The amount of sulfate ion ultimately present in a sulfated zirconia catalyst can be controlled by impregnating the solid with the desired quantity of sulfuric acid in water, evaporating the solvent, and calcining the residue. The surface area is directly related to the amount of sulfur (sulfate) incorporated into the catalyst. Compared to the usual method, consisting of ’percolation’ of zirconium oxide with sulfuric acid, or immersion of the oxide into a large excess of acid followed by filtration or decanting, the modified procedure leads to a material of similar surface area and of similar catalytic activity for the isomerization of methylcyclopentane to cyclohexane at 65 degrees C. The controlled impregnation technique allows variation of the sulfur content without a change in the calcination temperature. In addition, no waste sulfuric acid is generated in the modified process.