07/06/2026
By Kwok Fan Chow

The Kennedy College of Science, Department of Chemistry, invites you to attend a Ph.D. Dissertation defense by Kalsoom Jan entitled “Advancing Chemical Recycling Pathways for Polyethylene and Multilayer Plastics via Hydrothermal and Chemolytic Deconstruction Strategies.”

Date: Monday, July 13, 2026
Time: 11 a.m.
Location: Emerging Technologies and Innovation Center (ETIC), Room 445

Committee:

  • Wan-Ting (Grace) Chen, Ph.D., Plastics Engineering Department, University of Massachusetts Lowell
  • James Reuther, Ph.D., Department of Chemistry, University of Massachusetts Lowell
  • Michael Ross, Ph.D., Department of Chemistry, University of Massachusetts Lowell
  • Hsi-Wu Wong, Ph.D., Department of Chemical Engineering, University of Massachusetts Lowell
  • YuanQiao Rao, Ph.D., Polymer Engineering and Science, Pennsylvania State University at Erie
  • Marina Ruths, Ph.D., Department of Chemistry, University of Massachusetts Lowell

Abstract:
The increasing accumulation of plastic waste, especially from multilayer packaging, heterogeneous mixed plastic materials, and contaminated streams, poses major challenges to plastics recycling. This dissertation explores advanced and integrated chemical recycling strategies to valorize plastic waste using hydrothermal liquefaction (HTL) and chemolysis, supported by quantum mechanical methods. Firstly, Chapter 4 investigates the role and fate of CaCO3 during HTL of polyethylene (PE) across 1–19 wt% CaCO3 under 425–450 °C for 1–2 h. At 450°C/2 h the oil yield obtained is 76 ± 0.9 wt%, exceeding 59 ± 12 wt% at 425 °C/1.5 h; the higher-severity case generated gas upto 23 ± 0.5 wt%. GC–MS shows oil produced at 425 °C are mainly C₇–C₁₇ paraffins/olefins, while 450 °C/2 h favors formation of aromatics. Inductively coupled plasma analysis indicates >90% of Ca partitions to the post-HTL aqueous phase, suggesting that HTL simultaneously enables PE deconstruction and removal of inorganic filler as well. DFT study was employed to rationalize chain scission, hydrogen transfer, and carbonate-mediated steps observed across these reaction conditions. Secondly, Chapter 5 examines mixed-plastics relevant to multilayer packaging by co-liquefying PE with PP, PS, PET and EVOH at 400 °C for 2 h over controlled blend ratios (0, 25, 50, 75, 100 wt% non-PE) under HTL. Analysis of oil, gas, aqueous and solid products identified blend compositions exhibiting synergistic effects with different product selectivity. Results indicate that PE–PS and PE-PET mixtures at 1:1 ratios increase carboxylic acids in the aqueous phase and aromatics in the oil fraction. DFT provides a mechanistic understanding of β-scission, H-transfer, deoxygenation/dehydration, bond-dissociation reactions that helps explain interactions between these blend ratios under HTL. Additionally, the role of polymer stereochemistry in PP and PS on oil yield during HTL was investigated as well. Lastly, Chapter 6 develops a two-step chemolysis for multilayer laminated packaging films (MLPFs): acidolytic delamination (e.g., acetic or formic acid at 80 °C for ~5–10 min; succinic acid aqueous 80–90 °C for 2–5 h or in ethanol 70 °C for ~10 min) followed by PET glycolysis in ethylene glycol at 190 °C. With 1–30 wt% of Zn(OAc)2 or Ca(OAc)2 for catalytic PET glycolysis, ~100% PET depolymerization was achieved in ~10 min, with Zn(OAc)2 favoring BHET and Ca(OAc)2 favoring MHET (hydrate state tunes selectivity) as main products. Overall, these studies provide data-driven operating parameters and a mechanistic framework for integrating HTL and two-step chemolysis into existing chemical recycling approaches for complex packaging wastes.

All interested students and faculty members are invited to attend.