Propylene polymerization using combined syndio‐ and isospecific metallocene catalysts supported on silica/MAO

Abstract

Syndiotactic and isotactic polypropylene were produced using the metallocene compounds Ph 2 C(Flu)(Cp)ZrCl 2 and SiMe 2 (2-Me,4-Ph-Ind) 2 ZrCl 2 in homogeneous system and supported on silica/MAO. These catalysts were evaluated either isolated or as a binary system. In the latter case, the iso-and syndiospecific metallocene complexes were immobilized together during the preparation of the supported catalyst. In a further experimental set, the syndio-and isospecific isolated heterogeneous catalysts were mixed at the moment of propylene polymerization. The polypropylenes obtained were evaluated using differential scanning calorimetry. The catalytic activities were also investigated. At all the studied polymerization temperatures, the results showed that the binary catalyst produced polypropylenes with lower melting temperatures in comparison with those obtained when the mixture of isolated supported syndio-and isospecific catalysts was employed. Moreover, the activation energies for the polymerization of all catalysts systems were calculated, resulting in a lower value for the binary system when compared to that employing the catalyst mixture and to both the isolated supported metallocene catalysts.

Thermal Behavior of Polyethylene Reactor Alloys Polymerized by Ziegler–Natta/Late Transition Metal Hybrid Catalyst

“…Up to now various types of hybrid catalysts including Ziegler–Natta/metallocene, metallocene/metallocene, metallocene/LTM, and finally LTM/LTM have been studied in polymerizing different types of monomers and comonomers for producing polymeric reactor alloys; however to the best of our knowledge, no report could be found on the application of any kind of Ziegler–Natta/LTM hybrid catalyst in polymerization of alpha‐olefins. In the present article, a Ziegler–Natta/LTM hybrid catalyst of the type forth generation ZN catalyst pretreated with triethylaluminum (TEA) before combining with the late transition metal (LTM) catalyst (I) (Scheme ).…”