A simple and realistic fixed bed model for investigating Fischer-Tropsch catalyst activity at lab-scale and extrapolating to industrial conditions

In the present work, a ready-to-use tool in the form of a comprehensive fixed-bed reactor model (2-dimensional, pseudo-homogeneous, gas-solid and steady state model) for Fischer-Tropsch synthesis is proposed. The model is based on the main governing processes in terms of physical and chemical laws and considers internal mass transfer resistance. The model allows: (a) determining kinetic parameters from laboratory experiments; (b) estimating productivity, CO conversion, selectivities (CH ₄ and C ₅₊) under relevant industrial conditions for various catalyst structures (foam, extrudates, grains, etc.). The application of this tool in basic scale-up studies is illustrated in the simulation of a three-stage FT unit of 30,000 barrels/day of diesel+naphtha. It is shown that a foam catalyst allows better performances (activity per unit mass, C ₅₊ selectivities and overall pressure drop) than packed extrudates, but at the expense of higher catalyst and reactor volumes.