Catalytic combustion of soot particulates over La2-xKxNiMnO6 catalysts

Nanosized La2-xKxNiMnO6 catalysts with ABO3 type perovskite-like structure were prepared by auto-combustion method using citric acid as a ligand to control particle size and morphology. The structures and properties of these perovskite-like oxides were investigated by X-ray powder diffraction (XRD) and temperature-programmed reduction (TPR). The catalytic activities for soot combustion were evaluated by temperature-programmed oxidation (TPO) with pure O2 and O2/NOx as oxidant, respectively. In the La2-xKxNiMnO6 catalysts, the partial substitution of K at A-site leads to an increase of the concentrations of high valence cation and oxygen vacancy, which enhance the catalytic activity for soot combustion. The optimal substitution amount of K was equal to x = 0.4 among these samples. Tp (peak temperature) in O2-TPO profile was 420 °C and Tp in O2/NOx-TPO profile was 370 °C over La1.6K0.4NiMnO6 catalyst for soot particulates combustion under loose contact conditions between catalyst and soot.