1. Tuning the reactivity of ethylene oligomerization by HZSM-5 framework AlfproximityElectronic supplementary information (ESI) available. See DOI: 10.1039/d0cy00632g
- Author
-
ChenGC, Genwei, paper., HL contributed equally to this, Liu, Hua, Fadaeerayeni, Siavash, Shan, Junjun, Xing, Aihua, Cheng, Jihong, Wang, Hui, and Xiang, Yizhi
- Abstract
Ethylene oligomerization with controlled chain lengthening over the shape-selective HZSM-5 catalyst provides alternative technologies for the production of C3+light olefins under the current circumstances of shifting hydrocarbon feedstocks from naphtha to ethane. Here, by tuning the MFI framework Alfsite to either isolated or in close proximity, we investigated the influence of the Alfproximity on the kinetics and mechanisms of ethylene oligomerization. We demonstrate that the HZSM-5 catalyst with a high concentration of Alfin close proximity (AlHProx) shows higher activity. The reaction rate of AlHProxis up to 14-fold that of AlIso(HZSM-5 with isolated Alf). Steady-state kinetic studies showed that the activation energy for AlIso(104.8 kJ mol−1) was lower than that for AlHProx(144.5 kJ mol−1). In addition, the kinetic compensation effect with the isokinetic point (Tiso) at 177 °C and Rateisoat 0.015 μmol g−1s−1was identified. Further reaction transient analysis suggested that the dual-cycle hydrocarbon-pool (HP) mechanism was involved. Unlike the steady state, the transient state favors the formation of alkanes and aromatics, indicating the establishment of cyclic carbocations through oligomerization, cyclization, and hydride transfer. The early-stage (HP build-up) behavior seemed to be independent of the Alfproximity, but the back-transient (HP clean-up) suggested decrease in the aromatic cycle over the AlHProxsample.
- Published
- 2020
- Full Text
- View/download PDF