Kinetic aspects of nonlinear phenomena in heterogeneous enantioselective catalysis

The nonlinear behavior of modifier mixtures has been discussed for heterogeneous enantioselective catalysis. A kinetic model is developed, which is based on molecular mechanism. Numerical calculations as well as comparison with experimental data on ketopantolactone, isophorone and 4-methoxy-6-methyl-2-pyrone hydrogenation demonstrate applicability of the model to explain nonlinear phenomenon. Within the framework of the advanced model, which has several simplifications, an attempt is made to analyze striking nonlinear phenomena in terms of rate constants and adsorption enthalpies. In order to account for this behavior solely based on adsorption enthalpy (i.e., neglecting the possible difference between adsorption entropy) corresponding difference between two modifiers should be 8-17 kJ mol(-1). Alternatively, the reaction rates should have two to three orders of magnitude difference over different modifiers in order to observe strong nonlinear phenomena in a system with modifier mixtures.