Metal-Promoted La2O2SO4 for High-Temperature Soot Oxidation in Catalyzed Gasoline Particulate Filters

Cu- and Co-promoted lanthanum oxysulfates were investigated as potential catalysts for the combustion of carbon soot in a gasoline particle filter (GPF)at high temperatures. The materials were characterized by XRD, XRF, TEM, N2-adsorption analysis, and experiments of soot combustion were carried out in a coupled TG-MS apparatus under O2-free or 1% O2 flow. It was demonstrated that the metal-promoted lanthanum oxysulfates were able to completely oxidize soot even in the absence of O2, thanks to the high oxygen storage capacity related to their fast and fully reversible conversion into the corresponding oxysulfides. Doping with small amounts of transition metals (1 wt %) inhibits the undesired and irreversible decomposition of the La-oxysulfate releasing SO2 and decreases the temperature of soot oxidation