Optimisation of Ag loading and alumina characteristics to give sulphur-tolerant Ag/Al2O3 catalyst for H2-assisted NH3-SCR of NOx

Role of the support on the behavior of Ag-based catalysts for NH 3 selective catalytic oxidation (NH 3 -SCO)

“…In low-temperature NH 3 -SCO reaction, Ag based catalyst has been proven to be one of the most active catalysts, but with a poor N 2 selectivity [10][11][12]. A lot of reports have demonstrated that the state of silver active species played an important role in the various reactions [13][14][15]. Ag + was proposed as the active sites for NO conversion, while Ag 0 was favor for the formation of N 2 O and hydrocarbon combustion for SCR reaction.…”

Formation of silver active states in Ag/ZSM-5 catalysts for CO oxidation

“…It is important for preparation of catalytically stable bimetal Au-Ag systems. Some supports and modifying additives of transient metal oxides can stabilize the active sites both silver and gold [31][32][33][36][37][38][39][40][41][50][51][52]. At higher temperatures (>300-400°C) formation of the metal active states follows other way; in this case big metal particles, metal crystals and films can also catalyze oxidation reactions (for example, methanol selective oxidation [33,53]).…”

“…In the range of absorption bands of ions and charged clusters of silver (200-380 nm [34][35][36][37][38][39][40][41]) we observe only strong unstructured absorption. Usage of the catalysts in CO oxidation process lead to noticeable growth of the bands at 440-450 nm in all spectra except the first one and display of the pronounced signals at 250-270 nm attributed to silver charged clusters Ag n [ [34][35][36][37][38][39][40][41]. Obviously, 1% Ag/ZSM-5 sample contains too small concentration of silver; and UV-vis spectroscopy method is not sensitive enough for detection of the metal particles of such a low concentration.…”

“…Probably, it is explained by steric restrictions. Role of ionic states of silver in catalytic oxidation processes was discussed in many articles [33][34][35][36][37][38][39][40][41], although usually silver metal nanoparticles are considered as active sites.…”

Increased NO2 concentration in the diesel engine exhaust for improved Ag/Al2O3 catalyst NH3-SCR activity

“…Even more, recent studies also demonstrated successful NH3 -SCR on the Ag/Al2O3 catalyst in addition to HC-SCR, as long as the reaction is assisted by H2 [11,12]. The H2 promoted NH3 -SCR on Ag/Al2O3 can start at comparatively lower temperature and achieve high NOx conversion [13,14]. …”