Critical Appraisal of Kinetic Calculation Methods Applied to Overlapping Multistep Reactions

Abstract

Thermal decomposition of solids often includes simultaneous occurrence of the overlapping processes with unequal contributions in a specific physical quantity variation during the overall reaction (e.g., the opposite effects of decomposition and evaporation on the caloric signal). Kinetic analysis for such reactions is not a straightforward, while the applicability of common kinetic calculation methods to the particular complex processes has to be justified. This study focused on the critical analysis of the available kinetic calculation methods applied to the mathematically simulated thermogravimetry (TG) and differential scanning calorimetry (DSC) data. Comparing the calculated kinetic parameters with true kinetic parameters (used to simulate the thermoanalytical curves), some caveats in the application of the Kissinger, isoconversional Friedman, Vyazovkin and Flynn–Wall–Ozawa methods, mathematical and kinetic deconvolution approaches and formal kinetic description were highlighted. The model-fitting approach using simultaneously TG and DSC data was found to be the most useful for the complex processes assumed in the study.

Activation Energy Determination in Case of Independent Complex Kinetic Processes

“…On the other hand, the Friedman method and the incremental modified Vyazovkin method provided (as expected) a different course of E-α dependence, which was found to almost always cover the whole E 1 -E 2 range. Similar conclusion was reported also in [28] for overlaps of sub-processes with opposite I values. (b) Based on the presence and shape of the over-and undershoots manifesting from the integral and differential isoconversional methods, a guide to estimation of the true E 1 and E 2 values utilizing a combined interpretation of the integral and differential approaches was introduced for the JMA asymmetry and confirmed also for AC model with opposite (positive) asymmetry.…”

“…Most of these papers provide qualitative testing of the considered methodologies in only few types of complex process situations. An exception from this trend is the recent study by Muravyev et al [28], who excellently summarize the current methodological tools utilized in the field of kinetic analysis and test the particular methodologies in various complex-process scenarios. Despite this great paper, we still feel that a highly systematic study, delivered via a series of papers evaluating the performance of the methods of kinetic analysis under various different types of complex-process scenarios (including the influences of, e.g., the number and type of involved reaction mechanisms and overall reaction scheme, as well as the specific simulation conditions such as the degree of overlap, its change with the range of applied heating rates, or relative intensity of the involved sub-processes) may be of use to the thermo-analytic community.…”

Kissinger Method in Kinetics of Materials: Things to Beware and Be Aware of

“…It needs to be stressed that checking for potential systematic variation of α p with β should be taken as a general prerequisite for using the Kissinger method. The existence of such variation can be an indication of the process complexity as discussed by Muravyev et al [8]. They have also demonstrated that even a moderate change of 0.06 in α p , caused by a change of β from 1 to 10 K min −1 , can result in a systematic error in E as large as 15%.…”

Thermal Stability of Amorphous Solid Dispersions

“…It is difficult to determine whether the isoconversional or model-fitting method would provide more accurate predictions, therefore by using both the greatest reliability is achieved [ 32 ]. It should be noted that thermal decomposition of solid is quite a complex process [ 33 , 34 ] and determination of the kinetic parameters for the thermal decomposition is not always straightforward. For a successful kinetic analysis, examination of different kinetic calculation methods should go along with rigorous physicochemical insight on the process.…”

“…Nowadays, specific commercial software programmes for calculating kinetics parameters such as Kinetics Neo (Netzsch), AKTS (Advanced Kinetic and Technology Solution), Kinetics2015 (GeoIsoChem) are available and can assist researchers in the field of kinetic analysis of the solid state. Since the scope of this review is on the thermal stability of drugs, readers interest in further details about solid-state kinetics can refer to the following references [ 25 , 26 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ]…”