Generation of active site confined inside supercage of NaY zeolite on a nano-scale and its ethylene polymerization

Abstract

To generate an active site that consisted of one Cp2ZrCl2 molecule and 1-2 MAO molecules inside supercage of NaY zeolite, two preparation ways for supported catalyst were estimated. First, higher concentration of MAO and Cp2ZrCl2, and long reaction time were introduced during the preparation of supported catalyst. It showed activity in ethylene polymerization without any additional MAO. It indicates that Cp2ZrCl2 coordinated with only 1-2 MAO molecules could be an active site due to the fact that supercage has nano-scaled diameter of supercage, 1.2 nm, and it could contain only 1-2 MAO molecules inside it theoretically. In situ generation of active site between NaY/MAO and homogeneous Cp2ZrCl2 also showed experimental evidence that an active site was generated inside the supercage of NaY zeolite. It showed low activity with long activation time, suggesting the presence of a diffusion effect of Cp2ZrCl2 in the pore of NaY. However, NaY/Cp2ZrCl2 and homogeneous MAO system showed the characteristic PE polymerization with homogeneous catalyst, indicating that active site was not generated inside the supercage of NaY. (C) 2003 Elsevier Ltd. All rights reserved.