Dimerization of rosin using Brønsted–Lewis acidic ionic liquid as catalyst

Ionic liquids (3-sulfonic acid)-propyltriethylammonium chlorozincinates [HSO3–(CH2)3–NEt3]Cl–ZnCl2 were synthesized and characterized. The characterized results indicate that ionic liquids [HSO3–(CH2)3–NEt3]Cl–ZnCl2(molar fraction of ZnCl2x > 0.5) were both Brønsted and Lewis acidic. The catalytic properties of these ionic liquids were investigated in the dimerization of rosin. It is found that ionic liquid [HSO3–(CH2)3–NEt3]Cl–ZnCl2(x = 0.64) was of good catalytic property. The product was easily separated from reaction mixture and the ionic liquid catalyst was of good reusability. Hence, a clean and environmentally friendly strategy for synthesis of polymerized rosin is developed.