Mechanistic pathways and influencing factors in the liquefaction of single and mixed plastics toward waste-to-energy conversion: A structured and critical review

Document Type

Review

Publication Date

3-15-2026

Abstract

Hydrothermal plastic liquefaction is recognized as a promising approach for the conversion of waste polymers to fuels and high-value chemicals. Despite recent advancements, an in-depth understanding of governing mechanisms continues to encounter fundamental challenges. This review systematically explores 599 peer-reviewed articles published between 2015 and 2025 and provides a structured and critical analysis of single-component, multi-layer and mixture of polymers including municipal solid waste from a mechanistic perspective. This study also explores the combined influence of polymer and reactor types, process operating conditions, solvent categories and the role of water in different thermodynamic states. The findings from this review demonstrate that differences in feedstocks, equipment, and reaction conditions impede the formulation of a scientifically reliable mechanism. Despite these insights, critical gaps persist in understanding the governing reaction pathways for polymer mixtures, solvent polarity effects, polymer decomposition thermal behavior modeling, synergistic or antagonistic effects of multi-layer polymers and deep learning for tuning kinetic model parameters. This article is useful for kinetic modeling and serves as an important source for researchers who work on thermochemical conversion. In addition to theoretical contributions, these findings have practical applications by supporting the process intensification and scale-up of HTL technology for industrial plastic waste valorization.

Publication Title

Process Safety and Environmental Protection

ISSN

09575820

DOI

10.1016/j.psep.2026.108542

Volume

209

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