Titanium and vanadium catalysts with oxazoline ligands for ethylene-norbornene (co)polymerization

Abstract

A series of catalysts, (Py-ox)TiCl4, (Py-box)TiCl4, (Py-ox)VCl3, (Py-box)VCl3, SIL/(Py-ox)VCl3, SIL/(Py-box)VCl3, with 2-(1,3-oxazolin-2-yl)pyridine (Py-ox) and 2,6-bis(1,3-oxazolin-2-yl)pyridine (Py-box) ligands, silica support modified by 1-[3-(triethoxysilyl)propyl]pyridinium ethylchloroaluminate ionic liquid (SIL), activated by AlEt2Cl, AlEtCl2, and methylaluminoxane (MMAO) were studied in ethylene polymerization and ethylene-norbornene copolymerization. Single-crystal X-ray diffraction is given for both Py-ox and Py-box. The complexation was confirmed by NMR and ESI-MS methods. All complexes were found to be active in ethylene polymerization with better performance of the vanadium catalysts. Properties of polyethylene (PE) obtained using these catalysts are characterized by the molecular weight (Mw) within the range of 1.5–2.4 × 106 g/mol, narrow molecular weight distribution (1.9 < Mw/Mn < 2.9), melting temperature (131 < Tm < 144 °C), and crystallinity degree (42 < X < 81%). The sup.ported SIL/(Py-box)VCl3 catalyst activated by AlEt2Cl shows the best activity in ethylene polymerization (8120 kg PE/molV h) and copolymerization with norbornene (7135 kg Cop/molV h). The vanadium systems show high norbornene (NB) incorporation within the range of 17–40 mol% at low NB concentration (0.5–1.5 mol/L). Copolymer is characterized by Mw from 107 to 960 × 103 g/mol and narrow Mw/Mn (1.6–2.6). Glass transition temperature (Tg up to 61 °C) depends linearly on the amount of comonomer incorporated.