(152g) Continuum Approximation of Large Reaction Mixtures

Continuum approximation has long been used for analyzing the kinetic behavior of reaction mixtures of very many components. For irreversible first-order reactions, we showed previously that the approximation breaks down at large times. This work presents a fairly comprehensive analysis of the validity of the approximation for mixtures with complex kinetics. The approximation can be conditionally or universally valid, depending on kinetics, reactor type, and feed properties. The validity conditions for a variety of situations take a simple, generalized power-law form. Backmixing and pore diffusion widen the range of validity. The underlying physics and some dichotomies/subtleties are discussed. The results are applied to catalytic hydroprocessing reactions.