Sulfortated polystyrene grafted silica gel particles were synthesized for use as an acid catalyst in the liquid phase esterification of acetic acid with ethanol at 313-353 K. The synthesis of the grafted silica gel particles consists of three steps: polymerization, grafting, and sulfortation. The synthesized catalyst is non-cross-linked, non-swelling, and mechanically as well as chemically stable. It contains 29% covalently-bound sulfonated polystyrene chains that give an acid capacity of 0.99 mmol g(-1). The kinetics of the grafted silica gel is as rapid as that of a commercial ion-exchange resin. Since the acid capacity of the grafted silica gel is only 25% of the ion-exchange resin, the catalytic activity of acid groups in the grafted silica gel is higher than in the resin. A pseudohomogeneous kinetic model provides a satisfactory fit for both catalysts. (c) 2006 Elsevier B.V. All rights reserved.