Question

Problem 4. The first order reaction

A →B

was carried out over two different-sized spherical pellets. The pellets were contained in a spinning basket reactor that was operated at sufficiently high rotation speeds that external mass transfer resistance was negligible. The results of two experimental runs made under identical conditions are given in Table 1.

Table 1. Data from a spinning basket reactor

	Measured rate (obs) (mol/g cat – h)	Pellet radius (cm)
Run 1	0.108	1.0
Run 2	0.540	0.1

a) Estimate the Thiele modulus and effectiveness factor for each pellet.

HINT. Use criteria based on Weisz-Prater number. Notice that reported rate is r’_obs (weight based reaction rate). (15 points)

b) How small should the pellets be made to virtually eliminate all internal diffusion resistance? (5 points)

Answer 1