(673a) SO2 Interactions with Hydrothermally Treated Colloidal Pd-Based Catalysts: Influence of Particle Size on SO2 Poisoning

The high operating temperature and the presence of high percentages of water vapor in aftertreatment systems lead to the loss of activity due to the agglomeration of the active components. Plus, the accumulation over time of the residual sulfur of the fuel has a detrimental effect on the aftertreatment system performance due to the strong chemisorption of sulfur species on the catalyst surface. Resistance to SO₂ poisoning depends on the precious metal (PM) and support used in the catalyst composition. Taking a closer look to the interactions between SO₂ and noble metals, previous studies have shown that PM particle size greatly influences what type of sulfur species form on the catalyst surface in Al₂O₃-supported catalysts: smaller particle size form a greater amount of high temperature aluminum sulfate species, while catalysts with larger particle sizes form a greater amount of low temperature sulfur species, such as molecular SO₂ and aluminum sulfite species [1]. To alleviate the effects of agglomeration at high temperatures, exposure to hydrothermal treatments leads to the redispersion of clustered Pd nanoparticles which resulted in the improved activity and stability of the catalyst. Plus, this treatment led to improved resistance to SO₂ poisoning [2]. In this study, we evaluated the SO₂ interactions on colloidal Pd-based catalysts with 2.9 and 10 nm particle sizes after hydrothermal treatments, and the Pd particle size after H₂O + SO₂ exposure was assessed by TEM and CO pulse injection.

References

[1] Wilburn, M. S., & Epling, W. S. (2017). SO₂ adsorption and desorption characteristics of Pd and Pt catalysts: Precious metal crystallite size dependence. Applied Catalysis A: General, 534, 85–93. https://doi.org/10.1016/j.apcata.2017.01.015

[2] Jeong, H., Bae, J., Han, J. W., & Lee, H. (2017). Promoting effects of hydrothermal treatment on the activity and durability of Pd/CeO₂ catalysts for CO oxidation. ACS Catalysis, 7(10), 7097–7105. https://doi.org/10.1021/acscatal.7b01810