Mixed-Phase Oxide Catalyst Based on Mn-Mullite (Sm, Gd)Mn2O5for NO Oxidation in Diesel Exhaust

• Published in: Science (American Association for the Advancement of Science) Vol. 337; no. 6096; pp. 832 - 835
• Main Authors: Wang, Weichao, McCool, Geoffrey, Kapur, Neeti, Yuan, Guang, Shan, Bin, Nguyen, Matt, Graham, Uschi M., Davis, Burtron H., Jacobs, Gary, Cho, Kyeongjae, Hao, Xianghong (Kelly)
• Format: Journal Article
• Language: English
• Published: American Association for the Advancement of Science 17-08-2012
• Subjects: Diesel engines; Diesel exhaust; Dimers; Energy; Materials; Materials science; Nitrates; Oxidation; Oxides; Oxygen
• ISSN: 0036-8075; 1095-9203

Oxidation of nitric oxide (NO) for subsequent efficient reduction in selective catalytic reduction or lean NO x trap devices continues to be a challenge in diesel engines because of the low efficiency and high cost of the currently used platinum (Pt)—based catalysts. We show that mixed-phase oxide materials based on Mn-mullite (Sm, Gd)Mn 2 O 5 are an efficient substitute for the current commercial Pt-based catalysts. Under laboratory-simulated diesel exhaust conditions, this mixed-phase oxide material was superior to Pt in terms of cost, thermal durability, and catalytic activity for NO oxidation. This oxide material is active at temperatures as low as 120°C with conversion maxima of ∼45% higher than that achieved with Pt. Density functional theory and diffuse reflectance infrared Fourier transform spectroscopy provide insights into the NO-to-NO 2 reaction mechanism on catalytically active Mn-Mn sites via the intermediate nitrate species.