DETERMINATION OF SURFACE-ACIDITY AND BASICITY OF TIO2-ZRO2 BY TEMPERATURE-PROGRAMMED DESORPTION OF AMMONIA AND ACETIC-ACID

This study examined the surface acidity and basicity of TiO2-ZrO2 cata lysts by temperature programmed desorption (TPD) of ammonia and acetic acid. Changes in the acidity and basicity of TiO2-ZrO2 were observed after addition of small amounts of K2O and B2O3. Adding 0.5-2.0 wt% B2 O3 to TiO2-ZrO2 significantly decreased the base sites on the solid su rface without affecting the acid sites. Conversely, addition of 0.5-2. 0 wt% K2O to TiO2-ZrO2 decreased the acid amount on the solid surface without changing the base sites. The ammonia TPD spectra revealed that the acid strength of TiO2-ZrO2 was decreased by K2O. The acetic acid TPD spectra, were first recorded to characterize the acid-base propert ies of TiO2-ZrO2. Results showed that doping with B2O3 on TiO2-ZrO2 di d not change the base strength of the solid surface and that the amoun t of desorbed acetic acid was related to the base amount of the solid surface. However, doping with K2O on TiO2-ZrO2 decreased the desorptio n temperature of acetic acid without significantly affecting the amoun t of desorbed acetic acid. (C) 1998 Elsevier Science B.V.