IR study of interaction of propylene at CoO-MgO and CoO-MoO3-MgO surfaces

IR spectra of propylene adsorbed in CoO-MgO and CoO-MgO-MoO₃ solid solutions show that a surface -complex with Co²⁺ ions is formed, strongly bonded in the former case and weakly in the latter. Thus, introduction of Mo strongly modifies the catalytic properties of Co²⁺ active centers. In the presence of oxygen, allylic species, aldehyde and carboxylate complexes appear.

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, CoO-MgO CoO-MgO-MoO₃ - Co²⁺, . , Mo Co²⁺. - .

     

Hydrogenation and double bond isomerization of hexenes over EUROPT-1

Hexenes give large amounts of hexane and isomeric hexenes over EUROPT-1. A constant hydrocarbon coverage can be assumed in the steady-state period of the reaction; the direction of reactions of these surface species depends on the hydrogen excess and also on the structure of starting hydrocarbon.

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EUROPT-1 , . , . , .

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Based on the diploma work of Mr. M. Räth and Ms. B. Brose.     

Homogeneous catalytic oxidation of pyrocatechol in the presence of transition metal ions

Pyrocatechol oxidation by oxygen in aqueous solutions containing different metal ions, proceeds via the intermediate formation of pyrocatechol-metal ion-oxygen complexes, Catalytic activity of metal ions depends on their donor-acceptor properties.

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- -. - .

     

Calorimetric studies of aluminosilicate catalysts heats and entropies of cumene adsorption on cation substituted metakaolinite

Differential heats of cumene adsorption at 293 K on Ca-, Sr- and Ba-substituted metakaolinites at surface coverages up to 0.1 have been measured on a Calvet microcalorimeter. The presence of two energetically different adsorption centers are shown to be determined by the nature of the exchanged cation; the adsorption heats decrease in the sequence Ba, Sr, Ca, Mg.

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293 Ca-, Sr, Ba- 0.1. . , Ba, Sr, Ca, Mg.

     

Catalysts for metathesis of olefins, prepared by anchoring of MoO2(acac)2 to Al2O3

New highly active catalysts for metathesis of olefins were obtained through the interaction of bis(acetylacetonato)dioxymolybdenum(VI) with surface OH groups of -Al₂O₃ and subsequent reduction in H₂ or CO.

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()(VI) OH -Al₂O₃ H₂ CO .

     

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 . , , .

     

Modification of Fe species in FeNaY zeolite by NaCl treatment

The treatment of Fe(III)NaY zeolite with NaCl solution does not lead to a back-exchange of ferric species but the cationic Fe rearranges into new complexes which are more deeply reduced by hydrogen and less self-reduced by vacuum heat treatment than the parent Fe species in FeNaY zeolite.

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Fe(III)NaY NaCl . , Fe , , , Fe FeNaY.

     

M?ssbauer spectroscopic studies of passivated layers of iron-containing catalysts for ammonia synthesis

Combined conversion electron (CEMS) and transmission -ray (MS) Mössbauer spectroscopy was used to study the structure of passivated layers of promoted and unpromoted iron-containing catalysts. In both catalysts the oxide-coated films were found to consist of small paramagnetic (at 300 K) clusters of ferric oxide.

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. , ( 300 ) .

     

Adsorption properties of microporous silica

The study of CCl₄ adsorption shows that the increase of dispersion potential can increase the specific adsorption in pores up to 3 nm in size.

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CCl₄ , 3 .

     

Partial oxidation of methane on Cr2O3/Al2O3

The oxidation of methane on supported chromia was studied at temperatures varying between 423 and 743 K and CH₄/O₂ ratios between 1 and 9 in a differential reactor. The main reaction products observed were carbon monoxide and formaldehyde. The rates of reaction obey a power law expression.

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, 423 743 CH₄/O₂ 1 9, . . .

     

Effect of water on hydrogen desorption from the surface of Rh/C catalysts

An increase in the number of titration cycles results in a considerable decrease in H_T and O_T values, which in turn, brings about a decrease in the amount of desorbed hydrogen. This shows that water, being a product of titration reaction, is adsorbed on the oxidized surface of rhodium and represents a kinetic-diffusive barrier for hydrogen titration.

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, H_T O_T, , , . , , , , , - .

     

Some investigations on the photostabilization of polypropylene

The effect of substituted hydroxybenzophenone, benzotriazole and organic metal complexes on the photooxidation of PP films has been studied. It has been established that NiDBTC added in 1.0 wt. % is the most effective photostabilizer.While in the case of other stabilizers there is a slight increase in the Co content even during the induction period, with the application of NiDBTC practically no oxidation can be observed before the stabilizer completely disappears. This means that NiDBTC inhibits the photooxidation of the polymer even in low concentration.

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, - . , Ni, 1,0 . %. . , Ni , . , Ni .

     

Kinetics and mechanism of OsO4 catalyzed oxidation of chalcones by Ce4 in aqueous acetic sulfuric acid media

Kinetics of OsO₄ catalyzed oxidation of chalcones by Ce⁴⁺ has been studied in aqueous acetic-sulfuric acid medium in the temperature range 313 to 338 K. The order in [oxidant] is zero while the order with respect to [substrate] and [catalyst] are each fractional. The rate of the reaction decreased with increase in percentage of acetic acid while [H⁺] had practically no effect on the rate The rates of various substituted chalcones (with substituents in the phenyl. ring attached to the moiety) are in the orderp-CH₃>m-CH₃>H>p-Cl>m-Cl>m-NO₂>p-NO₂. A mechanism in which formation of a cyclic ester between chalcone and OsO₄ in a fast step followed by its decomposition in a rate-determining step is envisaged.

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Ce⁴⁺, OsO₄, - 313–338 . —, —. , [H⁺] . ( , : -CH₃>-CH₃>H>-Cl>-NO₂>-NO₂. , OsO₄ , , .

     

Effect of the support on the coking of nickel catalysts in hydrocarbon steam reforming

Experiments on the coking rates of variously prepared nickel catalysts on TiO₂, Al₂O₃ and MgO in n-butane steam reforming show that changes in the relative coking rate at a rising steam excess in the gas phase depend mainly on the kind of support. The results obtained are accounted for by changes in the electron density at the site of nickel crystallite contact with the surface of various supports.

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, TiO₂, Al₂O₃ MgO, - , , , , , . .

     

Catalytic activity of palladium-containing zeolites in the complete oxidation of benzene

The dependence of palladium distribution in zeolites on the temperature of thermal treatment has been established from the data on oxygen chemisorption and the statistical processing of electron micrographs. The influence of palladium distribution in zeolites on their catalytic activity towards the complete oxidation of benzene has been shown.

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- . .

     

Liquid-phase hydrogenation of cyclohexene by dihydrogen in the presence of dimolybdenum tetraacetate

Catalytic liquid-phase hydrogenation of cyclohexene in DMF by dihydrogen in the presence of dinuclear bridged complex Mo₂(OAc)₄ has been studied. A kinetic equation for the steady-state rate of cyclohexene hydrogenation and the activation parameters are suggested.

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Mo₂(OAc)₄. .

     

Kinetics of oxidation of acrolein on a vanadium-molybdenum oxide catalyst

A kinetic study has shown that, in the range of low conversions, the reaction rate depends only on the partial pressure of oxygen. Comparison of the oxidation of acrolein and I-deuteroacrolein suggests that the splitting of the H–CO bond is not rate-limiting.

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, , , . 1- , H–CO .

     

Thermal and infrared spectrum analyses of natural and synthetic andersonites

The thermal decompositions of natural and synthetic andersonites were studied. Two partly overlapping dehydration steps and three partly overlapping decarbonation steps were observed. The second dehydration and the first decarbonation steps also partly overlap. During decarbonation, the gradual formation of sodium diuranate and monoclinic and hexagonal phases in the Na₂U₂O₇-CaUO_4–x system was proved. The results were correlated with measured infrared spectra using site and factor group analysis and X-ray structure analysis. The chemical formula inferred for natural andersonite, Na₂Ca[UO₂(CO₃)₃] 5.6H₂O, agrees with that proposed for its synthetic analogue.

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Zusammenfassung Die thermische Zersetzung von natürlichem und synthetischem Andersonit wurde untersucht. Sie umfasst zwei teilweise überlappende Entwässerungs- und drei teilweise überlappende Decarboxylierungsstufen. Der zweite Entwässerungs- und der erste Decarboxylierungsschritt überlagern einander ebenfalls teilweise. Während der Decarboxylierung wird die allmähliche Bildung von Natriumdiuranat und monoklinen und hexagonalen Phasen des Systems Na₂U₂C₇-CaUO_4–x nachgewiesen. Die Ergebnisse wurden mit den gemessenen IR-Spektren unter Benutzung der site- und Faktor-Gruppenanalyse sowie Röntgenbeugungsuntersuchungen korreliert. Die für natürlichen Andersonit abgeleitete Formel Na₂Ca[UO₂(CO₃)₃].5,6H₂O stimmt mit der für synthetischen Andersonit vorgeschlagenen überein.

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. . . , Na₂U₂O₇-CaUO_4–x. . Na₂Ca[UO₂(CO₃)₃] 5,6₂, ** , .

     

Formation of methane in methanol synthesis on zinc-chromium catalysts

The rate of methane formation on zinc-chromium catalysts is described by zero-order rate law, If the catalyst is activated by copper, the rate of methane formation increases due to a decrease in the activation energy of the reaction. Presumably the formation of methane and methanol takes place on different active centers.

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, . , . , .

     

Activity of Ni?Mo hydrodesulfurization catalysts supported on mixed alumina-zirconia

The hydrodesulfurization (HDS) of thiophene by nickel-molybdenum catalysts supported on alumina-zirconia has been investigated. The effect of varying the ratios of oxides in the support is to produce a minimum in the activity for HDS, and the coimpregnated catalysts are shown to be more active than the analogous co-precipitated catalysts.

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(HDS) -, . HDS. , .