Modeling of the Unsteady State Methanol Synthesis at the Level of Catalyst Pellet

In a fixed bed of porous catalyst pellets, there are developed two composition and temperature fields, one in the fluid phase and the other one at the level of solid pellets. The objective of this work is to evaluate, by numerical simulation, the unsteady state behavior of a catalyst pellet in typical operating conditions for methanol synthesis reactors. The process kinetics was described by the model published by Graaf et al (1990) and the reaction-diffusion process inside the pellet is based on the Wilke-Bosanquet model. The results showed a short composition and temperature stabilization time, generally below 4 seconds, for a spherical catalyst pellet having typical dimensions for industrial applications.