Modeling and experimental study of hollow cylindrical catalysts for prediction of transient behaviors of suspension photoreaction systems by Langmuir-Hinshelwood kinetics

Abstract

Effectiveness factor was derived for hollow cylindrical pellets with finite length by assuming Langmuir-Hinshelwood (LH) kinetics. Transient intra-particle concentration was predicted by solving reaction-diffusion equations using finite element method for various values of reaction parameters in LH kinetics and thickness of hollow core. At stationary state, numerical values of intra-particle concentration was integrated to calculate effectiveness factor (η) under various shape factors of hollow cylindrical pellet including infinite length as well as finite height. The results were compared with those of infinitely long cylinder and spherical pellets to determine optimum morphologies of catalytic pellets. η could be enhanced by increasing hollow-core size and decreasing aspect ratio of the pellet. For the same value of Thiele modulus, which was calculated from volume-equivalent radius, hollow cylindrical catalyst exhibited largest value of η, compared to solid cylindrical or spherical pellets. For simulation of catalytic reactors such as batch reactor, CSTR, and fixed bed, pseudo-steady state was adopted in material balance equation using computed values of η. The modeling results were compared with experimental data from batch photocatalytic reactor containing hollow catalytic fibers synthesized by electrospinning to determine reaction parameters in LH kinetics by minimizing errors of transient concentration between calculated and measured values using optimization method.