Ultrafast and selective chemical recycling of PLA to methyl lactate by using MHMDS as simple catalysts

Abstract

The depolymerization of waste plastics into high-value products is a promising solution to address the plastic crisis. Among this field, catalytic activity and selectivity of depolymerization catalyst are of great concerns. Accordingly, in this work, a simple catalytic system was explored in detail to achieve the fast and selective chemical recycling of PLA into methyl lactate. Using commercially available M[bis(trimethylsilyl)amide] (MHMDS, M = Li, Na, K) as catalysts, the depolymerization of PLA was completed within a few minutes at room temperature. The selectivity and optical purity of the depolymerized product methyl lactate are greater than 99 %. The effect of conditions such as metal center, catalyst form, and solvent on depolymerization was investigated. Moreover, the gram-grade depolymerization, selective depolymerization of blended or mixed PLA plastic, and the recyclability of catalyst were further explored. This work accomplishes the path of highly selective and active depolymerization of PLA under mild conditions, thereby promoting sustainable development of PLA.