On the way from the activation model of solid decomposition to the thermochemical model

Abstract

The development of the technology and the theory of electrothermal atomization, which began in atomic absorption spectrometry about 60 years ago, led to a confrontation between the two alternative models used in the kinetics of heterogeneous chemical reactions: the activation model proposed by Arrhenius (Z Phys Chem 4:226-248, 1889) and based on the effect of activation, and the thermochemical model (TM) proposed by Langmuir (Phys Rev 2:329-342, 1913), which excludes the existence of this effect. An analysis of the events surrounding the creation and evolution of both models and a comparison of their fundamental principles and their application to the solution of actual problems show the shortcomings of the activation model and fundamental limitations in its applicability. The TM for the first time in the history of these studies allowed a quantitative estimation and a prediction of the lifetime for substances depending on the environment and temperature of their storage. It allows the calculation of the rate of reaction and the Arrhenius parameters taking into account the composition, stoichiometry and thermochemical characteristics of the reaction, the excess pressure of the gaseous product in the reactor and the physical properties of the reactant (sample size and the density of the reactant). Within the TM, it was possible to solve many of the accumulated problems, including the physical nature of the parameters of the Arrhenius equation, the effect of autocatalysis, the kinetic compensation effect and the Topley-Smith effect. To overcome the lasting crisis in the kinetics of heterogeneous reactions, it is necessary to advance the public discussion of the current situation and search for appropriate ways to replace the activation model by the TM.

COMF: Comprehensive Model-Fitting Method for Simulating Isothermal and Single-Step Solid-State Reactions

“…As for the validity of the Arrhenius type rate constant in the case of heterogeneous reactions the reader is referred to the works of L'vov B. [35,36]. Although these doubts must be considered carefully, in our work we are interested in how the model-fitting method can be algorithmically more robust for identifying the BCM.…”

Kinetic Analysis of Nonisothermal Decomposition of Acetyl Ferrocene

“…Nonisothermal thermogravimetry with a linear heating rate is the most frequently used technique for thermal analysis of materials . In nonisothermal TG, model‐fitting and model‐free methods have been used quite commonly for the evaluation of kinetic parameters despite severe criticism recently raised on the use of the activation model for the interpretation of the kinetics of heterogeneous solid‐state reactions . Although, single‐heating‐rate‐‐based model‐fitting methods were among the first and most popular methods for kinetic calculations, multiheating rate‐based methods (e.g., model‐free isoconversional method) have drawn considerable attention in recent times and gained popularity for better kinetic descriptions.…”