Analysis of a membrane enclosed catalytic reactor for butane dehydrogenation

Abstract

A mathematical model consisting of component mass balances and a mechanical energy balance was formulated and simulated for butane dehydrogenation in a cocurrent, packed bed, isothermal membrane enclosed catalytic reactor at 723 K and 152 kPa (1.5 atm). Properties of a γ-alumina membrane with 4-nm diameter pores were use din the simulations. The mechanical energy balance accounted for the axial pressure change and affected the flows in the reactor, but due to the low reaction rate, it did not significantly alter the conversion calculated. Butane conversion higher than the equilibrium conversion were calculated. A single reactor system that consists of a packed catalyst bed enclosed in a tube with an impermeable section at the reactor entrance, followed by a permeable section was proposed. For maximum butane conversion, the length of the impermeable section was determined to be about 2.4 cm, and the amount of butane converted in this section was 2.2% (equilibrium conversion at these conditions was 10.3%). For reactors with butane space times less than 0.1 sec, permeation reduced the butane conversion. Gas that entered the reactor on the low pressure side displayed a reversal in the permeation direction. This phenomenon is observed for the gases that permeable through the membrane by Knudsen diffusion, and have sufficient reactor space time. This sufficient space time limit was 0.5 sec for the investigated system.