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)- . .

     

Influence of the particle size of metal in the hydrogenolysis of n-butane on carbon supported iron catalysts

The hydrogenolysis of n-butane on different carbon supported iron catalysts has been studied. Changes in activity, product distribution, apparent activation energy and frequency factor were found to be a function of particle size. This behavior is explained as a change in the reaction mechanism, which also leads to the isomerization of n-butane in the case of catalysts with higher dispersity.

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- . , , . , - .

     

Kinetic study of the permanganate oxidation of DL-valine in acidic media

The kinetics of permanganic oxidation of DL-valine in a concentrated sulfuric acid medium (3.0–5.0 M) has been studied by spectrophotometry. The rate law found shows that the reaction is autocatalyzed by Mn(II) ions. The influence of the reagent and Mn(II) concentrations and acidity of the medium has been analyzed. A reaction mechanism is proposed according to the experimental results.

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DL- (3,0–5,0 M) . Mn(II). Mn(II) . .

     

Decomposition of ammonia on rhenium III. Interaction of ammonia with rhenium

The adsorption and steady-state decomposition of ammonia on rhenium has been studied. A mechanism for the interaction of ammonia with the Re surface is suggested.

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. .

     

Activation of hydrocarbons in the oxidative dimerization of methane over alkaline earth metals

Oxidative dimerization of methane over alkaline earth metal oxides and phosphates has been studied. The ratedetermining step is heterolytic C–H bond dissociation of methane on surface basic sites of the catalysts.

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- . , C–H .

     

Benzene hydrogenation on nickel/honeycomb catalysts

Monolithic supported nickel catalysts were investigated in benzene hydrogenation between 100 and 280 °C. The conversion of benzene to cyclohexane reaches a maximum around 210 °C with a maximum yield at a ratio p^oH₂/p^oBz=3. The experimental results and some kinetic aspects are discussed.

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100 280 °C. 210 °C p^oH₂/p^oB=3. .

     

The influence of CSH phase nuclei on Ca3SiO4Cl2 hydration

The influence of CSH phase nuclei on calcium chlorosilicate hydration has been studied by means of calorimetry, QXRD, DTA and TG methods.

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Zusammenfassung Mittels kalorimetrischen, QXRD-, DTA- und TG-Verfahren wurde der Einfluß von CSH Phasenkörpern auf die Hydratierung von Kalziumchlorosilikat untersucht.

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, , .

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C=CaO, S=SiO₂, H=H₂O     

Modelling of self-oscillations in the combustion of n-heptane-isooctane mixtures

A mathematical model has been constructed to describe the self-oscillation regime of the cool-flame combustion of an n-heptane-isooctane mixture. The character of the dependence of the amplitude and oscillation period on the temperature and mixture composition is in a qualitative agreement with the similar experimental data.

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, --. .

     

Kinetics and mechanism of oxidation of methanol by acid bromate

The kinetics of oxidation of methanol by bromate ion in hydrochloric acid medium has been investigated. A mechanism consistent with the experimental observations is suggested.

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. , .

     

Combined use of calorimetric and adsorption kinetic methods for the study of the mechanisms of catalytic processes

Consideration is given to the main results obtained in studies based on calorimetric methods at high temperatures (above room temperature) of the following aspects of the mechanisms of catalytic and sorption processes on powder catalysts: 1) relation between chemisorption and dissolution of gases in the subsurface layers of solids; 2) influence of surface-adsorbed substance on the adsorption of another substance from the gas phase; 3) nature of intermediate species formed during catalytic processes on the catalyst surface. Results are presented of the application of calorimetric methods to measuring the enthalpy change of polymerization in a dry system: gaseous monomer — solid catalyst — solid polymer, and to investigating the mechanisms of such processes. Anomalous solubility of gases in the subsurface layers of solids has been shown to be significant for the mechanism of nucleation during phase transitions in solids.

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Zusamenfassung Die wichtigsten Ergebnisse der auf kalorimetrischen Methoden bei hohen Temperaturen (über Raumtemperatur) beruhenden Untersuchungen der Mechanismen von katalytischen und Sorptionsprozessen an pulverförmigen Katalysatoren werden behandelt: 1) Zusammenhang zwischen Chemisorption und Lösung von Gasen in den Schichten von Festkörpern unterhalb der Oberfläche; 2) Einfluß der an der Oberfläche adsorbierten Substanz auf die Adsorption einer anderen Substanz aus der Gasphase; 3) Beschaffenheit der während des katalytischen Vorgangs an der Katalysator-Oberfläche entstandenen Intermediärteilchen.Ergebnisse der Anwendung der kalorimetrischen Methode zur Messung der Enthalpie-Änderungen der Polymerisation im trockenen System: gasförmiges Monomer — fester Katalysator — festes Polymer und zur Untersuchung der Mechanismen solcher Vorgänge werden mitgeteilt. Es wurde gezeigt, daß die anomale Löslichkeit von Gasen in den Schichten unterhalb der Oberfläche von Festkörpern für den Mechanismus der Keimbildung während des Phasenüberganges in Festkörpern von Bedeutung ist.

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Résumé On examine les principaux résultats obtenus lors des études effectuées à l'aide de méthodes calorimétriques à hautes températures (au-dessus de la température ambiante), sous les aspects suivants du mécanisme des réactions catalytiques et de Sorption sur des catalyseurs en poudre: 1) relation entre la chimisorption et la dissolution des gaz dans les sous-couches superficielles des solides, 2) influence d'une substance adsorbée en surface sur l'adsorption d'une autre substance de la phase gazeuse, 3) nature des particules intermédiaires formées lors de la réaction catalytique à la surface du catalyseur. Les résultats de l'application de la méthode calorimétrique à la mesure des variations d'enthalpie au cours de la polymérisation en système «sec» sont présentés: monomère gazeux — catalyseur solide — polymère solide, ainsi que ceux relatifs à l'étude du mécanisme de ces réactions. On montre que la solubilité anormale des gaz dans les sous-couches superficielles des solides joue un rôle important sur le mécanisme de la nucléation lors des transitions de phases dans les solides.

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, ( ) : 1) : 2) ; 3) , . » « — . .

     

The relationship between the structures of Cu(II) complexes and their chemical transformations

The paper presents the results of a study of M ₂ ^I M ^II(SO₄)₂ compounds withM ^I= K, Rb, Cs or Tl, andM ^II=Cu or Ni, in the interval from room temperature to the melting temperature. All the compounds studied show endo- or exothermic excursions in their DTA curves, corresponding to phase transitions connected with colour changes of the compounds. For M ₂ ^I Cu(SO₄)₂, whereM ^I is K or Tl, several modifications could be prepared at laboratory temperature, probably distortion isomers. No modifications of this type could be prepared, however, for M ₂ ^I Ni(SO₄)₂ compounds.

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Zusammenfassung Die Ergebnisse einer Untersuchung von M ₂ ^I M ^II(SO₄)₂-Verbindungen Cs, Tl;M ^II=Cu, Ni) im Temperaturbereich von Raum- bis Schmelztemperatur werden beschrieben. Alle untersuchten Verbindungen zeigen in ihren DTA-Kurven mit Farbänderungen einhergehende, durch Phasenumwandlungen bedingte endo- und exotherme Peaks. Bei Laboratoriumstemperatur konnten verschiedene Modifikationen von M ₂ ^I Cu(SO₄)₂ (mitM ^I gleich K oder Tl) hergestellt werden, wobei es sich wahrscheinlich um Distorsionsisomere handelt. Keine Modifikationen dieses Typs konnten jedoch für M ₂ ^I Ni(SO₄)₂ erhalten werden.

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M ₂ ^I M ^II(SO₄)₂, ¹-, Rb, Cs Tl, aM ¹¹-Cu Ni, . - -, , . M ₂ ^I Cu(SO₄)₂, ¹- l, , , , . , M _i ² Ni(SO₄)₂ .

     

Development of phase composition for mixed Ni?Cu chromite catalysts. Conversions under calcination

IR spectroscopic and X-ray studies of variations in the composition of Ni, Cu and (Ni+Cu) ammonium chromates under thermal treatment show that the Ni–Cr system consists of spinel and NiO, and Cu–Cr systems consist of the spinel CuCr₂O₄ only. In mixed Ni–Cu–Cr systems part of Ni- and Cu-containing components remain independent and part of them form common Ni+Cu phases.

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Ni-, Cu- (Ni+Cu)- . , Ni–Cr NiO, Cu–Cr — CuCr₂O₄. Ni–Cu–Cr Ni- Cu- , Ni+Cu .

     

Quantum chemical calculations on the catalytic dehydration of 2-propanol

The charge on atoms and the bond strengths in CH₃CHOHCH₃, CH₃ CH₃, CH₃CHOHCH ₂ ^– , CH₃ CH ₂ ^– and CH₃ CH₃...O(H)CH(CH₃)₂ have been calculated by the CNDO/2 method. The results are in agreement with published experimental observations on catalytic dehydration. A modified mechanism of anti-elimination on solid catalysts is proposed.

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CH₃CHOHCH₃, CH₃ CH₃, CH₃CHOHCH ₂ ^– , CH₃ CH ₂ ^– CH₃ CH₃...O(H)CH(CH₃)₂, CNDO/2. . .

     

Non quasi-stationary state pyrolysis. Induction period of neopentane pyrolysis

The principle of an apparatus using an isothermal continuous flow stirred tank reactor to study homogeneous gas phase reactions at space times of the order of 1 sec is given. With this apparatus, the induction period of neopentane pyrolysis (as an example) has been clearly shown.

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, , 1 . , , .

     

Calculation of the mass transfer coefficient with a chemical reaction in a gas-liquid system

A solution of the problem of mass transfer in a turbulent boundary layer has been obtained with a first-order chemical reaction occurring in the liquid phase. The dependence of the enhancement factor for absorption and of the mass transfer coefficient on the model parameters can be used for building up a hierarchic model of the gas-liquid reactor.

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Thermische Eigenschaften und Aufschlussreaktionen von Natriummetaphosphat

Zusammenfassung Die thermischen Eigenschaften des Natriummetaphosphats sowie die Aufschlußreaktion zwischen Natriummetaphosphat und Natriumchlorid wurden durch Thermogravimetrie, Differentialthermoanalyse, Dilatometrie und Thermogasanalyse untersucht. Hierbei wurden die Zusammenhänge zwischen der Gewichtszunahme beim Schmelzen von NaPO₃, der Art der Atmosphäre und dem Verlauf der Reaktion zwischen Natriummetaphosphat und Natriumchlorid beobachtet.

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The thermal behaviour of sodium metaphosphate and the reaction thereof with sodium chloride have been investigated by thermogravimetry, differential thermal analysis, dilatometry and thermo-gas-analysis. Relationship has been established between the weight increase of NaPO₃ in the course of melting, the nature of the atmosphere and the proceeding of the reaction with NaCl.

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Résumé On a étudié par ATG, ATD, dilatométrie et analyse de la phase gazeuse les propriétés thermiques du métaphosphate de sodium et la réaction chlorure de sodium-métaphosphate de sodium. On a pu trouver une corrélation entre l'augmentation de poids de NaPO₃ lors de la fusion, la nature de l'atmosphère et la réaction NaPO₃-NaCl.

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NaPO₃-NaCl , , . NaPO₃, NaPO₃-NaCl.

     

Variation of the dispersity and phase composition of a ferrous oxide catalyst in the burning of an ammonium perchlorate-polymethylmethacrylate mixture

Products of conversion of the ferrous oxide catalyst collected from the burning region of an AP-PMMA mixture show the significant aggregation of the catalyst, with large (40–50 m) spherical particles having a metallic glitter. Significant variations in the phase composition are observed, Fe₃O₄·-Fe₂O₃ solid solution and tetragonal and monoclinic Fe₂O₃ being formed.

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- a-Fe₂O₃ . . ( 40–50 ) . : Fe₃O₄·-Fe₂O₃, Fe₂O₃.

     

Physical interpretation of the boundary conditions for isothermal hyperbolic reactors

A new mathematical model is proposed for one-phase isothermal chemical reactors, which eliminates a physical inconvenience caused by conventional equations. Instead of the usual parabolic equations a hyperbolic system of first-order partial differential equations is used. The boundary conditions and their physical meaning are treated for this type of reactor model.

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, . . .

     

Thermal study of date kernels via TG and DTA

Thermal analyses was performed on Egyptian date kernels to assess the value of the products as possible sources of valuable compounds. It also furnished technical data necessary for determination of the optimum degree of temperature for the design and operation of units for the pyrolytic processing of date kernels.Two different sets of experiments were carried out, involving thermogravimetry (TG) and differential thermal analysis (DTA).The TG results revealed a purely kinetically controlled, first-order reaction. The activation energy and the Arrhenius constant were 8.17 kJ/mol and 0.0115 min^–1, respectively.The DTA results indicated the nature of the reactions involved in the pyrolysis and the corresponding products.

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Zusammenfassung Ägyptische Dattelkerne wurden thermisch untersucht, um die Möglickkeit einer Verwendung als Quellen für wertvolle Verbindungen zu ergründen. Außerdem wurden technische Daten ermittelt, die zur Festlegung der Optimumtemperatur für die Gestaltung und den Betrieb der Geräte zur pyrolytischen Behandlung von Dattelkernen benötigt werden. Es wurden zwei Versuchsreihen durchgeführt, bei denen einerseits Thermogravimetrie (TG) und andererseits Differentialthermoanalyse (DTA) Anwendung fand. Die TG Ergebnisse eröffnen eine rein kinetisch kontrollierte Reaktion erster Ordnung. Die Aktivierungsenergie und die Arrheniuskonstante betrugen 8,17 kJ/mol bzw. 0,0115 min^–1. DTA Resultate gaben Auskunft über den Charakter und Reaktionsprodukte der Reaktionen bei der Pyrolyse.

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, , . , . , . . , , 8,17 -^–1 0,0115 ^–1. , .

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The authors wish to express their sincere appreciation to Prof. Dr. S. G. Serag El-Din, Professor of the Chemical Engineering Department, Cairo University, and Dr. H. H. Abou El-Naga, Manager of Analytical and Research Centre, Misr Petroleum Company, for their sincere and helpful co-operation.