JPH08301924A - Production of low alpha-olefin polymer - Google Patents

Abstract

PURPOSE: To remove the chromium component of a chromium-base catalyst from a liquid reaction product formed in the reaction for forming a low α-olefin polymer in the presence of the catalyst. CONSTITUTION: A reaction for forming a low α-olefin polymer is performed in a solvent in the presence of a catalyst comprising either a combination essentially consisting of a chromium compound (a), a nitrogenous compound (b) selected from the group consisting of amines, amides and imides and an alkylaluminum compound (c) or a combination containing these components and a halogen compound (d). The obtained liquid reaction product containing the catalyst components is treated with an oxidizing agent to remove the chromium component of the catalyst from the liquid. In this way, the chromium component of the catalyst can be removed at good efficiency by a simple operation.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an α-olefin low polymer, particularly 1-hexene, by low polymerization of an α-olefin, particularly ethylene, in a liquid phase. More specifically, the present invention relates to a method for removing a chromium component of a catalyst from a reaction product liquid produced by a low polymerization reaction.

[0002]

2. Description of the Related Art It is known to low-polymerize α-olefins such as ethylene by using a chromium-based catalyst composed of at least a chromium compound and an organoaluminum compound. For example, Japanese Patent Publication No. 43-18707 describes a method for producing 1-hexene by low-polymerizing ethylene using a catalyst composed of a VIB group transition metal compound containing chromium and poly (hydrocarbylaluminum oxide). There is.

Further, JP-A-3-128904 discloses a method of trimerizing an α-olefin using a catalyst obtained by reacting a chromium compound having a chromium-pyrrolyl bond with a metal alkyl compound or a Lewis acid. Has been described. Further, USP 5,376,612 describes a method for low-polymerizing an α-olefin using a catalyst obtained by mixing a chromium compound, a pyrrole-containing compound, a metal alkyl compound and a halogen-containing compound in a solvent. ing.

On the other hand, some of the inventors have used a catalyst system consisting of at least a combination of a chromium compound and an amine or a metal amide and an alkylaluminum compound, and the chromium compound and the alkylaluminum compound are not pre-contacted. In a mode, a method has been proposed in which an α-olefin low polymer can be obtained with high activity by contacting an α-olefin with a chromium-based catalyst (Japanese Patent Application No. 5-28007).
issue).

[0005]

The reaction product liquid obtained by the low polymerization of α-olefin is then separated into each component by distillation. However, the catalyst component in the reaction product liquid is relatively unstable, and if the reaction product liquid containing the catalyst component is distilled as it is, the catalyst component, especially the chromium component, may be deposited and adhere to the distillation apparatus. Therefore, it is desirable to remove the catalyst component, especially the chromium component, from the reaction product solution prior to distillation.

The present inventors have previously proposed a method of treating the reaction product solution with an acid or alkali aqueous solution to remove the catalyst component (see Japanese Patent Application No. 5-329668). The present invention provides a method for removing a chromium component in a catalyst without using an acid or alkali aqueous solution.

[0007]

According to the present invention, at least (a) a chromium compound, (b) a nitrogen-containing compound selected from the group consisting of amines, amides and imides, and (c)
The chromium component of the catalyst in the reaction product liquid is obtained by low-polymerizing α-olefin in a solvent in the presence of a chromium-based catalyst composed of an alkylaluminum compound, and treating the reaction product liquid containing the formed catalyst component with an oxidizing agent. How to remove,
Will be provided.

The present invention will be described in detail below. The chromium-based catalyst used in the present invention comprises at least (a) a chromium compound, (b) a nitrogen-containing compound selected from the group consisting of amines, amides and imides, and (c) an alkylaluminum compound in combination. It is preferable to further combine (d) a halogen-containing compound with this because the catalyst performance will be further improved.

The chromium compound used in the present invention is a chromium compound having a valence of 0 to 6, and has a general formula:

## STR1 ## This is represented by CrX _n (1). In the above formula, X represents any organic or inorganic group, negative atom or coordinating molecule. n is 1
It represents an integer of ˜6, but is preferably 2 or more. When n is 2 or more, X may be different from each other.

The above organic group usually has 1 to 3 carbon atoms.
Various groups of 0 are mentioned. Examples thereof include hydrocarbon groups such as alkyl groups, cycloalkyl groups, aryl groups, alkylaryl groups, aralkyl groups, and cyclopentadienyl groups, carbonyl groups, and alkoxy groups. Further, a hydrocarbon group having a carboxyl group, a β-diketonate group, a β-ketocarboxyl group, a β-ketoester group, an amide group, or the like is also included. Examples of the inorganic group include chromium salt-forming groups such as nitric acid group and sulfuric acid group. Examples of negative atoms include enzymes and halogens.

Preferred chromium compounds are chromium alkoxy salts, carboxyl salts, β-diketonate salts,
Examples thereof include salts of β-ketoesters with anions, and chromium halides. Specifically, chromium (IV) -t
-Butoxide, chromium (III) acetylacetonate,
Chromium (III) trifluoroacetylacetonate, chromium (III) hexafluoroacetylacetonate, chromium (III) (2,2,6,6-tetramethyl-3,5
-Heptane dionate), Cr (PhCOCHCOP)
h) ₃ (where Ph represents a phenyl group), chromium (II) acetate, chromium (III) acetate, chromium (III) -2-ethylhexanoate, chromium (III)
Benzoate, chromium (III) naphthenate, Cr (C
H ₃ COCHCOOCH ₃ ) ₃ , Chromium chloride, Chromium chloride, Chromium bromide, Chromium bromide, Chromium iodide, Chromium iodide, Chromium fluoride, Chromium fluoride Examples include dichrome.

Further, a complex composed of the above-mentioned chromium compound and an electron donor can also be preferably used. The electron donor is selected from compounds containing nitrogen, oxygen, phosphorus or sulfur. Examples of the nitrogen-containing electron donor include nitriles, amines, amides, nitro compounds, and the like, and specifically, acetonitrile, pyridine, dimethylpyridine, dimethylformamide, N-methylformamide, aniline, nitrobenzene, tetramethylethylenediamine. , Diethylamine, isopropylamine,
Hexamethyldisilazane, pyrrolidone and the like can be mentioned.

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

Examples of the electron donor containing phosphorus include hexamethylphosphoramide, hexamethylphosphorus triamide, triethylphosphite, tributylphosphine oxide, triethylphosphine and the like. Further, as the electron donor containing sulfur, carbon disulfide,
Examples thereof include dimethyl sulfoxide, tetramethylene sulfone, thiophene and dimethyl sulfide.

Of such an electron donor and a chromium compound
Examples of the complex include chromium halide ether complex,
Ester complex, ketone complex, aldehyde complex, alcohol
Complex, amine complex, nitrile complex, phosphine complex,
Examples thereof include thioether complexes. Specifically, Cr
Cl₃・ 3THF, CrCl₃・ 3dioxane, C
rCl₃・ (CH₃CO₂n-C_FourH₉), CrCl₃
・ (CH₃CO₂C₂H_Five), CrCl₃・ 3 (i-C
₃H₇OH), CrCl₃・ 3 [CH₃(CH ₂)₃C
H (C₂H_Five) CH₂OH], CrCl₃・ 3pyri
dine, CrCl₃・ 2 (i-C₃H₇NH₂),
[CrCl₃・ 3CH₃CN] ・ CH₃CN, CrCl
₃・ 3PPh₃, CrCl₂・ 2THF, CrCl₂・
2pyridine, CrCl₂・ 2 [(C₂H_Five)₂
NH], CrCl₂・ 2CH₃ CN, CrCl₂・ 2
[P (CH₃)₂Ph] and the like. (Where T
HF represents tetrahydrofuran and Ph represents a phenyl group.
You )

The chromium compound is preferably used in a form soluble in a hydrocarbon solvent, and examples of such a soluble compound include chromium β-diketonate salts, carboxylates, and β-diketonate salts.
Examples thereof include salts of ketoesters with anions, β-ketocarboxylic acid salts, amide complexes, carbonyl complexes, carbene complexes, various cyclopentadienyl complexes, alkyl complexes and phenyl complexes. Examples of various carbonyl complexes of chromium, carbene complexes, cyclopentadienyl complexes, alkyl complexes, and phenyl complexes include 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 (where Cp represents a cyclopentadienyl group), (Cp * CrClCH
₃ ) ₂ (where Cp * represents a pentamethylcyclopentadienyl group), (CH ₃ ) ₂ CrCl and the like.

The chromium compound can be used by supporting it on a carrier such as an inorganic oxide, but usually it is used in combination with other catalyst components without supporting it on the carrier. That is, in the present invention, it is preferable to use the chromium compound and the alkylaluminum compound constituting the catalyst in a specific contact mode described later, but according to such an embodiment, the chromium compound is not supported on the carrier. High catalytic activity can be obtained.

The amine used in the present invention is a primary or secondary amine.
A class amine, or a mixture thereof. Examples of primary amines include ethylamine, isopropylamine, cyclohexylamine, benzylamine, aniline and naphthylamine, and examples of secondary amines include diethylamine, diisopropylamine, dicyclohexylamine, dibenzylamine, bis (trimethylsilyl) amine and morpholine. , Imidazole, indoline, indole, pyrrole, 2,5-dimethylpyrrole, 3,4-dimethylpyrrole, 3,4-diethylpyrrole, 2,3,
4-trimethylpyrrole, 3,4-dichloropyrrole,
Examples include 2,3,4,5-tetrachloropyrrole, 2-acetylpyrrole, 3,3 ', 4,4'-tetramethyldipyrrolomethane, pyrazole and pyrrolidine.

The amides used in the present invention include metal amides and acid amides. As a metal amide,
Mention may be made of metal amides derived from primary or secondary amines, or mixtures thereof, such as the abovementioned primary or secondary amines with groups IA, IIA, IIIA and IV.
Mention may be made of amides obtained by reaction with metals selected from Group B.

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 pyrrolid, potassium pyrrolidide, aluminum diethylpyrrolid, ethylaluminum dipyrrolid, aluminum tripyrrolid, lithium (2,5-dimethylpyrrolid) and the like.

In the present invention, a secondary amine among the above amines and metal amides, a metal amide derived from a secondary amine, or a mixture thereof is preferably used. In particular, pyrrole or 2,5-dimethylpyrrole, 3,4-dimethylpyrrole, 2,3,4-trimethylpyrrole, 3,4-dichloropyrrole, 2,3,4,
5-tetrachloropyrrole, 2-acetylpyrrole,
Pyrrole derivatives such as 3,3 ′, 4,4′-tetramethyldipyrrolomethane, or metal amides derived therefrom, such as aluminum pyrrolide, ethylaluminum dipyrrolide, aluminum tripyrrolid, sodium pyrrolide, lithium Pyrrolide, potassium pyrrolide, aluminum (2,5-dimethylpyrrolide), ethylaluminum bis (2,5-dimethylpyrrolide), aluminum tris (2,5-dimethylpyrrolide), sodium (2,5-dimethyl) Pyrrolide), lithium (2,5-dimethylpyrrolide), potassium (2,5-dimethylpyrrolide) and the like are preferable. Among them, a pyrrole derivative having a hydrocarbon group on the pyrrole ring is particularly preferable.

Examples of the acid amides or imides used in the present invention other than the above include compounds represented by the following general formulas (2) to (4).

Embedded image

In the general formula (2), M ¹ is a hydrogen atom or a periodic table (in this specification, the periodic table is CAS versi).
based on. Therefore, Group IIIA is IUPAC 3
It is a B group. ), A metal element selected from the group IA, IIA, IB, IIIA, R ¹ is a hydrogen atom, a carbon number of 1 to
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 COR ³ (wherein R ³ is the same as R ¹ There, R ¹ and represents may also) be different, R ¹ and R ² may form a ring.

In the general formula (3), M ² and M ³ are hydrogen atoms or metal elements selected from the groups IA, IIA, IB and IIIA of the periodic table, and 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, and R ⁴ and R ⁵ represent a ring. And A represents an alkylene group which may contain an unsaturated bond.

Examples of the acid amides represented by the general formula (2) or the general formula (3) include acetamide, N-methylhexanamide, succinamide, maleamide and N-.
Methylbenzamide, imidazole-2-carbonamide, 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. Is mentioned. Examples of the imides include 1,2-cyclohexanedicarbonimide, succinimide, phthalimide, maleimide, 2,4,6-piperidinetrione, perhydroazecin-2,10-dione, and IA of the periodic table. , IIA, IB or IIIA metal salts.

In the general formula (4), M ⁴ is a hydrogen atom or a metal element selected from the groups IA, IIA, IB, and IIIA of the periodic table, and R ⁶ is a hydrogen atom or a carbon number of 1 to 1. Three
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 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 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 (4) are benzenesulfonamide, N-methylmethanesulfonamide, N-
Methyltrifluoromethanesulfonamide and salts thereof with metals of Group IA, IIA, IB or IIIA of the Periodic Table. Among these amide or imide compounds, the compound represented by the general formula (2) is preferable, and in particular, R ² in the general formula (2) represents an acyl group COR ³ , and R ¹ and R ² represent a ring. The imide compound formed is preferred.

As the alkylaluminum compound used in the present invention, an alkylaluminum compound represented by the following general formula (5) is preferably used.

Embedded image R ¹ _m Al (OR ² ) _n H _p X _q (5)

In the general formula (5), 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 from each other. Represents a halogen atom, m is 0 <m ≦ 3, n is 0 ≦ n <3, p
Represents a number of 0 ≦ p <3, q represents a number of 0 ≦ q <3, and represents a number of m + n + p + q = 3.

Examples of the above alkylaluminum compound include trialkylaluminum compounds represented by the following general formula (6), halogenated alkylaluminum compounds represented by the general formula (7), and alkoxy represented by the general formula (8). Examples thereof include an alkylaluminum compound and an alkylaluminum hydride compound represented by the general formula (9). The definitions of R ¹ , X and R ² in each formula are the same as in the case of the general formula (5).

[0031]

Embedded image R ¹ ₃ Al (6) R ¹ _m AlX _3-m (7) (m is 1.5 ≦ m <3) R ¹ _m Al (OR ² ) _3-m (8) ( m is 0 <m <3, preferably 1.5 ≦ m <3) R ¹ _m AlH _3-m (9) (m is 0 <m <3, preferably 1.5 ≦ m <3)

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

The halogen-containing compound used in the present invention includes III A, III B, IVA, IVB, VA,
A halogen-containing compound containing an element selected from the group consisting of VB and VIB groups is preferably used. And, as the halogen, chlorine or bromine is preferable.

Specific examples of the above halogen-containing compound include scandium chloride, yttrium chloride, lanthanum chloride, titanium tetrachloride, zirconium tetrachloride, hafnium tetrachloride, boron trichloride, aluminum chloride, diethylaluminum chloride, ethylaluminum sesquichloride. , Gallium chloride, carbon tetrachloride, chloroform, methylene chloride, dichloroethane, hexachlorobenzene, 1,
1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, pentachloroethane, hexachloroethane, 1,1,1-trichloropropane, 1,1,2,2-tetrachloropropane , 1,1,1-trichlorobutane, 1,1,2,2-
Tetrachlorobutane, 1,1,1-trichloropentane, 1,1,2,2-tetrachloropentane, 1,1,
1-tribromoethane, 1,1,2,2-tetrabromoethane, 1,2,3,4,5,6-hexachlorocyclohexane, 1,3,5-trichlorobenzene, trityl chloride, silicon tetrachloride, trimethyl Chlorosilane, germanium tetrachloride, tin tetrachloride, tributyltin chloride, phosphorus trichloride, antimony trichloride, trityl hexachloroantimonate, antimony pentachloride, bismuth trichloride, boron tribromide, aluminum tribromide, carbon tetrabromide,
Examples include bromoform, bromobenzene, iodomethane, silicon tetrabromide, hexafluorobenzene, aluminum fluoride and the like.

Of the above halogen-containing compounds, those having a large number of halogen atoms are preferable, and compounds soluble in the reaction solvent are preferable. Examples of particularly preferred halogen-containing compounds include carbon tetrachloride, chloroform, 1,1,1
-Trichloroethane, 1,1,2,2-tetrachloroethane, pentachloroethane, hexachloroethane, 1,
2,3,4,5,6-hexachlorocyclohexane, titanium tetrachloride, germanium tetrachloride, tin tetrachloride and the like can be mentioned. The halogen-containing compound may be used as a mixture of two or more kinds.

In the present invention, a catalyst system comprising the above catalyst components is used to carry out low polymerization of α-olefin in a reaction solvent. Then, α- in a mode in which the chromium compound (a) and the alkylaluminum compound (c) do not come into contact with each other in advance.
It is preferable to contact the olefin and the chromium-based catalyst. As a result, the trimerization reaction is selectively carried out and 1-hexene can be obtained in high yield from the raw material ethylene.

As a specific example of such a contact mode,
(1) A method of introducing α-olefin and catalyst component (a) into a solution containing catalyst components (b) and (c), (2) α-olefin in a solution containing catalyst components (a) and (b) Method of introducing olefin and catalyst component (c), (3) α-olefin in solution containing catalyst component (a), catalyst component (b)
And (c), (4) a method of introducing α-olefin, catalyst components (a) and (b) into a solution containing the catalyst component (c), and (5) catalyst components (a) to (). c)
And α-olefin can be simultaneously and independently introduced into the reactor. And each said solution is normally prepared using a reaction solvent.

As the above-mentioned contact mode when the halogen-containing compound is used, specifically, (1) the α-olefin and the catalyst component (a) are added to a solution containing the catalyst components (b) to (d). ) Is introduced, (2) catalyst component (a),
A method of introducing an α-olefin and a catalyst component (c) into a solution containing (b) and (d), (3) an α-olefin and a catalyst component (in a solution containing the catalyst components (a) and (d) b) and (c) are introduced, (4) α-olefin, catalyst components (a) and (b) are introduced into a solution containing catalyst components (c) and (d), (5) catalyst Method of introducing α-olefin, catalyst components (c) and (d) into a solution containing components (a) and (b), (6) α into a solution containing catalyst components (b) and (c) A method of introducing olefin, catalyst components (a) and (d), (7) introducing α-olefin, catalyst components (a), (b) and (d) into a solution containing catalyst component (c). (8) a method of introducing α-olefin and catalyst components (b) to (d) into a solution containing the catalyst component (a), (8) ) Alpha-olefin and the catalyst components (a) ~ (d) can be conducted by a method of introducing into the reaction system simultaneously and independently, respectively. And each said solution is normally prepared using a reaction solvent.

Among these, the chromium compound (a) and the alkylaluminum compound (c) are maintained in a mode in which they do not come into contact with each other in advance, and the chromium compound (a) and the alkylaluminum compound (c) are subjected to a low polymerization reaction. It is preferable to employ a method in which the α-olefin is simultaneously contacted.

In the present invention, "a mode in which the chromium compound and the alkylaluminum compound do not come into contact in advance"
Means not only at the start of the reaction, but also after the additional α-
It is meant that such an aspect is maintained in the supply of the olefin and the catalyst component to the reactor. However, this is the preferred mode required in forming the catalyst system from the catalyst components and is irrelevant after the catalyst system is formed. Therefore, the circulation of the catalyst liquid recovered from the reaction system after the formation of the catalyst system according to the above-mentioned embodiment is not contrary to the above-mentioned preferred embodiment.

The reason why the activity of the low polymerization reaction of α-olefin is lowered when the chromium-based catalyst is used in such a manner that the chromium compound and the alkylaluminum compound are in contact with each other in advance is not clear, but it is presumed as follows. To be done. 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 with the chromium compound and the alkyl group in the alkylaluminum compound. And, the alkyl-chromium compound produced by such a reaction is unstable in itself, unlike the alkyl-chromium compound obtained by a usual method. Therefore, the decomposition-reduction reaction of the alkyl-chromium compound preferentially proceeds, as a result, inappropriate demetallation is induced in the low polymerization reaction of the α-olefin, and the activity of the low polymerization reaction of the α-olefin decreases. Presumed.

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 suitable as the raw material α-olefin, and according to the present invention, 1-hexene, which is a trimer of ethylene, can be obtained from ethylene in high yield and high selectivity.

In the present invention, the reaction solvent is carbon such as butane, pentane, 3-methylpentane, hexane, heptane, 2-methylhexane, octane, 2,2,4-trimethylpentane, cyclohexane, methylcyclohexane, decalin. A chain or alicyclic saturated hydrocarbon of the number 3 to 20, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, mesitylene, and tetralin are used. These may be used alone or as a mixed solvent.

Further, 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. For example, α-olefin having 4 to 30 carbon atoms can be used.
Olefin is used, but α-olefin which is liquid at room temperature is particularly preferable. Particularly preferred as the reaction solvent is
It is a chain saturated hydrocarbon or alicyclic saturated hydrocarbon having 4 to 10 carbon atoms. By using these solvents,
There is an advantage that by-products of the polymer can be suppressed, and further, when an alicyclic hydrocarbon is used, high catalytic activity can be obtained.

In the present invention, the amount of the chromium compound used is usually 1.0 × 10 ⁻⁷ to 1 liter of the reaction solvent.
It is 0.5 mol. Preferably 1.0 * 10 < ^-6 > -0.
It is in the range of 2 mol, particularly 1.0 × 10 ^{−5 to} 0.05 mol. On the other hand, the amount of the alkylaluminum compound used is usually 50 mmol or more per 1 mol of the chromium compound, but it is preferably 0.1 mol or more from the viewpoint of catalytic activity and selectivity of the trimer. And the upper limit is usually 1.0 × 10 ⁴ mol. Also, amine,
The amount of the amide or imide used and the amount of the halogen-containing compound used are usually 0.001 per mol of the chromium compound.
It is more than mol. Preferably 0.005-1000 m
ol, particularly in the range of 0.01 to 100 mol.

In the present invention, (a) a chromium compound,
The molar ratio of (b) a nitrogen-containing compound selected from the group consisting of amines, amides and imides, (c) an alkylaluminum compound, and (d) a halogen-containing compound used for improving yield and selectivity is 1 : 0.1 to 10: 1 to
100: 0.1-20 is preferable, and 1: 1-5: 5-5
0: 1 to 10 is particularly preferable. By adopting such specific conditions, for example, as a low polymer of ethylene, 90% of hexene can be obtained.
It can be produced at a yield of more than 100% (ratio to the total amount produced), and the content of 1-hexene in hexene can be increased to 99% or more.

The low polymerization reaction of the present invention is usually 0 to 250 ° C.
It is done in. Suitable reaction temperatures are 0 to 150 ° C., especially 2
0-100 ° 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 , but usually 1
Pressures up to 00 kg / cm ² are sufficient. The reaction time is usually 1 minute to 20 hours, preferably 0.5 to
The range is 6 hours. The reaction system may be a batch system, a semi-batch system or a continuous system.

If hydrogen is allowed to coexist in the reaction system,
Since the shape of the by-produced polymer can be made into powder, it is possible to prevent the polymer from adhering to the device. The amount of hydrogen to coexist is usually 0.1 to 10 as a hydrogen partial pressure.
0 kg / cm ² , preferably 1.0 to 80 kg / cm ²
Range.

In the present invention, the reaction product solution thus obtained is treated with an oxidizing agent to precipitate the chromium component.
The oxidizing agent is not particularly limited and various known ones can be used. Specifically, for example, peroxides such as hydrogen peroxide, heavy metal ions having an extremely small ionization tendency, for example, various salts of Ag ⁺ , Ag ²⁺ , Pb ⁴⁺ , and metal ions having variable valences, For example, Fe ³⁺ , Co ³⁺ , Cr ⁶⁺ , Mn
Examples thereof include various salts of ³⁺ and Ce ⁴⁺ , oxides thereof, and the like. Among them, Ag ⁺ , Fe ³⁺ , Co ³⁺ , Cr ⁶⁺ , M
Salts of n ³⁺ and Ce ⁴⁺ are preferable from the viewpoint of easy handling and safety.

The treatment with an oxidant is carried out by adding an oxidant to the reaction product liquid and then in an atmosphere of an inert gas such as nitrogen for 0-100
C., preferably 10 to 80.degree. C., for 0.1 to 48 hours, preferably 0.25 to 24 hours by stirring. The amount of the oxidizing agent used is 1 to 200,000 mol, preferably 1 to 2 mol, per 1 mol of chromium metal.
It is in the range of 10,000 mol.

As a result, chromium formation of the catalyst in the reaction product liquid is precipitated as a solid, and it is removed by a solid-liquid separation means such as filtration or centrifugation which is a conventional method. Although the by-produced polymer exists in the reaction product liquid, solid-liquid separation may be performed also for removing the by-produced polymer. Although the reaction product liquid after removing the chromium component by the method of the present invention contains the aluminum component, it can be directly subjected to distillation. If it is desired to remove the aluminum component, the reaction product solution after removing the chromium component by the method of the present invention is treated with an aqueous solution of sodium hydroxide or potassium hydroxide, preferably a high-concentration aqueous solution of 10 wt% or more. Good.

The recovered α-olefin low polymer is purified if necessary. Distillation purification is usually employed for purification, and the target component can be recovered in high purity. In the present invention, in particular, a highly pure 1
-Hexene can be produced industrially advantageously.

[0053]

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 unless it exceeds the gist. Example 1 A 2 L autoclave dried in a dryer at 150 ° C. was assembled while hot and then replaced with vacuum nitrogen. A catalyst feed tube equipped with a rupture plate was attached to this autoclave. n-heptane (486 ml), 2,5-dimethylpyrrole (0.30 mmol) in n-heptane, triethylaluminum (1.52 mmol) in n-heptane, 1,1,2,2-tetrachloroethane (0. 5
0 mmol) of n-heptane solution was charged to the autoclave, while the catalyst feed tube was charged with Cr (III) -2-ethylhexanoate (0.10 mmol) of n-heptane solution. The total amount of n-heptane was 500 ml.

First, the autoclave is heated to 80 ° C.,
Then ethylene was introduced into the catalyst feed tube at 80 ° C.
The rupture disk bursts due to ethylene pressure, and the chromium compound
Introduced into the toclave to start the low polymerization reaction of ethylene.
It was Total pressure is 35 kg / cm ²Ethylene so that
Introduced. Total pressure 35kg / cm², Temperature 80 ℃ for 30 minutes
Reacted for a while. The reactor is then cooled and autoclaved.
Was released to perform degassing.

As a result of composition analysis of the produced α-olefin low polymer by gas chromatography, the catalyst activity (g-α
-Olefin / g-Cr · hr) is 104,832, C6 content in all products is 91.4 (wt%), C6
The content of 1-hexene in the body was 98.2 (wt%). Part of reaction product (865 ml) (100 ml)
Was collected under nitrogen, to which 0.5 g of silver sulfate was added,
The mixture was stirred at room temperature for 5 hours under a nitrogen atmosphere. After allowing to stand, the solid was allowed to settle, the supernatant was collected under nitrogen, extracted with a 10% sodium hydroxide aqueous solution, and then the extract and the supernatant of the extract were subjected to a high-frequency plasma emission spectroscopic apparatus "ICAP-88".
Chromium was not detected at all in any of the liquids as measured by (Japan Jarrell Ash).

As an oxidizing agent, nitric acid was used instead of silver sulfate.
Cerium ammonium [(NH_Four) ₂Ce (N
O₃)₆], Ferric nitrate, cobalt (III) acetylacea
Setonate or manganese (III) acetylacetonate
The reaction liquid was treated in the same manner as described above except that 1 g of each was used.
Even if it was performed, chromium was not detected in the reaction product solution after the treatment.
I couldn't.

[0057]

According to the present invention, a combination of at least (a) a chromium compound, (b) a nitrogen-containing compound selected from the group consisting of amines, amides and imides and (c) an alkylaluminum compound, and further to d) In the low polymerization method of an α-olefin which uses a chromium-based catalyst formed by combining a halogen-containing compound, the chromium component of the catalyst contained in the reaction product liquid can be easily removed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Okano 3-10 Shiotsu, Kurashiki-shi, Okayama Mizushima Development Laboratory, Mitsubishi Chemical Co., Ltd. (72) Shinji Iwade 3--10 Shiotsu, Kurashiki, Okayama Mitsubishi Mizushima Development Laboratory, Kagaku Co., Ltd.

Claims (6)

[Claims] 1. A method for producing an α-olefin low polymer by low-polymerizing an α-olefin in a solvent in the presence of a chromium-based catalyst, wherein the chromium-based catalyst is at least
(A) a chromium compound, (b) a nitrogen-containing compound selected from the group consisting of amines, amides and imides, and (c) an alkylaluminum compound, and a reaction product solution containing a catalyst component is treated with an oxidizing agent. The method for producing an α-olefin low polymer, characterized by precipitating a chromium component in the catalyst. 2. A chromium-containing catalyst, at least (a) a chromium compound, (b) a nitrogen-containing compound selected from the group consisting of amines, amides and imides, (c) an alkylaluminum compound, and (d) a halogen-containing compound. The method for producing an α-olefin low polymer according to claim 1, which comprises: 3. The halogen-containing compound is III in the periodic table.
The method for producing an α-olefin low polymer according to claim 2, which contains an element selected from the group consisting of A, IIIB, IVA, IVB, VA, VB and VIB groups. 4. The method for producing an α-olefin low polymer according to claim 1, wherein the α-olefin and the chromium-based catalyst are contacted with each other without previously contacting the chromium compound with the alkylaluminum compound. . 5. The α-olefin is ethylene, and α-
The method for producing an α-olefin low polymer according to any one of claims 1 to 4, wherein the olefin low polymer is mainly composed of 1-hexene. 6. The α-olefin low polymer according to claim 1, wherein a solid oxidizing agent selected from metal salts is added to a reaction product liquid containing a catalyst component to precipitate a chromium component. Production method.