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991.
In this work, by applying Materials Studio 2.2 software package, molecular dynamics (MD) was performed to investigate the dynamic processes of 1:4 acetone/nitrogen mixed gas permeating through different Al2O3 microporous membranes. Three systems were modeled by considering different box lengths, microporous sizes, and textures of Al2O3 membranes to compare different permeation behaviors. In each system, initial mixed gas contained 20 acetone molecules and 80 nitrogen molecules, and its density was set to 0.1 g/cm3. Analysis on the concentration profiles of nitrogen molecules (N2) and acetone molecules (Ace) in each system at different sampling times was implemented to discuss the permeation behaviors of smaller N2 and larger Ace. The results showed that adsorption and diffusion occurred synchronously but adsorption was dominant for acetone molecules and that the adsorption on the floor surface of the feed gas region more easily reached equilibrium (local equilibrium) than the diffusion and the adsorption on the ceiling of the initially vacuum region. Furthermore, for nitrogen, adsorption followed diffusion. Higher temperature is in favor of the enrichment of acetone on the floor surface of the feed gas region but against the adsorption of nitrogen. The adsorptive layer was found to be a double-layer with COMPASS force field and to be a monolayer with PCFF force field. 相似文献
992.
城市污水生物脱氮除磷技术的研究进展 总被引:6,自引:0,他引:6
评述了近年来城市污水生物脱氮除磷技术的研究进展,重点介绍了生物处理的新方法:ANAMMOX–SHARON组合法、好氧同步脱氮除磷法和倒置A2/O法,并比较了各种工艺的优缺点。指出反硝化聚磷技术在倒置A2/O工艺中的应用将成为城市污水同步脱氮除磷研究的一个重要发展方向。 相似文献
993.
The effect of SO2 on catalytic activity for NO reduction to N2 by methanol in excess oxygen over $\gamma$ -alumina has been investigated. SCR activity increased initially upon exposure of a fresh $\gamma$ -alumina catalyst to SO2 which is attributed to formation of Brønsted acid sites. Longer exposure to SO2 leads to a decline in catalytic activity to a lower steady-state NOx reduction activity which is independent of the SO2 content in the feed gas. 相似文献
994.
K. G. Shkadinskii N. I. Ozerkovskaya S. V. Kostin 《Combustion, Explosion, and Shock Waves》2004,40(3):285-294
The specific features of dynamics of the thermal explosion in systems porous reagent–active gas–solid product under conditions where the heattransfer and masstransfer regions are separated from the ambient medium are considered. In addition to the competition of heat release and heat removal, the process of initiation of exothermal chemical interaction in these systems under normal pressures depends significantly on conditions of filtration transport of the gaseous reagent. The induction and postinduction periods of the thermal explosion are studied. The theoretical analysis of thermalexplosion issues is supplemented by an experimental study of the process for the porous titanium–nitrogen–titanium nitride system. 相似文献
995.
Patrick McGrath 《Electrochimica acta》2007,53(3):1365-1371
We use cyclic voltammetry (CV) on fuel cell electrodes to elucidate the important differences between adsorbates resulting from carbon monoxide adsorption and methanol adsorption onto commercial Pt/C electrocatalysts in a sulfuric acid electrolyte. Under open circuit conditions, methanol was found to adsorb preferentially onto the Pt sites associated with “strongly bound” hydrogen. The sites associated with “weakly bound” hydrogen adsorbed methanol more slowly. In the case of CO adsorption, which requires no adsorbate dehydrogenation, all adsorption sites showed similar affinity towards the adsorbate. Electrochemical oxidation of the adsorbates derived from both methanol and CO exposure exhibit slower oxidation when the adsorbate is associated with cubic-packed-like sites than from close-packed-steps and other sites. NMR of a 13CO-adlayer prepared by electrochemical adsorption from low concentration 13CH3OH shows a lower NMR shift and smaller linewidth than the previously reported values for electrochemically adsorbed 13CO gas. These results are interpreted in terms of adsorbate motion on the electrocatalyst surface. 相似文献
996.
Luis Fernando Crdoba Wolfgang M.H. Sachtler Consuelo Montes de Correa 《Applied catalysis. B, Environmental》2005,56(4):269-277
A series of sulfated zirconia supported Pd/Co catalysts was synthesized by the sol–gel method and examined for NOx reduction by methane. The NO conversion increased up to a Co/S ratio of 0.43, and then decreased at a higher Co loading (Co/S = 0.95). Sulfate content was also essential for obtaining high selectivity to molecular nitrogen. A catalyst loaded with 0.06 wt.% Pd, 2.1 wt.% Co and 2.1 wt.% S (Pd/Co-SZ-2) exhibited remarkable performance under lean conditions and displayed stability in a long-term durability test using a synthetic reaction mixture containing 10% water vapor. This catalyst exhibited the highest sulfur retention most probably as cobalt sulfide. Besides, the catalytic oxidation of NO to NOy groups was confirmed by FT-IR, in agreement with the general mechanism for the SCR of NO by hydrocarbons. In the absence of oxygen in the feed stream, the catalyst was highly active for NO reduction with methane. IR stretching bands assigned to N2O and adsorbed nitro groups were identified upon adsorbing NO on Pd/Co-SZ-2. This indicates that under rich conditions disproportionation of NO to N2O and NO2 occurs and confirms that the formation of NO2 species is an essential step for NO reduction by CH4. 相似文献
997.
998.
Luis A. Pérez-Maqueda José Manuel Criado Concepción Real 《Journal of the American Ceramic Society》2002,85(4):763-768
A new method for the kinetic analysis of the initial stage of sintering for constant-heating-rate data has been proposed. Unlike all of the methods previously reported in the literature, this new method proposed here allows the simultaneous determination of the activation energy and the kinetic model from a single dilatometric curve recorded under a linear-heating-rate program. The proposed method has been tested with simulated sintering curves and experimental results have been obtained for the sintering of a rutile sample. 相似文献
999.
Synthesis of Dimethyl Carbonate from Methanol and Carbon dioxide using Potassium Methoxide as Catalyst under Mild Conditions 总被引:2,自引:0,他引:2
Pd-supported on WO3–ZrO2 (W/Zr atomic ratio=0.2) calcined at 1073 K was found to be highly active and selective for gas-phase oxidation of ethylene to acetic acid in the presence of water at 423 K and 0.6 MPa. Contact time dependence demonstrated that acetic acid is formed via acetaldehyde formed by a Wacker-type reaction, not through ethanol by hydration of ethylene. 相似文献
1000.
在选择三元共聚尼龙(PA)、聚氯乙烯(PVC)、丁腈橡胶(NBR)为主体材料,制备PA/PVC/NBR(10/30/60)三元共混弹性体的工作基础上,进一步探讨了填料品种和用量,共混温度,加料顺序等因素PA/PVC/NBR三元共混弹性体的影响。试验结果表明:在PA/PVC/NBR(10/30/60)共混体系中,补强型填料的补强效果优于非补强型的填料,6种填料补强效果依次是:快压出炭黑>半补强炭黑>白炭黑>活性重质,CaCO3>陶土>滑石粉,快压出炭黑的适宜用量是20-50份。在制备PA/PVC/NBR三元共混物时,适宜的共混温度是122-140℃,并且采用二段法混工艺制得的共混物性能优于采用一段法共混工艺。 相似文献