Investigation of Transition Metal Oxide Catalysts for Diesel PM Removal Under Plasma Discharge Conditions

Abstract

Seven different transition metal oxides (TiO2, ZnO, V2O5, Fe2O3, Co3O4, MnO2, and CuO) have been investi- gated for oxidation of diesel particulate matter (PM) under plasma discharge conditions. The experiments were carried out by measuring PM oxidation rates over each catalyst using a batch-type dielectric barrier discharge reactor. It was found that TiO2, ZnO, V2O5, and Fe2O3 can promote PM oxidation, among which Fe2O3 is a most desirable catalyst for PM oxi- dative removal as PM oxidation rate promoted by Fe2O3 is highest under plasma discharge conditions. The mechanism of PM catalytic oxidation over the metal oxides has been suggested to follow the redox catalytic cycles from the correlation of the catalytic oxidation rates with the formation enthalpies per oxygen atom of the catalysts. O atoms generated by plasma discharges may play an important role in promoting the re-oxidation of the catalysts. The highest catalytic activity for the PM oxidation with Fe2O3 has been suggested to be due to the balance between the reduction rate and the re- oxidation rate within the redox catalytic cycles.