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1.
2.
CeO2-ZrO2 hydrosols are synthesized and the size, shape, phase composition, density, and electrophoretic mobility of particles are
studied. The pH ranges of the stability of hydrosols and the thresholds of their fast coagulation in the presence of some
electrolytes are determined. The nature of the aggregation stability of CeO2-ZrO2 hydrosols is discussed. 相似文献
3.
M. F. Pinheiro da Silva L. S. Soeira K. R. P. Daghastanli T. S. Martins I. M. Cuccovia R. S. Freire P. C. Isolani 《Journal of Thermal Analysis and Calorimetry》2010,102(3):907-913
Three different cerium citrate-based precursors were used for synthesizing CeO2 through thermal treatment. Three morphological types of CeO2 were obtained. Characterization of these oxides was carried out by XRD patterns, SEM microscopy, N2 adsorption isotherms, Raman spectroscopy, zeta potential, and UV/Vis luminescence. Ozonation of phenol catalyzed by CeO2 was studied as a representative reaction of environmental interest. The differences on the catalytic activity showed by these
three oxides could be correlated to amounts of Ce3+ on CeO2 surface and, consequently, to the demand for oxygen needed to burn each precursor. 相似文献
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5.
P. Šulcová 《Journal of Thermal Analysis and Calorimetry》2005,82(1):51-54
Summary The synthesis of new compounds based on the CeO2-PrO2-Nd2O3system, which can be used as pigments for colouring of ceramic glazes, is investigated in our laboratory. The optimum conditions
for the syntheses of these compounds have been estimated. The methods of thermal analysis provided first information about
the temperature region of the formation of the pigments investigated. The synthesis of these compounds was followed by thermal
analysis using STA 449/C Jupiter (Netzsch, Germany). 相似文献
6.
It is demonstrated by ESR measurements that O
2
−
(CO + O2) radical anions result from CO + O2 adsorption on the oxidized surface of CeO2. These radical anions are stabilized in the coordination sphere of Ce4+ cations located in isolated and associated anionic vacancies. This reaction shows an activation behavior determined by CO adsorption. The variation of O
2
−
(CO + O2) concentration with CO adsorption temperature suggests that surface carbonates and carboxylates participate in this reaction. In the (0.5– 10.0)%CeO2/ZrO2 system, O
2
−
forms on supported CeO2 and is stabilized on Ce4+ and Zr4+ cations. The stability of O
2
−
-Ce4+ complexes is lower on supported CeO2 than on unsupported CeO2, indicating a strong interaction between the cerium cations and the support.__________Translated from Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 423–429.Original Russian Text Copyright © 2005 by Il’ichev, Kuli-zade, Korchak. 相似文献
7.
Mingshi Jin Jung-Nam Park Jeong Kuk Shon Zhenghua Li Min Young Yoon Hyun Jung Na Young-Kwon Park Ji Man Kim 《Research on Chemical Intermediates》2011,37(9):1181-1192
Highly ordered mesoporous cerium dioxide (meso-CeO2) was successfully synthesized using a facile solvent-free infiltration method from a mesoporous silica template, KIT-6. The
meso-CeO2 material, thus obtained, exhibited well-defined mesostructure and high surface area (153 m2 g−1). The physicochemical properties of meso-CeO2 material and Pd-supported on meso-CeO2 (Pd/meso-CeO2) were characterized by electron microscopy, X-ray diffraction, N2 adsorption–desorption, and temperature-programmed experiments. The Pd/meso-CeO2 catalyst exhibited excellent catalytic activity for CO oxidation compared with those of other Pd/CeO2 catalysts which were prepared using nanocrystalline CeO2 and bulk-CeO2 as the supports. Moreover, a hydrogen pretreatment of the Pd/meso-CeO2 catalyst resulted in a remarkable increase of catalytic activity (T
100 = 52 °C). 相似文献
8.
A. A. Firsova T. I. Khomenko A. N. Il’ichev V. N. Korchak 《Kinetics and Catalysis》2008,49(5):682-691
The catalytic activity of the CoO/CeO2 and CuO/CoO/CeO2 systems in selective CO oxidation in the presence of hydrogen at 20–450°C ([CuO] = 1.0–2.5%, [CoO] = 1.0–7.0%) is reported. The maximum CO conversion (X) decreases in the following order: CuO/CoO/CeO2 (X = 98–99%, T = 140–170°C) > CoO/CeO2 (X = 67–84%, T = 230–240°C) > CeO2 (X = 34%, T = 350°C). TPD, TPR, and EPR experiments have demonstrated that the high activity of CuO/CoO/CeO2 is due to the strong interaction of the supported copper and cobalt oxides with cerium dioxide, which yields Cu-Co-Ce-O clusters on the surface. The carbonyl group in the complexes Coδ+-CO and Cu+-CO is oxidized by oxygen of the Cu-Co-Ce-O clusters at 140–160°C and by oxygen of the Co-Ce-O clusters at 240°C. The decrease in the activity of the catalysts at high temperatures is due to the fact that hydrogen reduces the clusters on which CO oxidation takes place, yielding Co0 and Cu0 particles, which are inactive in CO oxidation. The hydrogenation of CO into methane at high temperatures is due to the appearance of Co0 particles in the catalysts. 相似文献
9.
S. F. Santos M. C. de Andrade J. A. Sampaio A. B. da Luz T. Ogasawara 《Journal of Thermal Analysis and Calorimetry》2007,87(3):743-746
TiO2–CeO2 oxides
for application as ceramic pigments were synthesized by the Pechini method.
In the present work the polymeric network of the pigment precursor was studied
using thermal analysis. Results obtained using TG and DTA showed the occurrence
of three main mass loss stages and profiles associated to the decomposition
of the organic matter and crystallization. The kinetics of the degradation
was evaluated by means of TG applying different heating rates. The activation
energies (E
a) and
reaction order (n) for each stage were
determined using Horowitz–Metzger, Coats–Redfern, Kissinger and
Broido methods. Values of E
a
varying between 257–267 kJ mol–1 and n=0–1 were found. According to the kinetic
analysis the decomposition reactions were diffusion controlled. 相似文献
10.
Hao Li Guang-Fei Qu Yan-Kang Duan Ping Ning Qiu-Lin Zhang Xin Liu Zhong-Xian Song 《Chemical Papers》2015,69(6):817-826
Ce-Ti-W-O x catalysts were prepared and applied to the NH3-selective catalytic reduction (SCR) reaction. The experimental results showed that the Ce-Ti-W-O x catalyst prepared by the hydrothermal method exhibited higher NO conversion than those synthesised via the sol-gel and impregnating methods, while the optimal content of WO3 and molar ratio of Ce/Ti were 20 mass % and 4: 6, respectively. Under these conditions, the catalyst exhibited the highest level of catalytic activity (the NO conversion reached values higher than 90 %) across a wide temperature range of 225–450°C, with a range of gas hourly space velocity (GHSV) of 40000–140000 h?1. The catalyst also exhibited good resistance to H2O and SO2. The influences of morphology, phase structure, and surface properties on the catalytic performance were investigated by N2 adsorption-desorption measurement, XRD, XPS, H2-TPR, and SEM. It was found that the high efficiency of NO removal was due to the large BET surface area, the amorphous surface species, the change to element valence states, and the strong interaction between Ce, Ti, and W. 相似文献
11.
D. Z. de Florio V. Esposito E. Traversa R. Muccillo F. C. Fonseca 《Journal of Thermal Analysis and Calorimetry》2009,97(1):143-147
The sintering behavior of gadolinia-doped ceria powders was studied by the master sintering curve (MSC). Dilatometric analyses
of powders produced by a soft chemical method were performed to provide the experimental data set for the construction of
the MSC. The assumed model provided good fittings of the MSC and the activation energy for the sintering of Ce1−x
Gd
x
O3−δ, with x = 0, 0.05, 0.1, and 0.2 were found to be in the 218–325 KJ/mol range, depending on the dopant content. The results supported
that both the nanometric size of the particles and the difference in ionic radii between Gd3+ and Ce4+ affects the sintering of Gd-doped CeO2. 相似文献
12.
Daotong You Bao Pan Yishan He Xuxu Wang Wenyue Su 《Research on Chemical Intermediates》2017,43(9):5103-5112
CdS-Pt@CeO2 ternary composites are successfully prepared by an in situ redox precipitation followed by a subsequent precipitation. The prepared CdS-Pt@CeO2 sample exhibits high photocatalytic activity for hydrogen evolution from lactic acid aqueous solution under visible light irradiation, with a H2-evolation rate of 20.09 mmol h?1g?1 and apparent quantum yield (AQY) of 15.32%. With techniques such as XRD, TEM, DRS, XPS, N2 adsorption/desorption and electrochemistry measurements, the physicochemical properties of the CdS-Pt@CeO2 ternary composites are discussed, and a possible mechanism for the hydrogen evolution is proposed. 相似文献
13.
In this paper, magnetic chitosan microspheres were prepared by the emulsification cross-linking technique, with glutaraldehyde as the cross-linking agent, liquid paraffin as the dispersant, and the Span-80 as emulsifier. The time of cross-linking and the ratio of Co0.5Ni0.5Fe2O4/chitosan were investigated. The morphology was studied by different instruments. The adsorption performance was investigated and the effects of initial concentration of methyl orange, the time of cross-linking, and the amount of adsorbent were discussed. It is found that the product has uniform morphology when the ratio of magnetic Co0.5Ni0.5Fe2O4/chitosan is 1 : 2 and the time of cross-linking is 5 h; At room temperature, magnetic Co0.5Ni0.5Fe2O4–chitosan has a good adsorption toward methyl orange when the magnetic Co0.5Ni0.5Fe2O4/chitosan dosage is 20 mg. 相似文献
14.
The stability and solubility of UO2(OH)2 has been studied as a function of the humic acid concentration in 0.1M NaClO4, in the pH range from 4 to 7 under normal atmospheric conditions. The solid phase under investigation has been prepared by
alkaline precipitation and characterized by TGA, ATR-FTIR, XRD, SEM and solubility measurements. According to the experimental
data UO2(OH)2 is stable and remains the solubility limiting solid phase even in the presence of increased humic acid concentration in the
solution. However, humic acid affects texture and particle size of the solid phase. Increasing humic acid concentration results
in decreasing crystallite size of the UO2(OH)2 solid phase. Based on the solubility data, the logK
sp
(UO2(OH)2) has been evaluated to be −22.0±0.3 and the stability constant for the UO2(OH)HA(I) species has been estimated to be logβ
1101 = 15.3±0.5. 相似文献
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16.
A procedure is developed for the synthesis of concentrated CeO2-ZrO2 hydrosols based on the peptization of a precipitate obtained by the hydrolysis of a cerium nitrate-zirconium oxynitrate mixture.
The time intervals and optimum [H+]/[Me
n+] molar ratios giving rise the formation of CeO2-ZrO2 hydrosols stable to aggregation with a narrow particle size distribution are established. The size, shape, density, and phase
composition of the hydrosol particles are determined. 相似文献
17.
18.
A method for synthesizing aggregation-stable CeO2-ZrO2 hydrosols with different particle compositions is developed based on the peptization of hydrated oxide precipitates at elevated
temperature. It is shown that, by varying heat treatment time, sols can be obtained with particles that have different degrees
of crystallinity and sizes of no larger than 6 nm. 相似文献
19.
Yuanjiang Wang Wenhui Ge Yue Fang Xuanxuan Ren Shinian Cao Guixiang Liu Mingqi Li Jiangbiao Xu Yu Wan Xiguang Han Hui Wu 《Research on Chemical Intermediates》2017,43(2):631-640
Porous CeO2 nanorod has been used as efficient and recyclable heterogeneous catalyst for the synthesis of highly functionalized imino-pyrrolidine-thiones via the reaction of aromatic aldehyde (especially one bearing an electron-donating group), malononitrile, isocyanide and unactivated weakly acidic heterocyclic thiophenol. The high catalytic efficiency of porous CeO2 nanorod in this reaction was discussed preliminarily based on their morphology and structure. 相似文献
20.
E. Saab S. Aouad E. Abi-Aad M. N. Bokova E. A. Zhilinskaya A. Aboukaïs 《Kinetics and Catalysis》2007,48(6):841-846
The catalytic combustion of carbon black was investigated in the presence of CeO2 and Al2O3. The influence of contact type between carbon particles and these oxides was examined by thermal analysis, the BET specific
area, and EPR spectroscopy. For tight contact carbon black-catalyst mixtures, a new paramagnetic species is observed and can
be considered as a fingerprint of the contact between the two solids. These new paramagnetic species increase the reactivity
of the catalytic reaction of carbon black (CB) combustion and take part in the oxidation mechanism of CB.
Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 6, pp. 899–904.
This article was submitted by the authors in English. 相似文献