January 28, 2014
New Technique Could Convert Plastic Polymers Into Liquid Fuel
redOrbit Staff & Wire Reports - Your Universe Online
Discarded plastic bags and similar products could be converted into liquid fuel thanks to a new process developed by researchers in India and detailed in the latest edition of the International Journal of Environment and Waste Management.
Dr. Achyut Kumar Panda, an assistant chemistry professor and the Centurion University of Technology and Management, and his colleagues have developed a relatively low-temperature process to develop fuel from waste comprised of low-density polyethylene (LDPE), a common polymer used to make plastic bags, medical equipment and computer components.
A tremendous amount of plastic waste is produced in this day and age, the researchers explained, and much of this polyethylene-based matter winds up in landfills, strewn throughout the environment, or in oceans and rivers. However, Dr. Panda and chemical engineer Raghubansh Kumar Singh, of the National Institute of Technology in Orissa, India, are working together to develop a new technology that could solve this problem.
The engineers report that they are working on a commercially-viable method of rendering LDPE into a liquid fuel. Since the majority of plastics are comprised of petrochemicals, their efforts could recycle plastics as an oil substitute, and if implemented on a large-enough scale, it could help not only limit waste but also offset the potential effects of the planet’s declining petroleum supply and increasing demand for oil.
“Waste low-density polyethylene samples were subjected to thermo-catalytic degradation using kaolin as catalyst in a batch reactor at temperature range of 400 to 500°C and atmospheric pressure,” the study authors wrote. “The quality and yield of the condensable product has been studied as a function of temperature and amount of catalyst. Both in thermal and catalytic degradation, the condensable fraction was less viscous liquid oil at low temperatures (up to 450°C), whereas with increase of temperature (from 475°C) the fraction became viscous and waxy.”
Essentially, by heating the plastic waste to these temperatures, the investigators said they were able to cause the plastic’s polymer chains to break apart. This released a large amount of smaller, carbon-rich molecules. They then used a technique known as gas chromatography coupled mass spectrometry to characterize those product molecules. The liquid fuel was found to be composed primarily of paraffins and olefins 10-16 carbon atoms long.
This composition was said to be extremely similar chemically to conventional petrochemical fuels. As for the kaolin used as the catalyst, this clay mineral (which is comprised of aluminum and silicon) provides a large reactive surface upon which the polymer molecules could rest. As a result, they were exposed to high batch reactor temperatures, which caused them to be broken apart, according to the researchers.
Dr. Panda’s team optimized the reaction at 450 degrees Celsius, which was the temperature with the lowest amount of kaolin which produces over 70 percent of the liquid fuel. Essentially, for every kilogram of waste plastic exposed to these conditions, the chemical engineers could produce 700 grams of liquid fuel. The yield could be increased to nearly 80 percent and minimize reaction times, but far more kaolin catalyst would be required.