Effect of water on the desorption of carbon dioxide from the surface of alumina

Based on investigations of temperature-programmed desorption of CO₂ from -Al₂O₃ surface, three forms of CO₂ adsorption differing considerably in quantitative contributions and temperature ranges of desorption have been distinguished. A significant inhibiting influence of water on CO₂ adsorption has been observed. Water adsorption results in gradual blocking of high and medium-energy adsorptive centers of CO₂ on -Al₂O₃.

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- CO₂ -Al₂O₃ CO₂, . CO₂. CO₂ Al₂O₃ .

     

Light olefin production from CO/H2 over silica supported Fe/Mn/K catalysts derived from a bimetallic carbonyl anion, [Fe2Mn(CO)12]?

Fe/Mn/K catalysts derived from support of the anionic carbonyl, [Fe₂Mn(CO)₁₂]^– on silica were compared with catalysts prepared by aqueous impregnation methods, and found to be more selective for production of C₂–C₄ olefins. Addition of K had little effect, whereas variations in reaction conditions altered selectivity owing to secondary reactions of the alkene products.

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Fe/Mn/K, , [Fe₂Mn(CO)₁₂]^–, , , , C₂–C₄. , , .

     

Competitive uptake of Cs+, Ba2+, and Zn2+ ions from binary aqueous mixtures by zeolite-13X

The preferential exchange uptake of the cations Cs⁺, Ba²⁺ and Zn²⁺ from pure solutions by zeolite-13X follows the order Q [Cs⁺]>Q [Ba²⁺]>Q [Zn²⁺], while in case of binary mixtures the order is Q [Ba²⁺(Zn²⁺)]>Q [Ba²⁺(Cs⁺)]>Q [Cs⁺(Zn²⁺)]>Q [Cs⁺(Ba²⁺)]>Q [Zn²⁺(Cs⁺)]>Q [Zn²⁺(Ba²⁺)]. Ba²⁺ uptake from mixtures shows the least suppression effect.

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Cs⁺, Ba⁺² Zn⁺² -13 Q[Cs⁺]>Q[Ba⁺²]>Q[Zn⁺²] Q[Ba⁺²(mix Zn⁺²)]>Q[Ba⁺²(mix Cs⁺)]>Q[Cs⁺(mix Zn⁺²)]>Q[Cs⁺(mix Ba⁺²)]>Q[Zn⁺²(mix Cs⁺)]>Q[Zn⁺²(mix Ba⁺²)]. Ba⁺² .

     

The structures and thermal decomposition of cupric mono,di and trichloracetates

Magnetic moment measurements and ultra-violet diffuse reflectance spectroscopy have been used to investigate the structure of the chloroacetates of copper(II). These studies indicate that cupric monochloroacetate dihydrate is dimeric and cupric trichloracetate tetrahydrate is monomeric. Cupric dichloracetate tetrahydrate forms an intermediate case. The thermal decomposition of these compounds under nitrogen has been studied using thermogravimetry and differential thermal analysis, together with analysis of the products of the decomposition. The major organic product formed in the thermal decomposition of the mono- and dichloracetates is the corresponding chlorinated acetic acid; the solid inorganic product is cuprous chloride. Thermal decomposition of the trichloracetate yields cupric chloride and a mixture of trichloracetic acid and trichloracetyl chloride.

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Zusammenfassung Messungen des magnetischen Momentes sowie diffuse UV-Remissionspektroskopie wurden zur Untersuchung der Struktur der Kupfer(II)-chloracetate eingesetzt. Die Ergebnisse deuten darauf hin, daß Kupfermonochloracetat-Dihydrat dimer und Kupfertrichloracetat-Tetrahydrat monomer ist. Das Kupferdichloracetat-Tetrahydrat bildet hierbei eine Zwischenstufe. Die thermische Zersetzung dieser Verbindungen wurde in Stickstoffatmosphäre unter Anwendung der Thermogravimetrie und Differentialthermoanalyse untersucht, bei gleichzeitiger Analyse der Zersetzungsprodukte. Das bei der thermischen Zersetzung des Mono- und Dichloracetats gebildete organische Hauptprodukt ist die entsprechende chlorierte Essigsäure; der feste anorganische Rückstands das Kupfer(I)-chlorid. Die thermische Zersetzung des Trichloracetats ergibt Kupfer(II)-chlorid sowie eine Mischung von Trichloressigsäure und Trichloracetylchlorid.

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Résumé La mesure du moment magnétique et la spectroscopie de réflexion diffuse dans l'U. V. sont utilisées pour étudier la structure des chloroacétates de cuivre (II). Les résultats indiquent que le monochloroacétate de cuivre (II) dihydraté est dimère et que le trichloroacétate de cuivre (II) tétrahydraté est monomère. Le dichloroacétate de cuivre (II) tétrahydraté représente un cas intermédiaire. La décomposition de ces composés dans l'azote a été suivie par thermogravimétrie et analyse thermique différentielle, en analysant simultanément les produits de décomposition. Le principal produit organique formé lors de la décomposition thermique des mono et dichloroacétates est l'acide chloroacétique correspondant; le produit solide inorganique est le chlorure de cuivre (I). La décomposition thermique du trichloroacétate fournit le chlorure de cuivre (II) et un mélange d'acide trichloracétique et de chlorure trichloroacétylique.

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(II). , (II) , (II) - . (II) . , , . , - , , (I). (II) (II) .

     

Catalytic activity of transition metal silicides in hydrogen oxidation

The catalytic activity of transition metal silicides in H₂ oxidation is much higher compared to metal-like carbides, which can be due to the lower electronegativity of silicon compared to carbon.

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, , .

     

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) . , . , -.

     

Recombination of polyatomic ester peroxy radicals in solution

Termination rate constants of peroxy radicals of seven polyatomic esters in benzene and perflouorooctane media have been measured by pulse photolysis. Recombination of peroxy radicals for all esters examined proves to be diffusion controlled. Reactivity of peroxy radicals in the termination reaction grows with increasing number of ester groups.

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. . .

     

Combined thermoanalytical-mass-spectrometric investigation of crupodexR dextranomer

A cross-linked dextranomer, which is used as a wound drying and cleansing powder (Crupodex^R), has been investigated by several thermoanalytical methods. First the TG, DTG and DTA characteristics were studied and compared with those of another product (Debrisan^R), marketed earlier. The TG curves were also used for the examination of water uptake and the drying process. The traces of organic solvents (mainly ethanol) remaining from the manufacturing process were studied with a quadrupole mass-spectrometer coupled to a derivatograph. From the results of these experiments, several conclusions were drawn about the mechanism of water and solvent uptake.

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Zusammenfassung Crupodex^R-Puder, ein vernetztes Dextranomer zum Trocknen und Säubern von Wunden, wurde mittels einiger thermoanalytischer Methoden untersucht. Zuerst wurden die TG, DTG und DTA Charakteristiken betrachtet und mit denen eines schon früher auf den markt gekommenen Produktes (Debrisan^R) verglichen. Die TG-Kurven wurden auch zur Untersuchung der Wasseraufnahme- und Trocknungsprozesse verwendet. Aus dem Produktionsprozeß verbliebene Lösungsmittelreste — hauptsächlich Ethanol — wurden mit einer Instrumentenanordnung Quadrupolmassenspektrometer-Derivatograph bestimmt. Mittels dieser Ergebnisse konnten einige Schlußfolgerungen betreffs des Mechanismus der Wasser- und Lösungsmittelaufnahme getroffen werden.

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

     

Formation of nitrogen oxides during the oxidation of nitromethane on copper-chromium catalyst

Principles of the oxidation of nitromethane on a 30% CuCr₂O₄/-Al₂O₃ catalyst over the temperature range from 210 to 485 °C have been studied. The conversion of bound nitrogen to oxides depends on initial concentrations of nitromethane and oxygen in the range corresponding to the complete conversion of nitromethane (350–485 °C). The composition of oxidation products is determined by the oxygen to nitromethane ratio.

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30% CuCr₂O₄/-Al₂O₃ 210–485°C. (350–485°C) . , .

     

Retrieval of thermodynamic properties of M(OH)2 (M=Mn,Ni and Cd) phases from hydrothermal phase equilibria of MO-H2O systems

The standard thermodynamic properties of M(OH)₂ (M=Mn, Ni and Cd) solid phases have been retrieved using a graphical approach based on the already reportedP vs. T curves obtained from hydrothermal studies of MO-H₂O systems. This approach avoids the use of heat capacity effects. The values retrieved by this modified approach are in good agreement with the calorimetric values.

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Zusammenfassung Basierend auf unlängst beschriebenen, aus hydrothermischen Untersuchungen von MO-H₂O Systemen gewonnenenp-T Kurven wurden mittels einer graphischen Näherung die thermodynamischen Standardeigenschaften von M(OH)₂ Festphasen (M=Mn, Ni und Cd) bestimmt. Dieses Verfahren umgeht den Gebrauch von Wärmekapazitätseffekten. Die durch dieses modifizierte Verfahren erhaltenen Werte stehen in guter Übereinstimmung mit den kalorimetrischen Werten.

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- , O-H₂O, M(OH)₂, M=, . . .

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The authors express their grateful thanks to Prof. V. Venkatachalapathy, Director of the Minerological Institute, for his encouragement during the course of this work.     

Application of deuteroacetonitrile to characterize surface aprotic acidic centers on heterogeneous catalysts

Correlations between adsorption heats CD₃Cn and CO ( and Q_CO) for the cations of Ca-, Mn-, Co-, Ni- and CrNaY zeolites have been studied. Isosteric ranging within determined by IR spectroscopy are proportional to Q_CO.

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CD₃CN CO( Q_CO) Ca-, Mn-, Co-, Ni- CrNaY. , , - Q_CO.

     

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- . , , . . , .

     

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 .

     

Influence of dehydration conditions on the state of nickel in Y-zeolites

Infrared spectroscopic studies have revealed that the presence of water in dehydrated samples of Ni-containing Y-zeolites rises the number of nickel cations accessible for CO adsorption in NiNH₄Y and leads to their partial screening in NiNaY.

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- , CO NiNH₄Y NiNaY.

     

Kinetics of solid polypropylene oxidation inhibited by aromatic nitrons

C-phenylcarbamoyl-N-phenylnitron and C(2,4-di-tert-butyl-3-hydroxyphenylcarbamoyl)-N-(p-di-methylaminophenyl) nitron inhibit the oxidation of solid polypropylene. In this case the nitrons studied demonstrate properties of polyfunctional inhibitors: they interrupt oxidation chains by chains by reactions with alkyl and peroxyl radicals.

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C--N- C-(2,4----3-)-N-(-) . , .

     

DTA equipment for investigations of liquid-phase reactions

An exact kinetic evaluation is practicable in homogeneous systems if no gradients of concentration or temperature appear. With permanent stirring, the measurement of the real difference temperature and absolute temperature at a suitable heating rate allows the application of liquid-phase DTA in the range between 170 and 380 K. For the examination of air — and moisture-sensitive substance too, equipment has been developed, that operates under inert conditions.

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Zusammenfassung Eine exakte kinetische Auswertung kann in homogenen Systemen durchgeführt werden, wenn keine Konzentrations- oder Temperaturgradienten erscheinen. Unter ständigem Rühren gestattet die Messung der wahren Temperaturdifferenz und der absoluten Temperatur bei einer entsprechenden Aufheizgeschwindigkeit den Einsatz der Flüssigphasen-DTA im Bereich zwischen 170 und 380 K. Für die Untersuchung von luftund feuchtigkeitempfindlichen Substanzen wurde ebenfalls ein Gerät entwickelt, das unter inerten Bedingungen arbeitet.

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, . , 170–380 . , , .

     

Conversion of dehydrolinalyl acetate in catalytic hydrogenation on metals

Low selectivity of dehydrolinalyl acetate (DeHLA) hydrogenation into linalyl acetate and ester group detachment are predicted in accordance with quantum-chemical data obtained for its homologue dimethyl ethynyl carbinol acetate. Experimental data are confirmed by theoretical calculations. DeHLA hydrogenation produces a variety of products.

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, - . . .

     

Mechanism of methane photooxidation on V/SiO2 catalyst

CH₄ photooxidation on V/SiO₂ catalyst in the presence of gaseous oxygen has been studied by the mass-spectometric method. It has been established that CO₂ forms due to the interaction of CH₄ with surface oxygen anions bonded to vanadium ions. Photodecomposition of V⁴⁺O ₂ ^– species formed in O₂ adsorption on reduced vanadium ions leads to the reoxidation of the latter.

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- CH₄ V/SiO₂ . , CO₂ CH₄ , . V⁴⁺O ₂ ^– O₂ , .