Zirconia aerogel, prepared by hydrolysis of zirconium sulfate with aqueous ammonia followed by supercritical drying in ethanol at 280 degrees C, has a tetragonal crystal structure. Sulfated zirconia, tungsten-trioxide modified zirconia and molybdenum-trioxide modified zirconia that are prepared by sulfation of the zirconia aerogel or impregnation of the zirconia aerogel with ammonium tungstate or ammonium molybdate, followed by calcination, have identical acidity and structure with the conventional catalysts prepared from amorphous zirconia hydrate. The high activity of all these materials for hydrocarbon conversion is a consequence of the chemical interaction between tetragonal zirconia with the surface dispersed sulfate, tungstate or molybdate entities.