Thermolysis of complex cyanides,XV

The thermal decompositions of K₂[Fe(CN)₄ L]·4 H₂O, H₂[Fe(CN)₄ L] and H[Fe(CN)L](L=1,1-bipyridine, of 1,10-phenanthroline) were studied. The experimental results showed that the protonated ferrous complexes decompose with formation of HCN at lower temperature than the corresponding potassium salts. The decomposition of K₂[Fe(CN)₄ L] starts by removal of the ligand L. HCN elimination is followed by a redox reaction with formation of cyanogen in the case of H[Fe^III(CN)₄ L].

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Zusammenfassung Die thermische Zersetzung von K₂ [Fe(CN)₄ Z]·4H₂O, H₂[Fe(CN)₄ L] und H[Fe(CN)₄ L] (L=1,1'-Dipyridin, 1,10-Phenantrolin) wurde untersucht. Die Versuchsergebnisse zeigten, dass die protonierten Ferrokomplexe unter Bildung von HCN bei niedrigeren Temperaturen zersetzt werden, als die entsprechenden Kaliumsalze. Die Zersetzung von K₂ [Fe(CN)₄ L] beginnt durch die Abspaltung des LigandenL. Nach Eliminierung des HCN folgt eine Redox-Reaktion unter Bildung von Dizyan im Falle von H[Fe^III(CN)₄ Z].

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K₂[Fe(CN)₄ L]·4₂, H₂[Fe(CN)₄ L] H[Fe(CN)₄ L] L=1,1- 1.10-. , , . K₂[Fe(CN)₄ L] L. H[Fe¹¹¹(CN)₄ L] HCN - .

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XIV. A. Hantshmann, J. Salvetter, H. Hennig and B. Mohai, Thermochim. Acta. 25 (1978) 341

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The authors thank I. Ötvös for mass-spectroscopic investigations, and Mrs. Csukás, Mrs. Csiszár and Mrs. Haeffner for experimental assistance.     

Thermal studies on aluminium substituted CuCr2O4

Thermal studies on aluminium substituted copper chromite spinel oxide, CuCr_2–x Al _x O₄ (x=0.2 tox=0.8) by DSC show that with 20% replacement of Cr by Al, the phase transition temperature of the spinel is lowered but on further increasing the percentage of Al the phase transition temperature becomes higher than that of CuCr₂O₄. The enthalpy change for phase transition however decreases gradually with increasingx.

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Zusammenfassung Mittels DSC wurde ein aluminium-substituiertes Kupferchromitspinelloxid, CuCr_2–x Al _x O₄ mitx=0,2-0,8 thermisch untersucht. Wird 20% des Cr durch Al ersetzt, sinkt die Phasenübergangstemperatur ab, bei weiterem Anwachsen des Aluminiumgehaltes steigt sie jedoch über die von CuCr₂O₄ hinaus an. Die Enthalpieänderung des Phasenüberganges steigt mit anwachsendemx allmählich an.

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CuCr_2–x Al _x O₄ (x=0,2–0,8) , 20% , , , , CuCr₂O₄. , x.

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The authors thank Mrs P. P. De of Rubber Technology Centre, Indian Institute of Technology, Kharagpur for her help with the DSC studies.     

Oxidation of hydrocarbon mixtures over a complex vanadium catalyst

Vapor-phase oxidation of hydrocarbon mixtures over vanadium oxide (promoted by potassium sulfate)-silica catalyst has been studied. It is shown that the inhibition of the rates of formation of individual products depends on the ability of the added hydrocarbons to similar specific interaction with the catalyst.

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. , , .

     

Modification of the catalytic activity of Ni/SiO2 in ethane hydrogenolysis, benzene and co hydrogenation by reduction at high temperatures and restoration by O2?H2 treatments

An increase of the temperature of reduction of Ni/SiO₂ from 900 to 1120 K results in a decrease of catalytic activity per unit area in benzene hydrogenation and ethane hydrogenolysis. O₂–H₂ treatments restore the activities. This behavior is similar to that observed on Pt-based catalysts. In contrast, the CO+H₂ reaction on nickel is not affected by such treatments.

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Ni/SiO₂ 900 1120 . O₂–H₂ . , , CO+H₂ .

     

Influence of phosphorus additives on the properties of Fe?Sb?O oxide catalysts

Modification of the surface of Fe–Sb–O oxide catalysts by phosphorus additives increases the yield of acrylonitrile in the oxidative ammonolysis of propylene, which can be attributed to the increase of the surface concentration of weakly acidic aprotic centers, viz. Sb³⁺ ions.

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, --Sb³⁺.

     

Catalytic relevance of phase transformations accompanying the gas phase oxidation of ethanol on silica supported vanadia

Nonsteady state activity during the gas phase oxidation of ethanol in a simple flow reactor and its dependence on pretreatment and reaction conditions can be explained utilizing the previously presented model of possible surface vanadia phases on silica.

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.

     

Thermodynamic aspects of conformational transitions in synthetic polypeptides

The helix-coil transition of organic solvent soluble homopolypeptides has been discussed from a largely thermodynamic view-point. The present state and the future prospects are considered.

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Zusammenfassung Der Helix-Ungeordnete Übergang von in organischen Lösungsmitteln löslichen Homopolypeptiden wurde aus einem breiten Gesichtspunkt diskutiert, gegenwärtige Lage und zukünftige Entwicklungsaussichten erörtert.

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R'esumé On a discuté d'une pointe de vue thermodynamique large la transition helix—non helix des homopolypeptides solubles dans des solvants organiques et considéré la situation actuelle ainsi que les perspectives futures.

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, , . .

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The present paper was supported by NSF Grant GB 33484.     

Preparation and characterization of Ru?Pb supported catalysts

Decomposition of Mn₃Mo₂TeO₁₂ during oxidation of toluene to benzaldehyde was observed. Depending on the surface composition of the initial catalyst, the decomposition leads to less active but highly selective MnMoTeO₆ or to MnMoO₄ which is not selective in toluene oxidation.

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Mn₃Mo₂TeO₁₂ . , MnMoTeO₆, MnMoO₆.

     

Influence of external electric field on the rate of hydrogen isotope exchange between hydroxyl-containing molecules in CCl4

Rates of the fast proton-deuteron exchange between CH₃OD and C₆H₅OH (1), and CH₃OD and CH₃COOH (2) in dilute CCl₄ solutions have been measured by a kinetic IR spectroscopy technique. Under an imposed external electric field (10 V/m), the exchange rate in system (2) increases, which is not observed in (1). The effect is interpreted assuming that, in the second case, a cyclic ion pair with a high dipole moment is formed as a reaction intermediate.

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- CH₃OD C₆H₅OH (1), CH₃OD CH₃COOH (2) CCl₄. (IO⁷ B/) (2) , (1). (2) , .

     

Effect of the surface composition of silica supported Pt?Ru Bimetallic catalysts on methane-deuterium exchange reaction

The exchange reaction of methane and deuterium was studied over a series of silica-supported Pt–Ru bimetallic catalysts, whose surface composition was determined by means of O₂–CO titration. The stepwise exchange, giving CH₃D as the main product, proceeded on each surface Pt atom. The multiple exchange, which formed CD₄ directly, proceeded on an ensemble of several Ru atoms.

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Pt–Ru, SiO₂, O₂–CO . , CH₃D , Pt. , CD₄, Ru.

     

Study of interaction between nitrogenous gases and ruthenic catalysts

The effect of temperature on the interaction of nitrogenous gases with Ru-black has been studied by the method of temperature-programmed desorption.

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Ru- - .

     

Mechanism of action of sulfur-containing complexes in oxidation processes

A mechanism of the inhibiting action of Cu(II), Ni(II), Pb(II), Zn bis(N, N-dialkyldithiocarbamates) and Cu(II) bis (-thiopicolineanilides) in the AIBN initiated oxidation of ethylbenzene, styrene and nonene-1 is proposed. Inhibition is due to the deactivation of free radicals upon interaction with the chelate active center consisting of a metal with coordinated ligand atoms. As supported by the experimental data, the reaction occurs by an electron transfer mechanism.

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-(N,N-) Cu(II), Ni(II), Pb(II), Zn -(-) Cu(II) , -1. . . .

     

Zum Thermischen Verhalten von Zitronensäure

Zusammenfassung Mit Hilfe der thermo-optischen Analyse wird gezeigt, daß die widersprüchlichen Angaben in der Literatur zum thermischen Verhalten von Zitronensäuremonohydrat und dem Zitronensäureanhydrit auf eine Überlagerung verschiedener thermischer Reaktionen (Schmelze, Zersetzung, Entmischung und Kristallisation), die mit unterschiedlicher Geschwindigkeit ablaufen, zurückzuführen sind. Die thermo-optische Methode ist besonders für die Aufklärung solch komplexer Reaktionsabläufe geeignet. Das Beispiel des thermischen Verhaltens der Zitronensäure zeigt modellhaft die Erscheinungen, die bei der thermischen Analyse technischer Prozesse, wie dem Einschmelzen von Rohstoffgemengen, zu erwarten sind.

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By means of the thermomicroscopy was demonstrated that the discrepancy between the experimental DSC- and TG-data on the decomposition of citric acid in the literature can be explained in terms of superimposing reactions (melting, decomposition, immiscibility, and crystallization), which have different reaction rates. The thermomicroscopy is especially useful explaining such kind of reactions. The thermal behaviour of citric acid can be used as a model reaction in technology.

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, ( , , ), . . .

     

Propylene oxidation over tin-molybdenum oxide catalysts

The influence of preparation of tin-molybdenum catalysts on their phase composition and activity has been elucidated. The mutual dissolution of Sn and Mo oxides leads to a considerable increase in their activities and selectivities in the partial oxidation of propylene to acetone.

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. , .

     

Role of acid centers of Sn/Mo oxide catalyst in propylene conversion to acetone

Infrared spectroscopic studies of the nature of catalyst centers indicate the presence of Brönsted and Lewis acid centers on the surface. Propylene conversion to acetone proceeds via proton transfer from the surface to propylene with the formation of a (CH₃)₂–C(H)–O–Me type compound, and its subsequent dehydration.

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- , . (CH₃)₂–C(H)–OMe .

     

Catalytic properties of ion-exchanged carnegieite powders. Isomerization of n-butenes

The mist decomposition method was applied to the solgel type synthesis. Resulting carnegieite and its ionexchanged derivatives were tested by means of butene isomerization. Carnegieite showed weak but stable activity originating from its base sites. The results of the reaction suggested the development of more active sites by the magnesium ion exchange and new acid sites by the ammonium ion exchange. These are examined by acid-base measurements.

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. - . , , . , , — . — .

     

Effect of ligands on the hydrogenation selectivity in the presence of rhenium catalysts

It has been established that the catalytic activity of rhenium oxohalide complexes with phosphorus- or sulfur-containing ligands in hydroganation of C₆–C₁₀ olefins, nitrobenzene and p-nitrotoluene is primarily determined by the original ligand to rhenium ion bond. Chain length of olefins does not affect their hydrogenation rate.

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- C₆–C₁₀, - - . .

     

Catalytic action of cation-substituted forms of oxidized charcoal in the liquid phase oxidation of cumene

The catalytic properties of cation-substituted forms of oxidized charcoal in the liquid-phase oxidation of cumene have been investigated. It has been shown that oxidized charcoal inhibits, and its salt forms catalyze the reaction. The catalytic activities of ion-substituted charcoals depend on both the nature of the metal and the amount of supported ions.

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. , , — . , .

     

Thermal behaviours of barium ortho-, meta- and para-nitrobenzoates

The thermal behaviours of barium ortho-, meta- and para-nitrobenzoates were studied by DTA, TG and Emanation Thermal Analysis (ETA) in the temperature range 20 – 300°. The application of ETA as a supplement to the classical thermoanalytical methods (DTA and TG) for the study of organic compounds in the solid state is demonstrated.Absolute values of emanating power, measured at room temperature for samples quenched from temperatures before and after the effects in the thermoanalytical curves, provide valuable characteristics of the intermediate products of thermal treatment, especially with regard to the degree of disorder of the molecular structure. The evolution of the molecular structure of each isomer during heating is discussed, and new X-ray patterns of the different compounds are given.

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Zusammenfassung Das thermische Verhalten von Ortho-, Meta- und Para-Isomerem des Bariumnitrobenzoats wurde durch DTA, TG und Emanations-Thermoanalyse (ETA) im Temperaturbereich von 20–300°C untersucht. Die Anwendung der ETA als Ergänzung klassischer thermoanalytischer Verfahren (DTA und TG) zum Studium organischer Verbindungen wird beschrieben.Die absoluten Werte der Emanationskraft, gemessen an Mustern, welche von Temperaturen vor und nach den Effekten abgekühlt worden waren, werden an Hand thermoanalytischer Kurven gezeigt. Sie stellen wertvolle Charakteristika von Zwischenprodukten der thermischen Behandlung dar, besonders hinsichtlich des zerstörten Ordnungsgrades der Molekularstruktur. Die Entwicklung der Molekularstruktur jedes Isomers während der Aufheizung wird erörtert und neue Röntgenspektra der verschiedenen Verbindungen werden angeführt.

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Résumé Par TG, ATD et ATE on a étudié, dans le domaine compris entre 20 et 300°C, le comportement thermique des nitrobenzoates de baryum (isomères ortho, méta et para) et on a montré l'intérêt de l'ATE utilisée comme technique complémentaire de la TG et de l'ATD pour l'étude de composés organiques à l'état solide.En mesurant, pour chaque composé, les valeurs absolues du pouvoir émanateur avant et après chaque effet endothermique ou exothermique, on a pu mettre en évidence les caractéristiques des produits intermédiaires qui apparaissent au cours du traitement thermique, notamment en ce qui concerne le degré de désordre de la structure moléculaire. On a discuté l'évolution de cette structure pour chaque isomère au cours du chauffage. Les diagrammes de diffraction X présentés sont tous nouveaux.

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-, - - 20–300° , (). . , , . , . .

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The authors are obliged to Dr. M. V. Mathieu and Ing. C. Quet, Institute for Catalysis Researches, Villeurbanne, France, for valuable discussion of the I.R. spectra and for assistance in the experimental work, respectively.