Recycling of mixed plastics is undermined by attendant high labor and energy costs. Producing new plastic products is currently more economical than sorting and repurposing used materials. A new organocatalyst devised by researchers from U.S. Oak Ridge National Laboratory and the University of Virginia offers scope to reduce process complexity and improve prospects for achieving circularity in the mixed plastics sector.

The triazabicyclododecane:methanesulfonic acid (TBD:MSA) organocatalyst selectively and sequentially deconstructs multiple polymers in mixed plastics into pristine monomers for reuse. Relative to existing catalytic options, the new process would generate up to 95% fewer greenhouse gases, require up to 94% less energy input and result in up to a 96% reduction in fossil fuel consumption.

Multiple polymers are deconstructed by the TBD:MSA agent in around two hours. The catalyst has proven effective in treating and reclaiming polycarbonates, polyurethanes, polyethylene terephthalates and polyamides, which account for more than 30% of global plastic production.

Deconstruction proceeds at different temperatures, which facilitates sequentially recovering the individual monomers separately and in reusable form. Polycarbonates deconstruct at 266° F (130° C), polyurethanes at 320° F (160° C), polyethylene terephthalates at 356° F (180° C) and polyamides at 410° F (210° C).

This advance in closed-loop chemical recycling of mixed plastics is described in Energy Matters.