Evaluation of rate constants from thermogravimetric data

The thermal decomposition of potassium chlorate was investigated as a function of doping and there seems to be a correlation between the polarizing nature of the dopant cation and the thermal degradation temperature of potassium chlorate. In particular, transition metal cations influence strongly the temperature of decomposition. Irradiation and mechanical shock defects influence also the process. A possible mechanism in terms of the semi-conductive properties of the defective chlorates is discussed.Chlorine oxy-salts are subject to thermal decomposition at relatively low temperatures. Their thermal stability depends on various conditions. In particular, the coordinative saturation of the oxygen surrounding the chlorine atom within the complex anions and the nature of the cations seem to determine the outcome of the thermal decomposition of these salts.Thus, the thermal stability decreases apparently from the perchlorates to the chlorates to the chlorites and hypochlorites [1,2], since only the chlorine atom in the perchlorate anions is coordinatively saturated with four oxygen atoms. Also, bonding energies between the central chlorine and the surrounding oxygens decrease quantummechanically in that order [3].On the other hand, the nature of the cations of an oxy-chlorine compound affects significantly the stability and reaction path [4,5], In fact, there seems to be a distinct correlation between the polarizing power of the cations [6] or the ionic character of the cation-oxychlorine bond [7,8] and the thermal stability. The less ionic the bond, or the stronger the polarization power of the cation, the less stable is the compound.The apparent heterogeneous catalytic effects of metal oxides on the solid state and molten phase decomposition of potassium chlorate and perchlorate have been studied previously [9], and it was found that the defect nature of the metal oxides played an important part in the catalytic efficiency with respect to the thermal decomposition of the chlorates and perchlorates [10].As a logical consequence of these studies we investigated the influence which intra-crystalline defects such as cationic impurities might have on the thermal decomposition of potassium chlorate. To this end, chlorate samples were prepared

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“…A method is described in the literature [13], where the inflection point in the TG curve is determined. The final equation is as follows:…”

Section: Discussionmentioning

confidence: 99%

The effect of defect structure due to doping and irradiation on the thermal decomposition of potassium chlorate

Rudloff

Freeman

1980

Journal of Thermal Analysis

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“…Fuoss, Salyev and Wilson [13] suggested an expression for the evaluation of E and A for first-order kinetics. These are calculated using the relationships …”

Section: (D) Fuoss Methods [13]mentioning

confidence: 99%

“…the Horowitz-Metzger [10], the Freeman-Carroll [11], the Coats-Redfern [12] and the Fuoss [13] methods. The data were then subjected to the method of least squares.…”

Section: Kinetic Parametersmentioning

confidence: 99%

Structure and thermal characterization of tris-thallium(III) glycollate

Khadikar

1987

Journal of Thermal Analysis

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The thermal decarboxylation of TI(GLA)3 (where GLA stands for the anion ofglycollic acid) was studied by TG, DTG and DTA techniques. The results showed the escape of all three glycollic acid moieties in a single step. The I R spectra of the ligand and the complex indicated the bidentate character of carboxylate ion and the fact that the proton from the hydroxy group is not replaced during complex formation, The various kinetic and thermodynamic parameters were estimated from analysis of the TG, DTG and DTA curves of the sample, employing several computational methods. Precise results were then obtained by the method of least squares and are discussed.The thermal decomposition of metal carboxylates has attracted great interest during recent years [1,2]. However, work on the thermal decomposition of heavy metal carboxylates started only a short time ago [3]. Recently, we reported on the thermal dehydration and decomposition of metal complexes of salicylic and nuclear substituted salicylic acids [4][5][6][7][8][9]. The work on the thermal decomposition of metal complexes of hydroxy acids is very limited. As an extension of our previous studies [4][5][6][7][8][9], the present report deals with the thermal decarboxylation of TI(III) glycollate, with a view to understanding the mechanism of the decomposition and the nature of the decomposition products. The characterization ofTl(IlI) glycollate was carried out through elemental analysis, IR spectra, TG, DTG and DTA studies. Attempts were also made to estimate the kinetic parameters from thermal studies, employing different computational methods, e.g. the Horowitz-Metzger

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“…There are several methods for this purpose, which differ in the manner of thermogravimetric curve approximation (e.g. the Redfern [5], Freeman-Carroll [6] and Fuosse [7] methods). We In the version used here, the straight line log~-~ vs. 1/T is obtained by the application of the least-square method.…”

Section: John Wiley and Sons Limitea[ Chichester Kiad6 Budat~stmentioning

confidence: 99%

The thermal decomposition of some Cr(III) complexes

Grotowska

Wojciechowska

Wojciechowski

1990

Journal of Thermal Analysis

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The thermal decomposition reactions of the following chromium(III) complexes were investigated:Cr(CH3COO)3 "2 H20, [Cr30(CH3COO)6(H20)3]CI "2 H20 and [Cr30(CH2CICOO)6(H20)3]CI'6H20. Simultaneous TG/DTG/DTA were applied nonisothermal conditions. From the recorded curves, the activation energies Ea were calculated for all the thermal decomposition steps. Appropriate chemical reactions were attributed to the thermal effects, with consideration to the X-ray diffraction and IR spectra results.The coordination compounds are subject to ever increasing research by derivatography because of the various molecular structures of these compounds and the great variety of ligands and central ions, and also because of the role played by coordination compounds and their high-temperature decomposition products in catalytic processes. Application of derivatography may also provide qualitative information regarding the stability of the crystal lattice, the character of the bonding in the molecules, the mechanism of their decomposition and the kinetics of these reactions. Obviously, this research must be related with the results of other structural investigations, e.g. X-ray crystallography or spectroscopy. This work presents the results of such studies on the following compounds:Cr (CH3COO)3" 2 H20, [Cr30(CH2C1COO)6(H20)3]C1-2 H20 and [CraO(CH3COO)6(H20)3]CI" 6 H20.

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Evaluation of rate constants from thermogravimetric data

Cited by 42 publications

References 7 publications

The effect of defect structure due to doping and irradiation on the thermal decomposition of potassium chlorate

The effect of defect structure due to doping and irradiation on the thermal decomposition of potassium chlorate

Structure and thermal characterization of tris-thallium(III) glycollate

The thermal decomposition of some Cr(III) complexes

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