Time-dependent hysteresis in the NO oxidation to NO2 on Pt-based catalysts

Aging of Commercial Diesel Oxidation Catalysts: A preliminary Structure/Reactivity Study

“…which increases with the aging effect. This result is in agreement with the literature, since bigger Pt/Pd particles favor NO oxidation[11], Hovewer, when only NO as NOx is present in the feed an opposite trend is observed[12,13]. Moreover for both fresh and aged catalysts, in Mix 1, NO 2 is not detected atFig.…”

A Review on the Impact of SO2 on the Oxidation of NO, Hydrocarbons, and CO in Diesel Emission Control Catalysis

“…No effect is shown for propane because of the lack of activity at the test temperature of 200 °C. This inhibition impact is more pronounced with a high SO 2 dose. ,,,,,,− Compared with HCs and NO, the negative impact of sulfur is less significant for CO in the practical application of DOCs.…”

“…100,122−124 Some possible ways to redistribute sulfates (i.e., catalyst "baking") include a treatment of the catalyst in its sulfated state under moderately high temperatures and net oxidizing conditions, and field-aging (e.g., commercial DOCs used after vehicle or engine aging in different types and times of S fuel duration). 100,104,122,124 For instance, the NO oxidation activity decreases linearly in response to the amount of freshly deposited sulfur, until it reaches a plateau. 124 While the catalyst after baking or the asreceived DOC from vehicle or engine-aging demonstrates no sign of poisoning albeit with high sulfur loading.…”

“…An early review by Russell and Epling has offered in-depth coverage in relation to the reaction models of HCs, NO, and CO oxidation over PGM-based DOCs and toward precious metal characteristics (oxidation state, particle size/dispersion, active site location) and O 2 variation, which we will not expand here . A common feature appeared for HCs, NO, and CO oxidation is that all proceed via interfacial or superficial reactions, where trapping of HCs, NO, and CO on metals serves as the precursor for total oxidation (which is secondary to C–H bond cleavage in the case of HCs). ,,− Those adsorbed molecules reacts with neighboring activated lattice oxygen (route i), oxygen adsorbed in the support vacancies (route ii), or oxygen species adsorbed on metals (route iii), as shown in Figure b.…”

“…The behavior that the freshly formed sulfates undergoes displacement to interfacial sites/supports or kinetically irrelevant sites allows for the redistribution of sulfates on non-noble sites. ,− Some possible ways to redistribute sulfates (i.e., catalyst “baking”) include a treatment of the catalyst in its sulfated state under moderately high temperatures and net oxidizing conditions, and field-aging (e.g., commercial DOCs used after vehicle or engine aging in different types and times of S fuel duration). ,,, For instance, the NO oxidation activity decreases linearly in response to the amount of freshly deposited sulfur, until it reaches a plateau . While the catalyst after baking or the as-received DOC from vehicle or engine-aging demonstrates no sign of poisoning albeit with high sulfur loading. , Obviously, the redistribution of sulfate helps to free active sites and delay the negative effect of sulfur on noble metals.…”