Mechanism of Propene Poisoning on Fe-ZSM-5 for Selective Catalytic Reduction of NO_x with Ammonia

Abstract

Application of Fe-zeolites for urea-SCR of NO(x) in diesel engine is limited by catalyst deactivation with hydrocarbons. In this work, we investigated the effect of propene on the activity of Fe-ZSM-5 for selective catalytic reduction of NO(x) with ammonia (NH(3)-SCR), and proposed a deactivation mechanism of Fe(3+) active site blockage by propene residue. The NO conversion decreased in the presence of propene at various temperatures, while the effect was not significant when NO was replaced by NO(2) in the feed, especially at low temperatures (<300 degrees C). The surface area and pore volume were decreased due to carbonaceous deposition. The site blockage was mainly on Fe(3+) sites on which NO was to be oxidized to NO(2). The activity for NO oxidation to NO(2) was significantly inhibited on a propene poisoned catalyst below 400 degrees C. The adsorption of NH(3) on the Bronsted acid sites to form NH(4)(+) was not hindered even on the propene poisoned catalyst, and the amount of absorbed NH(3) was still abundant and enough to react with NO(2) to generate N(2). The hydrocarbon oxygenates such as formate, acetate, and containing nitrogen organic compounds were observed on catalyst surface, however, no graphitic carbonaceous deposit was formed.

Fe‐Beta@CeO2 core‐shell catalyst with tunable shell thickness for selective catalytic reduction of NOx with NH3

“…It is generally accepted that SCR process for Fe-Beta catalyst follows the dual site mechanism and the adsorption and activation of NH 3 is a crucial step. 31 Therefore, low acidity should be unfavorable for the NH 3 -SCR process.…”

“…Of course, as the core materials, the size of Beta crystal should be as small as possible. For shell materials, CeO 2 may be one of the most suitable metal oxides owing to its outstanding oxygen-storage capacity and easy conversion between Ce 31 and Ce 41 , which has been extensively used in various catalytic reactions.…”

“…31 Too thick CeO 2 shell will cover the acid and active sites of the catalysts. Hence, the suitable thickness of CeO 2 oxide film is of importance for high activity catalyst in the NH 3 -SCR reaction.…”

Effects of post-treatment method and Na co-cation on the hydrothermal stability of Cu–SSZ-13 catalyst for the selective catalytic reduction of NO with NH3

“…Cu and Fe have been the most widely used transition metal ions in NH 3 -SCR zeolite catalysts, owing to their good redox capacity [8,9]. Most of these catalysts show good NH 3 -SCR performance under high gas hourly space velocity (GHSV), which is crucial for their practical application in diesel vehicles with limited installation space on board [10][11][12]. Nowadays, diesel particulate filters (DPF) are widely used in diesel particulate emission control, and are often used in upstream of the SCR catalyst.…”

Influence of calcination temperature on iron titanate catalyst for the selective catalytic reduction of NOx with NH3

“…Fe-based catalysts such as Fe/ZSM-5 [7][8][9][10][11][12], Fe/HBEA [13][14][15][16], Fe-TiO 2 -PILC [17], Fe 2 O 3 /WO 3 /ZrO 2 [18] and Fe-Mn/USY [19] usually show good SCR activity and N 2 selectivity, and TiO 2 is usually used as support for SCR catalysts because of its high resistance to SO 2 poisoning [20]. Under the consideration to combine the merits of Fe active component and TiO 2 support, in our previous study [21][22][23] we reported a novel and environmental-friendly iron titanate catalyst FeTiO x prepared by co-precipitation method, showing high NH 3 -SCR activity, N 2 selectivity and H 2 O/SO 2 dura-bility in the medium temperature range (250-400 • C).…”