Catalysts for the determination of oxygen in organic compounds

Summary Thermal decomposition of metal-organic complexes of nickel, cobalt and iron has given catalysts which are very effective at about 900° for the conversion of carbon dioxide, water and other oxygencontaining sample decomposition products to carbon monoxide in the direct determination of oxygen in organic compounds when using a modified Unterzaucher type apparatus. A copper catalyst similarly prepared required a temperature of 1030° whereas a manganese complex decomposition product was ineffective.

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Katalysatoren zur Sauerstoffbestimmung in organischen Substanzen

Zusammenfassung Durch thermische Zersetzung metallorganischer Komplexe von Ni, Co und Fe erhält man Katalysatoren, die die Umwandlung von CO₂, H₂O und anderen sauerstoffhältigen Zerfallsprodukten zu CO bei etwa 900° C bei der direkten Sauerstoffbestimmung in einer modifizierten Unterzaucher-Apparatur sehr wirksam fördern. Ein ähnlich hergestellter Cu-Katalysator erfordert 1030° C und das Zersetzungsprodukt eines Mn-Komplexes ist unwirksam.

     

利用高炉水淬渣制备(Ca/Y)-α-Sialon陶瓷的组织与性能

以高炉水淬渣合成的Ca-α-Sialon粉体为原料采用无压烧结技术制备了（Ca/Y）-α-Sialon陶瓷。通过用排水法、三点弯曲实验法、金相显微镜法、XRD法等手段研究了（Ca/Y）-α-Sialon陶瓷的烧结致密化过程、材料的力学性能、显微组织、相组成和材料的断裂特征。结果表明,适量的Y2O3促进材料的烧结致密化和提高材料的力学性能,但Y2O3过量（大于10%）时对材料的烧结和力学性能不利。掺杂Y^3＋的（Ca/Y）-α-Sialon呈柱状晶,随着Y2O3含量的增加和烧结温度的提高,（Ca/Y）-α-Sialon呈柱状晶出现粗化和等轴化。含10%Y2O3的材料在1700℃烧结时可获得较高的力学性能。     

硅胶担载四核羰基钴催化剂的EXAFS和IR研究

本文以透射法EXAFS和IR等手段研究了四核羰基钴金属簇Co_4(CO)_(10)(PPh)_2担载在SiO_2上以后及用于烯烃醛化反应前后的变化,确定了相应的结构参数并探讨了催化活性与结构的关系。     

Theoretical study of the local structure and Raman spectra of CaO-SiO2 binary melts

A procedure for the Raman spectra calculation of vitreous and molten silicates was presented in this paper. It includes molecular dynamics MD simulation for the generation of equilibrium configurations, Wilson's GF matrix method for the calculations of eigenfrequencies and corresponding vectors, electro-optical parameters method (EOPM) for the Raman intensity calculations, and the bond polarizability model (BPM) for the determination of polarizability and polarizability derivative. One of the most important characteristics of this procedure is the achievement of the partial Raman spectra of five tetrahedral units, as well as the total spectral envelope. In this paper, the calculation was carried out for the vitreous and molten calcium silicates with different compositions and at various temperatures. It is worthwhile to note that the calculation is based on statistical configurations distribution in the space and so it is not needed to artificially adjust the full width at half maximum (FWHM) of spectra. It was also tested through the good agreement of the calculated spectra with the experimental, including some regularity of spectral properties. According to the calculation, the symmetrical stretching of whole tetrahedral units, to which the stretching of Si-O(nb) bond gives the main contribution to intensity, is proven to be the dominance in the high-frequency range (800-1200 cm(-1)) and the symmetrical bending of Si-O(b)-Si, to which the stretching of Si-O(b) bond exhibits the main contribution, is the dominance in the medium-frequency range (400-700 cm(-1)). As the first theoretical results, the Raman scattering coefficient of each Q(i) was found little change along with the variation of composition and temperature.     

Monodisperse chloromethyl-functionalized macroporous polymer particles by seeded polymerization in aqueous media

This study presents a method to produce monodisperse chloromethyl-functionalized macroporous poly(styrene-co-divinylbenzene) polymer particles by seeded polymerization in aqueous media. We observed that the molecular structure of polystyrene seed particles, the composition of the secondary monomer mixtures, and the type of solvents were very important factors that determine the morphology and porosity of the final particles. This study proposes that the molecular chemistry of polystyrene seed polymers, increasing molecular weight or crosslinking, is another factor that can control the porosity of the final particles. Also, the selection of a poor solvent was effective in forming the larger surface area. In this study, it was confirmed that the chloromethyl groups introduced on the surface of porous particles were quantified chemically and their effective incorporation had a close relationship with the surface area.     

Nonlinear electrokinetics and "superfast" electrophoresis

Nonlinear and nonequilibrium electrophoresis of spherical particles of radius a is shown to be possible when the solid surface allows field or current penetration. At low particle Peclet numbers, transient capacitative charging occurs until the surface polarization completely screens the external field. For a DC applied field [see text], the resulting electrokinetic velocity reaches Dukhin's maximum value of [formula: see text], where [see text] and mu are the liquid permittivity and viscosity. At high Peclet numbers, electroosmotic convection of the electroneutral bulk stops the transient charging before complete field-line exclusion. For an ion-selective and conducting spherical granule, the polarization is then determined by the steady-state Ohmic current driven by the penetrated external field. The high-Peclet electrokinetic velocity is lower, diffusivity-dependent and scales as [see text].     

Ion-pair formation in aqueous solutions of silver nitrate: A Raman and infrared spectral study

A detailed study of the Raman and infrared spectral line shapes and line parameters of aqueous solutions (both H₂O and D₂O) of AgNO₃ is interpreted in terms of an equilibrium between “free” ions and the ion pair Ag⁺NO ₃ ^? . An association constant of 0.1M ^?1 was obtained from both the 717 cm^?1 and 1047 cm^?1 line intensities. Spectral features suggest a significant degree of covalence in the interaction. A C_s(σ_V) model with Ag⁺ above the plane of NO ₃ ^? is consistent with the data.     

Stereochemistry of the thermal isomerizations of (2S,3R-methoxymethyl-2,3-dideuterio-1-(dideuteriomethylene)cyclopropane

The (2S,3R) isomer of 2-methoxymethyl-2,3-dideuterio-1-(dideuteriomethylene)cyclopropane has been synthesized and heated at 198.8°: from the experimentally observed mol fractions of the eight isomers of 2,3,α,α,- and 2,3,3,α - tetradeuterio - 2 - methoxymethyl - 1 - methylenecyclopropane in the pyrolysis product mixture have been derived rate constants for seven distinct modes of isomerization. One-center thermal epimerizations at C(2) and C(3) and the C(2)C(3) two-center epimerization are of kinetic importance. Only two of four observable stereochemical modes for carbon [1,3] shifts are seen: there is inversion of stereochemistry at the migrating C atom, while the C(3)H trans to C(2)-CH₂OCH₃ in starting material becomes syn 4 : 1 C(α)-H in the [1,3] shift product. Stereomutation at C(2) does not occur along the reaction coordinate for [1,3] carbon shifts.     

Potential bile acid metabolites. 1. The epimeric 3ϵ,7α,12β-trihydroxy-5β-cholanic acids. Raney nickel as an epimerizing catalyst.

The epimeric 3α,7α,12β- and 3β,7α,12β-trihydroxy-5β-cholanic acids have been prepared. Under ambient hydrogenation conditions with Raney nickel as catalyst the axial 3β-ester ($\text{4b}$) is epimerized to the 3α-compound ($\text{2b}$).     

Effects of polystyrene-encapsulated magnesium hydroxide on rheological and flame-retarding properties of HIPS composites

In this study, polystyrene (PS)-encapsulated magnesium hydroxide (Mg(OH)₂) was successfully prepared by in situ polymerization of styrene on the surface of Mg(OH)₂ in a high-speed mixer. A large amount of PS chemically bonded on Mg(OH)₂ surface was confirmed by means of FT-IR, TGA and SEM. A series of composites of high impact polystyrene (HIPS) were prepared by melt blending in a co-rotating twin-screw extruder. The effects of PS-encapsulated filler on the properties of HIPS composites were studied by SEM, rheology and combustion tests (horizontal burning tests and cone calorimetry). The dispersion and adhesion patterns of PS-encapsulated Mg(OH)₂ in HIPS matrix were investigated through FT-IR and SEM. The experimental results demonstrated that comparing to the composites containing untreated filler, the rheological and flame retardant properties of those containing PS-encapsulated filler were found to be significantly improved. This improvement is mostly attributed to a better dispersion of the encapsulated filler and a strong adhesion between the filler and matrix.