Method for removing polymer in olefin oligomerization reactor

Abstract

The present invention relates to a method for removing a polymer which is generated in an olefin oligomerization process and accumulates inside a reactor to cause fouling, said method enabling simultaneous oligomerization and polymer removal so that the process operation is efficient, a separate heat source or cooling water is not required, the economic feasibility is improved, the polymer solution is rapidly cooled, and the production cost is reduced. The polymer is easily removed from the solvent, so that the solvent recovery rate can be improved.

Description

Technical Field

[0001] The present invention relates to a method for removing polymers in an olefin oligomerization reactor, and more particularly, to a method for effectively removing polymers that accumulate inside the reactor and cause fouling without interrupting the process. Background Art

[0002] During the oligomerization reaction of olefins, in addition to oligomers such as 1-hexene and 1-octene as target materials, a large amount of polymers such as polyethylene are also produced as by-products. The polymers adhere to the pipes and reactors, resulting in pipe blockages, or the polymers accumulated in the reactor can reduce the fluid flow rate, act as an insulator, and interfere with heat transfer. To remove the polymers that have an adverse effect on the process, traditionally, the reactor is opened after the process is shut down, and workers directly remove the polymers inside the reactor. However, since this requires a large amount of manpower, increases working hours, and requires additional processes (such as removing impurities from the reactor to restart the process and then purging with an inert gas), the process efficiency and economic feasibility are poor.

[0003] Therefore, it is necessary to study a method for removing polymers in an oligomerization reactor, which can continuously remove the polymers in the reactor while performing the olefin oligomerization reaction without opening the reactor, so as to obtain a higher solvent recovery rate and achieve efficient and economical operation. Summary of the Invention

[0004]

Technical Problem

[0005] To solve the problems in the prior art, an object of the present invention is to provide a method for removing polymers in an oligomerization reactor, which can effectively remove the polymers without interrupting the process. These polymers are by-products of the olefin oligomerization reaction and accumulate in the reactor and cause fouling.

[0006] Another object of the present invention is to provide a method for removing polymers in an oligomerization reactor and an oligomer manufacturing apparatus, which can improve the solvent recovery rate in the polymer removal process.

[0007]

Technical Solution

[0008] In one general aspect, a method for removing polymers in an olefin oligomerization reactor includes: (a) preparing vinyl oligomers in a reactor from reactants including ethylene, a solvent, and a catalyst; (b) removing the polymers included in the oligomer product solution; (c) distilling the oligomer product solution from which the polymers have been removed in step (b) in a distillation column to separate the solution into hydrocarbons having 4 or fewer carbon atoms, 1-hexene, 1-octene, hydrocarbons having 10 or more carbon atoms, and a solvent; (d) recycling a heated recycled solvent obtained by heating a portion of the solvent separated in step (c) to the reactor to dissolve residual polymers in the reactor and prepare a polymer dissolution solution; (e) mixing the polymer dissolution solution with the remaining recycled solvent in step (c) and rapidly cooling the polymer dissolution solution to precipitate the polymers; and (f) separating the polymers from the solvent in the polymer dissolution solution in which the polymers have precipitated.

[0009] In an exemplary embodiment, in step (d), a portion of the separated solvent can be heated by heat exchange with the hydrocarbons having 10 or more carbon atoms separated from the distillation column.

[0010] In an exemplary embodiment, in step (d), the temperature of the heated recycled solvent can be from 50°C to 200°C.

[0011] In an exemplary embodiment, in step (d), the temperature of the hydrocarbons having 10 or more carbon atoms can be from 150 to 300°C.

[0012] In an exemplary embodiment, in step (e), the temperature of the remaining recycled solvent can be from 30 to 70°C.

[0013] In an exemplary embodiment, in step (e), the temperature of the rapidly cooled polymer dissolution solution can be from 20 to 80°C.

[0014] In an exemplary embodiment, in step (e), the mixing ratio of the polymer dissolution solution to the remaining recycled solvent can be from 1:1 to 7.

[0015] In an exemplary embodiment, in step (d), the flow rate ratio of the portion of the separated solvent to the hydrocarbons having 10 or more carbon atoms can be from 1:0.5 to 3.

[0016] In an exemplary embodiment, in the solvent separated in step (c), the flow rate ratio of the heated recycled solvent to the remaining recycled solvent can be from 1:20 to 150.

[0017] In an exemplary embodiment, in step (e), the polymer dissolution solution and the remaining recycled solvent may be mixed in a polymer precipitation device.

[0018] In an exemplary embodiment, in step (f), the solvent separated from the polymer separator may be recycled and reused in the oligomerization reaction in step (a).

[0019] In an exemplary embodiment, after step (b), it may further include a monomer recovery step of separating unreacted monomers from the oligomers from which the polymer has been removed using a gas-liquid separator and recycling the monomers to the reactor.

[0020] In an exemplary embodiment, the solvent may include aliphatic hydrocarbons or aromatic hydrocarbons.

[0021] In an exemplary embodiment, in step (a), a plurality of reactors may be included.

[0022] In an exemplary embodiment, the plurality of reactors may be arranged in parallel.

[0023] In an exemplary embodiment, after step (d), it may further include a step of transporting a part of the heated recycled solvent to a polymer removal device and dissolving the residual polymer in the polymer removal device to prepare the polymer dissolution solution.

[0024] In an exemplary embodiment, after step (a), it may further include a step of injecting a catalyst deactivator into the oligomer product solution.

[0025] In an exemplary embodiment, the catalyst deactivator may include water, an alcohol-based compound, or a combination thereof.

[0026]

Beneficial Effects

[0027] Since the method for removing polymers in an olefin oligomerization reactor according to the present invention can continuously remove the polymers accumulated in the reactor while performing the oligomerization reaction, the process efficiency can be improved.

[0028] In addition, the solvent used in the oligomerization reaction can be recycled and used to remove the polymers accumulated in the reactor. During the polymer removal process, heating can be achieved by heat exchange with the high-temperature and high-boiling hydrocarbons generated in the process without adding a separate heat source. Therefore, excellent economic feasibility can be provided.

[0029] Furthermore, rapid cooling is performed during polymer precipitation, so that the polymer and the solvent can be effectively separated, thereby improving the polymer removal rate and the solvent recovery rate. Description of the Drawings

[0030] Figure 1 It is a process diagram of a conventional olefin oligomerization process.

[0031] Figure 2 It is a process diagram of an olefin oligomerization process according to Example 1.

[0032] Figure 3 It is a flow chart showing the oligomerization process (blue dotted line) and the polymer removal process (red solid line) in the oligomerization process diagram according to Example 1.

[0033] Figure 4 It is a graph showing the difference in polymer aggregation depending on the cooling rate of the polymer dissolution solution.

[0034] Figure 5 It is a process diagram showing an embodiment in which the number of reactors is 3 in the olefin oligomerization process according to Example 1.

[0035] Figure 6 It is a process diagram showing an embodiment including a process of removing the polymer accumulated in the polymer removal device in the olefin oligomerization process according to Example 1. Detailed Description

[0036] A method for removing polymers in an olefin oligomerization reactor of the present invention will be described in detail. The terms used in this specification are selected as common and currently widely used terms as much as possible while considering the functions of the present invention, but these terms may vary depending on the intentions of those skilled in the art, conventions, or the emergence of new technologies. Unless otherwise defined, the technical and scientific terms used may have the meanings commonly understood by those of ordinary skill in the art.

[0037] Terms such as "including" or "having" in this specification and the appended claims mean the presence of the features or components described in the specification, and unless otherwise specifically defined, the possibility of adding one or more other features or components is not precluded in advance.

[0038] In this specification and the appended claims, terms such as "first", "second", etc. are not used in a limiting sense, but are used to distinguish one component from other components.

[0039] The singular expressions in this specification and the appended claims include plural expressions unless otherwise clearly specified as singular. In addition, plural expressions include singular expressions unless otherwise clearly specified as plural.

[0040] In this specification and the appended claims, terms such as "first", "second", etc. are not used in a limiting sense, but are used to distinguish one component from other components.

[0041] In addition, the numerical ranges used in this specification include all values within the range, including the lower and upper limits, increments derived from the form and span logic defining the range, all doubly-defined values, and all possible combinations of the upper and lower limits in numerical ranges defined in different forms. Unless otherwise defined in the specification of the present invention, values that may exceed the numerical range due to experimental errors or rounding of values are also included in the defined numerical range.

[0042] Degree terms such as "about" used in this specification and the appended claims are used to indicate the meaning of covering the allowable error when there is an allowable error.

[0043] The present invention will be described in more detail below with reference to the accompanying drawings.

[0044] To prepare vinyl oligomers, ethylene, a solvent, and a catalyst are added to a reactor for oligomerization reaction. Through the trimerization and tetramerization reactions of ethylene, in addition to target substances such as α-olefins like 1-hexene and 1-octene, polymers such as polyethylene can also be produced as by-products. The by-product polyethylene accumulates on the inner wall or pipes of the reactor as the reaction continues, causing pipe blockages, reducing the fluid velocity, and acting as a heat insulator, interfering with the heat transfer of the reactor. Therefore, it is very important to remove the polymer accumulated on the inner wall of the reactor.

[0045] However, as Figure 1 shown, in traditional and common ethylene oligomerization reaction processes, since there is no separate process to remove the polymer generated in the inner wall of the reactor, it is necessary to stop the process and open the reactor, and workers enter the reactor to directly remove the polymer. This method requires a large amount of manpower, increases working hours, and requires additional processes (such as removing impurities from the reactor to restart the process and then purging with an inert gas), resulting in very poor process efficiency and economic feasibility.

[0046] Therefore, after in-depth research, the applicant of the present invention invented a method for removing polymers in an olefin oligomerization reactor that improves the solvent recovery rate by recycling the solvent used in the reaction into the reactor without opening the reactor to dissolve the polymer accumulated on the inner wall of the reactor, thereby removing the polymer remaining on the inner wall of the reactor, and effectively separating the polymer from the solvent by rapidly cooling the solvent in which the polymer is dissolved.

[0047] The present invention will be described in more detail below with reference to the accompanying drawings.

[0048] As Figure 2As shown, the method for removing polymers in an oligomerization reactor according to the present invention includes: (a) preparing vinyl oligomers from reactants including ethylene, a solvent, and a catalyst in a reactor; (b) removing the polymers included in the oligomer product solution; (c) distilling the oligomer product solution from which the polymers have been removed in step (b) in a distillation column to separate the solution into hydrocarbons having 4 or fewer carbon atoms, 1-hexene, 1-octene, hydrocarbons having 10 or more carbon atoms, and a solvent; (d) recycling a part of the heated solvent obtained by heating a part of the solvent separated in step (c) to the reactor to dissolve the residual polymers in the reactor and prepare a polymer-dissolved solution; (e) mixing the polymer-dissolved solution with the remaining recycled solvent in step (c) and rapidly cooling the polymer-dissolved solution to precipitate the polymers; and (f) separating the polymers from the solvent in the polymer-dissolved solution in which the polymers have precipitated.

[0049] In step (a), reactants including ethylene, a solvent, and a catalyst may be added to the reactor 110 to form vinyl oligomers through an oligomerization reaction.

[0050] The solvent may include aliphatic hydrocarbons or aromatic hydrocarbons. Specifically, the aliphatic hydrocarbon solvent may be an aliphatic hydrocarbon solvent having 3 to 20 carbon atoms or an aromatic hydrocarbon solvent having 6 to 20 carbon atoms.

[0051] More specifically, the hydrocarbon solvent may be selected from the group consisting of toluene, xylene, chlorobenzene, dichlorobenzene, dichloromethane, hexane, methylcyclohexane, and cyclohexane. Preferably, the solvent may include methylcyclohexane. When using the solvent, the polymerization activity may be high, the product after the olefin oligomerization reaction is easily separated from the solvent, and the polymer is easily dissolved.

[0052] The catalyst may be a catalyst used in common olefin oligomerization processes, but preferably may include a chromium-based catalyst. The reactants may further include a cocatalyst. For example, the cocatalyst may include an organoaluminum compound, but the present invention is not limited thereto. By including the catalyst, vinyl oligomers can be prepared with high selectivity, conversion rate, and excellent catalytic activity even at low temperatures.

[0053] In step (a), the reactants are added to the reactor 110 to enable the trimerization and tetramerization reactions of ethylene. Among them, before injecting ethylene and the solvent into the reactor 110, a pretreatment process may be performed. The pretreatment process can generally be carried out through an adsorption process, and oxygen and moisture contained in ethylene and the solvent can be removed through the pretreatment process.

[0054] A plurality of reactors may be included, and the plurality of reactors may be arranged in parallel. Among the plurality of reactors arranged in parallel, a part is subjected to an oligomerization reaction process. At the same time, in the reactors that are not subjected to the oligomerization reaction process, the polymers accumulated on the inner wall of the reactor are removed to clean the reactor.

[0055] More specifically, referring to Figure 3 , the second reactor 110 performs an oligomerization process through multiple reactors, and during the preparation of vinyl oligomers, a process of removing polymers can be carried out, in which polyethylene accumulated on the inner wall of the first reactor 100 is removed. Conversely, when the process of preparing vinyl oligomers is carried out in the first reactor 100, the process of removing polyethylene can be carried out in the second reactor 110.

[0056] In addition, as Figure 5 shown, the three reactors can be arranged in parallel. The ethylene oligomerization process is carried out in the second reactor 110 and the third reactor 120, while the process of removing polymers accumulated on the inner wall of the reactor is carried out in the first reactor 100, so as to continuously prepare α-olefins. Therefore, since the process of preparing oligomers and the process of removing polymers can be carried out continuously and simultaneously without stopping the process, the process efficiency can be improved.

[0057] The reactor can be one or more reactors selected from the group consisting of a batch reactor, a continuous stirred tank reactor, a tubular reactor, a loop reactor, a bubble cap reactor, and a fluidized bed reactor, and preferably a continuous stirred tank reactor can be used.

[0058] The oligomer product solution prepared in step (a) may include α-olefins (including 1-hexene and 1-octene), unreacted ethylene, polyethylene, and methylcyclohexane. In addition to α-olefins as the target materials, polymers including polyethylene are also generated, and these polymers accumulate on the inner wall of the reactor and in the pipeline, resulting in process interruption. Therefore, since the solvent used in the oligomerization process is recycled and the polymers in the reactor are rapidly removed (as described below), fouling can be effectively inhibited without interrupting the process.

[0059] After step (a), it may further include a step of injecting a catalyst deactivator into the oligomer product solution by using a catalyst deactivator injector 150 to deactivate the catalyst. The catalyst deactivator injector 150 can be placed at the front end or the rear end of the polymer removal device 200. After the residual catalyst contained in the oligomer product solution is deactivated by the catalyst deactivator, the residual catalyst and the catalyst deactivator can be discharged from the polymer removal device 200 to improve the solvent recovery efficiency.

[0060] The catalyst deactivator can be any material known in the art. Specifically, the catalyst deactivator may include water, an alcohol-based compound, or a combination thereof, and preferably may include 2-ethylhexanol as the alcohol-based compound.

[0061] The polyethylene contained in the oligomer product solution described above can be removed in step (b) using the polymer removal device 200. The polymer removal device 200 can use one selected from centrifugal separation, pressure filtration, gravity filtration, metal filters, ceramic membrane filters, sand filters, and adsorption devices to remove polyethylene, but the present invention does not limit the specific type of the polymer removal device 200.

[0062] In an exemplary embodiment, after step (b), it may further include a step of using a gas-liquid separator 300 to remove unreacted ethylene included in the oligomer product solution from which the polymer has been removed. The unreacted ethylene separated in the gas-liquid separator 300 is recycled to the reactor and reused for the ethylene oligomerization reaction in step (a). As a non-limiting example, a plurality of gas-liquid separators 300 can be installed continuously.

[0063] After the step of removing unreacted ethylene, the polymer removal device 200 can be further provided to further perform step (b). A plurality of polymer removal devices 200 can be provided to effectively remove the polyethylene included in the oligomer product solution.

[0064] In an exemplary embodiment, in step (c), the oligomer product solution from which polyethylene and unreacted ethylene have been removed can be distilled in the distillation column of the distillation device 500 to separate the solution into hydrocarbons having 4 or less carbon atoms, 1-hexene, 1-octene, hydrocarbons having 10 or more carbon atoms, and a solvent. Hydrocarbons having 4 or less carbon atoms may include hydrogen, ethylene, and 1-butene, and the distillation device 500 may include a plurality of distillation columns and separate the oligomer product solution according to the boiling point.

[0065] In an exemplary embodiment, in step (d), a part of the solvent separated in the distillation device 500 in step (c) is heated to form a heated recycled solvent, the heated recycled solvent is recycled to the reactor, and the residual polyethylene accumulated on the inner wall of the reactor 100 can be dissolved with the heated recycled solvent to prepare a polymer solution.

[0066] Among them, it is preferably achieved by heat exchange with the high-temperature hydrocarbons having 10 or more carbon atoms separated in the distillation device 500 using the heat exchanger 800 to heat the solvent. Conventionally, low-pressure steam has been mainly used to heat the solvent. When a part of the solvent separated using low-pressure steam is heated to a high temperature, a large amount of fluid is required. However, when the solvent is heated using the heat exchanger 800 as in the present invention, the solvent can be heated to a high temperature using only a significantly smaller amount of fluid compared to low-pressure steam, which is advantageous.

[0067] In an exemplary embodiment, in step (d), the flow rate ratio of a portion of the separated solvent to the C10 or higher hydrocarbon can be 1:0.5 to 3, 1:0.7 to 3, or 1:1 to 3, preferably 1:1 to 2. At this flow rate ratio, the solvent can be heated to a temperature at which the solvent can dissolve the polymer.

[0068] More specifically, the temperature of the C10 or higher hydrocarbon can be 150 to 300 °C, 160 to 270 °C, 170 to 240 °C, or 180 to 220 °C, and can substantially be 190 to 200 °C. The temperature of the heated recycled solvent heated by heat exchange with the C10 or higher hydrocarbon within the above temperature range can be 50 to 200 °C, 55 to 180 °C, or 60 to 150 °C, and the solvent can substantially be heated to 70 °C to 110 °C to easily dissolve the polyethylene accumulating on the inner wall of the reactor.

[0069] By heat exchange with the C10 or higher hydrocarbon, the solvent can be simply heated without adding a separate heating process and equipment, effectively saving the energy used in the oligomerization reaction process.

[0070] In an exemplary embodiment, by heat exchange with the solvent, the C10 or higher hydrocarbon can be cooled to 250 °C or lower, 230 °C or lower, 200 °C or lower, 180 °C or lower, 150 °C or lower, or 130 °C or lower, and advantageously 100 °C or lower. By using the process of heat exchange with the solvent in the heat exchanger 800, the amount of cooling water used can be significantly reduced. Generally, an additional cooling process is required to store the C10 or higher hydrocarbon at a high temperature. However, when using the heat exchanger 800 for heat exchange with the solvent, the C10 or higher hydrocarbon is cooled to about 100 °C or lower to reduce the amount of cooling water used, which is advantageous in terms of energy efficiency.

[0071] In an exemplary embodiment, in step (e), the polymer dissolution solution obtained by dissolving the residual polyethylene accumulating on the inner wall of the reactor 100 can be mixed with the remaining recycled solvent separated in the distillation apparatus 500, and the polymer dissolution solution can be rapidly cooled to precipitate the polyethylene.

[0072] In the step of rapidly cooling the polymer dissolution solution, an additional cooling source may not be required. Since the recycled solvent remaining after use in the oligomer preparation reaction can be used without providing a separate cooling solution for rapid cooling, excellent energy efficiency and economic feasibility can be provided.

[0073] In an exemplary embodiment, the temperature of the remaining recycled solvent may be 30 to 70 °C, 35 to 65 °C, 40 to 60 °C, 45 to 55 °C, or 45 to 50 °C. When the temperature is lower than that of the recycled solvent of the polymer dissolution solution when they are mixed, the polymer dissolution solution is rapidly cooled, so that the polymer in the solution rapidly aggregates. The aggregated polymer can precipitate, and polyethylene can be separated from the solvent and easily removed.

[0074] The mixing ratio of the polymer dissolution solution and the remaining recycled solvent can be mixed at a mixing ratio of 1:1 to 7, 1:1 to 6, or 1:2 to 5, preferably at a mixing ratio of 1:2 to 4. By mixing the polymer dissolution solution and the remaining recycled solvent in this ratio, the polymer dissolution solution can be rapidly cooled to ensure a cooling temperature at which polyethylene is easily precipitated.

[0075] Specifically, the temperature of the polymer dissolution solution after rapid cooling can be 20 to 80 °C, 30 to 77 °C, 40 to 75 °C, 50 to 75 °C, or 60 to 70 °C.

[0076] When the polymer dissolution solution at a high temperature cools naturally, the polymer does not aggregate well and is dispersed in the solvent in the form of, for example, a gel, so it may be difficult to separate and remove the polymer from the solvent. However, when the polymer dissolution solution and the remaining recycled solvent are rapidly cooled at a low temperature, the polymer can easily aggregate into a solid phase. Since the size of the polymer particles aggregated in the rapidly cooled polymer dissolution solution is larger than that of the polymer particles in the polymer dissolution solution cooled naturally, the polymer can be easily separated and removed from the solvent.

[0077] In an exemplary embodiment, in the solvent separated in step (c), the flow rate ratio of the heated recycled solvent to the remaining recycled solvent can be 1:20 to 150, 1:30 to 140, 1:40 to 130, or 1:50 to 120. The solvent is separated at the flow rate ratio, and the residual polymer in the inner wall of the reactor 100 is removed with the heated recycled solvent to prepare a polymer dissolution solution, and the polymer dissolution solution is rapidly cooled with the remaining recycled solvent to make the polymer easy to precipitate.

[0078] In another exemplary embodiment, in step (d), it may further include the step of conveying a part of the heated recycled solvent to a polymer removal device to prepare a polymer dissolution solution, wherein the residual polymer is dissolved in the polymer removal device.

[0079] Specifically, referring to Figure 6, it may further include a first transfer pipeline - through which a part of the heat-recovered solvent is transferred to the polymer removal device 200, and a second transfer pipeline - through which the polymer-dissolved solution generated in the polymer removal device 200 is transferred to the polymer precipitation device 600.

[0080] A part of the heat-recovered solvent recycled to the reactor 100 can be transferred to the polymer removal device 200 to dissolve the polymer accumulated on the inner wall of the polymer removal device 200. The generated polymer-dissolved solution can move from the polymer removal device 200 to the polymer precipitation device 600 through the second transfer pipeline. The polymer-dissolved solution transferred to the polymer precipitation device 600 can be precipitated by rapid cooling, and the polymer can be separated and removed from the polymer-dissolved solution.

[0081] When the method for removing polymers in the oligomerization reactor of the present invention is used in the olefin oligomerization process, it is also beneficial to easily remove the polymers accumulated in the plurality of polymer removal devices 200 and the first reactor 100 and the second reactor 110 by using the heat-recovered solvent.

[0082] In an exemplary embodiment, in step (f), in the polymer-dissolved solution in which the polymer is precipitated by rapid cooling in step (e), the polymer can be separated from the solvent by a polymer separator 700.

[0083] The solvent separated by the polymer separator 700 can be recycled to step (a) and reused for preparing vinyl oligomers. When the solvent obtained after passing through the polymer separator 700 is recycled and reused in the oligomerization reaction, there is no need for a separate pretreatment process to remove the oxygen and moisture contained in the solvent, which is more efficient.

[0084] As a non-limiting example, a plurality of polymer separators 700 can be arranged in parallel, so that the polymer removal effect can be further improved.

[0085] In an exemplary embodiment, the polymer separator 700 can include one selected from a centrifuge, a three-phase separator, a filter press, a screw press, a screw decanter, a sieve, a rotary drum flaker, and a filter, but the present invention is not limited thereto.

[0086] The present invention will be described in detail below through examples and comparative examples.

[0087] (Preparation Example 1)

[0088] The oligomerization reaction process and the polymer removal process in the reactor are carried out according to Figure 2 the process diagram shown.

[0089] Steps for preparing vinyl oligomer

[0090] 1.5 liters per hour of methylcyclohexane, 250 grams per hour of ethylene, 0.02 micromoles per hour of catalyst, and 7 micromoles per hour of cocatalyst are injected into the first reactor 100 and the second reactor 110. Both the first reactor 100 and the second reactor 110 are 2-liter continuous stirred tank reactors heated to 40°C. While maintaining the reaction temperature at 40°C, ethylene is continuously introduced to keep the internal pressure of the reactor at 30 bar, and the reaction proceeds for 90 hours. Then, the injection of reactants into the first reactor 100 is stopped, and the product in the reactor is discharged to end the reaction.

[0091] Steps for removing and precipitating residual polymer in the reactor

[0092] After the oligomer preparation step, the product is separated into low-boiling hydrocarbons with C4 or lower, 1-hexene, 1-octene, high-boiling hydrocarbons with C10 or higher, and methylcyclohexane. A heated recycled solvent heated to 110°C by heat-exchanging a part of the separated methylcyclohexane with the high-boiling hydrocarbons is injected into the first reactor and stirred for 20 minutes to prepare a polymer dissolution solution that dissolves the residual polyethylene accumulated in the reactor.

[0093] Subsequently, the polymer dissolution solution is mixed with the remaining recycled methylcyclohexane to rapidly cool the polymer dissolution solution. The rapid cooling is carried out for about 10 minutes, and polyethylene precipitates from the cooled polymer dissolution solution. In the polymer dissolution solution containing the precipitated polyethylene, polyethylene is separated from methylcyclohexane by a centrifuge.

[0094] The composition of the product obtained during the oligomerization reaction was analyzed, and the heat and material balances in the polymer removal device 200, the gas-liquid separator 300, the distillation device 500, and the heat exchanger 800 were derived using chemical process simulation software (Aspen Plus v.11).

[0095] The temperature of the remaining recycled methylcyclohexane obtained by the process simulation software is 52°C, and the temperature of the hydrocarbons with C10 or higher discharged from the lower part of the high-boiling separation distillation column is 196°C.

[0096] (Example 1)

[0097] When the ethylene oligomerization process is carried out according to the method of Preparation Example 1, a part of the separated methylcyclohexane is heat-exchanged with the high-boiling hydrocarbons with C10 or higher at a flow rate ratio of 1:2 to prepare a heated recycled solvent. In addition, during the rapid cooling of the polymer dissolution solution in the polymer precipitation device 600, the polymer dissolution solution is mixed with the remaining recycled methylcyclohexane at a mixing ratio of 1:2 to carry out the ethylene oligomerization process.

[0098] (Example 2)

[0099] The ethylene oligomerization process is carried out in the same manner as in Example 1, except that during the rapid cooling in the polymer precipitation device 600, the polymer dissolved solution is mixed with the remaining recycled methylcyclohexane at a ratio of 1:1.

[0100] (Example 3)

[0101] The ethylene oligomerization process is carried out in the same manner as in Example 1, except that during the rapid cooling in the polymer precipitation device 600, the polymer dissolved solution is mixed with the remaining recycled methylcyclohexane at a ratio of 1:3.

[0102] (Example 4)

[0103] The ethylene oligomerization process is carried out in the same manner as in Example 1, except that during the rapid cooling in the polymer precipitation device 600, the polymer dissolved solution is mixed with the remaining recycled methylcyclohexane at a ratio of 1:4.

[0104] (Example 5)

[0105] The ethylene oligomerization process is carried out in the same manner as in Example 1, except that during the rapid cooling in the polymer precipitation device 600, the polymer dissolved solution is mixed with the remaining recycled methylcyclohexane at a ratio of 1:5.

[0106] (Comparative Example 1)

[0107] The ethylene oligomerization process is carried out in the same manner as in Example 1, except that the polymer dissolved solution is naturally cooled from room temperature to 25 °C in the polymer precipitation device 600.

[0108] (Comparative Example 2)

[0109] The ethylene oligomerization process is carried out in the same manner as in Example 1, except that a part of the separated methylcyclohexane is heated with low-pressure steam to prepare a heated recycled solvent. The pressure of the low-pressure steam is 3.3 bar (gauge pressure) and the temperature is 147 °C.

[0110] (Experimental Example 1) Evaluation of polymer aggregation based on the cooling rate of the polymer dissolution solution

[0111] The ethylene oligomerization process is carried out according to Example 1 and Comparative Example 1, and the aggregation of the cooled polymer dissolved solution is observed. As Figure 4 shown, the amount of the polymer separated in the polymer separator 700 is as shown in Table 1 below.

[0112] [Table 1]

[0113] Amount of precipitated polymer (g) Example 1 7.8 Comparative Example 1 3.2

[0114] As Figure 4 shown, it was confirmed that in the polymer dissolution solution (a) rapidly cooled according to Example 1, the polymer aggregated and separated into the polymer and the solvent. However, in the polymer dissolution solution (b) naturally cooled according to Comparative Example 1, the solvent and the polymer did not separate, and the polymer was dispersed in the solvent in the form of a gel. When the polymer dissolution solution was naturally cooled as in Comparative Example 1, the size of the aggregated polymer particles was very small and dispersed in the solvent, making it difficult to separate the polymer from the solvent. Therefore, compared with Example 1, the amount of the polymer precipitated in the polymer separator 700 was very small.

[0115] However, in the polymer dissolution solution rapidly cooled in Example 1, the polymer aggregated and separated from the solvent, and the size of the aggregated polymer particles was large, so that the solvent and the polymer were easily separated in the polymer separator 700, and the polymer was easily removed. As the amount of the polymer separated in the polymer separator 700 increased, the amount of the solvent recovered into the reactor also increased. The solvent recovered into the reactor can be reused for the ethylene oligomerization reaction, which is advantageous.

[0116] (Experimental Example 2) Evaluation of the cooling temperature based on the mixing ratio of the heated recycled solvent and the polymer dissolution solution

[0117] In the ethylene oligomerization processes according to Examples 1 to 4, during the rapid cooling of the polymer dissolution solution, the temperature after mixing according to the mixing ratio of the remaining recovered solvent and the polymer solution was derived by chemical process simulation software (Aspen Plus v.11) as shown in Table 2 below.

[0118] [Table 2]

[0119] Polymer dissolution solution: Remaining recycled solvent Temperature after mixing (°C) Example 1 1:2 70 Example 2 1:1 81 Example 3 1:3 66 Example 4 1:4 62 Example 5 1:5 60

[0120] [[ID=2,23]]In all cases of Examples 1 to 5, when the remaining recovered solvent and the polymer dissolution solution were mixed at 110°C, it was confirmed that the polymer dissolution solution was rapidly cooled, thereby forming a temperature at which the polymer in the polymer dissolution solution could precipitate.

[0121] As Figure 4 shown in (a) below, in Example 1, the polymer dissolution solution was rapidly cooled to 70°C, and the particle size of the aggregated polymer increased. Therefore, the precipitated polymer was easily separated in the polymer separator 700.

[0122] When the polymer dissolution solution is rapidly cooled, as the amount of the remaining recycled solvent to be mixed increases, the temperature of the mixed polymer dissolution solution decreases. In Examples 1 and 3 to 5, where the amount of the remaining recycled solvent to be mixed is twice the amount of the polymer dissolution solution, the polymer dissolution solution is rapidly cooled, enabling the temperature at which the polymer can effectively aggregate to be ensured.

[0123] In addition, in Example 1, although a smaller amount of the remaining recycled solvent is mixed with the polymer dissolution solution compared to Examples 3 to 5, the polymer dissolution solution is rapidly cooled to a temperature at which the polymer is prone to precipitate. Therefore, Example 1, in which the mixing ratio of the polymer dissolution solution to the remaining recycled solvent is 1:2, saves the amount of the remaining recycled solvent, providing excellent economic feasibility.

[0124] (Experimental Example 3) Evaluation of the required amount of heating fluid based on the fluid heating part of the solvent

[0125] When the ethylene oligomerization process is carried out according to the methods of Example 1 and Comparative Example 2, the amount of the heating fluid required according to the method for heating a part of the methylcyclohexane separated in the distillation apparatus 500 is derived by a chemical process simulation software (Aspen Plus v.11), as shown in Table 3 below.

[0126] [Table 3]

[0127]

[0128] When a part of the methylcyclohexane separated in the distillation apparatus is heated at the same temperature (110 °C), it is confirmed that the amount of the heating fluid required in Example 1 is significantly reduced compared to Comparative Example 2. The results of the process simulation show that since the temperature of the C10 or higher hydrocarbons in Example 1 (196 °C) is higher than that of the low-pressure steam (147 °C), the solvent can be heated to a high temperature with only a small amount of fluid.

[0129] To heat the solvent using low-pressure steam as in Comparative Example 2, additional equipment is required, and a large amount of fluid and energy are also consumed. However, when the oligomerization reaction process is carried out according to the method of Example 1, the solvent can be heated to the target temperature with only a small amount of fluid and energy through the process of heat exchange with the C10 or higher hydrocarbons generated in the process using a heat exchanger.

[0130] In addition, the C10 or higher hydrocarbons at a high temperature are also cooled from 196 °C to about 100 °C only through the heat exchange process with the solvent, without using a separate cooling water for cooling. Therefore, it is advantageous that the amount of the fluid required to heat the solvent, the amount of the cooling water, and the energy consumption can be saved.

[0131] Above, although the present invention has been described through specific matters, limited exemplary embodiments, and the accompanying drawings, they are only used to assist in the overall understanding of the present disclosure, and the present disclosure is not limited to the exemplary embodiments, and those skilled in the art to which the present disclosure pertains can make various modifications and changes according to the description.

[0132] Therefore, the spirit of the present invention should not be limited to the above exemplary embodiments, and the following claims and all modifications equivalent or equivalent to the claims are intended to fall within the scope and spirit of the present invention.

[0133] [Detailed Description of Main Components]

[0134] 100: First Reactor 110: Second Reactor

[0135] 120: Third Reactor 150: Catalyst Deactivator Injector

[0136] 200: Polymer Removal Device 300: Gas-Liquid Separator

[0137] 500: Distillation Device 600: Polymer Precipitation Device

[0138] 700: Polymer Separator 800: Heat Exchanger

[0139] 900: Valve.

Claims

1. A method for removing polymers in an oligomerization reactor, the method comprising: (a) preparing vinyl oligomers in a reactor from reactants including ethylene, a solvent, and a catalyst; (b) removing the polymers included in the oligomer product solution; (c) distilling the oligomer product solution from which the polymers have been removed in (b) to separate the solution into hydrocarbons having 4 or fewer carbon atoms, 1-hexene, 1-octene, hydrocarbons having 10 or more carbon atoms, and a solvent; (d) recycling a part of the solvent separated in (c) that has been heated to obtain a heated recycled solvent to the reactor to dissolve residual polymers in the reactor and prepare a polymer dissolution solution; (e) mixing the polymer dissolution solution with the remaining recycled solvent in (c) and rapidly cooling the polymer dissolution solution to precipitate the polymers; and (f) separating the polymers from the solvent in the polymer dissolution solution in which the polymers have precipitated.

2. The method for removing polymers in an oligomerization reactor according to claim 1, wherein in (d), a part of the separated solvent is heated by heat exchange with the hydrocarbons having 10 or more carbon atoms separated from the distillation column.

3. The method for removing polymers in an oligomerization reactor according to claim 1, wherein in (d), the temperature of the heated recycled solvent is 50°C to 200°C.

4. The method for removing polymers in an oligomerization reactor according to claim 2, wherein in (d), the temperature of the hydrocarbons having 10 or more carbon atoms is 150 to 300°C.

5. The method for removing polymers in an oligomerization reactor according to claim 4, wherein in (e), the temperature of the remaining recycled solvent is 30 to 70°C.

6. The method for removing polymers in an oligomerization reactor according to claim 4, wherein in (e), the temperature of the rapidly cooled polymer dissolution solution is 20 to 80°C.

7. The method for removing polymers in an oligomerization reactor according to claim 1, wherein in (e), the mixing ratio of the polymer dissolution solution to the remaining recycled solvent is 1:1 to 7.

8. The method for removing polymers in an oligomerization reactor according to claim 2, wherein in (d), the flow rate ratio of a part of the separated solvent to the hydrocarbons having 10 or more carbon atoms is 1:0.5 to 3.

9. The method for removing polymers in an oligomerization reactor according to claim 1, wherein in the solvent separated in (c), the flow rate ratio of the heated recycled solvent to the remaining recycled solvent is 1:20 to 150.

10. The method for removing polymers in an oligomerization reactor according to claim 1, wherein in (e), the polymer dissolution solution and the remaining recycled solvent are mixed in a polymer precipitation device.

11. The method for removing polymers in an oligomerization reactor according to claim 1, wherein in (f), the solvent separated in the polymer separator is recycled and reused for the oligomerization reaction in (a).

12. The method for removing polymers in the oligomerization reactor according to claim 1, further comprising: After (b), an unreacted monomer is separated from the oligomer from which the polymer has been removed using a gas-liquid separator, and the monomer is recycled to the monomer recovery step of the reactor.

13. The method for removing a polymer from an oligomerization reactor according to claim 1, wherein the solvent comprises an aliphatic hydrocarbon or an aromatic hydrocarbon.

14. The method for removing a polymer from an oligomerization reactor according to claim 1, wherein in (a), a plurality of reactors are included.

15. The method for removing a polymer from an oligomerization reactor according to claim 14, wherein the plurality of reactors are arranged in parallel.

16. The method for removing polymers in an oligomerization reactor according to claim 1, further comprising: After (d), a part of the heated recycled solvent is fed to a polymer removal device, and the residual polymer in the polymer removal device is dissolved to prepare a polymer dissolution solution.

17. The method for removing polymers in an oligomerization reactor according to claim 1, further comprising: After (a), a catalyst deactivator is injected into the oligomer product solution.

18. The method for removing a polymer from an oligomerization reactor according to claim 17, wherein the catalyst deactivator comprises water, an alcohol-based compound, or a combination thereof.

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