Turning Polyethylene Waste to Hydrocarbons Using a Sustainable Acidic Carbocatalyst

According to Majd Al-Naji & Markus Antonietti, "Careless release of plastic waste is a pressing problem for the marine and other eco-environments, and materials recycling of this stream an open problem. For this purpose, a new metal-free acidic carbocatalyst with 8 wt.-% sulfur is constructed on base of a side product of paper industry, Na-lignosulfonate. 

The catalyst shows an extraordinary performance for the fragmentation of polymer waste which smoothly occurs above the ceiling temperature of the polymers. The reaction is run without hydrogen and at ambient pressure with commercially available high density polyethylene (HDPE) as well as a real polymer waste mixture of high and low density polyethylene (HDPE, LDPE), and in all cases a homologous series of n-alkanes and n-alkenes are obtained. The unique sulfur-rich carbonaceous structure (transfer hydrogenation functionality) and the metal-free character of the acidic carbocatalyst makes it inert against many typical catalyst poisons, among them water, salt, polar functionalities, and sulfur species. The described performance in plastic recycling, as well as the low cost and large-scale availability of lignosulfonate from pulp industry makes this metal-free acidic carbocatalyst promising for real life environmental applications."

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