TPD study of catalyst surface acidity

Acidity of catalyst surfaces of different nature such as -Al₂O₃, natural zeolite-clinoptilolite, and synthetic zeolite zeokar by adsorption of ammonia over a wide temperature range has been studied. Ammonia is adsorbed on the catalysts with different strengths, as evidenced by the presence of different types of acid sites.

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(-Al₂O₃, - , () . , , .

     

ESCA study of (Mo+Pt)/SiO2, (W+Pt)/SiO2 and (Re+Pt)/SiO2 catalysts

Supported catalysts obtained from organometallic compounds have been studied by ESCA. The data obtained indicate a decrease in electron density on the Pt atoms as a result of interaction with Mo, W and Re ions bound to silica.

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, . , Mo, W, Re, .

     

Thermal behaviour of trimethoxy silane modified alkyl methacrylates

The paper deals with the thermal behaviour of trimethoxy silane (MTS) modified ethyl methacrylate (EMA) and butyl methacrylate (BMA). Several copolymer samples were prepared by varying the molar ratio of MTS with respect to EMA or BMA. The copolymerisation was carried out at 78 °C for 120 min using benzoyl peroxide as an initiator. Incorporation of MTS in alkyl methacrylates resulted in an increase in thermal stability. Hydrolytic cross-linking of copolymer having higher mole fraction of MTS gave a cross-linked product with better thermal stability.

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Zusammenfassung Vorliegende Arbeit beschäftigt sich mit dem thermischen Verhalten von Äthylmethakrylat (EMA) und Bulhylmethakrylat (BMA), das mit Trimethoxysilan (MTS) modifiziert wurde. Unter Anwendung verschiedener Molverhältnisse von MTS und EMA bzw. BMA wurden einige Kopolymerproben hergestellt. Die Kopolymerisation wurde 120 Minuten lang bei 78 °C und mit Benzoylperpxid als Initiator durchgeführt. Der Einbau von MTS in Alkylmethakrylate führt zu einer Steigerung der thermischen Stabilität. Eine hydrolytische Vernetzung der Kopolymere mit größeren Molanteilen an MTS ergeben vernetzte Produkte mit verbesserter thermischer Stabilität.

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() ( ), (). . 78 °C 120 , . . , , .

     

Pyrolysis of propane in the presence of acetylene

Pyrolysis of propane in the presence of acetylene and acetylene labeled with C-14 has been studied in the temperature range of 833–1019 K. The inhibition effect of acetylene on the thermal decomposition of propane is turning into an accelerating effect at higher temperature.

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C¹⁴ 833–1019 . .

     

On the structure and activity of a Pt/C catalyst subjected to repeated deactivation and regeneration cycles

Electron microscopic studies reveal that repeated air/hydrogen regeneration cycles cause irreversible structural changes of a Pt/C catalyst involving sintering and migration of the platinum over the support. This is reflected by a serious decrease of the catalytic activity. With hydrogen treatment only, these effects are less significant.

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, / Pt/C, . . .

     

Theory of differential thermal analysis taking into account heat exchange between the specimen and reference cells

A basic formula of differential thermal analysis is evolved for the case when the heat transfer coefficient between the specimen cell and the reference cell is not zero. The more general formula obtained differs from the classical formula by including the parameters of the reference cell and the heat transfer coefficient between the cells. It indicates that utilization of the classical formula is not correct if heat exchange occurs between the cells. To utilize the generalized formula, additional measurements of the temperature changes of the reference material are required. However, if the time constants of the two cells are identical, the formula can be changed to assume the form of the classical formula for DTA if a correction factor is introduced which takes into account the effect of heat exchange between the cells.

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Zusammenfassung Für den Fall, dass der Übertragungskoeffizient zwischen der Proben- und der Referenzzelle nicht Zero ist, wurde eine Grundformel der Differentialthermoanalyse entwickelt. Die entstandene Formel, die vielmehr allgemein ist, weicht von der klassischen dadurch ab, dass sie auch die Parameter der Referenzzelle, und den Wärmeübertragungskoeffizient zwischen den Zellen enthält. Sie deutet darauf hin, dass die Anwendung der klassischen Formel in dem Fall nicht einwandfrei ist, wenn ein Wärmeaustausch zwischen den Zellen zustande kommt. Zur Anwendung der verallgemeinerten Formel sind weitere Messungen des Temperaturaustausches vom Referenzmaterial erforderlich. Sind aber die Zeitkonstanten der zwei Zellen identisch, kann die Formel so geändert werden, dass sie die Gestalt der klassischen DTA-Formel annimt, wenn ein, mit der Wirkung des Wärmeaustausches zwischen den Zellen rechnender Korrektionsfaktor eingeführt wird.

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, . , , . . , , , , .

     

Kinetics of solid polypropylene oxidation inhibited by aromatic nitrons

C-phenylcarbamoyl-N-phenylnitron and C(2,4-di-tert-butyl-3-hydroxyphenylcarbamoyl)-N-(p-di-methylaminophenyl) nitron inhibit the oxidation of solid polypropylene. In this case the nitrons studied demonstrate properties of polyfunctional inhibitors: they interrupt oxidation chains by chains by reactions with alkyl and peroxyl radicals.

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C--N- C-(2,4----3-)-N-(-) . , .

     

Simultaneous measurement of thermal properties in ferroelectric crystals

Simultaneous measurement of the influence of the electric field on specific heat, thermal conductivity and pyroelectric coefficient is described as a summary of previous papers. From these coefficients, which are determined by means of a flux calorimeter, the behaviour of other properties, such as thermal diffusivity and electrocaloric coefficient, is deduced.The data are compared with the findings obtained by other authors with traditional methods.

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Zusammenfassung In Zusammenfassung vorhergehender Arbeiten wurde die simultane Messung des Einflusses von elektrischen Feldern auf spezifische Wärme, Wärmeleitfähigkeit und pyroelektrischen Koeffizienten beschrieben. Auf Grundlage dieser Konstanten, die mittels eines Fluxkalorimeters bestimmt wurden, konnte das Verhalten anderer Eigenschaften wie z. B. thermische Diffusionskonstante und elektrokalorischer Koeffizient abgeleitet werden. Die Daten wurden mit durch herkömmliche Methoden erhaltenen Ergebnissen anderer Autoren verglichen.

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, . , , , . , .

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This work has been supported by the Spanish C.A.I.C. y T.     

Inhibiting action of divalent copper compounds on microsomal oxidative demethylation of N,N-dimethylaniline

CuCl₂ is a non-competitive inhibitor whereas CuTyr₂ and CuLys₂ complexes are characterized by mixed-type inhibition. The inhibition action mechanism is discussed.

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CuCl₂ , . .

     

n-Butane oxidation over a vanadium-phosphorus catalyst

The activity of vanadium-phosphorus oxide catalysts with respect to maleic anhydride formation in n-butane oxidation has been found to correlate with the concentration of V⁴⁺ ions in the catalysts. The steady catalytic activitv of the samples examined is achieved more rapidly upon prereduction.

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, - - . , .

     

State of components in group IV A metal modified nickel catalysts prepared via decomposition of metal complexes

The dispersity and state of components in (M+Ni)/SiO₂ catalysts (M=Ge, Sn, Pb), prepared via the reduction of anchored complexes, have been studied by chemisorption and electron microscopy. High dispersity of metallic particles (6Å) has been revealed. According to Mössbauer spectroscopy, in (Ni+Sn)/SiO₂ catalysts reduced at 873 K, a partial reduction of Sn to the metallic state is observed.

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(M+Ni)/SiO₂ ( M=Ge, Sn, Pb), , , - . 873 ° K (Sn+Ni)/SiO₂ , , , 6 Å.

     

Lattice oxygen removal from V6O13 by the TPD method

Removal of the lattice oxygen from the V₆O₁₃ phase has been measured and the activation energy determined.

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V₆O₁₃ .

     

Hydrogen adsorption on chromia-supported iridium catalyst

Effect of thermal pretreatment of chromia-supported iridium catalyst on hydrogen adsorption was studied. It was found that the hydrogen uptake by Ir/Cr₂O₃ was highly dependent on the reduction temperature. The catalyst proved to be resistant to sintering in oxygen atmosphere at temperatures up to 700 °C and it showed symptoms of redispersion even at 650 °C.

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. Ir/Cr₂O₃ . 700°C, , 650°C .

     

Synthesis of high-silicon zeolites in bialkaline systems

Rubidium and cesium zeolites (SiO₂Al₂O₃=4–9.2) of the faujasite, chabazite, erionite, offretite, phillipsite and pollucite type, L-zeolites as well as ZKF-2, ZKF-8 and ZKF-18 of unknown structure have been obtained. Their pore size is 4–10 Å and their thermostability is 1073–1223 K, which permits to use these zeolites as catalyst components.

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, , , , , , L, -2 -8 (SiO₂Al₂O₃=4–9,2). 4–10 Å 1073–1223 K, .

     

Thermal and structural properties of rare earth exchanged zeolites

A series of rare earth zeolites of types X and Y were prepared by cation exchange. Thermal analysis curves (TG/DTA) were employed to estimate the structural changes in the zeolite framework. Analogous investigations were carried out by independent methods such as XRD and IR spectroscopy. The results indicate increased thermal stability on the replacement of sodium by rare earth. Partial replacement of rare earth by ammonium/hydrogen enhances the thermal stability. The type Y zeolites are more stable than those of X type.

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Zusammenfassung Eine Reihe von Ionen der Seltenen Erdmetalle enthaltenden Zeolithen des Typs X und Y wurden durch Ionenaustausch hergestellt. Thermoanalytische Kurven (TG/DTA) wurden zur Beurteilung der strukturellen Veränderungen des Zeolithgitters herangezogen. Analoge Untersuchungen wurden mit unabhängigen Methoden (XRD und IR-Spektroskopie) ausgeführt. Es wurde festgestellt, daß ein Ersatz der Natriumionen durch Ionen der Seltenen Erdmetalle zu einer Erhöhung der thermischen Stabilität führt. Ein teilweiser Ersatz der Seltenen Erdmetallionen durch Ammonium-/Wasserstoffionen erhöht die thermische Stabilität. Zeolithe des Typs Y sind stabiler als die des X-Typs.

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X . (/) . - . . . X .

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NCL Communication No: 2186     

Etude enthalpique de l'interaction du chelate Eu(DPM)3 avec une serie de pyridines en solution

Résumé Les constantes d'équilibre et les variations d'enthalpie entre une série de pyridines méthylées et le chélate tris(dipivaloylméthanato) europium (III) ont été déterminées à 36° dans le chloroforme par des mesures calorimétriques. Nous constatons que la chaleur de complexation de l'adduit 1/1 est sensible à l'encombrement stérique du ou des méthyles en de l'hétéroatome. Cependant, lorsque le rapport des concentrations entre la base et le chélate est supérieur à l'unité, l'enthalpie de la réaction est modifiée. Dans ce cas, nous attribuons cette modification à l'existence d'un équilibre supplémentaire entre le chélate et les bases conduisant à la formation de l'adduit 1/2.

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Equilibrium constants and enthalpy changes are reported between a series of substituted methylpyridines and the chelate tris(dipivaloylmethanato)europium(III) in chloroform solution at 36° as obtained by calorimetric measurements. The 11 adduct enthalpies are ordered in agreement with the electronic and steric effects of the methyl group in a to the heteroatom. Some anomalies are observed when the concentration ratio between ligand and chelate is higher than unity. These findings conform with the hypothesis of the existence of a supplementary equilibrium which may be assigned to the formation of the 12 adduct.

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Zusammenfassung Es wird über durch kalorimetrische Messungen ermittelte Gleichgewichtskonstanten und Enthalpie-Änderungen zwischen einer Reihe substituierter Methylpyridine und dem Tris(dipivaloylmethanato)-Europium (III) Chelat in Chloroform bei 36° berichtet. Die 1/1 Addukt-Enthalpien befinden sich in Übereinstimmung mit dem elektronischen und sterischen Effekt der Methylgruppe im a des Heteroatoms. Einige Anomalien werden beobachtet, wenn das Konzentrationsverhältnis zwischen dem Liganden und dem Chelat höher als eins ist. Diese Feststellungen sind im Einklang mit der Hypothese der Existenz eines supplementären Gleichgewichts und können der Bildung des 1/2-Adduktes zugeordnet werden.

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, , // () 36°. 11 , - . , . . . 12.

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Les auteurs souhaitent exprimer ici leurs remerciements au Docteur J. F. Gal pour l'intérêt qu'il a porté á ce présent travail.     

Peculiarities of formation of ZnO and CuO-based solid solutions

Low-temperature (623 K) treatment of hydroxocarbonate compounds of copper-zinc and copper-zinc-aluminium leads to the formation of phases with CuO and ZnO structures, which are solid solutions of the promoter ions. The formation of solid solutions is attributed to structural distortions (uniform or local) in the oxide lattice due to the incomplete removal of OH^– and CO ₃ ^2– groups at low temperatures.

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, (623 ) - -- CuO ZnO, . , ( ) - OH ₃ ^–– - .

     

ESR studies of the state of Ti3+ and Ti2+ in Ti?Mg catalysts for olefin polymerization

ESR studies have revealed that in Ti–Mg catalysts after interaction with organoaluminium compounds, the Ti³⁺ ions formed are present mainly as TiCl₃ associates. Isolated Ti³⁺ ions of various types are also detected. Part of titanium ions is in the divalent state and provides an ESR signal after oxidation by water to the trivalent state in the form of Ti³⁺ ordered by cooperative Jahn-Teller interaction.

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, - , Ti³⁺ TiCl₃. Ti³⁺ . Ti³⁺ - -.