The nature of active sites in Ba(OH)2 catalyst

A general and repetitive method to determine the base strength and number of basic sites of catalysts with low surface area is reported. The nature of the titrating agent is discussed. The nature of the active sites of a Ba(OH)₂ catalyst with low surface area is discussed.

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. . Ba(OH)₂, .

     

Influence of fluorine-modified SiO2-surfaces on the properties of V2O5/SiO2 catalysts

The preparation of vanadium catalysts is described using fluorine modified Aerosil as support. It is shown that modification with fluorine changes the concentration and topology of the surface silanol groups and, as a consequence, the catalytic properties.

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, , . , , , .

     

Improved deactivation profile observed for Pt/H-chabazites and Pt/H-Y zeolite

The presence of small platinum crystallites in the framework of protonic offretite, erionite and Y-zeolite causes an improved deactivation profile during n-butane conversion and reflects a stronger shape-selectivity compared to the analogous behavior of the monofuctional (protonic) zeolites.

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, - - () .

     

Effect of water vapour on the aging of a polyurethane elastomer

An analysis of differential scanning calorimetry and elastic modulus data for a polyester-based polyurethane elastomer is presented. The material was annealed at 170°C for 5 min. The DSC curves were recorded at different times following thermal treatment, with different aging conditions. In particular, aging in the presence of humidity and under vacuum has been analyzed and the results are discussed in terms of the Wilkes model based on disruption of the domain structure with thermal treatment and the restoration of the previous situation at room temperature.

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Zusammenfassung Es wird eine Analyse von DSC-Daten und elastischen Modulwerten von Polyurethanelastomeren auf Polyesterbasis ausgeführt. Das Material wurde bei 170° 5 min getempert. DSC-Kurven wurden zu unterschiedlichen Zeiten nach der unter verschiedenen Alterungsbedingungen ausgeführten thermischen Behandlung aufgenommen. Insbesondere wurde die Alterung in Gegenwart von Feuchtigkeit und im Vakuum untersucht. Die Ergebnisse wurden dem Wilkes-Modell entsprechend diskutiert, das auf einer bei thermischer Behandlung eintretenden lokalen Zerstörung der Struktur und der Wiederherstellung der ursprünglichen Situation bei Raumtemperatur basiert.

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. . , .

     

Reactivity of Cl(2P1/2) atoms towards CH3F

The photochlorination of methyl fluoride has been studied at low pressures. Excited (²P_1/2) chlorine atoms have been found to participate in the reaction. The ratio of the excited and ground state rate constants has been estimated at room temperature.

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. (²P_1/2) . .

     

Influence of molecular nitrogen and irradiation temperature on radiolysis of N2O?Al2O3 system

Molecular nitrogen and irradiation temperature are shown to affect the radiationchemical yield of O _st ^– in the radiolysis of N₂O adsorbed on alumina with large surface areas and to exert no influence in the case of small surface areas of Al₂O₃.

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, - O _st ^– N₂O, Al₂O₃ .

     

Ammonium nitrate changes during thermal analysis

A study was made of the difference occurring in ammonium nitrate during investigation by DTA and by DSC. The results show that the DTA of ammonium nitrate (p.a.) is accompanied by the crystal transformation IV III II I and melting. During DSC investigation of the same ammonium nitrate samples, the salt undergoes the transformations IV III and IV II in parallel; then follow the crystal transformations III II I and melting. The investigation conditions and the history of the samples do not essentially influence the crystal transformations during thermal analysis.

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Zusammenfassung Bei DTA und DSC von Ammoniumnitrat zu beobachtende Unterschiede wurden untersucht. Bei der DTA von p.a. Ammoniumnitrat verlaufen die Kristallumwandlungen IV III II I sowie der Schmelzvorgang. Während der DSC der gleichen Ammoniumnitratproben verlaufen die Übergänge IV III und IV II parallel, worauf die Kristallumwandlungen III II I und der Schmelzvorgang folgen. Die experimentellen Bedingungen und die Vorgeschichte der Proben hat keinen wesentlichen Einfluß auf die während der thermischen Analyse verlaufenden Kristallumwandlungen.

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. ( ..) IV III II I . , IV III IV II - , III II ar I . .

     

Use of Pd/Sepiolite systems as hydrogenation catalysts I. Hydrogenolysis of N-blocked amino acids and dipeptides with molecular hydrogen

In this work we have assessed the use of sepiolites from Vallecas (Madrid, Spain) as supports of Pd catalysts applicable to the liquid-phase unblocking of amino acids and dipeptides protected by a benzyloxycarbonyl group (Z) with gaseous hydrogen. The sepiolites used have been compared with other supports employed by our team. We have also discussed the influence of the type of amino acid or dipeptide, the catalytic support and the precursor Pd salt on the unblocking rate.

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(, ) Pd , , (Z), . , . , Pd .

     

Modifying action of carbon dioxide in catalytic oxidation of ethylene on silver

Carbon dioxide exerts a strong inhibitory effect on oxygen adsorption and complete oxidation of ethylene on silver but has little effect on the rate of ethylene oxidation to ethylene oxide.

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.

     

Kinetics of isotope exchange of dioxygen with a powdered high-temperature superconducting material Ba2YCu3O7?x

It has been found that the rate of isotope exchange in Ba₂YCu₃O_7–x–O₂ system is high. Its kinetics is exponential, first order with respect to dioxygen and the exchange is of the mixed first/third type.

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Ba₂YCu₃O_7–x–O₂ . -, -, - .

     

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.

     

M?ssbauer spectroscopic studies of the state of Pt?Sn/Al2O3 catalyst for hydrocarbon conversion

Mössbauer spectroscopic studies of the state of Pt–Sn catalyst for hydrocarbon conversion supported on prechlorinated -Al₂O₃ indicate that, unlike nonchlorinated Al₂O₃, this system is much more reduced and besides Pt₃Sn–PtSn₂, its surface contains sigfificant amounts of Sn(II) and Sn(IV) chlorides bonded to the surface.

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Pt–Sn , -Al₂O₃. , Al₂O₃, Pt–Sn Pt₃Sn–PtSn₂ Sn(II) (IV), .

     

Infrared spectroscopic study of CO adsorption on supported bimetallic Pt?Pb/SiO2 catalysts

With increasing Pb content, the IR band of linearly adsorbed CO is significantly shifted to lower frequencies. The greatest influence of lead is observed up to 15% Pb. An X-ray diffraction study indicates the formation of Pt_5–7–Pb and Pt–Pb alloys for bimetallic catalysts with a Pt/Pt+Pb ratio equal to 30%.

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Pb CO . 15% Pb. 30% , , Pt–Pb Pt_5–7–Pb.

     

V2O5/TiO2 oxidation catalysts, IV. Adsorption of acrolein on sodium-containing systems

Adsorption of acrolein on vanadia/titania catalysts fits a polymerization kinetics if Na–V compounds are not present or the vanadium content is lower than that corresponding to formation of a monolayer of vanadia on the titania support.

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, Na–V .

     

The use of microcalorimetry in studies of mammalian cells

Recent developments in instrumentation and working procedure in microcalorimetry have led to an increased interest in the direct measurements of heat production rates of living cells. Specific problems connected in particular with work on mammalian cells are briefly discussed and a system of microcalorimeters suitable for work on such cells is described. A few examples of its use in studies ofT-lymphoma cells are briefly discussed.

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Zusammenfassung In letzter Zeit führte die Entwicklung von Geräten und Arbeitsvorschriften in der Mikrokalorimetrie zu erhöhtem Interesse an direkten Messungen der Wärmeproduktionsgeschwindigkeit von lebenden Zellen. Spezifische Probleme im Zusammenhang mit der Arbeit an Säugetierzellen werden kurz dargelegt und ein zur Arbeit an solchen Zellen geeignetes Mikrokalorimetriesystem beschrieben. Einige Anwendungsbeispiele werden and Hand der Untersuchungen vonT-Lymphozyten kurz beschrieben.

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, . , , , . T- .

     

Computation in kinetics, III. A new method for kinetic model search based on simultaneous regression estimation of rate constants, stoichiometry and/or reaction order

Modified samples of natural mordenites have been found to catalyze the oxidative condensation of methane to yield ethane and ethylene. The selectivity towards C₂ hydrocarbons increases, whereas the acidity of zeolites falls.

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, . C₂ .

     

Evaluation par analyse thermique differentielle des chaleurs de deshydratation de plusieurs aluns de chrome,aluminium et fer

Résumé L'emploi d'un analyseur thermique différentiel semi-micro a permis de déterminer semi-quantitativement les variations d'enthalpie accompagnant la déshydratation des aluns M^I M^III (SO₄)₂ 12 H₂O (M^III=Cr, Al; M^I=K, NH₄) et d'établir ainsi une distinction entre l'eau de cristallisation ( H < 13 kcal/mole) et l'eau de constitution ( H > 13 kcal/mole).

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The semi-quantitative determination of the heat of dehydration reactions has been realised by using a differential thermal analysis apparatus and differences in the heat of dehydration between water of crystallization ( H < 13 kcal/mole) and water of constitution ( H > 13 kcal/mole) have been established for some alums M^I M^III (SO₄)₂ 12 H₂O (M^III=Cr, Al; M^I=K, NH₄).

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Zusammenfassung Durch Anwendung eines differentialthermoanalytischen Halbmikrogeräts gelang es, die Enthalpieänderung der Dehydratation von Alaunen der Zusammensetzung M^IM^III(SO₄)₂ 12 H₂O (M^III=Cr, Al; M^I=K, NH₄) zu bestimmen und Kristallwasser ( H < 13 kcal/Mol) und Strukturwasser ( H > 13 kcal/Mol) zu unterscheiden.

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() ( < 13 /) ( > 13 /) M^I M^III (SO₄)₂ · 12 ₂ · (^III=Cr, l; ^I= K, NH₄).

     

Modification of preparation technique for highly dispersed Ni/γ?Al2O3 catalysts

Highly dispersed Ni/–Al₂O₃ catalysts have been prepared by the method of double impregnation. The application of ethylenediaminetetraacetic acid (H₄Y) as a chelating agent for activation of the -Al₂O₃ support enables us to prepare highly dispersed Ni/Al₂O₃ catalysts. The use of this chelating agent according to the described modification of the impregnation technique results in the highest dispersity of the metal component in the catalysts obtained.

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Ni/-Al₂O₃ . (H₄Y) -Al₂O₃ Ni/Al₂O₃ . , .

     

Some peculiarities in ESR spectra of titanium complexes in catalysts for isoprene polymerization in excess A1R3

It has been established that at low temperatures of TiCl₄+AOC catalyst preparation in solution (with Ti/Al1/15), ESR spectra exhibit rhombic anisotropy of the g-factor. Experiments with the sample having 61 % concentration of⁴⁷Ti isotopes suggest the formation of associates of Ti³⁺ with magnetic ordering, apparently due to the Jahn-Teller cooperative effect.

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TiCl₄+ AOC ( Ti/Al1/15) g-. ⁴⁷Ti (61%) Ti³⁺ , , -.