Kinetic conversion of complex hydrocarbon mixtures in reforming on platinum/alumina catalysts

General forms of the kinetic equations for the conversion of various hydrocarbons in reforming of multicomponent gasoline fractions on platinum/alumina catalysts have been confirmed experimentally by using a gradientless method.

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Specificity of hydrogen adsorption on chromia-supported platinum group metal catalysts

Hydrogen adsorption on chromia supported Pd, Rh and Pt was studied under various pretreatment conditions. The reduction temperature influences strongly the hydrogen uptake for all these metals. Platinum supported on chromia shows an unusually high hydrogen adsorption stoichiometry.

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Pd, Rh Pt, Cr₂O₃, . , . Cr₂O₃ .

     

Catalytic oxidation of cycloalkane heteroanalogs as a way to polyfunctional compounds

Liquid phase oxidation of cycloalkane diheteroanalogs catalyzed by compounds of Cu²⁺, Ni²⁺, Co²⁺, Cr³⁺, Fe³⁺ has been studied. It has been established that these catalysts can be applied to intensify, oxidize and increase the selectivity of this process.

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: Cu², Ni²⁺, Co²⁺, Cr³⁺, Fe³⁺. .

     

Spectroscopic studies of the state of Cu2+ ions in Cu?Zn?Al oxide catalysts

ESR and electronic spectroscopy have reveled that in low-temperature ZnO the copper ions form Cu–O–Cu type cluster structures with highly covalent bonds and strong exchange interaction between the ions. The nearer environment of the Cu²⁺ ions is an octahedron with distortion towards square planar coordination.

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, ZnO Cu–O–Cu . Cu²⁺- , .

     

Determination of organic- and carbonate-carbon in freshwater lake sediments by a microcombustion procedure

A microcombustion procedure specific for the determination of total-, organic- and carbonate-C in freshwater lake sediments is described. The procedure involves combustion of the sample at 650° to obtain organic-C. Total-C is obtained by combustion at 950° and carbonate-C calculated by difference. The procedure was evaluated by differential thermal analyses of representative sediments and known carbonate minerals. A procedure for the identification of dolomite in lake sediments by differential thermal analysis under CO₂ is also described.

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Zusammenfassung Es wurde über ein zur Bestimmung des Gesamt-, Karbonat- und organischen Kohlenstoffgehaltes von Süßwasserrückständen geeigneten Mikroverbrennungsverfahren berichtet. Durch Verbrennen bei 650° erhält man den organischen Kohlenstoff, durch Verbrennen bei 950° den Gesamtkohlenstoff. Der Karbonatkohlenstoff ergibt sich aus der Differenz. Die Methode wurde durch differentialthermoanalytische Prüfung von charakteristischen Sedimenten und bekannten Karbonatmineralien getestet. Ein Verfahren zur Identifizierung von Dolomit in Seesedimenten durch Differentialthermoanalyse unter CO₂ wurde ebenfalls beschrieben.

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Résumé On décrit une méthode spécifique de microcombustion pour déterminer la teneur en carbone total, organique et carbonate dans des sédiments des lacs à eau froide. On reçoit le C organique par combustion à 650°, le C total par combustion à 950° et le carbone à l'état de carbonate, par la différence. On a évalué le procédé par ATD des sédiments représentatifs et de minérais de carbonate connus. On a décrit une méthode pour identifier le dolomite dans les sédiments des lacs, par ATD sous CO₂.

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, , C . C 650° 950°C, , C . . , , CO₂.

     

Pulse-chromatographic determination of molybdenum surface by oxygen adsorption in Co?Mo catalysts

A pulse-chromatographic method has been developed for the estimation of molybdenum surface by selective adsorption of oxygen at –78°C in cobalt-molybdenum-alumina catalysts. The surface concentrations of molybdenum in a series of catalysts of different compositions were compared with the activities for cyclohexene hydrogenation and for thiophene hydrogenolysis.

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- –78°C -- . - .

     

Non-empirical calculations of adsorbability of paired Lewis acid sites of alumina

The non-empirical LCAO SCF MO method on the STO-3G basis was applied to calculate adsorption of H₂O, NH₃ and CO molecules on paired Lewis acid sites (LAS) of alumina formed as a result of the removal of the OH groups which are common for two aluminium atoms.

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, STO-3G, H₂O, NH₃, CO () Al₂O₃, OH. , H₂O, NH₃, CO .

     

CeO2-supported nickel catalysts. Evidence of a strong metal-support ineraction

An increase of the reduction temperature of a Ni/CeO₂ solid results in a continuous decrease of the catalytic activity toward C₂H₆ hydrogenolysis and of the quantity of adsorbed H₂. O₂ treatments with subsequent reduction at low temperature restore a part of the initial properties. This behavior, typical of a strong metal support interaction, is similar to that of Ni/TiO₂, Ni/SiO₂ and Ni/ZrO₂ solids and shows that the SMSI phenomenon is general.

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Ni/CeO₂ C₂H₆ H₂. . , (), Ni/TiO₂, Ni/SiO₂ Ni/ZrO₂ , .

     

Catalytic deactivation dynamics of zeolites in multicycle processes

Catalytic deactivation dynamics of zeolites in multicycle processes has been calculated. It has been revealed that in naphthalene sorption on NaX zeolites surface deactivation is predominant with its similarity criterion close to unity and a high fraction of deactivation. Calculated data for several multicycle processes are given.

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. , NaX . .

     

Catalytic relevance of phase transformations accompanying the gas phase oxidation of ethanol on silica supported vanadia

Nonsteady state activity during the gas phase oxidation of ethanol in a simple flow reactor and its dependence on pretreatment and reaction conditions can be explained utilizing the previously presented model of possible surface vanadia phases on silica.

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Relation between the catalytic and acidic properties of zeolite catalysts

Influence of the strength and concentration of non protic centers on the catalytic activity of metal-zeolite catalysts in isomerization of n-butane has been studied. A relationship between the specific activity and the center strength is suggested.

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-. , .

     

Effect of free phosphine on the reactivity of phosphine-containing rhodium(I) complexes

The photolysis products of SO₂-pentane-NO mixtures are N₂O, H₂O and a compound designated as RNO. Kinetic data obtained by OC method confirm the previously proposed scheme of photolysis. Also studied was the photolysis of SO₂, NO and cyclohexane mixtures. From comparison of spectral characteristics of RNO and its analog 2-methyl-2-nitrosopropane, the probable structure of RNO is suggested.

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SO₂--NO N₂O, H₂O , RNO. , , . SO₂ NO . RNO 2--2- RNO.

     

Steady conduction of heat in prolate spheroidal systems

The steady local temperature distribution has been determined for arbitrary prolate spheroidal systems with various boundary conditions. The temperature was derived for all possible systems, such as when the temperature was kept constant on the hyperbolic surfaces and variable on the prolate spheroidal surfaces, and vice versa. In'the latter case, roots with respect to the degree of the associated Legendre function for arguments larger than unity had to be determined. Some of the presented solutions have been evaluated numerically, and the isothermal surfaces have been presented.

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Zusammenfassung Für beliebig ausgedehnte sphäroide Systeme wurde mit verschiedenen Randbedingungen eine stationäre lokale Temperaturverteilung ermittelt. Die Temperatur wurde für alle möglichen Fälle ermittelt, so auch für den Fall, in dem die Temperatur an der Hyperbeloberfläche konstant gehalten und an den ausgedehnten sphäroiden Flächen veränderlich ist bzw. umgekehrt. Für letzteren Fall mußten für Argumente größer als eins Wurzeln betreffs des Grades der zugehörigen Legendre Funktion ermittelt werden. Einige der dargestellten Lösungen wurden numerisch ermittelt und die isothermen Flächen dargestellt.

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. , . , . .

     

Isotope exchange of molecular nitrogen on barium nitride

The activity of barium nitride in the isotope exchange of nitrogen is 2–3 orders of magnitude higher than that of Fe and Ru. In the temperature range from 373 to 673 K the activation energy of exchange is 40 kJ/mol.

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2–3 Fe Ru. 373–673 40 /.

     

Gas phase thermolysis of cyclohexyl thiol

The pyrolysis of cyclohexyl thiol has been studied in a static system at subambient pressures in the temperature range 420–497°C. It is proposed that in the presence of a large excess of cyclohexene the mechanism is a radical non-chain process.

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, , 420–497°C. , .

     

Structural and thermal analysis of phosphoramidothioate,phosphorodiamidothioate and N,N′-diphenylphosphorodiamidothioate complexes of Zn(II), Cd(II) and Hg(II)

A new series of complexes of Zn(II), Cd(II) and Hg(II) with phosphoramidothioate (PAT), phosphorodiamidothioate (PDAT) and N,N-diphenylphosphorodiamidothioate (N,N-DPDAT) ligands have been synthesized and studied. The structures of the new compounds are discussed on the basis of their spectroscopic and thermal data. Thermoanalytical studies of these compounds have shown a dependence of the thermal stability on the size of the metal cation; the PAT complexes have greater thermal stability than the others.

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Zusammenfassung Komplexe von Zn(II), Cd(II) und Hg(II) mit Phosphoramidothioat (PAT), Phosphorodiamidothioat (PDAT) und N,N-Diphenylphosphorodiamidothioat (N,N-DPDAT) als Liganden wurden synthetisiert und untersucht. Die Strukturen der neuen Verbindungen werden basierend auf deren spektroskopischen und thermischen Daten diskutiert. Die thermoanalytische Untersuchung dieser Verbindungen hat eine Abhängigkeit der thermischen Stabilität von der Größe der Metallkationen ergeben, und zwar sind die PAT-Komplexe thermisch stabiler als die anderen.

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, , N,N . N,N . . . .

     

Differential thermoanalyse in der Strukturuntersuchung der als Formmassenbindestoffe in der Giessereitechnik angewandten montmorillonitischen Formlehme

Zusammenfassung Die Differentialthermoanalyse eignet sich zur Bestimmung der thermischen Stabilität der in Formmassen angewandten montmorillonitischen Bindestoffe. Mit der DTA-Methode können die bei hohen Temperaturen in diesen Bindestoffen auftretenden strukturellen Änderungen bestimmt werden. Waschöl erhöht die Dehydratisierungs- und Dehydroxylierungstemperatur des montmorillonitischen Bindestoffes. In der Folge steigert also die Suszeptibilität des Obigen zur Hydratation und auch die thermische Stabilität.

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The hitherto presented results of researches of DTA of montmorillonite binding agent, applied in the moulding sand for foundry practice. With the aid of this method the temperature of dehydratation and dehydroxylation of binding agent with the addition and without of wash oil have been defined.As a result of our investigations it has been found that the same oil rises the appearance of these effects.With the aid of DTA these has also been defined structural changes occurring in montmorillonite binding agent, subjected to the activity of high temperature.

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, . . , . , , .

     

Synthesis and thermal decomposition of double dimethylammonium sulphate hexahydrates of aluminium and chromium

Double sulphates of trivalent aluminium and chromium with dimethylammonium, with general formula (CH₃NH₂M(SO_{4 2}·6H₂O, were synthesized and studied by means of thermogravimetry and differential thermal analysis over the range 20–600 °C under dynamic conditions in a flow of dry nitrogen or air, and with the methods of chemical analysis. An X-ray powder diffraction study of the above compound was also undertaken. It is assumed that dimethylammonium aluminium sulphate hexahydrate and dimethylammonium chromium sulphate hexahydrate are isostructural. The mechanism of thermal decomposition of these double salts is also suggested.

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Zusammenfassung Verbindungen der Formel (CH₃)₂NH₂M(SO₄)₂·6H₂O mit M=Al(III) oder Cr(III) wurden synthetisiert und mittels TG und DTA im Intervall 20–600 °C unter dynamischen Bedingungen in bewegtem trockenen Stickstoff-oder Luftstrom sowie mittels chemischer Analyse untersucht. Auf Grund einer ebenfalls durchgeführten röntgenografischen Pulvermethode wurde festgestellt, daß Dimethylammonium-aluminiumsulfat-hexahydrat sowie Dimethylammoniumchromsulfat-hexahydrat isostrukturell sind. Ein Mechanismus für die thermische Zersetzung dieser Doppelsalze wird ebenfalls vorgeschlagen.

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(CH₃)₂NH₂M(SO₄)₂· 6H₂O, 20–600° . , . .

     

Pure pseudoboehmite from sodium aluminate

The influence of the Na₂O/Al₂O₃ mole ratio in sodium aluminate, the pH and the temperature of precipitation upon physicochemical properties of pseudoboehmite obtained from sodium aluminate has been studied. A mole ratio of 11 and low pH are favorable for the preparation of pure alumina.

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Na₂O/Al₂O₃ , pH , . , Na₂ O/Al₂O₃=1 , pH, .

     

Thermal behaviour of acidic salts of mixed tetravalent metals

The results of investigations on intercalated crystalline zirconium phosphate are described in the literature. The behaviour of crystalline phosphates containing both zirconium and titanium metal ions has not been investigated previously. Within these investigations, the thermal behaviour of such materials has been studied in the temperature interval 25–1000 °C by simultaneous recording of TG, DTG and DTA curves. The results are presented in this paper.

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Zusammenfassung Ergebnisse über Untersuchungen an in Schichten eingelagerten kristallinen Zirkoniumphosphat sind in der Literatur beschrieben. Das Verhalten kristalliner Phosphate, die sowohl Zirkoniumals auch Titanmetallionen enthalten, wurde bis jetzt nicht untersucht. Als Teil dieser Untersuchungen wurde das thermische Verhalten solcher Materialien im Temperaturbereich 25–1000 °C durch simultanes Registrieren der TG-, DTG- und DTA-Kurven näher bestimmt, dessen Ergebnisse hier dargelegt werden.

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. , . , , 25–1000°. .