Feasibility of Plasma Aftertreatment for Simultaneous Control of NOx and Particulates

Abstract

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NOx reduction behavior on alumina with discharging nonthermal plasma in simulated oxidizing exhaust gas

“…In this reaction system, when HC was added to the oxidizing gas containing NO, the NO oxidation to NO 2 was significantly enhanced and the NO conversion with HC increased three times compared with that without HC at 400 °C. This is consistent with the chemical kinetics model of Penetrante et al ,28 which suggested that NO oxidation occurs with the discharging nonthermal plasma containing HC by the following process: high energy electrons in the discharging nonthermal plasma generate O radicals, HC + O radicals → HO 2 radicals, NO + HO 2 radicals → NO 2 + OH radicals and that HC suppresses the reduction of NO 2 back to NO by O radicals and further oxidation of NO 2 to nitric acid by OH radicals by consuming these excess radicals. …”

“…Above 300 °C, the NO conversions for both the plasma and the Pt/alumina approached the value of the thermal equilibrium condition. Similar phenomena have been reported by many researchers 17–21, 28. In this reaction system, when HC was added to the oxidizing gas containing NO, the NO oxidation to NO 2 was significantly enhanced and the NO conversion with HC increased three times compared with that without HC at 400 °C.…”

“…On the other hand, the γ‐alumina catalyst with the discharging nonthermal plasma showed a superior NO x reduction activity compared with the Pt/alumina and Cu‐ZSM‐5 catalysts even under high space velocity conditions (60 000 h −1 ). Under the low space velocity conditions, it has been reported that γ‐alumina shows a high NO x reduction activity with plasma‐assist and that the NO 2 produced by the discharging nonthermal plasma plays an important role 20, 21, 28. In addition, N 2 O was hardly detected when using γ‐alumina with plasma‐assist (>5 ppm, below detection limit).…”

Pulsed dielectric barrier discharge reactor for diesel particulate matter removal

“…Additional aftertreatments are required to reduce 97% PM emission to the same PM emission level with that without EGR. Plasma technology has potential to reduce this excess PM emission (Chae et al, 2001; Chang, 1993; Chang et al, 1991; Dorai and Kushner, 1999; Dorai et al, 2000; Eliasson, 1991; Franick and Bykowski, 1994; Herling et al, 2000; Larkin et al, 1998; Lepperhoff et al, 1999; Liu et al, 1996; Matsui et al, 2001; Okubo and Yamamoto, 2002; Penetrante, 1993; Penetrante et al, 1999; Tamon et al, 1995, 1998; Thanyachotpaiboon et al, 1998; Thomas et al, 2000; Vercammen et al, 1997).…”

An Investigation on the Principal Paths to Plasma Oxidation of Propylene and NO

“…Fast NH 3 −selective catalytic reduction (SCR) technology based on vanadium catalyst is an effective approach to improve NO x reduction efficiency under low temperature conditions of diesel engines. − The precondition to achieve fast SCR is to oxidize part of NO to NO 2 in the upstream of the SCR reactor. It was found that in a nonthermal plasma process, the rate of NO oxidation is 2 orders of magnitude larger than that of SO 2 oxidation. Therefore, plasma oxidation of NO is more tolerant to sulfur content as compared to NO oxidation over noble catalysts. − …”