共查询到20条相似文献,搜索用时 15 毫秒
1.
Wei Yan Yuesong Shen Shemin Zhu Qijie Jin Youlin Liu Xihong Li 《Catalysis Letters》2016,146(7):1221-1230
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Sang Ok Choi In Young Ahn Sang Heup Moon 《Korean Journal of Chemical Engineering》2009,26(5):1252-1258
Two types of CeO2-modified Ni/Al2O3 catalysts were prepared by a consecutive impregnation method with different sequences in the impregnation of Ni and CeO2, and their performance in autothermal reforming (ATR) of isooctane was investigated. Catalysts prepared by adding CeO2 prior to the addition of Ni, Ni/CeO2-Al2O3, produced larger amounts of hydrogen than those obtained using catalysts prepared by adding the two components in an opposite
sequence, Ni-CeO2/Al2O3. The results of H2 chemisorption and temperature-programmed reduction revealed that added CeO2 increased the dispersion of the Ni species on Al2O3 and suppressed the formation of NiAl2O4 in the catalyst such that large amounts of Ni species were present as NiO, the active species for the ATR. The elemental
and thermogravimetric analyses of deactivated catalysts indicated that Ni/CeO2-Al2O3, which showed a longer lifetime than Ni-CeO2/Al2O3, contained lesser amounts and different types of coke on the surface. 相似文献
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Qifu Huang Wenzhi Li Yanyan Lei Shengnan Guan Xusheng Zheng Yang Pan Wu Wen Junfa Zhu Haitao Zhang Qizhao Lin 《Catalysis Letters》2018,148(9):2799-2811
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Pb, Sb, Bi and Te doped Ni catalysts were prepared and used for methane reforming with CO2 in order to diminish coke deposition. It was found that small amounts of Pb doped Ni catalysts exhibited excellent coke resistance ability with minor loss of the reforming activity. As the added amount of Pb increased from 0 to 0.015 (mole ratio between Pb/Ni), coke formation rate decreased from 166.7 mg-coke/g-cat h (on Ni/SiO2) to 0, while the reforming activity decreased slightly from 73.2% to 63.3% (conversion of CO2) at 800 °C, 60,000 ml(STP)/g-cat·h (CH4 CO2=1:1, no dilution gas in feed). Higher amounts of Pb and Sb, Bi, Te made Ni catalyst deactivated for methane reforming with CO2. 相似文献
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A systematic study of the size effect of zirconia nanocrystals on nickel-catalyzed reforming of methane with CO2 shows that extremely stable Ni/ZrO2 catalysts are obtainable by hydrogen reduction of impregnated nickel nitrate on zirconia particles with sizes less than 25 nm. The same preparation method with larger particles of zirconia results in catalyst samples that deactivate rapidly in the reforming reaction. Comprehensive characterization with XRD, TPR/TPD, and TEM shows that the stable Ni/ZrO2 catalysts are better described as nanocomposites of size comparable to Ni metal (9-15 nm) and zirconia (7-25 nm) nanoparticles. The high percentage of the Ni-zirconia boundary or perimeter in the nanocomposite catalysts is believed to be crucial for the extremely stable catalytic activity. 相似文献
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A K-promoted 10Ni-(x)K/MgAl2O4 catalyst was investigated for the combined H2O and CO2 reforming (CSCR) of coke oven gas (COG) for syngas production. The 10Ni-(x)K/MgAl2O4 catalyst was prepared by co-impregnation, and the K content was varied from 0 to 5 wt%. The BET, XRD, H2-chemisorption, H2-TPR, and CO2-TPD were performed for determining the physicochemical properties of prepared catalysts. Except under the condition of a K/Ni=0.1 (wt%/wt%), the Ni crystal size and dispersion decreased with increasing K/Ni. The coke resistance of the catalyst was investigated under conditions of CH4: CO2: H2: CO:N2=1 : 1 : 2 : 0.3 : 0.3, 800 °C, 5 atm. The coke formation on the used catalyst was examined by SEM and TG analysis. As compared to the 10Ni/MgAl2O4 catalyst, the Kpromoted catalyst exhibited superior activity and coke resistance, attributed to its strong interaction with Ni and support, and the improved CO2 adsorption characteristic. The 10Ni-1K/MgAl2O4 catalyst exhibited optimum activity and coke resistance with only 1wt% of K. 相似文献
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Performance of CeO2-La2O3/ZSM-5 sorbents for sulfur removal was examined at temperature ranging from 500 oC to 700 oC. The sulfur capacity of 5Ce5La/ZSM-5 was much bigger than that of CeO2/ZSM-5. H2 had a negative impact on the sulfidation; however, CO had little influence on sulfur removal. The characterization results showed that CeO2 and La2O3 were well dispersed on ZSM-5 because of the intimate admixing of La2O3 and CeO2, the major sulfidation products were Ce2O2S and La2O2S, the XRD and SEM results revealed that ZSM-5 structure could remain intact during preparation and sulfidation process, the H2-TPR showed that the reducibility of CeO2 can be remarkably enhanced by addition of La. 相似文献
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Kamila Michalska Paweł Kowalik Wiesław Próchniak Tadeusz Borowiecki 《Catalysis Letters》2018,148(3):972-978
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Abstract
Ce X Zr1−X O2 catalysts with different cerium content (X) (X = 0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0) were prepared by a sol–gel method for use in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. Among these catalysts, Ce0.6Zr0.4O2 was found to show the best catalytic performance. In order to enhance the acidity and basicity of Ce0.6Zr0.4O2 catalyst, Ga2O3 was supported on Ce0.6Zr0.4O2 (XGa2O3/Ce0.6Zr0.4O2 (X = 1, 5, 10, and 15)) by an incipient wetness impregnation method with a variation of Ga2O3 content (X, wt%). Effect of acidity and basicity of Ga2O3/Ce0.6Zr0.4O2 on the catalytic performance in the direct synthesis of dimethyl carbonate was investigated using NH3-TPD and CO2-TPD experiments. Experimental results revealed that both acidity and basicity of the catalysts played a key role in determining the catalytic performance in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. Large acidity and basicity of the catalyst facilitated the formation of dimethyl carbonate. The amount of dimethyl carbonate produced over XGa2O3/Ce0.6Zr0.4O2 catalysts increased with increasing both acidity and basicity of the catalysts. Among the catalysts tested, 5Ga2O3/Ce0.6Zr0.4O2, which retained the largest acidity and basicity, showed the best catalytic performance in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. 相似文献14.
Cerium oxide is one of the most important rare earth elements that is introduced into glass compositions due to its great effects on the optical properties. CeO2 was introduced in Hench’s patented SiO2-Na2O-CaO-P2O5 glasses with different concentrations in order to study its effect on the optical behavior of this glass including optical band gap, transmittance, reflectance and refractive index and to give a complete view for the optical properties on cerium oxide-doped silicate glasses. 相似文献
15.
Jeong Gil Seo Min Hye Youn Kyung Min Cho Sunyoung Park Sang Hee Lee Joohyung Lee In Kyu Song 《Korean Journal of Chemical Engineering》2008,25(1):41-45
An Al2O3-ZrO2 xerogel (AZ-SG) was prepared by a sol-gel method for use as a support for a nickel catalyst. The Ni/AZ-SG catalyst was then
prepared by an impregnation method, and was applied to hydrogen production by steam reforming of LNG. A nickel catalyst supported
on commercial alumina (A-C) was also prepared (Ni/A-C) for comparison. The hydroxyl-rich surface of the AZ-SG support increased
the dispersion of nickel species on the support during the calcination step. The formation of a surface nickel aluminate-like
phase in the Ni/AZ-SG catalyst greatly enhanced the reducibility of the Ni/AZ-SG catalyst. The ZrO2 in the AZ-SG support increased the adsorption of steam onto the support and the subsequent spillover of steam from the support
to the active nickel sites in the Ni/AZ-SG catalyst. Both the high surface area and the well-developed mesoporosity of the
Ni/AZ-SG catalyst improved the gasification of adsorbed surface hydrocarbons in the reaction. In the steam reforming of LNG,
the Ni/AZ-SG catalyst showed a better catalytic performance than the Ni/A-C catalyst. Moreover, the Ni/AZ-SG catalyst showed
strong resistance toward catalyst deactivation. 相似文献
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Zhong-Wen Liu Hyun-Seog Roh Ki-Won Jun Sang-Eon Park Taek-Yong Song 《Korean Journal of Chemical Engineering》2002,19(5):742-748
The catalytic behavior of Ni/Ce-ZrO2/θ-Al2O3 has been investigated in the partial oxidation of methane (POM) toward synthesis gas. The catalyst showed high activity and
selectivity due to the heat treatment of the support and the promotional effect of Ce-ZrO2. It is suggested that the support was stabilized through the heat treatment of γ-Al2O3 and the precoating of Ce-ZrO2, on which a protective layer was formed. Moreover, sintering of the catalyst was greatly suppressed for 24 h test. Pulse
experiments of CH4, O2 and/or CH4/O2 with a molar ratio of 2 were systematically performed over fresh, partially reduced and well reduced catalyst. Results indicate
that CH4 can be partially oxidized to CO and H2 by the reactive oxygen in complex NiOx species existing over the fresh catalyst. It is demonstrated that POM over Ni/Ce-ZrO2/θ-Al2O3 follows the pyrolysis mechanism, and both the carbonaceous materials from CH4 decomposition over metallic nickel and the reactive oxygen species present on NiOx and Ce-ZrO2 are intermediates for POM. 相似文献
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The highly ordered mesoporous CoFe2O4 and CuFe2O4 with crystalline walls can be synthesized by hard template with using mesoporous silica SBA-15 as hard template and using ferric nitrate, cobalt nitrate, and copper nitrate as metal precursors. These new mesoporous materials above have high surface areas, narrow pore size distribution, and large pore volumes, which are believed to be valuable for the potential application in the field of sensors, catalysis, message recording, magnetics, and biology. This work provides a method to fabricate the highly ordered mesoporous materials composed of multi-metal oxides with crystalline walls. The development of such versatile approach is of great significance in practical application. It can be envisaged that this established method is significantly expandable to the controlled synthesis of the mesoporous functional materials with diverse compositions. 相似文献
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Jung-Hyun Park Eunpyo Hong Sang Hee An Dong-Hee Lim Chae-Ho Shin 《Korean Journal of Chemical Engineering》2017,34(10):2610-2618
Ni(x)/Al2O3 (x=wt%) catalysts with Ni loadings of 5–25 wt% were prepared via a wet impregnation method on an γ-Al2O3 support and subsequently applied in the reductive amination of ethanol to ethylamines. Among the various catalysts prepared, Ni(10)/Al2O3 exhibited the highest metal dispersion and the smallest Ni particle size, resulting in the highest catalytic performance. To reveal the effects of reaction parameters, a reductive amination process was performed by varying the reaction temperature (T), weight hourly space velocity (WHSV), and NH3 and H2 partial pressures in the reactions. In addition, on/off experiments for NH3 and H2 were also carried out. In the absence of NH3 in the reactant stream, the ethanol conversion and selectivities towards the different ethylamine products were significantly reduced, while the selectivity to ethylene was dominant due to the dehydration of ethanol. In contrast, in the absence of H2, the selectivity to acetonitrile significantly increased due to dehydrogenation of the imine intermediate. Although a small amount of catalyst deactivation was observed in the conversion of ethanol up to 10 h on stream due to the formation of nickel nitride, the Ni(10)/Al2O3 catalyst exhibited stable catalytic performance over 90 h under the optimized reaction conditions (i.e., T=190 °C, WHSV=0.9 h?1, and EtOH/NH3/H2 molar ratio=1/1/6). 相似文献