Parametric sensitivity of complex temperature-programmed desorption,reaction and reduction

Through simulation of the temperature-programmed desorption, reaction and reduction in a system of parallel reactions. it is shown that the experimental conditions influence the simultaneous or consecutive occurrence of the individual reactions of the system. Adjustment of the concentration of a gaseous reaction component or optimization of the temperature program results in a shift to the desired consecutive occurrence of the reactions. Therefore, a better resolution of the individual reactions can be achieved through a judicious choice of the experimental conditions of the temperature-programmed methods.

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Zusammenfassung Durch Simulierung temperaturprogrammierter Desqrption, Reaktion und Reduzierung in einem System von Parallelreaktionen konnte gezeigt werden, daß die experimentellen Bedingungen die Simultanität bzw. Konsekutivität der Einzelreaktionen des Systems beeinflussen. Durch eine Einstellung der Konzentration der gasförmigen Reaktionsprodukte oder durch Optimalisierung des Temperaturprogrammes kann eine gewünschte Folge der Einzelreaktionen erreicht werden. Somit kann durch eine geschickte Wahl der experimentellen Bedingungen bei temperaturprogrammierten Verfahren eine bessere Separierung der Einzelreaktionen erreicht werden.

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- , , , . . , - .

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The reaction of hypophosphorous acid with chloral

Conclusions The condensation of chloral with hypophosphorous acid has given,,-triebloro--hydroxyethyl phosphonous and bis-(, ,-trichloro--hydroxyethyl)-phosphinic acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, p. 1095, June, 1966.     

Steroid saponins and sapogenins ofAllium IX. The structure of aginoside

Summary From a methanolic extract of the skins of the bulbs ofAllium giganteum Rgl, a new steroid glycoside has been isolated — aginoside, which is (25R)-5-spirostan-2, 3, 6-triol 3-0-{[0--D-xylopyranosyl-(13)-]-[0--D-glucopyranosyl-(12)]-0--D-glucopyranosyl-(14)-0--D-galactopyranoside}.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 480–486, July–August, 1976.     

A method for preliminary estimation of solid oxidation kinetics and mechanism

The possibility of preliminary estimation of the oxidation kinetics and mechanism using the quantity t_o from the exponential kinetic rate equation is discussed.

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, t_o .

     

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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, .

     

Retro-michael reaction of 28-methoxy-18,19-secolupane-18,19-dione derivatives

The interactions with KOH in boiling diethyleneglycol of 3,28-dimethoxy- and 3-acetoxy-28-methoxy-18,19-secolupane-18,19-diones have been studied. In the first case, 3-methoxy-19,20,21,22,29,30-hexanor-18,19-seco(17H)lupan-18-one and the corresponding 18-ol were isolated from the mixture of products, and in the second case 3-hydroxy-19,20,21,22,29,30-hexanor-18,19-seco(17H)lupan-18-one — which was also obtained by an analogous reaction from 3-acetoxy-18,19-secolupan-18,19-dione — and 3-hydroxy-19,20,21,22,28,29,30-heptanor-18,19-secolupan-18-one. Thus, it has been found that in this case the retro-Michael reaction is accompanied by 28-demethoxylation and partially by 28-demethoxy-methylation.Pacific Ocean Institute of Bioorganic Chemistry, Far-Eastern Branch, Russian Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 210–215, March–April, 1992.     

Potential for coal calorific value corrections,dependent on the carbonate mineral type present

In addition to calcite, other carbonate minerals in coal all undergo endothermic reactions on heating, i.e. dolomite, ankerite, siderite, aragonite, magnesite, rhodochrosite, witherite and strontianite. Of these, when determined in air, siderite and rhodochrosite give small exothermic resultants, while the amount of Fe in ankerites affects the actual endothermic values obtained. The magnitude of these carbonate decomposition reactions can be shown by DTA to be different and will need to be allowed for individually in calorific value corrections of coals containing them.

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Zusammenfassung Nicht nur Kalkspat, sondern auch andere in Kohle vorkommende Karbonatmineralien wie z. B. Dolomit, Ankerit, Spateisenstein, Aragonit, Magnesit, roter Braunstein, Witherit und Strontionit gehen bei Erhitzen endothermische Reaktionen ein. Von diesen zeigen Spateisenstein und roter Braunstein exotherme Ergebnisse kleinen Wertes, während der Betrag an Eisengehalt in Ankeriten den jeweils gemessenen endothermischen Wert beeinflußt. Das Ausmaß dieser Karbonatzersetzungsreaktionen kann durch DTA-Messungen als unterschiedlich nachgewiesen werden und muß bei den Kaloriewertkorrektionen für Kohlen, die diese Mineralien enthalten, berücksichtigt werden.

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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.

     

Kinetics of oxidation of methanol by chlorine dioxide

The kinetics of oxidation of methanol by chlorine dioxide has been investigated at 35 °C. The reaction is first order with respect to both substrate and chlorine dioxide. Molecular chlorine dioxide is the principal oxidant. The influence of various factors, e.g. ionic strength, inorganic salts, D₂O and temperature on the initial rate has been studied. The activation parameters have been calculated and a mechanism involving hydride abstraction has been suggested.

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35 °C. , . . , . , , D₂O , . , .

     

Alkylation of toluene with ethylene on HZSM-5

Alkylation of toluene with ethylene on unmodified large-crystal HZSM-5 has been studied in a flow system at 673 K, atmospheric pressure. The yield of ethyltoluenes increased and that of benzene and xylenes decreased with time on stream. This change in yields was accelerated by increasing the ethylene content of feed and by pretreating the catalyst with ethylene. Selectivity for toluene ethylation increase with increasing space velocity.

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HZSM-5 673 . - , . - - -. .

     

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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, , .

     

Comparative basicities of substituted pyridines and electronegativity series for substituents in the pyridine series

Relationships between basicity of the pyridine ring and the nature and position of substituents are found. Comparative electronegativity series are constructed for substituents (, , and ) in the pyridine series. In isolated cases transmission of an effect from the position by a M effect is found.     

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 , . .

     

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.     

XPS, UPS and TDS studies of CO adsorption on platinum

XPS, UPS and TDS studies of the adsorption of carbon monoxide on partially recrystallized platinum foil at 300 K indicate that the adsorption is of nondissociative character and there are two CO_ads states.

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300 K. , . CO.

     

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. ' . , .

     

On the dissociation mechanism of carbonates and their isomorphous mixture

The thermal decomposition processes of carbonate minerals are analyzed by comparison of the notions on chemical bonds in crystals and modern concepts on solid-phase reactions. It is shown that depending on the mechanism of thermal dissociation, the carbonate minerals most widespread in nature may be divided into two groups: first, CaCO₃, SrCO₃ and BaCO₃, characterized by decomposition temperatures close to the equilibrium values and undergoing recombination on cooling; and second, MgCO₃, MnCO₃, FeCO₃ and ZnCO₃, with dissociation temperatures exceeding the equilibrium values by 250° and recombining only at high partial pressures of CO₂ (above 1000 bar).

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Zusammenfassung Die thermischen Zersetzungsprozesse von Carbonatmineralien wurden auf der Basis der Vorstellungen über die chemischen Bindungen in Kristallen und moderner Konzeptionen über Festphasenreaktionen analysiert. Es wird gezeigt, dass die in der Natur weitverbreitetsten Carbonatmineralien, abhängig vom Mechanismus der thermischen Zersetzung, in zwei Gruppen unterteilt werden können: die erste umfasst CaCO₃, SrCO₃ und BaCO₃ und ist durch Zersetzungstemperaturen nahe den Gleichgewichtswerten und durch Rekombination beim Abkühlen charakterisiert, zur zweiten gehören MgCO₃, MnCO₃, FeCO₃ und ZnCO₃ mit Dissoziationstemperaturen, die die Gleichgewichtswerte um etwa 250° überschreiten, und die nur bei hohen CO₂-Partialdrücken (über 1000 bar) rekombinieren.

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, . , , . CaCO₃, SrCO₃, BaCO₃ , . MgCO₃, MnCO₃, FeCO₃, ZnCO₃ , 250°, ( 1000 .).

     

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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( ) . .

     

Activity in CO oxidation of manganese dioxide for batteries

The low temperature oxidation of CO over MnO₂ containing samples for batteries has been investigated. It is found that the samples contain compositional and hydrate water and Mn⁴⁺, Mn³⁺, Mn²⁺ ions. The high efficiency is due to Mn⁴⁺ content.

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CO MnO₂, . , Mn⁴⁺, Mn³⁺, Mn²⁺. Mn⁴⁺.