The Effect of Potassium Inclusion in a Silver Catalyst for N2O-Mediated Oxidation of Soot in Oxidising Exhaust Gases

• Published in: Catalysts 2022-07, Vol.12 (7), p.753
• Main Authors: Cooper, Anna, Golunski, Stan, Taylor, Stuart H.
• Format: Article
• Language: English
• Subjects: Ammonia; Carbon black; Catalysts; Chemical reactions; Diesel fuels; Exhaust gases; Gases; Hydrocarbons; Low temperature; Nitration; Nitrous oxide; Oxidation; Potassium; Reduction; Soot
• ISSN: 2073-4344; 2073-4344
• DOI: 10.3390/catal12070753

It has previously been shown that an Ag/CZA catalyst can simultaneously remove NOx and soot from an oxygen-rich exhaust gas at low temperatures, by utilising the N2O generated preferentially during incomplete NOx reduction. Here, we examine the effect of reformulating the catalyst to include potassium, which is a known promoter of soot combustion. On including 2 wt% K, NOx-reduction occurs both in the absence and presence of soot, but the N2O formed does not play a part in the oxidation of soot. At higher K loadings (5, 10 and 15 wt%), NOx reduction is almost completely disabled, and only contributes to the activity of the catalyst containing 5 wt% K when tested in the presence of soot. At a loading of 20 wt% K, the potassium phase segregates, leaving NO and NH3 adsorption sites exposed. In the absence of soot, this catalyst can remove NOx by reduction on the Ag/CZA component and through nitration of the potassium phase. Although the presence of potassium lowers the onset temperature for soot oxidation to within the range of NOx reduction over Ag/CZA, the mobile K species prevents the desirable C+N2O reaction.