A groundbreaking method for the depolymerization of PET (polyethylene terephthalate) has been developed by a research team led by Professor Kotohiro Nomura from Tokyo Metropolitan University. This innovative approach utilizes alcohols and an inexpensive iron trichloride catalyst, making it a promising solution for the selective chemical recycling of both textile and plastic waste mixtures.
At present, plastic waste poses a critical environmental challenge that demands immediate attention. Despite this urgency, the rate of plastic material recycling, particularly through chemical recycling into raw materials, remains dismally low. Polyesters, commonly found in plastic bottles and clothing, are composed of repeated “ester bonds” formed by the reaction of carboxylic acid and alcohol.
A complete breakdown of these ester bonds would allow polyester to be converted back into its raw materials. Conventional methods, however, typically require high temperatures and significant amounts of acidic or basic substances. Therefore, the quest for a simple, cost-effective, and environmentally friendly method for this process is of paramount importance.
Moreover, there is a pressing global need for the development of selective depolymerization of polyester from plastic waste, particularly from textile waste, which constitutes a blend of polyester and cotton.
The exceptional research team has recently unveiled a groundbreaking method for depolymerizing PET bottles without the use of harmful acids or bases. By using ethanol in conjunction with either FeCl3 or FeBr3, they have achieved an impressive 98-99% selectivity in producing diethyl terephthalate (DET) and ethylene glycol (EG). What’s more, the readily available and cost-effective iron trichloride (FeCl3) demonstrated remarkable catalytic performance at 160-180 ºC, rivaling the team’s previous results with titanium catalysts.
This method stands out for its unique ability to selectively depolymerize PET from various waste sources. Whether it’s textile waste comprising PET and a blend of PET and cotton or plastic waste including polyethylene, this innovative approach consistently delivers high yields of DET and EG while enabling the complete recovery of cotton waste. This breakthrough has the potential to revolutionize PET recycling and significantly reduce environmental impact.
The urgent need for a straightforward method to exclusively and selectively depolymerize PET has never been more evident, especially in the context of chemical recycling of textile waste. This innovative approach to chemical recycling of PET from plastic waste holds the key to realizing a sustainable circular economy.
This work has been made possible through the generous support of the JST CREST program (Grant Number JPMJCR21L5). This research is situated within the Research Area “Precise Material Science for Degradation and Stability” and the Research Theme “Development of Bio-Based Advanced Polymers and their Depolymerization, Chemical Recycle.”
Journal reference:
- Nor Wahida Binti Awang, Muhammad Aidel Bin Ratno Hadiyono, Mohamed Mehawed Abdellatif and Kotohiro Nomura. Depolymerization of PET with ethanol by homogeneous iron catalysts applied for exclusive chemical recycling of cloth waste. Industrial Chemistry and Materials, 2024; DOI: 10.1039/D4IM00081A
