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.

Removal of ethylene from air stream by adsorption and plasma-catalytic oxidation using silver-based bimetallic catalysts supported on zeolite

“…These observations are consistent with the previous study [45]. The moderate formation enthalpy of F 2 O 3 results in a balance between the oxidation and reduction in the redox catalytic cycle, which is responsible for the high oxidation activity.…”

Synergetic effects of plasma and metal oxide catalysts on diesel soot oxidation

“…Increasing CO 2 selectivity in the presence of the catalysts is referred to their CO oxidation activity, which may be related to the accelerated oxygen transfer from the catalysts [50]. Maximum values of soot removal efficiency (SRE) in the presence of The activated oxygen from the catalyst surface can oxidize soot particulates and CO and then the reduced catalyst is re-oxidized by plasma discharge products such as O and O 3 [51]. As a result, the catalyst with a high O 2 storage capacity and reducibility has higher activity toward soot and CO oxidation.…”

“…The dominating mechanism for refilling of the surface oxygen vacancy may be via reactive species generated by the plasma discharge as active oxidants. This is the main reason for the synergetic effect of plasma and catalyst [51]. Also, CO oxidation to CO 2 occurs by oxygen atoms on the surface of the metal oxides (Eq.…”

Characterization of Catalyst-Supported Dielectric Barrier Discharge Reactor

“…Very recently, we found some transition metal oxides (TiO 2 , ZnO, V 2 O 5 , Fe 2 O 3 ) that can be used as catalysts for diesel PM oxidation under plasma discharge conditions. From the correlation of the catalytic oxidation rates with the formation enthalpies per oxygen atom of the catalysts, the redox catalytic cycles have been found to act practically as the catalytic mechanisms of the transition metal oxides [26,27]. It has been suggested that O atoms generated by plasma discharges can play an important role in promoting the re-oxidation of metal under plasma discharge conditions.…”

“…The alumina spacers were used to form a discharge space of 30x30x0.5 mm 3 between two alumina plates; where the discharge gap is 0.5 mm. Fe 2 O 3 and TiO 2 catalyst layers were coated on one surface of two alumina plates according to the method reported elsewhere [27]. The surfaces with catalyst layers were set facing to the discharge space.…”