On the deactivation of Fe2O3?MoO3/SiO2 catalysts in the oxidation of methanol to formaldehyde

The deactivation behavior of Fe₂O₃–MoO₃/SiO₂ catalysts with different Fe₂O₃+MoO₃ content in the oxidation of methanol to formaldehyde is investigated. A simplified reaction-deactivation kinetic model is presented and used to compare and discuss the different behaviors.

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Fe₂O₃–MoO₃/SiO₂ Fe₂O₃+MoO₃ . : -.

     

Contribution a l'etude des associations aminophenazone-uree aminophenazone-thiouree et aminophenazone-noxythioline

The phase diagrams for aminophenazone-urea (a), aminophenazone-thiourea (b) and aminophenazone-noxythioline (c), established by differential scanning calorimetry, transparency method and thermomicroscopy, revealed the presence of definite compounds (1–3). These compounds are formed during eutectic fusion for (a) and (c); the definite compound for (b) displays non-congruent fusion.

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Zusammenfassung Aus den durch DSC ermittelten Phasendiagrammen für Aminophenazon-Harnstoff (a), Aminophenazon-Thioharnstoff (b) und Aminophenazon-Noxythiolin (c) sowie durch die Transparenzmethode und Thermomikroskopie wurde die Existenz der definierten Verbindungen (1–3) nachgewiesen. Diese Verbindungen werden im Falle von (a) und (c) in eutektischen Schmelzen gebildet. Die definierte Verbindung für (b) schmilzt nicht-kongruent.

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

     

Relative enthalpies and related thermodynamic functions of some organic compounds by drop calorimetry

The values of thermodynamic functions of the following eight organic compounds under non-reacting conditions within the temperature range 298.15 – 550 K are given: N,N dimethylformamide, CHO · N(CH₃)₂; 4-nitro-1-chlorobenzene, Cl · C₆H₄ · NO₂; sodiump-nitrophenoxide, NO₂ · C₆H₄ · ONa; 1-methyl-2-pyrrolidone, 4,4-dinitrodiphenyl ether, (NO₂ · C₆H₄)₂O; 4,4-diaminodiphenyl ether, (NH₂ · C₆H₄)₂O; bis-(4-aminophenyl)methane, (NH₂ · C₆H₄)₂CH₂; bis(4-maleic acidimidphenyl)methane, The relative enthalpy was obtained from calorimetric data by drop calorimetry. The heat capacity and relative entropy are functions derived from the foregoing. The equations of the temperature variation of the relative enthalphy were obtained by computer processing of the calorimetric data by the least squares method. The parameters of solid-liquid transitions were determined from the discontinuity of the temperature variation of the relative enthalpy.

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Zusamenfassung Die Werte der thermodynamischen Funktionen folgender 8 organischer Verbindungen werden unter nicht-reagierenden Bedingungen im Temperaturbereich von 298.15 bis 550 K angegeben: Dimethylformamid, CHO · N(CH₃)₂;p-Nitrochlorbenzol, Cl · C₆H₄NO₂; Natrium-p-Nitrophenoxid, NO₂ · C₆H₄ONa; N-Methylpyrrolidon, 4-4-Dinitrodiphenyläther, (NO₂ · C₆H₄)₂O; 4-4-Diaminodiphenyläther, (NH₂C₆H₄)₂O; 4-- 4-Diaminodiphenylmethan, (NH₂ · C₆H₄)₂CH₂; 4-4-bis-Maleinimid-Diphenylmethan, Die relative Enthalpie wird aus kalorimetrischen Daten der Temperaturgefällekalorimetrie erhalten. Die Wärmekapazität und die relative Entropie sind Funktionen der erwähnten Werte. Die Gleichungen der Temperaturänderung der relativen Enthalpie wurden mittels Computerverarbeitung der kalorimetrischen Daten, mit der Methode der kleinsten Quadrate erhalten. Die Parameter der fest-flüssig Übergänge wurden an Hand der Diskontinuität der Temperaturänderung der relativen Enthalpie bestimmt.

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Résumé On donne les valeurs des fonctions thermodynamiques des 8 composés organiques suivants, en conditions non réactionnelles, dans l'intervalle de températures 298.15–550 K: diméthylformamide CHO · N(CH₃)₂,p-nitrochlorobenzène Cl · C₆H₄ · NO₂,p-nitrophé noxysodium NO₂ · C₆H₄ · ONa, N-méthylpyrrolidone dinitrodiphényl-4,4 éther (NO₂ · C₆H₄)₂O, diaminodiphényl-4,4 méthane (NH₂ ·H ₄CH₂, 4-4 bis maléinimide diphénylméthane L'enthalpie relative a été obtenue à partir de données calorimétriques fournies par un calorimètre à chute. La chaleur spécifique et l'entropie relative sont des fonction dérivées de la précédente. Les équations donnant la variation de l'enthalpie relative en fonction de la température sont obtenues par traitement des données calorimétriques sur ordinateur par la méthode des moindres carrés. Les paramètres des transitions solide-liquide ont été déterminés à partir de la discontinuité de la variation de l'enthalpie relative avec la température.

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, 298,15–550 , : — · N(CH₃)₂;- — l · ₆₄ · NO₂.- -NO₂·₆₄·ONa; N-—₃·N··₂·₂₂; 4,4- — (NO₂·₆₄)₂; 4,4- — (NH₂·₆₄)₂; 4,4- — (NH₂·₆₄)₂₂; 4,4-- —(₆₄.N. . :. )₂₂. . , . . - .

     

Some peculiarities of cyclohexane conversion on zeolite catalysts

Cyclohexane conversion on zeolite and zeolite-containing catalysts has been examined. The formation of cracking, isomerization and dehydrogenation products is suggested to follow two parallel independent mechanisms through different intermediate carbocations.

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. , .

     

A variational formulation of the rate equations for closed chemical systems

This paper presents a variational formulation of the kinetic equations corresponding to a closed chemical system.

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, .

     

Depolymerization kinetics of the polymer formed in the reaction of 1-bromobutane on unmodified alumina

The slow processes accompanying the reaction of 1-bromobutane on unmodified alumina have been studied. Butenes and octane are formed via depolymerization of a low polymeric complex formed from the reaction product. The activation energy for the formation of products from the polymer has been determined.

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, 1- . , , , , . .

     

Catalytic performance in Co hydrogenation over triruthenium ketenylidene cluster-derived catalyst

The ruthenium catalyst prepared from triruthenium ketenylidene cluster exhibited high catalytic activity in CO hydrogenation, compared with the catalyst from [HRu₃(CO)₁₁]^–. The high activity possibly resulted from the ketenyl group (CCO) that could be partly converted to carbide species.

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, , CO, [HRu₃(CO)₁₁]^–. , , (CCO), .

     

Effect of carbon dioxide on the catalytic oxidation of ethylene over silver. Kinetic reaction model accounting for the modification of catalyst surface by carbonate groups

Changes in the character of catalytic oxidation of ethylene over silver upon increasing pressure of reaction mixture, reflected in increased ethylene oxide selectivity, are due to the modifying effect of suface carbonate groups. A kinetic reaction model is suggested based on the individual investigations of reaction steps.

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, , . , .

     

Competitive hydrogenation of 2-methyl-3-butene-2-ol and 1-hexene on a platinum catalyst modified by amines

The effect of the amount of diethylamine and triethylamine on the degree of poisoning of a hydrogenation catalyst 10% Pt on silica gel was examined. The dependence of the selectivity of competitive catalytic hydrogenation of 2-methyl-3-butene-2-ol and 1-hexene in methanol and cyclohexane on the degree of poisoning was investigated.

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(10% Pt ), 2--3--2- 1- .

     

The influence of the structure and composition of complexes of the type CuA2X2 on the courses of their thermal decomposition

The influence of different degrees of distortion of the coordination polyhedra in some Cu(II) complexes on the courses of their thermal destruction was studied. It was found that differences in the thermal stability and stoichiometry of thermal decomposition may be satisfactorily explained by the different degrees of distortion of the coordination polyhedra in the Cu(II) complexes under discussion. This fact appears to be significant with respect to the chemical reactivities of these complexes, though the influence of other factors cannot be excluded.

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Zusammenfassung Der Einfluß der verschiedenen Grade der Koordinations-Polyeder-Verzerrung in einigen Cu(II) Komplexen auf den Verlauf ihrer thermischen Zersetzung wurde untersucht. Es wurde festgestellt, daß Unterschiede in der thermischen Stabilität und der Stöchiometrie der thermischen Zersetzung durch die verschiedenen Verzerrungsgrade der Koordinations-Polyeder in den erörterten Cu(II) Komplexen befriedigend erklärt werden können. Diese Tatsache scheint hinsichtlich der chemischen Reaktivität dieser Komplexe von grosser Bedeutung zu sein, obwohl der Einfluß anderer Faktoren nicht ausgeschlossen werden kann.

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Résumé On a étudié l'influence des différents degrés de distortion des polyhèdres de coordination sur l'allure de leur décomposition thermique, dans le cas de quelques complexes du Cu(II). On a trouvé que les différences de stabilité thermique et de stoechiométrie pouvaient expliquer de manière satisfaisante les différents degrés de distortion des polyhèdres de coordination dans les complexes du Cu(II) étudiés. Ce fait semble être plutôt significatif de la réactivité chimique de ces complexes, bien que l'influence d'autres facteurs ne doive pas être exclue.

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Cu(II) . , -, Cu(II). , -, , .

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Presented at the 7th Czechoslovak National Conference on Thermal Analysis (TERMANAL); The High Tatras, 1976.     

Mechanism of carbon monoxide oxidation on nickel oxide and its solid solutions

On the basis of studying the isotope exchange of oxygen and the position of the Fermi level in the system MiO–Li_xNi_1–xO, an explanation is proposed for the compensation effect in the reaction of CO oxidation on nickel oxide and its solid solutions.

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NiO–Li_xNi_1–xO CO .

     

Kinetic data on the interaction between triplet anthraquinone and 2-naphthol in oxygen

During the photooxidation of ethylbenzene in the presence of 2-naphthol a new interaction has been found between the sensitizer anthraquinone and the inhibitor. The quantum yield and the kinetics of this interaction have been investigated in the temperature interval of 28–98°C.

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-, , 28–98°C , .

     

Ba(OH)2 as catalyst in organic reactions, part XIV. Michael addition catalyzed by barium complex salts in the homogeneous phase

Michael addition to chalcone is catalyzed by barium complex salts in the homogeneous phase under various conditions. The nature of these intermediates is analyzed. These complex salts are described for the first time. The Michael adduct of malonodinitrile to chalcone is described for the first time.

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, , . . . . .

     

Low-temperature ortho-para conversion of hydrogen on films of rare-earth metals and their copper alloys

Kinetic data for the ortho-para conversion of H₂ at 77 k rear earth metals (REM) and their Cu alloy films are given. Conversion on the surface of Sc, Y, La, Yb and Lu has been shown previously to follow a chemical mechanism, for the others it is magnetic. When alloyed with Cu, the specific catalytic activity (K_sp) of Sc, Y, La, Yb and Lu sharply increases. A sharp increase of K_sp is also observed on Cu alloys of Ce, Sm, Nd, Pr, Eu and Gd and the chemical conversion mechanism becomes predominant. On Tb, Dy, Er, Ho and Tm, K_sp rises only slightly and the magnetic mechanism preserves.

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- H₂ 77 P3M . , Sc, Y, La, Yb Lu , . Cu () Sc, Y, La, Yb, Lu, Ce, Sm, Nd, Pr, Eu Gd, . Ha Tb, Dy, Er, Ho Tm .

     

Thermal study of fast reactions by means of apparatus connected directly to a computer

An automated system of thermal analysis is described for the study of fast exothermic reactions (intensive burning, self-inflammation, transition from the non-equilibrium state to the equilibrium state, etc.). The system includes a complex of technical means for connecting the measuring instrument with the computer (hardware), and a special mathematical supply (software).The use of this system provides data required for thermal and chemical calculations in the high-temperature range.Two examples of DTA data-processing are presented.

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Zusammenfassung Ein automatisches Thermoanalyse-System zum Studium schneller exothermer Reaktionen (intensives Brennen, Selbstzündung, Übergang vom Nicht-Gleichgewichtszustand in den Gleichgewichtszustand usw.) wird beschrieben. Das System enthält eine Reihe technischer Vorrichtungen zur Verbindung des Meßgerätes mit dem Komputer und dem speziellen mathematischen Apparat.Die Anwendung dieses Systems ermöglicht die Ermittelung von Daten, welche zu thermischen und chemischen Berechnungen im Hochtemperatur-Bereich nötig sind.Zwei Beispiele der DTA-Datenverarbeitung werden gegeben.

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Résumé On décrit un système automatique d'analyse thermique pour l'étude de réactions exothermiques rapides (combustion intense, autoinflammation, transition de l'état de nonéquilibre à celui d'équilibre, etc....). Le système comprend un ensemble de moyens techniques pour coupler l'instrument de mesure à l'ordinateur et à l'appareillage mathématique spécial.L'utilisation de ce système permet d'obtenir les données nécessaires aux calculs des effets thermiques et chimiques dans le domaine des températures élevées.On présente deux exemples du traitement des données de l'ATD.

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

     

Kinetic model and mechanism for selective hydrogenation of acetylene alcohols

A complex approach to the development of kinetic models in terms of the joint kinetic and physicochemical methods is suggested. To establish kinetic models for the hydrogenation of C₅, C₁₅ and C₂₀ acetylene alcohols on a modified Pd/Al₂O₃ (0.5% Pd) catalyst, the kinetics of their selective hydrogenation and the adsorption of their components have been studied.

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- . C₅, C₁₅, C₂₀ Pd/Al₂O₃ (0,5% Pd), .

     

Acidity and cyclohexene isomerization activity of aluminas from sodium aluminate

The relationship between the catalytic activity of aluminas and the pH of precipitation of the corresponding aluminium hydroxides and the Na₂O/Al₂O₃ molar ratio of sodium aluminate is shown. The precipitation agent exerts a strong effect on the catalytic activity of the aluminas.

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pH , Na₂ O/Al₂O₃ . .

     

Br?nsted sites in H-forms of faujasites obtained from ammonium and guanidine forms

The infrared spectra of H-forms of Y zeolite made from the guanidine and ammonium forms were compared. The Brönsted acid sites have been characterized by adsorption of pyridine. Good correlation between the concentration of Brönsted acid sites and the catalytic activity of the samples has been found. It was concluded that guanidine cations limited localization of OH groups on the surface of the supercages.

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, . , . . , OH .