Recovery polymerization solvent purification agent and method for purifying a recovered polymerization solvent using the same

Abstract

To provide a purifier which can efficiently remove contaminants and impurities in a recovered polymerization solvent that has been used for polymerization and a method for purifying a recovered polymerization solvent using the same.SOLUTION: A purifier for recovered polymerization solvents contains high silica zeolite selected from the group consisting of hydrogen cationic beta zeolite, hydrogen cationic ZSM-5 zeolite and hydrogen cationic Y-type zeolite. There is also provided a method for purifying a recovered polymerization solvent using the same.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a recovery polymerization solvent purifying agent and a method for purifying a recovered polymerization solvent using the same. More specifically, even for a recovered polymerization solvent used in slurry polymerization of olefins in the presence of a solid catalyst containing titanium, magnesium, and a halogen, the present invention relates to a recovery polymerization solvent purifying agent capable of efficiently removing harmful substances and impurities present therein, and a method for purifying a recovered polymerization solvent using the same.

Background Art

[0002] A method of slurry polymerizing olefins in a polymerization solvent using a polymerization catalyst such as a so-called Ziegler-Natta catalyst or a metallocene catalyst, which is a solid catalyst containing titanium, magnesium, and a halogen, is widely used. When slurry polymerization is carried out industrially, from the viewpoints of cost and reduction of waste amount, the solvent after separating the produced polymer is generally recovered and reused for polymerization. The recovered polymerization solvent from which the produced polymer has been separated contains impurities such as raw material residues, by-products, and decomposition products of the catalyst, and there is concern that these may become harmful substances that have various adverse effects on the polymerization reaction. Therefore, except for some cases, it is avoided to use it as it is.

[0003] That is, the purification of the polymerization solvent is important for controlling the polymerization reaction, and polymer manufacturers are making efforts to suppress the influence on the polymerization reaction by making full use of their own purification technologies. In recent years, the amount of catalyst used has been reduced due to the high activation of the polymerization catalyst, and the form of co-producing (swing operation) a metallocene catalyst for producing higher value-added polymers and a conventional Ziegler-Natta catalyst has increased. However, the solvent recovered by the conventional purification method is highly active but tends to deteriorate the performance of the metallocene catalyst, which has low impurity resistance. Therefore, the development of a solvent recovery method capable of more advanced purification has been desired.

[0004] For the purpose of removing and purifying water or alkyl halide contained in a solvent, it has been proposed to use zeolite. For example, a solvent recovered from a product slurry obtained by polymerizing α-olefin using a Ziegler or Wacker catalyst is treated with a synthetic zeolite having pores of 8 Å or more, preferably molecular sieves 10X or molecular sieves 13X (see, for example, Patent Document 1). Also, a method of obtaining a high solvent purification effect by exchanging sodium cations of zeolite with transition metal ions such as iron (see, for example, Patent Document 2). Further, a solvent separated from a slurry obtained by slurry polymerizing α-olefin in the presence of a Ziegler-Natta catalyst is contact-treated with a combination of two types of zeolites having different pore diameters, preferably molecular sieves 10X and molecular sieves 3A, to remove trace amounts of polymerization-inhibiting impurities that could not be removed conventionally (see, for example, Patent Document 3), etc. have been proposed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, any of the proposals in Patent Documents 1 to 3 is for reusing the purified solvent in the slurry polymerization of a Ziegler-Natta catalyst. For example, the applicability to highly active and highly precise polymerization catalysts typified by metallocene catalysts has not been studied. According to the study by the present inventors, a decrease in activity, etc. was observed when applied to a metallocene catalyst or the like.

[0007] Therefore, in the swing operation of polyolefins using a high-performance catalyst typified by a metallocene-based catalyst that enables high-activity and high-precision polymerization and a polyolefin using a conventional Ziegler-Natta catalyst, the emergence of a recovery polymerization solvent purifying agent capable of efficiently removing influencing substances and impurities and a purification method using the same has been desired.

Means for Solving the Problems

[0008] Therefore, the present inventors have proceeded with investigations aiming to establish a method capable of meeting the high requirements for the purification of the recovered polymerization solvent, and have found that a recovery polymerization solvent purifying agent containing a specific hydrogen cation type high-silica zeolite can efficiently purify the recovered polymerization solvent, leading to the completion of the present invention.

[0009] That is, the present invention relates to a recovery polymerization solvent purifying agent characterized by containing a high-silica zeolite selected from the group consisting of a hydrogen cation type beta-type zeolite, a hydrogen cation type ZSM-5 type zeolite, and a hydrogen cation type Y-type zeolite, and a method for purifying a recovered polymerization solvent using the same.

[0010] The present invention will be described in detail below.

[0011] The recovery polymerization solvent purifying agent of the present invention contains a high-silica zeolite selected from the group consisting of hydrogen cation type beta zeolite, hydrogen cation type ZSM-5 zeolite, and hydrogen cation type Y zeolite. Here, zeolite is a general term for crystalline aluminosilicates, and has a chemical composition represented by the general formula Me2 / XO·Al2O3·mSiO2·nH2O (where Me represents an alkali metal or an alkaline earth metal, and X represents the valence of Me), and also has a unique crystal structure that can be identified by X-ray diffraction. Among such zeolites, high-silica zeolites belonging to hydrogen cation type beta zeolite, hydrogen cation type ZSM-5 zeolite, and hydrogen cation type Y zeolite, particularly hydrogen cation type Y zeolite, exhibit excellent performance in purifying the recovered polymerization solvent. Those other than the hydrogen cation type, beta zeolite, ZSM-5 zeolite, and (high-silica) zeolites other than Y zeolite result in insufficient purification of the recovered polymerization solvent.

[0012] There is no limitation on the SiO2 / Al2O3 (molar ratio) of the high-silica zeolite. Among them, those with SiO2 / Al2O3 = 5 to 40 are preferred because they exhibit particularly excellent solvent purification ability, and particularly those with SiO2 / Al2O3 = 5 to 30, 5 to 20, and further 5 to 10 are preferred. Generally, it is known that the higher the molar ratio of SiO2 / Al2O3, the higher the acid strength of the high-silica zeolite. Surprisingly, in the recovery polymerization solvent purifying agent of the present invention, high-silica zeolites having a relatively low molar ratio of SiO2 / Al2O3 exhibit excellent recovered solvent purification ability.

[0013] The high-silica zeolite constituting the recovery polymerization solvent purifying agent of the present invention may be a high-silica zeolite in which a part of the hydrogen cations is replaced with transition metal ions for the purpose of imparting impurity removal ability, high durability, and easy regenerability. For example, it can be prepared by the method described in Japanese Patent Publication No. 1-58202. The exchange rate varies depending on the recovered polymerization solvent species, but generally, it is preferably 40% or less of the total amount of hydrogen cations, particularly preferably 1 to 20%, and further preferably 1 to 10%.

[0014] There are no particular restrictions on the form of the high-silica zeolite that constitutes the recovery polymerization solvent purifying agent of the present invention, and general forms such as powder, granular, and pellet forms can be used. In particular, from the viewpoint of operation, granular or pellet forms are preferred, and from the viewpoint of purification ability, powder forms with a large specific surface area are excellent. When forming pellets, it may further contain binders such as silica, alumina, silica alumina, and clay.

[0015] The high-silica zeolite that constitutes the recovery polymerization solvent purifying agent of the present invention can be obtained by generally known methods. It may also be obtained as a commercially available product. For example, as a hydrogen cation type Y-type high-silica zeolite, (trade name) HSZ-330HUD1A (manufactured by Tosoh Corporation), as a hydrogen cation type beta-type high-silica zeolite, (trade name) HSZ-931HOD1A (manufactured by Tosoh Corporation), as a hydrogen cation type ZSM-5 type high-silica zeolite, (trade name) HSZ-822HOD1A (manufactured by Tosoh Corporation), (trade name) HSZ-840HOD1A (manufactured by Tosoh Corporation), etc. can be mentioned.

[0016] The recovery polymerization solvent purifying agent of the present invention can remove and purify polymerization inhibitor substances and impurities by contacting with the recovered polymerization solvent after the polymerization reaction. At that time, it is preferably subjected to contact treatment at the final stage of the recovery polymerization solvent purification after performing normal purification steps such as filtration, distillation, and water removal of the recovered polymerization solvent. This indicates that the inhibitor substances and impurities that cannot be removed by normal purification treatment can be removed by the recovery polymerization solvent purifying agent of the present invention.

[0017] And as the recovered polymerization solvent by the recovery polymerization solvent purifying agent of the present invention, any polymerization solvent recovered by a polymerization reaction may be used. Among them, it is suitable for those containing by-products due to side reactions and metal-containing substances derived from catalysts. Examples of such polymerization reactions include slurry polymerization for polymerizing olefins in the presence of a Ziegler-Natta catalyst.

[0018] As the Ziegler-Natta catalyst in this case, a solid catalyst containing titanium, magnesium, and halogen can be mentioned. As appropriate, it is used for olefin polymerization in combination with an organoaluminum compound for catalyst activation and / or impurity removal. More specifically, the solid catalyst is a composite solid formed by stepwise or primary contact of a magnesium compound with a titanium compound containing halogen or an addition compound of the compound and an electron donor. Many preparation methods with various devices have been developed for such catalysts. However, in the present invention, it can be applied when using various known ones without particular limitation. Specifically, methods disclosed in Japanese Patent Publication No. 46-34092, Japanese Patent Laid-Open No. 54-41985, Japanese Patent Laid-Open No. 55-729, Japanese Patent Laid-Open No. 55-13709, Japanese Patent Laid-Open No. 57-12006, Japanese Patent Laid-Open No. 57-141409, Japanese Patent Publication No. 4-22163, etc. can be mentioned.

[0019] Examples of the olefin include α-olefins such as ethylene, propylene, butene-1, hexene-1, and octene-1.

[0020] And as the solvent in slurry polymerization, there is no particular limitation as long as it is a hydrocarbon solvent. For example, aliphatic hydrocarbons such as butane, pentane, hexane, heptane, octane, decane, dodecane, and kerosene; aliphatic hydrocarbons having a cyclic structure such as cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; etc. can be mentioned.

[0021] As the recovered polymerization solvent when contacting the recovered polymerization solvent purifying agent of the present invention, in order to make the efficiency in purification more excellent, it is preferable to perform filtration, distillation, water removal, etc. in advance. Particularly, when it is a slurry polymerization in which olefin polymerization is carried out in the presence of a Ziegler-Natta catalyst, it is preferable that the treatments shown in the following 1) to 4) are carried out. 1) After recovering and removing the polymer, hydrolyze the solvent and separate and recover the organic layer. In some cases, adjust the pH of the aqueous layer of the hydrolysis solution. 2) Steam-distill the organic layer recovered in 1) and separate the organic layer from the effluent by liquid separation. 3) Simple distill the organic layer separated in 2). 4) For the purpose of dehydrating the recovered solvent simply distilled in 3), conduct a contact treatment with molecular sieves 3A or 4A.

[0022] And there are no particular restrictions on the conditions when contacting the recovered polymerization solvent, the pretreated recovered polymerization solvent, and the recovered polymerization solvent purifying agent. Among them, since the high-silica zeolite constituting the recovered polymerization solvent purifying agent of the present invention is hydrophobic and also exhibits water removal ability, it is desirable to reduce the water content by dehydration treatment before the treatment. Specifically, it is desirable to set the water content measured by the Karl Fischer method to 20 ppm or less. Also, the treatment temperature can be arbitrarily set in the range of -10°C to 150°C in consideration of the freezing point, boiling point, viscosity, etc. of the recovered polymerization solvent to be treated. Basically, a higher temperature gives preferable results, but sufficient performance can usually be obtained by treating in the range of 25°C to 50°C. Also, in the contact treatment of the recovered polymerization solvent and the recovered polymerization solvent purifying agent of the present invention, care should be taken so that the recovered polymerization solvent purifying agent does not entrap air bubbles. A method of statically immersing the recovered polymerization solvent purifying agent in the recovered polymerization solvent may be used, but in consideration of industrial use, it is preferable to pass the recovered polymerization solvent through a column filled with the recovered polymerization solvent purifying agent so as to be an upflow. The contact time can be adjusted using the column diameter, packing length, and flow rate of the liquid passing through as parameters. The contact time depends on the amount of residual impurities in the recovered solvent. For example, when contacting 5 L of the solvent with 10 g of zeolite, the contact time can be arbitrarily adjusted in the range of 1 second to 24 hours.

[0023] And the recovered polymerization solvent purifying agent of the present invention can have its performance restored and be subjected to recycling by baking at a temperature in the range of 150°C to 700°C under a flow of an inert gas such as nitrogen periodically or when the decrease in activity becomes significant.

[0024] The recovered polymerization solvent purified by the recovery polymerization solvent purifying agent of the present invention can be reused as a polymerization solvent during the polymerization reaction again without affecting the production of the polymer, and can be reused as a polymerization solvent during the slurry polymerization of olefins in the presence of an olefin polymerization catalyst typified by a Ziegler-Natta catalyst and a metallocene catalyst. And it can be applied particularly to the slurry polymerization of olefins by a metallocene catalyst known as an olefin polymerization catalyst having excellent polymerization activity and suitable for precision polymerization. Further, it can also be reused as a reaction solvent for various reactions.

Effect of the Invention

[0025] According to the present invention, it becomes possible to efficiently purify the recovered polymerization solvent, and its industrial value is extremely high.

Examples

[0026] Examples are shown below to explain the present invention in more detail, but the present invention is not limited by these examples.

[0027] Unless otherwise specified, commercially available reagents or those synthesized according to known methods were used.

[0028] Reference Example 1 According to the method described in Japanese Patent Publication No. 4-22163, a Ziegler-Natta catalyst was prepared, and ethylene polymerization was carried out to prepare a polymerization solvent after polymerization.

[0029] (1) Preparation of Ziegler-Natta catalyst 70 g (0.94 mol) of butanol was placed in a 1.6 L autoclave equipped with a stirring device, and 0.55 g of iodine, 11 g (0.45 mol) of metallic magnesium powder, and 61 g (0.18 mol) of titanium tetrabutoxide were added thereto. Further, 450 ml of dry hexane was added, and the temperature was raised to 80°C, followed by stirring for 1 hour under a nitrogen seal while excluding the generated hydrogen gas. Subsequently, the temperature was raised to 120°C and the reaction was carried out for 1 hour to obtain a solution containing magnesium and titanium.

[0030] A solution containing magnesium and titanium corresponding to 0.048 mol in terms of magnesium atoms was added to a flask having an internal volume of 500 ml, and the temperature was raised to 45°C. A hexane solution of tri-i-butylaluminum (0.048 mol) was added over 1 hour. After all had been added, the mixture was stirred at 60°C for 1 hour. Next, 2.8 ml of methylhydropolysiloxane (viscosity at 25°C: 30 centistokes, silicon: 0.048 gram atoms) was added, and the reaction was carried out for 1 hour under reflux. After cooling to 45°C, 82 ml of a 50% hexane solution of i-butylaluminum dichloride was added over 2 hours. After all had been added, the mixture was stirred at 70°C for 1 hour. Hexane was added to the product, and washing was carried out 15 times by the decantation method. A slurry of a solid catalyst (including 9.5 g of the solid catalyst), which is a Ziegler-Natta catalyst containing titanium, magnesium, and halogen and suspended in hexane, was obtained. A part thereof was sampled and subjected to elemental analysis. As a result, the dried solid contained 9.0 wt% of Ti.

[0031] (2) Ethylene polymerization The inside of a 20 L stainless steel autoclave equipped with a stirring device, a thermometer, and a pressure gauge was thoroughly purged with nitrogen, charged with 12 L of hexane, and the internal temperature was adjusted to 80 °C. Thereafter, 2.3 g (12 mmol) of tri-i-butylaluminum and a slurry containing the solid catalyst obtained in the above (1) were sequentially added. After adjusting the internal pressure of the autoclave to 0.1 MPa with nitrogen, hydrogen was added to a pressure of 0.5 MPa, and then ethylene was continuously added while the internal pressure of the autoclave reached 1.1 MPa, and polymerization was carried out for 1.5 hours. After completion of the polymerization, the mixture was cooled, and the slurry containing polyethylene was taken out and filtered to remove solids, and hexane, which is the polymerization solvent after the polymerization reaction, was obtained.

[0032] (3) Pretreatment of the polymerization solvent The solvent containing impurities obtained in (2) was contacted with water for hydrolysis, separated, and the organic layer was recovered. Next, high-boiling impurities were removed by steam distillation. The organic layer was obtained by separating the distillation product, and simple distillation was carried out under a nitrogen atmosphere. Further, dehydration treatment was performed with molecular sieve 3A to obtain hexane (hereinafter, may be referred to as crude hexane), which is the recovered polymerization solvent before purification. When the water content in the crude hexane was measured by the Karl Fischer method, it was 10 ppm. When the crude hexane was analyzed by gas chromatography, peaks other than hexane were observed, confirming the presence of impurities.

[0033] Example 1 5 L of the crude hexane obtained in Reference Example 1 was introduced into a 5 L flask equipped with a stirring device under a nitrogen atmosphere, and 2.5 g of pellet-shaped hydrogen cation type Y-type high silica zeolite (manufactured by Tosoh Corporation, (trade name) HSZ-330HUD1A; SiO2 / Al2O3 molar ratio 6, alumina binder) was added. Thereafter, the mixture was left standing for 24 hours while stirring at room temperature. The water content of the purified hexane had decreased to 6 ppm. Further, the high silica zeolite was slightly yellowish. As a result of analysis by gas chromatography, no peaks other than hexane were observed. The evaluation results and the like are shown in Table 1.

[0034] Example 2 A column for chromatography with a diameter of 2.2 cm was filled with pellet-shaped hydrogen cation type Y-type high-silica zeolite (manufactured by Tosoh Corporation, trade name HSZ-330HUD1A, SiO2 / Al2O3 molar ratio 6, alumina binder) to a height of 20 cm and purged with nitrogen. The packing density of the high-silica zeolite at this time was 0.463 g / cm 3 and the filling amount of the high-silica zeolite was 34.7 g. Coarse hexane obtained in Reference Example 1 was flowed from the bottom of this column in an upflow manner under a nitrogen atmosphere, and the residence time was set to 130 seconds to obtain purified hexane. The flow rate here was 5 L. As a result of analysis by gas chromatography, no peaks other than hexane were observed. The evaluation results and the like are shown in Table 1.

[0035] Example 3 Purified hexane was obtained in the same manner as in Example 2 except that the residence time of the coarse hexane was set to 40 seconds. As a result of analysis by gas chromatography, no peaks other than hexane were observed. The evaluation results and the like are shown in Table 1.

[0036] Example 4 Purified hexane was obtained in the same manner as in Example 2 except that the residence time of the coarse hexane was set to 15 seconds. As a result of analysis by gas chromatography, no peaks other than hexane were observed. The evaluation results and the like are shown in Table 1.

[0037] Example 5 Purified hexane was obtained in the same manner as in Example 4 except that the column part was heated to 50°C. As a result of analysis by gas chromatography, no peaks other than hexane were observed. The evaluation results and the like are shown in Table 1.

[0038] Example 6 Purified hexane was obtained in the same manner as in Example 1, except that the high-silica zeolite was beta-type high-silica zeolite having hydrogen cations in pellet form (manufactured by Tosoh Corporation, trade name: HSZ-931HOD1A, SiO2 / Al2O3 molar ratio 27, alumina binder). When the water content of the treated hexane was measured, the water content had decreased to 7 ppm. As a result of analysis by gas chromatography, no peaks other than hexane were observed. The evaluation results and the like are shown in Table 1.

[0039] Example 7 Purified hexane was obtained in the same manner as in Example 1, except that the high-silica zeolite was hydrogen cation type ZSM-5 type high-silica zeolite having hydrogen cations in pellet form (manufactured by Tosoh Corporation, trade name: HSZ-822HOD1A, SiO2 / Al2O3 molar ratio 23, alumina binder). When the water content of the treated hexane was measured, the water content had decreased to 8 ppm. As a result of analysis by gas chromatography, no peaks other than hexane were observed. The evaluation results and the like are shown in Table 1.

[0040] Example 8 Purified hexane was obtained in the same manner as in Example 1, except that the high-silica zeolite was hydrogen cation type ZSM-5 type high-silica zeolite having hydrogen cations in pellet form (manufactured by Tosoh Corporation, trade name: HSZ-840HOD1A, SiO2 / Al2O3 molar ratio 40, alumina binder). When the water content of the treated hexane was measured, the water content had decreased slightly to 9 ppm. As a result of analysis by gas chromatography, no peaks other than hexane were observed. The evaluation results and the like are shown in Table 1.

[0041] Example 9 Purified hexane was obtained in the same manner as in Example 4, except that the high-silica zeolite was hydrogen cation type Y-type high-silica zeolite having hydrogen cations in pellet form (manufactured by Tosoh Corporation, trade name: HSZ-330HUD1C, SiO2 / Al2O3 molar ratio 6, clay binder). As a result of analysis by gas chromatography, no peaks other than hexane were observed. The evaluation results and the like are shown in Table 1.

[0042] Comparative Example 1 Purification of crude hexane was attempted in the same manner as in Example 1, except that 10 g of zeolite (Zeolam F-9, manufactured by Tosoh Corporation) was used instead of high-silica zeolite. The water content of the recovered hexane was reduced to 5 ppm, but peaks other than hexane were observed as a result of analysis by gas chromatography. The evaluation results and the like are shown in Table 1.

[0043] Comparative Example 2 Purification of crude hexane was attempted in the same manner as in Example 1, except that molecular sieves 10X (MS10X, manufactured by Fujifilm Wako Pure Chemical Corporation) and molecular sieves 3A (MS3A, manufactured by Fujifilm Wako Pure Chemical Corporation), which had been dried after washing with water, were used and contact treatment was carried out in this order. The water content of the recovered hexane was reduced to 3 ppm, but peaks other than hexane were observed as a result of analysis by gas chromatography. The evaluation results and the like are shown in Table 1.

[0044] Comparative Example 3 Purification of crude hexane was attempted in the same manner as in Example 1, except that the high-silica zeolite was a pellet-shaped sodium cation type Y-type high-silica zeolite (HSZ-320NAD1C, manufactured by Tosoh Corporation, SiO2 / Al2O3 molar ratio 5.5, clay binder). When the water content of the recovered hexane was measured, the water content had decreased to 7 ppm, but peaks other than hexane were observed as a result of analysis by gas chromatography. The evaluation results and the like are shown in Table 1.

[0045] [Table 1]

[0046] Reference Example 2 As a result of analyzing purchased hexane (reagent special grade, manufactured by Fujifilm Wako Pure Chemical Corporation) by gas chromatography, no peaks other than hexane were observed.

Industrial Applicability

[0047] The method of the present invention can be effectively used for the purification of solvents reused in the production of various olefin polymerization polymers and olefin copolymerization polymers such as high-density polyethylene and linear low-density polyethylene.

Claims

1. A purifying agent for a recovered polymerization solvent when slurry polymerization of an olefin is carried out in the presence of a Ziegler-Natta catalyst, comprising a high-silica zeolite selected from the group consisting of a hydrogen cation type beta-type zeolite, a hydrogen cation type ZSM-5 type zeolite, and a hydrogen cation type Y-type zeolite.

2. The high-silica zeolite has a SiO ２ / Al ２ O ３ molar ratio of 5 to 10 and has a pellet shape, and the recovery polymerization solvent purifying agent according to claim 1, characterized in that.

3. Further comprising a binder selected from the group consisting of silica, alumina, silica alumina, and clay, and having a pellet shape, the purifying agent for a recovered polymerization solvent according to claim 1 or 2.

4. The purifying agent for a recovered polymerization solvent according to any one of claims 1 to 3, wherein the high-silica zeolite is a transition metal-substituted zeolite.

5. The purifying agent for a recovered polymerization solvent according to any one of claims 1 to 4, wherein the polymerization solvent is selected from the group consisting of pentane, hexane, heptane, octane, decane, cyclopentane, cyclohexane, and methylcyclopentane.

6. A method for purifying a recovered polymerization solvent, characterized in that the recovered polymerization solvent after the slurry polymerization reaction of an olefin in the presence of a Ziegler-Natta catalyst is subjected to contact treatment with a high-silica zeolite selected from the group consisting of a hydrogen cation type beta-type zeolite, a hydrogen cation type ZSM-5 type zeolite, and a hydrogen cation type Y-type zeolite.

7. The method for purifying a recovered polymerization solvent according to claim 6, wherein the olefin polymerization reaction is a reaction in which an olefin is slurry polymerized in a polymerization solvent selected from the group consisting of pentane, hexane, heptane, octane, decane, cyclopentane, cyclohexane, and methylcyclopentane in the presence of a solid catalyst containing at least titanium, magnesium, and a halogen as a Ziegler-Natta catalyst.

8. The method for purifying a recovered polymerization solvent according to claim 6 or 7, characterized in that the contact treatment is carried out under contact conditions of a temperature of 25 to 50 ° C and a time of 1 second to 24 hours.

9. The method for purifying a recovered polymerization solvent according to any one of claims 6 to 8, characterized in that the contact treatment is carried out in a flow mode.

10. The method for purifying a recovered polymerization solvent according to any one of claims 6 to 9, characterized in that the contact treatment is carried out after dehydration treatment of the polymerization solvent.

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