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Two-Step Chemolytic Delamination of Multilayer Laminated Packaging Films into Valuable Chemicals

Publication Date
Authors
Author Name
Kalsoom Jan
Author Organization
University of Massachusetts Lowell, MA USA
Author Name
Taofeng Lu
Author Organization
University of Massachusetts Lowell, MA USA
Author Name
Christian Ayafor
Author Organization
University of Massachusetts Lowell, MA USA
Author Name
Hsi-Wu Wong
Author Organization
University of Massachusetts Lowell, MA USA
Author Name
Wan-Ting Chen
Author Organization
University of Massachusetts Lowell, MA USA

The mechanical recycling of multilayer laminated packaging films (MLPF) poses a considerable challenge due to the heterogeneity in plastic types and adhesives utilized. To address this challenge, this study uses two-step integrated chemolysis to upcycle MLPF. First, acids (acetic acids, formic acids, and succinic acids) were used to delaminate MLPF into separate layers that are made of polyethylene terephthalate (PET) and metalized polyethylene (PE/Al). Subsequently, glycolysis was used to depolymerize the delaminated PET layer into (bis(2-hydroxyethyl) terephthalate (BHET) and other valuable chemicals. Besides the non-catalytic glycolysis approach, for higher efficiency and selectivity, zinc acetate and calcium acetate were utilized to catalyze glycolysis of the delaminated PET film. The effect of reaction temperature, reaction time, and the loading of catalysts on catalytical glycolysis were also evaluated. Both catalysts with 0.0125-0.3 weight percent reached 100 percent PET conversion within 10 mins at 190°C using ethylene glycol (EG). Using this reaction condition (190°C and 10 min, which is determined as the optimal condition in this study), zinc acetate with higher loading (0.3 weight percent) led to a higher selectivity towards BHET. However, under the same optimal reaction conditions, calcium acetate resulted in a higher yield of byproducts (e.g., mono(2- hydroxyethyl) terephthalate, MHET) over BHET. This study suggests that different metals present in the catalysts can affect the selectivity of glycolysis products. The obtained BHET can be used to synthesize new PET to support the circular economy. Additionally, a density functional theory (DFT) study is ongoing, aiming to offer a mechanistic understanding regarding the role of zinc and calcium-acetates on glycolysis of PET at the atomistic and molecular

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