| Abstract
| - There is growing interest in the use of a nonthermalplasma combined with a catalyst for NOx removal fromdiesel engine exhaust streams. Such exhaust streams containexcess oxygen (typically 6−10%), low concentrations ofhydrocarbons (typically 100−1000 ppm), and significantconcentrations of water (typically 5−12%). Conversion ofNOx to environmentally acceptable compounds, withoutrequiring a scrubber or an added reductant, is the desiredend result. In our research we observe the formation ofsubstantial amounts of methyl nitrate (CH3ONO2) by the plasmadischarge. Since similar compounds have been proposedas reaction intermediates in NOx removal, tests wereperformed to elucidate the effect of CH3ONO2 in the plasma−catalyst system. CH3ONO2 was prepared and added tothe gas blend on test equipment simulating a diesel exhaustgas. A dielectric barrier plasma discharge was followedby a zeolite-based catalyst. Methyl nitrate introduced upstreamof the plasma discharge is largely unreacted uponpassing through the plasma. CH3ONO2 arriving at thecatalyst is converted to methanol and NO2. While methylnitrate was shown to be formed in this system, it is not asignificant intermediate in the mechanism of conversionof NOx to nitrogen.
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