Dynamic Simulation of Heterogeneous Catalysis at Particle Scale to Estimate the Kinetic Parameters for the Pore Diffusion Model

Abstract

In this work, dynamic simulation at particle scale is carried out to predict the kinetics of solid catalyzed esterification reaction between acetic acid and methanol to produce methyl acetate and water. The reaction kinetic data utilized for modeling and validation is with solid catalyst as Indion 180. It was observed that the reaction rate and kinetics inside the pores of the catalyst is of higher magnitude as compared to bulk liquid. Each solid catalyst particle is surrounded by reactant solution of equal volume. A dynamic simulation is carried out using COMSOL Multiphysics which has solver for diffusion-reaction equation for both in liquid phase and inside porous catalyst particle. The intrinsic reaction rate constants for bulk liquid phase and inside the particle are obtained by solving the full diffusion-reaction equation and optimization method. Three different models (model 1,2,3) were proposed for evaluating the rate constants from the experimental kinetic data. The three models differ in the way the boundary condition of acetic acid concentration is defined at the interface of a catalyst particle and its immediate surrounding liquid. The different models originated based on the possibility of numerical solution to partial differential equations pertaining to particle scale catalytic reactions as distributed parameter models by various software such as MATLAB and COMSOL multiphysics. They also differ in the way the initial kinetics is utilized in evaluating the rate constants for outside and inside the catalyst particle. One of the proposed models (model 3) has shown good agreement with the experimental data.

Keywords

• diffusion
• reaction
• esterification
• kinetics
• simulation
• catalysis