Enhancement of Combustive Removal of Soot at Low Temperatures (~ 150 °C) Using Ozone as an Oxidant and Potassium-Substituted Lanthanum Manganite as a Catalyst

Ozone (O₃) is a strong oxidant, which is able to oxidize carbonaceous solid soot even at ambient temperature. In this study, we found that the ozone-induced oxidation of soot was noticeably enhanced in the range 100–150 °C when La_1-xK _x MnO₃ (x = 0, 0.1, 0.25) was used as a catalyst. The oxidation was limited at T < 300 °C owing to the thermal instability of ozone, but during temperature-programmed oxidation of soot from 25 to 700 °C, more than 70% of the carbon was combusted at T < 300 °C. The O₃-induced soot oxidation rate over LaMnO₃ at 150 °C was comparable to the NO₂ (and O₂)-induced soot oxidation rates over LaMnO₃ at 430 °C and Pt/γ-Al₂O₃ at 410 °C. The K-substitution degree (x) of La_1-xK _x MnO₃ had little influence on the catalytic activity in ozone-induced soot oxidation, which is a reflection of the similarity of the substituted catalysts in the number of surface oxygen vacancies.