Dynamic Modeling of CATOFIN® Fixed-Bed Iso-Butane Dehydrogenation Reactor for Operational Optimization

The catalytic dehydrogenation of iso-butane to iso-butylene is an equilibrium limited endothermic reaction and requires high temperature. The catalyst deactivates quickly, due to deposition of carbonaceous species and countered by periodic regeneration. The reaction-engineering constraints are tied up with operation and/or technology design features. CATOFIN is a sophisticated commercialized technology for propane/iso-butane dehydrogenation using multiple adiabatic fixed-bed reactors having Cr /Al as catalyst, that undergo cyclic operations (~18–30m); dehydrogenation, regeneration, evacuation, purging and reduction. It is always a concern, how to maintain CATOFIN reactor at an optimum production, while overcoming gradual decrease of heat in catalyst bed and deactivation. A homogeneous one-dimensional dynamic reactor model for a commercial CATOFIN fixed-bed iso-butane dehydrogenation reactor is developed in an equation oriented (EO) platform Aspen Custom Modeler (ACM), for operational optimization and process intensification. Both reaction and regeneration steps were modeled and results were validated. The model predicts the dynamic behavior and demonstrates the extent of catalyst utilization with operating conditions and time, coke formation and removal, etc. The model computes optimum catalyst bed temperature profiles, feed rate, pre-heating, rates for reaction and regeneration, fuel gas requirement, optimum catalyst amount, overall cycle time optimization, and suggest best operational philosophy.