Interaction and exchange of propene with OH groups of HX zeolites

The interaction of C₃H₆ and the exchange of C₃D₆ with a HX zeolite dehydroxylated to various degrees was studied at the temperature of the IR beam and at 300 °C. The exchange was followed by the analysis of the gas phase (MS) and the solid phase (IR). The properties of HX and HY zeolites were compared.

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C₃H₆ C₃D₆ 300 °C HX . () () . HX HY .

     

Temperature-programmed reduction of bimetallic Ir?Fe/Al2O3 catalysts

Investigations on the temperature-programmed reduction of 3% Ir–Fe/Al₂O₃ catalysts after their oxidation at different temperatures T_ox have been carried out. A substantial promoting effect of iridium on the reducibility of iron has been observed for all the investigated catalysts, at T_ox applied.

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- 3% Ir–Fe/Al₂O₃ (T_ox). T_ox.

     

Oxidation of n-propanol over vanadium oxide catalysts

The kinetics of catalytic oxidation of n-propanol on V₂O₅ and V₂O₅ modified with BeO, MgO, CaO and SrO has been investigated. A high selectivity of the oxidation to propionaldehyde was observed. The activation energies of the reaction and of the exchange of oxygen in these catalysts with molecular oxygen and CO₂ were found to change in parallel.

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- V₂O₅ V₂O₅ BeO, CaO, MgO SrO. . .

     

Influence of alkali promoters on the direction of CO conversion on precipitated Fe catalysts

It has been established that at small conversion degrees of CO on precipitated Fe catalysts the parallel formation of paraffins and olefins takes place. Sodium introduction inhibits the formation of paraffins in the independent direction, which increases the selectivity to olefins.

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, CO . , .

     

The maximum kinetic mechanism and rate constants in the H2?O2 system

The maximum (in a combinatorial sense) kinetic mechanism of hydrogen oxidation is defined and the rate constants of all elementary steps are given. The possible error limit is given for each elementary step.

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( ) . .

     

Investigation of thermooxidative stability of oils by thermal analysis methods

Two base oils, obtained on a laboratory scale, were investigated with a derivatograph and by means of DSC. The sensitivities of the oils to some antioxidants were also examined. The high thermooxidative stability of the oil obtained from a preoxidized atmospheric crude residue was confirmed.

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Zusammenfassung Zwei im Labormaßstab hergestellte Rohöle wurden mit einem Derivatographen und mittels DSC untersucht. Die Empfindlichkeit der Öle gegenüber Antioxidanten wurde ebenfalls geprüft. Es wurde eine hohe thermooxidative Stabilität des aus einem präoxidierten atmosphärischen Rohstoffrestes erhaltenen Öls nachgewiesen.

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, . . , .

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The authors are grateful to the Institute of Petroleum Technology for the DSC measurements.     

Li/MgO catalysts. III. Effect of precursor salts on the catalytic activity in methane oxidative coupling

Oxidative coupling of methane has been studied on Li/MgO catalysts prepared from three different MgO precursors and from lithium carbonate or nitrate. In samples prepared from Li₂CO₃, the persistence of this on the support surface favors formation of carbon oxides.

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Li/MgO, MgO . , Li₂CO₃, .

     

Ethylene hydroformylation over a nafion-supported rhodium catalyst

Ethylene hydroformylation over a Nafion-supported rhodium catalyst has been studied under atmospheric pressure in the temperature range of 100–135 °C, using the transient response method.

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, , 100–135°C, .

     

Vapor phase oxidation of methylpyridines on zeolite catalysts

It has been established that zeolites containing Pd and Cu ions catalyze the vapor phase oxidation of methylpyridines. In oxidation of 2-methylpyridine on PdCuNa-mordenite at 375 °C the yield of 2-pyridinecarbaldehyde is 40 % of its theoretical values.

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, , Pd Cu, . 2- PdCuNa- 2- 375°C 40% .

     

Collisional energy transfer in the decomposition of 2-methyloxetane and 3-methyloxetane, I. Gas/gas collisions

The pressure dependence of the unimolecular rate constants for the thermal decomposition of 2-methyloxetane and 3-methyloxetane has been studied. The average energy transferred downward in gas-gas collision was determined by the application of RRKM theory and a stepladder model of energy transfer.

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2- 3-. , - , .

     

Studies on thermal decomposition of rare earth element complexes with glycolic acid

The rare earth complexes with glycolic acid were prepared as crystalline solids with general formula [Ln(CH₂OHCOO)₃H₂O]·nH₂O, wheren=0 for La-Gd andn=2 for Y and Tb-Lu. During heating the monohydrates of La and Pr-Gd decomposed in two steps to Ln₂O₃ and Pr₆O₁₁, with intermediate formation of Ln₂O₂CO₃; monohydrated Ce(III) glycolate decomposed directly to CeO₂. The trihydrated glycolates of Y and Tb-Lu first lost two water molecules and the monohydrated complexes then decomposed to Ln₂O₃ and Tb₄O₇ through Ln₂O₂CO₃.

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Zusammenfassung Komplexe der Seltenerden mit Glykolsäure wurden in Form von kristallinen Substanzen mit der allgemeinen Formel [Ln(CH₂OHCOO)₃·H₂O]·nH₂O mitn=0 für La-Gd undn=2 für Y und Tb-Lu dargestellt. Die Monohydrate von La und Pr-Gd zersetzen sich beim Erhitzen in zwei Stufen über die Zwischenstufe Ln₂O₂CO₃ in Ln₂O₃ und Pr₆O₁₁. Das Monohydrat von Ce(III) glykolat zerfiel direkt in CeO₂. Die Trihydrate der Glykolate von Y und Tb-Lu gaben zunächst zwei Moleküle Wasser ab und die so entstandenen Monohydratkomplexe zersetzen sich dann über Ln₂O₂CO₃ in Ln₂O₃ bzw. Tb₄O₇.

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[Ln(CH₂OHCOO)₃·₂]·n₂, =0 La-Gd =2 Tb-Lu. Pr-Gd Ln₂O₃ r₆₁₁ Ln₂O₂CO₃. ₂. Tb-Lu , Ln₂O₃ b₄₇ Ln₂O₂CO₃.

     

Topochemical reactions

A survey of topochemical reactions is given and the theory of their kinetics is discussed.

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Zusammenfassung Eine Übersicht über die topochemische Reaktion wird gegeben und die Theorie ihrer Kinetik erörtert.

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Résumé On présente une étude d'ensemble sur les réactions topochimiques en discutant la théorie de la cinétique.

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.

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This paper was written from a series of lectures read by the author at the First All-Union School on the Chemistry of Solids (Novotsherkask, September 1972).     

Formation and thermal decomposition of silicon oxynitride compounds. Part III

The formation of a previously unknown compound with stoichiometry Li₆SiN₂O₂ was found during studies on the reactivity of Li₂SiN₂ with Li₂O, of SiO₂ with Li₃N and of Li₃SiNO₂ with Li₃N.

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Zusammenfassung Die Bildung einer bisher unbekannten Verbindung der Stöchiometrie Li₆SiN₂O₂ wurde bei Untersuchungen der Reaktivität von Li₂SiN₂ mit LiO, von SiO₂ mit Li₃N und von Li₃SiNO₂ mit Li₃N beobachtet.

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Li₆SiN₂O₂ Li₂SiN₂ , , Li₃SiNO₂ .

     

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 , . . .

     

Oxidation of 2,6-xylenol by Co(III) chelates in toluene

A simple reaction scheme and kinetic data are presented for the oxidation of 2,6-xylenol by Co(III) chelates in toluene.

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2,6- Co(III) .

     

Kinetic studies of Pt/Al2O3 catalyst pellets with nonuniform activity

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al₂O₃) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

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(Pt) (Al₂O₃). , , .

     

Kinetics and mechanism of high-temperature decomposition of di-methyl-di (tert-butyl-peroxy) silane

Kinetic parameters and rate constants for initiation reaction during thermal decomposition of di-methyl-di (tert-bytylperoxy) silane in tetravalerate-pentaerythrol solution have been determined at temperatures ranging from 170 to 220°C. It has been established that tert-butyl hydroperoxide, the product of homolytic peroxysilane decomposition, takes part in the initiation reaction.

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-- (--) 170–220°C. , , .

     

Some supplementary data on particular features of the thermal behaviour of potassium persulfate

The effects of preliminary mechanical activation and thermal treatment of potassium persulfate on the thermal and electrical characteristics of its thermal decomposition were studied by DTA, TG, evolved gas volumetry and high-frequency thermal analysis.

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Zusammenfassung Die Wirkungen von einer vorausgehenden mechanischen Aktivierung und der thermischen Behandlung von Kaliumpersulfat auf die thermischen und elektrischen Charakteristika der Zersetzung dieser Verbindung wurde mittels DTA, TG, volumetrische Messung des freigesetzten Gases und thermische Hochfrequenz-Analyse untersucht.

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, , .

     

Determination calorimetrique des enthalpies de formation en metallurgie

The calorimetric methods used for the measurement of the enthalpy of formation of metallic systems are described and discussed. Special attention is paid to direct reaction calorimetry, dissolution calorimetry, precipitation calorimetry, combustion calorimetry... and non-reacting calorimetry is considered as an additional method from this point of view. Emphasis is placed on their particular field of application. Some recent developments are given.

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Zusammenfassung Kalorimetrische Verfahren zut Messung der Bildungsenthalpie von metallischen Systemen wurden beschrieben und diskutiert. Besondere Aufmerksamkeit wurde dabei der Hinreaktionskalorimetrie, der Lösungskalorimetrie, der Fällungskalorimetrie, der Verbrennungskalorimetrie geschenkt, Nichtreaktionskalorimetrie wurde als eine zusätzliche Methode in dieser Hinsicht betrachtet. Das spezielle Anwendungsgebiet dieser Verfahren wird hervorgehoben und einige Neuentwicklungen gegeben.

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, . , , , . . .

     

The measurement of meaningful activation energies

The uncertainty surrounding the significance of the measured kinetic parameters of solid state decomposition reactions is discussed briefly. Some suggestions are made about what precautions should be taken in order to favour the measurement of undistorted results. Some criteria are proposed for deciding whether a measuredE value can be considered to have its usual meaning. The results of a series of experiments aimed at measuring the activation energy of the decomposition of calcium carbonate using a variety of methods, sample sizes and experimental conditions are presented. These results are compared with results found in the literature and it is concluded that it is possible to measure a reproducible value forE and it is tentatively proposed that this value is meaningful in terms of the energy barrier model of chemical reaction kinetics.

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Zusammenfassung Die sich auf die Signifikanz gemessener kinetischer Parameter von Zersetzungsreaktionen fester Stoffe beziehende Unsicherheit wird kurz diskutiert. Es werden einige Vorschläge hinsichtlich der Vorkehrungen unterbreitet, die zu treffen sind, um unverfälschte Meßergebnisse zu erhalten. Einige Kriterien werden vorgeschlagen, die geeignet sind zu entscheiden, ob ain gemessenerE-Wert die übliche Bedutung hat. Ergebnisse einer Reihe von Experimenten werden angegeben, die ausgeführt wurden, um die nach verschiedenen Methoden, bei Anwendung unterschiedlicher Probenmengen und unter verschiedenen Versuchsbedingungen für die Aktivierungsenergie der Zersetzung von CaCO₃ erhaltenen Werte zu vergleichen. Es wird gefolgert, daß es möglich ist, den Wert vonE reproduzierbar zu messen, und versuchsweise vorgeschlagen, diesen Wert als sinnvoll für das Energiebarrierenmodell der chemischen Reaktionskinetik anzusehen.

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. , . , E . , , . . , .