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991.
Stefan?DiethelmEmail author Joseph?Sfeir Frank?Clemens Jan?Van herle Daniel?Favrat 《Journal of Solid State Electrochemistry》2004,8(9):611-617
Dense planar and tubular oxygen separation membranes of La0.6Ca0.4Fe0.75Co0.25O3– were investigated as reactors for the partial oxidation (POX) of methane to syngas. Their permeation properties were measured in an air/argon
pO2 gradient as a function of temperature. At 900 °C, the oxygen flux through a 1.26-mm-thick membrane was 0.075 mol/cm2·s and through a 0.25-mm-thick tube, 0.24 mol/cm2·s.For the POX measurements, a catalyst was added to the membrane and methane was introduced on the argon side. This resulted in a gradual increase of the oxygen flux with increasing concentration of methane, reaching 2 mol/cm2·s at 900 °C with pure methane. For the planar reactor, the CO selectivity reached 99% and the CH4 conversion 75% at 918 °C with pure methane. For the tubular reactor, the CO selectivity and CH4 conversion were 83 and 99%, respectively, under the same conditions. After 1,400 h of operation in a tubular POX reactor, the membrane was examined revealing phase demixing and local decomposition.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003 相似文献
992.
The synthesis of a novel class of functionalized benzophanes in which a (2′-hydroxy)ethoxy pendant arm is attached to the phenyl ring is reported. The reported approach, utilizes simple starting materials, and skillful organization of the synthetic steps allows for simultaneous transforms of the macrocyclic ring and the pendant arm. Binding studies of these systems with Pd2+ and Cd2+ cations is described. A chromatographic stationary phase containing the benzodiazacoronand moiety was also synthesized, and found to interact specifically with isomeric nitrobenzene derivatives. 相似文献
993.
Rafa? Bogel-?ukasik 《Monatshefte für Chemie / Chemical Monthly》2007,2(3):1137-1144
Secondary chiral alcohols are very attractive intermediates in organic synthesis of pharmaceutical and the fine-chemical industries.
The processes employing ionic liquids to obtain enantiomers of secondary alcohols have become sustainable. Furthermore, physico-chemical
properties of ionic liquids opened new possibilities to design “solvent free” processes for the resolution of racemic secondary
alcohols. This review is aimed to highlight some of the most important achievements in resolution of secondary alcohols. 相似文献
994.
Organic and inorganic anions are analyzed using capillary zone electrophoresis with indirect fluorescence detection. As electrolyte 2,5-dihydroxybenzoic acid is used. By adding Pb2+ to the electrolyte the migration time of SO4(2-) can be selectively influenced and the separation of Cl- and SO4(2-) considerably improved. The fluorescence intensity of 2,5-dihydroxybenzoic acid increases in the presence of Pb2+ up to a concentration of 6*10(-4) mol/L Pb2+. Limits of detection in the lower mumol/L range were obtained. 相似文献
995.
The Raman and 1H NMR-spectra of mixtures of 2-cyclopentenone and 2cyclohexenone with 1-hexyne show that the enone-alkyne association in the ground state is weak and cannot account for the difference in the regioselectivity observed in photocycloadditions of enones to alkynes and alkenes. The comparison of dipole moments and the calculation of π-electronic charges on the interacting orbitals of both enone and substrate lead to the conclusion that the regioselectivity of enone-alkyne photoannelation may be controlled by the dipole-dipole interactions between the 3(π, π*) state of the enone and the ground state of the substrate. This effect is the stronger, the weaker are π-donating capacity and polarization of the multiple bond in the substrate. 相似文献
996.
J. Monaselidze Ya. Kalandadze D. Khachidze 《Journal of Thermal Analysis and Calorimetry》1996,46(2):431-440
The influence of mitoxantron (M) and benz(a)pyrene (BP) on chromatin DNA in composition of spleen and liver tissues and cells of BALB/c mice were studied using a high-sensitive differential scanning microcalorimeter. It was established that BP can cause a) the specific breaks in inactive chromatin DNA chain and unfolding of the whole domain (a loop of chromatin) which should lead to uncontrolled genome activation; b) the breaks in the DNA double-helix creating short duplexes.M at low doses, interacting with naked linker DNA of tumor restores the chromatin structure, at high doses or at repeated injections,M causes the disturbance of chromatin structure. 相似文献
997.
U. Baltaev M. B. Gorovits Ya. V. Rashkes N. K. Abubakirov 《Chemistry of Natural Compounds》1979,14(4):393-395
Summary A new phytoecdysone has been isolated from the flower heads ofRhaponticum integrifolium, and for it the structure of 24(28)-dehydromakisterone A has been established.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 463–465, July–August, 1978. 相似文献
998.
O. S. Chizhov B. A. Dmitriev B. M. Zolotarev A. Ya. Chernyak N. K. Kochetov 《Journal of mass spectrometry : JMS》1969,2(10):947-952
The trifluoroacetyl derivatives of alditols are convenient compounds for mass spectrometric investigation as they are easily obtainable and highly volatile. They show simple fragmentation patterns with intensive peaks in the high mass range. Trifluoroacetates of alditols may be used for detection and location of deoxy groups in the molecule. 相似文献
999.
Yu. A. Mikheev L. N. Guseva E. Ya. Davydov Yu. A. Ershov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(12):1897-1913
A model of the hydration of hydrophobic substances in water is suggested. The models of fluctuation formation of empty cavities in water as a stage of hydration extensively used in the literature were shown to be at variance with experiment. The fundamental role played by the interphase boundary surface was emphasized. On this surface, the successive addition of water molecules with the formation of capsules around hydrophobic molecules occurred. The physical meaning of the Ostwald equation was revealed. This equation characterized the distribution of hydrophobic volatile substances between the gas and aqueous phases. The method of optical probes (hydrophobic aromatic molecules) was used to reveal the synergistic character of autocorrelation of dispersion interactions between water and hydrophobic substance molecules. This synergism was at variance with the Lennard-Jones potential. The synergism (superadditivity) of dispersion attraction forces, which strengthened their directional character, caused the self-organization and enhanced stability of hydration capsules with encapsulated hydrophobic molecules. Computer models were used to show that the spatially directional character of dispersion interactions necessary for the self-organization of hydrated aggregates could be simulated by the molecular mechanics method on the basis of orientational correlation of water molecules and hydrophobic substances in the starting system. 相似文献
1000.
Enn?LustEmail author Alar?J?nes Tanel?P?rn Priit?Nigu 《Journal of Solid State Electrochemistry》2004,8(4):224-237
Electrochemical characteristics for the nanoporous carbon|Et4NBF4+acetonitrile interface have been studied by cyclic voltammetry and impedance spectroscopy methods. The influence of the electrolyte concentration and thickness of the nanoporous electrode material on the shape of the cyclic voltammetry and impedance curves has been established and the reasons for these phenomena are discussed. A value of zero charge potential, depending slightly on the structure and concentration of the electrolyte, the region of ideal polarizability and other characteristics have been established. The nanoporous nature of the carbon electrodes introduces a distribution of resistive and capacitive elements, giving rise to complicated electrochemical behaviour. Analysis of the complex plane plots shows that the nanoporous carbon|Et4NBF4+acetonitrile electrolyte interface can be simulated by an equivalent circuit, in which two parallel conduction paths in the solid and liquid phases are interconnected by the double-layer capacitance in parallel with the complex admittance of the hindered reaction of the charge transfer or of the partial charge transfer (i.e. adsorption stage limited) process. The values of the characteristic frequency depend on the electrolyte concentration and electrode potential, i.e. on the nature of the ions adsorbed at the surface of the nanoporous carbon electrode. The value of the solid state phase resistance established is independent of the thickness of the electrode material. 相似文献