Supported SiO2-nBuSnCl3/MAO/(nBuCp)2ZrCl2 catalyzing MAO cocatalyst-free ethylene polymerization: Study of hydrogen responsiveness
✍ Scribed by M. Atiqullah; A. A. Moman; M. N. Akhtar; H. A. Al-Muallem; A. H. Abu-Raqabah; Neaz Ahmed
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 324 KB
- Volume
- 106
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
Abstract
A supported metallocene catalyst was synthesized by sequentially loading methylaluminoxane (MAO) (30 wt % in toluene) and (^n^BuCp)~2~ZrCl~2~ on partially dehydroxylated silica ES 70 modified by ^n^BuSnCl~3~. Its shock load hydrogen responsiveness was evaluated by polymerizing ethylene for 1 h at 8.5 bar (g) and 75°C without separately feeding the MAO cocatalyst.
The shock load hydrogen feeding increased the ethylene consumption (at a fairly constant rate), catalyst productivity, as well as the resin bulk density and average particle size at Δ__P__ (of hydrogen) ≥∼3.0 psi. The bulk density increased from 0.25 to 0.31 g/cm^3^. This shows a procedure for overcoming the inherent drop in catalyst productivity caused by heterogenization of metallocenes (that is a method for catalyst activation) and improving the resulting resin bulk density. The volume‐weighted mean particle diameter of the resulting polyethylenes was found to be 5.80–11.12‐fold that of the catalyst corresponding to Δ__P__ = 0.00–7.11 psi, respectively. The resulting kinetic profiles showed to be fairly stable. However, M~w~ and polydispersity index were not affected. The particle size distribution, average particle size, and the scanning electron microscope photographs of the resulting resin particles confirmed the occurrence of the replication phenomenon. On the basis of the above findings, the mechanism of ethylene polymerization under the present experimental conditions has been revisited. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007