Solvent-Assisted Poly(lactic acid) Upcycling under Mild Conditions

Abstract

Poly(lactic acid) (PLA) is a biosourced green plastic derived from natural sources that can replace polyolefins in many applications; however, it is seldom recycled. PLA is a prime candidate for chemical recycling by depolymerization, which produces valuable commodity chemicals and/or fresh monomer for new production, compared to mechanical/thermal reprocessing which produces lesser-quality resin. A scalable, low-cost depolymerization process could render PLA the premier choice for designed-to-be-recycled products in a future circular plastics economy. Here, we report a novel process for depolymerization of PLA under mild conditions using alcoholysis with ionic liquid catalysts in the presence of dimethyl (or diethyl) carbonate as a green solvent, along with critical technoeconomic analysis of the potential impact of this process. The effects of catalyst structures, the solvent system, and PLA resin type on conversion and yield were studied. The reaction kinetics were statistically analyzed with experimental and modeling data, suggesting a fast first-order reaction in PLA degradation. Predictive modeling results based on empirical data further guide the design of scenarios and potential for practical application.

Recommendations for life-cycle assessment of recyclable plastics in a circular economy

“…There has been a rapid expansion in the volume of research aimed at increasing the quantity and quality of recycled plastics. 1–8 Recycling technologies and infrastructure for waste recovery ( i.e. collection and sorting) are key to this transition, 9 yet the methods by which different options can be evaluated and compared are nascent and inconsistently applied.…”

Novel Strategies for Recycling Poly(butylene adipate-co-terephthalate)-Starch-Based Plastics: Selective Solubilization and Depolymerization–Repolymerization Processes

“…The industrial production pathways that are used today for manufacturing the PBAT monomers adipic acid (AA), terephthalic acid (TA), and 1,4-butanediol (1,4-BD) are based on fossil-based platform chemicals (e.g., benzene) and require highly energy demanding (e.g., cracking or reforming) catalytic multistep processes (Figure ), − which make PBAT-SBP composting an enormous waste of resources. While much attention has been focused on the recycling of bioplastics such as polylactic acid (PLA) , and polyhydroxyalkanoates (PHAs), , only a few studies have been conducted on PBAT and its starch-based blends: (i) the mechanical recycling of PBAT has been successfully proposed, demonstrating that it can be subjected to more cycles of reprocessing; (ii) the slow pyrolysis of SBP bags has been used to obtain the main monomers of PBAT, TA, AA, levoglucosan, and char; and (iii) the fungal fermentation of the starch component for the production of lactic acid has been reported …”