Experimental and kinetic Modeling Study of Aged Three-way Catalyst Performance

A comprehensive global kinetic model has been developed for an aged commercial Three-Way Catalyst (TWC), incorporating key reaction pathways including oxidation of CO, CH₄, C₂H₆, and H₂; reforming of CH₄ and C₂H₆; the water-gas shift reaction; and NO reduction via CO and H₂. The model also accounts for oxygen storage capacity (OSC) and its dynamic interaction with CO and H₂. To calibrate kinetic parameters, systematic bench-scale flow reactor experiments were conducted under lean, stoichiometric, and rich conditions. Performance metrics focused on CH₄ and C₂H₆ oxidation and reforming across varying O₂ and CO concentrations, and NO reduction with CO and H₂ under different oxygen levels. Experimental results revealed CO inhibition effects on CH₄ and C₂H₆ reforming. NO conversion was observed between 150°C and 600°C, with H₂-driven reduction producing NH₃, N₂, and N₂O depending on lambda (λ). Under rich conditions, complete NO conversion occurred from 150°C, while lean conditions showed reduced NO conversion at elevated temperatures due to H₂ oxidation. NO reduction with CO initiated at 250°C, achieving full conversion under rich conditions. The model accurately captures the influence of λ on NO reduction with both H₂ and CO, predicts NH₃ formation under rich conditions, and simulates H₂ generation via the water-gas shift reaction above 400°C which aids in catalyst sizing and robust controller calibration. It successfully reproduces λ sweep data (λ = 0.95–1.02) and demonstrates CO inhibition effects on H₂ oxidation and NO reduction. Model is validated with dithering reactor data and qualitatively captures key trends in data. Validation of the current developed model with lean-rich cycle tests confirm the model’s ability to predict NOx slip at the onset of rich cycles. supporting its application in NOx control strategies for real-world driving conditions.