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Abstract: CeO2–ZrO2 (CZ) doped with different transition metals was prepared through a co-precipitation and supercritical drying method and the corresponding Pd-only TWCs were characterized. Pd/CZFe and Pd/CZCo exhibit the best catalytic activity and the widest operation window, in accordance with the decrease of the light-off and full-conversion temperature. However, Pd/CZCr restrains the catalytic property. It may be due to the different effect of transition metals on the property of CZ. The introduction of Fe and Co promotes the surface atom ratios of Ce/Zr, makes part of Ce4+ transferred into Ce3+ in order to maintain the electrical neutrality and seems to facilitate the reduction of Ce4+ →Ce3+ or the formation of oxygen vacancies of CZ. The increasing concentration of oxygen vacancies for CZFe leads to the enhancement of DOSC. Moreover, the introduction of Fe favors the transfer of oxygen in different atmospheres. [Copyright &y& Elsevier]

Abstract: Different contents of praseodymia were introduced to modify Ce0.2Zr0.8O2 (CZ) and the supported Pd-only three-way catalysts before and after aging were also prepared. The influence of praseodymia doping on the structural/textural properties of CZ and the effect on the three-way catalytic activity were investigated. Structural and textural characterizations reveal that the addition of praseodymia results in the formation of Ce–Zr–Pr ternary solid solution (CZP) with higher specific surface area, better thermal stability and larger oxygen storage capacity (OSC) than that of CZ. It is more credible that Zr is replaced by Pr during the formation of CZP. The modified Pd-only three-way catalysts present relatively higher catalytic activity to the main target pollutants in gasoline engine exhaust and exhibit wider air/fuel operation window due to the improved properties of CZP. [Copyright &y& Elsevier]

Abstract: In this paper, five types of ceria–zirconia modified alumina (CZA) were prepared by co-precipitation with supercritical drying (CPS), co-precipitation with common drying (CPC), sol–gel (SG), micro-emulsion (ME) and impregnation (IM) methods, respectively. The corresponding supported Pd-only three-way catalysts (TWC) were also prepared and evaluated in the simulative gasoline engine exhaust. The influence of different preparation methods on the physicochemical properties of CZA mixed oxide and its supported TWC was characterized by X-ray diffraction (XRD), N2 adsorption/desorption and transmission electron microscopy (TEM) techniques. The redox behavior was investigated with H2 temperature-programmed reduction (H2-TPR) experiments. The results reveal that the CZA mixed oxides derived from CPS and ME methods exhibit the relatively higher textural and structural properties as well as better redox behavior, which lead to the better catalytic activity and wider air-to-fuel operation window of the corresponding Pd-only three-way catalysts. [Copyright &y& Elsevier]

Abstract: A series of ceria–zirconia–neodymia mixed oxides with different contents of neodymia and the supported Pd-only three-way catalysts before and after aging have been prepared and characterized. The influence of Nd doping on the structural/textural properties of ceria–zirconia (CZ) and the effect on the three-way catalytic performance are also investigated. The results demonstrate that the addition of neodymia results in the formation of ceria–zirconia–neodymia ternary solid solution (CZN) with better textural and structural properties as well as improved reducibility and redox behavior, leading to the promoted three-way catalytic activity and enlarged air/fuel operation window. The modified solid solution with 5wt.% neodymia shows the preferable textural/structural properties considering that the capacity of foreign cation is limited in the crystal lattice of ceria–zirconia solid solution, and Pd/CZN5 shows the optimum three-way catalytic performance and wider air/fuel operation window, especially for the corresponding aged one. [Copyright &y& Elsevier]

Abstract: The influence of rare earth elements (La, Nd, Pr, Sm and Y) addition to Ce0.2Zr0.8O2 and its supported Pd-only three-way catalysts has been investigated by X-ray diffraction (XRD), N2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS) and H2 temperature programmed reduction (H2-TPR) techniques, and that the dynamic oxygen storage capacity (DOSC) has also been evaluated under transient conditions. Special attention was given to the information of structural modification and the effect of doping on the three-way catalytic performance. The phase for all the ceria–zirconia-rare earth ternary solid solution is single tetragonal, irrespective of the treatment temperature applied. The presence of La, Nd and Pr results in enhanced thermal stability, improved reducibility and increased strong metal–support interaction, leading to the relatively higher three-way catalytic activity for all the target pollutants over the corresponding catalysts. The air/fuel operation window is also enlarged due to the increased dynamic oxygen storage capacity. [Copyright &y& Elsevier]

Abstract: Ce0.67Zr0.33O2 doped with iron oxide was prepared and the corresponding Pd-only three-way catalysts were examined and characterized. Pd/CZFe(1%) catalyst exhibits the best catalytic performance for CO, HC, NO and NO2 elimination and the widest operation window. The doping of iron oxide with 1% loading suggests the formation of more homogeneous Ce–Zr–Fe–O ternary solid solution, which seems to facilitate the reduction of Ce4+ →Ce3+ or the formation of oxygen vacancy and to promote the interaction between Ce–Zr and Fe. Moreover, the Ce redox behaviour for surface reduction suggests depending not only on the formation of homogeneous Ce–Zr–Fe–O but also on the surface property of the sample. The increase in the concentration of oxygen vacancies under all atmospheres for CZFe(1%) sample also results in the enhancement of oxygen storage complete capacity. [Copyright &y& Elsevier]

Abstract: Ce0.67Zr0.33O2 (CZ) mixed oxide was prepared by coprecipitation and effect of the synthesis conditions on CZ properties were investigated in this work, as well as the catalytic performance of Pd-only three-way catalyst (TWC) supported on the prepared CZ. With the increase of aging temperature during precipitation, the crystallite size of CZ increases significantly, while the oxygen storage capacity complete (OSCC) drops and no notable effect on porosity of CZ is observed. The porosity is mainly determined by drying temperature and pH value during precipitation. Prepared under optimized conditions (precipitation at the pH of 9.5, aging at 25°C and then drying under supercritical condition in alcohol), the CZ samples exhibit good properties. This preparation procedure leads to CZ with proper pore size distribution, larger average pore size (20.42nm), higher pore volume (0.69cm3/g) and enhanced OSCC value (383.0μmol/g). Furthermore, the Pd-only TWC supported on the CZ synthesized under the optimized conditions exhibits satisfactory catalytic activity and very low reduction temperature (53°C). [ABSTRACT FROM AUTHOR]

Abstract: In this work, supercritical drying technology is investigated as a new method contrast with the conventional drying techniques to obtain La modified ceria–zirconia solid solution (CZL) with advanced textural/structural properties, and its supported Pd-only three-way catalysts (TWCs) were also prepared and studied. The results demonstrate that the CZL sample prepared by supercritical drying method shows relatively larger specific surface area, better thermal stability and higher redox properties, as well as the prominent oxygen storage capacity compared with samples prepared by conventional drying method. Moreover, it also exhibits remarkable porosity and wide pore size distribution due to the elimination of vapor–liquid interface in the process of supercritical drying, which is beneficial to the adsorption/desorption of pollutant in TWCs. The excellent structural/textural properties of the forenamed CZL support lead to the outstanding catalytic activity, wide air-to-fuel operation window of the corresponding three-way catalyst, indicating its tremendous potential possibilities. [ABSTRACT FROM AUTHOR]