Method and apparatus for gas-phase polymerization of alpha-olefins


 

The invention relates to the field of chemical technology. The described method of gas-phase polymerization-olefins at temperatures between 20 and 130°C and pressures from 1 to 100 bar. The method is characterized by the fact that the polymerization is carried out in a tubular reactor with a ratio of length : diameter >100. The growing polymer particles pass through a tubular reactor in its longitudinal direction without the occurrence of appreciable part of the flow of polymer particles in recycling. Effect: method allows to obtain bimodal and polymodal polymers with high homogeneity. 2 N. and 12 C.p. f-crystals, 1 Il.

The subject of the invention is a method of gas-phase polymerization-olefins at temperatures between 20 and 130C and a pressure of from 1 to 100 bar. Further, the invention relates to a tubular reactor for gas-phase polymerization-olefins with the ratio of length : diameter >100.

For polymerization-olefins, in particular for Homo - and copolymerization of ethylene and propylene and copolymerization of these olefins with higher-olefins, gas-phase methods for the development specified gas-phase polymerization carried out mostly in the fluidized bed reactor. Examples of the specified gas-phase method in the fluidized bed is described in patents US-A-5208109 and US-A-5041473.

In the known gas-phase methods fluidized bed reaction gas, which, along with the monomers, if necessary, may also contain a polymerization regulator and an inert gas, is introduced into the cycle and for mixing use a fluidized bed, which consists of fine particles of the polymer. During the process of polymerization of the polymer particles grow and removed from the reactor either continuously or intermittently. Because of the almost complete mixing of the fluidized bed and the conclusion only a small part of the contents of the reactor polymer particles are characterized by very different time in the reactor. So, partially submitted particles that were subjected to the polymerization process only a very short time, and, accordingly, have a small diameter. On the other hand, there are particles that linger long in the polymerization reactor before they are removed from the reactor. The result is that the polymer particles have a very wide distribution of the processing time.

In order to achieve a certain structural heterogeneity of polymers, nepaly can be carried out either in multiple devices or in different reaction zones of the same apparatus, but in each case, the polymer particles must be in different reaction conditions. These various reaction conditions can be characterized, for example, different temperatures, different pressures, different concentrations of monomers and / or different concentrations of the polymerization regulator, such as hydrogen, or combinations thereof. If the distribution of the residence time of polymer particles in different reaction zones or in different reaction apparatus is wide, as is the case with the above-described gas-phase polymerization in the fluidized bed, the properties of the polymers obtained under different process parameters, "fuzzy" (i.e., apply to a wider range of values), and the polymer product is characterized by a wide statistical distribution of various polymer particles.

To reduce the effect of a wide distribution of residence time and the associated wide range of properties of particles, attempts were made to increase the number connected to each other reactors. Thus, in patent US-A-5504166 described horizontal reactor, the volume of which section the x if this can happen almost ideal mixing. The polymer powder in a separate cameras mixed by mechanical stirring.

This method of gas-phase polymerization described in the patent US-A-5378434. With this method a separate reaction chamber consists of a fluidized polymer, at the same time in different cells may be different gas composition, so that you may receive bi - or polymodal polymers. However, due to the almost ideal mixing of polymer particles in separate chambers of the reactor, this process also gives a relatively large heterogeneity of the product because of the wide distribution of residence time of polymer particles in separate reactors.

Differences in the structure of the polymer from particle to particle and, thus, the heterogeneity of the polymer product is greater, the wider the distribution of the residence time. From the foundations of the reaction technology it is known that a single well-mixed reactor, such as a boiler with a mixer or reactor with a fluidized bed, has the widest distribution time, and a tubular reactor with piston over has the most narrow distribution of residence time. In theoretical ideal case of a tubular reactor with a piston for the b gas-phase polymerization, carried out in a flow tube. The specified flow tube is made, however, in the form of a loop, so that the polymer particles during the polymerization process are introduced into the cycle. Since the circulation time of particles in the specified loop reactor is very small, in order to achieve intensive mixing of particles in the circulation time of the particles is much smaller than the average time of transformation, this process is characterized by the distribution of the residence time of the particles, which is not significantly different from normal reactor fluidized bed.

The basis of the invention lies in the task of developing a method of gas-phase polymerization, the polymerization-olefins, which is characterized by a narrow distribution of residence time of the polymer particles and thus is applicable to obtain, in particular, bimodal and polymodal polymers with excellent homogeneity.

Accordingly, it is proposed a method of gas-phase polymerization-olefins at temperatures between 20 and 130C and pressures from 1 to 100 bar, which differs in that the polymerization is carried out in a tubular reactor with a ratio of length : diameter >100, with the growing polymer clay the polymer particles in recycling. In addition, a tubular reactor for gas-phase polymerization-olefins with the ratio of length : diameter >100, which contains at least one device for supplying reaction gases, at least one device for introducing the catalyst system of unloading polymer and at least one device for separating the reaction gases from the polymer particles and return the reaction gases at the entrance to the reactor or feeding the reaction gas upstream with respect to the place of separation.

Reaction conditions, the proposed method correspond in terms of the temperature and the degree of compression is mostly known methods of gas-phase reactions fluidized bed, and the method gives, of course, possible to vary the specified temperature within normal limits in various parts of the reactor. The method can be carried out at temperatures between 20 and 130With, in particular at temperatures between 70 and 120And particularly preferably between 80 and 110C. the Pressure of the reaction can also be within that standard for gas-phase polymerization in the fluidized bed. Thus, the method preferably to be conducted under dvlm sign the proposed reactor is the ratio of length : diameter. More than a specified ratio of length : diameter, in General, the narrower the distribution of the residence time of polymer particles. In the case of extremely long and thin reactor or a pressure drop in the longitudinal direction is too large from the point of view of economy, or the achieved performance is too low, so that the geometry of the reactor is limited to these circumstances. A good correspondence between the flow of polymer particles approximately porshneva stream, and a narrow distribution of residence time of polymer particles is achieved in the case of a polymerization reactor with a ratio of length : diameter >100, preferably tubular reactor has a length : diameter >300, particularly preferably between 300 and 1000.

The preferred geometry of the proposed reactor for technical, industrial scale production of different pipe diameter in the range from 10 to 100 cm and a length of 50 to 2000 m

In contrast described in the patent WO 97/04015 method gas-phase polymerization carried out in a tubular loop reactor, the proposed method of polymerization is characterized by the fact that the polymer particles are passed through a tubular reactor in its longitudinal direction is and polymer particles may for example, in the proposed reactor, in which during the polymerization of the composition of the gas phase must change, and in this part of the reaction gases are separated and sent back to the beginning or located upstream position to get involved with a specified circulating gas and thus be involved in recycling. Also in parts of the reactor, the total length of which is less than the length of the reactor, it is possible to carry out intensive back mixing of the powder, for example, on the basis of means of heat, for a better introduction into the mixture of feed components, to create the possibility of even sorption of monomer in the polymer powder or to separate unwanted polymer fractions, no significant deterioration because of this, the width of the overall distribution time. However, the main number of particles passes through the proposed reactor only in the longitudinal direction.

A small percentage is involved in recycling of polymer powder can also be described by the ratio of circulation (KLV):

Features KLV, typically <0,1, preferably <0,05. The proposed method is preferably carried out so that the mass ratio of the solids mass flow at the entrance to react thelen <1:1000. In addition, in the General case, the ratio of the weight of the obtained polymer to the weight of the catalytic metal component is >50000, preferably >100000, particularly preferably >500000.

The proposed method is preferably carried out in a tubular reactor, which is located in a mostly upright. Such a reactor is alternately directed up or down pipe pieces, which are optionally connected to each other by arcs with a relatively small radius. The diameter of the pipes may vary. So it is preferable that, for example, the diameter of the upward pipe segments, at least partially, was less than the downward facing segments. In the case of the reactor above the ratio of length : diameter refers to the average diameter of the reactor. Due to the vertical tubes of the reactor is achieved particularly good contact of the gas and powder polymer particles and can much better avoid undesirable sedimentation of the powder due to gravity with catastrophic consequences (settling on the walls, local areas of overheating).

In the vertical parts of the pipes with upward flow velocity of the stream is generally several times more min gas flow can be significantly lower. When occurring in the upper part of the reactor, the separation of gas and solids gas can even be directed in counterflow to the particle phase, that is to be directed upwards in separated from the main stream of the cycle gas. Part of the reactor with downward directed flow of particles can give the weakening of fluidization and to go to work the irrigated reactor with a relatively high proportion of the solid phase.

The preferred form of embodiment of the proposed method differs in that the effective axial velocity of the polymer powder in parts of the reactor with upward direction of flow is less than 80% of the speed of the reaction gases in these parts of the reactor. Effective axial velocity of the polymer powder in these parts of the reactor with upward direction of flow is preferably from 5 to 200 cm/sec, particularly preferably from 10 to 100 cm/sec. In aiming down the same tubular parts specified speed is between 200 cm/s (in case of parallel flow of gas and particles) and 2 cm/s (in case of counter-current).

Especially preferred is when aimed down parts of the pipes prevails effective axial velocity of the polymer powder is from about 1 to 5 cm/s

Nadivana grains". The diameter increasing along the length of the reactor gas bubbles in the well-known specialists conditions reaches the pipe diameter, and are formed clogging of the polymer powder ("clumps") of different lengths, which can be transported up gas with a relatively uniform speed. When the lumps are located along the reactor alternately so rich solid clumps interspersed with poor solid gas tubes. During transport the powder from one end of the ball through the intermediate gas bubble streams to the "head" of the next ball, while at the same time each gas tube goes in the direction of flow with negligible velocity. The time between formation and destruction of the lump is on the order of a few seconds, so even with a relatively large heat of polymerization in the lump may not be really noticeable temperature gradient.

Particularly advantageous for the specified production method are optional:

a) purification of the walls of the reactor due to the shifting action of the powder near the walls of the reactor;

b) varied within wide limits and controlled residence time of the powder;

C) difficulty vidiniuose with clumping of grains enriched solid upward tubular part facing down operating mode, parallel flow of gas and powder tubular parts, further, economically particularly advantageous modification of the reactor, which is characterized by simple design and operation, as well as the relatively short length of the reactor.

Since polymerization-olefins is an exothermic process, it is necessary that the heat of reaction can effectively be dissipated. The heat is preferably carried out through the walls of the reactor. Advantageously, for example, if the reaction pipe is provided with a cooling jacket, which can circulate the coolant, for example water. In order to maintain the reaction temperature constant or, if it is desirable to be able to install in different parts of the various reactor temperature, an additional advantage is the segmentation of the cooling system.

Under the proposed method of polymerization can be subjected to polymerization different Ethylenediamine monomers. Can be called, for example, ethylene, propylene, 1-butene, isobutene, 1-penten, 1-hexene, 1-hepten, 1-octene and higher-olefins; in addition, also take into account, for example, diene, such as butadiene and cyclopentadiene, and cycloolefin, such as cyclopenten and is maintained as comonomers polar monomers, such as esters of acrylic acid or vinyl acetate. Ethylenediamine monomers can be depolimerization individually or in mixtures. The preferred form of embodiment of the proposed method differs in that asthe olefin is injected ethylene, propylene, 1-butene, 1-penten, 1-hexene, 1-octene, or a mixture of these monomers, particularly preferred are the copolymerization of ethylene with 1-butene or 1-hexene, as well as homopolymerization ethylene and propylene.

The advantages of the proposed method, in particular, the possibility to obtain a very homogeneous polymer products, made especially noticeable if the reaction conditions vary along the tubular reactor. So, is the advantage that along the reaction tube set different temperatures, as mentioned at the beginning. Even more pronounced is possible to vary the properties of the product and, in particular, to get advantaged of bi - or polymodal polymer products by feeding in different areas of the tubular reactor different gas compositions. The simplest option to change the gas composition along the tubular reactor is that along the reaction tube through sootvetstvuuschey gas fresh monomers or you can enter additional controller molecular weight, as, for example, hydrogen. In particular, when along the reaction tube in various positions fresh monomer, the advantage is that the specified monomer can be used for removal of heat of reaction. This can be accomplished, for example, so that the monomer is served chilled as possible at a temperature below the dew point of the added monomer mixture.

More opportunities are variations in the regulation of the properties of polymers can be achieved by installing in the reactor, at least one device for separating gas and solids in the region between the inlet and outlet of the reactor; in this part of the solids takes place further in the direction of flow through the reactor and separated the reaction gas is returned into the reactor upstream. This separation of gas and solids can be most simply accomplished with the help of the cyclone. The specified cyclone preferably located at the upper end downward tubular part so that the polymer powder in this tubular part under the influence of gravity to drain inside. Separated, the reaction gas may then be returned and again entered either at the beginning of the reactor, or at least to the position above poison to process the additional heat of reaction. In the General case it is also advisable to enter into the cycle of the reaction gas was enriched used in the process of monomers and other components of the reaction, so you can set static gas conditions in the relevant sections of the reactor.

The preferred form of embodiment of the proposed method is characterized by the fact that along the reactor feed gases are served in the lower end part of the reactor with upward flow direction below the seat, which includes a stream of particles in this part of the reactor. This is the simplest way can be achieved by the fact that in the bottom part of the reactor with upward direction of flow of the inserted gas distribution plate such as are commonly used in the gas-phase method, the fluidized bed. The stream of polymer particles also passes through the lower arc in the upward part of the reaction tube, flows through the specified gas distribution plate and through the newly supplied gas pseudogiants up.

The preferred method in the sense of the invention differs in that the reactor comprises at least one device for separating gas and solids, preferably even and, can vary widely. So, depending on the desired polymer can be installed sequentially changing reaction conditions which are known to experts from other gas-phase methods of polymerization, particularly of the single-stage processes. Thus, the desired density can be, in particular, it is established through the composition of the comonomers, the molecular weight of the polymer can generally be effectively influenced through concentration, for example, hydrogen.

A significant influence on the properties of the polymer have, of course, the catalysts are introduced for polymerization. As catalysts primarily considered catalysts on carriers, which are usually loaded with other gas-phase methods of polymerization.

As carriers for catalysts applicable, for example, inorganic oxides such as silicon oxide, aluminum oxide or magnesium oxide, as well as the media can be used in complex media, such as aluminosilicates or zeolites. For this assignment, you must also take into account organic media, for example, on the basis of polystyrene.

As catalysts may be used, for example, all known to experts chrome to catalizatorului; in this proposed method does not impose specific requirements. It may be additionally advantageous catalyst particles on the carrier first to be terpolymerization. This terpolymerization, in which only a small amount of monomer is applied on the particles of the catalyst for polymerization can be carried out of the reactor, for example, in a known manner, for example, by polymerization in solution or in suspension. However, it is also possible to carry out such terpolymerization in liquid or gas phase at the beginning of the tubular reactor, in the first field. In the specified terpolymerization, however, should be imposed only minor amounts of monomer, which comprise at most 5%, preferably less than 2%, the desired polymer product. For possible terpolymerization, as well as in the whole first area polymerization in the proposed reactor is preferably introduced only one monomer, for example ethylene or propylene. Containing comonomer the flow of the reaction gas preferably is served at the end of this first stage of polymerization in the reactor.

In a preferred form of embodiment, the initial portion of the proposed reactor, that is, the first upward period Tr is thus, so he had a significantly greater diameter than the upper portion of this pipe section. In specified lower pipe section is placed catalyst. The removal of the heat of reaction is happening in this piece of pipe mainly by filing a liquid monomer, preferably liquid propylene and/or liquid inert gas, such as propane. In the technical form of embodiment of the lower section of pipe shall have a diameter of at least 1 m, preferably at least 2 m Because of this, among other things, achieve effective cooling. The velocity of the gas in the lower portion of the tube is preferably from 0.2 to 0.6 MS-1the density of the layer is preferably from 150 to 400 kg/m3. On the contrary, the upper portion of the first upstream pipe section has a smaller diameter, resulting in a higher flow rate. This part of the reactor may also be designed as Novotrubny reactor, in which you can achieve better heat dissipation through the shell of the reactor, as well as very limited back-mixing.

The proposed tubular reactor contains at least one device for supplying reaction gases, at least one device for feeding catalyst, the discharge system of the polymer, and p is different gases in the region of the inlet of the reactor. In the case when the reactor has only one device for separating the reaction gases from the polymer particles, it is located at the end of the reactor and combined with the discharge system of the polymer. Preferably the separation of the polymer from the gas flow carried out by the cyclone. Then the particle stream is preferably introduced into the down arrow part of the tubular reactor, and this flow is easily pseudogiants gas stream with minor monomer concentration, while the selection of the product is preferably carried out periodically or continuously at the lower end of this pipe section, whereby the filling level in the specified section of pipe support permanent.

The preferred form of embodiment of the proposed reactor shown in the drawing. The flow of the reaction gas passes through the input (1), the catalyst, if necessary in combination with a suitable socialization, may be injected into the reactor via the input (2). The polymerization mixture first passes through a vertically disposed pipe system of the upward and downward parts of the pipes, which are connected to each other arcs. In the cyclone (4) is the first Department of polymer particles from the reaction gas. The separated reaction gas through to Adumim device, again fed into the reactor, and the composition of the gas can be set by dosing the reaction gas stream 1. Separated from the reaction gas in the cyclone (4) polymer powder is passed first through the down arrow part of the pipe, and then again sent to the ascending part of the pipe, and at the lower end of the ascending part of the tube is placed a gas separating plate (7), through which the tubular reactor serves the second recycle gas stream(6), if necessary, enriched with fresh monomer or additional co monomer which is suitable for fluidization and for the further transportation of the polymer particles. Schematically shown in the drawing, the reactor contains three devices for separating the reaction gases from the polymer particles, and the third is the device at the same time is part of the unloading of the polymer.

Example. Obtaining bimodal ethylene copolymers.

The polymerization is carried out in a reactor consisting of a first part of the tubular reactor (length 80 m, inner diameter 5 cm), device for separating gas and solids (cyclone) with attached (subsequent) irrigation reactor (length 5 m, internal diameter 10 cm) and the second parts of the separation of gas and solids with gated locking and subsequent discharge of the product. Part of the reactor due to the further circulation of gas in a direction against the flow of the polymer support in a fluidized bed state, allowing at the same time manage a well-regulated branch of hydrogen. In the beginning part of the reactor And inject 40 gramsh-1catalyst terpolymerization (Caligraphy catalyst of Ziegler-Natta supported on silica gel, with terpolymerization in suspension propylene), the average activity which is part of the reactor And 5,98 kg PE (polyethylene) (g prepolymer in h), in part of the reactor At 0.51 kg PE (g prepolymer in h), and part of the reactor From 8.05 kg PE (g prepolymer in h). The average diameter of the particles of the prepolymer is about 150 microns. Intermediate feeding ethylene and hydrogen establish the molar ratio of ethylene : hydrogen in parts of the reactor And equal to 4.8, and in parts of the reactor and With equal 100. Similarly, the support ratio hexene : ethylene in part of the reactor And equal to 0, and in parts of the reactor and is equal to 0.1. By regulating the speed of gas set the residence time of the solid phase (polymer) in 9 minutes, 0.5 minutes and 6 min for the three parts of the reactor. At an average temperature of 70C, 90And 85Claims

1. The method of gas-phase polymerization-olefins at temperatures 20-130°C and a pressure of 1-100 bar, characterized in that the polymerization is carried out in a tubular reactor with a ratio of length : diameter >100, with the growing polymer particles pass through the tubular reactor in the longitudinal direction without the occurrence of appreciable part of the flow of polymer particles in recycling.

2. The method according to p. 1, wherein the tubular reactor has a length : diameter >300.

3. The method according to p. 1 or 2, characterized in that the tubular reactor is located in a mostly upright.

4. The method according to PP.1-3, characterized in that the effective axial velocity of the polymer powder in the part of the reactor with upward direction of flow is less than 80% of the speed of the reaction gas in this part of the reactor.

5. The method according to PP.1-4, characterized in that the effective axial velocity of the polymer powder in the part of the reactor with upward direction of flow is 5-200 cm/s

6. The method according to PP.1-5, characterized in that the temperature of polymerization is 70-120°C.

7. The method according to PP.1-6, characterized in that as-olefins introducing ethylene, propylene, 1-butene, 1-penten, 1-hexene, 1-octene th least one device for separating gas and solids.

9. The method according to p. 8, characterized in that at least one device for separating gas and solids is located in the area between the entrance and exit of the reactor, a part consisting of solids, passes through the reactor in the flow direction, and separated the reaction gas return and again fed into the reactor upstream.

10. The method according to PP.1-9, characterized in that the supplied along the reactor gases is introduced into the lower end part of the reactor with upward flow direction below the seat, which in this part of the reactor is fed a stream of particles.

11. The method according to PP.1-10, characterized in that in different areas of the tubular reactor set different compositions of the gas phase.

12. The method according to PP.1-11, characterized in that along the reactor tube through the respective power device serves fresh gaseous components of the reaction.

13. The method according to PP.1-12, characterized in that along the reactor tubes establish different temperatures.

14. Tubular reactor for gas-phase polymerization-olefins with the ratio of length : diameter >100 containing at least one device for feeding the reaction is the bottom of the device for separating the reaction gases from the polymer particles and return the reaction gases in the region of the inlet of the reactor or to supply the reaction gases upstream of the place of separation.

 

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