Polymer Reaction Engineering Approach to Assess the Effect of Poisons On Metallocene Catalyst Performance and Polymer Molecular Properties Development in a Multistage Polypropylene Process

This study presents a comprehensive polymer reaction engineering approach to evaluate the impact of catalyst poisons, specifically carbon dioxide (CO₂) and oxygen (O₂), on metallocene-catalyzed polypropylene polymerization in a multistage process representative of Borstar PP technology. A combination of thermodynamic modeling, kinetic analysis, and a simplified single-particle model is employed to simulate the dynamic evolution of catalyst activity, polymer molecular properties, and particle growth under various poisoning scenarios. The simulations are categorized into three cases: (i) a baseline scenario under ideal, impurity-free conditions; (ii) full-process poisoning with reversible (O₂) or irreversible (CO₂) impurities; and (iii) stage-specific poisoning introduced only during prepolymerization. The results demonstrate that the nature and timing of impurity exposure significantly influence catalyst activity as well as the molecular properties of the produced polypropylene. Notably, reversible poisons allow partial recovery of catalyst activity, particularly in the gas-phase stage, whereas irreversible poisons lead to sustained deactivation. These findings offer valuable insights into the sensitivity of metallocene catalysts to trace impurities and underscore the importance of impurity control in achieving consistent polymer quality in industrial multistage propylene polymerization processes.