The diffusion and reaction phenomenon in a Fe-based catalyst pellet for Fischer-Tropsch synthesis was studied.It was considered that the pores of catalyst pellets were full of liquid wax under Fischer-Tropsch synthesis conditions.The reactants diffused from the bulk gas phase to the external surface of the pellet,and then the reactants diffused through the wax inside the pellet and reacted on the internal surface formed along the pore passages of the pellet.On the basis of reaction kinetics and doubleα-ASF product distribution model,a diffusion and reaction model of catalyst pellet was established.The effects of diffusion and reaction interaction in a catalyst pellet,the bulk temperature,the reaction pressure and the pellet size on the reactivity were further investigated.The relationship between the internal diffusion effectiveness factor of spherical catalyst pellet and the Thiele modulus were also discussed.The bulk temperature and pellet size have significant effects on the reactivity,while the pressure shows only a slight influence on the reactivity.The internal diffusion effectiveness factor decreases with an increasing Thiele modulus.
