Converting plastic scrap at low temperatures

Researchers at the Technical University of Munich have found an innovative low-energy, low-temperature recycling method for plastic scrap. 

‘Polyethylene and polypropylene have many useful properties but their resistance to chemical degradation makes processing their waste a challenge, writes Wei Zhang, lead author of the R&D project in the journal Science. ‘In particular, heating to high temperatures to crack the underlying carbon–carbon bonds can be energy intensive.’ 

The researchers report that an aluminium chloride–based ionic liquid medium can break down these polyolefin plastics into liquid fuels at temperatures below 100°C. The entire reaction takes place in a single vessel. ‘It takes only three hours and occurs at 70°C. By comparison, existing recycling techniques typically require two stages, take much longer and need temperatures of over 200°C.’

The new recycling process ultimately converts unprocessed post-consumer items into high-quality liquid alkanes with high yields. The alkylate product is easily separated from the reactant catalyst mixture.