Impact of Mg on Pd-based methane oxidation catalysts for lean-burn natural gas emissions control

• Published in: Applied catalysis. B, Environmental Environmental, 2024-02, Vol.341, p.123253, Article 123253
• Main Authors: Sinha Majumdar, Sreshtha, Moses-DeBusk, Melanie, Deka, Dhruba Jyoti, Kidder, Michelle K., Thomas, Calvin R., Pihl, Josh A.
• Format: Article
• Language: English
• Subjects: Alumina; Catalyst; Lean burn; Light-off; Magnesium; Methane oxidation; MOC; Natural gas; Palladium catalyst; Zeolite
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2023.123253

More efficient lean-burn, natural gas engines are limited by greenhouse gas emissions due to methane oxidation catalysts (MOC) that suffer from water inhibition and high temperature activation. Herein, we report that the addition of Mg to supported 1 wt% Pd MOCs improved hydrothermal stability even after severe hydrothermal aging. The superior methane oxidation activity compared to the corresponding Mg-free catalyst was attributed to (1) influence of Mg during surface roughening and restructuring at 700 °C on metal-support interaction, (2) reducibility of PdOx sites and (3) preferential stabilization of active Pd (1 0 0) facets in the sample as was evidenced by H2 TPR and CO TPD characterization experiments. Methane conversion under synthetic exhaust conditions relevant to natural gas, lean-burn engines were investigated. BET, TPR, CO pulse chemisorption followed by TPD provided valuable insights into the surface area, pore volume, reducibility, Pd dispersion and Pd particle size of the selected catalyst samples. [Display omitted] •Mg modified Pd MOCs increase hydrothermal stability and inhibit PdOx agglomeration.•Mg presence during aging preferentially exposed CH4 oxidation active PdOx facets.•Route of Pd and Mg introduction into SSZ-13 impacted catalyst activity.•Pd+Mg supported on Al2O3 exhibited better low temperature activity than SSZ-13.•Increased TOF with PdOx particle size consistent with Mars-van Krevelen mechanism.