Oxidation Of Diesel Particulate Matter Research Articles

Effects of O3 and NO2 on Catalytic Oxidation of Diesel PM

Abstract Oxidative activities of ten different catalysts to particulate matter (PM) emitted from a diesel engine have been compared by thermogravimetric analysis under an atmosphere containing O3 and NO2. MnO2 has been found to exceed noble metal catalysts in the PM oxidation efficiency even at 300 °C. The PM oxidative activities of transition-metal oxides possessing high formation enthalpies are enhanced by the active oxygen species owing to acceleration of redox catalytic cycles.

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

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.

Temperature-programmed oxidation of diesel particulate matter in a hybrid catalysis–plasma reactor

Nonthermal plasma (NTP) technology was used to promote the temperature-programmed oxidation (TPO) of particulate matter (PM) over a perovskite type of La 0.8K 0.2MnO 3 catalyst. The ionic wind induced by plasma enhances the quantity of the nitrogen oxides (NO x ) adsorbed onto the catalyst surface, and therefore promotes the reactions between the soluble organic fraction (SOF) and NO x , as well as the redox reaction between soot and NO x . Furthermore, the plasma process improved SOF oxidation by enhancing the NO 2 amount, which is an indispensable intermediate in SOF oxidation and NO x reduction. It was found that the O radicals originating from the decomposition of O 2 advance PM oxidation, and the ignition temperatures of soot can be reduced efficiently by the plasma process. The reactions between PM and NO x , as well as the decomposition of nitrogen monoxide (NO) in plasma, will create N 2, and the N 2/NO rate (conversion rate of NO into N 2) can be promoted markedly by the plasma process.

Investigation of the oxidation behavior of diesel particulate matter

In this work, an attempt was made to identify and decouple several effects contributing to the complexity of kinetics of diesel particulate matter oxidation by oxygen. Adsorbed hydrocarbons provided limited contribution to the overall reactivity of the un-pretreated particulate matter. Even upon their thermal desorption, the first few percents of carbon in particulate matter were oxidized at an anomalously high rate. Further oxidation occurred at a lower rate with rather uniform kinetic characteristics. The high initial reactivity can be restored repeatedly by exposure of particulate matter to the ambient air for the prolonged periods of time (weeks) at room temperature. The experimental results suggest that these changes in reactivity of carbon are chemical, not morphological, in nature. The results are consistent with the hypothesis that prolonged ambient aging leads to formation of some highly reactive groups on the carbon surface, responsible for the subsequent relatively facile initial oxidation. A high density of these surface groups presumably cannot be obtained during the more vigorous oxidation process at higher temperatures.