A lumped kinetic model of a pulsed corona discharge reactor, where the high-voltage dischargeinduced electron density fluctuation and hence the electron collision rate fluctuation are approximated with a uniform electron distribution and a new Arrhenius-type rate model, is found to capture the effect of power input, NO x composition, and residence time. An N atom and N 2 (A) are found to control the conversion of nitrogen oxides and the evolution of byproducts; the N atom controls the NO conversion, N 2 (A) controls the N 2 O conversion, and the N atom and N 2 (A) control the NO 2 conversion.

All species that are likely to be responsible for nitrogen oxides (N 2 O, NO, and NO 2 ) conversion in nitrogen plasma are analyzed in detail through carefully designed systematic experiments and theoretical analysis. The effect of ppm-level CO 2 , CO, and 1% CO on N 2 O conversion reveals that the N 2 O conversion occurs mainly by interaction with N 2 (A 3 ∑ u + ) excited species. The effect of 1% CO on the NO conversion suggests that only N atom radicals are predominantly involved in NO conversion. NO 2 conversion, on the other hand, occurs by interaction with both N 2 (A 3 ∑ u + ) and N atom radicals. Therefore, only two active species, N 2 (A 3 ∑ u + ) and N atom radicals, are found to be responsible for nitrogen oxides conversion in nitrogen plasma.

in Wiley InterScience (www.interscience.wiley.com). NO is mainly converted to NO 2 by chemical oxidation in the presence of oxygen. Initial selectivity analysis shows that three electron collision reactions are important for NO x evolution in O 2 /N 2 . The rate constants of these reactions decrease with increasing oxygen concentration. This is because oxygen is electronegative and thus reduces electron concentration. The rate constant of O 2 dissociation by electron collision reaction is almost two orders of magnitude higher than that of N 2 dissociation. NO formation occurs predominantly through N( 2 D) ϩ O 2 3 NO ϩ O. The critical oxygen concentration, defined as the concentration at which the NO x formation rate counterbalances the NO x decomposition rate, increases with increasing initial NO concentration.

Hydrogen sulfide (H 2 S) dissociation into hydrogen and sulfur has been studied in a pulsed corona discharge reactor (PCDR). Due to the high dielectric strength of pure H 2 S (~2.9 times higher than air), a non-thermal plasma could not be sustained in pure H 2 S at discharge voltages up to 30 kV with our reactor geometry. Therefore, H 2 S was diluted with another gas with lower dielectric strength to reduce the breakdown voltage. Breakdown voltages of H 2 S in four balance gases (Ar, He, N 2 and H 2) have been measured at different H 2 S concentrations and pressures. Breakdown voltages are proportional to the partial pressure of H 2 S and the balance gas. With increasing H 2 S concentrations, H 2 S conversion initially increases, reaches a maximum, and then decreases. H 2 S conversion and the reaction energy efficiency depend on the balance gas and H 2 S inlet concentrations. H 2 S conversion in atomic balance gases, such as Ar and He, is more efficient than that in diatomic balance gases, such as N 2 and H 2. These observations can be explained by proposed reaction mechanisms of H 2 S dissociation in different balance gases. The results show that nonthermal plasmas are effective for dissociating H 2 S into hydrogen and sulfur.

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