Structural characterization of sulfated zirconia and their catalytic activity in dehydration of ethanol

The effect of the incorporation of SO42− in ZrO2 was studied. Materials were prepared by wet impregnation method with varying SO42− content (5, 10, 15, 20, 25 and 30 wt%). The structural properties of these catalytic materials were studied by thermal analysis, X-ray diffraction, nitrogen adsorption at −196 °C, potentiometric titration with n-butylamine and adsorption of pyridine at room temperature. DTA measurements showed that SO42− addition tends to slow down the formation of ZrO2 crystallites. XRD shows that the samples contain mixture of tetragonal and monoclinic zirconia phases. The percentage of tetragonal zirconia phase was found to depend on sulfate content and calcination temperature. After calcination at temperature as high as 600 °C, the amount of tetragonal phase is reduced. The surface areas of the investigated samples were influenced with the sulphate content and calcination temperature. The acidity studies demonstrate the presence of mixture of Bronsted and Lewis acid sites. SO42−/ZrO2 containing 15 wt.% SO42− and calcined at 500 °C exhibited maximum catalytic activity for ethanol dehydration. The catalytic activity was strongly influenced with the structural properties and surface acidities of the catalysts investigated.