Studies of V?Mo?O systems with small vanadium content in acrolein oxidation

A solid solution of vanadium in MoO₃ with a solubility limit of about 3 mol.% V₂O₅ is shown to be formed. Its catalytic properties are discussed.

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MoO₃ 3 . % V₂O₅ .

     

Formation of methyl platinum complex in the reaction of methane with chloroplatinic acid

The¹HNMR method and chemical analysis indicate that a complex of Pt(IV) containing a CH₃–Pt fragment is formed in the reaction of H₂PtCl₆+H₂PtCl₄ with methane at 120 °C in aqueous CF₃CO₂H. The complex was isolated from the solution as an adduct of Ph₃P.

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, H₂PtCl₆ H₂PtCl₄ CF₃COOH 120°C (IV), Pt–CH₃. Ph₃P , .

     

Influence of the various forms of molybdena on the adsorptive and catalytic (dehydrogenation and hydrogenolysis) properties of molybdena-alumina catalysts

The contents of three forms of molybdenum oxide compounds in molybdena-alumina catalysts have been determined by their solubility in water and ammonia. The form which is readily soluble in water and reducible to Mo(IV) at 400°C and P_H2=10⁵ Pa is active in cyclohexane dehydration, and the forms soluble in water and ammonia are active in thiophene hydrogenolysis.

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. , 400°C P_{H 2}=I Mo(IV); — .

     

Residual entropy of glasses and their relation with the crystallization behaviour

For the alloy of eutectic composition in the quasibinary GeSe₂-Sb₂Se₃ system the heat capacities of the glass, undercooled and stable liquid and crystalline phases have been measured using differential scanning calorimetry. Enthalpy, entropy and Gibbs free energy differences of vitreous and crystalline forms have been deduced for this alloy. The kinetic parameters of crystallization for glasses of nearby composition have been obtained by continuous heating experiments. The effective activation energy obtained has a value that accounts for the activation energy for nucleation calculated using simple nucleation theory formulae.

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Zusammenfassung Die Wärmekapazitäten von Glas, unterkühlter und stabiler Flüssigkeit und kristallinen Phasen von Mischungen der eutektischen Zusammensetzung des quasibinären Systems GeSe₂-Sb₂Se₃ werden mittels DSC gemessen. Aus den Ergebnissen werden Enthalpie, Entropie und freie Enthalpie der glasartigen und kristallinen Formen dieser Mischung abgeleitet. Die kinetischen Parameter der Kristallisation von Gläsern benachbarter Zusammensetzungen wurden durch temperaturprogrammierte Untersuchungen ermittelt. Die erhaltenen effektiven Aktivierungsenergien entsprechen dem für die Keimbildung nach einfachen theoretischen Formeln berechneten Wert.

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, , GeSe₂-Sb₂Se₃. , . . , .

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This research was supported by the Comisión Asesora de Investigatión Cientifica y Técnica (CAICYT) project no. 759-84 which is gratefully acknowledged.     

Study of the interaction of atomic oxygen and nitrogen with ruthenium by the bond interaction method

The heats of atomically adsorbed oxygen and nitrogen on Ru(0001) and Ru(1010) planes have been calculated by the semiempirical bond interaction method. The calculations show that oxygen is strongly adsorbed on ruthenium, while molecular nitrogen cannot be chemisorbed on ruthenium.

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- (000I) (I0I0) . , Ru , .

     

Application of thermokinetics in chemical process analysis,as illustrated by the reaction of phenyl isocyanate andn-Butanol

Shortening the time required for chemical process development from the first laboratory trial through technical and pilot plants to industrial installation is a long-standing aim. Knowledge of the reaction kinetics is of major importance for this purpose. The usefulness of thermokinetics in chemical process engineering is illustrated by reaction of phenyl isocyanate andn-butanol.

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Zusammenfassung Die Abkürzung der Verfahrensentwicklung vom ersten Laborversuch über Technikums- und Pilotanlagen bis zur großtechnischen Anlage ist ein seit langem erstrebtes Ziel. Dabei ist bekanntlich die Kenntnis der Reaktionskinetik von großer Bedeutung. Am Beispiel der Reaktion Phenylisocyanat undn-Butanol wird die Nützlichkeit der Thermokinetik in der chemischen Verfahrensentwicklung aufgezeigt.

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, , , . . -.

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Studies of coke distribution in high-silica ZSM zeolites

A method for studying coke distribution in zeolites is suggested. It has been established that two forms of coke can form: one is intracrystalline and the other is located on the outer surface of ZSM zeolites.

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. : ZSM.

     

Kinetics of heterogeneous catalytic hydroformylation of propylene on rhodium-cobalt catalysts. Effect of metal dispersity

Selectivity of heterogeneous catalytic hydroformylation of propylene on rhodium-cobalt catalysts increases with decreasing size of metal crystallites. The data are interpreted in terms of a reaction mechanism.

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- - . .

     

Poly(vinylpyridine) complexes of palladium as hydrogenation catalysts. Effect of polymeric ligand structure

The title complexes exhibit high catalytic activity, selectivity and stability in hydrogenation of allyl alcohol. The structure of a polymeric ligand (i.e. the position of the nitrogen atom in the pyridine ring) affects catalyst activity. According to the hydrogenation rates of allyl alcohol, the complexes studied are arranged in the sequence: P4VP-Pd>P2VP-Pd>P2M5VP-Pd.

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, - - . ( ) . : 4->2-Pd>25-.

     

Investigation of the interaction between zinc oxide and phosgene

It has been shown that in the interaction of zinc oxide and phosgene, the most active are the samples having oxygen vacancies. A mechanism for this process is suggested.

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, , . .

     

Variations in electronic state of silver catalysts for methanol oxidation

Variations in the electronic state of silver catalysts for methanol oxidation under the effect of the reaction medium have been studied, using diffuse reflectance spectroscopy. The nature of active centers-Ag⁺ cations, Ag _n ⁺ complexes and clusters of various sizes for bulk and supported catalysts are shown to be identical.

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. - Ag⁺, Ag _n ⁺ .

     

Catalytic properties of palladium oxide systems in the hydrogenation of crotonaldehyde

Catalytic properties of Pd black-oxide systems have been studied in hydrogenation of crotonaldehyde. It has been revealed that the additions of basic and amphoteric oxides (MgO, Fe₂O₃ and ZnO) increase the hydrogenation rate of the ethylenic bond in crotonaldehyde.

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Pd-- . , (MgO, Fe₂O₃, ZnO) .

     

Effect of oxygen on reduction of NO with carbon monoxide over NiO and Cr2O3

Cr₂O₃ is found to be a less active catalyst than NiO in reduction of nitrogen oxides. Introduction of molecular oxygen into the NO–CO mixture decreases the conversion of NO_x on both catalysts. On NiO it is due to competition between O₂ and nitrogen oxides for CO. On Cr₂O₃ it is caused by the complete suppression of this reaction.

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Cr₂O₃ , NiO. NO CO NO_x ; NiO CO , Cr₂O₃- .

     

Pt(alizarine)2 complex adsorbed on titanium dioxide as a sensitizer in photocatalytic evolution of dihydrogen

Pt(alizarine)₂ complex adsorbed on the surface of titanium dioxide has been found to cause spectral sensitization of the photocatalytic activity of TiO₂. Adsorption of the complex provides simultaneously sensitization of the photoprocess and catalysis of dark steps of dihydrogen formation.

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, Pt()₂ TiO₂. , , .

     

Catalytic properties of phosphorus-containing rhenium complexes in the hydrogenation of hexene-1

Rhenium (V, VI) complexes with organophosphorus ligands proved to be catalytically active in hexene-1 hydrogenation. The kinetics of this process catalyzed by ReOCl₃(PPh₃)₂ has been examined. The organic ligand in the coordination sphere of rhenium complexes was found to affect selectivity to olefin bonds or nitro groups in the hydrogenation of hydrocarbons.

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(V, VI) -1. , ReOCl₃ (PPh₃)₂. , .

     

Infrared study of photooxidation of nitrogen oxides and ammonia adsorbed on alumina

Changes in the IR spectra of nitrogen oxides and ammonia adsorbed on Al₂O₃ caused by UV irradiation indicate that in the presence of gaseous or liquid (–196°C) O₂ photooxidation takes place, resulting mostly in the formation of surface NO ₃ ^– ions.

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- - , Al₂O₃, , (–196°C) NO ₃ ^– .

     

CO oxidation to CO2 by Mo?V?P heteropolyacid in the presence of an aqua complex of Pd(II)

Kinetic oxidation of CO to CO₂ by Mo–V–P heteropolyacid in the presence of an aqua complex of Pd(II) has been studied. The reaction is suggested to involve the participation of carbonyl complexes of Pd(I). It has been established that VO ₂ ⁺ ions formed in HPA dissociation inhibits the reaction.

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CO CO₂ - Pd(II). Pd(I). , VO ₂ ⁺ , , .