Zirconium sulfate (ZS) varying in crystalline phase from hydrate to anhydrous was prepared at different treatment temperature. The relationship between microcrystal structure at different treatment temperature and activity in esteritication was evaluated. The number of acid groups was found to increase with increased of pretreatment temperature, except for the samples treated above 330 degrees C. For that sample, it is observed that hydration of crystalline water to anhydrous phase is significant at temperature of 330-420 degrees C, reducing the surface acidity. The reaction was poisoned by the exchange of surface protons on ZS with Cs+. Thus, the major effective active sites must be the protons acidity. It was demonstrated that the microcrystal structure and catalytic activity of ZS was affected by thermal treatment due to changes in crystalline water. (c) 2007 Elsevier B.V. All rights reserved.