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.
Highlights
Reactive polyisobutylene (HR PIB), a low molecular weight polyisobutylene bearing mainly exo-olefin terminal group, is used as a precursor in the preparation of ashless dispersants for fuel and motor oil.[1]
AlCl3 × OiPr2 as Catalyst Equimolar complex of AlCl3 with diisopropyl ether was selected for the comparative study of cationic polymerization of IB and C4 mixed feed as one of the most active representatives of the first generation catalysts for the synthesis of highly reactive polyisobutylene (HR PIB).[2,3,9,10,11,12,13,14,15,16,17,18,19,20,21]
Since adventitious water acts as the initiator in these experiments and the solubility of H2O in IB/n-hexane mixture and C4 mixed feed may be different, we investigated the effect of adding external H2O on the cationic polymerization of these two monomers
Summary
Reactive polyisobutylene (HR PIB), a low molecular weight polyisobutylene bearing mainly exo-olefin terminal group, is used as a precursor in the preparation of ashless dispersants for fuel and motor oil.[1] Among different catalytic systems for the synthesis of HR PIB discovered during the last decade,[2,3,4,5,6,7,8] the use of complexes of AlCl3 with ethers, which was independently reported in 2010 by Kostjuk et al.[9] and Wu et al.[10], is more promising due to their low cost as well as high activity and regioselectivity at ambient conditions Since this discovery, the complexes of other metal halides such as FeCl3,[11,12,13,14,15] GaCl3,[13] TiCl4,[16,17] HfCl4,[18] and WCl4[18] with ethers/alcohols were shown to be suitable for the synthesis of HR PIB. Despite the huge progress achieved in the synthesis of HR PIB from neat isobutylene using complexes www.cjps.org link.springer.com
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