Catalytic activity of transition metal silicides in hydrogen oxidation

The catalytic activity of transition metal silicides in H₂ oxidation is much higher compared to metal-like carbides, which can be due to the lower electronegativity of silicon compared to carbon.

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, , .

     

Thermoanalytical investigations on the decomposition of double salts

The melting and decomposition behaviour of carnallite was investigated in the closed system under dynamic heating conditions and in the open system under dynamic and quasi-isothermal and quasi-isobaric conditions in the temperature range between 20 and 300°. DTA heating and cooling cycles in the closed system illustrate the incongruent melting of carnallite and the occurrence of different magnesium chloride hydrate phases. The thermal decomposition under quasi-isothermal and quasi-isobaric conditions begins at a pressure of at least 100 kPa from the melt and under reduced pressure from the solid. In any case KCl · MgCl₂ · 2 H₂O is formed which is decomposed to a basic product KMgCl_2.84–2.90(OH_0.10–0.16.

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Zusammenfassung Die Schmelz- und Zersetzungseigenschaften des Carnallits wurden im geschlossenen System unter dynamischen Heizbedingungen und im offenen System under dynamischen und quasi-isothermen und quasi-isobaren Bedingungen im Temperaturbereich von 20 bis 300°C untersucht. DTA Heiz- und Kühlzyklen im geschlossenen System verdeutlichen das inkongruente Schmelzen des Carnallits und das Auftreten verschiedener Magnesiumchlorid-Hydratphasen. Die thermische Zersetzung beginnt unter quasi-isothermen und quasi-isobaren Bedingungen bei einem Druck von mindestens 100 kPa aus der Schmelze und unter verminderten Druck aus der festen Phase. Die Zersetung verläuft stets über KCl · MgCl₂ · 2 H₂O zu einem basischen Produkt KMgCl_2.84–2.90(OH)_0.10–0.16.

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— -, - V 20–300°. . - - 100 , — . KCl · l₂ · 2 ₂, Kgl_2.84–2.90()_0.10–0.16.

     

Influence of calcination on the electrical properties of tin-antimony mixed oxide catalysts

The electrical conductivity study of Sn–Sb mixed oxide powders is consistent with an enrichment in Sb (due to calcination) of the surface region where a solid solution of Sb in SnO₂ and a Sb₂O₄ surface phase coexist.

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Sn–Sb Sb- — , Sb SnO₂ Sb₂O₄.

     

Influence of HCl on butene isomerization catalyzed by ethanolic rhodium trichloride II. Calculation and interpretation of the rate constants of the triangle scheme

The values of the rate constants of the triangle scheme, calculated by means of a non-linear least-squares method, depend systematically on the HCl concentration. The alteration of the cis-trans selectivity expressed by the ratio k_1c/k_1t might indicate a change in the mechanism of isomerization with the HCl concentration.

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, , . - , k_1c/k_1t, .

     

Infrared study of the adsorption and reactions of nitric oxide on CuY zeolites

The adsorption and the reactions of nitric oxide on CuY zeolites with copper ions in various states have been studied by IR-spectroscopy. Forms of NO adsorbed on individual Cu²⁺ ions, on weak and strong magnetic formations, and on Cu⁺ ions have been observed. Processes of oxidation and reduction of NO to NO₂, N₂O and N₂ occurring on CuY zeolites are discussed. Adsorption of nitrogen on coordinatively unsaturated copper ions has been observed.

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- CuY . NO Cu²⁺, Cu¹⁺. --, CuY NO₂, N₂O N₂. .

     

Heat capacities of diphenyl,p-terphenyl andp-quaterphenyl from 180 K to their melting points

The heat capacities of diphenyl,p-terphenyl andp-quaterphenyl from 180 K to their melting points were measured with a Perkin-Elmer DSC 1B scanning calorimeter. Anomalies were observed in the heat capacity curves forp-terphenyl (from 400 K to the melting point) andp-quaterphenyl (from 190 to 260 K, and from 450 to 540 K). It is assumed that the anomalies near the melting points of the compounds under consideration could be related both to modification of the motion of the phenyl rings (external or/and internal) and to change in the motion of the molecules as a whole (diffusion phase).

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Zusammenfassung Die Wärmekapazitäten von Diphenyl,p-Terphenyl undp-Quaterphenyl wurden im Bereich von 180 K bis zum Schmelzpunkt der Verbindungen mit einem Perkin-Elmer DSC 1B Scanning-Kalorimeter gemessen. Anomalien der Wärmekapazitätskurven wurden beip-Terphenyl (von 400 K bis zum Schmelzpunkt) und beip-Quaterphenyl (von 190–260 K und von 450–540 K) beobachtet. Es wird angenommen, daß die Anomalien nahe der Schmelzpunkte der betreffenden Verbindungen auf Veränderungen der Bewegung der Phenylringe (äußere und/oder innere) und der Moleküle an sich (Diffusionsphase) zurückzuführen sind.

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- 1 , - - 180 . - 400 , - — 190 260 450 540 ., ( ), ( ).

     

Preparation of some α,α-diaryl-substitutedβ-thiolactones andβ-lactones

Conclusions The general method of obtaining-propiothiolactones that we have proposed previously has been used for the synthesis of a series of new,-diaryl-substituted-propiothiolactones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2025–2027, November, 1966.     

Surface forms of unsaturated hydrocarbons and their transformations on group VIII metals

IR-spectroscopic and kinetic studies of the surface forms of unsaturated hydrocarbons and their catalytic transformations on group VIII metals have been carried out. Data on the nature and properties of surface compounds in hydrogenation and hydrocracking reactions have been obtained, yielding the sequence of selectivities in these processes.

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- VIII . , .

     

Benzene hydrogenation on nickel/honeycomb catalysts

Monolithic supported nickel catalysts were investigated in benzene hydrogenation between 100 and 280 °C. The conversion of benzene to cyclohexane reaches a maximum around 210 °C with a maximum yield at a ratio p^oH₂/p^oBz=3. The experimental results and some kinetic aspects are discussed.

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100 280 °C. 210 °C p^oH₂/p^oB=3. .

     

Oscillation chemiluminescence in liquid phase oxidation of organic compounds

It is for the first time that distinct chemiluminescence oscillations have been observed in the liquid phase oxidation for the system: oxidative substrate — thermal initiator — photosensitizer — O₂. Oscillations and their parameters are dependent on the experimental conditions.

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: — — —O₂. .

     

A new Ba(OH)2 catalyst for synthesis of diacetone alcohol

The application of new Ba(OH)₂ catalysts for the preparation of diacetone alcohol is described. No loss of activity is observed when they are stored in a dessiccator over NaOH. The same yield as that described in the literature is obtained, but in a much shorter reaction time (9.5 h against 72–120 h)

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Ba(OH)₂ . NaOH . , , (9,5 72–120 ).

     

Reaction between the OH group of hydroxyproline and diisocyanate catalyzed by an organotin compound

We have studied the kinetics of the reaction of L-hydroxyproline with OCH(CH₂)₆NCO, catalyzed by organotin, avoiding side reactions by protecting the other active hydrogens of the aminoacid, and comparing it with the MeOH/n-BuNCO system.

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L-- -OCN(CH₂)₆NCO, , . . - .

     

Kaolinite-mullite series: Firing vs. reactive hot-pressing

The effect of an applied pressure on the transformation of metakaolin to spinel has been studied under reactive hot-pressing conditions and the results are compared with the conventionally fired clays. For the experiments both Georgia kaolin and a Canadian fireclay (kaolinitic) were used. The results indicated that the transformation temperature of metakaolin to spinel can be lowered by the application of an external pressure, confirming the earlier work of Carruthers and Wheat. The application of Clapeyron-Clausius equation showed that in order to lower the transformation temperature, the enthalpy change (H) for this transformation has to be positive, contrary to experimental DTA plots, where an exothermic reaction is generally encountered. This anomalous behaviour can be explained, if it is accepted that the exothermic peak at about 900°C in the kaolinite to mullite transformation sequence is due to the crystallization of amorphous silica, as suggested by Nicholson and Fulrath.

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Zusammenfassung Der Einfluß eines geeigneten Druckes auf die Umwandlung von Metakaolin in Spinell wurde unter den Bedingungen des reaktiven Warmpressens untersucht und die Resultate mit den für konventionell gebrannten Ton erhaltenen verglichen. Die Versuche erfolgten mit einem Kaolin aus Georgia und einer Tonart aus Kanada. Die Ergebnisse zeigen, daß die Übergangstemperaturen Metakaolin-Spinell durch Anwendung eines äußeren Druckes erheblich vermindert werden können. Mit Hilfe der Clausius-Clapeyronschen Gleichung wurde für die Umwandlung eine positive Enthalpieänderung errechnet, hingegen deuteten die experimentellen DTA Spitzen eine exothermische Reaktion an. Dieses anomalische Verhalten läßt sich durch die Annahme von Nicholson und Fulrath erklären, nach der die exothermische Spitze bei 900° beim Kaolinite-Mullit Übergang der Kristallisation des amorphen Siliziumdioxyds zuzuschreiben ist.

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Résumé Etude de l'influence de la pression exercée à chaud sur la transformation du métakaolin en spinelle et comparaison des résultats avec ceux obtenus avec les argiles calcinées de manière conventionnelle. Les expériences ont été pratiquées sur un kaolin de Géorgie et sur une argile kaolinitique du Canada. Les résultats montrent que le fait d'exercer une pression extérieure abaisse d'une manière importante la température de la transformation du métakaolin en spinelle. La variation d'enthalpie correspondante a été calculée à l'aide de l'équation de Clausius-Clapeyron. On l'a calculé positif, cependant les pics ATD montrent une réaction exothermique. On peut expliquer ce comportement anomalistique par la suggestion de Nicholson et Fulrath, selon laquelle le pic exothermique de 900° dans la transformation kaolinite/mullite est due à la cristallisation de l'oxyde de silice amorphe.

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, . . , . (+H) - .

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Thanks are due to Dr. D. Coates for his helpful suggestions on the applicability of the Clapeyron-Clausius equation in this transformation sequence.     

Über das 2-Dichlormethyl-oxazolin und seine Kondensation mit 4-Nitrobenzaldehyd

Zusammenfassung N-Dichloracetyläthanolamin (I) wurde über das mit SOCl₂ erhaltene N-Dichloracetyl--chloräthylamin (II) durch Alkali in das 2-Dichlormethyl-oxazolin (III) übergeführt, dessen sehr leicht erfolgende hydrolytische Umwandlungen beschrieben werden. Kondensation von 4-Nitrobenzaldehyd mit (III) erfolgt ohne jedweden Katalysatorzusatz unter den mildesten. Bedingungen an der überaus reaktiven Methingruppe des Dichlormethylrestes von (III) zu 2-[-(4-Nitrophenyl)--oxy-, -dichloräthyl]-oxazolin (VI), dessen Konstitution an Hand eines O-Acetats und durch die saure Hydrolyse zu einer -(4-Nitrophenyl)-, -dichlorhydracrylsäure und Äthanolamin bewiesen wird.Herrn Prof. Dr.L. Ebert zum 60. Geburtstag gewidmet.     

A simple model for oscillations in a chain-branching reaction

A model of a chain-branching reaction with reactant consumption and regeneration is suggested to describe weakly damped oscillations. The number of variables in the model is two and the order of reactions steps is not more than two. Taking into account of the step of quadratic branching leads to the appearance of sustained oscillations (to the limit cycle).

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- , . , . ( ).

     

Selectivity of the steam reforming of methane over metallic catalysts

The activity and selectivity of the methane-steam reaction has been studied in a gradientless reactor at atmospheric pressure and 700–850 °C. Differences were found in the course of the reaction on Pd relative to other metals, viz. Ni, Pt and Ru, and an interpretation of the results is proposed.

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700–850°C. Pd , ., Ni, Pt Ru, .

     

Study of hydrogen isotope exchange on calcium, strontium and barium hydrides

The isotope exchange of hydrogen on rare-earth metal hydrydes has been studied. When passing from Ca to Sr and Ba, the activation energy decreases and, correspondingly, the rate of exchange increases. A similar dependence is observed for the isotope exchange of oxygen on the corresponding oxides and of nitrogen on nitrides.

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. Ca Sr Ba . .

     

Determination of CO adsorption heats from kinetic data for CO hydrogenation over metals

Studies of catalytic CO hydrogenation following the Langmuir-Hinshelwood mechanism indicate that the observed decrease in the activation energy with increasing temperature is due to the decreased surface coverage with reactants. The relationships obtained permit to carry out approximate estimates for the adsorption heat of CO.

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CO, -, , . CO.

     

Assay of nitro and nitroso compounds by solution thermochemistry

Some nitro and nitroso compounds have been determined by direct reduction with Ti(III) chloride without the necessity for degassing the analyte solutions. Methods have been developed for the determination of some binary mixtures by both enthalpimetry and catalytic thermometric titrimetry. The accuracy at the 0.1 mMole level is±1%, and the time taken for a single titration is less than 2 minutes.

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Zusammenfassung Einige Nitro- und Nitrosoverbindungen wurden durch direkte Reduktion mit Ti(III)-chlorid bestimmt, ohne dass die Notwendigkeit der Verdampfung der Analysenlösung besteht. Es wurden Methoden zur Bestimmung einiger binärer Gemische durch Enthalpimetrie und katalytische thermometrische entwickelt. Die Genauigkeit beträgt im Bereich von 0.1 mMol±1%, und eine Titration erfordert weniger als 2 Minuten.

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- . . 0,1 ± 1%, , 2 .

     

Spinels as heterogeneous catalysts for oxidation of water to dioxygen by tris-bipyridyl complexes of iron(III) and ruthenium(III)

Cobaltites, ferrites and chromites of some metals were found to be catalytically active in oxidation of water to dioxygen by trisbipyridyl complexes of Fe(III) and Ru(III). The possible catalytic action of surface compounds of hydroxide type is discussed.

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, , - (III) (III). .