Promotion of nickel catalysts for the steam reforming of methane

The influence of additives (Cu, Fe and Al₂O₃) on the textural and catalytic properties of nickel in steam reforming of methane is described. The effects of structural promoting by Al₂O₃ and of electronic promoting by copper are reported. The rate of steam reforming of methane was measured in a gradientless reactor at atmospheric pressure.

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(Cu, Fe Al₂O₃) . Al₂O₃ . .

     

Displacement of hydrogen from rhodium surface by carbon monoxide under conditions of pulsed-gas chromatography

Interaction of carbon monoxide with hydrogen on the surface of rhodium catalysts has been investigated under conditions of pulsed-gas chromatography within the temperature range of –80 to 500 °C. At temperatures up to about 180 °C adsorbed hydrogen was found to be displaced to the gaseous phase as a result of carbon oxide adsorption. At higher temperatures conversion of carbon monoxide and hydrogen to methane takes place.

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–80 500 °C. 180 °C . .

     

Influence of cerium and lanthanum cations on the thermal stability of HY zeolite. Characterization of the zeolitic structure by nitrogen adsorption

Capacities for nitrogen adsorption of HY, CeHY and LaHY zeolites have been measured after calcination at several temperatures. CeHY and LaHY zeolites were prepared by ion exchange of HY, both presenting the same rare earth exchange ratio of 41%. Rare earth HY zeolites calcined at 1073 K present higher adsorption capacity than HY, which allows to conclude that cerium and mainly lanthanum increase the thermal stability of HY zeolite.

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HY, CeHY LaHY . CeHY LaHY HY, , 41%. 1073 K HY. , , , HY.

     

Effect of heating rate on the thermal decomposition of lead dioxide

Experimental data are presented on the kinetics and mechanism of PbO₂ decomposition at heating rates varying from 0 to 2.5 · 10³ °/sec. The studies were carried out with a time-of-flight mass spectrometer MSKH-4, a Paulik-Paulik-Erdey derivatograph and an X-ray diffractometer DRON-0.5At low heating rates (0 to 0.2 °/s) oxygen is evolved in four stages: PbO₂ PbO_1.56 PbO_1.44 PbO. At extremely high heating rates (2 · 10²–2.5 · 10³ °/s) the number of stages is reduced to two: PbO₂ PbO_1.4 PbO. An attempt is made to connect the observed change in the decomposition mechanism of PbO₂ with the crystal structure formation of the lead oxides.

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Zusammenfassung Versuchsergebnisse bezüglich der Kinetik und des Mechanismus der Zersetzung von PbO₂ bei Aufheizgeschwindigkeiten zwischen 0 und 2.5 · 10³°/s werden mitgeteilt. Die Untersuchungen wurden mittels eines time-of-flight Massenspektrometers MSKH-4, eines Derivatographen des Typs Paulik-Paulik-Erdey und eines Röntgendiffraktometers DRON-0.5 durchgeführt.Bei niedrigen Aufheizgeschwindigkeiten (0 bis 0.2 °/sec) wird Sauerstoff in vier Stufen entwickelt: PbO₂ PbO_1.56 PbO_1.44 PbO. Bei extrem hohen Aufheizgeschwindigkeiten (2 · 10² – 2.5 · 10³°/s) wird die Zahl der Stufen auf zwei herabgesetzt: PbO₂ PbO_1.4 PbO. Es wird versucht die beobachtete Ánderung in dem Zersetzungsmechanismus von PbO₂ mit der Kristallstrukturbildung der Bleioxide in Verbindung zu bringen.

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Résumé On présente des résultats expérimentaux concernant la cinétique et le mécanisme de la décomposition de PbO₂ pour des vitesses de chauffage allant de 0 à 2.5 · 10³°/s. Les études ont été effectuées à l'aide d'un spectromètre de masse du type MSKH-4, d'un Dérivatograph du type Paulik-Paulik-Erdey et d'un diffractomètre des rayons X du type DRON-0,5.Aux faibles vitesses de chauffage (0 à 0.2°/s) l'oxygène se dégage en quatre étapes: PbO₂ PbO_1.56 PbO_1.44 PbO. Aux vitesses de chauffage très élevées (2 · 10² à 2.5 · 10³°/s) le nombre des étapes se réduit à deux: PbO₂ PbO_1.4 PbO. On essaye de relier le changement observé dans le mécanisme de décomposition de PbO₂à la structure cristalline des oxydes de plomb.

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PbO₂ 2.5 · 10³°/c. — — MCX — 4, — — — 0.5. (0–0.2°/c) : PbO₂ PbO_1.56. PbO_1.44 PbO. (2 · 10²–2.5 · 10³°/c) : PbO₂ PbO_1.4 PbO. PbO₂ .

     

Studies with a derivatograph of the properties of a water film on a marble surface modified by tetradecylammonium chloride (TDACl)

The properties of water layers on bare marble and on marble samples covered with various amounts of tetradecylammonium chloride (TDACl) after flotation were investigated by thermal analysis methods. The dependences of the layer thickness, activation energy, enthalpy and entropy of the bonded watervs. the amount of TDACl previously deposited on the marble surface were determined. The results obtained and the literature data were used to propose an interpretation of the changes caused in these parameters by the coverage of the marble surface with TDACl molecules. A correlation between these parameters and the changes in water structure and marble flotatibility is also presented.

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Zusammenfassung Eigenschaften von Wasserfilmen auf unbeschichteten und mit Tetradecylammoniumchlorid (TDACl) in unterschiedlichen Mengen bedeckten Marmorproben wurden nach Flotation thermoanalytisch untersucht. Die Abhängigkeit der Schichtdicke, der Aktivierungsenergie und der Enthalpie und Entropie des gebundenen Wassers von der Menge des vorhergehend auf die Marmoroberfläche aufgebrachten TDACl wurden ermittelt. Die durch die Bedeckung der Marmoroberfläche mit TDACl verursachten Veränderungen dieser Parameter werden anhand der erhaltenen Resultate und von Literaturangaben interpretiert. Beziehungen zwischen diesen Parameters und Veränderungen der Wasserstrukturen und der Flotierbarkeit des Marmors werden angegeben.

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

     

Kinetics and mechanism of the permanganate oxidation of trans-crotonic acid

The kinetics and intermediates of the permanganate oxidation of trans-crotonic acid have been investigated in the pH range of 0.5–5.0 using the stoppedflow technique. The formation of manganese(III) as a short-lived intermediate has been established. The reaction is first order with respect to both MnO ₄ ^– and crotonic acid (crotonate). The resolved rate constants at 25°C are 730 and 410 M^–1 sec^–1 for the acid and the anion, respectively. The reaction mechanism is discussed.

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pH=0,5–5,0, . (III) . MnO ₄ ^– , (). 25°C 730 410 M^{–1 –1} , . .

     

Selective hydrogenation of fatty oils on alloyed Ni?Al catalyst. I. Kinetic model

On the basis of literature data concerning the reaction mechanism, a kinetic model for the selective hydrogenation of cotton-seed oil on the S-3 commercial alloyed Ni–Al catalyst is suggested. Its parameters have been identified according to the experimental data obtained in an agitated slurry reactor at T=140–200°C and P=0.2–0.8 MPa.

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, C-3. , , t=140–120°C, P=0.2–0.8 .

     

An approximation to the dependence of activation energies of simple catalytic reactions and the initial heats of adsorption of gases on metals on the nature of adsorbent and adsorbate

The activation energy, E, of simple catalytic reactions over 3d-oxides and the initial heats of adsorption, Q_ads, of gases on metals are related in a complex way to the enthalpy of formation of oxides and to the electronegativity of the gases involved in the processes.

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, , 3d- , Q_ads, , .

     

Catalytic properties of plantinized polycyanogens

The effect of various inorganic polymers on the catalytic activity and selectivity of platinum in the hydrogenation of 4-chloronitrobenzene and dinitrotoluene has been studied. Platinized iron-containing polycyanogens are less active but more selective catalysts for the hydrogenation of 4-chloronitrobenzene than Pt/C or Pt/BaSO₄.

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4- . , , , 4-, Pt/C Pt/BaSO₄.

     

Pt catalyst for the liquid-phase epoxidation of cyclohexene with an O2/H2 mixture

Conditions are found for the preparation of Pt catalysts providing the formation of epoxy-derivative in the reaction of cyclohexene with an O₂/H₂ mixture.

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Pt .

     

Ausbrennen von Kohlenstoffhaltigen,in den Ziegelrohstoff Eingepressten Stoffen

Zusammenfassung Die Kinetik der Ausbrennung organischer Stoffe im Ziegelscherben wird verfolgt und erläutert. Die Möglichkeiten der Beeinflussung des energetischen Aufwandes unter Nutzung moderner analytischer Methoden sind festzustellen. Bei einem diffusen Ausbrennen ist die Dichte und Durchlässigkeit des Scherbens massgebend. Praktische Anwendungsmöglichkeiten verschiedener auszubrennender Stoffe in unterschiedlichen Rohstoffen der Ziegelindustrie.

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The kinetics of burn-out of organic materials in bricks has been followed and explained. It is to establish that using new analytical methods the energy consumption can be influenced. The diffuse burn-out is determined by the density and permeability of bricks. There is a possibility for practical use of the results in the brick-industry with the different compounds to be burnt out from various raw materials.

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$ . , . . .

     

Specific activity of ruthenium for hydrogenation and hydrogenolysis of benzene in relation to metal dispersity

The specific activity V_sp of ruthenium supported on -alumina (0.084–0.84 wt.%, average particle size 1=1–7 nm) has been investigated for hydrogenation and hydrogenolysis of benzene at 80–320°C and compared with that of Ru powder of 1>1400 nm. A decrease of V_sp with increasing Ru dispersity was found for both reactions, the decrease having been more pronounced for hydrogenolysis. The effect is considered to be due mainly to an influence of dispersity of supported metal on the mode and extent of benze chemisorption.

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(V_Sp) , - (0,084–0,84 .%, 1=1–7 ), 80–320°C - 1>1400 . V_Sp , . , -, - .

     

Adsorption of formaldehyde and butynediol from aqueous solutions on a Cu2C2-silica gel catalyst

The effect of equilibrium concentration on adsorption has been studied at different temperatures and the nature of isotherms is discussed. For the formaldehyde-Cu₂C₂-silica gel system, Freundlich type equations describe the data satisfactorily.

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. . -Cu₂C₂- .

     

Interaction of CO and O2 on the oxidized surface of polycrystalline palladium

The interaction of CO and O₂ on the oxidized surface of polycrystalline palladium under steady state reaction conditions has been studied. The adsorption of carbon monoxide leads to the appearance of its and states. The state on the surface shifts the temperature dependence of the CO oxidation rate under s.s. conditions by about 200 K.

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CO O₂ . , CO. CO 200° CO .

     

Kinetics of molecular exchange in CF3COOH complexes with proton acceptors

The kinetics of hydrogen bond dissociation and formation in solution has been studied by a lineshape analysis of the¹H NMR signals of the proton donor (CF₃COOH) and proton acceptor (DMF) between –100 and –170°C. It has been found that proton exchange is much slower than molecular exchange and it does not affect the lineshape. A stepwise mechanism has been confirmed.

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( ) () — –100°–170°C. , . .

     

Investigation of kinetics and mechanism of maleic anhydride interaction with pentachlorinated phosphorus

Kinetics and mechanism of the interaction of maleic anhydride with pentachlorinated phosphorus have been studied. Kinetic parameters of a model making it possible to control this reaction have been calculated.

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, , .

     

Novel type of oscillatory chemical reactions

Chemical oscillations occur during the uncatalyzed oxidation of a number of phenol and aniline derivatives by acidic bromate.

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.

     

Thermal investigation of active carbons in presence of air

Thermal analysis data on the oxidation reaction between air and active carbons obtained during activation by carbon dioxide are presented. The correlation between the modified DTA curves and the TG curves leads to the conclusion that the oxidation of active carbons in the temperature range from 20 to 1000° is a two-step process. It is pointed out that the oxidation reactions in the low-temperature region (450–550°) are governed by the oxygen content of the samples, whereas the reactions in the higher temperature region (550–850°) are controlled by the diffusion process.

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Zusammenfassung Die thermoanalytischen Ergebnisse über die während der Aktivierung durch Kohlendioxid stattfindende Oxidationsreaktion zwischen Luft und Aktivkohlen werden vorgestellt. Die Korrelation zwischen den modifizierten DTA-Kurven und den TG-Kurven führte zur Schlußfolgerung, daß die Oxidation der Aktivkohlen im Temperaturbereich von 20 bis 1000° ein Zweistufen-Vorgang ist. Es wird betont, daß die Oxidationsreaktion im niedrigen Temperaturbereich (450 bis 550°) durch den Sauerstoffgehalt der Proben gesteuert wird, während er im Bereich der höheren Temperaturen (550 bis 850°) durch Diffusionsvorgänge geregelt wird.

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Résumé On présente les résultats de l'étude par analyse thermique de la réaction d'oxydation des charbons actifs par l'air qui a lieu lors de l'activation par l'anhydride carbonique. La corrélation entre les courbes ATD modifiées et les courbes TG conduit à la conclusion que l'oxydation des charbons actifs s'effectue entre 20 et 1000°, suivant un processus en deux étapes. Dans l'intervalle des températures faibles (450 à 550°) les réactions d'oxydation sont gouvernées par la teneur en oxygène des échantillons tandis qu aux températures plus élevées (550 à 850°) elles le sont par le processus de diffusion.

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, . , 20 1000° . , (450–550°) , (550–850°) .

     

Poissonian stationary distribution in a class of detailed balanced reactions

We investigate those detailed balanced (vectorial) complex chemical reactions that belong to the class of simple Markovian population processes and show that there is no chemical reaction with independent reaction rates having a Poissonian stationary distribution. There exists, however, a manifold of reactions with dependent (as given) reaction rates and with Poissonian stationary distribution.

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() , , , . , () .

     

Effect of quantization of molecular rotations on the rate of capture in the ion-linear dipole system

The version of transition state theory that accounts for quantization of the rotational energy of a dipole gives ion-dipole capture rate constants in good agreement with the statistical adiabatic channel model and, in the region , gives results more accurate than those obtained by numerical trajectory calculations.

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, , - . , .