Dynamic Modeling of Reaction Pathways on the Gibbs Energy Surface

Based on irreversible thermodynamics and kinetic rate theory developed a number of years ago, modern computer graphics provide new methods to optimize selectivity in multiple reactors or single reactions with multiple reaction mechanisms. Initial conditions and standard Gibbs energies of reaction are sufficient to provide a Gibbs energy surface as a function of reaction extents for the rate-limiting reactions. These conditions also provide the kinetic boundaries, as defined here on the extent plane, over which reaction pathways cannot cross. However, product yields higher than those at equilibrium can, nevertheless, be achieved within the kinetic boundaries in some cases. The industrial term for this feat, cheating thermodynamics, is shown to be incorrect. For simplicity the results presented are for perfect gas mixtures under isobaric/isothermal reaction conditions; other cases are cited. Last, electrical analogue diagrams for complex reaction systems and the meaning of the term rate limiting are considered.