The aim of this work was to study the Fischer-Tropsch (FT) synthesis of a model biosyngas (33% H-2, 17% CO and 50% N-2) in a single tube fixed-bed FT reactor. The FT reactor consisted of a shell and tube with high-pressure boiling water circulating throughout the shell. A spherical unpromoted cobalt catalyst was used with the following reaction conditions: a wall temperature of 473 K, a pressure of 20 bars and a gas hour space velocity (GHSV) of 37 to 180 NmLg(cat)(-1).h(-1). The performance of the FT reactor was also validated by developing a 2D pseudo-homogeneous model that includes transport equations and reaction rate equations. Good agreement between the model predictions and experimental results were obtained. This developed model was extended to predict and quantify the influence of the FT kinetics as well as determine the influence of the tube diameter and the wall temperature. The predicted behaviors for CO and H-2 conversion. productivity of hydrocarbons (mainly CH4 and C-54) and fluid temperature along the axis of the reactor have been analyzed. Crown Copyright (c) 2010 Published by Elsevier B.V. All rights reserved.