Relation between the catalytic and acidic properties of zeolite catalysts

Influence of the strength and concentration of non protic centers on the catalytic activity of metal-zeolite catalysts in isomerization of n-butane has been studied. A relationship between the specific activity and the center strength is suggested.

---

-. , .

     

Kinetics of oxidation of acrolein on a vanadium-molybdenum oxide catalyst

A kinetic study has shown that, in the range of low conversions, the reaction rate depends only on the partial pressure of oxygen. Comparison of the oxidation of acrolein and I-deuteroacrolein suggests that the splitting of the H–CO bond is not rate-limiting.

---

, , , . 1- , H–CO .

     

Determination of the active surface of supported oxide catalysts on the basis of their reduction rate

A method for the determination of the active surface of supported oxide catalysts, based on measurement of their rate of reduction with carbon monoxide has been developed. The surface of silica gel-supported CuO was measured. The catalytic activity of the samples was found to be proportional to their active surface.

---

, . , . , .

     

Chloride ion oxidation on various Pt surfaces in the presence of adsorbing organic substance

While chlorine evolution in the low overpotential region takes place preferentially on the weakly adsorbing surface sites, in the presence of cyclohexene the strongly adsorbing region is involved. This change in the reaction zone is the result of the occurrence of a new reaction which dominates the recombination of chlorine atoms.

---

, . , .

     

Thermal decomposition of some homobinuclear dihalide-bridged iron(III) complexes

Thermal studies by TG and DTG on some homobinuclear dihalide-bridged iron(III) complexes of the general type [Fe(S₂CNR₂)₂X]₂(}-X ₂) were carried out in air and nitrogen atmospheres. The apparent activation energies were determined by graphical methods and the TIN temperatures were calculated from the TG profiles. Finally, a possible mechanism of the decomposition is suggested on the basis of the pyrolysis and mass spectral data.

---

Zusammenfassung Einige homobinukleare Eisen(III)-Komplexe mit Dihalidbrücken der allgemeinen Formel [Fe(S₂CNR₂)₂X]₂(–X₂) wurden mittels TG und DTG in Luft und Stickstoffatmosphäre untersucht. Die scheinbaren Aktivierungsenergien wurden nach graphischen Methoden aus den TG-Profilen bestimmt. Ein möglicher, auf pyrolytischen und massenspektrometrischen Daten basierender Zersetzungsmechanismus wird vorgeschlagen.

---

[Fe(S₂CNR₂)₂X]₂ (-₂) . , . - .

---

---

Thanks are due to Dr. G. Karagiannidis, Laboratory of Organic Chemical Technology, Aristotelian University, for technical assistance.     

Propos sur l'interpretation de l'energie d'activation experimentale

Résumé Les résultats de divers travaux montrent que la valeurE _e de l'énergie activation expérimentale tirée des diagrammes d'Arrhénius varie avec la pression, dans le cas de réactions de décompositions endothermiques.L'analyse de divers modèles permet d'expliquer cette constatation en montrant que la grandeurE _e n'a pas le sens d'une énergie d'activation mais est une fonction de nombreux paramètres. Deux d'entre eux ont été retenus dans le cadre de cette étude: le terme d'écart à l'équilibre et le terme de gradient thermique, provoqué par l'endothermicité du phénomène.Cette analyse permet d'établir une prévision de la fonctionE _e (P) conforme aux résultats expérimentaux.

---

The results from various investigations show that the experimental activation energy valueE _e derived from the Arrhenius diagrams varies with pressure for endothermic decomposition reactions.The analysis of various models allows this fact to be accounted for by showing thatE _e should be regarded not in its fundamental formulation, but as being a function of numerous parameters. Two of these were taken into account in the present study, i.e. deviation from equilibrium and a thermal gradient due to the fact that the phenomenon is endothermic.FunctionE _e (P) fitting the experimental results may be predicted by such an analysis.

---

Zusammenfassung Die Ergebnisse verschiedener Untersuchungen zeigen, dass die aus den Arrhenius-Diagrammen abgeleiteten experimentellen Werte der AktivierungsenergieE _e bei endothermen Zersetzungsreaktionen mit dem Druck variieren.Die Analyse verschiedener Modelle ermöglicht eine Erklärung dieser Tatsache, indem gezeigt wird, dassE _e nicht in ihrer grundliegenden Formulierung betrachtet werden darf, sondern als Funktion einer Anzahl von Parametern. Zwei dieser Parameter wurden in der vorliegenden Untersuchung berücksichtigt d.h. die Abweichung von dem Gleichgewicht und der thermische Gradient, welcher infolge der endothermen Beschaffenheit der Erscheinung auftritt.Eine den Versuchsergebnissen entsprechende FunktionE _e (P) kann mittels einer solchen Analyse vorausgesagt werden.

---

, _e, , . , _ee , . , : , , . _e (), , .

     

Energy dissipation and selectivity in the catalytic oxidation of ammonia

A qualitative interpretation of selectivity changes in ammonia oxidation, based on considerations of energy dissipation processes is presented.

---

, .

     

Hydrocarbon cool flame-induced transformations of alkali metal chlorides

Studies of the effect of stabilized cool flame propane oxidation on alkali metal chlorides have revealed the partial removal of surface chlorine and the formation of alkali and formiate. Formiate formation was tentatively detected by IR spectroscopy. Excess heating (up to 23°C) established on such surfaces in the zone of cool flame compared to untreated ones, can be due to the recombination of surface radicals.

---

. , . . , . , 23°C, .

     

Homogeneous catalysts for dioxygen evolution from water. Oxidation of water by trisbipyridylruthenium(III) in the presence of metallophthalocyanines

Catalytic action of sulfonated phthalocyanines of Cr, Mn, Ni, Al, Cu, Zn, Fe and Co and of Co-tetra(sulfophenyl)porphine in the oxidation of water by Ru(bpy) ₃ ³⁺ , has been studied. The most efficient catalysts appear to be cobalt and iron complexes. A possible relation between catalytic and some redox properties of the compounds studied is discussed.

---

Cr, Mn, Ni, Al, Cu, Zn, Fe Co, џ Co- () , Ru(bpy) ₃ ³⁺ . , . , .

     

Some peculiarities in regeneration of zeolite-containing cracking catalysts by carbon dioxide

Catalytic properties of Mn and La oxides that are acceptors of CO₂ in regeneration of zeolite-containing cracking catalysts in the presence of carbon dioxide have been studied. Regeneration rate of coked catalysts by carbon dioxide in the presence of Mn and La significantly increases. During regeneration, coke oxidation to Co and redistribution of hydrogen in carbonaceous fragments take place to produce methane and hydrogen. Activation energy of methane and hydrogen formation equals 46 kcal/mol. Variation of activation energy with temperature is typical for Co formation.

---

, Mn La . CO . 46 /. CO .

     

Fatcors influencing thermoanalytical curves

The experimental conditions influencing thermoanalytical results are summarized and subdivided into three groups: sample properties, experimental parameters, apparative parameters. By means of selected examples, some experimental conditions are discussed, mainly for TG and DTA. Special care is given to particle size, the atmosphere as part of the reacting system and as experimental parameter, the buoyancy problem, dynamic re-impact phenomena of molecules, heat transfer and supercooling problems in melting, and DTA under different isobaric conditions. In quantitative thermal analysis, experimental conditions need careful control. Standard reference materials as well as automatic data collection and processing techniques help in achieving better thermoanalytical results.

---

Zusammenfassung Die die thermoanalytischen Ergebnisse beeinflussenden Versuchsbedingungen wurden zusammengefaßt und in drei Gruppen unterteilt: Eigenschaften der Probe, Versuchsparameter, Parameter des Geräts. An Hand ausgewählter Beispiele werden einige Versuchsbedingungen, hauptsächlich betreffs TG und DTA, erörtert. Eine besondere Aufmerksamkeit wird der Partikelgröße, der Atmosphäre als Teil des Reaktionssystems und als Versuchsparameter, dem Problem der Auftriebskraft, dem dynamischen Wieder-Einschlagphänomen der Moleküle, der Wärmeübertragung und den Problemen der Unterkühlung beim Schmelzen und der DTA bei verschiedenen isobaren Bedingungen gewidmet. Bei der quantitativen Thermoanalyse benötigen die Versuchsbedingungen ein sorgfältiges Regeln. Standard Referenzsubstanzen sowie Techniken der automatischen Datensammlung und -verarbeitung können zum Erhalten besserer thermoanalytischer Ergebnisse verhelfen.

---

Résumé On passe en revue les conditions d'expériences qui influencent les rés iltats de l'analyse thermique et on les classe en trois groupes: les propriétés de l'échantillon, les paramètres d'expérience et les paramètres propres aux appareils. On discute, à l'aide d'exemples, quelques conditions d'expérience, en considérant surtout la TG et l'ATD. On examine en particulier la grandeur des particules, l'atmosphère en tant que partie du système réagissant et en tant que paramètre d'expérience, le problème de la force ascensionnelle, le phénomène de choc dynamique répété des molécules, le transfert de chaleur et les problèmes de retard à la fusion lors du refroidissement ainsi que l'ATD sous diverses conditions isobares. Lors de l'analyse thermique quantitative, les conditions d'expériences doivent être minutieusement contrôlées. L'emploi de substances étalons de référence ainsi que l'acquisition et le traitement automatiques des données peuvent contribuer à parvenir à de meilleurs résultats.

---

, , : , - . , . , , , , . . , .

---

---

Paper presented at the Scientific Session on Thermal Analysis held at Balatonfüred Hungary, on 14–16 October 1976.     

Photochemical reactions of anthraquinone with hydrocarbons in the presence and absence of oxygen: Trapping of radical intermediates

Radical intermediates formed at 25°C in the presence and absence of oxygen during the photolysis of anthraquinone in aromatic, cyclic and aliphatic hydrocarbon solvents were trapped by 2,6-dichloronitrosobenzene, 2,6-dibromonitrosobenzene and 2,4,6-tribromonitrosobenzene. The resulting nitroxide radicals have been characterized in situ by ESR spectra.

---

: 2,6-, 2,6- 2,4,6-— , , 25°C. .

     

Study of the thermal decomposition of solids in a fluidized bed,II

In order to eliminate the errors of the TG method with a static layer, and to determine the influence of the heating rate, the composition of the carrier gas and the particle size of the solids, a method of thermal gas evolution from a fluidized bed (FTGE) with continuous and linear increase of temperature was worked out and the thermal decomposition of diammonium hydrogen phosphate was followed. This method gives reproducible results and makes possible the determination of the apparent activation energies and kinetic parameters.

---

Zusammenfassung Um die Fehler der TG Methode unter fixierten Verhältnissen zu eliminieren, den Einfluß der Temperaturerhöhung, der Zusammensetzung des Trägergases und des Ausmaßes der Festkörper zu klären, wurde eine thermogasanalytische Methode im fluidisierten Bett (FTGE) mit kontinuierlichem und linearem Temperaturanstieg entwickelt und die thermische Zersetzung des Diammonium-biphosphates verfolgt. Man erhielt mit dieser Methode reproduzierbare Ergebnisse. Sie ist zur Bestimmung der scheinbaren Aktivierungsenergien und kinetischer Parameter geeignet.

---

Résumé Dans le but d'éliminer les erreurs des procédés thermogravimétriques avec couches fixes, et de mettre en évidence l'influence de la vitesse d'échauffement de la composition du gaz porteur et de la dimension des solides, on a développé une méthode d'analyse des gaz dégagés, avec lit fluidifié et élévation de la température continue et linéaire. On a suivi ainsi la décomposition thermique de (NH₄)₂HPO₄. Cette méthode donne des résultats reproductibles et rend possible la détermination des énergies d'activation apparentes et des paramètres cinétiques.

---

, , . . , .

---

---

Some parts presented at the IIIrd Analytical Conference, Budapest, 1970     

Influence of CO2 and H2O on methane conversion over oxide catalysts

It has been established that the introduction of CO₂ and H₂O to the reaction mixture when using freshly prepared catalysts, increases the overall methane conversion and decreases the yield of hydrocarbons. On coked MgO their effect is insignificant.

---

, CO₂ H₂O . MgO CO₂ H₂O .

     

Relations between the probability of heterogeneous-homogeneous radical-chain mechnism and oxygen bond energy in oxide catalysts

Transition metal oxides increase the first ignition limit for 2 H₂+O₂ mixture (P₁) due to their reduction by H atoms, which leads to chain termination. The dependence of P₁ on the metal-oxygen bond energy and also on the heterogeneous catalytic activity of oxides has been established.

---

(P₁) -, . P₁ -, P₁ - .

     

Catalysts for metathesis of olefins, prepared by anchoring of MoO2(acac)2 to Al2O3

New highly active catalysts for metathesis of olefins were obtained through the interaction of bis(acetylacetonato)dioxymolybdenum(VI) with surface OH groups of -Al₂O₃ and subsequent reduction in H₂ or CO.

---

()(VI) OH -Al₂O₃ H₂ CO .

     

Tunnel recombination of surface and bulk radiation defects in finely dispersed CaO at 4.2 and 77 K

Recombination of radiation defects in CaO is shown to occur through electron tunneling from surface F_s ⁺ to V^–-center stabilized in the bulk.

---

, CaO F_s ⁺- V^–-, .

     

Discrimination of the kinetic model of overlapping solid-state reactions from non-isothermal data

A method has been developed that allows the deconvolution of up to 15 overlapping solidstate reactions without previous assumptions. Both the kinetic parameters and the reaction mechanisms fitted by the unit reactions can be determined from a series of non-isothermal experiments carried out at different heating rates.

---

Zusammenfassung Es wurde eine methode zur Dekonvolution von bis zu 15 einander überlappenden Festphasenreaktionen entwickelt, die keinerlei vorherige Annahmen notwendig macht. Mittels einer Reihe nichtisothermer Experimente mit unterschiedlichen Aufheizgeschwindigkeiten können sowohl die kinetischen Parameter als auch der Reaktionsmechanismus der Teilreaktionen bestimmt werden.

---

, 15. .

     

Mechanism of carbon monoxide oxidation on nickel oxide and its solid solutions

On the basis of studying the isotope exchange of oxygen and the position of the Fermi level in the system MiO–Li_xNi_1–xO, an explanation is proposed for the compensation effect in the reaction of CO oxidation on nickel oxide and its solid solutions.

---

NiO–Li_xNi_1–xO CO .