A commercial Cu-based catalyst for methanol synthesis was studied using a stirred autoclave reactor system in the present study. The synthesis reactions were conducted for different time under the same reaction conditions in order to get catalyst samples with different deactivation degrees. The composition and morphology of the catalyst samples before and after reaction were characterized by the means of temperature programmed reduction (TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), elemental analysis (EA) and nitrogen adsorption techniques. The experimental results indicated that Cu composition of the catalyst had not changed significantly during the reaction, and sintering of Cu particles of the catalysts was the main cause of the catalyst deactivation with time on stream. (c) 2007 Elsevier Ltd. All rights reserved.