Issue 7, 2012

Ethylenepolymerization on a SiH4-modified Phillips catalyst: detection ofin situ produced α-olefins by operando FT-IR spectroscopy

Abstract

Ethylene polymerization on a model Cr(II)/SiO2 Phillips catalyst modified with gas phase SiH4 leads to a waxy product containing a bimodal MW distribution of α-olefins (Mw < 3000 g mol−1) and a highly branched polyethylene, LLDPE (Mw ≈ 105 g mol−1, Tm = 123 °C), contrary to the unmodified catalyst which gives a linear and more dense PE, HDPE (Mw = 86 000 g mol−1 (PDI = 7), Tm = 134 °C). Pressure and temperature resolved FT-IR spectroscopy under operando conditions (T = 130–230 K) allows us to detect α-olefins, and in particular 1-hexene and 1-butene (characteristic IR absorption bands at 3581–3574, 1638 and 1598 cm−1) as intermediate species before their incorporation in the polymer chains. The polymerization rate is estimated, using time resolved FT-IR spectroscopy, to be 7 times higher on the SiH4-modified Phillips catalyst with respect to the unmodified one.

Graphical abstract: Ethylene polymerization on a SiH4-modified Phillips catalyst: detection ofin situ produced α-olefins by operando FT-IR spectroscopy

Article information

Article type
Paper
Submitted
17 Oct 2011
Accepted
29 Nov 2011
First published
29 Nov 2011

Phys. Chem. Chem. Phys., 2012,14, 2239-2245

Ethylene polymerization on a SiH4-modified Phillips catalyst: detection ofin situ produced α-olefins by operando FT-IR spectroscopy

C. Barzan, E. Groppo, E. A. Quadrelli, V. Monteil and S. Bordiga, Phys. Chem. Chem. Phys., 2012, 14, 2239 DOI: 10.1039/C2CP23269C

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