Mechanism of the liquid-phase oxidation of diethyl sulfide catalyzed by heteropoly acids

It has been established that in the oxidation of diethyl sulfide by¹⁸O₂ in CH₃C¹⁶O₂H–H₂ ¹⁶O solution at 369 K catalyzed by heteropoly acids, sulfoxide and sulfone with 44–54%¹⁸O enrichment are formed. The process is accompanied by isotope exchange of molecular oxygen.

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, ¹⁸O₂ CH₃C¹⁶O₂H–H₂ ¹⁶O 369 ¹⁸O 44–54%, .

     

Testing the photocatalytic activity of cyanogen-and thiocyanogen-based inorganic polymers

The photocatalytic properties of some cyanogen-and thiocyanogen-based inorganic polymers, such as paracyanogens containing different metals (Hg, Ag, Cu), polythiocyanogens of different iodine contents, polycyanogen and poly (cyanogenthiocyanate), have been tested in two systems. Cu-containing paracyanogen and the iodine-poor polythiocyanogens catalyze the photoreduction of methylviologen under visible light, furthermore the Cu-containing paracyanogen catalyzes the photoreduction of water to hydrogen under UV irradiation.

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, , , , (Hg, Ag, Cu), , (), . , , , , , , -.

     

Iron-chromium catalysts in the conversion of methanol with water vapor

The catalytic properties of iron-chromium catalysts in methanol conversion with water vapor were studied. The activity of the catalysts is shown to depend on the method of preparation and their Cr₂O₃ content. The Cr₂O₃ admixture is found to play the role of a stabilizer of the active surface.

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. Cr₂O₃. Cr₂O₃ .

     

Kinetics and mechanism of elimination of methoxyphenethyl chlorides in the gas phase

The kinetics for the gas phase elimination of o-and m-methoxy-2-phenylethyl chlorides have been investigated over the temperature range of 390-464°C and pressure range of 38–119 Torr. The reactions in seasoned vessels and in the presence of the free radical inhibitor propene, are homogeneous and unimolecular and follow a first-order rate law. The o-anisyl and p-anisyl substituents at the -position of ethyl chloride assist anchimerically the elimination processes. The formation of a cyclic product, benzodihydrofuran, from o-methoxy-2-phenylethyl chloride suggests an intimate ion pair mechanism operating in this reaction.

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- --2- 390–464°C 38–119 . - , , , . - - - . , , --2- , .

     

Zeolite content determination in kaolinic clays via thermal effects

For application in catalysis and adsorption processes, zeolites are synthesized on the surface of spray-dried kaolin microspheres. Various thermal effects are used for the rapid characterization of the zeolite type and content. From DTA measurements, the exothermic lattice break-down peak gives information on the zeolite type and the thermal stability of the sample. Measurements of the heats of immersion by a very simple and quick method allow conclusions about the type and the sorption properties of the zeolite part of the clay. The most precise method to estimate the zeolite content was a standardized technique of desorption and readsorption of water or organic compounds by means of a thermobalance.

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Zusammenfassung Zur Anwendung in der Katalyse und bei Adsorptinsprozessen werden Zeolithe auf der Oberfläche sprüh-getrockneter Kaolin-Mikrokugeln eingesetzt. Verschiedene thermische Effekte werden zur schnellen Charakterisierung des Zeolith-Typs und -Gehalts genutzt. Der exotherme DTA-peak beim Gitterzusammenbruch liefert Informationen über Zeolith-Typ und thermische Stabilität der Probe. Eine sehr einfache Schnellmethode zur Messung der Immersionswärmen erlaubt Schlussfolgerungen über Typ und Sorptionseigenschaften des zeolithischen Anteils des Tons. Die genaueste Methode zur Bewertung des Zeolithgehalts war eine standardisierte thermogravimetrische Desorptions- und Readsorptions-Methode mit Wasser oder organiscen Verbindungen.

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, , , . . , . , , . , .

     

Isomerization and dehydrobromination of 1-bromo-2-methylpropane on alumina modified with alkali halides

The kinetics of the dehydrobromination of 1-bromo-2-methylpropane on alumina modified with NaI and KI have been investigated. A mechanism for the isomerization reactions on alumina modified with alkali halides is proposed in order to explain the catalytic behavior of iodide ion as compared with that of chloride and bromide ions, reported in a previous paper.

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1--2- , NaJ KJ. , , , , .

     

Modification of catalytic properties of silica-supported rhodium

A sharp change in the catalytic properties of rhodium in benzene hydrogenation, propane hydrogenolysis and n-hexane conversion has been found for catalysts prepared via interaction between Rh(CO)₂Cl₂ and silica modified by Sn, Pb, Mo and W ions.

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, Rh(CO)₂Cl₂ , Sn, Pb, Mo W, , , -.

     

Properties of highly dispersed supported catalysts in hydrogenation reactions

Pt/sol and Pt/support catalysts with 6–15 Å Pt particles have been established to be low active in the hydrogenation of propargyl alcohol, butyn-l-ol-3 and dimethylethynylcarbinol. The specific catalytic activity significantly rises with increasing d_Pt above 15 Å and after the thermal treatment of highly dispersed catalysts in a hydrogen flow.

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, -30 -- 6–15 Å , -1, -3 . d_Pt>15 Å .

     

Characterization of the redox-reactivity of transition metal oxides by temperature-programmed limited thermal decomposition (TPLTD)

The concept of labile lattice oxygen (LLO) as a consequence of the Mars-Van Krevellen model was reminded, and contrasted with the surface oxygen species. Methods of characterizing of the Me-O bond strength were reviewed emphasizing the temperature-programmed limited thermal decomposition (TPLTD). A series of Ag_xV₂Mo_yO_z was characterized by TPLTD. Two forms of LLO were distinguished. The weaker form is independent on Ag-doping, in contrast to the stronger one. Activation energy of TPLTD of the stronger bound LLO was a linear function of the anion vacancy concentration.

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Zusammenfassung Aus dem Konzept des labilen Gittersauerstoffs (LLO) als Konsequenz des Mars-Van Krevellen-Modells wird die Rolle der Oberflächen-Sauerstoff-Spezies hervorgehoben. Ein Überblick über die Methoden zur Charakterisierung der Me-O-Bindung wird unter besonderer Betonung der temperaturprogrammierten begrenzten thermischen Zersetzung (TPLTD) gegeben.Eine Reihe Ag _x V₂Mo _y O₂ wurde mittels TPLTD charakterisiert, dabei konnten zwei Arten von LLO unterschieden werden. Die schwächere Form ist im Gegensatz zu der stärkeren unabhängig vom Silbergehalt. Die Aktivierungsenergie der TPLTD der stärker gebundenen LLO hängt linear von der Konzentration der Anionenfehlstellen ab.

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, - , . Me- . Ag_xV₂Mo_yO_z, . , , . n.

     

Electronic spectrum and thermal decomposition of nickel(II) complex with bis(N-γ-pyridyl-4-phenylbenzamide-hydrazone)

The unit cell parameters and the space group of the investigated compound were determined by means of X-ray diffraction.Analysis of the diffusion-reflection spectra of the crystalline powder and the absorption spectra of its alcoholic solutions permitted identification and quantitative characterization of the absorption bands of the crystalline complex of NiL₂(ClO₄)₂·3H₂O.Application of differential-thermal analysis allowed determination of the mechanism of thermal decomposition of the compound. From these measurements, the expected configuration of the basic molecule was verified, involving determination of the number of non-coordinated water molecules.

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Zusammenfassung Mittels Röntgendiffraktionsmethoden wurden Gitterzellenkonstanten sowie die Raumgruppe der untersuchten Verbindung bestimmt. Durch Analyse der erhaltenen Diffusions-Reflexionsspektren von kristallinem Pulver und des Absorptionsspektrums einer alkoholischen Lösung der Verbindung war es möglich, die Absorptionsbanden des Kristallkomplexes NiL₂(ClO₄)₂·3H₂O zu identifizieren und quantitativ zu charakterisieren. Anwendung von Differentialthermoanalyse ermöglicht die Bestimmung des Mechanismus der Zersetzungsreaktion der Verbindung. Durch diese Messungen, einschliesslich der Bestimmung der Anzahl nichtkoordinierter Wassermoleküle, wurde die erwartete Konfiguration des Grundmoleküles überprüft.

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NiL₂(ClO₄)₂·₂, L-N-- -4- . L-N---4- . , , . . , .

     

Determination of acid sites on carbon surface

Pyridine chemisorbed on acid sites of active carbon was displaced by n-butylamine and the displaced amount was measured spectrophotometrically. This amount, supposed to be proportional to the surface concentration of carboxy groups, depends on the chemical pretreatment of active carbon.

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, , . , , .

     

Effect of acio properties of the alumina surface on the formation of chlorides during its interaction with CCl4

IR spectroscopy was employed to study acid properties of a series of alumina samples different in the phase composition and in the porous structure. The comparison of the surface acidity with the data on the quantitative formation of Cl^– during the interaction of CCl₄ with alumina indicates that the extent of chlorination of the samples tends to increase with increasing the surface acidity.

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- , . Cl^– CCl₄ , .

     

UV-VIS spectroscopic study of interaction and transformation of allyl alcohol on zeolites HZSM-5

Formation of alkenylcarbenium ions has been proved during transformation of allyl alcohol on zeolite HZSM-5.

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HZSM-5.

     

Catalytic effect of metal ions on photochemical reactions of molecular oxygen, III. Photochemical autoxidation of sulfite catalyzed by manganese(II) ions

The rate of photoinitiated autoxidation of sulfite is influenced by manganese(II) ions even in trace concentrations. An increase in the concentration of manganese(II) ions in the reaction system increases the quantum yield of the photoinitiated reaction.

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(II), - . (II) - .

     

27Al NMR studies of pentasil zeolites related to their stability towards coke formation

MAS²⁷Al NMR has been used to study the state of Al atoms in various pentasil zeolites characterized by different rates of deactivation in the reaction of methanol conversion to hydrocarbons. In contrast to previous suggestions, extra-lattice Al atoms in octahedral environment of oxygen atoms are shown to exert no decisive effect on the deactivation rate for zeolites of the pentasil type.

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²⁷Al Al , . . , Al .

     

Catalytic conversion of 2-propanol on La2MnZnO6

The perovskite La₂MnZnO₆ has been synthesized by a ceramic technique and its catalytic activity has been tested for 2-propanol decomposition. The catalyst is totally selective to dehydrogenation of the alcohol. A possible mechanism for the reaction is proposed.

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La₂MnZnO₆ 2-. . .

     

p-Hydrogen conversion on sulfide catalysts as a function of bond ionicity

The activity of Group IV–VI transition metal sulfides in p-hydrogen conversion shows an inverse dependence on their bond ionicity.

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IV–VI- .