SCHEDULED MAINTENANCE
Mechanism of Pd and K co-doping to enhance the simultaneous removal of NOx and soot over LaMnO3
a
Abstract
A series of La0.5K0.5Mn1−yPdyO3 catalysts with different doping amounts of Pd (y = 0, 0.01, 0.02, 0.03, 0.04) were synthesized by the citric acid complexation method and tested for the simultaneous removal of NOx and soot. The X-ray diffraction (XRD), specific surface area and scanning electron microscopy (SEM) results reveal the microscopic morphology and structure of the catalysts, and the catalytic performance of the materials was investigated by temperature-programmed experiments. The noble metal Pd was uniformly dispersed on the surface of the materials, as shown in the SEM images. Among all the catalysts, La0.5K0.5Mn0.97Pd0.03O3 exhibited the best NOx removal rate and the lowest soot ignition temperature. The mechanism of Pd in the simultaneous removal of NOx and soot was characterized by XPS, HRTEM and H2-TPR (the redox properties), and the results illustrate that Pd2+ substitution for Mn3+ and generation of oxygen vacancies are the key factors in promoting soot combustion. Based upon the NOx-storage test and kinetic calculation, the excellent catalytic performance of a small amount of palladium (0.03 atomic ratio) was confirmed, and this system exhibited the high simultaneous removal rate of NOx and soot under lean conditions.
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