Structure-activity relationships for sulfated zirconias - comparison of mesoporous samples based on organic precursors

Sulfated zirconias were obtained by hydrolysis of zirconium propoxide precursors. Digestion of the hydrous oxides in ammonia or sodium hydroxide resulted in materials with different active centres as revealed by the catalytic conversion of n-butane to iso-butane. The activity correlates to the number of highly acidic centres. The pHs of the solutions were systematically varied from 9 to 13. Moreover, the formation of crystalline phases and the pore size distribution were studied in dependence of the variation of the calcination temperature (773 and 873 K) and the aging time (3 h or 24 h). It could be shown that the activity can be directed via preparation of a special morphology. Sulfation of the samples changed the pore size distribution from monomodal to bimodal and caused a shift to lower pore diameters. The samples were characterized by means of N2-physisorption, X-ray diffraction, temperature programmed desorption of ammonia, DTG.