Kinetic parameters of the thermal decomposition of Cu(II) and Zn(II) salts of carboxylic acids

The kinetic parameters of thermal decomposition of Cu(II) and Zn(II) salts of carboxylic acids were investigated on the basis of the respective thermal curves. The values of the activation energy (E _a) of thermal decomposition, reaction order (n), frequency factor (A) and velocity constant (k) (in the Arrhenius kinetic equation), established from thermal data, were compared. Based on the initial decomposition temperature, the following sequences of stabilities of the studied compounds have been proposed:

1. Cu(CH₃COO)₂ (235°)>Cu(C₆H₅O₇)₂ (220°)>Cu(HCOO)₂ (150°)>>Cu(OH)₂·Cu(CO₃) (50°)
2. Zn(C₁₈H₃₅O₂)₂ (305°)>ZnCO₃ (210°)>Zn(CH₃COO)₂ (170°)

     

Kinetic parameters for thermal decomposition of hydrazine

The propulsion of most of the operating satellites comprises monopropellant (hydrazine––N₂H₄) or bipropellant (monometilydrazine—MMH and nitrogen tetroxide) chemical systems. When some sample of the propellant tested fails, the entire sample lot shall be rejected, and this action has turned into a health problem due to the high toxicity of N₂H₄. Thus, it is interesting to know hydrazine thermal behavior in several storage conditions. The kinetic parameters for thermal decomposition of hydrazine in oxygen and nitrogen atmospheres were determined by Capela–Ribeiro nonlinear isoconversional method. From TG data at heating rates of 5, 10, and 20 °C min^?1, kinetic parameters could be determined in nitrogen (E = 47.3 ± 3.1 kJ mol^?1, lnA = 14.2 ± 0.9 and T _b = 69 °C) and oxygen (E = 64.9 ± 8.6 kJ mol^?1, lnA = 20.7 ± 3.1 and T _b = 75 °C) atmospheres. It was not possible to identify a specific kinetic model for hydrazine thermal decomposition due to high heterogeneity in reaction; however, experimental f(α)g(α) master-plot curves were closed to F _1/3 model.     

Kinetic parameters of the thermal decompositions of nitritonickelates(II)

Kinetic parameters of thermal decomposition of compounds of general formulaM ₂ ^I M ^II[Ni(NO₂)₆], whereM ^I= K⁺, Rb⁺ or Cs⁺ andM ^II= Ca²⁺, Sr²⁺ or Ba²⁺, were investigated on the basis of the respective thermal curves. Calculations of the reaction order and activation energy carried out by the Coats-Redfern method and by Doyle's method (modified by Zsakó) gave similar results, The reaction order is 2 for all the compounds investigated. In the group of potassium salts the activation energy increases fromM ^II=Ca²⁺ toM ^II=Ba²⁺. In the groups of rubidium and caesium salts, the lowest activation energy is observed whenM ^II=Sr²⁺. Such behaviour of the nitritonickelates is explained in terms of structures and the principle of maximum density.

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Zusammenfassung Die kinetischen Parameter der thermischen Zersetzung von Verbindungen der allgemeinen FormelM ₂ ^I M ^II [Ni(NO₂)₆] (M ^I= K⁺, Rb⁺ oder Cs⁺ und M^II = =Ca²⁺, Sr²⁺ oder Ba²⁺) wurden auf Grund der entsprechenden thermischen Kurven untersucht. Die an Hand der Coats-Redfern Methode und der durch Zsakó modifizierten Doyleschen Methode durchgeführten Berechnungen der Reaktionsordnung und der Aktivierungsenergie ergaben ähnliche Resultate. Die Reaktionsordnung ist 2 für sämtliche untersuchten Verbindungen. In der Gruppe der Kaliumsalze steigt die Aktivierungsenergie vonM ^II=Ca²⁺ in RichtungM ^II=Ba²⁺ an. In der Gruppe der Rubidium- und Caesiumsalze wird die niedrigste Aktivierungsenergie beiM ^II=Sr²⁺ beobachtet. Dieses Verhalten der Nitritonickelate wird durch die Strukturen und das Prinzip der maximalen Dichte erklärt.

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₁ ^{2 II}[Ni(NO₂)₆], ^I= ⁺, Rb⁺Cs⁺,a ^II= ²⁺,8r²⁺²⁺. , - ( ), . 2. ^{+ 2+}. ^II=S²⁺. .

     

Kinetic and thermodynamic parameters of the thermal decomposition of zinc(ii) dialkyldithiocarbamate complexes

The thermodynamic and kinetic parameters of the thermal decomposition of Zn(S₂CNR₂)₂ complexes (R=CH₃, C₂H₅ and n-C₃H₇) were determined with the dynamic thermogravimetric method. Superimposed TG/DTG/DSC curves show that thermal decomposition reactions for chelates with R=C₂H₅ and n-C₃H₇ occur in the liquid phase, at temperatures far away from their melting points, whereas for the complex with R=CH₃ the thermal decomposition begins at a temperature closer to its melting point, suggesting a rather complex decomposition mechanism. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effect of outer sphere cations on the thermal stability of nitritocuprates(II)

Thermal analyses by Derivatograph were made for salts of the general formula M ₂ ^I M^II[Cu(NO₂)₆] where M^I=K⁺, Rb⁺ or Cs⁺; and M^II=Ca²⁺, Sr²⁺, Ba²⁺ or Pb²⁺. From the results and the chemical and diffractometric analysis of sinters of chosen salts, the mechanism of thermal decomposition was established. Some conclusions concerning the effects of outer sphere cations on the thermal stabilities of these salts are also drawn.

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Zusammenfassung Es wurden thermische Analysen mit einem Derivatographen für die Salze der allgemeinen Formel M₂ ^IM^II [Cu(NO₂)₆] durchgeführt [M^I=K⁺, Rb⁺, Cs⁺; M^II=Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺]. Aus den Ergebnissen dieser sowie der chemischen und diffraktometrischen Analysen der Sinterprodukte der jeweiligen Salze wurde der Mechanismus ihrer chemischen Zersetzung ermittelt. Einige Folgerungen bezüglich der Wirkung von Kationen der äusseren Sphäre auf die thermische Stabilität konnten ebenfalls gemacht werden.

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Résumé Le mécanisme de la décomposition thermique des sels de formule générale M₂ ^IM^II [Cu(NO₂)₆] où M^I=K⁺, Rb⁺, Cs⁺ et M^II=Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺ a été établi à partir des données thermiques obtenues à l'aide d'un Derivatograph, ainsi que par des analyses thermiques et diffractométriques sur les produits frittés. L'effet des cations de la couche externe sur la stabilité thermique de ces sels est discuté.

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M ₂ ^I M^II[Cu(NO₂)₆], M^I=K⁺, Rb⁺, Cs⁺; M^II=Ca²⁺, Sr²⁺, Ba²⁺, b²⁺. , , . , .

     

Kinetic studies on the decomposition of cyano complexes. I. the thermal decomposition of cyanoferrate(II) acids

The formation of HCN from solid iron(II) cyano complex acids is studied by a non-isothermal kinetic method. A derivatograph is used for the measurements and the kinetic parameters are calculated by different methods using the Horowitz—Metzger, Coats—Redfern and Zsako equations. The results are discussed and the kinetic parameters (energy and entropy of activation) are compared with IR and Mössbauer spectroscopic data.     

Kinetic parameters of thermal decomposition of complex of β-cyclodextrin with water

The apparent kinetic parameters of the thermal decomposition of the-cyclodextrin-water complex were estimated from thermogravimetric data. Various calculation methods were used and the results compared. All methods except the Kissinger method gave a reaction order near to zero and an activation energy in the range 60 to 65 kJ/mol. Some trials were made to extrapolate the activation energy values to semi-isothermal conditions (65.7 kJ/mol). The loss in weight indicated the presence of 11 water molecules in the complex. This was liberated in single stage, despite its occurrence as two distinct types, as shown by crystallographic studies.

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Zusammenfassung Auf Grundlage von thermogravimetrischen Daten wurden die scheinbaren kinetischen Parameter des Thermozerfalles von-Cyclodextrin-Wasser- Komplexen geschätzt. Die durch verschiedene Rechenmethoden erhaltenen Ergebnisse wurden in Tabelle 3 verglichen. Mit Ausnahme der Kissinger-Methode ergaben alle Verfahren eine Reaktionsordnung von annähernd Null und eine Aktivierungsenergie im Bereich 60–65 kJ/mol. Ausserdem wurde versucht, die Aktivierungsenergiewerte auf halbisotherme Bedingungen zu extrapolieren (65.7 kJ/mol). Der Masseverlust weist elf Wassermoleküle im Komplex nach, die in einem einzigen Schritt abgegeben werden, ungeachtet dessen, dass kristallographische Untersuchungen die Wassermoleküle zwei verschiedenen Typen zuordnen.

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-- . , . , , — 60–65 · ^–1. (65,7 · ^–1). , , , , .

     

Kinetic study of the thermal decomposition of cobalt(III) oxyhydroxide

The kinetics of thermal decomposition of CoOOH have been studied by analysis of isothermal weight loss data under vacuum. The comparison of linear correlation coefficients of different kinetic expressions applied to these data does not allow an understanding of the mechanism, even when significance tests are performed (t test). A single value of the activation energy (193 kJ mol^?1) is obtained from the Arrhenius plots, and is relatively independent of the choice of rate law. On the other hand, a change in the mechanism of formation of Co₃O₄ with temperature cannot be inferred from analysis of isothermal data. Thus, the statement of some authors that from formal kinetics it is possible to distinguish the proton and electron transfers involved in the transformation appears unacceptable.     

Kinetic analysis of thermal decomposition of praseodymium(III) nitrate hexahydrate

The kinetics of thermal decomposition of praseodymium(III) nitrate hexahydrate was studied by using isothermal and dynamic thermogravimetric techniques. Kinetic analysis of the isothermal data with respect to various solid-state reaction models showed that the reaction is best described by phase boundary-controlled and random nucleation models. Kinetic analysis of the dynamic TG curves was discussed and a critical comparison was made of two integral methods, that of Coats and Redfern and that of Ozawa. The results showed that the Ozawa method gives a better correlation, and the results are in good agreement with those obtained under isothermal thermogravimetric conditions.

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Zusammenfassung Mittels isothermer und dynamischer thermogravimetrischer Methoden wurde die Kinetik der thermischen Zersetzung des Hexahydrates von Praseodymnitrat untersucht. Eine kinetische Auswertung der isothermen Meßdaten unter Anwendung verschiedener Feststoffreaktionsmodelle ergab, daß die Reaktion am besten durch ein phasengrenzenkontrolliertes Randomkeimbildungsmodell beschrieben werden kann. Die kinetische Auswertung der dynamischen TG-Kurven wurde diskutiert und ein kritischer Vergleich zwischen zwei Integriermethoden, der von Coats und Redfern und der von Ozawa, angestellt. Die Betrachtungen ergaben, daß die Methode von Ozawa eine bessere Korrelation liefert und daß die Resultate gut mit denen der isothermen thermogravimetrischen Messungen übereinstimmen.

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. , , , . - . , , .

     

Kinetic and activation thermodynamic parameters on thermal decomposition of synthetic lubricant oils

The kinetic and thermodynamic study of synthetic lubricant oils was accomplished in this work, using isothermal and non-isothermal thermogravimetry based on mass loss as a function of time and temperature. The thermodynamic and kinetic behavior of the synthetic lubricant oils depends on atmosphere and heating rates used in TG analysis. The kinetic and thermodynamic results were satisfactory, presenting good correlation.     

Kinetic parameters for thermal decomposition of supramolecular polymers derived from flunixin-meglumine adducts

Meglumine, (2R,3R,4R,5S)-6-methylaminohexane-1,2,3,4,5-pentol, is a carbohydrate derived from sorbitol in which the hydroxyl group in position one is replaced by a methylamine group. It forms binary adducts with substances having carboxyl groups, which have in common the presence of hydrogen bonding as the main force in the stabilization of these species. During melting, adducts of meglumine with flunixin (2-[[2-methyl-3-(trifluoromethyl)phenyl]amino]pyridine-3-carboxylic acid) polymerize or self-assemble in amorphous supramolecular structures with molecular weights around 2.0 × 10⁵ kDa. DSC curves, in a first heating, show isomorphic transitions where the last one at 137 °C for the flunixin-meglumine adduct originated the supramolecular amorphous polymers with glass transition around 49.5 °C. The kinetic parameters for the thermal decomposition step of the polymers were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and heating rates of 5, 10, 15, and 20 °C min⁻¹, the E _α and B _α terms could be determined and, consequently, the pre-exponential factor, A_α, as well as the kinetic model, g(α).     

Solid-phase thermal decomposition of polynuclear nickel(II) and cobalt(II) complexes

Solid-phase thermal decomposition of polynuclear Ni^II and Co^II pivalate complexes was studied by differential scanning calorimetry and thermogravimetry. The decomposition of the polynuclear (from bi-to hexanuclear) Co^II carboxylate complexes is accompanied by aggregation to form a volatile octanuclear complex. Thermolysis of the polynuclear NiII carboxylates results in their destructure, and the phase composition of the decomposition products is determined by the nature of coordinated ligands. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 250—260, February, 2006.     

The thermal decomposition of manganese(II) sulphite trihydrate

Thermal studies have shown that manganese(II) oxide and trimanganese tetroxide are the final decomposition products when manganese(II) sulphite trihydrate is heated in nitrogen and oxygen respectively. However, in each atmosphere, there are several decomposition routes involving the intermediate formation of manganese(II) sulphate and manganese(II) sulphide. The reactions can be summarized as follows:

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Zusammenfassung Thermische Untersuchungen haben gezeigt, da\ Mangan(II)oxid und Trimangan-Tetroxid die Endprodukte der Zersetzung sind, wenn Mangan(II)sulfit Trihydrat in Stickstoff bzw. Sauerstoff erhitzt wird. In jeder der AtmosphÄren gibt es jedoch erschiedene Zersetzungswege, wobei vorübergehend Mangan(II)sulfat und Mangan(II)sulfid gebildet werden. Die Reaktionen können, wie folgt, zusammengefa\t werden:

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Résumé Les études thermiques montrent que l'oxyde de manganèse(II) et le tétroxyde de trimanganèse constituent les produits finaux de la décomposition du sulfite de manganèse(II) chauffé respectivement dans l'azote et dans l'oxygène. Cependant dans chacune de ces atmosphères, plusieurs chemins de décomposition peuvent Être suivis. Ils font intervenir la formation intermédiaire de sulfate de manganèse(II) et de sulfure de manganèse(II). Les réactions peuvent Être résumées comme suit:

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, , , , MnO Mn₃O₄. , , - (II). :

     

Kinetic analysis of thermal decomposition reactions

The effect of⁶⁰C0-gamma radiation on the kinetic parameters of the thermal decomposition of potassium bromate crystals has been investigated. Radiation did not modify the mechanism of thermal decomposition reaction, but resulted in a decrease in activation energy and frequency factor with a rate which is large at small doses and decreases at higher doses. The results showed that the increase in the concentration of decomposition nuclei tends to be more important than the increase in the porous character of the solid.     

Kinetic parameters of the thermal decomposition processes of certain cobalt and titanium coprecipitates

Journal of Thermal Analysis and Calorimetry - The kinetic parameters of the thermal decomposition reactions of certain coprecipitates were calculated by a thermogravimetric method. The significance...     

Kinetic parameters of the thermal decomposition of thiocyanatobismuthates(III) : Part 1. Single salts of alkali metals

Kinetic parameters of the thermal decomposition of alkali metal thiocyanatobismuthates, of general formula M₃[Bi(SCN)₆], where M ≡ Li, Na, K, Rb, and M[Bi(SCN)₄], where M ≡ Rb and Cs, and bismuth thiocyanate Bi(SCN)₃ have been determined. The reaction order and activation energy of several stages of the decomposition have been determined and the effect of the outer-sphere cations on the thermal stability and activation energy has been defined. The thermal stabilities of thiocyanatobismuthates and thiosulphatobismuthates have been compared.     

Kinetic parameters for thermal decomposition of microcrystalline,vegetal, and bacterial cellulose

Cellulose can be obtained from innumerable sources such as cotton, trees, sugar cane bagasse, wood, bacteria, and others. The bacterial cellulose (BC) produced by the Gram-negative acetic-acid bacterium Acetobacter xylinum has several unique properties. This BC is produced as highly hydrated membranes free of lignin and hemicelluloses and has a higher molecular weight and higher crystallinity. Here, the thermal behavior of BC, was compared with those of microcrystalline (MMC) and vegetal cellulose (VC). The kinetic parameters for the thermal decomposition step of the celluloses were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and at heating rates of 5, 10, and 20 °C/min, the E _α and B _α terms could be determined and consequently the pre-exponential factor A _α as well as the kinetic model g(α). The pyrolysis of celluloses followed kinetic model g(a) = [ - ln(1 - a)]^{1 mathord}

The thermal decomposition of platinum(II) and (IV) complexes

The decomposition characteristics of Pt(II) and Pt(IV) complexes in hydrogen, air and argon were investigated by thermal gravimetric and differential thermal analysis. Based on weight-loss measurements, the thermal stability in hydrogen increased in the order: hexachloroplatinic acid<platinum acetyl acetonate<platinum diamino dinitrite<tetrammine platinous hydroxide<tetrammine platinous chloride<platinum phthalocyanine; whereas in air, the order was: hexachloroplatinic acid<tetrammine platinous hydroxide<platinum acetyl acetonate<platinum diamino dinitrite<tetrammine platinous chloride. The platinum complexes were more stable in air than in hydrogen where decomposition was observed in all platinum samples at temperatures below 200°C.     

Mössbauer studies of thermal decomposition of metal(II) hexacyanoferrates(II)

The thermal decompositions of metal(II) hexacyanoferrates(II) (Co, Ni and Zn) were studied in air with Mössbauer, infrared, thermal analysis and magnetic susceptibility techniques. Dehydration is almost complete at 200° and decomposition starts at 250° in the cases of cobalt and nickel hexacyanoferrates(II), and at 300° for zinc hexacyanoferrates (II). Finally, ferrites are formed as decomposition products.     

Synthesis and thermal decomposition of cobalt(II) bis(oxalato)cobaltate(II) tetrahydrate

Cobalt(II) bis(oxalato)cobaltate(II) tetrahydrate (Co[Co(C₂O₄)] · 4H₂O) was synthesized and characterized on the basis of elemental and spectral analysis. The thermal decomposition of the complex was investigated in air and nitrogen media. In air, complete dehydration of the complex occured at 251°, followed by rapid decomposition to a mixture of CO₂O₃ and Co₃O₄ at 300°; in nitrogen, dehydration occurred at 206°, followed by decomposition to a mixture of Co and CoC₂O₄, and finally to Co + CoO, at 394° and 420°, respectively. The activation energies for the dehydration and decomposition reactions in nitrogen and air media were evaluated and a tentative reaction mechanism for the thermal decomposition of the complex was proposed.

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Zusammenfassung Das Tetrahydrat von Kobalt(H)bisoxalatokobaltat(II) wurde dargestellt und mittels Elementar- und Spektralanalyse characterisiert. Die thermische Zersetzung der Komplexe wurde sowohl in Luft- als auch in Stickstoffatmosphäre untersucht. In Luft erfolgt bei 251 °C eine vollständige Dehydratierung, gefolgt von einer schnellen Zersetzung bei 300 °C in Co₂O₃ und Co₃O₄. In Stickstoff erfolgt die Dehydratierung bei 206 °C, gefolgt von einer Zersetzung bei zunächst 394 °C in Co und CoC₂O₄, anschliessend bei 420 °C in Co und CoO. Die Aktivierungsenergien für die Dehydratierung und Zersetzung in Stickstofo- und Luftatmosphäre wurden ermittelt und für die thermische Zersetzung der Komplexe ein Reaktionsmechanismus gegeben.

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- -() ([(₂₄)₂]·4₂), - . 251 ° _{23 34} 300 °. 260 ° ₂₄, , , 394 420 °. - , .

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The authors thank the RSIC, CDRI, Lucknow for the C, H analyses and IR spectra: RSIC, IIT, Madras for the low-frequency IR spectra; RSIC, IIT, Bombay for the e.s.r. spectra; RSIC, Nagpur University for the TG and DTG measurements; and Dr. S. K. Datta of Forensic Science Laboratory, Gauhati, Assam for the DSC measurements.