20-Jun-16 Chinese chemists have developed a remarkably efficient method for converting polyethylene into liquid fuel. It's scalability needs to be tested. Zheng Huang, an organic chemist at the Chinese Academy of Sciences, has spent the last four years developing a different approach. Writing in Science Advances, Huang and his colleagues describe their method for degrading polyethylene at temperatures as low as 150°C, by adding an organometallic catalyst — a small, commercially available organic molecule doped with the metal iridium — to the reaction. The catalyst weakens bonds responsible for polyethylene’s stiff structure, accelerating its breakdown into a liquid product.
“Our products are much cleaner than those obtained by conventional [combustion] methods,” Huang told Gizmodo, adding that his method is also easier to control and can be used as a diesel fuel. It’s been proven on small samples of plastic bags, bottles and food packaging. The challenge, of course, will be scaling up from grams to tons if we want to make a dent in the mountains of plastic waste that litter our planet. “The first challenge is the efficiency of the catalyst,” Huang said. Right now, his procedure works well at a plastic-to-catalyst ratio of roughly 30 to one. “That’s not good enough if you want to commercialise,” he continued. “We want to see ten thousand to one, or a million to one.” Huang’s team is also looking into replacing iridium — a rare and precious metal in the platinum family — with a cheaper alternative, although this may prove more difficult, given the highly specific nature of metal catalysts.
“We think that the future potential is there — as long as we can improve the efficiency and reduce the cost of the iridium,” Huang said. “Hopefully, very soon we can scale up the process from gram scale in the lab to kilogram and even ton scale.”
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