Oxidative coupling of methane over Bi2O3?P2O5?K2O/Sm2O3

Oxidative coupling of methane over Bi₂O₃–P₂O₅–K₂O/Sm₂O₃ takes place giving more C₂H₄ as compared to C₂H₆. Sm₂O₃ supported Bi–P–K is a more active and selective catalyst, than TiO₂, -Al₂O₃, SiO₂ and MgO supported catalysts.

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Bi₂O₃–P₂O₅–K₂O/Sm₂O₃ , . Bi–P–K, Sm₂O₃, , TiO₂, -Al₂O₃, SiO₂, MgO.

     

The thermoanalytical determination of deactivation types of cation-exchanger catalyst's

The dependence of the thermal decomposition of a cation-exchanger catalyst on its deactivation type has been ascertained, and thermal analysis has been suggested as a diagnostic method for the determination of the condition of such a catalyst.

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Zusammenfassung Die Abhängigkeit der thermischen Zersetzung eines Kationaustauscher-Katalysators von seinem Inaktivierungstyp wurde bewiesen und die Thermoanalyse als diagnostische Methods für die Bestimmung des Zustandes eines solchen Katalysators vorgeschlagen.

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. , .

     

AES studies on a Pd-modified silver catalyst

Silver crystals electrodeposited from AgNO₃ (8%) and Pd²⁺ (250 mg/dm³) electrolyte before and after exposing to the conditions of the methanol to formaldehyde oxidation process were investigated by AES. Carbon, sulfur, oxygen and palladium on the surface were observed. Higher Pd concentration on the silver surface than in the bulk was found. Its amount on the surface decreased with the temperature increase.

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, - , AgNO₃ (8%) Pd⁺² (250 /), AES. , , - . , - Pd , , .

     

Temperature-dependence of electromechanical coupling and strain in barium titanate hafnate transducer

The electromechanical coupling factor and ferroelectric hysteresis loops were investigated at different temperatures for BaTi_0.85Hf_0.15O₃ transducer. Maximum polarization and strain were obtained near the transition of the crystal structure. This correlated with increases in the ease and extent of ferroelectric domain boundary motion. The change in the crystal structure varied the unit cell volume, leading to higher strain.

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Zusammenfassung Der elektromechanische Kopplungsfaktor und die ferroelektrische Hysteresisschleife wurde für BaTi_0.85Hf_0.15O₃-Transducer bei verschiedenen Temperaturen untersucht. Polarisation und Deformation nehmen in der Nähe des Umwandlungspunktes der Kristallstruktur maximale Werte an. Dies korreliert mit Leichtigkeit und Außmaß der Grenzbewegung im ferromagnetischen Bereich. Die mit der Umwandlung der Kristallstruktur zusammenhängende Veränderung des Elementarzellenvolumens führt zu größerer Verformung.

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BaTi_0.85Hf_0.15O₃ . . . , .

     

Peculiarities of propylene metathesis over catalysts prepared by anchoring of Mo(V) oxalate to γ-Al2O3

Propylene metathesis over catalysts prepared by coordination of Mo(V) oxalate to -Al₂O₃ has been studied.

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, (V) -Al₂O₃.

     

Kinetics and mechanism of micellar effects upon the hydrolysis of 0-(2,4-dinitrophenyl) cyclohexanone oxime

A modification in the reaction mechanism of 0-(2,4-dinitrophenyl)cyclohexanone Oxime with OH^– in 30% aqueous methanol is suggested. The cationic micelles of cetyltrimethyl ammonium bromide enhance the reaction by a factor ofca. 3. The pseudo first order rate constant at the micellar surface was found to be 10.9×10^–4 s^–1 at 35±0.1°C. Anionic and nonionic micelles inhibit the rate of the reaction. Bromide ion inhibits the catalysis, which indicates that catalysis is partially due to a concentration effect. The catalytic efficiency increases with decreasing [OH^–), which implies that the efficiency of the surfactant could be related to some standard parameter(s).

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0-(2,4-)-- OH^– 30%- . . 3. - 10.9·10^{–4 –1} 35±0.1°C. . . , - . - [OH^–], , - - .

     

Developpement de la methode thermique de mesure de la tension superficielle liquide-solide

A thermal method connects the solid-liquid surface tension/s of a substance to its triple point temperature depression. Here a practical process for application of this method is described. A previous determination of the thickness of the condensate layer which does not freeze near the wall of the porous material is no longer necessary. The process is applied to some organic substances and to a metal (indium).

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Zusammenfassung Eine thermische Methode ermöglicht die Oberflächenspannung/s einer Substanz mit der Erniedrigung der Tripelpunkttemperatur in Bezug zu bringen. Eine vorangehende Bestimmung der Dicke der Kondensatschicht, deren Aggregatzustand sich bei Kontakt mit dem porösen Material nicht ändert, ist überflüssig. Die Methode wird auf einige organische Verbindungen und ein Metall (Indium) angewandt.

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, _.,. — . , , . .

     

A stochastic analysis of catalyst deactivation in presence of external transfer limitations

The paper analyzes the simplest case of concentration independent deactivation of a catalyst surface in the presence of external transport limitations and accounts for the variations around the mean value of the activity of the catalysts leading to a stochastic formulation. The results reveal interesting features which would not be evident from the conventional deterministic analysis.

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- , , . , .

     

Chemiluminescence and auto-oscillations in the (S?Cr2O72+?UO22+) system

Quasi-harmonic oscillations of chemiluminescence intensity at certain concentrations of the components for the (S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) system in concentrated sulfuric acid and chemiluminescence and dark stages with the participation of intermediates Cr(V), U(IV) and sulfur peroxide radicals (HS₂O₆ ^.) have been discovered. Chemiluminescence is attributed to the interaction of HS₂O₆ ^. compounds. The processes of deactivation of the excited states of uranyl involve the participation of Cr(V). A scheme for the oscillation chemiluminescence reactions is suggested.

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(S–Cr₂O ₇ ^2– –UO ₂ ²⁺ ) H₂SO₄ , . Cr(V), U(IV) (HS₂O₆ ^.) HS₂O₆ ^. Cr(V) . .

     

Spectral and thermal studies of copper(II) complexes of 3- and 4-pyridinealdoxime

Copper(II) complexes of 3- and 4-pyridinealdoxime have been prepared and analyzed by spectroscopic (ir and diffuse reflectance) and thermoanalytical (TG, DTG and DTA) techniques. For both these systems, only species with metal: organic ligand: chloride ratio of 122 were found, and the organic ligand appears as a neutral molecule. The spectral data suggest a polymeric structure where the copper(II) ions are in a distorted octahedral environment.The thermal decompositions occur through the reduction of copper(II) to copper(I) and the conversion of the residual organic ligand into acid amide, as found for dihydrogenbis(pyridine-2-aldoxime) copper(II) chloride, but the initial decomposition temperatures are slightly increased, giving rise to the thermal stability sequence:

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Zusammenfassung Kupfer(II)-Komplexe von 3- und 4-Pyridinaldoxim wurden hergestellt und spektroskopisch (IR und diffuse Reflexion) sowie thermoanalytisch (TG, DTG und DTA) analysiert. Für beide Systeme wurden nur Species mit einem Metall:Ligand:Chlorid-Verhältnis von 122 gefunden. Der organische Ligand liegt als neutrales Molekül vor. Die Spektren deuten auf eine polymère Struktur hin, in der die Kupfer(II)-Ionen in einer verzerrten oktaedrischen Koordination vorliegen. Die thermischen Zersetzungen verlaufen über die Reduktion von Cu(II) zu Cu(I) und die Umwandlung des verbleibenden organischen Liganden in Säureamid, wie für Dihydrogen-bis(pyridin-2-aldoxim)-kupfer(II)-chlorid gefunden wurde, aber die Temperaturen des Beginns der Zersetzung und damit die thermische Stabilität steigen in der Reihenfolge [Cu(Py₄-CHNOH)₂Cl₂][Cu(Py₃-CHNOH)₂Cl₂]>[Cu(Py₂-CHNOH)₂]Cl₂ etwas an.

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(, ) ( ) 3- 4- . 122, . , . -( -2-)- . , , , : Cu(4-Py-CHNOH)₂Cl₂Cu(3-Py-CHNOH)₂Cl₂>Cu(2-Py-CHNOH)₂Cl₂.

     

Reduction of an amorphous NiO?Al2O3/SiO2 catalyst by different olefins and hydrogen

By static magnetic measurements it was found that the ability to reduction of an amorphous NiO–Al₂O₃/SiO₂ catalyst decreases in the order: but-2-eneshydrogen isobutene>but-1-ene>propeneethene. The reduction temperatures are significantly higher than the dimerization reaction temperatures.

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, NiO–Al₂O₃/SiO₂ : -2>-1> . .

     

Differential scanning calorimetry studies on influence of microstructure on transformation of γ-Fe2O3 to α-Fe2O 3 +

The transition-Fe₂O₃-Fe₂O₃ has been investigated in oxygen and argon using DSC measurements in the temperature range 298 to 820 K. The results have been interpreted by taking into account the method of preparation, the specific microstructure of the samples and the nature of the gas used. It has been shown that the transformation temperature, and in general the absolute value of the negative enthalpy of the transformation as well, rises with increase of the specific surface area of the -Fe₂O₃. The observed fluctuations in this trend are attributed to differences in the microporosity, gas sensitivity and crystallinity of the samples.

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Zusammenfassung Der Übergang -Fe₂O₃-Fe₂O₃ in Sauerstoff- und Argonatmosphäre wurde mittels DSC im Temperaturbereich von 298–820 K untersucht. Die Ergebnisse werden unter Berücksichtigung der Präparationsmethode, der spezifischen Mikrostruktur der Proben und der Natur des benutzten Gases interpretiert. Die Phasenumwandlungstemperatur und im allgemeinen die Absolutwerte der negativen Enthalpie der Phasenumwandlung erhöhen bzw. vergrößern sich mit steigender spezifischer Oberfläche des -Fe₂O₃. Die in diesem Trend auftretenden Fluktuationen werden Unterschieden in der Mikroporosität, der Gasempfindlichkeit und der Kristallinität der Proben zugeschrieben.

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-Fe₂O₃ -Fe₂O₃ 298–820 . , . , , -Fe₂O₃. , .

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The authors are grateful to Mr. Christian Sarda for his help during the sample preparation and characterization, and to Mr. B. Maachi and Dr. M. Gougeon for their help in surface area measurements. A. C. Vajpei expresses his gratefulness for the award of a Postdoctoral Fellowship in Materials Science by the French Government, made through the Indo-French Scientists' Exchange Programme.

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Paper presented at the World Conference on Thermal Analysis, Madeira (Portugal), 1986.     

Ba(OH)2 as catalyst in organic reactions, part XIV. Michael addition catalyzed by barium complex salts in the homogeneous phase

Michael addition to chalcone is catalyzed by barium complex salts in the homogeneous phase under various conditions. The nature of these intermediates is analyzed. These complex salts are described for the first time. The Michael adduct of malonodinitrile to chalcone is described for the first time.

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, , . . . . .

     

Anwendung der Momentenmethode bei thermophysikalischen Messungen

Zusammenfassung Es wird die Anwendung der Momentenmethode zur Auswertung von instationären Versuchen zur Bestimmung der spezifischen Wärmekapazität und der Temperaturleitfähigkeit beschrieben und anhand von eigenen Untersuchungen illustriert.

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Moment equations have been derived for the evaluation of non-stationary thermophysical measurements for determining the specific heat capacities and thermal conductivities of solids. For specific examples the application of these equations is shown, with evaluation of temperature response curves of a solid in an agitated vessel for the cases of a step change in the surrounding gas, a rectangular thermal pulse and linear temperature rise (DTA).

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Résumé On a utilisé la méthode des moments pour dépouiller les résultats des expériences en régime non-stationnaire afin de déterminer la chaleur spécifique et la conductibilité thermique des corps solides. La méthode est illustrée à l'aide d'exemples spécifiques.

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. , ( ).

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Thermal decomposition kinetics of thorium(IV) chelates of two naphthol dyes

The thermal decomposition of thorium(IV) chelates of 1-(2-fluorenylazo)-2-naphthol ando-carboxyphenylazo-2-naphthol was studied by TG. Thermoanalytical data (TG and DTG) of these chelates are presented in this communication. Interpretation and mathematical analysis of these data and evaluation of order of reaction, the energy and entropy of activation based on the differential method employing the Freeman-Carroll equation, the integral method using Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation are also given. On the basis of experimental findings in the present course of studies the relative thermal stabilities of the thorium chelates can be given as [Th(FAN)₂(NO₃)₂]>[Th(CPAN)₂(H₂O)₂]2H₂O.

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Zusammenfassung Die thermische Zersetzung von Thorium(IV)-Chelaten von 1-(2-Fluorenylazo)-2-naphthol undo-Carboxyphenylazo-2-naphthol wurde thermogravimetrisch untersucht. Thermoanalytische Daten (TG und DTG) dieser Chelate werden angegeben und interpretiert. Reaktionsordnung sowie Aktivierungsenergie und -entropie wurden nach der differentiellen Methode unter Anwendung der Freeman-Carroll-Gleichung, nach der integralen Methode unter Verwendung der Coats-Redfern-Gleichung und nach der Näherungsmethode von Horowitz-Metzger bestimmt. Für die relative thermische Stabilität wird die Reihenfolge [Th(FAN)₂(NO₃)₂]>[Th(CPAN)₂(H₂O)₂]2H₂O angegeben.

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1(2- )-2- 1(2-)-2- --2-, . , . -, , - -. .

     

Magnetic fluorescence and phosphorescence quenching of gas-phase sulfur dioxide

Sulfur dioxide fluorescence and phosphorescence are quenched by a magnetic field. A model is suggested for the qualitative interpretation of the results.

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. , - .

     

A metal reactor for the diaphragm method with chambers providing complete mixing

A new metal reactor with two chambers in which complete mixing of gases is achieved has been developed for use in the diaphragm method. This apparatus is suitable for the determination of the effective diffusion coefficient and its temperature dependence. It can also be used to determine the type of transport, the gas permeability coefficient and to investigate the macrokinetics of catalytic processes.

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. : ; ; .

     

A mathematical model of the regeneration of the catalytic solution in the liquid-phase oxidation of unsaturated hydrocarbons

The study describes the mathematical model, calculation and optimization of the technological scheme of the regeneration of the catalytic solution in the liquid-phase oxidation of hydrocarbons.

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, .

     

Modifying action of carbon dioxide in catalytic oxidation of ethylene on silver

Carbon dioxide exerts a strong inhibitory effect on oxygen adsorption and complete oxidation of ethylene on silver but has little effect on the rate of ethylene oxidation to ethylene oxide.

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.