Three-way catalysts (TWCs) deactivation due to exposure to severe operating conditions has been an important challenge in automotive catalysis. Thus, development of TWCs with enhanced thermal stability is of great interest. A few studies have focused on the effect of promoters on the TWC activity and thermal stability at the temperature of 1050°C. In most of the previous studies, simplified catalyst formulations and operating conditions have been employed, thus their results may not be realistic for commercial applications. In addition, the effect of promoters on the textural properties and stability of ceria-zirconia-based TWCs are not well understood. This work aims to investigate the effects of rare earth metals, as promoters, on the properties of ceria-zirconia-based supports under practical operating conditions of TWCs. A set of commercial support formulations, including ceria, zirconia, alumina, La, Y and Nd, were selected based on their specific surface area before and after aging. The Euro V aging protocol using 10% H<sub>2</sub>O in air at 1050°C for 8 h was employed for aging. The selected supports were impregnated with Pd (1 wt%), Pt (2 wt%), and Rh (0.2 wt%). The properties and performance of the fresh and aged samples were investigated using XRD, H<sub>2</sub>-TPR, BET, FESEM, and reactor tests. For the alumina-containing samples, a direct relationship was observed between the hydrogen consumption and the catalyst activity toward conversion of CO, hydrocarbon (HC) and NO. Table 1 shows the temperatures corresponding to 50% conversion (T50) of CO, HC and NO for the fresh and aged samples. Among the aged samples, Ce-Zr-Y catalyst represented the highest activity due to redispersion of active sites after aging. Among the fresh samples, the Ce-Zr-La-Y-Nd catalyst had the best light-off performance. However, its activity significantly decreased after aging due to strong metal-support interactions. Our results can facilitate development of TWC formulations with enhanced hydrothermal stability.

Modification of three-way catalyst (TWC) formulation for gasoline vehicles with the goal of improving its thermal stability

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