Direct DRIFTS evidences for the active surface intermediates responsible for the improved catalytic performance of Na-promoted Pt/γ-Al2O3 catalysts during NO reduction by hydrocarbonsDirect DRIFTS evidences for the active surface intermediates responsible for the improved catalytic performance of Na-promoted Pt/γ-Al2O3 catalysts during NO reduction by hydrocarbons Πλήρης Δημοσίευση σε Συνέδριο Conference Full Paper 2015-11-152008enThe reactivity of species formed on the surface of un-promoted and sodium promoted Pt catalysts supported on γ-Al2O3 was investigated by the transient response of IR spectra under the cycle: NO→He→C3H6→NO. It was found that NO adsorption on the unpromoted Pt/Al2O3 catalyst results mainly in the formation of small amounts of nitrate species, which are relatively inactive towards C3H6, leading to the formation of limited amounts of formates, acetates and cyanide compounds. The latter species are very stable towards NO, indicating that carboxylate and cyanide species should be considered as spectator species; the inactivity of such species is consistent to the low activity of un-promoted Pt/γ-Al2O3 catalyst during the NO reduction by propene. In complete contrast, NO interaction with the surface of Na-promoted catalysts results in the formation of nitro/nitrite as well as nitrosyl species, which are highly active towards propene, leading to the formation of enolic species (R-CH=C-O), organic compounds (CxHyNOz), isocyanates (NCO) and carbonyl (CO) species. Among these species isocyanates are very active towards NO, leading to the formation of reaction products. The present results strongly indicate that the excellent catalytic behaviour of sodium modified Pt/Al2O3 catalysts during the NO reduction by propene, can be attributed to the pronounced effect of alkalis on the NO chemisorption bond, which in turn favours the formation of active intermediates such as isocyanates.http://creativecommons.org/licenses/by-nc-nd/4.0/1st International Conference on Hazardous Waste ManagementProc. 1st International Conference on Hazardous Waste Management Matsouka Vasiliki Ματσουκα Βασιλικη Konsolakis Michail Κονσολακης Μιχαηλ Yentekakis Ioannis.V.