The importance of hydrodynamics, particularly gas density, superficial gas velocity, and total pressure in axial and radial directions, was analyzed for the modelling of a catalytic reactor using a non-isothermal pseudo-homogeneous approach. The modelling of a fixed-bed reactor in one and two stages for CO conversion by Fischer-Tropsch synthesis was taken as a study case. For the validation of the proposed model, the results of the simulations for the CO conversion and temperature profiles were compared with experimental data reported in the literature. Simulations for CO conversion and reactor temperature profiles confirmed the model's ability to predict the selectivity of the liquid products in the Fischer-Tropsch synthesis reactor in one and two stages. The proposed model predicts more suitable profiles of CO conversion and temperature along the reactor, which makes it a more robust and efficient tool for design, optimization, and control purposes.