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《Petroleum Science and Technology》2013,31(5-6):647-664
Abstract Typically, when ultraviolet and visible absorbance of asphaltenes is employed to measure asphaltene concentration, linear calibrations of absorbance vs. asphaltene concentration are prepared from a sample of asphaltenes in a given solvent. This calibration is shown to be sensitive to: (a) the inorganic solids content of the asphaltenes; (b) physical–chemical differences between asphaltenes from different sources or extracted with different methods; and (c) selective adsorption of asphaltenes on liquid–liquid or solid–liquid interfaces. Calibration constants were determined at wavelengths of 288 and 800 nm for samples of Athabasca and Cold Lake asphaltenes obtained using different extraction methods, from precipitation experiments, and from adsorption experiments on water-in-hydrocarbon emulsions and on powdered metals. It was found that the inorganic solids content did not affect absorbance but the asphaltene concentrations must be corrected to a solids-free basis for accurate results. Calibration constants were found to correlate to the average associated molar masses of the asphaltenes. Therefore, any change in molar mass of asphaltenes during the course of an experiment may change the calibration constant. Partial precipitation and the selective adsorption of asphaltenes can lead to a change in the molar mass of asphaltenes left in solution. The corresponding change in the calibration constants can lead to errors of 5–25% in the estimated concentration. 相似文献
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通过设定不同温度、光强度、光波长、时间对大豆油进行脱色试验,对大豆油的过氧化值、酸价及色泽进行了测定,研究分析了大豆油过氧化值、酸价及色泽随温度、光强度、光波长及照射时间变化的基本规律.通过单因素及正交试验,VIS-450光照脱色的最优工艺条件:光通量2400 lm,温度35℃,时间3h,脱色率为53.2%.UV-365光照脱色的最优工艺条件:光通量2 400 lm,温度35℃,时间2h,脱色率为42.4%.结果表明:UV-365比VIS-450对大豆油品质劣变影响较大;VIS-450比UV-365对大豆油脱色率影响较大. 相似文献
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针对CdS(CdSe)等半导体纳米粒子制备过程中使用的有机溶剂难回收、成本高、难以实现工业化等问题,以油酸钠为稳定剂,乙醇为溶剂,乙酸镉和硫脲(或硒氢化钠)为前驱物,制备了CdS和CdSe纳米粒子.采用紫外-可见吸收光谱、荧光光谱、广角x射线衍射和透射电子显微分析等方法,对CdS和CdSe纳米粒子的光学性质、晶体结构、形貌及尺寸等进行了表征.结果表明,当以油酸钠为稳定剂,乙醇为溶剂时,通过控制一定的前驱物浓度、反应温度和反应时间,在温和的反应条件下,可以得到尺寸分布均匀的CdS和CdSe纳米粒子,从而为在环境友好条件下合成CdS和CdSe半导体纳米粒子提供了一种新途径. 相似文献
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《国际聚合物材料杂志》2012,61(9):785-798
Electrocopolymerization of N-methylpyrrole (NMePy) and Carbazole (Cz) was conducted in acetonitrile. Oxidative chemical random copolymerization of NMePy and Cz was also realized by Cerium (IV) ammonium nitrate (CAN) for comparison. The properties of the resulting copolymers were investigated by spectroscopic methods (UV-VIS, FT-IR), cyclic voltammetry and four point probe conductometer, to understand the oligomeric pyrrole ring interaction with carbazole ring where the reactive nitrogen of pyrrole ring was capped (substituted) by methyl group. 相似文献
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Zirconium silicalite-1 (ZS-1) catalysts with MFI structure were prepared using a hydrothermal synthesis method. XRD, SEM, IR,29Si MAS NMR, UV-VIS DRS, physical adsorption of nitrogen, and elemental analysis were then performed to evaluate its physico-chemical properties, and evidences of Zr4+ incorporation into the zeolite framework were provided : The unit cell volume of zirconium silicalite-1 increased linearly with increases in zirconium content, and the characteristic framework i.r. spectra shifted to lower frequencies as Zr4+ was incorporated into the silicalite-1 lattice. For its catalytic reaction test, liquid phase 2-butanol oxidation using hydrogen peroxide as an oxidant was carried out. All of the zirconium silicalite-1 samples synthesized were active for the 2-butanol oxidation, but activities obtained using ZS-1 catalysts were lower than TS-1 catalyst. Zirconium in the zeolite frameworkwas found to be the active site for the 2-butanol oxidation. 相似文献
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A series of yellow to greenish-blue aziridinyl azo dyes and their azo precursors containing a thienyl coupling moiety has been prepared from 2-aminothiophenes. The 2-aminothiophenes were readily obtained by using the Gewald reaction. It was found that cyclisation of the precursor dyes to the corresponding aziridinoazo dyes brought about bathochromic shifts in absorption maxima. Further spectral comparisons with N-phenylazo dyes derived from other terminal cyclic groups, such as four-, five-, six-, seven- and eight-membered rings, showed that the N-thienylaziridinoazo dyes are relatively bathochromic. From the viewpoint of solvatochromism, a clear contrast existed between λmax values in different solvents; thus, a positive solvatochromism was observed in aprotic solvents, whereas a hypsochromic shift was brought about in polar protic solvents. PPP–MO calculations provided reliable predictions of absorption maxima for the various aziridinyl azo dyes and their precursor dyes. 相似文献
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通过对白色条带的浅粉红色翡翠进行X射线荧光(XRF)光谱、拉曼光谱和紫外-可见光(UV-VIS)吸收光谱的测试分析,得出其属于硬玉型翡翠,特征拉曼位移有377,700和1039 cm-1,分别是由S-iO的不对称弯曲振动、对称弯曲振动和对称伸缩振动引起的;粉色调的产生与硬玉晶体结构中[MO6]八面体中心位置的Mn3+有关,产生的吸收峰值位于520 nm宽吸收带;浅粉红色翡翠中还可能存在着微量的致色离子Fe3+,Mn2+和Cr3+,并对它们产生的吸收峰也进行了指派。 相似文献