Two different porous catalyst particles having equal surface to volume ratios and pore areas are used to carry out a liquid phase reaction with a first order reaction rate- one is disk-shaped with thickness B=4 mm and diameter d=48 mm while the other is spherical with radius R=6 mm. The effective first order reaction rate constant k = 2.5 s-1 and the effective diffusivity D = 1.5 x 10-5 m2/s for both particles.
a. Evaluate the external surface area Sp and the volume Vp as well as the ratio Sp/Vp for the two particles.
b. Evaluate the Thiele modulus for each particle and then the effectiveness factor for each particle from the results derived in class. Compare the two sets of values and comment briefly on their physical significance. Which of the particles has the greater diffusion limitation - (a) from the Thiele modulus comparison and (b) from the effectiveness factor comparison?