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 catalysts 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% B2O3 to TiO2-ZrO2 significantly decreased the base sites on the solid surface 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 properties of TiO2-ZrO2. Results showed that doping with B2O3 on TiO2-ZrO2 did not change the base strength of the solid surface and that the amount of desorbed acetic acid was related to the base amount of the solid surface. However, doping with K2O on TiO2-ZrO2 decreased the desorption temperature of acetic acid without significantly affecting the amount of desorbed acetic acid. (C) 1998 Elsevier Science B.V.