Critical analysis of the isoconversional methods for evaluating the activation energy. II. The activation energy obtained from isothermal data corresponding to two successive reactions

An analysis is presented of the consequences of the use of a one term equat ion containing apparent activation parameters, instead of the true rate equ ation to describe two successive decomposition reactions undergone by a sol id compound. It is demonstrated that the apparent activation energy, obtain ed by means of isoconversional differential and integral methods, varies wi th the conversion degree for a relatively narrow temperature range and with temperature at a given value of the conversion degree. The activation ener gy values obtained with the isoconversional differential method are higher than the corresponding values obtained with the isoconversional integral me thod.