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 .

     

Thermal and spectroscopic study of the solid complexes of furan-2-hydroxamic acid and several divalent metallic cations

Solid crystalline complexes of furan-2-hydroxamic acid (FHA) and six metallic divalent cations (Ca(II), Ba(II), Co(II), Ni(II), Cu(II), and Cd(II)) were prepared. In all cases the stoichiometry was 2(FHA)1 (cation). The solids were characterized by elemental analysis, TG, DSC and IR techniques.

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Zusammenfassung Es wurden feste, kristalline Komplexe von Furan-2-hydroxamsäure (FHA) und sechs verschiedenen bivalenten Metallkationen hergestellt: Ca(II), Ba(II), Co(II), Ni(II), Cu(II) und Cd(II). Die stöchiometrische Zusammensetzung betrug in allen Fällen 2(FHA)1(Kation). Die Feststoffe wurden mittels Elementaranalyse, TG-, DSC- und IR-Techniken charackterisiert.

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-2- , , , , . : 21. , , .

     

Role of high temperature hydrogen treatment in n-hexane aromatization over Pt/Al2O3 catalyst. Temperature programmed reaction study

Ultrazet zeolites (Polish counterparts of the ZSM-5 zeolite) with SiO₂/Al₂O₃ ratios ranging from 40 to 186, have been studied to elucidate the correlation of SiO₂/Al₂O₃ ratio with transformation of the orthorhombic into monoclinic symmetry in the zeolite (during preparation), cracking reaction of n-hexane and 3-methylpentane and zeolite acidity.

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( ZSM-5) SiO₂/Al₂O₃ 40 186 SiO₂/Al₂O₃ ( ), - - .

     

Problems of non-linear theory in differential scanning calorimetry

The problems of DSC non-linear theory, connected with the dependence of the thermophysical parameters upon the temperature, are discussed. The changes in thle form of the thermal energy curve recorded by the device as results of the thermaconductivity jump and heat capacity shift taken into account in the course of transformation are shown. A correct non-linear DSC model is formulated. The mather matical apparatus and some simplifying notions for calculation with the non-lineamodel are suggested. The interpretation of a calorimetric curve of an adiabatic scan. ning microcalorimeter over a pretransition range of temperatures is given as an example

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Zusammenfassung Der Beitrag erörtert das Problem der nicht-linearen DSC-Theorie im Zusammenhang mit der Abhängigkeit der thermophysikalischen Parameter von der Temperatur. Die Änderungen der durch das Gerät registrierten Form der Wärme-Kraft-Kurve rühren, wie gezeigt wird, von einer jähen Änderung der Wärmeleitfähigkeit her und Änderungen der Wärmekapazität spielen im Laufe des Prozesses ebenfalls mit. Ein korrektes nicht-lineares DSC-Modell wird formuliert. Der mathematische Apparat und einige vereinfachende Begriffe zur Errechnung des nicht-linearen Modells werden vorgeschlagen. Als Beispiel wird die Interpretation einer kalorimetrischen Kurve eines adiabatischen Scanning-Mikrokalorimeters gegeben, das den Vor-Übergangs-Bereich von Temperaturen erfaßt.

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Résumé L'article discute les problèmes concernant la théorie de l'analyse calorimétrique différentielle (DSC) non linéaire, en rapport avec le fait que les paramètres thermophysiques dépendent de la température. On montre que les variations de forme de la courbe enregistrée par l'instrument résultent d'un saut de conductibilité thermique et d'un changement de chaleur spécifique lors de la transformation. On donne un modèle correct de DSC non linéaire. On propose un traitement mathématique et quelques notions simplificatrices pour le calcul du modèle non linéaire. On donne comme exemple l'interprétation d'une courbe; calorimétrique fournie par un analyseur microcalorimétrique adiabatique, dans le domaine de température précédant la transition.

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, . . . . .

     

Pyrolysis of n-pentane on ZSM-5 zeolite

Pyrolysis of n-pentane has been studied at the temperature range 653–753 K on ZSM-5 zeolite. High catalytic activity and selectivity of H-ZSM-5 zeolite was found. The yield of propane was about 80 wt. %. A mechanism of the process is proposed.

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H-ZSM-5 n- 653–153 . . 80%. n-.

     

Determination of the active surface of supported oxide catalysts on the basis of their reduction rate

A method for the determination of the active surface of supported oxide catalysts, based on measurement of their rate of reduction with carbon monoxide has been developed. The surface of silica gel-supported CuO was measured. The catalytic activity of the samples was found to be proportional to their active surface.

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, . , . , .

     

Kinetic analysis of thermogravimetric data XIII. Thermal decomposition of complexes of type [Co(en)2(pyridine)Cl]X2

Kinetic parameters of the dehydration of AC1₂.1.5 H₂O, and of the substitution of pyridine by the outer sphere anion, have been derived from the TG curves of ACI₂. 1.5 H₂O, ABr₂ and AI₂ (A=[Co(en)₂(pyridine)Cl]) by using the author's nomogram method and the Coats-Redfern method. The influences of sample weight and of heating rate have been studied. Statistical analysis of the results shows the apparent activation energyE of the substitution reaction to decrease in the order CI > Br > I, while bothE and the pre-exponential factor values decrease with increasing sample weight and increasing heating rate. The kinetic compensation effect is discussed.

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Zusammenfassung Kinetische Parameter der Dehydratationsreaktion von AC1₂ · 1.5H₂O und der Substitutionsreaktion von Pyridin für das Anion der Äusseren SphÄre wurden aus den TG-Kurven von AC1₂ · 1.5H₂O, ABr₂ und AI₂ (A=[Co(en)₂(pyridin)Cl] unter Anwendung der Nomogramm-Methode der Autoren sowie der von Coats-Redfern abgeleitet. Der Einfluss des Probengewichts und der Aufheizgeschwindigkeit wurde untersucht. Die statistische Analyse der Ergebnisse zeigte eine Abnahme der scheinbaren Aktivierungsenergie der Substitutionsreaktion in der Reihenfolge Cl > Br > I, sowie die Abnahme vonE und des prÄ-exponentiellen Faktors mit zunehmendem Gewicht der Probe und zunehmender Aufheizgeschwindigkeit. Der kinetische Kompensationseffekt wird diskutiert.

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Résumé On déduit des courbes TG d'ACl₂ · 1.5 H₂O, ABr₂ et AI₂ (A=[Co(en)₂(pyridine)Cl]) en se servant de la méthode nomographique des auteurs et de celle de Coats-Redfern, les paramètres cinétiques de la réaction de déshydratation d'ACl₂ -1.5 H₂O et de la réaction de substitution de la pyridine à l'anion de la sphère externe. On a étudié l'influence du poids du prélèvement et de la vitesse du chauffage. L'analyse statistique des résultats montre que l'énergie d'activation apparenteE de la réaction de substitution diminue dans l'ordre Cl > Br > I et queE et les valeurs du facteur pré-exponentiel diminuent toutes deux avec l'augmentation du poids du prélèvement et de la vitesse de chauffage. On discute l'effet de la compensation cinétique.

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l₂ · 1.5₂ - , l₂ · 1.5₂, ₂ l₂ (=[ /en)₂()l]), — . . , () l > > I. E « » . « ».

     

IR spectroscopic studies of CO interaction with surface zirconium hydrides

IR spectroscopic studies of CO interaction with surface zirconium hydrides have revealed that it proceeds through a step of CO adsorption on these hydrides at 163–273 K with the subsequent insertion of CO across the Zr-H bonds at T>293 K and the formation of surface formyl compounds.

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CO . , CO 163–273 CO Zr-H 293 .

     

Kinetics of thermal decomposition of gelled UO3 microspheres

The kinetics of decomposition of gelled UO₃ microspheres has been studied by thermal analysis (DTA and TG) and by X-ray examination. UO₃ microspheres prepared via a hydrolysis process were used in the study. The DTA and TG curves were obtained in various atmospheres at different heating rates. The activation energies for the various stages of decomposition were calculated using the Carrol and Manche method.

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Zusammenfassung Die Kinetik der Zersetzung von Gel UO₃ Mikrokügelchen wurde mittels Thermoanalyse (DTA und TG) und Röntgenstrukturanalyse untersucht. Die in dieser Abhandlung benutzten UO₃ Mikrokügelchen wurden unter Zuhilfenahme von Hydrolyseprozessen hergestellt. Die DTA- und TG-Kurven wurden in verschiedenen Atmosphären und bei verschiedenen Aufheizgeschwindikeiten aufgenommen. Mit der Methode von Carrol und Manche wurden die Aktivierungsenergien für die einzelnen Schritte der Zersetzung berechnet.

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, UO₃, . . .

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The authors wish to express their thanks to Professor F. H. Hammad for his guidance and encouragement throughout this work.     

A gradientless airtight glass reactor with a detachable catalyst chamber

A gradientless airtight glass reactor supplied with a detachable chamber for the catalyst has been developed. It is designed for investigations on the kinetics of heterogeneous catalytic processes and the determination of catalytic activities at atmospheric and reduced pressures by the flow-circulation and quasi-static techniques.

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. - . , .

     

Dehydration-dehydrogenation of 1- and 2-butanols on lanthanide oxide catalysts

Catalytic decomposition of 1- and 2-butanols on the rare earth oxides CeO₂, Pr₆O₁₁, and Me₂O₃ (Me=La, Sm, Eu, Dy, Ho and Yb) has been studied. Dehydration-dehydrogenation selectivity of these oxides was analyzed from the point of view of the fractional selectivity (S_F). For the decomposition of 2-butanol and the product distribution on the lanthanide oxides, preferential orientation to Hofmann olefin as well as a cis/trans ratio slightly higher than that of the equilibrium value is observed.

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1- 2- CeO₂, Pr₆O₁₁ Me₂O₃ (Me=La, Sm, Eu, Dy, Ho Yb). - (S_F). 2- , , / .

     

Catalysts for selective hydrogenation of conjugated dienes into olefins in the presence of PdCl2 complexes

Complexes of PdCl₂ with amines or pyridine reduced by (iso-Bu)₂ AlH are shown to be catalytically active in the selective hydrogenation of conjugated dienes into olefins in aromatic media. The promoting effect of H₂O and O₂ has been established.

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PdCl₂ , (-Bu)₂ AlH, . H₂O O₂.

     

Dependence between electrocatalytic activity and the size of platinum crystallites

The dependence of the electrocatalytic activity of platinum deposited on a carbon carrier by anodic oxidation of hydrogen on the size of platinum crystallites has been investigated. The influence of the basic character of the surface compounds existing on the carbon carrier on the size of the crystallites and the rate of their growth has been established.

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, , . , , .

     

Application of emissionless infrared diffuse reflectance spectrometry for following reactions of adsorbed alcohols on an alumina catalyst

IR spectra of adsorbed alcohols on alumina were measured under the reaction conditions at elevated temperatures. The transient response of IR absorption intensity indicates that alkoxides are reactive adsorbed species but carboxylates are not. The rate constants of surface reactions were calculated from the transient response.

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, . , , , —, .

     

Interrelation of addition reactions of hexachlorocyclopentadiene and bromine to N-arylimides of endo-and exo-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acids

A comparative analysis of the relative reactivities of N-arylimides of endo-and exobicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acids for the addition reactions of hexachlorocyclopentadiene and bromine has been carried out. According to different correlations the transition states of these two processes are shown to be similar.

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N- - - [2,2,1] -5--2,3- . .

     

Kinetics of cerium(IV) oxidation of propionic acid in perchloric acid: Role of solvent

The oxidation rate of propionic acid (PROA) by cerium(IV) in aqueous perchloric acid (1.0–6.0 mol/dm³) is proportional to the PROA concentration, the total order of the reaction being two. It was found that the rate is related to the values of Hammett's acidity function (H₀) in agreement with both Zucker-Hammett's hypothesis and Bunnett-Olsen's criterion, the water acting as a proton transfer agent. A mechanism consistent with the findings is proposed.

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() (IV) (1,0–6,0 /³) . (H₀) -, -. . .

     

Coke deposits on Pt/Al2O3 catalysts of varying dispersities

Coke deposition during cyclopentane reaction was investigated on Pt/Al₂O₃ catalysts of varying dispersity. For all working pressures the higher the metallic accessibility, the higher the amount of coke deposited on the catalyst. Nevertheless, coke deposited on the less dispersed catalysts is more toxic for the metallic function. An increasing metal accessibility improves the graphitization of coke on the support and so, prevent the deactivation of the metal of a bifunctional catalyst.

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Pt/Al₂O₃ . , , , . , , , . , .

     

Capacité calorifique molaire du composé Bi.4 Te.6 dans les états solide et liquide

The heat capacities of Bi.4Te. 6 in the solid and liquid states are calculated from the results of the experimental drop calorimetric method, and the heat of fusion of the compound is deduced.

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Zusammenfassung Die Wärmekapazitäten von Bi.4Te. 6 in fester und flüssiger Phase werden aus experimentellen Daten berechnet, die mit der tropfenkalorimetrischen Methode erhalten wurden. Die Schmelzwärme der Verbindung wird abgeleitet.

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« » Bi₄Te₆ , .

     

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 .