Abstract
In this work, a series of aliovalent additives M (M=La3+, Nd3+, Pr3+/4+, and Y3+) have been introduced to CeO2-ZrO2-Al2O3 (CZA) to increase the surface oxygen vacancies by surface modification according to electrical neutrality principle, in which Pr exhibited the most significant promotion effect. Then by in-situ infrared, X-ray photoelectron spectroscopy (XPS) and CO-Fourier transform infrared spectroscopy (CO-FTIR) measurements, it could be indicated that Pr/CZA with increased oxygen vacancies can establish strong electronic interactions with the supported Pd species, which stabilizes the Pd species in oxidation states and smaller particle size for achieving more active centers. Meanwhile, more monodentate nitrate/nitrite intermediates, which are highly active to be transformed by C3H8, could easily be formed on the surface of modified Pd/Pr/CZA catalyst. As a result, the Pd/Pr/CZA exhibited the best conversion efficiency of C3H8 and NO, the T90 (the light-off temperature at 90 % conversion) of which was reduced by 25 °C and 20 °C comparing with that of Pd/CZA even being thermally aged at 900 ℃ for 6 h, respectively.
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