Is the Friedman Method Applicable to Transformations with Temperature Dependent Reaction Heat?

The kinetic parameters of the pyrolysis of miscanthus and its acid hydrolysis residue (AHR) were determined using thermogravimetric analysis (TGA). The AHR was produced at the University of Limerick by treating miscanthus with 5 wt.% sulphuric acid at 175°C as representative of a lignocellulosic acid hydrolysis product. For the TGA experiments, 3 to 6 g of sample, milled and sieved to a particle size below 250 μm, were placed in the TGA ceramic crucible. The experiments were carried out under non-isothermal conditions heating the samples from 50 to 900°C at heating rates of 2.5, 5, 10, 17 and 25°C/min. The activation energy (E A ) of the decomposition process was determined from the TGA data by differential analysis (Friedman) and three isoconversional methods of integral analysis (Kissinger-Akahira-Sunose, Ozawa-Flynn-Wall, Vyazovkin). The activation energy ranged from 129 to 156 kJ/mol for miscanthus and from 200 to 376 kJ/mol for AHR increasing with increasing conversion. The reaction model was selected using the non-linear least squares method and the preexponential factor was calculated from the Arrhenius approximation. The results showed that the best fitting reaction model was the third order reaction for both feedstocks. The pre-exponential factor was in the range of 5.6 × 10 10 to 3.9 × 10 +13 min −1 for miscanthus and 2.1 × 10 16 to 7.7 × 10 25 min −1 for AHR.

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“…Therefore, f(α) can be considered constant and taking natural logarithms at both sides of Eq. (7) gives the following equation [12,27]:…”

Section: Friedman Methodsmentioning

confidence: 99%

Kinetic study of the pyrolysis of miscanthus and its acid hydrolysis residue by thermogravimetric analysis

Cortes

Bridgwater

2015

Fuel Processing Technology

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“…It has been shown that the causes for these differences between the integral and differential methods are due to their intrinsic nature [51][52][53][54]. The approximations of temperature integral are obtained under the assumption that the activation energy does not depend on the degree of conversion.…”

Section: Model Free Methodsmentioning

confidence: 99%

Kinetic analysis of the polymer burnout in ceramic thermoplastic processing of the YSZ thin electrolyte structures using model free method

Salehi¹,

Clemens²,

Graule³

et al. 2012

Applied Energy

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Polymeric binder burnout during thermoplastic processing of yttria stabilized zirconia (YSZ) ceramics were analyzed using thermogravimetric analysis (TGA). The debinding kinetics of the stearic acid/polystyrene binder have been described using model free methods and compared with the decomposition rate of the pure polymers. The apparent activation energy E a as a function of debinding progress a was calculated in two atmospheres (argon and air) by three different methods: Ozawa-Flynn-Wall (OFW), Kissinger-Akahira-Sunose (KAS) and Friedman. The evolution of E a with a is compatible with the evaporation of stearic acid and the unzipping and thermo-oxidative decomposition mechanisms proposed for polystyrene. The apparent activation energies obtained for the experiments under argon revealed the increased concentration of weak links in polystyrene introduced during kneading of the feedstock. Extrapolation of the kinetic parameters obtained in one run to calculate decomposition rates under different heating rates confirmed the excellent predictive power of the direct methods.

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“…A homemade kinetic software regularly upgraded was used to compute the kinetic parameters from MFit-DIF, MFit-INT, MFree-DIF and MFree-INT methods [21][22][23][24][25].…”

Section: Isoconversional Integral Methodsmentioning

confidence: 99%

Deconvolution of calorimeter response from electrical signals for extracting kinetic data

Barale¹,

Vincent²,

Sauder³

et al. 2015

Thermochimica Acta

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Is the Friedman Method Applicable to Transformations with Temperature Dependent Reaction Heat?

Cited by 143 publications

References 36 publications

Kinetic study of the pyrolysis of miscanthus and its acid hydrolysis residue by thermogravimetric analysis

Kinetic study of the pyrolysis of miscanthus and its acid hydrolysis residue by thermogravimetric analysis

Kinetic analysis of the polymer burnout in ceramic thermoplastic processing of the YSZ thin electrolyte structures using model free method

Deconvolution of calorimeter response from electrical signals for extracting kinetic data

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