Problem 2. Internal and external mass transfer (Total: 15 Marks) The first order, gas-phase catalytic reaction A-B with reaction rate constant, k = 0.017-10 cm/s, catalyst surface area, S, 150, and

catalyst density, p. = 3.95 g/cm³) takes place in a spherical catalyst pellet of radius, R=2.5 cm. The effective diffusivity of A in the pellet is, D, = 0.015 cm²/s. The reactant A is carried in a stream at a bulk concentration, CA = 10 mol/cm³. The concentration of A at the surface of the pellet is, C3-10-5 mol/cm². a) Determine the value of the external mass transfer coefficient. [5] b) Calculate the conversion achieved in a packed bed reactor, where the catalyst pellets operate with the same internal and external resistances as above. Assume the reactor operates as a pseudo-homogeneous PFR with a space time of 30 s, an inlet reactant concentration, CA= 10 mol/cm³, bed void fraction = 0.4 and negligible pressure drop. [10]