Modeling of a Multizone Circulating Reactor for Gas-Phase Propylene (Co)Polymerization: From Pilot to Full Scale Reactors

A multiscale steady state model of a multizone circulating reactor (MZCR) is developed for propylene homo- and copolymerization on supported pseudo-single-site catalyst. The model includes nonideal thermodynamics to describe monomer sorption effects, a population balance to predict the particle size distribution (PSD), momentum balances to describe the residence time distribution (RTD) of the particles, and a full kinetic model to calculate the polymerization rate, cumulative molecular weight (MWD), and chemical composition (CCD) distributions of a pseudo-single-site ZN catalyst. The model was first compared with the available literature data that was based on simplified kinetics and Henry’s law for monomer sorption. The full kinetic and thermodynamic models were then included to demonstrate that they are quite important to consider. The full model was then used to understand the relationship among the reactor operating conditions, reactor performance, and product characteristics in a commercial-scale MZCR reactor. When model predictions are compared to available patent data, the proposed model is shown to be capable of describing the MZCR performance in a large-scale operation as well as predicting the monomodal and bimodal shapes of the MWDs.