Conversion of dehydrolinalyl acetate in catalytic hydrogenation on metals

Low selectivity of dehydrolinalyl acetate (DeHLA) hydrogenation into linalyl acetate and ester group detachment are predicted in accordance with quantum-chemical data obtained for its homologue dimethyl ethynyl carbinol acetate. Experimental data are confirmed by theoretical calculations. DeHLA hydrogenation produces a variety of products.

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, - . . .

     

Kinetics of edta catalyzed oxidation of I? by Cr(VI)

The activity of various iron-containing ore catalysts during hydrogenation of Kansk-Achinsk lignite into liquid products in H-donor solvent (tetraline) has been studied. Ore samples contained pyrite, hematite and magnetite minerals. The most active appear to be pyrite samples. The catalytic effect of ore systems is, apparently, associated with the fact that during hydrogenation more active than tetraline H-donors are formed due to the hydrogenation of polycyclic aromatic molecules produced by thermal destruction of lignite.

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- H- . , , . , . , , , , , .

     

The thermal dehydration of Sr(HCOO)2·2(H,D)2O. Influence of the isotopic substitution on the kinetics

The kinetics of thermal dehydration of Sr(HCOO)₂·2(H, D)₂O were investigated using a dynamic thermogravimetric technique. Differences were found when the hydrogen was partially substituted by deuterium. These differences were explained by means of a microscopic approach based on the static and dynamic microscopic properties.

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Zusammenfassung Die Kinetik der thermischen Dehydratisierung von Sr(HCOO)₂·2(H, D)₂O wurde mittels dynamischer Thermogravimetrie untersucht. Bei partieller Substitution von Wasserstoff durch Deuterium wurden Unterschiede gefunden, die durch eine auf den statischen und dynamischen mikroskopischen Eigenschaften beruhende Betrachtungsweise erklärt werden.

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Sr(HCOO)₂ · 2(H, D)₂O. , .

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The authors whish to thank Dr. J. M. Pastor for valuable discussions, and Prof. O. Garcia of the Instituto de Quimica Inorgánica Elhuyar (C.S.I.C.) for the use of the experimental devices.     

Generation of model reactions leading to limit cycle behavior

The system of differential equations by Feistel and Ebeling has been generalized. Some new formal kinetic reactions with two internal components, which may exhibit limit cycle behavior have been studied. Based upon the numerical integration of the deterministic models of these reactions the oscillatory character of the systems has been confirmed.

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. , . .

     

Energy dissipation and selectivity in the catalytic oxidation of ammonia

A qualitative interpretation of selectivity changes in ammonia oxidation, based on considerations of energy dissipation processes is presented.

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, .

     

Thermal analysis of thermosetting resins

Applications of thermoanalytical methods for the study of the resinification and curing of phenolic resins are reviewed. Examples are given to illustrate the use of DSC for practical industrial systems such as paper impregnants and saturated papers.

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Zusammenfassung Es wird eine Übersicht über die Anwendungen thermoanalytischer Methoden zur Untersuchung der Harzbildung und der Aushrtung von phenolischen Harzen gegeben. Anhand von Beispielen wird die Verwendung der DSC für praktische industrielle Systeme wie Papierfüllstoffe und gefüllte Papiere aufgezeigt.

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, . , .

     

Gas phase thermolysis of phenylazoethane

The pyrolysis of phenylazoethane has been studied in a stirred-flow system using cyclohexene as carrier gas at sub-ambient pressures, in the temperature range of 380–416°C. The activation energy is examined in relation to the C–N bond dissociation energy and the heat of formation of the phenyldiazenyl radical.

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, - 380–416°C. C–N .

     

Kinetics of oxidation of acrolein on a vanadium-molybdenum oxide catalyst

A kinetic study has shown that, in the range of low conversions, the reaction rate depends only on the partial pressure of oxygen. Comparison of the oxidation of acrolein and I-deuteroacrolein suggests that the splitting of the H–CO bond is not rate-limiting.

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, , , . 1- , H–CO .

     

Influence of the gas phase on metallic reference electrodes used in work function measurements

Contact potential differences between electrodes of Pt, Au and Ta of different surface finishing were measured by the dynamic condenser method in propylene and oxygen. Propylene is irreversibly adsorbed, thus changing the work function. This renders the electrodes unsuitable as standard electrodes for work function measurements on catalysts in the atmosphere of hydrocarbons, but they may be used in adsorption studies on oxygen.

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Pt, Au Ta . , , . , .

     

Thermal decomposition of yttrium,lanthanum and lanthanide complexes of square acid in air atmosphere

The conditions of thermal decomposition of the Y, La and lanthanide complexes of square acid in air atmosphere have been studied. On heating, the complexes of Y, La, Ce(III), Pr(III), Nd, Sm, Eu(III), Gd, Tb(III) and Ho decompose in two steps. First, the hydrated complexes lose crystallization water to form anhydrous salts. The complexes of Dy and Er decompose in three steps; they are dehydrated in two steps to form anhydrous salts. The complexes of Tm, Yb and Lu are dehydrated in three steps; in two steps they lose water molecules to form octahydrates, which in the third step are dehydrated during decomposition. On heating, the anhydrous complexes of Y, Ce(III), Pr(III), Eu(III), Gd, Tb(III), Dy, Ho and Er and the octahydrated salts of Tm, Yb and Lu decompose directly to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇. The anhydrous complexes of La, Nd and Sm decompose to Ln₂O₃ with intermediate formation of Ln₂O₂CO₃.

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Zusammenfassung Die thermische Zersetzung von Komplexen von Y, La und Lanthaniden mit Squaresäure in Luft wurde untersucht. Beim Erhitzen zerfallen die Komplexe von Y, La, Ce(III), Pr(III), Nd, Sm, Eu(III), Gd, Tb(III) und Ho in zwei Schritten. Die hydrierten Komplexe geben zuerst Wasser ab und bilden wasserfreie Salze. Die Komplexe von Dy und Er zerfallen in drei Schritten, wobei sie in zwei Schritten zu wasserfreien Salzen dehydriert werden. Die Komplexe von Tm, Yb und Lu werden in drei Schritten dehydriert. Sie geben in zwei Schritten einige Wassermoleküle ab, um Octahydrate zu bilden, die dann während des Zerfalles dehydriert werden. Die wasserfreien Komplexe von Y, Ce(III), Pr(III), Eu(III), Gd, Tb(III), Dy, Ho und Er sowie die Octahydratsalze von Tm, Yb, und Lu zerfallen beim Erhitzen direkt zu den Oxiden Ln₂O₃, CeO₂, Pr₆O₁₁ und Tb₄O₇. Die wasserfreien Komplexe von La, Nd und Sm zerfallen über das Zwischenprodukt Ln₂O₂CO₃ zu Ln₂O₃.

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, . , , , , , , , . , . . . , . , , . , , , , , , , , , , Ln₂O₃, CeO₂, Pr₆O₁₁ Tb₄O₇. , Ln₂O₃ Ln₂O₂CO₃.

     

Stereochemistry of heterogeneous catalytic reactions; epimerization of alicyclic diols on copper catalysts

During the reactions of 8 isomeric alicyclic diols on Cu/Al and Cu catalysts, epimerization of the isomers was observed. The epimerization proceeds via a hydroxy-oxo intermediate.

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8 Cu/Al Cu . -.

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Part XLII of the series Study of the transformations of diols and cyclic ethers.     

High activity of MgO catalyst prepared from magnesium oxalate for the hydrogenation of butadiene

High activity of magnesium oxide prepared by thermal decomposition of magnesium oxalate for the hydrogenation of 1,3-butadiene has been examined by XPS and IR, together with the isomerization of 1-butene. XPS spectra of MgO differed from those of two other MgO catalysts. With Ar etching, the binding energies of Mg2p and 01s shift, which is related to the surface basicity. Both basic and acidic sites are responsible for hydrogenation, but isomerization proceeds only on basic sites.

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, 1,3- 1-, . MgO ; Ar 2p 1s Mg, . , , , - .

     

Photolysis of alkylperoxy radicals frozen out from the gas phase

Photolysis of alkylperoxy radicals with 250 nm light has been studied and proposed for investigation of heterogeneous-homogeneous reactions by freezing out radicals from the gas phase and their ESR identification. Using amine decomposition reaction in the presence of O₂ as an example, we have shown that photodissociation of frozen peroxy radicals can be used to reduce the structure of initial alkyl radicals.

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- 250 . , .

     

Kinetics and mechanism of homogeneous catalytic oxidation of pyrocatechol in aqueous solutions containing Cu(II) and histidine

Kinetic studies of pyrocatechol oxidation by oxygen in weakly acidic aqueous solutions containing pyrocatechol, Cu(II) ions and histidine, indicate that the reaction involves mixed copper-pyrocatechol histidine complexes. The proposed mechanism of the process agrees with the kinetic relationships obtained.

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, , Cu(II) . , . , -.

     

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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, , .

     

Synthesis of dimethyl sulfide in the presence of zeolites

In the presence of zeolites, dimethyl sulfide is produced either through CH₃OH interaction with H₂S or via CH₃SH decomposition. In accordance with their activities, in both reactions, zeolites arrange in the same sequence: HZSMHNaY>NaXNaY. Realization of the reaction CH₃OH+H₂S is more difficult compared to methanethiol decomposition.

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CH₃OH H₂S CH₃SH. : HZSMHNaY>NaXNaY. CH₃OH+H₂S , .

     

Cadmium induced changes of the metabolic activity of the freshwater snailPlanorbis corneus estimated by direct calorimetry

By use of f1ow-microcalorimetric studies the effect of cadmium in the sublethal concentration range (0.5-h LC_{5 0} is 1.69 mg/l) on the metabolic activity of the freshwater snailPlanorbis corneus was revealed. The high toxicity was confirmed by the change in the heat production rate (mean value is 453 W/g fresh weigth) in a cadmium perfusate down to a concentration of 0.01 g/l. The decrease in heat output depended on the cadmium concentration and amounted from 19% at 0.01 g/l to 88% at 1000 g/l. The microcalorimetric method proved to be a useful continuous-f1ow technique to assess qualitatively and quantitatively the toxic effects of cadmium on an aquatic organism already 4 hours after exposure.

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Zusammenfassung Mit Hilfe der Flow-Mikrokal orimetrie wurde die Uirkung von Cadmiumchlorid im subletalen Konzentrationsbereich auf die Stoffwechselaktivitat der SüwasserschneckeP1anorbis corneus untersucht. Die Wärmeproduktion der Tiere sank im Mittel von 435W/g Frischgewicht bei einer Cadmiumkonzentrat i on von 0.01 g/l auf 81Z und bei 1000 g/1 auf 19Z. Die Kalorimetrie eruies sich als eine nützliche Flow-Technik, mit der die Toxizität von Cadmium qualitativ und quantitativ bereits 4 Stunden nach der Exposition erfat werden kann.

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$ /LC₅₀=1,69 // planorbis corneus. $ / 453 / 0,01 /. 19% 0,01 / 88% 1000 /. , $ $ .

     

Catalytic properties of V?Mo?O systems in acrolein oxidation

Catalytic properties of V–Mo–O systems have been studied in acrolein oxidation. When catalysts are activated in reaction mixtures at 673 K, then a solid solution of molybdenum oxides in reduced vanadium oxides is formed, which is responsible for deep oxidation. Also, several compounds are produced, which by their activity and selectivity to acrylic acid formation are arranged in the sequences VMo₃O₁₁VMo₂O_8+x>V₆Mo₄O₂₅, and VMo₃O₁₁>VMo₂O_8+xV₆Mo₄O₂₅, respectively.

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V–Mo–O . 673 K , , , : VMo₃O₁₁VMo₂O_8+x>V₆Mo₄O₂₅, : VMo₃O₁₁>VMo₂O_8+xV₆Mo₄O₂₅.