Ammonia adsorption on the surface of Ni(II)-, Cu(II)-and Co(II)-phthalocyanine

Ammonia adsorption on the surface of Ni(II)–, Cu(II)- and Co(II)-phthalocyanine has been studied by means of reflection spectroscopy. Ammonia bonds to the metal ions in the surface layers of phthalocyanines preferably in octahedral coordination. In the case of Co(II)-phthalocyanine the trivalent state of cobalt is stabilized. Close similarity between coordination in liquid phase and adsorption on the surface is observed.

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- , , . , - . Co (II)- . .

     

Promoting effect of sodium on catalytic and adsorption properties of Fe?Mn catalysts for CO hydrogenation

It has been established that alkali metal (sodium) additives affect both texture and adsorption properties of Fe–Mn catalysts for olefin synthesis thus promoting their catalytic properties.

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() , Fe–Mn , .

     

Kinetic measurements on polymers — Applications and limits

A modern kinetic evaluation method for nonisothermal reactions measured with TG or DSC is presented. The obtained kinetic data are the basis for computation of a reaction process under any condition, e.g. isothermal or adiabatic. The measurements were performed on a Mettler TA3OOO system with built-in evaluation software. Mainly the following reactions are discussed: polyaddition of an epoxy premix and pyrolysis of polystyrene. To judge the reliability of the results, 4 check procedures are recommended.

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Zusammenfassung Es wird eine moderne kinetische Auswertungsmethode für durch TG oder DSC verfolgte nichtisotherme Reaktionen vorgestellt. Die erhaltenen kinetischen Daten stellen die Basis der Berechnung der Reaktionsprozesse unter jeder, z.B. isothermer oder isobarer Bedienung dar. Die Messungen wurden mit dem Mettler-System TA3000 mit Auswertungs-software ausgeführt. In erster Linie werden die folgenden Reaktionen diskutiert: Polyaddition eines Epoxy-Vorgemisches, Pyrolyse von Polystyrol. Zur Beurteilung der Zuverlässigkeit der Ergebnisse werden 4 Testverfahren empfohlen.

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, . - , , . TA 3000 . - . .

     

Applications of evolved gas analysis to the study of inorganic materials and processes

The value and versatility of evolved gas analysis (EGA) are described by the use of selected recent examples. Three particular attributes of EGA methods are stressed. The first, specificity, reveals the frequent necessity of using EGA to substantiate conclusions based upon other thermal analytical techniques e.g. thermogravimetry (TG) or differential thermal analysis (DTA). To this end, the weaknesses of other thermal analytical techniques for the analysis of asbestos is reveladed by EGA. However, because of EGA's specificity it could be used for this purpose. Second, sensitivity, is demonstrated by use of mass spectrographic EGA techniques to study the kinetics of the early stages for the thermal decomposition of InP. This is further illustrated by qualitative assessments of the effects of various films in contact with the InP upon its thermal decomposition. A third advantage of EGA, insensitivity to experimental perturbations arising from an external magnetic field gradient, allows for its use to study the effects of such field gradients with less ambiguity than occurs with TG or DTA. This is shown for studies of the reduction of NiO, Fe₂O₃, and Co₃O₄ by H₂.

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Zusammenfassung Die Bedeutung und die Vielseitigkeit der EGA wird anhand ausgewählter neuerer Beispiele beschreiben. Drei besondere Merkmale der EGA-Methoden werden hervorgehoben. Die erste, die Spezifität, wird der häufigen Notwendigkeit zur Anwendung der EGA gerecht, um auf andere thermische Analysentechniken, z.B. auf TG oder DTA beruhende Schlussfolgerungen zu stützen. Dies wird demonstriert, indem gezeigt wird, dass die EGA die Unzulänglichkeiten anderer thermischer Verfahren zur Analyse von Asbest in Erscheinung treten lässt und infolge ihrer Spezifität für diesen Zweck geeignet ist. Das zweite Merkmal, die Empfindlichkeit, wird durch Anwendung der massenspektrographischen EGA-Technik zur Untersuchung des frühen Stadiums der thermischen Zersetzung von InP demonstriert. Dies wird weiter durch qualitative Beurteilung der Wirkungen von verschiedenen in Kontakt mit dem InP befindlichen Filmen auf dessen thermische Zersetzung illustriert. Ein dritter Vorteil der EGA is deren Unempfindlichkeit gegenüber von äusseren magnetischen Feldgradienten herrührenden experimentellen Störungen, wodurch diese Methode bei der Untersuchung der Wirkungen solcher Feldgradienten eindeutigere Ergebnisse als die TG oder DTA liefert. Dies wird anhand von Untersuchungen der Reduktion von NiO, Fe₂O₃ und Co₃O₄ mit H₂ gezeigt.

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//, . , , , : , , . . , - InP. , In P . , . . , .

     

A heterogeneous oscillator of the Belousov-Zhabotinskii-type in the bromate-malonic acid-cerium system induced by commercial ion-sensitive electrodes

In the title system we may induce oscillations under very special conditions near the borderline of the oscillating region by introducing ion-sensitive electrodes in the reaction mixture. The effect is caused by changing the conditions for oxygen transport via interface.

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, , - . .

     

H/D isotope exchange during ethylene adsorption on a clean iridium surface

The H/D isotope exchange of C₂D₄ adsorbed on an Ir surface has been studied by the thermal desorption method. Only deuterium atoms detached from the molecule after its adsorption on the metal surface participate in the exchange with a relatively high rate.

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H/D C₂D₄, Ir, . , , .

     

Some peculiarities in regeneration of zeolite-containing cracking catalysts by carbon dioxide

Catalytic properties of Mn and La oxides that are acceptors of CO₂ in regeneration of zeolite-containing cracking catalysts in the presence of carbon dioxide have been studied. Regeneration rate of coked catalysts by carbon dioxide in the presence of Mn and La significantly increases. During regeneration, coke oxidation to Co and redistribution of hydrogen in carbonaceous fragments take place to produce methane and hydrogen. Activation energy of methane and hydrogen formation equals 46 kcal/mol. Variation of activation energy with temperature is typical for Co formation.

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, Mn La . CO . 46 /. CO .

     

Power rate law in kinetics of adsorption processes on exponentially inhomogeneous surfaces

A power rate equation is derived based on the dependences which characterize the adsorption equilibrium on exponentially inhomogeneous surfaces. It is established that the power of the rate equation is temperature-dependent. The latter is used for the determination of the energy and entropy factors on which the process rate depends.

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, - , . , , , .

     

Kinetics of the oxidation of aliphatic ketones by thallic salts in sulfuric acid medium

: - - 1–3 .

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With increasing partial pressure of molecules in atomic-molecular mixtures, the yield and intensity of radical-recombination luminescence of inorganic luminophors increase by 1–3 orders of magnitude.

     

Electron spectroscopic investigation of oxygen desorption and dissolution in silver

The behavior of oxygen adsorbed on epitaxial silver films has been studied by electron spectroscopy in the temperature range of 110–610 K. A method is proposed for determining whether desorption or dissolution in the bulk of silver is responsible for the observed decrease of the surface adsorbate concentration. As found, at T=300 K adsorbed oxygen may readily diffuse into the bulk of silver.

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110–610 , . , , — , . , >300 .

     

Aniline hydrogenation in the presence of alumina-supported rhodium under hydrogen pressure

Aniline hydrogenation over 5% Rh/Al₂O₃ in water and an universal queous buffer has been studied at temperatures of 323–363 K and pressures of 2.02–10.10 MPa.

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5% Rh/Al₂O₃ 323–363 K 0,5–10,10 .

     

Catalytic properties of Cu(Acac)2 anchored to shock-compressed MgO and MgF2 supports

Catalytic properties of Cu(Acac)₂ anchored to shock-compressed MgO and MgF₂ in model reactions of hydrogenation and isomerization of heptene-1 have been studied. It is shown that by changing the defect structure of the support via shock treatment at various temperatures, the activity and selectivity of metal complex catalysts can be affected.

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Cu(Acac)₂, MgO MgF₂ -1. , , , .

     

Interaction between catalysts for ammonia synthesis and oxygen

Reversible poisoning of the catalysts for ammonia synthesis by oxygen has been used to eliminate the pyrophoric nature of the reduced catalysts via their treatment by the mixtures of nitrogen, hydrogen or helium with oxygen at catalysis temperatures. Kinetic studies of oxygen sorption, catalyst structure, activity and stability to the secondary oxidation of the samples partially oxidized at various temperatures have revealed that the optimum temperatures to eliminate the pyrophoric effect are 673–773 K.

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, . , , , 673–773 K.

     

Homogeneous catalysts for dioxygen evolution from water. Oxidation of water by trisbipyridylruthenium(III) in the presence of metallophthalocyanines

Catalytic action of sulfonated phthalocyanines of Cr, Mn, Ni, Al, Cu, Zn, Fe and Co and of Co-tetra(sulfophenyl)porphine in the oxidation of water by Ru(bpy) ₃ ³⁺ , has been studied. The most efficient catalysts appear to be cobalt and iron complexes. A possible relation between catalytic and some redox properties of the compounds studied is discussed.

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Cr, Mn, Ni, Al, Cu, Zn, Fe Co, џ Co- () , Ru(bpy) ₃ ³⁺ . , . , .

     

Regularities of oxygen chemisorption on coked exchanged Y zeolites

Two types of paramagnetic centers have been revealed in the composition of coke formation products on zeolite surfaces. The oxygen effect on the paramagnetic properties of these systems is determined by the concentration of these centers, which in turn characterizes the structure of coke precursors on their surface.

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, . , , , .

     

Temperature-programmed desorption of hydrogen from Fe?Ni/Al2O3 catalysts

The aim of this paper is to investigate temperature activated hydrogen adsorption on Fe–Ni/Al₂O₃ catalyst and for the sake of comparison also on monometallic systems Fe/Al₂O₃ and Ni/Al₂O₃.

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- Fe–Ni/Al₂O₃ , , Fe/Al₂O₃ Ni/Al₂O₃.

     

ESR studies of coke formation on zeolite catalysts for methanol conversion

Pentasil type zeolite catalysts with different SiO₂/Al₂O₃ ratios carbonized during methanol conversion at 380–420°C have been studied by the ESR method. Factors responsible for the formation of condensed coke structures on their surface have been established. SiO₂/Al₂O₃, 380–420°C. , .