Photochemical reactions of anthraquinone with hydrocarbons in the presence and absence of oxygen: Trapping of radical intermediates

Radical intermediates formed at 25°C in the presence and absence of oxygen during the photolysis of anthraquinone in aromatic, cyclic and aliphatic hydrocarbon solvents were trapped by 2,6-dichloronitrosobenzene, 2,6-dibromonitrosobenzene and 2,4,6-tribromonitrosobenzene. The resulting nitroxide radicals have been characterized in situ by ESR spectra.

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: 2,6-, 2,6- 2,4,6-— , , 25°C. .

     

The thermal behaviour of cis-1,4-polyisoprene in the presence of cobalt salt

The effects of synthetic fatty acids (Versatic 10, average formula C₁₁H₂₂O₂) and the cobalt salts of these acids (cobalt siccative) on the thermal properties of cis-1,4-polyisoprene were examined, using a rheometer and a derivatograph. It was found that both Versatic 10 and the cobalt siccative accelerate the peroxide vulcanization of the isoprene rubber considerably, simultaneously decreasing the cross-linking density and increasing the sol fraction content in the vulÇanizates. This is brought about by parallel radical and ionic decomposition of the peroxide initiator in the presence of these compounds. The addition of Versatic 10 or the cobalt siccative to the polyisoprene rubber does not alter the general character of its thermal changes, but decreases the temperatures of these processes and the degradation degree of the elastomer.

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Zusammenfassung Der Einfluss synthetischer Fettsäuren (Versatic 10, mittlere Summenformel C₁₁H₂₂O₂) und ihres Kobaltsalzes (Kobalt-Sikkativ) auf die thermischen Eigenschaften von cis-1,4-Polyisopren wurde mittels Rheometer und Derivatograph untersucht. Sowohl Versatic 10 als auch das Kobaltsikkativ beschleunigen die Peroxid-initiierte Vulkanisation des Isoprenkautschuk, gleichzeitig wird die Vernetzungsdichte verringert und der Gehalt an löslichen Stoffen in den Vulkanisaten erhöht. Ursache dafür ist der parallelle Ablauf der radikalischen und ionischen Zersetzung des Peroxids in Gegenwart der Zusätze. Die Beimengung von Versatic 10 oder Kobaltsikkativ zum Polyisoprenkautschuk ändert nicht den allgemeinen Charakter der thermischen Umwandlungen, aber die Temperatur dieser Reaktionen und der Abbau des Elastomeren werden verringert.

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, C₁₁H₂O₂ ( 10) -1,4-. , 10, , . . 10 , , .

     

ESR spectra of47Ti-enriched titanium catalysts for polymerization

For the first time ESR spectra of⁴⁷Ti-enriched Ziegler system Ti-TIBA in toluene have been studied. For the ratio Ti/Al1, more accurate h. f. s. constants have been found. For Ti/Al1/15 no h. f. s. have been observed, which is ascribed to ordering due to the cooperative Jahn-Teller effect.

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TiCl₄+ ⁴⁷Ti. Ti/Al1 . Ti/Al1/15 , -.

     

IR study of adsorbed piperidine dehydrogenation on oxidic or sulfided Ni?W/Al2O3 catalysts

IR spectroscopy has been used to follow the transformation at different temperatures of piperidine chemisorbed on oxidic or sulfided Ni–W/Al₂O₃ catalysts. Formation of an intermediate species, possibly tetrahydropyridine, and pyridine is evidenced. Their formation temperature on the sulfided samples accounts for the catalyst activity in pyridine hydrogenation under H₂ pressure.

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- , Ni–W/Al₂O₃, . , , . .

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This work was supported by the Groupement scientifique Hydrotraitement catalytique (CNRS-IFP, TOTAL. ELF).     

Effect of preparation conditions on the properties of carbon-supported nickel catalysts

Carbon-supported Ni catalysts were prepared from nickel nitrate or chloride. Characterization was carried out by H₂ and CO chemisorption, XRD and TEM. Catalysts were further tested in the hydrogenolysis of n-butane.

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, , . H₂ CO, ., -.

     

Activity in CO oxidation of manganese dioxide for batteries

The low temperature oxidation of CO over MnO₂ containing samples for batteries has been investigated. It is found that the samples contain compositional and hydrate water and Mn⁴⁺, Mn³⁺, Mn²⁺ ions. The high efficiency is due to Mn⁴⁺ content.

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CO MnO₂, . , Mn⁴⁺, Mn³⁺, Mn²⁺. Mn⁴⁺.

     

Reactions of isoflavone and 2-hydroxyisoflavanone with sodium ethoxide in anhydrous ethanol

Recent observation /1,4/ on the existence and unreactivity of IV under basic conditions, as well as its part in the inhibitory effect on the decomposition into deoxybenzoin is unequivocally proved by comparing the decompositions of I and VI. It is also shown that the decomposition of I is detemined neither by the character of the solvent nor by the nucleophilic character of the reactant, but by the possibility of the formation of IV.

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IV , I VI. , I . , , IV.

     

Exchange kinetics of amino acid anions in solutions of ternary copper(II) complexes with diethylenetriamine

Rate constants for the chemical exchange of some amino acid anions in solutions of copper(II) ternary complexes with diethylenetriamine have been determined by the NMR method. The coordination of amino acid anions in ternary and binary species is different and ligand substitution in the Cu(II) complexes follows an associative mechanism.

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- (II) . - (II).

     

Temperature effects on coprecipitated Al,Fe-hydroxides during hydrothermal transformations

Studies of the hydrothermal behaviour of coprecipitated Al, Fe-hydroxides with aluminium contents from 5 to 50 mol% reveal that the temperature of the hydrothermal process strongly affects the reciprocal influence of Al(III) and Fe(III) ions on the direction of transformation of the initially amorphous gels.It has been found by X-ray diffraction analysis and IR spectroscopic investigations that at 373 K, up to 10 mol% Al, well-crystallized Al-substituted hydrohematite is formed; at 15–25 mol% Al the crystallinity falls off and the products are amorphous; and at 27.5–50 mol% Al the poorly-crystallized hydrohematite appears, accompanied by different crystalline aluminium trihydroxides, the equilibria of which depend essentially on the AlFe ratio and on the pH of the medium.The hydrothermal process carried out at 413 K yields the Al-substituted protohematite for samples with 15–50 mol% Al, whereas the unique crystalline phase of Al-hydroxide is a well-crystallized boehmite.

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Zusammenfassung Untersuchungen des hydrothermalen Verhaltens von kopräzipierten Al, Fe-Hydroxiden mit Aluminiumgehalten von 5–50 mol% haben ergeben, daß die Temperatur des hydrothermalen Prozesses den gegenteiligen Effekt von Al(III)- und Fe(III)-Ionen auf die Richtung der Umwandlung der anfänglich amorphen Gele wesentlich beeinflußt. Durch Röntgendiffraktion und IR-Spektroskopie wurde ermittelt, daß bei 373 K bis zu 10 mol% Al gut kristallisierter, Al-substitutierter Hydrohämatit gebildet wird. Bei 15–25 mol% Al sind die Produkte amorph und bei 27,5–50 mol% Al liegt schlecht kristallisierter Hydrohämetit vor, begleitet von verschiedenen kristallinen Aluminiumtrihydroxiden, deren Gleichgewicht im wesentlichen vom Al/Fe-Verhältnis und vom pH des Mediums abhängt. Der bei 413 K. ausgeführte hydrothermale Prozeß ergibt Al-substituiertes Protohämatit für Proben mit 15–50 mol% A, während ein gut kristallisierter Boehmit die einzige kristalline Al-Hydroxidphase ist.

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5 50 , . , 373 10 , . 15 25 , , 27,5–50 — . , , , AlFe pH . , 413 15–50 , , .

     

Studies of dynamic properties of heterogeneous catalytic reactions in a closed isothermal gradientless system over biographically inhomogeneous catalyst surface

The dynamics of a closed isothermal system of constant volume consisting of an ideal gaseous mixture and particles adsorbed over the biographically inhomogeneous catalyst surface, has been studied. The existence, uniqueness and asymptotic stability of the point of detailed equilibrium in each positive reaction simplex has been proved.

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, , . , , .

     

Structure, activity and selectivity of V2O5-TiO2 catalysts for o-xylene conversion

The formation of needle shaped crystallites of V₆O₁₃ at low V concentrations on V₂O₅-anatase coated catalysts explains the low selectivity for phthalic anhydride during o-xylene oxidation. The (010) plane of V-oxide, most active for selective oxidation of o-xylene, is not accessible and the contact of this plane with the anatase faces promotes the anatase-rutile transformation and the incorporation and blocking of V⁴⁺ ions.

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V₆O₁₃ V , V₂O₅-, -. (010) , -, , - V⁺⁴.

     

Thermochemistry of Carbonization of Polypyromellitimide

The mechanisms of thermal degradation processes in polypromellitimide films were investigated by mass-spectrometric thermal analysis and high-resolution NMR spectroscopy in the solid state. Both the structures of the solid residues of pyrolysis products of the PM polyimide and the process of carbonization proper up to 1200° were studied. It was established that the breaking of the C_ar-O-C_ar bond in the diamine moiety is not the primary act of degradation of the molecular structure of the polymer, as might be expected on the basis of the value of the bond energy. The process of intermolecular crosslinking following polymer degradation under high-temperature conditions is completed by the formation of a complex nitrogen-containing heterocyclic structure.

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Zusammenfassung Der Mechanismus der in Polypyromellitfilmen ablaufenden thermischen Zersetzungsprozesse wurde durch massenspektrometrische thermische Analyse und hochauflösende Festkörper-NMR-Spektroskopie untersucht. Sowohl die Struktur des festen Rückstandes des Pyrolyseproduktes des PM-polyamids als auch der Prozeß der Verkokung bis 1200 °C wurden Untersucht. Es wurde festgestellt, daß das Aufbrechen der Bindung C _ar ,-O-C _ar im Diaminteil nicht der primäre Schritt der Zersetzun der molekularen Struktur des Polymers ist, wie nach dem Wert der Bindungsenergie zu erwarten wäre. Der auf die Hochtemperatur-Polymerzersetzung folgende Prozeß der intermolekularen Vernetzung endet mit der Bildung einer komplexen stickstoffhaltigen heterozyklischen Struktur.

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- (MTA) (MP BPTT) , 1200 °C. . , C _ap -C _ap , , .

     

Infrared spectra of nitric oxide adsorbed on photoreduced V/SiO2 catalyst

Studies of the IR spectra of surface species produced via NO adsorption on selectively photoreduced V/SiO₂ catalysts indicate that at low coverages NO is adsorbed on V³⁺ ions to form strongly bonded mononitrosyl species V³⁺...... NO. With increasing NO coverage, V³⁺ is oxidized to V⁴⁺, which is accompanied by the appearance of gaseous N₂O and weak adsorption of NO on V⁴⁺.

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- , NO V/SiO₂ . , V³⁺ NO V³⁺... NO. V³⁺ V⁴⁺, N₂O NO V⁴⁺.

     

Oxygen interaction with rhodium at low pressures II. Oxygen desorption

Oxygen desorption on polycrystalline Rh and single crystal Rh(100) at 400–1600 K has been studied using thermal desorption and numerical calculation methods. With low surface coverages (<0.3) the adsorbed oxygen particles pentrate the metal and the diffuse back to the surface (peak ₂). At >0.3 the processes of formation/decomposition of surface oxide Rh₂O₃ takes place (peak ₁).

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- O₂ Rh Rh(100) 400–1600 . (<0,3) O ë ( ₂), >0,3 - - (Rh₂O₃) ( ₁).

     

Reduction of CuO-containing catalysts: CuO/ZnO

CO reduction of CuO in CuO/ZnO samples at 423 K isnot retarded by the support and occurs with no evidence of Cu₂O formation as reported (Porta et al. 1989). The positive order with regard to CO concentration varies with the precise range of CO partial pressure.

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CuO CO CuO/ZnO 423 Cu₂O , (Porta etal Solid State Ionics 32–33, 1019, (1989)). CO CO.

     

DSC characterization of ZSM-5/MgO/Al2O3 catalysts

The physico-chemical characterization of magnesium-modified ZSM-5 zeolite catalysts has been performed by differential scanning calorimetry. Evidence has been found of the formation of magnesium oxide and the magnesium spinel phase in alumina-bonded ZSM-5 catalysts. DSC proved a suitable technique for characterization of these systems.

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Zusammenfassung Mg-modifizierte ZSM-5-Zeolithkatalysatoren wurden durch DSC charakterisiert. Es wurden Beweise für die Bildung von Magnesiumoxid und Magnesiumspinell in ZSM-5/Aluminiumoxid-Katalysatoren gefunden. DSC hat sich zur Characterisierung dieser Systeme als geeignet erwiesen.

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- 3CM-5, . - - . .

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This work was carried out within the Progetto finalizzato Energetica 2 of the National Research Council of Italy.     

Cracking of cumene on vanadium doped silica-alumina

The influence of small admixtures of vanadium on the activity of a silica-alumina catalyst in cumene cracking has been investigated. A correlation has been established between the catalytic and acidic properties of the vanadium doped catalyst.

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. .

     

Methane synthesis from CO/H2O mixture on supported nickel catalysts, II. Surface species in CO?H2 and CO?D2O interaction by IR spectroscopy

The species resulting in CO, CO+H₂ or CO+D₂O adsorption on supported Ni catalysts were followed by IR spectroscopy and their role in methane synthesis mechanism is discussed.

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- , CO, CO+H₂ CO+D₂O . .

     

A study of the heavy fractions and residues from West Siberian crude oil by thermogravimetric and differential thermal analysis techniques

A method for comparing the thermochemical properties of high- boiling fractions and residues has been developed. The thermal effects vary in intensity and range, depending on the fractional and structure group compositions of the studied samples. Good agreement between DTA and TG data is observed. The thermal analysis of samples, obtained by liquid adsorption chromatography, reveals the specific differences of the individual structure group fractions in the processes of evaporation, thermal decomposition and coke formation. The observed effects are interpreted from the point of view of the different thermal stabilities and reactivities of the compounds contained in the Chromatographic fractions. The results show that the TG-DTA method allows the quick determination of some characteristics depending on the group compositions of the high-boiling fractions and residues from West Siberian crude oiL.

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Zusammenfassung Ein Verfahren zum Vergleich der thermochemischen Eigenschaften von schwersiedenden Fraktionen und Rückständen wurde entwickelt. Die thermischen Effekte unterscheiden sich in Intensität und Bereich des Auftretens, immer abhängig von der chemischen und strukturellen Zusammensetzung der Proben. Zwischen DTA- und TG-Daten konnte gute Übereinstimmung beobachtet werden. Die Thermoanalyse der durch Adsorptionsflüssigkeitschromatographie erhaltenen Proben offenbart die spezifischen Unterschiede der einzelnen strukturellen Fraktionen während des Verdampfungs-, thermischen Zersetzungs- und Verkokungsprozesses. Die beobachteten Effekte wurden unter Gesichtspunkten der unterschiedlichen thermischen Stabilität und Reaktivität der aus den chromatographischen Fraktionen gewonnenen Verbindungen diskutiert. Die Ergebnisse zeigen, dass das TG-DTA-Verfahren eine schnelle Bestimmung einiger von der funktionellen Gruppenzusammensetzung abhängigen Eigenschaften schwersiedender Fraktionen und Rückstände aus westsibirischem Rohöl ermöglicht.

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. , - . . , , - , , , . , - - .

     

Isomerization of unsaturated compounds on Pd/Al2O3 in the presence of additives

Studies of the effect of zinc chloride and aluminium additives on the activity of a Pd/Al₂O₃ catalyst (5 wt.%Pd) in the isomerization of heptene-1, allylbenzene,p-allylphenol and 4-allyl-2-methoxyphenol (eugenol) indicate that the rate and selectivity of isomerization depend on the sequence of addition of salts and reagent to the catalytic system. The simultaneous addition of ZnCl₂ or AlCl₃ with olefin, produces a 2–3 fold increase in the isomer yield compared to ethanol.

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Pd/Al₂O₃- (5 .% Pd) -1, , -, 4--2- (). , . ZnCl₂ AlCl₃ 2–3 .