A novel insight into the preparation method of Pd/Ce0.75Zr0.25O2-Al2O3 over high-stability close coupled catalysts.

Graphical abstract The different preparation methods about ceria-zirconia modified alumina influence palladium dispersion by the interaction, which is main factor in influencing close coupled catalytic activity. The catalyst obtained by deposition precipitation owns higher surface palladium species than the sample synthesized by coprecipitation method, and higher palladium dispersion than the catalyst prepared by wet-impregnation method. A simple process is described as is shown above, and specific process is illustrated in my article. Highlights • The different methods influence the interaction, resulting in different activities. • Interaction is investigated by different methods, such as TPR, XPS and CO adsorption. • The reason why different methods influence dispersion is explained by the brief mode. Abstract A series of Ce 0.75 Zr 0.25 O 2 -Al 2 O 3 samples were prepared by conventional coprecipitation, wet impregnation method and novel deposition precipitation, after the corresponding Pd-only close coupled catalysts were obtained by incipient wet impregnation. Differences in surface properties and catalytic performance were investigated systematically by a wealth of characterizations. XPS, H 2 -TPR and CO chemisorption revealed that the different preparation methods of Ce 0.75 Zr 0.25 O 2 -Al 2 O 3 led to different intensity of interaction between PdO species and support, thus forming different palladium dispersions. BET, XRD and activity evaluation indicated the catalyst obtained by novel deposition precipitation presented superior textural properties, catalytic performance and thermal stability, due to the strongest interaction proved by H 2 -TPR, XPS and CO chemisorption, which could retard the sintering of noble metal during the aging process. HRTEM images indicate for the catalysts, PdO species are mainly dispersed and stabilized on the ceria resulting from the lower redox potential of Pd2+/Pd0 (0.95 V) than that of Ce4+/Ce3+ (1.72 V). Consequently, it owned higher surface PdO content and dispersion than the catalysts prepared by coprecipitation and impregnation method, presenting its higher catalytic properties. [ABSTRACT FROM AUTHOR]