Combination of non-thermal plasma and Pd/LaMnO3 for dilute trichloroethylene abatement

Abstract

In this study, the oxidative abatement of dilute trichloroethylene (TCE) in humid air (RH=18%) was studied with combined use of a negative DC corona multi-pin-to-plate discharge and Pd/LaMnO3 catalyst downstream of the discharge. For this post-plasma catalytic (PPC) system the catalyst temperature was varied and the outcome on the TCE abatement and by-product distribution was investigated. The poor COx selectivity for the plasma system is attributed to the formation of unwanted polychlorinated by-products such as phosgene, dichloroacetylchloride (DCAC) and trichloroacetaldehyde (TCAD). At an energy density (ED) of 460J/L, the TCE abatement decreased as follows: PPC-150°C (96.2%)>PPC-200°C (91.7%)>PPC-100°C (89.1%)>NTP (82.3%). When the temperature of Pd/LaMnO3 was increased to 200°C the formation of DCAC was suppressed while the formation of phosgene was decreased in the order of 50% compared to the plasma alone system. For each PPC experiment, no ozone was detected in the outlet stream which proves that Pd/LaMnO3 is effective for ozone decomposition and substantially enhances the mineralization of TCE compared to the plasma alone system. Finally, XPS and ToF-SIMS studies have been performed after PPC experiments in order to investigate the possible surface modifications of the catalyst in the course of the reaction.