Recent developments in Ziegler-Natta catalysts for olefin polymerization and their processes

Abstract

The chemistry of Ziegler-Natter catalysts in olefin polymerization is reviewed. Factors determining catalyst activity are identified for the current generation of high activity-high selectivity catalysts. These include the nature of transition metal, its oxidation states and the ligands around it, the nature of alkylaluminium compounds, the physical state of the catalyst and its dependence on the method of preparation as well as activation of support and the role of internal and external donors. The effect of reaction parameters on catalyst performance as well as effect of nature of catalysts on polymer properties such as molecular weight, molecular weight distribution and stereoregularity are discussed. Current developments in soluble titanium/zirconium, vanadium and magnesium--titanium catalysts are reviewed. Different classes of industrial processes for production of polyethylene and polypropylene, namely slurry phase, gas phase and solution processes are discussed. The nature of contemporary catalysts is exemplified by selected patents from current literature. The various reactor types for polyolefins and salient reactor design aspects are discussed. The dependence of polymer properties on reactor design as well as kinetic modelling and simulation of polyolefin processes are briefly reviewed.