Acidity of sulphated zirconia aerogels: Correlation between XPS studies, surface potential measurements and catalytic activity in isopropanol dehydration reaction

Sulphated zirconias with various atomic S/Zr ratios were prepared by sol–gel method. The acidity of these solids has been studied through qualitative and quantitative XPS studies, surface potential measurements and isopropanol dehydration reaction. The Correlation between corresponding results show that when zirconia is doped by sulfate groups the surface becomes more acidic in term of Lewis acidity and that the oxygen species in the sample exist in many types, which one is related to solid acidity. This type of oxygen species, probably in the hydroxyl groups, is other than the oxygen species of zirconia network and the oxygen sulphate groups. Consequently, acidity of sulphated zirconia is mainly due to a strong Lewis nature of the surface, which can give a Brönsted acidity by water or reactant chemisorptions