复合催化剂NdPW12O40/TiO2的制备、表征及光催化性能

 采用溶胶-凝胶法制备了NdPW12O40/TiO2复合催化剂,并用热重-差热分析、红外光谱、紫外-可见漫反射光谱、荧光发射光谱、扫描电镜和X射线衍射对催化剂进行了表征. 在紫外光照射下,以有机污染物丙酮和甲醇的气相光催化消除为模型反应,考察了催化剂的光催化活性. 结果表明, NdPW12O40的掺杂使TiO2纳米晶粒细化(粒径为11～14 nm), 表面积增大,同时有效抑制了TiO2粒子的团聚. 0.1 g 1%NdPW12O40/TiO2光催化消除初始浓度为6.58 g/m3的丙酮,空时为2.4 s时消除率可达96.74%, 达到排放要求; 催化消除初始浓度为8.82 g/m3的甲醇,空时为2.0 s时消除率可达100%, 实现完全矿化. 与纯的TiO2相比,复合催化剂吸收光的能力增强,吸收带边向长波方向延伸了20 nm.     

气相色谱法测定胰酶中的丙酮溶剂残留量

采用气相色谱测定了胰酶中残留的丙酮溶剂,并通过外标法定量分析其含量。气相色谱条件为:氢火焰离子化检测器(FID),DMF作为溶剂,DM-WAX色谱柱(30 m×0.53 mm×1μm),载气为氮气,进样口温度为200℃,检测器温度为300℃,柱温采取程序升温。气相色谱法检测丙酮的加标回收率为92.5%～98.0%,检出限(3S/D)为0.05μg/mL。     

A detailed analysis of volatile constituents of <Emphasis Type="Italic">Aquilegia pancicii</Emphasis> Degen,a Serbian steno-endemic species

Chemical composition of the essential oil of Aquilegia pancicii Degen endemic to Serbia is reported. Essential oil obtained by hydrodistillation from the aerial parts was analyzed by GC and GC/MS. The major constituents were hexadecanoic acid (24.3 %) and hexahydrofarnesyl acetone (14.1 %), among 130 identified compounds, representing 90.3 % of the total essential oil. The oil was marked by the presence of 69 fatty acid derivatives and low content of terpenoids representing 60.4 % and 7.8 % of the oil, respectively.     

Conductance of electrolytes in dipolar aprotic solvent mixtures. I. Conductance of lithium chloride in mixtures of methylethylketone and acetone with N,N-dimethylformamide at 25°C

The conductances of LiCl in acetone-N,N-dimethylformamide (AC-DMF) and methylethylketone-N,N-dimethylformamide (MEK-DMF) binary mixtures have been measured at 25°C. The data were fitted to the 1978 Fuoss equation to obtain ion association constants K_A and limiting molar conductances ₀. The Bjerrum ion association theory modified by Fernandez-Prini and Prue was also used for evaluation of K_A and a, the contact ion-pair distance. LiCl is more associated in AC-DMF mixtures than in the MEK-DMF system. Addition of DMF to either AC or MEK decreases K_A and ₀ as expected from the increase in the dielectric constant and the viscosity. The distance parameter a is almost constant and equal to 2.6 A in these mixed solvent systems. The Walden products pass through minima in both ketone-rich regions.     

Synthesis and structures of triphenylantimony oximates

The reactions of triphenylantimony or trimethylantimony with tert-butyl hydroperoxide in the presence of acetone oxime, acetophenone oxime, cyclohexanone oxime, or benzaldehyde oxime afforded monomeric triorganoantimony oximates Ph₃Sb(ON=CMe₂)₂, Ph₃Sb(ON=CMePh)₂, Ph₃Sb[ON=C(CH₂)₅]₂, Ph₃Sb(ON=CHPh)₂, and Me₃Sb(ON=CMe₂)₂ in 87—96% yields. X-ray diffraction analysis demonstrated that Ph₃Sb(ON=CMe₂)₂ and Ph₃Sb(ON=CHPh)₂ have trigonal-bipyramidal structures. An analogous reaction with dimethylglyoxime gave rise to polymeric triphenylantimony dioximate in 96% yield. The reaction with butane-2,3-dione monoxime yielded chelate cyclic bis(triphenylantimony) oxides.     

Chemistry of 2-methylene-2,3-dihydro-3-furanones

[3+2]-Cycloaddition of 2-methoxycarbonylmethylene-5-phenyl-2,3-dihydro-3-furanone to acetone azine has been studied. This results in a monospirocycloadduct,viz., 9,9-dimethyl-6-methoxycarbonyl-2-phenyl-1-oxa-7,8-diazaspiro[4.4]nona-2,6-dien-4-one. Its structure has been confirmed by X-ray diffraction analysis.For the previous communication see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 306–308, February, 1994.     

Physicochemical Characterization and Catalytic Properties of Titania Gel Doped with Lithium and Rubidium

The effect on titania of doping with lithium and rubidium titania gels has been studied in samples prepared with titanium (IV) tetra-n-butoxide co-gelling with the alkaline metal precursors. Titania and doped titania were characterized by X-Ray diffraction, which showed that the catalysts were nanostructured. In samples calcined at 400°C, the crystallite size of the anatase phase was 17 and 14 nm, and 78 and 38 nm for samples calcined at 600°C, for Li/TiO₂ and Rb/TiO₂, respectively. The specific surface areas of doped samples (400°C) are lower in Li/TiO₂ (90 m²/g) than in Rb/TiO₂(125 m²/g). Evaluation of their basic properties has been carried out in the acetone condensation reaction. It was found that the activity strongly depended on the Li and Rb ionic radii.     

Voltammetric response and electrochemical properties of the O2/O 2 •− couple in acetone

Voltammetric responses of the O₂/O ₂ ^•− couple as a function of aprotic solvents are investigated. The results show that acetone is a suitable solvent for examining the electrode reaction of the O₂/O ₂ ^•− couple. Studying the electrochemical behavior of the O₂/O ₂ ^•− couple at different electrodes in acetone by cyclic voltammetry suggests that the reversibility of the O₂/O ₂ ^•− couple and the redox peak currents at glassy carbon are better than those at gold and platinum. The kinetic parameters (electron transfer rate constant k ₀ and cathodic transfer coefficient α) of the oxygen reduction to superoxide ion (O ₂ ^•− ) are evaluated using normal-pulse voltammetry. The obtained values of k ₀ (cm/s) and α are (1.95 ± 0.05) × 10⁻⁴ and 0.34 ± 0.01, respectively. The scavenging activities of ascorbic acid and bilirubin are tested and the experimental results confirm that ascorbic acid is a better scavenger toward O ₂ ^•− . Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 2, pp. 188–194. The text was submitted by the authors in English.     

Dielectric properties of mixtures of acetylene tetrachloride with toluene and acetone

Relative permittivities are reported for binary liquid mixtures of acetylene tetrachloride (ATC) with toluene and acetone at 35°C. Measurements of refractive indices have also been made for the mixtures. The values of the quantity , the deviations of the relative permittivities of these mixtures from ideality, have been calculated. The negative values of obtained for ATC+ toluene mixtures may be explained as being due to a decrease in the degree of alignment of the molecular dipoles with changing composition of the mixture, whereas the positive values of obtained for ATC+acetone mixtures are attributed to the formation of molecular complex between acetone and CHCl₂CHCl₂. The values of the Kirkwood correlation parameter g for both sets of mixtures have been calculated using the relative permittivity data.     

Theoretical Analysis and Experimental Study of the Spatial Structure and Isomerism of Acetone Azine and Its Cyclization to 3,5,5-Trimethyl-4,5-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrazole

An ab initio (RHF/6-31G*and MP2/6-31G*) study has been undertaken to investigate the spatial structure and relative stability of the acyclic isomers of acetone azine (acetone N-(1-methylethylidene) hydrazone (CH₃)₂C=N-N=C(CH₃)₂), differing in the position of multiple bonds, and of the cyclic isomer 3,5,5-trimethyl-4,5-dihydro-1H-pyrazole. In the series of structures under study, the latter possesses the greatest thermodynamic stability so that formation of acyclic isomers such as 1-isopropenyl-2-isopropyldiazene, acetone N-isopropenylhydrazone, and 1,2-diisopropenylhydrazine from acetone azine is thermodynamically unfavorable. For each structure, stable conformations have been found, and the internal rotation barriers of molecules relative to the N-N, C-N, and C-C single bonds have been estimated. The noncoplanar goshconformer of acetone azine was found to possess the greatest thermodynamic stability. The acetone azine molecule is considered in comparison with model hydrazine, butadiene, and vinylamine molecules. Acetone azine is conformationally preferable not only because of steric factors, but also due to the interaction of the lone electron pair (LEP) of nitrogen atoms with adjacent N=C multiple bonds.Original Russian Text Copyright © 2004 by V. B. Kobychev, N. M. Vitkovskaya, N. V. Pavlova, E. Yu. Schmidt, and B. A. Trofimov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 792–799, September–October, 2004.