Dynamic Experimental Methods Using in situ Measurements of the Surface Intermediates Applied to the Fine Chemistry

Abstract

Unsteady-state kinetics can be used for the determination of the reaction mechanism of a heterogeneous catalytic reaction, and the characteristic shape of the time evolution curves of the concentrations at the outlet of the reactor can be associated with rate-limiting steps. To complete the information, in situ measurements of surface intermediates can be correlated with those response curves to get a physical meaning to the determined kinetic parameters. It is shown, how such an experimental setup can be realized. That the knowledge of the reaction mechanism and the identification of the active sites on the catalyst are of great use for reaction engineering is shown with the example of the methylation of catechol, an intermediate in fine chemistry, where the catalyst has been selectively modified to increase the yield of the desired 3-methylated product from 25 to nearly 70%.