DeNOx performance of Ag/Al2O3 catalyst by n-dodecane: Effect of calcination temperature

Discerning the Role of Ag–O–Al Entities on Ag/γ-Al2O3 Surface in NOx Selective Reduction by Ethanol

“…Silver metal species is predominant on surface of Al(OH) 3 derived samples. It is consistent with other work 22,23,26 that silver metal cluster accelerate unselective combustion of reductant. The formation of unreactive acetone speices on Al(OH) 3 derived catalyst may attribute to the predominant silver metal clusters.…”

Intimate contact of enolic species with silver sites benefits the SCR of NOx by ethanol over Ag/Al2O3

“…Since the pioneering work of Iwamoto et al [1] and Held et al [2], many catalysts such as zeolitic oxide, base oxide/metal and noble metal catalysts have been found to be effective for the SCR of NOx by hydrocarbons (HCASCR) in the presence of excess oxygen [3][4][5][6][7][8][9][10][11]. Among them, Ag/Al 2 O 3 is known as one of the most effective catalysts for HCASCR [4][5][11][12][13][14][15][16][17][18][19][20][21][22]. When using oxygenated hydrocarbons as reductants, particularly ethanol, Ag/Al 2 O 3 shows high activity even in the presence of SO 2 and H 2 O [23].…”

“…Generally, oxidized silver present as isolated Ag + cations and/or oxidized silver clusters (Ag dþ n ) on the Al 2 O 3 surface are responsible for the HCASCR reaction, while metallic silver clusters are responsible for the direct combustion of hydrocarbons at the expense of NOx reduction [27,[40][41][42][43][44][45]. More recently, Nam and co-workers [22,30] proposed that Ag + and Ag dþ n are active for the reduction of NOx by diesel fuel-ethanol mixtures and n-dodecane, while metallic Ag is responsible for the partial oxidation of hydrocarbons, which promotes the initiation of the HCASCR process in the low temperature range. This result indicates that an optimal ionic/metallic ratio of Ag species on Al 2 O 3 surface is probably needed, which is in agreement with the result of Pârvulescu et al [21].…”

Autocatalytic synergism observed during lean-NO reduction with a bifunctional reductant over Ag/Al2O3 catalyst

“…The higher the catalyst Ag content, the more the metallic Ag formed on the catalyst surface [22]. It is generally recognized that the ionic and metallic forms of Ag are responsible for the reduction of NO and the formation of the reaction intermediates derived from the oxidation of both NO and/or reductant, respectively [17,[23][24][25]. The appropriate combination of the ionic and metallic Ag on the catalyst surface is critical for achieving high de-NO x performance over the Ag/Al 2 O 3 catalyst by the MEA-SCR.…”

“…When the temperature increased to 400°C, the intensity of most peaks decreased and/or disappeared, except for the acetate species (1466 and 1579 cm À1 ). This may be due to the fast reaction of the reaction intermediates formed on the surface of the Ag/Al 2 O 3 catalyst at high temperatures [25].…”