Originally published on CleanTechnica
A new, relatively low-temperature means of creating liquid fuels from common plastic waste has been developed by researchers from the Centurion University of Technology and Management, and the National Institute of Technology, both in India.
The new process utilizes a common waste material, low-density polyethylene (LDPE), to produce an effective oil-substitute — helping to limit the quantity of plastic waste that ends up in the world’s landfills, as well as potentially helping to ameliorate some of the effects of dwindling oil supplies (economically recoverable oil supplies that is).
The press release provides the specifics on the process:
Chemist Achyut Kumar Panda of Centurion University of Technology and Management Odisha, India is working with chemical engineer Raghubansh Kumar Singh of the National Institute of Technology, Orissa, India, to develop a commercially viable technology for efficiently rendering LDPE into a liquid fuel. In their approach, the team heats the plastic waste to between 400 and 500 Celsius over a kaolin catalyst. This causes the plastic’s long chain polymer chains to break apart in a process known as thermo-catalytic degradation. This releases large quantities of much smaller, carbon-rich molecules. The team used the analytical technique of gas chromatography coupled mass spectrometry to characterize these product molecules and found the components of their liquid fuel to be mainly paraffins and olefins 10 to 16 carbon atoms long. This, they explain, makes the liquid fuel very similar chemically to conventional petrochemical fuels.
In terms of the catalyst, Kaolin is a clay mineral — containing aluminum and silicon. It acts as a catalyst by providing a large reactive surface on which the polymer molecules can sit and so be exposed to high temperature inside the batch reactor, which breaks them apart. The team optimized the reaction at 450 Celsius a temperature with the lowest amount of kaolin at which more than 70% of the liquid fuel is produced. In other words, for every kilogram of waste plastic they could produce 700 grams of liquid fuel. The byproducts were combustible gases and wax. They could boost the yield to almost 80% and minimize reaction times, but this required a lot more catalyst 1 kg of kaolin for every 2 kg of plastic.