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- .

     

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 .

     

Electronic spectral study of the interaction of CoNaX zeolite with C1?C5 hydrocarbons

Interaction of both satured and unsaturated hydrocarbons with tetrahedral Co²⁺ ion complexes lodged in the zeolite skeleton is reported on the basis of diffuse reflectance spectra. While saturated hydrocarbons do not affect the coordination sphere of the Co-complex, the unsaturated hydrocarbons change considerably the distortion of the tetrahedral Co-complex.

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- Co²⁺ - . - Co-, - - Co-.

     

Reactivity of coordinated O2? ion-radicals in the oxidation of organic compounds

By the flow ESR method, the rates of the reaction of the radical complex Ti(IV)(O ₂ ^– ) with some aromatic compounds in aqueous solution have been measured. An elementary step of these reactions seems to be one-electron oxidation with the formation of a substrate cation-radical.

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- Ti(IV)(O ₂ ^– ) . - -.

     

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); — .

     

On the deactivation of Fe2O3?MoO3/SiO2 catalysts in the oxidation of methanol to formaldehyde

The deactivation behavior of Fe₂O₃–MoO₃/SiO₂ catalysts with different Fe₂O₃+MoO₃ content in the oxidation of methanol to formaldehyde is investigated. A simplified reaction-deactivation kinetic model is presented and used to compare and discuss the different behaviors.

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Fe₂O₃–MoO₃/SiO₂ Fe₂O₃+MoO₃ . : -.

     

Interaction of methanol with hydrogen sulfide in the presence of K2WO4/Al2O3

Kinetic data show that in the presence of K₂WO₄/Al₂O₃, methanethiol is largely produced by the reaction of H₂S with metanol and partly with dimethyl ether. Dimethyl sulfide is formed during the interaction of methanethiol with methanol, of H₂S with dimethyl ether and as a result of methanethiol disproportionation. Methane and carbon oxides are the decomposition products of methanethiol and dimethyl sulfide and of methanol and dimethyl ether, respectively.

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, K₂WO₄/Al₂O₃ H₂S — . , H₂S . , — .

     

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. , , .

     

Mutual effect of benzene and maleic acid anhydride in their adsorption on V2O5?MoO3 catalysts

TPD studies have revealed that benzene and maleic anhydride are adsorbed on different active sites of the V₂O₅–MoO₃ catalyst.

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, - .

     

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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- - . .

     

Analysis of various metal oxide/organohalide-based flame retardants

The mechanism of evaporation of various metal oxides and the formation and evaporation of metal halides in the presence of chlorine-containing compounds have been studied by complex thermal analysis including atomic absorption measurement of the evolved species. The retardation process in the case of the MoO₃+ and the ZnO + system and that for Al₂O₃ ·3H₂O has been discussed.

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Zusammenfassung Der Verdampfungsmechanismus verschiedener Metalloxide sowie Bildung und Verdampfen von Metallhalogeniden im Falle von chlorhaltigen Additiven wurde untersucht. Es wurden Messungen mittels komplexer Thermoanalyse einschließlich von Atomabsorptionsuntersuchungen der entweichenden Stoffe durchgeführt. Die Hemmungsprozesse von MoO₃ + Halogen, ZnO +Halogen und Al₂O₃ · 3H₂O werden besprochen.

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, . , - . MoO₃ + , ZnO + l₂O₃·₂.

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The authors are indebted to Prof. B. Mohai for valuable discussions and suggestions.     

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 ⁺ .

     

Interaction of PM12?nVnO40?(3+n) (M=Mo, W) heteropoly complexes with nitrogen oxide

In aqueous solution, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) hetero-polyanions provide a much faster oxidation of NO than mononuclear VO ₂ ⁺ ions, yielding HNO₂, NO ₃ ^– and reduced HPA.

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, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) , VO ₂ ⁺ , NO HNO₂ NO ₃ ^– .

     

Kinetics of SO2 oxidation on K2S2O7?V2O5 catalyst in non-steady conditions

Studies of SO₂ oxidation on a molten component of vanadium catalysts in non-steadystate conditions indicates that the kinetics agree fairly well with an oxidation-reduction mechanism. In the low temperature range (<790 K) tetravalent vanadium can be partially crystallized.

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. , - . ( 790 ) .

     

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 oxidation of some aliphatic ketones by ditelluratocuprate(III) in alkaline medium

The kinetics of oxidation of some ketones by ditelluratocuprate(III) were followed spectrophotometrically by estimating the disappearence of potassium ditelluratocuprate(III). The reaction follows first order kinetics in both substrates and oxidant. A correlation is found between the order of reactivity and partial rates of enolization of these ketones. By assuming that the mechanism of oxidation involves the enol form of the ketone in a slow step, the observed order of reactivity of these ketones is explained.

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(III) , (III). , , . . , , .

     

Strong H2 chemisorption on Al2O3 or SiO2 supported group VIII metals

Following hydrogen treatments at high temperature a decrease in hydrogen chemisorption at room temperature is observed in almost all group VIII elements supported on SiO₂ or Al₂O₃. The effect is attributed to self inhibition by strongly chemisorbed hydrogen on the metals.

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VIII , SiO₂ Al₂O₃. .

     

Thermal desorption of hydrogen and carbon monoxide from Pd?Pb/Al2O3 catalysts

Thermal desorption of CO and H₂ from the surface of Pd/Al₂O₃ and Pd–Pb/Al₂O₃ catalysts has been investigated. No significant effects of adding lead to palladium catalysts on the activation energy of desorption process have been observed.

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CO H₂ Pd/Al₂O₃ Pd–Pb/Al₂O₃. - .