Adsorptive reactors for enhancing equilibrium gas-phase reactions—two case studies

Abstract

The conversion enhancement potential of fixed-bed adsorptive reactors has been evaluated for two heterogeneously catalysed gas-phase equilibrium reactions: the Claus reaction used in sulphur recovery and the direct synthesis of hydrogen cyanide from carbon monoxide and ammonia. It was found that kinetics of both reaction and adsorption as well as adsorbent capacity have to be very compatible to achieve high conversions. The specific parameters of the reaction/catalyst system, such as the deposition of solids (e.g. sulphur, coke) or the formation of undesirable by-products have to be taken into account for the successful application of adsorptive reactor concepts. A crucial point is the selection of the reaction conditions (i.e. temperature), since the occurrence of side reactions may be enhanced in adsorptive reactor operation due to the inherently distorted concentration profiles.