Identification of active crystalline phase in La-K-Cu-V mixed oxide for the simultaneous removal of nitrogen oxides and diesel soot

The oxide catalyst having an overall metal composition of La/K/Cu/V = 9/1/7/3 (denoted as LKCVO) showed an excellent selectivity to NOx reduction into N-2 in the simultaneous NOx-soot removal reaction, though it was a mixture of several crystalline phases. In order to identify the real active phase, LKCVO was characterized by X-ray diffraction (XRD) and by elemental analysis of individual grains in a transmission electron microscope (TEM) equipped with an energy dispersive spectrometer (EDS). LKCVO was found to be composed of CuO and mixed metal oxides analogous to La2CuO4, LaVO4, and La3VO7. By comparing the catalytic activity of LKCVO with those of single-phase oxides synthesized according to the results of XRD and TEM/EDS, (La2-xKx)(Cu0.95V0.05)O-4 With 0.05 less than or equal to x less than or equal to 0.1 was identified to be the real active phase in LKCVO for the simultaneous NOx-soot removal reaction.