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The performances of fresh and sulfated MnOx-CeO₂ catalysts for selective catalytic reduction of NOx by NH₃ (NH₃-SCR) in a low-temperature range (T < 300 °C) were investigated. Characterization of these catalysts aimed at elucidating the role of additive and the effect of sulfation. The catalyst having a Sn:Mn:Ce = 1:4:5 molar ratio showed the widest SCR activity improvement with near 100% NOx conversion at 110-230 °C. Raman and X-ray photoelectron spectroscopy (XPS) indicated that Sn modification significantly increases the concentration of oxygen vacancies that may facilitate NO oxidation to NO₂. NH₃-TPD characterization showed that the low-temperature NH₃-SCR activity is well correlated with surface acidity for NH3 adsorption, which is also enhanced by Sn modification. Furthermore, as compared to MnOx-CeO₂, Sn-modified MnOx-CeO₂ showed remarkably improved tolerance to SO₂ sulfation and to the combined effect of SO₂ and H₂O. In the presence of SO₂ and H₂O, the Sn-modified MnOx-CeO₂ catalyst gave 62% and 94% NOx conversions as compared to 18% and 56% over MnOx-CeO₂ at temperatures of 110 and 220 °C, respectively. Sulfation of SnO₂-modified MnOx-CeO₂ may form Ce(III) sulfate that could enhance the Lewis acidity and improve NO oxidation to NO₂ during NH₃-SCR at T > 200 °C.

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Steam reforming is a process where a hydrocarbon is converted into hydrogen and oxygenated carbon species. Ni is often used as catalyst for the reaction. Long term stability of steam reforming catalysts is governed by their ability to selectively oxidize C atoms while preventing C-C bond formation. In this communication we demonstrate that C atom chemistry over Ni surfaces can be controlled by surface alloying. We show that bimetallic Sn/Ni catalyst is much more carbon-tolerant that monometallic Ni. The main reason for this is that Sn alloying results in dramatically lower rates of C-C bond formation as compared to C-oxidation. The bimetallic catalyst was identified in quantum computational studies of the underlying atomic-scale phenomena that govern C atom surface chemistry. The catalysts were also characterized with various electron- and X-ray-based microscopies and spectroscopies.

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