Kinetics of reduction of tris(4,4,4-trifluoro-1-(2-thienyl)-butane-1,3-dionato)ruthenium(III) in methanol

Reduction of tris(4,4,4-trifluoro-1-(2-thienyl)-butane-1,3-dionato) ruthenium(III) in methanol solution containing potassium hydroxide has been studied kinetically. The results suggest outer-sphere complex formation between ruthenium(III) species and methoxide anion.

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(4,4,4--1-(2-)--1,3)(III) . , -.

     

Effect of the metal atom of acetylacetonates on the autoxidation of cumene

The oxidation of cumene and a cumene-nitrobenzene (12) mixture at 60°C in the presence of AIBN and acetylacetonates of Co(II), Cu(II), Fe(II), Fe(III), V(III), Cr(III), Mn(III) and MoO ₂ ²⁺ has been investigated.

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(12) 60°C - Co(II), Cu(II), Fe(II), Fe(III), V(III), Cr(III), Mn(III), MoO ₂ ⁺² .

     

Microthermographie infrarouge et decomposition des solides

Infrared microthermography was used to study dynamically the decomposition of single cristalline platelets (surface 1 cm²) of copper sulfate pentahydrate. The measurement of the local self cooling allows to plot the thermal profiles in front of the reaction and yields the temperature of the reactive interface. It is also possible to plot the thermal maps of the samples for their evolution, and thereby gets permitted knowledge of the gradients of temperature in those reactions. The evolution of these values with pressure, orientation of the platelets or of the reactive interface is envisaged.

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Zusammenfassung Die Infrarotmikrothermographie wurde zur dynamischen Untersuchung der Zersetzung von Kupfersulfat-Pentahydrat in Form von Einkristallplättchen (Oberfläche 1 cm²) herangezogen. Die Messung der lokalen Selbstabkühlung ermöglicht, die thermischen Profile in der Reaktionsfront aufzuzeichnen und die Temperatur der reaktiven Grenzfläche zu erhalten. Es ist auch möglich, die thermischen Karten der Proben darzustellen und damit eingehende Kenntnisse über die Temperaturgradienten bei solchen Reaktionen zu gewinnen. Untersuchungen sind vorgesehen, um zu klären, wie Druck und Orientierung der Plättchen oder der reaktiven Grenzfläche diese Werte beeinflussen.

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( 1 ²) . . . . .

     

New alternatives for high specific area γ-Al2O3 synthesis

-Al₂O₃ was synthesized from trisec-butoxide by the sol-gel method. pH was varied during reaction and solvents of different polarity were used. Solids with specific areas, greater than 200 m²/g, were obtained, which depend directly on the reaction parameters.

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-Al₂O₃ - -. . pH . , 200 ²/ .

     

51V-NMR spectra of vanadates and oxosulfato-vanadates of alkali metals

A relation between the type of vanadium environment and the chemical shift anisotropy in the⁵¹V-NMR spectra has been established. The results obtained are compared with spectra of real catalysts.

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⁵¹V , .

     

Hydrogenation of nitric oxide on platinum black in acidic solution

By comparison of the catalytic hydrogenation and electrochemical reduction of NO on platinum black catalysts it has been shown that the hydrogenation of NO to ammonia and to hydroxylamine occurs in the diffusion controlled region only.

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NO , NO .

     

On the nature of active centers in catalysts for propylene oxidation to acetone

Acid-base properties of binary tin-oxide catalysts for the oxidation of propylene to acetone have been studied. It has been revealed that active catalysts should have both Brönsted acid- and base centers.

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- . , .

     

Oxidation of carbon monoxide on the (001) plane of ruthenium

The Ru(001) plane is shown to possess high but variable activity in the reaction of CO oxidation. A drop of activity is attributed to the transformation of surface oxygen into the unreactive state.

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, (001) Ru , . .

     

Effect of P2O5 content in phosphogypsum on its thermal decomposition to CaCO and SO2

The effect of P₂O₅ on the thermal decomposition of phosphogypsum to phospholime and sulphur dioxide has been studied.

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Zusammenfassung Es wurde der Einfluß von P₂O₅ auf die thermische Zersetzung von Phosphogips zu Phospholim und Schwefeldioxid untersucht.

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.

     

Influence of water vapor on propylene oxidation on VMo catalyst

The dependence of reaction rates for acetone and acetic acid formation on the concentration of water vapor is determined on the basis of the participation of surface hydroxy groups and Brönsted acid centers of the catalyst.

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.

     

Scanning electron microscopic study of an industrial catalyst for ammonia synthesis

The surface topography and elemental composition of the near-surface layers of a reduced passivated catalyst for ammonia synthesis have been studied on a scanning electron microscope in the initial state and after high-temperature oxygen treatment as well as removal of the alkali promoter.

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CA-IB , .

     

Unimolecular decomposition of CF3OF-calculation by reduced Kassel integral in factorized form

The fall-off curves were calculated for the unimolecular decomposition of the trifluoromethyl hypofluorite at 475.8, 496.9 and 507.3 K by means of the Reduced Kassel Integral in Factorized Form.

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475,8,496,9 507,3 .

     

Über die SystemeABr/VBr2 (A=Na-Cs,Tl) [1]

Zusammenfassung Die Systeme ABr/VBr₂(A= Na, K, Tl, Rb, Cs) wurden mit der Differenzthermoanalyse untersucht. Das System mit NaBr ist rein eutektisch, in den übrigen Systemen existieren VerbindungenAVBr₃. Sie kristallisieren im CsNiCl₃-Typ: Säulen flächenverknüpfter Oktaeder werden durch die Alkaliionen zusammengehalten. Dies bedingt durch antiferromagnetische Kopplung reduzierte magnetische Momente. Das Fehlen von Verbindungen mit tetraedrisch koordiniertem V²⁺ wird mit der site-preference-energy der Ligandenfeldtheorie erklärt.

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The systemsABr/VBr₂ (A= Na, K, Tl, Rb, Cs) were investigated by means of differential thermal analysis. The system with NaBr is purely eutectic, in all other systems a compoundAVBr₃ exists. The compounds crystallize with the CsNiCl₃-structure: columns of face-shared octahedra are held together by the alkali ions. This involves reduced magnetic moments (antiferromagnetism). The lack of compounds with tetrahedral coordination of the V²⁺-ion is explained by the site-preferenceenergy according to ligand field theory.

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Résumé On a étudié par analyse thermique différentielle les systèmes ABr/VBr₂ (A=Na, K, Tl, Rb, Cs). Le système contenant NaBr est purement eutectique; dans tous les autres systèmes, il existe un composéAVBr₃. Les composés cristallisent avec la structure CsNiCl₃: les colonnes d'octaèdres ayant des surfaces communes sont maintenues par les ions alcalins. Cela implique des moments magnétiques réduits (antiferromagnétisme). L'absence de composés a coordination tétraédrique de l'ion V²⁺ s'explique par l'énergie de site préférentielle d'après la théorie de champ de ligand.

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Ar/Vr₂, =Na, K, Tl, Rb, Cs. NaBr , AVBr₃. CsNiCl₃:: - , . ( ). V²⁺ , , .

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Wir danken Herrn Prof. Hoppe, Universität Gießen, für die Berechnung von Madelung-faktoren, Herrn Prof. Babel, Universität Marburg, für die Erlaubnis, eine Hochtemperatur-DTA-Apparatur zu benutzen. Die Arbeit wurde von der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie mit Sachmitteln unterstützt.     

XPS study of ethylene adsorption on Ir (110)

The state of adsorption layers and adsorption kinetics of C₂H₄/Ir (110) at 300–1000 K has been studied using XPS method.

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C₂H₄/Ir (110) 300–1000 K.

     

Kinetics and mechanism of oxidation of methanol by acid bromate

The kinetics of oxidation of methanol by bromate ion in hydrochloric acid medium has been investigated. A mechanism consistent with the experimental observations is suggested.

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. , .

     

Thermal behaviour of rigid polyurethane foams

By means of a combined thermal analysis technique, the thermal behaviour of rigid polyurethane foams containing additive antipyrenes was studied. The presence of phosphorus- and phosphorus/chlorine-containing antipyrenes based on phosphate and phosphonate and a combination of them led to decreases in the rates of heat and weight loss during heating. More steps of decomposition were formed and the interval of decomposition was widened and shifted to higher temperatures. Some thermal characteristics make it possible to predict the optimum antipyrene compositions and concentrations with minimum time, labour and material consumption under laboratory conditions.

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Zusammenfassung Mittels einer kombinierten Technik wurde das thermische Verhalten eines starren, Antipyrene als Additiv enthaltenden Polyurethanschaumes untersucht. Phosphor und Phosphor/Chlor enthaltende Antipyrene auf Phosphat- und Phosphonatbasis und eine Kombination dieser Substanzen vermindern die Geschwindigkeit der Wärmeentwicklung und des Gewichtsverlustes während des Aufheizvorganges. Es treten mehr Zersetzungsschritte auf und das Temperaturintervall der Zersetzung ist größer und nach höheren Temperaturen hin verschoben. Einige thermische Kennwerte ermöglichen die Voraussage der optimalen Zusammensetzung und Konzentration des Antipyren-Additivs für minimalen Zeit-, Arbeits- und Materialaufwand unter Laboratoriumsbedingungen.

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, . /- , . , . .

     

Hydroxylation selectivity of phenol and O-protected phenols in the Fe(III)-catechol-H2O2 system

Oxidation selectivity of phenol and its O-protected derivatives in the Hamilton system has been studied. Modification of OH groups by acyl substituents and addition of -cyclodextrin markedly enhance paraselectivity of this reaction.

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O- . , OH- - - .

     

A new concept explaining catalytic synergy between two solid phases

We propose a new mechanism for explaining the synergy between MoS₂ and Co₉S₈ in hydrodesulfurization. We suppose that spill-over hydrogen produced by Co₉S₈ exerts an effect ofremote control on the active center of MoS₂, a slight reduction leading to hydrogenation centers and stronger reduction to hydrodesulfurization centers.

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MoS₂ CoS₈ . , , CO₉S₈, MoS₂, , , , .

     

Unusual selectivity in photooxygenation of alkanes by air in CH3CN solutions catalyzed by CrCl3?C6H5CH2N(C2H5)3Cl

A new system CrCl₃–C₆H₅CH₂N(C₂H₅)₃Cl–CH₃CN for photooxygenation of alkanes is suggested. Unlike metal chlorides and oxocomplexes, it oxidizes alkanes to produce ketones and small amounts of alcohol. Adding of benzene, methylene chloride or ethanol to the cyclohexane solution rises the oxygenation rate and changes the ketone/alcohol ratio. With small amounts of hydroquinone the formation rate of cyclohexanone (but not of cyclohexanol) sharply decreases. Kinetic isotope effect in the oxidation of C₆H₁₂ and C₆D₁₂ is 1 for cyclohexanol and 2.9 for cyclohexanone. Cyclohexanol formation is assumed to follow a mechanism that does not involve free radicals. Free radicals can participate in the route toward ketone.

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CrCl₃–C₆H₅CH₂N(C₂H₅)₃Cl–CH₃CN . , . , /. ( ) . C₆H₁₂ C₆D₁₂ 1 2,9 . , , . , .