Mutual effect of benzene and maleic acid anhydride in their adsorption on V2O5?MoO3 catalysts

TPD studies have revealed that benzene and maleic anhydride are adsorbed on different active sites of the V₂O₅–MoO₃ catalyst.

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, - .

     

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 .

     

Pulse studies of cyclohexane oxidative ammonolysis to adiponitrile over Ti?Sb?O catalysts

The catalytic activities in ammoxidation of cyclohexane to adiponitrile (ADN) was compared with the phase compositions of Ti–Sb–O catalysts. It was shown that the reaction is limited by the step of ADN desorption from the catalyst.

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Ti–Sb–O (). , .

     

Influence of thermal activation of chalcopyrite on activity and selectivity of catalytic decomposition of isopropyl alcohol

The decomposition of isopropyl alcohol on natural chalcopyrite was studied by the microcatalytic pulse method in the region 473–673 K. The activity and selectivity of the catalyst was confronted with the temperature of its thermal activation. The apparent activation energies of decomposition were calculated for chalcopyrite activated in argon atmosphere at temperatures of 673, 773, and 873 K. The values of activation energy thus obtained are 61, 38, and 44 kJ mol^–1 The liberation of sulfur from the lattice of chalcopyrite caused by thermal activation gives preference to dehydration over dehydrogenation at lower temperatures. The proportion of hydrogen and acetone in reaction products increases with temperature.

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473–673 . , 673, 773 873 , 61, 38 44 /, . . .

     

Acidity and oxidation activity of MoO3?UO3/SiO2 catalysts

The effect of UO₃ on the acidity of MoO₃–UO₃/SiO₂ catalysts has been studied by means of infrared spectroscopy of adsorbed pyridine. The surface acidity exhibited a maximum for the same U/(U+Mo) atomic ratio (=0.11) that yielded a maximum in total conversion for isobutene oxidation. The catalytic properties for oxidation are discussed in terms of the acidic properties of the samples.

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UO₃ MoO₃–UO₃/SiO₂ . U/(U+Mo)=0,11, . , .

     

Ba(OH)2 as catalyst in organic reactions, III. The structure of adsorbed ylids

The nature of adsorbed sulfonium and phosphonate ylids on a new barium hydroxide catalyst (C-200) is analyzed by IR. The catalytic activity of C-200 in solid-liquid phase transfer conditions is explained by these IR studies.

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(C-200) . C-200 - .

     

Mechanism of reactions in mixtures of calcium polyphosphate with apatite and accompanying minerals during heating

The thermal interaction of Kovdor apatite, calcite, dolomite and forsterite with calcium polyphosphate up to 1200 °C were studied by chemical, thermal (under dynamic and quasiisothermal and isobaric conditions), X-ray, electronmicroscopic and chromatographic methods. It was found that the accompanying minerals of apatite react with calcium polyphosphate at lower temperature in comparison with apatite, complicating the process of thermal defluorination of papatite.

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Zusammenfassung Die thermische Wechselwirkung von Kovdor-Apatit, Calcit, Dolomit und Forsterit mit Calciumpolyphosphat bei Temperaturen bis 1200 °C wurde durch chemische, thermische (unter dynamischen, quasiisothermen und isobaren Bedingungen), röntgenographische, elektronenmikroskopische und chromatographische Methoden untersucht. Es wurde festgestellt, daß die Begleitminerale des Apatits im Vergleich zum Apatit selbst bei niedrigeren Temperaturen mit Calciumpolyphosphat reagieren und so den Prozeß der thermischen Entfluorierung von Apatit komplizieren.

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, , 1200° , ( ), , - . , , .

     

Catalytic isomerization of olefins on BeO, I

The catalytic activity of BeO for the double bond shift of 1-pentene has been investigated. The maximum activity was exhibited by samples calcined at 1173 K. The effect of pyridine, CO₂ and CCl₄ on the activity was also studied. Lewis acid-base site pairs appear to be active for the isomerization.

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BeO 1- . , 1173 . , CO₂ CCl₄ . - .

     

Reaction routes for hydrogenation of acetylene-ethylene mixtures using a double labelling method

Hydrogenation of C₂H₂:C₂H₄ mixtures using a double labelling method has been studied. Both in the presence and absence of ethylene the rate of acetylene hydrogenation on its partial pressure proceeds through a maximum and the rate is higher when ethylene is added. Using¹⁴C–C₂H₂ it was demonstrated that at low acetylene partial pressures the main route of acetylene hydrogenation was the formation of ethane and C₄ hydrocarbons. Using¹⁴C–C₂H₄ it was also shown that at certain acetylene partial pressures the formation of ethane from ethylene completely ceased. Different surface species are suggested and a reaction mechanism is proposed.

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C₂H₂:C₂H₄, . , , . C¹⁴–C₂H₂, , C₄. C¹⁴–C₂H₄, , . .

     

Gel-immobilized catalytic systems for propylene dimerization containing organophosphorus ligands

Catalytic dimerization of propylene in the presence of macromolecular nickel complexes containing organophosphorus ligands has been studied. It has been established that the substitution of alkoxy groups of phosphorus atoms in the polymeric ligands does not affect the dimer composition but permits, within certain limits, to control catalyst activity.

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, . , , .

     

Mechanism of NO adsorption and decomposition on ruthenium catalysts

Thermal desorption and IR spectroscopic studies of NO adsorption on disperse Ru-black and Ru/Al₂O₃ catalysts have revealed that NO is adsorbed as a surface nitrosyl, nitrite and nitrate complex, the stability of which depends on the temperature. A mechanism for the interaction of adsorbed NO with Ru catalysts is suggested.

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NO Ru Ru/Al₂O₃ , NO , , . (II) .

     

Oxidative conversion of butane and pentane on superacid catalysts

Catalytic properties of AlBr₃, AlBr₃–CuCl₂ and AlBr₃–NiSO₄ in liquid-phase conversion of butane and pentane have been examined. A possibility for the oxidative condensation has been revealed due to both the stoichiometric reduction of Ni²⁺ and Cu²⁺ ions entering into the composition of superacid catalysts, and the catalytic oxidation in the presence of bromine as an oxidant. Nature of the centers responsible for the oxidative condensation of lower paraffins is discussed.

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AlBr₃; AlBr₃–CuCl₂; AlBr₃–NiSO₄ . , Ni²⁺, Cu²⁺, , . , .

     

Active component of vanadium catalysts in oxidation of gases with low concentrations of SO2

EPR and NMR studies show that in oxidation of gases with low concentrations of SO₂ the molten active component of K/V and Cs/V catalysts becomes inhomogeneous and contains V⁵⁺ compounds having different activities.

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, SO₂ K/V Cs/V , V⁵⁺.

     

X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber

X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber have revealed that for the catalysts obtained by the reduction of preactivated samples, no complete reduction of platinum takes place.

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, , , .

     

Investigation of proton-acceptor properties of oxide surfaces by IR spectroscopy of hydrogen-bonded complexes

Strength of the basic centers on catalyst surfaces is suggested to be characterized by the IR spectra of adsorbed chloroform. The existence of centers with different proton-acceptor properties on several oxides is shown experimentally.

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- . , .

     

Kinetics of the reaction of peracetic acid with naphthalene and anisol

The kinetics of the bimolecular reaction of peracetic acid with naphthalene (58–75 °C) and anisol (37.5–50.5 °C) have been studied in 21 dichlorethane-acetic acid. The rate constans for naphthalene and anisol are K_napht=2.0×10⁹ exp (–21000/RT) 1 mol^–1 sec^–1, K_anis=6.3×10⁸ exp (–17000/RT) 1 mol^–1 sec^–1.

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(58–75 °C) (37.5–50.5 °C) (21). : ()=2,0×10⁹ (–21000/RT) /. . ()=6,3 10⁸ (17000/RT) /. .

     

Rapid analysis of dosage forms of some pharmaceuticals by nonaqueous thermometric titrimetry

The use of the technique of solution thermochemistry is proposed for the rapid assay for quality control and quality assurance of dosage amounts of some ethical formulations of some antimalarial drugs. The active ingredients are chloroquine, hydroxychloroquine, dapsone, proguanil hydrochloride, and pyrimethamine.Assay is done without the separation of the excipients and without isolation or derivatisation of the analytes. The titrations are done in glacial acetic acid and utilise the catalysed hydrolysis of acetic anhydride by perchloric acid to indicate the endpoint of the reactions.The time taken for a typical assay, of a typical dosage amount is about 3–5 minutes. The reproducibility is of the order of 1% for the milligramme amounts of analyte present in the dosage amounts of the drugs.

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Zusammenfassung Es wird die Anwendung eines lösungsthermochemischen Verfahrens zu Schnellbestimmungen bei der Qualitätskontrolle und — sicherung von Wirkstoffeinsatzmengen einiger rezeptpflichtiger Präparate von einigen antimalarischen Arzneimitteln empfohlen. Die aktiven Bestandteile sind Chloroquin, Hydroxychloroquin, Dapson, Proguanilhydrochlorid und Pyrimethamin.Die Bestimmungen werden ohne jegliche Abtrennung der Bindestoffe und ohne Isolierung oder Derivatisierung der zu bestimmenden Substanzen durchgeführt. Die Titrierungen werden in Eisessig durchgeführt und bedienen sich der katalytischen Hydrolyse von Essigsäureanhydrid durch Perchlorsäure als Endpunktindikation der Reaktion.Die Dauer für eine typische Probe bei einer typischen Wirkstoffmenge beträgt etwa 3–5 Minuten. Die Reproduzierbarkeit liegt in der Größenordnung von 1% für Milligrammengen der zu analysierenden Stoffe im Arzneimittel.

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. , , , . - . . 3–5 . 1% , .

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We acknowledge the Nigerian Government for the provision of a grant to one of us (S.I.A.). We acknowledge the following for the gifts of samples of the authentic drugs and the tablets assayed in this work: Imperial Chemical Industries plc; May and Baker plc; Winthrop Laboratories plc; Wellcome Foundation (Medical Division).     

Recent progress in titration calorimetry

Research developments in titration calorimetry over the past ten years by personnel at the Thermochemical Institute have resulted in new techniques and instrumentation that have greatly increased the usefulness of calorimetry in the study of chemical problems. During this time, problems associated with the components of the calorimeter (i.e., constant temperature bath, constant rate buret, reaction vessel, temperature sensing circuit, and data analysis procedure) have been solved so that the continuous titration method now gives results comparable in accuracy to those obtained with conventional solution calorimeters. These developments have opened new avenues of research in the fields of biochemistry, microbiology, and environmental analysis.

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Zusammenfassung Die Fortschritte der Forschung auf dem Gebiete der Titrationskalorimetrie, welche in den vergangenen Jahren von Mitarbeitern des Thermochemischen Instituts erreicht worden sind, führten zu neuen Techniken und neuer Instrumentation, die die Einsatzfähigkeit der Kalorimetrie zur Untersuchung chemischer Probleme wesentlich erhöhten. Während dieser Zeit wurden Probleme in Zusammenhang mit den Bestandteilen des Kalorimeters (d.h. Konstanttemperaturbad, Burette mit konstanter Geschwindigkeit, Reaktionsbehälter, Temperatur, Wärmefühler-Stromkreis und Datenverarbeitungsvorgang) gelöst, so daß die kontinuierliche Titrationsmethode jetzt Ergebnisse von einer Genauigkeit liefert, welche mit der in herkömmlichen Lösungskalorimetern erhaltenen vergleichbar ist. Diese Entwicklungsarbeit eröffnet neue Wege der Forschung auf den Gebieten der Biochemie, Mikrobiologie und Umweltschutzanalyse

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Résumé Les recherches effectuées durant les dix dernières années par le personnel de l'Institut de Thermochimie ont eu pour résultat la mise au point d'appareils nouveaux qui augmentent, considérablement l'applicabilité de la calorimétrie à l'étude des problèmes chimiques. Ainsi les problèmes associés aux composants d'un calorimètre (c'est-à-dire bain à température constante, burette à vitesse constante, récipient réactionnel, circuit détecteur de température et procédés d'analyse des données) ont été résolus. C'est pourquoi la technique du titrage en continu donne maintenant des résultats d'une exactitude comparable à celle obtenue avec les calorimètres en solutions conventionnels. Ces développements ont ouvert de nouvelles perspectives de recherche dans les domaines de la biochimie, de la microbiologie et des analyses liées à la protection de l'environnement.

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, , , . , : , , , - . , , , . , .

     

Thermal and spectral studies on some tetrachloroaurates of 8-alkyltheophylline derivatives

Tetrachloroaurates of 8-ethyl-, 8-isopropyl-, 8-propyl- and 8-pentyltheophylline were synthesized and studied by¹H-NMR, TG and DSC techniques. The metal is not coordinated to the 8-alkyltheophylline derivatives and forms a salt-like structure.

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Zusammenfassung Tetrachloroaurate von 8-Äthyl-, 8-Isopropyl-, 8-Propyl- und 8-Pentyltheophillin wurden synthetisiert und mittels¹H-NMR, TG und DSC untersucht. Die 8-Alkyltheophillin-Derivate sind nicht koordinativ an das Metall gebunden, es liegt vielmehr eine salzartige Struktur vor.

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8--, 8--, 8-- 8- , . , 8- .