Deactivation of the palladium catalyst in the hydrogenation of 2-ethyl-5,6,7,8-tetrahydroanthraquinone

Abstract

Publisher Summary The hydrogenation of 2-ethyl-5,6,7,8-tetrahydroanthraquinone (THEAQ) at the oxygen in the presence of a palladium-supported catalyst is a key step in the industrial production of hydrogen peroxide. Palladium is a very active catalyst in THEAQ hydrogenation, therefore mass-transfer limitation strongly affects reaction rates. In industrial plants, the performance of the catalyst slowly decreases because of deactivation. The hydrogenation of THEAQ is a zero-order reaction with respect to hydrogen and a first order reaction with respect anthraquinone. The kinetics of the catalyst deactivation has been studied in a laboratory continuous reactor. Two types of catalyst poisoning are operative, a reversible one, related to the presence of water, and a permanent one, probably due to the condensation of two or more anthraquinone molecules on the palladium surface. The kinetic data obtained from laboratory runs are used to simulate the performance in industrial plants. The kinetic law for catalyst poisoning and the corresponding kinetic constants, determined from runs performed in a slurry continuous reactor, have been tested on two industrial reactors.