Response studies of the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst

A response method has been used to study the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst. The products of partial and destructive oxidation are shown to be formed under the influence of molecular oxygen on the surface intermediates produced by the interaction between o-xylene and oxidized surface sites.

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- . , , - .

     

Studies on the thermal decompositions of As-triazine derivatives and their compounds with metal ions

The thermal decompositions of the new complex salts of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 5,6-diethoxyearbonylmethyl-3-seleno-1,2,4-triazine (HSeTEK) and 5,6-diethoxycarbonylmethyl-3-thio-1,2,4-triazine (HTTEK) were investigated on the basis of the respective thermal curves. The thermoanalytical investigations indicate that HSeTEK, HTTEK, and their complexes with metal ions all undergo three-stage changes as the temperature is raised. The stages of pyrolysis established from the thermal data were compared, and the rates and stages of pyrolysis were related to the structures of the compounds.

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Zusammenfassung Die thermische Zersetzung der neuen Komplexsalze von Mn(II), Co(II), Ni(II) und Cu(II) mit 5,6-Diäthoxycarbonylmethyl-3-seleno-1,2,4-triazin (HSeTEK) und 5,6-Diäthoxycarbonylmethyl-3-thio-1,2,4-triazin (HTTEK) wurden auf der Grundlage der entsprechenden thermischen Kurven untersucht. Die thermoanalytischen Untersuchungen zeigen, daß HSeTEK, HTTEK und deren mit Metallionen gebildeten Komplexe bei Temperaturerhöhung einer jeweils dreistufigen Umwandlung unterliegen. Die auf der Basis der thermischen Daten festgestellten Pyrolysestufen wurden verglichen und Geschwindigkeit und Abschnitte der Pyrolyse mittels der Struktur der Verbindungen erläutert.

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, , 5,6- -3--1,2,4- 5,6 5,6 -3--1,2,4-. , . . - .

     

FTIR investigation of the structure of vanadium oxides on ZrO2 and oxidation of toluene on it

The oxidation of toluene has been studied on V₂O₅/ZrO₂ by both FTIR spectroscopy and pulse method. The results suggest that Lewis-acidic sites play a significant role in the formation of benzaldehyde from toluene.

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V₂O₅/ZrO₂ - , . .

     

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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. , .

     

Preparation and characterization of Ru?Pb supported catalysts

Decomposition of Mn₃Mo₂TeO₁₂ during oxidation of toluene to benzaldehyde was observed. Depending on the surface composition of the initial catalyst, the decomposition leads to less active but highly selective MnMoTeO₆ or to MnMoO₄ which is not selective in toluene oxidation.

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Mn₃Mo₂TeO₁₂ . , MnMoTeO₆, MnMoO₆.

     

Reaction scheme in the non-isothermal decomposition of (C6H5NH3)4Mo8O26 · 2 H2O

The thermogravimetric decomposition of anilinum octamolybdate has been studied under non-isothermal conditions to elucidate the chemical reactions taking place in the first step of decomposition of the anhydrous compound.The decomposition products were analyzed by gas-liquid chromatography, gas chromatography-mass spectrometry (GC/MS), infrared spectroscopy and X-ray powder diffraction.The main decomposition product of aniline turned out to be indole, which is different from the major product in the isothermal decomposition at the same temperature, i.e. N-ethyl-aniline.A dehydrocyclization reaction is suggested as the rate-dependent process. This is probably due to the catalytic effect of the octamolybdate anion.

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Zusammenfassung Die thermische Zersetzung von Anilinoctamolybdat wurde unter nicht-isothermen Bedingungen thermogravimetrisch untersucht, um die im ersten Zersetzungsschritt der wasserfreien Verbindung verlaufenden chemischen Reaktionen aufzuklären. Die Zersetzungsprodukte wurden mittels Gas-Flüssigkeits-Chromatographie, Gaschromatographie-Massenspektrometrie (GC/MS), Infrarotspektroskopie und Röntgendiffraktometrie analysiert. Als Hauptprodukt der Zersetzung von Anilin wurde Indol gefunden, während bei isothermer Zersetzung bei gleicher Temperatur vorwiegend N-Äthylanilin entsteht. Es wird angenommen, daß beim nicht-isothermen Prozeß eine wahrscheinlich durch das Octamolybdat katalysierte Dehydrocyclisierungsreaktion verläuft.

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, . - , -- , . , -N- . , , -.

     

Cyclohexane photooxygenation by air oxygen in CH2Cl2 in the presence of chromium oxocomplex-iodosylbenzene system

Cyclohexane is oxidized by air oxygen in CH₂Cl₂ solution to yield cyclohexanol, cyclohexanone and cyclohexyl chloride when irradiated by light (>310 nm) in the presence of (Bu₄N)₂CrO₄ or (Bu₃SnO)₂CrO₂. The addition of PhIO greatly accelerates the reaction and increases the yield of products. The reaction mixture contains neither cyclohexanol nor cyclohexanone when the photoreaction in the presence of the Cr(VI)–PhIO system is carried out in argon atmosphere. Hence neither iodosylbenzene nor oxochromium compounds can be oxygen atom donors in alkane oxygenation. The accelerating effect of iodosylbenzene may be due to the enhanced oxidizing power of photo-excited oxochromium species when coordinated to iodosylbenzene.

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CH₂Cl₂ , , (>310 ) (Bu₄N)₂CrO₄ (Bu₃SnO)₂CrO₂. PhIO . Cr(VI)–PhIO , , . , ( ) . .

     

Characterization of the interaction of CO and H2 at the ZnO surface by adsorption microcalorimetry

CO and H₂ are both chemisorbed by ZnO but H₂ is more sensitive than CO to the surroundings of adsorption sites. When the two gases are coadsorbed, a strong interaction occurs, ascribed to the formation of a possible precursor in methanol synthesis.

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CO H₂ ZnO, H₂ , , CO. , , .

     

The role of lattice and adsorbed oxygen in the oxidation of n-butene-1 and furan with MnMoO4-based catalysts

In this paper the adsorption properties towards oxygen and the catalytic oxidation properties of furan and n-butene-1 on a MnMoO₄-based catalyst have been compared. Different forms of adsorbed oxygen are responsible either for the oxidation of furan to maleic anhydride or of furane and n-butene-1 to carbon oxides.

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--q MnMoO₄. , --1 .

     

Effect of ligands on the hydrogenation selectivity in the presence of rhenium catalysts

It has been established that the catalytic activity of rhenium oxohalide complexes with phosphorus- or sulfur-containing ligands in hydroganation of C₆–C₁₀ olefins, nitrobenzene and p-nitrotoluene is primarily determined by the original ligand to rhenium ion bond. Chain length of olefins does not affect their hydrogenation rate.

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- C₆–C₁₀, - - . .

     

Zum Thermischen Verhalten von Zitronensäure

Zusammenfassung Mit Hilfe der thermo-optischen Analyse wird gezeigt, daß die widersprüchlichen Angaben in der Literatur zum thermischen Verhalten von Zitronensäuremonohydrat und dem Zitronensäureanhydrit auf eine Überlagerung verschiedener thermischer Reaktionen (Schmelze, Zersetzung, Entmischung und Kristallisation), die mit unterschiedlicher Geschwindigkeit ablaufen, zurückzuführen sind. Die thermo-optische Methode ist besonders für die Aufklärung solch komplexer Reaktionsabläufe geeignet. Das Beispiel des thermischen Verhaltens der Zitronensäure zeigt modellhaft die Erscheinungen, die bei der thermischen Analyse technischer Prozesse, wie dem Einschmelzen von Rohstoffgemengen, zu erwarten sind.

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By means of the thermomicroscopy was demonstrated that the discrepancy between the experimental DSC- and TG-data on the decomposition of citric acid in the literature can be explained in terms of superimposing reactions (melting, decomposition, immiscibility, and crystallization), which have different reaction rates. The thermomicroscopy is especially useful explaining such kind of reactions. The thermal behaviour of citric acid can be used as a model reaction in technology.

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, ( , , ), . . .

     

Determination of the strength of Lewis acid centers via IR spectroscopic measurement of adsorbed pyridine

According to high-temperature IR spectroscopic studies, the isosteric heats of pyridine adsorption on the Lewis centers of Al₂ O₃, ZrO₂ and zeolite HNaY have been estimated. The dependence between the frequency _8a (1580–1630 cm^–1) and the adsorption heat is shown to take place only for centers formed by cations of the same metal.

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, - HNaY. , _8a (1580–1630 cm^–1) , - .

     

Solid-gas reactions: Study of sulphation of limestone using thermogravimetry

Comparative data are presented on the absorption rate and capacity for SO₂ capture by a natural Polish limestone with and without sodium chloride additive. Two sets of experiments were carried out, under dry and wet conditions during limestone calcination and sulphation.The presence of water vapour brought about a higher reactivity of the sorbent, probably as a result of an effect on the sintering of lime and through the influence of the CaSO₄ layer. Further morphological investigations could provide confirmation of the present hypothesis.

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Zusammenfassung Absorptionsgeschwindigkeit und -kapazität für SO₂ an einem polnischen Kalkstein mit oder ohne NaCl-Zusatz werden verglichen. Zwei Reihen von Experimenten wurden in trockener bzw. wasserdampfhaltiger Atmosphäre bei der Calcination und Sulfatbildung durchgeführt. In Gegenwart von Wasserdampf wird die Reaktivität des Absorbens infolge Sinterung des Kalks und trotz des Einflusses der CaSO₄-Schicht erhöht. Künftige morphologische Untersuchungen sollen diese Hypothese eventuel bestätigen.

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. . , , . .

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The author would like to thank Prof. E. M. Bulewicz of this Institute for valuable discussions, and Mr. W. Balcerowiak for making available the facilities of the Laboratory of the Institute of Heavy Organic Synthesis in Kdzierzyn-Kole.     

Thermodynamic aspects of conformational transitions in synthetic polypeptides

The helix-coil transition of organic solvent soluble homopolypeptides has been discussed from a largely thermodynamic view-point. The present state and the future prospects are considered.

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Zusammenfassung Der Helix-Ungeordnete Übergang von in organischen Lösungsmitteln löslichen Homopolypeptiden wurde aus einem breiten Gesichtspunkt diskutiert, gegenwärtige Lage und zukünftige Entwicklungsaussichten erörtert.

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R'esumé On a discuté d'une pointe de vue thermodynamique large la transition helix—non helix des homopolypeptides solubles dans des solvants organiques et considéré la situation actuelle ainsi que les perspectives futures.

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, , . .

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The present paper was supported by NSF Grant GB 33484.     

Mixed suspensions of semiconductors forming microheterojunctions. A new type of highly efficient photocatalysts: Photocatalytic production of dihydrogen from a water solution of sulfide ions in the presence of platinized ZnyCd1-y/CuxS suspension

A new method is proposed for increasing the quantum efficiency of H₂ production for the photocatalysts based on semiconductor suspensions. The method consists of the formation of suspended particles with microheterojunctions between their components--semiconductor phase.

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H₂ .

     

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% .

     

Effect of specific and nonspecific interactions on deutero-protium exchange in solution

The effect of electrostatic type interactions on the deutero-protium heteroexchange of dihydrogen with solutions catalyzed by bases, with the decisive role of hydrogen bonds and particularly of the H-bonds having increased strength, is discussed.

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- .

     

The thermoanalytical determination of deactivation types of cation-exchanger catalyst's

The dependence of the thermal decomposition of a cation-exchanger catalyst on its deactivation type has been ascertained, and thermal analysis has been suggested as a diagnostic method for the determination of the condition of such a catalyst.

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Zusammenfassung Die Abhängigkeit der thermischen Zersetzung eines Kationaustauscher-Katalysators von seinem Inaktivierungstyp wurde bewiesen und die Thermoanalyse als diagnostische Methods für die Bestimmung des Zustandes eines solchen Katalysators vorgeschlagen.

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. , .