Effect of traces of water vapor on the rate of ammonia decomposition on polycrystalline platinum

The influence of small (lower than 0.02) molar fractions of water on the rate of ammonia decomposition on platinum wires was studied for ammonia pressures varying between 6.7 and 93.3 kPa and temperatures between 800 and 1700 K. The presence of water strongly inhibited the rate of reaction in all experiments.

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( 0,02) , 6,7 93,3 , 800 1700 K. .

     

Catalytic and acidic properties of different metal-zeolite catalysts

Catalytic and acidic properties of bifunctional catalysts containing faujasite, superhigh-silica zeolite and mordenite have been studied in isomerization of C₈-alkylaromatic hydrocarbons.

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C₈ , , - .

     

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. . , -. .

     

Reduction behavior of Cu?SiO2 catalyst prepared by ion exchange for selective dehydrogenation to produce methyl formate from methanol

Reducibility of Cu–SiO₂ catalyst prepared by ion exchange method, being effective for selective dehydrogenation to produce methyl formate from methanol at lower temperatures, has been studied by a TPR technique. The results suggest that easier reduction leads to an increase of dispersity of Cu particles.

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, - , , . , , Cu.

     

Beitrag zur aufeinanderfolgenden thermochemischen Bestimmung von SiO2 und Al2O3 Aus flusssaurer lösung

Zusammenfassung Die vorliegende Arbeit gibt eingangs einen Überblick von Publikationen, die sich mit der thermochemischen Bestimmung von SiO₂ und Al₂O₃ aus flußsaurer Lösung befassen. Davon ausgehend werden Versuche beschrieben und Ergebnisse diskutiert, die mit konstanten Einwaagen von 700 mg SiO₂ und etwa 100 mg Al₂O₃ aus flußsaurer Lösung und verschiedenen Kombinationen von Injektionsreagenzien erhalten wurden und die auf die Belange der Analyse von gefällten Natriumaluminiumsilicaten abgestimmt waren. Die vorgenommenen Untersuchungen führen zu den Schluß, daß Al₂O₃ und SiO₂ in Natriumaluminiumsilicaten aus flußsaurer Lösung mit der Injektionsreagenskombination SrCl₂KCl bestimmt werden sollten.

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The first part of the paper gives a review of the literature dealing with thermochemical determinations of SiO₂ and Al₂O₃ in hydrofluoric acid solution. The results of experiments with constant samples weights of 700 mg SiO₂ and about 100 mg Al₂O₃ in hydrofluoric acid solution with differently combined injection reagents are discussed. The determinations were based on the analysis of precipitated sodium aluminium silicates.The investigations revealed that combined SrCl₂/KCl solution should be used as injection reagent for determination of the Al₂O₃ and SiO₂ contents of sodium aluminium silicates in hydrofluoric acid.

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, . , (700 ) ( 100 ) , . . , SrCl₂-KCl .

     

V2O5/TiO2 oxidation catalysts, III. Oxidation of CO on pure and sodium-doped systems

The activity of vanadia/titania catalysts in CO oxidation has been tested and found to be of the same order as that observed for unsupported vanadia; the simultaneous presence of vanadium-sodium compounds cancels the activity, probably because of the elimination of labile V=0 species at surface defects.

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V₂O₅/TiO₂ CO, V₂O₅; - , , V=0 .

     

Die γ-Bestrahlung von synthetischem β-Carotin

Zusammenfassung Das feste -Carotin ist gegen -Strahlung ziemlich stabil. Bei Bestrahlung unter Sauerstoffbegasung treten deutliche -Carotin-Verluste erst bei der hohen Dosis von 12 Mrad auf; bei Bestrahlung an der Luft werden ähnliche Radiolyseerscheinungen erst durch wesentlich höhere Strahlendosen ausgelöst. Spaltungsprodukte, die bei 12 Mrad und Sauerstoffbegasung auftraten und dünnschichtchromatographisch aufgetrennt werden konnten, waren Isozeaxanthin, -Carotin-5,6-5, 6-diepoxid, -Carotin-5,8-5,8-diepoxid, -Apo-12-carotinal, -Apo-10-carotinal, 3,3,6-Trihydroxy--carotin-5,8-epoxid und Vitamin-A-Alkohol. Es ist bemerkenswert, daß ein Teil der Radiolyseprodukte (z. B. Vitamin-A₁-Alkohol, -Apo-12-carotinal und -Apo-10-carotinal) Vitamin-A-Wirksamkeit besitzt.

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The -Irradiation of synthetic -carotene. Some physico-chemical and thin-layer chromatographic studies of radiolysis products

Solid -carotene is remarkably stable to -irradiation. In an oxygen atmosphere doses as high as 12 Mrad were required to bring about significant losses of -carotene, whereas in air even larger doses had to be applied in order to effect a comparable degree of radiolysis. Cleavage products which arose in O₂ at a dose of 12 Mrad and which could be separated from each other by thin-layer chromatography were isozeaxanthin, -carotene-5,5-5,6-diepoxide, -apo-12-carotenal, -apo-10-carotenal, 3, 3, 6-trihydroxy--carotene-5,8-epoxide and vitamin A₁. It is notable that some of the radiolysis products (e.g., vitamin A₁, -apo-12-carotenal and -apo-10-carotenal) possess vitamin A activity.

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Herrn Prof. Dr.O. Hromatka zum 65. Geburtstag gewidmet.     

Gas-phase hydroformylation of propylene on Ru/SiO2 catalysts

Ru/SiO₂ catalysts prepared by reduction of supported RuCl₃·xH₂O are active in gas-phase hydroformylation of propylene at low pressure (ca. 0.3 MPa) of H₂+CO+C₃H₆ mixtured and show unexpectedly high selectivity towards unbranched oxo-products. Data concerning the effect of electronic state and dispersity of Ru on their catalytic behavior have been obtained.

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Ru/SiO₂, RuCl₃·xH₂O, (0,3 ) - . .

     

Ethanolysis of penta- and tetramethyldisiloxane catalyzed by aqueous hydrochloric acid

The rates of cleavage of the Si–H bond of penta- and tetramethyldisiloxane have been studied. The reaction is first order in the silane and in the dilute acid. However, at high acid concentrations, the rate of reaction is governed by the acidity function of the system: this may indicate fast reversible proton transfer from the solvent to the organosilane in the rate-determining step.

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Si–H - . . , : , .

     

Dynamics of nickel catalyst carbonization in heating-cooling cycles

Carbonization of a nickel catalyst for methane reforming in methane-carbon dioxide mixture has been studied in heating-cooling cycles at different heating temperatures. Thermogravimetric carbonization curves obtained with different quantities of carbon deposited on the catalyst practically coincide in a very wide range of carbon coverages. Temperature limits for the appearance and disapearance of carbon deposition centers have been determined.

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- . , , . .

     

γ-Induced reduction of Eu(III) in aqueous solution

-radiation of Co⁶⁰ has been applied to reduce Eu(III) to Eu(II) in aqueous solutions of the mixture of rare earths. The kinetics of the process has been investigated as a function of the absorbed radiation dose and organic additive concentration.

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+3 - Co⁶⁰: Eu(III)Eu(II). .

     

Kinetic equation of heterogeneous catalytic isotope exchange

A kinetic equation is derived for the bimolecular isotope exchange reaction between AX _n ^* and BX _m ^o , all atoms of element X in each molecule being equivalent. The equation can be generalized for homogeneous and heterogeneous catalytic isotope exchange.

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, AX _n ^* BX _m ^o , X . , - .

     

X-ray and thermal studies of ferroelectric Dy2(MoO4)3

Dysprosium molybdate, Dy₂(MoO₄)₃, displays a ferroelectric phase transition at 145 °C. The X-ray and thermal (DTA, TG and DSC) properties of this compound have been studied. The X-ray study confirmed the ferroelectric phase in the orthorhombic space group Pba2. Thermal analysis demonstrated the existence of a ferroelectric and another phase transition in this compound.

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Zusammenfassung Dysprosiummolybdat, Dy₂(MoO₄)₃ (Abk.: DMO), ein Vertreter der Seltener-denmolybdatreihe zeigt bei 145 °C einen ferroelektrischen Phasenübergang. Röntgendiffraktion und thermische Eigenschaften (DTA, TG, DSC) der genannten Verbindung wurden untersucht. Auf Grund der Röntgendiffraktionsuntersuchung gehört die ferroelektrische Phase in die orthorhombische Raumgruppe Pba2. Mittels Thermoanalyse konnte bei dieser Verbindung die Existenz ferroelektrischer und anderer Phasenübergänge nachgewiesen werden.

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145 °C. (, ) . , Pba2. .

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The authors wish to thank Prof. A. Paul and Mr. R. Bhatnagar for their kind help in some of the experimental work. One of us (MR) gratefully acknowledges a Fellowship from DST, Government of India.     

Thermal decomposition of the solvent-extracted chloro complexes of vanadium(IV) with trioctylamine and trioctylmethylammonium chloride

The complexes (R₃NHVO(OH)Cl₂)₂ and (R₃RNVO(OH)Cl₂)₂ prepared by drying in vacuo the organic solutions from the extraction into benzene of aqueous vanadyl chloride solution with trioctylamine (TOA, R₃N) and trioctylmethylammonium chloride (TOMAC, R₃RNCl), were studied by thermogravimetry and differential thermal analysis under an atmosphere of nitrogen, and the products of their thermal decomposition, such as volatile matter and residues, by gas chromatography. X-ray diffraction and infrared spectroscopy. It was found that the complexes with TOA and TOMAC thermally decompose to V₂O₃ at 200–300° by cracking of the compounds R₃NHVO(OH)Cl₂ and R₃RNVO(OH)Cl₂ formed via dissociation of the complexes at about 150°.

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Zusammenfassung Die Komplexe (R₃NHVO(OH)Cl₂)₂ und (R₃RNVO(OH)Cl₂)₂ wurden hergestellt, indem benzolische und wässrige Vanadylchlorid-Lösungen mit Trioctylamin (TOA, R₃N) und Trioctylmethylammoniumchlorid (TOMAC, R₃RNCl) extrahiert und die erhaltenen Lösungen im Vakuum eingedampft wurden. Die Komplexen wurden in Stickstoffatmosphäre mittels TG und DTA untersucht und die thermischen Zersetzungsprodukte, und zwar sowohl die flüchtigen Verbindungen als auch die Rückstände, gaschromatographisch bzw. röntgendiffraktometrisch und IR-spektroskopisch bestimmt. Es wurde festgestellt, daß die Komplexe mit TOA und TOMAC bei 150° in die Verbindungen R₃NHVO(OH)Cl₂ und R₃RNVO(OH)Cl₂ dissoziieren, die bei 200–300° thermisch zu V₂O₃ zersetzt werden.

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(R₃NHVO(OH)Cl₂)₂ (R₃RNVO(OH)Cl₂)₂ (R₃,) ( , R₃RNCl). , , . , 200–300° V₂₃ R₃NV()l₂ R₃RNVO(OH)Cl₂, 150°.

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We wish to thank the Koei Chemical Co. Ltd. for samples of TOA and TOMAC.     

A thermoanalytical study on some compounds of Zr(IV) with azopyrazolonic derivatives

Thermoanalytical data on six reagents and on their compounds with Zr(IV) are reported. Except for H acid, all reagents were azopyrazolonic derivatives obtained by synthesis. The purpose of this study was to obtain data on the thermal stabilities of the reagents and their zirconium compounds, and to establish the reagent: zirconium: water combination ratio.

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Zusammenfassung Thermoanalytische Daten von 6 Reagenzien und deren Verbindungen mit Zr(IV) werden mitgeteilt. Außer H-Säure waren alle Reagenzien durch Synthese erhaltene Azopyrazolon-Derivate. Zweck der Untersuchung war, Daten über die thermische Stabilität dieser Reagenzien und ihrer Zirkonverbindungen zu erhalten und das Verhältnis Reagens: Zirkon: Wasser festzustellen.

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. , , - . , : : .

     

The consistency of repeated H2?O2 titration cycles on supported Pt catalysts

H₂ and O₂ uptakes at 296 K on a Pt/Al₂O₃ catalyst remained constant during repeated H₂–O₂ titration cycles conducted in a high vacuum adsorption system. Previously reported variations in these uptakes are attributed to adsorption of contaminants during desorption conditions. Also, it was found that nearly 40% of the H₂ adsorbed could be removed by degassing at 296 K for 1 hr.

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H₂ O₂ 296 Pt/Al/₂O₃ H₂–O₂, . . , 40% H₂ 1 296 .

     

Nature of the active component of copper-zinc-aluminium catalyst for methanol synthesis

Comparative studies of the catalytic properties and thermal stability of a copper-zinc-aluminium catalyst and its components have revealed that the catalytic activity is determined by a solid solution of copper and aluminium in zinc oxide containing OH^– and CO ₃ ^2– groups in its anion skeleton. The presence of aluminium in the solid solution ensures the increase of the catalyst thermal stability in the reaction medium.

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-- , , OH^– CO ₃ ^2– -. .

     

Experiences with the use of DSC in the determination of vapor pressure of organic compounds

This paper describes the arrangement of measuring apparatus for vapor pressure determination by means of DSC according to the dynamic method (measurement of boiling temperatures at various pressures). Measuring conditions, main test parameters, typical disturbances and measuring errors are discussed. In the measuring range accessible (0.1 to 7000 kPa/ –30 to 600°C), certain boiling points and vapor pressure curves plotted therefrom agree very well with values specified in the literature. Extrapolation of these vapor pressure curves to the pressure range up to 0.1 mPa gives approximate values, the orders of magnitude of which are in agreement with those measured by means of other methods. Vapor pressure curves of oleochemical substances are presented.

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Zusammenfassung Der Aufbau eines Meßplatzes zur Dampfdruckbestimmung mit der DSC nach der dynamischen Methode (Messung der Siedetemperaturen bei verschiedenen Drücken) wird beschrieben. Meßbedingungen, wesentliche Versuchsparameter, typische Störungen und Meßfehler werden diskutiert. Im zugänglichen Meßbereich (0,1 bis 7000 kPa/–30 bis 600°C) bestimmte Siedepunkte und daraus ermittelte Dampfdruckkurven stimmen sehr gut mit Literaturangaben überein. Die Extrapolation der Dampfdruckkurven in den Druckbereich bis 0,1 mPa liefert näherungsweise Werte, die mit nach anderen Verfahren gemessenen Werten in der Größenordnung übereinstimmen. Dampfdruckkurven von fettchemischen Substanzen werden vorgestellt.

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, / /. , , . , 0,1–7000 –30° 600°, . 0,1 , , . .

     

Ba(OH)2 as catalyst in organic reactions. VIII. Nature of the adsorbed species in Claisen-Schmidt reaction

The nature of the adsorbed species in the synthesis ofo-hydroxychalcones by Claisen-Schmidt reaction catalyzed by C-200 is analyzed by IR. The presence of the adsorbed carbanion fromo-hydroxyacetophenone in the surface of the catalyst is proved. The aldehyde molecule is adsorbed too. The mechanism of the surface reaction is discussed.

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- -, C-200, -. - . . .