Effect of NH3 and SO2 on n-butane oxidation

It has been established that NH₃ and SO₂ adsorption on the surface of V–P–O catalysts at reaction temperatures modifies its acid-base properties, which changes its activity and selectivity.

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, NH₃ SO₂ V–P–O -C₄H₁₀, - .

     

Some peculiarities of coke formation and burning on catalysts for reforming

Presence of two maxima on the DTA curves of coked catalysts is attributed to the metal-catalyzed oxidation of less polymerized coke in a higher temperature region.

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.

     

Study of the evolution of a MoO3+Bi2MoO6 mixture in air and in the conditions of mild propene oxidation

MoO₃ can react with the gamma phase of bismuth molybdate (Bi₂MoO₆) in the conditions of propene oxidation to form the alpha phase (Bi₂Mo₃O₁₂) resulting in a more selective catalyst for propene oxidation to acrolein. Intimate contact between MoO₃ and the gamma phase is an important factor favoring the formation of the alpha phase.

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MoO₃ - (Bi₂MoO₆), - (Bi₂Mo₃O₁₂), .

     

Thermal and magnetization studies on Heusler alloys

Saturation magnetization measurements as a function of temperature were performed on Cu₂Mn(Al_1–xSn_x) Heusler alloys to study the existence of stable structures. The derivatograph was applied to study the thermal effects.

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Zusammenfassung Sättigungsmagnetisierungsmessungen als Funktion der Temperatur sowie Derivatographie wurden an Heusler-Legierungen der Formel Cu₂Mn(Al_1–xSn_x) zu Untersuchungen der Existenz einer stabilen Struktur vorgenommen.

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Résumé Etude de l'existence d'une structure stable dans les alliages de Heusler Cu₂Mn(Al_1–xSn_x), à l'aide d'un Derivatograph et par des mesures de magnétisation à saturation en fonction de la température.

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XecnepaCu₂Mn(Al_1–xSn_x), , , . .

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Work supported in part by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and Banco Nacional de Desenvolvimento Economico, Brasil.     

Non-catalyzed oscillation reaction in aniline-KBrO3?H2SO4 system, I. Potentiometric study of oscillations

The non-catalyzed oscillation reaction of the aniline-KBrO₃–H₂SO₄ system has been followed potentiometrically. The concentration regions of the beginning of oscillation are given in a triangular diagram. Also studied was the dependence of the induction period on concentration of the participants, which was described by a kinetic equation. The oscillation region extends to lower KBrO₃ concentrations, the number of the oscillation jumps increases, and the induction period is shortened with increasing acidity.

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-KBrO₃–H₂SO₄. . . KBrO₃, .

     

Thermoanalytische und Kalorimetrische Untersuchung von CoOOH und CoOOD

Zusammenfassung CoOOH und CoOOD wurden definiert hydrothermal synthetisiert, chemischanalytisch und röntgenographisch charakterisiert sowie thermoanalytisch untersucht.Nach den Ergebnissen verläuft der thermische Abbau zu CO₃O₄, H₂O_(g) bzw. D₂O_(g) und O₂ in einer für Hydroxide typischen Einstufenreaktion. Ihre Temperaturlage ist vom Partialdruck der Reaktionsgase abhängig.Die hochtemperaturkalorimetrische Untersuchung erbrachte Werte für die Standardbildungsenthalpien _B H ₂₉₈ (CoOOH: –456±3; CoOOD: –455±3 kJ mol^–1) sowie die Standardreaktionsenthalpien ihrer Zersetzungsreaktionen.

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Hydrothermally synthesized CoOOH and CoOOD were characterized by chemical, X-ray and thermal analysis. The thermal decomposition leads to CO₃O₄, H₂O_(g) or D₂O_(g) and O₂ in a one-step reaction typical for hydroxides. The decomposition temperature depends on the partial pressure of the gaseous reaction products. High-temperature calorimetric studies allowed determination of the standard enthalpy of formation _B H ₂₉₈ (CoOOH: – 456±3; CoOOD: –455±3 kJ mol^–1) and the standard enthalpy of the decomposition reactions.

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CoOOD , . , , Co₃O₄, ₂ D₂ O₂. . . _BH ₂₉₈ (: –456±3; CoOOD: – 455±3 kJ ml^{– 1}.

     

On a large difference in enthalpic virial coefficient among some isomers of alkoxyalcohol

Molar excess enthalpies for aqueous solutions of 3-methoxy-1-butanol (3-MB) and 1-methoxy-2-butanol (M-2B) have been measured at 298.15 K over the whole concentration range with a flow microcalorimeter. From the experimental data, we evaluated the enthalpic interaction parameter h_xx and obtained the following order:h _xx (3 MB) h_xx(M-2B)This large difference in h_xx. provided us some new factors which might have the influence on hydrophobic interaction: fundamental frame, hydroxyl group, and ether oxygen atom.

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Zusammenfassung Mittels eines Fluß-Mikrokalorimeters wurden bei 298.15 K im gesamten Konzentrationsintervall die molaren Überschußenthalpien für wäßrige Lösungen aus 3-Methoxy-1-Butanol (3-MB) und 1-Methoxy-2-Butanol (M-2B) gemessen. Anhand der experimentellen Daten erstellten wir den Enthalpiepaar-Wechselwirkungsparameter h_xx und erhielten folgende Reihenfolge: h_xx(3-MB) h_xx(M-2B)Diese große Abweichung bei h_xx legte uns einige neue Faktoren nahe, die einen Einfluß auf die hydrophobe Wechselwirkung haben können: Grundgerüst, Hydroxylgruppen als auch Sauerstoffatome.

     

Studies on the catalytic decomposition of N2O over the solid solution La2CuxZn1?xO4 (0

U. Kameswari  J. Christopher  C. S. Swamy 《Reaction Kinetics and Catalysis Letters》1990,41(2):381-388

Effect of DMSO on the kinetic behavior of alkali catalyzed hydrolysis of methyl salicylate

Kinetic studies of the alkaline hydrolysis of methyl salicylate in aqueous DMSO medium at various compositions starting from 10 to 70 vol. % DMSO at temperatures ranging from 15 to 35°C are reported. The specific rate constant was found to decrease with increasing proportion of DMSO at all the temperatures and the prediction of Parker is not supported. Both isocomposition activation energy, E_c and isodielectric energy E_D increase. Variations in other activation parameters, S^*, H^* and G^* are also evaluated and interpreted on the basis of solvation phenomena.

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( 10 70 . % ), 15 35°C. , . , E_c, , E_D, . , S^*, H^* G^*, .

     

Etude cinetique non isotherme de la decomposition thermique du complexe dipyridinique de bromure de cadmium

Résumé Les paramètres cinétiques de la décomposition du complexe CdPy₂Br₂ ont été déterminés à l'aide de plusieurs méthodes nonisothermes à l'aide des données fournies par la thermogravimétrie et l'ATD. Les valeurs obtenues concordent de faÇon satisfaisante.

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Six nonisothermal thermogravimetric and DTA methods have been applied for determining the kinetic parameters of the decomposition of CdPy₂Br₂. The values obtained are in satisfactory agreement.

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Zusammenfassung Die kinetischen Parameter der Zersetzung des Komplexes CdPy₂Br₂ wurden durch verschiedene nicht-isotherme Methoden, durch Thermogravimetrie und Differentialthermoanalyse bestimmt. Die Resultate stimmten gut überein.

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6 CdPy₂Br₂. .

     

Influence of excess MoO3 in a non-stoichiometric cadmium-molybdenum catalyst on the catalytic properties in methanol oxidation

By IR and Raman spectroscopy it has been shown that excess MoO₃ is bound molecularly on the surface of CdMoO₄, presumably on sites of C₂ and C_i symmetry. This increases the activity and selectivity of the catalyst in methanol oxidation to formaldehyde.

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, , MoO₃ CdMoO₄, C₂ C_i. .

     

Catalytic decomposition of N2O on La2CuO4 in the presence of LaNi5 alloy

Decomposition of N₂O has been studied on pure La₂CuO₄, La₂CuO₄ with 5 and 10 wt. % LaNi₅ and oxidized LaNi₅ in the temperature range of 240–490 °C at 50 and 200 Torr initial pressures of N₂O. The addition of LaNi₅ decreases the energy of activation compared to that of La₂CuO₄ which has been explained based on the dispersity of NiO over La₂CuO₄.

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N₂O La₂CuO₄ La₂CuO₄ LaNi₅ 5–10 .%, 240–490°C N₂O 50 200 . LaNi₅ , . NiO La₂CuO₄.

     

Temperature dependence of the X-ray induced adsorption of oxygen and methane on ZnO

The capacity of ZnO with respect to the photo- and X-ray adsorbed, as well as postadsorbed oxygen is shown to depend on the temperature. It is suggested that this dependence cannot be attributed to either the thermal annealing of the induced sites or the thermal desorption of the adsorbed molecules.

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O , - , , , . , .

     

Kinetic studies of ozonation of polyhydric alcohols

Kinetic studies of the oxidation of polyhydric alcohols by ozone-oxygen mixtures in aqueous solutions at 284–302 K indicate that the second-order effective rate constantk decreases with increasing substrate concentration.

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- 284–302 . , .

     

n-Pentane isomerization in a continuous-flow reactor on Pt/Al2O3 catalysts modified by adsorbed bismuth and palladium

Isomerization of n-pentane has been studied in a continuous-flow reactor at atmospheric pressure on Pt/Al₂O₃ catalysts modified by adsorbed bismuth and palladium. Lower activity and higher selectivity have been obtained on a catalyst modified by bismuth. Both activity and selectivity have decreased on a catalyst modified by palladium. After oxygen treatment the Pd–Pt/Al₂O₃ catalyst showed the most pronounced change in catalytic properties and its stability was lower than that of the unmodified Pt/Al₂O₃ catalyst.

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- , Pt/Al₂O₃, . , . , , . Pd–Pt/Al₂O₃ , Pt/Al₂O₃.

     

On the application of exponential kinetic equations

An exponential kinetic equation for complex chemical reactions in solid-liquid heterogeneous systems is discussed. The integral form of the equation is analyzed and the conditions specified for the application of an approximate form. The meaning of constant t₀ is explained.

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, . . t₀.

     

Modification effect of Cu upon Pt In Pt?Cu?Al2O3 catalysts

In Pt–Cu–Al₂O₃ catalysts Cu might display either Electronic Ligand Effect or Ensemble Effect, depending on the preparation method of catalysts. For catalysts with Pt added before Cu, the latter exhibits an Electronic Ligand Effect. However, for catalysts with Cu added before Pt or with co-added Pt and Cu, Cu mainly demonstrates an Ensemble Effect.

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Pt–Cu/Al₂O₃ , . Pt Cu, , .

     

Thermal reactions of inorganic hydroxy-compounds under applied electric fields,III

The energy level separation in symmetrical and unsymmetrical double minimum potentials in the presence of electric fields is calculated by first-order perturbation theory, from which the tunnelling probability of protons is obtained for both perturbed and unperturbed potentials. Tunnelling probability is slightly increased by fields of about 10⁵ V/m, but a greater increase in tunnelling probability occurs when a symmetric potential becomes unsymmetric. The tunnelling process is too rapid to account for observed differences in dehydroxylation behaviour of Al(OH)₃, Mg(OH)₂ and kaolinite under electrolysis. Estimates, from indirect evidence, of the rates of anion defect generation and annihilation support the theory that the rate-determining field-dependent process is the surmounting of anionic lattice vacancies by oxygen-containing species.

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Zusammenfassung Die Trennung des Energieniveaus in symmetrischen und unsymmetrischen doppelten Minimumpotentialen in Gegenwart von elektrischen Feldern wird mittels einer Störungstheorie erster Ordnung berechnet, aus welcher die Wahrscheinlichkeit der Tunnelbildung von Protonen für gestörte sowie ungestörte Potentiale erhalten wird. Felder von 10⁵V/m erhöhen die Wahrscheinlichkeit der Tunnelbildung in geringem Maße, eine bedeutendere Zunahme der Wahrscheinlichkeit der Tunnelbildung tritt jedoch auf, wenn ein symmetrisches Potential unsymmetrisch wird. Der Vorgang der Tunnelbildung ist zu schnell um die Unterschiede des Verhaltens von Al(OH)₃, Mg(OH)₂ und Kaolinit bei der elektrolytischen Dehydroxylierung zu erklären. Schätzungen der Geschwindigkeiten der Anionen-Defektbildung und -Vernichtung aus indirekten Angaben unterstützen die Theorie, daß der geschwindigkeitsbestimmende, feldbedingte Vorgang die Überdeckung der Lücken im Anionengitter durch sauerstoffhaltige Arten ist.

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Résumé La séparation des niveaux d'énergie des potentiels à minimum double, symétrique et asymétrique, se calcule à l'aide de la théorie des perturbations du premier ordre, à partir de quoi la probabilité de l'effet tunnel des protons s'obtient aussi bien pour les potentiels perturbés que pour les non perturbés. La probabilité de l'effet tunnel augmente quelque peu sous l'influence de champs d'environ 10⁵ V/m, mais une augmentation plus notable de cette probabilité apparaît quand un potentiel symétrique devient asymétrique. Le processus de l'effet tunnel est trop rapide pour rendre compte des différences de comportement observées pour Al(OH)₃, Mg(OH)₂ et la kaolinite lors de l'électrolyse déshydroxylante. Des estimations faites à partir de données indirectes pour connaître les vitesses d'apparition des défauts anioniques et celles de leur disparition, viennent à l'appui de la théorie suivant laquelle le processus dépendant du champ et déterminant la vitesse est celui de l'occultation des lacunes du réseau anionique par des espèces contenant de l'oxygène.

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. , . 10⁵V/; , . , Al(OH)₃, Mg(OH)₂ . , , .

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Part of this work was carried out under an S.R.C. research grant. The author is indebted to Dr. J.P.M. Bailey for advice on the quantum-mechanical calculations, Dr. W.T. Raines and Dr. P.G. Rouxhet for helpful discussion. and to Mrs. F. Jackson for the computing.