Dynamic simulation of a Lurgi type industrial methanol reactor has been studied in the presence of long term catalyst deactivation. The performance of the reactor was investigated using two different dynamic models: (a) a simple homogeneous model, and (b) a heterogeneous model. The models were validated against measured daily process data of a methanol plant recorded for a period of four years. Good agreements were achieved and both models were found to predict almost identical results under industrial operating conditions. The high velocity of the reactant stream was found to be the most important reason for this phenomenon. The simple model represents a useful tool for dynamic simulation, optimization and control of methanol synthesis. Introducing such a simple model reduces the number of typical states to half, and this in itself will significantly reduce the level of computation in the model base estimators. (c) 2004 Elsevier B.V. All rights reserved.