Catalytic dehalogenation of 7,7-dichloro-bicyclo(3,2,0)-hept-2-en-6-one

Dehalogenation of an unhindered haloolefin has been studied on carbon supported palladium catalyst in liquid phase, at room temperature and atmospheric pressure. The yield of bicyclo(3,2,0) hept-2-en-6-one could be multiplied by using pyridine (catalyst poison to retard bond hydrogenation) besides Et₃N (base to enhance the rate of dehalogenation).

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, , , . (3,2,0) -2--6- ( , ) (, )

     

Properties of template-free synthetic (B, Al) pentasil type zeolites

Template-free synthetic, boron-containing pentasil type zeolites exhibit structural and catalytic properties similar to those of SABO zeolites made in the presence of n-propylamine.

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, , , SABO, -.

     

Phase composition of a selective V2O5?Fe2O3 catalyst of methanol oxidation to formaldehyde

Redispersion of Re/SiO₂ catalysts during air-aging at ambient temperature has been confirmed by TEM analysis. The splitting of large primary crystallites (>10 nm) under the influence of the strain energy of the oxide layer formed on the Re surface has been proposed to explain the observed phenomenon.

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Re/SiO₂ . , Re(>10 nm), , .

     

Thermometrische und Enthalpimetrische Titrationsmethoden

Zusammenfassung Ausgehend von der allgemeinsten Form der Wärmeleistungsbilanzgleichung für thermometrische und enthalpiemetrische Titrationsmethoden werden die Möglichkeiten dieser Methoden in der analytischen Chemie und im Bereich der Stoffdatenbestimmung aufgezeigt und kritisch gewürdigt. Der Bedarf an zuverlässigen Stoffdaten erschließt den thermometrischen und enthalpiemetrischen Titrationsmethoden im Bereich der Thermo chemie der Lösungen neue Anwendungsgebiete.

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Starting from the most general form of the balance equation of thermal performance for thermometric and enthalpimetric methods of titration, the possibilities of these methods in analytical chemistry and in the field of determining data on materials are demonstrated and critically appreciated. The demand for reliable data on materials opens new fields of application of thermometric and enthalpimetric titration methods in the sphere of the thermal chemistry of solutions.

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Résumé A partir de la forme la plus générale de l'équation du bilan de puissance calorifique pour les méthodes de titrages thermométriques et enthalpimétriques, on montre les possibilités de ces méthodes en chimie analytique et dans le domaine de la détermination des données des substances et on en donne une appréciation critique. Les exigences sur les données sûres relatives aux constituants ouvrent aux méthodes de titrations thermpmétriques et enthalpimétriques de nouveaux domaines d'application dans le domaine de la thermochimie en solution.

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, , . .

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Vorgetragen anläßlich des II. Seminars Thermometrische Analyse (II. Thermometriás Szeminárium) Budapest, 2–7 September 1980.

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Teile dieser Arbeit sind Ergebnisse, die im Rahmen eines vom Bundesministerium für Forschung und Technologie gef6rderten Forschungsprogramms der DECHEMA (F91-J) am Lehrstuhl für Chemie VI der Universität Regensburg erhalten wurden. Herrn Prof. Dr. R. Wachter, Universität Regensburg, danke ich für Diskussionen und Hinweise.     

Vapor phase oxidation of methylpyridines on zeolite catalysts

It has been established that zeolites containing Pd and Cu ions catalyze the vapor phase oxidation of methylpyridines. In oxidation of 2-methylpyridine on PdCuNa-mordenite at 375 °C the yield of 2-pyridinecarbaldehyde is 40 % of its theoretical values.

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, , Pd Cu, . 2- PdCuNa- 2- 375°C 40% .

     

Ethylene hydroformylation over a nafion-supported rhodium catalyst

Ethylene hydroformylation over a Nafion-supported rhodium catalyst has been studied under atmospheric pressure in the temperature range of 100–135 °C, using the transient response method.

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, , 100–135°C, .

     

Evidence of blockage of PtH offretite channels by platinum crystallites

The introduction of platinum in a protonic offretite causes a decrease of its activity for m-xylene isomerization and an increase of its constraint index. This is due to the blockage of the offretite channels by small platinum crystallites (<8 Å), as confirmed by the study of m-xylene adsorption.

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- . (<8 Å), -.

     

Thermogravimetric changes influenced by the compaction of graphite-CrO3 intercalation compounds

The changes resulting from the compression of graphite-CrO₃ intercalation compounds are demonstrated in the TG curves. In comparison with the samples examined in the form of a flake bed, the compacted compounds begin to decompose at lower temperatures and their weight loss is higher, particularly above 220 °C. To explain the obtained results, the pressure-induced changes in the structures and the activities of the compounds are considered in relation to the method of intercalation, the concentration of the intercalant and the extent of exfoliation.

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Zusammenfassung Anhand von TG-Kurven wurden Veränderungen demonstriert, die durch das Verdichten von Graphit-CrO₃-Einlagerungsverbindungen hervorgerufen werden. Im Vergleich zu Proben, untersucht in Form von Flocken, beginnen die kompakten Verbindungen sich bei niedrigeren Temperaturen zu zersetzen und zeigen einen grösseren Masseverlust, insbesondere beim Überschreiten von 220 °C. Zur Deutung der erhaltenen Ergebnisse wurden die druckverursachten Veränderungen in Hinsicht auf das Verfahren der Einlagerung, die Einlagerungskonzentration und auf das Ausmass der Abbröckelung in Betracht gezogen.

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, -r₃. , , , 220°. , , .

     

Studies of vanadium catalysts for sulfur dioxide oxidation by51V-NMR

Studies of the⁵¹V-NMR spectra of a series of industrial catalysts and systems modelling the active catalyst component indicate that the catalyst composition depends on the preparation method and during thermal treatment the support interacts with the active component. The local environment of vanadium is being formed in the process of catalytic reactions.

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⁵¹V , -I-4, , : KVO₃, KVO₃–SiO₂, KVO₃–K₂SO₄ , , . .

     

Propylene oxidation over tin-molybdenum oxide catalysts

The influence of preparation of tin-molybdenum catalysts on their phase composition and activity has been elucidated. The mutual dissolution of Sn and Mo oxides leads to a considerable increase in their activities and selectivities in the partial oxidation of propylene to acetone.

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. , .

     

Homogeneous catalytic oligomerization of terminal alkynes and metathesis of internal alkynes using group VIB metal carbonyl based complexes

Terminal alkynes oligomerize in the presence of group VIB metal carbonyl catalysts when they are thermally activated, but internal ones undergo metathesis instead.

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VIB , , , .

     

Effect of the medium in hexacyanoferrate (III)-iodide and peroxodisulfate-iodide reaction

The kinetics of the two reactions hexacyanoferrate (III)-iodide and peroxodisulfate-iodide in several isodielectric water-cosolvent mixtures have been studied. The results can be rationalized as a consequence of the cosolventwater interaction.

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(III) -. -.

     

Coke deposition on naphtha reforming catalysts: I. Influence of the hydrocarbon feed

During hydrocarbons reactions over Pt/Al₂O₃ the catalyst is covered by coke. It is accepted that coke formation occurs on metal and acid sites. During normal heptane and methylcyclopentane reforming it was found that the nature and the rate of coke deposited on the catalyst surface was not same, depending on the structure of the hydrocarbon feed.

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Pt/Al₂O₃ . , . , - .

     

Catalytic desulfurization of ethanethiol over zinc-forms of NaX zeolites

Zinc exchanged zeolite X was found to catalyze effectively the dehydrosulfurization of ethanethiol. The catalytic activity correlated linearly with the degree of ion exchange and increased with the reaction temperature. The role of zinc cations in the reaction examined is discussed and suggestions concerning the reaction mechanism are put forward.

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X, Zn, . . .

     

Estimation of kinetic parameters in oxidative dehydrogenation of n-butenes over SnO2?Sb2O4 catalysts

Kinetic curves measured in the oxidation of n-butenes over a SnSb=31 mixed oxide catalyst were fitted by the kinetic model put forward in a previous paper. The goodness of fitting shows that the kinetic behavior of this complex reaction system can be described by a mechanism involving acidic and redox sites on the catalyst surface.

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- SnSb=31 , . , , - .

     

Formation and thermal decomposition of silicon oxynitride compounds. Part III

The formation of a previously unknown compound with stoichiometry Li₆SiN₂O₂ was found during studies on the reactivity of Li₂SiN₂ with Li₂O, of SiO₂ with Li₃N and of Li₃SiNO₂ with Li₃N.

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Zusammenfassung Die Bildung einer bisher unbekannten Verbindung der Stöchiometrie Li₆SiN₂O₂ wurde bei Untersuchungen der Reaktivität von Li₂SiN₂ mit LiO, von SiO₂ mit Li₃N und von Li₃SiNO₂ mit Li₃N beobachtet.

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Li₆SiN₂O₂ Li₂SiN₂ , , Li₃SiNO₂ .

     

51V NMR studies of systems V2O5-KHSO4 and V2O5?K2SO4

Systems V₂O₅–KHSO₄ and V₂O₅–K₂SO₄ have been studied by the⁵¹V NMR method. The first system demonstrates the same states of vanadium as the previously studied V₂O₅–K₂S₂O₇, in this system a compound with an equimolar ratio of components has been found. In V₂O₅–K₂SO₄ the state of vanadium differs from the above systems and the formation of a compound with V/K=4 is observed.

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⁵¹V KHSO₄–V₂O₅ K₂SO₄–V₂O₅. , K₂S₂O₇–V₂O₅, . K₂SO₄–V₂O₅ V/K4.

     

Epoxidation of propylene with tert-butyl hydroperoxide in the presence of heterogeneous polymeric catalysts

A series of heterogeneous polymeric molybdenum containing catalysts on the basis of weak acid cation exchanger Amberlite IRC-84 in an organic and water medium was prepared. The catalysts activity and selectivity in the epoxidation of propylene with tert-butyl hydroperoxide are compared. Data about the chemical structure of catalytically active molybdenum containing centres of the modified cation exchanger were obtained.

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, , IRC-84 . .. , .

     

Heteropolyacids as catalysts for synthesis of methyl tert-butyl ether

The influence of the composition and structure of heteropolyacids (HPA) on their catalytic activity in the liquid phase synthesis of methyl tert-butyl ether (MTBE) at 42 °C has been studied. The activity of HPA is compared with that of other acid catalysts. The most active are HPA's of the Dawson structure, then come HPA's of the Keggin and Dexter-Silverton structures. HPA salts have low activity in the synthesis of MTBE.

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() () 42°C. . , -. .