A highly systematic size series of Ziegler catalysts with similar porosities and surface textures are synthesized by varying the stirring speed during the MgCl 2 support synthesis. Besides the mean particle size, the only substantial difference observed between the various catalysts is the size and number of nodules per particle. Varying the mean diameter of the catalyst particles between 1.5 and 11.9 mm, leads to a pronounced impact on the activity in ultra-high molecular weight polyethylene (UHMWPE) polymerization, while the M w capabilities are only affected to a limited extend. In addition, it is observed that both the M w s as the polymer bulk density (BD) increases during the course of the polymerization. This particularity allows to optimize the M w and/or BD at a set polymer size, by tuning the catalyst particle size. This is particularly interesting in UHMWPE production, as control of the morphological and structural properties of the UHMWPE reactor powders are critical for efficient processing as well as the performance of the final product.

A thermal switch of selectivity for a phenoxy-imine titanium catalyst was studied by combining kinetic studies and a “polymer-to-catalyst” approach.