Modelling of mass transfer in combination with radical reactions

The diffusion–reaction equations for different model versions have been solved using a finite-differencing technique. In all models a reactant A is transferred from the gas to the liquid phase and reacts in the liquid with B to form P. The calculations comprised a simple stoichiometric model, a system with radical intermediates involved in the propagation steps and a version where also the termination reactions were included. The results show that the diffusion coefficients of radical intermediates can have significant influence on the profiles of concentrations and reaction rates near the G/L interface. Furthermore, it is shown that for very fast reactions differences in diffusion coefficients of the intermediates influence the by-product formation. For systems of two radical intermediates, the so-called mixed termination product is only formed in low quantities whereas the other two termination products dominate. The calculation of enhancement factors required in the design of a G/L reaction system can be performed with simplified models where the reactive intermediates do not occur in the expressions for the reaction rates. The optimum model for a specific design purpose can be found by tuning the functions that correlate the parameters of the complex model to the parameters of the simplified model. In principle it is possible to very easily evaluate a large number of alternatives.