Structure of amorphous Fe(III) hydroxides and their ageing products

X-ray analysis has revealed that at pH=7.5–12.0 similar amorphous Fe(III) hydroxides are formed. Their structural peruliarity is the presence of local regions with ordered arrangement of atoms typical for -FeOOH in the volume of primary particles. Ageing at pH=7.5 and 353 K leads to structure rearrangement to -Fe₂O₃.

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pH 7,5–12,0 Fe(III). , -FeOOH. pH 7,5 353 -Fe₂O₃.

     

Thermal properties of elastin-fatty acid complexes

Differential scanning calorimetry has been applied to study the interaction of fibrous or of soluble elastin with fatty acids and their trialanine derivatives. The DSC curves of elastin-fatty acid preparations exhibited an endothermic transition in the temperature range - 10° to + 50°. The peak temperatures and the enthalpy changes were independent of the chain length and of the saturation of the fatty acid. The interaction with the trialanine derivatives was similar to that with the fatty acids.Such interactions between elastin and lipids might take place in vivo as well, resutling in the loss of elasticity of elastin fibres and consequently in the development of arteriosclerotic lesions.

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Zusammenfassung Zur Untersuchung der Wechselwirkung zwischen dem fibrösen oder lösbaren Elastin, und den Fettsäuren und ihren Trialanin-Derivaten wurde die DSC-Methode angewandt. Die DSC-Kurven der Elastin-Fettsäure-Präparate zeigten in dem Temperaturbereich von - 10° bis + 50° einen endothermischen Übergang. Die Peak-Temperaturen und die Änderungen der Enthalpie waren von der Kettenlänge und der Sättigung der Fettsäure unabhängig. Die Wechselwirkung mit den Trialanin-Derivaten war der mit den Fettsäuren ähnlich.Solche Wechselwirkungen zwischen Elastin und den Lipiden können auch in vivo stattfinden, und die Abnahme der Elastizität der Elastin-Fibern, und folglich die Entfaltung der arteriosklerotischen Schädigungen resultieren.

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. - — — 10° - + 50°. , . , . , , .

     

Investigation of surface phenomena on solid catalysts by simultaneous thermogravimetry and DTA

Thermogravimetry and simultaneous DTA were used to investigate the phenomena of adsorption, desorption and surface reactions on solid catalysts. The measurements were carried out with NaX and X-type ion-exchanged zeolites and silica-alumina gels (Ketjen) treated with sodium hydroxide in the presence of carbon dioxide. On the basis of the quantitative results it is possible to give an interpretation of the surface phenomena and to establish the existence of various active centres on the surfaces of the catalysts. In the case of the adsorption of carbon dioxide on X-type zeolites, the quantity of carbon dioxide adsorbed is much smaller on ion-exchanged zeolites than on NaX.

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Zusammenfassung Thermogravimetrie und simultane DTA wurden zur Untersuchung der Adsorptions-, Desorptions-Erscheinungen und Oberflächenreaktionen an festen Katalysatoren eingesetzt. Die Messungen wurden and NaX und Zeolithen des Typs X sowie an Silika-Aluminiumoxidgelen Ketjen durchgeführt, welche mit Natriumhydroxid in Gegenwart von Kohlendioxid behandelt worden waren. Aufgrund der quantitativen Ergebnisse ist es möglich eine Deutung der Oberfiächenerscheinungen zu geben und die Existenz verschiedener aktiver Zentren an der Katalysatorenoberfläche nachzuweisen. Im Falle der Adsorption von Kohlendioxid an Zeolithen des Typs X ist die Menge des adsorbierten Kohlendioxids am Ionenaustauscher viel niedriger als am NaX.

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Résumé Application de la TG et de l'ATD simultanées à l'étude des phénomènes d'adsorption, de désorption et de réactions de surface sur des catalyseurs solides. Les mesures ont été effectuées avec des zéolites échangeuses d'ions de type NaX et X ainsi qu'avec des gels Ketjen silice-alumine traités par NaOH en présence de CO₂. Les résultats quantitatifs permettent de donner une interprétation des phénomènes de surface et d'établir l'existence de divers centres actifs à la surface des catalyseurs. Dans le cas de l'adsorption de CO₂ sur les zéolites de type X, la quantité de CO₂ adsorbé est beaucoup plus faible que sur les zéolites de type NaX.

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DTA , . - NaX X - « », . . X, - , NaX.

     

Kinetics and mechanism of the permanganate oxidation of trans-crotonic acid

The kinetics and intermediates of the permanganate oxidation of trans-crotonic acid have been investigated in the pH range of 0.5–5.0 using the stoppedflow technique. The formation of manganese(III) as a short-lived intermediate has been established. The reaction is first order with respect to both MnO ₄ ^– and crotonic acid (crotonate). The resolved rate constants at 25°C are 730 and 410 M^–1 sec^–1 for the acid and the anion, respectively. The reaction mechanism is discussed.

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pH=0,5–5,0, . (III) . MnO ₄ ^– , (). 25°C 730 410 M^{–1 –1} , . .

     

Kinetics and mechanism of homogeneous catalytic oxidation of pyrocatechol in aqueous solutions containing Cu(II) and histidine

Kinetic studies of pyrocatechol oxidation by oxygen in weakly acidic aqueous solutions containing pyrocatechol, Cu(II) ions and histidine, indicate that the reaction involves mixed copper-pyrocatechol histidine complexes. The proposed mechanism of the process agrees with the kinetic relationships obtained.

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, , Cu(II) . , . , -.

     

Effect of acid treatment on the properties of an activated carbon

The enhancement of the activity of a carbon treated with HF is due to the drastic diminution of its inorganic impurities, which produces an increase of the surface area of the carbon, a stronger Pt-C interaction and a higher Pt dispersity.

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, HF, , , Pt-C Pt.

     

Kinetics and mechanism of phenylacetylene hydrogenation under hydrogen pressure

Kinetic and potentiometric curves of phenylacetylene hydrogenation on a 5% Pt/C catalyst in ethanol under hydrogen pressure have been studied. On the basis of chromatographic data a possible scheme of the process is suggested.

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. 5% Pt/C . .

     

Oxidation of propylene to acrylic acid on a Fe?Mo?Bi oxide system

Data obtained in a flow reactor show that iron(III) molybdate doped by bismuth can oxidize propylene to acrylic acid directly in one step. Part of the catalyst works in a partially reduced form and in the preparation of the catalyst the surface acidity must be controlled.

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, , (III), , . .

     

The thermal behaviour of solvates in the LiCI(MgCl2, AlCl3) water-1,4-dioxane systems

The thermal behaviour of the solvates and mixed solvates in the LiCl(MgCl₂, AlCl₃)-water-1,4-dioxane systems was investigated by means of DTA measurements of the melting behaviour and by quasi-isothermal and quasi-isobaric investigations of the thermal decomposition processes.The compounds melt incongruently. The positions of the melting points and the processes of thermal decomposition confirm the assumption that 1,4-dioxane is bonded in the first coordination sphere in the mixed solvate of lithium, but in the cases of magnesium and aluminium chloride it is bonded via hydrogen-bonds and not directly to the cations. Only for the lithium and magnesium compounds does the decomposition of the anhydrous solvates result in anhydrous chlorides.

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Zusammenfassung Das thermische Verhalten der Solvate und Mischsolvate der Systeme LiCl, (MgCl₂, AlCl₃)-Wasser-1,4 Dioxan wurde mit Hilfe von DTA-Messungen zum Schmelzverhalten, und quasi-isothermen und quasi-isobaren Untersuchungen zum Ablauf der thermischen Zersetzung Untersucht. Die Verbindungen schmelzen inkongruent. Die Lage der Schmelzpunkte und der Verlauf der thermischen Zersetzung bekräftigen die Vorstellungen, daß 1,4 Dioxan im Mischsolvat des Lithiums in der ersten Koordinationsphäre direkt am Kation, hingegen bei Magnesium und Aluminium über Wasserstoffbrücken gebunden ist. Die Zersetzung der wasserfreien Solvate führt nur im Fall der Lithium- und Magnesiumverbindungen zu den wasserfreien Chloriden.

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( , )--1,4- , - - — . . , 1,4- . , , . .

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The valuable assistance of Dr. Frahghänel in the separation of the solid phase by means of the hightemperature centrifuge is gratefully acknowledged.     

Synthesis of A C18 alcohol from methyl oleate over hydrogen storage alloys

Catalytic hydrogenolysis of methyl oleate to C₁₈ alcohol is tested with a pulse reaction system under atomspheric pressure at 503 K over a series of hydrogen storage alloys. Mg₂Cu alloy shows the highest efficiency and the yield of alcohol is about three times larger than the classical Cu–Cr–O catalyst.

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-C₁₈ 503 K , . Mg₂Cu Cu–Cr–O.

     

Interaction of nitric oxide with NiCr2O4

Interaction of NO with NiCr₂O₄ has been studied at 473–1173 K. It has been established that on nickel-chromium spinels NO decomposition practically does not take place. Nitric oxide can interact only with prereduced samples to reoxidize them.

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473–1173 NO NiCr₂O₄. , NO . (II) ; .

     

Effect of α-methylstyrene of the curing behaviour of vinyl ester resins

The curing behaviour of bismethacryloxy derivative of diglycidyl ether of bisphenol A (vinyl ester resin) containing styrene as the reactive diluent (40% w/w) was studied using gel point determination method and DSC. Seven samples of styrene/-methylstyrene in the ratio 400, 355, 3010, 2515, 2020, 1525 and 040 were studied. Delayed curing was observed in samples containing increasing proportions of -methylstyrene. The energy of activation decreased from 869 kJ mol^–1 to 333 kJ mol^–1 as the concentration of -methylstyrene increased in the formulations. However, no difference in thermal stability was observed by replacement of styrene by -methylstyrene. It was concluded that in vinyl ester resin samples 10–15% -methylstyrene and 30-25% styrene can be used as reactive diluent.

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Zusammenfassung Mittels DSC und Bestimmung der Gelierungstemperatur wurde das Aushärteverhalften des Bismethakryloxyderivaten des Diglycidyläthers von Bisphenol A (Vinylesterharz) mit 40 Gewichtsprozenten Styrol als reaktives Streckmittel untersucht. Es würden sieben Proben mit einem Styrol/-Methylstyrol Verhältnis von 400, 355, 3010, 2515, 2020, 1525 und 040 untersucht. Mit steigendem Anteil an -Methylstyrol konnte eine Verzögerung der Aushärtung sowie ein Absinken der Aktivierungsenergie von 869 kJ · mol^–1 auf 333 kJ · mol^–1 beobachtet werden. Der Ersatz von Styrol durch -Methylstyrol veränderte jedoch die thermische Stabilität in keiner Weise. Vinylesterharzproben mit 10–15% -Methylstyrol und 30–25% Styrol können als reaktive Streckmittel in Vinylesterharzen verwendet werden.

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- - , 40 .% . /-, 400, 355, 3010, 2515, 2020, 1525 040. - . - 869 333 · ^–1. , .. , , 10–15% - 30–25% .

     

Reactivity of benzoic acid esters towards cumylperoxy radicals

The alkoxy groups of aromatic carboxylic acid esters are attacked by cumylperoxy radicals. The rate constants for the abstraction of a hydrogen atom by cumylperoxy radicals are: for methyl benzoate k₂=(4.28±0.8)×10¹⁰ exp (–20.5±1.5/RT) and for ethyl benzoate k₂=(9.41±0.8)×10¹⁰ exp(–18.5±1.5/RT) l/mol sec. The strengths of the primary and the secondary C–H bonds of these compounds have been estimated.

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, . k₂=(4,28±0,8)·10¹⁰ exp (–20,5±1,5/RT) k₂=(9,41±0,8)·10¹⁰ exp (–18,5±1,5/RT) /·. C–H .

     

Kinetic data on the interaction between triplet anthraquinone and 2-naphthol in oxygen

During the photooxidation of ethylbenzene in the presence of 2-naphthol a new interaction has been found between the sensitizer anthraquinone and the inhibitor. The quantum yield and the kinetics of this interaction have been investigated in the temperature interval of 28–98°C.

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-, , 28–98°C , .

     

Coke deposition on naphtha reforming catalysts: II. Influence of the addition of a second metal to platinum

The nature and rate of coke deposited on mono-and bimetallic reforming catalysts have been studied for normal heptane reforming. For bimetallic catalysts it has been shown that coke deposition is less extensive than on monometallic catalyst, depending on the degree of polymerization and the type of bimetallic catalyst.

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-. , , , .

     

Kinetics of ammonia decomposition of polycrystalline rhodium at pressures between 0.013 and 103 kPa

The rates of ammonia decomposition on polycrystalline Rh wires between 600 and 1800 K and at pressures between 13.3 Pa and 103 kPa were measured and fitted with a Langmuir-Hinshelwood unimolecular reaction rate expression. At high temperatures and pressures the reaction seems to be mass transfer controlled.

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Rh 600–1800 K 13,3 –103 . , -. .

     

Steady state catalytic properties and oxygen binding energy of cadmium-molybdenum catalysts in methanol oxidation

On normal cadmium molybdate the products of methanol oxidation are primarily CO₂ and H₂. After the introduction of excess MoO₃ to reach Mo/Cd=1.2, methanol is oxidized to formaldehyde and carbon monoxide via a consecutive scheme. The oxygen binding energy in the steady state for the first sample is by 30 kcal/mol higher than that for the second catalyst. The activation energies of methanol conversion are 11.5 and 20 kcal/mol, respectively.

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CO₂ H₂. MoO₃ Mo/Cd=1, 2 . 1- 30 / , , , , 11,5 20 /.

     

Use of EGD for the characterization of fining processes of glass melt

The control and optimization of the glass-making process is a serious problem in glass production. An EGD procedure involving high-temperature vacuum extraction and total pressure measurement allows determination of the fining state (Läuterzustand) and fining behaviour (Läuterverhalten). The fining state is characterized by the contents of CO₂, N₂ and other gases from the batch reactions, and gas inclusions. Oxygen evolved in a second step is characteristic for the fining behaviour.

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Zusammenfassung Die Kontrolle und Optimierung des Gasgehaltes von Glasschmelzen ist eine wichtige Voraussetzung für eine gleichbleibende Qualität der Glasprouktion. Eine EGD-Technik mit Hilfe der Hochvakuumheißextraktion und Gasdruckmessung erlaubt, den Läuterzustand und das Läuterverhalten einer Glasprobe zu bestimmen. Der Läuterzustand wird durch die Gase aus den Gemengereaktionen und Gemengeeinschlüssen (CO₂, N₂ u. a.) bestimmt. Das Läuterverhalten ergibt sich aus der Menge des in einer zweiten Stufe extrahierbaren Sauerstoffs.

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. , , . , , , . , , .

     

Reaction kinetics by thermal analysis

The application of thermal analysis in the study of reaction kinetics and reaction mechanisms in combination with presently available powerful analytical tools, in the sphere of materials with particular reference to high energy materials is presented and discussed. Also an attempt has been made to correlate the kinetic data obtained by TA with the performance characteristics, for some important materials.

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Zusammenfassung Es wird die Anwendung der Thermoanalyse bei der Untersuchung der Reaktionskinetik und des Reaktionsmechanismus in Zusammenwirkung mit den gegenwärtig zur Verfügung stehenden leistungsfähigen analytischen Werkzeugen auf dem Gebiet von Materialien mit speziellem Bezug auf energiereiche Stoffe dargestellt Und besprochen. Es wurde auch versucht, die durch TA erhaltenen kinetischen Daten einiger wichtiger Stoffe mit deren Leistungskenndaten in Beziehung zu stellen.

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. , , .