Issue Date: May 13, 2013
Exhaust Catalyst Traps And Scrubs NOx
Automobile engines designed to combust fuel in a large excess of oxygen can achieve higher fuel efficiency than other common engines. But standard catalytic cleanup technology cannot readily scrub (chemically reduce) the nitrogen oxides (NO and NO2, or NOx) in the exhaust of these so-called lean-burn engines because of the overwhelming excess of O2. A research team led by Hui Xian of Tianjin University, in China, has demonstrated that NOx can be scrubbed effectively by using a palladium-doped LaSrCoO3 material to trap and treat the pollutants (ACS Catal. 2013, DOI: 10.1021/cs400136t). The method works by oxidizing NOx compounds in excess O2 and trapping them as nitrates. The nitrates are periodically purged and reduced by hydrocarbons, which are deliberately generated by briefly switching the engine from a fuel-lean to a fuel-rich mode. In contrast to previously studied lean NOx trap materials, the new compound resists sulfur poisoning and does not depend on costly platinum. In addition, lean NOx trap technology could be simpler and smaller than an alternative NOx treatment method that requires carrying an onboard tank of a reductant such as urea.
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