Model selection and parameters estimation in kinetic thermal evaluations using semiempirical models

Abstract

The minimum number of thermoanalytical experiments that should be considered with the aim of performing a complete and reliable kinetic analysis when using semiempirical models is the problem of concern. It is shown by means of a series of numerical experiments that three differential scanning calorimetric (DSC) dynamic runs performed at different heating rates provide a complete and reliable kinetic analysis while the topological structure of two DSC curves is enough to determine the semiempirical model (among reaction order and Sestack–Bergrenn) that better describe the experimental data. The procedure is analyzed by means of the simulation of a complex kinetic scheme and the results verified considering the thermal decomposition of cumene hydroperoxide. The proposed approach can be easily generalized to different kinetic models and is provided with a possible criterion devoted to identify autocatalytic processes by means of dynamical DSC experiments. © 2011 American Institute of Chemical Engineers AIChE J, 58: 1869–1879, 2012

Adiabatic behavior of thermal unstable compounds evaluated by means of dynamic scanning calorimetric (DSC) techniques

“…This means that the behavior of the system under study can be explained "lumping" in a single process its complex nature. 10,14,15 It has to be stressed that although the lumped models are generally accurate often the physical meaning of the detailed reactions that really occur can be lost.…”

“…9 do not consider the tails. 10 In fact, if two curves are too close (as it is evident, if we consider by visual inspection the highly dispersed behavior of the values reported forln…”

“…The procedures discussed above will be shortly illustrated in discussion section and is described in detail in Ref. 10.…”

“…When using a semiempirical approach 10,16,17 (which allows us to lump in a simple kinetic model, the complex kinetic behavior often observable during the thermal decomposition of a substance or during a runaway phenomenon), the choice of the kinetic models generally reduces to the reaction order n…”

“…This approach would be particularly useful for small or medium factories, which generally are not equipped with sophisticated adiabatic calorimeters. In this article, it is shown that, when particular conditions are satisfied, 10 a set of three DSC runs is sufficient to gather reliable information useful both for interpolation and for extrapolation purposes. Based on the thermokinetic parameters determined a new procedure is presented that allows us to evaluate the adiabatic behavior of a thermal decomposition process with particular attention to the numerical assessment of the adiabatic onset temperature.…”