JP3518965B2 - Method and apparatus for controlling hydrogen concentration in polymerization reactor - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for controlling the hydrogen concentration in a gas phase polymerization reactor, which is useful when the polymerization reaction conditions are changed according to the desired physical properties of the polymer, and more particularly to a method for controlling the hydrogen concentration in the gas phase polymerization reactor. The present invention relates to a method for reducing hydrogen concentration.

[0002]

2. Description of the Related Art Generally, in a polymerization reaction such as bulk polymerization, solution polymerization, suspension polymerization, gas phase polymerization, etc., in which polymerization is carried out in the presence of a gas phase containing hydrogen, it is necessary to change the hydrogen concentration in the reactor. May be. For example, when changing the polymerization conditions to produce a polymer with different physical properties in a single polymerization reactor, such as changing the polymer produced in the plant from one with a low molecular weight to one with a high molecular weight, hydrogen in the reactor It is necessary to change the concentration. In general, the larger the difference in the molecular weight between the polymers, the larger the range of hydrogen concentration to be changed. Even if the difference in molecular weight is not so large, the hydrogen concentration range to be changed may be large if the catalyst system used is changed.

The hydrogen concentration in the reactor is usually changed by changing the hydrogen concentration in the gas phase of the reactor by using a method such as adjusting the amount of hydrogen supplied to the reactor.
This is a method used not only in gas phase polymerization but also in liquid phase polymerization and the like. This is because the amount of hydrogen in the gas phase is generally larger than that in the liquid phase, and the hydrogen concentration in the entire reactor can be controlled by controlling the hydrogen concentration in the gas phase.

However, when the hydrogen concentration is increased, it can be controlled relatively easily by increasing the hydrogen supply amount, but it has not been easy to reduce the hydrogen concentration efficiently.

That is, in the prior art, as a method for reducing the hydrogen concentration, the amount of hydrogen supplied to the reactor is suppressed and sometimes stopped, or the gas phase in the polymerization reactor is partially polymerized. Although it was extracted to the outside or combined with these methods depending on the case, in such a method, the reaction conditions gradually changed, and the physical properties of the obtained polymer, that is, the product quality, fluctuated, and sometimes a large amount of Was sometimes forced to manufacture nonstandard products. This tendency is particularly remarkable in the case of a gas phase polymerization reaction having a large gas phase volume.

[0006] For example, when the hydrogen concentration in the gas phase is reduced by the above-mentioned method, the hydrogen concentration in the polymerization reactor decreases slowly, or the pressure changes due to the withdrawal of gas from the polymerization reactor. May occur, and a large amount of nonstandard products tended to occur. Further, when a large amount of gas phase is withdrawn from the polymerization reactor in order to increase the rate of change of hydrogen concentration, it is necessary to add a gas component corresponding to the withdrawal amount, and the faster the withdrawal rate, the more difficult its control becomes. Non-standard products are likely to occur. Even in the case of liquid phase polymerization, particularly when a solvent is used, the solvent corresponding to the vapor pressure is also extracted out of the system together with the extraction of the gas phase.Therefore, it is necessary to change the solvent supply amount according to the extraction of the gas phase. As a result, the operation tends to be complicated, and sophisticated control equipment tends to be required. In addition, these methods require a facility for recovering the monomer from the extracted hydrogen-containing gas, resulting in an increase in facility costs and operating costs.

Such a problem is not limited to the case of changing the polymerization conditions in a single reactor as described above,
It also tends to occur in multistage polymerization using a plurality of polymerization reactors having different polymerization conditions.

The term "multistage polymerization" as used herein refers to a method in which two or more polymerization reactors are used and polymerization is performed stepwise under mutually different polymerization conditions. For example, a method in which two polymerization reactors are used and a powdery polymer is first produced in the polymerization reactor in the first stage and then the powdery polymer is transferred to the polymerization reactor in the second stage to carry out further polymerization can be mentioned. The polymerization form in each polymerization reactor may be any of gas phase polymerization, bulk polymerization, solution polymerization, suspension polymerization and the like, and the polymerization forms in each stage may be the same or different from each other.

The problem in the multi-stage polymerization will be explained by taking the multi-stage polymerization in which the former stage is gas phase polymerization as an example. In the case where the latter stage is under the condition that the hydrogen concentration is lower than that of the former stage,
In order to reduce the amount of hydrogen that accompanies the powder that flows into the latter stage from the polymerization reactor in the first stage, before the powder enters the polymerization reactor in the second stage, one of the entrained gases (including hydrogen) in the monomer in the middle of the inflow line from the first stage By purging the parts or purging with an inert gas, the amount of hydrogen mixed in the latter-stage polymerization reactor was reduced.

However, even using such a purging system, it was not easy to replace the gas in the powder. In order to perform sufficient replacement, it is necessary to carry out a long-time purge, or to pressurize with fresh monomer etc. and then carry out a cycle of depressurizing several times or more, which requires expensive equipment or operation. Tended to be complicated. Furthermore, even if the purged gas is fed into the polymerization reactor again, a separate pressurizing system and piping system are required.

Further, the longer the residence time in the purge system is, the more the powder is held up (storage amount).
Is increased, and it takes a long time to change the type (brand) of the polymer to be produced, or a large amount of unnecessary polymer is likely to be produced, which is not economical. Such a problem similarly occurs even if the former stage is liquid phase polymerization.

[0012]

SUMMARY OF THE INVENTION A first object of the present invention is to provide a method and a device for controlling the hydrogen concentration in a polymerization reactor, particularly in the gas phase in the polymerization reactor which is required when changing the polymerization reaction conditions. By quickly reducing the hydrogen concentration,
The goal is to minimize the production of non-standard products with physical properties.

A second object of the present invention is to provide a method and apparatus for controlling the hydrogen concentration in a polymerization reactor, which does not require extraction of the gas in the reactor out of the system when changing the polymerization reaction conditions.
Therefore, it is to reduce the hydrogen concentration economically and rapidly.

A third object of the present invention is to perform a multi-stage polymerization using at least two or more polymerization reaction facilities, if the hydrogen concentration of the pre-stage polymerization reactor is higher than that of the post-stage polymerization reactor as the polymerization condition, It is an object of the present invention to provide a method for controlling a hydrogen concentration in a rear stage by transferring a polymer from the front stage to the rear stage without requiring extraction of the gas in the reactor out of the system during the rear stage.

[0015]

The present invention adopts the following means in order to solve the above problems. That is, the present invention, in the presence of a gas containing hydrogen, at the time of polymerizing an olefin in the polymerization reactor, at least a part of the gas in the polymerization reactor is extracted, and then hydrogen in the extracted gas is removed. Addition reaction to the olefin, that is, the gas is hydrotreated, and then the gas after the hydrotreatment is supplied to the polymerization reactor again to reduce the hydrogen concentration in the polymerization reactor. A method for controlling the hydrogen concentration in a reactor is provided.

The invention also relates to a polymerization reactor for polymerizing olefins in the presence of a gas containing hydrogen.
Aside from the above, it is composed of a hydrogenation reactor filled with a hydrogenation catalyst for adding hydrogen in the gas extracted from the polymerization reactor to an olefin to hydrotreate the gas, and the hydrogenation reactor is a polymerization reactor. The gas withdrawn from the reactor is introduced into the hydrogenation reactor, and the gas after the hydrotreatment is connected to the polymerization reactor so as to return to the polymerization reactor again, whereby the hydrogen concentration in the polymerization reactor is increased. A hydrogen concentration control device in a polymerization reactor is provided.

The method of the present invention comprises a gas phase containing hydrogen.
When the olefin is polymerized in the polymerization reactor in the presence of, the hydrogen concentration in the polymerization reactor is controlled, and particularly lowered. Specifically, the method of the present invention is, in one polymerization reactor, changing the hydrogen concentration necessary when changing the polymerization conditions when sequentially producing product polymers having different physical properties, or from the previous stage in multi-stage polymerization. Is also used for controlling the hydrogen concentration in the latter stage when lowering the hydrogen concentration in the latter stage.

In this method, at least a part of the gas in the polymerization reactor is extracted and passed through a hydrogenation reactor, hydrogen in the gas is added to an olefin to hydrotreate the gas, and then after the hydrotreatment. It is carried out by returning the above gas to the polymerization reactor again.

Further, the apparatus of the present invention comprises a hydrogenation reactor which is connected to and attached to a polymerization reactor used for polymerizing an olefin in the presence of a gas containing hydrogen. This hydrogenation reactor is used for the addition reaction of hydrogen in the gas withdrawn from the polymerization reactor with olefins. To carry out this hydrogenation reaction, the hydrogenation reactor is preferably filled with a hydrogenation catalyst. The hydrogenation reactor is connected such that the gas extracted from the polymerization reactor is introduced into the hydrogenation reactor, and the gas after the addition reaction and the hydrotreatment is returned to the polymerization reactor. There is.

When changing the polymerization conditions of one polymerization reactor, the hydrogenation reactor may be connected to the polymerization reactor only when the polymerization conditions are changed. In the case of multi-stage polymerization, it is usually connected to the latter part.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The present invention can be applied to any of gas phase polymerization, bulk polymerization, solution polymerization, and suspension polymerization, and there is no difference in the constitution of the present invention except for a reactor unique to each polymerization method and a reaction condition. Therefore, unless otherwise specified, description will be made without distinction.

In order to carry out the method of the present invention, a hydrogenation reactor filled with a hydrogenation catalyst is connected to the polymerization reactor, and the polymerization reactor is provided with the hydrogenation reactor. At least a part of the gas in the reactor, that is, all or part of the gas is extracted and passed through a hydrotreating reactor for hydrotreatment, and then part or all of the gas after the hydrotreatment is returned to the polymerization reactor again. , Just circulate.

The gas withdrawn from the polymerization reactor contains hydrogen, olefin, etc., and the hydrogen in the gas introduced into the hydrogenation reactor should be eliminated or significantly reduced by being added to the olefin. You can By returning the gas whose hydrogen concentration has decreased to the polymerization reactor again, the hydrogen concentration of the gas in the polymerization reactor can be rapidly decreased, and the polymerization conditions can be changed promptly. Further, in the multi-stage polymerization, the hydrogen mixed in the latter-stage polymerization reactor is rapidly consumed, whereby the inside of the latter-stage polymerization reactor can be maintained at a predetermined hydrogen concentration.

When the control method of the present invention is used when changing the polymerization conditions of one polymerization reactor, the polymerization reactor whose polymerization conditions are to be changed and the hydrogenation reactor are connected, After a part or all of the gas in the polymerization reactor is extracted from the polymerization reactor and passed through a hydrogenation reactor, hydrogen is added to the olefin in the hydrogenation reactor to hydrotreate the olefin, and then a part thereof Alternatively, return all to the polymerization reactor. This operation is continued until the polymerization reactor has a predetermined hydrogen concentration.

This operation may be carried out batchwise or continuously, as long as it does not allow undesired reactions to proceed in the polymerization reactor. Polymerization reaction may runaway due to changes in hydrogen concentration,
It is preferable to carry out continuously except for special cases where the change range of hydrogen concentration is relatively small.

When the present invention is applied, the polymerization reactor used in the polymerization step may be a batch-type polymerization reactor as long as it can polymerize an olefin in a gas phase containing hydrogen. A continuous polymerization reactor (single-stage or multi-stage polymerization reactor) may be used, but in the present invention, it is more effective when changing the polymerization conditions of the continuous polymerization reaction for the following reasons.

That is, when the polymerization conditions are changed according to the physical properties of the polymer product, in the case of a batchwise polymerization process, the polymerization is temporarily interrupted, and a part or all of the contents are replaced, and then the polymerization is performed under new polymerization conditions. On the other hand, in the case of a continuous polymerization process, the polymerization is carried out continuously under new polymerization conditions without interrupting the polymerization.Therefore, when lowering the hydrogen concentration in the polymerization reactor, the continuous system has better physical properties. Will increase the production of non-standard products. Since the method of the present invention is configured to rapidly reduce the hydrogen concentration under such a situation, it is particularly effective when applied to a continuous polymerization step.

Other changes in the polymerization conditions may be carried out at the same time as the main hydrotreatment, before or after, or partially overlapped with each other. In order to shorten the change time, in general, it is often done at the same time, but if the gas composition after the condition change is higher in the high boiling olefin content than the gas composition before the change, change the gas composition after the hydrogenation treatment. Preferably.

Next, the case where the hydrogen concentration of the latter stage is lower than that of the former stage in the multi-stage polymerization will be described. When the powdery polymer polymerized in the first stage is introduced into the second stage, since the powdery polymer is transferred from the first stage to the second stage in a state of containing hydrogen, when the required hydrogen concentration in the latter stage is lower than that in the first stage, for example, in the latter stage, In the case where the catalyst of (1) is hypersensitive to hydrogen, or when the facility is a facility for producing a remarkably high molecular weight, the leakage of hydrogen from the preceding stage becomes a problem. A metallocene catalyst is known as a catalyst that is sensitive to hydrogen.When a metallocene catalyst is used in both the first and second stages, or when the first stage is a Ziegler catalyst and the second stage is a metallocene catalyst, hydrogen leaks from the first stage to the second stage. Prevention of inclusion is important for product quality control. The method of the present invention has an excellent effect in controlling the subsequent polymerization conditions in the multi-stage polymerization reaction step in which the influence of the hydrogen concentration on the physical property control is severe.

Here, the step of transferring the powdery polymer from the former stage to the latter stage is largely different between the case where the former stage is gas phase polymerization and the other case. For example, when the former stage is gas phase polymerization, usually,
The powdery polymer is once transported to a gas-solid separation step (a step of separating a gas phase and a solid phase), where it is gas-solid separated, and then the powdery polymer is transferred to a subsequent stage by a means such as gas transportation. After the gas-solid separation step, it may be replaced with a gaseous monomer in the former stage or the latter stage.

On the other hand, when the former stage is liquid phase polymerization (solution, bulk, suspension polymerization, etc.), only the liquid phase (solution containing polymer) is often withdrawn from the lower part of the reactor or the side wall. The extracted polymer solution may be directly transferred to the subsequent stage, but when the amount of bubbles in the liquid phase is large or when the liquid phase is extracted from the polymerization reactor in an overflow form, a gas-liquid separation step is required. In many cases, the polymer solution is transferred to the subsequent stage after such a gas-liquid separation step.

The powdery polymer or polymer solution from the former stage is introduced into the latter stage in a state where hydrogen in the former stage is mixed in both the gas phase and liquid phase polymerization. Although it is not possible to control the value, a hydrogenation reactor filled with a hydrogenation catalyst is connected to the latter-stage polymerization reactor, and is installed side by side, and when the olefin is polymerized in the polymerization reactor, the gas in the polymerization reactor is At least a part of, i.e., all or part of, is passed through a hydrogenation reactor, and then part or all of the gas is returned to the polymerization reactor and circulated so that the hydrogen concentration in the latter stage is controlled to a predetermined value. You can control the value of.

The embodiments of the present invention will be described below separately for the polymerization step and the hydrotreating step.

(1) Polymerization Step and Polymerization Reactor As long as the polymerization reactor used in the polymerization step in the method of the present invention can polymerize an olefin in the presence of a gas phase (gas) containing hydrogen, A batch (batch) type polymerization reactor or a continuous type polymerization reactor (single-stage or multi-stage polymerization reactor) may be used, but as described above, the method of the present invention is used when changing the polymerization conditions of the continuous polymerization reaction or in the multi-stage polymerization reaction. Since it has a further effect in controlling the polymerization conditions in the latter stage of
A polymerization reactor used for such continuous polymerization reaction or multi-stage polymerization reaction is preferable. Further, generally, as the polymerization method performed in the presence of a gas phase containing hydrogen, bulk polymerization, solution polymerization, suspension polymerization, gas phase polymerization and the like can be mentioned, and the polymerization reactor used in the present invention can be any of these. It may be used in the above polymerization method.

In the present invention, the olefin is polymerized in such a polymerization reactor to produce a polymer. In this case, hydrogen is contained in the gas phase (gas), but in the gas phase polymerization, the concentration range of hydrogen in the gas is 5% or less, preferably 2% or less. Even if the hydrogen concentration is as high as more than 5%, there is no particular problem in carrying out the method of the present invention, but the concentration of the olefin hydride (eg ethane, propane) produced in the polymerization reactor becomes high, and as a result, Since it is necessary to take it out of the system, it is not preferable to set it too high.

In the liquid phase polymerization, hydrogen in the gas phase is 10
% Or less, preferably 2% or less. When the polymerization is carried out using a metallocene catalyst, the hydrogen concentration in the gas phase in the gas phase polymerization is 0.1% or less, preferably 0.01% or less,
In liquid phase polymerization, it is 1% or less, preferably 0.2% or less.

When the present invention is used to change the polymerization conditions in one polymerization reactor, any hydrogen concentration may be used as long as the hydrogen concentration after the condition change is lower than that before the change. And the hydrogen concentration after change is 1/5
It is 1/1000 or less, preferably 1/10 to 1/200 or less, and particularly preferably 1/20 to 1/100 or less.

In the case of multistage polymerization, the hydrogen concentration in the latter stage is generally 1/5 to 1/1000 or less as compared with that in the former stage.
It is preferably 1/10 to 1/200 or less, and particularly preferably 1/20 to 1/100 or less.

In the hydrogen concentration control method of the present invention, depending on the polymerization method, other polymerization conditions, etc., the above-mentioned hydrogen concentration range, conditions having a concentration difference range, when changing the polymerization conditions of the condition difference, and in multistage During the polymerization, the hydrogen concentration in the polymerization reactor can be quickly adjusted.

The polymer produced in the polymerization reactor by the method of the present invention may be a homopolymer or a copolymer. As the olefin polymerized in the present invention, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 4-methyl-1-
Pentene, 3-methyl-1-pentene, styrene, butadiene, isoprene, 1,4-hexadiene, dicyclopentadiene, 5-ethylidene-2-norbornene and the like can be exemplified, but they are determined by the kind of the desired polymer product. That is, as a homopolymer product, for example, polyethylene, polypropylene, polybutene, etc., and as a copolymer product, a copolymer of polyethylene, homopolypropylene or random polypropylene, and another monomer, so-called EPR (ethylene-propylene rubber), P
When producing a block copolymer or the like with ER (propylene-ethylene rubber), PBR (propylene-butene rubber), etc., the monomers used in the polymerization step of the present invention include ethylene, propylene, 1-butene, 1-Pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene and the like are preferable.

Although the polymerization temperature varies depending on the kind of the monomer, the molecular weight of the product, etc., it is lower than the melting point of the olefin polymer, preferably 10 ° C. or more lower than the melting point, more preferably room temperature to 200 ° C., and particularly preferably. 40-1
The temperature is about 60 ° C, most preferably about 60 to 130 ° C. Further, in order to maintain the polymerization temperature within this range, the polymerization system is cooled by a cooler. In addition, the polymerization pressure is from atmospheric pressure to 1
About 50 kg / cm ² , preferably ² to 70 kg / cm ²
And more preferably about 10 to ²⁰ kg / cm ² .

As a polymerization catalyst, Japanese Patent Publication No. 60-4564 is used.
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. 5, a transition metal catalyst, in particular, an olefin polymerization catalyst in which a highly active transition metal catalyst component and an organometallic compound catalyst component of a metal of Groups 1 to 3 of the periodic table are combined is preferably used. it can. Above all, a highly active catalyst capable of producing about 5,000 g or more, particularly about 8,000 g or more of an olefin polymer per 1 mmol of transition metal is preferable.

(2) Hydrotreating Step and Hydrogenating Reactor In the hydrotreating step, first, a gas containing hydrogen is extracted from the polymerization reactor. Here, the gas is usually extracted from the gas part, that is, the deceleration region in the gas phase polymerization equipment, and the gas phase part in the liquid phase reaction. In this case, gas-solid (gas phase and solid phase), gas-liquid (gas phase and liquid phase), and other mixed materials were extracted and separated into gas phase and solid phase or gas phase and liquid phase, followed by separation. The gas phase (gas) may be introduced into the hydrogenation reactor.

The gas withdrawn from the polymerization reactor in this manner contains hydrogen, olefins, etc., and the hydrogen in the gas introduced into the hydrogenation reactor disappears or remarkably disappears by the addition reaction of olefin. Can be reduced. By supplying the gas whose hydrogen concentration is lowered to the polymerization reactor again, the hydrogen concentration in the polymerization reactor can be rapidly lowered. After the hydrogen concentration has reached the predetermined condition, the hydrogenation process may be stopped.

When the extracted gas has a large amount of condensed components, the condensed components may be separated by cooling in advance with a heat exchanger or the like before the hydrogenation treatment, and only the residual gas may be subjected to the hydrogenation treatment.
The separated condensed component is usually returned to the polymerization reactor, but part or all of it may be taken out of the polymerization system if necessary.

The gas extracted from the polymerization reactor in this manner is introduced into the hydrogenation reactor which is connected to the polymerization reactor and is provided side by side. This hydrogenation reactor is a device for adding hydrogen in the gas extracted from the polymerization reactor to an olefin to hydrogenate the olefin. In this addition reaction, a small amount of hydrogen reacts with an excess of olefin to produce an olefin hydride such as ethane and propane.
Hydrogen in the gas is consumed, and as a result, the hydrogen concentration in the polymerization reactor can be reduced. In this case, some or all of the gas after passing through the hydrogenation reactor is returned to the polymerization reactor and circulated, or the hydrogenation reactor is connected so that the gas returns to the polymerization reactor. .

The hydrogenation reactor may be connected to the polymerization reactor when necessary such as when the polymerization conditions are changed. In a multi-stage polymerization facility, depending on the product to be manufactured, the polymerization reactor used in the subsequent stage, for example, the second stage or the third stage may be used in some cases, and in the other products, the first stage or the second stage may be used. In some cases, it may be relatively upstream or downstream, so that all or part of the polymerization reactor may be connected to the hydrogenation reactor as needed.

Such a hydrogenation reactor is sufficient if it can hydrogenate the olefin in the gas extracted from the polymerization reactor. For example, only the reaction temperature may be set, but it is usually filled with a hydrogenation catalyst. . The hydrogenation catalyst used in the hydrogenation reactor basically has a high hydrogenation performance, has a hardness that does not become powdered due to an impact at the time of filling or gas circulation, and has a side reaction such as dimerization. It is necessary to meet the conditions such as not causing it. If the hydrogenation catalyst enters the polymerization reactor due to pulverization or the like, it may affect or be affected by the polymerization reaction conditions such as the polymer product, the polymerization catalyst and the hydrogen concentration. In the worst case, the hydrogenation reaction always occurs in the polymerization reactor, and the hydrogen concentration cannot be controlled. In addition, it is not preferable to mix it in the product because of the quality of the product.

As the hydrogenation catalyst satisfying these conditions, a so-called solid catalyst, for example, a metal-supported catalyst having Pt or Pd as a carrier metal and SiO ₂ or Al ₂ O ₃ or a mixture thereof as a carrier, Examples thereof include a metal catalyst in which copper-chromium-barium-manganese is supported on silica or alumina, and a copper catalyst in which copper is supported on silica. Preferably Pd
/ Al ₂ O ₃ , Pd / SiO ₂ · Al ₂ O ₃ , Pd / Si
O ₂ , Pt / Al ₂ O _{3 and the} like, among which Pd / Al ₂ O ₃ is preferable.

Pd / Al ₂ O ₃ is particularly preferable because the reaction proceeds relatively mildly, the selectivity is high, the activity is high (usable at a low hydrogen concentration), and the life is long. Etc.

The basic way to control the hydrogen concentration in the polymerization reactor is to control the amount of gas passing through the hydrogenation reactor. When controlling the hydrogen concentration to a constant value, the passing gas amount is set so that the same amount of hydrogen as the gas in the gas entrained in the powder from the polymerization reactor at the preceding stage undergoes an addition reaction. If necessary, the amount of gas passing through the hydrogenation reactor can be set within an appropriate range while supplying a slight amount of hydrogen to the polymerization reactor. The proper range here is a range that can be controlled in process design, and changes depending on the design flow rate. Therefore, there is no particular limitation on the appropriate range of the passing gas amount, but in general, GHSV is 1000 to 50,
It is preferably about 500 to 100. Here, "GH
“SV” represents a gas space velocity per unit time, and is a volume velocity (m ³ / m ³ of feed gas at temperature and pressure during reaction
hr) divided by the volume (m ³ ) of the hydrogenation reactor, the unit being hr ⁻¹ . The volume of the hydrogenation reactor at this time is an empty volume not filled with the catalyst.

In the hydrogenation reactor, the hydrogen concentration in the gas after the hydrogenation reaction can be made almost zero by appropriately selecting the type and amount of the hydrogenation catalyst. In this case, the amount of hydrogen removed is the product of the hydrogen concentration in the polymerization reactor and the amount of passing gas, so the amount of passing gas can be easily set. If the internal volume of the hydrogenation reactor and the filter installed in the preceding stage of the hydrogenation reactor is relatively large, the gas in the polymerization reactor before connecting the hydrogenation reactor to the polymerization reactor The operation can be smoothly started by pressurizing the inside of the hydrogenation reactor and the filter with a gas having the same composition as that of the composition and reaching the same pressure as that of the polymerization reactor, and then connecting to the polymerization reactor.

The hydrogenation reaction temperature is not particularly limited, but is usually 20 to 90 ° C, preferably about 50 to 70 ° C. The hydrogenation reaction pressure is not particularly limited, but it is usually almost the same as the polymerization pressure, and the atmospheric pressure to 150 kg / cm ² f, preferably ^{2 to} 70 kg / cm ² f, more preferably 10 to 2
It is 0 kg / cm ² f. These conditions are controlled such that hot spots are not formed in the catalyst and disproportionation reaction does not occur, and the hydrogen concentration becomes a predetermined value.

When the operation of the hydrogenation reactor is stopped, the connection with the polymerization reactor is cut off, the gas in the hydrogenation reactor is discharged to the outside of the system, and if necessary, the inside is slightly added with nitrogen gas. Put in pressure.

Since the gas supplied from the polymerization reactor to the hydrogenation reactor contains the polymer in a fine powder state,
When the gas accompanied with the fine powder is passed through the hydrogenation reactor and the temperature of the hydrogenation catalyst is partially higher than the melting point of the polymer, there is a possibility that the fine powder may be melted and coated on the portion to lower the catalytic activity. is there. Therefore, in the present invention, in order to remove fine powder between the polymerization reactor and the hydrogenation reactor, that is, in the middle of the route for introducing the gas extracted from the polymerization reactor into the hydrogenation reactor. It is desirable to install the above filter and remove the fine powder product contained in the gas by filtering the gas before passing through the hydrogenation reactor with the filter.

The method and apparatus of the present invention comprises a copolymer of olefinic polymers, especially olefinic copolymers such as polyethylene, homopolypropylene or random polypropylene, with other monomers, ie EPR, PE.
In the case of producing a block copolymer with R, PBR, etc., it is particularly effective in reducing the hydrogen concentration in the polymerization reactor, which is necessary when changing the polymerization reaction conditions.

The gas withdrawn from the polymerization reactor by the method and apparatus of the present invention is passed through the hydrogenation reactor, returned to the polymerization reactor, and circulated to rapidly reduce the hydrogen concentration in the polymerization reactor. You can Further, by filtering the fine powder of the olefin polymer with the filter, there is no fear that the catalytic activity will decrease due to the fusion of the fine powder even if the temperature of the hydrogenation catalyst in the hydrogenation reactor is partially higher than the melting point of the polyolefin. .

(3) Example of apparatus of the present invention FIG. 1 shows an example of a suitable apparatus for carrying out the method of the present invention in continuous polymerization. In the figure, 1 is a gas phase polymerization reactor, 2 is a hydrogenation reactor, 3 is a filter, 4 is a cooler, 5 and 5'are blowers, and 6 is a gas circulation path.

A gas containing olefin and hydrogen flows into the gas phase polymerization reactor 1 from the polymerization reactor at the previous stage, and further gas phase polymerization is carried out there. Most of the gas extracted from the gas phase polymerization reactor 1 is cooled to a predetermined temperature through a cooler 4 and then circulated to the gas phase polymerization reactor 1 by a blower 5. Part of the circulating gas is taken out from the downstream side of the blower 5 and sent to the filter 3,
Here, the finely divided product in the gas is filtered and then passed through the blower 5 ′ into the hydrogenation reactor 2. Here, the hydrogen in the gas is added to and disappears from the olefin by the hydrogenation catalyst filled in the hydrogenation reactor 2, and an olefin hydride is produced. Further, this gas is returned from the hydrogenation reactor 2 to the gas phase polymerization reactor 1 again by the route shown by 6 and circulates in the above process. By the above operation, the hydrogen concentration in the gas in the polymerization reactor 1 can be controlled to the target concentration.

The apparatus of FIG. 1 is an example in which the filter 3 is provided in the preceding stage of the hydrogenation reactor 1, but in the present invention, the filter 3 may be omitted as shown in FIG. That is, FIG. 2 is an example of a device in which the filter 3 is removed from FIG.

The above is an example of an apparatus for carrying out the present invention in a continuous system, but as an example of an apparatus (not shown) for carrying out a batch system,
1 to 2 except that the polymerization reactor 1 is replaced with a gas phase polymerization reactor used in a batch type gas phase polymerization process (for example, one composed of one of the multistage polymerization reactors 1) Is mentioned.

In any case, among the above apparatus examples, FIG.
And the device of FIG. 2 is preferred.

[0063]

Embodiments of the method of the present invention will be described below with reference to the drawings. All% in the examples are% by volume.

[0064]

Example 1 As shown in FIG. 1, in a gas phase polymerization reactor 1, a gas obtained by gas phase polymerization of ethylene and propylene (manufacturing EPR) (hydrogen gas concentration: 0.6%, temperature: 70%) was used.
C.) is circulated through a cooler (outlet gas temperature 60 C). A part thereof was taken out at a flow rate of 4500 Nm ³ / hr (4% of the total flow rate), passed through the hydrogenation reactor 2 through the filter 3, and this gas was returned to the gas phase polymerization reactor 1 again and circulated. When this operation was performed for 10 minutes, the hydrogen concentration in the polymerization reactor 1 dropped from 0.6% to 0.3%. The catalyst used in the hydrogenation reactor 2 is Pd / Al ₂ O ₃
Is. The amount of monomer consumed in the hydrogenation reaction is 6 kg,
The ethane and propane in the gas in the polymerization reactor 1 were each 0.
Increased by 1%. The analysis of hydrogen concentration was performed by online gas chromatography.

[0065]

Comparative Example 1 In Example 1, the hydrogenation reactor 2 was not used, and the gas was directly extracted from the gas phase polymerization reactor 1 at a flow rate of 70 Nm ³ / hr outside the system. It took 6.9 hours to reduce the hydrogen concentration in the polymerization reactor 1 from 0.6% to 0.3%. The amount of the monomer extracted outside the system by this operation reached 405 kg.

[0066]

Comparative Example 2 The same operation as in Comparative Example 1 was repeated except that the amount of gas taken out was increased to 220 Nm ³ / hr. It took 3.1 hours to reduce the hydrogen concentration in the polymerization reactor 1 from 0.6% to 0.3%. The amount of the monomer extracted outside the system by this operation reached 670 kg.

[0067]

Example 2 Multistage polymerization was carried out by using the apparatus shown in FIG. 1 in the latter stage. (In FIG. 1, the latter-stage gas phase polymerizer is mainly shown, and the former-stage polymerizer is not shown).

In the first stage, polypropylene was produced at 6000 kg / hr under the condition that the hydrogen concentration in the reactor was 1% by weight. The obtained polymer is a gas-solid separation drum (residence time:
After gas-solid separation in 1 minute), it was fed to the gas phase polymerization vessel 1 in the subsequent stage.

In the gas phase polymerization reactor 1, a gas (hydrogen gas concentration of 0.05%, temperature 70 ° C.) obtained by gas phase polymerization of ethylene and propylene (production of EPR) was used as a cooler (outlet gas temperature 60 ℃). 20 part of it
With a flow rate of 00 Nm ³ / hr (2% of the total flow rate),
After passing through the hydrogenation reactor 2 through the filter 3, this gas was returned to the gas phase polymerization reactor 1 again and circulated. By this operation, the inside of the gas phase reactor 1 has a hydrogen gas concentration of 0.05.
I was able to keep it at%.

The catalyst used in the hydrogenation reactor 2 is Pd / A.
1 ₂ O ₃ . 2k monomer consumed in hydrogenation reaction
It was g / hr.

[0071]

Comparative Example 3 In Example 2, the hydrogenation reactor 2 was not used, and the gas was directly extracted from the gas phase polymerization reactor 1 at a flow rate of 500 Nm ³ / Hr outside the system. The hydrogen concentration in the polymerization reactor 1 could only be reduced to 0.2%. The amount of the monomer extracted outside the system by this operation is 78
It reached 0 kg / hr. This is the same as the amount of polymerization in the gas phase polymerizer 1, and the control of the hydrogen concentration by further extraction has to be abandoned.

[0072]

According to the present invention, when the polymerization reaction conditions are changed,
The hydrogen concentration in the polymerization reactor in which the olefin is polymerized decreases. This brings about an effect that the nonstandard product of the physical properties produced during the change of the polymerization reaction condition can be suppressed to the minimum. Further, the amount of gas discharged and removed outside the system is also reduced, so that the effect of being economical is produced.

Further, by providing a filter between the polymerization reactor and the hydrogenation reactor to remove fine powder in the gas extracted from the polymerization reactor, the catalyst temperature in the hydrogenation reactor is partially increased. Even if it is, there is an effect that there is no fear of lowering the catalytic activity.

[Brief description of drawings]

FIG. 1 is an apparatus diagram of an example for carrying out the method of the present invention.

FIG. 2 is an apparatus diagram of an example for carrying out the method of the present invention.

[Explanation of symbols]

1 ... Multi-stage gas phase polymerization reactor 2 ... Hydrogenation reactor 3 ………… Filter 6 ... Gas circulation path

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshio Akiyama 3 Chikusaigan, Ichihara, Chiba Mitsui Petrochemical Co., Ltd. (56) Reference JP-A-8-151413 (JP, A) JP-A-9- 216913 (JP, A) JP-A-10-36412 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G08F 2/00-2/60 G08F 10/00-10/14 G08F 110/00-110/14 G08F 210/00-210/18

Claims (18)

(57) [Claims] 1. When polymerizing an olefin in a polymerization reactor in the presence of a gas containing hydrogen, at least a part of the gas in the polymerization reactor is extracted, and the extracted gas is extracted.
Is filtered with a filter to remove fine powder products contained in the gas.
After the removal , hydrogen in the filtered gas is added to the olefin to hydrotreate the gas, and then the gas after the hydrotreatment is supplied to the polymerization reactor again, whereby the hydrogen in the polymerization reactor is reduced. Characterized by reducing the concentration,
Method of controlling hydrogen concentration in polymerization reactor. 2. The control method according to claim 1, wherein the control of the hydrogen concentration is an operation performed when the polymerization reaction conditions are changed. 3. The control method according to claim 1, wherein the polymerization reactor is a multi-stage polymerization reactor. 4. The control method according to claim 1, 2 or 3, wherein the polymerization reactor is a gas phase polymerization reactor. 5. The control method according to claim 4, wherein the gas phase polymerization reactor is used for copolymer polymerization. 6. The range of hydrogen concentration in the gas phase polymerization reactor is 5
The control method according to claim 4, which has a capacity of not more than%. 7. The control method according to claim 1, wherein hydrogen in the extracted gas is passed through a hydrogenation catalyst to be added to the olefin. 8. The control method according to claim 7, wherein the hydrogenation catalyst is a solid catalyst. 9. The control method according to claim 8 , wherein the solid catalyst is a metal-supported catalyst having Pt or Pd as a supported metal and SiO ₂ or Al ₂ O ₃ or a mixture thereof as a carrier. 10. The control method according to claim 9, wherein the solid catalyst is Pd / Al ₂ O ₃ . 11. A polymerization reactor for polymerizing an olefin in the presence of a gas containing hydrogen, which is connected to and installed side by side to add hydrogen in the gas extracted from the polymerization reactor to the olefin so that the gas is hydrogen. Which comprises a hydrogenation reactor filled with a hydrogenation catalyst for chemical treatment, wherein the hydrogenation reactor is
The gas withdrawn from the polymerization reactor is introduced into the hydrogenation reactor, and the gas after the hydrotreatment is connected to the polymerization reactor so as to return to the polymerization reactor, and the polymerization reaction is further performed.
The hydrogenation reactor between the reactor and the hydrogenation reactor.
Fine powder contained in the gas by filtering the gas before
A hydrogen concentration control device in a polymerization reactor, wherein a filter for removing a product is connected to thereby reduce the hydrogen concentration in the polymerization reactor. 12. The control device according to claim 11 , wherein the polymerization reactor is a multi-stage polymerization reactor. 13. The control device according to claim 11 or 12 , wherein the polymerization reactor is a gas phase polymerization reactor. 14. The controller of claim 13 wherein the gas phase polymerization reactor is used for copolymer polymerization. 15. The control device according to claim 11 , 12 or 13 , wherein the hydrogenation catalyst in the hydrogenation reactor is a solid catalyst. 16. The control device according to claim 15, wherein the solid catalyst is a metal-supported catalyst having Pt or Pd as a supported metal and SiO ₂ or Al ₂ O ₃ or a mixture thereof as a carrier. 17. The control device according to claim 16 , wherein the solid catalyst is Pd / Al ₂ O ₃ . 18. The control device according to claim 11 or 13, which is used when the polymerization reaction conditions are changed.