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991.
992.
苯酐法合成蒽醌固体酸催化剂的进展 总被引:3,自引:0,他引:3
蒽醌(AQ)是重要的有机合成中间体,采用固体酸催化剂代替传统的液体酸催化剂可以使蒽醌合成过程绿色环保。笔者对固体酸催化剂硅-铝酸盐、粘土矿物、金属氧化物、分子筛、杂多酸催化剂、阳离子交换树脂应用于蒽醌合成的研究进展进行了综述,认为固体酸催化剂对蒽醌合成有很好的研究前景。 相似文献
993.
Sang-Mok Lee Woo-Jin Chang Ah-Rom Choi Yoon-Mo Koo 《Korean Journal of Chemical Engineering》2005,22(5):687-690
Ionic liquids are compounds that composed only of ions and are liquid at room temperature. Thus, it is normally named room
temperature ionic liquid (RTIL). In this study, the application of RTILs to the extractive fermentation of biomaterials was
investigated as a substitute of organic solvents. The relative toxicity of the RTILs on the growth ofE. coli was tested. The inhibition of cell growth in the presence of various ionic liquids was measured using solid and liquid culture,
and EC50 of each RTILs was calculated. The number of viable and total cells was measured by the number of colonies and optical density,
respectively. Effective concentrations of toxicity (EC50) in these tested systems were similar with conventional solvents, such as acetone, acetonitrile, and ethanol. The viability
ofE. coli was affected by the polarity and ionic properties of ionic liquids. The resistance of the microorganisms against ionic liquids
was different with the cations and anions composing ionic liquids. No general influence of the anionic compound of the ionic
liquids was found on toxicity comparing with distinctive influence of cationic moiety. 相似文献
994.
以Fe(NO3)3、煤矸石和NaOH为原料,采用沸腾回流法制得了一系列不同质量比的α-Fe2O3/煤矸石复合光催化剂。采用场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)及紫外-可见漫反射光谱(UV-Vis DRS)等多种手段对产物做了表征。以五氯酚为目标降解物,考察了模拟太阳光照下样品的光催化效果。结果表明,将球形α-Fe2O3负载于改性煤矸石表面可有效提高其光催化活性,且α-Fe2O3/煤矸石复合光催化剂的性能与α-Fe2O3的含量有关,当α-Fe2O3与煤矸石的质量比为30∶100时,样品的光催化效果最佳,180 min内即可将五氯酚降解完全。此外,α-Fe2O3/煤矸石复合光催化剂还具有可重复使用的特点。 相似文献
995.
Eddy characteristics on mass transfer close to free interface 总被引:1,自引:0,他引:1
The velocity fluctuations in the immediate vicinity of a free interface were measured with a hot film anemometer. And mass
transfer rates and eddy exposure times were analyzed by using the method of deterministic approach. These mass transfer rates
were compared with the mass transfer rates by means of concentration measurements in the air-water system.
The eddy exposure time distributions obtained from velocity data were skewed toward the lower time value. The contribution
of eddies wi:h small exposure time was increased as the liquid became more turbulent. The mass transfer rates were mainly
contributed by the Prandtl size eddies and even larger eddies. The mass transfer predictions by the single eddy model employing
a deterministic method were in good agreement with the experimental results by independent measurements of concentration. 相似文献
996.
In this Account, we explore the role constant curvature structures play in amphiphilic small molecule crystals and extended coordination solids. A constant curvature structure is one in which there is a surface or interface that has the same curvature throughout its surface. Simple examples of such structures contain spheres (micelles), columns, or layers. Yet another family are cubic as is found in the gyroid topology. For amphiphilic systems, there are two domains, one generally hydrophobic and the other hydrophilic. We find that the interfaces between these two domains in small molecule structures resemble those in larger scale systems and adopt topologies related to constant curvature structures. The hydrophobic-to-total volume ratio, a molecular parameter, can be used to predict which type of constant curvature structure is adopted. In the case of three coordinate extended solids, constant curvature plays a role both in the extended net topology and in the hydrophobic-to-hydrophilic interface. 相似文献
997.
998.
Advances in Manufacturing Boron Carbide-Aluminum Composites 总被引:2,自引:0,他引:2
An infiltration method for preparing a boron carbide-aluminum (B4 C-AI) composite was modified so as to reduce the processing temperature and time. Titanium metal and titanium-based compounds were added to B4 C powders to enhance the wettability of the liquid aluminum on boron carbide skeletons. As expected, the time required for infiltration was significantly reduced on using the additives. Of these additives titanium metal was the most effective in facilitating aluminum infiltration. Another method, involving the heat treatment of boron carbide compacts at 1300°3C for 1 h before infiltration, was attempted, and a significant improvement was gained. These findings show that the treatment modified the surface condition of boron carbide powders via the removal of oxides. An additional attempt was made to increase the boron carbide content of the system by using a bimodal powder mixture. A maximum green density of 78% was achieved by mixing fine particle size and coarse particle size powders. The infiltrated boron carbide composites prepared using a bimodal powder with a preinfiltration heat treatment of the compacts exhibited promising mechanical properties, such as a Vickers hardness ( H V ) of 11 Gpa and an indentation toughness ( K IC ) in the range of 5–7.5 MPa·m1/2 . 相似文献
999.
This work investigates the electric field effect on nitrogen oxide (NO) pollutant formation and emission composition of premixed flames in order to provide better insight on the mechanism of controlling the combustion process by electro-physical means. The present study aims to investigate experimentally the effect of radial DC electric field on premixed laminar methane flame. The electric field effect on flame shape, emission composition and NO emission index of flame is investigated experimentally under the action of direct-current electric field under varying equivalence ratio and level of oxygen enrichment. The results show that ionic wind effects cause the distortion in flame shape. The ionic wind effects diminish with increasing flow rate and level of oxygen enrichment. Minimal effects on NO are measured for flames under the influence of electric field and vanished as the level of oxygen enrichment is increased. This was well supported by the temperature profile measurement in the post flame gas showing no field-induced modification also. It seemed that the action of an electric field on a flame with a geometry that remains practically undeformed produces very minimal effect on pollutant emission. 相似文献
1000.
Chanho Pak Seung Jae Lee Seol-Ah Lee Hyuk Chang 《Korean Journal of Chemical Engineering》2005,22(2):214-218
To reduce the effect of methanol permeated from the anode, the structure of the cathode was modified from a single layer with
Pt black catalyst to two-layer with PtRh black and Pt black catalysts, respectively. The current density of the direct methanol
fuel cell (DMFC) using the two-layer cathode was improved to 228 mA/cm-2 compared to that (180 mA/cm-2) of the DMFC using the single layer cathode at 0.3 V and 303 K. From the cyclic voltammograms (CVs), it is indicated that
the amount of adsorbates on the metal catalyst in the two-layer cathode is less than that of adsorbates in the single layer
cathode after methanol test. In addition, the adsorbates were removed very rapidly by electrochemical oxidation from the two-layer
cathode. It is suggested fromex situ X-ray absorption near edge structure analysis that the d-electron vacancy of Pt atom in the two-layer cathode is not changed
by the methanol test. Thus, Pt is not covered with the adsorbates, which agrees well with the results of CV. 相似文献