JP3882836B2 - Method for producing α-olefin low polymer - Google Patents

Description

  The present invention uses a catalyst composed of a chromium compound containing a chromium-pyrrolyl bond and an alkylaluminum compound to low-polymerize an α-olefin, particularly ethylene, and selectively produces a product mainly composed of trimers in a high yield. On how to get in.

Conventionally, low polymerization of α-olefins such as ethylene using a catalyst composed of a combination of a specific chromium compound and a specific organoaluminum compound is known. For example, Japanese Patent Publication No. 43-18707 describes a method for obtaining 1-hexene and polyethylene from ethylene by a catalyst system comprising a transition metal compound of group VIA containing Cr represented by the general formula MXn and polyhydrocarbyl aluminum oxide. In addition, in Japanese Patent Application Laid-Open No. 3-128904, a catalyst obtained by combining a chromium-containing compound obtained from a mixture of a chromium salt, a metal amide and an electron-pair donating solvent with a metal alkyl or a Lewis acid is used. Thus, a method for trimerizing α-olefin is described.
Japanese Patent Publication No. 43-18707 Japanese Patent Laid-Open No. 3-128904

  However, among the above, the former has a problem that the amount of polyethylene produced simultaneously with 1-hexene is large, and if the amount of polyethylene is reduced, the overall activity is lowered, while the latter has a high molecular weight. Although the amount of coalescence is small, there is a problem that the catalytic activity is low.

  The present invention provides a novel low polymerization method for α-olefin, which can solve the problems of the conventional methods as described above.

  The present invention relates to an α-olefin low polymer comprising a chromium compound containing at least one chromium-pyrrolyl bond and an alkylaluminum compound, and low-polymerizing an α-olefin in the presence of a solvent-soluble catalyst. Manufacturing method.

  According to the method of the present invention, an α-olefin, particularly ethylene, can be polymerized low, and a product mainly composed of trimer can be selectively obtained in a high yield, and a high molecular weight polymer can be produced. Since it can be suppressed, it provides a great industrial advantage.

  The chromium compound containing a chromium-pyrrolyl bond used in the present invention is a compound having at least one chromium-pyrrolyl bond, which may have other organic groups and inorganic groups, and further, other metals May be included. In the present invention, a chromium compound is obtained as a mixture with a group IA, IIA, IIIB, and IVB metal compound by a method for producing a chromium compound having a chromium-pyrrolyl bond as described below. In the present invention, such a mixture is collectively referred to as a chromium compound.

  The chromium compound containing a chromium-pyrrolyl bond can be obtained, for example, by reacting a chromium salt and a metal pyrrolide in an electron donating solvent. Here, the chromium salt is represented by the general formula CrXn (wherein X is the same or different arbitrary organic or inorganic groups, and n is an integer of 1 to 6). The number of n is preferably 2 or 3. Examples of the organic group include a hydrocarbon group, an alkoxy group, a carboxyl group, a β-diketonate group, and an amide group. The organic group usually has 1 to 30 carbon atoms, and 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 halogen, nitric acid group, sulfuric acid group, and oxygen. Preferably, the chromium salt is a halide and is chromium chloride, chromium chloride, chromium chloride, chromium bromide, chromium bromide, chromium iodide, chromium iodide, chromium fluoride. , Chromium fluoride and the like, and particularly preferable are chromium chloride and chromium chloride. Moreover, the complex which consists of these chromium salts and the below-mentioned electron donor can also be used.

  Metal pyrrolide refers to those derived from pyrrole and derivatives of pyrrole. Examples of pyrrole derivatives include 2,5-dimethylpyrrole, 3,4-dimethylpyrrole, 3,4-dichloropyrrole, 2,3,4,5- Examples thereof include tetrachloropyrrole and 2-acylpyrrole, and the metal is selected from group IA, group IIA, group IIIB and group IVB containing hydrogen. Preferable metal pyrrolides include lithium pyrrolide, sodium pyrrolide, potassium pyrrolide, cesium pyrrolide and the like. Further, pyrrole or a pyrrole derivative itself may be used in place of the metal pyrrolide.

  The electron donating solvent is selected from nitrogen, oxygen, phosphorus, and sulfur-containing compounds. Nitrogen-containing compounds include nitriles, amines, and amides, specifically acetonitrile, pyridine, dimethylpyridine, dimethylformamide, N-methylformamide, aniline, nitrobenzene, tetramethyldiaminomethane, hexamethyldisilazane, pyrrolidone. Etc. Examples of the oxygen-containing compound include esters, ethers, ketones, alcohols, aldehydes, and the like. Specifically, ethyl acetate, methyl acetate, tetrahydrofuran, dioxane, diethyl ether, dimethoxyethane, diglyme, triglyme, acetone, methyl ethyl ketone, methanol, Examples include ethanol and acetaldehyde. Examples of the phosphorus compound include hexamethylphosphoramide, hexamethylphosphoric triamide, triethyl phosphite, tributyl phosphine oxide, triethyl phosphine and the like. Examples of the sulfur-containing compound include carbon disulfide, dimethyl sulfoxide, tetramethylene sulfone, thiophene, and dimethyl sulfide. Among the above electron donor solvents, ethers are preferable, and tetrahydrofuran, diethyl ether, and dimethoxyethane are particularly preferable.

  As a method of reacting the chromium salt and the metal pyrrolide in the electron donating solvent, the chromium salt and the metal pyrrolide are mixed in a desired ratio, and preferably reacted in the absence of oxygen molecules, usually at normal pressure. The reaction temperature may be any temperature, but the reaction is preferably carried out under reflux of the solvent. The reaction time is usually between 30 minutes and 48 hours. After completion of the reaction, it is preferable to remove the by-product by filtration and then remove the excess electron donating solvent. As a method for removing the electron donating solvent, a method of distilling off at a high temperature or normal temperature by reducing pressure or flowing an inert gas, or adding a solvent other than an electron donating solvent in which a chromium compound is insoluble, and then forming chromium For example, the compound precipitate may be filtered off and further washed with an added solvent to remove the electron donating solvent. Solvents other than the electron donor medium include linear or alicyclic saturated hydrocarbons such as pentane, hexane, heptane, and cyclohexane, aromatic hydrocarbons such as benzene, toluene, and xylene, chloroform, methylene chloride, and dichloroethane. Chain chlorinated hydrocarbons such as tetrachloroethane, and chlorinated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene, etc., and linear or alicyclic saturated hydrocarbons are preferably used.

Another method for obtaining a chromium compound containing at least one chromium-pyrrolyl bond used in the present invention is a method in which a chromium compound soluble in a solvent other than an electron-donating solvent is reacted with a metal pyrrolide. As the solvent other than the electron donating solvent, the solvent used for removing the electron donating solvent is used. Examples of chromium compounds that are soluble in solvents other than electron donating solvents include chromium halides and electron donor complexes described above, such as ether complexes, ester complexes, ketone complexes, aldehyde complexes, alcohol complexes, amines of chromium halides. Complexes, nitrile complexes, phosphine complexes, thioether complexes, etc., specifically, CrCl ₃ · 3THF, CrCl ₃ · 3dioxane, CrCl ₃ · (CH ₃ CO ₂ n-C ₄ H ₉ ), CrCl ₃ · (CH ₃ COC ₂ H ₅ ), CrCl ₃ · 3 (i-C ₃ H ₇ OH), CrCl ₃ · 3 [CH ₃ (CH ₂ ) ₃ CH (C ₂ H ₅ ) CH ₂ OH], CrCl ₃ · ₃ Pyridine, _{CrCl 3 · 2 (i-C} 3 H 7 NH 2), [CrCl 3 · 3MeCN] · MeCN (MeCN = _{acetonitrile), CrCl 3 · 3PPh 3 (} PPh 3 _{Triphenylphosphine), CrCl 2 · 2THF, CrCl} 2 · 2Pyridine, CrCl 2 · 2 [(C 2 H 5) 2 NH], CrCl 2 · 2MeCN (MeCN = _{acetonitrile), CrCl 2 · 2 [P} (CH 3 ₂ Ph] (Ph = phenyl group) and the like, and also β-diketonate salt of chromium, carboxylate salt of chromium, carbonyl complex of chromium, various cyclopentadienyl complexes of chromium, alkyl complex, phenyl complex, _{Specifically, Cr [CH 3 COCH = C} (O-) CH 3] 3, Cr [CH 3 (CH 2) 3 CH (C 2 H 5) CO 5] 3, Cr (CO) 6, CpCrCl 2 (Cp = cyclopentadienyl _{group), (Cp * CrClCH 3)} 2 (Cp * = pentamethylcyclopentadienyl _{group), (CH 3) 2 CrCl} , CrPhCl 2 · TH _3, and the like.

  As a method of reacting the chromium compound and the metal pyrrolide in a solvent other than the electron-donating solvent, the chromium compound and the metal pyrrolide are mixed in a desired ratio, and preferably reacted at normal pressure in the absence of oxygen molecules. . The reaction temperature can be a temperature from −100 ° C. to the boiling point of the solvent, depending on the kind of chromium compound and metal pyrrolide. The reaction time is usually between 30 minutes and 48 hours.

  After completion of the reaction, the by-product may be removed by filtration, but the reaction product can be directly subjected to the α-olefin low polymerization reaction without being removed. Further, the reaction product can be directly subjected to a low polymerization reaction of α-olefin without removing the solvent. When removing the reaction solvent, the solvent is distilled off at a high temperature or room temperature by reducing the pressure or circulating an inert gas, or after adding a solvent in which the formed chromium compound is insoluble, the precipitate containing the chromium compound is filtered off. Further, the reaction solvent can be removed by washing with the added solvent.

  In the present invention, a chromium compound having a chromium-pyrrolyl bond can be used by being supported on a carrier such as an inorganic oxide for high activation, but in this case, the amount of polymer produced tends to increase. Therefore, it is preferable to use the chromium compound simply by combining it with the alkylaluminum compound without supporting the chromium compound on the carrier. That is, according to the method of the present invention, high catalytic activity can be obtained without using a complicated method of loading on a carrier, and the total amount of catalyst used by the carrier (total amount of carrier, chromium catalyst, and alkylaluminum). ) Does not occur.

  In the present invention, the low polymerization of α-olefin is usually carried out in a hydrocarbon solvent. The concentration of the chromium compound is 0.1 mg to 5 g, preferably 1 mg to 2 g, more preferably 1 mg to 0, per liter of the solvent. .5g. In the present invention, α-olefin is polymerized by combining the chromium compound containing at least one chromium-pyrrolyl bond obtained as described above with an alkylaluminum compound. As the alkylaluminum compound, the following general formula

(In the formula, R ¹ and R ² may be the same or different from each other, and generally represent a hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 8 carbon atoms, X represents a halogen atom, An alkylaluminum compound represented by 0 <m ≦ 3, 0 ≦ n <3, 0 ≦ p <3, 0 ≦ q <3, m + n + p + q = 3) is preferable. For example, the following general formulas (2) to (7 The alkylaluminum compound shown by this is mentioned.

(Wherein R ¹ is the same as defined above),

(Wherein R ¹ is the same as described above, X represents a halogen atom, and 1.5 ≦ m <3),

(Wherein R ¹ and R ² are the same as described above, 0 <m <3, preferably 1.5 ≦ m <3),

(Wherein R ¹ is the same as described above, 0 <m <3, preferably 1.5 ≦ m <3),

(In the formulas (6) and (7), R ¹ is the same as described above. M is an integer of 0 to 30 and is particularly preferably 10 or more), specifically, triethylaluminum, tri Examples thereof include isobutylaluminum, diethylaluminum monochloride, diethylaluminum ethoxide, diethylaluminum hydride, methylaluminoxane, isobutylaluminoxane, and the like, among which trialkylaluminum is most preferable.

  In the present invention, a low polymerization reaction is usually carried out using a solvent, and linear or alicyclic saturated hydrocarbon such as butane, pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, decalin, benzene, Solvents include aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and tetralin, chain chlorinated hydrocarbons such as chloroform, methylene chloride, dichloroethane, trichloroethane, and tetrachloroethane, and chlorinated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene. Used as. Of these solvents, linear or alicyclic saturated hydrocarbons are preferred. Moreover, the α-olefin itself as a reaction raw material or an α-olefin other than the main raw material of the reaction can also be used as a solvent. As these α-olefins, those having 4 to 30 carbon atoms are used, and those which are liquid at room temperature are particularly preferred. Of these solvents, it is particularly preferable to use alicyclic hydrocarbon in that high activity is obtained.

  The raw material α-olefin used in the present invention has a substituted or unsubstituted 2 to 30 carbon atoms. Specific examples include ethylene, propylene, 1-butene, 1-pentene, 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, and 1-hexene can be selectively obtained in a high yield.

The temperature of the low polymerization reaction is usually 0 to 250 ° C., preferably 0 to 150 ° C., and the pressure is normal pressure to 250 kg / cm ² , but 100 kg / cm ² or less is sufficient. The reaction can be carried out either batchwise or continuously. The residence time is in the range of 1 minute to 20 hours, preferably 0.5 to 6 hours. In the present invention, the α-olefin is contacted with the chromium compound and the alkylaluminum compound without contacting the chromium compound with any of the α-olefin and the alkylaluminum compound in advance, or the alkylaluminum compound with respect to 1 g of the chromium compound. It is necessary to make the amount used of 20 mmol or more, but the greatest effect can be obtained when all of the above conditions are satisfied.

  When using the former contact method, the usage-amount with respect to the chromium compound of the said alkyl aluminum compound should just be 5 mmol / chrome compound g or more. As a specific contact method, in the case of a batch-type reaction system, an alkylaluminum compound is present in a solvent and a chromium compound is injected simultaneously with an α-olefin, or initially an α-olefin. And a method in which a chromium compound is pressed into the aluminum alloy compound. In the case of a continuous reaction mode, a method in which each component is directly and independently supplied to a reaction vessel, and the like are exemplified. Since the interaction between the alkylaluminum compound and the α-olefin is small under the conditions of the present invention, the contact method described above can be said to be substantially the same method.

  By adopting the above contact method, effects such as significant improvement in activity and suppression of the formation of a high molecular weight polymer are exhibited. In the catalyst system of the present invention, it is presumed that the solvent-soluble component produced as a result of the reaction between the chromium compound and the alkylaluminum compound has a polymerization activity. When the α-olefin is brought into contact with the chromium compound and the alkylaluminum compound without contacting, the active species generated by the coordination of the existing α-olefin is stabilized, and the amount of the active species is considered to increase. . On the other hand, when the α-olefin is contacted after contacting the chromium compound and the alkylaluminum compound in the absence of the α-olefin, the amount of active species decreases for the above reasons, It is considered that the reduction of the activity is caused by the progress of the reduction beyond the appropriate reduction degree of the chromium compound before the contact and the polymerization reaction are started. In addition, the activity decreases when the alkylaluminum compound is brought into contact with the chromium compound in advance after contacting the chromium compound with the α-olefin. In this case, the alkylaluminum is brought into contact with the α-olefin in advance. It is presumed that it becomes difficult to solubilize when reacting with a compound.

  Even when the above contact method is not adopted, the amount of the alkylaluminum compound used relative to the chromium compound is 20 mmol / chromium compound g or more, preferably 30 mmol / chromium compound g or more. Mermer selectivity can be obtained. When the amount of alkylaluminum compound used is smaller than 20 mmol / chromium compound g, trimer selectivity and activity decrease.

  Increasing the amount of the alkylaluminum compound used relative to the chromium compound promotes solubilization of the chromium compound and increases the amount of active species. Therefore, even when the above contact method is not used, a certain degree of low polymerization activity and It is considered that a monomer selectivity can be obtained. The upper limit of the amount of the alkylaluminum compound used is not particularly limited, but even if an unnecessarily large amount of the alkylaluminum compound is used, only the yield of the product per alkylaluminum compound is lowered. Preferably, the upper limit of the amount of alkylaluminum compound used is 1,000 mmol / chromium compound g, more preferably 500 mmol / chromium compound g.

  In addition, in the low polymerization of α-olefin of the present invention, activity and trimer selectivity are improved by coexisting hydrogen during the reaction, and the effect is that hydrogen is allowed to coexist under conditions other than the present invention. It is more prominent than the case. In particular, in the present invention, the activity and trimer selectivity are remarkably improved by conducting the low polymerization reaction in an alicyclic hydrocarbon solvent and in the presence of hydrogen. The production of the high molecular polymer (insoluble in a hydrocarbon solvent at room temperature) in the present invention is 25% by weight or less of the total product, and according to the preferred method of the present invention, it is 15% by weight or less. By using a simple method, the content can be made 5% by weight or less.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
Catalyst Production Example 1 (Production of Cr Compound-1)
15 ml of THF was added to 0.815 g (20.3 mmol) of NaH, and 1.4 ml (20 mmol) of pyrrole dissolved in 5 ml of THF was added dropwise. After stirring at room temperature for 1 hour, this solution was added dropwise to 1.23 g (10 mmol) of CrCl2 suspended in 20 ml of THF. After dropwise addition, 5 ml of THF was added, and the mixture was heated to reflux for 20 hours. After the precipitate was filtered off, 100 ml of pentane was added to the filtrate and allowed to stand at 5 ° C. The formed 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.
Cr: 19.1%, C: 52.3%, H: 5.45%, N: 11.6%.

Catalyst Production Example 2 (Production of Cr Compound-2)
At −78 ° C., 2.1 ml (30 mmol) of pyrrole dissolved in 20 ml of THF was added dropwise to 19 ml of n-BuLi / normal hexane solution (n-BuLi 30 mmol) and stirred for 15 minutes. Thereafter, the temperature was returned to room temperature, and stirring was continued at room temperature for 2 hours. To this solution, 1.58 g (10 mmol) of CrCl3 was added as a powder, and then heated under reflux for 5 hours. The precipitate formed after standing to cool was filtered off, and the filtrate was dried up to obtain a powder. The content of each element in this powder was as follows.
Cr: 6.6%, C: 69.2%, H: 7.3%, N: 15.1%.

Catalyst Production Example 3 (Production of Cr Compound-3)
To 0.79 g (16.5 mmol) of NaH was added 15 ml of THF, and 1.0 ml (15 mmol) of pyrrole dissolved in 5 ml of THF was added dropwise. After stirring at room temperature for 1 hour, this solution was added dropwise to 0.79 g (5 mmol) of CrCl3 suspended in 25 ml of THF. After dropping, the mixture was heated to reflux for 20 hours. After the precipitate was filtered off, the solvent was distilled off to obtain 1.65 g of a black powder. The content of each element in this powder was as follows.
Cr: 6.5%, C: 58.0%, H: 6.6%, N: 10.5%.

Example 1
A 300 cc autoclave heat-dried with a dryer at 150 ° C. was assembled while hot and purged with vacuum nitrogen. The autoclave was fitted with a catalyst feed tube equipped with a rupture disc. 50 cc of heptane and 0.4 mmol of triethylaluminum were charged to the autoclave barrel side, while 10 mg of chromium compound-1 slurried in 1 cc of heptane was charged to the catalyst feed tube. At this point, the chromium compound and triethylaluminum are not in contact. The autoclave was heated to 80 ° C., and ethylene was introduced from the catalyst feed tube at 80 ° C. The rupturable plate burst due to ethylene pressure, and ethylene, chromium catalyst, and triethylaluminum simultaneously contacted to initiate low polymerization of ethylene. Ethylene total pressure was introduced to 40 kg / cm ^2, was low polymerization of one hour the ethylene to maintain the subsequent total pressure 40 kg / cm ^2. Since the internal temperature of the autoclave became 90 ° C. due to the polymerization heat, the reaction temperature was subsequently maintained at 90 ° C. After 1 hour, the reaction was stopped by injecting ethanol, and the product was quantified by gas chromatography. The results are shown in Table-2.

Example 2
In the same autoclave as that used in Example 1, 10 mg of a chromium compound and 0.4 mmol of triethylaluminum were similarly charged. Hydrogen was introduced at 3.5 kg / cm ² and the autoclave was heated to 90 ° C. At this point, the chromium compound and triethylaluminum are not in contact. Next, ethylene was introduced from the catalyst feed tube at 90 ° C. The rupturable plate was ruptured by ethylene pressure, and ethylene, chromium compound, and triethylaluminum were simultaneously contacted to initiate ethylene polymerization. Ethylene total pressure was introduced to 40 kg / cm ^2, the polymerization was carried out for 0.5 hour ethylene and maintained thereafter the total pressure 40 kg / cm ^2. Although the internal temperature of the autoclave became 110 ° C. due to the polymerization heat, the autoclave was cooled, and thereafter the reaction temperature was maintained at 100 ° C. After 0.5 hour, the reaction was stopped by injecting ethanol, and the product was quantified by gas chromatography. The results are shown in Table-2.

Examples 3-7
The reaction was performed in the same manner as in Example 1 except that the reaction conditions were changed as described in Table-1. The results are shown in Table-2.

Example 8
First, 10 mg of the chromium compound used in Example 1 and then 50 ml of heptane were charged into the autoclave, and then the temperature was raised to 90 ° C., and then ethylene was introduced up to 35 kg / cm ² . Since absorption of ethylene was not recognized, 0.4 mmol of triethylaluminum was injected into this. Absorption of ethylene began, and after 30 minutes, the reaction was stopped by injecting ethanol. The reaction temperature was maintained at 90 ° C. The results are shown in Table-2.

Example 9
Low-polymerization of ethylene was performed in the same manner as in Example 4 except that the chromium compound was changed to that obtained in Production Example 3. The reaction conditions are shown in Table-1 and the results are shown in Table-2.

Example 10
Low polymerization of ethylene was performed in the same manner as in Example 9 except that the reaction solvent was changed to cyclohexane. The reaction conditions are shown in Table-1 and the results are shown in Table-2.

Example 11
Low polymerization of ethylene was carried out in the same manner as in Example 10 except that the amount of triethylaluminum was 0.4 mmol and hydrogen was introduced at 3.5 kg / cm ² . The reaction conditions are shown in Table-1 and the results are shown in Table-2.

Comparative Example 1
The reaction was performed in the same manner as in Example 8 except that the amount of triethylaluminum was changed to 0.12 mmol. The results are shown in Table-2.

Comparative Example 2
The reaction was performed in the same manner as in Comparative Example 1 except that 3.5 kg / cm ² of hydrogen was introduced and the total pressure was 40 kg / cm ² before the triethylaluminum was injected. The results are shown in Table-2.

Comparative Example 3
The autoclave was charged with triethylaluminum and a chromium compound in a heptane solvent, heat-treated at 90 ° C. for 30 minutes, and then reacted in the same manner as in Comparative Example 1 except that ethylene was introduced and the reaction temperature was 100 ° C. . The results are shown in Table-2.

Claims (5)

A method for producing an α-olefin low polymer, which comprises a chromium compound containing at least one chromium-pyrrolyl bond and an alkylaluminum compound and low-polymerizes an α-olefin in the presence of a catalyst soluble in a solvent. The method for producing an α-olefin low polymer according to claim 1, wherein the low polymerization is carried out in the presence of hydrogen. The method for producing an α - olefin low polymer according to claim 1 or 2, wherein the solvent is an alicyclic hydrocarbon. The method for producing an α - olefin low polymer according to any one of claims 1 to 3, wherein the low polymerization is carried out in an alicyclic hydrocarbon solvent. The method for producing an α-olefin low polymer according to any one of claims 1 to 4, wherein the concentration of the chromium compound in the solvent is 0.1 mg to 5 g per liter of the solvent.