Thermoanalytical assessment of the quality of edible and technical oils

An investigation of the thermal decomposition of fish oils and motor lubricating oils resulted in the elaboration of a new method, which, by utilizing the relationship between the temperatures of mass losses and the changes in the cnemical composition due to the oxidative and hydrolytic decomposition of fish oils and to the processes occuring in lubricating oils in the course of their service in the oils system of combustion engines, allows estimations of the physicochemical properties of these oils.

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Zusammenfassung In Zusammenhang mit der Ausarbeitung einer neuen Methode, die die Abschätzung der physikalisch-chemischen Eigenschaften von Fischölen und Motorschmierölen ermöglicht, wurde eine Untersuchung über die thermische Zersetzung dieser Öle durchgeführt. Als Grundlage dafür diente der Zusammenhang zwischen der Masseverlusttemperatur und der mit der oxidativen bzw. hydrolytischen Zersetzung von Fischölen und den Alterungsprozessen von Motorschmierölen in Verbrennungsmotoren in Verbindung stehenden Veränderung der chemischen Zusammensetzung.

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, - , , , , .

     

Study of the solid solution of MoO3 in Fe2V4O13

Differential thermal and phase X-ray analyses have shown that MoO₃ and Fe₂V₄O₁₃ form a solid substitution solution, in which Mo⁶⁺ ions are incorporate into the crystal lattice of Fe₂V₄O₁₃ in place of V⁵⁺ ions. The solubility limit of MoO₃ in Fe₂V₄O₁₃ at ambient temperature is 18 mole % of MoO₃. The phase equilibria in the system Fe₂V₄O₁₃-FeVMoO₇, were also studied. Results are presented in the form of a phase diagram.

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Zusammenfassung Durch DTA und Röntgenphasenanalyse wurde gezeigt, daß MoO₃ und Fe₂V₄O₁₃ Substitutionsmischkristalle bilden, in denen Mo⁶⁺-Ionen anstelle von V⁵⁺-Ionen in das Kristallgitter von Fe₂V₄O₁₃ eingebaut sind. Die Löslichkeitsgrenze von MoO₃ in Fe₂V₄O₁₃ beträgt bei Umgebungstemperatur 18 Mol-% MoO₃. Ebenfalls wurden die Phasengleichgewichte im System Fe₂V₄O₁₃-FeVMoO₇ untersucht. Die Ergebnisse sind in Form eines Phasendiagramms dargestellt.

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- , ₃ Fe₂V₄O₁₃ , o⁶⁺ V^5– Fe₂V₄O₁₃. ₃ Fe₂V₄O₁₃ 18 %. Fe₂V₄O₁₃-FeVMoO₇ .

     

Thermal degradation of transition metal carbonyl complexes. Part II

The thermal degradation of three monosubstituted hexacarbonyl complexes, M(CO)₅py (where M=Cr, Mo, and W; py=pyridine) has been studied by thermogravimetry (TG) and differential scanning calorimetry (DSC) and their results reported. It was found that for each of the three complexes studied, the starting material M(CO)₆ was formed which immediately sublimed unchanged with or without concomitant loss of carbonyl (CO) ligands to give the first large weight loss step. This was closely followed by the volatilisation of the pyridine ligands and at higher temperatures the loss of further CO ligands. The enthalpy changes associated with the above-mentioned steps are reported. The conversion of M(CO)₅py to M(CO)₆ and other products was confirmed by the analysis of residue after pyrolysis in a tube furnace under conditions similar to those observed in TG experiments.

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Zusammenfassung Der thermische Abbau von drei monosubstituierten Hexacarbonylkomplexen der allgemeinen Formel M(CO)₅py (mit M=Cr, Mo und W; py=Pyridin) wurden mittels TG und DSC untersucht. Von jeder der drei Komplexe wird die Ausgangssubstanz M(CO)₆ erhalten, die sofort unverändert mit oder ohne gleichzeitigem Verlust an Carbonyl (CO)-Liganden sublimiert und die erste große Gewichtsverluststufe ergibt. Diesem Schritt folgt gleich die Verflüchtigung des Pyridinliganden und bei höheren Temperaturen die Abgabe weiterer CO-Liganden. Die mit den genannten Schritten einhergehenden Enthalpieveränderungen werden mitgeteilt. Die Umwandlung von M(CO)₅py zu M(CO)₆ und anderen Produkten wurden durch Analyse des Rückstandes nach der Pyrolyse in einem Röhrenofen unter ähnlichen Bedingungen wie in den TG-Versuchen bestätigt.

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()₅, M=, , =. , , , . , . . , .

     

Activation of magnesia by hydrogen spillover

Magnesia aerogel activated by hydrogen spillover at 430 °C or at 200 °C becomes a catalyst for the hydrogenation of ethylene. This catalytic activity, observed already at 50 °C, is further enhanced by a treatment in oxygen at 430 °C.

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, 430 200°C, . 50°C 430°C.

     

Cyclohexene skeletal isomerization activity of sepiolites modified with B3+ or Al3+ ions

The effect of sepiolite modification by B³⁺ and Al³⁺ ions on catalytic performance were investigated in cyclohexene skeletal isomerization (CSI) reaction. Catalytic activity to 1- and 3-methylcyclopentenes (1- and 3-MCP) fit the Bassett-Habgood kinetic model for first order processes. These ions induced strong acidity in the sepiolite and the best results (greater activity and selectivity to 1-MCP) were found when the sepiolite was exchanged with an BF₃/methanol solution which contained 3 wt.% of the B³⁺ ion.

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B³⁺ Al³⁺ . 1- 3- - . . - 1-- , BF₃/, 3 . % B³⁺.

     

Mössbauer study of the thermal decompositions of alkaline earth tris(oxalato)ferrates(III)

The thermal decompositions of alkaline earth tris(oxalato)ferrates(III) (Mg, Ca, Sr and Ba) have been studied by Mössbauer spectroscopy and other techniques. During the thermal decomposition, dehydration occurs first, followed by reduction to iron(II) species, and oxides and ferrites (MFe^IIIO₄) are then formed at higher temperature. In the case of strontium tris(oxalato)ferrate(III), strontium ferrite (SrFe^IVO₄) is formed at 700°.

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Zusammenfassung Die thermische Zersetzung von Tris(oxalato)ferraten(III) der Erdalkalimetalle (Mg, Ca, Sr, Ba) wurde durch Mössbauer-Spektroskopie und andere Techniken untersucht. Im Verlaufe der thermischen Zersetzung verläuft zunächst die Dehydratisierung, gefolgt von der Reduktion zu Eisen(II)-Species. Oxide und Ferrite (MFe^IIIO₄) werden danach bei höheren Temperaturen gebildet. Strontium-tris(oxalato)-ferrat(III) geht bei 700 °C in Strontiumferrit (SrFe^IVO₄) über.

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() () , , ë . , , MFe^IIIO₄. 700° SrFe^IVO₄.

     

Composition and properties of the cobalt-molybdenum oxide system

The physico-chemical and catalytic properties of the Co–Mo oxide system have been studied in a wide range of various molybdenum to cobalt ratios. The activity increase at 1.21Mo:Co?11 is assumed to be due to the formation of solid solutions.

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- Co–Mo- . , - 1,21Mo:Co>11 .

     

Study of the polymerization of some methacrylic acid esters by differential scanning calorimetry

The strengths of the gel effect, and the monomer conversions at which the gel effect sets in for the polymerizations of some methacrylic acid esters, were determined at different temperatures from the courses of polymerization measured by differential scanning calorimetry. It was found that the strength of the gel effect is greatly influenced by the reaction temperature and the ester residue in the molecule of the monomer, whereas the critical conversion for individual monomers is practically independent of the reaction temperature in the measured interval, but is strongly dependent on the length of the ester residue.

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Zusammenfassung Die Stärke des Geleffektes und die Monomerkonversion, bei der der Geleffekt bei der Polymerisation einiger Methacrylsäureester einsetzt, werden aus dem Verlauf der Polymerisation in Abhängigkeit von der Temperatur mittels DSC gemessen. Es wurde festgestellt, daß die Stärke des Geleffekts stark von der Temperatur und dem Esterrest im Molekül des Monomeren beeinflußt wird, während die kritische Konversion individueller Monomere praktisch unabhängig von der Temperatur im untersuchten Bereich ist, jedoch im starken Maße von der Länge des Esterrestes abhängt.

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- , - , . , . , - , , .

     

Dispersity of oxidized and reduced palladium on Al2O3

The amount of PdO not dissolving in dilute HCl as a function of its content in palladium catalysts calcined in air has been determined. Mean size of Pd particles in the same samples has been evaluated from oxygen chemisorption. A comparison of these data indicates their correlation, which permits to determine Pd dispersity variations according to the solubility of supported PdO before reduction.

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. . , .

     

Effect of carbon support on the hydrogen sorption of platinum

The hydrogen sorption of carbon-supported platinum catalysts, studied by the potentiodynamic method, differs significantly from that of unsupported platinum. The difference depends on the preparation method and on the nature of the support. Possible explanations are suggested as (i) some kind of interaction between metal and support atoms during impregnation, (ii) high dispersity (amorphous structure) and (iii) hydrogen spillover onto the carbon support.

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Pt/C, . . (I) , (II) ( ), (III) .

     

Relaxation of the rate of o-xylene oxidation to phthalic anhydride on vanadium catalysts

Based on numerical analysis of experimental data, the main ideas of the reaction mechanism have been confirmed and kinetic principles of the non-steady=state reaction have been determined.

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, .

     

Potassium addition to Fe/MgO, Ni/MgO and Ni/SiO2: Reducibility, dispersity and stabilization of the promoter by the support

The influence of potassium addition on the morphological properties of Fe/MgO and Ni/MgO has been investigated: KNO₃ addition to precursors results in a decrease of the reducibility and in a smaller dispersity of the metallic phase. A loss of potassium is observed at reduction temperatures in excess of 773 K. Silica-supported Ni behaves differently: silica inhibits the potassium volatilization and nickel reducibility is enhanced. This illustrates how promoter effects can be influenced by the nature of support.

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Fe/MgO Ni/MgO: KNO₃ . , 773 K. , : . .

     

Thermal decomposition of homo- and copolymers of isobutylene

The thermal properties of polyisobutylene and isobutylene-isoprene copolymers were studied. Thermal curves were interpreted with regard to supplementary data. It was found that the degradation of both homo- and copolymers proceeds to a much higher extent in air than in argon. It follows from the results that peroxide formation plays a significant role in the degradation of this group of polymers.This finding correlates well with the influence of dicumyl peroxide and phenyl--naphthylamine on the thermal properties of the isobutylene polymers investigated in this work.

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Zusammenfassung Die thermischen Eigenschaften von Polyisobutylen- und Isobutylen-Isopren-Kopolymeren wurden untersucht. Die thermischen Kurven wurden unter Berücksichtigung ergänzender Angaben gedeutet. Es wurde festgestellt, dass die Zersetzung sowohl von Homoals auch von Kopolymeren in Luft in einem viel grösseren Ausmass verläuft, als in Argon. Aus den Ergebnissen folgt, dass die Peroxidbildung bei der Zersetzung dieser Gruppe von Polymeren eine bedeutende Rolle spielt.Diese Aussage ist in guter Übereinstimmung mit dem Einfluss von Dicumylperoxid und Phenyl- naphthylamin auf die thermischen Eigenschaften der untersuchten Isobutylenpolymere.

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Résumé On a étudié les propriétés thermiques des copolymères polyisobutylène et isobutylèneisoprène. On a interprété les courbes thermiques en considérant des données supplémentaires. On a établi que la dégradation tant des homoque des copolymères s'effectue d'une manière beaucoup plus importante dans l'air que dans l'argon. Nos résultats montrent que la formation du peroxyde joue un rôle important sur la dégradation de ce groupe de polymères.Cette conclusion est en bon accord avec l'influence du peroxyde de dicumyle et de la phényl-naphtylamine sur les propriétés thermiques des polymères d'isobutylène étudiés dans notre travail.

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- . . , , . , . -- .

     

Differential-thermal and thermogravimetric analysis of some gagates from Bulgaria

The thermal behaviour of three gagates (Bulgaria) was investigated by DTA and TG. The characteristic endo- and exoeffects and the sequence of the thermal stabilities are established.

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Zusammenfassung Das thermochemische Verhalten von drei Gagaten (Bulgarien) wurde mittels DTA und TG untersucht. Die charakteristischen endo- und exothermen Effekte und die Reihenfolge der thermischen Stabilitäten wurden ermittelt.

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(). - .

     

Flow-pulsation method to study the activity of catalyst in high-pressure processes

Generation of gradientless conditions by the pulsation method with variable reciprocating gas flow method through the isothermal catalyst bed is suggested as one of the trends in the further development of external circulation flow systems. The conditions ensuring continuous stirring have been established. Flowcirculation and pulsation methods have been tested under similar conditions.

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- - . , , - .

     

Catalytic conversion of dimethylsulfide to methylmercaptan

The effect of reaction conditions on the methylmercaptan formation from dimethylsulfide in H₂S catalyzed by -Al₂O₃ has been studied. The reaction is first order with respect to dimethylsulfide. It has been revealed that the maximum activity in this reaction is observed for the catalysts whose surface contains a large number of aprotonic acid centers and moderate-strength basic sites.

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-Al₂O₃. , . . , , .

     

Measurement of the rate constant of hydrogen atoms with carbon monoxide in tubular and jet stirred open reactors

The reaction of hydrogen atoms with carbon monoxide has been studied in discharge flow systems with a new method of detection of atoms. The results obtained with tubular and jet stirred open reactors agree with those of other authors working in transient conditions and with more sophisticated techniques.

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. , , , .

     

Effect of the roughness factor on the surface oxidation of ruthenium catalysts

The surface oxidation of ruthenium catalysts with different roughness factor values has been analyzed. It is shown that electro formation of oxidized species on the exposed surface of ruthenium is strongly affected by the rougher characteristics of the surface. This effect has been explained through the addition and removal of protons to and from the oxidized species.

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. , . .

     

Effect of the network structure on the flammability ofcis-1,4-polyisoprene vulcanizates

The combustibilities ofcis-1,4-polyisoprene and its peroxide and sulphur vulcanizates have been investigated by means of the oxygen index method. The temperature distribution in the sample and the molecular weight of the liquid products formed as a result of elastomer destruction in the combustion zone have been measured. It has been found that the combustibility ofcis- 1,4-polyisoprene diminishes as its cross-link density increases. This effect is much stronger for sulphur than for peroxide vulcanizates. The investigations lead to the conclusion that a mechanism of network degradation and volatile sulphur compounds penetrating to the flame are responsible for this difference.

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Zusammenfassung Die Brennbarkeit des unvernetztencis-1,4-Polyisoprens und seiner Peroxid- und Schwefelvulkanisate wurde mit der Sauerstoffindexmethode untersucht. Messungen der Temperaturverteilung im Prüfling wurden ebenfalls ausgeführt und das Molekulargewicht der infolge der Zersetzung der Elastomere in der Verbrennungszone entstehenden flüssigen Produkte mit der Methode der dynamischen Osmometrie bestimmt. Es wurde festgestellt, daß die Brennbarkeit des cis-1,4-Polyisoprens mit zunehmender Vernetzungsdichte abnimmt, und zwar viel ausgeprägter im Falle der Schwefel- als im Falle der Peroxidvulkanisate. Es wurde gefolgert, daß flüchtige, in die Flamme gelangende Schwefelverbindungen als Verbrennungsinhibitoren wirken.

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-1,4- . , . , -1,4- . . , .

     

IR spectroscopic studies of H2S adsorption on acid and base catalysts

IR spectra of H₂S adsorbed on various types of catalysts have been studied by monitoring changes in the properties of their surfaces from the spectra of probe molecules. It is shown that H₂S is adsorbed only dissociatively on basic centers (BC); on proton centers (PC) it forms H-complexes, while with the participation of strong Lewis acid centers (LAC), it is adsorbed both associatively and dissociatively.

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- H₂S , -. , H₂S (), () -, ()- , .