Calorimetric study of the BrO3?/Ce4+/cyclohexanone and BrO3?/Ce4+/cyclopentanone oscillating systems

The heat output (Q) during the induction period of a Belousov-Zhabotinskii oscillating reaction usually evolves at a constant rate /6/; we observe in the BrO ₃ ^– /Ce⁴⁺/Cyclohexanone system a sudden change in the slope of the function Q=f(t), which corresponds to the beginning of the quasistationary phase /3/.

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(Q) - ; BrO ₃ ^– /Ce⁺⁴/ Q=f(t), .

     

Mechanism of RuIV-catalyzed oxidation of alkanes in aqueous solutions

The Ru^IV-catalyzed oxidation of alkanes in aqueous solutions includes activation of the oxidant Ox (Cr^VI, HNO₃, HClO₄, etc.) via Ox–Ru^IV complex formation and is accompanied by H atom abstraction from the alkane by the activated oxidant.

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Ru^IV - Ox (Cr^IV, HNO₃, HClO₄ .) Ox–Ru^IV - .

     

Application of deuteroacetonitrile to characterize surface aprotic acidic centers on heterogeneous catalysts

Correlations between adsorption heats CD₃Cn and CO ( and Q_CO) for the cations of Ca-, Mn-, Co-, Ni- and CrNaY zeolites have been studied. Isosteric ranging within determined by IR spectroscopy are proportional to Q_CO.

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CD₃CN CO( Q_CO) Ca-, Mn-, Co-, Ni- CrNaY. , , - Q_CO.

     

Non-isothermal thermogravimetry of polymer

A Model of polymer decomposition is proposed which formally involves the termination of active centres. It yields reasonable activation energies for the decompositions of polypropylene, polyethylene, polystyrene and polymethyl methacrylate investigated by non-isothermal thermogravimetry. In the value of a formal reaction orders the model reflects the reaction conditions, such as initial sample weight, atmosphere, ventilation conditions, sample holder nature and shape, etc.

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Zusammenfassung Ein Modell für Zersetzungsreaktionen von Polymeren wurde entworfen, das auf dem Abbau von aktiven Zentren basiert. Es liefert richtige Aktivierungsenergien für die Zersetzung von Polypropylen, Polyäthylen, Polystyren und Polymethylmethakrylat (bestimmt durch nichtisotherme Thermogravimetrie) und macht es ausserdem möglich, die äusseren Reaktionsbedingungen, wie Einwaage, Atmosphäre, Ventillationsbedingungen, Art und Form des Probenhalters usw. zu berücksichtigen.

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, . , , , . «» , , , , . .

     

Electronic spectrum and thermal decomposition of nickel(II) complex with bis(N-γ-pyridyl-4-phenylbenzamide-hydrazone)

The unit cell parameters and the space group of the investigated compound were determined by means of X-ray diffraction.Analysis of the diffusion-reflection spectra of the crystalline powder and the absorption spectra of its alcoholic solutions permitted identification and quantitative characterization of the absorption bands of the crystalline complex of NiL₂(ClO₄)₂·3H₂O.Application of differential-thermal analysis allowed determination of the mechanism of thermal decomposition of the compound. From these measurements, the expected configuration of the basic molecule was verified, involving determination of the number of non-coordinated water molecules.

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Zusammenfassung Mittels Röntgendiffraktionsmethoden wurden Gitterzellenkonstanten sowie die Raumgruppe der untersuchten Verbindung bestimmt. Durch Analyse der erhaltenen Diffusions-Reflexionsspektren von kristallinem Pulver und des Absorptionsspektrums einer alkoholischen Lösung der Verbindung war es möglich, die Absorptionsbanden des Kristallkomplexes NiL₂(ClO₄)₂·3H₂O zu identifizieren und quantitativ zu charakterisieren. Anwendung von Differentialthermoanalyse ermöglicht die Bestimmung des Mechanismus der Zersetzungsreaktion der Verbindung. Durch diese Messungen, einschliesslich der Bestimmung der Anzahl nichtkoordinierter Wassermoleküle, wurde die erwartete Konfiguration des Grundmoleküles überprüft.

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NiL₂(ClO₄)₂·₂, L-N-- -4- . L-N---4- . , , . . , .

     

Influence of carbon support pretreatment on properties of Pd/C catalysts

Preoxidation of the surface of carbon support was found to increase the dispersity of palladium and activity of Pd/C catalysts obtained by reduction of supported Pd(OAc)₂, in hydrogenation of olefins. Probable reasons for this effect are discussed.

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, Pd/C , Pd(OAc), . .

     

Use of DSC robotic systems in pharmaceutical analysis

DSC is extremely valuable for analysis of pharmaceuticals. The introduction of robotic systems with data acquisition and processing makes it very competitive to other methods in the field of purity determination or solid state characterization of raw materials. Some applications are also possible to dosage forms. Applications of DSC robotics with statistical results are given.

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Zusammenfassung Zur Analyse von Arzneimitteln ist DSC außerst wertvoll. Die Einführung von Robotersystemen mit Datenaquisition und -aufarbeitung macht dieses Verfahren auf dem Gebiet der Reinheitsuntersuchung und Feststoffcharakterisierung der Rohmaterialien konkurrenzfähig im. Vergleich zu anderen Methoden. Einige Varianten lassen sich auch auf fertige Präparate anwenden. Es wird die Anwendung von computerisierten DSC-Systemen einschließlich statistischen Ergebnissen gegeben.

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. . . .

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Many thanks to Mrs C. Goldbronn and Mr P. Piechon for their technical assistance.     

Interaction between nitrous oxide and ruthenium catalysts

TPD data indicate that N₂O is desorbed from Ru and -Al₂O₃ without decomposition in one step and from Ru/Al₂O₃ in two steps with simultaneous decomposition to nitrogen and oxygen.

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, N₂O Ru -Al₂O₃ , Ru/Al₂O₃— .

     

Thermal study of some sulphosuccinates

The thermal properties of some sulphosuccinates and their intermediates were studied by using combined dynamic thermal analysis and mass spectrometry. The temperature ranges were similar in the two methods, and a scheme of thermal decomposition of the compounds investigated was suggested. In the first temperature range of thermal decomposition of the sulphosuccinate a-rupture of the molecular ion occurs. In the second temperature range, the fragmentation proceeds in two directions: either-rupture of the ethoxylated nonylphenol, or-rupture of the acid residue of the sulphosuccinates.

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Zusammenfassung Mittels einer Kombination von dynamischer Thermoanalyse und Massenspektroskopie wurden die thermischen Eigenschaften einiger Sulfosukzinate und deren Zwischenprodukte untersucht. Im ersten Temperaturbereich der thermischen Zersetzung des Sulfosukzinates findet eine-Spaltung des Molekülions statt. Im zweiten Temperaturbereich tritt auch ein alternativer Fragmentierungsweg auf: eine-Spaltung des Säurerestes des Sulfosukzinates.

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- . . - -. : - - .

     

Study of crystal transformations by an evolved gas analysis technique

Small organic molecules can be entrapped within inorganic crystalline materials during precipitation. The material has no apparent influence on solid-solid transition temperatures, but some of it is released during the transition.Detection of the escape is reproducible within 1°C and may be used for temperature calibration. More generally, the escape of the organic during chemical reactions could be used for many of the applications of emanation thermal analysis.In coupled systems such as DTA or TG with mass spectrometry, or other systems involving gas transport, the time delay of the system can be measured accurately.

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Zusammenfassung Kleine organische Moleküle können während der Fällung in anorganische kristalline Substanzen eingeschlossen werden. Die Substanz hat keine scheinbare Wirkung auf Fest-Fest-Übergangstemperaturen, doch wird ein Teil derselben während des Überganges freigesetzt. Der Nachweis der freigesetzten Substanz ist innerhalb von 1°C reproduzierbar und kann zur Temperatureichung eingesetzt werden. Verallgemeinert könnte das Entfliehen organischer Substanzen im Laufe chemischer Reaktionen bei vielen Anwendungen der Emanations-Thermalanalyse eingesetzt werden. In gekoppelten Systemen, wie z.B. DTA oder TG mit Massenspektrometrie, oder andere Systeme mit Gastransport, kann die Verzögerung des Systems genau gemessen werden.

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Résumé De petites molécules organiques peuvent se trouver incluses dans des substances inorganiques cristallines, au moment de la précipitation. Les températures de transition solidesolide ne s'en trouvent apparemment pas affectées mais une partie de ces molécules incluses peut être éliminée pendant la transition. La détection du matériau qui s'échappe est reproductible à 1°C près et se prête à l'étalonnage de la température. En termes plus généraux, le départ de la substance organique au cours des réactions chimiques peut être utilisé pour de nombreuses applications de l'analyse thermique d'émanation. Dans le cas de techniques associées, comme l'ATD ou la TG avec la spectrométrie de masse, ou encore d'autres techniques avec transport de gaz, on peut mesurer exactement le temps de réponse du système.

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. —, . 1°, . . , , - , , , .

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The authors are grateful to the National Science Foundation for support of parts of this work through institutional and research grants and to the Goodyear Tire and Rubber Company for use of the Chromatograph and other facilities.     

Calorimetric studies of adsorptive properties of metallic carbides and nitrides of transition elements. Adsorption of H2, CO and O2 on titanium nitrides

Adsorption heats of hydrogen, oxygen and carbon monoxide on titanium nitrides have been measured calorimetrically in the temperature range from 473 to 673 K. With increasing Me/N ratio, the adsorption heat of oxygen grows.

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, 473–673 . Me/N.

     

Kinetics of methane conversion over microspherically grained nickel-alumina catalysts

Kinetics of methane conversion in a fluidized bed of microspherically grained nickel-alumina catalyst has been studied at pressures from 0.3 to 3.1 MPa. The rate equation shows that the reaction is inhibited by H₂O.

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0,3 3,1 . , .

     

Kinetics of cerium(IV) oxidation of propionic acid in perchloric acid: Role of solvent

The oxidation rate of propionic acid (PROA) by cerium(IV) in aqueous perchloric acid (1.0–6.0 mol/dm³) is proportional to the PROA concentration, the total order of the reaction being two. It was found that the rate is related to the values of Hammett's acidity function (H₀) in agreement with both Zucker-Hammett's hypothesis and Bunnett-Olsen's criterion, the water acting as a proton transfer agent. A mechanism consistent with the findings is proposed.

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() (IV) (1,0–6,0 /³) . (H₀) -, -. . .

     

Photooxygenation of 9-methyl-1,2,3,4-tetrahydrocarbazole: A kinetic study

The reaction of the singlet oxygen with 9-methyl-1,2,3,4-tetrahydrocarbazole has been undertaken to give a benzazonine derivative in good yield. Rose-bengal supported on an anionic resin was used as heterogeneous photosensitizing agent. Kinetic evaluation has been made for the additon of singlet oxygen to the indole ring at room temperature.

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9--1,2,3,4- . , , . .

     

Interaction of oxygen with preadsorbed hydrogen on magnesium oxide studied by temperature-Programmed desorption method

The interaction of oxygen with preadsorbed hydrogen on thermally activated magnesium oxide has been studied by temperature-programmed desorption (TPD) method. It was found that oxygen at 450 K reacts with preadsorbed hydrogen and the resulting hydroxylation suppresses the adsorptive capacity of magnesia with respect to oxygen.

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. , 450 K , .

     

Kinetics of heterogeneous catalytic hydroformylation of propylene on rhodium-cobalt catalysts. Reaction mechanism

Steady-state kinetics of combined heterogeneous catalytic hydrogenation and hydroformylation of propylene on Rh–Co-containing catalysts has been studied at atmospheric pressure and T=140–170 °C. A reaction mechanism is suggested. The kinetic model adequately describes all observations.

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- Rh–Co- 140–170 °C. . , .

     

Thermogravimetric and kinetic study of a clodronic acid complex formed with sodium

Thermal stability of the clodronic acid complex formed with sodium (Na₂CCl₂(HPO₃)₂ ·4H₂O) was studied using both dynamic and isothermal thermogravimetric analyses as well as mass spectra. The thermal decomposition has two stages: dehydration and loss of two molecules of hydrogen chloride. Using the isothermal TG data the first step was found to be a phase-boundary reaction while the second step obviously cannot be described with just one reaction mechanism. The final residue of the dynamic TG analyses above 810 K was found to be sodium metaphosphate.

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Zusammenfassung Sowohl mittels dynamischer und thermogravimetrischer Untersuchungen als auch and Hand von Massenspektren wurde die thermische Stabilität des mit Natrium gebildeten Säurekomplexes Na₂CCl₂(HPO₃)₂·4H₂O untersucht. Die thermische Zersetzung vollzieht sich in zwei Schritten: Dehydratation und Verlust von zwei Molekülen HCl. Auf Grund der isothermen TG Angaben ist der erste Schritt eine Phasengrenzreaktion, während der zweite Schritt mit einem einzigen Reaktionsmechanismus nicht eindeutig beschrieben werden kann. Das Endprodukt der DTG Analyse oberhalb 810 K erwies sich als Natriummethaphosphat.

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-Na₂CCl₂/HPO_3/2·4H₂O — , - . , , , . , , . 810 .

     

Routes of nitrogen formation in reduction of nitrogen oxide by carbon monoxide and hydrogen over nickel chromite catalyst

The route of NO reduction to N₂ over nickel chromite catalyst is dependent on the nature of the reducing agent. NO reduction by dihydrogen proceeds mainly through the step of N₂O formation, whereas NO reduction to N₂ by carbon monoxide is mainly direct without a step of N₂O formation.

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NO N₂ NO , , N₂O, NO , , NO N₂, . . N₂O.