USE OF V AND V-CR CATALYSTS INTERCHANGED IN Y-ZEOLITES FOR THE POLYMERIZATION OF ETHYLENE

Ethylene polymerization has been studied in the presence of catalyst b ased on vanadium or vanadium-chromium supported on a zeolite HY. The e ffect of vanadium over chromium has been investigated as a function of the sequence of exchange of metals on the support and metal contents. Both effects were investigated in relation to the characteristics of the polyethylene (PE) obtained. Low activity has been found for the V (II) zeolite HY catalyst. Moreover, vanadium acts either as an inhibit or or as a promoter for the polymerizing activity of the Cr (III)/zeol ite catalyst, depending on the preparation method. (C) 1994 John Wile & Sons Inc.