JPH1036435A - Production of alpha-olefin oligomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an α-olefin oligomer in a high selectivity and high yields by oligomerizing an α-olefin by using a specified chromium catalyst prepared in the absence of any α-olefin and feeding an additional halogen-containing compound into the reaction system during the reaction. SOLUTION: In producing an α-olefin oligomer by oligomerizing an α-olefin in a solvent by a continuous or semi-batch reaction by using a chromium catalyst prepared by reacting at least a chromium compound, a pyrrole compound, an alkylaluminum compound and a halogen-containing compound in an organic solvent free from any αolefin, an additional halogen-containing compound is fed into the reaction system during the reaction. When a halogen-containing compound, especially both a halogen-containing compound and an alkylaluminum compound are additionally fed into the reaction zone according to this process, the catalyst in the reaction zone can be activated with a consequent improved catalyst efficiency. Besides, such activation can be repeated whenever the catalytic activity becomes low.

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 in particular,
The present invention relates to an industrially advantageous method for producing an α-olefin low polymer which can produce an α-olefin low polymer mainly composed of 1-hexene from ethylene with high yield and high selectivity.

[0002]

2. Description of the Related Art Heretofore, as a method for low polymerization of an α-olefin such as ethylene, a method using a chromium catalyst comprising a combination of a chromium compound, a pyrrole compound, an organoaluminum compound and a halogen-containing compound has been known. . For example, South African Patent ZA93 / 0350
The specification describes a method for trimerizing ethylene using a chromium-based catalyst obtained by mixing a chromium salt, a pyrrole compound, a metal alkyl and a halide source in a common solvent. In addition, EP 668105 describes a method for stabilizing a catalyst by adding an aromatic compound as a method for suppressing deterioration of the catalytic activity of the catalyst.

On the other hand, recently, when using a chromium-based catalyst comprising a chromium-containing compound, a pyrrole compound, a metal alkyl compound and a halide source, the present inventors have found that a chromium-containing compound and a metal are not brought into contact with an α-olefin. A low-polymerization reaction of an α-olefin employing an aspect in which it does not come into contact with an alkyl compound has been proposed (see JP-A-8-3216). According to this method, 1-hexene can be obtained from ethylene with higher catalytic activity.

[0004]

However, according to the method described in the specification of ZA93 / 03350 in South Africa, the selectivity of 1-hexene is high, but from the viewpoint of an industrial method for producing an α-olefin low polymer. Therefore, the catalyst activity is still insufficient and the catalyst activity is significantly deteriorated. On the other hand, in the method described in JP-A-8-3216, a sufficiently high activity is achieved from the viewpoint of an industrial production method of an α-olefin low polymer, but the selectivity of 1-hexene is increased. Has a disadvantage that the catalyst activity is slightly low and the catalyst activity is also significantly deteriorated. That is, in any of the catalyst systems, the catalyst starts to be deactivated about 30 to 60 minutes after the catalyst is supplied to the reaction zone.
As a method for suppressing the deterioration of the catalyst activity, EP 6881
Although described in the specification of Japanese Patent No. 05, this method can slightly suppress the activity deterioration, but its effect is insufficient. Further, a method of activating a catalyst deactivated during the reaction has not yet been known.

The present invention has been made in view of the above circumstances, and an object of the present invention is to activate a catalyst in a reaction zone in producing an α-olefin low polymer using a chromium-based catalyst. An object of the present invention is to provide a method for producing an α-olefin low polymer mainly composed of 1-hexene from ethylene at an extremely high selectivity and a high yield.

[0006]

According to the present invention, a chromium compound prepared by reacting at least a chromium compound, a pyrrole compound, an alkylaluminum compound and a halogen-containing compound in an organic solvent substantially free of α-olefins. Using a catalyst, when producing an α-olefin low polymer by low-polymerizing an α-olefin in a solvent by a continuous or semi-batch reaction, a halogen-containing compound is additionally supplied during the reaction to achieve high selection. By activating a catalyst with reduced activity while maintaining the activity, an α-olefin low polymer can be produced with high catalytic activity.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, a chromium-based catalyst comprising at least a chromium compound, a pyrrole compound, a halogen-containing compound and an alkylaluminum compound is used. In the present invention, the chromium compound used for preparing the chromium-based catalyst is
It is represented by the following general formula (1).

[0008]

Embedded image CrXn (1)

In the above formula, the valence of chromium is from 0 to 6
And X represents the same or different organic or inorganic groups or negative atoms. n represents an integer of 1 to 6, preferably 2 or more. Examples of the organic group include various groups having usually 1 to 30 carbon atoms. For example, hydrocarbon group, carbonyl group, alkoxy group, carboxyl group, β
A diketonate group, a β-ketocarboxyl group, a β-ketoester group, an amide group and the like. Examples of the hydrocarbon group include an alkyl group, a cycloalkyl group, an aryl group,
Examples include an alkylaryl group, an aralkyl group, and a cyclopentadienyl group. Examples of the inorganic group include chromium salt-forming groups such as a nitrate group and a sulfate group, and examples of the negative atom include oxygen and halogen.

[0010] A complex comprising the above chromium compound and an electron donor can also be suitably used. The electron donor is selected 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, diethylamine, isopropylamine, hexa Methyldisilazane,
And pyrrolidone.

Examples of the oxygen-containing compound include esters, ethers, ketones, alcohols, aldehydes and the like.
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, hexamethylphosphorustriamide, triethyl phosphite, tributyl phosphine oxide, and triethyl phosphine. Examples of the sulfur-containing compound include carbon disulfide, dimethyl sulfoxide, tetramethylene sulfone, thiophene, and dimethyl sulfide.

Examples of complexes comprising a chromium compound and an electron donor include chromium halide ether complexes, ester complexes, ketone complexes, aldehyde complexes, alcohol complexes, amine complexes, nitrile complexes, phosphine complexes, thioether complexes and the like. Can be As chromium compounds,
Compounds soluble in hydrocarbon solvents or halogenated hydrocarbon solvents described below are preferable. Examples of such compounds include chromium β-diketonate salts, carboxylate salts, salts with β-ketoester anions, and β-ketocarboxylic acid. Examples include salts, amide complexes, carbonyl complexes, carbene complexes, various cyclopentadienyl complexes, alkyl complexes, phenyl complexes and the like.

Some examples of chromium compounds include chromium (III) acetylacetonate, chromium (III) trifluoroacetylacetonate, chromium (III) hexafluoroacetylacetonate, and chromium (III) (2,2,3).
6,6-tetramethyl-3,5-heptanedionate), Cr (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,
Chromium (II) bis (trimethylsilyl) amide, Cr
(CO) ₆ , (C ₆ H ₆ ) Cr (CO) ₃ , (CO) ₅
Cr (= CCH ₃ (OCH ₃ )), (CO) ₅ Cr (=
CC ₆ H ₅ (OCH ₃ )), CpCrCl ₂ (however, Cp
Represents a cyclopentadienyl group. ), (Cp * CrC
lCH ₃ ) ₂ (where Cp * indicates a pentamethylcyclopentadienyl group), (CH ₃ ) ₂ CrCl, and the like. Among these, particularly preferred chromium compounds are
β-diketonate salts, salts with β-ketoester anions, carboxylate salts, β-ketocarboxylate salts and the like. In the present invention, the chromium compound only needs to contain a chromium atom, and may contain another metal.

The pyrrole compound used for preparing the chromium-based catalyst is pyrrole or a substituted pyrrole or a metal salt corresponding to these, ie, metal pyrrolide. As the substituted pyrroles, in addition to 2,5-dimethylpyrrole, 3,4
-Dichloropyrrole, 2,3,4,5-tetrachloropyrrole, 2-formylpyrrole, 2-acetylpyrrole, 2,3,4-trimethylpyrrole, 3,4-diethylpyrrole, tetrahydroindole, 3,3 ', 4,
4'-tetramethyl-2,2'-dipyrrolomethane and the like.

The metal of the metal pyrrolide is Group 1 or 2,
It belongs to Group 3 or 14. Preferred metal pyrrolides include lithium pyrrolide, sodium pyrrolide, potassium pyrrolide, cesium pyrrolide, diethylaluminum pyrrolide, ethylaluminum dipyrrolide, aluminum tripyrolide, lithium-2,5-dimethylpyrrolide, and sodium-pyrrolide. 2,5-dimethylpyrrolide, potassium-2,5-dimethylpyrrolide, cesium-2,5-dimethylpyrrolide, diethylaluminum-2,5-dimethylpyrrolide, ethylaluminum-bis (2,5-dimethylpyrrolide C) and the like.

Further, lithium-3,4-dichloropyrrolide, sodium-2,3,4,5-tetrachloropyrrolide, lithium-2,3,4-trimethylpyrrolide, diethylaluminum-2,3,4 -Trimethylpyrrolide,
Sodium-3,4-diethylpyrrolide, diethylaluminum-3,4-diethylpyrrolide and the like can also be mentioned.
Suitable alkyl aluminum compounds used for preparing the catalyst include alkyl aluminum compounds represented by the following general formula (2).

[0018]

## STR2 ## _{^{R 1 m Al (OR 2)}} n H p X q ... (2)

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

[0020]

Embedded image _{^{R 1 3 Al ... (3)}} R 1 m AlX 3-m (1.5 ≦ m <3) ... (4) R 1 m Al (OR 2) 3-m ... (5) (0 < m <3, preferably ^{1.5 ≦ m <3) R 1} m AlH 3-m ... (6) (0 <m <3, preferably ^{1.5 ≦ m <3) R 1} 2 (AlO) (R ^{_{1 AlO) m AlR 1 2 ...}} (7) (0 ≦ m ≦ 30, preferably 1 ≦ m)

Specific examples of the above alkylaluminum compound include trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylaluminum monochloride, diethylaluminum ethoxide, diethylaluminum hydride, methylaluminoxane, isobutylaluminoxane and the like. The above alkylaluminum compounds can be used as a mixture of two or more. Further, from the viewpoint that by-products of the polymer are small, a trialkylaluminum compound,
Particularly, triethylaluminum is preferably used. Further, a mixture of a trialkylaluminum compound and an alkylaluminum halide compound (such as alkylaluminum monochloride and alkylaluminum dichloride) is also preferably used.

The halogen-containing compound used for preparing the catalyst may be any compound containing a halogen atom. Among them, the 3rd, 4th, 6th and 13th groups of the periodic table
A halogen-containing compound containing an element selected from the group consisting of Group 14, Group 14, and Group 15 is preferred. As halogen, chlorine,
Bromine is preferred, but chlorine is particularly preferred. In preparing a catalyst by adding an alkylaluminum compound to a mixture of a chromium compound, a pyrrole compound and a halogen-containing compound, an inorganic halogen-containing compound is preferably used because of its high reactivity with the pyrrole compound.

Specific examples of the halogen-containing compound include 3
Scandium chloride, yttrium chloride containing group III elements,
Lanthanum chloride, such as titanium tetrachloride containing group 4 elements, zirconium tetrachloride, hafnium tetrachloride, etc., boron trichloride containing group 13 elements, boron tribromide, aluminum chloride,
Aluminum bromide, aluminum fluoride, diethylaluminum chloride, ethylaluminum dichloride, ethylaluminum sesquichloride, gallium chloride, etc.
Carbon tetrachloride, carbon tetrabromide, chloroform, bromoform, iodomethane, dichloromethane, diiodomethane, dichloroethane, tetrachloroethane, containing elements of group 4
Hexachloroethane, allyl chloride, trichloroacetone, hexachloroacetone, hexachlorocyclohexane, bromobenzene, 1,3,5-trichlorobenzene, hexachlorobenzene, hexafluorobenzene,
Phosphorus trichloride, antimony trichloride, trityl hexachloroantimonate, pentachloride containing Group 15 elements such as trityl chloride, tetrachloride silane, tetrabromide silane, trimethylchlorosilane, germanium tetrachloride, tin tetrachloride, tributyltin dichloride, dibutyltin dichloride, etc. Examples include antimony chloride, bismuth trichloride, and the like, and molybdenum pentachloride and tungsten hexachloride containing a Group 6 element.

Among the above-mentioned halogen-containing compounds, those having a large number of halogen atoms are preferable, and those compounds which are soluble in a hydrocarbon solvent or a halogenated hydrocarbon solvent described below are preferable. Such halogen-containing compounds include:
Examples include carbon tetrachloride, chloroform, dichloroethane, tetrachloroethane, hexachloroethane, trichloroacetone, hexachloroacetone, titanium tetrachloride, germanium tetrachloride, tin tetrachloride and the like. The halogen-containing compound can also be used as a mixture of two or more.

In the present invention, a hydrocarbon solvent or a halogenated hydrocarbon solvent is used as an organic solvent as a reaction medium when preparing a chromium-based catalyst. Usually, hydrocarbons having 30 or less carbon atoms or halogenated hydrocarbons are used. Specific examples of such a solvent include aliphatic or alicyclic saturated hydrocarbons such as n-hexane, cyclohexane, n-heptane and n-octane, and aliphatic or alicyclic rings such as 2-hexene, cyclohexene and cyclooctene. Examples include unsaturated hydrocarbons of the formula, aromatic hydrocarbons such as toluene, benzene, and xylene, and halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, chlorobenzene, and dichlorobenzene.

Among the above-mentioned solvents, aliphatic or alicyclic saturated hydrocarbons, aromatic hydrocarbons and mixtures thereof are preferred. Specifically, cyclohexane, n-heptane, benzene, toluene and two kinds thereof are preferred. A mixture of the above is mentioned. In the present invention, a chromium compound, a pyrrole compound in an organic solvent in the absence of an α-olefin,
A chromium-based catalyst is prepared by reacting an alkylaluminum compound and a halogen-containing compound.

The catalyst obtained by the above-mentioned catalyst preparation method is as follows:
High catalytic activity and very high trimer selectivity. Further, there is an advantage that the purity of the α-olefin in the obtained trimer is extremely high. When a chromium-based catalyst is prepared in the presence of an α-olefin, the selectivity of a low polymerization reaction of the α-olefin tends to be low. In the present invention, the activity of the chromium-based catalyst for the α-olefin low polymerization reaction largely depends on the concentration of the chromium compound at the time of preparing the catalyst. The lower the chromium concentration at the time of preparing the catalyst, the higher the activity of the catalyst. Therefore, the amount of the chromium compound used depends on the amount of the solvent 1
As chromium in liter, usually 1 × 10 ^{-7 to} 1 mo
1, preferably 1 × 10 ^{−6 to} 0.5 mol. In particular, 1 × 10 ^{−5 to} 0.05 mol is preferable.

The pyrrole compound is usually used in an amount of 0.001 mol or more per 1 g of chromium. Preferably 0.005 to 1000 mol, particularly 0.01 to 100
mol. The amount of the alkylaluminum compound used is usually 50 mmol per g atom of chromium.
It is at least 1 but preferably at least 0.1 mol from the viewpoint of improving the catalytic activity and the selectivity of the trimer. The upper limit is 10 ⁴ mol or less from the viewpoint of economy.

The halogen-containing compound is used in an amount of usually 1 mmol or more, preferably 50 mmol or more, per 1 g of chromium. There is no particular upper limit on the amount of the halogen-containing compound used. For example, a catalyst can be prepared by adding a chromium compound, a pyrrole compound and an alkylaluminum compound to a halogenated hydrocarbon solvent. The catalyst preparation is preferably carried out in the absence of oxygen and water. The temperature at the time of preparing the catalyst can be arbitrarily selected.
Is preferable. The generation of the catalyst is considered to be substantially completed within a short time, usually a few minutes, after mixing the components, and the generation of the catalyst is completed within a few hours at most.

When a chromium-based catalyst is prepared by adding an alkylaluminum compound to a mixture obtained by adding a chromium compound, a pyrrole compound and a halogen-containing compound (particularly an inorganic halogen-containing compound) to an organic solvent, ,
Before adding the alkylaluminum compound, the reaction product of the pyrrole compound and the halogen-containing compound is
It is preferably formed as a precipitate exhibiting a characteristic broad infrared absorption at 0-3300 cm ^-1 . This absorption is attributed to hydrogen-bonded NH stretching vibration.

The time required to form the above precipitate depends on the reaction temperature and the concentration of each component, but is generally about several minutes when maintaining the above-mentioned reaction temperature and each component concentration. Therefore, when the catalyst is prepared by adding an alkylaluminum compound to a mixture of a chromium compound, a pyrrole compound and a halogen-containing compound, the total required time is 3 minutes or more, preferably 7 minutes or more. In particular, the method of using an inorganic halogen-containing compound as the halogen-containing compound is preferable because the reaction between the pyrrole compound and the halogen-containing compound proceeds rapidly at about room temperature. The catalyst is prepared by various preparation methods according to the order of adding each catalyst component to the solvent.

Usually, the chromium compound and the alkyl aluminum compound are brought into contact last. That is, at the stage of contacting the chromium compound with the alkylaluminum compound, the pyrrole compound and the halogen-containing compound are preferably mixed with the chromium compound or the alkylaluminum compound. For example, the following preparation method is used.

(1) A method in which a mixed solution of a chromium compound, a pyrrole compound and a halogen-containing compound is mixed with an alkylaluminum compound and reacted. (2) A method in which a mixed solution of a pyrrole compound, an alkylaluminum compound and a halogen-containing compound is mixed with a chromium compound and reacted. (3) A method of mixing and reacting a mixture of a chromium compound and a pyrrole compound with a mixture of an alkylaluminum compound and a halogen-containing compound.

In the above-mentioned preparation method, which one is added to which at the time of mixing is optional. For example, in the above-mentioned preparation method (3), a mixture of a chromium compound and a pyrrole compound may be added to a mixture of an alkylaluminum compound and a halogen-containing compound, or vice versa.
In the above preparation method (1), when an inorganic halogen compound is used as the halogen-containing compound,
Before mixing the mixed solution of the chromium compound, the pyrrole compound and the halogen-containing compound with the alkylaluminum compound, it is preferable to form a reaction product of the pyrrole compound and the halogen-containing compound as a precipitate. As a result, a catalyst having high activity for the low polymerization reaction of α-olefin can be obtained.

A chromium-based catalyst prepared by a method of forming a reaction product of a pyrrole compound and a halogen-containing compound as a precipitate before adding the alkylaluminum compound has a high α-olefin low polymerization activity. The reason has not been elucidated yet, but is presumed as follows.

That is, when a pyrrole compound is reacted with a halogen-containing compound, a substrate is produced which is essential for the production of highly active catalytically active species which gives a highly selective α-olefin trimer. When adding an alkylaluminum compound to a mixture of a chromium compound, a pyrrole compound, and a halogen-containing compound, if the chromium compound and the alkylaluminum are in contact with each other unless the reaction is sufficiently performed to generate a substrate in advance, The reaction of the chromium compound with the unreacted pyrrole compound and the alkylaluminum compound occurs simultaneously to produce an extremely unstable alkyl-chromium compound. As described in JP-A-6-145241, this alkyl-chromium compound further undergoes a decomposition-reduction reaction in the absence of an α-olefin, resulting in a low polymerization reaction of the α-olefin. Inappropriate demetalation is caused. Therefore, when an alkylaluminum compound is added to a mixture of a chromium compound, a pyrrole compound and a halogen-containing compound, a pyrrole compound and a halogen-containing compound are added before adding the alkylaluminum compound in order to efficiently generate catalytically active species. Is preferably formed as a precipitate.

The most preferred of the above-mentioned preparation methods is a method (2) in which a chromium compound is added to a mixture of a pyrrole compound, an alkylaluminum compound and a halogen-containing compound. According to this preparation method, a chromium-based catalyst having a low polymerization activity of an α-olefin is obtained, and the reaction between the pyrrole compound and the halogen-containing compound is promoted by the coexistence of the alkylaluminum compound regardless of the type of the halogen-containing compound. The advantage is that a more soluble product is produced.

The catalyst thus obtained can be used as it is in the low polymerization reaction of α-olefin. If desired, the solvent can be distilled off from the solution containing the catalyst to concentrate or isolate the catalyst, and this can be used as it is or dissolved in an appropriate solvent for the low polymerization reaction of α-olefin. Although the catalyst can be used by being supported on a carrier such as an inorganic oxide, it is preferable to use the catalyst without being supported by a carrier. That is, according to the present invention, high catalytic activity can be obtained without using a supported catalyst. Further, by using the catalyst without being supported on the carrier, it is possible to omit the support on the carrier with complicated operations, and to increase the total amount of the catalyst used (the total amount of the carrier and the catalyst component) due to the use of the carrier. Problems can be avoided.

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

[0040] Solvents for the low polymerization reaction include those having 4 to 2 carbon atoms such as butane, pentane, hexane, heptane, cyclohexane, octane, methylcyclohexane and decalin.
Zero-chain or alicyclic saturated hydrocarbons, aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, and tetralin are used. These can be used alone,
It can also be used as a mixed solvent. When these solvents are used, the catalyst can be prepared in these solvents in the polymerization reaction zone prior to the initiation of the olefin low polymerization reaction.

As the solvent for the low polymerization reaction, α-olefin itself as a reaction raw material or α-olefin other than the main raw material can be used. As a solvent, it is preferable to use an α-olefin having 4 to 30 carbon atoms, but an α-olefin that is liquid at room temperature is particularly preferable. Among the above solvents, in particular, butane, pentane, hexane,
A chain saturated hydrocarbon having 4 to 7 carbon atoms or an alicyclic saturated hydrocarbon such as heptane and cyclohexane is preferred. When these solvents are used, there is an advantage that high catalytic activity can be obtained.

The concentration of the catalyst in the α-olefin low polymerization reaction zone is usually 1 × 1 as the amount of chromium in 1 liter of the solvent.
0 ^{-7 to} 0.5 mol, preferably 1 × 10 ^{-6 to} 0.2 m
ol, more preferably in the range of 1 × 10 ^{−5 to} 0.05 mol. The reaction temperature of the low polymerization reaction is usually from 0 to 250.
° C, preferably 0-200 ° C, more preferably 20-1 ° C.
It is in the range of 50 ° C. On the other hand, the reaction pressure is from normal pressure to 2
It can be selected from the range of 50 kg / cm ² G, but usually
Pressures up to 100 kg / cm ² G are sufficient. The reaction time is generally in the range of 1 minute to 20 hours, preferably 0.5 to 6 hours.

If hydrogen is allowed to coexist in the reaction system,
This is preferable because the properties of the by-produced polymer are improved. The amount of hydrogen coexisting is usually 0.1 to 1 as a hydrogen partial pressure.
00 kg / cm ² , preferably 1.0 to 80 kg / cm
It is in the range of ² . In the present invention, low polymerization of an α-olefin is carried out as a semi-batch reaction or a continuous reaction using a chromium-based catalyst prepared according to the above catalyst preparation method.

In a semi-batch reaction, usually, α-
The olefin is continuously supplied and reacted at a constant pressure. In a continuous reaction, a pipe reactor or a multi-stage mixing tank is used. A pipe reactor is basically a type of reactor in which a reaction component is introduced from one end of a straight pipe or a coiled or U-shaped curved pipe, and a reaction product is discharged from the other end. The multi-stage mixing tank is basically of a type in which the reaction components are introduced into the first tank of a plurality of mixing tanks arranged in series, sequentially moved to the subsequent tank, and the reaction product is discharged from the final tank. It is a reactor.

In the present invention, a halogen-containing compound is additionally supplied to the reaction zone during the reaction. It is also preferable to additionally supply a pyrrole compound or an alkylaluminum compound in addition to the halogen-containing compound. It is particularly preferable to additionally supply a halogen-containing compound and an alkylaluminum compound. As one aspect of additionally supplying the halogen-containing compound, the halogen-containing compound can be additionally supplied together with the catalyst. For example, a catalyst is prepared in a halogenated hydrocarbon solvent, and a catalyst liquid containing a large amount of the generated free halogenated hydrocarbon can be additionally supplied to the reaction zone. As the halogen-containing compound to be additionally supplied, the pyrrole compound and the alkylaluminum compound,
Usually, the same ones used for the catalyst preparation are used, but other ones can be used if desired. Preferred as the halogen-containing compound to be additionally supplied are group 13 or 1 of the periodic table, such as carbon tetrachloride, hexachloroethane and other halogenated hydrocarbons, ethylaluminum dichloride, diethylaluminum chloride and tin tetrachloride.
It is a compound containing a halogen, especially chlorine, bonded to a Group 4 element.

When a halogen-containing compound, particularly a halogen-containing compound and an alkylaluminum compound, are additionally supplied to the reaction zone by the method of the present invention, the catalyst in the reaction zone is activated, and the catalyst efficiency is significantly improved. That is, the activity of the catalyst subjected to the reaction decreases with time, but when a halogen-containing compound is supplied thereto, the catalyst is activated to improve the activity. Moreover, the activation of the catalyst by the halogen-containing compound is not limited to one time, but can be repeated every time the catalytic activity decreases. Therefore, the additional supply of the halogen-containing compound to the reaction zone is preferably performed at the time when the catalytic activity starts to decrease or at the stage when the catalytic activity is decreasing. It can be added to a catalyst whose activity has decreased to activate it, but this is not a desirable method from the viewpoint of productivity. The activity of the chromium-based catalyst used in the method of the present invention starts to decrease as soon as about 5 minutes, generally about 15 minutes after the reaction,
Thereafter, the activity often decreases over 70 to 80 minutes. Therefore, the additional supply of the halogen-containing compound is usually performed in a zone where the catalyst is present for 5 minutes or more, particularly 15 minutes or more after the reaction. The additional supply may be performed once or may be performed several times each time the activity decreases. The supply amount of the halogen-containing compound at one time is as follows per 1 g of chromium atoms of the catalyst to be activated.
0.1 to 200 mol, especially 1 to 100 mol, is preferred.
Similarly, the pyrrole compound is 0.1 to 100 mol, particularly 1 to 100 mol.
50 moles are preferred, and the alkyl aluminum compound is 1 mole.
It is preferably from 1000 to 1000 mol, particularly preferably from 5 to 500 mol.

Therefore, when the present invention is carried out by a semi-batch reaction, the halogen-containing compound may be additionally supplied at a stage where the consumption rate of the α-olefin has decreased after 5 minutes or more from the start of the reaction. By repeating this additional supply once or several times, the production amount of the α-olefin low polymer per catalyst can be increased. In the case of performing a continuous reaction using a pipe reactor, a solvent, a catalyst, an α-olefin, or the like is supplied from the tip of the reactor, and a halogen-containing compound is supplied from a point in the reactor where the residence time is 5 minutes or longer. Supply additional. Also in this case, the halogen-containing compound may be additionally supplied from several places further downstream.

When the reaction is carried out using a multi-stage mixing tank,
A solvent, a catalyst, and an α-olefin may be supplied to the first tank, and a halogen-containing compound may be additionally supplied to a tank in which the average residence time after the second tank is 5 minutes or more. In this case, the halogen-containing compound may be additionally supplied to an arbitrary tank after the first additional supply tank. The by-product polymer is first removed from the reaction solution, and a solution containing the α-olefin low polymer as a main product is recovered.

Separation and removal of the by-product polymer in the reaction solution are appropriately performed by using a known solid-liquid separation device, and the recovered α
-The olefin low polymer is purified if necessary. For purification, distillation purification is usually employed, and a target component can be recovered with high purity. In the present invention, in particular, 1-hexene of high purity can be industrially advantageously produced from ethylene.

[0050]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples unless it exceeds the gist of the present invention. The product was analyzed by gas chromatography.

Preparation of catalyst 2,5-dimethylpyrrole at room temperature under a nitrogen atmosphere
54.1 mg (0.208 mmol) of tin tetrachloride was added to 5 ml of a toluene solution containing 65 mg (0.312 mmol).
l) was added to give a suspension of a yellow precipitate. After stirring for 15 minutes, 178.9 of triethylaluminum was added to the above suspension.
1.6 ml of a toluene solution containing mg (1.56 mmol) was added and stirred for 15 minutes. Chromium in the resulting solution
(III) 2-ethylhexanoate 50 mg (0.104
mmol) in 1 ml toluene solution. One more
After stirring for 5 minutes, toluene was distilled off under reduced pressure at room temperature. Dilute the resulting brown oil with 5 ml of cyclohexane,
5.2 ml of catalyst solution were obtained.

Low Polymerization of Ethylene A 300 ml autoclave dried in a dryer at 150 ° C. was assembled while heating, and then replaced with vacuum nitrogen. 80 ml of cyclohexane and 0.44 ml of the above-mentioned catalyst solution were charged into this autoclave at room temperature under a nitrogen atmosphere. The autoclave is heated to 80 ° C and the total pressure is 38kg / cm
Ethylene was introduced into the autoclave until ² G was reached. Thereafter, the total pressure was increased to 38 kg / cm ² G, and the reaction temperature was increased to 80 ° C.
And the reaction was carried out.

After 30 minutes, the reaction solution was sampled. Then 2.61 mg (0.017 mmol) of carbon tetrachloride and 14.91 mg (0.13 mm) of triethylaluminum
ol) was introduced into the autoclave, and the reaction was continued for another 30 minutes under the same conditions as above. Thereafter, ethanol was injected into the autoclave to stop the reaction. Table 1 shows the results.

Comparative Example A low-polymerization of ethylene was carried out in the same manner as in the example except that the catalyst prepared in the above example was used and no additional halogen-containing compound and alkylaluminum compound were added during the reaction. . Table 1 shows the results.

[0055]

[Table 1] * 1 Ratio of 1-hexene in C ₆ (%) * 2 g-α-olefin / g-Cr · Hr

Claims (12)

[Claims] 1. A continuous or semi-batch method using a chromium-based catalyst prepared by reacting at least a chromium compound, a pyrrole compound, an alkylaluminum compound and a halogen-containing compound in an organic solvent substantially free of α-olefin. A method for producing an α-olefin low polymer, which comprises additionally supplying a halogen-containing compound during the reaction when an α-olefin is low-polymerized in a solvent by a formula reaction to produce the α-olefin low polymer. 2. A chromium-based catalyst prepared by a process of contacting at least one of a pyrrole compound and a halogen-containing compound with a chromium compound or an alkylaluminum compound before contacting the chromium compound with an alkylaluminum compound. The method for producing an α-olefin low polymer according to claim 1, wherein: 3. The chromium-based catalyst is prepared by contacting a mixture of a chromium compound, a pyrrole compound and a halogen-containing compound in advance with an alkylaluminum compound. Item 2
The method for producing an α-olefin low polymer according to the above. 4. The chromium-based catalyst is prepared by contacting a chromium compound with a mixture of an alkylaluminum compound, a pyrrole compound and a halogen-containing compound in advance. 3. The method for producing an α-olefin low polymer according to item 2. 5. A chromium-based catalyst prepared by contacting a premixed chromium compound and a pyrrole compound with a premixed mixture of an alkylaluminum compound and a halogen-containing compound. The method for producing an α-olefin low polymer according to claim 2, wherein 6. The method according to claim 1, wherein the low-polymerization reaction of the α-olefin is carried out by a continuous reaction, and a halogen compound is additionally supplied to a place where the residence time in the reactor is 5 minutes or more. 5. The method for producing an α-olefin low polymer according to any one of 5. 7. The method according to claim 1, wherein the low-polymerization reaction of the α-olefin is carried out by a semi-batch reaction, and a halogen-containing compound is additionally supplied to the reactor at the time when 5 minutes or more have elapsed from the start of the reaction. 5. The α- according to any one of
A method for producing an olefin low polymer. 8. The low-density α-olefin according to claim 1, wherein the chromium compound is a salt of chromium with β-diketone, β-ketocarboxylic acid or another carboxylic acid. Manufacturing method of coalescence. 9. The halogen-containing compound used for preparing the catalyst is a halogen-containing compound containing an element selected from the group consisting of groups 3, 4, 6, 13, 14, and 15 of the periodic table. The method for producing an α-olefin low polymer according to any one of claims 1 to 8, wherein: 10. The method for producing an α-olefin low polymer according to claim 1, wherein an alkylaluminum compound is additionally supplied in addition to the halogen-containing compound. 11. The halogen-containing compound additionally supplied contains a halogen bonded to an element of group 13 or 14 of the periodic table.
The method for producing an α-olefin low polymer according to any one of the above. 12. The α-olefin according to claim 1, wherein the α-olefin to be subjected to the low polymerization reaction is ethylene, and the low polymer is mainly 1-hexene. Manufacturing method of coalescence.