Propylene oxidation over tin-molybdenum oxide catalysts

The influence of preparation of tin-molybdenum catalysts on their phase composition and activity has been elucidated. The mutual dissolution of Sn and Mo oxides leads to a considerable increase in their activities and selectivities in the partial oxidation of propylene to acetone.

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. , .

     

Vapor phase oxidation of methylpyridines on zeolite catalysts

It has been established that zeolites containing Pd and Cu ions catalyze the vapor phase oxidation of methylpyridines. In oxidation of 2-methylpyridine on PdCuNa-mordenite at 375 °C the yield of 2-pyridinecarbaldehyde is 40 % of its theoretical values.

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, , Pd Cu, . 2- PdCuNa- 2- 375°C 40% .

     

Preparation and characterization of Ru?Pb supported catalysts

Decomposition of Mn₃Mo₂TeO₁₂ during oxidation of toluene to benzaldehyde was observed. Depending on the surface composition of the initial catalyst, the decomposition leads to less active but highly selective MnMoTeO₆ or to MnMoO₄ which is not selective in toluene oxidation.

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Mn₃Mo₂TeO₁₂ . , MnMoTeO₆, MnMoO₆.

     

Zum Thermischen Verhalten von Zitronensäure

Zusammenfassung Mit Hilfe der thermo-optischen Analyse wird gezeigt, daß die widersprüchlichen Angaben in der Literatur zum thermischen Verhalten von Zitronensäuremonohydrat und dem Zitronensäureanhydrit auf eine Überlagerung verschiedener thermischer Reaktionen (Schmelze, Zersetzung, Entmischung und Kristallisation), die mit unterschiedlicher Geschwindigkeit ablaufen, zurückzuführen sind. Die thermo-optische Methode ist besonders für die Aufklärung solch komplexer Reaktionsabläufe geeignet. Das Beispiel des thermischen Verhaltens der Zitronensäure zeigt modellhaft die Erscheinungen, die bei der thermischen Analyse technischer Prozesse, wie dem Einschmelzen von Rohstoffgemengen, zu erwarten sind.

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By means of the thermomicroscopy was demonstrated that the discrepancy between the experimental DSC- and TG-data on the decomposition of citric acid in the literature can be explained in terms of superimposing reactions (melting, decomposition, immiscibility, and crystallization), which have different reaction rates. The thermomicroscopy is especially useful explaining such kind of reactions. The thermal behaviour of citric acid can be used as a model reaction in technology.

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, ( , , ), . . .

     

Effect of ligands on the hydrogenation selectivity in the presence of rhenium catalysts

It has been established that the catalytic activity of rhenium oxohalide complexes with phosphorus- or sulfur-containing ligands in hydroganation of C₆–C₁₀ olefins, nitrobenzene and p-nitrotoluene is primarily determined by the original ligand to rhenium ion bond. Chain length of olefins does not affect their hydrogenation rate.

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- C₆–C₁₀, - - . .

     

The role of lattice and adsorbed oxygen in the oxidation of n-butene-1 and furan with MnMoO4-based catalysts

In this paper the adsorption properties towards oxygen and the catalytic oxidation properties of furan and n-butene-1 on a MnMoO₄-based catalyst have been compared. Different forms of adsorbed oxygen are responsible either for the oxidation of furan to maleic anhydride or of furane and n-butene-1 to carbon oxides.

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--q MnMoO₄. , --1 .

     

Cyclohexane photooxygenation by air oxygen in CH2Cl2 in the presence of chromium oxocomplex-iodosylbenzene system

Cyclohexane is oxidized by air oxygen in CH₂Cl₂ solution to yield cyclohexanol, cyclohexanone and cyclohexyl chloride when irradiated by light (>310 nm) in the presence of (Bu₄N)₂CrO₄ or (Bu₃SnO)₂CrO₂. The addition of PhIO greatly accelerates the reaction and increases the yield of products. The reaction mixture contains neither cyclohexanol nor cyclohexanone when the photoreaction in the presence of the Cr(VI)–PhIO system is carried out in argon atmosphere. Hence neither iodosylbenzene nor oxochromium compounds can be oxygen atom donors in alkane oxygenation. The accelerating effect of iodosylbenzene may be due to the enhanced oxidizing power of photo-excited oxochromium species when coordinated to iodosylbenzene.

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CH₂Cl₂ , , (>310 ) (Bu₄N)₂CrO₄ (Bu₃SnO)₂CrO₂. PhIO . Cr(VI)–PhIO , , . , ( ) . .

     

Thermodynamic aspects of conformational transitions in synthetic polypeptides

The helix-coil transition of organic solvent soluble homopolypeptides has been discussed from a largely thermodynamic view-point. The present state and the future prospects are considered.

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Zusammenfassung Der Helix-Ungeordnete Übergang von in organischen Lösungsmitteln löslichen Homopolypeptiden wurde aus einem breiten Gesichtspunkt diskutiert, gegenwärtige Lage und zukünftige Entwicklungsaussichten erörtert.

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R'esumé On a discuté d'une pointe de vue thermodynamique large la transition helix—non helix des homopolypeptides solubles dans des solvants organiques et considéré la situation actuelle ainsi que les perspectives futures.

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, , . .

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The present paper was supported by NSF Grant GB 33484.     

Studies on the thermal decompositions of As-triazine derivatives and their compounds with metal ions

The thermal decompositions of the new complex salts of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 5,6-diethoxyearbonylmethyl-3-seleno-1,2,4-triazine (HSeTEK) and 5,6-diethoxycarbonylmethyl-3-thio-1,2,4-triazine (HTTEK) were investigated on the basis of the respective thermal curves. The thermoanalytical investigations indicate that HSeTEK, HTTEK, and their complexes with metal ions all undergo three-stage changes as the temperature is raised. The stages of pyrolysis established from the thermal data were compared, and the rates and stages of pyrolysis were related to the structures of the compounds.

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Zusammenfassung Die thermische Zersetzung der neuen Komplexsalze von Mn(II), Co(II), Ni(II) und Cu(II) mit 5,6-Diäthoxycarbonylmethyl-3-seleno-1,2,4-triazin (HSeTEK) und 5,6-Diäthoxycarbonylmethyl-3-thio-1,2,4-triazin (HTTEK) wurden auf der Grundlage der entsprechenden thermischen Kurven untersucht. Die thermoanalytischen Untersuchungen zeigen, daß HSeTEK, HTTEK und deren mit Metallionen gebildeten Komplexe bei Temperaturerhöhung einer jeweils dreistufigen Umwandlung unterliegen. Die auf der Basis der thermischen Daten festgestellten Pyrolysestufen wurden verglichen und Geschwindigkeit und Abschnitte der Pyrolyse mittels der Struktur der Verbindungen erläutert.

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, , 5,6- -3--1,2,4- 5,6 5,6 -3--1,2,4-. , . . - .

     

Determination of the strength of Lewis acid centers via IR spectroscopic measurement of adsorbed pyridine

According to high-temperature IR spectroscopic studies, the isosteric heats of pyridine adsorption on the Lewis centers of Al₂ O₃, ZrO₂ and zeolite HNaY have been estimated. The dependence between the frequency _8a (1580–1630 cm^–1) and the adsorption heat is shown to take place only for centers formed by cations of the same metal.

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, - HNaY. , _8a (1580–1630 cm^–1) , - .

     

Response studies of the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst

A response method has been used to study the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst. The products of partial and destructive oxidation are shown to be formed under the influence of molecular oxygen on the surface intermediates produced by the interaction between o-xylene and oxidized surface sites.

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- . , , - .

     

Pulse-chromatographic determination of molybdenum surface by oxygen adsorption in Co?Mo catalysts

A pulse-chromatographic method has been developed for the estimation of molybdenum surface by selective adsorption of oxygen at –78°C in cobalt-molybdenum-alumina catalysts. The surface concentrations of molybdenum in a series of catalysts of different compositions were compared with the activities for cyclohexene hydrogenation and for thiophene hydrogenolysis.

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- –78°C -- . - .

     

Ru(III) catalyzed oxidation of some aliphatic alcohols by N-bromosuccinimide (NBS). A kinetic study

Kinetics of Ru(III) catalyzed oxidation of methanol, ethanol, n-propanol, n-butanol, isopropanol and iso-butanol by N-bromosuccinimide (NBS) in the presence of Hg(II) acetate have been studied in acid medium. The oxidation exhibits a fractional order in [alcohol] and first order in [NBS]. The applicability of Taft's equation was tested. The probable mechanism is discussed.

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, , -, -, - () Hg(II), Ru(III), . . . .

     

Evaluation of quantum yields in the presence of an absorbing additive

A method is proposed for the evaluation of quantum yields of photochemical reactions studied in the presence of absorbing additives using cylindrical sample tubes.

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.

     

Microcalorimetric studies of slag alkaline binders

Calorimetric measurements were carried out on the hydration of slag activated by sodium hydroxide, sodium carbonate and water glass at 60 °C. The results can be correlated with the mechanical properties of the cured cements. The studies confirmed the applicability of calorimetry in the testing of activators used in concrete technology.

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Zusammenfassung Die Hydratation von Schlacke bei 60 °C und Aktivierung mit Natriumhydroxid, Natriumcarbonat oder Wasserglas wurde durch kalorimetrische Messungen verfolgt. Die Ergebnisse lassen sich mit den mechanischen Eigenschaften der erhärteten Zemente korrelieren. Die Untersuchungen bestätigen die Brauchbarkeit der kalorimetrischen Methode zum Testen von Aktivatoren in der Betontechnologie.

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, 60° , . . , - .

     

Localization of gallium in erionite type Ga?Al zeolites by71Ga,27Al and29Si NMR

The state of Al³⁺, Ga³⁺ and Si⁴⁺ in erionites obtained by hydrothermal crystallization from Ga–Al–Si gels has been examined. The results suggest that gallium cations can isomorphously substitute a part of silicon cations in the zeolite framework, to a notable extent in the sites having no aluminium cations in the second coordination sphere of silicon.

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Al³⁺, Ga³⁺ Si⁴⁺ , . , , .

     

Effect of the central metal ion on the inhibiting properties of metal dithiocarbamates in oxidation processes

The dependence of inhibiting properties of M(dtc) on M for the complexes of M(II) and n M(III) has been studied. Inhibition is due to the interaction of M(dtc)_n with RO₂.

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M(dtc)_n M M(II) M(III). M(dtc)_n RO₂.

     

Chemical reaction and phase transformations of the components of low temperature shift catalyst in various atmospheres

The systems CuO–Al₂O₃ and ZnO–Al₂O₃, as model systems of low temperature shift catalysts, have been studied in the temperature interval 100–700°C. The changes of their phase composition and surface area, influenced by gas atmosphere have been studied by X-ray, IR analysis and low temperature nitrogen adsorption.

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CuO–Al₂O₃ ZnO–Al₂O₃ CO 100–700°C. , - .

     

Testing of nickel phosphate (NiP) catalyst for ethylbenzene oxydehydrogenation by means of isopropanol dehydration

It has been shown that NiP catalyst, if fresh, contains a high concentration of the same type acid-base surface centers as those participating in i-PrOH dehydration on -Al₂O₃. The concentration of these centers diminishes rapidly after a modification of NiP surface in a stream of ethylbenzene (EtPh) oxydehydrogenation products.

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, NiP - , , i-PrOH -Al₂O₃. NiP .

     

How is an acceptable Nomenclature system achieved?

The philosophy and procedure adopted by the Nomenclature Committee of the International Confederation for Thermal Analysis are briefly outlined with illustrative examples taken from the contents of the two reports so far prepared.

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Zusammenfassung Prinzipien und Verfahrungsweise der Problembehandlung in dem Ausschuß für Nomenklatur der Internationalen Conföderation für Thermische Analyse werden erörtert, illustriert durch Beispiele [die zwei kürzlich entworfenen Referaten des Ausschusses entnommen wurden.

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Résumé On indique les principes dui ont guidé les travaux du Comité Nomenclature de l'ICTA et la préparation de deux rapports.

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, .