A mathematical model of the regeneration of the catalytic solution in the liquid-phase oxidation of unsaturated hydrocarbons

The study describes the mathematical model, calculation and optimization of the technological scheme of the regeneration of the catalytic solution in the liquid-phase oxidation of hydrocarbons.

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, .

     

Effect of vibrational excitation on the reactivity of methyl fluoride with bromine atoms

The influence of non-equilibrium vibrational excitation of CH₃F molecules on the rate of their reaction with bromine atoms has been investigated. A three-fold increace in the reaction rate has been registered at CH₃F and Br₂ pressures of 0.07 Torr and at 100°C. The increase is shown not to be associated with equilibrium thermal heating.

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CH₃F . CH₃F Br₂ 0,07 100°C. , .

     

Overall kinetic model for oscillating catalytic oxidation of methanol

An overall kinetic model for the deep catalytic oxidation of methanol is presented. It is based on the balance of chemical species and could described self-sustained oscillations.

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. .

     

Energetic state of hydrogen on Os-black

Hydrogen adsorption on Os-black has been studied by the TPD method in the range from –85 to 450°C. Energetic inhomogeneity of hydrogen chemisorbed at adsorption temperatures of 150 to 450°C has been elucidated.

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OS (–85)–450°C. , 150 450°C.

     

Conformational transition of kappa-carrageenan

The calorimetry of kappa carrageenan using differential scanning calorimetry and calorimetry at constant temperature is presented. Both sets of experimental results confirmed the formation of a helical dimer in the absence of gel formation. When gel is formed, the formation of a helical dimer is the major effect, the contribution of gelation represents only 20% of the enthalpy recorded.

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Zusammenfassung Es wird über die Kalorimetrie von Kappacarrageen mittels DSC und Kalorimetrie bei konstanter Temperatur berichtet. Die experimentellen Resultate bestätigen beim Ausbleiben der Gelbildung, daß ein helixartiges Dimer gebildet wird. Auch bei Gelbildung steuert die Bildung des helixartigen Dimers den Hauptanteil zum thermischen Effekt bei, der Beitrag der Gelierung stellt nur etwa 20% der registrierten Enthalpie dar.

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- . . , , 20% .

     

Chlorination of V2O5 by CCl4. The proposed reaction mechanism

Initial stage of the reaction of CCl₄ with V₂O₅ has been studied by MS and XPS techniques. According to the proposed mechanism dissociatively chemisorbed CCl₄ transforms to CO₂ via adsorbed COCl₂, while surface vanadium atoms involved are gaining step by step two chlorine atoms before the formation of the volatile end-product VOCl₃.

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CCl₄ V₂O₅ . - CCl₄ CO₂ COCl₂, VOCl₃.

     

Theory of differential thermal analysis taking into account heat exchange between the specimen and reference cells

A basic formula of differential thermal analysis is evolved for the case when the heat transfer coefficient between the specimen cell and the reference cell is not zero. The more general formula obtained differs from the classical formula by including the parameters of the reference cell and the heat transfer coefficient between the cells. It indicates that utilization of the classical formula is not correct if heat exchange occurs between the cells. To utilize the generalized formula, additional measurements of the temperature changes of the reference material are required. However, if the time constants of the two cells are identical, the formula can be changed to assume the form of the classical formula for DTA if a correction factor is introduced which takes into account the effect of heat exchange between the cells.

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Zusammenfassung Für den Fall, dass der Übertragungskoeffizient zwischen der Proben- und der Referenzzelle nicht Zero ist, wurde eine Grundformel der Differentialthermoanalyse entwickelt. Die entstandene Formel, die vielmehr allgemein ist, weicht von der klassischen dadurch ab, dass sie auch die Parameter der Referenzzelle, und den Wärmeübertragungskoeffizient zwischen den Zellen enthält. Sie deutet darauf hin, dass die Anwendung der klassischen Formel in dem Fall nicht einwandfrei ist, wenn ein Wärmeaustausch zwischen den Zellen zustande kommt. Zur Anwendung der verallgemeinerten Formel sind weitere Messungen des Temperaturaustausches vom Referenzmaterial erforderlich. Sind aber die Zeitkonstanten der zwei Zellen identisch, kann die Formel so geändert werden, dass sie die Gestalt der klassischen DTA-Formel annimt, wenn ein, mit der Wirkung des Wärmeaustausches zwischen den Zellen rechnender Korrektionsfaktor eingeführt wird.

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, . , , . . , , , , .

     

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, .

     

Kinetic studies of Pt/Al2O3 catalyst pellets with nonuniform activity

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al₂O₃) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

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(Pt) (Al₂O₃). , , .

     

Thermoanalytical and thermogastitrimetric investigation of oil-shales

From thermoanalytical curves (DTG, TG) recorded in an oxygen atmosphere, the moisture and carbonate contents of oil-shales were determined with acceptable accuracy. The nature of the carbonates was predicted from the shape of the DTG curves above 550°C Dolomite (ankeritc) as found in Gérce oil-shale, and calcite in Pula-9 oil-shale. The clay content was determined from the signal of a water-detector recorded in a nitrogen atmosphere. The peaks at 80°C and 150°C for Gérce oil-shale were attributed to montmorillonite, and the sharp peak at 525°C for Pula-9 oil-shale to kaolinite.The volatile and fixed carbon contents of the oil-shales were calculated from the thermogastitrimetric curves.

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Zusammenfassung Feuchtigkeits- und Carbonatgehalt von Ölschiefern werden aus in Sauerstoffatmosphäre aufgenommenen thermoanalytischen Kurven (DTG, TG) mit annehmbarer Genauigkeit bestimmt. Die Natur der Carbonate wurde aus dem Verlauf der DTG-Kurve oberhalb 550 °C vorausgesagt. Dolomit (Ankerit) wurde im Gérce-Ölschiefer, Calcit im Pula-9-Ölschiefer gefunden. Der Gehalt an Tonen wurde aus dem in Stickstoffatmosphäre erhaltenen Signal eines Wasserdetektors bestimmt. Die Peaks bei 80 und 150 °C in der DTG-Kurve des Gérce-Ölschiefers werden Montmorillonit, der scharfe Peak bei 525 °C im Falle von Pula-9-ölschiefer Kaolinit zugeschrieben. Die Gehalte der Ölschiefer an flüchtigem und fixiertem Kohlenstoff werden aus gastitrimetrischen Kurven berechnet.

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(, ) , , . 550°. (), -9-. . , 80 150° , 525° -9 — . , .

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The authors are indebted to J. Kristóf (Dept. of Anal. Chem., Univ. of Veszprém) for carrying out the continuous water measurements; to K. Labdy (Central Laboratory, Univ. of Veszprém) for the elemental analysis results; to I. Vassányi (Dept. of Mineralogy, Univ. of Veszprém) for the diffractometric results; and to I. Koncz (Hydrocarbon Research and Development Institute, Nagykanizsa) for donating the oil-shale samples.     

Low temperature oxidation of isobutene on heterogeneous photoimmobilized copper-containing catalysts

A new photoimmobilization method to synthesize heterogeneous metal complex catalysts for low temperature oxidation of isobutene to methacrolein is suggested. The process selectivity is 100%.

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- -- . - 100%.

     

Decomposition of ammonia on rhenium II. Nitrogen adsorption on rhenium

Field emission microscopy and thermal desorption studies of nitrogen adsorption on a monocrystal tip and a polycrystalline rhenium wire indicate the formation of molecular () and dissociative () forms of adsorption. Adsorption-desorption characteristics have been measured.

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. - - , - .

     

The evaporation of potassium from phlogopite

The evaporation of potassium from phlogopite was investigated by roasting phlogopite with different chemical reagents. The possible reactions between reactants and the sample at different temperatures were investigated by thermogravimetry. Gypsum, calcite, sodium chloride, activated carbon, calcium chloride and fluoride were used as chemical reactants. Similar tests were carried out by batch experiments using muffle furnace and tube oven and finally the sample mixtures were heated in a vacuum. The use of a vacuum enabled an almost complete extraction of potassium in solid state at the lowest temperature so far investigated. The structure of phlogopite was shown to be destroyed by raising the temperature. The extraction of potassium from feldspar, a sample from Lohja, Finland was also investigated.

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Zusammenfassung Beim Abrösten von Phlogopit mit verschiedenen chemischen Stoffen wurde das Verdampfen von Kalium aus Phlogopit untersucht. Die möglichen Reaktionen zwischen der Probe und der Reaktionspartnern bei verschiedenen Temperaturen wurden mittels Thermogravimetrie untersucht. Als Reaktant wurden Gips, Kalzit, Natriumchlorid, Aktivkohle, Kalziumchlorid und -fluorid verwendet. Ähnliche Untersuchungen wurden in Reihenexperimenten mittels Muffel- und Röhrenofen und letztlich durch Erhitzen der Proben im Vakuum durchgeführt. Die Anwendung von Vakuum ermöglicht bei den niedrigsten der angewendeten Temperaturen einen fast vollständigen Auszug des Kaliums aus dem Feststoff, Durch Erhöhen der Temperatur wurde die Struktur von Phlogopit nachweislich zerstört. Die Extraktion von Kalium aus einer Feldspatprobe aus Lohja, Finnland, wurde ebenfalls untersucht.

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. . , , , , . , , . , , . , . //.

     

Selective oxidation and ammoxidation of isobutene over mixed oxides of tin and antimony

The oxidation and ammoxidation of isobutene were studied over mixed oxides SnO₂/Sb₂O₄ as catalysts, in a pulse reactor between 598 and 698 K. From the point of view of methacrylonitrile production the catalysts of compositions SnSb=4–51 behaved most appropriately at the optimum reaction temperature of 673 K. Below this temperature the production of methacrolein was preferred, even in the presence of ammonia, whereas at higher temperatures total oxidation prevailed.

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SnO₂/Sb₂O₄, 598 698 . SnSb=4–51 , 673 . , , .

     

Mössbauer study of the thermal decomposition of iron(III) citrate pentahydrate

The thermal decomposition of iron(III) citrate pentahydrate, Fe(C₆H₅O₇) · 5 H₂O, has been investigated at different temperatures in air using Mössbauer spectroscopy, nonisothermal techniques (DTA-TG) and X-ray diffraction. The reduction of iron(III) to iron(II) takes place at 553 K. At higher temperature the formation of -Fe₂O₃ and -Fe₂O₃ as the ultimate thermal decomposition products has been confirmed.

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Zusammenfassung Die thermische Zersetzung des Pentahydrates von Eisen(III)-citrat in Luft wurde bei verschiedenen Temperaturen durch Mössbauer-Spektroskopie, nicht-isotherme Techniken (DTA, TG) und Röntgendiffraktometrie untersucht. Die Reduktion von Eisen(III) zu Eisen(II) erfolgt bei 553 K. Bei höheren Temperaturen entstehen -Fe₂O₃ und -Fe₂O₃ als End-produkte der thermischen Zersetzung.

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(- ), - , (***) . 553 . , -F₂₃ -Fe₂O₃. .

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The authors are grateful to Dr. B. Mukherjee, C. G. C. R. Institute, Calcutta, for recording the X-ray diffraction pattern.     

A Study of solid state thermal decomposition characteristics of some metallo-organic compounds. IV

Solid state dehydration of the hydrated Ca(II), Co(II), Ni(II) and Cu(II) salts of furan-2-carboxylic acid (furoic acid) and subsequent decarboxylation of the corresponding anhydrous salts have been studied by simultaneous TG, DTA and DTG techniques. The order of thermal stability of the hydrated and the anhydrous compounds have been determined from the analysis of the TG, DTA and DTG traces for the dehydration of the hydrated salts and for the decarboxylation of the anhydrous compounds. Thermal parameters such as activation energy, enthalpy change and order of reaction for the different stages of each process have been computed by standard methods. An attempt has been made to account for the observed trend in the thermal stability of the anhydrous salts towards decarboxylation. A mechanism of thermal decarboxylation of calcium furoate has also been proposed.

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Zusammenfassung Die Dehydratisierung in fester Phase der hydratisierten Salze von Ca(II), Co(II), Ni(II) und Cu(H) mit Furan-2-carboxylsäure und die darauffolgende Decarboxylierung der entsprechenden wasserfreien Salze wurde mittels simultan ausgeführter TG, DTA and DTG untersucht. Die Reihenfolge der thermischen Stabilität der hydratisierten und wasserfreien Verbindungen wurde aus dem Verlauf der TG-, DTA- und DTG-Kurven ermittelt. Die thermischen Parameter (Aktivierungsenergie, Enthalpieveränderung, Reaktionsordnung) wurden für die verschiedenen Schritte eines jeden Prozesses nach Standardmethoden berechnet. Es wurde ein Versuch zur Erklärung des beobachteten Trends in der Thermostabilität der wasserfreien Salze gegenüber Decarboxylierung unternommen und ein Mechanismus für die themische Decarboxylierung von Calciumfuorat in Vorschlag gebracht.

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, 2- , , , . , . , . . 2- .

     

Reduction of NO by carbon monoxide on tin dioxide

The reduction of NO by carbon monoxide on SnO₂ has been studied in the temperature range from 90 to 450°C. The complicated temperature dependence of the reaction rate is due to the interaction of CO an CO₂ with the catalyst.

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NO SnO₂ 90–450°C. , CO CO₂ .

     

Morphology and structure of composite catalysts of nickel on metal-ceramic substrate

A catalyst grain is shown to consist of microparticles constituting a metal nucleus of aluminium covered by an oxide (-Al₂O₃) film. On this film a nickel-aluminium spinel is localized with metallic nickel (Ni⁰) particles on its surface. This morphological structure of catalysts accounts for the increased electron density on nickel particles and hence for the high catalytic activity in steam reforming of methane.

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, , , (-Al₂O₃). - , (Ni⁰). , , .

     

ESR studies of slow relaxations of the rate of sulfur dioxide oxidation on vanadium catalyst

Slow changes in the rate of the title reaction are shown to be due to pahse transformations of the active component, in particular, the agglomeration or crystallization of vanadyl complexes. The possible mechanism of these phenomena is discussed.

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, , , . .