Cationic Polymerization of Isobutylene and C4 Mixed Feed Using Complexes of Lewis Acids with Ethers: A Comparative Study

Abstract

The cationic polymerization of C4 mixed feed and isobutylene co-initiated by AlCl3×OiPt2, iBuAlCl2×nOiPr2, and [emim]Cl-FeCl3×nOiPr2 ([emim]Cl: 1-ethyl-3-methylimidazolium chloride) has been investigated. AlCl3×OiPr2 co-initiated cationic polymerization of C4 mixed feed proceeds at a lower rate than polymerization of isobutylene affording polymers with higher molecular weight. Complexes of iBuAlCl2 with diisopropyl ether of different compositions are more suitable co-initiators than AlCl3×OiPr2 for the synthesis of highly reactive polyisobutylene (HR PIB) from C4 mixed feed due to their higher activity in the polymerization as well as possibility to prepare polyisobutylenes with lower molecular weight and higher content of exo-olefin end groups. However, iBuAlCl2 needs activating via addition of external water (initiator) and/or interaction with salts hydrates in order to increase the reaction rate and the saturated monomer conversion. [Emim]Cl-FeCl3/iPr2O is a quite promising catalyst for the preparation of HR PIB with high exo-olefin end group content (> 80%) and relatively low polydispersity (Mw/Mn < 2.8) via cationic polymerization of C4 mixed feed. The sonication of reaction mixture in case of using [emim]Cl-FeCl3 allowed increasing the reaction rate and decreasing the molecular weight.