THERMAL-DECOMPOSITION AND REFORMATION OF PDO CATALYSTS - SUPPORT EFFECTS

The thermal decomposition of PdO and the reformation of Pd to PdO is dependent on the support upon which they are dispersed indicating significant metal(oxide) support interactions. The study defines temperature regions of different stabilities for Pd:O species. The nature of the Pd:O structure is of great importance for a large number of environmental catalytic applications including the gasoline automobile catalytic converter, ozone decomposition catalysts, abating emissions from natural gas fueled vehicles, primary combustion catalysts, etc. The ZrO2 support shows the largest hysteresis effect between the temperature of decomposition and reformation. In contrast both TiO2 and CeO2 have small hysteresis effects because of a significant increase in the temperature for reformation of the PdO. There exists a large region of temperature stability of the PdO when dispersed on these two carriers. This is quite favorable for those catalytic reactions where the oxide state is important such as the primary catalytic combustion of natural gas. Further evidence of the importance of PdO for methane oxidation is presented.