, IIA, IB or IIIA of the periodic table, and R ⁶ is a hydrogen atom or a carbon number of 1 to 3
0 represents an alkyl group, an alkenyl group, an aralkyl group, an aryl group which may have a substituent, or an aryl group which may contain a hetero element, and R ⁷ is a hydrogen atom, a carbon atom having 1 to 30 carbon atoms. An alkyl group, an alkenyl group, an aralkyl group, an aryl group optionally having a substituent, an aryl group optionally containing a hetero element, or SO ₂
R ⁸ groups (the definition of R ⁸ is the same as R ⁶ may be different from R ⁶⁾ represents, R ⁶ and R ⁷ may form a ring.

Examples of the sulfonamides and sulfonimides represented by the general formula (3) include benzenesulfonamide, N-methylmethanesulfonamide, N-
Methyltrifluoromethanesulfonamide and salts thereof with metals of Group IA, IIA, IB or IIIA of the Periodic Table.

Among the above acid amide or imide compounds, the compound represented by the general formula (1) is preferable, and particularly,
An imide compound in which R ² in the general formula (1) represents an acyl group C (═O) R ³ and R ¹ and R ³ form a ring is preferable. As the alkylaluminum compound (c) used in the present invention, an alkylaluminum compound represented by the following general formula (4) is preferably used.

[0034]

[Chemical 6]

In the formula (4), R ¹ and R ² are hydrocarbon groups having a carbon number of usually 1 to 15, preferably 1 to 8 and may be the same or different, and X is Represents a halogen atom, m is 0 <m ≦ 3, n is 0 ≦ n <3, p is 0 ≦ p <3, and q is a number of 0 ≦ q <3.
Moreover, it represents a number that is m + n + p + q = 3. Examples of the alkylaluminum compound include a trialkylaluminum compound represented by the following general formula (5), a halogenated alkylaluminum compound represented by the general formula (6), an alkoxyalkylaluminum compound represented by the general formula (7), Examples thereof include an alkylaluminum hydride compound represented by the general formula (8). The definitions of R ¹ , X and R ² in each formula are the same as in formula (4).

[0036]

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Specific examples of the alkylaluminum compound include trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylaluminum monochloride, diethylaluminum ethoxide, diethylaluminum hydride and the like. Further, these alkylaluminum compounds may be a mixture of two or more kinds, and for example, a mixture of a trialkylaluminum compound and a halogenated alkylaluminum compound can be used. Among these, trialkylaluminum compounds are particularly preferable in that the amount of by-products of the polymer is small.

In the present invention, the halogen-containing compound (d)
Is an allylic position represented by the following general formula (I) is 1
Allyl halide compounds substituted with one or two halogen atoms are used.

[0039]

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In the general formula (I), X _{1 to} X ₃ represent a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, and X _{4 to} X ₆ represent a hydrogen atom, an alkyl group having 1 to 30 carbon atoms or a halogen atom. And one or two of X _{4 to} X ₆ are halogen atoms. As the halogen atom for the substituent in the general formula (I), chlorine or bromine is preferably used, and chlorine is preferably used in view of the activity and the selectivity of the target product.
Specific examples of the halogen compound represented by the general formula (I) include allyl chloride, 3,3-dichloro-1-propene, and 3
-Chloro-1-butene, 3,3-dichloro-1-butene, 1-chloro-2-butene, 1,1-dichloro-2-
Butene, 3-chloro-3-methyl-1-butene, 3-chloro-1-pentene, 3,3-dichloro-1-pentene, 4-chloro-2-pentene, 4,4-dichloro-2
-Pentene, 1-chloro-2-pentene, 1,1-dichloro-2-pentene and the like can be mentioned, with allyl chloride being most preferred.

In the present invention, by using the above halogen-containing compound, not only the catalytic activity and the trimer selectivity are significantly improved, but also the activity per halogen atom is high. A small amount is required, and since the halogen-containing decomposed product generated during the reaction step or distillation purification is small, it is possible to easily separate the halogen-containing decomposed product when purifying the obtained trimer,
There is an advantage that the target product can be recovered with high purity.

In the present invention, the low polymerization reaction of α-olefin is carried out in a solvent using a chromium-based catalyst comprising a combination of the above catalyst components (a) to (d). Then, in the reaction solvent, the above components (a) to (d) and α-
The α-olefin is supplied to the reaction system in such a manner that the chromium compound (a) and the alkylaluminum compound (c) do not come into contact with each other before the low polymerization reaction is initiated by the simultaneous presence of the olefin. And a low polymerization reaction of α-olefin is carried out. By adopting this contact mode, there are advantages that the catalytic activity is remarkably improved, the trimer selectivity is very high, and the content of the obtained α-olefin low polymer is extremely high.

The reason why the activity of the low polymerization reaction of α-olefin becomes low when the chromium-based catalyst is used in such a manner that the chromium compound (a) and the alkylaluminum compound (c) are in contact with each other in advance is not clear. , Is estimated as follows. That is, it is considered that when the chromium compound and the alkylaluminum compound are brought into contact with each other, the ligand exchange reaction proceeds between the ligand coordinated to the chromium salt and the alkyl group in the alkylaluminum compound. The alkyl-chromium compound produced by such a reaction is unstable in itself, unlike the alkyl-chromium compound obtained by the usual method. Therefore, the decomposition-reduction reaction of the alkyl-chromium compound preferentially proceeds, and as a result, inappropriate demetallation is induced in the low polymerization reaction of the α-olefin, and the low polymerization reaction activity of the α-olefin is considered to decrease. To be

In this particular contact mode, it is preferable to use a high concentration of α-olefin in order to improve the catalytic activity and the selectivity of the target product. In particular,
The α-olefin concentration in the reaction solvent is usually 5 to 100 m.
It is preferable to bring the chromium-based catalyst and the α-olefin into contact with each other under the conditions of ol%, preferably 10 to 100 mol%, and particularly preferably 20 to 100 mol%. Especially,
When a low-boiling α-olefin such as ethylene is used as the α-olefin, the α-olefin pressure is usually about 3 to.
250 kg / cm ² , preferably about 5-100 kg / c
It is preferable that the contact is carried out under the condition of m ² , more preferably about 5 to 50 kg / cm ² . By contacting under such conditions, the α
-Low polymerization of olefins can be carried out.

Specific examples of the above specific contact modes include the following modes (1) to (9). In addition,
The following solutions are usually prepared using a reaction solvent. (1) A method of introducing a chromium compound (a) and an α-olefin into a solution containing a nitrogen-containing compound (b), an alkylaluminum compound (c) and a halogen-containing compound (d).

(2) A method of introducing an alkylaluminum compound (c) and an α-olefin into a solution containing a chromium compound (a), a halogen-containing compound (d) and a nitrogen-containing compound (b). (3) A method of introducing a nitrogen-containing compound (b), an alkylaluminum compound (c) and an α-olefin into a solution containing a chromium compound (a) and a halogen-containing compound (d).

(4) Alkyl aluminum compound (c)
And a method of introducing the chromium compound (a), the nitrogen-containing compound (b) and the α-olefin into a solution containing the halogen-containing compound (d). (5) A method of introducing an alkylaluminum compound (c), a halogen-containing compound (d) and an α-olefin into a solution containing a chromium compound (a) and a nitrogen-containing compound (b).

(6) A method of introducing a chromium compound (a), a halogen-containing compound (d) and an α-olefin into a solution containing a nitrogen-containing compound (b) and an alkylaluminum compound (c). (7) A method of introducing a chromium compound (a), a nitrogen-containing compound (b), a halogen-containing compound (d) and an α-olefin into a solution containing the alkylaluminum compound (c).

(8) A method of introducing a halogen-containing compound (d), a nitrogen-containing compound (b), an alkylaluminum compound (c) and an α-olefin into a solution containing the chromium compound (a). (9) A method in which the chromium compound (a), the nitrogen-containing compound (b), the alkylaluminum compound (c), the halogen-containing compound (d) and the α-olefin are simultaneously and independently introduced into the reaction system.

Before starting the reaction, the chromium compound and the alkylaluminum compound are kept in a contact-free state.
In addition, it is possible to employ a method in which the chromium compound and the alkylaluminum compound are independently supplied to the reaction system simultaneously with the α-olefin during the low polymerization reaction of the α-olefin.

In the present invention, the phrase "a mode in which the chromium compound and the alkylaluminum compound are not brought into contact with each other before the start of the reaction" means not only at the start of the reaction but also to the reactor of the additional α-olefin and the catalyst component thereafter. It means that such a mode is maintained in the supply of. However, the particular contact mode described above is the preferred mode required in the formation of the catalyst system from the catalyst components and is irrelevant after the catalyst system is formed. Therefore, circulating the catalyst liquid recovered from the reaction system through the reaction system after the formation of the catalyst system according to the above mode is not contrary to the above contact mode.

In the present invention, the amount of chromium compound (a) present in the reaction system is usually 1 × 1 per liter of solvent.
0 ^{−7 to} 0.5 mol, preferably 5 × 10 ^{−7 to} 0.2 m
and more preferably 1 × 10 ^{−6 to} 5 × 10 ⁻² mol. The amount of the nitrogen-containing compound (b) present is usually 1 × 10 ^{−7 to} 0.1 mol, preferably 5 × 10 ^{−7 to} 5 × 10 ⁻² mol, and more preferably 1 × 10 ⁻⁶ per 1 liter of the solvent. ˜1 × 10 ⁻² mol. The amount of the alkylaluminum compound (c) present is 1 × 10 ^{−7 to} 7 × 10 ⁻² mol, preferably 5 × 10 ^{−7 to} 5 × 10 ⁻² mol, and more preferably 1 ×, per 1 liter of the solvent.
It is set in the range of 10 ⁻⁶ to 1 × 10 ⁻² mol. The amount of the halogen-containing compound (d) present is usually 1 × 10 ^{−7 to} 0.1 mol, preferably 5 × 10 ⁻⁷ to 1 mol of the solvent.
5 × 10 ⁻² mol, more preferably 1 × 10 ⁻⁶ to 1 × 1
The range is 0 ^-2 mol. It is preferable to use a catalytic amount of each of the above catalyst components.

In the present invention, the molar ratio of the chromium compound (a), the nitrogen-containing compound (b), the alkylaluminum compound (c) and the halogen-containing compound (d) in the reaction system (a) :( b) :( c). ): (D) is usually 1: 0.1
~ 100: 0.1-500: 0.1-100,
The ratio is more preferably 1: 0.1 to 10: 1 to 100: 0.1 to 20, and particularly preferably 1: 1 to 5: 5 to 50: 1 to 10. By combining under such specific conditions, as the α-olefin low polymer, for example, hexene can be produced at a yield of 90% or more (ratio to the total amount produced), and
The content of 1-hexene in hexene can be increased to 99% or more.

In the present invention, as the starting α-olefin, a substituted or unsubstituted α-olefin having 2 to 30 carbon atoms is used. Specific examples include ethylene, propylene, 1-butene, 1-hexene, 1-octene, 3-methyl-1-butene, 4-methyl-1-pentene and the like. In particular, ethylene is preferable as the raw material α-olefin, and 1-hexene, a trimer thereof, can be obtained from ethylene with high yield and high selectivity.

In the present invention, as the reaction solvent, butane, pentane, 3-methylpentane, hexane, heptane, 2-methylhexane, octane, cyclohexane,
A chain or alicyclic saturated hydrocarbon having 1 to 20 carbon atoms such as methylcyclohexane and decalin, and aromatic hydrocarbon such as benzene, toluene, xylene, ethylbenzene, mesitylene, and tetralin are used. These can be used alone or as a mixed solvent.

As the reaction solvent, the α-olefin itself as a reaction raw material or an α-olefin other than the main raw material can be used. The α-olefin can also be incorporated into the catalyst system as a catalyst component before the start of the low polymerization reaction. For the reaction solvent, α-olefins having 4 to 30 carbon atoms are used, and α-olefins which are liquid at room temperature are particularly preferred.

Particularly, as the solvent, a chain saturated hydrocarbon having 4 to 7 carbon atoms or an alicyclic saturated hydrocarbon is preferable.
By using these solvents, by-products of the polymer can be suppressed, and when an alicyclic saturated hydrocarbon is used, there is an advantage that a high catalytic activity can be obtained. The reaction temperature is generally 0 to 250 ° C., preferably 10
The temperature is 150 ° C, more preferably 20 to 100 ° C. On the other hand, the reaction pressure can be selected from the range of usually 3 to 250 kg / cm ² , but preferably about 5 to 100 kg / cm 2.
² pressure. The residence time is usually 1 minute to 2
It is set to 0 hours, preferably 0.5 to 6 hours. The reaction system may be a batch system, a semi-batch system or a continuous system.

Separation and removal of the by-produced polymer in the reaction solution is carried out by appropriately using a known solid-liquid separation device, and the recovered α-olefin low polymer is purified if necessary.
Distillation purification is usually employed for the purification. In the present invention, the amount of the halogen-containing compound used is small and the decomposition products are small, so that the target component can be recovered in high purity. In the present invention, in particular, highly pure 1-hexene can be industrially advantageously produced from ethylene.

[0059]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. Example 1 A 2 L autoclave that had been heated and dried in a dryer at 120 ° C. was assembled while hot, and the atmosphere was replaced with vacuum nitrogen. The autoclave was equipped with a catalyst feed tube equipped with a rupture plate having a pressure resistance of 5 kg / cm ² G. Cyclohexane (730
ml), 2,5-dimethylpyrrole (0.140 mmo
l) n-heptane solution, allyl chloride (18.0 mg,
0.234 mmol) n-heptane solution and triethylaluminum (0.70 mmol) n-heptane solution were charged in this order to the autoclave barrel side, while:
A catalyst feed tube was charged with a solution of chromium (III) -2-ethylhexanoate (22.5 mg, 0.047 mmol) in n-heptane. The total amount of n-heptane is 20 ml
Met. At this point, there is no contact between the chromium compound and triethylaluminum.

First, the autoclave is heated to 80 ° C.,
Next, ethylene was introduced from the catalyst feed pipe at 80 ° C. The rupture disk ruptured due to ethylene pressure, and the chromium compound was introduced into the autoclave barrel side to start low polymerization of ethylene. Ethylene was introduced until the total pressure reached 35 kg / cm ² , then the total pressure was maintained at 35 kg / cm ² and the reaction temperature was maintained at 80 ° C.

After a predetermined reaction time, each reaction solution was sampled. After the reaction, the pressure of the autoclave was released and degassing was performed, and then the by-product polymer (mainly polyethylene) in the reaction solution was recovered by a filter. The results of the composition analysis of the α-olefin low polymer by gas chromatography are shown in Table-1. The reaction liquid (1000 ml) obtained after separating the by-produced polymer was distilled using a glass distillation column having an inner diameter of 32 mmφ (20 plates). The distillation was performed by batch distillation at R / D = 2 and a column top pressure of 760 mmHg.
The amount of 1-hexene recovered was 330 ml. The amount of halogen in the recovered 1-hexene was measured by a trace amount of sulfur and chlorine analyzer (TOX-10Σ manufactured by Mitsubishi Chemical), but it was not detected.

Comparative Example 1 A low polymerization reaction and distillation were carried out in the same manner as in Example 1 except that carbon tetrachloride (14.3 mg, 0.093 mmol) was used in place of allyl chloride. Table 2 shows the results of analysis of the composition of the reaction solution after the predetermined reaction time. 350 ml of 1-hexene recovered
2 ppm of halogen was detected in this.

In each table, the solvent type "HP" represents n-heptane, "CHX" represents cyclohexane, and the Cr compound type Cr (2EHA) ₃ represents chromium (III) -2-ethylhexanoate. 2,5-DMPy is 2,5-
Represents dimethylpyrrole. The unit of catalyst efficiency is g
-[Alpha] -olefin / g-chromium, and the unit of catalyst efficiency per mol of Cl is g- [alpha] -olefin / g-chromium.mol-Cl. The content of chromium metal in the chromium compound used in the present invention was 10.4 wt% (analytical value).

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[Table 1]

[0065]

[Table 2]

[0066]

Industrial Applicability According to the method of the present invention, a low polymerization product of α-olefin such as 1-hexene can be produced industrially advantageously in a high yield and a high selectivity without complicated operations.
Since the activity of halogen-containing compounds per halogen atom is high, the amount of halogen-containing compounds used can be small.
The catalyst cost can be kept low. Further, the decomposition of the halogen-containing compound can be suppressed during the reaction step and the distillation purification, and the trimerized product which is the target product can be recovered with high purity, which is of great industrial utility value.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Miaki Namba 3-10 Shiodori, Kurashiki-shi, Okayama Mitsubishi Chemical Corporation Mizushima Development Laboratory (72) Inventor Takeshi Okano 3-10 Shiodori, Kurashiki-shi, Okayama Mizushima Development Laboratory, Mitsubishi Chemical Corporation

Claims (7)

[Claims] 1. A method for producing an α-olefin low polymer using a chromium-based catalyst, wherein the chromium-based catalyst is:
A catalyst system comprising at least a combination of a chromium compound (a), at least one nitrogen-containing compound (b) selected from the group consisting of amines, amides and imides, an alkylaluminum compound (c) and a halogen-containing compound (d). Used in a reaction solvent, the above components (a) to (d) and α-
Before the low-polymerization reaction is initiated by the simultaneous presence of olefin, each of the above-mentioned components (a) in such a manner that the chromium compound (a) and the alkylaluminum compound (c) do not come into contact with each other.
To (d) are supplied to a reaction system and contacted with an α-olefin to produce an α-olefin low polymer, wherein the halogen-containing compound is an allyl halide compound represented by the following general formula (I). A method for producing an α-olefin low polymer, which is characterized by being present. Embedded image (Wherein, X ₁ to X ₃ represents a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, X ₄ to X ₆ is a hydrogen atom, 1 to 3 carbon atoms
It is an alkyl group of 0 or a halogen atom, and one or two of X _{4 to} X ₆ are halogen atoms. ) 2. The method for producing an α-olefin low polymer according to claim 1, wherein the halogen-containing compound is allyl chloride. 3. The method for producing an α-olefin low polymer according to claim 1, wherein the chromium compound (a) and the alkylaluminum compound (c) are brought into contact with the α-olefin simultaneously during the low polymerization reaction. 4. The method according to claim 1 or 2, wherein the α-olefin and the chromium compound (a) are introduced into a solution containing the halogen-containing compound (d), the nitrogen-containing compound (b) and the alkylaluminum compound (c). A method for producing an α-olefin low polymer. 5. An α-olefin, a halogen-containing compound (d) and a chromium compound (a) in a solution containing a nitrogen-containing compound (b) and an alkylaluminum compound (c).
The method for producing an α-olefin low polymer according to claim 1, wherein the α-olefin low polymer is introduced. 6. The α-olefin is ethylene, and α-
The method for producing an α-olefin low polymer according to claim 1, wherein the olefin low polymer is mainly 1-hexene. 7. A chromium compound (a) and an alkylaluminum compound (c) are added at an ethylene pressure of about 5 to 100 kg /
The method for producing an α-olefin low polymer according to claim 6, wherein the contact is performed under a condition of cm ² .