High-viscosity poly-alpha-olefin production from Fischer-Tropsch mixed α-olefins: Synthesis, kinetics and mechanism

The high-viscosity poly-alpha-olefin was prepared from Fischer-Tropsch mixed α-olefins (FTO) polymerization under [EBIZrCl 2 /Al( i Bu) 3 /[Ph 3 C] + [B(C 6 F 5 ) 4 ] - system (EBI =  rac -C 2 H 4 (1-Ind) 2 ), and its mechanism was investigated by in situ UV–Vis, 1 H NMR and ESI-MS. The results show that the kinematic viscosity at 100°C (KV 100 ), viscosity index (VI) and yield of product reach to 306.3 cSt, 244 and 81.12 % under optimum reaction condition, respectively. Through adjusting temperature to 20°C, in situ UV–Vis, 1 H NMR and ESI-MS are conducted to monitor the formation of origin species (EBIZr( i Bu) 2 + ), active species (EBIZr-σ-y n + (y = nonenyl, decenyl and undecenyl, n ≥ 1)), reactivated species and dormant species (EBIZr-η 3 -(1-R-C m H m+1 ) + (R = n-propyl and m = 6 or 7 or 8)). The simultaneous generation of active and dormant species is observed, and the reaction process is described as [FTO] + [catalyst] → [active species] + [dormant species]. This reaction fitting curve also conforms to the Boltzmann (R 2  ≥ 0.993). The effect of different types of olefins on catalytic evolution and product properties is investigated. The existence of multiple α-olefins inhibits the formation of the second inactivate species found in 1-decene polymerization. However, the multiple isomeric olefins further enhance the possibility of dormant species generation, because of the promotion of β-H concentration in catalytic system, leading to the higher activation energy (19.597kJ/mol) than pure 1-decene (10.949kJ/mol). Based on those findings, a possible mechanism in ansa-zirconocene catalyzed to prepare high-viscosity poly-alpha-olefin from Fischer-Tropsch mixed α-olefins is proposed.