Hydrocarbon conversion on promoted rhodium/Al2O3 catalysts

In (E+Rh)/Al₂O₃ catalysts (E=Sn, Pb, Mo and W) the catalytic properties of rhodium in benzene hydrogenation, propane hydrogenolysis and n-hexane conversion change drastically. For modified rhodium the decrease in the hydrogenolysis rate of C–C bonds in paraffins leads to an increased yield of the products of non-destructive conversion of n-hexane.

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(E+Rh)/Al₂O₃ (E:Sn, Pb, Mo, W) , , -. C–C -.

     

Redistribution kinetics of isotope molecules due to reversible bimolecular reactions with several atomic channels

Isotope kinetic equations for reversible bimolecular reactions describe the rearrangement of atoms in activated complexes. It has been established from the model reaction CH₄+HCH₃+H₂ that the isotopic homoexchange of methane via two atomic channels is given by one set of equations with different sets of parameters.

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- . CH₄+HCH₃+H₂ , .

     

Kinetics of oxidative sulfonation of butylamine in the presence of CuCl2

Kinetic regularities of butylamine sulfonation to N, N-dibutylsulfamide in the presence of copper(II) chloride have been studied. Reaction mechanism involves the formation of Cu(II) amine complexes, their subsequent interaction with SO₂ and the redox decomposition of an intermediate to final products.

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N-N- (II). Cu(II), SO₂ - .

     

Reactivity of the carbonaceous surface overlayer on supported platinum catalysts studied by high temperature pyrolysis gas chromatography

The reactivity of the carbonaceous surface overlayer formed on Pt/Al₂O₃ catalysts in n-hexane dehydrocyclization has been studied by high temperature Pyrolysis Gas Chromatography. This method can be used to characterize surface carbon overlayers formed on different catalysts in the course of hydrocarbon reactions.

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, Pt/Al₂O₃ -, . , .

     

Determination of hydrogen chemisorbed on supported nickel catalysts by dimethyl zinc

Nickel supported on various metal oxides was titrated with dimethyl zinc tetrahydrofuranate at 130°C. The amount of hydrogen chemisorbed on nickel was evaluated from the amount of methane evolved after subtraction of OH groups of the support. The fraction of hydrogen bonded to nickel varied between 24–83 % of the overall hydrogen measured in dependence of support and correlated with activity of catalysts in the reaction of diethylene glycol with ammonia.

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, , 130°C. , , OH . , , 24 83% .

     

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

X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber indicate that in a stream of hydrogen starting from 550–600 K, platinum is practically completely reduced. In several cases at higher temperatures a platinum hydride is also formed.

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, , 550–600 ; .

     

Diffusion of hydrocarbons in mordenite and molecular-sieve selectivity of mordenite catalysts

The diffusion of n-octane and n-propylbenzene in mordenite and the molecularsieve selectivity in hydrocracking of octane-propylbenzene binary mixtures over a mordenite catalyst have been studied. The hydrocarbon diffusivities and molecular-sieve selectivity change are accounted for by diffusion through mordenite channel mouths poisoned with an easily adsorbable hydrocarbon.

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- , () -. , , .

     

Thermal decomposition of calcium sulphate in carbon monoxide

Simultaneous TG and DTA studies were performed on analytical grade calcium sulfate and on samples of natural gypsum and phosphogypsum in carbon monoxide atmosphere. The decomposition temperatures and mechanism are influenced by the mineral impurities of the sample and the heating rate as well as the CO content of the gas atmosphere.

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Zusammenfassung Simultane TG- und DTA-Untersuchungen von analytisch reinem Calciumsulfat und Proben von natürlichem Gips und Phosphogips wurden in Kohlenmonoxidatmosphäre ausgeführt. Temperatur und Mechanismus der Zersetzung werden durch mineralische Verunreinigungen der Probe, durch die Aufheizgeschwindigkeit und durch den CO-Gehalt der Gasatmosphäre beeinflußt.

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. - , , .

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The authors are indebted to Professor M. Veiderma for fruitful discussions and continuous support. The scholarship from Finnish Government to one of us (R. K.) is gratefully acknowledged.     

Temperature-programmed desorption of hydrogen from Rh/C catalysts

A strong temperature-activated character of hydrogen adsorption on the surface of Rh/C catalyst has been found, especially in relation to high-temperature form. The unreactivity of this form toward oxygen at room temperature suggests that its source is the carbon surface.

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- Rh/C, . .

     

Oxidation of naphthalene on olefin oxidation catalysts

Oxidation of naphthalene on Co–Mo–O, NiMoO₄ and Mg–Mo–O catalysts gives phthalic anhydride, its maximal yield being about 40% on nickel molybdate. On bismuth molybdates and the Sn–Sb–O system, naphthalene is mainly oxidized to carbon oxides.

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Co–Mo–O, NiMoO₄ Mg–Mo–O , ( 40%) . Sn–Sb–O .

     

Characterization of active species in alumina and silica supported CuCl2 catalysts by EPR

In a recent paper [1] we proposed that a Cu²⁺ species interacting with the support was responsible for maintaining the catalytic activity of CuCl₂ catalysts used in the methane oxyhydrochlorination reaction (CH₄+HCl+O₂ chloromethanes). This species was detected on Al₂O₃ and TiO₂ supports but it did not appear on SiO₂. In this paper we report EPR results which provide a direct characterization of this species and correlate well with the observed trends in activity.

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[1] , Cu²⁺, , CuCl₂, (CH₄+HCl+O₂ ). Al₂O₃ TiO₂, SiO₂. , .

     

Enhancement of H2- and retardation of O2-adsorption during O2?H2 titration cycles on Pt?Al2O3 catalyst surfaces

The title effects can be eliminated if the slow bleeding of H₂ from freshly reduced CuO-towers (often used as O₂-getters in purifying N₂ carrier gas) can be avoided, then H₂–O₂ titrations of Pt surfaces give consistent values from almost the first titration. Water injected at 25 °C also hardly affects the titer values.

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H₂ O₂ , H₂ CuO ( O₂ N₂ — -). H₂–O₂ Pt . , 25° C, .

     

Reaction specificity in catalysts reported to exhibit strong metal-support interactions

The specific activities of a 10% Ni/TiO₂ and a 10% Ni/SiO₂ catalyst for the hydrogenolysis of n-hexane and for the methanation reaction have been investigated. Both catalysts have very similar activities and selectivities for hydrogenolysis. However, the titania-supported catalyst exhibits a considerably greater specific activity for methanation. It is concluded that this enhancement of activity is reaction specific, and we propose a mechanism involving the adsorption of CO onto the surface of titania.

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10% Ni/TiO₂ 10% Ni/SiO₂ - . . , TiO₂ . , . , CO .

     

The compound Rh[HN((CH2)3P(C6H5)2)2]Cl in a hydrogenation reaction

The tridentate chelate ligand bis(diphenylphosphinopropyl) amine and its title complex were prepared and characterized by³¹P n.m.r. and other spectroscopic data. Its activation energy E_A for hydrogenation of cyclohexene is 52.3 kJ mol^–1.

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³¹P. 52,3 /.

     

Hydrodenitrogenation activity of sulfided catalysts

Activities of hydrodenitrogenation catalysts were compared using a batch mode autoclave reactor. The hydrodenitrogenation of carbazole, a model coal nitrogen compound, was the reaction studied. The highest activity and the highest rate constant for carbazole and total nitrogen removal were found in the case of NiMo/Al₂O₃ catalyst.

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. , . , NiMo/Al₂O₃.

     

Influence of thermal and hydrothermal activation on the adsorptive, acidic and catalytic properties of high-silica zeolites

Influence of HS-zeolite calcination up to 1023 K in air and steam on its adsorptive, acidic and catalytic properties in n-hexane cracking has been studied.

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- 1023 , -.

     

Exchange kinetics of amino acid anions in solutions of ternary copper(II) complexes with diethylenetriamine

Rate constants for the chemical exchange of some amino acid anions in solutions of copper(II) ternary complexes with diethylenetriamine have been determined by the NMR method. The coordination of amino acid anions in ternary and binary species is different and ligand substitution in the Cu(II) complexes follows an associative mechanism.

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- (II) . - (II).

     

PMR study of the lifetime of complexes with a strong hydrogen bond at low temperatures

The kinetics of formation and cleavage of hydrogen bonds in complexes of carboxylic acids with proton acceptors have been studied by PMR spectroscopy over the range –100 to 150°C. The activation parameters of the processes have been measured.

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¹H –100° ÷–155°C . .

     

Differential scanning calorimetry study of reactions of phenyl glycidyl ether with phosphoric acid

The reactions of phenyl glycidyl ether (PGE) with phosphoric acid in three molar ratios have been studied by means of DSC alone. The results obtained from isothermal measurements are as follows:H=–91.0 kJ/mole PGE(1:1 molar ratio);H=–100.5 kj/mole PGE (1:2/3 molar ratio).The DSC curves obtained from dynamic experiments are multipeaked and giveHvalues higher than those obtained from isothermal measurements. These results can be explained by taking into account the acid concentration, the different reactivities of the hydrogens of the phosphoric acid and the possibility that secondary reactions occur.

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Zusammenfassung Die Reaktion von Phenylglycidyläther (PGE) mit Phosphorsäure wurde bei drei verschiedenen molaren Verhältnissen allein mittels DSC untersucht. Isotherme Messungen ergaben folgende Werte:H=–91.0kJ/mol PGE (molares Verhältnis 1:1);H=–100.5 kJ/mol PGE (molares Verhältnis 3:2). Die bei dynamischen Experimenten erhaltenen DSC-Kurven weisen viele Peaks auf und ergebenH-Werte, die größer als die durch isotherme Messungen erhaltenen sind. Diese Ergebnisse können erklärt werden, wenn die Säurekonzentration, die unterschiedliche Reaktivität der Wasserstoffatome der Phosphorsäure und die Möglichkeit des Verlaufs sekundärer Reaktionen in Rechnung gestellt werden.

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() () . 11 12/3, H, –91.0 –100.5 ·^–1. , , H . , , .

     

Effect of adsorbed water on the activity of MoO3 catalysts in the double bond isomerization of olefins

Adsorbed water on molybdena catalysts calcined at different temperatures, may both increase or decrease the catalytic activity, depending upon the mode of adsorption and the number of adsorbed molecules. Our results prove that Brönsted acidic hydroxy groups are principal parts of the active sites, and Lewis acidic and/or basic centers are also required for catalytic activity in the double bond isomerization of olefins.

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, , , , . , , / .