Kinetic Modeling of Hydrothermal Aging Deactivation of a Pt–Pd-Based Wiremesh Catalyst as a Motorcycle Emission Control System

Motorcycle oxidation catalysts can reduce urban CO and VOC emissions by over 80%, but their catalytic performance progressively degrades due to hydrothermal aging and active metal sintering. This work presents a kinetic study of CO and propylene oxidation over fresh and hydrothermally aged Pt–Pd-based motorcycle catalysts with a wiremesh structure, using a global kinetic modeling approach. Incorporating surface intermediate formation and desorption successfully reproduced the characteristic two-step CO light–off behavior in the presence of propylene, in good agreement with experimental data (R2 > 0.92). Despite notable variations in experimentally determined activation energies under different oxygen contents, a single set of kinetic parameters─scaled with catalytic surface area─accurately described the oxidation reactions for both fresh and aged catalysts. This finding indicates that hydrothermal aging primarily reduces the available active surface area rather than altering the intrinsic reaction pathways. An empirical polynomial correlation between normalized activity and aging temperature predicted a rapid activity loss exceeding 50% between 750 and 900 °C, revealing substantial deactivation in the early stages of aging. Aging model results further showed that after hydrothermal treatment at 920 °C under reducing conditions and 980 °C under oxidizing conditions, the catalyst activity stabilized, with no further deactivation observed.