Influence of sodium on the phase composition of bismuth-molybdenum oxide catalysts supported on SiO2

Using an x-ray phase analysis, it has been shown that the application of sodiumstabilized sols to the Bi₂O₃·2.75MoO₃/SiO₂ system leads to the interaction of molybdenum and bismuth oxides with sodium, and the formation of a double Na–Bi-molybdate.

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, Bi₂O₃·2.75 MoO₃/SiO₂ , , Na–Bi-.

     

Radiochromatographic studies of isobutylene oxidation over SnO2

Radiochromatographic studies of isobutylene oxidation over SnO₂ confirm the formation of carbon dioxide from the products of oxidative olefin condensation.

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.

     

Selective hydrogenation of dehydrolinalool and dehydrolinalyl acetate to linalool and linalyl acetate

Hydrogenation of dehydrolinalool and dehydrolinalyl acetate on 0.5% Pd/Al₂O₃ in C₂–C₅ alcohols of various structure has been studied at atmospheric and higher pressures of hydrogen. It is shown that the differences in selectivity of hydrogenation of dehydrolinalool to linalool and of dehydrolinalyl acetate to linalyl acetate is due to peculiarities in their structure.

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0,5% Pd/Al₂O₃ C₂–C₅ . , .

     

Influence of phosphorus additives on the properties of Fe?Sb?O oxide catalysts

Modification of the surface of Fe–Sb–O oxide catalysts by phosphorus additives increases the yield of acrylonitrile in the oxidative ammonolysis of propylene, which can be attributed to the increase of the surface concentration of weakly acidic aprotic centers, viz. Sb³⁺ ions.

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, --Sb³⁺.

     

13C NMR study of propene dimerization on NiO/SiO2 catalysts

¹³C NMR studies of propene adsorbed on NiO/SiO₂ catalysts show -complex formation for propene with Ni²⁺ ions at low temperatures. Via a coordinative mechanism, 4-methylpentenes and, to a lower extent, 1-hexene are formed. No other isomers are formed as primary products but only via isomerization of the primary products.

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¹³C , NiO/SiO₂ - Ni²⁺ . 4- 1- . .

     

Catalyzed reactions of epoxide groups on the solid polymer phase

The catalytic reaction of epoxide bonded on a grafted isotactic polypropylene powder with acids and amines in the presence of organic liquids is studied. The speciality of this reaction is that relatively high catalyst concentrations are used, due to the presence of epoxide in the heterogeneous phase. Rate constants of bonding of model compounds, and also compounds with special effect by means of epoxide groups are quoted.

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, , . , , , . , .

     

Correlations between photosorption and photocatalytic activities of alkali metal halides

An analysis of the correlation suggests that the common stages in photosorption, photooxidation and photodecomposition of some simple molecules on alkali metal halides are connected with catalyst photoexcitation.

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, , , .

     

Ammonia adsorption on the surface of Ni(II)-, Cu(II)-and Co(II)-phthalocyanine

Ammonia adsorption on the surface of Ni(II)–, Cu(II)- and Co(II)-phthalocyanine has been studied by means of reflection spectroscopy. Ammonia bonds to the metal ions in the surface layers of phthalocyanines preferably in octahedral coordination. In the case of Co(II)-phthalocyanine the trivalent state of cobalt is stabilized. Close similarity between coordination in liquid phase and adsorption on the surface is observed.

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- , , . , - . Co (II)- . .

     

State of copper in Cu?Zn?Al oxide catalysts for methanol synthesis

Nature of the catalytically active component in Cu–Zn–Al oxide catalysts for methanol synthesis and water-gas shift reaction and the peculiarities of copper ions, responsible for the high rates of methanol synthesis, are discussed.

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-- , .

     

Effect of additives on acidic and catalytic properties of V?Mo?O catalysts for acrolein oxidation to acrylic acid

Variations of acid-base properties on catalyst surface when modifying V–Mo–O catalyst by various additives changes the reaction course and the catalyst activity.

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- V-Mo-O .

     

Reasons for different activities of various type catalysts in reactions of oxidation of inorganic substances

The dual role of catalysts in the interaction between an inorganic molecule AB and adsorbed oxygen ZO, as an electron donor (in the oxidative addition of AB) and as an electron acceptor (in subsequent ZO reduction), permits to interpret the orders of activities of various optimal catalysts and their dependence on the AB structure.

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AB ZO — ( AB) ( ZO). AB.

     

Interaction of propylene with a V2O5/Al2O3 catalyst

IR-spectroscopic studies indicate that on the oxidized surface of V₂O₅/Al₂O₃ catalysts propylene interacts mainly with Brönsted acid centers to form an alcoholate type complex transforming into acetone. On the reduced surface propylene is stabilized as a -complex of V³⁺ and V⁴⁺ ions.

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- , V₂O₅/Al₂O₃ , . - V³⁺ V⁴⁺.

     

Enantioface-differentiating transfer hydrogenation of ethyl acetoacetate on modified Raney nickel

Ethyl acetoacetate was hydrogenated on tartaric acid-NaBr-modified Raney nickel in the presence of isopropanol as hydrogen source—the first example concerning the asymmetric transfer hydrogenation using a chiral modified metal catalyst.

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, — NaBr — . , .

     

Cobalt complex with immobilized porphyrin in hydrazine oxidation

Porphyrin immobilized on silica and its complex with cobalt have been prepared and identified. Oxidation kinetics is described by the Michaelis-Menten equation.

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- . - --.

     

The determination of urea and other nitrogen compounds in urine by the DIE method

The heat of reaction of hypobromite with the non-protein nitrogen compounds contained in urine is very high. This fact can be utilized for the determination of these compounds by the inverse DIE method. The DIE method also allows a separate determination of urea based on the specific action of the enzyme urease.

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Zusammenfassung Die Reaktionswärme von Hypobromit mit den im Urin enthaltenen nicht-Protein Stickstoffverbindungen ist sehr hoch. Dieser Umstand kann zur Bestimmung dieser Verbindungen durch die inverse DIE-Methode verwendet werden. Die DIE-Methode gestattet auch die separate Bestimmung von Karbamid aufgrund der spezifischen Wirkung des Enzyms Urease.

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, , . -. , .

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By describing the abowe two determinations, we wished to present the applicability of the inexpensive Hungarian instruments for fast and simple determinations in the biochemical field.

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This paper completes the material of the Hungarian Symposium on Thermal Analysis.     

Kinetic-morphological peculiarities of solid-state isomerization of complexes

The thermal solid-state isomerizations of Copy₂Cl₂ (py=pyridine), Nien₂(NO₂)₂ and Nien₂(NCS)₂ (en=ethylenediamine) were studied by thermal analysis, thermomicroscopy, X-ray diffraction and IR-spectroscopy. It was shown that the reactions proceed by nuclear formation and growth. The kinetic-morphological peculiarities of the processes suggest that the process-determining stage is a phase stage, i. e. structural transformation. The topography and kinetics of processes are therefore determined by the crystal structures of the initial material and the reaction product, and by the contact conditions at the interface. The stress relaxation processes affect the morphology of the products and the kinetics of the transformation.

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Zusammenfassung Thermische Isomerisierungsreaktionen in fester Phase wurden durch thermische Analyse, Thermomikroskopie, Röntgenbeugung und IR-Spektroskopie an CoPy₂Cl₂ (Py=Pyridin), Nien₂(NO₂)₂ und Nien₂(NCS)₂ (en=Ethylendiamin) untersucht. Es wird gezeigt, dass die Reaktionen durch Keimbildung und Wachstum ablaufen. Die kinetischen und morphologischen Charakteristika der Prozesse weisen darauf hin, dass der geschwindigkeitsbestimmende Schritt ein Phasenschritt, d. h. eine Strukturumwandlung ist. Deshalb sind Topographie und Kinetik der Vorgänge durch die Kristallstrukturen des Ausgangsstoffe und des Reaktionsprodukts und durch die Kontaktbedingungen an der Grenfläche bestimmt. Die Spannungsrelaxationsprozesse beeinflussen die Morphologie der Produkte und die Umwandlungskinetik.

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, , ₂l₂, Nien₂(NO₂)₂ Nien₂(NCS)₂, en= , = . , . - , . , . .

     

On the mechanism of autocatalysis in carbohydrate synthesis from formaldehide

From the analysis of kinetic behaviour in carbohydrate synthesis from formaldehyde and spectral data on the structure of catalytically active Ca(OH)₂ complexes with carbohydrates a step-wise mechanism of autocatalysis of formaldehyde condensation to carbohydrates in the presence of Ca(OH)₂ is proposed. A kinetic equation to describe the initial step of autocatalysis is given.

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- - Ca(OH)₂. , .

     

Study of vanadium distribution in supported V?Mg catalysts by XPS and SIMS

The catalyst surface is occupied predominantly by mono- and bilayer vanadium oxide species, vanadium being mainly in the form of polylayer species that occupy a small part of the surface.

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- , , .

     

Collisional energy transfer in the thermal decomposition of oxetane

The first order rate coefficient for the thermal decomposition of oxetane and oxetane-d₂ has been investigated at two temperatures as a function of pressure. Gas phase collisional relaxation results are obtained by using RRKM theory and various energy tranfer probability models.

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-d₂ . , RRKM .