REDUCTION OF RH CEO2-ZRO2 WITH HYDROGEN

The effects of the addition of rhodium to CeO2(70 wt%)-ZrO2 support on hydrogen reduction of the support have been studied. The effects chan ge significantly with an increase in calcination temperature of the su pport. The lattice constant of CeO2-ZrO2 decreases with an increase in calcination temperature. The correlation curve between the lattice co nstant and calcination temperature as well as that between crystalline growth and calcination temperature has an inflection point at 900 deg rees C. Thus, the structure of the CeO2-ZrO2 solid solutions depends o n the calcination temperature. In particular, the structure changes si gnificantly at 900 degrees C and calcination at 900 degrees C shows a maximum amount of surface oxygen-deficient sites catalyzing N2O decomp osition. Moreover, the reduction extent at 400 degrees C is directly p roportional to rhodium concentration per unit surface area in addition to the considerable structure change of CeO2-ZrO2. Hence, the localiz ation and/or aggregation effect of rhodium particles also contributes to the reduction creating surface oxygen vacancy.