Propylene polymerization using modified silica based catalyst

Abstract

A process for making a propylene polymer which comprises polymerizing propylene under propylene polymerization conditions in the presence of a catalyst system which includes a catalyst component comprising (I) the product obtained by (a) treating silica to remove surface hydroxyl groups; (b) contacting said treated silica with (1) a modifying compound selected from the group consisting of silicon halides, boron halides, aluminum halides, alkyl silicon halides and mixtures thereof; and (2) at least one hydrocarbon soluble magnesium-containing compound; (c) contacting the product of step (b) with at least one titanium-containing compound having the structural formula Ti(OR).sub.n X.sub.m, where R is aryl, alkyl or mixtures thereof; X is halogen; n is an integer of 1 to 4; m is 0 or an integer of 1 to 3; and the sum of m and n is 4; and (d) treating the product of step (c) with a titanium-containing compound having the structural formula TiX.sup.1.sub.p (OR.sup.1).sub.q, where X.sup.1 is halogen; R.sup.1 is aryl or alkyl; p is an integer of 1 to 4; q is 0 or an integer of 1 to 3; and the sum of p and q is 4; a second catalyst component (II), an aluminum-containing compound selected from the group consisting of an alkyl aluminum, an alkyl aluminum halide and mixtures thereof; and a third catalyst component (III), a silane compound.