Polymerization of α-pinene using Lewis acidic ionic liquid as catalyst for production of terpene resin

• A Lewis acidic ionic liquid efficiently catalyzed α-pinene polymerization to form terpene resin.
• The group of alkyl carboxylate enhanced the catalytic performance of Lewis acidic ionic liquid.
• Solid resin was easily separated from ionic liquid and ionic liquid had a good reusability.

The polymerization of α-pinene was investigated in the presence of Lewis acidic ionic liquids (ILs). The results indicated that ILs 1-(1-ethyl acetate-yl)-3-methylimidazolium chloroaluminates ([EtOCOCH2-mim]Cl-AlCl3), especially molar fraction of AlCl3x = 0.67, had excellent catalytic performance for the polymerization of α-pinene. The yield and softening point of solid resin reached to 52.0% and 115 °C, respectively, when the polymerization was carried out at −5 °C for 4 h. IL was reused for five times without a decrease in the catalytic performance. Compared with the traditional catalyst AlCl3, IL exhibited some advantages such as simplicity and efficiency of the product isolation, higher yield and softening point of the product, and excellent reusability.