Zirconia catalysts doped with sulfates or heteropolytungstic acid (HPW) prepared by sal-gel method and dried in supercritical conditions of solvent have been evaluated in n-hexane isomerization in the temperature range 150-220 degrees C. Using HPW as dopant, the obtained catalyst is active at 220 degrees C and selective towards isomers having higher Individual Octane Number, i.e., 2,2-DMB and 2,3-DMB compared with using sulfates as dopant. Based on N2-physisorption, XRD, SEM and TEM analyses, low specific area, particular morphology of grains and the lack of tetragonal ZrO2 particles reduce the adsorption of n-hexane reactant and led to inefficient catalyst throughout the temperature range 150-200 degrees C. The catalyst doped with sulfur deactivates at T> 200 degrees C since agglomerates of zirconia particles (TEM and SEM results) favor the coke formation. Using HPW, agglomerates of W oxide as well as phosphate groups (revealed by TGA, FTIR, EDX and UV/visible DRS) favor the formation of more valuable isomers at 220 degrees C. (C) 2015 Published by Elsevier Ltd.