Mechanistic study on three-way catalysis over Pd/La/Al2O3 with high La loading

Although La-loaded Al2O3 (La/Al2O3) is a widely used support material for three-way catalysis (TWC), little is known about the promotional effect of La in the La/Al2O3 supported Pd catalyst (Pd/La/Al2O3) in the catalytic NO reduction (DeNOx) for automotive emission control. Previously (Jing et al., 2020 [1]), we assessed the promotional effect of La and observed that the supported metallic Pd nanoparticles on the La/Al2O3 support were more electron-deficient than those on Al2O3 without La, which led to suppression of CO poisoning and a higher catalytic activity for NO reduction. Here, we further investigated the role of La in Pd/La/Al2O3 for the DeNOx process by various spectroscopic methods. The results obtained suggest that the efficient generation of nitrite species and its facile reactivity are important for the promotional effect of La in NO reduction. In addition, we investigated the effects of hydrothermal aging. For the TWC, Pd/La/Al2O3 with high La loading (15 wt%) was identified to be superior to the conventional industrial catalyst having a loading of 5 wt%. It was also found to show relatively high Pd dispersion even after aging at 800 degrees C. The observed stabilizing effect is an important benefit of the addition of La.

Automated summary

This study investigates the promotional effect of La in the Pd/La/Al2O3 catalyst for catalytic NO reduction. Spectroscopic methods were used to further explore the mechanism. The results indicate that the promotional effect of La is related to the efficient generation and reactivity of nitrite species. Additionally, the high-loading Pd/La/Al2O3 catalyst is superior in the TWC process and exhibits good stability even after aging at 800°C.