Abstract
The desulfation of presulfated Pt-BaO/CeO2 lean NOx trap catalyst was investigated by H2 TPRX (temperature programmed reaction), in situ TR-XRD (time-resolved X-ray diffraction), and in situ S K-edge XANES (X-ray absorption near edge spectroscopy) techniques. Compared with Pt-BaO/Al2O3 materials, a reductive treatment in H2 for the CeO2-supported sample up to 1073 K removes, at most, only a very small amount of sulfur species. However, the results of in situ TR-XRD measurements demonstrate that the quantity of a BaS phase formed on Pt-BaO/CeO2 is much smaller than that on Pt-BaO/Al2O3, implying that the formation of BaS crystallites, which occurs during the reduction from sulfate (SO42−) to sulfide (S2−), is significantly suppressed in the CeO2-supported catalyst. As the desulfation temperature increases under reducing conditions (in H2), in situ S XANES spectra show that, compared with alumina-supported samples, the reduction temperature for sulfates (S6+) decreases by about 150 K. Concomitantly, the for...
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