Some aspects of mathematical statistics as applied to nonisothermal kinetics V

The paper gives a quantitative comparison of two methodological approaches to the solution of the inverse kinetic problem: the traditional approach and the nontraditional approach suggested by the authors. It is shown that the amount of information (in the sense of Shannon) obtained within the scope of the nontraditional approach is always greater than that obtained with the use of the traditional approach.

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Zusammenfassung Zwei methodologische Näherungen der Lösung des inversen kinetischen Problems werden quantitativ verglichen, nämlich die traditionelle und die von den Autoren vorgeschlagene nicht-traditionelle Näherung. Es wird gezeigt, daß mit der nicht-traditionellen Näherung erhaltene (im Sinne von Shannon verstandene) Informationsmenge immer größer als die durch Anwending der traditionellen Näherung erhaltene ist.

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Hydrocarbon conversion over Pt?Re/Al2O3-ZSM-5 bifunctional catalysts. I. Influence of the addition of ZSM-5

The influence of ZSM-5 on the behavior of a Pt–Re/Al₂O₃ catalyst was studied in normal heptane reforming in order to compare activity, selectivity and life of Pt–Re/Al₂O₃ and a mixture of Pt–Re/Al₂O₃ and ZSM-5 catalysts. It is suggested that the presence of ZSM-5 results in less pronounced catalyst deactivation but not in a sufficient increase in aromatic selectivity.

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ZSM-5 Pt–Re/Al₂O₃ - , Pt–Re/Al₂O₃ ZSM-5. , ZSM-5 , , .

     

Application of emissionless infrared diffuse reflectance spectrometry for following reactions of adsorbed alcohols on an alumina catalyst

IR spectra of adsorbed alcohols on alumina were measured under the reaction conditions at elevated temperatures. The transient response of IR absorption intensity indicates that alkoxides are reactive adsorbed species but carboxylates are not. The rate constants of surface reactions were calculated from the transient response.

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IR spectroscopic studies of CO interaction with surface zirconium hydrides

IR spectroscopic studies of CO interaction with surface zirconium hydrides have revealed that it proceeds through a step of CO adsorption on these hydrides at 163–273 K with the subsequent insertion of CO across the Zr-H bonds at T>293 K and the formation of surface formyl compounds.

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CO . , CO 163–273 CO Zr-H 293 .

     

A procedure for comparing the reactivity of different hydrocarbons in cracking over zeolites

The cracking of hydrocarbons over zeolites is accompanied by a significant production of coke, which causes their rapid deactivation. The coking and deactivation rates depend very much on the reactant. This makes necessary to compare the reactivities for the same coke content but not for the same time on stream.

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Preparation and properties of borosilicates with a zeolite structure

The dependence of the state of boron atoms on the preparation conditions of borosilicates and the effect of this state on their catalytic properties in methanol conversion have been studied.

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, .

     

Kinetics of EDTA-catalyzed oxidation of Indigo Carmine by vanadium(V)

The reaction is first order both in vanadium(V) and substrate and is markedly inhibited by H⁺ ions. Kinetic evidence for the formation of a 11 complex of vanadium(V) and EDTA is obtained. The stability constant of this complex and its thermodynamic parameters were evaluated. A suitable mechanism is proposed.

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(V), H⁺. 11 (V) . . .

     

Catalytic properties of sodium-containing silica gel in n-heptane decomposition

n-Heptane decomposition reactions on silica catalysts containing various amounts of sodium ions were studied. Ethylene, methane and propylene as well as unbrached -olefins were the main reaction products. The comparison of the experimental and theoretical results suggests a free-radical reaction mechanism.

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Evaluation of the activation energies of elementary propagation steps in the catalytic polymerization of olefins

The possible relation between the activation energies of adsorption and insertion reactions and the heat of olefin adsorption for the two-step mechanism of propagation have been evaluated on the basis of calculated preexponential factors for the propagation rate constants and the experimental activation energies of propagation.

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On the calculation of activation energies using a modified Kissinger method

Augis and Bennett (J. Thermal Anal. 13 (1978) 283.) [6] recently proposed a modified Kissinger method for determining the activation energy of a transformation. It is shown that the proposed method was, in fact, based upon a modification to the equation for the rate of reaction under non-isothermal conditions. The apparent discrepancy between the proposed method and the original Kissinger method is therefore resolved. The modified rate equation appears to have, at best, only a limited application. However, if the equation should be appropriate for a particular transformation, it is demonstrated that Augis and Bennett's method would be the correct method for determining the activation energy.

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Zusammenfassung Von Augis und Bennett (J. Thermal Anal.13, (1978) 283) wurde eine modifizierte Kissinger-Methode zur Bestimmung der Aktivierungsenergie einer Umwandlung vorgeschlagen. Es wird gezeigt, dass die vorgeschlagene Methode tatsächlich in einer Modifizierung der Gleichung für die Reaktionsgeschwindigkeit unter nicht-isothermen Bedingungen ihren Ursprung hat. Die scheinbare Diskrepanz zwischen der vorgeschlagenen Methode und der ursprünglichen Kissinger-Methode wird dadurch behoben. Die modifizierte Geschwindigkeitsgleichung hat bestenfalls nur eine begrenzte Anwendung. Jedoch, bei Eignung dieser Gleichung für eine bestimmte Umwandlung zeigt sich, dass die Methode von Augis und Bennett die richtige Methode zur Bestimmung der Aktivierungsenergie sein kann.

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(J. Thermal Anal. 13 (1978) 283.) - . , , , . , . , , , . , , .

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The author is indebted to the Senate of the University of Queensland for the award of a University Research Fellowship; and to Professor R. R. Stephens for providing laboratory facilities.     

Catalytic performance in Co hydrogenation over triruthenium ketenylidene cluster-derived catalyst

The ruthenium catalyst prepared from triruthenium ketenylidene cluster exhibited high catalytic activity in CO hydrogenation, compared with the catalyst from [HRu₃(CO)₁₁]^–. The high activity possibly resulted from the ketenyl group (CCO) that could be partly converted to carbide species.

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, , CO, [HRu₃(CO)₁₁]^–. , , (CCO), .

     

Formation of oxalates and carbonates in the thermal decompositions of alkali metal formates

The influences of gaseous and solid reactants on the yields of oxalates and carbonates in the thermal decompositions of alkali metal formates have been studied. A mechanism of formation of these products is proposed, which explains the influences of basic and acidic species formed in the medium on the thermal decompositions of the alkali metal formates.

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Zusammenfassung Der einfluß von gasförmigen und festen Reaktanten auf die Ausbeute von oxalaten und Karbonaten bei der thermischen Zersetzung von Alkalimetallformiaten wurde untersucht. Es wurde ein Mechanismus für die Bildung dieser Produkte vorgeschlagen, der den Einfluß der während der thermischen Zersetzung von Alkalimetallformiaten entstehenden Basen und Säuren erklärt.

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Ethylene oxidation by lithium nitrate in the presence of palladium acetate in acetic acid

Data are reported on variations of the gas phase volume and product accumulation in ethylene oxidation by lithium nitrate in acetic acid solutions, catalyzed by palladium acetate. An assumption is made on the routes of nitrate ion reduction.

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Thermal analysis of thermosetting resins

Applications of thermoanalytical methods for the study of the resinification and curing of phenolic resins are reviewed. Examples are given to illustrate the use of DSC for practical industrial systems such as paper impregnants and saturated papers.

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Zusammenfassung Es wird eine Übersicht über die Anwendungen thermoanalytischer Methoden zur Untersuchung der Harzbildung und der Aushrtung von phenolischen Harzen gegeben. Anhand von Beispielen wird die Verwendung der DSC für praktische industrielle Systeme wie Papierfüllstoffe und gefüllte Papiere aufgezeigt.

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, . , .

     

High-temperature reduction of SO2 by methane at various CH4/SO2 ratios

The character of the effect of initial reaction mixture and temperature on the selectivity of catalytic reduction of sulfur dioxide by methane in the presence of oxygen has been studied.

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.

     

Generation of model reactions leading to limit cycle behavior

The system of differential equations by Feistel and Ebeling has been generalized. Some new formal kinetic reactions with two internal components, which may exhibit limit cycle behavior have been studied. Based upon the numerical integration of the deterministic models of these reactions the oscillatory character of the systems has been confirmed.

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Crystallization kinetics of LDPE/Ny6 blends

The crystallization behaviour of low density polyethylene/nylon 6 blends has been investigated as a function of the composition.The melting points of the polymers are almost uninfluenced by the presence of the other homopolymers except for blends with a nylon content of 75–90%.Blends with 10% nylon content do not exhibit the crystallization peak during the cooling step probably because of the low concentration and high viscosity of the low density polyethylene matrix.The crystallinity degree of the polyethylene is independent of the composition, while some variations are shown by the polyamide.Finally the rate of nucleation is strongly affected by the composition, in particular for the nylon phase.

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Zusammenfassung Die Abhängigkeit des Kristallisationsverhaltens von 6 Polyethylen/Nylon-Gemischen geringer Dichte von der Zusammensetzung wurde untersucht. Der Schmelzpunkt eines jeden Polymers ist nahezu unbeeinflußt von der Anwesenheit des anderen Homopolymers ausgenommen die Gemische mit einem Nylongehalt von 75–90%. Die Gemische mit einem Gehalt von 10% Nylon zeigen während des Abkühlungsschrittes keinen Kristallisationspeak, was wahrscheinlich auf die niedrige Konzentration und auf die hohe Viskosität der Polyethylenmatrix mit geringer Dichte zurückzuführen ist. Der Kristallinitätsgrad des Polyethylens ist unabhängig von der Zusammensetzung, während ein Einfluß des Polyamids festzustellen ist. Die Keimbildungsgeschwindigkeit ist stark von der Zusammenstzung abhängig, was besonders für die Nylonphase gilt.

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— 6 . , 75–90% , . 10% , , , . , . , , .

     

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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