Measurement of adsorption heats of nitrogen on metal nitrides

Adsorption heats q and activation energies of the nitrogen exchange on several metal nitrides have been compared. For the systems capable of changing readily their composition upon varying conditions, the isotope exchange is suggested to be the most reliable method of the determination of q.

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. , , , .

     

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 . , , . , .

     

Interaction between particles in solution and the mechanism of dihydrogen activation in base catalyzed isotope exchange reactions

A previously suggested mechanism for the H-D isotope exchange of dihydrogen with aqueous alkaline and amide-ammonia solutions is discussed to be generalized and extended to hydrogen isotope exhange with other protolytic solvents.

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- () - () - (). ().

     

Kinetics of solid polypropylene oxidation inhibited by aromatic nitrons

C-phenylcarbamoyl-N-phenylnitron and C(2,4-di-tert-butyl-3-hydroxyphenylcarbamoyl)-N-(p-di-methylaminophenyl) nitron inhibit the oxidation of solid polypropylene. In this case the nitrons studied demonstrate properties of polyfunctional inhibitors: they interrupt oxidation chains by chains by reactions with alkyl and peroxyl radicals.

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C--N- C-(2,4----3-)-N-(-) . , .

     

m-Xylene conversion over dealuminated Y zeolites studied by the pulse method

m-Xylene conversion was studied over dealuminated Y type zeolites in hydrogen forms, SiO₂ to Al₂O₃ ratios were varied from 4.86 to 12.95.

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- . SiO₂/Al₂O₃ 4,86 12,95.

     

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- . , , . , . , , , , , .

     

Hydrocarbon hydrogenolysis on nickel-tin catalysts

Hydrogenolysis of ethane, n-hexane and cyclohexane has been studied on nickel-kieselguhr catalysts modified by organic and inorganic compounds of tin. Tin additives decrease nickel reactivity with respect to C–C dissociation, which is ascribed to the formation of surface intermetallides on the catalyst.

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, - - , . . C–C .

     

Mechanism of methane photooxidation on V/SiO2 catalyst

CH₄ photooxidation on V/SiO₂ catalyst in the presence of gaseous oxygen has been studied by the mass-spectometric method. It has been established that CO₂ forms due to the interaction of CH₄ with surface oxygen anions bonded to vanadium ions. Photodecomposition of V⁴⁺O ₂ ^– species formed in O₂ adsorption on reduced vanadium ions leads to the reoxidation of the latter.

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- CH₄ V/SiO₂ . , CO₂ CH₄ , . V⁴⁺O ₂ ^– O₂ , .

     

Mechanism of isotope exchange of dihydrogen with liquid water catalyzed by hydroxide ions

In the analysis of the reaction between dissolving hydrogen and aqueous alkali hydroxide solutions the interaction of hydrogen with the molecular ion (H₃O₂)^– should be studied. This interaction is analyzed by the interacting bonds method. The activation energy (E_a) is estimated.

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, (H₃O₂)^–. . (E_a).

     

Oxidation of propylene to acrylic acid on a Fe?Mo?Bi oxide system

Data obtained in a flow reactor show that iron(III) molybdate doped by bismuth can oxidize propylene to acrylic acid directly in one step. Part of the catalyst works in a partially reduced form and in the preparation of the catalyst the surface acidity must be controlled.

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, , (III), , . .

     

Oxidative coupling of alkylbenzenes to diaryls catalyzed by the palladium(II)-heteropolyacid system

Oxidative coupling of alkylbenzenes (benzene, toluene, o-xylene, durene) is shown to proceed in the presence of palladium salts and heteropolyacids under the action of oxygen with a high yield of diaryls. The addition of mercury salts and variation of the solvent affect the reaction rate and isomer composition of the products.

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, (, , -, ) . .

     

Recombination of polyatomic ester peroxy radicals in solution

Termination rate constants of peroxy radicals of seven polyatomic esters in benzene and perflouorooctane media have been measured by pulse photolysis. Recombination of peroxy radicals for all esters examined proves to be diffusion controlled. Reactivity of peroxy radicals in the termination reaction grows with increasing number of ester groups.

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. . .

     

Effect of medium composition on the monooxygenase activity of immobilized hemin in aniline oxidation

The effect of the composition of the reaction medium on the rate of aniline oxidation to p-aminophenol by hydrogen peroxide on hemin immobilized on -propylimidazole-modified silica has been studied. Organic solvent additives (alcohols, esters and nitriles) are shown to increase the reaction rate. The observed effect is attributed to the decrease of the medium dielectric constant.

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- , , --. , (, , ) . .

     

Thermische Zersetzung des Caesiumjodobismutats(III)

Zusammenfassung Es wurde die thermische Analyse des Caesiumjodobismuthats(III) ausgeführt. Aus den Ergebnissen dieser sowie der chemischen und diffraktometrischen Analysen der Sinterprodukte wurde der Reaktionsmechanismus der thermischen Zersetzung dieser Verbindung festgestellt.

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The thermal analysis of caesiumjodobismuthate(III) was carried out. From the results and the chemical and diffractometric analysis of sinters, the mechanism of thermal decomposition of this compound was established.

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(III) . , .

     

Stability of hyperbolic reactors

For the one-phase tubular reactor, a new mathematical model is suggested, viz. a hyperbolic system of first order partial differential equations instead of the usual second order parabolic ones. This physically better model is investigated from the point of view of stability via the second Lyapunov method.

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. .

     

Oxidation of trimethoxybenzenes to benzoquinones with hydrogen peroxide in the presence of heteropolyacid

Trimethoxybenzenes were oxidized to dimethoxy-p-benzoquinones in fairly good yields (50–60%) with hydrogen peroxide in the presence of heteropolyacid in the solvent of acetic or formic acid.

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-- (50–60%) , , .

     

Interaction of ammonia with the surface of Cr?Mo and Cr?Mo?Te oxide catalysts

The adsorption of NH₃ on Cr–Mo and Cr–Mo–Te catalysts has been investigated by IR spectroscopy. It is shown that there are both electron acceptor and proton donor acid centers on the surface of these catalysts. The introduction of tellurium into a Cr–Mo catalyst decreases adsorption on the electron acceptor centers.

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NH₃ Cr–Mo Cr–Mo–Te . , -, - . Cr–Mo .

     

Interaction between peroxyl radicals of polyatomic esters and aromatic nitrons

Reactivity and rate constants in reactions between peroxyl radicals of ethylene glycol diacetate and aromatic nitrons have been investigated.

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.

     

Preparation and properties of supported vanadium-phosphorus catalysts studied by chemical analysis and ESR

The preparation of vanadium-phosphorus catalysts is described, showing the considerable influence of phosphorus on the concentration of V⁴⁺ ions. The oxidation properties were studied by chemical analysis and electron spin resonance. Moreover, ESR spectra show a strong influence of moisture on the structure of the catalysts.

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- , V⁺⁴. , . , , .

     

Dilution effect on catalytic pyrolysis of hydrocarbons

It is shown that unlike thermal pyrolysis, the rate of catalytic pyrolysis is greatly affected by dilution of hydrocarbons with inert gases. The nature of this effect has been analyzed.

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, . .