Effect of traces of water vapor on the rate of ammonia decomposition on polycrystalline platinum

The influence of small (lower than 0.02) molar fractions of water on the rate of ammonia decomposition on platinum wires was studied for ammonia pressures varying between 6.7 and 93.3 kPa and temperatures between 800 and 1700 K. The presence of water strongly inhibited the rate of reaction in all experiments.

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( 0,02) , 6,7 93,3 , 800 1700 K. .

     

Kinetics of isotope exchange of dioxygen with a powdered high-temperature superconducting material Ba2YCu3O7?x

It has been found that the rate of isotope exchange in Ba₂YCu₃O_7–x–O₂ system is high. Its kinetics is exponential, first order with respect to dioxygen and the exchange is of the mixed first/third type.

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Ba₂YCu₃O_7–x–O₂ . -, -, - .

     

Hydrocondensation of CO: Catalytic activity of modified iron-alumina catalysts

The activity of modified Fe/Al₂O₃ catalysts in the hydrocondensation of CO has been studied in terms of the selectivity for light olefins and of repartition of the hydrocarbon products.

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Fe/Al₂O₃ CO, .

     

Kinetic laws for dehydrogenation of cyclohexane over Pd/C catalysts

A kinetic equation for cyclohexane dehydrogenation at P_O=1.0 MPa has been obtained.

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1,0 .

     

Basic condensation of triphenylsilane. II. Kinetics in anhydrous isopropanol and influence of silanol

Condensation of triphenylsilane with isopropanol in presence of isopropoxide has been studied in anhydrous medium and the activation parameters have been measured. Dehydration of the medium has been obtained by means of a pre-reaction of triphenylsilane with the residual water in the solvent. In this medium the reaction is extremely slow, moreover, it is inhibited by silanol whose effect would lower the actual catalyst concentration.

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. . , .

     

The application of thermoanalytical methods in the investigation of biological substances

The equilibria and thermodynamics of a number of naturally occuring isolated compounds (e.g. proteins, amino acids, carbohydrates) have recently been studied in several laboraties in different temperature ranges, and thermoanalytical methods have been used to study structural changes of biological materials, among them human tissues.In our investigations we succeeded in appling the derivatograph for the assay of glycosaminoglycans and for the characterization of the stability of crosslinked proteins in intact human and animal tissues. By means of this method age-related and pathological changes and repair reactions were studied in various connective and vascular tissues.Other temperature-dependent techniques (DSC, polarizing microscopy) were used successfully in another series of experiments. Alterations in the characteristic order-disorder transition temperatures of human serum lipoproteins could be demonstrated in pathological conditions; the altered physical structure of lipoproteins might give an additional explanation to the assumed mechanism of different metabolic disorders.

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Zusammenfassung Die Gleichgewichte und die Thermodynamik einer Reihe von natürlich vorkommenden isolierten Verbindungen (z. B. Proteine, Aminosäuren, Kohlenhydrate) wurden in verschiedenen Laboratorien in verschiedenen Temperaturbereichen untersucht. Hierbei wurden thermoanalytische Methoden zum Studium der Strukturänderungen von biologischem Material, u. a. von menschlichem Gewebe, eingesetzt.In unseren Untersuchungen gelang es den Derivatographen zur Prüfung von Glycosaminoglycanen und zur Charakterisierung der Stabilität quervernetzter Proteine in intakten menschlichen und tierischen Geweben einzusetzen. Durch diese Methode wurden altersbedingte und pathologische Änderungen sowie Reaktionen zur Wiederherstellung in verschiedenen Binde und Vasculärgeweben studiert.Andere temperaturabhängige Techniken (DSC, Polarisationsmikroskopie) wurden in anderen Versuchsserien mit Erfolg eingesetzt.

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, . , , , , . . , . .

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Plenary lecture     

Thermal and photochemical stability of polystyrene and its blends with polyvinyl chloride

The influence of some irregularities in polystyrene (PS) and polyvinyl chloride (PVC) chains on their thermal stability was investigated. UV irradiation caused an increase in the content of these irregularities in the polymers. It was found that the presence of carbonyl groups and crosslinking of the polymer chains hamper the thermal dehydrochlorination of PVC and the total decomposition of both polymers. On the other hand, weak peroxy linkages (which facilitate degradation processes) and conjugated double bonds decrease the temperature of total decomposition of PS and PVC blends.

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Zusammenfassung Es wurde der Einfluß von Unregmlmäßigkeiten in Polystyrol (PS)- und Polyvinylchlorid (PVC)-Ketten auf deren thermische Stabilität untersucht. UV-Bestrahlung verursacht ein Ansteigen des Gehaltes an Unregelmäßigkeiten in den Polymeren. Es wurde festgestellt, daß die Gegenwart von Carbonylgruppen und Querverbindungen der Polymerketten die thermische Dehydrochlorierung von PVC und eine vollständige Zersetzung beider Polymere verhindern. Andererseits senken Peroxidverknüpfungen (die die Degradierungsvorgänge erleichtern) und konjugierte Doppelbindungen die Temperatur für eine vollständige Zersetzung von PS und PVC Gemischen.

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. - . , . , , , .

     

Radiolysis of nitrous oxide adsorbed on alumina ionic mechanism of radiolysis of nitrous oxide on alumina with small surface areas

A mechanism is proposed for the radiolysis of adsorbed N₂O describing the experimental dependences of the radiation-chemical yields of O _st ^– and N₂ on N₂O coverages.

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N₂O, - O _st ^– N₂ N₂O.

     

Kinetic equation of heterogeneous catalytic isotope exchange

A kinetic equation is derived for the bimolecular isotope exchange reaction between AX _n ^* and BX _m ^o , all atoms of element X in each molecule being equivalent. The equation can be generalized for homogeneous and heterogeneous catalytic isotope exchange.

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, AX _n ^* BX _m ^o , X . , - .

     

Oxidative dehydrogenation of ethylbenzene over a charcoal catalyst

The oxidative dehydrogenation of ethylbenzene over a charcoal catalyst has been studied by the pulse technique. The styrene yields for the oxidation of ethylbenzene by gaseous oxygen and upon the interaction of ethylbenzene with oxygen adsorbed on charcoal are shown to be the same.

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. , , , .

     

Parent and mixed ligand complexes in the copper(II)-ethylene glycol-sulphate system

Eleven copper(II)-ethylene glycol-sulphate complexes of different compositions were prepared, one of them-CuGl₂(H₂O)₂SO₄-in single-crystal form. A thermoanalytical study of these complexes revealed three types of thermal decomposition pattern. The X-ray structure of the single-crystal demonstrated the presence of ethylene glycol bridges resulting in endless chains in the crystal.

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Zusammenfassung Elf Kupfer(II)-äthylenglykol-sulfat-Komplexe unterschiedlicher Zusammensetzung wurden dargestellt, einer davon — CuGl₂(H₂O)₂SO₄ — in Form von Einkristallen. Die thermoanalytische Untersuchung dieser Komplexe ergab drei Typen der thermischen Zersetzung. Die röntgendiffraktometrische Bestimmung der Struktur des in Form von Einkristallen erhaltenen Komplexes zeigte, daß den Kristall endlose Ketten von Äthylenglykolbrücken durchziehen.

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() — , — CuGl₂(H₂O)₂SO₄ — . . , , .

     

A thermal synthesis of a new tin(IV) dithiocarbamate

A new tin dithiocarbamate containing sulphur bridges, di--sulphidobis [bis(N,N-diethyldithiocarbamato)tin(IV)], has been isolated from the thermal decomposition of tetrakis(N,N-diethyldithiocarbamato)tin(IV). A dimeric structure is proposed on the basis of results from mass spectrometry, infrared spectroscopy, thermal analysis and vapour pressure osmometry.

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Zusammenfassung Ein neues, Schwefelbrücken enthaltendes Zinn-Dithiocarbamat, Di--sulfidobis[bis(N,N-diäthyldithiocarbamato)Zinn(IV)], wurde bei der Zersetzung von Tetrakis(N,N-diäthyl-dithiocarbamato)Zinn(IV) isoliert. Aufgrund der Ergebnisse der Massenspektrometrie, der Infrarotspektroskopie, der Thermoanalyse und der Dampfdruck-Osmometrie wird eine Dimerstruktur vorgeschlagen.

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Résumé Un nouveau dithiocarbamate d'étain contenant des ponts de soufre, le di--sulfidobis[bis(N,N-diéthyl-dithiocarbamato)é tain(IV)], a été isolé lors de la décomposition thermique du tétrakis(N,N-diethyl-dithiocarbamato) étain(IV). Une structure dimère est proposéeà partir des résultats obtenus par spectrométrie de masse, spectroscopie infrarouge, analyse thermique et osmométrie sous pression de vapeur.

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—-- [/N,N- (/IV)], [/N,N- (/IV)], , (N,N- ) (IV). - , , .

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The authors gratefully acknowledge the assistance given by Dr. A. G. Wedd with the vacuum sublimation technique. One of us, G. K. B., is grateful for a research scholarship provided by La Trobe University.     

Gas-phase hydroformylation of propylene on Ru/SiO2 catalysts

Ru/SiO₂ catalysts prepared by reduction of supported RuCl₃·xH₂O are active in gas-phase hydroformylation of propylene at low pressure (ca. 0.3 MPa) of H₂+CO+C₃H₆ mixtured and show unexpectedly high selectivity towards unbranched oxo-products. Data concerning the effect of electronic state and dispersity of Ru on their catalytic behavior have been obtained.

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Ru/SiO₂, RuCl₃·xH₂O, (0,3 ) - . .

     

Oxidative dehydrogenation (OXD) of n-butane I. Activity of natural quartz II. Kinetic and catalytic activity of nickel oxides

The oxidative dehydrogenation of n-butane on nickel oxide catalysts and on natural quartz, used as catalysts diluent, were studied. It is assumed that oxygen ions from the oxide lattice participate in the initial step of the reaction.

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- , . , .

     

Isomerization, dehydrogenation and cracking of methylcyclohexane over HNaY zeolites

On HNaY zeolites the fractions of acid sites which are active for cracking, isomerization and dehydrogenation of methylcyclohexane do not increase linearly with increasing degree of exchange. Isomerization and dehydrogenation seem to involve a similar activated complex, while cracking proceeds through a different one and requires stronger acid sites. Activation energies are independent of exchange degree.

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HNaY, , . , . .

     

A device for pulse investigation of heterogeneous catalytic reactions

In the present work a simple device is described for the pulse investigation of heterogeneous catalytic reactions and catalysts. Owing to the possibility for separate adjustment of the gas flow rate in the catalytic reactor and in the chromatographic column, it can be used for kinetic measurements too.

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- . , .

     

Oxidative dehydrogenation of n-butane, III. Kinetic and catalytic activity of ferric oxide

Catalytic activity of ferric oxide was evaluated in the oxidative dehydrogenation of n-butane. The apparent activation energy determined in the kinetic region was 37.7 kcal/mol. The activity of this oxide was undetectable up to 430°C. Reaction product distributions are shown as functions of temperature in the range of 430–650°C.

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(III) -. 37,7 /. 430°C. 430–650°C.

     

A thermogravimetric study of the solid-state reaction between alumina and strontium carbonate

The kinetics of the solid-state reaction between alumina and strontium carbonate were studied by thermogravimetry. The effects of the structure ( or) and/or doping (with Li⁺ or Cd²⁺) of the alumina on the kinetics of the reaction were examined. The results obtained were correlated with the phase composition and structural changes, followed by a number of physicochemical analyses (DTA, XRA and IRA) throughout the course of the reaction.

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Zusammenfassung Die Kinetik der Festkörperreaktion zwischen Aluminiumoxid und Strontium-carbonat wurde thermogravimetrisch untersucht. Die Effekte der Struktur ( und) und/oder des Dopens des Aluminiumoxids (mit Li⁺ oder Cd²⁺) auf die Kinetik der Reaktion wurde untersucht. Die erhaltenen Ergebnisse wurden mit der Phasenzusammensetzung und mit durch physikalisch-chemische Analysenverfahren (DTA, XRA und IRA) während des Reaktionsverlaufs verfolgten strukturellen Veränderungen in Beziehung gebracht.

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. ( ) Li⁺ Cd²⁺ . , , - .

     

Acetylene adsorption on a clean iridium surface

The interaction of C₂H₂ with a polycrystalline iridium surface at 140 KT500 K has been studied by AES, XPS and UPS. A model of the bonding between C₂H₂ and Ir by the 1 orbitals of the hydrocarbon is proposed. The more pronounced energy splitting between the orbitals of acetylene during adsorption compared to that in the gas phase is ascribed to deformation of the acetylene molecule.

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C₂H₂ . 140 KT500 K AES, XPS UPS. C₂H₂ Ir 1- . - , , .

     

V2O5/TiO2 oxidation catalysts, IV. Adsorption of acrolein on sodium-containing systems

Adsorption of acrolein on vanadia/titania catalysts fits a polymerization kinetics if Na–V compounds are not present or the vanadium content is lower than that corresponding to formation of a monolayer of vanadia on the titania support.

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, Na–V .