Review of some metallurgical problems suitable for quantitative calorimetric treatment

A review is given of various metallurgical problems treated in the author's laboratory, for which quantitative calorimetry gave very valuable information. Measurements of thermodynamic data for phase diagram calculations, vacancies in ordered alloys, annealing of steels, and the recovery and crystallization of amorphous alloys are successively examined.

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Zusammenfassung Es wird eine Übersicht über verschiedene, in unserem Laboratorium bearbeitete metallurgische Probleme gegeben, für die durch quantitative Kalorimetrie sehr genaue Informationen erhalten werden. Es wird auf Messungen thermodynamischer Daten für Phasendiagrammberechnungen, auf Fehlstellen in geordneten Legierungen, auf das Tempern von Stahl sowie auf Aufarbeitung und Kristallisation von amorphen Legierungen eingegangen.

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Dedicated to Professor Dr Kurt Komarek on his 60th birthday.     

Asymmetric hydrogenation in the presence of bicyclic chiral phosphines

Both enantiomers of trans-2,3-diphenylphosphinomethyl-norbornene-(5), prepared by two independent synthetic routes, were used as ligands in the asymmetric hydrogenation of -acetamidocinnamic acid in the presence of rhodium(I). Small variations in the ligand structure have a remarkable influence on the activity of the catalytic system.

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-2,3----(5), , - (I). .

     

Interdependence between the dispersion of a solid decomposition product and its formation rate

In an analysis of the possible mechanism and kinetics of a thermal decomposition reaction with the formation of a solid product, the following features were considered: the collective rearrangement character of the transformation; the formation of a product with a different non-equilibrium defectiveness and free energy; the free energy relationship in the series of processes leading to products with different dispersions; the formation of intermediate structures; and the spinodal character of their decomposition. Relationships are presented between the rate of solid product formation, the process temperature, and the surface area and size of the particles.

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Zusammenfassung In einer Analyse des möglichen Mechanismus und der Kinetik einer unter Bildung eines festen Produktes verlaufenden thermischen Zersetzungsreaktion werden folgende Besonderheiten erörtert: der kollektive Umordnungscharakter der Umwandlung, die Bildung eines Produktes mit unterschiedlicher Nichtgleichgewichts-Gitterstörung und unterschiedlicher freier Energie, die Beziehung der freien Energie in zu Produkten unterschiedlicher DispersitÄt führenden Prozessen, die Bildung intermediÄrer Strukturen und der spinodalen Charakter ihrer Zersetzung. Beziehungen zwischen der Bildungsgeschwindigkeit des festen Produktes, der Temperatur des Prozesses und der OberflÄchengrö\e und Grö\e der Partikel werden angegeben.

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: ; ; , ; . , , .

     

Influence of pressure reduction on the shapes of thermoanalytical curves of red muds

The effect of reduction of pressure on the shapes of the TG, DTG and DTA curves and the mass-spectra of hydroxide and carbonate phases was investigated in some typical Hungarian red muds. The pressure change caused different decomposition rates of the phases and resulted in better separation of the overlapping thermal curves; this led to advantages as regards phase analysis. For phase analysis the red muds were extracted with water, and the extracts and solid residues were identified by IR- and X-ray methods.

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Zusammenfassung Die Wirkung der Druckänderung auf die Form der TG-, DTG- und DTA-Kurven, sowie der MS-Spektra der Hydroxid- und Carbonatphasen in einigen typischen ungarischen Rotschlamm-Sorten wurde geprüft. Die Druckänderung verursachte verschiedene Zersetzungsgeschwindigkeiten der Phasen, führte zur besseren Auftrennung der sich überlappenden thermischen Kurven, und war ausserdem auch hinsichtlich der Phasenanalyse vom Vorteil. Zur Phasenanalyse wurden die Rotschlämme mit Wasser extrahiert und die Extrakte und festen Rückstände mittels IR- und Röntgenmethoden identifiziert.

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Résumé On a étudié dans quelques espèces typiques de boues rouges de Hongrie l'effet des variations de pression sur la forme des courbes TG, TGD et ATD ainsi que les spectres de masse des phases hydroxyde et carbonate. La variation de la pression entraîne des vitesses de décomposition différentes. Il en résulte une meilleure séparation des phénomènes dans le cas où ceux-ci se chevauchent ainsi que des avantages du point de vue de l'analyse des phases. L'analyse des phases présentes dans les boues rouges a été effectuée par extraction à l'eau. Les extraits et les résidus solides ont été identifiés par spectrométrie infrarouge et par diffraction des rayons X.

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Paper presented at the Scientific Session on Thermal Analysis held at Balatonfüred, Hungary, on 14–16 October 1976.     

Kinetics and mechanism of the oxidation of benzyl alcohol by potassium chlorochromate

The kinetics of the oxidation of benzyl alcohol by potassium chlorochromate, KCrClO₃, has been studied in dimethyl sulfoxide-dichloromethane medium. The reaction is catalyzed by acid. The effects of temperature and solvent composition were studied and activation parameters evaluated. Probable mechanisms are discussed.

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, KCrClO₃, . . . .

     

Preparation and properties of supported vanadium-phosphorus catalysts studied by chemical analysis and ESR

The preparation of vanadium-phosphorus catalysts is described, showing the considerable influence of phosphorus on the concentration of V⁴⁺ ions. The oxidation properties were studied by chemical analysis and electron spin resonance. Moreover, ESR spectra show a strong influence of moisture on the structure of the catalysts.

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- , V⁺⁴. , . , , .

     

Formation and creeping of the crystalline phase wavefront within the bed of vanadium sulfuric acid catalyst

Kinetics of the reduction of sulfur dioxide by methane in the presence of molecular oxygen at 732–831°C have been obtained.

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732–831°C.

     

Reactivity of radical complexes Zr(IV) (O2?) in electron transfer reactions

Rate constants of the reactions of the radical complex Zr(IV) (O ₂ ^– ) with Fe(II), Ti(III), resorcinol, guaiacol and ascorbic acid in aqueous solutions have been measured by the ESR flow method. They are similar to the values obtained for the radical complex Ti(IV) (O ₂ ^– ).

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Zr(IV)(O ₂ ^– ) , , , . , Ti(IV)(O ₂ ^– ).

     

Determination of heats of decomposition of some 1,3,5,7-tetraazacyclooctane and 1,3,5-triazacyclohexane derivatives using differential scanning calorimetry

Differential scanning calorimetry was used to determine the heats of decomposition of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane(HMX), 1,5-diacetyl-3,7-dinitro-1,3, 5,7-tetraazacyclooctane(DADN), 1,5-endomethylene-3,7-dinitro-1,3,5,7-tetraazacyclooctane(DPT), 1,3,5-trinitro-1,3,5-triazacyclohexane(RDX), 1,3,5-trinitroso-1,3,5-triazacyclohexane (R-salt), and 1,5-endomethylene-3,7-dinitroso-1,3,5,7-tetraazacyclooctane(DNPT). The value of the decomposition heat of unit mass of sample was found to increase inHMX, DADN andRDX with decreasing degree of filling of the reaction volume. In the R-salt and inDNPT, however, the trend of this dependence was found to be the reverse and more pronounced. No analogous dependence was found to exist forDPT under the given experimental conditions.

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Zusammenfassung Die Bestimmung der Zersetzungswärmen von 1,3,5,7-Tetranitro-1,3,5,7-tetraazacyclooktan(HMX), 1,5-Diacetyl-3,7-dinitro-1,3,5,7-tetraazacyclooktan(DADN), 1,5-Endomethylen-3,7-dinitro-1,3,5,7-tetraazacyclooktan (DPT), 1,3,5-Trinitro-1,3,5-triazacyclohexan(RDX), 1,3,5-Trinitroso-1,3,5-triazacyclohexan (R-salz) und 1,5-Endomethylen-3,7-dinitroso-1,3,5,7-tetraazacyclooktan(DNPT) wurde mittels Differential-Abtastkalorimetrie durchgeführt. Es wurde festgestellt, daß der Wert der Zersetzungswärme der Masseneinheit der Probe beiHMX, DADN undRDX mit abnehmendem Füllungsgrad des Reaktionsvolumens zunimmt. Bei R-salz undDNPT war hingegen die Richtung der Abhängigkeit umgekehrt und stärker. Keine analoge Abhängigkeit wurde fürDPT unter den Bedingungen des obigen Versuchs gefunden.

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Résumé On a déterminé par analyse calorimétrique différentielle les chaleurs de décomposition des composés suivants: 1,3,5,7-tétranitro-1,3,5,7-tétraazacyclooctane (HMX), 1,5-diacé tyle-3,7-dinitro-1,3,5,7-tétraazacyclooctane(DADN), 1,5-endométhylène-3,7-dinitro-1,3,5,7-tétraazacyclooctane(DPT), 1,3,5-trinitro-1,3,5-triazacyclohexane(RDX), 1,3,5-trinitroso-1,3,5-triazacyclohexane (selR) et 1,5-endométhylène-3,7-dinitroso-1,3,5,7-tétraazacyclooctane(DNPT). La valeur de la chaleur de décomposition par masse unité d'échantillon augmente dans le cas deHMX, DADN etRDX, quand le degré de remplissement du volume réactionnel diminue. On a trouvé, cependant, avec le selR et leDNPT, une dépendance inverse et plus prononcée. Aucune dépendance similaire n'a été trouvée, dans les conditions expérimentales appliquées dans le cas duDPT.

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-5- . . , , .

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The authors express their gratitude to Mr. Milan Andoga for his precise DSC measurements.     

Synthesis of dimethyl sulfide in the presence of zeolites

In the presence of zeolites, dimethyl sulfide is produced either through CH₃OH interaction with H₂S or via CH₃SH decomposition. In accordance with their activities, in both reactions, zeolites arrange in the same sequence: HZSMHNaY>NaXNaY. Realization of the reaction CH₃OH+H₂S is more difficult compared to methanethiol decomposition.

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CH₃OH H₂S CH₃SH. : HZSMHNaY>NaXNaY. CH₃OH+H₂S , .

     

Effect of intramolecular rotational reorganization of reagents on the ratio between free energies of activation and reaction

Conclusions The relationship between the free energies of activation G and reaction G_o for proton transfer processes have been analyzed, taking into account the effect of hindered rotation of the reagents. We have shown that the considered effect can considerably affect the shape of the G=f(G_o) curve.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 77–81, January 1989.     

Thermogravimetric and kinetic study of a clodronic acid complex formed with sodium

Thermal stability of the clodronic acid complex formed with sodium (Na₂CCl₂(HPO₃)₂ ·4H₂O) was studied using both dynamic and isothermal thermogravimetric analyses as well as mass spectra. The thermal decomposition has two stages: dehydration and loss of two molecules of hydrogen chloride. Using the isothermal TG data the first step was found to be a phase-boundary reaction while the second step obviously cannot be described with just one reaction mechanism. The final residue of the dynamic TG analyses above 810 K was found to be sodium metaphosphate.

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Zusammenfassung Sowohl mittels dynamischer und thermogravimetrischer Untersuchungen als auch and Hand von Massenspektren wurde die thermische Stabilität des mit Natrium gebildeten Säurekomplexes Na₂CCl₂(HPO₃)₂·4H₂O untersucht. Die thermische Zersetzung vollzieht sich in zwei Schritten: Dehydratation und Verlust von zwei Molekülen HCl. Auf Grund der isothermen TG Angaben ist der erste Schritt eine Phasengrenzreaktion, während der zweite Schritt mit einem einzigen Reaktionsmechanismus nicht eindeutig beschrieben werden kann. Das Endprodukt der DTG Analyse oberhalb 810 K erwies sich als Natriummethaphosphat.

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-Na₂CCl₂/HPO_3/2·4H₂O — , - . , , , . , , . 810 .

     

Routes of catalytic oxidation of o-xylene to phthalic anhydride

Relative reactivity of o-xylene, o-tolualdehyde, phthalide, and phthalane and the rate of phthalic anhydride formation from them have been determined. The main route of o-xylene oxidation to phthalic anhydride is due to the o-arrangement of methyl groups, proceeding through bicyclic products, such as dihydrobenzofuran (phthalane) and 3,4-benzofuran.

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-, - , , . - - : () 3,4-.

     

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, . . . .

     

Synthesis of A C18 alcohol from methyl oleate over hydrogen storage alloys

Catalytic hydrogenolysis of methyl oleate to C₁₈ alcohol is tested with a pulse reaction system under atomspheric pressure at 503 K over a series of hydrogen storage alloys. Mg₂Cu alloy shows the highest efficiency and the yield of alcohol is about three times larger than the classical Cu–Cr–O catalyst.

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-C₁₈ 503 K , . Mg₂Cu Cu–Cr–O.

     

IR-spectroscopic studies of strength and concentration of acid centers on V2O5/Al2O3 catalysts

The strength of protonic sites and the concentration of acid centers in V₂O₅/Al₂O₃ catalysts have been estimated according to pyridine and ammonium adsorption.

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V₂O₅/Al₂O₃.

     

Effect of vanadium content on the character of acidic sites on V2O5/Al2O3 catalysts

By IR spectroscopy and TPD the effect of vanadium content on the relative proportion of strongly acidic sites of V₂O₅/Al₂O₃ catalyst was studied.

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- - V₂O₅/Al₂O₃.

     

Kinetic regularities for the interaction of anion-radicals O2? with benzene and toluene on Mo?Mg oxide systems

Interaction of anion-radicals O ₂ ^– with adsorbed forms of benzene and toluene at 293–473 K is shown to be described by an equation corresponding to exponential activation energy distribution of O ₂ ^– . It has been established that under the same conditions the decay rate of O ₂ ^– is higher in the presence of toluene than with benzene.

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, - O ₂ ^– 293–473 , O ₂ ^– . , O ₂ ^– , .

     

Evaluation of the activation energies of elementary propagation steps in the catalytic polymerization of olefins

The possible relation between the activation energies of adsorption and insertion reactions and the heat of olefin adsorption for the two-step mechanism of propagation have been evaluated on the basis of calculated preexponential factors for the propagation rate constants and the experimental activation energies of propagation.

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, .

     

Kinetics of cumene hydroperoxide-dependent aniline hydroxylation with hemoglobin participation

The kinetics of cumene hydroperoxide-dependent aniline hydroxylation to p-aminophenol with hemoglobin (Hb³⁺) participation has been studied in a phosphate buffer at pH 7.4 and 37°C. The data obtained point to hemoglobin complexing with aniline and cumene hydroperoxide (CHP). The character of aniline hydroxylation by the CHP-Hb³⁺ system is discussed.

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37°C pH 7,4 - (Ho³⁺). Hb³⁺ . -Hb³⁺.