Effect of intraparticle convection on the steady-state behavior of fixed-bed catalytic reactors

Abstract

The effect of intraparticle convection on the behavior of fixed-bed reactors containing large-pores catalysts (e.g. selective oxidation catalysts) is analysed by comparing three reactor models : pseudohomogeneous model ( PH), heterogeneous diffusion ( HT d ) and heterogeneous diffusion/convection model ( HT dc ). Runaway diagrams were constructed based on the “maxima-curve”, allowing system properties to change with temperature and on the method of isoclines. It is shown that the “maxima-curve” method fails in the case of the HT dc model since then the “maxima-curve” P bm = f( T bm ) has two maxima. The stable region of operation predicted by the HT dc model. Energy savings can be obtained by using large-pore catalysts since then it is possible to operate at lower wall/feed temperatures than those used with conventional catalysts. New catalysts can be designed to take advantage of the improvement on the effectiveness factor due to intraparticle convection and energy savings due to the use of more favorable operating conditions.