Albemarle Corporation

Troy E DeSoto

Ronny W Lin

John F Balhoff

Jamie R Strickler

John M Power

Bruce C Berris

Jameel Ibrahim

Richard J Fendley

Jerry G Hitchens

A metallocene having one or two hydrocarbyl groups bonded to a Group 4 metal are produced from a crude impure pasty or non-wet mixture containing at least 50% by weight of a metallocene having two halogen atoms bonded to a Group 4 metal atom, by (a) mixing liquid aromatic hydrocarbon with the crude impure pasty or non-wet mixture; (b) mixing a solution of an organolithium compound in a suitable anhydrous ether or paraffinic hydrocarbon solvent or a mixture thereof, with the mixture from (a) and agitating the resulting mixture so that lithium halide solids are formed; and (c) separating the solids and recovering the resultant liquid portion which is mainly a solution of the metallocene having one or two hydrocarbyl groups bonded to a Group 4 metal. Additional optional steps include (d) replacing the original solvent from the solution from (c) with a liquid paraffinic hydrocarbon diluent to form a slurry of product solids; and (e) recovering the product metallocene solids. Preferred organolithium compounds have the formula, RLI.nLiX, where R is tert-alkyl, aryl, alkaryl, benzyl, or alkyl-substituted benzyl, or most preferably, methyl, and X is Br or I.

Metallocene synthesis

Enhanced synthesis of racemic metallocenes

An essentially anhydrous agitated mixture of (i) finely-divided essentially anhydrous alkali metal fluoride (e.g., KF), (ii) haloaromatic compound having at least one halogen atom of atomic number greater than 9 on an aromatic ring (e.g., C.sub.6 Cl.sub.6), and (iii) an aminophosphonium catalyst (e.g., (Et.sub.2 N).sub.4 PBr), is heated at a temperature at which fluorine replaces one or more of the ring halogen atom of the haloaromatic compound.

Zirconocene ismerization process

The reaction between a hafnium tetrahalide-diamine adduct and a metallated bis(cyclopentadienyl-moiety containing) ligand, offers great promise as a way of producing racemic hafnocenes, but involves a number of complications. Tetrahydrofuran, a commonly-used solvent/diluent for such reactions, when present in substantial portions in the liquid reaction medium containing the reactants and/or reaction product(s) has been found to cause a substantial reduction in yields of chiral hafnocenes. Apparently the presence of a substantial amount of THF causes or at least results in the formation of increased amounts of the undesirable meso isomer, tends to cause or result in tar formation, and results in a product having poor filterability. Thus large amounts of THF if fed to the reactor with the reactant(s) are purged to a suitably low level, replaced by a liquid aromatic hydrocarbon, and then the reaction mixture is heated to a higher reaction temperature. Large amounts of liquid paraffins and free diamine in the reaction mixture during reaction also contribute to tar formation and reduction in yields of chiral hafnocene. Thus the presence of such materials in the reaction mixture is kept to a minimum. These process modifications make it possible to increase yields of the chiral hafnocene, to reduce formation of the meso isomer, and to sharply reduce the amount of tar formation in the synthesis of chiral hafnocenes from diamine adducts of hafnium tetrahalide and metallated bis(cyclopentadienyl-moiety containing) ligands. Moreover, the hafnocene reaction product so formed has significantly improved filterability characteristics.

Enhanced production of bridged hafnocenes

This invention relates to a process for etching a silicon coat on the inside wall of a tube. The tube may be a product discharge tube associated with a fluidized bed reactor used in the thermal production of silicon from a silicon containing compound, e.g., silane. The process features: a) heating the silicon coat to a temperature within the range of from about 500.degree. to about 750.degree. C., such heating occurring principally with radiant heat from a heating means inserted within the interior of the tube; and (b) contacting the heated silicon coat with a mineral acid which etches the heated silicon coat.

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Baton Rouge, LA, United States of America

Troy E DeSoto