JPH08283330A - Production of low alpha-olefin polymer - Google Patents

Abstract

PURPOSE: To obtain an improved process for producing a low α-olefin polymer in the presence of a chromium catalyst, the process having been improved so that a by-product polymer and the catalyst component can be efficiently removed, enabling the polymer to be produced industrially advantageously. CONSTITUTION: A low polymn. of an α-olefin is conducted in a solvent in the presence of a catalyst system at least comprising a chromium compd., at least one compd. selected from among an amine, an amide, and an imide, and an alkylalumium compd. Then, after the catalyst component is removed from the reaction soln. while keeing the soln. at such a temp. as not to cause the precipitation of a by-product polymer, the soln. is condensed by distillation, thus separating the by-product polymer together with high-boiling components.

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 particularly, to a high yield of an α-olefin low polymer mainly composed of ethylene and 1-hexene. The present invention relates to a method for producing an industrially advantageous α-olefin low polymer which can be produced with a high selectivity.

[0002]

2. Description of the Related Art Conventionally, as a method for low polymerization of α-olefin such as ethylene, there has been known a method of using a chromium-based catalyst comprising a combination of a specific chromium compound and a specific organoaluminum compound. For example, Japanese Patent Publication No.
No. 8707 describes a method for obtaining 1-hexene from ethylene with a catalyst system comprising a Group VIB transition metal compound containing chromium and polyhydrocarbyl aluminum oxide.

Further, in JP-A-3-128904, α-olefin is trimerized by using a catalyst obtained by previously reacting a chromium-containing compound having a chromium-pyrrolyl bond with a metal alkyl or Lewis acid. How to do is described.

[0004]

By the way, by any of the above-mentioned methods, the by-product of the polymer is unavoidable. In particular, in the industrial production method of the α-olefin low polymer, the method of producing the by-product polymer is determined. It is an important issue to separate them. The present invention has been made in view of such circumstances, and an object thereof is a method for producing an α-olefin low polymer using a chromium-based catalyst, in which a by-product polymer is efficiently produced by a compact process. It is an object of the present invention to provide an industrially advantageous method for producing an α-olefin low polymer which is improved so that it can be separated.

[0005]

That is, the gist of the present invention is, in a method for producing an α-olefin low polymer using a chromium-based catalyst, at least as a chromium-based catalyst,
Low polymerization of α-olefin in a solvent using a catalyst system comprising a combination of a chromium compound (a), one or more compounds (b) selected from the group of amines, amides and imides, and an alkylaluminum compound (c). And removing the catalyst component while maintaining the temperature of the reaction liquid at a temperature at which the by-product polymer does not precipitate, and then the by-product polymer is concentrated and separated together with the high boiling point component in a distillation separation operation.
-A method for producing olefin low polymers.

The present invention will be described in detail below. In the present invention, as the chromium-based catalyst, a catalyst system comprising a combination of at least one compound (b) selected from the group of chromium compound (a), amine, amide and imide and alkylaluminum compound (c). use. And in a preferred embodiment, a catalyst system comprising a combination of a chromium compound (a), one or more compounds (b) selected from the group of amines, amides and imides, an alkylaluminum compound (c) and a halogen-containing compound (d). To use.

The chromium compound used in the present invention is represented by the general formula CrXn. However, in the general formula, X represents an arbitrary organic group or inorganic group or a negative atom, n represents an integer of 1 to 6, and when n is 2 or more, X may be the same or different from each other. Good. The valence of chromium is 0 to 6, and n in the above formula is preferably 2 or more.

Examples of the organic group include various groups having usually 1 to 30 carbon atoms. Specific examples thereof include a hydrocarbon group, 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, a cyclopentadienyl group and the like. Examples of the inorganic group include a chromium salt-forming group such as a nitrate group and a sulfate group, and examples of the negative atom include oxygen and halogen.

The preferable chromium compound is an alkoxy salt of chromium, a carboxyl salt, a β-diketonate salt, a salt of β-ketoester with an anion, or a chromium halide, specifically, chromium (IV) -t- Butoxide, Chromium (III) Acetylacetonate, Chromium (III)
Trifluoroacetylacetonate, chromium (III) Hexafluoroacetylacetonate, chromium (III) (2
2,6,6-tetramethyl-3,5-heptanedionate), Cr (PhCOCHCOPh) ₃ (provided that P is
h represents a phenyl group. ), Chromium (II) acetate, chromium (III) acetate, chromium (III) -2-ethylhexanoate, chromium (III) benzoate, chromium (III)
_{Naphthenates, Cr (CH 3 COCHCOOCH 3)} 3,
Chromium chloride, Chromium chloride, Chromium bromide, Chromium bromide, Chromium iodide, Chromium iodide,
Chromium fluoride, chromic fluoride, etc. may be mentioned.

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 compound include nitrile, amine and amide, and specifically, acetonitrile, pyridine, dimethylpyridine, dimethylformamide, N-methylformamide, aniline, nitrobenzene, tetramethylethylenediamine, diethylamine, isopropylamine, hexa Methyldisilazane,
Examples thereof include pyrrolidone.

Examples of the oxygen-containing compound 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 phosphorus-containing compounds 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, it is composed of a chromium compound and an electron donor.
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,
CrCl₃ ・ (CH₃ CO₂ n-C_Four H₉ ), C
rCl₃ ・ (CH₃ CO₂ C₂ H_Five ), CrCl₃ ・
3 (i-C₃ H₇ OH), CrCl₃ ・ 3 [CH ₃ (C
H₂ )₃ CH (C₂ H_Five ) CH₂ OH], CrCl₃ ・
3pyridine, CrCl₃ ・ 2 (i-C₃ H₇ N
H₂ ), [CrCl₃ ・ 3CH₃ CN] ・ CH₃ CN,
CrCl₃ ・ 3PPh₃ , CrCl₂ ・ 2THF, Cr
Cl₂ ・ 2pyridine, CrCl₂ ・ 2 [(C₂ 
H_Five)₂ NH], CrCl₂ ・ 2CH ₃ CN, CrCl₂ 
・ 2 [P (CH₃ )₂ Ph] and the like.

The chromium compound can be used in a hydrocarbon solvent.
Soluble compounds are preferred, chromium β-diketonate salts,
Carboxylates, salts with anions of β-ketoesters, β
-Ketocarboxylates, amide complexes, carbonyl complexes,
Ruben complex, various cyclopentadienyl complexes, alkyl
Examples thereof include complexes and phenyl complexes. Various chrome power
Rubonyl complex, carbene complex, cyclopentadienyl complex
As the body, the alkyl complex, and the phenyl complex,
Is Cr (CO)₆ , (C₆ H₆) Cr (CO) ₃ ,
(CO)_Five Cr (= CCH₃ (OCH₃ )), (CO)
_Five Cr (= CC₆ H _Five (OCH₃ )), CpCrCl₂ 
(Where Cp represents a cyclopentadienyl group), (
Cp * CrClCH₃)₂ (Where Cp * is pentamethyl
Indicates a cyclopentadienyl group. ), (CH₃)₂ CrC
1 and the like are exemplified.

The chromium compound can be used by supporting it on a carrier such as an inorganic oxide, but it is preferable to use it in combination with other catalyst components without supporting it on the carrier. That is, in the present invention, the chromium-based catalyst is used in a specific contact mode 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. You can avoid the problem.

The amine used in the present invention is a primary or secondary amine.
It is a class amine. Examples of primary amines include ethylamine, isopropylamine, cyclohexylamine, benzylamine, aniline, naphthylamine, and the like.
As the secondary amine, diethylamine, diisopropylamine, dicyclohexylamine, dibenzylamine,
Bis (trimethylsilyl) amine, morpholine, imidazole, indoline, indole, pyrrole, 2,5-
Dimethylpyrrole, 3,4-dimethylpyrrole, 3,4
-Dichloropyrrole, 2,3,4,5-tetrachloropyrrole, 2-acetylpyrrole, pyrazole, pyrrolidine and the like are exemplified.

Examples of the amide used in the present invention include metal amides derived from primary or secondary amines, such as the above primary or secondary amines and Group IA.
Mention may be made of amides obtained by reaction with metals selected from the groups IIA, IIIA and 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 and potassium. Examples thereof include pyrrolide, potassium pyrrolidide, aluminum diethylpyrrolide, ethylaluminum dipyrrolide and aluminum tripyrolide.

In the present invention, the above-mentioned secondary amine,
Metal amides derived from secondary amines or mixtures thereof are preferably used. Particularly, as the secondary amine, pyrrole, 2,5-dimethylpyrrole, 3,4-dimethylpyrrole, 3,4-dichloropyrrole, 2,3,3.
Examples of the metal amide derived from 4,5-tetrachloropyrrole, 2-acetylpyrrole, and a secondary amine include
Aluminum pyrrolide, ethylaluminum dipyrrolide, aluminum tripyrolide, sodium pyrrolide, lithium pyrrolide and potassium pyrrolide are preferred. Among the pyrrole derivatives, those having a hydrocarbon group on the pyrrole ring are particularly preferable.

Examples of the amide or imide compound other than the above used in the present invention include compounds represented by the following general formulas (1) to (3).

[0020]

Embedded image

In the general formula (1), M ¹ is a hydrogen atom or a metal element selected from groups IA, IIA, IB and IIIA of the periodic table, and R ¹ is a hydrogen atom and has 1 to 30 carbon atoms. It 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 an alkyl group having 1 to 30 carbon atoms. Group, alkenyl group, aralkyl group, aryl group which may have a substituent, aryl group which may contain a hetero element, or acyl group CO
R ³ (R ³ is the same definition as R ^1, R ¹ and may be different) represents, R ¹ and R ² may form a ring.

In the general formula (2), 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. A may be formed, and A represents an alkylene group which may contain an unsaturated bond.

The acid amides represented by the general formula (1) or (2) include, for example, acetamide, N-methylhexanamide, succinamide, maleamide, N-.
Methylbenzamide, imidazole-2-carbonamide, di-2-thenoylamine, β-lactam, δ-lactam, ε-caprolactam, and salts of these with metals of group IA, IIA, IB or IIIA of the periodic table are Listed. Examples of the imides include 1,2-cyclohexanedicarboximide, succinimide, phthalimide, maleimide, 2,4,6-piperidinetrione, perhydroazecin-2,10-dione, and those of the periodic table. Mention may be made of salts with metals of group IA, IIA, IB or IIIA.

In the general formula (3), M^Four Is a hydrogen atom or
Gold selected from IA, IIA, IB and IIIA groups of the periodic table
R is a genus element⁶ Is a hydrogen atom or an atom having 1 to 30 carbon atoms.
Having a rualkyl group, an alkenyl group, an aralkyl group, and a substituent
Optionally containing an aryl group or a hetero element
Represents an optional aryl group, R⁷ Is a hydrogen atom, carbon
Number 1 to 30 alkyl group, alkenyl group, aralkyl
Group, aryl group optionally having substituent (s), hetero element
An aryl group which may contain₂R⁸ Base
(R⁸ Is R⁶ Is the same definition as⁶ Even if different from
Good), R ⁶ And R⁷ 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 these amide or imide compounds, the compound represented by the general formula (1) is preferable, and in particular, R ² in the general formula (1) represents an acyl group COR ³ ,
An imide compound in which R ¹ and R ² form a ring is preferable.

In the present invention, an alkylaluminum compound represented by the following general formula (4) is preferably used as the alkylaluminum compound.

[0027]

Embedded image R ¹ _m Al (OR ² ) _n H _p X _q (4)

In the general 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 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 (5), halogenated alkylaluminum compounds represented by the general formula (6), and alkoxy groups represented by the general formula (7). Examples thereof include an alkylaluminum compound and 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 above.

[0030]

Embedded image R ¹ ₃ Al (5) R ¹ _m AlX _3-m (m is 1.5 ≦ m <3) (6) R ¹ _m Al (OR ² ) _3-m ( m is 0 <m <3, preferably 1.5 ≦ m <3) (7) R ¹ _m AlH _3-m (8) (m is 0 <m <3, preferably 1. 5 ≦ m <3)

Specific examples of the above alkylaluminum compound 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.

In the present invention, the halogen-containing compound includes IIIA, IIIB, IVA, IVB and V of the periodic table.
A halogen-containing compound containing an element selected from the group consisting of A, VB and VIB 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, trichloroethane, tetrachloroethane, hexachlorobenzene, 1,3,5-trichlorobenzene, hexachlorocyclohexane, trityl chloride, tetrachlorosilane, trimethylchlorosilane,
Germanium tetrachloride, tin tetrachloride, tributyltin chloride, phosphorus trichloride, antimony trichloride, trityl hexachloroantimonate, antimony pentachloride, bismuth trichloride, boron tribromide, aluminum tribromide, carbon tetrabromide, bromoform, bromo Examples thereof include benzene, iodomethane, silicon tetrabromide, hexafluorobenzene, aluminum fluoride and the like.

Of the above-mentioned 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 preferable halogen-containing compounds include carbon tetrachloride, chloroform, dichloroethane, tetrachloroethane, titanium tetrachloride, germanium tetrachloride, tin tetrachloride and the like. The halogen-containing compound may be used as a mixture of two or more kinds.

In the present invention, it is preferable to contact the α-olefin with the chromium-based catalyst in such a manner that the chromium compound (a) and the alkylaluminum compound (c) do not come into contact with each other in advance. According to such a specific contact mode, it is possible to selectively carry out the trimerization reaction and obtain 1-hexene from the raw material ethylene in a high yield.

The above-mentioned specific contact mode is specifically as follows.
(1) A method of introducing α-olefin and catalyst component (a) into a solution containing catalyst components (b) and (c), (2) α-in a solution containing catalyst components (a) and (b) Method of introducing olefin and catalyst component (c), (3) α-olefin and catalyst component (b) in a solution containing the catalyst component (a)
And (c) are introduced, (4) α-olefin, catalyst components (a) and (b) in a solution containing the catalyst component (c).
And (5) α-olefin and each of the catalyst components (a) to (c) are simultaneously and independently introduced into the reaction system. And each said solution is normally prepared using a reaction solvent.

Further, as the above-mentioned specific contact mode when the halogen-containing compound is used, specifically, (1)
Method of introducing α-olefin and catalyst component (a) into a solution containing catalyst components (b) to (d), (2) α into a solution containing catalyst components (a), (b) and (d) -A method of introducing olefin and catalyst component (c), (3) a method of introducing α-olefin, catalyst components (b) and (c) into a solution containing catalyst components (a) and (d), (4) ) A method of introducing α-olefin, catalyst components (a) and (b) into a solution containing catalyst components (c) and (d), (5) into a solution containing catalyst components (a) and (b) , Α-olefin, catalyst components (c) and (d) are introduced, (6) α-olefin, catalyst components (a) and (d) are added to a solution containing the catalyst components (b) and (c). Method of introduction, (7) α-olefin, catalyst components (a), (b) and (d) in a solution containing the catalyst component (c) Method of introducing, (8) method of introducing α-olefin, catalyst components (b) to (d) into a solution containing the catalyst component (a), (9) α-olefin and each catalyst component (a) to ( It can be carried out by a method of introducing d) into the reaction system simultaneously and independently. And each said solution is normally prepared using a reaction solvent.

In the present invention, "a mode in which a chromium compound and an 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 means that such a mode is maintained in the supply of the olefin and the catalyst component to the reactor. However, the particular embodiment described above is the preferred embodiment required in the preparation of the catalyst and is irrelevant once the catalyst has been prepared. Therefore, the catalyst recovered from the reaction system can be recycled without violating the above preferred embodiment.

The reason why the activity of the low polymerization reaction of α-olefin is low 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 yet, 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 to 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, and as a result, inappropriate demetallation is caused in the low polymerization reaction of α-olefin, and the activity of the low polymerization reaction of α-olefin decreases. .

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

In the present invention, as the reaction solvent, butane, pentane, 3-methylpentane, hexane, heptane, 2-methylhexane, octane, cyclohexane,
C1-C20 chain or alicyclic saturated hydrocarbons such as methylcyclohexane, 2,2,4-trimethylpentane and decalin, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, mesitylene and tetralin Is used. These may be used alone or as a mixed solvent.

As the reaction solvent, it is possible to use α-olefin as the reaction raw material itself or α-olefin other than the main raw material. As the reaction solvent, α-olefin having 4 to 30 carbon atoms is used, and α-olefin which is liquid at room temperature is particularly preferable. In particular, a chain saturated hydrocarbon or alicyclic saturated hydrocarbon having 4 to 10 carbon atoms is preferable as the reaction solvent. By using these solvents, it is possible to suppress the by-product of the polymer, and further, when the alicyclic hydrocarbon is used, there is an advantage that a high catalytic activity can be obtained.

In the present invention, the amount of the chromium compound used is usually 1.0 × 10 ^{−7 to} 0.
5 mol, preferably 1.0 × 10 ^{−6 to} 0.2 mol,
More preferably, it is in the range of 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 each amide or imide used is 1 mol of the chromium compound.
The amount is usually 0.001 mol or more, preferably 0.005 to 1000 mol, and more preferably 0.01.
It is set in the range of ˜100 mol. The amount of halogen-containing compound used is in the same range as the amount of amine, amide or imide used.

In the present invention, the chromium compound (a),
The molar ratio (a) :( b) of at least one compound (b) selected from the group of amines, amides and imides, the alkylaluminum compound (c) and the halogen-containing compound (d):
(C) :( d) is 1: 0.1-10: 1 to 100: 0.
1-20 are preferable and 1: 1-5: 5-50: 1-10
Is particularly preferable. By combining under such specific conditions, for example, hexene can be produced at a yield of 90% or more (ratio to the total amount produced) as an α-olefin polymer, and the content of 1-hexene in hexene is high. Quantity 99
% Or more.

The reaction temperature is usually 0 to 250 ° C, preferably 0 to 150 ° C, more preferably 20 to 100 ° C. On the other hand, the reaction pressure is from normal pressure to 250 kg / cm ²
However, it is usually 100 kg / cm ²
Is sufficient. The residence time is usually in the range of 1 minute to 20 hours, preferably 0.5 to 6 hours. Coexistence of hydrogen during the reaction is preferable because improvement of catalytic activity and selectivity of trimer can be observed. In addition, the coexistence of hydrogen brings about an effect that the properties of the by-produced polymer become powdery with less adhesion. The amount of hydrogen to coexist is usually 0.1 to 100 kg / c as hydrogen partial pressure.
m ² , preferably in the range of 1.0 to 80 kg / cm ² .

In the present invention, the temperature of the reaction product liquid after the completion of the low polymerization reaction is a temperature at which the by-produced polymer does not precipitate until the step of concentrating and separating the by-produced polymer, usually 80 ° C. or higher, preferably 80. ℃ to 200 ℃, particularly preferably 1
It is necessary to maintain at 00 ° C to 150 ° C. Precipitation of a by-product polymer in the reaction solution causes troubles such as clogging of pipes and valves.

In the present invention, the reaction liquid is usually supplied to the degassing tank prior to the removal of the catalyst component. At that time, the reaction liquid is maintained at a temperature at which the by-produced polymer in the reaction liquid does not precipitate as described above. Further, the degassed reaction liquid is supplied to the catalyst component separation step while being maintained at a temperature at which the by-product polymer does not precipitate. The catalyst component is preferably extracted and separated with an acid or alkaline aqueous solution.

The acid used for removing the catalyst component includes
Nitric acid, hydrochloric acid and sulfuric acid are preferably used, and caustic soda is preferably used as the alkali. These acids or alkalis are usually used as a 2 to 20% by weight aqueous solution. The reaction liquid containing the catalyst component and the acid or alkali aqueous solution can be brought into contact with each other by using various extraction devices, but it is preferable to use a stirring tank and a stationary separation tank. The combination of these may be one stage or multiple stages, and may be either a batch type or a continuous type extraction method.

The catalyst component which is easily removed by the above-mentioned extraction is mainly a metal component such as a chromium compound, a metal amide or an alkylaluminum compound, although it depends on the extractant (acid or alkaline aqueous solution) used. In the present invention, if necessary, two stirring tanks may be used, and extraction with both an acid aqueous solution and an alkaline aqueous solution may be performed.

The extraction conditions are not particularly limited, but when a stirring tank and a stationary separation tank are used, the ratio of oil layer: water layer in the stirring tank is usually 1: 0.1 to 10, preferably 1 :. The treatment time is 0.5 to 5 and the treatment time is usually 5 to 120 minutes, preferably 30 to 90 minutes.

The feature of the present invention is that the temperature of the reaction liquid is maintained at a temperature at which the by-product polymer does not precipitate, and the catalyst component causing the contamination of the distillation column is dissolved while the by-product polymer is dissolved in the reaction liquid. The point is that after separation, then a distillation separation step is performed, and then the by-product polymer is concentrated and separated. Separation and removal of by-product polymer can be performed by a solid-liquid separation device,
In that case, not only the process becomes complicated, but also the operation is hindered by troubles such as clogging due to the precipitated polymer. On the other hand, in the case of the present invention, since the by-produced polymer is dissolved and concentrated to be separated, a solid-liquid separation device for the by-produced polymer can be omitted, and furthermore troubles such as clogging due to the precipitated by-produced polymer can be prevented. I can.

In the present invention, the reaction liquid from which the catalyst has been separated and removed is usually purified by distillation separation. For example, α-
When the olefin is ethylene, 1-hexene is obtained as an α-olefin low polymer, and in this case, a deethylene column for separating ethylene, and then a dehexene column for separating 1-hexene and a solvent for separating a solvent are separated. Purification is performed by a solvent tower, and by-product polyethylene is concentrated and separated at the bottom of the desolvent tower.

The ethylene distillation column usually has 5 to 3 theoretical plates.
0, the pressure in the tower is atmospheric pressure or higher, preferably atmospheric pressure or higher, 1
The operation is performed at 0 Kg / cm ² G or less and a reflux ratio of 0.1 to 10, preferably 0.3 to 5. The hexene distillation column normally has a theoretical plate number of 5 to 30 and an internal pressure of 5 Kg / cm.
² G or less, preferably atmospheric pressure or less, and a reflux ratio of 0.1 to 1
It is operated in the range of 0, preferably 1-5. Desolvation tower,
For example, a heptane distillation column is usually operated at a theoretical plate number of 5 to 30, an internal pressure of atmospheric pressure or less, preferably 500 mHg or less, and a reflux ratio of 0.1 to 10, preferably 1 to 5.

It is preferable that the by-produced polymer and the high boiling point component concentrated in the desolvation tower are further supplied to a heating evaporator to separate them into the high boiling point component and the by-produced polymer and to discard them respectively.

As the heating evaporator, various conventionally known ones can be used. For example, a thin-film evaporator, such as a thin-film evaporator having a scraping blade that rotates with respect to a heat transfer surface of a cylindrical type may be used. However, the evaporator with a built-in plate-fin heater can instantly heat the high-viscosity fluid by the fins arranged at high density and efficiently remove the volatile substances contained in it. Since it is possible, it can be used particularly preferably. Examples of the heating evaporator having such a structure include “Hibiscus evaporator” (trade name) manufactured by Mitsui Shipbuilding Co., Ltd. When these are used, the by-product polymer concentrated by the built-in plate fin type heater flows down from the lower part due to the plasticity of the by-product polymer. Therefore, it can be easily recovered by cutting in an appropriately cooled state.

In the present invention, in particular, highly pure 1-hexene can be industrially advantageously produced from ethylene. Then, by a polymerization reaction using a known polymerization catalyst, L-LDPE, which is a useful resin, can be produced from 1-hexene obtained by the production method of the present invention.

[0058]

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 complete mixing tank reactor, a degassing tank, an alkali washing tank, an ethylene distillation column, a hexene distillation column, a heptane distillation column, and an evaporator, and degassing was performed between the reactor and the degassing tank. A continuous low polymerization reaction of ethylene was carried out according to a process equipped with a compressor for circulating ethylene to the reactor. In addition, as a complete mixing tank type reactor, 2 L equipped with two supply pipes
"Hibiscus evaporator" (trade name, manufactured by Mitsui Engineering & Shipbuilding Co., Ltd.) was used as the evaporator. The ethylene distillation column has 15 stages, and the hexene distillation column and the heptane distillation column have 20 stages.

From one supply pipe of the complete mixing tank reactor, n-heptane solution of chromium (III) -2-ethylhexanoate (Cr (2EHA) ₃ ) together with ethylene and 1,1,
An n-heptane solution of 2,2-tetrachloroethane (TCE) is continuously supplied, and an n-heptane solution of 2,5-dimethylpyrrole (DMP) and n-heptane of triethylaluminum (TEA) are continuously supplied from the other supply pipe. -The heptane solution was fed continuously.

The reaction liquid continuously withdrawn from the reactor was heated to 100 ° C. and supplied to the degassing tank. The degassed reaction liquid was supplied to an alkaline washing tank while maintaining the temperature of 100 ° C., the catalyst component was extracted and removed with a 5% NaOH aqueous solution, and then sequentially fed to an ethylene distillation column, a hexene distillation column, and a heptane distillation column. Processed.

The bottom liquid of the heptane distillation column was supplied to the evaporator and concentrated. In the evaporator, the evaporated high boiling point component was condensed and recovered, and the concentrated by-product polyethylene was recovered as a solid content after cooling. On the other hand, ethylene degassed in the degassing tank is pressurized in the compressor and circulated in the reactor, and n-heptane separated in the heptane distillation column is circulated in the reactor through the circulation pipe. Was done. Table 1 shows the operating conditions of each unit in the above process.

[0062]

[Table 1]

[0063]

[Table 2]

The operation in the above process was carried out stably without any trouble of clogging by the polymer because the operation was carried out while the by-product polymer was dissolved. Also, since the operation of the distillation column was also performed after separating and removing the catalyst component,
No trouble such as catalyst adhesion occurred.

[0065]

According to the present invention, a method for producing an α-olefin low polymer using a chromium-based catalyst, wherein a by-product polymer and a catalyst component can be efficiently separated by a compact process. An industrially advantageous method for producing an improved α-olefin low polymer is provided.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Tsuboi, 3-10-10, Shiodotsu, Kurashiki-shi, Okayama Mitsubishi Chemical Corporation Mizushima Plant

Claims (7)

[Claims] 1. A method for producing an α-olefin low polymer using a chromium catalyst, wherein the chromium catalyst is at least one compound selected from the group consisting of a chromium compound (a), an amine, an amide and an imide. (B), using a catalyst system comprising a combination of an alkylaluminum compound (c), low polymerization of α-olefin is carried out in a solvent,
After removing the catalyst component while maintaining the temperature of the reaction liquid at a temperature at which the by-product polymer does not precipitate, the by-product polymer is concentrated and separated together with the high-boiling component in the distillation separation operation. Production method. 2. A chromium-based catalyst is a chromium compound (a),
The production of the α-olefin low polymer according to claim 1, which comprises a combination of at least one compound (b) selected from the group of amines, amides and imides, an alkylaluminum compound (c) and a halogen-containing compound (d). Method. 3. A molar ratio of catalyst components (a) :( b):
(C): (d) is 1: 0.1-10: 1 to 100: 0.
It is 1-20, The manufacturing method of the alpha-olefin low polymer of Claim 2. 4. The low polymerization of α-olefin is carried out by contacting α-olefin with a chromium-based catalyst in such a manner that the chromium compound (a) and the alkylaluminum compound (c) do not come in contact with each other in advance. The method for producing an α-olefin low polymer according to any one of claims 1. 5. The method for producing an α-olefin low polymer according to claim 1, wherein the catalyst component is removed by extraction and separation with an acid or alkali aqueous solution. 6. The α- according to any one of claims 1 to 5, wherein the by-produced polymer and the high boiling point component which are concentrated and separated in the distillation separation operation are separated into the high boiling point component and the by-produced polymer by a heating evaporator. Method for producing olefin low polymer. 7. The α-olefin is ethylene, and α-olefin is α-olefin.
The olefin low polymer is mainly 1-hexene, and after the reaction, after removing ethylene and removing the catalyst component while maintaining the temperature of the reaction solution at a temperature at which the by-product polymer in the reaction solution does not precipitate, the reaction solution is The method for producing an α-olefin low polymer according to any one of claims 1 to 6, wherein the by-produced polymer is concentrated and separated together with the high boiling point component by distillation separation.