Effect of Sulfation on the Acid-Base Properties of Tetragonal Zirconia. A Calorimetric and IR Spectroscopic Study

The RT adsorption of CO2 was studied in order to compare the surface acid-base properties of yttria-stabilized tetragonal ZrO2, either plain or variously sulfated. The nature of the species formed upon CO2 adsorption, as well as their stability upon outgassing, was monitored by IR spectroscopy, whereas the population of the sites and their energy distribution was studied by microcalorimetry. The effect of sulfation on the basicity of cus Zr4+/O2- pairs and on the Lewis acidic strength of cus Zr4+ cations, as well as the influence of calcination on the amount and nature of surface sulfates were studied and correlated with the catalytic activity of SZ systems.