A MgCl 2 -supported catalyst containing diisobutyl phthalate (DIBP) and 2,4-pentadiol dibenzoate (PDDB) as internal donors was prepared. Propylene polymerizations were carried out using the catalyst in the absence or presence of an external donor. The resulting polymers were characterized by 13 C-NMR, crystallization analysis fraction (CRYSTAF) and gel permeation chromatography (GPC). The performance of the catalyst was compared with that of other catalysts containing donor-free, DIBP and PDDB as internal donors respectively. The results demonstrated that the catalyst containing mixed internal donors not only had high activity and stereospecificity but also produced the polymer with relatively broad molecular weight distribution and the highest [mmmm] value. 13C-NMR analysis results indicated that strongly coordinating donors gave more stereoregular polymers, which was further confirmed by CRYSTAF data. The effects of mixed internal donors on the catalyst properties were discussed systematically.

This study reports a novel one-step method to synthesize a new spherical support for Ziegler-Natta catalyst under moderate condition. The support is obtained from a dispersion system where the particle stabilizer polyvinylpyrrolidone plays a main role to stabilize the spherical particles. The new chemical of the support is CH 3 CH 2 OMgOCH(CH 2 Cl) 2 , which is first reported here, has been approved by newly filed patents and also confirmed by solution NMR, solid state NMR, pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), and ICP-MS. The support and catalyst particles have uniform distributions. The catalyst prepared from this support has been evaluated with high activity. The polypropylene obtained has high isotacticity.