METALLOCENE PURIFICATION PROCESS

Abstract: Group 4 metallocenes are separated from hydrocarbonaceous tarry material typically formed during their synthesis. This is done by mixing polar organic solvent and non-polar organic solvent with the impure mixture, these solvents being substantially incompatible with each other (e.g., acetonitrile and hexanes), so that after the mixing there are formed at least two separate phases comprising (i) a polar phase comprising mostly metallocene and the polar solvent, and (ii) a non-polar phase comprising mostly non-polar organic solvent and hydrocarbonaceous tarry material, and some metallocene. After separating these phases the non-polar phase is extracted with fresh polar organic solvent to form another polar phase comprising mainly metallocene and polar organic solvent. The metallocene can then be recovered from the polar phases, for example by distillation.

Description: METALLOCENE PURIFICATION PROCESS TECHNICAL FIELD This invention relates to the purification of metallocenes, particularly metallocene halides such as dicyclopentadienyl Group 4 metal dihalides. More particularly, this invention relates to separation of such metallocenes from tarry oligomeric materials with which they are often associated during their synthesis. BACKGROUND Metallocenes such as bridged and unbridged dicyclopentadienyl Group 4 metal dihalides are useful as components of olefin polymerization catalyst systems. As such, their purity is of considerable importance. Unfortunately, large scale processes for producing such metallocenes often coproduce significant amounts of hydrocarbonaceous tarry materials. These tars result in part from oligomerization of exo-isomers of the metallocene ligand such as alkenyl-substituted cyclopentene hydrocarbons in the presence of Group 4 metal halides used in the synthesis process. For example, during the production of, say, bis(n- butylcyclopentadienyl)zirconium dichloride, ligands such as 3-but-l-enylcyclopentene (an exo- isomer) and n-butylcyclopentadiene (an endo-isomer) can be formed in situ. In the presence of zirconium tetrachloride, the exo-isomer can be oligomerized to form an oligomer (dimers and trimers) of which the hydrocarbonaceous tarry material is comprised. Commonly-owned U.S. Pat. No. 5,648,308 describes a process for removing inorganic and organic impurities from a metallocene catalyst compound. The process comprises (a) separating inorganic impurities from the compound by forming a solution of the compound in an organic solvent medium which is substantially a non-solvent for the inorganic impurities, (b) treating the solution of the compound with a particulate absorbing material so as to absorb and remove organic impurities from the solution, and (c) separating the solid material, including the particulate absorbing material, from the solution. Preferred absorbing material are dried, porous silicas having low water and -OH group contents. Although very effective for removing various inorganic and organic impurities, the process of U.S. Pat. No. 5,648,308 is unable to remove the oligomers formed from exo- isomers of the metallocene ligand. These oligomers result from oligomerization of the exo- isomers catalyzed by inadvertent use of excess Group 4 metal halides in the synthesis process. Such oligomers are not absorbed by absorbent materials such as dried, porous silicas having 1 low water and -OH group contents. Indeed, metallocenes containing these oligomers readily pass through a silica column and remain with the metallocene even though other organic impurities such as color bodies are removed by absorption on the silica. The organic impurities that are readily removed by the process of U.S. Pat. No. 5,648,308 tend to be black-brown colored materials, and result primarily from overheating or hot-spot charring of the reaction mixture during synthesis of the metallocene. The quantity of such materials typically falls in the range of 1 to 10,000 parts by weight per million parts by weight of the metallocene product. In sharp contrast, the oligomers formed from exo-isomers of the metallocene ligand differ from the organic materials removed by process of U.S. Pat. No. 5,648,308 at least in that: a) the oligomers are formed differently (i.e., by Friedel-Crafts catalysis of the exo-isomers due to the presence of inadvertent excess of the Group 4 metal halide used in the synthesis of the metallocene); b) the oligomers are indifferent to and thus not absorbed by absorbent materials such as dried, porous silicas having low water and -OH group contents; c) in severe cases the oligomers can be formed in quantities in the range 20 to 60 wt% of the total metallocene product; and d) when the oligomers are formed, they can be, and often are, accompanied by formation of conventional small amounts of the organic materials that can be removed by the use of absorbent materials such as silica. When isolated in the fluid state the oligomers not only can be in admixture with organic materials resulting primarily from overheating or hot-spot charring of the reaction mixture, but in addition the endo-isomer of the ligand as well as some exo-isomer of the ligand that has not been oligomerized. A need thus exists for an effective, economical way of separating the metallocene halide from such oligomeric materials — whether or not accompanied by organic materials resulting primarily from overheating or hot-spot charring of the reaction mixture, and/or the endo- isomer of the ligand and/or exo-isomer of the ligand that has not been oligomerized — without significant loss of the metallocene product and without adversely affecting its usefulness as a catalyst component. This invention is deemed to fulfill this need remarkably well. THE INVENTION Pursuant to this invention, a two-stage extraction process is provided which is highly effective and economical, and moreover, facile in execution. Indeed, the two stages of the process can be carried out in the same extraction vessel. In addition, the process is capable of providing a product which satisfies purity specifications for polymerization catalyst applications. In essence, the process enables efficient separation of an unbridged or bridged dihalo Group 4 metallocene wherein the pair of hydrocarbyl groups containing the cyclopentadienyl moiety each contains, individually and independently, in the range of 5 to 18 carbon atoms, from a mixture comprising such metallocene and hydrocarbonaceous tarry material. The metallocenes which can suffer from undesired copresence of the oligomeric material of which the hydrocarbonaceous tarry material is comprised, have the formula Q-R^MXj where (i) R 1 and R 2 can be the same or different and are cyclopentadienyl, indenyl, fluorenyl, hydrocarbyl-substituted cyclopentadienyl, hydrocarbyl-substituted indenyl, or hydrocarbyl-substituted fluorenyl groups; (ii) each of R 1 and R 2 contains, individually and independently, in the range of 5 to 18 carbon atoms; (iii) at least one of R 1 and R is a hydrocarbyl-substituted cyclopentadienyl, hydrocarbyl-substituted indenyl, or hydrocarbyl- substituted fluorenyl group in which the substitution includes at least one primary alkyl substituent having at least 2 carbon atoms; (iv) M is Ti, Zr, or Hf; (v) each X is a bromine or chlorine atom; (vi) Q, if present, is a divalent linking group having a univalent bond attached directly to each of the cyclopentadienyl rings of or in R 1 and R 2 ; and (vii) n is zero or 1. As used in this specification and in the appended claims the term "hydrocarbonaceous tarry material" means the oligomeric materials referred to above, whether or not such oligomeric materials are accompanied by organic materials resulting primarily from overheating or hot- spot charring of the reaction mixture, and/or the endo-isomer of the ligand and/or exo-isomer of the ligand that has not been oligomerized. Thus the hydrocarbonaceous tarry material is composed (comprises) at least oligomerized exo-isomer of the ligand, and can, and usually does further include organic materials resulting primarily from overheating or hot-spot charring of a small portion of the reaction mixture, which materials are typically dark-colored organic color bodies. Other materials that may or may not be present in hydrocarbonaceous tarry material include the endo-isomer of the ligand and/or a portion of the exo-isomer of the ligand that has not been oligomerized. Therefore the mixtures with which this invention is concerned comprise a metallocene of the above formula, hydrocarbonaceous tarry material, and optionally, but typically, a least a portion of the aromatic hydrocarbon solvent or diluent in which the metallocene was produced. The hydrocarbonaceous tarry material is not removed from the mixture by absorption with an absorbent material such as dry silica. The efficient separation made possible by this invention is accomplished by: a) mixing polar organic solvent and non-polar organic solvent with the foregoing mixture, these solvents being substantially incompatible with each other, so that after the mixing there are formed at least two separate phases comprising (i) a substantially polar phase comprising the unbridged or bridged metallocene and polar organic solvent, and (ii) a substantially non-polar phase comprising non-polar organic solvent, hydrocarbonaceous tarry material and some of the metallocene; b) separating the polar phase and the non-polar phase; and c) extracting the non-polar phase with fresh polar organic solvent to form another substantially polar phase comprising the metallocene and polar organic solvent. The metallocene can readily be recovered from the polar phases, for example by distilling off the polar solvent. Preferably, therefore, the polar organic solvent and the non-polar organic solvent have boiling temperatures low enough to be distillable from the metallocene. In this way, any residual non-polar solvent associated with the polar solvent after the phase separation is removed during the distillation. To expedite the procedure, it is preferred to combine the separate polar phases and subject the resultant combined polar solutions to the distillation. The distillation is itself is typically performed at reduced pressures and is conducted at temperatures below the sublimation temperature and/or thermal decomposition temperature of the metallocene. In a preferred embodiment the initial mixture of metallocene and hydrocarbonaceous tarry material is subjected to a pretreatment before the above two-stage extraction process. In the pretreatment the mixture is treated with a dilute aqueous acid such as 10 to about 13 wt% aqueous hydrochloric acid, hydrobromic acid, or the like, and the mixture is stirred or otherwise agitated for about 0.5 to about 5 hours at one or more temperatures in the range of -10 to 25 °C, and preferably in the range of -10 to 10°C. Then the aqueous and organic phases are separated, for example by phase-cutting. (If the solvent or diluent of the initial mixture is predominately an aromatic solvent or diluent, it is possible, though not recommended, to replace the solvent with a predominately paraffinic solvent or diluent before conducting the treatment with dilute acid, to enhance precipitation of inorganic salt impurities such as zinc halide and iron halide) In any event, after the separation of the organic and aqueous phases, the organic phase is then treated with an aqueous brine solution (preferably a saturated solution) and stirred or otherwise agitated for about 0.5 to about 5 hours at one or more temperatures in the range of 0 to 30 °C and preferably in the range of 10 to 25 °C. The phases are then separated, e.g., by phase-cutting. The organic phase is subjected to distillation at reduced pressure (up to 70-100°C and 1-100 mm of mercury pressure) to remove volatile organics and, azeotropically, the water. The resultant organic phase remaining after the distillation is then subjected to the two-stage extraction process of this invention referred to above. Use of the above pretreatment procedure removes inorganic impurities and certain soluble organic impurities from the initial mixture. In addition, the pretreatment serves to improve the color of the end product metallocene as recovered from the ensuing two-stage extraction process. It is preferred to conduct the above pretreatment procedure in an aromatic hydrocarbon solvent or diluent as this simplifies the operation and enables removal of the water as an azeotrope in the reduced pressure distillation. Another preferred embodiment in this invention involves use of a post-treatment procedure for further improving the color characteristics of the purified metallocene end product. In this embodiment, the organic phase from the substantially polar phase comprising the metallocene and polar organic solvent formed in step c) above is replaced by a paraffinic solvent or diluent and the resultant mixture is passed through a column containing silica gel or other suitable absorbent material. Use of the pretreatment and post-treatment procedures constitutes a particularly preferred embodiment of this invention. The unbridged metallocenes have the formula R 1 R 2 MX 2 where (i) R 1 and R 2 can be the same or different and are cyclopentadienyl, indenyl, fluorenyl, hydrocarbyl-substituted cyclopentadienyl, hydrocarbyl-substituted indenyl, or hydrocarbyl-substituted fluorenyl groups; (ii) each of R 1 and R 2 contains, individually and independently, in the range of 5 to 18 carbon atoms; (iii) at least one of R 1 and R 2 is a hydrocarbyl-substituted cyclopentadienyl, hydrocarbyl-substituted indenyl, or hydrocarbyl-substituted fluorenyl group in which the hydrocarbyl substituent(s) can be, for example, alkyl, alkenyl, cycloalkyl, aryl and aralkyl, and in which the substitution includes at least one primary alkyl substituent having at least 2 carbon atoms or at least one alkenyl substituent having at least 2 carbon atoms; (iv) M is Ti, Zr, or Hf; and (v) each X is a bromine or chlorine atom. While the two X atoms may be different from each other, most preferably they are the same. The bridged metallocenes have the formula QR 1 R 2 MX 2 where M and X are as just described, and R 1 and R 2 are as described above except that they are linked or bridged together by means of a divalent linking group, Q, having a univalent bond attached directly to each of the cyclopentadienyl rings that constitute, or that form part of, R 1 and R 2 . Examples of Q include silylene (R 2 Si<), phenylene (C 6 H 4 <) or substituted phenylene, methylene (CH 2 <) or substituted methylene, and ethylene (-CH 2 CH 2 -) or substituted ethylene bridges. The metallocene whether bridged or unbridged may contain 60 or more carbon atoms in the molecule, but typically will contain from 10 to about 40 carbon atoms in the molecule. The process of this invention is preferably applied to the unbridged metallocenes. Examples of metallocenes to which this invention is applicable include such compounds as: bis(n-butylcyclopentadienyl)zirconium dichloride; bis(diethylcyclopentadienyl)zirconium dichloride; bis(n-butylmethylcyclopentadienyl)zirconium dichloride; bis(n-propylcyclopentadienyl)zirconium dichloride; bis(methylethylcyclopentadienyl)zirconium dichloride; (butylcyclopentadienyl)(cyclopentadienyl)zirconium dichloride; (butylcyclopentadienyl)(fluorenyl)zirconium dichloride; (diethylcyclopentadienyl)(fluorenyl)zirconium dichloride; bis( 1 -ethylindenyl)zirconium dichloride; bis(l -ethyl-3-methylindenyl)zirconium dichloride; bis(l -butylindenyl)zirconium dichloride; bis(butylcyclopentadienyl)hafhium dichloride; bis(diethylcyclopentadienyl)hafhium dichloride; bis(n-butylmethylcyclopentadienyl)hafhium dichloride; (butylcyclopentadienyl)(cyclopentadienyl)hafnium dichloride; (butylcyclopentadienyl)(fluorenyl)hafnium dichloride; dimethylsilylenebis(l-ethylindenyl)zirconium dichloride; dimethylsilylenebis(l-butyl-3-methylindenyl)zirconium dichloride; 1 ,2-ethylenebis( 1 -propylindenyl)zirconium dichloride; l,2-ethylenebis(l-butylindenyl)zirconium dichloride; 2,2-propylidenebis(n-pentylcyclopentadienyl)(fluorenyl)zirconium dichloride; dimethylsilylenebis( 1 -butyl-6-phenylindenyl)zirconium dichloride; and analogous bromine derivatives. The origin of the initial mixture of metallocene and hydrocarbonaceous tarry material, is of little importance, as the separation/purification procedure of this invention is deemed applicable to any mixture containing these two materials in a liquid organic medium. Typically, the initial mixture is a reaction product from a synthesis procedure for the formation of the dihalo Group IV metallocene. See for example, U.S. Pat. No. 5,569,746, issued October 29, 1996, the entire disclosure of which is incorporated herein by reference, which describes one such synthesis procedure. As noted hereinabove, the hydrocarbonaceous tarry material is or comprises oligomeric or relatively low molecular polymeric material resulting from oligomerization/polymerization of exo-isomers of the metallocene ligand, such as bridged or unbridged cyclopentadiene hydrocarbons having a primary alkyl (or alkenyl) substituent of at least 2 carbon atoms in the presence of Group 4 metal halides used in the synthesis process. For the purposes of this invention a tarry material containing silicon by virtue of use of a silyl- bridged metallocene ligand is included within the term "hydrocarbonaceous tarry material" as the material possesses the characteristics and exhibits in the practice of this invention the behavior of analogous completely hydrocarbonaceous tarry materials. Polar solvents for use in the process include suitable alcohols, nitriles, amides, and similar polar solvents which preferably are distillable liquids at temperatures of up to 100°C at pressures as low as 1 mm Hg. Examples of such solvents include acetonitrile, propionitrile, n-butyronitrile, isobutyronitrile, methanol, N,N-dimethylformamide, and N,N-dimethyl- acetamide. Mixtures of different polar solvents can be used. Acetonitrile is a particularly preferred polar solvent. The non-polar solvent is typically an inert liquid hydrocarbon solvent which can be paraffinic or cycloparaffinic. Preferred are paraffinic hydrocarbons, especially those which can be distilled at temperatures of up to 100° C at pressures as low as 1 mm Hg. Examples include n-hexane, 2-methylpentane, 3-methylpentane, n-heptane, 2,2-dimethylpentane, 2,3-dimethyl- pentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 3-ethylpentane, 2-methyl-hexane, 3-me- thylhexane, n-octane, 2-methylheptane, 4-methylheptane, 2,3-dimethyl-hexane, 2,4-dimethyl- hexane, 2,5-dimethylhexane, 3,4-dimethylhexane, 3-ethylhexane, 2,2,4-trimethylpentane, 3- ethyl-2-methylpentane, n-nonane, 2,6-dimethylheptane, n-decane, cyclohexane, methylcy- clopentane, methylcyclohexane, cycloheptane, and similar hydrocarbon solvents. Thus, mixtures of the same types of hydrocarbons (e.g., mixed paraffinic hydrocarbons such as Isopar-C and Isopar-E) and mixtures of different types of these hydrocarbons (i.e., a mixture of paraffins and cycloparaffins) can be used. Preferred non-polar solvents are those which can be distilled at temperatures below 100°C and at a pressure as low as 1 mm Hg, such as Isopar-E™. As noted above, an important feature of the polar and non-polar solvents used in the process is that they are selected so as to be substantially insoluble in each other. By this is meant that at O°C to 50°C neither the polar solvent nor the non-polar solvent of the mixed solvents selected should be capable of dissolving more than about 15 weight percent of the other. In general, the more incompatible the polar and non-polar solvents, the better. The following numbered examples illustrate procedures for conducting the process of this invention. All percentages given in these examples are by weight. It is to be clearly understood that these examples are presented for the purpose of illustrating current best modes contemplated for carrying out the two-stage purification procedure of this invention. The examples are not intended to limit, and should not be construed as limiting, the invention to the specific details set forth therein. EXAMPLE 1 A portion of a dark blue-green reaction product mixture (300 kg) containing bis(l- butyl-3-methylcyclopentadienyl)zirconium dichloride, toluene, some inorganic metal chloride salts, and approximately 150 kg of a hydrocarbonaceous tarry or oligomeric material is subjected to purification pursuant to this invention as follows: At 5-10°C with stirring, 100 grams of 11 wt% aqueous HCl is slowly added over a period of 30 minutes to 100 grams of the above dark green solution having a content of about 29 wt% of bis(l-butyl-3-methyl- cyclopentadienyl)zirconium dichloride, and about 15 wt% of tarry oligomeric material. The resulting mixture is stirred at 22 °C for one hour and allowed to stand at 22 °C for two hours. The organic and aqueous phases are then separated to remove 101 grams of aqueous phase. To the organic phase is added 100 grams of saturated, aqueous NaCl with stirring of 22 °C over a period of 30 minutes. The resultant mixture is stirred at 22°C for an additional period of 30 minutes and then allowed to stand for two hours. The organic and aqueous phases are then separated to remove 99 grams of aqueous salt solution. The organic phase is then subjected to reduced pressure distillation (up to 70°C with a vacuum of 1-100 mm Hg (e.g., at least 27 inches of mercury) to remove toluene and trace amounts of residual water and leave as pot residue 41.5 grams of crude mixture. Following this pretreatment, 160 grams of acetonitrile and 160 grams of Isopar- E™ paraffinic solvent (a product available from Exxon Chemical Company, and that has a boiling range at atmospheric pressure of 115-141 °C) are added to the pot residue with stirring at 22 °C and the resultant mixture is stirred at this temperature for an additional two hours. The mixture is then allowed to stand for three hours and the phases are then separated. To the isolated upper paraffinic layer is added 80 grams of acetonitrile and the mixture is stirred for two hours at 22 °C and then allowed to stand for three hours. The upper paraffinic layer is again separated by decantation. The two acetonitrile fractions are then combined, and the acetonitrile and some residual paraffinic solvent are removed therefrom by subjecting the combined fractions to distillation under reduced pressure (1-100 mm Hg, e.g., at least 28 inches of mercury) of vacuum up to a temperature of 70°C). In operations conducted as above, yields of 27.5 to 29.1 grams of purified light-tan, solid bis(l-butyl-3-methylcyclopentadienyl)zirconium dichloride were recovered. The products were found by proton NMR to be 96-98% pure. The melting points of the products were 45 to 48°C. The yield of recovered product was in the range of 93-96%. EXAMPLE 2 The procedure of Example 1 is repeated except that the combined acetonitrile fractions are mixed with another 50 grams of the paraffinic solvent to remove additional small quantities of tarry material and further improve product quality. To achieve a better phase separation between lower acetonitrile phase and the upper paraffinic phase, the mixture is allowed to stand for a period of 2-5 hours before decanting off the upper paraffinic layer. The acetonitrile fraction is then subjected to a final distillation as in Example 1. EXAMPLE 3 Examples 1 and 2 are repeated with the exception that the paraffinic solvent used in each case is hexane instead of the Isopar-E™ paraffinic solvent. EXAMPLE 4 Abis(l-butyl-3-methylcyclopentadienyl)zirconium dichloride product treated generally as in Example 1 (3.63 grams) is dissolved in 16.52 grams of dry heptane and the solution is passed through a short column containing 1 gram of silica gel (dried 952W silica gel from Grace Davison). The column is rinsed with 5 grams of fresh heptane and the resultant metallocene solution containing has a lighter color. The solution when passed through the column one or two more times is even lighter in color. After flashing off the heptane, solid, purified pale yellow bis(l-butyl-3-methylcyclopentadienyl)zirconium dichloride is obtained. EXAMPLE 5 A portion (1.25 grams) of a crude reaction product mixture from which toluene has been stripped off at reduced pressure at 50-70°C containing about 0.93-0.95 gram of bis(l- butyl-3-methylcyclopentadienyl)zirconium dichloride and about 0.30-0.32 gram of a hydrocarbonaceous tarry or oligomeric material is subjected to purification pursuant to this invention as follows: To this portion of the crude reaction product are added 4.40 grams of acetonitrile, and then 1.44 grams of Isopar-E with stirring. After standing for about 10 minutes at 22 °C, an upper Isopar-E layer and a lower acetonitrile layer form. The phases are separated to give about 2 grams of acetonitrile solution and about 1.59 grams of Isopar-E solution. The dark-brown Isopar-E/tar solution is again extracted with 2.0 grams of fresh acetonitrile at 22°C. After standing for about 20 minutes at 22°C, the upper Isopar- E™ layer and the lower acetonitrile layer are phase-cut to give about 5.5 grams of acetonitrile solution and about 1.59 grams of Isopar-E solution. The combined orange acetonitrile solutions (7.5 grams) are washed with 0.5 gram of fresh Isopar- E™ at 22°C. The resultant mixture, after standing for 20 minutes at 22°C, is phase-cut to give 7.4 grams of pale-orange acetonitrile solution and 0.6 gram of light-brown Isopar- E™ solution. The liquids are vacuum distilled from the acetonitrile solution to leave purified product solids. In a run conducted in this manner, about 0.87 gram of product solids were recovered, which amounts to a recovered yield of about 92.6%. Proton NMR indicated the bis(l-butyl-3-methylcyclopentadienyl)zir- conium dichloride product had a purity of at least 98% and contained no detectible amount of either acetonitrile or Isopar- E™. EXAMPLE 6 The procedure of Example 5 above is repeated except that the steps wherein the combined orange acetonitrile solutions (7.5 grams) are washed with 0.5 gram of fresh Isopar- 10 E™ at 22 °C, and the resultant mixture, after standing for 20 minutes at 22 °C, is phase-cut to give 7.4 grams of pale-orange acetonitrile solution and 0.6 gram of light-brown Isopar-E™ solution, are omitted. Instead, after allowing the mixture from the second acetonitrile extraction to stand for about 20 minutes at 22 °C, the lower acetonitrile layer is isolated and the combined acetonitrile solutions are vacuum distilled to leave purified product solids. In a run conducted in this manner, about 0.90 gram of product solids was recovered, which amounts to a recovered yield of about 95.8%. Proton NMR indicated the bis(l-butyl-3- methylcyclopentadienyl)zirconium dichloride product had a purity of at least 94% and contained no detectible amount of either acetonitrile or Isopar- E™. The following comparative example illustrates the fact that absorbent materials such as dry silica are incapable of removing the oligomer content of the hydrocarbonaceous tarry material. COMPARATIVE EXAMPLE A portion of a reaction mixture for producing bis(l-butyl-3-methylcyclopenta- dienyl)zirconium dichloride that contained, inter alia, hydrocarbonaceous tarry material, was subjected to treatment with silica absorbent according to the process of U.S. Pat. No. 5,648,308. The dark brown sample contained 27.1 wt% of bis(l-butyl-3-methylcyclo- pentadienyl)zirconium dichloride, 1.9 wt% gram of oligomeric material, in the range of 30 to 3000 ppm (wt/wt) of organic color body impurities, toluene solvent, and some inorganic metal chloride salts. The toluene was removed from a 10-gram sample of this reaction mixture by reduced pressure distillation, leaving 2.90 grams of solids containing 2.71 grams of bis(l-butyl- 3-methylcyclopentadienyl)zirconium dichloride, 0.19 gram of oligomeric material, in the range of 10 to 1000 ppm (wt/wt) of organic color body impurities, and some inorganic metal chloride salts. The sample thus contained 7 wt% of oligomeric material. The sample was dissolved in 17.30 grams of dry pentane. The resultant dark brown solution, which contained some insoluble solids, was passed through a column packed with 0.30 gram of dried Grace 948 silica. The silica absorbed the dark brown organic color bodies from the solution. After rinsing the silica bed with 3.00 grams of dry pentane and combining the rinse liquid with the silica-treated solution, the silica bed remained dark brown in color, and the combined liquids were yellow-orange in color. The pentane was evaporated from the combined solution to yield 2.82 grams of solids. Proton NMR analysis indicated that these solids contained more than 11 97% of the original bis(l-butyl-3-methylcyclopentadienyl)zirconium dichloride, and more than 97% of the original oligomeric material. Thus the silica treatment did not remove the oligomeric material; it remained with the metallocene. The materials referred to by chemical name or formula anywhere in the specification or claims hereof are identified as ingredients to be brought together in connection with performing a desired operation or in forming a mixture to be used in conducting a desired operation. Accordingly, even though the claims hereinafter may refer to substances in the present tense ("comprises", "is", etc.), the reference is to the substance, as it existed at the time just before it was first contacted, blended or mixed with one or more other substances in accordance with the present disclosure. Although unlikely, the fact that a substance may lose its original identity through a chemical reaction, complex formation, solvation, or other transformation during the course of contacting, blending or mixing operations, if done in accordance with the disclosure hereof, is within the purview and scope of this invention. 12

Claims: CLAIMS 1. A process for separating a metallocene from a mixture comprising a metallocene and hydrocarbonaceous tarry material, said metallocene having the formula Q n R 1 R 2 MX 2 where (i) R 1 and R 2 can be the same or different and are cyclopentadienyl, indenyl, fluorenyl, hydrocarbyl-substituted cyclopentadienyl, hydrocarbyl-substituted indenyl, or hydrocarbyl-substituted fluorenyl groups; (ii) each of R 1 and R 2 contains, individually and independently, in the range of 5 to 18 carbon atoms; (iii) at least one of R 1 and R is a hydrocarbyl-substituted cyclopentadienyl, hydrocarbyl-substituted indenyl, or hydrocarbyl- substituted fluorenyl group in which the substitution includes at least one primary alkyl substituent having at least 2 carbon atoms; (iv) M is Ti, Zr, or Hf; (v) each X is a bromine or chlorine atom; (vi) Q, if present, is a divalent linking group having a univalent bond attached directly to each of the cyclopentadienyl rings of or in R 1 and R 2 ; and (vii) n is zero or 1, which process comprises: a) mixing a polar organic solvent and a non-polar organic solvent with said mixture, said solvents being substantially insoluble with each other, so that after the mixing there are formed at least two separate phases comprising (i) a substantially polar phase comprising said metallocene and polar organic solvent, and (ii) a substantially non- polar phase comprising non-polar organic solvent, hydrocarbonaceous tarry material and some of said metallocene; b) separating phase (i) and phase (ii) from each other; and c) extracting separated phase (ii) with fresh polar organic solvent to form another substantially polar phase comprising said metallocene and polar organic solvent. 2. A process according to claim 1 which further comprises recovering said metallocene from the polar phases. 3. A process according to claim 1 wherein the polar organic solvent and the non- polar organic solvent have boiling temperatures low enough to be distillable from the metallocene. 4. A process according to claim 3 which further comprises recovering metallocene from the polar phases by distilling off the polar organic solvent and, if any, residual non-polar organic solvent therein. 5. A process according to claim 4 wherein the polar phases are combined for said distillation. 13 6. A process according to claim 4 wherein the distillation is performed at reduced pressures and at temperatures below the sublimation temperature, if any, and the thermal decomposition temperature of the metallocene. 7. A process according to claim 6 wherein the distillation is performed at temperatures below about 100° C. 8. A process according to claim 3 wherein the polar organic solvent is a nitrile and the non-polar organic solvent is a hydrocarbon solvent. 9. A process according to claim 1 wherein each of R 1 and R 2 contains, individually and independently, in the range of 5 to 10 carbon atoms, and n is zero. 10. A process according to claim 1 wherein M is Zr. 11. A process according to claim 1 wherein: a) the polar organic solvent and the non-polar organic solvent have boiling temperatures low enough to be distillable from the metallocene; b) the polar phases formed in a) and c) are combined and the metallocene is recovered from the combined polar phases by distilling off the polar organic solvent and, if any, residual non-polar organic solvent therein at reduced pressures and at temperatures below the sublimation temperature, if any, and the thermal decomposition temperature of the metallocene. 12. A process according to claim 11 wherein n is 1 and wherein the distillation is performed at temperatures below about 100°C. 13. A process according to claim 11 wherein n is zero and wherein the distillation is performed at temperatures below about 100°C. 14. A process according to claim 13 wherein each of R 1 and R 2 contains, individually and independently, in the range of 5 to 10 carbon atoms. 15. A process according to claim 14 wherein the polar organic solvent is acetonitrile and the non-polar organic solvent is a liquid paraffinic solvent that at atmospheric pressure boils between room temperature and 100°C. 16. A process according to claim 1 wherein said mixture comprising a metallocene and hydrocarbonaceous tarry material is subjected to pretreatment prior to subjecting the mixture to a), said pretreatment being characterized in that dilute aqueous mineral acid is mixed with said mixture, the resultant aqueous and organic phases are separated, an aqueous brine solution is mixed with said separated organic phase, the resultant aqueous and organic 14 phases are separated, and last-mentioned separated organic phase is subjected to distillation at reduced pressure to remove volatile organics and water therefrom and leave a pretreated mixture comprising the metallocene and hydrocarbonaceous tarry material. 17. A process according to claim 16 wherein in said pretreatment: (i) said dilute aqueous mineral acid that is mixed with said mixture comprising a metallocene and hydrocarbonaceous tarry material is dilute aqueous HCl which is mixed with said last- mentioned mixture at at least one temperature in the range of -10 to 10°C; (ii) the aqueous brine solution is mixed with the separated organic phase at at least one temperature in the range of 10 to 25°C; and (iii) the distillation is conducted at a temperature in the range of up to l00°C at l-100 mm Hg. 18. A process according to claim 16 wherein the initial mixture in said pretreatment comprising a metallocene and hydrocarbonaceous tarry material with which said acid is mixed contains an aromatic hydrocarbon solvent or diluent, wherein said aromatic hydrocarbon solvent or diluent is replaced by a paraffinic solvent or diluent, and wherein the aqueous mineral acid is mixed with the resultant mixture containing the paraffinic solvent or diluent. 19. A process according to claim 16 wherein the dilute aqueous mineral acid is dilute aqueous HCl, wherein the polar organic solvent and the non-polar organic solvent have boiling temperatures low enough to be distillable from the metallocene, wherein the substantially polar phases formed in a) and c) are combined and the metallocene is recovered from the combined substantially polar phases by distilling off the polar organic solvent and, if any, residual non-polar organic solvent therein at one or more reduced pressures and at one or more temperatures below the sublimation temperature, if any, and the thermal decomposition temperature of the metallocene. 20. A process according to claim 19 wherein: each of R 1 and R 2 contains, individually and independently, in the range of 5 to 10 carbon atoms, M is Zr, each X is a chlorine atom and n is zero; and wherein in said pretreatment: (i) the dilute aqueous HCl is mixed with the mixture comprising a metallocene and hydrocarbonaceous tarry material at at least one temperature in the range of -10 to 10°C, (ii) the aqueous brine solution is mixed with the separated organic phase at at least one temperature in the range of 10 to 25 °C, and (iii) the distillation is conducted at a temperature in the range of up to 100°C at 1-100 mm Hg. 15 21. A process according to claim 20 wherein the polar organic solvent is acetonitrile and the non-polar organic solvent is a liquid paraffinic solvent that at atmospheric pressure boils between room temperature and 100°C. 22. A process according to claim 18 wherein the dilute aqueous mineral acid is dilute aqueous HCl, wherein the polar organic solvent and the non-polar organic solvent have boiling temperatures low enough to be distillable from the metallocene, wherein the substantially polar phases formed in a) and c) are combined and the metallocene is recovered from the combined substantially polar phases by distilling off the polar organic solvent and, if any, residual non-polar organic solvent therein at one or more reduced pressures and at one or more temperatures below the sublimation temperature, if any, and the thermal decomposition temperature of the metallocene. 23. A process according to claim 22 wherein: each of R 1 and R 2 contains, individually and independently, in the range of 5 to 10 carbon atoms, M is Zr, each X is a chlorine atom and n is zero; and wherein in said pretreatment: (i) the dilute aqueous HCl is mixed with said initial mixture in said pretreatment at least one temperature in the range of -10 to 10°C, (ii) the aqueous brine solution is mixed with the separated organic phase at at least one temperature in the range of 10 to 25 °C, and (iii) the distillation is conducted at a temperature in the range of up to 100°C at l-100 mm Hg. 24. A process according to claim 23 wherein the polar organic solvent is acetonitrile and the non-polar organic solvent is a liquid paraffinic solvent that at atmospheric pressure boils between room temperature and 100°C. 25. A process according to claim 1 wherein the non-polar solvent is a liquid paraffinic solvent that boils at 115-141 °C at atmospheric pressure. 26. A process according to claim 25 wherein the polar solvent is acetonitrile. 27. A process according to claim 20 wherein the non-polar organic solvent is a liquid paraffinic solvent that boils at 115-141 °C at atmospheric pressure. 28. A process according to claim 27 wherein the polar solvent is acetonitrile. 29. A process according to any of claims 1-28 wherein the metallocene is bis(l- butyl-3-methylcyclopentadienyl)zirconium dichloride. 16

Inventors: HAMLIN JOSEPH L, JONES KARL R, LAMBERT JULES A, LEE JOHN Y, HAMLIN, JOSEPH, L., JONES, KARL, R., LAMBERT, JULES, A., LEE, JOHN, Y.
Applicants: ALBEMARLE CORP, ALBEMARLE CORPORATION
Application year: 1999
Main classification: C07F17
IPC codes: C07F17