The question of thermal decomposition of pyrite

The thermal decomposition of monomineral pyrite was studied in an inert atmostphere. From an analysis of the values of the thermal effects, an interpretation of the hree physicochemical processes recorded in the thermoanalytical curves is proposed.

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Zusammenfassung Die thermische Zersetzung von monomineralem Pyrit wurde in inerter Atmosphäre untersucht. An Hand der Analyse der Werte der thermischen Effekte wird eine Beschreibung dreier, in den thermoanalytischen Kurven festgehaltener physikalischchemischer Vorgänge vorgeschlagen.

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Résumé On a étudié la décomposition thermique de la pyrite, en atmosphère inerte. On propose une interprétation des trois processus physicochimiques enregistrés sur les courbes thermoanalytiques, qui repose sur l'analyse des effects thermiques.

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Thermal decomposition ofC-iodotetrazoles

Thermal decomposition of 1-substitutedC-iodotetrazoles in melt and solutions has been investigated. Thermal stabilities, kinetic and activation parameters, and compositions of products of thermolysis ofC-iodotetrazolcs depend on the substituent nature. The scheme of thermolysis ofC-iodotetrazoles has been suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 68–71, January, 1996.     

Kinetics of thermal decomposition of pyrite in an inert atmosphere

The thermal decomposition of pyrite in an inert atmosphere was studied in order to obtain a detailed knowledge of the kinetics and mechanism of the reaction 2 FeS₂=2FeS+S₂, which is one of the methods of producing elementary sulphur. The process was studied under isothermal conditions at temperatures of 600, 660, 700, 750, 800 and 850 °C in a nitrogen atmosphere, by means of a thermobalance. The rate-controlling processes were determined and their kinetic parameters were calculated. The optimum temperature for the process was found to be 800 °C.

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Zusammenfassung Es wurde die thermische Zersetzung von Pyrit in inerter Atmosphäre bestimmt, um detaillierte Informationen über Kinetik und Mechanismus der Reaktion 2 FeS₂=2FeS+S₂, einer der Darstellungsreaktionen von elementarem Schwefel zu erlangen. Der Vorgang wurde mittels einer Thermowaage unter isothermen Bedingungen bei Temperaturen von 600, 660, 700, 750, 800 und 850 °C untersucht. Es wurden die geschwindigkeitsbestimmenden Schritte bestimmt und deren kinetische Parameter errechnet. Als Optimumtemperatur für diesen Prozeß erwies sich 800 °C.

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- 2FeS₂=2FeS + S₂, . 600, 660, 700, 750, 800 850 ° . , 800°.

     

Thermal decomposition of benzotrifuroxane

The thermal decomposition of benzotrifuroxane proceeds through cleavage of the C-C and O-N(O) bonds of the furoxane ring with formation of dinitriloxodifuroxanyl.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1914–1915, August, 1991.     

Thermal decomposition of dicyanofuroxane

The thermal decomposition of dicyanofuroxane (DCFO) proceeds through cleavage of the O-N(O) and C-C bonds of the furoxane ring with formation of dicyanogen N-oxide. The autocatalytic reactions of this N-oxide with DCFO lead to a pentamer, most likely, with 1,2,4-oxadiazole structure.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1916–1918, August, 1991.     

Thermal decomposition of hydromagnesite

Non isothermal decomposition of synthetically prepared hydromagnesite phase with two different morphologies (2-D micro sheets and nests) was studied in dynamic nitrogen atmosphere by thermogravimetric analysis, differential thermogravimetric analysis, and differential scanning calorimetric techniques. Two different kinetic models, i.e. the Friedman isoconversion and the Flynn–Wall methods were employed for the analysis of thermal decomposition. The apparent activation energy (E _a) of the hydromagnesite phases having 2-D micro sheet and nest morphology were calculated and compared. The activation energy of nest morphology was found to be relatively higher than 2-D micro sheets. The higher activation energy for the relatively close packed ‘nest’ morphology is attributed to the difficulty of thermal transport in the core.     

Thermal decomposition of stichtite

The mineral stichtite was synthesised and its thermal decomposition measured using thermogravimetry coupled to an evolved gas mass spectrometer. Mass loss steps were observed at 52, 294, 550 and 670°C attributed to dehydration, dehydroxylation and loss of carbonate. The loss of carbonate occurred at higher temperatures than dehydroxylation.     

Thermal decomposition of methylxanthines

The thermal decomposition of theophylline, theobromine, caffeine, diprophylline and aminophylline were evaluated by calorimetrical, thermoanalytical and computational methods. Calorimetrical studies have been performed with aid of a heat flux Mettler Toledo DSC system. 10 mg samples were encapsulated in a 40 μL flat-bottomed aluminium pans. Measurements in the temperature range form 20 to 400°C were carried out at a heating rate of 10 and 20°C min⁻¹ under an air stream. It has been established that the values of melting points, heat of transitions and enthalpy for methylxanthines under study varied with the increasing of heating rate. Thermoanalytical studies have been followed by using of a derivatograph. 50, 100 and 200 mg samples of the studied compounds were heated in a static air atmosphere at a heating rate of 3, 5, 10 and 15°C min⁻¹ up to the final temperature of 800°C. By DTA, TG and DTG methods the influence of heating rate and sample size on thermal destruction of the studied methylxanthines has been determined. For chemometric evaluation of thermoanalytical results the principal component analysis (PCA) was applied. This method revealed that first of all the heating rate influences on the results of thermal decomposition. The most advantageous results can be obtained taking into account sample masses and heating rates located in the central part of the two-dimensional PCA graph. As a result, similar data could be obtained for 100 mg samples heated at 10°C·min⁻¹ and for 200 mg samples heated at 5°C min⁻¹.     

Thermal decomposition of ethane

The decomposition of C₂H₆ in Ar was studied by laser-absorption and laser-schlieren measurements of the reaction rate behind incident shock waves with 1300 < T < 2500°K and 1.1 < ρ < 4.4 × 10^?6 mol/cm³. The experimental profiles were parameterized by suitable measures of reaction progress. Computer simulations using a 14-reaction mechanism were used to compare assumptions about rate constant expressions with the experimental parameters and to investigate the sensitivity of computed parameters to these assumptions. A rate constant expression k(cm³/mol˙sec) = 2 × 10¹¹¹ T^?25.26 exp(?80 320/T) was found for the primary dissociation step C₂H₆ + M ? CH₃ + CH₃ + M under the conditions studied; no difference in rate was discernable between M ? Ar and M ? C₂H₆. Rate constant expressions found to be suitable for the remaining reactions of the mechanism, to some of which the computed parameters were sensitive, were in accord with previous proposals. Our results and results from earlier investigations of the primary decomposition reaction, in both forward and reverse directions, were extrapolated, using RRK methods, to obtain low-pressure limiting rate constants and found to be concordant.     

Thermal decomposition of polypyrroles

The thermal stability of polypyrrole (PPy) samples has been studied by thermogravimetry/mass spectrometry and pyrolysis-gas chromatography/mass spectrometry in inert atmospheres. PPy has been prepared by chemical oxidative polymerization using ferric sulfate as an oxidant and anionic surfactants, such as dodecylbenzenesulfonic acid and sodium dodecylbenzenesulfonate as co-dopants. For comparison we have studied polypyrrole (PPy-SO₄) prepared without any additive. It was found that the presence of anionic surfactants improved the thermal stability of PPy. The decomposition of PPy doped with ferric sulfate and anionic surfactants occurs at relatively high temperature indicating that chemical interactions exist between the polymer and the surfactants.     

Thermal decomposition of dicitratoborates

The thermal decompositions of dicitratoborates M¹[B(C₆H₆O₇)₂]·nH₂O (n=0–2, M¹=Rb, K, Li, NH₄) and M¹¹[B(C₆H₆O₇)₂]₂·8H₂O (M¹¹=Co, Ni, Mn, Cu, Zn, Cd) were investigated by means of TG, DTA and DTG methods. It was found that these thermal decompositions involve three successive stages: dehydration, the endothermal decomposition of the ligand, and oxidation of the residual organic component. The volatile products of decomposition in each stage were detected by means of gas chromatography. The method of TG-curve transformation into the curvedm/d T vs.m, wherem is the loss of weight at each moment of time, was used for a more detailed study of dehydration. The optimal conditions for TG-curve modification were found.

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Zusammenfassung Die thermische Zersetzung von Dicitratboraten der allgemeinen Formeln M¹[B(C₆H₆O₇)₂]·nH₂O (n=0–2;M ¹=Rb, K, Li, NH₄) und M¹¹[B(C₆H₆O₇)₂]₂·8H₂O (M ¹¹=Co, Ni, Mn, Cu, Zn, Cd) wurden mittels TG, DTA und DTG untersucht. Es wurde gefunden, daß die thermische Zersetzung dieser Verbindungen in drei Schritten verläuft: Dehydratisierung, endotherme Zersetzung des Liganden und Oxydation des organischen Rückstandes. Die flüchtigen Zersetzungsprodukte eines jeden Stadiums wurden gaschromatographisch detektiert. Zur detailierten Untersuchung der Dehydratisierung wurden die TG-Kurven zu Kurven transformiert, in denendm/dT gegenm dargestellt ist, wobeim der Gewichtsverlust zu einer gegebenen Zeit ist. Die optimalen Bedingungen für die TG-Kurvenmodifikation wurden festgestellt.

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, , ¹[(₆₆₇)₂]-n₂, =0–2, ^II[(₆₆₇)₂]₂ 8₂, Me^I=Rb, , Li, NH₄, Me^II=Co, Ni, Zn, Cd, Mn, . : , . . dm/dT- (). .

     

Thermal decomposition of gem-dinitroethylnitramines

Thermal decomposition of C,N-disubstituted gem-dinitroethylnitramines in dilute solutions in inert solvents is a first-order reaction and it is unaffected by the polarity of the solvent. The rate constant is largely controlled by the steric effect of the substituent at the carbon atom bearing gem-nitro groups. A correlation is found between the rate constant and the steric constant E _s of the substituent. This correlation permits prediction not only of thermal stability of yet unexplored compounds, but also of change of the decomposition mechanism.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1669–1673.Original Russian Text Copyright © 2004 by Stepanov, Kruglyakova, Astakhov.This revised version was published online in April 2005 with a corrected cover date.     

Thermal decomposition of mononitroalkanes

Conclusions The contribution of the heterogeneous reaction to the rate of the gas phase decomposition of nitroethane, 1-nitropropane, and 2-nitropropane was determined by varying the ratio of the surface to the volume of the reaction vessel (S/V).The activation energies of the homogeneous decomposition of the enumerated compounds differ from the literature data.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1412–1416, July, 1971.     

Thermal decomposition of azoethane

The thermal decomposition of azoethane (AE) was studied by detailed product analysis in the temperature and pressure intervals 508–598 K and 2.7–13.3 kPa. Besides the hydrocarbon products, three characteristic and quantitatively important nitrogen-containing compounds were also determined: ethyl-2-butyldiimide, ethanal-diethylhydrazone, and tetraethyl-hydrazine. Apart from the predominant termination reactions of the ethyl radical with itself and with the μ₂ radical, the decomposition is characterized by a very short chain reaction. The measurements led to determination of the following rate constants and rate constant ratios: for the following reactions:      

Thermal decomposition of cellulose

Journal of Thermal Analysis and Calorimetry - Cellulose has been pyrolysed in nitrogen at two heating rates, and the rates of formation of total gases, and the oxides of carbon, have been measured....     

Thermal decomposition of deuterofullerite

The volative products of thermal decomposition of deuterofullerite C₆₀D₁₉ were studied by mass spectrometry. It was found that D₂, CD₄, and C₆D₆ molecules are present in the gas phase above deuterofullerite heated to 773 K. Deuterocarbons appear in the gas phase already at 673 K.     

Thermal decomposition of complexes

The iron(II) complex of the Schiff bases trans-N,N'-bis(salicylidene)-1,2-cyclohexanediamine (Salcn), manganese(II) and vanadyl complexes of the Schiff bases cis- andtrans-N,N'-bis(salicylidene)-1,2-cyclohexanediamine (Salcn) were prepared and characterized by IR spectroscopy, and elemental analysis. These new complexes were submitted to thermal analysis (TG and DSC) under dynamic air atmosphere. The differences in the decomposition profiles were related to the structure of isomers and decomposition intermediates were characterized according to their X-ray diffraction pattern and by their infrared spectrum. This revised version was published online in August 2006 with corrections to the Cover Date.