Gas absorption with autocatalytic reaction

Abstract

The film theory has been employed to investigate gas absorption accompanied by an autocatalytic chemical reaction of the form A + Ṙ → Ṙ + Ṙ. This reaction has been taken to be the simplest analogue of the autocatalytic features of chain reactions encountered in the industrially important gas-liquid oxidation and chlorination reactions. Numerical solutions have been obtained using standard library subroutines for integrating systems of first order equations, having transformed the two describing second order non-linear differential equations into suitable first order initial value form. Predictions of the Enhancement Factor show that it can be very considerably larger than that for the ‘equivalent’ first order reaction. This is due to the accumulation of radicals within the mass transfer film. An asymptotically exact empirical approximation for the Enhancement Factor is also presented. The ‘degree of conversion’ of the absorbed gas across the mass transfer film is shown to be more sensitive to the kinetic and diffusional parameters than is the case for a first order reaction.