Excellent Catalytic Activity of a Pd‐Promoted MnO<sub>x</sub> Catalyst for Purifying Automotive Exhaust Gases
Saburo Hosokawa, Takuya Shibano, Hiroaki Koga, Masafuyu Matsui, Hiroyuki Asakura, Kentaro Teramura, Mitsutaka Okumura, Tsunehiro Tanaka
Abstract
Abstract Currently, there is a strong demand for new automotive catalysts with improved low‐temperature activity and reduced precious metal use. Such catalysts must undergo simultaneous CO/hydrocarbon oxidations and NO reduction. A Pd catalyst supported on Mn‐modified hexagonal YbFeO 3 (Pd/Mn‐YFO) exhibited extremely high activity at low temperature via a Mars‐van Krevelen (MvK) mechanism involving lattice oxygen and oxygen vacancy site in the catalyst support. NO reduction proceeded by high CO and C 3 H 6 oxidation activity of Pd/Mn‐YFO, and the catalytic activity of 1.0 wt% Pd/Mn‐YFO was higher than that of 5.0 wt% Pd/Al 2 O 3 , despite the lower Pd loading. We clarified that the lattice oxygen in MnO x , which existed on the surface of YFO, consumed by CO and C 3 H 6 oxidation was recovered by NO to form N 2 via MvK‐type NO reduction, while the Pd species promoted NO adsorption and dissociation on MnO‐like species.