Porous cylindrical pellets are used in packed beds for catalytic reaction of the type A Products. Intraparticle diffusion controls the reaction rate owing to the tortuous passage of reactant through the uniform porous structure of the pellet. Performing a steady material balance for the diffusion-reaction of species A it is obtained (for a first order kinetics) dC = 0 r dr dr where DA is pore diffusivity of species A, CA is molar composition, ks is surface reaction constant, and as represent internal area per unit volume of pellet (constant). a. If the bulk gas composition is a constant, CAO, and the gas velocity is so slow that a finite film resistance exists at the particle boundary (where r = R), then introduce the variables transformation 1 d DA b. Apply the boundary condition 1. 2. and show and show the material balance equation becomes dy dx dC dr y = C CAD 20 dy + X- dx The concentration at r= x= 0 is finite. -DA = K (CAR-C40) ka, V DA x=r. -xy=0 kas DA = C0 Dksas 1, RD kc + lo ksas D