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The decomposition of toluene on c-alumina, MnO 2 -alumina and Ag 2 Oalumina catalysts in a plasma-catalytic reactor is tested. A comparison between catalytic, catalyst-after-plasma and catalyst-in-plasma systems is made in 150-400°C temperature range. An Arrhenius plot is made in order to deduce the mechanism of plasma activation. It was found that there is no difference between the measured activation energy for catalytic and catalyst-after-plasma systems. On the other hand it was found that plasma could activate catalyst placed inside of the discharge. Plasma treatment decreases the activation energy for the silver-alumina catalyst but does not increase the number of active centers on the surface of Ag 2 O-alumina. In case of MnO 2 -alumina, the activation mechanism is different: plasma does not change the activation energy and but does increase its efficiency due to formation of additional active centers. The mechanism of catalyst activation in plasma, which includes the structural change of manganese ions, is suggested.

A comparison has been made of plasma-catalysis with thermal-catalysis and plasma alone for the removal of low concentrations of propane and propene from synthetic air using a one-stage, catalyst-in discharge configuration. In all cases, plasma-catalysis produces better hydrocarbon destructions (*40%) than thermal catalysis at low temperatures. At higher temperatures, little difference is observed between plasma-catalytic and thermal-catalytic operation. Plasma operation by itself had a similar effectiveness to plasma-catalysis at low temperatures but was significantly lower (up to 50%) as the temperature was raised. By examining the form of the temperature dependence for the plasma-catalytic destruction processes, it is possible to phenomenologically distinguish two contributions to the destruction; one that is specifically plasma-induced and another (at higher temperatures) in which both plasma and thermal activation have similar mechanisms.

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This study investigated the decomposition of hydrofluorocarbons (HFCs) having high global warming potentials by using a dielectric-packed-bed nonthermal plasma reactor with barium titanate beads as the packing material. The target HFCs were 1,1,1,2-tetrafluoroethane (HFC-134a) and 1,1-difluoroethene (HFC-132a). The effects of several parameters such as reaction temperature, oxygen content, and initial concentration on the HFC decomposition efficiency were evaluated. There was essentially no temperature dependence of the HFC decomposition efficiency in the range 150-250 degrees C. The optimum oxygen content for HFC decomposition was found to be about 0.5 vol %. Variations in the initial concentration did not affect the decomposition efficiency. The decomposition products were analyzed, and some decomposition pathways were elucidated. The energy requirements for the decomposition of HFC-134a and HFC-132a were found to be 0.038 and 0.062 mol MJ-1, respectively, based on the initial concentrations of 200 and 120 ppm (parts per million, volumetric).