排序方式: 共有52条查询结果,搜索用时 187 毫秒
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Stephanie L. Brock Tomoko Shimojo Steven L. Suib Yuji Hayashi Hiroshige Matsumoto 《Research on Chemical Intermediates》2002,28(1):13-24
Methane conversions of 11.9%, yields of hydrogen as high as 23.3% and energy yields of 1.0 mol H2/kWh have been achieved from CO2 reforming of CH4 in non-thermal, atmospheric pressure plasma reactors with Pt coated electrodes. Two reactors have been studied. A novel fan type reactor consisting of a movable rotor and immobile stator produced the highest yields in contrast to a tube type (silent discharge) reactor with a glass dielectric barrier. Conversions, yields of hydrogen and energy yields (expressed as mol H2/kWh) were studied for CO2/CH4 concentrations of 1.1% and 5.0% in He as a function of flow rate and input voltage. Hydrogen yields are observed to increase as the input voltage is increased from 411 V to 911 V and the flow rate is decreased from 100 cc/min to 30 cc/min. Energy yields vary only slightly with input voltage and flow rate. Hydrogen yields show little dependence on CO2/CH4 concentrations, but energy yields are approximately five times greater for the 5.0% mixture than the 1.1% mixture. Selectivities to H2, CO, coke, and low molecular weight hydrocarbons were also evaluated and compared to data obtained without CO2 in the feed. Hydrogen selectivities of nearly 100% were obtained, with small amounts of ethane and propane as the only observed side products and the selectivites were approximately the same whether CO2 was present or absent in the mixture. However, the reaction proceeds much more cleanly when CO2 is present, producing CO. The syngas product has an H2 : CO ratio of 1.5 with the fan type reactor and 0.67 with the tubular reactor. In the absence of CO2, coke is the main carbonaceous product. Under all conditions studied the fan type reactor demonstrated higher methane conversions (up to 11.9%) and selectivities to hydrogen. 相似文献
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A new route for higher valency ion substitution into the manganese oxide (OMS-2) framework is reported. Isomorphously substituted vanadium and niobium OMS-2 were hydrothermally synthesized at 200 degrees C for a period of 2 days. Characterization by XRD, elemental analysis, Raman spectroscopy, and resistivity studies proved that vanadium was incorporated into the manganese oxide structure. The presence of vanadium in the framework changes the electrical properties, making the material very attractive for water sensing applications. 相似文献
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Tin oxide thin films prepared by thermal oxidation of Sn films were used for the detection of chlorinated methanes (CH2Cl2, CHCl3 and CCl4). This resulted in better chemical selectivity, sensitivity, response speed and detection limit than seen with previous detectors. The temperature dependence of the sensing of 1% CCl4 gas was studied and the best sensing behavior was observed at 300 degrees C. The films showed different chemical selectivity in both speed and direction of sensing response to each gas and were stable for more than 3 weeks under operating conditions. The films showed rapid gas sensing (<40 s to reach 90% of full response) and low detection limits (< 4 ppm CCl4). The role of oxygen in the detection of chlorinated methanes and in resistance changes without chlorinated methanes was also studied. The changes at the surface of the film after gas sensing were examined using scanning electron microscopy with energy-dispersive X-ray spectrometry. 相似文献
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Biosynthesis of iron and silver nanoparticles at room temperature using aqueous sorghum bran extracts 总被引:3,自引:0,他引:3
Njagi EC Huang H Stafford L Genuino H Galindo HM Collins JB Hoag GE Suib SL 《Langmuir : the ACS journal of surfaces and colloids》2011,27(1):264-271
Iron and silver nanoparticles were synthesized using a rapid, single step, and completely green biosynthetic method employing aqueous sorghum extracts as both the reducing and capping agent. Silver ions were rapidly reduced by the aqueous sorghum bran extracts, leading to the formation of highly crystalline silver nanoparticles with an average diameter of 10 nm. The diffraction peaks were indexed to the face-centered cubic (fcc) phase of silver. The absorption spectra of colloidal silver nanoparticles showed a surface plasmon resonance (SPR) peak centered at a wavelength of 390 nm. Amorphous iron nanoparticles with an average diameter of 50 nm were formed instantaneously under ambient conditions. The reactivity of iron nanoparticles was tested by the H(2)O(2)-catalyzed degradation of bromothymol blue as a model organic contaminant. 相似文献
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King'ondu CK Iyer A Njagi EC Opembe N Genuino H Huang H Ristau RA Suib SL 《Journal of the American Chemical Society》2011,133(12):4186-4189
Short reaction times and morphology control in the synthesis of inorganic materials under nonthermal conditions remain a challenge. Herein we report a rapid, self-templating, and nonthermal method based on ultraviolet light to prepare metal oxide hierarchical structures. With this method, the morphology of the metal oxides was controlled readily without using templates. 相似文献
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M. V. Badani J. Huang S. L. Suib J. B. Harrison M. Kablauoi 《Research on Chemical Intermediates》1995,21(6):621-630
The methanol selectivity in partial oxidation of methane in microwave plasma reactors is improved by using H2O in the presence or absence of O2. The use of H2O2 as an oxygen source has a similar effect, although it is less effective than H2O. The addition of H2 to the system has little effect on selectivity. Two pathways are suggested for the formation of methanol. One involves a CH3O* or CH3O2 * intermediate, while the other involves a direct combination of CH3 * and OH* radicals. The first pathway is favored in the presence of O2 while the latter is favored in the presence of H2O or H2O2. The best results are obtained for the CH4-O2-H2O system when methanol is formed through both pathways. 相似文献
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Mark W. Simon Jeffrey R. Rozak Steven L. Suib Jeffrey Harrison Mahmoud Kablauoi 《Research on Chemical Intermediates》2000,26(6):529-548
Pure hydrocarbon plasmas have been generated at low pressures with good efficiency using methane as a reactant. Hydrocarbon
plasma discharges containing high energy, free radical, and ionized intermediates were analyzed in situ using emission spectroscopy. Emission spectra were correlated with analytical data obtained from resultant product mixtures
and literature assignments of emission bands in order to identify these intermediates. Stabilization of atmospheric methane
plasmas using argon as a diluent has also been demonstrated in this study. Emission spectroscopy has also been used to identify
reaction intermediates formed in plasmas at high pressures. Distinct differences in plasma discharges have been observed as
a function of pressure, power, and methane concentrations at the molecular level using in situ spectroscopic techniques. 相似文献
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