Transformations of C<Subscript>2</Subscript>-C<Subscript>4</Subscript> alcohols on the surface of a copper catalyst

The interaction of monoatomic alcohols C₂-C₄ with the surface of a copper catalyst preliminarily oxidized under various conditions was studied by the temperature-programmed reaction method to determine the detailed mechanism of partial oxidation. The conditions of oxygen preadsorption on the surface of copper for the preparation of the desired products were determined. The selective formation of carbonyl compounds was shown to occur at the boundary between reduced and oxidized copper surface regions. The role played by Cu₂O was the deep oxidation of alcohols to CO₂. Alcohols with branched hydrocarbon structures experienced parallel partial oxidation and dehydrogenation, which was related to the high stability of intermediate keto-type compounds.     

Catalytic conversion of C<Subscript>2</Subscript>-C<Subscript>3</Subscript> alcohols on detonation nanodiamond and its modifications

The catalytic activity of detonation nanodiamond and its modifications obtained through treatment with hydrogen or air at elevated temperatures is studied in the conversion of C₂-C₃ alcohols. The catalysts were characterized by means of electron microscopy, optical (FTIR) spectroscopy, elemental analysis and pulse microcatalytic method. It has been established that nanodiamond exhibits high catalytic activity in the conversion of alcohols. The oxidizing and reducing treatment of nanodiamond changes its activity and selectivity, and the activity of oxidized nanodiamond is considerably higher than that of reduced nanodiamond.     

Conversion of C<Subscript>2</Subscript>-C<Subscript>4</Subscript> alcohols over copper-containing catalysts on carbon and fluorocarbon fibers

Carbon and fluorocarbon fibers were used as carriers for the preparation of copper catalysts from copper oxalate as precursor. The catalytic properties of catalyst were studied in the reaction of the dehydrogenation of C₂-C₄ alcohols by the pulsed microcatalytic method. The effect of the copper content in the catalyst, the reaction temperature on the degree of conversion, and the relation of the reaction channels were studied. The electron microphotographs were obtained, specific surfaces were measured, and X-ray pictures and infrared spectra of catalysts were taken. The activity of the catalysts on the carbon and fluorocarbon fibers in the dehydration-dehydrogenation reactions of C₂-C₄ alcohols was comparatively estimated. It was shown that the selectivity of the products from the dehydrogenation reaction is higher for the Cu-fluorocarbon fiber catalyst.     

Mesoporous micelle templated silica with incorporated C<Subscript>8</Subscript> and C<Subscript>18</Subscript> phase

Mesoporous silica material of MCM-41 type was synthesized by co-condensation of highly concentrated octyltriethoxysilane (OTEOS), octadecyltriethoxysilane (ODTEOS) and tetraethoxysilane (TEOS). The obtained hybrid materials were characterized using XRD, TG-DSC and low temperature adsorption/desorption of nitrogen. It was shown that the applied method of synthesis allows to obtain silica of MCM-41 type with a high degree of hydrocarbon saturation.     

Reactivity of C<Subscript>3</Subscript>-C<Subscript>8</Subscript> alkanes with nitronium ions in sulfuric acid

We have determined the parameters of the Arrhenius equation (E, log A) for reactions between \textNO₂⁺ {\text{NO}}_2^{+} ions and C₃-C₈ alkanes in HNO₃–93 wt.% H₂SO₄ solutions at 277–353 K, and we have also estimated the activation parameters E _j , log A _j for secondary and tertiary C—H bonds of these alkanes. We show that the following compensation relations are satisfied: E = 2.3R βlog A + C with isokinetic temperature β = 360 ± 65 K, and also E _j =2.3Rβ _j log A _j  + C _j , for secondary C—H bonds, β₂ =300 ± 60, and for tertiary C—H bonds, β₃ =310 ± 50.     

Gas-Chromatographic Determination of C<Subscript>1</Subscript>-C<Subscript>4</Subscript> Hydrocarbon Trace Impurities in Silicon Tetrafluoride

A procedure was developed for the gas-chromatographic determination of hydrocarbons in silicon tetrafluoride of natural and isotopically enriched compositions. For improving the efficiency of the chromatographic determination of impurities, it was proposed that the major compound be removed from the test sample with the subsequent cryofocusing of impurity hydrocarbons. The detection limits of C₁-C₄ hydrocarbons were 2 × 10^?6?6 × 10^?6 vol %.     

Determination of C<Subscript>1</Subscript>-C<Subscript>3</Subscript> carboxylic acids in air using a sensor

The adsorption of C₁-C₃ carboxylic acids on modified films of different natures and polarities is studied in exposuring piezoelectric sensors to acid vapors. The method of film fabrication and the ratio of components in the mixed films are optimized; the sensitivity and selectivity of films are calculated; piezoelectric sensors are proposed for the separate determination of acids in air; and equations for calculating their concentrations are derived.     

Distribution coefficients in the water-dodecane system and heats of adsorption of ethylene glycol monoalkyl ethers on hydrophilic and hydrophobic carriers

The distribution coefficients in the water-dodecane system and the heats of adsorption of ethylene glycol monoalkyl ethers on hydrophilic (Silochrom S-80) and hydrophobic (Apiezon L on Chromaton) carriers were determined by gas chromatography. At low concentrations and 25°C, ethers with C₁-C₄ alkyl radials predominantly occurred in the aqueous phase, whereas the amyl ether of ethylene glycol was better soluble in the organic phase. Ethers adsorbed formed monomolecular and polymolecular coatings on the hydrophobic and hydrophilic adsorbents, respectively. The heats of adsorption of ethers on the hydrophilic adsorbent were higher than the heats of adsorption on the hydrophobic adsorbent by factors of from 1.93 to 2.20.     

The structural-phase state of C<Subscript>60</Subscript>-C<Subscript>70</Subscript> fullerene mixtures

The structural and phase state of the C₆₀-C₇₀ system at various C₆₀/C₇₀ ratios in mixtures obtained by the vaporization of solutions in toluene at ∼98°C was studied by X-ray structure analysis, differential scanning calorimetry, and infrared spectroscopy. Solid solutions based on the face-centered cubic packing of C₆₀ are not formed in the C₆₀-C₇₀ system at C₇₀ contents from 0.5 to 50 wt %. The hexagonal close packing of a solid solution of C₆₀ in C₇₀ can be formed as a result of the thermally activated decomposition of the ternary crystal solvate in the C₆₀-C₇₀-C₆H₅CH₃ system. The structural state of multiphase mixtures formed under conditions far from equilibrium is characterized by a high degree of structure imperfection and greater ability to undergo oxidation compared with C₆₀ and C₇₀.     

Benzene Adsorption on C<Subscript>24</Subscript>, Si@C<Subscript>24</Subscript>, Si-Doped C<Subscript>24</Subscript>, and C<Subscript>20</Subscript> Fullerenes

The absorption feasibility of benzene molecule in the C₂₄, Si@C₂₄, Si-doped C₂₄, and C₂₀ fullerenes has been studied based on calculated electronic properties of these fullerenes using Density functional Theory (DFT). It is found that energy of benzene adsorption on C₂₄, Si@C₂₄, and Si-doped C₂₄ fullerenes were in range of –2.93 and –51.19 kJ/mol with little changes in their electronic structure. The results demonstrated that the C₂₄, Si@C₂₄, and Si-doped C₂₄ fullerenes cannot be employed as a chemical adsorbent or sensor for benzene. Silicon doping cannot significantly modify both the electronic properties and benzene adsorption energy of C₂₄ fullerene. On the other hand, C₂₀ fullerene exhibits a high sensitivity, so that the energy gap of the fullerene is changed almost 89.19% after the adsorption process. We concluded that the C₂₀ fullerene can be employed as a reliable material for benzene detection.     

Thermokinetics on the reaction of formation of Dy[(C<Subscript>5</Subscript>H<Subscript>8</Subscript>NS<Subscript>2</Subscript>)<Subscript>3</Subscript>(C<Subscript>12</Subscript>H<Subscript>8</Subscript>N<Subscript>2</Subscript>)]

The enthalpy change of formation of the reaction of hydrous dysprosium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen?H₂O) in absolute ethanol at 298.15 K has been determined as (-16.12 ± 0.05) kJ?mol^-1 by a microcalormeter. Thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), rate constant and kinetics parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of the reaction have also been calculated. The enthalpy change of the solid-phase reaction at 298.15 K has been obtained as (53.59 ± 0.29) kJ?mol^t-1 by a thermochemistry cycle. The values of the enthalpy change of formation both in liquid-phase and solid-phase reaction indicated that the complex could only be synthesized in liquid-phase reaction.     

Kinetic absorption of vapors of alkyl acetates C<Subscript>1</Subscript>-C<Subscript>4</Subscript> and diethyl ether on thin films of modified piezoelectric quartz resonators

Sorption of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and diethyl ether on thin films of esters: poly(ethylene glycol) sebacate and phthalate, dinonyl phthalate, tween-40, pentaerythritol tetrabenzoate, triphenyl phosphate, Triton X-305, and stearic acid was studied. The mass of sorbent films was optimized, the sensitivity and selectivity of modifiers toward analytes was evaluated, and the time of maximum sorption was determined.     

Phenyl- and cyclopentylimino derivatization for double bond location in unsaturated C<Subscript>37</Subscript>-C<Subscript>40</Subscript> alkenones by GC-MS

A method for the identification of double bond locations in polyunsaturated long chain alkenones adapted to nanogram amounts as currently analyzed by gas chromatography coupled to mass spectrometry (GC-MS) has been developed. The method is based on interpretation of the electron impact mass spectra of the imino derivatives of the carbonyl groups using either cyclopentyl or phenyl substitutents. Other complementary derivatization methods such as elaidization and hydrogenation have also been used for structural characterization of these compounds. This application has led to the identification of a novel homologous series of di-, tri-, and tetraunsaturated ketones with carbon number chain lengths between 37 and 40 in coastal hypersaline sediments. The novel series identified shows a distribution in which the double bond position between different homologs is established by reference to the distance from the carbonyl group whereas the previously known alkenones were constituted by unsaturated homologs with double bonds located at defined distances of the terminal methyl. This difference points out to a dissimilar, but still unknown, biogenic precursor of these novel alkenones.     

Study on the cluster of floating dross before nucleating during hot-dipping process

At present, hot-dipping anticorrosion metalliccoating on the surface of steel base is the main methodto prevent atmospheric corrosion of steel. With thechange of atmospheric environment, the traditionalidea of hot-dipping pure Zn cladding already does not…     

C<Subscript>6</Subscript> dispersion coefficients from reduced dipole pseudospectra

A recently proposed interpolation tech- nique for FDPs is extended to cover static pseudospectra of monomers as well. Reduced 4-term dipole pseudospectra are obtained for the ground states of H, He, , LiH, BeH₂, BH, giving dispersion constants from which highly accurate C₆ dispersion coefficients for all homo- and hetero-dimers are obtained by use of the generalized London formula. Contribution to the Fernando Bernardi Memorial Issue.     

Studies of C<Subscript>8</Subscript> aromatics adsorption in BaY and mordenite molecular sieves using the headspace technique

A headspace technique, that consists in analyzing the composition of the vapor phase in equilibrium with the condensed phase of a mixture in a sealed vial containing the adsorbent sample, has been recently applied to acquire equilibrium data for adsorption of xylenes in liquid phase. In this study, we used this technique to measure experimental binary equilibrium data for C₈ aromatics in Y and mordenite zeolitic molecular sieves. For the Y zeolite, we also measured C₈ aromatics quaternary equilibrium data. Measurements were made at temperatures between C 40–80 °C. A more tedious, but traditional, chromatographic pulses method was also used to validate some of the results.     

Sorption of light fullerenes C<Subscript>60</Subscript> and C<Subscript>70</Subscript> on NORIT-AZO carbon

Sorption of fullerenes C₆₀ and C₇₀ from o-xylene, toluene, and dichlorobenzene solutions on NORIT-AZO carbons was studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1638–1642.Original Russian Text Copyright © 2004 by Semenov, Seregin, Arapov, Charykov.     

Electron interactions in the (η<Superscript>2</Superscript>-C<Subscript>60</Subscript>)Pd[P(Ph<Subscript>2</Subscript>)C<Subscript>5</Subscript>H<Subscript>4</Subscript>]<Subscript>2</Subscript>Fe complex

The electronic structure of the (η²-C₆₀)Pd[P(Ph₂)C₅H₄]₂Fe complex was calculated by the “hybrid” B3LYP method. Comparison of the experimental X-ray emission C-Kα spectrum and theoretical spectrum of the compound demonstrated that the electron interactions between the C₆₀ core, palladium atom, and organometallic fragment are described correctly in the framework of the quantum chemical method used. The electronic structure of the organometallic fullerene complex can be presented as a set of blocks of orbitals corresponding to different types of chemical bond. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2640–2644, December, 2005.     

Protein separation on a polar-copolymerized C<Subscript>8</Subscript> stationary phase

A novel polar-copolymerized C₈ stationary phase composed of octyl and chloropropyl (C₈-C₃Cl)-bonded silica has been developed for protein separation. Separation of standard proteins on this homemade column was investigated and compared with separation on a Waters Symmetry 300 C₄ column. Results indicated that the chromatographic performance of the homemade column in the separation of proteins was excellent. The new polar copolymerized C₈ stationary phase enabled glycoprotein separation with good resolution and reproducibility. It was also used for purification of ovalbumin glycoprotein in order to improve identification of the protein.     

Copolymerization of styrene and 1-hexene with a TiCl<Subscript>4</Subscript>-Al(C<Subscript>6</Subscript>H<Subscript>13</Subscript>)<Subscript>3</Subscript> · Mg(C<Subscript>6</Subscript>H<Subscript>13</Subscript>)<Subscript>2</Subscript> catalytic system

The copolymerization of styrene and 1-hexene with the TiCl₄-Al(C₆H₁₃)₃ · Mg(C₆H₁₃)₂ catalytic system has been investigated. The microstructure of polymer chains, molecular-mass characteristics, and thermophysical properties of the resulting copolymers have been studied. These copolymers contain 15 to 65 mol % styrene and mostly consist of isotactic polystyrene and poly(1-hexene) blocks.