Conversion of C1?C2 alkanes over manganese catalysts reoxidized by carbon dioxide and oxygen

Reoxidation of Mn-containing catalysts by oxygen and carbon dioxide in the conversion of C₁–C₂ alkanes has been studied. Reoxidation of these catalysts by carbon dioxide and oxygen added at a certain ratio permits to obtain optimum degree of surface oxidation, ensuring the high selectivity of conversion of C₁–C₂ alkanes to C₂H₄.

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Mn- C₁–C₂. , Mn- , C₁–C₂ C₂H₄.

     

Kinetics of aluminium hydroxide dehydration

Non-isothermal thermogravimetric analysis was used for determination of the kinetics of aluminium hydroxide dehydration in an air atmosphere and for processing of the experimental results by the method due to Chatterjee.Aluminium hydroxide dehydration proceeds according to the following mechanism: Al(OH)₃AlOOH + H₂O 2 AlOOHAl₂O₃ + H₂OBoth reactions proceed in the diffusion region, the first up to 526 K and the second up to 700 K, and the corresponding activation energy values are 15.7 and 0.2 kJ/mole, respectively.

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Zusammenfassung Die nicht-isotherme thermogravimetrische Analyse wurde zur Bestimmung der Kinetik der Dehydration von Aluminiumhydroxid in Luft-Atmosphäre eingesetzt und die Methode von P. K. Chatterjee zur Verarbeitung der Versuchsergebnisse angewendet.Der Dehydratisierungsvorgang von Aluminiumhydroxid verläuft nach folgendem Mechanismus: Al(OH)₃AlOOH + H₂O 2 AlOOHAl₂O₃ + H₂OBeide Reaktionen spielen sich in der Diffusionszone ab, die erstere bis zur Temperatur von 526 K und die zweite bis zur Temperatur von 700 K. Die entsprechenden Aktivierungsenergien sind 15.70 kJ/Mol für die erste und 0.20 kJ/Mol für die zweite Reaktion.Bei kontinuierlicher Erhöhung der Temperatur über 526 K im ersten und über 700 K im zweiten Fall werden die Geschwindigkeiten dieser Reaktionen durch kristallchemische Umwandlungen begrenzt und die Aktivierungsenergie beträgt 116.97 kJ/Mol für die erste und 91.92 kJ/Mol für die zweite Reaktion.

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Résumé On détermine la cinétique de la déshydratation de l'hydroxyde d'aluminium dans l'air, par thermogravimétrie non-isotherme, en dépouillant les résultats suivant la méthode proposée par P. K. Chatterjee.Le processus de la déshydratation de l'hydroxyde d'aluminium s'effectue suivant le mécanisme: Al(OH)₃AlOOH + H₂O 2AlOOHAl₂O₃ + H₂OLes deux réactions ont lieu par diffusion, la première jusqu'à la température de 526 K et la seconde jusqu'à 700 K, les valeurs correspondantes des énergies d'activation étant 15.70 kJ · mol^–1 pour la première et 0.20 kJ · mol^–1 pour la seconde réaction.Lors d'une élévation continue de la température au-dessus de 526 K dans le premier cas et au-dessus de 700 K dans le deuxième cas, les vitesses de ces réactions deviennent limitées en raison des transformations cristallochimiques et les valeurs des énergies d'activation sont 116.97 pour la première et 91.92 kJ · mol^–1 pour la seconde réaction.

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, — . : Al(OH)₃AlOOH + H₂O 2 AlOOHAl₂O₃ + H₂O , 526 , — 700 . 15,70 0,20 / . 526 700 — , - , , 116,97 91,92 /.

     

The catalytic effect of rare earth oxides on the thermal decomposition of ammonium perchlorate

The kinetics of the decomposition of ammonium perchlorate (AP) in the presence of rare earth oxides, yttrium oxide (Y₂O₃) and lanthanum oxide (La₂O₃) as catalysts have been investigated. The Prout-Tompkins and contracting-cube equations have been found to fit the isothermal thermogravimetry data of catalysed AP decomposition. Gases evolved during catalytic decomposition of AP were analysed by infrared spectroscopy by matrix isolation technique. The mechanism of the catalysed thermal decomposition of AP has also been discussed in terms of an electron transfer process.

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Zusammenfassung Es wurde die Reaktionskinetik der thermischen Zersetzung von Ammoniumperchlorat (AP) in Gegenwart der Seltenerdenoxide Yttriumoxid (Y₂O₃) und Lanthanoxid (La₂O₃) als Katalysatoren untersucht. Zum Fitting der isothermen thermogravimetrischen Daten der katalysierten Zersetzung von AP läßt sich die Prout-Tompkins- und die Schrumpfwürfelgleichung erfolgreich anwenden. Die bei der katalytischen Zersetzung von AP freigesetzten Gase wurden durch IR-Spektroskopie untersucht. Der Mechanismus der katalytischen thermischen Zersetzung wurde auch vom Gesichtspunkt eines Elektronentransferprozesses aus besprochen.

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. , - . . .

     

Calorimetric measurements of adsorption power for active centers of aluminosilicate catalysts

Direct calorimetric measurements for the interaction energy of cumene and benzene with active centers of an aluminosilicate catalyst have been carried out to determine the potential energies of the centers catalyzing selective cracking with minimum coke formation. Kinetics of cumene cracking has been examined.

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. , .

     

Influence of organic reagents on alumina supported nickel catalysts. I. Preparation of catalysts

Nickel/-alumina catalysts have been prepared by a version of the impregnation technique called double impregnation. The application of different organic reagents for activation of the -Al₂O₃ support promotes the formation of nickel-aluminate and large nickel crystallites in the catalysts obtained.

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/- , . . . -Al₂O₃, -, .

     

Time dependence of the rate constant in the free radical oxidation in solid phase

ESR studies of oxidation kinetics of ethyl and dimethylpentyl radicals have been performed in glassy deuterium-containing alcohols, toluene-d₈ and in glassy 2,4-dimethylpentane-h₁₆, respectively. The kinetics is interpreted by assuming time-dependent reaction rate constant.

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, -d₈ 2,4--h₁₆. .

     

Synthesis of Pd(II) nitro and nitrate complexes and studies of their reactivity towards oxidation of olefins in organic solvents

Complexes of the composition Pd(NO_n)_2–mCl_mL₂ (n=2, 3; m=0, 1, 2; L=CH₃CN) have been synthesized and their reactivity in ethylene and propylene oxidation has been examined. Data on the influence of the ligands, solvents and olefins on the composition of reaction products are reported.

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Pd(NO_n)_2–mCl_mL₂ (n=2, 3; m=0, 1, 2; L=CH₃CN) . , .

     

Thiophene hydrodesulfurization on P?Mo, Si?Mo and Ti?Mo catalysts

Studies of the catalysts obtained by supporting P–Mo, Si–Mo and Ti–Mo heteropolyacids on anatase in thiophene hydrodesulfurization have revealed that the presence of HPA in the initial catalysts promotes the formation of the molybdenum state ensuring high reaction rates. A possibility for HPA synthesis when supporting paramolybdate on TiO₂, accounts for the great effect of the support on the properties of the catalyst.

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

     

Oxidation of organic sulfides and sulfoxides by oxygen in the presence of copper complexes

In liquid-phase oxidation of sulfides and sulfoxides by air oxygen in acetone solution a high catalytic activity is shown by copper(II) phenolates containing electrodonor substituents in their benzene ring. Reactivity of aliphatic sulfides with R=C₁–C₅ in sulfoxide formation is 5–10 times higher than that of petroleum sulfides. Oxidation rate of sulfides to sulfoxides is by an order of magnitude higher than that of sulfoxides to sulfones.

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(II), - . R=C₁–C₅ 5–10 , . .

     

Proton transfer to palladium during phenylacetylene hydrogenation in ethanol

Exchange processes over palladium during the liquid-phase hydrogenation of phenylacetylene have been studied by successive substitution of starting substances by deuterated products. It has been revealed that on the catalyst surface a proton transfer to unsaturated substance, gas phase and solvent takes place. Rates of the processes have been calculated.

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. , , . .

     

Influence of chemical non-steady-state on SO2 conversion in fluidized catalyst bed

The effect of the influence of catalyst non-steady-state on SO₂ conversion ion a fluidized catalyst bed has been studied depending on the ratio of relaxation time for the catalytic reaction step to the characteristic time of particles diffusion.

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.

     

Preparation and characterization of iron(II) complexes of ethylene glycol

Nine iron(II) ethylene glycol sulphate complexes were prepared. Their compositions were determined by standard analytical methods. They were characterized by means of temperature-dependent magnetic susceptibility and Mössbauer spectroscopic measurements. On the basis of the patterns of their thermal decompositions, the complexes could be classified into three groups.

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Zusammenfassung Neun Eisen(II)-ethylenglykol-sulfat-Komplexe wurden dargestellt. Die Zusammensetzung dieser Komplexe wurde nach analytischen Standardmethoden bestimmt. Die Verbindungen wurden durch Messungen der temperaturabhängigen magnetischen Susceptibilität sowie mittels Mössbauer-Spektroskopie charakterisiert. Nach dem Verhalten bei der thermischen Zersetzung konnten diese Komplexe in drei Gruppen klassifiziert werden.

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, . . , .

     

Simple catalytic mechanism permitting a multiplicity of catalyst steady states

The conditions of the existence of several steady states for a three-step mechanism, viz. a catalytic trigger (consecutive), are discussed.

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- ().

     

Phase formation in Na2O?MnOx catalysts for oxidative dimerization of methane

Na₂O–MnO_x catalysts of different composition, pretreated in air or nitrogen at 1020 and 1170 K, have been investigated in oxidative dimerization of methane. Under the reaction conditions -NaMnO₂ and -Na_0.7Mn_2+y are formed as catalytically active phases.

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Na₂O–MnO_x , 1020 1170 K, . -NaMnO₂ -Na_0,7Mn_2+y.

     

Cyclooctadiene transformations over alkali metal doped MgO under hydrogenation conditions

The transformations of 1,3- and 1,5-cycloctadiene under hydrogenation conditions were investigated. The main product of the reactions studied was Z-[3.3.0]bicyclooctene.

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1,3- 1,5- . Z-[3.3.0].

     

Samarium hydroxide as catalyst in hydrogen evolution

Hydrogen evolution on a platinum cathode taking place in Na₂SO₄ as electrolyte, is catalyzed by the formation of samarium hydroxide deposited on platinum. It is shown by voltammetric experiments that the quantity of adsorbed hydrogen is greater with samarium than without it and the H₂O reduction reaction is an irreversible process due, presumably, to a reaction between the adsorbed hydrogen and samarium hydroxide.

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Na₂SO₄, , . , , H₂O .

     

Catalytic and chemisorption activity of rare-earth element oxides modified by copper and silver ions in oxidation processes

It has been established that the modification of rareearth element oxides by copper or silver ions leads to the formation of paramagnetic ions of divalent silver and greatly increases the activity of catalytic and chemisorption centers on their surface in catalytic oxidation processes.

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(. . .) . . . .

     

Promoting effect of alkali oxides on Bi?Mn catalysts activity in oxidative coupling of methane

The addition of small amounts of alkali metal oxides into Bi–Mn oxide catalysts enhances both their activity and selectivity in oxidative coupling of methane. A linear dependence between the concentration of basic sites on catalyst surface and the rate of catalytic reaction have been established.

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Bi–Mn . .

     

The application of simultaneous recording of electrical conductivity and DTA in the study of binary and ternary salt systems

The advantages of the simultaneous recording of electrical conductivity curve and DTA curves in the investigation of salt mixtures is demonstrated on a number of examples. With sufficiently slow recording, at a heating rate of 5–10°/min, all the changes occurring in the mixture investigated, and connected with the differing electrical conductivities of the different phases which appear and disappear in the process of heating or cooling, are well reflected on the electrical conductivity curve.

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Zusammenfassung Die simultane Anwendung der Methoden der elektrischen Leitfähigkeitsmessung und der Differentialthermoanalyse ist sehr vorteilhaft für die Untersuchung von Salzgemischen. Bei genügend langsamer Aufheizgeschwindigkeit (ca 5–10°/Min) werden alle Vorgänge, die während des Aufheizens und Abkühlens auftreten und mit verschiedener elektrischer Leitfähigkeit in den verschiedenen Phasen verbunden sind, in der Leitfähigkeits-Kurve widerspiegelt.

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Résumé On montre à l'aide de plusieurs exemples relatifs à l'étude de mélanges de sels les avantages de l'enregistrement simultané de la conductivité électrique et de la courbe d'ATD. Pour une vitesse d'échauffement suffisamment lente, de 5 à 10°/mn, l'enregistrement de la conductivité électrique reflète tous les changements qui se produisent dans le mélange étudié et qui sont liés à une différence de conductivité électrique des différentes phases qui apparaissent et disparaissent au cours de léchauffement ou du refroidissement.

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. , , 5– 10° , , , .