Effects of Al/Zr ratio on ethylene–propylene copolymerization with supported-zirconocene catalysts

Effect of MAO silica surface loading on (nBuCp)2ZrCl2 anchoring, on catalyst activity and on polymer properties

“…5a. An intense band is observed at 271 nm with a shoulder at 289 nm, which is much closer to that reported in the case of MAO in benzene solution (286 nm) [27]. The transition in the near UV-Vis region can only be attributed to the nonbonding electrons of bridging oxygens, which are available for the eletronic transition.…”

Video Microscopy for the Investigation of Gas Phase Copolymerization

“…Moreover, catalyst 1 produces propylene blocks at the same feed gas ratio (P:E 0.25) whereas 2 and 3 only show isolated propylene units. It has also been shown that ethylene propylene copolymerizations carried out with Et(Ind) 2 ZrCl 2 supported on silica gel [20,21] lead to similar copolymers as those from the homogeneous system. The observation that copolymers obtained from both catalyst 2 and 3 do not contain propylene blocks leads to the conclusion that the 4 atom bridge possibly produces a narrower bite angle and a more constrained geometry of the complex, resulting in a less favored propylene insertion with respect to ethylene.…”

Novel Indenylzirconium Complexes as Supported Catalysts in the Polymerization of Ethylene

“…Sect.). The spectrum of silica preheated at 773 K has a sharp band at 3747 cm -1 (assigned to isolated OH groups) with a small broad shoulder at 3670 cm -1 , which can be attributed to silanols that are perturbed due to interparticle contact [16] or to OH groups retained deep within the pores [17] (Figure 2a). The magnitude of the silanol number, which is independent of the origin and structural characteristics of amorphous silica, is considered to be ca.…”