Decomposition of ammonia on rhenium II. Nitrogen adsorption on rhenium

Field emission microscopy and thermal desorption studies of nitrogen adsorption on a monocrystal tip and a polycrystalline rhenium wire indicate the formation of molecular () and dissociative () forms of adsorption. Adsorption-desorption characteristics have been measured.

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. - - , - .

     

Overall kinetic model for oscillating catalytic oxidation of methanol

An overall kinetic model for the deep catalytic oxidation of methanol is presented. It is based on the balance of chemical species and could described self-sustained oscillations.

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. .

     

Kinetics and mecahnism of oxidation of benzoins by peroxydisulfate catalyzed by Ag(I)

The kinetics of Ag(I) catalyzed oxidation of benzoin and four substituted benzoins by peroxydisulfate have been investigated in 30 vol. % acetic acid-water mixture at constant ionic strength. The parameters of Arrhenius and transition state theories have been computed. The rate laws are explained on the basis of a free radical mechanism.

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, Ag(I), (30 .%) . . - .

     

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 .

     

Thermal decomposition kinetics of vanillidene anthranilic acid complexes of cobalt(II), nickel(II), copper(II) and zinc(II)

The thermal decomposition of cobalt(II), nickel(II), copper(II) and zinc(II) complexes of the Schiff base vanillidene anthranilic acid was studied by TG. The chelates show somewhat similar TG plots when heated in an atmosphere of air. Thermoanalytical data (TG and DTG) of these chelates are presented in this communication. Interpretation and mathematical analysis of these data and evaluation of order of reaction, the energy and entropy of activation based on the differential method employing the Freeman-Carroll equation, the integral method using Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation are also given. On the basis of experimental findings in the present course of studies, it is concluded that the relative thermal stability of vanillidene anthranilic acid chelates can be aligned as Co(II)Ni(II)>Zn(II)>Cu(II).

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Zusammenfassung Die thermische Zersetzung von Cobalt(II)-, Nickel(II)-, Kupfer(II)- und Zink(II)-Komplexen der Schiffschen Base Vanillidenanthranilsäure wurde thermogravimetrisch untersucht. Die Chelate zeigen in einer Luftatmosphäre ähnliche TG-Kurven. Thermoanalytische Daten (TG and DTG) dieser Chelate werden mitgeteilt, interpretiert und mathematisch analysiert. Ebenfalls werden die Reaktionsordnung und die Energie und Entropie der Aktivierung nach der von Freeman-Carroll angewandten differentiellen Methode, nach der auf der Coats-Redfern-Gleichung basierenden integralen Methode und nach der die Horowitz-Metzger Gleichung benutzenden Näherungsmethode bestimmt. Aus den Befunden wird geschlossen, dass die thermische Stabilität von Vanillidenanthranilsäure-Chelaten in der Reihenfolge Co(II)Ni(II)>Zn(II)> >Cu(II) abnimmt.

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, , . - . . , , - , , - . , Ni>Zn>u.

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We thank Dr. C. P. Savariar, Professor of Chemistry, University of Calicut for encouragement. We are also grateful to the University Grants Commission for the award of a Senior Research Fellowship to one of us (J. C).     

Vapor phase oxidation of methylpyridines on zeolite catalysts

It has been established that zeolites containing Pd and Cu ions catalyze the vapor phase oxidation of methylpyridines. In oxidation of 2-methylpyridine on PdCuNa-mordenite at 375 °C the yield of 2-pyridinecarbaldehyde is 40 % of its theoretical values.

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, , Pd Cu, . 2- PdCuNa- 2- 375°C 40% .

     

Catalytic oxidation of carbon monoxide by oxygen and nitrogen oxides on a copper-chromium oxide catalyst

The kinetics of CO oxidation by O₂, NO and NO₂ has been studied on a Cu–Cr-oxide catalyst. A comparison with the kinetics of the CO–N₂O interaction has been made. In all cases the reaction rate is described by the equation:r=k p _CO ¹ P _0x ⁰ . The oxidation of CO has been studied in the presence of different oxidants in the reaction mixture.

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CO , . CO . CO . CO .

     

Adsorption heats of acrolein and acrylic acid on promoted V?Mo?O catalysts

Adsorption heats of acrolein and acrylic acid on promoted V–Mo–O catalysts for selective oxidation of acrolein have been measured by the calorimetric technique. It has been established that modification changes the energy characteristics of the interaction of acrolein and acrylic acid with catalyst surface.

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- . , .

     

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.     

The evaporation of potassium from phlogopite

The evaporation of potassium from phlogopite was investigated by roasting phlogopite with different chemical reagents. The possible reactions between reactants and the sample at different temperatures were investigated by thermogravimetry. Gypsum, calcite, sodium chloride, activated carbon, calcium chloride and fluoride were used as chemical reactants. Similar tests were carried out by batch experiments using muffle furnace and tube oven and finally the sample mixtures were heated in a vacuum. The use of a vacuum enabled an almost complete extraction of potassium in solid state at the lowest temperature so far investigated. The structure of phlogopite was shown to be destroyed by raising the temperature. The extraction of potassium from feldspar, a sample from Lohja, Finland was also investigated.

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Zusammenfassung Beim Abrösten von Phlogopit mit verschiedenen chemischen Stoffen wurde das Verdampfen von Kalium aus Phlogopit untersucht. Die möglichen Reaktionen zwischen der Probe und der Reaktionspartnern bei verschiedenen Temperaturen wurden mittels Thermogravimetrie untersucht. Als Reaktant wurden Gips, Kalzit, Natriumchlorid, Aktivkohle, Kalziumchlorid und -fluorid verwendet. Ähnliche Untersuchungen wurden in Reihenexperimenten mittels Muffel- und Röhrenofen und letztlich durch Erhitzen der Proben im Vakuum durchgeführt. Die Anwendung von Vakuum ermöglicht bei den niedrigsten der angewendeten Temperaturen einen fast vollständigen Auszug des Kaliums aus dem Feststoff, Durch Erhöhen der Temperatur wurde die Struktur von Phlogopit nachweislich zerstört. Die Extraktion von Kalium aus einer Feldspatprobe aus Lohja, Finnland, wurde ebenfalls untersucht.

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. . , , , , . , , . , , . , . //.

     

Thermal decomposition kinetics of thorium(IV) chelates of two naphthol dyes

The thermal decomposition of thorium(IV) chelates of 1-(2-fluorenylazo)-2-naphthol ando-carboxyphenylazo-2-naphthol was studied by TG. Thermoanalytical data (TG and DTG) of these chelates are presented in this communication. Interpretation and mathematical analysis of these data and evaluation of order of reaction, the energy and entropy of activation based on the differential method employing the Freeman-Carroll equation, the integral method using Coats-Redfern equation and the approximation method using the Horowitz-Metzger equation are also given. On the basis of experimental findings in the present course of studies the relative thermal stabilities of the thorium chelates can be given as [Th(FAN)₂(NO₃)₂]>[Th(CPAN)₂(H₂O)₂]2H₂O.

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Zusammenfassung Die thermische Zersetzung von Thorium(IV)-Chelaten von 1-(2-Fluorenylazo)-2-naphthol undo-Carboxyphenylazo-2-naphthol wurde thermogravimetrisch untersucht. Thermoanalytische Daten (TG und DTG) dieser Chelate werden angegeben und interpretiert. Reaktionsordnung sowie Aktivierungsenergie und -entropie wurden nach der differentiellen Methode unter Anwendung der Freeman-Carroll-Gleichung, nach der integralen Methode unter Verwendung der Coats-Redfern-Gleichung und nach der Näherungsmethode von Horowitz-Metzger bestimmt. Für die relative thermische Stabilität wird die Reihenfolge [Th(FAN)₂(NO₃)₂]>[Th(CPAN)₂(H₂O)₂]2H₂O angegeben.

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1(2- )-2- 1(2-)-2- --2-, . , . -, , - -. .

     

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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.

     

Studies on coordination compounds vii,chromatographic, thermoanalytical and spectroscopic studies on thermal decomposition of cadmium(II) and lead(II) salicyl-aldoximates

On the basis of decomposition temperatures and infrared spectra, cadmium(II) and lead(II) bissalicylaldoximates were considered to havetrans andcis structures, respectively.In the first stage bis(salicylaldoximato)cadmium(II) decomposes thermally like bis(salicylaldoximato)lead(II), with one ligand molecule leaving, but the intermediate is unstable and immediately decomposes further. The oxidation of the end- product is a rapid, exothermic reaction, probably catalyzed by cadmium metal. The mass spectrum of (C₇H₆O₂N)₂ Cd points to a different decomposition scheme than that elucidated through the pyrolysis decomposition products. This may be due to a catalytic effect of the ionization chamber. The thermal properties of (C₇H₅O₂N) Cd support the preceding views.TG curves showed the decompositions of mono(salicyl-aldoximato) lead(II) and the intermediate of bis(salicyl-aldoximato) lead(II) to be similar. The mass spectra of the chelates confirmed the formation of the same polymer (m/e 222) in both decompositions. Only the mass spectrum of (C₇H₅O₂N)Pb exhibited the molecular peakm/e 343. The decomposition schemes of the lead(II) salicylaldoximates were therefore elucidated more exactly. The metallic lead seems not to catalyze the oxidation of the organic part.

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Zusammenfassung Aufgrund der Zersetzungstemperatur und der Infrarotspektrum werden Cadmium(II)- und Blei(II)-bisalicylaldoximate als Verbindungen mit trans- bzw. cis-Struktur angesehen. Im ersten Schritt wird Bis-(salicylaldoximato)-blei(II) unter Abspaltung eines Ligandmoleküls zersetzt, die Zwischenverbindung ist jedoch nicht stabil und zersetzt sich sofort weiter. Die Oxydation des Endproduktes ist eine schnelle exotherme, wahrscheinlich durch metallisches Cadmium katalysierte Reaktion. Das Massenspektrum von (C₇H₆O₂N)₂ Cd weist auf ein Zersetzungsschema hin, das sich von dem aus den pyrolytischen Zersetzungsprodukten abgeleiteten unterscheidet. Dies ist möglicherweise auf einen katalytischen Effekt der Ionisationskammer zurückzuführen. Die thermischen Eigenschaften von (C₇H₅O₂N)Cd unterstützen diese Auffassungen. Aus den TG-Kurven ist zu ersehen, dass die Zersetzungen von Mono(salicylaldoximato)-blei(II) und des Zwischenproduktes von Bis(salicylaldoximato)-blei(II) ähnlich sind. Massenspektren der Chelate bestätigen die Bildung des gleichen Polymers (m/e 222) bei der Zersetzung beider Verbindungen. Nur im Massenspektrum von (C₇H₅O₂N)Pb tritt der Molekularpeak (m/e343) auf. Die Zersetzungsschemata der Salicylaldoximate von Blei(II) sind deshalb genauer aufgeklärt. Metallisches Blei scheint die Oxydation der organischen Komponente nicht zu katalysieren.

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- , , , - - . , . , , . - - , , . . . - - . - 222. - 343. . , .

     

Ethylene hydroformylation over a nafion-supported rhodium catalyst

Ethylene hydroformylation over a Nafion-supported rhodium catalyst has been studied under atmospheric pressure in the temperature range of 100–135 °C, using the transient response method.

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, , 100–135°C, .

     

Testing the photocatalytic activity of cyanogen-and thiocyanogen-based inorganic polymers

The photocatalytic properties of some cyanogen-and thiocyanogen-based inorganic polymers, such as paracyanogens containing different metals (Hg, Ag, Cu), polythiocyanogens of different iodine contents, polycyanogen and poly (cyanogenthiocyanate), have been tested in two systems. Cu-containing paracyanogen and the iodine-poor polythiocyanogens catalyze the photoreduction of methylviologen under visible light, furthermore the Cu-containing paracyanogen catalyzes the photoreduction of water to hydrogen under UV irradiation.

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, , , , (Hg, Ag, Cu), , (), . , , , , , , -.

     

Oxidation of ethanol on platinum/alumina and copper oxide catalysts

The oxidation of ethanol on CuO, CuO/Al₂O₃ and Pt/Al₂O₃ catalysts has been studied at various concentrations of alcohol, oxygen and water vapor in the reaction mixture. The reaction order and activation energies have been determined for both complete and partial oxidation processes. A consecutive oxidation scheme is suggested.

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CuO, CuO/Al₂O₃ Pt/Al₂O₃ , . . .

     

Liquid-phase hydrogenation on new AlPO4?SiO2 supported rhodium catalysts

The liquid-phase catalytic hydrogenation of various organic compounds was carried out using new rhodium catalysts supported on AlPO₄–SiO₂ (2080 wt. %) system, in methanol as solvent, under low hydrogen pressure (0.55 MPa) and at 293 K. Neither alkene isomerization nor hydrogenolysis products were detected in any of the cases.

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AlPO₄–SiO₂ (2080 . %), , , (0,55 MPa) 293 . , .

     

Chemical composition of solid LixNi1?xO solutions

A study of oxygen isotope exchange and Auger spectra has shown the presence of lithium oxide (dissociating when heated in vacuum) on the surface of solid Li_xNi_1–xO solutions.

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( ) . Li_xNi_1–xO.

     

ESR studies of slow relaxations of the rate of sulfur dioxide oxidation on vanadium catalyst

Slow changes in the rate of the title reaction are shown to be due to pahse transformations of the active component, in particular, the agglomeration or crystallization of vanadyl complexes. The possible mechanism of these phenomena is discussed.

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, , , . .