On the dynamic behavior of the catalytic fixed-bed reactor in the region of multiple steady states—II. The influence of the boundary conditions in the catalyst phase

Abstract

It has been shown in a preceding paper that a reasonable two-phase model for the catalytic fixed-bed reactor in the region of multiple steady states should take into account heat conduction in the catalyst phase. In this paper the study of the proposed model will be continued using the example of the adiabatic fixed-bed reactor. It turns out that the behavior in the region of multiple steady states is essentially affected by the boundary conditions of the catalyst phase. If one assumes that the catalyst phase is isolated adiabatically at the front of the reactor, threefold stable states in a wide range of hysteresis can be obtained. If heat exchange by radiation takes place in the frontal surface of the catalyst phase threefold stable steady states can also occur but the range of hysteresis is much narrower. Twofold stable steady states exist only if the fixed-bed is composed of three parts; the first and third parts consist of inert material and the second contains the active catalyst. The results of the computation of this example will be compared qualitatively with the experiments of Padberg and Wicke.