Role of Methyl Nitrate in Plasma Exhaust Treatment

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• 作者：John W. Hoard ; Timothy J. Wallington ; James C. Ball ; Michael D. Hurley ; Kenneth Wodzisz ; and M. Lou Balmer
• 刊名：Environmental Science & Technology
• 出版年：1999
• 出版时间：October 1, 1999
• 年：1999
• 卷：33
• 期：19
• 页码：3427 - 3431
• 全文大小：83K
• 年卷期：v.33,no.19(October 1, 1999)
• ISSN：1520-5851

文摘

There is growing interest in the use of a nonthermalplasma combined with a catalyst for NO_x 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 ofNO_x 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 NO_x 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 NO_x to nitrogen.