On the use of Diefallah's composite integral method for the non-isothermal kinetic analysis of heterogeneous solid-gas reactions

The paper contains an analysis of the used of Diefallah's composite integral method of kinetic parameters evaluation. It is shown that the application of this method should be preceded by the application of an isoconversional method through which the dependence of the activation energy, E, on the conversion degree, alpha, should be established. If E depends on alpha, Diefallah's composite integral method leads to erroneous results. If E does not depend on alpha, the true kinetic model should be comprised in the pre-established set of kinetic models. These observations were checked for two sets of non-isothermal data, namely: ( a) the TG curves corresponding to the dehydration of CaC2O4 center dot H2O; ( b) the TG curves corresponding to the thermal decomposition of polyvinyl chloride ( PVC).