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1.
The catalytic performance of Co-Mo-Ce-K/γ-Al2O3 catalyst for the shift reaction of CO in coke oven gas is investigated using X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The results indicate that Ce and K have a synergistic effect on promoting the catalytic activity, and the Co-Mo-Ce-K/γ-Al2O3 catalyst with 3.0 wt-% CeO2 and 6.0 wt-% K2O exhibits the highest activity. CeO2 favors Co dispersion and mainly produces an electronic effect. TPR characterization results indicate that the addition of CeO2-K2O in the Co-Mo-Ce-K/γ-Al2O3 catalyst decreases the reduction temperature of active components, and part of octahedrally coordinated Mo6+ transforms into tetrahedrally coordinated Mo6+, which has a close relationship with the catalytic activity. 相似文献
2.
3.
Xianghua Liu Xingyao Xiong Canming Liu Dengyou Liu Anjun Wu Qiulong Hu Chunlin Liu 《Journal of the American Oil Chemists' Society》2010,87(7):817-823
We report here the preparation of biodiesel by transesterification of rapeseed oil with methanol using calcined K2CO3/γ-Al2O3 as a solid base catalyst. The prepared catalysts were characterized using SEM, IR and BET, and their catalytic activities
were evaluated. The reaction conditions were optimized, and in particular, the conversion can be as high as 98.62% under the
optimal reaction conditions. In addition, the effect of the presence of water in the reaction system on the catalytic activity
was also studied. 相似文献
4.
Prapan Kuchonthara Tharapong Vitidsant Atsushi Tsutsumi 《Korean Journal of Chemical Engineering》2008,25(4):656-662
The effects of potassium on the reactivity of biomass-char steam gasification with the presence of a porous material were
investigated by using a thermogravimetric reactor with high-heating rates. Lignin was employed as a char-rich biomass model
compound. The potassium carbonate (K2CO3) was added to lignin and a mixture of lignin and γ-Al2O3 porous particles by means of aqueous impregnation. The effects of K2CO3 and γ-Al2O3 addition on pyrolysis of lignin and steam gasification of lignin-derived char were evaluated in terms of lignin conversion
and the gaseous products. Results showed that K2CO3 slightly increased the steam gasification rate of lignin-derived char, but it did not influence the conversion in both the
pyrolysis and steam gasification steps. In addition, tar was reduced by adding K2CO3 because of the increment of carbon conversion to gas product. The presence of γ-Al2O3 was found to induce the lower reactivity of resulting char after pyrolysis, reducing the gasification rate and conversion.
A significant improvement in gasification conversion was observed with the presence of both K2CO3 and γ-Al2O3. Especially, almost complete gasification was achieved at a reaction temperature of 1,073 K. 相似文献
5.
R. S. Bubnova E. S. Derkacheva S. K. Filatov V. L. Ugolkov 《Glass Physics and Chemistry》2010,36(1):61-69
Solid solutions K1 − x
Cs
x
BSi2O6 (x (atomic fraction) = 0.00, 0.20, 0.30, 0.35, 0.40, 0.80, 0.90,1.00) have been prepared by solid-phase synthesis and crystallization
of glasses in the KBSi2O6-CsBSi2O6 borosilicate series. The thermal behavior of the solid solutions has been investigated using the annealing and quenching
techniques, dilatometry, and high-temperature X-ray powder diffraction. It has been shown that solid solutions with x = 0.00–0.35 and 0.40–1.00 correspond to space groups I
$
\bar 4
$
\bar 4
3d and I
a
$
\bar 3
$
\bar 3
d, respectively. The cubic-cubic phase transition I
$
\bar 4
$
\bar 4
3d ai Ia
$
\bar 3
$
\bar 3
d occurs in the composition range x = 0.35−0.40 at room temperature. In the series of solid solutions with x = 0−0.30, the reversible cubic-cubic polymorphic transition I
$
\bar 4
$
\bar 4
3d ai ia
$
\bar 3
$
\bar 3
d with an increase in the temperature has been revealed, the temperature of the polymorphic transition has been determined,
and the thermal expansion in both polymorphic modifications has been studied using high-temperature X-ray diffraction and
dilatometry. The solid solutions belonging to the space group Ia
$
\bar 3
$
\bar 3
d are characterized by a lower thermal expansion than the solid solution belonging to the space group I
$
\bar 4
$
\bar 4
3d. According to the calculations, the equivalents α/γ for the space groups I
$
\bar 4
$
\bar 4
3d and Ia
$
\bar 3
$
\bar 3
d are 0.03 and 0.02 (in cesium atomic fractions per degree Celsius), respectively. 相似文献
6.
Marco Ocsachoque Jose Bengoa Delia Gazzoli María Gloria González 《Catalysis Letters》2011,141(11):1643-1650
Abstract
The Rh/α-Al2O3 catalyst was modified by CeO2 in order to improve the thermal stability and the carbon deposition resistance during the CO2 reforming of methane The carbon formation was determined by TPO, TEM and Raman spectroscopy. Characterization results showed that the incorporation of Ce in the support inhibits the carbon deposition, increasing the useful life and the stability of the Rh base catalysts. 相似文献7.
Carbon free LiFe1−x
Mn
x
PO4 (x = 0, 0.05, 0.1, 0.2, 0.4) cathode materials were prepared by a direct-hydrothermal process at 170 °C for 10 h. The structural
and electrochemical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy
(SEM), charge–discharge experiments, cyclic voltammetry (CV) and alternating current (AC) impedance spectroscopy. The electrochemical
performance of LiFePO4 prepared in this manner showed to be positively affected by Mn2+-substitution. Among the Mn2+-substitution samples, the LiFe0.9Mn0.1PO4 exhibited an initial discharge capacity of 141.4 mA h g−1 at 0.1 C, and the capacity fading is only 2.7% after 50 cycles. 相似文献
8.
M. I. Georgievskaya R. S. Bubnova S. K. Filatov V. L. Ugolkov 《Glass Physics and Chemistry》2008,34(4):436-442
Continuous solid solutions and the reversible phase transition from the I-43d cubic phase to the Ia-3d cubic phase are revealed in the borosilicate series K1 ? x Rb x BSi2O6. Samples in the KBSi2O6-RbBSi2O6 system are prepared by solid-phase synthesis and crystallization of glasses and investigated using the annealing and quenching technique, high-temperature X-ray diffraction, and dilatometry. The above polymorphic phase transition is observed in all solid solutions at temperatures in the range from 330 to 430°C depending on the composition: an increase in the rubidium content in the solid solution leads to a gradual decrease in the phase transition temperature. The linear thermal expansion coefficients α are determined for solid solutions of different crystalline modifications and glasses. The linear thermal expansion coefficients α for the I-43d low-temperature phase are equal to (20–23) × 10?6 K?1 according to the X-ray diffraction data and (21–24) × 10?6 K?1 according to the dilatometric data. The values of α for the Ia-3d high-temperature phase lie in the range (4–9) × 10?6 K?1 according to the X-ray diffraction data and in the range (6–9) × 10?6 K?1 according to the dilatometric data. The linear thermal expansion coefficients for both modifications decrease with an increase in the rubidium content in the solid solutions. The linear thermal expansion coefficients for glasses α = (10–11) × 10?6 K?1 are close to those for the high-temperature modification and virtually independent of the sample composition. The I-43d (cubic) ai I41/a (tetragonal) o Ia-3d (cubic) polymorphic phase transitions in the KBSi2O6 compound are revealed by differential scanning calorimetry (DSC) and dilatometry. Their reversibility is confirmed by the DSC data. 相似文献
9.
We report on bifurcate reactions on the surface of well-aligned Si1−x
Ge
x
nanowires that enable fabrication of two different coaxial heterostructure nanowires. The Si1−x
Ge
x
nanowires were grown in a chemical vapor transport process using SiCl4 gas and Ge powder as a source. After the growth of nanowires, SiCl4 flow was terminated while O2 gas flow was introduced under vacuum. On the surface of nanowires was deposited Ge by the vapor from the Ge powder or oxidized
into SiO2 by the O2 gas. The transition from deposition to oxidation occurred abruptly at 2 torr of O2 pressure without any intermediate region and enables selectively fabricated Ge/Si1−x
Ge
x
or SiO2/Si1−x
Ge
x
coaxial heterostructure nanowires. The rate of deposition and oxidation was dominated by interfacial reaction and diffusion
of oxygen through the oxide layer, respectively. 相似文献
10.
11.
The possibility of increasing the laminar flame velocity in a hydrogen-air mixture by excitation of O2 molecules into the a
1Δ
g
singlet state. The presence of 10% of O2(a
1Δ
g
) molecules in oxygen is demonstrated to result in noticeable (up to 50%) enhancement of mixture burning. The temperature
of combustion products and also the concentrations of H2O, NO, and other constituents increase. The greatest effect of O2(a
1Δ
g
) molecules is manifested in combustion of lean mixtures; the least pronounced effect is observed in rich mixtures. These
effects are caused by intensification of the chain mechanism in the presence of a super-equilibrium amount of excited O2(a
1Δ
g
) molecules in a hydrogen-air mixture.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 4, pp. 3–12, July–August, 2008. 相似文献
12.
S. R. Pratap M. Shyamsundar S. Z. Mohamed Shamshuddin 《Journal of Porous Materials》2018,25(5):1265-1273
Mixed metal oxide based solid acids like ZrO2–Al2O3 (ZA) with Al2O3 different loadings (2, 4, 6, 8 and 10 mol%) were prepared by wet impregnation method and characterized by PXRD, NH3-TPD, BET, ICP-OES, SEM, and TEM techniques. These solid acids were evaluated for their catalytic activity in the synthesis of a series of O-methoxymethylated products under solvent-free conditions at a moderate temperature in shorter reaction time (~20 min). This is achieved by various substituted alcohols and dimethoxy methane in good yields. Solid acids containing ZA used in this study exhibited good catalytic activity in the reaction. In case of 6 mol% ZA which has highest surface acidity, surface area and catalytically active tetragonal phase was found to be highest active in the O-methoxymethylation reaction up to ~99% yield. These catalysts were found to be reactivable and reusable. 相似文献
13.
BaCe0.9−x
Zr
x
Y0.1O3−δ powders were synthesized by a solid-state method at 1,400 °C. Two compositions were studied (x = 0.3 and x = 0.7). Pellets were prepared and conventionally sintered in air at 1,700 °C. Then, the samples were heated at 600 °C for
3 h in different reducing atmospheres: dry hydrogen, wet hydrogen and wet deuterium. After each treatment, the proton diffusion
depth profile was obtained using Secondary Ion Mass Spectroscopy (SIMS). Protons were not incorporated in the material when
the gas was not wet, and the isotope effect suggests that protons present in the pellet come from water and not from hydrogen. 相似文献
14.
The parameters of the tensor of the electric field gradient (EFG) in cation sites of the La2 ? x Sr x CuO4 lattice have been determined by the method of emission Mössbauer spectroscopy on 57Co(57m Fe), 67Cu(67Zn), 67Ga(67Zn), and 155Eu(155Gd) isotopes. There is no quantitative agreement between the calculated (the pointcharge model) and experimental values of the main component of the tensor EFG V zz , which is explained by the absence of the reliable data on the Sternheimer coefficients for Fe3+, Zn2+, and Gd3+ ions. Based on the comparison of the calculated and experimental dependences of V zz on x it was shown that the holes appearing during the substitution of La3+ for Sr2+ are localized preferably on the oxygen atoms that are in the same plane as the copper atoms, which is in agreement with the model discussed in the literature and assumes that the mechanism responsible for the high-temperature superconductivity of solid solutions La2 ? x Sr x CuO4 is the interaction between the conductivity electrons and two-atomic two-electron centers with negative correlation energy. 相似文献
15.
E. A. Buluchevskii E. D. Fedorova A. V. Lavrenov M. V. Zhuravleva 《Catalysis in Industry》2018,10(2):118-125
The effect of the hydroisomerization conditions of the benzene-containing fraction of catalytic reforming gasoline on the yield and composition of products is studied on Pt/B2O3–Al2O3 and Pt/WO3–Al2O3 catalysts. These catalysts allow benzene to be completely removed from the raw material. At the same time, the greatest yields of liquid products are obtained with minimal losses of the octane number at 2 MPa, a mass feedstock hourly space velocity (MFHSV) of 2 h?1, and 325°C: 96.3 and 95.4 wt % on Pt/B2O3–Al2O3 and Pt/WO3–Al2O3 catalysts, respectively. The activity of the catalysts is maintained for 100 h during their operation. 相似文献
16.
Lead and indium selenide films with an area of 3 × 3 mm2 and thickness of ~1 μm each are deposited successively by thermal vacuum deposition on C-29 glass substrates. The films are heat-treated in a dry air atmosphere at a temperature of 550°С. X-ray microanalysis and scanning electron microscopy show the possibility of the formation of the thread-like nanocrystals of a xInSe(1 – x)In2O3 composite from two-layer PbSe and In films deposited on glass substrates in the process of heat treatment in an air atmosphere. 相似文献
17.
Hongfeng Li Guanzhong Lu Dongsheng Qiao Yanqin Wang Yun Guo Yanglong Guo 《Catalysis Letters》2011,141(3):452-458
Abstract
Co–Ce–O composite oxides with high surface areas were firstly prepared by a modified citrate sol–gel method with N2 thermal treatment prior to calcination in air. The prepared Co–Ce–O catalysts have higher Brunauer–Emmett–Teller surface areas than those prepared by conventional calcination in air, and thus exhibit more effective catalytic activities. Adding CeO2 into Co3O4 can not only increase the activity of Co3O4 but also greatly enhance its thermal stability. When the bulk atomic ratio of Co/Ce is 3/1, Co–Ce–O composite oxide possesses the best activity and stability for the methane combustion. 相似文献18.
Liang Chen Junhua Li Wijdan Ablikim Jun Wang Huazhen Chang Lei Ma Jiayu Xu Maofa Ge Hamidreza Arandiyan 《Catalysis Letters》2011,141(12):1859-1864
Abstract
A series of cerium-tungsten oxide catalysts was prepared by the co-precipitation method and was evaluated for the selective catalytic reduction of NO x by ammonia (NH3-SCR) over a wide temperature range. These catalysts were characterized by BET, XRD, XPS and H2-TPR analyses. The experimental studies demonstrated that, among cerium-tungsten oxides, CeO2–WO3 with a Ce/W molar ratio of 3/2 exhibited the best activity toward NH3-SCR reactions, N2 selectivity and SO2 durability over a broad temperature range of 175–500 °C at a space velocity of 47,000 h−1. The strong interaction between Ce and W could be the main factor leading to the high activity of the CeO2–WO3 mixed oxide catalyst. 相似文献19.
The electrochemical properties of amorphous vanadium pentoxide (V2O5) thin films deposited by reactive r.f.-sputtering were investigated using galvanostatic charge/discharge cycling and galvanostatic
intermittent titration technique (GITT). As x in Li
x
V2O5−y
increased (x = 0–2.0), the electromotive force of the lithium (Li)∣1 M LiClO4–propylene carbonate∣Li
x
V2O5−y
cell decreased gradually without a potential plateau or an abrupt potential reduction, demonstrating that an irreversible
structural change did not occur in the entire Li content. Chemical diffusivity of the Li ion in the Li
x
V2O5−y
thin film measured using GITT was determined to be 4 × 10−13–7 × 10−14 cm2 s−1 in the Li content range investigated. 相似文献
20.
E. V. Mikhaleva V. G. Vasil’ev A. P. Nosov E. V. Vladimirova B. V. Slobodin 《Glass Physics and Chemistry》2009,35(1):81-86
Single-phase finely dispersed perovskite-like manganites La1 ? x Sr x MnO3 + δ (0 ≤ x ≤ 0.33) with an average particle size of approximately 3μm were synthesized by the pyrohydrolytic method from a stoichiometric mixture of the corresponding metal nitrates at a temperature of 500°C in a water vapor atmosphere. The parameter δ was changed as a result of the subsequent heat treatment. It was established that the manganite La0.67Sr0.33MnO3 + δ synthesized by the pyrohydrolytic method is characterized by a more pronounced change in the magnetoresistance as compared to the manganite that had the same composition but was synthesized according to the conventional ceramic technique. 相似文献