A simulation model for a catalytic polymerization reactor in a dilute spouted bed regime is described. The model, which is of dispersed plug flow, is based on solving the mass conservation equation for the monomer. The input parameters in the simulation program are the geometric factors of the contactor, the kinetic equations of polymerization and of catalyst deactivation, reaction temperature, monomer concentration in the feed, mean residence time of the catalyst in the reactor, and bed voidage. The following are calculated : (a) parameters that describe the state of the catalyst in the reactor (particle size distribution of the catalyst coated with polymer, catalyst amount, activity distribution); (b) hydrodynamic conditions of the bed (feed flow, dispersion coefficient, radial and longitudinal distribution of gas velocities, and alcohol concentration profiles); (c) catalyst flow required in the feed; (d) polymer yield. The simulation model has been verified with results from a pilot plant using, as test reaction, the polymerization of benzyl alcohol on a silica/alumina catalyst in order to obtain thermally stable polybenzyls.