COMPETITIVE AUTOCATALYSIS IN REACTION-DIFFUSION SYSTEMS - EXCLUSIVE PRODUCT SELECTIVITY

The behaviour of a system comprising two competitive autocatalytic pro cesses, A + B --> 2B, rate = k(1)<(ab)over bar> and A + C --> 2C, rate = k(2)<(ac)over bar>, where (a) over bar, (b) over bar and (c) over b ar represent the concentrations of the various species, is considered. In a well-stirred batch reactor, the final equilibrium composition al ways corresponds to a mixture of the two product species B and C, with their respective equilibrium concentrations depending on the ratio of the rate coefficients kappa = k(2)/k(1) and the initial concentration s b(0) and c(0). If the same reactions are carried out in a reaction-d iffusion system, with local initiation of the reaction at one end of t he reactor, travelling waves of reaction develop. This system can show exclusive product selectivity, with only one of the products being fo rmed in the reactor, provided either the rate coefficient ratio kappa or the diffusion coefficient ratio delta = D-B/D-C differs from unity. If both differ from unity the system will select pure production of B if delta > kappa and pure production of C otherwise. Some interesting complex transient behaviour close to the marginal condition delta = k appa is reported.