Real-time observation of the effect of oxygen storage materials on Pd-based three-way catalysts under ideal automobile exhaust conditions: an operando study

The dynamic behavior of Pd species and the CeO2 support of 1 wt% Pd/Al2O3 and Pd/CeO2 catalysts during three-way catalysis was examined in real time with operando multi-probe analysis.

Copper-Containing Mixed Metal Oxides (Al, Fe, Mn) for Application in Three-Way Catalysis

Mixed oxides were synthesized by co-precipitation of a Cu source in combination with Al, Fe or Mn corresponding salts as precursors. The materials were calcined at 600 and 1000 °C in order to crystallize the phases and to mimic the reaction conditions of the catalytic application. At 600 °C a mixed spinel structure was only formed for the combination of Cu and Mn, while at 1000 °C all the materials showed mixed spinel formation. The catalysts were applied in three-way catalysis using a reactor with a gas mixture containing CO, NO and O2. All the materials calcined at 600 °C displayed the remarkable ability to oxidize CO with O2 but also to reduce NO with CO, while the pure oxides such as CuO and MnO2 were not able to. The high catalytic activity at 600 °C was attributed to small supported CuO particles present and imperfections in the spinel structure. Calcination at 1000 °C crystallized the structure further which led to a dramatic loss in catalytic activity, although CuAl2O4 and CuFe2O4 still converted some NO. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, H2-Temperatrue Programmed Reduction (H2-TPR), N2-sorption and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX).

Identification of Ru/Ceria Among Single Atom Ceria Catalysts as a Stable and Superior Material for Abatement of Diesel and Gasoline Engine Pollutants

Atomically dispersed transition metals (Ru, Pd and Pt) have been prepared on CeO₂ and evaluated for NOx/CO abatement applications for diesel and gasoline engines, such as low temperature passive NOx adsorption (PNA), NO and CO oxidation, and three-way-catalysis (TWC). 0.5 wt% Ru/CeO₂ catalyst (Ru is ~27 and ~7 times cheaper than Rh and Pd) shows remarkable PNA performance, better than 1 wt% Pd/Zeolite: it achieves 100% removal of NOx during vehicle cold start. FTIR measurements reveal the formation of stable Ru(NO) complexes as well spill-over of NO to CeO₂ surface via the Ru-O-Ce shuttle, explaining high NO storage. Notably, Ru/ceria survives hydrothermal aging at 750 ⁰C without loss of PNA capacity. It is also a robust NO oxidation catalyst, considerably more active than Pt or Pd/CeO₂. Expanding the repertoire of Ru/CeO₂ catalytic applications, we further find 0.1 and 0.5 wt% Ru/CeO₂ to be excellent TWC catalysts, rivaling best single-atom Rh supported materials. Our study pushes the frontier of precious metal atom economy for environmental catalysis from uber expensive Rh/Pd/Pt to more sustainable cheaper Ru and highlights the utility of single-atom catalysts for industrially relevant applications.

Identification of Ru/Ceria Among Single Atom Ceria Catalysts as a Stable and Superior Material for Abatement of Diesel and Gasoline Engine Pollutants

Atomically dispersed transition metals (Ru, Pd and Pt) have been prepared on CeO₂ and evaluated for NOx/CO abatement applications for diesel and gasoline engines, such as low temperature passive NOx adsorption (PNA), NO and CO oxidation, and three-way-catalysis (TWC). 0.5 wt% Ru/CeO₂ catalyst (Ru is ~27 and ~7 times cheaper than Rh and Pd) shows remarkable PNA performance, better than 1 wt% Pd/Zeolite: it achieves 100% removal of NOx during vehicle cold start. FTIR measurements reveal the formation of stable Ru(NO) complexes as well spill-over of NO to CeO₂ surface via the Ru-O-Ce shuttle, explaining high NO storage. Notably, Ru/ceria survives hydrothermal aging at 750 ⁰C without loss of PNA capacity. It is also a robust NO oxidation catalyst, considerably more active than Pt or Pd/CeO₂. Expanding the repertoire of Ru/CeO₂ catalytic applications, we further find 0.1 and 0.5 wt% Ru/CeO₂ to be excellent TWC catalysts, rivaling best single-atom Rh supported materials. Our study pushes the frontier of precious metal atom economy for environmental catalysis from uber expensive Rh/Pd/Pt to more sustainable cheaper Ru and highlights the utility of single-atom catalysts for industrially relevant applications.