Method of transitioning between incompatible catalysts

Abstract

The present invention relates to a gas phase olefin polymerization process comprising the steps of: (a) operating the process in a continuous manner in the presence of a Ziegler-Natta catalyst system (ZN1) wherein a stream (10) comprising unreacted and inert materials is (partially) recycled back into the reactor; (b) stopping the circulation of the stream (10) back into the reactor; (c) gradually stopping the introduction of ZN1 while gradually introducing a Ziegler-Natta catalyst system (ZN2) into the reactor such that the polymer production rate is maintained at a rate that does not decrease by more than 30% than the production rate in step (a); and (d) after stopping the introduction of ZN1 and the feed of ZN2 reaching a full speed, (in part) resuming the recycle of the stream (10) back to the reactor; wherein ZN1 comprises an internal electron donor moiety which reduces the polymerization activity of ZN2.

Description

[0001] This invention relates to a method for switching between incompatible polymerization catalysts. In particular, this invention relates to a method for switching between olefin polymerization using a first Ziegler-Natta catalyst and olefin polymerization using a second Ziegler-Natta catalyst during a continuous polymerization process.

[0002] It is often necessary to switch from one class of catalysts that produces polymers with certain properties and characteristics to another catalyst capable of producing polymers with different chemical and / or physical properties. Switching between similar Ziegler-Natta catalysts or compatible catalysts is generally straightforward. Compatible catalysts are those with similar termination and insertion kinetics of monomers and (one or more) comonomers and / or those that do not exhibit detrimental interactions with each other. However, the process is often complicated when the catalysts are incompatible or of different types. For example, when switching between two incompatible catalysts (e.g., a first Ziegler-Natta catalyst and a second Ziegler-Natta catalyst), it has been found that some components of the Ziegler-Natta catalyst can act as poisons to the second Ziegler-Natta catalyst. Therefore, components of the first Ziegler-Natta catalyst inhibit the second Ziegler-Natta catalyst from promoting polymerization.

[0003] Furthermore, particularly in continuous conversion processes, the interaction between two incompatible catalysts can lead to the generation of high levels of particles smaller than approximately 120 micrometers, referred to as “fine particles.” Fine particles can cause operational problems and / or scaling and sheeting incidents in the reactor.

[0004] In the past, to achieve efficient conversion between incompatible catalysts, the first catalytic olefin polymerization process was stopped using various techniques known in the art. The reactor was then emptied, reloaded, and a second catalyst was introduced. Such catalyst conversion was time-consuming and costly due to the extended reactor shutdown required during the conversion and the generation of substandard materials. Numerous attempts have been made to improve the conversion process between incompatible catalysts.

[0005] To suppress the polymerization of the first incompatible catalyst, the injection of catalyst into the reactor must be interrupted. Stopping the feed of the first catalyst into the reactor does not immediately stop the polymerization occurring within the reactor, because the fluidized bed contains catalyst particles that can still polymerize over an extended period. Even if polymerization within the reactor is allowed to continue for a period, the catalyst within the reactor will not be completely deactivated for a considerable time.

[0006] Therefore, polymerization inhibitors or catalyst killers are used to at least partially deactivate the first Ziegler-Natta catalyst. Two general types of catalyst killers exist: reversible catalyst killers and irreversible catalyst killers. Reversible catalyst killers typically initially inhibit catalyst activity and polymerization for a period of time, but do not irreversibly deactivate the catalyst. In fact, after a period of time under normal polymerization conditions, the catalyst will reactivate and polymerization will continue. These reversible catalyst killers can be used in the process in any combination or in any order of introduction. Irreversible catalyst killers irreversibly deactivate the catalyst's ability to polymerize olefins. The use of catalyst killers and / or deactivators is disclosed in U.S. Patents 5,442,019, 5,753,786, and 6,949,612B2 to Agapiou et al., U.S. Patent 5,672,666 to Muhle et al., and U.S. Patent 6,858,684B2 to Burdett et al.

[0007] It would be advantageous to provide a catalyst conversion method that eliminates the need to stop polymerization, empty the reactor to remove the original catalyst, and restart polymerization with a different catalyst. Furthermore, it would be advantageous if the conversion method could reduce the amount of defective material generated during the conversion process, shorten the conversion time, increase the reliability and stability of the conversion process, and avoid the need to open the reactor to load the seed bed. It would be even more advantageous to provide a catalyst conversion process that prevents reactor fouling.

[0008] The purpose of this invention is to provide a method for solving the above and / or other problems.

[0009] This invention relates to a method for switching from a first Ziegler-Natta catalyst system to a second Ziegler-Natta catalyst system in a gas-phase olefin polymerization unit.

[0010] • The polymerization unit includes a polymerization reactor (8), which includes at least one inlet (11) for supplying the reaction mixture (A) to the polymerization reactor, at least one outlet (12) for removing the polymerization product (30) from the reactor, and at least one outlet (13) for removing the stream (40) of unreacted and inert materials from the reactor.

[0011] • The outlet (13) is connected to the inlet (11), through which the material flow (10) or a portion thereof can be circulated back into the reactor.

[0012] The method includes the following steps in this order:

[0013] (a) The polymerization process is operated in a continuous manner in the presence of a first Ziegler-Natta catalyst system (ZN1), wherein the feed stream (10) or a portion thereof is recycled back to the reactor;

[0014] (b) Stop the flow of material (10) and return it to the reactor for circulation;

[0015] (c) Gradually stop the introduction of ZN1 while gradually introducing the second Ziegler-Natta catalyst system (ZN2) into the reactor, such that the polymer production rate is maintained at a rate not exceeding 30% of the production rate in step (a); and

[0016] (d) After stopping the introduction of ZN1 and the feed of ZN2 reaches full speed, the feed flow (10) or a portion thereof is returned to the reactor for recirculation;

[0017] ZN1 contains an internal electron donor structure, which reduces the polymerization activity of ZN2.

[0018] Therefore, the present invention relates, for example, to a method for switching between incompatible catalysts to change a reactor from producing one type of product to another with minimal reactor downtime. For the purposes of this specification and the appended claims, the term "incompatible catalyst" is understood to be those catalysts that, in the presence of each other, reduce the productivity of at least one of the catalysts by more than 30%.

[0019] In this paper, productivity is understood as the number of kilograms of product per kilogram of catalyst over a given time period. Mw is understood as the weight-average molecular weight determined using SEC (size exclusion chromatography) with 1,2,4-trichlorobenzene as the eluent and calibrated with linear polyethylene standards. The amount of comonomer introduced was determined by analytical temperature rise elution fractionation (aTREF) according to the method described in U.S. Patent No. 4,798,081 and Wilde, L; Ryle, TR; Knobeloch, DC; Peat, LR; Determination of Branching Distributions in Polyethylene and Ethylene Copolymers, J. Polym. ScL, 20, 441-455 (1982). The analyte was dissolved in analytical grade 1,2-dichlorobenzene, filtered through a 0.2 μm filter, and allowed to crystallize in a column containing an inert support (a 2500 μl column packed with 150 μm stainless steel beads) by slowly cooling to 20 °C at a cooling rate of 0.1 °C / min. The column was equipped with an infrared detector. An ATREF chromatogram was then generated by eluting the crystallized polymer sample from the column by slowly increasing the temperature of the eluent (1,2-dichlorobenzene) from 20 °C to 130 °C at a rate of 1 °C / min.

[0020] Preferably, the method according to the invention further includes step (b2), which introduces an organometallic compound, particularly an organometallic compound containing aluminum, after step (b) and before step (c). The organometallic compound can bind to the internal electron donor structure portion present in the reactor 8, thereby reducing the deactivation effect of the internal electron donor structure portion on the activity of ZN2.

[0021] Subsequently, in step (c), a second Ziegler-Natta catalyst, ZN2, is introduced into the reactor. In step (d), a gaseous composition for the second polymerization using catalyst ZN2 is introduced into the reactor.

[0022] Preferably, the method of the present invention is continuous.

[0023] polymerization

[0024] The first and second polymerizations can be continuous polymerizations of one or more α-olefin monomers, at least one of which is ethylene or propylene. Preferred α-olefin monomers include, for example, α-olefins having 4 to 8 carbon atoms. However, if desired, small amounts of α-olefin monomers having more than 8 carbon atoms (e.g., 9 to 18 carbon atoms), such as conjugated dienes, can be used. Thus, homopolymers of ethylene or propylene, or copolymers of ethylene and / or propylene with one or more α-olefin monomers having 4 to 8 α-olefin monomers, can be prepared. Preferred α-olefin monomers include, but are not limited to, 1-butene, isobutene, 1-pentene, 1-hexene, hexadiene, isoprene, styrene, 4-methylpent-1-ene, 1-octene, and butadiene. Examples of α-olefin monomers having more than 8 carbon atoms (which may be copolymerized with ethylene and / or propylene monomers or used as partial substitutes for α-olefin monomers having 4 to 8 α-olefin monomers) include, but are not limited to, 1-decene and ethylidene norbornene.

[0025] Examples of producible polyolefins include a wide variety of polymers, such as polyethylene, such as linear low-density polyethylene (LLDPE) (which may be prepared, for example, from ethylene and 1-butene, 4-methylpent-1-ene, 1-hexene, or 1-octene), and high-density polyethylene (HDPE) (which may be prepared, for example, from ethylene or from ethylene with a small amount of α-olefin monomers having 4-8 carbon atoms, such as 1-butene, 1-pentene, 1-hexene, or 4-methylpent-1-ene). Other examples include, but are not limited to, plasmons, elastomers, medium-density polyethylene, polypropylene homopolymers and polypropylene copolymers (including random copolymers and block or multiblock copolymers), and ethylene propylene rubber (EPR). Preferably, in the method of the present invention, the polyolefin produced is polyethylene, more preferably linear low-density polyethylene, which comprises ethylene and a monomer selected from the group consisting of 1-butene, 4-methylpent-1-ene, 1-hexene, and 1-octene.

[0026] When the method of the present invention is used for copolymerization of ethylene and / or propylene with α-olefin monomers, the ethylene and / or propylene is preferably used as the major component of the copolymer. For example, based on the total copolymer, the amount of ethylene and / or propylene present in the copolymer is at least 65% by weight, for example at least 70% by weight, for example at least 80% by weight.

[0027] In this document, "continuous polymerization of one or more α-olefins" or "continuous preparation of polyolefins" refers to feeding one or more α-olefin monomers (at least one of which is ethylene or propylene) into a reactor, preferably continuously, and the resulting polyolefin being (semi-)continuously removed via a polymer discharge system connected to the reactor. Continuous polymerization of one or more olefin monomers will produce polyolefins in particulate form, also referred to herein as "polyolefins".

[0028] Ziegler-Natta catalysts typically contain transition metal halides, such as titanium or vanadium halides, and organometallic compounds of Group 1, 2, or 3 metals, usually trialkylaluminum compounds, which act as co-catalysts for the transition metal halides. Ziegler-Natta catalysts may also contain internal electron donors that can form complexes with alkylaluminum and / or transition metals. Transition metal halides can be supported on or complexed with magnesium halides. Such Ziegler-Natta catalysts can also be impregnated onto inorganic supports (e.g., silica or alumina). For further details regarding the Ziegler-Natta catalyst, see, for example, U.S. Patent Nos. 3,687,920, 4,086,408, 4,376,191, 5,019,633, 4,482,687, 4,101,445, 4,560,671, 4,719,193, 4,755,495, and 5,070,055, all of which are incorporated herein by reference.

[0029] Ziegler-Natta catalysts can have different electron donors, which can tune the activity of the catalyst and the selectivity for polymerization of certain olefins.

[0030] In this invention, the first Ziegler-Natta catalyst includes an internal electron donor structure portion; however, this internal electron donor structure portion adversely affects the activity and / or selectivity of the second Ziegler-Natta catalyst. This internal electron donor structure portion becomes part of the circulating feed stream in the gas-phase polymerization reactor and can affect the activity of the second Ziegler-Natta catalyst when switching from polymerization using the first Ziegler-Natta catalyst to polymerization using the second Ziegler-Natta catalyst.

[0031] Examples of substances that can affect the internal electron donor structure of a second Ziegler-Natta catalyst include certain alcohols, organosilicon compounds, polysiloxanes, phenols, ketones, aldehydes, inorganic acid esters, polycarboxylic acid esters, ethers, acid amides, acid anhydrides, nitrogen-containing compounds, and acyl halides.

[0032] Such alcohols can be, for example, alcohols having 1-18 carbon atoms and having an alkyl group, such as methanol, ethanol, propanol, pentanol, hexanol, octanol, 2-ethylhexanol, dodecanol, octadecanol, benzyl alcohol, phenethyl alcohol, cumyl alcohol, and isopropylbenzyl alcohol. Such polysiloxanes can be, for example, polydimethylsiloxane, such as hexamethyldisiloxane. Such phenols can be, for example, phenols having 6-25 carbon atoms, such as phenol, methyl phenolic resin, xylenol, ethylphenol, propylphenol, cumylphenol, nonylphenol, and naphthol. Such ketones can be, for example, ketones having 3-15 carbon atoms, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, and benzophenone. Such aldehydes can be, for example, aldehydes having 2-15 carbon atoms, such as acetaldehyde, propionaldehyde, octanol, benzaldehyde, tolualdehyde, and naphthaldehyde. Such inorganic esters can be, for example, ethyl silicate, butyl silicate, vinyltriethoxysilane, phenyltriethoxysilane, or diphenyldiethoxysilane. Such polycarboxylic acid esters can be, for example, ethyl acetate, polyvinyl acetate, dibutyl maleate, diethyl butyl malonate, dibutyl malonate, diethyl 1,2-cyclohexanedicarboxylate, di(2-ethylhexyl) 1,2-cyclohexanedicarboxylate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, or dioctyl phthalate. Such ethers can be, for example, ethers having 2-20 carbon atoms, such as methyl ether, diethyl ether, isopropyl ether, butyl ether, pentyl ether, tetrahydrofuran, anisole, and diphenyl ether; amides can be, for example, acetamide, benzamide, and toluamide. Such acid anhydrides can be, for example, benzoic anhydride or phthalic anhydride. Such nitrogen-containing compounds can be, for example, ammonia, amines such as methylamine, ethylamine, diethylamine, tributylamine, piperidine, tribenzylamine, aniline, pyridine, methylpyridine, and tetramethylethylenediamine, nitriles such as acetonitrile, benzonitrile, and toluenenitrile, and isocyanates. Such acyl halides can be, for example, acyl halides having 2-15 carbon atoms, such as acetyl chloride, benzoyl chloride, o-chlorotoluene, anisyl chloride, and phthaloyl dichloride.

[0033] A preferred example of the internal electron donor structure is tetrahydrofuran (THF).

[0034] In embodiments of the invention, an alkylaluminum compound may be added to the polymerization to bind the internal electron donor structure portion in reactor 8 and / or circulating feed stream 10, thereby preventing or limiting the deactivation of the second Ziegler-Natta catalyst due to complexation through the internal electron donor structure portion.

[0035] The aluminum compound used in the reaction that binds to the internal electron donor structure can be a single organoaluminum compound or a mixture of two or more different organoaluminum compounds. The aluminum compound of the present invention is preferably trialkylaluminum or dialkylaluminum hydride.

[0036] In one embodiment of the invention, the aluminum compound is selected from the group consisting of: trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, triisopropylaluminum, triisobutylaluminum, or dimethylaluminum hydride, diethylaluminum hydride, dipropylaluminum hydride, dibutylaluminum hydride, diisopropylaluminum hydride, diisobutylaluminum hydride, preferably selected from the group consisting of triethylaluminum and triisobutylaluminum.

[0037] In a preferred embodiment of the invention, the amounts of aluminum compound and internal electron donor structure portion are selected such that the molar ratio of Al to internal electron donor structure portion is in the range of 10:1 to 1:1, preferably in the range of 5:1 to 2:1.

[0038] The addition of aluminum compound to bind the internal electron donor structure portion can be performed between steps (a) and (b), during step (b), between steps (b) and (c), or even during step (c). Preferably, the addition of aluminum compound to bind the internal electron donor structure portion is stopped during step (d).

[0039] Step (c) is preferably carried out in such a manner that the introduction of the first Ziegler-Natta catalyst is gradually reduced over a period of time, for example, over a period of 0.5 to 2 hours or 0.5 to 4 hours, until it is stopped, while the second Ziegler-Natta catalyst is gradually increased over the period of time.

[0040] During step (b), the circulation of the feed stream (10) is stopped, and preferably the feed stream is removed from the polymerization unit. In an embodiment, the feed stream (10) may be subjected to a condensation step, or any step designed to remove portions of the internal electron donor structure from the feed stream (10).

[0041] In a preferred embodiment, in step (d), the recirculation of the feed stream (10) is restored when the amount of the internal electron donor structure portion is less than 5 ppm, more preferably less than 4, 3, 2 or even less than 1 ppm.

[0042] The second Ziegler-Natta catalyst ZN2 is preferably an advanced Ziegler-Natta catalyst (AZN), wherein the Ziegler-Natta catalyst is prepared in a method comprising the following steps:

[0043] a) Contacting a dehydrated solid support having hydroxyl groups with a magnesium compound having the general formula MgR'R" wherein R' and R" are the same or different and are independently selected from the group consisting of alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl and dienylaryl.

[0044] b) Contact the product obtained in step (a) with modified compounds (A), (B) and (C), wherein: compound (A) is at least one compound selected from the group consisting of carboxylic acids, carboxylic esters, ketones, acyl halides, aldehydes and alcohols; compound (B) is a compound having the general formula R 1 a (R 2 O) b SiY 1 c In a compound, where a, b, and c are each integer from 0 to 4 and the sum of a, b, and c equals 4, the modified compound (A) is not an alcohol if c equals 4, Si is a silicon atom, O is an oxygen atom, and Y is a silicon atom. 1 It is a halideatom, and R 1 and R 2 The compounds (C) are selected independently and are either identical or different from those in the group consisting of alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl, and dienylaryl; the compound (C) has the general formula (R). 11 O)4M 1 The compound in which M 1 It is a titanium atom, a zirconium atom, or a vanadium atom; O is an oxygen atom and R... 11 Selected from the group consisting of alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl, and dienylaryl; and c) Contact the product obtained in step (b) with a titanium halide compound having the general formula TiY4, wherein Ti is a titanium atom and Y is a halogen atom.

[0045] For example, this advanced Ziegler-Natta catalyst can be prepared in a method including the following first step (a): contacting a support (preferably a dehydrated solid support having hydroxyl (OH) groups) with a magnesium compound to form a magnesium-containing solid support material.

[0046] For example, the support can be any material containing hydroxyl groups. Suitable examples of such materials include inorganic oxides, such as silica, alumina, magnesium oxide, thorium oxide, zirconium oxide, and mixtures of such oxides. Porous silica is preferred as a support because it results in higher packing density and higher catalyst productivity. Silica can exist in particulate form with an average particle size of 1 micrometer to 500 micrometers, preferably 5 micrometers to 150 micrometers, and most preferably 10 micrometers to 100 micrometers. Silica with a lower average particle size produces a higher level of polymer fineness, while silica with a higher average particle size reduces the polymer packing density. Silica can have a particle size of 5 μm. 2 / g to 1500m 2 / g, preferably 50m 2 / g to 1000m 2 Specific surface area per g and 0.1 cm²3 / g to 10.0cm 3 / g, preferably 0.3cm 3 / g to 3.5cm 3 / g pore volume, because a higher catalyst productivity is obtained in this range.

[0047] For example, a dehydrated solid support can be obtained by drying the support to remove physically bound water and reducing the hydroxyl content to a level that can be from 0.1 mmol to 5.0 mmol of hydroxyl per gram of support, preferably from 0.2 mmol to 2.0 mmol of hydroxyl per gram of support, because this range allows sufficient active catalyst components to be introduced onto the support. This hydroxyl content can be achieved by methods such as those described in J.J. Fripiat and J. Uytterhoeven, J. Phys. Chem. 66, 800, 1962, or by applying... 1 Determination by ¹H NMR spectroscopy. The hydroxyl content within this range can be achieved by heating and fluidizing the support at a temperature of 150°C to 900°C under a nitrogen or air stream for 1 to 15 hours. The dehydrated support can be slurried (preferably by stirring) in a suitable hydrocarbon solvent in which each catalyst component is at least partially soluble. Examples of suitable hydrocarbon solvents include n-pentane, isopentane, cyclopentane, n-hexane, isohexane, cyclohexane, n-heptane, isoheptane, n-octane, isooctane, and n-decane. The amount of solvent used is not critical, but should be sufficient to provide a good mix of catalyst components.

[0048] Magnesium compounds are represented by the general formula MgR'R", wherein R' and R" are the same or different and are independently selected from the group consisting of alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl and dienylaryl, and may have, for example, 1 to 20 carbon atoms. Suitable examples of magnesium compounds include dimethyl magnesium, diethyl magnesium, ethylmethyl magnesium, di-n-propyl magnesium, diisopropyl magnesium, n-propylethyl magnesium, isopropylethyl magnesium, di-n-butyl magnesium, diisobutyl magnesium, n-butylethyl magnesium, n-butyl-n-propyl magnesium, n-butylisopropyl magnesium, isobutylethyl magnesium, isobutyl-n-propyl magnesium, isobutylisopropyl magnesium, di-n-pentyl magnesium, diisopentyl magnesium, n-pentylethyl magnesium, n-pentyl-n-propyl magnesium, n-pentylisopropyl magnesium, n-pentyl-n-butyl magnesium, n-pentylisobutyl magnesium, di-n-hexyl magnesium, diisohexyl magnesium, n-hexylethyl magnesium, n-hexyl-n-propyl magnesium, n-hexylisopropyl magnesium, n-hexyl-n-butyl magnesium, n-hexylisobutyl magnesium, isohexylethyl magnesium, isohexyl-n-propyl magnesium, isohexyl... Isopropyl magnesium, isohexyl-n-butyl magnesium, isohexyl-n-butyl magnesium, di-n-octyl magnesium, diisooctyl magnesium, n-octylethyl magnesium, n-octyl-n-propyl magnesium, n-octyl-isopropyl magnesium, n-octyl-n-butyl magnesium, n-octyl-isobutyl magnesium, isooctylethyl magnesium, isooctyl-n-propyl magnesium, isooctyl-n-butyl magnesium, isooctyl-n-butyl magnesium, dicyclopentyl magnesium, cyclopentylethyl magnesium, cyclopentyl-n-propyl magnesium, cyclopentyl-isopropyl magnesium, cyclopentyl-n-butyl magnesium, cyclopentyl-isobutyl magnesium, dicyclohexyl magnesium, cyclohexylethyl magnesium, cyclohexyl-n-propyl magnesium, cyclohexyl-isopropyl magnesium, cyclohexyl-n-butyl magnesium, cyclohexyl-isobutyl magnesium, diphenyl magnesium, phenylethyl magnesium, phenyl-n-propyl magnesium, phenyl-n-butyl magnesium, and mixtures thereof.

[0049] Preferably, the magnesium compound is selected from the group consisting of di-n-butylmagnesium, n-butylethylmagnesium, and n-octyl-n-butylmagnesium.

[0050] For example, the magnesium compound can be used at an amount of 0.01 to 10.0 mmol per gram of solid support, preferably 0.1 to 3.5 mmol per gram of support, and more preferably 0.3 to 2.5 mmol per gram of support, because by applying this range, the level of polymerized fine powder of the product is reduced and a higher catalyst yield is obtained. The magnesium compound can be reacted with the support at a temperature of 15°C to 140°C for a period of 5 to 150 minutes (preferably by stirring), preferably at a temperature of 20°C to 80°C for a duration of 10 to 100 minutes.

[0051] The molar ratio of Mg to OH groups in the solid support can, for example, be in the range of 0.01 to 10.0, preferably in the range of 0.1 to 5.0, and more preferably in the range of 0.1 to 3.5, because the level of polymer fineness of the product is reduced and a higher catalyst productivity is obtained.

[0052] The modified compound (A) is at least one compound selected from the group consisting of carboxylic acids, carboxylic esters, ketones, acyl halides, aldehydes, and alcohols. The modified compound (A) can be derived from the general formula R. 3 COOH, R 4 COOR 5 R 6 COR 7 R 8 COY 2 R 9 COH or R 10 OH represents, where Y 2 It is a halogen atom and R 3 R 4 R 5 R 6 R 7 R 8 R 9 and R 10 It is independently selected from the group consisting of compounds including alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl and dienylaryl and may have 1 to 20 carbon atoms.

[0053] Suitable examples of carboxylic acids include acetic acid, propionic acid, isopropionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, hexanoic acid, isohexanoic acid, heptanoic acid, isohexanoic acid, octanoic acid, isooctanoic acid, nonanoic acid, isononanoic acid, decanoic acid, isodecanic acid, cyclopentanecarboxylic acid, benzoic acid, and mixtures thereof.

[0054] Suitable examples of carboxylic acid esters include methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, isoamyl acetate, ethyl butyrate, n-butyl butyrate and / or isobutyl butyrate.

[0055] Suitable examples of ketones include dimethyl ketone, diethyl ketone, methyl ethyl ketone, di-n-propyl ketone, di-n-butyl ketone, methyl-n-propyl ketone, methyl isobutyl ketone, cyclohexanone, methyl phenyl ketone, ethyl phenyl ketone, n-propyl phenyl ketone, n-butyl phenyl ketone, isobutyl phenyl ketone, diphenyl ketone, and mixtures thereof.

[0056] Suitable examples of acyl halides include acetyl chloride, propionyl chloride, isopropionyl chloride, n-butyryl chloride, isobutyryl chloride, benzoyl chloride, and mixtures thereof.

[0057] Suitable examples of aldehydes include acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-pentanaldehyde, isopentanaldehyde, n-hexanaldehyde, isohexanaldehyde, n-heptanaldehyde, benzaldehyde, and mixtures thereof. Suitable examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, cyclobutanol, n-pentanol, isopentanol, cyclopentanol, n-hexanol, isohexanol, cyclohexanol, n-octanol, isooctanol, 2-ethylhexanol, phenol, cresol, ethylene glycol, propylene glycol, and mixtures thereof.

[0058] Preferably, the modified compound (A) is at least one compound selected from the group consisting of methyl propyl ketone, ethyl acetate, butyl acetate, acetic acid, isobutyric acid, isobutyraldehyde, acetyl chloride, ethanol, and sec-butanol, and more preferably selected from methyl propyl ketone, butyl acetate, isobutyric acid, and acetyl chloride, because higher catalyst productivity and higher product bulk density are obtained and these compounds can be used to modify the molecular weight distribution of the product.

[0059] The molar ratio of the modified compound (A) to magnesium in the solid support can, for example, range from 0.01 to 10.0, preferably from 0.1 to 5.0, more preferably from 0.1 to 3.5, and most preferably from 0.3 to 2.5, because a higher catalyst yield and a higher product packing density are obtained. The modified compound (A) can be added to the reaction product obtained in step (a) at a temperature of 15°C to 140°C for a duration of 5 to 150 minutes (preferably by stirring), preferably at a temperature of 20°C to 80°C for a duration of 10 to 100 minutes.

[0060] The modified compound (B) is derived from the general formula R 1 a (R 2 O) b SiY 1 c The expression represents a silicon compound, where a, b, and c are each integers from 0 to 4, and the sum of a, b, and c equals 4, provided that when c equals 4, then the modified compound (A) is not an alcohol, Si is a silicon atom, O is an oxygen atom, and Y... 1 It is a halogen atom and R 1 and R 2 Same or different. R 1 and R 2 Independently selected from the group consisting of compounds including alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl, and dienylaryl. For example, R 1 and R 2 It can have 1 to 20 carbon atoms.

[0061] Suitable silicon compounds include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isopropyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, isooctyltrimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, and isobutylmethyldimethoxysilane. Diisopropyldimethoxysilane, Diisobutyldimethoxysilane, Diisobutyldimethoxysilane, Isobutylisopropyldimethoxysilane, Dicyclopentyldimethoxysilane, Cyclohexylmethyldimethoxysilane, Phenylmethyldimethoxysilane, Diphenyldimethoxysilane, Trimethylmethoxysilane, Triethylmethoxysilane, Methyltriethoxysilane, Ethyltriethoxysilane, n-Propyltriethoxysilane, Isopropyltriethoxysilane, n-Butyltriethoxysilane, Isobutyltriethoxysilane, n-Pentyltriethoxysilane, n-Hexyltriethoxysilane, n-Octyltriethoxysilane, Isooctyltriethoxysilane Silane, vinyltriethoxysilane, phenyltriethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, isobutylmethyldiethoxysilane, diisopropyldiethoxysilane, diisobutyldiethoxysilane, isobutylisopropyldiethoxysilane, dicyclopentyldiethoxysilane, cyclohexylmethyldiethoxysilane, phenylmethyldiethoxysilane, diphenyldiethoxysilane, trimethylethoxysilane, triethylethoxysilane, silicon tetrachloride, methyltrichlorosilane, ethyltrichlorosilane, n-propyltrichlorosilane, isopropyltrichlorosilane, n-butyltrichlorosilane, isobutyltrichlorosilane, n-Pentyltrichlorosilane, n-Hexyltrichlorosilane, n-Octyltrichlorosilane, Isooctyltrichlorosilane, Vinyltrichlorosilane, Phenyltrichlorosilane, Dimethyldichlorosilane, Diethyldichlorosilane, Isobutylmethyldichlorosilane, Diisopropyldichlorosilane, Diisobutyldichlorosilane, Isobutylisopropyldichlorosilane, Dicyclopentyldichlorosilane, Cyclohexylmethyldichlorosilane, Phenylmethyldichlorosilane, Diphenyldichlorosilane, Trimethylchlorosilane, Triethylchlorosilane, Chlorotrimethoxysilane, Dichlorodimethoxysilane, Trichloromethoxysilane, Chlorotriethoxysilane, Dichlorodiethoxysilane and / or Trichloroethoxysilane. Preferably, the modified compound (B) used is tetraethoxysilane, n-propyltriethoxysilane, isobutyltrimethoxysilane, dimethyldichlorosilane, n-butyltrichlorosilane, and silicon tetrachloride, and more preferably isobutyltrimethoxysilane, tetraethoxysilane, n-propyltriethoxysilane, n-butyltrichlorosilane, and silicon tetrachloride, because by using these preferred compounds, higher catalyst productivity and higher packing density are obtained and the molecular weight distribution of the product can be changed.

[0062] The molar ratio of modified compound (B) to magnesium can be in the range of 0.01 to 5.0, preferably in the range of 0.01 to 3.0, more preferably in the range of 0.01 to 1.0, and most preferably in the range of 0.01 to 0.3, because a higher catalyst yield and a higher packing density are obtained. Modified compound (B) can be added to the reaction product obtained in step (a) at a temperature of 15°C to 140°C over a period of 5 to 150 minutes (preferably by stirring), preferably at a temperature of 20°C to 80°C over a period of 10 to 100 minutes. Modified compound (C) is derived from general formula (R... 11 O)4M 1 The transition metal alkoxide represents M. 1 It is a titanium atom, a zirconium atom, or a vanadium atom; O is an oxygen atom and R... 11 It is a compound selected from the group consisting of alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl, and dienylaryl compounds. R 11 It can have 1 to 20 carbon atoms.

[0063] Suitable transition metal alkoxides include tetramethoxytitanium, tetraethoxytitanium, tetran-n-propoxytitanium, tetraisopropoxytitanium, tetran-n-butoxytitanium, tetraisobutoxytitanium, tetran-n-pentoxytitanium, tetraisopentoxytitanium, tetran-n-hexyloxytitanium, tetran-n-heptoxytitanium, tetran-n-octyloxytitanium, tetracyclohexyloxytitanium, tetrabenzyloxytitanium, tetraphenoxytitanium, tetramethoxyzirconium, tetraethoxyzirconium, tetran-n-propoxyzirconium, tetraisopropoxyzirconium, tetran-n-butoxyzirconium, tetraisobutoxyzirconium, tetran-n-... Zirconium pentoxy, zirconium tetraisopentoxy, zirconium tetrahexyloxy, zirconium tetraheptyloxy, zirconium tetraoctyloxy, zirconium tetracyclohexyloxy, zirconium tetrabenzyloxy, zirconium tetraphenoxy, vanadium tetramethoxy, vanadium tetraethoxy, vanadium tetrapropoxy, vanadium tetraisopropoxy, vanadium tetrabutoxy, vanadium tetraisobutoxy, vanadium tetrapentoxy, vanadium tetraisopentoxy, vanadium tetrahexyloxy, vanadium tetraheptyloxy, vanadium tetraoctyloxy, vanadium tetracyclohexyloxy, vanadium tetrabenzyloxy, vanadium tetraphenoxy, or mixtures thereof. Preferably, titanium tetraethoxy, titanium tetrabutoxy, and zirconium tetrabutoxy are used because higher catalyst productivity and higher packing density are achieved through the use of these preferred compounds, and the molecular weight distribution of the products can be modified.

[0064] The molar ratio of modified compound (C) to magnesium can be in the range of 0.01 to 5.0, preferably in the range of 0.01 to 3.0, more preferably in the range of 0.01 to 1.0, and most preferably in the range of 0.01 to 0.3, because higher catalyst productivity, higher packing density, and improved hydrogen response are obtained in the polymerization. Modified compound (C) can be reacted with the product obtained in step (a) at a temperature of 15°C to 140°C for a duration of 5 minutes to 150 minutes (preferably by stirring), preferably at a temperature of 20°C to 80°C for a duration of 10 minutes to 100 minutes. Modified compounds (A), (B), and (C) can be contacted with the magnesium-containing solid support obtained in step (a) in any order or simultaneously.

[0065] Preferably, (A) is added first to the reaction product obtained in step (a), followed by (B) and then (C), because this order of adding the modified compounds results in higher catalyst productivity and higher product bulk density. Premixes of the individual catalyst components can also be utilized effectively.

[0066] Preferably, when the modified compound (A) is methyl n-propyl ketone and the modified compound (C) is tetraethoxytitanium, at the same level as the titanium halide compound, when the modified compound (B) is selected from the group consisting of isobutyltrimethoxysilane, n-propyltriethoxysilane, tetraethoxysilane, n-butyltrichlorosilane and silicon tetrachloride in the following order, a further increase in molecular weight distribution is obtained.

[0067] In a preferred embodiment, when the modified compound (B) is silicon tetrachloride and the modified compound (C) is titanium tetraethoxy, at the same level as the titanium halide compound, when the modified compound (A) is selected from the group consisting of isobutyraldehyde, ethyl acetate, n-butyl acetate, methyl n-propyl ketone and isobutyric acid in the following order, a combination of further improved catalyst productivity and packing density is obtained.

[0068] Titanium halide compounds are represented by the general formula TiY4, where Ti is a titanium atom and Y is a halogen atom.

[0069] Suitable titanium halide compounds include titanium tetrachloride, titanium tetrabromide, titanium tetrafluoride, or mixtures thereof. Titanium tetrachloride is preferred because it yields higher catalyst productivity. The molar ratio of the titanium halide compound to magnesium can range from 0.01 to 10.0, preferably from 0.01 to 5.0, and more preferably from 0.05 to 1.0, to achieve a better balance between high catalyst productivity and high packing density.

[0070] The titanium halide compound can be added to the reaction mixture obtained by carrying out steps (a) and (b) in any conventional manner (e.g., by stirring) at a temperature of 15°C to 140°C for a duration of 5 to 150 minutes, preferably at a temperature of 20°C to 80°C for a duration of 10 to 100 minutes. The reaction mixture can then be dried by purging with nitrogen and / or by vacuum at a temperature of 15°C to 140°C, preferably at a temperature of 30°C to 100°C, and most preferably at a temperature of 50°C to 80°C, thereby obtaining an advanced Ziegler-Natta catalyst composition. The total molar ratio of the modified compound (C) and the titanium halide compound to magnesium can be in the range of 0.01 to 10.0, preferably in the range of 0.01 to 5.0, and more preferably in the range of 0.05 to 1.0, because a better balance between high catalyst productivity and high packing density is achieved.

[0071] The total molar ratio of the modified compound (C) and the titanium halide compound to the hydroxyl (OH) groups in the dehydrated support can range from 0.01 to 10.0, preferably from 0.01 to 5.0, and more preferably from 0.05 to 1.0, because a better balance between high catalyst productivity and high packing density is achieved. Higher levels result in high catalyst productivity, despite a lower packing density, especially in gas-phase polymerization. Furthermore, applying these amounts eliminates the need for solvent decantation, solvent filtration, and solvent washing steps in catalyst preparation, and thus eliminates the generation of highly hazardous solvent waste.

[0072] In one embodiment, an advanced Ziegler-Natta catalyst system may comprise a catalyst component and a co-catalyst. The co-catalyst is typically an organometallic compound, such as alkylaluminum, alkylaluminum hydride, alkylaluminum lithium, alkylzinc, alkylcalcium, alkylmagnesium, or mixtures thereof. Preferred co-catalysts are of the general formula R. 12 n AlY 3 3-n It means that Y 3 Represents a halogen atom; n represents an integer from 0 to 3; and R 12 Selected from the group consisting of compounds containing alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl, and dienylaryl groups. R 12 It can have 1 to 20 carbon atoms. Suitable examples of co-catalysts include trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum chloride, diisobutylaluminum chloride, ethylaluminum dichloride, isobutylaluminum dichloride, and mixtures thereof. Preferably, the co-catalyst is trimethylaluminum, triethylaluminum, and / or triisobutylaluminum; and more preferably, the co-catalyst is triethylaluminum.

[0073] The co-catalyst can be used at a molar ratio of aluminum in the co-catalyst to titanium in the solid catalyst component of 1 to 500 (more preferably 10 to 250) to obtain a high catalyst productivity.

[0074] Ziegler-Natta catalysts can be fed as suspensions in solvents or as dry catalysts.

[0075] fluidized bed

[0076] The method of the present invention can be used in any polymerization process in a gas-phase reactor. The gas-phase reactor can be any reactor suitable for gas-phase polymerization and can be, for example, a vertical or horizontal mechanically stirred reactor or a fluidized bed reactor. Preferably, the gas-phase polymerization process is carried out in a gas-phase fluidized bed reactor. In a typical continuous gas-flow fluidized bed polymerization process for preparing polymers from monomers, a gaseous stream containing monomers is passed through a fluidized bed reactor in the presence of a catalyst under reaction conditions.

[0077] Conventionally, gas-phase polymerization processes are typically continuous, thus the heat of polymerization is continuously removed by circulating the gas leaving the fluidized bed to a condenser / heat exchanger outside the reactor and recirculating the cooled gas stream back into the reactor, thereby maintaining the fluidized bed reactor temperature at a substantially isothermal level. When the temperature of the recirculated stream introduced into or circulated into the fluidized bed polymerization reactor is above the dew point temperature, there is essentially no liquid. This process is called a "dry mode" process. One way to maximize heat removal capacity is to reduce the temperature of the gaseous feed stream entering the reactor to the lowest possible value throughout operation. According to the "condensation mode" process, a two-phase mixture containing liquid and gas is used as the fluidizing medium in the fluidized bed, the liquid portion of which vaporizes upon exposure to the reactor's heat. Fluid can be formed by cooling the recirculated stream taken from the reactor to below the dew point temperature, thereby converting a portion of the gas into liquid, and then the cooled recirculated stream is reintroduced into the fluidized bed polymerization reactor. The aim here is to utilize the cooling effect of vaporization, i.e., by lowering the temperature of the fluidized bed to a degree that polymer and catalyst degradation can be avoided and polymer agglomeration and clumping can be prevented. The liquid / liquid phase is provided by a portion of the circulating gas and condensation, which includes monomers and low-boiling-point liquid hydrocarbons that are inert to the reaction conditions required for polymerization. Condensation-mode fluidized bed reactor polymerization processes are disclosed, for example, in US 4543399 and US4588790. These publications describe the introduction of inert liquids into the circulating feed to increase the dew point temperature of the circulating feed and allow the process to operate at levels up to 17.4% by weight of liquid based on the total weight of the cooled circulating feed. Condensation-mode processes are advantageous because their ability to remove a larger amount of heat generated by polymerization increases the polymerization production capacity of the fluidized bed polymerization reactor. A commonly used liquid hydrocarbon in the liquid / liquid phase is isopentane, which has a boiling point of approximately 27 degrees Celsius and thus becomes vapor in the circulating line due to the heat present in the circulating gas. The recirculated gas exits the reactor, is cooled, and then condenses to the point of forming both a gaseous / gas phase and a liquid / liquid phase. The velocity of the recirculated gas / liquid mixture should be sufficient to support the fluidized bed, but slow enough to avoid excessive entrainment of fine particles. The cooling capacity should be sufficient to improve productivity in terms of space / time / yield.

[0078] "Ultra-condensation mode" fluidized bed reactor polymerization processes operate with a liquid concentration of more than 17.4% by weight in a cooled circulating feed stream, as described in, for example, US 5352749. These must be limited to certain more specific and stringent conditions within a finite and known range of operating conditions to avoid destabilizing the fluidized bed and thus halting the process.

[0079] Gas fluidized bed polymerization processes typically employ continuous gas circulation. In one portion of the circulation, the circulating gas stream is heated by the heat of polymerization within the reactor. In another portion of the circulation, this heat is removed by a cooling system external to the reactor. In one embodiment, the circulating gas stream is cooled to form a gas-liquid mixture, which is then introduced into the reactor. The polymer product is then removed from the reactor. For a detailed description of the gas-phase process, see U.S. Patent Nos. 4,543,399 and 4,588,790, the entire contents of which are incorporated herein by reference.

[0080] Compared to other polymerization processes, fluidized bed polymerization significantly reduces energy requirements and, most importantly, reduces the capital investment required to operate such a polymerization process. In a preferred embodiment, the fluidized bed is kept in a fluidized state in the method of the present invention.

[0081] Figure 1 A schematic overview of a fluidized bed reactor.

[0082] There are many types of fluidized bed reactors, including bubbling fluidized bed reactors, circulating fluidized bed reactors, annular fluidized bed reactors, multi-zone fluidized bed reactors, and flash reactors.

[0083] As used herein, “fluidized bed” refers to a solid and / or polymeric particle (preferably a solid catalyst and / or a solid catalyst with monomers attached thereto) acting as a fluid in a solid / fluid mixture. This can be achieved by placing the solid and / or polymeric particle under appropriate conditions, for example, by introducing fluid through the solid and / or polymeric particle at a sufficient rate to suspend the solid and / or polymeric particle and make them behave like a fluid.

[0084] Examples of processes using fluidized beds to produce polyolefins are disclosed in U.S. Patent No. 4,882,400. Other examples of processes using fluidized beds to produce polyolefins are described, for example, in U.S. Patent Nos. 3,709,853; 4,003,712; 4,011,382; 4,302,566; 4,543,399; 4,882,400; 5,352,749; 5,541,270; 7,122,607 and 7,300,987. The bottom of the fluidized bed reactor (FBR) may include, for example, an inlet connected to a feeder for a reaction composition, such as ethylene, nitrogen (N2), hydrogen (H2), comonomers, triisobutylamine (TIBAL)-amine, and triethylaluminum (TEAL) . The central zone above the distribution plate in the reactor includes an inlet for a polymerization catalyst that can be fed into the reactor in combination with nitrogen (N2). The intermediate zone of the reactor also includes an outlet to a product discharge tank. The top zone of the reactor includes an outlet for a top circulating feed stream, which is connected to the inlet of a compressor. The compressor includes an outlet for compressed fluid, and the compressor outlet is connected to the inlet of a cooling unit for compressed fluid. The cooling unit includes an outlet for providing a bottom circulating feed stream, and this outlet of the cooling unit is connected to an inlet at the bottom of the reactor.

[0085] Fluidized bed reactors can be such as Figure 2 The illustrated multi-zone fluidized bed reactor (FBR) system is a multi-zone reactor that can operate in condensation mode. The multi-zone reactor includes a first zone, a second zone, a third zone, a fourth zone, and a distribution plate. The first zone is separated from the second zone by the distribution plate. The multi-zone reactor extends vertically. The second zone of the multi-zone reactor is located above the first zone. The third zone of the multi-zone reactor is located above the second zone. The fourth zone of the multi-zone reactor is located above the third zone. The second zone contains an inner wall, at least a portion of which is in the form of a gradually increasing inner diameter or a continuously opening conical shape, wherein the diameter or opening increases vertically toward the top of the multi-zone reactor. The third zone contains an inner wall, at least a portion of which is in the form of a gradually increasing inner diameter or a continuously opening conical shape, wherein the diameter or opening increases vertically toward the top of the multi-zone reactor. The maximum diameter of the inner wall of the third zone is greater than the maximum diameter of the inner wall of the second zone.

[0086] The multi-zone reactor of this example can operate in a so-called "condensing mode" or "condensed mode," which is effective for removing heat generated during exothermic polymerization. In this mode, heat removal is achieved by cooling the gaseous recirculation stream to a temperature below its dew point, causing at least a portion of the recirculation stream to condense to form a bottom recirculation stream containing both liquid and gas. This bottom recirculation stream is then introduced into a fluidized bed polymerization reactor, where the liquid portion vaporizes upon exposure to the reactor's heat. This vaporization removes heat from the reactor and allows for the feeding of one or more highly active catalysts. Details of the FBR operating in condensing mode are further described in application EP13195141.0, which is incorporated herein by reference.

[0087] Figure 2 The FBR system is described, which includes a multi-zone reactor (8), a compressor (400), and a cooling unit (5).

[0088] The multi-zone reactor (8) of this example extends vertically and includes four reaction zones (1), (2), (3) and (4). In the vertical direction toward the top of the reactor, zone (4) may preferably be located above zone (3), zone (3) may be located above zone (2) and zone (2) may be located above zone (1).

[0089] The first zone (1) includes a first inlet for receiving the bottom circulating feed (10) and is separated from the second zone (2) by a distribution plate (6). The second zone (2) includes a first inlet for receiving the solid polymerization catalyst (20). The third zone (3) includes a first outlet for providing polyolefin (30). This outlet may also be located in the second zone (2). At least one of the second zone (2) or the third zone (3) may include at least one section in which the inner wall of the reactor is in the form of an inner diameter that gradually increases in the vertical direction toward the top of the reactor or in the form of a continuously open cone. Here, both the second zone (2) and the third zone (3) include such sections, denoted by 2A and 3A, respectively. In the second zone (2), at least one section (2A) may preferably be located directly above the distribution plate (6), in which the inner wall of the reactor is in the form of an inner diameter that gradually increases in the vertical direction toward the top of the reactor or in the form of a continuously open cone. Therefore, being located directly above the distribution plate (6) preferably means that liquid accumulation can be reduced or avoided. Furthermore, at least one of the second zone (2) or the third zone (3) may include at least one section in which the inner wall of the reactor is cylindrical. Both the second zone (2) and the third zone (3) here include such sections, denoted by 2B and 3B respectively. The fourth zone (4) includes a first outlet of the top circulating feed stream (40), which is connected via a first connecting device (AA) to the first inlet of the compressor (400). Thus, the fourth zone is a decoupling zone, which may be designed such that polymer particles preferably do not reach this zone or remain there as little as possible, but instead return to the third zone (3) or the second zone (2), particularly to allow for the avoidance of clogging of the compressor (400). The connecting device (AA) includes a first inlet for receiving the feed (60). The compressor (400) includes a first outlet of compressed fluid (50), which is connected via a second connecting device (BB) to the first inlet of the compressed fluid in the cooling unit (5). The second connecting device (BB) includes an inlet for receiving feed (70). The cooling unit (5) includes a first outlet for providing bottom circulating material flow (10), which is connected to the first inlet of the first zone (1).

[0090] An FBR system may also include a polymer removal system, a polymer degassing system, and an exhaust gas recovery system. Figure 1 (Not shown in the image). The outlet of the recovered component (in liquid form) (80) from the exhaust gas recovery system can be transported by pump (7) to the first inlet (70) of the second connection device (BB).

[0091] This system can be used in continuous polymerization processes, the processes including:

[0092] • The solid polymerization catalyst is supplied to the second zone (2) through the first inlet for receiving the solid polymerization catalyst (20);

[0093] • A feed (60) containing olefin monomers is supplied to the first connecting unit (AA).

[0094] • Optionally, a feed (70) containing a condensable inert component is supplied to the second connecting device (BB).

[0095] • Use the first outlet of the second zone (2) and / or the third zone (3) to remove polyolefin (30) and

[0096] • Circulate the fluid from the first outlet of the fourth zone (4) to the first inlet of the first zone (1).

[0097] The fluid is circulated in the following manner:

[0098] • The feed (60) and top circulating flow (40) are compressed using a compressor (400) to form a compressed fluid (50).

[0099] The compressed fluid (50) is then cooled to below its dew point using a cooling unit (5) to form a bottom circulating flow (10).

[0100] • The bottom circulating material stream (10) is fed into the first zone of the multi-zone reactor (8) via an inlet for receiving the bottom circulating material stream from the first zone, and

[0101] • The apparent gas velocity in this process is in the range of 0.5 to 5 m / s.

[0102] The feed (60) may contain, for example, a chain transfer agent, such as hydrogen, and may also contain gaseous olefin monomers and inert gaseous components, such as nitrogen.

[0103] The feed (70) may, for example, contain condensable inert components, such as condensable inert components selected from the group consisting of alkanes having 4 to 20 carbon atoms, preferably 4 to 8 carbon atoms, such as propane, n-butane, isobutene, n-pentane, isopentane, neopentane, n-hexane, isohexane or other saturated hydrocarbons having 6 carbon atoms, n-heptane, n-octane and other saturated hydrocarbons having 7 or 8 carbon atoms and any mixture thereof; and may also contain condensable α-olefin monomers, α-olefin comonomers and / or mixtures thereof.

[0104] The aforementioned FBR system has the advantage of allowing the introduction of higher volumes of liquid without causing fluidized bed instability.

[0105] Attached Figure

[0106] Figure 1 A typical gas-phase polymerization apparatus is shown.

[0107] Figure 2 The equipment for a multi-zone fluidized bed polymerization process is shown.

[0108] Figure 3 The activity of the catalyst system ZN2 in the presence of THF (30 ppmw) is shown as a function of time (Example 1).

[0109] Figure 4 The effect of adding 30 ppmw THF on the sensitivity of the ZN2 catalyst to hydrogen is shown (Example 1).

[0110] Figure 5 The activity of the catalyst system ZN2 in the presence of THF (45-55 ppmw) is shown as a function of time (Example 2) and as a function of TEAL addition.

[0111] Figure 6 The effect of adding 45-55 ppmw THF on the sensitivity of ZN2 catalyst to hydrogen is shown (Example 2), and it is a function of TEAL addition.

[0112] The invention will now be illustrated by the following non-limiting embodiments.

[0113] Preparation of supported Ziegler-Natta catalyst (Catalyst I) on silica:

[0114] Under a dry nitrogen atmosphere, 33 g of silica (Davison 955) previously calcined at 600 °C for 4 hours was added to a Schlenk flask, and 19 mL of an isopentane solution of 1 M triethylaluminum (TEAL) was added to the silica to form a slurry. The slurry was maintained at 37 °C for 1.0 hour. Then, 4 g of MgCl2 and 2.46 g of TiCl3 were dissolved in 1.5 L of THF (100%) at 75 °C for 2 hours (Mg / Ti molar ratio of 3.1). After dissolving the MgCl2-TiCl3 precursor in THF, the solution was transferred to a Schlenk flask (with TEAL on silica) and mixed at 75 °C for another 1 hour. Drying was carried out at 105 °C, followed by drying at 100 °C under nitrogen purging, so that the final dried catalyst powder contained 14.0% by weight of THF. Finally, 4.1 g of pure DEAC was added to the previously dried powder and mixed for 20 minutes, followed by the addition of 4.8 g of TnHAL for 30 minutes, and then dried at 65°C to obtain a free-flowing catalyst.

[0115] Preparation of supported Ziegler-Natta catalyst (Catalyst II) on silica:

[0116] In a glove box, attach a mechanical stirrer to a 3-L three-necked flask and add 150 g of silica, followed by 1.2 L of dry isopentane. Plug the neck with a septa and stir the mixture at 350 rpm until the silica is completely suspended. Add dibutylmagnesium (108 mL, 1.0 M in heptane) via syringe over a 15-minute period and further stir the suspension for 45 minutes. Increase the stirrer speed to 450 rpm and slowly add Et over a 10-minute period. 1.5 AlCl 1.5 (40.2 mmol). Add Et 1.5 AlCl 1.5 The suspension then became gel-like and was stirred for another 20 minutes. Tetrachlorosilane (30 mmol) was added over 10 minutes, and the still gel-like suspension was stirred for another 20 minutes. 2-Pentanone (210 mmol) was slowly added; the suspension quickly lost its gel-like properties, and the stirrer speed was reduced to 350 rpm to avoid splashing. Tetraethoxytitanium (10.8 mmol) was slowly added over a 10-minute period, at which point the suspension turned pale yellow. Stirring was continued for another 20 minutes. Finally, titanium tetrachloride (24 mmol) was added over a 10-minute period, and the suspension slowly darkened in color. Stirring was continued for another 20 minutes. The suspension was then purged with nitrogen until it became almost solid; at this point, stirring was stopped, and nitrogen purging continued until a free-flowing beige powder formed.

[0117] Methods for preparing catalyst systems to be used in the production of polyethylene and its copolymers are generally known in the art. Key components used in the preparation of such catalysts typically include supported magnesium compounds, titanium compounds supported thereon, and organoaluminum compounds. Such catalysts are generally referred to in the art as supported Ziegler-Natta catalysts, and an overview of such catalyst types is given, for example, by T. Pullukat and R. Hoff in Catal. Rev.-Sci. Eng. 41, Vols. 3 and 4, 389-438, 1999.

[0118] Two examples simulating the online conversion between catalyst I and catalyst II in a commercial-scale reactor are provided below. The simulation examples were conducted in a continuous gas-phase fluidized bed reactor with an inner diameter of 45 cm and a reaction zone height of 140 cm. The polymer particle bed in the reaction zone was kept fluidized by the circulating feed stream, which served as both a fluidizing medium and a heat-dissipating agent to absorb the exothermic flow generated within the reaction zone. The reactor was maintained at a constant temperature of approximately 86 °C and a constant pressure of approximately 21.7 bar. Ethylene and 1-butene were used as the starting materials for polymerization. These materials formed the makeup feed stream. A co-catalyst was mixed with the makeup feed stream as a 5% by weight solution in an isopentane carrier solvent.

[0119] Purified nitrogen was used as the carrier gas to directly inject the solid catalyst composition into the fluidized bed reaction zone. The injection rate was adjusted to maintain a constant production rate of approximately 10 kg / hr. The produced polymer was semi-continuously discharged from the reaction zone into a fixed-volume chamber via a series of valves.

[0120] Example 1:

[0121] Based on the typical production rate of approximately 4000 kg of PE resin per kg of catalyst I at pilot-scale, the corresponding THF concentration in the reactor bed is approximately 30 ppmw. It is important to note that free THF in the gas phase is not considered in the above estimate. This test was conducted by running the reactor with catalyst II to produce membrane-grade LLDPE. A 0.15 wt% solution of THF as a solvent in isopentane was then mixed with the makeup feed. Once THF was injected into the reactor, the system was allowed to reach a steady state where the THF concentration in the reactor bed reached the target value of 30 ppmw.

[0122] Figure 2 and Figure 3 The results of the first pilot-scale device test were summarized. Figure 2 The ash and APS results for the produced resin are shown, with the red shaded area in the figure representing the time period when the reactor bed THF concentration was 30 ppmw. The ash and APS results can be considered as two independent productivity measures. Taking this into account and observing these two trends, it is clear that THF has a significant poisoning effect on catalyst I. At a THF concentration of 30 ppmw, the productivity of catalyst I decreased by approximately 25%. Figure 3 The MI response in the reactor to the H2 / C2 molar ratio is shown. It can be seen that the MI response to H2 decreases in the presence of THF.

[0123] Example II:

[0124] In this test, in addition to the THF absorbed in the resin, the free THF present in the gas phase was also estimated. In the commercial-scale gas-phase process using catalyst I, most of the gaseous components leaving the reactor through the product discharge system are recovered in the exhaust gas recovery unit and recycled back to the reaction system. This means that THF will accumulate in the reaction system until a steady-state concentration is reached. The concentrations of both free and absorbed THF were significantly higher than those estimated in the first test described above. The target THF concentration in the reactor bed in this test was in the range of 45-55 ppmw. Similar to the first test, the reactor was run with catalyst II to produce membrane-grade LLDPE. A 0.75 wt% solution of THF as a solvent in isopentane was then mixed with the makeup feed. Once THF was injected into the reactor, the system was allowed to reach steady state, at which the THF concentration in the bed reached the target value of 45-55 ppmw.

[0125] Figure 4 and Figure 5 The results of the second pilot plant test were summarized. Figure 4 The ash content and APS results of the produced resin are shown, with two shaded areas in red and yellow in this noteworthy figure. The red shaded area represents the time period when the THF concentration in the reactor bed is in the range of 45-55 ppmw, while the yellow shaded area represents the time period when the THF concentration is the same but the Teal concentration is increased by about 30%. Similar to the first test, it is clear that THF has a significant poisoning effect on catalyst II. In the THF concentration range of 45-55 ppmw, the productivity of catalyst II decreases by about 45%. However, the yellow shaded area in this figure indicates that the negative impact of THF is mitigated to some extent. It is worth emphasizing that this second test was designed to test whether increasing the Teal concentration in the reactor bed would reduce the poisoning effect of THF on catalyst II, and this is exactly the case. Since Teal and THF will act as Lewis acid and Lewis base, respectively, and will form Lewis adducts, this result is expected. This is confirmed by a slight increase of 16% in the APS results by volume, indicating an increase in productivity. Similar to the first test, Figure 5 The MI response to the H2 / C2 molar ratio in the reactor is shown. It can be seen that the MI response to H2 decreases in the presence of THF. Table 2 shows the process parameters for Example II.

[0126] The properties of polymers are determined using the following test methods:

[0127]

[0128] Table 1

[0129]

[0130] Table 2

Claims

1. A method for switching from a first Ziegler-Natta catalyst system to a second Ziegler-Natta catalyst system in a gas-phase olefin polymerization unit. • The polymerization unit comprises a polymerization reactor (8) including at least one inlet (11) for supplying the reaction mixture (A) to the polymerization reactor, at least one outlet (12) for removing the polymerization product (30) from the reactor, and at least one outlet (13) for removing a stream (40) of unreacted and inert materials from the reactor. The outlet (13) is connected to the inlet (11), through which the feed stream (10) or a portion thereof can be circulated back into the reactor. The method includes the following steps in this order: (a) The polymerization process is operated in a continuous manner in the presence of a first Ziegler-Natta catalyst system (ZN1), wherein the feed stream (10) or a portion thereof is recycled back to the reactor; (b) Stop the flow of material (10) and return it to the circulation in the reactor; (c) Gradually stop the introduction of ZN1 while gradually introducing the second Ziegler-Natta catalyst system (ZN2) into the reactor, such that the polymer production rate is maintained at a rate not exceeding 30% of the production rate in step (a); and (d) After stopping the introduction of ZN1 and the feed of ZN2 reaches full speed, the feed flow (10) or a portion thereof is restored to the reactor for recirculation; ZN1 contains an internal electron donor structure, which reduces the polymerization activity of ZN2.

2. The method of claim 1, wherein the polymerization process involves the polymerization of ethylene with one or more comonomers selected from propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene.

3. The method according to any one of claims 1-2, wherein in step C, a trialkylaluminum co-catalyst is added to the reactor to incorporate the internal electron donor structure portion of ZN1.

4. The method according to claim 3, wherein the molar ratio between trialkylaluminum and the internal electron donor structure portion is in the range of 10:1 to 1:

1.

5. The method according to any one of claims 1-4, wherein the internal electron donor structure portion present in ZN1 is selected from alcohols, organosilicon compounds, polysiloxanes, phenols, ketones, aldehydes, inorganic acid esters, polycarboxylic acid esters, ethers, amides, acid anhydrides, nitrogen-containing compounds, and acyl halides, preferably wherein the internal electron donor structure portion is tetrahydrofuran.

6. The method according to any one of claims 1-5, wherein ZN1 is a supported catalyst system, preferably wherein the support is selected from inorganic oxides, such as silica, alumina, magnesium oxide, thorium oxide, zirconium oxide and mixtures of such oxides, more preferably, the support is porous silica.

7. The method according to any one of claims 1-6, wherein ZN2 is prepared in a method comprising the following steps: a) Contacting a dehydrated solid support having hydroxyl groups with a magnesium compound having the general formula MgR'R" wherein R' and R" are the same or different and are independently selected from the group consisting of alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl and dienylaryl. b) Contact the product obtained in step (a) with modified compounds (A), (B) and (C), wherein: Compound (A) is at least one compound selected from the group consisting of carboxylic acids, carboxylic esters, ketones, acyl halides, aldehydes, and alcohols; compound (B) is a compound having the general formula R. 1 a (R 2 O) b SiY 1 c In a compound, where a, b, and c are each integers from 0 to 4 and the sum of a, b, and c equals 4, the modified compound (A) is not an alcohol if c equals 4, Si is a silicon atom, O is an oxygen atom, and Y is a silicon atom. 1 It is a halogen atom, and R 1 and R 2 The compounds (C) are selected independently from the group consisting of alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl, and dienylaryl, whether identical or different; the compound (C) has the general formula (R). 11 O)4M 1 The compound in which M 1 It is a titanium atom, a zirconium atom, or a vanadium atom; O is an oxygen atom; and R... 11 The product is selected from the group consisting of alkyl, alkenyl, dienyl, aryl, alkylaryl, alkenylaryl, and dienylaryl; and c) contacting the product obtained in step (b) with a titanium halide compound having the general formula TiY4, wherein Ti is a titanium atom and Y is a halogen atom.

8. The method according to any one of claims 3-7, wherein the trialkylaluminum compound is selected from trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, triisopropylaluminum, triisobutylaluminum, dimethylaluminum hydride, diethylaluminum hydride, dipropylaluminum hydride, dibutylaluminum hydride, diisopropylaluminum hydride, and diisobutylaluminum hydride, preferably selected from triethylaluminum and triisobutylaluminum.

9. The method according to any one of claims 1-6, wherein ZN2 is a supported catalyst system, preferably wherein the support is selected from inorganic oxides, such as silica, alumina, magnesium oxide, thorium oxide, zirconium oxide and mixtures of such oxides, more preferably, the support is porous silica.

10. The method according to any one of claims 1-9, wherein during steps (b) and (c), the feed stream (10) is removed from the polymerization unit.

11. The method according to any one of claims 1-10, wherein the feed stream (10) is condensed before being recycled back to the polymerization reactor via inlet (11).

12. The method according to any one of claims 1-11, wherein the polymerization reactor is a fluidized bed gas-phase polymerization reactor.

13. The method of claim 12, wherein the polymerization process is carried out in a multi-zone reactor, the polymerization process comprising: • The solid polymerization catalyst is supplied to the second zone (2) through the first inlet for receiving the solid polymerization catalyst (20); • A feed (60) containing olefin monomers is supplied to the first connecting unit (AA). • Optionally, a feed (70) containing a condensable inert component is supplied to the second connecting device (BB). • Use the first outlet (12) of the second zone (2) and / or the third zone (3) to remove the polyolefin (30), and • The fluid is circulated from the first outlet (13) of the fourth zone (4) to the first inlet (11) of the first zone (1). The fluid is circulated in the following manner: • The feed (60) and top circulating flow (40) are compressed using a compressor (400) to form a compressed fluid (50). The compressed fluid (50) is then cooled to below its dew point using a cooling unit (5) to form a bottom circulating flow (10). • The bottom circulating material stream (10) is fed into the first zone of the multi-zone reactor (8) via the inlet (11) for receiving the bottom circulating material stream from the first zone, and • The apparent gas velocity in the process is in the range of 0.5 to 5 m / s.

14. The method according to any one of claims 1-13, wherein the recovery of the recycling in step (d) is performed when the content of the internal electron donor structure portion in the feed stream (10) decreases to 5 ppm or less by weight.

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