Highly active chromium-based selective ethylene tri-/tetramerization catalysts supported by alkenylphosphanyl PNP
Tao Zhou1, Jing Zuo1, Haojie Xie1
1Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, China. zhangj@ecust.edu.cn.
Abstract:
A series of novel diphosphinoamine (PNP) ligands bearing a P-alkenyl group were synthesized and applied in chromium-catalyzed selective ethylene tri-/tetramerization by in situ combination of Cr(acac)3 and modified methylalumoxane (MMAO-3A). The ligand substitution and oligomerization conditions have a remarkable influence on the catalytic activity and controllable selectivity. Most of these PNP ligands are highly active for ethylene tri-/tetramerization with considerable selectivity. An asymmetric diisopropenylphosphanyl ligand with an N-cyclohexyl group achieved the highest activity of 2036 kg (g Cr h-1)-1 with a high total selectivity of 81.1 wt% toward valuable 1-hexene (43.0 wt%) and 1-octene (38.1 wt%) at 40 bar ethylene and 60 °C. An asymmetric mixed isopropenyl/ethylphosphanyl ligand with an N-isopropyl group exhibited a high 1-octene selectivity of 65.5 wt% and a high total 1-hexene/1-octene selectivity (91.5 wt%) with a high activity of 1256 kg (g Cr h-1)-1.
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