Catalytic methanol synthesis in a 2D rectangular microchannel reactor is modelled in OpenFOAM. This type of reactors offers several advantages from the fluid-dynamic viewpoint, such as enhanced mass and heat transfer, in addition to high single-pass efficiencies. However, the main drawback of these reactors is their limited methanol throughput as compared to their conventional fixed-bed counterparts. Therefore, the goal of this thesis is to analyse the impact of different thermo-fluid dynamic settings on methanol production, seeking for an optimal methanol yield. In the present analysis, only surface reactions are accounted for. They are implemented over the catalytic walls of the channel according to the Langmuir Hinshelwood-Hougen-Watson (LHHW) kinetics.