JPH0158202B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for purifying an olefin polymerization solvent. More specifically, the present invention relates to a method suitable for removing impurities that adversely affect olefin polymerization from a polymerization solvent. Many methods are known for polymerizing olefins in the presence of catalysts and solvents. The solvent recovered by separating the olefin polymer from the polymerization solution or decomposing the catalyst is often used again in the polymerization. However, even when olefin polymerization is performed using such a solvent that has been used once for polymerization, the expected polymerization activity may not be obtained. These include by-products during polymerization, catalyst decomposition products, reagents used for catalyst decomposition, such as alcohols, carboxylic acids, chelate compounds, etc., and products resulting from oxidation and thermal deterioration of solvents during polymerization and post-treatment. This is assumed to be due to the inclusion of various impurities. These impurities can be removed to some extent by combining various purification methods such as washing with water, distillation, and dehydration. Therefore, depending on the degree of purification, even if the solvent is reused, there will be no significant decrease in polymerization activity. It can be prevented. However, this level is not sufficient, and with repeated use, the polymerization activity eventually decreases to an unsatisfactory level. In recent years, there has been remarkable progress in high activation technology for polymerization catalysts, but while these highly active catalysts have the great advantage of being able to be used in very small quantities, they are particularly susceptible to The influence of impurities is likely to be large, and the above-mentioned disadvantages in solvent reuse are likely to occur. A decrease in polymerization activity due to the influence of impurities not only impairs the advantages of highly active catalysts and increases catalyst consumption, but also causes changes in the composition and molecular weight of the polymer, making it difficult to control product quality. It is to make it. Therefore, it has been desired to further remove trace amounts of polymerization-inhibiting impurities that could not be completely removed by conventional purification methods. Therefore, the inventors of the present invention conducted intensive studies to solve such problems, and found that
We have discovered a very effective method for purifying olefin polymerization solvents. That is, according to the present invention, there is provided a method for purifying a solvent, which comprises treating an olefin polymerization solvent consisting of a hydrocarbon with a zeolite ion-exchanged with transition metal ions. It is already known to use zeolites for the purpose of dehydration in solvents or for the purpose of removing alkyl halides in solvents (for example, JP-A-51-20791). However, even with this conventional purification method using zeolite treatment,
Although the effect of preventing a decrease in the activity of olefin polymerization is not sufficient, a significant improvement in the purification effect is observed by replacing the metal ions of zeolite with transition metal ions. In the present invention, zeolite ion-exchanged with transition metal ions is used as a solvent treatment agent. Zeolites used for ion exchange include, for example, molecular sieves 3A, 4A, and 5.
Zeolite known by trade names such as A, 10X, 13X, etc., synthetic zeolite such as Y-type zeolite,
Examples include natural zeolites such as borosite, siabasite, and mordenite. The transition metal ions to be ion-exchanged with these zeolites include titanium, vanadium, chromium,
Manganese, iron, cobalt, nickel, copper, zinc,
Yttrium, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, lanthanum, cerium, neodymium, promethium, samarium, coropium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, actinium, thorium, Examples include ions such as uranium. Among these, ions of elements or rare earth elements belonging to the fourth period or group 8 of the periodic table are particularly preferred, particularly ions of elements of the fourth period of the periodic table or rare earth elements. Methods for replacing metal ions, mainly alkali metal ions, in zeolites with these transition metal ions are already known and can be carried out by conventionally taught methods. For example, zeolite that has been pretreated such as washing with water or calcined, or zeolite that has not been pretreated is immersed in an aqueous solution of a compound containing transition metal ions and heated. After replacing the aqueous solution and repeating the same operation several times, the product may be washed with distilled water, dried, and fired. The exchange rate with transition metal ions is arbitrary, but usually 10 to 100%,
In particular, about 20 to 100% is preferable. The solvent purified with zeolite ion-exchanged with transition metal ions is an olefin polymerization solvent consisting of hydrocarbons. Such olefin polymerization solvents include, for example, aliphatic hydrocarbons such as butane, pentane, hexane, hebutane, octane, decane, dodecane, and kerosene; aliphatic hydrocarbons such as cyclopetane, methylcyclopetane, cyclohexane, and methylcyclohexane; Aromatic hydrocarbons such as benzene, toluene, xylene, etc. can be used. Furthermore, it is particularly effective to treat materials that have been used once or repeatedly in olefin polymerization when they are to be reused in olefin polymerization. Olefin polymerization is carried out using, for example, Ziegler-type catalysts.
This was done using a Phillips-type catalyst. More specifically, transition metal compounds such as titanium compounds, such as titanium trichloride, titanium tetrachloride, titanium compounds supported on magnesium compounds, etc.; vanadium compounds, such as vanadium tetrachloride, vanadium oxychloride, vanadium alkoxyhalides, etc. It can be applied to a solvent used in the polymerization of an olefin using an organic aluminum compound such as a trialkylaluminium, an alkylaluminium halide, etc., or a solvent used in the polymerization of an olefin using the catalyst. When applied to the solvent used in polymerization, it is applied to the solvent recovered by adding a catalytic decomposition agent such as alcohol to the polymerization solution, or by performing arbitrary operations such as steam distillation, water washing, alkaline washing, dehydration, distillation, etc. be able to. Examples of such olefin polymerization include ethylene, propylene, 1-butene, 1-
Polymerization or copolymerization of pentene, 1-hexene, 1-octene, 1-decene, 4-methyl-1-pentene, etc., and polyenes with these olefins, such as butadiene, isoprene, piperylene, 1,4-hexadiene, 5-ethylidene. 2-Norbonene,
Examples include copolymerization with 5-vinyl-2-norbornene, dicyclopentadiene, and the like. In the present invention, it can be used not only to remove impurities that adversely affect olefin polymerization from the above-mentioned polymerization solvent, but also to remove -SO ₃ H contained in the above-mentioned hydrocarbons and other hydrocarbon oils. , ―COOH, ―OH, ―NH ₂ , ―SH, ―
CHO, -C=O, -COOR, -S-, -O-,
It can also be used for the purpose of removing specific compounds having functional groups such as halogens and unsaturated bonds. To treat a solvent with a zeolite ion-exchanged with transition metal ions, it is sufficient to simply bring the two into contact. The zeolite can be used in various forms such as powder, flakes, and granules. For example, a method of suspending and contacting the zeolite in a solvent in a batch manner, a continuous treatment method of continuously passing a solvent through a packed bed filled with the zeolite, etc. can be employed. The contact temperature between the solvent and the zeolite is arbitrary, but it is usually preferably about -50 to 150°C. The contact time also varies depending on the type and amount of supported metal, the yield of zeolite, the type and amount of impurities in the solvent, etc., but for example, when treating solvent 1 with 100 g of zeolite, it is generally 0.1 seconds. A contact time of about 5 to 5 hours is sufficient. If the performance of the zeolite deteriorates after repeated use, it can be easily regenerated by heating and firing it at a temperature of about 200 to 600°C in an atmosphere of an inert gas such as nitrogen gas or in the air. So it is reusable. Next, an example will be explained. Example 1 1 Polymerization and Post-Treatment EPDM polymerization reaction was carried out continuously using 15 stainless steel polymerization vessels equipped with stirring blades.
That is, hexane is continuously supplied as a polymerization solvent from the top of the polymerization vessel at a rate of 5 per hour. On the other hand, the polymerization liquid is continuously drawn out from the lower part of the polymerization vessel so that the polymerization liquid in the polymerization vessel is always 5%. The concentration of vanadium oxytrichloride as a catalyst in the polymerization vessel was 0.3 mmol/, and the concentration of ethylaluminum sesquichloride in the polymerization vessel was 0.3 mmol/.
Each was continuously fed into the polymerization vessel from the top of the vessel at a concentration of 2.4 mmol/each. In addition, a mixed gas of ethylene, propylene, and hydrogen (34 mol% ethylene, 56 mol% propylene, 10 mol% hydrogen) was supplied from the top of the polymerization vessel at a rate of 500 N/hour, and dicyclopentadiene was added to the polymerization vessel at a concentration of 4.3 g/hour.
Supply so that The copolymerization reaction was carried out at 35°C by circulating hot water through a jacket attached to the outside of the polymerization vessel. The extracted polymerization liquid was sent to a post-treatment system and continuously treated to obtain EPDM. That is, after removing unreacted monomer gas from the polymerization solution in a demonomer tower, methanol was added to the polymerization solution 1 to deactivate the catalyst. Next, this polymerization solution was subjected to a steam stripping treatment to obtain EPDM at a rate of 52 g per polymerization solution. That is, the polymer yield per 1 mmol of vanadium catalyst was 173 g. The physical properties of the polymer were as follows: ethylene content: 70.2 mol%, iodine number: 8.6, Mooney viscosity (ML1+4, 100°C): 46. 2 Recovery of Solvent The solvent separated from the polymer by steam stripping was continuously sent to a solvent recovery step and recovered. That is, the mixture was separated into an aqueous layer and an oil layer in a stationary drum, the oil layer was continuously extracted, and a hexane fraction was obtained by removing low-boiling components and high-boiling components in a distillation column. 3 Polymerization using recovered hexane When the hexane recovered by the above operation was dehydrated with Monocube Sieve 4A and then reused, the polymerization activity decreased. In other words, the polymerization yield under the same polymerization conditions as at the start of recycled use is 1 vanadium.
The amount was 83 g per mmol, the ethylene content was 79.1 mol%, the iodine number was 17.1, and the Mooney viscosity was 103. 4 Synthesis of zeolite for solvent purification A zeolite for solvent purification was synthesized by exchanging the sodium ions of Union Carbide Y-type zeolite (SK-40) with ferrous ions. That is, ferrous chloride was dissolved in nitrogen-substituted distilled water to prepare a 20% ferrous chloride aqueous solution. Under a nitrogen atmosphere, 1 part ferrous chloride aqueous solution was added to 100 g of SK-40, and the reaction was carried out at 60°C for 3 hours. The ferrous chloride aqueous solution was replaced with a new one and the same operation was repeated two more times. Finally, the zeolite was washed with nitrogen-substituted distilled water and calcined at 500°C for 3 hours in a nitrogen atmosphere. The exchange rate of iron was 70.0% on a sodium basis. 5 Purification of Solvent 100 g of the above zeolite for solvent purification was added to 50 g of recovered hexane and immersed in a nitrogen atmosphere for one day. 6 Polymerization with Purified Hexane EPDM was polymerized under the conditions described above using the purified hexane described above as a solvent. Polymer yield is 177/mmol vanadium
The physical properties of the g-polymer are as follows: ethylene content: 70.5 mol%;
The iodine value was 8.5 and the Mooney viscosity was 44, and both the polymerization activity and the physical properties of the polymer were equivalent to those of hexane before recycling. This indicates that the hexane was completely purified. Examples 2 to 4 The same operations as in Example 1 were repeated except that 5A, 10X, and 13X type zeolites were used instead of Y type zeolite. The results are shown in Table 1.

[Table] Comparative Examples 1 to 4 Here, for comparison with the present invention, it is shown that zeolite before exchange with iron ions is not effective for solvent purification. The same operation as in Example 1 was performed except that instead of using zeolite exchanged with iron ions, zeolites (SK-40, 5A, 10X, 13X) before iron ion exchange were used. The results are shown in Table 2.

[Table] Examples 5 to 9 The same operations as in Example 1 were repeated except that various reduction metal compounds were used instead of FeCl ₂ . The results are shown in Table 3.

【table】

[Table] Example 19 Same procedure as in Example 1 except that instead of using iron-supported Y-type zeolite as the zeolite for solvent purification, Union Carbide's Y-type zeolite (SK-500) supporting cesium and lanthanum was used. The operation was repeated. The polymer yield was 159 g/mmolV, the ethylene content of the polymer was 73.9 mol%, the iodine number was 9.5, and the Mooney viscosity was 54.
It was hot. Example 20 Here, an example of purification of a polypropylene polymerization solvent will be shown. 1 Catalyst preparation 20 g of anhydrous magnesium chloride, 4.6 ml of ethyl benzoate and 3.0 ml of methylpolysiloxane (viscosity 20 c.s. (25°C) were mixed in a nitrogen atmosphere with a diameter of 15 mm.
The balls were placed in a stainless steel (SUS-32) ball mill cylinder with an internal volume of 800 ml and an inner diameter of 100 mm containing 2.8 kg of stainless steel (SUS-32) balls and left in contact for 100 hours at an impact acceleration of 7.8 G. 10 g of the obtained solid treated product was suspended in 100 ml of titanium tetrachloride, and after contact at 80°C for 2 hours with stirring, the solid component was collected by filtration, and free titanium tetrachloride was no longer detected in the washing liquid. After washing with hexane until
It was dried to obtain a titanium-containing solid component (a). 2 Polymerization and Post-Treatment Slurry polymerization of polypropylene was carried out continuously using 15 stainless steel polymerization vessels equipped with stirring blades. That is, hexane as a polymerization solvent is continuously drawn out from the top of the polymerization vessel at a rate of 5 ml/hour so that the polymerization liquid is always 5 ml/hour.
The composite (a) as a catalyst was polymerized so that the concentration of titanium in the polymerization vessel was 1.0 mmol/, and the third component of the catalyst was methyl P-toluate so that the concentration in the polymerization vessel was 0.33 mmol/. It was continuously fed into the polymerization vessel from the middle of the vessel. In addition, 3.1 kg of propylene is supplied per hour from the top of the polymerization vessel.
Hydrogen was supplied at a rate of 8.3N per hour. The reaction was carried out at 70°C by circulating hot water through a jacket attached to the outside of the polymerization vessel. The extracted polymer solution was sent to a post-treatment system and continuously subjected to the following treatment to collect a polymer. That is, the monomer in the polymerization solution was removed in a tower and then separated into a slurry and a solvent in a decanter. A polymer was obtained at a ratio of 310 g per hexane. That is, the polymer yield per 1 mmol of titanium catalyst was 15,500 g. In addition, the melt index (MI
230℃) was 10.2. 3 Recovery of solvent The mother liquor separated from the slurry was supplied to a distillation column, low boiling point components and high boiling point components were removed, and a hexane fraction was recovered. 4 Polymerization using recovered hexane When the hexane recovered by the above operation was dehydrated with Molecular Sieve 4A and reused, the polymerization activity decreased. That is, under the same polymerization conditions as at the beginning of use, the polymer yield was 5000 g/mmol titanium. 5 Purification of Solvent Hexane was purified in the same manner as in Example 1 using zeolite for solvent purification. 6 Polymerization with Purified Hexane Polypropylene was polymerized under the conditions described above using the purified hexane described above as a solvent. Polymer yield was 15,300 g/mmol titanium. Moreover, MI230°C was 10.5, and both the polymerization activity and melt index were equivalent to that of hexane before recycling. This indicates that the hexane was completely purified. Example 21 Here, an example of purification of a polyethylene polymerization solvent using a Ziegler catalyst will be described. 1 Preparation of Catalyst 2 moles of commercially available anhydrous magnesium chloride were suspended in dehydrated and purified hexane 4 under a nitrogen atmosphere, and 12 moles of ethanol was added dropwise over 2 hours with stirring, followed by reaction at 70°C for 1 hour. To this was added dropwise 5.85 mol of diethylaluminum chloride at room temperature, and the mixture was stirred for 2 hours. Subsequently, 3 mol of titanium tetrachloride was added dropwise, and the reaction was carried out at room temperature for 2 hours. After the reaction was completed, the solid portion produced was washed repeatedly with hexane to obtain a titanium-containing solid component (b). 2 Polymerization and post-treatment In Example 20, instead of using the composite (a), triethylaluminum, and methyl P-toluate as the catalyst and propylene as the monomer, the above composite (b) was used as the catalyst, and the titanium concentration in the polymerization vessel was increased.
The concentration of triethylaluminum in the polymerization vessel was 1.0 mmol/0.02 mmol/
Also, ethylene as a monomer is added per hour so that
A similar operation was performed except that 1.5Kg hydrogen was supplied at a rate of 18N/hour. The results are shown in Table 4.

【table】

Claims (1)

[Scope of Claims] 1. A method for purifying a solvent, which comprises treating an olefin polymerization solvent consisting of carbon and hydrogen under zeolite ion-exchanged with transition metal ions. 2. The method according to claim 1, wherein the olefin polymerization solvent is a polymerization solvent used in olefin polymerization using a transition metal compound catalyst.