Calorimetric study of the BrO3?/Ce4+/cyclohexanone and BrO3?/Ce4+/cyclopentanone oscillating systems

The heat output (Q) during the induction period of a Belousov-Zhabotinskii oscillating reaction usually evolves at a constant rate /6/; we observe in the BrO ₃ ^– /Ce⁴⁺/Cyclohexanone system a sudden change in the slope of the function Q=f(t), which corresponds to the beginning of the quasistationary phase /3/.

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(Q) - ; BrO ₃ ^– /Ce⁺⁴/ Q=f(t), .

     

Electrocatalytic oxidation of cyclohexane by molecular oxygen in non-aqueous solvents in the presence of perchloric acid and perchlorates

Several new electrocatalytic systems are described for the oxidation of cyclohexane by molecular oxygen at room temperature. The solvent is acetonitrile. Perchloric acid and perchlorates are used as supporting electrolytes. The maximum electrochemical yield amounts to 9.6% and is observed in the presence of perchloric acid.

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, . , — . 9,6% — .

     

Mechanism of RuIV-catalyzed oxidation of alkanes in aqueous solutions

The Ru^IV-catalyzed oxidation of alkanes in aqueous solutions includes activation of the oxidant Ox (Cr^VI, HNO₃, HClO₄, etc.) via Ox–Ru^IV complex formation and is accompanied by H atom abstraction from the alkane by the activated oxidant.

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Ru^IV - Ox (Cr^IV, HNO₃, HClO₄ .) Ox–Ru^IV - .

     

Kinetics of the selective hydrogenation of phenol to cyclohexanone over a Pd-alumina catalyst

The most suitable kinetic equation for the selective hydrogenation of phenol to cyclohexanone on a 0.96wt.% Pd-9.63wt.%CaO-alumina (Harshaw AL-3965) catalyst is determined among a series of models based on Langmuir-Hinshelwood-Hougen-Watson theory.

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0,96 . %Pd-9,63 .%CaO/Al₂O₃ (Harshaw AL-3965). , ---.

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Simulation of synergism phenomena in inhibition of styrene oxidation by organic phosphite and chromium(III) acetylacetonate

The rate constants for the reaction of styrene peroxy radicals with free and complexed phosphite molecules have been determined together with the rate constant for complex formation of Cr³⁺ with phosphite.

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(Cr⁺³) .

     

Characterization of perovskite-type oxide catalysts RECoO3 by TPR

Reducibility of a series of RECoO₃ (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy) perovskite-type oxides were measured by temperature programmed reduction (TPR) technique. Catalytic activity for CO oxidation of them were investigated. The relation among T_max in TPR, catalytic activity and surface oxygen binding energy is discussed.

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RECoO₃ (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy) . CO. T_max , .

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Project Supported by the Science Fund of the Chinese Academy of Sciences     

Alcohol formation from synthesis gas: A thermodynamic study

A thermodynamic study is presented for the simultaneous synthesis of C₁–C₄ alcohols from synthesis gas. The equilibrium composition was calculated for the gaseous mixture containing Co, H₂, CH₃OH, C₂H₅OH, C₃H₇OH, n-C₄H₉OH and H₂O. Operating industrial conditions were specifically considered.

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C₁–C₄ -. , CO, H₂, CH₃OH, C₂H₅OH, C₃H₇OH, -C₄H₉OH H₂O. .

     

Synthesis of modified amino acids containing nucleic acid purine bases

The reaction of hydrazides of adenylyl- or hypoxanthinyl-9-alkylcarboxylic acids with sodium nitrite in acid media gives reactive azides of purinyl-9-alkylcarboxylic acids which condense with ()-aminocarboxylic and ,-diaminocarboxylic acids to give N(N)-(adenylyl-9-alkanoyl) aminocarboxylic, N-(adenylyl-9-)- and N-(hypoxanthinyl-9-alkanoyl)-,-diaminocarboxylic acids. The deamination of N-(adenyl-yl-9-alkanoyl)aminocarboxylic acids gives N-(hypoxanthinyl-9-alkanoyl)aminocarboxylic acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 126–130, January, 1985.     

Theoretical studies on the N-containing radicals formed in thermal decompositions of dimethyl- and diethyldiazenes

The geometries and energies of ₁ and ₂ radicals, formed in the thermal reaction of dimethyl- and diethyldiazenes, were investigated by means of UHF-MINDO/3. The stability of radicals was found greater than that of allyl radical. The calculated SOMO energies show a lower reactivity in H-abstraction reactions than that of alkyl and allyl radicals.

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UHF-MINDO/3 _{1 2}, - . ₁ , . SOMO , .

     

Effect of hydrolysis catalyst and thermal treatment on titania synthesis via sol-gel

The effect of acidic and basic catalysts and of thermal treatment on the preparation of TiO₂ by the sol-gel method has been studied. The resultant solids were characterized by UV-Vis spectroscopy. A displacement of the band due to a fundamental transition to lower energies was observed when acid catalysts were used.

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, TiO₂ - . . .

     

On the pattern of hydrogenolysis of hexane isomers over four Group VIIIB metals

The hydrogenolysis patterns of five hexane isomers have been compared over Rh, Pd, Ir and Pt. The selectivity of rupture of various C–C bond types is different for various metals. The fingerprint-like patterns are, as a rule, similar to those reported in the literature, their correlation with the position of the metal in the periodic system is pointed out.

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5- Rh, Pd, Ir Pt. C–C , . .

     

TPD studies of benzene adsorption over vanadium-molybdenum oxide catalysts

Benzene is shown to be adsorbed on the surface of a V₂O₅-MoO₃ catalyst in two forms. The activation energies of benzene desorption for its first and second forms are 50 and 134 kJ/mol, respectively, in the latter case the adsorption proceeding with dissociation.

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, - . 50 / –134 /, .

     

Hysteresis of thermogravimetric curves of nickel catalysts for methane conversion in CH4+CO2 mixture

Characteristic peculiarities of the supercarbonization peak, i. e. the effect of carbon accumulation on the catalyst surface and its subsequent removal under heating in the CH₄+CO₂ mixture have been studied. Hysteresis of thermogravimetric curves in the heating/cooling cycle has been established.

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— . -.

     

On the applicability of the first-order equation for the reactions of solids

It is suggested that besides its traditional application to describe random nucleation, the first-order equation F1 can be used for the diffusion kinetics of gas-solid small particles reactions.

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, F1 - - .

     

Temperature-programmed desorption (TPD) of hydrogen from a NiNaY zeolite after reduction

By TPD it could be shown that hydrogen desorption of a reduced NiY-zeolite stoichiometrically corresponds to the decrease of reduction degree. Therefore, the reason for hydrogen abstraction should be a partial reoxidation of Ni⁰.

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, NiY- . Ni⁰.

     

Physico-chemical properties of silica-supported vanadium oxide catalysts

- . TiO₂ ZnO. - CO₂ H₂O. — .

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The effect of visible light on propane and n-butane oxidation has been sutied on a seires of metal oxides. TiO₂ and ZnO have been found to exert a photocatalytic effect. On TiO₂, propane and n-butane are oxidized to CO₂ and H₂O. On ZnO as catalyst, partial oxidation products, aldehydes and ketones, are formed.

     

A bifunctional stopcock-winch device in cells for infrared investigations of solids

A simple glass device is described acting as stopcock and winch at the same time. The device is especially suitable for the dislocation of solid sample holders in IR cells.

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, . .

     

Free electron model and magnetic susceptibility of aromatic hydrocarbons

Using a free electron model for the -electron system in aromatic hydrocarbons the - electron susceptibility due to Langevin diamagnetism and Van Vleck High frequency para-magnetism (H. F.) have been calculated. The H. F. term has been found to increase rapidly with the ring size.

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Zusammenfassung Mit Hilfe eines Modells freier Elektronen für das -Elektronensystem in aromatischen Kohlenwasserstoffen wird der Langevinsche diamagnetische Anteil und der Van Vlecksche paramagnetische Beitrag zur -Elektronensuszeptibilität berechnet. Dabei findet man, daß letzterer mit der Ringgröße schnell wächst.

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Résumé Au cadre du modèle de l'électron libre, la susceptibilité -électronique des hydrocarbures benzéniques due au diamagnétisme de Langevin et au paramagnétisme de Van Vleck (H. F.) a été calculée. Le terme H. F. s'agrandit rapidement avec les dimensions de la molécule.

     

Thermal behaviour of some 2-benzylamino-2-deoxyheptonic acids

The thermal behaviour of some 2-benzylamino-2-deoxyheptonic acids obtained from 2-benzylamino-2-deoxy-D-glycero-L-gluco, 2-benzylamino-2-deoxy-D-glycero-D-ido and 2-benzylamino-2-deoxy-D-glycero-D-taloheptononitriles (reported) previously has been studied in air (static atmosphere) and N₂ (dynamic atmosphere, flow rate 200 ml/min).

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Zusammenfassung Das thermische Verhalten einiger aus 2-Benzylamino-2-desoxy-D-glycero-L-gluco-, 2-Benzylamino-2-desoxy-D-glycero-D-ido und 2-Benzylamino-2-desoxy-D-glycero-D-talo-heplononitril (kürzlich beschrieben) erhaltenen 2-Benzylamino-2-desoxy-heptonsäuren wurde ín Luft (statische Atmosphäre) und N₂ (dynamische Atmosphäre, Strömungsgeschwindigkeit 200 ml/min) untersucht.

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( 200 /) 2--2- , 2--2---uepo-L, 2-2- ---- 2-2--- -- 2--2----ma .

     

Palladium/sepiolite systems as hydrogenation catalysts, III. Hydrogenation of variously substituted olefins

The application of a Spanish sepiolite variety known as Pansil (commercialized by Tolsa S.A.): as a Pd support in the reduction of variously substituted carbon-carbon double bonds, both with gaseous hydrogen and by hydrogen transfer with cyclohexene as donor is described.

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, Pansil, Tolsa S.A., Pd C=C, , ( ).