THE LEWIS ACIDITY OF SULFATE-DOPED ZRO2 - FTIR AND MICROCALORIMETRIC STUDY OF CO UPTAKE AT SIMILAR-TO-300-K ON LOW S-LOADED SPECIMENS

When loading sulfates on a microcrystalline ZrO2, using H2SO4, the first sulfate groups form on crystal defects, then on regular crystal planes, and eventually complex sulfates (e.g., pyrosulfates) are formed. CO uptake at approximately 300 K onto SO4/ZrO2 decreases fast with increasing sulfate loading, while the Lewis acidity of the residual sites is variably enhanced by the presence of the various types of sulfates, as shown by the spectral features of the sigma-coordinated CO complexes and by the relevant adsorption heats.