PET Recycling Breakthrough Uses Iron Catalyst System

Probably the best-known and certainly the most widely used thermoplastic polymer resin of the polyester family, polyethylene terephthalate (PET) was invented and patented in 1941 by John Rex Whinfield and James Tennant Dickson, chemists with the Calico Printers' Association, a textile manufacturing firm based in Manchester, UK.

Within a couple of years, both DuPont in the U.S. and ICI in the UK had acquired various rights, which led to the development of their Dacron and Terylene fibers, respectively.

It took another 30 years for DuPont to patent the technology for the ubiquitous blow-molded PET bottles seen today. 

With its light weight, low cost, strength, weatherability and chemical resistance, the polymer has found numerous other uses, too, not least in packaging and textiles. So much so that by 2024, its global market size was estimated to be $39.25 billion. In the Polyethylene Terephthalate (PET) Market: Demand, Production, and Future Projections from the market research organization Towards Chem & Materials, it is predicted to reach $68 billion by 2034. 

PET Growth Fuels Recycling and Regulatory Pressure

However, it’s not undiluted happiness for PET manufacturers and their shareholders. The report highlights multiple market challenges, including rising raw material costs, stricter regulations and a growing negative public perception of plastics, particularly in terms of recyclability. 

This is particularly true for PET, which doesn’t degrade naturally and is often dyed and mixed with other polymers when used, adding extra complexity to recycling efforts.

While most post-consumer PET ends up in landfills or is incinerated for energy recovery, other strategies are under investigation. All have their limitations, however.

A study in the recent issue of Progress in Polymer Science highlights these points.  

Take physical processing. PET is often mixed or interwoven with other polymers or contains dyes and additional chemicals, which make this approach tricky and can compromise the mechanical properties of the end product.

Biological recycling can be highly selective when it comes to PET, but the presence of other polymers and chemicals affects enzyme activity, i.e., the catalyst. There can also be complex purification stages needed.

Chemical Recycling Emerges as a Viable Path for PET Waste

Chemical recycling, the authors noted, shows greater potential for processing mixed PET waste. Here, post-consumer PET waste becomes a low-cost, abundant raw material for synthesizing new chemicals or materials. Hence, the focus on chemical recycling methods for PET has increased steadily over the last decade. 

However, this route also poses challenges in terms of chemistry, engineering, catalysts and heat requirements. 

Research published in November 2025 by scientists at the Graduate School of Science, Tokyo Metropolitan University (TMU), Japan, illustrates some of the novel developments being used to broach these hurdles. 

Headed by Professor Kotohiro Nomura, the group has developed what they describe as an efficient method for the exclusive depolymerization of PET, even when it’s included in mixed wastes.

Described in detail in ACS Sustainable Resource Management, their process relies on alcohols, an inexpensive, readily available and earth-abundant iron (FeCl₃) catalyst, and a temperature in the range of 120-180ºC.

The group previously reported on an acid- and base-free PET depolymerisation process which achieved over 99% conversion to diesters and diols. This formed a one-pot closed-loop chemical recycling process using a FeCl3 catalyst that worked not only with PET (both pellets and sheets), but also achieved the selective chemical recycling of textile waste containing PET and cotton and a mixed plastic containing PET and polyethylene.  

Now they report a >99 % chemical conversion of PET, including waste bottles collected from public stations and textile waste, using a FeCl3–benzimidazole catalyst system, even under scale-up conditions – from 500 mg to 30g. 

The one-pot system produced analytically pure terephthalates, including dimethyl terephthalate (DMT) and diethyl terephthalate (DET).

The method also enables the selective depolymerization of PET from a mixture of cotton and other plastics. 

This exclusive recycling of PET from plastic wastes offers a promising solution for achieving a circular economy, they believe.

When asked about the chemical and engineering challenges of scaling the process up further, Nomura said that he didn’t foresee any great difficulties. “We probably need to investigate the engineering aspect with collaborators, especially for chemical recycling of textile wastes,” he added.

Nomura also points out that conventional PET recycling processes using inorganic salts require tedious purification down the line, including vacuum distillation, which is especially sensitive to such chemicals. 

Then there is the question of funding. 

This latest research was conducted under the Japan Science and Technology Agency (JST) CREST program, in a section dedicated to developing bio-based advanced polymers, their depolymerization, and chemical recycling.

When questioned about whether the program would provide additional funds, Nomura responded that developing the process would need more financial support, without committing to specifics. 

“Since we have received so much interest from companies, we hope to proceed with the project through international collaborations,” he explained.