Impact of Sulfur Poisoning on the NO_xUptake of a NO_xStorage and Reduction (NSR) Model Catalyst

Abstract

Toward obtaining a more detailed understanding of the influence of SO x poisoning on the mechanism of NO x uptake on a NO x storage and reduction (NSR) catalyst, we have performed a model study under ultrahigh vacuum (UHV) conditions. A supported model catalyst based on a thin well-ordered alumina film grown on a NiAl(110) single crystal is used onto which BaO and Pd particles are deposited. Time-resolved (TR) infrared reflection absorption spectroscopy (IRAS) is applied to identify the species formed during NO 2 uptake on the catalyst surface, which has been pretreated with SO 2 . These results are compared to the NO 2 uptake on the corresponding fresh samples. It is shown that SO 2 readily decomposes upon adsorption on both the pristine Al 2 O 3 surface and the BaO and Pd loaded model systems. NO 2 reoxidizes the decomposition products to surface sulfites and sulfates. A pronounced influence of the SO 2 species on the interaction with NO 2 is observed leading to reduced NO 2 uptake and to a change of the preferential adsorption geometry from bridging to monodentate. A comparison of the integral intensity of the nitrate bands on the Ba-free and the Ba-containing samples furthermore suggests that SO 2 adsorbs preferentially on Ba 2+ centers rather than on the Al 3+ centers.

Ordered Nanostructure Catalysts Efficient for NOx Storage/Reduction (NSR) Processes

“…The introduction of 10 torr 15 NO at room temperature afforded the spectrum shown in Figure 23 (curve a). Similar adsorption characteristics as those of 14 NO presented, and two main bands and a shoulder with narrow FWHM were observed at 1842, 1826, and 1853 cm −1 . The positions of these bands showed about 30 cm −1 red shift compared with those of 14 NO, which confirmed that these adsorbed bands were from the NO species.…”

“…Typical model of an NSR catalyst is Pt-Ba/Al 2 O 3 , which was developed by Toyota's research group [6][7][8][9]. Although considerable amounts of experimental and theoretical investigations of Pt-Ba/Al 2 O 3 have been conducted, serious problems still remain with respect to sulfur poisoning [6,[13][14][15][16]. Meanwhile, high-NO x storage NSR catalysts are desirable because increasing NO x storage capacity can decrease the necessary catalyst and, in turn, decrease the amount of precious metals required and the cost.…”

Ultrathin ionic liquid films on metal surfaces: adsorption, growth, stability and exchange phenomena

“…Replacement effects of this kind are further related to stability concerns in IL-based catalysts. One example could be the poisoning of a SCILL system, where the adsorption of large molecular reactants might block the reactive sites on the surface, irreversibly lowering the catalytic activity over time, similar to poisoning of Pt catalysts by sulfur or other nonreactive species [60,[195][196][197][198]. Another example would concern SILP systems based on large molecules (like metalloporphyrin derivates) as catalytic centers [171].…”

Surface Decoration of MgO Nanocubes with Sulfur Oxides: Experiment and Theory

“…Because of similar IR band positions for both types of adsorbates with their mono- or multidentate bonding character a clear and unambiguous discrimination between them is impossible on the basis of the experimental data presented. 55 The presence of sulfur in a positive oxidation state, however, was confirmed with XPS and is further strengthened by FT-IR spectroscopy.…”