Mixed-Phase Oxide Catalyst Based on Mn-Mullite (Sm, Gd)Mn 2 O 5 for NO Oxidation in Diesel Exhaust

Cleaning Diesel Exhaust One strategy for removing pollutants from diesel engine exhaust is to trap the unburned carbon soot and then to combust the soot with the NO 2 that is generated from NO; the two pollutants are then converted to N 2 and CO 2 . Diesel exhaust is relatively cold, compared to gasoline engine exhaust, and conversion of NO to NO 2 has required the use of platinum catalysts. W. Wang et al. (p. 832 ) now report that a more earth-abundant catalyst, based on Mn-mullite (Sm, Gd)Mn 2 O 5 metal oxides was able to oxidize NO in simulated diesel exhaust at temperatures as low as 75°C. Spectroscopic studies and quantum chemical modeling suggested that Mn-nitrates formed on Mn-Mn dimer sites were the key intermediates responsible for NO 2 formation.