Super acidity confirmed on a monolayer of sulfate species loaded on zirconia

Abstract

Acidic property of sulfated zirconia catalyst was measured by temperature-programmed desorption of ammonia with water vapor treatment method, and the spectrum was theoretically analyzed to determine the acid strength (adsorption heat of ammonia). The desorption of ammonia was controlled by equilibrium, and the entropy change of elementally step of desorption was ca . 100 J K −1 mol −1 , as well as on various zeolites and tungsta-zirconia catalyst. Therefore, the common theory was applied to the sulfated zirconia. Monolayer of sulfated species loaded on zirconia showed quite high adsorption heat, ca . 200 kJ mol −1 , corresponding to the super acidity. Loading of excess sulfur diminished the strong acidity and generated the weaker acid sites with ca . 150 kJ mol −1 of the adsorption heat. It was observed that skeletal isomerization of butane was catalyzed by the latter type of acid site.