Partial oxidation of methane to synthesis gas on Rh/ZrxCe1−xO2–Al2O3

A series of ZrxCe1−xO2–Al2O3 (x = 0, 0.25, 0.5, 1) nanocomposites were prepared through a citric acid mediated route. The thermal stability of these materials was investigated by calcination at temperatures between 1173 and 1473 K for a certain time. The nanocomposites were characterized by XRD, DTA, nitrogen adsorption–desorption measurements, Raman spectroscopy, TEM and SEM. It was found that coating ZrxCe1−xO2 on the surface of Al2O3 could substantially enhance the thermal stability of the composites, as evidenced by preventing the formation of α-Al2O3. Rh/ZrxCe1−xO2–Al2O3 catalysts were prepared by incipient wetness impregnation, followed by calcination at 1173 K for 5 h. The Rh dispersion was measured by volumetric H2-chemisorption. The effect of the catalyst support, the reaction temperature, the Rh loading and the gas hourly space velocity in the catalytic partial oxidation of methane was studied in a quartz fixed-bed reactor, concerning activity, selectivity and stability. The ignition and extinction behaviors of the reactor on different catalysts were also investigated showing that the ignition temperature depends significantly on the composition of the supports. It was observed that the presence of cerium in the composites would lower the ignition temperature and enhance the activities of methane partial oxidation and water gas shift reaction.