Solvent-Free Chemical Recycling of Polyolefins and Polystyrene under Mild Conditions via GaCl3-Based Molten Catalysts

Here, we report a solvent-free, low-temperature, and synergistic depolymerization strategy using a GaCl3-based molten Lewis acid catalyst for the efficient conversion of PE, PP, and PS, both individually and in mixed plastics streams. The low melting point of the catalyst ensures liquid-phase mobility and efficient contact between polymer and catalysts, achieving complete PS conversion and over 60% PE/PP conversion within 30 min. In mixed plastics, a synergistic reaction pathway mediated by carbocation-type intermediates enables Friedel-Crafts alkylation between PS-derived aromatics and polyolefin-derived olefins, enhancing overall conversion (~85%) and selectivity toward mono-alkylated aromatics (up to 33.5%). Raman spectra confirmed the formation of [GaCl4]- and [Ga2Cl7]- chlorogallate species during the reaction. This study demonstrates a novel, integrated approach for solvent-free, selective, and energy-efficient chemical recycling of mixed plastics, highlighting GaCl3-based molten salts as versatile catalysts for circular and sustainable plastic recycling. All data sets involed in manuscript are attached.