KINETICS, MASS-TRANSFER, AND PALLADIUM CATALYST DEACTIVATION IN THE HYDROGENATION STEP OF THE HYDROGEN-PEROXIDE SYNTHESIS VIA ANTHRAQUINONE

Hydrogenation of 2-ethYl-5,6,7,8-tetrahydroanthraquinone is a key step in the industrial production of hydrogen peroxide via anthraquinone w ith the process named all-TETRA. This reaction on palladium-supported catalysts is very fast; consequently, the chemical regime can hardly b e achieved and kinetics is always masked by mass-transfer limitations. Nevertheless, it is possible to demonstrate that the reaction occurs with a zero- and first-order kinetics with respect to hydrogen and to the organic reagent, respectively. These reaction orders can be explai ned on the basis of reasonable reaction mechanisms described and discu ssed in this paper. Kinetics has been studied by performing runs in tw o different laboratory reactors: a semibatch and a continuous stirred tank reactor. In particular, the continuous reactor has been used for studying catalyst deactivation. Two types of catalyst poisoning have b een recognized, a reversible one, related to the presence of water, an d a permanent, not yet explained one. A kinetic expression is given al so for deactivation. The kinetic parameters obtained from the experime ntal runs have been verified by simulating the behavior of an industri al reactor also considering catalyst deactivation.