Properties of highly dispersed supported catalysts in hydrogenation reactions

Pt/sol and Pt/support catalysts with 6–15 Å Pt particles have been established to be low active in the hydrogenation of propargyl alcohol, butyn-l-ol-3 and dimethylethynylcarbinol. The specific catalytic activity significantly rises with increasing d_Pt above 15 Å and after the thermal treatment of highly dispersed catalysts in a hydrogen flow.

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, -30 -- 6–15 Å , -1, -3 . d_Pt>15 Å .

     

Study of the adsorption properties of a natural Hungarian mordenite and its ion-exchanged derivatives

The texture and adsorption properties of a natural, Hungarian mordenite were investigated by electron microscopy and BET adsorption measurements. The properties of the ion-exchanged adsorbents were characterized by CO₂ and SO₂ isotherms. The measurements were evaluated on the basis of the pore-filling theory of Dubinin. We have found that at 20°C the H⁺-form of mordenite interacts preferably with CO₂, while on the Na⁺- and Ca²⁺-derivatives stronger adsorption of SO₂ takes place. This fact accounts for their applicability as selective adsorbents.

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, . CO₂ SO₂. . , 20°C H⁺- CO₂, Na⁺- Ca²⁺- SO₂ . .

     

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- . , , . . , .

     

Light and X-ray-induced chemistry of methane on TiO2

TPD studies of the established formation of ethane, ethylene and propylene in the irradiated CH₄/TiO₂ system indicate that the process is most effective under X-ray or long-wavelength light irradiation behind the edge of the fundamental absorption band of the oxide.

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, CH₄/TiO₂, .

     

Sensitization of the photoadsorption of O2 and NO on SnO2

Photoadsorption activity of SnO₂ with respect to O₂ and NO after CO chemisorption has been revealed to be drastically increased. Photoadsorption is suggested to be sensitized by surface carbonates formed due to CO chemisorption.

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. , .

     

On the sub-Tg annealing of uniaxially oriented and unoriented atactic polystyrene

DSC analysis was performed on uniaxially oriented and unoriented atactic polystyrene samples prior to and after annealing at 80 °C. With increasing annealing times, an endothermic peak appeared, whose area increased with the duration of the annealing period. No difference was found between the endotherm areas for the oriented and the unoriented polymer.The DSC curve of the unannealed oriented polystyrene exhibited a relaxation exotherm. DSC and relaxation studies indicated that this relaxation exotherm was independent of the main chain orientation; it may rather be due to sample densification.

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Zusammenfassung Uniaxial orientierte und unorientierte ataktische Polystyrenproben wurden vor und nach dem Tempern bei 80° mittels DSC untersucht. Mit länger werdender Temperungszeit erscheint in endothermer Peak, dessen Fläche mit der Dauer der Temperungsperiode ansteigt. Die Flächen der endothermen Peaks von orientierten und unorientierten Polymeren unterscheiden sich nicht. Die DSC-Kurve von ungetempertem orientiertem Polystyren zeigt einen exothermen Relaxationseffekt. DSC und Relaxationsuntersuchungen ergaben, daß dieser exotherme Relaxationseffekt unabhängig von der Orientierung der Hauptkette ist und eher einer Probeverdichtung zuzuschreiben ist.

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80°. , . . , , . , , .

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We are grateful to Prof. B. Wunderlich of the Rensselaer Polytechnic Institute, New York, for useful discussions.

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The financial support of C.N.R. (progetto finalizzato chimica fine e secondaria) is gratefully acknowledged.     

Acid-base properties of Sn?Mo?Ox catalysts

The acidity and basicity of Sn–Mo–O_x catalysts with different Mo/Mo+Sn atomic ratios were measured by determining the adsorption isotherms of pyridine and acetic acid by chromatographic method. It was found that acidity and basicity go through a maximum at a Mo content of 15–20 at.%.

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Sn–Mo–O_x Mo/Mo+Sn, . Mo=15–20 at.%.

     

ESR studies of Mo?Mg oxide catalysts

For 0.1–0.5 wt.% Mo–Mg oxide samples with high concentration of⁹⁵Mo isotopes two types of Mo⁵⁺ have been identified. Their role in the formation of O ₂ ^– anion-radicals in low-temperature oxygen adsorption on reduced samples has been established.

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, ⁹⁵Mo, Mo⁵⁺ Mo–Mg (0,1–0,5 .% Mo) - O ₂ ^– .

     

Determination of liquid vapour adsorption and desorption on and from solids by means of the derivatograph II

Studies of water adsorption and desorption on silica gel with a modified derivatograph are described. The dynamic gas chromatography step profile method was used to determine isotherms of adsorption and desorption from the TG curve. The obtained isotherms agree with those from other methods. The properties of surface liquid layers can be investigated by this method.

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Zusammenfassung Die Untersuchung der Adsorption und Desorption von Wasser an Silikagel mittels eines modifizierten Derivatographen wird beschrieben. Die dynamische gaschromatographische Stufenprofilmethode wurde zur Bestimmung der Ad- und Desorptionsisothermen aus den TG-Kurven herangezogen. Die erhaltenen Isothermen stimmen gut mit denen nach anderen Methoden bestimmten überein. Die Eigenschaften flüssiger Oberflächenschichten können mit dieser Methode untersucht werden.

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. . , . .

     

Le systeme eau-theophylline

The binary system water—theophylline was studied by DTA and radiocrystallography. The slow dehydration of theophylline monohydrate was observed at room temperature at relative humidities lower than 60%, without the formation of any other hydrate. The isochoric phase diagram was established. At 78 °C, a peritectic invariant occurred, owing to decomposition of the monohydrate. The existence of only one binary compound (theophylline H₂O) was confirmed by the.Tammann diagram.

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Zusammenfassung Mittels DTA und Radiokristallographie wurde das binäre System Wasser-Theophyllin untersucht. Bei einer relativen Luftfeuchtigkeit unter 60% wird bei Raumtemperatur eine langsame Dehydratation von Theophyllinemonohydrat ohne Formung anderer Hydrate beobachtet. Es wurde ein isochores Phasendiagramm entwickelt. Wegen der Zersetzung des Monohydrates tritt bei 78 °C eine peritektische Invariantheit auf. Die Existenz nur einer binären Verbindung (Theophyllin, H₂O) wird mittels eines Tammanndiagrammes bekräftigt.

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— . 60% - . . 78° , . -.