Formation and thermal decomposition of silicon oxynitride compounds. Part III

The formation of a previously unknown compound with stoichiometry Li₆SiN₂O₂ was found during studies on the reactivity of Li₂SiN₂ with Li₂O, of SiO₂ with Li₃N and of Li₃SiNO₂ with Li₃N.

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Zusammenfassung Die Bildung einer bisher unbekannten Verbindung der Stöchiometrie Li₆SiN₂O₂ wurde bei Untersuchungen der Reaktivität von Li₂SiN₂ mit LiO, von SiO₂ mit Li₃N und von Li₃SiNO₂ mit Li₃N beobachtet.

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Li₆SiN₂O₂ Li₂SiN₂ , , Li₃SiNO₂ .

     

Kinetics of perborate oxidation of quinol

The perborate oxidation of quinol in aqueous acetic acid is first order with respect to perborate, zero order with respect to quinol, and first order with respect to H⁺. The oxidation is faster than H₂O₂ oxidation. Breakdown of protonated perboric acid is suggested as the rate-limiting step.

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, H⁺. . , , , .

     

Chemiluminescent method to measure generation rates of active centers in reaction of hydrogen peroxide with hemin and pyridinehemichrome

A chemiluminescent method was used to measure generation rates of active intermediates in the interaction of hemin with hydrogen peroxide with and without pyridine at pH=8–9. The effect of various inhibitors in these two cases has been examined.

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pH=8+9. .

     

IR characterization of surface hydroxy groups on haematite

The OH stretching absorptions (3670, 3640 and 3460 cm^–1) detected on haematite samples obtained by thermal decomposition of goethite, are assigned to monocoordinated and bridged free surface OH's and to hydrogen bonded OH's in surface micropores, respectively, on the basis of their behavior to successive adsorption of methanol, pyridine and D₂O and surface structural models.

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OH (3670, 3640 3460 ^–1) , . OH, OH, , , , D₂O, .

     

Studies of the structure of multicomponent Raney nickel catalysts

Genesis and structure of Raney nickel catalysts modified by Mo, Fe and Ca have been studied by XPS, SIMS and Auger and electron microprobe methods. It has been established that these catalysts are inhomogeneous and their structure can be described by models accounting for the interaction and localization character of metal components, their oxides and hydroxides.

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, - Ni-, Mo, Fe Ca. , , , .

     

TPD studies of hydrogen adsorption on group VIII metals

Hydrogen desorption proceeds in several temperature regions and differs by its order of magnitude and activation energy. Differential curves of adsorbed hydrogen distribution with respect to the desorption activation energy, dN/dE (E), show a considerable inhomogeneity of adsorbed atomic species and the energetic homogeneity of molecular species.

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. dN/dE (E) .

     

Hydrogenation of nitric oxide on platinum black in acidic solution

By comparison of the catalytic hydrogenation and electrochemical reduction of NO on platinum black catalysts it has been shown that the hydrogenation of NO to ammonia and to hydroxylamine occurs in the diffusion controlled region only.

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NO , NO .

     

Acidity and aniline alkylation activity of oxides and supported vanadia oxides

Aniline alkylation activity of simple oxides and supported vanadia oxides are compared from the point of view of acidity and vanadia-support interaction.

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.

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IICT communication No. 2915     

A new method of DTA: Theory and practice

A novel differential thermoanalytical technique is described and discussed with regard to function, operation, performance, theory and application. Information is provided about the nature of the internal processes taking place at the time of absorption or release of energy. Notable features of the technique include high sensitivity and independence of a reference sample.

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Zusammenfassung Eine neue differentialthermoanalytische Technik wird hinsichtlich ihrer Funktion, Arbeitsweise, Leistung, Theorie und Anwendung beschrieben. Es wird über die Beschaffenheit der inneren Vorgänge bei der Energie-Absorption oder -Freisetzung berichtet. Vorteile der neuen Technik sind die hohe Empfindlichkeit und die Unabhängigkeit von der Referenzprobe.

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Résumé On décrit et discute une nouvelle technique d'ATD en considérant sa fonction, son utilisation, ses possibilités, sa théorie et son application. On indique les processus internes qui se produisent lors de l'absorption ou de la libération d'énergie. Les principales caractéristiques de la technique se rapportent à la sensibilité élevée et à l'indépendance de l'échantillon de référence.

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, , , , , . .

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We wish to acknowledge support of this research by the National Research Council of Canada and Dalhousie University, Halifax.     

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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, , . -.

     

Recent progress in numerical methods for the determination of thermokinetics

The results of a multinational concerted programme on the determination of thermokinetics are presented. The purpose of the programme was to compare different numerical methods which have been independently proposed for the determination of thermokinetics from experimental calorimetric data. To achieve this end, the same experimental data, obtained from two heat-flow calorimeters, were distributed and successively analyzed by the different methods. Numerical methods based on the state function theory, on Fourier transform analysis, on dynamic optimization and on a simple differentiation of the data were thus critically tested.

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Zusammenfassung Es wurden die Ergebnisse der gemeinsamen Arbeiten über die Bestimmung der Thermokinetik mit 4 numerischen Methoden (dynamische Optimalisierung, Methode der Zustandfunktionen, harmonische Analyse und umgekehrte Korrektion) vorgestellt. Die experimentellen Daten wurden mit Hilfe von 2 Kalorimetern mit einer konstanten Temperatur des Isoliermantels ermittelt. Die Durchführung der Versuche ermöglichte ein Vergleich der angewandten Methoden.

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Résumé Les résultats d'un programme de recherches concerté multinational sur la détermination des données thermocinétiques sont présentés. Le but du programme était de comparer différentes méthodes numériques proposées indépendamment pour la détermination des données thermocinétiques à partir des mesures calorimétriques expérimentales. Pour celà, les mêmes données expérimentales fournies par deux calorimètres à flux de chaleur ont été distribué es et analysées successivement par 4 méthodes: utilisation des variables d'état, analyse de la transformée de Fourier, optimalisation dynamique et simple différentiation des données.

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. , . , , . , , , .

     

Nature of propene chemisorption centers on molybdenum trioxide

As shown by temperature-programmed desorption (TPD), the quantity of reversibly chemisorbed propane on MoO₃ passes through a maximum depending on the degree of surface reduction. Using the ESR method, it is shown that the centers of propene chemisorption do not contain Mo⁵⁺ ions but presumably isolated Mo⁴⁺ ions.

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, MoO₃ . , Mo⁺⁵. , Mo⁺⁴.

     

The concentrations of radicals in hexane pyrolysis

The concentrations of the radicals CH₃, C₂H₅ and H have been determined by a kinetic method at 973–1088 K using additives of D₂. The values obtained are compared with results of the analysis of the kinetic model for n-alkane pyrolysis. The rate constants of the reactions of CH₃ and C₂H₅ with hexane have been determined.

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D₂ CH₃, C₂H₅ H 973–1088 K. -. CH₃ C₂H₅ .

     

Adsorption characteristics of some zeolites

Attempts have been made to correlate the Si/Al atom ratio, the degree of crystallinity, crystallite dimensions and the mean diameter of crystalline particles with the relative adsorption affinity index (RAI). Differences in molecular sieving effect and in some diffusional aspects between traditional zeolites and the new shape-selective ZSM are revealed by the adsorption characteristics of cyclohexane, benzene, toluene, neopentane and xylenes.

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Si/Al , , , (RAI). - ZSM , , , .

     

The activity of Ni/AlPO4, Ni/AlPO4?Al2O3 and Ni/AlPO4?SiO2 catalysts in the hydrogenation of e-cinnamaldehyde

Liquid-phase catalytic hydrogenatio of E-cinnamaldehyde was carried out by using new supported nickel catalysts (Ni/AlPO₄, Ni/AlPO₄–Al₂O₃ and Ni/AlPO₄–SiO₂) in methanol as solvent under low hydrogen pressure (4.1 bar) and 298 K. The kinetic orders are zero in H₂ and aldehyde. The selectivity to the hydrogenaton of the C=C double bond is very high (>99%)

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- (Ni/AlPO₄, Ni/AlPO₄–Al₂O₃ Ni/AlPO₄–SiO₂) (4,1 ) 298 . H₂ . C–C (>90%).

     

Methanol conversion to lower hydrocarbons over proton exchanged NaY zeolite catalysts

Various NaY zeolites protonated with an aqueous NH₄Cl solution were effective catalysts for methanol conversion to lower hydrocarbons. Even NaY zeolite protonated up to the degree of 4% showed a high catalytic activity at relatively low reaction temperatures.

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NaY, NH₄Cl, . 4%- NaY .

     

Effect of the state of vanadium cations on the IR spectra of adsorbed carbon monoxide

ESR and IR-spectrosocpic studies of the effect of the state of vanadium ions on the IR-spectra of adsorbed CO have revealed complex formation of CO with V⁴⁺ (vCO at 2192 and 2205 cm^–1) and V³⁺ (vCO at 2178 and 2185 cm^–1) ions.

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-- - CO. CO V⁴⁺ (vCO 2192, 2205 cm^–1) V³⁺ (vCO 2178, 2185 cm^–1).

     

Transient response study of the participation of adsorbed forms of ammonia in propene ammoxidation

On the basis of transient response studies, it is suggested that ammonia on the surface of a Mo–Si–Bi–P oxide catalyst forms a compound that is stable at the reaction temperature and whose reaction with propene yields acrylonitrile.

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, Mo–Si–Bi–P , .