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1.
Moo-Jin Kim Soo-Hyun Chang Jung-Sik Choi Wha-Seung Ahn 《Reaction Kinetics and Catalysis Letters》2004,82(1):27-32
Partial oxidation of n-heptane to syngas at 400–450°C was investigated over Rh and Rh-Ni based catalysts. The Rh/-Al2O3 catalyst exhibited much better catalytic activity than the Rh-Ni/-Al2O3 catalyst. A combination of the Rh-based catalyst with the WGS reaction catalyst (Fe3O4—Cr2O3) increases the hydrogen selectivity but has no distinct effect on shifting the balance of the partial oxidation of n-heptane.This revised version was published online in December 2005 with corrections to the Cover Date. 相似文献
2.
We studied on the function of the metal in the sulfated zirconia(SO42–/ZrO2) catalyst for the isomerization reaction of light paraffins. The addition of Pt to the SO42–/ZrO2 carrier could keep the high catalytic activity. The improvement in this isomerization activity is because Pt promotes removal of the coke precursor deposited on the catalyst surface. Though this catalytic function was observed in other transition metals, such as Pd, Ru, Ni, Rh and W, Pt exhibited the highest effect among them. It was further found that the Pd/SO42–/ZrO2–Al2O3 catalyst possessed a catalytic function for desulfurization of sulfur-containing light naphtha in addition to the skeletal isomerization. The sulfur tolerance of catalyst depended on the method of adding Pd, and the catalyst prepared by impregnation of the SO42–/ZrO2–Al2O3 with an aqueous solution of Pd exhibited the highest sulfur tolerance.Further, we investigated the improvement in sulfur tolerance of the Pt/SO42–/ZrO2–Al2O3 catalyst by impregnation of Pd. The results of EPMA analysis indicated that this catalyst was a hybrid-type one (Pt/SO42–/ZrO2–Pd/Al2O3) in which Pt/SO42–/ZrO2 particles and Pd/Al2O3 particles adjoined closely. This hybrid catalyst possessed a very high sulfur tolerance to the raw light naphtha that was obtained from the atmospheric distillation apparatus, although this light naphtha contained much sulfur. We assume that such a high sulfur tolerance in the hybrid catalyst is brought about by the isomerization function of Pt/SO42–/ZrO2 particles and the hydrodesulfurization function of Pd/Al2O3 particles. Besides, since the hybrid catalyst also provides high catalytic activity in the isomerization of HDS light naphtha, we suggest that the Pd/Al2O3 particles supply atomic hydrogen to the Pt/SO42–/ZrO2 particles by homolytic dissociation of gaseous hydrogen and also enhance the sulfur tolerance of Pt/SO42–/ZrO2 particles. Finally, we also propose the most suitable location of Pd and Pt in the metal-supported SO42–/ZrO2–Al2O3 catalyst. 相似文献
3.
Strong acid catalysts were synthesized by the impregnation of hydrated ZrO2 and TiO2 with sulfuric acid followed by thermal treatment at different temperatures. The surface acidity and crystallochemical characteristics of the catalysts were studied by potentiometry and X-ray diffraction analysis, respectively. It was found that the surface acidity gradually increased as the temperature of thermal treatment was increased from 350 to 600°C for SO2–
4/ZrO2 or to 200°C for SO2–
4/TiO2; this increase correlated with the degrees of crystallinity of the samples. A hypothesis was proposed to explain the gradual accumulation of acid sites in the surface layer in the course of thermal treatment. It was assumed that, because of crystallographic changes that caused the weakening or even rupture of Zr–O–S and Ti–O–S bonds in modified surface layers, these layers exhibited an enhanced reactivity in contact with water vapor. Subsequently, this resulted in the formation of strongly acidic grafted M–O–SO3–H+ groups. 相似文献
4.
Guiying Wang Wenxiang Zhang Honglei Lian Qingsheng Liu Dazhen Jiang Tonghao Wu 《Reaction Kinetics and Catalysis Letters》2002,75(2):343-351
Catalytic decomposition of ethanol in the presence of steam over Pd supported on a porous carbonaceous material was studied. XPS and TEM were used for the catalyst characterization. Experiments were performed under atmospheric pressure, temperature of 320-360°C and H2O/C2H5OH molar ratio 8.1. It was found that the catalyst exhibited a high activity and long-term stability for the ethanol decomposition into a gas mixture containing carbon oxides, methane and hydrogen. 相似文献
5.
Metal promoted zirconia-based oxide sorbents, such as Pt–ZrO2/Al2O3 for NO
x
have been investigated. To clarify the role of the catalyst component, sorption of NO and NO2 was compared using the samples with and without Pt. The catalytic oxidation of NO to NO2 and successively to nitrate ions is an important role for the Pt catalyst. The experimental results indicate that a high-temperature calcination is essential to remove residual Cl from Pt–ZrO2–Al2O3 prepared from H2PtCl6 in order to provide more active NO
x
sorption sites. Of M–ZrO2–Al2O3 samples investigated, ruthenium as well as Pt demonstrated relatively good performance as a catalyst component in the sorbent. The FT-IR spectra after sorption of NO and NO2 demonstrated a strong band attributed to stored nitrate ions. The Pt catalyst was more resistant to sulfur poisoning than a base metal catalyst. However, the NO
x
sorptive capacities of the Pt–ZrO2/Al2O3 sorbents were expected to be deteriorated in dilute SO2 as far as observed from FT-IR spectra. 相似文献
6.
S. N. Antonyuk A. L. Lapidus V. B. Kazanskii V. I. Yakerson A. A. Khanumyan E. Z. Golosman A. I. Nechugovskii O. Yu. Pesin 《Kinetics and Catalysis》2000,41(6):753-755
Methanol decomposition in a water–methanol equimolar mixture is studied in the presence of a nickel-promoted copper–zinc–cement catalyst. Methanol decomposition at 200–300°C on the oxide and reduced forms of the catalyst yields a gas with an H2/CO ratio close to two. The use of an equimolar CH3OH–H2O mixture under analogous conditions enables obtaining gaseous products with a hydrogen concentration up to 75 vol %. 相似文献
7.
The kinetics of oxidation of the chromium(III)–dipicolinic acid complex [CrIII(DPA)2(H2O)2]– by N-bromosuccinimide (NBS) in aqueous solution to CrVI have been studied spectrophotometrically over the 20–40 °C range. The reaction is first order with respect to both [NBS] and [CrIII], and increases with pH over the 5.92–6.93 range. Thermodynamic activation parameters were calculated. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of [NBS] to chromium(III). 相似文献
8.
V. F. Tret’yakov T. N. Burdeinaya Yu. P. Zakorchevnaya V. A. Matyshak V. N. Korchak 《Kinetics and Catalysis》2005,46(4):516-524
According to X-ray diffraction data, the STK catalyst is a mixture of Fe2O3 and Cr2O3. The temperature-programmed reduction spectrum exhibited two reduction peaks: one, with T
max = 250°C, corresponds to the reduction process Cr2O3 → CrO and the other, with T
max = 360°C, corresponds to the reduction Fe2O3 → Fe3O4. The results of thermal desorption measurements suggest that the individual adsorption of oxygen on the surface of the STK catalyst is low; in this case (according to IR-spectroscopic data), an atomic form is the main species. Surface nitrite-nitrate complexes are formed upon the adsorption of NO. Nitrite and nitrate complexes desorbed at maximum rates at 105 and 160°C, respectively. Unlike the NTK-10-1 catalyst, the NO species, which desorbed at high temperatures (250–400°C), was absent from the surface of STK. Propane adsorbed at room temperature to form surface compounds containing an acetate group. The interaction of propane with the surface of the STK catalyst at reaction temperatures resulted in strong surface reduction.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 550–558.Original Russian Text Copyright © 2005 by Tret’yakov, Burdeinaya, Zakorchevnaya, Matyshak, Korchak. 相似文献
9.
Randolph K. Belter 《Journal of fluorine chemistry》2007,128(5):552-556
Propyne and propadiene have been previously reported to readily undergo vapor phase catalyzed chlorofluorination at temperatures to 285 °C to form C3F4Cl4 mixtures that are primarily CFCl2-CF2-CFCl2. Continued fluorination at temperatures up to 485 °C produce the rearranged C3F6Cl2 isomers CF3-CCl2-CF3 and CF2Cl-CFCl-CF3. 相似文献
10.
The formation of active particles and their changes in the course of 1,3-butadiene decomposition on a Ni/Al2O3catalyst at temperatures from 400 to 800°C were studied by high-resolution electron microscopy. It was found that carbon filaments of different types were formed at 400–800°C. The growth of thin filaments (20–30 nm in diameter) takes place at 400–600°C on a conical Ni particle located at the growing end of the filament, whereas di-symmetrical filaments 50–100 nm in diameter grow on biconical metal particles. As the carbonization temperature was increased to 700–800°C, graphite nanotubes 5–20 nm in diameter were formed. It was found that the mechanism of formation and the structure of filaments are related to the state of catalytically active species, which consist of a solid solution of carbon in the metal. It is suggested that the metastable surface nickel carbide Ni3C1 – x
is an intermediate compound in the catalytic formation of graphite filaments from 1,3-butadiene. Upon termination of the reaction, the metastable Ni3C1 – x
microphase is decomposed with the formation of hexagonal nickel microinclusions. The role of epitaxy in the nucleation and growth of a graphite phase on the metal is discussed. Models are presented for the growth of structurally different carbon filaments depending on the formation of active metal species at various temperatures. Considerable changes in the structure of carbon and the formation of nanotubes at 700–800°C are related to the appearance of a viscous-flow state of metal–carbon particles. 相似文献