ETHYLENE POLYMERIZATION OVER TRANSITION METAL-EXCHANGED MONTMORILLONITE CATALYSTS

Polymerization of ethylene over transition-metal exchanged montmorillo nite (K 10) was studied at room temperature. It was found that over Ni 2+-Mont, dimerization of ethylene to n-butenes proceeded selectively. Over Cr3+-Mont, high polymerization occurred, and the polyethylene pro duced had a high melting point and density. The catalytic activities f or the ethylene dimerization and polymerization were closely correlate d with the acidity of the catalysts. The active sites for the ethylene dimerization consisted of nickel ion and Bronsted acid, while the act ive site for the polymerization was related to the Lewis acid, chromiu m ion.