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151.
The predictive accuracy for estimating infinite dilution activity coefficients by a modification of the UNIFAC method wherein the group interaction parameters were based on only data (referred to as -based UNIFAC) has been studied. Estimates and measured values were compared for six prototypical solutes in a series of homologous n-alkanes, l-alcohols and alkanenitrile solvents. Despite the fact that the interaction parameters were derived using only data, this approach still gave serious errors due to several inherent problems in the original UNIFAC model. Its performance is sometimes even poorer than that of the original UNIFAC method. For example for nitromethane in alcohols and p-dioxane in nitriles values predicted by the -based UNIFAC are essentially zero. The large errors for these systems are most likely due to inaccurate interaction parameters in the -based UNIFAC method. 相似文献
152.
R. M. Zolotar' A. I. Bykhovets S. K. Ananich N. V. Kovganko 《Chemistry of Natural Compounds》2002,38(2):164-166
The toxicity of steroid benzoates 4-10 for Colorado beetle (Leptinotarsa decemlineata Say.) larvae was studied by a contact-intestinal method. The most active growth and development regulator for this insect is 3-benzoyloxy-5-hydroxy-7-6-ketosteroid 9a. 相似文献
153.
5,7,8位取代的喹诺酮类化合物定量构效关系的量子化学研究 总被引:2,自引:0,他引:2
5,7,8位取代的喹诺酮类化合物定量构效关系的量子化学研究俞庆森,朱龙观,林瑞森,蔡国强(浙江大学化学系杭州310027)关键词:氟喹喏酮类,定量构效关系,CNDO/2氟喹诺酮类是一类重要的抗感染化疗药物 ̄[1],近十年对其研究进展神速 ̄[2],结构... 相似文献
154.
Physicochemical and catalytic properties of phosphorus and boron modified HZSM-5 zeolites treated with 100% steam at 673K were investigated.The acidity and distribution of acidic sites were studied by infrared spectroscopy using pyridine as probe molecule and temperature programmed desortion (TPD) of ammonia.The structure of the samples was characterized by XRD,and the textural properties of the catalysts were determined by nitrogen isothermal adsorption-desorption measurements and scanning electron microscopy(SEM).The XRD results show that the modified samples have no novel crystalline phase,indicating a high dispersion of phosphorus and boron species.After treatment,the microporous volume and surface area of the samples markedly decrease,implying the bolockage of the channel.The nitrogen adsorption-desorption measurements suggest that the isothermal type of all samples is a combination of isothermal type Ⅰ and Ⅳ,and all hysteresis loops resemble the H4-type in the IUPAC classification.The total acidity of the modified samples,determined by pyrldine adsorption IR and TPD of ammonia,decreases in contrast to that of the parent HZSM-5.The conversion of n-heptane over P and B steammodified HZSM-5 is higher than that of P and B-modified HZSM-5 zeolites but lower than that of the parent HZSM-5. 相似文献
155.
以共沉淀法合成了硅铝系载体(AS和SA),并采用改性天然高铝石为原料合成了矿物质载体(MC-1和MC-2),采用浸渍法合成了镍负载型催化剂。用常压固定床管式反应器,考察了液化石油气水蒸气重整反应活性,通过XRD、物理吸附等手段对催化剂进行了表征。结果表明,以MC-1、MC-2和SA、AS为载体的催化剂的水蒸气重整活性明显高于目前普遍使用的Ni/α-Al2O3催化剂。以SA为载体,负载5%镍的催化剂具有最好的水蒸气重整活性。在750 ℃,水碳比为2.0的条件下转化率达100%,C1选择性达94.46%。XRD分析结果表明1 300 ℃焙烧后的SA载体中存在α-Al2O3晶型和莫来石结构。硅、铝添加次序对水蒸气重整活性影响较大,硅-铝添加次序的催化剂样品的活性高于铝-硅添加次序的样品,C1选择性提高12.7%。 相似文献
156.
157.
158.
An ionic liquid-type carbon paste electrode and its polyoxometalate-modified properties 总被引:1,自引:0,他引:1
Hongtao Liu Ping He Zhiying Li Chunyan Sun Lihong Shi Yang Liu Guoyi Zhu Jinghong Li 《Electrochemistry communications》2005,7(12):1357-1363
The replacement of a non-conductive organic binder with a conductive room temperature ionic liquid in fabricating carbon paste electrode has been made. This new electrode due to its enhanced conductivity presented very large current response from electroactive substrates. The novel carbon paste electrode was bulk-modified via the uniform dispersion of Keggin-type phospho polyoxomolybdate (PMo12) in bulky carbons, which possessed excellent electrocatalytic activity for the reduction of nitrite. The pronounced multi-electron catalytic ability was ascribed to the used hydrophobic ionic liquid which constructed an excellent charge-transfer bridge in the bulk of carbon paste electrode, thus facilitated the intake of electrons from reduced PMo12 mediators. In view of their prominent properties, the carbon paste electrode using ionic liquid binder and its bulk-modified electrode take on good prospects of the application in physical chemistry and electroanalytical chemistry fields. 相似文献
159.
Mohamed El Guendouzi Abderrahim Dinane Abdelfetah Mounir 《Journal of solution chemistry》2002,31(2):119-129
The mixed aqueous electrolyte system of ammonium and lithium chlorides has been studied by the hygrometric method at 25°C. The relative humidities of this system are measured at total molalities from 0.3 to 6 mol-kg– 1 for different ionic-strength fractions y of NH4Cl with y = 0.33, 0.50, and 0.67. The data obtained allow the deduction of new water activities and osmotic coefficients. The experimental results are compared with the predictions of the ECA (extended composed additivity) law proposed in our previous work. The Zdanovskii–Stokes–Robinson (ZSR), the Robinson–Stokes (RS), Reilly–Wood–Robinson (RWR), the Pitzer, and the Lietzke–Stoughton (LS II) models are also compared with our results. Predictions made using these models are, in general, consistent with our results. From these measurements, new Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture for different ionic-strength fractions. 相似文献
160.
从唇形科植物铁轴草中分离得去甲克罗烷二萜化合物Teucvidin,通过催化氢化、酯交换、水解等反应合成了8个衍生物,用^1HNMR、MS和IR确定了其结构,初步生物活性测定结果表明,化合物Ⅱ和Ⅳa的拒食作用显著。 相似文献