Reaction of triphenyl phosphite ozonide with thioacetals

Kinetic regularities in the reaction of triphenyl phosphite ozonide with several thioacetals in CH₂Cl₂ solution at –15°C have been studied. The consumption rate of ozonides is described by the kinetic equation W=k₀[(C₆H₅O)₃P·O₃]+k₁[(C₆H₅O)₃P·O₃][R₁R₂C(SR₃)₂] Rate constants k₀ and k₁ for the thioacetals: (CH₃H₇S)₂CH₂, (C₆H₅S)₂CH₂, (C₆H₅CH₂S)₂CH, (n=C₁₂H₂₅–S)₂CH₂, (C₃H₇S)₂C(H)CH₃, (C₃H₇S)₂C(H)C₆H₅, (C₃H₇S)₂C(CH₃)C₆H₅ and (C₃H₇S)₂C(H)C₁₀H₉, increases with increasing the electron-donating power of subtituents R_i.

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CH₂Cl₂ –15°C. : W=k₀[(C₆H₅O)₃P·O₃]+k₁[(C₆H₅O)₃P·O₃][R₁R₂C(SR₃)₂] k₀ k₁ (C₃H₇S)₂CH₂, (C₆H₅S)₂CH₂, (C₆H₅CH₂S)₂CH₂, (n-C₁₂H₂₅S)₂CH₂, (C₃H₇S)₂C(H)CH₃, (C₃H₇S)₂C(H)C₆H₅, (C₃H₇S)₂C(CH₃)C₆H₅, (C₃H₇S)₂C(H)C₁₀H₉. .

     

Kinetics of deuterium isotope exchange between thiophenol or t-butylthiol and i-propylthiol

The rate constants and activation energies of bimolecular deuterium exchange in the systems: C₅H₅SD+i-C₃H₇SH and t-C₄H₉SD+i-C₃H₇SH in dilute C₆H₁₂ solutions have been established. The concerted H-transfer inside the cyclic dimer with two H-bonds formed in these systems is probably the rate-limiting step. The rate constant for H-transfer inside the cyclic dimer is independent of the acidic properties of the thiols.

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: C₆H₅SD+i-C₃H₇SH -C₄H₉SD+i-C₃H₇SH C₆H₁₂. -, , , . .

     

Temperature programmed reduction and oxidation of Ir/Al2O3 catalysts

3 % Ir/Al₂O₃ catalysts have been studied by means of temperature programmed reduction and oxidation. With growing degree of metal oxidation (higher T_ox) reducibility of the catalysts at low temperatures decreases.

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3% Ir/Al₂O₃ . ( ) .

     

Acid properties and stability of operation of vanadium catalysts in benzene oxidation to phenol

Catalytic properties of V₂O₅/SiO₂ in benzene oxidation by N₂O were examined. Sodium additive was shown to affect the catalyst operation stability.

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V₂O₅/SiO₂ N₂O. .

     

Temperature dependence of CO insertion on S-, Ag-, and Cu-promoted Rh/SiO2 catalysts

The addition of sulfur and silver to Rh/SiO₂ inhibits hydrogenation of C₂H₄, but promotes CO insertion and extends the linearity of Arrhenius curves for CO insertion above 543 K.

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Rh/SiO₂ C₂H₄, CO CO 543 .

     

Thermal study of some sulphosuccinates

The thermal properties of some sulphosuccinates and their intermediates were studied by using combined dynamic thermal analysis and mass spectrometry. The temperature ranges were similar in the two methods, and a scheme of thermal decomposition of the compounds investigated was suggested. In the first temperature range of thermal decomposition of the sulphosuccinate a-rupture of the molecular ion occurs. In the second temperature range, the fragmentation proceeds in two directions: either-rupture of the ethoxylated nonylphenol, or-rupture of the acid residue of the sulphosuccinates.

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Zusammenfassung Mittels einer Kombination von dynamischer Thermoanalyse und Massenspektroskopie wurden die thermischen Eigenschaften einiger Sulfosukzinate und deren Zwischenprodukte untersucht. Im ersten Temperaturbereich der thermischen Zersetzung des Sulfosukzinates findet eine-Spaltung des Molekülions statt. Im zweiten Temperaturbereich tritt auch ein alternativer Fragmentierungsweg auf: eine-Spaltung des Säurerestes des Sulfosukzinates.

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- . . - -. : - - .

     

Heterogeneous catalytic oxidation of ethanol: A new process for acetic acid

ESR investigations on ZnO doped with various amounts of -Al₂O₃ thermally treated, are reported. Experimental data are related to the electronic structure of ZnO--Al₂O₃ and to desulfurization specific activity for natural gas.

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ZnO, -Al₂O₃. ZnO/-Al₂O₃ .

     

Silylation of porous glass supported platinum catalysts

Effect of silylation with hexamethyldisilazane on adsorption and catalytic properties of porous glass-supported platinum catalysts has been studied. Catalytic activity decreases markedly with an increase in surface coverage by trimethylsilyl groups for all the following reactions examined: hydrogenation of benzene, dehydrogenation of cyclohexane and dehydrocyclization of n-hexane.

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, . , : , -.

     

IR spectra of oxygen adsorbed on SnO2

IR spectra of oxygen adsorbed on SnO₂ with and without lattice defects have been studied. At low temperatures oxygen is adsorbed on defect SnO₂ in two forms of O ₂ ^– . This supports the earlier results obtained by ESR. The low-temperature forms of adsorbed oxygen (unrevealed in ESR spectra) were detected on defectless SnO₂. High-temperature forms of adsorbed oxygen appear in the IR-spectra as bands due to vibrations of the cation-oxygen bond.

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- SnO₂. , O ₂ ^– , . SnO₂ .

     

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.

     

Novel evidence for the selective behaviour of tungsten carbide in liquid phase heterogeneous catalytic hydrogenation

Liquid (aqueous) phase catalytic hydrogenation of compounds containing two oxo-groups in -position (biacetyl, glyoxal, alloxan) was studied in the presence of tungsten carbide catalyst. It has been shown that only one of the oxo-groups is affected in the course of the process and is transformed into a >CH–OH group. Comparative studies carried out in the presence of platinum catalyst attest the selective behaviour of tungsten carbide.

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- - (, , ). , >C=O >CH–OH, . .

     

Analysis of thermal desorption spectra of oxygen desorbed from rhodium

Thermal desorption spectra of oxygen desorbed from rhodium have been analyzed in terms of models accounting for the effect of lateral interactions between adsorbed particles and of their diffusion into the bulk of metal on the desorption kinetics of O₂. Complex configuration of these spectra is ascribed to the processes of formation/decomposition of surface Rh oxides and the diffusion of particles into the near-surface layers of metal and back to the surface.

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- , O₂ . - O₂ Rh - .

     

Исследование роли фосфиновых комплексов никеля различных степеней окисления в каталитической димеризации олефинов

Ni(II), Ni(I) Ni(O) . , , , Ni(O) Ni(I) - Ni(I) Ni(II) Ni(O).

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The interaction of organoaluminium compounds with phosphine complexes of Ni(II), Ni(I) and Ni(0) has been studied under the conditions of catalytic propylene dimerization. The active complexes are formed from Ni(II) compounds, the regeneration of the latter is ensured by repeated reduction, oxidation of Ni(0) to Ni(I), and by disproportionation of Ni(I) into Ni(II) and Ni(0).

     

Le calcul des parametres cinetiques des Reactions de Decomposition thermique a l'aide des donnees de l'analyse thermique differentielle

Résumé On a modifié la méthode différentielle pour le calcul des paramètres cinétiques des réactions de décomposition thermique du type: A_(s) B_(s) + C_(g), en utilisant les données de l'analyse thermodifférentielle. En effectuant le calcul des paramètres cinétiques des réactions de déshydratation de l'oxalate de calcium monohydraté et de décomposition du carbonate de calcium on obtient des résultats qui concordent d'une manière satisfaisante avec ceux obtenus par d'autres méthodes.

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A modification of the differential method is presented in order to evaluate the kinetic parameters of thermal decomposition reactions of the type A _s B _s + +C_g, using differential thermal analysis (DTA) data. The kinetic parameters calculated for the dehydration and decomposition of calcium oxalate and carbonate agree satisfactorily with those mentioned in the literature.

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Zusammenfassung Es wird über eine Abänderung der Differentialmethode zur Errechnung der kinetischen Parameter von thermischen Zersetzungsreaktionen des Typs A_(s) B_(s) + C_(g) mit Hilfe von differentialthermoanalytischen Daten berichtet. Die am Beispiel der Dehydratation des Calciumoxalat-Monohydrats und der Zersetzung des Calciumcarbonats erhaltenen Ergebnisse der auf angegebene Weise durchgeführten kinetischen Berechnungen stimmen gut mit den nach anderen Methoden erhaltenen Resultaten überein.

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A_{(s) (s)} + C_(g), (). , , , .

     

The thermal properties of carbon-silica adsorbents (carbosils) prepared by methylene chloride pyrolysis

The thermal properties of complex carbon-silica adsorbents (carbosils) were investigated using differential thermal analysis. The adsorbents were prepared by pyrolysis of methylene chloride. Pyrolysis reaction on silica surface was carried out at different temperatures (400–700 °C) and at different pressures of CH₂Cl₂ vapours. Thermal analysis was carried out in air atmosphere. The following parameters characterizing the properties of the adsorbents were determined: carbon content, specific surface area, carbon layer thickness, pore volume, mean pore radius, differential of heats of adsorption ofn-hexane and benzene, and micrographs. The correlation between topography and morphology of carbon deposits (dependent on the parameters of the pyrolysis process) and the courses of DTA and TG curves corresponding to individual carbosils have been determined.

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Zusammenfassung Mittels DTA wurden die thermischen Eigenschaften von komplexen Kohlenstoff-Silikaadsorptionsmitteln (Carbosil) untersucht. Die Adsorptionsmittel wurden durch Pyrolyse von Methylenchlorid gefertigt. Die Pyrolyse wurde an der Oberfläche von Silika bei verschiedenen Temperaturen (400–700 °C) und bei verschiedenen CH₂Cl₂-Drücken durchgeführt. Die Thermoanalyse geschah in Luftatmosphäre. Folgende Parameter zur Charakterisierung der Eigenschaften der Adsorbenten wurden ermittelt: Kohlenstoffgehalt, spezifische Oberfläche, Kohlenstoffschichtdicke, Porenvolumen, Porendurchmesser, Ableitung der Adsorptionswärme vonn-Hexan und Benzol sowie Oberflächenmikrogramme. Es konnte der Zusammenhang zwischen Topografie und Morfologie der Kohlenstoffablagerungen (abhängig von den Parametern des Pyrolysevorganges) sowie dem Verlauf der DTA- und TG-Kurven der entsprechenden Carbosile festgestellt werden.

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- (). . (400–700°) . . : , , , , - , . , , .

     

Kinetic and mechanistic studies on the oxidation of sulfanilic acid by peroxomonophosphoric acid

Oxidation of sulfanilic acid to the corresponding azoxy derivative by peroxomonophosphoric acid (PMPA) has been studied in aqueous medium. The observed bell-shaped pH-rate profile has been rationalized on the basis of protonation of the amino group and ionization into different PMPA species and a suitable rate law has been proposed. The mechanism of oxidation involves the nucleophilic attack of nitrogen on the electrophilic peroxo oxygen.

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- (PMPA) . pH— , PMPA . .

     

Hydrogenation of xylenes over supported Pt catalysts. Influence of different variables on their catalytic activity

In this work we studied and compared the catalytic activity of various supported Pt systems on the gas-phase hydrogenation of o-, m- and p-xylene. We analyzed the influence of different catalyst preparation variables (solvent, precursor, salt, support and catalyst reduction temperature used) on the catalytic activity and selectivity towards the corresponding cis-and trans-dimethylcyclohexanes.

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- o-, m- -. (, , ) - -.

     

Basic condensation of triphenylsilane. II. Kinetics in anhydrous isopropanol and influence of silanol

Condensation of triphenylsilane with isopropanol in presence of isopropoxide has been studied in anhydrous medium and the activation parameters have been measured. Dehydration of the medium has been obtained by means of a pre-reaction of triphenylsilane with the residual water in the solvent. In this medium the reaction is extremely slow, moreover, it is inhibited by silanol whose effect would lower the actual catalyst concentration.

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. . , .

     

Kinetics of thermal decomposition of pyrite in an inert atmosphere

The thermal decomposition of pyrite in an inert atmosphere was studied in order to obtain a detailed knowledge of the kinetics and mechanism of the reaction 2 FeS₂=2FeS+S₂, which is one of the methods of producing elementary sulphur. The process was studied under isothermal conditions at temperatures of 600, 660, 700, 750, 800 and 850 °C in a nitrogen atmosphere, by means of a thermobalance. The rate-controlling processes were determined and their kinetic parameters were calculated. The optimum temperature for the process was found to be 800 °C.

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Zusammenfassung Es wurde die thermische Zersetzung von Pyrit in inerter Atmosphäre bestimmt, um detaillierte Informationen über Kinetik und Mechanismus der Reaktion 2 FeS₂=2FeS+S₂, einer der Darstellungsreaktionen von elementarem Schwefel zu erlangen. Der Vorgang wurde mittels einer Thermowaage unter isothermen Bedingungen bei Temperaturen von 600, 660, 700, 750, 800 und 850 °C untersucht. Es wurden die geschwindigkeitsbestimmenden Schritte bestimmt und deren kinetische Parameter errechnet. Als Optimumtemperatur für diesen Prozeß erwies sich 800 °C.

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- 2FeS₂=2FeS + S₂, . 600, 660, 700, 750, 800 850 ° . , 800°.

     

Physico-chemical properties of silica-supported vanadium oxide catalysts

- . TiO₂ ZnO. - CO₂ H₂O. — .

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The effect of visible light on propane and n-butane oxidation has been sutied on a seires of metal oxides. TiO₂ and ZnO have been found to exert a photocatalytic effect. On TiO₂, propane and n-butane are oxidized to CO₂ and H₂O. On ZnO as catalyst, partial oxidation products, aldehydes and ketones, are formed.