A geometric representation of species concentrations in chemical kinetics

Abstract

The concept of ternary diagrams from equilibrium thermodynamics is applied to the geometric representation of species concentrations in dynamic systems. First, exact solutions of three-species kinetic systems are studied. Constants of motion based on properties of chemical reactions such as mass balance are used to obtain 2D trajectories in place of 3D ones; the triangular simplex structure is convenient for geometric representation. Then application of a quasi-stationary state approximation for successive reactions introduces another constant of motion so that the trajectory becomes 1D. Finally, using acetaldehyde pyrolysis as an example it is shown how to apply this method to complex multicomponent systems in order to obtain the representation s. time of three species or three groups of species concentrations in a triangular space.