Plasma-catalysis of low TCE concentration in air using LaMnO3+δ as catalyst

Abstract

The oxidative decomposition of trichloroethylene (TCE; 500–600ppmv) was investigated in synthetic (dry air) and humid air (RH=18%) with NTP (non thermal plasma) at atmospheric pressure, both in the absence and presence of lanthanum manganite catalyst at 150°C. In the absence of catalyst, TCE removal is enhanced with humidity (RH=18%) while O3 production is decreased. However, whatever the carrier gas the carbon mass balances are poor amounting to 25–30% due to the presence of polychlorinated by-products such as phosgene, dichloroacetyl chloride (DCAC) and trichloroacetaldehyde (TCAD). In the presence of catalyst, the TCE conversion significantly increased as compared to that of the plasma alone system. The perovskite catalyst can dissociate the in plasma produced ozone to oxygen radicals that decompose TCE. In dry air, the carbon mass balance keep rather poor (35% – 460J/L) due to the structural transformation of the catalyst with chlorine. In dry air, an optimum temperature of the catalytic reactor is found to be 100°C resulting from a compromise between catalyst deactivation and enhancement of the catalytic reactions. However, water remarkably promotes the carbon mass balance (75% – 460J/L) due to the beneficial role of water which acts as a chlorine scavenger at the surface of the catalyst, therefore retarding the perovskite degradation.