α-olefin production method

Abstract

The method for producing α-olefin comprises: a step 1 of obtaining a reaction mixture by continuously introducing ethylene and a catalyst into a reactor, mixing, and carrying out a polymerization reaction; a step 2 of continuously separating the reaction mixture into a gas A and a liquid B at a flasher having a separated droplet diameter dL according to formula (1) of not more than 1.0 × 10-4 m; a step 3 of contacting the gas A with a solvent in a scrubber to obtain a gas C containing unreacted ethylene and a liquid D containing the solvent; and a step 4 of reutilizing the gas C in a polymerization reaction. (In formula (1), v represents the ascending velocity (m / s) of the gas in the flasher, ρV represents the density (kg / m3) of the gas A, ρL represents the density (kg / m3) of the liquid B, g represents gravitational acceleration (m / s2), and μ represents the viscosity (Pa·s) of the gas A.)

Description

[Technical Field]

[0001] The present invention relates to a method for producing α-olefins. [Background technology]

[0002] α-Olefins are useful substances that are widely used as raw monomer materials for olefin polymers, as comonomers for various high molecular weight polymers, and as raw materials for plasticizers, surfactants, etc. Various studies have been conducted on methods for producing α-olefins. In general, for example, ethylene (carbon number: 2) is oligomerized using a Ziegler catalyst to obtain a mixture of α-olefins. Then, using multiple distillation columns, α-olefins having 4 to 20 carbon atoms, such as butene (carbon number: 4), hexene (carbon number: 6), and octene (carbon number: 8), or a mixture of α-olefins having 20 or more carbon atoms, are isolated or separated in order of decreasing carbon number to obtain a single product or a mixture required for each application.

[0003] This production process generally comprises a polymerization reaction step, an unreacted ethylene recovery step, a catalyst deactivation step, a deashing step, and a solvent and α-olefin distillation step. In the production process, since the polymerization reaction liquid obtained in the polymerization reaction step contains unreacted ethylene, a method is usually carried out in which ethylene is recovered in the unreacted ethylene recovery step to reduce the raw material consumption rate. Patent Document 1 discloses a method for producing an ethylene low polymer, which includes a step of recovering unreacted ethylene from a polymerization reaction liquid, in which non-volatile components such as α-olefins and a gas component mainly composed of unreacted ethylene are separated from the polymerization reaction liquid using a flasher, and then the unreacted ethylene, which is the gas component, is compressed again and reused in the polymerization reaction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-064105 Summary of the Invention [Problem to be solved by the invention]

[0005] The gaseous components obtained by separating the polymerization reaction liquid using a flasher contain impurities other than ethylene, such as catalyst. In the process of recovering unreacted ethylene and reusing it in the polymerization reaction, these impurity components cause blockages in pipes, compressors, heat exchangers, etc., making long-term continuous production of α-olefins difficult. Therefore, a method was needed that could suppress blockages caused by such components and enable long-term continuous operation. An object of the present invention is to provide an α-olefin production method which reduces clogging of pipes etc. in the unreacted ethylene recovery step and enables long-term continuous operation. [Means for solving the problem]

[0006] The present inventors have conducted extensive research in light of the above-mentioned circumstances and have found that the above-mentioned problems can be solved by a production method including the steps of separating gas contained in a reaction mixture after an ethylene polymerization reaction using a flasher having a specific separation droplet size, and then contacting the gas with a solvent using a scrubber. That is, the present invention relates to the following [1] to [7]. [1] Step 1: continuously introducing ethylene and a catalyst into a reactor, mixing them, and polymerizing them to obtain a reaction mixture; The reaction mixture is separated into droplets having a diameter d L is 1.0×10 -4 Step 2: Continuously separating the wastewater into gas A and liquid B using a flasher of 1000 m or less. Step 3: contacting the gas A with a solvent in a scrubber to obtain a gas C containing unreacted ethylene and a liquid D containing the solvent; and A method for producing an α-olefin, comprising a step 4 of recycling the gas C to a polymerization reaction.

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[0007] According to the method for producing α-olefins of the present invention, it is possible to reduce clogging of pipes, etc. in the step of recovering unreacted ethylene after the polymerization reaction for reuse in the polymerization reaction, thereby enabling long-term continuous operation. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic process diagram showing an example of a process for carrying out the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an example of a scrubber (tray type) used in step 3 of the present invention. [Figure 3] FIG. 2 is a schematic diagram showing an example of a scrubber (bubble column type) used in step 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention includes a step 1 of continuously introducing ethylene and a catalyst into a reactor, mixing them, and carrying out a polymerization reaction to obtain a reaction mixture; a step 2 of polymerizing the reaction mixture into a polymer having a separated droplet diameter d L is 1.0×10 -4 The method for producing α-olefins includes: step 2, continuously separating the reaction mixture into gas A and liquid B using a flasher with a capacity of 1000 m or less; step 3, contacting the gas A with a solvent in a scrubber to obtain gas C containing unreacted ethylene and liquid D containing the solvent; and step 4, recycling the gas C in a polymerization reaction.

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[0010] [Process 1] In step 1, ethylene and a catalyst are continuously introduced into a reactor, mixed, and polymerized to obtain a reaction mixture. In this step, ethylene is polymerized to obtain a reaction mixture containing an α-olefin. <Catalyst> In step 1, a catalyst is used to polymerize ethylene. The catalyst is preferably a Ziegler catalyst. The Ziegler catalyst preferably comprises a combination of (A) a transition metal compound, (B) an organoaluminum compound, and (C) an optional third component. The transition metal compound (A) may be a compound represented by general formula (I): MX x Y y O z (I) [In the formula, M represents a zirconium atom or a titanium atom, X represents a chlorine atom, a bromine atom or an iodine atom, and Y represents RO—, R 2 N—, —OCOR, —OSO 3 R, R—, —Cp or a β-diketonate represented by formula (II). -Cp represents a cyclopentadienyl group, and R represents a linear or branched alkyl group having 1 to 20 carbon atoms. [ka] (In formula (II), R 1 , R 2 and R 3 R each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an alkyl group having 1 to 20 carbon atoms substituted with a halogen atom. 1 , R 2 and R 3 At least one of the groups is an alkyl group having 1 to 20 carbon atoms substituted with a halogen atom. x, y, and z each independently represent an integer of 0 to 4, and x + y + z = 4. M is preferably a zirconium atom. X is preferably a chlorine atom. x is preferably 4. y is preferably 0. z is preferably 0.

[0011] ZrCl4,ZrBr4,ZrI4,ZrBrCl3,ZrBr2Cl2,TiCl4,TiBr 4,TiI4,TiBrCl3,TiBr2Cl2,Zr(OC2H5)4,Zr(OC2H5)2Cl2,Zr(On-C3H7)4 ,Zr(On-C3H7)2Cl2,Zr(O-iso-C3H7)4,Zr(O-iso-C3H7)2Cl2,Zr(On-C4H 9)4,Zr(On-C4H9)2Cl2,Zr(O-iso-C4H9)4,Zr(O-iso-C4H9)2Cl2,Zr(O-t ert-C4H9)4,Zr(O-tert-C4H9)2Cl2,Zr((CH3)2N)4,Zr((C2H5)2N)4,Zr((n-C3H7)2N)4,Zr((iso-C3H7)2N)4,Zr((n-C4H9)t-C4H9) 2N)4,Zr(OSO3CH3)4,Zr(OSO3C2H5)4,Zr(OSO3C3H7)4,Zr(OSO3C4H9)4,ZrCp2Cl2,ZrCp2ClBr,Ti(OC2H5)4,Ti(OC2H5)2Cl2,Ti(OC2H5)4,Ti(OC2H5)2Cl2,Ti(OC2H5)4,Ti(OSO3C2-4) 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)2Clter-OH 9)4,Ti(O-tert-C4H9)2Cl2,Ti((CH3)2N)4,Ti((C2H5)2N)4,Ti((n-C3H7)2N)4,Ti((iso-C3H7)2N)4,Ti((n-C4H9)2N)4,Ti((Tit-C4H9)2N)4,Ti((Tit-C4H9)2N)4 OSO3CH3)4,Ti(OSO3C2H5)4,Ti(OSO3C3H7)4,Ti(OSO3C4H9)4,TiCp2Cl2,TiCp2ClBr,Zr(OCOC2H5)4,Zr(OCOC2H5)2Cl2,Zr(OCOC3H7)4,ZOCH 7)2Cl2,Zr(OCOC4H9)4,Zr(OCOC4H9)2Cl2,Ti(OCOC2H5)4,Ti(OCOC2H5)2Cl2,Ti(OCOC3H7)4,Ti(OCOC3H7)2Cl2,Ti(OCOC4H9)4,Ti(OCOC4H9)2,2Cl2Examples include ZrCl2(HCOCFCOF)2 and ZrCl2(CH3COCFCOCH3)2. Among these, ZrCl4, Zr(On-C3H7)4, and Zr(On-C4H9)4 are preferred, with ZrCl4 being more preferred.

[0012] (B) Organoaluminum compounds include compounds represented by general formula (III) and / or general formula (IV). AlY a X b O c N d (III) [In the formula, X represents a chlorine atom, a bromine atom, or an iodine atom, Y represents RO-, RN-, -OCOR, or R-, and R represents a linear or branched alkyl group having 1 to 20 carbon atoms. a, b, c, and d each independently represent an integer of 0 to 3, and a+b+c+d=3.] Al2Y a’ X b’ O c’ N d’ (IV) [In the formula, X represents a chlorine atom, a bromine atom, or an iodine atom; Y represents RO-, RN-, -OCOR, -RCOCR'COR" or R-; R, R', and R" each independently represent a linear or branched alkyl group having 1 to 20 carbon atoms; a', b', c', and d' each independently represent an integer of 0 to 6, and a'+b'+c'+d'=6.]

[0013] Examples of the compound represented by the general formula (III) include Al(CH3)3, Al(C2H5)3, Al(C3H7)3, Al(iso-C3H7)3, Al(C4H9)3, Al(iso-C4H9)3, and Al(C5H 11 )3,Al(C6H 13 )3,Al(C8H 17)3,Al(C2H5)2Cl,Al(C2H5)2Br,Al(C2H5)2I,Al(C2H5)Cl2,Al(C2H5)Br2,Al(C2H5)I2,AlC2H5(OC2H5)2,AlC2H5(OC3H7)2,AlC2H5(OC 4H9)2,Al(OC2H5)2Cl,Al(OC3H7)2Cl,Al(OC4H9)2Cl,Al(OC2H5)Cl2,Al(OC3H7)Cl2,Al(OC4H9)Cl2,AlC2H5(OCOC2H5)2,AlC2H5(OCOC 3H7)2, AlC2H5(OCOC4H9)2, Al(OCOC2H5)2Cl, Al(OCOC3H7)2Cl, Al(OCOC4H9)2Cl, Al(OCOC2H5)Cl2, Al(OCOC3H7)Cl2, Al(OCOC4H9)Cl2, Al(C2H5)2OC2H5, Al(C2H5)2OC3H7, Al(C2H5)2OC4H9, Al(C2H5)2(N(C2H5)2), Al(C2H5)2(N(C3H7)2), and Al(C2H5)2N(C4H9)2. Among these, Al(C2H5)3, Al(iso-C4H9)3, Al(C8H 17 )3 is preferred, with Al(C2H5)3 being more preferred.

[0014] Examples of the compound represented by the general formula (IV) include Al2(CH3)3Cl3, Al2(CH3)3Br3, Al2(C2H5)3Cl3, Al2(C2H5)3Br3, Al2(C2H5)3I3, Al2(C2H5)3BrCl2, Al2(C3H7)3Cl3, Al2(iso-C3H7)3Cl3, Al2(C4H9)3Cl3, Al2(iso-C4H9)3Cl3, and Al2(C5H 11 )3Cl3,Al2(C8H 17 )3Cl3, Al2(C2H5)2(CH3)Cl3, Al2(OC2H5)3Cl3, Al2(OC3H7)3Cl3, Al2(OC4H9)3Cl3, Al2(OCOC2H5)3Cl3, Al2(OCOC3H7)3Cl3 and Al2(OCOC4H9)3Cl3. Among these, Al2(CH3)3Cl3, Al2(C2H5)3Cl3 and Al2(iso-C4H9)3Cl3 are preferred, and Al2(C2H5)3Cl3 is more preferred.

[0015] The optional third component (C) can be at least one compound selected from the group consisting of sulfur compounds, phosphorus compounds, and nitrogen compounds, and contributes to improving the purity of the resulting α-olefin. The sulfur compound may be any organic sulfur compound without any particular limitation. For example, preferred examples include thioethers such as dimethyl sulfide, diethyl sulfide, dipropyl sulfide, dihexyl sulfide, dicyclohexyl sulfide, and diphenylthioether; dialkyl disulfide compounds such as dimethyl disulfide, diethyl disulfide, dipropyl disulfide, dibutyl disulfide, dihexyl disulfide, dicyclohexyl disulfide, and ethylmethyl disulfide; thiophenes such as thiophene, 2-methylthiophene, 3-methylthiophene, 2,3-dimethylthiophene, 2-ethylthiophene, and benzothiophene; heterocyclic sulfur compounds such as tetrahydrothiophene and thiopyran; aromatic sulfur compounds such as diphenyl sulfur, diphenyl disulfide, methylphenyl disulfide, and methylphenyl sulfur; thiourea; and sulfides such as methyl sulfide, ethyl sulfide, and butyl sulfide.

[0016] The phosphorus compound is not particularly limited as long as it is an organic phosphorus compound, but for example, phosphines such as triphenylphosphine, triethylphosphine, tributylphosphine, tripropylphosphine, trioctylphosphine, and tricyclohexylphosphine are preferably used. The nitrogen compound is not particularly limited as long as it is an organic nitrogen compound, but preferred examples include organic amines such as methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, cyclohexylamine, octylamine, decylamine, aniline, benzylamine, naphthylamine, dimethylamine, diethylamine, dibutylamine, diphenylamine, methylphenylamine, trimethylamine, triethylamine, tributylamine, triphenylamine, pyridine, and picoline.

[0017] Among the sulfur compounds, phosphorus compounds, and nitrogen compounds, for example, one or more compounds selected from the group consisting of dimethyl disulfide, thiophene, thiourea, triphenylphosphine, tributylphosphine, trioctylphosphine, and aniline can be suitably used.

[0018] <Polymerization reaction conditions, etc.> The polymerization reaction of ethylene is preferably carried out in an organic solvent. The amount of organic solvent used in the polymerization reaction of ethylene is preferably 0.5 to 5 times by mass relative to the α-olefin produced. Examples of the organic solvent that can be used include alicyclic compounds such as cyclohexane and decalin; aromatic hydrocarbons and halides thereof such as benzene, toluene, xylene, chlorobenzene, ethylbenzene, dichlorobenzene, and chlorotoluene; aliphatic hydrocarbons such as pentane, hexane, heptane, octane, nonane, and decane; and halides of aliphatic hydrocarbons such as dichloroethane and dichlorobutane. Among these, alicyclic compounds are preferred, and cyclohexane is more preferred.

[0019] In this step, the proportions of the (A) transition metal compound, (B) organoaluminum, (C) third component, and organic solvent in the catalyst are preferably 0.01 to 5 mmol, more preferably 0.03 to 1 mmol, per 250 mL of organic solvent for the (A) transition metal compound, 0.05 to 15 mmol, more preferably 0.06 to 3 mmol, for the (B) organoaluminum, and 0.05 to 20 mmol for the (C) third component. When the (C) third component is a sulfur compound, the proportion is preferably 0.1 to 10 mmol. When the (C) third component is a nitrogen compound or phosphorus compound, the proportion is preferably 0.05 to 5 mmol. Furthermore, the proportion of the (A) transition metal compound to the (B) organoaluminum is preferably set such that the Al / Zr or Ti molar ratio is in the range of 1 to 15. The compounding ratio of the (A) transition metal compound to the (B) organoaluminum compound [Al / Zr or Ti (molar ratio)] is more preferably 2-10, and even more preferably 4-9.

[0020] The polymerization reaction in this step is preferably carried out at a temperature of 100 to 150°C and a pressure of 30 to 90 kg / cm 2 The reaction is carried out under pressure of 2.94 to 8.82 MPa. The ethylene gas pressure is 30 to 90 kg / cm 2 G (2.94 to 8.82 MPa) is preferred, and 50 to 80 kg / cm 2 ·G (4.90 to 7.84 MPa) is more preferred. The reaction time depends on the temperature and pressure and cannot be determined uniformly, but is preferably 10 minutes or more, and preferably 60 minutes or less, and more preferably 50 minutes or less. When a continuous reactor is used, the residence time in the reactor is preferably 10 minutes or more, more preferably 30 minutes or more, and preferably 60 minutes or less, and more preferably 50 minutes or less. The reactor is preferably a complete mixing tank type.

[0021] [Process 2] In the production method of the present invention, step 2 is to separate the reaction mixture obtained in step 1 into a separated droplet having a diameter d L is 1.0×10 -4This is a process in which gas A and liquid B are continuously separated using a flasher of less than 1000 m.

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[0022] This step will be explained with reference to Fig. 1. Fig. 1 is an example of a conceptual diagram of an apparatus used in the production method of the present invention. In reactor 1, the ethylene polymerization reaction of step 1 above is carried out. The reaction mixture obtained here contains, in addition to the target α-olefin, catalyst, solvent, by-product polymer, unreacted ethylene, etc. This reaction mixture is supplied to flasher 3 via control valve 2. In flasher 3, the pressure is reduced and the mixture is separated into gas A and liquid B. Gas A mainly contains unreacted ethylene, and liquid B mainly contains α-olefin, catalyst, and solvent. Gas A is discharged from the top of flasher 3, and liquid B is discharged from the bottom of flasher 3. In this embodiment shown in FIG. 1, a second-stage flasher 5 is further provided, but the flasher 5 is optional and not a required component. The use of the second-stage flasher 5 allows for more effective recovery of unreacted ethylene. Liquid B discharged from the bottom of the first-stage flasher 3 is supplied to the flasher 5 via a control valve 4. In the flasher 5, as in the flasher 3, the liquid is separated into a gas (gas E) containing mainly unreacted ethylene and a liquid (liquid F) containing mainly α-olefins, catalyst, and solvent. The separated gas E is discharged from the top of the flasher 5, and the separated liquid F is discharged from the bottom of the flasher 5. The liquid F discharged from the bottom of the flasher 5 is sent to the catalyst deactivation step. That is, when a second-stage flasher is provided, the step 2 is performed to obtain the separated droplet diameter d L is 1.0×10 -4 After continuously separating the gas A and liquid B in a flasher of 0.1 m or less, the liquid B is further separated into droplets with a diameter of separated droplets d L is 1.0×10 -4 In this step, the liquid is continuously separated into gas E and liquid F by a flasher having a diameter of 100 mm or less. More specifically, when a second flasher is provided, step 2 is carried out by separating the separated liquid into gas E and liquid F by a diameter of 100 mm or less, the diameter of the separated liquid being ... L is 1.0×10 -4 After the gas A and liquid B are continuously separated in the first flasher of 1000 m or less, the liquid B is further separated into the separated droplets d L is 1.0×10 -4 This is the process where the gas E and liquid F are continuously separated in the second stage flasher below m.

[0023] Control valve 2 may be attached directly to flasher 3. Control valve 4 may be attached directly to flasher 5. By attaching the control valves directly to the flashers, it is possible to prevent blockages from occurring in the piping from the control valves to the flashers, so it is preferable to attach each control valve directly to the flashers. When a second-stage flasher is provided, in this specification, gas A in the description of the first-stage flasher will be read as gas E and liquid B will be read as liquid F in relation to the second-stage flasher. In the case of an embodiment that does not include the second-stage flasher 5, the liquid B discharged from the bottom of the flasher 3 is sent to the catalyst deactivation step.

[0024] The flasher used in this step has a separated droplet diameter d L is 1.0×10 -4 At least one of the flashers 3 and 5 has a separated droplet diameter d L is 1.0×10 -4 m or less, and the separated droplet diameter d L is 1.0×10 -4It is preferable that the length is m or less.

[0025] The diameter of the separated droplets d L is 1.0×10 -4 By keeping the ethylene content at or below 1000 ppm, it is possible to reduce the amount of components other than ethylene, such as catalyst, that accompany the gas discharged from the flasher. Reducing the amount of components other than ethylene that accompany the gas reduces blockage of pipes, etc., and also reduces the load on the scrubber in step 3, thereby improving production efficiency. In particular, it is possible to reduce fouling and blockage of the pipes from the flasher to the scrubber. The separated droplet diameter d L is 1.0 x 10 -4 m or less, preferably 7.0 × 10 -5 m or less, and more preferably 5.0 × 10 -5 There is no lower limit, but from the viewpoint of preventing the inner diameter of the flasher from becoming too large, it is preferably 1.0 × 10 -5 The inner diameter of the flasher is preferably not too large, which reduces the cost of the flasher and reduces the installation area. The separated droplet diameter d L can be adjusted to the above range by, for example, adjusting the rising speed (v) of the gas in the flasher. Specific methods include, for example, adjusting the inner diameter of the flasher and the pressure in the flasher. In other words, by increasing the inner diameter of the flasher, the rising speed of the gas in the flasher can be slowed down, and as a result, the separated droplet diameter d L In addition, by reducing the difference between the pressure in the flasher and the pressure in the polymerization reaction process, the amount of gas generated by separation can be reduced, and the rising speed of the gas in the flasher can be slowed down, resulting in the diameter d of the separated droplets. L can be made smaller. The flasher may be provided with an inlet for introducing a solvent in addition to the inlet for introducing the reaction mixture, and the solvent may be sprayed into the gas phase in the flasher during separation of the gas (A or E) and the liquid (B or F). By spraying the solvent into the gas phase in the flasher, the amount of catalyst and by-produced polymer entrained in the gas A or gas E can be reduced. The droplet diameter of the solvent sprayed into the gas phase in the flasher is set to the separation droplet diameter d of the flasher. L Preferably equal to or greater than 1.0 × 10 -4 It is more preferable that the length is m or more.

[0026] The temperature when gas A and liquid B are continuously separated in the flasher is preferably 100°C or higher. There is no upper limit to the temperature when gas A and liquid B are separated, but it is preferably 150°C or lower. The pressure when continuously separating gas A and liquid B in the flasher is preferably set so that the ratio of the pressure in the first-stage flasher to the pressure in the reactor [first-stage flasher / reactor] is 1 / 3 to 1 / 2. When a second-stage flasher is used, the temperature at which gas E and liquid F are continuously separated by the flasher is preferably 100°C or higher. There is no upper limit to the temperature at which gas E and liquid F are separated, but it is preferably 150°C or lower. The pressure when continuously separating gas E and liquid F in the flashers is preferably such that the ratio of the pressure in the second-stage flasher to the pressure in the first-stage flasher [second-stage flasher / first-stage flasher] is 1 / 15 to 1 / 2, more preferably 1 / 12 to 1 / 4, and even more preferably 1 / 10 to 1 / 6. Furthermore, one or more additional flashers may be provided after the second-stage flasher 5. Specifically, a third-stage flasher may be provided, or a fourth-stage flasher may be provided after the third-stage flasher. In the third-stage flasher and fourth-stage flasher, gas and liquid are separated in the same manner as in the first-stage flasher and second-stage flasher. In the third-stage and subsequent flashers, the ratio of the pressure in the flasher to the pressure in the previous flasher is in the same preferred range as the ratio of the pressure in the second-stage flasher to the pressure in the first-stage flasher.

[0027] [Process 3] In the production method of the present invention, step 3 is a step of contacting gas A obtained in step 2 with a solvent in a scrubber to obtain gas C containing unreacted ethylene and liquid D containing the solvent. By this step, components other than ethylene, such as the catalyst, contained in gas A can be separated into the solvent and removed.

[0028] The main component of gas A obtained in step 2 is unreacted ethylene, but the gas flow also entrains small amounts of components other than unreacted ethylene, such as catalyst, solvent, product α-olefin, and by-product polymer. The catalyst and by-product polymer that accompanies unreacted ethylene adhere to piping, heat exchanger 6 (and heat exchanger 7), the ethylene recycle compressor, etc., causing blockages and hindering long-term continuous production. Therefore, this step is preferably carried out immediately after gas A is separated in the flasher and before gas A is sent to a device such as a heat exchanger. In particular, since there is a high risk of deposits being formed when gas A is cooled in the heat exchanger, it is preferable to install a scrubber before the heat exchanger. In the scrubber 8, the gas discharged from the top of the flasher 3 is brought into contact with the solvent. The solvent used here is preferably the same as the organic solvent used in the polymerization reaction in step 1. Specific examples include alicyclic compounds such as cyclohexane and decalin; aromatic hydrocarbons and halides thereof such as benzene, toluene, xylene, chlorobenzene, ethylbenzene, dichlorobenzene, and chlorotoluene; aliphatic hydrocarbons such as pentane, hexane, heptane, octane, nonane, and decane; and halides of aliphatic hydrocarbons such as dichloroethane and dichlorobutane. Among these, it is preferable that the organic solvent used in the polymerization reaction in step 1 and the solvent used in step 3 are the same. Using the same solvent as in the polymerization reaction facilitates separation of the α-olefins obtained in the continuous reaction from the solvent. Also, the condensate from heat exchangers 6 and 7, which are located downstream of the scrubber, can be used to replace part or all of the solvent used in the scrubber. In this case, it is preferable to mix the condensate with the solvent to be introduced into the scrubber and use it in the scrubber, which has the advantage of being able to reduce the amount of solvent used.

[0029] Gas C containing unreacted ethylene is discharged from the top of the scrubber 8. Furthermore, liquid D containing the solvent is discharged from the bottom of the scrubber 8.

[0030] In the embodiment shown in FIG. 1, a second-stage flasher 5 is further provided, and therefore, in the scrubber 9, the gas E discharged from the upper part of the flasher 5 is brought into contact with the solvent. The scrubber 9 may have a configuration similar to that of the scrubber 8. A gas G containing unreacted ethylene is discharged from the upper part of the scrubber 9. Furthermore, a liquid H containing the solvent is discharged from the lower part of the scrubber 9. The second stage flasher 5 is an optional and not a required component, and the scrubber 9 is also not a required component. That is, when a second-stage flasher is provided, step 3 comprises the steps of bringing the gas A and the solvent into contact with each other in a scrubber to obtain a gas C containing unreacted ethylene and a liquid D containing the solvent, and bringing the gas E and the solvent into contact with each other in a scrubber to obtain a gas G containing unreacted ethylene and a liquid H containing the solvent. More specifically, when a second-stage flasher is provided, a second-stage scrubber is provided, and step 3 comprises the steps of bringing the gas A and the solvent into contact with each other in a first-stage scrubber to obtain a gas C containing unreacted ethylene and a liquid D containing the solvent, and bringing the gas E and the solvent into contact with each other in a second-stage scrubber to obtain a gas G containing unreacted ethylene and a liquid H containing the solvent. When a second-stage flasher is provided, in this specification, gas C in the description of the first-stage flasher will be read as gas G and liquid D will be read as liquid H in relation to the second-stage flasher.

[0031] It is preferable to send the liquid D discharged from the bottom of the scrubber 8 to the flasher. By sending the liquid D to the flasher, it is possible to further recover remaining unreacted ethylene. The same applies to the liquid H discharged from the scrubber 9. That is, when a second-stage flasher is provided, it is preferable to send the liquid H obtained in step 3 to the second-stage flasher. If a third stage flasher is provided after the second stage flasher 5, the third stage flasher may also be provided with a scrubber after it, similar to the first and second stage flashers, and if a fourth stage flasher is provided, the fourth stage flasher may also be provided with a scrubber after it, similar to the first and second stage flashers.

[0032] The type of scrubber is not particularly limited as long as it does not impair the purpose of this step, which is to contact gas A (or the gas E) with a solvent and separate components other than ethylene, such as the catalyst contained in gas A (or the gas E) and the by-produced polymer, but a type that can efficiently contact the gas with the solvent is preferred. Specifically, the scrubber may be one selected from the group consisting of a bubble column type and a tray type.

[0033] From the viewpoint of effectiveness, the scrubber used in this process is preferably a tray type. Figure 2 shows an example of a tray type scrubber. In the tray type, the gas A (or the gas E) is introduced from the bottom and the solvent is introduced from the top, allowing the gas and solvent to come into contact with each other in multiple stages, thereby effectively removing the catalyst and by-product polymer. The white arrows in Figure 2 schematically show the gas flow. After the gas and solvent come into contact with each other in multiple stages, the gas from which the catalyst and by-product polymer have been removed (the gas C or the gas G) is obtained from the top of the scrubber. The number of stages in a tray type scrubber is preferably, for example, 3 to 15, and more preferably 5 to 10 from the viewpoint of removal effect and efficiency.

[0034] The scrubber used in this process is preferably a bubble column type from the viewpoint of ease of installation. Figure 3 shows an example of a bubble column type scrubber. In a bubble column type scrubber, the gas A (or the gas E) is blown in the form of bubbles into the solvent in the column through a gas disperser at the bottom of the column, dispersing or dissolving the catalyst, by-product polymer, etc. contained in the gas A (or the gas E) in the solvent, and obtaining a gas (the gas C or the gas G) from which these have been removed at the top of the column. In this way, the bubble column type is able to remove the catalyst despite its simple structure by introducing the gas from the bottom of the column filled with the solvent. Bubble column type scrubbers may be packed with packing such as Raschig rings, which are preferable because the packing can prevent short-passing of bubbles and enhance the effect of removing catalysts, etc.

[0035] The gas discharged from the first-stage flasher tends to contain more components (impurities) other than ethylene, such as catalyst, than the gas discharged from the second-stage flasher. Therefore, the scrubber installed immediately after the first-stage flasher (in this embodiment, scrubber 8 installed immediately after first-stage flasher 3) is preferably a tray-type scrubber, which is highly effective. On the other hand, the scrubber installed immediately after the second-stage flasher (in this embodiment, scrubber 9 installed immediately after second-stage flasher 5), which contains a relatively small amount of components other than ethylene, such as catalyst, is preferably a bubble column-type scrubber, which is easy to install and cost-effective.

[0036] The temperature of the liquid in the scrubber in this step is preferably maintained at 100°C or higher. The temperature of the liquid in the scrubber is more preferably maintained at 105°C or higher, and even more preferably maintained at 120°C or higher. The temperature is preferably 150°C or lower. By maintaining the temperature of the liquid in the scrubber within the above range, the by-produced polymer can be dissolved, making it possible to separate the gas and the catalyst more efficiently. The liquid in the scrubber mainly consists of the solvent, and after contact with the gas, it contains impurities such as the catalyst and by-produced polymer.

[0037] [Step 4] In the production method of the present invention, step 4 is a step of reusing the gas C obtained in step 3 in the polymerization reaction. In Fig. 1, gas C discharged from the top of scrubber 8 is separated into unreacted ethylene and solvent, etc. by heat exchanger 6 and gas-liquid separation tank 10. Unreacted ethylene is discharged from the top of gas-liquid separation tank 10, and solvent, etc. are discharged from the bottom of gas-liquid separation tank 10. The solvent, etc. discharged from the bottom is preferably returned to flasher 3. Unreacted ethylene discharged from the top of gas-liquid separation tank 10 is introduced into an ethylene recycling compressor and supplied to reactor 1. The unreacted ethylene supplied to reactor 1 in this manner is used as a raw material for step 1. In this way, the raw material ethylene can be used without being discharged outside the system and without being wasted.

[0038] Similarly, the gas G discharged from the top of the scrubber 9 is separated into unreacted ethylene and the solvent, etc. by the heat exchanger 7 and the gas-liquid separation tank 11. The unreacted ethylene is discharged from the top of the gas-liquid separation tank 11, and the solvent, etc. are discharged from the bottom of the gas-liquid separation tank 11. The solvent, etc. discharged from the bottom are preferably returned to the flasher 5. That is, when a second-stage flasher is provided, step 4 is a step of reusing the gas C and gas G obtained in step 3 for the polymerization reaction. Unreacted ethylene discharged from the top of the gas-liquid separation tank 11 is introduced into an ethylene recycling compressor and supplied to the reactor 1. The same applies when a third flasher is provided after the second flasher 5, and also when a fourth flasher is provided.

[0039] [α-Olefin recovery process (process 5)] This step is a step (step 5) for recovering α-olefins contained in the liquid (liquid B or liquid F) obtained in step 2. This process includes a catalyst deactivation step, a deashing treatment step, and a distillation step.

[0040] In the embodiment shown in Fig. 1, in which two flashers are used, liquid F is sent to the catalyst deactivation step via control valve 12. In the embodiment shown in Fig. 1, in which one flasher is used, flasher 5 is not installed, and liquid B is sent to the catalyst deactivation step via control valve 4. In the catalyst deactivation step, a deactivation treatment of the catalyst is performed using a deactivator. Examples of the deactivator include basic nitrogen compounds, water, alcohols, carboxylic acids, and phenols. Examples of basic nitrogen compounds include amines such as methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, cyclohexylamine, octylamine, decylamine, aniline, benzylamine, naphthylamine, dimethylamine, diethylamine, dibutylamine, diphenylamine, methylphenylamine, trimethylamine, triethylamine, tributylamine, triphenylamine, pyridine, and picoline, as well as ammonia. The liquid obtained after the catalyst deactivation step is sent to the de-ashing treatment step.

[0041] In the de-ashing process, the material is washed with water using a de-ashing machine. The resulting mixture is then separated into an oil phase and an aqueous phase in a separation tank. The aqueous phase is discarded as wastewater, while the oil phase is heated as needed and sent to the distillation process. In the distillation process, the solvent is removed and the target α-olefin is recovered. If necessary, fractional distillation can be performed to obtain α-olefins with the carbon number (degree of polymerization) appropriate for the application. [Example]

[0042] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0043] Example 1 [Catalyst Preparation] The catalyst was prepared in the following manner. 3 Dry cyclohexane was introduced into a stirred vessel under a nitrogen atmosphere. Next, triethylaluminum [(C2H5)3Al] was introduced. Anhydrous zirconium tetrachloride [ZrCl4] was then introduced. Next, ethylaluminum sesquichloride [(C2H5)3Al2Cl3] was introduced. The amounts of the raw materials and solvents were determined based on the amount of anhydrous zirconium tetrachloride as follows: Triethylaluminum and ethylaluminum sesquichloride were introduced so that the molar ratios were (C2H5)3Al2Cl3 / (C2H5)3Al = 3.5 and [(C2H5)3Al2Cl3 + (C2H5)3Al] / ZrCl4 = 7, and cyclohexane was introduced so that the concentration of anhydrous zirconium tetrachloride was 80 mmol per 1 L of cyclohexane. After all the components had been added, the mixture was heated and stirred at 70°C for 2 hours under a nitrogen atmosphere to form a complex, thereby preparing a catalyst solution.

[0044] [Step 1: Polymerization Reaction] The reaction was carried out in a complete mixing tank type reactor (internal volume: approximately 20 m 3 The reaction was carried out continuously using a cyclohexane reactor. The reaction solvent (cyclohexane) was fed at a rate of 30 ton / hour, and the catalyst solution was fed at a rate of 25 kg / hour. The average residence time was about 45 minutes based on the solvent. The reaction was carried out at 130°C and 70 kg / cm. 2 The reaction was carried out at a pressure of 70 kg / cm. 2 The polymerization reaction was carried out by continuously feeding the components so as to maintain the temperature at 1000 K. G, and a reaction mixture was obtained.

[0045] [Step 2: Gas-liquid separation] The reaction mixture obtained in step 1 is separated into droplets with a diameter of d L is 3.0×10 -5 The mixture was introduced into a flasher (Figure 1: Flasher 3) at 1000 m, where gas-liquid separation was performed to obtain gas and liquid components. Furthermore, the liquid component obtained in the flasher 3 in this process has a separated droplet diameter d L is 5.0×10 -5 The mixture was introduced into a second flasher (Flasher 5 in Figure 1) with a flow rate of 100 sq m, where gas-liquid separation was carried out to obtain gas and liquid components. The temperature in Flasher 3 was 115°C and the pressure was 33.0 kg / cm. 2 The temperature in flasher 5 was 110°C and the pressure was 3.5 kg / cm 2 Processing was carried out with G. v and ρ for Flasher 3 and Flasher 5 V , ρ L、 g and μ are as follows:

[0046] Flasher 3 v:0.023(m / s) ρ V :41.2(kg / m 3 ) ρ L :655(kg / m 3 ) g: 9.81 (m / s 2 ) μ:1.30×10 -5 (Pa·s) Flasher 5 v:0.090(m / s) ρ V :5.76(kg / m 3 ) ρ L :714(kg / m 3 ) g: 9.81 (m / s 2 ) μ:1.07×10 -5 (Pa·s)

[0047] [Step 3: Separation and removal of catalyst, etc.] The gaseous components obtained in step 2 were passed through scrubber 8 and scrubber 9, respectively, to remove impurities such as catalysts from the gaseous components. Cyclohexane was used as the solvent in both scrubbers. Scrubber 8 was a nine-tray type, and scrubber 9 was a bubble column type. The liquid temperature in scrubber 8 was 120°C during treatment, and the liquid temperature in scrubber 9 was 120°C during treatment.

[0048] [Step 4: Gas-liquid separation and ethylene recycling step] The gaseous components from which the catalyst was removed in step 3 were cooled in heat exchangers 6 and 7, and introduced into gas-liquid separation tanks 10 and 11, respectively, where they were separated into unreacted ethylene and a liquid component. The unreacted ethylene was introduced into an ethylene recycle compressor and then reintroduced into reactor 1.

[0049] [Step 5: α-olefin recovery step] The liquid component obtained from the second flasher (Figure 1: Flasher 5) was continuously supplied to a deactivation tank, where the catalyst was deactivated. A 10% by mass concentration of aqueous ammonia was used as the deactivator. The resulting liquid after the deactivation treatment was separated into oil and water and introduced into a distillation apparatus. In the distillation apparatus, the distillation conditions were appropriately adjusted to recover α-olefins with carbon numbers ranging from 4 to 24.

[0050] After the above continuous operation was carried out for 180 days, the insides of the heat exchangers 6 and 7 were examined and no deposits were found. As described above, the method of the present invention, which includes a polymerization reaction step, a gas-liquid separation step using a specific flasher, a step of separating and removing impurities using a scrubber, and a step of recycling ethylene, can reduce blockages in pipes, etc. in the unreacted ethylene recovery step during the production of α-olefins, and enables long-term continuous operation.

[0051] Comparative Example 1 The same procedure as in Example 1 was carried out except that scrubbers 8 and 9 were bypassed and step 3 (catalyst separation and removal) was not carried out. After the above continuous operation was performed for 30 days, the inside of heat exchanger 6 and heat exchanger 7 became clogged, and the pressure loss increased, so the operation was stopped. When the inside of heat exchanger 6 and heat exchanger 7 was inspected, deposits were found.

[0052] Comparative Example 2 In Example 1, the diameter of the separated droplets d L to 1.0×10 -4 The same as in Example 1 except that the length is greater than m. If the above-mentioned continuous operation is performed, the piping from the flasher to the scrubber 8 or scrubber 9 will become dirty and clogged, making continuous operation difficult. [Explanation of symbols]

[0053] 1: Reactor 2, 4, 12: Control valve 3, 5: Flasher 8,9:スクラバー 6, 7: Heat exchanger 10, 11: Gas-liquid separation tank

Claims

1. Step 1: continuously introducing and mixing ethylene and a catalyst into a reactor to polymerize the mixture to obtain a reaction mixture; The reaction mixture is separated into droplets having a diameter d Ｌ is 1.0 x 10 －４ Step 2: continuously separating the gas A and the liquid B using a flasher of 1000 m or less; Step 3: contacting the gas A with a solvent in a scrubber to obtain a gas C containing unreacted ethylene and a liquid D containing the solvent; and A method for producing an α-olefin, comprising a step 4 of recycling the gas C to a polymerization reaction. [Equation 1] (In formula (1), v represents the ascending velocity of the gas in the flasher (m / s), and ρ Ｖ is the density of gas A (kg / m ３ ) and ρ Ｌ is the density of liquid B (kg / m ３ ), and g represents the gravitational acceleration (m / s ２ ) and μ represents the viscosity (Pa s) of gas A.

2. The method for producing an α-olefin according to claim 1, wherein the scrubber is of a tray type.

3. The method for producing α-olefins according to claim 1, wherein the scrubber is a bubble column type.

4. The method for producing an α-olefin according to any one of claims 1 to 3, wherein the temperature of the liquid in the scrubber in step 3 is maintained at 100°C or higher.

5. The method for producing an α-olefin according to any one of claims 1 to 3, wherein the liquid D obtained in step 3 is sent to the flasher.

6. Step 2 is to separate the droplets into droplets having a diameter d Ｌ is 1.0 x 10 －４ After the gas A and the liquid B are continuously separated in the first flasher of 1000 m or less, the liquid B is further separated into the separated droplets having a diameter d Ｌ is 1.0 x 10 －４ This is a process in which the mixture is continuously separated into gas E and liquid F in a second-stage flasher of 1000 m or less. Step 3 includes a step of contacting the gas A with a solvent in a first stage scrubber to obtain a gas C containing unreacted ethylene and a liquid D containing the solvent, and a step of contacting the gas E with a solvent in a second stage scrubber to obtain a gas G containing unreacted ethylene and a liquid H containing the solvent, The method for producing an α-olefin according to any one of claims 1 to 3, wherein step 4 is a step of recycling the gas C and the gas G for a polymerization reaction.

7. The method for producing an α-olefin according to claim 6, wherein the liquid H obtained in step 3 is sent to the second-stage flasher.

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