Mixed-phase oxide catalyst based on Mn-mullite (Sm, Gd)Mn2O5 for NO oxidation in diesel exhaust.
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.
Nanostellar Inc., 3696 Haven Avenue, Redwood City, CA 94063, USA. wwang@nanostellar.com
Weichao
W
Wang
Geoffrey
G
McCool
Neeti
N
Kapur
Guang
G
Yuan
Bin
B
Shan
Matt
M
Nguyen
Uschi M
UM
Graham
Burtron H
BH
Davis
Gary
G
Jacobs
Kyeongjae
K
Cho
Xianghong
X
Hao