Studies on catalytically active surface compounds, VIII. On the reaction of VCl4 with aerosil

The preparation and hydrolysis of silica supported vanadium catalysts have been investigated using VCl₄ as a paramagnetic probe. Chemical analysis shows the possibility of the VCl₄ molecule to react one, two, or three hydroxy groups of the surface. The type of reaction is influenced by the temperature of pretreatment of aerosil (TPA). ESR measurements show distortions of the tetrahedral coordination of the (SiO)_nVCl_4–n surface complex, which is strongest for the threefold attachment (n=3) of VCl₄ to the surface. Hydrolysis is accompanied by an increase of the coordination number and leads to highly mobile vanadium species.

---

, VCl₄ . , VCl₄ , . . (SiO)_nVCl_4–n, VCl₄ (n=3). .

     

Pt catalyst for the liquid-phase epoxidation of cyclohexene with an O2/H2 mixture

Conditions are found for the preparation of Pt catalysts providing the formation of epoxy-derivative in the reaction of cyclohexene with an O₂/H₂ mixture.

---

Pt .

     

Preparation and investigations of polyimides III

Polyamide acid powders of pyromellitic dianhydride and 4,4-diaminodiphenyl ether base were prepared in tetrahydrofuran, in the heterogeneous phase. The imidization of these powders was investigated by thermogravimetric, calorimetric and mass-spectrometric methods.According to the TG and DSC data, the temperatures of the beginning and maximum rate of imidization increase with increasing temperature and duration of imidization.A linear relationship has been found to exist between the weight loss and the reaction heat of the imidization process. The reaction heat corresponding to unit weight loss increases with decreasing molecular weight.Dicarboxylic anhydrides, applied as chain-terminators, do not affect the thermal properties of polyamide acids to an appreciable extent.Imidization has been found to be a complex process, in which decomposition of polyamide acids also takes place besides dehydrocyclization. The kinetics of imidization are satisfactorily described by a first-order dehydrocyclization and a parallel first-order decomposition. The weight loss during imidization is higher than the loss calculated on the basis of dehydrocyclization, which must be due to the release of the decomposition products of the polyamide acid, the release of solvated or complexed tetrahydrofuran, or that of possible oligomeric clusters.

---

Zusammenfassung Polyamidsäurepulver von Pyromellitdianhydrid und 4,4-Diamino-diphenyläther wurden in Tetrahydrofuran in heterogener Phase hergestellt. Die Imidisierung dieser Pulver wurde durch thermogravimetrische, kalorimetrische und Massenspektrometrische Methoden verfolgt.Nach TG- und DSC-Angaben steigt die Temperatur des Beginns und der Maximalgeschwindigkeit der Imidisierung mit steigender Temperatur und Imidisierungsdauer an.Ein linearer Zusammenhang wurde zwischen Gewichtsverlust und Reaktionswärme des Imidisierungsvorgangs gefunden. Die der Einheit des Gewichtsverlustes entsprechende Reaktionswärme nimmt mit abnehmendem Molekulargewicht zu.Als Kettenende angewandte Dicarboxylanhydride beeinflussen die thermischen Eigenschaften der Polyamidsäuren nicht in merklichem Maße.Es wurde festgestellt, daß die Imidisierung ein komplexer Vorgang ist, in dem außer der Dehydrocyclisierung auch eine Zersetzung der Polyamidsäuren stattfindet. Die Kinetik der Imidisierung kann durch eine Dehydrocyclisierung erster Ordnung und eine parallele Zersetzungsreaktion erster Ordnung befriedigend beschrieben werden. Der Gewichtsverlust während der Imidisierung ist höher als der aufgrund der Dehydrocyclisierung berechnete Verlust, was der Abspaltung von Zersetzungsprodukten der Polyamidsäure, der Freisetzung von solvatiertem oder komplexgebundenem Tetrahydrofuran oder eventueller oligomerer Einschlüsse zuzuschreiben ist.

---

Résumé Les polyamides en poudre résultant du dianhydride pyromellitique et de l'éther 4,4-diaminodiphénylique ont été préparés en phase hétérogène dans le té trahydrofuranne. La formation d'imides à partir de ces poudres a été étudiée par thermogravimétrie, calorimétrie et spectrométrie de masse.D'après les résultats obtenus par TG et DSC, les températures du début de la formation d'imide et la vitesse maximale de la réaction augmentent avec l'accroissement de la température et de la durée de la réaction.On a trouvé une corrélation linéaire entre la perte de poids et la chaleur de formation de l'imide. La chaleur de réaction correspondant à l'unité de perte de poids augmente quand le poids moléculaire diminue.Les anhydrides dicarboxyliques utilisés en bouts de chaines n'ont pas d'effet appréciable sur les propriétés thermiques des polyamides.On a établi que la formation d'imide est un processus complexe, au cours duquel, outre la déshydrocyclomérisation, une décomposition des polyamides a également lieu. La cinétique de la réaction peut être décrite de façon satisfaisante par une déshydrocyclomérisation du premier ordre et une réaction de décomposition parallèle également du premier ordre. Lors de la formation d'imide la perte de poids est plus élevée que celle calculée à partir de la déshydrocyclomé risation, ce qui provient sans doute du dégagement des produits de décomposition du polyamide, du dégagement du tétrahydrofuranne solvaté ou complexé ou bien de celui des inclusions oligomères éventuelles.

---

4,4- . , - . , . . , , . , , . , , , . . , , . , .

     

New data obtained by thermomagnetometry,on the phase transitions in Ni,Co, Pt,Cu and Fe-C alloys

On the basis of thermomagnetic and DTA measurements, together with data from the literature, it may be concluded that in some f.c.c. metals a phase transformation occurs just before melting.

---

Zusammenfassung Auf Grund thermomagnetischer und differentialthermoanalytischer Messungen sowie Literaturangaben wird geschlossen, dass in manchen kubisch-flächenzentrierten Metallen wenig unterhalb der Schmelztemperatur eine reversible Phasenumwandlung, wahrscheinlich in eine kubischraumzentrierte oder amorphe Phase, stattfindet.

---

, , , .

     

Ab initio investigation of the electron structure in bis-Cu+ acetylene and vinylidene complexes

[Cu(-C₂H₂)₂]⁺, [Cu(-CCH₂)₂]⁺ and [Cu(-C₂H₂) (-CCH₂]⁺ complexes have been studied by the ab initio double-zeta basis set method. It has been established that all calculated compounds are stable to decomposition into two C₂H₂ molecules and Cu⁺ cation and into one C₂H₂ molecules and the respective monocomplex. Calculation results suggest the possibility of intramolecular acetylene-vinylidene rearrangement in the coordination sphere of Cu⁺.

---

ab initio : [Cu(-C₂H₂)₂]⁺, [Cu(-CCH₂)₂]⁺, [Cu(-C₂H₂) (-CCH₂)]⁺. C₂H₂ Cu⁺ C₂H₂ . - Cu⁺.

     

Relative reactivities of phosphites in reactions with hydrotrioxides

Studies of the interaction of hydrotrioxides ROOOH of ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1,1-dimetoxyethane, 1,1-diethoxyethane, benzaldehyde and tetrahydrofuran with trimethyl triisopropyl, tributyl, triallyl, triphenyl and tri-o-chresyl phosphites (RO)₃P have revealed that in mild conditions ROOOH rapidly and selectively oxidizes (RO)₃P to the corresponding phosphates. The reaction stoichiometry has been established. Aromatic phosphites are shown to be of inferior reactivity to ROOOH as compared with aliphatic phosphites.

---

, 1-, 2-, 1-, 2-, 1,1-, 1,1-, -, -, -, -, -, -, -- (RO)₃P. ROOOH (RO)₃P . . , ROOOH .

     

Thermische Zersetzung des Lithiumhexacyanoferrats(III)

Zusammenfassung Die thermische Zersetzung von Lithiumhexacyanoferrat (III) in Luft führt in drei Temperaturbereichen, d.h. zwischen 250 und 400°, 500 und 650° und 925 und 1000° zur Bildung ferromagnetischer Produkte. Durch Röntgendiffraktionsuntersuchung und magnetische Messungen wurde bewiesen, daß im ersten Temperaturbereich-Fe₂O₃ die für die ferromagnetischen Eigenschaften der Zersetzungsprodukte verantwortliche Phase ist, während in den anderen Bereichen diese Eigenschaften durch Lithiumferrit der Formel Li_0.5Fe_2.5O₄ verursacht werden.

---

The thermal decomposition of lithium hexacyanoferrate (III) in air leads to the formation of ferromagnetic products in three temperature ranges, namely 250–400°, 500–650° and 925–1000°. By X-ray diffraction studies and magnetic measurements it has been proved that in the first temperature region-Fe₂O₃ is the phase responsible for the ferromagnetic properties of the decomposition products, whereas in the other regions these properties are due to the presence of the lithium ferrite Li_0.5Fe_2.5O₄.

---

Résumé La décomposition thermique du ferricyanure de lithium dans l'air conduit à des produits ferromagnétiques dans trois intervalles de température: 250–400°, 500–650° et 925–1000°. Par diffraction des rayons X et mesures magnétiques, on montre que lors de la première étape de décomposition c'est l'oxyde-Fe₂O₃ qui est responsable des propriétés ferromagnétiques des produits de décomposition, tandis que pour les deux autres étapes, le ferromagnétisme est dû à la présence de ferrite de lithium de formule Li_0.5Fe_2.5O₄.

---

-()- : 250–400°, 500–650° 925–1000°. - , , , , -Fe₂O₃. Li_0.5Fe_2.5O₄.

     

Dioxygen evolution from aqueous acid solutions of ruthenium complexes with nitrogen-containing ligands

Some peculiarities of reduction of one-electron oxidants, Ru(bpy) ₃ ³⁺ and Ru(bpy)₂(py) ₂ ³⁺ , in the absence of catalysts (when oxidation of the oxidant's ligands occurs) and in their presence (when also oxidation of water to dioxygen occurs) are discussed. Both oxidation reactions are thought to have a common intermediate.

---

Ru(bpy) ₃ ³⁺ Ru(bpy)₂(py) ₂ ³⁺ ( -) ( ). , .

     

Poissonian stationary distribution in a class of detailed balanced reactions

We investigate those detailed balanced (vectorial) complex chemical reactions that belong to the class of simple Markovian population processes and show that there is no chemical reaction with independent reaction rates having a Poissonian stationary distribution. There exists, however, a manifold of reactions with dependent (as given) reaction rates and with Poissonian stationary distribution.

---

() , , , . , () .

     

On the initial treatment of kinetic data

The kinetic methods usually employed to determine reaction orders involve some sort of mathematical approximation and provide values approximate and very often discrepant. Three methods are reported to determine accurate reaction orders without introducing approximations.

---

, , , , . .

     

Catalytic properties of plantinized polycyanogens

The effect of various inorganic polymers on the catalytic activity and selectivity of platinum in the hydrogenation of 4-chloronitrobenzene and dinitrotoluene has been studied. Platinized iron-containing polycyanogens are less active but more selective catalysts for the hydrogenation of 4-chloronitrobenzene than Pt/C or Pt/BaSO₄.

---

4- . , , , 4-, Pt/C Pt/BaSO₄.

     

Self-oscillations in the rate of CO oxidation on Pt(110)

The surface of Pt(110) was found to be metastable under the reaction conditions. The necessary condition for the appearance of self-oscillations in the system is the change of platinum surface properties under the action of reaction medium. Self-oscillations in the rate are maintained due to reversibility of these changes.

---

, Pt(110) . .

     

Kinetics of thermal decomposition of pyrite in an inert atmosphere

The thermal decomposition of pyrite in an inert atmosphere was studied in order to obtain a detailed knowledge of the kinetics and mechanism of the reaction 2 FeS₂=2FeS+S₂, which is one of the methods of producing elementary sulphur. The process was studied under isothermal conditions at temperatures of 600, 660, 700, 750, 800 and 850 °C in a nitrogen atmosphere, by means of a thermobalance. The rate-controlling processes were determined and their kinetic parameters were calculated. The optimum temperature for the process was found to be 800 °C.

---

Zusammenfassung Es wurde die thermische Zersetzung von Pyrit in inerter Atmosphäre bestimmt, um detaillierte Informationen über Kinetik und Mechanismus der Reaktion 2 FeS₂=2FeS+S₂, einer der Darstellungsreaktionen von elementarem Schwefel zu erlangen. Der Vorgang wurde mittels einer Thermowaage unter isothermen Bedingungen bei Temperaturen von 600, 660, 700, 750, 800 und 850 °C untersucht. Es wurden die geschwindigkeitsbestimmenden Schritte bestimmt und deren kinetische Parameter errechnet. Als Optimumtemperatur für diesen Prozeß erwies sich 800 °C.

---

- 2FeS₂=2FeS + S₂, . 600, 660, 700, 750, 800 850 ° . , 800°.

     

Displacement of hydrogen from rhodium surface by carbon monoxide under conditions of pulsed-gas chromatography

Interaction of carbon monoxide with hydrogen on the surface of rhodium catalysts has been investigated under conditions of pulsed-gas chromatography within the temperature range of –80 to 500 °C. At temperatures up to about 180 °C adsorbed hydrogen was found to be displaced to the gaseous phase as a result of carbon oxide adsorption. At higher temperatures conversion of carbon monoxide and hydrogen to methane takes place.

---

–80 500 °C. 180 °C . .

     

Studies on double malonates. III. Thermal decomposition of sodium lanthanide malonates,Na5Ln(C3H2O4)4.7.5H2O,where Ln=Gd,Tb or Ho

The double malonates of gadolinium, terbium and holmium with sodium, of the type Na₅Ln(C₃H₂O₄)₄.7.5H₂O, have been studied by means of thermal analysis. A mechanism of thermal dehydration and decomposition has been proposed on the basis of the results obtained.

---

Zusammenfassung Doppelmalonate von Gadolinium, Terbium und Holmium mit Natrium des Typs Na₅Ln(C₃H₂O₄)₄.7,5 H₂O wurden mittels thermischer Analyse untersucht. Für die thermische Dehydratisierung und Zersetzung wird ein auf den erhaltenen Ergebnissen basierender Mechanismus vorgeschlagen.

---

, Na₅Ln(C₃H₂O₄)₄.7.5H₂O. .

---

---

Part II. Communicated     

Possibility of thermal analysis of different types of bonding of water in minerals

Various types of water bonding were studied. e.g. water bound by occlusion, by adsorption, by capillary condensation, by chemisorption and as a solid solution, zeolitic water, interlayer water, crystal water and structural water bound in form of hydroxil groups. The differentiation of these various types of bonding is rather difficult, for on heating water is evolved at various temperatures and in rather wide temperature domains which overlap to different extents. Efforts were made to improve the detection by applying the quasi-isothermal quasi-isobaric measuring technique.

---

Zusammenfassung Es wurden verschiedene Bindungstypen von Wasser untersucht. Wasser kann unter anderem durch Einschlüsse, Adsorption. Kapillarkondensation, Chemisorption und in Form von Mischkristallen, zeolitisch, schichteingebettetem und Kristallwasser sowie als OH-Form gebunden sein. Die Untersuchung dieser zahlreichen Bindungstypen ist äußerst schwierig, da die Wasserabgabe bei verschiedenen Temperaturen geschieht und die ziemlich breiten Temperaturintervalle mehr oder weniger überlappen. Mittels quasiisothermen und quasiisobaren Meßtechniken wurde versucht, die Möglichkeit der Bestimmung zu verbessern.

---

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

     

MINDO/3 studies of surface OH groups of alumina

Cluster models for various types of OH groups of alumina have been calculated in terms of the MINDO/3 method. Dependence of the acidity and stretching vibration frequencies of OH groups on the number and coordination of neighboring aluminium atoms has been analyzed.

---

MINDO/3 OH- . OH- .

     

Infrared and mass spectroscopic evidence for hydrocarbon formation on a supported cobalt catalyst

Interrupting the surface carbonyl development at 345 K on an aerosilsupported cobalt oxide catalyst in CO/H₂ atmosphere at maximum surface concentration of linear carbonyl species by heating to 475 K results in the formation of Fischer-Tropsch type products detectable by combined IR and MS measurements.

---

345°K , , CO/H₂ , 475° -, .

     

Acid-base properties of supported vanadium oxide catalyst

Reduction of V₂O₅/Al₂O₃ and V₂O₅/silica-alumina produced Lewis acid sites which could strongly adsorb CO (heat of adsorption: 90 kJ/mol). Such strong acid sites were not formed in the cases of V₂O₅/SiO₂ and V₂O₅/MgO. V₂O₅ loaded on Al₂O₃ interacted with the basic sites of alumina but not with the acidic sites, while the V₂O₅ on silica-alumina interacted with the acidic sites of the silica-alumina and decreased its acidity.

---

V₂O₅/Al₂O₃ V₂O₅/SiO₂–Al₂O₃ , CO ( 90 /). V₂O₅/SiO₂ V₂O₅/MgO . V₂O₅, Al₂O₃, , , V₂O₅ SiO₂–Al₂O₃ - .

     

Investigation of the self-heating phenomenon in the bulk polymerization of acrylonitrile

The temperature of the polymerizing system was measured with a thermistor during the bulk polymerization of acrylonitrile initiated by azoisobutyronitrile. The temperature of self-heating suddenly rises at a conversion of about 2%. This jump of temperature is presumably caused by the formation of a gel structure and, consequently, the outfall of thermal convection within the system.

---

, -- . , - . - , .