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Preparation of Ce _x Zr_1-x O₂ by Different Methods and Its Catalytic Oxidation Activity for Diesel Soot.

ABSTRACT: Novel Ce _x Zr_1-x O₂ (x = 0.67, 0.8, 0.9, 1.0) catalysts were designed and synthesized by solvothermal, calcination, and sol-gel methods and were used to catalyze oxidation of soot from diesel vehicle exhaust. The influence of catalysts synthesized by different methods and Ce/Zr molar ratios on the performance was investigated. These catalysts were characterized by XRD, N₂ adsorption-desorption, FT-IR, TEM, XPS, H₂-temperature programmed reduction (TPR), and O₂-temperature programmed desorption (TPD) techniques. The results indicated that Ce_0.8Zr_0.2O₂ prepared by the calcination method has excellent activity and stability at low temperature. The soot ignition point is 322 °C, and the ratio of soot conversion reaches 90% at 497 °C, which is lower than that from the solvothermal and sol-gel methods. The XRD, Raman, SEM, XPS and H₂-TPR results reveal that the structure and oxygen adsorption properties are crucial to soot oxidation activity, and Zr⁴⁺ is successfully doped into the CeO₂ lattice and forms a homogeneous solid solution. Nanostructured Ce_0.8Zr_0.2O₂ with 110.2 m²/g surface areas is produced. The proportion of chemical oxygen and surface adsorbed oxygen in the catalyst prepared from the calcination method is the highest at 23.18%. The structure may lead to charge imbalance, unsaturated bonds, and oxygen vacancies, thus increasing the adsorption of oxygen on the catalyst surface.

SUBMITTER: Chen W

PROVIDER: S-EPMC9118398 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Preparation of Ce x Zr1-x O2 by Different Methods and Its Catalytic Oxidation Activity for Diesel Soot.

Chen Wenlin W Fan Li L Jiang Xiaohuan X Guo Jinfa J Liu Huanhuan H Tian Mengkui M

ACS omega 20220506 19

Novel Ce x Zr1-x O2 (x = 0.67, 0.8, 0.9, 1.0) catalysts were designed and synthesized by solvothermal, calcination, and sol-gel methods and were used to catalyze oxidation of soot from diesel vehicle exhaust. The influence of catalysts synthesized by different methods and Ce/Zr molar ratios on the performance was investigated. These catalysts were characterized by XRD, N2 adsorption-desorption, FT-IR, TEM, XPS, H2-temper ...[more]

PMID: 35601292

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Project description:Soot combustion experiments with 5%O2/He were conducted using model soot, and four distinct compositions of CexPr1-xO2-δ oxides of varying nominal cerium compositions (x = 0, 0.2, 0.3, and 1) were prepared. The catalyst samples were comprehensively characterized using techniques such as XRD, Raman spectroscopy, HR-TEM, N2 adsorption at -196 °C, XPS, O2-TPD, H2-TPR, and work function measurements. The Pr-rich compositions, ranging from Ce0.3Pr0.7O2-δ to PrO2-δ, resulted in a significant increase in the total evolved O2 amounts and enhanced catalyst reducibility. However, a decrease in the textural properties of the catalysts was noted, which was particularly important for the pure praseodymia under the synthesis route conducted. The catalytic activity was investigated under the two following contact modes of mixing between soot and catalyst: loose and tight. The results revealed that the catalytic performance is associated with the surface contact in tight contact mode and with the combination of surface/subsurface/bulk oxygen mobility and the BET surface area in loose contact mode. Notably, the temperatures estimated at 10% and 50% of the conversion (T10 and T50) parameters were achieved at much lower temperatures than the uncatalyzed soot combustion, even under loose contact conditions. Specifically, the 50% conversion was achieved at 511 °C and 538 °C for Ce0.3Pr0.7O2 and Ce0.2Pr0.8O2, respectively. While no direct correlation between catalytic activity and work function was observed, a significant relationship emerges between work function values and the formation of oxygen vacancies, whatever the conditions used for these measurements. On the other hand, the ability to generate a high population of oxygen vacancies at low temperatures, rather than the direct activation of gas-phase O2, influences the catalytic performance of Pr-doped ceria catalysts, highlighting the importance of surface/subsurface oxygen vacancy generation, which was the parameter that showed a better correlation with the catalytic activity, whatever the soot conversion value or the mode of contact considered.

Dataset Information

Preparation of Ce _x Zr_1-x O₂ by Different Methods and Its Catalytic Oxidation Activity for Diesel Soot.

Publications

Preparation of Ce <sub><i>x</i></sub> Zr<sub>1-<i>x</i></sub> O<sub>2</sub> by Different Methods and Its Catalytic Oxidation Activity for Diesel Soot.

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