The decomposition of p-xylene in air by plasma-assisted catalysis

The decomposition of p-xylene in contaminated air streams by using non-thermal plasma was studied in the absence and in the presence of AlAg catalysts. A dielectric barrier reactor packed with spherical quartz pellets was used at room temperature and atmospheric pressure. The conversion of p-xylene increased with increasing the specific input energy (SIE), reaching 66% for a SIE of 264 J/l. The main gaseous reaction products resulting from p-xylene decomposition were carbon monoxide and carbon dioxide, with selectivities towards CO₂ of 44%, independent of the SIE, over the range investigated. The catalyst was placed downstream of the plasma reactor, in a catalytic reactor that was heated up to 500°C. The catalyst became active above 300°C, however xylene conversion was rather low in purely catalytic experiments, reaching 11% at the maximum temperature investigated. In the plasma-catalytic system, it was found that the catalyst addition had little effect on the conversion of p-xylene. However, the selectivity towards CO₂ was significantly improved in the presence of AlAg catalyst as compared to the results obtained with plasma alone. The catalyst temperature influenced the CO₂ selectivity as well. Above 300°C the CO₂ selectivity reached 65-70%.