Kinetic concepts of thermally stimulated reactions in solids: A view from a historical perspective

TLDR

Historical analysis shows that solid‑state kinetic concepts were inherited from homogeneous kinetics, assuming a single‑step reaction that conflicts with the multi‑step nature of solid‑state processes and leads to unjustified assumptions such as constant activation energy. The study proposes the effective activation energy concept, which can vary with temperature and extent of conversion. The concept’s adequacy is demonstrated by literature and experimental data on the thermal dehydration of calcium oxalate monohydrate and the thermal decomposition of calcium carbonate, ammonium nitrate, and 1,3,5,7‑tetranitro‑1,3,5,7‑tetrazocine.

Abstract

Historical analysis suggests that the basic kinetic concepts of reactions in solids were inherited from homogeneous kinetics. These concepts rest upon the assumption of a single-step reaction that disagrees with the multiple-step nature of solid-state processes. The inadequate concepts inspire such unjustified anticipations of kinetic analysis as evaluating constant activation energy and/or deriving a single-step reaction mechanism for the overall process. A more adequate concept is that of the effective activation energy, which may vary with temperature and extent of conversion. The adequacy of this concept is illustrated by literature data as well as by experimental data on the thermal dehydration of calcium oxalate monohydrate and thermal decomposition of calcium carbonate, ammonium nitrate and 1,3,5,7- tetranitro-1,3,5,7-tetrazocine.