Catalysts and process for the preparation of catalysts which may be used for the polymerization of ethylene

Abstract

This catalyst consists of the reaction product, with at least one organomagnesium compound and/or organolithium compound R.sup.1 Li (R.sup.1 =alkyl) or ArLi (Ar=phenyl or benzyl), of the reaction product of (Cp).sub.2 MX.sub.2 Li(OR.sub.2).sub.2 (M=lanthanide, Sc, Y; (Cp)=optionally substituted cyclopentadienyl; and R=alkyl), with at least one bidentate ligand, such as .beta.-diketone or .beta.-keto imine CZ.sub.3 COCHZCDCZ.sub.3, Z selected from halogen, alkyl and H, D=O, NH or NR.sup.3 (R.sup.3 =alkyl or aryl); and phosphorus ylid R.sup.2.sub.3 P.dbd.CA--CO--R.sup.2, R.sup.2 chosen from alkyl and aryl; A=alkyl or H. It advantageously takes the form of a solution at least partially containing an aromatic hydrocarbon. The process for the polymerization of ethylene may be carried out at 20.degree.-250.degree. C. at a pressure which may range up to approximately 200 bars, in solution or in suspension in an at least C.sub.6 inert hydrocarbon or may be carried out continuously, in at least one autoclave or tubular reactor, at 150.degree.-300.degree. C., at 400-2000 bars, the reaction medium being in the supercritical state.

Dependencies are inferred from the claim text.