A first-order heterogeneous irreversible reaction is taking place within a spherical catal...

A first-order heterogeneous irreversible reaction is taking place within a spherical catalyst pellet which is plated with platinum throughout the pellet (see Figure 4). The reactant concentration halfway between the external surface and the center of the pellet (i.e., r = R/2) is equal to one-tenth the concentration of the pellet's external surface. The concentration at the external surface is 0.001 g mol/dm3, the diameter (2R) is 2 × 10-3 cm, and the diffusion coefficient is 0.1 cm2/s.

(a) What is the concentration of reactant at a distance of 3 × 10-4 cm in from the external pellet surface?

(b) To what diameter should the pellet be reduced if the effectiveness factor is to be 0.8?

(c) If the catalyst support were not yet plated with platinum, how would you suggest that the catalyst support be plated after it had been reduced by grinding?

Figure 4