Green Solvent-Assisted Methanolysis of Polycarbonate over Sodium Metasilicate

Although catalytic methanolysis of polycarbonate (PC) over solid base catalysts has recently been extensively investigated, achieving efficient depolymerization often requires harsh reaction conditions and hazardous solvents. Herein, we developed a catalytic system in which sodium metasilicate (Na2SiO3) and 1,3-dioxolane (1,3-DO) were used as a solid base catalyst and a green solvent, respectively, for the ambient-pressure methanolysis of PC. The reaction over Na2SiO3 at 60 °C afforded 96.9% crystalline BPA with a space-time yield (STY) of 44 gBPA gcat–1 h–1, which is one of the highest values reported for heterogeneous PC methanolysis so far. The suitability of 1,3-DO as a solvent was attributed to its high affinity for PC according to Hansen solubility parameters (HSPs). The reaction showed an apparent activation energy (Ea) of 98.5 kJ mol–1, and the catalyst was reusable for at least four cycles. Moreover, the reaction not only exhibited a low environmental energy impact factor (ξ) but was also applicable to real PC waste.