Interaction of SO₂ with Pt Model Supported Catalysts Studied by XPS

Abstract

Sulfur dioxide that exists in gaseous reaction media as a reagent or impurity can have various effects, both poisoning and promoting, on oxide-supported platinum catalysts. In this work, the interaction of Al2O3, Pt/Al2O3, CeO2, and Pt/CeO2 thin film model catalysts with SO2 (2.5 mbar) or a SO2 + O2 mixture (5 mbar) was studied by X-ray photoelectron spectroscopy (XPS). SO2 reacts with the bare supports to form mainly sulfite species at 200 °C and mainly sulfate species at 400 °C. For Pt/Al2O3 and Pt/CeO2, the reaction with SO2 produces additionally sulfide species on the platinum surface. Pt/Al2O3 reacts with the SO2 + O2 mixture to yield the sulfide and sulfate species in comparable amounts at ≤200 °C, whereas sulfates become the main product at higher temperatures (300–400 °C). The addition of oxygen to the Pt/CeO2 + SO2 system almost completely suppresses the formation of sulfide species and increases the yield of sulfate. The reduction of ceria accompanies the formation of sulfate; both processes proceed to a greater extent in the presence of supported platinum. To confirm the identification of surface species, the reactions of SO2 and SO2 + O2 with a Pt(111) single crystal were studied as well.

Kinetic study of adsorption and desorption of SO2 over γ-Al2O3 and Pt/γ-Al2O3

“…However, the presence of Pt influences the SO2 storage/release pattern significantly by increasing the sulfation rate as well as the sulfate spillover from the surface to the bulk. Sulfide formation on Pt sites upon SO2 exposure in the absence of oxygen is indeed possible according to the literature [20]. Our experiments were conducted in the absence of O2 in the feed, however, the presence of residual oxygen (in ppm levels, < 6 ppm based on measurement ability) in the gas stream could not be avoided.…”

“…Upon Pt/Al2O3 exposure to SO2 , surface sulfate formation started at lower temperatures and the yield of SO4 2-species was larger compared to that with the bare support, however all the sulfate formed resided on alumina, rather than Pt sites, attributed to the higher stability of sulfate species on the support. Formation of sulfide species (S 2-) on the Pt surface, with a lower binding energy compared to that for sulfite and sulfate species, was also observed in the absence of oxygen [20].…”

“…In another study [20], SO2 interactions with supported Pt catalysts were compared to those with the bare support. Upon SO2 reaction with Al2O3, SOx 2-species formed on the surface, where the chemical nature of the surface species changed with the reaction temperature such that SO3 2-was the main species at 200°C, SO4 2-became dominant at 400°C, with a mixture of SO3 2-and SO4 2-present at intermediate temperatures.…”

Adsorption and Reaction of SO2 on Graphene-Supported Pt Nanoclusters

“…On ceriaand alumina-supported Pt nanoparticles, the adsorption of SO 2 leads to SO 3 and SO 4 formation on the support material, in addition to adsorption on the metal particles [1,2,40]. Furthermore, spillover and inverse spillover effects of several sulfur-derived species [40] complicate the thorough analysis of these systems.…”

Ultrathin Coating of Confined Pt Nanocatalysts by Atomic Layer Deposition for Enhanced Catalytic Performance in Hydrogenation Reactions

“…The peaks located at 71.0 and 73.0 eV are related to Pt 0 and Pt 2 + species, respectively. [17] Pt species are dominated by metallicP t 0 in Pt-in-ANTs, whereas Pt speciesi n2Al-Pt-in-ANTs carry more positive charges (Pt 2 + ). This result is consistentwith the XRD and DRIFTS results.H owever,a fter reaction, Pt species in 2Al-Pt-in-ANTs existed mainly as metallic Pt 0 ( Figure 6D).…”