Kinetics of the 2,2′-bipyridyl catalyzed Cr(VI)?I? reaction

The kinetics of 2,2-bipyridyl catalyzed Cr(VI)–I^– reaction has been studied. The order with respect to Cr(VI) is one and fractional with respect to bipyridyl. The order in [I^–] changes from unity to zero. Plots of 1/k_obs vs. 1/[bipy] and 1/k_obs vs. 1/[I^–] are straight lines with positive slopes and intercepts.

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2,2-, Cr(VI)–I^–. Cr(VI) , -. [I^–] 1 0. 1/k_obs 1/[bipy] 1/k_obs 1/[I^–] .

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IICT Publication NO. 2586     

Tungsten hexachloride-tetraphenyltin based catalysts for metathesis, I. Spectroscopic investigation

WCl₆ in benzene is reduced not only by Ph₄ Sn but also by Ph₃SnCl or Ph₂ SnCl₂ (in contrast to alkyltin chlorides). In UV spectra of the reaction mixture two relatively stable intermediates have been detected, one of them being WCl₅ and the other one an unidentified species, presumably PhWCl₄, since the same compound is formed when WCl₅ is used as the starting tungsten chloride.

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WCl₆ P₄Sn, Ph₃ SnCl Ph₂ SnCl₂ ( ). , WCl₅, , , PhWCl₄, . , WCl₅ .

     

Differential scanning calorimetry of spin-oriented polyester yarn

Polyester yarn spun over a range of wind-up speeds has been characterized using differential scanning calorimetry. Samples prohibited from shrinking during the thermal analysis show slightly smaller heats of fusion and crystallization and reduced cold crystallization temperatures than samples that are free-to-shrink, particularly in the intermediate wind-up speed region. One critical observation made is that the cold crystallization temperature reaches a minimum at some relatively low overall molecular orientation (n 0.020) and fails to decrease further. A likely explanation is that crystallization continuously removes polymer from the melt in the spinline in regions where the local orientation reaches some critically high value.

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Zusammenfassung Mit verschiedenen Aufspulgeschwindigkeiten gesponnenes Polyestergarn wurde durch DSC charackterisiert. Die während der tyermischen Analyse am Schrumpfen gehinderten Proben zeigen, besonders bei mittleren Aufspulgeschwindigkeiten, eine etwas geringere Schmelz- und Kristallisationswärme und niedrigere kalte Kristallisationstemperaturen als Proben, die ungehindert schrumpfen konnten. Die kalte Kristallisationstemperatur erreicht bei enier relativ niedrigen Gesamtmolekularorientierung (n 0.020) ein Minimum und nimmt nicht weiter ab. Wahrscheinlich ist, dass durch die Kristallisation das Polymer in den Bereichen, in denen die lokale Orientierung einen kritischen Wert erreicht, kontinuierlich aus der Schmelze entfernt wird.

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, , . , - , , , , , , . , (n0.020) . , , .

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The author appreciates the input provided by Dr. R. M. Mininni and the help of Dr. W. E. Bessey in fiber spinning and Ms. E. Fernekess in thermal analysis. The author is grateful to Celanese Corporation for allowing publication of this work.     

Study of the thermal behaviours of some metal acrylates

The thermal behaviours of Na, Ca, Mg and Zn acrylates were investigated by TG and DTA. It was found that the anhydrous acrylates were subject to thermal polymerization processes, which preceded the main decomposition. The presence of oxygen influences the decomposition of the organic part of the molecule very strongly, but it does not markedly affect the extent of polymerization or the type of the resulting solid products. Metal carbonates or oxides make up the major proportion of the residue obtained after the decomposition of the metal acrylates, similarly as in the case of other low molecular monocarboxylic acid salts.

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Zusammenfassung Das thermische Verhalten von Na, Ca, Mg und Zn-Akrylaten wurde mittels TG und DTA untersucht. Es wurde festgestellt, daß die wasserfreien Akrylate einen termischen Polymerisierungsproze erleiden, der der Hauptzersetzung vorangeht. Die Gegenwart von Sauerstoff wirkt sich sehr stark auf die Zersetzung des organischen Teils des Moleküls aus, beeinflut jedoch das Ausma der Polymerisierung und den Typ der entstandenen festen Produkte nicht besonders. Die bei der Zersetzung von Metallakrylaten erhaltenen Substanzen bestehen größtenteils aus Metallkarbonaten oder -oxiden, analog wie bei anderen Salzen von niedermolekularen Monokarbonsäuren.

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Résumé Etude du comportement thermique des acrylates de Na, Ca, Mg et Zn par thermogravimétrie et par analyse thermique différentielle (TG et ATD). On observe que les acrylates anhydres subissent un processus de polymérisation thermique qui précède la décomposition principale. La présence d'oxygène exerce une forte influence sur la décomposition de la partie organique de la molécule mais elle n'affecte pas de manière importante le degré de polymérisation ni la nature des produits solides formés. La majeure partie du produit obtenu après la décomposition des acrylates métalliques est constituée de carbonates et d'oxydes métalliques comme c'est le cas pour les autres sels d'acides monocarboxyliques à faibles poids moléculaires.

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TG Na, , Mg Zn. , , . , . , , , .

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The authors thank Mr. J. Bobinski for his help in translating this paper into English.     

Thermal decomposition of calcium sulphate in carbon monoxide

Simultaneous TG and DTA studies were performed on analytical grade calcium sulfate and on samples of natural gypsum and phosphogypsum in carbon monoxide atmosphere. The decomposition temperatures and mechanism are influenced by the mineral impurities of the sample and the heating rate as well as the CO content of the gas atmosphere.

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Zusammenfassung Simultane TG- und DTA-Untersuchungen von analytisch reinem Calciumsulfat und Proben von natürlichem Gips und Phosphogips wurden in Kohlenmonoxidatmosphäre ausgeführt. Temperatur und Mechanismus der Zersetzung werden durch mineralische Verunreinigungen der Probe, durch die Aufheizgeschwindigkeit und durch den CO-Gehalt der Gasatmosphäre beeinflußt.

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. - , , .

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The authors are indebted to Professor M. Veiderma for fruitful discussions and continuous support. The scholarship from Finnish Government to one of us (R. K.) is gratefully acknowledged.     

Kinetic investigations of the formation of carbonate sodalite

The kinetics of sodium carbonate formation within a sodalite matrix by an intracage reaction of hydrothermally grown basic nitrite sodalite and carbon dioxide has been studied. This heterogeneous reaction inside the sodalite cages was followed in the 773 K–1153 K temperature interval by thermogravimetry, IR-spectroscopy, as well as X-ray powder diffraction. The weight uptake during heating and the increase of the unit cell volume has been discussed to describe the imbibition of CO₂ and the resulting intra-cage carbonate formation.

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. 773–1153 , . CO₂, .

     

Effect of the state of vanadium cations on the IR spectra of adsorbed carbon monoxide

ESR and IR-spectrosocpic studies of the effect of the state of vanadium ions on the IR-spectra of adsorbed CO have revealed complex formation of CO with V⁴⁺ (vCO at 2192 and 2205 cm^–1) and V³⁺ (vCO at 2178 and 2185 cm^–1) ions.

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-- - CO. CO V⁴⁺ (vCO 2192, 2205 cm^–1) V³⁺ (vCO 2178, 2185 cm^–1).

     

Kinetics and mechanism of isothermal dehydration of LiKC4H4O6 · H2O single-crystals

The kinetics of isothermal dehydration of LiKC₄H₄O₆.H₂O single-crystals was investigated in the [001] crystallographic direction under a dynamic vacuum of 6.7×10^–5 Pa with a quartz crystal microbalance. The removal of H₂O molecules may be described by a diffusion equation for a semi-infinite medium. The diffusion coefficients vary from 2.13×10^–11 cm² s^–1 at 391.7 K to 9.9×10^–9 cm² s^–1 at 453.2 K. The scanning electron microscope data provide some evidence that the dehydration is not a topochemical reaction. From the experimental data it is concluded that the anhydrous product is in the state of premelting. This explains the anomalous diffusion energyE _D=37±1 kcal mol^–1 and preexponential factorD ₀=5×10⁹ cm² s^–1.

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Zusammenfassung Die Kinetik der Entwässerung von LiKC₄H₄O₆.H₂O in [001] — Richtung unter dynamischem Vakuum wurde mit einer Quarzkristall-Mikrowaage verfolgt. Die Abgabe von Wasser kann mit einer Diffusionsgleichung für ein halb-unendliches Medium beschrieben werden, die Diffusionskoeffizienten variieren von 2, 13 · 10^–11 cm²s^–1 bei 391,7 K bis 9,9 · 10^–9 cm² s^–1 bei 453,2 K. Rasterelektronenmikroskopische Aufnahmen zeigen, daß die Entwässerung nicht topochemisch abläuft. Nach dem experimentellen Ergebnis befindet sich das entwässerte Produkt in einem Vorschmelz-Stadium. Daraus erklären sich die anomalen Werte für die DiffusionsenergieE _D=(37±1) kcal mol–1 und den präexponentiellen FaktorD ₀=5 · 10⁹ cm² s^–1.

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6,7 · 10. LiKC₄H₄O₆.H₂O [001]. . 2,13·10^{–11 2 –1} 391,7 9,9·10^{–9 2 –1} 453,2 . , . , «», E =37±1 ·^{– 1} ₀=5·10⁹²·^–1.

     

Application of the Q-derivatograph for evaluation of the melting enthalpies of low-melting compounds

A Q-derivatograph was used for quantitative studies on low-melting compounds. The apparatus was calibrated with four selected compounds. Their melting temperatures were between 30 and 90°, while their melting enthalpies were known from the literature and were verified by DSC. The calibration curve turned out to be a straight line, and a mean calibration coefficient was determined between 30 and 90°. The Q-derivatograph was then applied for quantitative studies of oligoethyleneadipate (OEA-2000), with a melting temperature between 46 and 55°, depending on its crystal form. The values ofH _m depended on its morphological form, which was associated with the magnitude of the internal stresses.

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Zusammenfassung Ein Q-derivatograph wurde zur quantitativen Untersuchung von tiefschmelzenden Verbindungen benutzt. Die Apparatur wurde mit vier ausgewählten Verbindungen kalibriert, deren Schmelzpunkte zwischen 30 und 90° liegen und deren Schmelzenthalpien aus der Literatur bekannt sind und mittels DSC verifiziert wurden. Die Kalibrationskurve ist eine Gerade und für den Bereich von 30–90° wurde ein mittlerer Kalibrierungskoeffizient ermittelt. Der Q-Derivatograph wurde dann zu quantitativen Untersuchungen von Oligoäthylenadiapat (OEA-2000) mit von der Kristallform abhängigen Schmelztemperaturen zwischen 46 und 55° eingesetzt. Die Werte vonH _m hängen von der morphologischen Form ab, die mit der Größe der inneren Spannung in Zusammenhang gebracht wird.

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Q- . , 30–90°, . 30– 90°. Q- , , , 46 55°. H _m , .

     

Physical properties of the catalyst used for the partial oxidation of anthracene to anthraquinone. I. M?ssbauer study

Mössbauer measurements on the intermediate and active material used for partial oxidation of anthracene to anthraquinone are reported. The fraction of ferric and ferrous ions as well as their coordination types are determined.

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, . , .

     

Temperature dependence of CO insertion on S-, Ag-, and Cu-promoted Rh/SiO2 catalysts

The addition of sulfur and silver to Rh/SiO₂ inhibits hydrogenation of C₂H₄, but promotes CO insertion and extends the linearity of Arrhenius curves for CO insertion above 543 K.

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Rh/SiO₂ C₂H₄, CO CO 543 .

     

Determination of hydroxyl groups and/or water on the surface of oxide catalysts by a pulse chromatographic method

A pulse chromatographic method based on the reaction of gaseous dimethylzinc tetrahydrofura nate was developed for the determination of surface hydroxyl groups and/or adsorbed water in solid porous materials. The procedure is rapid and gives results comparable to other methods. Some heterogeneous catalysts and supports have been analyzed.

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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. , : . .

     

A novel method for the preparation of extensively dealuminated faujasites

Open structure faujasites may be dealuminated with retention of crystallinity using phosgene (or similar reactants) provided the sample has been made ultrastable in a previous procedure.

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( ) . .

     

Cumene hydroperoxide decomposition in the presence of metal complex catalysts supported on amorphous SiO2

By the method of molecular deposition, ions of CrO ₂ ²⁺ VO³⁺ and MoO ₂ ²⁺ were supported on a matrix of amorphous SiO₂. Different types of organic ligands were supported subsequently on the surface compounds so formed. The catalytic activity of the samples was studied in the decomposition of comene hydroperoxide.

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SiO₂ CrO ₂ ²⁺ , VO³⁺, MoO ₂ ²⁺ . . .

     

The thermal decomposition of thaumasite from Mothae kimberlite pipe,Lesotho, Southern Africa

The endothermic decomposition of thaumasite from Mothae which has been investigated by DTA and TG shows a peak temperature of 138–203°, and reaction orders of 0.45–1.00, depending on the heating rate employed. The activation energy of the reaction was found to be about 19 kcal/mole; the enthalpy is 246 cal/g.The decomposition seems to be divided into one reaction withn=0.90, immediately followed by one withn=1.59. The first reaction is attributed to the loss of H₂O, the second one to the (partial) release of OH and CO₂.

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Zusammenfassung Die durch DTA und TG überprüfte endothermische Zersetzung von Thaumasit aus Mothae zeigt in Abhängigkeit der angewandten Aufheizgeschwindigkeiten Spitzentemperaturen zwischen 138 und 203° C, sowie Reaktionsordnungen von 0.45 bis 1.00. Die Aktivierungsenergie der Reaktion ergab sich zu 19 Kcal/Mol, die Enthalpie zu 246 cal/g.Die Zersetzung scheint in eine Reaktion vonn=0.90 und eine sofort darauffolgende vonn=1.59 geteilt zu sein. Die erste Reaktion wird dem Verlust von H₂O, die zweite der (teilweisen) Freisetzung von OH und CO₂ zugeschrieben.

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Résumé La décomposition endothermique de la thaumasite de Mothae a été étudiée par ATD et TG. Suivant la vitesse de chauffage utilisée la température au sommet du pic varie de 138 à 203° C et l'ordre de réaction de 0.45 à 1.00. On a trouvé que l'énergie d'activation s'élevait à 19 kcal, mol^–1 et l'enthalpie à 246 cal. g^–1.Il semble que la décomposition s'effectue suivant une réaction d'ordren=0.90, immédiatement suivie par une autre oùn=1.59. On attribue la première réaction à la perte d'eau et la seconde à la libération (partielle) d'hydroxyles OH et d'anhydride carbonique CO₂.

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, , 138–203° 0,45–1,00 . , 19 /, - 246 /. , n=0,90, n=1,59. , - OH CO₂.

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The material used for this study has been kindly supplied by Dr. P. H. Nixon, former chief geologist, Department of Mines, Maseru, Lesotho.     

Catalytic decomposition of N2O on La2CuO4 in the presence of LaNi5 alloy

Decomposition of N₂O has been studied on pure La₂CuO₄, La₂CuO₄ with 5 and 10 wt. % LaNi₅ and oxidized LaNi₅ in the temperature range of 240–490 °C at 50 and 200 Torr initial pressures of N₂O. The addition of LaNi₅ decreases the energy of activation compared to that of La₂CuO₄ which has been explained based on the dispersity of NiO over La₂CuO₄.

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N₂O La₂CuO₄ La₂CuO₄ LaNi₅ 5–10 .%, 240–490°C N₂O 50 200 . LaNi₅ , . NiO La₂CuO₄.

     

Studies on the catalytic decomposition of N2O over the solid solution La2CuxZn1?xO4 (0

U. Kameswari  J. Christopher  C. S. Swamy 《Reaction Kinetics and Catalysis Letters》1990,41(2):381-388

A study of thermal preparation OF c-Mn2P4O12

With the application of thermogravimetry under quasi-isothermal-isobaric conditions, the reaction course of the calcination of Mn(H₂PO₄ · H₂O to give dimanganese cyclotetraphosphate has been studied. Isothermal calcination was also carried out in an electric furnace at various temperatures (200 min). The reaction products were analyzed by chromatography, IR and NMR spectrocopy, and X-ray diffraction analysis. The compositions of the calcinates were determined through extraction with various inorganic and organic solvents.

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Zusammenfassung Der Verlauf der Dimangan-cyclotetraphosphat ergebenden Kalzinierung von Mn(H₂PO₄)₂ · H₂O wurde thermogravimetrisch unter quasi-isothermen-isobaren Bedingungen untersucht. Isotherme Kalzinierung wurde auch im elektrischen Ofen (200 min) bei verschiedenen Temperaturen ausgeführt. Die Reaktionsprodukte wurden chromatographisch, IR- und NMR-spektroskopisch sowie röntgendiffraktometrisch analysiert. Die Zusammensetzung der kalzinierten Produkte wurde via Extraktion mit verschiedenen anorganischen und organischen Lösungsmitteln bestimmt.

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Mn(H₂PO₄ · H₂O. . . - , - - . .

     

Effect of pressure on the rate of n-heptane conversion on Pt/Al2O3 catalysts

The effect of pressure on the rates of product formation in n-heptane conversion on Pt/Al₂O₃ has been studied at 490 °C over the pressure range of 10–50 atm. It has been shown that the rate of isomerization is practically independent of pressure, and the dependence of the rates of dehydrocyclization and hydrocracking on pressure is described by simple kinetic equations. The reaction order of dehydrocyclization with respect to hydrogen tends to –2.0 at high pressures.

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- 10–50 490°C. , , . –2,0.