Solid state reactions between nickel(II) sulphide and oxides of manganese and iron

Thermogravimetry and differential thermal analysis have shown that, when nickel(II) sulphide and manganese or iron oxides are heated together, several reactions occur depending on the molar ratio of the reactants. Detailed examinations of these reactions have shown that there are a number of intermediate stages, including the formation of sulphates.

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Zusammenfassung Thermogravimetrie und Differentialthermoanalyse zeigen, daß bei gemeinsamer Erhitzen von Nickel(II)-Sulfid und Manganoder Eisenoxiden, in Abhängigkeit von dem Molarverhältnis der Reaktionspartner verschiedene Reaktionen stattfinden. Das eingehende Studium dieser Reaktionen zeigte das Auftreten einer Anzahl Zwischenstufen, darunter auch die Bildung von Sulfaten.

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Résumé On montre par thermogravimétrie et analyse thermique différentielle que plusieurs réactions peuvent se produire suivant les rapports molaires des constituants lorsque l'on chauffe du sulfure de nickel(II) avec des oxydes de manganèse ou de fer. L'étude détaillée de ces réactions a mis en évidence un certain nombre d'étapes intermédiaires, avec formation de sulfates.

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, (II) , . , , .

     

Mechanism of o-xylene conversion on magnesium modifications of Y zeolite

o-Xylene conversions has been investigated in the presence of MgNaY zeolites with different Si/Al ratios and degrees of exchange. Disproportionation proceeds to a higher degree than does isomerization. The distribution of reaction products is attributed to geometric factors. The results are in agreement with a monomolecular mechanism of isomerization.

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- MgNaY Si/Al . , , . . .

     

Cyclohexane photooxygenation by air oxygen in CH2Cl2 in the presence of chromium oxocomplex-iodosylbenzene system

Cyclohexane is oxidized by air oxygen in CH₂Cl₂ solution to yield cyclohexanol, cyclohexanone and cyclohexyl chloride when irradiated by light (>310 nm) in the presence of (Bu₄N)₂CrO₄ or (Bu₃SnO)₂CrO₂. The addition of PhIO greatly accelerates the reaction and increases the yield of products. The reaction mixture contains neither cyclohexanol nor cyclohexanone when the photoreaction in the presence of the Cr(VI)–PhIO system is carried out in argon atmosphere. Hence neither iodosylbenzene nor oxochromium compounds can be oxygen atom donors in alkane oxygenation. The accelerating effect of iodosylbenzene may be due to the enhanced oxidizing power of photo-excited oxochromium species when coordinated to iodosylbenzene.

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CH₂Cl₂ , , (>310 ) (Bu₄N)₂CrO₄ (Bu₃SnO)₂CrO₂. PhIO . Cr(VI)–PhIO , , . , ( ) . .

     

Catalytic properties of V?Mo?O systems in acrolein oxidation

Catalytic properties of V–Mo–O systems have been studied in acrolein oxidation. When catalysts are activated in reaction mixtures at 673 K, then a solid solution of molybdenum oxides in reduced vanadium oxides is formed, which is responsible for deep oxidation. Also, several compounds are produced, which by their activity and selectivity to acrylic acid formation are arranged in the sequences VMo₃O₁₁VMo₂O_8+x>V₆Mo₄O₂₅, and VMo₃O₁₁>VMo₂O_8+xV₆Mo₄O₂₅, respectively.

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V–Mo–O . 673 K , , , : VMo₃O₁₁VMo₂O_8+x>V₆Mo₄O₂₅, : VMo₃O₁₁>VMo₂O_8+xV₆Mo₄O₂₅.

     

Kinetics of methane conversion over microspherically grained nickel-alumina catalysts

Kinetics of methane conversion in a fluidized bed of microspherically grained nickel-alumina catalyst has been studied at pressures from 0.3 to 3.1 MPa. The rate equation shows that the reaction is inhibited by H₂O.

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0,3 3,1 . , .

     

Effect of carbon support on the hydrogen sorption of platinum

The hydrogen sorption of carbon-supported platinum catalysts, studied by the potentiodynamic method, differs significantly from that of unsupported platinum. The difference depends on the preparation method and on the nature of the support. Possible explanations are suggested as (i) some kind of interaction between metal and support atoms during impregnation, (ii) high dispersity (amorphous structure) and (iii) hydrogen spillover onto the carbon support.

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Pt/C, . . (I) , (II) ( ), (III) .

     

Calculation of thermal effects in DTA

By considering that the temperature of the end of the thermal effect and the return of the thermal curve to the baseline do not coincide new calculation methods for the thermal effect become possible. Both the integral value of the thermal effect and its distribution over temperature may be calculated by processing only that part of the DTA curve which corresponds to the temperature interval of the transformation.It is demonstrated on the examples of non-variant transformation and transformation with an even distribution of the thermal effect over the temperature interval of the transformation that, under certain assumptions, the values of the thermal effect calculated by the suggested method and by the area of the peak are identical.

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Zusammenfassung Bei Berücksichtigung, daß die Temperatur des Endes des thermischen Effekts und die Rückkehr der thermischen Kurve zur Grundlinie nicht zusammenfallen, werden neue Methoden zur Berechnung des thermischen erschlossen. Sowohl der Integralwert des thermischen Effekts, als auch seine Verteilung in dem Temperaturbereich können durch Behandlung ausschließlich desjenigen Teils der DTA-Kurve berechnet werden, welcher dem Temperaturbereich der Umwandlung entspricht.Anhand von Beispielen der nicht-varianten Transformation und der Transformation mit gleichmäßiger Verteilung des thermischen Effekts im Temperaturbereich der Umwandlung wurde gezeigt, daß — unter gewissen Voraussetzungen — die Werte des durch die vorgeschlagene Methode und des aus der Peakfläche berechneten thermischen Effekts identisch sind.

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Résumé En considérant le fait que la température de la fin de l'effet thermique et le retour à la ligne de base de la courbe ATD ne coïncident pas, on a développé de nouvelles méthodes du calcul de l'effet thermique. La valeur intégrale de l'effet thermique ainsi que sa distribution dans l'intervalle de températures peuvent être calculées en ne considérant que la partie de la courbe ATD qui correspond à l'intervalle de température de la transformation.A l'aide d'exemples de transformations invariantes et de transformations à distribution uniforme de l'effet thermique dans l'intervalle de températures de la transformation, on a montré qu'avec certaines hypothèses, les valeurs de l'effet thermique calculées par la méthode proposée et à partir des surfaces des pics, sont identiques.

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. , -, . , , .

     

Oxygen diffusion in Me2O?V2O5 melts

The anodic and cathodic polarization of a platinum electrode in K₂O–V₂O₅ melt have been studied. The dissolved oxygen is shown to be ionized. Diffusion coefficients of oxygen in K₂O–V₂O₅ and Na₂O–V₂O₅ melts at various temperatures and K/V ratios are presented.

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K₂O–V₂O₅. , . K₂O–V₂O₅, Na₂O–V₂O₅ K/V.

     

Heats of adsorption of CO2 and NH3 on natural mordenites

The heats of adsorption of CO₂ and NH₃ were studied for sodium, lithium, calcium and decationized forms of natural mordenites. The exchange of Na⁺ for Ca²⁺ leads to increasing adsorption heats at low coverages. For CO₂ the region of elevated heats corresponds to the formation of Ca²⁺ ... CO₂ adsorption complexes. Two molecules of NH₃ probably interact with each Ca²⁺ ion (or with the Li⁺ ions in Li-mordenite). The heats of adsorption of NH₃ on decationized mordenite are much higher than those on calcium mordenite.

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Zusammenfassung Adsorptionswärmen von CO₂ und NH₃ an der Na-, Li-, Ca- und dekationisierten Form von natürlichem Mordenit wurden bestimmt. Der Austausch von Na⁺ gegen Ca²⁺ führt zu einer Erhöhung der Adsorptionswärmen bei geringen Bedeckungen. Bei CO₂ erfolgt im Bereich hoher Adsorptionswärmen die Bildung des Adsorptionskomplexes Ca²⁺ ...CO₂. Mit jedem Ca²⁺-Ion (bzw. Li⁺-Ion im Li-Mordenit) treten wahrscheinlich zwei NH₃-Moleküle in Wechselwirkung. An dekationisiertem Mordenit sind die Adsorptionswärmen von NH₃ höher als an Ca-Mordenit.

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, , . . Ca²⁺ ... CO₂. B , , ( -). , -.

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The authors would like to thank Dr. I. A. Belitsky for supplying the sample of natural mordenite. They also thank Professor S. P. Zhdanov for his interest and encouragement of this work.     

Quantum-chemical study of the optical properties of MgO surface hydroxy groups

Cluster models of MgO surface OH groups have been studied by the semi-empirical CNDO method. The calculated stretching vibration frequencies of OH bonds and localized electron excitation energies on the OH-groups are shown to depend on the oxygen atom coordination.

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OH- MgO. , OH- , OH-, .

     

Interrelation of addition reactions of hexachlorocyclopentadiene and bromine to N-arylimides of endo-and exo-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acids

A comparative analysis of the relative reactivities of N-arylimides of endo-and exobicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acids for the addition reactions of hexachlorocyclopentadiene and bromine has been carried out. According to different correlations the transition states of these two processes are shown to be similar.

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N- - - [2,2,1] -5--2,3- . .

     

Gasification in steam of a bituminous coal from Peñarroya (Cordoba,Spain) and of different samples prepared from it

The gasification with steam of a bituminous coal from Peñarroya (Cordoba, Spain) (H—O) and of several samples prepared from either by acid treatment (H—H, H—N, H—F and H—F(3)) or by thermal treatment (H—O—C) was studied under both dynamic and isothermal conditions (10 deg/min and 40 min at 1000°).It was found that only for the samples prepared by hydrofluoric acid treatment, H-F and H—F(3), did the gasification effected under such experimental conditions take place in a complete manner.

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Zusammenfassung Die Dampfvergasung von bituminöser Kohle (H—O) (Penarroya, Cordoba, Spanien) und von daraus durch Säurebehandlungen (H—H, H—N, H—F und H-F(3)) oder thermische Behandlung (H—O—C) hergestellten Proben wurde unter dynamischen und isothermen Bedingungen (10 °/min und 40 min bei 1000°) untersucht. Es wurde festgestellt, daß nur die durch Flußsäurebehandlung hergestellten Proben (H—F und H—F(3)) unter den experimentellen Bedingungen vollständig vergasbar sind.

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(10°/ 40 1000°) () , . , , , .

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The authors are grateful to the CAICYT of Spain for the financial support on Project No. 0794/82.     

Evolved gas analysis for examination of surface oxides on alloys

Temperature programmed reduction in a hydrogen flow with simultaneous evolved gas analysis was employed to determine surface oxides on oxide dispersion strengthened (ODS) nickel containing TiO₂, A1₂O₃ or Cr₂O₃ particles, and on a Ni-2OCr alloy, after exposure to air at elevated temperatures. Oxides on particles of water-atomized (WA) Ni-2OCr powder were analysed similarly. Significant differences in starting temperatures of the reaction between hydrogen and phases present in oxide layers made identification of the phases possible. NiO or NiO doped with Ti, Al or Cr are the major constituents of the scale formed on ODS Ni. NiTiO₃, NiCr₂O₄ and NiAl₂O₄ are formed as a result of a reaction between TiO₂, A1₂O₃ or Cr₂O₃ particles in the scale with NiO. The oxide layer formed on Ni-2OCr alloy consists of Cr₂O₃ and of NiO doped with Cr. Surface oxides on WA Ni-2OCr contain Cr₂O₃ and a small amount of NiO.

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Zusammenfassung Temperaturprogrammierte Reduktion im Wasserstoffstrom wurde zusammen mit gleichzeitiger Analyse des in Freiheit gesetzten Gases dazu benutzt, um Oberflächenoxide an Nickel enthaltenden TiO₂-, A1₂O₃- oder Cr₂O₃-Partikeln mit verstärkter Oxiddispersion (ODS) und an einer Ni-2OCr-Legierung nach Behandlung in Luft bei erhöhten Temperaturen zu bestimmen. Oxide auf Partikeln von wasser-zerstäubtem (WA) Ni-2OCr-Pulver wurden auf ähnliche Weise analysiert. Signifikante Unterschiede in der Starttemperatur der Reaktionen zwischen Wasserstoff und der in den Oxidschichten vorliegenden Phasen ermöglichen die Identifikation der Phasen. NiO oder mit Ti, Al oder Cr gedoptes NiO sind die Hauptbestandteile des auf ODS-Ni gebildeten Belags. NiTiO₃, NiCr₂O₄ und NiAl₂O₄ treten als Produkte der Reaktion von TiO₂-, Al₂O₃- oder Cr₂O₃-Partikeln mit NiO im Belag auf. Die auf der Ni-2OCr-Legierung gebildete Oxidschicht besteht aus Cr₂O₃ und aus mit Cr gedoptem NiO. Oberflächenoxide auf WA-Ni2OCr enthalten Cr₂O₂ und geringe Mengen an NiO.

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- , , , , , , Ni-2r, . Ni-2OCr. , , . , , , , . NiTiO₃, NiCr₂O₄ NiAl₂O₄ , , . , Ni-2r, , . Ni-2r .

     

Reduction of higher polymethylbenzenes by the rapid cation exchange of H-mordenite in the conversion of methanol to hydrocarbons

The product distribution in methanol conversion on mordenite is changed by potassium ion exchange depending on the method of ion exchange. The rapid exchange method was the most effective to suppress the formation of higher polymethylbenzenes.

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. .

     

Gas phase photoreaction of SO2 with n-pentane in the presence of NO

The spectrum of an intermediate, ascribed to nitrosopentane, has been detected in the photolysis of SO₂-pentane-NO mixtures. This may be explained by a radical photolysis mechanism involving an initial H-atom abstraction from the pentane molecule by SO₂.

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SO₂--NO , . , H .

     

On the mechanism of propylene oxidation over gallium-molybdenum oxide catalysts

The products of selective oxidation are shown to be formed via a stepwise mechanism with participation of surface allylic complexes. A successive transformation of -allyl to -allyl and further to acrolein is possible. The products of complete oxidation may be formed through surface carbonate-carboxylate complexes via either a stepwise mechanism involving the catalyst's oxygen, or a concerted mechanism with the participation of molecular oxygen.

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, . - -, . - , .

     

Thermal and spectral studies on some tetrachloroaurates of 8-alkyltheophylline derivatives

Tetrachloroaurates of 8-ethyl-, 8-isopropyl-, 8-propyl- and 8-pentyltheophylline were synthesized and studied by¹H-NMR, TG and DSC techniques. The metal is not coordinated to the 8-alkyltheophylline derivatives and forms a salt-like structure.

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Zusammenfassung Tetrachloroaurate von 8-Äthyl-, 8-Isopropyl-, 8-Propyl- und 8-Pentyltheophillin wurden synthetisiert und mittels¹H-NMR, TG und DSC untersucht. Die 8-Alkyltheophillin-Derivate sind nicht koordinativ an das Metall gebunden, es liegt vielmehr eine salzartige Struktur vor.

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8--, 8--, 8-- 8- , . , 8- .

     

Hydrogenolysis of n-butane on Ni-Pd/SiO2 catalysts

Supported Ni-Pd/SiO₂ catalysts of different Ni and Pd composition were studied in n-butane hydrogenolysis. The reaction rate, selectivity towards methane, ethane and propane were determined. On the basis of these data the relationship between the size and composition of the active center and the possibility of surface segregation of one of the components is discussed.

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Ni-Pd/SiO₂ Ni Pd -. , . .

     

Investigation of thermal degradation of polymers containing chlorine by thermogravimetry

The thermal degradation of chlorine-containing polymers used in a rubber technology has been investigated in a nitrogen atmosphere. The characteristics of degradation have been compared on the basis of thermogravimetry, carbon residues and chlorine elimination. The observed structure-dependent differences in degradation of the investigated polymers are discussed.

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Zusammenfassung Die thermische Zersetzung von in der Kautschuk-Technologie verwendeten chlorhaltigen Polymeren wurde unter Stickstoff untersucht.Die Charakteristika der Zersetzung durch die Thermogravimetrie, Kohlenrückstand und Chlorabspaltung wurden verglichen. Die in der Zersetzung der untersuchten Polymere in Abhängigkeit von ihrer Struktur beobachteten Unterschiede wurden diskutiert.

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Résumé On a étudié, en atmosphère d'azote, la dégradation thermique des polymères contenant du chlore, utilisés dans la technologie du caoutchouc.On a comparé les caractéristiques de la dégradation par thermogravimétrie, formation d'un résidu de carbone et élimination du chlore. On discute les différences observées dans la dégradation des polymères étudiés suivant leur structure.

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