TWC Performance of Honeycomb Catalysts Coated with Pd-Supported 10Al2O3 · 2B2O3 and Its Cation-Substituted Compounds

Abstract

TWC performances of honeycomb-coated Pd catalysts supported on 10Al2O3 · 2B2O3 (Al20B4O36, 10A2B) and its Fe-substituted analogue (FeAl19B4O36, Fe-10A2B) were studied using simulated exhaust gas mixtures. A monolayer-coated honeycomb containing Pd/10A2B was able to achieve higher conversion of CO, C3H6 and NO in stoichiometric gas mixtures after the light-off temperature compared to a honeycomb containing Pd/γ-Al2O3. Bilayer-coated honeycombs comprising a top Rh layer (Rh/CeO2-ZrO2) and a bottom Pd layer (Pd/10A2B or Pd/γ-Al2O3) with varying Rh:Pd ratios were evaluated under stoichiometric conditions. The Rh loading in the top layer could be decreased while preserving higher levels of conversion at 400 °C when Pd/10A2B was used as opposed to Pd/γ-Al2O3. Another monolayer-coated honeycomb comprising Pd/Fe-10A2B demonstrated higher NO conversion under fuel-rich conditions compared to conventional Pd catalysts that were loaded on 10A2B, γ-Al2O3 and Pd/CeO2-ZrO2. Pd/Fe-10A2B promoted the conversion of NO to NH3 because CO–H2O and subsequent NO–H2 reactions were accelerated.