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Sieghard E. Wanke 《加拿大化工杂志》1973,51(4):454-458
The oxidation of propane, over a concentration range of 0.30 to 1.04 mole % in air was investigated over a commercial diesel exhaust catalyst consisting of CuO, Cr2O3 and Pd supported on Al2O3. The rate of reaction was correlated by a first order, irreversible rate function; the resulting pre-exponential factor and activation energy were 3.15 × 107 cc/g-sec and 21.3 kcal/gmole, respectively. At high temperatures the reaction rate became influenced by pore diffusion. A temperature of 675°K was required to obtain 50% propane conversion. It was concluded that this catayst is unsuitable for catalytic mufflers on diesel buses since the measured value of diesel exhaust temperatures at the cataytic muffler inlet is significantly less than 675°K. 相似文献
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During the past decade, the sintering of model supported metal catalysts, i.e. catalysts consisting of metal deposited on very thin and flat oxide films, has been intensively investigated by transmission electron microscopy. In the current paper, a mathematical model, based on an atomic migration mechanism, for the sintering of these catalysts is presented. The predictions of the model, based on Monte Carlo simulations, are in very good agreement with the experimental observations, i.e. phenomena such as ‘apparent’ particle migration, splitting and neck formation between particles are predicated by the model. 相似文献
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Bunjerd Jongsomjit Paninee Kaewkrajang Sieghard E. Wanke Piyasan Praserthdam 《Catalysis Letters》2004,94(3-4):205-208
Activities of ethylene/α-olefin copolymerization were found to increase with silane-modified silica-supported MAO using ansa-zirconocene catalyst. The increase in activities was less pronounced when higher α-olefins were used. However, silane modification resulted in the narrower molecular weight distribution of polymers. 13C NMR revealed that ethylene incorporation in all systems gave polymers with the similar triad distribution. 相似文献
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Three catalysts obtained by supporting bis(n‐butylcyclopentadienyl)zirconium dichloride/methylaluminoxane on: (1) porous crosslinked poly(2‐hydroxyethylmethacrylate‐co‐styrene‐co‐divinylbenzene) particles (CAT1); (2) swellable crosslinked poly(styrene‐co‐divinylbenzene) particles (CAT2); and (3) by evaporating the catalyst precursors solution to dry powder, CAT3 were used in gas‐phase polymerization of ethylene, and ethylene/1‐hexene in a 2 L semi‐batch reactor at 80 °C and 1.4 MPa. The average polymerization activities of the three catalysts were 12.3–15.5, 4.2–10.1, and 14.3–62.9 ton PE (mol Zr h)?1 respectively. CAT1 and CAT3 produced polyethylenes with a polydispersity range of 2.3–2.7, while that of CAT2 was 3.5–6.4. The supported catalysts produced polyolefin particles with bulk density of 0.36–0.43 g ml?1, and essentially no fines. Ethylene/1‐hexene co‐polymerization (7 mol m?3 initial 1‐hexene concentration in the reactor) increased polymerization activities and produced lower‐molar‐mass co‐polymers. At 21 mol m?3 1‐hexene the polymerization activities decreased, but the relative amount of the low‐molar‐mass co‐polymer for CAT2 increased, leading to higher polydispersity. Copyright © 2006 Society of Chemical Industry 相似文献
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Electronic properties of Cu(In,Ga)Se2 solar cells on stainless steel foils without diffusion barrier
F. Pianezzi A. Chiril P. Blsch S. Seyrling S. Buecheler L. Kranz C. Fella A. N. Tiwari 《Progress in Photovoltaics: Research and Applications》2012,20(3):253-259
Compared with rigid glass, manufacturing of Cu(In,Ga)Se2 (CIGS) solar cells on flexible stainless steel (SS) substrates has potential to reduce production cost because of the application of roll‐to‐roll processing. Up to now, high‐efficiency cells on SS could only be achieved when the substrate is coated with a barrier layer (e.g. SiOx or Si3N4) for hindering the diffusion of impurities, especially Fe, into the CIGS layer. In this paper, the effect of these impurities on the electronic transport properties of the device is investigated. Using admittance spectroscopy, the presence of a deep defect level at around 320 meV is observed, which deteriorates the efficiency of the solar cells. Furthermore, it is shown that reducing substrate temperature during CIGS deposition is an effective alternative to a barrier layer for reducing diffusion of detrimental Fe impurities into the absorber layer. By applying a CIGS growth process for deposition at low substrate temperatures, an efficiency of 17.7%, certified by Fraunhofer Institute ISE, Freiburg, was achieved on Mo/Ti‐coated SS substrate without an additional metal‐oxide or metal‐nitride impurity diffusion barrier layer. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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The presence of a small amount of nitrogen in the feed gas is necessary to generate ozone efficiently out of oxygen. Operating an ozone generator with ultra-pure oxygen for extended periods results in highly deteriorated ozone generation efficiency. In extreme cases, when the nitrogen levels in the feed gas are in the lower ppm range, the efficiency of the ozone generation process even drops to zero. In this article, we present our results concerning the correlation between the N2O5 concentration in the off-gas and the ozone generation efficiency. After the ozone generator is run for a well-defined amount of time with an oxygen–nitrogen mixture, the N2 supply is shut off, and the behavior of the system is monitored by near-infrared spectroscopy. Different surface materials lead to different temporal behavior of both the nitrogen oxide levels and the ozone concentration after shutting down the nitrogen supply. The measurements show a good correlation between the evolution of ozone generation efficiency and the changes of the N2O5 concentration in the off-gas. 相似文献