A reaction model for batch reactive distillation is developed considering two-phase (vapor and liquid) reactions, and assuming equilibrium stages/compartments, constant pressure in each stage/compartment, and constant volumetric holdup. This reaction model was used to simulate the chlorination of toluene in a photo reactive distillation column operated in a semi-batch mode. A downward computational approach was employed to determine the initial values in solving the differential and algebraic equations. Simulation predictions were compared with experimental results.