Assessing the Downstream Contamination of Chemically Recycled Ethylene Feed Streams on the Kinetic Behavior of Ziegler‐Natta Catalysts and Microstructural Properties of HDPE and LLDPE

Abstract

The sustainability of consumer materials, such as plastics, belongs to the most important aspect of eco-efficiency analyses. Besides mechanical recycling, chemical recycling represents an interesting waste management pathway. In theory, this technique does not rely on single-grade feedstock to maintain product quality. However, cross-contamination of feedstocks potentially leads to above-specification impurities in obtained pyrolysis oils. This study investigates the potential downstream poisoning of a fourth-generation Ziegler-Natta catalyst, using selected model poisons at high (worst-case) concentrations. With experimental and computational analysis, economic feasibility factors such as catalyst activity and microstructural properties are evaluated during the synthesis of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). Noticeable effects on the catalyst activity can be observed when the poison interacts with the co-catalyst, whereas a lower impact is observed for interactions with the activated catalyst-co-catalyst complex. Molecular weight distribution (MWD) and comonomer composition distribution (CCD) modeling highlighted marginal to no polymer property changes caused by contaminants. Combined with the applicability of pyrolysis post-treatments, these observations show that chemical recycling can be a promising technique for post-consumer plastic waste treatment.

Branched Comonomers in LLDPE—Influence of Short Chain Branch Shape on Crystallinity

“…Thus, the differences in the incorporation behavior of the ZN catalyst for the various comonomers can be assigned to predefined active sites, and the correlation between MWD shift, comonomer content, and crystallinity can be extended by adding as a parameter the comonomer incorporation distribution, which allows a more detailed analysis. [12][13][14][15][16][17] The present work extends the knowledge on non-linear SCBs (Figure 1). Furthermore, the ability to characterize SCBs containing more than one CH 3 group using an IR detector (HT-SEC) is investigated.…”

“…In this analysis, the M n values for five active centers were fixed based on the center point of the n ‐hexene LLDPE samples, and all further samples were evaluated based on the M n values fixed by this method. [ 16,17 ] We found that the percentage for Active Site 3 was higher for iso ‐hexene than for the n‐ hexene LLDPE samples. In contrast, neo ‐hexene LLDPE samples showed a higher percentage for Active Site 4.…”

“…Thus, the differences in the incorporation behavior of the ZN catalyst for the various comonomers can be assigned to predefined active sites, and the correlation between MWD shift, comonomer content, and crystallinity can be extended by adding as a parameter the comonomer incorporation distribution, which allows a more detailed analysis. [ 12–17 ]…”

Crystallographic Texture Evolution in 3D Printed Polyethylene Reactor Blends

“…There are numerous studies involving the microstructure of HDPE and UHMWPE and their blends processed through different ways, − as well as X-ray diffraction studies of HDPE or UHMWPE-containing polymers. ,,− There have been studies on the evolution of microstructures in UHMWPE/HDPE blend fibers prepared by melt spinning, control of subinclusion microstructure in ternary blends consisting of HDPE, microstructural characterization of HDPE/polyamide blend through selective laser sintering processing, microstructural evaluation of HDPE along with its other properties after weathering, assessment of microstructure of HDPE post chemical recycling, post reinforcement for use as shielding materials against nuclear radiation, effect of various reinforcements on microstructure of UHMWPE consisting composites, , studies on microstructure of modified UHMWPE and UHMWPE consisting blend foams, and many more. Pandit et al investigated carbon-fiber-reinforced HDPE composites to improve printability of HDPE using FDM which otherwise show warping, shrinking, and weak bonding between HDPE and substrate .…”

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.…”