Dimerization of rosin using Bronsted-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 ZnCl2 x > 0.5) were both Bronsted 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. (C) 2008 Elsevier B.V. All rights reserved.