Method for producing α-olefin low polymers

Abstract

In one or more examples, a method for producing an α-olefin low polymer comprises a gas drying step of supplying gas into a reaction system, a solvent drying step of supplying a desiccant-containing solvent containing a desiccant into the reaction system after the gas drying step, a deactivator addition step of supplying a deactivator for the desiccant into the reaction system, and an α-olefin low polymerization reaction step of carrying out a low polymerization reaction of α-olefin, wherein the deactivator is supplied into the reaction system before the start of the low polymerization reaction of α-olefin.

Description

[Technical Field]

[0001] This invention relates to a method for producing α-olefin low polymers. This application claims priority based on Japanese Patent Application No. 2024-169055 and Japanese Patent Application No. 2024-168697, filed with the Japan Patent Office on September 27, 2024, and the contents of these applications are incorporated herein by reference. [Background technology]

[0002] Alpha-olefin low polymers are useful substances widely used as raw material monomers for olefin polymers, as comonomers for various polymers, and as raw materials for plasticizers, surfactants, lubricants, and the like. Among the many alpha-olefin low polymers, for example, 1-hexene is useful as a raw material for linear low-density polyethylene. 1-hexene can be obtained by trimerizing ethylene.

[0003] Typically, low-molecular-weight α-olefins are produced by low-molecular-weight polymerization of α-olefin raw materials in the presence of a chromium-based catalyst and a reaction solvent. For example, 1-hexene can be produced by the trimerization reaction of ethylene in the presence of a reaction solvent and a catalyst composition containing a transition metal-containing compound, an aluminum-containing compound, and optionally a halogen-containing compound or a nitrogen-containing compound.

[0004] In low-molecular-weight polymerization reactions of α-olefins, the presence of water in the reaction system reduces catalytic activity, thus promoting the formation of polymer by-products. When continuing low-molecular-weight polymerization reactions over long periods, separation and removal of the generated polymer are necessary. Furthermore, the generated polymer can adhere to or accumulate within the manufacturing equipment, leading to problems such as reduced manufacturing stability and equipment blockage. Therefore, it is necessary to remove water from the reaction system to control the water concentration within the system and carry out low-molecular-weight polymerization reactions under controlled conditions.

[0005] For example, Patent Document 1 discloses a method for adjusting the water content in a reactor, which involves introducing an aluminum-containing compound, one of the catalyst components, into the reaction system while the raw material α-olefin and reaction solvent are circulated beforehand, in order to supply the catalyst components for a low polymerization reaction into the reaction system.

[0006] Patent Document 2 discloses a method for adjusting the water content in a reactor, which involves pre-purifying the solvent supplied to the reaction system by distillation before supplying it to the reaction system. Furthermore, Patent Document 2 discloses a method of pre-purifying the solvent using an aluminum-containing compound, one of the catalyst components, as a desiccant before supplying the solvent to the reaction system. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2011-219474 [Patent Document 2] Japanese Patent Application Publication No. 8-239330 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the methods described in Patent Documents 1 and 2 have room for rationalization in the industrial-scale manufacturing process of α-olefin low polymers. In particular, it takes time to reduce the water content in the reactor to the desired level before initiating the low polymerization reaction of α-olefins. Therefore, the low polymerization reaction of α-olefins cannot be started quickly.

[0009] In addition, reducing raw material costs is important from the standpoint of manufacturing costs, etc. In this respect, the method described in Patent Document 1 may lead to an unnecessary increase in raw material costs. Furthermore, the burden of wastewater treatment after moisture reduction treatment may increase. Therefore, this may lead to an unnecessary increase in manufacturing costs. The method described in Patent Document 2 may lead to an unnecessary increase in refining costs.

[0010] The present invention aims to provide an industrially advantageous method for producing an α-olefin low polymer, which can reduce the amount of expensive alkylaluminum compounds used as a desiccant, efficiently reduce the moisture content in the reaction system while suppressing the amount of expensive alkylaluminum compounds used as a desiccant, quickly start the production operation, maintain good catalytic activity and product selectivity when starting the low polymerization reaction of α-olefin, and suppress the formation of polymers of by-products that cause process blockage.

Means for Solving the Problems

[0011] Preferred embodiments include, but are not limited to, the following. [1] A method for producing an α-olefin low polymer, comprising: a gas drying step of supplying a gas into the reaction system; a solvent drying step of supplying a desiccant-containing solvent into the reaction system after the gas drying step; a deactivator addition step of supplying a deactivator for the desiccant into the reaction system; an α-olefin low polymerization reaction step of performing a low polymerization reaction of α-olefin; and the deactivator is supplied into the reaction system before the start of the low polymerization reaction of α-olefin. [2] In the gas drying step, the gas is supplied into the reaction system until the moisture content in the reaction system becomes not more than a predetermined value (1). The production method according to [1]. [3] The production method according to [2], wherein the predetermined value (1) is 100 mol ppm. [4] The production method according to any one of [1] to [3], wherein the moisture content of the gas is 5 mol ppm or less. [5] In the solvent drying step, the desiccant-containing solvent is supplied into the reaction system until the moisture content in the reaction system becomes not more than a predetermined value (2). The production method according to any one of [1] to [4]. [6] The production method according to [5], wherein the predetermined value (2) is 10 mol ppm. [7] The production method according to any one of [1] to [6], wherein the desiccant-containing solvent contains an alkylaluminum compound. [8] The production method according to any one of [1] to [7], wherein the deactivator contains an alkyl alcohol. [9] The production method according to any one of [1] to [8], further comprising a raw material substitution step of supplying raw material α-olefin into the reaction system until the nitrogen gas content in the reaction system becomes not more than a predetermined value (3) after the gas drying step and before the solvent drying step.

[10] The production method according to [9], wherein the predetermined value (3) is 20% by volume.

[11] The production method according to [9], further comprising a solvent substitution step of supplying a reaction solvent into the reaction system until the content of α-olefin in the reaction system becomes not more than a predetermined value (4) after the raw material substitution step and before the solvent drying step.

[12] The production method according to

[11] , wherein the predetermined value (4) is 70% by volume.

[13] After the deactivator addition step and before the α-olefin low polymerization reaction step, the production method further comprises a measurement step of measuring the water content in the reaction system, and starting the α-olefin low polymerization reaction step when the water content measured in the measurement step is not more than a predetermined value (5). The production method according to any one of [1] to

[12] .

[14] The production method according to

[13] , wherein the predetermined value (5) is 10 mol ppm.

[15] The α-olefin low polymerization reaction step includes supplying a catalyst, a solvent, and raw material α-olefin into the reaction system. The production method according to any one of [1] to

[14] .

Advantages of the Invention

[0012] According to the present invention, when producing low-molecular-weight α-olefin polymers by a low-molecular-weight polymerization reaction of α-olefins, the amount of expensive alkylaluminum compounds used as desiccants is reduced before the start of production, while efficiently reducing the moisture content in the reaction system and enabling a rapid start of production. Furthermore, when initiating the low-molecular-weight polymerization reaction of α-olefins, catalytic activity and product selectivity can be well maintained, and the formation of polymer by-products that cause process blockage can also be suppressed. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 shows an example of a manufacturing apparatus for α-olefin low polymer (1-hexene). [Figure 2] Figure 2 shows the relationship between the H2O / Cr molar ratio and catalytic activity value obtained in Reference Experiment Example 1. [Figure 3] Figure 3 shows the relationship between the H2O / Cr molar ratio and polyethylene selectivity obtained in Reference Experiment Example 1. [Figure 4] Figure 4 shows the relationship between the molar ratio of the deactivator to the desiccant (TEA) and the isomerization rate of 1-hexene, obtained in Reference Experiment Example 4. [Modes for carrying out the invention]

[0014] Unless otherwise specified, numerical ranges expressed using "~" in this specification mean a range that includes the numbers before and after "~" as the lower and upper limits, respectively. "A~B" means A or greater and B or less.

[0015] In this specification, "including A or B" means "including A," "including B," and "including both A and B," unless otherwise specified.

[0016] In this specification, "mass%" refers to the percentage of a given component contained in 100% of the total amount. "Mass%" and "weight%" are synonymous.

[0017] In this specification, "mass ppm" refers to ppm calculated with mass as the unit, and indicates the content ratio of a given component in a total amount of 1 million mass ppm. Also, 1 mass ppm = 1 × 10⁻¹⁶ -4 It means mass percentage. "Mass ppm" and "weight ppm" are synonymous.

[0018] In this specification, "mol%" refers to the molar concentration of a given component contained in the total volume.

[0019] In this specification, "molar ppm" refers to "ppm" calculated with moles as the unit, and indicates the molar concentration of a given component contained in the total volume as parts per million.

[0020] In this specification, “optional” or “optionally” means that the circumstances described following these words may or may not occur. Such descriptions include both cases in which the circumstances occur and cases in which they do not occur.

[0021] All steps described herein may be carried out in any preferred order, unless otherwise specified herein or unless the context clearly contradicts it.

[0022] The embodiments of the present invention will be described in detail below, but the following description relates to some examples of embodiments of the present invention and is not limited to these.

[0023] <Method for producing α-olefin low polymers> The present invention relates to a method for producing α-olefin low polymers by a low polymerization reaction of α-olefins. The present invention provides a method for producing an α-olefin low polymer, comprising: a gas drying step of supplying gas into a reaction system; a solvent drying step of supplying a desiccant-containing solvent containing a desiccant into the reaction system after the gas drying step; a deactivator addition step of supplying a deactivator for the desiccant into the reaction system; and an α-olefin low polymerization reaction step (hereinafter sometimes simply referred to as the "low polymerization reaction step") in which an α-olefin low polymerization reaction is carried out, wherein the deactivator is supplied into the reaction system from before the start of the α-olefin low polymerization reaction.

[0024] Furthermore, the method for producing the α-olefin low polymer of the present invention may further include a measurement step, described later, in which the water content in the reaction system is measured after the deactivator addition step and before the α-olefin low polymerization reaction step, and the α-olefin low polymerization reaction step can be started when the water content measured in the measurement step is less than or equal to a predetermined value (5).

[0025] The present invention provides a method for producing a low-molecular-weight α-olefin, which includes first reducing the water content in the reaction system to a certain level by a gas drying step before the low-molecular-weight polymerization reaction step of the α-olefin, and then performing a solvent drying step to further reduce the water content to a desired value. Furthermore, the method for producing the α-olefin low polymer of the present invention includes a deactivator addition step before initiating the low polymerization reaction of the α-olefin, thereby deactivating the desiccant such as the alkylaluminum compound supplied in the solvent drying step. The present invention provides a method for producing α-olefin low polymers, which, when starting up the α-olefin low polymer production apparatus, particularly before the low polymerization reaction of the α-olefin, combines a gas drying step, a solvent drying step, and a deactivator addition step in this order. This allows for efficient reduction of the moisture content in the reaction system while minimizing the amount of desiccant used, and enables rapid commencement of production operations. Furthermore, the method for producing α-olefin low polymers of the present invention, by performing the deactivator addition step, can maintain good catalytic activity and product selectivity when initiating the α-olefin low polymerization reaction at the start of operation, and can also suppress the formation of polymer by-products that cause process blockage. In particular, when using expensive alkylaluminum compounds as desiccants, the amount used can be reduced, thereby enhancing economic advantages.

[0026] Furthermore, the method for producing the α-olefin low polymer of the invention can suppress the formation of polymers, which are by-products that cause process blockage, by performing the low polymerization reaction step after confirming that the water content in the reaction system has been reduced to a desired value by the measurement step.

[0027] In this invention, by performing a gas drying step before the solvent drying step, it is possible to reduce the amount of desiccant used in the solvent drying step, particularly the amount of expensive alkylaluminum compounds used as desiccants. As a result, unnecessary increases in raw material costs can be suppressed. In addition, since the moisture content in the reaction system can be reduced in a shorter time than in conventional methods, it is possible to quickly start the production of α-olefin low polymers. Thus, in this invention, by performing a gas drying step before the solvent drying step, the moisture content in the solvent drying step can be reduced more efficiently.

[0028] Furthermore, the method for producing the α-olefin low polymer of the present invention includes a low polymerization reaction step for α-olefin, which will be described later, in which the α-olefin low polymer is produced by supplying the raw material α-olefin, a solvent, and a catalyst into the reaction system after the deactivator addition step. Details of the low polymerization reaction step for α-olefin will be described later.

[0029] Furthermore, the method for producing the α-olefin low polymer of the present invention includes a deactivator addition step, described later, in which, before the start of the low polymerization reaction of the α-olefin, a deactivator for the desiccant is supplied into the reaction system from a deactivator supply unit located downstream of the desiccant-containing solvent supply unit.

[0030] Furthermore, the method for producing the α-olefin low polymer of the invention may include a raw material substitution step, described later, in which raw material α-olefin is supplied into the reaction system after the gas drying step and before the solvent drying step until the nitrogen gas content in the reaction system becomes less than or equal to a predetermined value (3).

[0031] Furthermore, the method for producing the α-olefin low polymer of the invention may include a solvent replacement step, described later, after the raw material replacement step and before the solvent drying step, in which the reaction solvent is supplied into the reaction system until the α-olefin content in the reaction system becomes less than or equal to a predetermined value (4).

[0032] In this specification, "reaction system" refers to the manufacturing equipment in which the raw materials and reaction products used to produce the α-olefin low polymer reside or flow. In the specific embodiments described above, the manufacturing equipment used to carry out the measurement step, the low polymerization reaction step, the gas drying step, the solvent drying step, the deactivator addition step, the raw material replacement step, and the solvent replacement step constitutes the reaction system.

[0033] The following describes in detail each step of the method for producing the α-olefin low polymer of the present invention. However, the following description relates to some examples of embodiments, and the present invention is not limited to the following.

[0034] [Gas drying process] In the gas drying process, gas is supplied into the reaction system before the low polymerization reaction of α-olefins. By performing a gas drying process, the reaction system can be dried before the low polymerization reaction of α-olefins, reducing the moisture content in the reactor before the start of production. This efficiently reduces the moisture content in the reaction system while minimizing the amount of desiccant used, allowing for a rapid start of production. Furthermore, during the low polymerization of α-olefins, catalytic activity and product selectivity can be maintained at a good level, and the formation of polymer by-products that cause process blockage can be more effectively suppressed. In particular, when using expensive alkylaluminum compounds as desiccants, reducing their usage can enhance economic benefits.

[0035] The gas is preferably oxygen-free in order to suppress catalyst degradation in the subsequent low polymerization reaction step. The gas is preferably at least one inert gas selected from the group consisting of nitrogen gas, helium gas, neon gas, and argon gas, and nitrogen gas is preferred from the viewpoint of manufacturing cost.

[0036] (Dry gas) As the aforementioned gas, a drying gas can be used for the purpose of drying the reaction system. For example, the drying gas can be a gas that has been previously dried with a desiccant such as a molecular sieve.

[0037] The upper limit of the moisture content of the drying gas is not particularly limited. However, from the viewpoint of reducing the amount of desiccant used in the solvent drying process, especially the amount of desiccant, and further reducing the moisture content in the reaction system in a short time to quickly start the production operation of the α-olefin low polymer, it is preferably 5 mol ppm or less, more preferably 4 mol ppm or less, even more preferably 3 mol ppm or less, and particularly preferably 2 mol ppm or less, relative to the total amount of drying gas. In particular, when using expensive alkylaluminum compounds as desiccants, the amount used can be reduced, thereby increasing economic advantages.

[0038] The lower limit of the moisture content of the dry gas is not particularly limited, and from the viewpoint of economics such as the manufacturing costs required to reduce the moisture content in dry nitrogen, it can usually be 0.0001 mol ppm or more, more preferably 0.001 mol ppm or more, even more preferably 0.01 mol ppm or more, and particularly preferably 0.1 mol ppm or more.

[0039] The above upper and lower limits can be combined in any way. For example, the moisture content of the dry gas is not particularly limited and can be between 0.0001 mol ppm and 5 mol ppm, more preferably between 0.001 mol ppm and 4 mol ppm, even more preferably between 0.01 mol ppm and 3 mol ppm, and particularly preferably between 0.1 mol ppm and 2 mol ppm.

[0040] The moisture content in dry gas can be accurately measured using known analytical methods employing a dew point meter. Specifically, the dew point can be calculated under atmospheric pressure conditions based on the relative humidity measured in accordance with JIS Z 8806-2001.

[0041] The method for adjusting the moisture content of the dry gas is not particularly limited, and known methods for removing moisture include, for example, passing nitrogen gas through a desiccant to remove moisture, or cooling nitrogen gas to condense the moisture in the gas.

[0042] (A predetermined value (1)) The predetermined value (1) is the upper limit of the permissible moisture content when reducing the moisture content in the reaction system during the gas drying process. In the gas drying process, it is preferable to supply gas to the reaction system until the moisture content in the reaction system is less than or equal to the predetermined value (1). The predetermined value (1) is the upper limit of the permissible moisture content when reducing the moisture content in the reaction system during the gas drying process. The predetermined value (1) is a value within which the moisture content in the reaction system when producing the α-olefin low polymer does not cause practical problems. The predetermined value (1) may be, for example, a value empirically determined using the manufacturing equipment used, or a value theoretically derived using simulations or the like.

[0043] The optimal values ​​for the water content and supply amount of gas required to keep the water content in the reaction system below a predetermined value (1) during the gas drying process can be determined by the volume of the reaction system, residence time, initial water content in the reactor, reaction temperature in the reactor, etc.

[0044] Depending on the combination of manufacturing conditions used in the gas drying process, the moisture content and supply amount of dry nitrogen gas can be determined experimentally in advance so that the moisture content in the reaction system remains below a predetermined value (1). These values ​​can also be calculated by simulation. In the experimental examples described later, empirical values ​​obtained from experimental results with an appropriate number of trials using the actual α-olefin low polymer manufacturing equipment were used as the predetermined value (1).

[0045] The predetermined value (1) is not particularly limited, and from the viewpoint of reducing the amount of desiccant used in the solvent drying process and further reducing the moisture content in the reaction system in a short time to quickly start the production operation of the α-olefin low polymer, the predetermined value (1) is preferably 100 mol ppm, more preferably 20 mol ppm, even more preferably 10 mol ppm, even more preferably 5 mol ppm, even more preferably 4 mol ppm, particularly preferably 3 mol ppm, and most preferably 2 mol ppm, relative to the total amount of gas in the reaction system. In particular, when using expensive alkylaluminum compounds as desiccants, reducing their usage can enhance economic benefits.

[0046] The lower limit of the moisture content in the reaction system during the gas drying process is not particularly limited. From the viewpoint of economics, such as the increased manufacturing costs required to reduce the moisture content in the reaction system, it can usually be 0.0001 mol ppm, more preferably 0.0003 mol ppm, even more preferably 0.001 mol ppm, even more preferably 0.003 mol ppm, even more preferably 0.01 mol ppm, particularly preferably 0.03 mol ppm, and most preferably 0.1 mol ppm. The above upper and lower limits can be combined in any way.

[0047] The moisture content in the reaction system during the gas drying process can be measured using a known moisture content analyzer. The moisture content analyzer may be an offline type or an online type installed at any point within the reaction system. For moisture content analysis, for example, capacitive, electrical resistance, microwave, near-infrared, or neutron type moisture content analyzers can be used.

[0048] [Solvent drying process] In the solvent drying process, after the gas drying process and before the low polymerization reaction process of α-olefin, a solvent containing a desiccant, as described later, is supplied into the reaction system from the supply unit. By performing a solvent drying process, the reaction system after the gas drying process is further dried, and the moisture content in the reactor can be further reduced before the low polymerization reaction of α-olefins. This allows for a more efficient reduction of moisture content in the reaction system, enabling a rapid start to production operations. Furthermore, when initiating the low polymerization reaction of α-olefins, catalytic activity and product selectivity can be well maintained, and the formation of by-product polymers that can cause process blockage can be more effectively suppressed.

[0049] (Solvent containing a desiccant) The solvent containing a desiccant used in the solvent drying process refers to a solvent containing a desiccant, as described later. The desiccant is not particularly limited as long as it is a compound that substantially reduces the amount of water in the system by reacting with water to incorporate water into its molecules or by adsorbing water into the desiccant, or a compound that has a hygroscopic effect.

[0050] (Desiccant) Examples of the desiccant include aluminum compounds, alkylaluminum compounds, silica gel, calcium salts, molecular sieves, pentoxide phosphate, and sodium sulfate. Among these, alkylaluminum compounds are preferred because they have excellent water removal performance in the reaction system, excellent solubility in reaction solvents used in the low polymerization reaction of α-olefins, and catalytic activity for the low polymerization reaction of α-olefins. In other words, it is preferable that the desiccant-containing solvent contains alkylaluminum compounds as the desiccant. Details of alkylaluminum compounds will be described later.

[0051] (solvent) The solvent is not particularly limited; for example, reaction solvents used in low polymerization reactions of α-olefins can be used.

[0052] The reaction solvent is not particularly limited, and saturated hydrocarbons are preferably used. Examples of the reaction solvent include chain-like saturated hydrocarbons having 1 to 20 carbon atoms, such as butane, pentane, 3-methylpentane, n-hexane, n-heptane, 2-methylhexane, octane, cyclohexane, methylcyclohexane, 2,2,4-trimethylpentane, and decalin, or alicyclic saturated hydrocarbons having 1 to 20 carbon atoms, as well as aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, mesitylene, and tetralin. One reaction solvent may be used alone, or two or more may be used in combination. Among these reaction solvents, chain-like saturated hydrocarbons having 4 to 10 carbon atoms and alicyclic saturated hydrocarbons are preferred from the viewpoint of suppressing the formation or precipitation of by-product polymers such as polyethylene, and from the viewpoint of high catalytic activity. Non-limiting examples include n-heptane and cyclohexane, and more preferably n-heptane.

[0053] The lower limit of the content of the desiccant in the desiccant-containing solvent is not particularly limited, but is usually preferably 0.000001% by weight or more, more preferably 0.0001% by weight or more, and even more preferably 0.0001% by weight or more, relative to the total mass of the desiccant-containing solvent. The upper limit of the content of the desiccant is not particularly limited, but is usually preferably 10% by weight or less, more preferably 1% by weight or less, and even more preferably 0.1% by weight or less.

[0054] The above upper and lower limits can be combined in any way. The proportion of the desiccant contained in the desiccant-containing solvent is not particularly limited, but for example, it is usually preferably 0.000001% by weight or more and 10% by weight or less, more preferably 0.0001% by weight or more and 1% by weight or less, and even more preferably 0.0001% by weight or more and 0.1% by weight or less.

[0055] (Alkylaluminum compounds) The alkylaluminum compounds used as desiccants are not particularly limited, as long as they are compounds in which one to three alkyl groups are bonded to an aluminum atom. From the viewpoint of excellent decomposition stability of the alkylaluminum compound in the reaction system and excellent moisture removal performance in the reaction system, linear alkylaluminum compounds in which at least one alkyl group directly bonded to the aluminum atom is a linear alkyl group are preferred, and linear alkylaluminum compounds in which all alkyl groups directly bonded to the aluminum atom are linear alkyl groups are more preferred.

[0056] Examples of alkylaluminum compounds include trialkylaluminum, alkylaluminum halides, alkoxyalkylaluminum, and alkylaluminum hydrides. Examples of trialkylaluminum include trimethylaluminum, triethylaluminum, and triisobutylaluminum. Examples of alkylaluminum halides include diethylaluminum monochloride, ethylaluminum sesquichloride, and ethylaluminum dichloride. Examples of alkoxyalkylaluminum include diethylaluminum ethoxide. Examples of alkylaluminum hydrides include diethylaluminum hydride.

[0057] Among alkylaluminum compounds, trialkylaluminum is preferred, and triethylaluminum is more preferred. Alkyl aluminium compounds may be used individually or in combination of two or more.

[0058] In this invention, by performing a solvent drying step after the gas drying step, the moisture content present in the reaction system can be more efficiently reduced by the alkylaluminum compound. Since the moisture content in the reaction system is reduced to a certain extent after the gas drying step, by performing an alkylaluminum compound solvent drying step after the gas drying step, the amount of expensive alkylaluminum compound used can be reduced while more efficiently reducing the moisture content in the reaction system. For the reasons stated above, when initiating the low polymerization reaction of α-olefins, catalytic activity and product selectivity can be well maintained, and the formation of polymer by-products that cause process blockage can also be suppressed.

[0059] The reason why the water content in the reaction system decreases due to the alkylaluminum compound is not clear, but it can be inferred as follows.

[0060] Alkylaluminum compounds are highly reactive with water, so their alkyl groups are substituted for hydrogen atoms in water, and they form alkanes with aluminum compounds containing hydroxyl or oxygen atoms. For example, in the case of trialkylaluminum represented by (R)3Al, the following reaction occurs. (R)3Al+H2O→R2AlOH+RH In the formula, R is any alkyl group.

[0061] Hydroxyalkylaluminum compounds (R2AlOH) further react with water. At this time, various chemical species such as RAl(OH)2, Al(OH)3, R2Al-O-AlR2, R-Al(OH)-O-Al-R(OH), (-AlRO-)n, and Al2O3 are produced.

[0062] Through the above reactions, some of the water in the reaction system is incorporated into the aluminum compounds. Therefore, it is presumed that the water content in the reaction system can be reduced by removing these aluminum compounds from the reaction system.

[0063] The reason why reducing the water content in the reaction system can suppress the formation of polymer by-products is not entirely clear, but it can be inferred as follows.

[0064] If water is present in the reaction system, the aluminum-containing compound (c), one of the catalyst components described later, may produce hydroxides or aluminum polymers. As a result, coordination inhibition between the aluminum-containing compound (c) and the transition metal-containing compound (a), another catalyst component, and coordination inhibition between the aluminum-containing compound (c) and the halogen-containing compound (d), another catalyst component, is presumed to occur. In this case, a catalyst species different from the original catalyst species may be produced, thus promoting the formation of polymers as by-products. It is presumed that reducing the water content in the reaction system can suppress the formation of polymers as by-products.

[0065] The upper limit of the temperature in the reaction system during the solvent drying process is not particularly limited, and can usually be 140°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower. Keeping the temperature below 140°C suppresses the thermal decomposition of the desiccant and maintains the dewatering performance. In particular, when an alkylaluminum compound is used as the desiccant, thermal decomposition can be suppressed by keeping the temperature in the reaction system below 140°C. The lower limit of the temperature in the reaction system is not particularly limited, and can usually be 0°C or higher, more preferably 20°C or higher, and even more preferably 50°C or higher. Keeping the temperature above 0°C allows for good dewatering rate maintenance without suppressing the reactivity between the alkylaluminum compound and water.

[0066] The above upper and lower limits can be combined in any way. The temperature in the reaction system during the solvent drying process is not particularly limited and can usually be between 0°C and 140°C, more preferably between 20°C and 120°C, and even more preferably between 50°C and 100°C.

[0067] In the drying process using a desiccant, the method of supplying the alkylaluminum compound is not particularly limited. It can be supplied as a solid or as a solution dissolved in the reaction solvent described later. From the viewpoint of efficiently removing moisture from the reaction system, it is preferable to supply the alkylaluminum compound as a solution dissolved in the reaction solvent.

[0068] (A predetermined value (2)) In the solvent drying process, it is preferable to supply a desiccant-containing solvent into the reaction system until the moisture content in the reaction system falls below a predetermined value (2).

[0069] The predetermined value (2) is the upper limit of the permissible value when reducing the moisture content in the reaction system during the solvent drying process. The predetermined value (2) is a value within which the moisture content in the reaction system when producing α-olefin low polymers does not cause practical problems. The predetermined value (2) may be, for example, a value empirically determined using the manufacturing equipment used, or a value theoretically derived using simulations or the like.

[0070] The amount of alkylaluminum compound supplied to keep the moisture content in the reaction system below a predetermined value (2) during the solvent drying process can be determined optimally based on the volume and residence time in the reactor, the moisture content in the reactor, the reaction temperature in the reactor, and so on.

[0071] Depending on the combination of manufacturing conditions used in the solvent drying process, the amount of desiccant such as alkylaluminum compound supplied can be determined experimentally in advance so that the moisture content in the reaction system is less than or equal to a predetermined value (2). These values ​​can also be calculated by simulation. In the experimental examples described later, empirical values ​​obtained from experimental results with an appropriate number of trials using the actual α-olefin low polymer manufacturing equipment were used as the predetermined value (2).

[0072] The predetermined value (2) is not particularly limited, and from the viewpoint of maintaining good catalytic activity and product selectivity when initiating the low polymerization reaction of α-olefins, and also suppressing the formation of polymer by-products that cause process blockage, the predetermined value (2) is preferably 10 mol ppm, more preferably 5.0 mol ppm, even more preferably 3.0 mol ppm, particularly preferably 1.0 mol ppm, and most preferably 0.5 mol ppm.

[0073] The lower limit of the moisture content in the reaction system during the solvent drying process is not particularly limited. From the viewpoint of economics, such as the increased manufacturing costs required to reduce the moisture content in the reaction system, it is generally preferred to be 0.0001 mol ppm, more preferably 0.001 mol ppm, even more preferably 0.01 mol ppm, particularly preferably 0.1 mol ppm, and most preferably 0.3 mol ppm.

[0074] The moisture content in the reaction system during the solvent drying process can be measured using a known moisture content analyzer. The moisture content analyzer may be an offline type or an online type installed at any point within the reaction system. For moisture content analysis, for example, capacitive, electrical resistance, microwave, near-infrared, or neutron type moisture content analyzers can be used.

[0075] [Inactivator addition process] In the deactivator addition step, the deactivator of the desiccant is supplied into the reaction system. As for the method of supplying the deactivator, when a desiccant, particularly an alkylaluminum compound, is used as the desiccant, the deactivator can be supplied from a deactivator supply unit located downstream of the desiccant-containing solvent supply unit. The deactivator only needs to be supplied into the reaction system before the start of the low polymerization reaction of α-olefin, and the start time of the deactivator addition step is not particularly limited. The deactivator addition step may be started after the start of the solvent drying step, before the start of the solvent drying step, or simultaneously with the solvent drying step.

[0076] If a drying agent such as an alkylaluminum compound supplied in the solvent drying step is present in the downstream reaction system after the reactor, the low polymerization reaction of α-olefin may continue at the start of the low polymerization reaction step described later, generating by-products and reducing the product selectivity. In the method for producing low-molecular-weight α-olefins of the present invention, by performing a deactivator addition step, the low polymerization of α-olefins after the reactor can be suppressed, and the reduction in product selectivity due to the generation of by-products and the formation of polymer by-products that cause process blockage can be suppressed more effectively.

[0077] The deactivator is not particularly limited, but when an alkylaluminum compound is used as a drying agent, examples include alkyl alcohols such as 2-ethylhexanol (2EH), methanol, ethanol, propanol, 1-butanol, 2-butanol, isobutanol, 1-petanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, and 1-octanol, as well as water. Alkyl alcohols are preferred because they efficiently deactivate the alkylaluminum compound by substituting the alkyl group of the alkylaluminum compound.

[0078] The method of supplying the raw material deactivator into the reaction system is not particularly limited. For example, this could involve supplying the alkyl alcohol itself to the reaction solvent from an appropriate position within the reaction system, or supplying a mixed solution of alkyl alcohol and a reaction solvent containing 1 to 99% by mass.

[0079] The amount of deactivator supplied in the deactivator addition step is not particularly limited, as long as it is an amount that can completely deactivate the alkylaluminum compound used as a desiccant. Typically, the amount supplied can be 1.5 times or more the amount required to completely deactivate the alkylaluminum compound. Preferably, the amount supplied is 2 times or more, and more preferably 3 times or more, the amount required to completely deactivate the alkylaluminum compound.

[0080] [Raw material replacement process] In the raw material substitution process, after the gas drying process and before the solvent drying process, raw material α-olefin is supplied to the reaction system until the nitrogen gas content in the reaction system falls below a predetermined value (3).

[0081] If nitrogen gas is selected in the gas drying process, nitrogen gas may remain in the reaction system until the low polymerization reaction process described later. If the low polymerization reaction process is carried out with nitrogen gas remaining in the reaction system, nitrogen gas will accumulate in the reactor during the reaction, resulting in a decrease in the gas partial pressure of the raw material α-olefin and a decrease in the low polymerization reaction rate of α-olefin. By performing a raw material replacement process after the gas drying process, the accumulation of nitrogen gas in the reactor during the low polymerization reaction process can be prevented, making it possible to more effectively maintain the productivity of α-olefin low polymerization.

[0082] The method of supplying the raw material α-olefin into the reaction system is not particularly limited. For example, the raw material α-olefin may be supplied alone in a liquid or gaseous state, or it may be supplied as a mixed solution with a reaction solvent containing the raw material α-olefin in an amount of 1 to 50% by mass. From the viewpoint of recycling and reusing the supplied raw material α-olefin, the method of supplying the raw material α-olefin in a gaseous state is preferred.

[0083] (A predetermined value (3)) The predetermined value (3) is the upper limit of the allowable nitrogen gas content when reducing the nitrogen gas content in the reaction system during the raw material substitution process. In the raw material substitution process, it is preferable to supply the raw material α-olefin into the reaction system until the nitrogen gas content in the reaction system is less than or equal to the predetermined value (3). The predetermined value (3) is a value within which the nitrogen gas content in the reaction system during the raw material substitution process when producing α-olefin low polymer does not cause practical problems. The predetermined value (3) may be, for example, a value empirically determined using the manufacturing equipment used, or a value theoretically derived using simulations or the like.

[0084] The amount of α-olefin raw material supplied to keep the nitrogen gas content in the reaction system during the raw material substitution process below a predetermined value (3) can be determined optimally by factors such as the volume and residence time in the reactor, the water content in the reactor, and the reaction temperature in the reactor.

[0085] Depending on the combination of manufacturing conditions adopted during the raw material substitution process, the amount of α-olefin raw material supplied can be determined experimentally in advance so that the nitrogen gas content in the reaction system is below a predetermined value. These values ​​can also be calculated by simulation. In the experimental examples described later, empirical values ​​obtained from experimental results with an appropriate number of trials using the actual α-olefin low polymer manufacturing equipment were used as predetermined values ​​(3).

[0086] The predetermined value (3) is not particularly limited. When the raw material α-olefin is in a gaseous state, from the viewpoint of suppressing the accumulation of residual nitrogen gas in the reactor while maintaining good productivity of the α-olefin low polymer, the predetermined value (3) is preferably 20% by volume, more preferably 10% by volume, even more preferably 5% by volume, even more preferably 3% by volume, particularly preferably 1% by volume, and most preferably 0.5% by volume, relative to 100% of the total volume of the raw material α-olefin.

[0087] The lower limit of the nitrogen gas content in the reaction system during the raw material substitution process is not particularly limited. From the viewpoint of economics, such as the increased manufacturing costs required to reduce the nitrogen gas content in the reaction system, the lower limit can usually be 0.0001 volume%, more preferably 0.0003 volume%, even more preferably 0.001 volume%, even more preferably 0.003 volume%, particularly preferably 0.01 volume%, and most preferably 0.1 volume%.

[0088] [Solvent replacement process] In the solvent replacement step, after the raw material replacement step and before the solvent drying step, the reaction solvent is supplied to the reaction system until the α-olefin content in the reaction system falls below a predetermined value (4).

[0089] Immediately after the raw material substitution step, the reaction system is filled with α-olefin gas. If alkylaluminum compounds are supplied to the reaction system in this state, sufficient drying may not be achieved. By performing a solvent substitution step and filling the reaction system with the reaction solvent, the drying process with alkylaluminum compounds can be carried out more efficiently.

[0090] The amount of reaction solvent supplied in the solvent replacement step is not particularly limited, as long as the reaction system is substantially filled with the reaction solvent. Typically, it can be 1.5 times or more the total volume to be replaced, more preferably 2 times or more, and even more preferably 3 times or more.

[0091] (A predetermined value (4)) The predetermined value (4) is the upper limit of the permissible amount of α-olefin content when the α-olefin content in the reaction system is reduced in the solvent replacement step. In the solvent replacement step, it is preferable to supply the reaction solvent to the reaction system until the α-olefin content in the reaction system is less than or equal to the predetermined value (4). The predetermined value (4) is a value that allows the α-olefin content in the reaction system during the solvent replacement step when producing the α-olefin low polymer to be within a range that does not cause practical problems. The predetermined value (4) may be, for example, a value empirically determined using the manufacturing equipment used, or a value theoretically derived using simulations or the like.

[0092] The predetermined value (4) is not particularly limited, and from the viewpoint of performing the drying treatment with a desiccant such as an alkylaluminum compound more efficiently, the predetermined value (4) is preferably 70% by volume, more preferably 65% ​​by volume, even more preferably 60% by volume, even more preferably 55% by volume, particularly preferably 50% by volume, and most preferably 40% by volume.

[0093] The lower limit of the α-olefin content in the reaction system during the solvent substitution step is not particularly limited. From the viewpoint of economics, such as the increased manufacturing costs required to reduce the α-olefin content in the reaction system, the lower limit can usually be 0.000001% by weight, more preferably 0.00001% by weight, even more preferably 0.0001% by weight, particularly preferably 0.001% by weight, and most preferably 0.003% by weight.

[0094] The upper limit of the water content of the reaction solvent in the solvent substitution step is not particularly limited, but from the viewpoint of performing the drying treatment with a desiccant more efficiently, it is usually preferably 10 mol ppm or less, more preferably 1 mol ppm or less, even more preferably 0.1 mol ppm or less, particularly preferably 0.01 mol ppm or less, and most preferably 0.005 mol ppm or less.

[0095] The lower limit of the water content of the reaction solvent is not particularly limited, and from the viewpoint of economics, such as the increased manufacturing costs required to reduce the water content in the reaction solvent during the solvent substitution step, it can usually be 0.000001 mol ppm or more, more preferably 0.00001 mol ppm or more, even more preferably 0.0001 mol ppm or more, particularly preferably 0.001 mol ppm or more, and most preferably 0.003 mol ppm or more.

[0096] The above upper and lower limits can be combined arbitrarily. For example, the water content of the reaction solvent in the solvent substitution step is not particularly limited and can be 0.000001 mol ppm or more and 10 mol ppm or less, more preferably 0.00001 mol ppm or more and 1 mol ppm or less, even more preferably 0.0001 mol ppm or more and 0.1 mol ppm or less, particularly preferably 0.001 mol ppm or more and 0.01 mol ppm or less, and most preferably 0.003 mol ppm or more and 0.005 mol ppm or less.

[0097] [Measurement process] In the measurement step, the water content in the reaction system is measured after the deactivator addition step and before the low polymerization reaction step of the α-olefin. The low polymerization reaction step of the α-olefin is started when the moisture content measured in the measurement step is less than or equal to a predetermined value (5) described later. This effectively suppresses the formation of polymer by-products that cause process blockage, while maintaining good catalytic activity and product selectivity.

[0098] (A predetermined value (5)) The predetermined value (5) is the upper limit permissible value for the moisture content when starting the low polymerization reaction process. The predetermined value (5) is also the upper limit permissible value for the moisture content applied when reducing the moisture content in the reaction system during the solvent drying process. Furthermore, the predetermined value (5) is a value that ensures the moisture content in the reaction system when producing the α-olefin low polymer is within a range that does not cause practical problems. The predetermined value (5) may be, for example, a value empirically determined using the manufacturing equipment used, or a value theoretically derived using simulations or the like.

[0099] The predetermined value (5) is not particularly limited. When initiating a low polymerization reaction of α-olefins, in order to maintain good catalytic activity and product selectivity and to suppress the formation of polymer by-products that cause process blockage, the predetermined value (1) is preferably 10 mol ppm, more preferably 5.0 mol ppm, even more preferably 3.0 mol ppm, particularly preferably 1.0 mol ppm, and most preferably 0.5 mol ppm, relative to the total amount of gas in the reaction system.

[0100] The lower limit of the water content in the reaction system during the measurement process is not particularly limited. From the viewpoint of economics, such as the increased manufacturing costs required to reduce the water content in the reaction system, it is usually preferably 0.0001 mol ppm, more preferably 0.001 mol ppm, even more preferably 0.01 mol ppm, particularly preferably 0.1 mol ppm, and most preferably 0.3 mol ppm.

[0101] The water content in the reaction system during the measurement process can be measured using a known water content analyzer. The water content analyzer may be an offline type or an online type installed at any point in the reaction system. For water content analysis, for example, capacitive, electrical resistance, microwave, near-infrared, and neutron type water content analyzers can be used.

[0102] [Low polymerization reaction process of α-olefins] The present invention provides a method for producing an α-olefin low polymer, which further comprises an α-olefin low polymerization reaction step in which a catalyst, solvent, and raw material α-olefin are supplied into the reaction system after a deactivator addition step to produce an α-olefin low polymer.

[0103] (raw material: α-olefin) The raw material α-olefin is not particularly limited as long as it is a compound having a double bond at the terminal carbon atom. Examples of raw material α-olefins include substituted or unsubstituted α-olefins having 2 to 30 carbon atoms. Examples include ethylene, propylene, 1-butene, 1-hexene, 1-octene, 3-methyl-1-butene, and 4-methyl-1-pentene. Ethylene, propylene, and 1-butene are preferred as raw material α-olefins, ethylene and 1-butene are more preferred, and ethylene is particularly preferred.

[0104] In the case of ethylene, it is preferable because its trimer, 1-hexene, can be obtained in high yield and with high selectivity by using a known selective catalyst. Furthermore, when ethylene is used as a raw material, it is acceptable for the raw material to contain impurities other than ethylene. Examples of impurities include methane, ethane, acetylene, and carbon dioxide.

[0105] The amount of impurity components is preferably 5 mol% or less relative to the raw material ethylene, more preferably 1 mol% or less, even more preferably 0.5 mol% or less, even more preferably 0.1 mol% or less, particularly preferably 0.05 mol% or less, and most preferably 0.01 mol% or less. By limiting the amount of impurity components to 5 mol% or less, the generation of catalyst species different from the original catalyst species due to the influence of impurity components on the catalyst's coordination can be suppressed, and the reaction can be controlled.

[0106] (α-olefin low polymer) α-olefin low polymers are obtained by undergoing a low polymerization reaction of α-olefin raw materials. A low polymerization reaction of α-olefins is the oligomerization of the α-olefin raw materials. Therefore, α-olefin low polymers refer to oligomers in which several α-olefin raw materials are bonded together.

[0107] The reaction solution after the low polymerization reaction may contain one type of α-olefin low polymer, or it may be a mixture of multiple types of α-olefin low polymers. The α-olefin low polymer is an oligomer in which 2 to 10, preferably 2 to 5, α-olefin molecules are bonded together.

[0108] When ethylene is used as a raw material, the target product, an α-olefin low polymer, is preferably a linear or branched α-olefin having 4 to 10 carbon atoms, either substituted or unsubstituted, and more preferably an unsubstituted linear α-olefin having 4 to 10 carbon atoms. Non-limiting examples of ethylene low polymers include 1-butene (a dimer of ethylene), 1-hexene (a trimer), 1-octene (a tetramer), and 1-decene (a pentamer). Among these, 1-butene, 1-hexene, and 1-octene are preferred, 1-hexene and 1-octene are more preferred, and 1-hexene is particularly preferred. When the target product is 1-hexene, the content of 1-hexene in the product is preferably 90% by weight or more.

[0109] (reaction solvent) Low polymerization reactions of α-olefins can be carried out in a reaction solvent. The reaction solvent is not particularly limited, and saturated hydrocarbons are preferably used. Examples include chain saturated hydrocarbons having 1 to 20 carbon atoms, such as butane, pentane, 3-methylpentane, n-hexane, n-heptane, 2-methylhexane, octane, cyclohexane, methylcyclohexane, 2,2,4-trimethylpentane, and decalin, or alicyclic saturated hydrocarbons having 1 to 20 carbon atoms. Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, mesitylene, and tetralin may also be used as reaction solvents. The reaction solvent may be used alone or in combination of two or more types.

[0110] Among these reaction solvents, chain-like saturated hydrocarbons and alicyclic saturated hydrocarbons having 4 to 10 carbon atoms are preferred from the viewpoint of suppressing the formation or precipitation of by-product polymers such as polyethylene, and from the viewpoint of high catalytic activity. Non-limiting examples include n-heptane and cyclohexane, with n-heptane being more preferred.

[0111] The amount of reaction solvent used is not particularly limited. The amount of reaction solvent used is usually 0.5 to 5.0 times, preferably 1.0 to 2.5 times, by weight relative to the amount of α-olefin raw material supplied to the reactor. The amount of α-olefin raw material supplied here is the sum of the amount of α-olefin raw material consumed in the reactor and the amount of α-olefin raw material dissolved in the reaction solvent.

[0112] (catalyst) The catalyst is not particularly limited as long as it is capable of causing a low polymerization reaction of α-olefins and producing a low polymer of α-olefins. It is preferable to use a catalyst system consisting of a combination of the transition metal-containing compound (a) and the aluminum-containing compound (c) described below as catalyst components. Furthermore, it is more preferable to use in combination with at least one of the halogen-containing compound (d) represented by the general formula (I) described below and the nitrogen-containing compound (b) described below, in addition to these two catalyst components.

[0113] (Transition metal-containing compounds (a)) The transition metal-containing compound (a) is preferably used as a component of the catalyst. The transition metal contained in the transition metal-containing compound (a) is not particularly limited, but transition metals from groups 4 to 6 of the periodic table are preferably used. The transition metal contained in the transition metal-containing compound (a) is preferably one or more metals selected from the group consisting of chromium, titanium, zirconium, vanadium, and hafnium, more preferably either chromium and titanium or both, and most preferably chromium.

[0114] The transition metal-containing compound (a) used as a catalyst raw material has the general formula MeZ n This includes one or more compounds represented by the formula . Here, in the general formula, Me represents a transition metal element, and Z represents any organic group, inorganic group, or negative atom. n represents an integer from 1 to 6, preferably 2 or more. When n is 2 or more, Z may be the same or different from each other. The organic group may be any hydrocarbon group having 1 to 30 carbon atoms, which may have substituents. Non-limiting examples include carbonyl groups, alkoxy groups, carboxyl groups, β-diketnate groups, β-ketocarboxyl groups, β-ketoester groups, and amide groups.

[0115] Non-restrictive examples of inorganic groups of Z include metal salt-forming groups such as nitrate groups and sulfate groups. Non-restrictive examples of Z-negative atoms include oxygen atoms and halogen atoms. However, transition metal-containing compounds (a) that contain halogen atoms are not included in halogen-containing compounds (d) described later.

[0116] In the case of transition metal-containing compounds (a) (hereinafter sometimes referred to as chromium-containing compounds) in which the transition metal is chromium, non-limiting examples include 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 (where Ph represents the phenyl group), chromium(II) acetate, chromium(III) acetate, chromium(III) 2-ethylhexanoate, chromium(III) benzoate, chromium(III) naphthenate, chromium(III) heptanoate, Cr(CH3COCHCOOCH3)3, chromium monochloride, chromium dichloride, chromium monobromide, chromium dibromide, chromium monoiodide, chromium diiodide, chromium monofluoride, and chromium difluoride.

[0117] In the case of transition metal-containing compounds (a) (hereinafter sometimes referred to as titanium-containing compounds) in which the transition metal is titanium, non-limiting examples include TiCl4, TiBr4, TiI4, TiBrCl3, TiBr2Cl2, Ti(OC2H5)4, Ti(OC2H5)2Cl2, Ti(On-C3H7)4, Ti(On-C3H7)2Cl2, Ti(O-iso-C3H7)4, Ti(O-iso-C3H7)2Cl2, Ti(On-C4H9)4, Ti(On-C4H9)2Cl2, Ti(O-iso-C4H9)4, Ti(O-iso-C4H9)2Cl2, Ti(O-tert-C4H9)4, Ti(O-tert-C4H9)2Cl2, and TiCl4(thf)2 (in the above chemical formula, thf is (represents tetrahydrofuran), Ti((CH3)2N)4, Ti((C2H5)2N)4, Ti((n-C3H7)2N)4, Ti((iso-C3H7)2N)4, T i((n-C4H9)2N)4, Ti((tert-C4H9)2N)4, Ti(OSO3CH3)4, Ti(OSO3C2H5)4, Ti(OSO3C3H7)4, Ti (OSO3C4H9)4, TiCp2Cl2, TiCp2ClBr, Ti(OCOC2H5)4, Ti(OCOC2H5)2Cl2, Ti(OCOC3H7)4, Ti(OCOC3H7)2Cl2, Ti(OCOC3H7)4, Ti(OCOC3H7)2Cl2, Ti(OCOC4H9)4, Ti(OCOC4H9)2Cl2.

[0118] In the case of transition metal-containing compounds (a) (hereinafter sometimes referred to as zirconium-containing compounds) in which the transition metal is zirconium, non-limiting examples include ZrCl4, ZrBr4, ZrI4, ZrBrCl3, ZrBr2Cl2, Zr(OC2H5)4, Zr(OC2H5)2Cl2, Zr(On-C3H7)4, Zr(On-C3H7)2Cl2, Z r(O-iso-C3H7)4, Zr(O-iso-C3H7)2Cl2, Zr(On-C4H9)4, Zr(On-C4H9)2Cl2, Zr(O-iso-C4H9) 4, Zr(O-iso-C4H9)2Cl2, Zr(O-tert-C4H9)4, Zr(O-tert-C4H9)2Cl2, Zr((CH3)2N)4, Zr((C2H 5)2N)4, Zr((n-C3H7)2N)4, Zr((iso-C3H7)2N)4, Zr((n-C4H9)2N)4, Zr((tert-C4H9)2N)4, Z r(OSO3CH3)4, Zr(OSO3C2H5)4, Zr(OSO3C3H7)4, Zr(OSO3C4H9)4, ZrCp2Cl2, ZrCp2ClBr, Zr(OC Examples include OC2H5)4, Zr(OCOC2H5)2Cl2, Zr(OCOC3H7)4, Zr(OCOC3H7)2Cl2, Zr(OCOC3H7)4, Zr(OCOC3H7)2Cl2, Zr(OCOC4H9)4, Zr(OCOC4H9)2Cl2, ZrCl2(HCOCFCOF)2, and ZrCl2(CH3COCFCOCH3)2.

[0119] In the case of transition metal-containing compounds (a) (hereinafter sometimes referred to as vanadium-containing compounds) in which the transition metal is vanadium, non-limiting examples include vanadium pentoxide, vanadium oxytrichloride, vanadium oxytribromide, methoxyvanadate, ethoxyvanadate, n-propylvanadate, isopropoxyvanadate, n-butoxyvanadate, isobutoxyvanadate, t-butylvanadate, 1-methylbutoxyvanadate, 2-methylbutoxyvanadate, n-propoxyvanadate, neopentoxyvanadate, 2-ethylbutoxyvanadate, cyclohexylvanadate, allylcyclohexylvanadate, phenoxyvanadate, vanadium(III) acetylacetonate, and vanadium(III) hexaph Examples include uroacetylacetonate, vanadium(III) (2,2,6,6-tetramethyl-3,5-heptanedione), V(C6H5COCHCOC6H5)3, vanadium(III) acetate, vanadium(III) 2-ethylhexanoate, vanadium(III) benzoate, vanadium(III) naphthenate, V(CH3COCHCOOCH3)3, vanadium(III) chloride, vanadium(III) bromide, vanadium(III) iodide, vanadium(III) fluoride, bis(cyclopentadienyl)vanadium dimethyl, bis(cyclopentadienyl)vanadium dimethyl chloride, bis(cyclopentadienyl)vanadium ethyl chloride, and bis(cyclopentadienyl)vanadium dichloride.

[0120] In the case of transition metal-containing compounds (a) (hereinafter sometimes referred to as hafnium-containing compounds) in which the transition metal is hafnium, non-limiting examples include dimethylsilylenebis{1-(2-methyl-4-isopropyl-4H-azlenyl)}hafnium dichloride, dimethylsilylenebis{1-(2-methyl-4-phenyl-4H-azlenyl)}hafnium dichloride, dimethylsilylenebis[1-{2-methyl-4-(4-chlorophenyl)-4H-azlenyl}]hafnium dichloride, and dimethylsilylenebis[1-{2-methyl [1-{2-methyl-4-(3-chlorophenyl)-4H-azlenyl}]hafnium dichloride, dimethylsilylenebis[1-{2-methyl-4-(2,6-dimethylphenyl)-4H-azlenyl}]hafnium dichloride, dimethylsilylenebis[1-{2-methyl-4-(2,6-dimethylphenyl)-4H-azlenyl}]hafnium dichloride, dimethylsilylenebis{1-(2-methyl-4,6-diisopropyl-4H-azlenyl)}hafnium dichloride, diphenylsilylenebis{1-(2-methyl-4-phenyl-4H-azlenyl)}hafnium dichloride, diphenylsilylenebis{1-(2-methyl-4-phenyl-4H-azlenyl)}hafnium dichloride, diphenylsilylenebis{1-(2-methyl-4-phenyl-4H-azlenyl)}hafnium dichloride Hafnium dichloride (1-(2-methyl-4-phenyl-4H-azlenyl)) hafnium dichloride, methylphenylsilylenebis[1-{2-methyl-4-(1-naphthyl)-4H-azlenyl}] hafnium dichloride, dimethylsilylenebis[1-(2-ethyl-4-phenyl-4H-azlenyl)] hafnium dichloride, dimethylsilylenebis[1-{2-ethyl-4-(1-anthracenyl)-4H-azlenyl}] hafnium dichloride, dimethylsilylenebis [1-{2-ethyl-4-(2-anthracenyl)-4H-azlenyl}]hafnium dichloride, dimethylsilylenebis[1-{2-ethyl-4-(9-phenanthuryl)-4H-azlenyl}]hafnium dichloride, dimethylmethylenebis[1-{2-methyl-4-(4-biphenylyl)-4H-azlenyl}]hafnium dichloride, dimethylgermylenebis[1-{2-methyl-4-(4-biphenylyl)-4H-azlenyl}]hafnium dichloride, dimethylsilylenebis{1-(2-ethyl-4-(3,Examples include 5-dimethyl-4-trimethylsilylphenyl-4H-azlenyl) hafnium dichloride, dimethylsilylene [1-{2-methyl-4-(4-biphenylyl)-4H-azlenyl}][1-{2-methyl-4-(4-biphenylyl)indenyl}] hafnium dichloride, dimethylsilylene {1-(2-ethyl-4-phenyl-4H-azlenyl)}{1-(2-methyl-4,5-benzoindenyl)} hafnium dichloride, dimethylsilylenebis{1-(2-methyl-4-phenylindenyl)} hafnium dichloride, and dimethylsilylenebis[1-{2-methyl-4-(1-naphthyl)indenyl}] hafnium dichloride.

[0121] The transition metal-containing compound (a) may be used alone or in combination of two or more types. Among the many transition metal-containing compounds (a), chromium-containing compounds are preferred, and among chromium-containing compounds, chromium(III)2-ethylhexanoate is particularly preferred.

[0122] (Aluminum-containing compound (c)) Aluminum-containing compound (c) is also suitably used as a component of the catalyst. The same alkylaluminum compound used in the solvent drying step described above can be used as aluminum-containing compound (c).

[0123] Examples of aluminum-containing compounds (c) include trialkylaluminum, alkylaluminum halides, alkoxyalkylaluminum, and alkylaluminum hydrides.

[0124] Examples of trialkylaluminum include trimethylaluminum, triethylaluminum, and triisobutylaluminum. Examples of alkylaluminum halides include diethylaluminum monochloride, ethylaluminum sesquichloride, and ethylaluminum dichloride. Examples of alkoxyalkylaluminum include diethylaluminum ethoxide. Examples of alkylaluminum hydrides include diethylaluminum hydride.

[0125] Aluminum-containing compound (c) may be used alone or in combination of two or more types. Among the many aluminum-containing compounds (c), trialkylaluminum is preferred, and triethylaluminum is even more preferred.

[0126] (Halogen-containing compound (d)) The catalyst may further contain a halogen-containing compound (d) as a component. The halogen-containing compound (d) used is a compound represented by the following general formula (I).

[0127] [ka]

[0128] In formula (I), X represents a halogen atom. R1 and R2 are independently a hydrogen atom, an optionally substituted hydrocarbon group, or an optionally substituted heteroatom-containing hydrocarbon group. R8 is an optionally substituted aromatic group or an optionally substituted aromatic heterocyclic group.

[0129] In formula (I), X represents a halogen atom. Examples include chlorine, bromine, fluorine, and iodine. X is preferably chlorine or bromine, and most preferably chlorine.

[0130] In formula (I), R1 and R2 may be the same or different, and may be a hydrogen atom, a hydrocarbon group which may have substituents, or a heteroatom-containing hydrocarbon group which may have substituents. Examples of hydrocarbon groups include alkyl groups, cycloalkyl groups, alkyl halides, allyl groups, aryl groups, and vinyl groups. Examples of heteroatom-containing hydrocarbon groups include oxygen-containing groups, nitrogen-containing groups, and sulfur-containing groups of the hydrocarbon groups exemplified above. R1 and R2 are preferably alkyl groups, and more preferably linear or branched alkyl groups having 1 to 10 carbon atoms. When R1 and R2 are hydrocarbon groups, they may have substituents on any carbon atom as long as they do not significantly impair the effects of the present invention, and examples of such substituents include alkyl groups, cycloalkyl groups, and aryl groups.

[0131] In formula (I), R8 is an aromatic group or an aromatic heterocyclic group which may have substituents. Aromatic groups are cyclic hydrocarbon groups that possess aromatic properties. Examples include phenyl groups, o-tolyl groups, m-tolyl groups, p-tolyl groups, 1-naphthyl groups, 2-naphthyl groups, o-xylyl groups, m-xylyl groups, and biphenylyl groups.

[0132] The aromatic heterocyclic group is not particularly limited. Examples include the furyl group, thienyl group, pyrrolyl group, oxazolyl group, isoxazolyl group, thiazolyl group, isothiazolyl group, imidazolyl group, pyrazolyl group, pyridyl group, pyrimidinyl group, pyridadinyl group, pyrazinyl group, quinolyl group, and isoquinolyl group.

[0133] Examples of substituents that an aromatic group or aromatic heterocyclic group may have include halogen atoms, alkyl groups, cycloalkyl groups, alkyl halides, allyl groups, aryl groups, vinyl groups, oxygen-containing groups, nitrogen-containing groups, and sulfur-containing groups.

[0134] The halogen-containing compounds represented by formula (I) are classified into aromatic halogen-containing compounds or heteroaromatic halogen-containing compounds.

[0135] Non-limiting examples of aromatic halogen-containing compounds in which X in formula (I) is chlorine include benzyl chloride, (1-chloroethyl)benzene, 2-methylbenzyl chloride, 3-methylbenzyl chloride, 4-methylbenzyl chloride, 4-ethylbenzyl chloride, 4-isopropylbenzyl chloride, 4-tert-butylbenzyl chloride, 4-vinylbenzyl chloride, α-ethyl-4-methylbenzyl chloride, α,α'-dichloro-o-xylene, α,α'-dichloro-m-xylene, α,α'-dichloro-p-xylene, and 2,4-dimethyl Benzyl chloride, 2,5-dimethylbenzyl chloride, 2,6-dimethylbenzyl chloride, 3,4-dimethylbenzyl chloride, 2,4,5-trimethylbenzyl chloride, 2,4,6-trimethylbenzyl chloride, 2,4,6-triisopropylbenzyl chloride, 2,3,5,6-tetramethylbenzyl chloride, 1-(chloromethyl)naphthalene, 1-(chloromethyl)-2-methylnaphthalene, 1,4-bis-chloromethyl-2,3-dimethylnaphthalene, 1,8-bis-chloromethyl-2,3,4,5,6,7-hexamethylnaphthalene Len, 9-(chloromethyl)anthracene, 9,10-bis(chloromethyl)anthracene, 7-(chloromethyl)benzanthracene, 7-chloromethyl-12-methylbenzanthracene, 2-chlorobenzyl chloride, 3-chlorobenzyl chloride, 4-chlorobenzyl chloride, 2-bromobenzyl chloride, 3-bromobenzyl chloride, 4-bromobenzyl chloride, 2-fluorobenzyl chloride, 3-fluorobenzyl chloride, 4-fluorobenzyl chloride, 2-nitrobenzyl chloride, 3-nitrobenzyl chloride, 4-nitrobenzyl chloride Trobenzyl chloride, 2-cyanobenzyl chloride, 3-cyanobenzyl chloride, 4-cyanobenzyl chloride, 2-methoxybenzyl chloride, 3-methoxybenzyl chloride, 4-methoxybenzyl chloride, 2-phenoxybenzyl chloride, 4-(methylthio)benzyl chloride, 4-(trifluoromethoxy)benzyl chloride, 1-(1-chloroethyl)-4-nitrobenzene, 2,3-dichlorobenzyl chloride, 2,4-dichlorobenzyl chloride, 2,6-dichlorobenzyl chloride, 3,4-dichlorobenzyl chloride, 2,Examples include 4-difluorobenzyl chloride, 2,6-difluorobenzyl chloride, 2-chloro-4-fluorobenzyl chloride, 2-chloro-6-fluorobenzyl chloride, 4-bromo-2-fluorobenzyl chloride, 2-methyl-3-nitrobenzyl chloride, 4-methyl-3-nitrobenzyl chloride, 5-methyl-2-nitrobenzyl chloride, 2-methyl-2-phenoxybenzyl chloride, α,α',2,3,5,6-hexachloro-p-xylene, and α,α',2,4,5,6-hexachloro-m-xylene.

[0136] Non-limiting examples of aromatic halogen-containing compounds in which X in formula (I) is bromine include benzyl bromide, (1-bromoethyl)benzene, 4-butylbenzyl bromide, α-bromo-o-xylene, α-bromo-m-xylene, α-bromo-p-xylene, α,α'-dibromo-o-xylene, α,α'-dibromo-m-xylene, α,α'-dibromo-p-xylene, 3,5-di-tert-butylbenzyl bromide, 2-(bromomethyl)naphthalene, 1,4-bis(bromomethyl)naphthalene, 2-chlorobenzyl bromide, and 3-chlorobenzyl Bromide, 4-chlorobenzyl bromide, 2-bromobenzyl bromide, 3-bromobenzyl bromide, 4-bromobenzyl bromide, 2-fluorobenzyl bromide, 3-fluorobenzyl bromide, 4-fluorobenzyl bromide, 2-iodobenzyl bromide, 3-iodobenzyl bromide, 4-iodobenzyl bromide, 2-nitrobenzyl bromide, 3-nitrobenzyl bromide, 4-nitrobenzyl bromide, 2-cyanobenzyl bromide, 4-cyanobenzyl bromide, 2-(trifluoromethoxy)benzyl bromide, 4-(trifluoro (Methoxy)benzyl bromide, 4-(trifluoromethylthio)benzyl bromide, 2,3-dichlorobenzyl bromide, 3,4-dichlorobenzyl bromide, 2,5-dichlorobenzyl bromide, 2,6-dichlorobenzyl bromide, 2,4-difluorobenzyl bromide, 3,4-difluorobenzyl bromide, 2,5-difluorobenzyl bromide, 3,5-difluorobenzyl bromide, 2,6-difluorobenzyl bromide, 3,5-dimethoxybenzyl bromide, 3,5-dibenzyloxybenzyl bromide, 2-chloro-4-fluoro Benzyl bromide, 2-chloro-5-fluorobenzyl bromide, 2-chloro-6-fluorobenzyl bromide, 3-chloro-2-fluorobenzyl bromide, 3-bromo-4-fluorobenzyl bromide, 4-bromo-2-fluorobenzyl bromide, 5-chloro-2-nitrobenzyl bromide, 2-hydroxy-5-nitrobenzyl bromide, 3-(2-fluoromethoxy)benzyl bromide, 3-(4-fluorophenoxy)benzyl bromide, 2,3,4-trifluorobenzyl bromide, 2,4,5-trifluorobenzyl bromide, 3,4,Examples include 5-trifluorobenzyl bromide, 3,5-bis(3,5-dimethoxybenzyloxy)benzyl bromide, 3,5-bis(tert-butylthio)benzyl bromide, 3,5-bis[3,5-bis(3,5-benzyloxy)benzyloxy]benzyl bromide, pentafluorobenzyl bromide, 2,3,4,5-tetrafluorobenzyl bromide, and 2,3,5,6-tetrafluorobenzyl bromide.

[0137] Examples of aromatic halogen-containing compounds in which X in formula (I) is fluorine or iodine include benzyl fluoride and benzyl iodide. Non-exclusive examples of heteroaromatic halogen-containing compounds include 2,6-bis(chloromethyl)pyridine, 2,6-bis(bromomethyl)pyridine, 2-(chloromethyl)-5-nitrofuran, 2-chloro-5-(chloromethyl)pyridine, and 2-chloro-5-(chloromethyl)thiophene.

[0138] The halogen-containing compound (d) may be used alone or in combination of two or more types. Among the many halogen-containing compounds (d), aromatic halogen-containing compounds in which X in formula (I) is chlorine or bromine are preferred from the viewpoint of improving catalytic activity and improving the selectivity of the target product. Among these, benzyl chloride is even more preferred from the viewpoint of ease of availability and the minimal influence of decomposition products on the reaction.

[0139] In addition to halogen-containing compound (d), halogen-containing compounds such as 5-chloro-1,3-pentadiene, 5-methyl-1,2,3,4,5-pentachloro-1,3-cyclopentadiene, and 5-chloro-1,3-cyclopentadiene may also be used as catalyst components as needed, provided they do not impair the effects of the invention.

[0140] (Nitrogen-containing compound (b)) In addition to the three catalytic components described above—the transition metal-containing compound (a), the aluminum-containing compound (c), and the halogen-containing compound—the catalyst may also contain a nitrogen-containing compound (b). Examples of nitrogen-containing compounds include amines, amides, and imides.

[0141] Examples of amines include pyrrole compounds. Non-limiting examples include pyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole, 2-methyl-5-ethylpyrrole, 2,5-dimethyl-3-ethylpyrrole, 3,4-dimethylpyrrole, 3,4-dichloropyrrole, 2,3,4,5-tetrachloropyrrole, 2-acetylpyrrole, dipyrrole in which two pyrrole rings are linked via substituents, and other pyrroles, as well as their derivatives. Examples of derivatives include metal pyrrolide derivatives. Examples include aluminum pyrrolides such as diethylaluminum pyrrolide, ethylaluminum dipyrrolide, aluminum tripyrrolide, diethylaluminum (2,5-dimethylpyrrolide), ethylaluminum bis(2,5-dimethylpyrrolide), and aluminum tris(2,5-dimethylpyrrolide); sodium pyrrolides such as sodium pyrrolide and sodium (2,5-dimethylpyrrolide); lithium pyrrolides such as lithium (2,5-dimethylpyrrolide); potassium pyrrolides such as potassium (2,5-dimethylpyrrolide). However, aluminum pyrrolides are not included in the above-mentioned aluminum-containing compounds (c). Also, pyrrole compounds containing halogens are not included in the above-mentioned halogen-containing compounds. Amines may be used individually or in combination of two or more.

[0142] Examples of amides include acetamide, N-methylhexaneamide, succinamide, maleamide, N-methylbenzamide, imidazole-2-carboxoamide, di-2-thenoylamine, β-lactam, δ-lactam, ε-caprolactam, and salts of these with metals from groups 1, 2, or 13 of the periodic table. A single amide may be used alone, or two or more amides may be used in combination.

[0143] Examples of imides include 1,2-cyclohexanedicarboximide, succinimide, phthalimide, maleimide, 2,4,6-piperidinetrione, perhydroazesin-2,10-dione, and salts of these with metals from groups 1, 2, or 13 of the periodic table. Examples of sulfonamides and sulfonimides include benzenesulfonamide, N-methylmethanesulfonamide, N-methyltrifluoromethylsulfonamide, and salts of these with metals from groups 1, 2, or 13 of the periodic table. Imides may be used individually or in combination of two or more types.

[0144] The nitrogen-containing compound (b) may be used alone or in combination of two or more types. Among the many nitrogen-containing compounds (b), amines are preferred, pyrrole compounds are more preferred as amines, and 2,5-dimethylpyrrole and diethylaluminum (2,5-dimethylpyrroleide) are particularly preferred as pyrrole compounds.

[0145] (Pre-preparation of catalyst) In low polymerization reactions, it is preferable to contact the raw material α-olefin with the catalyst, either before the transition metal-containing compound (a) and the aluminum-containing compound (c) have come into contact, or for a short period of time. By contacting them in this manner, the low polymerization reaction of the raw material α-olefin can be selectively carried out, and the low polymer of the raw material α-olefin can be obtained in high yield.

[0146] The condition that "the transition metal-containing compound (a) and the aluminum-containing compound (c) do not come into contact beforehand, or that the contact time is short" is maintained not only at the start of the low-weight reaction, but also when the raw material α-olefin and each catalyst component are added to the reactor. However, the above specific conditions are preferred conditions during catalyst preparation, and their effect after catalyst preparation is limited. For example, when the prepared catalyst is recovered from the reaction system and reused, the catalyst can be reused regardless of the above conditions.

[0147] The reason why the activity of the low polymerization reaction of α-olefins decreases when the transition metal-containing compound (a) and the aluminum-containing compound (c) come into contact beforehand is not clear, but it can be inferred as follows.

[0148] When a transition metal-containing compound (a) and an aluminum-containing compound (c) are brought into contact, a ligand exchange reaction is thought to occur between the ligand coordinated to the transition metal-containing compound (a) and the alkyl group in the aluminum compound, leading to instability. As a result, the decomposition and reduction reaction of the alkyl-transition metal-containing compound (a) proceeds preferentially, and consequently, inappropriate metallation occurs in the low polymerization reaction of α-olefins, reducing the activity of the low polymerization reaction of α-olefins.

[0149] When preparing catalysts using transition metal-containing compounds (a), nitrogen-containing compounds (b), aluminum-containing compounds (c), and halogen-containing compounds (d), contact between each component is typically carried out by the following methods. A method for introducing a transition metal-containing compound (a) into a solution containing a nitrogen-containing compound (b), an aluminum-containing compound (c), and a halogen-containing compound (d). A method for introducing an aluminum-containing compound (c) into a solution containing a transition metal-containing compound (a), a nitrogen-containing compound (b), and a halogen-containing compound (d). A method for introducing a nitrogen-containing compound (b) and an aluminum-containing compound (c) into a solution containing a transition metal-containing compound (a) and a halogen-containing compound (d). A method for introducing a transition metal-containing compound (a) and a nitrogen-containing compound (b) into a solution containing an aluminum-containing compound (c) and a halogen-containing compound (d). A method for introducing an aluminum-containing compound (c) and a halogen-containing compound (d) into a solution containing a transition metal-containing compound (a) and a nitrogen-containing compound (b). A method for introducing a transition metal-containing compound (a) and a halogen-containing compound (d) into a solution containing a nitrogen-containing compound (b) and an aluminum-containing compound (c). A method for introducing a transition metal-containing compound (a), a nitrogen-containing compound (b), and a halogen-containing compound (d) into a solution containing an aluminum-containing compound (c). A method for introducing a nitrogen-containing compound (b), an aluminum-containing compound (c), and a halogen-containing compound (d) into a solution containing a transition metal-containing compound (a). A method for simultaneously and independently introducing a transition metal-containing compound (a), a nitrogen-containing compound (b), an aluminum-containing compound (c), and a halogen-containing compound (d) into a reaction system. Each of the above solutions is typically prepared using the same solvent as the reaction solvent used in low polymerization reactions.

[0150] (Amount of catalyst component supplied) The ratio of each component of the transition metal atom-containing compound (a), nitrogen atom-containing compound (b), and alkylaluminum compound (c) is not particularly limited. Typically, for every 1 mole of transition metal atoms in the transition metal atom-containing compound (a), there are 1 to 100 moles, preferably 2 to 50 moles, of nitrogen atom-containing compound (b). For every 1 mole of transition metal atoms in the transition metal atom-containing compound (a), there are 1 to 2000 moles, preferably 10 to 500 moles, of aluminum atoms in alkylaluminum compound (c).

[0151] When using halogen-containing compound (d), the lower limit of halogen-containing compound (d) per mole of transition metal atoms in transition metal atom-containing compound (a) is usually 1 mole, preferably 2 moles, more preferably 3 moles, and the upper limit is usually 200 moles, preferably 150 moles, more preferably 100 moles, and even more preferably 50 moles. The number of moles of transition metal atom-containing compound (a) per mole of transition metal atoms is equivalent to the molar multiple of transition metal atoms in the low polymerization reaction system.

[0152] The amount of catalyst used, consisting of a transition metal-containing compound (a), a nitrogen-containing compound (b), an aluminum-containing compound (c), and a halogen-containing compound (d), is not particularly limited. Typically, it is 1.0 × 10¹⁶ per liter of the reaction solvent described later, calculated in terms of the transition metal elements in the transition metal atom-containing compound (a). -7 0.5 moles, preferably 5.0 × 10⁻⁶ moles -7 0.2 moles, more preferably 1.0 × 10⁻⁶ moles -6 This is an amount that is approximately 0.05 moles.

[0153] (Low polymerization reaction conditions) After confirming that the water concentration in the reaction system is within the above range, the catalyst and the raw material, α-olefin, can be introduced into the reaction system to carry out the low polymerization reaction of α-olefin.

[0154] In low polymerization reactions of α-olefins, the ratio of each component of the catalyst is typically 1 mole to 50 moles, preferably 1 mole to 30 moles, of the halogen-containing compound (d) per mole of the transition metal-containing compound (a). The ratio of the aluminum-containing compound (c) per mole of the transition metal-containing compound (a) is 1 mole to 200 moles, preferably 10 mole to 150 moles. When a nitrogen-containing compound (b) is used, the ratio of the nitrogen-containing compound (b) per mole of the transition metal-containing compound (a) is 1 mole to 50 moles, preferably 1 mole to 30 moles.

[0155] The amount of catalyst used is not particularly limited, but typically, the amount of transition metal in the transition metal-containing compound (a) is 1.0 × 10⁻⁶ per liter of solvent. -9from 0.5 mol to 0.5 mol, preferably 5.0×10 -9 mol to 0.2 mol, more preferably 1.0×10 -8 mol to 0.05 mol. Alternatively, usually, it is in an amount of 1.0×10 -8 to 1.0×10 -3 times, preferably 1.0×10 -7 to 1.0×10 -4 times, based on the weight ratio to the feed amount of the raw material α-olefin supplied to the reactor. The feed amount of the raw material α-olefin referred to here is the sum of the consumption amount of the raw material α-olefin reacting in the reactor and the dissolution amount of the raw material α-olefin dissolved in the reaction solvent. By using such a catalyst, for example, when ethylene is used as a raw material, hexene, which is a trimer of ethylene, can be obtained with a selectivity of 90% or more. Furthermore, in this case, the ratio of 1-hexene in hexene can be made 99% or more.

[0156] The reaction temperature of the low polymerization reaction of α-olefin is not particularly limited and is usually 0 to 250 °C, preferably 50 to 200 °C, more preferably 80 to 170 °C. The reaction pressure of the low polymerization reaction of α-olefin is not particularly limited and is usually from atmospheric pressure to 250 kgf / cm 2 and preferably 5 to 150 kgf / cm 2 more preferably 10 to 100 kgf / cm 2 range. The residence time in the reactor is not particularly limited and is usually in the range of 1 minute to 10 hours, preferably 3 minutes to 3 hours, more preferably 5 minutes to 60 minutes. The reaction mode of the low polymerization reaction of α-olefin is not particularly limited and may be any of batch, semi-batch or continuous.

[0157] (Moisture content in the reaction system during the low polymerization reaction of α-olefin) When carrying out the low polymerization reaction of α-olefins described above, the water content relative to the solvent in the reactor can be calculated by directly measuring the water concentration in the reactor where the α-olefin low polymerization reaction is carried out, or by pre-measuring the weight of water accompanying the raw materials, solvent, and catalyst components supplied to the reactor, and dividing the total weight by the weight of the solvent supplied to the reactor.

[0158] For ease of measurement and management of measured values, it is preferable to pre-measure the weight of water accompanying the raw materials, solvent, and catalyst components supplied to the reactor, and then divide the total weight by the weight of the solvent supplied to the reactor to calculate the water content relative to the solvent in the reactor (unit: mass ppm).

[0159] The water concentration in the reaction solution can be accurately measured using the Karl Fischer method. The water concentration in the raw material gas can be accurately measured using a dew point meter.

[0160] There is no particular upper limit to the water content in the solvent in the reactor when carrying out a low polymerization reaction of α-olefins. As the water content increases, the polymer selectivity increases, which may cause process clogging, and the catalytic activity also tends to decrease. Therefore, the water content can usually be preferably 5.0 ppm by mass or less, more preferably 1.5 ppm by mass or less, and even more preferably 0.5 ppm by mass or less, relative to the total mass of the solvent in the reactor.

[0161] The lower limit of the moisture content is not particularly limited. As the value of this moisture content tends to decrease, the equipment costs and load for removing moisture tend to increase. Therefore, it can usually be set to preferably 0.0001 ppm by mass or more, more preferably 0.001 ppm by mass or more, and even more preferably 0.01 ppm by mass or more, relative to the total mass of solvent in the reactor.

[0162] The above upper and lower limits for water content can be combined arbitrarily. When carrying out a low polymerization reaction of α-olefins, the water content relative to the solvent in the reactor can be preferably 0.0001 ppm by mass or more and 5.0 ppm by mass or less, more preferably 0.001 ppm by mass or more and 1.5 ppm by mass or less, and even more preferably 0.01 ppm by mass or more and 0.5 ppm by mass or less, relative to the total mass of the solvent in the reactor.

[0163] The method for reducing the water content of the reaction solvent is not particularly limited. For example, when n-heptane is used as the reaction solvent, commercially available n-heptane usually contains about 20-30 ppm by mass of water. Therefore, it is preferable to reduce the water content of the reaction solvent and the raw material α-olefin before supplying them to the reactor using a desiccant such as molecular sieves. If necessary, any remaining water in the reaction solvent may be removed by distillation separation.

[0164] [1- Method for producing hexene] Next, we will explain in more detail, using Figure 1, the case in which ethylene is used as the α-olefin and its trimer, 1-hexene, is produced as a low polymer. However, the dimensional ratios in the drawings are for illustrative purposes only and may differ from those of the actual components. In the following drawings, identical components are indicated by the same reference numerals, and descriptions of redundant components may be omitted.

[0165] Figure 1 shows an example of a production apparatus for α-olefin low polymers. The overall schematic diagram of the 1-hexene production apparatus using ethylene as a raw material shown in Figure 1 includes a fully mixed and stirred reactor 10 for polymerizing ethylene in the presence of a catalyst, a degassing tank 20 for separating unreacted ethylene gas from the reaction liquid withdrawn from the reactor 10, an ethylene separation column 30 for distilling ethylene from the reaction liquid withdrawn from the degassing tank 20, a high-boiling separation column 40 for separating high-boiling substances (hereinafter sometimes referred to as "HB: high boiler") from the reaction liquid withdrawn from the ethylene separation column 30, and a hexene separation column 50 for distilling the reaction liquid withdrawn from the top of the high-boiling separation column 40 to distill 1-hexene (1-HEX). A compressor 17 is also provided to circulate the unreacted ethylene separated in the degassing tank 20 and condenser 16 back to the reactor 10 via a circulation pipe 21.

[0166] In Figure 1, the reactor 10 can be a known reactor equipped with, for example, a stirrer 10a, baffles (not shown), a jacket (not shown), etc. The stirrer 10a may be a stirring blade of the type such as a paddle, foudler, propeller, or turbine, used in combination with baffles such as flat plates, cylinders, or hairpin coils as needed.

[0167] (Gas drying process) In the gas drying process, when starting the production of the α-olefin low polymer, dry nitrogen gas is supplied into the reaction system from the ethylene supply pipe 12a and the nitrogen gas supply port (not shown) on the catalyst tank 1c in Figure 1. In the production apparatus shown in Figure 1, the catalyst tank 1c, reactor 10, condenser 16, compressor 17, degassing tank 20, ethylene separation column 30, high-boiling separation column 40, hexene separation column 50, solvent drum 60, and all the process piping (11, 11a, 12, 13, 13a, 21, 22, 31, 32, 41, 42, 51, 31, 52) are collectively referred to as the "reaction system".

[0168] First, dry nitrogen gas with a water content of 2 mol ppm or less or a dew point of -70°C or less is supplied to the reaction system. The supply of dry nitrogen gas or other gas is continued until the water content measured at any point in the reaction system (for example, reactor 10, degassing tank 20, ethylene separation column 30, high-boiling separation column 40, hexene separation column 50 in Figure 1) falls below a predetermined value (1). At this time, the temperature within the reaction system is not specifically controlled and can be left to the ambient temperature.

[0169] The methods for measuring the moisture content are as follows, depending on whether the sample is in liquid or gaseous form.

[0170] The water content of a liquid sample can be measured using a coulometric titration water content analyzer (manufactured by Mitsubishi Chemical Corporation, model: CA-06) in accordance with ISO 6358:1989, "Measuring instruments for industrial process measurement and control - Dew point analyzers for general use".

[0171] The moisture content of a gaseous sample can be determined by measuring the dew point using a dew point meter (Techne Measurement Co., Ltd., Model: TK-100) in accordance with the dew point measurement method described in ISO 5725-2:1994 "Statistical methods for evaluating and examining precision (accuracy and reproducibility) - Part 2: Application of measurement methods." From this dew point, the amount of water molecules (in moles) and nitrogen molecules (in moles) in the gas, calculated using the relationship between saturated vapor pressure and temperature described in JIS Z 8806, can be used to calculate the moisture content (in mass ppm) using the following formula.

[0172] Molecular weight (in moles / ppm) in the reactor (or process piping) = [Number of moles of water molecules in the reactor (or process piping)] / [Number of moles of nitrogen molecules in the reactor (or process piping)]

[0173] (Raw material replacement process) Next, the dry nitrogen gas in the reaction system is replaced with the gas of the raw material α-olefin (e.g., ethylene) supplied from the ethylene supply pipe 12a in Figure 1. During this process, the system can be replaced with raw material olefin gas until the nitrogen gas content in the gas phase of the reaction system, as measured at any point in the reaction system (such as reactor 10, high-boiling separation column 40, or hexene separation column 50 in Figure 1), is 20% by volume or less.

[0174] (Solvent replacement process) The reaction solvent described above is supplied into the reaction system from the second supply pipe 13 in Figure 1 using a known liquid delivery means such as a pump or pressurized delivery. The reaction solvent after passing through can be discharged out of the reaction system at any point in the process, for example, from the bottom of each distillation column (ethylene separation column 30, high-boiling separation column 40, hexene separation column 50). The amount of reaction solvent supplied in the solvent replacement step is not particularly limited, as long as the reaction system is substantially filled with the reaction solvent. Typically, it can be 1.5 times or more the total volume of solvent replacement, as described above.

[0175] (Solvent drying process) In the solvent drying process, a solvent containing a desiccant is supplied into the reaction system. In the example shown in Figure 1, a reaction solvent solution containing an alkylaluminum compound that functions as a desiccant is supplied into the reaction system. For example, a reaction solvent containing an alkylaluminum compound (e.g., triethylaluminum (TEA)) (e.g., a heptane solution with a TEA content of 10% by mass) can be supplied into the reaction system from the third supply pipe 14 in Figure 1 using a known liquid delivery means such as a pump or pressurized delivery. In this case, the supply can continue until the water content in the process liquid within the reaction system becomes 1 mol ppm or less.

[0176] The moisture content in the reaction system can be measured using a moisture meter installed inside the reactor 10 or in the process piping (e.g., the piping 11 connecting the reactor 10 and the degassing tank 20). The reaction solvent after passing through can be discharged outside the reaction system from an outlet located at any position in the process, for example, at the bottom of reactor 10 or each distillation column (ethylene separation column 30, high-boiling separation column 40, hexene separation column 50), or from piping connected to reactor 10 or the distillation columns (11, 22, 32, 41, 42, 51).

[0177] (Inactivator addition process) The solvent drying step may include an inactivator addition step in which the reaction liquid, which is continuously drawn from the bottom of the reactor 10 through the piping 11, is supplied with the inactivator from an inactivator supply pipe 11a located in the middle of the piping 11. This inactivator inactivates the alkylaluminum compound in the reaction liquid. Furthermore, after the deactivator is supplied, the reaction solution is transferred through piping 11 to the degassing tank 20, and then sequentially to the ethylene separation column 30, the high-boiling separation column 40, and the hexene separation column 50.

[0178] The reaction solution containing the deactivator after passing through can be discharged out of the reaction system from an outlet located at any position in the process, for example, at the bottom of reactor 10 or each distillation column (ethylene separation column 30, high-boiling separation column 40, hexene separation column 50), or from piping connected to reactor 10 or the distillation columns (11, 22, 32, 41, 42, 51).

[0179] (Measurement process) The moisture content in the reaction system can be measured using a moisture meter installed inside the reactor 10 or in the process piping (e.g., the piping 11 connecting the reactor 10 and the degassing tank 20). The reaction solvent after passing through can be discharged outside the reaction system from an outlet located at any position in the process, for example, at the bottom of reactor 10 or each distillation column (ethylene separation column 30, high-boiling separation column 40, hexene separation column 50), or from piping connected to reactor 10 or the distillation columns (11, 22, 32, 41, 42, 51).

[0180] (Low polymerization reaction process) Next, we will describe the low polymerization reaction process for producing 1-hexene by low polymerization of ethylene. In the low polymerization reaction step, the catalyst, reaction solvent, and ethylene (the raw material) described above are supplied to the reaction system. By carrying out the low polymerization reaction of ethylene, 1-hexene, a trimer of ethylene, is produced.

[0181] Ethylene (ETY) is continuously supplied to the reactor 10 from the ethylene supply pipe 12a shown in Figure 1 via the compressor 17 and the first supply pipe 12. Here, if the compressor 17 is, for example, a two-stage compression type, electricity costs can be reduced by connecting the circulation pipe 31 to the first stage and the circulation pipe 21 to the second stage. The solvent used for the low polymerization reaction of ethylene is supplied to the reactor 10 from the second supply pipe 13.

[0182] In some examples, a transition metal-containing compound (a) and a nitrogen-containing compound (b), pre-prepared in catalyst tank 1c, are supplied to reactor 10 from second supply pipe 13 via catalyst supply pipe 13a. An aluminum-containing compound (c) is supplied to reactor 10 from third supply pipe 14. A halogen-containing compound (d) is supplied to reactor 10 from fourth supply pipe 15.

[0183] In some other cases, the halogen-containing compound (d) may be supplied to the reactor 10 from the second supply pipe 13 via a supply pipe (not shown). Similarly, the aluminum-containing compound (c) may be supplied to the reactor 10 from the second supply pipe 13 via the catalyst supply pipe 13a, provided that the contact time with the transition metal-containing compound (a) is within a few minutes. In this configuration, if a static mixer or the like is installed between the second supply pipe 13 and the reactor 10, a homogeneous mixture of each catalyst component can be supplied to the reactor 10, thereby reducing the stirring power required for the reactor 10.

[0184] Furthermore, the trimerization reaction of ethylene is preferably carried out such that the molar ratio of 1-hexene to ethylene in the reaction solution ((molar concentration of 1-hexene in the reaction solution) / (molar concentration of ethylene in the reaction solution)) is 0.05 to 1.5, and particularly 0.10 to 1.0. In the case of a continuous reaction, it is preferable to adjust the catalyst concentration, reaction pressure, and other conditions so that the molar ratio of ethylene to 1-hexene in the reaction solution is within the above range. In the case of a batch reaction, it is preferable to stop the trimerization reaction of ethylene when the molar ratio is within the above range. By carrying out the trimerization reaction of ethylene under these conditions, the by-product formation of components with higher boiling points than 1-hexene tends to be suppressed, and the selectivity for 1-hexene tends to be further increased.

[0185] Next, the reaction liquid, which is continuously drawn from the bottom of the reactor 10 through the piping 11, is supplied to the degassing tank 20 after the trimerization reaction of ethylene is stopped by the deactivator supplied from the deactivator supply piping 11a.

[0186] In the degassing tank 20, unreacted ethylene is degassed from the top. The degassed unreacted ethylene is circulated and supplied to the reactor 10 via the circulation pipe 21, condenser 16, compressor 17, and first supply pipe 12. The reaction liquid from which the unreacted ethylene has been removed is withdrawn from the bottom of the degassing tank 20.

[0187] The operating conditions for the degassing tank 20 are typically a temperature of 0°C to 250°C, preferably 50°C to 200°C, and a pressure of atmospheric pressure to 150 kgf / cm². 2 Preferably, at atmospheric pressure ~90 kgf / cm² 2 That is the case.

[0188] Next, the reaction liquid from which unreacted ethylene has been degassed in the degassing tank 20 is withdrawn from the bottom of the degassing tank 20 and supplied to the ethylene separation column 30 via piping 22. In the ethylene separation column 30, ethylene is distilled from the top of the column by distillation. The distilled ethylene is circulated and supplied to the reactor 10 via circulation piping 31 and the first supply piping 12. The reaction liquid from which ethylene has been removed is withdrawn from the bottom of the ethylene separation column 30.

[0189] The operating conditions for the ethylene separation column 30 are typically such that the top pressure of the column is atmospheric pressure to 30 kgf / cm². 2 Preferably, at atmospheric pressure ~20 kgf / cm² 2 The reflux ratio (R / D) is typically 0 to 500, preferably 0.1 to 100.

[0190] Next, the reaction liquid from which ethylene has been removed in the ethylene separation column 30 is withdrawn from the bottom of the ethylene separation column 30 and supplied to the high-boiling separation column 40 via piping 32. In the high-boiling separation column 40, the high-boiling component (HB: high boiler) is withdrawn from the bottom of the column. The distillate from which the high-boiling component has been separated is withdrawn from the top of the column via piping 42.

[0191] The operating conditions for the high-boiling separation column 40 are typically a top pressure of 0.1 kgf / cm². 2 ~10 kgf / cm² 2 Preferably, 0.5 kgf / cm² 2 ~5 kgf / cm² 2 The reflux ratio (R / D) is typically 0 to 100, preferably 0.1 to 20.

[0192] Next, the reaction liquid distilled from the top of the high-boiling separation column 40 is supplied to the hexene separation column 50 via piping 41. In the hexene separation column 50, 1-hexene is distilled from the top of the column via piping 51. Heptane is extracted from the bottom of the hexene separation column 50. This heptane is stored in the solvent drum 60 via solvent circulation piping 52 and then circulated back to the reactor 10 as the reaction solvent via the second supply piping 13.

[0193] The operating conditions for the hexene separation column 50 are typically a top pressure of 0.1 kgf / cm². 2 ~10 kgf / cm² 2 Preferably, 0.5 kgf / cm² 2 ~5 kgf / cm² 2 The reflux ratio (R / D) is typically 0 to 100, preferably 0.1 to 20.

[0194] [Experimental Results] The embodiments will be described in more detail below with reference to experimental examples. However, the present invention is not limited to the following experimental examples.

[0195] The various manufacturing conditions and evaluation results in the following experimental examples represent preferred upper or lower limits in embodiments of the present invention. The preferred range in the present invention may be defined by a combination of the aforementioned upper or lower limits and the values ​​in the experimental examples below, or the values ​​of the experimental examples themselves.

[0196] The measurement and evaluation methods for each physical property are as follows:

[0197] (Catalytic activity value) The catalytic activity [g / g-Cr] was determined by sampling the top liquid of hexene separation column 50 ("1-HEX" in Figure 1) and dividing the weight (in g) of the α-olefin low polymer (1-hexene), which is the reaction product obtained after the low polymerization reaction of α-olefin (ethylene), by the atomic weight (in g) of the transition metal (chromium atom) in the transition metal catalyst component (a) used in the low polymerization reaction.

[0198] (1 - Hexene selection rate) To determine the selectivity of the target product, 1-hexene, compositional analysis was performed on the circulating heptane solvent and the bottom liquid of the ethylene separation column (ethylene separation column 30 in Figure 1) using a gas chromatograph (model: GC-17AAF, manufactured by Shimadzu Corporation) and internal standard gas chromatography, and the selectivity of 1-hexene generated in the reactor was calculated.

[0199] (Polyethylene selectivity) The selectivity for polyethylene, a by-product, was calculated from polyethylene obtained by sampling the bottom liquid of the ethylene separation column (ethylene separation column 30 in Figure 1), cooling it to room temperature, filtering it (filter diameter 0.2 μm), and drying the residue.

[0200] [Experimental Example 1] In the manufacturing apparatus shown in Figure 1, the other end of the solvent circulation pipe 52 connected to the bottom of the hexene separation column 50 was connected to the second supply pipe 13, and the solvent was circulated directly to the reactor 10 without passing through the solvent drum 60. In this modified manufacturing process, ethylene (ETY) was used as the raw material α-olefin, and 1-hexene (1-HEX) was produced by a continuous low polymerization reaction of ethylene according to the following procedure.

[0201] (Gas drying process) Capacity 0.1m 3 Dry nitrogen gas with a moisture content of 1.5 mol ppm or less was supplied to reactor 10 and circulated throughout the entire reaction system. Dry nitrogen gas was supplied and circulated throughout the entire reaction system until the moisture content in the gas phase of reactor 10 was 3.5 mol ppm or less, and the moisture content in the gas phase of the high-boiling separation column 40 and the hexene separation column 50, as well as in the piping (41, 42, 51, 52), was 4.5 mol ppm or less. During this time, the temperature inside the reaction system was not specifically controlled and was left to the ambient temperature. The moisture content of each part was measured using a dew point meter.

[0202] The moisture content in the gas phase of reactor 10, in the high-boiling separation column 40, in the hexene separation column 50, and in each pipe (41, 42, 51, 52) before the gas drying process was 9300 mol ppm. The dry nitrogen gas after aeration was discharged from the reaction system through outlets (not shown) provided in the reactor 10, degassing tank 20, ethylene separation column 30, and high-boiling separation column 40 shown in Figure 1, as well as outlets (not shown) provided in piping 11, first supply piping 12, circulation piping 21, piping 22, circulation piping 31, piping 32, piping 41, piping 42, 50, piping 51, and solvent circulation piping 52.

[0203] (Raw material replacement process) Ethylene gas with a water content of 5 mol ppm or less was supplied to reactor 10 and circulated throughout the entire reaction system. Ethylene gas was supplied throughout the reaction system until the nitrogen gas content in the gas phase of reactor 10 was 0.5 volume% or less, and the nitrogen gas content in the degassing phase 20, the gas phase of the ethylene separation column 30, and each pipe (21, 22, 31), and, if necessary, in the high-boiling separation column 40, the gas phase of the hexene separation column 50, and each pipe (41, 42, 51, 52) was 0.5 volume% or less. During this time, the temperature in the reaction system was not specifically controlled and was left to the ambient temperature. The nitrogen gas content in each part was measured using a gas chromatograph in accordance with ASTM D2504. The ethylene gas after aeration was discharged from the reaction system through an outlet (not shown) provided in reactor 10 and an outlet (not shown) provided in circulation piping 21 or circulation piping 31.

[0204] (Solvent replacement process) Heptane was supplied to reactor 10 using a pump and circulated throughout the entire reaction system to seal it in. The supply of heptane in this process continued until the total ethylene gas in the reaction system was 60% by volume or less, and the ethylene gas in the reactor was 50% by volume or less. During this time, the temperature in the reaction system was not specifically controlled and was left to the ambient temperature. The excess heptane after the liquid had passed through was discharged from the bottom of the high-boiling separation column 40 shown in Figure 1.

[0205] (Solvent drying process, deactivator addition process, and measurement process) A TEA / heptane solution containing 10% by mass of triethylaluminum (TEA) was supplied to reactor 10 using a pump and circulated throughout the reaction system. In parallel with this operation, 2-ethylhexanol (2EH) was supplied alone to pipe 11 via deactivator supply pipe 11a as a deactivator to deactivate the triethylaluminum.

[0206] The TEA / heptane solution was supplied to the entire reaction system until the water content of the liquid phase (TEA / heptane solution) in reactor 10, as measured using an online water content analyzer (not shown) installed on the first supply pipe 12, was 1 mol ppm or less, and the water content of the TEA / heptane solution in the first supply pipe 12 was also 1 mol ppm or less. During this time, the temperature in the reaction system was not specifically controlled and was left to the ambient temperature. The TEA / heptane solution after flowing was discharged from the reaction system through pipe 42.

[0207] The moisture content in reactor 10 and the process piping before the start of the solvent drying process (moisture content before the start of the solvent drying process) was 6 mol ppm. During the solvent drying process, the time required from the start of the operation until the moisture content of the TEA / heptane solution in the liquid phase of reactor 10 became 1 mol ppm was 2880 minutes.

[0208] (Low polymerization reaction process) Following the procedure described below, n-heptane was supplied to reactor 10 as the reaction solvent and ethylene as the raw material α-olefin. Then, the catalyst components described later were supplied, and a low polymerization reaction of ethylene was carried out to polymerize 1-hexene as a low α-olefin polymer.

[0209] The catalyst components used were chromium 2-ethylhexanoate as the chromium compound (a), dimethylpyrrole as the pyrrole compound (b), triethylaluminum diluted with n-heptane as the aluminum-containing compound (c), and hexachloroethane diluted with n-heptane as the halogen-containing catalyst compound (d).

[0210] The temperature inside reactor 10 was raised to 140°C, and the low polymerization reaction of ethylene was started. During the low polymerization reaction, the temperature inside reactor 10 was maintained at 140°C and the total pressure at 7 MPaG. The reaction solution was sampled 9 hours after the start of the low polymerization reaction, and the catalytic activity was measured using the evaluation method described above. The values ​​were 842,000 g / g-Cr, the 1-hexene selectivity was 95.36% by mass, and the polyethylene (PE) selectivity was 0.08% by mass. These results were at a sufficiently satisfactory level for industrial purposes.

[0211] All n-heptane used in Experimental Example 1 was pre-dehydrated using molecular sieves. The water concentration before supplying it to the reaction system was measured to be 0.6 ppm by mass. A coulometric titration type water meter (manufactured by Mitsubishi Chemical Corporation, model: CA-06) was used for the measurement. The water content in the ethylene used in the reaction was 1.0 ppm by mass, as determined by dew point measurement. A dew point meter (Techne Measuring Instruments Co., Ltd., Model: TK-100) was used for the measurement.

[0212] [Reference Experiment Example 1] This reference experiment example 1 demonstrates that the higher the water content in the reaction system, the more likely catalytic activity is to be impaired during low-level polymerization of α-olefins, and that the production of polyethylene, a by-product that causes process blockage, increases. Specifically, 1-hexene was produced using ethylene under conditions where the water content in the reaction system was varied, following the procedure described below.

[0213] (Reference Experiment Example 1-1) All n-heptane used in this example was pre-dehydrated using molecular sieves, and its moisture content before being supplied to the reaction system was measured to be 0.6 ppm by mass. A coulometric titration moisture analyzer (manufactured by Mitsubishi Chemical Corporation, model: CA-06) was used for the measurement. The moisture content of the ethylene used in the reaction was 1.0 ppm by mass, as determined by dew point measurement. A dew point meter (manufactured by Techne Instruments Co., Ltd., model: TK-100) was used for the measurement.

[0214] First, in a 500 ml three-necked glass flask equipped with a stirrer that had been preheated and dried at 140 °C for more than 2 hours, 0.26 g (2.73 mmol) of 2,5-dimethylpyrrole as the nitrogen-containing catalyst compound (b) and 239 ml of n-heptane were charged under a nitrogen atmosphere. Next, 6.22 ml (2.73 mmol) of triethylaluminum diluted to 50 g / L with n-heptane was added as the aluminum-containing catalyst compound (c). Then, the flask was heated, and the n-heptane was refluxed under a nitrogen atmosphere at 98 °C for 3 hours to prepare the nitrogen-containing compound, aluminum pyrrolide. After that, it was cooled to 80 °C. Next, 4.38 ml (0.45 mmol) of chromium 2-ethylhexanoate diluted to 50 g / L with n-heptane was added as the transition metal-containing catalyst compound (a). After addition, the catalyst solution was prepared by heating and stirring at 80°C for 30 minutes under a nitrogen atmosphere.

[0215] Next, the 500 ml autoclave was heated and dried in a heated dryer at 140°C for more than 2 hours. Immediately after removing it from the dryer, components such as the catalyst feed tube, stirring section, various valves, and various connecting pipes were assembled. Then, the inside of the autoclave was purged with vacuum nitrogen. A catalyst feed tube equipped with a pressure-resistant rupture disc was attached to the autoclave. 2 mL of the catalyst solution described above was placed in the catalyst feed tube. On the body side of the autoclave, 162 ml of n-heptane, which is the reaction solvent, 5 ml of n-undecane, which is used as an internal standard for compositional analysis by gas chromatography, 3.36 ml (0.20 mmol) of triethylaluminum solution diluted to 6.67 g / L with n-heptane as the catalyst component aluminum-containing compound (c), and 2 ml (0.044 mmol) of benzyl chloride solution diluted to 2.76 g / L with n-heptane as the catalyst component halogen-containing compound (d). Analysis confirmed that no water was present in the autoclave. The molar ratio of water content to Cr content in chromium 2-ethylhexanoate (denoted as "H2O / Cr molar ratio") was "0".

[0216] Next, after heating the autoclave to 140°C, ethylene was introduced through the catalyst feed tube to initiate the low polymerization reaction of ethylene. During the reaction, the temperature inside the autoclave was maintained at 140°C and the total pressure at 7 MPaG. After 30 minutes, ethanol was added to stop the reaction. The total weight of ethylene introduced into the autoclave from the start to the stop of the reaction was 123 g, and the weight of n-heptane in the autoclave was 119 g. The reaction solution and reaction gas were then sampled, and the composition of the entire hydrocarbon compound with 6 carbon atoms, as well as the 1-hexene and C10-C30 components within the hydrocarbon compound, was analyzed by gas chromatography. After filtering and drying the reaction solution, the concentration of polymer solids contained in the reaction solution was measured. Catalytic activity was determined by dividing the mass of the reaction product obtained after 30 minutes of reaction by the atomic weight (grams) of the transition metal catalyst component used in the reaction.

[0217] During the low polymerization reaction process, the water content relative to the solvent in the autoclave was calculated as follows: The total ethylene weight includes not only the ethylene consumed by the reaction but also the unreacted ethylene remaining in the autoclave without reacting.

[0218] Water content in the solvent in the autoclave [mass ppm] = (weight of water in total ethylene [mg] + weight of water in solvent [mg]) / weight of solvent [g]

[0219] In Experimental Example 1, the total weight of ethylene introduced into the autoclave was 123 g, and the water concentration in the ethylene used was 1.0 ppm by mass. Therefore, the weight of water in the total ethylene is 0.12 mg. The weight of the solvent, n-heptane, was 119 g (175 ml), and the water concentration in it was 0.6 ppm by mass. Therefore, the weight of water in the solvent is 0.07 mg. From the above, the water content of the solvent in the autoclave is 1.6 ppm by mass.

[0220] In Experimental Example 1, the value of the catalytic activity was 338843 g / g-Cr, the selectivity for hydrocarbon compounds with 6 carbon atoms was 96.9% by mass, the selectivity for 1-hexene in the hydrocarbon compounds was 99.5% by mass, and the selectivity for polyethylene (PE) was 0.069% by mass. This result was at an industrially sufficient level.

[0221] (Reference Experimental Examples 1-2, 1-3, 1-4) In Reference Experimental Example 1-1, the polymerization reaction of 1-hexene was carried out under the same conditions as in Reference Experimental Example 1-1, except that water was added so that the molar ratio of the water content to the Cr amount was 9, 20, and 41, respectively. The evaluation results of the catalytic activity and the polyethylene (PE) selectivity are shown in Table 1.

[0222] [Table 1]

[0223] For Reference Experimental Examples 1-1 to 1-4, the evaluation results of the catalytic activity are shown in the graph of Figure 2, and the evaluation results of the polyethylene selectivity are shown in the graph of Figure 3.

[0224] As shown in Table 1, Figure 2, and Figure 3, it can be seen that the higher the water content in the reaction system, the more the catalytic activity tends to be impaired during the low polymerization of α-olefins, and the more the formation of polymers as by-products that cause process blockage increases.

[0225] [Reference Experimental Example 2] In this Reference Experimental Example 2, it is shown that the higher the water content in the reaction system, the more the catalytic activity and the selectivity for 1-hexene as the target product tend to be impaired during the low polymerization of α-olefins, and the more the formation of polyethylene as a by-product that causes process blockage increases. Specifically, 1-hexene was produced using ethylene under conditions where the water content in the reaction system was changed by the following procedure. Details are described below.

[0226] (Reference Experimental Example 2-1) Into an autoclave type reactor (capacity: 500 mL), as components of the catalyst, chromium 2-ethylhexanoate as the transition metal-containing compound (a), 2,5-dimethylpyrrole as the nitrogen-containing compound (b), triethylaluminum as the aluminum-containing compound (c), hexachloroethane as the halogen-containing compound (d), and heptane as the reaction solvent were charged. At that time, the H2O / Cr molar ratio, the molar ratio of triethylaluminum to the amount of Cr in chromium 2-ethylhexanoate (referred to as "TEA / Cr molar ratio"), the molar ratio of chlorine atoms in hexachloroethane to the amount of Cr in chromium 2-ethylhexanoate (referred to as "Cl / Cr molar ratio"), and the total concentration of the above four catalyst components (referred to as "catalyst concentration" in Table 2) were made to be the values described in Table 2. Next, ethylene was introduced as the raw material α-olefin by the same method as in Reference Experimental Example 1, and the low-polymerization reaction of ethylene was started. During the reaction, the temperature inside the autoclave was maintained at 140 °C and the total pressure was maintained at 7 MPaG. It was confirmed by analysis that there was no water in the reaction apparatus. Therefore, the molar ratio of the water content to the amount of Cr in chromium 2-ethylhexanoate was "0".

[0227] Next, the polymerization reaction of 1-hexene was carried out under the conditions of a pressure of 7 MPaG, a temperature of 140 °C, and a reaction time of 60 minutes. The evaluation results of the catalyst activity value, the selectivity of 1-hexene as the target product, the selectivity of olefin compounds having 4 to 22 carbon atoms excluding 1-hexene as by-products, and the polyethylene selectivity are shown in Table 2.

[0228] (Reference Experimental Examples 2-2, 2-3, 2-4) Water was further added to the conditions of Reference Experimental Example 1-1. The polymerization reaction of 1-hexene was carried out under the same conditions as in Reference Experimental Example 2-1, except that the H2O / Cr molar ratio, the TEA / Cr molar ratio, the Cl / Cr molar ratio, the catalyst concentration, and the water content were changed so as to be as described in Table 2. The evaluation results of the catalyst activity value, the selectivity of 1-hexene as the target product, the selectivity of olefin compounds having 4 to 22 carbon atoms excluding 1-hexene as by-products, and the polyethylene selectivity are shown in Table 2.

[0229] [Table 2]

[0230] As shown in Table 2, the higher the water content in the reaction system, the more likely it is that catalytic activity and the selectivity of the target product, 1-hexene, will be impaired during low polymerization of α-olefins. Additionally, the selectivity of by-products, such as olefin compounds with 4 to 22 carbon atoms excluding 1-hexene, and the selectivity of polyethylene, which can cause process blockage, will increase.

[0231] [Reference Experiment Example 3] In this reference experiment example 3, we demonstrate that by performing a gas drying step in the reaction system using dry nitrogen before the solvent drying step using alkylaluminum compounds, the time required for the solvent drying step can be shortened, and the amount of alkylaluminum compounds used can be reduced. Specifically, 1-hexene was produced using ethylene by varying the water content in the reaction system according to the following procedure. Details are provided below.

[0232] (Reference Experiment Example 3-1) A three-necked glass round-bottom flask equipped with a three-way stopcock, separatory funnel, and septum cap was sealed with air containing 1.0% by mass of moisture at room temperature (25°C) and atmospheric pressure. Next, a 10% by mass heptane solution of triethylaluminum was added to the round-bottom flask from the separatory funnel, and the flask was sealed. Immediately after the addition of the heptane solution, gas from the gas phase of the round-bottom flask was collected over time from the septum cap using a microsyringe, and the moisture content of the gas was measured over time using a dew point meter.

[0233] (Reference Experiment Example 3-2) In Reference Experiment 3-1, a round-bottom flask was sealed with air containing 1.0% by mass of water. Then, several types of nitrogen gas with water content ranging from 1 mol ppm to 100 mol ppm were supplied to the round-bottom flask to completely replace the air. Subsequently, using the same method as in Reference Experiment 3-1, a 10% by mass heptane solution of triethylaluminum was added, and the water content in the gas phase of the round-bottom flask was measured over time.

[0234] As shown in Reference Experiment Example 3-2, it is expected that the drying time required for the drying process using alkylaluminum compounds can be shortened by performing a gas drying treatment with dry nitrogen before drying the reaction system using alkylaluminum compounds. It is also expected that the amount of alkylaluminum compounds used can be reduced.

[0235] [Reference Experiment Example 4] If alkylaluminum compounds supplied as a desiccant in the solvent drying process remain in the downstream reaction system beyond the reactor, the low polymerization reaction of α-olefins may continue at the start of the low polymerization reaction process, generating by-products and reducing the selectivity of the product. This reference experiment example 4 demonstrates that by adding an inactivator, the generation of by-products and the resulting decrease in product selectivity caused by the alkylaluminum compound described above can be more effectively suppressed. Specifically, a 1-hexene / heptane solution containing a catalyst and a drying agent (TEA) was subjected to reflux treatment by varying the type of alcohol added as a deactivator and the molar ratio of the deactivator to the drying agent (TEA) according to the following procedure. The isomerization rate of 1-hexene was measured as the by-product selectivity. Details are described below.

[0236] (Reference comparative experiment example 4-1) 20 mL of 1-hexene / heptane solution (volume ratio: 1 / 5) was placed in a round-bottom flask (capacity 100 mL). Further, the following catalyst components were added: chromium 2-ethylhexanoate as a transition metal-containing compound (a), 2,5-dimethylpyrrole as a nitrogen-containing compound (b), triethylaluminum (TEA) as an aluminum-containing compound (c), and hexachloroethane as a halogen-containing compound (d). In this experiment, TEA acts as a desiccant. The molar ratio of chromium 2-ethylhexanoate (Cr) to aluminum in 2,5-dimethylpyrrole, hexachloroethane, and TEA was 1 / 6 / 6 / 600 (molar ratio). Next, reflux treatment was carried out for 4 hours while maintaining the temperature inside the round-bottom flask at 90°C. Before reflux treatment, analysis confirmed that no water was present in the reaction apparatus. After reflux treatment, the 1-hexene / heptane solution in the round-bottom flask was collected, and the amount of each by-product of 1-hexene—trans-3-hexene, cis-3-hexene, trans-2-hexene, and cis-2-hexene—relative to 100% of the total moles of 1-hexene before reflux treatment (in moles) was measured using an internal standard method with gas chromatography. This was defined as the selectivity (in mol%) of each by-product. Furthermore, the sum of the selectivity of these four by-products was defined as the isomerization rate of 1-hexene (in mol%). The evaluation results are shown in Table 3.

[0237] (Reference experimental examples 4-2, 4-3, 4-4) In Reference Comparative Experiment Example 4-1, 2-ethylhexanol (2EH) was added to the round-bottom flask as an inactivator for TEA before the reflux treatment was started. The reflux treatment was carried out under the same conditions as in Reference Comparative Experiment Example 4-1, except that the molar ratio of the inactivator (2EH) to the desiccant (TEA) (referred to as "molar ratio of inactivator / desiccant (TEA)") was set to the values ​​shown in Table 3. Table 3 shows the results of evaluation using the same method as in Reference Comparative Experiment Example 4-1.

[0238] (Reference Experiment Examples 4-5) In Reference Experimental Example 4-3, reflux treatment was carried out under the same conditions as in Reference Experimental Example 4-3, except that 1-butanol (1-BuOH) was used instead of 2-ethylhexanol (2EH) as the deactivator for TEA. The evaluation results are shown in Table 3.

[0239] (Reference Experimental Example 4-6) In Reference Experimental Example 4-3, reflux treatment was carried out under the same conditions as in Reference Experimental Example 4-3, except that 2-propylheptanol (2PH) was used instead of 2-ethylhexanol (2EH) as the deactivator for TEA. The evaluation results are shown in Table 3.

[0240]

Table 3

[0241] For each of the above Experimental Examples 4-1 to 4-6, the evaluation results of the isomerization rate of 1-hexene are shown in the graph of FIG. 4.

[0242] As shown in Table 3 and FIG. 4, when an alkylaluminum compound (TEA) remains in the reaction system as a desiccant, it was confirmed that as the addition amount of the deactivator increases, the decrease in the isomerization rate of the product (1-hexene) caused by the formation of by-products can be effectively suppressed.

Industrial Applicability

[0243] According to the present invention, in producing an α-olefin low polymer by the low polymerization reaction of an α-olefin, before starting the production operation, while suppressing the amount of an expensive alkylaluminum compound used as a desiccant, the water content in the reaction system can be efficiently reduced, and the production operation can be started promptly. Furthermore, during the low polymerization of an α-olefin, the catalytic activity and the product selectivity can be maintained well, and the formation of polymers of by-products that cause process blockage can also be suppressed.

Explanation of Signs

[0244] 1c Catalyst tank 10 Reactor 10a Stirrer 11,22,32,41,42,51 Piping 11a Inactivator supply piping 12 1st supply piping 12a Ethylene supply piping 13 2nd supply piping 13a Catalyst supply piping 14 3rd supply piping 15 4th supply pipe 21,31 Circulation piping 16 Capacitors 17 Compressor 20 Degassing tank 30 Ethylene separation tower 40 High boiling separation column 50 Hexen Separator 52 Solvent circulation piping 60 Solvent Drums 1-HEX 1-Hexene ETY (Ethylene)

Claims

1. A method for producing α-olefin low polymers, A gas drying process that supplies gas into the reaction system, Following the gas drying step, a solvent drying step is performed in which a desiccant-containing solvent containing a desiccant is supplied into the reaction system. A step of adding an inactivator to supply the deactivator of the desiccant into the reaction system, An α-olefin low polymerization reaction step for carrying out a low polymerization reaction of α-olefins, Equipped with, A method for producing an α-olefin, wherein the deactivator is supplied into the reaction system before the start of the low polymerization reaction of the α-olefin.

2. The manufacturing method according to claim 1, wherein in the gas drying step, the gas is supplied into the reaction system until the moisture content in the reaction system becomes less than or equal to a predetermined value (1).

3. The manufacturing method according to claim 2, wherein the predetermined value (1) is 100 mol ppm.

4. The manufacturing method according to claim 1, wherein the moisture content of the gas is 5 mol ppm or less.

5. The manufacturing method according to claim 1, wherein in the solvent drying step, the desiccant-containing solvent is supplied to the reaction system until the moisture content in the reaction system becomes less than or equal to a predetermined value (2).

6. The manufacturing method according to claim 5, wherein the predetermined value (2) is 10 mol ppm.

7. The manufacturing method according to claim 1, wherein the desiccant-containing solvent contains an alkylaluminum compound.

8. The manufacturing method according to claim 1, wherein the deactivator includes an alkyl alcohol.

9. The manufacturing method according to claim 1, further comprising a raw material substitution step after the gas drying step and before the solvent drying step, in which raw material α-olefin is supplied into the reaction system until the nitrogen gas content in the reaction system becomes less than or equal to a predetermined value (3).

10. The manufacturing method according to claim 9, wherein the predetermined value (3) is 20% by volume.

11. The manufacturing method according to claim 9, further comprising a solvent replacement step after the raw material replacement step and before the solvent drying step, in which a reaction solvent is supplied into the reaction system until the content of α-olefin in the reaction system becomes less than or equal to a predetermined value (4).

12. The manufacturing method according to claim 11, wherein the predetermined value (4) is 70% by volume.

13. The process further includes a measurement step for measuring the water content in the reaction system after the deactivator addition step and before the α-olefin low polymerization reaction step, The manufacturing method according to claim 1, wherein the α-olefin low polymerization reaction step is started when the moisture content measured in the measurement step is less than or equal to a predetermined value (5).

14. The manufacturing method according to claim 13, wherein the predetermined value (5) is 10 mol ppm.

15. The manufacturing method according to any one of claims 1 to 14, wherein the α-olefin low polymerization reaction step includes supplying a catalyst, a solvent, and a raw material α-olefin into the reaction system.

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