Mössbauer studies of thermal decomposition of metal(III) hexacyanoferrates(II)

The thermal decomposition of metal(III) hexacyanoferrates(II) (Al, As, Sb, Bi) was studied up to 700° in air by employing Mössbauer, infrared spectroscopy and thermal analysis techniques. With the exception of the bismuth compound, the isomer shift of these hexacyanoferrates(II) increases on dehydration at 200°. Dehydration is complete at 200°, decomposition into the ferrite at 300°, and formation of-Fe₂O₃ from aluminium and bismuth hexacyanoferrates(II) and Fe₃O₄ from antimony and arsenic hexacyanoferrates(II) at 700°.

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Zusammenfassung Die thermische Zersetzung von Metall(III)ferrocyaniden (Al, As, Sb, Bi) wurde bis zu 700° in Luft unter Anwendung der Mössbauer und Infrarotspektroskopie, sowie thermoanalytischer Techniken untersucht. Die Isomerverschiebung dieser Ferrocyanide nimmt mit der Dehydratisierung bei 200° zu, mit Ausnahme des Wismuts. Die Dehydratisierung ist bei 200° abgeschlossen, die Zersetzung zum Ferrit bei 300° und die Bildung von-Fe₂O₃ aus Aluminium- und Wismutferrocyanid, von Fe₃O₄ aus Antimon- und Arsenferrocyanid bei 700°.

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Résumé On a étudié dans l'air jusqu'à 700°, la décomposition thermique des ferrocyanures de métaux trivalents (Al, As, Sb, Bi), par spectroscopies Mössbauer et infrarouge, ainsi que par les techniques d'analyse thermique. Le déplacement des isomères de ces ferrocyanures augmente lors de la déshydratation à 200°, à l'exception du bismuth. La déshydratation est complète à 200°, la décomposition en ferrite à 300°, la formation d'-Fe₂O₃ à partir des ferrocyanures d'aluminium et de bismuth ainsi que du Fe₃O₄ à partir des ferrocyanures de l'antimoine et de l'arsenic à 700°

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-, , — Al, As, Sb, Bi- 700° . , , 200°. 200°, 300° -Fe₂O₃. 700° Fe₃O₄.

     

Benzene hydrogenation on platinum-tin bimetallic catalysts

Various catalysts were prepared by impregnating a commercial alumina with solutions containing the complex dichlorobis(trichlorostannato)platinate (II). [Pt Cl₂ (SnCl₃)₂]^2–. After reduction, 1–20 fold variations in the catalytic activity in benzene hydrogenation were observed in direct proportion to the stability of the complex in the impregnating solution.

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, — - ( ()-(II) [PtCl₂(SnCl₃)₂]^–2. , 1–20 . .

     

Magnetic study of alloy formation in Cu?Ni/zeolite Y-catalysts

The formation of a Cu–Ni solid solution supported on Y molecular sieve has been studied by measuring the changes in magnetization of the Cu–Ni/Y system heated in vacuum at 450°C. The aggregation of metal into crystals is comparatively fast in the first stage of sintering, while the homogenization of the solid solution by volume interdiffusion of the components constitutes the other, much slower stage.

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Cu–Ni Cu–Ni/Y, 450°C. , , .

     

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, .

     

Effect of the medium in hexacyanoferrate (III)-iodide and peroxodisulfate-iodide reaction

The kinetics of the two reactions hexacyanoferrate (III)-iodide and peroxodisulfate-iodide in several isodielectric water-cosolvent mixtures have been studied. The results can be rationalized as a consequence of the cosolventwater interaction.

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(III) -. -.

     

Kinetics of oxidation of phenanthrene by acidic hexacyanoferrate(III)

Under kinetically controlled conditions, phenanthrene is converted to 9-hydroxyphenanthrene by acid hexacyanoferrate(III) in 90% aqueous acetic acid. The value of –4.0 indicates that the reaction proceeds via the formation of a cation radical intermediate.

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(III) 9- 90%- . =–4,00, -.

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15^*     

Dehydroxylation and catalytic activity of dealuminated Y zeolites

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

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- .

     

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°. , , .

     

Shape selectivity and maximum molecular size in methanol to hydrocarbons transformation

The maximum product size obtained during methanol to hydrocarbons transformation on medium and large pore zeolites and amorphous silica-aluminas is not governed by shape selectivity but it is a consequence of operational conditions and other process characteristics such as the occurrence of cracking reactions.

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, , , .

     

Coke deposition on naphtha reforming catalysts: I. Influence of the hydrocarbon feed

During hydrocarbons reactions over Pt/Al₂O₃ the catalyst is covered by coke. It is accepted that coke formation occurs on metal and acid sites. During normal heptane and methylcyclopentane reforming it was found that the nature and the rate of coke deposited on the catalyst surface was not same, depending on the structure of the hydrocarbon feed.

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Pt/Al₂O₃ . , . , - .

     

Influence of functional rubbers on the curing process of unsaturated polyester resins

The influence of an elastomeric second-phase on the kinetics of the curing reaction and the gel-time of a standard unsaturated polyester resin, by using the isothermal and dynamic techniques of differential scanning calorimetry (DSC) and a thermocouple was investigated. In particular we examined two different rubbers (polybutadiene hydroxyl-terminated and polybutadiene isocyanate-terminated), that, in the presence of polyester resins, affect the overall curing reaction kinetics in two ways: the former reduces the rate of reaction whilst the latter increases it.

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Zusammenfassung Der Einfluß einer elastomeren Zweitphase auf die Kinetik der Aushärtung und der Gelierungszeit eines als Standard dienenden ungesättigten Polyesterharzes wurden mittels isothermer und dynamischer DSC untersucht. Insbesondere wurden zwei unterschiedliche Gummis (hydroxylendständiges und isocyanatendständiges Polybutadien) untersucht, die die Kinetik der Aushärtung des Polyasterharzes in unterschiedlicher Weise beeinflussen: hydroxylendständiges Polybutadien verringert, isocyanatendständiges dagegen erhöht die Reaktionsgeschwindigkeit.

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, , . ( ) : , — .

     

Studies on water retention and water release from some protein systems

The hydrogen-bond properties (WBI index), water retention and water release from the protein-water systems gluten-water, soya protein- water and casein-water, have been investigated using differential scanning calorimetry in the temperature range 223–423 K. The proteins were characterized by their isoelectric point, contents of carboxyl groups and sulfur-containing groups, and readiness of undergo chloromethylation. It was concluded that the marked difference in water-release behaviour is chiefly explained by conformational differences and charge effects.

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Zusammenfassung Wasserstoffbrückenbindugseigenschaften (WBI-Index), Wasserretention und Wasserabgabe von Protein-Masser-Systemen — Gluten-Wasser, Sojaprotein-Wasser und Casein-Wasser — wurden im Temperaturbereich von 233–423 K mit einem Scanning-Kalorimeter untersucht. Die Proteine wurden durch ihren isoelektrischen Punkt, den Gehalt an Carbonylgruppen und Schwefel enthaltenden Gruppen und durch ihre Reaktivität in der Chlormethylierung charakterisiert. Es wurde gefolgert, dass der ausgesprochene Unterschied im Wasserabgabeverhalten in erster Linie auf strukturelle Unterschiede und Ladungseffekte zurückzuführen ist.

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223–423 K , , — , — — . , , . , .

     

Hydrodenitrogenation activity of sulfided catalysts

Activities of hydrodenitrogenation catalysts were compared using a batch mode autoclave reactor. The hydrodenitrogenation of carbazole, a model coal nitrogen compound, was the reaction studied. The highest activity and the highest rate constant for carbazole and total nitrogen removal were found in the case of NiMo/Al₂O₃ catalyst.

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. , . , NiMo/Al₂O₃.

     

Influence of nucleating agents on crystallization of polypropylene

The effect of talc as an artificial nucleating agent in different concentrations on the crystallization of polypropylene (PP) has been studied. It is considered that the induction time should be taken into account in the Avrami evaluation of isothermal crystallization. From a study of nucleated PP samples prepared in different ways, it has been proved that the nucleating effect of talc slightly decreases with increasing time spent by the sample in the state of the polymer melt. It has been shown that crystallization of non-nucleated polypropylene strongly depends on the material of the sample pan. It has been established that dilatometry cannot be used to study the isothermal crystallization of nucleated polypropylene, since microcracks appear in the sample, partly compensating the volume decrease due to the crystallization process.

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Zusammenfassung Die Wirkung von in unterschiedlichen Konzentrationen als künstliches Keimbildungsmittel angewandtem Talk auf die Kristallisation von Polypropylen wurde untersucht. Bei der Auswertung der isothermen Kristallisation nach Avrami ist die Induktionszeit in Betracht zu ziehen. Bei der Untersuchung von auf verschiedene Weise hergestellten Polypropylenproben wurde festgestellt, dass die keimbildende Wirkung von Talk desto geringer ist, je länger sich die polymere Probe im geschmolzenen Zustand befand. Es wird gezeigt, dass die Kristallisation von keimbilden den Mitteln nicht ausgesetztem Polypropylen stark vom Material des Probengefässes abhängt. Es wurde festgestellt, dass die Dilatometrie nicht zur Untersuchung der isothermen Kristallisatior von mit keimbildenden Mitteln versetztem Polypropylen geeignet ist, da in der Probe Mikrokrack Produkte auftreten, die die durch den Kristallisationsprozess verursachte Abnahme des Volumens teilweise kompensieren.

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. , . , . . , , , .

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This work was presented in part at the 7th International Conference on Thermal Analysis, August 22–28, 1982, Kingston, Ontario.

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The authors are indebted to Messrs M. Pati and J. Volk for the preparation of the samples, and to Dr. A. Solti for her help during the dilatometric measurements.     

Catalytic properties of phosphorus-containing rhenium complexes in the hydrogenation of hexene-1

Rhenium (V, VI) complexes with organophosphorus ligands proved to be catalytically active in hexene-1 hydrogenation. The kinetics of this process catalyzed by ReOCl₃(PPh₃)₂ has been examined. The organic ligand in the coordination sphere of rhenium complexes was found to affect selectivity to olefin bonds or nitro groups in the hydrogenation of hydrocarbons.

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(V, VI) -1. , ReOCl₃ (PPh₃)₂. , .

     

Structure sensitivity and coke formation on Pt/Al2O3 catalysts

The initial rate of carbon formation during cyclopentane reaction has been studied on different Pt/Al₂O₃ catalysts of varying metal dispersity. It has been shown that coke deposition on the metal is a structure sensitive reaction which is preferably produced on large metallic particles. On the other hand, coke deposition on the whole catalyst is relevant to cyclopentadiene formation and is a structure insensitive reaction since the initial rate of coke deposition on the whole catalyst is proportional to the metallic surface area.

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Pt/Al₂O₃ . , , . , , , .. .

     

Nitrate and sulfite catalyzed reaction of monooxalatotetraaquachromium(III) and ethylenediaminetetraacetate

The kinetics of the reaction between monooxalatotetraaquachromium(III) and ethylenediamenetetraacetate have been studied in acidic media. The reaction is accelarated by nitrite and sulfite ions. The mechanism for the catalyzed reaction is discussed in terms of the formation of Cr(ONO)(ox)(H₂O)₃ and Cr(OSO₂H)(ox)(H₂O)₃. The catalytic effect of sulfite is greater than that of nitrite. Spectral evidence is presented for the formation of nitrito and sulfito species.

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() (III) . , . Cr(ONO)(ox)(H₂O)₃ Cr(OSO₂H)(ox)(H₂O)₃. . .

     

Crown ether salt catalysis of ester aminolysis in an aprotic solvent

The RCO ₂ ^– catalyzed n-butylaminolysis of 4-nitrophenyl acetate in chlorobenzene has been studied. Logarithms of the catalytic rate constants can be linearly correlated with Taft polar substituent constants for the R groups. Product analysis as well as the lack of steric hindrance by bulky R substituents indicate that the carboxylates act as general base catalysts.

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- 4- . R. , R , .