Catalytic decomposition of N2O over Rh/Zn–Al2O3 catalysts

Abstract

Zn–Al₂O₃ supports were prepared by impregnating commercial γ-Al₂O₃ powders with different amounts of Zn(NO₃)₂, followed by calcination in air at 500 or 800 °C. Rh/Zn–Al₂O₃ catalysts were then prepared by impregnating Zn–Al₂O₃ supports with Rh(NO₃)₃ followed by calcination in air at 500 °C. The catalysts and/or supports were characterized by ICP-OES, XRD, N₂ adsorption, Raman spectroscopy, TEM-EDX, XPS, CO₂-TPD, H₂-TPR, and O₂-TPD, and the catalytic performance of supported Rh catalysts in N₂O decomposition was tested. It is concluded that the support can be described as ZnO/Al₂O₃ (ZnO supported on Al₂O₃) when calcining Zn(NO₃)₂/Al₂O₃ at 500 °C, whereas ZnAl₂O₄ spinel forms on the Al₂O₃ surface at 800 °C. Rh/Zn–Al₂O₃ catalysts are much more active than Rh/Al₂O₃ and Rh/ZnO. The best catalyst (Rh/Zn–Al₂O₃-800 with 1 wt% Rh and 1 wt% Zn) has the smallest Rh₂O₃ particle size and can desorb O₂ at lower temperature than other catalysts. Both factors may be important for achieving high activity in N₂O decomposition.