ACIDIC AND BASIC PROPERTIES OF ZIRCONIA-ALUMINA AND ZIRCONIA-TITANIA MIXED OXIDES

Two series of mixed oxides ZrO2-Al2O3 and ZrO2-TiO2 were prepared from propylate hydrolysis, followed by drying and calcination. The acidic and basic properties of the various samples were characterized by adso rption of specific probe molecules (carbon dioxide, pyridine, 2,6-dime thylpyridine) studied by FT-IR spectroscopy and activity towards two t est reactions (2-propanol dehydration and carbon oxysulfide hydrolysis ). Both methods showed that a synergy occurred on ZrO2-TiO2 samples le ading to a maximum of Bronsted acidity and a minimum of basicity for Z rO2 (23%)-TiO2 (77%). On the other hand, the Lewis acidity of ZrO2-Al2 O3 samples increased with the alumina content whereas the basicity dec reased sharply as soon as alumina was introduced.