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

摘要

Ozone (O-3) 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 degrees C when La1-xKxMnO3 (x = 0, 0.1, 0.25) was used as a catalyst. The oxidation was limited at T < 300 degrees C owing to the thermal instability of ozone, but during temperature-programmed oxidation of soot from 25 to 700 degrees C, more than 70% of the carbon was combusted at T < 300 degrees C. The O-3-induced soot oxidation rate over LaMnO3 at 150 degrees C was comparable to the NO2 (and O-2)-induced soot oxidation rates over LaMnO3 at 430 degrees C and Pt/gamma-Al2O3 at 410 degrees C. The K-substitution degree (x) of La1-xKxMnO3 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.