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A series of Co-modified Ce0.5Zr0.5O2 catalysts with different concentrations of Co (mass %: 0, 2, 4, 6, 8, 10) was investigated for diesel soot combustion. Ce0.5Zr0.5O2 was prepared using the co-precipitation method and Co was loaded onto the oxide using the incipient wetness impregnation method. The activities of the catalysts were evaluated by thermogravimetric (TG) analysis and temperature-programmed oxidation (TPO) experiments. The results showed the soot combustion activities of the catalysts to be effectively improved by the addition of Co, 6 % Co/Ce0.5Zr0.5O2 and that the 8 % Co/Ce0.5Zr0.5O2 catalysts exhibited the best catalytic performance in terms of lower soot ignition temperature ( Ti at 349 °C) and maximal soot oxidation rate temperature ( Tm at 358 °C). The reasons for the improved activity were investigated by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), H2 temperature-programmed reduction (H2-TPR), X-ray photo-electron spectroscopy (XPS) and transmission electron microscopy (TEM). These results revealed that the presence of Co could lower the reduction temperature due to the synergistic effect between Co and Ce, thereby improving the activity of the catalysts in soot combustion. The 6 % Co catalyst exhibited the best catalytic performance, which could be attributed to the greater amounts of Co3+ and surface oxygen species on the catalyst. [ABSTRACT FROM AUTHOR]

Two Ce–Zr–La/Al2O3 composite oxides, CZLA-C and CZLA-B, were synthesized using a co-precipitation method in a continuous stirred-tank reactor (CSTR) and a batch reactor (BR), respectively. Two Rh-based three-way catalysts (TWCs), Rh/CZLA-C and Rh/CZLA-B were obtained by a wet-impregnation method using the two composites as the supports. The physicochemical properties of the samples before and after thermal treatment at 1000 °C were characterized by N2 adsorption–desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), H2-temperature programmed reduction (H2-TPR) and CO chemisorption. The results indicated that CZLA-C shows higher thermal stability than CZLA-B due to a sparsely-agglomerated morphology. Compared with Rh/CZLA-B, Rh/CZLA-C displayed better reducibility and higher thermal stability and exhibited significantly higher activity in the catalytic removal of the simulated gasoline vehicle exhaust emission (NO, CO and C3H8). Our work can provide a facile and economical synthesis route to advanced support materials and catalysts for exhaust emission control. [ABSTRACT FROM AUTHOR]

Abstract: Five monolithic catalysts with low noble metal content were prepared by immerge method (Pt/γ-Al2O3, Pt/La-Al2O3, Pt/YSZ-Al2O3, Pt+Pd/La-Al2O3 and Pd/La-Al2O3) and their activity measurements were carried out in a conventional fixed-bed flow reactor. The results show that La-Al2O3 can promote activity of the prepared catalysts and can decrease the complete conversion temperature of cooking fume. The Pt/La-Al2O3 catalyst has the highest activity and can be applied in wide range of gas hourly space velocity (GHSV). Some characterizations (XRD, TPR) were carried out with the objective to explain differences in catalytic behaviors. The prepared catalyst showed a great potential for application. [Copyright &y& Elsevier]

In this study, Al 2 O 3 , ZrO 2 , La 2 O 3 , and Y 2 O 3 were separately introduced into Pt/CeO 2 -MnO x catalyst to improve the thermal stability of catalysts and obtain a better soot and NO oxidation activity after thermal treatment. CeO 2 -MnO x -RO x (R = Al, La, Y, or Zr) mixed oxides were prepared by a co-precipitation method. The catalysts were characterized by XRD, BET, H 2 -TPR, CO chemisorption, XPS, TG analysis, soot–TPO, and NO–TPO. It is found that the introduction of R n + into CeO 2 -MnO x markedly increases the thermal stability of the catalysts for soot and NO oxidation, remaining a better catalytic oxidation activity. On the one hand, after high-temperature aging, for the modified catalyst Pt/CeMnRO x , the ignition temperature of soot oxidation ( T i ) and maximal soot oxidation rate temperature ( T m ) increase by 30–50 °C and 4–32 °C, respectively, whereas Al 3 + -modified catalyst shows the best thermal stability. On the other hand, due to a key role of NO 2 as a strong oxidizing agent in soot oxidation process, the NO oxidation activity is often considered as an important aspect. This work shows that R n + -modified catalysts display a better stability on NO oxidation activity after aging. Some factors leading to the thermal deactivation of catalysts are also discussed in this paper. [ABSTRACT FROM AUTHOR]

The reaction singlet potential energy curves of reactions Ni(d9 s1 3D)+CH2(3B1)→H2+NiC and Ni(d9s1 3D)+CH2(3B1)→trans-HNiCH, and the electronic and geometric structures and vibrational frequencies of all intermediates and transition states in the reactions above have been studied at B3LYP/6-311+G(2d,2p) and B3LYP/6-311++G(3df,2p) levels. The former reaction is predicted to be endothermic by about 32.9 kJ mol−1, and the latter exothermic by about 65.9 kJ mol−1. At low energy levels, the formation of trans-HNiCH would be the dominant process, while at high energy levels, the formation of H2+NiC would be the dominant process. [Copyright &y& Elsevier]

The reactions between Ni (d10 1S) and CH4 have been carried out at the B3LYP/6-311+G(2d, 2p) and B3LYP/6-311++G(3df,2p) theoretical levels. The reaction path in which the intermediates transfer from one to another via transition state is rationalized by their structures and natural bond orbital analysis. The reactions of Ni+CH4→NiCH2+H2, Ni+CH4→NiCH3⋅+H⋅ and Ni+CH4→NiH⋅+CH3⋅ are predicted to be endothermic, and the reaction Ni+CH4→NiH⋅+CH3⋅ is the easiest to occur. [Copyright &y& Elsevier]