CS209922B2 - Vertical reactor with the fluidic bed - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus comprising a fluidized bed vertical diameter fluidized bed reactor equipped with indirect cooling for the production of low-pressure solid phase polymers by exothermic polymerization, wherein a polymerization catalyst and a gas stream comprising at least one polymerizable monomer, the exothermic heat of the reaction is removed by indirect cooling in the reactor and the dry particulate polymer is removed.

U.S. Pat. Nos. 4,011,382 and 4,003,712 disclose a process for preparing gas phase olefinic polymers in the presence of a highly active catalyst. No. 4,011,382 discloses that low density polyethylene at pressures of less than 6.9 MPa can be commercially produced by gas-phase reactions in the absence of solvents using selected catalysts containing temple and titanium and optionally fluorine, under certain conditions in fluidized-bed form. loži.

The fluidized bed reactor is preferably described in these patents as a vertical reactor with a cylindrical lower section and an upper section whose cross section is larger than the cross section of the lower section, the upper section being described as a speed reduction zone.

In the fluidization process, the portion of the gaseous stream that does not react in the fluidized bed forms a recycle stream, which is discharged from the polymerization zone through a speed reduction zone located above the bed. In the speed reduction zone, the rate of the recycle stream is reduced, and entrained particles may fall back into the bed. The removal of particles from the recycle stream can be aided by a cyclone. The use of a speed reduction zone and a cyclone has hitherto been considered necessary because it prevented the particles entrained in the gas from being entrained into the recycle system where they accumulate and cause clogging of the heat exchanger. In a fluidized bed reactor having an upper velocity reduction zone having a cross-section greater than the lower bed section, both sections are connected by a transition section to the tapered walls. When using such a fluidized bed reactor, a portion of the fine particles entrained in the polymerization zone of the lower section and separated from the recycle stream in the velocity reduction zone impinges on the tapered walls of the transition section. These fine particles accumulate over a period of time. Because the fine particles -contain the active catalyst, they react with the monomer present in the recycle to form solid coatings that can increase - preventing the recycle gas from flowing or sliding along the tapered walls.

203922

Run sections of the reactor and into the polymerization zone. In the polymerization zone, these coatings block the gas flow in the portion of the bed above the coating, resulting in reduced fluidization and further melting of the polymer particles in the non-fluidized region due to insufficient heat dissipation from the particles by the gas. If the reaction does not stop and the coatings are not removed, large polymer clusters can be formed which can block the entire polymerization zen. In order to minimize the formation of coatings on the tapered walls of the transition section, it is necessary that the top surface of the fluidized bed be at or slightly below the level of the transition section bottom during operation. These operating conditions cause, due to the intense movement of gas bubbles on the surface of the fluidized bed, larger particles from the fluidized bed are thrown onto the tapered walls of the transition section where they tend to sweep more reactive fine particles back into the fluidized bed. This requires operation at a substantially constant fluidized bed level and avoids lowering to facilitate transition or initiation of the reaction.

U.S. Pat. No. 3,298,792 discloses a device for reducing the build-up of coatings on chamfered walls in a fluidized bed to a minimum, a vertically positioned wiper for removing particles adhering to the walls formed by a driven shaft. According to the examples given in the patent, this device works well for small fluidized bed reactors, but operation of this device on large industrial scale reactors would be difficult, if at all possible. The fluidized bed of this patent has a tapered shape with a smaller diameter at the bottom of the reactor than at the top, thus having distorted walls in both the fluidized bed or polymerization zone and the velocity reduction section above the polymerization zone. The vertically positioned wiper removes particles adhering to the walls, both in the polymerization zone and in the speed reduction zone. A vertical fluid bed mixing apparatus and / or for removing particles adhering to the reactor walls is described, for example, in U.S. Patent Nos. 3,300,457 and 4,012,573.

It has been found that a fluidized bed polymerization reactor can operate without a velocity reduction zone or a cyclone to separate fine particles from the gas, which has many advantages. The most important advantage is that there is no coating on the bevelled walls of the transition zone. As a result, the frequency of reactor interruption is greatly reduced in order to remove the coatings formed. The second advantage is that the depth of the bed in the polymerization zone can be varied over a wide range, allowing the reactor to operate with good yields over a much larger range. The possibility of varying the depth of the bed also contributes to minimizing the amount of contaminated material when changing production from one product to a new one. This can be accomplished by lowering the bed to a certain minimum level before commencing product change and maintaining the process until the product produced meets the characteristics of the new product. During product change at a lowered bed level, the production rate per unit of bed volume used, kg of product per hour per m ³ , heat dissipation capacity, and product removal capacity from the system can be increased to match normal 1-stroke volume. This allows the product change time to be shortened and the resin produced during the product change to be reduced.

A further advantage of a uniform diameter reactor is that a smaller initial batch of powdered material is sufficient to successfully initiate the reaction without coating deposition. The manufacturing cost of a fluidized bed reactor without an increased cross-sectional velocity reduction zone is considerably lower, since there is no need for larger diameter sections or tapered transition zones. In operation without a velocity reduction zone, cyclone or filter, entrainment of the particles usually increases from 100 to 100 times. This increase in the concentration of particles in the recycle stream was expected to disable the reactor due to the accumulation of fines in the recycle line and on the manifold plate under the bed. In addition, it was expected that the particles would cause the compressor to be recycled by abrasion or accumulation of particles on the moving parts of the compressor. Despite this, it has been found that if the velocity in all parts of the recycle line is kept high and if the recycle system is designed to contain at least a low speed or dead zone area, then there is no accumulation of particles in the recycle line and on the manifold plate. particle problem. It has also been found that the accumulation of particles on the moving parts of the compressor is minimal, so that it does not affect its operation or efficiency, and that fine polymer particles that have been entrained do not cause abrasion of the compressor. However, it has been found that fine particles rapidly accumulate on the heat exchanger.

The possibility of accumulating particles on the heat exchanger can be eliminated by incorporating a cooling device directly into the fluidized bed; so-called internal cooler. Since gas is used as the heat transfer medium with the external cooler, the reaction rate was previously limited by the gas velocity while passing through the bed, which should remain low enough not to tear large amounts of solids but high enough to allow adequate heat dissipation. The internal cooler dissipates the reaction heat directly from the solid particles and the gas velocity can be much lower, thus using much less energy. In addition, since heat dissipation does not depend on the gas mass flow rate, the reactor pressure can also be reduced to a value given by the polymerization kinetic value. When cooling tubes are vertically installed in the fluidized bed of the present invention, they tend to destroy large bubbles of bubbles and thus increase the quality of fluidization. When bubbles in the fluidized bed agglomerate, which is their natural tendency to ascend upwardly through the bed, the gas is drawn off from the edges of the bed towards the center, reducing the possibility of mixing at the walls and thus causing bed inhomogeneity. Vertical tubes, which act as stops, tend to interfere with the migration of bubbles to the center of the bed and increase mixing at the walls.

If external cooling is used in the gas phase fluidized bed, then the gas entering the bed bottom is cooler than the bed. Since the physical properties of the polymers produced with certain catalysts are temperature sensitive, the lower part of the bed, which is colder, produces polymers with different physical properties. These particles are then mixed with the rest of the bed, causing in particular an increase in the molecular weight distribution of the polymer. Using internal cooling, heat is removed directly from the polymer and the incoming fluidizing gas is therefore at the same temperature as the entire fluidized bed.

Another problem encountered in external cooling is that the low molecular weight oligomers that are formed during polymerization and that are volatile at reactor temperatures can condense on the cool surface of the external cooler and cause the fine particles to adhere to the heat exchanger, resulting in more frequent blockages. In addition, when producing olefin copolymers using relatively high-boiling comonomers, the monomers can also condense in an external cooler and cause clogging of the heat exchanger. This condensation cannot occur when using internal cooling because the recycle system has the same temperature as the reactor.

It has now been found that polymers or copolymers with a relatively low residual catalyst content for commercial purposes can be produced at low pressure in the gas phase if at least one polymerizable monomer is polymerized or copolymerized in the presence of a polymerization catalyst in a vertical fluidized bed uniform diameter reactor containing Indirect cooling device to remove the exothermic reaction heat.

The present invention provides a vertical fluidized bed reactor for the polymerization of at least one monomer with a polymerization catalyst comprising

a) polymerization zone in the lower section,

b) a distribution plate permeable to the fluidizing medium at the bottom of the lower section,

c) a gas supply line through which the fluidizing gas is introduced into the lower section below the manifold plate,

d] equipment for inje, catalyst pumping, through which the catalyst is introduced into the polymerization zone,

(e) a product take-off device which removes the polymer product from the polymerization zone above the manifold and fj a recirculation circuit through which the fluidization medium is removed from the top section of the reactor and recycled to the bottom section of the reactor below the manifold; a uniform internal diameter and includes a built-in indirect cooling device.

The olefin polymers that are prepared according to the present invention are solids. The olefin polymers have a density of about 910 to 970 kg / m 2. and a melt flow index of about 0.1 to 100 g / 10 min. or more.

The olefin polymers of the present invention are prepared by homopolymerizing or copolymerizing one or more α-olefins containing 2 to about 12 carbon atoms. The second N-olefinic monomers may be monoolefins or unconjugated diolefins.

Polymerizable mono-α-olefins include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-ethyl-1-bu. 1-heptene, 1-octene-1-decene, 4,4-dimethyl-1-pentene, 4,4-diethyl-1-hexene, 3,4-dimethyl-1-hexein, 4-butyl-1- octene, 5-ethyl-1-decene, 3,3-dimethyl-1-butene and the like. Suitable diolefins include

1,5-hexadiene, dicyclopentadiene, ethylidennorbornene and other unconjugated diolefins.

The catalyst used is a highly active catalyst comprising a transition metal, preferably chromium and / or titanium. A high-activity catalyst means that it must have a productivity of ≥ 50,000, preferably with 100,000 kg of polymer per kg of transition metal in the catalyst. This is because fluidized bed gas phase processes do not usually remove catalyst residues. Thus, the remainder of the catalyst in the polymer must be so small that it can be left in the polymer without causing undue problems to the resin processor and / or to the end consumer. The low residual catalyst content is important when the catalyst is produced using chlorine-containing substances such as titanium, magnesium and / or aluminum chlorides used in some of the so-called Ziegler or Ziegler-Natto catalysts. High residual chlorine values in the molding resin would cause pitting on the metal surfaces of the molds.

Highly active transition metal catalysts which can be used according to the invention include:

I. Silylchromate catalysts as described in U.S. Patent Nos. 3,324,101 and 3,324,095. A group of formula is present in these catalysts.

RO ' ^{1 11}

-4-St · -O-Ci-1ι '1

R O.

where

R is a hydrocarbon group having 1 to 14 carbon atoms.

Preferred are bistriarylsilylchromates and most preferred is bistriphenylsilylchromate.

This catalyst is used on a support such as silica, alumina, thorium, zirconium and the like, other supports such as carbon black, microcrystalline cellulose, unsulfonated ion exchangers and the like can also be used.

II. The bis (cyclopentadienyl chromium compounds described in U.S. Pat. No. 3,879,368). These bis (cyclopentadienyl chromium compounds have the formula

where

R ‘and R mohou may be the same or different hydrocarbon radicals having 1 to 20 carbon atoms, and n‘ and n mohou may be the same or different integers 0 to 5.

The hydrocarbon radicals R1 and R2 may be saturated or unsaturated, they may be aliphatic, alicyclic and aromatic radicals such as methyl, ethyl, propyl, butyl, pentyl, cyclopentyl, cyclohexyl, allyl, phenyl and naphthyl.

These catalysts are used on a support as described above.

III. The catalysts disclosed in U.S. Patent No. 4,011,382. These catalysts contain chromium and titanium in the form of oxides and optionally fluorine and a carrier. The catalysts contain, based on the total weight of the support and chromium, titanium and fluorine, about 0.05 to 3.0, preferably about 0.2 to 1.0% by weight of chromium (calculated as Cr), about 1.5 to 9, 0, preferably about 4.0 to 7.0% by weight of titanium (calculated as Ti), and 0.0 to about 2.5, preferably about 0.1 to 1.0% by weight of fluorine (calculated as F) ).

As chromium compounds, chromium oxide or any chromium oxide oxidizable to chromium oxide can be used under the activation conditions used. At least a portion of the chromium in the supported supported catalyst must be in the sixth mocein. Other suitable chromium compounds other than chromium oxide are described in U.S. Pat.

Nos. 825,721 and 3,622,521 and include chromacetylacetonate, chromium nitrate, chromium acetate, chromium chloride, chromium sulphate and ammonium chromate.

Water-soluble chromium compounds such as chromium oxide are preferred for the deposition of a chromium compound from solution onto a carrier. Chromium compounds soluble in organic solvents can also be used.

Titanium compounds which can be used are all compounds which are oxidizable to titanium dioxide under the conditions of activation used, for example those disclosed in U.S. Patent No. 3,622,521 and Dutch Patent Application No. 72-10881. These compounds have, for example, the structure (R) _n Ti (OR ') _m and (RO j _m Ti (OR'J _n , where m is 1, 2, 3 or 4, n is 0, 1, 2 or 3 am + n = 4 a

T1X4 where

R is C 1 -C 12 alkyl, aryl or cycloalkyl and combinations thereof, for example aralkyl, alkaryl and the like,

R 1 is R, cyclopentadienyl and C 2 -C 12 alkenyl, for example ethenyl, propenyl, isopropenyl, butenyl and the like, and

X is chlorine, bromine, fluorine or iodine,

Thus, titanium tetrachloride, titanium tetraisopropoxide and titanium tetrabutoxide may be used as titanium compounds. The titanium compounds are preferably applied to the support from a solution in a hydrocarbon solvent.

Titanium (such as Ti) is present in the catalyst relative to chromium (such as Grj) in a molar ratio of about 0.5 to 180, preferably about 4 to 35.

Fluoric acid which can be converted to hydrofluoric acid under the activation conditions used can be used as fluorine compounds. Suitable compounds other than hydrofluoric acid are described in Dutch Patent Application No. 72-10,881. These include ammonium hexafluorosilicate, ammonium tetrafluoroborate and amoinium hexafluorothitainate. The fluorine compounds are preferably applied to the support from an aqueous solution or dry mixing of the fluorine solids with the other catalyst components prior to activation.

Inorganic oxides which are porous and have a large specific surface area, i.e. a specific surface area in the range of about 50 to about 1000 m ² / g and an average particle size of about 50 to 200 μη) can be used as catalyst supports. , thorium, zirconium and other comparable inorganic oxides, as well as mixtures of these oxides.

The catalyst support, which is optionally already impregnated with a chromium and / or fluorine compound, must be dried before it is contacted with the titanium compound. Drying is normally carried out by heating or drying the catalyst support with dry inert gas or dry air. It has been found that the drying temperature has a considerable effect on the molecular weight distribution and on the melt index of the produced polymer. The preferred drying temperature is from 100 to 300 ° C.

The activation of the unsolicited catalyst can be carried out at almost any temperature, up to about the melt temperature. By blowing the dry air or oxygen stream through the carrier catalyst during activation, water removal from the carrier is aided. Sufficient activation time, when using well-dried air or oxygen, is about 6 hours, etc., at a temperature of 300 to 900 ^° C. At this temperature, the carrier is not sintered.

IV. Catalysts described in U.S. Patent Application Serial No. 892,325 of March 31, 1978 to F. J. Kar-o-1 and d. Entitled "Preparation of ethylene copolymers in a fixed bed reactor". These catalysts comprise at least one titanium compound, at least one magnesium compound, at least one electron donor, at least one activator, and at least one inert carrier as described below.

The titanium compound has the structure

Ti (ORj _and X _b where

R is a C 1 -C 10 aliphatic or aromatic hydrocarbon radical or

COR ‘, where

R 1 is a C 1 -C 14 aliphatic or aromatic hydrocarbon radical,

X is chlorine, bromine or iodine, a is 0 or 1, b is 2 to 4 and a + b = 3 or 4.

The titanium compounds may be used singly or in combinations and include

T1C13

Ti (OCH 3) Cl 3,

Ti (OC6H5) Cl3,

Ti (OCOCH 3) Cl 3 a

Ti (OCOC6 H5) Cl3.

The magnesium compound has the structure MgXž where

X is chlorine, bromine or iodine.

The magnesium compounds may be used alone or in combinations and include magnesium chloride, magnesium bromide, and magnesium iodide. Preferred is anhydrous magnesium chloride.

About 0.5 to 56, preferably about 1 to 10 moles of magnesium compound per mole of titanium compound are used in the preparation of these catalysts.

The titanium compound and the magnesium compound are to be used in a form that facilitates their dissolution in the electron donor.

An electron donor is an organic compound, liquid at 25 ° C, in which the titanium compound and the magnesium compound are partially or completely soluble. Electron donors are known as such or as Lewis bases.

Electron donors include, for example, alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers and aliphatic ketones. Preferred are alkyl esters of C 1 -C 4 saturated aliphatic carboxylic acids, alkyl esters of C 7 -C 6 aromatic carboxylic acids, C 5 -C 6, preferably C 3 -C 4 aliphatic ethers, C 5 -C 4 cyclic ethers, preferably C 4 cyclic mono- or diether, C 3 -C 6, preferably C3-C4 aliphatic ketones. Most preferred electron donors are methyl formate, ethyl acetate, butyl acetate, ethyl ether, hexyl ether, tetrahydrofuran, dioxane, acetone and m-ethylisobutyl ketone.

The electron donors can be used alone or in combination.

About 2 to 75, preferably about 3 to 10 moles of electron donor per mole of titanium are used.

The activator has a structure

Al (R 'j _c X' _d H _e.

where

X ‘is chlorine or ORi,

R 1 and R 4 are the same or different C 1 -C 14 saturated hydrocarbon radicals, d is 0 to 1.5, e is 1 or 0 and c + d + e = 3.

Activators can be used singly or in combination and are among them

A1 (C2H5) 3

A1 (C2H5) 2Cl,

Al (i-C4H9) 3,

A1ž (C2H5 33Cl3,

Al (i-C4H9) ₂ H,

A1 (C6H13) 3,

AlfCzHsjzH and

A1 (C2 H5) 2 (OC2 H5).

About 10 to 400, preferably about 10 to 100 moles of activator per mole of titanium compound are used to activate the catalyst of the invention.

Carriers are particulate solids and include inorganic materials such as silicon and aluminum oxides and molecular sieves, and organic materials such as olefin polymers such as polyethylene. The carriers are used in the form of a dry powder having an average particle size of about 10 to 250, preferably about 50 to 150 μΐη. They are also preferably porous and have a specific surface area of > 3, preferably with 50 m < ² > / g. The carrier material should be dry, i.e., free of absorbed water. Drying is usually accomplished by heating or forwarding with a dry inert gas. The inorganic carrier may be treated with about 1 to 8% by weight of one or more of the alkyl aluminum compounds described above for further activation.

A fluidized bed reaction system that can be used in the process of the invention is shown in Figure 1.

The reactor 10 consists of a reaction zone 12 comprising a bed of growing polymer particles, formed polymer particles, and a smaller amount of catalyst particles fluidized by a continuous flow of polymerizable and modifying gaseous components formed by the make-up gas and the gas recycled to the reaction zone. In order to maintain the fluidized bed in a fluidized state, the gas mass flow rate through the bed must be greater than the minimum flow rate required for fluidization. Preferably, a suitable gas mass flow rate through the bed is about 1.5- to about 1'D times higher, preferably about 2 to 6 times higher than the minimum gas mass flow rate required for fluidization (Gmf). The Gmf designation for the minimum gas mass flow rate required to achieve fluidization was suggested by C. Y. Wen and Y.H. Yu, "Mechanics of Fluldizatio", Chemical Engineering Progress Symposium Serles, Vol. 62, pp. 100-111 (1966).

It is important that the bed always contain particles that prevent "hot spots" and that trap and distribute the pulverulent catalyst in the reaction zone. Upon commencement of operation, a polymeric particle is usually introduced as a base into the reaction zone before the gas stream is introduced. The particles may be identical to the polymer formed or may be different. When different, they are drawn off with the resulting polymer particles as a leading product. Finally, the fluidized bed of the desired polymer particles displaces the starter bed.

The partially or fully activated precursor (catalyst) used in the fluidized bed is preferably stored in a standby container 32 under an atmosphere of an inert gas such as nitrogen or argon.

Fluidization is achieved by a high rate of gaseous recycle introduced into and through the bed, which is typically of the order of about 50 times higher than that of the make-up gas. The fluidized bed usually looks like a dense mass of moving particles flowing in the free vortex created by the passage of gas through the bed. Pressure loss. in the bed is equal to or somewhat higher than the weight of the bed divided by the cross-section of the bed, therefore it is dependent on the reactor geometry.

The make-up gas is introduced into the bed at least at the same rate as the withdrawal rate of the polymer product particles. The make-up gas composition is determined by an analyzer 16 located above the bed. The gas analyzer determines the loss of components in the gas to be recycled, and the composition of the make-up gas is adjusted accordingly to keep the composition of the gaseous mixture substantially steady state in the reaction zone.

In order to ensure complete fluidization, the recycle gas and possibly part of the make-up gas is fed into the reactor via an inlet 18 under the bed. Above the inlet 1B there is a gas distribution plate 20 which assists fluidization of the bed.

The part of the gaseous stream that does not react in the bed forms recycled gas, which is discharged from the polymerization zone through the drift section 14 located above the bed, in which entrained particles have the possibility to fall back into the bed.

The recycle gas is then compressed in the compressor 25 and then returned to the reactor. The reactor 10 includes an internal condenser consisting of a tube 50 disposed within the fluidized bed to transfer the heat of reaction to the refrigerant. Although smooth tubes are shown in Figure 1 as an internal heat sink, various types of heat sinks may be used, for example finned tubes or tray spirals.

The temperature of the resin in the bed is controlled by adjusting the temperature and / or flow rate of the coolant flowing into the internal cooler while maintaining the bed at a substantially constant temperature.

Since the heat of reaction is continuously removed, there is no observable temperature gradient in the bed. Since the recycle gas is not cooled, the temperature of the gas entering the fluidized bed 12 through the distributor plate 20 is substantially the same as the temperature of the recycled gas leaving the bed through the drift section 14.

The distributor plate 20 plays an important role in the operation of the reactor. The fluidized bed contains both the growing and formed polymer particles and catalyst particles. Since the polymer particles are hot and possibly active, they must be prevented from settling, since if any quiet mass were formed, the active catalyst contained in these particles could cause the reaction to continue and the particles would melt due to the heat generated. It is therefore important that the recycle gas is passed through the bed at a rate sufficient to fluidize the particles in the bed. For this purpose, the distributor plate 20 serves, and may be a sieve, a plate with slits, a perforated plate, a plate with caps (analogous to those of the distillation column trays) and the like. is a plate as described in U.S. Patent No. 3,298,792. Whatever the structure of the plate, the plate must disperse the recycle gas between the particles at the bottom of the bed and maintain it in a fluidized state. Around the plate is also to support a quiet bed of resin particles when the reactor is not in operation.

Hydrogen can be used to control the molecular weight of the post-polymerization reaction of the invention. The hydrogen / efhylene ratio used ranges from about 0 to about 2.0 moles of hydrogen per mole of monomer in the gas stream.

Any gas inert to the catalyst and reactants may also be present in the gas stream. The activator is preferably added to the reaction system in a recycle system. For example, it may be introduced into the recycle gas system from the reservoir 27 via line 27A.

The fluidized bed reactor must operate at a temperature below the sintering temperature of the polymer particles. In order to prevent sintering of the particles, the working temperature must be below the sintering temperature. The production of ethylene copolymers by the process of the invention is preferably carried out at a temperature of about 30 to 125 ° C, most preferably at a temperature of about 75 to 115 ° C.

The fluidized bed reactor is operated at a pressure of up to about 200 psig (6 MPa), preferably about 20 to 10 psig.

The partially or fully activated precursor (catalyst) is injected into the bed at a rate equal to the rate at which it is consumed by an inlet 30 located above the distributor plate 20. Preferably, the catalyst is injected into the bed from the side at about 1/4. up to 3/4 of its height. An important feature of the invention is that the catalyst is injected at a point above the manifold plate. Since the catalysts used according to the invention are highly active, injection of a fully activated catalyst into the space below the manifold plate could result in polymerization being initiated at this point, which could eventually lead to clogging of the manifold plate. Injection of the catalyst into the fluidized bed, in turn, aids in the distribution of the catalyst in the bed and avoids the formation of sites with high catalyst concentrations that could lead to hot spots.

A gas inert to the catalyst, such as nitrogen or argon, is used to introduce the partially or fully reduced precursor and any necessary activator or non-gaseous modifier into the bed.

Bed productivity is controlled by catalyst injection rate. Bed productivity can simply be increased by increasing the catalyst injection rate and reduced by reducing the catalyst injection rate.

Since any change in catalyst injection rate results in a change in reaction heat evolution rate, the temperature and / or coolant flow in the internal cooler is adjusted up or down. This ensures a substantially constant bed temperature. Both the fluidized bed and the internal cooling system must, of course, be equipped with appropriate devices for detecting changes in bed temperature so that the operator can make appropriate adjustments to the temperature and / or the flow of the refrigerant.

Under a certain combination of operating conditions, the fluidized bed is maintained at substantially the same height by withdrawing a portion of the bed as the product at the same rate as the particle formation rate of the polymer product. Since the rate of heat evolution is directly proportional to the product formation, the coolant rate measurement at a constant coolant rate determines the coolant temperature increase in the transverse direction, i.e. the difference between the coolant inlet temperature and the coolant outlet temperature.

The polymer product particles are suitably and preferably withdrawn by sequentially controlling a pair of timed valves 3fi and 38 limiting the separation zone 40. When the valve 38 is closed, the gas is vented via line 51. Then, the valve 38 is opened and the product is conveyed to the outer insulation zone. The valve 38 is then closed until the next product withdrawal.

Finally, the fluidized bed reactor is equipped with a suitable venting system that allows venting of the bed during start-up and shutdown. The reactor does not require the use of any mixing devices and / or wall scraping devices.

The highly active supported catalyst used provides a fluidized bed product having an average particle size of about 100 to about 1500, preferably about 500 to about 1000 µm.

To ensure proper operation of the plant, the cooling device in reactor 10 must be immersed in a fluidized bed. If the cooling device extends above or below the fluidized bed, particles that deposit on the non-vertical surfaces, which, because they contain an active catalyst, can grow and form pieces of solid polymer that could compromise or prevent reactor operation.

The cooling device in the reactor may be a cooler or heat exchanger. The design of the cooling device is such that the cross-sectional area of the cooling device does not reduce the free cross-section of the bed, so that the local surface speed is 10 times higher than the minimum fluidization rate. The cross-section at the point where the cross-section of the internal cooling device is the largest is the minimum free cross-section.

The reactor shown in FIG. 1 can operate at a diameter to height ratio of about 1: 1 to 1:10. The minimum depth of the fluidized bed depends on the design of the manifold plate and the size of the bubbles and not the reactor diameter, while the flight zone height is a complex function of particle size distribution, gas velocity, particle density, gas density etc. in the work of FA Zen, for DF Othmer, "Fluidization and Fluid Particle Systems," Reinhold Publishing Corp., 1960, pp. 374-387.

The properties of the polymers produced in the examples are determined by these test methods.

Density

For substances with a density> 940 kg / im ^3, the procedure of ASTM 1505 and the plate was conditioned for 1 hour at 100 ^Q C to approach equilibrium crystallinity. For substances with a density of 940 kg / m ³ , a modified procedure is used in which the test plate is conditioned for 1 hour at 120 ° C to approximate equilibrium crystallinity and then cooled rapidly to room temperature. All density values are given in kg / m ³ . All density measurements are performed in a density gradient column.

Melt Flow Index (MI)

ASTM S 1238 Condition E

Measurements are performed at 190 ° C, readings in g per 10 minutes.

Flow rate (ASTM D-1238-Condition F melt at higher load) (HLMI)

Measurements are made using 10-fold. load than when measuring the melt index.

Ratio of flow rates = flow rate-melt index

Density

Pour the resin into the 100 ml graduated cylinder to the 100 ml line without shaking the cylinder and weigh by the difference method. Yield per unit of time and volume

Kg of resin produced per hour per 1 m ³ bed volume.

Amount of compound in% wt. added to the carrier

CrO3

Ti (isopropyl) 4 (NH 4) 2 S 1 F 6

1S

Preparation of the catalyst

To a solution of the required amount of chromium trioxide in 3 liters of distilled water is added 500 g of porous silica as a carrier having a particle size of about 70 μΐη and a specific surface area of about 300 m ² / g. The carrier / water / chromium oxide mixture is mixed and then allowed to stand for about 15 minutes. It is then filtered to remove about 2200 to 2300 milliliters of solution. The chromium-containing silica is then dried in a stream of nitrogen at 200 ° C for about 4 hours.

About 400 g of supported chromium trioxide is then suspended in about 2000 ml of dry isopentane, and then the desired amount of tetralsopropyl titanate is added to the suspension. The system is then thoroughly mixed and then isopentene is removed by heating the reaction vessel.

The dried substance is transferred to a activating heated vessel, the desired amount of ammonium hexafluorosilicate [(NH4) 2S1F6) is added thereto, and the resulting mixture is mixed. Thereafter, the system is heated under nitrogen at about 50 ^° C for about 1 hour and at about 150 ° C for about 1 hour to ensure that all isopentane is removed and to slowly remove organic tetraisopropyltitanate residues without the risk of ignition. The nitrogen stream is then replaced with a dry air stream and the catalyst system is activated for about 2 hours at 300 ° C and then for about 8 hours at 825 ° C. The activated catalyst is cooled with dry air at room temperature to about 150 ° C and then further cooled from 150 ° C to room temperature with nitrogen (room temperature).

The amounts of chromium, titanium and fluorine compounds that are added to achieve the desired concentration of these elements in the activated catalyst are shown in the following table:

The amount of element in% wt.

in the activated catalyst

0/6 ~ Čř ^: 0/3

Ti 4,2

1.2 F 0.6

Catalyst B

About 2000 g of porous silica as a carrier having an average particle size of about 70 and a specific surface area of about 300 m ² / g is dehydrated in an activator (heated vessel). The silica is heated at 400 ° C for about 2 hours and then at 600 ° C for about 8 hours. The dehydrated silica is further cooled to room temperature by blowing nitrogen and stored under nitrogen. 462 g of dehydrated silica was then at ^70C C is suspended in about 4000 ml of dry isopentane was added about 350 ml of about 15 o / _o by weight.

of bis- (cyclopentadienyl) chromium, i.e. chromo-ocene, in toluene, and the mixture was stirred in a closed vessel for 1 h to avoid boiling off Isopentane. The catalyst was then dried at 90 ° C under a stream of nitrogen for 30 h and stored under nitrogen. The final catalyst contains about 6% by weight of chromocene.

Catalyst C

Catalyst C was prepared by adding 1000 g of the dehydrated silica described in Catalyst B to 5500 ml of dry isopentane at 45 ° C. The suspension was stirred for 30 min, then 30 g of bis-triphenylsilyl chromate was added and stirred for an additional 10 h. 200 ml of a 20% (w / w) solution of diethylaluminum ethoxide in hexane was added over 30 min. Stir for a further 4 h, then stop stirring and decant the liquid from the catalyst. Then resumes with stirring and the catalyst was dried for 24 hours at 70 ³ C. under a gentle stream of nitrogen and store under nitrogen. The final catalyst contains about 3% by weight bis-triphenylsilyl chromate and has an Al / Cr molar ratio of about 6: 1.

Catalyst D

1. Preparation of impregnated precursor

To a 12 L flask equipped with a mechanical stirrer was added 41.8 g (0.439 mol) anhydrous magnesium chloride and 2.5 L tetrahydrofuran (THF). To this mixture was added dropwise 27.7 g (0.184 mol) chloride over 1/2 hour. The mixture can be heated to 60 ° C for about 1/2 hour to dissolve completely.

500 g of porous silica is added and the mixture is stirred for 1/4 hour. The mixture was dried by passing nitrogen for about 3-5 h at 60 ^Q C to produce a dry free flowing powder, · having a particle size corresponding essential oil. The absorbed precursor compound has the formula

TiMg _{3 0} Cl ₁₀ (THFj _{6, 7}

2. Activation procedure

The required amount of precursor and activator together with a sufficient amount of anhydrous aliphatic hydrocarbon diluent such as isopentane is introduced into the mixing tank to form a suspension.

The activator and the precursor are used in an amount that allows the formation of a partially activated precursor having an Al / Ti ratio of 0 to 10, preferably 4 to 8.

The suspension is then thoroughly mixed at room temperature and atmospheric pressure for about 1/4 to 1/2 hour. It is then dried in a stream of an inert gas such as nitrogen or argon at atmospheric pressure and at a temperature of 65 ± 10 ° C to remove the hydrocarbon diluent. This process usually takes about 3 to 5 hours. The resulting catalyst is in the form of a partially activated precursor impregnated in the silica pores. The material consists of free-flowing particles of the size and shape of the silica. It is not pyrophoric if the alkyl aluminum content does not exceed 10% by weight. It is stored under a dry inert gas such as nitrogen or argon before further use. It is thus ready for use in which it is injected into a polymerization reactor in which it is fully activated.

When another activator is introduced into the polymerization reactor to complete the activation of the precursor, it is provided as a dilute solution in a hydrocarbon solvent such as isopentane. These dilute solutions contain 5 to 30% by volume of activator.

The activator is added to the polymerization reactor in an amount such that the Al / Ti ratio in the reactor is about 10 to 400, preferably 15 to 60: 1.

The following examples are provided to illustrate the process of the invention but are not intended to limit the scope of the invention in any way.

Examples 1 to 6

In these examples, the reactor shown in the drawing was used having an inner diameter of 34 cm and a height of 808 cm. Examples 1 to 6 are carried out at a gas velocity of 4 to 6 x Gmf and an overpressure of 2.07 MPa. The internal cooler consists of four vertical loops, about 122 cm long, made of 2.54 cm stainless steel tubes in which tempered water flows as coolant. Part of the piping between the compressor and the reactor is provided with a jacket that dissipates the heat added by the recycle compressor. Only in Example 1, the internal cooler is replaced by an external heat exchanger with one pass of a vertical bundle structure where the recycle gas flows down the tubes and tempered water flows in the jacket.

Example 1

The above-described external heat exchanger reactor has been used for 2 years to copolymerize ethylene with 1-butene or propyl. During the first year of operation, the reactor must be stopped 15 times to clean the external heat exchanger of deposited entrained resin particles. In the second year, the reactor must be stopped 17 times. The catalysts A to C described above are used in the reactor for two years.

Example 2

The reactor used in Example 1 is converted to the structure of Figure 1 by removing the external heat exchanger and installing the above-described internal heatsink. The reactor is used to copolymerize ethylene with 1-butene or propylene and operate at that design for 11 months without caused the need to stop. During these 11 months, catalysts A through D are used in the reactor.

Examples 3 to 6

In these examples, the same reactor as in Example 2 and catalysts A to D are used.

Example 3

The reactor of Example 2 operates with Catalyst A at a gas velocity of 4 to 6x

Gmf and at an overpressure of 2.07 MPa. The catalyst contains 0.3% by weight of chromium (Cr),

4.2% by weight of titanium (Ti) and 0.6% by weight of fluorine (F). Other reaction conditions and resin product properties:

Reaction conditions

Resin properties

temperature ° C 87.5 melt index (MI) g / 10 min 0.20 molar ratio C4H8 / C2H4 0.10 flow rate (HLMI) g / 10 min 21.8 bed level, m 2.44 HLMI / MI ratio 109 yield per unit of time density kg / m ³ 919 and bed capacity kg / h / m ³ average particle size μτη 965 density kg / m ³ 422 Example 4 in accordance with Example 2 at gas velocity 4 to 6x Gmf and at an overpressure of 2.07 MPa; Kata- Catalyst B prepared as described above the lysator contains about 1.7% by weight procedure is used in a single reactor of chromium (Cr). Other reaction conditions a fluidized bed diameter; and inner- Product features: Reaction conditions Resin properties temperature ^C C 95 melt flow index (MI) 1.7 g / 10 min C3H6 / C2H4 molar ratio 0.15 flow rate (HLMI) g / 10 min 83.4 H2 / C2H4 molar ratio 0.04 HLMI / MI ratio 48.0 density, kg / m ³ 953 bed level, m 1,02 average particle size, μτη 810 yield per unit of time and bed capacity kg / h / m ³ 61.7 density, kg / m ³ 422 The reactor operates under these conditions with in accordance with Example 2 at gas velocity analyzer B 26 hours without difficulties. 4 to 6x Gmf and at an overpressure of 2.07 MPa for

copolymerization of ethylene and 1-butene. Kataly-

Example 5 Catalyst C prepared as described above is used in a fluidized bed reactor with internal cooling. the source comprises 0.3% _by weight of chromium (Cr) and 0.9% by weight of aluminum (Al). Other reaction conditions and product properties: Reaction conditions Resin properties temperature ° C 103 melt index (MI) g / 10 min 0.6 molar ratio C4H8 / C2H4 0.009 flow rate (HLMI) g / 10 min 41.4 H2 / C2H4 molar ratio 0,073 HLMI / MI ratio, kg / m ³ 72.7 958 bed level, m yield per unit of time 1.52 average particle size, μτη 660 and bed volume, kg / h / m ³ density, kg / m ³ 455

The reactor is operated under these conditions with Catalyst C for 24 h without difficulty.

Example

Catalyst D prepared as described above was used in a fluidized bed, internally cooled, internally cooled reactor according to Example 2, at a gas velocity of 4 to 8x Gmf and at an overpressure of 2.07 MPa for the copolymerization of ethylene and 1-butene. The catalyst contains 1.0% by weight of titanium (Ti, 3.4% by weight of aluminum (Al), 3.4% by weight of magnesium (Mg) and about 9% by weight of tetrahydrofuran.

Reaction conditions Resin properties

temperature ^Q C 85 melt flow index (Mlj 1.87 molar ratio C4H8 / C2H4 0.42 g / 10 min flow rate (HLMI) g / 10 min 47.4 H2 / C2H4 molar ratio 0.26 HLMI / MI 24.8 bed level, m 1.52 density, kg / m ³ average particle size, μΐη 927 965 yield per unit time and bed volume, kg / h / m ³ 55.2 density, kg / m ³ 282

The catalyst operates under these conditions with catalyst D for 16 h without difficulty.

Claims (1)

A vertical fluidized bed reactor for polymerizing at least one monomer with a polymerization catalyst, also comprising a polymerization zone in the lower section, b) a distribution plate permeable to the fluidizing medium at the bottom of the lower section, c) a gas supply pipe through which the fluldising gas is fed to the lower section below the manifold plate; (d) a catalyst injection device through which the catalyst is introduced into the polymerization zone; OF THE INVENTION (e) a product take-off device which removes the polymer product from the poles of the measuring zone above the manifold plate; and (f) a recirculation circuit through which fluid to be withdrawn from the upper section of the reactor and recycled to the lower section of the reactor below the manifold plate, characterized in that the reactor has a uniform internal diameter and incorporates an indirect cooling device. 1 sheet of drawings