Kinetics and mechanism of TI(III) oxidation of cellobiose in acidic medium

TI(III) oxidation of cellobiose in the presence of H₂SO₄ in aqueous acetic acid is first order in each reactant and is acid catalyzed. TI(OAc) ₂ ⁺ is the active species. Products identified are gluconic acid and glucose. A mechanism consistent with the temperature, solvent, acidity and salt effects is been proposed.

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TI(III) H₂SO₄ . TI(OAc) ₂ ⁺ . . , , , .

     

Исследование роли фосфиновых комплексов никеля различных степеней окисления в каталитической димеризации олефинов

Ni(II), Ni(I) Ni(O) . , , , Ni(O) Ni(I) - Ni(I) Ni(II) Ni(O).

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The interaction of organoaluminium compounds with phosphine complexes of Ni(II), Ni(I) and Ni(0) has been studied under the conditions of catalytic propylene dimerization. The active complexes are formed from Ni(II) compounds, the regeneration of the latter is ensured by repeated reduction, oxidation of Ni(0) to Ni(I), and by disproportionation of Ni(I) into Ni(II) and Ni(0).

     

Measurement of thermal constants of calcium chromite by Laser Flash method

Calcium chromite, CaCr₂O₄, was prepared and its purity and stoichiometry were ascertained by chemical analysis and X-ray diffraction methods. The thermal diffusivity, specific heat capacity and thermal conductivity of calcium chromite were measured by Laser Flash method using an Ulvac-Sinku Riko TC-3000 series instrument in the temperature range of 298 to 1100 K. The heat capacity data were utilised to calculate the thermodynamic parametersenthalpy increments, entropy increments and free energy increments—in the above temperature range.

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Zusammenfassung Kalziumchromit, CaCr₂O₄, wurde hergestellt und seine Reinheit und stöchiometrische Zusammensetzung mit Hilfe chemischer Analyse und Röntgendiffraktionsmethoden ermittelt. Anhand eines Ulyac-Sinku Riko TC-3000 Gerätes wurde mit Laser Flash Verfahren die Temperaturleitfähigkeit, die spezifische Wärmekapazität und die Wärmeleitfähigkeit von Kalziumchromit im Temperaturbereich 298–1100 K bestimmt. Die Wärmekapazitätsdaten wurden zur Berechnung der thermodynamischen Größen (Enthalpie-, Entropie-, Freie Energieänderung) in obigem Temperaturbereich benutzt.

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CaCr₂O₄, . , - TC-3000, 298–1100K , . , , .

     

Reactions in the combustion of hydrocarbons

Combustion of LPG produces carbon dioxide directly up to a temperature of 525°C. In addition, the formation of unsaturates is observed at temperatures above 550°C as a result of oxidative dehydrogenation and subsequent combustion of unsaturates to carbon dioxide at temperatures higher than 575°C.

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525°C. , 550°C . 575°C .

     

X-ray study of palladium catalysts. Influence of thermal treatment in hydrogen on the phase composition

The thermal treatment of Pd catalysts in a reducing atmosphere of hydrogen leads to interaction of supported metal and support to form solid solutions.

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, .

     

ESR measurements of concentration for strong surface acceptor centers on zeolites and Al2O3 using nitroxide radical TEMPON

A method to measure concentrations of strong surface acceptor centers on aluminosilicate catalysts by their titration with a solution of TEMPON (2,2,6,6-tetramethyl-4-oxypiperidine-1-oxyl) is suggested. The concentration of these centers corresponds to that of CO test molecules for the strongest acceptor centers (_CO 2210 cm^–1) obtained using IR spectroscopy. It is shown that for ZSM-5 zeolites most of these centers are localized on their external surface.

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. - - CO (_CO 2210 cm^–1). , ZSM-5 .

     

Determination of basic sites on the surface of metal oxide catalysts by desorption of benzoic acid

A method has been developed for the determination of the concentration of basic sites on white and deeply colored solid porous materials, which is based on the displacement of adsorbed benzoic acid by acetic acid. The determination is rapid and gives results comparable with those obrained by the titration with benzoic acid using thymolphthalein as indicator.

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. . , , , .

     

Study of distribution of elements in the depth of V?P?Co catalyst grain

It has been shown that addition of cobalt to a vanadium-phosphorus oxide catalyst increases the P/V molar ratio on the surface, the surface acidity and the selectivity of butane oxidation. It has been established that in the V–P–Co–O catalyst the probability of the removal of phosphorus from the surface is markedly reduced.

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, , . , V–P–Co–O .

     

Catalytic properties and phase composition of multicomponent catalysts for oxidative ammonolysis of propane

Studies of the phase composition and catalytic properties of several complex oxide catalysts for oxidative ammonolysis of propane indicate that the active phases of these catalysts are antimonates of the respective metals. Phosphorus and tungsten additives to the catalysts promote the formation of such phase compositions, i.e. the formation of antimonates and the binding of excess antimony oxide.

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. , ; , .

     

Thermal investigation of the phase composition of poly(ethylene terephthalate). Analysis of different methods of determination of the degree of crystallinity of partially crystalline substances

The literature data on the degree of crystallinity of non-deformed poly(ethylene terephthalate) measured at various temperatures have been subjected to comparative analysis. There is no correlation between the results obtained by the different methods. The reason for this is shown to be the imperfections in the methods of determining the degree of crystallinity, which do not provide the true composition of the crystalline phase. Consideration has been paid to the validity of the main principles involved in the thermal method of determining the degree of crystallinity, so as to eliminate the imperfections in the existing methods and to provide the correct value of the mass of the crystalline phase. The phase composition of PET has been analyzed by the thermal method at different temperatures and conditions of crystallization. A marked difference from the literature data is observed in the range of low temperatures.

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Zusammenfassung Eine vergleichende Analyse der Literaturangaben bezüglich des bei verschiedenen Temperaturen gemessenen Kristallisationsgrades von nicht-deformiertem Poly(äthylen-terephthalat) wurde durchgeführt. Zwischen den mit verschiedenen Methoden erhaltenen Ergebnissen besteht keine Korrelation. Es wurde gezeigt, daß der Grund hierfür in der Unvollkommenheit der Methoden zur Bestimmung des Kristallisationsgrades liegt, da diese nicht die wahre Zusammensetzung der Kristallinen Phase angeben. Die Gültigkeit der wichtigsten Prinzipien, welche die thermische Bestimmung des Kristallisationsgrades unter Ausschaltung der Unvollkommenheit der bestehenden Methoden gewährleisten und den richtigen Wert der Masse der kristallinen Phase angeben, wurden in Erwägung gezogen. Die Analyse der Phasenzusammensetzung von PET wurde durch die thermische Methode bei verschiedenen Temperaturen und Kristallisationsbedingungen durchgeführt. Ein deutlicher Unterschied zu den Literaturangaben kann im Bereich der niedrigen Temperaturen beobachtet werden.

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. , , . , , . , , . . .

     

Oxygen adsorption on silver-gold alloy

Oxygen adsorption on Ag/Au alloys has been studied by field-emission microscopy (FEM). A decrease in the silver concentration of alloy is accompanied by a drastic fall in its ability to absorb oxygen. Using the interacting bonds method (IBM), the adsorption heat of atomic oxygen on the (100) plane of the silver-gold alloy has been calculated.

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. , . (100) .

     

Thermal analysis of mercury(I) sulfate and mercury(II) sulfate

The thermal decomposition of mercury(I) and (II) sulfates has been investigated by thermogravimetry. The solid-state decomposition products have been characterized by infrared and Raman spectroscopy, mass spectrometry and an X-ray diffraction method. It is concluded that mercury(I) sulfate decomposes in two steps, initially forming a mixture of metallic mercury and mercury(II) sulfate — the latter subsequently decomposes without forming a stable intermediate. The stoichiometry of disproportionation of mercury(I) sulfate and the thermal stability range of mercury(I) and mercury(II) sulfates have been established.

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Zusammenfassung Die thermische Zersetzung von Quecksilber(I) und (II)-sulfaten wurde durch Thermogravimetrie untersucht. Die Festphasen-Zersetzungsprodukte wurden durch Infrarot- und Ramanspektroskopie, Massenspektrometrie und Röntgendiffraktion charakterisiert. Es wurde gefolgert, dass Quecksilber(I)sulfat in zwei Stufen zersetzt wird, unter anfänglicher Bildung eines Gemisches von metallischem Quecksilber und Quecksilber(II)-sulfat, welches in der Folge ohne Bildung eines stabilen Zwischenproduktes zersetzt wird. Die Stöchiometrie der Disproportionierung des Quecksilber(I)sulfats und der Bereich der Thermostabilität der Quecksilber(I) und Quecksilber(II)sulfate wurden ermittelt.

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Résumé La décomposition thermique des sulfates de mercure(I) et de mercure(II) a été suivie par TG. On a caractérisé les produits de la décomposition en phase solide par spectroscopies infrarouge et Raman, spectrométrie de masse et diffraction des rayons X. On en a conclu que le sulfate de mercure(I) se décompose en deux étapes, formant initialement un mélange de mercure métallique et de sulfate de mercure(II), ce dernier se décomposant ensuite sans formation d'un intermédiaire stable. Les proportions stoechiométriques de la dismutation du sulfate de mercure(I) et de l'intervalle de stabilité thermique des sulfates de mercure(I) et de mercure(II) ont été établis.

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

     

Catalytic properties of silica-molybdenum catalysts in propylene oxidation

The activity of silica-molybdenum catalyts in propylene oxidation is shown to be determined by the partially dehydrated silica-molybdenum heteropolyacid stabilized by the SiO₂ surface.

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, , SiO₂.

     

H2O? radicals trapped in Y-type zeolites

The results of CHDO/SP calculations do not support the detection of H₂O^– ions in MgY and CaY zeolites.

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CNDO/SP H₂O^– MgY CaY.

     

A study of chloride moderated silver catalyst

The activity and selectivity of an industrial silver catalyst were found to increase in parallel when the catalyst surface was moderated by 1–7% chloride.

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1–7%.

     

Correlations between photosorption and photocatalytic activities of alkali metal halides

An analysis of the correlation suggests that the common stages in photosorption, photooxidation and photodecomposition of some simple molecules on alkali metal halides are connected with catalyst photoexcitation.

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, , , .

     

DTA investigation of the solid-liquid equilibrium for methyl derivatives of naphthalene with some nitroaromatics

The two-component solid—liquid phase eqilibria systems of some methyl derivatives of naphthalene with 2,4,6-trinitrophenol and 2,4,6-trinitrotoluene have been examined by DTA. All systems contain molecular complexes with 11 compositions.

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Zusammenfassung Zweikomponentige Fest-Flüssig-Phasengleichgewichtssysteme von einigen Methylderivaten von Naphthalen mit 2,4,6-Trinitrophenol und 2,4,6-Trinitrotoluol wurden mittels DTA untersucht. Alle Systeme enthalten Molekülkomplexe der Zusammenserzung 11.

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2,4,6- 2,4,6-. 11.

     

A quantum chemical study of the influence of an electrostatic field on the reactivity of methanol over zeolites

The INDO method with an electrostatic potential term in its Hamiltonian has been used to estimate the changes in the electronic structure of methanol and methanol dimer due to the electrostatic field of zeolites. It has been shown that fields of the strength F=2–8×10¹⁰V/m change significantly the electronic structure as well as the geometry of both molecules and can cause their decomposition leading to the species H₂O, CH₃, CH₃O, CH₂O, and CH₂.

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INDO . , F=2÷8·10¹⁰ / , , H₂O, CH₃, CH₃O, CH₂O CH₂.

     

Zur Frage der Quantitativen Differentialthermoanalyse Cristobalithaltiger Staubproben

Zusammenfassung Mit einer DTA-Anlage eigener Entwicklung werden an Cristobalitproben verschiedener Herkunft und Entstehungsgeschichte Umwandlungstemperatur und Wärmetönung der --Inversion bestimmt. Die dabei gefundene Beziehung zwischen diesen beiden Größen ermöglicht unter gewissen Bedingungen die Ermittlung des Cristobalitgehaltes einer Staubprobe.

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Temperature and heat of the --inversion in christobalite samples of various origin and way of production were measured with a self-constructed DTA-apparatus. A relationship was found between temperature and heat of reaction, which in certain circumstances enables to determine the christobalite content in dust samples.

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Résumé Détermination, à l'aide d'une installation d'ATD personnelle, de la température et de la chaleur de transformation de l'inversion - de divers échantillons de cristobalite d'origine et de préparation différentes. Une relation est apparue entre ces deux grandeurs permettant de déterminer, sous certaines conditions, la teneur en cristobalite d'un échantillon de poussière.

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– , . , .