JPH0548244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates in detail to a method for recovering a polymerization solvent, and more particularly to a method for recovering an inert hydrocarbon compound used when polymerizing propylene by a specific method. <Prior Art> A method of polymerizing propylene using a catalyst consisting of a titanium compound and an organoaluminum compound using propylene itself as a medium is well known. It is also known that at that time, the catalyst can be deactivated using a specific compound and the catalyst residue can be removed if necessary. (For example, Japanese Patent Publication No. 59-10684) <Problems to be solved by the invention> In the polymerization method using propylene itself as a medium, inert hydrocarbons other than propylene are not used as the polymerization medium, so there are always unresolved problems. Although it is thought that only the propylene of the reaction is recovered, in actual industrial-scale operations, it is necessary to use considerably larger amounts of inert hydrocarbon compounds, including those used for diluting the catalyst. Therefore, it is desired to recover and refine this inert hydrocarbon compound as simply as possible to the extent that it can be reused. The inventors of the present invention have already proposed a simple method to solve the above problem, such as in Japanese Patent Application No. 60-5920 and Japanese Patent Application No. 60-41867. It has been found that there are problems with the performance of the recovered solvent. <Means for Solving the Problems> The present inventors have completed the present invention by intensively studying methods for solving the above problems. That is, in the present invention, propylene is polymerized using a catalyst consisting of a titanium compound and an organoaluminum compound, an inert hydrocarbon compound is used at least for diluting the catalyst, and propylene itself is used as a catalyst. O(-C ₂ H ₅ O) _o --H (in the formula; n
is an integer of 1 or more, and R is an alkyl group or aryl group having 1 to 20 carbon atoms). The fraction removed as a boiling point is introduced into a distillation column, and an organoaluminum compound is charged into the upper stage from the introduction section to obtain a fraction from which high boiling points have been removed from the top of the distillation column. This is a method for recovering a polymerization solvent, which is characterized by charging the polymerization solvent into a distillation column to obtain a purified recovered inert hydrocarbon compound from which low-boiling components have been removed from the bottom of the column. In the present invention, there are no particular restrictions on the catalyst consisting of a titanium compound and an organoaluminum compound,
Any material that is used for normal propylene polymerization may be used, such as titanium trichloride and its eutectic, or those modified with ethers, esters, etc., titanium tetrachloride, titanium trichloride and magnesium halides, etc. Titanium compounds supported on carriers are known as titanium compounds, and trialkylaluminums such as triethylaluminum, tripropylaluminum, tributylaluminum, trihexylaluminum, diethylaluminum chloride, dipropylaluminum chloride, dibutylaluminum chloride, etc. Dialkyl aluminum halides and the like can be exemplified as organoaluminum compounds. Polymerization methods to which the present invention can be applied include bulk polymerization methods using propylene itself as a liquid medium and/or gas phase polymerization methods in which substantially no liquid medium is present. In these polymerization methods, hexane, heptane, Inert hydrocarbon compounds such as octane, decane, benzene, toluene, and ethylbenzene are used for diluting the catalyst, for flushing to prevent clogging of valve pumps, and for further improving catalyst efficiency in gas phase polymerization. The use of inert hydrocarbon compounds (for example, JP-A-57-31905) is practiced. In the present invention, after polymerizing propylene with the above-mentioned polymer reactant, the general formula R-O(-C ₂ H ₅ O) _o --H
(wherein, n is an integer of 1 or more, R is an alkyl group or aryl group having 1 to 20 carbon atoms). Although the catalyst is deactivated by this operation, it is also possible to wash the polypropylene with liquid propylene if necessary. The above-mentioned glycol ethers include ethylene glycol monomethyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, phenyl,
Substituted phenyl ethers, similar ethers of diethylene glycol, or similar ethers of triethylene glycol can be employed. Examples of inert hydrocarbon compounds recovered in the present invention include those recovered as high-boiling components from recovered unreacted monomers such as ethylene and propylene, and high-boiling components recovered during drying of polypropylene powder. It will be done. In order to use these recovered inert hydrocarbon compounds in the production of solid transition metal catalysts or as diluents, it is required to perform extremely precise rectification to separate the inert hydrocarbon compounds. To do this, it is necessary to remove a large amount of low-boiling and high-boiling components at a high reflux ratio using a distillation column with a large number of stages, resulting in a low yield of purified inert hydrocarbon compounds and high purification costs. In contrast, the method of the present invention makes it possible to obtain a reusable polymerization solvent with an extremely high recovery rate. The alkylaluminum compound used in the distillation can be the same as that used as the polymerization catalyst described above. As the distillation column into which the fraction from which unreacted propylene has been removed as a low-boiling fraction is introduced, it is more preferable to use a distillation column having a chimney stage as shown in Japanese Patent Application No. 60-41867, and the above-mentioned distillate is placed in a stage lower than the chimney stage. The organoaluminum compound is introduced into a stage above the chimney stage, and more preferably, a part of the fraction taken out from the top of the column is introduced below the chimney stage. In the present invention, if the polymerization-inhibiting component is known, it is sufficient to introduce the organoaluminum compound in an amount equal to or several times the amount of the polymerization-inhibiting component that rises from the chimney stage to the upper stage. In addition, if the polymerization-inhibiting component is not known, the amount of the polymerization-inhibiting component to be introduced may be varied to find conditions under which the polymerization-inhibiting component does not increase, or the fraction from the top of the column obtained without introducing an organoaluminum compound may be used as a polymerization solvent. It is also possible to find out the content of the polymerization-inhibiting component by comparing its performance with known polymerization-inhibiting components, and to adjust the content to equimolar to several times the molar amount. The distillation column used in the present invention has 5 or more stages, preferably 10 or more stages, and the reflux ratio at the top of the column is 0.01 or more, preferably 0.1 or more. <Functions and Effects> By the method of the present invention, among the polymerization inhibiting components, those that interact with the organoaluminum compound become high-boiling components by charging the organoaluminum compound into the distillation column, and do not rise to the top of the column. In addition, the components that do not interact with the organic aluminum compound have extremely low boiling points, and are presumed to be removed in the second distillation column as low boiling points. Therefore, it is an extremely excellent method for recovering polymerization solvents on an industrial scale. <Examples> The present invention will be further explained with reference to Examples below. Example 1, Comparative Example 1 (A) Production of catalyst slurry A vibratory mill equipped with two grinding pots each having an internal volume of 900 ml and containing 80 steel balls with a diameter of 12 mm was prepared. In this pocket, under a nitrogen atmosphere, add 30 g of magnesium chloride and 3 g of ethyl orthoacetate per container.
ml, 6 ml of 1,2-dichloroethane was added, and the mixture was ground for 40 hours. By repeating this operation twice, 80 g of the pulverized product was brought into contact with 500 ml of titanium tetrachloride in a No. 2 round-bottomed flask under stirring at 80° C. for 2 hours, and then allowed to stand, and the supernatant liquid was removed. Next, 1 portion of n-heptane was added, the mixture was stirred at room temperature for 15 minutes, left to stand, and the supernatant liquid was removed. This washing operation was repeated seven times, and then 500 ml of n-heptane was further added to obtain a solid reduced metal catalyst slurry. (B) Recovery of polymerization solvent (i) Preparation of catalyst slurry: Add 50 g of the solid reduced metal catalyst slurry obtained in Example 1 as a solid content to n-heptane 50, 214 ml of diethylaluminum chloride, 100 ml of methyl toluate, and add the catalyst. It was made into a slurry. Separately, 133 ml of triethylaluminum was diluted with 20 ml of n-heptane. (ii) Polymerization: In the apparatus shown in Figure 2, A is a polymerization reactor with an internal volume of 500, and the slurry obtained by polymerization in A is passed through line 15 and pump B.
The slurry is then sent to autoclave C (inner volume 200), and a portion of the slurry is circulated to A. In C, a catalyst deactivator (diethylene glycol monoisopropyl ether) is added, and the slurry is discharged from 16 and heated through heating tube D. Most of the medium (propylene and n-heptane) is separated in cyclone G, and the powder is sent to H. It is further dried. Drying is carried out by introducing propylene heated to 90°C from 24, and propylene, n-heptane, etc. are sent to heat exchanger F from line 18, and 0.1Kg/cm ² -gauge,
The recovered material cooled to 30℃ and liquefied is sent to line 20.
It is sent to Tank I. On the other hand, the vapor mainly containing propylene taken out from line 17 is cooled to 0.1 kg/cm ² -gauge in heat exchanger E to 30° C., and the recovered material is liquefied and sent to tank I via line 19. The unliquefied gases are sent to the propylene recovery system via lines 21, 22 and 23, respectively. The following polymerization and n-heptane recovery operations are performed using this apparatus. A catalyst slurry (3 g/hour as a solid catalyst), triethylaluminum (8 ml/hour), and propylene (80 kg/hour) were charged into polymerization reactor A, and polymerization was carried out at 70°C. At this time, n-heptane was charged at 8/1 hour for flushing the pump and valves. On the other hand, the polymerization slurry was sent from A to C at a rate of 80 kg/hour, and at C, diethylene glycol monoisopropyl ether was further sent at a rate of 100 ml/hour to deactivate the catalyst. Slurry comes from C.
Powder was removed from dryer H at a rate of 80 kg/hour, and liquid was collected in tank I at a rate of 10.8 kg/hour. The recovered n-heptane was purified using the distillation column shown in FIG. Distillation column inner diameter 40 mm, number of plates 20, organoaluminum compound 1 in the third plate
16 inlet, chimney 10 on 10th stage 101
5 (having a structure that prevents the condensed liquid from falling below it), a condensate outlet port 115, and a purified solvent inlet 111 at the 17th stage. The bottom of the column has a structure 102 that can be heated, and a bottom liquid outlet 114 is provided. From the extraction port 115, the condensate is charged into the evaporator 104 via the heating device 103, and from the evaporator, a high boiling point extraction port 112 and a steam inlet 113 are provided at the ninth stage. On the other hand, the vapor from the top of the column is refluxed through a condenser 106, and a portion is sent to a second distillation column via a line 110. In the second distillation column, the bottom boiling fraction is removed from the top of the column, and purified recovered n-heptane is taken out from the bottom of the column through line 121 118
119 is a heat exchanger for cooling, and 119 is a heat exchanger for heating. 30 from the inlet 111 using the above distillation column.
Introducing the recovered n-heptane at a rate of ml/min,
Triethyl aluminum from inlet 116
0.006ml/min, 0.15ml/min from 114, 1
High-boiling substances were extracted from line 110 at a rate of 29.75 ml/min at a reflux ratio of 0.12 and used as purified n-heptane (Comparative Example 1, recovered liquid 1), or a second liquid was extracted from line 110 at a rate of 0.10 ml/min. sent to the distillation tower. (Example 1, recovered liquid 2) One part of n-heptane (5 ml/
min) was refluxed to the column via line 117.
On the other hand, n-heptane from line 110 is introduced into the fifth stage of the second distillation column, which is a 10-plate plate column, and the low-boiling fraction is extracted from the top of the column at a rate of 0.05 ml/min at a reflux ratio of 5.0. 29.7 ml of purified n-heptane was extracted from the solution. (C) Using the above recovery liquids 1 and 2, (A) of Example 1
Same operation as above (but on 10g scale of crushed material)
A solid transition metal catalyst was produced. (D) Polymerization reaction Polymerization was carried out using the solid transition metal catalyst obtained in (C) and the one obtained in (A) as a comparison. For the polymerization reaction, 30 mg of solid transition metal catalyst, 0.06 ml of methyl toluate, 0.128 ml of diethylaluminum chloride, 0.08 ml of triethyl aluminum, and n-heptane used for dilution (all from Example 1A) were placed in an autoclave with an internal volume of 5. Use) Mix and charge 50ml, then add propylene
After adding 1.5 kg and 1.5 N of hydrogen and polymerizing at 75°C for 2 hours, unreacted propylene was purged and drying was carried out under reduced pressure at 60°C to obtain a powder (6 hours at 20 mmHg). Example 3, Comparative Example 4 As a solid transition metal catalyst, highly active titanium trichloride TGY-24 manufactured by Marubeni Solve A (92% as _TiCl3 ,
Polymerization was carried out using the same apparatus as in Example 1(B) using 8% of high boiling point ether. As the catalyst slurry, 100g of the above titanium trichloride,
Mix 100 toluene and 800 ml of diethyl aluminum chloride, charge 500 g of propylene, and make 40
The mixture was stirred at .degree. C. for 1 hour to polymerize 5 g of propylene per 1 g of titanium trichloride. Next, 0.5 ml of diethylene glycol monoisopropyl ether was added to form a catalyst slurry. This catalyst slurry was used as a solid transition metal catalyst and polymerized in the same manner as in Example 1(B)(ii) except that triethylaluminum was not charged at 7 g/hour, and the polymerization was performed using toluene for flushing the pump and valve. 14.3/ for Tank I
The liquid was collected in time. The recovered liquid, mostly consisting of toluene, was treated in the same manner as in Example 1 to convert the organic aluminum into diethylaluminum chloride.
Using 0.01 ml, the second distillation column was obtained either without (Comparative Example 2, Recovery Solution 1) or with (Example 2, Recovery Solution 2). 100 g of titanium trichloride catalyst was added to each recovered toluene, stirred and kept for 20 hours, and the catalyst slurry was used for polymerization. titanium trichloride
100mg, diethyl aluminum chloride 0.8ml,
A catalyst slurry consisting of 100 ml of toluene for dilution (all toluene used in the previous polymerization was used) was charged, and 1.5 kg of propylene, 3 N of hydrogen, and 3
Polymerization was carried out for a period of time to obtain a powder in the same manner as in Example 1-(D). The results are shown in the table. 【table】

[Brief explanation of drawings]

FIG. 1 is an example of a distillation column suitable for carrying out the method of the present invention. Figure 2 is a polymerization flow sheet, A: polymerization tank, B: pump, C: deactivation tank,
D, E, F; heat exchanger, G; cyclone, H; dryer, I; tank, J, J'; valve, 11; deactivator charging line, 12; propylene charging line, 1
3, 14; Catalyst charging line, 15; Slurry circulation line, 16; Slurry discharge line, 17, 1
8; Recovery vapor line, 19, 20; Recovery liquid line, 21, 22, 23; Uncondensed gas line, 2
4; dry gas charging line; 25; dry powder discharge line.

Claims (1)

[Claims] 1 Using a catalyst consisting of a titanium compound and an organoaluminium compound, propylene is polymerized by a polymerization method using propylene itself as a medium, using at least an inert hydrocarbon compound for diluting the catalyst, and then polymerizing with the general formula R-O (-C ₂ H ₅ O) _o --H (where n is an integer of 1 or more, R is an alkyl group or aryl group having 1 to 20 carbon atoms) to produce polypropylene, and When recovering hydrohydride compounds, the fraction from which unreacted propylene has been removed as a low-boiling fraction is introduced into a distillation column, and an organoaluminum compound is charged into the upper stage from the introduction section to remove high-boiling fractions from the top of the distillation column. Recovery of a polymerization solvent characterized by obtaining the removed fraction, and then charging the fraction into a second distillation column to obtain a purified recovered inert hydrocarbon compound from which low-boiling components have been removed from the bottom of the column. Method.