Method for initiating cationic polymerization of isobutylene by AlCl₃

In this work, an experiment was conducted to investigate the cationic polymerization of isobutylene (IB) with AlCl₃ as the initiator; the experiment was carried out with C₄ mixed gas as the raw material. The initial content of IB in the mixed C₄ gas was 22% and the proportion of isobutylene in the mixed C₄ was changed later by continuously adding pure IB. A suitable amount of the co-initiator toluene (C₇H₈) and a nucleophile such as diethyl ether (C₄H₁₀O) or ethyl acetate (C₄H₈O₂) are suitably cited. We carried out experiments to investigate the effects of different initiator systems, different temperatures, different initiator additions, and other factors on polymerization products. The results show that we choose the initiation system: AlCl₃ is 1% of the mass of isobutylene, and the two nucleophiles of diethyl ether and ethyl acetate account for 8% and 10% of the mass of AlCl₃, respectively, at a reaction temperature of −30 °C, and the reaction time was controlled at 30 min. It is possible to obtain a relatively low molecular weight (Mn: 1000–4000) of a polyisobutylene product, a highly active polyisobutylene with a polydispersity coefficient (PDI) < 2.3 and an exo-olefin content of >70%. Through several experiments, we explored the impact of changing the experimental conditions on the polymerization products, and then provided a theoretical basis for the next industrial production.