Kinetic regulaties in oxidative dehydrogenation of butene-1 over V?Mg catalyst at various temperatures

Kinetic studies of nonsteady-state steps in oxidative dehydrogenation of butene-1 over a supported V-Mg catalyst were carried out at temperatures of 573–748 K. The kinetic data were used to perform a numerical simulation of changes in the catalyst activity under stepwise variation of the reaction temperature.

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-1 573–748 . .

     

A kinetic study of the addition of mercury(II) acetate to substances with double bonds

The method of currentless potential-time curves was applied to the determination of rate constants for three reactions between mercury(II) acetate and substances with double bonds in methanol medium. These reactions had not yet been followed.

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—. .

     

Methanol conversion of various cation-exchanged forms of high-silica zeolites

Studies of the methanol conversion on various cation-exchanged forms of high-silica zeolites have revealed that the activity and selectivity of the intact pore structure zeolites depend on the cation composition. On decationated forms the selectivity of methanol conversion to aromatic hydrocarbons is much higher than on the hydrogen form, and it decreases with respect to paraffins.

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- . , . , , .

     

Enhanced methane production from methanol decomposition over Pt/TiO2 catalysts

The promoting effect of TiO₂ on CH₄ formation from CH₃OH decomposition has been investigated. Hydrogen and CO are products of CH₃OH decomposition which can subsequently react to produce CH₄. We observe an enhancement in this secondary reaction when the support is TiO₂. This enhancement is lost after a high temperature reduction.

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TiO₂ CH₄ CH₃OH. CH₃OH CO, , CH₄. TiO₂ . , , .

     

Peculiarities of propylene metathesis over catalysts prepared by anchoring of Mo(V) oxalate to γ-Al2O3

Propylene metathesis over catalysts prepared by coordination of Mo(V) oxalate to -Al₂O₃ has been studied.

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, (V) -Al₂O₃.

     

Dehydration of alcohols on iron Fischer-Tropsch type catalysts

The dehydration of 1-butanol was studied on iron Fischer-Tropsch type catalysts. Chemical trapping allowed us to propose a mechanism involving hydrogenolysis of the C–O bond with the selective formation of 1-butene.

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1- -. , C–O jqz 1-.

     

Effect of mechanical treatment on some properties of Fe2O3?MoO3 catalysts

Methanol oxidation on mechanically treated amorphous catalysts has been shown to lead to their crystallization and the restoration of their primary properties except for the surface area, which remains decreased. It is suggested that the amorphous state is not responsible for the catalytic properties.

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, . , , , . , .

     

Alkali-promoted AlPO4 catalysts, II. Cyclohexene skeletal isomerization to 1- and 3-methylcyclopentenes

Skeletal isomerization of cyclohexene to 1- and 3-methylcyclopentenes has been carried out at temperatures ranging from 250–400 °C using a microcatalytic pulse technique, over AlPO₄ catalysts having various amounts of alkali cations (1–5 wt.%, Li, Na and K). Apparent rate constants and activation energies were calculated in terms of Bassett and Habgood's kinetic model for first order processes in which the surface reaction is the controlling step and partial pressure of the reactant is low. The results show that alkali-containing catalysts exhibit lower activity and higher selectivity to 1-methylcyclopentene than pure AlPO₄ due to the modification of the surface acidity by alkali impregnation.

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1- 3- 250–400°C AlPO₄ (1–5 .% Li, Na K). , . 1-, AlPO₄ .

     

Improvement of the zeolite catalyst for olefin synthesis from methanol by regulating the shape factor with the aid of seed crystals

By the use of seed crystals in the initial stage of preparation of a new type of zeolite for olefin synthesis, shape and size distribution of the zeolite could be regulated uniformly, and the catalyst performance was improved markedly especially with respect to olefin selectivity and the catalyst life.

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, . , , .

     

Kinetics of reduction of an iron catalyst for ammonia synthesis

The kinetics of reduction of an iron catalyst have been studied at 450–550 °C. The overall kinetic equation was of the mixed-control type. The equation of the surface reaction was of the Langmuir-Hinshelwood type with the adsorption of only water vapor taken into account.

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450–550°C. . - .

     

Influence of sulfur compounds on the activity and selectivity of paraffin hydrocracking on nickel-zeolite catalysts

The influence of sulfur compounds on the rate of hydrocarbon conversion on acidic and hydrogenating components of nickel-zoelite catalysts as well as on the activity and selectivity of n-octane hydrocracking has been studied.

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, -.

     

Isomerization of 1-pentene catalyzed by Wilkinson's catalyst coordinatively bound to silica

Hydrogen thermodesorption from Co–Ni/Al₂O₃ catalysts has been investigated. Hydrogen sorption on Co/Al₂O₃ catalyst has a strong temperature-activated character. The sorptive capacity of hydrogen, after its preliminary sorption at 900 K, is similar for all catalysts under study.

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Co–Ni/Al₂O₃. Co/Al₂O₃ . , 900 K, .

     

Realisation d'un derivateur permettant la mesure precise et continue de tres faibles variations de temperature

Résumé Cet article présente un dérivateur de température à très bas niveau. Il permet la mesure exacte et continue des vitesses de chauffage ou de refroidissement, de l'ambiante à 900°C avec un seuil de détection de 30°C. s^–1. Cet appareil peut être utilisé pour faire de l'analyse thermique dérivée ou comme générateur de rampes linéaires.

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A very low level temperature derivative apparatus is described. It is able to give a true and continuous measurement of heating or cooling rate from room temperature up to 900° with a detection threshold as low as 30°Cs^–1. This apparatus can be used for derivative thermal analysis and as slope temperature generator.

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Zusammenfassung Ein Derivativgerät mit sehr niedrigem Temperaturniveau wird beschrieben. Es ermöglicht eine wahre und kontinuirliche Messung der Aufheiz- und Abkühlgeschwindigkeit von Raumtemperatur bis zu 900°C mit einer Nachweisschwelle von weniger als 30°C s^–1. Dieses Gerät kann zur derivativen Thermoanalyse und als Neigungstemperaturgenerator eingesetzt werden.

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. , 900° 30 °C. ^–1. , .

     

AES studies on a Pd-modified silver catalyst

Silver crystals electrodeposited from AgNO₃ (8%) and Pd²⁺ (250 mg/dm³) electrolyte before and after exposing to the conditions of the methanol to formaldehyde oxidation process were investigated by AES. Carbon, sulfur, oxygen and palladium on the surface were observed. Higher Pd concentration on the silver surface than in the bulk was found. Its amount on the surface decreased with the temperature increase.

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, - , AgNO₃ (8%) Pd⁺² (250 /), AES. , , - . , - Pd , , .

     

Acetylene hydrogenation selectivity control using Pd/Cu catalysts

The hydrogenation of acetylene impurity in ethylene has been studied over 0.04 wt% Pd/Al₂O₃ catalysts modified by Cu. The undesired hydrogenation of ethylene could be suppressed by Cu.¹⁴C labelling proved that the intrinsic selectivity is always 95–98% of Cu or gaseous CO reduces the parallel hydrogenation of ethylene on the support, leaving the intrinsic selectivity unchanged.

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0,04 . % Pd/Al₂O₃, Cu. . 14C , 95–98% , , CO .

     

Ethylene oligomerization on heterogenized titanium and zirconium complexes

Besides other products, linear middle-range olefins were obtained in the low temperature oligomerization of ethylene with a selectivity of 30–58% and a linearity up to 85%. Activated ticanium and zirconium complexes as catalysts were attached to SiO₂ through surface bounded bidentate S- and N-containing ligands, the former being superior to the latter with respect to product quality.

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30–58 .% 85%. - - , , SiO₂ S- N- . , , .

     

A stochastic analysis of catalyst deactivation in presence of external transfer limitations

The paper analyzes the simplest case of concentration independent deactivation of a catalyst surface in the presence of external transport limitations and accounts for the variations around the mean value of the activity of the catalysts leading to a stochastic formulation. The results reveal interesting features which would not be evident from the conventional deterministic analysis.

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- , , . , .

     

Synthesis and thermal studies of metal salts of 2,4, N-trinitroanilinoacetic acid

Copper(II), silver(I) and lead(II) salts of N-(2,4-dinitrophenyl)-N-nitroglycine were prepared and characterised. The thermal behaviour of the salts in air and nitrogen atmospheres was studied by means of DTA and TG techniques. The environment appeared to have no effect on the mode of decomposition. While metal oxides are formed as the end-products of decomposition of the copper and lead salts, metallic silver plus carbon was found to be final product from the silver salt. The thermal stabilities of these salts follow the sequence silver salt>lead salt>copper salt.

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Zusammenfassung Kupfer(II)-, Silber(I)- und Blei(II)-Salze von N-(2,4-Dinitrophenyl)-N-nitroglycin wurden hergestellt und charakterisiert. Mittels DTA- und TG-Techniken in Luft- und Stickstoffatmosphäre wurde das thermische Verhalten der Salze untersucht. Die Umgebung scheint auf die Art der Zersetzung keinen Einfluß zu besitzen. Zersetzungsendprodukte der Kupfer ui I Bleisalze sind Metalloxide, Zersetzungsendprodukte des Silbersalzes sind elementares Silber und Kohlenstoff. Die Wärmestabilität dieser Salze sinkt in der Reihenfolge Silbersalt — Bleisalz — Kupfersalz.

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, N-(2,4- )N-. . , . . . > > .

     

Contribution of one-electron acceptor centers to oxidative dimerization of methane

The ESR method was used to identify paramagnetic centers in the Pb–Mg oxide system and to study its catalytic properties in oxidative dimerization of methane. Reaction rate is shown to correlate well with the presence of one-electron acceptor centers in the sample.

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- Pb–Mg . , .

     

State of components in contact solutions based on Pd(II) salts and Fe(NO3)3 for ethylene oxidation to EGMA

Physico-chemical studies of contact solutions based on Pd(II) salts and Fe(NO₃)₃ for ethylene oxidation to EGMA have been carried out.

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- (II) .