Evaluation of quantum yields in the presence of an absorbing additive

A method is proposed for the evaluation of quantum yields of photochemical reactions studied in the presence of absorbing additives using cylindrical sample tubes.

---

.

     

Catalytic relevance of phase transformations accompanying the gas phase oxidation of ethanol on silica supported vanadia

Nonsteady state activity during the gas phase oxidation of ethanol in a simple flow reactor and its dependence on pretreatment and reaction conditions can be explained utilizing the previously presented model of possible surface vanadia phases on silica.

---

.

     

Catalytic action of cation-substituted forms of oxidized charcoal in the liquid phase oxidation of cumene

The catalytic properties of cation-substituted forms of oxidized charcoal in the liquid-phase oxidation of cumene have been investigated. It has been shown that oxidized charcoal inhibits, and its salt forms catalyze the reaction. The catalytic activities of ion-substituted charcoals depend on both the nature of the metal and the amount of supported ions.

---

. , , — . , .

     

Propylene oxidation over tin-molybdenum oxide catalysts

The influence of preparation of tin-molybdenum catalysts on their phase composition and activity has been elucidated. The mutual dissolution of Sn and Mo oxides leads to a considerable increase in their activities and selectivities in the partial oxidation of propylene to acetone.

---

. , .

     

Thermodynamic aspects of conformational transitions in synthetic polypeptides

The helix-coil transition of organic solvent soluble homopolypeptides has been discussed from a largely thermodynamic view-point. The present state and the future prospects are considered.

---

Zusammenfassung Der Helix-Ungeordnete Übergang von in organischen Lösungsmitteln löslichen Homopolypeptiden wurde aus einem breiten Gesichtspunkt diskutiert, gegenwärtige Lage und zukünftige Entwicklungsaussichten erörtert.

---

R'esumé On a discuté d'une pointe de vue thermodynamique large la transition helix—non helix des homopolypeptides solubles dans des solvants organiques et considéré la situation actuelle ainsi que les perspectives futures.

---

, , . .

---

---

The present paper was supported by NSF Grant GB 33484.     

Chemical reaction and phase transformations of the components of low temperature shift catalyst in various atmospheres

The systems CuO–Al₂O₃ and ZnO–Al₂O₃, as model systems of low temperature shift catalysts, have been studied in the temperature interval 100–700°C. The changes of their phase composition and surface area, influenced by gas atmosphere have been studied by X-ray, IR analysis and low temperature nitrogen adsorption.

---

CuO–Al₂O₃ ZnO–Al₂O₃ CO 100–700°C. , - .

     

Physical properties of the catalyst used for partial oxidation of anthracene to anthraquinone. II. Electron paramagnetic resonance study

Electron paramagnetic resonance studies on intermediates and final active catalyst material used for partial oxidation of anthracene to anthraquinone are reported.

---

, .

     

Thermal studies on aluminium substituted CuCr2O4

Thermal studies on aluminium substituted copper chromite spinel oxide, CuCr_2–x Al _x O₄ (x=0.2 tox=0.8) by DSC show that with 20% replacement of Cr by Al, the phase transition temperature of the spinel is lowered but on further increasing the percentage of Al the phase transition temperature becomes higher than that of CuCr₂O₄. The enthalpy change for phase transition however decreases gradually with increasingx.

---

Zusammenfassung Mittels DSC wurde ein aluminium-substituiertes Kupferchromitspinelloxid, CuCr_2–x Al _x O₄ mitx=0,2-0,8 thermisch untersucht. Wird 20% des Cr durch Al ersetzt, sinkt die Phasenübergangstemperatur ab, bei weiterem Anwachsen des Aluminiumgehaltes steigt sie jedoch über die von CuCr₂O₄ hinaus an. Die Enthalpieänderung des Phasenüberganges steigt mit anwachsendemx allmählich an.

---

CuCr_2–x Al _x O₄ (x=0,2–0,8) , 20% , , , , CuCr₂O₄. , x.

---

---

The authors thank Mrs P. P. De of Rubber Technology Centre, Indian Institute of Technology, Kharagpur for her help with the DSC studies.     

A gradientless flow microreactor

A simple flow microreactor can perform as a gradientless microreactor under suitable conditions so that, thanks to molecular diffusion, the reactant concentration is leveled out considerably. This was demonstrated on the basis of a mathematical analysis of the reactant concentration distribution in a flow reactor and the observation was confirmed experimentally. A simple flow microreactor was designed and its gradientless property was verified using carbon dioxide hydrogenation as a test reaction.

---

. . , . , .

     

Preparation and characterization of Ru?Pb supported catalysts

Decomposition of Mn₃Mo₂TeO₁₂ during oxidation of toluene to benzaldehyde was observed. Depending on the surface composition of the initial catalyst, the decomposition leads to less active but highly selective MnMoTeO₆ or to MnMoO₄ which is not selective in toluene oxidation.

---

Mn₃Mo₂TeO₁₂ . , MnMoTeO₆, MnMoO₆.

     

Calorimetry for thermokinetic determinations

The possibilities of using direct calorimetric measurements for the determination of kinetic parameters of processes are discussed in terms of the choice of an appropriate method of reproduction of the course of changes in the heat power generated in time, i.e. thermokinetics. Such methods are presented and it is concluded that many of these methods permit reproduction of the thermokinetics in the same way as if the experimental thermal curve were obtained in a calorimetric system characterized by a time constant 100–200 times as large as that for the thermal inertia of this calorimetric system.

---

Zusammenfassung Die Möglichkeiten zur Benutzung direkter kalorimetrischer Messungen zur Bestimmung kinetischer Parameter von Prozessen werden hinsichtlich der Wahl geeigneter Methoden zur Reproduzierung des Verlaufs der Änderungen der Wärmekraft mit der Zeit, d.h. zur Reproduzierung der Thermokinetik diskutiert. Solche Methoden werden angeführt und es wird die Schlussfolgerung gezogen, dass viele dieser Methoden die Reproduzierung der Thermokinetik auf gleiche Weise wie in den Fällen erlauben, in denen die thermische Kurve mit einem kalorimetrischen System erhalten wird, dessen Zeitkonstante um 100–200mal grösser als die des diskutierten Systems ist.

---

. . . , , , 100–200 .

---

---

Presented at the 2nd Czechoslovak Conference on Calorimetry, Liblice, Czechoslovakia, 1982.     

Polyfunctional zeolite catalysts in the benzene-olefin-hydrogen system

Benzene alkylation by C₂–C₄ olefins in the presence of hydrogen over a steam-treated zeolite catalyst containing lanthanum and nickel, has been studied. The promoting action of hydrogen on benzene alkylation by propylene has been established.

---

C₂–C₄ , . .

     

Calculation of recombination rate constants in (H2?O2) system

Rate constants of the three-body recombination for the elementary three-molecule stages in hydrogen oxydation have been calculated.

---

, .

     

Acidic and catalytic properties of boron-containing porous glasses

Heat treatment of porous glasses results in a migration of boron to the surface changing surface acidity. The surface acidity of thermally modified porous glasses was characterized by NH₃ desorption and the catalytic activity for conversion of alcohols was investigated.

---

, . NH₃, .

     

Studies on the thermal decompositions of As-triazine derivatives and their compounds with metal ions

The thermal decompositions of the new complex salts of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 5,6-diethoxyearbonylmethyl-3-seleno-1,2,4-triazine (HSeTEK) and 5,6-diethoxycarbonylmethyl-3-thio-1,2,4-triazine (HTTEK) were investigated on the basis of the respective thermal curves. The thermoanalytical investigations indicate that HSeTEK, HTTEK, and their complexes with metal ions all undergo three-stage changes as the temperature is raised. The stages of pyrolysis established from the thermal data were compared, and the rates and stages of pyrolysis were related to the structures of the compounds.

---

Zusammenfassung Die thermische Zersetzung der neuen Komplexsalze von Mn(II), Co(II), Ni(II) und Cu(II) mit 5,6-Diäthoxycarbonylmethyl-3-seleno-1,2,4-triazin (HSeTEK) und 5,6-Diäthoxycarbonylmethyl-3-thio-1,2,4-triazin (HTTEK) wurden auf der Grundlage der entsprechenden thermischen Kurven untersucht. Die thermoanalytischen Untersuchungen zeigen, daß HSeTEK, HTTEK und deren mit Metallionen gebildeten Komplexe bei Temperaturerhöhung einer jeweils dreistufigen Umwandlung unterliegen. Die auf der Basis der thermischen Daten festgestellten Pyrolysestufen wurden verglichen und Geschwindigkeit und Abschnitte der Pyrolyse mittels der Struktur der Verbindungen erläutert.

---

, , 5,6- -3--1,2,4- 5,6 5,6 -3--1,2,4-. , . . - .

     

Zum Thermischen Verhalten von Zitronensäure

Zusammenfassung Mit Hilfe der thermo-optischen Analyse wird gezeigt, daß die widersprüchlichen Angaben in der Literatur zum thermischen Verhalten von Zitronensäuremonohydrat und dem Zitronensäureanhydrit auf eine Überlagerung verschiedener thermischer Reaktionen (Schmelze, Zersetzung, Entmischung und Kristallisation), die mit unterschiedlicher Geschwindigkeit ablaufen, zurückzuführen sind. Die thermo-optische Methode ist besonders für die Aufklärung solch komplexer Reaktionsabläufe geeignet. Das Beispiel des thermischen Verhaltens der Zitronensäure zeigt modellhaft die Erscheinungen, die bei der thermischen Analyse technischer Prozesse, wie dem Einschmelzen von Rohstoffgemengen, zu erwarten sind.

---

By means of the thermomicroscopy was demonstrated that the discrepancy between the experimental DSC- and TG-data on the decomposition of citric acid in the literature can be explained in terms of superimposing reactions (melting, decomposition, immiscibility, and crystallization), which have different reaction rates. The thermomicroscopy is especially useful explaining such kind of reactions. The thermal behaviour of citric acid can be used as a model reaction in technology.

---

, ( , , ), . . .

     

Molecular-weight dependence of the glass transition temperatures of rigid SIS triblock copolymers studied by DSC

Differential scanning calorimetry (DSC) measurements have been carried out on a series of ABA poly(styrene-b-isoprene) triblock copolymers with 30% polyisoprene content and various molecular weights. The DSC data show an inward shift for the glass transition temperatures (T _g) of the blocks compared to the corresponding homopolymers. As a function of the molecular weight, one to three transitions were found. The additional thirdT _g gives some further evidence of the existence of an interphase between the microdomains.

---

Zusammenfassung DSC wurden an einer Reihe von ABA Poly(styrol-b-isopren) Dreiblock-Kopolymeren mit 30% Polyisoprengehalt und verschiedenen Molekulargewichten durchgeführt. Die DSC-Daten zeigen eine innere Verschiebung der Glas-Übergangstemperaturen (T _g) der Blöcke im Vergleich zu den entsprechenden Homopolymeren. Als Funktion des Molekulargewichts wurden ein bis drei Übergänge gefunden. Die zusätzliche dritteT _gerbringt weitere Beweise bezüglich der Existenz einer Interphase zwischen den Mikrodomänen.

---

- (--) 30% . (T _g) . . _g - .

     

Effect of medium composition on the monooxygenase activity of immobilized hemin in aniline oxidation

The effect of the composition of the reaction medium on the rate of aniline oxidation to p-aminophenol by hydrogen peroxide on hemin immobilized on -propylimidazole-modified silica has been studied. Organic solvent additives (alcohols, esters and nitriles) are shown to increase the reaction rate. The observed effect is attributed to the decrease of the medium dielectric constant.

---

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

     

Thermal analysis of manganese dioxide in controlled atmospheres

TG and DTA curves of-MnO₂ have been obtained in nitrogen, air and oxygen. The reactions MnO₂Mn₂O₃ and Mn₂O₃ Mn₃O₄ were observed in the ranges 450° to 600° and 750° to 1100° respectively, and the decomposition temperatures are affected by the partial pressure of oxygen. The endotherm at 1200° is unaffected by the atmosphere and is not accompanied by weight loss. It is, therefore, due to a polymorphic transformation of Mn₃O₄ rather than formation of MnO. Reaction to form MnO was observed by TG in nitrogen above 1400°, but did not occur on heating in oxygen to 1500°.

---

Zusammenfassung Die TG und DTA Kurven von-MnO₂ wurden in Stickstoff, Luft und Sauerstoff ermittelt. Die Umwandlungen MnO₂ Mn₂O₃ und Mn₂O₃ Mn₃O₄ wurden im Temperaturbereich von 450° bis 600° bzw. 750° bis 1100° beobachtet. Die Zersetzungstemperaturen werden durch den partiellen Sauerstoffdruck beeinflußt. Der endendothermische Vorgang von 1200° bleibt von der Atmosphäre unbeeinflußt, ist mit keinem Gewichtsverlust verbunden. Er ist eher einer polymorphen Umwandlung von Mn₃O₄ als der Bildung von MnO zuzuschreiben. Die Bildung von MnO wurde thermogravimetrisch in Stickstoff oberhalb 1400° beobachtet, nicht jedoch in Sauerstoff bis zu 1500°.

---

Résumé Etude de-MnO₂ par TG et par ATD, dans l'azote, dans l'air et dans l'oxygène. Entre 450 et 600° on observe la réaction MnO₂Mn₂O₃ et entre 750 et 1100° Mn₂O₃ Mn₃O₄. La pression partielle de l'oxygène influence la température de la décomposition. A 1200°, il apparaît un phénomène endothermique undépendant de la nature de l'atmosphère et qui ne s'accompagne d'aucune variation de poids. C'est pourquoi il est attribué à une transformation polymorphique de Mn₃O₄ plutôt qu'à la formation de MnO. Celle-ci s'observe en TG au-dessus de 1400°, dans l'azote, mais ne se produit pas par chauffage dans l'oxygène jusqu'à 1500°.

---

, -MnO₂. , MnO₂ Mn₂O₃ Mn₂O₃ Mn₃O₄ 450°–600° 750°–1100°, , . 1200° . , n₃₄, MnO. MnO 1400°, , 1500° .

---

---

The authors wish to thank Dr. D. Dollimore and Dr. R. C. Mackenzie for suggesting the problem, and the S.R.C. for a research assistantship to D.M.T.