Gas phase thermolysis of phenylazoethane

The pyrolysis of phenylazoethane has been studied in a stirred-flow system using cyclohexene as carrier gas at sub-ambient pressures, in the temperature range of 380–416°C. The activation energy is examined in relation to the C–N bond dissociation energy and the heat of formation of the phenyldiazenyl radical.

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, - 380–416°C. C–N .

     

Conversion of dehydrolinalyl acetate in catalytic hydrogenation on metals

Low selectivity of dehydrolinalyl acetate (DeHLA) hydrogenation into linalyl acetate and ester group detachment are predicted in accordance with quantum-chemical data obtained for its homologue dimethyl ethynyl carbinol acetate. Experimental data are confirmed by theoretical calculations. DeHLA hydrogenation produces a variety of products.

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, - . . .

     

Photolysis of alkylperoxy radicals frozen out from the gas phase

Photolysis of alkylperoxy radicals with 250 nm light has been studied and proposed for investigation of heterogeneous-homogeneous reactions by freezing out radicals from the gas phase and their ESR identification. Using amine decomposition reaction in the presence of O₂ as an example, we have shown that photodissociation of frozen peroxy radicals can be used to reduce the structure of initial alkyl radicals.

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- 250 . , .

     

Kinetics and mechanism of the oxidation of benzyl alcohol by potassium chlorochromate

The kinetics of the oxidation of benzyl alcohol by potassium chlorochromate, KCrClO₃, has been studied in dimethyl sulfoxide-dichloromethane medium. The reaction is catalyzed by acid. The effects of temperature and solvent composition were studied and activation parameters evaluated. Probable mechanisms are discussed.

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, KCrClO₃, . . . .

     

Catalytic oxidation of octene-1 in the presence of palladium(II) salts and heteropolyacids

In the presence of the catalytic system (PdSO₄+HPA), where HPA=H₉PMo₆V₆O₄₀, octene-1 is found to be selectively (95%) oxidized to octanone-2. The optimum concentration ratio for catalyst stability is [HPA]:[PdSO₄]=30–40. The substitution of PdCl₂ for PdSO₄ leads to the formation of all three isomeric octanones without decrease of the overall selectivity. Effective rate constants and the apparent activation energy have been determined in the temperature range from 60 to 80 °C.

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(PdSO₄+), =H₉PMo₆V₆O₄₀, -1 ( 95%) -2. []:[PdSO₄]=30–40. PdSO₄ PdCl₂ . 60–80 °C.

     

Kinetics of edta catalyzed oxidation of I? by Cr(VI)

The activity of various iron-containing ore catalysts during hydrogenation of Kansk-Achinsk lignite into liquid products in H-donor solvent (tetraline) has been studied. Ore samples contained pyrite, hematite and magnetite minerals. The most active appear to be pyrite samples. The catalytic effect of ore systems is, apparently, associated with the fact that during hydrogenation more active than tetraline H-donors are formed due to the hydrogenation of polycyclic aromatic molecules produced by thermal destruction of lignite.

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- H- . , , . , . , , , , , .

     

Study of CO and H2 sorption on supported bimetallic Pd?Pb catalysts

With increasing the lead content both CO and hydrogen sorption drop considerably. The influence of lead can be observed starting from a concentration of 0.5%. This may indicate that the surface is enriched in lead atoms.

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CO, H₂. , 0,5%. .

     

Study of selective dissociation in C6F5H?C6F5D mixtures induced by intense CO2 laser pulses

Irradiation of a C₆F₅H–C₆F₅D mixture at 1 Torr by a tunable CO₂ pulse laser brings about chiefly dissociation of one component depending on the frequency of emission absorbed by the proper molecules. The addition of radical acceptors increases the selectivity by suppressing secondary reactions.

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C₆F₅H C₆F₅D 1 CO₂-, , . .

     

Gas phase thermolysis of diisopropyl disulfide

The pyrolysis of diisopropyl disulfide was studied in a static system over the temperature range 274–304 °C at subambient pressures. The mechanism was examined by the pyrolysis of 3,4-dithia-2,5-dideuterohexane. The inhibited rate of consumption yielded the Arrhenius parameters logA=14.37±0.36; E_a=(192±4) kJ/mol.

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274–304°C . 3,4--2,5-. : logA=14,37±0,36; E_a=(192±4) /.

     

Differential thermal analysis studies of chemical systems in sealed cells

Many chemical systems illustrating major reaction types may be conveniently studied by differential thermal analysis. The problems of vaporization and sublimation have been avoided through the use of sealed glass vials. Sample sizes are in the range of 10 to 100 milligrams. This size though small is still more than adequate for chemical analysis by instrumental methods such as infrared spectroscopy and gas chromatography.

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Zusammenfassung Die Differentialthermoanalyse ist zur Untersuchung vieler Systeme mit den wesentlichsten Reaktionstypen geeignet. Durch Verdampfen und Sublimieren verursachte Veränderungen beseitigt man durch die Verwendung verschlossener Glasampullen. Die Größe der Probe bewegt sich von 10 bis 100 mg. Diese Menge reicht aus, um eine chemische Analyse durch Infrarotspektroskopie oder Gaschromatographie durchzuführen.

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Résumé De nombreux systèmes chimiques illustrant les principaux types de réaction peuvent être étudiés d'une manière commode par analyse thermique différentielle. On élimine les problèmes provenant de la vaporisation et de la sublimation par l'emploi d'ampoules de verre scellées. On prend des échantillons de 10 à 100 mg. Cette quantité, quoique déjà faible, est plus que suffisante pour faire l'analyse chimique par des méthodes instrumentales comme la spectroscopie infrarouge et la chromatographie en phase gazeuse.

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, , . . 10–100 . , , , .

     

Effect of iron on the behavior of Fe2O3?MoO3/SiO2 ammoxidation catalysts

Catalytic ammoxidation of propylene was studied using Fe₂O₃–MoO₃/SiO₂ catalysts, which have been prepared following a special method. Interaction of ammonia with the catalysts was studied by means of IR spectroscopy and gravimetrically using a McBain balance. Introduction of iron into MoO₃/SiO₂ catalysts modifies acidic as well as redox properties.

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Fe₂O₃–MoO₃/SiO₂ . . - . MoO₃/SiO₂ , .

     

Formation and creeping of the crystalline phase wavefront within the bed of vanadium sulfuric acid catalyst

Kinetics of the reduction of sulfur dioxide by methane in the presence of molecular oxygen at 732–831°C have been obtained.

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732–831°C.

     

Melting memory effect of the β-modification of polypropylene

The pure-modification of polypropylene has been prepared. It has been found that the nature of the melting of the-modification strongly depends on the thermal history of the sample (melting memory effect). The melting of samples cooled to room temperature after crystallization is a complex process consisting of three partially overlapping processes (-melting recrystallization in the-modification (-recrystallization) -melting). If heating starts at the temperature of crystallization, the-modification melts separately, without-recrystallization. Under melting conditions free from the interference caused by-recrystallization, the-modification exhibits the melting characteristics of thermodynamically stable modifications. The thermodynamic equilibrium melting point of the-modification has been determined to beT _m ⁰ ()=456 K.

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Zusammenfassung Die-Modifikation von Polypropylen wurde rein dargestellt. Es wurde festgestellt, daß die Natur des Schmelzens der-Modifikation stark von der thermischen Vorgeschichte der Probe (Schmelzerinnerungseffekt) abhängt. Das Schmelzen von nach der Kristallisation auf Zimmertemperatur abgekühlter Proben ist ein komplexer, aus drei sich teilweise überlappenden Prozessen (-Schmelzen Rekristallisation in der-Modifikation, die sog.-Rekristallisation -Schmelzen) bestehender Vorgang. Wenn das Aufheizen bei der Kristallisationstemperatur beginnt, so schmilzt die-Modifikation, ohne daß -Rekristallisation eintritt. Unter Schmelzbedingungen frei von störenden Einflüssen der -Rekristallisation zeigt die-Modifikation die Schmelzcharakteristiken von thermodynamisch stabilen Modifikationen. Der thermodynamische Gleichgewichtsschmelzpunkt der-ModifikationT _m ⁰ () liegt bei 456 K.

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- . , ( ). , , , : - -, - . , - - . , -,- . - T _m ⁰ ()=456 .

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The author is indebted to Attila Ille for his help in the experimental work.     

Some peculiarities in regeneration of zeolite-containing cracking catalysts by carbon dioxide

Catalytic properties of Mn and La oxides that are acceptors of CO₂ in regeneration of zeolite-containing cracking catalysts in the presence of carbon dioxide have been studied. Regeneration rate of coked catalysts by carbon dioxide in the presence of Mn and La significantly increases. During regeneration, coke oxidation to Co and redistribution of hydrogen in carbonaceous fragments take place to produce methane and hydrogen. Activation energy of methane and hydrogen formation equals 46 kcal/mol. Variation of activation energy with temperature is typical for Co formation.

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, Mn La . CO . 46 /. CO .

     

Le systeme eau-theophylline

The binary system water—theophylline was studied by DTA and radiocrystallography. The slow dehydration of theophylline monohydrate was observed at room temperature at relative humidities lower than 60%, without the formation of any other hydrate. The isochoric phase diagram was established. At 78 °C, a peritectic invariant occurred, owing to decomposition of the monohydrate. The existence of only one binary compound (theophylline H₂O) was confirmed by the.Tammann diagram.

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Zusammenfassung Mittels DTA und Radiokristallographie wurde das binäre System Wasser-Theophyllin untersucht. Bei einer relativen Luftfeuchtigkeit unter 60% wird bei Raumtemperatur eine langsame Dehydratation von Theophyllinemonohydrat ohne Formung anderer Hydrate beobachtet. Es wurde ein isochores Phasendiagramm entwickelt. Wegen der Zersetzung des Monohydrates tritt bei 78 °C eine peritektische Invariantheit auf. Die Existenz nur einer binären Verbindung (Theophyllin, H₂O) wird mittels eines Tammanndiagrammes bekräftigt.

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— . 60% - . . 78° , . -.

     

The thermal dehydration of Sr(HCOO)2·2(H,D)2O. Influence of the isotopic substitution on the kinetics

The kinetics of thermal dehydration of Sr(HCOO)₂·2(H, D)₂O were investigated using a dynamic thermogravimetric technique. Differences were found when the hydrogen was partially substituted by deuterium. These differences were explained by means of a microscopic approach based on the static and dynamic microscopic properties.

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Zusammenfassung Die Kinetik der thermischen Dehydratisierung von Sr(HCOO)₂·2(H, D)₂O wurde mittels dynamischer Thermogravimetrie untersucht. Bei partieller Substitution von Wasserstoff durch Deuterium wurden Unterschiede gefunden, die durch eine auf den statischen und dynamischen mikroskopischen Eigenschaften beruhende Betrachtungsweise erklärt werden.

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Sr(HCOO)₂ · 2(H, D)₂O. , .

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The authors whish to thank Dr. J. M. Pastor for valuable discussions, and Prof. O. Garcia of the Instituto de Quimica Inorgánica Elhuyar (C.S.I.C.) for the use of the experimental devices.     

Asymmetric hydrogenation in the presence of polycyclic chiral phosphines, II /8/

The enantiomers of trans-11, 12-bis-(diphenylphosphinomethyl)-9, 10-dihydro-9,10-ethanoanthracene and its perhydrogenated derivative were prepared and used as ligands in the asymmetric hydrogenation of prochiral olefinic substrates. Different selectivities and partiallyhigh optic al yields could be observed

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-11, 12--()-9, 10--9,10- . .

     

A thermal study on moisture absorption by epoxy composites

The water sorption kinetics of an epoxy matrix-carbon fiber composite with different degrees of polymerization was studied. It was observed that the diffusion coefficients, determined perpendicularly to the fiber direction, are increased by increasing the cure degree. Only a small portion of the bonded water is released when the specimen are heated to 200 °C.The effects of moisture on some properties of the composite were also investigated. TheT _g values determined on fully polymerized samples, show lowerings of 70 degrees; moreover, the plasticization power of the bonded water increases on decrease of the temperature of conditioning of the specimens.Finally, the water present in the matrix considerably reduces the thermal stability of the composite.

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Zusammenfassung Es wurde die Wassersorptionskinetik eines Graphitfaserverbundstoffes auf Epoxymatrixbasis mit verschiedenen Polymerisationsgraden untersucht. Es zeigte sich, daß die senkrecht zur Faserrichtung bestimmten Diffusionskonstanten mit anwachsendem Vernetzungsgrad zunehmen. Beim Erhitzen des Materials auf 200 °C wird nur ein geringer Teil des gebundenen Wassers abgegeben. Der Einfluß des Feuchtgehaltes auf einige Eigenschaften des Verbundstoffes wurde ebenfalls untersucht. Die an vollkommen polymerisierten Proben bestimmtenT _g Werte zeigen eine Abnahme von 70 Grad; die Plastifizierungswirkung des gebundenen Wassers ist um so höher, je niedriger die Konditionierungstemperatur der Probe war. Das in der Matrix gegenwärtige Wasser senkt beträchtlich die Wärmebeständigkeit des Verbundstoffes.

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- . , , , . 200 °. . Tg, , 70 °. . , , .

     

Influence of pressure reduction on the shapes of thermoanalytical curves of red muds

The effect of reduction of pressure on the shapes of the TG, DTG and DTA curves and the mass-spectra of hydroxide and carbonate phases was investigated in some typical Hungarian red muds. The pressure change caused different decomposition rates of the phases and resulted in better separation of the overlapping thermal curves; this led to advantages as regards phase analysis. For phase analysis the red muds were extracted with water, and the extracts and solid residues were identified by IR- and X-ray methods.

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Zusammenfassung Die Wirkung der Druckänderung auf die Form der TG-, DTG- und DTA-Kurven, sowie der MS-Spektra der Hydroxid- und Carbonatphasen in einigen typischen ungarischen Rotschlamm-Sorten wurde geprüft. Die Druckänderung verursachte verschiedene Zersetzungsgeschwindigkeiten der Phasen, führte zur besseren Auftrennung der sich überlappenden thermischen Kurven, und war ausserdem auch hinsichtlich der Phasenanalyse vom Vorteil. Zur Phasenanalyse wurden die Rotschlämme mit Wasser extrahiert und die Extrakte und festen Rückstände mittels IR- und Röntgenmethoden identifiziert.

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Résumé On a étudié dans quelques espèces typiques de boues rouges de Hongrie l'effet des variations de pression sur la forme des courbes TG, TGD et ATD ainsi que les spectres de masse des phases hydroxyde et carbonate. La variation de la pression entraîne des vitesses de décomposition différentes. Il en résulte une meilleure séparation des phénomènes dans le cas où ceux-ci se chevauchent ainsi que des avantages du point de vue de l'analyse des phases. L'analyse des phases présentes dans les boues rouges a été effectuée par extraction à l'eau. Les extraits et les résidus solides ont été identifiés par spectrométrie infrarouge et par diffraction des rayons X.

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, - . , , . .

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Paper presented at the Scientific Session on Thermal Analysis held at Balatonfüred, Hungary, on 14–16 October 1976.