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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: CeO2-ZrO2 doped by nickel oxide (CZN) with different method and Pd-only three-way catalysts (Pd/CZN) were prepared and characterized. The catalyst prepared by co-precipitation and supercritical drying process (Pd/CZN-s) exhibits the best catalytic activity and the widest operation working window before and after aging. Compared with other samples, CZN-s shows the formation of more homogeneous ternary solid solution with the smallest lattice parameter and crystallite size. Moreover, CZN-s maintains the high thermal and structural stability with higher surface area and larger pore volume after aging. Pd/CZN-s exhibits higher relative concentration of Ce3+ associated with the formation of more oxygen vacancies before and after aging, confirmed by X-ray photoelectron spectroscopy and Raman results. The more concentration of Ce3+ or oxygen vacancies leads to the enhancement of oxygen storage complete capacity of CZN-s. Moreover, the higher the oxygen storage capacity, the wider the working ranges of air/fuel variations. [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: The behavior of Pd-only three-way catalysts supported on Ce0.67Zr0.33O2 mixed oxides (CZ) doped by transition metals (M=Cr, Mn, Fe, Co, Ni) (Pd/CZM) have been examined under stoichiometric CO+HC+NO x +O2 reaction conditions and characterized. Different characterization techniques reveal that transition metal ions have entered into the ceria lattice and atomically more homogeneous mixed oxides have formed on the order of CZFe≈CZCo>CZNi≈CZ>CZMn>CZCr. It is confirmed that the homogeneity of ternary solid solution clearly modifies the properties of the samples and the catalytic behavior of the corresponding catalysts. The introduction of transition metals especially doped Fe and Co improves the oxygen mobility and strongly enhances the oxygen storage capacity of CZ and the corresponding catalysts. Moreover, the addition of Fe and Co into CZ forms more homogeneous Ce–Zr–M–O ternary solid solution and simultaneously promotes the reduction of CZ and Pd noble metal, respectively. It is worthwhile to note that it has a strong interaction between transition metals and Pd noble metal. Furthermore, the presence of Fe and Co obviously decreases the light-off temperature and significantly enhances the catalytic activity of the catalysts. Simultaneously, the windows of activity over Pd/CZFe and Pd/CZCo catalysts become wider compared to that of Pd/CZ. [ABSTRACT FROM AUTHOR]

Abstract: The role of La doping with different content in the structure of Ce0.2Zr0.8O2 solid solution (CZ) and the effect of modification on the catalytic activity of supported Pd-only three-way catalysts (TWCs) are clarified. The characterization results reveal that the introduction of La into the lattice of CZ is facile. Zr is replaced by the doped La firstly at low doping content and then Ce is substituted further with increasing La content. The substitution occurs in the bulk preferentially, and then in the surface. The addition of La results in preferable thermal stability, higher BET surface area and enhanced oxygen storage capacity (OSC) compared with CZ, due to the structure modification. La doped fresh samples are beneficial to the conversion of NO and the corresponding aged samples exhibit higher activity for the conversion of all the target pollutants. [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]

Abstract: The promotional effect of cobalt oxide on the catalytic performance and the physicochemical properties of Pd only three-way catalysts and Ce0.67Zr0.33O2 mixed oxides (CZ) prepared by co-precipitation and impregnation methods have been investigated. It is worthwhile to note that the role of Co significantly depends on the method of Co doping in the CZ. The introduction of cobalt oxide by co-precipitation exhibits significant influence on the catalytic activity of Pd only three-way catalyst with enhancing textural and structural properties, compared to the introduction of cobalt oxide by impregnation method. Furthermore, CZ doped with cobalt oxide by co-precipitation results in the formation of more homogeneous ternary solid solution, which promotes the metal–support interaction between CZ and cobalt metal and improves oxygen storage capacity (OSC) of samples. It also proves that the textural and structural properties of supports can affect the reducibility and oxygen storage capacity of samples at low temperature. [Copyright &y& Elsevier]

Abstract: Ce0.67Zr0.33O2 (CZ) doped by nickel oxide with different content and the corresponding Pd-only three-way catalysts before and after aging has been prepared and characterized. The investigations show that CZ doped with nickel oxide obviously results in more active fresh catalysts with enhanced textural properties, but suffers from a net loss of activity after aging. The introduction of Ni promotes the reducibility of samples, causing the enhancement of oxygen storage capacity (OSC) of fresh samples. CZNi(3%) exhibits better textural and structural properties because of the formation of more homogeneous Ce–Zr–Ni–O ternary solid solution, which promotes the interaction between Ce–Zr and Ni. However, the thermal aging leads to a loss of surface area and a significant decrease of the reducibility and OSC, except for CZNi(3%). Only Pd/CZNi(3%) represents better catalytic activity after aging. It reveals that the catalytic behavior of these bimetallic systems is strongly affected by the nature of support. [Copyright &y& Elsevier]

Abstract: Four types of Ce0.67Zr0.33O2 (CZCP, CZH, CZHP and CZM) mixed oxides as supports were prepared by coprecipitation, hydrothermal, homogeneous precipitation and microemulsion methods, respectively. The results show that both the preparation methods and the aging procedures have significant influences on the physicochemical properties of Ce0.67Zr0.33O2 mixed oxides. All these fresh Ce0.67Zr0.33O2 samples develop mesopore structure, especially that, CZCP obtains the largest diameter (20.87nm) and volume (0.455cm3/g). The XRD results indicate that fresh CZHP and CZCP samples contain cubic and tetragonal phases, while only cubic solid solution is found in fresh CZH and CZM samples, which show better low-temperature reducibility. Moreover, higher oxygen storage capacity complete (OSCC) values and faster O2 uptake are observed in CZH and CZM samples compared with those of fresh CZCP and CZHP. After calcination at 1100°C, it is found that the OSCC values and the kinetics of the O2 uptake for CZM and CZHP samples are deteriorated due to the coexistence of cubic and tetragonal phases as well as strong sintering of samples. On the contrary, the aged CZCP and CZH samples keep satisfactory low-temperature reducibility and oxygen storage capacity. For fresh catalysts, the pore-size distribution of mixed oxides seems to be important for catalytic activities. In contrast, for aged catalysts, their activities are related to both the redox properties and the textural properties of aged mixed oxides. Therefore, the Pd-only three-way catalyst supported on the CZCP exhibits the most promising amplified amplitude of stoichiometric window. [Copyright &y& Elsevier]