One vessel, cheap aluminium salts
Researchers at Oak Ridge National Laboratory have developed a process that converts polyethylene, the plastic used in bags, bottles and cutting boards, into gasoline- and diesel-like fuels in a single step. Molten aluminium-based salts act as both catalyst and solvent, so the reaction needs no added hydrogen, no extra solvent and no precious-metal catalysts. It runs below 200 degrees Celsius, far milder than the high-temperature pyrolysis and hydrocracking used at industrial scale today.
Why polyethylene is so hard to recycle
Polyethylene makes up a large share of plastic waste and is difficult to break back down into useful molecules. Mechanical recycling produces lower-grade material after a few cycles, and chemical routes have struggled to compete on cost with virgin plastic made from oil. The Oak Ridge approach produces liquid alkanes, the same class of molecules refineries already handle, which means existing equipment could process the output. The team describes the reaction as neat, meaning the molten medium does the job that added solvents and metal catalysts normally do in a one-pot system.
From lab bench to plant
The work was reported by ScienceDaily on September 21. Promising chemistry does not scale by itself: the next questions are how the salt mixture behaves in continuous flow, how it copes with mixed and contaminated plastic feed, and what the energy balance looks like after thousands of hours of operation. Oak Ridge has catalogued the technology for transfer, and its molten salt research dates back to the 1960s, when the lab's reactor experiment showed that salt mixtures could carry both fuel and coolant. If the process holds up outside the lab, it offers a route for waste plastic to displace some refinery feedstock instead of being burned or buried.