Influence of ionic liquid counterions on activity and selectivity of ethylene trimerization using chromium‐based catalysts in biphasic media

• Published in: Applied organometallic chemistry Vol. 34; no. 10
• Main Authors: Marefat, Mohamadreza, Ahmadi, Ebrahim, Mohamadnia, Zahra
• Format: Journal Article
• Language: English
• Published: Chichester Wiley Subscription Services, Inc 01.10.2020
• Subjects: 1‐hexene; Anions; biphasic catalysis; Catalysts; Catalytic activity; Chemistry; Chromium; Ethylene; ethylene trimerization; Hybrid structures; Ionic liquids; Ions; NMR; Nuclear magnetic resonance; Oligomerization; Selectivity; Spectrum analysis
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/aoc.5874

In recent years ionic liquids (ILs) have attracted much interest because of their widespread use in various fields. Several trimerization and oligomerization catalysts have been evaluated in ILs with different organic–inorganic hybrid structures. High catalytic activity and selectivity, easy product separation, and recycling of the catalyst are the advantages of a biphasic catalyst system compared to the homogeneous catalysts. In this study, the influence of IL counter‐anions on activity and selectivity of the ethylene trimerization catalysts based on Cr‐SNS‐R was investigated. All synthesized materials were characterized using Fourier‐transform infrared spectroscopy, 1H NMR, 13C NMR, UV–Vis. spectroscopy, thin‐layer chromatography, and elemental analysis (CHNS). In ethylene trimerization reaction, the dodecyl substituent in the SNS ligand exhibited better activity and selectivity than the butyl substituent. The results revealed that the presence of BF4− as a counter‐anion in the IL led to an increase in activity and selectivity compared to Br− and I− counter‐anions. It was found that the BF4− counter‐anion plays a conclusive role in the development of 1‐hexene activity and selectivity to a maximum amount of 71,132 g1‐C6/(gCr × h) and more than 99%, respectively. Finally, the catalyst was reused thrice without losing its 1‐hexene selectivity. The influence of ionic liquid counter‐anions on activity and selectivity of the ethylene trimerization catalysts based on Cr‐SNS‐R was investigated. The presence of BF4− as a counter‐anion in the ionic liquid led to an increase in activity and selectivity compared to Br− and I− counter‐anions. The BF4− counter‐anion play a conclusive role in the development of 1‐hexene activity and selectivity to the maximum amount of 71132 g1‐C6/(ggCr × h) and >99%, respectively.