Measurement of the rate constant of hydrogen atoms with carbon monoxide in tubular and jet stirred open reactors

The reaction of hydrogen atoms with carbon monoxide has been studied in discharge flow systems with a new method of detection of atoms. The results obtained with tubular and jet stirred open reactors agree with those of other authors working in transient conditions and with more sophisticated techniques.

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. , , , .

     

Principles of formation of nitrogen oxides in acetonitrile oxidation on copper-chromium and platinum catalysts

The dependence of the conversion of bound nitrogen to oxides on the temperature and concentrations of oxygen and acetonitrile have been determined. On copper-chromium catalysts the nitrogen of acetonitrile is oxidized predominantly to molecular nitrogen, whereas on platinum catalysts the conversion of bound nitrogen to oxides attains up to 90%.

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. , , 90%.

     

On the relationship between thermal stability and catalytic properties of supported molyboo-vanado-phosphoric heteropoly acids

Catalytic properties of four heteropoly acids of the molybdophosphoric type were studied in the selective oxidation of isobutene to methacrolein. Results show that the highest selectivities for methacrolein were achieved with samples in which the original structure of the heteropoly anion is least affected by thermal destruction.

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. , .

     

Chemical reaction and phase transformations of the components of low temperature shift catalyst in various atmospheres

The systems CuO–Al₂O₃ and ZnO–Al₂O₃, as model systems of low temperature shift catalysts, have been studied in the temperature interval 100–700°C. The changes of their phase composition and surface area, influenced by gas atmosphere have been studied by X-ray, IR analysis and low temperature nitrogen adsorption.

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CuO–Al₂O₃ ZnO–Al₂O₃ CO 100–700°C. , - .

     

Effect of the surface composition of silica supported Pt?Ru Bimetallic catalysts on methane-deuterium exchange reaction

The exchange reaction of methane and deuterium was studied over a series of silica-supported Pt–Ru bimetallic catalysts, whose surface composition was determined by means of O₂–CO titration. The stepwise exchange, giving CH₃D as the main product, proceeded on each surface Pt atom. The multiple exchange, which formed CD₄ directly, proceeded on an ensemble of several Ru atoms.

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Pt–Ru, SiO₂, O₂–CO . , CH₃D , Pt. , CD₄, Ru.

     

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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. , .

     

X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber

X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber have revealed that for the catalysts obtained by the reduction of preactivated samples, no complete reduction of platinum takes place.

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, , , .

     

Catalytic conversion of alcohols, IX. Effect of temperature on the direction of elimination of water from a tertiary alcohol

The amount of 1-alkene formed by the dehydration of 2-methyl-2-butanol with several metal oxide catalysts parallels the temperature dependence of acetate pyrolysis where the amount of 2-methyl-1-butene increases with increasing temperature.

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1-, 2--2- , , 2--1- .

     

Oxidative coupling of 5-membered heterocycles catalyzed by a Pd(II)-heteropolyacid system in dimethylformamide

Oxidative coupling of thiophene and 2-methylfuran to the corresponding dihetaryls in DMFA medium occurs in the presence of the homogeneous catalytic system Pd(II)-molybdovanodophosphoric heteropolyacid (HPA). The data obtained show that HPA may act as a reversible oxidant in polar aprotic media.

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, Pd(II)- 2- . , .

     

Possibilities of applying the Piloyan method of determination of decomposition activation energies in the differential thermal analysis of polynitroaromatic compounds and their derivatives

By means of non-isothermal DTA in its simple form the initial exotherm temperaturesT _D of 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2,4,6-trinitrotoluene, 1,5-dinitronaphtalene, 1,8-dinitronaphthalene and 1,4,5,8-tetranitronaphthalene have been determined. By application of the Piloyan method to these measurements, the activation energiesE arising from the decompositions of these compounds were established. The results are discussed from the point of view of the molecular structures of the polynitro compounds.

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Zusammenfassung Durch nicht-isotherme DTA in ihrer einfachen Form wurde der BeginnT _D der Exothermen von 2,4-Dinitrotoluol, 2,6-Dinitrotoluol, 2,4,6-Trinitrotoluol, 1,5-Dinitronaphthalin, 1,8-Dinitronaphthalin, 1,4,5-Trinitronaphthalin und 1,4,5,8-Tetranaphthalin bestimmt. Durch Anwendung der Methode von Piloyan auf diese Messungen wurden die aus der Zersetzung o.a. Verbindungen herrührenden AktivierungsenergienE spezifiziert. Die erhaltenen Ergebnisse werden unter dem Aspekt der Molekularstruktur der untersuchten Polynitroverbindungen erörtert.

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Résumé On a déterminé par ATD les températures initialesT _D des phénomènes exothermiques du 2,4-dinitrotoluène, 2,6-dinitrotoluène, 2,4,6-trinitrotoluène, 1,5-dinitronaphtalène, 1,8-dinitronaphtalène, 1,4,5-trinitronaphtalène et 1,4,5,8-tétranitrophtalène. Les énergies d'activationE de la décomposition de ces composés ont été déterminées à l'aide de la mé thode de Piloyan. Les résultats obtenus sont discutés sous l'aspect de la structure moléculaire de ces composés.

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T _D 2,4-, 2,6-, 2,4,6- , 1,5- 1,8- , 1,4,5- 1,4,5,8- . , E .

     

Study of the adsorption of C18O on iron catalysts

The adsorption of C¹⁸O on Fe/Al₂O₃ and Fe/SiO₂ at room temperature was studied by TPD-MS. Two desorption peaks were obtained, which corresponded to the evolution of C¹⁸O at low temperature and that of C¹⁶O at higher temperature. These results are in favor of a complete exchange of oxygen through the dissociation of the CO molecule.

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C¹⁸O Fe/Al₂O₃ Fe/SiO₂ -. , C¹⁸O C¹⁶O . CO.

     

Investigation of proton-acceptor properties of oxide surfaces by IR spectroscopy of hydrogen-bonded complexes

Strength of the basic centers on catalyst surfaces is suggested to be characterized by the IR spectra of adsorbed chloroform. The existence of centers with different proton-acceptor properties on several oxides is shown experimentally.

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- . , .

     

On the correlation between the mean electronegativities of phosphates and their asymmetric P?O?P stretching frequencies

The frequency of P–O–P asymmetric stretching vibration in tri- and tetra-metaphosphate salts is correlated with the mean electronegativity of the structure. A qualitative explanation for this phenomenon is discussed.

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P–O–P - . .

     

On the rate and deepness of 3-methylpentane hydrogenolysis over various transition metals

The 11 metals studied can be divided into two groups: Rh, Pd, Ir, Pt, inducing single, and Co, Ni, Cu, Ru, Ag, Re, Os, causing multiple breakdown of the 3-methylpentane molecule. A fragmentation factor was defined which was found to be independent of the preparation of the metal and its activity in hydrogenolysis.

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3- 11 : Rh, Pd, Ir Pt, 3-, Co, Ni, Cu, Ru, Ag, Re Os, . , , .

     

Characterization of nickel loaded mordenite catalysts by temperature programmed reduction

Temperature programmed reduction (TPR) has been used to study the redox behavior of Ni(II) ions in nickel sodium mordenite (NiNaM) and decationated nickel mordenite (NiHM). The TPR profiles suggest that Ni(II) ions occupy nonequivalent sites with different cooridination states in the mordenite. The reducibility of Ni(II) depends strongly on the zeolite acidity.

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() Ni^II NiNaM NiHM. . .

     

Differential-thermal and thermogravimetric analysis of some gagates from Bulgaria

The thermal behaviour of three gagates (Bulgaria) was investigated by DTA and TG. The characteristic endo- and exoeffects and the sequence of the thermal stabilities are established.

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Zusammenfassung Das thermochemische Verhalten von drei Gagaten (Bulgarien) wurde mittels DTA und TG untersucht. Die charakteristischen endo- und exothermen Effekte und die Reihenfolge der thermischen Stabilitäten wurden ermittelt.

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(). - .

     

Recent progress in titration calorimetry

Research developments in titration calorimetry over the past ten years by personnel at the Thermochemical Institute have resulted in new techniques and instrumentation that have greatly increased the usefulness of calorimetry in the study of chemical problems. During this time, problems associated with the components of the calorimeter (i.e., constant temperature bath, constant rate buret, reaction vessel, temperature sensing circuit, and data analysis procedure) have been solved so that the continuous titration method now gives results comparable in accuracy to those obtained with conventional solution calorimeters. These developments have opened new avenues of research in the fields of biochemistry, microbiology, and environmental analysis.

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Zusammenfassung Die Fortschritte der Forschung auf dem Gebiete der Titrationskalorimetrie, welche in den vergangenen Jahren von Mitarbeitern des Thermochemischen Instituts erreicht worden sind, führten zu neuen Techniken und neuer Instrumentation, die die Einsatzfähigkeit der Kalorimetrie zur Untersuchung chemischer Probleme wesentlich erhöhten. Während dieser Zeit wurden Probleme in Zusammenhang mit den Bestandteilen des Kalorimeters (d.h. Konstanttemperaturbad, Burette mit konstanter Geschwindigkeit, Reaktionsbehälter, Temperatur, Wärmefühler-Stromkreis und Datenverarbeitungsvorgang) gelöst, so daß die kontinuierliche Titrationsmethode jetzt Ergebnisse von einer Genauigkeit liefert, welche mit der in herkömmlichen Lösungskalorimetern erhaltenen vergleichbar ist. Diese Entwicklungsarbeit eröffnet neue Wege der Forschung auf den Gebieten der Biochemie, Mikrobiologie und Umweltschutzanalyse

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Résumé Les recherches effectuées durant les dix dernières années par le personnel de l'Institut de Thermochimie ont eu pour résultat la mise au point d'appareils nouveaux qui augmentent, considérablement l'applicabilité de la calorimétrie à l'étude des problèmes chimiques. Ainsi les problèmes associés aux composants d'un calorimètre (c'est-à-dire bain à température constante, burette à vitesse constante, récipient réactionnel, circuit détecteur de température et procédés d'analyse des données) ont été résolus. C'est pourquoi la technique du titrage en continu donne maintenant des résultats d'une exactitude comparable à celle obtenue avec les calorimètres en solutions conventionnels. Ces développements ont ouvert de nouvelles perspectives de recherche dans les domaines de la biochimie, de la microbiologie et des analyses liées à la protection de l'environnement.

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Mean configurational distribution function for the steady state and stern-volmer representation

A slight discrepancy appears between the treatment of the steady state of diffusion controlled bimolecular quenching of excited species either by the pair model or by the continuum model. A simplifying assumption is pointed out which helps to solve the steady state case but which is responsible for the discrepancy. The error involved is of small importance considering the experimental accuracy.

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- , . , , . , .

     

Characterization of the interaction of CO and H2 at the ZnO surface by adsorption microcalorimetry

CO and H₂ are both chemisorbed by ZnO but H₂ is more sensitive than CO to the surroundings of adsorption sites. When the two gases are coadsorbed, a strong interaction occurs, ascribed to the formation of a possible precursor in methanol synthesis.

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CO H₂ ZnO, H₂ , , CO. , , .

     

Mechanism of reactions in mixtures of calcium polyphosphate with apatite and accompanying minerals during heating

The thermal interaction of Kovdor apatite, calcite, dolomite and forsterite with calcium polyphosphate up to 1200 °C were studied by chemical, thermal (under dynamic and quasiisothermal and isobaric conditions), X-ray, electronmicroscopic and chromatographic methods. It was found that the accompanying minerals of apatite react with calcium polyphosphate at lower temperature in comparison with apatite, complicating the process of thermal defluorination of papatite.

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Zusammenfassung Die thermische Wechselwirkung von Kovdor-Apatit, Calcit, Dolomit und Forsterit mit Calciumpolyphosphat bei Temperaturen bis 1200 °C wurde durch chemische, thermische (unter dynamischen, quasiisothermen und isobaren Bedingungen), röntgenographische, elektronenmikroskopische und chromatographische Methoden untersucht. Es wurde festgestellt, daß die Begleitminerale des Apatits im Vergleich zum Apatit selbst bei niedrigeren Temperaturen mit Calciumpolyphosphat reagieren und so den Prozeß der thermischen Entfluorierung von Apatit komplizieren.

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, , 1200° , ( ), , - . , , .