JPS6057441B2 - Gas phase polymerization method of olefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [I] BACKGROUND OF THE INVENTION Technical Field The present invention relates to a process for the gas phase polymerization of olefins, which involves the direct conversion of olefins in a gaseous state into solid homo- or copolymers.

More specifically, the present invention relates to an improvement in the process of carrying out the gas phase polymerization of olefins in a fluidized bed reactor with an external gas phase cooling system. Still more specifically, the present invention relates to an improvement in the gas phase polymerization process of olefins using a catalyst system cocatalyzed by an organoaluminum compound that liquefies under the cooling conditions of this external gas phase cooling system. It is known to carry out gas phase polymerization of olefins in a so-called fluidized bed reactor, in which a solid polymer undergoing a polymerization reaction is maintained in a fluidized state by an upward flow of a gaseous mixture containing a reaction monomer. .

In such reactors, a heat exchanger is installed in the external gas phase circulation system to draw the gas mixture inside the reactor out of the reactor and recirculate it back to the reactor. A common method is to cool the reaction heat to remove the reaction heat. Recirculation of the gas mixture to the reactor is also necessary to maintain a fluidized bed within the reactor. By the way, in general, when carrying out gas phase polymerization of olefins using a Zieckler catalyst system that uses a liquid organoaluminum compound as a cocatalyst, the organoaluminum compound is present in a supersaturated state in the reactor to react with transition metals. In order to fully exhibit the catalyst performance, it is necessary to provide an opportunity for a sufficient amount of the organoaluminum compound to come into contact with the solid catalyst contained therein.

In other words, if the organoaluminum compound is present in the reactor in a gaseous state so dilute that it does not reach saturation, the performance of the catalyst will not be fully exhibited, and the activity will particularly decrease. In this way, when gas phase polymerization of olefins is carried out in a fluidized bed reactor, the reaction is carried out in a state in which the organoaluminum compound is supersaturated in the reactor. It is carried out in a fluidized bed reactor equipped with an external gas phase circulation system to maintain the temperature and remove the heat of reaction.

The organoaluminum compounds present in supersaturation in the withdrawn gas phase are therefore also subject to cooling conditions in the heat exchanger integrated in this external gas phase circulation system. Location of the problem Organoaluminum compounds are generally liquids with a high boiling point, and when subjected to the cooling conditions in the external gas phase circulation system described above, at least a portion of them condenses and liquefies, causing heat transfer on cooling surfaces, such as heat exchangers. Wet the face.

On the other hand, this gas mixture extracted from the reactor contains a small amount of active fine powder that escaped from the reactor.
This activated fine powder adheres to the wet heat transfer surface and starts an abnormal reaction with the condensed organoaluminum compound on the heat transfer surface, leading to a decrease in the heat transfer efficiency of the heat exchanger and possibly clogging. Ru. [Summary of the old invention The purpose of the present invention is to provide a solution to the above problem,
This objective is achieved by making use of the cleaning effect of an easily condensable inert gas present in the reaction gas and condensing it on the cooling surface of an external gas phase circulation system. .

Part or all of this condensed product is vaporized and sent to the reactor! Recirculate. Therefore, the gas phase polymerization method for olefins according to the present invention involves producing an organic aluminum compound which liquefies under the cooling conditions of the cooling zone in a fluidized bed reaction zone equipped with an external gas phase circulation system having a cooling zone. Co-catalyst and 5
The present invention is characterized by satisfying the following requirements when carrying out gas phase polymerization of olefins using a catalyst system according to the present invention.

(4) The number of carbon atoms in the reaction zone is 1 from the olefin for polymerization.
〜4 Large inert hydrocarbons coexist in the gas phase.

(B) liquefying the inert hydrocarbon together with the organoaluminum compound as the gas phase in the reaction zone is cooled in the cooling zone of the external gas phase circulation system.

(C) Part or all of the liquefied product in this cooling zone is vaporized and recycled to the reaction zone.

Effect The aforementioned problems are solved by condensing certain easily condensable inert hydrocarbons together with organoaluminum compounds in an external gas phase circulation system.

Furthermore, in the present invention, part or all of the condensed product in the external gas phase circulation system is vaporized at elevated temperature and returned to the reactor, but this condensate contains organoaluminum compounds. This organoaluminum compound cocatalyst will then be recycled to the reactor.

On the other hand, in the present invention, the solid catalyst component can be supplied to the reactor separately from the circulating organic/organoaluminum compound. This method of introducing an organoaluminum compound cocatalyst into the reaction system is a method of introducing a complex liquid organoaluminum compound and a solid catalyst component, which is essential in olefin polymerization using a fluidized bed reactor with an external gas phase circulation system. Merging (
The continuous gas phase polymerization can be carried out in such a manner that such a cocatalyst is introduced into the reaction system (although it may not be in the entire amount required for the reaction). The fact that it was possible was an unexpected feat. [■] Detailed Description of the Invention The method for gas phase polymerization of olefins according to the present invention comprises three steps in performing gas phase polymerization of olefins in a fluidized bed reaction zone equipped with an external gas phase circulation system having a cooling zone. There are some that require simultaneous fulfillment of conditions.

1. Use of a specific inert hydrocarbon In the present invention, an inert hydrocarbon having 1 to 4 more carbon atoms than the olefin for polymerization is present in a gas phase in the reaction zone or reactor.

Such hydrocarbons are generally saturated hydrocarbons and are usually aliphatic. Specifically, for example,
There are propane, butane, pentane, hexane, cyclohexane, heptane, etc., and depending on the type of olefin for polymerization, one can be selected as appropriate if it can be condensed under the conditions of the cooling zone in the external gas phase circulation system. The amount of inert hydrocarbon used varies depending on the number of carbon atoms in the inert hydrocarbon, and when the number of carbon atoms is large, a relatively small amount is used, and when the number of carbon atoms is small, a relatively large amount is used. Generally, it is appropriate to use 1 to 70% by mole, preferably 2 to 50% by mole of the olefin for polymerization. Such inert hydrocarbons, which have 1 to 4 more carbon atoms than the olefin for polymerization, should coexist with the olefin for polymerization in the gas phase in the reaction system.

In other words, in order to maintain a good flow state inside the reactor, it is necessary to keep the inside of the reactor in a substantially dry state (if kept in a wet state, particle agglomeration and reactor wall It is necessary to select an inert hydrocarbon whose boiling point is relatively close to that of the olefin for polymerization. On the other hand, if an inert hydrocarbon having the same carbon number as the olefin for polymerization is used, a small amount of unreacted olefin for polymerization accompanying the polymer extracted from the reactor may be unreacted in the recovery process. This is because it is not preferable to use it because separation of the olefin for reaction polymerization and the inert hydrocarbon becomes difficult. 2. Condensation in an External Gas Phase Circulation System According to the present invention, a heat exchanger installed outside the reactor cools the circulating gas to a temperature approximately 10°C lower than the polymerization temperature, thereby converting the organoaluminum compound into It is liquefied and recovered together with activated hydrocarbons.

If inert hydrocarbons are not used, the heat exchanger will be clogged with the abnormal polymer as described above, but surprisingly, if inert hydrocarbons are also condensed in the heat exchanger, this problem is completely eliminated. It was discovered that this does not occur.

The reason for this favorable phenomenon is not clear, but it is probably because the condensed liquefied inert hydrocarbon constantly cleans the heat exchanger heat transfer surfaces, while at the same time diluting the condensed liquid organoaluminum compound with the inert hydrocarbon liquid. It is presumed that this prevents abnormal reactions of olefins in the presence of high-concentration organoaluminum compounds.

3. Vaporization recirculation of condensed product Part or all of the liquefied product (mixture mainly consisting of organoaluminum compounds and inert hydrocarbons) thus recovered in the cooling zone of the external gas phase circulation system is recycled to the Warm up and recirculate to the reactor.

If this liquefied product is fed directly to the reactor, the area around the feed port on the wall of the reactor will be wetted by the liquefied mixture, and the active particles in the reactor will adhere to it, eventually blocking the feed port. being occluded by polymers, resulting in
The concentration of the organoaluminum compound in the reactor decreases and the performance of the catalyst decreases, and in order to prevent this, the liquefied product was vaporized at an elevated temperature and supplied to the reactor.
This is because it has been found that the above-mentioned blockage of the supply port can be completely eliminated.

4 Gas phase polymerization of olefins Except for simultaneously satisfying the above three conditions, the gas phase polymerization method of olefins according to the present invention is carried out in a so-called Ziegler type reaction zone in a fluidized bed reaction zone equipped with an external gas phase circulation system having a cooling zone. This method is not essentially different from a method in which olefins are polymerized in the gas phase using a catalyst, that is, olefin homopolymerization or copolymerization with olefins or other small amounts of copolymerizable monomers.

As catalyst systems, compounds of transition metals of Groups I to II of the periodic table, especially titanium, and especially halogen compounds can generally be used, and those compounds supported on various carriers,
In particular, those supported on a carrier mainly composed of magnesium hydroxide have particularly high activity and are often used.

The cocatalyst has the general formula AlR. X3-m (R is hydrogen or a hydrocarbon residue having 1 to 10 carbon atoms, X is a nitrogen or an alkoxy group having 1 to 12 carbon atoms, 1<m>
Organic aluminum compounds which are liquid at 75° C. and normal pressure, such as triethylaluminum, diethylaluminium chloride, ethylaluminum dichloride, diethylaluminum ethoxide, etc., preferably triethylaluminum, are used. In addition, various electron-donating compounds can be added during polymerization as the third component of the polymerization catalyst system.
It is also possible to improve the performance of catalysts. A representative group of olefins for polymerization are alpha-olefins (which are intended to include ethylene).

α-olefins having up to about 8 carbon atoms, particularly ethylene, propylene, butene-1, etc., are suitable. j These olefins may be in mixtures with each other or with small amounts of other ethylenically unsaturated monomers, such as methyl acrylate, methyl methacrylate, etc. 5
Gas Phase Polymerization Apparatus Polymerization is carried out in so-called fluidized bed reactors in which the polymer being polymerized is maintained in a fluidized state by an updraft of a gas mixture containing the olefin to be polymerized and the olefins.

The drawings show an example of an apparatus for carrying out the invention.

Fluidization in the reactor is maintained by gas which is withdrawn to the outside from the reactor by means of an external gas phase circulation system and then circulated to the bottom of the reactor by means of a blower 6.

The gas flow rate in the reactor is related to the physical factors of the polymer and the circulating gas, but generally +Cln/
seconds to several + Cm/second. Temperature inside the reactor is 20-90
The temperature is maintained at a temperature of about 10°C and a pressure of several to several tens of atmospheres (gauge). Preferably, the temperature is about 50-75°C and the pressure is about 10-75°C.
It is about 35k91c71T-G. The gas extracted from the top of the reactor 1 is led to a gas cooler 4 for removing reaction heat after most of the fine powder is removed by a cyclone 3. In this cooler, inert hydrocarbons in the gas and an organoaluminum compound as a cocatalyst are condensed. The condensed liquid is pressurized by the pump 5, vaporized by the inert hydrocarbon heater 12 (for example, by steam heating), and then circulated to the reactor through the circulation port 13. Note that this condensed liquid may be extracted out of the system if necessary. On the other hand, the gas cooled by the gas cooler 4 is pressurized by the booster 6 and recirculated to the bottom 9 of the reactor.

The catalyst and fresh inert hydrocarbons are fed to the side of the reaction bed through a feed port 8, and the olefin and hydrogen, which is a molecular weight control agent, are fed to the external gas phase circulation line A through a gas feed port 10.
Further, analysis of the gas composition of line A is performed by an analyzer 11. Regarding the supply position of each substance, it is an essential condition that the catalyst is supplied from the side of the reaction bed, but there are no particular limitations on other substances. Also, each substance is mixed,
It makes no difference whether they are supplied from one supply port or from separate supply ports. The catalyst does not need to be supplied using a special powder feeder, but can be supplied in suspension with the inert hydrocarbon used in the present invention or in the liquefied product of the olefin to be polymerized. It is also possible to previously polymerize a small amount of the olefin and supply it in the form of a suspension of the small amount of polymer and the olefin liquid. It goes without saying that in addition to the recycled organoaluminum compound, fresh organoaluminum compound can be introduced into the reaction zone. The polymer product is extracted from the vicinity of the gas baffle plate 7 via the extraction port 14 so that the height of the reaction bed 2 is substantially constant.

If desired, these reactors can be connected in series and used, for example, in the case of producing a copolymer. 6 Experimental Examples) Example 1 Production of Solid Catalyst Component A pot (S
20.0 f of anhydrous magnesium chloride and 6.0 ml of ethyl benzoate were collected in a tank (manufactured by US3l6) under a nitrogen atmosphere.

This pot was subjected to a vibration mill and processed for two cycles at a total amplitude of 4.0wn1 vibration frequency of 1200/min to obtain a solid product a.
On the other hand, titanium trichloride (eutectic with the composition TiCl3.1I3AICI3 obtained by reducing titanium tetrachloride with metal aluminum) was placed in a flask with an internal volume of 200 m1 in a nitrogen atmosphere at 10.0 V (50 mmol (W) as titanium atoms).
l. M) equivalent), 64 Tnt of 1,2-dichloroethane and 36 ml of a separately prepared solution of iodine trichloride in 1,2-dichloroethane (containing 8.6 TrLM of iodine trichloride) were charged, and the mixture was stirred at 35°C to 40°C for 3 hours. A black-purple uniform liquid b was obtained. The solid product AlO. Oy and 41.3 ml of the above solution were placed again in the above vibrating mill pot and subjected to sitting-time grinding in a nitrogen atmosphere.

The resulting slurry was dried at 25° C. under a reduced pressure of 2 TrOn of mercury to obtain a solid product. This solid was black, plate-like, coarse particles. This solid is further processed in a vibrating mill for two more times.
After being pulverized for a period of time, it was washed with purified n-hexane to obtain a finely powdered solid catalyst component c. The Ti loading rate was 2.4% by weight. Polymerization column diameter 300wrm 1 column height 150h reaction section and diameter 60
0 order, height 900wr! A separately polymerized and sufficiently dried polypropylene powder polymer (8.5k9) was fed to a fluidized bed reactor having an upwardly expanding section n, and the inside of the apparatus was replaced with propylene to make the inside of the reactor 10k9k i·G.

Next, the pressure booster was operated to maintain the polypropylene powder in the reactor in a fluid state. The discharge flow rate of the booster was 81 d/hour. Next, 6.72 y of triethylalkylaluminium (5 9.7 y of the previously produced solid catalyst component C suspended in n-hexane (equivalent to 235 mg titanium atoms)) was added to the reactor, and the total amount of n-hexane supplied was 1.5 liters. The reaction was started by supplying n-hexane such that
During the reaction, the inside of the reactor was controlled at 60°C, and the polymerization pressure was kept at 1
Polymerization was continued for 3 hours by supplying propylene in proportion to the amount consumed so that the concentration was 0k91c/G. The amount of n-hexane condensed in the reaction heat removal gas cooler during the polymerization was on average about 37 k9/h. This liquefied product was heated to about 60°C, vaporized, and then circulated to the reactor. The weight of the produced polymer is obtained by subtracting the polymer added in advance before polymerization, and 33.
It weighed 9 kg. In addition, the proportion of the heated heptane insoluble part of the produced polymer was 96% after correcting the contribution of the polymer added in advance.
．． It was 4% by weight. Polymerization was carried out under exactly the same conditions as above.
Although the test was repeated several times, no signs of clogging in the gas cooler 4 or the inert hydrocarbon circulation port 13 (see drawing) were observed.

As a precaution, the gas cooler and inert hydrocarbon circulation port were opened and inspected, and no polymer was found to be attached.

Example 2 The catalyst and equipment were exactly the same as in Example 1.

8.5 kg of separately polymerized and sufficiently dried polypropylene powder polymer was supplied to the fluidized bed reactor, and the inside of the reactor was heated to 10 kg.
It was set as 91c erase/G. Furthermore, n-butane was supplied, and the pressure inside the reactor was set to 15.5k91cTPt-G. Next, the pressure booster was operated to maintain the polypropylene powder in the reactor in a fluid state. The discharge flow rate of the booster was 81 d/hour as in Example 1. In a reactor, 6.72q of triethylalkylaluminium and 9.7Oy (235mg
(equivalent to titanium atoms) was supplied to start the reaction. During the reaction, the inside of the reactor was controlled at 60°C, and the polymerization pressure was further increased to 15.5k9.
Polymerization was continued for 3 hours by supplying propylene in proportion to the amount consumed so that the amount was 1 cd-G.

The amount of n-butane condensed in the reaction heat removal gas cooler during polymerization is on average about 74k9/h, including a trace amount of n-butane.
- Also contained hexane. This liquefied product was heated to about 60°C, vaporized, and then circulated to the reactor. The weight of the produced polymer is calculated by subtracting the polymer added in advance before the weight.
．． It was 3k9. In addition, the proportion of the heated heptane insoluble portion of the produced polymer is 95% after correcting the contribution of the polymer added in advance.
．． The heel volume was %. Polymerization was repeated w times under exactly the same conditions as above, but no signs of clogging in the gas cooler 4 or the inert hydrocarbon circulation port 13 were observed.

When I opened it up and inspected it just to be sure, no polymer adhesion was found. Comparative Example 1 Completely the same as Example 1 except that no n-hexane was added to the reactor.

Two hours and one minute after the start of polymerization, the temperature inside the fluidized bed reactor could no longer be controlled to 60°C even though the automatic cooling water control valve of the gas cooler was fully opened. , the rapid filtration reaction was stopped, and the gas cooler was opened and inspected. It was found that a film of polymer was attached to the heat transfer surface of the cooler.

The proportion of hot heptane insoluble portion of this deposited polymer was 48. The weight was %. Comparative Example 2 Same as Example 1 except that the inert hydrocarbon heater 12 was kept at room temperature.

It was found that the discharge pressure of the pump 5 began to gradually increase after 1 hour and 2 minutes had passed from the start of polymerization, and the supply port to the reactor began to become clogged. After 4 more episodes,
Since the discharge pressure of the pump showed the pressure when the flow rate was zero, the pump was stopped and polymerization was continued. After 3 hours from the start of polymerization, the reaction was stopped and the apparatus was opened.
Upon inspection, it was found that although there was no polymer attached to the gas cooler 4, polymer was attached near the inert hydrocarbon circulation port 13, completely blocking the supply port.

The weight of the produced polymer was 24.1k9 after subtracting the polymer charged in advance before polymerization.

The proportion of the hot heptane insoluble portion of the produced polymer was 93.1% by weight after correcting the contribution of the polymer introduced in advance. In addition, coarse polymer in which particles were aggregated was present in the produced polymer. BRIEF DESCRIPTION OF THE DRAWINGS The drawings schematically show an example of an apparatus for implementing the present invention.

1...Reactor, 2...Reaction zone, 3...
...Cyclone, 4...Gas cooler, 5...
... Pump, 6 ... Booster, 7 ...
・Gas baffle plate, 8... Catalyst/inert hydrocarbon supply port, 9... Circulating gas supply port, 10... Olefin/hydrogen supply port, 11... Gas composition analyzer,
12... Inert hydrocarbon heater, 13...
...Inert hydrocarbon circulation port, 14...Product outlet, A...External gas phase circulation line.

Claims (1)

[Claims] 1. In a fluidized bed reaction zone equipped with an external gas phase circulation system having a cooling zone, a catalyst system using an organoaluminum compound as a cocatalyst that liquefies under the cooling conditions of the cooling zone is used. A method for gas phase polymerization of olefins, which is characterized in that the following conditions are satisfied when performing gas phase polymerization of olefins. (A) The number of carbon atoms in the reaction zone is 1 from the olefin for polymerization.
~4 Large inert hydrocarbons coexist in the gas phase. (B) liquefying the inert hydrocarbon together with the organoaluminum compound as the gas phase in the reaction zone is cooled in the cooling zone of the external gas phase circulation system. (C) Part or all of the liquefied product in this cooling zone is vaporized and recycled to the reaction zone.