Abstract

The catalysts Pd/Ce0.8Tb0.2Ox/La2O3-Al2O3, Pd/La2O3-Al2O3 and Pd/Al2O3 were prepared by means of incipient wetness impregnation, using a palladium nitrate solution (pH=1). The amount of palladium in these catalysts was 7% w/w. The support Ce0.8Tb0.2Ox/La2O3-Al2O3 was also used in this research. The catalysts were characterized by Thermal Programmed Desorption of Hydrogen and Oxygen (TPD-H2 and TPD-O2), Thermal Programmed Reduction (TPR) and Thermal Gravimetric Analysis (TGA) measurements, to evaluate the use of palladium nitrate solution in these systems taking in account the chemical and redox properties. The TPD-H2 experiments of Pd/Ce0.8Tb0.2Ox/La2O3-Al2O3, shows that the catalyst underwent deactivation when it was reduced at 800 °C, while in the other two palladium catalysts the deactivation was observed at lower temperatures. Once the catalyst Pd/Ce0.8Tb0.2Ox/La2O3-Al2O3 underwent deactivation was not possible regenerate it by using the treatments with oxygen that was used in this investigation. This fact suggests that is not recommended to use an acid solution in the Pd/Ce0.8Tb0.2Ox/La2O3-Al2O3. The support Ce0.8Tb0.2Ox/La2O3-Al2O3 does not modify the PdO thermal stability in an inert environment, but it does so in an oxidant atmosphere. In the TGA measurements, it was observed the existence of hysteresis in the redox couple PdOx-PdO. The TPR, TPD-H2 and TPD-O2 experiments, suggest the existence of two or more palladium species in these catalytic systems