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Zusammenfassung Bei röntgenographischen Untersuchungen im System GeO2-P2O5 wird eine Verbindung der Zusammensetzung 2 GeO2·P2O5 aufgefunden. Einkristallaufnahmen ergeben eine hexagonale (trigonale) Elementarzelle mita=7,998 undc=24,86 Å. Die schon beschriebene Verbindung 2 SiO2·P2O5 erweist sich als isotyp:a=7,862 undc=24,13 Å. 相似文献
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本文提出一种Gibbs-Dubem关系的变通形式。应用該式可以从已知的二元系中二个组元的活度系数之此,分别求出二个組元的活度。将該式应用于PbCl_2-SnCl_2及PbCl_2-CdCl_2系,証明这二熔盐体系对Raoult定律仅呈較小的正偏差。此外,对反应Sn+PbCl_2→Pb+SnCl_2和Cd+PbCl_2→Pb+CdCl_2的标准自由能变化(△F°)作了修正。 相似文献
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2MgO·2B2O3·MgCl2·14H2O-MgCl2-H2O体系30℃相平衡 总被引:2,自引:0,他引:2
用相平衡方法研究2MgO@2B2O3@MgCl2@14H2O在30℃不同质量分数MgCl2水溶液中的溶解转化产物及其溶解度.结果表明,该复盐在MgCl2的质量分数0~2%浓度范围,发生不同步溶解并转化为多水硼镁石(2MgO@3B2O3@15H2O);在MgCl2的质量分数2%~13.8%浓度范围,转化为柱硼镁石(MgO@B2O3@3H2O),这一结果比文献报导的该硼酸盐的形成温度低了13℃,为盐湖硼酸镁矿物柱硼镁石形成的解释提供了物理化学依据;而在MgCl2质量分数大于13.8%时,同步溶解,不发生转化.提出了溶解相转化反应机理. 相似文献
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关于过渡金属Pd,Pt对C_2H_2的吸附和氢化实验研究前人已作了不少工作,但有关Pd,Pt与C_2H_2之间成键问题的理论研究还尚不多见。为了了解Pd,Pt d轨道对炔键的活化行为和成键特性,本文以MC_2H_2(M=Pd,Pt)为模型,用赝势计算方法,对Pd,Pt与C_2H_2键的相互作用进行了研究。一、计算方法由于重原子的内层轨道对形成分子贡献很小,内层电子的相对论效应极为严重。本文采用Ps—HONDO程序,选取Hay的有效核芯势和价轨道Gaussian基组,对重原子Pd和Pt进行了价电子从头计算,对C和H进行了全电子从头算.部分地消除重原子内层电子相对论效应所引起的误差。 相似文献
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P_2O_5-V_2O_5-TiO_2(简写为P-V-Ti)对芳烃氧化有良好的催化效果.丁烷氧化催化剂P-V体系的体相和表面结构已有一些报道.但P_2O_5对V-Ti的影响文献较少报道.本文用XRD,IR,TPD和ESR考察了P-V-Ti体系. 1.试剂和催化剂:草酸、偏钒酸铵、二氧化钛均为化学纯.将V_2O_5:TiO_2=11:89(重量)样品分别按 P/V原子比为0.1,0.3,0.6,1.0,1.5和2.5制成编号为P-0.1,P-0.3,P-O.6,P-1.0,P-1.5和P-2.5的催化剂. 相似文献
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Yu. A. Ferapontov M. A. Ul’yanova T. V. Sazhneva 《Russian Journal of Inorganic Chemistry》2008,53(10):1635-1640
The decomposition kinetics of peroxide products contained in the liquid phase of the LiOH-H2O2-H2O ternary system were studied, and the applicability of the solubility method to studying this system was demonstrated for hydrogen peroxide concentrations in the liquid phase from 2 to 6 wt % and temperatures of 21–33°C. The stabilizing influence of solid Li2O2 · H2O on hydrogen peroxide decomposition was demonstrated. The temperature and concentration boundaries of existence were determined for the Li2O2 · H2O phase, whose identity was verified by chemical analysis and qualitative X-ray powder diffraction analysis. 相似文献
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Crystal structure of the title complex was determined by X-ray diffraction method. It crystallizes in space group P21/n with cell dimensions:α=10. 041(5) , b=10. 719(4) , c= 1. 5671(6) nm, β=104. 36(3)°. The structure was solved by Patterson method. The final residual factor is R=0. 050. 相似文献
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This paper presents the design, fabrication and evaluation of a micro methanol reformer complete with a heat source. The micro system consists of the steam reforming reactor of methanol, the catalytic decomposition reactor of hydrogen peroxide, and a heat exchanger between the two reactors. In the present study, catalytic decomposition of hydrogen peroxide is used as a process to supply heat to the reforming reactor. The decomposition process of hydrogen peroxide produces water vapor and oxygen as a product that can be used efficiently to operate the reformer/PEMFC system. Cu/ZnO was selected as a catalyst for methanol steam reforming and Pt for the decomposition of hydrogen peroxide. Incipient wetness method was used to load catalysts on a porous support. Catalyst loaded supports were inserted in the cavity made on the glass wafer. The performance of the methanol steam reforming system was measured at various test conditions and the optimum operation condition was sought. At the optimum condition, the hydrogen selectivity was 86.4% and the thermal efficiency was 44.8%. The product gas included 74.1% H(2), 24.5% CO(2) and 1.4% CO and the total volume production rate was 23.5 ml min(-1). This amount of hydrogen can produce 1.5 W of power on a typical PEMFC. 相似文献
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Jean-Claude Brosse Gilbert Legeay Jean-Claude Lenain Christian Pinazzi 《European Polymer Journal》1977,13(10):805-809
Radical polymerizations in alcohols, with aqueous hydrogen peroxide cleaved by heat or u.v., give one or several products, according to monomer structure and experimental conditions. Results lead to a hypothesis of local overconcentrations, some with high concentration of monomer and low concentration of hydrogen peroxide and others rich in initiator but weak in monomer. 相似文献
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The decomposition reaction of aqueous solutions of hydrogen peroxide was examined by DSC at ambient pressure, and the heat of evaporation of H2O2 was determined. The reaction parameters for the oxidation reaction of lignocellulose (wood powder) with hydrogen peroxide were also examined. The pans made from gold and alodined (pyrophosphate /fluoride treated) aluminum were unsuitable for the work due to surface catalysis, in contrast to pure aluminum which proved to be acceptable within the temperature range examined. In pans made from pure aluminum, the reaction between lignocellulose and hydrogen peroxide takes place after the latter evaporates, i.e. it represents a gas—solid reaction. 相似文献
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A technique utilizing 1H NMR spectroscopy has been developed to measure the concentration of hydrogen peroxide from 10–3 to 10 M. Hydrogen peroxide produces a peak at around 10–11 ppm, depending upon the interaction between solvent molecules and hydrogen peroxide molecules. The intensity of this peak can be monitored once every 30 s, enabling the measurement of changes in hydrogen peroxide concentration as a function of time. 1H NMR has several advantages over other techniques: (1) applicability to a broad range of solvents, (2) ability to quantify hydrogen peroxide rapidly, and (3) ability to follow reactions forming and/or consuming hydrogen peroxide as a function of time. As an example, this analytical technique has been used to measure the concentration of hydrogen peroxide as a function of time in a study of hydrogen peroxide decomposition catalyzed by iron(III) tetrakispentafluorophenyl porphyrin.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
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Yitzhak Wolanov Ovadia Lev Andrei V. Churakov Alexander G. Medvedev Vladimir M. Novotortsev Petr V. Prikhodchenko 《Tetrahedron》2010,66(27-28):5130-5133
Hydrogen peroxide is one of the most versatile oxidation reagents, still it has not fully been exploited by synthetic chemists since anhydrous (let alone pure) hydrogen peroxide requires hazardous preparation protocols. We have recently reported on the crystallization of serine and other amino acid perhydrates, thus paving the way for a new method for laboratory-scale production of anhydrous hydrogen peroxide solutions. Serine is insoluble in most organic solvents (e.g., methanol, ethyl acetate, and methyl acetate) that readily dissolve hydrogen peroxide. Moreover, since the adduct of hydrogen peroxide and serine is unstable in these organic solvents, crystalline serine perhydrate readily decomposes to give anhydrous solutions of hydrogen peroxide and crystalline precipitate of the amino acid. This procedure can then yield an anhydrous hydrogen peroxide solution in a single step. Moreover, filtration of the amino acid, and room temperature evaporation of the volatile solvent (e.g., methyl acetate), yields over 99% hydrogen peroxide. 相似文献
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A fluorometric method for the determination of hydrogen peroxide using resorufin as a substrate for peroxidase is described. Two procedures were developed for the determination of hydrogen peroxide. One involves the addition of hydrogen peroxide sample to a solution of peroxidase and resorufin in phosphate buffer, pH 6.4. Fluorescence measurements are performed before and after hydrogen peroxide addition. The within-run CVs for final concentrations of hydrogen peroxide of 200 and 40 nmol/liter were 1.7 and 7.6%, respectively, and the limit of quantitation was 9 nmol/liter. The second procedure, in which the initial reaction of hydrogen peroxide with resorufin is performed in citrate buffer at pH 4.5, and then the fluorescence is measured after the pH is adjusted to 9.2 with borate buffer, has a limit of quantitation of 4.4 nmol/liter with a within-run CV of 6.5% for a final hydrogen peroxide concentration of 20 nmol/liter. The method is linear at least up to 1 μmol/liter. 相似文献
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Václav Čuba Tomáš Gbur Viliam Múčka Martin Nikl Romana Kučerková Milan Pospíšil Ivo Jakubec 《Radiation Physics and Chemistry》2010,79(1):27-32
Zinc oxide nanoparticles were prepared by irradiation of aqueous solutions containing zinc(II) ions, propan-2-ol, polyvinyl alcohol, and hydrogen peroxide. Zinc oxide was found in solid phase either directly after irradiation, or after additional heat treatment. Various physicochemical parameters, including scintillation properties of prepared materials, were studied. After decomposition of impurities and annealing of oxygen vacancies, the samples showed intensive emission in visible spectral range and well-shaped exciton luminescence at 390–400 nm. The best scintillating properties had zinc oxide prepared from aqueous solutions containing zinc formate as initial precursor and hydrogen peroxide. Size of the crystalline particles ranged from tens to hundreds nm, depending on type of irradiated solution and post-irradiation thermal treatment. 相似文献
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Anodic dissolution of copper in glycine solution at various hydrogen peroxide concentrations was investigated. The dissolution
rate increases, reaches a maximum, and then decreases with hydrogen peroxide concentration. Anodic polarization studies and
electrochemical impedance spectroscopy (EIS) studies were carried out to determine the mechanistic pathway of anodic dissolution
of copper in glycine system at three different hydrogen peroxide concentrations: one at low hydrogen peroxide concentration
in the active dissolution region, another in the maximum dissolution region, and the third at the high hydrogen peroxide concentration
in the post-peak-dissolution region. The EIS data in complex plane plots show presence of two capacitance loops and one negative
capacitance loop. The impedance plot patterns strongly depend on the hydrogen peroxide concentration in solution. Reaction
mechanism analysis technique was employed to model the EIS data. A three-step mechanism with two intermediate adsorbates and
a parallel dissolution by catalytic mechanism simulates EIS patterns which match the experimental trends. The intermediates
are likely to be cupric and cuprous oxides. The essential features of impedance spectra at various overpotentials at three
different hydrogen peroxide concentrations are captured by the proposed mechanism. The results also show that the film present
on the copper surface in glycine and hydrogen peroxide solutions does not passivate the surface. 相似文献
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Wei Wang Yongxin Pang Simon N. B. Hodgson 《Journal of Sol-Gel Science and Technology》2011,58(1):135-141
Thermally stable mesoporous tungsten oxide films (TOFs) were prepared by surfactant templated sol–gel method using tungstic
acid as tungsten oxide source. Influence of various experimental conditions on the obtained mesostructures was investigated,
including the solvent compositions, addition of hydrogen peroxide, substrates, and aging time, heat treatment, etc. It has
been found that the addition of hydrogen peroxide has a significant influence on the flexibility of formed meso-frameworks,
and just a small amount can regenerate the degraded coating sol. TOFs were also found to crystallize on ITO coating easier
than on bare glass, indicating that the different interactions with the substrates influence the crystallinity of obtained
meso-structured TOFs. Film thickness can be adjusted by simply changing the solvent compositions while keeping mesostructures
intact. This work clarified several key parameters in delivering well-defined mesostructured TOFs from cheap, moisture-insensitive
tungstic acid precursor via the process developed. 相似文献
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Feasibility is demonstrated for a novel gas-sensing, internal enzyme biosensing scheme for the selective measurement of hydrogen peroxide. Two horseradish peroxidase catalysed reactions are evaluated for the detection of hydrogen peroxide as it crosses a microporous Teflon membrane at 37 degrees C. The rate at which hydrogen peroxide crosses the membrane is determined by either a fluorescence or chemiluminescence measurement and this rate is related to the concentration of hydrogen peroxide in the sample solution. Detection limits of 0.7 mM and 10 muM are estimated for the fluorescence and chemiluminescence methods, respectively. Selectivity is demonstrated for hydrogen peroxide over ascorbic acid, uric acid and tyrosine. 相似文献