To date, very little work has been done to model Fischer Tropsch Synthesis startup. In this study, finite difference approximation is used to model the intra-pellet reaction and heat transport. Finite element analysis was used to model the catalyst inter-pellet heat and mass transport. Vapor-liquid equilibrium was assumed to be attained at each pore, fugacity coefficients were used to develop a quantitative correlation. The goal was to estimate the time required to fill the catalyst pores. This time represents the unsteady transient phase which requires fine temperature control to avoid reaction run away in an actual working packed bed reactor.
In the resulting kinetic model, coupled material and energy balance are used to assess the optimum reactor startup procedures. Another goal is to identify the impact of different types of inert packing used to control heat transfer and conversion in the fixed bed reactor with a view towards avoiding the hot spots and steep temperature gradients. The combined effect of heat transfer and kinetics present a challenging problem for both the bed design and for optimal startup procedure.