Volatilisation and subsequent deposition of platinum oxides from diesel oxidation catalysts
Artikel i vetenskaplig tidskrift, 2019

In this study, we have reproduced a DOC-upstream-of-SCR configuration in the laboratory, with washcoated model Pt/Al2O3, Pd-Pt/Al2O3and Pd/Al2O3catalysts, as well as a commercial DOC, upstream of an alumina-washcoated core. We studied vapour-phase noble metal poisoning of the alumina core, as noble metal from the model DOC catalysts deposited on the downstream alumina core. The mobile species were predominantly volatile platinum oxides, whereas Pd volatilised in such small traces that it was close or below detection limit by Inductively Coupled Plasma – Sector Field Mass Spectrometry (ICP-SFMS), even when the model DOC had only Pd as active species. Even after volatilisation at temperatures as low as 550 °C, the deposited trace amounts of noble metal were highly active for ammonia oxidation. The deposited platinum appears to be finely dispersed, but when subjected to reaction conditions, it likely undergoes sintering, causing a further increase of the ammonia oxidation ability, which will affect the extent of poisoning in a real exhaust aftertreament system. We investigated the dependence of volatilization on temperature, and, as predicted, found it to be exponential. Exposure to increasing temperatures causes different degrees of sintering of the noble metal particles and we found qualitative evidence that sintering decreases the amount of volatilisation. Adding a small amount of Pd (Pd:Pt = 0.5:1) to the catalyst had no effect on volatilisation. However, larger Pd concentrations (Pd:Pt = 1:1 or 2:1) decrease volatilisation. The results for the model DOCs were confirmed by volatilisation from a commercial DOC, where in fact the capturing core exhibited even higher ammonia oxidation ability compared to those downstream of the model DOCs, after evaporation at 700 °C.

Platinum poisoning

Noble metal volatilization

Palladium

Diesel oxidation catalyst

Författare

Kirsten Leistner

Kompetenscentrum katalys (KCK)

Chalmers, Kemi och kemiteknik, Kemiteknik, Kemisk apparatteknik

Carolina Gonzalez Braga

Kompetenscentrum katalys (KCK)

Ashok Kumar

Cummins Inc.

K. Kamasamudram

Cummins Inc.

Louise Olsson

Chalmers, Kemi och kemiteknik, Kemiteknik

Kompetenscentrum katalys (KCK)

Applied Catalysis B: Environmental

0926-3373 (ISSN) 1873-3883 (eISSN)

Vol. 241 338-350

Ämneskategorier

Kemiska processer

Annan kemiteknik

Metallurgi och metalliska material

DOI

10.1016/j.apcatb.2018.09.022

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Senast uppdaterat

2018-10-10