On the importance of the catalyst redox properties in the N2O decomposition over alumina and ceria supported Rh, Pd and Pt

Rh, Pd and Pt have been supported on γ-Al2O3, pure CeO2 and La- or Pr-doped CeO2, and these catalysts have been tested for N2O decomposition. The effect of CO and O2 in the feed has been studied. The characterisation techniques used were Raman spectroscopy, XRD, N2 adsorption at −196 °C, H2-TPR and TEM. The catalytic activity for N2O decomposition of the noble metals follows the trend Rh > Pd > Pt, and the support affects significantly the activity. For CeO2-containing catalyst, a relationship between N2O decomposition capacity and H2 reduction of ceria has been found, the easier is the reduction the higher is the catalytic activity. The rate-limiting step of the N2O decomposition mechanism over noble metal/ceria catalysts seems to be the reduction of the catalytic active sites. For Rh catalysts, ceria supports are involved actively in the decomposition of N2O, and all the ceria-based supports improve the catalytic activity of Rh with regard to γ-Al2O3 due to the redox properties of ceria. The Pd catalysts with pure and doped ceria support showed similar activity, this being higher than that of Pd/γ-Al2O3. Pt/CeO2 is the most active catalyst among those of Pt, but ceria doping by La or Pr has a negative effect on the activity. The most active catalyst among those prepared in this study is Rh/CeO2(Pr).