Mark C. Hsiao

Kinetic Analysis of Non-Thermal Plasmas Used for Pollution Control

Non-thermal plasma techniques are being developed for the treatment of many gas-phase pollutants. In these methods electrical energy from electron beams or electrical discharges is directed selectively into the production of electrons, ions and radicals, or into molecular excitations that will result in the efficient destruction of the unwanted species. The processes by which this can be achieved are described. Kinetic analysis of the deposition of energy into contaminated air is illustrated by studies of the decomposition of nitrogen oxides, methylene chloride, carbon tetrachloride and methanol.

Comparison of Pulsed Corona and Electron Beam Processing of Hazardous Air Pollutants

Abstract This paper presents a comparative assessment of the energy efficiencies of pulsed corona and electron beam methods for processing of dilute concentrations of hazardous air pollutants in atmospheric-pressure dry air streams. The four representative compounds investigated are ethylene, o-xylene, toluene and benzene. It is shown that the electron beam method requires much less electrical energy than the pulsed corona method to achieve the same level of pollutant decomposition. The results imply that the initial decomposition of these pollutant molecules is achieved more efficiently through reactions with either electrons or ions, rather than through oxidation by O radicals.

Effect of Gas Temperature on Pulsed Corona Discharge Processing of Acetone, Benzene and Ethylene

Abstract Experiments on the plasma-assisted oxidation of dilute concentrations of acetone, benzene, and ethylene in atmospheric pressure gas streams by pulsed corona electrical discharge processing show that temperature influences the oxidation chemistry. In dry air mixtures, the main oxidation products are CO and CO2, which account for most if not all of the oxidized acetone and benzene. Plasma-assisted oxidation of ethylene is less complete since the measured CO and CO2 amounts do not account for the decrease in ethylene. The energy efficiency for plasma-assisted oxidation of ethylene is also less temperature dependent than that for either acetone or benzene. These trends correlate with the temperature dependence in the rate constant expressions for reactions of these molecules with O atoms.

Reduction of NO2 in N2 by Non-Thermal Plasmas

Abstract Experimental results on the chemical reduction of dilute concentrations of NO2 in N2 by pulsed corona and dielectric-barrier discharge processing axe presented. The initial reduction of NO2 proceeds via N + NO2 → N2O + O. The subsequent reduction of NO2 then proceeds via O + NO2 -► NO + O2, followed by N + NO → N2 + O; the latter reaction reproduces O radicals to initiate the next NO2 reduction cycle.

Plasma Assisted Oxidation of Propene

Abstract Non-thermal plasma processing is an innovative technique for pollutant abatement. This approach involves the use of electrical energy for the production of free radicals which then react with the pollutant molecules. We have studied the oxidation of propene as a prototype hydrocarbon using a packed bed dielectric-barrier discharge reactor to generate the non-thermal plasma. We report the effect of three different types of material filling the reactor: glass, zirconia, and titania. The titania filled reactor shows the greatest selectivity for producing CO2 while the zirconia filled reactor has the greatest yield of total COx. In addition to COx, the plasma assisted oxidation produces small carbon containing compounds like methanol and formaldehyde.