Publisher: American Chemical Society (ACS)

Issue: 36

License: [{"start"=>{"date-parts"=>[[2023, 9, 1]], "date-time"=>"2023-09-01T00:00:00Z", "timestamp"=>1693526400000}, "content-version"=>"vor", "delay-in-days"=>0, "URL"=>"https://creativecommons.org/licenses/by/4.0/"}]

Publication date(s): 2023/09/13 (print) 2023/09/01 (online)

Pages: 19840-19848

Volume: 145 Issue: 36

Journal: Journal of the American Chemical Society

Link: [{"URL"=>"https://pubs.acs.org/doi/pdf/10.1021/jacs.3c05863", "content-type"=>"application/pdf", "content-version"=>"vor", "intended-application"=>"unspecified"}, {"URL"=>"https://pubs.acs.org/doi/pdf/10.1021/jacs.3c05863", "content-type"=>"unspecified", "content-version"=>"vor", "intended-application"=>"similarity-checking"}]

URL: http://dx.doi.org/10.1021/jacs.3c05863

Poly(l-lactic acid) (PLLA) is a leading commercial polymer produced from biomass, showing useful properties for plastics and fiber applications; after use, it is compostable. One area for improvement is postconsumer waste PLLA chemical recycling to monomer (CRM), i.e., the formation of l-lactide (l-LA) from waste plastic. This process is currently feasible at high reaction temperatures and shows low catalytic activity accompanied, in some cases, by side reactions, including epimerization. Here, a commercial Sn(II) catalyst, applied with nonvolatile commercial alcohol, enables highly efficient CRM of PLLA to yield l-LA in excellent yield and purity (92% yield, >99% l-LA from theoretical max.). The depolymerization is performed using neat polymer films at low temperatures (160 °C) under a nitrogen flow or vacuum. The chemical recycling operates with outstanding activity, achieving turnover frequencies which are up to 3000× higher than previously excellent catalysts and applied at loadings up to 6000× lower than previously leading catalysts. The catalyst system achieves a TOF = 3000 h–1 at 0.01 mol % or 1:10,000 catalyst:PLLA loading. The depolymerization of waste PLLA plastic packaging (coffee cup lids) produces pure l-LA in excellent yield and selectivity. The new catalyst system (Sn + alcohol) can itself be recycled four times in different PLLA “batch degradations” and maintains its high catalytic productivity, activity, and selectivity.