Microkinetic simulation of catalytic reactions

The study of the kinetics of heterogeneous catalyzed reactions consists of three different aspects: kinetics studies for design purposes, kinetics studies of mechanistic details and kinetics as a consequence of a reaction mechanism. The latter aspect is clearly the least explored of the three and it will not become routine until the development and analysis of microkinetic models is automated. Based on a survey of existing microkinetic models of heterogeneous catalytic reactions, three classes of Langmuir-Hinshelwood (LH) mechanisms are shown to be suitable for microkinetic modeling. The first model consists of an LH mechanism with the quasi-equilibrium approximation and a single, rate-limiting step. For this model detailed kinetic studies are possible and include the analytic determination of reaction rate, surface coverages, reaction orders and activation energy. The second model consists of an LH mechanism with the steady-state (SS) approximation. This model allows the treatment of some kinetic phenomena, which cannot be treated by Model 1. However, the treatment of Model 2 is much more difficult and the data which may be determined analytically from Model 2 are the reaction rate, the surface coverages and the degree of rate limitation. The third model is kinetic Monte Carlo (KMC) simulations which allow the modeling of even more mechanistic details, such as surface diffusion and adsorbate-adsorbate interactions. Analysis of this class of models are limited to numerical simulation. Two appendices present the implementation of a Runge-Kutta (RK) integration of the conversion through an isothermal plug-flow reactor and a KMC simulation of a reaction rate, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.