Oxidation of ethanol on platinum/alumina and copper oxide catalysts

The oxidation of ethanol on CuO, CuO/Al₂O₃ and Pt/Al₂O₃ catalysts has been studied at various concentrations of alcohol, oxygen and water vapor in the reaction mixture. The reaction order and activation energies have been determined for both complete and partial oxidation processes. A consecutive oxidation scheme is suggested.

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CuO, CuO/Al₂O₃ Pt/Al₂O₃ , . . .

     

Chemiluminescent method to measure generation rates of active centers in reaction of hydrogen peroxide with hemin and pyridinehemichrome

A chemiluminescent method was used to measure generation rates of active intermediates in the interaction of hemin with hydrogen peroxide with and without pyridine at pH=8–9. The effect of various inhibitors in these two cases has been examined.

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pH=8+9. .

     

Effect of the medium in hexacyanoferrate (III)-iodide and peroxodisulfate-iodide reaction

The kinetics of the two reactions hexacyanoferrate (III)-iodide and peroxodisulfate-iodide in several isodielectric water-cosolvent mixtures have been studied. The results can be rationalized as a consequence of the cosolventwater interaction.

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(III) -. -.

     

Preparation and properties of zeolite coating on metal surface

Crystals of mordenite were grown on metallic Cr surface by the vapor phase method. The material of zeolite coating on metal surface has been characterized by X-ray powder diffraction and microprobe. It is shown by the results that this material possesses good catalytic properties.

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(Cr) . . , .

     

Effect of carbon dioxide on the catalytic oxidation of ethylene over silver. Reaction rates and composition of adsorbed layer

It has been found that when the reaction is carried out at pressures of the reaction mixture ranging from 1 to 400 Pa, small surface coverages by adsorbed oxygen, carbonate groups and irreversibly adsorbed carbon-containing particles are obtained. Rate relaxations are due to the concentration variations of adsorbed oxygen and CO_3ads groups.

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, 1–400 , , . CO₃.

     

Thermal analysis of mercury(I) sulfate and mercury(II) sulfate

The thermal decomposition of mercury(I) and (II) sulfates has been investigated by thermogravimetry. The solid-state decomposition products have been characterized by infrared and Raman spectroscopy, mass spectrometry and an X-ray diffraction method. It is concluded that mercury(I) sulfate decomposes in two steps, initially forming a mixture of metallic mercury and mercury(II) sulfate — the latter subsequently decomposes without forming a stable intermediate. The stoichiometry of disproportionation of mercury(I) sulfate and the thermal stability range of mercury(I) and mercury(II) sulfates have been established.

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Zusammenfassung Die thermische Zersetzung von Quecksilber(I) und (II)-sulfaten wurde durch Thermogravimetrie untersucht. Die Festphasen-Zersetzungsprodukte wurden durch Infrarot- und Ramanspektroskopie, Massenspektrometrie und Röntgendiffraktion charakterisiert. Es wurde gefolgert, dass Quecksilber(I)sulfat in zwei Stufen zersetzt wird, unter anfänglicher Bildung eines Gemisches von metallischem Quecksilber und Quecksilber(II)-sulfat, welches in der Folge ohne Bildung eines stabilen Zwischenproduktes zersetzt wird. Die Stöchiometrie der Disproportionierung des Quecksilber(I)sulfats und der Bereich der Thermostabilität der Quecksilber(I) und Quecksilber(II)sulfate wurden ermittelt.

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Résumé La décomposition thermique des sulfates de mercure(I) et de mercure(II) a été suivie par TG. On a caractérisé les produits de la décomposition en phase solide par spectroscopies infrarouge et Raman, spectrométrie de masse et diffraction des rayons X. On en a conclu que le sulfate de mercure(I) se décompose en deux étapes, formant initialement un mélange de mercure métallique et de sulfate de mercure(II), ce dernier se décomposant ensuite sans formation d'un intermédiaire stable. Les proportions stoechiométriques de la dismutation du sulfate de mercure(I) et de l'intervalle de stabilité thermique des sulfates de mercure(I) et de mercure(II) ont été établis.

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- . , , . , , (), - . - .

     

Morphology and structure of composite catalysts of nickel on metal-ceramic substrate

A catalyst grain is shown to consist of microparticles constituting a metal nucleus of aluminium covered by an oxide (-Al₂O₃) film. On this film a nickel-aluminium spinel is localized with metallic nickel (Ni⁰) particles on its surface. This morphological structure of catalysts accounts for the increased electron density on nickel particles and hence for the high catalytic activity in steam reforming of methane.

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, , , (-Al₂O₃). - , (Ni⁰). , , .

     

Kinetics and mechanism of chlorination of p-aminobenzoic acid by chloramine-B

The chlorination of p-aminobenzoic acid (PABA) by chloramine-B (CAB) in HCl medium at 303 K indicates simultaneous catalysis by H⁺ and Cl^–. The reaction is first order in [CAB] and [HCl], but fractional order in [PABA]. The observed solvent isotope effect is 1.52. A suitable mechanism is proposed.

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- (PABA) -B (CAB) HCl 303 H⁺ Cl^–. [PABA]. 1,52. .

     

Thermal decompositions of ammonium and potassium alums

Simultaneous TG, DTG and DTA studies of NH₄Al(SO₄)₂.12H₂O and KAl(SO₄)₂.12H₂O under nonisothermal conditions were performed with a derivatograph, over the temperature range from 293 K to 1473 K under air and argon atmospheres. Appropriate chemical reactions were attributed to the thermal effects, with consideration to the results of X-ray diffraction and microscopic analyses. From the recorded curves, the activation energiesE _a were calculated for all steps of the thermal decomposition reactions.

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Zusammenfassung Simultane TG-DTG-DTA-Untersuchungen von NH₄Al(SO₄)₂.12H₂O und K.Al(SO₄)₂.12H₂O wurden unter nicht-isothermen Bedingungen mit einem Derivatographen von 293–1473 K an Luft und unter Argon durchgeführt. Den thermischen Effekten werden chemische Reaktionen zugordnet, wobei Röntgenbeugungs- und mikroskopische Ergebnisse berücksichtigt werden. Aus den thermoanalytischen Messkurven werden Aktivierungsenergien der Zersetzungsreaktionen berechnet.

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, NH₄Al(SO₄)₂.12₂ KAl(SO₄)₂.12₂ 293–1473 . , . _a .

     

Oxidative polymerization of durene and diphenyl oxide in the presence of palladium(II) and heteropolyacids

The possibility of obtaining tetramers from durene or diphenyl oxide in the presence of H₅PMo₁₀V₂O₄₀, a reversible oxidant, and palladium acetate as catalyst is demonstrated.

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— H₅PMo₁₀V₂O₄₀ .

     

Influence of the various forms of molybdena on the adsorptive and catalytic (dehydrogenation and hydrogenolysis) properties of molybdena-alumina catalysts

The contents of three forms of molybdenum oxide compounds in molybdena-alumina catalysts have been determined by their solubility in water and ammonia. The form which is readily soluble in water and reducible to Mo(IV) at 400°C and P_H2=10⁵ Pa is active in cyclohexane dehydration, and the forms soluble in water and ammonia are active in thiophene hydrogenolysis.

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. , 400°C P_{H 2}=I Mo(IV); — .

     

Kinetic and mechanistic studies on the oxidation of arginine and histidine by chloramine-T in hydrochloric acid medium

The oxidation of amino acids by chloramine-T (CAT) in HCl medium at 30°C indicates simultaneous catalysis by H⁺ and Cl^– ions in the HCl concentration range of 0.04–0.12 M. The reaction is first order with respect to concentrations [CAT], [H⁺] and [arginine], but zero order with respect to [histidine]. The rate depends also on Cl^– concentration following 0.7th order. At HCl concentrations >0.12 M, the rate equation is:w=k[CAT] [amino acid]^0.6 and is independent of the [Cl^–]. A suitable mechanism has been suggested.

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-T (CAT) HCl (30°C) H⁺, Cl^– [HCl]=0,04–0,12M. [CAT], [H⁺] [] []. [Cl^–]^0,7. [HCl]>0,12M =k · [CAT][]^0,6 [Cl^–]. .

     

On the quantitative reliability of heat flux DSC

In an attempt to explain how the calibration factor of a heat flux DSC cell depends both on the standard utilized and on the experimental variables, a study has been undertaken of the entire DSC trace.This report deals with the second half of the peak and shows that, other experimental conditons being fixed, the peak area increases with increasing heating rate.This accounts for the observed decrease in the calibration factors with increasing heating rate.

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Zusammenfassung Die gesamte DSC-Kurve wurde untersucht, um zu klären, wie der Eichfaktor einer Wärmefluss-DSC vom verwendeten Eichstandard und von den Versuchsbedingungen abhängt. Der vorliegende Teil behandelt den zweiten Abschnitt eines DSC-peaks (vom Maximum an). Es wird gezeigt, dass bei Konstanthalten aller anderen Versuchsbedingungen die peak-Flächen mit steigender Aufheizgeschwindigkeit zunehmen. Das wird als Ursache für die beobachtete Verringerung des Eichfaktors mit steigender Aufheizgeschwindigkeit angesehen.

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, . . , - , . .

     

Electronic spectral study of the interaction of CoNaX zeolite with C1?C5 hydrocarbons

Interaction of both satured and unsaturated hydrocarbons with tetrahedral Co²⁺ ion complexes lodged in the zeolite skeleton is reported on the basis of diffuse reflectance spectra. While saturated hydrocarbons do not affect the coordination sphere of the Co-complex, the unsaturated hydrocarbons change considerably the distortion of the tetrahedral Co-complex.

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- Co²⁺ - . - Co-, - - Co-.

     

Acid properties and stability of operation of vanadium catalysts in benzene oxidation to phenol

Catalytic properties of V₂O₅/SiO₂ in benzene oxidation by N₂O were examined. Sodium additive was shown to affect the catalyst operation stability.

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V₂O₅/SiO₂ N₂O. .

     

Characterization of platinum-nickel catalysts by hydrogen-oxygen chemisorption

The use of hydrogen-oxygen titration method to characterize platinum-nickel supported catalysts has shown that the number of oxidized or reduced nickel layers is dependent on the atomic composition. This phenome non involves dynamic changes of the surface probably by a spillover mechanism. A surface reaction scheme based on a previous work is proposed to explain the experimental results.

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- - , . , , . , .

     

IR spectra of NO and NO+CO mixtures adsorbed on Fe2O3

The interaction of NO and NO+CO mixtures with Fe₂O₃ has been studied by IR spectroscopy. The conclusion has been made that adsorption bands in the region of 1200–1700 cm^–1 belong to nitrite-nitrate structures, the band at 1810 cm^–1 characterizes catalytically active particles of NO adsorbed on reduced surface sites, Fe²⁺, the bands at 2210 and 2240 cm^–1 are due to vibrations of gaseous N₂O.

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- NO NO+CO Fe₂O₃. , 1200–1700 ^–1 - ; 1810 ^–1 NO, , Fe²⁺; 2210 2240 ^–1 N₂O.

     

Kinetics and mechanism of hydrazine oxidation by oxygenated Co2(L-his)4O2 complex

The kinetics of Co₂ (L-his)₄O₂ reduction by hydrazine in aqueous solution has been studied and the rate constants, the energy and entropy of activation have been determined.

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, , Co₂ (L-)₄O₂ .

     

Investigation of the interaction between zinc oxide and phosgene

It has been shown that in the interaction of zinc oxide and phosgene, the most active are the samples having oxygen vacancies. A mechanism for this process is suggested.

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, , . .

     

Kinetic and mechanistic studies on the oxidation of sulfanilic acid by peroxomonophosphoric acid

Oxidation of sulfanilic acid to the corresponding azoxy derivative by peroxomonophosphoric acid (PMPA) has been studied in aqueous medium. The observed bell-shaped pH-rate profile has been rationalized on the basis of protonation of the amino group and ionization into different PMPA species and a suitable rate law has been proposed. The mechanism of oxidation involves the nucleophilic attack of nitrogen on the electrophilic peroxo oxygen.

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- (PMPA) . pH— , PMPA . .