Non-thermal plasma mitigation of low concentration of air pollutants: removal of isopropyl alcohol using transition metal-oxide integration

The present work studied the decomposition of isopropyl alcohol (IPA), widely used in chemical industries and households, in a packed-bed dielectric barrier discharge (DBD) plasma reactor. Metal oxide (MO_x) coated on γ-Al₂O₃ (M = Cu, Mn, Co) was utilized for packing. The plasma-packed mode was a likely alternative to the conventional removal techniques, as it aids the conversion of dilute concentrations of IPA to CO and CO₂ at ambient conditions (room temperature and atmospheric pressure). The mean electron energy calculations suggest that electrons with higher energy are generated when the discharge zone is packed with catalysts. When comparing IPA conversion (input concentration of 25 ppm) for no packing mode and MO_x/γ-Al₂O₃ coupled plasma mode, the latter method enhances conversion to greater than 90% at an applied voltage of 18 kV. Also, MO_x/γ-Al₂O₃ showed the highest selectivity to CO₂ (70%) compared to plasma-only mode (45%). The metal-oxide layer provides the necessary catalytic surface facilitating the oxidation of IPA to CO_x through active oxygen species or the interaction of surface hydroxyl groups. The use of MO_x/γ-Al₂O₃ resulted in about 90% carbon balance and reduced ozone generation, demonstrating the significance of integrating metal oxide to achieve efficient conversion and maximal selectivity towards the desired products.