Thermogravimetric investigation of the pyrolysis of pitch materials. A compensation effect and variation in kinetic parameters with heating rate

Collett, G.W.; Rand, B.

doi:10.1016/0040-6031(80)80060-8

Cited by 54 publications

(17 citation statements)

References 8 publications

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“…The values of enthalpy and entropy given in Table 1 tells us about the changes in the internal structure or organization during the degradation process. The majority of the researchers have concluded that thermodynamic compensation in any chemical reaction occurs because of the linear relationship of the enthalpy-entropy plot, which is supported by the high correlation coefficient [24]. Plotting enthalpy against entropy yields a "compensation plot," typically a straight line when the compensation effect is noted in the system under investigation.…”

Section: Resultsmentioning

confidence: 92%

“…It has correlation coefficients greater than 0.99 for all the polyesters degraded in air and N 2 . In some systems, [24,25] it has been observed that the activation energy varies under different measuring conditions. It is also found that the variation in activation energy is accompanied by a change in A that is; a large activation energy is accompanied by a large preexponential factor and vice versa, a phenomena often referred to as compensation effect.…”

Section: Resultsmentioning

confidence: 99%

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Enthalpy-Entropy Compensation in Polyester Degradation Reactions

Al‐Mulla

2012

International Journal of Chemical Engineering

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In an earlier work the author had studied the degradation kinetics of polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polybutylene terephthalate (PBT) under nonisothermal conditions in air and N 2 at heating rates of 5, 10, 15, and 20• C/min. In this paper the kinetic degradation parameters of PET, PTT, and PBT were estimated using the CoatsRedfern method for two different weight loss regions ranging from 2-8% (Zone I) and 8-40% (Zone II). A comparative analysis of the enthalpy-entropy compensation effect for these polyesters in air and N 2 is presented. A linear relationship was found to exist between entropy and enthalpy values. The following criteria were applied to establish an enthalpy-entropy compensation effect and to check the presence of an isokinetic temperature: (a) Exner's plot of log k 3T1 versus log k 3T2 , and (b) Krug et al. linear regression of ΔH versus ΔG. By the use of the latter two methods, varying isokinetic temperatures were obtained. These temperatures were not in the range of the experimental work conducted, indicating that these systems do not display compensation phenomena.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Enthalpy-Entropy Compensation in Polyester Degradation Reactions

Al‐Mulla

2012

International Journal of Chemical Engineering

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“…Le choix de la méthode dépend de la nature de la substance à analyser ainsi que de l'information que l'on veut retirer des courbes thermogravimétriques (Collett et Rand, 1980 Reprenant la relation (5) appliquée à un constituant: …”

Section: Mise En Garde/adviceunclassified

Cinétique de dégagement des matières volatiles lors de la pyrolyse d'électrodes de carbone industrielles

Tremblay¹,

Charette²

1988

Can J Chem Eng

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Dans un complexe de fabrication d'aluminium, le procédé de cuisson des anodes donne lieu à une libération importante de matières volatiles combustibles. Le présent travail vise à mieux comprendre la cinétique de dégagement de ces substances. À cette fin, un dispositif thermogravimétrique de grandes dimensions a été mis au point de façon à pouvoir simuler le mieux possible l'environnement industriel. Des échantillons de deux masses distinctes ont été soumis à la pyrolyse à différents régimes de chauffage. La perte de poids et les concentrations des gaz dégagés ont été enregistrées tout au long de la montée en température. Les résultats cinétiques sont rapportés pour le méthane, l'hydrogène et le goudron. L'ordre de réaction ne varie pas avec la vitesse de chauffage alors que l'énergie d'activation et le facteur pré‐exponentiel augmentent. De plus, pour les grosseurs d'échantillons étudiés, il a été trouvé que la masse du solide n'influence pas la valeur des paramètres cinétiques.

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“…Calculated by different methods, A and E characterize the mathematical method used rather than the reaction itself. This also follows from [6][7][8][9]. The artefact can be eliminated, The invariant characteristics of the process can also be calculated with a different, quite general means, by constructing a statistical model of the process as a polynomial [3].…”

mentioning

confidence: 99%

A method of finding invariant values of kinetic parameters

Лесникович¹,

Levchik²

1983

Journal of Thermal Analysis

194

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A method of calculating the Arrhenius parameters has been proposed, based on an evaluation of the coordinates of intersection of greatly extended confidence regions determined in solving the inverse kinetic problem. The validity of this method is illustrated by comparison of the Arrhenius parameters found from non-isothermal and isothermal data reported by other investigators.The kinetic parameters characterizing the chemical stage of solid-phase reactions are determined by isothermal kinetic methods, provided certain approaches to the selection of a theoretical model are observed and rigid constraints are imposed on the experiment [1]. Such constraints may yield a positive result in non-isothermal kinetics [2] as well. However, finding t'he kinetic parameters from experimental data, i.e. solving an invers kinetic problem, may run into certain difficulties, for such problems are ill-posed mathematical problems characterized by a poor statement of the problem conditions (the determinant of the information matrix is close to zero). Therefore, such problems have no unique solution unless special methods are used [3]. This problem was analyzed in [4,5] for dynamic thermogravimetry conditions. The poor statement of the problem conditions determines its solution in the form of a greatly extended region, so that experimental data can be described with equal accuracy with the help of Arrhenius parameters A and E variable over a very wide range in this region, the compensative effect being an artefact of computation. Calculated by different methods, A and E characterize the mathematical method used rather than the reaction itself. This also follows from [6][7][8][9]. The artefact can be eliminated, The invariant characteristics of the process can also be calculated with a different, quite general means, by constructing a statistical model of the process as a polynomial [3]. In this paper a method is suggested for determining invariant values of the activation energy (E) and a pre-exponential factor (A), which corresponds to the above general approach. Isokinetic temperature and a polynomial as a polylinear expansion [12] are used in the method. This makes it very simple to use in computation and provides a very clear interpretation that reveals the physical meaning of the invariants

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Thermogravimetric investigation of the pyrolysis of pitch materials. A compensation effect and variation in kinetic parameters with heating rate

Cited by 54 publications

References 8 publications

Enthalpy-Entropy Compensation in Polyester Degradation Reactions

Enthalpy-Entropy Compensation in Polyester Degradation Reactions

Cinétique de dégagement des matières volatiles lors de la pyrolyse d'électrodes de carbone industrielles

A method of finding invariant values of kinetic parameters

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