Modeling of catalyst pellets for Fischer-Tropsch synthesis

The present work focuses on the transfer and reaction phenomenon in a catal yst pellet for Fischer-Tropsch synthesis. It is considered that the pores o f catalyst pellets are filled with liquid wax under Fischer-Tropsch synthes is conditions. The reactants in the bulk gas phase dissolve in the wax at t he external surface of the pellet, and the dissolved components diffuse thr ough the wax inside the pellet and react on the internal surface of the pel let. The thermodynamic equilibrium between the gases in the bulk and the li quid wax in the pores is correlated by a modified SRK equation of sate (MSR K EOS). On the basis of the phenomena observed from experiments, a comprehe nsive pellet model is suggested for catalyst design simulation, in which de tailed Fischer-Tropsch mechanistic kinetics is properly imbedded. The react ion and diffusion interaction in a catalyst pellet and its effect on the pr oduct selectivity are further investigated. The potential of using eggshell -type catalyst pellets is explored as a means of decoupling the severe tran sport restriction and, hence, enhancing the overall selectivity of desired products.