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

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 alpha 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 ln beta, where T is the temperature and beta is the heating rate. The slope of the linear equation is controlled by the activation energy E alpha and its intercept contains the inherent information of the kinetic triplet, i.e., the pre-exponential factor A alpha, the activation energy E alpha and the reaction model f(alpha). 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 alpha i to alpha i+1 at isothermal temperature Tiso is equal to the time to heat from Tiso to T alpha i+1${T}_{{\alpha }_i + 1}$ under heating rate beta alpha i${{{\beta}}}_{{{{\alpha}}}_i}$, where Tiso, T alpha i+1${T}_{{\alpha }_i + 1}$ and beta alpha i${{{\beta}}}_{{{{\alpha}}}_i}$must be determined from the isoconversional state diagram. A new concept called isoconversional state diagram is introduced for the kinetic prediction of single-step condensed phase reactions. A state represents a certain extent of conversion degree alpha in a reaction. The physical meaning of the relationship between reactions under isothermal and nonisothermal conditions is revealed by the geometric method derived from the diagram.image