Competitive autocatalysis in reaction-diffusion systems Exclusive product selectivity

Abstract

The behaviour of a system comprising two competitive autocatalytic processes, A+B→2B, rate=k₁āb̄and A+C→2C, rate=k₂āc̄, where ā, b̄and c̄represent the concentrations of the various species, is considered. In a well-stirred batch reactor, the final equilibrium composition always 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 κ=k₂/k₁ and the initial concentrations b₀ and c₀. If the same reactions are carried out in a reaction-diffusion system, with local initiation of the reaction at one end of the reactor, travelling waves of reaction develop. This system can show exclusive product selectivity, with only one of the products being formed in the reactor, provided either the rate coefficient ratio κ or the diffusion coefficient ratio δ=D_B/D_C differs from unity. If both differ from unity the system will select pure production of B if δ>κ and pure production of C otherwise. Some interesting complex transient behaviour close to the marginal condition δ=κ is reported.

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