JP3324163B2 - Low polymerization method of α-olefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for low polymerization of .alpha.-olefins using a chromium-containing compound. More specifically, a chromium-containing compound is produced by reacting a compound containing pyrrole with a chromium salt in a hydrocarbon solvent, and an α-olefin, particularly ethylene, is produced using a catalyst comprising the chromium-containing compound and an alkylaluminum compound. The present invention relates to a method for obtaining a product mainly comprising a trimer by low polymerization and selectively in a high yield.

[0002]

2. Description of the Related Art Conventionally, chromium salts and metal pyrrolides have been
A method for producing a chromium-containing compound having a chromium-pyrrolyl bond by reacting in tetrahydrofuran or dimethoxyethane containing an oxygen atom which is an electron-donating element is known (for example, VW Seidel an).
d W. Reichardt, Z .; Anorg. All
g. Chem. , 404 , 225 (1974), JP-A-3-128904).

JP-A-3-128904 describes a method for trimerizing an α-olefin using a catalyst obtained by combining the chromium-containing compound prepared by the above-mentioned method with a metal alkyl or Lewis acid. ing. First, the present inventors specified the method of contacting a chromium compound, an α-olefin, and an alkylaluminum and / or the amount of an alkylaluminum to a chromium compound with respect to JP-A-3-128904, thereby In particular, a method was proposed in which ethylene was subjected to low polymerization to selectively obtain 1-hexene in high yield (Japanese Patent Application No. 4-247611).

[0004]

However, of the above methods for producing a chromium-containing compound, Japanese Patent Application Laid-Open No. HEI 3-128904 describes the method.
In the method described in (1), the operation of isolating the compound is complicated, and it is extremely difficult to selectively obtain a single product. Further, regarding the low polymerization reaction of α-olefin using the chromium-containing compound as a catalyst, the catalyst activity is low, and the purity of 1-hexene relative to the obtained hexenes is low. It has the disadvantage of reduced activity.

According to the present invention, a chromium-containing compound can be produced at a high yield without using the above-mentioned complicated isolation operation, and an α-olefin, particularly ethylene When low polymerization is carried out, 1-hexene having high purity can be selectively obtained.

[0006]

It has been known that a compound containing an electron-donating element coordinates with a transition metal element such as chromium to form a complex. In the above method for producing a chromium-containing compound, the compound containing the electron-donating element is reacted with the metal pyrrolide using the compound containing the electron-donating element as a solvent. An attempt to coordinate to the salt results in a mixture of complex products in which the electron-donating compound ligand and the pyrrolyl group are coordinated in various proportions with respect to chromium element.

Further, as shown in the comparative example,
The reason why the purity of -hexene is generally low and the purity of 1-hexene changes depending on the amount of alkylaluminum is considered to be that the coordinated electron-donating compound is contained in the chromium-containing compound. The present inventors have conducted intensive studies to solve the above problems, and as a result, by reacting a compound containing a chromium salt and pyrrole in a hydrocarbon solvent, such a coordinated electron donating compound is contained. A simple method for obtaining a chromium-free compound has been found.

Further, when a low polymerization reaction mainly involving trimerization of an α-olefin, particularly ethylene, is carried out using a catalyst comprising a chromium-containing compound and an alkylaluminum compound obtained by the present method, 1-hexene formed It has been found that the purity of 1-hexene obtained is kept high even when the amount of alkylaluminum is reduced, and the present invention has been completed.

That is, the present invention is suitable for producing hexenes by selectively trimerizing ethylene, but has the feature that the purity of 1-hexene is extremely high among the produced hexenes. ing. The chromium-containing compound produced in the present invention may include a chromium atom and a pyrrolyl group, may have any other organic or inorganic group, and further contains another metal. Is also good. That is, according to the method for producing a chromium-containing compound described below, IA group, IIA group, IIIB group,
Alternatively, a chromium compound may be obtained as a mixture of IVB group metals, but in the present invention, such a mixture is generally referred to as a chromium-containing compound.

[0010] The method for producing the chromium-containing compound of the present invention comprises:
It is an essential condition that a chromium salt is reacted with a compound containing pyrrole in a hydrocarbon solvent. Here, chromium salts have the general formula CrX _n (wherein, X is identical or are mutually different arbitrary organic or inorganic radical, n is 1 to an integer of 6.) Represented by. The number n is preferably two or three. As the organic group, a hydrocarbon group, a carbonyl group,
Alkoxy group, carboxyl group, β-diketonate group,
a β-ketocarboxyl group and an amide group. The organic group usually has 1 to 30 carbon atoms, and the hydrocarbon group is an alkyl group, a cycloalkyl group, an aryl group,
Examples include an alkylaryl group and an aralkyl group. Examples of the inorganic group include a halogen atom, a nitrate group, a sulfate group, and oxygen. As the chromium salt, a compound soluble in a hydrocarbon solvent is preferable, and β-diketonate salt, carboxylate, β-ketocarboxylate, amide complex, carbonyl complex, various cyclopentadienyl complexes, and alkyl complexes of chromium are preferred. , Phenyl complexes and the like,
β-diketonate salts, carboxylate salts, β-ketocarboxylate salts and the like are preferred. More specifically, chromium (III) acetylacetonate, chromium (III) 2-ethylhexanoate, chromium (III) methyl acetoacetate, chromium (II) bis (trimethylsilyl) amide, Cr (C
O) ₆ , CpCrCl ₂ (Cp = cyclopentadienyl group), (Cp ^* CrClCH ₃ ) ₂ (Cp ^* = pentamethylcyclopentadienyl group), (CH ₃ ) ₂ CrCl
And the like.

As the compound containing pyrrole, pyrrole, a derivative of pyrrole and metal pyrrolide are used. Examples of the pyrrole derivative are 2,5-dimethylpyrrole, 3,4-dichloropyrrole, 2,3,4,5- Examples thereof include tetrachloropyrrole, 2-formylpyrrole, 2-acetylpyrrole, and 2-acylpyrrole. The metal pyrrolides refer to those derived from pyrrole and derivatives of pyrrole, and include metals such as Group IA, Group IIA, II
Preferred metal pyrrolides selected from Group IB and Group IVB include lithium pyrrolide, sodium pyrrolide, potassium pyrrolide, cesium pyrrolide and the like.

As a hydrocarbon solvent in the production of a chromium-containing compound, a hydrocarbon compound, a halogenated hydrocarbon compound and the like can be mentioned as typical examples. More specifically,
aliphatic and alicyclic saturated hydrocarbon compounds such as n-hexane, cyclohexane, n-heptane and n-octane;
-Aliphatic and alicyclic unsaturated hydrocarbon compounds such as hexene, cyclohexene and cyclooctene; aromatic hydrocarbon compounds such as toluene, benzene and xylene; and halogens such as carbon tetrachloride, chloroform, methylene chloride, chlorobenzene and dichlorobenzene. Illustrative are hydrocarbon compounds, among which aliphatic, alicyclic and aromatic hydrocarbon compounds are preferred.

As a method of reacting a compound containing chromium salt and pyrrole in a hydrocarbon solvent, a compound containing chromium salt and pyrrole is mixed at a desired ratio, preferably in the absence of oxygen molecules, usually in the presence of oxygen molecules. React under pressure. The reaction temperature may be any temperature, but is preferably not higher than the boiling point of the hydrocarbon solvent, and the reaction is carried out while heating at that temperature. If desired, the reaction may be separately performed while irradiating ultrasonic waves. The reaction time is usually between 30 minutes and 48 hours.

After completion of the reaction, the reaction product can be directly used for the low polymerization reaction of α-olefin without removing the solvent. When isolating the chromium-containing compound, the chromium-containing compound can be obtained by directly removing the hydrocarbon solvent as the solvent from the reaction mixture after the reaction. Alternatively, after completion of the reaction, the product is allowed to stand, and after filtration or removal of the supernatant, the residue is preferably n-
A method of obtaining a chromium-containing compound by washing with a hydrocarbon compound having a low boiling point, such as hexane, and removing the washing solution is exemplified. As a method of removing the reaction solvent or the washing solution, there is a method of removing the solvent by reducing the pressure or flowing an inert gas at a high temperature or a normal temperature.

In the present invention, the chromium-containing compound can be used by being supported on a carrier such as an inorganic oxide. Preferably, the chromium-containing compound is used only by combining it with an alkylaluminum compound without such an operation. Good. The low polymerization of the α-olefin in the present invention is usually performed in a hydrocarbon solvent, and the concentration of the chromium compound is 0.1 mg to 5 g, preferably 1 mg to 2 g per liter of the solvent.
It is.

In the present invention, a low polymerization reaction of an α-olefin is carried out by combining the chromium-containing compound obtained as described above with an alkylaluminum compound. The alkyl aluminum compound, the following formula _{^{R 1 m Al (OR 2)}} n H p X q ... (1) ( wherein, R ¹ and R ² may be independently identical or different from each other, the number of carbon atoms Is usually 1 to 15, preferably 1 to
8 represents a hydrocarbon group, X represents a halogen atom, and 0 <
m ≦ 3, 0 ≦ n <3, 0 ≦ p <3, 0 ≦ q <3, m + n
+ P + q = 3. The alkylaluminum compounds represented by the following formulas are preferred.
And an alkyl aluminum compound represented by the formula:

[0017] _{^{R 1 3 Al ... (2)}} ( In the formula, R ¹ is as defined above) trialkyl aluminum compounds represented ^{_{by, R 1 m AlX 3-m}} ... (3) ( wherein, R ¹ and X are The same as described above, wherein 1.5 ≦ m <3; an alkylaluminum halide compound represented by the formula: R ¹ _m Al (OR ² ) _3-m (4) (wherein R ¹ and R ² are An alkoxyaluminum compound represented by 0 <m <3, preferably 1.5 ≦ m <3), R ¹ _m AlH _{3 -m} (5) (wherein, R ¹ is the same as defined above) .0 <m <3, preferably is 1.5 ≦ m <3.) hydrogenated alkylaluminum compounds represented _{^{by, R 1 2 Al (OAl)}} m OAlR 1 2 ... (6) or

[0018]

Embedded image

(In the formulas (6) and (7), R ¹ is the same as described above.)
m is an integer of 0 to 30, and particularly preferably 10 or more. )
And specifically, trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylaluminum monochloride, diethylaluminum ethoxide, diethylaluminum hydride, methylaluminoxane, isobutylaluminoxane and the like, among which triethylaluminum is most preferred.

The amount of the alkylaluminum compound to be used per 1 g of the chromium compound is 0.1 mmol or more, but is preferably larger than 5 mmol from the viewpoint of improving the activity and the selectivity of the trimer. In the present invention, as compared with the case where a Cr-containing compound produced in an electron-donating solvent is used, even if the amount of the alkylaluminum compound used is small, the purity of the obtained 1-hexene does not decrease. Have.

In the present invention, a low polymerization reaction is usually carried out using a solvent, and a linear or alicyclic saturated hydrocarbon such as butane, pentane, hexane, heptane, octane, cyclohexane, benzene, toluene, etc. Xylene,
Aromatic hydrocarbons such as ethylbenzene and tetralin, chain chlorinated hydrocarbons such as chloroform, methylene chloride, dichloroethane, trichloroethane and tetrachloroethane,
And chlorinated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene are used as solvents. Among these solvents, linear or alicyclic saturated hydrocarbons are preferred.
Further, α-olefin itself as a reaction raw material or α-olefin other than the main raw material for the reaction can be used as a solvent. As these α-olefins, those having 4 to 30 carbon atoms are used, and those which are liquid at ordinary temperature are particularly preferable.

The starting α-olefin used in the present invention is a substituted or unsubstituted one having 2 to 30 carbon atoms. Specific examples include ethylene, propylene, 1-butene, 1-hexene, 1-octene, 3-methyl-1-butene, 4-methyl-1-pentene, and the like. In particular, the present invention is suitable for low polymerization of ethylene,
1-Hexene of high purity can be selectively obtained in high yield.

The temperature of the low polymerization reaction is from 0 to 250 ° C., preferably from 0 to 150 ° C., and the pressure is from normal pressure to 250 kg / cm ² , but 100 kg / cm ² or less is sufficient. The reaction can be carried out in either a batch system or a continuous system. Residence times range from 1 minute to 20 hours,
Preferably, it is 0.5 to 6 hours. In the low polymerization of the α-olefin of the present invention, the activity and the trimer selectivity are improved by coexisting hydrogen during the reaction. Further, as described in detail in Comparative Examples, when a low-polymerization reaction of α-olefin, particularly ethylene was performed using a catalyst comprising a chromium-containing compound and an alkylaluminum produced in an electron-donating solvent, hydrogen was converted to hydrogen. Although the activity and the trimer selectivity are improved by the coexistence, the purity of 1-hexene is reduced. A feature of the present invention is that when a low polymerization reaction is carried out using a catalyst comprising a chromium-containing compound obtained in a hydrocarbon solvent and an alkylaluminum, not only the activity due to the coexistence of hydrogen and the trimer selectivity are improved but also 1 Hexene purity is hardly reduced.

In the present invention, the α-olefin is contacted with the chromium compound and the alkylaluminum compound without previously contacting the chromium-containing compound with any of the α-olefin and the alkylaluminum compound. 20 mmol of alkyl aluminum compound used per 1 g
By using the above method, the activity and the selectivity of the trimer are further improved.

[0025]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples unless it exceeds the gist thereof. Chromium-containing compound production example 1 Chromium (III) acetylacetonate (2.55 g,
7.3 mmol) in toluene (15 ml) was added under a nitrogen atmosphere to a powdery separately prepared powder of rheutimpyrrolide (1.60 g, 21.9 mmol) in toluene (5 m
l) The suspension was added at room temperature. The reaction mixture was slowly warmed to 100 ° C. and stirring was continued for 25 hours while maintaining the temperature. After cooling the reaction mixture to room temperature, the solvent was distilled off from the reaction mixture under reduced pressure, and as a result, 4.15 g of a reddish brown powder was obtained. This powder was used as it was in the low-polymerization reaction of ethylene. The results of elemental analysis of this powder were as follows. C calculated from the analytical value of Cr and the yield
The yield per r was 100%. Fig. 1 shows the IR spectrum of this powder. Measurements made by PerkinElmer 1
The measurement was carried out by a Nuger method using a 650 type Fourier transform infrared spectrometer. Cr: 9.1%; C: 57.0%; H: 5.9%;
N: 7.4%

Preparation Example 2 of Chromium-Containing Compound Chromium (III) (2-ethylhexanoate) (1.14)
g, 2.36 mmol) of toluene pyrrolide (0.65 g, 7.26 mmol) in toluene (15 ml) solution under a nitrogen atmosphere.
ml) suspension was added at room temperature. The reaction mixture was irradiated with ultrasonic waves for 17 hours. During this time, the water temperature of the ultrasonic cleaner was 40
It rose to about ° C. After the reaction, remove the supernatant,
After removing unreacted chromium (III) (2-ethylhexanoate), the residue was washed with heptane, and the supernatant was removed as before. The remaining solid was vacuum-dried at room temperature to obtain 1.37 g of a dark green powder. The results of elemental analysis of this powder were as follows. The yield per Cr calculated from the analytical value and the yield of Cr was 83.7%. Cr: 7.5%; C: 58.1%; H: 7.4%;
N: 7.2%

Chromium-containing compound production Comparative Example 1 THF was added to NaH (0.815 g, 20.3 mmol).
(15 ml) was added, and pyrrole (1.4 ml) dissolved in THF (5 ml) was added dropwise. After stirring at room temperature for 1 hour, the solution was suspended in CrCl suspended in THF (20 ml).
₂ (1.23 g, 10 mmol). After the addition, THF (5 ml) was further added, and the reaction mixture was heated to reflux for 20 hours. After the precipitate was filtered off, pentane (100
ml), and the mixture was allowed to stand at 5 ° C. The resulting precipitate was separated by filtration and dried to obtain 0.506 g of a dark green powder. The content of each element in this powder was as follows. The yield per Cr calculated from the analytical value and the yield of Cr was 18.6%. Cr: 19.1%; C: 52.3%; H: 5.45
%; N: 11.6%

Preparation of Chromium-Containing Compound Comparative Example 2 n-BuLi / n-hexane solution (19 m
(1 ml, 30 mmol) was added dropwise pyrrole (2.1 ml, 30 mmol) dissolved in THF (20 ml) and stirred at that temperature for 15 minutes. Thereafter, the temperature was returned to room temperature, and stirring was continued at room temperature for 2 hours. To this solution was added CrCl ₃ (1.58 g,
10 mmol) was added as a powder. Thereafter, the mixture was heated under reflux for 5 hours. After allowing to cool, the formed precipitate was separated by filtration, and the filtrate was dried up to obtain 3.63 g of powder. The content of each element in this powder was as follows. The Cr yield calculated from the Cr analysis value and the yield was 46%. Cr: 6.6%; C: 69.2%; H: 7.3%;
N: 15.1%

Example 1 A 300 ml autoclave heated and dried with a dryer at 150 ° C. was assembled while hot, and the atmosphere was replaced with vacuum nitrogen. The autoclave is fitted with a catalyst feed tube with a rupture disk. Heptane (50 ml) and triethylaluminum (0.4 mmol) were charged into the autoclave barrel side, while the catalyst feed tube was slurried in heptane (1 ml), and the chromium-containing compound (10 mg) obtained in Chromium-containing compound production example 1 was prepared. Was charged. The autoclave was heated to 100 ° C., and ethylene was introduced at 100 ° C. from a catalyst feed tube. The rupture disk ruptured due to ethylene pressure, and ethylene, the chromium-containing compound, and triethylaluminum were simultaneously contacted, and low polymerization of ethylene started.
Ethylene was introduced up to a total pressure of 35 kg / cm ² ,
The total pressure was maintained at 35 kg / cm ² and the reaction temperature was maintained at 100 ° C. One hour later, the reaction was stopped by injecting ethanol,
The product was quantified by gas chromatography. Table 2 shows the results.
Shown in

Example 2 A chromium-containing compound (7 mg) similarly obtained in Preparation Example 1 and triethylaluminum (0.28 mm) were placed in the same autoclave as used in Example 1.
ol). Introduce 3.5 kg / cm ^{2 of} hydrogen,
The autoclave was heated to 100C. Then 100
At ℃, ethylene was introduced through a catalyst feed tube. The rupture disk ruptured due to ethylene pressure, and ethylene, the chromium-containing compound, and triethylaluminum were simultaneously contacted, and low polymerization of ethylene started. Total pressure of ethylene is 40kg / c
m ² , and thereafter, the total pressure was maintained at 40 kg / cm ² and the reaction temperature was maintained at 100 ° C. One hour later, the reaction was stopped by injecting ethanol, and the product was quantified by gas chromatography. Table 2 shows the results.

Examples 3 and 5 The reaction was carried out in the same manner as in Example 1 except that the reaction conditions were changed as described in Table 1. Table 2 shows the results. Example 4 A reaction was carried out in the same manner as in Example 1 except that the amount of heptane used was changed to 150 ml. Table 2 shows the results.

Comparative Example 1 Production of a chromium-containing compound was carried out in the same manner as in Example 1 except that the compound obtained in Comparative Example 1 was used and the reaction time was 0.5 hour. Table 2 shows the results. Comparative Example 2 The reaction was carried out in the same manner as in Example 2 except that the compound (10 mg) obtained in Comparative Example 1 was used as the chromium-containing compound, and the reaction time was changed to 0.5 hour. Table 2 shows the results.

Comparative Example 3 Preparation of Chromium-Containing Compound Same as Example 1 except that the compound (10 mg) obtained in Comparative Example 1 was used and the reaction conditions were changed as described in Table 1. The reaction was performed. Table 2 shows the results. Comparative Example 4 A reaction was carried out in the same manner as in Example 1 except that the compound obtained in Chromium-containing compound production Comparative Example 2 was used. Table 2 shows the results.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

By using the chromium-containing compound of the present invention as a catalyst, 1-hexene having a high purity can be selectively obtained when an α-olefin, particularly ethylene, is polymerized at a low polymerization rate. Furthermore, when hydrogen is allowed to coexist in the low polymerization reaction, the purity of 1-hexene is reduced according to the conventional method. However, by using the catalyst of the present invention, the activity and the trimer selectivity can be improved. , 1-Hexene.

[Brief description of the drawings]

FIG. 1 shows an IR spectrum of Production Example 1 of a chromium-containing compound of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-128904 (JP, A) JP-A-5-221882 (JP, A) JP-A-6-145241 (JP, A) JP-A-6-145241 157654 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 2/08-2/36 C07C 11/107-11/113 C08F 4/69 C07B 61/00-61/02

Claims (4)

(57) [Claims] 1. A low polymerization method for α-olefins, comprising using a catalyst comprising a chromium-containing compound and an alkylaluminum compound obtained by reacting a compound containing a chromium salt and pyrrole in a hydrocarbon solvent. 2. The method of claim 1, wherein the chromium salt is chromium β-diketonate, β-ketocarboxylate or carboxylate. 3. The method of claim 1, wherein the α-olefin is ethylene and the main product is 1-hexene. 4. The low polymerization method for an α-olefin according to claim 1, wherein the low polymerization reaction is carried out in the presence of hydrogen.