OP-II-3

OP-II-16MYTHOLOGY IN MULTIPHASE CATALYSIS:WHY DO THE CONVENTIONAL FIXED-BED TECHNOLOGIES HAVENO POTENTIAL FOR THE FURTHER PROCESS DEVELOPMENT?Leonid B. Datsevich 1,21 The University of Bayreuth (Germany)2 MPCP GmbH (Bayreuth, Germany)E-mail: datsevich@mpcp.de, datsevich@uni-bayreuth.deThe conventional multiphase fixed-bed (trickle-bed and bubble (packed) column)reactors are very often designated for exothermic reactions, for example, such ashydrogenation, hydrotreating, purification, the Fischer-Tropsch synthesis, etc.The contribution deals with the analysis of these reactors with regard to processefficiency, safety and design.The paper shows that these reactors do not possess any potential fordevelopment. Any attempt to improve substantially the reactor performance, e.g. toenhance the reactor productivity (not by several percent as it is always discussed inthe available literature, but by several times) cannot be realized because of therestrictions imposed by the process arrangements.The paper retraces the original ideas developed by the previous generation of theprocess developers and indicates how these ideas became the rigid paradigm thathindered the progress in the process development.The old mythology deeply established in the scientific and industrial communitiesis discussed in light of modern concepts in mass transfer and kinetics.The contribution disproves the following typical myths in the process design ofmultiphase fixed-bed reactors with a gas loop:(1) Operating pressure has to be high in order to increase the concentration ofthe gaseous compound in the liquid phase and, consequently, the reactorproductivity.(2) The reaction rate is limited by mass transfer of the gaseous compound and,therefore, operating pressure has to be high in order to enhance gas-liquid-solidmass transfer.(3) The high concentration of the liquid compound at the reactor inlet and highoperating pressure have to influence the reactor productivity nearly proportionally tothese factors if the reaction rate has the first order with respect to both gas and liquidreactants.128