Investigation of the interaction between zinc oxide and phosgene

It has been shown that in the interaction of zinc oxide and phosgene, the most active are the samples having oxygen vacancies. A mechanism for this process is suggested.

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, , . .

     

Image processing using the Briggs-Raucher oscillating chemical reaction

Some images obtained by illuminating the Briggs-Raucher oscillating chemical reaction are illustrated. This reaction gives more distinct and contrasty images than the Belousov-Zhabotinskii reaction.

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-. , , -.

     

Thermal effects of contamination,adsorbed water and annealing on the DTA of powdered quartz

During the grinding of quartz, water is adsorbed from the atmosphere, but this water gave no detectable thermal effect on DTA because it was evolved uniformly up to 1000°. However, in conjunction with an iron contaminant, the adsorbed water was involved in an oxidation reaction causing noticeable thermal effects for quartz powdered in a vibration mill constructed of steel parts. When powdered so finely that the - inversion peak at 573° had disappeared, annealing caused a partial redevelopment of the peak but recrystallization of disrupted quartz was too small an effect to give any detectable exothermic peak on DTA.

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Zusammenfassung Während des Vermahlens von Quartz wird Wasser aus der Atmosphäre adsorbiert, jedoch ergab dieses Wasser keinen nachweisbaren thermischen Effekt in der DTA, da es bis zu 1000° gleichmässig freigesetzt wird. Im Zusammenhang mit einer Eisen-Verunreinigung wurde jedoch das adsorbierte Wasser in eine Oxidationsreaktion einbezogen, welche beim in einer aus Stahlteilen gefertigten Vibrationsmühle zerpulvertem Quartz nachweisbare thermische Effekte verursachten. Wenn so fein pulverisiert wurde, daß der --Inversions-Peak bei 573° verschwunden war, verursachte eine Wärmebehandlung eine teilweise Wiederentwicklung des Peaks, jedoch war die Rekristallisation des zerstörten Quartzes zu geringfügig um einen nachweisbaren exothermen Peak in der DTA-Kurve zu ergeben.

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Résumé Lors du broyage du quartz, il se produit une adsorption de l'eau atmosphérique mais cette eau ne donne pas d'effet thermique décelable par ATD car elle se dégage régulièrement jusqu'à 1000°. Cependant, en présence de fer comme contaminant, l'eau adsorbée intervient dans une réaction d'oxydation qui donne des effets thermiques perceptibles dans le cas de quartz pulvérisé dans un vibrobroyeur en acier. Si le quartz est en poudre assez fine pour que le pic d'inversion - à 573° disparaisse, le recuit provoque la réapparition partielle du pic. La recristallisation du quartz est cependant trop faible pour donner un effet exothermique décelable par ATD.

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, , 1000°. , , . - 573° , , , - .

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We are grateful to the Science Research Council for supporting this work.     

Thermal conductivity of cemented carbides

The hypothetical salts Li₄SiN₂O and Li₇SiN₃O were sought in the course of studies on the reactions of Li₂SiN₂ and Li₅SiN₃ with lithium oxide, and of LiSiNO with lithium nitride.

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Zusammenfassung In einer Reihe von Studien der Reaktionen von Li₂SiN₂ und Li₅SiN₃ mit Lithiumoxid bzw. LiSiNO mit Lithiumnitrid wurde nach den hypothetischen Salzen Li₄SiN₂O und Li₇SiN₃O gesucht.

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Li₂SiN₂ Li₅SiN₃ LiSiNO Li₄SiN₂O Li₇SiN₃O.

     

Spectral dependence of photocatalytic CO oxidation on rutile

In the region of intrinsic rutile adsorption, CO oxidation follows a redox mechanism via the interaction of CO with O^– ion-radicals, and the photocatalytic activity is determined by the density of 2p states close to the top of the valence band.

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CO CO - O^–, 2- .

     

Inhomogeneity of strong Lewis acid centers on Al2O3 surface

Specificity of the bands at 1630–1620 cm^–1 in IR spectra of coordinatively bonded pyridine has been studied. Three strong Lewis-type acid centers have been revealed on Al₂O₃ surface.

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- 1630–1620 ^–1.

     

Ethylene hydroformylation over a nafion-supported rhodium catalyst

Ethylene hydroformylation over a Nafion-supported rhodium catalyst has been studied under atmospheric pressure in the temperature range of 100–135 °C, using the transient response method.

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, , 100–135°C, .

     

Hydrodemetallation and the promoter effect of vanadium compounds on a Co?Mo/Al2O3 hydrodesulfurization catalyst

The effect of the vanadium compounds [VO(phthalocyanine)], [VO(salen)] [salen=N,N-ethylenebis(salicylideneiminate)], petroporphyrins, and metal-free phthalocyanine on the hydrodesulfurization of thiophene over a Co/Mo/Al₂O₃ catalyst (350°C, 1 atm) is described. The compound [VO(salen)], which decomposes, acts as a promoter at low V (0.1–0.2 wt. %); the other compounds deactivate the catalyst, an effect which is due to the whole molecule binding to the catalyst in the same way as a nitrogen base.

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[VO()], [VO()] [=N,N-- ()], , , Co–Mo/Al₂O₃ (350°C, 1). [VO()], , V (0,1–0,2 . %-); , , .

     

Vapor phase oxidation of methylpyridines on zeolite catalysts

It has been established that zeolites containing Pd and Cu ions catalyze the vapor phase oxidation of methylpyridines. In oxidation of 2-methylpyridine on PdCuNa-mordenite at 375 °C the yield of 2-pyridinecarbaldehyde is 40 % of its theoretical values.

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, , Pd Cu, . 2- PdCuNa- 2- 375°C 40% .

     

Calorimetric models

The basis of the determination of mathematical models of calorimetic systems is presented. Examples of applications of these models are given for the elaboration of a classification of calorimetric systems; the analysis of the course of heat effects in calorimeters; the analysis of dynamic properties: and the analysis of total heat effects and thermokinetics. Special attention is paid to the application of the multi-body method for the construction of mathematical models of calorimetic systems.

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Zusammenfassung Die Grundlage zur Ableitung mathematischer Modelle von kalorimetrischen Systemen wird vorgestellt. Für diese Modelle werden folgende Anwendungsbeispiele ausgeführt: Fortgeschrittene Klassifizierung kalorimetrischer Systeme, Analyse des Verlaufs von Wärmeeffekten in Kalorimetern, Analyse der dynamischen Eigenschaften, Analyse der vollständigen Wärmeeffekte, Thermokinetik. Besondere Aufmerksamkeit gilt der Anwendung der Vielkörpermethode zur Aufstellung eines mathematischen Modells für kalorimetrische Systeme.

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. , , , . .

     

Studies of supported catalysts for ethylene polymerization, prepared using organovanadium compounds

Catalysts containing trimethylsilyl complexes of V(IV) and (III) supported on SiO₂ and Al₂O₃, have been synthesized and examined for ethylene polymerization. The state of vanadium in solution and on the support and catalysts interaction with C₂H₄, CO, H₂ and pyridine have been studied using ESR and IR spectroscopy.

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, (IV) (III), SiO₂ Al₂O₃. , C₂H₄, CO, H₂ .

     

Thermogravimetric changes influenced by the compaction of graphite-CrO3 intercalation compounds

The changes resulting from the compression of graphite-CrO₃ intercalation compounds are demonstrated in the TG curves. In comparison with the samples examined in the form of a flake bed, the compacted compounds begin to decompose at lower temperatures and their weight loss is higher, particularly above 220 °C. To explain the obtained results, the pressure-induced changes in the structures and the activities of the compounds are considered in relation to the method of intercalation, the concentration of the intercalant and the extent of exfoliation.

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Zusammenfassung Anhand von TG-Kurven wurden Veränderungen demonstriert, die durch das Verdichten von Graphit-CrO₃-Einlagerungsverbindungen hervorgerufen werden. Im Vergleich zu Proben, untersucht in Form von Flocken, beginnen die kompakten Verbindungen sich bei niedrigeren Temperaturen zu zersetzen und zeigen einen grösseren Masseverlust, insbesondere beim Überschreiten von 220 °C. Zur Deutung der erhaltenen Ergebnisse wurden die druckverursachten Veränderungen in Hinsicht auf das Verfahren der Einlagerung, die Einlagerungskonzentration und auf das Ausmass der Abbröckelung in Betracht gezogen.

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, -r₃. , , , 220°. , , .

     

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 .

     

Effect of the partial pressure of reactants on the selectivity of methylcyclopentane hydrogenolysis over a platinum catalyst

The kinetics of methylcyclopentane hydrogenolysis on a Pt/Al₂O₃ catalyst (10% Pt) has been studied at 230°C. The selectivity to 2-methyl- and methylpentane formation depends on the partial pressures of the starting reactants (methylcyclopentane and hydrogen); the surface coverage by these reactants must be taken into account in selectivity studies.

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Pt/Al₂O₃ (10% Pt) 230°C. 2-- 3- ( ). .

     

Dehydroxylation and catalytic activity of dealuminated Y zeolites

Dehydroxylation and catalytic conversion of m-xylene over dealuminated zeolites were studied.

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- .

     

Oxidation of 2,6-xylenol by Co(III) chelates in toluene

A simple reaction scheme and kinetic data are presented for the oxidation of 2,6-xylenol by Co(III) chelates in toluene.

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2,6- Co(III) .

     

Decomposition of cumene hydroperoxide in the presence of 1,5,9-cyclododecatriene catalyzed by MoO2 (ACAC)2: A kinetic study

The kinetics of decomposition of cumene hydroperoxide in the presence of 1,5,9-cyclododecatriene, catalyzed by MoO₂(acac)₂ has been studied at constant temperature (303 K) and at atmospheric pressure. The influence of substrate, catalyst and product concentrations on the rate has been established. The rate and equilibrium constants have been calculated.

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1,5,9-. MoO₂(acac)₂. , .

     

Testing the photocatalytic activity of cyanogen-and thiocyanogen-based inorganic polymers

The photocatalytic properties of some cyanogen-and thiocyanogen-based inorganic polymers, such as paracyanogens containing different metals (Hg, Ag, Cu), polythiocyanogens of different iodine contents, polycyanogen and poly (cyanogenthiocyanate), have been tested in two systems. Cu-containing paracyanogen and the iodine-poor polythiocyanogens catalyze the photoreduction of methylviologen under visible light, furthermore the Cu-containing paracyanogen catalyzes the photoreduction of water to hydrogen under UV irradiation.

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, , , , (Hg, Ag, Cu), , (), . , , , , , , -.

     

Contribution a l'étude de l'oxyde de cadmium en milieu alcalin

Résumé La thermogravimétrie et l'analyse thermique différentielle montrent que l'oxydation du cadmium à l'air est négligeable jusqu'à 400°, tandis qu'en présence de peroxyde de sodium de soude ou de peroxyde de baryum, elle est totale mais que l'agent oxydant est uniquement l'oxygène de l'air. Le calcul de la chaleur de réaction à partir de la mesure de l'air du pic d'ATD correspondant fait conclure à la seule formation de l'oxyde de cadmium, le pic de fusion étant utilisé comme référence.

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Thermogravimetric and differential thermoanalytical investigations have shown that the oxidation of cadmium in air is negligible up to 400°. In the presence of sodium peroxide, barium peroxide or sodium hydroxide complete oxidation takes place, the aerial oxygen acting as the only oxidizing agent. The heat of reaction, calculated from the DTA peak area using the peak corresponding to the melting of the sample as reference, indicated that exclusively cadmium oxide was formed.

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Zusammenfassung Thermogravimetrische und differentialthermoanalytische Untersuchungen zeigten, daß die Oxydation des Kadmiums in Luft bis zu 400° vernachlässigbar ist. In Gegenwart von Natriumperoxyd, Bariumperoxyd oder Natriumhydroxyd tritt vollständige Oxydation ein. Als Oxydationsmittel wirkt jedoch ausschließlich der Luftsauerstoff. Die aus der Messung der DTA Spitzenfläche erfolgte Berechnung der Reaktionswärme, wobei die dem Schmelzen entsprechende Spitze als Referenz diente, wies auf die alleinige Bildung von Kadmiumoxyd hin.

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, 400° . , , . , TA, , , .