Oxidative coupling of carbazole derivatives to dicarbazyls in the presence of Pd(OAc)2

The interaction of 9-R-carbazoles (R=H, Me, Et) with Pd(OAc)₂ in AcOH solution was used to obtain the corresponding derivatives of 3, 3-dicarbazyls, the yield of the coupling products being 30–58% based on Pd(OAc)₂. Under similar conditions poly(9-vinylcarbazole) gives 8.6% of intermolecular coupling products.

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9-R- (R=H, Me, Et) c Pd(OAc)₂ AcOH - 3,3- 30–58% Pd(OAc)₂. -9-- 8,6% - .

     

The autocatalytic character of the reaction methanol to hydrocarbons over amorphous silica-alumina catalysts

Conversion of methanol to hydrocarbons was studied on an amorphous silica-alumina over the 330–420°C temperature range and contact times up to 8 h. The reaction was confirmed as autocatalytic from the results of varying both contact time and temperature.

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330–420°C 8 . , , , .

     

n-Pentane isomerization in a continuous-flow reactor on Pt/Al2O3 catalysts modified by adsorbed bismuth and palladium

Isomerization of n-pentane has been studied in a continuous-flow reactor at atmospheric pressure on Pt/Al₂O₃ catalysts modified by adsorbed bismuth and palladium. Lower activity and higher selectivity have been obtained on a catalyst modified by bismuth. Both activity and selectivity have decreased on a catalyst modified by palladium. After oxygen treatment the Pd–Pt/Al₂O₃ catalyst showed the most pronounced change in catalytic properties and its stability was lower than that of the unmodified Pt/Al₂O₃ catalyst.

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- , Pt/Al₂O₃, . , . , , . Pd–Pt/Al₂O₃ , Pt/Al₂O₃.

     

The effect of sample geometry on the melting point of polyethylene

We have examined the influence which sample geometry has on the melting point of isothermally melt crystallized polyethylene. The peak positions of curves obtained using a Perkin-Elmer DSC were used as the apparent melting points (Tm). With a constant sample weight (ca. 0.05 mg), we observed an increase of 1.7 K for Tm when the sample thickness was increased from 1 to 8 m. Experiments which demonstrate the heat transfer problems related to the melting of polymer samples are also presented. This work indicates that, if one is attempting to reduce the heating rate dependence of polymer samples, reduction of sample weight alone is not suffiicient. Rather one should aim at increasing the sample pan contact area and reducing the sample thickness simultaneously.

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Zusammenfassung Der Einfluß der Probengeometrie auf den Schmelzpunkt isotherm geschmolzenen kristallinen Polyäthylens wurde untersucht. Die Peakpositionen in den mit einem Perkin-Eimer DSC erhaltenen Diagrammen wurden als scheinbare Schmelzpunkte (Tm) benutzt. Bei konstantem Probengewicht (etwa 0.05 mg) wurde für Im ein Anstieg um 1.7 K beobachtet, wenn die Schichtdicke der Probe von 1 auf 8 m erhöht wurde. An Experimenten werden auch die mit dem Schmelzvorgang bei Polymerproben zusammenhängenden Wärmeübergangsprobleme aufgezeigt. Diese Arbeit macht deutlich, daß eine Verminderung des Probengewichts allein zur Verminderung der Aufheizgeschwindigkeitsabhängigkeit der Polymerproben nicht ausreichend ist. Es soll vielmehr eine gleichzeitige Vergrößerung der Probenträgerkontaktfläche und Verringerung der Probenschichtdicke angestrebt werden.

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. , ( -), . ( 0.05 ), 1 8 , . 1.7 , , . , , . .

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The authors gratefully acknowledge the support of the National Science Foundation (Polymers Division) Grant No. DMR 78-25233.     

Effect of electronic interaction between metal and support, II. TPD, TPR and chemisorption studies on Ru/Al2O3?MgO catalysts

TPD, TPR and chemisorption were used to characterize Ru/Al₂O₃–MgO catalysts. It is suggested that the acidity of support may influence the properties of catalysts significantly.

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, Ru/Al₂O₃–MgO. , .

     

Formic acid decomposition on polycrystalline tungsten

The rates of HCOOH decomposition on polycrystalline tungsten are examined over a wide range of catalyst temperatures (600

HCOOH (600     

Modifying action of carbon dioxide in catalytic oxidation of ethylene on silver

Carbon dioxide exerts a strong inhibitory effect on oxygen adsorption and complete oxidation of ethylene on silver but has little effect on the rate of ethylene oxidation to ethylene oxide.

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.

     

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% .

     

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), , (), . , , , , , , -.

     

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, .

     

Oxidation of ethanol on platinum/alumina and copper oxide catalysts

The oxidation of ethanol on CuO, CuO/Al₂O₃ and Pt/Al₂O₃ catalysts has been studied at various concentrations of alcohol, oxygen and water vapor in the reaction mixture. The reaction order and activation energies have been determined for both complete and partial oxidation processes. A consecutive oxidation scheme is suggested.

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CuO, CuO/Al₂O₃ Pt/Al₂O₃ , . . .

     

Catalytic properties of silica-molybdenum catalysts in propylene oxidation

The activity of silica-molybdenum catalyts in propylene oxidation is shown to be determined by the partially dehydrated silica-molybdenum heteropolyacid stabilized by the SiO₂ surface.

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, , SiO₂.

     

Zeolite content determination in kaolinic clays via thermal effects

For application in catalysis and adsorption processes, zeolites are synthesized on the surface of spray-dried kaolin microspheres. Various thermal effects are used for the rapid characterization of the zeolite type and content. From DTA measurements, the exothermic lattice break-down peak gives information on the zeolite type and the thermal stability of the sample. Measurements of the heats of immersion by a very simple and quick method allow conclusions about the type and the sorption properties of the zeolite part of the clay. The most precise method to estimate the zeolite content was a standardized technique of desorption and readsorption of water or organic compounds by means of a thermobalance.

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Zusammenfassung Zur Anwendung in der Katalyse und bei Adsorptinsprozessen werden Zeolithe auf der Oberfläche sprüh-getrockneter Kaolin-Mikrokugeln eingesetzt. Verschiedene thermische Effekte werden zur schnellen Charakterisierung des Zeolith-Typs und -Gehalts genutzt. Der exotherme DTA-peak beim Gitterzusammenbruch liefert Informationen über Zeolith-Typ und thermische Stabilität der Probe. Eine sehr einfache Schnellmethode zur Messung der Immersionswärmen erlaubt Schlussfolgerungen über Typ und Sorptionseigenschaften des zeolithischen Anteils des Tons. Die genaueste Methode zur Bewertung des Zeolithgehalts war eine standardisierte thermogravimetrische Desorptions- und Readsorptions-Methode mit Wasser oder organiscen Verbindungen.

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, , , . . , . , , . , .

     

Kinetics and mechanism of elimination of methoxyphenethyl chlorides in the gas phase

The kinetics for the gas phase elimination of o-and m-methoxy-2-phenylethyl chlorides have been investigated over the temperature range of 390-464°C and pressure range of 38–119 Torr. The reactions in seasoned vessels and in the presence of the free radical inhibitor propene, are homogeneous and unimolecular and follow a first-order rate law. The o-anisyl and p-anisyl substituents at the -position of ethyl chloride assist anchimerically the elimination processes. The formation of a cyclic product, benzodihydrofuran, from o-methoxy-2-phenylethyl chloride suggests an intimate ion pair mechanism operating in this reaction.

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- --2- 390–464°C 38–119 . - , , , . - - - . , , --2- , .

     

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⁺. . , , , .

     

Collisional energy transfer in the decomposition of 2-methyloxetane and 3-methyloxetane, I. Gas/gas collisions

The pressure dependence of the unimolecular rate constants for the thermal decomposition of 2-methyloxetane and 3-methyloxetane has been studied. The average energy transferred downward in gas-gas collision was determined by the application of RRKM theory and a stepladder model of energy transfer.

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2- 3-. , - , .

     

Mass-spectrometric analysis of polymers based on furyl alcohol-polyamic acid compositions

Polymer compositions based on furyl alcohol and polyamic acid were investigated by using mass-spectrometric thermal analysis. It was established that polyamic acid catalyses both the polycondensation of furyl alcohol and the formation of a three-dimensional network of furan polymer.

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Zusammenfassung Mittels massenspektroskopischer Thermoanalyse wurden auf Furylalkohol und Polyamidsäure basierende Polymergemische untersucht. Es wurde festgestellt, daß Polyamidsäure sowohl die Polykondensation von Furylalkohol als auch die Bildung eines dreidimensionalen Furanraumnetzes katalysiert.

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- . , , .

     

Sensitization of the photoadsorption of O2 and NO on SnO2

Photoadsorption activity of SnO₂ with respect to O₂ and NO after CO chemisorption has been revealed to be drastically increased. Photoadsorption is suggested to be sensitized by surface carbonates formed due to CO chemisorption.

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. , .

     

Combinations of alkyl radicals with alkyl and substituted allyl radicals

In contrast with expectations based upon simple collision theory, reactions of alkyl radicals with substituted allyl radicals yield cross-combination ratios of =2. Reactions of CH ₃ ^\ with some C₅ radicals give >2, in accordance with theory.

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, =2. CH₃ ^\ C₅ >2, .