Abstract : Fluidized Catalytic Cracking (FCC) units convert high molecular compounds (from atmospheric distillation and vacuum distillation units) to light gases. The major compounds in the light gases are methane, ethane, propane and butane. These light gases are then converted to highly reactive propylene (raw material for polypropylene) and butylene (raw material for butadiene and polybutadiene) via dehydrogenation. Propane and butane are always available as mixture along with traces of methane and ethane. In any commercial dehydrogenation process, the propane and butane are separated first and then dehydrogenated separately. This certainly leads to high fixed and operating costs. In this study, mixed-feed dehydrogenation of propane and butane is proposed. An isothermal model for a multi-tubular fixed bed reactor using PtSn/Al2O3 as a catalyst for the dehydrogenation of mixed-paraffin feed is developed considering the axial and radial variation of concentration (2D model). The 2D model is solved using central difference scheme. The simulations were carried out using MATLAB and the developed model is tested for the effect of space velocity, reactor temperature, reactor pressure, and propane to butane ratio in the feed on total paraffin conversion and olefin yield.