A kinetic model for the synthesis of methanol over commercial catalysts was developed based on the adsorption of CO and CO2 onto various active sites of Cu, while the kinetic parameters were estimated by fitting 118 experimental sets of data under a variety of conditions. When both CO and CO2 hydrogenations take place, CO conversion was influenced by the change in temperature as well as in space velocity and pressure, while CO2 conversion was minimally influenced as a result of its correlation to the water-gas shift reaction. However, the CO and H-2 fractions significantly influenced both conversions. The analysis based on the model developed in this investigation clearly confirmed that the contribution of each reaction and the maximum methanol concentration was expressed as a function of temperature and the CO fraction. Additionally, catalysts with varying particle sizes were used to evaluate the effect of the internal diffusion limitation on catalytic performance and the effectiveness factors were subsequently calculated and regressed with respect to the particle size. (C) 2014 Elsevier B.V. All rights reserved.