Aromatic hydrocarbons and sulfur based catalyst deactivation for selective catalytic reduction of NOx

On the performance of Ag/Al2O3as a HC-SCR catalyst – influence of silver loading, morphology and nature of the reductant

“…Coking was suggested to be due to the aromatics and longer alkenes in the diesel fuel. 23 Arve et al 34 suggested an alternative explanation, taking into account the differences in adsorption kinetics of the different types of hydrocarbons, also supported by a recent study by Demidyuk et al 35 For alkanes and alkenes, catalysts with higher silver loadings (>4-5 wt%) are commonly reported to show lower activity for HC-SCR, due to combustion of the reductant. 9,13,18,24,25,27,29 Combustion of the reductant has been shown to proceed over larger metallic silver particles, which are formed in higher amounts on catalysts prepared by impregnation methods with silver loadings between or above 2 and 5 wt%.…”

“…As the same types and concentrations of hydrocarbons were used over both samples, the differences in activity cannot be attributed to the different bond energies in the hydrocarbons or varying availability of reductants due to concentration changes in the feed gas. Thus, a reasonable explanation is that the coverage of the hydrocarbon species depends on the size of the metal nanoparticles [34][35][36][37][38][39][40] and that the overall activity in the HC-SCR of NO x over Ag/Al 2 O 3 depends both on the C-H bond energy in the hydrocarbon as well as on the coverage of the hydrocarbon, which is a function of the nature of the hydrocarbon and the size of the silver particles. For alkanes, Burch et al 54 have proposed that the SCR mechanism includes dissociative chemisorption, involving breaking of a C-H bond by abstraction of hydrogen by adsorbed oxygen.…”

“…The opening of the carbon ring most likely occurs at special sites on the silver particles, including both terrace and step atoms. [34][35][36][37][38][39][40] However, although the smaller particles in the 2 wt% sample provide a higher fraction of step sites, compared to the larger particles in the 6 wt% sample (Fig. 3, right), the HC-SCR activity is lower at 400-450 1C (Fig.…”

Ambient Temperature Hydrocarbon Selective Catalytic Reduction of NOx Using Atmospheric Pressure Nonthermal Plasma Activation of a Ag/Al2O3 Catalyst

“…It has been discussed and accepted by many researchers that the activation of both NOx and hydrocarbons leads to the formation of surface NCO species, which is thought to be a key intermediate and involved in the final step of the SCR reaction over Ag/Al2O3 catalysts to form N2 [33][34][35][36][42][43][44][45]. It was reported that aromatics (toluene in this case) are inactive at temperatures below 400 C [5,46,47]. This would indicate that the activation and partial oxidation of toluene requires more energy andsubsequently a higher temperature than n-octane.…”

Mechanochemical preparation of Ag catalysts for the n-octane-SCR de-NOx reaction: Structural and reactivity effects

“…Silver-based catalysts are one of the most promising and cost effective systems for NO x HC-SCR but are relatively inactive at temperatures below 300 • C [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. Various modifications to the standard wet impregnation preparation technique have been G Model CATTOD-9316; No.…”