Cation-radical of pyridine N-oxide and its reactions with C?H bonds

Visible absorption spectrum for the cation-radical of pyridine N-oxide pyO⁺ obtained in the oxidation of the appropriate N-oxide by the photo-excited triplet state of chloranil, has a wide maximum at =430–460 nm. pyO⁺ reacts with cyclohexane, methanol or toluene with the formation of intermediate complexes. Equilibrium constants of their formation K×10^–2 dm³/mol amount to 0.1, 1.0 and 2.0, respectively. The (pyO⁺...RH) complex readily reacts with O₂, and in the absence of O₂ its decomposition is independent of the hydrocarbon nature.

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- N- (pyO⁺) N- . pyO⁺ , =430–460 . , pyO⁺ , , , (×10^{–2 3}/) 0,1, 1,0 2,0. , .

     

Methanol transformations on zirconium phosphate, CuX zeolite and their mixtures

It has been revealed that the mixtures of CuX zeolite and zirconium phosphate are more active catalysts for the oxidative dehydration of methanol than the individual components.

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- .

     

Isomerization of chemically activated secondary butyl radical

Photolytic decomposition of hydrogen sulfide followed by the addition of energized hydrogen atoms to cisbut-2-ene gives excited sec-butyl radicals. The radicals undergo a 1,3 hydrogen migration as is evidenced by the good agreement between the RRKM calculations and experiment. The contribution of a 1,2 hydrogen shift cannot be excluded. The threshold energies are 153.8 and 176.8 kJ mol^–1 for 1,3 and 1,2 isomerization, respectively.

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-2 .- . 1,3- , . , 1,2- . 153,8 176,8 / 1,3- 1,2-, .

     

Estimation of nonlinear relaxation of catalytic reactions

Nonlinear relaxation time has been considered as a differential characteristic determined by the reciprocal value of the relative decrease in the deviation rate of the current concentration vector of intermediates from that of their steady-state concentrations. This characteristic is used for the analysis of some model reactions.

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, , .

     

Kinetic laws for dehydrogenation of cyclohexane over Pd/C catalysts

A kinetic equation for cyclohexane dehydrogenation at P_O=1.0 MPa has been obtained.

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1,0 .

     

ESCA study of (Mo+Pt)/SiO2, (W+Pt)/SiO2 and (Re+Pt)/SiO2 catalysts

Supported catalysts obtained from organometallic compounds have been studied by ESCA. The data obtained indicate a decrease in electron density on the Pt atoms as a result of interaction with Mo, W and Re ions bound to silica.

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, . , Mo, W, Re, .

     

Preparation et proprietes physico-chimiques de l'alanate de magnesium Mg(AlH4)2

Résumé L'alanate de magnésium Mg(AlH₄)₂ désolvaté a été obtenu avec une pureté satisfaisante. La décomposition thermique a été étudiée par thermogravimétrie sous pression réduite (10^–3 torr). La capacité calorifique molaire à 298 K ainsi que l'enthalpie de formation ont été déterminées avec un microcalorimètre Calvet.C _p Mg(AlH₄)₂=32.5 cal·mol^–1·K^–1;H _fMg(AlH₄)₂=–19.2 kcal· mol^–1

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Solvent-free Mg(AlH₄)₂ has been prepared with good purity. Thermogravimetry has been used to investigate the thermal decomposition of Mg(AlH₄)₂ under low pressure (10^–3 torr). The molar heat capacity at 298 K and the heat of formation have been measured with a CALVET microcalorimeter.C _p Mg(AlH₄)₂=32.5 cal·mol^–1·K^–1 H _fMg(AlH₄)₂=–19.2 kcal·mol^–1

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Zusammenfassung Lösungsmittelfreies Mg(AlH₄)₂ wurde mit befriedigender Reinheit hergestellt. Scine thermische Zersetzung wurde durch Thermogravimetrie bei niedrigem Druck (10^–3 torr) untersucht. Die molare Wärmekapazität bei 298 K und die Bildungswärme wurden mit einem Calvet Mikrokalorimeter gemessen.C _p Mg(AlH₄)₂=32.5 cal·mol^–1·K^–1;H _f Mg(AlH₄)₂=–19.2 kcal· mol^–1

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Mg(AlH₄)₂, . Mg(AlH₄)₂ (10^–3 ) . 298 . C_pMg(AlH₄)₂=32.5 ^–1. ^–1 H _fMg(AlH₄)₂=–19.2 ^–1.

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Ce travail a été effectué dans le cadre d'un contrat de recherches passé par le Laboratoire de Chimie Minérale avec la Direction des Recherches et Moyens d'Essai. Nous remercions bien vivement cet organisme de l'aide qu'il a nous apportée.     

DTA and chemical characteristics of YBa2Cu3O6.5+γ superconductor processing from different raw materials

The YBaCu=123 coprecipitates of carbonates (precipitated with Na₂CO₃ or Na₂CO₃-NaOH solution) and of oxalates (obtained in aqueous, partly aqueous and non-aqueous media) were investigated as concerns the yield and stoichiometry of the precipitates, including their transmission electron microscopy and DTA characteristics. Oxalates coprecipitated from acetate solutions in non-aqueous media provide fine samples with increased reactivity. For comparison, when thermally treated, an oxide ceramic mixture containing aged BaO (with some Ba(OH)₂ and BaO₂) exhibits increased reactivity due to the formation of a liquid phase in the temperature range 400–500°.

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Zusammenfassung Gemeinsam gefällte Carbonate (aus Na₂CO₃- bzw. Na₂CO₃-NAOH-Lösung) und Oxalate (aus wässeriger, wässerig-akoholischer bzw. alkoholischer Lösung) von Y, Ba und Cu im Molverhältnis 123 wurden untersucht in Bezug auf die Ausbeute und Stöichiometrie der Fällungsprodukte, mittels Transmission-Elektronenmikroskopie und DTA. Durch Oxalatfällung aus Acetaten in nichtwässeriger Lösung wurden feinteilige Proben erhöhter Reaktivität erhalten. Zum Vergleich wurden oxidkeramische BaO-haltige Mischungen (die infolge Alterung durch Ba(OH)₂ und BaO₂ verunreinigt waren) thermisch behandelt und zeigten infolge Bildung einer flüssigen Phase im Temperaturbereich 400–500 °C ebenfalls erhöhte Reaktivität.

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, , 1:2:3 Na₂CO₃ Na₂CO₃-NaOH, , , . , . . , ()_{2 2}, , 400–500°.

     

Thermal decomposition kinetics of iron(III), cobalt(II), nickel(II) and copper(II) complexes of a Schiff base derived from quinoxaline-2-carboxaldehyde and glycine

Quinoxaline-2-carboxalideneglycine complexes of iron(III), cobalt(II), nickel(II) and copper(II) complexes were subjected to a systematic TG/DTG analysis. The decomposition process consists of two stages for all these complexes. Kinetic parameters were evaluated for each of these stages using the Coats-Redfern equation. The rate of decomposition at the second stage seems to have a bearing on the catalytic effect of the metal oxides formed during this stage.

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-2- (III) (II), (II) (II) /. . - . , -, , .

     

Catalytic autooxidation of hydroquinone in the presence of chelate complexes of transition metals

Autooxidation of hydroquinone was studied in the presence of Co and Cu complexes with salene, decamethyl-octadehydrocorrine, corrine and o-phenanthroline as ligands in aqueous solution and in protic and aprotic solvents. A possible mechanism of the catalytic action of some active complexes is discussed.

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, Co, Cu , , - . .

     

Kinetic studies of Pt/Al2O3 catalyst pellets with nonuniform activity

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al₂O₃) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

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(Pt) (Al₂O₃). , , .

     

Ethylene hydroformylation over a nafion-supported rhodium catalyst

Ethylene hydroformylation over a Nafion-supported rhodium catalyst has been studied under atmospheric pressure in the temperature range of 100–135 °C, using the transient response method.

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, , 100–135°C, .

     

FTIR investigation of the structure of vanadium oxides on ZrO2 and oxidation of toluene on it

The oxidation of toluene has been studied on V₂O₅/ZrO₂ by both FTIR spectroscopy and pulse method. The results suggest that Lewis-acidic sites play a significant role in the formation of benzaldehyde from toluene.

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V₂O₅/ZrO₂ - , . .

     

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⁺.

     

Influence of CO2 and H2O on methane conversion over oxide catalysts

It has been established that the introduction of CO₂ and H₂O to the reaction mixture when using freshly prepared catalysts, increases the overall methane conversion and decreases the yield of hydrocarbons. On coked MgO their effect is insignificant.

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, CO₂ H₂O . MgO CO₂ H₂O .

     

Traitement mecanique des materiaux

Résumé Les auteurs présentent les effets du broyage par percussion et par abrasion sur les caractéristiques morphologiques, cristallographiques et celles liées à l'état de surface pour une série d'oxalates hydratés (CaC₂O₄ · H₂O; K₂C₂O₄ · H₂O; BaC₂O₄ · nH₂O avecn=0, 1/2, 1 et 2). Il apparaît notamment que hormis les modifications de taille et des propriétés superficielles des cristallites, le broyage provoque dès le début du traitement des distorsions réticulaires importantes. Ces dernières s'atténuent très curieusement avec la durée du broyage mais elles réapparaissent, dans certains cas, après plusieurs heures de traitement. La signification de telles fluctuations, observées aussi pour l'état de cristallisation des sels broyés par abrasion, est discutée. Un rapprochement est fait entre les dimensions limites des grains d'hydrate auxquelles on aboutit par broyage et celles des cristallites obtenus par thermolyse de ces mêmes hydrates.

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The effects of a mechanical treatment involving impact and abrasive milling on the morphologic, crystallographic and superficial characteristics of a series of salts including CaC₂O₄ · H₂O, K₂C₂O₄ · H₂O, and BaC₂O₄ · nH₂O, withn=0, 1/2, 1 and 2, are described. It appears that, apart from changes in the granulometry and the surface properties of the crystallites, from the beginning of the treatment the grinding introduces important reticular distortions. These curiously decline when the grinding is extended, but also increase again after some hours of treatment. The significance of such fluctuations, also observed in the crystallization state of the abrasive milled salts, is discussed. A comparison is made between the limit dimensions of the crystallites of a given hydrate produced by grinding, and those of the crystallites of the same salt obtained by dehydration.

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Zusammenfassung Es wird über den Einfluß einer durch Schlag und Schleifmahlen durchgeführten mechanischen Behandlung auf die morphologischen, kristallographischen und Oberflächencharakteristika eine Reihe von Salzen, einschließlich CaC₂O₄ · H₂O; K₂C₂O₄ · H₂O; BaC₂O₄ · nH₂O mitn=0, 1/2, 1 und 2, berichtet. Es zeigte sich besonders, daß mit Ausnahme der Änderungen in der Korngröße und der Oberflächenbeschaffenheit der Kristallite, das Mahlen, von Anfang der Behandlung an bedeutende retikuläre Störungen herbeiführt. Diese verringern sich interessanterweise bei längerem Mahlen, nehmen aber nach mehrstündiger Behandlung wieder zu. Die Bedeutung solcher Schwankungen, wie sie auch in dem kristallinen Zustand der durch Schleifmahlen behandelten Salze beobachtet werden, wird erörtert. Ein Veggleich zwischen den Grenzdimensionen der durch Mahlen hergestellten Kristallite eines gegebenen Hydrats und der durch Dehydratisierung erhaltenen Kristallite desselben Salzes wird vorgenommen.

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, , ₂₄ · ₂; ₂₂₄ · ₂; ₂₄ ·n₂ (=, 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.     

Effect of acid-base properties of catalysts on their activity in methylmercaptane synthesis

Catalysts containing large amounts of surface acid sites are highly active, but in their presence equal yields of methylmercaptane and dimethyl sulfide are obtained. Catalysts containing predominantly strong basic sites on their surfaces are less active but more selective towards methylmercaptane formation than the former catalysts.

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, , , , . , , .

     

Collisional energy transfer in the decomposition of 2-methyloxetane and 3-methyloxetane, I. Gas/gas collisions

The pressure dependence of the unimolecular rate constants for the thermal decomposition of 2-methyloxetane and 3-methyloxetane has been studied. The average energy transferred downward in gas-gas collision was determined by the application of RRKM theory and a stepladder model of energy transfer.

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2- 3-. , - , .