Nitrogen Oxides Reactions in Diesel Oxidation Catalyst

Two catalyst formulations were tested on a diesel engine. A Fourier Transform Infrared (FTIR) analyzer was used to measure concentrations of nitric oxide (NO) and nitrogen dioxide (NO₂). Other exhaust gas components were measured by conventional analyzers.

The results indicate that nitrogen oxides (NO_x) undergo complex chemical reactions in the diesel oxidation catalyst (DOC). The increase of NO₂ occurring at a certain temperature range is accompanied by a decrease of the total NO_x emission. NO₂ is probably an important itermediate product in the lean NO_x catalyst reaction chain.