Sulphur tolerant diesel oxidation catalysts by noble metal alloying

Abstract

A series of Mn-alloyed Pt supported catalysts were investigated for the NO oxidation reaction applied in diesel oxidation catalysts under sulphur-containing conditions. The observed NO oxidation conversion correlated to the Pt amount in the catalyst under sulphur-free conditions. In the presence of SO2 in the feed, the Pt/Al2O3 catalyst heavily deactivated resulting in the lowest performance compared to Mn-alloyed Pt catalysts. Already small amounts of Mn improved the SO2-resistance significantly. Whilst pure Pt/Al2O3 catalyst deactivates fully within the first 30 min under NO oxidation conditions including 300 ppm SO2, an alloy with a Mn to Pt ratio of 1:1 performed with a remarkable high catalytic stability for the NO oxidation over at least 70 h under continuous testing conditions.

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

“…Combining above-mentioned interaction of SO 2 with DOCs (in Section ), one can see that SO 2 would block the oxidation pathways of HCs, NO, and CO by occupying the noble metal sites and consuming O 2 species because of the competition effect. ,, Just as observed in the simultaneous oxidation of HCs, NO, and CO (Figure c), the presence of sulfur results in lower conversions of all reactants over PGM catalysts. No effect is shown for propane because of the lack of activity at the test temperature of 200 °C.…”

“…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.…”

“…110,111 As for the much simpler NO and CO oxidation systems, the poisoning process may vary from inhibition of NO or CO adsorption to O 2 dissociation or to the formation or decomposition of intermediates (e.g., nitrate for the case of NO oxidation). 60,71,103 Especially, the equilibrium of SO 2 −O 2 -reactant adsorption waves with reaction conditions when the reactions compete with each other or the dominant reaction mechanism changes. On the basis of the uncertainty in the kinetic model, we extract major fundamentals underlying the apparent observation (inhibition vs promotion) of SO 2 effects on the three oxidation reactions, as is discussed below.…”

“…For instance, the inhibition effect of SO 2 on the conversion of HCs (especially unsaturated HCs) below light-off is proposed to be the blocking of active Pt sites by sulfur deposits, whereas it is unable to track which step (such as HC activation, decomposition, O incorporation, desorption, etc.) is accounting for the sulfur poisoning. , As for the much simpler NO and CO oxidation systems, the poisoning process may vary from inhibition of NO or CO adsorption to O 2 dissociation or to the formation or decomposition of intermediates (e.g., nitrate for the case of NO oxidation). ,, Especially, the equilibrium of SO 2 –O 2 -reactant adsorption waves with reaction conditions when the reactions compete with each other or the dominant reaction mechanism changes. On the basis of the uncertainty in the kinetic model, we extract major fundamentals underlying the apparent observation (inhibition vs promotion) of SO 2 effects on the three oxidation reactions, as is discussed below.…”

Effects of Different Mixture Ratios of Methanol-Diesel on the Performance Enhancement and Emission Reduction for a Diesel Engine

“…In the aftertreatment technology of diesel engine exhaust, a DOC is installed in the diesel engine's exhaust pipe, which is the first step of the whole aftertreatment of the diesel engine. A DOC has a honeycomb monolith shape with high cell density (large surface area) [17] and suitable catalytic material loading such as Pt [18] and/or Pd [19]. The DOC oxidizes CO [20], HC [21], and the organic fraction of diesel particles to harmless water and CO 2 .…”