JPH07149677A - Production of 1-hexene - Google Patents

Abstract

PURPOSE:To obtain a process for the production of an alpha-olefin oligomer such as 1-hexene in high yield and selectivity on an industrial scale at a low cost and especially improved to facilitate the separation of by-product polymers. CONSTITUTION:1-Hexene is produced by the oligomerization reaction of ethylene using a chromium-based catalyst consisting of at least a combination of a chromium compound, an amine or a metal amide and an alkylaluminum compound under >=10kg/cm<2> pressure in a reaction solvent having a boiling point higher than that of 1-hexene. The obtained alpha-olefin oligomer composition containing 1-hexene is subjected to degassing treatment and depressurized to <=3 kg/cm<2> and the by-product polymers are separated from the product.

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 1-hexene, and more particularly to a method for producing 1-hexene by a low polymerization reaction of ethylene using a chromium-based catalyst. The present invention relates to an industrially advantageous method for producing 1-hexene which is improved so that a separation operation of a raw polymer can be easily performed.

[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 by a catalyst system consisting of a transition metal compound (M) of Group VIA containing chromium and having a general formula MXn and polyhydrocarbyl aluminum oxide (X). ing.

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]

However, in the method described in Japanese Patent Publication No. 43-18707, the amount of polyethylene by-produced at the same time as 1-hexene is large and the amount of polyethylene by-produced is small. There is a problem that the catalytic activity is lowered. In addition, JP-A-3-12890
The method described in Japanese Patent No. 4 has a problem that although the amount of by-produced polymers such as polyethylene is small, the catalytic activity is not sufficient.

Further, in industrial practice, it is important to efficiently separate the by-produced polymer. That is, the low polymerization method of α-olefin such as ethylene is usually carried out under pressure, and the separation of the by-produced polymer thereafter is carried out without lowering the pressure and keeping the pressure in the reaction almost maintained. . The reason is that in the production of 1-hexene by the conventional method, the yield of 1-hexene is not sufficient, and a large amount of low boiling point components (1-butene) of about 15% by weight or more is produced as a by-product. This is because when the pressure is reduced to near normal pressure after the reaction, the cooling load required for the distillation separation of 1-butene (boiling point: -6.47 ° C) from unreacted ethylene becomes large.

Therefore, according to the conventional method, after the reaction, the by-produced polymer is separated without lowering the pressure, and then 1-
Butene must be separated by distillation, and the pressure must be gradually reduced in subsequent unit operations. However, the method of performing separation of the by-product polymer under pressure requires not only a special solid-liquid separation device but also poor operability, and sometimes the solid-liquid separation device is blocked by the by-product polymer. There are great disadvantages.

The present invention has been made in view of the above circumstances, and an object thereof is to be able to produce 1-hexene with a high yield and a high selectivity, and particularly to facilitate the separation operation of a by-produced polymer. It is an object of the present invention to provide an industrially advantageous method for producing 1-hexene which is improved so that it can be carried out.

[0008]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that if a specific chromium-based catalyst is used, α-olefin low weight other than 1-hexene can be obtained. Coalescence, especially by suppressing 1-butene by-product
Since it is possible to obtain hexene in high yield, it is not necessary to recover 1-butene, and even when recovering by atmospheric distillation, the finding that the cooling load required for distillation separation can be significantly reduced has been found. Obtained.

The present invention has been completed based on the above findings, and the gist thereof is at least as a chromium-based catalyst in a method for producing 1-hexene by a low polymerization reaction of ethylene using a chromium-based catalyst. Using a catalyst system consisting of a combination of a chromium compound and an amine or a metal amide and an alkylaluminum compound, a low polymerization of ethylene is carried out in a reaction solvent having a boiling point higher than that of 1-hexene under a pressure of 10 kg / cm ² or more. -Α-containing hexene
A method for producing 1-hexene is characterized in that an olefin low polymer composition is obtained, then degassed to reduce the pressure to 3 Kg / cm ² or less, and then a by-produced polymer is separated.

The present invention will be described in detail below. In the present invention, in order to produce 1-hexene with high yield and high selectivity, a catalyst system comprising at least a combination of a chromium compound and an amine or a metal amide and an alkylaluminum compound is used as the chromium-based catalyst. Then, in a preferred embodiment of the present invention, ethylene and the chromium-based catalyst are brought into contact with each other in such a manner that the chromium compound and the alkylaluminum compound do not come into contact with each other in advance, as described later.

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 and an aralkyl group. 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 preferred 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) tert-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) naphthenate, Cr (CH ₃ COCHCOOCH ₃ ) ₃ , chromium (III) chloride , Chromium chloride, chromium bromide, chromium bromide, chromium iodide, chromium iodide, chromium fluoride, chromium fluoride and the like.

Further, a complex composed of the above-mentioned chromium compound and an electron donor can also be preferably used. The electron donor is selected from compounds containing nitrogen, oxygen, phosphorus or sulfur.

Examples of the nitrogen-containing compound include nitrile, amine, amide and the like. Specific examples thereof include acetonitrile, pyridine, dimethylpyridine, dimethylformamide, N-methylformamide, aniline, nitrobenzene, tetramethylethylenediamine, diethylamine,
Examples include isopropylamine, hexamethyldisilazane, and pyrrolidone.

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

Examples of the phosphorus-containing compound include hexamethylphosphamide, 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, 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)₂N
H], CrCl₂・ 2CH₃CN, CrCl₂・ 2 [P
(CH₃)₂Ph] and the like.

As the chromium compound, a compound soluble in a hydrocarbon solvent is preferable, and a β-diketonate salt of chromium,
Carboxylates, salts with anions of β-ketoesters, β
-Ketocarboxylic acid salts, amide complexes, carbonyl complexes, carbene complexes, various cyclopentadienyl complexes, alkyl complexes, phenyl complexes and the like. 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 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, if a chromium-based catalyst is used in a specific contact mode in accordance with a preferred low polymerization reaction of ethylene, which will be described later, a high catalytic activity can be obtained without supporting a chromium compound on a carrier. When the chromium compound is used without being loaded on the carrier, the loading on the carrier which involves complicated operations can be omitted, and the total amount of the catalyst used (the total amount of the carrier and the catalyst component) is increased by the use of the carrier. It is possible to avoid the problem.

The amine used in the present invention is a primary or secondary amine.
It is a class amine. As the primary amine, ammonia,
Ethylamine, isopropylamine, cyclohexylamine, benzylamine, aniline, naphthylamine, etc. are exemplified, and secondary amines include 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-acylpyrrole, pyrazole and pyrrolidine.

The metal amide used in the present invention is a metal amide derived from a primary or secondary amine, specifically, a primary or secondary amine and a group IA or IIA,
An amide obtained by reaction with a metal selected from Group IIIB and Group IVB. Specific examples of such metal amides include lithium amide, sodium ethylamide, calcium diethylamide, lithium diisopropylamide, potassium benzylamide, sodium bis (trimethylsilyl) amide, lithium indolide, sodium pyrrolide, lithium pyrrolide and potassium. Examples thereof include pyrrolide, potassium pyrrolidide, aluminum diethylpyrrolide, ethylaluminum dipyrrolide and aluminum tripyrolide.

In the present invention, a secondary amine, a metal amide derived from a secondary amine, or a mixture thereof is preferably used. Particularly, as the secondary amine, pyrrole, 2,5-dimethylpyrrole, 3,4-dimethylpyrrole, 3,4-dichloropyrrole, 2,3,4,5
-Tetrachloropyrrole, 2-acylpyrrole, and metal amides derived from secondary amines include aluminum pyrrolide, ethylaluminum dipyrrolide, aluminum tripyrolide, sodium pyrrolide, lithium pyrrolide and potassium pyrrolide. It is suitable. Among the pyrrole derivatives, those having a hydrocarbon group on the pyrrole ring are particularly preferable.

In the present invention, an alkylaluminum compound represented by the following general formula (1) is preferably used as the alkylaluminum compound.

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

In the formula, R ¹ and R ² usually have a carbon number of 1 to
15, preferably 1 to 8 hydrocarbon groups, which may be the same or different from each other, X represents a halogen atom, m is 0 <m ≦ 3, n is 0 ≦ n <3, p Is 0 ≦ p <
3 and q are numbers of 0 ≦ q <3, and
It represents a number that is m + n + p + q = 3.

Examples of the above-mentioned alkylaluminum compound include trialkylaluminum compounds represented by the following general formula (2), halogenated alkylaluminum compounds represented by the general formula (3), and alkoxy groups represented by the general formula (4). Examples thereof include aluminum compounds and alkylaluminum hydride compounds represented by the general formula (5). The meanings of R ¹ , X and R ² in each formula are the same as above.

[0027]

Embedded image R ¹ ₃ Al (2) R ¹ _m AlX _3-m (m is 1.5 ≦ m <3) (3) R ¹ _m Al (OR ² ) _3-m ( m is 0 <m <3, preferably 1.5 ≦ m <3) (4) R ¹ _m AlH _3-m (5) (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.

In the present invention, first, a low-polymerization reaction of ethylene is carried out in a reaction solvent using a catalyst system comprising the above-mentioned catalyst components to obtain an α-olefin low-polymer composition containing 1-hexene. obtain.

The amount of chromium compound used is usually 0.1 × 10 ^{−3 to 5} g, preferably 1.0, per liter of solvent.
It is in the range of x10 ^{-3 to 2} g. On the other hand, the amount of the alkylaluminum compound used is usually 0.1 mmol or more per 1 g of the chromium compound, but is preferably 5 mmol or more from the viewpoint of catalytic activity and trimer selectivity.
And the upper limit is usually 50 mol. The amount of amine or metal amide used is 1 g of chromium compound,
It is usually 0.001 equivalent or more, preferably 0.005
To 1000 equivalents, and more preferably 0.01 to 100 equivalents.

In the present invention, the contact between ethylene and the chromium-based catalyst is preferably carried out in such a manner that the chromium compound and the alkylaluminum compound do not come in contact with each other in advance. According to such a 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. According to the present invention, the content of 1-butene (by-product amount) in the α-olefin low polymer composition is suppressed to 10% by weight or less, the content of 1-hexene is 70% by weight or more, and further 85
It can be increased to more than weight%.

The above-mentioned specific contact mode is specifically as follows.
When "amine or metal amide" is represented by amine, (1) a method of introducing ethylene and a chromium compound into a solution containing an amine and an alkylaluminum compound, (2) ethylene and alkyl into a solution containing a chromium compound and an amine A method of introducing an aluminum compound, (3) a method of introducing ethylene, an amine and an alkylaluminum compound into a solution containing a chromium compound,
(4) A method of introducing ethylene, a chromium compound and an amine into a solution containing an alkylaluminum compound,
(5) It can be carried out by a method of introducing each of a chromium compound, an amine, an alkylaluminum compound and ethylene into the reactor simultaneously and independently. And
Each of the above solutions is prepared using a reaction solvent.

In the above description, the phrase "a mode in which the chromium compound and the alkylaluminum compound do not contact in advance" means not only at the start of the reaction but also in the subsequent supply of additional ethylene and catalyst components to the reactor. It means that such an aspect is maintained.

The reason why the activity of the low polymerization reaction of ethylene becomes 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. .

That is, it is considered that when the chromium compound and the alkylaluminum 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 produced by the usual method. Therefore, alkyl-
Decomposition / reduction reaction of the chromium compound preferentially proceeds, and as a result, demetallation unsuitable for the low polymerization reaction of ethylene is caused, and the activity of the low polymerization reaction of ethylene decreases.

In the present invention, the reaction solvent is 1-
Solvents with a higher boiling point than hexene are used. In particular,
Hexane, heptane, octane, cyclohexane, methylcyclohexane, linear or alicyclic saturated hydrocarbon such as decalin, benzene, toluene, xylene, ethylbenzene, mesitylene, aromatic hydrocarbon such as tetralin, carbon tetrachloride, dichloroethane, Trichloroethane,
Chain chlorinated hydrocarbons such as tetrachloroethane and chlorinated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene are used. These may be used alone or as a mixed solvent.

As the solvent, a linear saturated hydrocarbon or alicyclic saturated hydrocarbon having 7 or less carbon atoms is particularly preferable. 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.

The reaction temperature is preferably in the range of 0 to 70 ° C. If a linear saturated hydrocarbon having 7 or less carbon atoms, specifically, hexane or heptane is used as the reaction solvent and a reaction temperature of 70 ° C. or less is adopted, the shape of the by-produced polymer in the reaction solution Become granular, and solid-liquid separation of the by-product polymer can be easily performed. On the other hand, the reaction pressure is may be selected from the range of 10~250kg / cm ^2, usually is sufficient pressure of 100 kg / cm ^2.
The residence time is usually in the range of 1 minute to 20 hours, preferably 0.5 to 6 hours. Also, the reaction format is
It may be a batch type, a semi-batch type or a continuous type,
Coexistence of hydrogen during the reaction is preferable because improvement of catalytic activity and selectivity of trimer is recognized.

Next, in the present invention, after degassing and reducing the pressure to 3 Kg / cm ² or less, the by-produced polymer is separated. If the pressure is reduced to 3 Kg / cm ² or less,
It is possible to use a relatively simple solid-liquid separation device, and
There is almost no risk of clogging of the solid-liquid separation device due to the by-product polymer. However, from the viewpoint of the handling regulations of the high-pressure container, it is preferable to reduce the pressure to 1.9 kg / cm ² or less, which is considered as a type 2 high-pressure container, and further 0.2 kg / cm ²
If the pressure is reduced to the level below, almost the same operation as at atmospheric pressure can be performed, and this is more preferable.

Separation and removal of the by-product polymer in the reaction solution can be carried out without melting the by-product polymer by appropriately using a known solid-liquid separation device. A filter or a centrifuge is preferably used as the solid-liquid separator. When the by-produced polymer is in the form of granules, the particle size of the by-produced polymer can be controlled by stirring the reaction liquid to disperse the by-produced polymer before the separation and removal thereof. on the other hand,
Distillation separation of 1-hexene and the reaction solvent is performed using a known distillation apparatus. The distillation mode may be either batch type or continuous, and 1-hexene is distilled from the top of the distillation column.

[0041]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 A 2.4 liter autoclave that had been heated and dried in a dryer at 150 ° C. was assembled while hot, and then vacuum nitrogen substitution was performed. The autoclave was equipped with a stirrer equipped with a catalyst feed tube equipped with a rupture plate. n-heptane (98
0 ml), a solution of pyrrole (1.244 mmol) in n-heptane, triethylaluminum (2.000 mmo)
The n-heptane solution of 1) was charged on the barrel side of the autoclave, while the catalyst feed tube was solubilized with n-heptane of chromium (III) 2-ethylhexanoate (200 m).
g, 0.420 mmol). The total amount of n-heptane was 1 liter.

First, the autoclave is heated to 60 ° C.,
Then, ethylene was introduced from the catalyst feed pipe at 60 ° C. The rupture plate ruptured due to ethylene pressure, and the chromium compound was introduced into the barrel side of the autoclave to start low polymerization of ethylene. Ethylene was introduced until the total pressure reached 35 Kg / cm ² , then the total pressure was increased to 35 Kg / cm ² , and the temperature was adjusted to 6
Maintained at 0 ° C. After 1 hour, ethanol was pressed into the autoclave to stop the reaction.

After depressurizing the pressure of the autoclave and carrying out degassing, the pressure was brought to normal pressure, and the by-produced polymer (mainly polyethylene) in the reaction solution was separated and removed by a filter to remove the reaction solvent and α-olefin low-weight. The reaction liquid containing the combined composition was recovered. In addition, in this example, the shape of the by-product polymer was granular, and the filtering operation could be performed extremely well. Table 1 shows the results of the composition analysis of the α-olefin low polymer by gas chromatography.

In the table, the solvent type "HP" represents n-heptane, the unit of catalytic efficiency is g-ethylene / 1g-chromium compound, and the unit of catalytic activity is g-ethylene / 1g-chromium.Hr. is there. The catalyst component molar ratio represents the molar ratio of Cr compound: pyrrole: triethylaluminum.

[0046]

[Table 1]

[0047]

According to the present invention described above, by using a specific chromium-based catalyst, by-products of a low-polymer α-olefin other than 1-hexene can be suppressed and a high yield of 1-hexene can be obtained. Therefore, the by-produced polymer separated after the reaction can be industrially advantageously performed under normal pressure or low pressure.

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Claims (6)

[Claims] 1. A method for producing 1-hexene by a low polymerization reaction of ethylene using a chromium-based catalyst, wherein the chromium-based catalyst is at least a combination of a chromium compound and an amine or a metal amide and an alkylaluminum compound. Used, low polymerization of ethylene is carried out in a reaction solvent having a boiling point higher than that of 1-hexene under a pressure of 10 kg / cm ² or more to obtain an α-olefin polymer composition containing 1-hexene, and then depolymerized. Gas processed to 3 kg /
A method for producing 1-hexene, which comprises separating the by-produced polymer after reducing the pressure to cm ² or less. 2. The method for producing 1-hexene according to claim 1, wherein ethylene and the chromium-based catalyst are brought into contact with each other in such a manner that the chromium compound and the alkylaluminum compound do not come into contact with each other in advance. 3. The method for producing 1-hexene according to claim 1, wherein the degassing treatment is carried out to 0.2 Kg / cm ² or less. 4. 1-in the alpha-olefin low polymer composition
The hexene content is 85% by weight or more.
The method for producing 1-hexene according to any one of 1. 5. The method for producing 1-hexene according to claim 1, wherein the reaction solvent is a linear saturated hydrocarbon having 7 or less carbon atoms or an alicyclic saturated hydrocarbon. 6. The reaction temperature is 70 ° C. or lower.
5. The method for producing 1-hexene according to any one of 5 above.