THERMAL STUDIES OF (NH4)(2) CR2O7, (NH4)(2) WO4, AND (NH4)(6)MO7O24-CENTER-DOT-4H(2)O DEPOSITED ON ZRO2

Ammonium molybdate, ammonium dichromate or ammonium tungstate modified zirconia are considered to be catalysts with superacid properties. Th e activation of these catalysts involves complex chemical changes. In the present study, combined TGA-DTA, TG-MS and TG-FTIR techniques were used to investigate the weight loss and the phase transformations of the solids and to monitor the chemical compounds that evolved under co ntrolled heating in different environments. Through online analysis of the evolved species, some insight into the activation mechanism can b e obtained. The phase transformation temperature of zirconia was shift ed to a higher temperature when the sample was treated with any of the se anions, which indicates that the thermal stability of the catalysts was enhanced.