Olefin gas purification method and polyolefin production method

Abstract

To provide a refining method which can suppress blockage of a refining system becoming an obstruction factor of long-term continuous operation, in a continuous process for removing precipitation of an organic aluminum component by bringing olefin gas containing the organic aluminum component into contact with water.SOLUTION: In a method for refining olefin gas, olefin gas 30 containing an organic aluminum component is brought into contact with water inside a scrubber 1, in order to remove the organic aluminum component. In the method for refining olefin gas, a surface 20 of a gas outlet peripheral edge part of a gas nozzle 10 for supplying the olefin gas to the scrubber has a contact angle 80° or larger relative to water.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a process technology for continuously removing organoaluminum components from an olefin gas containing such components. More specifically, the present invention relates to a purification method for removing organoaluminum components contained in unreacted olefin gas recovered from an olefin polymerization reactor for ethylene, propylene, or the like, and a method for producing polyolefins using the same. [Background technology]

[0002] Methods for polymerizing olefins, such as ethylene and propylene, using solid catalysts containing transition metal components are widely known. Known methods for polymerizing these olefins include slurry polymerization, in which polymerization is carried out in an inert hydrocarbon solvent, bulk polymerization, in which polymerization is carried out in a liquefied monomer such as liquefied propylene, and gas-phase polymerization, in which polymerization is carried out in a gas phase in the substantial absence of a liquid phase. Gas-phase polymerization has come to be widely used because it has been possible to achieve improved polymerization activity, is advantageous in terms of energy costs and plant construction costs, and ensures safety in terms of the amount of hazardous materials possessed.

[0003] Generally, polyolefin polymerization plants are often operated continuously from the viewpoint of economic rationality, and catalysts, monomers, and auxiliary agents such as organoaluminum components are continuously fed to a polymerization reactor, while reaction gas or slurry components are continuously withdrawn together with the granular or powdery polymerization product. The granular or powdery polymerization product is separated, dried, and then sent to a granulator to be made into pellets. Here, the reaction gas or slurry components withdrawn together with the polymerization product contain a large amount of monomer gas, and these gases are usually recycled and fed back to the polymerization reactor for reuse after necessary purification.

[0004] The reaction gas recovered from the polymerization reactor contains organoaluminum components supplied as cocatalysts, silicon compounds supplied to control the polymerization reaction, and the like. These components can clog pipes by precipitating solid products upon contact with alcohols or water, or can cause a decrease in heat transfer performance or blockage in heat exchangers such as reboilers due to the precipitation of solid products. Furthermore, organoaluminum compounds, in particular, can be extremely dangerous because they can ignite when piping or equipment is opened if unintentional concentration occurs during the process. For these reasons, there is a need for an efficient method of removing organoaluminum compounds from the reaction gas.

[0005] To achieve this objective, for example, Patent Document 1 discloses a method for removing organoaluminum components by contact treatment using a silicon oxide-containing compound with an adjusted water content. However, the method disclosed in Patent Document 1 does not necessarily achieve sufficient removal efficiency, and is not necessarily industrially satisfactory from the standpoint of the high pressure loss of the gas flowing through the packed column and the economical costs involved in replacing and installing the silicon oxide-containing compound.

[0006] On the other hand, an alternative treatment process using a scrubber (water washing tower, washing tower) is also known. In a scrubber treatment process, the recovered unreacted olefin gas (olefin gas containing organoaluminum components) is introduced from the bottom of the tower and flows to the top, while water is supplied from the top and middle of the tower and flows down through packing designed to promote gas-liquid contact. The water that flows down is recycled using a pump, but to maintain a constant accumulation concentration of aluminum hydroxide formed in the tower, some of the circulating water is discharged. However, during long-term operation of such a scrubber, solid products derived from organoaluminum precipitate near the insert nozzle for the unreacted olefin gas, which gradually grow and clog the gas flow path. In such cases, the relevant process must be stopped to remove the precipitated solid components, which hinders long-term continuous operation. In order to solve this problem, Patent Document 2 discloses a method characterized by including a step of contacting the unreacted olefin gas and water with each other using a double pipe through which the unreacted olefin gas and water flow respectively in an inner cylindrical tube and an outer cylindrical tube, as a pre-stage before the unreacted olefin gas is introduced into a scrubber. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 8-131707 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-171790 Summary of the Invention [Problem to be solved by the invention]

[0008] However, even when the method disclosed in Patent Document 2 was used, it was not possible to completely prevent clogging of the nozzle for unreacted olefin gas due to adhesion of solid products derived from organoaluminum, and the method was not necessarily satisfactory for achieving long-term continuous operation.

[0009] In view of the above circumstances, an object of the present invention is to provide a purification method which is effective in suppressing the clogging of gas nozzles, which is a factor hindering long-term continuous operation, in a continuous process in which an olefin gas containing an organoaluminum component is brought into contact with water to precipitate and remove the organoaluminum component. Another object of the present invention is to provide a method for efficiently producing polyolefins without long-term plant shutdown by recycling the olefin gas which has undergone this process to a polymerization reactor. [Means for solving the problem]

[0010] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that the clogging of the gas nozzle by the solid product can be suitably suppressed by adjusting the water contact angle to a specific value on the surface of the vicinity where the olefin gas containing an organoaluminum component comes into contact with water, specifically, on the surface of the peripheral portion of the gas outlet of the gas nozzle to which the solid product formed by the reaction of the organoaluminum component with water may adhere. They have also found that continuous and efficient polyolefin production is possible by recycling the olefin gas that has undergone this process to a polymerization reactor, and have thus completed the present invention.

[0011] The present invention provides a method for purifying an olefin gas, which removes an organoaluminum component from an olefin gas by contacting the olefin gas with water in a scrubber, comprising: The method for purifying an olefin gas is characterized in that the surface of the peripheral edge of the gas outlet of the gas nozzle that supplies the olefin gas to the scrubber has a water contact angle of 80° or more.

[0012] In the method for purifying an olefin gas of the present invention, the surface of the peripheral edge of the gas outlet of the gas nozzle may be made of or coated with a material that has a water contact angle of 80° or more.

[0013] The method for purifying an olefin gas of the present invention may include, since it is expected to complete the reaction between water and an organoaluminum component more efficiently, a gas nozzle configured with a double pipe consisting of an outer cylindrical pipe and an inner cylindrical pipe, the olefin gas is circulated through the inner cylindrical pipe and water is circulated through the outer cylindrical pipe, the length of the inner cylindrical pipe is shorter than that of the outer cylindrical pipe, and the olefin gas is brought into contact with water downstream of the end of the inner cylindrical pipe.

[0014] In the method for purifying an olefin gas of the present invention, the flow rate of the olefin gas flowing through the gas nozzle may be 5 to 20 m / s in order to prevent clogging of the gas nozzle.

[0015] In the method for purifying an olefin gas of the present invention, the olefin gas may contain ethylene or propylene.

[0016] In the method for purifying an olefin gas of the present invention, the organoaluminum component may be at least one selected from the group consisting of alkylaluminum halides, alkylaluminum hydrides, alkylaluminum alkoxides, alumoxanes, trialkylaluminums, complex organoaluminum compounds, and mixtures thereof.

[0017] In the method for purifying an olefin gas of the present invention, the water may be at least one selected from the group consisting of demineralized water, pure water, boiler water, and distilled water, in order to prevent precipitation or deposition of solids and corrosion in the supply pipes and heat exchangers.

[0018] The present invention provides a method for producing a polyolefin, which comprises purifying an olefin gas by the method for purifying an olefin gas of the present invention, and then polymerizing the olefin gas.

[0019] The method for producing a polyolefin of the present invention may include a step of purifying and recovering unreacted olefin gas recovered from a polymerization reactor by the method for purifying an olefin gas of the present invention, and a step of returning the recovered purified olefin gas to the polymerization reactor and polymerizing it. [Effects of the Invention]

[0020] According to the olefin gas purification method of the present invention, the effect of suppressing clogging of the gas nozzle in the purification process of an olefin gas for polymerization is improved, thereby enabling a longer continuous operation. Furthermore, by using the purification process to remove organoaluminum components contained in the olefin gas as residues such as co-catalysts from unreacted olefin gas recovered from a polymerization reactor after an olefin polymerization reaction and then recycling the unreacted olefin gas to the polymerization reactor again, it becomes possible to produce polyolefins more continuously and efficiently than before. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1(A) to (C) are schematic diagrams showing examples of gas nozzle insertion structures in an apparatus used in the purification method of the present invention. [Figure 2] FIG. 2(D) to (E) are schematic diagrams showing other examples of the gas nozzle insertion structure in the apparatus used in the purification method of the present invention. [Figure 3] FIG. 3(F) to (G) are schematic diagrams showing other examples of the gas nozzle insertion structure in the apparatus used in the purification method of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing an example of a gas nozzle in an apparatus used in the purification method of the present invention. [Figure 5] FIG. 5 is a schematic diagram showing an example of a double-pipe gas nozzle in an apparatus used in the purification method of the present invention. [Figure 6] FIG. 6 is a schematic diagram showing an example of the inner tube of a double-tube gas nozzle in the apparatus used in the purification method of the present invention. [Figure 7] FIG. 7 is a schematic diagram showing an example of an outer cylinder of a double-pipe gas nozzle in an apparatus used in the purification method of the present invention. [Figure 8] FIG. 8 is a schematic diagram showing the configuration of an apparatus used in the purification method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The following describes embodiments of the present invention. The scope of the present invention is not limited to these descriptions, and other than the following examples, the present invention can be implemented with appropriate modifications within the scope that does not depart from the spirit of the present invention.

[0023] I. Olefin gas purification method The method for purifying an olefin gas of the present invention is a method for purifying an olefin gas, which comprises contacting an olefin gas containing an organoaluminum component with water in a scrubber to remove the organoaluminum component, and The surface of the peripheral edge of the gas outlet of the gas nozzle that supplies the olefin gas to the scrubber has a water contact angle of 80° or more. The organoaluminum components to be removed in the purification method of the present invention are mainly compounds that are used as cocatalysts, scavengers, etc. in the polymerization of polyolefins and that can become undesirable components contained in the unreacted olefin gas recovered from the polymerization reactor.

[0024] In the "contact treatment of olefin gas with water" in the purification method of the present invention, the contact between water and gas is carried out using at least a scrubber, and there are no limitations on the contacting means or the structure of the equipment. There are also no limitations on the type of gas nozzle that supplies the olefin gas to the scrubber, and it is preferable that the gas introduction direction is not opposite to the water flow.

[0025] 1 to 3 are schematic diagrams showing examples of gas nozzle insertion structures in the apparatus used in the purification method of the present invention, respectively (A) to (G). As the structure of the terminal end of the gas nozzle inserted into the scrubber, for example, a scrubber 1 and a gas nozzle 10 having the structures shown in (A) to (G) of Fig. 1 to Fig. 3 can be used.

[0026] In the present invention, the surface of the peripheral edge of the gas outlet of the gas nozzle, where the olefin gas containing an organoaluminum component comes into contact with water, has a water contact angle of 80° or more. Here, the peripheral edge of the gas nozzle gas outlet where the water contact angle is 80° or more refers to the range where a phenomenon occurs in which a solid product formed by the reaction between the organoaluminum component and water adheres and grows. The surface of the gas nozzle peripheral portion of the gas outlet, which has a water contact angle of 80° or more, may be a surface to which a solid product formed by the reaction between the organoaluminum component and water can adhere.

[0027] The surface of the gas nozzle peripheral portion at the gas outlet, which has a water contact angle of 80° or more, can be appropriately selected based on the fact that it is a surface on which a phenomenon in which a solid product formed by the reaction between the organoaluminum component and water adheres and grows can occur. The surface of the gas nozzle peripheral part of the gas outlet that has a water contact angle of 80° or more can be a surface near the end of the gas nozzle, such as the surface 20 of the gas nozzle peripheral part of the gas outlet in the gas nozzle 10 having the structure shown in Figures 1 to 3 (A) to (G). However, the surface 20 of the gas outlet peripheral portion of the gas nozzle 10 is not limited to (A) to (G) of FIGS.

[0028] The portion of the surface 20 of the gas outlet periphery of the gas nozzle that has a water contact angle of 80° or more includes the inner surface of the terminal end of the gas nozzle where the olefin gas containing an organoaluminum component first comes into contact with water, as well as at least a part of the outer surface of the terminal end of the gas nozzle, as shown in (A) to (G) of Figures 1 to 3. Furthermore, it is effective to target the respective flow paths of the olefin gas and water, and the inner and outer surfaces of the nozzle or piping after contact. For example, the surface of the cover baffle of the scrubber at the periphery of the gas outlet of the gas nozzle in Figures 2(D) and 2(E) is also a surface where a phenomenon in which a solid product resulting from the reaction between the organoaluminum component and water adheres and grows can occur, so the surface 20 at the periphery of the gas outlet of the gas nozzle should have a water contact angle of 80° or more. The surface of the periphery of the gas outlet of the gas nozzle that has a water contact angle of 80° or more may be any surface to which a solid product resulting from the reaction between the organoaluminum component and water can adhere. For example, when the gas nozzle is a single tube, examples of such surfaces include the inner surface at a distance of about 1 to 20 times the tube diameter from the gas outlet of the gas nozzle, the surface at the tip of the gas outlet of the gas nozzle, and the outer surface at a distance of about 1 to 10 times the tube diameter from the gas outlet of the gas nozzle.

[0029] In the present invention, the technical significance of making the surface of the gas outlet peripheral portion of the gas nozzle have a water contact angle of 80° or more is considered to be as follows. Solid products precipitate when organoaluminum components in the gas react with water. The inventors conducted extensive research and found that these solid products are porous and therefore can absorb water by capillary action, leading to repeated deposition and growth upstream in the gas nozzle, which can lead to nozzle clogging. Further research into ways to suppress the adhesion of these solid products to the nozzle or piping led to the discovery that it is effective to construct the surface of the gas nozzle's gas outlet periphery from a material with a water contact angle of 80° or more, or to apply a coating to the surface, thereby completing the present invention. Conventional gas nozzles are made of materials such as carbon steel or stainless steel, and therefore the surface at the end of the gas nozzle typically has a water contact angle of 70° or less, making it highly wettable. In contrast, the surface at the end of the gas nozzle has a water contact angle of 80° or more, making the surface hydrophobic or water-repellent. It is presumed that water is less likely to adhere to a hydrophobic or water-repellent surface, and that the solid product formed by the reaction between the organoaluminum component and water is also less likely to adhere and is more likely to fall off. Therefore, the surface characteristics with the above water contact angle can effectively prevent the product from adhering to the inside of the nozzle, thereby improving the effect of preventing clogging of the gas nozzle, which is a factor hindering long-term continuous operation.

[0030] The surface of the peripheral portion of the gas outlet of the gas nozzle has a water contact angle of 80° or more, but from the viewpoint of improving the effect of suppressing clogging of the gas nozzle, the water contact angle is more preferably 90° or more, even more preferably 100° or more, and still more preferably 105° or more. On the other hand, the water contact angle of the surface of the peripheral portion of the gas outlet of the gas nozzle may be 130° or less. The water contact angle can be measured based on the sessile drop method of JIS R3257. For example, it can be measured using a contact angle meter (DMo-502) manufactured by Kyowa Interface Science Co., Ltd., and the contact angle can be measured 5 seconds after 2 μL of purified water is deposited on a smooth surface at 25° C. and 40% RH.

[0031] In order to achieve a water contact angle of 80° or more, the surface of the gas outlet periphery of the gas nozzle is made of or coated with a material that provides a water contact angle of 80° or more.

[0032] Examples of materials with a water contact angle of 80° or greater include fluororesins such as polytetrafluoroethylene (PTFE). If a nozzle made from these materials is predicted to lack sufficient physical strength under the temperature and pressure conditions of the process, it is possible to incorporate a nozzle with a terminal end made from these materials into a case made of a metal nozzle or metal piping that has sufficient strength. For example, as shown in Figure 4, a nozzle 11 with a terminal end made from these materials can be incorporated into a case 12 made of a metal piping or the like, and together with a short gas inlet tube 13, it can be used to form a gas nozzle 10.

[0033] On the other hand, there are no limitations on the method of coating the surface of the gas outlet periphery to achieve a water contact angle of 80° or more, as long as the desired water contact angle is achieved. For example, particularly good results can be obtained by applying a fluorine-based coating agent for antifouling purposes or by lining with a fluorine-based resin such as Teflon (registered trademark). Examples of fluorine-based coating agents include, but are not limited to, SFE-DP02H, SFE-DP02HL, SNF-DP20H, and HR-FX033E manufactured by AGC Seimi Chemical Co., Ltd. Silicone-based coating agents for antifouling purposes may also be used. The coating or lining method can be appropriately selected from conventionally known methods. The thickness of the coating layer formed by the coating process is not particularly limited, but may be, for example, about 1 μm to 100 μm.

[0034] The contact of the olefin gas with water does not have to be completed in one stage, but may be carried out in two or more stages. When the contact of olefin gas with water is carried out in two or more stages, the surface of the gas nozzle at the gas outlet periphery where the olefin gas containing an organoaluminum component is first contacted with water in at least the first stage should have a water contact angle of 80° or more, because this is likely to cause the phenomenon of solid products formed by the reaction of the organoaluminum component with water adhering and growing. However, when the contact of the olefin gas with water is carried out in two or more stages, if a solid product resulting from the reaction of the organoaluminum component with water may adhere not only in the first stage of contact treatment between the olefin gas and water but also in the second stage and subsequent stages of contact treatment, it is preferable that the surface of the gas outlet periphery of the gas nozzle has a water contact angle of 80° or more.

[0035] When the contact of the olefin gas with water is carried out in two or more stages, for example, the treatment may be carried out by arranging two or more scrubbers in series. Alternatively, the olefin gas may be contacted with water (first step), and then the olefin gas may be supplied to a scrubber and contacted with water (second step). In this case, the first step of contact treatment provides a site for the reaction of the organoaluminum component in the gas with water, and allows the organoaluminum-derived precipitated product to be introduced into the scrubber tower under fluidization conditions caused by the gas, while the second step of contact treatment completes the reaction of the organoaluminum component with water, and allows the precipitated product to be recovered at the bottom of the scrubber tower by spraying water.

[0036] For example, if the gas nozzle is configured with a double pipe consisting of an outer cylindrical pipe and an inner cylindrical pipe, the olefin gas is circulated through the inner cylindrical pipe and water is circulated through the outer cylindrical pipe, the length of the inner cylindrical pipe is shorter than that of the outer cylindrical pipe, and the olefin gas and water are brought into contact with each other downstream of the terminal end of the inner cylindrical pipe, the olefin gas flowing through the first flow path and the water flowing through the second flow path come into contact with each other downstream of the terminal end of the inner cylindrical pipe, thereby achieving more favorable contact. By bringing them into contact in the pipe beforehand and introducing them into the scrubber, it is expected that the reaction between water and the organoaluminum component can be completed more efficiently.

[0037] FIG. 5 is a schematic diagram showing an example of a double-tube gas nozzle in an apparatus used in the purification method of the present invention. In FIG. 5, the gas nozzle 10 is constructed of a double tube consisting of an outer tube 16 and an inner tube 15. The inner tube 15 is shorter than the outer tube 16. By passing the olefin gas through the inner tube and water through the outer tube, the olefin gas and water can be brought into contact with each other downstream of the end of the inner tube. When using such a double-tube gas nozzle, as shown in FIG. 6, in the inner tube 15, not only the inner surface 21 and the tip 23 of the inner tube but also the outer surface 22 of the inner tube correspond to surfaces onto which solid products formed by the reaction between the organoaluminum component and water can adhere, and these correspond to the surface around the gas outlet of the gas nozzle. Therefore, the inner surface 21, outer surface 22, and tip 23 of the inner tube may be made of a material with a water contact angle of 80° or more, or may be coated. As shown in FIG. 7, the inner surfaces 24 and 25 of the outer tube 16 correspond to the surfaces to which the solid product resulting from the reaction between the organoaluminum component and water can adhere, and correspond to the surface of the gas outlet periphery of the gas nozzle. Therefore, the inner surfaces 24 and 25 of the outer tube may be made of a material having a water contact angle of 80° or more, or may be coated.

[0038] The "contact treatment of olefin gas with water" in the purification method of the present invention is not limited to the above-mentioned two-stage embodiment, but can also be a multi-stage treatment of three or more stages. That is, the first stage of contact treatment can be further divided, for example, two or more double-pipe contact portions can be provided. The second stage can also be further divided, for example, two or more scrubbers can be provided.

[0039] The linear velocity of the olefin gas flowing through the nozzle can be designed and operated within the range of typical standard flow velocities, for example, 5 to 20 m / s. Under such conditions, solid products such as precipitated aluminum hydroxide can be transported to the scrubber without accumulating or depositing at the end of the gas nozzle. Inside the scrubber, the reaction is completed by countercurrent contact between water and gas via the packing, and the olefin gas cleaned by the scrubber can be extracted.

[0040] The quality of the water supplied for the contact treatment is not critical as long as it does not substantially contain factors that interfere with the reaction with the organoaluminum component and with the gas cleaning. However, it is preferable to use at least one type of water selected from the group consisting of demineralized water, pure water, boiler water, and distilled water in order to prevent precipitation or deposition of solids and corrosion in the supply piping and heat exchanger.

[0041] The scrubber (water washing tower, washing tower) used in the purification method of the present invention can be one having a general structure known in the art. Commonly used packings such as Raschig rings, Lessing rings, Pall rings, Bell saddles, interlock saddles, and wire structure packing can also be used in the tower. Polypropylene structure packing is particularly preferred, as it has a high porosity and is expected to reduce adhesion and clogging of solid products such as aluminum hydroxide. The packing density is 15,000 to 30,000 packings / m. 3 It is preferable that the packing has a void ratio of 83 to 93%. As for the operating conditions, there is no particular range of conditions that are required as long as the gas flow rate in the column can be controlled to be equal to or lower than the loading speed.

[0042] The water sprayed from the top of the scrubber tower can be recovered from the bottom of the tower and recycled, but in order to suppress the accumulation of solid products such as aluminum hydroxide, a certain amount of water may be replenished and a corresponding amount of process water may be withdrawn. The amount of this make-up water can be determined appropriately based on both the concentration of the organoaluminum component contained in the olefin gas introduced into the tower and the concentration of the aluminum hydroxide component that is acceptable in the step of treating the withdrawn process water.

[0043] The method for purifying an olefin gas according to the present invention can be suitably applied to unreacted olefin gas recovered from a reactor in a process for continuously producing polyolefins such as polyethylene and polypropylene. Accordingly, the olefin gas to be purified by the method of the present invention preferably contains ethylene or propylene.

[0044] The type of polymerization catalyst used in the polyolefin production process is not particularly limited, and known catalysts can be used. For example, so-called Ziegler-Natta catalysts, which combine a titanium compound and an organoaluminum compound, or metallocene catalysts, which combine a metallocene complex and an alumoxane, can be used. Ziegler-Natta catalysts include titanium trichloride or titanium trichloride compositions obtained by reducing a titanium compound with an organoaluminum or the like, and then further activating the titanium trichloride or titanium trichloride compositions by treating them with an electron donor compound, as well as supported catalysts obtained by supporting titanium tetrachloride on a support such as magnesium chloride.

[0045] Examples of organoaluminum compounds used as co-catalysts include trialkylaluminums such as trimethylaluminum, triethylaluminum, and triisobutylaluminum; alkylaluminum halides such as diethylaluminum chloride, diisobutylaluminum chloride, and ethylaluminum sesquichloride; alkylaluminum hydrides such as diethylaluminum hydride; alkylaluminum alkoxides such as diethylaluminum ethoxide; alumoxanes such as methylalumoxane and tetrabutylalumoxane; and composite organoaluminum compounds such as lithiumaluminum tetraethyl. Mixtures of two or more of these compounds may also be used.

[0046] The catalysts described above can also be used with various polymerization additives for the purposes of improving stereoregularity, controlling particle properties, controlling soluble components, controlling molecular weight distribution, etc. Examples of such additives include electron-donating compounds such as organosilicon compounds such as diphenyldimethoxysilane and tert-butylmethyldimethoxysilane, esters such as ethyl acetate, butyl benzoate, methyl p-toluate, and dibutyl phthalate, ketones such as acetone and methyl isobutyl ketone, ethers such as diethyl ether, organic acids such as benzoic acid and propionic acid, and alcohols such as ethanol and butanol.

[0047] The organoaluminum components to be removed in the purification method of the present invention are compounds that are used as cocatalysts, scavengers, etc. in polyolefin polymerization, as described above, and that can become undesirable components contained in the unreacted olefin gas recovered from the polymerization reactor. Therefore, such "organoaluminum components" can be the compounds listed above as examples of cocatalysts, and are typically at least one selected from the group consisting of alkylaluminum halides, alkylaluminum hydrides, alkylaluminum alkoxides, alumoxanes, trialkylaluminums, complex organoaluminum compounds, and mixtures thereof.

[0048] II. Polyolefin manufacturing methods The present invention also provides a method for producing a polyolefin, which comprises purifying an olefin gas by the method for purifying an olefin gas of the present invention, and then polymerizing the olefin gas. The method for producing polyolefins of the present invention preferably includes a step of purifying and recovering unreacted olefin gas recovered from a polymerization reactor by the method for purifying olefin gas of the present invention, and a step of returning the recovered purified olefin gas to the polymerization reactor and polymerizing it. That is, the olefin gas from which the organoaluminum components have been removed through the olefin gas purification method of the present invention can be recycled to a polymerization reactor after undergoing further purification processes such as distillation. This enables continuous and efficient production of polyolefins by removing organoaluminum components contained as residues of co-catalysts and the like from the unreacted olefin gas recovered from the polymerization reactor and then recycling the gas to the polymerization reactor again. [Example]

[0049] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0050] [Example] 60m of olefin gas recovered from a reactor continuously polymerizing propylene using triethylaluminum as a cocatalyst. 3 / h, a purification process using a scrubber was carried out to remove organoaluminum components. The concentration of triethylaluminum in the olefin gas was 140 ppm by mass. The apparatus configuration shown in Figure 8 was used. The scrubber had an inner diameter of 450 mm and was packed with polypropylene Terralet (registered trademark) S-type to a bed height of 4300 mm. As shown in Figure 8, before being supplied to the scrubber, the olefin gas underwent a first-stage contact with water through a double pipe configured so that the olefin gas containing organoaluminum was injected into the inner pipe and demineralized water was injected into the outer pipe. The double-walled pipe consisted of an inner and outer tube, as shown in Figure 5. The outer tube had an outer diameter of 89.1 mm and an inner diameter of 78.1 mm, while the inner tube had an outer diameter of 60.5 mm and an inner diameter of 52.7 mm. A fluorine-based antifouling coating was applied to the inner and outer tubes at the gas outlet periphery, corresponding to the surface 20 shown in Figures 6 and 7. The water contact angle on the fluorine-based antifouling coating surface was 105°. The double-walled pipe was made of carbon steel, but without the antifouling coating, it easily became wet with water, with a water contact angle of nearly 0°. Water was supplied between the outer and inner tubes at a rate of 50 L / h during operation. The flow rate of the olefin gas in the inner tube was approximately 7.6 m / s. The scrubber was operated by recirculating process wastewater recovered from the bottom of the tower using a pump, and purging was performed to maintain a constant amount of retained water in the tower. The concentration of particulate matter with a diameter of 2 mm or less in the purged process water was less than 500 mg / L. Propylene polymerization was carried out under these conditions for one year, and there was no clogging of the olefin gas insert nozzle during the operation, allowing stable operation of the scrubber. Furthermore, the double-walled pipe and the gas supply insert nozzle to the scrubber were opened and inspected, but no solid deposits or clogging were observed.

[0051] [Comparative Example] As a comparative example, a fluorine-based antifouling coating agent was not applied, and the water contact angle on the surface of the gas nozzle's gas outlet periphery was approximately 0°. As a result, approximately three months after the start of operation, olefin gas no longer flowed and operation became impossible. When operation was stopped and the scrubber was opened, it was confirmed that the inner tube of the double-walled tube had become clogged with deposited aluminum hydroxide.

[0052] <Considerations based on comparison between Examples and Comparative Examples> In the comparative example, the olefin gas stopped flowing and operation became impossible about three months after the start of operation, whereas in the example, blockage of the gas flow path was suppressed even after more than one year from the start of operation, demonstrating that long-term continuous operation is possible. Comparison of the results of the example and the comparative example demonstrates the significance of the configuration of the present invention, and furthermore, the superiority of the present invention over the prior art is clear. [Industrial Applicability]

[0053] The olefin purification method of the present invention is useful in the polyolefin production industry because it can prevent clogging of the insert nozzle of the scrubber and enable long-term continuous operation by making the surface of the gas outlet peripheral part of the gas nozzle that supplies olefin gas to the scrubber have a water contact angle of 80° or more. The polyolefin production method according to the present invention is advantageous in that it enables more continuous and efficient polyolefin production than conventional methods, by subjecting unreacted olefin gas recovered from a polymerization reactor after an olefin polymerization reaction to the purification process according to the present invention to remove organoaluminum components contained in the olefin gas as residues such as co-catalysts, and then recycling the gas to the polymerization reactor again. [Explanation of symbols]

[0054] 1 scrubber 10 Gas Nozzle 11 Nozzle with a terminal made of a material with a water contact angle of 80° or more 12 cases 13 Gas inlet short pipe 15 Inner tube 16 Outer tube 20 Surface of the gas outlet periphery 21 Inner surface of inner tube 22 Outer surface of inner tube 23 Tip of inner tube 24 Inner surface of outer tube 25 Inner surface of outer tube 30 Olefin gas containing organoaluminum components 40 water

Claims

1. A method for purifying an olefin gas, which removes organoaluminum components from an olefin gas containing the gas by contacting the gas with water in a scrubber, characterized in that the surface of the peripheral portion of the gas outlet of a gas nozzle that supplies the olefin gas to the scrubber has a water contact angle of 80° or more.

2. 2. The method for purifying an olefin gas according to claim 1, wherein the surface of the peripheral edge of the gas outlet of the gas nozzle is made of or coated with a material that has a water contact angle of 80° or more.

3. 3. The method for purifying an olefin gas according to claim 1 or 2, wherein the gas nozzle is constructed of a double pipe consisting of an outer cylindrical pipe and an inner cylindrical pipe, the olefin gas is passed through the inner cylindrical pipe and water is passed through the outer cylindrical pipe, the length of the inner cylindrical pipe is shorter than that of the outer cylindrical pipe, and the olefin gas is brought into contact with water downstream of the end of the inner cylindrical pipe.

4. 4. The method for purifying an olefin gas according to claim 1, wherein the flow rate of the olefin gas passing through the gas nozzle is 5 to 20 m / s.

5. The method for purifying an olefin gas according to any one of claims 1 to 4, wherein the olefin gas contains ethylene or propylene.

6. The method for purifying an olefin gas according to any one of claims 1 to 5, wherein the organoaluminum component is at least one selected from the group consisting of alkylaluminum halides, alkylaluminum hydrides, alkylaluminum alkoxides, alumoxanes, trialkylaluminums, composite organoaluminum compounds, and mixtures thereof.

7. 7. The method for purifying an olefin gas according to claim 1, wherein the water is at least one selected from the group consisting of demineralized water, pure water, boiler water, and distilled water.

8. A method for producing a polyolefin, comprising purifying an olefin gas by the method for purifying an olefin gas according to any one of claims 1 to 7, and then polymerizing the olefin gas.

9. 9. The method for producing a polyolefin according to claim 8, comprising: a step of purifying and recovering unreacted olefin gas recovered from a polymerization reactor by the method for purifying an olefin gas according to any one of claims 1 to 7; and a step of returning the recovered purified olefin gas to the polymerization reactor and polymerizing it.

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