Sulfated zirconium oxyhydroxide clays were prepared by adding ammonium sulfate to the intercalation solution. The main parameter controlled in this study was the SO4:Zr ratio in solution. The characterization of the catalysts, their acidic properties and catalytic activities were examined by N-2-BET adsorption, chemical analysis, adsorption-desorption of basic molecules and conversion of n-hexane and isopropanol. Two different types of SO4-Zr polycation binding were proposed and related with the acidic properties of these solids. To enhance the acidity of the sulfated zirconium oxyhydroxide clay, the SO4:Zr molar ratio must be higher than 0.125. The higher this ratio, the higher is the activity of these solids. It appears that polymerised entities are more active than individual sulfated polycations. Isopropanol dehydration to propene as well as isomerization of n-hexane seem to be related to the number and strength of Bronsted acid sites. (C) 2003 Elsevier B.V. All rights reserved.