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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: 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: 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]