Solid state reaction kinetics, mechanisms and catalysis: a retrospective rational review

Kinetic studies are widely used to characterize the factors that control the reactivity and the mechanisms of chemical changes that occur on heating solid reactants. This survey appraises the origins, assumptions and scientific foundations that underlie the theoretical methods that are conventionally, and unquestioningly, used to analyze and to interpret thermal analysis (TA) rate measurements. The extensive TA literature is reviewed in the context of the unusual history of this branch of science, in which TA has effectively superseded the formerly thriving subject of Thermal Decomposition of Solids (TDoS) (also reviewed). Such complete replacement of one scientific discipline by another is unusual, so that reasons for, and consequences of, this eclipse merit detailed consideration. The rapid rise of TA, after about 1970, resulted from the unprecedented advances in instrumental and computational methods which massively accelerated the collection and analysis of accurate rate data for thermal reactions (including solids). Consequently, TA theory initially tended to focus on developing experimental equipment together with facilitation of data interpretation by computer programs. These achievements have enabled each TA study to be completed very rapidly and with relatively much less effort than was usual in the former TDoS methodology. However, much less effort was also invested in developing coherent and soundly-based theory for the interpretation of TA kinetic data, with consequences that are critically appraised here in their historical context.