Upcycling waste polystyrene to adipic acid through a hybrid chemical and biological process
Hyunjin Moon, Jason S. DesVeaux, Elisabeth C. Van Roijen, Christine A. Singer, Hannah Alt, Mikhail O. Konev, Clarissa Lincoln, Young-Saeng C. Avina, Nicolette R. Meyer, Stefan J. Haugen, Hyeongeon Lee, Kwangjin An, Joel Miscall, Kelsey J. Ramirez, Christopher W. Johnson, Davinia Salvachúa, Bruno Colling Klein, Taylor Uekert, Allison Z. Werner, Shannon S. Stahl, Gregg T. Beckham
Abstract
Oxidative catalytic depolymerization of polystyrene (PS) can produce benzoic acid, but the annual consumption of benzoic acid is ~40 times lower than PS. For this catalytic oxidation method to be a viable means to manage PS waste, benzoic acid should be converted to higher-volume chemicals. We demonstrate a hybrid chemical and biological process that uses PS as feedstock for production of adipic acid, a high-volume co-monomer for nylon 6,6 via benzoic acid. Mn/Br co-catalyzed autoxidation of PS to benzoic acid proceeds with a yield of up to 94% in a solvent mixture of benzoic acid and water. The PS-derived benzoic acid undergoes bioconversion at near-quantitative yield to muconic acid, which is readily converted to adipic acid through catalytic hydrogenation. Process modeling, techno-economic analysis, and life cycle assessment estimate an adipic acid minimum selling price of $3.18/kg, with a 61% decrease in greenhouse gas emissions relative to production from fossil fuels. Oxidative catalytic depolymerization of polystyrene (PS) can produce benzoic acid, but the annual consumption of benzoic acid is ~40 times lower than PS, so benzoic acid should be converted to higher-volume chemicals for the process to be viable. Here, the authors report a hybrid chemical and biological process that uses PS as feedstock for production of adipic acid, a high-volume co-monomer for nylon 6,6, via benzoic acid.