A large corona reactor of wire/cylinder configuration was used to compare the performance of different regimes (–DC, +DC and +pulsed corona) in the removal of VOCs via oxidation in air at room temperature and atmospheric pressure. Mechanistic insight was gained through comparison of the different corona regimes with regard to process efficiency, response to the presence of humidity and, for DC coronas, current/voltage characteristics coupled with the analysis of the ionized component of the plasma. The results of ion analysis, performed by APCI-MS (Atmospheric Pressure Chemical Ionization – Mass Spectrometry), provide a powerful rationale for interpreting current/voltage characteristics of DC coronas. All experimental findings are consistent with the proposal that in the case of +DC corona the oxidation of hydrocarbons is initiated by reactions with ions (O2+•, H3O+ and their hydrates, NO+) both in dry as well as in humid air. In contrast, with –DC no evidence is found for any significant reaction of hydrocarbons with negatively charged ions. Thus, electron induced bond dissociation and reactions with O atoms and OH radicals must prevail in this case. Evidence is presented for the involvement of OH radicals in the initial stage of hydrocarbon oxidation induced both by –DC and +pulsed corona. Finally, the major role of VOC chemical composition is highlighted by the strikingly different effects on –DC corona produced by ppm concentrations of any of the hydrocarbons studied and of a chlorocarbon, dichloromethane: no effect is seen on the –DC corona current/voltage profiles for any of the former, as opposed to a significant increase in current for the latter. These observations are consistent with and rationalized by the detection of many Cl-containing anions in the APCI mass spectra of dichloromethane.

Chemistry of organic pollutants in atmospheric plasmas

MAROTTA, ESTER;SCHIORLIN, MILKO;PARADISI, CRISTINA
2010

Abstract

A large corona reactor of wire/cylinder configuration was used to compare the performance of different regimes (–DC, +DC and +pulsed corona) in the removal of VOCs via oxidation in air at room temperature and atmospheric pressure. Mechanistic insight was gained through comparison of the different corona regimes with regard to process efficiency, response to the presence of humidity and, for DC coronas, current/voltage characteristics coupled with the analysis of the ionized component of the plasma. The results of ion analysis, performed by APCI-MS (Atmospheric Pressure Chemical Ionization – Mass Spectrometry), provide a powerful rationale for interpreting current/voltage characteristics of DC coronas. All experimental findings are consistent with the proposal that in the case of +DC corona the oxidation of hydrocarbons is initiated by reactions with ions (O2+•, H3O+ and their hydrates, NO+) both in dry as well as in humid air. In contrast, with –DC no evidence is found for any significant reaction of hydrocarbons with negatively charged ions. Thus, electron induced bond dissociation and reactions with O atoms and OH radicals must prevail in this case. Evidence is presented for the involvement of OH radicals in the initial stage of hydrocarbon oxidation induced both by –DC and +pulsed corona. Finally, the major role of VOC chemical composition is highlighted by the strikingly different effects on –DC corona produced by ppm concentrations of any of the hydrocarbons studied and of a chlorocarbon, dichloromethane: no effect is seen on the –DC corona current/voltage profiles for any of the former, as opposed to a significant increase in current for the latter. These observations are consistent with and rationalized by the detection of many Cl-containing anions in the APCI mass spectra of dichloromethane.
2010
Industrial Plasma Technology
9783527325443
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2452060
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