ONLINE MONITORING, MODELING, AND MODEL VALIDATION OF SEMIBATCH EMULSION POLYMERIZATION IN AN AUTOMATED REACTOR CONTROL FACILITY

The modeling of the semibatch emulsion polymerization of styrene and i ts validation against data obtained from a reactor facility is present ed. The model, which describes the growth of a monodisperse polystyren e seed as neat monomer is fed to the reactor, incorporates recent find ings in radical diffusion and kinetics. The current controversy surrou nding radical absorption into particles is handled by considering abso rption via propagation, diffusion, and collision in the model. Simulat ion results including weight fraction polymer inside the particles and particle diameter are compared to data obtained from a custom-designe d and built automated reactor control facility capable of on-line dens ity and on-line particle diameter measurements. Good agreement between simulation results and experimental data are obtained for any of the three absorption mechanisms considered by varying only one adjustable parameter located in the absorption rate coefficient relation. A sensi tivity analysis of the model to this adjustable parameter, using the p rogram ODESSA, is also presented and shown to be an important tool in the validation procedure. Lastly, an analysis of the dynamics of the p rocess shows the variety of phenomena that can be obtained in a semiba tch reactor including regions that exhibit pseudosteady states, autoac celeration of the rate, and limiting conversion. (C) 1998 John Wiley & Sons, Inc.