title: Effect of barium loading on the desulfation of Pt-BaO/Al2O3 studied by H2 TPRX, TEM, sulfur K-edge XANES, and in situ TR-XRD.
abstract: Desulfation processes were investigated over sulfated Pt-BaO/Al2O3 with different barium loading (8 and 20 wt %) by using H2 temperature programmed reaction (TPRX), transmission electron microscope (TEM) with energy dispersive spectroscopy (EDS), sulfur K-edge X-ray absorption near-edge spectroscopy (XANES), and in situ time-resolved X-ray diffraction (TR-XRD) techniques. Both sulfated samples (8 and 20 wt %) form sulfate species (primarily BaSO4) as evidenced by S K-edge XANES and in situ TR-XRD. However, the desulfation behavior is strongly dependent on the barium loading. Sulfated Pt-BaO8/Al2O3, consisting predominantly of surface BaO/BaCO3 species, displays more facile desulfation by H2 at lower temperatures than sulfated Pt-BaO20/Al2O3, a material containing primarily bulk BaO/BaCO3 species. Therefore, after desulfation with H2 up to 1073 K, the amount of the remaining sulfur species on the former, mostly as BaS, is much less than that on the latter. This suggests that the initial morphology differences between the two samples play a crucial role in determining the extent of desulfation and the temperature at which it occurs. It is concluded that the removal of sulfur is significantly easier at lower barium loading. This finding can potentially be important in developing more sulfur resistant LNT catalyst systems.
authors.affiliation: Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, USA. do.kim@pnl.gov
authors.forename: Do Heui
authors.initials: DH
authors.lastname: Kim
authors.forename: Janos
authors.initials: J
authors.lastname: Szanyi
authors.forename: Ja Hun
authors.initials: JH
authors.lastname: Kwak
authors.forename: Tamas
authors.initials: T
authors.lastname: Szailer
authors.forename: Jonathan
authors.initials: J
authors.lastname: Hanson
authors.forename: Chong Min
authors.initials: CM
authors.lastname: Wang
authors.forename: Charles H F
authors.initials: CH
authors.lastname: Peden