PGM based catalysts for exhaust-gas after-treatment under typical diesel, gasoline and gas engine conditions with focus on methane and formaldehyde oxidation

Journal Article · Thu Dec 26 00:00:00 EST 2019 · Applied Catalysis B: Environmental

DOI:https://doi.org/10.1016/j.apcatb.2019.118571· OSTI ID:1617804

Gremminger, Andreas ^[1]; Pihl, Josh  ^[2]; Casapu, Maria ^[1]; Grunwaldt, Jan-Dierk  ^[1]; Toops, Todd J.  ^[2]; Deutschmann, Olaf  ^[1]

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1. Karlsruhe Inst. of Technology (KIT) (Germany)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

In this work the HC and CO oxidation activity of Pt/Al₂O₃, Pd/Al₂O₃ and Pd-Pt/Al₂O₃ catalysts was compared under three exhaust-gas model conditions typical for stoichiometric gasoline as well as lean burn diesel by means of temperature programed conversion tests on laboratory test benches. In order to understand the differences in emission reduction performance, the impact of gas mixture composition was systematically studied with a particular focus on methane and formaldehyde conversion. The catalysts used in this study were prepared by incipient wetness impregnation of Al₂O₃ followed by washcoating on ceramic honeycombs, and were pre-treated in an equal manner before each activity test. Distinct differences in pollutant conversion were observed over the three catalysts under the investigated conditions. Pd-based monometallic and bimetallic catalysts revealed the lowest temperature for CH₄ oxidation (<450 °C) under lean conditions, being lower under lean Diesel than Compressed Natural Gas (CNG) conditions. The reason for this behavior seems to be the higher water concentration in the CNG gas mixture. Furthermore, it was found that the presence of HCs shifts the conversion of methane to higher temperatures, most probably due to produced water during combustion of the HCs. Pt/Al₂O₃ on the other hand only converts methane at temperatures above 500 °C but no sensitivity to water or the amount of additional HCs was observed. The lowest light-out temperature for formaldehyde oxidation in excess of oxygen was measured on Pt/Al₂O₃ with full conversion below 125 °C. While this was the case for a model gas mixture of HCHO, H₂O and O₂, under simulated lean burn gas engine conditions, formaldehyde is oxidized at lower temperature on Pd-Pt/Al₂O₃ than on Pt/Al₂O₃ due to the strong inhibiting effect of CO on Pt-particles.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: Karlsruhe House of Young Scientists; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1617804
• Journal Information: Applied Catalysis B: Environmental, Vol. 265, Issue C; ISSN 0926-3373
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Methane oxidation
Formaldehyde oxidation
Gas engine
Pd
Pt
Pd-Pt/Al2O3
Three-way catalyst (TWC)
Diesel oxidation catalyst (DOC)