Coordination Polymerization of α-Olefins by Phillips Catalysts

From the first discovery of Phillips catalysts، extensive investigations have been conducted to explore the effect of catalyst textural properties on the kinetic control of polymerization and the obtained polymer properties. The findings have confirmed that both catalyst chemical structure and support porosity have great influence on the catalyst activity and the obtained polymer properties. Based on catalyst activity، control of molecular weight and its distribution، the degree of branching and its type، different commercial Phillips catalysts have been introduced until now. Furthermore، high sensitivity of polymer properties towards the process، especially activation methods and polymerization reaction conditions، has led to many variations of catalytic system and polymer grade diversity. This diversity is the main reason for credibility of the Phillips catalyst، CrOx/SiO2، in 40–50% of current world production of high-density polyethylene (HDPE). The largest fraction of HDPE is used for manufacturing bottles، drums، fuel tanks and other containers، film and pipe extrusion، cable and so on. Because of special importance of Phillips catalyst in polyethylene production، history، chemistry of this important catalyst، type and structure of catalytic system، different polymerization methods and produced polymer properties are reviewed here.