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

Abstract

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.

Impact of Polymerization Process Parameters on Improved Comonomer Incorporation Behavior in Ziegler‐Natta Catalysis

“…A detailed description of the reactor setup can be found in previous publications. [26,15] In order to minimize possible contaminant interference, the reactor was cleaned before each experiment using three cycles of nitrogen purging followed by evacuation the reactor. To remove remaining traces of moisture, 80 g propane was filled into the reactor, which was then heated to > 90 °C for at least 30 min.…”

“…The MWDs of all samples were deconvoluted using the Flory-Schultz distribution as described in the literature. [15][16][17][18][19] In addition, the CCD (comonomer composition distribution) was calculated using the Stockmayer bivariate distribution. [16][17][18][19] The comonomer molar fractions were subsequently calculated for each site type individually.…”

Customizing the comonomer incorporation distribution in Ziegler–Natta‐based LLDPE: Harnessing the influences of the titanation temperature during catalyst synthesis and of polymerization process parameters

“…In general, using the Levenberg Marquardt minimization method, the MWD curves are fitted to 4–6 active centres until a minimum is found. [ 9–11 ]…”

“…In general, using the Levenberg Marquardt minimization method, the MWD curves are fitted to 4-6 active centres until a minimum is found. [9][10][11] Building on these studies and on our previous work, [12][13][14] we explored extensively the influence of the titanation temperature during catalyst synthesis on the microstructure and the incorporation distribution of the comonomer in LLDPE samples (Figure 1). Varying the titanation temperature over a broad range, we found that it is possible to synthesize catalysts that produce a more uniform comonomer incorporation distribution.…”

Impact of Process Poisons on the Performance of Post‐Phthalate Supported Ziegler–Natta Catalysts in Gas Phase Propylene Polymerization

“…Though it is a wellknown fact that these catalysts are sensitive to impurities, there are not many studies that quantified the impact of some common poisons on the catalyst activity for the latest supported Ziegler-Natta generations in gas phase polymerizations, nor investigated the consequences on the polymer microstructure and powder morphology, though such studies are currently of more interest due to the growing interest in monomers produced via chemical recycling of plastics which would contain more contaminants in comparison to conventionally produced monomers. [1][2][3] In this introduction, we will take a brief look at the few publications that have investigated the effects of poisons on propylene polymerizations experimentally and theoretically.…”