A novel approach to selective oxidation of gaseous hydrocarbons

Selective oxidation of hydrocarbons can be performed by some microorganisms possessing monooxygenase activity. Biocatalytic activities of some strains of methanotrophic bacteria (which utilize methane as a sole source of carbon and energy for growth) were investigated in the reactions of partial oxidation of methane and propylene. Formation of commercially valuable oxy-products (methanol, epoxide) occurred with 100% selectivity under the mild reaction conditions studied.

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, . (, ) . , , , 100%- .

     

Hydrogenation of CO2

The hydrogenation of CO₂ has been studied on three different series of catalysts: Fe/MgO, Ni/Ti, Cr/Zn doped with potassium. Reaction was carried out in a conventional flow microreactor system at 15 bar at 250–350°C. Three independent competing reactions: Reverse gas-water shift (RGWS), Fischer-Tropsch (FT) and methanol synthesis were observed.

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CO₂ : Fe/MgO, Ni/Ti, Cr/Zn . 15 250–350°C. : RGWS, F.T. .

     

Possibility of thermal analysis of different types of bonding of water in minerals

Various types of water bonding were studied. e.g. water bound by occlusion, by adsorption, by capillary condensation, by chemisorption and as a solid solution, zeolitic water, interlayer water, crystal water and structural water bound in form of hydroxil groups. The differentiation of these various types of bonding is rather difficult, for on heating water is evolved at various temperatures and in rather wide temperature domains which overlap to different extents. Efforts were made to improve the detection by applying the quasi-isothermal quasi-isobaric measuring technique.

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Zusammenfassung Es wurden verschiedene Bindungstypen von Wasser untersucht. Wasser kann unter anderem durch Einschlüsse, Adsorption. Kapillarkondensation, Chemisorption und in Form von Mischkristallen, zeolitisch, schichteingebettetem und Kristallwasser sowie als OH-Form gebunden sein. Die Untersuchung dieser zahlreichen Bindungstypen ist äußerst schwierig, da die Wasserabgabe bei verschiedenen Temperaturen geschieht und die ziemlich breiten Temperaturintervalle mehr oder weniger überlappen. Mittels quasiisothermen und quasiisobaren Meßtechniken wurde versucht, die Möglichkeit der Bestimmung zu verbessern.

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. , , , , , , , . , , . , .

     

A mechanistic study of cycloaddition of carbon dioxide to propyne over supported Rh4 and Fex Rhy carbonyl cluster derived catalysts

CO₂ undergoes cycloaddition to propyne on a cationic rhodium site with the assistance of O^2–/OH^– of support or iron oxide over Rh₄ and Fex Rhy carbonyl clusterderived catalysts.¹³CO₁₂ labeling and FTIR studies suggest that monodentate carbonate formed on the catalyst surface is most likely a key species to offer an active CO₂ to be converted into a carbonyl intermediate prior to the product 4,6-dimethyl-2-pyrone.

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CO₂ O^2–/OH Rh₄ Fex Rhy. ¹³CO₂ , CO₂ , 4,6--2-.

     

Effects of radioactivity on surfaces: I. Influence of Cr-51 on the catalytic activity of chromium catalysts

Chromium catalysts were prepared on monolith supports, some of them with radioactive Cr-51 in the surface. The dehydrogenation-hydrogenation reaction of cyclohexene was used to compare the catalytic activities of the radioactive and inactive catalysts. Differences were observed in the distribution of the main products at low temperatures and of the byproducts also at high temperatures.

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, Cr-51. - . , — , .

     

Pyrolysis of 1-phenyl-3-pyrazolidinone

Pyrolysis of 1-phenyl-3-pyrazolidinone (phenidone) was examined in static air atmosphere by the conventional dynamic heating technique in a derivatograph. The thermal stability of 1-phenyl-3-pyrazolidinone, its melting point and the kinetic parametersE, A andn of the first partial process of the pyrolysis at different heating rates were determined. It is shown that the thermal decomposition of 1-phenyl-3-pyrazolidinone in the presence of oxygen is a rather complicated process composed of several overlapping reactions. The pyrolysis is influenced by the conditions of thermal analysis.

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Zusammenfassung Die Pyrolyse von 1-Phenyl-3-pyrazolidinon (Phenidon) wurde mit einem Derivatographen in einer statischen LuftatmosphÄre und bei konventioneller dynamischer Aufheizung untersucht. Die thermische StabilitÄt und der Schmelzpunkt von 1-Phenyl-3-pyrazolidinon sowie die kinetischen ParameterE, A undn des ersten Teilprozesses der Pyrolyse für verschiedene Aufheizgeschwindigkeiten wurden bestimmt. Es stellte sich heraus, da\ die in Gegenwert von Sauerstoff verlaufende thermische Zersetzung von 1-Phenyl-3-pyrazolidinon ein ziemlich komplizierter, aus mehreren sich überlappenden Teilschritten bestehender Proze\ ist. Die Pyrolyse wird durch die Bedingungen der thermischen Analyse beeinflu\t.

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1--3 () . , E, A n , . , 1--3- , . .

     

Bauxites as hydrotreatment catalysts

The effects of calcination temperature on structural and textural characteristics of two Greek bauxites were examined by different physicochemical techniques. Although the above minerals exhibited lower activity than a commercial CoMo/Al₂O₃ catalyst, they were evaluated as possible hydrotreating catalysts.

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. , CoMo/Al₂O₃, , .

     

Thermal decomposition of rare earth oxysulfides in air

The thermal decomposition of rare earth oxysulfides (excluding Sc, Ce and Pm) has been studied in air. The oxysulfides are oxidized to oxysulfates between 600 and 900 and the oxysulfate phase, which is unstable at higher temperatures, decomposes to oxide. The stability of the oxysulfate and its decomposition temperature decreases with decreasing radius of the rare earth ion. For the heavier rare earths the oxidation to oxysulfate takes place only partially before the decomposition to oxide begins.

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Zusammenfassung Die thermische Zersetzung der Oxysulfide der seltenen Erden (mit Ausnahme von Sc, Ce und Pm) wurde in Luft untersucht. Die Oxysulfide werden zwischen 600 und 900 zu Oxysulfaten oxidiert und die Oxysulfatphase, welche bei höheren Temperaturen instabil ist, wird zu Oxid zersetzt. Die Stabilität des Oxysulfats und seine Zersetzungstemperatur nehmen mit abnehmendem Radius des seltenen Erden-Ions ab. Bei den schwereren seltenen Erden erfolgt die Oxysulfatbildung nur teilweise vor den Einsetzen des Abbaus zu Oxid.

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- , Sc, m. 600 900° , , . - . - , .

     

Ferric chloride catalyzed photooxidation of alkanes by air in organic solvents

In the presence of catalytic amounts of FeCl₃, alkanes (cyclohexane, n-hexane), toluene and ethylbenzene are oxidized by air oxygen to CH₃CN, (CH₃)₂CO or CH₂Cl₂ under visible light irradiation to yield ketones and alcohols.

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FeCl₃ (, -), CH₃CN, (CH₃)₂CO CH₂Cl₂ .

     

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 ) .

     

Transalkylation of phenols over heteropoly acids

Transalkylation of 2,6-di-tert-butyl-4-R-phenols over solid heteropoly acids (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₃PW₁₂O₄₀/SiO₂, H₄SiW₁₂O₄₀/SiO₂) in the presence of toluene or o-xylene as acceptors of a tert-butyl group at 100–140 °C produces 4-R-phenols with 92–98% yield (R = H, alkyl, aryl, etc.). HPAs are effective catalysts for the transalkylation of p-cresol and 2, 6-ditert-butyl-4-methylphenol.

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2,6----4-R- (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₃PW₁₂O₄₀/SiO₂, H₄SiW₁₂O₄₀/SiO₂) 0- - 100–140°C 4-R- 92–98% (R = H, , ..). - 2,6----4-.

     

Catalytic and physico-chemical properties of Al2O3?H3PO4 system, II. Donor-acceptor properties

Donor-acceptor properties of catalysts containing different quantities of orthophosphoric acid on -alumina were studied. The decrease in N₂O decomposition rate was found to be parallel with that of one-electron donor sites. Catalysts containing more than 0.4 mmol H₃PO₄/g Al₂O₃ exhibit individual surface properties due to the formation of an aluminium phosphate phase in the surface layer.

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- , -Al₂O₃. , N₂O . , 0,4 H₃PO₄/ Al₂O₃ .

     

Non-isothermal crystallisation kinetics of nucleated poly(ethylene terephthalate)

Crystallisation of poly(ethylene terephthalate) in dependence on different crystallisation promotors has been studied by non-isothermal DTA runs with several heating and cooling rates. Using an evaluation method, proposed by Kissinger, activation parameters have been evaluated for crystallisation from the amorphous state and from the melt. Calculated rate constants and half time values of crystallisation, respectively, are in good agreement with crystallisation behaviour of different samples observed under technical conditions.

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Zusammenfassung Die Kristallisation von Polyethylenterephthalat in Abhängigkeit von verschiedenen Kristallisationspromotoren wurde durch nicht-isotherme DTA bei verschiedenen Aufheiz- und Abkühlgeschwindigkeiten gemessen. Unter Verwendung einer auf Kissinger zurückgehenden Auswertemethode wurden Aktivierungsparameter für die Kristallisation aus dem amorphen Zustand bzw. aus der Schmelze ermittelt. Die berechneten Geschwindigkeitskonstanten und Halbwertszeiten der Kristallisation zeigen gute übereinstimmung mit dem Kristallisationsverhalten verschiedener Proben unter technischen Bedingungen.

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. , . .

     

Thermal behaviour of trimethoxy silane modified alkyl methacrylates

The paper deals with the thermal behaviour of trimethoxy silane (MTS) modified ethyl methacrylate (EMA) and butyl methacrylate (BMA). Several copolymer samples were prepared by varying the molar ratio of MTS with respect to EMA or BMA. The copolymerisation was carried out at 78 °C for 120 min using benzoyl peroxide as an initiator. Incorporation of MTS in alkyl methacrylates resulted in an increase in thermal stability. Hydrolytic cross-linking of copolymer having higher mole fraction of MTS gave a cross-linked product with better thermal stability.

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Zusammenfassung Vorliegende Arbeit beschäftigt sich mit dem thermischen Verhalten von Äthylmethakrylat (EMA) und Bulhylmethakrylat (BMA), das mit Trimethoxysilan (MTS) modifiziert wurde. Unter Anwendung verschiedener Molverhältnisse von MTS und EMA bzw. BMA wurden einige Kopolymerproben hergestellt. Die Kopolymerisation wurde 120 Minuten lang bei 78 °C und mit Benzoylperpxid als Initiator durchgeführt. Der Einbau von MTS in Alkylmethakrylate führt zu einer Steigerung der thermischen Stabilität. Eine hydrolytische Vernetzung der Kopolymere mit größeren Molanteilen an MTS ergeben vernetzte Produkte mit verbesserter thermischer Stabilität.

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() ( ), (). . 78 °C 120 , . . , , .

     

X-ray study of Re/Al2O3 and Re+Pt/Al2O3 catalysts using synchrotron radiation

Uning synchrotron radiation, L_III rhenium absorption spectra have been studied for Re/Al₂O₃ and Re+Pt/Al₂O₃ catalysts obtained by impregnation. For individual rhenium compounds a linear dependence between the shift of absorption edge and the state of rhenium oxidation has been found. The absorption spectra of reduced catalysts are significantly broadened as compared with those of individual compounds of the same valency. This points to the presence of rhenium compounds in different oxidation states.

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L_III- , Re/Al₂O₃ Re+Pt/Al₂O₃, . . . .

     

Electronic state of the active site of A V?P?O/SiO2 catalyst in oxidation of chlorine-containing hydrocarbons

V⁴⁺ ions in slightly associated states are supposed to play the role of V–P–O/SiO₂ active sites. V⁴⁺ ions are reduced to V³⁺ during deactivation of the V–P–O/SiO₂ catalyst.

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V–P–O/SiO₂ V⁴⁺ . V–P–O/SiO₂ V⁴⁺ V³⁺.