Kinetics and mechanism of micellar effects upon the hydrolysis of 0-(2,4-dinitrophenyl) cyclohexanone oxime

A modification in the reaction mechanism of 0-(2,4-dinitrophenyl)cyclohexanone Oxime with OH^– in 30% aqueous methanol is suggested. The cationic micelles of cetyltrimethyl ammonium bromide enhance the reaction by a factor ofca. 3. The pseudo first order rate constant at the micellar surface was found to be 10.9×10^–4 s^–1 at 35±0.1°C. Anionic and nonionic micelles inhibit the rate of the reaction. Bromide ion inhibits the catalysis, which indicates that catalysis is partially due to a concentration effect. The catalytic efficiency increases with decreasing [OH^–), which implies that the efficiency of the surfactant could be related to some standard parameter(s).

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0-(2,4-)-- OH^– 30%- . . 3. - 10.9·10^{–4 –1} 35±0.1°C. . . , - . - [OH^–], , - - .

     

Derivatographic investigation of glass fibre adsorbents based on bentone clay

By means of thermal analysis the activation energy and the characteristics of glass fibre adsorbents upon dehydration were determined depending on the chemical composition, acidity and thermal treatment of bentone fibres.

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, .

     

Ba(OH)2 as catalyst in organic reactions, part XIV. Michael addition catalyzed by barium complex salts in the homogeneous phase

Michael addition to chalcone is catalyzed by barium complex salts in the homogeneous phase under various conditions. The nature of these intermediates is analyzed. These complex salts are described for the first time. The Michael adduct of malonodinitrile to chalcone is described for the first time.

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, , . . . . .

     

Analysis of complex thermoanalytical curves: The thermodynamic and kinetic parameters of isopropylammonium nitrate

A method is presented to determine thermodynamic and kinetic parameters from complex thermoanalytical curves. Such curves are obtained when thermoanalytical events like phase transition and chemical decomposition overlap.Isopropylammonium nitrate was taken as an example to demonstrate how these parameters were determined from non-isothermal TG and DSC curves by constructing DSC-DTG sum curves.

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Zusammenfassung Es wird ein Verfahren zur Bestimmung thermodynamischer und kinetischer Parameter von komplexen thermoanalytischen Kurven beschrieben. Kurven dieser Art entstehen bei der Überlappung thermoanalytischer Ereignisse wie z.B. Phasenumwandlungen und chenliche Zersetzungen.Am Beispiel von Isopropylammoniumnitrat wird demonstriert, wie die einzelnen Parameter der nicht-isothermen TG und DSC Kurven durch Konstruktion von DSC-DTG-Summenkurven ermittelt werden.

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$ . , $ . , -.

     

Electrocatalytic effect of metal ions on lead and lead dioxide electrode reactions

The electrochemical reactions which take place on lead and lead dioxide electrodes of a lead-acid battery are highly influenced by the presence in the electrolytic solution of ions Cd(II), Ni(II), Zn(II) and Co(II). Current density-potential curves were obtained in this work by using a Pb/Ca alloy. It was observed that Co(II) and Ni(II) ions catalyzed both hydrogen and oxygen evolution reactions. On the other hand, Cd(II) and Zn(II) ions decreased the hydrogen evolution rate.

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, - , Cd(II), Ni(II), Zn(II) Co(II). - , Pb/Ca. , Co(II) Ni(II) , . , Cd(II) Zn(II) .

     

Energetic state of hydrogen on Os-black

Hydrogen adsorption on Os-black has been studied by the TPD method in the range from –85 to 450°C. Energetic inhomogeneity of hydrogen chemisorbed at adsorption temperatures of 150 to 450°C has been elucidated.

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OS (–85)–450°C. , 150 450°C.

     

Activity and selectivity of superhigh silica zeolites in cyclohexane conversion

Cyclohexane conversion on superhigh silica (SHS) zeolites with different Si:Al ratios and on faujazite (HY) has been studied on a pulse microcatalytic setup. It has been found that the catalytic activity of SHS zeolites in cyclohexane conversion decreases with increasing Si:Al ratio. Unlike HY zeolite, SHS samples are highly selective to cyclohexane cracking and have low selectivity to the formation of cyclic hydrocarbons.

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(CBK) Si:Al HY. , Si:Al CBK- . HY, CBK- .

     

Kinetics and isotope effect of brown coal liquefaction in ethanol

Liquefaction kinetics are described by a first-order equation. Deuterium introduction into the -position of ethyl alcohol produces a considerable kinetic isotope effect. This effect is suggested to be due to the hydrogen donor capacity of the initial ethyl alcohol -CH₂-groups or of ethyl substituents inserted into the aromatic fragments of coal after alkylation.

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. -, , - -CH₂- , .

     

Photocatalytic electron transfer across the membranes of lipid vesicles mediated by diglycylamide of mesoporphyrin-IX N-metylglycomate

A peculiarity of the photocatalytic action of porphyrin molecules with different localization inside lipid bilayers of lecithin vesicles has been studied. The influence of an electrostatic field in the lipid membrane on the efficiency of electron photocatalytic transfer across the membrane is discussed.

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, - . . .

     

Kinetics of solid polypropylene oxidation inhibited by aromatic nitrons

C-phenylcarbamoyl-N-phenylnitron and C(2,4-di-tert-butyl-3-hydroxyphenylcarbamoyl)-N-(p-di-methylaminophenyl) nitron inhibit the oxidation of solid polypropylene. In this case the nitrons studied demonstrate properties of polyfunctional inhibitors: they interrupt oxidation chains by chains by reactions with alkyl and peroxyl radicals.

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C--N- C-(2,4----3-)-N-(-) . , .

     

Isomerization, dehydrogenation and cracking of methylcyclohexane over HNaY zeolites

On HNaY zeolites the fractions of acid sites which are active for cracking, isomerization and dehydrogenation of methylcyclohexane do not increase linearly with increasing degree of exchange. Isomerization and dehydrogenation seem to involve a similar activated complex, while cracking proceeds through a different one and requires stronger acid sites. Activation energies are independent of exchange degree.

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HNaY, , . , . .

     

A thermogravimetric study of the solid-state reaction between alumina and strontium carbonate

The kinetics of the solid-state reaction between alumina and strontium carbonate were studied by thermogravimetry. The effects of the structure ( or) and/or doping (with Li⁺ or Cd²⁺) of the alumina on the kinetics of the reaction were examined. The results obtained were correlated with the phase composition and structural changes, followed by a number of physicochemical analyses (DTA, XRA and IRA) throughout the course of the reaction.

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Zusammenfassung Die Kinetik der Festkörperreaktion zwischen Aluminiumoxid und Strontium-carbonat wurde thermogravimetrisch untersucht. Die Effekte der Struktur ( und) und/oder des Dopens des Aluminiumoxids (mit Li⁺ oder Cd²⁺) auf die Kinetik der Reaktion wurde untersucht. Die erhaltenen Ergebnisse wurden mit der Phasenzusammensetzung und mit durch physikalisch-chemische Analysenverfahren (DTA, XRA und IRA) während des Reaktionsverlaufs verfolgten strukturellen Veränderungen in Beziehung gebracht.

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. ( ) Li⁺ Cd²⁺ . , , - .

     

Dimerization of n-butenes on nickel mordenite catalysts

The catalytic activity of synthetic and natural nickel exchanged mordenites of different compositions has been investigated in dimerization of n-butenes at high pressure in the liquid phase. High selectivities to n-octenes and methylheptenes were found. It is suggested that the mordenite channel structure influences the product distribution.

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- . - . .

     

Reversibly adsorbed hydrogen on a molybdena-alumina catalyst reduced with hydrogen

The elution of hydrogen and water desorbed from a MoO₃Al₂O₃ catalyst reduced with hydrogen at 550°C was investigated at 550°C and at O°C. Only hydrogen may be eluted at 550°C, and neither hydrogen may be eluted at 550°C, and neither hydrogen, nor water desorbs at O°C. The reversibly adsorbed hydrogen is responsible for the deactivation of the catalyst used in disproportion ation of propylene at 0–80°C without evacuation at elevated temperatures after reduction.

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, MoO₃/Al₂O₃, 550°C, 550 0°C. 550°C , 0°C , . , 0–80°C , .

     

Analyse theoretique des lois cinetiques couramment utilisees en thermoanalyse pour l'etude des reactions solid-gaz. III. proposition d'une nouvelle methode d'approche en regime dynamique

Résumé Dans la première partie de ce travail, les auteurs mettent en évidence que la vitesse d'une réaction en régime non isotherme dépend d'un facteur supplémentaire: le régime de montée en température. Cette assertion est basée sur le fait que le taux de réactionx est une fonction de trois variables: températureT, tempst, et vitesse de chauffeT, variable qui n'avait pas été prise en considération jusqu'ici par les autres auteurs travaillant sur ce problème.Puis, se basant sur les deux hypothèses suivantes: a) l'équation de vitesse en régime isotherme est la forme limite de l'équation de vitesse en régime dynamique, b) la variation de température en régime dynamique affecte la fréquence d'apparition des germes de la nouvelle phase, une formulation théorique des loisg(x) est proposée pour le régime non-isotherme. Cette formulation est explicitée en fonction de l'écart, à une température donnée, entre les valeurs de Lnk _i (isotherme) et Lnk _d (dynamique) dans le diagramme Lnk = f(1/T).L'étude, par thermogravimétrie, de la décomposition du gypse, du sulfate de calcium semihydraté, et de l'oxalate de calcium monohydraté, réalisée en montée linéaire de température, permet de vérifier expérimentalement la formulation théorique proposée.Pour obtenir une bonne interprétation cinétique d'une réaction chimique en régime dynamique, la vitesse de chauffe ne doit pas excéder 20°/heure.

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In the first part of this paper, the authors point out that the rate of reaction with non-isothermal kinetics depends on a supplementary factor: the heating rate. This assertion is based on the fact that the degreex of reaction is a function of three variables:T (temperature),t (time) andT (heating rate); this was not taken into account by other authors concerned with the subject.Then from the two following hypotheses: a) the rate equation for isothermal conditions is the limit form of the rate equation for non-isothermal conditions, b) the temperature change under dynamic conditions affects the frequency of nucleus formation of the new phase, a theoretical formulation of non-isothermalg(x) laws is proposed. This formulation involves the value of the difference, at constant temperature, between Ink _i (isothermal) and In k_d (dynamic) in the Ink=f(1/T) diagram.The thermogravimetric study of the dehydration of gypsum, of calcium sulfate hemihydrate, and of calcium oxalate monohydrate, under non-isothermal conditions, allows experimental verification of the theoretical formulation proposed.For a good kinetic approach of a chemical reaction under dynamic conditions, the heating rate must not exceed 20°/hour.

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Zusammenfassung Im ersten Teil dieser Arbeit wird von den Autoren bewiesen, daß die Geschwindigkeit einer Reaktion unter nicht-isothermen Bedingungen von einem zusätzlichen Faktor, den Bedingungen des Temperaturenstiegs, abhängt. Diese Behauptung beruht auf der Tatsache, daß der Reaktionsverlauf eine Funktion dreier Variablen ist: der TemperaturT, der Zeitt und der AufheizungsgeschwindigkeitT, wobei letztere Variable bisher von den auf diesem Gebiet arbeitenden Autoren außer Acht gelassen worden ist.Nachfolgend wird an Hand der zwei Voraussetzungen, daß a) die Geschwindigkeitsgleichung unter isothermen Bedingungen die Grenzform der Geschwindigkeitsgleichung unter dynamischen Bedingungen ist und b) die Temperaturänderung unter dynamischen Bedingungen sich auf die Erscheinungsfrequenz der Keime der neuen Phase auswirkt, eine theoretische Formulierung der Gesetzeg(x) für nicht-isotherme Bedingungen vorgeschlagen. Diese Formulierung wird als Funktion der Abweichung ausgedrückt, welche bei einer gegebenen Temperatur zwischen den Werten von Lnk _i (isotherm) und Lnk _d (dynamisch) im Diagramm Lnk=f(1/T) besteht.Die bei linearem Temperaturanstieg thermogravimetrisch durchgeführte Untersuchung der Zersetzung von Gips, von Calciumsulfat Semihydrat und von Calciumoxalat Monohydrat ermöglicht die vorgeschlagene theoretische Formulierung experimentell zu bestätigen.Um unter dynamischen Bedingungen eine gute kinetische Interpretation einer chemischen Reaktion zu erhalten, darf die Aufheizungsgeschwindigkeit den Wert von 20° pro Stunde nicht überschreiten.

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, : . , : (),t () ' ( ), , . : ) ) t(x) . Lnk _j () Lnk _d ( ) Lnk=f(1/T) . , , . , 20° .

     

The question of thermal decomposition of pyrite

The thermal decomposition of monomineral pyrite was studied in an inert atmostphere. From an analysis of the values of the thermal effects, an interpretation of the hree physicochemical processes recorded in the thermoanalytical curves is proposed.

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Zusammenfassung Die thermische Zersetzung von monomineralem Pyrit wurde in inerter Atmosphäre untersucht. An Hand der Analyse der Werte der thermischen Effekte wird eine Beschreibung dreier, in den thermoanalytischen Kurven festgehaltener physikalischchemischer Vorgänge vorgeschlagen.

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Résumé On a étudié la décomposition thermique de la pyrite, en atmosphère inerte. On propose une interprétation des trois processus physicochimiques enregistrés sur les courbes thermoanalytiques, qui repose sur l'analyse des effects thermiques.

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- , .

     

A device for pulse investigation of heterogeneous catalytic reactions

In the present work a simple device is described for the pulse investigation of heterogeneous catalytic reactions and catalysts. Owing to the possibility for separate adjustment of the gas flow rate in the catalytic reactor and in the chromatographic column, it can be used for kinetic measurements too.

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- . , .

     

Control of purity and crystallinity of MVO4 compounds (M=Al,Cr, Fe,In, Y,Nd) by DTA

Two aqueous methods were followed for the synthesis of MVO₄ (M=trivalent element). The first, with vanadium pentoxide and M nitrate yielded crystalline InVO₄ III and amorphous FeVO₄. The second method, using ammonium metavanadate and M nitrate, led to amorphous compounds with M=In, Fe, Cr or Al, and semi-amorphous compounds with M=Nd or Y. The crystallinity and purity of these products were examined by DTA.Starting with amorphous compounds, two irreversible effects appeared; the first, at about 100°, was endothermic and corresponded to a considerable loss of water; the second was exothermic and corresponded to the crystallization of the compounds in the temperature range from 250 to 550°. Only InVO₄ presented two more irreversible exothermic peaks, corresponding to allotropic transformations, as proved by the X-ray diagrams.A reversible effect then appeared, showing an invariant equilibrium corresponding to a peritectic process for InVO₄ III, FeVO₄, CrVO₄ and AlVO₄ at 1134, 870 and 765°, respectively; these temperatures agreed with the known M₂O₃-V₂O₅ phase diagrams.The DTA curves of the semi-amorphous Nd and Y compounds showed only a loss of water at about 100°; crystallization then occurred gradually during heating; X-ray analysis confirmed these results.

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Zusammenfassung MVO₄ (M=dreiwertiges Element) wurde nach zwei Methoden in wässrigem Medium dargestellt. Die erste, bei der von Vanadinpentoxid und dem Nitrat von M ausgegangen wird, ergibt kristallines InVO₄ III und amorphes FeVO₄. Die zweite, von Ammoniummetavanadat und dem Nitrat von M ausgehende Methode ergibt amorphe Produkte für M=In, Fe, Cr oder Al und halbamorphe für M=Nd oder Y. Kristallinität und Reinheit dieser Produkte wurden mittels DTA untersucht. Bei den amorphen Verbindungen treten zwei irreversible Effekte in Erscheinung, nämlich bei etwa 100° ein durch Abgabe einer beträchtlichen Wassermenge bedingter endothermer Effekt und ein exothermer im Temperaturbereich von 250–550°, der der Kristallisation der Verbindungen zuzuschreiben ist. Nur InVO₄ zeigt zwei weitere irreversible exotherme Effekte, die auf allotropische Umwandlungen zurückzuführen sind, wie durch röntgendiffraktometrie gezeigt werden konnte. Danach tritt ein reversibler Effekt ein, der ein invariantes Gleichgewicht eines peritektischen Prozesses für InVO₄ III, FeVO₄, CrVO₄ und AlVO₄ bei 1134, 870, 880 bzw. 765° anzeigt. Diese Temperaturen stimmen mit den bekannten Phasendiagrammen von M₂O₃-V₂O₅ überein. Die DTA-Kurven der halbamorphen Nd- und Y-Verbindung lassen nur den Wasserverlust bei 100° erkennen, die Kristallisation erfolgt dann nach und nach während des Aufheizvorganges, wie dusch Röntgenanalyse gezeigt werden konnte.

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MVO₄ (M — ) . , , InVO₄ FeVO₄. , , , , — . . : 100° , , 250–550°, . InVO₄ , , , . InVO₄, FeVO₄, CrVO₄ AlVO₄ , , 1134, 870, 880 765°, , . , ₂₃-V₂O₅. - 100°. .

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Paper presented at the World Conference on Thermal Analysis Amsterdam, 1984.     

Chemiluminescence and auto-oscillations in the (S?Cr2O72+?UO22+) system

Quasi-harmonic oscillations of chemiluminescence intensity at certain concentrations of the components for the (S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) system in concentrated sulfuric acid and chemiluminescence and dark stages with the participation of intermediates Cr(V), U(IV) and sulfur peroxide radicals (HS₂O₆ ^.) have been discovered. Chemiluminescence is attributed to the interaction of HS₂O₆ ^. compounds. The processes of deactivation of the excited states of uranyl involve the participation of Cr(V). A scheme for the oscillation chemiluminescence reactions is suggested.

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(S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) H₂SO₄ , . Cr(V), U(IV) (HS₂O₆ ^.) HS₂O₆ ^. Cr(V) . .

     

Molybdenum complexes as catalysts for the reduction of molecular nitrogen in protic media

N₂-fixing systems in protic media consisting of different reducing agents and molybdenum complexes (initially Mo(V)) as N₂ activators form the same Mo(III) carbonyl upon replacing N₂ by carbon monoxide. When CO is removed from the carbonyl, the Mo(III) complex formed becomes again capable of catalyzing the reduction of N₂ to hydrazine by Ti(III) or Cr(II) hydroxide in aqueous alcohol. Sodium amalgam forms a particularly active system, reducting N₂ catalytically in the presence of a Mo(III) complex already at room temperature.

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, , , Mo(). - - - . , , - .