Cerium oxides incorporated into zeolite cavities and their reactivity

Mordenite catalysts incorporating CeO2 in their cavities have been prepared by the hydrolysis of Ce3+ ions in the cavities with moist ammonia gas, following calcination at 550 degrees C. The CeO2 mordenite zeolite (CeO2/MZ) is active for oxidation of p-xylene at 130 degrees C with oxygen, but CeO2 and mordenite are inactive even at 160 degrees C. X-Ray photoelectron spectroscopy (XPS) analyses indicate that the concentration of Ce in the mordenite surface regions is nearly equal to that in the bulk. The amount of saturated nitrogen adsorbed and the effective pore distribution decrease in CeO2/MZ has been compared with that for H+/MZ. The decreasing amount of adsorbed saturated nitrogen is nearly equal to the CeO2 volume in CeO2/MZ. Thus, the nitrogen adsorption isotherm for the CeO2/MZ indicates a decrease in the effective pore size due to the incorporation of CeO2 into the cavities. In addition, 1,3,5-trimethylbenzene is not oxidized at 160 degrees C over CeO2/MZ; the molecular size is larger than the diameter of the cavities. It has been concluded that CeO2 is incorporated into the mordenite cavities, and that this incorporation accelerates oxidation.