Influence of ferroelectric materials and catalysts on the performance of non-thermal plasma (NTP) for the removal of air pollutants

The introduction of ferroelectric and catalytically active materials into the discharge zone of NTP reactors is a promising way to improve their performance for the removal of hazardous substances, especially those appearing in low concentrations. In this study, several coaxial barrier-discharge plasma reactors varying in size and barrier material (glass, Al-2 O-3, and TiO2) were used. The oxidation of methyl tert-butyl ether (MTBE), toluene and acetone was studied in a gas-phase plasma and in various packed-bed reactors (filled with ferroelectric and catalytically active materials). In the ferroelectric packed-bed reactors, better energy efficiency and CO2 selectivity were found for the oxidation of the model substances. Studies on the oxidation of a toluene/acetone mixture in air showed an enhanced oxidation of the less reactive acetone related to toluene in the ferroelectric packed-bed reactors. It can be concluded that the change of the electrical discharge behaviour was caused by a larger number of non-selective and highly reactive plasma species formed within the ferroelectric bed. When combining ferroelectric (BaTiO3) and catalytically active materials (LaCoO3), only a layered implementation led to synergistic effects utilising both highly energetic species formed in the ferroelectric packed-bed and the potential for total oxidation provided by the catalytically active material in the second part of the packed bed.