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A comparative study of the H2-assisted selective catalytic reduction of nitric oxide by propene over noble metal (Pt, Pd, Ir)/γ-Al2O3 catalysts

Goula, Maria, Charisiou Nikolaos D., Papageridis Kiriakos N., Delimitis Andréas, Papista Eleni, Pachatouridou Eleni, Iliopoulou Eleni F., Marnellos, Georges E, Konsolakis Michail, Gentekakis Ioannis

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Περίληψη

The impact of H2 as additional reducing agent on the SCR of NO with C3H6 in excess oxygen, was comparatively explored over low noble metal loading (0.5 wt%), Pt/γ-Al2O3, Pd/γ-Al2O3, Ir/γ-Al2O3 catalysts. To gain insight into the role of H2, the reactions NO + C3H6 + O2 (R#1), NO + C3H6 + O2 + H2 (R#2), NO + H2 + O2 (R#3) were employed. In respect to propene oxidation, the Pd > Pt > Ir sequence was obtained under R#1, since they exhibit complete conversion at 220, 250, 325 °C, respectively; all metals exhibit moderate deNOx performances (XNO, <40%). H2 co-presence (R#2) promotes both the NO and C3H6 conversions, which is valid in the whole temperature interval investigated (50-400 °C), being more substantial for Pt/γ-Al2O3 and Ir/γ-Al2O3, less beneficial for Pd/γ-Al2O3. A two-maxima feature is obtained on XNO pattern (at ∼100 and ∼230 °C) of Pt and Pd during R#2. The low temperature maximum-attributed to NO reduction by H2-is substantially more pronounced on Pt than Pd, offering XNO ∼90% and SN2 ∼85%; the high temperature maximum-attributed to NO reduction by C3H6-is higher by ∼15% on both Pt and Pd, in respect to the values obtained during R#1, while SN2 remained unaffected. Different XNO pattern with one maximum is obtained over Ir, implying a synergistic interaction between H2 and C3H6. This synergy is accompanied by a substantial widening of the NO reduction window toward lower temperatures and a considerable increase on both XNO,max and SN2 (from XNO ∼30% with SN2 ∼55% during R#1 to XNO ∼70% with SN2 ∼95% during R#2). The specific features of all reactions and metals employed are comparatively discussed.

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