Single-Step Kinetic Predictions Based on a Constructed Isoconversional State Diagram

Abstract

A new concept called isoconversional state diagram, which can be used to predict the kinetics of single-step condensed phase reactions, is introduced. A state represents a certain extent of conversion degree α in a reaction. The construction of the isoconversional state diagram is based on the isoconversional state equation, which is a piecewise linear equation about 1/T and lnβ, where T is the temperature and β is the heating rate. The slope of the linear equation is controlled by the activation energy E_α and its intercept contains the inherent information of the kinetic triplet, i.e., the pre-exponential factor A_α, the activation energy E_α and the reaction model f(α). Consequently, the geometric methods for nonisothermal and isothermal kinetic predictions are derived. The latter reflects the physical meaning of the relationship between reactions under isothermal and nonisothermal conditions, i.e., the time to advance from α_i to α_i+1 at isothermal temperature T_iso is equal to the time to heat from T_iso to $T_{{\alpha }_i+1}$ under heating rate ${\beta }_{{\alpha }_i}$, where T_iso, $T_{{\alpha }_i+1}$ and ${\beta }_{{\alpha }_i}$must be determined from the isoconversional state diagram.