The role of catalyst acidity and microstructure on light olefin selectivity in polyethylene deconstruction in short contact time pulse Joule-heated reactors

Journal Article · Wed Oct 15 00:00:00 EDT 2025 · Applied Catalysis. B, Environmental

DOI:https://doi.org/10.1016/j.apcatb.2025.126083· OSTI ID:3001045

Ngu, Jacqueline ^[1]; Selvam, Esun ^[1]; Luo, Song ^[1]; Liu, Dongxia ^[1]; Vlachos, Dionisios G. ^[1]

---

1. University of Delaware, Newark, DE (United States)

The growing volume of plastics waste, compounded with a low recycling rate, has led to an alarming amount of plastics ending up in landfills or being incinerated. While pyrolysis offers a route for plastic waste deconstruction, its product distribution is often broad and poorly controlled due to unselective radical chemistry at high temperatures. We recently demonstrated that rapid pulse Joule-heated catalytic cracking over HZSM-5, combined with small fractions of steam, can achieve high selectivity (>80 %) toward C₂-C₄ olefins, while significantly reducing coking compared to continuous Joule heating. Here, we investigate how acid catalyst properties, such as silica/alumina ratio, zeolite topology, and catalyst porosity, influence light olefin selectivity during polyethylene deconstruction via rapid pulse Joule heating. We demonstrate that silica-to-alumina ratios of ∼30 yield high light olefin selectivity, and small-pore zeolites favor light olefins at the expense of increased coke formation. To mitigate coking, we synthesize HZSM-5 nanosheets and hierarchical zeolites (MFI, FAU, and CHA). Furthermore, these catalysts achieve an ethylene selectivity of approximately 35 %, a twofold increase over prior catalytic pyrolysis. Additionally, co-feeding steam and incorporating hierarchical porosity reduce coke formation and enhance catalyst stability.

• Research Organization: University of Delaware, Newark, DE (United States)
• Sponsoring Organization: Aramco; USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0021166
• OSTI ID: 3001045
• Journal Information: Applied Catalysis. B, Environmental, Journal Name: Applied Catalysis. B, Environmental Vol. 383; ISSN 0926-3373
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

Catalytic cracking
Hierarchical zeolites
Plastics recycling