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排序方式： 共有2177条查询结果，搜索用时 15 毫秒
991.
Step-change experiments between H2, CO, and syngas mixtures with time resolution of ca. 0.3 s were undertaken to critically test mechanisms proposed in the literature for the Fischer-Tropsch synthesis. A silica-supported cobalt catalyst was used. Results suggest C2+ olefins and branched paraffins form from a carbon deposit on the catalyst surface. Two pathways appear to exist for methane formation. The first of these is from the carbon deposit through direct hydrogenation and through hydrogenolysis of the long-chain materials formed. The second pathway is hydrogenation of strongly adsorbed CO. 相似文献
992.
In this paper the effects of surface energy and surface roughness on the deposition of calcium sulphate during convective and subcooled flow boiling heat transfer to aqueous CaSO4 solutions are studied. The surfaces of several test heaters have been treated by Ion Beam Implantation, Unbalanced Magnetron Sputtering, Mixed Sputtering and Plasma Arc Deposition to reduce surface energy. One heater was electropolished to reduce surface roughness and one heater was etched by an electrochemical method to increase surface roughness. Fouling runs with these heaters, and with an untreated surface as control, were carried out at different heat fluxes, flow velocities and salt concentrations. The results show that heat transfer surfaces with low surface energy experienced significantly reduced fouling, while electropolishing did not have a notable beneficial effect. The combined effect of reduced surface energy and flow velocity on fouling reduction is considerably stronger than previously reported for pool boiling. 相似文献
993.
Mojtaba Nabipoor Hassankiadeh Meisam Moghadamrezaee Morteza Golmohammadi Abbas Naderifar 《Chemical Engineering Communications》2013,200(8):993-999
A laboratory-scale fixed-bed adsorption system was used to evaluate the capability of various adsorbents for removing methyl iodide from the acetic acid solution. Ag/Amberlite IR 120, Dowex R W50-X8, as well as a new adsorbent namely Ag/Amberlyst 15 were implemented to evaluate their removal efficiencies. Effect of process parameters such as temperature, flow rate of acetic acid solution, and resin's silver content were investigated. The experimental results indicated that a significant improvement in iodide compound removal efficiency can be achieved by using Ag/Amberlyst 15. The results also showed that the removal efficiency was increased with increasing the temperature as well as the resin's silver content, while the flow rate of acetic acid solution had a negative effect on this efficiency. The maximum removal efficiency was found to be 99% at temperature 24.5°C, flow rate 5.73 BV/h, and with Ag/Amberlyst 15 92% silver impregnated. 相似文献
994.
Abbas Emamgholizadeh Maryam Khoshroo Abdollah Omrani Abbas A. Rostami 《应用聚合物科学杂志》2010,117(6):3107-3113
In this article, we report polypyrrole (PPy)/poly(vinyl sulfonate) (PVS) and PPy/perchlorate (ClO) composite films generated by the electrochemical oxidation of pyrrole on a glassy carbon electrode (GCE) in an aqueous solution. The response of the produced films to an applied potential at 0.7 V was obtained by a cyclic voltammetry study in acetonitrile media. The films were significantly similar in their electrochemical behavior when ClO ions doped during the redox process. We concluded that with an increasing number of cycles, the anodic current increased because the number of the electroactive participants transported in the copolymer matrix was increased. Theoretical studies based on the Nernst and Butler–Volmer equations indicated that the ClO ion was transported during the oxidation/reduction process of the PPY/PVS and PPY/ClO films. The produced films were characterized further by means of IR spectroscopy, electrochemical impedance spectroscopy, and scanning electron microscopy to verify that the anion of ClO was doped into the copolymer matrix as well. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
995.
Naeimeh Bahri‐Laleh Mehrdad Seifali Abbas‐Abadi Mehdi Nekoomanesh Haghighi Zahra Akbari Mohamad Reza Tavasoli Seyed Heydar Mirjahanmardi 《应用聚合物科学杂志》2010,117(3):1780-1786
In our previous study we found that addition of proper amount of halocarbons (HC) including chlorocyclohexane (CHC), chlorocyclopentane (CHP), butylchloride (BC), 1,4‐dichlorobutane (DCB), and chloroform (C) to the MgCl2 (Ethoxide type)/TiCl4/AlEt3 catalytic system leads to a strong productivity improvement. In this study, the effect of these halocarbons on the properties of resulting polymers was investigated using H2 as chain transfer agent at optimum HC/Ti molar ratio. The nature of halocarbon compound had a strong effect on polymer properties as well as on development of polymerization activity. Effect of halocarbon promoters on the polymer melt flow index (MFI), melt flow ratio (MFR), particle size distribution (PSD), bulk density, wax amount, crystallinity, and thermal properties of the polymers were studied. Results showed that, in the presence of halocarbons, polyethylenes with higher MFI and bulk density, broader MFR and lower wax amount have been obtained. Also, sieve analysis showed that, in the presence of halocarbons as promoter, polymers had better particle size distribution (PSD). DSC analysis showed that the Tm of PEs prepared with the different promoters were in the region commonly reported for HDPE and was not affected substantially by halocarbons, but, the crystallinity of the polymers has been improved using halocarbon promoters. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
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1000.
The toughening of epoxy resins by incorporating inorganic fillers is of great importance nowadays, due to their wide range of applications. The present work reports the results of the addition of barium carbonate into a polymeric matrix containing diglycidyl ether of bisphenol-A (DGEBA) epoxy resin using 1,8-naphthalene diamine (1,8-NDA) as hardener to produce a novel composite for industrial applications. Cure kinetics of the composite system was investigated by means of differential scanning calorimeter (DSC) in dynamic mode. Kinetics of the reaction was interpreted according to the two isoconversional methods of Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (OFW). Using non-isothermal conditions, average value of the cure reaction activation energy in the propagation step was determined to be 57 and 60.2 kJ/mol for the KAS and OFW models, respectively. DMTA and TGA measurements were used in order to assess the effectiveness of the filler amount (2 Phr) on the final mechanical and thermal properties of the produced composite. The results verified that the thermal stability of the composite could be improved with the incorporation of BaCO3. Microstructural observations from images analysis of SEM micrographs revealed that the barium salt was dispersed into polymer matrix homogeneously. 相似文献