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

Abstract

Seven different transition metal oxides (TiO 2 , ZnO, V 2 O 5 , Fe 2 O 3 , Co 3 O 4 , MnO 2 , and CuO) have been investigated 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 TiO 2 , ZnO, V 2 O 5 , and Fe 2 O 3 can promote PM oxidation, among which Fe 2 O 3 is a most desirable catalyst for PM oxidative removal as PM oxidation rate promoted by Fe 2 O 3 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 Fe 2 O 3 has been suggested to be due to the balance between the reduction rate and the reoxidation rate within the redox catalytic cycles.