Catalytic hydrogenation of diallyl fumarate

The catalytic hydrogenation of diallyl fumarate in cyclohexane and methanol at 20 °C and atmospheric pressure of hydrogen by means of palladium, platinum and rhodium catalysts was investigated. The system modelled parallel-consecutive reactions in which the effect of the type of the active metal and solvent on the reaction path was assessed.

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20 °C Pd, Pt Rh. .

     

Thermal decompositions of Y,La and lanthanide 3-hydroxybenzoates in air and nitrogen atmospheres

When heated, the 3-hydroxybenzoates of Y, Sm and Eu(III) decompose in two steps. The hydrates first lose crystallization water and the anhydrous complexes are then transformed to oxides in air, and to mixtures of oxide and C in nitrogen atmosphere. When heated in air, the pentahydrates of La, Pr and Nd are dehydrated in two stages and the anhydrous complexes are then transformed to oxides; when heated in nitrogen, they are dehydrated in one step and then decomposed to mixtures of oxides and C.

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Zusammenfassung Die 3-Hydroxybenzoate von Y, Sm und Eu(III) zersetzen sich beim Erhitzen in zwei Schritten. Die Hydrate verlieren zunächst Kristallwasser und die wasserfreien Komplexe werden in Luft in die Oxide und in Stickstoffatmosphäre in ein Gemisch des betreffenden Oxids und Kohlenstoff überführt. Beim Erhitzen in Luft werden die Pentahydrate von La, Pr und Nd in zwei Schritten dehydratisiert und die wasserfreien Komplexe in die Oxide überführt; beim Erhitzen in Stickstoff erfolgt dagegen die Dehydratisierung in nur einem Schritt und Endprodukt der Zersetzung ist ein Gemisch von Kohlenstoff und dem entsprechenden Oxid.

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3- , . , — . , . , .

     

Lattice oxygen removal from nearly stoichiometric V2O5

The activation energy of the removal of lattice oxygen connected with slight thermal dissociation of V₂O₅ was measured by the TPD method. The small value (24.7 kcal/mol O₂) of this energy is discussed as the result of bivariant equilibria V₂O_5–x–O₂ within the range x<0.01.

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, V₂O₅, . V₂O_5–x–O₂ x<0,01.

     

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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. .

     

The effect of defect structure due to doping and irradiation on the thermal decomposition of potassium chlorate

The thermal decomposition of potassium chlorate was investigated as a function of doping and there seems to be a correlation between the polarizing nature of the dopant cation and the thermal degradation temperature of potassium chlorate. In particular, transition metal cations influence strongly the temperature of decomposition. Irradiation and mechanical shock defects influence also the process. A possible mechanism in terms of the semi-conductive properties of the defective chlorates is discussed.

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Zusammenfassung Die thermische Zersetzung von Kaliumchlorat wurde in Abhängigkeit von der Zugabe von Zusätzen untersucht und es scheint eine Korrelation zwischen der polarisierenden Beschaffenheit des Additivkations und der thermischen Zersetzungstemperatur von Kaliumchlorat zu bestehen. Besonders die Übergangsmetallkationen beeinflussen die Zersetzungstemperatur stark. Bestrahlung und mechanische Stoßdefekte beeinflussen den Vorgang ebenfalls. Ein möglicher Mechanismus wird anhand der Halbleiter-Eigenschaften der defekten Chlorate erörtert.

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Résumé On a étudié la décomposition thermique du chlorate de potassium en fonction de l'ajout d'additifs. Il semble qu'une corrélation existe entre la nature polarisante du cation de l'additif et la température de la dégradation thermique du chlorate de potassium. Enparticulier, ce sont les cations des métaux de transition, qui exercent une forte influence sur la température de décomposition. L'irradiation et des défauts causés par choc mécanique influencent aussi le processus. On discute un mécanisme possible à partir des propriétés semi-conductrices des chlorates présentant des défauts.

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. . , , . .

     

The preparation, characterization, and thermal behaviour of some lithium aluminum oxides: Li3AlO3 and Li5AlO4

The purpose of this research was to study the best conditions for the synthesis of the double oxides Li₅AlO₄ and Li₃AlO₃ in the solid state starting from the simple oxides, and to determine their heats of formation.Li₅AlO₄ was obtained from Li₂O₂ or Li₂O and -Al₂O₃ in a Li/Al molar ratio of 51, and was characterized by X-ray methods. Lithium orthoaluminate, Li₃AlO₃, was obtained from Li₂O₂ and -Al₂O₃ in a molar ratio 31. The postulated formula, Li₃AlO₃, was confirmed by chemical analysis.The temperature ranges in which the compounds are stable were established by the DTA method, and were found to be very limited for Li₃AlO₃ (400–430°) but greater for Li₅AlO₄ (440 — more than 600°).The heats of formation of Li₅AlO₄ and Li₃A10₃, also determined by means of the DTA method, were found to be –552.3 ± 0.8 kcal/mole and –416.8 ± 2 kcal/mole, respectively.

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Zusammenfassung Es wurden die Bildungsverhältnisse der doppelten Oxide Li₅AlO₄ und Li₃AlO₃ in fester Phase ausgehend von den einfachen Oxyden geprüft und ihre Bildungswärmen bestimmt. Li₅AlO₄ wurde aus Li₂O₂ oder Li₂O und -Al₂O₃ beim Molverhältnis von Li/Al 5 1 erhalten und röntgenographisch identifiziert. Das Orthoaluminat Li₃AlO₃ erhielt man beim Molverhältnis 3 1 von Li₂O₂ und -Al₂O₃. Die Zusammensetzung von Li₃AlO₃ wurde durch chemische Analyse nachgewiesen. Die DTA-Prüfung zeigte, daß Li₃AlO₃ nur im sehr kleinen Temperaturgebiet (400–430°), Li₅AlO₄ hingegen im weiteren Bereich zwischen 440–600° stabil ist. Die Bildungswärmen betrugen für Li₅AlO₄ –552.3±0.8, für Li₃AlO₃ –416.8±2 kcal/Mol.

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Résumé On a recherché les meilleures conditions pour réaliser la synthèse à l'état solide des oxydes doubles Li₅AlO₃ et Li₃AlO₃ en partant des oxydes individuels et pour déterminer leur chaleur de formation. Li₅AlO₄ a été obtenu en partant de Li₂O₂ (ou Li₂O) et de -Al₂O₃ dans le rapport molaire Li/Al=5/1; il a été caractérisé par étude aux rayons X. L'orthoaluminate de lithium, Li₃AlO₃, a été obtenu en partant de Li₂O₂ et de -Al₂O₃ mélangés dans le rapport 3/1. L'analyse chimique a confirmé la formule présumée Li₃AlO₃. L'ATD a permis de déterminer le domaine de stabilité thermique de ces composés: très restreint pour Li₃AlO₃ (400–430°), plus grand pour Li₅AlO₄ (440-plus de 600°), ainsi que leurs chaleurs de formation: –416.8±2 kcal/mole et –552.3±0.8 kcal/mole, respectivement.

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— Li₅AlO₄ Li₃AlO₃ . Li₅AlO₄ Li₂O₂ Li₂O -l₂₃ Li/Al 51, . , Li₃AlO₃, Li₂O₂ -l₂₃ 31. . , , , Li₃AlO₃ (400—430 °?) Li₅AlO₄ (440- 600 °?). Li₅AlO₄ Li₃AlO₃ 552.3 ± 0.8 416.8 ± 2 /, .

     

Influence of carbonate upon adsorption and isomerization of n-butenes on zeolite ZnA. Some conclusions from an infrared study

Upon the formation of carbonates inside zeolite ZnA, weakly bound species of adsorbed n-butenes are observed together with a significant change in the catalytic behavior.

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. ZnA - .

     

Influence of ammonia on propane oxidation over a gallium-antimony oxide catalyst

The influence of ammonia on propane oxidation over a Ga–Sb oxide catalyst has been studied. Acrylonitrile is formed upon the interaction of acrolein with partially dehydrogenated ammonia. Ammonia increases the rates of overall and selective oxidation of propane. This is assumed to be due to the formation of electron-donor sites promoting proton separation from the propane molecule.

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. , . . , , .

     

Effect of oxygen on the catalytic reduction of nitric oxides by carbon monoxide over NiO

The catalytic reduction of nitrogen oxides (NO, N₂O and NO₂) by carbon monoxide over NiO has been studied in the temperature range from 200 to 500°C. The reaction of NO₂ with CO is much faster than that of NO with CO. The former reaction in the presence of a 3–4-fold excess of oxygen proceeds at a significant rate. In the temperature range studied, NO₂ decomposes to N₂ and O₂.

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200–500°C (NO, N₂O NO₂) NiO. NO₂ CO NO CO. NO₂ CO 3–4- . NO₂ N₂ O₂.

     

Hydrogen adsorption on Dy and Tm films

Variations in resistivity R and work function of thin Tm and Dy films due to H₂ adsorption on their surface at 77 K have been studied. It is suggested that on most surfaces hydrogen is strongly adsorbed as H^–, and only below 10% monolayer is its weakly adsorbed form H ₂ ⁺ . The observed decrease of is attributed to H^– penetrating into lattice vacancies and surface cavities.

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R Tm Dy, H₂ 77 K. , H^–°, 10% H ₂ ⁺ . H^– .

     

The reversibility of the octahedral → tetrahedral transition in bis(pyridine)-cobalt(III) chloride Co(py)2Cl2

The octahedral-tetrahedral structural transition of Co(py)₂Cl₂ was studied by high temperature reflectance spectroscopy and dynamic reflectance spectroscopy. The reversibility of the transition by standing at room temperature for 24 hrs was established.

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Zusammenfassung Es wurde durch Hochtemperatur-Reflexions-Spektroskopie und dynamische Reflexions-Spektroskopie bewiesen, daß die strukturelle Umwandlung des oktaedrischen Co(py)₂Cl₂ in die tetraedrische Form nach 24 stündigem Stehen bei Zimmertemperatur reversibel ist.

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Résumé On a pruvé par spectroscopie de reflexion de haute température et spectroscopie de reflexion dynamique la réversibilité de la transition structurale octaédrique-tetraédrique de Co(py)₂Cl₂ après 24 heures.

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— ë Co[Py]₂Cl₂ . 24 .

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The financial support of this work by the Robert A. Welch Foundation of Houston, Texas, is gratefully acknowledged. The assistance of Mr. Sherman Bradley is also acknowledged.     

Catalytic properties and phase composition of multicomponent catalysts for oxidative ammonolysis of propane

Studies of the phase composition and catalytic properties of several complex oxide catalysts for oxidative ammonolysis of propane indicate that the active phases of these catalysts are antimonates of the respective metals. Phosphorus and tungsten additives to the catalysts promote the formation of such phase compositions, i.e. the formation of antimonates and the binding of excess antimony oxide.

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. , ; , .

     

Oxidizing properties of alumina towards alcohols. Possible reaction scheme

By chemical trapping, an acyl species has been evidenced in the oxidation of alcohols to carboxylate on an alumina surface. A possible reacton scheme is discussed.

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. .

     

The enthalpy of α-Al2O3 up to 1900 K

The enthalpy of-Al₂O₃ (pure synthetic sapphire) was measured by means of a high-temperature drop calorimeter in the temperature range from 900 to 1900 K. The results may be interpolated by the polynomial with the estimated multiple correlation coefficient squared 0.99953: (accuracy ±0.4%),This sample is used as the reference standard for calorimetry.

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Zusammenfassung Die Enthalpie von-Al₂O₃ (reiner synthetischer Saphir) wurde mittels eines Kalorimeters mit hohem Temperaturgefälle im Temperaturbereich von 900 bis 1900 K gemessen. Die Ergebnisse können an Hand eines Polynoms mit dem geschätzten multiplen quadratischen Korrelationskoeffizienten 0.99953 interpoliert werden:H _T –H ₂₉₈=– 2.72079 · 10⁴ + 8.94978T · 10¹ + 1.56711T ²· 10^–2 [J mol^–1]; (Genauigkeit: ± 4%) Diese Probe wird als Referenz-Standard zur Kalorimetrie verwendet.

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Résumé L'enthalpie de-Al₂O₃ (saphir synthétique pur) a été mesurée entre 900 et 1900K à l'aide d'un calorimètre à chute pour hautes températures. Les résultats ont pu être interpolés à l'aide du polynôme suivant, avec un coefficient de corrélation estimé de 0.99953:H _t S-H ₂₉₈=– 2.72079 · 10⁴ + 8.94978T · 10¹ + 1.56711T ² · 10^–2 (J mol^–1); (exactitude ± 0.4%) Cet échantillon est utilisé comme étalon de référence en calorimétrie.

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-l₂₃ ( ) 900 1900 . 0,99953:H _T –H ₂₉₈==–2,72079 · 10⁴+8,94978 · 10¹ · 1,56711 T² · 10² (. ^–1) ±0,4%. .

     

X-ray study of palladium catalysts. Influence of thermal treatment in hydrogen on the phase composition

The thermal treatment of Pd catalysts in a reducing atmosphere of hydrogen leads to interaction of supported metal and support to form solid solutions.

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, .

     

Kinetic model for reaction of aspartic acid with magnesium carbonate in solution

A kinetic model has been developed for describing the non-catalytic liquid-solid reaction between aspartic acid and magnesium carbonate in solution, with parallel dissolution of aspartic acid particles. The effects of size distribution of both the aspartic acid and magnesium carbonate particles have been accounted for by using a population balance model. The parameters of the model have been estimated by fitting them to experimental data taken from literature.

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- , . , . , .

     

Conditions for the appearance of thermal oscillations during the catalytic oxidation of methanol

The experimental conditions in which thermal oscillations may be detected during methanol oxidation on palladium catalyst were determined for methanol concentration, oxygen flow rate, temperature of the gaseous reaction mixture and weight of the catalyst sample. Catalyst powder disposal may influence the characteristics of oscillations.

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, , , , , , . .

     

Thermal decomposition of ammonium uranates

The thermal decomposition of ammonium uranates precipitated from uranyl nitrate solution on the addition of aqueous ammonium hydroxide and hexamine under various conditions has been studied by means of thermogravimetry, differential thermal analysis, infrared spectroscopy and X-ray diffraction. Although all precipitates show the composition corresponding to UO₃ · NH₃ · H₂O, the precipitates with hexamine give X-ray diffraction patterns designed as types I and II, in which type I is similar to the precipitates with ammonia. As a result, it is concluded that ammonium uranates thermally decompose to amorphous UO₃ at about 400°, and transform to U₃O₈ via-UO₃ and/or-UO₃, latter being formed in the case of type II only.

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Zusammenfassung Die thermische Zersetzung von unter verschiedenen Bedingungen durch wässrige Lösungen von Ammoniumhydroxid und Hexamin aus Uranylnitrat-Lösung gefällten Ammoniumuranaten wurde mittels TG, DTA, IR-Spektroskopie und Röntgendiffraktometrie untersucht. Obwohl die Zusammensetzung aller Niederschläge der Formel UO₃ · NH₃ · H₂O entspricht, geben die mit Hexamin gefällten Niederschläge die als Typ I und II bezeichneten Röntgendiffraktogramme, von denen das des Typs I ähnlich dem der mit Ammoniak gefällten Niederschlage ist. Es wird festgestellt, daß Ammoniumuranate bei 400° thermisch zu amorphen UO₃ zersetzt werden und sich über-UO₃ und/oder-UO₃—wobei beim Typ II nur das letztere gebildet wird — in U₃O₈ umwandeln.

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, , - - , . @2 UO₃ · NH₃ · H₂O, , - I II. . , 400° UO₃ U₃O₈ -UO₃ -UO₃. II.

     

Benzyl chloride transformation as a probe for electron transfer on Rh/TiO2 under SMSI state

Benzyl chloride transformation has been studied over Rh/TiO₂ under SMSI state to give evidence for the transfer of electrons from support to metal.

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Rh/TiO₂, . .