| In this work, we investigated the catalytic performances and mechanism for thenitrogen oxide (NOx) storage reduction (NSR) reaction to eliminate NOxfromlean-burn engines using the perovskite-type La0.7Sr0.3Co1-xMxO3(M=Pd, Ru)catalysts.Through the NOxstorage and NOxstorage-reduction experiments, we found thebest doping proportion of the noble metals was0.03at the B sites of theLa0.7Sr0.3Co1-xMxO3(M=Pd, Ru) catalyst. Thereafter, the influence of thepreparation method and the reaction temperature to the catalystic activity, the sulfurresistance and stability of these catalysts were investigated in detail by X-raydiffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS) analysis, Fouriertransform infrared transmission spectroscopy (FT-IR) analysis, the field emissionscanning electron microscopy (FE-SEM) analysis.The La0.7Sr0.3Co0.97Pd0.03O3catalyst presented an excellent catalyticperformance for both the NOxstorage capacity and the NOxelimination efficiencyduring the NSR tests in a wide temperature range from275to400C. Meanwhile, thestructure and morphology of the catalysts were stablely mantained after the NOxstorage and reduction process. The activities of these catalysts could be suppressedby pre-sulfation, but would successifully be regenerated after a H2reductiontreatment. With100ppm SO2added in the reaction gases, the catalyst still kept highDe-NOxactivity, whereas with a higher SO2concentration (300ppm), the activitydropped seriously. We found the La0.7Sr0.3Co1-xRuxO3(x=0.01,0.03,0.05) presented arelatively poor catalytic activity than the Pd containing perovskites during theNSRtests.Here, we suppose that for the La0.7Sr0.3Co1-xPdxO3perovskite-type catalyst thesites on the perovskite structure, probably the oxygen vacancies, act as the activecenter of NO to NO2during the lean-burn period, the SrO in the perovskite andremained SrCO3act as the main storage component, while the doping Pd acts as theactive center for NOxreduction to N2during the fuel rich period,. |
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