Two mechanisms of the interaction between atoms and solids

The chemical action of atoms on solids can be due to both direct reactions with the structural units of solids and heterogeneous recombination energy transfer to the crystal lattice.

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, .

     

Molybdenum hexacarbonyl catalyzed photooxygenation of cyclohexane by air dioxygen in acetonitrile solution

ESR and XPS investigations on Cu/–Al₂O₃ catalysts with various amounts of Cu loading are reported. Experimental data are related to the surface structure and dispersed state of catalysts. The results show that ESR can be used as a means of charaterizing monolayer dispersed state for paramagnetic supported catalysts.

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Cu/–Al₂O₃ . . .

     

Hydrogenation of CO2 on carbon-supported nickel and cobalt

The hydrogenation of CO₂ has been studied at atmospheric pressure on Co/C and Ni/C catalysts and the results are compared with those obtained on unsupported Co and Ni. Specific activites in the form of turnover frequencies for CO₂ hydrogenation decrease with increasing metal dispersity. Carbon supported Co and Ni present a smaller selectivity for methane than bulk metals. Higher specific activities and smaller activation energies are obtained on Co catalysts, compared with those determined for Ni catalysts.

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CO₂ Co/ Ni/ Co Ni . CO₂ . Co Ni , . .

     

Influence of structural promoters on reduction dilatograms of iron catalyst

In each reduction step, changes in the catalyst pellet volume during reduction of precipitated iron catalysts are determined by the concentration of structural promoters and the reaction temperature.

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, , .

     

Study of solid-phase reaction of RbNO3 with V2O5

Using DTA, TG and DTG methods, the reaction between RbNO₃ and V₂O₅ in the molar ratio 65 in air atmosphere was studied. The reaction proceeds stepwise. In individual steps of the reaction the formation of RbV₃O₈, RbVO₃ and Rb₃V₅O₁₄ was observed. Rubidium pentavanadate is thermally unstable. At 1000°, RbVO₃ and Rb₂V₄O₁₁ were identified as products of its thermal decomposition. Rubidium tetravanadate was also prepared by the isothermal reaction of RbNO₃ with V₂O₅ in the molar ratio 11.

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Zusammenfassung Unter Anwendung der DTA-, TG- und DTG-Methoden wurde die Reaktion RbNO₃-V₂O₆ bei dem Molverhältnis von 65 in Luft untersucht. Die Reaktion verläuft stufenweise. Bei den einzelnen Stufen der Reaktion wurde die Bildung von RbV₃O₈, RbVO₃ und Rb₃V₅O₁₄ beobachtet. Rubidiumpentavanadat ist thermisch instabil. Bei 1000° wurden RbVO₃ und Rb₂V₄O₁₁ als Produkte seiner thermischen Zersetzung beobachtet. Rubidiumtetravanadat wurde auch durch die isotherme Reaktion von RbNO₃-V₂O₅ bei dem Molverhältnis von 11 hergestellt.

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Résumé On a étudié par ATD, TG et TGD dans l'air, la réaction RbNO₃-V₂O₅ (rapport molaire 65). La réaction s'effectue par étapes, avec formation de RbV₃O₈, RbVO₃ et Rb₃V₅O₁₄. Le pentavanadate de rubidium est thermiquement instable. A 1000°, RbVO₃ et Rb₂V₄O₁₁ ont été identifiés comme produits de la décomposition thermique. Le tétravanadate de rubidium a également été préparé par voie isotherme en faisant réagir RbNO₃-V₂O₅ (rapport molaire 11).

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, , RbNO₃-V₂O₅ 6 5. . RbV₃O₈, RbVO₃ Rb₃V₅O₁₄. 1000° RbVO₃ Rb₂V₄O₁₁, . RbVO₃-V₂O₅ 11.

     

Studies on the thermal behaviour of detonating fuse and detonators

Investigations of the thermal stability of detonating fuse containing 10 g pentaerythrol tetranitrate (PETN) revealed that the cord burnt under unconfinement at 403 K. Under confinement in a steel pipe or copper tube there was a partial detonation at 403 K. In order to characterize the thermal stability of PETN and pyrotechnic composition used in fuse head of electric detonators differential thermal analysis (DTA) was used.The electric detonators of aluminium cell and copper cell were heated from ambient temperature to 373 K at an average rate of 0.4 deg/min. The rate of heating was increased gradually to 1.5 deg/min till explosion. The detonation temperature varied between 373 K and 375 K.The impact and friction sensitivity of detonating fuse was poor. There was no detonation when a 5 kg hammer was repeatedly hit over the fuse from a height of one metre. There was no detonation when the detonating fuse was rubbed by a blunt edge of steel plate till it was smashed.

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Zusammenfassung Untersuchungen der thermischen Stabilität von Sprengschnuren mit 10 gm^–1 PETN zeigten, daß die Schnur frei bei 403 K verbrennt. Unter Abschluß in einem Stahloder Kupferrohr tritt bei 403 K eine partielle Detonation auf. Zur Charakterisierung der thermischen Stabilität von PETN und von pyrotechnischen Mischungen, die in Zünderköpfen von elektrischen Sprengkapseln verwendet werden, wurde Differentialthermoanalyse (DTA) angewendet. Die elektrischen Sprengkapseln von Aluminium- und Kupferzellen wurden mit einer durchschnittlichen Aufheizgeschwindigkeit von 0.4 Grad/min von Raumtemperatur auf 373 K erhitzt. Die Aufheizgeschwindigkeit wurde bis zur Explosion allmählich auf 1,5 Grad/min erhöht. Die einzelnen Detonationen erfolgten bei einer Temperatur zwischen 373 und 375 K. Die Stoß- und Reibempfindlichkeit der Sprengschnur war gering. Bei einem mehrmaligen Einwirken eines 5 kg-Hammers aus einer Höhe von 1 m erfolgte keine Detonation. Bei Reiben mit der unscharfen Kante einer Stahlplatte bis zur Zerstörung erfolgte keine Detonation.

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, 10 ^–1 PETN, , 403 , 403 . PETN , , . 373 0,4°/. 1,5°/ . 373 375 . . 5 1 . , .

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The authors are indebted to the Director, Central Mining Research Station for giving permission to publish this paper. The views expressed in the paper are those of the authors and not necessarily of the institute which they belong to.     

Applications of thermal analysis

This review paper outlines some current developments in thermal analysis. The current status of standard methods, in particular those issued by the American Society for Testing and Materials (ASTM), using thermal analysis techniques are discussed. In the second place a simple method for the determination of the oxidative stability of polyethylene by DTA is reviewed. Finally the paper surveys some of the more recent work being carried out in fossil fuels and fuel oils.

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Zusammenfassung Dieses Referat umreisst einige zeitgemässe Entwicklungen der Thermoanalyse. Es wird der derzeitige Stand der Standardmethoden besprochen, besonders derjenigen, die durch die American Society for Testing + Materials (ASTM) veröffentlicht wurden, und die ein thermoanalytisches Verfahren verwenden. In zweiter Reihe wird eine einfache Methode zur Bestimmung der oxydation Stabilität des Polyäthylens mittels DTA bekanntgemacht. Zum Schluss übersieht die Arbeit einige neuere Arbeiten, die an festen Heizmaterialien und Heizölen durchgeführt wurden.

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. , , , ASTM. ' . , .

     

Neighboring general acid participation in thiolester aminolysis in an aprotic solvent

The kinetics of n-butylaminolysis of acyl-substituted phenyl tiolbenzoates in acetonitrile at 25°C was studied. From the second order rate constants a Hammett rho value of 1.45 was obtained. The results indicate a proinounced neighboring group effect in the reaction of phenyl thiolsalicylate, providing the first kinetic evidence for intramolecular general acid participation by a hydroxy function in an aprotic solvent.

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- - 25 °C. , 1,45. -, .

     

Effect of medium composition on the monooxygenase activity of immobilized hemin in aniline oxidation

The effect of the composition of the reaction medium on the rate of aniline oxidation to p-aminophenol by hydrogen peroxide on hemin immobilized on -propylimidazole-modified silica has been studied. Organic solvent additives (alcohols, esters and nitriles) are shown to increase the reaction rate. The observed effect is attributed to the decrease of the medium dielectric constant.

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

     

Determination of acid sites on carbon surface

Pyridine chemisorbed on acid sites of active carbon was displaced by n-butylamine and the displaced amount was measured spectrophotometrically. This amount, supposed to be proportional to the surface concentration of carboxy groups, depends on the chemical pretreatment of active carbon.

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, , . , , .

     

Topochemical reactions

A survey of topochemical reactions is given and the theory of their kinetics is discussed.

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Zusammenfassung Eine Übersicht über die topochemische Reaktion wird gegeben und die Theorie ihrer Kinetik erörtert.

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Résumé On présente une étude d'ensemble sur les réactions topochimiques en discutant la théorie de la cinétique.

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This paper was written from a series of lectures read by the author at the First All-Union School on the Chemistry of Solids (Novotsherkask, September 1972).     

Specificity of states of Cu2+ ions in ZSM zeolites due to the cooperative Jahn-Teller effect

Crystalline silicate of ZSM zeolite structure was synthesized via hydrothermal crystallization at large contents of copper. ESR spectra of Cu²⁺ ions stabilized in this system are determined by the specific ordering due to the cooperative Jahn-Teller effect of Cu²⁺ ions with the d_x ²–y² ground state.

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423° ZSM . Cu(II), , - Cu²⁺ cdx²–y²— .

     

AlPO4?ZrO2 catalysts, II. Synthesis, textural properties and crystal structure of systems obtained in ethylene oxide

The effects of surface dehydration on textural properties, crystallinity and the structure of AlPO₄–ZrO₂ (weight ratio AlPO₄/ZrO₂=3) systems precipitated with ethylene oxide have been studied by N₂ adsorption and XRD measurements. The increase in calcination temperature in the range 773–1273 K decreases the textural parameters as a consequence of AlPO₄ crystallization to the tridymite form.

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, AlPO₄–ZrO₂ ( AlPO₄/ZrO₂=3), , N₂ - . 773 1273 , AlPO₄ .

     

Coordination polymers. IX

Poly-(butanediol-1,4-adipate) and poly-(diethyleneglycol-succinate) polyesters and their ionized derivatives, containing Mg²⁺ and Zn²⁺ ions with different stoichiometric ratios to the chain-end COOH groups of the polyesters have been investigated by derivatograph.The thermal decompositions of the metal-containing polyesters differ significantly from those of the unionized polyesters. These differences are connected with the chemical repeating unit of the polyesters and the chemical nature of the metal ions, and proportional to the amount of the latter.An explanation is given of the catalytic effect of metal ions on the process of decomposition of the polyesters.

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Zusammenfassung Poly-(butandiol-1,4-adipat) und Poly-(diethylenglycolsuccinat) polyester und ihre «ionisierten» Derivate — mit Mg²⁺ — und Zn²⁺-Ionengehalt in verschiedenen stöchiometrischen Verhältnissen zu den endständigen COOH-Gruppen der Polyester — wurden im Derivatographen untersucht.Die thermische Zersetzung der metallhaltigen Polyester unterscheidet sich wesentlich von nicht-ionisierten Polyestern. Diese Unterschiede sind mit den sich wiederholenden chemischen Einheiten der Polyester und der chemischen Beschaffenheit der Metallionen verbunden, und proportional dem Anteil derselben.Es wird eine Erklärung des katalytischen Effekts der Metallionen auf den Zersetzungsvorgang der Polyester gegeben.

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-1,4 «» , Mg²⁺ Zn²⁺ . , «» . . .

     

Computation in kinetics I. A general program KILET for simulation and evaluation of kinetic experimental data in multicomponent systems

A general regression program KILET written in FORTRAN IV for an IBM PC and other computers (MV 4000 Eclipse and EC 1033) enables (i) to model multicomponent kinetic data (ii) to load the smooth curves with random noise of required level (iii) to evaluate rate constants and/or simultaneously concentrations. Complete statistical analysis of residuals is performed. The program can be used for the discrimination of chemical kinetic models and for analytical purposes.

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KILET, FORTRAN IV IBM PC (MV 4000 Eclipce EC 1033), 1) , 2) , 3) / . . .

     

Some problems of diffusion controlled reactions treated by the Monte Carlo technique

The Monte Carlo technique is used to describe the kinetic behavior of radicals in spurs. The experimentally well established linear relationship between the yields of molecular products and cube root of scavenger concentration is explained by considering spur reactions as random walk with annihilating interactions.

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. , .

     

A novel method for the preparation of extensively dealuminated faujasites

Open structure faujasites may be dealuminated with retention of crystallinity using phosgene (or similar reactants) provided the sample has been made ultrastable in a previous procedure.

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( ) . .

     

Isomerization and hydrogenation of butene-1 on a zirconia aerogel catalyst

Zirconia is well known as a promising support for active metallic centers but it is also by itself an interesting catalyst for reactions involving hydrogen in particular. This paper describes the catalytic properties of ZrO₂-obtained in the form of an aerogel-, towards butene-1-isomerization and/or its hydrogenation at low temperature. Activation at 430°C in vacuum led to the best results in cis-trans isomerization in the temperature range of 80–200°C. It is shown that at temperatures 150°C a carbanion mechanism is operating while at higher temperatures the thermodynamic selectivity is attained. Selective poisoning experiments by NH₃ or CO₂ were carried out in order to identify the catalytic sites for the isomerization of n-butene.

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, , . ZrO₂, , / -1 . 430°C - 80–200°C. , 150°C , . NH₃ CO₂ -.

     

Catalytic desulfurization of ethanethiol over zinc-forms of NaX zeolites

Zinc exchanged zeolite X was found to catalyze effectively the dehydrosulfurization of ethanethiol. The catalytic activity correlated linearly with the degree of ion exchange and increased with the reaction temperature. The role of zinc cations in the reaction examined is discussed and suggestions concerning the reaction mechanism are put forward.

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X, Zn, . . .

     

Traitement mecanique des materiaux III

Résumé Les auteurs ont recherché l'effet du broyage sur la réactivité ultérieure des hydrates K₂C₂O₄ · H₂O; CaC₂O₄· H₂O et BaC₂O₄ ·nH₂O avecn=0, 1/2, 1 et 2. La thermolyse de ces hydrates préalablement broyés montre que le traitement mécanique provoque dans la plupart des cas un abaissement de la température de déshydratation mais aussi, dans certains cas, une modification des étapes de cette réaction. Ces effets se manifestent surtout lorsque le broyage préalable est de courte durée et ils peuvent être modifiés par les conditions de pression et de température imposées pendant le traitement mécanique. La comparaison des variations, en fonction du temps de broyage, de la température de déshydratation commençante et des autres caractéristiques physico-chimiques de l'hydrate broyé a permis de montrer que la tension superficielle des grains du matériau broyé est un facteur d'action prépondérant.

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The authors studied the effects of prior grinding on the reactivity of the hydrates K₂C₂O₄ · H₂O, CaC₂O₄ · H₂O and BaC₂O₄ ·nH₂O, withn= 0, 1/2, 1 and 2. The thermal decomposition of these previously ground hydrates showed that in most cases the mechanical treatment brings about a decrease in the thermal dehydration temperature, but also change in the reaction steps in some cases. These effects are mainly notable after short-time grinding, and they may be modified by changes in the grinding temperature and vapour pressure conditions. Comparison of the variations with time of the beginning dehydration temperature and the other physico-chemical characteristics of the ground hydrates showed the prevailing influence of the surface tension of the ground material.

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Zusammenfassung Es wurde der Einfluß eines vorhergehenden Mahlens auf die Reaktivität der Hydrate: K₂C₂O₄ · H₂O; CaC₂O₄ · H₂O; BaC₂O₄ ·n H₂O mitn=0. 1/2, 1 und 2 untersucht. Die Thermoanalyse dieser vorher gemahlenen Hydrate zeigt, daß die mechanische Behandlung in den meisten Fällen eine Abnahme der Dehydratisierungstemperatur zur Folge hat, in einigen Fällen jedoch auch eine änderung in den Reaktionsschritten. Diese Effekte werden hauptsächlich bei dem Kurzzeit-Mahlen sichtbar und müssen durch änderung de Mahltemperatur und der Dampfdruckbedingungen modifiziert werden. Der Vergleich der änderungen der anfänglichen Dehydratisierungstemperatur und der anderen physikalisch-chemischen Charakteristika des gemahlenen Hydrats mit der Zeit zeigt den dominierenden Einfluß der Oberfläche auf das Mahlgut.

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K₂C₂O₄· H₂O; CaC₂O₄· H₂O; BaC₂O₄·nH₂O cn=0, 1/2, 1 2 . , , — . . - , .

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Les auteurs remercient tout particulièrement Madame le Professeur G.Watelle pour l'aide précieuse qu'elle leur a apporté dans la discussion et la présentation de ce travail.