Combination of non-thermal plasma and heterogeneous catalysis for oxidation of volatile organic compounds: Part 1. Accessibility of the intra-particle volume

The treatment of polluted air streams containing volatile organic compounds (VOCs) by a non-thermal plasma (NTP) is an alternative to conventional thermal and thermo-catalytical techniques, especially for low hydrocarbon concentrations (<1 g/m3). However, the incomplete oxidation, leading to partially oxidised, possibly toxic by-products is a serious problem which hitherto prevented a broader application of this method. The combination of a NTP with in situ heterogeneous catalysis (denoted as “plasma catalysis”) is considered as a promising way to improve the performance of the ‘cold’ plasma. By studying the oxidation of three different non-VOCs immobilised on porous and non-porous alumina and silica, the accessibility of the intra-particle volume for short-lived oxidising species could be proved for the first time. This is an essential prerequisite for the applicability of the plasma catalysis concept. The porous materials showed an enhanced selectivity for CO2 formation.