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.     

Calorimetric models

The basis of the determination of mathematical models of calorimetic systems is presented. Examples of applications of these models are given for the elaboration of a classification of calorimetric systems; the analysis of the course of heat effects in calorimeters; the analysis of dynamic properties: and the analysis of total heat effects and thermokinetics. Special attention is paid to the application of the multi-body method for the construction of mathematical models of calorimetic systems.

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Zusammenfassung Die Grundlage zur Ableitung mathematischer Modelle von kalorimetrischen Systemen wird vorgestellt. Für diese Modelle werden folgende Anwendungsbeispiele ausgeführt: Fortgeschrittene Klassifizierung kalorimetrischer Systeme, Analyse des Verlaufs von Wärmeeffekten in Kalorimetern, Analyse der dynamischen Eigenschaften, Analyse der vollständigen Wärmeeffekte, Thermokinetik. Besondere Aufmerksamkeit gilt der Anwendung der Vielkörpermethode zur Aufstellung eines mathematischen Modells für kalorimetrische Systeme.

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. , , , . .

     

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.

     

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.

     

Thermal degradation of some polymers based on ethylene glycol dimethacrylate

Thermogravimetric analysis and pyrolysis in combination with gas chromatography were used to study the thermal behaviour of some cross-linked polymers of ethylene glycol dimethacrylate. The investigated polymers show a complex thermal degradation mechanism. The complexity of the reaction increases together with increase of the ethylene glycol chain in the macromolecule and with increase of the pyrolysis temperature. At low temperature, the thermal decomposition products of the analyzed polymers are mainly the constituent monomers. At high temperatures, besides the monomer, other decomposition products are formed as a result of thermal cracking reactions, i.e. secondary reactions of decomposition and recombination.

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Zusammenfassung Zur Untersuchung des thermischen Verhaltens einiger quervernetzter Polymere auf Äthylenglykoldimetacrylatbasis wurden thermogravimetrische Analyse und Pyrolyse in Zusammenhang mit der Gaschromatographie angewendet. Die untersuchten Polymere zeigten einen komplexen thermischen Zersetzungsmechanismus. Die Komplexizität der Reaktion nimmt mit Zunahme der Anzahl der Äthylenglykolketten im Makromolekül und mit Zunahme der Pyrolysentemperatur gleichermaßen zu. Bei niedrigeren Temperaturen stellen die Hauptzerfallsprodukte der analysierten Polymere hauptsächlich deren Monomere dar. Bei höheren Temperaturen werden als Ergebnis thermischer Krackreaktionen, z. B. sekundäre Zersetzungs- und Rekombinationsreaktionen, neben den Monomeren auch andere Zersetzungsprodukte gebildet.

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. . . . , , , .

     

Reaction routes for hydrogenation of acetylene-ethylene mixtures using a double labelling method

Hydrogenation of C₂H₂:C₂H₄ mixtures using a double labelling method has been studied. Both in the presence and absence of ethylene the rate of acetylene hydrogenation on its partial pressure proceeds through a maximum and the rate is higher when ethylene is added. Using¹⁴C–C₂H₂ it was demonstrated that at low acetylene partial pressures the main route of acetylene hydrogenation was the formation of ethane and C₄ hydrocarbons. Using¹⁴C–C₂H₄ it was also shown that at certain acetylene partial pressures the formation of ethane from ethylene completely ceased. Different surface species are suggested and a reaction mechanism is proposed.

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C₂H₂:C₂H₄, . , , . C¹⁴–C₂H₂, , C₄. C¹⁴–C₂H₄, , . .

     

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. . .

     

Methanol oxidation on copper-oxide catalysts

Complete oxidation of methanol on CuO and CuO/Al₂O₃ catalysts has been studied. The main kinetic parameters have been determined. A possible mechanism and the nature of the rate-determining step are discussed.

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CuO CuO/Al₂O₃. . .

     

Formation of O2? ion-radicals on reduced anatase. Influence of adsorbed CO on the stabilization of O2?

ESR studies of O₂ adsorption on reduced anatase have been performed. The amount of O ₂ ^– species is determined by adsorbed surface oxygen and their parameters are changed by CO adsorption.

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O₂ . , O ₂ ^– , CO.

     

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 . , .

     

Adaption of thermal analysis for the study of water vapour adsorption isotherms

Water vapour adsorption processes and equilibria on adsorbents with polar surfaces can be well tested with an adsorption method combined with thermal analysis. The first step involves the comparison of isothermal desorption-adsorption curves and thermal curves; in the second step different equilibrium points of the adsorption isotherms are tested by means of thermal analysis.Some examples of building materials are presented to demonstrate the possibilities of the method. The types of adsorption isotherms for the samples were formally equal in all examples; only the complex method presented was able to reveal that formation of the equilibiria was induced by essentially different processes. Such processes are: physical adsorption depending on the structure of the adsorbent and the activity of the external active centres, chemisorption, chemical reaction in the solid/vapour system and chemical reaction in the water phase condensed in the capillaries.

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Zusammenfassung Prozesse und Gleichgewichte der Wasserdampfadsorption an Adsorbenten mit polarer Oberfläche können gut mit einer mit thermischer Analyse kombinierten Adsorptionsmethode getestet werden. Der erste Schritt der Methode schließt den Vergleich der Desorptions-Adsorptionsisothermen und der thermischen Kurven in sich ein, im zweiten werden Gleichgewichtspunkte der Adsorptionsisothermen durch thermische Analyse getestet.Am Beispiel von einigen Baumaterialien werden die Möglichkeiten dieser Methode demonstriert. Die Adsorptionsisothermen waren formell in allen Fällen vom gleichen Typ und nur die vorgestellte komplexe Methode ergab, daß die Ausbildung des Gleichgewichtes durch grundsätzlich verschiedene Prozesse erfolgt. Solche Prozesse sind: von der Struktur des Adsorbenten und der Aktivität der aktiven Oberflächenzentren abhängige physikalische Adsorption Chemisorption, chemische Reaktion im Festkörper/Dampf-System und in der in Kapillaren kondensierten wässrigen Phase.

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- , . — . — . . , . : , , , — , .

     

Temperature effects on the fluorescence kinetics of excited cyclohexane

In agreement with the results reported by Lipsky, emission from cyclohexane depends on the temperature T and on the nature of the phase (liquid or solid). Determination of the lifetimes of the fluorescent state with a single photon counting apparatus gives similar results. Our experimental work shows that the rate constant of fluorescence for the solid phase I (face-centered cubic cell) practically does not depend on temperature. Variations of lifetime vs. T cannot easily be interpreted only with the classical theory of non-radiative transitions.

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, , ( ). , , . , I ( ) . .

     

Effects of tempering time and tempering temperature of caustic mercerization on the spectral and electrical properties of Egyptian cotton fibres

Several samples of Egyptian cotton fabric strips were subjected to various caustic mercerization conditions, varying in temperature and time. On these samples extensive measurements were undertaken, comprising X-ray diffraction, IR absorption spectra and the temperature-dependence of DC-electric conductivity.The phase constitution, % crystallinity, IR band assignment, activation energies for conduction and energy gap were evaluated as a function of caustic mercerization. The results obtained were correlated and discussed in detail, leading to valuable information of use in the cotton fabric strip industries.

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Zusammenfassung Verschiedene Proben von ägyptischen Baumwollstreifen wurden unter verschiedenen Bedingungen (Temperatur, Zeit) einer Laugung unterworfen. Die gelaugten Proben wurden eingehend durch Röntgendiffraktometrie, IR-Absorptionsspektroskopie und Messungen der Temperaturabhängigkeit der elektrischen Gleichstromleitfähigkeit untersucht. Phasenstruktur, Kristallinität, Zuordnung der Banden, Aktivierungsenergien für die Leitfähigkeit und verbotene Bänder wurden in Abhängigkeit von der Laugung ermittelt. Die erhaltenen Ergebnisse wurden miteinander verglichen und in Einzelheiten diskutiert, wobei für die Baumwollverarbeitungsindustrie wertvolle und empfehlenswerte Informationen erhalten wurden.

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. , . , , , . , .

     

Dimerization of n-butenes on nickel and ammonium ion exchanges NaY zeolites

Nickel and ammonium ion exchanged NaY zeolites have been investigated in dimerization of n-butenes in the liquid phase. The dimerization reaction proceeds by a coordinative as well as carbenium ion reaction mechanism.

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NaY, , - . , .

     

Determination of the strength of Lewis acid centers via IR spectroscopic measurement of adsorbed pyridine

According to high-temperature IR spectroscopic studies, the isosteric heats of pyridine adsorption on the Lewis centers of Al₂ O₃, ZrO₂ and zeolite HNaY have been estimated. The dependence between the frequency _8a (1580–1630 cm^–1) and the adsorption heat is shown to take place only for centers formed by cations of the same metal.

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, - HNaY. , _8a (1580–1630 cm^–1) , - .

     

Results of thermal analysis for investigation of salt hydrates as latent heat-storage materials

DTA and DSC methods and quasi-isothermal and quasi-isobaric thermogravimetry are of great importance in the investigation of salt hydrates as latent heat-storage materials. However, the transferability of the DTA and DSC results is given only for application in static latent heatstorage units. Special calorimetric methods adapted to the storage principle are preferred for the study of salt hydrates under dynamic storage conditions. The findings are discussed in connection with the examples of Na₂SO₄·10H₂O, CH₃COONa·3H₂O, Na₂S·9H₂O, Na₂S·5H₂O, Mg(NO₃)₂·6H₂O, MgCl₂·6H₂O and the eutectic mixture of Mg(NO₃)₂·6H₂O-MgCl₂·6H₂O.

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Zusammenfassung Bei der Untersuchung von Salzhydraten als Latentwärmespeichermaterialien besitzen DTA-, DSC-Methoden und die quasi-isotherme und quasi-isobare Thermogravimetrie eine wesentliche Bedeutung. Die Übertragbarkeit der DTA- und DSC-Ergebnisse ist jedoch nur für den Einsatz in statischen latentwärmespeichern gegeben. Für das Studium der Salzhydrate under dynamischen Speicherbedingungen werden spezielle, dem Speicherprinzip angepaßte kalorimetrische Methoden bevorzugt. Die Aussagen werden an den Beispielen Na₂SO₄·10H₂O, CH₃COONa·3H₂O, Na₂S·9H₂O, Na₂S·5H₂O, Mg(NO₃)₂·6H₂O, MgCl₂·6H₂O und der eutektischen Mischung von Mg(NO₃)₂·6H₂O-MgCl₂·6H₂O diskutiert.

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, . , . , . Na₂SO₄·10H₂O, CH₃COONa·3H₂O, Na₂S·5H₂O, Na₂S·9H₂O, Mg(NO₃)₂·6H₂O, MgCl₂·6H₂O Mg(NO₃)₂·6H₂O·MgCl₂·6H₂O.

     

Hydrogenation of benzene on sulfide catalysts in the presence of thiophene

The principles of benzene hydrogenation have been studied with sulfide catalysts NI/MS₂, Ni/SiO₂, M/SiO₂ and (Ni, M)/SiO₂ (M=Mo, W) obtained via metal complex precursors or by impregnation. In bimetallic catalysts active sites of benzene hydrogenation are formed upon reduction of the active component for thiophene hydrogenolysis.

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Ni/MS₂, Ni/SiO₂, M/SiO₂, (Ni,M)/SiO₂, M=Mo W, , . , .

     

Metal dispersity and activity for methylcyclohexane dehydrogenation on Pt/NaY zeolite

By changing the conditions of calcination prior to reduction, three samples with different metal dispersity of Pt/NaY zeolite have been obtained. Their behavior in methylcyclohexane dehydrogenation shows an insensitive character if a second order mechanism with respect to the active site concentration is assumed.

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, , Pt NaY. , .

     

Spectral properties and temperature-dependence of semiconductivity of various doped bismuth trioxide polycrystals

Several samples of Nb₂O₅-doped Bi₂O₃ and Y₂O₃-doped Bi₂O₃ were carefully prepared and sintered at 700° for 3 hours. Extensive measurements were carried out on these samples, including X-ray diffraction spectra, infrared absorption spectra and the temperature-dependence of the DC-electrical conductivity in the solid state. The results obtained were discussed, correlated and interpreted. Finally, the optimum compositions were established and recommended for doped-Bi₂O₃ in the electronics industry.

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Zusammenfassung Einige Proben von mit Nb₂O₅ und Y₂O₃ gedopten Bi₂O₃ wurden hergestellt und bei 700 °C 3 Stunden gesintert. Von den Proben wurden Röntgendiffraktogramme und IR-Absorptionsspektren aufgenommen und die Temperaturabhängigkeit der elektrischen Gleichstromleitfähigkeit im festen Zustand gemessen. Die erhaltenen Ergebnisse werden diskutiert, zueinander in Beziehung gesetzt und interpretiert. Optimale Zusammensetzungen werden ermittelt und für gedoptes Bi₂O₃ in der Elektronikindustrie empfohlen.

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Bi₂O₃, Nb₂O₅ Y₂O₃, 3 700°. , . . , .