Titanium-magnesium catalysts for propylene polymerization: Study of interrelations between composition, structure and activity

Abstract

Propylene polymerization titanium-magnesium catalysts (TMCs) were synthesized from different magnesium compounds with diphenylketone (DPK) as the internal donor. The catalysts differed by an order of magnitude and more in the content of titanium and donor, activity, specific surface area and pore size. Sizes of MgCl2 crystallites with 110 or 104 lateral cuts were calculated from the Ti/Mg and DPK/Mg values. For highly active TMCs the composition, XRD and specific surface area were in agreement with the MgCl2 crystallites with 104 lateral cuts, TiCl4 adsorption on one magnesium ion and elongated in the 001 direction. For low-activity TMCs obtained by reacting Mg with BuCl, the sizes of MgCl2 crystallites in different directions were close. Activity of the catalysts was inversely proportional to the crystallite size calculated from the TMC composition. This dependence was preserved for the catalysts obtained via the substitution of ketone by phthalate.