WO2013028283A1

WO2013028283A1 - Catalyst systems and methods for using same to produce polyolefin products

Info

Publication number: WO2013028283A1
Application number: PCT/US2012/047027
Authority: WO
Inventors: Kevin J. Cann; John H. Moorhouse; Phuong A. Cao; Mark G. Goode; C. Jeff Harlan; Wesley R. Mariott; Daniel P ZILKER; F. David Hussein; Lixin Sun
Original assignee: Univation Technologies, Llc
Priority date: 2011-08-19
Filing date: 2012-07-17
Publication date: 2013-02-28
Also published as: WO2013028283A8

Abstract

Catalyst systems and methods for making and using the same are provided. The catalyst system can include a catalyst compound having (1) at least one cyclopentadienyl ligand and at least one heteroatom ligand; (2) two non-bridged cyclopentadienyl ligands; or (3) two or more heteroatom ligands. The catalyst system further comprise a support comprising fluorinated silica. The support may be essentially free of alumina. The catalyst system further comprises an aluminoxane, preferably methylaluminoxane, modified methylaluminoxane, or a combination thereof.

Description

CATALYST SYSTEMS AND METHODS FOR USING SAME TO PRODUCE

POLYOLEFIN PRODUCTS

BACKGROUND

[0001] A number of catalyst compositions containing catalyst precursors have been used to prepare polyolefins, producing relatively homogeneous copolymers at good polymerization rates. In contrast to traditional Ziegler-Natta catalyst compositions, metallocene catalysts are catalytic compounds in which each catalyst molecule contains one or only a few polymerization sites.

[0002] To achieve acceptable and economically viable polymerization activities with catalyst systems having one or only a few polymerization sites, a large amount of activator, such as methylaluminoxane ("MAO"), is often required. Unfortunately, such activators are expensive and the large amount of activator required to produce an active catalyst system for polymerization has been an impediment to the broad commercial use of catalysts having one or only a few polymerization sites for polyolefin production. There is a need, therefore, for new catalyst systems for olefin polymerization that have improved productivity.

SUMMARY

[0003] Catalyst systems and methods for making and using the same are provided. The catalyst system can include a catalyst compound comprising: (1) at least one cyclopentadienyl ligand and at least one heteroatom ligand; (2) two non-bridged cyclopentadienyl ligands; or (3) two or more heteroatom ligands. The catalyst system further comprises a support comprising fluorinated silica and an aluminoxane. Preferably, the support is essentially free of alumina.

DETAILED DESCRIPTION

[0004] Applicants have found that fluorinating an inorganic oxide support that is used in a catalyst system can substantially increase the catalyst productivity as compared to the same catalyst system without the fluorinated support. For the purposes of this disclosure, the term "catalyst system" collectively refers to one or more catalyst compounds, one or more activators, and one or more supports. Thus, using a fluorinated inorganic oxide support may increase the catalyst productivity of the catalyst system by about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, or more as compared to the same catalyst system using a non-fluorinated inorganic oxide support, where the inorganic oxide supports are the same inorganic oxide. In other words, for a first catalyst system having a non-fluorinated support and a second catalyst system having a fluorinated support, where the two catalyst systems have the same activator concentrations, the same inorganic oxide support, and the same catalyst compound, the catalyst productivity for the second catalyst system can be greater than the catalyst productivity for the first catalyst system by the percentages noted.

[0005] It has also been surprisingly and unexpectedly discovered that when an inorganic oxide support has been fluorinated, a still higher level of catalyst productivity is obtained by increasing a concentration of the transition metal component in the catalyst compound. In other words, as between two catalyst compounds having different concentrations of transition metal component and the same fluorinated inorganic oxide support, increasing the amount of the transition metal component of the catalyst compound can further increase the catalyst productivity. For example, when using a fluorinated silica support having an increased productivity as described above, the catalyst productivity of the catalyst system can be further increased by about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, or more by increasing the amount of the transition metal component in the catalyst compound, as compared to the same catalyst system using the same fluorinated silica support.

[0006] The transition metal component of the catalyst compound can be present in an amount ranging from a low of about 0.2 wt%, about 0.3 wt%, about 0.4 wt%, about 0.5 wt%, about 0.6 wt%, or about 0.7 wt% to a high of about 1 wt%, about 2 wt%, about 2.5 wt%, about 3 wt%, about 3.5 wt%, or about 4 wt%, based on the total weight of the catalyst system, with suitable ranges comprising the combination of any lower amount and any upper amount. Depending, at least in part, on the particular transition metal component(s) selected and the desired degree of catalyst productivity increase, the amount of the transition metal component of the catalyst compound can vary. For example, if the transition metal component is hafnium, the transition metal component can be present in the catalyst system in an amount of about 0.5 wt% or more, about 0.6 wt% or more, about 0.7 wt% or more, about 0.8 wt% or more, about 0.85 wt% or more, about 0.9 wt% or more, about 0.95 wt% or more, about 1 wt% or more, about 1.05 wt% or more, about 1.1 wt% or more, about 1.15 wt% or more, about 1.2 wt% or more, about 1.25 wt% or more, or about 1.3 wt% or more, based on the total weight of the catalyst system. If the transition metal component is hafnium, the transition metal component can be present in the catalyst system in an amount ranging from a low of about 0.5 wt%, about 0.6 wt%, about 0.7 wt%, or about 0.8 wt% to a high of about 1 wt%, about 1.1 wt%, about 1.2 wt%, about 1.4 wt%, or about 1.6 wt%, based on the total weight of the catalyst system, with suitable ranges comprising the combination of any lower amount and any upper amount. In another example, if the transition metal component is zirconium, the transition metal component can be present in the catalyst system in an amount ranging from a low of about 0.2 wt%, about 0.25 wt%, about 0.3 wt%, or about 0.35 wt% to a high of about 0.4 wt%, about 0.8 wt%, about 1 wt%, about 1.2 wt%, or about 1.5 wt%, based on the total weight of the catalyst system, with suitable ranges comprising the combination of any lower amount and any upper amount.

[0007] It is also believed that the catalyst system can be combined with ethylene and one or more organo-aluminum compounds within a polymerization reactor at conditions sufficient to produce polyethylene having improved properties. For example, the presence of at least one organo-aluminum compound can increase a melt flow ratio ("MFR", or "I21/I2") of the polymer, as compared to using the same catalyst system in the absence of the at least one organo- aluminum compound. For example, the melt flow ratio (MFR) of a polymer can be increased by about 1%, about 3%, about 5%, about 8%, about 10%, about 13%, about 15%, about 18%, about 20%, about 23%, about 25%, about 27%, or about 30% by adding one or more organo- aluminum compounds to the polymerization reactor. In another example, the melt flow ratio (MFR) can be increased by about 10% to about 20%, or about 15% to about 25%, or about 15% to about 22%, or about 13% to about 25%, or about 3% to about 17%, by introducing at least one organo-aluminum compound to the polymerization reactor. As used herein, the terms "MFR" and "WW interchangeably refer to the ratio of the flow index ("FI" or "W) to the melt index ("MI" or "I₂"). The MI (I₂) can be measured in accordance with ASTM D 1238 (at 190°C, 2.16 kg weight). The FI (I_2i) can be measured in accordance with ASTM D1238 (at 190°C, 21.6 kg weight).

[0008] The amount of the one or more organo-aluminum compounds within the polymerization reactor can range from about 1 ppmw to about 100 ppmw. For example, the one or more organo-aluminum compounds can be present within the polymerization reactor in an amount of about 5 ppmw to about 15 ppmw, about 8 ppmw to about 14 ppmw, about 5 ppmw to about 60 ppmw, about 10 ppmw to about 40 ppmw, or about 5 ppmw to about 30 ppmw. In another example, the one or more organo-aluminum compounds can be present within the polymerization reactor in an amount ranging from a low of about 1 ppmw, about 3 ppmw, about 5 ppmw, about 7 ppmw, or about 10 ppmw to a high of about 15 ppmw, about 20 ppmw, about 25 ppmw, about 30 ppmw, about 40 ppmw, or about 50 ppmw, with suitable ranges comprising the combination of any lower amount and any upper amount. The one or more organo- aluminum compounds can be introduced separately or independently from the catalyst system to the polymerization reactor. The one or more organo-aluminum compounds can also be combined with the catalyst system and introduced to the polymerization reactor as a mixture. For example, the catalyst system and organo-aluminum compound(s) can be combined and introduced as a slurry to the polymerization reactor. [0009] The catalyst compound, the activator, and the support can be combined together in any order or sequence to produce the catalyst system. For example, the one or more catalyst compounds and activators can be combined to produce a catalyst/activator mixture, and the support and the catalyst/activator mixture can then be added independently to a polymerization reactor. Alternatively, the support, catalyst compound, and activator can be combined and introduced as a single catalyst system to the polymerization reactor. Alternatively, the catalyst compound and activator can be combined first to produce a catalyst/activator mixture and then the support can be added to the catalyst/activator mixture to produce the catalyst system. Alternatively, the catalyst compound and activator can be combined to produce a catalyst/activator mixture and then the catalyst/activator mixture can be added to the support to produce the catalyst system. Alternatively, the support and activator can be combined first to produce an activator/support mixture and then the catalyst compound can be added to activator/support mixture to produce the catalyst system. The catalyst compound can be added to the activator/support mixture before introduction to the polymerization reactor or the catalyst compound and the activator/support mixture can be independently introduced to the polymerization reactor and combined therein.

[0010] One or more diluents or carriers can be used to facilitate the combination of any two or more components of the catalyst system. For example, the catalyst compound and the activator can be combined together in the presence of toluene or another non-reactive hydrocarbon or hydrocarbon mixture to provide the catalyst/activator mixture. In addition to toluene, other suitable diluents can include, but are not limited to, ethylbenzene, xylene, pentane, hexane, heptane, octane, other hydrocarbons, or any combination thereof. The support, either dry or mixed with toluene, can then be added to the catalyst/activator mixture or the catalyst/activator mixture can be added to the support.

[0011] Suitable activators include aluminoxanes, and preferably methylaluminoxane ("MAO") or modified methylaluminoxane ("MMAO"), or a combination thereof. The amount of aluminoxane can be determined based on the amount of aluminum (Al) contained in the aluminoxane. The aluminoxane can be present in the catalyst system in an amount ranging from about 0.1 mmol to about 10 mmol per gram of the support. For example, the aluminoxane can be present in the catalyst system in an amount of about 9.5 mmol or less, about 9 mmol or less, about 8 mmol or less, about 7.5 mmol or less, about 7 mmol or less, about 6.5 mmol or less, about 6 mmol or less, about 5.5 mmol or less, about 5 mmol or less, about 4.5 mmol or less, about 4 mmol or less, about 3.5 mmol or less, about 3 mmol or less per gram of the support. In another example, the aluminoxane can be present in the catalyst system in an amount ranging from a low of about 0.1 mmol, about 0.5 mmol, about 1 mmol, or about 1.5 mmol to a high of about 3 mmol, about 5 mmol, about 6 mmol, about 6.3 mmol, about 6.5 mmol, about 6.7 mmol, about 7 mmol, or about 8 mmol per gram of the support, with suitable ranges comprising the combination of any lower amount and any upper amount. In another example, the aluminoxane can be present in the catalyst system in an amount ranging from about 3 mmol to about 9 mmol, about 4 mmol to about 8 mmol, about 5 mmol to about 7 mmol, about 5.5 mmol to about 6.5 mmol, or about 5.8 mmol to about 6.8 mmol per gram of the support.

[0012] The catalyst system, as described herein, can have a catalyst productivity of at least 7,000, at least 8,000, at least 9,000, at least 10,000, at least 11,000, at least 12,000, at least 13,000, at least 14,000, at least 15,000, at least 16,000, or at least 17,000 grams polymer per gram catalyst system. For example, the catalyst system having one or more aluminoxanes present in an amount of about 8 mmol or less per gram of support can have a catalyst productivity ranging from a low of about 7,000, about 8,000, or about 9,000 to a high of about 12,000, about 16,000, about 20,000, about 24,000, about 26,000, about 28,000, or about 30,000 grams polymer per gram catalyst system, with suitable ranges comprising the combination of any lower productivity and any upper productivity. In another example, the catalyst system having one or more aluminoxanes present in an amount of about 7 mmol or less per gram of support can have a catalyst productivity ranging from a low of about 5,000, about 6,000, about 7,000 or about 8,000 to a high of about 12,000, about 16,000, about 20,000, about 24,000, about 26,000, about 28,000, or about 30,000 grams polymer per gram catalyst system, with suitable ranges comprising the combination of any lower productivity and any upper productivity. In another example, the catalyst system having one or more aluminoxanes present in an amount ranging from about 5.5 mmol to about 6.5 mmol per gram of support can have a catalyst productivity ranging from a low of about 5,000, about 6,000, about 7,000 or about 8,000 to a high of about 12,000, about 16,000, about 20,000, about 24,000, about 26,000, about 28,000, or about 30,000 grams polymer per gram catalyst system, with suitable ranges comprising the combination of any lower productivity and any upper productivity. In another example, the catalyst system having one or more aluminoxanes present in an amount ranging from about 3 mmol to about 5 mmol per gram of the support can have a catalyst productivity ranging from a low of about 5,000, about 6,000, about 7,000 or about 8,000 to a high of about 12,000, about 16,000, about 20,000, about 24,000, about 26,000, about 28,000, or about 30,000 grams polymer per gram catalyst system, with suitable ranges comprising the combination of any lower productivity and any upper productivity. In another example, the catalyst system having one or more aluminoxanes present in an amount ranging from about 2 mmol to about 3 mmol, about 3 mmol to about 4 mmol, about 4 mmol to about 5 mmol, or about 5 mmol to about 6 mmol per gram of the support can have a catalyst productivity ranging from a low of about 5,000, about 6,000, about 7,000 or about 8,000 to a high of about 12,000, about 16,000, about 20,000, about 24,000, about 26,000, about 28,000, or about 30,000 grams polymer per gram catalyst system, with suitable ranges comprising the combination of any lower productivity and any upper productivity.

[0013] The catalyst system having MAO or MMAO or both present in an amount of about 1 mmol to about 10 mmol per gram of support and a transition metal amount ranging from about 0.2 wt% to about 1.4 wt% based on a total weight of the catalyst system, when the support is a silica-containing support that has been fluorinated, can have a catalyst productivity of at least 7,000, at least 8,000, at least 10,000, at least 1 1,000, at least 12,000, at least 13,000, at least 14,000, at least 15,000, at least 16,000, at least 17,000, at least 18,000, at least 19,000, at least 20,000, at least 21,000, at least 22,000, at least 23,000, at least 24,000, or at least 25,000 grams polymer per gram catalyst system. For example, the catalyst system having MAO or MMAO or a combination thereof present in an amount of about 5 mmol to about 7 mmol per gram of support and a transition metal amount, e.g., Hf, ranging from about 0.9 wt% to about 1.2 wt% based on the total weight of the catalyst system, when the support is a silica-containing support that has been fluorinated, can have a catalyst productivity ranging from a low of about 2,000, about 3,000, about 4,000, about 5,000, about 6,000, or about 7,000 to a high of about 8,000, about 10,000, about 12,000, about 14,000, about 16,000, about 18,000, about 20,000, about 22,000, about 24,000, about 26,000, about 28,000, or about 30,000 grams polymer per gram catalyst system, with suitable ranges comprising the combination of any lower productivity and any upper productivity.

[0014] The catalyst system having one or more aluminoxanes present in an amount ranging from about 3 mmol to about 5 mmol per gram of support and a transition metal amount ranging from about 0.2 wt% to about 1.4 wt% based on the total weight of the catalyst system can have a catalyst productivity of at least 2,000, at least 4,000, at least 6,000, at least 8,000, at least 10,000, at least 12,000, at least 14,000, at least 16,000, at least 18,000, at least 20,000, at least 22,000, or at least 24,000 grams polymer per gram catalyst system. The catalyst system having an aluminoxane in an amount ranging from about 5.5 mmol to about 8 mmol per gram of support and a transition metal amount ranging from about 0.2 wt% to about 1.4 wt% based on the total weight of the catalyst system can have a catalyst productivity of at least 2,000, at least 4,000, at least 6,000, at least 8,000, or at least 10,000, at least 12,000, at least 14,000, at least 16,000, at least 18,000, at least 20,000, at least 22,000, at least 24,000, at least 26,000, at least 28,000, or at least 30,000 grams polymer per gram catalyst.

[0015] Thus, the use of fluorinated silicas in the catalyst systems described herein allows for improved catalyst performance. Further increases in catalyst productivity may be seen when the metal content of the catalyst compound in the catalyst system is increased. The components of the catalyst system are described in further detail below.

Support

[0016] As used herein, the terms "support" and "carrier" are used interchangeably and refer to any support material, including a porous support material, such as talc, inorganic oxides, and inorganic chlorides. Other supports can include resinous support materials such as polystyrene, functionalized or crosslinked organic supports, such as polystyrene divinyl benzene polyolefins or other polymeric compounds, or any other organic or inorganic support material and the like, or mixtures thereof.

[0017] The one or more catalyst compounds of the present disclosure can be supported on the same or separate supports together with the activator, or the activator can be used in an unsupported form, or can be deposited on a support different from the catalyst compound(s), or any combination thereof. This may be accomplished by any technique commonly used in the art. There are various other methods in the art for supporting a catalyst compound. For example, the catalyst compound can contain a polymer bound ligand as described in, for example, U.S. Patent Nos. 5,473,202 and 5,770,755. The catalyst compounds can be spray dried as described in, for example, U.S. Patent No. 5,648,310. The support used with the catalyst compound can be functionalized, as described in EP 0 802 203, or at least one substituent or leaving group is selected, as described in U.S. Patent No. 5,688,880.

[0018] The support can be or include one or more inorganic oxides. The support can be an inorganic oxide that includes one or more metal oxides of Groups 2, 3, 4, 5, 13, or 14 elements. For example, the inorganic oxide can include, but is not limited to, silica, titania, zirconia, boron oxide, zinc oxide, magnesia, or any combination thereof. Illustrative combinations of inorganic oxides can include, but are not limited to, silica-titania, silica-zirconia, silica-boron oxide, and the like. In at least one specific example, the support can be or include silica.

[0019] In some embodiments, the support can be an inorganic oxide, e.g., silica, that is essentially free of alumina. As used herein, the term "essentially free of alumina" means the support does not include or contain any intentionally added alumina. Said another way, the term "essentially free of alumina" means the support does not contain alumina that was intentionally added thereto, but may include alumina present as an impurity. For example, the support can be an inorganic oxide, e.g., silica, having a concentration of alumina less than about 5 wt%, less than about 3 wt%, less than about 2 wt%, less than about 1 wt%, less than about 0.5 wt%, less than about 0.3 wt%, less than about 0.1 wt%, less than about 0.05 wt%, less than about 0.01 wt%, less than about 0.005 wt%, or less than about 0.001 wt%, based on the combined weight of the inorganic oxide and alumina.

[0020] Supports that include two or more inorganic oxides and have any ratio or amount of each oxide, relative to one another, can be used. For example, a silica-titania support can include from about 1 wt% to about 99 wt% silica, based on the total amount of titania and silica. In one or more embodiments, silica-titania support can have a silica concentration ranging from a low of about 2 wt%, about 5 wt%, about 15 wt%, or about 25 wt% to a high of about 50 wt%, about 60 wt%, about 70 wt%, or about 90 wt%, based on the total amount of titania and silica. For example, the silica concentration of the silica-titania catalyst support can be about 20 wt%, about 25 wt%, about 30 wt%, about 35 wt%, about 40 wt%, about 45 wt%, about 50 wt%, about 55 wt%, about 60 wt%, about 70 wt%, about 80 wt%, or about 90 wt%.

[0021] A mixed inorganic oxide catalyst support can be prepared using any suitable method. For example, a silica catalyst support can be mixed, blended, contacted, or otherwise combined with one or more titanium compounds to produce a silica support and titanium compound(s) mixture. The silica catalyst support can be mixed with the one or more titanium compounds in a water and/or alcohol solution and dried to produce the silica support and titanium compound(s) mixture. Suitable alcohols can include, but are not limited to, alcohols having from 1 to 5 carbon atoms, and mixtures or combinations thereof. For example, the alcohol can be or include methanol, ethanol, propan-l-ol, propan-2-ol, and the like. Suitable titanium compounds can include, but are not limited to, titanium tetrabutoxide, titanium tetraethoxide, titanium tetraisopropoxide, or any combination thereof.

[0022] The inorganic support can be heated (calcined) in the presence of one or more inert gases, oxidants, reducing gases to produce an activated catalyst support. As used herein, the term "oxidant" can include, but is not limited to, air, oxygen, ultra-zero air, oxygen/inert gas mixtures, or any combination thereof. Inert gases can include, but are not limited to, nitrogen, helium, argon, or combinations thereof. Reducing gases can include, but are not limited to, hydrogen, carbon monoxide, or combinations thereof.

[0023] For example, in the case of forming a silica-titania catalyst support, the silica support and titanium compound(s) mixture can be heated to a first temperature under nitrogen gas or other inert gas. After heating to the first temperature the nitrogen gas can be stopped, one or more oxidants can be introduced, and the temperature can be increased to a second temperature. For example, the silica support and titanium compound(s) mixture can be heated under an inert atmosphere to a temperature of about 200°C, where the temperature can be stabilized and the oxidant can be introduced, and the mixture can then be heated to a temperature of from about 450°C to about 1,500°C to produce a titania-silica catalyst support. The second temperature can range from a low of about 250°C, about 300°C, about 400°C, or about 500°C to a high of about 600°C, about 650°C, about 700°C, about 800°C, or about 900°C. For example, the second temperature can range from about 400°C to about 850°C, about 800°C to about 900°C, about 600°C to about 850°C, or about 810°C to about 890°C. The silica support and titanium compound(s) mixture can be heated and held at the second temperature for a period of time ranging from about 1 minute to about 100 hours. For example, the silica support and titanium compound(s) mixture can be heated and held at the second temperature for a time ranging from a low of about 30 minutes, about 1 hour, or about 3 hours to a high of about 10 hours, about 20 hours, or about 50 hours. In one or more embodiments, the silica support and titanium compound(s) mixture can be heated from ambient temperature to the second or upper temperature without heating to and holding at the intermediate or first temperature. The silica support and titanium compound(s) mixture can be heated under a nitrogen or other inert atmosphere initially, which can be modified to include the one or more oxidants or the atmosphere can be or include the one or more oxidants at the initial heating from ambient temperature.

[0024] The support can be mixed, blended, contacted, or otherwise combined with one or more sources of halide ions, sulfate ions, or a combination of anions to produce an inorganic oxide catalyst support and anion mixture, which can be heated or calcined to produce an activated support. For example, one or more halide ion sources, sulfate ion sources, metal ion sources, or any combination thereof, can be dry mixed, i.e., mixed without the presence of a liquid or intentionally added liquid, with the inorganic oxide support. In another example, the one or more halide ion sources, sulfate ion sources, metal ion sources, or any combination thereof, can be wet mixed, i.e., in the presence of a liquid, with the inorganic oxide catalyst support. Illustrative liquids can include, but are not limited to, alcohols, water, or a combination thereof. Suitable alcohols can include, but are not limited to, alcohols having from 1 to 5 carbon atoms, and mixtures or combinations thereof. The mixture, either dry mixed or wet mixed, can be calcined to produce an activated support.

[0025] The activated support can include, but is not limited to, fluorinated silica, fluorinated silica-zirconia, fluorinated-chlorinated silica, fluorinated silica-titania, or any combination thereof. The support can be treated with one or more metal ions in addition to or in lieu of the one or more halide ion sources and/or sulfate ion sources. Illustrative metal ions can include, but are not limited to, copper, gallium, molybdenum, silver, tin, tungsten, vanadium, zinc, or any combination thereof.

[0026] Illustrative fluorinating or fluoriding agents can include, but are not limited to, ammonium hexafluorosilicate (( FL^SiFe), fluorine (F₂), hydrofluoric acid (HF), ammonium fluoride (NH4F), ammonium bifluoride (NH4HF2), ammonium tetrafluoroborate (NH4BF4), ammonium hexafluorophosphate ( H4PF₆), ammonium heptafluorotantalate(V) ( FL^TaF_?, Ammonium hexafluorogermanate(IV) ( H4)2GeF₆, ammonium hexafluorotitanate(IV) ( H4)2TiF₆, ammonium hexafluorozirconate (NH^ZrFe, aluminum fluoride (AIF₃), sodium hexafluoroaluminate ( a3AlF6), molybdenum(VI) fluoride (MoFe), bromine pentafluoride (BF₅), nitrogen trifluoride ( F₃), ammonium hydrogen difluoride (NHF₂), perfluorohexane C₆F14, hexafluorobenzene (C₆F₆), fluoromethane (CH₃F), trifluoroethanol (C2H₃F₃O), freons, derivatives thereof, or any combination thereof. Illustrative chlorinating or chloriding agents can include, but are not limited to, freons, perchlorobenzene, chloromethane, dichloromethane, chloroform, carbon tetrachloride, trichloroethanol, hydrogen chloride, chlorine, derivatives thereof, or any combination thereof. Illustrative sulfating agents can include, but are not limited to, sulfuric acid, sulfate salts such as ammonium sulfate, or any combination thereof.

[0027] Illustrative freons can include, but are not limited to, trichlorofluoromethane (CCI₃F), trichlorodifluoromethane (CCI2F2), chlorotrifluoromethane (CCIF₃), chlorodifluoromethane (CHCIF2), dichlorofluoromethane (CHC1₂F), chlorofluoromethane (CH₂C1F), bromochlorodifluoromethane (CBrClF₂), l, l,2-trichloro-l,2,2-trifluoroethane (CI2FC-CCIF2),

1.1.1- trichloro-2,2,2-trifluoroethane (CI₃C-CF₃), l,2-dichloro-l, l,2,2-tetrafluoroethane (C1F₂C- CC1F₂), l-chloro-l, l,2,2,2-pentafluoroethane (C1F₂C-CF₃), 2-chloro-l, l,l,2-tetrafluoroethane (CHFCICF₃), 1, 1-dichloro-l-fluoroethane (C1₂FC-CH₃), l-chloro-l, l-difluoroethane (C1F₂C- CH₃), tetrachloro-l,2-difluoroethane (CC1₂FCC1₂F), tetrachloro-l, l-difluoroethane (CC1F₂CC1₃),

1.1.2- trichlorotrifluoroethane (CCI2FCCIF2), 1 -bromo-2-chloro- 1 , 1 ,2-trifluoroethane (CHClFCBrF₂), 2-bromo-2-chloro-l,l, l-trifluoroethane (CF₃CHBrCl), l, l-dichloro-2,2,3,3,3- pentafluoropropane (CF₃CF2CHCI2), l,3-dichloro-l,2,2,3,3-pentafluoropropane (CCIF2CF2CHCIF).

[0028] The amount of the halide ion source(s), sulfate ion source(s), and/or metal ion source(s) mixed with the support can range from a low of about 0.01 wt%, about 0.1 wt%, or about 1 wt% to a high of about 10 wt%, about 20 wt%, about 30 wt%, about 40 wt%, or about 50 wt%, based on the total weight of the mixture, i.e., the support, halide ion source, sulfate ion source, and/or metal ion source. For example, a fluorinating agent in an amount of from about 0.01 g to about 0.5 g can be combined per gram of inorganic oxide catalyst support. In another example, the halide ion source can be a fluorinating agent, the support can be silica, and the amount of fluoride on the support can range from a low of about 1 wt%, about 2 wt%, about 3 wt%, about 3.5 wt%, about 4 wt%, about 4.5 wt%, or about 5 wt% to a high of about 8 wt%, about 9 wt%, about 10 wt%, about 1 1 wt%, or about 12 wt%, based on the weight of the support. For example, the halide ion source can be a fluorinating agent, the support can be silica, and the amount of fluoride on the support can range from a low of about 1.5 wt%, about 2 wt%, or about 2.5 wt% to a high of about 3.5 wt%, about 4 wt%, about 4.5 wt%, or about 5 wt%, based on the weight of the support.

[0029] The mixture of the support and the one or more sources of halide ions, sulfate ions, metal ion source, or any a combination thereof can be heated (calcined) in the presence of one or more inert gases, oxidants, reducing gases, in any order, any combination thereof, or any order/combination thereof to produce an activated support. The one or more halide ion source(s), sulfate ion source(s), and/or metal ion source(s) can be introduced during heating or calcining, in lieu of, or in addition to combining the halide ion source(s), sulfate ion source(s), and/or metal ion source(s), and the support prior to heating. For example, a fluorinating agent/silica support mixture can be heated to a first temperature under a nitrogen gas purge or other inert gas or combination of inert gases. After heating to the first temperature the inert gas can be stopped, the one or more oxidants can be introduced, and the temperature can be increased to a second temperature. For example, the fluorinating agent/silica support mixture can be heated under an inert atmosphere to a temperature of about 200°C, the oxidant can be introduced, and the mixture can be heated to a temperature of about 600°C or more to produce the activated support. The fluorinating agent/silica support mixture can be heated to a second temperature ranging from a low of about 250°C, about 300°C, or about 400°C to a high of about 600°C, about 750°C, or about 900°C. The fluorinating agent/silica support mixture can be heated and held at the second temperature for a period of time ranging from about 1 minute to about 100 hours. For example, the fluorinating agent/silica support mixture can be heated and held at the second temperature for a time ranging from a low of about 30 minutes, about 1 hour, or about 3 hours to a high of about 10 hours, about 20 hours, or about 50 hours.

[0030] The activated catalyst support can have a surface area ranging from a low of about 1 m /g, about 50 m /g, or about 100 m /g to a high of about 400 m /g, about 500 m /g, or about 800 m²/g. The activated catalyst support can have a pore volume ranging from a low of about 0.01 cm /g, about 0.1 cm /g, about 0.8 cm /g, or about 1 cm /g to a high of about 2 cm /g, about 2.5 cm³/g, about 3 cm³/g, or about 4 cm³/g. The activated catalyst support can have an average particle size ranging from a low of about 0.1 μιη, about 0.3 μιη, about 0.5 μιη, about 1 μιη, about 5 μιη, about 10 μιη, or about 20 μιη to a high of about 50 μιη, about 100 μιη, about 200 μιη, or about 500 μιη. The average pore size of the activated catalyst support can range from about 10 A to about 1,000 A, preferably from about 50 A to about 500 A, and more preferably from about 75 A to about 350 A.

[0031] Suitable catalyst supports can be as discussed and described in Hlatky, Chem. Rev. (2000), 100, 1347 1376 and Fink et al., Chem. Rev. (2000), 100, 1377 1390, U.S. Patent Nos.: 4,701,432, 4,808,561, 4,912,075, 4,925,821, 4,937,217, 5,008,228, 5,238,892, 5,240,894, 5,332,706, 5,346,925, 5,422,325, 5,466,649, 5,466,766, 5,468,702, 5,529,965, 5,554,704, 5,629,253, 5,639,835, 5,625,015, 5,643,847, 5,665,665, 5,698,487, 5,714,424, 5,723,400, 5,723,402, 5,731,261, 5,759,940, 5,767,032 and 5,770,664, and WO 95/32995, WO 95/14044, WO 96/06187, and WO 97/02297.

Activator

[0032] As used herein, the terms "activator" and "cocatalyst" are used interchangeably and refer to any compound or combination of compounds, supported or unsupported, which can activate a catalyst compound or component, such as by creating a cationic species of the catalyst component. For example, this can include the abstraction of at least one leaving group (the "X" group in the catalyst compounds described herein) from the metal center of the catalyst compound/component.

[0033] For example, the activator can include a Lewis acid or a non-coordinating ionic activator or ionizing activator, or any other compound including Lewis bases, aluminum alkyls, and/or conventional-type cocatalysts. In addition to methylaluminoxane ("MAO") and modified methylaluminoxane ("MMAO") mentioned above, illustrative activators can include, but are not limited to, aluminoxane or modified aluminoxane, and/or ionizing compounds, neutral or ionic, such as tri (n-butyl)ammonium tetrakis(pentafluorophenyl)boron, a trisperfluorophenyl boron metalloid precursor, a trisperfluoronaphthyl boron metalloid precursor, or any combinations thereof.

[0034] Aluminoxanes can be described as oligomeric aluminum compounds having -Al(R)-0- subunits, where R is an alkyl group. Examples of aluminoxanes include, but are not limited to, methylaluminoxane ("MAO"), modified methylaluminoxane ("MMAO"), ethylaluminoxane, or isobutylaluminoxane. Aluminoxanes can be produced by the hydrolysis of the respective trialkylaluminum compound. For example, MMAO can be produced by the hydrolysis of trimethylaluminum and a higher trialkylaluminum such as triisobutylaluminum. There are a variety of methods for preparing aluminoxanes and modified aluminoxanes; non-limiting examples are described in U.S. Patent Nos. 4,665,208; 4,952,540; 5,091,352; 5,206, 199; 5,204,419; 4,874,734; 4,924,018; 4,908,463; 4,968,827; 5,308,815; 5,329,032; 5,248,801 ; 5,235,081; 5, 157, 137; 5, 103,031 ; 5,391,793; 5,391,529; 5,693,838; 5,731,253; 5,731,451 ; 5,744,656; 5,847, 177; 5,854,166; 5,856,256; and 5,939,346; and EP 0 561 476; EP 0 279 586; EP 0 594-218; and EP 0 586 665; and WO Publications WO 94/10180 and WO 99/15534.

[0035] A visually clear MAO can be used. For example, a cloudy and/or gelled aluminoxane can be filtered to produce a clear aluminoxane or clear aluminoxane can be decanted from a cloudy aluminoxane solution. A cloudy and/or gelled aluminoxane can also be used. Another aluminoxane can include a modified methyl aluminoxane ("MMAO") type 3A (commercially available from AkzoNobel Polymer Chemicals LLC, a company with a business office in Chicago, Illinois, under the product name MMAO-3A, discussed and described in U.S. Patent No. 5,041,584). A suitable MAO or MMAO can also be any solution having from about 1 wt% to about a 50 wt% MAO, MMAO, or combination thereof. MAO solutions can include 10 wt% and 30 wt% MAO solutions commercially available from Albemarle Corporation, a company with a business office in Baton Rouge, Louisiana.

[0036] The catalyst system can be free or substantially free from any intentionally added organo-aluminum compounds. In other words, the use of organo-aluminum compounds can be avoided or otherwise not intentionally added to the catalyst system.

[0037] Alternatively, one or more organo-aluminum compounds, such as one or more trialkylaluminum compounds, can be used in conjunction with the catalyst system. Examples of trialkylaluminum compounds include, but are not limited to, trimethylaluminum, triethylaluminum ("TEAL"), triisobutylaluminum ("TiBAl"), tri-n-hexylaluminum, tri-n- octylaluminum, tripropylaluminum, tributylaluminum, and the like. Other alkylaluminum species that may be used are diethylaluminum ethoxide, diethylaluminum chloride, and/or diisobutylaluminum hydride.

[0038] One or more ionizing or stoichiometric activators, neutral or ionic, can be used in combination with aluminoxane or modified aluminoxane. For example, tri (n-butyl) ammonium tetrakis (pentafluorophenyl) boron, other trisperfluorophenyl borons, trisperfluoronaphthyl borons, polyhalogenated heteroborane anions (WO 98/43983), boric acid (U.S. Patent No. 5,942,459), or combinations thereof can be used. Examples of neutral stoichiometric activators can include tri-substituted boron, tellurium, aluminum, gallium, indium, or any combination thereof. The three substituent groups can each be independently selected from alkyls, alkenyls, halogen, substituted alkyls, aryls, arylhalides, alkoxy and halides. Preferred neutral stoichiometric activators include trisperfluorophenyl borons or trisperfluoronaphthyl borons. Catalyst Compound

[0039] The catalyst system described herein may comprise a catalyst compound that can include (1) at least one cyclopentadienyl ligand and at least one heteroatom ligand; (2) two non-bridged cyclopentadienyl ligands; or (3) two or more heteroatom ligands. In some embodiments, the catalyst compound may be such that it would qualify as one or more of (1) at least one cyclopentadienyl ligand and at least one heteroatom ligand; (2) two non-bridged cyclopentadienyl ligands; or (3) two or more heteroatom ligands. That is the catalyst compound may be such that it has at least one cyclopentadienyl ligand and at least one heteroatom ligand, and has two non-bridged cyclopentadienyl ligands, and/or two or more heteroatom ligands.

[0040] The catalyst system may further comprise an additonal catalyst compound that can include one or more metallocene catalysts, chromium-based catalysts, Ziegler-Natta catalysts, transition metal catalyst, bimetallic catalysts, AICI₃, cobalt, iron, palladium, chromium/chromium oxide or "Phillips" catalysts. The catalyst system may comprise one catalyst compound or may comprise more than one catalyst compound that are used in combination, i.e., a "mixed" catalyst.

[0041] The catalyst compound may comprise one or more Cp ligands (cyclopentadienyl and ligands isolobal to cyclopentadienyl) bound to a metal atom of the catalyst. When the catalyst compound includes two or more cyclopentadienyl ligands, the two or more cyclopentadienyl ligands can be bridged with one another or not bridged with one another. The catalyst compound can include two or more heteroatom ligands bound to a metal atom of the catalyst. For example, the catalyst compound can include two heteroatom ligands or three heteroatom ligands, or more. The catalyst compound can include at least one cyclopentadienyl ligand and at least one heteroatom ligand bound to a metal atom of the catalyst compound. Heteroatom ligands include any ligand comprising at least one non-hydrogen/non-carbon atom, e.g., N, S, O, P, and Si. If one or more heteroatom ligands is present, the heteroatom ligand(s) is directly bound to a transition metal atom.

Metallocene Catalyst Compounds

[0042] Metallocene catalyst compounds are generally described throughout in, for example, 1 & 2 METALLOCENE-BASED POLYOLEFINS (John Scheirs & W. Kaminsky eds., John Wiley & Sons, Ltd. 2000); G. G. Hlatky in 181 COORDINATION CHEM. REV. 243-296 (1999) and in particular, for use in the synthesis of polyethylene in 1 METALLOCENE-BASED POLYOLEFINS 261-377 (2000). The metallocene catalyst compounds can include "half sandwich" compounds having one cyclopentadienyl ligand or ligand isolobal to cyclopentadienyl ("Cp" ligand) and/or "full sandwich" compounds having two or more Cp ligands bound to at least one Group 3 to Group 12 metal atom, and one or more leaving group(s) bound to the at least one metal atom. When the metallocene catalyst compound includes two or more cyclopentadienyl ligands, the two or more cyclopentadienyl ligands can be bridged with one another or not bridged with one another.

[0043] As used herein, all reference to the Periodic Table of the Elements and groups thereof is to the NEW NOTATION published in HAWLEY'S CONDENSED CHEMICAL DICTIONARY, Thirteenth Edition, John Wiley & Sons, Inc., (1997) (reproduced there with permission from IUPAC), unless reference is made to the Previous IUPAC form noted with Roman numerals (also appearing in the same), or unless otherwise noted.

[0044] The Cp ligands are one or more rings or ring system(s), at least a portion of which includes π-bonded systems, such as cycloalkadienyl ligands and heterocyclic analogues. The ring(s) or ring system(s) typically comprise atoms selected from the group consisting of Groups 13 to 16 atoms.For example, the atoms that make up the Cp ligands may be selected from the group consisting of carbon, nitrogen, oxygen, silicon, sulfur, phosphorous, germanium, boron, aluminum, and combinations thereof, where carbon makes up at least 50% of the ring members. For another example, the Cp ligand(s) may be selected from the group consisting of substituted and unsubstituted cyclopentadienyl ligands and ligands isolobal to cyclopentadienyl, non- limiting examples of which include substituted and unsubstituted cyclopentadienyls, indenyls, fluorenyls, and other structures. Further non-limiting examples of such ligands include cyclopentaphenanthreneyl, benzindenyl, octahydrofluorenyl, cyclooctatetraenyl, cyclopentacyclododecene, phenanthrindenyl, 3,4-benzofluorenyl, 9-phenylfluorenyl, 8-H- cyclopent[a]acenaphthylenyl, 7-H-dibenzofluorenyl, indeno[l,2-9]anthrene, thiophenoindenyl, thiophenofluorenyl, hydrogenated versions thereof (e.g., 4,5,6,7-tetrahydroindenyl, or "H₄ Ind"), and substituted versions thereof (as discussed and described in more detail below).

[0045] The metal atom "M" of the metallocene catalyst compound can be selected from the group consisting of Groups 3 through 12 atoms and lanthanide Group atoms. For example, "M" may be selected from the group consisting of Groups 3 through 10 atoms; selected from the group consisting of Sc, Ti, Zr, Hf, V, Nb, Ta, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, and Ni; selected from the group consisting of Groups 4, 5, and 6 atoms; or selected from Ti, Zr, Hf atoms. The oxidation state of the metal atom "M" can range from 0 to +7, or can be +1, +2, +3, +4 or +5. The Cp ligand(s) forms at least one chemical bond with the metal atom M to form the "metallocene catalyst compound." The Cp ligands are distinct from the leaving groups bound to the catalyst compound in that they are not highly susceptible to substitution/abstraction reactions. [0046] The one or more metallocene catalyst compound can be represented by the formula (I):

Cp^ACp^BMX_n (I)

where M is as described above; each X is chemically bonded to M; each Cp group is chemically bonded to M; and n is 0, an integer from 1 to 4, or either 1 or 2.

[0047] The ligands represented by Cp^A and Cp^B in formula (I) can be the same or different cyclopentadienyl ligands or ligands isolobal to cyclopentadienyl, either or both of which can contain heteroatoms and either or both of which can be substituted by a group R. In at least one specific embodiment, Cp^A and Cp^B are independently selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, and substituted derivatives of each.

[0048] Independently, each Cp^A and Cp^B of formula (I) can be unsubstituted or substituted with any one or combination of substituent groups R. Non-limiting examples of substituent groups R as used in structure (I) as well as ring substituents in structures Va-d, discussed and described below, include groups selected from the group consisting of hydrogen radicals, alkyls, alkenyls, alkynyls, cycloalkyls, aryls, acyls, aroyls, alkoxys, aryloxys, alkylthiols, dialkylamines, alkylamidos, alkoxycarbonyls, aryloxycarbonyls, carbomoyls, alkyl- and dialkyl-carbamoyls, acyloxys, acylaminos, aroylaminos, and combinations thereof. Additional non-limiting examples of alkyl substituents R associated with formulas (I) through (Va-d) include methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopentyl, cyclohexyl, benzyl, phenyl, methylphenyl, and tert-butylphenyl groups and the like, including all their isomers, for example, tertiary-butyl, isopropyl, and the like. Other possible radicals include substituted alkyls and aryls such as, for example, fluoromethyl, fluroethyl, difluroethyl, iodopropyl, bromohexyl, chlorobenzyl, hydrocarbyl substituted organometalloid radicals including trimethylsilyl, trimethylgermyl, methyldiethylsilyl, and the like, and halocarbyl-substituted organometalloid radicals, including tris(trifluoromethyl)silyl, methylbis(difluoromethyl)silyl, bromomethyldimethylgermyl and the like; and disubstituted boron radicals including dimethylboron, for example; and disubstituted Group 15 radicals including dimethylamine, dimethylphosphine, diphenylamine, methylphenylphosphine, as well as Group 16 radicals including methoxy, ethoxy, propoxy, phenoxy, methylsulfide and ethylsulfide. Other substituent groups R include, but are not limited to, olefins such as olefinically unsaturated substituents including vinyl-terminated ligands such as, for example, 3-butenyl, 2-propenyl, 5-hexenyl and the like. At least two R groups (two adjacent R groups in a particular exemplary embodiment) can be joined to form a ring structure having from 3 to 30 atoms selected from the group consisting of carbon, nitrogen, oxygen, phosphorous, silicon, germanium, aluminum, boron and combinations thereof. Also, a substituent group R such as 1-butanyl can form a bonding association to the element M. [0049] Each X in the formula (I) above and for the formula/structures (II) through (Va-d) below may be independently selected from the group consisting of: halogen ions, hydrides, Ci to C₁₂ alkyls, C2 to C₁₂ alkenyls, Ce to C₁₂ aryls, C7 to C20 alkylaryls, Ci to C₁₂ alkoxys, Ce to Ci6 aryloxys, C7 to Cs alkylaryloxys, Ci to C₁₂ fluoroalkyls, Ce to C₁₂ fluoroaryls, and Ci to C₁₂ heteroatom containing hydrocarbons and substituted derivatives thereof. Additionally, each X may be selected from the group consisting of: hydrides, halogen ions, Ci to Ce alkyls, C2 to Ce alkenyls, C7 to C₁₈ alkylaryls, Ci to Ce alkoxys, Ce to C14 aryloxys, C7 to Ci₆ alkylaryloxys, Ci to Ce alkylcarboxylates, Ci to Ce fluorinated alkylcarboxylates, Ce to C₁₂ arylcarboxylates, C7 to Ci₈ alkylarylcarboxylates, Ci to Ce fluoroalkyls, C2 to Ce fluoroalkenyls, and C7 to C₁₈ fluoroalkylaryls. Additionally, each X may be selected from the group consisting of: hydride, chloride, fluoride, methyl, phenyl, phenoxy, benzoxy, tosyl, fluoromethyls and fluorophenyls. Additionally, each X may be selected from the group consisting of: Ci to C₁₂ alkyls, C2 to C₁₂ alkenyls, Ce to C₁₂ aryls, C7 to C2₀ alkylaryls, substituted Ci to C₁₂ alkyls, substituted Ce to C₁₂ aryls, substituted C7 to C2₀ alkylaryls and Ci to C₁₂ heteroatom containing alkyls, Ci to C₁₂ heteroatom containing aryls, and Ci to C₁₂ heteroatom containing alkylaryls. Additionally, each X may be selected from the group consisting of: chloride, fluoride, Ci to Ce alkyls, C2 to Ce alkenyls, C7 to C₁₈ alkylaryls, halogenated Ci to Ce alkyls, halogenated C2 to Ce alkenyls, and halogenated C7 to C₁₈ alkylaryls. Additionally, each X may be selected from the group consisting of: fluoride, methyl, ethyl, propyl, phenyl, methylphenyl, dimethylphenyl, trimethylphenyl, fluoromethyls (mono-, di- and trifluoromethyls) and fluorophenyls (mono-, di-, tri-, tetra- and pentafluorophenyls). In an embodiment, each X is fluoride.

[0050] Each X in the formula (I) above and for the formula/structures (II) through (Va-d) below may also be independently selected from the group consisting of: amines, phosphines, ethers, carboxylates, dienes, hydrocarbon radicals having from 1 to 20 carbon atoms, fluorinated hydrocarbon radicals (e.g., — C₆F5 (pentafluorophenyl)), fluorinated alkylcarboxylates (e.g., CF₃C(0)CT), hydrides, halogen ions and combinations thereof, or alkyl groups such as cyclobutyl, cyclohexyl, methyl, heptyl, tolyl, trifluoromethyl, tetramethylene, pentamethylene, methylidene, methyoxy, ethyoxy, propoxy, phenoxy, bis(N-methylanilide), dimethylamide, dimethylphosphide radicals and the like. Two or more X's form a part of a fused ring or ring system. X can also be a leaving group selected from the group consisting of chloride ions, bromide ions, Ci to C₁₀ alkyls, and C2 to C₁₂ alkenyls, carboxylates, acetylacetonates, and alkoxides. [0051 ] The one or more metallocene catalyst compounds also includes those of formula (I) where Cp^A and Cp^B are bridged to each other by at least one bridging group, (A), such that the structure is represented by formula (II):

Cp^A(A)Cp^BMX_n (II)

[0052] These bridged compounds represented by formula (II) are known as "bridged metallocenes." The elements Cp^A, Cp^B, M, X and n in structure (II) are as defined above for formula (I); where each Cp ligand is bonded to M, and (A) is bonded to each Cp. The bridging group (A) can include divalent hydrocarbon groups containing at least one Group 13 to 16 atom, such as, but not limited to, at least one of a carbon, oxygen, nitrogen, silicon, aluminum, boron, germanium, tin atom, and combinations thereof. The heteroatom can also be Ci to C₁₂ alkyl or aryl substituted. The bridging group (A) can also include substituent groups R as defined above (for formula (I)) including halogen radicals and iron. The bridging group (A) can be represented by Ci to Ce alkylenes, substituted Ci to Ce alkylenes, oxygen, sulfur, R'2C=, R'2Si=, =Si(R')2Si(R' 2 )=, R'2Ge=, and R'P=, where "=" represents two chemical bonds, R' is independently selected from the group consisting of hydride, hydrocarbyl, substituted hydrocarbyl, halocarbyl, substituted halocarbyl, hydrocarbyl-substituted organometalloid, halocarbyl-substituted organometalloid, disubstituted boron, disubstituted Group 15 atoms, substituted Group 16 atoms, and halogen radical; and where two or more R' can be joined to form a ring or ring system. The bridged metallocene catalyst compound of formula (II) can include two or more bridging groups (A). (A) can be a divalent bridging group bound to both Cp^A and Cp^B, selected from the group consisting of divalent Q to C2₀ hydrocarbyls and Q to C2₀ heteroatom containing hydrocarbonyls, where the heteroatom containing hydrocarbonyls comprise from one to three heteroatoms.

[0053] The bridging group (A) can also include methylene, ethylene, ethylidene, propylidene, isopropylidene, diphenylmethylene, 1 ,2-dimethylethylene, 1 ,2-diphenylethylene, 1 , 1,2,2- tetramethylethylene, dimethyls ilyl, diethylsilyl, methyl-ethylsilyl, trifluoromethylbutylsilyl, bis(trifluoromethyl)silyl, di(n-butyl)silyl, di(n-propyl)silyl, di(i-propyl)silyl, di(n-hexyl)silyl, dicyclohexylsilyl, diphenylsilyl, cyclohexylphenylsilyl, t-butylcyclohexylsilyl, di(t- butylphenyl)silyl, di(p-tolyl)silyl and the corresponding moieties where the Si atom is replaced by a Ge or a C atom; as well as dimethyls ilyl, diethylsilyl, dimethylgermyl and diethylgermyl.

[0054] The bridging group (A) can also be cyclic, having, for example, 4 to 10 ring members or 5 to 7 ring members. The ring members can be selected from the elements mentioned above. For example, they can be selected from one or more of B, C, Si, Ge, N and O. Non-limiting examples of ring structures which can be present as, or as part of, the bridging moiety are cyclobutylidene, cyclopentylidene, cyclohexylidene, cycloheptylidene, cyclooctylidene and the corresponding rings where one or two carbon atoms are replaced by at least one of Si, Ge, N and O. One or two carbon atoms can be replaced by at least one of Si and Ge. The bonding arrangement between the ring and the Cp groups can be either cis-, trans-, or a combination thereof.

[0055] The cyclic bridging groups (A) can be saturated or unsaturated and/or can carry one or more substituents and/or can be fused to one or more other ring structures. If present, the one or more substituents can be selected from the group consisting of hydrocarbyl (e.g., alkyl, such as methyl) and halogen (e.g., F, CI). The one or more Cp groups to which the above cyclic bridging moieties can optionally be fused can be saturated or unsaturated, and are selected from the group consisting of those having 4 to 10, more particularly 5, 6, or 7 ring members (selected from the group consisting of C, N, O, and S in a particular exemplary embodiment) such as, for example, cyclopentyl, cyclohexyl and phenyl. Moreover, these ring structures can themselves be fused such as, for example, in the case of a naphthyl group. Moreover, these (optionally fused) ring structures can carry one or more substituents. Illustrative, non-limiting examples of these substituents are hydrocarbyl (particularly alkyl) groups and halogen atoms.

[0056] The ligands Cp^A and Cp^B of formulas (I) and (II) can be the same or different from each other. The metallocene catalyst compound can include bridged mono-ligand metallocene compounds (e.g., mono cyclopentadienyl catalyst components). Exemplary but non-limiting metallocene catalyst compounds are further described in U.S. Patent No. 6,943, 134.

[0057] It is contemplated that the metallocene catalyst components discussed and described above include their structural or optical or enantiomeric isomers (racemic mixture), and, in one exemplary embodiment, can be a pure enantiomer. As used herein, a single, bridged, asymmetrically substituted metallocene catalyst compound having a racemic and/or meso isomer does not, itself, constitute at least two different bridged, metallocene catalyst components.

[0058] As noted above, the amount of the transition metal component of the one or more metallocene catalyst compounds in the catalyst system can range from a low of about 0.2 wt%, about 3 wt%, about 0.5 wt%, or about 0.7 wt% to a high of about 1 wt%, about 2 wt%, about 2.5 wt%, about 3 wt%, about 3.5 wt%, or about 4 wt%, based on the total weight of the catalyst system. The metallocene catalyst compound can include any combination of any embodiment discussed and described herein. For example, the metallocene catalyst compound can include, but is not limited to, bis(n-propylcyclopentadienyl) hafnium (CH₃)₂, bis(n- propylcyclopentadienyl) hafnium F₂, bis(n-propylcyclopentadienyl) hafnium CI2, bis(n-butyl, methyl cyclopentadienyl) zzirconium Cl₂, (tetramethylcyclopentadienyl)(n- propylcyclopentadienyl)zirconiumCl2, (tetramethylcyclopentadienyl)(n- propylcyclopentadienyl)zirconium(CH₃)₂, [(2,3,4,5,6 Me₅C6 )CH₂CH2]2 HZrBz2, where Bz is a benzyl group, or any combination thereof.

[0059] In addition to the metallocene catalyst compounds discussed and described above, other suitable metallocene catalyst compounds can include, but are not limited to, metallocenes discussed and described in U.S. Patent Nos.: 7,741,417; 7, 179,876; 7, 169,864; 7, 157,531; 7,129,302; 6,995, 109; 6,958,306; 6,884,748; 6,689,847; and WO Publications WO 97/22635; WO 00/699/22; WO 01/30860; WO 01/30861 ; WO 02/46246; WO 02/50088; WO 04/026921 ; and WO 06/019494.

[0060] The catalyst system can include other catalysts such as Group 15-containing catalysts. The catalyst system can include one or more second catalysts such as chromium-based catalysts, Ziegler-Natta catalysts, one or more additional catalysts such as metallocenes or Group 15- containing catalysts, bimetallic catalysts, and mixed catalysts. The catalyst system can also include AICI₃, cobalt, iron, palladium, or any combination thereof.

Group 15 Atom and Metal-Containing Catalyst Compounds

[0061] The catalyst system can include one or more Group 15 metal-containing catalyst compounds. The Group 15 metal-containing compound generally includes a Group 3 to 14 metal atom, preferably a Group 3 to 7, more preferably a Group 4 to 6, and even more preferably a Group 4 metal atom, bound to at least one leaving group and also bound to at least two Group 15 atoms, at least one of which is also bound to a Group 15 or 16 atom through another group.

[0062] In one or more embodiments, at least one of the Group 15 atoms is also bound to a Group 15 or 16 atom through another group which may be a Ci to C20 hydrocarbon group, a heteroatom containing group, silicon, germanium, tin, lead, or phosphorus, wherein the Group 15 or 16 atom may also be bound to nothing or a hydrogen, a Group 14 atom containing group, a halogen, or a heteroatom containing group, and wherein each of the two Group 15 atoms are also bound to a cyclic group and can optionally be bound to hydrogen, a halogen, a heteroatom or a hydrocarbyl group, or a heteroatom containing group.

[0063] The Group 15-containing metal compounds can be described more particularly with formulas (VI) or (VII):

where M is a Group 3 to 12 transition metal or a Group 13 or 14 main group metal, preferably a Group 4, 5, or 6 metal, and more preferably a Group 4 metal, and most preferably zirconium, titanium or hafnium; each X is independently a leaving group, preferably, an anionic leaving group, and more preferably hydrogen, a hydrocarbyl group, a heteroatom or a halogen, and most preferably an alkyl; y is 0 or 1 (when y is 0 group L' is absent); n is the oxidation state of M, preferably +3, +4, or +5, and more preferably +4; m is the formal charge of the YZL or the YZL' ligand, preferably 0, -1, -2 or -3, and more preferably -2; L is a Group 15 or 16 element, preferably nitrogen; L' is a Group 15 or 16 element or Group 14 containing group, preferably carbon, silicon or germanium; Y is a Group 15 element, preferably nitrogen or phosphorus, and more preferably nitrogen; Z is a Group 15 element, preferably nitrogen or phosphorus, and more preferably nitrogen; R¹ and R² are independently a Q to C20 hydrocarbon group, a heteroatom containing group having up to twenty carbon atoms, silicon, germanium, tin, lead, or phosphorus, preferably a C2 to C20 alkyl, aryl or aralkyl group, more preferably a linear, branched or cyclic C2 to C20 alkyl group, most preferably a C2 to Ce hydrocarbon group. R¹ and R² can also be interconnected to each other; R³ is absent or a hydrocarbon group, hydrogen, a halogen, a heteroatom containing group; preferably a linear, cyclic or branched alkyl group having 1 to 20 carbon atoms, more preferably R³ is absent, hydrogen or an alkyl group, and most preferably hydrogen; R⁴ and R⁵ are independently an alkyl group, an aryl group, substituted aryl group, a cyclic alkyl group, a substituted cyclic alkyl group, a cyclic aralkyl group, a substituted cyclic aralkyl group or multiple ring system, preferably having up to 20 carbon atoms, more preferably between 3 and 10 carbon atoms, and even more preferably a Ci to C20 hydrocarbon group, a Ci to C20 aryl group or a Ci to C20 aralkyl group, or a heteroatom containing group, and/or R⁴ and R⁵ may be interconnected to each other; R⁶ and R⁷ are independently absent, hydrogen, an alkyl group, halogen, heteroatom, or a hydrocarbyl group, preferably a linear, cyclic or branched alkyl group having 1 to 20 carbon atoms, and more preferably absent, and R* is absent, or is hydrogen, a Group 14 atom containing group, a halogen, or a heteroatom containing group.

[0064] By "formal charge of the YZL or YZL' ligand," it is meant the charge of the entire ligand absent the metal and the leaving groups X. By "R¹ and R² may also be interconnected" it is meant that R¹ and R² may be directly bound to each other or may be bound to each other through other groups. By "R⁴ and R⁵ may also be interconnected" it is meant that R⁴ and R⁵ may be directly bound to each other or may be bound to each other through other groups. An alkyl group may be linear, branched alkyl radicals, alkenyl radicals, alkynyl radicals, cycloalkyl radicals, aryl radicals, acyl radicals, aroyl radicals, alkoxy radicals, aryloxy radicals, alkylthio radicals, dialkylamino radicals, alkoxycarbonyl radicals, aryloxycarbonyl radicals, carbomoyl radicals, alkyl- or dialkyl- carbamoyl radicals, acyloxy radicals, acylamino radicals, aroylamino radicals, straight, branched or cyclic, alkylene radicals, or combination thereof. An aralkyl group is defined to be a substituted aryl group.

[0065] In one or more embodiments, R⁴ and R⁵ are independently a group represented by the following formula (VII):

where R⁸ to R¹² are each independently hydrogen, a Ci to C₄o alkyl group, a halide, a heteroatom, a heteroatom containing group containing up to 40 carbon atoms, preferably a Ci to C2₀ linear or branched alkyl group, preferably a methyl, ethyl, propyl or butyl group, any two R groups may form a cyclic group and/or a heterocyclic group. The cyclic groups may be aromatic. In a preferred embodiment R⁹, R¹⁰ and R¹² are independently a methyl, ethyl, propyl or butyl group (including all isomers), in a preferred embodiment R⁹, R¹⁰ and R¹² are methyl groups, and R⁸ and R¹¹ are hydrogen.

[0066] In one or more embodiments, R⁴ and R⁵ are both a group represented by the following formula (VIII):

(VIII) where M is a Group 4 metal, preferably zirconium, titanium or hafnium, and even more preferably zirconium; each of L, Y, and Z is nitrogen; each of R¹ and R² is -CH₂-CH₂-; R³ is hydrogen; and R⁶ and R⁷ are absent.

[0067] The Group 15 metal-containing catalyst compound can be represented by the formula (IX):

where Ph equals phenyl. Representative Group 15 -containing metal compounds and preparation thereof can be as discussed and described in U.S. Patent Nos. 5,318,935; 5,889,128; 6,333,389; 6,271,325; and 6,689,847; WO Publications WO 99/01460; WO 98/46651; WO 2009/064404; WO 2009/064452; and WO 2009/064482; and EP 0 893 454; and EP 0 894 005.

Chromium Catalysts

[0068] Suitable chromium catalysts can include di-substituted chromates, such as Cr0₂(OR)2; where R is triphenylsilane or a tertiary polyalicyclic alkyl. The chromium catalyst system may further include Cr03, chromocene, silyl chromate, chromyl chloride (Cr02Cl2), chromium-2- ethyl-hexanoate, chromium acetylacetonate (Cr(AcAc)s), and the like.

Ziegler-Natta Catalysts

[0069] Illustrative Ziegler-Natta catalyst compounds are disclosed in Ziegler Catalysts 363-386 (G. Fink, R. Mulhaupt and H.H. Brintzinger, eds., Springer-Verlag 1995); or in EP 103 120; EP 102 503; EP 0 231 102; EP 0 703 246; RE 33,683; US 4,302,565; US 5,518,973; US 5,525,678; US 5,288,933; US 5,290,745; US 5,093,415 and US 6,562,905. Examples of such catalysts include those comprising Group 4, 5 or 6 transition metal oxides, alkoxides and halides, or oxides, alkoxides and halide compounds of titanium, zirconium or vanadium; optionally in combination with a magnesium compound, internal and/or external electron donors (alcohols, ethers, siloxanes, etc.), aluminum or boron alkyl and alkyl halides, and inorganic oxide supports. Transition Metal Catalysts

[0070] Conventional-type transition metal catalysts are those traditional Ziegler-Natta catalysts that are well known in the art. These conventional-type transition metal catalysts may be represented by the formula: MR_X, where M is a metal from Groups 3 to 17, or a metal from Groups 4 to 6, or a metal from Group 4, or titanium; R is a halogen or a hydrocarbyloxy group; and x is the valence of the metal M. Examples of R include alkoxy, phenoxy, bromide, chloride and fluoride. Examples of conventional-type transition metal catalysts where M is titanium include TiCl₄, TiBr₄, Ti(OC₂H₅)₃Cl, Ti(OC₂H₅)Cl₃, Ti(OC₄H₉)₃Cl, Ti(OC₃H₇)₂Cl₂, Ti(OC₂H₅)₂Br₂, TiCl₃/AlCl₃ and Ti(OCl₂H₂₅)Cl₃.

[0071] Catalysts derived from Mg/Ti/Cl/THF can be used. One example of the general method of preparation of such a catalyst includes the following: dissolve TiCl₄ in THF, reduce the compound to TiCl₃ using Mg, add MgCl₂, and remove the solvent. Specific examples of other conventional-type transition metal catalysts are discussed in more detail in U.S. Patent Nos. 4,1 15,639; 4,077,904; 4,482,687; 4,564,605; 4,721,763; 4,879,359; and 4,960,741. Conventional-type transition metal catalyst compounds based on magnesium/titanium electron- donor complexes are described in, for example, U.S. Patent Nos. 4,302,565 and 4,302,566.

Mixed Catalyst System

[0072] The catalyst system can include a mixed catalyst, which can be a bimetallic catalyst composition or a multi-catalyst composition. As used herein, the terms "bimetallic catalyst composition" and "bimetallic catalyst" include any composition, mixture, or system that includes two or more different catalyst components, each having a different metal group. The terms "multi-catalyst composition" and "multi-catalyst" include any composition, mixture, or system that includes two or more different catalyst components regardless of the metals. Therefore, the terms "bimetallic catalyst composition," "bimetallic catalyst," "multi-catalyst composition," and "multi-catalyst" will be collectively referred to herein as a "mixed catalyst" unless specifically noted otherwise. The mixed catalyst can include at least one metallocene catalyst compound and at least one non-metallocene compound.

Continuity Additive/ Static Control Agent

[0073] In processes disclosed herein, it may also be desired to additionally use one or more static control agents to aid in regulating static levels in the reactor. As used herein, a static control agent is a chemical composition which, when introduced into a fluidized bed reactor, may influence or drive the static charge (negatively, positively, or to zero) in the fluidized bed. The specific static control agent used may depend upon the nature of the static charge, and the choice of static control agent may vary dependent upon the polymer being produced and the catalyst compound(s) being used. For example, the use of static control agents is disclosed in European Patent No. 0229368 and U.S. Patent Nos. 4,803,251 ; 4,555,370; and 5,283,278, and references cited therein.

[0074] Control agents such as aluminum stearate may also be employed. The static control agent used may be selected for its ability to receive the static charge in the fluidized bed without adversely affecting productivity. Other suitable static control agents may also include aluminum distearate, ethoxylated amines, and anti-static compositions such as those provided by Innospec Inc., a company with a business office in Newark, Delaware, under the trade name OCTASTAT^®. For example, OCTASTAT^® 2000 is a mixture of a polysulfone copolymer, a polymeric polyamine, and oil-soluble sulfonic acid.

[0075] Any of the aforementioned control agents, as well as those described in, for example, WO 01/44322, listed under the heading "Carboxylate Metal Salt" and including those chemicals and compositions listed as antistatic agents may be employed either alone or in combination as a control agent. For example, the carboxylate metal salt may be combined with an amine containing control agent (e.g., a carboxylate metal salt with any family member belonging to the ΚΕΜΑΜΓΝΕ^® (available from Chemtura Corporation, a company with a business office in Middlebury, Connecticut) or ATMER^® (available from AkzoNobel Polymer Chemicals LLC, a company with a business office in Chicago, Illinois) family of products).

[0076] Other useful continuity additives include, ethyleneimine additives useful in embodiments disclosed herein may include polyethyleneimines having the following general formula:

- (CH₂ - CH₂ - NH)_n - where n may be from about 10 to about 10,000. The polyethyleneimines may be linear, branched, or hyperbranched (i.e., forming dendritic or arborescent polymer structures). They can be a homopolymer or copolymer of ethyleneimine or mixtures thereof (referred to as polyethyleneimine(s) hereafter). Although linear polymers represented by the chemical formula — [CH₂ CH₂ NH]— may be used as the polyethyleneimine, materials having primary, secondary, and tertiary branches can also be used. Commercial polyethyleneimine can be a compound having branches of the ethyleneimine polymer. Suitable polyethyleneimines are commercially available from BASF Corporation, a company with a business office in Florham Park, NJ, under the trade name LUPASOL®. These compounds can be prepared as a wide range of molecular weights and product activities. Examples of commercial polyethyleneimines sold by BASF suitable for use in the present invention include, but are not limited to, LUPASOL® FG and LUPASOL® WF. Another useful continuity additive can include a mixture of aluminum distearate and an ethoxylated amine type compound, e.g., IRGASTAT® AS-990, available from Huntsman Corporation, a company with a business office in Salt Lake City, Utah (formerly Ciba Specialty Chemicals). The mixture of aluminum distearate and ethoxylated amine type compound can be slurried in mineral oil e.g., Hydrobrite 380. For example, the mixture of aluminum distearate and an ethoxylated amine type compound can be slurried in mineral oil to have total slurry concentration of ranging from about 5 wt% to about 50 wt% or about 10 wt% to about 40 wt%, or about 15 wt% to about 30 wt%. Other useful static control agents and additives are disclosed in U.S. Patent Application Publication No. 2008/0045663.

[0077] The continuity additive(s) or static control agent(s) may be added to the reactor in an amount ranging from 0.05 to 200 ppm, based on the weight of all feeds to the reactor, excluding recycle, more preferably in an amount ranging from 2 to 100 ppm; more preferably from 4 to 50 ppm.

Polymerization Process

[0078] The catalyst system can be used to polymerize one or more olefins to provide one or more polymer products therefrom. Any polymerization process including, but not limited to, high pressure, solution, slurry, and/or gas phase processes can be used. Preferably, a continuous gas phase process utilizing a fluidized bed reactor is used to polymerize ethylene and one or more optional comonomers to provide a polyethylene.

[0079] The term "polyethylene" refers to a polymer having at least 50 wt% ethylene-derived units, preferably at least 70 wt% ethylene-derived units, more preferably at least 80 wt% ethylene-derived units, or 90 wt% ethylene-derived units, or 95 wt% ethylene-derived units, or 100 wt% ethylene-derived units. The polyethylene can thus be a homopolymer or a copolymer, including a terpolymer, having one or more other monomeric units. A polyethylene described herein can, for example, include at least one or more other olefin(s) and/or comonomer(s). Suitable comonomers can contain 3 to 16 carbon atoms in one embodiment; from 3 to 12 carbon atoms in another embodiment; from 4 to 10 carbon atoms in another embodiment; and from 4 to 8 carbon atoms in yet another embodiment. Illustrative comonomers include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-l-ene, 1- decene, 1-dodecene, 1-hexadecene, and the like.

[0080] A suitable fluidized bed reactor can include a reaction zone and a so-called velocity reduction zone. The reaction zone can include a bed of growing polymer particles, formed polymer particles and a minor amount of catalyst particles fluidized by the continuous flow of the gaseous monomer and diluent to remove heat of polymerization through the reaction zone. Optionally, some of the re-circulated gases can be cooled and compressed to form liquids that increase the heat removal capacity of the circulating gas stream when readmitted to the reaction zone. A suitable rate of gas flow can be readily determined by simple experiment. Make-up of gaseous monomer to the circulating gas stream can be at a rate equal to the rate at which particulate polymer product and monomer associated therewith is withdrawn from the reactor and the composition of the gas passing through the reactor can be adjusted to maintain an essentially steady state gaseous composition within the reaction zone. The gas leaving the reaction zone can be passed to the velocity reduction zone where entrained particles are removed. Finer entrained particles and dust can be removed in a cyclone and/or fines filter. The gas can be passed through a heat exchanger where at least a portion of the heat of polymerization can be removed, compressed in a compressor, and then returned to the reaction zone. Additional reactor details and means for operating the reactor are described in, for example, U.S. Patent Nos. 3,709,853; 4,003,712; 4,01 1,382; 4,302,566; 4,543,399; 4,882,400; 5,352,749; and 5,541,270; EP 0802202; and Belgian Patent No. 839,380.

[0081] The reactor temperature of the fluid bed process can range from 30°C or 40°C or 50°C to 90°C or 100°C or 1 10°C or 120°C or 150°C. In general, the reactor temperature can be operated at the highest feasible temperature taking into account the sintering temperature of the polymer product within the reactor. Regardless of the process used to make the polyolefins, the polymerization temperature, or reaction temperature, should be below the melting or "sintering" temperature of the polyolefins to be formed. Thus, the upper temperature limit is the melting temperature of the polyolefin produced in the reactor.

[0082] Hydrogen gas can be used in olefin polymerization to control the final properties of the polyolefin, such as described in Polypropylene Handbook, at pages 76-78 (Hanser Publishers, 1996). Using certain catalyst systems, increasing concentrations (partial pressures) of hydrogen can increase the flow index (FI) of the polyolefin generated. The flow index can thus be influenced by the hydrogen concentration. For example, a concentration of hydrogen within the reactor can be adjusted to control at least one of the density and the melt index (I₂) of the polyethylene. In another example, at least one comonomer comprising one or more C₄ to Cs alpha olefins can be contacted with the catalyst system in the polymerization reactor, and at least one of a concentration of the one or more C₄ to Cs alpha olefins and a concentration of hydrogen within the polymerization reactor can be adjusted to control at least one of the density and the melt index (I₂) of the polyethylene.

[0083] The amount of hydrogen in the polymerization can be expressed as a mole ratio relative to the total polymerizable monomer, for example, ethylene, or a blend of ethylene and hexene or propylene. The amount of hydrogen used in the polymerization process can be an amount necessary to achieve the desired flow index of the final polyolefin resin. In one embodiment, the mole ratio of hydrogen to total monomer (H^monomer) can be in a range from greater than 0.0001 in one embodiment, and from greater than 0.0005 in another embodiment, and from greater than 0.001 in yet another embodiment, and less than 10 in yet another embodiment, and less than 5 in yet another embodiment, and less than 3 in yet another embodiment, and less than 0.10 in yet another embodiment, where a desirable range can include any combination of any upper mole ratio limit with any lower mole ratio limit described herein. Expressed another way, the amount of hydrogen in the reactor at any time can range to up to 5,000 ppm, and up to 4,000 ppm in another embodiment, and up to 3,000 ppm in yet another embodiment, and between 50 ppm and 5,000 ppm in yet another embodiment, and between 50 ppm and 2,000 ppm in another embodiment. The amount of hydrogen in the reactor can range from a low of about 1 ppm, about 50 ppm, or about 100 ppm to a high of about 400 ppm, about 800 ppm, about 1,000 ppm, about 1,500 ppm, or about 2,000 ppm. In yet another embodiment, the ratio of hydrogen to total monomer (H2:monomer) can be about 0.00001 : 1 to about 2: 1, about 0.005: 1 to about 1.5: 1, or about .0001 : 1 to about 1 : 1.

[0084] The one or more reactor pressures in a gas phase process (either single stage or two or more stages) can vary from about 690 kPa to about 3,450 kPa, and in the range from about 1,380 kPa to about 2,759 kPa in another embodiment, and in the range from about 1,724 kPa to about 2,414 kPa in yet another embodiment.

[0085] The gas phase reactor can be capable of producing from about 10 kg of polymer per hour to about 90,900 kg/hr, greater than about 455 kg/hr, greater than about 4,540 kg/hr, greater than about 1 1,300 kg/hr, greater than about 15,900 kg/hr, greater than about 22,700 kg/hr, or from about 29,000 kg/hr to about 45,500 kg/hr.

[0086] A slurry polymerization process can also be used. A slurry polymerization process generally uses pressures in the range of from about 101 kPa to about 5,070 kPa and even greater and temperatures in the range of from about 0°C to about 120°C, and more particularly from about 30°C to about 100°C. In a slurry polymerization, a suspension of solid, particulate polymer can be formed in a liquid polymerization diluent medium to which ethylene and comonomers and often hydrogen along with catalyst are added. The suspension, including diluent, can be intermittently or continuously removed from the reactor where the volatile components are separated from the polymer and recycled, optionally after a distillation, to the reactor. The liquid diluent employed in the polymerization medium can be an alkane having from 3 to 7 carbon atoms, such as, for example, a branched alkane. The medium employed should be liquid under the conditions of polymerization and relatively inert. When a propane medium is used the process should be operated above the reaction diluent critical temperature and pressure. In one embodiment, a hexane, isopentane, or isobutane medium can be employed.

[0087] The polyethylene can have a melt index ratio ( i/ ) ranging from about 2 to about 300 or from about 10 to less than about 250 or from about 15 to about 200. FI (I₂₁) can be measured in accordance with ASTM D 1238 (190°C, 21.6 kg). The MI (I₂) can be measured in accordance with ASTM D1238 (at 190°C, 2.16 kg weight). FI (¾) can be measured in accordance with ASTM D 1238 (at 190°C, 5.0 kg weight).

[0088] Density can be determined in accordance with ASTM D-792. Density is expressed as grams per cubic centimeter (g/cm³) unless otherwise noted. The polyethylene can have a density ranging from a low of about 0.89 g/cm³, about 0.90 g/cm³, or about 0.91 g/cm³ to a high of about 0.95 g/cm³, about 0.96 g/cm³, or about 0.97 g/cm³. The polyethylene can have a bulk density, measured in accordance with ASTM D1895 method B, of from about 0.25 g/cm³ to about 0.5 g/cm³. For example, the bulk density of the polyethylene can range from a low of about 0.30 g/cm³, about 0.32 g/cm³, or about 0.33 g/cm³ to a high of about 0.40 g/cm³, about 0.44 g/cm³, or about 0.48 g/cm³.

[0089] The polyethylene can be suitable for such articles as films, fibers, nonwoven and/or woven fabrics, extruded articles, and/or molded articles. Examples of films include blown or cast films formed by coextrusion or by lamination useful as shrink film, cling film, stretch film, sealing films, oriented films, snack packaging, heavy duty bags, grocery sacks, baked and frozen food packaging, medical packaging, industrial liners, membranes, etc. in food-contact and nonfood contact applications, agricultural films and sheets. Examples of fibers include melt spinning, solution spinning and melt blown fiber operations for use in woven or non-woven form to make filters, diaper fabrics, hygiene products, medical garments, geotextiles, etc. Examples of extruded articles include tubing, medical tubing, wire and cable coatings, pipe, geomembranes, and pond liners. Examples of molded articles include single and multi-layered constructions in the form of bottles, tanks, large hollow articles, rigid food containers, and toys.

Examples

[0090] To provide a better understanding of the foregoing discussion, the following non- limiting examples are provided. One of ordinary skill in the art would readily understand that other embodiments are possible without departing from the spirit or scope of the invention. All parts, proportions and percentages are by weight unless otherwise indicated.

Preparation of Activated Supports

[0091] In Examples 1-5, a silica support (ES757), supplied by PQ Corporation, a company with a business office in Malvern, Pennsylvania, was combined with ammonium hexafluorosilicate to provide a support mixture. For comparative examples C1-C6, the same silica support (ES757), supplied by PQ Corporation, was used, but the support was not combined with ammonium hexafluorosilicate. The resulting support mixtures (Examples 1-5) or supports (Examples C1-C6) were loaded into a single zone, vertical hinged, tube furnace and heated to convert the support mixture to a fluorinated-activated support (Examples 1-5) or convert the supports to activated supports (Examples C1-C6). The silica supports all had a surface area of about 300 m²/g, a pore volume of about 1.5 cm³/g, and a particle size of about 25 μιη.

[0092] To activate the support or support mixture, a nitrogen gas flow at a velocity of between 0.1 ft/sec and 0.2 ft/sec was started. The furnace was heated from room temperature to 200°C at 50°C per hour and held at 200°C for 2 hours. After 2 hours the nitrogen flow was stopped and air was introduced at about the same velocity, i.e., between 0.1 ft/sec and 0.2 ft/sec. The furnace was then heated to 600°C at a rate of 50°C per hour and held at 600°C for 3 hours. After 3 hours the furnace was allowed to cool down to room temperature. At approximately 195°C the flow of air was stopped and the nitrogen gas was started again. The furnace was purged with nitrogen gas for at least 30 minutes before removing the activated catalyst. The activated support or activated fluorinated-support was transferred into an oven-dried bottle.

Preparation of Catalyst Systems

[0093] Each catalyst system for Examples 1-5 and comparative examples C1-C6 included a metallocene catalyst compound, MAO, and a support. For Examples 1-3 and 5 and comparative examples C1-C4 and C6, the metallocene catalyst compound was bis(n-propylcyclopentadienyl) hafnium (CHs)2. For Example 4 and comparative example C5, the catalyst was bis(n-butyl, methyl cyclopentadienyl) zirconium CI2. One of two methods was used to prepare the catalyst systems.

[0094] Method 1 : To prepare the supported catalyst systems, a 10 wt% to 30 wt% solution of MAO in toluene and additional toluene (dried and degassed) were introduced to a mixer at room temperature and slowly stirred. The metallocene catalyst compound was dissolved in 100 g of toluene and introduced to the mixer containing the MAO and toluene mixture. The stirring speed was increased to 130 rpm and continued for 1 hour at room temperature. The activated support (or activated- fluorinated support) was then introduced to the mixer and stirred for 1 hour at room temperature. A vacuum was applied to remove the free liquid. Once the material was through the "mud stage," i.e., no free liquid was visible, a nitrogen gas purge was introduced to the mixer. During the mixing of the activated support (or activated-fluorinated support), metallocene catalyst, and MAO, the temperature of the mixture was increased to a final temperature of about 78°C to 80°C and mixed for about 2 hours. The mixture was then cooled down to room temperature and stored in an oven-dried container under a nitrogen atmosphere.

[0095] Method 2: The metallocene catalyst was added to 10 wt% to 30 wt% MAO in toluene. This mixture was added to a mixer containing a slurry of the activated support (or activated- fluorinated support) and toluene. The mixture was dried with vacuum and heat.

[0096] The catalyst system for Example 1 was prepared by Method 1 above and used about 24.88 g of the Hf compound, about 2,528 g of the 10 wt% MAO, about 219 g toluene, and about 693 g of the support. The catalyst system for Example 2 was also prepared by Method 1 above and used about 18.21 g of the Hf compound, about 2,480 g of the 10 wt% MAO, about 163 g toluene, and about 685 g of the support. The catalyst system for comparative examples CI and C3 were also prepared by Method 1 above and used about 19.5 g of the Hf compound, about 2,629 g of the 10 wt% MAO, about 172 g toluene, and about 728 g of the support. The catalyst system for comparative example C2 was also prepared by Method 1 above and used about 23.84 g of the Hf compound, about 2,602 g of the 10 wt% MAO, about 160 g toluene, and about 705 g of the support.

Gas Phase Fluidized Bed Polymerization Process

[0097] A gas phase fluidized bed polymerization reactor of the U IPOL™ process design having a nominal diameter of about 35.6 cm (about 14 inches) was used for the continuous production of both linear low density polyethylene ("LLDPE") and high density polyethylene ("HDPE"). In these cases, the cycle gas blower was situated upstream of the cycle gas heat exchanger in the gas recirculation loop but the two could have been reversed to reduce the gas temperature where it entered the heat exchanger. The cycle pipe was about 5.1 cm (about 2 inches) in diameter and its flow rate was manipulated by a ball valve in the cycle line to control the superficial gas velocity in the fluid bed at the desired rate. Monomers and gaseous components were added upstream of the cooler before the blower, at the blower impeller or after the blower. The catalyst system was continuously added in discrete small aliquots via an about 0.317 cm (about 0.125 inch) tube directly to the fluidized bed at a height about 0.1 m to 2 m above the distributor plate and most preferably at about the 0.2 m to about 1.2 m range using a nitrogen carrier gas flow at a location about 15% to about 50% of the reactor diameter. The mixture of aluminum distearate and ethoxylated amine type compound can be slurried in mineral oil e.g., Hydrobrite® 380 available from Sonneborn, Inc., a company with a business office in Mahwah, New Jersey. Polymer product was withdrawn periodically from the reactor through a discharge isolation tank in aliquots of about 0.2 kg to 5 kg to maintain a desired approximate average fluidized bed level or weight. [0098] In Examples 1 and 2 and C1-C3 LLDPEs were produced. Table 1 summarizes the polymerization results below.

[0099] Example 1 exhibited greater catalyst productivity than the comparative example C2 while using the same amount of MAO and having similar Hf loading in the catalyst system with Example 1 using a fluorinated-support while C2's support was not fluorinated. Thus, fluorinating silica supports can substantially increase the catalyst productivity.

[00100] Example 1 also exhibited greater catalyst productivity as compared to Example 2, where Example 1 used a higher Hf loading than Example 2. Comparative example C2 also had increased Hf loadings as compared to comparative example CI (1.1 wt% versus 0.785 wt%), however, comparative example C2 actually showed reduced catalyst productivity as compared to comparative example CI . As such, simply increasing the Hf loading did not necessarily produce a catalyst system that had increased catalyst productivity. However, using a fluorinated silica support while also increasing the Hf loading in the catalyst system was unexpectedly shown to produce catalyst systems with even greater increases in catalyst productivity.

[00101] More particularly, the catalyst productivity of comparative example CI was 14,018 lb PE/lb catalyst system. The catalyst productivity for comparative example C2 that increased Hf loading had a reduced catalyst productivity of only 11,1 11 lb PE/lb catalyst system as compared to comparative example CI . The catalyst productivity of Ex. 1 (18,462 lb PE/lb catalyst system) that had an increased Hf loading on a fluorinated silica support, however, showed a surprising and unexpected increase in catalyst productivity (about 31.7%) as compared to comparative example CI and an even greater increase in catalyst productivity (about 66.1%) as compared to comparative example C2.

[00102] In comparative example C3 and Example 2, the Hf loading was kept about the same, i.e., 0.785 wt% and 0.82 wt%, based on the total weight of the catalyst system, respectively. Example 2, however, also included a fluorinated silica support and Example 2 showed a substantial increase in catalyst productivity as compared to comparative example 3. More particularly, the catalyst productivity for Example 2 was about 9, 11 1 lb PE/lb catalyst system, which was an increase of about 24.2% over the comparative example C3 that had a catalyst productivity of only 7,336 lb PE/lb catalyst system.

[00103] Accordingly, from the data shown in Table 1, fluorinating silica supports can substantially increase the catalyst productivity. Additionally, fluorinated silica supports while also increasing the Hf loading in the catalyst system can produce catalyst systems with even greater increases in catalyst productivity.

Lab Stirred Gas Phase Polymerization Process

[00104] Additional examples using catalysts employing higher MAO levels were conducted in a 1.5 liter stirred gas phase reactor with a 400g salt bed (NaCl). The reactor was operated with about 220 psi ethylene, about 400-450 ppm hydrogen, and a hexane/ethylene charge ratio of about 0.026 at about 85°C for one hour. The catalyst was charged under reactor pressure and about 5 grams of a mixture of MAO on silica (about 6.5 mmol MAO per gram silica) was pre- charged as a scavenger.

[00105] The supports used for Examples 3 and 4 were fluorinated silica supports (ES757) having about 1.38 wt% F (0.76 mmol F/g), based on the weight of the support. The supports used for comparative examples C4 and C5 were non-fluorinated silica supports (ES757).

[00106] The catalyst systems used in Examples 3 and 4 and comparative example C5 were prepared according to Method 2 above. For Example 3, 7.9 cm³ of a solution containing 0.134 g of the Hf compound in 20.39 cm³ of 10% MAO is added to a toluene slurry containing 2.0 g of fluorinated ES-757 silica. For Example 4, 8.06 cm³ of a solution containing 0.112 g of the Zr compound in 18.43 cm³ of 10% MAO is added to 2.01 g fluorinated ES-757 silica. For comparative example C4, the catalyst from CI was used. The catalyst system for comparative example C5 the catalyst used the same amounts of reagents as that used in example 4 with about 2.01 g of the non-flourinated support.

[00107] In Examples 3 and 4 and comparative examples C4 and C5 LLDPEs were produced. Catalyst activity was measured in grams of polyethylene ("PE") per gram of catalyst system in one hour (gPE/g catalyst system-hr). Table 1 summarizes the polymerization results below.

[00108] In these examples, using a fluorinated silica support greatly increased the catalyst activity. Example 3 used a silica support having a fluoride concentration of about 1.38 wt%, based on the weight of the support, versus the comparative example C4 that was not fluorinated. Both Example 3 and the comparative example C4 had about the same Hf loading. However, the catalyst productivity for Example 3 (8,750 gPE/g catalyst system hr) increased by about 65.6% as compared to the comparative example C4 that only had a catalyst activity of about 5,285 gPE/g catalyst system hr.

[00109] Example 4, as compared to comparative example C5, also shows a surprising and unexpected increase in catalyst activity when the silica support is fluorinated with the Zr loading and the amount of MAO remaining the same. More particularly, Example 4 had fluorinated silica support (about 1.38 wt%, based on the weight of the support) but had the same Zr loading (0.34 wt%, based on the total weight of the catalyst system) and the same amount of MAO (6.25 mmol MAO/g support). Example 4, however, showed an increase in catalyst activity of about 84.4% as compared to the comparative example C5.

Slurry Polymerization Process

[00110] Example 5 and comparative example C6 were prepared in a laboratory slurry process. Triisobutyaluminum (TiBAl) was added to the reaction mixture. The ratio of the TiBAl to the total molar amount of catalyst metal was about 150: 1. The TiBAl or TEAL was added to scavenge impurities contained in the reactor or within the catalyst system that can render the catalyst ineffective.

[00111] The support used for Example 5 was a fluorinated silica supports (ES757) having about 1.38 wt% F (0.76 mmol F/g), based on the weight of the support. The support used for comparative example C6 was non-fluorinated silica supports (ES757).

[00112] The catalyst systems used in Example 5 and comparative example C6 were prepared according to Method 2 above. For Example 5, 3.83 cm³ of a solution containing 0.1 15 g of the Hf compound and 9.53 cm³ of 10% MAO was added to a toluene slurry containing 2.01g of support. For comparative example C6, 3.8 cm³ of the same solution used in Example 5 was added to 2.015 g of support.

[00113] A 1.5 liter autoclave reactor under a nitrogen purge was charged with catalyst, then 10 mL hexene and 400 cm³ isobutane diluent. The reactor was heated to 90°C and from about 10 mg to about 60 mg, depending on the particular example of each catalyst system was then each introduced to the reactor. For each example, ethylene (200 psig) was introduced to the reactor to provide a total reactor pressure of 434 psig. The reactor temperature was maintained at 90°C and the polymerization was allowed to proceed for 21 to 70 minutes, depending on the particular example, and the reactor was then cooled. Ethylene was vented off and the polymer was dried and weighed to obtain the polymer yield. The polymerization results are summarized below in Table 3. Table 3

Examples C6 Ex. 5

Additon Cocatalyst/Scavenger TiBAl TiBAl

Weight of Catalyst System (g) 0.04 0.04

mmol MAO/g support 3.00 3.00

Hf (wt%, based on the total weight

of the catalyst system) 0.72 0.74

F (wt%, based on the weight of the

support) 1.38

Weight of Catalyst (mg) 0.0408 0.0284

Polymer Yield (g) 154 145

Catalyst Activity (gPE/g catalyst

system- hr) 3,775 5, 106

[00114] Example 5 exhibited greater catalyst activity than comparative example C6, by fluorinating the silica support. Comparative example C6 had a catalyst activity of about 3,775 gPE/g catalyst system per hour. Example 6, which included a fluorinated silica support, had a catalyst activity of about 5, 106 gPE/g catalyst system per hour. Accordingly, by fluorinating the silica support the catalyst activity was increased by about 35%.

[00115] All numerical values are "about" or "approximately" the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

[00116] Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.

[00117] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention can be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

CLAIMS What is claimed is:

1. A catalyst system, comprising:

a catalyst compound comprising: (1) at least one cyclopentadienyl ligand and at least one heteroatom ligand; (2) two non-bridged cyclopentadienyl ligands; or (3) two or more heteroatom ligands;

a support comprising fluorinated silica, wherein the support is essentially free of alumina; and

an aluminoxane.

2. The catalyst system of claim 1, further comprising one or more organo-aluminum compounds.

3. The catalyst system of claim 1 or 2, wherein the catalyst compound comprises a transition metal and wherein the transition metal is present in an amount ranging from about 0.2 wt% to about 1.4 wt%, based on a total weight of the catalyst system.

4. The catalyst system according to any one of claims 1 to 3, wherein the catalyst compound comprises hafnium, and wherein the hafnium is present in an amount ranging from about 0.5 wt% to about 1.3 wt%, based on a total weight of the catalyst system.

5. The catalyst system according to any one of claims 1 to 3, wherein the catalyst compound comprises zirconium, and wherein the zirconium is present in an amount ranging from about 0.25 wt% to about 1 wt%, based on a total weight of the catalyst system.

6. The catalyst system according to any one of claims 1 to 5, wherein the support has a fluoride concentration ranging from about 1 wt% to about 10 wt%, based on a weight of the support.

7. The catalyst system according to any one of claims 1 to 5, wherein the support has a fluoride concentration ranging from about 1 wt% to about 4 wt%, based on a weight of the support.

8. The catalyst system according to any one of claims 1 to 5, wherein the support has a fluoride concentration ranging from about 1 wt% to about 2 wt%, based on a weight of the support.

9. The catalyst system according to any one of claims 1 to 8, wherein the aluminoxane is present in an amount of about 10 mmol or less per gram of the support.

10. The catalyst system according to any one of claims 1 to 8, wherein the aluminoxane is present in an amount of about 3 mmol or less per gram of the support.

11. The catalyst system according to any one of claims 1 to 8, wherein the aluminoxane is present in an amount of about 5 mmol to about 6.5 mmol per gram of the support.

12. The catalyst system according to any one of claims 1 to 1 1, wherein the aluminoxane comprises methylaluminoxane, modified methylaluminoxane, or a combination thereof.

13. The catalyst system according to any one of claims 1 to 12, wherein the catalyst compound comprises a metallocene catalyst.

14. The catalyst system according to claim 13, wherein the metallocene catalyst has the formula:

Cp^ACp^BMX_n,

wherein M is a Group 4, 5 or 6 atom; Cp^A and Cp^B are each bound to M and are independently selected from the group consisting of cyclopentadienyl ligands, substituted cyclopentadienyl ligands, ligands isolobal to cyclopentadienyl and substituted ligands isolobal to cyclopentadienyl; X is a leaving group selected from the group consisting of chloride ions, bromide ions, Ci to C₁₀ alkyls, and C₂ to C₁₂ alkenyls, carboxylates, acetylacetonates, and alkoxides; and n is an integer from 1 to 3.

15. The catalyst system according to any one of claims 1 to 13, wherein the catalyst compound has the formula:

wherein M is a Group 3 to 12 transition metal or a Group 13 or 14 main group metal; each X is independently an anionic leaving group; y is 0 or 1 ; n is the oxidation state of M; m is the formal charge of the ligand represented by YZL or YZL'; L is a Group 15 or 16 element; L' is a group 15 or 16 element or Group 14 containing group; Y is a Group 15 element; Z is a Group 15 element; R¹ and R² are independently a Ci to C₂₀ hydrocarbon group, a heteroatom containing group having up to twenty carbon atoms, silicon, germanium, tin, lead, or phosphorus; R¹ and R² may be interconnected to each other; R³ is absent, a hydrocarbon group, hydrogen, a halogen, or a heteroatom containing group; R⁴ and R⁵ are independently an alky group, an aryl group, a substituted aryl group, a cyclic alkyl group, a substituted cyclic alkyl group, a cyclic aralkyl group, a substituted cyclic aralky group, or a multiple ring system; R⁴ and R⁵ may be interconnected to each other; R⁶ and R⁷ are independently absent, hydrogen, an alkyl group, a halogen, a heteroatom, or a hydrocarbyl group; and R^* is absent, hydrogen, a Group 14 atom containing group, a halogen, or a heteroatom containing group.

16. The catalyst system according to any one of claims 1 to 13, wherein the catalyst compound comprises bis(n-propylcyclopentadienyl) hafnium (CH₃)₂, bis(n- propylcyclopentadienyl) hafnium F₂, bis(n-propylcyclopentadienyl) hafnium (¾, bis(n-butyl, methyl cyclopentadienyl) zirconium CI₂, (tetramethylcyclopentadienyl)(n- propylcyclopentadienyl)zirconiumCl2, (tetramethylcyclopentadienyl)(n- propylcyclopentadienyl)zirconium(CH₃)₂, [(2,3,4,5,6 Me₅C6 )CH₂CH2]2 HZrBz2, where Bz is a benzyl group, or any combination thereof.

17. The catalyst system according to any one of claims 1 to 16, wherein the catalyst system further comprises one or more second catalysts selected from a metallocene, a Ziegler-Natta catalyst, chromium catalyst, transition metal catalyst, Group 15- containing catalyst, or any combination thereof.

18. The catalyst system according to any one of claims 1 to 17, wherein the catalyst system has a productivity of at least 2,000 grams of polyethylene per gram of the catalyst system.

19. The catalyst system according to any one of claims 1 to 17, wherein the catalyst system has a productivity of at least 4,000 grams of polyethylene per gram of the catalyst system.

20. The catalyst system according to any one of claims 1 to 17, wherein the catalyst system has a productivity of at least 8,000 grams of polyethylene per gram of the catalyst system when polymerization is carried in a gas phase fluidized bed reactor.

21. The catalyst system according to any one of claims 1 to 17, wherein a catalyst productivity of the catalyst system is at least 10% greater than a catalyst productivity of the same catalyst system but having a non-fluorinated support.

22. The catalyst system according to any one of claims 1 to 17, wherein a catalyst productivity of the catalyst system is at least 20% greater than a catalyst productivity of the same catalyst system but having a non-fluorinated support.

23. A method for making the catalyst system according to any one of claims 1 to 22, comprising:

combining the catalyst compound, the support comprising fluorinated silica, and the aluminoxane,

wherein the catalyst compound comprises: (1) at least one cyclopentadienyl ligand and at least one heteroatom ligand; (2) two non-bridged cyclopentadienyl ligands; or (3) two or more heteroatom ligands; and

wherein the support is essentially free of alumina.

24. The method of claim 23, further comprising combining one or more organo-aluminum compounds with the catalyst compound and the support.

25. The method of claim 23 or 24, wherein the fluorinated silica is prepared by calcining a silica support in the presence of a fluorine source.

26. The method of claim 25, wherein the fluorine source comprises ammonium

hexafluorosilicate, ammonium bifluoride, ammonium tetrafluoroborate, or any combination thereof.

27. The method of claim 25 or 26, wherein the calcining occurs at a temperature of from about 200°C to about 1,000°C to produce the support.

28. A method for olefin polymerization, comprising:

combining ethylene with the catalyst system of any one of claims 1 to 22 in a polymerization reactor at conditions sufficient to produce a polyethylene.

29. The method according to claim 28, further comprising contacting at least one comonomer comprising one or more C₄ to Cs alpha olefins with the catalyst system in the polymerization reactor.

30. The method according to claim 28 or 29, further comprising introducing one or more organo-aluminum compounds to the polymerization reactor, wherein the one or more organo- aluminum compounds are present in an amount ranging from about 1 ppmw to about 100 ppmw.

31. The method according to any one of claims 28 to 30, further comprising adjusting a concentration of hydrogen within the reactor to control at least one of the density and the melt index (I₂) of the polyethylene.

32. The method according to any one of claims 28 to 30, wherein at least one comonomer comprising one or more C₄ to Cs alpha olefins is contacted with the catalyst system in the polymerization reactor, the method further comprising adjusting at least one of a concentration of the one or more C₄ to Cs alpha olefins and a concentration of hydrogen within the polymerization reactor to control at least one of the density and the melt index (I₂) of the polyethylene.

33. The method according to any one of claims 28 to 32, wherein the ethylene is contacted with the catalyst system under gas phase conditions.