Calculation of the Activation Energy by Iterative Procedure

One ofthe simplest approximations by Doyle [41] gives rise to the following Eq. (22.14), which is used in the popular isoconversional Ozawa-Flynn-Wall (OFW) methods [13, 25]  

According to this method, the activation energy is calculated at given values of conversion from a plot of ln(q) versus 1/T. This method provides estimation of E at every selected and constant value of conversion without knowledge of the specific reaction function. The OFW method assumes that E is constant, consequently some systematic error in the estimation of E should be expected, whenever E varies with a. 

Use of another asymptotic approximation for the temperature integral yielded the following equation, known as the Kissinger-Akahira-Sunose (KAS) equation [25, 26]  

Evaluation of the activation energy is achieved from the plot of ln(q/F) versus 1/T at constant degrees of conversion and heating rate. 

The iterative procedure performed involved the following steps (i) assume /z(x) = 1 or H x) = 1 to estimate the initial value of the activation energy E. The conventional isoconversional methods stop the calculation at this step (ii) using calculate a new value of 2 for the activation energy from the plot of ln[g/H(x)] versus 1/T or n[qlh x) 7 ] versus 1/T (iii) repeat step (ii), replacing E with E. When E. - 0.1 kj mol  

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