Premature failure of the three-way catalytic converter (TWC) has become a significant challenge in the automotive industry an‎d environmental protection. According to recent studies, the performance of this system decreases significantly after approximately 5,000 to 10,000 kilometers of vehicle operation. This research aims to investigate the potential mechanisms behind this degradation. Evidence suggests that the growth of platinum group metal (PGM) particles, through processes such as Ostwald ripening an‎d surface migration, plays a major role in the performance decline. These processes reduce the number of active surface sites, leading to decreased catalytic activity. In this study, a fresh TWC an‎d a used TWC (obtained after vehicle operation) were prepared. Both converters were powdered an‎d milled to be compatible with transmission electron microscopy (TEM). The powders were then subjected to a reduction process to enhance imaging quality. Using TEM, the nanostructure of the fresh an‎d aged converters was examined, an‎d the average particle size of the PGMs was measured in both samples. Furthermore, X-ray fluorescence (XRF) analysis was conducted to determine the weight percentage of precious metals in both fresh an‎d aged samples, revealing that their content remained nearly constant. Therefore, the increase in particle size of the precious metals was identified as the primary reason for performance degradation. Subsequently, the kinetic processes contributing to particle growth an‎d system degradation were identified an‎d modeled using GT-SUITE software. The model was validated by comparing experimental data with simulation results. Finally, for each pollutant, a distinct correlation was developed to predict its emission level. The studied metals include platinum, palladium, an‎d rhodium.

ايمان چيت ساز , امين موسائي

عليرضا نجفي چرمهيني

محسن دوازده امامي , محمدرضا توكلي نژاد