Influence of Poisons Originating from Chemically Recycled Plastic Waste on the Performance of Ziegler-Natta Catalysts

Chemically recycled monomer feed streams from postconsumer plastic packaging waste are expected to contain impurities that act as catalyst poisons. This work investigates the impact of such impurities on a commercial fourth-generation Ziegler-Natta catalyst system. A recycled monomer feed stream in two different procedures by adding representative catalyst poisons (pyridine and n-butanol) in various quantities to the reactor setup is simulated. Measuring catalyst activity and molecular weight distribution (MWD) and performing kinetic and MWD deconvolution modeling, the impact of the catalyst poisons on polymer product properties at the microstructural level is evaluated. The results demonstrate that, beyond a certain concentration (120 ppm), catalyst poisons have a substantial impact on the activity levels of the catalyst system tested. MWD deconvolution modeling shows an influence of the poisons on the composition of the resulting polymer product in the form of a shift toward lower or higher molecular weights (depending on the procedure). This microstructural analysis highlights the importance of purifying chemically recycled monomer feed streams.

Automated summary

Chemically recycled monomer feed streams from postconsumer plastic packaging waste may contain impurities that act as catalyst poisons, impacting the activity levels of a commercial Ziegler-Natta catalyst system and influencing the molecular weight distribution and composition of the resulting polymer products. Purifying the chemically recycled monomer feed streams is crucial for ensuring the quality of polymer products.