Patent Description:
An economically important class of olefin polymerization catalysts includes chromium-silica-titanium (Cr/Si-Ti) catalysts prepared from silica-based catalyst supports. Rigorous drying of the water-sensitive catalyst components used to produce Cr/Si-Ti catalysts increases the time and cost of production. Development of an aqueous solution suitable for depositing titanium onto a silica-based catalyst support would reduce the costs of production of olefin polymerization catalysts. Thus, there is an ongoing need to develop new methods of producing olefin polymerization catalysts.

<CIT> describes a polymerization catalyst and method which produces substantially pure silica that is uncontaminated with alkali metal or alkaline earth metal ions before associating with the resulting support silica the chromium compound which is either a chromium oxide or a chromium compound convertible to the oxide in the heat activating of the catalyst. <CIT> discloses a silica-titania cogel or silica-titanic-chromium tergel that is first aged at a substantially neutral pH, then aged at an alkaline pH, and then spray dried or azeotrope dried to form a xerogel.

The subject matter of the invention is set out in the appended claims.

The following figure forms part of the present specification and is included to further demonstrate certain aspects of the present disclosure. The subject matter of the present disclosure may be better understood by reference to the figure in combination with the detailed description of specific aspects presented herein.

The Figure illustrates relationships between zeta potential and pH value for silica and titania.

While the subject matter disclosed herein is susceptible to various modifications and alternative forms, only a few specific aspects have been shown by way of example in the drawing and are described below in detail. The figure and detailed descriptions of these specific aspects are not intended to limit the breadth or scope of the subject matter disclosed or the appended claims in any manner. Rather, the figure and detailed written descriptions are provided to illustrate the present disclosure to a person skilled in the art and to enable such person to make and use the concepts disclosed herein.

The present disclosure encompasses olefin polymerization catalysts and pre-catalysts thereof, methods of preparing olefin polymerization catalysts and pre-catalysts thereof, and methods of utilizing olefin polymerization catalysts. In an aspect, a method of the present disclosure comprises contacting a silica support or a chromium-silica support (i.e., support) with titanium to produce a Cr/Si-Ti catalyst. The methodologies disclosed herein contemplate the use of a solubilized titanium mixture (STM) to facilitate the association of titanium with the support in the presence of water. Herein a methodology for preparation of the olefin polymerization catalyst comprises contacting the chromium-silica support with the STM under conditions suitable to form the catalyst composition. An alternative methodology for preparation of the olefin polymerization catalyst comprises contacting the silica support with the STM and chromium under conditions suitable to form a catalyst composition. While these aspects may be disclosed under a particular heading, the heading does not limit the disclosure found therein. Additionally, the various aspects and embodiments disclosed herein can be combined in any manner.

Aspects of the present disclosure are directed to catalyst compositions and pre-catalyst compositions. In an aspect, a catalyst composition comprises an olefin polymerization catalyst. In a further aspect, the olefin polymerization catalyst comprises a treated pre-catalyst composition. In yet a further aspect, the treated pre-catalyst composition comprises a pre-catalyst that has been subjected to an activation treatment (e.g., calcination) as disclosed herein.

Disclosed herein are pre-catalyst compositions. In an aspect, a pre-catalyst composition comprises a silica support, a chromium-containing compound, a titanium-containing compound, a carboxylic acid, and a nitrogen-containing compound. Alternatively, the pre-catalyst composition comprises the silica support, the chromium-containing compound, and a titano-organic salt.

An olefin polymerization catalyst and a pre-catalyst thereof of the present disclosure comprise a silica support. The silica support may be any silica support suitable for preparation of the olefin polymerization catalyst and the pre-catalyst thereof as disclosed herein. In a further aspect, preparation of the olefin polymerization catalyst and the pre-catalyst thereof excludes thermal treatment of the silica support prior to contact with any other catalyst component. Consequently, the silica support suitable for use in the present disclosure may be a termed a hydrated silica support. Without wishing to be limited by theory, the hydrated silica support comprises a silica support wherein water evolution occurs when the silica support is heated within a range of from about <NUM> to about <NUM> under vacuum conditions for a period of time ranging from about <NUM> hours to about <NUM> hours. In a further aspect, the silica support may contain from about <NUM> wt. % to about <NUM> wt. % water; alternatively, about <NUM> wt. % to about <NUM> wt. % water; alternatively, about <NUM> wt. % to about <NUM> wt. % water; or alternatively, about <NUM> wt. % to about <NUM> wt. % water based upon the total weight of the silica support.

The silica support suitable for use in the present disclosure may have a surface area and a pore volume effective to provide for the production of an active olefin polymerization catalyst. In an aspect of the present disclosure, the silica support possesses a surface area in a range of from about <NUM><NUM>/gram to about <NUM><NUM>/gram; alternatively, from about <NUM><NUM>/gram to about <NUM><NUM>/gram; alternatively, from about <NUM><NUM>/gram to about <NUM><NUM>/gram; alternatively, from about <NUM><NUM>/gram to about <NUM><NUM>/gram; or alternatively, greater than about <NUM><NUM>/gram. The silica support may be further characterized by a pore volume of greater than about <NUM><NUM>/gram; alternatively, greater than about <NUM><NUM>/gram; or alternatively, greater than about <NUM><NUM>/gram. In an aspect of the present disclosure, the silica support is characterized by a pore volume in a range of from about <NUM><NUM>/gram to about <NUM><NUM>/gram. The silica support may be further characterized by an average particle size in a range of from about <NUM> microns to about <NUM> microns; alternatively, about <NUM> microns to about <NUM> microns; or alternatively, about <NUM> microns to about <NUM> microns. Generally, an average pore size of the silica support may be in a range of from about <NUM> Angstroms to about <NUM> Angstroms. In one aspect of the present disclosure, the average pore size of the silica support is in a range of from about <NUM> Angstroms to about <NUM> Angstroms; alternatively, from about <NUM> Angstroms to about <NUM> Angstroms.

The silica support suitable for use in the present disclosure comprises an amount of silica in a range of from <NUM> wt. % to <NUM> wt. % based upon a total weight of the silica support. The silica support may be prepared using any suitable method, e.g., the silica support may be prepared by hydrolyzing tetrachlorosilane (SiCl<NUM>) with water or by contacting sodium silicate and a mineral acid. In a particular aspect, the silica support may be a hydrogel or a preformed silica support wherein the preformed silica support optionally has been dried prior to contact with any other catalyst component. The silica support may include additional components that do not adversely affect the catalyst, such as zirconia, alumina, thoria, magnesia, fluoride, sulfate, phosphate, or a combination thereof. In a particular aspect, the silica support of the present disclosure comprises alumina. Non-limiting examples of silica supports suitable for use in this disclosure include ES70, which is a silica support material with a surface area of <NUM><NUM>/gram and a pore volume of <NUM><NUM>/gram, that is commercially available from PQ Corporation and V398400, which is a silica support material that is commercially available from Evonik.

In a particular aspect of the present disclosure, a silica support suitable for use in the present disclosure comprises chromium. The silica support comprising chromium may be termed a chrominated silica support or a chromium-silica support. In another aspect, the chromium-silica support comprises the characteristics disclosed herein for the silica support while additionally containing chromium. A non-limiting example of the chrominated silica support is HW30A, which is a chromium-silica support material that is commercially available from W. Grace and Company.

The silica support may be present in the olefin polymerization catalyst and a pre-catalyst thereof in an amount in a range of from about <NUM> wt. % to about <NUM> wt. %; or alternatively, from about <NUM> wt. % to about <NUM> wt. Herein a silica support percentage refers to a weight percent (wt. %) of the silica support associated with the olefin polymerization catalyst based upon the total weight of the olefin polymerization catalyst after completion of all processing steps (i.e., after activation via calcination). Alternatively, the silica support percentage refers to a weight percent (wt. %) of the silica support associated with the pre-catalyst based upon the total weight of the pre-catalyst after completion of all relevant processing steps excluding activation via calcination.

An olefin polymerization catalyst and a pre-catalyst thereof of the present disclosure comprise chromium. The source of chromium may be any chromium-containing compound capable of providing a sufficient amount of chromium to the olefin polymerization catalyst and the pre-catalyst thereof. In an aspect, the chromium-containing compound may be a water-soluble chromium compound or a hydrocarbon-soluble chromium compound. Examples of water-soluble chromium compounds include chromium trioxide, chromium acetate, chromium nitrate, or a combination thereof. Examples of hydrocarbon-soluble chromium compounds include tertiary butyl chromate, biscyclopentadienyl chromium(II), chromium(III) acetylacetonate, or a combination thereof. In one aspect of the present disclosure, the chromium-containing compound may be a chromium(II) compound, a chromium(III) compound, or a combination thereof. Suitable chromium(III) compounds include, but are not limited to, chromium(III) carboxylates, chromium(III) naphthenates, chromium(III) halides, chromium(III) sulfates, chromium(III) nitrates, chromium(III) dionates, or a combination thereof. Specific chromium(III) compounds include, but are not limited to, chromium(III) sulfate, chromium(III) chloride, chromium(III) nitrate, chromium(III) bromide, chromium(III) acetylacetonate, and chromium(III) acetate. Suitable chromium(II) compounds include, but are not limited to, chromium(II) chloride, chromium(II) bromide, chromium(II) iodide, chromium(II) sulfate, chromium(II) acetate, or a combination thereof.

An amount of chromium present in the olefin polymerization catalyst may be in a range of from about <NUM> wt. % to about <NUM> wt. %; alternatively, from about <NUM> wt. % to about <NUM> wt. %; alternatively, from about <NUM> wt. % to about <NUM> wt. %; or alternatively, from about <NUM> wt. % to about <NUM> wt. % chromium based upon the total weight of the olefin polymerization catalyst. In another aspect, the amount of chromium present in the olefin polymerization catalyst may be in a range of from about <NUM> wt. % to about <NUM> wt. % chromium based upon the total weight of the olefin polymerization catalyst. Herein, a chromium percentage refers to a weight percent (wt. %) of chromium associated with the olefin polymerization catalyst based upon the total weight of the olefin polymerization catalyst after completion of all processing steps (i.e., after activation via calcination). In a further aspect, an amount of chromium present in a pre-catalyst may be in a range of from about <NUM> wt. % to about <NUM> wt. %; or alternatively, from about <NUM> wt. % to about <NUM> wt. % chromium based upon a total weight of silica within the pre-catalyst. Herein, a chromium percentage refers to a weight percent (wt. %) of chromium associated with the pre-catalyst based upon the total weight of silica within the pre-catalyst after completion of all processing steps excluding activation via calcination.

An olefin polymerization catalyst and a pre-catalyst thereof of the present disclosure comprise titanium. The source of titanium may be any titanium-containing compound capable of providing a sufficient amount of titanium to the olefin polymerization catalyst and the pre-catalyst thereof. In a further aspect, the titanium-containing compound comprises a tetravalent titanium (Ti(IV)) compound or a trivalent titanium (Ti(III)) compound. The Ti(IV) compound may be any compound that comprises Ti(IV); alternatively, the Ti(IV) compound may be any compound that is able to release a Ti(IV) species upon dissolving into solution. The Ti(III) compound may be any compound that comprises Ti(III); alternatively, the Ti(III) compound may be any compound that is able to release a Ti(III) species upon dissolving into solution.

In an aspect, the titanium-containing compound suitable for use in the present disclosure comprises a Ti(IV) compound having at least one alkoxide group; or alternatively, at least two alkoxide groups. Ti(IV) compounds suitable for use in the present disclosure include, but are not limited to, Ti(IV) compounds that have the general formula TiO(ORK)<NUM>, Ti(ORK)<NUM>(acac)<NUM>, Ti(ORK)<NUM>(oxal), a combination thereof wherein RK may be ethyl, isopropyl, n-propyl, isobutyl, n-butyl, or a combination thereof; "acac" is acetylacetonate; and "oxal" is oxalate. Alternatively, the titanium-containing compound comprises a titanium(IV) alkoxide. In an aspect, the titanium(IV) alkoxide may be titanium(IV) ethoxide, titanium(IV) isopropoxide, titanium(IV) n-propoxide, titanium(IV) n-butoxide, titanium(IV) <NUM>-ethylhexoxide, or a combination thereof. In a particular aspect, the titanium-containing compound may be titanium(IV) isopropoxide.

In a still further aspect, the titanium-containing compound suitable for use in the present disclosure may comprise hydrous titania, titanium hydroxide, titanic acid, titanyl sulfate, titanium acetylacetonate, titanium oxyacetylacetonate, or a combination thereof.

In yet another aspect, the titanium-containing compound suitable for use in the present disclosure may comprise a titanium(IV) halide, non-limiting examples of which include titanium tetrachloride, titanium tetrabromide, titanium (IV) oxychloride, and titanium(IV) oxybromide. In a further aspect the titanium(IV) halide may comprise a titanium alkoxyhalide having the general formula Ti(ORK)nQ<NUM>-n; wherein RK may be ethyl, isopropyl, n-propyl, isobutyl, n-butyl, or a combination thereof; wherein Q may be a fluoride, a chloride, a bromide, an iodide, or a combination thereof; and wherein n may be an integer from <NUM> to <NUM>.

An amount of titanium present in an olefin polymerization catalyst of the present disclosure may range from about <NUM> wt. % to about <NUM> wt. %; alternatively, from about <NUM> wt. % to about <NUM> wt. %; alternatively, from about <NUM> wt. % to about <NUM> wt. %; or alternatively, from about <NUM> wt. % to about <NUM> wt. % titanium based upon the total weight of the olefin polymerization catalyst. In another aspect, the amount of titanium present in the olefin polymerization catalyst may range from about <NUM> wt. % to about <NUM> wt. % titanium based upon the total weight of the olefin polymerization catalyst. Herein, a titanium percentage refers to a weight percent (wt. %) of titanium associated with the olefin polymerization catalyst based upon the total weight of the olefin polymerization catalyst after completion of all processing steps (i.e., after activation via calcination). In a further aspect, an amount of titanium present in a pre-catalyst of the present disclosure ranges from <NUM> wt. % to <NUM> wt. %; alternatively, from about <NUM> wt. % to about <NUM> wt. %; alternatively, from about <NUM> wt. % to about <NUM> wt. %; or alternatively, from about <NUM> wt. % to about <NUM> wt. % titanium based upon a total weight of silica within the pre-catalyst. Herein, a titanium percentage refers to a weight percent (wt. %) of titanium associated with the pre-catalyst based upon a total weight of silica within the pre-catalyst after completion of all processing steps excluding activation via calcination.

An olefin polymerization catalyst and a pre-catalyst thereof of the present disclosure comprise a carboxylic acid. The carboxylic acid may be a monocarboxylic acid, a dicarboxylic acid, a tricarboxylic acid, an α-hydroxycarboxylic acid, a β-hydroxycarboxylic acid, an α-ketocarboxylic acid, or a combination thereof. In an aspect, the carboxylic acid may be a C<NUM> to C<NUM> monocarboxylic acid or a C<NUM> to C<NUM> monocarboxylic acid; alternatively, a C<NUM> to C<NUM> dicarboxylic acid or a C<NUM> to C<NUM> dicarboxylic acid; alternatively, a C<NUM> to C<NUM> tricarboxylic acid or a C<NUM> to C<NUM> tricarboxylic acid; alternatively, a C<NUM> to C<NUM> α-hydroxycarboxylic acid or a C<NUM> to C<NUM> α-hydroxycarboxylic acid; alternatively, a C<NUM> to C<NUM> P-hydroxycarboxylic acid or a C<NUM> to C<NUM> P-hydroxycarboxylic acid; or alternatively, a C<NUM> to C<NUM> α-ketocarboxylic acid or a C<NUM> to C<NUM> α-ketocarboxylic acid.

In a particular aspect, the carboxylic acid may be acetic acid, citric acid, gluconic acid, glycolic acid, glyoxylic acid, lactic acid, malic acid, malonic acid, oxalic acid, phosphonoacetic acid, tartaric acid, or a combination thereof. In yet a further aspect, the carboxylic acid may be oxalic acid.

A pre-catalyst of the present disclosure comprises an equivalent molar ratio of titanium to carboxylic acid in a range of from <NUM>:<NUM> to <NUM>:<NUM>; alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM> or alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>. In an aspect, the equivalent molar ratio of titanium to carboxylic acid is in a range of from about <NUM>:<NUM> to about <NUM>:<NUM>.

An olefin polymerization catalyst and a pre-catalyst thereof of the present disclosure comprise a nitrogen-containing compound. In a further aspect, the nitrogen-containing compound may have Structure <NUM>, Structure <NUM>, Structure <NUM>, Structure <NUM>, Structure <NUM>, Structure <NUM>, or a combination thereof.

N(R<NUM>)xH(<NUM> - x)OH     Structure <NUM>.

NR<NUM>R<NUM>(CR<NUM>R<NUM>)yOH     Structure <NUM>.

Z=C(N(R<NUM>)<NUM>)<NUM>     Structure <NUM>.

R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> within the nitrogen-containing compound utilized as described herein are independent elements of the nitrogen-containing compound structure in which they are present and are independently described herein. The independent descriptions of R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and/or R<NUM> provided herein can be utilized without limitation, and in any combination, to further describe any nitrogen-containing compound structure which comprises an R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and/or R<NUM>.

Generally, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and/or R<NUM> of a respective nitrogen-containing compound which has an R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and/or R<NUM> may each independently be hydrogen, an organyl group, a hydrocarbyl group, or an aryl group. In an aspect, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and/or R<NUM> may each independently be a C<NUM> to C<NUM> organyl group; alternatively, a C<NUM> to C<NUM> organyl group; or alternatively, a C<NUM> to C<NUM> organyl group. In an aspect, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and/or R<NUM> may each independently be a C<NUM> to C<NUM> hydrocarbyl group; alternatively, a C<NUM> to C<NUM> hydrocarbyl group; or alternatively, a C<NUM> to C<NUM> hydrocarbyl group. In yet other aspects, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and/or R<NUM> may each independently be a C<NUM> to C<NUM> aryl group; or alternatively, a C<NUM> to C<NUM> aryl group. In a further aspect, any organyl group, hydrocarbyl group or aryl group which may be used as R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and/or R<NUM> within the nitrogen-containing compound of the present disclosure may be substituted or non-substituted. It will be understood by one skilled in the art that the terms "alkyl", "organyl", "hydrocarbyl", and "aryl" are used herein in accordance with the definitions from the <NPL>).

R<NUM> of a respective nitrogen-containing compound which has an R<NUM> may be an organyl group, a hydrocarbyl group or an aryl group. In an aspect, R<NUM> may be a C<NUM> to C<NUM> organyl group; alternatively, a C<NUM> to C<NUM> organyl group; or alternatively, a C<NUM> to C<NUM> organyl group. In an aspect, R<NUM> may be a C<NUM> to C<NUM> hydrocarbyl group; alternatively, a C<NUM> to C<NUM> hydrocarbyl group; or alternatively, a C<NUM> to C<NUM> hydrocarbyl group. In yet other aspects, R<NUM> may be a C<NUM> to C<NUM> aryl group; or alternatively, a C<NUM> to C<NUM> aryl group. In a further aspect, any organyl group, hydrocarbyl group or aryl group which may be used as R<NUM> within the nitrogen-containing compound of the present disclosure may be substituted or non-substituted.

In a particular aspect, any substituted organyl group, substituted hydrocarbyl group or substituted aryl group which may be used as R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and/or R<NUM> may contain one or more non-hydrogen substituents. The non-hydrogen substituents suitable for use herein may be a halogen, a C<NUM> to C<NUM> hydrocarbyl group, a C<NUM> to C<NUM> hydrocarboxy group, or a combination thereof. In an aspect, the halogen utilized as the non-hydrogen substituent may be fluorine, chlorine, bromine, or iodine. Non-limiting examples of the C<NUM> to C<NUM> hydrocarboxy group suitable for use herein include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, a hexoxy group, a phenoxy group, a toloxy group, a xyloxy group, a trimethylphenoxy group, and a benzoxy group.

R<NUM> and/or R<NUM> of a respective nitrogen-containing compound which has an R<NUM> and/or R<NUM> may each independently be hydrogen or a methyl group.

R<NUM> of a respective nitrogen-containing compound which has an R<NUM> may be a branched alkyl group or a linear alkyl group. In an aspect, R<NUM> may be a C<NUM> to C<NUM> branched alkyl group; alternatively, a C<NUM> to C<NUM> branched alkyl group; or alternatively, a C<NUM> to C<NUM> branched alkyl group. In a further aspect, R<NUM> may be a C<NUM> to C<NUM> linear alkyl group; alternatively, a C<NUM> to C<NUM> linear alkyl group; or alternatively, a C<NUM> to C<NUM> linear alkyl group.

In still another aspect, a nitrogen-containing compound of the present disclosure which has Structure <NUM> may have x wherein x is an integer from <NUM> to <NUM>. In an aspect, the nitrogen-containing compound which has Structure <NUM> may have y wherein y is an integer from <NUM> to <NUM>. In yet a further aspect, the nitrogen-containing compound which has Structure <NUM> may have Z wherein Z is oxygen.

A nitrogen-containing compound suitable for use in the present disclosure is an alkanolamine, an amide, an amine, an alkylamine, an ammonium hydroxide, an aniline, a hydrazide, a hydroxylamine, an imine, a urea, or a combination thereof. In a further aspect, the alkanolamine, the amide, the amine, the ammonium hydroxide, the hydrazide, the hydroxylamine, the imine, and/or the urea used as the nitrogen-containing compound may contain one or more substituent groups. In an aspect, any substituent group contained within any nitrogen-containing compound of the present disclosure may be a halogen, a C<NUM> to C<NUM> organyl group, a C<NUM> to C<NUM> hydrocarbyl group, a C<NUM> to C<NUM> hydrocarboxy group, or a combination thereof. The halogen utilized as the substituent group of any aspect disclosed herein may be fluorine, chlorine, bromine, or iodine. Non-limiting examples of the C<NUM> to C<NUM> hydrocarboxy group suitable for use herein include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, a hexoxy group, a phenoxy group, a toloxy group, a xyloxy group, a trimethylphenoxy group, and a benzoxy group.

In a still further aspect, non-limiting examples of specific nitrogen-containing compounds suitable for use in the present disclosure include acetamide, acryl amide, allyl amine, ammonia, ammonium hydroxide, butyl amine, tert-butyl amine, N,N'-dibutyl urea, creatine, creatinine, diethanol amine, diethylhydroxy amine, diisopropanol amine, dimethylaminoethanol, dimethyl carbamate, dimethyl formamide, dimethyl glycine, dimethylisopropanol amine, N,N'-dimethyl urea, ethanol amine, ethyl amine, glycol amine, hexyl amine, hydroxyamine, imidazole, isopropanol amine, methacryl amide, methyl amine, N-methyl aniline, N-methyl-<NUM>-propanol amine, methyldiethanol amine, methyl formamide, propyl amine, <NUM>-propanol amine, pyrazole, pyrrolidine, pyrrolidinone, succinimide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, triethanol amine, triisopropanol amine, trimethyl amine, urea, <NUM>,<NUM>-diazabicyclo[<NUM>. <NUM>]undec-<NUM>-ene, or a combination thereof.

A pre-catalyst of the present disclosure comprises an equivalent molar ratio of titanium to nitrogen-containing compound in a range of from <NUM>:<NUM> to <NUM>:<NUM>; alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>; or alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>. In an aspect, the equivalent molar ratio of titanium to nitrogen-containing compound is in a range of from about <NUM>:<NUM> to about <NUM>:<NUM>.

In a particular aspect, a pre-catalyst composition of the present disclosure comprises a titano-organic salt. The pre-catalyst composition comprising the titano-organic salt further comprises a silica support and a chromium-containing compound, both of the type previously disclosed herein. The titano-organic salt suitable for use herein comprises titanium, a protonated nitrogen-containing compound, and a carboxylate.

The titano-organic salt comprises titanium. The source of titanium may be any titanium-containing compound capable of providing a sufficient amount of titanium to a pre-catalyst as disclosed herein. In a further aspect, the source of titanium is a titanium-containing compound of the type previously disclosed herein.

The titano-organic salt comprises a protonated nitrogen-containing compound.

The protonated nitrogen-containing compound comprises a protonated alkanolamine, a protonated amide, a protonated amine, a protonated alkylamine, a protonated ammonium hydroxide, a protonated aniline, a protonated hydroxylamine, a protonated urea, or a combination thereof.

In yet a further aspect, the protonated nitrogen-containing compound comprises protonated acetamide, protonated acryl amide, protonated allyl amine, ammonium, protonated ammonium hydroxide, protonated butyl amine, protonated tert-butyl amine, protonated N,N'-dibutyl urea, protonated creatine, protonated creatinine, protonated diethanol amine, protonated diethylhydroxy amine, protonated diisopropanol amine, protonated dimethylaminoethanol, protonated dimethyl carbamate, protonated dimethyl formamide, protonated dimethyl glycine, protonated dimethylisopropanol amine, protonated N,N'-dimethyl urea, protonated ethanol amine, protonated ethyl amine, protonated glycol amine, protonated hexyl amine, protonated hydroxyamine, protonated imidazole, protonated isopropanol amine, protonated methacryl amide, protonated methyl amine, protonated N-methyl aniline, protonated N-methyl-<NUM>-propanol amine, protonated methyldiethanol amine, protonated methyl formamide, protonated propyl amine, protonated <NUM>-propanol amine, protonated pyrazole, protonated pyrrolidine, protonated pyrrolidinone, protonated succinimide, protonated tetraethylammonium hydroxide, protonated tetramethylammonium hydroxide, protonated triethanol amine, protonated triisopropanol amine, protonated trimethyl amine, protonated urea, protonated <NUM>,<NUM>-diazabicyclo[<NUM>. <NUM>]undec-<NUM>-ene, or a combination thereof.

The titano-organic salt comprises a carboxylate. The carboxylate may be any carboxylate capable of providing a sufficient amount of titanium to a pre-catalyst as disclosed herein. In an aspect, the carboxylate may comprise an anionic form of any carboxylic acid of the type previously disclosed herein.

In a further aspect, the carboxylate comprises a C<NUM> to C<NUM> monocarboxylate, a C<NUM> to C<NUM> dicarboxylate, a C<NUM> to C<NUM> tricarboxylate, a C<NUM> to C<NUM> α-hydroxycarboxylate, or a combination thereof.

In a still further aspect, the carboxylate comprises acetate, citrate, gluconate, glycolate, glyoxylate, lactate, malate, malonate, oxalate, phosphonoacetate, tartrate, or a combination thereof.

In a further aspect, an amount of titanium present in the titano-organic salt of the present disclosure may range from about <NUM> wt. % to about <NUM> wt. %; or alternatively, from about <NUM> wt. % to about <NUM> wt. % titanium based upon a total weight of silica of a pre-catalyst as disclosed herein. The titano-organic salt comprises an equivalent molar ratio of titanium to carboxylate in a range of from <NUM>:<NUM> to <NUM>:<NUM>; alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM> or alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>. In some aspects, the equivalent molar ratio of titanium to carboxylate may be about <NUM>:<NUM>. The titano-organic salt comprises an equivalent molar ratio of titanium to nitrogen-containing compound in a range of from <NUM>:<NUM> to <NUM>:<NUM>; alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>; or alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>. In a still further aspect, the equivalent molar ratio of titanium to nitrogen-containing compound may be about <NUM>:<NUM>.

In an aspect of the present disclosure, a method for preparation of an olefin polymerization catalyst comprises utilization of a solubilized titanium mixture (STM). In a particular aspect, the STM of the present disclosure comprises a carboxylic acid, a titanium-containing compound, a nitrogen-containing compound, and a solvent. In an aspect, the STM comprises a carboxylic acid of the type used as a component of a pre-catalyst as disclosed herein. In a further aspect, the STM comprises a titanium-containing compound of the type used as a component of the pre-catalyst as disclosed herein. In a further aspect, the STM comprises a nitrogen-containing compound of the type used as a component of the pre-catalyst as disclosed herein.

In a further aspect, the STM of the present disclosure comprises a solvent. The solvent may be an aqueous solvent, an alcohol, an organic solvent, a hydrocarbon, or a combination thereof. A non-limiting example of an aqueous solvent suitable for use in the present disclosure comprises deionized water, distilled water, filtered water, or a combination thereof. Non-limiting examples of alcohols suitable for use as the solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, pentanol, hexanol, cyclohexanol, heptanol, octanol, benzyl alcohol, phenol, or a combination thereof. In a further aspect, the organic solvent suitable for use in the present disclosure may be an ester, a ketone, or a combination thereof. Non-limiting examples of esters suitable for use as the solvent include ethyl acetate, propyl acetate, butyl acetate, isobutyl isobutyrate, methyl lactate, ethyl lactate, or a combination thereof. Non-limiting examples of ketones suitable for use as the solvent include acetone, ethyl methyl ketone, methyl isobutyl ketone, or a combination thereof. In a particular aspect, the hydrocarbon suitable for use as the solvent may be a halogenated aliphatic hydrocarbon, an aromatic hydrocarbon, a halogenated aromatic hydrocarbon, or a combination thereof. Non-limiting examples of the hydrocarbon suitable for use as the solvent include methylene chloride, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, benzene, toluene, ethylbenzene, xylenes, chlorobenzene, dichlorobenzene, or a combination thereof.

In a particular aspect, a solubilized titanium mixture (STM) as disclosed herein comprises an acidic mixture that may be prepared by contacting a carboxylic acid and a solvent. In an aspect, the STM is prepared by sequential addition of a titanium-containing compound followed by a nitrogen-containing compound to the acidic mixture as disclosed herein. In an alternative aspect, the titanium-containing compound and the nitrogen-containing compound may be contacted to form a basic mixture that is subsequently contacted with the acidic mixture to form the STM as disclosed herein. In a further aspect, the nitrogen-containing compound utilized to form the basic mixture may be a component of an aqueous solution.

In an aspect, a solubilized titanium mixture (STM) of the present disclosure comprises an acidic mixture having a weight ratio of solvent to carboxylic acid in a range of from about <NUM>:<NUM> to about <NUM>:<NUM>; alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>; or alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>. In a further aspect, the STM comprises an equivalent molar ratio of titanium-containing compound to carboxylic acid in a range of from about <NUM>:<NUM> to about <NUM>:<NUM>; alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>; or alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>. In some aspects, the equivalent molar ratio of titanium-containing compound to carboxylic acid may be about <NUM>:<NUM>. In another aspect, the STM comprises an equivalent molar ratio of nitrogen-containing compound to carboxylic acid in a range of from about <NUM>:<NUM> to about <NUM>:<NUM>; alternatively, from about <NUM>:<NUM> to about <NUM>: <NUM>; alternatively, from about <NUM>: <NUM> to about <NUM>:<NUM>; or alternatively, from about <NUM>: <NUM> to about <NUM>:<NUM>.

In yet a further aspect, the STM comprises an equivalent molar ratio of titanium-containing compound to nitrogen-containing compound in a range of from about <NUM>:<NUM> to about <NUM>: <NUM>; alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>; alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>; or alternatively, from about <NUM>:<NUM> to about <NUM>:<NUM>. In still further aspects, the equivalent molar ratio of titanium-containing compound to nitrogen-containing compound may be about <NUM>:<NUM>.

In a particular aspect, the STM suitable for use in the present disclosure may be characterized by a pH of less than about <NUM>. Alternatively, the STM may be characterized by a pH in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>.

In an aspect of the present disclosure the catalyst components disclosed herein may be contacted in any order or fashion deemed suitable to one of ordinary skill in the art with the aid of the present disclosure to produce an olefin polymerization catalyst having the characteristics disclosed herein.

In a particular aspect, a method for preparation of an olefin polymerization catalyst comprises contacting a solvent and a carboxylic acid, both of the type disclosed herein, to form an acidic mixture. The method may further comprise contacting a titanium-containing compound of the type disclosed herein and the acidic mixture to form an acidic titanium mixture. In an aspect, a nitrogen-containing compound of the type disclosed herein, and the acidic titanium mixture may be contacted to form a solubilized titanium mixture (STM) as disclosed herein, e.g., the nitrogen-containing compound may be added to the acidic titanium mixture to form the STM. In some aspects, the nitrogen-containing compound is added to the acidic titanium mixture as a single portion of an amount sufficient to form an equivalent molar ratio of titanium-containing compound to nitrogen-containing compound of about <NUM>:<NUM> within the STM. In a particular aspect, an amount of nitrogen-containing compound to be added to the acidic titanium mixture is determined with an acid-base indicator, (e.g., bromocresol green), wherein the nitrogen-containing compound is added to the acidic titanium mixture in multiple portions and wherein a single portion comprises from about <NUM> % to about <NUM> % of the amount of nitrogen-containing compound that comprises an equivalent molar ratio of titanium-containing compound to nitrogen-containing compound of about <NUM>:<NUM>. Addition of the multiple portions of the nitrogen-containing compound may be ceased when a green-hued endpoint of a bromocresol green indicator is achieved. In some aspects, the green-hued endpoint of the bromocresol green indicator correlates to a pH value within the STM of about <NUM>. In a further aspect, addition of the nitrogen-containing compound to the acidic titanium mixture comprises neutralizing the acidic titanium mixture partially; or alternatively, neutralizing the acidic titanium mixture completely. The method for preparation of the olefin polymerization catalyst may further comprise contacting a chromium-silica support of the type disclosed herein and the STM to form an addition product. In a further aspect, the addition product may be dried by heating the addition product to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the addition product in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form a pre-catalyst.

In a further aspect, a method for preparation of an olefin polymerization catalyst comprises contacting a solvent and a carboxylic acid, both of the type disclosed herein, to form an acidic mixture. The method may further comprise contacting a titanium-containing compound of the type disclosed herein and the acidic mixture to form an acidic titanium mixture. In an aspect, a nitrogen-containing compound of the type disclosed herein, and the acidic titanium mixture may be contacted to form a solubilized titanium mixture (STM) as disclosed herein, e.g., the nitrogen-containing compound may be added to the acidic titanium mixture to form the STM. In some aspects, the nitrogen-containing compound is added to the acidic titanium mixture as a single portion of an amount sufficient to form an equivalent molar ratio of titanium-containing compound to nitrogen-containing compound of about <NUM>:<NUM> within the STM. In a particular aspect, an amount of nitrogen-containing compound to be added to the acidic titanium mixture is determined with an acid-base indicator, (e.g., bromocresol green), wherein the nitrogen-containing compound is added to the acidic titanium mixture in multiple portions and wherein a single portion comprises from about <NUM> % to about <NUM> % of the amount of nitrogen-containing compound that comprises an equivalent molar ratio of titanium-containing compound to nitrogen-containing compound of about <NUM>:<NUM>. Addition of the multiple portions of the nitrogen-containing compound may be ceased when a green-hued endpoint of a bromocresol green indicator is achieved. In some aspects, the green-hued endpoint of the bromocresol green indicator correlates to a pH value within the STM of about <NUM>. In a further aspect, addition of the nitrogen-containing compound to the acidic titanium mixture comprises neutralizing the acidic titanium mixture partially; or alternatively, neutralizing the acidic titanium mixture completely. The method for preparation of the olefin polymerization catalyst may further comprise contacting a silica support of the type disclosed herein and the STM to form a titanated support. In a further aspect, the titanated support may be dried by heating the titanated support to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the titanated support in the range of from <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form a dried titanated support. The method may further comprise contacting a chromium-containing compound of the type disclosed herein and the dried titanated support to form an addition product that may be dried by heating the addition product to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the addition product in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form a pre-catalyst. In an alternative aspect, prior to drying the titanated support as disclosed herein the chromium-containing compound and the titanated support may be contacted to form the addition product that may be dried by heating the addition product to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the addition product in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form the pre-catalyst. In yet another alternative aspect, the chromium-containing compound and the silica support may be contacted to form a chromium-silica support that may be contacted with the STM to form the addition product that may be dried by heating the addition product to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the addition product in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form the pre-catalyst.

In yet a further aspect, a method for preparation of an olefin polymerization catalyst comprises contacting a titanium-containing compound and a nitrogen-containing compound, both of the type disclosed herein, to form a basic mixture. The method may further comprise contacting a solvent and a carboxylic acid, both of the type disclosed herein, to form an acidic mixture. The basic mixture and the acidic mixture may be contacted to form a solubilized titanium mixture (STM) as disclosed herein, e.g., the basic mixture may be added to the acidic mixture to form the STM. In some aspects, the basic mixture is added to the acidic mixture as a single portion of an amount sufficient to form an equivalent molar ratio of titanium-containing compound to carboxylic acid of about <NUM>:<NUM>. In a particular aspect, an amount of basic mixture to be added to the acidic mixture is determined with an acid-base indicator, (e.g., bromocresol green), wherein the basic mixture is added to the acidic mixture in multiple portions and wherein a single portion comprises from about <NUM> % to about <NUM> % of the amount of basic mixture that comprises an equivalent molar ratio of titanium-containing compound to carboxylic acid of about <NUM>:<NUM>. Addition of the multiple portions of the basic mixture may be ceased when a green-hued endpoint of a bromocresol green indicator is achieved. In some aspects, the green-hued endpoint of the bromocresol green indicator correlates to a pH value within the STM of about <NUM>. In a further aspect, addition of the basic mixture to the acidic mixture comprises neutralizing the acidic mixture partially; or alternatively, neutralizing the acidic mixture completely. The method for preparation of the olefin polymerization catalyst may further comprise contacting a chromium-silica support of the type disclosed herein and the STM to form an addition product. In a further aspect, the addition product may be dried by heating the addition product to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the addition product in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form the pre-catalyst.

In a still further aspect, a method for preparation of an olefin polymerization catalyst comprises contacting a titanium-containing compound and a nitrogen-containing compound, both of the type disclosed herein, to form a basic mixture. The method may further comprise contacting a solvent and a carboxylic acid, both of the type disclosed herein, to form an acidic mixture. The basic mixture and the acidic mixture may be contacted to form a solubilized titanium mixture (STM) as disclosed herein, e.g., the basic mixture may be added to the acidic mixture to form the STM. In some aspects, the basic mixture is added to the acidic mixture as a single portion of an amount sufficient to form an equivalent molar ratio of titanium-containing compound to carboxylic acid of about <NUM>:<NUM>. In a particular aspect, an amount of basic mixture to be added to the acidic mixture is determined with an acid-base indicator, (e.g., bromocresol green), wherein the basic mixture is added to the acidic mixture in multiple portions and wherein a single portion comprises from about <NUM> % to about <NUM> % of the amount of basic mixture that comprises an equivalent molar ratio of titanium-containing compound to carboxylic acid of about <NUM>:<NUM>. Addition of the multiple portions of the basic mixture may be ceased when a green-hued endpoint of a bromocresol green indicator is achieved. In some aspects, the green-hued endpoint of the bromocresol green indicator correlates to a pH value within the STM of about <NUM>. In a further aspect, addition of the basic mixture to the acidic mixture comprises neutralizing the acidic mixture partially; or alternatively, neutralizing the acidic mixture completely. The method for preparation of the olefin polymerization catalyst may further comprise contacting a silica support of the type disclosed herein and the STM to form a titanated support. In a further aspect, the titanated support may be dried by heating the titanated support to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the titanated support in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form a dried titanated support. The method may further comprise contacting a chromium-containing compound of the type disclosed herein and the dried titanated support to form an addition product that may be dried by heating the addition product to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the addition product in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form a pre-catalyst. In an alternative aspect, prior to drying the titanated support as disclosed herein the chromium-containing compound and the titanated support may be contacted to form the addition product that may be dried by heating the addition product to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the addition product in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form the pre-catalyst. In yet another alternative aspect, the chromium-containing compound and the silica support may be contacted to form a chromium-silica support that may be contacted with the STM to form the addition product that may be dried by heating the addition product to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. The method further comprises maintaining the temperature of the addition product in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period of from about <NUM> minutes to about <NUM> hours to form the pre-catalyst.

Utilization of a solubilized titanium mixture (STM) in the preparation of an olefin polymerization catalyst of the present disclosure may be advantageous because the STM can facilitate the association of titanium with a silica support in the presence of an aqueous solvent (e.g., water). Further advantages may occur when the STM utilized to form the olefin polymerization catalyst comprises an aqueous solvent (e.g., water). The solubility of titanium in the aqueous solvent may be sufficient to allow the use of spray drying methodologies for contacting the STM and the silica support. Spray drying as used herein refers to a method of producing a dry powder from a liquid or slurry by rapidly drying with a hot gas. Spray drying methodologies may be utilized in the preparation of olefin polymerization catalysts in a continuous production method with the potential to produce large volumes of olefin polymerization catalysts. Spray drying methodologies may also be utilized in the preparation of olefin polymerization catalysts having a consistent particle size distribution. Utilization of the STM comprising the aqueous solvent may permit use of a hydrated silica support and obviate the thermal treatment required for anhydrous methods of catalyst preparation, (e.g., drying the hydrated silica support prior to contact with any other catalyst component).

In some aspects of the present disclosure, contacting of the components utilized in preparation of the olefin polymerization catalyst may be carried out in the presence of a reaction media. In a further aspect, the reaction media may be formed during contacting of the components utilized in preparation of the olefin polymerization catalyst. The reaction media may comprise a solvent (e.g., water) as disclosed herein and one or more liquids associated with the components utilized in preparation of the olefin polymerization catalyst (e.g., water associated with the silica support). In an aspect, the reaction media excludes any solid component utilized in the preparation of the olefin polymerization catalyst disclosed herein (e.g., silica support and any solids associated therewith). In some aspects, a sum of an amount of water present in the reaction media may be in a range of from about <NUM> wt. % to about <NUM> wt. %; alternatively, from about <NUM> wt. % to about <NUM> wt. %; alternatively, from about <NUM> wt. % to about <NUM> wt. %; or alternatively, from about <NUM> wt. % to about <NUM> wt. % based upon the total weight of the reaction media. In yet a further aspect, the reaction media may contain greater than about <NUM> wt. % water; alternatively, about <NUM> wt. % water; alternatively, about <NUM> wt. % water; alternatively, about <NUM> wt. % water; or alternatively, about <NUM> wt. % water based upon the total weight of the reaction media wherein the water may originate from one or more components utilized in preparation of the olefin polymerization catalyst.

In any aspect of the present disclosure, a method for preparation of an olefin polymerization catalyst further comprises activating a pre-catalyst prepared as disclosed herein via a calcination step. In some aspects, calcination of the pre-catalyst comprises heating the pre-catalyst in an oxidizing environment to produce the olefin polymerization catalyst. For example, the pre-catalyst may be calcined by heating the pre-catalyst in the presence of air to a temperature in a range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM>. Calcination of the pre-catalyst may further comprise maintaining the temperature of the pre-catalyst in the presence of air in the range of from about <NUM> to about <NUM>; alternatively, from about <NUM> to about <NUM>; or alternatively, from about <NUM> to about <NUM> for a time period in a range of from about <NUM> minute to about <NUM> hours; alternatively, from about <NUM> minute to about <NUM> hours; alternatively, from about <NUM> minutes to about <NUM> hours; alternatively, from about <NUM> hour to about <NUM> hours; alternatively, from about <NUM> hours to about <NUM> hours; or alternatively, from about <NUM> hours to about <NUM> hours to produce the olefin polymerization catalyst.

The olefin polymerization catalysts of the present disclosure are suitable for use in any olefin polymerization method, using various types of polymerization reactors. In an aspect of the present disclosure, a polymer of the present disclosure is produced by any olefin polymerization method, using various types of polymerization reactors. As used herein, "polymerization reactor" includes any reactor capable of polymerizing olefin monomers to produce homopolymers and/or copolymers. Homopolymers and/or copolymers produced in the reactor may be referred to as resin and/or polymers. The various types of reactors include, but are not limited to, those that may be referred to as batch, slurry, gas-phase, solution, high pressure, tubular, autoclave, or other reactor and/or reactors. Gas phase reactors may comprise fluidized bed reactors or staged horizontal reactors. Slurry reactors may comprise vertical and/or horizontal loops. High pressure reactors may comprise autoclave and/or tubular reactors. Reactor types may include batch and/or continuous processes. Continuous processes may use intermittent and/or continuous product discharge or transfer. Processes may also include partial or full direct recycle of un-reacted monomer, un-reacted comonomer, olefin polymerization catalyst and/or co-catalysts, diluents, and/or other materials of the polymerization process.

Polymerization reactor systems of the present disclosure may comprise one type of reactor in a system or multiple reactors of the same or different type, operated in any suitable configuration. Production of polymers in multiple reactors may include several stages in at least two separate polymerization reactors interconnected by a transfer system making it possible to transfer the polymers resulting from the first polymerization reactor into the second reactor. Alternatively, polymerization in multiple reactors may include the transfer, either manual or automatic, of polymer from one reactor to subsequent reactor or reactors for additional polymerization. Alternatively, multi-stage or multi-step polymerization may take place in a single reactor, wherein the conditions are changed such that a different polymerization reaction takes place.

The desired polymerization conditions in one of the reactors may be the same as or different from the operating conditions of any other reactors involved in the overall process of producing the polymer of the present disclosure. Multiple reactor systems may include any combination including, but not limited to, multiple loop reactors, multiple gas phase reactors, a combination of loop and gas phase reactors, multiple high pressure reactors, and a combination of high pressure with loop and/or gas reactors. The multiple reactors may be operated in series or in parallel. In an aspect of the present disclosure, any arrangement and/or any combination of reactors may be employed to produce the polymer of the present disclosure.

According to one aspect of the present disclosure, the polymerization reactor system may comprise at least one loop slurry reactor. Such reactors are commonplace and may comprise vertical or horizontal loops. Generally, continuous processes may comprise the continuous introduction of a monomer, an olefin polymerization catalyst, and/or a diluent into a polymerization reactor and the continuous removal from this reactor of a suspension comprising polymer particles and the diluent. Monomer, diluent, olefin polymerization catalyst, and optionally any comonomer may be continuously fed to a loop slurry reactor, where polymerization occurs. Reactor effluent may be flashed to remove the liquids that comprise the diluent from the solid polymer, 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; separation by centrifugation; or other appropriate method of separation.

Typical slurry polymerization processes (also known as particle-form processes) are disclosed in <CIT>,<CIT>, <CIT>,<CIT>,<CIT>, <CIT> and <CIT>, for example.

Diluents suitable for use 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 the polymerization of propylene monomer as disclosed in <CIT>.

According to yet another aspect of the present disclosure, 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 olefin polymerization 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 an olefin polymerization catalyst-containing polymer formed in a first polymerization zone to a second polymerization zone. One type of gas phase reactor suitable for use is disclosed in <CIT>, <CIT>, and <CIT>.

According to still another aspect of the present disclosure, 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 olefin polymerization catalysts are added. Monomer may be entrained in an inert gaseous stream and introduced at one zone of the reactor. Initiators, olefin polymerization 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 present disclosure, the polymerization reactor may comprise a solution polymerization reactor wherein the monomer is contacted with the olefin polymerization catalyst composition by suitable stirring or other means. A carrier comprising an organic diluent or excess monomer may be employed. If desired, the monomer may be brought in the vapor phase and 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 use in the present disclosure may further comprise any combination of at least one raw material feed system, at least one feed system for an olefin polymerization catalyst or catalyst components, and/or at least one polymer recovery system. Suitable reactor systems for the present disclosure 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 polymer properties include, but are not limited to, temperature, pressure, type and quantity of the olefin polymerization catalyst or co-catalyst, and the concentrations of various reactants. Polymerization temperature can affect catalyst productivity, polymer molecular weight and molecular weight distribution. Suitable polymerization temperatures may be any temperature below the depolymerization temperature, according to the Gibbs Free Energy Equation. Typically, this includes from about <NUM> to about <NUM>, for example, and/or from about <NUM> to about <NUM>, depending upon the type of polymerization reactor and/or polymerization process.

Suitable pressures will also vary according to the reactor and polymerization process. The pressure for liquid phase polymerization in a loop reactor is typically less than <NUM> psig (<NUM> MPa). Pressure for gas phase polymerization is usually in a range of from about <NUM> psig (<NUM> MPa) - <NUM> psig (<NUM> MPa). High-pressure polymerization in tubular or autoclave reactors is generally run in a range of from about <NUM>,<NUM> psig (<NUM> MPa) to <NUM>,<NUM> psig (<NUM> MPa). Polymerization reactors can also be operated in a supercritical region occurring at generally higher temperatures and pressures. Operation at conditions above the critical point as indicated by a pressure/temperature diagram (supercritical phase) may offer advantages.

The concentration of various reactants can be controlled to produce polymers with certain physical and mechanical properties. The proposed end-use product that will be formed by the polymer and the method of forming that product may be varied to determine the desired final product properties. Mechanical properties include, but are not limited to tensile strength, flexural modulus, impact resistance, creep, stress relaxation and hardness test values. Physical properties include, but are not limited to density, molecular weight, molecular weight distribution, melting temperature, glass transition temperature, temperature melt of crystallization, density, stereoregularity, crack growth, short chain branching, long chain branching and rheological measurements.

The concentrations of monomer, comonomer, hydrogen, co-catalyst, modifiers, and electron donors are generally important in producing specific polymer properties. Comonomer may be used to control product density. Hydrogen may be used to control product molecular weight. Co-catalysts may be used to alkylate, scavenge poisons and/or control molecular weight. The concentration of poisons may be minimized, as poisons may impact the reactions and/or otherwise affect polymer product properties. Modifiers may be used to control product properties and electron donors may affect stereoregularity.

Polymers such as polyethylene homopolymers and copolymers of ethylene with other mono-olefins may be produced in the manner described above using the olefin polymerization catalysts prepared as described herein. Polymers produced as disclosed herein may be formed into articles of manufacture or end use articles using techniques known in the art such as extrusion, blow molding, injection molding, fiber spinning, thermoforming, and casting. For example, a polymer resin may be extruded into a sheet, which is then thermoformed into an end use article such as a container, a cup, a tray, a pallet, a toy, or a component of another product. Examples of other end use articles into which the polymer resins may be formed include pipes, films, and bottles.

A method of the present disclosure comprises contacting an olefin polymerization catalyst of the type described with an olefin monomer under conditions suitable for the formation of a polyolefin and recovering the polyolefin. In an aspect the olefin monomer is an ethylene monomer and the polyolefin is an ethylene polymer (polyethylene).

Polyethylene prepared as described herein may be characterized by a high load melt index (HLMI), in a range of from about <NUM>/<NUM>. to about <NUM>/<NUM>. ; alternatively, from about <NUM>/<NUM>. to about <NUM>/<NUM>. ; alternatively, from about <NUM>/<NUM>. to about <NUM>/<NUM>. ; or alternatively, from about <NUM>/<NUM>. to about <NUM>/<NUM>. In a further aspect, the polyethylene prepared as described herein may be characterized by an HLMI that is from about <NUM> to about <NUM> times greater than the HLMI of a polymer produced by utilizing an otherwise similar olefin polymerization catalyst produced in the absence of a nitrogen-containing compound.

In a particular aspect, polyethylene may be prepared with a de-titanated catalyst that was produced from a water-extracted pre-catalyst. In a further aspect, the water-extracted pre-catalyst is a pre-catalyst that was extracted with water prior to being calcined. For example, a pre-catalyst prepared as described herein may be extracted with water and subsequently calcined to provide the de-titanated catalyst (i.e., olefin polymerization catalyst derived from the water-extracted pre-catalyst). In a further aspect, polyethylene prepared with a de-titanated catalyst may be characterized by an HLMI in the range of from about <NUM> dg/min to about <NUM> dg/min. Such an HMLI value can indicate that the de-titanated catalyst has an amount of titanium based upon an amount of silica in a range of from about <NUM> wt. % to about <NUM> wt. %; or alternatively, about <NUM> wt. % to about <NUM> wt.

The melt index (MI) represents the rate of flow of a molten polymer through an orifice of <NUM> inch diameter when subjected to a force of <NUM>,<NUM> grams at <NUM> as determined in accordance with ASTM D1238-<NUM> condition E. The I10 represents the rate of flow of a molten polymer through an orifice of <NUM> inch diameter when subjected to a force of <NUM>,<NUM> grams at <NUM> as determined in accordance with ASTM D1238-<NUM> condition N. The HLMI (high load melt index) represents the rate of flow of a molten polymer through an orifice of <NUM> inch diameter when subjected to a force of <NUM>,<NUM> grams at <NUM> as determined in accordance with ASTM D1238-<NUM> condition F.

The following examples are given as particular aspects of the present disclosure and to demonstrate the practice and advantages thereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification or the claims to follow in any manner.

It will be appreciated by one skilled in the art that the surfaces of oxides, including silica (SiO<NUM>) and titania (TiO<NUM>), commonly terminate with hydroxyl groups which are protic groups that can participate in acid-base reactions. In strongly acidic conditions the hydroxyl groups can be protonated to establish a positive charge upon the oxide surface. In strongly alkaline conditions the hydroxyl groups may be deprotonated to establish a negative charge upon the oxide surface. There is a pH value somewhere between the two limits at which zero net charge exists upon the oxide surface. The pH value correlating to zero net charge is the isoelectric point. Every oxide possesses a characteristic acidity and a specific isoelectric point controlled by the chemical properties of the metal or non-metal element of the oxide.

The Figure displays zeta potential as a function of solution pH value for silica and titania along with the isoelectric point value of both oxides. A curve of the coulombic Si-Ti attraction is also shown. Zeta potential is the difference in electrical charge potential existing between the surface of a solid particle immersed in a conducting liquid (e.g., water) and the bulk of the liquid. The Figure displays that titania is positively charged and silica is negatively charged within a zone of pH values between <NUM> and <NUM>. The Figure also indicates that coulombic Si-Ti attraction is greatest around a pH value of about <NUM>. Not wishing to be limited by theory, highly effective titanation of an olefin polymerization catalyst from an aqueous Ti solution may result when the coulombic Si-Ti attraction is maximized by maintaining a pH value of the solution at about <NUM>. To explore this theory, several series of experiments were conducted to establish conditions leading to the formation of an aqueous Ti solution with a pH value of about <NUM>.

All of the silica support materials, chemical reagents, and solvents described herein were used as received and were not dried prior to use.

Catalysts used in the experiments described below include Magnapore® a commercial Cr/silica-titania catalyst obtained from W. Grace and Company and activated at various temperatures. Magnapore® is made by tergellation of Si, Ti and Cr, containing <NUM> wt. % Ti and <NUM> wt. % Cr, having a surface of about <NUM><NUM>/g, a pore volume of <NUM>/g, and an average particle size of about <NUM> microns. Another commercial Cr/silica-titania catalyst that was used, called C-25305HM, was obtained from Philadelphia Quartz (PQ) Corporation. It also contains <NUM> wt. % Ti and <NUM> wt. % Cr, having has a surface of about <NUM><NUM>/g, a pore volume of <NUM>/g, and an average particle size of about <NUM> microns. The main base catalyst used for the titanations described below was Sylopol® HA30W, a commercial Cr/silica obtained from W. This catalyst contained no titanium but did contain <NUM> wt. It had a surface area of about <NUM><NUM>/g, a pore volume of about <NUM>/g, and an average particle size of about <NUM> microns. Three other commercial Cr/silica catalysts were also used; one called EP30X from PQ Corporation, another under the trade name D-<NUM>-150A(LV) from Asahi Glass Corporation (AGC), and the third was Sylopol® 969MPI from W. All three of these catalysts contained no titanium but did contain <NUM> wt. All three had a pore volume of about <NUM>/g. EP30X and 969MPI had a surface area of about <NUM><NUM>/g and an average particle size of about <NUM> microns. AGC D-<NUM>-150A(LV) had a surface area of about <NUM><NUM>/g and an average particle size of about <NUM> microns.

Activity tests were conducted in a <NUM> liter steel reactor equipped with a marine stirrer running at <NUM> rpm. The reactor was surrounded by a steel jacket circulating water, the temperature of which was controlled by use of steam and water heat exchangers. These were connected in an electronic feed-back loop so that the reactor temperature could be maintained at +/- <NUM> during the reaction.

Unless otherwise stated, a small amount (<NUM> to <NUM> grams normally) of the solid chromium catalyst was first charged under nitrogen to the dry reactor. Next about <NUM> of sulfate-treated alumina (<NUM>) was added as a scavenger for poisons. Then <NUM> liter of isobutane liquid was charged and the reactor heated up to the specified temperature, usually <NUM> degrees C. Finally, ethylene was added to the reactor to equal a fixed pressure, normally <NUM> psig (<NUM> MPa), which was maintained during the experiment. The stirring was allowed to continue for the specified time, usually around one hour, and the activity was noted by recording the flow of ethylene into the reactor to maintain the set pressure.

After the allotted time, the ethylene flow was stopped and the reactor slowly depressurized and opened to recover a granular polymer powder. In all cases the reactor was clean with no indication of any wall scale, coating or other forms of fouling. The polymer powder was then removed and weighed. Activity was specified as grams of polymer produced per gram of solid catalyst charged per hour.

Several control runs were conducted, and the results of the control runs are listed in Table <NUM>. Performance of the experimental catalysts shown in the further examples in terms of productivity, activity, and melt index potential may be compared to these control runs. Runs <NUM> -<NUM> display the performance of two non-titanated catalysts the latter of which, HA30W, provides a metric of the effectiveness of the titanations of Runs <NUM> - <NUM>. The titanations displayed in Runs <NUM> - <NUM> used Ti(OiPr)<NUM> to titanate HA30W. The titanation in Run <NUM> exposed the support to TiCl<NUM> vapor at <NUM> in an attempt to produce a titanated catalyst uncontaminated by organic or alcohol by-products. In both of these methods, the support must be dried to remove free water from the surface, usually by a thermal treatment from about <NUM> to about <NUM>. Otherwise the titanium will react with the free adsorbed water and be ineffective. In Runs <NUM> - <NUM> the catalyst was dried at <NUM> before being titanated by either gas phase or anhydrous solvent (usually heptane).

The first series of experiments studied the ability of carboxylic acids to form an acidic Ti-containing solution capable of providing effective titanation to an olefin polymerization catalyst of the type disclosed herein (i.e., catalyst). The results are listed in Table <NUM>. All of these experiments started with hydrated silica supports that were not subjected to thermal treatment prior to contact with any other catalyst component. The carboxylic acids listed were mixed with water, or an alternate solvent system as listed, to form a solution, but in all cases the solvents were not dried, and no attempt was made to use anhydrous conditions. Ti(OiPr)<NUM> was added and when dissolution occurred the acidic Ti-containing solution formed thereby was impregnated onto a chromium-silica support (HA30W). The product was then dried and calcined in air for three hours at <NUM> prior to use in polymerization experiments.

Table <NUM> summarizes the study of a variety of carboxylic acids. The use of carboxylic acids alone (no base added) did not produce very effective titanation. Run <NUM>, which used acetic acid in propanol solvent, provided the most effective titanation. Successful results were also observed when HA30W was impregnated with the acidic Ti-containing solution and dropped into a <NUM> activator tube ("hot-drop", Runs <NUM> - <NUM>). This rapid method of drying was moderately effective as evidenced by the higher melt index obtained when the catalyst was produced using this method compared to oven drying. The "hot-drop" method of drying resulted in more effective titanation when citric acid was used in place of oxalic acid. This result may have occurred because the first pKa of citric acid (<NUM>) is higher than the first pKa of oxalic acid (<NUM>). The lower acidity of citric acid may produce a Ti-containing solution with a pH value that is higher and closer to <NUM> when compared to the Ti-containing solution produced with oxalic acid.

The next series of experiments studied the ability of a base to form an alkaline Ti-containing solution capable of providing effective titanation to a catalyst. The results are listed in Table <NUM>. The experimental approach was essentially identical to the method described in Example <NUM>. Ti dissolved in some strong bases, e.g., organic bases were effective, but ammonium hydroxide and alkali hydroxides were not effective. Quaternary ammonium hydroxides dissolved Ti but uncharged primary, secondary, or tertiary amines were less effective. The melt index potentials resulting from the use of alkaline solutions were all low, like the non-titanated support, and thus did not display evidence of effective titanation of the chromium-silica support.

The results in Table <NUM> and Table <NUM> confirmed that attaching titania to silica can be problematic at both high pH and low pH. The next series of experiments were conducted to probe the theory that maximum coulombic Si-Ti attraction occurs at a pH value of about <NUM>. Ti(OiPr)<NUM> was hydrolyzed to titania which was dissolved in an aqueous solution of oxalic acid (<NUM> equivalents of oxalic acid per Ti), to produce an acidic Ti-containing solution with a pH value of about <NUM>. Ammonium hydroxide, or a quaternary derivative as listed in Table <NUM>, was added until a green-hued endpoint of a bromocresol green indicator was reached, indicating a pH value of about <NUM>, to produce a solubilized Ti mixture (STM) of the type disclosed herein. The stoichiometry required to partially neutralize the acidic Ti-containing solution, and produce the STM thereby, was usually about two equivalents of base per Ti. An HA30W support was impregnated with the STM and the product was dried and calcined in air for three hours at <NUM> prior to use in polymerization experiments.

The results listed in Table <NUM> indicate that the approach was successful. Quaternary ammonium hydroxides were more effective when compared to ammonium hydroxide. This result may be explained by the lower volatility of tetraalkylammonium hydroxides. The results in Table <NUM> also indicate that the amount of base used to prepare the STM impacted the melt index potential conferred by the resultant catalyst. The method also allowed for effective titanation upon a hydrogel, rather than a pre-formed silica support (Run <NUM>). The catalyst of Run <NUM> was prepared by inverse addition and displayed remarkable performance: Ti was dissolved in aqueous NMe<NUM>OH to form an alkaline solution that was added to an aqueous solution of oxalic acid to prepare the STM used for impregnation of the HA30W support.

The next series of experiments studied the ability of urea to partially neutralize an acidic Ti-containing solution and create an STM capable of providing effective titanation to a catalyst. Urea is easily decomposed upon heating into volatile products. Replacement of carbon-containing catalyst components with urea compounds has the potential to reduce emissions of volatile organic and highly reactive volatile organic compounds created during calcination of the catalysts. The experimental approach was essentially identical to the method described in Example <NUM> but without the use of the bromocresol green indicator. The results are shown in Table <NUM>. Addition of urea to the acidic Ti-containing solution provided increasingly effective titanation as the amount of urea was increased. This effect was not observed in experiments that investigated the use of urea in spray drying applications, possibly because the urea decomposed and/or evaporated during the spray drying operation. Effective titanation was also observed with N,N'-dimethyl urea, which is less volatile than urea.

The next series of experiments studied the ability of alkanolamines to partially neutralize an acidic Ti-containing solution and create an STM capable of providing effective titanation to a catalyst. Ethanol amines and isopropanol amines were chosen because they generally exhibit low toxicity, have low cost, are readily available from multiple sources, and have less odor in contrast to most amines. The experimental approach was essentially identical to the method described in Example <NUM> and the results are shown in Table <NUM>. The results were varied, and bulkier amines appeared to perform best. Not wishing to be limited by theory, this could be a result of the lower volatility of the bulkier compounds and/or the lower permittivity of Ti ions resulting from the bulkier compounds. Dimethylaminoethanol (DMAE) provided a relatively high melt index, is low in cost, available from multiple suppliers, and has low odor. The catalyst of Run <NUM> was prepared by dissolving titania into two equivalents of aqueous oxalic acid, followed by addition of two equivalents of DMAE to form a solubilized Ti solution (STM) of the type disclosed herein. An HA30W support was impregnated with the STM to form a titanated support that was dried in vacuum conditions overnight at <NUM>. The resultant dried titanated support was extracted with water prior to being calcined at <NUM> and subjected to polymerization experiments. The melt index data suggest that the catalyst had experienced extensive loss of Ti, presumably during the water extraction step. This observation indicates that the Ti may not have been attached thoroughly to the silica after drying at <NUM> and supports previous observations that attachment between Ti and silica occurs at least partly at temperatures greater than <NUM>.

The next series of experiments studied the ability of a variety of other amines to partially neutralize an acidic Ti-containing solution and create an STM capable of providing effective titanation to a catalyst. The experimental approach was essentially identical to the method described in Example <NUM> and the results are shown in Table <NUM>. A general trend of higher performance from bulkier amines was observed but was sometimes compromised by a lack of solubility, e.g., <NUM>-ethylhexylamine or DABCO. Bases capable of delocalizing a positive charge obtained upon protonation displayed very good performance; examples include DBU, creatine, and imidazole.

The next series of experiments studied the ability of inorganic bases to partially neutralize an acidic Ti-containing solution and create an STM capable of providing effective titanation to a catalyst. The experimental approach was essentially identical to the method described in Example <NUM> and the results are shown in Table <NUM>. This approach was generally unsuccessful. Not wishing to be limited by theory, higher permittivity may have been an influence, but the presence of divalent or trivalent metal cations could have interfered with the delicate balance of surface charge between silica and titania. Runs <NUM> and <NUM> were partially successful and co-introduced equal amounts of Al ions with Ti ions. Three equivalents of oxalic acid were added to dissolve two equivalents of metal (<NUM> Ti(OiPr)<NUM> + <NUM> Al(OH)<NUM>) which is a lower acid/metal ratio than in most of the other experiments described herein. Run <NUM> included partial neutralization of the acid with tetraethylammonium hydroxide in an amount of <NUM> equivalents of base per Ti. This is a lower base/metal ratio than in most of the other experiments described herein but an increase in HLMI was observed. Not wishing to be limited by theory, coating titania onto alumina may be more facile than coating titania onto silica. Ti and Al are both metals and the chemical properties of the two are in many ways more similar than the chemical properties of Ti and Si.

The next series of experiments studied the ability of carboxylic acids other than oxalic acid to be partially neutralized and create an STM capable of providing effective titanation to a catalyst. The experimental approach was essentially identical to the method described in Example <NUM> and the results are shown in Table <NUM>. The experiments were generally less successful than experiments using oxalic acid. Several of the experiments added two equivalents of base per Ti, which was more than needed to obtain a pH value of <NUM> because the acids tested were weaker than oxalic acid. In other experiments, base was added until a green-hued endpoint of the bromocresol green indicator was reached, indicating a pH value of <NUM>. An example of this method is Run <NUM> where the use of citric acid and tetramethylammonium hydroxide produced highly effective titanation as evidenced by an HLMI value of almost <NUM>. Run <NUM> indicated that titanyl sulfate, in the absence of a carboxylic acid, could be partially neutralized by DMAE to produce moderately effective titanation.

Claim 1:
A pre-catalyst composition comprising:
a) a silica support comprising silica wherein an amount of silica is in a range of from <NUM> wt. % to <NUM> wt. % based upon a total weight of the silica support;
b) a chromium-containing compound wherein an amount of chromium is in a range of from <NUM> wt. % to <NUM> wt. % based upon the amount of silica;
c) a titanium-containing compound wherein an amount of titanium is in a range of from <NUM> wt. % to <NUM> wt. % based upon the amount of silica;
d) a carboxylic acid wherein an equivalent molar ratio of titanium-containing compound to carboxylic acid is in a range of from <NUM>:<NUM> to <NUM>:<NUM>; and
e) a nitrogen-containing compound with a molecular formula containing at least one nitrogen atom wherein an equivalent molar ratio of titanium-containing compound to nitrogen-containing compound is in a range of from <NUM>:<NUM> to <NUM>:<NUM> and wherein: the nitrogen-containing compound comprises an alkanolamine, an amide, an amine, an alkylamine, an ammonium hydroxide, an aniline, a hydrazide, a hydroxylamine, an imine, a urea, or a combination thereof; or wherein the nitrogen-containing compound comprises acetamide, acryl amide, allyl amine, ammonia, ammonium hydroxide, butyl amine, tert-butyl amine, N,N'-dibutyl urea, creatine, creatinine, diethanol amine, diethylhydroxy amine, diisopropanol amine, dimethylaminoethanol, dimethyl carbamate, dimethyl formamide, dimethyl glycine, dimethylisopropanol amine, N,N'-dimethyl urea, ethanol amine, ethyl amine, glycol amine, hexyl amine, hydroxyamine, imidazole, isopropanol amine, methacryl amide, methyl amine, N-methyl aniline, N-methyl-<NUM>-propanol amine, methyldiethanol amine, methyl formamide, propyl amine, <NUM>-propanol amine, pyrazole, pyrrolidine, pyrrolidinone, succinimide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, triethanol amine, triisopropanol amine, trimethyl amine, urea, <NUM>,<NUM>-diazabicyclo[<NUM>.<NUM>]undec-<NUM>-ene, or a combination thereof.