Patent Publication Number: US-2009240010-A1

Title: Alumina-silica activator-supports for metallocene catalyst compositions

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to the field of olefin polymerization catalysis, supported catalyst compositions, methods for the polymerization and copolymerization of olefins, and polyolefins. More specifically, this invention relates to chemically-treated alumina-silica activator-supports and to catalyst compositions employing these activator-supports. 
     SUMMARY OF THE INVENTION 
     The present invention is directed generally to chemically-treated alumina-silica activator-supports, catalyst compositions employing these supports, methods for preparing activator-supports and catalyst compositions, methods for using the catalyst compositions to polymerize olefins, the polymer resins produced using such catalyst compositions, and articles produced using these polymer resins. In particular, the present invention relates to chemically-treated alumina-silica activator-supports and to catalyst compositions employing such activator-supports. Catalyst compositions containing alumina-silica supports of the present invention can be used to produce, for example, ethylene-based homopolymers and copolymers. 
     According to one aspect of the present invention, an activator-support is provided which comprises at least one alumina-silica compound treated with at least one electron-withdrawing anion. Generally, the at least one alumina-silica compound has a weight ratio of alumina to silica in a range from about 1:1 to about 100:1, while the at least one electron-withdrawing anion is fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, and the like, or any combination thereof. 
     An activator-support comprising at least one alumina-silica compound is provided in another aspect of this invention, the at least one alumina-silica compound having a weight ratio of alumina to silica in a range from about 2:1 to about 4:1. The at least one alumina-silica compound in this aspect is also treated with at least one electron-withdrawing anion, which is selected from fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, and the like, or any combination thereof. 
     Catalyst compositions containing these activator-supports are also provided by the present invention. In one aspect, the catalyst composition can comprise a contact product of at least one metallocene compound and at least one activator-support. The at least one activator-support comprises at least one alumina-silica compound having a weight ratio of alumina to silica in a range from about 1:1 to about 100:1, and is treated with at least one electron-withdrawing anion such as, for example, fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, and the like, or combinations thereof. This catalyst composition can further comprise at least one organoaluminum compound. In other aspects, the catalyst composition comprising at least one metallocene compound and at least one activator-support can further comprise at least one optional co-catalyst. Suitable optional co-catalysts in this aspect include, but are not limited to, aluminoxane compounds, organozinc compounds, organoboron or organoborate compounds, ionizing ionic compounds, and the like, or combinations thereof. 
     Another catalyst composition contemplated herein comprises a contact product of at least one metallocene compound, at least one organoaluminum compound, and at least one activator-support. The at least one organoaluminum compound is selected from trimethylaluminum, triethylaluminum, tri-n-propylaluminum, diethylaluminum ethoxide, tri-n-butylaluminum, diisobutylaluminum hydride, triisobutylaluminum, diethylaluminum chloride, and the like, or combinations thereof. The at least one activator-support comprises at least one alumina-silica compound treated with at least one electron-withdrawing anion, such as those electron-withdrawing anions provided above. The at least one alumina-silica compound has a weight ratio of alumina to silica in a range from about 2:1 to about 4:1 in this aspect of the invention. 
     Catalyst compositions of the present invention can be used to polymerize olefins to form homopolymers or copolymers. One such process for polymerizing olefins in the presence of a catalyst composition of the present invention comprises contacting the catalyst composition with at least one olefin monomer and optionally at least one olefin comonomer under polymerization conditions to produce a polymer or copolymer, wherein the catalyst composition comprises a contact product of at least one metallocene compound and at least one activator-support. The at least one activator-support comprises at least one alumina-silica compound treated with at least one electron-withdrawing anion, wherein the at least one alumina-silica compound generally has a weight ratio of alumina to silica in a range from about 1:1 to about 100:1. The at least one electron-withdrawing anion can be fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, and the like, or a combination thereof. Other co-catalysts, including organoaluminum compounds, can be employed in this process. 
     Polymers produced from the polymerization of olefins, resulting in either homopolymers or copolymers, can be used to produce various articles of manufacture. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  presents a plot of catalyst activity, in units of grams of polyethylene per gram of activator-support (A-S) per hour, versus the concentration of MET 1, in units of micromoles of MET 1 per gram of the A-S, for the activator-supports of Examples 1-3. 
         FIG. 2  presents a plot of catalyst activity, in units of grams of polyethylene per gram of MET 1 per hour, versus the concentration of MET 1, in units of micromoles of MET 1 per gram of the activator-support (A-S), for the activator-supports of Examples 1-3. 
         FIG. 3  presents a plot of catalyst activity, in units of grams of polyethylene per gram of A-S per hour, versus the concentration of MET 2, in units of micromoles of MET 2 per gram of the A-S, for the activator-supports of Examples 1-3. 
         FIG. 4  presents a plot of catalyst activity, in units of grams of polyethylene per gram of MET 2 per hour, versus the concentration of MET 2, in units of micromoles of MET 2 per gram of the A-S, for the activator-supports of Examples 1-3. 
         FIG. 5  presents a plot of catalyst activity, in units of grams of polyethylene per hour, for the precontacted catalyst system and the catalyst system which was not precontacted of Example 6. 
         FIG. 6  presents a plot of catalyst activity, in units of grams of polyethylene per gram of A-S per hour, versus the concentration of MET 3, in units of micromoles of MET 3 per gram of the A-S, for the activator-supports of Examples 2-3. 
         FIG. 7  presents a plot of catalyst activity, in units of grams of polyethylene per gram of MET 3 per hour, versus the concentration of MET 3, in units of micromoles of MET 3 per gram of the A-S, for the activator-supports of Examples 2-3. 
     
    
    
     DEFINITIONS 
     To define more clearly the terms used herein, the following definitions are provided. To the extent that any definition or usage provided by any document incorporated herein by reference conflicts with the definition or usage provided herein, the definition or usage provided herein controls. 
     The term “polymer” is used herein to include homopolymers comprising ethylene and copolymers of ethylene and a comonomer. “Polymer” is also used herein to mean homopolymers and copolymers of any olefin monomer disclosed herein (e.g., propylene). 
     The term “co-catalyst” is used generally herein to refer to organoaluminum compounds that can constitute one component of a catalyst composition. Additionally, “co-catalyst” also refers to other optional components of a catalyst composition including, but not limited to, aluminoxanes, organozinc compounds, organoboron or organoborate compounds, ionizing ionic compounds, as disclosed herein. The term “co-catalyst” is used regardless of the actual function of the compound or any chemical mechanism by which the compound may operate. In one aspect of this invention, the term “co-catalyst” is used to distinguish that component of the catalyst composition from the metallocene compound. 
     The term “fluoroorgano boron compound” is used herein with its ordinary meaning to refer to neutral compounds of the form BY 3 . The term “fluoroorgano borate compound” also has its usual meaning to refer to the monoanionic salts of a fluoroorgano boron compound of the form [cation] + [BY 4 ] − , where Y represents a fluorinated organic group. Materials of these types are generally and collectively referred to as “organoboron or organoborate compounds.” 
     The term “contact product” is used herein to describe compositions wherein the components are contacted together in any order, in any manner, and for any length of time. For example, the components can be contacted by blending or mixing. Further, contacting of any component can occur in the presence or absence of any other component of the compositions described herein. Combining additional materials or components can be done by any suitable method. Further, the term “contact product” includes mixtures, blends, solutions, slurries, reaction products, and the like, or combinations thereof. Although “contact product” can include reaction products, it is not required for the respective components to react with one another. 
     The term “precontacted” mixture is used herein to describe a first mixture of catalyst components that are contacted for a first period of time prior to the first mixture being used to form a “postcontacted” or second mixture of catalyst components that are contacted for a second period of time. The precontacted mixture can describe a mixture of metallocene compound (or compounds), olefin monomer, and organoaluminum compound (or compounds), before this mixture is contacted with at least one activator-support and optional additional organoaluminum compound. The precontacted mixture also can describe a mixture of metallocene compound (or compounds), organoaluminum compound (or compounds), and activator-support compound (or compounds) which is contacted for a period of time prior to being fed to a polymerization reactor. Thus, precontacted describes components that are used to contact each other, but prior to contacting the components in the second, postcontacted mixture. Accordingly, this invention may occasionally distinguish between a component used to prepare the precontacted mixture and that component after the mixture has been prepared. For example, in one aspect of this invention, it is possible for a precontacted organoaluminum compound, once it is contacted with a metallocene and an olefin monomer, to have reacted to form at least one different chemical compound, formulation, or structure from the distinct organoaluminum compound used to prepare the precontacted mixture. In this case, the precontacted organoaluminum compound or component is described as comprising an organoaluminum compound that was used to prepare the precontacted mixture. 
     Similarly, the term “postcontacted” mixture is used herein to describe a second mixture of catalyst components that are contacted for a second period of time, and one constituent of which is the “precontacted” or first mixture of catalyst components that were contacted for a first period of time. For example, the term “postcontacted” mixture can describe the mixture of metallocene compound, olefin monomer, organoaluminum compound, and activator-support (e.g., a chemically-treated solid oxide), formed from contacting the precontacted mixture of a portion of these components with any additional components added to make up the postcontacted mixture. In some cases, the additional component added to make up the postcontacted mixture is a chemically-treated solid oxide, and, optionally, can include an organoaluminum compound which is the same as or different from the organoaluminum compound used to prepare the precontacted mixture, as described herein. Accordingly, this invention may also occasionally distinguish between a component used to prepare the postcontacted mixture and that component after the mixture has been prepared. 
     The term “metallocene,” as used herein, describes a compound comprising at least one η 3  to η 5 -cycloalkadienyl-type moiety, wherein η 3  to η 5 -cycloalkadienyl moieties include cyclopentadienyl ligands, indenyl ligands, fluorenyl ligands, and the like, including partially saturated or substituted derivatives or analogs of any of these. Possible substituents on these ligands include hydrogen, therefore the description “substituted derivatives thereof” in this invention comprises partially saturated ligands such as tetrahydroindenyl, tetrahydrofluorenyl, octahydrofluorenyl, partially saturated indenyl, partially saturated fluorenyl, substituted partially saturated indenyl, substituted partially saturated fluorenyl, and the like. In some contexts, the metallocene is referred to simply as the “catalyst,” in much the same way the term “co-catalyst” is used herein to refer to, for example, an organoaluminum compound or an aluminoxane compound. Metallocene is also used herein to encompass mono-cyclopentadienyl or half-sandwich compounds, as well as compounds containing at least one cyclodienyl ring and compounds containing boratabenzene ligands. Further, metallocene is also used herein to encompass dinuclear metallocene compounds, i.e., compounds comprising two metallocene moieties linked by a connecting group, such as an alkenyl group resulting from an olefin metathesis reaction or a saturated version resulting from hydrogenation or derivatization. 
     The terms “catalyst composition,” “catalyst mixture,” “catalyst system,” and the like, do not depend upon the actual product resulting from the contact or reaction of the components of the mixtures, the nature of the active catalytic site, or the fate of the co-catalyst, the metallocene compound, any olefin monomer used to prepare a precontacted mixture, or the activator-support, after combining these components. Therefore, the terms “catalyst composition,” “catalyst mixture,” “catalyst system,” and the like, can include both heterogeneous compositions and homogenous compositions. 
     The terms “chemically-treated solid oxide,” “activator-support,” “treated solid oxide compound,” and the like, are used herein to describe a solid, inorganic oxide of relatively high porosity, which exhibits Lewis acidic or Brønsted acidic behavior, and which has been treated with an electron-withdrawing component, typically an anion, and which is calcined. The electron-withdrawing component is typically an electron-withdrawing anion source compound. Thus, the chemically-treated solid oxide compound comprises a calcined contact product of at least one solid oxide compound with at least one electron-withdrawing anion source compound. Typically, the chemically-treated solid oxide comprises at least one ionizing, acidic solid oxide compound. The terms “support” and “activator-support” are not used to imply these components are inert, and such components should not be construed as an inert component of the catalyst composition. 
     Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the typical methods, devices and materials are herein described. 
     All publications and patents mentioned herein are incorporated herein by reference for the purpose of describing and disclosing, for example, the constructs and methodologies that are described in the publications, which might be used in connection with the presently described invention. The publications discussed throughout the text are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention. 
     For any particular compound disclosed herein, the structure presented also encompasses all conformational isomers, regioisomers, and stereoisomers that may arise from a particular set of substituents. The structure also encompasses all enantiomers, diastereomers, and other optical isomers whether in enantiomeric or racemic forms, as well as mixtures of stereoisomers, as would be recognized by a skilled artisan. 
     Applicants disclose several types of ranges in the present invention. These include, but are not limited to, a range of weight ratios, a range or molar ratios, a range of surface areas, a range of pore volumes, a range of average particle sizes, and so forth. When Applicants disclose or claim a range of any type, Applicants&#39; intent is to disclose or claim individually each possible number that such a range could reasonably encompass, including end points of the range as well as any sub-ranges and combinations of sub-ranges encompassed therein. For example, when the Applicants disclose or claim a weight ratio of alumina to silica in an alumina-silica compound, Applicants&#39; intent is to disclose or claim individually every possible number that such a range could encompass, consistent with the disclosure herein. By a disclosure that the weight ratio of alumina to silica in a alumina-silica compound is in a range from about 1:1 to about 100:1, Applicants intend to recite that the weight ratio can be selected from about 1:1, about 1.1:1, about 1.2:1, about 1.3:1, about 1.4:1, about 1.5:1, about 1.6:1, about 1.7:1, about 1.8:1, about 1.9:1, about 2:1, about 2.1:1, about 2.2:1, about 2.3:1, about 2.4:1, about 2.5:1, about 2.6:1, about 2.7:1, about 2.8:1, about 2.9:1, about 3:1, about 3.1:1, about 3.2:1, about 3.3:1, about 3.4:1, about 3.5:1, about 3.6:1, about 3.7:1, about 3.8:1, about 3.9:1, about 4:1, about 4.1:1, about 4.2:1, about 4.3:1, about 4.4:1, about 4.5:1, about 4.6:1, about 4.7:1, about 4.8:1, about 4.9:1, about 5:1, about 5.1:1, about 5.2:1, about 5.3:1, about 5.4:1, about 5.5:1, about 5.6:1, about 5.7:1, about 5.8:1, about 5.9:1, about 6:1, about 6.5:1, about 7:1, about 7.5:1, about 8:1, about 8.5:1, about 9:1, about 9.5:1, about 10:1, about 11:1, about 12:1, about 13:1, about 14:1, about 15:1, about 16:1, about 17:1, about 18:1, about 19:1, about 20:1, about 30:1, about 40:1, about 50:1, about 60:1, about 70:1, about 80:1, about 90:1, about 95:1, about 96:1, about 97:1, about 98:1, about 99:1, or about 100:1. Additionally, the weight ratio can be within any range from about 1:1 to about 100:1 (for example, the weight ratio is in a range from about 2:1 to about 6:1), and this also includes any combination of ranges between about 1:1 to about 100:1 (for example, the weight ratio is in a range from about 1.8:1 to about 5:1 or from about 8:1 to about 20:1). Likewise, all other ranges disclosed herein should be interpreted in a manner similar to this example. 
     Applicants reserve the right to proviso out or exclude any individual members of any such group, including any sub-ranges or combinations of sub-ranges within the group, that can be claimed according to a range or in any similar manner, if for any reason Applicants choose to claim less than the full measure of the disclosure, for example, to account for a reference that Applicants may be unaware of at the time of the filing of the application. Further, Applicants reserve the right to proviso out or exclude any individual substituents, analogs, compounds, ligands, structures, or groups thereof, or any members of a claimed group, if for any reason Applicants choose to claim less than the full measure of the disclosure, for example, to account for a reference that Applicants may be unaware of at the time of the filing of the application. 
     While compositions and methods are described in terms of “comprising” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components or steps. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates generally to chemically-treated alumina-silica activator-supports, catalyst compositions employing these supports, methods for preparing activator-supports and catalyst compositions, methods for using the catalyst compositions to polymerize olefins, the polymer resins produced using such catalyst compositions, and articles produced using these polymer resins. 
     In particular, the present invention is directed to chemically-treated alumina-silica activator-supports and to catalyst compositions employing such activator-supports. These activator-supports comprise at least one alumina-silica compound, that is, the alumina-silica compound has a weight ratio of alumina to silica ranging from about 1:1 to about 100:1. Catalyst compositions containing the alumina-silica supports of the present invention can be used to produce, for example, ethylene-based homopolymers and copolymers. 
     Catalyst Compositions 
     Catalyst compositions disclosed herein employ at least one activator-support. According to one aspect of the present invention, a catalyst composition is provided which comprises a contact product of at least one metallocene compound and at least one activator-support. The at least one activator-support comprises at least one alumina-silica compound having a weight ratio of alumina to silica ranging from about 1:1 to about 100:1, which is treated with at least one electron-withdrawing anion such as, for example, fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, and the like, or combinations thereof. This catalyst composition can further comprise at least one organoaluminum compound. These catalyst compositions can be utilized to produce polyolefins, both homopolymers and copolymers, for a variety of end-use applications. 
     In accordance with this and other aspects of the present invention, it is contemplated that the catalyst compositions disclosed herein can contain more than one metallocene compound and/or more than one activator-support. Additionally, more than one organoaluminum compound is also contemplated. 
     In other aspects of this invention, optional co-catalysts can be employed. For example, a catalyst composition comprising at least one metallocene compound and at least one activator-support can further comprise at least one optional co-catalyst. Suitable co-catalysts in this aspect can be selected from at least one aluminoxane compound, at least one organozinc compound, at least one organoboron or organoborate compound, at least one ionizing ionic compound, and the like, or combinations thereof. More than one co-catalyst can be present in the catalyst composition. 
     Another catalyst composition contemplated herein comprises a contact product of at least one metallocene compound, at least one organoaluminum compound, and at least one activator-support. Said activator-support comprises at least one alumina-silica compound treated with at least one electron-withdrawing anion. The at least one alumina-silica compound has a weight ratio of alumina to silica in a range from about 2:1 to about 4:1 in this aspect of the invention. 
     Catalyst compositions of the present invention comprising a contact product of at least one metallocene compound and at least one chemically-treated, high alumina content, alumina-silica activator-support can further comprise additional activator-supports. For instance, the additional activator-support can be fluorided alumina, chlorided alumina, bromided alumina, sulfated alumina, fluorided silica-alumina, chlorided silica-alumina, bromided silica-alumina, sulfated silica-alumina, fluorided silica-zirconia, chlorided silica-zirconia, bromided silica-zirconia, sulfated silica-zirconia, and the like, or a combination thereof. If the additional activator-support is a chemically-treated silica-alumina, this is distinguished from the high alumina content, alumina-silica variations of the present invention. The optional, additional activator-support can contain a known silica-alumina material having an alumina to silica weight ratio of less than 1:1. For example, the weight ratio of alumina to silica in these known silica-alumina materials is often in a range from about 0.05:1 to about 0.25:1, as reflected in Example 1 that follows. These chemically-treated silica-alumina materials having a weight ratio of alumina to silica of less than 1:1 are not the inventive activator-supports of this invention, however, such silica-alumina materials can optionally be used in combination with the activator-supports of the present invention in a catalyst composition. 
     Alternatively, catalyst compositions of the present invention can further comprise an activator-support which comprises a solid oxide treated with an electron-withdrawing anion, wherein the solid oxide is silica, alumina, silica-alumina, aluminum phosphate, heteropolytungstates, titania, zirconia, magnesia, boria, zinc oxide, a mixed oxide thereof, or a mixture thereof. As noted above, an additional silica-alumina material in this context has an alumina to silica weight ratio of less than 1:1. The electron-withdrawing anion can be fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, and the like, or combinations thereof. 
     Activator-supports of this invention can further comprise a metal or metal ion such as, for example, zinc, titanium, nickel, vanadium, silver, copper, gallium, tin, tungsten, molybdenum, and the like, or any combination thereof. 
     In yet another aspect, catalyst compositions of the present invention can further comprise an activator-support selected from a clay mineral, a pillared clay, an exfoliated clay, an exfoliated clay gelled into another oxide matrix, a layered silicate mineral, a non-layered silicate mineral, a layered aluminosilicate mineral, a non-layered aluminosilicate mineral, and the like, or combinations of these materials. Additional activator-support materials will be discussed in more detail below. 
     Alumina-Silica Activator-Supports 
     Activator-supports of the present invention are considered to be “high alumina content” because the weight ratio of alumina to silica in the alumina-silica compound is greater than about 1:1. Generally, activator-supports provided in this invention comprise at least one alumina-silica compound treated with at least one electron-withdrawing anion, the at least one alumina-silica compound having a weight ratio of alumina to silica ranging from about 1:1 to about 100:1. The at least one electron-withdrawing anion is typically selected from fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, and the like, but combinations of these anions also can be employed. 
     In one aspect of this invention, the weight ratio of alumina to silica in the at least one alumina-silica compound is in a range from about 1.2:1 to about 90:1, such as, for example, from about 1.3:1 to about 50:1, from about 1.4:1 to about 20:1, or from about 1.5:1 to about 10:1. Yet, in another aspect, the weight ratio of alumina to silica in the at least one alumina-silica compound ranges from about 1.7:1 to about 9:1. For instance, the alumina to silica weight ratio in the alumina-silica compound can be in a range from about 1.8:1 to about 8:1, from about 1.9:1 to about 7:1, or from about 2:1 to about 6:1. 
     According to still another aspect of the invention, an activator-support comprising at least one alumina-silica compound treated with at least one electron-withdrawing anion is provided. In this aspect, the at least one alumina-silica compound has a weight ratio of alumina to silica ranging from about 2:1 to about 4:1. The alumina to silica weight ratio in the alumina-silica compound falls within the narrower range from about 2.2:1 to about 3.8:1 in other aspects of the present invention. For example, alumina to silica weight ratios of about 2.5:1, about 2.6:1, about 2.7:1, about 2.8:1, about 2.9:1, about 3:1, about 3.1:1, about 3.2:1, about 3.3:1, and about 3.4:1, are contemplated herein. 
     High alumina content alumina-silica compounds of the present invention generally have surface areas ranging from about 100 to about 1000 m 2 /g. In some aspects, the surface area falls within a range from about 150 to about 750 m 2 /g, for example, from about 200 to about 600 m 2 /g. The surface area of the alumina-silica compound can range from about 250 to about 500 m 2 /g in another aspect of this invention. High alumina content alumina-silica compounds having surface areas of about 300 m 2 /g, about 350 m 2 /g, about 400 m 2 /g, or about 450 m 2 /g, can be employed in this invention. 
     The pore volume of the high alumina content alumina-silica compounds is generally greater than about 0.5 mL/g. Often, the pore volume is greater than about 0.75 mL/g, or greater than about 1 mL/g. In another aspect, the pore volume is greater than about 1.2 mL/g. In yet another aspect, the pore volume falls within a range from about 0.8 mL/g to about 1.8 mL/g, such as, for example, from about 1 mL/g to about 1.6 mL/g. 
     The high alumina content alumina-silica compounds disclosed herein generally have average particle sizes ranging from about 5 microns to about 150 microns. In some aspects of this invention, the average particle size falls within a range from about 30 microns to about 100 microns. For example, the average particle size of the alumina-silica compounds can be in a range from about 40 to about 80 microns. 
     Alumina-silica compounds of the present invention can be produced using various methods. For instance, alumina and silica can be co-gelled or co-precipitated to form an alumina-silica mixed oxide having a weight ratio of alumina to silica in the alumina-silica compound of greater than about 1:1. Alternatively, the alumina-silica compound of the present invention can be an alumina which is coated with silica to form an alumina-silica compound having a weight ratio of alumina to silica ranging from about 1:1 to about 100:1, for example, from about 2:1 to about 6:1. 
     In accordance with the present invention, activator-supports comprise at least one alumina-silica compound treated with at least one electron-withdrawing anion. Suitable electron-withdrawing anions include, but are not limited to, fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, and the like, or combinations thereof. Compounds useful for the chemical treatment of the solid oxide, and methods for chemical treating the solid oxide are provided below in the discussion of additional activator-supports. In one aspect of this invention, the alumina-silica compound is treated with an electron-withdrawing anion selected from fluoride or sulfate. 
     Generally, the alumina-silica activator-supports of the present invention are calcined. The alumina-silica compound can be calcined prior to chemical treatment. Either during or after chemical treatment, the alumina-silica activator-support can be calcined. Calcining conditions are provided below in the discussion of additional activator-supports. Activator-supports comprising at least one high alumina content alumina-silica compound treated with at least one electron-withdrawing anion, after calcining, generally have surface areas ranging from about 100 to about 1000 m 2 /g. In some aspects, the surface area falls within a range from about 150 to about 750 m 2 /g, for example, from about 200 to about 600 m 2 /g. The surface area of the activator-support can range from about 250 to about 500 m 2 /g in another aspect of this invention. For instance, activator-supports having surface areas of about 300 m 2 /g, about 350 m 2 /g, about 400 m 2 /g, or about 450 m 2 /g, can be employed in this invention. 
     After calcining, the pore volume of the activator-support is generally greater than about 0.5 mL/g. Often, the pore volume is greater than about 0.75 mL/g, or greater than about 1 mL/g. In another aspect, the pore volume is greater than about 1.2 mL/g. In yet another aspect, the pore volume falls within a range from about 0.8 mL/g to about 1.8 mL/g, such as, for example, from about 1 mL/g to about 1.6 mL/g. 
     The calcined activator-supports disclosed herein generally have average particle sizes ranging from about 5 microns to about 150 microns. In some aspects of this invention, the average particle size falls within a range from about 30 microns to about 100 microns. For example, the average particle size of the activator-supports can be in a range from about 40 to about 80 microns. 
     Additional Activator-Supports 
     The present invention encompasses various catalyst compositions which can include an activator-support. For example, a catalyst composition is provided which comprises a contact product of at least one metallocene compound and at least one activator-support. The at least one activator-support comprises at least one alumina-silica compound having a weight ratio of alumina to silica ranging from about 1:1 to about 100:1, which is treated with at least one electron-withdrawing anion. 
     Such catalyst compositions can further comprise an additional activator-support, such as a chemically-treated solid oxide, that is different from the chemically-treated, high alumina content, alumina-silica of the present invention. Alternatively, the catalyst composition can further comprise an activator-support selected from a clay mineral, a pillared clay, an exfoliated clay, an exfoliated clay gelled into another oxide matrix, a layered silicate mineral, a non-layered silicate mineral, a layered aluminosilicate mineral, a non-layered aluminosilicate mineral, and the like, or any combination thereof. 
     Generally, chemically-treated solid oxides exhibits enhanced acidity as compared to the corresponding untreated solid oxide compound. The chemically-treated solid oxide also functions as a catalyst activator as compared to the corresponding untreated solid oxide. While the chemically-treated solid oxide activates the metallocene in the absence of co-catalysts, it is not necessary to eliminate co-catalysts from the catalyst composition. The activation function of the activator-support is evident in the enhanced activity of catalyst composition as a whole, as compared to a catalyst composition containing the corresponding untreated solid oxide. However, it is believed that the chemically-treated solid oxide can function as an activator, even in the absence of organoaluminum compounds, aluminoxanes, organoboron compounds, ionizing ionic compounds, and the like. 
     Chemically-treated solid oxides comprise at least one solid oxide treated with at least one electron-withdrawing anion. While not intending to be bound by the following statement, it is believed that treatment of the solid oxide with an electron-withdrawing component augments or enhances the acidity of the oxide. Thus, either the activator-support exhibits Lewis or Brønsted acidity that is typically greater than the Lewis or Brønsted acid strength of the untreated solid oxide, or the activator-support has a greater number of acid sites than the untreated solid oxide, or both. One method to quantify the acidity of the chemically-treated and the untreated solid oxide materials is by comparing the polymerization activities of the treated and the untreated oxides under acid catalyzed reactions. 
     Chemically-treated solid oxides of this invention are formed generally from an inorganic solid oxide that exhibits Lewis acidic or Brønsted acidic behavior and has a relatively high porosity. The solid oxide is chemically-treated with an electron-withdrawing component, typically an electron-withdrawing anion, to form an activator-support. 
     The pore volume and surface area of high alumina content alumina-silica compounds were discussed in the preceding section. Solid oxides used to prepare an additional chemically-treated solid oxide generally have a pore volume greater than about 0.1 mL/g. According to another aspect of the present invention, the solid oxide has a pore volume greater than about 0.5 mL/g. According to yet another aspect of the present invention, the solid oxide has a pore volume greater than about 1 mL/g. 
     In another aspect, the solid oxide used to prepare the additional chemically-treated solid oxide has a surface area ranging from about 100 to about 1000 m 2 /g, for example, in a range from about 200 to about 800 m 2 /g. In still another aspect of the present invention, the solid oxide has a surface area in a range from about 250 to about 600 m 2 /g. 
     In still another aspect, the additional chemically-treated solid oxide can comprise a solid inorganic oxide comprising oxygen and at least one element selected from Group 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 of the periodic table, or comprising oxygen and at least one element selected from the lanthanide or actinide elements. (See: Hawley&#39;s Condensed Chemical Dictionary, 11 th  Ed., John Wiley &amp; Sons; 1995; Cotton, F. A.; Wilkinson, G.; Murillo; C. A.; and Bochmann; M. Advanced Inorganic Chemistry, 6 th  Ed., Wiley-Interscience, 1999.) For example, the inorganic oxide can comprise oxygen and at least one element selected from Al, B, Be, Bi, Cd, Co, Cr, Cu, Fe, Ga, La, Mn, Mo, Ni, Sb, Si, Sn, Sr, Th, Ti, V, W, P, Y, Zn or Zr. 
     Suitable examples of solid oxide materials or compounds that can be used to form the additional chemically-treated solid oxide include, but are not limited to, Al 2 O 3 , B 2 O 3 , BeO, Bi 2 O 3 , CdO, CO 3 O 4 , Cr 2 O 3 , CuO, Fe 2 O 3 , Ga 2 O 3 , La 2 O 3 , Mn 2 O 3 , MoO 3 , NiO, P 2 O 5 , Sb 2 O 5 , SiO 2 , SnO 2 , SrO, ThO 2 , TiO 2 , V 2 O 5 , WO 3 , Y 2 O 3 , ZnO, ZrO 2 , and the like, including mixed oxides thereof, and combinations thereof. For example, the solid oxide that can be used to prepare the additional chemically-treated solid oxide can be silica, alumina, silica-alumina, aluminum phosphate, heteropolytungstates, titania, zirconia, magnesia, boria, zinc oxide, mixed oxides thereof, or any combination thereof. As noted above, if the solid oxide is a silica-alumina, this material is distinguished from the alumina-silica solid oxides of the present invention, which have high alumina content. These known silica-alumina materials having an alumina to silica weight ratio of less than 1:1 can be used to form an additional activator-support. For example, the weight ratio of alumina to silica in these known silica-alumina materials is often in a range from about 0.05:1 to about 0.25:1, as reflected in Example 1. Such silica-alumina materials having a weight ratio of alumina to silica of less than 1:1 are not the inventive activator-supports of this invention. However, these silica-alumina materials can optionally be used in combination with (i.e., in addition to) the high alumina content alumina-silica activator-supports of the present invention. 
     Solid oxides of this invention, which can be used to prepare additional chemically-treated solid oxides, encompass oxide materials such as alumina, “mixed oxide” compounds thereof such as silica-alumina, and combinations and mixtures thereof. The mixed oxide compounds such as silica-alumina can be single or multiple chemical phases with more than one metal combined with oxygen to form a solid oxide compound. Examples of mixed oxides that can be used in the additional activator-support of the present invention include, but are not limited to, silica-alumina, silica-titania, silica-zirconia, zeolites, various clay minerals, alumina-titania, alumina-zirconia, zinc-aluminate, and the like. 
     The electron-withdrawing component used to treat the solid oxide can be any component that increases the Lewis or Brønsted acidity of the solid oxide upon treatment (as compared to the solid oxide that is not treated with at least one electron-withdrawing anion). According to one aspect of the present invention, the electron-withdrawing component is an electron-withdrawing anion derived from a salt, an acid, or other compound, such as a volatile organic compound, that serves as a source or precursor for that anion. Examples of electron-withdrawing anions include, but are not limited to, sulfate, bisulfate, fluoride, chloride, bromide, iodide, fluorosulfate, fluoroborate, phosphate, fluorophosphate, trifluoroacetate, triflate, fluorozirconate, fluorotitanate, trifluoroacetate, triflate, and the like, including mixtures and combinations thereof. In addition, other ionic or non-ionic compounds that serve as sources for these electron-withdrawing anions also can be employed in the present invention. 
     Thus, for example, the additional chemically-treated solid oxide optionally used in the catalyst compositions of the present can be fluorided alumina, chlorided alumina, bromided alumina, sulfated alumina, fluorided silica-alumina, chlorided silica-alumina, bromided silica-alumina, sulfated silica-alumina, fluorided silica-zirconia, chlorided silica-zirconia, bromided silica-zirconia, sulfated silica-zirconia, and the like, or combinations thereof. Again, in this context, if the additional activator-support or additional chemically-treated solid oxide comprises a silica-alumina, this optional treated silica-alumina is not the high alumina content alumina-silica of the present invention. These known silica-alumina materials have an alumina to silica weight ratio of less than 1:1 such as, for example, in a range from about 0.05:1 to about 0.25:1. 
     When the electron-withdrawing component comprises a salt of an electron-withdrawing anion, the counterion or cation of that salt can be selected from any cation that allows the salt to revert or decompose back to the acid during calcining. Factors that dictate the suitability of the particular salt to serve as a source for the electron-withdrawing anion include, but are not limited to, the solubility of the salt in the desired solvent, the lack of adverse reactivity of the cation, ion-pairing effects between the cation and anion, hygroscopic properties imparted to the salt by the cation, and the like, and thermal stability of the anion. Examples of suitable cations in the salt of the electron-withdrawing anion include, but are not limited to, ammonium, trialkyl ammonium, tetraalkyl ammonium, tetraalkyl phosphonium, H + , [H(OEt 2 ) 2 ] + , and the like. 
     Further, combinations of one or more different electron-withdrawing anions, in varying proportions, can be used to tailor the specific acidity of the activator-support to the desired level. Combinations of electron-withdrawing components can be contacted with the oxide material simultaneously or individually, and in any order that affords the desired chemically-treated solid oxide acidity. For example, one aspect of this invention is employing two or more electron-withdrawing anion source compounds in two or more separate contacting steps. 
     Thus, one example of such a process by which a chemically-treated solid oxide is prepared is as follows: a selected solid oxide compound, or combination of oxide compounds, is contacted with a first electron-withdrawing anion source compound to form a first mixture; this first mixture is calcined and then contacted with a second electron-withdrawing anion source compound to form a second mixture; the second mixture is then calcined to form a treated solid oxide compound. In such a process, the first and second electron-withdrawing anion source compounds are either the same or different compounds. 
     According to another aspect of the present invention, the additional chemically-treated solid oxide comprises a solid inorganic oxide material, a mixed oxide material, or a combination of inorganic oxide materials, that is chemically-treated with an electron-withdrawing component, and optionally treated with a metal source, including metal salts, metal ions, or other metal-containing compounds. Non-limiting examples of the metal or metal ion include zinc, nickel, vanadium, titanium, silver, copper, gallium, tin, tungsten, molybdenum, and the like, or combinations thereof. Examples of additional chemically-treated solid oxides that contain a metal or metal ion include, but are not limited to, zinc-impregnated chlorided alumina, titanium-impregnated fluorided alumina, zinc-impregnated fluorided alumina, zinc-impregnated chlorided silica-alumina, zinc-impregnated fluorided silica-alumina, zinc-impregnated sulfated alumina, chlorided zinc aluminate, fluorided zinc aluminate, sulfated zinc aluminate, and the like, or any combination thereof. 
     Any method of impregnating the solid oxide material with a metal can be used. The method by which the oxide is contacted with a metal source, typically a salt or metal-containing compound, can include, but is not limited to, gelling, co-gelling, impregnation of one compound onto another, and the like. If desired, the metal-containing compound is added to or impregnated into the solid oxide in solution form, and subsequently converted into the supported metal upon calcining. Accordingly, the solid inorganic oxide can further comprise a metal selected from zinc, titanium, nickel, vanadium, silver, copper, gallium, tin, tungsten, molybdenum, and the like, or combinations of these metals. For example, zinc is often used to impregnate the solid oxide because it can provide improved catalyst activity at a low cost. 
     The solid oxide can be treated with metal salts or metal-containing compounds before, after, or at the same time that the solid oxide is treated with the electron-withdrawing anion. Following any contacting method, the contacted mixture of oxide compound, electron-withdrawing anion, and the metal ion is typically calcined. Alternatively, a solid oxide material, an electron-withdrawing anion source, and the metal salt or metal-containing compound are contacted and calcined simultaneously. 
     Various processes are used to form chemically-treated solid oxides useful in the present invention. The chemically-treated solid oxide can comprise the contact product of at least one solid oxide compound and at least one electron-withdrawing anion source. It is not required that the solid oxide compound be calcined prior to contacting the electron-withdrawing anion source. The contact product typically is calcined either during or after the solid oxide compound is contacted with the electron-withdrawing anion source. The solid oxide compound can be calcined or uncalcined. Various processes to prepare solid oxide activator-supports that can be employed in this invention have been reported. For example, such methods are described in U.S. Pat. Nos. 6,107,230, 6,165,929, 6,294,494, 6,300,271, 6,316,553, 6,355,594, 6,376,415, 6,388,017, 6,391,816, 6,395,666, 6,524,987, 6,548,441, 6,548,442, 6,576,583, 6,613,712, 6,632,894, 6,667,274, and 6,750,302, the disclosures of which are incorporated herein by reference in their entirety. 
     According to one aspect of the present invention, the solid oxide material is chemically-treated by contacting it with at least one electron-withdrawing component, typically an electron-withdrawing anion source. Further, the solid oxide material optionally is chemically treated with a metal ion, and then calcined to form a metal-containing or metal-impregnated chemically-treated solid oxide. According to another aspect of the present invention, the solid oxide material and electron-withdrawing anion source are contacted and calcined simultaneously. 
     The method by which the oxide is contacted with the electron-withdrawing component, typically a salt or an acid of an electron-withdrawing anion, can include, but is not limited to, gelling, co-gelling, impregnation of one compound onto another, and the like. Thus, following any contacting method, the contacted mixture of the solid oxide, electron-withdrawing anion, and optional metal ion, is calcined. 
     The solid oxide activator-support (i.e., chemically-treated solid oxide), whether the inventive activator-supports of this invention or optional, additional activator-supports, thus can be produced by a process comprising: 
     1) contacting a solid oxide compound with at least one electron-withdrawing anion source compound to form a first mixture; and 
     2) calcining the first mixture to form the solid oxide activator-support. 
     According to another aspect of the present invention, the solid oxide activator-support (chemically-treated solid oxide) is produced by a process comprising: 
     1) contacting at least one solid oxide compound with a first electron-withdrawing anion source compound to form a first mixture; 
     2) calcining the first mixture to produce a calcined first mixture; 
     3) contacting the calcined first mixture with a second electron-withdrawing anion source compound to form a second mixture; and 
     4) calcining the second mixture to form the solid oxide activator-support. 
     According to yet another aspect of the present invention, the chemically-treated solid oxide is produced or formed by contacting the solid oxide with the electron-withdrawing anion source compound, where the solid oxide compound is calcined before, during, or after contacting the electron-withdrawing anion source, and where there is a substantial absence of aluminoxanes, organoboron or organoborate compounds, and ionizing ionic compounds. 
     Calcining of the treated solid oxide generally is conducted in an ambient atmosphere, typically in a dry ambient atmosphere, at a temperature from about 300° C. to about 900° C., and for a time of about 1 minute to about 30 hours. Calcining can be conducted at a temperature from about 400° C. to about 800° C., or alternatively, at a temperature from about 500° C. to about 700° C. Calcining can be conducted for about 30 minutes to about 20 hours, or for about 1 hour to about 15 hours. Thus, for example, calcining can be carried out for about 3 to about 10 hours at a temperature from about 450° C. to about 650° C. Any suitable ambient atmosphere can be employed during calcining. Generally, calcining is conducted in an oxidizing atmosphere, such as air or oxygen. Alternatively, an inert atmosphere, such as nitrogen or argon, or a reducing atmosphere, such as hydrogen or carbon monoxide, can be used. 
     According to one aspect of the present invention, the solid oxide material is treated with a source of halide ion, sulfate ion, or a combination of anions, optionally treated with a metal ion, and then calcined to provide the chemically-treated solid oxide in the form of a particulate solid. For example, the solid oxide material is treated with a source of sulfate (termed a “sulfating agent”), a source of chloride ion (termed a “chloriding agent”), a source of fluoride ion (termed a “fluoriding agent”), or a combination thereof, and calcined to provide the solid oxide activator. Exemplary additional, or optional, activator-supports that can be employed in catalyst compositions of the present invention include, but are not limited to, bromided alumina, chlorided alumina, fluorided alumina, sulfated alumina, bromided silica-alumina, chlorided silica-alumina, fluorided silica-alumina, sulfated silica-alumina, bromided silica-zirconia, chlorided silica-zirconia, fluorided silica-zirconia, sulfated silica-zirconia; a pillared clay, such as a pillared montmorillonite, optionally treated with fluoride, chloride, or sulfate; phosphated alumina or other aluminophosphates optionally treated with sulfate, fluoride, or chloride; or any combination of the above. Further, any of these activator-supports optionally can be treated with a metal ion. 
     A chemically-treated solid oxide can comprise a fluorided solid oxide in the form of a particulate solid. The fluorided solid oxide can be formed by contacting a solid oxide with a fluoriding agent. The fluoride ion can be added to the oxide by forming a slurry of the oxide in a suitable organic or aqueous solvent, such as alcohol or water including, but not limited to, the one to three carbon alcohols because of their volatility and low surface tension. Examples of suitable fluoriding agents include, but are not limited to, hydrofluoric acid (HF), ammonium fluoride (NH 4 F), ammonium bifluoride (NH 4 HF 2 ), ammonium tetrafluoroborate (NH 4 BF 4 ), ammonium silicofluoride (hexafluorosilicate) ((NH 4 ) 2 SiF 6 ), ammonium hexafluorophosphate (NH 4  PF 6 ), analogs thereof, and combinations thereof. Triflic acid and ammonium triflate can also be employed. For example, ammonium bifluoride (NH 4 HF 2 ) can be used as the fluoriding agent, due to its ease of use and availability. 
     If desired, the solid oxide is treated with a fluoriding agent during the calcining step. Any fluoriding agent capable of thoroughly contacting the solid oxide during the calcining step can be used. For example, in addition to those fluoriding agents described previously, volatile organic fluoriding agents can be used. Examples of volatile organic fluoriding agents useful in this aspect of the invention include, but are not limited to, freons, perfluorohexane, perfluorobenzene, fluoromethane, trifluoroethanol, an the like, and combinations thereof. Calcining temperatures generally must be high enough to decompose the compound and release fluoride. Gaseous hydrogen fluoride (HF) or fluorine (F 2 ) itself also can be used with the solid oxide if fluorided while calcining. Silicon tetrafluoride (SiF 4 ) and compounds containing tetrafluoroborate (BF 4 —) can also be employed. One convenient method of contacting the solid oxide with the fluoriding agent is to vaporize a fluoriding agent into a gas stream used to fluidize the solid oxide during calcination. 
     Similarly, in another aspect of this invention, the chemically-treated solid oxide comprises a chlorided solid oxide in the form of a particulate solid. The chlorided solid oxide is formed by contacting a solid oxide with a chloriding agent. The chloride ion can be added to the oxide by forming a slurry of the oxide in a suitable solvent. The solid oxide can be treated with a chloriding agent during the calcining step. Any chloriding agent capable of serving as a source of chloride and thoroughly contacting the oxide during the calcining step can be used. For example, volatile organic chloriding agents can be used. Examples of suitable volatile organic chloriding agents include, but are not limited to, certain freons, perchlorobenzene, chloromethane, dichloromethane, chloroform, carbon tetrachloride, trichloroethanol, and the like, or any combination thereof. Gaseous hydrogen chloride or chlorine itself also can be used with the solid oxide during calcining. One convenient method of contacting the oxide with the chloriding agent is to vaporize a chloriding agent into a gas stream used to fluidize the solid oxide while calcination. 
     The amount of fluoride or chloride ion present before calcining the solid oxide generally is from about 1 to about 50% by weight, where weight percent is based on the weight of the solid oxide, for example, silica-alumina, before calcining. According to another aspect of this invention, the amount of fluoride or chloride ion present before calcining the solid oxide is from about 1 to about 25% by weight, from about 2 to about 15%, or from about 3% to about 12% by weight. According to yet another aspect of this invention, the amount of fluoride or chloride ion present before calcining the solid oxide is from about 5 to about 10% by weight. Once impregnated with halide, the halided oxide can be dried by any suitable method including, but not limited to, suction filtration followed by evaporation, drying under vacuum, spray drying, and the like, although it is also possible to initiate the calcining step immediately without drying the impregnated solid oxide. 
     The pore volume and surface area of high alumina content alumina-silica compounds were discussed in the preceding section. Silica-aluminas (having an alumina to silica weight ratio of less than 1:1) used to prepare the additional or optional treated silica-alumina typically have a pore volume greater than about 0.5 mL/g. According to one aspect of the present invention, the pore volume is greater than about 0.8 mL/g, and according to another aspect of the present invention, greater than about 1 mL/g. Further, the silica-alumina used to prepare the additional chemically-treated silica-alumina generally has a surface area greater than about 100 m 2 /g. According to another aspect of this invention, the surface area is greater than about 250 m 2 /g. Yet, in another aspect, the surface area is greater than about 350 m 2 /g. 
     According to yet another aspect of this invention, the solid oxide component comprises alumina without silica, and according to another aspect of this invention, the solid oxide component comprises silica without alumina. 
     The sulfated solid oxide comprises sulfate and a solid oxide component, such as alumina or silica-alumina, in the form of a particulate solid. Optionally, the sulfated oxide is treated further with a metal ion such that the calcined sulfated oxide comprises a metal. According to one aspect of the present invention, the sulfated solid oxide comprises sulfate and alumina. In some instances, the sulfated alumina is formed by a process wherein the alumina is treated with a sulfate source, for example, sulfuric acid or a sulfate salt such as ammonium sulfate. This process is generally performed by forming a slurry of the alumina in a suitable solvent, such as alcohol or water, in which the desired concentration of the sulfating agent has been added. Suitable organic solvents include, but are not limited to, the one to three carbon alcohols because of their volatility and low surface tension. 
     According to one aspect of this invention, the amount of sulfate ion present before calcining is from about 0.5 parts by weight to about 100 parts by weight sulfate ion to about 100 parts by weight solid oxide. According to another aspect of this invention, the amount of sulfate ion present before calcining is from about 1 part by weight to about 50 parts by weight sulfate ion to about 100 parts by weight solid oxide, and according to still another aspect of this invention, from about 5 parts by weight to about 30 parts by weight sulfate ion to about 100 parts by weight solid oxide. These weight ratios are based on the weight of the solid oxide before calcining. Once impregnated with sulfate, the sulfated oxide can be dried by any suitable method including, but not limited to, suction filtration followed by evaporation, drying under vacuum, spray drying, and the like, although it is also possible to initiate the calcining step immediately. 
     According to another aspect of the present invention, the catalyst composition further comprises an ion-exchangeable activator-support, including but not limited to silicate and aluminosilicate compounds or minerals, either with layered or non-layered structures, and combinations thereof. In another aspect of this invention, ion-exchangeable, layered aluminosilicates such as pillared clays are used as optional activator-supports. The ion-exchangeable activator-support optionally can be treated with at least one electron-withdrawing anion such as those disclosed herein, though typically the ion-exchangeable activator-support is not treated with an electron-withdrawing anion. 
     According to another aspect of the present invention, the catalyst composition further comprises clay minerals having exchangeable cations and layers capable of expanding. Typical clay mineral activator-supports include, but are not limited to, ion-exchangeable, layered aluminosilicates such as pillared clays. Although the term “support” is used, it is not meant to be construed as an inert component of the catalyst composition, but rather is to be considered an active part of the catalyst composition, because of its intimate association with the metallocene component. 
     According to another aspect of the present invention, the clay materials of this invention encompass materials either in their natural state or that have been treated with various ions by wetting, ion exchange, or pillaring. Typically, the clay material activator-support of this invention comprises clays that have been ion exchanged with large cations, including polynuclear, highly charged metal complex cations. However, the clay material activator-supports of this invention also encompass clays that have been ion exchanged with simple salts, including, but not limited to, salts of Al(III), Fe(II), Fe(III) and Zn(II) with ligands such as halide, acetate, sulfate, nitrate, or nitrite. 
     According to another aspect of the present invention, the additional activator-support comprises a pillared clay. The term “pillared clay” is used to refer to clay materials that have been ion exchanged with large, typically polynuclear, highly charged metal complex cations. Examples of such ions include, but are not limited to, Keggin ions which can have charges such as 7+, various polyoxometallates, and other large ions. Thus, the term pillaring refers to a simple exchange reaction in which the exchangeable cations of a clay material are replaced with large, highly charged ions, such as Keggin ions. These polymeric cations are then immobilized within the interlayers of the clay and when calcined are converted to metal oxide “pillars,” effectively supporting the clay layers as column-like structures. Thus, once the clay is dried and calcined to produce the supporting pillars between clay layers, the expanded lattice structure is maintained and the porosity is enhanced. The resulting pores can vary in shape and size as a function of the pillaring material and the parent clay material used. Examples of pillaring and pillared clays are found in: T. J. Pinnavaia, Science 220 (4595), 365-371 (1983); J. M. Thomas, Intercalation Chemistry, (S. Whittington and A. Jacobson, eds.) Ch. 3, pp. 55-99, Academic Press, Inc., (1972); U.S. Pat. No. 4,452,910; U.S. Pat. No. 5,376,611; and U.S. Pat. No. 4,060,480; the disclosures of which are incorporated herein by reference in their entirety. 
     The pillaring process utilizes clay minerals having exchangeable cations and layers capable of expanding. Any pillared clay that can enhance the polymerization of olefins in the catalyst composition of the present invention can be used. Therefore, suitable clay minerals for pillaring include, but are not limited to, allophanes; smectites, both dioctahedral (Al) and tri-octahedral (Mg) and derivatives thereof such as montmorillonites (bentonites), nontronites, hectorites, or laponites; halloysites; vermiculites; micas; fluoromicas; chlorites; mixed-layer clays; the fibrous clays including but not limited to sepiolites, attapulgites, and palygorskites; a serpentine clay; illite; laponite; saponite; and any combination thereof. In one aspect, the pillared clay activator-support comprises bentonite or montmorillonite. The principal component of bentonite is montmorillonite. 
     The pillared clay can be pretreated if desired. For example, a pillared bentonite is pretreated by drying at about 300° C. under an inert atmosphere, typically dry nitrogen, for about 3 hours, before being added to the polymerization reactor. Although an exemplary pretreatment is described herein, it should be understood that the preheating can be carried out at many other temperatures and times, including any combination of temperature and time steps, all of which are encompassed by this invention. 
     The activator-supports used to prepare the catalyst compositions of the present invention can be combined with other inorganic support materials, including, but not limited to, zeolites, inorganic oxides, phosphated inorganic oxides, and the like. In one aspect, typical support materials that are used include, but are not limited to, silica, silica-alumina, alumina, titania, zirconia, magnesia, boria, thoria, aluminophosphate, aluminum phosphate, silica-titania, coprecipitated silica/titania, mixtures thereof, or any combination thereof. 
     According to yet another aspect of the present invention, one or more of the metallocene compounds can be precontacted with an olefin monomer and an organoaluminum compound for a first period of time prior to contacting this mixture with the activator-support. Once the precontacted mixture of the metallocene compound(s), olefin monomer, and organoaluminum compound is contacted with the activator-support, the composition further comprising the activator-support is termed the “postcontacted” mixture. The postcontacted mixture can be allowed to remain in further contact for a second period of time prior to being charged into the reactor in which the polymerization process will be carried out. 
     Metallocene Compounds 
     The activator-supports of the present invention can be employed in a catalyst composition with one or more metallocene compounds. Generally, there is no limitation on the selection of the metallocene compound that can be used in combination with the alumina-silica activator-supports of the present invention. Often, the transition metal employed is Ti, Zr, or Hf. Some examples of suitable bridged metallocene compounds include, but are not limited to: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     and the like. Applicants have used the abbreviations Ph for phenyl, Me for methyl, and t-Bu for tert-butyl. 
     The following representative bridged metallocene compounds can be employed in catalyst compositions of the present invention: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     and the like. 
     Additional examples of metallocene compounds that are suitable for use in catalyst compositions of the present invention are contemplated. These include, but are not limited to: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     and the like. 
     The following non-limiting examples of two-carbon bridged metallocene compounds also can be used in catalyst compositions of the present invention: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     and the like. The integer n′ in these metallocene compounds generally ranges from 0 to about 10, inclusive. For example, n′ can be 1, 2, 3, 4, 5, 6, 7, or 8. 
     Additional bridged metallocene compounds can be employed in catalyst compositions of the present invention. Therefore, the scope of the present invention is not limited to the bridged metallocene species provided above. 
     Likewise, unbridged metallocene compounds can be used in accordance with the present invention. Such compounds include, but are not limited to: 
     
       
         
         
             
             
         
       
     
     and the like. 
     Other suitable unbridged metallocene compounds include, but are not limited, to the following: 
     
       
         
         
             
             
         
       
     
     and the like. 
     Additional unbridged metallocene compounds can be employed in catalyst compositions of the present invention. Therefore, the scope of the present invention is not limited to the unbridged metallocene species provided above. Other metallocene compounds, including half-sandwich and cyclodienyl compounds, are suitable for use in catalyst compositions of the present invention, and such compounds include, but are not limited to, the following: 
     
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
     
     and the like, wherein i-Pr is an abbreviation for isopropyl. 
     Organoaluminum Compounds 
     In one aspect, organoaluminum compounds that can be used with the present invention include, but are not limited to, compounds having the formula: 
       (R 2 ) 3 A; 
     where R 2  is an aliphatic group having from 2 to 6 carbon atoms. For example, R 2  can be ethyl, propyl, butyl, hexyl, or isobutyl, and the like. 
     Other organoaluminum compounds which can be used in accordance with the present invention include, but are not limited to, compounds having the formula: 
       Al(X 5 ) m (X 6 ) 3-m , 
     where X 5  is a hydrocarbyl; X 6  is an alkoxide or an aryloxide, a halide, or a hydride; and m is from 1 to 3, inclusive. 
     In one aspect, X 5  is a hydrocarbyl having from 1 to about 20 carbon atoms. In another aspect of the present invention, X 5  is an alkyl having from 1 to 10 carbon atoms. For example, X 5  can be ethyl, propyl, n-butyl, sec-butyl, isobutyl, or hexyl, and the like, in yet another aspect of the present invention. 
     According to one aspect of the present invention, X 6  is an alkoxide or an aryloxide, any one of which has from 1 to 20 carbon atoms, a halide, or a hydride. In another aspect of the present invention, X 6  is selected independently from fluorine or chlorine. Yet, in another aspect, X 6  is chlorine. 
     In the formula, Al(X 5 ) m (X 6 ) 3-m , m is a number from 1 to 3, inclusive, and typically, m is 3. The value of m is not restricted to be an integer; therefore, this formula includes sesquihalide compounds or other organoaluminum cluster compounds. 
     Examples of organoaluminum compounds suitable for use in accordance with the present invention include, but are not limited to, trialkylaluminum compounds, dialkylaluminum halide compounds, dialkylaluminum alkoxide compounds, dialkylaluminum hydride compounds, and combinations thereof. Specific non-limiting examples of suitable organoaluminum compounds include trimethylaluminum (TMA), triethylaluminum (TEA), tripropylaluminum, diethylaluminum ethoxide, tributylaluminum, diisobutylaluminum hydride, triisobutylaluminum (TIBA), diethylaluminum chloride, and the like, or combinations thereof. 
     The present invention contemplates precontacting at least one metallocene compound with at least one organoaluminum compound and an olefin monomer to form a precontacted mixture, prior to contacting this precontacted mixture with an activator-support to form a catalyst composition. When the catalyst composition is prepared in this manner, typically, though not necessarily, a portion of the organoaluminum compound is added to the precontacted mixture and another portion of the organoaluminum compound is added to the postcontacted mixture prepared when the precontacted mixture is contacted with the solid oxide activator-support. However, the entire organoaluminum compound can be used to prepare the catalyst composition in either the precontacting or postcontacting step. Alternatively, all the catalyst components are contacted in a single step. 
     Further, more than one organoaluminum compound can be used in either the precontacting or the postcontacting step. When an organoaluminum compound is added in multiple steps, the amounts of organoaluminum compound disclosed herein include the total amount of organoaluminum compound used in both the precontacted and postcontacted mixtures, and any additional organoaluminum compound added to the polymerization reactor. Therefore, total amounts of organoaluminum compounds are disclosed regardless of whether a single organoaluminum compound or more than one organoaluminum compound is used. 
     Aluminoxane Compounds 
     The present invention further provides a catalyst composition which can comprise an aluminoxane compound. As used herein, the term “aluminoxane” refers to aluminoxane compounds, compositions, mixtures, or discrete species, regardless of how such aluminoxanes are prepared, formed or otherwise provided. For example, a catalyst composition comprising an aluminoxane compound can be prepared in which aluminoxane is provided as the poly(hydrocarbyl aluminum oxide), or in which aluminoxane is provided as the combination of an aluminum alkyl compound and a source of active protons such as water. Aluminoxanes are also referred to as poly(hydrocarbyl aluminum oxides) or organoaluminoxanes. 
     The other catalyst components typically are contacted with the aluminoxane in a saturated hydrocarbon compound solvent, though any solvent that is substantially inert to the reactants, intermediates, and products of the activation step can be used. The catalyst composition formed in this manner is collected by any suitable method, for example, by filtration. Alternatively, the catalyst composition is introduced into the polymerization reactor without being isolated. 
     The aluminoxane compound of this invention can be an oligomeric aluminum compound comprising linear structures, cyclic structures, or cage structures, or mixtures of all three. Cyclic aluminoxane compounds having the formula: 
     
       
         
         
             
             
         
       
     
     wherein R is a linear or branched alkyl having from 1 to 10 carbon atoms, and p is an integer from 3 to 20, are encompassed by this invention. The AlRO moiety shown here also constitutes the repeating unit in a linear aluminoxane. Thus, linear aluminoxanes having the formula: 
     
       
         
         
             
             
         
       
     
     wherein R is a linear or branched alkyl having from 1 to 10 carbon atoms, and q is an integer from 1 to 50, are also encompassed by this invention. 
     Further, aluminoxanes can have cage structures of the formula R t   5r+α R b   r−α Al 4r O 3r , wherein R t  is a terminal linear or branched alkyl group having from 1 to 10 carbon atoms; R b  is a bridging linear or branched alkyl group having from 1 to 10 carbon atoms; r is 3 or 4; and α is equal to n Al(3) −n O(2) +n O(4) , wherein n Al(3)  is the number of three coordinate aluminum atoms, n O(2)  is the number of two coordinate oxygen atoms, and n O(4)  is the number of 4 coordinate oxygen atoms. 
     Thus, aluminoxanes which can be employed in the catalyst compositions of the present invention are represented generally by formulas such as (R—Al—O) p , R(R—Al—O) q AlR 2 , and the like. In these formulas, the R group is typically a linear or branched C 1 -C 6  alkyl, such as methyl, ethyl, propyl, butyl, pentyl, or hexyl. Examples of aluminoxane compounds that can be used in accordance with the present invention include, but are not limited to, methylaluminoxane, ethylaluminoxane, n-propylaluminoxane, iso-propylaluminoxane, n-butylaluminoxane, t-butyl-aluminoxane, sec-butylaluminoxane, iso-butylaluminoxane, 1-pentylaluminoxane, 2-pentylaluminoxane, 3-pentylaluminoxane, isopentylaluminoxane, neopentylaluminoxane, and the like, or any combination thereof. Methylaluminoxane, ethylaluminoxane, and iso-butylaluminoxane are prepared from trimethylaluminum, triethylaluminum, or triisobutylaluminum, respectively, and sometimes are referred to as poly(methyl aluminum oxide), poly(ethyl aluminum oxide), and poly(isobutyl aluminum oxide), respectively. It is also within the scope of the invention to use an aluminoxane in combination with a trialkylaluminum, such as that disclosed in U.S. Pat. No. 4,794,096, incorporated herein by reference in its entirety. 
     The present invention contemplates many values of p and q in the aluminoxane formulas (R—Al—O) p  and R(R—Al—O) q AlR 2 , respectively. Is some aspects, p and q are at least 3. However, depending upon how the organoaluminoxane is prepared, stored, and used, the value of p and q can vary within a single sample of aluminoxane, and such combinations of organoaluminoxanes are contemplated herein. 
     In preparing a catalyst composition containing an aluminoxane, the molar ratio of the total moles of aluminum in the aluminoxane (or aluminoxanes) to the total moles of metallocene compound (or compounds) in the composition is generally between about 1:10 and about 100,000:1. In another aspect, the molar ratio is in a range from about 5:1 to about 15,000:1. Optionally, aluminoxane can be added to a polymerization zone in ranges from about 0.01 mg/L to about 1000 mg/L, from about 0.1 mg/L to about 100 mg/L, or from about 1 mg/L to about 50 mg/L. 
     Organoaluminoxanes can be prepared by various procedures. Examples of organoaluminoxane preparations are disclosed in U.S. Pat. Nos. 3,242,099 and 4,808,561, the disclosures of which are incorporated herein by reference in their entirety. For example, water in an inert organic solvent can be reacted with an aluminum alkyl compound, such as (R 2 ) 3 Al, to form the desired organoaluminoxane compound. While not intending to be bound by this statement, it is believed that this synthetic method can afford a mixture of both linear and cyclic R—Al—O aluminoxane species, both of which are encompassed by this invention. Alternatively, organoaluminoxanes are prepared by reacting an aluminum alkyl compound, such as (R 2 ) 3 Al with a hydrated salt, such as hydrated copper sulfate, in an inert organic solvent. 
     Organoboron/Organoborate Compounds 
     According to another aspect of the present invention, a catalyst composition comprising organoboron or organoborate compounds is provided. Such compounds include neutral boron compounds, borate salts, and the like, or combinations thereof. For example, fluoroorgano boron compounds and fluoroorgano borate compounds are contemplated. 
     Any fluoroorgano boron or fluoroorgano borate compound can be utilized with the present invention. Examples of fluoroorgano borate compounds that can be used in the present invention include, but are not limited to, fluorinated aryl borates such as N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, triphenylcarbenium tetrakis(pentafluorophenyl)borate, lithium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, triphenylcarbenium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, and the like, or mixtures thereof. Examples of fluoroorgano boron compounds that can be used as co-catalysts in the present invention include, but are not limited to, tris(pentafluorophenyl)boron, tris[3,5-bis(trifluoromethyl)phenyl]boron, and the like, or mixtures thereof. Although not intending to be bound by the following theory, these examples of fluoroorgano borate and fluoroorgano boron compounds, and related compounds, are thought to form “weakly-coordinating” anions when combined with organometal or metallocene compounds, as disclosed in U.S. Pat. No. 5,919,983, the disclosure of which is incorporated herein by reference in its entirety. Applicants also contemplate the use of diboron, or bis-boron, compounds or other bifunctional compounds containing two or more boron atoms in the chemical structure, such as disclosed in J. Am. Chem. Soc., 2005, 127, pp. 14756-14768, the content of which is incorporated herein by reference in its entirety. 
     Generally, any amount of organoboron compound can be used. According to one aspect of this invention, the molar ratio of the total moles of organoboron or organoborate compound (or compounds) to the total moles of metallocene compound (or compounds) in the catalyst composition is in a range from about 0.1:1 to about 15:1. Typically, the amount of the fluoroorgano boron or fluoroorgano borate compound used as a co-catalyst for the metallocene is from about 0.5 moles to about 10 moles of boron/borate compound per mole of metallocene compound. According to another aspect of this invention, the amount of fluoroorgano boron or fluoroorgano borate compound is from about 0.8 moles to about 5 moles of boron/borate compound per mole of metallocene compound. 
     Ionizing Ionic Compounds 
     The present invention provides a catalyst composition which can further comprise an ionizing ionic compound. An ionizing ionic compound is an ionic compound that can function as a co-catalyst to enhance the activity of the catalyst composition. While not intending to be bound by theory, it is believed that the ionizing ionic compound is capable of reacting with a metallocene compound and converting the metallocene into one or more cationic metallocene compounds, or incipient cationic metallocene compounds. Again, while not intending to be bound by theory, it is believed that the ionizing ionic compound can function as an ionizing compound by completely or partially extracting an anionic ligand, possibly a non-alkadienyl ligand from the metallocene. However, the ionizing ionic compound is an activator regardless of whether it is ionizes the metallocene, abstracts a ligand in a fashion as to form an ion pair, weakens the metal-ligand bond in the metallocene, simply coordinates to a ligand, or activates the metallocene by some other mechanism. 
     Further, it is not necessary that the ionizing ionic compound activate the metallocene compounds only. The activation function of the ionizing ionic compound can be evident in the enhanced activity of catalyst composition as a whole, as compared to a catalyst composition that does not contain an ionizing ionic compound. 
     Examples of ionizing ionic compounds include, but are not limited to, the following compounds: tri(n-butyl)ammonium tetrakis(p-tolyl)borate, tri(n-butyl) ammonium tetrakis(m-tolyl)borate, tri(n-butyl)ammonium tetrakis(2,4-dimethylphenyl)borate, tri(n-butyl)ammonium tetrakis(3,5-dimethylphenyl)borate, tri(n-butyl)ammonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tri(n-butyl)ammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetrakis(p-tolyl)borate, N,N-dimethylanilinium tetrakis(m-tolyl)borate, N,N-dimethylanilinium tetrakis(2,4-dimethylphenyl)borate, N,N-dimethylanilinium tetrakis(3,5-dimethylphenyl)borate, N,N-dimethylanilinium tetrakis[3,5-bis(trifluoro-methyl)phenyl]borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, triphenylcarbenium tetrakis(p-tolyl)borate, triphenylcarbenium tetrakis(m-tolyl)borate, triphenylcarbenium tetrakis(2,4-dimethylphenyl)borate, triphenylcarbenium tetrakis(3,5-dimethylphenyl)borate, triphenylcarbenium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, triphenylcarbenium tetrakis(pentafluorophenyl)borate, tropylium tetrakis(p-tolyl)borate, tropylium tetrakis(m-tolyl)borate, tropylium tetrakis(2,4-dimethylphenyl)borate, tropylium tetrakis(3,5-dimethylphenyl)borate, tropylium tetrakis[3,5-bis(trifluoro-methyl)phenyl]borate, tropylium tetrakis(pentafluorophenyl)borate, lithium tetrakis(pentafluorophenyl)borate, lithium tetraphenylborate, lithium tetrakis(p-tolyl)borate, lithium tetrakis(m-tolyl)borate, lithium tetrakis(2,4-dimethylphenyl)borate, lithium tetrakis(3,5-dimethylphenyl)borate, lithium tetrafluoroborate, sodium tetrakis(pentafluorophenyl)borate, sodium tetraphenylborate, sodium tetrakis(p-tolyl)borate, sodium tetrakis(m-tolyl)borate, sodium tetrakis(2,4-dimethylphenyl)borate, sodium tetrakis(3,5-dimethylphenyl)borate, sodium tetrafluoroborate, potassium tetrakis-(pentafluorophenyl)borate, potassium tetraphenylborate, potassium tetrakis(p-tolyl)borate, potassium tetrakis(m-tolyl)borate, potassium tetrakis(2,4-dimethyl-phenyl)borate, potassium tetrakis(3,5-dimethylphenyl)borate, potassium tetrafluoro-borate, lithium tetrakis(pentafluorophenyl)aluminate, lithium tetraphenylaluminate, lithium tetrakis(p-tolyl)aluminate, lithium tetrakis(m-tolyl)aluminate, lithium tetrakis(2,4-dimethylphenyl)aluminate, lithium tetrakis(3,5-dimethylphenyl)aluminate, lithium tetrafluoroaluminate, sodium tetrakis(pentafluoro-phenyl)aluminate, sodium tetraphenylaluminate, sodium tetrakis(p-tolyl)aluminate, sodium tetrakis(m-tolyl)aluminate, sodium tetrakis(2,4-dimethylphenyl)aluminate, sodium tetrakis(3,5-dimethylphenyl)aluminate, sodium tetrafluoroaluminate, potassium tetrakis(pentafluorophenyl)aluminate, potassium tetraphenylaluminate, potassium tetrakis(p-tolyl)aluminate, potassium tetrakis(m-tolyl)aluminate, potassium tetrakis(2,4-dimethylphenyl)aluminate, potassium tetrakis (3,5-dimethylphenyl)aluminate, potassium tetrafluoroaluminate, and the like, or combinations thereof. Ionizing ionic compounds useful in this invention are not limited to these; other examples of ionizing ionic compounds are disclosed in U.S. Pat. Nos. 5,576,259 and 5,807,938, the disclosures of which are incorporated herein by reference in their entirety. 
     Olefin Monomers 
     Unsaturated reactants that can be employed with catalyst compositions and polymerization processes of this invention typically include olefin compounds having from about 2 to 30 carbon atoms per molecule and having at least one olefinic double bond. This invention encompasses homopolymerization processes using a single olefin such as ethylene or propylene, as well as copolymerization reactions with at least one different olefinic compound. The resulting copolymers generally contain a major amount of ethylene (&gt;50 mole percent) and a minor amount of comonomer (&lt;50 mole percent), though this is not a requirement. The comonomers that can be copolymerized with ethylene often have from 3 to 20 carbon atoms in their molecular chain. 
     Acyclic, cyclic, polycyclic, terminal (α), internal, linear, branched, substituted, unsubstituted, functionalized, and non-functionalized olefins can be employed in this invention. For example, typical unsaturated compounds that can be polymerized with the catalyst compositions of this invention include, but are not limited to, ethylene, propylene, 1-butene, 2-butene, 3-methyl-1-butene, isobutylene, 1-pentene, 2-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 2-hexene, 3-hexene, 3-ethyl-1-hexene, 1-heptene, 2-heptene, 3-heptene, the four normal octenes, the four normal nonenes, the five normal decenes, and the like, or mixtures of two or more of these compounds. Cyclic and bicyclic olefins, including but not limited to, cyclopentene, cyclohexene, norbornylene, norbornadiene, and the like, can also be polymerized as described above. Styrene can also be employed as a monomer. 
     When a copolymer is desired, the monomer can be, for example, ethylene or propylene, which is copolymerized with a comonomer. Examples of olefin comonomers include, but are not limited to, 1-butene, 2-butene, 3-methyl-1-butene, isobutylene, 1-pentene, 2-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 2-hexene, 3-ethyl-1-hexene, 1-heptene, 2-heptene, 3-heptene, 1-octene, and the like. According to one aspect of the present invention, the comonomer is selected from 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, or styrene. 
     Generally, the amount of comonomer introduced into a reactor zone to produce the copolymer is from about 0.01 to about 50 weight percent of the comonomer based on the total weight of the monomer and comonomer. According to another aspect of the present invention, the amount of comonomer introduced into a reactor zone is from about 0.01 to about 40 weight percent comonomer based on the total weight of the monomer and comonomer. In still another aspect, the amount of comonomer introduced into a reactor zone is from about 0.1 to about 35 weight percent comonomer based on the total weight of the monomer and comonomer. Yet, in another aspect, the amount of comonomer introduced into a reactor zone is from about 0.5 to about 20 weight percent comonomer based on the total weight of the monomer and comonomer. 
     While not intending to be bound by this theory, where branched, substituted, or functionalized olefins are used as reactants, it is believed that a steric hindrance can impede and/or slow the polymerization process. Thus, branched and/or cyclic portion(s) of the olefin removed somewhat from the carbon-carbon double bond would not be expected to hinder the reaction in the way that the same olefin substituents situated more proximate to the carbon-carbon double bond might. According to one aspect of the present invention, at least one monomer/reactant is ethylene, so the polymerizations are either a homopolymerization involving only ethylene, or copolymerizations with a different acyclic, cyclic, terminal, internal, linear, branched, substituted, or unsubstituted olefin. In addition, the catalyst compositions of this invention can be used in the polymerization of diolefin compounds including, but not limited to, 1,3-butadiene, isoprene, 1,4-pentadiene, and 1,5-hexadiene. 
     Preparation of the Catalyst Composition 
     In one aspect, the present invention encompasses a catalyst composition comprising a contact product of at least one metallocene compound and at least one activator-support. The at least one activator-support comprises at least one alumina-silica compound having a weight ratio of alumina to silica ranging from about 1:1 to about 100:1, which is treated with at least one electron-withdrawing anion. This catalyst composition can further comprise at least one organoaluminum compound. Additionally, this catalyst composition can further comprise at least one optional co-catalyst, wherein the at least one optional co-catalyst is at least one aluminoxane compound, at least one organozinc compound, at least one organoboron or organoborate compound, at least one ionizing ionic compound, or any combination thereof. 
     This invention further encompasses methods of making these catalyst compositions, such as, for example, contacting the respective catalyst components in any order or sequence. 
     The at least one metallocene compound can be precontacted with an olefinic monomer if desired, not necessarily the olefin monomer to be polymerized, and an organoaluminum compound for a first period of time prior to contacting this precontacted mixture with an activator-support. The first period of time for contact, the precontact time, between the metallocene compound or compounds, the olefinic monomer, and the organoaluminum compound typically ranges from a time period of about 0.1 hour to about 24 hours, for example, from about 0.1 to about 1 hour. Precontact times from about 10 minutes to about 30 minutes are also employed. 
     Alternatively, the precontacting process is carried out in multiple steps, rather than a single step, in which multiple mixtures are prepared, each comprising a different set of catalyst components. For example, at least two catalyst components are contacted forming a first mixture, followed by contacting the first mixture with at least one other catalyst component forming a second mixture, and so forth. 
     Multiple precontacting steps can be carried out in a single vessel or in multiple vessels. Further, multiple precontacting steps can be carried out in series (sequentially), in parallel, or a combination thereof. For example, a first mixture of two catalyst components can be formed in a first vessel, a second mixture comprising the first mixture plus one additional catalyst component can be formed in the first vessel or in a second vessel, which is typically placed downstream of the first vessel. 
     In another aspect, one or more of the catalyst components can be split and used in different precontacting treatments. For example, part of a catalyst component is fed into a first precontacting vessel for precontacting with at least one other catalyst component, while the remainder of that same catalyst component is fed into a second precontacting vessel for precontacting with at least one other catalyst component, or is fed directly into the reactor, or a combination thereof. The precontacting can be carried out in any suitable equipment, such as tanks, stirred mix tanks, various static mixing devices, a flask, a vessel of any type, or combinations of these apparatus. 
     In another aspect of this invention, the various catalyst components (for example, metallocene, activator-support, organoaluminum co-catalyst, and optionally an unsaturated hydrocarbon) are contacted in the polymerization reactor simultaneously while the polymerization reaction is proceeding. Alternatively, any two or more of these catalyst components can be precontacted in a vessel prior to entering the reaction zone. This precontacting step can be continuous, in which the precontacted product is fed continuously to the reactor, or it can be a stepwise or batchwise process in which a batch of precontacted product is added to make a catalyst composition. This precontacting step can be carried out over a time period that can range from a few seconds to as much as several days, or longer. In this aspect, the continuous precontacting step generally lasts from about 1 second to about 1 hour. In another aspect, the continuous precontacting step lasts from about 10 seconds to about 45 minutes, or from about 1 minute to about 30 minutes. 
     Once the precontacted mixture of the metallocene compound, olefin monomer, and organoaluminum co-catalyst is contacted with the activator-support, this composition (with the addition of the activator-support) is termed the “postcontacted mixture.” The postcontacted mixture optionally remains in contact for a second period of time, the postcontact time, prior to initiating the polymerization process. Postcontact times between the precontacted mixture and the activator-support generally range from about 0.1 hour to about 24 hours. In a further aspect, the postcontact time is in a range from about 0.1 hour to about 1 hour. The precontacting step, the postcontacting step, or both, can increase the productivity of the polymer as compared to the same catalyst composition that is prepared without precontacting or postcontacting. However, neither a precontacting step nor a postcontacting step is required. 
     The postcontacted mixture can be heated at a temperature and for a time period sufficient to allow adsorption, impregnation, or interaction of precontacted mixture and the activator-support, such that a portion of the components of the precontacted mixture is immobilized, adsorbed, or deposited thereon. Where heating is employed, the postcontacted mixture generally is heated to a temperature of from between about 0° F. to about 150° F., or from about 40° F. to about 95° F. 
     In another aspect, the metallocene, organoaluminum, and activator-support can be precontacted for a period of time prior to being contacted with the olefin to be polymerized in the reactor, as demonstrated in Example 6 that follows. 
     According to one aspect of this invention, the molar ratio of the moles of metallocene compound to the moles of organoaluminum compound in a catalyst composition generally is in a range from about 1:1 to about 1:10,000. In another aspect, the molar ratio is in a range from about 1:1 to about 1:1,000. Yet, in another aspect, the molar ratio of the moles of metallocene compound to the moles of organoaluminum compound is in a range from about 1:1 to about 1:100. These molar ratios reflect the ratio of total moles of metallocene compound or compounds to the total amount of organoaluminum compound (or compounds) in both the precontacted mixture and the postcontacted mixture combined, if precontacting and/or postcontacting steps are employed. 
     When a precontacting step is used, the molar ratio of the total moles of olefin monomer to total moles of metallocene in the precontacted mixture is typically in a range from about 1:10 to about 100,000:1. Total moles of each component are used in this ratio to account for aspects of this invention where more than one olefin monomer and/or more than metallocene is employed. Further, this molar ratio can be in a range from about 10:1 to about 1,000:1 in another aspect of the invention. 
     Generally, the weight ratio of organoaluminum compound to activator-support is in a range from about 10:1 to about 1:1000. If more than one organoaluminum compound and/or more than one activator-support is employed, this ratio is based on the total weight of each respective component. In another aspect, the weight ratio of the organoaluminum compound to the activator-support is in a range from about 3:1 to about 1:100, or from about 1:1 to about 1:50. 
     In some aspects of this invention, the weight ratio of metallocene to activator-support is in a range from about 1:1 to about 1:1,000,000. If more than one metallocene and/or more than one activator-support is employed, this ratio is based on the total weight of each respective component. In another aspect, this weight ratio is in a range from about 1:5 to about 1:100,000, or from about 1:10 to about 1:10,000. Yet, in another aspect, the weight ratio of the metallocene compound to the activator-support is in a range from about 1:20 to about 1:1000. 
     Yet, in another aspect of this invention, the concentration of the metallocene, in units of micromoles of the metallocene per gram of the activator-support, is in a range from about 0.5 to about 150. If more than one metallocene and/or more than one activator-support is employed, this ratio is based on the total weight of each respective component. In another aspect, the concentration of the metallocene, in units of micromoles of the metallocene per gram of the activator-support, is in a range from about 1 to about 120, for example, from about 5 to about 100, from about 5 to about 80, from about 5 to about 60, or from about 5 to about 40. In still another aspect, the concentration of the metallocene, in units of micromoles of the metallocene per gram of the activator-support, is in a range from about 5 to about 20. 
     According to some aspects of this invention, aluminoxane compounds are not required to form the catalyst composition. Thus, the polymerization proceeds in the absence of aluminoxanes. Accordingly, the present invention can use, for example, organoaluminum compounds and an activator-support in the absence of aluminoxanes. While not intending to be bound by theory, it is believed that the organoaluminum compound likely does not activate the metallocene catalyst in the same manner as an organoaluminoxane compound. 
     Additionally, in some aspects, organoboron and organoborate compounds are not required to form a catalyst composition of this invention. Nonetheless, aluminoxanes, organozinc compounds, organoboron or organoborate compounds, ionizing ionic compounds, or combinations thereof can be used in other catalyst compositions contemplated by and encompassed within the present invention. Hence, co-catalysts such as aluminoxanes, organozinc compounds, organoboron or organoborate compounds, ionizing ionic compounds, or combinations thereof, can be employed with the metallocene compound, and either in the presence or in the absence of an organoaluminum compound. 
     Catalyst compositions of the present invention generally have a catalyst activity greater than about 100 grams of polyethylene per gram of activator-support per hour (abbreviated gPE/gA-S/hr). In another aspect, the catalyst activity is greater than about 200, greater than about 300, greater than about 400, or greater than about 500 gPE/gA-S/hr. In still another aspect, catalyst compositions of this invention are characterized by having a catalyst activity greater than about 750, greater than about 1000, or greater than about 1500 gPE/gA-S/hr. The catalyst activity can be greater than about 2000, or greater than about 4000 gPE/gA-S/hr, in certain aspects of this invention. This activity is measured under slurry polymerization conditions using isobutane as the diluent, at a polymerization temperature of about 90° C. and an ethylene pressure of about 420 psig. 
     Generally, catalyst compositions of the present invention have a catalyst activity greater than about 25,000 grams of polyethylene per gram of metallocene per hour (abbreviated gPE/gMET/hr). For example, the catalyst activity can be greater than about 30,000, greater than about 40,000, or greater than about 50,000 gPE/gMET/hr. In another aspect, catalyst compositions of this invention are characterized by having a catalyst activity greater than about 75,000, greater than about 100,000, or greater than about 125,000 gPE/gMET/hr. Yet, in another aspect of this invention, the catalyst activity can be greater than about 150,000, or greater than about 200,000 gPE/gMET/hr. This activity is measured under slurry polymerization conditions using isobutane as the diluent, at a polymerization temperature of about 90° C. and an ethylene pressure of about 420 psig. 
     As discussed above, any combination of the metallocene compound, the activator-support, the organoaluminum compound, and the olefin monomer, can be precontacted in some aspects of this invention. When any precontacting occurs with an olefinic monomer, it is not necessary that the olefin monomer used in the precontacting step be the same as the olefin to be polymerized. Further, when a precontacting step among any combination of the catalyst components is employed for a first period of time, this precontacted mixture can be used in a subsequent postcontacting step between any other combination of catalyst components for a second period of time. For example, the metallocene compound, the organoaluminum compound, and 1-hexene can be used in a precontacting step for a first period of time, and this precontacted mixture then can be contacted with the activator-support to form a postcontacted mixture that is contacted for a second period of time prior to initiating the polymerization reaction. For example, the first period of time for contact, the precontact time, between any combination of the metallocene compound, the olefinic monomer, the activator-support, and the organoaluminum compound can be from about 0.1 hour to about 24 hours, from about 0.1 to about 1 hour, or from about 10 minutes to about 30 minutes. The postcontacted mixture optionally is allowed to remain in contact for a second period of time, the postcontact time, prior to initiating the polymerization process. According to one aspect of this invention, postcontact times between the precontacted mixture and any remaining catalyst components is from about 0.1 hour to about 24 hours, or from about 0.1 hour to about 1 hour. 
     Polymerization Process 
     Catalyst compositions of the present invention can be used to polymerize olefins to form homopolymers or copolymers. One such process for polymerizing olefins in the presence of a catalyst composition of the present invention comprises contacting the catalyst composition with at least one olefin monomer and optionally at least one olefin comonomer under polymerization conditions to produce a polymer or copolymer, wherein the catalyst composition comprises a contact product of at least one metallocene compound and at least one activator-support. The at least one activator-support comprises at least one alumina-silica compound treated with at least one electron-withdrawing anion, wherein the at least one alumina-silica compound generally has a weight ratio of alumina to silica in a range from about 1:1 to about 100:1. The at least one electron-withdrawing anion can be fluoride, chloride, bromide, phosphate, triflate, bisulfate, sulfate, and the like, or any combination thereof. 
     Often, a catalyst composition of the present invention, employed in a polymerization process, will further comprise at least one organoaluminum compound. Suitable organoaluminum compounds include, but are not limited to, trimethylaluminum, triethylaluminum, tri-n-propylaluminum, diethylaluminum ethoxide, tri-n-butylaluminum, diisobutylaluminum hydride, triisobutylaluminum, diethylaluminum chloride, and the like, or any combination thereof. 
     The catalyst compositions of the present invention are intended for any olefin polymerization method using various types of polymerization reactors. As used herein, “polymerization reactor” includes any polymerization reactor capable of polymerizing olefin monomers to produce homopolymers or copolymers. Such homopolymers and copolymers are referred to as resins or polymers. The various types of reactors include those that may be referred to as batch, slurry, gas-phase, solution, high pressure, tubular or autoclave reactors. Gas phase reactors may comprise fluidized bed reactors or staged horizontal reactors. Slurry reactors may comprise vertical or horizontal loops. High pressure reactors may comprise autoclave or tubular reactors. Reactor types can include batch or continuous processes. Continuous processes could use intermittent or continuous product discharge. Processes may also include partial or full direct recycle of un-reacted monomer, un-reacted comonomer, and/or diluent. 
     Polymerization reactor systems of the present invention may comprise one type of reactor in a system or multiple reactors of the same or different type. Production of polymers in multiple reactors may include several stages in at least two separate polymerization reactors interconnected by a transfer device making it possible to transfer the polymers resulting from the first polymerization reactor into the second reactor. The desired polymerization conditions in one of the reactors may be different from the operating conditions of the other reactors. Alternatively, polymerization in multiple reactors may include the manual transfer of polymer from one reactor to subsequent reactors for continued polymerization. Multiple reactor systems may include any combination including, but not limited to, multiple loop reactors, multiple gas reactors, a combination of loop and gas reactors, multiple high pressure reactors or a combination of high pressure with loop and/or gas reactors. The multiple reactors may be operated in series or in parallel. 
     According to one aspect of the invention, the polymerization reactor system may comprise at least one loop slurry reactor comprising vertical or horizontal loops. Monomer, diluent, catalyst and optionally any comonomer may be continuously fed to a loop reactor where polymerization occurs. Generally, continuous processes may comprise the continuous introduction of a monomer, a catalyst, and a diluent into a polymerization reactor and the continuous removal from this reactor of a suspension comprising polymer particles and the diluent. Reactor effluent may be flashed to remove the solid polymer from the liquids that comprise the diluent, monomer and/or comonomer. Various technologies may be used for this separation step including but not limited to, flashing that may include any combination of heat addition and pressure reduction; separation by cyclonic action in either a cyclone or hydrocyclone; or separation by centrifugation. 
     A typical slurry polymerization process (also known as the particle form process), is disclosed, for example, in U.S. Pat. Nos. 3,248,179, 4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191 and 6,833,415, each of which is incorporated by reference in its entirety herein. 
     Suitable diluents used in slurry polymerization include, but are not limited to, the monomer being polymerized and hydrocarbons that are liquids under reaction conditions. Examples of suitable diluents include, but are not limited to, hydrocarbons such as propane, cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, and n-hexane. Some loop polymerization reactions can occur under bulk conditions where no diluent is used. An example is polymerization of propylene monomer as disclosed in U.S. Pat. No. 5,455,314, which is incorporated by reference herein in its entirety. 
     According to yet another aspect of this invention, the polymerization reactor may comprise at least one gas phase reactor. Such systems may employ a continuous recycle stream containing one or more monomers continuously cycled through a fluidized bed in the presence of the catalyst under polymerization conditions. A recycle stream may be withdrawn from the fluidized bed and recycled back into the reactor. Simultaneously, polymer product may be withdrawn from the reactor and new or fresh monomer may be added to replace the polymerized monomer. Such gas phase reactors may comprise a process for multi-step gas-phase polymerization of olefins, in which olefins are polymerized in the gaseous phase in at least two independent gas-phase polymerization zones while feeding a catalyst-containing polymer formed in a first polymerization zone to a second polymerization zone. One type of gas phase reactor is disclosed in U.S. Pat. Nos. 5,352,749, 4588,790 and 5,436,304, each of which is incorporated by reference in its entirety herein. 
     According to still another aspect of the invention, a high pressure polymerization reactor may comprise a tubular reactor or an autoclave reactor. Tubular reactors may have several zones where fresh monomer, initiators, or catalysts are added. Monomer may be entrained in an inert gaseous stream and introduced at one zone of the reactor. Initiators, catalysts, and/or catalyst components may be entrained in a gaseous stream and introduced at another zone of the reactor. The gas streams may be intermixed for polymerization. Heat and pressure may be employed appropriately to obtain optimal polymerization reaction conditions. 
     According to yet another aspect of the invention, the polymerization reactor may comprise a solution polymerization reactor wherein the monomer is contacted with the catalyst composition by suitable stirring or other means. A carrier comprising an inert organic diluent or excess monomer may be employed. If desired, the monomer may be brought in the vapor phase into contact with the catalytic reaction product, in the presence or absence of liquid material. The polymerization zone is maintained at temperatures and pressures that will result in the formation of a solution of the polymer in a reaction medium. Agitation may be employed to obtain better temperature control and to maintain uniform polymerization mixtures throughout the polymerization zone. Adequate means are utilized for dissipating the exothermic heat of polymerization. 
     Polymerization reactors suitable for the present invention may further comprise any combination of at least one raw material feed system, at least one feed system for catalyst or catalyst components, and/or at least one polymer recovery system. Suitable reactor systems for the present invention may further comprise systems for feedstock purification, catalyst storage and preparation, extrusion, reactor cooling, polymer recovery, fractionation, recycle, storage, loadout, laboratory analysis, and process control. 
     Conditions that are controlled for polymerization efficiency and to provide resin properties include temperature, pressure and the concentrations of various reactants. Polymerization temperature can affect catalyst productivity, polymer molecular weight and molecular weight distribution. Suitable polymerization temperature may be any temperature below the de-polymerization temperature according to the Gibbs Free energy equation. Typically this includes from about 60° C. to about 280° C., for example, and from about 70° C. to about 110° C., depending upon the type of polymerization reactor. 
     Suitable pressures will also vary according to the reactor and polymerization type. The pressure for liquid phase polymerizations in a loop reactor is typically less than 1000 psig. Pressure for gas phase polymerization is usually at about 200 to 500 psig. High pressure polymerization in tubular or autoclave reactors is generally run at about 20,000 to 75,000 psig. Polymerization reactors can also be operated in a supercritical region occurring at generally higher temperatures and pressures. Operation above the critical point of a pressure/temperature diagram (supercritical phase) may offer advantages. 
     The concentration of various reactants can be controlled to produce resins with certain physical and mechanical properties. The proposed end-use product that will be formed by the resin and the method of forming that product determines the desired resin properties. Mechanical properties include tensile, flexural, impact, creep, stress relaxation and hardness tests. Physical properties include density, molecular weight, molecular weight distribution, melting temperature, glass transition temperature, temperature melt of crystallization, density, stereoregularity, crack growth, long chain branching and theological measurements. 
     The concentrations of monomer, co-monomer, hydrogen, co-catalyst, modifiers, and electron donors are important in producing these resin properties. Comonomer is used to control product density. Hydrogen can be used to control product molecular weight. Co-catalysts can be used to alkylate, scavenge poisons and control molecular weight. Modifiers can be used to control product properties and electron donors affect stereoregularity. In addition, the concentration of poisons is minimized because poisons impact the reactions and product properties. 
     The polymer or resin may be formed into various articles, including, but not limited to, bottles, drums, toys, household containers, utensils, film products, drums, fuel tanks, pipes, geomembranes, and liners. Various processes may be used to form these articles, including, but not limited to, blow molding, extrusion molding, rotational molding, thermoforming, cast molding and the like. After polymerization, additives and modifiers can be added to the polymer to provide better processing during manufacturing and for desired properties in the end product. Additives include surface modifiers such as slip agents, antiblocks, tackifiers; antioxidants such as primary and secondary antioxidants; pigments; processing aids such as waxes/oils and fluoroelastomers; and special additives such as fire retardants, antistats, scavengers, absorbers, odor enhancers, and degradation agents. 
     Homopolymers and copolymers of ethylene produced in accordance with this invention generally have a melt index from about 0.01 to about 100 g/10 min. For example, a melt index in the range from about 0.1 to about 50 g/10 min, or from about 0.5 to about 25 g/10 min, are contemplated in some aspects of this invention. 
     The density of ethylene-based polymers produced using one or more metallocene compounds and activator-supports of the present invention typically falls within the range from about 0.88 to about 0.97 g/cc. In one aspect of this invention, the polymer density is in a range from about 0.90 to about 0.95 g/cc. Yet, in another aspect, the density is generally in a range from about 0.91 to about 0.94 g/cc. 
     If the resultant polymer produced in accordance with the present invention is, for example, a polymer or copolymer of ethylene, it can be formed into various articles of manufacture. Such articles include, but are not limited to, molded products, household containers, utensils, film or sheet products, drums, fuel tanks, pipes, geomembranes, liners, and the like. Various processes can be employed to form these articles. Non-limiting examples of these processes include injection molding, blow molding, film extrusion, sheet extrusion, profile extrusion, and the like. Additionally, additives and modifiers are often added to these polymers in order to provide beneficial polymer processing or end-use product attributes. 
     EXAMPLES 
     The invention is further illustrated by the following examples, which are not to be construed in any way as imposing limitations to the scope of this invention. Various other aspects, embodiments, modifications, and equivalents thereof which, after reading the description herein, may suggest themselves to one of ordinary skill in the art without departing from the spirit of the present invention or the scope of the appended claims. 
     Melt theological characterizations were performed as follows. Small-strain (10%) oscillatory shear measurements were performed on a Rheometrics Scientific, Inc. ARES rheometer using parallel-plate geometry. All theological tests were performed at 190° C. The complex viscosity |η*| versus frequency (ω) data were then curve fitted using the modified three parameter Carreau-Yasuda (CY) empirical model to obtain the zero shear viscosity—η 0 , characteristic viscous relaxation time—τ η , and the breadth parameter—α. The simplified Carreau-Yasuda (CY) empirical model is as follows. 
     
       
         
           
             
               
                  
                 
                   
                     η 
                     * 
                   
                    
                   
                     ( 
                     ω 
                     ) 
                   
                 
                  
               
               = 
               
                 
                   η 
                   0 
                 
                 
                   
                     [ 
                     
                       1 
                       + 
                       
                         
                           ( 
                           
                             
                               τ 
                               η 
                             
                              
                             ω 
                           
                           ) 
                         
                         a 
                       
                     
                     ] 
                   
                   
                     
                       ( 
                       
                         1 
                         - 
                         n 
                       
                       ) 
                     
                     / 
                     a 
                   
                 
               
             
             , 
           
         
       
     
     wherein:
         |η*(ω)|=magnitude of complex shear viscosity;   η 0 =zero shear viscosity;   τ η =viscous relaxation time;   α=“breadth” parameter;   n=fixes the final power law slope, fixed at 2/11; and   ω=angular frequency of oscillatory shearing deformation.       

     Details of the significance and interpretation of the CY model and derived parameters may be found in: C. A. Hieber and H. H. Chiang,  Rheol. Acta,  28, 321 (1989); C. A. Hieber and H. H. Chiang,  Polym. Eng. Sci.,  32, 931 (1992); and R. B. Bird, R. C. Armstrong and O. Hasseger,  Dynamics of Polymeric Liquids, Volume  1,  Fluid Mechanics,  2nd Edition, John Wiley &amp; Sons (1987); each of which is incorporated herein by reference in its entirety. The CY “a” parameter (CY-a) is reported for some of the polymer resins produced herein. 
     Molecular weights and molecular weight distributions were obtained using a PL 220 SEC high temperature chromatography unit (Polymer Laboratories) with trichlorobenzene (TCB) as the solvent, with a flow rate of 1 mL/minute at a temperature of 145° C. BHT (2,6-di-tert-butyl-4-methylphenol) at a concentration of 0.5 g/L was used as a stabilizer in the TCB. An injection volume of 200 μL was used with a nominal polymer concentration of 1.5 mg/mL. Dissolution of the sample in stabilized TCB was carried out by heating at 150° C. for 5 hours with occasional, gentle agitation. The columns used were three PLgel Mixed A LS columns (7.8×300 mm) and were calibrated with a broad linear polyethylene standard (Phillips Marlex® BHB 5003) for which the molecular weight had been determined. 
     Ethylene was polymerization grade ethylene obtained from Union Carbide Corporation. This ethylene was then further purified through a column of ¼-inch beads of Alcoa A201 alumina, activated at about 250° C. in nitrogen. Isobutane was polymerization grade obtained from Phillips Petroleum Company, which was further purified by distillation and then also passed through a column of ¼-inch beads of Alcoa A201 alumina, activated at about 250° C. in nitrogen. The 1-hexene was polymerization grade obtained from Chevron Chemical Company, which was further purified by nitrogen purging and storage over 13× molecular sieve activated at about 250° C. Triisobutylaluminum (TIBA) was obtained from Akzo Corporation as a one molar solution in heptane. 
     All polymerizations were carried out in a one-gallon stirred reactor. First, the reactor was purged with nitrogen and heated to about 120° C. After cooling to below about 40° C. and purging with isobutane vapor, the metallocene compound was charged to the reactor under nitrogen. The metallocene quantity varied based on the metallocene to activator-support ratio, but was generally in the 0.1 to 3.5 milligram range. Approximately 100 mg of the activator-support (A-S) were then added to the reactor, followed by about 0.3 mL of 1M triisobutylaluminum (TIBA) co-catalyst. The reactor was then closed and, if noted, about 48 g of 1-hexene was injected into the reactor. Two liters of isobutane were added under pressure, and the reactor was subsequently heated to about 90° C. The reactor contents were mixed at 700 rpm. Ethylene was then added to the reactor and fed on demand to maintain a constant total pressure of about 420 psig. The reactor was maintained and controlled at 90° C. throughout the 60-minute run time of the polymerization. Upon completion, the isobutane and ethylene were vented from the reactor, the reactor was opened, and the polymer product was collected and dried. 
     Example 1 
     Synthesis of a Fluorided Silica-Alumina Activator-Support 
     A silica-alumina was obtained from W.R. Grace Company containing about 13% alumina by weight and having a surface area of about 400 m 2 /g and a pore volume of about 1.2 mL/g. This material was obtained as a powder having an average particle size of about 70 microns. Approximately 100 grams of this material were impregnated with a solution containing about 200 mL of water and about 10 grams of ammonium hydrogen fluoride, resulting in a damp powder having the consistency of wet sand. This mixture was then placed in a flat pan and allowed to dry under vacuum at approximately 110° C. for about 16 hours. 
     To calcine the support, about 10 grams of this powdered mixture were placed in a 1.75-inch quartz tube fitted with a sintered quartz disk at the bottom. While the powder was supported on the disk, air (nitrogen can be substituted) dried by passing through a 13× molecular sieve column, was blown upward through the disk at the linear rate of about 1.6 to 1.8 standard cubic feet per hour. An electric furnace around the quartz tube was then turned on and the temperature was raised at the rate of about 400° C. per hour to the desired calcining temperature of about 450° C. At this temperature, the powder was allowed to fluidize for about three hours in the dry air. Afterward, the fluorided silica-alumina was collected and stored under dry nitrogen, and was used without exposure to the atmosphere. The fluorided silica-alumina activator-support of Example 1 is abbreviated A-SI. The weight ratio of alumina to silica in A-S1 is about 0.15:1. 
     Example 2 
     Synthesis of a Sulfated Alumina Activator-Support 
     Bohemite was obtained from W.R. Grace Company under the designation “Alumina A” and having a surface area of about 300 m 2 /g and a pore volume of about 1.3 mL/g. This material was obtained as a powder having an average particle size of about 100 microns. This material was impregnated to incipient wetness with an aqueous solution of ammonium sulfate to equal about 15% sulfate. This mixture was then placed in a flat pan and allowed to dry under vacuum at approximately 110° C. for about 16 hours. 
     To calcine the support, about 10 grams of this powdered mixture were placed in a 1.75-inch quartz tube fitted with a sintered quartz disk at the bottom. While the powder was supported on the disk, air (nitrogen can be substituted) dried by passing through a 13× molecular sieve column, was blown upward through the disk at the linear rate of about 1.6 to 1.8 standard cubic feet per hour. An electric furnace around the quartz tube was then turned on and the temperature was raised at the rate of about 400° C. per hour to the desired calcining temperature of about 600° C. At this temperature, the powder was allowed to fluidize for about three hours in the dry air. Afterward, the sulfated alumina was collected and stored under dry nitrogen, and was used without exposure to the atmosphere. The sulfated alumina activator-support of Example 2 is abbreviated A-S2. 
     Example 3 
     Synthesis of a Fluorided, High Alumina Content, Alumina-Silica Activator-Support 
     A high alumina content alumina-silica was obtained from Sasol Company under the designation “Siral 28M” containing about 72% alumina by weight and having a surface area of about 340 m 2 /g and a pore volume of about 1.6 mL/g. This material was obtained as a powder having an average particle size of about 70 microns. This material was first calcined at about 600° C. for approximately 6 hours, then impregnated to incipient wetness with a 10% ammonium bifluoride solution in methanol. This mixture was then placed in a flat pan and allowed to dry under vacuum at approximately 110° C. for about 16 hours. 
     To calcine the support, about 10 grams of this powdered mixture were placed in a 1.75-inch quartz tube fitted with a sintered quartz disk at the bottom. While the powder was supported on the disk, air (nitrogen can be substituted) dried by passing through a 13× molecular sieve column, was blown upward through the disk at the linear rate of about 1.6 to 1.8 standard cubic feet per hour. An electric furnace around the quartz tube was then turned on and the temperature was raised at the rate of about 400° C. per hour to the desired calcining temperature of about 600° C. At this temperature, the powder was allowed to fluidize for about three hours in the dry air. Afterward, the fluorided alumina-silica was collected and stored under dry nitrogen, and was used without exposure to the atmosphere. The fluorided alumina-silica activator-support of Example 3 is abbreviated A-S3. The weight ratio of alumina to silica in A-S3 is about 2.6:1. 
     Example 4 
     Comparison of Polymerization Catalyst Activity Using Met 1 and the Activator-Supports of Examples 1-3 
     The metallocene compound of Example 4, abbreviated “MET 1,” has the following structure (Ph=Phenyl; t-Bu=tert-butyl): 
     
       
         
         
             
             
         
       
     
     The MET 1 metallocene compound can be prepared in accordance with any suitable method. One such technique is described in U.S. Patent Publication No. 2007-0179044, the disclosure of which is incorporated herein by reference in its entirety. 
     The activator-supports of Examples 1-3 were charged in separate experiments to the reactor with various levels of MET 1, along with a constant amount of TIBA co-catalyst. No hexene was introduced.  FIG. 1  illustrates the resultant polymerization catalyst activity for each of the three activator-supports, as a function of MET 1 to activator-support ratio. The activity is measured in units of grams of polyethylene produced per gram of A-S per hour. The MET 1 concentration varied from about 5 to about 20 micromoles of MET 1 per gram of the A-S.  FIG. 1  demonstrates that A-S3 provided better catalyst activity at low MET 1 levels, far superior to that of A-S1 and almost twice that of A-S2. Hence, less metallocene would be needed in a catalyst system employing A-S3 to provide the same catalyst activity achieved with a higher loading of metallocene with the A-S2 activator-support. Since the metallocene compound employed in a polymerization catalyst system can be an expensive component, reducing the amount of metallocene can be a significant benefit.  FIG. 1  also indicates that the activity using A-S3 was comparable to that of A-S2 at the highest metallocene loading. 
       FIG. 2  illustrates the same polymerization catalyst activity data, but instead, the activity is measured in units of grams of polyethylene produced per gram of MET 1 per hour. The catalyst activity using A-S2 is relatively constant across the MET 1 concentration range from about 5 to about 20 micromoles of MET 1 per gram of A-S. The higher catalyst activity of a system employing A-S3 at lower MET 1 loadings is also evidenced in  FIG. 2 . 
     The molecular weight and other properties of the polymer resins produced using A-S3 are compared to those produced using A-S2, at a Met 1 loading of 3.5 mg per 100 grams of the activator-support, in Table I below. The polymer produced using A-S3 had a lower molecular weight than that produced using A-S2. 
     
       
         
           
               
             
               
                 TABLE I 
               
             
            
               
                   
               
               
                 Property comparison of polymers produced using A-S2 and A-S3. 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 A-S 
                   
                   
                   
                   
                   
                   
               
               
                 Type 
                 Mn/1000 
                 Mw/1000 
                 Mz/1000 
                 PDI 
                 η 0   
                 CY-a 
               
               
                   
               
               
                 AS-2 
                 87.3 
                 212 
                 385 
                 2.42 
                 5.86E+04 
                 0.4615 
               
               
                 AS-3 
                 67.7 
                 194 
                 346 
                 2.86 
                 4.36E+04 
                 0.4930 
               
               
                   
               
               
                 Notes on Table I: 
               
               
                 Mn - number-average molecular weight. 
               
               
                 Mw - weight-average molecular weight. 
               
               
                 Mz - z-average molecular weight. 
               
               
                 PDI - polydispersity index, Mw/Mn. 
               
               
                 η 0  - zero shear viscosity at 190° C. 
               
               
                 CY-a - Carreau-Yasuda breadth parameter. 
               
            
           
         
       
     
     Example 5 
     Comparison of Polymerization Catalyst Activity Using Met 2 and the Activator-Supports of Examples 1-3 
     The metallocene compound of Example 5 is bis(n-butylcyclopentadienyl) hafnium dichloride (abbreviated “MET 2”), which can be prepared in accordance with any suitable method for synthesizing metallocene compounds. 
     The activator-supports of Examples 1-3 were charged in separate experiments to the reactor with various levels of MET 2, along with a constant amount of TIBA co-catalyst. For Example 5, the reactor was maintained and controlled at 95° C. throughout the 60-minute run time of the polymerization. No hexene was introduced.  FIG. 3  compares the resultant polymerization catalyst activity for each of the three activator-supports, as a function of MET 2 to activator-support ratio. The activity is measured in units of grams of polyethylene produced per gram of A-S per hour. The MET 2 concentration varied from about 5 to about 40 micromoles of MET 2 per gram of the A-S.  FIG. 3  demonstrates that A-S3 provided over twice the catalyst activity at all metallocene loading levels when compared to the catalyst activity achieved using either A-S1 or A-S2. 
       FIG. 4  illustrates the same polymerization catalyst activity data, but instead, the activity is measured in units of grams of polyethylene produced per gram of MET 2 per hour. Not only is the catalyst activity at all MET 2 loadings (micromoles MET 2 per gram of A-S) higher for the catalyst system containing A-S3, but the activity at the lowest metallocene loading is over 100,000 grams of polyethylene (per gram of MET 2 per hour) higher than that activity of the catalyst systems using either A-S1 or A-S2. Thus, less metallocene can be used in a catalyst system employing A-S3 to provide the same catalyst activity as that achieved with much higher loadings of metallocene using either the A-S1 or A-S2 activator-supports. 
     Example 6 
     Effect of Precontacting on the Polymerization Catalyst Activity of a Catalyst System Containing MET 2 and A-S3 
       FIG. 5  compares the grams of polyethylene produced per hour for a precontacted catalyst system and for a catalyst system which was not precontacted. The polymerization procedure used for the catalyst system which was not precontacted was substantially the same as that employed in Example 5. In this case, however, a fixed quantity of about 0.3 milligrams of MET 2 was used. For the precontacted catalyst system, the MET-2, A-S3 and TIBA were first mixed in a separate vessel for about 30 minutes before being introduced into the reactor and exposed to ethylene. As shown in  FIG. 5 , the precontacted catalyst system gave a significant improvement in polymerization activity versus the catalyst system which was not precontacted. 
     Example 7 
     Comparison of Polymerization Catalyst Activity Using Met 3 and the Activator-Supports of Examples 2-3 
     The metallocene compound of Example 7, abbreviated “MET 3,” has the following structure: 
     
       
         
         
             
             
         
       
     
     The MET 3 metallocene compound can be prepared in accordance with any suitable method. One such technique is described in U.S. Pat. No. 7,064,225, the disclosure of which is incorporated herein by reference in its entirety. 
     The activator-supports of Examples 2-3 were charged in separate experiments to the reactor with various levels of MET 3, along with a constant amount of TIBA co-catalyst. No hexene was introduced.  FIG. 6  compares the resultant polymerization catalyst activity for A-S2 and A-S3, as a function of MET 3 to activator-support ratio. The activity is measured in units of grams of polyethylene produced per gram of A-S per hour. The MET 3 concentration varied from about 5 to about 120 micromoles of MET 3 per gram of the A-S.  FIG. 6  demonstrates that A-S3 provided higher catalyst activity at lower metallocene loadings on the activator-support as compared to A-S2. 
       FIG. 7  illustrates the same polymerization catalyst activity data, but instead, the activity is measured in units of grams of polyethylene produced per gram of MET 3 per hour. At metallocene loadings of about 60 and above (micromoles MET 3 per gram of A-S), the activities of catalyst systems containing A-S2 and A-S3 appeared very similar. However, at low metallocene loadings, the catalyst activity was much greater for the catalyst system employing A-S3. As mentioned above, less metallocene can be used in a catalyst system employing A-S3 to provide the same catalyst activity as that achieved with much higher loadings of metallocene using the A-S2 activator-support. 
     Examples 8-10 
     Effect of Fluoride Concentration on the Activity of Fluorided Alumina-Silica Activator-Supports 
     The alumina-silica support used in Examples 8-10 was the same as the high alumina content alumina-silica employed in Example 3, containing about 72% alumina by weight. For Examples 8-10, this uncalcined material was impregnated to incipient wetness with a 5%, a 10%, or a 15% ammonium bifluoride solution in methanol, followed by calcining at a temperature of about 600° C. for about three hours, in the manner described in Example 3. 
     Ethylene polymerizations were conducted as described in Example 7, except that in this case, the loading of MET 3 was fixed at 3.5 milligrams per 100 g of the activator-support. 
     Table II summarizes the catalyst activity data for Examples 8-10. For this set of conditions, the fluoride level at about 10 weight percent NH 4 HF 2  provided the highest catalyst activity. The results in Table II also indicate that precalcining the alumina-silica support before the fluoride treatment also can provide an activity improvement. For instance, the catalyst activities in  FIGS. 6-7 , using a precalcined support, were significantly higher than that achieved with Example 9, which did not precalcine the support prior to the fluoride treatment. 
     
       
         
           
               
             
               
                 TABLE II 
               
             
            
               
                   
               
               
                 Examples 8-10 using the MET 3 metallocene compound. 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Fluoride 
                 Activity 
                 Activity 
               
               
                   
                 Example 
                 Added 
                 (based on A-S) 
                 (based on MET 3) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 8 
                  5% 
                 2433 
                 41.7 
               
               
                   
                 9 
                 10% 
                 3129 
                 55.4 
               
               
                   
                 10 
                 15% 
                 1833 
                 31.4 
               
               
                   
                   
               
               
                   
                 Notes on Table II: 
               
               
                   
                 Fluoride added is the weight percent of the NH 4 HF 2  solution. 
               
               
                   
                 Activity based on the A-S is in units of grams of polyethylene per gram of A-S per hour. 
               
               
                   
                 Activity based on MET 3 is in units of kilograms of polyethylene per gram of MET 3 per hour. 
               
            
           
         
       
     
     Examples 11-17 
     Effect of the Weight Ratio of Alumina to Silica on the Activity of Fluorided Alumina-Silica Supports 
     Table III lists the silica, alumina, silica-alumina, or alumina-silica supports having different ratios of alumina to silica, employed in Examples 11-17. These materials were obtained from Sasol, each made by the same technique, but with a different alumina to silica ratio. 
     Each support was first precalcined at 600° C., then impregnated with 10% ammonium bifluoride in methanol, then calcined again at 600° C., in the manner described in Example 3. Ethylene polymerizations were conducted as described in Example 7 (e.g., 100 mg A-S, 0.3 mmol TIBA), except that in this case, the loading of MET 3 was fixed at approximately 3.5 mg, and about 48 grams of 1-hexene were charged to the reactor. 
     As shown in Table III, the catalyst activities of Examples 13-15 were superior to the catalyst activities of Examples 11-12 and 16-17. Due to the excess of MET 3 that was used, the activities based on the amount of MET 3 that was employed, in units of kilograms of polyethylene per gram of MET 3 per hour, are low. 
     
       
         
           
               
             
               
                 TABLE III 
               
             
            
               
                   
               
               
                 Examples 11-17 using the MET 3 metallocene compound. 
               
            
           
           
               
               
               
               
            
               
                   
                 Alumina to 
                 Activity 
                 Activity 
               
               
                 Example 
                 Silica Ratio 
                 (based on A-S) 
                 (based on MET 3) 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 11 
                 Alumina 
                 1688 
                 46 
               
               
                 12 
                 19:1  
                 2109 
                 74 
               
               
                 13 
                 4:1 
                 5291 
                 192 
               
               
                 14 
                 2.6:1   
                 6300 
                 200 
               
               
                 15 
                 1.5:1   
                 7295 
                 174 
               
               
                 16 
                 0.15:1   
                 60 
                 6 
               
               
                 17 
                 Silica 
                 0 
                 0 
               
               
                   
               
               
                 Notes on Table III: 
               
               
                 The alumina to silica ratio is the weight ratio in the silica-alumina or alumina-silica support. 
               
               
                 Activity based on the A-S is in units of grams of polyethylene per gram of A-S per hour. 
               
               
                 Activity based on MET 3 is in units of kilograms of polyethylene per gram of MET 3 per hour.